Radiation 2006. In association with the Polymer Division, Royal Australian Chemical Institute. Incorporating the 21st AINSE Radiation Chemistry Conference and the 18th Radiation Biology Conference, conference handbook

Full text: The mechanism by which charges migrate in DNA continues to be an area of active fundamental research. We have used bibenzimidazole ligands, which bind tightly to the minor groove of DNA, to study the migration of electron deficient centers produced by abstraction of an electron from DNA bases, using the pulse radiolysis technique, in aqueous solution at ambient temperature. Formation of one-electron oxidized ligands by migration of the hole is monitored by time-resolved spectrophotometry, at various ligand/DNA base ratios. These studies build on our previous work with methylpromine and Hoechst 33342 to include a series of ligands which possess both electron donating and withdrawing substituents on the terminal benzene ring. By establishing redox equilibria with promethazine, which binds only weakly to DNA, it has been possible to measure the one-electron reduction potentials, E(1)R, of the DNA-bound ligand radicals for comparison with E(1)R values for the unbound ligands. In all cases E(1)R values are found to increase upon binding of the ligands to DNA. The extent of hole migration along DNA is found to correlate with the rate of electron transfer, a process which is activation energy-controlled