PROTEINS. 8 1 



Proline was first obtained as a decomposition product of casein. 

 Proline obtained from proteins is laevo-rotatory and is the only 

 protein decomposition product which is readily soluble in alcohol. 

 It is also one of the few heterocyclic compounds obtained from pro- 

 teins. Proline was quite recently discovered but has since been 

 found among the decomposition products of all proteins except the 

 protamines. The maximum yield reported is 13.73 P er cen t obtained 

 by Osborne and Clapp from the hydrolysis of hordein. The crystal- 

 line form of lcevo-a-proline is shown in Fig. 30, and the copper 



FIG. 31. 





COPPER SALT OF PROLINE. 



Reproduced from a micro-photograph made by Prof. E. T. Reichert, of the University 



of Pennsylvania. 



salt of proline is represented by a micro-photograph in Fig. 31, 

 above. The crystals of the copper salt have a deep blue color but 

 when they lose their water of crystallization they assume a char- 

 acteristic violet color. 



Oxyproline, C 5 H 9 NO 3 . Oxyproline was recently discovered by 

 Fischer. It has as yet been obtained from only a few proteins, but 

 this may be due to the fact that only a few have been examined for 

 its presence. Its structure has not yet been established. 



Diaminotrihydroxydodecanoic Acid, C 12 H 26 N 2 O 5 . This amino 

 acid was discovered by Fischer and Abderhalden as a product of 

 the hydrolysis of casein. It has thus far been obtained from no 

 other source. It is laevo-rotatory and its constitution has not been 

 determined. 



