3o6 



PROTEINS 



Mono-carboxylic 

 di-amino acids. 



Dicarboxylic 

 di-amino acid. 



Ornithine or a-5-di-amino-valeric acid 



NHjCHoCHaCHaCHNHijCOOH 

 Arginine or 5-guanidine o-amino-valeric acid 



HN=C 



\NH CH2CH2CH2CHNH2COOH 

 Lysine or o-e-di-amino-caproic acid 



NHoCHoCHoCHoCHaCHNHoCOOH 

 L Di-amino-trihydroxy-dodecanic acid * CjoHoijOsNa 

 Cystine or di [/3-thio o-amino propionic] acid 

 CH2-S— S— CH2 



CHNH, CHNH. 



I 

 COOH 



I 

 COOH 



Mono-carboxylic 

 mono-aniino acids. 



(2) Aromatic Compounds. 



Phenyl alanine or ;8-phenyl o-amino propionic acid 



C^HgCH^CHNHoCOOH 

 Tyrosine or /3-parahydroxyphenyl a-amino-propionic acid 



HOCgH^CHoCHNHoCOOH 



(3) Heterocyclic Compounds. 



CH„ — CH, 



I " I " 

 Proline or a-pyrrolidine carboxylic acid CHo CHCOOH 



NH 

 Hydroxyproline or hydroxy a-pyrrolidine carboxylic acid 

 Histidine or ;3-imidazol a-amino propionic acid 

 CH= C— CH.CHNHaCOOH 



II" 

 N NH 



CH 

 Tryptophane j8-indole o-amino propionic acid 

 C— CH^CHNHXOOH 



CfiH./^^CH 



NH 



The above list comprises most of the more important 

 cleavage products of proteins, the constitution of which has 

 been definitely established. 



Since different proteins give rise to different amounts of 

 these various substances, it is obvious that a careful quantita- 

 tive determination of the amounts of these acids produced by 

 the hydrolysis of different proteins must be of considerable 

 value. 



The constitutional formula of this substance has not yet been determined. 



