ac 



THE PROTEINS 81 



sids obtained by the hydrolysis can then be further purified by means of 



crystallisation. 



THE DISINTEGRATION PRODUCTS OF THE PROTEINS 



By the methods just described the following substances have been 

 isolated from proteins : 



A. FATTY SERIES 

 (1) Mono-amino-acids (Monobasic) 



GLYCINE or GLYCOCOLL. This, the simplest member of the group, is 

 ammo-acetic acid : 



CH 2 NH 2 



COOH 



It occurs in considerable quantities among the disintegration products of 

 gelatin and to a slight extent among those derived from certain of the pro- 

 teins. Like the other a-amino-acids, it has a sweetish taste, whence its name 

 was derived (yXu/coo- = sweet, /coAAr? = glue). 

 ALANINE is a-amino-propionic acid : 



CH 3 



CH.NH* 



COQH 



It is optically active, the alanine derived from proteins being dextro- 

 rotatory. 



Closely allied to alanine is the amino-acid SERINE, which was first ob- 

 tained by the hydrolysis of silk and has since been found as a constituent 

 of a large number of proteins. Its formula is : 



CH 2 OH 



CH.NH 2 



COOH 



i.e. it is amino-oxypropionic acid. Its special interest lies in the fact that 

 it was one of the first of the amino-oxy acids to be isolated, and i 

 in these acids that we must seek the intermediate stages betwee 

 hydrates and proteins. 



AMINO-VALERIANIC ACID has the formula 



CH 3 CH 3 



\/ 

 CH 



CH.NH 2 



COOH 



It occurs only in small quantities in the protein molecule. 



