Radiosensitization and radioprotection of E. coli by thiourea in nitrous oxide saturated suspensions

N2O did not modify the radiosensitivity of E. coli BH and H/r-30 strains as to colony-forming ability and DNA single-strand breaks. In N2O-saturated suspensions of E. coli, thiourea and thiosemicarbasite sensitized at low concentrations, while cysteamine and cysteine protected at all concentrations. Protection by thiourea in N2O-saturated suspensions was observed only in the frozen state. These results suggest that the conversion of e-aq to OH radicals may be responsible for sensitization and this sensitization is probably due to the thiourea and thiosemicarbasite radicals produced extracellularly.