8o 



PHYSIOLOGICAL CHEMISTRY. 



amount of any single decomposition product yet obtained from any 

 protein except the protamines. 1 



Glutamic acid and aspartic acid are the only dibasic acids which 

 have thus far been obtained as decomposition products of proteins. 

 As there is an apparent relation between the proportion of these 

 acids and that of ammonia which the different proteins yield it is 

 possible that one of the carboxyl groups of these acids is united with 

 NH 2 as an amide, the other carboxyl group being united in poly- 

 peptide union (see page 66) with some other amino acid. This 

 might be represented by the following formula : 



R-CHNH-COOH 



CO-CHNH 2 -CH 2 -CH 2 -CONH 2 . 



It has not been definitely proven, however, that this form of link- 

 ing actually occurs. 



The glutamic acid, yielded by proteins upon hydrolysis, is dextro- 

 rotatory. Crystals of glutamic acid are reproduced in Fig. 29, page 79. 



Proline, C 5 H 9 NO 2 . Proline is a-pyrrolidine-carboxylic acid and 

 possesses the following graphic structure : 



HC 



H 2 C\/CH-COOH. 

 NH 



FIG. 30. 



LjEVO-a-PROLINE. 



^p to this time the yield of 37.33 per cent obtained by Osborne and Harris 

 from gliadin of wheat was the maximum yield 



