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Photochemie - Neueste Forschungsartikel der Fachverlage


 
Aktuelle Fachartikel zur Photochemie und Photobiologie, sortiert nach Erscheinungsdatum.

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Photochemical & Photobiological Sciences - published by The Royal Society of Chemistry -
PPS meets the growing information needs of scientists working in the areas of photochemistry and photobiology, and indeed, encourages a synergism between these two important research areas. This international journal is published monthly on behalf of the European Photochemistry Association (EPA), the European Society for Photobiology (ESP), the Asia and Oceania Society for Photobiology (AOSP) and the Korean Society of Photoscience (KSP), and is available in both print and electronic formats.

Photochemistry and Photobiology - published by Wiley-Interscience -
... publishes original research articles and reviews on current topics in photoscience.



Aktuelle wissenschaftliche Fachartikel der genannten Journale:


Photostability of Cosmetic UV Filters on Mammalian Skin Under UV Exposure

Abstract

Previous studies showed that the common UV filter substances benzophenone-3 (BP–3), butyl methoxydibenzoylmethane (BM–DBM), octocrylene (OCR), ethylhexyl methoxycinnamate (EHMC), ethylhexyl salicylate (EHS) and ethylhexyl triazone (EHT) were able to react with amino side chains of different proteins in vitro. To transfer the results to mammalian skin conditions, sunscreen products were applied on both prepared fresh porcine skin and glass plates, followed by UV irradiation and the determination of depletion of the respective UV filters. Significantly lower recoveries of the UV filters extracted from skin samples than from glass plates indicated the additional reaction of the UV filters with skin constituents, when proteins will be the most important reactants. Among the products tested, BP-3 showed the greatest differences in recoveries between glass and skin samples of about 13% and 24% after 2 and 4 h of irradiation, respectively, followed by EHS > BM-DBM > OCR > EHMC > EHT. The obtained results raise the question, whether the common in vitro evaluations of sunscreens, using inert substrate materials like roughened quartz or polymethyl methacrylate (PMMA) plates are really suitable to fully replace in vivo methods, as they cannot include skin-typical reactions.

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Previous studies showed that common UV filter substances like BP-3, BM-DBM, EHS, OCR, EHMC and EHT were able to react with amino side chains of different proteins in vitro. The present work confirms that also in the case of real skin samples, differences in the recoveries could be observed when sunscreen samples were irradiated on either glass plates or pig skin, indicating the occurrence of certain skin-typical reactions, as the formation of protein adducts. The results were in good accordance with a recently developed HPTLC screening method, indicating a different photocontact allergenic potential of the UV filters.

Quelle: Photochemistry and Photobiology | 25 Oct 2014 | 9:40 am CEST

Singlet oxygen photosensitisation by the fluorescent protein Pp2FbFP L30M, a novel derivative of Pseudomonas putida flavin-binding Pp2FbFP

Photochem. Photobiol. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4PP00338A, Paper
Joaquim Torra, Andres Burgos-Caminal, Stephan Endres, Marcus Wingen, Thomas Drepper, Thomas Gensch, Ruben Ruiz-Gonzalez, Santi Nonell
Flavin-binding fluorescent proteins (FbFPs) are a class of fluorescent reporters that are being increasingly used as reporters for the study of cellular structures and dynamics. Flavin's intrinsic high singlet oxygen...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 24 Oct 2014 | 1:00 am CEST

Upgrading a Microplate Reader for Photobiology and All-Optical Experiments

Photochem. Photobiol. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4PP00361F, Paper
Florian Richter, Ulrike S Scheib, Jennifer Mehlhorn, Roman Schubert, Jonas Wietek, Oliver Gernetzki, Peter Hegemann, Tilo Mathes, Andreas Moglich
Automation can vastly reduce the cost of experimental labor and thus facilitate high experimental throughput, but little off-the-shelf hardware for the automation of illumination experiments is commercially available. Here, we...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 24 Oct 2014 | 1:00 am CEST

Transparent thin films of Cu-TiO2 with visible light photocatalytic activity "Special Issue of 8TH EUROPEAN MEETING ON SOLAR CHEMISTRY AND PHOTOCATALYSIS: ENVIRONMENTAL APPLICATIONS (SPEA 8)"

Photochem. Photobiol. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4PP00271G, Paper
Marcin Janczarek, Anna Zielinska-Jurek, Irmina Markowska, Jan Hupka
Thin films of Cu-TiO2 with high level of transparency were prepared by the dip-coating procedure on the glass surface. CuCl2 was used as copper precursor added during sol-gel synthesis of...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 24 Oct 2014 | 1:00 am CEST

Analysis of Oxyluciferin Photoluminescence Pathways in Aqueous Solutions

Abstract

We evaluated the pKa values of oxyluciferin and its conjugate acids and bases theoretically with the help of experimental correction values, from which free energies for the first excited and the ground states of all the species were estimated. On the basis of these results, we calculated pH-dependent absorption spectra, where the relative absorption intensities of various species strongly depend on photo-excitation energy, and we further analysed the photoluminescence pathways of oxyluciferin in aqueous solutions with various pH. In the case of 350 nm photo-excitation, in particular, experiments have shown that dominant emission colour is green and it attenuates with pH decreasing, while blue (3 < pH < 8) and red (pH < 3) emissions appear. Our present results clarify the pathways of these photoluminescence depending on the pH values and thus should be useful in further analyses of photoluminescence pathways for other photo-excitation wavelength in comparison with experiments.

This article is protected by copyright. All rights reserved.

Quelle: Photochemistry and Photobiology | 21 Oct 2014 | 2:52 pm CEST

Temperature dependence of flash duration of the firefly Luciola praeusta

Photochem. Photobiol. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4PP00319E, Paper
Upamanyu Sharma, Angana Goswami, Mridusmita Phukan, Subhash Rajbongshi, Anurup Gohain Barua
Firefly flashing has been attracting attentions of both poets and scientists for over a century. Here we study the effect of temperature on flash-duration of the Indian species of the...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 21 Oct 2014 | 1:00 am CEST

A novel set of symmetric methylene blue derivatives exhibits effective bacteria photokilling - a structure-response study

Photochem. Photobiol. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4PP00309H, Paper
Anita Gollmer, Ariane Felgentraeger, Wolfgang Baeumler, Tim Maisch, Andreas Spaeth
This study focuses on the structure-response relationship of symmetrically substituted phenothiazinium dyes. Four hydrophilic derivatives with the ability of additional hydrogen bonding (5, 6) or additional electrostatic interaction (3, 4)...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 21 Oct 2014 | 1:00 am CEST

Specific Features of Early Stage of the Wound Healing Process Occurring Against the Background of Photodynamic Therapy Using Fotoditazin Photosensitizer–Amphiphilic Polymer Complexes

Abstract

There is a growing demand on the studies of the wound healing potentials of photodynamic therapy. Here we analyze the effects of Fotoditazin, an e6 chlorine derivative, and its complexes with amphiphilic polymers, on the early stage of wound healing in a rat model. A skin excision wound model with prevented contraction was developed in male albino rats divided into eight groups according to the treatment mode. All animals received injections of one of the studied compositions into their wound beds and underwent low-intensity laser irradiation or stayed un-irradiated. The clinical monitoring and histological examination of the wounds were performed. It has been found that all the Fotoditazin formulations have significant effects on the early stage of wound healing. The superposition of the inflammation and regeneration was the main difference between groups. The aqueous solution of Fotoditazin alone induced a significant capillary hemorrhage, while its combinations with amphiphilic polymers did not. The best clinical and morphological results were obtained for the Fotoditazin–Pluronic F127 composition. Compositions of Fotoditazin and amphiphilic polymers, especially Pluronic F127, probably, have a great potential for therapy of wounds. Their effects can be attributed to the increased regeneration and suppressed reactions changes at the early stages of repair.

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Here we analyze the effects of Fotoditazin, a e6 chlorine derivative, and its complexes with amphiphilic polymers, on the early stage of wound healing in a rat model. In this hematoxylin–eosin stained tissue (magnification ×200) one can see the difference between an untreated wound (1) with a thick fibrinous-leucocytic layer and immature granulation tissue, and a wound treated with the Fotoditazin–Pluronic 127 complex (2), showing relatively mature granulation tissue with vertical capillaries. Compositions of Fotoditazin and amphiphilic polymers, especially Pluronic F127, probably have a great potential for therapy of wounds.

Quelle: Photochemistry and Photobiology | 20 Oct 2014 | 1:24 pm CEST

Highly Efficient Photodegradation of Organic Pollutants Assisted by Sonoluminescence

Abstract

The mechanism of the photodegradation of azo dyes via ultrasonication is studied using a combination of the high-performance liquid chromatography and UV–vis spectroscopy with detailed analysis of the kinetics. Based on the kinetics studies of the sonodegradation, it was proposed that the degradation of azo dyes was a multistage process that involved: (1) the direct attack of azo bonds and phenyl rings of dyes by the sonochemically formed reactive oxygen species; (2) the activation of semiconductor particles by the light emitted during cavitation and the triggering of the photocatalytic pathways of dye degradation and (3) increase of the adsorption capacity of the semiconductor particles due to the sonomechanically induced interparticle collisions. The detailed kinetics study can help in following an effective process up-scaling. It was demonstrated that extremely short pulses of light flashes in a cavitated mixture activated the surface of photocatalysts and significantly enhanced dye degradation processes.

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The kinetics of dye degradation via ultrasonication was studied. It was shown that Light emitted in cavitated liquid was essential for initiation of the photoreactions on the surface of the semiconductor particles. Direct attack of dye molecules by sonochemically formed reactive oxygen species causes relatively slow degradation of azo dyes. The mechanism of ultrasound-assisted degradation of azo dyes is mostly based on the activation of photocatalysts by sonoluminescence.

Quelle: Photochemistry and Photobiology | 20 Oct 2014 | 12:55 pm CEST

Combination of Er:YAG Laser and CO2 Laser treatment on skin tissue

Abstract

The skin is the most important organ in our body, as it protects us from external environmental effects. The study of the ability of the skin to stretch and the histological examinations of irradiated tissues have significant values in scientific and medical applications. Only a few studies have been done to study the correlation between epidermis ablation and the changes that occur at dermal levels when using dual lasers in ablative resurfacing mode. The aim of this work is to determine this correlation and to estimate the effects of multiple pulses on induced collagen remodelling and the strength of skin exposed with dual lasers in an in vivo rat model. All laser exposures led to marked improvements in the skin's strength compared to their own controls. The histological investigation indicated that there was a thickness loss in the epidermis layer with the induction of deep collagen coagulation in the dermis layer as the dual laser pulses increased. Additionally, more collagen fibres were remoulded in the treated samples by dual wavelengths. We conclude that by combining dual lasers with multiple pulses targeted at not only the epidermis layer of the skin, it could also induce some heat diffusion in the dermis layer which causes more coagulation of collagen fibres. The tensile results confirmed by our histological data demonstrates that the strength of irradiated skin with dual wavelengths increased more than using both lasers separately on the skin tissue since more collagen is induced.

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Quelle: Photochemistry and Photobiology | 18 Oct 2014 | 12:22 pm CEST

Oxidatively generated damage to cellular DNA by UVB and UVA radiation

Abstract

This review article focuses on a critical survey of the main available information on the UVB and UVA oxidative reactions to cellular DNA as the result of direct interactions of UV photons, photosensitized pathways and biochemical responses including inflammation and bystander effect. UVA radiation appears to be much more efficient than UVB in inducing oxidatively generated damage to the bases and 2-deoxyribose moieties of DNA in isolated cells and skin. The UVA-induced generation of 8-oxo-7,8-dihydroguanine is mostly rationalized in terms of selective guanine oxidation by singlet oxygen generated through type II photosensitization mechanism. In addition, hydroxyl radical whose formation may be accounted for by metal-catalyzed Haber-Weiss reactions subsequent to the initial generation of superoxide anion radical contributes in a minor way to the DNA degradation. This leads to the formation of both oxidized purine and pyrimidine bases together with DNA single strand breaks at the exclusion however of direct double strand breaks. No evidence has been provided so far for the implication of delayed oxidative degradation pathways of cellular DNA. In that respect putative characteristic UVA-induced DNA damage could include single and more complex lesions arising from one-electron oxidation of the guanine base together with aldehyde adducts to amino-substituted nucleobases.

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Quelle: Photochemistry and Photobiology | 18 Oct 2014 | 12:21 pm CEST

Photoisomerization of cis-1,2-di(1-Methyl-2-naphthyl)ethene at 77 K in Glassy Media

Abstract

cis-1,2-Di(1-methyl-2-naphthyl)ethene, c-1,1, undergoes photoisomerization in methylcyclohexane, isopentane and diethyl ether/isopentane/ethanol glasses at 77 K. On 313 nm excitation the fluorescence of c-1,1 is replaced by fluorescence from t-1,1. Singular value decomposition reveals that the spectral matrices behave as two component systems suggesting conversion of a stable c-1,1 conformer to a stable t-1,1 conformer. However, the fluorescence spectra are λexc dependent. Analysis of global spectral matrices shows that c-1,1 is a mixture of two conformers each of which gives one of four known t-1,1 conformers. The λexc dependence of the c-1,1 fluorescence spectrum is barely discernible. Structure assignments to the resolved fluorescence spectra are based on the principle of least motion and on calculated geometries, energy differences and spectra of the conformers. The relative shift of the c-1,1 conformer spectra is consistent with the shift of the calculated absorption spectra. The calculated structure of the most stable conformer of c-1,1 agrees well with the X-ray crystal structure. Due to large deviations of the naphthyl groups from the ethenic plane in the conformers of both c- and t-1,1 isomers, minimal motion of these bulky substituents accomplishes cis [RIGHTWARDS ARROW] trans interconversion by rotation about the central bond.

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Quelle: Photochemistry and Photobiology | 18 Oct 2014 | 12:21 pm CEST

Cellular Changes Associated with the Acclimation of the Intertidal Sea Anemone Actinia tenebrosa to Ultraviolet Radiation

Abstract

To assess the relative importance of long- and short-term cellular defense mechanisms in seasonally UV-R-acclimated Actinia tenebrosa (Anthozoa, Actiniidae), individuals were exposed to summer doses of PAR, UV-A, UV-B and enhanced UV-B (20%) for a period of 4 days. Mycosporine-like amino acids (MAAs) and cyclobutane pyrimidine dimer (CPD) concentrations were quantified, while oxidative damage to lipids and proteins, and the activities or levels of the antioxidant enzymes SOD, CAT, GR, GPOX and total glutathione were determined. Our results show that summer UV-R-acclimated individuals had a higher UV-R tolerance, with no significant increases in CPDs levels, than winter-acclimated sea anemones possibly due to higher MAA concentrations. Summer-acclimated individuals showed increased lipid and protein oxidation and GPOX activity only when they were exposed to UV-B at 20% above ambient UV-R levels. In contrast, winter-acclimated sea anemones showed elevated levels of oxidative damage, GPOX and SOD activities after exposure to UV-A or UV-B at ambient and elevated levels. Thus, this study indicates that long-term UV-R acclimation mechanisms such as the accumulation of MAAs could be more important than short-term increases in antioxidant defenses with respect to reducing indirect UV-R damage in intertidal sea anemones.

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Cyclobutane pyrimidine dimers (CDPs) levels in summer (A) and winter (B) UV-B-acclimated Actinia tenebrosa exposed to four radiation treatments (P [PAR], PA [PAR + UVA], PAB [PAR + UVA + UVB] and PAB-20% [PAR + UVA + UVB-20%]). Animals sampled in summer, exposed to artificially enhanced levels of UV-B and allowed to recover following exposure, showed no accumulation of CPDs over a 4-day experimental period. In contrast, organisms sampled in winter accumulated CPDs in a dose-dependent manner.

Quelle: Photochemistry and Photobiology | 18 Oct 2014 | 12:18 pm CEST

Inspection of Feasible Calibration Conditions for UV Radiometer Detectors with the KI/KIO3 Actinometer

Abstract

UV radiometers are widely employed for irradiance measurements, but their periodical calibrations not only induce an extra cost but also are time-consuming. In this study, the KI/KIO3 actinometer was applied to calibrate UV radiometer detectors at 254 nm with a quasi-collimated beam apparatus equipped with a low-pressure UV lamp, and feasible calibration conditions were identified. Results indicate that a washer constraining the UV light was indispensable, while the size (10 or 50 mL) of a beaker containing the actinometer solution had little influence when a proper washer was used. The absorption or reflection of UV light by the internal beaker wall led to an underestimation or overestimation of the irradiance determined by the KI/KIO3 actinometer, respectively. The proper range of the washer internal diameter could be obtained via mathematical analysis. A radiometer with a longer service time showed a greater calibration factor. To minimize the interference from the inner wall reflection of the collimating tube, calibrations should be conducted at positions far enough away from the tube bottom. This study demonstrates that after the feasible calibration conditions are identified, the KI/KIO3 actinometer can be applied readily to calibrate UV radiometer detectors at 254 nm.

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Under feasible calibration conditions, the KI/KIO3 actinometer can be easily applied to calibrate UV radiometer detectors at 254 nm in a quasi-collimated beam apparatus in ordinary laboratories, which saves the cost and time for periodic detector recalibrations.

Quelle: Photochemistry and Photobiology | 18 Oct 2014 | 12:18 pm CEST

A search for radical intermediates in the photocycle of LOV domains

Photochem. Photobiol. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4PP00155A, Paper
Bernhard Dick, Roger-Jan Kutta, Kathrin Magerl, Uwe Kensy
LOV domains are the light sensitive parts of phototropins and many other light-activated enzymes that regulate the response to blue light in plants and algae as well as some fungi...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 17 Oct 2014 | 1:00 am CEST

NpR3784 is the prototype for a distinctive group of red/green cyanobacteriochromes using alternative Phe residues for photoproduct tuning

Photochem. Photobiol. Sci., 2014, Advance Article
DOI: 10.1039/C4PP00336E, Paper
Nathan C. Rockwell, Shelley S. Martin, Fei Gan, Donald A. Bryant, J. Clark Lagarias
We report chromophore-protein interactions used by cyanobacteriochrome NpR3784 and related proteins for spectral tuning of the green-absorbing photoproduct state. These interactions are distinct from those used by canonical red/green cyanobacteriochromes.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 17 Oct 2014 | 1:00 am CEST

Combined cytotoxic effect of UV-irradiation and TiO2 microbeads in normal urothelial cells, low-grade and high-grade urothelial cancer cells

Photochem. Photobiol. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4PP00272E, Paper
roghayeh imani, Peter Veranic, Ales Iglic, Mateja Erdani Kreft, Meysam Pazoki, Samo Hudoklin
The differentiation of urothelial cells results in normal terminally differentiated cells or by alternative pathways in low-grade or high-grade urothelial carcinomas. Treatments with traditional surgical and chemotherapeutical approaches are still...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 17 Oct 2014 | 1:00 am CEST

Lophine derivatives as activators in peroxyoxalate chemiluminescence

Photochem. Photobiol. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4PP00311J, Paper
Jessica Alves, Andreia Boaro, Jessica Soares da Silva, Tiago Luiz Ferreira, Vinicius Blasio Keslarek, Cauai Antunes Cabral, Ronaldo Barros Orfao Jr., Luiz Francisco Monteiro Leite Ciscato, Fernando Heering Bartoloni
Lophine and four of its derivatives were used as activators (ACTs) of the chemiluminescent peroxyoxalate (PO) reaction of bis(2,4,6-trichlorophenyl)oxalate with H2O2, catalysed by imidazole. Kinetic emission assays have shown that...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 17 Oct 2014 | 1:00 am CEST

Photoactive Chitosan: A Step Toward a Green Strategy for Pollutant Degradation

Abstract

This article is a highlight of the paper by Ferrari et al. in this issue of Photochemistry and Photobiology. It describes the innovative use of rose bengal-conjugated chitosan as a reusable green catalyst that photo-degrades phenolic compounds in aqueous media, and thereby has decontamination potential of polluted waters. Whether a next-generation photoactive polymer that produces singlet oxygen is a solution to pollutant degradation can be argued. It is as yet unclear what polymeric sensitizer would be practical on a large scale. Nonetheless pursuing this goal is worthwhile.

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This article highlights the work of Ferrari et al. who describe the use of rose bengal-chitosan conjugate as a reusable green photosensitizer that degrades phenolic compounds in aqueous media.

Quelle: Photochemistry and Photobiology | 16 Oct 2014 | 11:32 am CEST

N4-Methylation of cytosine drastically favors the formation of (6–4) photoproducts in a TCG context

Abstract

Methylation of cytosine is a common biological process both in prokaryotic and eukaryotic cells. In addition to 5–methylcytosine (5mC), some bacterial species contain in their genome N4–methylcytosine (N4mC). Methylation at C5 has been shown to enhance the formation of pyrimidine dimeric photoproducts but nothing is known of the effect of N4 methylation on UV-induced DNA damage. In the present work, we compared the yield and the nature of bipyrimidine photoproducts induced in a series of trinucleotides exhibiting a TXG sequence where X is either T, C, 5mC or N4mC. HPLC associated to tandem mass spectrometry was used to quantify cyclobutane pyrimidine dimers (CPD), (6-4) photoproducts (64PP) and their Dewar valence isomer. Methylation at position N4 was found to drastically increase the reactivity of C upon exposure to both UVC and UVB and to favor the formation of 64PP. In contrast methylation at C5 increased the yield of CPD at the expense of 64PP. In addition, enhancement of photoreactivity by C5 methylation was much higher in the UVB than in the UVC range. These results show the drastic effect of the methylation site on the photochemistry of cytosine.

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Quelle: Photochemistry and Photobiology | 15 Oct 2014 | 5:42 pm CEST

Solar UV Irradiances Modulate Effects of Ocean Acidification on the Coccolithophorid Emiliania huxleyi

Abstract

Emiliania huxleyi, the most abundant coccolithophorid in the oceans, is naturally exposed to solar UV radiation (UVR, 280-400 nm) in addition to photosynthetically active radiation (PAR). We investigated the physiological responses of E. huxleyi to present-day and elevated CO2 (390 vs 1000 μatm; with pHNBS 8.20 vs 7.86) under indoor constant PAR and fluctuating solar radiation with or without UVR. Enrichment of CO2 stimulated the production rate of particulate organic carbon (POC) under constant PAR, but led to unchanged POC production under incident fluctuating solar radiation. The production rates of particulate inorganic carbon (PIC) as well as PIC/POC ratios were reduced under the elevated CO2, ocean acidification (OA) condition, regardless of PAR levels and the presence of UVR. However, moderate levels of UVR increased PIC production rates and PIC/POC ratios. OA treatment interacted with UVR to influence the alga's physiological performance, leading to reduced specific growth rate in the presence of UVA (315-400 nm) and decreased quantum yield, along with enhanced non-photochemical quenching, with addition of UVB (280-315 nm). The results clearly indicate that UV radiation needs to be invoked as a key stressor when considering the impacts of ocean acidification on E. huxleyi.

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Quelle: Photochemistry and Photobiology | 15 Oct 2014 | 5:41 pm CEST

Skin Responses to Micro Scale Field Size of Solar-Simulated Radiation – Preliminary Evaluation by Reflectance Confocal Microscopy in vivo

Abstract

Erythema and pigment responses of human skin following an acute exposure to ultraviolet radiation (UVR) are frequently used to determine the photosensitivity of the skin. In this study we investigated the responses of the skin to a micro-scale area of UVR exposure (MiR) and compared the responses to a macro-scale area of exposure (MaR). Ten human volunteers were tested with solar-simulated radiation on their upper arm or back using a beam size of 8 mm and 0.2 mm in diameter. The fluence required to produce a minimally perceptible erythema (MED) using the MiR was found to be higher than that for the MaR. The erythema response extended beyond the exposed area and this became pronounced when the beam size was microscopic. Reflectance confocal microscopy in vivo revealed that MiR induced cellular alterations within a confined area of smaller dimensions than the area of exposure. Pigment responses were confined within the areas of cellular damage. The erythema expression of exposed skin recovered faster for the sites receiving MiR even when the applied fluence was higher than the MED for the MaR. Through the use of MiR we were able to visualize spatially dissimilar skin responses of erythema and pigmentation suggesting different cellular mechanisms.

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We investigated the link between the areas of exposure from solar-simulated radiation and that of cellular changes, delayed erythema and pigmentation, and to determine if a microscopic skin site might be used when photo testing is necessary in clinical studies of photodermatoses or in testing for protection by various modalities. Through the use of micro scale beam size for radiation we were able to visualize spatially dissimilar skin responses of delayed erythema and pigmentation suggesting different cellular mechanisms.

Quelle: Photochemistry and Photobiology | 15 Oct 2014 | 1:37 pm CEST

Recent Advances in the Application of Chlorophyll a Fluorescence from Photosystem II

Abstract

In the photosynthesis process, part of the absorbed photon energy in photosystem II (PSII) may be re-emitted as chlorophyll a fluorescence (ChlF). Environmental and plant physiological changes affect the emission of ChlF, which makes ChlF a potentially useful tool to sense these changes. Volumes of research on ChlF are published each year and some published work has been controversial. In order to facilitate the application of ChlF, it is important to have a holistic picture of the field. This review summarizes ChlF applications published in the last 10 years.

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Quelle: Photochemistry and Photobiology | 14 Oct 2014 | 6:59 pm CEST

DNA damage checkpoint responses in the S phase of synchronized diploid human fibroblasts

Abstract

We investigated the hypothesis that the strength of the activation of the intra-S DNA damage checkpoint varies within the S phase. Synchronized diploid human fibroblasts were exposed to either 0 or 2.5 J/m2 UVC in early, mid- and late-S phase. The endpoints measured were the following: (I) radio-resistant DNA synthesis (RDS), (II) induction of Chk1 phosphorylation, (III) initiation of new replicons, and (IV) length of replication tracks synthesized after irradiation. RDS analysis showed that global DNA synthesis was inhibited by approximately the same extent (30±12%), regardless of when during S phase the fibroblasts were exposed to UVC. Western blot analysis revealed that the UVC-induced phosphorylation of Chk1 on serine 345 was high in early and mid S but 10-fold lower in late S. DNA fiber immunostaining studies indicated that the replication fork displacement rate decreased in irradiated cells at the three time points examined; however, replicon initiation was inhibited strongly in early and mid S, but this response was attenuated in late S. These results suggest that the intra-S checkpoint activated by UVC-induced DNA damage is not as robust toward the end of S phase in its inhibition of the latest firing origins in human fibroblasts.

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Quelle: Photochemistry and Photobiology | 14 Oct 2014 | 6:43 pm CEST

Green photocatalytic organic transformations by polyoxometalates vs mesoporous TiO2 nanoparticles: Selective aerobic oxidation of alcohols. the article is invited paper for the "Special Issue of 8TH EUROPEAN MEETING ON SOLAR CHEMISTRY AND PHOTOCATALYSIS: ENVIRONMENTAL APPLICATIONS (SPEA 8)"

Photochem. Photobiol. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4PP00268G, Paper
Ioannis Lykakis, Theodoros S Symeonidis, Ioannis Tamiolakis, Gerasimos S Armatas
In this study, the catalytic activity of decatungstate (W10O324-) supported on mesoporous TiO2 assemblies (DT-MTA) was compared with that of homogeneous [Bu4N]4W10O32 catalysts under mild conditions. Our experiments showed that...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 14 Oct 2014 | 1:00 am CEST

Kinetic Analysis of Nitroxide Radical Formation Under Oxygenated Photolysis: Toward Quantitative Singlet Oxygen Topology

Photochem. Photobiol. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4PP00318G, Paper
Malcolm Forbes, David F Zigler, Eva Chuheng Ding, Renat Khatmullin, Vanessa M DiPasquale, Valery F Tarasov, R. Brendan Sykes, Lauren E Jarocha
Reaction kinetics for two sterically hindered secondary amines with singlet oxygen have been studied in detail. A water soluble porphyrin sensitizer, 5,10,15,20-tetrakis-(4-sulfunatophenyl)-21,23H-porphyrin (TPPS), was irradiated in oxygenated aqueous solutions containing...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 14 Oct 2014 | 1:00 am CEST

The Employment of a Removable Chitosan-Derivatized Polymeric Sensitizer in the Photooxidation of Polyhydroxylated Water-Pollutants

Abstract

The known O2(1g)-sensitizer system Chitosan bounded Rose Bengal (CH-RB), with Rose Bengal (RB) immobilized by irreversible covalent bonding to the polymer Chitosan (CH), soluble in aquous acidic medium, was employed in the photodegradation of three tri-hydroxy benzene water-contaminants (THBs). The system sensitizes the O2(1g)-mediated photodegradation of THBs by a process kinetically favored, as compared to that employing free RB dissolved in the same solvent. Additionally the free xanthene dye, degradable by O2(1g) through self-sensitization upon prolonged light-exposure, is considerably protected when bonded to CH-polymer. The polymeric sensitizer, totally insoluble in neutral medium, can be removed from the solution after the photodegradative cycle by precipitation through a simple pH change. This fact constitutes an interesting aspect in the context of photoremediation of confined polluted waters. In other words, the sensitizing system could be useful for avoiding to dissolve dyestuffs in the polluted waters, in order to act as conventional sunlight-absorbing dye-sensitizers. In parallel the interaction CH - O2(1g) in acidic solution was evaluated. The polymer quenches the oxidative species with a rate constant 2.4 × 108 M−1 s−1 being the process mostly attributable to a physical interaction. This fact promotes the photoprotection of the bonded dye in the CH-RB polymer.

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The known O2(1g)-sensitizer system Chitosan-bounded-Rose Bengal (CH-RB), with the dye immobilized by irreversible covalent bonding to the polymer Chitosan (CH), soluble in aqueous acidic medium, was employed in the photodegradation of tri-hydroxy benzene water-contaminants (THBs). The system sensitizes the O2(1g)-mediated photodegradation of THBs. The polymeric sensitizer, totally insoluble in neutral medium, can be removed from the solution after the photodegradative cycle by precipitation through a simple pH change.

Quelle: Photochemistry and Photobiology | 13 Oct 2014 | 1:18 pm CEST

Interleukin-17 Mediated Inflammatory Responses Are Required for Ultraviolet Radiation-Induced Immune Suppression

Abstract

Ultraviolet radiation (UVR) induces immunosuppression and is a major factor for development of skin cancer. Numerous efforts have been made to determine mechanisms for UVR-induced immunosuppression and to develop strategies for prevention and treatment of UVR-induced cancers. In the current study, we use IL-17 receptor (IL-17R) deficient mice to examine whether IL-17 mediated responses have a role in UVB (290–320)-induced immunosuppression of contact hypersensitivity responses. Results demonstrate that IL-17 mediated responses are required for UVB-induced immunosuppression of contact hypersensitivity responses. The systemic immune suppression and development of regulatory T cells are inhibited in UVB-treated IL-17R deficient mice compared to wild-type animals. The deficiency in IL-17R inhibits the infiltration and development of a tolerogenic myeloid cell population in UVB-treated skin, which expresses CD11b and Gr-1 and produces reactive oxygen species. We speculate that the development of the tolerogenic myeloid cells is dependent on IL-17-induced chemokines and inflammatory mediators in UVB-treated skin. The inhibition of the tolerogenic myeloid cells may be attributed to the suppression of regulatory T cells in UVR-treated IL-17R−/− mice. The findings may be exploited to new strategies for prevention and treatment of UVR-induced skin diseases and cancers.

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Ultraviolet radiation (UVR) causes immune suppression which is associated with an increased risk of skin cancers. Exposure to UVR induces inflammation with an increased level of interleukin-17 in the skin. Our data show that blockade of interleukin-17 inhibits UVR-induced immune suppression. The lack of interleukin-17-mediated inflammation reduces the infiltration and development of suppressive myeloid cells in the ultraviolet-irradiated skin and development of regulatory T cells. The results implicate that interleukin-17 is an important mediator for UVR-induced immune suppression and may be a target for development of new strategies for the prevention of UVR-induced skin cancers.

Quelle: Photochemistry and Photobiology | 13 Oct 2014 | 1:18 pm CEST

Sun Exposure and Vitamin D Status as Northeast Asian Migrants Become Acculturated to Life in Australia

Abstract

Vitamin D deficiency is more common in Northeast-Asian immigrants to western countries than in the local population; prevalence equalizes as immigrants adopt the host country's culture. In a community-based study of 100 Northeast-Asian immigrants in Canberra, Australia, we examined predictors of vitamin D status, its association with indicators of acculturation (English language use; time since migration) and mediators of that association. Participants completed a sun and physical activity diary and wore an electronic ultraviolet radiation (UVR) dosimeter for 7 days. Skin colour was measured by reflectance spectrophotometry. Serum concentrations of 25-hydroxyvitamin D (25(OH)D) and cardio-metabolic biomarkers were measured on fasting blood. In a multiple linear regression model, predictors for 25(OH)D concentration were season of blood collection, vitamin D supplementation, UVR exposure, body mass index, physical activity and having private health insurance (R2 = 0.57). Greater acculturation was associated with lower risk of vitamin D deficiency (de-seasonalized 25(OH)D level <50 nmol L−1) (Adjusted Odds Ratio (AOR): 0.22 [95%CI 0.04–0.96]); this association was statistically mediated by physical activity and time outdoors. Vitamin D deficiency was associated with higher total cholesterol levels (>5.0 mmol L−1) (AOR: 7.48 [95%CI 1.51–37.0]). Targeted public health approaches are required to manage the high prevalence of vitamin D deficiency in migrants retaining a traditional lifestyle.

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In this community-based study of 100 Northeast-Asian immigrants in Canberra, Australia, we examined predictors of vitamin D status, its association with indicators of acculturation (English language use; time since migration) and mediators of that association. In a multiple linear regression model, predictors for 25(OH)D concentration were season of blood collection, vitamin D supplementation, UVR exposure, body mass index, physical activity and having private health insurance. Greater acculturation was associated with lower risk of vitamin D deficiency (de-seasonalized 25(OH)D level <50 nmol L−1); this association was statistically mediated by physical activity and time outdoors. Vitamin D deficiency was associated with higher total cholesterol levels. This figure shows that the odds of having higher cholesterol decrease with higher 25(OH)D levels.

Quelle: Photochemistry and Photobiology | 13 Oct 2014 | 9:41 am CEST

Improving Photoprotection Attitudes in the Tropics: Sunburn vs Vitamin D

Abstract

The ultraviolet radiation of type B (the UVB) stimulates both the production of vitamin D (VD) and the incorporation of erythema dose (ED). The UVA also contributes to ED. The turning point between the benefit of producing VD and the harm of incorporating ED cannot be determined easily. However, the casual behavior regarding the exposure to the Sun can be changed in order to improve the protoprotection attitudes and create a trend towards benefit. In the case, people living in the low latitudes should exposure themselves to the Sun for a determined time interval within the noon time and avoid the Sun in other periods. This would produce an adequate amount of VD through the VD dose (207–214 J m−2) against minimum ED (≈105 J m−2) for skin type II. For it, unprotected forearms and hands must be exposed to the noon Sun (cloudless) for 11 min (winter) and 5 min (summer). The exposure at other times different from noon can represent increases of up to 24% in ED and up to 12 times in the time interval to be in the Sun in relation to the minimum amounts of both ED and time interval at noon.

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Time in the Sun for adequate Standard Vitamin D dose (SDD) in the Tropics for cloudless days in the winter and summer. The annual average SDD is 210 J m−2.

Quelle: Photochemistry and Photobiology | 13 Oct 2014 | 9:40 am CEST

Steam reduction of CO2 on Pd/TiO2 catalysts: a comparison between thermal and photocatalytic reaction

Photochem. Photobiol. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4PP00252K, Paper
Vincenzo Vaiano, Diana Sannino, Paolo Ciambelli
The aim of this work is to compare traditional catalysis, which drives chemical reactions by thermal energy, with a photocatalytic process that can induce chemical reactions by light activation. Taking...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 13 Oct 2014 | 1:00 am CEST

Photocatalytic Degradation of Ofloxacin and Evaluation of Residual Antimicrobial Activity

Photochem. Photobiol. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4PP00256C, Paper
Marcela Souza Peres, Milena Guedes Maniero, J GUimaraes
Ofloxacin is an antimicrobial agent frequently found in significant concentrations in wastewater and surface water. Its continuous introduction into the environment is a potential risk to non-target organisms or to...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 13 Oct 2014 | 1:00 am CEST

The use of chemical actinometry for the evaluation of light absorption efficiency in scattering photopolymerizable miniemulsions

Photochem. Photobiol. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4PP00323C, Paper
Marta Penconi, Emeline Lobry, Florent Jasinski, Abraham CHEMTOB, Celine Croutxe-Barghorn, Adrien Criqui, Andre M. Braun, Esther Oliveros
Oil-in-water miniemulsions containing a mixture of monomers as the dispersed organic phase have been shown recently to be promising media for the development of photoinitiated polymerization processes. Albeit a crucial...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 10 Oct 2014 | 1:00 am CEST

Ultraviolet-activated persulfate oxidation of methyl orange: a comparison between artificial neural networks and factorial design for process modelling

Photochem. Photobiol. Sci., 2014, Advance Article
DOI: 10.1039/C4PP00277F, Paper
Zacharias Frontistis, Evroula Hapeshi, Despo Fatta-Kassinos, Dionissios Mantzavinos
In this work, the degradation of the azo dye methyl orange in model aqueous solutions by UVC light-induced persulfate oxidation was studied.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 10 Oct 2014 | 1:00 am CEST

Firefly inspired one-pot chemiluminescence system using n-propylphosphonic anhydride (T3P)

Photochem. Photobiol. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4PP00250D, Communication
Dai-ichiro Kato, Daiki Shirakawa, Robin Polz, Mika Maenaka, Masahiro Takeo, Seiji Negoro, Kazuki Niwa
A simple reaction procedure for chemiluminescence of firefly luciferin (D-luc) using n-propylphosphonic anhydride (T3P) is reported. A luminescence photon is produced as the result of one-pot reaction, only requiring mixing...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 10 Oct 2014 | 1:00 am CEST

Substituent effects on fluorescence properties of thiazolo[4,5-b]pyrazine derivatives

Photochem. Photobiol. Sci., 2014, Advance Article
DOI: 10.1039/C4PP00298A, Paper
Tatsuki Nakagawa, Minoru Yamaji, Shojiro Maki, Haruki Niwa, Takashi Hirano
A study of fluorescence properties of thiazolo[4,5-b]pyrazine derivatives with the phenyl group at C2, prepared from amidopyrazines. The introduction of electron-donating groups onto the 2-phenyl moiety increases the fluorescence yield and appearance of solvatochromic character.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 10 Oct 2014 | 1:00 am CEST

Wastewater remediation using a spiral shaped reactor for photochemical reduction of hexavalent chromium

Photochem. Photobiol. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4PP00263F, Paper
Tiele Caprioli Machado, Marla Azario Lansarin, Camila Silva Ribeiro
The hexavalent chromium contained in wastewater of some industries is toxic to most microorganisms and potentially harmful to human health. The application of photochemical reduction of Cr(VI) in the treatment...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 10 Oct 2014 | 1:00 am CEST

Synthesis of nitrogen-doped ZnO by sol-gel method: characterization and its application on visible photocatalytic degradation of 2,4-D and picloram herbicides

Photochem. Photobiol. Sci., 2014, Advance Article
DOI: 10.1039/C4PP00273C, Paper
J. J. Macias-Sanchez, L. Hinojosa-Reyes, A. Caballero-Quintero, W. de la Cruz, E. Ruiz-Ruiz, A. Hernandez-Ramirez, J. L. Guzman-Mar
The photocatalytic performance of modified 30% wt. N-ZnO nanoparticles under visible light irradiation was demonstrated by the oxidation of picloram and 2,4-D.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 10 Oct 2014 | 1:00 am CEST

Energy metabolism targeted drugs synergize with photodynamic therapy to potentiate breast cancer cell death

Photochem. Photobiol. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4PP00288A, Paper
Xiaolan Feng, Yi Zhang, Pan Wang, Quanhong Liu, Xiaobing Wang
Abstract: Malignant cells are highly dependent on aerobic glycolysis, which differs significantly from normal cells (Warburg effect). Interference of this metabolic process has been considered as an innovative method for...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 9 Oct 2014 | 1:00 am CEST

Electronic Interactions of Michler's Ketone with DNA Bases in Synthetic Hairpins

Abstract

The mechanism and dynamics of photoinduced electron transfer in two families of DNA hairpins possessing Michler's Ketone linkers have been investigated by means of steady state and time-resolved transient absorption and emission spectroscopies. The excited state behavior of the diol linker employed in hairpin synthesis is similar to that of Michler's ketone in methanol solution. Hairpins possessing only a Michler's ketone linker undergo fast singlet state charge separation and charge recombination with an adjacent purine base, attributed to well-stacked ground state conformations, and intersystem crossing to the triplet state, attributed to poorly-stacked ground state conformations. The failure of the triplet to undergo electron transfer reactions on the 7 ns time scale of our measurements is attributed to the low triplet energy and reduction potential of the twisted triplet state. Hairpins possessing both a Michler's ketone linker and a perylenediimide base surrogate separated by four base pairs undergo photoinduced hole transport from the diimide to Michler's ketone upon excitation of the diimide. The efficiency of hole transport is dependent upon the sequence of the intervening purine bases.

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Quelle: Photochemistry and Photobiology | 8 Oct 2014 | 5:41 pm CEST

Oculocutaneous Albinism in Sub-Saharan Africa: Adverse Sun-Associated Health Effects and Photoprotection

Abstract

Oculocutaneous albinism (OCA) is a genetically inherited autosomal recessive condition. Individuals with OCA lack melanin and therefore are susceptible to the harmful effects of solar ultraviolet radiation, including extreme sun sensitivity, photophobia and skin cancer. OCA is a grave public health issue in sub-Saharan Africa with a prevalence as high as 1 in 1 000 in some tribes. This article considers the characteristics and prevalence of OCA in sub-Saharan African countries. Sun-induced adverse health effects in the skin and eyes of OCA individuals are reviewed. Sun exposure behaviour and the use of photoprotection for the skin and eyes are discussed to highlight the major challenges experienced by these at-risk individuals and how these might be best resolved.

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Quelle: Photochemistry and Photobiology | 8 Oct 2014 | 5:41 pm CEST

Interspecific Variation in the Repair of UV Damaged DNA in the Genus Xiphophorus as a Factor in the Decline of the Rio Grande Platyfish

Abstract

The fish genus Xiphophorus consists of 26 species distributed along the eastern slopes of mountain ranges extending from northern Mexico to Belize and Nicaragua. We analyzed light-dependent repair of UV-induced DNA damage in at least two species from each of the four monophyletic Xiphophorus groups. We found that the northern platyfish had significantly reduced photoenzymatic repair compared to the other three groups, including the northern swordtails, southern platyfish and southern swordtails. All of the species of the platyfish, including the Marbled (meyeri), Northern (gordoni) and Monterrey Platyfish (couchianus) are the northernmost species in the genus and are the only three species in the genus that are currently found on the IUCN Red List of Threatened Species. Satellite data from the past 30 years (1979-2008) correlates greater increases in shorter wavelength UVB with higher latitudes within the Xiphophorus range. We suggest that, combined with other consequences of human population growth, anthropogenic deozonation resulting in a disproportionate increase in UVB in temperate latitudes may be a contributing factor in the decline and extirpation of the northern platyfish.

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Quelle: Photochemistry and Photobiology | 8 Oct 2014 | 5:40 pm CEST

Photochromic conversion in a red/green cyanobacteriochrome from Synechocystis PCC6803: quantum yields in solution and photoswitching dynamics in living E.coli cells

Photochem. Photobiol. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4PP00337C, Paper
Francesca Pennacchietti, Aba Losi, Xiu-ling Xu, Kai-Hong Zhao, Wolfgang Gartner, Cristiano Viappiani, Francesca Cella Zanacchi, Alberto Diaspro, Stefania Abbruzzetti
The protein encoded by the gene slr1393 from the cyanobacterium Synechocystis sp. PCC6803 (Slr1393) is composed of three GAF domains, a PAS domain, and a histidine kinase motif. The third...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 8 Oct 2014 | 1:00 am CEST

Fisetin Inhibits UVB-induced Cutaneous Inflammation and Activation of PI3K/AKT/NFκB Signaling Pathways in SKH-1 Hairless Mice

Abstract

Solar ultraviolet B (UVB) radiation has been shown to induce inflammation, DNA damage, p53 mutations and alterations in signaling pathways eventually leading to skin cancer. In this study, we investigated whether fisetin reduces inflammatory responses and modulates PI3K/AKT/NFκB cell survival signaling pathways in UVB-exposed SKH-1 hairless mouse skin. Mice were exposed to 180 mJ cm−2 of UVB radiation on alternate days for a total of seven exposures, and fisetin (250 and 500 nmol) was applied topically after 15 min of each UVB exposure. Fisetin treatment to UVB-exposed mice resulted in decreased hyperplasia and reduced infiltration of inflammatory cells. Fisetin treatment also reduced inflammatory mediators such as COX-2, PGE2 as well as its receptors (EP1–EP4) and MPO activity. Furthermore, fisetin reduced the level of inflammatory cytokines TNFα, IL-1β and IL-6 in UVB-exposed skin. Fisetin treatment also reduced cell proliferation markers as well as DNA damage as evidenced by increased expression of p53 and p21 proteins. Further studies revealed that fisetin inhibited UVB-induced expression of PI3K, phosphorylation of AKT and activation of the NFκB signaling pathway in mouse skin. Overall, these data suggest that fisetin may be useful against UVB-induced cutaneous inflammation and DNA damage.

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Exposure to solar UVB radiation has been implicated as the main cause for skin cancer. In this study, we investigated whether fisetin, a flavonoid abundantly present in fruits and vegetables, reduces inflammatory responses and modulates PI3K/AKT/NFκB cell survival signaling pathways in UVB-exposed SKH-1 hairless mouse skin. Our data demonstrated that topical application of fisetin to SKH-1 mice inhibited UVB-induced inflammation and proliferation by modulating PI3K/AKT/NFκB signaling pathways. In addition, fisetin treatment augmented UVB-induced protein expression of p53 and p21 as well as reduced DNA damage caused by UVB exposure. Overall, these findings suggest that fisetin could be developed as a novel photochemopreventive agent.

Quelle: Photochemistry and Photobiology | 7 Oct 2014 | 1:24 pm CEST

Antitumor Effect of Sinoporphyrin Sodium-Mediated Photodynamic Therapy on Human Esophageal Cancer Eca-109 Cells

Abstract

The aim of this study was to evaluate the photodynamic effect of Sinoporphyrin sodium (DVDMS). In this study, Eca-109 cells were treated with DVDMS (5 μg mL−1) and subjected to photodynamic therapy (PDT). The uptake and subcellular localization of DVDMS were monitored by flow cytometry and confocal microscopy. The phototoxicity of DVDMS was studied by MTT assay. The morphological changes were observed by scanning electron microscopy (SEM). DNA damage, reactive oxygen species (ROS) generation and mitochondria membrane potential (MMP) changes were analyzed by flow cytometry. Studies demonstrated maximal uptake of DVDMS occurred within 3 h, with a mitochondrial subcellular localization. MTT assays displayed that DVDMS could be effectively activated by light and the phototoxicity was much higher than photofrin under the same conditions. In addition, SEM observation indicated that cells were seriously damaged after PDT treatment. Furthermore, activation of DVDMS resulted in significant increases in ROS production. The generated ROS played an important role in the phototoxicity of DVDMS. DVDMS-mediated PDT (DVDMS-PDT) also induced DNA damage and MMP loss. It is demonstrated that DVDMS-mediated PDT is an effective approach on cell proliferation inhibition of Eca-109 cells.

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The chemical structure of DVDMS.

Quelle: Photochemistry and Photobiology | 7 Oct 2014 | 1:24 pm CEST

Design of a Gd-DOTA-Phthalocyanine Conjugate Combining MRI Contrast Imaging and Photosensitization Properties as a Potential Molecular Theranostic

Abstract

The design and synthesis of a phthalocyanine – Gd-DOTA conjugate is presented to open the way to novel molecular theranostics, combining the properties of MRI contrast imaging with photodynamic therapy. The rational design of the conjugate integrates isomeric purity of the phthalocyanine core substitution, suitable biocompatibility with the use of polyoxo water-solubilizing substituents, and a convergent synthetic strategy ended by the use of click chemistry to graft the Gd-DOTA moiety to the phthalocyanine. Photophysical and photochemical properties, contrast imaging experiments and preliminary in vitro investigations proved that such a combination is relevant and lead to a new type of potential theranostic agent.

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A Gd-DOTA-phthalocyanine conjugate designed to combine MRI contrast imaging and photosensitization properties as a potential molecular theranostic has been prepared. The singlet oxygen generation ability of the phthalocyanine core is retained. Relaxivity of the complex is suitable for imaging purposes. The conjugate is well internalized in MCF-7 cells.

Quelle: Photochemistry and Photobiology | 7 Oct 2014 | 1:24 pm CEST

The relationship between ambient ultraviolet radiation (UVR) and objectively measured personal UVR exposure dose is modified by season and latitude

Photochem. Photobiol. Sci., 2014, Advance Article
DOI: 10.1039/C4PP00322E, Paper
J. Sun, R. M. Lucas, S. Harrison, I. van der Mei, B. K. Armstrong, M. Nowak, A. Brodie, M. G. Kimlin
Despite the widespread use of ambient ultraviolet radiation (UVR) as a proxy measure of personal exposure to UVR, the relationship between the two is not well-defined.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 7 Oct 2014 | 1:00 am CEST

Comparison of the solar photocatalytic activity of ZnO-Fe2O3 and ZnO-Fe0 on 2,4-D degradation in a CPC reactor

Photochem. Photobiol. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4PP00274A, Paper
Aracely Hernandez-Ramirez, Ma. de Lourdes Maya Trevino, Minerva Villanueva Rodriguez, Jorge Luis Guzman-Mar, Laura Hinojosa-Reyes
In this work a comparative study of the catalytic activity of ZnO-Fe2O3 and ZnO-Fe0 0.5 wt% materials was carried out in the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) as commercial formulation...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 6 Oct 2014 | 1:00 am CEST

From ultraviolet to Prussian blue: a spectral response for the cyanotype process and a safe educational activity to explain UV exposure for all ages

Photochem. Photobiol. Sci., 2014, Advance Article
DOI: 10.1039/C4PP00166D, Paper
J. Turner, A. V. Parisi, N. Downs, M. Lynch
The cyanotype process is characterised via dynamic and spectral response in an educational toy (blue print paper) that can be used to provide outreach activities for UV exposure applications.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 6 Oct 2014 | 1:00 am CEST

Temperature and oxygen-concentration dependence of singlet oxygen production by RuPhen as induced by quasi-continuous excitation

Photochem. Photobiol. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4PP00202D, Paper
Jaroslav Varchola, Veronika Huntosova, Daniel Jancura, Georges Wagnieres, Pavol Miskovsky, Gregor Bano
Assessment of oxygen partial pressure (pO2) by luminescence lifetime measurements of ruthenium coordination complexes has been studied intensively during the last decades. RuPhen (dichlorotris(1,10-phenanthroline) ruthenium(II) hydrate) is a water soluble...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 6 Oct 2014 | 1:00 am CEST

ANG-2 for quantitative Na+ determination in living cells by time-resolved fluorescence microscopy

Photochem. Photobiol. Sci., 2014, Advance Article
DOI: 10.1039/C4PP00061G, Paper
Phillip Roder, Carsten Hille
A new Na+-sensitive fluorescent dye ANG-2 was characterised photophysically (1P- and 2P-absorption, steady-state and time-resolved fluorescence) and its usability for quantitative Na+ recordings in living cells by time-resolved fluorescence measurements was demonstrated.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 2 Oct 2014 | 1:00 am CEST

Opsin Expression in Human Epidermal Skin

Abstract

Human skin is constantly exposed to solar light containing visible and ultraviolet radiation (UVR), a powerful skin carcinogen. UVR elicits cellular responses in epidermal cells via several mechanisms: direct absorption of short wavelength UVR photons by DNA, oxidative damage caused by long wavelength UVR, and, as we recently demonstrated, via a retinal-dependent G protein-coupled signaling pathway. Because the human epidermis is exposed to a wide range of light wavelengths, we investigated whether opsins, light-activated receptors that mediate photoreception in the eye, are expressed in epidermal skin to potentially serve as photosensors. Here we show that four opsins — OPN1-SW, OPN2, OPN3 and OPN5 — are expressed in the two major human epidermal cell types, melanocytes and keratinocytes, and the mRNA expression profile of these opsins does not change in response to physiological UVR doses. We detected two OPN3 splice variants present in similar amounts in both cell types and three OPN5 splice isoforms, two of which encode truncated proteins. Notably, OPN2 and OPN3 mRNA were significantly more abundant than other opsins and encoded full-length proteins. Our results demonstrate that opsins are expressed in epidermal skin cells and suggest that they might initiate light-induced signaling pathways, possibly contributing to UVR phototransduction.

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Quelle: Photochemistry and Photobiology | 30 Sep 2014 | 12:57 pm CEST

Photo-Wolff Rearrangement of 2-Diazo-1,2-naphthoquinone: Stern–Volmer Analysis of the Stepwise Reaction Pathway

Abstract

2-Diazo-1,2-naphthoquinone (1) and its derivatives are the photoactive components in Novolak photoresists. A femtosecond infrared study has established that the photoreaction of 1 proceeds largely by a concerted Wolff rearrangement yielding the ketene 1H-inden-1-ylidene-methanone (3) within 300 fs after excitation, but earlier trapping studies gave evidence for a minor reaction path via a carbene intermediate 1-oxo-2(1H)-naphthalenylidene (2) with a lifetime of about 10 ps. Here, we provide a quantitative assessment of the stepwise pathway by Stern–Volmer analysis of the trapping of 2 by methanol to yield 2-methoxy-1-naphthol (4). We conclude that the lifetime of the carbene 2 is at least 200 ps. Moreover, [3 + 2]cycloaddition of 2 and acetonitrile yielding 2-methylnaphth[2,1-d]oxazole (5) was observed. A comparison of the yields of 5 formed upon photolysis and upon thermolysis of 1 in acetonitrile provides evidence that a substantial part of the hot nascent carbene 2 formed photolytically rearranges to the ketene 3 during its vibrational relaxation (hot ground-state reaction).

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A quantitative assessment of the stepwise versus concerted photodeazotization pathways of 2-diazo-1,2-naphthoquinone (1) forming ketene 3 is provided. Trapping of the carbene intermediate 2 by methanol yields 2-methoxy-1-naphthol (4) in up to 12% yield. [3+2]Cycloaddition of 2 and acetonitrile yielding 2-methylnaphth[2,1-d]oxazole (5) was also observed. The lifetime of the thermalized carbene 2 is at least 200 ps. A comparison of the yields of 5 formed upon photolysis and upon thermolysis of 1 in acetonitrile provides evidence that a substantial part of the hot nascent carbene 2 formed photolytically rearranges to the ketene 3 during its vibrational relaxation (hot ground-state reaction).

Quelle: Photochemistry and Photobiology | 30 Sep 2014 | 12:24 pm CEST

Comparison of Templating Abilities of Urea and Thioruea During Photodimerization of Bipyridylethyelene and Stilbazole Crystals

Abstract

Photodimerization of co-crystals of four bispyridylethylenes and two stilbazoles with urea as a template in the solid state has been investigated following our success with thiourea. Four investigated olefins photodimerized quantitatively to a single dimer in the crystalline state only. The reactivity of urea-olefin crystals is understood on the basis of their packing arrangements in the crystalline state. In reactive crystals the adjacent reactive molecules are within 4.2 Å and parallel, while the unreactive ones have their adjacent molecules are farther than 4.6Å and non-parallel. Thus, with the knowledge of crystal packing the reactivity of urea-olefin crystals is predictable on the basis of Schmidt's topochemical postulates. The templating property of urea, similar to thiourea, derives from its ability to form hydrogen bonds with itself and the guest olefins. Despite the similarities in molecular structures of urea and thiourea their subtle electronic properties, yet to be fully understood, affect the crystal packing and consequently their reactivity in the crystalline state. Further work is needed to fully exploit the templating properties of urea.

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Quelle: Photochemistry and Photobiology | 29 Sep 2014 | 4:12 am CEST

Chemical control of photochromism and a multiresponsive molecular switch based on a diarylethene derivative containing naphthol

Photochem. Photobiol. Sci., 2014, Advance Article
DOI: 10.1039/C4PP00093E, Paper
Wenju Liu, Ziyong Li, Fang Hu, Jun Yin, Guang-Ao Yu, Sheng Hua Liu
A diarylethene derivative with a naphthol group was synthesized, and its photochromic reaction could be regulated by chemical inputs.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 29 Sep 2014 | 1:00 am CEST

Synthesis, properties and drug potential of the photosensitive alkyl- and alkylsiloxy-ligated silicon phthalocyanine Pc 227

Photochem. Photobiol. Sci., 2014, Advance Article
DOI: 10.1039/C4PP00321G, Paper
Jun Li, Yang Yang, Ping Zhang, James R. Sounik, Malcolm E. Kenney
Photolysis of Pc 227 yields the extensively studied photodynamic therapy drug Pc 4. The photolytic pathway is a homolysis involving a phthalocyanine [small pi] radical and low bond dissociation energy.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 29 Sep 2014 | 1:00 am CEST

A Novel Chemiluminescence from the Reaction of Singlet Oxygen with [small beta]-Diketonates of Europium(III), Neodymium(III) and Ytterbium(III)

Photochem. Photobiol. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4PP00234B, Communication
Dmitri V. Kazakov, Farit E. Safarov
Decomposition of 1,4-dimethylnaphthalene endoperoxide, the source of singlet oxygen, in the presence of [small beta]-diketonates of europium (III), neodymium (III) and ytterbium (III) is accompanied by bright chemiluminescence (CL) in visible...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 29 Sep 2014 | 1:00 am CEST

Applicability of new degradable hypericin-polymer-conjugates as photosensitizers: principal mode of action demonstrated by in vitro models

Photochem. Photobiol. Sci., 2014, 13,1607-1620
DOI: 10.1039/C4PP00251B, Paper
Daniela Feinweber, Thomas Verwanger, Oliver Bruggemann, Ian Teasdale, Barbara Krammer
Novel degradable polymers are shown to be promising carriers for the delivery of hypericin for PDT, significantly enhancing solubility of the free drug without compromising the photoactivity.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 26 Sep 2014 | 1:00 am CEST

Photocatalysis of Chloroform Decomposition by Tetrachlorocuprate (II) on Dowex 2-X8

Abstract

Heterogenized on a polystyrene anion exchange resin and in the presence of oxygen, inline image catalyzes the photodecomposition of chloroform at wavelengths above 345 nm with greater efficiency than an equivalent amount in homogeneous solution. The reaction is proposed to proceed in two stages, the first stage yielding CCl4 and inline image as products, the second consisting of a chain reaction resulting from the inline image-catalyzed photodissociation of CCl4, yielding phosgene with CCl3 radicals as chain carriers. Photodecomposition is retarded by added Cl, CH3CN, C6H12 or C2H5OH, which is ascribed to the displacement of CHCl3 molecules from the vicinity of the copper by attraction to the polystyrene matrix or to the alkylammonium cation sites.

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In the presence of CuCl42- heterogenized on a Dowex anion exchange resin, chloroform is decomposed under irradiation at wavelengths above 345 nm.

Quelle: Photochemistry and Photobiology | 25 Sep 2014 | 12:39 pm CEST

Photocatalytic Degradation of Glyphosate in Water by N-Doped SnO2/TiO2 Thin-Film-Coated Glass Fibers

Abstract

Photocatalytic degradation of glyphosate contaminated in water was investigated. The N-doped SnO2/TiO2 films were prepared via sol–gel method, and coated on glass fibers by dipping method. The effects of nitrogen doping on coating morphology, physical properties and glyphosate degradation rates were experimentally determined. Main variable was the concentration of nitrogen doping in range 0–40 mol%. Nitrogen doping results in shifting the absorption wavelengths and narrowing the band gap energy those lead to enhancement of photocatalytic performance. The near optimal 20N/SnO2/TiO2 composite thin film exhibited about two- and four-folds of glyphosate degradation rates compared to the undoped SnO2/TiO2 and TiO2 films when photocatalytic treatment were performed under UV and solar irradiations, respectively, due to its narrowest band gap energy (optical absorption wavelength shifting to visible light region) and smallest crystallite size influenced by N-doping.

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The N-doped SnO2/TiO2 films were prepared via sol–gel method, and coated on E-glass fibers by dipping method. Nitrogen doping resulted in shifting the absorption wavelength and narrowing the band gap energy leads to enhancement of photocatalytic performance. The optimal 20N/SnO2/TiO2 composite thin film exhibits about four-folds of glyphosate degradation rates compared to TiO2 and undoped SnO2/TiO2 as the tests performed under solar light irradiation.

Quelle: Photochemistry and Photobiology | 25 Sep 2014 | 12:18 pm CEST

Photoinduced transformation of UVR8 monitored by vibrational and fluorescence spectroscopy

Photochem. Photobiol. Sci., 2014, Advance Article
DOI: 10.1039/C4PP00246F, Paper
Monika Heilmann, John M. Christie, John T. M. Kennis, Gareth I. Jenkins, Tilo Mathes
The plant photoreceptor UVR8 uses tryptophan side chains to absorb UV-B radiation to induce photoprotective responses via a so far unknown molecular signaling mechanism. We investigated structural transformations and quantum efficiency of UVR8 photoactivation by vibrational and fluorescence spectroscopy.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 25 Sep 2014 | 1:00 am CEST

Novel application of pH-sensitive firefly luciferases as dual reporter genes for simultaneous ratiometric analysis of intracellular pH and gene expression/location

Photochem. Photobiol. Sci., 2014, Advance Article
DOI: 10.1039/C4PP00278D, Paper
Gabriele V. M. Gabriel, Vadim R. Viviani
Firefly luciferase pH-sensitivity can be harnessed for ratiometric intracellular pH estimation, providing the first dual reporter system using a single luciferase gene.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 24 Sep 2014 | 1:00 am CEST

Directed Improvement of Luciferin Regenerating Enzyme Binding Properties: Implication of Some Conserved Residues in Luciferin-Binding Domain

Abstract

Luciferin regenerating enzyme (LRE) contributes to in vitro recycling of d-luciferin to produce persistent and longer light emission by luciferase. Luciferin binding domains I and II among LREs regarded as potential candidates for luciferin-binding sites. In this study, for the first time, amino acids T69, G75 and K77 located at luciferin binding domain I of LRE from L. turkestanicus (T-LRE) substituted by using site-directed mutagenesis. Single mutant T69R increased luciferase light output more than two-fold over a longer time in comparison with a wild-type and other mutants of T-LRE. Nevertheless, double mutant (K77E/T69R) increased the amount of bioluminescent signal more than two-fold over a short time. In addition, G75E, K77E and G75E/T69R mutants did not improve luciferin–luciferase in vitro bioluminescence. Based on our results, addition of K77E/G75E and K77E/G75E/T69R mutants caused intermediate changes in bioluminescence from in vitro luciferin–luciferase reaction. These findings indicated that the amino acids in question are possible to be located within T-LRE active site. It may also be suggested that substituted Arg69 (Arg218) plays an important role in luciferin binding and the existence of Gly75 as well as Lys77 is essential for T-LRE which has already evolved to have different functions in nature.

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The addition of T-LRE single mutant T69R (LRE from Iranian firefly L. turkestanicus) to luciferin–luciferase reaction leads to decrease in bioluminescence decay over the time in comparison with wild-type T-LRE and control.

Quelle: Photochemistry and Photobiology | 22 Sep 2014 | 8:02 am CEST

Observation of In vivo Morphologic Changes after Carbon Dioxide Ablative Fractional Laser in a Mouse Model Using Noninvasive Imaging Modalities and Comparison with Histologic Examination

Abstract

Ablative fractional carbon dioxide (CO2) lasers have been widely used for several types of cosmetic dermatosis. A number of previous studies have evaluated this technique in animals or human beings by observing morphologic changes using an invasive modality such as skin biopsy. In this study, we assessed in vivo skin changes after CO2 ablative fractional laser treatment in a mouse model using noninvasive imaging modalities (Folliscope® and Visioscan 98®), and each results was compared with data from histologic examination. An ablative fractional CO2 laser was applied with different pulse energy between 7 to 35 mJ/microspot. As results of above methods, we also confirmed that the CO2 ablative fractional laser generated injuries with increasing width and depth with increasing pulse energy. Although numerous papers have described application of this laser in vivo skin specimens, our study evaluated the feasibility of using relative noninvasive imaging modalities for assessing the outcome of laser ablation. Based on our data, we suggest that these technologies may be useful alternative modalities for assessing laser ablation that are easier to perform and less invasive than skin biopsy.

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The ability to observe skin changes in vivo is important when evaluating the efficacy of laser treatment. This study was conducted to investigate the efficacy of the CO2 ablative fractional laser through using noninvasive imaging modalities (Folliscope® and Visioscan 98®) and tissue analysis. Although numerous previous reports have described a similar function of this laser in in vivo skin specimens, in this study we analyzed treatment effectiveness by noninvasive imaging modalities. Based on our data, we suggest that these technologies may be useful alternative modalities for assessing laser ablation that are easier to perform and less invasive than skin biopsy.

Quelle: Photochemistry and Photobiology | 22 Sep 2014 | 8:01 am CEST

Photodynamic Inactivation of Bacterial and Yeast Biofilms With a Cationic Porphyrin

Abstract

The efficiency of 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin tetra-iodide (Tetra-Py+-Me) in the photodynamic inactivation of single-species biofilms of Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans and mixed biofilms of S. aureus and C. albicans was evaluated. The effect on the extracellular matrix of P. aeruginosa was also assessed. Irradiation with white light up to an energy dose of 64.8 J cm−2 in the presence of 20 μm of Tetra-Py+-Me caused significant inactivation in all single-species biofilms (3–6 log reductions), although the susceptibility was attenuated in relation to planktonic cells. In mixed biofilms, the inactivation of S. aureus was as efficient as in single-species biofilms but the susceptibility of C. albicans decreased. In P. aeruginosa biofilms, a reduction of 81% in the polysaccharide content of the matrix was observed after treatment with a 20 μm PS concentration and a total light dose of 64.8 J cm−2. The results show that the Tetra-Py+-Me causes significant inactivation of the microorganisms, either in biofilms or in the planktonic form, and demonstrate that polysaccharides of the biofilm matrix may be a primary target of photodynamic damage.

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Irradiation with white light up to an energy dose of 64.8 J cm−2 in the presence of 20 µm of the cationic porphyrin 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin tetra-iodide caused a reduction of 3–6 log in the concentration of viable cells in biofilms of Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans and a 81% decrease in the concentration of polysaccharides in the matrix of P. aeruginosa biofilms. The results indicate that the biofilm matrix may be a primary target of photodynamic damage.

Quelle: Photochemistry and Photobiology | 22 Sep 2014 | 7:43 am CEST

A new antitumoral Heteroarylaminothieno[3,2-b]pyridine derivative: its incorporation into liposomes and interaction with proteins monitored by fluorescence

Photochem. Photobiol. Sci., 2014, Advance Article
DOI: 10.1039/C4PP00287C, Paper
C. N. C. Costa, A. C. L. Hortelao, J. M. F. Ramos, A. D. S. Oliveira, R. C. Calhelha, M.-J. R. P. Queiroz, P. J. G. Coutinho, E. M. S. Castanheira
The affinity of an antitumoral thienopyridine derivative to BSA and multidrug resistance protein MDR1 was evaluated by FRET. The compound was encapsulated in liposome formulations.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 22 Sep 2014 | 1:00 am CEST

What Caused the Formation of the Absorption Maximum at 421 nm in vivo Spectra of Rhodopseudomonas palustris

Abstract

A spectral peak at ~421 nm appeared in vivo spectrum of Rhodopseudomonas palustris CQV97 cultured in acetate–glutamate medium (M1) but not in acetate–ammonium sulfate medium (M2). However, the spectral origin of 421 nm peak was not clear and frequently attributed to carotenoid component(s). In this study, comparative analysis of the extracted components showed that magnesium protoporphyrin IX monomethylester (MPE) was accumulated as one of the predominate components in M1 culture. The amounts of bacteriochlorophyll a in M1 culture were higher than that in M2, whereas the amounts of carotenoids were nearly identical in both cultures. A simple, rapid and minimum interference with carotenoid and bacteriochlorophyll method to efficiently extract the compounds involving in the formation of 421 nm peak was developed in this study. Assembly of purified MPE with protein components from R. palustris in vitro demonstrated that MPE caused the formation of 421 nm peak. The localization analysis in vivo demonstrated it is MPE associating to protein components and accounting for the peak at ~421 nm. This work clarified the 421 nm peak in vivo mainly originated from MPE accumulation, and will be very helpful to further explore the physiological roles of MPE or its derivatives in photosynthesis.

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The 421 nm peak is frequently observed in various absorption spectra. However, less attention is attracted to examine its spectral origin. This study explored the formation origin of the absorption maximum at 421 nm in vivo with Rhodopseudomonas palustris for the first time. Our results ascertain that the 421 nm peak was a consequence of incorporation of magnesium protoporphyrin IX monomethylester (MPE), its accumulation inside cells could result in the formation of 421 nm peak. In addition, a simple, rapid, minimum interference and selective extraction strategy for MPE was developed. This work will helpful to characterize rationally the absorption spectra.

Quelle: Photochemistry and Photobiology | 18 Sep 2014 | 2:25 pm CEST

Elucidation of photophysical changes and orientation of acridine orange dye on the surface of borate capped gold nanoparticles using multi-spectroscopic techniques

Photochem. Photobiol. Sci., 2014, Advance Article
DOI: 10.1039/C4PP00223G, Paper
Arumugam Selva Sharma, Malaichamy Ilanchelian
In the present work, we have carried out a detailed investigation on the binding interaction of acridine orange (AO) with borate capped gold nanoparticles (Au NPs) by multi spectroscopic techniques.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 18 Sep 2014 | 1:00 am CEST

Static magnetic field (SMF) sensing of the P723/P689 photosynthetic complex

Photochem. Photobiol. Sci., 2014, Advance Article
DOI: 10.1039/C4PP00295D, Paper
Abhishek Bhattacharya, Madhurima Chakraborty, Sufi O. Raja, Avijit Ghosh, Maitrayee Dasgupta, Anjan Kr. Dasgupta
Amplification of the light driven photosynthetic circuit (P723/P689) by static magnetic field leading to a reversible and controllable uncoupler (N denotes nigericin).
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 18 Sep 2014 | 1:00 am CEST

The study of polyplex formation and stability by time-resolved fluorescence spectroscopy of SYBR Green I-stained DNA

Photochem. Photobiol. Sci., 2014, Advance Article
DOI: 10.1039/C4PP00242C, Paper
Cosimo D'Andrea, Daniele Pezzoli, Chiara Malloggi, Alessia Candeo, Giulio Capelli, Andrea Bassi, Alessandro Volonterio, Paola Taroni, Gabriele Candiani
Time-resolved fluorescence spectroscopy in combination with SYBR Green I-DNA dye is a reliable tool for the characterization of DNA/vector complexation state.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 18 Sep 2014 | 1:00 am CEST

MicroRNAs and Photocarcinogenesis

Abstract

As a new class of sequence-specific regulators of gene expression, the microRNAs (miRNA) form a regulatory network with growth factors and transcription factors participating in various biological processes. It is now being recognized that the various key processes involved in cancer induction are under the control of these small non-coding RNAs, which regulate ~30% of all human genes by targeting sequences in their 3′-untranslated regions. Photocarcinogenesis is a complex interplay of signaling events in the UV exposed human skin including DNA damage and repair, apoptosis, cell survival, mutations and the immune system. In this review, we have scrutinized the role of miRNAs in skin cancer biology focusing on the three most common types of skin cancer namely the basal cell carcinoma, squamous cell carcinoma and cutaneous malignant melanoma. An overview of these studies will be useful in gaining insights into the mechanisms of cancer development in the human skin. A better understanding of the functionality of miRNAs will have enormous implications to risk assessment, and to target interventions against signaling events involved in photocarcinogenesis.

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Quelle: Photochemistry and Photobiology | 17 Sep 2014 | 2:50 am CEST

Ceramide synthase inhibitor fumonisin B1 inhibits apoptotic cell death in SCC17B human head and neck squamous carcinoma cells after Pc4 photosensitization

Photochem. Photobiol. Sci., 2014, 13,1621-1627
DOI: 10.1039/C4PP00292J, Paper
Nithin B. Boppana, Mohamed Kodiha, Ursula Stochaj, Ho-sheng Lin, Adriana Haimovitz-Friedman, Alicja Bielawska, Jacek Bielawski, George W. Divine, John A. Boyd, Mladen Korbelik, Duska Separovic
The data imply that CERS-dependent ceramide accumulation is required for apoptotic cell death post-PDT.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 16 Sep 2014 | 1:00 am CEST

UVR exposure and vitamin D in a rural population. A study of outdoor working farmers, their spouses and children

Photochem. Photobiol. Sci., 2014, 13,1598-1606
DOI: 10.1039/C4PP00188E, Paper
M. Bodekaer, B. Petersen, E. Thieden, P. A. Philipsen, J. Heydenreich, P. Olsen, H. C. Wulf
UVR exposure was high during the summer. Farmers exceeded the recommended maximum UVR dose on work days. Differences in UVR exposure among the outdoor working farmers, their spouses and children were not reflected in vitamin D levels. Most participants were vitamin D insufficient the following winter.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 16 Sep 2014 | 1:00 am CEST

phyA-GFP is spectroscopically and photochemically similar to phyA and comprises both its native types, phyA[prime or minute] and phyA[prime or minute][prime or minute]

Photochem. Photobiol. Sci., 2014, Advance Article
DOI: 10.1039/C4PP00220B, Paper
Vitaly Sineshchekov, Artem Sudnitsin, Eva Adam, Eberhard Schafer, Andras Viczian
phyA-GFP is spectroscopically and photochemically similar or identical to the native phyA. It comprises phyA[prime or minute]-GFP and phyA[prime or minute][prime or minute]-GFP, suggesting that both of them are potential participants in nuclear-cytoplasmic partitioning.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 16 Sep 2014 | 1:00 am CEST

Forty Years of Research on Xeroderma Pigmentosum at the US National Institutes of Health

Abstract

In 1968, Dr. James Cleaver reported defective DNA repair in cultured cells from patients with xeroderma pigmentosum. This link between clinical disease and molecular pathophysiology has sparked interest in understanding not only the clinical characteristics of sun sensitivity, damage and cancer that occurred in XP patients but also the mechanisms underlying the damage and repair. While affected patients are rare, their exaggerated UV damage provides a window into the workings of DNA repair. These studies have clarified the importance of a functioning DNA repair system to the maintenance of skin and neurologic health in the general population. Understanding the role of damage in causing cancer, neurologic degeneration, hearing loss and internal cancers provides an opportunity for prevention and treatment. Characterizing complementation groups pointed to the importance of different underlying genes. Studying differences in cancer age of onset and underlying molecular signatures in cancers occurring either in XP patients or the general population has led to insights into differences in carcinogenic mechanisms. The accelerated development of cancers in XP has been used as a model to discover new cancer chemopreventive agents. An astute insight can be a “tipping point” triggering decades of productive inquiry.

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Quelle: Photochemistry and Photobiology | 15 Sep 2014 | 10:16 am CEST

The Effects of NO3- Supply on Mazzaella laminarioides (Rhodophyta, Gigartinales) from Southern Chile

Abstract

The effects of nitrate supply on growth, pigments, mycosporine-like amino acids (MAAs), C:N ratios, and carrageenan yield were investigated in Mazzaella laminarioides cultivated under solar radiation. This species is economically important in southern Chile where an increase of nitrogen in coastal waters is expected as a consequence of salmon aquaculture activity. Apical segments were cultivated in enriched seawater with five different NO3 concentrations (0, 0.09, 0.18, 0.38, and 0.75 mM) during 18 days. Although phycoerythrin and phycocyanin content, as well as C:N ratios, were reduced in the control treatment (without NO3 supply), when compared to NO3- treatments, total MAA concentration, carrageenan yield, and growth rates were similar in all tested conditions. Nevertheless, during the experiment, an important synthesis of mycosporine-glycine took place in a nitrate concentration-dependent manner, with accumulation being saturated around 0.18 mM of nitrate. These results indicate that exposure to high NO3 concentration of more than 100 times the values observed in the nature did not impair the photoprotection system, as determined by MAAs, nor did it have a deleterious effect on growth or carrageenan yield of M. laminarioides, a late successional species from Chile.

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Quelle: Photochemistry and Photobiology | 11 Sep 2014 | 6:17 pm CEST

Development of refractoriness of HO-1 induction to a second treatment with UVA radiation and the involvement of Nrf2 in human skin fibroblasts

Abstract

UVA treatment of cultured human skin fibroblasts (FEK4) has been shown previously to reduce transcriptional activation of hemeoxygenase 1 (HO-1) following a second dose of UVA radiation, a phenomenon known as refractoriness. This study demonstrates that the levels of HO-1 protein are also reduced after a second dose of UVA radiation as are Nrf2 levels, and there is less accumulation of Nrf2 in the nucleus where as Bach1 does accumulate in the nucleus. Cell viability is further reduced and cell membrane damage increased as compared with a single UVA treatment when an initial UVA treatment was followed by a second dose. Knockdown of Nrf2 by siRNA (siNrf2) targeting caused additional refractoriness of HO-1 protein induction to a second UVA or heme treatment and this treatment also further enhanced cell damage by a second dose of UVA radiation. However, transfection with Nrf2 caused less refractoriness of HO-1 to a second dose of UVA and reduced cell damage by a second dose of UVA radiation. These findings are consistent with the proposal that Nrf2 is involved in HO-1 refractoriness and could serve as a cytoprotective factor against cell damage caused by repeated exposure to moderate doses of UVA radiation. We propose that protection by the Nrf2-HO-1 pathway protection may have clinical relevance since human skin is exposed repeatedly to UVA radiation.

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Quelle: Photochemistry and Photobiology | 11 Sep 2014 | 6:17 pm CEST

UVA irradiation induced heme oxygenase-1 (HO-1): A novel phototherapy for morphea

Abstract

Long wave UVA radiation (340-400 nm) causes detrimental as well as beneficial effects on human skin. Studies of human skin fibroblasts irradiated with UVA demonstrate increased expression of both anti-fibrotic heme oxygenase-1 (HO-1) and matrix metalloproteinase 1 (MMP-1). The use of UVA -induced MMP-1 is well studied in treating skin fibrotic conditions such as localised scleroderma, now called morphea. However, the role that UVA-induced HO-1 plays in phototherapy of morphea has not been characterized. In the present manuscript, we have illustrated and reviewed the biological function of HO-1 and the use of UVA1 wavebands (340-400 nm) for phototherapy; the potential use of HO-1 induction in UVA therapy of morphea is also discussed.

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Quelle: Photochemistry and Photobiology | 10 Sep 2014 | 2:22 pm CEST

Hypericin Damages the Ectatic Capillaries in a Roman Cockscomb Model and Inhibits the Growth of Human Endothelial Cells More Potently Than Hematoporphyrin Does through Induction of Apoptosis

Abstract

Hypericin (HY) is a promising photosensitizer (PS) for use in photodynamic therapy (PDT). Port-wine stains (PWSs) are congenital superficial dermal capillary malformations. In this study, we evaluated the photocytotoxic effects of HY for PDT in human vascular endothelial cells and a chicken cockscomb model. HY significantly inhibited the growth of human umbilical vein endothelial cells (HUVECs), as determined by colorimetric assays and morphological observation, and flow cytometry assays indicated induction of apoptosis and collapse of the mitochondrial membrane potential. In addition, HY more effectively inhibited growth of and induced apoptosis in HUVECs compared with hematoporphyrin (HP). Further experiments performed in a Roman chicken cockscomb model also showed a clear photocytotoxic effect on the cockscomb dermal capillary upon intravenous injection of HY. This effect may be due to the role of HY in the induction of apoptosis. Transmission electron microscopical analysis showed mitochondrial morphological changes such as incomplete ridges and swelling, and immunohistochemical assays showed an increase in the release of cytochrome c. In conclusion, HY exhibited a greater photocytotoxic activity than did HP toward the growth of endothelial cells and may thus represent a potent PS for PWS PDT.

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Hypericin possesses more potent effects than hematoporphyrin in inhibition of growth and induction of apoptosis in a Roman Cockscomb Model and HUVECs.

Quelle: Photochemistry and Photobiology | 9 Sep 2014 | 9:35 am CEST

UVB Irradiation Enhances TiO2 Nanoparticle-induced Disruption of Calcium Homeostasis in Human Lens Epithelial Cells

Abstract

Currently, titanium dioxide nanoparticles (TiO2 NPs) have been widely used in various applications including cosmetics, food additives and biomedicine. However, there are few reports available using TiO2 NPs to treat ocular diseases. Posterior capsular opacification (PCO) is the most frequent complication after cataract surgery, which is induced by the proliferation and migration of lens epithelial cells. Thus, inhibiting the proliferation of lens epithelial cells will efficiently reduce the occurrence of PCO. In this study, we investigated the effects of TiO2 NPs on HLE B-3 cells with or without ultraviolet B (UVB) irradiation in vitro. We found that TiO2 NPs can inhibit HLE B-3 cell growth, cause the elevation of intracellular [Ca2+], produce excessive reactive oxygen species (ROS), further reduce Ca2+-ATPase activity and decrease the expression of plasma membrane calcium ATPase 1 (PMCA1), finally disrupt the intracellular calcium homeostasis and induce cell damage. Importantly, UVB irradiation can apparently enhance these effects on HLE B-3 cells in the presence of TiO2 NPs. Taken together, the generation of excessive ROS and the disruption of intracellular calcium homeostasis may be both involved in TiO2 nanoparticle-induced HLE B-3 cell damage under UVB irradiation.

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The scheme illustrates the possible pathway of intracellular Ca2+ elevation mediated by plasma membrane Ca2+-ATPase (PMCA). Excessive reactive oxygen species (ROS) were generated after HLE B-3 cells exposure to TiO2 NPs in the presence of UVB irradiation and the level of intracellular calcium ions was further elevated. The excessive ROS and the elevated intracellular Ca2+ level are both harmful to HLE B-3 cells via decreasing the expression of PMCA1 at gene and protein levels and inhibiting the Ca2+-ATPase activity, and further aggravate the disrupted intracellular calcium homeostasis, initiate Ca2+-dependent cellular apoptosis/necrosis signaling pathway and finally cause cell death.

Quelle: Photochemistry and Photobiology | 9 Sep 2014 | 9:35 am CEST

Proanthocyanidins from Grape Seeds Inhibit UV–Radiation-Induced Immune Suppression in Mice: Detection and Analysis of Molecular and Cellular Targets

Abstract

Ultraviolet (UV)–radiation-induced immunosuppression has been linked with the risk of skin carcinogenesis. Approximately, 2 million new cases of skin cancers, including melanoma and nonmelanoma, diagnosed each year in the USA and therefore have a tremendous bad impact on public health. Dietary phytochemicals are promising options for the development of effective strategy for the prevention of photodamaging effects of UV radiation including the risk of skin cancer. Grape seed proanthocyanidins (GSPs) are such phytochemicals. Dietary administration of GSPs with AIN76A control diet significantly inhibits UV-induced skin tumor development as well as suppression of immune system. UV-induced suppression of immune system is commonly determined using contact hypersensitivity (CHS) model which is a prototype of T–cell-mediated immune response. We present evidence that inhibition of UV-induced suppression of immune system by GSPs is mediated through: (i) the alterations in immunoregulatory cytokines, interleukin (IL)-10 and IL-12, (ii) DNA repair, (iii) stimulation of effector T cells and (iv) DNA repair-dependent functional activation of dendritic cells in mouse model. These information have important implications for the use of GSPs as a dietary supplement in chemoprevention of UV-induced immunosuppression as well as photocarcinogenesis.

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Prevention of UV–radiation-induced immunosuppression by dietary grape seed proanthocyanidins is mediated through: (i) alterations in immunoregulatory cytokines, such as, IL-10 and IL-12, (ii) stimulation of DNA repair and (iii) DNA repair-dependent functional activation of dendritic cells in mice.

Quelle: Photochemistry and Photobiology | 8 Sep 2014 | 8:42 am CEST

The Effects of UV-B Radiation Intensity on Biochemical Parameters and Active Ingredients in Flowers of Qi Chrysanthemum and Huai Chrysanthemum

Abstract

The article studied UV-B effects on biochemical parameters and active ingredients in flowers of Qi chrysanthemum and Huai chrysanthemum during the bud stage. The experiment included four UV-B radiation levels (CK, ambient UV-B; T1, T2 and T3 indicated a 5%, 10% and 15% increase in ambient UV-BBE, respectively) to determine the optimal UV-B radiation intensity in regulating active ingredients level in flowers of two chrysanthemum varieties. Flower dry weight of two cultivars was not affected by UV-B radiation under experimental conditions reported here. UV-B treatments significantly increased the rate of superoxide radical production, hydrogen peroxide (H2O2) (except for T1) and malondialdehyde concentration in flowers of Huai chrysanthemum and H2O2 concentration in flowers of Qi chrysanthemum. T2 and T3 treatments induced a significant increase in phenylalanine ammonia lyase enzyme (PAL) activity, anthocyanins, proline, ascorbic acid, chlorogenic acid and flavone content in flowers of two chrysanthemum varieties, and there were no significant differences in PAL activity, ascorbic acid, flavone and chlorogenic acid content between the two treatments. These results indicated that appropriate UV-B radiation intensity did not result in the decrease in flower yield, and could regulate PAL activity and increase active ingredients content in flowers of two chrysanthemum varieties.

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The article mainly studied UV-B effects on active ingredients in flowers of two chrysanthemum varieties during the bud stage. The experiment included four UV-B radiation levels (CK, ambient UV-B; T1, T2 and T3 indicated a 5%, 10% and 15% increase in ambient UV-BBE, respectively). The results indicated that appropriate UV-B radiation intensity did not result in the decrease in flower yield, and could increase chlorogenic acid and flavone content in flowers of two varieties.

Quelle: Photochemistry and Photobiology | 8 Sep 2014 | 8:32 am CEST

A New Series of Fluorescent Indicators for Super Acids

Abstract

The photophysical properties of fluorescent Hammett acidity indicator derived from 3,4,5,6-tetrahydrobis(pyrido[3,2-g]indolo)[2,3-a:3′,2′-j]acridine (1a), 6-bis(pyrido[3,2-g]indol-2′-yl)pyridine (1b) and their analogues have been investigated in sulfuric acid solutions by means of absorption, fluorimetry, relaxation dynamics and computational approach. These new indicators undergo a reversible protonation process in the Hammett acidity range of H0 < 0, accompanied by a drastic increase of the bright blue-green (1a) or yellow (1b) fluorescence intensity upon increasing the acidity. For 1a in H2SO4, the emission yield increases as large as 200 folds from pH = −0.41 to the Hammett acidity range of −5.17, the results of which are rationalized by a much increase of the steric hindrance upon third protonation toward the central pyridinic site, together with their accompanied changes of electronic configuration from charge transfer to a delocalized ππ* character in the lowest lying excited state. The combination of 1a and 1b renders a wide and linear range of H0 measurement from −1.2 to −5.1 detected by highly intensive fluorescence.

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A new series of fluorescent indicators are developed for sensing super acids. The fluorescence intensity switches from the nonemissive state (the diprotonated form) to the intense emissive state (the triprotonated form) with pKa as low as −3.16. This super acid indicator with the highly emissive intensity, great chemical stability and excitation/emission wavelengths in the visible region may find potential applications in industry.

Quelle: Photochemistry and Photobiology | 6 Sep 2014 | 2:11 pm CEST

Rapid Sonosynthesis of N-Doped Nano TiO2 on Wool Fabric at Low Temperature: Introducing Self-cleaning, Hydrophilicity, Antibacterial/Antifungal Properties with low Alkali Solubility, Yellowness and Cytotoxicity

Abstract

Nano nitrogen-doped titanium dioxide was rapidly prepared by hydrolysis of titanium isopropoxide at 75–80°C using in situ sonochemical synthesis by introducing ammonia. Various concentrations of titanium isopropoxide were examined to deposit nano nitrogen-doped titanium dioxide through impregnation of the wool fabric in ultrasound bath followed by curing. The antibacterial/antifungal activities of wool samples were assessed against two common pathogenic bacteria including Escherichia coli and Staphylococcus aureus and the diploid fungus Candida albicans. The sonotreated wool fabrics indicated no adverse effects on human dermal fibroblasts. The presence of nanoparticles on the sonotreated wool fabrics were confirmed by FE-SEM images and EDS patterns and X-ray mapping and the crystalline size of nanoparticles were estimated through XRD results. The role of both pH and precursor concentration on the various properties of the fabric was investigated and the optimized conditions introduced using response surface methodology.

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A novel simple short time in situ sonosynthesis method for simultaneous synthesis of N-doped TiO2 on wool is introduced. This is provided through treatment of wool fabric in ultrasound bath including TTIP in water/ethanol at pH = 7.5 (using ammonia) and 80°C for 1 h. This produces wool fabric with self-cleaning, antibacterial/antifungal and hydrophilicity properties with lower yellowness and alkali solubility at higher tensile strength along with no cytotoxicity. All of these confirmed through different analysis techniques and optimized through RSM.

Quelle: Photochemistry and Photobiology | 6 Sep 2014 | 9:37 am CEST

Hydroxyl Radical as an Unlikely Key Intermediate in the Photodegradation of Emerging Pollutants

Abstract

In this work, a kinetic model, in combination with time-resolved experiments, is applied to assess the involvement of ·OH in the photodegradation of emerging pollutants (EPs) by means of advanced oxidation processes. In contrast with the general assumption, quenching of the short-lived ·OH in the real waters by the (highly diluted) EPs must be very inefficient, so removal of EPs cannot purely rely on the generation and reaction of ·OH. This suggests that more complex pathways have to be considered to explain the photodegradation of EPs actually achieved under the employed oxidative conditions, possibly involving other reactive species with longer lifetimes or chain degradation processes.

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In the real (diluted) emerging pollutants (EPs)-containing waters, quenching of the short-lived ·OH must be very inefficient. In other words, EPs photodegradation cannot purely rely on the generation and reaction of ·OH. Hence, alternative pathways have to be considered to explain the oxidative photodegradation of EPs actually achieved under AOPs conditions.

Quelle: Photochemistry and Photobiology | 6 Sep 2014 | 9:37 am CEST

Biochemical Composition and Antioxidant Properties of Lavandula angustifolia Miller Essential Oil are Shielded by Propolis Against UV Radiations

Quelle: Photochemistry and Photobiology | 5 Sep 2014 | 9:14 pm CEST

Enhanced Light-Harvesting Capacity by Micellar Assembly of Free Accessory Chromophores and LH1-like Antennas

Abstract

Biohybrid light-harvesting antennas are an emerging platform technology with versatile tailorability for solar-energy conversion. These systems combine the proven peptide scaffold unit utilized for light harvesting by purple photosynthetic bacteria with attached synthetic chromophores to extend solar coverage beyond that of the natural systems. Herein, synthetic unattached chromophores are employed that partition into the organized milieu (e.g. detergent micelles) that house the LH1-like biohybrid architectures. The synthetic chromophores include a hydrophobic boron-dipyrrin dye (A1) and an amphiphilic bacteriochlorin (A2), which transfer energy with reasonable efficiency to the bacteriochlorophyll acceptor array (B875) of the LH1-like cyclic oligomers. The energy-transfer efficiencies are markedly increased upon covalent attachment of a bacteriochlorin (B1 or B2) to the peptide scaffold, where the latter likely acts as an energy-transfer relay site for the (potentially diffusing) free chromophores. The efficiencies are consistent with a Förster (through-space) mechanism for energy transfer. The overall energy-transfer efficiency from the free chromophores via the relay to the target site can approach those obtained previously by relay-assisted energy transfer from chromophores attached at distant sites on the peptides. Thus, the use of free accessory chromophores affords a simple design to enhance the overall light-harvesting capacity of biohybrid LH1-like architectures.

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Biohybrid light-harvesting antennas have been created that comprise LH1-like biohybrid architectures (with or without an attached synthetic bacteriochlorin) and free synthetic chromophores (hydrophobic boron-dipyrrin dye or an amphiphilic bacteriochlorin) in detergent micelles. The synthetic chromophores transfer energy directly or via relay processes to the bacteriochlorophyll acceptor array (B875) of the LH1-like cyclic oligomers.

Quelle: Photochemistry and Photobiology | 5 Sep 2014 | 12:51 pm CEST

A comparative study on photoperiodic control of seasonal cycles in the females of migratory yellow breasted bunting and the resident tree sparrow

Photochem. Photobiol. Sci., 2014, 13,1568-1579
DOI: 10.1039/C4PP00141A, Paper
Anand S. Dixit, Namram S. Singh, Ramita Sougrakpam
The paper investigates photoperiodic regulation of seasonality in the females of migratory yellow breasted bunting and the resident tree sparrow to compare their responses and adaptive strategies in subtropics.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 3 Sep 2014 | 1:00 am CEST

Location and freedom of single and double guest in dye-doped polymer nanoparticles

Photochem. Photobiol. Sci., 2014, 13,1580-1589
DOI: 10.1039/C4PP00203B, Paper
Cristina Martin, Maria Rosaria di Nunzio, Boiko Cohen, Abderrazzak Douhal
We report on time-resolved fluorescence anisotropy studies of poly(9-vinylcarbazole) (PVK) nanoparticles (NPs) encapsulating Coumarin 153 (C153) and Nile Red (NR).
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 3 Sep 2014 | 1:00 am CEST

Enhanced photocatalytic hydrogen production from an MCM-41-immobilized photosensitizer-[Fe-Fe] hydrogenase mimic dyad

Photochem. Photobiol. Sci., 2014, 13,1590-1597
DOI: 10.1039/C3PP50446H, Paper
Wen Wang, Tianjun Yu, Yi Zeng, Jinping Chen, Guoqiang Yang, Yi Li
A covalently linked photosensitizer-[Fe-Fe] hydrogenase mimic dyad is stabilized by immobilizing it into MCM-41, giving an enhanced catalytic efficiency for hydrogen production.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 2 Sep 2014 | 1:00 am CEST

Self-aggregation of Synthetic Zinc Chlorophyll Derivatives Possessing 31-Hydroxy or Methoxy Group and 131-Mono- or Dicyanomethylene Moiety in Nonpolar Organic Solvents as Models of Chlorosomal Bacteriochlorophyll-d Aggregates

Abstract

Methyl 131-(di)cyanomethylene-pyropheophorbides were synthesized by Knoevenagel reactions of the corresponding 131-oxo-chlorins prepared from modifying chlorophyll-a with malononitrile or cyanoacetic acid. Alternatively, methyl 131-cyanomethylene-pyropheophorbides were produced by Wittig reactions of 131-oxo-chlorins with Ph3P=CHCN. Self-aggregation of zinc complexes of the semi-synthetic chlorophyll derivatives possessing a hydroxy or methoxy group at the 31-position was examined in 1%(v/v) tetrahydrofuran or dichloromethane and hexane by electronic absorption and circular dichroism spectroscopy. Although intermolecular hydrogen-bonding between the 31-hydroxy and 131-oxo groups of bacteriochlorophylls-c/d/e/f was essential for their self-aggregation in natural light-harvesting antenna systems (=chlorosomes), zinc 31-hydroxy-131-di/monocyanomethylene-chlorins self-aggregated in the less/lesser polar organic solvents to form chlorosome-like large oligomers in spite of lacking the 131-oxo moiety as the hydrogen-bonding acceptor. Zinc 31-methoxy-131-dicyanomethylene-chlorin gave similar self-aggregates regardless of lack of both the 31-hydroxy and 131-oxo groups. The present self-aggregation was ascribable to stronger coordination of the 31-oxygen atom to the central zinc than the conventional systems, where the electron-withdrawing cyano group(s) increased the coordinative ability of the central zinc through the chlorin π-system.

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A synthetic zinc chlorophyll-a derivative possessing the 31-hydroxy and 131-dicyanomethylene groups self-aggregated in 1% THF–hexane despite lacking the 131-oxo moiety as a hydrogen-bonding acceptor to give chlorosome-like large oligomers with its Qy band at a near-infrared region.

Quelle: Photochemistry and Photobiology | 1 Sep 2014 | 1:12 pm CEST

Validation and Application of a Model of Oxygen Consumption and Diffusion During Photodynamic Therapy In Vitro

Abstract

The photophysical parameters for the photosensitizer Pd(II) meso-Tetra(4-carboxyphenyl) porphine (PdT790) acquired in a previous study were incorporated into the PDT oxygen diffusion models for cell suspensions and cell monolayers. The time-dependent phosphorescence signals generated by the diffusion models are shown to match signals previously measured by M.A.W. and M.S.P. when reasonable physical and photophysical parameters are used. Simulations were performed to investigate the effects of metabolic and photodynamic oxygen consumption rates on the PDT dose in each of the treatment geometries. It was found that in cell suspensions of <1 million cells per mL, PDT should not be inhibited by hypoxia if the photodynamic consumption rate is <1 mm s−1. For cell monolayers the optimal photodynamic oxygen consumption rate was found to depend on the metabolic rate of oxygen consumption. If cells remained well oxygenated in the absence of PDT, then maximum PDT dose was delivered with the lowest practical photodynamic oxygen consumption rate. Simulations of PDT treatments for multicell tumor spheroids showed that large anoxic cores develop within the spheroids and, as a consequence, less PDT dose is delivered in comparison with similar treatments in cell suspensions and cell monolayers.

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Previously acquired phosphorescence signals generated during Pd(II) meso-Tetra(4-carboxyphenyl) porphine-PDT of cells in monolayers and suspensions are shown to be well described by PDT oxygen diffusion models. The diffusion models are used to determine the photodynamic oxygen consumption rates and in essence the treatment fluence rates, that maximize PDT dose in each of the treatment geometries. The cell suspension diffusion model was extended to describe multicell tumor spheroids. Due to large anoxic cores that develop during PDT, much less PDT dose is delivered to spheroids in comparison with similar treatments in cell suspensions and cell monolayers.

Quelle: Photochemistry and Photobiology | 1 Sep 2014 | 1:11 pm CEST

Photophysical Properties and Singlet Oxygen Generation Efficiencies of Water-Soluble Fullerene Nanoparticles

Abstract

As various fullerene derivatives have been developed, it is necessary to explore their photophysical properties for potential use in photoelectronics and medicine. Here, we address the photophysical properties of newly synthesized water-soluble fullerene-based nanoparticles and polyhydroxylated fullerene as a representative water-soluble fullerene derivative. They show broad emission band arising from a wide-range of excitation energies. It is attributed to the optical transitions from disorder-induced states, which decay in the nanosecond time range. We determine the kinetic properties of the singlet oxygen (1O2) luminescence generated by the fullerene nanoparticles and polyhydroxylated fullerene to consider the potential as photodynamic agents. Triplet state decay of the nanoparticles was longer than 1O2 lifetime in water. Singlet oxygen quantum yield of a series of the fullerene nanoparticles is comparably higher ranging from 0.15 to 0.2 than that of polyhydroxylated fullerene, which is about 0.06.

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Conventional and time-resolved spectroscopy has been used to investigate polyhydroxylfullerene molecule and five fullerene-based nanoparticles. Our results demonstrate formation of disorder-induced states both in the polyhydroxylfullerene and in the nanoparticles.

Quelle: Photochemistry and Photobiology | 1 Sep 2014 | 6:51 am CEST

The structure and UV spectroscopy of benzene-water (Bz-W6) clusters using time-dependent density functional theory

Photochem. Photobiol. Sci., 2014, 13,1549-1560
DOI: 10.1039/C4PP00211C, Paper
Divya Sharma, Martin J. Paterson
MP2, DFT and TD-DFT applied to benzene-(water)6 clusters show how both perturb the electronic spectra of each other and give rise to new charge transfer features from the benzene to the water cluster.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 1 Sep 2014 | 1:00 am CEST

Photocatalytic degradation of pentachlorophenol by N-F-TiO2: identification of intermediates, mechanism involved, genotoxicity and ecotoxicity evaluation

Photochem. Photobiol. Sci., 2014, Advance Article
DOI: 10.1039/C4PP00254G, Paper
M. Antonopoulou, D. Vlastos, I. Konstantinou
Heterogeneous photocatalysis using N-F codoped TiO2 was successfully applied for degradation, mineralization as well as for genotoxicity and ecotoxicity elimination of PCP in the aqueous phase.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 1 Sep 2014 | 1:00 am CEST

Simultaneous Irradiation with Different Wavelengths of Ultraviolet Light has Synergistic Bactericidal Effect on Vibrio parahaemolyticus

Abstract

Ultraviolet (UV) irradiation is an increasingly used method of water disinfection. UV rays can be classified by wavelength into UVA (320–400 nm), UVB (280-320 nm), and UVC (<280 nm). We previously developed UVA sterilization equipment with a UVA light-emitting diode (LED). The aim of this study was to establish a new water disinfection procedure using the combined irradiation of the UVA-LED and another UV wavelength. An oxidative DNA product, 8-hydroxy-2’-deoxyguanosine (8-OHdG), increased after irradiation by UVA-LED alone, and the level of cyclobutane pyrimidine dimers (CPDs) was increased by UVC alone in Vibrio parahaemolyticus. Although sequential irradiation of UVA-LED and UVC-induced additional bactericidal effects, simultaneous irradiation with UVA-LED and UVC-induced bactericidal synergistic effects. The 8-OHdG and CPDs production showed no differences between sequential and simultaneous irradiation. Interestingly, the recovery of CPDs was delayed by simultaneous irradiation. The synergistic effect was absent in SOS response-deficient mutants, such as the recA and lexA strains. Because recA- and lexA-mediated SOS responses have crucial roles in a DNA repair pathway, the synergistic bactericidal effect produced by the simultaneous irradiation could depend on the suppression of the CPDs repair. The simultaneous irradiation of UVA-LED and UVC is a candidate new procedure for effective water disinfection.

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Bactericidal damages induced by UVA (320–400 nm) and UVC (<280 nm) are different. In this study, we revealed that simultaneous irradiation with UVA-LED (365 nm) and UVC (254 nm) induced bactericidal synergistic effects and suppressed the recovery of cyclobutane pyrimidine dimers (CPDs). The synergistic effect was absent in SOS response-deficient strains, such as the recA and lexA mutants. Because recA- and lexA- mediated SOS responses have crucial roles in DNA repair pathway, the synergistic bactericidal effect produced by the simultaneous irradiation could depend on suppression of the CPDs repair. This simultaneous irradiation is a candidate new procedure for effective water disinfection.

Quelle: Photochemistry and Photobiology | 28 Aug 2014 | 1:58 pm CEST

Photobiostimulation reduces edema formation induced in mice by Lys-49 phospholipases A2 isolated from Bothrops moojeni venom

Photochem. Photobiol. Sci., 2014, 13,1561-1567
DOI: 10.1039/C4PP00111G, Paper
Nikele Nadur-Andrade, Camila Squarzone Dale, Adriano Silvio dos Santos, Andreimar M. Soares, Carlos J. de Lima, Stella Regina Zamuner
The prominent local myotoxic effects induced by Bothrops snake venom are due, in part, to myotoxins.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 28 Aug 2014 | 1:00 am CEST

MC1R, Eumelanin and Pheomelanin: their role in determining the susceptibility to skin cancer;

Abstract

Skin pigmentation is due to the accumulation of two types of melanin granules in the keratinocytes. Besides being the most potent blocker of ultraviolet radiation (UVR), the role of melanin in photo-protection is complex. This is because one type of melanin called eumelanin is UV absorbent whereas the other, pheomelanin, is photo-unstable and may even promote carcinogenesis. Skin hyperpigmentation may be caused by stress or exposure to sunlight, which stimulates the release of α-melanocyte stimulating hormone (α-MSH) from damaged keratinocytes. Melanocortin 1 receptor (MC1R) is a key signaling molecule on melanocytes that responds to α-MSH by inducing expression of enzymes responsible for eumelanin synthesis. Persons with red hair have mutations in the MC1R causing its inactivation; this leads to a paucity of eumelanin production and makes red-heads more susceptible to skin cancer. Apart from its effects on melanin production, the α-MSH/MC1R signaling is also a potent anti-inflammatory pathway and has been shown to promote anti-melanoma immunity. This review will focus on the role of MC1R in terms of its regulation of melanogenesis and influence on the immune system with respect to skin cancer susceptibility.

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Quelle: Photochemistry and Photobiology | 22 Aug 2014 | 5:23 pm CEST

Chemical and Biological Mechanisms of Pathogen Reduction Technologies

Abstract

Within the last decade new technologies have been developed and implemented which employ light, often in the presence of a photosensitizer, to inactivate pathogens that reside in human blood products for the purpose of transfusion. These pathogen reduction technologies attempt to find the proper balance between pathogen kill and cell quality. Each system utilizes various chemistries that not only impact which pathogens they can inactivate and how, but also how the treatments affect the plasma and cellular proteins and to what degree. This paper aims to present the various chemical mechanisms for pathogen reduction in transfusion medicine that are currently practiced or in development.

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Illustrated summary of photochemical mechanisms for Theraflex UVC, Mirasol, Intercept and Theraflex MB pathogen reduction technologies.

Quelle: Photochemistry and Photobiology | 20 Aug 2014 | 11:11 am CEST

In Vitro Investigations on the Effect of Dermal Fibroblasts on Keratinocyte Responses to Ultraviolet B Radiation

Abstract

Exposure to ultraviolet radiation is closely linked to the development of skin cancers in humans. The ultraviolet B (UVB) radiation wavelength (280–320 nm), in particular, causes DNA damage in epidermal keratinocytes, which are linked to the generation of signature premalignant mutations. Interactions between dermal fibroblasts and keratinocytes play a role in epidermal repair and regeneration after UVB-induced damage. To investigate these processes, established two and three-dimensional culture models were utilized to study the impact of fibroblast–keratinocyte crosstalk during the acute UVB response. Using a coculture system it was observed that fibroblasts enhanced keratinocyte survival and the repair of cyclobutane pyrimidine dimers (CPDs) after UVB radiation exposure. These findings were also mirrored in irradiated human skin coculture models employed in this study. Fibroblast coculture was shown to play a role in the expression and activation of members of the apoptotic cascade, including caspase-3 and Bad. Interestingly, the expression and phosphorylation of p53, a key player in the regulation of keratinocyte cell fate postirradiation, was also shown to be influenced by fibroblast-produced factors. This study highlights the importance of synergistic interactions between fibroblasts and keratinocytes in maintaining a functional epidermis while promoting repair and regeneration following UVB radiation-induced damage.

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Cellular cross-talk between dermal fibroblasts and epidermal keratinocytes is critical for orchestrating cutaneous repair and regeneration. Herein, we describe the influence of keratinocyte–fibroblast interactions on key processes in the ultraviolet B photoresponse. Importantly, fibroblast-produced factors were observed to enhance keratinocyte survival and DNA repair by regulating the expression of specific apoptotic and cell cycle regulation proteins.

Quelle: Photochemistry and Photobiology | 19 Aug 2014 | 9:17 am CEST

Therapeutic Effect of Irradiation of Magnetic Infrared Laser on Osteoarthritis Rat Model

Abstract

Osteoarthritis (OA) is a degenerative joint disease caused by articular cartilage loss. Many complementary and alternative medicines for OA have been reported so far, but the effectiveness is controversial. Previously, we have shown anti-inflammatory effects of low level laser therapy with static magnetic field, magnetic infrared laser (MIL), in various animal models. Therefore, the beneficial effects were examined in OA rat model. Rats were divided by six groups; no treatment controls of sham and OA model, three MIL treatment groups of OA model at 6.65, 2.66 and 1.33 J cm−2, and Diclofenac group of OA model with 2 mg kg−1 diclofenac sodium. The OA control exhibited typical symptoms of OA, but 4-week MIL treatment improved the functional movement of knee joint with reduced edematous changes. In addition, cartilage GAGs were detected more in all MIL treatment groups than OA control. It suggests that 4-week MIL irradiation has dose-dependent anti-inflammatory and chondroprotective effects on OA. Histopathological analyses revealed that MIL treatment inhibits the cartilage degradation and enhances chondrocyte proliferation. The fact that MIL has an additional potential for the cartilage formation and no adverse effects can be regarded as great advantages for OA treatment. These suggest that MIL can be useful for OA treatment.

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Eight rats per group received a surgical operation for osteoarthritis (OA) or sham. Controls for sham (A) and OA (B) had no treatment, and other OA models were treated with either of diclofenac sodium at 2 mg kg−1 (Diclofenac, C) as a reference or magnetic infrared laser (MIL) at 6.65 J cm−2 (D), 2.66 J cm−2 (E) and 1.33 J cm−2 (F) with constant magnetic field. Comparing to OA control, 4-week MIL treatment improved maximum extension angle of knee joint dose dependently. Histopathological analyses revealed that the MIL treatment inhibits the cartilage degradation. Together with other results, these suggest that MIL can be useful for OA treatment.

Quelle: Photochemistry and Photobiology | 19 Aug 2014 | 7:52 am CEST

Short-term UV-B Dose Stimulates Production of Protective Metabolites in Matricaria chamomilla Leaves

Abstract

Physiological response of two cultivars of Matricaria chamomilla plants on UV irradiation was studied. The impact of used short-time UV dose was evaluated in three time points; 2, 24 and 48 h after irradiation. Used UV irradiation immediately resulted in changes in plant oxidative status monitored as increased concentration of H2O2. Decrease in chlorophyll a and b indicated the impact on photosynthetic apparatus. For phenolic secondary metabolites, an increase in total soluble phenols and AlCl3-reactive flavonols was observed. The activity of main phenolic enzyme, phenylalanine ammonia-lyase, increased with time after irradiation. Significant changes, mainly decreasing trends, in the content of free coumarins and their glycosidic precursors were observed. Enhanced accumulation in chlorogenic and 1,5-dicaffeoylquinic acid and in (Z)-isoform of dicycloethers was detected. From these results, the redirecting precursors of coumarin biosynthesis to biosynthesis of substances with higher antioxidative potential can be assumed. Different reactions in diploid and tetraploid plants were recorded, too.

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Short-term irradiation with UV-A and UV-B influenced some physiological processes (photosynthesis, enzyme activity) in 7-week-old rosette leaves of chamomile and stimulated protective response. Enhanced accumulation of simple phenylpropanoid derivatives, like chlorogenic and 1,5-dicaffeoylquinic acid, coumarin glycoside, daphnin and flavonols related to UV-stimulated PAL activity. Decreased content of free coumarins and their glycosides may indicate redirecting precursors of coumarin biosynthesis to biosynthesis of substances with higher antioxidative potential. Two chamomile cultivars, differed in ploidy level, were irradiated. Tetraploids were more damaged by oxidative stress, but in the course of experiment diploids expressed enhanced accumulation of compounds with higher antioxidative potential.

Quelle: Photochemistry and Photobiology | 19 Aug 2014 | 7:12 am CEST

Red Light Interferes in UVA-Induced Photoaging of Human Skin Fibroblast Cells

Abstract

The possible regulation mechanism of red light was determined to discover how to retard UVA-induced skin photoaging. Human skin fibroblasts were cultured and irradiated with different doses of UVA, thus creating a photoaging model. Fibroblasts were also exposed to a subtoxic dose of UVA combined with a red light-emitting diode (LED) for five continuous days. Three groups were examined: control, UVA and UVA plus red light. Cumulative exposure doses of UVA were 25 J cm−2, and the total doses of red light were 0.18 J cm−2. Various indicators were measured before and after irradiation, including cell morphology, viability, β-galactosidase staining, apoptosis, cycle phase, the length of telomeres and the protein levels of photoaging-related genes. Red light irradiation retarded the cumulative low-dose UVA irradiation-induced skin photoaging, decreased the expression of senescence-associated β-galactosidase, upregulated SIRT1 expression, decreased matrix metalloproteinase MMP-1 and the acetylation of p53 expression, reduced the horizon of cell apoptosis and enhanced cell viability. Furthermore, the telomeres in UVA-treated cells were shortened compared to those of cells in the red light groups. These results suggest that red light plays a key role in the antiphotoaging of human skin fibroblasts by acting on different signaling transduction pathways.

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This study demonstrated the use of LED red light with a wavelength of 633 nm leads to an attenuation of subtoxic UVA irradiation-induced skin photoaging. Red light intervention decreased the expression of senescence-associated β-galactosidase, upregulated SIRT1 expression, decreased matrix metalloproteinase MMP-1 and the acetylation of p53 expression. Our results suggest that red light plays a key role in the antiphotoaging of human skin fibroblasts by acting on different signaling transduction pathways.

Quelle: Photochemistry and Photobiology | 18 Aug 2014 | 1:53 pm CEST

Photooxidation of Tryptophan Leading to 2-Aminoacetophenone – A Possible Reason for the Untypical Aging Off-flavor in Wine

Abstract

2-Aminoacetophenone (AAP) was recognized as the key compound for the so-called untypical aging off-flavor (UTA) in Vitis vinifera wines. In this study, it was shown that AAP can be formed by photooxidation of free and protein-bound tryptophan (TRP) in combination with a subsequent storage in model wine. Solutions of TRP and lysozyme were exposed to artificial sunlight both in the presence and in the absence of the photosensitizer riboflavin. Aliquots of the irradiation batches were stored in model wine solutions containing tartaric acid, sulfite and ethanol in different combinations. AAP formation could be identified from both free and bound (lysozyme) TRP, while free TRP resulted in higher yields. The presence of riboflavin during irradiation generally favored the AAP formation. AAP formation increased with increasing irradiation times, but AAP was not detectable, if TRP was directly incubated in model wine. Not only the irradiation time but also the storage time of model wines favored the formation of AAP. Concerning the model wine composition, it became evident that the presence of tartaric acid resulted in the highest AAP formation during storage.

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2-Aminoacetophenone (AAP) is known as the key compound for the so-called untypical aging off-flavor (UTA) in Vitis vinifera wines. In the present work we show that photooxidation of tryptophan (free and bound) in combination with a subsequent storage in model wine leads to the formation of AAP. Furthermore, we could show that the AAP formation mechanism proceeds via N-formyl-2-aminoacetophenone (FAP), but not exclusively. Both time of irradiation and time of storage in model wines greatly favored the formation of AAP.

Quelle: Photochemistry and Photobiology | 18 Aug 2014 | 1:53 pm CEST

Sun protection Provided by Regulation School Uniforms in Australian Schools: An Opportunity to Improve Personal Sun protection During Childhood

Abstract

Childhood sun exposure is linked to excessive pigmented mole development and melanoma risk. Clothing provides a physical barrier, protecting skin from ultraviolet radiation (UVR). Extending sleeves to elbow length and shorts to knee length has been shown to significantly reduce mole acquisition in preschoolers from tropical Queensland. We used publicly available uniform images and guidelines from primary schools in Townsville (latitude 19.25°S, n = 43 schools), Cairns (16.87°S, n = 46) and the Atherton Tablelands (17.26°S, n = 23) in tropical Australia to objectively determine the body surface proportion covered by regulation school uniforms. Uniforms of nongovernment, large (≥800 students), urban, educationally advantaged schools with comprehensive sun protection policies covered more skin than those of government schools (63.2% vs 62.0%; P < 0.001), smaller schools (63.4% vs 62.3%; P = 0.009), rural (62.7% vs 61.9%; P = 0.002) and educationally disadvantaged schools (62.8% vs 62.3%; P < 0.001) with underdeveloped sun protection policies (62.8% vs 62.2%; P = 0.002). Overall, SunSmart and non-SunSmart school uniforms covered identical body surface proportions (62.4%, P = 0.084). Although wearing regulation school uniforms is mandatory at most Australian primary schools, this opportunity to improve children's sun protection is largely overlooked. Recent evidence suggests that even encouraging minor alterations to school uniforms (e.g. slightly longer sleeves/dresses/skirts/shorts) to increase skin coverage may reduce mole acquisition and melanoma risk, especially in high-risk populations.

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Ultra violet exposure during the childhood years is linked to the development of melanocytic nevi (moles) which are a risk factor for the development cutaneous melanoma. Sun-protective clothing protects the skin from ultra violet radiation, reducing the development of melanocytic nevi and skin cancer risk. Simple alterations to school uniforms (such as slightly longer sleeves and hems) would increase body surface area covered without causing heat stress. Sensibly designed school uniforms/clothing would be a practical way to protect school children from ultra violet radiation. Body surface area covered needs to be added to clothing standards.

Quelle: Photochemistry and Photobiology | 18 Aug 2014 | 1:52 pm CEST

Effect of Immunosuppressants Tacrolimus and Mycophenolate Mofetil on the Keratinocyte UVB Response

Abstract

Nonmelanoma skin cancer, derived from epidermal keratinocytes, is the most common malignancy in organ transplant recipients, causes serious morbidity and mortality, and is strongly associated with solar ultraviolet (UV) exposure. Preventing and treating skin cancer in these individuals has been extraordinarily challenging. Following organ transplantation, the immunosuppressants are used to prevent graft rejection. Until now, immunosuppression has been assumed to be the major factor leading to skin cancer in this setting. However, the mechanism of skin carcinogenesis in organ transplant recipients has not been understood to date; specifically, it remains unknown whether these cancers are immunosuppression-dependent or -independent. In particular, it remains poorly understood what is the mechanistic carcinogenic action of the newer generation of immunosuppressants including tacrolimus and mycophenolate mofetil (MMF). Here, we show that tacrolimus and MMF impairs UVB-induced DNA damage repair and apoptosis in human epidermal keratinocytes. In addition, tacrolimus inhibits UVB-induced checkpoint signaling. However, MMF had no effect. Our findings have demonstrated that tacrolimus and MMF compromises proper UVB response in keratinocytes, suggesting an immunosuppression-independent mechanism in the tumor-promoting action of these immunosuppressants.

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This study investigated the effects of the newer generation of immunosuppressants including tacrolimus and mycophenolate mofetil (MMF) on keratinocyte UVB response. Tacrolimus and MMF impairs UVB-induced DNA repair and apoptosis in human keratinocytes. In addition, tacrolimus inhibits UVB-induced checkpoint signaling, while MMF had no effect. Our findings have demonstrated that tacrolimus and MMF compromises proper keratinocyte UVB response, suggesting an immunosuppression-independent mechanism in the tumor-promoting action of these immunosuppressants.

Quelle: Photochemistry and Photobiology | 12 Aug 2014 | 8:36 am CEST

Study of the Photodegradation Kinetics and Pathways of Hexaflumuron in Liquid Media

Abstract

Hexaflumuron, one of the benzoylphenylurea insect growth regulators, can be leached into surface water and thus having a potential impact on aquatic organisms. In this study, the photodegradation processes of hexaflumuron under high-pressure mercury lamp irradiation were assessed. The photodegradation kinetics were studied, as were the effects of pH, different light sources, organic solvents and environmental substances, including nitrate ions (NO3), nitrite ions (NO2), ferrous ions (Fe2+), ferric ions (Fe3+), humic acid, sodium dodecyl sulfate (SDS) and hydrogen peroxide (H2O2). Three photodegradation products in methanol were identified by gas chromatography-mass spectrometry (GC-MS). In general, the degradation of hexaflumuron followed first-order kinetics. In the four media studied, the photodegradation rate order was n-hexane > methanol > ultrapure water > acetone. Faster degradation was observed under high-pressure mercury lamp irradiation than under xenon lamp irradiation. The pH had a considerable effect, with the most rapid degradation occurring at pH 5.0. The photodegradation rate of hexaflumuron was promoted in the presence of NO3, NO2, Fe2+, humic acid, SDS and H2O2, but inhibited by Fe3+. Moreover, the presumed photodegradation pathway was proposed to be the cleavage of the urea linkage.

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  1. The photodegradation kinetics of hexaflumuron under irradiation were investigated.
  2. Effects of light sources, pH values, organic solvents and water substances on hexaflumuron photodegradation were analyzed.
  3. Three photodegradation products were identified by GC-MS and the presumed photodegradation pathways of hexaflumuron in methanol were proposed.

Quelle: Photochemistry and Photobiology | 12 Aug 2014 | 8:36 am CEST

The effect of amphiphilic polymers on the association, morphology and photophysical properties of hypocrellin coordination polymer/fullerene assemblies

Photochem. Photobiol. Sci., 2014, 13,1529-1540
DOI: 10.1039/C4PP00027G, Paper
Zhize Ou, Guixia Liu, Yunyan Gao, Shayu Li, Huizhen Li, Yi Li, Xuesong Wang, Guoqiang Yang, Xin Wang
Y3+-PyrHA/fullerene can form nanoparticles in the size range of 10-60 nm and exhibits a higher singlet oxygen quantum yield than Y3+-PyrHA and the corresponding fullerene in 1% P123 solution.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 7 Aug 2014 | 1:00 am CEST

The Injury and Cumulative Effects on Human Skin by UV Exposure from Artificial Fluorescence Emission

Abstract

The injury and cumulative effects of UV emission from fluorescence lamp were studied. UV intensity from fluorescence lamp was measured, and human skin samples (hips, 10 volunteers) were exposed to low-dose UV irradiation (three times per week for 13 consecutive weeks). Three groups were examined: control group without UV radiation; low-dose group with a cumulative dose of 50 J cm−2 which was equivalent to irradiation of the face during indoor work for 1.5 years; and high-dose group with 1000 J cm−2 cumulative dose equivalent to irradiation of the face during outdoor activities for 1 year. Specific indicators were measured before and after UVA irradiation. The findings showed that extending the low-dose UVA exposure decreased the skin moisture content and increased the transepidermal water loss as well as induced skin color changes (decreased L* value, increased M index). Furthermore, irradiated skin showed an increased thickness of cuticle and epidermis, skin edema, light color and unclear staining collagen fibers in the dermis, and elastic fiber fragmentation. In addition, MMP-1, p53 and SIRT1 expression was also increased. Long-term exposure of low-dose UVA radiation enhanced skin photoaging. The safety of the fluorescent lamp needs our attention.

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The injury and cumulative effects of UV emission from compact fluorescence lamp (CFL) were studied on human skin. (A) HE staining. The thickness of the cuticle and epidermis increased. Dermal collagen fibers were clumped and aggregated with light color and unclear staining; (B) Elastic fiber staining. Fragmentation of the elastic fibers and intermittent zonal distribution was observed; (C) MMP-1 expression. The staining intensity of MMP-1 increased; (D) SIRT1 expression. Both staining intensity and area of SIRT1 increased; (E) p53 expression. The staining intensity of p53 expression increased.

Quelle: Photochemistry and Photobiology | 5 Aug 2014 | 6:04 am CEST

Disinfection of Escherichia Coli Gram Negative Bacteria Using Surface Modified TiO2: Optimization of Ag Metallization and Depiction of Charge Transfer Mechanism

Abstract

The antibacterial activity of silver deposited TiO2 (Ag-TiO2) against Gram negative Escherichia coli bacteria was investigated by varying the Ag metal content from 0.10 to 0.50% on the surface of TiO2. Ag depositions by the photoreduction method were found to be stable. Surface silver metallization was confirmed by EDAX and XPS studies. Photoluminescence studies show that the charge carrier recombination is less for 0.1% Ag-TiO2 and this catalyst shows superior bactericidal activity under solar light irradiation compared to Sol gel TiO2 (SG-TiO2) due to the surface plasmon effect. The energy levels of deposited Ag are dependent on the Ag content and it varies from −4.64 eV to −1.30 eV with respect to the vacuum energy level based on atomic silver to bulk silver deposits. The ability of electron transfer from Ag deposit to O2 depends on the position of the energy levels. The 0.25% and 0.50% Ag depositions showed detrimental effect on bactericidal activity due to the mismatch of energy levels. The effect of the EROS (External generation of the Reactive Oxygen Species by 0.1% Ag-TiO2) and IROS (Interior generation of Reactive Oxygen Species within the bacteria) on the bactericidal inactivation is discussed in detail.

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Metallization of silver on the surface of TiO2 is carried out by the photodeposition method and its evaluation for disinfection of 10Escherichia coli cell suspension in the presence of solar light illumination is depicted.

Quelle: Photochemistry and Photobiology | 1 Aug 2014 | 11:02 am CEST

Photoactive Hybrid Materials of Lanthanide (Eu3+, Tb3+, Sm3+) Beta-Diketonates and Polymer Resin Through Ionic Liquid Bridge

Abstract

A special multifunctional ionic liquid compound (1-methyl-3-(2-(thiocarboxyoxy)-ethyl)-2H-imidazole-1,3-diium bromide (SHIL)) is used as the chemical bridge to link lanthanide beta-diketonates and polymer resin, which are designated as Ln(L)4-SHIL-WR/MR (Ln = Eu, Tb, Sm; L = thenoyltrifluoroacetonate (TTA), acetylacetonate (AA), dibenzoylmethane (DBM); WR = Wang resin, MR = Merrifield resin). Among SHIL and polymer resin are assembled to form covalently bonded system through condensation reaction. Then tetrakis lanthanide beta-diketonates are linked to SHIL through ion-exchange reaction. Physical characterization and especially the photoluminescent performance of the multicomponent hybrids are studied. The hybrid materials possess good stability and excellent luminescent property. The results provide useful path to obtain luminescent hybrids for further practical application.

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A special multifunctional ionic liquid compound (1-methyl-3-(2-(thiocarboxyoxy)-ethyl)-2H-imidazole-1,3-diium bromide (SHIL)) is engaged as the chemical bridge to link lanthanide beta-diketonates and polymer sphere-like resin to construct the hybrid materials Ln(L)4-SHIL-WR/MR. The results provide a novel path to construct photofunctional hybrids for further device application.

Quelle: Photochemistry and Photobiology | 31 Jul 2014 | 11:06 am CEST

ROS and p53 in Regulation of UVB-induced HDM2 Alternative Splicing

Abstract

Alternative splicing plays an important role in proteasome diversity and gene expression regulation in eukaryotic cells. Hdm2, the human homolog of mdm2 (murine double minute oncogene 2), is known to be an oncogene as its role in suppression of p53. Hdm2 alternative splicing, occurs in both tumor and normal tissues, is believed to be a response of cells for cellular stress, and thus modulate p53 activity. Therefore, understanding the regulation of hdm2 splicing is critical in elucidating the mechanisms of tumor development and progression. In this study, we determined the effect of ultraviolet B light (UVB) on alternative splicing of hdm2. Our data indicated that UVB (50 mJ cm−2) alone is not a good inducer of alternative splicing of hdm2. The less effectiveness could be due to the induction of ROS and p53 by UVB because removing ROS by L-NAC (10 mm) in p53 null cells could lead to alternative splicing of hdm2 upon UVB irradiation.

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Hdm2, the human homologue of mdm2 (murine double minute oncogene 2), is an oncogene for its role in suppression of p53. Hdm2 alternative splicing, occurs in both tumor and normal tissues, is suggested to be a response of cells for cellular stress, and thus modulate p53 activity. In this study, we demonstrated that UVB is weaker inducer of alternative splicing than UVC is. We also provided evidences that the UV-induced alternative splicing is promoted by DNA-damage, but suppressed by ROS formation and p53 activity of the irradiated cells.

Quelle: Photochemistry and Photobiology | 26 Jul 2014 | 7:02 am CEST

Selective and sensitive fluorescence-shift probes based on two dansyl groups for mercury(II) ion detection

Photochem. Photobiol. Sci., 2014, 13,1521-1528
DOI: 10.1039/C4PP00094C, Paper
Li-Jun Ma, Jialun Liu, Lefang Deng, Meili Zhao, Zhifu Deng, Xutian Li, Jian Tang, Liting Yang
Two probes were synthesized and used to detect Hg2+ in aqueous solution. The probes showed a blue-shift of the fluorescence as Hg2+ was added, along with a color change.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 23 Jul 2014 | 1:00 am CEST

Role of hydrogen bonds in molecular packing of photoreactive crystals: templating photodimerization of protonated stilbazoles in crystalline state with a combination of water molecules and chloride ions

Photochem. Photobiol. Sci., 2014, 13,1509-1520
DOI: 10.1039/C4PP00221K, Paper
Barnali Mondal, Tingting Zhang, Rajeev Prabhakar, Burjor Captain, V. Ramamurthy
A combination of water molecules and chloride ions pre-orient protonated stilbazole molecules towards photodimerization the solid state.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 23 Jul 2014 | 1:00 am CEST

New cyanopyridone based luminescent liquid crystalline materials: synthesis and characterization

Photochem. Photobiol. Sci., 2014, 13,1496-1508
DOI: 10.1039/C4PP00031E, Paper
Ahipa T. N., Airody Vasudeva Adhikari
A series of new luminescent mesogens carrying cyanopyridone, triazole, and polar groups were successfully synthesized. Also, their liquid crystalline and photophysical properties were investigated.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 21 Jul 2014 | 1:00 am CEST

Influence of Dye Content on the Conduction Band Edge of Titania in the Steam-treated Dye-dispersing Titania Electrodes

Abstract

The titania and dye-dispersing titania electrodes were prepared by a nitric acid-catalyzed sol-gel process. The dye-dispersing titania contains the dye molecules dispersed on the surface of the individual nanosized titania particles. The photo-cyclic voltammetry (Photo-CV) and photoelectric measurements of the dye-dispersing titania electrodes were conducted to clarify the factors changing the conduction band edge of the titania and the open-circuit voltage (Voc) of the electrodes. The remaining nitrate ions caused a negative shift of conduction band edge of the titania of the dye-dispersing titania. The conduction band edge of the titania was shifted in a negative direction in the electrode containing a greater amount of the dye. These results are due to the adsorption of nitrate ions and the dye-titania complex formation on the titania particle surface. The effect of the dye-titania complex formation on the shift in the titania conduction band edge was greater than that of the adsorption of nitrate ions due to strong interaction between the dye and titania through the carboxylate and quinone-like groups of the dye. The shift in the titania conduction band edge corresponded to the change in the Voc value.

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The titania and dye-dispersing titania electrodes were prepared by a nitric acid-catalyzed sol-gel process. The dye-dispersing titania contains the dye molecules dispersed on the surface of the individual nanosized titania particles. The conduction band edge of the titania was shifted in a negative direction in the electrode containing a greater amount of the dye due to the dye-titania complex formation on the titania particle surface. The effect of the dye-titania complex formation on the shift in the titania conduction band edge was greater than that of the adsorption of nitrate ions due to strong interaction between the dye and titania.

Quelle: Photochemistry and Photobiology | 18 Jul 2014 | 8:07 am CEST

Retarded Photooxidation of Cyamemazine in Biomimetic Microenvironments

Abstract

Cyamemazine (CMZ) is a neuroleptic drug that mediates cutaneous phototoxicity in humans. Here, the photobehavior of CMZ has been examined within α1-acid glycoproteins, β- and γ-cyclodextrins and SDS micelles. In all these microenvironments, CMZ emission was enhanced and blue-shifted, and its lifetime was longer. Irradiation of the entrapped drug at 355 nm, under air; led to the N,S-dioxide. Within glycoproteins or SDS micelles the reaction was clearly slower than in phosphate buffered solution (PBS); protection by cyclodextrins was less marked. Transient absorption spectroscopy in PBS revealed formation of the triplet state (3CMZ*) and the radical cation (CMZ+•). Upon addition of glycoprotein, the contribution of CMZ+• became negligible, whereas 3CMZ* dominated the spectra; in addition, the triplet lifetime became considerably longer. In cyclodextrins, this occurred to a lower extent. In all microheterogeneous systems, quenching by oxygen was slower than in solution; this was most remarkable inside glycoproteins. The highest protection from photooxidation was achieved inside SDS micelles. The results are consistent with photooxidation of CMZ through photoionization and subsequent trapping of the resulting radical cation by oxygen. This reaction is extremely sensitive to the medium and constitutes an appropriate probe for localization of the drug within a variety of biological compartments.

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The photobehavior of cyamemazine (CMZ) has been examined within α1-acid glycoproteins, cyclodextrins and SDS micelles. Irradiation of the entrapped drug, under air, leads to the corresponding N,S-dioxide (CMZ-SONO). Within glycoproteins or SDS micelles the photooxidation reaction is clearly slower than in phosphate buffered solution, while the effect of cyclodextrins is less marked. The highest protection is achieved inside SDS micelles. The results of the steady-state irradiations in combination with laser flash photolysis studies are consistent with photoxidation of CMZ through photoionization and subsequent trapping of the resulting radical cation by oxygen, ultimately leading to CMZ-SONO.

Quelle: Photochemistry and Photobiology | 18 Jul 2014 | 6:39 am CEST

Possible Involvement of a Tetrahydrobiopterin in Photoreception for UV-B-induced Anthocyanin Synthesis in Carrot

Abstract

Our previous studies of action spectra for UV-B-induced anthocyanin accumulation in cultured carrot cells indicated that a reduced form of pterin, possibly tetrahydrobiopterin, contributes to UV-B photoreception. In this report, we provide additional evidence for the involvement of pterin in UV-B light sensing. UV-B-induced phenylalanine ammonia-lyase (PAL) activity was considerably suppressed by N-acetylserotonin (an inhibitor of tetrahydrobiopterin biosynthesis), and this suppression was partially recovered by adding biopterin or tetrahydrobiobiopterin. In addition, protein(s) specifically bound to biopterin were detected by radiolabeling experiments in N-acetylserotonin-treated cells. Furthermore, diphenyleneiodonium, a potent inhibitor of electron transfer, completely suppressed UV-B-induced PAL activity. These results suggest the occurrence of an unidentified UV-B photoreceptor (other than UVR8, the tryptophan-based UV-B sensor originally identified in Arabidopsis) with reduced pterin in carrot cells. After reexamining published action spectra, we suggest that anthocyanin synthesis is coordinately regulated by these two UV-B sensors.

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On the basis of inhibitor studies in cultured carrot cells and a re-examination of action spectra reported previously, the authors propose that anthocyanin synthesis is coordinately regulated by a reduced pterin-type UV-B sensor and UVR8.

Quelle: Photochemistry and Photobiology | 16 Jul 2014 | 6:40 am CEST

Ultraviolet Erythematic Radiation Dose Received by Golfers in Winter, in Valencia

Abstract

This article analyzes Ultraviolet Erythematic Radiation (UVER) dose received by several golf players in winter in Valencia. Playing golf involves spending several hours outdoors because of the length of golf matches and training. Moreover, in Valencia there are many golf players coming from northern Europe, with a phototype very sensitive (I–II). For that reason, these people have an increasing risk while playing. This article shows that harmful effects coming from UVER radiation may occur not only in summer time but also in winter, especially at these latitudes. VioSpor dosimeters have been used to develop this analysis over several golf players on January 2013 between 10:00 h and 15:00 h, local time.

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This article analyzes Ultraviolet Erythematic Radiation (UVER) dose received by several golf players in winter in Valencia. Playing golf involves spending several hours outdoors because of the length of golf matches and training. Moreover, in Valencia there are many golf players coming from northern Europe, with a very sensitive phototype (I–II). For that reason these people have an increased risk while playing. This article shows that harmful effects coming from UVER radiation may occur not only in summer time but also in winter, especially at cities with a latitude similar to Valencia's one (39°28′N, 0°22′W).

Quelle: Photochemistry and Photobiology | 14 Jul 2014 | 8:27 am CEST

Xeroderma Pigmentosum in the United Kingdom

Abstract

The seminal discovery by James Cleaver of defective DNA repair in xeroderma pigmentosum (XP) opened up an ever-expanding field of DNA repair-related disorders. In addition, it put XP on the map and has led to improved diagnosis, care and management of affected patients. In the United Kingdom, we recently established a multidisciplinary specialist clinic for XP patients. All XP patients in the United Kingdom are able to visit the clinic where they are examined and advised by a team of specialists with detailed knowledge of the different aspects of XP.

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Early diagnosis and rigorous protection from daylight can completely prevent the skin problems in XP. Patient XP59BR (left) has had poor protection from daylight and has developed many skin cancers. In contrast, patient XPJCLO was diagnosed in his first year of life, has been rigorously protected from sunlight and has not developed any significant skin lesions. Curiously, despite having similar mutations in the XPD gene, XP59BR has no severe neurological problems, whereas XPJCLO has shown features of neurological degeneration since the age of 2. Photographs published with consent of patient or their family.

Quelle: Photochemistry and Photobiology | 14 Jul 2014 | 7:37 am CEST

The Light-Induced FOS Response in Melanopsin Expressing HEK-293 Cells is Correlated with Melanopsin Quantity and Dependent on Light Duration and Irradiance

Abstract

We established a cell line (HEK-hMel) expressing melanopsin in a tetracycline dependent manner to elucidate new aspects of melanopsin's light response. Different light stimuli were evaluated using FOS expression as response parameter. Immunoblotting was used to evaluate expression of melanopsin and FOS and qPCR to quantify FOS mRNA responses. The magnitude of the FOS response was found to correlate with the amount of melanopsin expressed by the cells, and a transient FOS mRNA induction followed by FOS protein still elevated after 24 h of illumination was revealed. Exposing the cells to darkness after light resulted in reduction of the response compared to exposure to light solely showing dependency on continuous light. Increasing irradiances of blue light (480 nm) up to 1011 quanta cm−2 s−1 elicited steep increases in FOS mRNA, while increases between 1012 and 5 × 1013 quanta  cm−2 s−1 resulted in equally high FOS expression. The HEK-hMel cells were used to characterize facets of melanopsin's light-induced FOS response not approachable in vivo. Novel information such as dependency of the FOS response on both melanopsin amount and light intensity in addition to a detailed time-course of both FOS mRNA and protein were revealed.

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HEK-293 cells expressing tetracycline inducible melanopsin were used to evaluate aspects of the melanopsin dependent light inducible FOS response. The FOS response's dependency on melanopsin amount and irradiance are shown to the left and right, respectively. Furthermore, we evaluated the time-course of the response to both continuous light and light followed by darkness. The study reveals new facets of melanopsin's response, which hopefully will be of value for future studies of effects mediated by melanopsin.

Quelle: Photochemistry and Photobiology | 3 Jul 2014 | 3:28 am CEST

5-Aminolevulinic acid-Loaded Fullerene Nanoparticles for In Vitro and In Vivo Photodynamic Therapy

Abstract

This report explores some properties of 80–200 nm nanoparticles containing 5-aminolevulinic acid (ALA) and fullerene (C60) for photodynamic therapy (PDT). Compared with ALA, the nanoparticles yielded more protoporphyrin IX (PpIX) formation in cells and tissues and to a significant improvement in antitumor efficacy in tumor-bearing mice. Maximum levels of PpIX were obtained 4 h after administration and selective PpIX formation in tumor was observed. These nanoparticles appear to be a useful vehicle for drug delivery purposes. In this study, a procedure for preparing fullerene nanoparticles containing ALA was developed. The product alone exhibited no detectable toxicity in the dark and was superior to ALA alone in promoting PpIX biosynthesis and PDT efficacy both in culture and in a murine tumor model. These results suggest that this procedure could be the basis for an improved PDT protocol for cancer control.

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Nonfluorescent C60-5-ALA is taken up by tumor cells and then induces the biosynthesis and accumulation of fluorescent protoporphyrin IX (PpIX).

Quelle: Photochemistry and Photobiology | 1 Jul 2014 | 8:20 am CEST

On the Role of Exponential Smoothing in Circadian Dosimetry

Abstract

The effects lighting has on health through modulation of circadian rhythms are becoming increasingly well documented. Data are still needed to show how light exposures are influenced by architecture and lighting design and circadian dosimetry analyses should provide duration, phase and amplitude measures of 24 h exposure profiles. Exponential smoothing is used to derive suitable metrics from 24 h light measurements collected from private dwellings. A further application of these modified exposure time series as physiological models of the light drive is discussed. Unlike previous light drive models, the dose rate persists into periods of darkness following exposures. Comparisons to long duration exposure studies suggest this type of persistent light drive model could be incorporated into contemporary physiological models of the human circadian oscillator.

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Exponential smoothing is used to convert noisy light exposure time series into circadian variables for amplitude, phase and duration of light exposures (or photoperiod). This modifies the reciprocity view of dose calculation, and matches the duration-response of melatonin suppression to light. As well as applying these calculations to personal light exposures, available light exposures within buildings can be analyzed using these metrics to investigate the effects of design on circadian entrainment. Data for a sample of private UK dwellings are analyzed in contrasting seasons.

Quelle: Photochemistry and Photobiology | 24 Jun 2014 | 3:30 pm CEST

Effects of Ultraviolet Radiation (UVA+UVB) on Young Gametophytes of Gelidium floridanum: Growth Rate, Photosynthetic Pigments, Carotenoids, Photosynthetic Performance, and Ultrastructure

Abstract

This study investigated the effects of radiation (PAR+UVA+UVB) on the development and growth rates (GRs) of young gametophytes of Gelidium floridanum. In addition, photosynthetic pigments were quantified, carotenoids identified, and photosynthetic performance assessed. Over a period of 3 days, young gametophytes were cultivated under laboratory conditions and exposed to photosynthetically active radiation (PAR) at 80 μmol photons m−2 s−1 and PAR+UVA (0.70 W m−2)+UVB (0.35 W m−2) for 3 h per day. The samples were processed for light and electron microscopy to analyze the ultrastructure features, as well as carry out metabolic studies of GRs, quantify the content of photosynthetic pigments, identify carotenoids and assess photosynthetic performance. PAR+UVA+UVB promoted increase in cell wall thickness, accumulation of floridean starch grains in the cytoplasm and disruption of chloroplast internal organization. Algae exposed to PAR+UVA+UVB also showed a reduction in GR of 97%. Photosynthetic pigments, in particular, phycoerythrin and allophycocyanin contents, decreased significantly from UV radiation exposure. This result agrees with the decrease in photosynthetic performance observed after exposure to ultraviolet radiation, as measured by a decrease in the electron transport rate (ETR), where values of ETRmax declined approximately 44.71%. It can be concluded that radiation is a factor that affects the young gametophytes of G. floridanum at this stage of development.

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The radiation (PAR+UVA+UVB) on the young gametophytes of Gelidium floridanum affected the structure and resulted in depigmentation of the thallus and growth rate reduction. PAR+UVA+UVB promoted increase in cell wall thickness, increased of carotenoids compounds, accumulation of floridean starch grains in the cytoplasm and disruption of chloroplast internal organization. Photosynthetic pigments, in particular, phycoerythrin and allophycocyanin, suffered significant reduction in concentration after exposure to PAR+UVA+UVB. This result agrees with the decrease in photosynthetic performance observed after exposing to ultraviolet radiation, as measured by a decrease in the electron transport rate (ETR).

Quelle: Photochemistry and Photobiology | 23 Jun 2014 | 12:16 pm CEST

Neurotransmitter Transporter Family Including SLC6A6 and SLC6A13 Contributes to the 5-Aminolevulinic Acid (ALA)-Induced Accumulation of Protoporphyrin IX and Photodamage, through Uptake of ALA by Cancerous Cells

Abstract

δ-Aminolevulinic acid (ALA)-induced protoporphyrin accumulation is widely used in the treatment of cancer, as photodynamic therapy (PDT). To clarify the mechanisms of ALA uptake by tumor cells, we have examined the ALA-induced accumulation of protoporphyrin by the treatment of colon cancer DLD-1 and epithelial cancer HeLa cells with γ-aminobutyric acid (GABA)-related compounds. When the cells were treated with GABA, taurine and β-alanine, the level of protoporphyrin was decreased, suggesting that plasma membrane transporters involved in the transport of neurotransmitters contribute to the uptake of ALA. By transfection with neurotransmitter transporters SLC6A6, SLC6A8 and SLC6A13 cDNA, the ALA- and ALA methylester-dependent accumulation of protoporphyrin markedly increased in HEK293T cells, dependent on an increase in the uptake of ALA. When ALA-treated cells were exposed to white light, the extent of photodamage increased in SLC6A6- and SLC6A13-expressing cells. Conversely, knockdown of SLC6A6 or SLC6A13 with siRNAs in DLD-1 and HeLa cells decreased the ALA-induced accumulation. The expression of SLC6A6 and SLC6A13 was found in some cancer cell lines. Immunohistochemical studies revealed that the presence of these transporters was elevated in colon cancerous cells. These results indicated that neurotransmitter transporters including SLC6A6 and SLC6A13 mediate the uptake of ALA and can play roles in the enhancement of ALA-induced accumulation of protoporphyrin in cancerous cells.

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GABA-related compounds, including taurine and β-alanine inhibited the ALA-induced accumulation of protoporphyrin in colon canerous cells. The expression of Na+- and Cl-dependent neurotransmitter transporter SLC6A6 and SLC6A13 increased the uptake of ALA by the cells, the ALA-induced accumulation of protoporphyrin and photodamage. Silencing of SLC6A6 and SLC6A13 reduced the accumulation of protoporphyrin. Based on observations that SLC6A6 and SLC6A13 were expressed in various cancerous cells and in adenocarcinoma cells, neurotransmitter transporters are involved in the uptake of ALA, followed by ALA-PDT.

Quelle: Photochemistry and Photobiology | 23 Jun 2014 | 12:15 pm CEST

A Tandem Mass Spectrometric Method for Singlet Oxygen Measurement

Abstract

Singlet oxygen, a harmful reactive oxygen species, can be quantified with the substance 2,2,6,6-tetramethylpiperidine (TEMP) that reacts with singlet oxygen, forming a stable nitroxyl radical (TEMPO). TEMPO has earlier been quantified with electron paramagnetic resonance (EPR) spectroscopy. In this study, we designed an ultra–high-performance liquid chromatographic—tandem mass spectrometric (UHPLC-ESI-MS/MS) quantification method for TEMPO and showed that the method based on multiple reaction monitoring (MRM) can be used for the measurements of singlet oxygen from both nonbiological and biological samples. Results obtained with both UHPLC-ESI-MS/MS and EPR methods suggest that plant thylakoid membranes produce 3.7 × 10−7 molecules of singlet oxygen per chlorophyll molecule in a second when illuminated with the photosynthetic photon flux density of 2000 μmol m−2 s−1.

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Singlet oxygen, a harmful reactive oxygen species, can be detected with TEMP (2,2,6,6-tetramethylpiperidine) that reacts with singlet oxygen, forming a stable nitroxyl radical called TEMPO. TEMPO has earlier been quantified with electron paramagnetic resonance (EPR) spectroscopy. In this study, we show that TEMPO can be measured from both nonbiological and biological samples with an ultra–high-performance liquid chromatography—tandem mass spectrometry (UHPLC-ESI-MS/MS) method. The results suggest that thylakoid membranes produce 3.7 × 10−7 molecules of singlet oxygen per chlorophyll molecule in a second when illuminated with the photosynthetic photon flux density of 2000 μmol m−2 s−1.

Quelle: Photochemistry and Photobiology | 20 Jun 2014 | 10:00 am CEST

Comparative Antibacterial Efficacy of Photodynamic Therapy and Ultrasonic Irrigation Against Enterococcus faecalis In Vitro

Abstract

Enterococcus faecalis poses a challenge to the efficacy of traditional root canal disinfection methods. This study was aimed to establish a synergistic root canal disinfection strategy combining ultrasonic irrigation with photodynamic therapy (PDT) together and to test its antibacterial efficacy against E. faecalis. Twenty-seven bovine root canals infected with E. faecalis were randomly divided into three groups and treated with different disinfection methods as follows: ultrasonic irrigation with 2.5% NaOCl, methylene blue (MB)-mediated PDT, or combined ultrasonic irrigation and PDT as described above. Quantification of E. faecalis was performed on the root canals before and immediately after the disinfection treatment. Residual bacteria were determined by counting colony-forming units. Samples were randomly selected from the three groups, and the morphology of residual bacteria inside the dentinal tubules was studied by scanning electron microscopy. The number of surviving E. faecalis in the group treated with the combination method was significantly lower (P < 0.05) than those in the ultrasonic irrigation-treated or PDT-treated groups. Similar results were found in the morphological studies of the three groups. The results of our study highlighted the importance of combination of ultrasonic irrigation and PDT to produce significant antibacterial efficacy against E. faecalis during root canal disinfection.

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Enterococcus faecalis is one of the primary organisms that play an important role in post-treatment endodontic failure. The results of this study shown that a synergistic root canal disinfection strategy combining ultrasonic irrigation with photodynamic therapy together had a significant effect on the viability of Enterococcus faecalis in infected root canals.

Quelle: Photochemistry and Photobiology | 18 Jun 2014 | 1:53 pm CEST

New Advances in Protection Against Solar Ultraviolet Radiation in Textiles for Summer Clothing

Abstract

Clothing is considered one of the most important tools for photoprotection against harmful solar ultraviolet radiation (UVR). The standard for sun-protective clothing is based on erythema despite other biological effects of UVR on the skin. We analyzed the potential protection against UVR in fabrics destined for summer clothing based on several action spectra. We examined 50 garments classified by type of fabric composition, structure of the fiber yarn and color. The ultraviolet protection factor was calculated based on fabric ultraviolet transmittance corrected for erythema according to the EU standard E-13758 as well as the UVA transmittance of fabrics. UVR protection was also analyzed in base of different action spectra as for previtamin D3, nonmelanoma skin cancer, photoimmunosuppression and photoaging. Most knitted fabrics used for sports T-shirts offered excellent ratings for ultraviolet protection while normal shirts showed very low ratings, particularly against photoaging. The cover is the most influential variable in fabric photoprotection, having an exponential relationship with the UPF. The relation between cover and UVA protection was linearly negative. Information about ultraviolet protection in textiles used for summer clothing should be included in labeling as some types of fabrics, especially those used for shirts, offer very low UVR protection.

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Microscopic analysis of different types of fabrics used in traditional summer clothing shows differences in structure, yarn and composition. Five different types of fabric were classified as follows: linen shirts (A), polyester shirts (B), T-shirts (C), polo T-shirts (D) and the latest generation of sport textiles (E), which leads to different abilities of light transmission, namely cover. Ultraviolet protection factor, based on the potential of protection against the erythematic fraction of UV radiation increases exponentially as the fabric cover does.

Quelle: Photochemistry and Photobiology | 18 Jun 2014 | 1:53 pm CEST

Photophysics, Excited-state Double-Proton Transfer and Hydrogen-bonding Properties of 5-Deazaalloxazines

Abstract

The photophysical properties of 5-deazaalloxazine and 1,3-dimethyl-5-deazaalloxazine were studied in different solvents. These compounds have higher values of fluorescence quantum yields and longer fluorescence lifetimes, compared to those obtained for their alloxazine analogs. Electronic structure and S0Si transitions were investigated using the ab initio methods [MP2, CIS(D), EOM-CCSD] with the correlation-consistent basis sets. Also the time-dependent density functional theory (TD-DFT) has been employed. The lowest singlet excited states of 5-deazaalloxazine and 1,3-dimethyl-5-deazaalloxazine are predicted to have the π, π* character, whereas similar alloxazines have two close-lying π, π* and n, π* transitions. Experimental steady-state and time-resolved spectral studies indicate formation of an isoalloxazinic excited state via excited-state double-proton transfer (ESDPT) catalyzed by an acetic acid molecule that forms a hydrogen bond complex with the 5-deazaalloxazine molecule. Solvatochromism of both 5-deazaalloxazine and its 1,3-dimethyl substituted derivative was analyzed using the Kamlet–Taft scale and four-parameter Catalán solvent scale. The most significant result of our studies is that the both scales show a strong influence of solvent acidity (hydrogen bond donating ability) on the emission properties of these compounds, indicating the importance of intermolecular solute–solvent hydrogen-bonding interactions in their excited state.

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Photophysics of 5-deazaalloxazine and its 1,3-methyl substituted derivatives in different solvents indicate strong influence of solvent acidity on their emission properties. The experimental results are compared to the theoretical calculations on different level of theory. Excited-state double-proton transfer of 5-deazaalloxazine in methylene chloride in the presence of acetic acid has been detected and studied.

Quelle: Photochemistry and Photobiology | 5 Jun 2014 | 1:04 pm CEST

The Photolytic Activity of Poly-Arginine Cell Penetrating Peptides Conjugated to Carboxy-tetramethylrhodamine is Modulated by Arginine Residue Content and Fluorophore Conjugation Site

Abstract

Upon light irradiation, Fluorophore–cell-penetrating peptide (Fl-CPP) conjugates can disrupt the integrity of biological membranes. This activity can in turn be used to photoinduce the disruption of endocytic organelles and promote the delivery of entrapped macromolecules such as proteins or RNAs into live cells. Recent mechanistic studies have shown that ROS production by the fluorophore and a latent lytic ability of CPPs act in synergy to elicit photolysis. However, how the structure of fluorophore-CPP conjugates impacts this synergistic activity remains unclear. Herein, using red blood cells (RBCs) as a model of biological membranes, we show that the number of arginine residues in a CPP as well as the position of fluorophore with respect to the CPP dramatically affect the photolytic activity of a fluorophore-CPP conjugate. These factors should therefore be considered for the development of effective photoinducible delivery agents.

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Fluorophore–cell-penetrating peptide (Fl-CPP) conjugates can disrupt membranes of endocytic organelles upon light irradiation and promote the delivery of entrapped macromolecules such as proteins or nucleic acids into a cells’ cytosol. ROS production by the fluorophore and a latent lytic ability of CPPs act in synergy to elicit photolysis. In this report, using red blood cells as a model of biological membranes, we show that the number of arginine residues in a CPP as well as the position of fluorophore with respect to the CPP dramatically affect the photolytic activity of a fluorophore–CPP conjugate. These factors should therefore be considered for the development of effective photoinducible delivery agents.

Quelle: Photochemistry and Photobiology | 3 Jun 2014 | 9:28 am CEST

Combination of Oral Vitamin D3 with Photodynamic Therapy Enhances Tumor Cell Death in a Murine Model of Cutaneous Squamous Cell Carcinoma

Abstract

Photodynamic therapy (PDT), in which 5-ALA (a precursor for protoporphyrin IX, PpIX) is administered prior to exposure to light, is a nonscarring treatment for skin cancers. However, for deep tumors, ALA-PDT is not always effective due to inadequate production of PpIX. We previously developed and reported a combination approach in which the active form of vitamin D3 (calcitriol) is given systemically prior to PDT to improve PpIX accumulation and to enhance PDT-induced tumor cell death; calcitriol, however, poses a risk of hypercalcemia. Here, we tested a possible strategy to circumvent the problem of hypercalcemia by substituting natural dietary vitamin D3 (cholecalciferol; D3) for calcitriol. Oral D3 supplementation (10 days of a 10-fold elevated D3 diet) enhanced PpIX levels 3- to 4-fold, and PDT-mediated cell death 20-fold, in subcutaneous A431 tumors. PpIX levels and cell viability in normal tissues were not affected. Hydroxylated metabolic forms of D3 were only modestly elevated in serum, indicating minimal hypercalcemic risk. These results show that brief oral administration of cholecalciferol can serve as a safe neoadjuvant to ALA-PDT. We suggest a clinical study, using oral vitamin D3 prior to PDT, should be considered to evaluate this promising new approach to treating human skin cancer.

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We report the results of a preclinical study in mice, showing that a combination of oral vitamin D (vit D3) and PDT can improve therapeutic killing of subcutaneous SCC tumors without the risk of hypercalcemia usually associated with calcitriol, the active hormonal form of vit D3. Dietary supplementation with vit D3 (10 days) enhanced PpIX levels, promoted tumor differentiation and proliferation and resulted in enhanced tumor cell death following PDT. These data suggest that a clinical study using oral vit D3 prior to PDT could establish a promising new approach for effective therapy of nonmelanoma skin cancer.

Quelle: Photochemistry and Photobiology | 26 May 2014 | 6:46 am CEST

Risk of Ocular Exposure to Biologically Effective UV Radiation in Different Geographical Directions

Abstract

To quantify ocular exposure to solar ultraviolet radiation (UVR) and to assess the risk of eye damage in different geographical directions due to UVR exposure, we used a spectrometer and a manikin to measure horizontal ambient and ocular exposure UVR in different geographical directions at four different locations at the Northern Hemisphere. Describing the relationship of exposure to risk of eye damage requires the availability of UV hazard weighting function. So, we used the UV hazard weighting function (ICNIRP) proposed by International Commission on Non-Ionizing Radiation Protection to determine the biologically effective UV irradiance (UVBEeye) and then cumulative effective radiant exposure (Heye) to shown the risk of eye. We found that in different geographical directions, distributions of ocular exposure to UVR were markedly different from those of horizontal ambient UVR. When the midday maximum SEA > 50°, eye received more UVR from the east and west directions during the morning and evening hours, respectively. However, when the midday maximum SEA < 50°, eye received more UVR from the south direction at noon. The results of this research indicate that the higher risk of eye caused by UVR varies according to the midday maximum SEA corresponding to different geographical direction.

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The image shows the distributions of the 1-h cumulative effective radiant exposure (Heye, in J m−2) in 60 geographical directions. The maximum 1-h cumulative Heye values in the six trials ranged from 45 to 59 J m−2. The dangerous periods in summer (Trials 1–3) occurred between 9:00 and 10:00 CST around east and between 15:00 and 16:00 CST around west. In Trials 4–6, the dangerous period was at noon (12:00–13:00 CST) around south. The higher risk of eye caused by biologically effective UV radiation varies according to the midday maximum SEA corresponding to different geographical direction.

Quelle: Photochemistry and Photobiology | 23 May 2014 | 9:26 am CEST

Photooxidation of Tetrahydrobiopterin under UV Irradiation: Possible Pathways and Mechanisms

Abstract

Tetrahydrobiopterin (H4Bip) is a cofactor for several key enzymes, including NO synthases and aromatic amino acid hydroxylases (AAHs). Normal functioning of the H4Bip regeneration cycle is extremely important for the work of AAHs. Oxidized pterins may accumulate if the H4Bip regeneration cycle is disrupted or if H4Bip autoxidation occurs. These oxidized pterins can photosensitize the production of singlet molecular oxygen 1O2 and thus cause oxidative stress. In this context, we studied the photooxidation of H4Bip in phosphate buffer at pH 7.2. We found that UV irradiation of H4Bip affected its oxidation rate (quantum yield Φ300 = (2.7 ± 0.4) × 10−3). The effect of UV irradiation at λ = 350 nm on H4Bip oxidation was stronger, especially in the presence of biopterin (Bip) (Φ350 = (9.7 ± 1.5) × 10−3). We showed that the rate of H4Bip oxidation linearly depends on Bip concentration. Experiments with KI, a selective quencher of triplet pterins at micromolar concentrations, demonstrated that the oxidation is sensitized by the triplet state biopterin 3Bip. Apparently, electron transfer sensitization (Type-I mechanism) is dominant. Energy transfer (Type-II mechanism) and singlet oxygen generation play only a secondary role. The mechanisms of H4Bip photooxidation and their biological meaning are discussed.

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The photochemistry of tetrahydrobiopterin (H4Bip) has never been studied, probably because it is pretty unstable. This cofactor is essential for higher organisms as it participates in several important biocatalytic reactions. We studied the photooxidation of H4Bip using HPLC and absorption spectroscopy. The process of H4Bip oxidation is induced by triplet state biopterin 3Bip. Apparently, electron transfer sensitization (Type-I mechanism) is dominant. Energy transfer (Type-II mechanism) and singlet oxygen generation play only a secondary role. The mechanisms of H4Bip photooxidation and their biological application are discussed in the context of vitiligo etiology.

Quelle: Photochemistry and Photobiology | 20 May 2014 | 8:28 am CEST

Therapeutic Effects of Full Spectrum Light on the Development of Atopic Dermatitis-like Lesions in NC/Nga Mice

Abstract

Full spectrum light (FSL) includes UVA, visible light and infrared light. Many studies have investigated the application of FSL in severe cases of atopic dermatitis (AD) in humans; however, FSL has not yet been studied in an animal model. The purpose of this study was to evaluate the therapeutic effects of FSL on AD-like skin lesions using NC/Nga mice, with the aim of mitigating itching and attenuating the expression of adhesion molecules. We examined the effects of FSL on mite allergen-treated NC/Nga mice by assessing skin symptom severity, ear thickness, serum IgE levels, and the cytokine expression. We examined the histology of lesions using hematoxylin–eosin, toluidine blue and immunohistochemical staining. Our findings suggest that FSL phototherapy exerts positive therapeutic effects on Dermatophagoides farinae (Df)-induced AD-like skin lesions in NC/Nga mice by reducing IgE levels, thus promoting recovery of the skin barrier. The mechanisms by which FSL phototherapy exerts its effects may also involve the inhibition of scratching behavior, reduction of IL-6 levels and reductions in adhesion molecule expression. The present study indicates that FSL phototherapy inhibits the development of AD in NC/Nga mice by suppressing cytokine, chemokine and adhesion molecule expression, and thus, could potentially be useful in treating AD.

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Full spectrum light includes UVA, visible light and infrared light. FSL phototherapy exerts positive therapeutic effects on Df-induced AD-like skin lesions in NC/Nga mice by reducing IgE levels, thus promoting recovery of the skin barrier. The mechanisms by which FSL phototherapy exerts its effects may involve the inhibition of scratching behavior, reduction of IL-6 levels and reductions in the levels of expression of adhesion molecules. The present study indicates that FSL phototherapy inhibits the development of AD in NC/Nga mice by suppressing the expression of cytokines, chemokines and adhesion molecules, and thus could potentially be useful in treating AD.

Quelle: Photochemistry and Photobiology | 19 May 2014 | 11:05 am CEST

Reversible Effects of Photodamage Directed Toward Mitochondria

Abstract

When the initial effect of photodynamic therapy (PDT) involves mitochondrial photodamage, an early effect is loss of the mitochondrial membrane potential (ΔΨm). Using murine hepatoma 1c1c7 cells and a photosensitizing agent known to target mitochondria, we examined loss of ΔΨm, initiation of apoptosis and loss of viability as a function of time and light dose. There was a correlation between loss of viability and the rapid disappearance of ΔΨm, as detected by the potential-sensitive probe Mitotracker Orange (MTO). Loss of ΔΨm was, however, reversible even with a substantial loss of viability. Unless there was a supralethal level of photodamage, 1c1c7 cells recovered their mitochondrial membrane potential, even if the cell population was on the pathway to apoptosis and cell death. These results indicate that when mitochondria are the initial PDT target, a qualitative estimate of photokilling can be provided by assessing the initial loss of ΔΨm.

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Loss of mitochondrial membrane potential (Δψm) directly after mitochondrial photodamage predicts for the subsequent loss of viability as determined by a clonogenic assay. MitoTracker Orange was used as the fluorescent probe for Δψm.

Quelle: Photochemistry and Photobiology | 14 May 2014 | 8:41 am CEST

Potentiation of photoinactivation of Gram-positive and Gram-negative bacteria mediated by six phenothiazinium dyes by addition of azide ion

Photochem. Photobiol. Sci., 2014, 13,1541-1548
DOI: 10.1039/C4PP00021H, Paper
Kamola R. Kasimova, Magesh Sadasivam, Giacomo Landi, Tadeusz Sarna, Michael R. Hamblin
Antimicrobial photodynamic inactivation (APDI) using six different phenothiazinium dyes is mediated by singlet oxygen (quenched by azide) and hydroxyl radicals (potentiated by azide) depending on Gram-classification of the bacteria and whether the dye is washed from the cells.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 7 May 2014 | 1:00 am CEST

Activation of Sperm EGFR by Light Irradiation is Mediated by Reactive Oxygen Species

Abstract

To acquire fertilization competence, spermatozoa must undergo several biochemical and motility changes in the female reproductive tract, collectively called capacitation. Actin polymerization and the development of hyperactivated motility (HAM) are part of the capacitation process. In a recent study, we showed that irradiation of human sperm with visible light stimulates HAM through a mechanism involving reactive-oxygen-species (ROS), Ca2+ influx, protein kinases A (PKA), and sarcoma protein kinase (Src). Here, we showed that this effect of light on HAM is mediated by ROS-dependent activation of the epidermal growth factor receptor (EGFR). Interestingly, ROS-mediated HAM even when the EGFR was activated by EGF, the physiological ligand of EGFR. Light irradiation stimulated ROS-dependent actin polymerization, and this effect was abrogated by PBP10, a peptide which activates the actin-severing protein, gelsolin, and causes actin-depolymerization in human sperm. Light-stimulated tyrosine phosphorylation of Src-dependent gelsolin, resulting in enhanced HAM. Thus, light irradiation stimulates HAM through a mechanism involving Src-mediated actin polymerization. Light-stimulated HAM and in vitro-fertilization (IVF) rate in mouse sperm, and these effects were mediated by ROS and EGFR. In conclusion, we show here that irradiation of sperm with visible light, enhances their fertilization capacity via a mechanism requiring ROS, EGFR and HAM.

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We previously showed that light irradiation of human sperm induces ROS production in the mitochondria. In turn, ROS activate voltage–dependent-Ca2+ channels causing elevation of intracellular Ca2+ which activates soluble adenylyl cyclase (sAC) resulting in cAMP production and PKA activation. We also show that PKA activates Src, which phosphorylates EGFR and gelsolin, resulting in increased actin polymerization and hyperactivation. Here, we show that visible-light irradiation of human spermatozoa, enhances ROS-dependent-EGFR phosphorylation/activation and actin polymerization leading to stimulation of hyperactivated motility. Moreover, light irradiation of mouse sperm enhances fertilization capacity mediated by ROS, EGFR and hyperactivated motility.

Quelle: Photochemistry and Photobiology | 2 May 2014 | 11:12 am CEST

Photoactive Titania Float for Disinfection of Water; Evaluation of Cell Damage by Bioanalytical Techniques

Abstract

A photoactive float was fabricated with the modified titania to cause a feasible disinfection of water, contaminated with E. coli. The commercially available titania was doped with neodymium by pulverization technique to enhance its activity in sunlight and a multiapproach technique was used to evaluate the extended efficiency of the doped sample. X-ray diffraction patterns depicted the retention of anatase phase on doping and the existence of neodymium was confirmed by the energy dispersive atomic X-ray analysis and the X-ray photoelectron spectroscopy. Transmission electron microscopy and Bruner–Emmett–Teller analysis depicted a marginal increase in the particle size and a decrease in the surface area, respectively. Doping induces semiconductor behavior with lower band energy that could respond to visible light and exhibit better disinfection activity. The “f” and “d” transitions of the lanthanide in doped sample caused new electronic behavior of trapping/detrapping effect together with bandgap narrowing. The amount of malondialdehyde, protein, DNA and RNA released on destruction of E. coli was observed to be 0.915 × 10−3 μg mL−1, 859.912 μg mL−1, 20.173 μg mL−1 and 1146.073 μg mL−1, respectively. The above analytical methods along with standard plate count method substantiated the enhanced disinfection efficiency of the doped sample in sunlight.

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The titania-coated polymeric float effectively disintegrates the bacteria by adsorption and diffusion to cause complete disintegration of cell membrane and thus disinfects water.

Quelle: Photochemistry and Photobiology | 25 Apr 2014 | 9:24 am CEST

Preliminary Ultrasonication Affects the Rate of the Bacteriorhodopsin Bleaching and the Effectiveness of the Reconstitution Process in Bacterioopsin

Abstract

The formation process of polymer films based on bacteriorhodopsin (BR) analogs requests a high amount of BR samples one time only. The common technique for apomembrane formation (preparation of bacterioopsin, BO) is not designed to be operated with high concentrations and high volumes of BR, so the use of this technique results in a low rate of BR bleaching. To accelerate the process of BR bleaching preliminary sonication was used. It was used just as preliminary sonication before bleaching of BR samples, so also sonication was used before reconstitution of resulted BO samples. These modifications of the common technique lead to an acceleration of BR bleaching and an increase in effectiveness of reconstitution of BO in comparison with the nonmodified technique. The quantitative results of sonication's effect on the bleaching acceleration and the effectiveness of reconstitution are different depending on the BR strains.

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A high-concentrated BR suspension is bleached in a PHA reaction at a very low rate. To accelerate this reaction the preliminary ultrasonication (kGz range) has been used. This is largely responsible for increasing the rate of this reaction and high quality of resulted apomembrane. A further process of apomembrane reconstitution with retinal relies upon preliminary ultrasonication (kGz range) of a high-concentrated apomembrane either. After ultrasonication the effectiveness of reconstitution has been increased. The quantitative characteristics of two processes depend upon types of BR strains. So, we offer a simple way to enhance the PM bleaching and AM reconstitution.

Quelle: Photochemistry and Photobiology | 21 Apr 2014 | 7:56 am CEST

Sun exposure and Protection Behavior of Danish Farm Children: Parental Influence on Their Children

Abstract

Healthy sun habits acquired in childhood could reduce skin cancer incidence. We examined the sun exposure and protection behavior of an expected high-exposure group of children, and the association to their parents. Open, prospective cohort study. One hundred and thirty nine participants (40 families) kept daily sun behavior diaries (sun exposure, sunscreen use, sunburns) over a 4-month summer period (15 985 diary days). The Pigment Protection Factor (PPF), an objective measure of sun exposure, was measured at two body sites, before and after summer. All participants presented data from the same 115 days. Risk behavior (sun exposure of upper body) took place on 9.5 days (boys) and 15.6 days (girls). Sunburn and sunscreen use were infrequent. Boys’ sun exposure resulted in an increased photo protection over the study period of 1.7 SED (upper arm) and 0.8 SED (shoulder) to elicit erythema. Corresponding values for girls were as follows: 0.9 SED (upper arm) and 0.5 SED (shoulder). Boys’ sunscreen use correlated to their mothers’ (= 0.523, = 0.02). Girls’ number of risk days (= 0.552, = 0.005) and sun exposure (upper arm: = 0.621, < 0.001) correlated to their mothers’. The children's sun exposure was substantial. Only mothers influenced children's sun behavior and exposure. This may be of relevance in future sun protection campaigns.

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We examined sun exposure and protection behavior in children, and the association to their parents. Sun behavior was recorded daily during summer (15 985 diary days) and the Pigment Protection Factor (PPF) was used as an objective measure of sun exposure. Risk behavior (upper body sun exposure) was exhibited on 9.5 days (boys) and 15.6 days (girls). Sunburn and sunscreen use were infrequent. Boys’ and girls’ sun exposure produced an increased photo protection of 1.7 and 0.9 SED (upper arm), respectively, and 0.8 and 0.5 SED (shoulder), respectively. Boys’ sunscreen use and girls’ number of risk days and sun exposure correlated with their mothers.

Quelle: Photochemistry and Photobiology | 21 Apr 2014 | 7:56 am CEST

“Pointsource” Delivery of a Photosensitizer Drug and Singlet Oxygen: Eradication of Glioma Cells In Vitro

Abstract

We describe a pointsource sensitizer-tipped microoptic device for the eradication of glioma U87 cells. The device has a mesoporous fluorinated silica tip which emits singlet oxygen molecules and small quantities of pheophorbide sensitizer for additional production of singlet oxygen in the immediate vicinity. The results show that the device surges in sensitizer release and photokilling with higher rates about midway through the reaction. This was attributed to a self-amplified autocatalytic reaction where released sensitizer in the extracellular matrix provides positive feedback to assist in the release of additional sensitizer. The photokilling of the glioma cells was analyzed by global toxicity and live/dead assays, where a killing radius around the tip with ~0.3 mm precision was achieved. The implication of these results for a new PDT tool of hard-to-resect tumors, e.g. in the brain, is discussed.

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A sensitizer-tipped microoptic device for the eradication of glioma U87 cells is described. The device has a porous silica tip that emits 1O2 molecules and small quantities of pheophorbide sensitizer for additional production of 1O2 in the immediate vicinity. The implication of these results for a new PDT tool of hard-to-resect tumors, e.g. in the brain, is discussed.

Quelle: Photochemistry and Photobiology | 21 Apr 2014 | 7:54 am CEST

Excited State Photoreaction between the Indole Side Chain of Tryptophan and Halocompounds Generates New Fluorophores and Unique Modifications

Abstract

Photoreaction of indole containing compounds with chloroform and other trichlorocompounds generates products with redshifted fluorescence. In proteins, this reaction can be used for the fluorescent detection of proteins. Little characterization of products generated through the photochemical reaction of indoles with halocompounds has been done, yet is fundamental for the development of other fluorophores, protein labeling agents, and bioactive indole derivatives. Here, we have characterized which isomers form in the photoreaction between tryptophan and chloroform using 1H-NMR of tryptophan and methylated derivatives to reveal that the two major products that are formed result from modification at the 4- and 6-carbon positions of the indole ring. Reaction at position 6 generates 6-formyl tryptophan and the reaction at position 4 generates an imine because the formyl derivative that is initially formed reacts further with the tryptophan amine group. The spectroscopic properties and product molecular weights of photoproducts formed from photoreaction of tryptophan with other trihalo and monohalocompounds are also determined. The indole ring of tryptophan can be modified with various additions from halocompounds, including the addition of labels to the indole ring via methylene groups. This opens possibilities for generating novel tryptophan based fluorophores and protein labeling strategies using this photochemistry.

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Several fluorophores were produced by photoreactions between the amino acid tryptophan and halocompounds. The reaction with trihalocompounds in aqueous solution yielded products with carbonyl groups conjugated to the aromatic system at the 4 and 6 positions of the indole fluorophore and led to emission near 500 nm. This photoreaction also proceeded with monohalocompounds, but resulted in additions to the indole fluorophore without enlarging the conjugated systems so that the fluorescence properties of the indole in tryptophan did not change significantly.

Quelle: Photochemistry and Photobiology | 17 Apr 2014 | 12:54 pm CEST

Observation of Magnetic Field Effects on Transient Fluorescence Spectra of Cryptochrome 1 From Homing Pigeons

Abstract

Cryptochromes are suggested to be involved in the bird magnetoreception based on the radical pair mechanism (RPM), a well established theory of weak magnetic field effects on chemical reactions. Two members of cryptochrome/photolyase family were found to respond to magnetic field, however, no direct responses of bird cryptochrome to magnetic field as weak as the Earth's magnetic field have been obtained so far. In this study, we used transient fluorescence spectroscopy to characterize the weak magnetic field effects of bird cryptochromes. To do this, we cloned the cryptochrome 1 gene (clCRY1) from the retina of homing pigeons (Columba livia), expressed it in insect Sf9 cells and analyzed the transient fluorescence of purified clCRY1 by application of 45–300 μT magnetic fields. The flavin adenine dinucleotide (FADox) and glucose oxidase (GOD) in PBS buffer were set as controls which could be excited by light to generate radicals, but would not be sensitive to magnetic field. We observed that the transient fluorescence spectra of clCRY1 were sensitive to the applied magnetic field at room temperature. Our result provides a new proof of the cryptochrome-based model of avian magnetoreception in vitro.

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Cryptochrome is suggested to be the most probable candidate magnetoreceptor in bird magnetoreception. Two members of cryptochrome/photolyase family have been found to be sensitive to the magnetic field and the magnetic sensitivity was proposed to be the general feature of this protein family. In this study, we constructed a magnetic field by Helmholtz coils and tested the magnetic field effects on the transient fluorescence of cryptochrome from homing pigeons at room temperature. Our results showed that, comparing to other flavin controls, the transient fluorescence of clCRY1 protein is sensitive to microtesla level magnetic field.

Quelle: Photochemistry and Photobiology | 17 Apr 2014 | 12:54 pm CEST

Chlorin e6 Derivative Radachlorin Mainly Accumulates in Mitochondria, Lysosome and Endoplasmic Reticulum and Shows High Affinity toward Tumors in Nude Mice in Photodynamic Therapy

Abstract

The efficacy of photodynamic therapy (PDT) depends upon the amount of photosensitizer accumulated in the malignant tissues. Radachlorin is a popular photosensitizer used in photodynamic therapy to treat various types of cancer. In this study, we have studied the main organelles responsible for the accumulation of radachlorin in human anaplastic thyroid cancer in vitro and in vivo. The optimal time window for uptake and clearance of radachlorin also was studied. Confocal microscopic images confirmed that the radachlorin is mainly acquired by mitochondria and partially by lysosome and endoplasmic reticulum. Studies also showed that the maximum amount of radachlorin was accumulated within 3–6 h after the treatment. Radachlorin also showed a higher affinity toward malignant tumors compared to the other organs in mice xenograft model. Uptake of radachlorin reached an optimum amount within 6 h and most of the radachlorins were also cleared from the body in next 48 h. Therefore, detailed information regarding exact accumulation sites and a time window in which maximum amount of drug is accumulated and cleared were obtained by this study. Hence, not only the efficacy of the treatment can be increased but the phototoxicity after the treatment also can be controlled.

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Cellular uptake and tumor affinity of chlorin e6 photosensitizer, radachlorin were studied in anaplastic thyroid cancer cells and xenograft nude mice model. Results showed radachlorin mainly accumulated in mitochondria and partially in lysosome and endoplasmic reticulum. It showed a higher accumulation in tumor site within 3–6 h and was further cleared from the tumor in next 24–48 h. Radachlorin also showed a higher efficacy in photodynamic therapy after 6 h of drug injection. Therefore, the knowledge of possible sites and time of photosensitizers accumulation in tumor cells may help in optimizing the efficacy of PDT.

Quelle: Photochemistry and Photobiology | 17 Apr 2014 | 12:54 pm CEST

Effect of Light on Expression of Clock Genes in Xenopus laevis Melanophores

Abstract

Light-dark cycles are considered important cues to entrain biological clocks. A feedback loop of clock gene transcription and translation is the molecular basis underlying the mechanism of both central and peripheral clocks. Xenopus laevis embryonic melanophores respond to light with melanin granule dispersion, response possibly mediated by the photopigment melanopsin. In order to test whether light modulates clock gene expression in Xenopus melanophores, we used qPCR to evaluate the relative mRNA levels of Per1, Per2, Clock and Bmal1 in cultured melanophores exposed to light-dark (LD) cycle or constant darkness (DD). LD cycles elicited temporal changes in the expression of Per1, Per2 and Bmal1. A 10-min pulse of blue light was able to increase the expression of Per1 and Per2. Red light had no effect on the expression of these clock genes. These data suggest the participation of a blue-wavelength sensitive pigment in the light-dark cycle-mediated oscillation of the endogenous clock. Our results add an important contribution to the emerging field of peripheral clocks, which in non-mammalian vertebrates have been mostly studied in Drosophila and Danio rerio. Within this context, we show that Xenopus laevis melanophores, which have already led to melanopsin discovery, represent an ideal model to understanding circadian rhythms.

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Quelle: Photochemistry and Photobiology | 26 Dec 2013 | 1:09 pm CET




 


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