1 62 PHYSIOLOGY OF NUTRITION 



The simple proteins just considered act as reserve materials. The complex 

 proteins, on the other hand, which are contained in protoplasm, sperms and egg 

 cells, are differently constructed. Here belong nucleo-proteins, histones and 

 protamins. Nucleo-proteins are combinations of simple proteins with other 

 substances, they split up into simple proteins and nucleins. Nucleins are soluble 

 in water to a considerable degree; they often fail to exhibit either the biuret or the 

 Millon reaction. They are acid, and are not decomposed by gastric juice. 

 Treatment with alkalies produces a splitting up of nucleins into simple proteins 1 

 and nucleic acids. These latter are rich in phosphorus and have very large 

 molecular weights. The simplest formula of the nucleic acid derived from yeast 

 cells is C40H59N14O22-2P2O6; another nucleic acid, from salmon sperm, maybe 

 expressed in simplest form as C40H56N14O16-2P2O5. The hydrolysis of nucleic 

 acids gives phosphoric acid, pyrimidin and purin derivatives, pentoses and 

 levulinic acid. Among these decomposition products, phosphoric acid and 

 the purin bases — xanthin, hypoxanthin, guanin and adenin — are especially 

 noteworthy. 



For an understanding of the physiological role of the nucleo-proteins quan- 

 titative determinations of these compounds are requisite, but, unfortunately, 

 no exact methods are available for the determination of nucleins. Treatment of 

 nucleo-proteins with gastric juice leaves an insoluble residue which contains 

 nitrogen and phosphorus. From the amount of either one of these two elements 

 can be approximated the amount of nucleo-proteins. This method is useful only 

 in qualitative studies, however, since different nucleo-proteins are differently 

 affected bv gastric juice. The determination of the purine bases contained in 

 nucleo-proteins is complex and tedious. The method of Plimmer 2 has hitherto 

 proved to be the best for this purpose. After the nucleo-proteins have been 

 treated for from twenty-four to forty-eight hours with a i-per cent, solution 

 of sodium hydroxide, at 37°C, the nucleic acid remains unchanged while the 

 entire phosphorus content of other organic compounds is split off in the form of 

 phosphoric acid. The determination of the remaining phosphorus thus gives 

 a starting point for the estimation of the nucleic acids. In the tips of etiolated 

 stems of Viciafaba, for example, 57 per cent, of the total protein-phosphorus is 

 present in nucleic acids and 37 per cent, is present in the indigestible protein 

 residue. 3 



Histones and protamins have hitherto not been found in plants. These 

 compounds can best be isolated from fish sperm. It thus seems legitimate to 

 suppose that they may also be present in plant sperms. The decomposition 

 products of the histones and protamins are mainly diamino acids. Among the 

 protamins arginin is most frequently encountered (from 58 to 84 per cent.). 



1 Altmann, Richard, Ueber Nucle'insauren. Arch. Anat. Physiol. (Physiol. Abt.) 1889: 524-536. 

 1889. 



2 Plimmer, R. H. Aders, The proteins of egg yolk. Jour. Chem. Soc. London (Transactions) 93" : 

 1500-1506. 1908. Plimmer, R. H. Aders, and Scott, F. H., A reaction distinguishing phosphoprotein 

 from nucleoprotein and the distribution of phosphoproteins in tissues. Ibid. 93 : 1699-1721. 1908. 

 Abstracted in Biochem. Centralbl. 8s 7// : 109. 1909. 



3 Zaleski, W., Ueber den Umsatz des Nucleoproteid-phosphors in den Pflanzen. Ber. Deutsch. Bot. 

 Ges. 27: 202-210. 1909. 



