PROTEINS 169 



C. Diamino-monocarboxylic acids: 



Ornithine, C 5 Hi2N 2 O 2 , H 2 N CH 2 CH 2 CH 2 CHNH 2 



COOH, di-amino-valerianic acid. 

 Lysine, C 6 Hi 4 N 2 O 2 , H 2 N-CH 2 -CH 2 -CH 2 -CH 2 -CHNH 2 . 



COOH, di-amino-caproic acid. 

 Arginine, C6Hi4N4O 2 , 



/NH 2 

 HN=C< 

 \ 



CH 2 CH 2 CH 2 CHNH 2 COOH, 



guanidine-amino-valerianic acid. 

 Di-amino-oxysebacic acid, CnHi 2 N 2 O3. 

 Di-amino-trioxydodecanic acid, Ci 2 H 2 eN 2 03. 



D. Monoimido-monocarboxylic acids: 



Proline, C 5 H 9 NO 2 , H 2 C - CH 2 



H 2 C CH-COOH, pyrrolidine-carboxy- 

 \/ lie acid 



N 



H 



Oxyproline, CsHgNOs, proline with one (OH) group. 



E. Monoimido-monoamino-monocarboxylic acids. 



Histidine, C 6 H 9 N 3 O 2 , HC=C CH 2 CHNH 2 COOH, 



imidazole-amino- 

 ,v , propionic acid. 



C 



( N C CH 2 -CHNH 2 -COOH, indole-amino-propionic acid. 



II 

 II CH 



\/ \AT/ 



H 



As has been said, other amino-acids are being found, from time 

 to time, as additional proteins are examined, or as better methods 

 of examination of the cleavage products of the natural proteins are 

 devised. 



