EFFECT OF RADIATION ON PHAGE PARTICLES 



77 



of its DNA into the bacterial host cells, whereas a similar popula- 

 tion inactivated by ultraviolet light to the same extent is still 

 able to do so (Hershey, Garen, Fraser, and Hudis, 1954). It 

 would appear that T2 phage is a rather complex organism, which 

 can be functionally dissected by means of radiations. 



The indirect inactivation of viruses by X-irradiation in the 

 absence of protective substances is in reality an inactivation by 

 chemical agents generated by the radiant energy. These chemi- 

 cal agents, as stated above, are of two kinds : the short-lived free 

 radicals and the long-lived "peroxides." Because of the brief 

 life of the free radicals, their range of action is short, and only 

 those radicals produced in the water of hydration of the phage 

 particles can have an appreciable probability of causing physio- 

 logical damage. The properties of phage particles damaged by 

 the short-lived radicals (indirect effect) can be studied by ir- 



TABLE V 

 The Properties of Bacteriophage T2 Inactivated by X-rays and Ultraviolet 



Light" 



From J. D. Watson, J. BacterioL, 63, 473 (1952), with permission. 



