Ion interaction with biomolecular systems and the effect of the environment

To fully understand the mechanisms of radiation damage in living tissues, a detailed knowledge of the processes occurring at the molecular level is needed. In the gas phase, most of the investigations concerning the ionization and fragmentation of biologically relevant molecular systems are performed with isolated molecules. The importance of such studies is limited to the intrinsic properties of these molecules because of the lack of a chemical environment. To probe the effect of such an environment on the behavior of small biomolecules under irradiation, the molecules (α-amino acids, adenine) were embedded into clusters. The present results, obtained with multiply charged ions, clearly indicate the protective role of the clusters since the total fragmentation yield is reduced for all systems. The surrounding molecules allow for a redistribution of the excess energy and of the charge within the cluster. In the case of adenine clusters, a new fragmentation channel is identified. Moreover, for hydrated adenine clusters, low-energy ion induced chemical reactions are observed, namely the proton transfer from the water cluster to the adenine molecule.