TANDEM LESIONS AND OTHER PRODUCTS IN X-IRRADIATED DNA OLIGOMERS

Free radicals interact with DNA bases to produce secondary radicals. T he secondary radicals are reactive species and tend to interact with n eighboring bases, resulting in DNA lesions with two adjacent modified bases. In this study the DNA oligomers d(CpApTpG) and d(CpCpTpA) were exposed to free radicals generated in anoxic aqueous solution by X irr adiation. Four new lesions were identified in which adjacent guanine a nd pyrimidine bases are covalently bonded. One of the tandem lesions f ormed in d(CpGpTpA) has the C5 carbon atom of cytosine covalently bond ed to the C8 carbon atom of guanine. Interestingly, the same bond is f ormed between the terminal bases in d(CpApTpG), resulting in a cyclize d molecule. (C) 1998 by Radiation Research Society.