DEOXYPENTOSE NUCLEOPROTEINS 43 



biological test procedures have been found. The nucleoproteins 

 of calf thymus and of fish sperm remain the only readily acces- 

 sible deoxynucleoproteins, and most of our knowledge is derived 

 from the study of these compounds. Nucleohistone is soluble at 

 a very low ionic strength. As the electrolyte concentration in- 

 creases, the solubility first drops rapidly, reaching a minimum 

 in isotonic solutions, and then rises gradually. Though variations 

 are found, freshly prepared nucleohistone is, in general, soluble 

 in NaCl solutions stronger than 0.7 or 0.8 M. Small amounts of 

 phosphorylated impurities can be extracted from nucleohistone 

 by 0.02-0.15 M NaCl solutions; but they usually lack the typical 

 nucleic acid spectrum (see Table 16). The solubility properties 

 of nucleoprotamine seem to be essentially similar. 



The absorption spectrum in the ultraviolet of a nucleoprotein 

 is, in general, identical with that of its nucleic acid moiety (maxi- 

 mum around 260 mu). No depression of the extinction coef- 

 ficient of the nucleic acid component is noticeable, nor does the 

 extent of extinction change materially under conditions of ahnost 

 complete dissociation (compare Table 16). This is of interest, 

 since the extinction of a nucleoprotein could have been expected 

 to be less than that of the free nucleic acid, if the purines and 

 pyrimidines of the latter were involved in the architecture of the 

 intact conjugated protein in such a manner as to bring about the 

 suppression of some of the chromophores^^. 



The nucleic acid content of different nucleoproteins varies 

 from about 35 to 60% of the dry weight. In most nucleohistone 

 preparations it is around 50%. In trout and herring nucleopro- 

 tamines a phosphorus to arginine ratio of 1 has been found^^. 



Although there exists considerable evidence that deoxypentose 

 nucleoproteins, or at any rate thenucleoprotamines and nucleo- 

 histones, occur in strong salt solutions in a largely dissociated 

 state, in which a far-reaching separation between nucleic acid 

 and protein has taken place, it would probably be wrong to 

 regard such solutions as representing no more than a mixture of 

 these components. 



References p. 60 



