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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.
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.
Robyn M Lucas, Mary Norval, Caradee Yael Wright Most information on the harmful health effects of solar ultraviolet radiation (UVR) has been obtained in populations in which the majority has fair skin. Here a systematic review of publications... The content of this RSS Feed (c) The Royal Society of Chemistry
Photochem. Photobiol. Sci., 2015, Accepted Manuscript DOI: 10.1039/C5PP00305A, Paper
Md. Rakibuddin, Rajakumar Ananthakrishnan In the present work, graphene encapsulated ZnO/Co3O4 (GE/ZnO/Co3O4) core-shell hybrid is fabricated through a facile self-assembly approach, where the mutual electrostatic interaction force drives the ZnO/Co3O4 heteronanostructures to be fully... The content of this RSS Feed (c) The Royal Society of Chemistry
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.
Mechanism involved for degradation of dye with (a) undoped TiO2 (b) N-doped TiO2 (c) N, metal codoped TiO2 under visible light.
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.
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 post-transcriptional 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 non-photosensory photoreceptors control AS in light-grown plants.
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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 the Solarmeter 6.5 UVR readings were comparable to those of the adjacent rooftop instruments. The practicalities of using the dosimeters and Solarmeters for behavioural 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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Photochem. Photobiol. Sci., 2015, Accepted Manuscript DOI: 10.1039/C5PP00197H, Paper
Wieslaw Wiczk, Irena Bylinska, Malgorzata Wierzbicka, Cezary Czaplewski A series of symmetrically substituted diarylacetylenes and diaryl-1,3-butadiynes were prepared and studied with an emphasis on their spectral and photophysical properties. The photophysical characteristics of these compounds were studied in... The content of this RSS Feed (c) The Royal Society of Chemistry
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.
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.
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 pro-inflammatory 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. Topical treatment with phloroglucinol attenuated phosphorylation of MAP kinases, including ERK, JNK, and p38.
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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.
Current knowledge (and unknowns) about photocatalytic activity of Fe3O4@Ag-NPs.
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.
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.
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.
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.
Fan Xiang, Robyn Lucas, Frank de Gruijl, Mary Norval Does skin colour influence the production of vitamin D metabolites following UV irradiation? The paper reviews the studies addressing this important question and discusses possible reasons for the contradictory results. The content of this RSS Feed (c) The Royal Society of Chemistry
Understanding the effects of substituents on spectral properties is essential for the rational design of tailored bacteriochlorins for light-harvesting and other applications. Towards 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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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 d intervals beginning at 4 wk after sowing. The spraying of solution continued until saturation of droplets on the leaves was achieved. The levels of water deficit stress applied were non-stress, moderate water stress and severe water stress. The results showed there was a significant difference (p ≤ 0.05) between the methanol and water deficit stress treatments for chlorophyll a (Chl a) and b (Chl b), carotenoid, total chlorophyll (Total Chl), net-photosynthesis (PN), intercellular CO2 (Ci), maximal quantum yield of photosystem II photochemistry (Fv/Fm), leaf moisture (LM), water use efficiency (WUE) and water relative content (RWC). The application of foliar methanol at all levels of water deficit stress significantly decreased the catalase activity (CAT) of the roots. Under all levels of water deficit stress, the 30% (v/v) methanol treatment significantly decreased peroxidase activity (POX) 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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Photochem. Photobiol. Sci., 2015, 14,2251-2260 DOI: 10.1039/C5PP00150A, Paper
Malgorzata Wierzbicka, Irena Bylinska, Artur Sikorski, Cezary Czaplewski, Wieslaw Wiczk A series of symmetrically substituted diphenylbuta-1,3-diyne (DPB) derivatives possessing electron-donating or electron-accepting groups have been prepared and studied with emphasis on their spectral and photophysical properties. The content of this RSS Feed (c) The Royal Society of Chemistry
Janneke Ravensbergen, Chelsea L. Brown, Gary F. Moore, Raoul N. Frese, Rienk van Grondelle, Devens Gust, Thomas A. Moore, Ana L. Moore, John T. M. Kennis Proton-coupled electron transfer (PCET) plays a central role in photosynthesis and potentially in solar-to-fuel systems. The content of this RSS Feed (c) The Royal Society of Chemistry
Photochem. Photobiol. Sci., 2016, Advance Article DOI: 10.1039/C5PP00285K, Paper
C. Nganou, L. David, N. Adir, M. Mkandawire Comparison of kinetics of photoexcitation migration from PC620 to APC Core in extracted and intact pentacyclic phycobilisomes of T. vulcanus. The extracted PBS does not have linker protein, while intact has them and they facilitate the migration. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
A summary of the major findings concerning light modulation in Acinetobacter baumannii, which governs aspects related to the success of this microorganism as a nosocomial pathogen, is presented. Particularly, the evidence shows that light modulates the ability of the bacteria to persist in the environment, its virulence against eukaryotic hosts and even susceptibility to certain antibiotics. The light signal is sensed through different mechanisms, in some cases involving specialized photoreceptors of the BLUF-type, whereas in others, directly by a photosensitizer molecule. We also provide new data concerning the genomic context of BLUF-domain containing proteins within the genus Acinetobacter, as well as further insights into the mechanism of light-mediated reduction in susceptibility to antibiotics. The overall information points toward light being a crucial stimulus in the lifestyle of members of the genus Acinetobacter as well as in other clinically relevant species, such as members of the ESKAPE group, playing therefore an important role in the clinical settings.
In Acinetobacter baumannii light modulates physiological aspects related to the success of the microorganism as a nosocomial pathogen. In the figure are outlined models for light perception and signal transduction in A. baumannii. (A) Light absorption induces a conformational change in the A. baumannii BLUF photoreceptor BlsA, now able to bind unknown partners that modulate the response, resulting ultimately in regulation of surface motility, biofilm formation and virulence against Candida albicans. (B) Light can also induce reduction in susceptibility to antibiotics in a photoreceptor-independent manner in A. baumannii and other clinically relevant pathogens. In this case, light application could result in the excitation of an unknown photosensitizer molecule with the concomitant production of ROS such as 1O2, leading ultimately to the induction of expression of antibiotic resistance genes such as those coding for the AdeABC pump. This results in reduction in susceptibility to the antibiotics MIN and TIG. All these phenotypes occur at 25°C.
Here, a novel and efficient process is introduced for producing wool fabric with multi-functional features through facile in situ photo sonochemical 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 sonotreated samples were 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 sonotreated 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 sonotreated 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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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 non-mammalian vertebrates there are two Opn4 genes, Opn4m and Opn4x, the mammalian and Xenopus orthologs, respectively. Opn4x is only expressed in non-mammalian 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 non-mammalian 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 (RPE) 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 non-visual photochemistry of vertebrates.
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Synthesis, photophysical and metal ion recognition properties of a series of amino acid-linked free-base and Zn-porphyrin derivatives (5–9) are reported. These porphyrin derivatives showed favorable photophysical properties including high molar extinction coefficients (>1 × 105m−1 cm−1 for the Soret band), quantum yields of triplet excited states (63–94%) and singlet oxygen generation efficiencies (59–91%). Particularly, the Zn-porphyrin derivatives, 6 and 9 showed higher molar extinction coefficients, decreased fluorescence quantum yields, and higher triplet and singlet oxygen quantum yields compared to the corresponding free-base porphyrin derivatives. Further, the study of their interactions with various metal ions indicated that the proline-conjugated Zn-porphyrins (6 and 9) showed high selectivity toward Cu2+ ions and signaled the recognition through changes in fluorescence intensity. Our results provide insights on the role of nature of amino acid and metallation in the design of the porphyrin systems for application as probes and sensitizers.
Synthesis, photophysical properties and metal ion interactions of few proline/tryptophan-linked free-base and Zn-porphyrins are described. These porphyrins exhibit excellent triplet quantum yields and singlet oxygen generation efficiencies, making them desirable for PDT applications. Proline – Zn-porphyrin conjugates selectively interact with Cu2+ leading to significant changes in absorption properties and strong quenching of fluorescence.
Photochem. Photobiol. Sci., 2015, 14,2261-2269 DOI: 10.1039/C5PP00266D, Paper
Reza Omidyan, Mohammad Salehi, Zahra Heidari MPE profiles of the ground and S1 excited states of protonated furan along C-O bond-stretching reaction coordinate, computed at the RI-CC2/aug-cc-pVDZ level of theory. The content of this RSS Feed (c) The Royal Society of Chemistry
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 defence strategies adopted against elevated UV-B (ambient + 7.2 kJ m−2 day−1) 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 towards higher unsaturation of fatty acids and changes in other oil quality parameters (acid, iodine and saponification value) indicated that eUV-B favoured the synthesis of long chain fatty acids with fewer carboxylic acid groups, making the oil rancid, with undesirable flavour 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 defence 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 defence strategies like higher wax deposition, increase of lignin and flavonoids (quercetin and kaempferol) contents.
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Currently, plants have gained widespread interest as a source of natural sunscreen. In specific, 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 (S. meridense, C. effusa, L. alopecuroides, M. parvifolia, B. antioquensis, P. pulchella, C. fissifolia, H. ferruginea and H. 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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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 to 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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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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Photochem. Photobiol. Sci., 2015, 14,2213-2224 DOI: 10.1039/C5PP00328H, Paper
Natalia P. Malikova, Aren J. Borgdorff, Eugene S. Vysotski The semisynthetic Ca2+-regulated photoprotein obelin from Obelia longissima charged by coelenterazine analogue hcp is a promising reporter to keep track of fast intracellular Ca2+ transients. The content of this RSS Feed (c) The Royal Society of Chemistry
Diabetes mellitus is a metabolic disorder characterized by high blood sugar levels which give rise to complications in the eye, kidneys and the brain. Diabetes triggers the development of ocular diseases like diabetic retinopathy and cataracts which are the leading cause of blindness around the world. The most common method for the diagnosis of diabetes involves measuring the blood sugar levels in the body. One major disadvantage of this method is the fluctuating blood sugar levels which contribute to false negative results. This leads to delay in treatment, eventually causing permanent damage to the organs. Therefore, diagnosis of diabetes at an early stage is very crucial. One biomarker for diabetes related diseases is the formation of Advanced Glycation End-products (AGEs) that result from the Maillard reaction of proteins with glucose. α-crystallin in the ocular lens is a small heat shock protein with no protein turnover and hence acts as a record for post-translational modifications especially glycation which forms AGEs. We have used steady state and time resolved fluorescence measurements to study the spectroscopic changes in α-crystallin with increase in time of glycation and the intact lenses from diabetic and nondiabetic donors. Overall, this study was focused on developing a noninvasive diagnostic tool for early detection of diabetes mellitus.
Diabetes mellitus is a metabolic disorder characterized by high blood sugar levels which give rise to complications in the eye, kidney and brain. Current standard diagnostic methods are less than accurate for diagnosis at a very early stage due to fast hemoglobin turnover. The lens is avascular and has no protein turnover and therefore accumulates AGEs with aging and disease. By screening the fluorescence lifetimes from the eye lens and eye lens model protein systems, we can discriminate between nondiabetic and diabetic tissue which may lead to new, noninvasive diagnostic methods.
SnO2–TiO2/fly ash cenospheres (FAC) were prepared via hydrothermal method and used as an active photocatalyst in a photocatalytic system. Scanning electron microscopy, X-ray diffraction analysis, UV–Vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy and N2 adsorption–desorption measurements were used to determine the structure and optical property of SnO2–TiO2/FAC. Phenol was selected as the model substance for photocatalytic reactions to evaluate catalytic ability. Results showed that the degradation efficiency of phenol by SnO2–TiO2/FAC was 90.7% higher than that decomposed by TiO2/FAC. Increased efficiency could be due to the enhanced synergistic effect of semiconductors and FAC could provide more adsorption sites for the pollutant in the photocatalytic reaction. Furthermore, SnO2–TiO2/FAC composites exhibited excellent photocatalytic stability in four reuse cycles. Radical-trapping experiments further revealed the dominating functions of holes in the photocatalytic reaction.
Under UV light irradiation, TiO2 and SnO2 are excited. The photo-generated electrons of TiO2 transfer from the valence band to the conduction band and then injected into the conduction band of SnO2. Thus, electrons could be trapped by the absorbed O2 to produce on the catalyst surface and then react with phenol. The photo-generated holes are also transferred from the valence band of SnO2 to the valence band of TiO2; this transfer induces phenol degradation. The active species would decompose phenol to the final carbon dioxide or other intermediate products.
This article analyzes the influence of Ultraviolet Erythematic Radiation (UVER) dose received by construction workers in Valencia highlighting the upper limit of the dose received for a worker in different periods of a year. Building construction usually implies workers to stand for several hours outdoors while working until roof top is finished. In Valencia, construction carried out near the coastline has been very intense in the last few years with the construction of a great amount of summer flats. This article focuses on the maximum values UVER can reach in different seasons of the year for cities with similar latitude to Valencia (39°28′N, 0°22′W), as an important way of warning construction workers about the necessity of taking preventive actions. Viospor dosimeters placed on a mannequin have been used in this study. The measurements took place between 2012 December and 2013 July.
This article analyzes the influence of Ultraviolet Erythematic Radiation (UVER) dose received by construction workers in Valencia highlighting the upper limit of the dose received for a worker in different periods of a year. Viospor dosimeters placed on a mannequin have been used in this study. The measurements took place between 2012 December and 2013 July.
Macroalgae distributed in intertidal zones experience a series of environmental changes, such as periodical desiccation associated with tidal cycles, increasing CO2 concentration and solar UVB (280–315 nm) irradiance in the context of climate change. We investigated how the economic red macroalga, Pyropia haitanensis, perform its photosynthesis under elevated atmospheric CO2 concentration and in the presence of solar UV radiation (280–400 nm) during emersion. Our results showed that the elevated CO2 (800 ppmv) significantly increased the photosynthetic carbon fixation rate of P. haitanensis by about 100% when the alga was dehydrated. Solar UV radiation had insignificant effects on the net photosynthesis without desiccation stress and under low levels of sunlight, but significantly inhibited it with increased levels of desiccation and sunlight intensity, to the highest extent at the highest levels of water loss and solar radiation. Presence of UV radiation and the elevated CO2 acted synergistically to cause higher inhibition of the photosynthetic carbon fixation, which exacerbated at higher levels of desiccation and sunlight. While P. haitanensis can benefit from increasing atmospheric CO2 concentration during emersion under low and moderate levels of solar radiation, combined effects of elevated CO2 and UV radiation acted synergistically to reduce its photosynthesis under high solar radiation levels during noon periods.
As one of the most economically important intertidal macroalga, Pyropia haitanensis experiences periodic exposures to air with tidal cycles either in its niche or on farming rafts. Subsequently, the alga often suffers from dehydration due to desiccation, especially during daytime under the sun with presence of UV radiation and heat stresses. During such exposures, CO2 is the only exogenous carbon source for its photosynthesis. Although increasing atmospheric CO2 can enhance the photosynthesis during the exposures, such benefit diminished with increased levels of water loss and in the presence of solar UV radiation.
A fluorescent self-assembly of cephalexin is obtained by pulsed laser irradiation process. An intense fluorescence emission is found in the self-assembled form due to occurrence of a typical aggregation-induced emission in cephalexin molecules. It is observed that fluorescence quenching of the self-assembled fluorescent nanostructures occurs in the presence of extremely low Hg++ ions concentrations (10−7m) as compared to other heavy metal ions e.g. Ferrous (Fe++), Manganese (Mn++), Magnesium (Mg++), Cobalt (Co++), Nickel (Ni++) and Zinc (Zn++) at the same concentrations.
Pulsed UV laser irradiation of cephalexin solution in water makes aggregation-induced fluorescent mesostructures. These fluorescent structures can be used for mercury ion (Hg++) sensing in aqueous solution.
Brimonidine at 0.18%, 1% and 2% concentrations applied topically in hairless mice significantly decreased tumor burden and incidences of erythema, flaking, wrinkling and skin thickening induced by UVR. The unbiased median week to tumor ≥1 mm was increased by the 1% and 2% concentrations. The tumor yield was reduced by all concentrations at week 40 for all tumor sizes but the ≥4 mm tumors with the 0.18% concentration. At week 52, the tumor yield was reduced for all tumor sizes and all brimonidine concentrations. The tumor incidence was reduced by all concentrations at week 40 for all tumor sizes, but the ≥4 mm tumor with the 0.18% concentration and at week 52 for all tumor sizes with the 1% and 2% concentrations and with the 0.18% concentration only for the ≥4 mm tumors. Reductions in ≥4 mm tumor incidences compared to the vehicle control group were 54%, 91% and 86% by week 52 for the 0.18%, 1% and 2% concentrations, respectively. Brimonidine at 2% applied 1 h before or just after UVB irradiation on hairless mice decreased epidermal hyperplasia by 23% and 32% and epithelial cell proliferation by 59% and 64%, respectively, similar to an epidermal growth factor receptor (EGFR) inhibitor.
Brimonidine applied topically in hairless mice exposed to UVR in a photocarcinogenicity study significantly increased survival, reduced the tumor yield and tumor incidence and increased the unbiased median week to tumor and decreased incidences of erythema, flaking, wrinkling and skin thickening, compared to the vehicle group + UVR. All effects occurred dose-dependently. Brimonidine at 2% applied 1 h before or just after UVB irradiation on hairless mice decreased epidermal hyperplasia and epithelial cell proliferation induced by UVB similar to an EGFR inhibitor.
In this study, the effect of caffeic acid (CA) on both acute and chronic UVB-irradiation–induced inflammation and photocarcinogenesis was investigated in Swiss albino mice. Animals were exposed to 180 mJ cm−2 of UVB once daily for 10 consecutive days and thrice weekly for 30 weeks for acute and chronic study respectively. UVB exposure for 10 consecutive days showed edema formation, increased lipid peroxidation and decreased antioxidant status with activation of inflammatory molecules such as TNF-α, IL-6, COX-2 and NF-κB. However, CA (15 mg per kg.b.wt.) administration before each UVB exposure decreased lipid peroxidation, inflammatory markers expression and enhanced antioxidant status probably through the activation of peroxisome proliferator-activated receptors (PPARγ) in the mice skin. PPARγ is considered a potential target for photochemoprevention because it inhibits UVB-mediated inflammatory responses. In this study, UVB exposure for 30 weeks caused squamous cell carcinoma and upregulation of iNOS, VEGF and TGF-β and downregulation of p53 and tumor incidence in the mice skin. Both topical (CAT) and intraperitoneal (CAIP) treatment before each UVB exposure downregulates iNOS, VEGF, TGF-β, upregulates p53 and reduces tumors multiplicity in the mice skin. Thus, CA offers protection against UVB-induced photocarcinogenesis probably through activation of anti-inflammatory transcription factor PPARγ in the mice.
Excessive UVB irradiation increased the skin tumor incidence, oxidative imbalance, angiogenic and inflammatory signaling and activation of NF-κB, a transcription factor involved in inflammation in mouse skin. Caffeic acid administration before each UVB irradiation decreased the angiogenic and inflammatory signaling with decreased expression of NF-kB. Caffeic acid might act as agonist of PPARγ, a transcription factor involved in the anti-inflammation reaction, and inhibit NF-κB-mediated inflammatory reactions thereby inhibiting photocarcinogenesis in mouse skin.
Although ultraviolet radiation (UVR) has a genotoxicity for inducing skin cancers, the skin may tolerate UVC component because the epidermal layer prevents this short wavelength range from passing through. Here, UVC genotoxicity for mouse skin was evaluated in terms of DNA damage formation and mutagenicity. UVC induced UVR photolesions and mutations remarkably in the epidermis but poorly in the dermis, confirming the barrier ability of the epidermis against shorter UVR wavelengths. Moreover, the epidermis itself responded to UVC mutagenicity with mutation induction suppression, which suppressed the mutant frequencies to a remarkably low, constant level regardless of UVC dose. The mutation spectrum observed in UVC-exposed epidermis showed a predominance of UV-signature mutation, which occurred frequently in 5′-TCG-3′, 5′-TCA-3′ and 5′-CCA-3′ contexts. Especially, for the former two contexts, the mutations recurred at several sites with more remarkable recurrences at the 5′-TCG-3′ sites. Comparison of the UVC mutation spectrum with those observed in longer UVR wavelength ranges led us to a mechanism that explains why the sequence context preference of UV-signature mutation changes according to the wavelength, which is based on the difference in the mCpG preference of cyclobutane pyrimidine dimer (CPD) formation among UVR ranges and the sequence context-dependent cytosine deamination propensity of CPD.
The sequence context preference of UV signature mutation results from the wavelength-dependent preference of CPD formation for mCpG sites and the context-oriented cytosine deamination propensity of cyclobutane pyrimidine dimers.
Photochem. Photobiol. Sci., 2015, 14,2225-2237 DOI: 10.1039/C5PP00339C, Paper
Santosh Kumar Behera, G. Krishnamoorthy The mechanism for the dual emission of 2-(4[prime or minute]-N,N-dimethylaminophenyl)imidazo[4,5-c]pyridine (DMAPIP-c) in protic solvents was investigated by synthesizing and studying its analogues. The content of this RSS Feed (c) The Royal Society of Chemistry
Conventional photodynamic therapy with aminolevulinate (ALA-PDT) selectively induces apoptosis in diseased cells and is highly effective for treating actinic keratoses. However, similar results are achieved only in a subset of patients with cutaneous T-cell lymphoma (CTCL). Our previous work shows that the apoptotic resistance of CTCL correlates with low expression of death receptors like Fas cell surface death receptor (FAS), and that methotrexate upregulates FAS by inhibiting the methylation of its promoter, acting as an epigenetic derepressor that restores the susceptibility of FAS-low CTCL to caspase-8-mediated apoptosis. Here, we demonstrate that methotrexate increases the response of CTCL to ALA-PDT, a concept we refer to as epigenetically enhanced PDT (ePDT). Multiple CTCL cell lines were subjected to conventional PDT versus ePDT. Apoptotic biomarkers were analyzed in situ with multispectral imaging analysis of immunostained cells, a method that is quantitative and 5× more sensitive than standard immunohistology for antigen detection. Compared to conventional PDT or methotrexate alone, ePDT led to significantly greater cell death in all CTCL cell lines tested by inducing greater activation of caspase-8-mediated extrinsic apoptosis. Upregulation of FAS and/or tumor necrosis factor-related apoptosis-inducing ligand pathway components was observed in different CTCL cell lines. These findings provide a rationale for clinical trials of ePDT for CTCL.
Aminolevulinate photodynamic therapy (ALA-PDT) induces apoptosis and effectively eradicates actinic keratoses, but has limited efficacy in cutaneous T-cell lymphoma (CTCL). Cutaneous T-cell lymphoma resists apoptosis due to low expression of death receptors like Fas cell surface death receptor (FAS). We showed previously that methotrexate (MTX) upregulates FAS epigenetically by promoter derepression and restores the susceptibility of CTCL to extrinsic apoptosis. Here, we demonstrate that MTX increases the response of CTCL to ALA-PDT—a concept we call epigenetically enhanced PDT (ePDT). ePDT caused upregulation of death receptors/ligands (DR/DRL) with increased activation of extrinsic apoptosis as compared to conventional PDT. These findings warrant clinical trials of ePDT for CTCL.
Photochem. Photobiol. Sci., 2015, 14,2203-2212 DOI: 10.1039/C5PP00274E, Paper
Estelle Bastien, Raphael Schneider, Steffen Hackbarth, Dominique Dumas, Jordane Jasniewski, Beate Roder, Lina Bezdetnaya, Henri-Pierre Lassalle Covalent conjugates between the photosensitizer chlorin e6 and PAMAM G4.5 dendrimers. The content of this RSS Feed (c) The Royal Society of Chemistry
Photochem. Photobiol. Sci., 2015, 14,2238-2250 DOI: 10.1039/C5PP00110B, Paper
Stefanos Giannakis, Sami Rtimi, Efthymios Darakas, Antoni Escalas-Canellas, Cesar Pulgarin Solar disinfection of E. coli was followed by PHR and dark conditions. The assessment elucidated the relationship between the emitted PHR wavelengths and the survival response in the dark. The content of this RSS Feed (c) The Royal Society of Chemistry
Studies on the antimicrobial properties of light have considerably increased due in part to the development of resistance to actual control methods. This study investigates the potential of light-emitting diodes (LED) blue light for controlling Penicillium digitatum and Penicillium italicum. These fungi are the most devastating postharvest pathogens of citrus fruit and cause important losses due to contaminations and the development of resistant strains against fungicides. The effect of different periods and quantum fluxes, delaying light application on the growth and morphology of P. digitatum strains resistant and sensitive to fungicides, and P. italicum cultured at 20°C was examined. Results showed that blue light controls the growth of all strains and that its efficacy increases with the quantum flux. Spore germination was always avoided by exposing the cultures to high quantum flux (700 μmol m−2 s−1) for 18 h. Continuous light had an important impact on the fungus morphology and a fungicidal effect when applied at a lower quantum flux (120 μmol m−2 s−1) to a growing fungus. Sensitivity to light increased with mycelium age. Results show that blue light may be a tool for P. digitatum and P. italicum infection prevention during handling of citrus fruits.
The effect of LED blue light on growth and morphology of Penicillium digitatum strains resistant and sensitive to fungicides and Penicillium italicum, the major postharvest pathogens of citrus fruits, has been investigated. The photographs show how blue light (L) affects morphology and delays fungal growth with respect to the control cultures held under darkness (D). Results also show that blue light has a nonreversible detrimental effect on fungal growth and that spore germination is avoided by exposing the cultures of all strains to high blue light quantum flux.
Photochem. Photobiol. Sci., 2015, 14,2151-2158 DOI: 10.1039/C5PP00334B, Paper
Duncan E. McLain, Adam. C. Rea, Magnus B. Widegren, Timothy M. Dore Quinoline-based photoremovable protecting groups mediate the photoactivation of the signaling molecules serotonin, octopamine, capsaicin, N-vanillyl-nonanoylamide, estradiol, and tyrosine through 1- and 2-photon excitation and enable physiological studies. The content of this RSS Feed (c) The Royal Society of Chemistry
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 photo-reactivity. 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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Photochem. Photobiol. Sci., 2015, 14,2179-2186 DOI: 10.1039/C5PP00215J, Paper
Andreas Ekebergh, Peter Sandin, Jerker Martensson Observation of unexpectedly rapid photodegradation of the cyanobacterial UV-screener scytonemin in vitro. The content of this RSS Feed (c) The Royal Society of Chemistry
Photochem. Photobiol. Sci., 2015, 14,2195-2202 DOI: 10.1039/C5PP00318K, Paper
Radhika Khanna, Aarti Dalal, Ramesh Kumar, Ramesh C. Kamboj The phototransformation of some 2-(3-methoxyphenyl)-4H-chromen-4-ones bearing a propynyloxy moiety at the 3-position into 5-ethynyl-2-methoxy-6-oxa-benzo[5,6-c]xanthen-7-ones and 2-(3-methoxyphenyl)-4H-chromen-4-ones via regioselective cyclisation and dealkoxylation respectively has been described. The content of this RSS Feed (c) The Royal Society of Chemistry
Better noninvasive techniques are needed to monitor protoporphyrin IX (PpIX) levels before and during photodynamic therapy (PDT) of squamous cell carcinoma (SCC) of the skin. Our aim was to evaluate (1) multispectral fluorescent imaging of ultraviolet light (UV)-induced cancer and precancer in a mouse model of SCC and (2) multispectral imaging and probe-based fluorescence detection as a tool to study vitamin D (VD) effects on aminolevulinic acid (ALA)-induced PpIX synthesis. Dorsal skin of hairless mice was imaged weekly during a 24-week UV carcinogenesis protocol. Hot spots of PpIX fluorescence were detectable by multispectral imaging beginning at 14 weeks of UV exposure. Many hot spots disappeared after cessation of UV at week 20, but others persisted or became visible after week 20, and corresponded to tumors that eventually became visible by eye. In SCC-bearing mice pretreated with topical VD before ALA application, our optical techniques confirmed that VD preconditioning induces a tumor-selective increase in PpIX levels. Fluorescence-based optical imaging of PpIX is a promising tool for detecting early SCC lesions of the skin. Pretreatment with VD can increase the ability to detect early tumors, providing a potential new way to improve efficacy of ALA-PDT.
Newly formed squamous cell skin cancers on the back of a hairless mouse (top panel), observed at 24 weeks after the start of a UV-exposure protocol, selectively express high levels of protoporphyrin IX following a 4-h application of aminolevulinate and noninvasive fluorescence detection (bottom panel).
The effect of different ultraviolet radiation (UVR) treatments combining PAR (P), UVA (A) and UVB (B) on the molecular physiology of Dunaliella tertiolecta was studied during 6 days to assess the response to chronic UVR exposure. UVR reduced cell growth but did not cause cell death, as shown by the absence of SYTOX Green labeling and cellular morphology. However, caspase-like enzymatic activities (CLs), (regarded as cell death proteases), were active even though the cells were not dying. Maximal quantum yield of fluorescence (Fv/Fm) and photosynthetic electron transport rate (ETR) dropped. Decreased nonphotochemical quenching (NPQ) paralleled a drop in xanthophyll cycle de-epoxidation under UVB. Reactive oxygen species (ROS) and D1 protein accumulation were inversely correlated. PAB exhibited elevated ROS production at earlier times. Once ROS decayed, D1 protein recovered two-fold compared with P and PA at later stages. Therefore, PsbA gene was still transcribed, suggesting ROS involvement in D1 recovery by its direct effect on mRNA-translation. We add evidence of an UVB-induced positive effect on the cells when P is present, providing photoprotection and resilience, by means of D1 repair. This allowed cells to survive. The photoprotective mechanisms described here (which are counterintuitive in principle) conform to an important ecophysiological response regarding light stress acclimation.
Two modes of photoprotection under P and UVB, respectively (light-gray areas). The white area represents the photoprotective mechanism observed only under simultaneous P+UVB, i.e. incomplete protection if one of them is absent. Dark-gray area represents UVB-caused damage.
Photothermal characteristics and light-induced structural (volume) changes of carotenoid-containing and noncontaining photosynthetic reaction centers (RCs) were investigated by wide frequency band hydrophone. We found that the presence of carotenoid either does not play considerable role in the light-induced conformational movements, or these rearrangements are too slow for inducing a photoacoustic (PA) signal. The kinetic component with a few tens of microseconds, exhibited by the carotenoid-less RCs, appears to be similar to that of triplet state lifetimes, identified by other methods. The binding of terbutryn to the acceptor side is shown to affect the dynamics of the RC. Our results do not confirm large displacements or volume changes induced by the charge movements and by the charge relaxation processes in the RCs in few hundreds of microseconds time scale that accompanies the electron transfer between the primary and secondary electron acceptor quinones.
Photothermal characteristics and light induced structural (volume) changes of carotenoid containing and noncontaining photosynthetic reaction centers were investigated by wide frequency band hydrophone and compared. The presence of carotenoid either does not play considerable role in the light induced conformational movements or these rearrangements are slow enough for inducing the photoacoustic signal. Binding of terbutryne to the acceptor side of the RC contributes specifically to the overall RC dynamics. Our results do not confirm large displacements and volume changes induced by the charge relaxation processes existing in RCs in the microseconds time scale that accompanies the interquinone electron transfer.
Photochem. Photobiol. Sci., 2015, 14,2187-2194 DOI: 10.1039/C5PP00297D, Paper
Satoshi Horikoshi, Akihiro Tsuchida, Tomohiro Shinomiya, Nick Serpone A novel microwave discharge electrodeless lamp (MDEL) with enhanced performance was fabricated for the microwave-assisted remediation of wastewaters contaminated with the 2,4-D herbicide and such microorganisms as E coli. The content of this RSS Feed (c) The Royal Society of Chemistry
Photochem. Photobiol. Sci., 2015, 14,2168-2178 DOI: 10.1039/C5PP00280J, Paper
Aniruddha Ganguly, Soumen Ghosh, Nikhil Guchhait Binding interactions of an anthracene-based fluorescent probe with a series of bile-salt aggregates of varying hydrophobicity, as well as salt induced alterations of the binding behavior have been thoroughly demonstrated. The content of this RSS Feed (c) The Royal Society of Chemistry
After a critical review of the fundamental equations describing photobiological and photochemical processes occurring in a medium exposed to a quasi-collimated monochromatic UV light beam, the analysis in this review is extended to analogous processes driven by polychromatic UV light, such as that emitted by medium pressure mercury-vapor arc lamps. The analysis is based on the Second Law of Photochemistry, namely that all photochemical events must be independent, and the rate of such events must be proportional to the rate of photon absorption. A consistent application of the Second Law of Photochemistry leads to a concept change; hence it is proposed herein to use photon fluence and photon fluence rate, rather than fluence (UV dose) and fluence rate, respectively, in the analysis and interpretation of photobiological and photochemical processes. As a consequence, many equations that have been used in the past must be revised, and some experimental information (e.g. action spectra) needs to be re-analyzed.
This diagram depicts the reactor that could be used to study photochemical or photobiological reactions in a collimated beam apparatus. The reactor is configured so that photons from the UV lamp that pass through the hole in the mask impinge directly on the surface of the solution, but no photons impinge on the walls of the dish. This diagram illustrates the fundamental concept in the paper, namely that photochemical and photobiological reactions should use photon-based terms, such as photon irradiance (einstein m−2 s−1), rather than power-based terms, such as irradiance (W m−2).
Fifty years ago, a new thymine dimer was discovered as the dominant DNA photolesion in UV-irradiated bacterial spores [Donnellan, J. E. & Setlow R. B. (1965) Science, 149, 308–310], which was later named the spore photoproduct (SP). Formation of SP is due to the unique environment in the spore core that features low hydration levels favoring an A-DNA conformation, high levels of calcium dipicolinate that acts as a photosensitizer, and DNA saturation with small, acid-soluble proteins that alters DNA structure and reduces side reactions. In vitro studies reveal that any of these factors alone can promote SP formation; however, SP formation is usually accompanied by the production of other DNA photolesions. Therefore, the nearly exclusive SP formation in spores is due to the combined effects of these three factors. Spore photoproduct photoreaction is proved to occur via a unique H-atom transfer mechanism between the two involved thymine residues. Successful incorporation of SP into an oligonucleotide has been achieved via organic synthesis, which enables structural studies that reveal minor conformational changes in the SP-containing DNA. Here, we review the progress on SP photochemistry and photobiology in the past 50 years, which indicates a very rich SP photobiology that may exist beyond endospores.
In 1965, a thymine dimer was discovered as the dominant DNA photolesion in UV-irradiated endospores, which was later named the spore photoproduct (SP). Formation of SP is due to the unique environment in central core of endospores surrounded by several spore-specific layers, in which the genomic DNA adopts an A-conformation supporting SP photochemistry. Spore photoproducts, if unrepaired, are toxic to germinated bacteria; developments on synthetic chemistry now make it possible to understand the molecular basis of SP toxicity. This review covers the SP research in the past 50 years, which indicates a rich SP biology existing beyond endospores.
UV sensitivity of the vegetative and reproductive tissues of two Antarctic brown macroalgae was compared. Photosynthesis as well as the content and localization of phenolic substances were determined. Responses to UV radiation were quantified as chlorophyll fluorescence (Fv/Fm). Ascoseira mirabilis showed high UV tolerance, while in Cystosphaera jacquinotii Fv/Fm decreased by 15–21%, the receptacles being more tolerant than the vegetative blades. The phlorotannin contents showed an opposite pattern: the soluble fraction dominated in C. jacquinotii while in A. mirabilis the insoluble fraction was more abundant. Soluble phlorotannins were higher in the reproductive than in vegetative tissues in both species. Images of tissue cross-sections under violet-blue light excitation confirmed a high allocation of phenolic compounds (as blue autofluorescence) in C. jacquinotii, both in reproductive and vegetative blades. The allocation and proportions of the soluble and insoluble phlorotannins could be related with the observed UV tolerance of the vegetative and reproductive tissues.
Allocation and proportions of the soluble and insoluble phlorotannins could be related with UV tolerance of two Antarctic brown algae. In highly UV tolerant (measured as chlorophyll fluorescence) Ascoseira mirabilis, the insoluble phlorotannins were more abundant, while in the more UV sensitive Cystosphaera jacquinotii, the soluble fraction dominated. In C. jacquinotii, the receptacles showed higher UV tolerance than the vegetative blades. The reproductive tissues of both species contained more soluble phlorotannins than the vegetative tissues. High allocation of phenolic compounds in both reproductive and vegetative tissues of C. jacquinotii was confirmed by microscopical blue autofluorescence images of tissue cross-sections.
We evaluated the feasibility of 5-aminolevulinic acid (5-ALA)-mediated photodynamic diagnosis (PDD) in the biopsy for primary central nervous system lymphoma (PCNSL). 5-ALA (20 mg kg−1) was administered orally 4 hours preoperatively. Forty-one biopsies obtained under PDD in 47 consecutive biopsies (46 patients) that were finally pathologically diagnosed as PCNSL were evaluated. Positive fluorescence was observed in 34 of those 41 biopsies (82.9%). An intraoperative pathological diagnosis (IOD) of suspected PCNSL was made in 21 of the biopsies with positive fluorescence (61.8%). However, the eight IODs in the remaining 13 biopsies (23.5%) were not correct (atypical cell, 4; high-grade glioma, 1; gliosis, 1; unremarkable, 2). In those 8 biopsies, PCNSL was confirmed by the final pathological diagnosis. There was no difference in the mean Mib-1 labeling index between the biopsies with positive fluorescence (86.5%) and those without positive fluorescence (90.0%). IOD was not performed in 6 biopsies; however, 5 of those biopsies (83.3%) showed positive fluorescence and were finally pathologically diagnosed as PCNSL. Use of PDD in biopsies for patients with suspected PCNSL is a reliable way of obtaining specimens of adequate quality for the final pathological diagnosis and may lead to improved diagnostic yield in the biopsy of PCNSL.
Positive fluorescence was observed in 34 of 41 biopsies (82.9%) obtained under 5-aminolevulinic acid-mediated photodynamic diagnosis (PDD) for primary central nervous system lymphoma (PCNSL) as final pathological diagnosis. In 21 of the 34 biopsies (61.8%), an intraoperative pathological diagnosis (IOD) of suspected PCNSL was made. In the remaining 13 biopsies, however, the IOD was either incorrect (atypical cell, 4; high-grade glioma, 1; gliosis, 1; unremarkable, 2) or not performed (5). PDD of biopsy samples in patients with suspected PCNSL is a feasible way to obtain accurate samples and may lead to improved diagnostic yield in the biopsy of PCNSL.
Lignocellulosic biomass can be converted to high-value phenolic compounds, such as food additives, antioxidants, fragrances and fine chemicals. We investigated photochemical and heterogeneous photocatalytic oxidation of two isomeric phenolic compounds from lignin, isoeugenol and eugenol, in several nonprotic solvents, for the first time by experiment and the density functional theory (DFT) calculations. Photooxidation was conducted under ambient conditions using air, near-UV light and commercial P25 TiO2 photocatalyst, and the products were determined by TLC, UV–Vis absorption spectroscopy, HPLC-UV and HPLC-MS. Photochemical and photocatalytic oxidation of isoeugenol proceeds via the mild oxidative “dimerization” to produce the lignan dehydrodiisoeugenol (DHDIE), while photooxidation of eugenol does not proceed. The DFT calculations suggest a radical stepwise mechanism for the oxidative “dimerization” of isoeugenol to DHDIE as was calculated for the first time.
We report a selective photochemical and photocatalytic oxidative activation of C=C bond in sustainable phenolic compound from lignin, isoeugenol vs its isomer eugenol, as found for the first time. Photooxidation of isoeugenol to lignan dehydrodiisoeugenol (DHDIE) in solution has the following advantages vs chemical oxidation: 1) reaction proceeds only via internal C=C bond in isoeugenol, but not via terminal C=C bond in isomeric eugenol and 2) photooxidation of isoeugenol leads to fewer molecular products. We also report, for the first time, the density functional theory calculations of the stage-wise mechanism of oxidative “dimerization” of isoeugenol to DHDIE.
Ultraviolet-A (UV-A)-mediated bactericidal activity was enhanced by combined treatment with trans-ferulic acid (trans-FA, compound 1) or its derivatives. Derivative compounds 4 and 10 contain a phenyl group or an l-tyrosine HCl tert-butyl ester, respectively, linked to the carboxyl group of trans-FA. Of the three compounds, 10 exhibited the highest synergistic activity in a photobactericidal assay based on treating Escherichia coli with a derivative compound and UV-A irradiation (wavelength 350–385 nm). Inactivation of viable cells at a 4.9 J cm−2 UV-A fluence increased from 1.90 to 5.19 logs in the presence of 10 (100 μm); a 4.95-log inactivation was achieved with 10 (5 μm) and a 7.4 J cm−2 UV-A fluence. Addition of antioxidants significantly suppressed photosynergistic bactericidal activity, suggesting that reactive oxygen species (ROS) are involved in the combined bactericidal mechanism. Flow cytometry revealed that combined treatment with UV-A and compound 10, which showed the highest photobactericidal activity, generates an excess of oxidative radicals in bacterial cells. The bactericidal activity of compound 10 may be due to electrostatic interaction between the molecule's cationic moiety and the cell surface, followed by amplification of ROS generation in the cells.
This study describes the inactivation of Escherichia coli by combined treatment with trans-ferulic acid or its derivatives and UV-A LED light. In particular, a trans-ferulic acid derivative modified with l-tyrosine (FA-Tyr) as a cationic moiety significantly reduced E. coli viability during UV-A irradiation, compared with UV-A irradiation alone. The strong photobactericidal effect results from the generation of reactive oxygen species such as hydroxyl radicals within bacterial cells, suggesting that the cationic property of the trans-ferulic acid derivative is important in mediating interaction with the bacterial cell surface.
UVB radiation contributes to both direct and indirect damage to the skin including the generation of free radicals and reactive oxygen species (ROS), inflammatory responses, immunosuppression and gene mutations, which can ultimately lead to photocarcinogenesis. A plant-derived flavonoid, baicalin, has been shown to have antioxidant, anti-inflammatory and free radical scavenging activities. Previous studies from our laboratory have shown that in murine skin, Toll-like receptor-4 (TLR4) enhanced both UVB-induced DNA damage and inflammation. The aim of this study was to investigate the efficacy of baicalin against TLR4-mediated processes in the murine keratinocyte PAM 212 cell line. Our results demonstrate that treating keratinocytes with baicalin both before and after UV radiation (100 mJ cm−2) significantly inhibited the level of intracellular ROS and decreased cyclobutane pyrimidine dimers and 8-Oxo-2′-deoxyguanosine (8-oxo-dG)—markers of DNA damage. Furthermore, cells treated with baicalin demonstrated an inhibition of TLR4 and its downstream signaling molecules, MyD88, TRIF, TRAF6 and IRAK4. TLR4 pathway inhibition resulted in NF-κB inactivation and down-regulation of iNOS and COX-2 protein expression. Taken together, baicalin treatment effectively protected keratinocytes from UVB-induced inflammatory damage through TLR pathway modulation.
UVB radiation causes both direct and indirect damage to the skin including the generation of reactive oxygen species (ROS), inflammation and immunosuppression, which ultimately contribute to photocarcinogenesis. A plant-derived flavonoid, baicalin, has been shown to be effective as an antioxidant, anti-inflammatory and free radical scavenger. Baicalin treatment before and after UV radiation protected PAM212 keratinocytes from UVB-induced damage by inhibiting Toll-like receptor-4 (TLR4) and its downstream signaling molecules, MyD88, TRIF, TRAF6 and IRAK4. This inhibition resulted in NF-κB inactivation and downregulation of iNOS and COX-2. Intracellular ROS and markers of DNA damage, including cyclobutane pyrimidine dimers and 8-Oxo-2′-deoxyguanosine, were significantly reduced.
Proteins from the cryptochrome/photolyase family utilize UV-A, blue or even red light to achieve such diverse functions as repair of DNA lesions by photolyases and signaling by cryptochromes. DASH-type cryptochromes retained the ability to repair cyclobutane pyrimidine dimers (CPDs) in single-stranded DNA regions in vitro. However, most organisms possess conventional CPD photolyases responsible for repair of these lesions in vivo. Recent work showed that the DASH-type cryptochrome CryD plays a regulatory role in diverse light-dependent processes in Fusarium fujikuroi. Here, we report our in vitro studies on heterologously expressed FfCryD. The purified protein contains N5,N10-methenyltetrahydrofolate and flavin adenine dinucleotide as cofactors. Photoreduction and DNA photorepair experiments confirmed that FfCryD is active in light-driven electron transfer processes. However, the protein showed comparable affinities for CPD-comprising and undamaged DNA probes. Surprisingly, after purification, full-length FfCryD as well as a truncated version containing only the PHR domain bound RNA which influenced their behavior in vitro. Moreover, binding of FfCryD to RNA indicates a putative role in RNA metabolism or in posttranscriptional control of gene expression.
The study biochemically characterizes the heterologously expressed and purified DASH-type cryptochrome CryD that plays regulatory roles in Fusarium fujikuroi. As an example, CryD inhibits the light-induced accumulation of a red polyketide pigment bikaverin in F. fujikuroi mycelia. Colonies of F. fujikuroi wild-type strain (Wild type) and of a representative CryD null-mutant strain (ΔcryD) grown for 7 days at 30°C on a minimal medium with low nitrogen content in white light (Light) are colored differently whereas colonies of the two strains grown in darkness (Dark) show the same color.
A series of ortho-, meta- and para-substituted trans-nitro aryl (phenyl and pyridyl) butadienes have been synthesized and characterized. The effect of substitution and positional selectivity on their fluorescence and photoisomerization were systematically investigated. Among all dienes, meta- and para-nitro phenyl-substituted derivatives exhibit remarkable solvatochromic emission shifts due to intramolecular charge transfer. On the other hand, ortho derivatives undergo regioselective isomerization upon photoexcitation in contrast to inefficient isomerization of para and meta nitro-substituted dienes. Single crystal X-ray analysis revealed existence of intramolecular hydrogen bonding between the nitro group and the hydrogen of the proximal double bond. This restricts the rotation of the proximal double bond thereby allowing regioselective isomerization. The observations were also supported by NMR spectroscopic studies.
Regioselective isomerization of o-nitrobutadiene derivatives.
Photochem. Photobiol. Sci., 2015, 14,2159-2167 DOI: 10.1039/C5PP00179J, Paper
Harsha Agnihotri, Anuji K. Vasu, Veerabhadraiah Palakollu, Sriram Kanvah Characteristic ICT emission in solvents and enhanced emission intensity in presence of sodium cholate. The content of this RSS Feed (c) The Royal Society of Chemistry
Visible light-driven photocatalyst is the current research focus and silver oxyacid salts with p-block elements are the promising candidates. In this research, Ag2CO3 was prepared by a facile precipitation method and used to degrade the pollutants from waters. The results revealed that the silver carbonate with monoclinic structure quickly decomposed methyl orange and rhodamine B in less than 15 min under visible light irradiation. When it was recycled six times, the degradation of methyl orange still can reach 87% after 30 min. The calculated band gap of Ag2CO3 was 2.312 eV with Valence band edge potential of 2.685 eV and Conduction band 0.373 eV vs NHE, which endowed the excellent photo-oxidation ability of silver carbonate. Photogenerated holes and ozone anion radicals were the primary active species in the photo-oxidization degradation of dye. The generation of metallic silver resulted from photocorrosion and the consequent reduction in the ozone anion radical amount led to the performance degradation of Ag2CO3. The simple preparation method and high photocatalytic performance of Ag2CO3 increases its prospect of application in future.
As-prepared Ag2CO3 possessed high photocatalytic performance which can quickly decompose methyl orange and rhodamine B in less than 15 min under visible light irradiation. The calculated band gap of Ag2CO3 was 2.312 eV with VB edge potential of 2.685 eV and CB 0.373 eV. Photogenerated ozone anion radicals and holes are determined as the major active species in the oxidation–reduction degradation of dye with Ag2CO3. The generation of metallic silver resulted from photocorrosion slightly decayed the performance of Ag2CO3 after recycling. The simple preparation method and high photocatalytic performance of Ag2CO3 increases its prospect of application in future.
Doxycycline is a commonly used tetracycline antibiotic showing the broad spectrum of antibacterial action. However, the use of this antibiotic is often connected with the risk of phototoxic reactions that lead to various skin disorders. One of the factors influencing the photosensitivity reactions is the melanin content in melanocytes. In this study, the impact of doxycycline and UVA irradiation on cell viability, melanogenesis and antioxidant defense system in cultured normal human epidermal melanocytes (HEMn-DP) was examined. The exposure of cells to doxycycline and UVA radiation resulted in concentration-dependent loss in melanocytes viability and induced melanin biosynthesis. Significant changes were stated in cellular antioxidant enzymes activity: SOD, CAT and GPx, which indicates alterations of antioxidant defense system. The results obtained in vitro may explain the mechanisms of phototoxic reactions that occur in normal human epidermal melanocytes in vivo after exposure of skin to doxycycline and UVA radiation.
Doxycycline enhances an UVA-mediated phototoxicity in normal human melanocytes.
To achieve the maximum level of collagen strengthening within the shortest treatment time possible, we have developed a mathematical model which is used to optimize the process of corneal cross-linking. This model is able to predict the temporal and spatial distribution of generated cross-links within the corneal stroma and hence the increase in the elasticity modulus. Theory predicts corneal strengthening at low radiation intensities and the absence of the strengthening effect at radiation intensities above the threshold level, which agrees with the experimental results. The model takes account of the initial riboflavin concentration and bleaching, light intensity and time of illumination.
To achieve the maximum level of collagen strengthening within the shortest treatment time possible, we have developed a mathematical model which is used to optimize the process of corneal cross-linking. This model is able to predict the temporal and spatial distribution of generated cross-links within the corneal stroma and hence the increase in the elasticity modulus. Theory predicts corneal strengthening at low radiation intensities and the absence of the strengthening effect at radiation intensities above the threshold level, which agrees with the experimental results. The model accounts for the initial riboflavin concentration and bleaching, light intensity and time of illumination.
In this study, the characterization and photocatalytic activity of TiO2 nanotube arrays prepared by anodization process with starch addition were investigated in detail. The results suggested that the optimum mass fraction of starch added in anodization process was 0.1%, with which TiO2 nanotube arrays owning good tubular structure were synthesized. The tube length and average inner diameter of nanotubes were approximately 4 μm and 30 nm, respectively. Through the characterization of TiO2 nanotube arrays by energy dispersive spectrometer, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier Transform Infrared (FTIR) spectroscopy, it was found that the as-prepared nanotubes possessed well uniformed and higher photodegradation responsive than the pure TiO2. Moreover, it was expected that the as-prepared nanotubes exhibited good photocatalytic activity for the degradation of RhB under UV-light irradiation, which could be ascribed to their good morphology, enhanced UV-light absorption property and electron transmission ability during the photocatalytic reaction. In addition, the nanotubes were not significantly regenerated during the cycling runs experiment. Overall, this study could provide a principle method to synthesize TiO2 nanotube arrays with enhanced photocatalytic activity by anodization process with starch addition for environmental purification.
The TiO2 nanotube arrays were prepared by anodization process with starch addition. With the starch addition, the viscosity of the electrolyte was controlled, which modified the prepared nanotubes grew completely. The as-prepared nanotubes possessed well uniformed and higher photodegradation responsive than the pure TiO2, and consequently enhancing the photochromic properties.