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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:


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

Abstract

In this present work, Bismuth vanadate composited photocatalyst were synthesized and characterized. The X-ray diffractometry and Raman results showed that the particles were well crystallized, and performed as the complex of monoclinic BiVO4 and TiO2. Electron microscopy expressed the photocatalyst were high crystallization, agglutination and irregular shape, and adhered by a lot of 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 of pure BiVO4. The ultraviolet-visible diffuse reflectance spectra indicated the composited photocatalyst were effectively in visible light. The activity of photocatalytic water splitting was studied. The results showed that monomer BiVO4 photocatalyst was not able to produced hydrogen under any light source. BiVO4/TiO2 composited photocatalyst, however, were capable of generating hydrogen. Under UV light irradiated 120 min, 1 g catalyst dispersed in 50 mL deionized water produced almost 1 mL hydrogen, such productivity of hydrogen was higher than that of P25-TiO2. And the experiment of photocatalytic decomposition water under visible light also confirmed that BiVO4/TiO2 composited photocatalyst had the ability of water splitting.

This article is protected by copyright. All rights reserved.

Quelle: Photochemistry and Photobiology | 6 Feb 2016 | 7:33 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

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 (p<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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Quelle: Photochemistry and Photobiology | 1 Feb 2016 | 9:34 am 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

Regulatory mechanism of ion permeation through a channelrhodopsin derived from Mesostigma viride (MvChR1)

Photochem. Photobiol. Sci., 2016, Accepted Manuscript
DOI: 10.1039/C5PP00290G, Paper
Shota Watanabe, Toru Ishizuka, Shoko Hososhima, Alemeh Zamani, Mohammad Razuanul Hoque, Hiromu Yawo
The five glutamate (E) residues of transmembrane (TM)-2 of channelrhodopsin (CrChR)-2 are conserved among several members of the ChR family. A point mutation of one of them, E97 to a...
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 29 Jan 2016 | 1:00 am CET

An appraisal of the need for infrared radiation protection in sunscreens

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00451A, Paper
Brian Diffey, Benoit Cadars
Many sunscreens claim to protect against IR radiation. We review biological and clinical effects attributed to IR, as well as solar and industrial IR exposure levels and question whether IR protection in sunscreens is necessary.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 29 Jan 2016 | 1:00 am CET

Environmental effects of ozone depletion and its interactions with climate change: progress report, 2015

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C6PP90004F, Perspective
United Nations Environment Programme, Environmental Effects Assessment Panel
Model-derived percentage increases in the zonal-mean noon UV Index for 2011 that would have occurred without the implementation of the Montreal Protocol.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 28 Jan 2016 | 1:00 am CET

Inter-laboratory 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 hrs. 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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Quelle: Photochemistry and Photobiology | 27 Jan 2016 | 3:47 pm 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 fs, 42 fs and 100 fs) near infrared (~800 nm) laser pulses with an average power of 5 mW 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 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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Quelle: Photochemistry and Photobiology | 27 Jan 2016 | 3:45 pm CET

Some remarks on the first law of photochemistry

Photochem. Photobiol. Sci., 2016, Accepted Manuscript
DOI: 10.1039/C5PP00445D,
Angelo Albini
This is an Accepted Manuscript, which has been through the RSC Publishing peer review process and has been accepted for publication. Accepted manuscripts are published online shortly after acceptance. This version of the article will be replaced by the fully edited, formatted and proof read Advance Article as soon as this is available.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 26 Jan 2016 | 1:00 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 regardless of the L values, suggesting that the apparatus has a high potential to disinfect water. The inactivation at L=20 mm was significantly higher than that at L=0 in all cases tested (ANOVA, p < 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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Quelle: Photochemistry and Photobiology | 25 Jan 2016 | 5:17 pm CET

Evaluation of O-alkyl and aryl sulfonyl aromatic and heteroaromatic amidoximes as novel potent DNA photo-cleavers

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00439J, Paper
A. Papastergiou, S. Perontsis, P. Gritzapis, A. E. Koumbis, M. Koffa, G. Psomas, K. C. Fylaktakidou
O-Alkyl and aryl p-pyridine sulfonyl amidoxime derivatives are effective novel DNA photo-cleavers, generating highly efficient sulfonyloxyl radicals, able to cause a high ratio of single to double strand nicks.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 22 Jan 2016 | 1:00 am CET

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

Abstract

The resistance to pulsed light (PL) of spores of B. 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 nine mutant strains (sspA, sspB, sspAB, cotA, gerE, cotE, spl1, 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 nm to 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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Quelle: Photochemistry and Photobiology | 21 Jan 2016 | 2:26 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 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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Quelle: Photochemistry and Photobiology | 21 Jan 2016 | 2:26 am CET

The internal heavy-atom effect on 3-phenylselanyl and 3-phenyltellanyl BODIPY derivatives studied by transient absorption spectroscopy

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00366K, Paper
Jamaludin Al Anshori, Tomas Slanina, Eduardo Palao, Petr Klan
The extent of intersystem crossing related to the heavy-atom effect of Se and Te atoms was investigated on monosubstituted 3-phenylselanyl and 3-phenyltellanyl BODIPY derivatives.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 21 Jan 2016 | 1:00 am CET

Issue Information

Quelle: Photochemistry and Photobiology | 20 Jan 2016 | 8:55 am CET

Comparing Handheld Meters and Electronic Dosimeters for Measuring Ultraviolet Levels under Shade and in the Sun

Abstract

This study aimed to compare the validity, reliability and practicality of alternative portable methods for measuring erythemal UVR levels in passive recreation areas in public parks. UVR levels were measured for point in time comparisons between Solarmeter 6.5 handheld meters and time-stamped electronic dosimeters in a large central park in Melbourne, Australia. Observations were made at 20 locations in the park by two research assistants under two conditions: (1) matched shade (2) contrasting shade—no shade. Comparisons were also made with scientific instruments on the UVR monitoring station rooftop and by remotely selecting UV records and forecasts on cloud-free dates of park observations. There was good agreement between the portable UVR instruments in the park setting as confirmed via Bland Altman plots, while the dosimeter appeared less sensitive to change in shade conditions. The rooftop measurements showed that the Solarmeter 6.5 UVR readings were comparable to those of the adjacent rooftop instruments. The practicalities of using the dosimeters and Solarmeters for behavioral studies are discussed. These findings provide a basis for use of the Solarmeter 6.5 to measure changes in UVR levels due to different environmental conditions with relative accuracy for intervention studies in outdoor settings.

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Comparisons of UV measurements and other practical information are provided to assist public health researchers with choice of portable radiometers for future studies.

Quelle: Photochemistry and Photobiology | 20 Jan 2016 | 8:55 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 post-annealing process in reductive atmosphere. The XRD patterns show a single orthorhombic phase of 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 micro grains 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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Quelle: Photochemistry and Photobiology | 20 Jan 2016 | 8:03 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 fourteen patients included, eleven 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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Quelle: Photochemistry and Photobiology | 20 Jan 2016 | 7:46 am CET

Rhodopsins carrying modified chromophores - the 'making of', structural modelling and their light-induced reactivity

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00322A, Paper
Andreas Ockenfels, Igor Schapiro, Wolfgang Gartner
Vitamin-A aldehydes (retinals) with modified alkyl group substituents (9-demethyl-, 9-ethyl-, 9-isopropyl-, 10-methyl, 10-methyl-13-demethyl-, and 13-demethyl retinal) were synthesized to probe the chromophore-proteininteractions in rhodopsin.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 20 Jan 2016 | 1:00 am CET

Mechanism of Aloe Vera extract protection against UVA: shelter of lysosomal membrane avoids photodamage

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00409H, Paper
Daniela Rodrigues, Ana Claudia Viotto, Robert Checchia, Andreza Gomide, Divinomar Severino, Rosangela Itri, Mauricio S. Baptista, Waleska Kerllen Martins
Aloe Vera extract exhibited remarkable ability of reducing both in vitro and in vivo photodamage, even though it does not have anti-radical properties.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 18 Jan 2016 | 1:00 am CET

Preparation and photophysical properties of fluorescent difluoroboronated [small beta]-diketones having phenanthrene moieties studied by emission and transient absorption measurements

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00454C, Paper
Michitaka Mamiya, Yurie Suwa, Hideki Okamoto, Minoru Yamaji
Six difluoroboronated [small beta]-diketones having the phenanthrene skeleton (Phe@Ar) are prepared, and the photophysical features are studied.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 14 Jan 2016 | 1:00 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 term of UV protection.

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Quelle: Photochemistry and Photobiology | 12 Jan 2016 | 1:37 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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Quelle: Photochemistry and Photobiology | 12 Jan 2016 | 1:35 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 via increasing the expression and the binding of hnRNP A1 to hdm2 full-length mRNA.

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Quelle: Photochemistry and Photobiology | 12 Jan 2016 | 1:34 pm 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 red-shifted 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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Quelle: Photochemistry and Photobiology | 12 Jan 2016 | 1:08 pm CET

Enhanced upconversion luminescence through core/shell structures and its application for detecting organic dyes in opaque fishes

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00310E, Paper
Pan Hu, Xiaofeng Wu, Shigang Hu, Zenghui Chen, Huanyuan Yan, Zaifang Xi, Yi Yu, Gangtao Dai, Yunxin Liu
It confirms based on LRET that no Rhodamine B is absorbed by fishes after incubating in the aqueous solution of 1 [small mu ]g ml-1 Rhodamine B for one day, contrary to sodium fluorescein.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 11 Jan 2016 | 1:00 am CET

Unusually slow intramolecular proton transfer dynamics of 4[prime or minute]-N,N-dimethylamino-3-hydroxyflavone in high n-alcohols: involvement of solvent relaxation

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00377F, Paper
Deborin Ghosh, Shaikh Batuta, Naznin Ara Begum, Debabrata Mandal
The S1 energy surface of DMA3HF as a function of solvation and ESIPT coordinates, viewed down the energy axis as a 2-dimensional projection.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 8 Jan 2016 | 1:00 am CET

A study on bioluminescence and photoluminescence in the earthworm Eisenia lucens

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00412H, Communication
O. Pes, A. Midlik, J. Schlaghamersky, M. Zitnan, P. Taborsky
Eisenia lucens is a bioluminescent earthworm found in the organic soil layer of decomposing wood. Many lines of evidence indicate that riboflavin stored in coelomycetes plays an important role in this glowing reaction.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 8 Jan 2016 | 1:00 am CET

Specific excitonic interactions in the aggregates of hyaluronic acid and cyanine dyes with different lengths of methine group

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00343A, Paper
H. Tobata, T. Sagawa
The absorption and circular dichroism (CD) spectra of three types of cyanine dyes with different lengths of methine group (3,3[prime or minute]-diethylthiadicarbocyanine iodide, DTDC; 3,3[prime or minute]-diethylthiacarbocyanine iodide, DTC; and 3,3[prime or minute]-diethylthiacyanine iodide, DTTHC) in an aqueous solution were compared with and without hyaluronic acid (HA), which has a helical structure.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 8 Jan 2016 | 1:00 am CET

Quenching the firefly bioluminescence by various ions

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00432B, Paper
Huateng Zhang, Haixiu Bai, Tianyu Jiang, Zhao Ma, Yanna Cheng, Yubin Zhou, Lupei Du, Minyong Li
Some specific ions could selectively inhibit firefly luciferase while having a negligible effect on renilla luciferase, which may be used in the improved dual luciferase reporter gene assay.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 7 Jan 2016 | 1:00 am CET

A facile method to in situ fabricate three dimensional gold nanoparticle micropatterns in a cell-resistant hydrogel

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00426H, Communication
Ming-Hao Yao, Jie Yang, Dong-Hui Zhao, Rui-Xue Xia, Rui-Mei Jin, Yuan-Di Zhao, Bo Liu
A facile method for in situ fabrication of three-dimensional gold nanoparticles micropatterns throughout a polyethylene glycol hydrogel substrate has been developed by combining photochemical synthesis of gold nanoparticles with photolithography technology.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 7 Jan 2016 | 1:00 am CET

Acute Ultraviolet Radiation Perturbs Epithelialization but not the Biomechanical Strength of Full-thickness Cutaneous Wounds

Abstract

We hypothesized that priming of the skin with ultraviolet radiation (UVR) before being injured would enhance wound healing. Four groups, each comprising 20 immunocompetent hairless mice, were exposed to simulated solar irradiation in escalating UVR doses; 0 standard erythema dose (SED) = control, 1 SED, 3 SED and 5 SED. Twenty-four hours after UV irradiation, inflammation was quantified by skin reflectance (erythema) and myeloperoxidase (MPO) tissue levels, and two 6 mm full-thickness excisional wounds and one 3 cm incisional wound were inflicted. Epidermal hyperplasia was assessed by quantitative histology. Five days after wounding, wound coverage by neoepithelium and wound width of the excisional wounds was quantified in hematoxylin–eosin sections, and breaking strength was measured in strips from incisional wounds. Erythema (< 0.001), MPO levels (< 0.0005) and epidermal cell layers (< 0.001) increased dose-dependently by UV exposure of dorsal skin. In the excisional wounds, epithelial coverage decreased (= 0.024) by increasing the UVR dose, whereas there was no significant difference (= 0.765) in wound MPO levels. Neither wound width (= 0.850) nor breaking strength (= 0.320) differed among the groups. Solar-simulated UVR 24 h before wounding impaired epithelialization but was not detrimental for surgical incisional wound healing.

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Ultraviolet radiation (UVR) elicits an inflammatory response in the skin and increases the proliferation of basal cells of the epidermis. The consequences of these effects on wound healing remain unknown and were therefore studied here. We exposed immunocompetent hairless mice for escalating does of solar-simulated UVR. Twenty-four hours later full-thickness wounds were made in the skin and their postoperative healing followed. We found that UVR dose-dependently impaired epidermal coverage of the wounds (Figure), whereas UVR had no effect on the biomechanical strength of the surgical wounds. Our results ought to be taken into account when planning for surgical procedures in the skin.

Quelle: Photochemistry and Photobiology | 4 Jan 2016 | 1:21 pm CET

Near-infrared unsymmetrical blue and green squaraine sensitizers

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00335K, Paper
G. Hanumantha Rao, A. Venkateswararao, L. Giribabu, Surya Prakash Singh
Two novel panchromatic asymmetrical squaraine sensitizers (SPSQ1 and SPSQ2) have been synthesized, characterized and effectively used for TiO2-based dye sensitized solar cells.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 4 Jan 2016 | 1:00 am CET

Fluorescence quenching in [small beta]-cyclodextrin vesicles: membrane confinement and host-guest interactions

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00226E, Paper
Open Access Open Access
Frauke Schibilla, Linda Stegemann, Cristian A. Strassert, Fabio Rizzo, Bart Jan Ravoo
Host-guest interactions of nitro compounds at different pH values determine the fluorescence quenching of a spirobifluorene dye confined in the membrane of [small beta]-cyclodextrin vesicles.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 4 Jan 2016 | 1:00 am CET

Forged Under the Sun: Life and Art of Extremophiles from Andean Lakes

Abstract

High-altitude Andean lakes (HAAL) are a treasure chest for microbiological research in South America. Their indigenous microbial communities are exposed to extremely high UV irradiation and to multiple chemical extremes (Arsenic, high salt content, alkalinity). Microbes are found both, free-living or associated into microbial mats with different degrees of mineralization and lithification, including unique modern stromatolites located at 3570 m above sea level. Characterization of these polyextremophilic microbes began only recently, employing morphological and phylogenetic methods as well as high-throughput sequencing and proteomics approach. Aside from providing a general overview on microbial communities, special attention is given to various survival strategies; HAAL's microbes present a complex system of shared genetic and physiological mechanisms (UV-resistome) based on UV photoreceptors and stress sensors with their corresponding response regulators, UV avoidance and protection strategies, damage tolerance and UV damage repair. Molecular information will be provided for what is, so far the most studied HAAL molecule, a CPD-Class I photolyase from Acinetobacter Ver3 (Laguna Verde, 4400 m). This work further proposes some strategies that make an appeal for the preservation of HAAL, a highly fragile environment that offers promising and ample research possibilities.

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High-altitude Andean lakes are a treasure chest for microbiological research in South America. Their indigenous microbial communities including the highest modern stromatolites are exposed to outstandingly high UV irradiation and share a complex system of genetic and physiological mechanisms called as UV-resistome.

Quelle: Photochemistry and Photobiology | 30 Dec 2015 | 6:47 am CET

Improved Photodegradation of Organic Contaminants Using Nano-TiO2 and TiO2–SiO2 Deposited on Portland Cement Concrete Blocks

Abstract

The photocatalytic activity of TiO2 nanoparticles (nano-TiO2) and its hybrid with SiO2 (nano-TiO2–SiO2) for degradation of some organic dyes on cementitious materials was studied in this work. Nanohybrid photocatalysts were prepared using an inorganic sol–gel precursor and then characterized using XRD, SEM and UV–Vis. The grain sizes were estimated by Scherrer's equation to be around 10 nm. Then, a thin layer was applied to Portland cement concrete (PCC) blocks by dipping them into nano-TiO2 and nano-TiO2–SiO2 solution. The efficiency of coated PCC blocks for the photocatalytic decomposition of two dyes, Malachite Green oxalate (MG) and Methylene Blue (MB), was examined under UV and visible irradiation and then monitored by the chemical oxygen demand tests. The results showed that more than 80% and 92% of MG and MB were decomposed under UV–Vis irradiation using blocks coated with nano-TiO2–SiO2. TiO2/PCC and TiO2–SiO2/PCC blocks showed a significant ability to oxidize dyes under visible and UV lights and TiO2–SiO2/PCC blocks require less time for dye degradation. Based on these results, coated blocks have increased photocatalytic activity which can make them commercially accessible photocatalysts.

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We studied the photocatalytic activity of nano-TiO2 and TiO2–SiO2 particles for degradation of some organic dyes on cementitious materials. Grain sizes were calculated by Scheerer's equation and were estimated to be around 10 nm. For the photocatalytic degradation test, 10 mg L−1 aqueous solution of Methylene Blue and Malachite Green oxalate at acidic pH were used as organic pollutants. The results showed that both samples have significant ability to oxidize dyes completely under visible and UV lighting. With other conditions unchanged, the lower the pH value, the lower the concentration of dyes, the higher decolorizing rate recorded for TiO2–SiO2/Portland cement concrete blocks.

Quelle: Photochemistry and Photobiology | 29 Dec 2015 | 10:31 am CET

Interaction of Methanol Spray and Water-Deficit Stress on Photosynthesis and Biochemical Characteristics of Phaseolus vulgaris L. cv. Sadry

Abstract

This study was a factorial experiment with a completely randomized design and three replications. The four levels of methanol spraying were used. Spraying was carried out three times during the growing season at 10-day intervals beginning at 4 weeks after sowing. The spraying of solution continued until saturation of droplets on the leaves was achieved. The levels of water-deficit stress applied were nonstress, moderate water stress and severe water stress. The results showed that there was a significant difference (P ≤ 0.05) between the methanol and water-deficit stress treatments for chlorophyll (Chl) a and Chl b, carotenoid, total chlorophyll, net photosynthesis (PN), intercellular CO2 (Ci), maximal quantum yield of photosystem II photochemistry (Fv/Fm), leaf moisture, water use efficiency and relative water content. The application of foliar methanol at all levels of water-deficit stress significantly decreased the catalase activity of the roots. Under all levels of water-deficit stress, the 30% (v/v) methanol treatment significantly decreased peroxidase activity in the roots over that for the control. The results suggest that foliar application of methanol can decrease the negative effects of water-deficit stress on Phaseolus vulgaris L. cv. Sadry.

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The study of interaction of methanol spray and water-deficit stress on beans characteristics showed that there was a significant increase between these treatments for chlorophyll (Chl) a and Chl b, carotenoid (Car), total Chl, PN (net photosynthesis), Ci (intercellular CO2), Fv/Fm (maximal quantum yield of photosystem II photochemistry), water use efficiency (WUE) and relative water content (RWC) and decrease in superoxide dismutase (SOD), peroxidase activity (POX) and catalase activity (CAT). The trait, leaf moisture (LM), was not significant. The results suggest that foliar application of methanol can decrease the negative effects of water-deficit stress on Phaseolus vulgaris L. cv. Sadry.

Quelle: Photochemistry and Photobiology | 29 Dec 2015 | 10:31 am CET

The Bioluminescence Resonance Energy Transfer from Firefly Luciferase to a Synthetic Dye and its Application for the Rapid Homogeneous Immunoassay of Progesterone

Abstract

The sensitive BRET system for the homogeneous immunoassay of a low-molecular weight antigen was developed using progesterone as an example. Two thermostable mutants of the Luciola mingrelica firefly luciferase (Luc)—the “red” mutant with λmax.em = 590 nm (RedLuc) and the “green” mutant with λmax.em = 550 nm (GreenLuc)—were tested as the donors. The water-soluble Alexa Fluor 610× (AF) dye was selected as the acceptor because its two absorption maxima, located at 550 and 610 nm, are close to the bioluminescence maxima of the GreenLuc and RedLuc, respectively. The methods for the synthesis of the luciferase–progesterone (Luc–Pg) conjugate and the conjugate of the dye and the polyclonal antiprogesterone antibody (AF–Ab) were developed. Both conjugates retained their functional properties, had high antigen–antibody binding activity, and demonstrated a high BRET signal. The homogeneous immunoassay system based on the BRET from the firefly luciferase to the synthetic dye was established to assay progesterone as a model antigen. Optimization of the assay conditions, the composition of the reaction mixture, and the concentrations of the donor and the acceptor made it possible to reach the minimum detectable progesterone concentration of 0.5 ng mL−1.

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The sensitive BRET system for homogeneous immunoassay was developed using progesterone as an example. Two thermostable mutants of the Luciola mingrelica firefly luciferase (the “red” and “green” with λmax.em at 590 and 550 nm, respectively) were tested as the donors. The water-soluble Alexa Fluor 610× (AF) dye was selected as acceptor. The luciferase–progesterone (Luc–Pg) conjugate and the conjugate of the dye and the polyclonal antiprogesterone antibody (AF–Ab) were obtained, that retained their functional properties and demonstrated a high BRET signal. The homogeneous immunoassay system based on the BRET demonstrated the minimum detectable progesterone concentration of 0.5 ng mL−1.

Quelle: Photochemistry and Photobiology | 29 Dec 2015 | 10:30 am CET

Gp91phox-derived Reactive Oxygen Species/Urocortin 2/Corticotropin-releasing Hormone Receptor Type 2 Play an Important Role in Long-term Ultraviolet A Eye Irradiation-induced Photoaging

Abstract

Photoaging is induced by long-term ultraviolet A (UVA) eye irradiation. However, the mechanism of skin damage due to UVA eye irradiation is still not well understood. In this study, we used C57BL/6j and gp91phox knockout (gp91phox−/−) mice for the long-term effects of UVA irradiation. The eye or dorsal skin of the mice was locally exposed to UVA for 12 months. The reactive oxygen species (ROS), gp91phox, corticotropin-releasing hormone (CRH), urocortin 2, and CRH receptor (CRHR) type 1 and type 2 levels in the brain and mast cell tryptase and histamine levels in the dorsal skin all increased after UVA irradiation. The levels of CRH, urocortin 2, CRHR type 1 and type 2 in the brain also increased more after UVA eye irradiation than after UVA skin irradiation. Moreover, photoaging of the UVA eye irradiation mice was not induced following the administration of a ROS inhibitor in the brain. In addition, in gp91phox−/− mice, photoaging by UVA eye irradiation was not induced. These results indicate that long-term UVA eye irradiation led to increased gp91phox-derived ROS in the brain and the increased expression of urocortin 2 and CRHR type 2, resulting in photoaging; however, further studies are needed to confirm these findings.

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In this experiment, photoaging was induced using long-term ultraviolet A (UVA) eye irradiation for 12 months. According to our observations, UVA eye irradiation increases the production of ROS from gp91phox in the brain, and this gp91phox-induced ROS stimulates urocortin 2. Moreover, urocortin 2 increases the degranulation of tryptase and histamine from mast cells of the skin, thereby leading to photoaging.

Quelle: Photochemistry and Photobiology | 28 Dec 2015 | 6:05 am CET

UV-induced DNA Damage: The Role of Electronic Excited States

Abstract

The knowledge of the fundamental processes induced by the direct absorption of UV radiation by DNA allows extrapolating conclusions drawn from in vitro studies to the in-vivo DNA photoreactivity. In this respect, the characterization of the DNA electronic excited states plays a key role. For a long time, the mechanisms of DNA lesion formation were discussed in terms of generic “singlet” and “triplet” excited state reactivity. However, since the beginning of the 21st century, both experimental and theoretical studies revealed the existence of “collective” excited states, i.e. excited states delocalized over at least two bases. Two limiting cases are distinguished: Frenkel excitons (delocalized ππ* states) and charge-transfer states in which positive and negative charges are located on different bases. The importance of collective excited states in photon absorption (in particular in the UVA spectral domain), the redistribution of the excitation energy within DNA, and the formation of dimeric pyrimidine photoproducts is discussed. The dependence of the behavior of the collective excited states on conformational motions of the nucleic acids is highlighted.

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Electronic interactions among DNA bases give rise to excited states delocalized over two or more bases. As a result, the excited state properties depend strongly on conformational motions.

Quelle: Photochemistry and Photobiology | 18 Dec 2015 | 1:28 pm CET

Phloroglucinol Reduces Photodamage in Hairless Mice via Matrix Metalloproteinase Activity Through MAPK Pathway

Abstract

We investigated the photoprotective activity of phloroglucinol on ultraviolet B (UVB)-induced deleterious effects in hairless mice in vivo. To assess the photoprotective effect of phloroglucinol, phloroglucinol-treated HR-1 hairless male mice were exposed to UVB irradiation. The inhibitory activity of phloroglucinol on wrinkle formation was determined by analysis of skin replicas, epidermal thickness based on histological examination and collagen damage. Matrix metalloproteinase-1 (MMP-1), matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinase (TIMP) mRNA levels were measured by real-time PCR. UVB induced transcription of proinflammatory cytokines, including interleukin-1 beta (IL-1β, IL-6) and IL-8 (IL-8). The protective effects of phloroglucinol on UVB-induced skin photoaging were examined by measuring protein levels of MMPs and mitogen-activated protein (MAP) kinases. The results of these experiments suggest that phloroglucinol has a significant beneficial effect on the barrier function of the skin. In hairless mice, signs of photoaging and photodamage, including coarse wrinkle formation, epidermal thickness and elastic fiber degeneration, were reduced in severity by phloroglucinol application. The phloroglucinol-treated group showed remarkably decreased mRNA levels of MMP-1, MMP-9 and inflammatory cytokines in comparison with those of the UVB-induced group. Oral administration of phloroglucinol attenuated phosphorylation of MAP kinases, including extracellular signal-regulated kinase, c-Jun N-terminal kinase and p38.

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The phloroglucinol showed the photoprotective effect on UVB-induced skin damage in terms of epidermis thickness and collagen change based on histological examination.

Quelle: Photochemistry and Photobiology | 18 Dec 2015 | 1:20 pm CET

Integration of Cyanine, Merocyanine and Styryl Dye Motifs with Synthetic Bacteriochlorins

Abstract

Understanding the effects of substituents on spectral properties is essential for the rational design of tailored bacteriochlorins for light-harvesting and other applications. Toward this goal, three new bacteriochlorins containing previously unexplored conjugating substituents have been prepared and characterized. The conjugating substituents include two positively charged species, 2-(N-ethyl 2-quinolinium)vinyl- (B-1) and 2-(N-ethyl 4-pyridinium)vinyl- (B-2), and a neutral group, acroleinyl- (B-3); the charged species resemble cyanine (or styryl) dye motifs whereas the neutral unit resembles a merocyanine dye motif. The three bacteriochlorins are examined by static and time-resolved absorption and emission spectroscopy and density functional theoretical calculations. B-1 and B-2 have Qy absorption bathochromically shifted well into the NIR region (822 and 852 nm), farther than B-3 (793 nm) and other 3,13-disubstituted bacteriochlorins studied previously. B-1 and B-2 have broad Qy absorption and fluorescence features with large peak separation (Stokes shift), low fluorescence yields, and shortened S1 (Qy) excited-state lifetimes (~700 ps and ~100 ps). More typical spectra and S1 lifetime (~2.3 ns) are found for B-3. The combined photophysical and molecular-orbital characteristics suggest the altered spectra and enhanced nonradiative S1 decay of B-1 and B-2 derive from excited-state configurations in which electron density is shifted between the macrocycle and the substituents.

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The photophysical properties (Φf, τs, ΦT, τT, kf, kic, kisc) of three free base bacteriochlorins bearing previously unexplored conjugating substituents have been characterized and interpreted with the aid of molecular-orbital calculations. The bacteriochlorins absorb strongly in the 780–850 nm region and provide models for photosynthetic bacteriochlorophylls.

Quelle: Photochemistry and Photobiology | 18 Dec 2015 | 1:18 pm CET

Suberythemal Sun Exposures at Swedish Schools Depend on Sky Views of the Outdoor Environments – Possible Implications for Pupils’ Health

Abstract

More scheduled outdoor stay is increasingly advocated for school children. This study measured 2nd, 5th and 8th graders’ erythemal UV-exposure in September, March and May at four Swedish schools. We related those exposures, as fractions of total available ambient radiation, to the schools outdoor environments differing in amount of shade, vegetation, and peripheral city-scape quantified as percentage of free sky view calculated from fish-eye photographs. Exposures correlated with the sky views (with exceptions in May) and were suberythemal. The exposures were also below the threshold limit of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) for hazard evaluation of UVR but were potentially enough for adequate vitamin D formation according to a cited model calculation – as illustrated in the results and discussed. The school environments, typical in southern and middle Sweden, offer enough shade to protect children from overexposure during seasons with potentially harmful solar UV radiation. Pupils’ outdoor stay may be extended during September and March. In May extended outdoor stay of the youngest pupils requires a more UVR-protective environment.

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Erythemal UV- exposures in Swedish pupils were measured. Exposures largely correlated to the schools’ outdoor environments differing in amount of shade, vegetation, and peripheral city-scape quantified as percentage of free sky view calculated from fish-eye photographs. The exposures were suberythemal and below the threshold limit of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) for hazard evaluation of UVR but were potentially enough for adequate vitamin D formation according to a cited model calculation.

Quelle: Photochemistry and Photobiology | 18 Dec 2015 | 1:17 pm CET

Role of Cr(III) deposition during the photocatalytic transformation of hexavalent chromium and citric acid over commercial TiO2 samples

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00420A, Paper
V. N. Montesinos, C. Salou, J. M. Meichtry, C. Colbeau-Justin, M. I. Litter
A larger specific area makes UV100 more efficient than P25 for Cr(VI) and citric acid removal. Citric and 3-oxoglutaric acids prevent surface deposition of Cr(III) recombining centers.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 18 Dec 2015 | 1:00 am CET

Photobiological Origins of the Field of Genomic Maintenance

Abstract

Although sunlight is essential for life on earth, the ultraviolet (UV) wavelengths in its spectrum constitute a major threat to life. Various cellular responses have evolved to deal with the damage inflicted in DNA by UV, and the study of these responses in model systems has spawned the burgeoning field of DNA repair. Although we now know of many types of deleterious alterations in DNA, the approaches for studying them and the early mechanistic insights have come in large part from pioneering research on the processing of UV-induced bipyrimidine photoproducts in bacteria. It is also notable that UV was one of the first DNA damaging agents for which exposure was directly linked to cancer; the sun-sensitive syndrome, xeroderma pigmentosum, was the first example of a cancer-prone hereditary disease involving a defect in DNA repair. We provide a short history of advances in the broad field of genomic maintenance as they have emerged from research in photochemistry and photobiology.

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Although sunlight is essential for life, the UV wavelengths constitute a threat to life. Cellular responses evolved to deal with DNA damage inflicted by UV; the study of these responses spawned the burgeoning field of DNA repair and genomic maintenance.

Quelle: Photochemistry and Photobiology | 16 Dec 2015 | 1:48 pm CET

Protoporphyrin IX Functionalised AgSiO2 Core-shell Nanoparticle: 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) localised 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 of 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 of photogenerated 1O2 production of up to 5 times are obtained using 100 nm Ag cores coated with a 5 nm thick silica coating.

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Quelle: Photochemistry and Photobiology | 15 Dec 2015 | 1:50 pm CET

Melanopsin and the Non-visual Photochemistry in the Inner Retina of Vertebrates

Abstract

Melanopsin (Opn4), a member of the G-protein-coupled receptor family, is a vitamin A-based opsin in the vertebrate retina that has been shown to be involved in the synchronization of circadian rhythms, pupillary light reflexes, melatonin suppression and other light-regulated tasks. In nonmammalian vertebrates there are two Opn4 genes, Opn4m and Opn4x, the mammalian and Xenopus orthologs respectively. Opn4x is only expressed in nonmammalian vertebrates including reptiles, fish and birds, while Opn4m is found in a subset of retinal ganglion cells (RGCs), the intrinsically photosensitive (ip) RGCs of the inner retina of both mammals and nonmammalian vertebrates. All opsins described utilize retinaldehyde as chromophore, photoisomerized from 11-cis- to all-trans-retinal upon light exposure. Visual retinal photoreceptor cones and rods, responsible for day and night vision respectively, recycle retinoids through a process called the visual cycle that involves the retinal pigment epithelium or glial Müller cells. Although Opn4 has been characterized as a bistable photopigment, little is known about the mechanism/s involved in its chromophore regeneration. In this review, we will attempt to shed light on the visual cycle taking place in the inner retina and discuss the state of the art in the nonvisual photochemistry of vertebrates.

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The inner retina of most vertebrates expresses the photopigment melanopsin (Opn4). Opn4 has been involved in a number of nonimage forming tasks (synchronization of circadian rhythms, pupillary light reflexes, etc.) and although it has been characterized as a bi/tristable photopigment, little is known about the mechanism/s involved in its chromophore regeneration. Based on some molecular and biochemical similarities with rhabdomeric photoreceptors (the biochemical nature of phosphoinositol-photocascade and opsin homology), we can infer that a novel visual cycle may operate in Opn4 (+) cells further cooperating to the chromophore regeneration via a supplementary alternative process as described in Drosophila.

Quelle: Photochemistry and Photobiology | 15 Dec 2015 | 7:42 am CET

In Situ Photo Sonosynthesis of Organic/Inorganic Nanocomposites on Wool Fabric Introducing Multifunctional Properties

Abstract

Here, a novel and efficient process is introduced for producing wool fabric with multifunctional features through facile in situ photosonochemical synthesis of organic/inorganic nanocomposites. The fabric was treated with titanium isopropoxide, silver nitrate and ammonia in a sonobath for 1 h at 75–80°C. The crystal phase of the sono-treated samples was characterized by X-ray diffraction. The uniform distribution of the nanocomposite on the fiber surface was proved by field emission scanning electron microscope, energy dispersive X-ray and mapping patterns. Further, the composition of the nanocomposites was investigated by X-ray photoelectron spectroscopy. The sono-treated wool fabrics illustrated excellent photocatalytic activities toward discoloration of Methylene Blue under sunlight and UV-A irradiation. Also the fabrics indicated reasonable antibacterial/antifungal activities against Staphylococcus aureus, Escherichia coli and Candida albicans. The tensile properties of the sono-treated fabrics enhanced comparing to the untreated and even conventional stirrer-treated fabrics. Moreover, a central composite design based on response surface methodology was used to study the influence of titanium isopropoxide and silver molar ratio on the prepared nanocomposites sonobath. Finally, the optimum molar ratio was reported for the best responses.

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A novel efficient process is introduced for wool fabric with multifunctional features through facile in situ photo sonosynthesis of organic/inorganic nanocomposites. The fabric was treated with titanium isopropoxide, silver nitrate and ammonia in a sonobath at 75–80°C for 1 h. The uniform distribution of the nanocomposites on the fiber surface was proved by SEM, EDX and mapping. The sono-treated wool fabrics illustrated excellent photocatalytic activities toward discoloration of Methylene Blue under sunlight. Also the fabrics indicated reasonable antibacterial/antifungal activities against S. aureus, E. coli and C. albicans. The tensile properties of the sono-treated fabrics was also enhanced.

Quelle: Photochemistry and Photobiology | 15 Dec 2015 | 7:41 am CET

Acute Effects of Light on Alternative Splicing in Light-Grown Plants

Abstract

Light modulates plant growth and development to a great extent by regulating gene expression programs. Here, we evaluated the effect of light on alternative splicing (AS) in light-grown Arabidopsis thaliana plants using high-throughput RNA sequencing (RNA-seq). We found that an acute light pulse given in the middle of the night, a treatment that simulates photoperiod lengthening, affected AS events corresponding to 382 genes. Some of these AS events were associated with genes involved in primary metabolism and stress responses, which may help to adjust metabolic and physiological responses to seasonal changes. We also found that several core clock genes showed changes in AS in response to the light treatment, suggesting that light regulation of AS may play a role in clock entrainment. Finally, we found that many light-regulated AS events were associated with genes encoding RNA processing proteins and splicing factors, supporting the idea that light regulates this posttranscriptional regulatory layer through AS regulation of splicing factors. Interestingly, the effect of a red-light pulse on AS of a gene encoding a splicing factor was not impaired in a quintuple phytochrome mutant, providing unequivocal evidence that nonphotosensory photoreceptors control AS in light-grown plants.

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Light modulates plant growth and development to a great extent by regulating gene expression programs. Here, we evaluated the effect of light on alternative splicing (AS) in light-grown Arabidopsis thaliana plants using high-throughput RNA sequencing (RNA-seq). Interestingly, the effect of a red-light pulse on AS of a gene encoding a splicing factor was not impaired in a quintuple phytochrome mutant, providing unequivocal evidence that nonphotosensory photoreceptors control AS in light-grown plants.

Quelle: Photochemistry and Photobiology | 15 Dec 2015 | 7:40 am CET

A comparative study on the antibacterial photodynamic efficiency of a curcumin derivative and a formulation on a porcine skin model

Photochem. Photobiol. Sci., 2016, Advance Article
DOI: 10.1039/C5PP00393H, Paper
Nicole Tortik, Peter Steinbacher, Tim Maisch, Andreas Spaeth, Kristjan Plaetzer
The novel cationic curcumin derivative SACUR-3 is phototoxic to bacteria on porcine skin and does not penetrate the stratum corneum.
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Quelle: RSC - Photochem. Photobiol. Sci. latest articles | 14 Dec 2015 | 1:00 am CET

Novel In Vitro Antioxidant and Photoprotection Capacity of Plants from High Altitude Ecosystems of Colombia

Abstract

Currently, plants have gained widespread interest as a source of natural sunscreen. Specifically, plants from high altitude ecosystems are exposed to high UVR levels; therefore, they must produce an adaptive chemical response. The aim of this study was to evaluate the photo-protection and antioxidant capacity in vitro of nine plants from high altitude ecosystems in Antioquia, Colombia (Sphagnum meridense, Calamagrostis effusa, Lycopodiella alopecuroides, Morella parvifolia, Baccharis antioquensis, Pentacalia pulchella, Castilleja fissifolia, Hesperomeles ferruginea and Hypericum juniperinum). B. antioquensis and P. pulchella extracts showed the best results over a broad spectrum UVA-UVB with antioxidant capacity in vitro. However, B. antioquensis extracts presented the highest absorption coefficient in UVB-UVA range among plants under study. Furthermore, the gel formulation containing the crude extract of B. antioquensis showed significant values of UVAPF, UVA/UVB ratio, critical wavelength (λc) and SPF (3, 0.78 380 nm and 4.73 ± 0.26; respectively), indicating interesting photostability and antiradical capacities. All of these properties could be improve in order to satisfy the requirements for broad-spectrum UVB/UVA protection. Finally, P. pulchella and B. antioquensis extracts could be a potential source of a new natural sunscreen compounds with photostable and antiradical properties.

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Selected plants grow on high mountains of tropical zones that are exposed to high UVR levels all year long. Their extracts showed an exceptional absorption coefficient and their sunscreen formulations displayed values of SPF, UVAPF, UVA/UVB ratio, and critical wavelength high enough to satisfy requirements for broad-spectrum UVB/UVA protection. In addition, the photostability study in formulations showed an in vitro SPF effectiveness (%SPFeff) greater than 80%. Therefore, the proposed natural formulation could be considered as a photostable product.

Quelle: Photochemistry and Photobiology | 12 Dec 2015 | 7:58 am CET

Assessment of Fatty Acid Profile and Seed Mineral Nutrients of Two Soybean (Glycine max L.) Cultivars Under Elevated Ultraviolet-B: Role of ROS, Pigments and Antioxidants

Abstract

Current scenarios under global climate change envisage a considerable increase in ultraviolet B (UV-B) radiation in near future which may affect the productivity and yield quality of major agricultural crops. Present investigation was conducted to examine various defense strategies adopted against elevated UV-B (ambient + 7.2 kJ mˉ2 dayˉ1) and their impact on seed nutrients, content and quality of oil including fatty acid profile of two soybean cultivars (JS-335 and PS-1042). Elevated UV-B (eUV-B) exposure leads toward higher unsaturation of fatty acids and changes in other oil quality parameters (acid, iodine and saponification value) indicated that eUV-B favored the synthesis of long-chain fatty acids with fewer carboxylic acid groups, making the oil rancid, with undesirable flavor and low nutritional value. The effect was more severe in JS-335 as compared to PS-1042. Negative effects were also seen on nutrients of soybean seeds. Adverse effects resulted due to insufficient quenching of ROS (superoxide radical and hydrogen peroxide) by the defense system and thus unable to overcome the imposed oxidative stress. Credit of better performance by PS-1042 against eUV-B may be given to the adoption of efficient defense strategies like higher wax deposition, increase in lignin and flavonoids (quercetin and kaempferol) contents.

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Elevated UV-B exposure to soybean led to an increase in unsaturation of fatty acids and changes in acid, iodine and saponification values of oil. This indicated that eUV-B stress favored the synthesis of long-chain fatty acids with fewer carboxylic acid groups, making the oil more rancid, with undesirable flavor and low nutritional value. Negative effects were also observed on seeds mineral nutrients. Adverse effects resulted due to insufficient quenching of ROS by the defense system (i.e. antioxidative enzymes, flavonoids, lignin and wax) and thus unable to counteract the imposed oxidative stress.

Quelle: Photochemistry and Photobiology | 12 Dec 2015 | 7:58 am CET

Estimating Sun Exposure of Children in Day Care Nurseries in South Oxfordshire, UK

Abstract

Exposure to ultraviolet radiation and sunburn during childhood and adolescence is linked to increased risks of melanoma and basal cell carcinoma later in life. Infants and toddlers are thought to be unusually vulnerable to UVR because of lower levels of melanin, a thinner stratum corneum and a higher surface area/body mass ratio. The aim of this study was to assess variations in the available erythema effective radiant doses to young children in day care nurseries in South Oxfordshire, UK over 7 years between 2008 and 2014. The data were analyzed in three distinct seasons according to a series of realistic exposure scenarios taking into account nursery routines. The results indicate the time of year when high doses are to be expected and provide strong support for arguments in favor of raising public awareness of sun protection earlier in the year.

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The aim of this study was to assess variations in the available erythema effective radiant doses to young children in day care nurseries in South Oxfordshire, UK over 7 years between 2008 and 2014. The data were analyzed in three distinct seasons according to a series of realistic exposure scenarios, taking into account nursery routines. The results indicate the time of year when high doses are to be expected and provide strong support for arguments in favor of raising public awareness of sun protection earlier in the year.

Quelle: Photochemistry and Photobiology | 27 Nov 2015 | 5:18 am CET

Choline Chloride Assisted Synthesis of N and Metal Codoped TiO2 and their Photocatalytic Activity under Visible Light

Abstract

A few nanocrystalline N,metal codoped TiO2 (metal = Cr, Mn, Fe, Co, Ni, Cu and Zn) have been synthesized by a simple sol–gel method using choline chloride which is biodegradable, low cost, nontoxic ionic salt both as a structure directing agent and source of nitrogen. The prepared samples were well characterized by XRD, HRTEM, FTIR, DRS, EDX, XPS and BET techniques. The photocatalytic activity of all synthesized N, metal codoped TiO2 has been carried out for the degradation of Reactive Black 5 dye under visible light irradiation and among them, N, Fe codoped TiO2 was found to be the best for the degradation of Reactive Black 5 dye. The effect of incorporated metals on the photocatalytic activity of the various modified TiO2 has been discussed in detail based on the mechanism involved in the degradation of dye and their physico-chemical properties which includes surface area, particle size, defect sites, phase, band gap and electron–hole recombination effect.

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Mechanism involved for degradation of dye with (a) undoped TiO2 (b) N-doped TiO2 (c) N, metal codoped TiO2 under visible light.

Quelle: Photochemistry and Photobiology | 18 Nov 2015 | 5:28 am CET

Emerging Hubs in Plant Light and Temperature Signaling

Abstract

Due to their nature as sessile organisms, plants must accurately sense their surroundings and then translate this information into efficient acclimation responses to maximize development. Light and temperature are two major stimuli that provide immediate cues regarding energy availability, daylength, proximity of other species and seasonal changes. Both cues are sensed by complex systems and the integration of these signals is of very high value to properly respond to environmental changes without being disguised by random changes. For instance a cold day has a different significance if it occurs during the illuminated phase of the day or during the night, or when days are shortening during the fall instead of a long-day in spring. Here, we summarize recent advances in the nature of signaling components that operate as connectors of light and temperature signaling, with emphasis on the emerging hubs. Despite the nature of the thermosensors is still in its infancy compared to an important body of knowledge about plant sensory photoreceptors, the interaction of both types of signaling will not only bring clues of how plants integrate environmental information, but also will help in leading research in the nature of the thermosensors themselves.

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Temperature and Light Perception integration.

Quelle: Photochemistry and Photobiology | 18 Nov 2015 | 5:27 am CET

Oxidative Modification in Human Hair: The Effect of the Levels of Cu (II) Ions, UV Exposure and Hair Pigmentation

Abstract

Protein oxidative degradation is implicated in a wide range of deleterious effects. For human hair, this oxidative damage can lead to significant observable changes in fiber physical and visual properties. A redox proteomic approach was applied to map molecular modification in human hair proteins and correlate this modification with the abundance of copper (II) ions, the levels of UV exposure and the general level of hair pigmentation. An increase in oxidative modification was observed with increasing copper (II) ion levels, regardless of the pigmentation level. Significantly, increased protein oxidative modification was also observed to occur in both lightly and darkly pigmented hair tresses even in the absence of irradiation, albeit at lower relative levels. Modification levels increased with increased copper (II) ion concentration. This new finding indicates that the level of copper (II) ions in human hair plays a key role in mediating protein oxidation, with or without exposure to UV light. Overall, these results strongly suggest that minimization of the level of copper (II) ions in human hair will mitigate and/or slow protein oxidative modification and therefore lower overall hair damage.

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Human hair is exposed to a wide range of potentially modifying or damaging factors through daily routine, including sunlight and chemicals. This study describes molecular mapping of the effects of UV insult on the proteins of human hair, and how this modification varies with varying levels of copper (II) ions (introduced through washing) and differing levels of hair pigmentation. Advanced redox proteomic approaches were used to locate and track protein oxidation and correlate this modification to hair treatment.

Quelle: Photochemistry and Photobiology | 5 Nov 2015 | 12:57 pm CET

Charge Separation and Catalytic Activity of Fe3O4@Ag “Nanospheres”

Abstract

Nanospheres of Ag-coated Fe3O4 were successfully synthesized and characterized. Photocatalytic properties of Fe3O4@Ag composites have been investigated using steady-state studies and laser pulse excitations. Accumulation of the electrons in the Ag shell was detected from the shift in the surface plasmon band from 430 to 405 nm, which was discharged when an electron acceptor such as O2, Thionine (TH) or C60 was introduced into the system. Charge equilibration with redox couple such as C60●–/C60 indicated the ability of these core–shell structures to carry out photocatalytic reduction reactions. As well, outer Ag layer could boost charge separation in magnetic core through dual effects of Schottky junction and localized surface plasmonic resonance (LSPR)-powered band gap breaking effect under sunlight irradiation; resulted in higher photocatalytic degradation of diphenylamine (DPA). The maximum photocatalytic degradation rate was achieved at optimum amount of Ag-NP loading to products. Adsorption studies confirmed that degradation of DPA dominantly occurred in solution. Moderately renewability of the nanocatalysts under sunlight was due to oxidation and dissolution of the outer Ag layer.

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Current knowledge (and unknowns) about photocatalytic activity of Fe3O4@Ag-NPs.

Quelle: Photochemistry and Photobiology | 5 Nov 2015 | 5:31 am CET

Fluorinated Photodynamic Therapy Device Tips and their Resistance to Fouling for In Vivo Sensitizer Release

Abstract

We describe progress on a one-step photodynamic therapy (PDT) technique that is simple: device tip delivery of sensitizer, oxygen and light simultaneously. Control is essential for their delivery to target sites to generate singlet oxygen. One potential problem is the silica device tip may suffer from biomaterial fouling and the pace of sensitizer photorelease is slowed. Here, we have used biomaterial (e.g. proteins, cells, etc.) from SQ20B head and neck tumors and whole blood for an assessment of fouling of the silica tips by adsorption. It was shown that by exchanging the native silica tip for a fluorinated tip, a better nonstick property led to an increased sensitizer output by ~10%. The fluorinated tip gave a sigmoidal photorelease where singlet oxygen is stabilized to physical quenching, whereas the native silica tip with unprotected SiO–H groups gave a slower (pseudolinear) photorelease. A further benefit from fluorinated silica is that 15% less biomaterial adheres to its surface compared to native silica based on a bicinchoninic acid assay (BCA) and X-ray photoelectron spectroscopy (XPS) measurements. We discuss how the fluorination of the device tip increases biofouling resistance and can contribute to a new pointsource PDT tool.

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A one-step process (i.e. simultaneous delivery of sensitizer, oxygen and light) has been developed to simplify the application of PDT. We have analyzed the potential fouling of the PDT device tips with biomaterial from SQ20B squamous cell carcinoma tumors and whole blood. Measurements included sensitizer output inhibition and also biomaterial adhesion by a bicinchoninic acid assay and X-ray photoelectron spectroscopy. A fluorinated device tip led to improved biofouling resistance based on sensitizer photorelease performance and other factors.

Quelle: Photochemistry and Photobiology | 5 Nov 2015 | 5:30 am CET

Sensitivity of UV Erythemal Radiation to Total Ozone Changes under Different Sky Conditions: Results for Granada, Spain

Abstract

This study focuses on the analysis of the sensitivity of UV erythemal radiation (UVER) to variations in the total ozone column (TOC) under different sky conditions at Granada (southeastern Spain). The sensitivity is studied both in relative terms by means of the Radiation Amplification Factor (RAF) and in absolute terms using the Ozone Efficiency (OE). These two variables are determined for diverse sky conditions characterized by the cloud cover information given by a sky camera (in oktas) and the cloud optical depth (COD) estimated from global solar radiation measurements. As expected, in absolute terms, the TOC variations cause substantially smaller UVER changes during completely overcast situations than during cloud-free cases. For instance, the OE (SZA = 30°, TOC = 290 DU) decreases from 0.68 mW m−2 per unit of TOC (0 oktas) to 0.50 mW m−2 per unit of TOC (8 oktas). However, the opposite is observed when the analysis is performed in relative terms. Thus, the RAF (determined for SZA cases below 80°) increases from 1.1 for cloud-free cases (0 oktas) to 1.4 for completely overcast situations (8 oktas). This opposite behavior is also found when both RAF and OE are analyzed as functions of COD. Thus, while the OE strongly decreases with increasing COD, the RAF increases as COD increases.

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The analysis of the sensitivity of UV erythemal radiation (UVER) to total ozone changes during different sky conditions differs if the analysis is performed in relative terms (from the RAF) or in absolute terms (from the OE). Both RAF and OE exhibit a great dependence on the cloud optical depth (COD) during overcast conditions, but with opposite sign: while RAF increases with increasing COD, the OE substantially reduces its value as COD increases. To sum up, the UVER sensitivity to ozone changes is strongly affected by the sky conditions related to the cloud cover.

Quelle: Photochemistry and Photobiology | 5 Nov 2015 | 5:29 am CET




 


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