THERMAL INACTIVATION OF VIRUSES 



117 



that the changing of three ionically bonded groups is necessary 

 for the unfolding, and hence denaturation, of pepsin. The T-1 

 inactivation-reaction constant varies more slowly, more nearly 

 as the first power, and so perhaps corresponds to the changing 

 of a single ionically bonded group. Much better data is really 

 needed for this sort of analysis. 



(£20- 



FiG. 4.6. Percent survival of T-1 phage after exposure to different pH values 

 for 24 hr. 



Pressure Effects on Thermal Inactivation 



A systematic study of the effects of pressure on micro- 

 organisms has been made by Johnson. By way of illustration of a 

 case which behaves regularly and is susceptible of analysis in 

 terms of the Eyring theory we show, in Fig. 4.7, data taken by 

 Foster, Johnson, and Miller (1949) on T-5. The inactivation in 

 the presence of a small concentration of Mg++ ions obeys first- 

 order kinetics, and it can be seen that as the pressure is increased 

 the rate of inactivation is lessened. This corresponds to a posi- 

 tive change, or an increase in volume, to reach the activated 

 state. The value of AF^ found is 113 cmVmole, or 1.87 X 10~22 

 cm^/ virus particle. The total volume of the virus is about 



