DEOXYPENTOSE NUCLEOPROTEINS 



45 



d. Dissociation and cleavage 



Before the discussion of the nucleic acids proper a few words 

 should be said about the cleavage and dissociation of the nucleo- 

 proteins, especially the nucleohistones and nucleoprotamines. The 

 cleaving effect of high electrolyte concentrations was first ob- 

 served by Bangle ; it is of great importance for the isolation of 

 reasonably intact deoxypentose nucleic acids. 



A systematic study in our laboratory of the behavior of 

 nucleoproteins towards electrolytes has opened a promising ap- 

 proach to the problem of the fractionation of deoxypentose 

 nucleic acids. When calf thymus nucleohistone is exposed to 

 increasing NaCl concentrations under conditions permitting the 

 removal of both undissociated nucleoprotein and liberated 

 protein, increasing quantities of sodium nucleate will be found 

 in solution^' ^^. Similar results are obtained when the time of 

 contact with the salt solution is varied rather than the concen- 

 tration of the latter^^. When the removal of the non-dissociated 

 portion is brought about in the presence of a denaturing phase, 



Fig. 2. Fractional dissociation of calf thymus nucleohistone (curve A) 

 and of wheat germ nucleoprotein (curve B) in the presence of a CHCI3 

 phase. The quantities of nucleic acid P (as percentage of P in the starting 

 material) extracted at the NaCl concentrations indicated on the abscissa 

 are plotted as the ordinate. 



References p. 60 



