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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:


Angelica archangelia Prevented Collagen Degradation by Blocking Production of Matrix Metalloproteinases in UVB-exposed Dermal Fibroblasts

Abstract

Angelica archangelia (AA), a traditional herb, has attracted attention as an agent with potential for use in the prevention of chronic skin diseases. This study examined the photoprotective effects of AA on the inhibition of matrix metalloproteinases (MMPs) and collagen degradation in UVB-irradiated normal human dermal fibroblasts (NHDFs). Our results showed that AA markedly blocked collagen degradation by restraining the production of MMPs in UVB-exposed fibroblasts. We also investigated the underlying mechanism behind the effects of AA. AA attenuated UVB-triggered interleukin-6 (IL-6) and promoted the expression of transforming growth factor β1 (TGF-β1). Application of AA extract (10, 100 μg/mL) significantly diminished UVB-induced extracellular signal-regulated kinase (ERK) and Jun N-terminal kinase (JNK) phosphorylation, which consequently reduced phosphorylated c-Fos and c-Jun. Our results indicated that AA inhibited the UVB-induced expression of MMPs by inhibiting mitogen-activated protein kinase (MAPK) signaling pathways and activator protein-1 (AP-1) activation. Our results suggest that AA is a promising botanical agent for use against skin photoaging.

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Quelle: Photochemistry and Photobiology | 29 Apr 2016 | 5:57 pm CEST

Melatonin Mediates Monochromatic Light-induced Insulin-like Growth Factor 1 Secretion of Chick Liver: Involvement of Membrane Receptors

Abstract

Monochromatic lights influenced the proliferation and differentiation of skeletal satellite cells in broilers by the enhancement of insulin-like growth factor 1 (IGF-1) secretion. However, whether melatonin (MEL) mediated monochromatic lights influenced the IGF-1 secretion is not clear. Newly hatched broilers, including intact, sham operation, and pinealectomy groups, were exposed to blue (BL), green (GL), red (RL) and white light (WL) from a light-emitting diode system for 14 days. The results showed that GL effectively promoted the secretion of MEL and IGF-1, the expression of proliferating cell nuclear antigen and MEL receptor subtypes Mel1a, Mel1b and Mel1c in the liver compared to BL and RL in vivo. Moreover, those was a positive correlation between MEL and IGF-1 (r = 0.834). After pinealectomy, however, these parameters declined, and there were no differences between GL and other monochromatic light treatments. In vitro, exogenous MEL increased hepatocyte proliferation and IGF-1 secretion. Meanwhile, the MEL enhancements were suppressed by prazosin (selective Mel1c antagonist), followed by luzindole (nonselective Mel1a/Mel1b antagonist), but not suppressed by 4-phenyl-2-propionamideotetralin (selective Mel1b antagonist). These findings demonstrated that MEL mediated the monochromatic light-induced secretion of IGF-1 in chicks’ livers by Mel1c and that Mel1a may be involved in this process.

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Quelle: Photochemistry and Photobiology | 29 Apr 2016 | 5:15 pm CEST

Photooxygenation of alkanes by dioxygen with p-benzoquinone derivatives with high quantum yields

Photochem. Photobiol. Sci., 2016, Accepted Manuscript
DOI: 10.1039/C6PP00102E, Communication
Kei Ohkubo, Kensaku Hirose, Shunichi Fukuzumi
Alkanes were oxygenated by dioxygen with p-benzoquinone derivatives such as p-xyloquinone in alkanes used as solvents to yield the corresponding alkyl hydroperoxides, alcohols and ketones under visible light irradiation with...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 29 Apr 2016 | 1:00 am CEST

Activated T cells exhibit increased uptake of silicon phthalocyanine Pc 4 and increased susceptibility to Pc 4-photodynamic therapy-mediated cell death

Photochem. Photobiol. Sci., 2016, Accepted Manuscript
DOI: 10.1039/C6PP00058D, Paper
David Soler, Jennifer Ohtola, Hideaki Sugiyama, Myriam E Rodriguez, Ling Han, Nancy Oleinick, Minh Lam, Elma Baron, Kevin D Cooper, Thomas S McCormick
Photodynamic therapy (PDT) is an emerging treatment for malignant and inflammatory dermal disorders. Photoirradiation of the silicon phthalocyanine (Pc) 4 photosensitizer with red light generates singlet oxygen and other reactive...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 27 Apr 2016 | 1:00 am CEST

A new luminescent lanthanide supramolecular network possessing free Lewis base sites for highly selective and sensitive Cu2+ sensing

Photochem. Photobiol. Sci., 2016, Accepted Manuscript
DOI: 10.1039/C6PP00059B, Paper
Tian-Shu Chu, Yun-Song Hu, Jinlun Wu, Cheng-Hui Zeng, Yang-Yi Yang, Ng Seik Weng
A series of new lanthanide complexes, formulated as [Ln2(DCSAL)3(H2O)11][round bullet, filled]3DCSAL[round bullet, filled]4H2O [Ln = Eu (1), Gd (2) and Tb (3); HDCSAL = 3,5-dichlorosalicylic acid], have been synthesized and characterized by single crystal...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 26 Apr 2016 | 1:00 am CEST

Cytotoxicity of antimicrobial photodynamic inactivation on epithelial cells when co-cultured with Candida albicans

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00387C, Paper
Claudia Viviane Guimaraes Pellissari, Ana Claudia Pavarina, Vanderlei Salvador Bagnato, Ewerton Garcia de Oliveira Mima, Carlos Eduardo Vergani, Janaina Habib Jorge
This study assessed the cytotoxicity of antimicrobial Photodynamic Inactivation (aPDI), mediated by curcumin, using human keratinocytes co-cultured with Candida albicans.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 25 Apr 2016 | 1:00 am CEST

Photocatalytic Treatment of Desalination Concentrate Using Optical Fibers Coated With Nanostructured Thin Films: Impact of Water Chemistry and Seasonal Climate Variations

Abstract

Treatment of desalination concentrate can reduce concentrate volume for disposal, increase water recovery and convert waste to resource. However, concentrate treatment is costly and energy intensive due to high concentrations of salt and recalcitrant organic matter in concentrate. Photocatalytic oxidation provides a novel energy neutral technology for concentrate treatment by degrading organic contaminants. Polymer-assisted hydrothermal deposition method was used to synthesize innovative pure and Fe-doped TiO2 mixed-phase nanocomposite thin films on side-glowing optical fibers (SOFs). The properties of the photocatalysts-coated SOF were characterized by surface morphology, nanostructure, crystallite size and phase and zeta potential. Photodegradation efficiency and durability of the photocatalysts treating different types of desalination concentrate was studied under natural sunlight. Synthetic solutions and reverse osmosis (RO) concentrates from brackish water and municipal wastewater desalination facilities were tested to elucidate the impact of water chemistry, operating conditions and seasonal climate variations (solar irradiation intensity and temperature) on photocatalytic efficiency. High ionic strength and divalent electrolyte ions in RO concentrate accelerated photocatalytic process, whereas the presence of carbonate species and organic matter hindered photodegradation. Outdoor testing of immobilized continuous-flow photoreactors suggested that the catalyst-coated SOFs can utilize a wide spectrum of natural sunlight and achieved durable photocatalytic performance.

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High ionic strength and divalent electrolyte ions in desalination concentrate accelerated photocatalytic process, whereas the presence of carbonate species and organic matter hindered photodegradation of organic contaminants. Photodegradation efficiency increased with increasing solar irradiation intensity and temperature. Outdoor testing of immobilized continuous-flow photoreactors suggested that the catalyst-coated SOFs can utilize a wide spectrum of natural sunlight and achieved durable photocatalytic performance.

Quelle: Photochemistry and Photobiology | 22 Apr 2016 | 10:20 am CEST

An Understanding of the Photocatalytic Properties and Pollutant Degradation Mechanism of SrTiO3 Nanoparticles

Abstract

Strontium titanate nanoparticles have attracted much attention due to their physical and chemical properties, especially as photocatalysts under ultraviolet irradiation. In this paper, we analyze the effect of heating rate during the crystallization process of SrTiO3 nanoparticles in the degradation of organic pollutants. The relationship between structural, morphological and photocatalytic properties of the SrTiO3 nanoparticles was investigated using different techniques. Transmission electron microscopy and N2 adsorption results show that particle size and surface properties are tuned by the heating rate of the SrTiO3 crystallization process. The SrTiO3 nanoparticles showed good photoactivity for the degradation of methylene blue, rhodamine B and methyl orange dyes, driven by a nonselective process. The SrTiO3 sample with the largest particle size exhibited higher photoactivity per unit area, independent of the molecule to be degraded. The results pointed out that the photodegradation of methylene blue dye catalyzed by SrTiO3 is caused by the action of valence band holes (direct pathway), and the indirect mechanism has a negligible effect, i.e. degradation by O2−• and OH radicals attack.

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Strontium titanate (SrTiO3) nanoparticles have attracted much attention due to their physical and chemical properties, especially as photocatalysts under UV irradiation. SrTiO3 nanospheres were obtained by polymeric precursor method and evaluated on the degradation of organic pollutants. All of the photocatalysts showed a good activity for the photodegradation of methylene blue, rhodamine B and methyl orange dyes, driven by a nonselective process. The SrTiO3 sample with the largest particle size exhibited a higher photoactivity per unit area, independent of the molecule to be degraded. The photodegradation of MB dye catalyzed by SrTiO3 is caused by the action of valence band holes.

Quelle: Photochemistry and Photobiology | 22 Apr 2016 | 7:20 am CEST

Microfluidic-based photocatalytic microreactor for environmental application: A review of fabrication substrates and techniques, and operating parameters

Photochem. Photobiol. Sci., 2016, Accepted Manuscript
DOI: 10.1039/C5PP00469A, Perspective
Susmita Das, Vimal Chandra Srivastava
Photochemical technology with microfluidic is emerging as new platform in environmental science. Microfluidic technology has various advantages like better mixing because of large surface to volume ratio and shorter diffusion...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 22 Apr 2016 | 1:00 am CEST

Cucurbit[7]uril inclusion complexation as a supramolecular strategy for color stabilization of anthocyanin model compounds

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C6PP00060F, Paper
Open Access Open Access
Creative Commons Licence  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Barbara Held, Hao Tang, Palani Natarajan, Cassio Pacheco da Silva, Volnir de Oliveira Silva, Cornelia Bohne, Frank H. Quina
Complete stabilization of the color of a flavylium cation by the formation of a higher order (1 : 2) complex with cucurbit[7]uril.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 22 Apr 2016 | 1:00 am CEST

Estimation of fluorescence lifetime for optically inaccessible exciplexes in nonpolar solutions under ionizing irradiation

Photochem. Photobiol. Sci., 2016, Accepted Manuscript
DOI: 10.1039/C6PP00033A, Paper
Anatoly Melnikov, Evgeny Kalneus, Valeri Korolev, Peter Sergeevich Sherin, Vsevolod Borovkov, Dmitri Stass
X-irradiation of nonpolar solutions likely opens a possibility to create exciplexes for any donor-acceptor pair that would energetically and sterically allow this. Thorough study and characterization of X-radiation generated exciplexes...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 22 Apr 2016 | 1:00 am CEST

Quenching Effect of Uranyl Species in the Photoluminescence Emission and Visible-light-driven Water Dissociation Activity of CdS and TiO2 Photocatalysts: A Case Study on Reverse Energy Transfer

Photochem. Photobiol. Sci., 2016, Accepted Manuscript
DOI: 10.1039/C6PP00022C, Paper
N Gupta, Sarika Kelkar, Prakash V. Korake
Anchoring of uranyl species (2-4 mol%) led to the complete quenching of photoluminescence emission and the visible-light-driven water photodissociation activity of TiO2 (Degussa-P25) and a hydrothermally synthesized CdS photocatalyst. Photophysical...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 22 Apr 2016 | 1:00 am CEST

The CO Photodissociation and Recombination Dynamics of the W172Y/F282T Ligand Channel Mutant of Rhodobacter sphaeroides aa3 Cytochrome c Oxidase

Abstract

In the ligand channel of the cytochrome c oxidase from Rhodobacter sphaeroides (Rs aa3) W172 and F282 have been proposed to generate a constriction that may slow ligand access to and from the active site. To explore this issue, the tryptophan and phenylalanine residues in Rs aa3 were mutated to the less bulky tyrosine and threonine residues, respectively, which occupy these sites in Thermus thermophilus (Tt) ba3 cytochrome oxidase. The CO photolysis and recombination dynamics of the reduced wild-type Rs aa3 and the W172Y/F282T mutant were investigated using time-resolved optical absorption spectroscopy. The spectral changes associated with the multiple processes are attributed to different conformers. The major CO recombination process (44 μs) in the W172Y/F282T mutant is ~500 times faster than the predominant CO recombination process in the wild-type enzyme (~23 ms). Classical dynamic simulations of the wild-type enzyme and double mutant showed significant structural changes at the active site in the mutant, including movement of the heme a3 ring-D propionate toward CuB and reduced binuclear center cavity volume. These structural changes effectively close the ligand exit pathway from the binuclear center, providing a basis for the faster CO recombination in the double mutant.

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We investigated the effect of mutating the tryptophan and phenylalanine residues that define the narrowing of the ligand channel in Rhodobacter sphaeroides aa3 to the less bulky tyrosine and threonine, respectively. Our time-resolved optical absorption results show that the major CO recombination process in the mutant (44 μs) is 500 times faster than in the wild type (~23 ms). Classical molecular dynamics simulations of the double mutant show significant changes at the active site that effectively close the ligand exit pathway from the binuclear center, providing a structural basis for the faster CO recombination in the double mutant.

Quelle: Photochemistry and Photobiology | 21 Apr 2016 | 7:07 am CEST

Caffeic Acid Inhibits Chronic UVB-Induced Cellular Proliferation Through JAK-STAT3 Signaling in Mouse Skin

Abstract

Signal transducers and activators of transcription 3 (STAT3) play a critical role in inflammation, proliferation and carcinogenesis. Inhibition of JAK-STAT3 signaling is proved to be a novel target for prevention of UVB-induced skin carcinogenesis. In this study, chronic UVB irradiation (180 mJ cm−2; weekly thrice for 30 weeks) induces the expression of IL-10 and JAK1 that eventually activates the STAT3 which leads to the transcription of proliferative and antiapoptotic markers such as PCNA, Cyclin-D1, Bcl2 and Bcl-xl, respectively. Caffeic acid (CA) inhibits JAK-STAT3 signaling, thereby induces apoptotic cell death by upregulating Bax, Cytochrome-C, Caspase-9 and Caspase-3 expression in mouse skin. Furthermore, TSP-1 is an antiangiogeneic protein, which is involved in the inhibition of angiogenesis and proliferation. Chronic UVB exposure decreased the expression of TSP-1 and pretreatment with CA prevented the UVB-induced loss of TSP-1 in UVB-irradiated mouse skin. Thus, CA offers protection against UVB-induced photocarcinogenesis probably through modulating the JAK-STAT3 in the mouse skin.

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Caffeic acid (CA) inhibits chronic UVB-induced carcinogenesis in mouse skin through modulating JAK-STAT3 signaling. UVB-mediated inflammatory cytokines like IL-10 activate membrane receptors which activate JAK signaling. Activated JAK induces phosphorylation and dimerization of STAT3 which translocates to the nucleus for transcription. STAT3 activates the expression of inflammatory proteins (IL-6, IL-10), proliferative markers (Cyclin-D1, PCNA) and apoptotic markers (Bcl2, Bcl-xl) in mouse skin. CA inhibits STAT3 phosphorylation and dimerization by binding Leu706, thereby preventing STAT3-mediated carcinogenesis. Crosses indicate preventive role of CA. Green color sticky tool indicates inhibitory role of CA. Green arrow indicates downregulation of JAK by CA.

Quelle: Photochemistry and Photobiology | 21 Apr 2016 | 7:06 am CEST

Proteomic and Physiological Studies Provide Insight into Photosynthetic Response of Rice (Oryza sativa L.) Seedlings to Microgravity

Abstract

The mechanisms whereby how photosynthesis is regulated and maintained under conditions of microgravity remain incompletely understood. Herein, we took a combination of proteomic and physiological approaches to examine the response of rice (Oryza sativa L.) seedlings to spaceflight conditions. Our results show that both PSI fluorescence emission peak and P700 absorbance amplitude are severely decreased in spaceflight seedlings under microgravity. This is consistent with an observed significant reduction of PSI efficiency (ΦI). To further analyze global changes of protein profiles under microgravity, isobaric tags for relative and absolute quantization (iTRAQ) labeling technology were deployed. 454 differentially expressed proteins were identified by comparison of spaceflight and ground control. Of proteins relevant to photosynthesis thirty-four were down-regulated and four were up-regulated. The significantly down-regulated ones are essential components of PSI, NDH and the Cytb6f complex. This down-regulation of PSI proteins and/or protein structure changes may cause the overall reduction of PSI activity. Intriguingly, although abundance of some PSII proteins was altered under microgravity, no significant changes in PSII activity were detected. Taken together, our results suggest that PSI, rather than PSII being usually much more sensitive to environmental stresses, is more susceptible to spaceflight conditions in rice seedlings.

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Quelle: Photochemistry and Photobiology | 20 Apr 2016 | 3:47 pm CEST

Promotion of Pro-Apoptotic Signals by Lysosomal Photodamage: Mechanistic Aspects and Influence of Autophagy

Abstract

Prior studies demonstrated that a low level (LD10-15) of lysosomal photodamage can sensitize cells to the apoptotic death that results from subsequent mitochondrial photodamage. We have proposed that this process occurs via a calpain-catalyzed cleavage of the autophagy-associated protein ATG5 to form a pro-apoptotic fragment. In this report, we provide evidence for the postulated ATG5 cleavage and show that the sequential photodynamic therapy (PDT) protocol can also partly overcome the adverse effect of hypoxia on the initiation of apoptosis. While autophagy can offer cytoprotection after mitochondrial photodamage, this does not appear to apply when lysosomes are the target. This may account for the ability of very low PDT doses directed at lysosomes to evoke ATG5 cleavage. The resulting pro-apoptotic effect overcomes intrinsic cytoprotection from mitochondrial photodamage along with a further stimulation of phototoxicity.

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Quelle: Photochemistry and Photobiology | 20 Apr 2016 | 3:46 pm CEST

Effect of solvent polarity on the spectroscopic properties of an alkynyl gold(I) gelator. The particular case of water

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C6PP00057F, Paper
Raquel Gavara, Joao Carlos Lima, Laura Rodriguez
The spectroscopic properties of an aurophilic hydrogelator depend on solvent polarity and concentration.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 19 Apr 2016 | 1:00 am CEST

Co-axial Electrospinning Method for the Preparation of TiO2@CdS/PVA Composite Nano-fiber Mat and Investigation on its Photodegradation Catalysis

Abstract

TiO2/PVA composite nano-fiber mat was prepared via an electro-spinning technology. SH-TiO2-SiO2 hybrid particles and PVA solution were injected through a co-axial syringe, yielding a composite nano-fiber mat. The as-prepared SH-TiO2-SiO2/PVA composite nano-fiber mat was immersed in Cd2+ cation solution and S2- anion solution in turn. Thus, yellow TiO2@CdS/PVA composite nano-fiber mats were prepared. By adjusting the number of times a mat was immersed in the Cd2+ and S2- solutions, different amounts of CdS particles attaching to the mats were obtained. Both SH-TiO2-SiO2/PVA and TiO2@CdS/PVA composite nano-fiber mats were employed to catalyze the photo-degradation of a model dye, methylene blue. The photo-degradation performance could be greatly enhanced by the introduction of CdS particles anchoring onto TiO2 particles. The photo-degradation efficiency reached 99.2% within 180 min. Also, the nano-fiber mat could be recycled and reused at least 10 times. The photo-degradation efficiency of TiO2@CdS/PVA composite nano-fiber mats remained 68.8% for 10 cycles.

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Quelle: Photochemistry and Photobiology | 18 Apr 2016 | 4:10 pm CEST

Accelerated Regeneration of ATP Level after Irradiation in Human Skin Fibroblasts by Coenzyme Q10

Abstract

Human skin is exposed to a number of harmful agents of which the ultraviolet (UV) component of solar radiation is most important. UV-induced damages include direct DNA lesions as well as oxidative damage in DNA, proteins and lipids caused by reactive oxygen species (ROS). Being the main site of ROS generation in the cell, mitochondria are particularly affected by photostress. The resulting mitochondrial dysfunction may have negative effects on many essential cellular processes. To counteract these effects, coenzyme Q10 (CoQ10) is used as a potent therapeutic in a number of diseases. We analyzed the mitochondrial respiration profile, the mitochondrial membrane potential and cellular ATP level in skin fibroblasts after irradiation. We observed an accelerated regeneration of cellular ATP level, a decrease in mitochondrial dysfunction as well as a preservation of the mitochondrial membrane potential after irradiation in human skin fibroblasts by treatment with CoQ10. We conclude that the faster regeneration of the ATP level was achieved by a preservation of mitochondrial function by the addition of CoQ10 and that the protective effect of CoQ10 is primarily mediated via its antioxidative function. We suggest also that it might be further dependent on a stimulation of DNA repair enzymes by CoQ10.

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Being the main site of ROS generation in the cell, mitochondria are particularly affected by photostress. The resulting mitochondrial dysfunction may have negative effects on many essential cellular processes. To counteract these effects, CoQ10 is used as a therapeutic in a number of diseases. We observed that CoQ10 is able to preserve the mitochondrial membrane potential after SSL-UVA irradiation (d, e), decrease the level of mitochondrial dysfunction (a, b) and lead therefore to a more rapid regeneration of the cellular ATP levels in human fibroblasts (c). We conclude that the protective effect of CoQ10 is primarily mediated via its antioxidative function.

Quelle: Photochemistry and Photobiology | 18 Apr 2016 | 7:05 am CEST

Role of certain amino acid residues of the coelenterazine-binding cavity in bioluminescence of light-sensitive Ca2+-regulated photoprotein berovin

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C6PP00050A, Paper
Ludmila P. Burakova, Galina A. Stepanyuk, Elena V. Eremeeva, Eugene S. Vysotski
We suggest that in the inner cavity of ctenophore photoproteins coelenterazine is bound as a 2-peroxy anion which is stabilized owing to Coulomb interaction with a guanidinium group of R41 paired with Y204.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 11 Apr 2016 | 1:00 am CEST

Photoinduced chemiluminescence determination of carbamate pesticides

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C6PP00056H, Paper
M. Catala-Icardo, S. Meseguer-Lloret, S. Torres-Cartas
Selective and sensitive HPLC-photoinduced chemiluminescence detection of carbamate pesticides containing sulphur in surface and ground water samples.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 11 Apr 2016 | 1:00 am CEST

Delivery of a hydrophobic phthalocyanine photosensitizer using PEGylated gold nanoparticle conjugates for the in vivo photodynamic therapy of amelanotic melanoma

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00463B, Paper
Monica Camerin, Miguel Moreno, Maria J. Marin, Claire L. Schofield, Isabelle Chambrier, Michael J. Cook, Olimpia Coppellotti, Giulio Jori, David A. Russell
Gold nanoparticles functionalised with PEG and a phthalocyanine photosensitiser achieved 40% no tumour regrowth and complete survival following in vivo PDT.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 11 Apr 2016 | 1:00 am CEST

Photoenolization of o-Methylvalerophenone Ester Derivative

Abstract

Photolysis of ester 1 in argon-saturated methanol and acetonitrile does not produce any product, whereas irradiation of 1 in oxygen-saturated methanol yields peroxide 2. Laser flash photolysis studies demonstrate that 1 undergoes intramolecular H atom abstraction to form biradical 3 (λmax ~340 nm), which intersystem crosses to form photoenols Z-4 and E-4 (λmax ~380 nm). Photoenols 4 decay by regenerating ester 1. With the aid of density functional theory calculations, it was concluded the photoenol E-4 does not undergo spontaneous lactonization or electrocyclic ring closure because the transition state barriers for these reactions are too large to compete with reketonization of E-4 to form 1.

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Quelle: Photochemistry and Photobiology | 9 Apr 2016 | 8:55 am CEST

Enhanced photocatalytic bacteriostatic activity towards Escherichia coli using 3D hierarchical microsphere BiOI/BiOBr under visible light irradiation

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00406C, Paper
Ya Wang, Li Lin, Fang Li, Liang Chen, Donghui Chen, Chongyang Yang, Manhong Huang
With an improved separation efficiency of photogenerated holes, the BiOI/BiOBr composite exhibited enhanced photocatalytic bacteriostatic activity towards E. coli compared to the pure BiOI or BiOBr under visible light.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 7 Apr 2016 | 1:00 am CEST

In vitro photodynamic inactivation of conidia of the phytopathogenic fungus Colletotrichum graminicola with cationic porphyrins

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00372E, Paper
Camila Chevonica Vandresen, Alan Guilherme Goncalves, Diogo Ricardo Bazan Ducatti, Fabio Seigi Murakami, Miguel Daniel Noseda, Maria Eugenia Rabello Duarte, Sandra Mara Woranovicz Barreira
Photodynamic inactivation (PDI) of the conidial form of the C. graminicola employing five cationic porphyrins.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 7 Apr 2016 | 1:00 am CEST

Hydrothermal Preparation and Characterization of TiO2/BiVO4 Composite Catalyst and its Photolysis of Water to Produce Hydrogen

Abstract

In the present work, bismuth vanadate composited photocatalysts were synthesized and characterized. X-ray diffractometry and Raman results showed that the particles were well crystallized, and formed by the complex of monoclinic BiVO4 and TiO2. On electron microscopy, the photocatalyst exhibited high crystallization, agglutination and irregular shape, and was surrounded by numerous TiO2 particles. The study of surface areas showed that the specific surface area of 30-BiVO4/TiO2 composited was 112 m2·g−1, which was nearly 10 times that of pure BiVO4. The ultraviolet–visible diffuse reflectance spectra indicated the composited photocatalyst were activated in visible light. The activity of photocatalytic water splitting was studied. The results showed that monomer BiVO4 photocatalyst was not able to produce hydrogen under any light source. BiVO4/TiO2 composited photocatalysts, however, were capable of generating hydrogen. Under UV light irradiation for 120 min, 1 g catalyst dispersed in 50 mL deionized water produced almost 1 mL hydrogen, such that the productivity of hydrogen was higher than that of P25-TiO2. Photocatalytic decomposition of water under visible light also confirmed that the BiVO4/TiO2 composited photocatalyst had the ability of water splitting.

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TiO2/BiVO4 composite catalyst was synthesized using a reverse microemulsion method. Hydrothermal aging treatment was carried out on the as-made mixture to produce BVO composite catalyst. The formed samples were chunky grains of irregular crystals 30–70 nm in diameter, with specific surface areas of up to 112 m2 g−1, and wide light response ranges to the visible region. For water photolysis, the prepared bismuth vanadate was incapable of producing hydrogen under any light source, but the composite catalyst had good hydrogen production capability. After 120 min ultraviolet light irradiation, 1 mL of hydrogen was produced.

Quelle: Photochemistry and Photobiology | 6 Apr 2016 | 6:44 am CEST

Electric Field-Assisted Photochemical Water Splitting Should Operate with 287 nm Light

Abstract

The major photoreaction of water is the homolytic splitting of one O–H bond starting from the 11B1 excited state (λmax = 167 nm). This reaction produces H• and •OH radicals. The combination of two H• atoms leads to the potential energy carrier dihydrogen. However, the energy required to obtain the photoreactive 11B1 electronic state is about 7.4 eV, which cannot be effectively provided by solar radiation. The sun light spectrum on earth comprises the visible and ultraviolet region, but shows vanishing intensity near 7 eV (177.1 nm). This work provides theoretical evidence that the photoreactive 11B1 state of water can be shifted into the ultraviolet (UV-B) light region (≈287 nm) by including explicitly an electric field in the calculations of the water absorption spectrum. To accomplish such bathochromic shift, a large field strength of 3.08 VÅ−1 is required. The field-dependent excitation energies were calculated by applying the symmetry-adapted cluster configuration interaction (SAC-CI) procedure. Based on this theoretical analysis, we propose that photochemical water splitting can be accomplished by means of 287 nm light provided the water molecule is favorably oriented by an external electric field and is subsequently activated by a reversal of the field orientation.

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MOs characterizing the electronic structure of the Frank-Condon 11B1 and 11A2 states of water influenced by an external electric field. The field impact should induce homolytic water splitting.

Quelle: Photochemistry and Photobiology | 6 Apr 2016 | 6:43 am CEST

Functional and Photochemical Characterization of a Light-Driven Proton Pump from the Gammaproteobacterium Pantoea vagans

Abstract

Photoactive retinal proteins are widely distributed throughout the domains of the microbial world (i.e., bacteria, archaea, and eukarya). Here we describe three retinal proteins belonging to a phylogenetic clade with a unique DTG motif. Light-induced decrease in the environmental pH and its inhibition by carbonyl cyanide m-chlorophenylhydrazone revealed that these retinal proteins function as light-driven outward electrogenic proton pumps. We further characterized one of these proteins, Pantoea vagans rhodopsin (PvR), spectroscopically. Visible spectroscopy and high-performance liquid chromatography revealed that PvR has an absorption maximum at 538 nm with the retinal chromophore predominantly in the all-trans form (>90%) under both dark and light conditions. We estimated the pKa values of the protonated Schiff base of the retinal chromophore and its counterion as approximately 13.5 and 2.1, respectively, by using pH titration experiments, and the photochemical reaction cycle of PvR was measured by time-resolved flash-photolysis in the millisecond timeframe. We observed a blue-shifted and a red-shifted intermediate, which we assigned as M-like and O-like intermediates, respectively. Decay of the M-like intermediate was highly sensitive to environmental pH, suggesting that proton uptake is coupled to decay of the M-like intermediate. From these results, we propose a putative model for the photoreaction of PvR.

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Photoactive retinal proteins are widely distributed throughout the domains of the microbial world. Here we describe new retinal proteins belonging to a phylogenetic clade with a unique DTG motif. They function as light-driven outward electrogenic proton pumps. We further characterized one of these proteins, Pantoea vagans rhodopsin (PvR), spectroscopically. On the basis of the results, we propose a putative model for the photoreaction of PvR.

Quelle: Photochemistry and Photobiology | 31 Mar 2016 | 6:51 am CEST

An in vitro cell irradiation protocol for testing photopharmaceuticals and the effect of blue, green, and red light on human cancer cell lines

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00424A, Paper
Open Access Open Access
Creative Commons Licence  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
S. L. Hopkins, B. Siewert, S. H. C. Askes, P. Veldhuizen, R. Zwier, Michal Heger, Sylvestre Bonnet
A LED-based cell irradiation system was built that can irradiate a 96-well plate with monochromatic light at controlled temperature and with a built-in dark control. This system was used to study the response of six human cancer cell lines to blue, green, and red light.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 31 Mar 2016 | 1:00 am CEST

Photolysis quantum yield measurements in the near-UV; a critical analysis of 1-(2-nitrophenyl)ethyl photochemistry

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00440C, Forum
John E. T. Corrie, Jack H. Kaplan, Biff Forbush, David C. Ogden, David R. Trentham
The photolysis quantum yield, Qp, of 1-(2-nitrophenyl)ethyl phosphate (caged Pi) measured in the near-UV (342 nm peak with 60 nm half-bandwidth) is 0.53. Some general principles relating to measurement of Qp values are discussed.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 30 Mar 2016 | 1:00 am CEST

High Temperature Affects Photosynthetic and Molecular Processes in Field-Cultivated Vitis vinifera L. × Vitis labrusca L.

Abstract

High-temperature stress markedly influences grape growth and development. However, how high-temperature stress response differs between controlled and field-cultivated grape is poorly understood. In this study, the effects of heat treatment on grapevines were studied for changes in photosystem II (PSII) activity and expression levels of heat-responsive genes and heat shock protein HSP21. July 31st, 2015 was considered as the post high-temperature treatment (“42°C”; temperatures above 40°C for a period of time each day ranging from 1–7 h) under field cultivation in our experiment. The recovery of chlorophyll fluorescence indicators and the increasing expression of heat-responsive genes and the heat shock protein HSP21 suggested the development of heat tolerance in the form of acclimation in grape. Changes in various parameters of photosynthetic pigment fluorescence and of the electron transport chain (Fv/Fm, PIABS, Wk, RCQA, ΦPo, and ΦEo) between “42°C” and the 45°C treatment demonstrated that the donor side, reaction center, and acceptor side of PSII were influenced by a critical high temperature. Furthermore, the difference between the two cultivation conditions studied was attributed to other environmental factors and inherent tree vigor.

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Protective mechanisms of PS II, which included the changes in PS II activity and the expression levels of heat-response genes and HSP21, rapidly responded to heat stress at a critical high temperature (above 40°C) under field or controlled condition. Finally, the recovery of changes at 6 day suggested that grapes enhanced thermotolerance under heat stress by photosynthetic processes.

Quelle: Photochemistry and Photobiology | 29 Mar 2016 | 7:00 am CEST

Self-Reported Changes in Sun-Protection Behaviors at Different Latitudes in Australia

Abstract

Sun exposure is the most important source of vitamin D, but is also a risk factor for skin cancer. This study investigated attitudes toward vitamin D, and changes in sun-exposure behavior due to concern about adequate vitamin D. Participants (n = 1002) were recruited from four regions of Australia and completed self- and interviewer-administered surveys. Chi-square tests were used to assess associations between participants' latitude of residence, vitamin D-related attitudes and changes in sun-exposure behaviors during the last summer. Multivariate logistic regression analyses were used to model the association between attitudes and behaviors. Overall, people who worried about their vitamin D status were more likely to have altered sun protection and spent more time in the sun people not concerned about vitamin D. Concern about vitamin D was also more common with increasing latitude. Use of novel item response theory analysis highlighted the potential impact of self-reported behavior change on skin cancer predisposition due concern to vitamin. This cross-sectional study shows that the strongest determinants of self-reported sun-protection behavior changes due to concerns about vitamin D were attitudes and location, with people at higher latitudes worrying more.

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Exposure to ultraviolet radiation from the sun is the most important source of vitamin D, but is also a risk factor for skin cancer. People who worried about their vitamin D status were more likely to have altered their sun protection behaviors and spent more time in the sun than those not worried about vitamin D. Use of novel item response theory analysis highlighted the potential impact of such behavior change on skin cancer predisposition. The strongest determinants of self-reported sun protection behavior changes due to vitamin D concerns were attitudes and location, with people at higher latitudes worrying more.

Quelle: Photochemistry and Photobiology | 22 Mar 2016 | 6:00 am CET

The dark and bright sides of an enzyme: a three dimensional structure of the N-terminal domain of Zophobas morio luciferase-like enzyme, inferences on the biological function and origin of oxygenase/luciferase activity

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C6PP00017G, Paper
R. A. Prado, C. R. Santos, D. I. Kato, M. T. Murakami, V. R. Viviani
The structure and catalytic activities of a Malpighian luciferase-like enzyme indicate a generalistic xenobiotic CoA-ligase and a catalytic residue for bioluminescence.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 22 Mar 2016 | 1:00 am CET

Stress Tolerance of the Endemic Antarctic Brown Alga Desmarestia anceps to UV Radiation and Temperature is Mediated by High Concentrations of Phlorotannins

Abstract

The endemic Antarctic brown macroalga Desmarestia anceps is strongly shade-adapted, but shows also a high capacity to cope with different environmental stressors, e.g. UV radiation and temperature. Therefore, this species colonizes wide depth gradients, which are characterized by changing environmental conditions. In this study, we examine whether the different physiological abilities allowing D. anceps to grow across a wide depth range is determined by high levels of phlorotannins. Photosynthesis, measured by PAM-fluorometry, the contents of soluble phlorotannins, antioxidant capacities of field grown were analyzed in response to different conditions of radiation (PAR and PAR + UV) and temperature (2, 7 and 12°C). The results show that maximal quantum of fluorescence (Fv/Fm) decreased with increasing doses of UV radiation, but remained unaffected by temperature. High levels of soluble phlorotannins were detected and confirmed by microscopic observation revealing the abundance of large physodes. Exposure to UV radiation and elevated temperature showed that phlorotannins were not inducible by UV but increased at 12°C. ROS scavenging capacity was positively correlated with the contents of phlorotannins. In general, highest contents of phlorotannins were correlated with the lowest inhibition of Fv/Fm in all experimental treatments, highlighting the UV-protective role of these compounds in D. anceps.

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In this study, we examine whether the different physiological abilities allowing D. anceps to grow across a wide depth range is determined by high levels of phlorotannins (UV-protective compounds). Photosynthesis, soluble phlorotannins content and antioxidant capacities were analyzed in response to different radiation (PAR and PAR+UV) and temperature (2, 7 and 12°C) conditions. High levels of soluble phlorotannins were detected and positively correlated with ROS scavenging capacity. In general, highest contents of phlorotannins were correlated with the lowest inhibition of Fv/Fm in all experimental treatments, highlighting the UV-protective role of these compounds in D. anceps.

Quelle: Photochemistry and Photobiology | 21 Mar 2016 | 5:15 am CET

Synthesis, regioselective aerobic Pd(II)-catalyzed C-H bond alkenylation and the photophysical properties of pyrenylphenylpyrazoles

Photochem. Photobiol. Sci., 2016, 15,580-588
DOI: 10.1039/C6PP00009F, Paper
Open Access Open Access
Creative Commons Licence  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Rafal Flamholc, Janusz Zakrzewski, Anna Makal, Arnaud Brosseau, Remi Metivier
Pd(II)-catalyzed C-H alkenylation of a pyrenylphenylpyrazole afforded fluorophore exhibiting solvent-dependent dual emission, resulting from locally-excited (LE) and intramolecular charge transfer (ICT) excited states.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 21 Mar 2016 | 1:00 am CET

meso-Mono-[4-(1,4,7-triazacyclononanyl)]-tri(phenyl)]porphyrin and the respective zinc(II)-complex: complete characterization and biomolecules binding abilities

Photochem. Photobiol. Sci., 2016, 15,564-579
DOI: 10.1039/C6PP00016A, Paper
Bruna L. Auras, Vanessa A. Oliveira, Hernan Terenzi, Ademir Neves, Bernardo A. Iglesias
We aimed to synthesize a new series of triazacyclononanyl-porphyrins (4 and 5) with the potential ability to bind DNA.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 21 Mar 2016 | 1:00 am CET

Effects of Narrow-band IR-A and of Water-Filtered Infrared A on Fibroblasts

Abstract

Exposures of the skin with electromagnetic radiation of wavelengths between 670 nm and 1400 nm are often used as a general treatment to improve wound healing and reduce pain, for example, in chronic diabetic skin lesions. We investigated the effects of water-filtered infrared A (wIRA) and of narrow-band IR-A provided by a light-emitting diode LED (LED-IR-A) irradiation in vitro on 3T3 fibroblast cultures under defined conditions with and without glyoxal administration. Glyoxal triggers the formation of advanced glycation end products, thereby mimicking a diabetic metabolic state. Cell viability and apoptotic changes were determined by flow cytometry after vital staining with Annexin V, YO-PRO-1 and propidium iodide (PI), and by SubG1 assay. Mitochondrial function and oxidative stress were examined by vital staining for radical production, mitochondrial membrane potential (MMP) and the ratio of reduced-to-oxidized glutathione (GSH/GSSG). The metabolic state was monitored by a resazurin conversion assay. The numbers of apoptotic cells were reduced in cultures irradiated with wIRA or LED-IR-A. More mitochondria showed a well-polarized MMP after wIRA irradiation in glyoxal damaged cells. LED-IR-A treatment specifically restored the GSH/GSSG ratio. The immediate positive effects of wIRA and LED-IR-A observed in living cells, particularly on mitochondria, reflect the therapeutic benefits of wIRA and LED-IR-A.

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Irradiating the skin with electromagnetic radiation of wavelengths between 670 nm and 1400 nm is often used to improve wound healing and reduce pain. We investigated the effects of water-filtered infrared-A (wIRA) and of light-emitting diode (LED)-emitted narrow-band IR-A (LED-IR-A) on 3T3 fibroblast cultures. Glyoxal was added to mimic a diabetic metabolic state. We observed that IR-A treatment enhanced the vital status of the cells, especially the oxidative status. The immediate positive effects of wIRA and LED-IR-A observed in living cells, particularly on their mitochondria, reflect the therapeutic benefits of wIRA and LED-IR-A.

Quelle: Photochemistry and Photobiology | 17 Mar 2016 | 6:10 am CET

The Lack of Lutein Accelerates the Extent of Light-induced Bleaching of Photosynthetic Pigments in Thylakoid Membranes of Arabidopsis thaliana

Abstract

The high light-induced bleaching of photosynthetic pigments and the degradation of proteins of light-harvesting complexes of PSI and PSII were investigated in isolated thylakoid membranes of Arabidopsis thaliana, wt and lutein-deficient mutant lut2, with the aim of unraveling the role of lutein for the degree of bleaching and degradation. By the means of absorption spectroscopy and western blot analysis, we show that the lack of lutein leads to a higher extent of pigment photobleaching and protein degradation in mutant thylakoid membranes in comparison with wt. The highest extent of bleaching is suffered by chlorophyll a and carotenoids, while chlorophyll b is bleached in lut2 thylakoids during long periods at high illumination. The high light-induced degradation of Lhca1, Lhcb2 proteins and PsbS was followed and it is shown that Lhca1 is more damaged than Lhcb2. The degradation of analyzed proteins is more pronounced in lut2 mutant thylakoid membranes. The lack of lutein influences the high light-induced alterations in organization of pigment–protein complexes as revealed by 77 K fluorescence.

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The lack of lutein accelerates the process of high light-induced bleaching of photosynthetic pigments and protein degradation in isolated thylakoid membranes of Arabidopsis thaliana. The most intensive bleaching is observed for chlorophyll a followed by that of carotenoids. High-light treatment leads to intensive degradation of the (light-harvesting complex) LHCI proteins and of PsbS and to a less extent of LHCII proteins. The lack of lutein affects to some extent the light-induced reorganization of pigment–protein complexes in thylakoid membranes as revealed by 77 K fluorescence.

Quelle: Photochemistry and Photobiology | 15 Mar 2016 | 5:51 am CET

UVB Generates Microvesicle Particle Release in Part Due to Platelet-activating Factor Signaling

Abstract

The lipid mediator platelet-activating factor (PAF) and oxidized glycerophosphocholine PAF agonists produced by ultraviolet B (UVB) have been demonstrated to play a pivotal role in UVB-mediated processes, from acute inflammation to delayed systemic immunosuppression. Recent studies have provided evidence that microvesicle particles (MVPs) are released from cells in response to various signals including stressors. Importantly, these small membrane fragments can interact with various cell types by delivering bioactive molecules. The present studies were designed to test if UVB radiation can generate MVP release from epithelial cells, and the potential role of PAF receptor (PAF-R) signaling in this process. We demonstrate that UVB irradiation of the human keratinocyte-derived cell line HaCaT resulted in the release of MVPs. Similarly, treatment of HaCaT cells with the PAF-R agonist carbamoyl PAF also generated equivalent amounts of MVP release. Of note, pretreatment of HaCaT cells with antioxidants blocked MVP release from UVB but not PAF-R agonist N-methyl carbamyl PAF (CPAF). Importantly, UVB irradiation of the PAF-R-negative human epithelial cell line KB and KB transduced with functional PAF-Rs resulted in MVP release only in PAF-R-positive cells. These studies demonstrate that UVB can generate MVPs in vitro and that PAF-R signaling appears important in this process.

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In this study, we demonstrated that ultraviolet B (UVB) radiation generates microvesicle particles (MVP) release from epithelial cells. We have discovered that activation of the keratinocyte platelet-activating factor receptor (PAF-R) results in MVP release, and using an epithelial cell line with/without PAF-Rs, we demonstrate that UVB generates MVP via PAF-R signaling. Importantly, UVB-generated PAF agonist formation and MVP release are blocked by antioxidants. Yet, antioxidants do not affect MVP release in response to a PAF agonist. This study suggests that UVB generates MVP release from epithelial cells, which could provide a potential mechanism for UVB-mediated systemic signaling.

Quelle: Photochemistry and Photobiology | 15 Mar 2016 | 5:50 am CET

Major inter-personal variation in the increase and maximal level of 25-hydroxy vitamin D induced by UVB

Photochem. Photobiol. Sci., 2016, 15,536-545
DOI: 10.1039/C5PP00462D, Paper
Pameli Datta, Peter A. Philipsen, Peter Olsen, Bibi Petersen, Peter Johansen, Niels Morling, Hans C. Wulf
Individual differences in vitamin D formation and metabolism after long-term UVB exposure were at least 131 nmol l-1, even after eliminating most of the known external and behavioural sources of variation.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 15 Mar 2016 | 1:00 am CET

New Insight into the Water-Soluble Chlorophyll-Binding Protein from Lepidium virginicum

Abstract

This study describes new recombinant water-soluble chlorophyll (Chl)-binding proteins (WSCP) from Lepidium virginicum (LvWSCP). This complex binds four Chls (i.e. two dimers of Chls) per protein tetramer. We show that absorption, emission, hole-burned (HB) spectra and the shape of the zero-phonon hole (ZPH) action spectrum are consistent with the presence of uncorrelated excitation energy transfer between two Chl dimers. Thus, there is no need to include slow protein relaxation within the lowest excited state (as suggested in a previous analysis of cauliflower WSCP [Schmitt, F.-J. et al. (2008) J. Phys. Chem. B, 112, 13951; Pieper, J. et al. (2011) J. Phys. Chem. B, 115, 4053]) in order to explain the large shift observed between the maxima of the ZPH action and emission spectra. Experimental evidence is provided which shows that electron exchange between lowest energy Chls and the protein may occur, i.e. electrons can be trapped at low temperature by nearby aromatic amino acids. The latter explains the shape of nonresonant HB spectra (i.e. the absence of antihole), demonstrating that the hole-burning process in LvWSCP is largely photochemical in nature, though a small contribution from nonphotochemical hole burning (in resonant holes) is also observed.

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The water-soluble chlorophyll protein from Lepidium virginicum binds four chlorophyll pigments per protein tetramer. The presence of uncorrelated energy transfer between dimers is demonstrated, which explains the red shifted fluorescence origin band. Experimental evidence is provided that electron exchange between lowest energy chlorophylls and the protein may occur, i.e. electrons can be trapped at low temperature by nearby tryptophan residues. The latter explains the shape of nonresonant hole-burned spectra, demonstrating that the hole-burning process in this pigment-protein complex is largely photochemical in nature.

Quelle: Photochemistry and Photobiology | 14 Mar 2016 | 1:23 pm CET

Photochemical control of microphase structure in biocompatible polyester membranes generated by ultraviolet irradiation

Photochem. Photobiol. Sci., 2016, 15,517-524
DOI: 10.1039/C5PP00181A, Paper
Rui Li, Wenmin Pang, Liming Tian, Kangming Nie
The semi-IPN morphology of biocompatible polyester membranes is affected by the dynamic factors of the UV photochemical reaction. A novel pathway for photochemical control of the morphology was provided for biomedical materials.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 11 Mar 2016 | 1:00 am CET

Near infrared fluorescent biliproteins generated from bacteriophytochrome AphB of Nostoc sp. PCC 7120

Photochem. Photobiol. Sci., 2016, 15,546-553
DOI: 10.1039/C5PP00442J, Paper
Che Yuan, Hui-Zhen Li, Kun Tang, Wolfgang Gartner, Hugo Scheer, Ming Zhou, Kai-Hong Zhao
Near infrared fluorescent proteins are assembled in E. coli, which relies on the chromophorylation ability of PAS-GAFs with biliverdin. The strong brightness of the construct makes it a promising biomarker.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 11 Mar 2016 | 1:00 am CET

Topical formulation containing hesperidin methyl chalcone inhibits skin oxidative stress and inflammation induced by ultraviolet B irradiation

Photochem. Photobiol. Sci., 2016, 15,554-563
DOI: 10.1039/C5PP00467E, Paper
Renata M. Martinez, Felipe A. Pinho-Ribeiro, Vinicius S. Steffen, Carla V. Caviglione, Danilo Pala, Marcela M. Baracat, Sandra R. Georgetti, Waldiceu A. Verri, Rubia Casagrande
Skin exposure to UVB irradiation has increased significantly in recent years due to ozone depletion, and it represents the main cause of many skin diseases.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 11 Mar 2016 | 1:00 am CET

Lighting up bioluminescence with coelenterazine: strategies and applications

Photochem. Photobiol. Sci., 2016, 15,466-480
DOI: 10.1039/C5PP00456J, Perspective
Tianyu Jiang, Lupei Du, Minyong Li
This review article summarizes coelenterazine analogues and their bioluminescence properties, as well as the rational design of caged coelenterazine towards biotargets and their applications in bioassays.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 8 Mar 2016 | 1:00 am CET

Effective photosensitization-based inactivation of Gram (-) food pathogens and molds using the chlorophyllin-chitosan complex: towards photoactive edible coatings to preserve strawberries

Photochem. Photobiol. Sci., 2016, 15,506-516
DOI: 10.1039/C5PP00376H, Paper
Irina Buchovec, Viktorija Lukseviciute, Arunas Marsalka, Ignas Reklaitis, Zivile Luksiene
This study is focused on the novel approaches to enhance the inactivation of the Gram (-) food pathogen Salmonella enterica and harmful molds in vitro and on the surface of strawberries using the chlorophyllin-chitosan complex.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 7 Mar 2016 | 1:00 am CET

Incident Ultraviolet Irradiances Influence Physiology, Development and Settlement of Larva in the Coral Pocillopora damicornis

Abstract

Ultraviolet radiation (UVR, 280–400 nm) is one of the potential factors involved in the induction of coral bleaching, loss of the endosymbiotic dinoflagellate Symbiodinium or their photosynthetic pigments. However, little has been documented on its effects on the behavior and recruitment of coral larvae, which sustains coral reef ecosystems. Here, we analyzed physiological changes in larvae of the scleractinian coral Pocillopora damicornis and examined the photophysiological performance of the symbiont algae, following exposure to incident levels of UVR and subsequently observed the development of coral larvae. The endosymbiotic algae exhibited a high sensitivity to UV-B (295–320 nm) during a 6 h exposure, showing lowered photosynthetic performance per larva and per algal cell, whereas the presence of UV-A (320–395 nm) significantly stimulated photosynthesis. UVR decreased chlorophyll a concentration only at higher surface temperature or at the higher doses or intensities of UVR. Correlations between UV-absorbing compound (UVAC) contents or UVR sensitivity and temperature were identified, implying that UVACs might act as a screen or antioxidants in Pocillopora damicornis larvae. Larvae reared under UVR exposures showed lower levels of survivorship, metamorphosis and settlement, with inhibition by UV-A being much greater than that caused by UV-B.

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In southern Taiwan, the coral Pocillopora damicornis releases well-developed planula larvae, which contain the symbiotic dinoflagellates, Symbiodinium, transferred from parental colonies. The planktonic larvae are exposed to considerable levels of solar radiation, containing ultraviolet radiation (280–400 nm), before their settlement. We show here that the levels of UV were high enough to induce inhibition of photosynthesis in the symbiotic algae, lowering the numbers of coral larvae that either survived, settled or metamorphosed.

Quelle: Photochemistry and Photobiology | 1 Mar 2016 | 10:01 am CET

Effects of Arrangement of UV Light-Emitting Diodes on the Inactivation Efficiency of Microorganisms in Water

Abstract

Ultraviolet light-emitting diodes (UV-LEDs) offer high flexibility in the reactor design for water disinfection. To specify the key design factors affecting the performance of a reactor, we examined how the arrangement of UV-LEDs in a cylindrical reactor affects the inactivation efficiency of Escherichia coli and coliphage Qβ. A ring-shaped UV-LED apparatus, composed of two units containing ten 285-nm UV-LEDs each, were attached to a quartz cylinder, and microbial suspensions flowed through the cylinder for single pass at altered flow rates. The distance between the two units, L, was altered to examine its effects on inactivation efficiencies. Over 4 log inactivation of E. coli was achieved at 800 mL min−1 regardless of the L values, suggesting that the apparatus has a high potential to disinfect water. The inactivation at = 20 mm was significantly higher than that at = 0 in all cases tested (ANOVA,< 0.05), while this was not true when L was extended to 40 and 60 mm. Therefore, a separate arrangement of UV-LEDs at a certain distance can improve the efficiency, and the distance matters to enhance the performance. This study involves a design concept on how to arrange UV-LEDs in a water disinfection apparatus.

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Ultraviolet light-emitting diodes (UV-LEDs) offer high flexibility in the reactor design for water disinfection. To specify the key design factors, UV-LEDs were arranged in a cylindrical reactor in several ways to examine the impacts on inactivation efficiency of Escherichia coli and coliphage Qβ. A ring-shaped UV-LED apparatus, containing twenty 285-nm UV-LEDs in total, was adopted for flow-through tests. The result indicated that a separate arrangement of UV-LEDs at a certain distance can improve the inactivation efficiency, and the distance matters to enhance the performance. This study involves a design concept on how to arrange UV-LEDs in a water disinfection apparatus.

Quelle: Photochemistry and Photobiology | 1 Mar 2016 | 10:01 am CET

Enhancing the Photocatalytic Activity of Sr4Al14O25: Eu2+, Dy3+ Persistent Phosphors by Codoping with Bi3+ Ions

Abstract

The photocatalytic activity of Bismuth-codoped Sr4Al14O25: Eu2+, Dy3+ persistent phosphors is studied by monitoring the degradation of the blue methylene dye UV light irradiation. Powder phosphors are obtained by a combustion synthesis method and a postannealing process in reductive atmosphere. The XRD patterns show a single orthorhombic phase Sr4Al14O25: Eu2+, Dy3+, Bi3+ phosphors even at high Bismuth dopant concentrations of 12 mol%, suggesting that Bi ions are well incorporated into the host lattice. SEM micrographs show irregular micrograins with sizes in the range of 0.5–20 μm. The samples present an intense greenish-blue fluorescence and persistent emissions at 495 nm, attributed to the 5d–4f allowed transitions of Eu2+. The fluorescence decreases as Bi concentration increases; that suggest bismuth-induced traps formation that in turn quench the luminescence. The photocatalytic evaluation of the powders was studied under both 365 nm UV and solar irradiations. Sample with 12 mol% of Bi presented the best MB degradation activity; 310 min of solar irradiation allow 100% MB degradation, whereas only 62.49% MB degradation is achieved under UV irradiation. Our results suggest that codoping the persistent phosphors with Bi3+ can be an alternative to enhance their photocatalytic activity.

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This work demonstrates that the presence of Bi3+ ions is detrimental for the photoluminescent and phosphorescent properties Sr4Al14O25: Eu2+, Dy3+ phosphor, but benefits the photocatalytic activity of the phosphors, since the Bi substitution into the host lattice generates additional defects (even more than the ones produced by the sole presence of Dy and Eu ions), which in turn reduce the recombination rate of holes and electrons and increases the lifetime of free carriers which are necessary for efficient photocatalysis. The best sample (doped with 12% Bi) produced total degradation of methylene blue after 310 min under solar irradiation.

Quelle: Photochemistry and Photobiology | 1 Mar 2016 | 10:01 am CET

Application of Deuteporfin in the Metastatic Lymph Node Mapping of Pancreatic Cancer: An in vivo Study

Abstract

For most cancer patients, the presence of metastatic lymph nodes usually indicates regional recurrence and poor prognosis. Therefore, lymph node mapping is a requisite for disease staging, prognosis prediction and decision making in the treatment of cancer. Deuteporfin, a second-generation photosensitizer, has a maximum excitation wavelength that can reach the near infrared (NIR) region (650–700 nm). We aimed to take advantage of these aspects of deuteporfin and use it as a fluorescent probe for metastatic lymph node mapping in vivo using NIR fluorescent imaging. In our study, we further investigated whether a photosensitizer could be used as a tracer for metastatic lymph node mapping of pancreatic cancer based on previous reports. Compared to normal tissues, tumor tissues including primary tumors and metastatic lymph nodes had a higher uptake ability of deuteporfin (< 0.05). Our research confirmed this targeting property of deuteporfin using in vivo fluorescent imaging. Consistent with observations from in vivo imaging experiments, frozen sections of metastatic lymph nodes intuitively displayed significantly higher and wider distributions of deuteporfin than normal sections.

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The graphical abstract shows application of deuteporfin as a fluorescent probe for tumor and metastatic lymph node mapping in vivo using NIR fluorescent imaging.

Quelle: Photochemistry and Photobiology | 1 Mar 2016 | 10:01 am CET

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Quelle: Photochemistry and Photobiology | 1 Mar 2016 | 10:01 am CET

Protoporphyrin IX-Functionalized AgSiO2 Core–Shell Nanoparticles: Plasmonic Enhancement of Fluorescence and Singlet Oxygen Production

Abstract

Metal-enhanced processes arising from the coupling of a dye with metallic nanoparticles (NPs) have been widely reported. However, few studies have simultaneously investigated these mechanisms from the viewpoint of dye fluorescence and photoactivity. Herein, protoporphyrin IX (PpIX) is grafted onto the surface of silver core silica shell NPs in order to investigate the effect of silver (Ag) localized surface plasmon resonance (LSPR) on PpIX fluorescence and PpIX singlet oxygen (1O2) production. Using two Ag core sizes, we report a systematic study of these photophysical processes as a function of silica (SiO2) spacer thickness, LSPR band position and excitation wavelength. The excitation of Ag NP LSPR, which overlaps the PpIX absorption band, leads to the concomitant enhancement of PpIX fluorescence and 1O2 production independently of the Ag core size, but in a more pronounced way for larger Ag cores. These enhancements result from the increase in the PpIX excitation rate through the LSPR excitation and decrease when the distance between PpIX and Ag NPs increases. A maximum fluorescence enhancement of up to 14-fold, together with an increase in photogenerated 1O2 production of up to five times are obtained using 100 nm Ag cores coated with a 5 nm thick silica coating.

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Schematic representation of protoporphyrin IX (PpIX)-functionalized AgSiO2 core–shell nanoparticles (NPs), which present both metal-enhanced fluorescence and singlet oxygen production resulting from the good overlap between PpIX and Ag NPs absorption spectra.

Quelle: Photochemistry and Photobiology | 1 Mar 2016 | 10:01 am CET

Interlaboratory Evaluation of Ultraviolet Radiation Emissions from Compact Fluorescent Lamps

Abstract

There have been many recent reports regarding the potential risks of UV emissions from compact fluorescent lamps (CFLs). In some of these reports, the robustness of the measurements was difficult to discern. We conducted round-robin measurements, involving three lamp manufacturers and two government research laboratories to gather reliable data on the UV emissions from commercially available CFLs. The initial sample of lamps consisted of 71 spiral-shaped CFLs purchased from local retailers. From the initial sample, 14 “high UV emitting” CFLs were chosen for further evaluation. We compared the UV emissions at a distance of 20 cm with the UV exposure limits (ELs) published by the International Commission on Non-ionizing Radiation Protection (ICNIRP). We found that the allowable exposure time for measured lamps ranged from 21 to 415 h. This indicates that the emissions would not exceed the short-term ELs that have been established by the ICNIRP for healthy individuals. We also evaluated the potential long-term risk and found it to be insignificant. There was a large variation in the UV emissions found, even for lamps from a single package, indicating that it is impossible to predict the UV output of a CFL based on its physical appearance and model designation.

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To address concerns about hazardous UV emissions from compact fluorescent lamps (CFLs), we conducted round-robin measurements to gather reliable data on the UV emissions from commercially available CFLs. We compared the UV emissions at a distance of 20 cm with published UV exposure limits (ELs) and found that the emissions would not exceed the short-term ELs that have been established for healthy individuals. There was a large variation in the UV emissions found, even for lamps from a single package, indicating that it is impossible to predict the UV output of a CFL based on its physical appearance and model designation.

Quelle: Photochemistry and Photobiology | 1 Mar 2016 | 10:01 am CET

Twisting in the excited state of an N-methylpyridinium fluorescent dye modulated by nano-heterogeneous micellar systems

Photochem. Photobiol. Sci., 2016, 15,525-535
DOI: 10.1039/C5PP00388A, Paper
A. Cesaretti, B. Carlotti, P. L. Gentili, R. Germani, A. Spalletti, F. Elisei
The fluorescence of an N-methylpyridinium dye was modulated by nano-heterogeneous micellar systems, where its excited state twisting is gradually impaired by the increasing viscosity of the surrounding environment.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 24 Feb 2016 | 1:00 am CET

A ruthenium(II) based photosensitizer and transferrin complexes enhance photo-physical properties, cell uptake, and photodynamic therapy safety and efficacy

Photochem. Photobiol. Sci., 2016, 15,481-495
DOI: 10.1039/C5PP00450K, Paper
Pavel Kaspler, Savo Lazic, Sarah Forward, Yaxal Arenas, Arkady Mandel, Lothar Lilge
Mixing the novel Ru2+ complex TLD1433 with transferrin prior to administration generates a photosensitizing drug with reduced dark toxicity and improved photophysical properties including NIR activation.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 23 Feb 2016 | 1:00 am CET

Construction of a multipurpose photochemical reactor with on-line spectrophotometric detection

Photochem. Photobiol. Sci., 2016, 15,589-594
DOI: 10.1039/C5PP00407A, Technical Note
Tamas Ditroi, Jozsef Kalmar, Jose Angel Pino-Chamorro, Zsolt Erdei, Gabor Lente, Istvan Fabian
A versatile photoreactor was constructed from commercially available parts, which is capable of recording high quality kinetic traces in homogeneous and heterogeneous photoreactions and also easily adaptable to flow-through operation.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 23 Feb 2016 | 1:00 am CET

A simple and sensitive flow injection method based on the catalytic activity of CdS quantum dots in an acidic permanganate chemiluminescence system for determination of formaldehyde in water and wastewater

Photochem. Photobiol. Sci., 2016, 15,496-505
DOI: 10.1039/C5PP00452G, Paper
Alireza Khataee, Roya Lotfi, Aliyeh Hasanzadeh, Mortaza Iranifam
The intensity of emitted light from KMnO4-HCHO-CdS QDs system is linearly proportional to HCHO concentration.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 19 Feb 2016 | 1:00 am CET

Intravital Imaging Study on Photodamage Produced by Femtosecond Near-infrared Laser Pulses In Vivo

Abstract

Ultrashort femtosecond pulsed lasers may provide indispensable benefits for medical bioimaging and diagnosis, particularly for noninvasive biopsy. However, the ability of femtosecond laser irradiation to produce biodamage in the living body is still a concern. To solve this biosafety issue, results of theoretical estimations as well as the in vitro and in situ experiments on femtosecond biodamage should be verified by experimental studies conducted in vivo. Here, we analyzed photodamage produced by femtosecond (19, 42 and 100 fs) near-infrared (NIR; ~800 nm) laser pulses with an average power of 5 and 15 mW in living undissected Drosophila larvae (in vivo). These experimental data on photodamage in vivo agree with the results of theoretical modeling of other groups. Femtosecond NIR laser pulses may affect the concentration of fluorescent biomolecules localized in mitochondria of the cells of living undissected Drosophila larva. Our findings confirm that the results of the mathematical models of femtosecond laser ionization process in living tissues may have a practical value for development of noninvasive biopsy based on the use of femtosecond pulses.

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Ultrashort femtosecond pulses may provide indispensable benefits for medical bioimaging and diagnosis, particularly for noninvasive biopsy. However, the ability of femtosecond laser irradiation to produce biodamage in the living body is still a concern. Here, we analyzed photodamage produced by femtosecond near-infrared (NIR) laser pulses of different duration with an average power of 5 and 15 mW in living undissected Drosophila larvae (in vivo). These experimental data on photodamage in vivo agree with the results of theoretical modeling of other groups. Femtosecond NIR laser pulses may affect the concentration of fluorescent biomolecules localized in mitochondria of the cells of living undissected animals.

Quelle: Photochemistry and Photobiology | 14 Feb 2016 | 8:01 pm CET

The Involvement of Splicing Factor hnRNP A1 in UVB-induced Alternative Splicing of hdm2

Abstract

Human homolog double minute 2 (hdm2), an oncoprotein, which binds to tumor suppressor p53 to facilitate its degradation, has been known to contribute to tumorigenesis. Its splicing variants are reported to be highly expressed in many cancers and can be induced by ultraviolet B light (UVB). However, the mechanisms of how UVB radiation induces hdm2 alternative splicing still remain unclear. In this study, we investigated the roles of two common splicing factors, heterogeneous nuclear ribonucleoproteins (hnRNP) A1 and serine/arginine-rich splicing factor 1 (SRSF1), in regulating UVB-induced hdm2 splicing. Our study indicated that while the expression of both hnRNP A1 and SRSF1 are induced, only hnRNP A1 is involved in hdm2 alternative splicing upon UVB irradiation. Overexpression of hnRNP A1 resulted in decrease of full-length hdm2 (hdm2-FL) and increase of hdm2B, one of hdm2 alternate-splicing forms; while down-regulated hnRNP A1 expression led to the decrease of the hdm2-FL and hdm2B in HaCaT cells. Protein-mRNA binding assay confirmed that UVB irradiation could increase the binding of hnRNP A1 to hdm2 pre-mRNA. In conclusion, we elucidated that UVB induces alternative splicing of hdm2 by increasing the expression and the binding of hnRNP A1 to hdm2 full-length mRNA.

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hnRNP A1 mediates UVB-induced alternative splicing of hdm2 and apoptosis.

Quelle: Photochemistry and Photobiology | 12 Feb 2016 | 5:38 am CET

Stereoselective Self-Aggregation of 31-Epimerically Pure Amino Analogs of Zinc Bacteriochlorophyll-d in an Aqueous Micelle Solution

Abstract

Zinc bacteriochlorophyll-d analogs possessing an amino group instead of the original hydroxy group at the C31 position were prepared by chemical modification of naturally occurring chlorophyll-a. The synthetic 31-epimers were successfully separated by reverse phase HPLC to give diastereomerically pure samples. The stereochemistry of the chiral C31-center in the separated amines was determined by NMR analysis of their diastereomeric amides as well as by their asymmetric synthesis from authentic stereoisomers. Both the epimers were monomeric in tetrahydrofuran to give sharp electronic absorption bands, while they self-aggregated to form chlorosomal oligomers with the redshifted bands in an aqueous Triton X-100 micelle solution (pH = 6.9). The resulting oligomers deaggregated by addition of p-toluenesulfonic acid to give monomeric N-protonated ammonium species. The aggregation and deaggregation were dependent on the 31-stereochemistry, indicating that each epimer produced supramolecularly different self-aggregates.

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31-Epimers of bacteriochlorophyll -d amino analogs self-aggregated in an aqueous micelle solution to form large oligomers. The self-aggregates were deaggregated by addition of a surfactant or an acid to give 31N-protonated monomers. Both the aggregation and deaggregation were controlled on the 31-stereochemistry.

Quelle: Photochemistry and Photobiology | 11 Feb 2016 | 7:31 pm CET

Inactivation by Pulsed Light of Bacillus subtilis Spores with Impaired Protection Factors

Abstract

The resistance to pulsed light (PL) of spores of Bacillus subtilis strain 168 and of strains with mutations increasing sensitivity to UV-C or affecting spore structure was evaluated and compared to resistance to continuous UV-C and moist heat, in order to reveal original mechanisms of inactivation by PL. Spores of B. subtilis strain 168 (1A1) and eight mutant strains (sspA, sspB, sspAB, cotA, gerE, cotE, uvrA and recA) were exposed to PL (up to 1.77 J cm−2), continuous UV-C (up to 147 mJ cm−2) and moist heat at 90°C. Spores of the strains lacking proteins linked to coat formation or structure (cotA, gerE and cotE) were markedly more sensitive to PL than 1A1, while their sensitivity to continuous UV-C or to moist heat was similar to the one of strain 1A1. Coat proteins had a major contribution to the resistance of B. subtilis spores to PL irradiation characterized by short-time and high-energy pulses of white light in the wavelengths 200–1100 nm. In contrast the role of coat proteins to UV-C or to moist heat resistance was marginal or null.

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Inactivation rates of intact (●) and decoated (∆) spores of Bacillus subtilis 168 and of B. subtilis cotE (○) mutant strain exposed to pulsed light (A) and continuous UV-C (B). Spores lacking coats or the coat protein CotE were more sensitive to pulsed light. In contrast their resistance to UV-C was not affected.

Quelle: Photochemistry and Photobiology | 11 Feb 2016 | 7:30 pm CET

The Triplet State of 6-thio-2′-deoxyguanosine: Intrinsic Properties and Reactivity Toward Molecular Oxygen

Abstract

Thiopurine prodrugs are currently among the leading treatment options for leukemia, immunosuppression, and arthritis. Patients undergoing long-term thiopurine treatment are at a higher risk of developing sunlight-induced skin cancers than the general population. This side effect originates from the cellular metabolization of thiopurine prodrugs to form 6-thio-2′-deoxyguanosine, which can absorb UVA radiation, populating its reactive triplet state and leading to oxidatively generated damage. However, the photo-oxidation mechanism is not fully understood. In this contribution, the oxidation potential and the adiabatic triplet energy of 6-thio-2′-deoxyguanosine are estimated computationally, whereas the intrinsic rate of triple-state decay and the rate constant for triplet quenching by molecular oxygen are determined using time-resolved spectroscopic techniques. A singlet oxygen quantum yield of 0.24 ± 0.02 is measured in aqueous solution (0.29 ± 0.02 in acetonitrile). Its magnitude correlates with the relatively low percentage of triplet-O2 collision events that generate singlet oxygen (SΔ = 37%). This behavior is rationalized as being due to the exergonic driving force for electron transfer between the triplet state of 6-thio-2′-deoxyguanosine and molecular oxygen (ΔGET = −69.7 kJ mol−1), resulting in the formation of a charge-transfer complex that favors nonradiative decay to the ground state over triplet energy transfer.

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6-thio-2′-deoxyguanosine is a common metabolite of the widely prescribed thiopurine prodrugs. The triplet state of 6-thio-2′-deoxyguanosine is populated upon UVA absorption, which can lead to cytotoxic side-effects. A mechanism is presented wherein the interaction between the triplet state of 6-thio-2′-deoxyguanosine and molecular oxygen leads to two competitive pathways—triplet-energy transfer or the formation of a charge-transfer complex. The former pathway generates singlet oxygen, whereas the latter decays back to the ground state. The identification of these two competitive relaxation pathways can assist in evaluating the primary mode of photosensitization that leads to the phototoxicity of 6-thio-2′-deoxyguanosine in biological environments.

Quelle: Photochemistry and Photobiology | 11 Feb 2016 | 8:24 am CET

Comparison of UV Protection Properties of Cotton Fabrics Treated with Aqueous and Methanolic Extracts of Achyranthes aspera and Alhagi maurorum Plants

Abstract

UV radiations are high-energy radiations present in sunlight that can damage human skin. Protection against these radiations becomes vital especially in those areas of the globe where UV index is quite high that makes the inhabitants more prone to dangerous effects of UV radiations. Clothing materials are good blockers of UV radiations, particularly when the fabric cover factor is high and/or the fabrics contain suitable UV-blocking finishes. In this study, effect of application of aqueous and methanolic extracts of two different plants, i.e., Achyranthes aspera and Alhagi maurorum on UV protection properties of cotton fabric was investigated. The results showed that the fabric samples treated with extracts of both the plants have excellent UV protection properties as indicated by their ultraviolet protection factor. It was concluded that both the aqueous and methanolic plant extracts are very effective in blocking UVA and UVB radiations, when applied on cotton fabrics. The UV protection performance of Achyranthes aspera extracts was much better as compared to that of Alhagi maurorum, and methanolic extracts of both the plants outperformed the aqueous extracts in terms of UV protection.

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Application of extracts from some plants on clothes can protect the wearer from dangerous ultraviolet radiations.

Quelle: Photochemistry and Photobiology | 11 Feb 2016 | 8:23 am CET

Actinic Prurigo in Singaporean Chinese: A Positive Association with HLA-DRB1*03:01

Abstract

Studies have reported the association of human leukocyte antigen (HLA) genes with susceptibility to develop actinic prurigo (AP) in Caucasians, but there were no studies in Asian populations, including the Chinese. Our study was performed to determine if AP is associated with susceptibility or protective HLA alleles or haplotypes in Singaporean Chinese. All Chinese patients diagnosed with AP at National Skin Center, Singapore, from January 2002 to April 2015 were invited to participate in the study. Clinical data and phototesting results were collated, and HLA typing was performed. Among 14 patients included, 11 were male and the mean age was 49.6 (37.9–61.3) years. All patients did not have a family history of AP and none had mucosal involvement, as such these clinical features differed from Caucasian AP patients. The frequency of DRB1*03:01 in AP patients was significantly higher compared to healthy controls (43% vs 16%, P = 0.022, odds ratio (OR) 3.89). Concurrently, the frequency of HLA-B*58:01-DRB1*03:01 haplotype was also significantly increased (25% vs 7%, P = 0.004, OR 4.23). In conclusion, HLA-DRB1*03:01 was associated with AP in Singaporean Chinese patients. This novel allelic association may possibly be utilized as a biological marker to aid in the diagnosis of AP in Chinese patients.

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Studies have reported the association of human leukocyte antigen (HLA) genes with susceptibility to develop actinic prurigo (AP) in Caucasians, but there were no studies in Asian populations, including the Chinese. Our study was performed to determine if AP is associated with susceptibility or protective HLA alleles or haplotypes in Singaporean Chinese. We found that HLA-DRB1*03:01 was associated with AP in Singaporean Chinese patients. This novel allelic association may possibly be utilized as a biological marker to aid in the diagnosis of AP in Chinese patients.

Quelle: Photochemistry and Photobiology | 11 Feb 2016 | 8:23 am CET

Enhanced Photocatalytic Degradation of 17α-Ethinylestradiol Exhibited by Multifunctional ZnFe2O4–Ag/rGO Nanocomposite Under Visible Light

Abstract

In this paper, ZnFe2O4, a visible light active photocatalyst, was comodified by graphene oxide (GO) and Ag nanoparticles (NPs) to form ZnFe2O4–Ag/rGO nanocomposite (NC) by facile one-pot hydrothermal method. Reduction of GO and formation of ZnFe2O4 and Ag nanoparticles occurred simultaneously during hydrothermal reaction. The photocatalytic activity of the NC was investigated under visible light, for the degradation of 17α-ethinylestradiol (EE2), a nondye compound, which also is an emerging pollutant with endocrine-disrupting activity. The pseudo rate constant (k′) of as-synthesized ZnFe2O4–Ag/rGO NC was higher by the factor of 14.6 and 5.6 times than the corresponding ZnFe2O4 and ZnFe2O4/rGO respectively. The synergistic interactions between ZnFe2O4, Ag and rGO leading to decreased aggregation of the NPs, increased surface area, better absorption in visible region, effective electron–hole generation transfer. However, in the presence of humic acid (HA), the photosensitization effect was predominated by competitive interaction resulting in only 80% removal of EE2 within the same time. Moreover, the composite can easily be magnetically separated for reuse.

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ZnFe2O4–Ag/rGO nanocomposite (NC) was fabricated by facile hydrothermal method. The efficiency of the nanocomposite was tested under visible light by degrading a nondye compound, 17α-ethinylestradiol, which is known to have endocrine-disrupting properties. Modification of ZnFe2O4 by addition of Ag nanoparticles (NP) and reduced graphene oxide (rGO) enhanced the photocatalytic efficiency. Moreover, the composite can easily be separated magnetically and reused. The competitive interaction of humic acid resulted in reduced removal of the model compound overshadowing its photosensitization.

Quelle: Photochemistry and Photobiology | 3 Feb 2016 | 12:47 pm CET

Can Mycosporine-Like Amino Acids Act as Multifunctional Compounds in Gymnodinium catenatum (Dinophyceae)?

Abstract

MAAs originating from Gymnodinium catenatum were subjected to H2O2 oxidation, light and heat. Shinorine and porphyra-334 were the more resistant to all treatments, mycosporine-glycine (MYGL) was the least resistant to oxidation and heat, whereas palythene and M-370 were the least resistant to light. MYGL and M-311 were similarly resistant to photodegradation and oxidation in the dark and low temperature, but M-311 was more resistant to oxidation under light or heat. The ratio M-370/M-365 changed from 29:1 to 6:1 ratio after 240 h of exposure to fluorescent light, indicating that M-365 could represent the M-370 cis-isomer. The role of MAAs as antioxidants and/or osmolytes was evaluated by studying effects of abrupt salinity reduction. Both increases or decreases in concentrations were observed and were dependent on the MAA initial concentration and its chemical structure. The relative increase in MAAs with a known antioxidant capacity (MYGL, palythene) followed an exponential decay trend related to initial concentration. The relative decrease in highly polar MAAs (shinorine, porphyra-334, M-332) with a suspected osmolyte role followed a rise to a maximum with the increase in initial concentration. Whether or not MAAs play a significant role in osmoregulation, their loss can occur upon hypoosmotic shock.

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MAA's stability to hydrogen peroxide, heat and light was dependent on the respective chemical structure. The unknown M-370 was undistinguishable from palythene (an MAA with a double bound absorbing in near-UVA) in chemical and photochemical stability. High polar MAAs, such as shinorine and porphyra-334 were rapidly lost upon hypoosmotic shock, in a concentration dependent manner, and can probably have an osmolyte role. The MAAs mycosporine-glycine and palythene increased upon hypoosmotic shock, indicating the need of an antioxidant response upon stress.

Quelle: Photochemistry and Photobiology | 3 Feb 2016 | 12:46 pm CET

Fiber-Optic Probes for Small-Scale Measurements of Scalar Irradiance

Abstract

A new method for producing fiber-optic microprobes for scalar irradiance (=fluence rate) measurements is described. Such fine-scale measurements are important in many photobiological disciplines. With the new method, it is possible to cast spherical 30–600 μm wide light integrating sensor tips onto tapered or untapered optical fibers. The sensor tip is constructed by first casting a clear polymethyl methacrylate (PMMA) sphere (~80% of the size of the final probe tip diameter) onto the optical fiber via dip-coating. Subsequently, the clear sphere is covered with light diffusing layers of PMMA mixed with TiO2 until the fiber probe exhibits a satisfactory isotropic response (typically ±5–10%). We also present an experimental setup for measuring the isotropic response of fiber-optic scalar irradiance probes in air and water. The fiber probes can be mounted in a syringe equipped with a needle, facilitating retraction of the spherical fiber tip. This makes it, e.g. possible to cut a hole in cohesive tissue with the needle before inserting the probe. The light-collecting properties of differently sized scalar irradiance probes (30, 40, 100, 300 and 470 μm) produced by this new method were compared to probes produced with previously published methods. The new scalar irradiance probes showed both higher throughput of light, especially for blue light, as well as a better isotropic light collection over a wide spectral range. The new method also allowed manufacturing of significantly smaller scalar irradiance microprobes (down to 30 μm tip diameter) than hitherto possible, and such sensors allow minimally invasive high-resolution scalar irradiance measurements in thin biofilms, leaves and animal tissues.

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Total radiant flux from all directions around a point is called the fluence rate (or scalar irradiance) and is an important parameter in photosynthesis and photodynamic therapy studies. It can be measured by fiber-optic probes with spherical measuring tips that collect light isotropically. We describe a new method for manufacturing such fiber probes, and the measuring characteristics of these new probes are compared to existing types made by other procedures. With the new method, it is possible to produce fluence rate fiber probes with spherical tip diameters down to 30 µm on tapered fibers and up to 600 µm on untapered fibers.

Quelle: Photochemistry and Photobiology | 2 Feb 2016 | 2:46 pm CET

Synthesis, Characterization and Photocatalytic Activity of Ag+- and Sn2+-Doped KTi0.5Te1.5O6

Abstract

In this study, the photocatalytic dye degradation efficiency of KTi0.5Te1.5O6 synthesized through solid-state method was enhanced by cation (Ag+/Sn+2) doping at potassium site via ion exchange method. As prepared materials were characterized by XRD, SEM-EDS, IR, TGA and UV–Vis Diffuse reflectance spectroscopic (DRS) techniques. All the compounds were crystallized in cubic lattice with inline image space group. The bandgap energies of parent, Ag+- and Sn+2-doped KTi0.5Te1.5O6 materials obtained from DRS profiles were found to be 2.96, 2.55 and 2.40 eV, respectively. Photocatalytic efficiency of parent, Ag+- and Sn+2-doped materials was evaluated against the degradation of methylene blue (MB) and methyl violet (MV) dyes under visible light irradiation. The Sn+2-doped KTi0.5Te1.5O6 showed higher activity toward the degradation of both MB and MV dyes and its higher activity is ascribed to the lower bandgap energy compared to the parent and Ag+-doped KTi0.5Te1.5O6. The mechanistic degradation pathway of methylene blue (MB) was studied in the presence of Sn2+-doped KTi0.5Te1.5O6. Quenching experiments were performed to know the participation of holes, super oxide and hydroxyl radicals in the dye degradation process. The stability and reusability of the catalysts were studied.

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The structure of defect pyrochlore, ABB'O6, is built up of corner sharing BO6 (B'O6) octahedra creating networks of hexagonal BB'O6 tunnels as shown in figure. The “A” ions are present in these tunnels.

Quelle: Photochemistry and Photobiology | 1 Feb 2016 | 8:53 am CET

Proteomonas sulcata ACR1: A Fast Anion Channelrhodopsin

Abstract

Natural channelrhodopsins with strictly anion selectivity and high unitary conductance have been recently discovered in the cryptophyte alga Guillardia theta. These proteins, called anion channelrhodopsins (ACRs), are of interest for their novel function and also because they were shown to be highly efficient tools to inhibit neuronal action potentials with light. We show that a homologous protein from the cryptophyte alga Proteomonas sulcata (named here PsuACR1) exhibits similar strict anion selectivity as the previously identified G. theta ACRs. Like G. theta ACRs, PsuACR1 lacks a protonatable residue at the position of the proton acceptor Asp-85 in bacteriorhodopsin, which may be a key characteristic of ACR family members shared by haloarchaeal chloride pumps. Of importance for its potential use in optogenetics, despite its 10-fold lower channel activity than the GtACRs, PsuACR1 exhibits an ~eightfold more rapid channel closing half-time making it uniquely suitable for silencing the subclass of high-frequency firing neurons when high-time resolution is needed. The existence of a rhodopsin with properties similar to G. theta ACRs in a different cryptophyte genus indicates that such proteins may be widespread in the phylum of cryptophyte algae.

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Natural channelrhodopsins with strictly anion selectivity and high unitary conductance (ACRs) were recently discovered in the alga Guillardia theta (Govorunova et al. Science 349:647–650. 2015). ACRs are of interest for their novel function and because they were shown to be highly efficient tools to inhibit neuronal firing with light. We characterize here a homolog present in the cryptophyte Proteomonas sulcata (PsuACR1), suggesting ACRs may be widespread in the cryptophyte phylum. Of importance for optogenetics, despite its 10-fold lower channel activity than the GtACRs, PsuACR1 exhibits a several fold faster channel closing and peak recovery uniquely enabling silencing high-frequency firing neurons.

Quelle: Photochemistry and Photobiology | 1 Feb 2016 | 8:52 am CET




 


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