Reactions of ·OH with thymine studied using density functional theory

We studied three possible reactions of a free ·OH radical with thymine by using density functional theory calculations. The results indicate that there is no energy barrier in the reactions of a free ·OH radical adding to the C6 position of thymine, while the reactions of a free ·OH radical adding to the C5 position of thymine and the reaction of an ·OH abstracting a hydrogen from the C5 methyl group should overcome the energy barriers of ∼0.70 kcal/mol and ∼1.88 kcal/mol, respectively. The C6-hydroxylated radical formed is energetically more favorable than the C5-hydroxylated radical. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005