Modification of the Radiation Sensitivity of Bacteriophage T7 by O₂and N₂O

Abstract

SummaryThe radiation sensitivity of T7 suspensions is strongly dependent on chemical additives. We have compared the response to x-irradiation in the presence of 100 per cent N2, 100 per cent O2 (eaq− and H· scavenger) and 100 per cent N2O an eaq−(scavenger that increases ·OH concentration), in the presence of a 10−2 dilution of medium and a 10−5 dilution (equivalent to medium free).Survival curves are frequently multicomponent, with sharp break points, and radiation sensitivity must be measured at varying dosage levels. In the 10−3 dilution, the order of radiation sensitivity at low doses is, kL = N2 > N2O > O2, and at high doses, kH = O2 ≅ N2O > N2. In the 10−5 dilution, or medium free, the order at low doses is kL = N2O > N2 ≅ O2 with kH difficult to define.It is concluded: (1) the OH radical is an important damaging species for T7, and (2) ‘O2 protection’ is an experimental artifact associated with impurities in the suspension.