DERIVATIVES 44 1 



THE DECOMPOSITION PRODUCTS OF THE PROTEINS. 



The most direct way of obtaining an insight into the 

 probable groups or groupings which occur in the molecule of 

 some complex substance, is to break it up into simpler ones, 

 whose constitution is already known, or may be determined 

 with comparative ease. This is the method which has been em- 

 ployed to elucidate the very complex structure of the proteins. 



Various processes have been employed for breaking down 

 the protein molecule, such as acid hydrolysis, fusion with 

 alkalis, the action of enzymes or putrefactive bacteria, oxida- 

 tion, etc. As a result of all these various methods, a number 

 of simple compounds have been obtained, which fall primarily 

 into two main groups : — 



1. Biuretic Derivatives, such as albumoses, peptones, etc., 

 which are still very complex substances, but have, at any rate, 

 a lower molecular weight than the original unaltered protein. 

 These substances all give the Biuret reaction. 



2. Abiuretic Derivatives. — In this group of cleavage pro- 

 ducts, which give no Biuret reaction, are included the various 

 amino acids. 



By an amino acid is meant an acid in which one or more 

 of the hydrogen atoms other than the carboxylic hydrogen 

 are replaced by the amino group — NHg. Thus acetic acid 

 CH3COOH gives rise to the amino acid known as glycine 

 CH2NH2COOH. Theoretically it should be possible to re- 

 place two or even three atoms of hydrogen in acetic acid 

 by the — NHg group to produce diamino acetic acid 

 CH(NH2)2COOH and triamino acetic acid C(NH2)3COOH ; 

 these compounds are, however, not known, and appear to be 

 incapable of existing. 



The next homologue after acetic acid, namely, propionic 

 acid CH3CH2COOH, can give two mono - amino acids 

 CH3CHNH2COOH and CH2NH2CH2COOH known re- 

 spectively as a- and ^-amino propionic acids, according as 

 the amino group is attached to the a-carbon atom, adjacent 

 to the carboxyl group, or to the jS-carbon atom, which is 

 next but one from the carboxyl. 



In the case of the higher homologues, diamino acids are 



