Radiation damage on biomolecular systems: Dynamics of ion induced collision processes

The collision of carbon ions on DNA and RNA bases thymine, uracil and 5-halouracil is investigated with regard to the action of radiations on the biological medium. The charge transfer process is studied theoretically in a wide collision range by means of ab initio quantum chemistry molecular methods. A strong influence of the electronic structure and charge of the Cq+ projectile may be observed correlated to previous experimental studies on the ionization and fragmentation processes. The charge transfer appears markedly anisotropic in the whole energy domain, and interesting specific features may be pointed out at low energies. For 5-halouracil targets, both electronic and steric effects drive a lowering of the cross sections, inducing an enhancement of the complementary fragmentation process in good agreement with the radio sensitivity widely recognized for such biomolecules.