Free electron attachment to hydrated biomolecules

In recent years there has been a significant interest in processes induced by low energy electrons in biological systems, especially in relation to DNA damage. Ionizing radiation releases a large number of secondary electrons in cells. This secondary species with initial kinetic energies of up to few tens of eV interacts further inelastically with building blocks of cells before they enter a (pre-)hydrated stage. It was shown that low energy electrons can induce single and double strand breaks in a film of plasmid DNA upon dissociative electron attachment (DEA). Subsequently a large number of studies on electron attachment to various simple biomolecules (e.g. DNA bases, sugars, amino acids) in the gas phase have been carried out. It was also shown, that electron attachment to biomolecules embedded in cold helium droplets led to significant changes in the molecular fragmentation pattern upon solvation. Thus the environment may cause strong modification of the DEA process. Consequently, it is feasible to use clusters to surround biomolecules by a realistic environment and because the main component of living cells is water, it is important to study also molecule-water clusters. In this project we will investigate how the presence of such water environment will modify the electron attachment to a biomolecule and alter the dissociation process. Free electron attachment experiments with hydrated biomolecules in the gas phase have not been carried so far to our best knowledge. It is worth mentioning that water is a polar matrix compared to the inert helium droplet matrix used before to study solvation effects. There are few important aspects to be considered, like buffering of the fragmentation process, shifts of resonance energies and intracluster secondary reactions of DEA water products with the biomolecule. The latter is also related to indirect damage of DNA in cells, where water radiolysis products attack DNA. In order to study the influence of a water matrix on DEA to a biomolecule we propose the development of a new water cluster source with the subsequent combination to available mass spectrometers in the institute. Since hydrated biomolecular clusters are complex systems, we will study simple biomolecules such as nucleobases and amino acids. These molecules have been extensively studied in the gas phase and also already in helium droplets which allows a detailed analysis of the effect of hydration upon DEA.