Irradiation of biomolecular clusters: model systems for the study of radiation damage in living material

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Abstract from the Case for Support document (section 2):This research project is centred upon the parallel construction, development, and use of two complimentary experimental systems to study processes induced by ionisation in irradiated biomolecular systems. The principle objective is to compare the effects of irradiating a specific target molecule within a cluster with the case of the molecule in isolation. In addition to their fundamental interest in molecular and statistical physics, these experiments will help to bridge the complexity gap between the current understanding of radiation effects in the gas phase and in an absorbing biological medium. This represents a major current research challenge for physicists, chemists, and biologists, with important applications in quantifying the effects of exposure to different types of radiation during cancer therapies.The first experimental system is a versatile and mobile source for hydrated DNA base clusters, proposed for construction at the Open University. During the three year programme, this source will be used to carry out 2- and 1-photon electronic excitation experiments to probe the effects of solvated water molecules upon the valence and Rydberg energy states of key biomolecules and the associated dissociation pathways. The second experimental system, located at the Nuclear Physics Institute of Lyon, will enable a detailed study to be carried out on collisions between fast protons and mass-selected cluster ions comprising DNA bases and water molecules. The major technical challenge in this part of the project is the development of a multi-coincidence detection system for the characterisation of ionisation showers, electron emission, and free radical production induced by proton-cluster collisions. These inter-molecular processes are believed to play important roles in radiation damage to living material.