Oxidative Damage to DNA*

The initial stage of the reaction of a guanine radical cation with water is investigated using ab-initio methods coupled with molecular mechanics. We explore the influence of the sugar- phosphate backbode, the complementary cytosine base, the adjacent base pairs in the B-DNA double strand, the state of hydration, and finally the distribution of counter-ions on the barrier and reaction path leading to 8-oxo-G.