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Direct effects of ionizing radiation on biological molecular systems

Jean-Christophe Poully

To understand the effects of ionizing radiation on biological molecular systems, it is crucial to control the experimental conditions, especially in terms of temperature and phase. Irradiation of a solution at room temperature mainly leads to the formation of free radicals from the solvent. These species then chemically react with biomolecules, leading to secondary processes such as bond cleavage, cross-linking and generally quenching of biological activity. All these indirect effects require diffusion of free radicals from the solvent to the biomolecule, which occurs at rates that decrease by several orders of magnitude from room to cryogenic temperatures. To study direct effects, frozen, lyophilized, crystallized, dried but also isolated molecules can be used. These last years, at the CIMAP lab, we have investigated the structure and stability of isolated collagen mimetic peptides and antibiotic/receptor non-covalent complexes of controlled mass and stoichiometry, by means of home-made experimental set-ups and through international collaborations.