ELUCIDATION OF PRIMARY RADIATION-DAMAGE IN DNA THROUGH APPLICATION OFAB-INITIO MOLECULAR-ORBITAL THEORY

This review summarizes the results of recent ab initio molecular orbit al calculations performed on DNA constituents that attempt to further our understanding of the radiation-induced damage to DNA. The results reviewed include calculations performed on the four individual DNA bas es, the base pairs in gas phase and modelled aqueous phase, the deoxyr ibose moiety, and a portion of the sugar-phosphate backbone. The empha sis is on the electron affinities and ionization potentials of the rad ical species calculated under various conditions (i.e. gas phase, aque ous phase, proton transfer, base stacking), as it has been shown that the initial ion radical distribution is largely a function of these tw o properties. Theoretical studies of the electronic excited states of the individual bases and radioprotection of the biomolecule by Various thiol compounds are also reviewed. Finally, a summary is provided to allow for further elaboration of the current model for radiation damag e to DNA and to show the present advantages and limitations of ab init io theory in the investigation of such processes.