PATTERN OF OH RADICAL ADDITION TO CYTOSINE AND 1-, 3-, 5-, AND 6-SUBSTITUTED CYTOSINES. ELECTRON TRANSFER AND DEHYDRATION REACTIONS OF THE OH ADDUCTS.

Article abstract of DOI:10.1021/ja00351a042

By use of the technique of pulse radiolysis with optical detection, the isomer distribution of the radicals formed in aqueous solution by addition of OH radicals to cytosine, 5-methylcytosine, 5-carboxylcytosine, 3-methylcytosine, 1-methylcyptosine, cytidine, 5-methylcytidine, cytidylic acid, 2 prime -deoxycytidine, 2 prime -deoxycytidylic acid, and 2-amino-4-hydroxy-6-methylpyrimidine has been determined by utilizing differences between the isomeric OH adducts with respect to electron-transfer reactions with the reductant N,N,N prime N prime -tetramethyl-p-phenylenediamine (TMPD) or the oxidant tetranitromethane (TNM). The radicals Cy-5-OH, formed by addition of OH to C(5) or cytosine (87% of the OH radicals), 3- and 5-methylcytosine (92% and 65%, respectively), 5-carboxylcytosine (82%), and 2-amino-4-hydroxy-6-methylpyrimidine (95%) reduce TNM to yield nitroform anion. The radicals Cy-6-OH, formed by addition to C(6), oxidize TMPD to yield TMPD** plus . The Cy-5-OH radicals undergo a base-catalyzed dehydration reaction to yield radicals that are able to oxidize TMPD to yield TMPD** plus multiplied by (times) .