26 



C. L. SADRON 



- 20 - 



0.5 



Molarity of No CI 



M 1 1 Saturated 



Fig. 10. Values of M w from light scattering (AMJi , hen erythrocytes) as a func- 

 tion of the concentration of NaCl. Curves I and II are relative to solutions not treated 

 with chymotrypsin; they correspond to different treatments (precipitation at differ- 

 ent concentrations of NaCl) before being brought again into solution at the desired 

 NaCl concentration. Curve III is relative to the sample treated by the enzyme: M w 

 is then independent of the concentration of NaCl. 



of DNA (AMJi , hen erythrocytes) isolated from the nucleoprotein with- 

 out precipitation, by use of a modified Sevag's method 2 . The result of the 

 extraction is a solution of DNA in saturated NaCl. The value of M w meas- 

 ured on this solution before any treatment, is found to be 14 X 10 . 



3. It is possible to shift the value of M w from group II to group I by 

 different means: (a) By moderate heating at 75°C. of a salt solution of 

 DNA. 10e ' 21 A rapid drop of M w to one-half is observed and, afterward, the 

 ordinary process of degradation begins to appear ( Fig. 11). 



(b) By the action of a proteolytic enzyme such as chymotrypsin, as was 

 first shown by J. A. V. Butler and collaborators. 



Table III contains the values of M w for different samples of DNA be- 

 fore and after treatment by chymotrypsin taken from the work of J. Her- 

 mans' 106 and from our own experiments (samples AMJi and MAV). 



4. These experiments strongly suggest that particles in group II are 

 aggregates of stable particles of group I held together by a polypeptide or 

 protein residue. 2 



21 A. M. Freund, J. Pouyet, and C. Sadron, Compt. rend. acad. set. 246, 1306 (1957). 



22 J. A. V. Butler, D. H. Philipps, and K. V. Shooter, Arch. Biochem. Biophys. 71, 

 423 (1957). 



