INTRODUCTION 



5. Isoleucine, C 6 H 13 NO 2 , or o-ammo-/3-methyl-/8-ethyl-propionic acid. 



CH 3 v 



>CH . CH(NH 2 ) . COOH 

 C 2 H 5 X 



6. Phenylalanine, C 9 H n NO 2 , or /8-phenyl-a-aminopropionic acid. 



C 6 H 5 . CH 2 . CH(NH 2 ) . COOH 



7. Tyrosine, C 9 H n NO 3 , or /3-parahydroxyphenyl-o-aminopropionic acid. 



HO . C 6 H 4 . CH 2 . CH(NH 2 ) . COOH 



8. Serine, C 3 H 7 NO 3 , or /8-hydroxy-a-aminopropionic acid. 



CH 2 (OH) . CH(NH 2 ) . COOH 



g. Cystine, C 6 H 12 N 2 O 4 S 2 , or dicysteine, or di-(j8-thio-a-aminopropionic acid). 

 HOOC . CH(NH 2 ) . CH 2 . S S . CH 2 . CH(NH 2 ) . COOH 



B. Monoaminodicarboxylic acids. 



10. Aspartic acid, C 4 H 7 NO 4 , or aminosuccinic acid. 



HOOC . CH 2 . CH(NH 2 ) . COOH 



11. Glutamic acid, C 5 H 9 NO 4 , or a-aminoglutaric acid. 



HOOC . CH 2 . CH 2 . CH(NH 2 ) . COOH 



C. Diaminomonocarboxylic acids. 



12. Arginine, C 6 H 14 N 4 O 2 , or o-amino-5-guanidinevalerianic acid. 



xNH 2 

 HN=C\ 



\NH . CH 2 . CH 2 . CH 2 . CH(NH 2 ) . COOH 



13. Lysine, C 6 H 14 N 2 O 2 , or a, e-diaminocaproic acid. 



H 2 N . CH 2 . CH 2 . CH 2 . CH 2 . CH(NH 2 ) . COOH 



D. Diamino-oxy-monocarboxylic acid. 



14. Caseinic acid, or diaminotrioxydodecanic acid. 



C 12 H 26 N 2 5 



E. Heterocyclic compounds. 



15. Histidine, C 6 H 9 N 3 O 2 , or /8-imidazole-a-aminopropionic acid. 



CH 



NH 



/ 



= C CH 2 . 



CH == C CH 2 . CH(NH 2 ) . COOH 



16. Proline, C 5 H 9 NO 2 , or a-pyrrolidine carboxylic acid. 

 CH 2 CH a 



12 CH . COOH 



I 



CH, 



NH 



17. Oxyproline, or oxypyrrolidine carboxylic acid. 



C 5 H 9 N0 3 



1 8. Tryptophane, C n H I2 N 2 O 2 , or |8-indole-a-aminopropionic acid. 



C CH 2 . CH(NH 2 ) . COOH 



/ \ 

 C 6 H 4 CH 



\ / 

 NH 



