A model for oxygen-dependent damage from OH radicals in irradiated suspensions of bacterial spores.

When suspensions of bacterial spores are irradiated, damage from hydroxyl radicals (·OH) requires the presence of oxygen within the range 10-6 to 10-4M. If the O2 concentration is outside this range, ·OH removal by an added scavenger does not protect. Data are presented to show that the biologically important concentration of OH radicals is unaffected by the [O2] present at the time of irradition; thus, it is the specific [O2] that determines how much damage is caused by a constant concentration of ·OH. A model is proposed to provide a mechanistic basis for this complex relationship between damage from O2 and damage from OH radicals in irradiated spores.