UV-inducible

Chemical properties of deposited monolayers have been studied in various ways. The degree of ionization of a substituted coumarin film deposited on quartz was determined as a function of the pH of a solution in contact with the film, from which comparison with Gouy-Chapman theory (see Section V-2) could be made [151]. Several studies have been made of the UV-induced polymerization of monolayers (as well as of multilayers) of diacetylene amphiphiles (see Refs. 168, 169). Excitation energy transfer has been observed in a mixed monolayer of donor and acceptor molecules in stearic acid [170]. Electrical properties have been of interest, particularly the possibility that a suitably asymmetric film might be a unidirectional conductor, that is, a rectifier (see Refs. 171, 172). Optical properties of interest include the ability to make planar optical waveguides of thick LB films [173, 174]. 

Numerous studies have shown that increased levels of UV affect photosynthetic activity (10-23), growth rate (24), nitrogen metabolism (25), and locomotion (26) of phytoplankton. Additionally, increases in UV-B are likely to alter community diversity as well as phytoplankton species composition. Thus, by weakening the base of the food web and altering trophodynamic relationships, UV-induced changes could potentially have far-reaching effects on the entire ecosystem. 

Lyamichev, V., Frank-Kamenetskii, M., Soyfer, V. Protection against UV-induced pyrimidine dimerization in DNA by triplex formation. Nature, Vol.344, No. 6266, (1990), pp. 568-570, ISSN 1476-4687... 

Flavins — Riboflavin is first of all essential as a vitamin for humans and animals. FAD and FMN are coenzymes for more than 150 enzymes. Most of them catalyze redox processes involving transfers of one or two electrons. In addition to these well known and documented functions, FAD is a co-factor of photolyases, enzymes that repair UV-induced lesions of DNA, acting as photoreactivating enzymes that use the blue light as an energy source to initiate the reaction. The active form of FAD in photolyases is their two-electron reduced form, and it is essential for binding to DNA and for catalysis. Photolyases contain a second co-factor, either 8-hydroxy-7,8-didemethyl-5-deazariboflavin or methenyltetrahydrofolate. ... 

The use of a UV filter or alternate visible light source is the next step to ensure that no UV induced reactions are occurring in parallel with the photocatalytic process. 

UV-induced surface grafting of a polymer sheet using vapor phase transfer of sensitizer and monomer from a volatile solution (9). 

UV-induced surface grafting of a polymer tape or a fiber bundle as substrate in a continuous operation with pretreatment of the substrate (presoaking) in a solution of sensitizer and monomer (10). The grafting takes place in a thin layer of solution on the surface of the moving substrate. 

The interaction of UV radiation with nucleic acids is of great importance since it can lead to UV-induced damage in DNA with profound consequences, including photocarcinogenesis [1,2]. The nucleobases are the primary chromophores in DNA and RNA, and consequently, the photophysical and photochemical behavior of the nucleobases has been the focus of extensive theoretical and experimental work over the years [4, 6, 81, 82],... 

The HPLC-MS/MS assay was also successfully applied to the measurement of UV-induced dimeric pyrimidine photoproducts [123, 124]. The latter lesions were released from DNA as modified dinucleoside monophosphates due to resistance of the intra-dimer phosphodiester group to the exonuclease activity during the hydrolysis step [125, 126]. The hydrolyzed photoproducts exhibit mass spectrometry and chromatographic features that allow simultaneous quantification of the three main classes of photolesions, namely cyclobutane dimers, (6-4) photoproducts, and Dewar valence isomers, for each of the four possible bipyrimidine sequences. It may be added that these analyses are coupled to UV detection of normal nucleosides in order to correct for the amount of DNA in the sample and obtain a precise ratio of oxidized bases or dimeric photoproducts to normal nucleosides. 

Electron donation to nucleobases is a fundamental process exploited by nature to achieve the efficient repair of UV induced lesions in DNA [27, 28]. Nature developed to this end two enzymes, CPD photolyases and (6-4) photolyases, which both inject electrons into the UV damaged DNA bases [29, 30]. Both enzymes are, in many species, including plants, essential for the repair of the UV-light induced DNA lesions depicted in Scheme 1 [31]. 

Although the reduction potentials of DNA bases and UV induced DNA lesions inside a DNA double strand or inside the active site of a DNA photolyase, together with the reduction potential of the photoexcited FADH- in the photolyases, are not known, currently available redox potentials indicate that the single electron reduction of a nucleobase or a UV induced dimer lesion by a reduced and deprotonated flavin coenzyme is a weakly exothermic process. The reduced and deprotonated FADH- in its photoexcited state is... 

Bode, A.M. and Dong, Z. 2003. Mitogen-activated protein kinase activation in UV-induced signal transduction. 

Comparelli, R., Fanizza, E., Curri, M.L., Cozzoli, P.D., Mascolo, G. and Agostiano, A. (2005) UV-induced photocatalytic degradation of azo dyes by organic-capped ZnO nanocrystals immobilized onto substrates. Applied Catalysis B Environmental, 60, 1—11. 

Ando R, Hama H, Yamamoto-Hino M, Mizuno H, Miyawaki A (2002) An optical marker based on the UV-induced green-to-red photoconversion of a fluorescent protein. Proc Natl Acad Sci USA 99 12651-12656... 

Wiedenmann J, Ivanchenko S, Oswald F, Schmitt F, Rocker C, Salih A, Spindler KD, Nienhaus GU (2004) EosFP, a fluorescent marker protein with UV-inducible green-to-red fluorescence conversion. Proc Natl Acad Sci USA 101 15905-15910... 

Phycocymes shows a positive UV-induced light-growth-response (Fig. 3 3) as well as a negative phototropic curvature, as depicted in Fig. 5 1. The exceptionally good fit of this action spectrum and auxin absorption (Fig. 5 2) might indicate that auxin is the UV-photoreceptor. 

On the other hand, the observation that 95% of the UV induced base substitution mutations arose at the very sites (pyrimidine-pyrimidine sequences) where the major fraction of UV damage is deposited suggested that at least the UV induced mutations were targeted (24). 

Scheme 7.27 Microwave-mediated synthesis and UV-induced cleavage of cyclic triazines on a cellulose membrane.

Mercier J, Ponnampalam R, Berard LS and Aral J. 1993. Polyacetylene content and UV-induced 6-methoxymellein accumulation in carrot cultivars. J Sci Food Agric 63(3) 313-316. 

Heinrich U, Gartner C, Wiebusch M, Eichler O, Sies H, Tronnier H and Stahl W. 2003. Supplementation with beta-carotene or a similar amount of mixed carotenoids protects humans from UV-induced erythema. J Nutr 133 98-101. 

Studies of the solid state photopolymerization of deposited multilayer films reveal that uv induced photopo1ymerizati0n of disubstituted diacetylenes... 

Plants are continuously exposed to biotic and abiotic (notably harmful UV radiation) stress elements and have evolved mechanisms to reduce their deleterious effects. The UV-inducibility of a number of DNA repair15 and metabolic pathways has previously been determined.16 20 To date, no global... 

Urocanic acid (2-propanoic acid 3-[lH-imidazol-4-yl] is located superficially in the stratum comeum. Metabolism of epidermal UCA does not occur in situ due to the absence of urocanase, resulting in the accumulation of UCA in the epidermis. Upon UV exposure, naturally occurring trans-UCA converts to the d.s-isomer, in a dose dependent manner, until the photostationary state is reached, when equal quantities of trans- and m-UCA are found in the skin.15 Based on an analysis of the action spectrum for UV-induced immune suppression, and the fact that no immune suppression was observed in mice whose stratum comeum was previously removed by tape stripping, De Fabo and Noonan suggested that urocanic acid was the photoreceptor for UV-induced immune suppression.16 Since the initial experiments many others have documented, the ability of ris-UCA to initiate immune suppression, documented its presence in the serum of UV-irradiated mice, and demonstrated that m-UCA plays a role in UV-induced skin cancer induction. (For a more complete review of the role of m-UCA in immune suppression see two excellent reviews by Norval and colleagues.1718)... 

How does UV-induced free radical formation activate immune suppression Some have suggested that UV-induced cytokine production is involved. Because both DNA damage and oxidative stress can activate transcription of the cytokines that activate immune suppression,23>24one of the problems faced by investigators in the field was to divorce the effects of DNA damage from membrane oxidation. One approach was to look at the activation of transcription factors in UV-irradiated enucleated cells. Devary and colleagues25 observed that both NF-kB and AP-1 were activated in enucleated... 

UV-irradiated cells. Using cell-free cytosolic keratinocyte extracts, Simon and colleagues26 confirmed the role of membrane oxidation in NF-kB activation. Particularly important aspects of the experimental design employed by Simon and colleagues was the use of keratinocytes versus cells derived from a cervical cancer patient, and the use of biologically relevant UVB (290 to 320 nm) radiation versus UVC (200 to 290 nm) radiation, which is filtered out by the atmospheric ozone layer and does not reach the earth s surface. Overall, these data indicate that the activation of cytokine transcription, a step essential for the induction of immune suppression, can occur independently of UV-induced DNA damage and suggest that membrane lipid oxidation can serve as a UV photoreceptor. 

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