Site of hatom attack on uracil and its derivatives in aqueous solution

Abstract

Hydrogen atoms from the radiolysis of water at pH 1.6 add to the 5,6-double bond of pyrimidines.The preferential site of attack is the C(5) position (values in brackets) in the case of 6-methyluracil (87%), 1,3- (71%), uracil(69%) and poly(U)(60%).This reaction yields a radical of reducing properties which can be monitored by its reaction with tetranitrom ethane in a radiolysis experiment. In thymine (37%), thymidine (and 1,3-dimethylthymine (25%) H -addition no longer occurs at C(5), but addition is now mainly C(6). Hydrogen abstraction from the methyl groups or sugar moiety is negligible (⪳ 5.5%). A comparison is with literature values for the equivalent reactions of OH radicals. © 1985, Walter de Gruyter. All rights reserved.