14] TOBACCO MOSAIC VIRUS 253 



degraded by acid (+SDS) require correction for the light scattering by the 

 intact virus. Comparison of the spectra of virus which was degraded by 

 SDS either in an acid solution or at pH 8 need no such correction. In both 

 cases a shift in the opposite direction from that given by the protein alone 

 was obtained, the acid solution giving the positive difference spectrum with 

 a maximum about 290 m/x. However, virus nucleic acid alone was found to 

 show a similar behavior, and its presence makes such reaction mixture too 

 complex to attempt any interpretation of the spectral changes. 



ÛÛ 



Q5 - 



,11% Prettin 



^ 



f— 



Protein 



I \ difference \ 



260 



300 260 



m \L 



300 



Fig. 1. Ultraviolet absorption of TMV-protein in 67% acetic acid, HCl (pH 2-2) and 

 in water at neutrality. 



NATURE OF INTER-UNIT BONDS 



Previous studies by Harrington, Levy and Schachman^* have indicated that 

 OH~ ions are rapidly consumed when TMV is degraded in weakly alkaline 

 solutions. These studies have now been extended to other experimental con- 

 ditions leading to the splitting of the virus. One type of experiment is based 

 on the new finding that the virus is degraded rapidly at room temperature 

 in 1% SDS adjusted to pH 3-5 with dilute HCl. (Nucleic acid of similar or 

 slightly higher infectiousness as the standard preparations can be isolated 

 from such reaction mixtures, as well as nucleic acid-free, though denatured, 



