Radical cations of the nucleic bases and radiation damage to DNA:: Ab initio study

This review summarizes the contribution of high level quantum chemical calculations to the investigation of some elementary reactive processes related to the radiation damage to DNA. It is focused on the biomimetic species that govern these processes at the molecular level. These species are the DNA bases, isolated or embedded in base clusters. Their cations, formed by ionization in their ground and first excited electronic states, are at the center of the present work. We present a synthetic and critical overview of the computational methods used to predict accurate ionization potentials, to correctly describe the non-bonding interactions (stacking, H-bonding and cation-pi) stabilizing the studied biornimetic clusters, to characterize their excited states and to investigate the topology of the corresponding potential energy surfaces (minima, transition states, avoided crossings, conical intersections, reaction paths). All these aspects are illustrated by the recent literature and by our own research work, namely on the electron transfer occurring within a stacked dimer of guanines.