SIZE, SHAPP], AND HYDRATION OF VIRUSES 



39 



not necessary to proceed to the actual point of no sedimenta- 

 tion, for we can rewrite Eq. 2.13 in the form 





(2.23) 



and by plotting r]S versus p there appears a straight line of 

 descending slope with intercept on the density axis where 



8x10 



Fig. '2. 5. Product of sedimentation constant and viscosity for PR 8 influenza 

 plotted against solvent density as the concentration of serum albumin is in- 

 creased, thus raising the density. The intercept value for the density deter- 

 mines the hydrated partial specific volume. Data due to Sharp, Taylor, 

 McLean, Beard, and Beard (1944). 



VoP = 1- Such a line for PR-8 influenza virus, plotted from 

 data due to Sharp, Taylor, McLean, Beard, and Beard (1944), is 

 shown in Fig. 2.5. The additional solvent material is bovine 

 serum albumin, which is a relatively large molecule and so does 

 not introduce effects due to osmotic pressure. The intercept at a 



