TIKVAH ALPER 



radiation in suspensions of pH about 9, 7 and 5, the inactivation yield was 

 o-reatest in the most alkaUne suspension, and least in the most acid. Since 

 reaction (4) occurs only in oxygenated suspensions, it is in these that pH 

 dependence should occur, if reaction with the Og" radical ion is responsible 

 for inactivation in the presence of oxygen. The pairs of curves presented 

 in Figure 4 show that there was more marked pH dependence under oxygena- 

 tion than with hydrogen bubbling. An explanation must, however, be 

 sought for the fact that some pH dependence was found with no oxygen 

 present, and it seems that this may lie in the reaction 



H + H+ 



H, 



(6) 



which was originally postulated by Weiss i" to account for pH dependence 

 of the ferrous-ferric system in deaerated solutions. This pH dependent 



.§ 





TO 

 0-5 



0-1 



005 



0-07 r 



0-005 



0001 







5 

 pH 8-92 



70 



5 



10 



5 

 pH7-05 pH4-83 



Figure 4. Effect o/pH on survival curves of SI 3 {Abscissa: minutes' irradiation at ISOOradjmin) 



75 



reaction would act as a scavenger mechanism for H radicals. It appears 

 that Hg+is fairly stable in aqueous solutionis. It may be eliminated by 

 reaction with a reducing substance, in a reaction of the type 



R- + H2+ ^ R + H2 t , 



or possibly by reactions which lead ultimately to water and gas molecules. 

 From the experiments which have been described, it can be seen that 

 bacteriophage in dilute suspensions can be vised as an indicator for radiation 

 chemical reactions, and, since phage is inactivated by reduction, it is useful 

 as a complementary system to those in which oxidations are studied, which 

 at present are in the majority. It is worth remembering, however, that 

 phage is a self-reproducing entity, and if the effectiveness of radiation is so 

 strongly influenced by factors such as gas treatment and hydrogen ion con- 

 centration, it seems reasonable to suppose that these factors operate also in 

 the living cell. 



43 



