NUCLEOPROTEINS. 171 



b. Nucleoproteins. 



By this name we designate those compound proteins which yield 

 protein and nucleic acid on cleavage. The nucleoproteins seem to be 

 widely diffused in the animal body. They occur chiefly in the cell-nuclei, 

 but they also often occur in the protoplasm. They may pass into the 

 animal fluids on the destruction of the cells, hence nucleoproteins have 

 also been found in blood serum and other fluids. 



The nucleoproteins may be considered as combinations of a protein 

 with a side-chain, which KOSSEL calls the prosthetic group. This side 

 chain, which contains the phosphorus, may be split off as nucleic acid on 

 treatment with alkali. The protein may be of different kinds. In cer- 

 tain cases this is histone, and the combinations between nucleic acid and 

 protamines are also sometimes classified as nucleoproteins. The com- 

 bination between protamine and nucleic acid is, it seems, a salt-like 

 combination, and entirely different from the combination of the proteins 

 with nucleic acid in the nucleoproteins. The following facts, given in 

 connection with the nucleoproteins, do not apply to the nucleoprot amines. 

 The nucleoproteins differ not only according to the protein component 

 they contain, but also as to the nucleic acids, which vary among them- 

 selves. There are essentially different nucleic acids, some among which 

 contain a pentose carbohydrate while others contain a hexose carbo- 

 hydrate. The nucleic acids also differ in regard to the amount of purine 

 and pyrimidine bases they contain (see below) . 



The native nucleoproteins contain a variable, but not a high percentage 

 of phosphorus, which in most of the nucleoproteins investigated, ranges 

 between 0.5 and 1.6 per cent. They also regularly contain iron, and in 

 Octopodes HENZE l has observed an iron-free nucleoprotein with 0.96 

 per cent copper. The nucleoproteins behave like weak acids, especially 

 those having considerable protein in the molecule. They therefore 

 give the ordinary protein reactions and behave in this regard like the 

 proteins. The nucleoproteins prepared from organs rich in cell nuclei 

 seem to be characterized by containing more phosphorus and having a 

 stronger acid character. All nucleoproteins are bodies that are insoluble 

 in water, but whose alkali combination is soluble in water. From such 

 a solution the nucleoprotein can be precipitated by acetic acid, and the 

 precipitate dissolves with more or less difficulty and in some cases not 

 at all, in an excess of the acid. It dissolves, on the contrary, in very dilute 

 hydrochloric acid. In this respect nucleoproteins are similar to the nucleo- 

 albumins and the mucin substances, but differ from these two groups in 

 that they yield purine bases on hydrolysis. According to PLIMMER 



1 Zeitschr. f. physiol. Chem., 55. 



