Radiosensitization of Bacterial Spores by Ketonic Agents of Differing Electron-affinities

SummaryThree ketonic agents, acetone, acetophenone and p-nitroacetophenone, sensitize spores of Bacillus megaterium in anoxic buffer suspension (pH 7·0) to the lethal effects of gamma-rays. For all three agents, increases in concentration cause increases in the extent of sensitization to a common maximal level and, for acetone and p-nitroacetophenone, increases beyond that responsible for the maximal effect give decreases in sensitization. The maximal increase represents about 40 per cent of the oxygen effect. The sensitizing actions of agents and oxygen are not additive. A correlation between the effectiveness of agents as sensitizers on a molar basis and their relative electron-affinities is seen, substantiating the proposal that the radiation-induced electron is involved in radiosensitization by ketonic agents.