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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:


Early Diagnosis of Diabetes Through The Eye

Abstract

Diabetes mellitus is a metabolic disorder characterized by high blood sugar levels which give rise to complications in the eye, kidneys and the brain. Diabetes triggers the development of ocular diseases like diabetic retinopathy and cataracts which are the leading cause of blindness around the world. The most common method for the diagnosis of diabetes involves measuring the blood sugar levels in the body. One major disadvantage of this method is the fluctuating blood sugar levels which contribute to false negative results. This leads to delay in treatment, eventually causing permanent damage to the organs. Therefore, diagnosis of diabetes at an early stage is very crucial. One biomarker for diabetes related diseases is the formation of Advanced Glycation End-products (AGEs) that result from the Maillard reaction of proteins with glucose. α-crystallin in the ocular lens is a small heat shock protein with no protein turnover and hence acts as a record for post-translational modifications especially glycation which forms AGEs. We have used steady state and time resolved fluorescence measurements to study the spectroscopic changes in α-crystallin with increase in time of glycation and the intact lenses from diabetic and non-diabetic donors. Overall, this study was focused on developing a non-invasive diagnostic tool for early detection of diabetes mellitus.

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Quelle: Photochemistry and Photobiology | 27 Aug 2015 | 4:37 pm CEST

The diffuse component of erythemal ultraviolet radiation

Photochem. Photobiol. Sci., 2015, Advance Article
DOI: 10.1039/C5PP00131E, Paper
Abel A. Silva
The diffuse (Dif) component of ultraviolet radiation (UVR) plays an important role in the daily exposure of humans to solar radiation.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 27 Aug 2015 | 1:00 am CEST

More Than Just Light: Clinical Relevance of Light Perception in the Nosocomial Pathogen Acinetobacter baumannii and Other Members of the Genus Acinetobacter

Abstract

A summary of the major findings concerning light modulation in Acinetobacter baumannii, which governs aspects related to the success of this microorganism as a nosocomial pathogen, is presented. Particularly, the evidence shows that light modulates the ability of the bacteria to persist in the environment, its virulence against eukaryotic hosts and even susceptibility to certain antibiotics. The light signal is sensed through different mechanisms, in some cases involving specialized photoreceptors of the BLUF-type, while in others, directly by a photosensitizer molecule. We also provide new data concerning the genomic context of BLUF-domain containing proteins within the genus Acinetobacter, as well as further insights into the mechanism of light-mediated reduction of susceptibility to antibiotics. The overall information points towards light being a crucial stimulus in the lifestyle of members of the genus Acinetobacter as well as in other clinically-relevant species, such as members of the ESKAPE group, playing therefore an important role in the clinical settings.

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Quelle: Photochemistry and Photobiology | 25 Aug 2015 | 9:21 am CEST

Epigenetically Enhanced Photodynamic Therapy (ePDT) is Superior to Conventional Photodynamic Therapy for Inducing Apoptosis in Cutaneous T-Cell Lymphoma

Abstract

Conventional photodynamic therapy with aminolevulinate (ALA-PDT) selectively induces apoptosis in diseased cells and is highly effective for treating actinic keratoses. However, similar results are achieved only in a subset of patients with cutaneous T-cell lymphoma (CTCL). Our previous work shows that the apoptotic resistance of CTCL correlates with low expression of death receptors like FAS, and that methotrexate upregulates FAS by inhibiting the methylation of its promoter, acting as an epigenetic derepressor that restores the susceptibility of FAS-low CTCL to caspase 8-mediated apoptosis. Here, we demonstrate that methotrexate increases the response of CTCL to ALA-PDT, a concept we refer to as epigenetically enhanced PDT (ePDT). Multiple CTCL cell lines were subjected to conventional PDT versus ePDT. Apoptotic biomarkers were analyzed in situ with multispectral imaging analysis of immunostained cells, a method that is quantitative and 5x more sensitive than standard immunohistology for antigen detection. Compared to conventional PDT or methotrexate alone, ePDT led to significantly greater cell death in all CTCL cell lines tested by inducing greater activation of caspase 8-mediated extrinsic apoptosis. Upregulation of FAS and/or TRAIL pathway components was observed in different CTCL cell lines. These findings provide a rationale for clinical trials of ePDT for CTCL.

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Quelle: Photochemistry and Photobiology | 25 Aug 2015 | 9:08 am CEST

Caffeic Acid Inhibits UVB-induced Inflammation and Photocarcinogenesis Through Activation of Peroxisome Proliferator-activated Receptor-γ in Mouse Skin

Abstract

In this study, the effect of caffeic acid (CA) on both acute and chronic UVB-irradiation induced inflammation and photocarcinogenesis was investigated in Swiss albino mice. Animals were exposed to 180 mJ/cm2 of UVB once daily for 10 consecutive days and thrice weekly for 30 weeks for acute and chronic study, respectively. UVB exposure for 10 consecutive days showed edema formation, increased lipid peroxidation, decreased antioxidant status with activation of inflammatory molecules such as TNF-α, IL-6, COX-2 and NF-κB. Whereas, CA (15 mg/kg.b.wt.) administration before each UVB exposure decreased lipid peroxidation, inflammatory markers expression and enhanced antioxidant status probably through the activation of peroxisome proliferator-activated receptors (PPARγ) in the mice's skin. PPARγ is considered to be a potential target for photochemoprevention because it inhibits UVB mediated inflammatory responses. In this study, UVB exposure for 30 weeks caused squamous cell carcinoma and upregulation of iNOS, VEGF, TGF-β and down-regulation of p53 and tumor incidence in the mice's skin. Both topical (CAT) and intraperitoneal (CAIP) treatment before each UVB exposure downregulates iNOS, VEGF, TGF-β, upregulates p53 and reduces tumors multiplicity in the mice's skin. Thus, CA offers protection against UVB-induced photocarcinogenesis probably through activation of anti-inflammatory transcription factor PPARγ in the mice.

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Quelle: Photochemistry and Photobiology | 25 Aug 2015 | 9:07 am CEST

Novel coumarin sensitizers based on 2-(thiophen-2-yl)thiazole [small pi]-bridge for dye-sensitized solar cell

Photochem. Photobiol. Sci., 2015, Accepted Manuscript
DOI: 10.1039/C5PP00216H, Paper
Liang Han, Rui Kang, Xiaoyan Zu, Yan-Hong Cui, Jianrong Gao
2-(Thiophen-2-yl)thiazole was introduced as a [small pi]-bridge into diethylamino coumarin and novel coumarin sensitizers were synthesized with cyanoacrylic acid or rhodanine acetic acid as electron acceptor. Their light-harvesting capabilities and photovoltaic...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 25 Aug 2015 | 1:00 am CEST

Determination of N-retinylidene-N-retinylethanolamine (A2E) levels in central and peripheral areas of human retinal pigment epithelium

Photochem. Photobiol. Sci., 2015, Accepted Manuscript
DOI: 10.1039/C5PP00156K, Paper
Leopold Adler IV, Nicholas P Boyer, David M Anderson, Jeffrey M Spraggins, Kevin L. Schey, Anne Hanneken, Zsolt Ablonczy, Rosalie Crouch, Yiannis Koutalos
The bis-retinoid N-retinylidene-N-retinylethanolamine (A2E) is one of the major components of lipofuscin, a fluorescent material that accumulates with age in the lysosomes of the retinal pigment epithelium (RPE) of the...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 25 Aug 2015 | 1:00 am CEST

Neutral and Cationic Pyridylbutadienes: Solvatochromism and Fluorescence Response with Sodium Cholate

Photochem. Photobiol. Sci., 2015, Accepted Manuscript
DOI: 10.1039/C5PP00179J, Paper
Harsha Agnihotri, Anuji K Vasu, Veerabhadraiah Palakollu, Sriram Kanvah
Neutral and cationic diarylbutadienes with pyridine and pyridinium groups as electron acceptor with dimethylamine and diphenylamine as electron donors were synthesized. The absorption and emission properties of these dienes were...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 25 Aug 2015 | 1:00 am CEST

Nonvisual Opsins and the Regulation of Peripheral Clocks by Light and Hormones

Abstract

The molecular clock machinery is conserved throughout evolution. However, how environmental cues are perceived has evolved in such a way that peripheral clocks in mammals require a variety of signals, including hormones. On the other hand, in nonmammalian cells able to directly detect light, light seems to play a major role in the synchronization of the clock. The interaction between perception of circadian light by nonvisual opsins and hormones will be discussed under the perspective of clock synchronization at the molecular level.

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Nonvisual opsins have a wide distribution in all vertebrate classes, even though their role in the modulation of peripheral clocks remains elusive. Together with light, hormones represent an important zeitgeber in the entrainment of peripheral clocks. In this review, we focus the entrainment of peripheral clocks of nonmammalian vertebrates by light and hormones, highlighting the main differences between mammalian and nonmammalian models. In addition, the putative photopigments and the signaling pathways triggered by light in ectothermic vertebrates are also discussed.

Quelle: Photochemistry and Photobiology | 24 Aug 2015 | 5:22 pm CEST

International Intercomparison of Solar UVR Spectral Measurement Systems in Melbourne in 2013

Abstract

Monitoring ambient solar UVR levels provides information on how much there is in both real time and historically. Quality assurance of ambient measurements of solar UVR is critical to ensuring accuracy and stability and this can be achieved by regular intercomparisons of spectral measurement systems with those of other organizations. In October and November of 2013 a solar UVR spectroradiometer from Public Health England (PHE) was brought to Melbourne for a campaign of intercomparisons with a new Bentham spectrometer of Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) and one at the Australian Bureau of Meteorology (BOM), supported by New Zealand's National Institute for Water and Atmosphere (NIWA). Given all three spectroradiometers have calibrations that are traceable to various national standards, the intercomparison provides a chance to determine measurement uncertainties and traceability that support UV measurement networks in Australia, New Zealand and the UK. UV Index measurements from all three systems were compared and ratios determined for clear sky conditions when the scans from each instrument were within 2 min of each other. While wavelengths below 305 nm showed substantial differences between the PHE unit and the two other systems, overall the intercomparison results were encouraging, with mean differences in measured UV Index between the BOM/NIWA and those of PHE and ARPANSA of <0.1% and 7.5%, respectively.

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A new CCD array spectrometer from the UK and two double monochromators based in Australia that make regular measurements of solar ultraviolet radiation were intercompared in Melbourne for a week in October and November of 2013. Each of the units is calibrated independently via a different calibration pathway and are used to underpin UV measurement networks in Australia, New Zealand and the UK. The CCD array spectrometer performed well in measuring UV index values in comparison with the other two traditional spectral systems.

Quelle: Photochemistry and Photobiology | 22 Aug 2015 | 7:34 am CEST

Functional Characterization of a LOV-Histidine Kinase Photoreceptor from Xanthomonas citri subsp. citri

Abstract

The blue-light (BL) absorbing protein Xcc-LOV from Xanthomonas citri subsp. citri is composed of a LOV-domain, a histidine kinase (HK) and a response regulator. Spectroscopic characterization of Xcc-LOV identified intermediates and kinetics of the protein's photocycle. Measurements of steady state and time-resolved fluorescence allowed determination of quantum yields for triplet (ΦT = 0.68 ± 0.03) and photoproduct formation (Φ390 = 0.46 ± 0.05). The lifetime for triplet decay was determined as τT = 2.4–2.8 μs. Fluorescence of tryptophan and tyrosine residues was unchanged upon light-to-dark conversion, emphasizing the absence of significant conformational changes. Photochemistry was blocked upon cysteine C76 (C76S) mutation, causing a seven-fold longer lifetime of the triplet state (τT = 16–18.5 μs). Optoacoustic spectroscopy yielded the energy content of the triplet state. Interestingly, Xcc-LOV did not undergo the volume contraction reported for other LOV domains within the observation time window, although the back-conversion into the dark state was accompanied by a volume expansion. A radioactivity-based enzyme function assay revealed a larger HK activity in the lit than in the dark state. The C76S mutant showed a still lower enzyme function, indicating the dark state activity being corrupted by a remaining portion of the long-lived lit state.

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Xanthomonas citri subsp. citri (Xcc) is the bacterium responsible for citrus canker. Xcc-LOV is a blue-light (BL) sensing, hybrid histidine-kinase protein. This spectroscopic characterization confirmed that Xcc-LOV presents a canonical LOV-photochemistry, involving the BL-induced formation of a covalent cystein-chromophore (flavin) adduct, preceded by a transient flavin triplet state and followed by thermal conversion into the dark state. Moreover, Xcc-LOV showed BL-induced kinase activity, initiating a signal transduction cascade. Therefore, we correlated the previously observed regulatory effects of BL on Xcc physiology and synthesis of effectors for maintaining plant energetic metabolism and counteracting plant defense, with the molecular activation of Xcc-LOV.

Quelle: Photochemistry and Photobiology | 20 Aug 2015 | 8:32 am CEST

Two-photon uncageable enzyme inhibitors bearing targeting vectors

Photochem. Photobiol. Sci., 2015, Advance Article
DOI: 10.1039/C5PP00245A, Communication
Philipp Anstaett, Vanessa Pierroz, Stefano Ferrari, Gilles Gasser
We report herein the development of two-photon sensitive protecting groups, which can be functionalized with targeting vectors, and are capable of releasing cyclooxygenase-II inhibitors upon irradiation at 800 nm.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 20 Aug 2015 | 1:00 am CEST

Applications of phototransformable fluorescent proteins for tracking dynamics of cellular components

Photochem. Photobiol. Sci., 2015, Accepted Manuscript
DOI: 10.1039/C5PP00174A, Perspective
Ina Nemet, Philip Ropelewski, Yoshikazu Imanishi
In the past few decades, fluorescent proteins have revolutionized the field of cell biology. Phototransformable fluorescent proteins are capable of changing their excitation and emission spectra after being exposed to...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 20 Aug 2015 | 1:00 am CEST

Effect of LED Blue Light on Penicillium digitatum and Penicillium italicum Strains

Abstract

Studies on the antimicrobial properties of light have considerably increased due in part to the development of resistance to actual control methods. This study investigates the potential of Light Emitting Diodes (LED) blue light for controlling Penicillium digitatum and Penicillium italicum. These fungi are the most devastating postharvest pathogens of citrus fruit and cause important losses due to contaminations and to the development of resistant strains against fungicides. The effect of different periods and quantum fluxes and of delaying light application on the growth and morphology of P. digitatum strains resistant and sensitive to fungicides and of P. italicum cultured at 20 °C was examined. Results showed that blue light controls the growth of all strains and that its efficacy increases with the quantum flux. Spore germination was always avoided by exposing the cultures to high quantum flux (700 μmolm−2s−1) for 18 h. Continuous light had an important impact on the fungus morphology and a fungicidal effect when applied at a lower quantum flux (120 μmolm−2s−1) to a growing fungus. Sensitivity to light increased with mycelium age. Results show that blue light may be a tool for P. digitatum and P. italicum infection prevention during handling of citrus fruits.

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Quelle: Photochemistry and Photobiology | 19 Aug 2015 | 5:14 pm CEST

Photodynamic Diagnosis Using 5-Aminolevulinic Acid in 41 Biopsies for Primary Central Nervous System Lymphoma

Abstract

We evaluated the feasibility of 5-aminolevulinic acid (5-ALA)-mediated photodynamic diagnosis (PDD) in the biopsy for primary central nervous system lymphoma (PCNSL). 5-ALA (20 mg/kg) was administered orally 4 hours preoperatively. Forty-one biopsies obtained under PDD in 47 consecutive biopsies (46 patients) that were finally pathologically diagnosed as PCNSL were evaluated. Positive fluorescence was observed in 34 of those 41 biopsies (82.9%). An intraoperative pathological diagnosis (IOD) of suspected PCNSL was made in 21 of the biopsies with positive fluorescence (61.8%). However, the 8 IODs in the remaining 13 biopsies (23.5%) were not correct (atypical cell, 4; high-grade glioma, 1; gliosis, 1; unremarkable, 2). In those 8 biopsies, PCNSL was confirmed by the final pathological diagnosis. There was no difference in the mean Mib-1 labeling index between the biopsies with positive fluorescence (86.5%) and those without (90.0%). IOD was not performed in 6 biopsies; however, 5 of those biopsies (83.3%) showed positive fluorescence and were finally pathologically diagnosed as PCNSL. Use of PDD in biopsies for patients with suspected PCNSL is a reliable way of obtaining specimens of adequate quality for the final pathological diagnosis and may lead to improved diagnostic yield in the biopsy of PCNSL.

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Quelle: Photochemistry and Photobiology | 16 Aug 2015 | 11:43 am CEST

Thermal Effects and Structural Changes of Photosynthetic Reaction Centers Characterized by Wide Frequency Band Hydrophone: Effects of Carotenoids and Terbutryn

Abstract

Photothermal characteristics and light-induced structural (volume) changes of carotenoid-containing and non-containing photosynthetic reaction centers were investigated by wide frequency band hydrophone. We found that the presence of carotenoid either does not play considerable role in the light-induced conformational movements, or these rearrangements are too slow for inducing a photoacoustic (PA) signal. The kinetic component with a few tens of microseconds, exhibited by the carotenoid-less reaction centers, appears to be similar to that of triplet state lifetimes, identified by other methods. The binding of terbutryn to the acceptor side is shown to affect the dynamics of the reaction center (RC). Our results do not confirm large displacements or volume changes induced by the charge movements and by the charge relaxation processes in the RCs in few hundreds of microseconds time scale that accompanies the electron transfer between the primary and secondary electron acceptor quinones.

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Quelle: Photochemistry and Photobiology | 16 Aug 2015 | 11:43 am CEST

Rethinking the Concepts of Fluence (UV Dose) and Fluence Rate: The Importance of Photon-based Units – A Systemic Review

Abstract

After a critical review of the fundamental equations describing photobiological and photochemical processes occurring in a medium exposed to a quasi-collimated monochromatic UV light beam, the analysis in this review is extended to analogous processes driven by polychromatic UV light, such as that emitted by medium pressure mercury-vapor arc lamps. The analysis is based on the Second Law of Photochemistry, namely that all photochemical events must be independent, and the rate of such events must be proportional to the rate of photon absorption. A consistent application of the Second Law of Photochemistry leads to a concept change; hence it is proposed herein to use photon fluence and photon fluence rate, rather than fluence (UV dose) and fluence rate, respectively, in the analysis and interpretation of photobiological and photochemical processes. As a consequence, many equations that have been used in the past must be revised, and some experimental information (e.g., action spectra) needs to be re-analyzed.

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Quelle: Photochemistry and Photobiology | 16 Aug 2015 | 11:43 am CEST

Preparation of Silver Carbonate and its Application as Visible Light-driven Photocatalyst Without Sacrificial Reagent

Abstract

Visible light-driven photocatalyst is the current research focus and silver oxyacid salts with p-block elements are the promising candidates. In this research, Ag2CO3 was prepared by a facile precipitation method and used to degrade the pollutants from waters. The results revealed that the silver carbonate with monoclinic structure quickly decomposed methyl orange and rhodamine B in less than 15 min under visible light irradiation. When it was recycled six times, the degradation of methyl orange still can reach 87% after 30 min. The calculated band gap of Ag2CO3 was 2.312 eV with Valence band edge potential of 2.685 eV and Conduction band 0.373 eV vs NHE, which endowed the excellent photo-oxidation ability of silver carbonate. Photogenerated holes and ozone anion radicals were the primary active species in the photo-oxidization degradation of dye. The generation of metallic silver resulted from photocorrosion and the consequent reduction in the ozone anion radical amount led to the performance degradation of Ag2CO3. The simple preparation method and high photocatalytic performance of Ag2CO3 increases its prospect of application in future.

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As-prepared Ag2CO3 possessed high photocatalytic performance which can quickly decompose methyl orange and rhodamine B in less than 15 min under visible light irradiation. The calculated band gap of Ag2CO3 was 2.312 eV with VB edge potential of 2.685 eV and CB 0.373 eV. Photogenerated ozone anion radicals and holes are determined as the major active species in the oxidation–reduction degradation of dye with Ag2CO3. The generation of metallic silver resulted from photocorrosion slightly decayed the performance of Ag2CO3 after recycling. The simple preparation method and high photocatalytic performance of Ag2CO3 increases its prospect of application in future.

Quelle: Photochemistry and Photobiology | 14 Aug 2015 | 11:43 am CEST

The Effect of pH Values on the Synthesis, Microstructure and Photocatalytic Activity of Ce-Bi2O3 by a Two-Step Hydrothermal Method

Abstract

In this study, the effect of pH values on the microstructure and photocatalytic activity of Ce-Bi2O3 under visible light irradiation was investigated in detail. In alkaline condition (e.g. pH = 9), the as-prepared Ce-Bi2O3 exhibited an agglomerated status and mesoporous structures without a long-range order. While in weak acid condition (e.g. pH = 5), the Ce-Bi2O3 exhibited a best morphology with irregular nanosheets. Correspondingly, it possessed largest surface area (24.641 m2 g−1) and pore volume (9.825E-02 cm3 g−1). These unique nanosheets can offer an attachment for pollutant molecules and reduce the distance of electron immigration from inner to surface, thus facilitating the separation of photoelectron and hole pairs. Compared with the pure Bi2O3, the band gap of Ce-Bi2O3 prepared at different pH was much lower. Among them, the band gap of Ce-Bi2O3 (pH of 5) was lowest (2.61 eV). Ce-Bi2O3 (pH of 5) exhibited as tetragonal crystal with the bismuth oxide in the form of the composites, which could reduce the band gap width or suppress the charge-carrier recombination, subsequently possessing great photocatalytic activity for acid orange II under visible light irradiation. After 2 h degradation under visible light, the degradation rate of acid Orange II was up to 96.44% by Ce-Bi2O3 prepared at pH 5. Overall, it can be concluded that the pH values had effects on the microstructure and photocatalytic activity of Ce-Bi2O3 catalysts.

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The pH values had effect on the microstructure and photocatalytic activity of Ce-Bi2O3 catalysts. At pH 5, the Ce-Bi2O3 exhibited a best morphology with irregular nanosheets. Correspondingly, it possessed largest surface area (24.641m2 g−1) and pore volume (9.825E-02cm3 g−1). Ce-Bi2O3 (pH of 5) exhibited as tetragonal crystal with the bismuth oxide in the form of the composites, which could reduce the band gap width (2.61 eV) and suppress the charge-carrier recombination, subsequently possessing great photocatalytic activity for acid orange II under visible light irradiation.

Quelle: Photochemistry and Photobiology | 13 Aug 2015 | 9:32 am CEST

Modulation of Melanogenesis and Antioxidant Status of Melanocytes in Response to Phototoxic Action of Doxycycline

Abstract

Doxycycline is a commonly used tetracycline antibiotic showing the broad spectrum of antibacterial action. However, the use of this antibiotic is often connected with the risk of phototoxic reactions that lead to various skin disorders. One of the factors influencing the photosensitivity reactions is the melanin content in melanocytes. In this study, the impact of doxycycline and UVA irradiation on cell viability, melanogenesis and antioxidant defense system in cultured normal human epidermal melanocytes (HEMn-DP) was examined. The exposure of cells to doxycycline and UVA radiation resulted in concentration-dependent loss in melanocytes viability and induced melanin biosynthesis. Significant changes were stated in cellular antioxidant enzymes activity: SOD, CAT and GPx, which indicates alterations of antioxidant defense system. The results obtained in vitro may explain the mechanisms of phototoxic reactions that occur in normal human epidermal melanocytes in vivo after exposure of skin to doxycycline and UVA radiation.

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Doxycycline enhances an UVA-mediated phototoxicity in normal human melanocytes.

Quelle: Photochemistry and Photobiology | 13 Aug 2015 | 9:30 am CEST

Synergistic Photobactericidal Activity Based on Ultraviolet-A Irradiation and Ferulic Acid Derivatives

Abstract

Ultraviolet-A (UV-A)-mediated bactericidal activity was enhanced by combined treatment with trans-ferulic acid (trans-FA, compound 1) or its derivatives. Derivative compounds 4 and 10 contain a phenyl group or an L-tyrosine HCl tert-butyl ester, respectively, linked to the carboxyl group of trans-FA. Of the three compounds, 10 exhibited the highest synergistic activity in a photobactericidal assay based on treating Escherichia coli with a derivative compound and UV-A irradiation (wavelength 350-385 nm). Inactivation of viable cells at a 4.9 J/cm2 UV-A fluence increased from 1.90 to 5.19 logs in the presence of 10 (100 μM); a 4.95-log inactivation was achieved with 10 (5 μM) and a 7.4 J/cm2 UV-A fluence. Addition of antioxidants significantly suppressed photosynergistic bactericidal activity, suggesting that reactive oxygen species (ROS) are involved in the combined bactericidal mechanism. Flow cytometry revealed that combined treatment with UV-A and compound 10, which showed the highest photobactericidal activity, generates an excess of oxidative radicals in bacterial cells. The bactericidal activity of compound 10 may be due to electrostatic interaction between the molecule's cationic moiety and the cell surface, followed by amplification of ROS generation in the cells.

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Quelle: Photochemistry and Photobiology | 13 Aug 2015 | 9:29 am CEST

Selective Activation of C=C Bond in Sustainable Phenolic Compounds from Lignin via Photooxidation: Experiment and DFT Calculations

Abstract

Lignocellulosic biomass can be converted to high-value phenolic compounds: food additives, antioxidants, fragrances, and fine chemicals. We investigated photochemical and heterogeneous photocatalytic oxidation of two isomeric phenolic compounds from lignin, isoeugenol and eugenol, in several non-protic solvents, for the first time by experiment and the DFT calculations. Photooxidation was conducted under ambient conditions using air, near-UV light, and commercial P25 TiO2 photocatalyst, and the products were determined by TLC, UV-Vis absorption spectroscopy, HPLC-UV, and HPLC-MS. Photochemical and photocatalytic oxidation of isoeugenol proceeds via the mild oxidative “dimerization” to produce the lignan dehydrodiisoeugenol (DHDIE), while photooxidation of eugenol does not proceed. The DFT calculations suggest a radical step-wise mechanism for the oxidative “dimerization” of isoeugenol to DHDIE as was calculated for the first time.

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Quelle: Photochemistry and Photobiology | 13 Aug 2015 | 9:29 am CEST

Photoactivated cyclases: In memoriam Masakatsu Watanabe

Photochem. Photobiol. Sci., 2015, Advance Article
DOI: 10.1039/C5PP00233H, Perspective
Peter Hegemann
In memoriam Masakatsu Watanabe.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 13 Aug 2015 | 1:00 am CEST

Photochemistry and Photobiology of the Spore Photoproduct: A Fifty Year Journey

Abstract

Fifty years ago, a new thymine dimer was discovered as the dominant DNA photolesion in UV irradiated bacterial spores [Donnellan, J. & Setlow R. (1965) Science, 149, 308-310], which was later named the spore photoproduct (SP). Formation of SP is due to the unique environment in the spore core that features low hydration levels favoring an A-DNA conformation, high levels of calcium dipicolinate that acts as a photosensitizer, and DNA saturation with small, acid-soluble proteins that alters DNA structure and reduces side reactions. In vitro studies reveal that any of these factors alone can promote SP formation; however, SP formation is usually accompanied by the production of other DNA photolesions. Therefore, the nearly exclusive SP formation in spores is due to the combined effects of these three factors. SP photoreaction is proved to occur via a unique H-atom transfer mechanism between the two involved thymine residues. Successful incorporation of SP into an oligonucleotide has been achieved via organic synthesis, which enables structural studies that reveal minor conformational changes in the SP-containing DNA. Here, we review the progress on SP photochemistry and photobiology in the past fifty years, which indicates a very rich SP photobiology that may exist beyond endospores.

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Quelle: Photochemistry and Photobiology | 12 Aug 2015 | 10:23 am CEST

Model for Optimization of the UV-A/Riboflavin Strengthening (cross-linking) of the Cornea: Percolation Threshold

Abstract

To achieve the maximum level of collagen strengthening within the shortest treatment time possible, we have developed a mathematical model which is used to optimize the process of corneal cross-linking. This model is able to predict the temporal and spatial distribution of generated cross-links within the corneal stroma and hence the increase in the elasticity modulus. Theory predicts corneal strengthening at low radiation intensities and the absence of the strengthening effect at radiation intensities above the threshold level, which agrees with the experimental results. The model takes account of the initial riboflavin concentration and bleaching, light intensity and time of illumination.

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To achieve the maximum level of collagen strengthening within the shortest treatment time possible, we have developed a mathematical model which is used to optimize the process of corneal cross-linking. This model is able to predict the temporal and spatial distribution of generated cross-links within the corneal stroma and hence the increase in the elasticity modulus. Theory predicts corneal strengthening at low radiation intensities and the absence of the strengthening effect at radiation intensities above the threshold level, which agrees with the experimental results. The model accounts for the initial riboflavin concentration and bleaching, light intensity and time of illumination.

Quelle: Photochemistry and Photobiology | 11 Aug 2015 | 2:34 pm CEST

The Evolution and Functional Role of Flavin-based Prokaryotic Photoreceptors

Abstract

Flavin-based photoreceptor proteins of the LOV (light, oxygen and voltage) superfamily are ubiquitous and appear to be essential blue-light sensing systems not only in plants, algae and fungi, but also in prokaryotes, where they are represented in more than 10% of known species. Despite their broad occurrence, only in few cases LOV proteins have been correlated with important phenomena such as bacterial infectivity, selective growth patterns or/and stress responses; nevertheless these few known roles are helping us understand the multiple ways by which prokaryotes can exploit these soluble blue-light photoreceptors. Given the large number of sequences now deposited in databases, it becomes meaningful to define a signature for bona fide LOV domains, a procedure that facilitates identification of proteins with new properties and phylogenetic analysis. The latter clearly evidences that a class of LOV proteins from alpha-proteobacteria is the closest prokaryotic relative of eukaryotic LOV domains, whereas cyanobacterial sequences cluster with the archaeal and the other bacterial LOV domains. Distance trees built for LOV domains suggest complex evolutionary patterns, possibly involving multiple horizontal gene transfer events. Based on available data, the in vivo relevance and evolution of prokaryotic LOV is discussed.

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Blue-light photosensors of the LOV type, related to plant phototropins, are wide spread among bacteria. What is their role in vivo and by which pathways did they evolve? Why to bacterial pathogens often see the same blue color as they host plants and in the same way? News and views on a burning photobiology topic.

Quelle: Photochemistry and Photobiology | 11 Aug 2015 | 11:56 am CEST

Activation of the General Stress Response of Bacillus subtilis by Visible Light

Abstract

A key challenge for microbiology is to understand how evolution has shaped the wiring of regulatory networks. This is amplified by the paucity of information of power-spectra of physicochemical stimuli to which microorganisms are exposed. Future studies of genome evolution, driven by altered stimulus regimes, will therefore require a versatile signal transduction system that allows accurate signal dosing. Here, we review the general stress response of Bacillus subtilis, and its upstream signal transduction network, as a candidate system. It can be activated by red and blue light, and by many additional stimuli. Signal integration therefore is an intricate function of this system. The blue-light response is elicited via the photoreceptor YtvA, which forms an integral part of stressosomes, to activate expression of the stress regulon of B. subtilis. Signal transfer through this network can be assayed with reporter enzymes, while intermediate steps can be studied with live-cell imaging of fluorescently tagged proteins. Different parts of this system have been studied in vitro, such that its computational modeling has made significant progress. One can directly relate the microscopic characteristics of YtvA with activation of the general stress regulon, making this system a very well-suited system for network evolution studies.

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The general stress response of Bacillus subtilis can be activated with blue and red light. The mechanism of its activation is well understood, to the extent that computational analysis allows one to recognize mutationally altered properties of blue-light photoreceptor protein YtvA (one of the components of high-molecular-weight complexes called stressosomes) in the in vivo output characteristics of the stress response. This system qualifies exceptionally well as a model system for future studies of genome evolution, driven by altered stimulus regimes.

Quelle: Photochemistry and Photobiology | 11 Aug 2015 | 11:55 am CEST

Microbial rhodopsins of Halorubrum species isolated from Ejinoor salt lake in Inner Mongolia of China

Photochem. Photobiol. Sci., 2015, Advance Article
DOI: 10.1039/C5PP00161G, Paper
Chaoluomeng, Gang Dai, Takashi Kikukawa, Kunio Ihara, Tatsuo Iwasa
A halophilic archaea that has three microbial rhodopsin-type genes in its genome was isolated from Ejinoor salt lake in Inner Mongolia of China.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 11 Aug 2015 | 1:00 am CEST

Broadband ultrafast photoprotection by oxybenzone across the UVB and UVC spectral regions

Photochem. Photobiol. Sci., 2015, Advance Article
DOI: 10.1039/C5PP00217F, Communication
Lewis A. Baker, Michael D. Horbury, Simon E. Greenough, Michael N. R. Ashfold, Vasilios G. Stavros
Recent studies have shed light on the energy dissipation mechanism of oxybenzone, a common ingredient in commercial sunscreens.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 11 Aug 2015 | 1:00 am CEST

Baicalin Protects Keratinocytes From Toll-Like Receptor-4 Mediated DNA Damage and Inflammation Following Ultraviolet Irradiation

Abstract

UVB radiation contributes to both direct and indirect damage to the skin including the generation of free radicals and reactive oxygen species (ROS), inflammatory responses, immunosuppression, and gene mutations, which can ultimately lead to photocarcinogenesis. A plant-derived flavonoid, baicalin, has been shown to have antioxidant, anti-inflammatory, and free radical scavenging activities. Previous studies from our laboratory have shown that in murine skin, Toll like receptor-4 (TLR4) enhanced both UVB-induced DNA damage and inflammation. The aim of the current study is to investigate the efficacy of baicalin against TLR4-mediated processes in the murine keratinocyte PAM 212 cell line. Our results demonstrate that treating keratinocytes with baicalin both before and after UV radiation (100 mJ/cm2) significantly inhibited the level of intracellular ROS and decreased cyclobutane pyrimidine dimers (CPDs) and 8-Oxo-2′-deoxyguanosine (8-oxo-dG)—markers of DNA damage. Furthermore, cells treated with baicalin demonstrated an inhibition of TLR4 and its downstream signaling molecules, MyD88, TRIF, TRAF6, and IRAK4. TLR4 pathway inhibition resulted in NF-κB inactivation and down-regulation of iNOS and COX-2 protein expression. Taken together, baicalin treatment effectively protected keratinocytes from UVB-induced inflammatory damage through TLR pathway modulation.

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Quelle: Photochemistry and Photobiology | 10 Aug 2015 | 9:42 am CEST

A Family of Potent Ru(II) Photosensitizers with Enhanced DNA Intercalation: Bimodal Photokillers

Abstract

A new family of Ru(II)-based photosensitizers was synthesized and systematically characterized. The ligands employed to coordinate the ruthenium metal center were the commercially available 2,2′-bipyridine and a pyridine-quinoline hybrid bearing an anthracene moiety. The complexes obtained carry either inline image or Cl counterions. These counterions determine the complexes' hydrophobic or hydrophilic character, respectively, therefore dictating their solubility in biologically related media. All photosensitizers exhibit characteristic, relatively strong and wide UV–Vis absorption spectral profiles. Their high efficiency in generating cytotoxic singlet oxygen was established (up to ΦΔ ~0.8). Moreover, the interaction of these photosensitizers with double-stranded DNA was studied fluoro- and photospectroscopically and their binding affinities were found to be of the order of 3 × 107 M−1. All complexes are photocytotoxic to DU145 human prostate cancer cells. The highest light-induced toxicity was conferred by the photosensitizers bearing Cl counterions, probably due to the looser ionic “chaperoning” of Cl, in comparison to inline image, leading to higher cell internalization.

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“Bipolar killers”: A novel series of Ru-based photosensitizers was synthesized and extensively characterized. All photosensitizers exhibited strong absorbance bands, widely spread in the UV–Vis spectral region and were found to be highly efficient in generating cytotoxic singlet oxygen, with quantum yields up to ΦΔ~0.8. More importantly, the Ru compounds were found to possess a bimodal cytotoxic profile: (1) They proved to be excellent DNA intercallators with potent DNA-photocleavage abilities; and (2) The compounds were very efficiently internalized by DU145 human prostate cancer cells, against which they exerted profound phototoxicity.

Quelle: Photochemistry and Photobiology | 8 Aug 2015 | 11:03 am CEST

Photoreceptors in Chemotrophic Prokaryotes: The Case of Acinetobacter spp. Revisited

Abstract

A comprehensive description of blue light using flavin (BLUF) photosensory proteins, including preferred domain architectures and the molecular mechanism of their light activation and signal generation, among chemotrophic prokaryotes is presented. Light-regulated physiological responses in Acinetobacter spp. from environmental and clinically relevant strains are discussed. The twitching motility response in A. baylyi sp. ADP1 and the joint involvement of three of the four putative BLUF-domain-containing proteins in this response, in this species, is presented as an example of remarkable photoreceptor redundancy.

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Most members of the genus Acinetobacter have at least one BLUF protein encoded in their genome. A. baylyi ADP1 has four of them, of which three are jointly involved in the inhibition of twitching motility in response to blue light at suboptimal temperatures.

Quelle: Photochemistry and Photobiology | 8 Aug 2015 | 11:03 am CEST

Identification and Purification of the CPD Photolyase in Vibrio parahaemolyticus RIMD2210633

Abstract

Photoreactivation is an error-free mechanism of DNA repair, utilized by prokaryotes and most eukaryotes and is catalyzed by specific enzymes called DNA photolyases. Photoreactivation has been reported in Vibrio parahaemolyticus WP28; however, information on photolyases in V. parahaemolyticus (V.p) strains has not been reported. This study examined the photoreactivation in V.p RIMD2210633. The photolyase responsible for repairing cyclobutane pyrimidine dimer (CPD) in DNA was identified, and the corresponding gene was determined as VPA1471. The protein was overexpressed in Escherichia coli and was purified for functional assessment in vitro. The mRNA level and protein expression level of this gene increased after ultraviolet A (UVA) illumination following ultraviolet C (UVC) irradiation. In vitro experiments confirmed that the protein encoded by VPA1471 could reduce the quantity of CPD in DNA. We designated the corresponding gene and protein of VPA1471 phr and Phr, respectively, although the function of two other photolyase/cryptochrome family members, VPA0203 and VPA0204, remains unclear. UV (ultraviolet) irradiation experiments suggest that these two genes possess some photorepairing ability. Therefore, we hypothesize that VPA0203 and VPA0204 encode (6-4) photolyase in V. parahaemolyticus RIMD2210633.

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Vibrio parahaemolyticus possesses the photoreactivation ability when it utilizes blue light as energy. However, ΔVPA1471 abolished this capacity completely, whereas complementation of VPA1417 could make this ability recover partly. Some cells of UVC radiated VPA0203 KO and VPA0204 KO strains recovered by the following UVA illumination.

Quelle: Photochemistry and Photobiology | 7 Aug 2015 | 2:16 pm CEST

Upconverting the IR-A Range of the Sun Spectrum using Palladium Tetraaryltetraanthra[2,3]porphyrins

Photochem. Photobiol. Sci., 2015, Accepted Manuscript
DOI: 10.1039/C5PP00212E, Paper
Vladimir Yakutkin, Mikhail A. Filatov, Iliyana Z. Ilieva, Katharina Landfester, Tzenka Miteva, Stanislav Baluschev
An ensemble of symmetrical palladium tetraaryltetraanthra[2,3]porphyrin sensitizers bearing different substitution patterns, efficiently transforming the IR-A range of the sun-spectrum excitation (720 ‒ 840 nm) into VIS-emission (520 ‒ 680 nm)...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 7 Aug 2015 | 1:00 am CEST

Anomalous behavior of visible light active TiO2 for the photocatalytic degradation of different Reactive dyes

Photochem. Photobiol. Sci., 2015, Advance Article
DOI: 10.1039/C5PP00165J, Paper
Navneet Kaur, Satwant Kaur Shahi, Vasundhara Singh
This article illustrates important substrate-catalyst interaction studies using Reactive dyes and various modified TiO2 powders under visible light irradiation and demonstrates the need for developing new catalysts for the degradation of dyes having different structural features present in textile effluents.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 7 Aug 2015 | 1:00 am CEST

First detection of the presence of naturally occurring grapevine downy mildew in the field by a fluorescence-based method

Photochem. Photobiol. Sci., 2015, Advance Article
DOI: 10.1039/C5PP00121H, Communication
Gwendal Latouche, Christian Debord, Marc Raynal, Charlotte Milhade, Zoran G. Cerovic
The presence of a major grapevine disease was detected in the field by a new fluorescence proximal sensor. The approach based on UV-induced fluorescence of phytoalexins can be extended to vineyard mapping.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 7 Aug 2015 | 1:00 am CEST

Photoisomerization of Trans Ortho-, Meta-, Para- Nitro Diarylbutadienes: A Case of Regioselectivity

Abstract

A series of ortho, meta and para substituted trans-nitro aryl (phenyl and pyridyl) butadienes have been synthesized and characterized. The effect of substitution and positional selectivity on their fluorescence and photoisomerization were systematically investigated. Among all dienes, meta- and para-nitro phenyl substituted derivatives exhibit remarkable solvatochromic emission shifts due to intramolecular charge transfer. On the other hand, ortho derivatives undergo regioselective isomerisation upon photoexcitation in contrast to inefficient isomerization of para and meta nitro substituted dienes. Single crystal X-ray analysis revealed existence of intramolecular hydrogen bonding between the nitro group and the hydrogen of the proximal double bond. This restricts the rotation of the proximal double bond thereby allowing regioselective isomerization. The observations were also supported by NMR spectroscopic studies.

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Quelle: Photochemistry and Photobiology | 6 Aug 2015 | 7:08 pm CEST

Melanopsins: Localization and Phototransduction in Xenopus laevis Melanophores

Abstract

Xenopus laevis melanophores express two melanopsins, Opn4x and Opn4m. We identified Opn4x immunoreactivity throughout the melanophore cytoplasm and in the cell membrane. The strongest immunopositivity for Opn4m was observed in the nuclear region, and no labeling was seen in the cell membrane. This immunodistribution suggests Opn4x as the functional photopigment. In X. laevis melanophores, light triggers pigment dispersion and clock gene induction at blue wavelength, which maximally activates melanopsins. Although light stimulation activates phospholipase C and increases intracellular calcium and cGMP, this nucleotide does not participate in photo-induced melanin dispersion. Nevertheless, the guanylyl cyclase activator YC-1 stimulates Per1 expression, similar to blue light pulse, and the use of pharmacological inhibitors indicates the participation of the phosphoinositide cascade. Since cAMP levels does not change after blue light stimulation, the cAMP/PKA pathway most probably is not involved in blue light induction of Per in X. laevis melanophores. Given the localization of melanopsins and our pharmacological data, the light-induced clock gene expression seems to be mediated by Opn4x through phosphoinositide cascade and rise in cGMP, thus leading to the reset of the biological clock in our model.

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Xenopus laevis melanophores express two melanopsins, Opn4x and Opn4m. Their proteins are differentially located: Opn4x is present in the cytoplasm and the cell membrane, and Opn4m is located in the nuclear region. In this model, blue light, which maximally activates melanopsins, increases clock gene expression. Given the localization of melanopsins and our pharmacological data, the light-induced clock gene expression seems to be mediated by Opn4x through the activation of the phosphoinositide cascade. This intracellular signaling ultimately cross-talks with cGMP-producing pathway, leading to the reset of the biological clock in X. laevis melanophores.

Quelle: Photochemistry and Photobiology | 6 Aug 2015 | 3:33 pm CEST

Functional inactivation of lymphocytes by methylene blue with visible light

Photochem. Photobiol. Sci., 2015, Advance Article
DOI: 10.1039/C5PP00220F, Paper
Bo Zhang, Zhenzhen Cheng, Qin Mo, Li Wang, Xun Wang, Xiaofei Wu, Yao Jia, Yuwen Huang
Upon visible light excitation, MB can cause damage to pathogen nucleic acids, thereby inhibiting lymphocyte proliferation and cytokine secretion.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 5 Aug 2015 | 1:00 am CEST

Helical rearrangement of photoactivated rhodopsin in monomeric and dimeric forms probed by high-angle X-ray scattering

Photochem. Photobiol. Sci., 2015, Advance Article
DOI: 10.1039/C5PP00175G, Paper
Yasushi Imamoto, Keiichi Kojima, Toshihiko Oka, Ryo Maeda, Yoshinori Shichida
The light-induced conformational change of monomeric and dimeric rhodopsin in the nanodisc membrane was directly monitored by high-angle solution X-ray scattering.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 5 Aug 2015 | 1:00 am CEST

Solvent dependent photosensitized singlet oxygen production from an Ir(III) complex: pointing to problems in studies of singlet-oxygen-mediated cell death

Photochem. Photobiol. Sci., 2015, Advance Article
DOI: 10.1039/C5PP00230C, Paper
Shin-ya Takizawa, Thomas Breitenbach, Michael Westberg, Lotte Holmegaard, Anita Gollmer, Rasmus L. Jensen, Shigeru Murata, Peter R. Ogilby
The photophysics of an Ir(III) complex with phenanthroline and phenylpyridine ligands depends appreciably on the local environment.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 5 Aug 2015 | 1:00 am CEST

Properties and evolution of emission in molecular aggregates of a perylene ammonium derivative in polymer matrices

Photochem. Photobiol. Sci., 2015, Advance Article
DOI: 10.1039/C5PP00196J, Paper
Fuyuki Ito, Hirofumi Sato, Yuri Ugachi, Narumi Oka, Syoji Ito, Hiroshi Miyasaka
Size-dependent fluorescent properties and the evolution of emission in molecular aggregates of a perylene ammonium derivative in polymer matrices were investigated by steady-state and time-resolved spectroscopic methods.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 5 Aug 2015 | 1:00 am CEST

Phototherapy on the Treatment of Burning Mouth Syndrome: A Prospective Analysis of 20 Cases

Abstract

The aim of this study was to report the effect of laser phototherapy (LPT) on the treatment of burning mouth syndrome (BMS). This prospective clinical study reports on preliminary outcomes of twenty volunteers diagnosed with BMS who have undergone the conventional treatment prior to laser phototherapy. LPT consisted of weekly sessions of LPT (660 nm), for a period of 10 weeks. The laser protocol consisted of the following parameters: 40 mW, 10 J cm2 and 0.4 J per point, irradiation time of 10 s. In all sessions, the burning intensity was evaluated with a 10 cm Visual Analogue Scale (VAS). The burning intensity evaluation by VAS was performed immediately before and after each LPT session. Nonparametric test of Wilcoxon was used for statistical analysis, considering a significance level of 5%. All volunteers reported reduced burning intensity in all sessions when compared to the previous one and reduction in VAS scores by up to 49% in the last clinical session when compared to the first session. When only the VAS baseline of the first session was compared with the consecutive sessions, there was a statistically significant reduction in VAS scores in almost all sessions. The LPT may be an alternative treatment for the relief of oral burning symptoms in patients with BMS.

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Laser Phototherapy (LPT) consists of an effective alternative for treating the symptoms of Burning Mouth Syndrome. This prospective clinical study reports on preliminary outcomes of volunteers diagnosed with BMS that have undergone the conventional treatment prior to laser phototherapy (660 nm). All volunteers reported reduced burning intensity in all sessions when compared to the previous one and reduction in Visual Analog Scale scores by up to 49% in the last clinical session when compared to the first session.

Quelle: Photochemistry and Photobiology | 4 Aug 2015 | 1:33 pm CEST

DNA Ligases I and III Support Nucleotide Excision Repair in DT40 Cells with Similar Efficiency

Abstract

In eukaryotic cells helix-distorting DNA lesions like cyclobutane pyrimidine dimers (CPDs) and 6–4 pyrimidine-pyrimidone photoproducts (6–4 PPs) are efficiently removed by nucleotide excision repair (NER). NER is a multistep process where in the end, subsequent to replication over the gap, the remaining nick is sealed by a DNA ligase. Lig1 has been implicated as the major DNA ligase in NER. Recently, Lig3 has been implicated as a component of a NER subpathway that operates in dividing cells, but which becomes particularly important in nondividing cells. Here, we use DT40 cells and powerful gene targeting approaches for generating DNA ligase mutants to examine the involvement and contribution of Lig1 and Lig3 in NER using cell survival measured by colony formation, and repair kinetics of CPD by immunofluorescence microscopy and immuno-slot-blotting. Our results demonstrate an impressive and previously undocumented potential of Lig3 to substitute for Lig1 in removing helix-distorting DNA lesions by NER in proliferating cells. We show for the first time in a clean genetic background a functional redundancy in NER between Lig1 and Lig3, which appears to be cell cycle independent and which is likely to contribute to the stability of vertebrate genomes.

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Higher eukaryotes utilize three types of DNA ligases, Lig1, Lig3 and Lig4, which, in the classical view, have dedicated functions in DNA metabolism. We have reported that contrary to previous assumptions, Lig3 can efficiently support DNA replication and DNA double strand break repair. Here, we demonstrate that Lig3 also supports nucleotide excision repair with efficiency similar to Lig1. Collectively, these observations lead to a new model of DNA ligase functions and raise Lig3 from a niche ligase to a universal ligase that can efficiently substitute or backup the functions of Lig1 and Lig4.

Quelle: Photochemistry and Photobiology | 3 Aug 2015 | 1:58 pm CEST

Explaining the mobility of retinal in activated rhodopsin and opsin

Photochem. Photobiol. Sci., 2015, Accepted Manuscript
DOI: 10.1039/C5PP00173K, Paper
B Mertz, Jun Feng, Conor Corcoran, Brandon Neeley
Rhodopsin, the mammalian dim light photoreceptor, is the canonical model for G protein-coupled receptors. Activation of rhodopsin occurs when the covalently bound inverse agonist, retinal, absorbs a photon and undergoes...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 31 Jul 2015 | 1:00 am CEST

Impact of Substituents in Tumor Uptake and Fluorescence Imaging Ability of Near-Infrared Cyanine-like Dyes

Abstract

This report presents a simple strategy to introduce various functionalities in a cyanine dye (bis-indole-N-butylsulfonate-polymethine bearing a fused cyclic chloro-cyclohexene ring structure), and assess the impact of these substitutions in tumor uptake, retention and imaging. The results obtained from the structural activity relationship (SAR) study demonstrate that certain structural features introduced in the cyanine dye moiety make a remarkable difference in tumor avidity. Among the compounds investigated, the symmetrical CDs containing an amino-phenyl thioether group attached to a cyclohexene ring system and the two N-butyl linkers with terminal sulfonate groups in benzoindole moieties exhibited excellent tumor imaging ability in BALB/c mice bearing Colon26 tumors. Compared to indocyanine green (ICG), approved by FDA as a blood pooling agent, which has also been investigated for the use in tumor imaging, the modified CD selected on the basis of SAR study produced enhanced uptake and longer retention in tumor(s). A facile approach reported herein for introducing a variety of functionalities in tumor-avid CD provides an opportunity to create multi-imaging modality agent(s). Using a combination of mass spectrometry and absorbance techniques, the photobleaching of one of the CDs was analyzed and significant regioselective photooxidation was observed.

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Impact of substituents in tumor uptake and fluorescence imaging ability of near-infrared heterocyclic polymethine dyes.

Quelle: Photochemistry and Photobiology | 30 Jul 2015 | 2:21 pm CEST

Effects of Light and Salinity Stresses in Production of Mycosporine-Like Amino Acids by Gymnodinium catenatum (Dinophyceae)

Abstract

Mycosporine-like amino acids (MAAs) were analyzed in a Portuguese Gymnodinium catenatum strain when transferred to high salinity and high light conditions. Total MAA concentrations increased progressively between 30 and 36 psu, attaining at 36 psu 2.9-fold the 30 psu treatment. When abruptly transferred to solar light in an outdoor shadowed location, MAA concentration increased steadily along the day for most compounds. After 8 h, mycosporine–glycine, palythene and M-319 attained or surpassed 25-fold their initial concentration, while M-370 only attained 4-fold concentration. When transferred from halogen to fluorescent light, polar MAAs such as shinorine and porphyra-334, increased until day two and then declined, while M-370 increase slowly, becoming the dominant compound from the profile after 1 week. These experiments put into evidence the relation of palythene with M-319, which was further identified as its acid degradation product, palythine. Acid degradation of M-370 originated M-324, while M-311 seems to be the precursor of M-370. Under high salinity and high light conditions chain formation was altered toward shorter chains or solitary cells. This alteration can represent a morphological stress sign, which in the natural environment could affect average population speed during daily vertical migrations.

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Mycosporine-like amino acids concentration increased with salinity, in particular high polar MAAs. Abrupt changes in light intensity increased rapidly the low polar palythene. In both cases, mycosporine–glycine was one of the MAAs with the greatest increase, while biosynthesis of M370, a major MAA in G. catenatum, progressed slowly. Experiments put into evidence the biosynthetic relations between MAAs and its degradation pathways. MAAs might play a multifunctional role to cope with salinity (shinorine, porphyra-334) and photooxidative (mycosporine–glycine, palythene, M-370) stresses. High salinity and high light conditions also altered chain formation toward shorter chains or solitary cells.

Quelle: Photochemistry and Photobiology | 30 Jul 2015 | 2:21 pm CEST

Dunaliella tertiolecta (Chlorophyta) Avoids Cell Death Under Ultraviolet Radiation (UVR) By Triggering Alternative Photoprotective Mechanisms

Abstract

The effect of different ultraviolet radiation (UVR) treatments combining PAR (P), UVA (A), and UVB (B) on the molecular physiology of Dunaliella tertiolecta was studied during 6 days to assess the response to chronic UVR exposure. UVR reduced cell growth but did not cause cell death, as shown by the absence of SYTOX Green labelling and cellular morphology. However, caspase-like enzymatic activities (CLs), (cell death proteases), were active even though the cells were not dying. Maximal quantum yield of fluorescence (Fv/Fm) and photosynthetic electron transport rate (ETR) dropped. Decreased non-photochemical quenching (NPQ) paralleled a drop in xanthophyll cycle de-epoxidation under UVB. Reactive oxygen species (ROS) and D1 protein accumulation were inversely correlated. PAB exhibited elevated ROS production at earlier times. Once ROS decayed, D1 protein recovered 2-fold compared with P and PA at later stages. Therefore PsbA gene was still transcribed, suggesting ROS involvement in D1 recovery by its direct effect on mRNA-translation. We add evidence of an UVB-induced positive effect on the cells when P is present, providing photoprotection and resilience, by means of D1 repair. This allowed cells to survive. The photoprotective mechanisms described here (which are counterintuitive in principle) conform to an important ecophysiological response regarding light stress acclimation.

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Quelle: Photochemistry and Photobiology | 30 Jul 2015 | 10:39 am CEST

Noninvasive Optical Imaging of UV-Induced Squamous Cell Carcinoma in Murine Skin: Studies of Early Tumor Development and Vitamin D Enhancement of Protoporphyrin IX Production

Abstract

Better noninvasive techniques are needed to monitor protoporphyrin IX (PpIX) levels before and during photodynamic therapy (PDT) of squamous cell carcinoma (SCC) of the skin. Our aim was to evaluate: (1) multispectral fluorescent imaging of ultraviolet light (UV)-induced cancer and precancer in a mouse model of SCC; (2) multispectral imaging and probe-based fluorescence detection as a tool to study Vitamin D (VD) effects on aminolevulinic acid (ALA)-induced PpIX synthesis. Dorsal skin of hairless mice was imaged weekly during a 24-week UV carcinogenesis protocol. Hot spots of PpIX fluorescence were detectable by multispectral imaging beginning at 14 weeks of UV exposure. Many hot spots disappeared after cessation of UV at week 20, but others persisted or became visible after week 20, and corresponded to tumors that eventually became visible by eye. In SCC-bearing mice pretreated with topical VD before ALA application, our optical techniques confirmed that VD preconditioning induces a tumor-selective increase in PpIX levels. Fluorescence-based optical imaging of PpIX is a promising tool for detecting early SCC lesions of the skin. Pretreatment with VD can increase the ability to detect early tumors, providing a potential new way to improve efficacy of ALA-PDT.

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Quelle: Photochemistry and Photobiology | 30 Jul 2015 | 10:37 am CEST

Biochemical Characterization of the DASH-Type Cryptochrome CryD from Fusarium fujikuroi

Abstract

Proteins from the cryptochrome/photolyase family utilize UV-A, blue or even red light to achieve such diverse functions as repair of DNA lesions by photolyases and signaling by cryptochromes. DASH-type cryptochromes retained the ability to repair cyclobutane pyrimidine dimers (CPDs) in single-stranded DNA regions in vitro. However, most organisms possess conventional CPD photolyases responsible for repair of these lesions in vivo. Recent work showed that the DASH-type cryptochrome CryD plays a regulatory role in diverse light-dependent processes in Fusarium fujikuroi. Here we report our in vitro studies on heterologously-expressed FfCryD. The purified protein contains N5,N10-methenyltetrahydrofolate and flavin adenine dinucleotide as cofactors. Photoreduction and DNA photorepair experiments confirmed that FfCryD is active in light-driven electron transfer processes. However, the protein showed comparable affinities for CPD-comprising and undamaged DNA probes. Surprisingly, after purification, full-length FfCryD as well as a truncated version containing only the PHR domain bound RNA which influenced their behavior in vitro. Moreover, binding of FfCryD to RNA indicates a putative role in RNA metabolism or in posttranscriptional control of gene expression.

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Quelle: Photochemistry and Photobiology | 28 Jul 2015 | 12:16 pm CEST

The role of the non-covalent [small beta]-ionone-ring binding site in rhodopsin: historical and physiological perspective

Photochem. Photobiol. Sci., 2015, Advance Article
DOI: 10.1039/C5PP00158G, Perspective
Hiroyuki Matsumoto, Tatsuo Iwasa, Toru Yoshizawa
Rhodopsin regenerates by way of a non-covalent complex formation between the 11-cis retinal and opsin, rendering the [small beta]-ionone ring-binding pocket a distinct physiological role.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 28 Jul 2015 | 1:00 am CEST

UV Sensitivity of Vegetative and Reproductive Tissues of Two Antarctic Brown Algae is Related to Differential Allocation of Phenolic Substances

Abstract

UV sensitivity of the vegetative and reproductive tissues of two Antarctic brown macroalgae was compared. Photosynthesis as well as the content and localization of phenolic substances were determined. Responses to UV radiation were quantified as chlorophyll fluorescence (Fv/Fm). Ascoseira mirabilis showed high UV tolerance, while in Cystosphaera jaquinotii Fv/Fm decreased by 15-21%, the receptacles being more tolerant than the vegetative blades. The phlorotannin contents showed an opposite pattern: the soluble fraction dominated in C. jacquinotii while in A. mirabilis the insoluble fraction was more abundant. Soluble phlorotannins were higher in the reproductive than in vegetative tissues in both species. Images of tissue cross-sections under violet-blue light excitation confirmed a high allocation of phenolic compounds (as blue autofluorescence) in C. jacquinotii, both in reproductive and vegetative blades. The allocation and proportions of the soluble and insoluble phlorotannins could be related with the observed UV tolerance of the vegetative and reproductive tissues.

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Quelle: Photochemistry and Photobiology | 27 Jul 2015 | 4:37 pm CEST

Comment to the Paper: “Endogenous Retinoic Acid Required to Maintain the Epidermis Following Ultraviolet Light Exposure in SKH-1 Hairless Mice” by Katherine L. Gressel et al., Photochemistry & Photobiology DOI: 10.1111/php.12441

Quelle: Photochemistry and Photobiology | 27 Jul 2015 | 1:03 pm CEST

Response to Mr. Fluegge's Comment on Our Paper: “Endogenous Retinoic Acid Required to Maintain the Epidermis Following Ultraviolet Light Exposure in SKH-1 Hairless Mice” by Katherine L. Gressel et al., Photochemistry & Photobiology DOI: 10.1111/php.12441

Quelle: Photochemistry and Photobiology | 27 Jul 2015 | 1:03 pm CEST

Effectiveness of the Photoactive Dye Methylene Blue versus Caspofungin on the Candida parapsilosis Biofilm in vitro and ex vivo

Abstract

This research studied the effectiveness of the photoactive compound methylene blue (MB) activated with red LED light (576–672 nm) compared to that of caspofungin (CAS) on 1 Candida albicans and 3 Candida parapsilosis strains. Results were evaluated in terms of SMIC50 for CAS or in PDI (photodynamic inactivation)-SMIC50 for MB (minimal inhibitory concentration inhibiting sessile biofilm to 50% in comparison to the control without CAS or after irradiation in comparison to the control without MB). While all strains were susceptible to CAS in planktonic form, the SMIC50 was determined to be >16 μg mL−1 when CAS was added to a 24 h biofilm. However, PDI-MIC50s (1.67 mW cm−2, fluence 15 J cm−2) were 0.0075–0.03 mmol L−1. For biofilm, PDI-SMIC50s were in the range from 0.7 to 1.35 mmol L−1. MB concentration of 1 mmol L−1 prevented a biofilm being formed ex vivo on mouse tongues after irradiation regardless of the application time, in contrast to CAS, which was only effective at a concentration of 16 μg mL−1 when it was added at the beginning of biofilm formation. PDI seems to be a promising method for the prevention of microbial biofilms that do not respond significantly to conventional drugs.

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PDI (photodynamic inactivation) is useful approach for eradication of microorganisms. This work compared effectiveness of methylene blue (MB) with clinically used drug – caspofungin (CAS). Biofilms of Candida parapsilosis were formed in 96-well microtiter plates and irradiated with red LED light (15 J cm−2) for 2.5 h after addition of different MB concentrations. Evaluation of results using CFU and XTT reduction assay showed effectiveness of PDI in contrast to CAS. Microscopic examination of in vitro and ex vivo biofilms formed on mouse tongues confirmed effect of MB on C. parapsilosis strains in the concentration range of 0.7–1.35 mmol L−1.

Quelle: Photochemistry and Photobiology | 24 Jul 2015 | 2:00 pm CEST

Photodynamic Action Mechanism Mediated by Zinc(II) 2,9,16,23-Tetrakis[4-(N-methylpyridyloxy)]phthalocyanine in Candida albicans Cells

Abstract

The photoreaction type I/type II pathways mediated by zinc(II) 2,9,16,23-tetrakis[4-(N-methylpyridyloxy)]phthalocyanine (ZnPPc4+) was studied in Candida albicans cells. This photosensitizer was strongly bound to C. albicans cells at short times. After 30 min irradiation, 5 μM ZnPPc4+ produced ~5 log decrease in cell viability. Different probes were used to detect reactive oxygen species (ROS) in cell suspensions (~106 CFU mL−1). Singlet molecular oxygen, O2(1Δg), was observed by the reaction with 9,10-dimethylanthracene (DMA) and tetrasodium 2,2-(anthracene-9,10-diyl)bis(methylmalonate) (ABMM), whereas the nitro blue tetrazolium (NBT) method was used to sense superoxide anion radical (inline image). Moreover, the effects produced by an anoxic atmosphere and cell suspensions in D2O, as well as the addition of sodium azide and mannitol as ROS trapping were evaluated in the PDI of C. albicans. These investigation indicates that O2(1Δg) is generated in the cells, although a minor extension other radical species can also be involved in the PDI of C. albicans mediated by ZnPPc4+.

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The photoreaction type I/type II pathways mediated by ZnPPc4+ was studied in Candida albicans cells. Photoinactivation was investigated in presence of specific molecular probes to detect the presence of ROS, under different experimental conditions and in presence of scavengers of ROS to find information about the photoprocesses that produces the cell death. These investigation indicates that O2(1Δg) is generated in the cells, although a minor extension other radical species can also be involved in the photoinactivation of C. albicans mediated by ZnPPc4+.

Quelle: Photochemistry and Photobiology | 24 Jul 2015 | 1:58 pm CEST

Effect of 808 nm Diode Laser on Swimming Behavior, Food Vacuole Formation and Endogenous ATP Production of Paramecium primaurelia (Protozoa)

Abstract

Photobiomodulation (PBM) has been used in clinical practice for more than 40 years. To clarify the mechanisms of action of PBM at cellular and organism levels, we investigated its effect on Paramecium primaurelia (Protozoa) irradiated by an 808 nm infrared diode laser with a flat-top handpiece (1 W in CW). Our results led to the conclusion that: (1) the 808 nm laser stimulates the P. primaurelia without a thermal effect, (2) the laser effect is demonstrated by an increase in swimming speed and in food vacuole formation, (3) the laser treatment affects endogenous adenosine triphosphate (ATP) production in a positive way, (4) the effects of irradiation dose suggest an optimum exposure time of 50 s (64 J cm−2 of fluence) to stimulate the Paramecium cells; irradiation of 25 s shows no effect or only mild effects and irradiation up to 100 s does not increase the effect observed with 50 s of treatment, (5) the increment of endogenous ATP concentration highlights the positive photobiomodulating effect of the 808 nm laser and the optimal irradiation conditions by the flat-top handpiece.

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Photobiomodulation and Low-Level Laser Therapy are terms applied to the manipulation of cellular behavior using low-intensity light sources and work on the principle of inducing a biological response through energy transfer. In our work, the effect of laser therapy by 808-nm infrared diode laser with a flat-top handpiece (1 W in CW–64 J cm−2) on Paramecium (Protozoa) has been investigated. The therapy increases Paramecium's swimming speed and food vacuole formation and positively affects adenosine triphosphate (ATP) production. The increment of ATP without a thermal effect highlights the positive photobiomodulating effect of the therapy and the optimal irradiation conditions by the flat-top handpiece.

Quelle: Photochemistry and Photobiology | 24 Jul 2015 | 1:58 pm CEST

Enhanced Self-Cleaning Properties on Polyester Fabric Under Visible Light Through Single-Step Synthesis of Cuprous Oxide Doped Nano-TiO2

Abstract

Nowadays, introducing self-cleaning properties on various fabrics under daylight irradiation for automotive and upholstery application is in a central point of research. This can be achieved by application of metal-doped TiO2 nano particles on the textile fabrics. Here, alkali hydrolysis of polyester fabric has been carried out along with synthesis of Cu2O/TiO2 nanoparticles in a single-step process by using sonochemical technique. CuSO4.5H2O was used as a source of copper in the presence of glucose as reducing and stabilizing agent. Moreover, central composite design based on response surface methodology (RSM) was used to determine the role of variables (CuSO4.5H2O, glucose and pH) and their effects on the self-cleaning properties and weight of the fabric. The self-cleaning property was investigated by degradation of Methylene blue on the surface of the treated fabrics under daylight. Further, the tensile properties, colorimetric measurement, and washing fastness of the treated fabric produced in the optimum conditions were investigated. The morphology of Cu2O/TiO2 nanoparticles was examined using X-ray diffraction and field emission scanning electron microscopy (FESEM). The new polyester fabric obtained through in situ synthesis of Cu2O/TiO2 nanoparticles can be used as a desirable stable fabric with high tensile strength and visible-light self-cleaning properties.

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Here, Cu2O-doped TiO2 nanoparticles were synthesized simultaneous with alkali hydrolysis on the polyester fabric through a simple sonochemical technique. A statistical method namely central composite design was used to determine the effect of three different variables including CuSO4.5H2O, glucose and pH on the self-cleaning properties and weight of the fabric. FE-SEM images and XRD/EDX patterns confirmed formation of Cu2O-doped TiO2 nanoparticles on the polyester fabric. The treated polyester fabric indicated superior durable self-cleaning properties along with high tensile strength.

Quelle: Photochemistry and Photobiology | 20 Jul 2015 | 8:44 am CEST

Reclamation of Water Polluted with Flubendiamide Residues by Photocatalytic Treatment with Semiconductor Oxides

Abstract

The photodegradation of flubendiamide (benzenedicarboxamide insecticide), a relatively new insecticide was investigated in aqueous suspensions binary (ZnO of and TiO2) and ternary (Zn2TiO4 and ZnTiO3) oxides under artificial light (300–460 nm) irradiation. Photocatalytic experiments showed that the addition of semiconductors, especially ZnO and TiO2, in tandem with an electron acceptor (Na2S2O8) enhances the degradation rate of this compound in comparison with those carried out with catalyst alone and photolytic tests. The photocatalytical degradation of flubendiamide using ZnO/Na2S2O8 and TiO2/Na2S2O8 followed first-order kinetics. In addition, desiodo-flubendiamide was identified during the degradation of flubendiamide. Finally, application of these reaction systems in different waters (tap, leaching and watercourse) showed the validity of the treatments, which allowed the removal of flubendiamide residues in these drinking and environmental water samples.

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The degradation of flubendiamide in aqueous suspensions of binary (ZnO and TiO2) and ternary (Zn2TiO4 and ZnTiO3) oxides of zinc and titanium under artificial light (300–460 nm) irradiation has been studied. The results show that the use of photosensitizer/Na2S2O8, especially with TiO2 and ZnO, is a very effective and rapid method for the elimination of this pesticide in water. In addition, the main photocatalytic intermediate (desiodo-flubendiamide) detected during the degradation of flubendiamide was identified. These results have high environmental interest for the treatment of polluted water and therefore a significant scientific impact.

Quelle: Photochemistry and Photobiology | 17 Jul 2015 | 7:22 am CEST

The Effect of Surface Charge Saturation on Heat-induced Aggregation of Firefly Luciferase

Abstract

We present here the effect of firefly luciferase surface charge saturation and the presence of some additives on its thermal-induced aggregation. Three mutants of firefly luciferase prepared by introduction of surface Arg residues named as 2R, 3R and 5R have two, three and five additional arginine residues substituted at their surface compared to native luciferase; respectively. Turbidimetric study of heat-induced aggregation indicates that all three mutants were reproducibly aggregated at higher rates relative to wild type in spite of their higher thermostability. Among them, 2R had most evaluated propensity to heat-induced aggregation. Therefore, the hydrophilization followed by appearing of more substituted arginine residues with positive charge on the firefly luciferase surface was not reduced its thermal aggregation. Nevertheless, at the same condition in the presence of charged amino acids, e.g. Arg, Lys and Glu, as well as a hydrophobic amino acid, e.g. Val, the heat-induced aggregation of wild type and mutants of firefly luciferases was markedly decelerated than those in the absence of additives. On the basis of obtained results it seems, relinquishment of variety in charge of amino acid side chains, they via local interactions with proteins cause to decrease rate and extent of their thermal aggregation.

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The effect of surface charge saturation on heat-induced aggregation of firefly luciferase. Different surface charge distribution has an effect on thermal aggregation of mutant luciferases at 45°C.

Quelle: Photochemistry and Photobiology | 14 Jul 2015 | 4:11 pm CEST

Spectral fine tuning of cyanine dyes: electron donor-acceptor substituted analogues of thiazole orange

Photochem. Photobiol. Sci., 2015, 14,1703-1712
DOI: 10.1039/C5PP00117J, Paper
Elizabeth E. Rastede, Matteus Tanha, David Yaron, Simon C. Watkins, Alan S. Waggoner, Bruce A. Armitage
Strategically placed electron donor and acceptor groups allow fine-tuning of cyanine dye absorption and emission spectra while preserving recognition of biomolecular hosts such as DNA and proteins.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 14 Jul 2015 | 1:00 am CEST

Photo-damage, photo-protection and age-related macular degeneration

Photochem. Photobiol. Sci., 2015, 14,1560-1577
DOI: 10.1039/C5PP00188A, Perspective
Melisa D. Marquioni-Ramella, Angela M. Suburo
The course of Age-related Macular Degeneration (AMD) is described as the effect of light (400-580 nm) on various molecular targets in photoreceptors and the retinal pigment epithelium (RPE). Photo-damage is followed by inflammation, increasing oxidative stress and, probably, unveiling new photosensitive molecules.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 9 Jul 2015 | 1:00 am CEST

Pyrimidinone: versatile Trojan horse in DNA photodamage?

Photochem. Photobiol. Sci., 2015, 14,1598-1606
DOI: 10.1039/C5PP00114E, Paper
Open Access Open Access
Creative Commons Licence  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Mathias Micheel, Christian Torres Ziegenbein, Peter Gilch, Gerald Ryseck
The triplet state of 1-methyl-2(1H)-pyrimidinone (1MP)-a model system for the chromophore in (6-4) photolesions-abstracts hydrogen: a further potential pathway for secondary photochemistry in DNA.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 8 Jul 2015 | 1:00 am CEST

Light, lipids and photoreceptor survival: live or let die?

Photochem. Photobiol. Sci., 2015, 14,1737-1753
DOI: 10.1039/C5PP00194C, Paper
Olga Lorena German, Daniela L. Agnolazza, Luis E. Politi, Nora P. Rotstein
DHA, released from membrane phospholipids upon oxidative damage, activates retinoid X receptors (RXR), thus triggering multiple mechanisms, including upregulation or activation of pro-survival proteins, antioxidant defense mechanisms and the ERK/MAPK pathway to promote photoreceptor survival.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 7 Jul 2015 | 1:00 am CEST

Photo-control of DNA binding by an engrailed homeodomain-photoactive yellow protein hybrid

Photochem. Photobiol. Sci., 2015, 14,1729-1736
DOI: 10.1039/C5PP00160A, Paper
A. Kumar, A. M. Ali, G. A. Woolley
A photo-controlled version of the engrailed homeodomain (zENG) was created by inserting the homeodomain into a surface loop of a circularly permuted version of the photoactive yellow protein (cPYP).
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 7 Jul 2015 | 1:00 am CEST

Influence of a chromophore analogue in the protein cage of a photoactive yellow protein

Photochem. Photobiol. Sci., 2015, 14,1722-1728
DOI: 10.1039/C5PP00176E, Paper
Norio Hamada, Zhe Tan, Yasuo Kanematsu, Naoya Inazumi, Ryosuke Nakamura
To understand the mechanism of photo-isomerization, photoactive yellow protein (PYP) containing cyano-p-coumaric acid (CHCA) were investigated.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 3 Jul 2015 | 1:00 am CEST

Atomic and molecular analysis highlights the biophysics of unprotonated and protonated retinal in UV and scotopic vision

Photochem. Photobiol. Sci., 2015, 14,1660-1672
DOI: 10.1039/C5PP00091B, Paper
Carlos Kubli-Garfias, Ricardo Vazquez-Ramirez, Blanca M. Cabrera-Vivas, Baldomero Gomez-Reyes, Juan Carlos Ramirez
Unprotonated (UR) and protonated (PR) retinal have marked atomic and molecular differences in cis and trans configurations. In conclusion, UR and PR uphold UV and light vision through their different biophysical properties.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 3 Jul 2015 | 1:00 am CEST

Effects of UV-C and Vacuum-UV TiO2 Advanced Oxidation Processes on the Acute Mortality of Microalgae

Abstract

Advanced oxidation processes/technologies (AOT) that combine a semiconductor, such as titanium dioxide (TiO2), with a UV source have been used to eliminate microorganisms in various water treatment applications. To facilitate the applicability of this technique, the gain in efficiency from the semiconductor compared to the UV source alone with respect to different target organisms requires evaluation. The primary objective of this study was to determine the effects of TiO2 and UV wavelength on a freshwater alga, Pseudokirchneriella subcapitata and a marine alga, Tetraselmis suecica. For each species, dose–response experiments were conducted to determine the median lethal dose (LC50) of the following treatments: UV light emitted with a peak of 254 nm, UV light emitted with a peak of 254 nm in the presence of TiO2 and UV light emitted with a peak of 254 and 185 nm in the presence of TiO2. In both species, the presence of TiO2 significantly increased mortality. Across all three treatments, P. subcapitata was more sensitive than T. suecica; moreover, the addition of the 185 nm wavelength significantly increased cell mortality in P. subcapitata but not in T. suecica.

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In response to the transport of invasive species through ballast tanks, the shipping industry has begun employing disinfection treatment systems. This study compares the efficiencies of common treatment systems that employ TiO2 and different UV wavelengths on a freshwater alga (Pseudokirchneriella subcapitata) and a marine alga (Tetraselmis suecica). Treatment efficacy increased in the presence of TiO2 and when Vacuum UV light was added as a part of the irradiation. However, the effects were dependent on the algal species used as test organisms.

Quelle: Photochemistry and Photobiology | 2 Jul 2015 | 1:22 pm CEST

Measuring the Physiologic Properties of Oral Lesions Receiving Fractionated Photodynamic Therapy

Abstract

Photodynamic therapy (PDT) can treat superficial, early-stage disease with minimal damage to underlying tissues and without cumulative dose-limiting toxicity. Treatment efficacy is affected by disease physiologic properties, but these properties are not routinely measured. We assessed diffuse reflectance spectroscopy (DRS) for the noninvasive, contact measurement of tissue hemoglobin oxygen saturation (StO2) and total hemoglobin concentration ([tHb]) in the premalignant or superficial microinvasive oral lesions of patients treated with 5-aminolevulinic acid (ALA)-PDT. Patients were enrolled on a Phase 1 study of ALA-PDT that evaluated fluences of 50, 100, 150 or 200 J cm−2 delivered at 100 mW cm−2. To test the feasibility of incorporating DRS measurements within the illumination period, studies were performed in patients who received fractionated (two-part) illumination that included a dark interval of 90–180 s. Using DRS, tissue oxygenation at different depths within the lesion could also be assessed. DRS could be performed concurrently with contact measurements of photosensitizer levels by fluorescence spectroscopy, but a separate noncontact fluorescence spectroscopy system provided continuous assessment of photobleaching during illumination to greater tissue depths. Results establish that the integration of DRS into PDT of early-stage oral disease is feasible, and motivates further studies to evaluate its predictive and dosimetric value.

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Diffuse reflectance spectroscopy with a contact probe was employed as part of a fluorescence and reflectance spectroscopy system to measure the tissue hemoglobin oxygen saturation and hemoglobin content of lesions of premalignant or early microinvasive cancer of the oral cavity. Studies demonstrate the feasibility of incorporating these measurements into treatment with fractionated (two-part) photodynamic therapy (PDT) using 5-aminolevulinic acid. Patient-specific differences in physiologic parameters were detectable at baseline and at times during and after PDT. Photobleaching of photosensitizer was measured by its fluorescence. Results establish the utility of rationally designed spectroscopy probes toward personalized dosimetry in PDT of oral disease.

Quelle: Photochemistry and Photobiology | 2 Jul 2015 | 1:21 pm CEST

Current concept of photocarcinogenesis

Photochem. Photobiol. Sci., 2015, 14,1713-1721
DOI: 10.1039/C5PP00185D, Paper
Chikako Nishisgori
Schematic pathway of UV induced inflammation and the formation of oxidative stress.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 30 Jun 2015 | 1:00 am CEST

Characterization of photo-intermediates in the photo-reaction pathways of a bacteriorhodopsin Y185F mutant using in situ photo-irradiation solid-state NMR spectroscopy

Photochem. Photobiol. Sci., 2015, 14,1694-1702
DOI: 10.1039/C5PP00154D, Paper
Kyosuke Oshima, Arisu Shigeta, Yoshiteru Makino, Izuru Kawamura, Takashi Okitsu, Akimori Wada, Satoru Tuzi, Tatsuo Iwasa, Akira Naito
Photo-reaction pathways of a Y185F-bR mutant and, CS*- and O-intermediates were examined using in situ photo-irradiation solid-state 13C NMR spectroscopy.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 30 Jun 2015 | 1:00 am CEST

Kinetic Model of Photoautotrophic Growth of Chlorella sp. Microalga, Isolated from the Setúbal Lagoon

Abstract

In this work, a kinetic expression relating light availability in the culture medium with the rate of microalgal growth is obtained. This expression, which is valid for low illumination conditions, was derived from the reactions that take part in the light-dependent stage of photosynthesis. The kinetic expression obtained is a function of the biomass concentration in the culture, as well as of the local volumetric rate of absorption of photons, and only includes two adjustable parameters. To determine the value of these parameters and to test the validity of the hypotheses made, autotrophic cultures of the Chlorella sp. strain were carried out in a modified BBM medium at three CO2 concentrations in the gas stream, namely 0.034%, 0.34% and 3.4%. Moreover, the local volumetric rate of photon absorption was predicted based on a physical model of the interaction of the radiant energy with the suspended biomass, together with a Monte Carlo simulation algorithm. The proposed intrinsic expression of the biomass growth rate, together with the Monte Carlo radiation field simulator, are key to scale up photobioreactors when operating under low irradiation conditions, independently of the configuration of the reactor and of its light source.

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Photosynthesis and Microalgal growth rate depends on the local light availability; in this work a kinetic expression for algal growth under light controlling conditions has been derived from a simplified pathway of the light-dependent step of photosynthesis.

Quelle: Photochemistry and Photobiology | 29 Jun 2015 | 1:59 pm CEST

Photophysics and Rotational Dynamics of a Hydrophilic Molecule in a Room Temperature Ionic Liquid

Abstract

We have studied the photophysics and rotational diffusion of hydrophilic solute 7-(N, N′-diethylamino)coumarin-3-carboxylic acid (7-DCCA) in a room temperature ionic liquid methyltrioctylammonium bis(trifluoromethylsulfonyl) imide ([N1888][NTf2]). Comparison of activation energies of viscous flow and nonradiative decay shows that the photophysical properties of 7-DCCA are not guided by the bulk viscosity of the medium but are dependent on the specific solute solvent interaction and structural heterogeneity of the medium. The rotational relaxation behaviour of 7-DCCA in [N1888][NTf2] shows significant deviation from the Stokes Einstein Debye hydrodynamic model of rotational diffusion. This is indicative of the influence of specific solute solvent interaction on the rotational relaxation behaviour of 7-DCCA. Comparison of activation energy of rotational relaxation with activation energy of viscous flow clearly reinforces our assumption that the structural heterogeneity of the medium and specific solute solvent interaction plays a dominant role on the rotational diffusion instead of bulk viscosity.

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This paper focuses on the photophysics and rotational diffusion of a hydrophilic solute 7-(N, N′-diethylamino)coumarin-3-carboxylic acid (7-DCCA) in a room temperature ionic liquid methyltrioctylammonium bis(trifluoromethylsulfonyl) imide ([N1888][NTf2]).

Quelle: Photochemistry and Photobiology | 24 Jun 2015 | 9:23 am CEST

Doping of Zinc Oxide with Selected First Row Transition Metals for Photocatalytic Applications

Abstract

ZnO doped with Cr, Mn, Fe, Co, Ni and Cu was prepared by homogeneous hydrolysis of sulfates with urea. The samples were annealed at various temperatures and characterized by X-ray powder diffraction, UV/VIS reflectance spectroscopy, BET (Brunauer-Emmet-Teller) surface area and porosity measurements. The photocatalytic activity of the samples was evaluated by measuring the degradation of an organic dye Reactive Black 5. The morphology of the samples was determined by scanning electron microscopy and atomic force microscopy. For the Cu-doped ZnO sample, EPR spectra were obtained. All samples annealed at 800°C contained hexagonal ZnO. In the VIS region, the best photocatalytic performance had the ZnO samples doped with Cr, Fe and Cu.

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ZnO samples doped with selected first row transition metals were used for degradation of an organic dye Reactive Black 5. The results of the photocatalytic experiments showed that the samples were active under VIS light. The most photocatalytically active was the Fe-doped ZnO.

Quelle: Photochemistry and Photobiology | 24 Jun 2015 | 9:22 am CEST

Optimizing optogenetic constructs for control over signaling and cell behaviours

Photochem. Photobiol. Sci., 2015, 14,1578-1585
DOI: 10.1039/C5PP00171D, Perspective
P. R. O'Neill, N. Gautam
This perspective highlights recent advances in the design of optogenetic tools that provide dynamic subcellular control over signaling and cell behaviour.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 24 Jun 2015 | 1:00 am CEST

Characterizing rhodopsin signaling by EPR spectroscopy: from structure to dynamics

Photochem. Photobiol. Sci., 2015, 14,1586-1597
DOI: 10.1039/C5PP00191A, Perspective
Ned Van Eps, Lydia N. Caro, Takefumi Morizumi, Oliver P. Ernst
Perspective on how EPR spectroscopy brings insights into rhodopsin and GPCR dynamics.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 23 Jun 2015 | 1:00 am CEST

Nanostructured anatase TiO2 densified at high pressure as advanced visible light photocatalysts

Photochem. Photobiol. Sci., 2015, 14,1685-1693
DOI: 10.1039/C5PP00149H, Paper
Giovanni Carini Jr., Francesco Parrino, Giovanni Palmisano, Gabriele Scandura, Ilaria Citro, Giuseppe Calogero, Antonino Bartolotta, Gaetano Di Marco
Uniaxial high pressure up to 2.1 GPa on anatase TiO2 nanopowders induces structural defects, increases visible light absorption and enhances acetaldehyde production.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 22 Jun 2015 | 1:00 am CEST

Photochemical reactions of halogenated aromatic 1,3-diketones in solution studied by steady state, one- and two-color laser flash photolyses

Photochem. Photobiol. Sci., 2015, 14,1673-1684
DOI: 10.1039/C5PP00211G, Paper
Minoru Yamaji, Yurie Suwa, Rieko Shimokawa, Cecilia Paris, Miguel Angel Miranda
Photoreactions of 1,3-diketones having halogen atoms at the C2 position are investigated by steady state, one- and two-color laser photolyses and DFT calculation.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 18 Jun 2015 | 1:00 am CEST

The Synthesis and Photocatalytic Properties of TiO2 Nanotube Array by Starch-Modified Anodic Oxidation

Abstract

In this study, the characterization and photocatalytic activity of TiO2 nanotube arrays prepared by anodization process with starch addition were investigated in detail. The results suggested that the optimum mass fraction of starch added in anodization process was 0.1%, with which TiO2 nanotube arrays owning good tubular structure were synthesized. The tube length and average inner diameter of nanotubes were approximately 4 μm and 30 nm, respectively. Through the characterization of TiO2 nanotube arrays by energy dispersive spectrometer, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier Transform Infrared (FTIR) spectroscopy, it was found that the as-prepared nanotubes possessed well uniformed and higher photodegradation responsive than the pure TiO2. Moreover, it was expected that the as-prepared nanotubes exhibited good photocatalytic activity for the degradation of RhB under UV-light irradiation, which could be ascribed to their good morphology, enhanced UV-light absorption property and electron transmission ability during the photocatalytic reaction. In addition, the nanotubes were not significantly regenerated during the cycling runs experiment. Overall, this study could provide a principle method to synthesize TiO2 nanotube arrays with enhanced photocatalytic activity by anodization process with starch addition for environmental purification.

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The TiO2 nanotube arrays were prepared by anodization process with starch addition. With the starch addition, the viscosity of the electrolyte was controlled, which modified the prepared nanotubes grew completely. The as-prepared nanotubes possessed well uniformed and higher photodegradation responsive than the pure TiO2, and consequently enhancing the photochromic properties.

Quelle: Photochemistry and Photobiology | 17 Jun 2015 | 2:18 pm CEST

Estimating the Diurnal Cycle and Daily Insolation of Ultraviolet and Photosynthetically Active Radiation at the Sea Surface

Abstract

Accurate determination of the diurnal variability and daily insolation of surface (0+) and subsurface (0) irradiance are essential to estimate several physical, chemical and biological processes occurring at the surface layer of marine environments. Natural downwelling PAR and spectral UVR were examined on eight occasions at 0+ and 0 to refine empirical models, particularly in the UVR spectrum. The diurnal variability in UVR and PAR were wavelength dependent and were modeled by a sinusoidal equation. The best fit for PAR at 0+ and 0 was the sinusoid power of = 2 and = 2.5, respectively. In the UVR spectrum, sinusoids increased as wavelengths decreased ranging from = 2–5. Higher n values in the UV-B spectrum suggest sharper increase/decrease near sunrise and sunset hours, ultimately reducing the final value of daily insolation at specified wavelengths. Calculated daily insolation of UV-B/(UV-A + PAR) ratio suggests that photoinhibition from exposure to UV-B occurs within a shorter biologically effective day length than PAR, and is high during summer and low during winter. These results suggest that biogeochemical calculations based on diurnal models of irradiance measurements would benefit from accurate solar noon references and wavelength specificity, particularly in the UVR spectrum.

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The diurnal variability of in situ surface (0+) and subsurface (0) ultraviolet radiation and photosynthetically active radiation were measured, modeled and tested. The diurnal variability in UVR and PAR were wavelength dependent and were modeled by a simple sinusoidal equation. Higher n values in the UV-B spectrum suggest sharper increase/decrease near sunrise and sunset hours, ultimately reducing the daily insolation at specific wavelengths and altering the UV-B/(UV-A + PAR) ratio throughout the day.

Quelle: Photochemistry and Photobiology | 17 Jun 2015 | 2:17 pm CEST

Optical and electron paramagnetic resonance studies of the excited triplet states of UV-B absorbers: 2-ethylhexyl salicylate and homomenthyl salicylate

Photochem. Photobiol. Sci., 2015, 14,1651-1659
DOI: 10.1039/C5PP00138B, Paper
Kazuto Sugiyama, Takumi Tsuchiya, Azusa Kikuchi, Mikio Yagi
UV-B absorbers, 2-ethylhexyl salicylate and homomenthyl salicylate, show a photoinduced phosphorescence enhancement, which originates from the photoinduced intermolecular hydrogen-bond formation.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 16 Jun 2015 | 1:00 am CEST

How Does Photoreceptor UVR8 Perceive a UV-B Signal?

Abstract

UVR8 is the only known plant photoreceptor that mediates light responses to UV-B (280–315 nm) of the solar spectrum. UVR8 perceives a UV-B signal via light-induced dimer dissociation, which triggers a wide range of cellular responses involved in photomorphogenesis and photoprotection. Two recent crystal structures of Arabidopsis thaliana UVR8 (AtUVR8) have revealed unusual clustering of UV-B-absorbing Trp pigments at the dimer interface and provided a structural framework for further mechanistic investigation. This review summarizes recent advances in spectroscopic, computational and crystallographic studies on UVR8 that are directed toward full understanding of UV-B perception at the molecular level.

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Light perception of UV-B photoreceptor UVR8 is triggered by light-induced molecular events originating in two epicenters located at the dimer interface. Clustered tryptophan residues serve as UV-B pigments and undergo concerted conformational changes upon absorbing UV-B photons, which disrupt the dimer interface and lead to dimer dissociation of UVR8.

Quelle: Photochemistry and Photobiology | 11 Jun 2015 | 8:24 am CEST

Green Light to Plant Responses to Pathogens: The Role of Chloroplast Light-Dependent Signaling in Biotic Stress

Abstract

Light has a key impact on the outcome of biotic stress responses in plants by providing most of the energy and many signals for the deployment of defensive barriers. Within this context, chloroplasts are not only the major source of energy in the light; they also host biosynthetic pathways for the production of stress hormones and secondary metabolites, as well as reactive oxygen species and other signals which modulate nuclear gene expression and plant resistance to pathogens. Environmental, and in particular, light-dependent regulation of immune responses may allow plants to anticipate and react more effectively to pathogen threats. As more information is gathered, increasingly complex models are developed to explain how light and reactive oxygen species signaling could interact with endogenous defense pathways to elicit efficient protective responses against invading microorganisms. The emerging picture places chloroplasts in a key position of an intricate regulatory network which involves several other cellular compartments. This article reviews current knowledge on the extent and the main features of chloroplast contribution to plant defensive strategies against biotic stress.

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The effect of light on ROS production by chloroplasts during a non-host pathogen interaction causing LCD is illustrated by infiltrating tobacco leaves with Xanthomonas campestris (see reference [16] in the text). Leaves were incubated with a ROS-reacting probe and observed 19 h post-infiltration by confocal laser microscopy, merging bright field, chlorophyll self-fluorescence (red), and ROS fluorescence (green). In leaves kept in the dark (left), chloroplasts were visualized as a red necklace around the central vacuole. Illuminated tissue (right) shows chloroplasts in yellow due to combination of red and green fluorescence, indicating that pathogen interaction results in light-dependent plastid ROS production.

Quelle: Photochemistry and Photobiology | 11 Jun 2015 | 8:23 am CEST

Applications of a new type of poly(methyl methacrylate)/TiO2 nanocomposite as an antibacterial agent and a reducing photocatalyst

Photochem. Photobiol. Sci., 2015, 14,1637-1643
DOI: 10.1039/C5PP00065C, Paper
Alireza Salabat, Farid Mirhoseini
A new poly(methyl methacrylate)/TiO2 nanocomposite film sensitized by an ionic liquid with a very low concentration of TiO2 nanoparticles was fabricated and applied in the photoreduction of 4-nitrophenol and destruction of some bacteria.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 10 Jun 2015 | 1:00 am CEST

Luminescent zinc metal-organic framework (ZIF-90) for sensing metal ions, anions and small molecules

Photochem. Photobiol. Sci., 2015, 14,1644-1650
DOI: 10.1039/C5PP00107B, Paper
Chang Liu, Bing Yan
We synthesize ZIF-90, which exhibits an intense blue luminescence excited under visible light. Luminescent studies indicate that ZIF-90 could be an efficient multifunctional fluorescence material for sensing metal cations, anions and organic small molecules.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 10 Jun 2015 | 1:00 am CEST

Phototherapeutic Effect of Low-Level Laser on Thyroid Gland of Gamma-Irradiated Rats

Abstract

One inescapable feature of life on the earth is exposure to ionizing radiation. The thyroid gland is one of the most sensitive organs to gamma-radiation and endocrine disrupters. Low-level laser therapy (LLLT) has been used to stimulate tissue repair, and reduce inflammation. The aim of this study was to gauge the value of using Helium–Neon laser to repair the damaged tissues of thyroid gland after gamma-irradiation. Albino rats were used in this study (144 rats), divided into control, gamma, laser, and gamma plus laser-irradiated groups, each group was divided into six subgroups according to time of treatment (total six sessions). Rats were irradiated once with gamma radiation (6 Gy), and an external dose of laser (Wavelength 632.8 nm, 12 mW, CW, Illuminated area 5.73 cm2, 2.1 mW cm−2, 120 s, 1.4 J, 0.252 J cm−2) twice weekly localized on thyroid region of the neck, for a total of six sessions. Animals were sacrificed after each session. Analysis included thyroid function, oxidative stress markers, liver function and blood picture. Results revealed improvement in thyroid function, liver function and antioxidant levels, and the blood cells count after LLLT.

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Low-level laser therapy (LLLT) would provide a protective effect against radiation-induced oxidative damage in the thyroid, liver and hemopoietic system depending on the frequency of its application.

Quelle: Photochemistry and Photobiology | 4 Jun 2015 | 9:37 am CEST

Structural and functional roles of the N- and C-terminal extended modules in channelrhodopsin-1

Photochem. Photobiol. Sci., 2015, 14,1628-1636
DOI: 10.1039/C5PP00213C, Paper
Satoko Doi, Arisa Mori, Takashi Tsukamoto, Louisa Reissig, Kunio Ihara, Yuki Sudo
The extended modules of channelrhodopsin-1 (ChR-1) are involved both in the maintenance of suitable photochemical properties and their functions.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 4 Jun 2015 | 1:00 am CEST

Origins of the Intermediate Spectral Form in M100 Mutants of Photoactive Yellow Protein

Abstract

Numerous single-site mutants of photoactive yellow protein (PYP) from Halorhodospira halophila and as well as PYP homologs from other species exhibit a shoulder on the short wavelength side of the absorbance maximum in their dark-adapted states. The structural basis for the occurrence of this shoulder, called the “intermediate spectral form,” has only been investigated in detail for the Y42F mutation. Here we explore the structural basis for occurrence of the intermediate spectral form in a M121E derivative of a circularly permuted H. halophila PYP (M121E-cPYP). The M121 site in M121E-cPYP corresponds to the M100 site in wild-type H. halophila PYP. High-resolution NMR measurements with a salt-tolerant cryoprobe enabled identification of those residues directly affected by increasing concentrations of ammonium chloride, a salt that greatly enhances the fraction of the intermediate spectra form. Residues in the surface loop containing the M121E (M100E) mutation were found to be affected by ammonium chloride as well as a discrete set of residues that link this surface loop to the buried hydroxyl group of the chromophore via a hydrogen bond network. Localized changes in the conformational dynamics of a surface loop can thereby produce structural rearrangements near the buried hydroxyl group chromophore while leaving the large majority of residues in the protein unaffected.

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Mutations at the M100 site (large red ball) in photoactive yellow protein produce the intermediate spectral form (shoulder in the UV-Vis spectrum) by affecting a network of residues (cyan balls) including those that are H-bonded to the hydroxyl group of the chromophore (small red balls).

Quelle: Photochemistry and Photobiology | 28 May 2015 | 10:54 am CEST

Reviewing the relevance of fluorescence in biological systems

Photochem. Photobiol. Sci., 2015, 14,1538-1559
DOI: 10.1039/C5PP00122F, Perspective
M. Gabriela Lagorio, Gabriela. B. Cordon, Analia Iriel
We review the state of the art in the research on the fluorescence emitted by plant leaves, fruits, flowers, avians, butterflies, beetles, dragonflies, millipedes, cockroaches, bees, spiders, scorpions and sea organisms and discuss its relevance in nature.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 27 May 2015 | 1:00 am CEST

Photochemical degradation of the UV filter octyl methoxycinnamate in solution and in aggregates

Photochem. Photobiol. Sci., 2015, 14,1607-1616
DOI: 10.1039/C5PP00074B, Paper
Kerry M. Hanson, Swathi Narayanan, Valerie M. Nichols, Christopher J. Bardeen
The photodegradation of the ultraviolet (UV) filter octyl methoxycinnamate (OMC) is investigated in both dilute solution and in aggregated form.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 26 May 2015 | 1:00 am CEST

Vibronic Structures in Absorption and Fluorescence Spectra of Firefly Oxyluciferin in Aqueous Solutions

Abstract

To elucidate the factors determining the spectral shapes and widths of the absorption and fluorescence spectra for keto and enol oxyluciferin and their conjugate bases in aqueous solutions, the intensities of vibronic transitions between their ground and first electronic excited states were calculated for the first time via estimation of the vibrational Franck–Condon factors. The major normal modes, overtones and combination tones in absorption and fluorescence spectra are similar for all species. The theoretical full widths at half maximum of absorption spectra are 0.4–0.7 eV and those for the fluorescence spectra are 0.4–0.5 eV, except for phenolate-keto that exhibits exceptionally sharp peak widths due to the dominance of the 0–0′ or 0′–0 band. These spectral shapes and widths explain many relevant features of the experimentally observed spectra.

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The intensities of vibronic transitions for keto and enol oxyluciferin and their conjugate bases in aqueous solutions between their ground and first electronic excited states were calculated for the first time via estimation of the vibrational Franck–Condon factors. The theoretical spectral shapes and widths explain many relevant features of the experimentally observed spectra.

Quelle: Photochemistry and Photobiology | 20 May 2015 | 1:28 pm CEST

Solar Ultraviolet Radiation Exposure of South African Marathon Runners During Competition Marathon Runs and Training Sessions: A Feasibility Study

Abstract

Marathon runners spend considerable time in outdoor training for and participating in marathons. Outdoor runners may experience high solar ultraviolet radiation (UVR) exposure. South Africa, where running is popular, experiences high ambient solar UVR levels that may be associated with adverse health effects. This feasibility study explores the use of personal dosimeters to determine solar UVR exposure patterns and possible related acute health risks of four marathon runners during marathons and training sessions in Cape Town and Pretoria. Runners running marathons that started early in the day, and that did not exceed 4 hours, yielded low total solar UVR exposure doses (mean 0.093 SED per exposure period run, median 0.088 SED, range 0.062–0.136 SED; average of 16.54% of ambient solar UVR). Training sessions run during early morning and late afternoon presented similar results. Several challenges hindered analysis including accounting for anatomical position of personal dosimeter and natural shade. To assess health risks, hazard quotients (HQs) were calculated using a hypothetical runner's schedule. Cumulative, annual solar UVR exposure-calculated acute health risks were low (HQ = 0.024) for training sessions and moderate (HQ = 4.922) for marathon runs. While these data and calculations are based on 18 person-days, one can measure marathon runners' personal solar UVR exposure although several challenges must be overcome.

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Marathon runners spend considerable time outdoors training for and participating in marathons, and may experience high solar ultraviolet radiation (UVR) exposure. South Africa, where running is popular, experiences high UVR levels that may be associated with adverse health effects. This feasibility study explores use of personal dosimeters to determine solar UVR exposure patterns of four marathon runners during marathons and training sessions. Runners running marathons that started early in the day, and that did not exceed 4 h, yielded low total solar UVR exposure doses. Several challenges hindered analysis including accounting for anatomical position of personal dosimeter and natural shade.

Quelle: Photochemistry and Photobiology | 19 May 2015 | 12:11 pm CEST

Aminolevulinic acid dendrimers in photodynamic treatment of cancer and atheromatous disease

Photochem. Photobiol. Sci., 2015, 14,1617-1627
DOI: 10.1039/C5PP00126A, Paper
L. Rodriguez, P. Vallecorsa, S. Battah, G. Di Venosa, G. Calvo, L. Mamone, D. Saenz, M. C. Gonzalez, A. Batlle, A. J. MacRobert, A. Casas
ALA dendrimers are taken up by caveolae-mediated endocytosis in macrophages. Intracellular ALA release gives rise to PpIX synthesis and subsequent photosensitization of key cells in atheromas and tumour diseases.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 19 May 2015 | 1:00 am CEST

Ultraviolet B Inhibits Skin Wound Healing by Affecting Focal Adhesion Dynamics

Abstract

As the most important interface between human body and external environment, skin acts as an essential barrier preventing various environmental damages, among which DNA-damaging UV radiation from the sun remains the major environmental risk factor causing various skin diseases. It has been well documented that wavelengths in the ultraviolet B (UVB) radiation range (290–320 nm) of the solar spectrum can be absorbed by skin and lead to cutaneous injury and various other deleterious effects. During process such as wound healing, the orchestrated movement of cells in a particular direction is essential and highly regulated, integrating signals controlling adhesion, polarity and the cytoskeleton. Cell adhesion and migration are modulated through both of actin and microtubule cytoskeletons. However, little was known about how UVB affects skin wound healing and migration of epidermal keratinocytes. Here, we demonstrate that UVB can delay the wound healing progress in vivo with a murine model of full-thickness skin wound. In addition, UVB significantly inhibited keratinocyte motility by altering focal adhesion turnover and cytoskeletal dynamics. Our results provide new insights into the etiology of UVB exposure-induced skin damages.

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Skin is the most important barrier protecting us from various environmental damages such as DNA-damaging UV radiation from the sun. Little was known about how UVB affects skin wound healing and migration of epidermal keratinocytes. The aim of this work is to estimate the effects of UVB on keratinocyte cell motility, focal adhesion turnover, cytoskeletal dynamics and skin wound healing both in vitro and in vivo mouse model.

Quelle: Photochemistry and Photobiology | 16 May 2015 | 7:17 am CEST

Hybrid Membrane of Agarose and Lanthanide Coordination Polymer: a Selective and Sensitive Fe3+ Sensor

Abstract

A new hybrid membrane was prepared by a facile method based on a highly luminescent lanthanide coordination polymer and agarose. The soft membrane was characterized by FT-IR, PXRD, SEM and luminescence. It is found that the soft membrane is a highly selective and sensitive sensor, among 19 metal ion solutions of Fe3+, Mg2+, Li+, Ca2+, Zn2+, Cu2+, Ba2+, Mn2+, Ru3+, Cr3+, Ag+, Sr2+, Cd2+, Na+, Ni2+, Pb2+, Fe2+, Hg2+ and Ca2+, only Fe3+ quench the luminescence. The sensing results can be distinguished by the naked eye in daylight or by irradiation of a portable UV light at the scene. Mechanism studies reveal the sensing is due to the decomposition of the coordination polymer 1 which induced by slow permeation of Fe3+. Further studies found anions of inline image, inline image, inline image, Br, Cl, inline image, inline image, I, inline image and inline image will not quench the luminescence of the hybrid membrane, which imply that other anions in water would not disturb the detection result.

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A new hybrid membrane was prepared by a facile method. It is a highly selective and sensitive Fe3+ sensor. The sensing results can be easily distinguished by the naked eye in daylight or irradiated by a portable UV device.

Quelle: Photochemistry and Photobiology | 14 May 2015 | 7:24 am CEST

Minimizing Concentration of Sodium Hypochlorite in Root Canal Irrigation by Combination of Ultrasonic Irrigation with Photodynamic Treatment

Abstract

Concentration of sodium hypochlorite (NaOCl) is positively correlated with its effectiveness in root canal disinfection but negatively correlated with its biocompatibility. The objective of this in vitro study was to compare the bactericidal effects among ultrasonic irrigation with different concentration of NaOCl alone or together with photodynamic treatment (PDT) against Enterococcus faecalis (E. faecalis) in infected root canals. One hundred and twenty bovine root canals contaminated with E. faecalis were randomly distributed into 12 groups treated with different disinfection methods: PDT, ultrasonic irrigation with NaOCl at different concentrations (0.5%, 1.0%, 2.0%, 2.5% and 5.25%), and ultrasonic irrigation with NaOCl at different concentrations plus PDT. Data of microorganism load were collected before and after disinfection and analyzed by one-way ANOVA and LSD tests. Significantly enhanced antibacterial effects were noticed in groups treated by PDT plus 2.0% or 2.5% NaOCl irrigation (P < 0.05). No statistical differences existed in bactericidal efficacy among groups of PDT plus ultrasonic irrigation with 2.0%, 2.5% or 5.25% NaOCl, and ultrasonic irrigation with 5.25% NaOCl alone (> 0.05). Our study confirmed the feasibility to reduce the concentration of NaOCl to a safer level while maintaining its antibacterial efficiency through synergistic effect of PDT with NaOCl ultrasonic irrigation.

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Enterococcus faecalis plays an important role in root canal treatment failures and persistent periapical infection. The results of this in vitro study confirmed the feasibility to reduce the concentration of NaOCl to a safer level while maintaining its antibacterial efficiency through synergistic effect of PDT with NaOCl ultrasonic irrigation.

Quelle: Photochemistry and Photobiology | 11 May 2015 | 6:04 am CEST

Promotion of Proapoptotic Signals by Lysosomal Photodamage

Abstract

We previously reported that low-level lysosomal photodamage enhanced the efficacy of subsequent mitochondrial photodamage, resulting in a substantial promotion of apoptotic cell death. We now extend our analysis of the sequential PDT protocol to include two additional lysosomal-targeting photosensitizers. These agents, because of enhanced permeability, are more potent than the agent (N-aspartyl chlorin E6, NPe6) used in the initial study. Addition of the cell-permeable cysteine protease inhibitor E-64d and calcium chelator BAPTA-AM almost completely suppressed sequential PDT-induced loss of mitochondrial membrane potential and activation of procaspases-3 and -7. These inhibitors did not, however, suppress the proapoptotic effect of a BH3 mimetic or mitochondrial photodamage. Knockdowns of ATG7 or ATG5, proteins normally associated with autophagy, suppressed photodamage induced by the sequential PDT protocol. These effects appear to be independent of the autophagic process as pharmacological inhibition of autophagy offered no such protection. Effects of ATG7 and ATG5 knockdowns may reflect the role that ATG7 plays in regulating lysosome permeability, and the likelihood that a proteolytic fragment of ATG5 amplifies mitochondrial proapoptotic processes. Our results suggest that low-dose photodamage that sequentially targets lysosomes and mitochondria may offer significant advantages over the use of single photosensitizers.

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Dose–response curves showing the ability of a prior low level of lysosomal photodamage (NPe6) to markedly potentiate photokilling by the benzoporphyrin derivative (BPD).

Quelle: Photochemistry and Photobiology | 8 May 2015 | 1:42 pm CEST

Light-mediated DNA Repair Prevents UVB-induced Cell Cycle Arrest in Embryos of the Crustacean Macrobrachium olfersi

Abstract

High levels of ultraviolet-B (UVB) radiation can negatively affect aquatic animals. Macrobrachium olfersi is a prawn that lives in clear freshwaters and during the breeding season, females carry eggs in an external brood pouch. Therefore, we hypothesize that eggs are also exposed to environmental UVB radiation. The aim of this study was to investigate whether UVB radiation induces DNA damage and compromises cell cycle in embryos of M. olfersi. In laboratory, UVB irradiance (310 mW. cm−2) that embryos receive in the natural environment was simulated. After irradiation, embryos were kept under different light conditions in order to recognize the presence of cell repair. UVB radiation induces DNA damage, specifically thymine dimers. After 48 h of UVB exposure, a significant decrease in the level of these dimers was observed in embryos kept under visible light while it remained constant in the dark. Moreover, under visible light and darkness, a decrease in proliferation was observed after 48 h of irradiation. An increase in PCNA expression and decrease in p53 expression were observed after, respectively, 1 and 48 h of exposure. Our results showed that UVB radiation disturbs the cell cycle and induces DNA damage in M. olfersi embryos. However, under visible light these embryos showed successful DNA repair.

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In this paper, we simulated in laboratory the UVB irradiance that embryos receive in the natural environment. After irradiation, embryos were kept under different visible light conditions in order to recognize the presence of cell damage repair. In summary, our results showed that UVB radiation negatively impacts embryos of M. olfersi. The impairments observed in proliferation probably resulted from unrepaired DNA damage, which was responsible for the overexpression in darkness of p53 after 48 h and PCNA after 1 h. Moreover, in this study we demonstrated that, under visible light, embryos showed successful DNA repair.

Quelle: Photochemistry and Photobiology | 4 May 2015 | 7:02 am CEST

An Optimized Firefly Luciferase Bioluminescent Assay for the Analysis of Free Fatty Acids

Abstract

A firefly luciferase (LUC)-based bioluminescent assay for total free fatty acids (FFA) is presented. It is based on LUC's capability of converting FFA into fatty acyl-adenylates with consumption of adenosine 5′-triphosphate (ATP). Since ATP is a cosubstrate in LUC's bioluminescent reaction, together with firefly d-luciferin (d-LH2) and atmospheric oxygen (O2), any reduction in the assay's ATP content will lead to a decrease in the bioluminescent signal, which is proportional to the amount of FFA. Using FFA mixtures containing myristic (14:0), palmitic (16:0), stearic (18:0), oleic (18:1) and arachidonic acid (20:4) in ethanol, the assay was optimized through statistical experimental design methodology, namely fractional factorial (screening) and central composite (optimization) designs. The optimized method requires 2 μL of sample per tube in a final reaction volume of 50 μL. It is linear in the concentration range from 1 to 20 μm, with limits of detection (LOD) and quantitation (LOQ) of 1.3 and 4.5 μm, respectively. The method proved to be simple to perform, demands low reagent volumes, it is sensitive and robust and may be adapted to high-throughput screening.

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An optimized bioluminescent assay for free fatty acids is herein presented. The method is based on ATP depletion followed by bioluminescence detection. Optimization was achieved through experimental design methodology. The method is linear from 1 to 20 μm, with limits of detection and quantitation of 1.3 and 4.5 μm, respectively. The method is fast, simple to perform, sensitive and robust.

Quelle: Photochemistry and Photobiology | 4 May 2015 | 6:35 am CEST

Photo and Chemical Reduction of Copper onto Anatase-Type TiO2 Nanoparticles with Enhanced Surface Hydroxyl Groups as Efficient Visible Light Photocatalysts

Abstract

In this study, the photocatalytic efficiency of anatase-type TiO2 nanoparticles synthesized using the sol–gel low-temperature method, were enhanced by a combined process of copper reduction and surface hydroxyl groups enhancement. UV–light-assisted photo and NaBH4-assisted chemical reduction methods were used for deposition of copper onto TiO2. The surface hydroxyl groups of TiO2 were enhanced with the assistance of NaOH modification. The prepared catalysts were immobilized on glass plates and used as the fixed-bed systems for the removal of phenazopyridine as a model drug contaminant under visible light irradiation. NaOH-modified Cu/TiO2 nanoparticles demonstrated higher photocatalytic efficiency than that of pure TiO2 due to the extending of the charge carriers lifetime and enhancement of the adsorption capacity of TiO2 toward phenazopyridine. The relationship of structure and performance of prepared nanoparticles has been established by using various techniques, such as XRD, XPS, TEM, EDX, XRF, TGA, DRS and PL. The effects of preparation variables, including copper content, reducing agents rate (NaBH4 concentration and UV light intensity) and NaOH concentration were investigated on the photocatalytic efficiency of NaOH-modified Cu/TiO2 nanoparticles.

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The visible–light-induced photocatalytic activity of anatase-type TiO2 nanoparticles was enhanced by a combined process of copper reduction and surface hydroxyl groups enhancement.

Quelle: Photochemistry and Photobiology | 8 Apr 2015 | 10:51 am CEST

Effects of Silencing Heme Biosynthesis Enzymes on 5-Aminolevulinic Acid-mediated Protoporphyrin IX Fluorescence and Photodynamic Therapy

Abstract

Aminolevulinic acid (ALA)-mediated protoporphyrin IX (PpIX) production is being explored for tumor fluorescence imaging and photodynamic therapy (PDT). As a prodrug, ALA is converted in heme biosynthesis pathway to PpIX with fluorescent and photosensitizing properties. To better understand the role of heme biosynthesis enzymes in ALA-mediated PpIX fluorescence and PDT efficacy, we used lentiviral shRNA to silence the expression of porphobilinogen synthase (PBGS), porphobilinogen deaminase (PBGD) and ferrochelatase (FECH) in SkBr3 human breast cancer cells. PBGS and PBGD are the first two cytosolic enzymes involved in PpIX biosynthesis, and FECH is the enzyme responsible for converting PpIX to heme. PpIX fluorescence was examined by flow cytometry and confocal fluorescence microscopy. Cytotoxicity was assessed after ALA-mediated PDT. Silencing PBGS or PBGD significantly reduced ALA-stimulated PpIX fluorescence, whereas silencing FECH elevated basal and ALA-stimulated PpIX fluorescence. However, compared with vector control cells, the ratio of ALA-stimulated fluorescence to basal fluorescence without ALA was significantly reduced in all knockdown cell lines. PBGS or PBGD knockdown cells exhibited significant resistance to ALA-PDT, while increased sensitivity to ALA-PDT was found in FECH knockdown cells. These results demonstrate the importance of PBGS, PBGD and FECH in ALA-mediated PpIX fluorescence and PDT efficacy.

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Three heme biosynthesis enzymes porphobilinogen synthase (PBGS), porphobilinogen deaminase (PBGD) and ferrochelatase (FECH) were silenced to evaluate its effects on aminolevulinic acid (ALA)-mediated protoporphyrin IX (PpIX) fluorescence and photodynamic therapy (PDT) in human breast cancer SkBr3 cells. Knockdown of PBGS or PBGD significantly decreased ALA-PpIX fluorescence and rendered resistance to PDT. In contrast, silence of FECH greatly sensitized cells to PDT by increasing ALA-PpIX production.

Quelle: Photochemistry and Photobiology | 8 Apr 2015 | 9:51 am CEST

Effects of Enhanced UV-B Radiation on Biochemical Traits in Postharvest Flowers of Medicinal Chrysanthemum

Abstract

This article reported UV-B radiation effects on biochemical traits in postharvest flowers of chrysanthemum. The experiment included six levels of UV-B radiation (UV0, 0 μW cm−2; UV50, 50 μW cm−2; UV200, 200 μW cm−2; UV400, 400 μW cm−2; UV600, 600 μW cm−2 and UV800, 800 μW cm−2). Enhanced UV-B radiation significantly increased hydrogen peroxide content (except for UV50), but did not evidently affect malondialdehyde content in flowers. Chlorophyll b and total chlorophyll content were significantly increased by UV600 and UV800. UV400 and UV600 significantly increased anthocyanins, carotenoids and UV-B absorbing compounds content, and the activities of phenylalanine ammonia lyase (PAL) and cinnamic acid-4-hydroxylase (C4H) over the control. 4-coumarate CoA ligase (4CL) activity was significantly decreased by enhanced UV-B radiation (except for UV50). The relationships between UV-B radiation intensities and the activities of secondary metabolism enzymes were best described by a second-order polynomial. The R2 values for UV-B radiation intensities and the activities of PAL, C4H and 4CL were 0.8361, 0.5437 and 0.8025, respectively. The results indicated that enhanced UV-B radiation could promote secondary metabolism processes in postharvest flowers, which might be beneficial for the accumulation of medically active ingredients in medicinal plants. The optimal UV-B radiation intensities in the study were between UV400-UV600.

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This article mainly studied enhanced UV-B radiation effects on biochemical traits in postharvest flowers of chrysanthemum. The experiment included six levels of UV-B radiation (UV0, 0 μW cm−2; UV50, 50 μW cm−2; UV200, 200 μW cm−2; UV400, 400 μW cm−2; UV600, 600 μW cm−2 and UV800, 800 μW cm−2). The results indicated that UV-B effects on biochemical traits in postharvest flowers depended on UV-B radiation intensities, and enhanced UV-B radiation could promote secondary metabolism processes in postharvest flowers.

Quelle: Photochemistry and Photobiology | 6 Apr 2015 | 7:24 am CEST

Photodegradation of Hydrophobic Pyridineketoximes in Toluene and Heptane

Abstract

The goal of the research was to study the reactivity of the hydrophobic 2- and 3-pyridineketoximes under exposure to UV-VIS light. The photodegradation was conducted in both toluene and heptane for 10 h under atmosphere of argon. Ten-hour irradiation experiments demonstrated that the pyridineketoximes underwent the facile E-Z photoisomerization, photo-Beckmann rearrangement, and to a lesser extent, the photosubstitution to the pyridine ring. From LC-MS and NMR analysis of the irradiated solutions, it was found that the photosubstitution proceeded to give the corresponding 6-substituted 2- or 3-pyridylketoxime via the replacement of the ring hydrogen by the benzyl or heptyl group. The photo-Beckmann rearrangement led to the formation of the corresponding amides, but also other products formed in the photo-decomposition reaction.

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This study presents the photochemical reactivity of the hydrophobic 2- and 3- pyridineketoximes – (Z)-oxime of 1-(2-pyridyl)tridecan-1-one and (E)-oxime of 1-(3-pyridyl)tridecan-1-one – in toluene and heptane as solvent. The data indicated that the both oximes underwent significant E-Z photoisomerization, photo-Beckmann rearrangement and the photosubstitution to the pyridine ring. For example, in aliphatic solvent, the photo-Beckmann rearrangement of (Z)-oxime of 1-(2-pyridyl)tridecan-1-one led to the formation of 2-aminopyridine, eicosan-8-one and N-dodecylpyridine-2-carboxamide. In the case of (E)-oxime of 1-(3-pyridyl)tridecan-1-one, the photodegradation led to formation of N-dodecylpyridine-3-carboxamide, 3-aminopyridine and eicosan-8-one.

Quelle: Photochemistry and Photobiology | 6 Apr 2015 | 7:03 am CEST

Effects of PAR and UV Radiation on the Structural and Functional Integrity of Phycocyanin, Phycoerythrin and Allophycocyanin Isolated from the Marine Cyanobacterium Lyngbya sp. A09DM

Abstract

An in vitro analysis of the effects of photosynthetically active and ultraviolet radiations was executed to assess the photostability of biologically relevant pigments phycocyanin (PC), phycoerythrin (PE) and allophycocyanin (APC) isolated from Lyngbya sp. A09DM. Ultraviolet (UV) irradiances significantly affected the integrity of PC, PE and APC; however, PAR showed least effect. UV radiation affected the bilin chromophores covalently attached to phycobiliproteins (PBPs). Almost complete elimination of the chromophore bands associated with α- and β-subunit of PE and APC occurred after 4 h of UV-B exposure. After 5 h of UV-B exposure, the content of PC, PE and APC decreased by 51.65%, 96.8% and 96.53%, respectively. Contrary to PAR and UV-A radiation, a severe decrease in fluorescence of all PBPs was observed under UV-B irradiation. The fluorescence activity of extracted PBP was gradually inhibited immediately after 15–30 min of UV-B exposure. In comparison to the PC, the fluorescence properties of PE and APC were severely lost under UV-B radiation. Moreover, the present study indicates that UV-B radiation can damage the structural and functional integrity of phycobiliproteins leading to the loss of their ecological and biological functions.

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UV irradiances significantly affected the structural and functional integrity of biologically relevant molecules phycocyanin (PC, λmax: 615 nm), phycoerythrin (PE, λmax: 563 nm) and allophycocyanin (APC, λmax: 652 nm). UV radiation also affected the bilin chromophores covalently attached to phycobiliproteins (PBPs). The spectroscopic as well as sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE) analyses of the PC, PE and APC of Lyngbya sp. showed a marked decrease in the PBPs content with an increase in UV exposure time. In comparison to the PC, the fluorescence properties of PE and APC were severely lost under UV-B radiation.

Quelle: Photochemistry and Photobiology | 2 Apr 2015 | 12:02 pm CEST

Susceptibility of Ureaplasma urealyticum to Methylene Blue-Mediated Photodynamic Antimicrobial Chemotherapy: An in vitro Study

Abstract

The aim of this study was to detect the susceptibility of Ureaplasma urealyticum to methylene blue-mediated photodynamic antimicrobial chemotherapy (PACT). Three U. urealyticum strains including the standard serotype 1 and 5, and a clinically collected strain were used in this study. Strains were first incubated in 96-well culture plates in the presence of methylene blue with decreasing concentrations (from 1 to 0.015625 mg mL−1) for 20 or 60 min, and then submitted to irradiation with a light-emitting diode laser with a power density of 100 mW cm−2 for 8, 17, 34 or 68 min. Regrowth of the strains was performed soon after irradiation. A significant inactivation effect was observed after PACT. Longer incubation time induced more extensive inactivation of U. urealyticum. No difference in response to PACT was observed between the two biovars of U. urealyticum. It was concluded that PACT had a significant inactivation effect on U. urealyticum, and it might be a promising alternative treatment for resistant U. urealyticum infections.

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This work investigated the susceptibility of Ureaplasma urealyticum to methylene blue-mediated photodynamic antimicrobial chemotherapy (PACT). When U. urealyticum strains were incubated with methylene blue for 20 or 60 min, irradiation with 633 nm red light led to a significant inactivation effect on the growth of U. urealyticum. Higher light dose, or longer incubation time with methylene blue induced more extensive inactivation of U. urealyticum. Thus, PACT provides a promising alternative treatment for resistant U. urealyticum infections.

Quelle: Photochemistry and Photobiology | 2 Apr 2015 | 12:01 pm CEST

Photosensitizing Activity of Endogenous Eye Lens Chromophores: An Attempt to Unravel Their Contributions to Photo-Aging and Cataract Disease

Abstract

UVA-visible light has been proposed as a risk factor in the photo-aging of the human eye lens, as well as in the etiology of cataract disease. There is accumulating evidence indicating that photosensitizing reactions mediated by endogenous chromophores, which are generated during human eye lens aging, can play an important role in the generation of these processes. These reactions can lead to protein impairment by inducing non-enzymatic post-translational modifications such as protein oxidation and crosslinking. Although numerous chromophores have been characterized as both bound to human eye lens proteins and as unbound low-molecular-mass compounds, their contribution to eye lens photoaging and cataract disease is not completely understood. In this article we discuss the photochemical contribution of UV-filters derived from tryptophan catabolism and advanced glycation end products (AGEs) to human eye lens aging and cataract disease. We also discuss the recently described photosensitizing capacity of chromophores derived from newly discovered glucose and ascorbate degradation as a parallel pathway to their role in AGEs generation.

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Human eye lens aging is accompanied with the generation of numerous chromophores, which can be found at higher concentrations in cataractous lenses. In this review we discuss the presence and UVA-visible photosensitizing capacity of the main families of chromophores associated with the etiology and progression of human cataract disease.

Quelle: Photochemistry and Photobiology | 28 Mar 2015 | 9:57 am CET

High Final Energy of Low-Level Gallium Arsenide Laser Therapy Enhances Skeletal Muscle Recovery without a Positive Effect on Collagen Remodeling

Abstract

The aim of this study was to evaluate the effects of a Gallium Arsenide (GaAs) laser, using a high final energy of 4.8 J, during muscle regeneration after cryoinjury. Thirty Wistar rats were divided into three groups: Control (C, n = 10); Injured (I, n = 10) and Injured and laser treated (Injured/LLLT, n = 10). The cryoinjury was induced in the central region of the tibialis anterior muscle (TA). The applications of the laser (904 nm, 50 mW average power) were initiated 24 h after injury, at energy density of 69 J cm−1 for 48 s, for 5 days, to two points of the lesion. Twenty-four hours after the final application, the TA muscle was removed and frozen in liquid nitrogen to assess the general muscle morphology and the gene expression of TNF-α, TGF-β, MyoD, and Myogenin. The Injured/LLLT group presented a higher number of regenerating fibers and fewer degenerating fibers (P < 0.05) without changes in the collagen remodeling. In addition, the Injured/LLLT group presented a significant decrease in the expression of TNF-α and myogenin compared to the injured group (P < 0.05). The results suggest that the GaAs laser, using a high final energy after cryoinjury, promotes muscle recovery without changing the collagen remodeling in the muscle extracellular matrix.

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This study investigated the effects of low-level laser therapy (LLLT) at a high final energy (4.8 J) during muscle regeneration after cryoinjury. Gallium Arsenide (GaAs, 904 nm) laser applied for 5 days in two points of the lesion resulted in a significant decrease in the TNF-α and myogenin, without change in the TGF-β gene expression. The Injured/LLLT group presented a higher number of regenerating fibers and fewer degenerating fibers without changes in the collagen remodeling. The results suggest that the GaAs laser at a high final energy (4.8 J) promotes muscle recovery without changing the collagen remodeling.

Quelle: Photochemistry and Photobiology | 28 Mar 2015 | 9:54 am CET

A Novel Microsensor for Measuring Angular Distribution of Radiative Intensity

Abstract

This article presents the design, construction and characterization of a novel type of light probe for measuring the angular radiance distribution of light fields. The differential acceptance angle (DAA) probe can resolve the directionality of a light field in environments with steep light gradients, such as microbial mats, without the need to remove, reorient, and reinsert the probe, a clear advantage over prior techniques. The probe consists of an inner irradiance sensor inside a concentric, moveable light-absorbing sheath. The radiative intensity in a specific zenith direction can be calculated by comparing the irradiance onto the sensor at different acceptance angles. We used this probe to measure the angular radiance distribution of two sample light fields, and observed good agreement with a conventional radiance probe. The DAA probe will aid researchers in understanding light transfer physics in dense microbial communities and expedite validation of numerical radiative transfer models for these environments.

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Measurement of the directional dependence of radiative intensity is essential for understanding light transport in microbial mats, plant leaves, soils and phototrophic biofilms. Previously, measuring the directional intensity in these environments required inserting a field radiance probe with a small acceptance angle into a tissue at multiple angles, which required significant time and labor. This paper presents a novel differential acceptance angle (DAA) light probe, which can measure the directional intensity in light fields from a single location without reorienting the probe. We discuss the construction of the DAA probe and its performance compared to a conventional field radiance probe.

Quelle: Photochemistry and Photobiology | 28 Mar 2015 | 9:37 am CET

Endogenous Retinoic Acid Required to Maintain the Epidermis Following Ultraviolet Light Exposure in SKH-1 Hairless Mice

Abstract

Ultraviolet light B (UVB) exposure induces cutaneous squamous cell carcinoma (cSCC), one of the most prevalent human cancers. Reoccurrence of cSCC in high-risk patients is prevented by oral retinoids. But oral retinoid treatment causes significant side effects; and patients develop retinoid resistance. Exactly how retinoids prevent UVB-induced cSCC is currently not well understood. Retinoid resistance blocks mechanistic studies in the leading mouse model of cSCC, the UVB-exposed SKH-1 hairless mouse. To begin to understand the role of retinoids in UVB-induced cSCC we first examined the localization pattern of key retinoid metabolism proteins by immunohistochemistry 48 h after UVB treatment of female SKH-1 mice. We next inhibited retinoic acid (RA) synthesis immediately after UVB exposure. Acute UVB increased RA synthesis, signaling and degradation proteins in the stratum granulosum. Some of these proteins changed their localization; while other proteins just increased in intensity. In contrast, acute UVB reduced the retinoid storage protein lectin:retinol acyltransferase (LRAT) in the epidermis. Inhibiting RA synthesis disrupted the epidermis and impaired differentiation. These data suggest that repair of the epidermis after acute UVB exposure requires endogenous RA synthesis.

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Ultraviolet light B (UVB) exposure alters the expression of some retinoid metabolism proteins; but an analysis of the complete system in vivo is lacking. We analyzed the expression of retinoid metabolism proteins by immunohistochemistry 48 h after UVB treatment of SKH-1 mice. Acute UVB localized retinoic acid (RA) synthesis and signaling to the upper stratum granulosum; localized RA degradation to the lower stratum granulosum and stratum spinosum; and reduced retinoid storage. Inhibition of RA synthesis by disulfiram damaged the epidermis (image). These results suggest that endogenously synthesized RA is important in epidermal differentiation and repair following UVB exposure.

Quelle: Photochemistry and Photobiology | 28 Mar 2015 | 9:34 am CET

Biomodulation of Inflammatory Cytokines Related to Oral Mucositis by Low-Level Laser Therapy

Abstract

This study evaluated the effects of LLLT on the expression of inflammatory cytokines related to the development of oral mucositis by gingival fibroblasts. Primary gingival fibroblasts were seeded on 24-well plates (105 cells/well) for 24 h. Fresh serum-free culture medium (DMEM) was then added, and cells were placed in contact with LPS (Escherichia coli, 1 μg mL−1), followed by LLLT irradiation (LaserTABLE—InGaAsP diode prototype—780 nm, 25 mW) delivering 0, 0.5, 1.5 or 3 J cm². Cells without contact with LPS were also irradiated with the same energy densities. Gene expression of TNF-α, IL-1β, IL-6 and IL-8 was evaluated by Real-Time PCR, and protein synthesis of these cytokines was determined by enzyme-linked immunosorbent (ELISA) assay. Data were statistically analyzed by the Kruskal–Wallis test, complemented by the Mann–Whitney test (< 0.05). LPS treatment increased the gene expression and protein synthesis of TNF-α, IL-6 and IL-8, while the expression of IL-1β was not affected. For LPS-treated groups, LLLT promoted significant decreases in the expression of TNF-α, IL-6, and IL-8 at 1.5 J cm−2 and 3 J cm−2. These results demonstrate that LLLT promoted a beneficial biomodulatory effect on the expression of inflammatory cytokines related to oral mucositis by human gingival fibroblasts.

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This study evaluated the effects of low level laser therapy (LLLT) on the expression of inflammatory cytokines involved in the development and severity of oral mucositis. Human gingival fibroblasts treated with LPS (Escherichia coli, 1 μg mL−1) were subjected to LLLT irradiation (LaserTABLE—InGaAsP diode prototype—780 nm, 25 mW) delivering 0, 0.5, 1.5, or 3 J cm². LLLT promoted significant decreases in the expression of TNF-α, IL-6 and IL-8 at 1.5 J cm−2 and 3 J cm−2. These results demonstrate that LLLT promoted a beneficial biomodulatory effect on the expression of inflammatory cytokines related to oral mucositis by human gingival fibroblasts.

Quelle: Photochemistry and Photobiology | 28 Mar 2015 | 9:24 am CET

Fluorescence Properties of Diphenylthiazolo[4,5-b]pyrazines Tuned by Donor-Acceptor Substituent Effects

Abstract

Fluorescence properties of 2,6- and 2,5-diphenylthiazolo[4,5-b]pyrazine (TPy) derivatives having an electron-donating substituent (methoxy and dimethylamino) on the 6- and 5-phenyl groups were studied. It was found that 2,6-diphenyl derivatives fluoresce more efficiently than 2,5-diphenyl derivatives. Furthermore, a 2,6-diphenyl derivative having an additional cyano group on the 2-phenyl ring was an excellent fluorophore showing a wide solvatochromism with great fluorescence yields. Based on the obtained spectroscopic data and mechanistic explanations concerning the substituent effects on the fluorescence properties, useful information on designing new TPy fluorophores is provided.

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Fluorescence properties of 2,6- and 2,5-diphenylthiazolo[4,5-b]pyrazines having an electron-donating substituent (methoxy and dimethylamino) on the 6- and 5-phenyl groups were studied. Furthermore, 2,6-diphenyl derivatives having an additional cyano group on the 2-phenyl ring were developed, to give an excellent fluorophore.

Quelle: Photochemistry and Photobiology | 18 Mar 2015 | 7:09 am CET

Salvianolic Acid B Protects Normal Human Dermal Fibroblasts Against Ultraviolet B Irradiation-Induced Photoaging Through Mitogen-Activated Protein Kinase and Activator Protein-1 Pathways

Abstract

Exposure to ultraviolet (UV) light causes increased matrix metalloproteinase (MMP) activity and decreased collagen synthesis, leading to skin photoaging. Salvianolic acid B (SAB), a polyphenol, was extracted and purified from salvia miltiorrhiza. We assessed effects of SAB on UVB-induced photoaging and investigated its molecular mechanism of action in UVB-irradiated normal human dermal fibroblasts. Our results show that SAB significantly inhibited the UVB-induced expression of metalloproteinases-1 (MMP-1) and interleukin-6 (IL-6) while promoting the production of type I procollagen and transforming growth factor β1 (TGF-β1). Moreover, treatment with SAB in the range of 1–100 μg/mL significantly inhibited UVB-induced extracellular signal-regulated kinase (ERK), Jun N-terminal kinase (JNK) and p38 phosphorylation, which resulted in decreasing UVB-induced phosphorylation of c-Fos and c-Jun. These results indicate that SAB downregulates UV-induced MMP-1 expression by inhibiting Mitogen-activated protein kinase (MAPK) signaling pathways and activator protein-1 (AP-1) activation. Our results suggest a potential use for SAB in skin photoprotection.

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UV causes increased matrix metalloproteinase (MMP) activity and decreased collagen synthesis, leading to skin photoaging. We found that salvianolic acid B (SAB) significantly inhibited the UVB-induced expression of metalloproteinases-1 (MMP-1) while promoting the production of transforming growth factor β1 (TGF-β1). Moreover, SAB strongly inhibited UVB-induced extracellular signal-regulated kinase (ERK), Jun N-terminal kinase (JNK) and p38 phosphorylation, which resulted in decreasing UVB-induced phosphorylation of c-Fos and c-Jun. These results indicate that SAB down-regulates UV-induced MMP-1 expression by inhibiting mitogen-activated protein kinase (MAPK) signaling pathways and activator protein-1 (AP-1) activation.

Quelle: Photochemistry and Photobiology | 18 Mar 2015 | 7:09 am CET

Luciferin-Regenerating Enzyme Mediates Firefly Luciferase Activation Through Direct Effects of D-Cysteine on Luciferase Structure and Activity

Abstract

Luciferin-regenerating enzyme (LRE) contributes to in vitro recycling of D-luciferin. In this study, reinvestigation of the luciferase-based LRE assay is reported. Here, using quick change site-directed mutagenesis seven T-LRE (Lampyris turkestanicusLRE) mutants were constructed and the most functional mutant of T-LRE (T69R) was selected for this research and the effects of D- and L-cysteine on T69R T-LRE-luciferase-coupled assay are examined. Our results demonstrate that bioluminescent signal of T69R T-LRE-luciferase-coupled assay increases and then reach equilibrium state in the presence of 5 mm D-cysteine. In addition, results reveal that 5 mm D- and L-cysteine in the absence of T69R T-LRE cause a significant increase in bioluminescence intensity of luciferase over a long time as well as decrease in decay rate. Based on activity measurements, far-UV CD analysis, ANS fluorescence and DLS (Dynamic light scattering) results, D-cysteine increases the activity of luciferase due to weak redox potential, antiaggregatory effects, induction of changes in conformational structure and kinetics properties. In conclusion, in spite of previous reports on the effect of LRE on luciferase bioluminescent intensity, the majority of increase in luciferase light output and time-course originate from the direct effects of D-cysteine on structure and activity of firefly luciferase.

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The addition of D-cysteine in the absence of T69R T-LRE (closed circle) to luciferase reaction increased the bioluminescent level over time in comparison with a luciferase reaction containing D-cysteine in the presence of T69R T-LRE (closed diamond) and control (solid line). Thus, even in the presence of LRE the majority of this increase occurs from the direct effects of D-cysteine.

Quelle: Photochemistry and Photobiology | 18 Mar 2015 | 7:07 am CET

Variability of Solar Radiation and CDOM in Surface Coastal Waters of the Northwestern Mediterranean Sea

Abstract

Atmospheric and in-water solar radiation, including UVR-B, UVR-A and PAR, as well as chromophoric dissolved organic matter absorption [aCDOM(λ)] in surface waters were monthly measured from November 2007 to December 2008 at a coastal station in the Northwestern Mediterranean Sea (Bay of Marseilles, France). Our results showed that the UVR-B/UVR–A ratio followed the same trend in the atmosphere and at 2 m depth in the water (P < 0.0001) with an increase (eight-fold higher) during summer. The low diffuse attenuation coefficients for downward irradiance [Kd(λ)] of UVR-B, UVR-A and PAR indicated that the waters were highly transparent throughout the year. The relationships between aCDOM(λ) and Kd(λ) in this oligotrophic system suggested that CDOM contributed to UVR attenuation in the UVA domain, but also played a significant role in PAR attenuation. Mean UV doses received in the mixed layer depth were higher by a factor 1.4–33 relative to doses received at fixed depths (5 and 10 m) in summer (stratified period), while the inverse pattern was found in winter (mixing period). This shows the importance of taking into account the vertical mixing in the evaluation of UVR effects on marine organisms.

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The wavelengths 305 and 380 nm have been chosen as biologically effective wavelengths for the induction of DNA damages (CPDs) and photorepairs (PERs) respectively. The ratio of the mean doses received within the mixed layer at 305 and 380 nm [Q in % = H(m,305)]/H(m,380) × 100] along with the mixed layer depth (Zm) are presented. Q ratio can be considered as an indicator of changes in the balance between DNA damages (CPDs) and repairs (PERs). Clearly, Q increased with the stratification of the water column.

Quelle: Photochemistry and Photobiology | 16 Mar 2015 | 6:18 am CET

Actual Isothermal Effects of Water-Filtered Infrared A-Irradiation

Abstract

In this study, the athermal effects of water-filtered infrared A (wIRA)-irradiation (780–1400 nm) on human dermal fibroblasts were investigated. For this purpose, cells were exposed to wIRA-irradiation (178 mW cm−2 for 1 h), while a sophisticated experimental setup prevented warming of the samples exceeding 0.1°C. The investigated parameters were the formation of reactive oxygen species (ROS), mitochondrial membrane potential and superoxide release, protein oxidation, proliferation rate, as well as intracellular Ca2+-release in single cells, most of them quantified via fluorescence microscopy and fluorimetric techniques. The existence of actual athermal wIRA-effects is still intensively discussed, since their detection requires a careful experimental setup and both efficient and powerful temperature regulation of the exposed samples. Here, we can definitively show that some of the supposed athermal wIRA-effects may be rather artifacts, since wIRA did not reveal any impact on the above mentioned parameters—as long as the temperature of the exposed cells was carefully maintained. Though, we were able to identify an athermal DNA-protective wIRA-effect, since the induced DNA damage (quantified via 8-Oxo-G-formation) was significantly decreased after a subsequent UVB-exposure. These results suggest that many of the supposed athermal wIRA-effects can be induced by pure warming of the samples, independent from any wIRA-irradiation.

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In this work, we exposed human dermal fibroblasts to water-filtered infrared A (wIRA)-irradiation under isothermal conditions in order to investigate changes in the parameters intracellular free calcium, mitochondrial membrane potential and radical production, DNA and protein oxidation, cell proliferation and protection against UVB.

Quelle: Photochemistry and Photobiology | 12 Mar 2015 | 6:30 am CET

Human Hair as a Natural Sun Protection Agent: A Quantitative Study

Abstract

The rising incidence of skin cancers attributable to excessive sun exposure has become a major health concern worldwide. While numerous studies have analyzed the sun protective effect of sunscreens, clothing and antioxidants, none to date have measured the photoprotective effect of hair, despite clinical evidence that individuals with balding or thinning hair are at greater risk of skin lesions that can progress to cancer, hence the recommendation to use hats or umbrellas. We analyzed the level of protection offered by hair according to hair density, thickness and color using the spectral transmittance and corrected for relative erythema effectiveness. Our results show that hair provides a barrier against both UVB and UVA radiation which is significantly increased with respect to the hair density, thickness and the presence of melanins. This is the first study to quantify sun protection factor offered by hair, namely hair ultraviolet protection factor (HUPF). We believe that hair should be recognized as an important natural sun barrier in the prevention of UV-induced skin cancers.

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Hair provides a barrier against both UVB and UVA radiation which is significantly increased with respect to the hair density (A), thickness (B) and the presence of melanins (hair color) (C). This is the first study to quantify sun protection factor offered by hair, namely hair ultraviolet protection factor (HUPF). Hair should be recognized as an important natural sun barrier in the prevention of UV-induced skin cancers.

Quelle: Photochemistry and Photobiology | 12 Mar 2015 | 6:30 am CET

Histopathological Analysis of UVB and IR Interaction in Rat Skin

Abstract

To determine the chronic skin effects caused by the interaction of infrared and ultraviolet B radiations, male Rattus norvegicus (Wistar) (2 months old) were exposed for 15 days to infrared radiation (600–1500 nm, with a peak at 1000 nm, n = 12) for 30 min (1080 J cm−2) (IRo); to ultraviolet B radiation (peak emission at 313 nm, n = 9) for 90 min (55.08 J cm−2) (UVB); to infrared radiation followed after 90 min by ultraviolet B (n = 6) (IRUVB) and to ultraviolet B followed after 90 min by infrared radiation (n = 9) (UVBIR). Skin samples were collected and histopathological analysis showed the presence of acanthosis, parakeratotic and orthokeratotic hyperkeratosis, intraepidermal pustules, keratin pearls, detachment of epidermis, collagen necrosis, inflammatory infiltrate, vasodilation, basal cell vacuolization and superficial dermis degeneration both in UVB and UVBIR treatments. IRUVB animals showed the same characteristics as above except for parakeratotic hyperkeratosis, keratin pearls and superficial dermis degeneration. To conclude, infrared radiation exposure after ultraviolet B irradiation increases skin damage without protecting the tissue, while infrared radiation exposure before ultraviolet B irradiation showed a protective effect against ultraviolet skin damage.

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Chronic IR exposure before UVB irradiation can reduce some of the histopathological alterations caused by UVB while chronic IR exposure after UVB irradiation can enhance most of the histopathological features caused by UVB skin damage.

Quelle: Photochemistry and Photobiology | 12 Mar 2015 | 6:14 am CET

Interfacial Engineering of CdO–CdSe 3D Microarchitectures with in situ Photopolymerized PEDOT for an Enhanced Photovoltaic Performance

Abstract

In the present work, porous 3D CdO-microstructured electrode obtained by pyrolysis of 3D CdCO3 microstructures is self-sensitized with CdSe using an ion exchange reaction. After sensitization, an interfacial treatment of the CdO–CdSe interface is performed by depositing a thin film of PEDOT using a photoinduce polymerization route. The microstructured electrode before and after interfacial treatment is characterized using field-emission scanning microscope, energy dispersive X-ray analyzer, contact angle measurement, UV–Visible absorption spectrophotometer and X-ray photoelectron spectrometer. After constructing a liquid junction solar cell with a Pt counter electrode, the photovoltaic performance and interfacial charge transfer kinetics across the CdO–CdSe interface before and after PEDOT treatment are investigated. The results exhibit an improved interfacial charge-transfer resistance after the PEDOT treatment, which leads to enhance the short-circuit current by 15.81% and the power conversion efficiency by 19.82%.

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Interfacial engineering of 3D CdO–CdSe-microstructured film by deposition of PEDOT accelerates the interfacial electron transfer rate, and thereby the interfacial electron collection efficiency is enhanced. Thus, the short-circuit current of the device is enhanced significantly.

Quelle: Photochemistry and Photobiology | 28 Feb 2015 | 8:27 am CET




 


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