- Salicylic acid as a photosensitizer for thymidine dimerization induced by UV
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When a neutral solution of a nucleoside mixture was irradiated with UV light having wavelength longer than 300nm, addition of salicylic acid to the solution greatly accelerated the reaction of thymidine. The UV light irradiation of thymidine solution in the presence of salicylic acid resulted in four major product peaks in HPLC. All the products were identified as isomers of cyclobutane thymidine dimers by MS and NMR. The cyclobutane thymidine dimers were generated from thymidine almost exclusively. UV irradiation with the longer wavelength of 350nm induced almost no reaction. The results indicate that salicylic acid is a photosensitizer for thymidine dimerization excited by UV light of wavelength 300 to 350nm.
- Suzuki, Toshinori,Ota, Hiroki,Namba, Yuma,Fujino, Toshifumi
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- Photochemically and photoenzymatically cleavable DNA
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Methodology for the synthesis of site-specifically modified DNA has facilitated the physical, chemical, and enzymatic manipulation of DNA, as well as the study of important biological processes and the development of new classes of reagents and drugs. Herein we report the design, synthesis, and characterization of a DNA synthesis building block for the site-specific introduction of a photochemically and photoenzymatically cleavable linkage that is based on the photochemistry and photoenzymology of the cis-syn thymidine dimer. The phosphoramidite building block was synthesized in six steps from 5′-O-DMT-thymidine and 3′-O-TBDMS-thymidine and used to prepare a 22-mer containing a central dimer by standard automated DNA synthesis. Direct 254-nm photolysis of the 22-mer led to formation of the expected cleavage products in quantitative yield, as did visible light photolysis in the presence of Escherichia coli photolyase. An appreciable amount of cleavage (20%) by photolyase could also be induced by a single camera flash. The ability to photochemically and photoenzymatically cleave DNA site-specifically might find useful applications in the study of nucleic acid conformational transitions and enzymatic reactions, as well as the activation of prodrug forms of antisense oligonucleotides and ribozymes.
- Nadji, Sourena,Wang, Cheng-I.,Taylor, John-Stephen
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p. 9266 - 9269
(2007/10/02)
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- Characterization of thymidine ultraviolet photoproducts. Cyclobutane dimers and 5,6-dihydrothymidines
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We describe the preparation of the six configurationally distinct cyclobutane-type photodimers generated by the acetone-sensitized uv irradiation of thymidine in aqueous solution.Also prepared as minor photoproducts are the 5R and 5S diastereoisomers of 5,6-dihydrothymidine, and two novel molecules, the 5R ans 5S diastereoisomers of 5-acetonyl-5,6-dihydrothymidine.The purification of the ten molecules by chromatographic techniques (hplc, tlc) is described, along with their extensive characterization by uv, ir, cd, FAB-ms and 1H nmr.The proton chemical shifts and coupling constants are discussed in terms of the geometry of the pyrimidine, cyclobutane, and sugar rings.
- Cadet, Jean,Voituriez,Lucienne,Hruska, Frank E.,Kan, Lou-Sing,Leeuw, Frank A. A. M. de,Altona, Cornelis
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p. 2861 - 2868
(2007/10/02)
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