Modeling proton-induced damage on 2-deoxy-D-ribose. Conformational analysis.

Modeling proton-induced damage in biological systems, in particular in DNA building blocks, is of major concern in studies on cancer proton therapy. This is indeed an extremely complex process and analysis of the mechanism at the molecular level is of crucial interest. Such collision reactions of protons on biological targets induce different reactions: excitation and ionization of the biomolecule, fragmentation of the ionized species, and charge transfer from the projectile ion toward the biomolecular target. In order to have an insight into such mechanisms, we have performed a theoretical approach of two of the most important steps, the fragmentation and the charge transfer processes. For that purpose, we have considered collision of protons with isolated 2-deoxy-D-ribose by means of ab-initio molecular dynamics and quantum chemistry molecular methods. The conformation of the sugar moiety has been analyzed and appears to induce important effects, in particular different fragmentation patterns have been pointed out with regard to the conformation, and significant variations of the charge transfer cross sections have been exhibited.