Radiation-induced damage in E. coli B: The effect of superoxide radicals and molecular oxygen. Progress report, December 1, 1978--November 30, 1979

The roles of superoxide radicals and of molecular oxygen in the radiodamage of E. coli B suspended in dilute phosphate buffer were studied. The presence of high concentrations of polyethylene glycol in the γ-irradiated cell suspensions, had no effect on bacterial radiosensitivity. This indicates that the damage was primarily endogenous, i.e. originated intracellularly. Saturation of the cell suspensions with N2O doubled the radiosensitivity, thus indicating that OH radicals are responsible for the majority of the damage (indirect radiation effect). The presence of oxygen either in the absence or presence of N2O brought about roughly a three-fold increase in the radiosensitivity. Since in the presence of N2O all e-/sub aq/ are scavenged by the nitrous oxide rather than by oxygen, this shows that superoxide radicals play no role in the bacterial radiodamage. Our results substantiate the attribution of the oxygen effect to a direct interaction of O2 with the hydroxyl-radical-damaged sites on vital biomolecules, and exclude any significant contribution of e-/sub aq/ and superoxide radicals to the cellular radiodamage