Water-derived Radicals and Radiation Sensitivity of Bacteriophage T7

Summary

The coliphage T7 was x-irradiated in the presence and absence of ethanol, an effective ·OH and ·H scavenger, in buffered suspensions saturated with N₂, N₂O and O₂. In 10⁻³ × dilution of the original suspending organic medium, ethanol was protective in all three experimental conditions. In 10⁻⁵ × dilution of the original medium (equivalent to contaminant free), ethanol is also protective in all three experiments and to a greater extent; but the relative order of radiation sensitivities changes. It is concluded that, when irradiated in pure suspension, T7 phage is inactivated partly by ·OH, and that ·H and e_aq⁻ play small, if any, roles as inactivating species. Additional observations were that the ‘O₂-protection’ phenomenon absent in purified suspension is observed in 10⁻³ M ethanol solutions; and that there is evidence that exhaustion of additives and, perhaps, build-up of products are responsible for the biphasic natures of some response lines. Also, there is evidence that radiation-induced sub-lethal damage to the phage particles may be important in determining sensitivity.