Current address: Department of Molecular and Cell Biology, Beckman Research Institute of the City of Hope, Duarte, CA, USA.
The (α-4) Photoconjugates of 5-Methylcytosine, 1,5-Dimethylcytosine, 1-Methylthymine and Thymidine
Article first published online: 23 JAN 2012
© 2011 Wiley Periodicals, Inc. Photochemistry and Photobiology © 2011 The American Society of Photobiology
Photochemistry and Photobiology
Volume 88, Issue 2, pages 336–343, March/April 2012
How to Cite
Shetlar, M. D. and Chung, J. (2012), The (α-4) Photoconjugates of 5-Methylcytosine, 1,5-Dimethylcytosine, 1-Methylthymine and Thymidine. Photochemistry and Photobiology, 88: 336–343. doi: 10.1111/j.1751-1097.2011.01070.x
- Issue published online: 1 MAR 2012
- Article first published online: 23 JAN 2012
- Accepted manuscript online: 29 DEC 2011 02:53PM EST
- Received 17 October 2011, accepted 21 December 2011
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.