Pulse-radiolytic studies on the reactions of SO4-· with uracil derivatives

Results of pulse-radiolytic studies on the reaction of SO in aqueous solution with different uracil derivatives are 4-· reported. From 1-methyluracil, 1,3-dimethyluracil and 1,3,6-trimethyluracil upon reaction with SO 4- · the C(5)-OH adduct radicals are quickly formed in quantitative yields. With 1,3-dimethylthymine strong evidence is presented that additionally a C(5)-CH 2 · allyl-type radical is formed. The latter is thought to be the result of a deprotonation from the methyl group at position C(5) of a short-lived radical cation which is preceded by an SO 4-· adduct radical whose half-life is 2 μs. When the N(1) position of the uracil carries a sugar moiety, further transient absorbing species were observed, the structures of which are not known at present and which cannot be assigned to any of the known intermediates derived from uracil or its derivatives. The results suggest that the presence of a sugar moiety strongly determines the ultimate fate of the base radicals