136 



THE PHYSICS OF VIRUSES 



southern bean mosaic virus are shown in Fig. 5A. The data 

 for TMV are not too satisfactory because of a marked tendency 

 for the virus to precipitate without addition of antibody after 

 the very heavy irradiations necessary. This was allowed for 



— — -.-__i__TMV Serology 



50r"~~-— — — \v ^ — ...^^^_^° SBMV Serology 



30 1 \ 1^?'^^!'!^°^'=^ 



SBMV Small Antigen 



SBMV Large Antigen 



[ 



SBMV 

 infectlvity 



-TMV 

 Infectivity 



10 20x10" 



Deuterons per square centimeter 



Fig. 5.4. Deuteron inactivation applied to the serological affinity of TMV 

 and SBMV. The loss of activity is small compared to the loss of infectivity. 

 The points for TMV fit best with a single antigen of surface area 1.5 X 10~" 

 cm^ whereas for SBMV, two antigens of area 3 X 10~^^ and 1.5 X lO"*'' cm'^ 

 are apparently present. 



as best could be done, and the points are plotted. For SBMV the 

 data are better and form two semilogarithmic lines which can 

 be analyzed into two effective sensitive sizes. The values found 

 are: 



