Comparison of Radiolysis Products of Thymine and Thymidine with E.S.R. Results

Summary

Radicals determined by e.s.r. spectrometry of irradiated thymine or thymidine and radiolytic products generated under the action of gamma rays in aerated aqueous solutions have been compared. This comparison lies mainly in the fact that a radical R· gives rapidly the corresponding peroxide ROOH. The authors have isolated and characterized twenty peroxides, i.e., the four isomers cis (−), cis (+), trans (−), trans (+) of 6-hydroperoxy-5-hydroxy-5,6-dihydrothymidine; the four isomers cis (−), cis (+), trans (−), trans (+) of 5-hydroperoxy-6-hydroxy-5,6-dihydrothymidine; 5-hydroperoxy-2′-deoxyuridin; cis and trans 6-hydroperoxy-5-hydroxy-5,6-dihydrothymine; cis and trans 5-hydroperoxy-6-hydroxy-5,6-dihydrothymine; 5-hydroperoxymethyl-uracil; 5-hydroperoxy-5,6-dihydrothymine; cis and trans 6-hydroperoxy-5,6-dihydrothymine; 5-hydroperoxy-5-methyl barbituric acid; 5-hydroperoxy-5-methyl hydantoin; trans 5,6-dihydroperoxy-5,6-dihydrothymine. Most of the thymine and thymidine radicals hypothesized or described in the literature were correlated to these peroxides. However, the presence of certain peroxides could not be explained by recognized radicals. Taking advantage of this fact, the existence of new thymine or thymidine radicals so far unknown can be predicted.