SINGLE-STRAND BREAKS IN DOUBLE-STRANDED DNA IRRADIATED IN ANOXIC SOLUTION - CONTRIBUTION OF TERT-BUTANOL RADICALS

Yields of single-strand breaks induced by Co-60 gamma or pulse irradia tion in double-stranded calf thymus DNA have been measured in N2O-satu rated aqueous solution as a function of the concentration of tert-buta nol. The yields were found to be dependent on dose rate. The experimen tal data were analyzed using a theoretical model based on non-homogene ous scavenging kinetics. It is concluded from this analysis that after Co-60 gamma irradiation in the absence of oxygen, aside from breaks c aused by hydroxyl radicals, additional breaks occur which are initiate d by hydrogen atoms and secondary radicals of tert-butanol. The effici ency of hydrogen atoms in causing single-strand breaks in double-stran ded calf thymus DNA was determined to be 2.3%, while the rate constant for the reaction of tert-butanol radicals with DNA and their efficien cy in causing single-strand breaks was determined to be 4.1 x 10(3) dm (3) mol(-1) s(-1) and 2%, respectively. (C) 1996 bg Radiation Research Society.