Attacking mechanism of hydroxyl radical to DNA base-pair: density functional study in vacuum and in water.

Recently, the influence of radiation on human body has been recognized as a serious problem. In particular, highly reactive hydroxyl radicals produced by the radiation react with DNA, resulting in a great damage on its structure and electronic properties. It is thus important to investigate the reaction mechanism of to DNA for elucidating the initial damage in DNA induced by the radiation. In the present study, we search for transition states (TS) of the reaction between G–C/A–T base-pair and in vacuum and in water, by the density functional theory (DFT) calculations. At first, we obtain the stable structures for the dehydrogenated G–C and A–T, in which the hydrogen atom of NH2 group of G or A base is abstracted by . From the structures of the dehydrogenated as well as the natural base-pairs, the TS between these structures is searched for and the activation free energy (AFE) is estimated for the reaction. In vacuum, AFEs for the G–C and A–T are almost the same each other, while the stabilization energy b...