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The (α‐4) Photoconjugates of 5‐Methylcytosine, 1,5‐Dimethylcytosine, 1‐Methylthymine and Thymidine
Author(s) -
Shetlar Martin D.,
Chung Janet
Publication year - 2012
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.2011.01070.x
Subject(s) - thymine , nucleobase , moiety , chemistry , pyrimidine , adduct , thymidine , cyclobutane , stereochemistry , dna , pyrimidine dimer , photochemistry , ring (chemistry) , dna damage , organic chemistry , biochemistry
The pyrimidine nucleobases contained in DNA undergo a variety of photoinduced reactions in which two moieties become joined to form a product ( e.g. formation of cyclobutane dimers and [6‐4] adducts). Herein, we describe a new type of photoconjugation reaction that has been shown to occur for 5‐methylcytosine (5‐MeC), 1,5‐dimethylcytosine (1,5‐diMeC), 1‐methylthymine and thymidine; in this reaction the 5‐methyl group of one nucleobase (or nucleoside) becomes attached to the 4‐position of the second moiety. For example, 5‐MeC forms α‐4′‐(5′‐methylpyrimidin‐2′‐one)‐5‐methylcytosine. The various (α‐4) conjugates are produced upon irradiation of the parent compound in frozen aqueous solution at −78.5°C. The UV spectra of these compounds display a characteristic “double humped” profile, similar to that expected from overlaying the spectrum of parent nucleobase with that of a 2′‐pyrimidone moiety. Preliminary results suggest that thymine and 5‐methyl‐2′‐deoxycytidine (5‐MedCyd) form analogous photoproducts. A variety of other previously unreported photoproducts are described as well for the 5‐MeC, 1,5‐diMeC and 5‐MedCyd systems.