THE SIZE AND SHAPE OP VIRUSES 



25 



CONCENTRATION IN G/iOOCC, 



FIGURE 19 - SPECIFIC VISCOSITY 0? TOBACCO 

 MOSAIC VIRUS PLOTTED AS A 1<'UNCTI0N OP VIRUS 

 CONCENTRATION. 



It was observed that the slope of this second linear relationship was almost 

 the SELne as that of the first. This observation suggested that the dependence 

 of the sedimentation rate of tobacco mosaic virus upon concentration was the 

 same sort of phenomenon as the dependence of the solution viscosity upon con- 

 centration and that, therefore, if one corrected the sedimentation rate of the 

 virus for the viscosity of the virus solution, one would obtain a value which 

 is essentially independent of virus concentration. This is the equivalent of 

 assuming that the virus particle sediments through a virus solution rather than 

 through the solvent. When the sedimentation rate of the virus is corrected for 

 the viscosity of the virus solution, a value for the sedimentation rate is ob- 

 tained which is essentially independent of virus concentration. This result is 

 Illustrated by the data in Table IV. 



TABLE IV 



THE SEDIMENTATION CONSTANTS CALCULATED IN THE USUAL MANNER AND THOSE 

 CORRECTED FOR SOLUTION VISCOSITY OF TOBACCO MOSAIC AT VARIOUS CONCENTRATIONS 



20 



Concentration 

 (g./lOO cc. J 



20 

 (Svedberg units ) 



0.05 

 .102 

 .20 

 .20 

 .20 

 .20 

 .204 

 .408 

 .816 

 1.02 

 1.43 



1.84 



181 

 180 



173 



170 

 170 

 170 



Hi 

 153 



146 



134 



131 

 125 



184 



185 

 183 

 180 

 180 

 180 

 183 

 188 

 189 

 189 

 188 

 184 

 191 



A review of the literature showed that the dependence of sedimentation rate 

 upon concentration for a great variety of materials was reduced substantially 

 when correction was made for the actual viscosity of the solution. These re- 

 sults tempt one to formulate as a working hypothesis that the displacement 



