The effect of 1,4-diazabicyclo 2.2.2 octane on the radiosensitivity of bacteria

Hydroxyl radicals (OH) are scavenged by 1,4-diazabicyclo[2.2.2]octane (DABCO) at a diffusion-controlled rate of 1.25 +- 0.1 x 109 M-1s-1. Unlike other efficient OH scavengers which exhibit protection of bacteria against irradiation both in oxic and hypoxic conditions, DABCO has been shown to protect Serratia marcescens and various strains of Escherichia coli only in oxic conditions. DABCO appears to eliminate a component of the sensitization afforded by oxygen in all strains of E. coli tested. The level of this protection increased from approximately 15% in the wild type AB 1157 to approximately 100% in the recA uvrA mutant AB 2480. It is suggested that DABCO protects against lethal events that can occur on macromolecules other than DNA such as the cell membrane. Results with added glycerol, as well as work in D20 solution, indicate that DABCO is more likely to be acting by scavenging radicals rather than by quenching 102. If 102 is a component of the sensitization afforded by oxygen, then it is unlikely to be formed in a hydrophilic environment in the cell. (author)