Potential Path of DNA Damage: Electron Attachment–Induced DNA Single-Strand Breaks

Abstract

The theoretical study of the electron attachment to DNA reveals the possible mechanism of one of the possible paths of damages in DNA single strands – the low energy electron induced strand breaks. This mechanism includes the formation of an electronically stable radical anion at the nascent stage, and the bond breaking at the C–O σ-bonds at the subsequent steps. In the gas phase, the strand break in the pyrimidine diphosphates is dominated by the C3′–O3′ σ-bond cleavage pathway. Moreover, due to the low electron affinities of the purine diphosphates and the low vertical electron detachment energies of the corresponding radical anions, the bond breaks is unlikely to occur in the gas phase. However, the existence of the polarizable surroundings appreciably changes the scenarios. The comparatively high electron affinities of the 3′,5′-dGDP and the vertical detachment energy of 3′,5′-dGDP ·– ensure the formation of the electronically stable radical anion. Furthermore, the surrounding-solute interactions greatly reduce the activation barriers of the C–O bond cleavage, which facilitates the C5′–O5′ or C3′–O3′ bond ruptures at the guanosine site in DNA dominating the damages in aqueous solutions.