5^ THE PHYSICS OB^ VIRUSES 



Since the wart tissues were stored at 2-5° C for several years, 

 it is obvious that this is a stable virus. 



Sedimentation measurements gave a value of S2Q = 278 S. 

 Diffusion measurements by the refractometric method gave D^o 

 as 5.85 X 10~^ cm^/sec, and the anhydrous partial specific 

 volume was found to be 0.754. These, when put together, give 

 the particle mass as 7.81 X 10~^' gm and the particle molecular 

 weight as 47 X 10«. 



Putting together the sedimentation and diffusion data to 

 calculate f /o, the value obtained is 1.486, which is rather high. 

 If an unhydrated virus is assumed, the axial ratio deduced is 

 9 for a ])rolate ellipsoid and 11 for an oblate ellipsoid. However, 

 there is no reason to assume an unhydrated virus, and if, instead, 

 a spherical virus is assumed, the application of Eq. 2.18 gives 

 1.73 for r. 



In addition to sedimentation and diffusion measurements, the 

 viscosity at various concentrations was observed. The data are 

 very good and show a straight line with a slope of 0.063 for 

 17/170 — 1 plotted against gram-percent concentration of virus. 

 The value of V/m is, accordingly, 2.52, and the resulting hydra- 

 tion is 1.77 gm water per gram dry virus. This agrees well with 

 the value above. Subsequent observation of the virus in the 

 electron microscope showed a spherical particle of diameter 

 420 A, which fits the molecular weight of 47 X 10*^ reasonably 

 well, if the partial specific volume of the dry virus as measured 

 is used. 



The conclusion seems to be, therefore, that, in solution, rabbit 

 j)apilloma virus is considerably hydrated but is still spherical. 



Lauffer and Stanley (1944) describe electron micrographs, 

 sedimentation, specific volume, buoyancy, and viscosity meas- 

 urements on PR8 influenza virus. The electron micrographs give 

 a diameter of 1,150 A and an apparently spherical shape. The 

 specific volume of the dry virus was 0.79. The density of sucrose 

 for flotation was 1.18, so that the wet density is 1.18. The 

 viscosity measurements did not show a linear increase in relative 

 viscosity with virus concentration, a fact probably due to the 

 presence of non virus components in the preparation. From these 



