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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:


Plantamajoside Inhibits UVB and Advanced Glycation End Products-induced MMP-1 Expression by Suppressing the MAPK and NF-ĸB Pathways in HaCaT Cells

Abstract

Photoaging and glycation stress are major causes of skin deterioration. Oxidative stress caused by ultraviolet B (UVB) irradiation can upregulate matrix metalloprotease 1 (MMP-1), a major enzyme responsible for collagen damage in the skin. Advanced glycation end products (AGEs) accumulate via gradual formation from skin proteins, especially from long-lived proteins such as dermal elastin and collagen. Plantamajoside (PM), isolated from Plantago asiatica, has various biological effects including anti-inflammatory and antioxidant effects. In this study, we assessed the protective effects of PM on a human keratinocyte cell line (HaCaT) and primary human dermal fibroblasts (HDF) against stress caused by glyceraldehyde-induced AGEs (glycer-AGEs) with UVB irradiation. We found that PM attenuated UVB-and-glycer-AGEs–induced MMP-1 expression in HaCaT and HDF cells and proinflammatory cytokines expression by inhibiting the phosphorylation of mitogen-activated protein kinases (MAPKs) activated by reactive oxygen species. Specific inhibitors of NF-κB and MAPKs attenuated the induced expression of MMP-1. PM also inhibited the phosphorylation of IκBα, and reduced nuclear translocation of NF-κB in these cells. Furthermore, PM attenuated the upregulation of receptor for AGEs (RAGE) by glycer-AGEs with UVB irradiation. Therefore, our findings strongly suggest that PM is a promising inhibitor of skin photoaging.

This article is protected by copyright. All rights reserved.

Quelle: Photochemistry and Photobiology | 27 Jun 2016 | 10:05 am CEST

Ground and excited state interactions of metalloporphyrin PtTMPyP4 with polynucleotides [poly(dG-dC)]2 and [poly(dA-dT)]2

Photochem. Photobiol. Sci., 2016, Accepted Manuscript
DOI: 10.1039/C6PP00105J, Paper
Paraic M Keane, J M Kelly
The ground- and excited-state interactions of Pt(II) meso-tetrakis(4-N-methylpyridyl)porphyrin (PtTMPyP4) with polynucleotides [poly(dG-dC)]2 and [poly(dA-dT)]2 have been investigated using UV/visible, circular dichroism, and steady-state and time-resolved emission spectroscopy. PtTMPyP4 intercalates into...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 27 Jun 2016 | 1:00 am CEST

Harnessing and storing visible light using a heterojunction of WO3 and CdS for sunlight-free catalysis

Photochem. Photobiol. Sci., 2016, Accepted Manuscript
DOI: 10.1039/C6PP00091F, Paper
Seonghun Kim, Yiseul Park, Wooyul Kim, Hyunwoong Park
CdS and WO3 (CdS/WO3) bilayer film electrodes are fabricated to harness solar visible light ([small lambda] > 420 nm) and store photogenerated electrons for possible use during periods of unavailable sunlight....
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 27 Jun 2016 | 1:00 am CEST

A Possible Phenom of Persistence in Pseudomonas aeruginosa Treated With Methylene Blue and Red Light

Abstract

Planktonic Pseudomonas aeruginosa cells harvested in stationary phase were exposed to red light in presence of methylene blue to study the potential occurrence of persistence in bacterial populations submitted to photodynamic antimicrobial therapy. Survival curves revealed the existence of small subpopulations of cells exhibiting increased ability to tolerate the treatment. These subpopulations were detected even using high concentrations of photosensitizer, whether added in a single step or following a fractionated scheme, and when the irradiation medium was modified to delay the photodecomposition of methylene blue. When cells grown from survivors to the treatment were cultured and exposed to red light and dye, their responses were similar to that of the original strain. These results exclude exhaustion of the photosensitizer and selection of resistant mutants as explanations for the features of the survival curves. Cells able to tolerate the treatment were found even when radiation was imparted at a high dose rate. They exhibit a response typical of persisters, which tolerate antimicrobial agents due to transient and reversible changes in their phenotype, suggesting that persistence is a factor to consider upon evaluating the efficacy of photodynamic antimicrobial therapy.

This article is protected by copyright. All rights reserved.

Quelle: Photochemistry and Photobiology | 25 Jun 2016 | 4:50 pm CEST

Surface Arginine Saturation Effect on Unfolding Reaction of Firefly Luciferase: A Thermodynamic and Kinetic Perspective

Abstract

Replacement of some hydrophobic solvent-exposed residues in Lampyris turkestanicus luciferase with arginine increases thermostability of this enzyme. Herein, thermodynamic and kinetic of unfolding reactions of wild type (WT), E354R/356R, E354R/356R-I232R and E354R/356R-Q35R/L182R/I232R variants has been investigated. Fluorescence and Far-UV circular dichroism signals using urea as chemical denaturant indicated that the value of ∆G(H2O) for all variants is greater than that of WT enzyme. Analysis of m-values, as a measure of difference in the solvent accessible surface area between the native and denatured states of protein, revealed that higher stability of mutants is related to their higher degree of compactness in the folded state. Results of unfolding kinetic experiments showed that all variants have three-exponential behavior in which, they unfolded with three rate constants and corresponding amplitudes. Increasing the rate constants of fast unfolding phase in mutants relative to WT protein may be attributed to more compactness and more kinetic sensitivity of their folded state to urea. However, more population of WT protein was unfolded from fast unfolding phase. Results of this investigation highlight kinetic stability of luciferase via a slow rate of unfolding.

This article is protected by copyright. All rights reserved.

Quelle: Photochemistry and Photobiology | 25 Jun 2016 | 4:45 pm CEST

Mechanism and Analyses for Extracting Photosynthetic Electrons using Exogenous Quinones - What Makes a Good Extraction Pathway?

Photochem. Photobiol. Sci., 2016, Accepted Manuscript
DOI: 10.1039/C6PP00076B, Paper
Guillaume Longatte, Fabrice Rappaport , Francis-Andre Wollman, Manon Guille Collignon, Frederic Lemaitre
Plants or algae take many benefits from oxygenic photosynthesis by converting the solar energy into a chemical one through the synthesis of carbohydrates from carbon dioxide and water. However, the...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 24 Jun 2016 | 1:00 am CEST

Photo-induced Electron Transfer in a Diamino-substituted Ru(bpy)3[PF6]2 Complex and Its Application as Triplet Photosensitizer for Nitric Oxide (NO)-Activated Triplet-Triplet Annihilation Upconversion

Photochem. Photobiol. Sci., 2016, Accepted Manuscript
DOI: 10.1039/C6PP00153J, Paper
Kejing Xu, Jianzhang Zhao, Evan G Moore
A system demonstrating Nitric Oxide (NO) activated Triplet-Triplet Annihilation (TTA) upconversion has been devised, based on a substituted [RuII(bpy)3](PF6)2 complex (bpy = 2,2'-dipyridine) bearing a single 1,2-diaminophenyl moiety as an...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 22 Jun 2016 | 1:00 am CEST

Reduced Levels of Tissue Inhibitors of Metalloproteinases (TIMPs) in UVB Irradiated Corneal Epithelium

Abstract

Tissue inhibitors of metalloproteinases (TIMPs) are the major endogenous regulators of metalloproteinase activity in tissues. TIMPs are able to inhibit activity of all known matrix metalloproteinases (MMPs) and thus participate in controlling extracellular matrix synthesis and degradation. We showed previously elevated expressions of MMPs in the rabbit corneal epithelium upon UVB exposure and suggested that these enzymes might be involved in corneal destruction caused by excessive proteolysis. The aim of this study was to investigate TIMPs in the corneal epithelium after UV irradiation using immunohistochemical and biochemical methods. We found that as compared to control rabbit corneas where relatively high levels of TIMPs were present in the epithelium, repeated irradiation of the cornea with UVB rays (not with UVA rays of similar doses) significantly decreased TIMPs in corneal epithelial cells. The results of this study point to the suggestion that the decrease of TIMPs in the corneal epithelium after UVB irradiation contributes to increased proteolytic activity of MMPs in UVB irradiated corneal epithelium found previously.

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Quelle: Photochemistry and Photobiology | 18 Jun 2016 | 9:25 am CEST

Development of a Novel Covalent Folate-Albumin-Photosensitizer Conjugate

Abstract

There is considerable interest in the development of novel and more efficient delivery systems for improving the efficacy of photodynamic therapy (PDT). The authors in this highlighted issue describe the synthesis and the photobiological characterizations of two photosensitizer (PS) conjugates based on β-carboline derivatives covalently conjugated to folic acid (FA) coupled to bovine serum albumin (BSA) as a carrier system specifically targeting cancer cells overexpressing FA receptor alpha (FRα). Accordingly, only the FA–BSA–β-carboline conjugates are internalized specifically in FRα-positive cells and are proved to be phototoxic. On the other hand, albumin–β-carboline conjugates without FA or β-carboline derivatives alone are not internalized and nontoxic. This conjugate is among the first to produce a conjugate composed of a PS and FA molecules that are directly conjugated to BSA. In addition, the in vitro studies are the first evidence that directly conjugated FA-BSA can be used as carriers to selectively enhance cytotoxicity by PDT relative to unmodified PS or nontargeted BSA-PS. This strategy is a positive step forward for the covalent design and construction of a photodynamic nanomedicine for FR-positive tumors.

Quelle: Photochemistry and Photobiology | 17 Jun 2016 | 8:40 pm CEST

Selective Photoreceptor Gene Knock-out Reveals a Regulatory Role for the Growth Behavior of Pseudomonas syringae

Abstract

The plant pathogen Pseudomonas syringae (Ps) is a well-established model organism for bacterial infection of plants. The genome sequence of two pathovars, pv. syringae and pv. tomato, revealed one gene encoding a blue- and two genes encoding red/far red light sensing photoreceptors. Continuing former molecular characterization of the photoreceptor proteins, we here report selective photoreceptor gene disruption for pv. tomato aiming at identification of potentially regulatory functions of these photoreceptors. Transformation of Ps cells with linear DNA constructs yielded interposon mutations of the corresponding genes. Cell growth studies of the generated photoreceptor knock-out mutants revealed their role in light-dependent regulation of cell growth and motility. Disruption of the blue-light (BL) receptor gene caused a growth deregulation, in line with an observed increased virulence of this mutant (Moriconi et al., Plant J., 2013, 76, 322). Bacterial phytochrome-1 (BphP1) deletion mutant caused unaltered cell growth, but a stronger swarming capacity. Inactivation of its ortholog, BphP2, however, caused reduced growth and remarkably altered dendritic swarming behavior. Combined knock-out of both bacteriophytochromes reproduced the swarming pattern observed for the BphP2 mutant alone. A triple knock out mutant showed a growth rate between that of the BL (deregulation) and the phytochrome-2 mutant (growth reduction).

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Quelle: Photochemistry and Photobiology | 11 Jun 2016 | 3:15 pm CEST

Identification of a Fluorescent Protein from Rhacostoma atlantica

Abstract

We have cloned a novel fluorescent protein from the jellyfish Rhacostoma atlantica. The closest known related fluorescent protein is the Phialidium yellow-fluorescent protein, with only a 55% amino acid sequence identity. A somewhat unusual alanine-tyrosine-glycine amino acid sequence forms the presumed chromophore of the novel protein. The protein has an absorption peak at 466 nm and a fluorescence emission peak at 498 nm. The fluorescence quantum yield was measured to be 0.77 and the extinction coefficient is 58,200 M−1 cm−1. Several mutations were identified that shift the absorption peak to about 494 nm and the emission peak to between 512 and 514 nm.

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Quelle: Photochemistry and Photobiology | 11 Jun 2016 | 3:15 pm CEST

Peroxyoxalate High Energy Intermediate is Efficiently Decomposed by the Catalyst Imidazole

Abstract

The peroxyoxalate reaction is a highly efficient chemiluminescence system, its chemiexcitation process involving the intermolecular interaction between an activator (ACT) and the High Energy Intermediate (HEI) of the reaction. Typically, the HEI is generated through the reaction of an oxalate ester with H2O2, on the presence of a basic/nucleophilic catalyst, such as imidazole (IMI-H). IMI-H, besides of catalysing the formation of the HEI, is also known to decompose this peroxidic intermediate. Despite of that, up to now no rate constant value has been determined for such significant interaction. Through kinetic measurements, we have observed that IMI-H is roughly four times more efficient than 9,10-diphenylanthracene (DPA), a classic ACT, in catalysing the decomposition of the HEI by a bimolecular electron transfer reaction through a CIEEL-like process. For instance, when IMI-H and DPA are at the same concentration, 78% of the generated HEI is actually consumed by the non-emissive bimolecular interaction with IMI-H. We have obtained an average singlet excited state formation quantum yield, at infinite ACT concentration, of (5.5 ± 0.5) × 10–2 E mol−1, determined at five different IMI-H concentrations. This ultimately suggests that the yield of formation of HEI actually does not depend on the IMI-H concentration.

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Quelle: Photochemistry and Photobiology | 10 Jun 2016 | 4:51 pm CEST

Diffuse Reflectance Spectroscopy Versus Mexameter® MX18 Measurements of Melanin and Erythema in an African Population

Abstract

Melanin provides protection against excess exposure to solar ultraviolet radiation (UVR) and related adverse health effects. Diffuse Reflectance Spectroscopy (DRS) can be used to calculate cutaneous melanin and erythema, but this is complex and has been mostly used for light-to-medium pigmented skin. Handheld reflectance spectrophotometers, such as the Mexameter® MX18, can also be used. We compared DRS-calculated melanin and erythema values with Mexameter melanin and erythema index values to understand how these techniques / measurements correlate in an African population of predominantly deeply-pigmented skin. 503 participants comprised 68.5% self-identified Black African, 9.9% Indian/Asian, 18.4% White and 2.9% Coloured. The majority of Black African (45%), Indian/Asian (34%) and Coloured (53%) participants self-identified their skin as being ‘brown’. Measured melanin levels increased with darker self-reported skin colour. DRS-calculated and Mexameter melanin values demonstrated a positive correlation (Spearman rho=0.87, p<0.001). The results from both instruments showed erythema values were strongly correlated with their own melanin values. This finding is considered spurious and may result from the complexity of separating brown and red pigment when using narrowband reflectance techniques. Further work is needed to understand melanin, erythema and colour in Black skin given sun-related health risks in vulnerable groups in Africa.

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Quelle: Photochemistry and Photobiology | 8 Jun 2016 | 4:50 pm CEST

Red Light Treatment in an Axotomy Model of Neurodegeneration

Abstract

Red light has been shown to provide neuroprotective effects. Axotomising the optic nerve initiates retinal ganglion cell (RGC) degeneration, and an early marker of this is dendritic pruning. We hypothesised that 670 nm light can delay axotomy induced dendritic pruning in the retinal explant. To test this hypothesis, we monitored the effects of 670 nm light (radiant exposure of 31.7 J/cm2), on RGC dendritic pruning in retinal explants from C57BL/6J mice, at 40 minutes, 8 hours and 16 hours post axotomy. For sham-treated retinae, area under the Sholl curve, peak of the Sholl curve and dendritic length at 8 hours post axotomy showed statistically significant reductions by 42.3% (p=0.008), 29.8% (p=0.007) and 38.4% (p=0.038), respectively, which were further reduced after 16 hours by 40.56% (p<0.008), 33.9% (p<0.007), 45.43% (p<0.006), respectively. Dendritic field area was also significantly reduced after 16 hours, by 44.23% (p<0.019). Such statistically significant reductions were not seen in light-treated RGCs at 8 or 16 hours post axotomy. The results demonstrate the ability of 670 nm light to partially prevent ex vivo dendropathy in the mouse retina, suggesting that it is worth exploring as a treatment option for dendropathy associated neurodegenerative diseases, including glaucoma and Alzheimer's disease.

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Quelle: Photochemistry and Photobiology | 8 Jun 2016 | 4:45 pm CEST

Regulation of Black Pepper Inflorescence Quantity by Shading at Different Growth Stages

Abstract

Black pepper is a perennial plant that can bloom throughout the year. It is generally expected that pepper inflorescence quantity could be minimized at the nonfull-bloom stage. The objective of this study was to find an appropriate shading measure that could inhibit blooming at other growing stages except the full-bloom stage and did not cause any reduction in pepper yield and quality. In this study, pepper trees were shaded up to 15%, 30%, 60% and 75%, respectively, and the inflorescence quantity, photosynthetic characteristics, pepper yield and quality traits were investigated at every growing stage. The results showed that the effect of shading on pepper yield decreased as time progressed. Shading treatment did not alter the composition of piperine and volatile oil, but reduced the moisture content. Based on the correlation between photosynthetic parameter and inflorescence number, the appropriate shading intensities for regulating inflorescence quantity at different phenological stages were determined. Moreover, it was found that the regulation of inflorescence quantity could be achieved by controlling leaf temperature during recovery to filling period. This research outcome also will give us some guidelines to develop other management strategies that control leaf temperature and regulate inflorescence quantity to consequently improve pepper yield.

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We examined the effect of duration of shading on pepper yield and quality. An appropriate shading measure could regulate inflorescence quantity.

Quelle: Photochemistry and Photobiology | 8 Jun 2016 | 9:25 am CEST

Vibrationally Resolved Absorption and Fluorescence Spectra of Firefly Luciferin: A Theoretical Simulation in the Gas Phase and in Solution

Abstract

Firefly bioluminescence has been applied in several fields. However, the absorption and fluorescence spectra of the substrate, luciferin, have not been observed at the vibrational level. In this study, the vibrationally resolved absorption and fluorescence spectra of firefly luciferin (neutral form LH2, phenolate ion form LH and dianion form L2−) are simulated using the density functional method and convoluted by a Gaussian function, with displacement, distortion and Duschinsky effects in the framework of the Franck–Condon approximation. Both neutral and anionic forms of the luciferin are considered in the gas phase and in solution. The simulated spectra have desired band maxima with the experimental ones. The vibronic structure analysis reveals that the features of the most contributive vibrational modes coincide with the key geometry-changing region during transition between the ground state and the first singlet excited state.

Thumbnail image of graphical abstract

This figure shows the simulated absorption and fluorescence spectra of phenolate-carboxylate ion of firefly luciferin in water. They are generally a mirror image of each other. Moreover, the 0–0 band position is also shown.

Quelle: Photochemistry and Photobiology | 8 Jun 2016 | 9:25 am CEST

Relative Contributions of UVB and UVA to the Photoconversion of (6-4) Photoproducts into their Dewar Valence Isomers

Abstract

Dewar valence isomers are photoisomerization products of pyrimidine (6-4) pyrimidone photoproducts, a major class of UV-induced DNA lesions which exhibits a maximal absorption around 320 nm. However, Dewar isomers are not produced in significant amounts in cells exposed to biologically relevant doses of UVB. In contrast, they are readily produced when cells are exposed to a combination of UVA and UVB. The present computational work demonstrates that, on the basis of known absorption properties and formation quantum yields, the difference in Dewar formation between the two types of radiation can be explained by the role of normal bases. In the UVB range, at the low level of (6-4) photoproducts present in cells exposed to realistic doses, normal bases are present in overwhelming amounts and absorb the vast majority of the incident photons. In contrast, the absorption of DNA bases is much weaker in the UVA range while that of (6-4) photoproducts is still significant, making photoisomerization possible. This two-photon process makes it difficult to define an action spectrum for the formation of Dewar isomers.

This article is protected by copyright. All rights reserved.

Quelle: Photochemistry and Photobiology | 8 Jun 2016 | 7:19 am CEST

Problems on the Evaluation of the Critical Wavelength of Sunscreens for “Broad Spectrum” Approval Brought on by Viscous Fingering During Sunscreen Application

Abstract

When a viscous liquid is applied to a solid substrate, a patterned liquid layer is usually formed by the phenomenon called viscous fingering, since the moving liquid surface is in far-from-equilibrium conditions to let the morphological fluctuation to grow. Pseudosunscreen solutions were prepared and applied on a flat quartz plate. A spatially periodic stripe pattern was formed on the pseudosunscreen layer when a block applicator was used, whereas a flat surface layer was formed when a four-sided applicator was used. UV absorbance of the patterned layer was lower than that of the flat layer having the same average thickness. In addition, a larger decrease in the UV absorbance by the pattern formation was observed at wavelengths at which the UV absorbance of the flat layer was large, which was consistent with theoretical simulations. In 2011, US FDA introduced a new rule using the term “Broad Spectrum” for labeling the sunscreens. The different decrease in the UV absorbance at each wavelength was found to change the critical wavelength, which is a criterion for sunscreens to be labeled as “Broad Spectrum” protection. The result of this study makes the problem on the evaluation of the critical wavelength come to the surface.

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Pseudosunscreen solutions were prepared and applied on a flat quartz plate. A spatially periodic stripe pattern was always formed on the pseudosunscreen layer when a block applicator was used. UV absorbance of the patterned layer was lower than that of the flat layer having the same average thickness. Larger decrease in the UV absorbance by the pattern formation was observed at wavelength at which the UV absorbance of the flat layer was large to change the critical wavelength for “Broad Spectrum” approval.

Quelle: Photochemistry and Photobiology | 7 Jun 2016 | 7:55 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 in 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. Four hundred fifty-four differentially expressed proteins were identified by comparison of spaceflight and ground control. Of proteins relevant to photosynthesis, 34 were downregulated and 4 were upregulated. The significantly downregulated ones are essential components of PSI, NDH and the Cytb6f complex. This downregulation of PSI proteins and/or protein structure changes may cause the overall reduction in 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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Shenzhou-8 spaceship was launched for a 17-day unmanned mission with a Long March rocket from the Jiuquan Satellite Launch Center. SIMBOX situated on Shenzhou-8 contained 17 biomedical experiments from both Chinese and German researchers. Our group contributed rice seedlings, investigating the role of microgravity on rice seedlings for further studies on photosynthetic physiology and proteomics. Our results indicate that microgravity condition causes reduction in photosystem I (PSI) activity in rice seedlings; and some side effects of the spaceflight conditions seem to have negative effects on PSI.

Quelle: Photochemistry and Photobiology | 6 Jun 2016 | 8:05 am 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 remains unclear. 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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Monochromatic light affects the secretion of avian melatonin by acting on the pineal through the cranium. Melatonin influence the secretion of insulin-like growth factor 1 in hepatocyte through the membrane receptor pathway.

Quelle: Photochemistry and Photobiology | 6 Jun 2016 | 8:05 am CEST

Efficient Degradation of Aqueous Rhodamine B Irradiation Under Indoor Light Using a SiO2–Hypocrellin B Complex

Abstract

An efficient method for the degradation of the dye Rhodamine B (RhB) is reported. A SiO2–hypocrellin B (SiO2–HB) complex was found to work as a catalyst to degrade RhB in aqueous solution at room temperature and atmospheric pressure, over the pH range 1–10, under indoor light conditions. This method is capable of removing 82.68% of RhB within 20 min at pH 9. The SiO2–HB complex was characterized by both scanning electron microscopy and surface area analysis. The reaction progress was examined using ultrahigh pressure liquid chromatography/mass spectrometry and UV–visible spectroscopy. This process represents an efficient means of decontaminating dye-containing wastewaters in either highly acidic or weakly alkaline environments.

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The natural photosensitizer hypocrellin B (HB) was used to prepare a SiO2–HB catalyst to degrade wastewater by an impregnation method. The results demonstrate that the SiO2–HB complex is capable of rapidly degrading Rhodamine B (RhB) at room temperature and ambient atmospheric pressure in aqueous solutions with wide pH values ranging from 1 to 10, and under indoor light. And the SiO2–HB complex appears to be an efficient catalyst for the degradation of the model dye RhB in wastewater and can be separated easily.

Quelle: Photochemistry and Photobiology | 6 Jun 2016 | 8:05 am CEST

Chemiexcitation Efficiency of Intermolecular Electron-transfer Catalyzed Peroxide Decomposition Shows Low Sensitivity to Solvent-cavity Effects

Abstract

Intermolecular chemically initiated electron exchange luminescence (CIEEL) systems are known to possess low chemiluminescence efficiency; whereas, the corresponding intramolecular transformations are highly efficient. As the reasons for this discrepancy are not known, we report in this work our studies of the solvent-cavity effect on the efficiency of two intermolecular CIEEL systems, the catalyzed decomposition of diphenoyl peroxide and of a relatively stable 1,2-dioxetanone derivative, spiro-adamantyl-1,2-dioxetanone. The results indicate a very low medium viscosity effect on the quantum yields of these systems, a priori not compatible with these bimolecular transformations, showing also that their low efficiency cannot be due to solvent-cavity escape of intermediate radical ion pairs. In addition, the solvent-cage effect on the CIEEL efficiency, after the occurrence of the initial electron transfer, proved also to be very low, indicating the intrinsic low viscosity effect on the chemiexcitation step. Therefore, it is concluded that the low efficiency of these systems is intrinsic to the chemiexcitation step and cannot be improved by medium viscosity effects, being possibly due to sterical hindrance on charge-transfer complex formation in the initial step of the CIEEL.

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The low quantum yields determined in the rubrene and perylene catalyzed decomposition of diphenoyl peroxide and spiro-adamantyl-1,2-dioxetanone are not subject to significant solvent cavity effects in binary ethyl acetate/dibutyl phthalate mixtures, indicating that the low efficiency is not due to solvent cavity escape of intermediate radical pairs but might be caused by steric effects on the interaction between the peroxide and the catalyst.

Quelle: Photochemistry and Photobiology | 6 Jun 2016 | 8:05 am CEST

Aggregation induced enhanced emission of 2-(2[prime or minute]-hydroxyphenyl)benzimidazole

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C6PP00122J, Paper
Ashim Malakar, Manishekhar Kumar, Anki Reddy, Himadree T. Biswal, Biman B. Mandal, G. Krishnamoorthy
Only cis-enol aggregates form microparticles and the hydroxyl group plays a vital role in the aggregation process. Proton transfer is an intramolecular process even in aggregates.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 6 Jun 2016 | 1:00 am CEST

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. 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. Application of AA extract (10, 100 μg mL−1) significantly diminished UVB-induced extracellular signal-regulated kinase and Jun-N-terminal kinase 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 signaling pathways and activator protein-1 activation. Our results suggest that AA is a promising botanical agent for use against skin photoaging.

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Solar ultraviolet radiation is mainly responsible for photoaging. UV-induced radical oxygen species (ROS) increase matrix metalloproteinase (MMPs) expression, which degrades collagen in the extracellular matrix (ECM). Angelica archangelia (AA) extract inhibited UVB-induced MMPs expression 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.

Quelle: Photochemistry and Photobiology | 3 Jun 2016 | 8:12 am CEST

Heterodimerization at the dye sensitized TiO2 surface: an efficient strategy toward quick removal of water contaminants

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C6PP00071A, Paper
Zaki S. Seddigi, Saleh A. Ahmed, Samim Sardar, Samir Kumar Pal
Crucial dye sensitization of porous TiO2 MS for filtering pollutants through heterodimerization and their solar light mediated degradation via ROS are demonstrated.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 3 Jun 2016 | 1:00 am CEST

Photochemically-assisted synthesis and photophysical properties of difluoroboronated [small beta]-diketones with fused four-benzene-ring chromophores, chrysene and pyrene

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C6PP00089D, Paper
Michitaka Mamiya, Yurie Suwa, Hideki Okamoto, Minoru Yamaji
We report synthesis and photophysical properties of difluoroboronated [small beta]-diketone complexes having chrysene and pyrene. Intense fluorescence is observable in solution and the solid state.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 3 Jun 2016 | 1:00 am CEST

Solvent-induced multicolour fluorescence of amino-substituted 2,3-naphthalimides studied by fluorescence and transient absorption measurements

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C6PP00048G, Paper
Mayu Fujii, Misa Namba, Minoru Yamaji, Hideki Okamoto
Amino-substituted 2,3-naphthalimide derivatives showed marked positive solvatofluorochromism, and the fluorescence emission was effectively quenched in methanol via the internal conversion process.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 2 Jun 2016 | 1:00 am CEST

Ethylenediamine-modified graphene oxide covalently functionalized with a tetracarboxylic Zn(II) phthalocyanine hybrid for enhanced nonlinear optical properties

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C6PP00063K, Paper
Zongle Li, Chunying He, Zhao Wang, Yachen Gao, Yongli Dong, Cheng Zhao, Zhimin Chen, Yiqun Wu, Weina Song
An investigation of the enhanced optical nonlinearity of ethylenediamine-modified graphene oxide covalently functionalized with a tetracarboxylic Zn(II) phthalocyanine.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 31 May 2016 | 1:00 am CEST

Synthesis of TiO2/CNT Composites and its Photocatalytic Activity Towards Sudan (I) Degradation

Abstract

Semiconductor photocatalysis has the potential for achieving sustainable energy generation and degrading organic contaminants. In TiO2, the addition of carbonaceous nanomaterials has attracted extensive attention as a means to increase its photocatalytic activity. In this study, composites of TiO2 and carbon nanotubes (CNT) in various proportions were synthesized by the hydrothermal method. The crystalline structures, morphologies, and light absorption properties of the TiO2/CNT photocatalysts were characterized by PXRD, TEM, and UV-Vis absorption spectra. The photocatalytic efficiency of the composites was evaluated by the degradation of Sudan (I) in UV-Vis light. Introducing 0.1-0.5 wt% CNT was shown to substantially improve the photoactivity of TiO2. The composite with 0.3 wt% CNT showed the best catalytic activity, and its reaction activation energy was calculated as 39.57 kJ/mol from experimental rates. The degradation products of Sudan (I) with different irradiation durations were characterized by Fourier transform infrared spectroscopy, and a degradation reaction process was proposed.

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Quelle: Photochemistry and Photobiology | 25 May 2016 | 8:20 am CEST

Albumin-folate-conjugates for Drug-targeting in Photodynamic Therapy

Abstract

Photodynamic therapy (PDT) is based on the cytotoxicity of photosensitizers in the presence of light. Increased selectivity and effectivity of the treatment is expected if a specific uptake of the photosensitizers into the target cells, often tumor cells, can be achieved. An attractive transporter for that purpose is the folic acid receptor α (FRα), which is over-expressed on the surface of many tumor cells and mediates an endocytotic uptake. Here, we describe the synthesis and photobiological characterization of polar β-carboline derivatives as photosensitizers covalently linked to folate-tagged albumin as carrier system. The particles were taken up by KB (human carcinoma) cells within < 90 min and then co-localized with a lysosomal marker. FRα antibodies prevented the uptake and also the corresponding conjugate without folate was not taken up. Accordingly, a folate-albumin-β-carbolinium conjugate proved to be phototoxic, while the corresponding albumin-β-carbolinium conjugates without FA were non-toxic, both with and without irradiation. An excess of free folate as competitor for the FRα-mediated uptake completely inhibited the photocytotoxicity. Interestingly, the albumin conjugates are devoid of photodynamic activity under cell-free conditions, as shown for DNA as a target. Thus, phototoxiciy requires cellular uptake and lysosomal degradation of the conjugates. In conclusion, albumin-folate-conjugates appear to be promising vehicles for a tumor cell targeted PDT.

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Quelle: Photochemistry and Photobiology | 25 May 2016 | 8:15 am CEST

Biospectroscopy, biospectrometry and imaging of Ilex paraguariensis. Basis for non-destructive quality evaluation using artificial vision

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C6PP00054A, Paper
Tamara L. Parapugna, Gabriela Petroselli, Rosa Erra-Basells, M. Gabriela Lagorio
Optical indicators related to the nutraceutical content derived from fluorescence, reflectance and imaging of Ilex paraguariensis have been developed. The results are complemented with mass spectrometry analysis.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 25 May 2016 | 1:00 am CEST

Repartition of oil miscible and water soluble UV filters in an applied sunscreen film determined by confocal Raman microspectroscopy

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C6PP00024J, Paper
Myriam Sohn, Theodor Buehler, Georgios Imanidis
Repartition of UV filters responsible for sun protection in the sunscreen film upon application depends on the formulation of the sunscreen.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 25 May 2016 | 1:00 am CEST

The action spectrum for vitamin D3: initial skin reaction and prolonged exposure

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C6PP00034G, Paper
Arjan van Dijk, Peter den Outer, Henk van Kranen, Harry Slaper
The action spectrum concept for vitamin D photosynthesis in skin is assessed for prolonged exposure, including side- and return-reactions. A generalized expression for the action spectrum is presented. Production estimates per erythemal dose are given.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 24 May 2016 | 1:00 am CEST

Chemical quenching of singlet oxygen by betanin

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C6PP00037A, Paper
Monika Wendel, Stanislaw Nizinski, Mateusz Gierszewski, Dorota Prukala, Marek Sikorski, Karolina Starzak, Slawomir Wybraniec, Gotard Burdzinski
Singlet oxygen produced upon UV excitation of perinaphthenone in D2O leads to oxidation of betanin.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 24 May 2016 | 1:00 am CEST

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

Photochem. Photobiol. Sci., 2016, 15,832-832
DOI: 10.1039/C6PP90018F, Correction
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
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 24 May 2016 | 1:00 am CEST

Experimental evidence of incomplete fluorescence quenching of pyrene bound to humic substances: implications for Koc measurements

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C6PP00052E, Paper
E. A. Shirshin, G. S. Budylin, N. Yu. Grechischeva, V. V. Fadeev, I. V. Perminova
Fluorescence quenching (FQ) is extensively used for quantitative assessment of partition coefficients (KOC) of polycyclic aromatic hydrocarbons (PAHs) to natural organic materials - humic substances (HS).
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 24 May 2016 | 1:00 am CEST

Coaxial Electrospinning Method for the Preparation of TiO2@CdS/PVA Composite Nanofiber Mat and Investigation on its Photodegradation Catalysis

Abstract

TiO2/PVA composite nanofiber mat was prepared via an electrospinning technology. SH-TiO2-SiO2 hybrid particles and PVA solution were injected through a coaxial syringe, yielding a composite nanofiber mat. The as-prepared SH-TiO2-SiO2/PVA composite nanofiber mat was immersed in Cd2+ cation solution and S2− anion solution in turn. Thus, yellow TiO2@CdS/PVA composite nanofiber 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 nanofiber mats were employed to catalyze the photodegradation of a model dye, methylene blue. The photodegradation performance could be greatly enhanced by the introduction of CdS particles anchoring onto TiO2 particles. The photodegradation efficiency reached 99.2% within 180 min. Also, the nanofiber mat could be recycled and reused at least 10 times. The photodegradation efficiency of TiO2@CdS/PVA composite nanofiber mats remained 68.8% for 10 cycles.

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A TiO2/PVA composite nanofiber mat was prepared first, and then the mat was immersed in Cd2+ and S2− solutions to obtain a TiO2@CdS/PVA composite nanofiber mat. The as-prepared mat exhibited excellent photodegradation ability for a model dye, methylene blue.

Quelle: Photochemistry and Photobiology | 18 May 2016 | 10:26 am CEST

Promotion of Proapoptotic 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 proapoptotic 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 proapoptotic effect overcomes intrinsic cytoprotection from mitochondrial photodamage along with a further stimulation of phototoxicity.

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Scheme whereby release of calcium from photodamaged lysosomes activates calpain. This enzyme then catalyzes activation of calpain. This enzyme then cleaves the autophagy-associated protein ATG5 to a truncated form that potentiates the initiation of apoptotic death after a subsequent PDT dose directed at mitochondria. The net result is substantially enhanced photokilling that can circumvent suboptimal delivery of light and oxygen.

Quelle: Photochemistry and Photobiology | 18 May 2016 | 10:25 am CEST

The preventive effect of linalool on acute and chronic UVB-mediated skin carcinogenesis in Swiss albino mice

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C6PP00075D, Paper
Srithar Gunaseelan, Agilan Balupillai, Kanimozhi Govindasamy, Ganesan Muthusamy, Karthikeyan Ramasamy, Mohana Shanmugam, N. Rajendra Prasad
Acute UVB-exposure induces erythema and edema. Repeated UVB-exposure causes chronic inflammation and mutated p53 expression which leads to carcinogenesis. Linalool through its (i) sunscreen effect, (ii) modulation of NF-[small kappa]B signaling and (iii) apoptotic signaling prevents photocarcinogenesis.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 18 May 2016 | 1:00 am CEST

YM155, a small molecule inhibitor of survivin expression, sensitizes cancer cells to hypericin-mediated photodynamic therapy

Photochem. Photobiol. Sci., 2016, 15,812-821
DOI: 10.1039/C5PP00438A, Paper
Katarina Gyuraszova, Jaromir Mikes, Andrea Halaburkova, Rastislav Jendzelovsky, Peter Fedorocko
Here we show for the first time that the repression of survivin expression by YM155 is effective in sensitizing cancer cells to HY-PDT, as measured by the decrease in cell viability and induction of apoptosis.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 13 May 2016 | 1:00 am CEST

Photodeoxygenation of dinaphthothiophene, benzophenanthrothiophene, and benzonaphthothiophene S-oxides

Photochem. Photobiol. Sci., 2016, 15,791-800
DOI: 10.1039/C5PP00466G, Paper
X. Zheng, S. M. Baumann, S. M. Chintala, K. D. Galloway, J. B. Slaughter, R. D. McCulla
The benzannulation of dibenzothiophene S-oxide to extend the photorelease of atomic oxygen to longer wavelengths.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 11 May 2016 | 1:00 am CEST

Topical application of spent coffee ground extracts protects skin from ultraviolet B-induced photoaging in hairless mice

Photochem. Photobiol. Sci., 2016, 15,779-790
DOI: 10.1039/C6PP00045B, Paper
Hyeon-Son Choi, Eu Ddeum Park, Yooheon Park, Sung Hee Han, Ki Bae Hong, Hyung Joo Suh
The topical application of SCG-derived OSCG and ESCG effectively protected the skin against UVB-induced photoaging in mice.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 10 May 2016 | 1:00 am CEST

A quantitative structure-property relationship (QSPR) study of singlet oxygen generation by pteridines

Photochem. Photobiol. Sci., 2016, 15,801-811
DOI: 10.1039/C6PP00084C, Paper
Andrey A. Buglak, Taisiya A. Telegina, Mikhail S. Kritsky
Singlet oxygen production quantum yields of pteridine photosensitizers were analyzed with the QSPR method. The ability of pterins and flavins to generate 1O2 in D2O correlated with EHOMO and electronegativity, as well as with the dipole moment and some other parameters.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 9 May 2016 | 1:00 am CEST

Influence of Donor on the Sensing Performance of a Series of TBET-based Two-photon Fluorescent Cu2+ Probes

Abstract

Optical properties of a series of molecular two-photon fluorescent Cu2+ probes containing the same acceptor (rhodamine group) are analyzed by using time-dependent density functional theory in combination with analytical response theory. Special emphasis is placed on evolution of the probes’ optical properties in the presence of Cu2+. In this study, the compound with naphthalene as the donor is shown to be excellent ratiometric fluorescent chemosensor, while the compound with quinoline derivative as the donor shows off/on-typed colorimetric fluorescent response. For the compound with naphthalimide derivative as the donor, changing the connection between the donor and acceptor can efficiently prevent the fluorescent quenching of the probe both in the absence and presence of Cu2+. The donor moiety and the connection between donor and acceptor are thus found to play dominant roles on sensing performance of these probes. Moreover, distributions of molecular orbitals involved in the excitation and emission of the probes are analyzed to explore responsive mechanism of the probes. The through-bond energy transfer (TBET) process is theoretically demonstrated. Our results are used to elucidate the available experimental measurements. This work is helpful to understand the relationships of structure with optical properties for the studied probes.

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Quelle: Photochemistry and Photobiology | 4 May 2016 | 4:10 pm CEST

Effect of enhanced UV-B radiation on methane emission in a paddy field and rice root exudation of low-molecular-weight organic acids

Photochem. Photobiol. Sci., 2016, 15,735-743
DOI: 10.1039/C6PP00023A, Communication
Yongmei He, Fangdong Zhan, Yuan Li, Weiwei Xu, Yanqun Zu, Ming Yue
Solar UV-B radiation had a notable effect on the emission of CH4 from a rice paddy, of which the mechanism was related to its influence on the excretion by roots of LMWOAs in the rhizosphere.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 4 May 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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o-Methylvalerophenone ester undergoes photoenolization upon exposure to UV light. The E-photoenol does not undergo intramolecular lactonization or electrocyclic ring closure because these processes cannot compete with reketonization via the solvent.

Quelle: Photochemistry and Photobiology | 3 May 2016 | 7:01 am CEST

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Quelle: Photochemistry and Photobiology | 3 May 2016 | 7:01 am CEST

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

Photochem. Photobiol. Sci., 2016, 15,731-734
DOI: 10.1039/C6PP00102E, Communication
Open Access Open Access
Creative Commons Licence  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Kei Ohkubo, Kensaku Hirose, Shunichi Fukuzumi
Alkanes were oxygenated by dioxygen with p-xyloquinone in cyclohexane which is used as a solvent to yield the corresponding oxygenated products under visible light photoirradiation with high quantum yields higher than 1000%.
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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, 15,822-831
DOI: 10.1039/C6PP00058D, Paper
David C. Soler, Jennifer Ohtola, Hideaki Sugiyama, Myriam E. Rodriguez, Ling Han, Nancy L. Oleinick, Minh Lam, Elma D. Baron, Kevin D. Cooper, Thomas S. McCormick
Resting (A) or activated (B) T cells were assessed for Pc 4 incorporation and the median uptake values of Pc 4 MFI was calculated (C).
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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, 15,744-751
DOI: 10.1039/C6PP00059B, Paper
Tianshu Chu, Yunsong Hu, Jinlun Wu, Chenghui Zeng, Yangyi Yang, Seik Weng Ng
Illustration of the probable quenching mechanism and the qualitative/quantitative relationship between Tb luminescent intensity and the analyte concentration.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 26 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

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

Photochem. Photobiol. Sci., 2016, 15,752-757
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

The quenching effect of uranyl species in the photoluminescence emission and visible-light-driven water dissociation activity of CdS and TiO2 photocatalysts

Photochem. Photobiol. Sci., 2016, 15,758-766
DOI: 10.1039/C6PP00022C, Paper
Narendra M. Gupta, Sarika Kelkar, Prakash Korake
Photoexcitation and non-radiative transfer of energy from the TiO2 or CdS photocatalyst to the surface-bound uranyl species lead to the quenching of the PL emission of the substrate matrix and the resultant loss of its visible-light-mediated water dissociation activity.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 22 Apr 2016 | 1:00 am CEST

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

Photochem. Photobiol. Sci., 2016, 15,714-730
DOI: 10.1039/C5PP00469A, Perspective
Susmita Das, Vimal Chandra Srivastava
This article gives an overview of photocatalytic microreactors with an application in environmental science, in particular, the degradation of different toxic dyes within microchannels.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 22 Apr 2016 | 1:00 am CEST

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

Photochem. Photobiol. Sci., 2016, 15,767-778
DOI: 10.1039/C6PP00033A, Paper
Anatoly R. Melnikov, Evgeny V. Kalneus, Valeri V. Korolev, Peter S. Sherin, Vsevolod I. Borovkov, Dmitri V. Stass
Previously unknown fluorescence lifetimes for optically inaccessible exciplexes of diphenylacetylene-DMA and p-terphenyl-DMA in n-dodecane are obtained by a simple oxygen quenching approach.
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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

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

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

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

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

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

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




 


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