INACTIVATION OF VIRUSES 363 



reviewed by Elpiner, 1952). Added protein was found to protect against 

 inactivation. 



The seven coliphages of the T series were tested by Anderson et al. (1948). 

 The T2, T4, T5, and T6 phages, which are large and complex structures, 

 were found to be considerably more sensitive than the host cell, E. coli, strain 

 B, which, in turn, is more sensitive than the small phages Tl, T3, and T7. 

 Except in the case of T3, infectivity was lost exponentially. The T2, T4, and 

 T6 phages were changed into "ghosts"; i.e., the DNA was liberated into the 

 medium, leavmg empty heads with the tail still attached, as in the case of 

 osmotic shock (see Section III, D, 2). Exponential killing has also been ob- 

 served with staphylococcus phage (Kreuger et al., 1941). No careful study 

 seems to have been made of inactivation rates as function of temperature or 

 ionic environment, or in suspensions to which protective compounds, such as 

 proteins, were added. 



2. Surface Inactivation 



The surface tension at liquid/air or liquid/liquid interfaces is known to 

 denature protein. Thus, certain enzymes and toxins lose their biological 

 activity when shaken in dilute solutions; Langmuir and Waugh (1938) have 

 shown that protein which is "spread" on a liquid surface is denatured and 

 becomes insoluble. 



Surface inactivation of viruses has not received much attention, despite 

 the fact that rather drastic effects can be obtained. Campbell-Renton (1937) 

 observed that phage particles gradually lost infectivity on shaking or when 

 air was bubbled through the suspension. Grubb et al. (1947) observed a 

 similar effect on influenza virus, and McLimans (1947), studying equine 

 encephalitis virus, noted that the degree of inactivation resulting from agita- 

 tion depended strongly on the pH of the suspension. 



The only thorough study of surface inactivation of viruses was made by 

 Adams (1948) with the coliphages of the T-series. The important points 

 brought out by Adams are: (1) that aU seven phages are inactivated exponen- 

 tially (phage T4, which in most respects is very similar to the two other even- 

 niunbered phages, T2 and T6, is very resistant compared to the other two); 

 (2) the rate constants increase with temperature (observations between and 

 38°C.), and at pH values below about 5; (3) neutral proteins in small amounts 

 protect the phages against inactivation. Gelatin was found to be particu- 

 larly effective. 



Careful control experiments proved that inactivation occurs at the liquid/ 

 gas interfaces, and that it is independent of the gas phase used (air, Hg, or 

 CO 2) and of the surface properties of the container. 



The gelatin employed as protecting agent could be shown to act by com- 

 peting with the phage particles for the available surface. Thus, if a dilute 



