124 



THE PROTEIN SUBSTANCES. 



1 Cited from Abderhalden's Lehrbuch. d. physiol Chem., 1909. 



2 Kossel and Kutscher, Zeitschr. f. physiol. Chem., 31. 



3 K. B. Hofmann and F. Pregl, ibid., 52. 



4 E. von Knaffl-Lenz, ibid., 52. 

 5 E. Fischer, ibid., 53. 



8 Calculated as arginine. 



7 This figure is somewhat uncertain. 



C. Cleavcage Products of Simple Proteins. 



On the hydrolysis of proteins by the aid of acids, alkalies or by 

 enzymes, cleavage products are obtained which represent various inter- 

 mediary steps between the native proteins on one side and the simple 

 cleavage products, the amino-acids, on the other side. Among these 

 products we have for a long time known two chief groups which still 

 retain, to a high degree, their protein character, namely, the albuminates 

 and the proteoses (and peptones). 



i. Albuminates. 



Alkali and Acid Albuminates. The native proteins are modified 

 by the action of sufficiently strong acids or- alkalies. By the action of 

 alkalies all native albuminous bodies are converted, with the elimina- 

 tion of nitrogen, or by the action of stronger alkali, with the extraction 

 of sulphur also, into a new modification, called alkali albuminate, whose 

 specific rotation is increased at the same time. If caustic alkali in sub- 

 stance or in strong solution be allowed to act on a concentrated proteid 

 solution, such as blood-serum or egg-albumin, the alkali albuminate 

 may be obtained as a solid jelly which dissolves in water on heating, 

 and which is called "LIEBERKUHN'S solid alkali albuminate." By the- 

 action of dilute caustic alkali solutions on dilute proteid solutions we have- 



