Oxidative damage of thymidines by the atmospheric free-radical oxidant NO3 •

Abstract

Analysis of the products formed in the reaction of nitrate radicals, NO3 •, with the N-and O-methylated and acetylated thymidines 1a and 1b revealed, for the first time, insight regarding how this important atmospheric free-radical oxidant can cause irreversible damage to DNA building blocks. Mechanistic studies indicated that the initial reaction step likely proceeds via NO3 • induced electron transfer at the pyrimidine ring, followed by deprotonation of the methyl group at C5. The oxidation ultimately leads to formation of nitrates 2, aldehydes 4 and, in the case of high [NO3 •], also to carboxylic acids 5. In addition to this, through a very minor pathway, loss of the methyl group at C5 a..