BACTERIOPHAGE INACTIVATION UNDER VARYING CONDITIONS OF IRRADIATION 



agents (hydrogen peroxide and ascorbic acid). I have called this 

 ' part-inactivation ' of the phage. 

 (3) The phage may be rendered inactive immediately by free radicals. 



To some extent it has been possible to study these mechanisms separately. 

 The effect of irradiated suspending medium, i.e. of radiation-produced 

 HgOg, was studied by introducing non-irradiated phage into irradiated 

 buffer solution. Part-inactivation was studied by comparing the suscepti- 

 bility of irradiated and non-irradiated phage to radiation-formed hydrogen 

 peroxide, commercial hydrogen peroxide, or ascorbic acid. The immediate 

 effects of radical action could to some extent be separated from the other 

 two mechanisms by irradiating at a high dose rate, so that radiation was 



Figure 1 



completed within a time which was short, compared with that required for 

 the action of formed hydrogen peroxide. It was necessary, in these experi- 

 ments, to sample as quickly as possible after the end of each period of irradia- 

 tion. The immediate effects of free radicals on phage were studied in this 

 way, in varying conditions of gas treatment and of hydrogen ion 

 concentration. 



The techniques followed in the phage experiments were those used by 

 Dr. Ebert^ in examining formation of hydrogen peroxide. Information 

 was almost always derived by plotting survival curves, which involved 

 taking several samples of the phage during the course of each irradiation. 

 Such curves can of course be regarded as reciprocal yield-dose curves, since 

 survivors are counted instead of inactivated particles. It was reported 

 previously^' ''• ^ that the immediate indirect effects of radiation on phage 

 appear to be reductions. This was fully confirmed l^y irradiating phage in 



40 



