3i6 



PROTEINS 



Mono-carboxylic 

 di-amino acids. 



Dicarboxylic 

 di-amino acid. 



f Ornithine or o-5-di-amino-valeric acid 



NH.CHaCHXHaCHNHXOOH 

 Arginine or 5-guanidine a-amino-valeric acid 



HN=C 



\NH CH2CH2CH2CHNH2COOH 

 Lysine or a-€-di-amino-caproic acid 



NH2CH2CH2CH2CH2CHNH2COOH 

 Di-amino-trihydroxy-dodecanic acid * CjoHogOgNj 

 Cystine or di fj8-thio a-amino prop ionic] acid 



CHo-S— S— CH, 



I I 



CHNH2 CHNH2 



I I 



COOH COOH 



(2) Aromatic Compounds. 



I Phenyl alanine or /3-phenyl a-amino propionic acid 

 Mono-carboxylic I C6H5CH2CHNH2COOH 



mono-amino acids. ] Tyrosine or /3-parahydroxyphenyl a-amino-propionic acid 

 \ HOC6H4CH2CHNH2COOH 



(3) Hetetvcyclic Compounds. 



CHa CH2 



Proline or a-pyrrolidine carboxylic acid CH2 CHCOOH 



NH 

 Hydroxyproline or hydroxy a-pyrrolidine carboxylic acid 

 Histidine or /3-imidazol a-amino propionic acid 

 CH= C— CH2CHNH2COOH 



I I 



N NH 



CH 

 Tryptophane )3-indole o-amino propionic acid 

 C— CH2CHNH2COOH 



CeH,<;^^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 



