30 



C. L. SADRON 



0.5 



Molarity of NaCI 



Fig. 14. The value of M/L depends on the concentrations of NaCI for samples 

 not having been treated previously by chymotrypsin. M/L, however, is the same in 

 1 molar NaCI solutions and is practically equal to the theoretical value (200 per A); 

 • = MAV and • = AMJ, . 



of 204 corresponding to the Watson-Crick model. However, in the case of 

 CV71 (Fig. 13), the slope of the asymptote gives the much larger value 

 M/L = 1.400 per A. 



4. It is evident from Figs. 12 and 13 that the ordinate of the intercept 

 of the asymptote with the c/K axis is negative. Hence, the particle of 

 DNA cannot be a single rod, an inference confirmed by the value of the in- 

 trinsic viscosity of the solution. On the contrary, its configuration can be 

 the one discussed in Section II,2,a,l. 



3. Hydrodynamical Methods 



Intensive work has been done in the field of the application of hydro- 

 dynamical methods to DNA solutions. Till now, only the values of S and 

 [tj] have been systematically used and discussed. No values of the Brownian 

 diffusion constant A have yet been published owing to the difficulty of 

 experiments at the large dilutions that are required for such extrapolation. 



We have already given some of the conclusions that can be drawn from 

 the consideration of [tj]. We shall now briefly discuss the results of the sedi- 

 mentation experiments and, afterward, give a brief survey of the conclu- 

 sions that have been drawn from the comparison of $ and [v] values for 

 different samples. 



