Characterization of Radiation-induced Damage in d(TpApCpG)

The radiation chemistry of the oligomer d(TpApCpG) X-irradiated in aqueous solution containing glutathione was studied. Four products were isolated by HPLC and characterized by NMR spectroscopy. Two of the major products are isomers of a 5-hydroxy-5,6-dihydrothymine modification of d(TpApCpG). A dihydrothymine modification is also formed. The other major product is a result of strand scission. These products are different from the major products identified previously in a study of d(TpApCpG) X-irradiated in oxygenated solution. The effect of specific radiation-induced lesions on the behaviour of d(TpApCpG) as substrate to a spleen phosphodiesterase-micrococcal nuclease combination of enzymes and to nuclease P1 was studied. These enzymes are of interest because they are used in postlabelling assays of DNA damage.