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Photochemistry and Photobiology

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https://www.readbyqxmd.com/read/28084040/type-i-and-ii-photosensitized-oxidation-reactions-guidelines-and-mechanistic-pathways
#1
Maurício da Silva Baptista, Jean Cadet, Paolo Di Mascio, Ashwini A Ghogare, Alexander Greer, Michael R Hamblin, Carolina Lorente, Silvia Cristina Nunez, Martha Simões Ribeiro, Andrés H Thomas, Mariana Vignoni, Tania Mateus Yoshimura
Here, ten guidelines are presented for a standardized definition of type I and II photosensitized oxidation reactions. Because of varied notions of reactions mediated by photosensitizers, a checklist of recommendations is provided for their definitions. Type I and type II photoreactions are oxygen-dependent and involve unstable species such as the initial formation of radical cation or neutral radicals from the substrates and/or singlet oxygen ((1) O2(1) ∆g ) by energy transfer to molecular oxygen. In addition, superoxide anion radical (O2(•-) ) can be generated by a charge transfer reaction involving O2 or more likely indirectly as the result of O2 -mediated oxidation of the radical anion of type I photosensitizers...
January 13, 2017: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/28084029/bioluminescence-imaging-of-spheroids-for-high-throughput-longitudinal-studies-on-3d-cell-culture-models
#2
Luca Cevenini, Maria M Calabretta, Antonia Lopreside, Bruce R Branchini, Tara L Southworth, Elisa Michelini, Aldo Roda
Bioluminescent (BL) cell-based assays based on two-dimensional (2D) monolayer cell cultures represent well-established bioanalytical tools for pre-clinical screening of drugs. However, cells in 2D cultures do not often reflect the morphology and functionality of living organisms, thus limiting the predictive value of 2D cell-based assays. Conversely, 3D cell models have the capability to generate the extracellular matrix and restore cell-to-cell communications; thus, they are the most suitable model to mimic in vivo physiology...
January 13, 2017: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/28084012/uva-light-mediated-ascorbate-oxidation-in-human-lenses
#3
Stefan Rakete, Ram H Nagaraj
Whether ascorbate oxidation is promoted by UVA light in human lenses and whether this process is influenced by age and GSH levels are not known. In this study, we used paired lenses from human donors. One lens of each pair was exposed to UVA light whereas the other lens was kept in the dark for the same period of time as the control. Using LC-MS/MS analyses, we found that older lenses (41 to 73 years) were more susceptible to UVA-induced ascorbate oxidation than younger lenses (18 to 40 years). Approximately 36% of the ascorbate (relative to control) was oxidized in older lenses compared to ~16% in younger lenses...
January 13, 2017: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/28083883/a-comparison-of-dose-metrics-to-predict-local-tumor-control-for-photofrin-mediated-photodynamic-therapy
#4
Haixia Qiu, Michele M Kim, Rozhin Penjweini, Jarod C Finlay, Theresa M Busch, Tianhao Wang, Wenshen Guo, Keith A Cengel, Charles B Simone, Eli Glatstein, Timothy C Zhu
This preclinical study examines light fluence, PDT dose, and "apparent reacted singlet oxygen", [(1) O2 ]rx , to predict local control rate (LCR) for Photofrin-mediated photodynamic therapy (PDT) of radiation-induced fibrosarcoma (RIF) tumors. Mice bearing RIF tumors were treated with in-air fluences (50-250 J/cm(2) ) and in-air fluence rates (50-150 mW/cm(2) ) at Photofrin dosages of 5 and 15 mg/kg and a drug-light interval of 24 hours using a 630nm 1-cm diameter collimated laser. A macroscopic model were used to calculate [(1) O2 ]rx and PDT dose based on in vivo explicit dosimetry of the drug concentration, light fluence, and tissue optical properties...
January 13, 2017: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/28083878/the-b6-vitamer-pyridoxal-is-a-sensitizer-of-uva-induced-genotoxic-stress-in-human-primary-keratinocytes-and-reconstructed-epidermis
#5
Rebecca Justiniano, Joshua D Williams, Jessica Perer, Ahn Hua, Jessica Lesson, Sophia L Park, Georg T Wondrak
UVA-driven photooxidative stress in human skin may originate from excitation of specific endogenous chromophores acting as photosensitizers. Previously, we have demonstrated that 3-hydroxypyridine-derived chromophores including B6 -vitamers (pyridoxine, pyridoxamine, and pyridoxal) are endogenous photosensitizers that enhance UVA-induced photooxidative stress in human skin cells. Here, we report that the B6 -vitamer pyridoxal is a sensitizer of genotoxic stress in human adult primary keratinocytes (HEKa) and reconstructed epidermis...
January 13, 2017: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/28063175/bioluminescence-in-dinoflagellates-evidence-that-the-adaptive-value-of-bioluminescence-in-dinoflagellates-is-concentration-dependent
#6
Karen A Hanley, Edith A Widder
Three major hypotheses have been proposed to explain why dinoflagellate bioluminescence deters copepod grazing: startle response, aposematic warning, and burglar alarm. These hypotheses propose dinoflagellate bioluminescence (A) startles predatory copepods, (B) warns potential predators of toxicity, and (C) draws the attention of higher-order visual predators to the copepod's location. While the burglar alarm is the most commonly accepted hypothesis, it requires a high concentration of bioluminescent dinoflagellates to be effective, meaning the bioluminescence selective advantage at lower, more commonly observed, dinoflagellate concentrations may result from another function (e...
January 7, 2017: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/28063169/progress-in-the-study-of-bioluminescent-earthworms
#7
Natalja S Rodionova, Emilia Rota, Aleksandra S Tsarkova, Valentin N Petushkov
Even though bioluminescent oligochaetes rarely catch people's eyes due to their secretive lifestyle, glowing earthworms sighting reports have come from different areas on all continents except Antarctica. A major breakthrough in the research of earthworm bioluminescence occurred in the 1960s with the studies of the North American Diplocardia longa. Comparative studies conducted on 13 earthworm species belonging to six genera showed that N-isovaleryl-3-aminopropanal (Diplocardia luciferin) is the common substrate for bioluminescence in all examined species, while luciferases appeared to be responsible for the color of bioluminescence...
January 7, 2017: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/28063168/phytochemicals-for-the-prevention-of-photocarcinogenesis
#8
Mary Katherine Montes de Oca, Ross L Pearlman, Sarah F McClees, Rebecca Strickland, Farrukh Afaq
Ultraviolet (UV) exposure has an array of damaging effects and is the main cause of skin cancer in humans. Non-melanoma skin cancer (NMSC), including basal cell carcinoma and squamous cell carcinoma, is the most common type of cancer. Incidence of NMSC has increased due to greater UV radiation, increased life expectancy, and other changes in lifestyle; the annual cost of skin cancer treatment in the United States has increased concurrently to around eight billion dollars. Because of these trends, novel approaches to skin cancer prevention have become an important area of research to decrease skin cancer morbidity and defray the costs associated with treatment...
January 7, 2017: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/28063161/changes-in-time-spent-outdoors-during-the-daytime-in-rural-populations-in-four-geographically-distinct-regions-in-china-a-retrospective-study
#9
Qian Gao, Fang Wang, Liwen Hu, Jiaming Yu, Rong Liu, Yang Wang, Yang Liu
Changes in time-activity patterns may influence personal exposure to various environmental factors and affect individual health. However, few studies have investigated the changes in patterns of time spent outdoors. To investigate the trends in outdoor activity in recent decades in China, a retrospective questionnaire was used to examine the amount and pattern of time spent outdoors during the day by 2076 subjects in four geographically distinct rural regions of China. Rural Chinese people spent less time outdoors than they used to because of the economic development, increase in education, and changes in working conditions that occurred over time...
January 7, 2017: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/28063150/mutants-of-ca-2-regulated-photoprotein-obelin-for-site-specific-conjugation
#10
Vasilisa V Krasitskaya, Ludmila P Burakova, Anastasia A Komarova, Eugenia E Bashmakova, Ludmila A Frank
Color variants of Ca(2+) -regulated photoprotein obelin were shown to be an important tool for dual-analyte binding assay. To provide site-directed conjugation with biospecific molecules, several obelin color mutants carrying unique cysteine residues were obtained and characterized for their novel properties. A pair of obelins Y138F,A5C and W92F,H22E,D12C was found to be most suitable (in terms of high bioluminescent activity and stability) as reporters in simultaneous assay of two targets in a sample. Availability of SH-groups, accessible for chemical modification essentially simplifies the synthesis of biospecific conjugates, increases their yield and conserves obelins' bioluminescence activity...
January 7, 2017: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/28055118/fret-in-a-synthetic-flavin-and-bilin-binding-protein
#11
Julian Simon, Aba Losi, Kai-Hong Zhao, Wolfgang Gärtner
The last decade has seen development and application of a large number of novel fluorescence-based techniques that have revolutionized fluorescence microscopy in life sciences. Preferred tags for such applications are genetically encoded fluorescent proteins (FP), mostly derivatives of the green fluorescent protein (GFP). Combinations of FPs with wavelength-separated absorption/fluorescence properties serve as excellent tools for molecular interaction studies, e.g., protein-protein complexes or enzyme-substrate complexes, based on the FRET phenomenon (Förster resonance energy transfer)...
January 5, 2017: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/28055111/there-and-back-again-loss-and-reacquisition-of-two-cys-photocycles-in-cyanobacteriochromes
#12
Nathan C Rockwell, Shelley S Martin, J Clark Lagarias
Cyanobacteriochromes (CBCRs) are cyanobacterial photoreceptors distantly related to phytochromes. Both families use linear tetrapyrrole (bilin) chromophores that are covalently attached to a conserved Cys residue. CBCRs are more spectrally diverse than phytochromes, with known examples detecting light from the near ultraviolet to the edge of the infrared (370-750 nm). Detection of ultraviolet to blue light by CBCRs is mediated by a second Cys residue, which forms a covalent linkage to the bilin C10 atom. Second linkage formation is best understood in a subfamily possessing a conserved Asp-Xaa-Cys-Phe (DXCF) motif...
January 5, 2017: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/28052361/the-properties-and-activity-of-tio2-beta-sic-nanocomposites-in-organic-dyes-photodegradation
#13
Katarzyna Pstrowska, Bartłomiej Maciej Szyja, Hanna Czapor-Irzabek, Adam Kiersnowski, Jerzy Walendziewski
The TiO2 /beta-SiC nanocomposites containing 0-25 wt. % of beta-SiC were synthesized by the sol-gel method and tested in the photodegradation of methylene blue and methyl orange water solutions. With the increase of SiC content, only a slight decrease in energy band gap was observed (3.19-3.12 eV), together with significant increase of the surface area of the catalysts (42.7-80.4 m(2) /g). In the synthesized material the anatase phase of TiO2 was present in the form of small agglomerates resulting from the mechanical mixing process...
January 4, 2017: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/28052331/computed-regioselectivity-and-conjectured-biological-activity-of-ene-reactions-of-singlet-oxygen-with-the-prenylnatural-product-hyperforin
#14
Inna Abramova, Benjamin Rudshteyn, Joel F Liebman, Alexander Greer
Hyperforin is a constituent of St. John's wort and coexists with the singlet oxygen sensitizer hypericin. Density functional theory, molecular mechanics and Connolly surface calculations show that accessibility in the singlet oxygen 'ene' reaction favors the hyperforin "southwest" and "southeast" prenyl (2-methyl-2-butenyl) groups over the northern prenyl groups. While the southern part of hyperforin is initially more susceptible to oxidation, up to 4 'ene' reactions of singlet oxygen can take place. Computational results assist in predicting the fate of adjacent hydroperoxides in hyperforin, where the loss of hydrogen atoms may lead to the formation of a hydrotrioxide and a carbonyl instead of a Russell reaction...
January 4, 2017: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/28039876/selected-least-studied-but-not-forgotten-bioluminescent-systems
#15
Yuichi Oba, Cassius V Stevani, Anderson G Oliveira, Aleksandra S Tsarkova, Tatiana V Chepurnykh, Ilia V Yampolsky
Bioluminescence is a form of chemiluminescence generated by luminous organisms. Luminous taxa have currently been reported from about 800 genera and probably over 10,000 species in the world. On the other hand, their bioluminescent systems, including chemical structures of luciferins/chromophores and the genes encoding luciferases/photoproteins, have been elucidated from only a few taxonomic groups; e.g. beetles, bacteria, dinoflagellates, ostracods, and some cnidarians. Research efforts to understand unknown bioluminescence systems are being conducted around the world, and recently, for example, novel luciferin structures of luminous enchytraeid potworms and fungi were identified by the authors...
December 31, 2016: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/28039861/uvb-generated-microvesicle-particles-a-novel-pathway-by-which-a-skin-specific-stimulus-could-exert-systemic-effects
#16
Katherine Fahy, Langni Liu, Christine M Rapp, Christina Borchers, Ji C Bihl, Yanfang Chen, Richard Simman, Jeffrey B Travers
Ultraviolet B radiation (UVB) exerts profound effects on human skin. Much is known regarding the ability of UVB to generate a plethora of bioactive agents ranging from cytokines and other bioactive proteins, lipid mediators and micro-RNAs. It is presumed that these agents are in large part responsible for the effects of UVB, which only is absorbed appreciably in the epidermis. However, the exact mechanism by which these bioactive agents can leave the epidermis are as yet unclear. This review addresses the potential role of microvesicle particles (MVP) as UVB signaling agents through transmitting biologic mediators...
December 31, 2016: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/28027411/dna-repair-by-the-radical-sam-enzyme-spore-photoproduct-lyase-from-biochemistry-to-structural-investigations
#17
Olivier Berteau, Alhosna Benjdia
Radical S-adenosyl-L-methionine (SAM) enzymes have emerged as one of the last superfamilies of enzymes discovered to date. Arguably, it is the most versatile group of enzymes involved in at least 85 biochemical transformations. One of the founding members of this enzyme superfamily is the Spore Photoproduct (SP) lyase, a DNA repair enzyme catalyzing the direct reversal repair of a unique DNA lesion, the so-called spore photoproduct, back into two thymidine residues. Discovered more than 20 years ago in the bacterium Bacillus subtilis, SP lyase has been shown to be widespread in the endospore-forming Firmicutes from the Bacilli and Clostridia classes and to use radical-based chemistry to perform C-C bond breakage, a chemically challenging reaction...
December 27, 2016: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/28027397/in-vivo-confocal-raman-spectroscopic-analysis-of-the-effects-of-ir-radiation-in-the-human-skin-dermis
#18
Monica Bergamo Lopes, Ramu Rajasekaran, Ana Clara Figueira Lopes Cançado, Airton Abrahão Martin
Human skin is the outer covering of the body and its composition changes with over exposure to environmental pollution and solar radiation. IR radiation is capable of penetrating more deeply into the skin producing free radicals causing irreversible damage. Confocal Raman spectroscopy was considered as a potential tool for the in vivo analysis of the different metabolic conditions with respect to different depths of the skin. In this regard, this work verifies the influence of infrared radiation on the skin dermis after having been exposed to 432 J/cm(2) which corresponds to the dose received in a day in the summer time in a tropical region...
December 27, 2016: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/27992654/repair-of-6-4-lesions-in-dna-by-6-4-photolyase-20-years-of-quest-for-the-photoreaction-mechanism
#19
Junpei Yamamoto, Pascal Plaza, Klaus Brettel
Exposure of DNA to ultraviolet (UV) light from the Sun or from other sources causes formation of harmful and carcinogenic crosslinks between adjacent pyrimidine nucleobases, namely cyclobutane pyrimidine dimers and pyrimidine(6-4)pyrimidone photoproducts. Nature has developed unique flavoenzymes, called DNA photolyases, that utilize blue light, i.e. photons of lower energy than those of the damaging light, to repair these lesions. In this review, we focus on the chemically challenging repair of the (6-4) photoproducts by (6-4) photolyase and describe the major events along the quest for the reaction mechanisms, over the 20 years since the discovery of (6-4) photolyase...
December 19, 2016: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/27992649/kinetic-isotope-effects-and-hydrogen-deuterium-exchange-reveal-large-conformational-changes-during-the-catalysis-of-the-clostridium-acetobutylicum-spore-photoproduct-lyase
#20
Linlin Yang, Jagat Adhikari, Michael L Gross, Lei Li
Spore photoproduct lyase (SPL) catalyzes the direct reversal of a thymine dimer 5-thyminyl-5,6-dihydrothymine (i.e., the spore photoproduct (SP)) to two thymine residues in germinating endospores. Previous studies suggest that SPL from the bacterium Bacillus subtilis (Bs) harbors an unprecedented radical transfer pathway starting with cysteine 141 proceeding through tyrosine 99. However, in SPL from the bacterium C. acetobutylicum (Ca), the cysteine (at position 74) and tyrosine are located on the opposite sides of a substrate binding pocket that has to collapse to bring the two residues into proximity, enabling the C→Y radical passage as implied in SPL(Bs) ...
December 19, 2016: Photochemistry and Photobiology
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