AMINO ACIDS 



325 



Mono-carboxylic 

 di-amino acids. 



Dicarboxylic 

 di-amino acid. 



' Ornithine or a-8-di-amino-valeric acid 



NH 2 CH 2 CH 2 CH 2 CHNH 2 COOH 

 Arginine or 8-guanidine o-amino-valeric acid 



/NH 2 

 HN=C 



\NH CH 2 CH 2 CH 2 CHNH 2 COOH 

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



NH 2 CH 2 CH 2 CH 2 CH 2 CHNH 2 COOH 

 . Di-amino-trihydroxy-dodecanic acid * C 12 H 26 O 6 N 2 

 Cystine or di [-thio a-amino propionic] acid 

 CH 2 -S S CH 2 



CHNH 2 

 COOH 



CHNH 2 

 COOH 



(2) Aromatic Compounds. 



( Phenyl alanine or /J-phenyl o-amino propionic acid 

 Mono-carboxylic j C 6 H 5 CH 2 CHNH 2 COOH 



mono-amino acids. 1 Tyrosine or $-parahydroxyphenyl a-amino-propionic acid 

 I HOC 6 H 4 CH 2 CHNH 2 COOH 



(3) Heter acyclic Compounds. 



CH 2 - CH 2 

 Proline or o-pyrrolidine carboxylic acid CH 2 CHCOOH 



NH 



Hydroxyproline or hydroxy a-pyrrolidine carboxylic acid 

 Histidine or )8-imidazol a-amino propionic acid 

 CH= C CH 2 CHNH 2 COOH 



N NH 



CH 



Tryptophane 0-indole o-amino propionic acid 

 C CH 2 CHNH 2 COOH 



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. 



To this end Fischer, in 1901, introduced his so-called 



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



