DEOXYPENTOSE NUCLEOPROTEINS 



47 



Fig. 3. In general, globin nucleates appear to undergo dissociation 

 more readily than histone nucleates. The relative proportions of 

 histone and nucleic acid and the state of polymerization of the 

 latter are of great importance for the properties of the artifacts 

 (Fig. 4). It can be seen that the ease of dissociation of the com- 

 plexes increases with the relative amount of nucleic acid present 

 and decreases very markedly with the viscosity of the nucleic 

 acid. It may be mentioned that under appropriate conditions 

 nucleohistone is rendered soluble at a low ionic strength by the 

 addition of large amounts of degraded deoxyribonucleic acid^*^. 



0.5 0.8 1.0 2.6 0.5 



Af NaCI 



0.8 1.0 2.6 



Fig. 4. Successive extraction with NaCl solutions, in the presence of a 

 CHCI3 phase, of artificial histone complexes with calf thymus deoxy- 

 ribonucleic acid. In (a) the amount of histone varied, in (b) the degree of 

 polymerization of the nucleic acid. The weight ratio of histone to nucleic 

 acid P was 23 (curve 1), 18 (curve 2), 14 (curve 3), 4.5 (curve 4), 17 

 (curves 5-7). The viscosities, as r]^^ (P), i.e., the specific viscosity divided 

 by the molarity of the solution with respect to P, were: curve 5, 1000 

 (intact preparation); curve 6, 420 (0.1% solution heated at 75° for 5 min); 

 curve 7, 240 (0.1% solution heated at 75° for 40 min). Co-ordinates as 

 in Fig. 2. (Taken from Crampton et ciI.^k) 



The cationic species used also influences the progress of the dis- 

 sociation. The remarkable effect of an admixture of as little as 

 0.06 M MgClo to the NaCl solutions is shown in Fig. 5. When 



References p. 60 



