INTRODUCTION 



5. Isoleucine, C 6 H 13 NO 2 , or a-amino-/3-methyl-/3-ethyl-propionic acid. 



CH 3 \ 



>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 11 NO 3 , or )8-parahydroxyphenyl-o-aminopropionic acid. 



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



8. Serine, C 3 H 7 NO 3 , or /3-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 a . S S . CH a . 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 o-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 a-amino-5-guanidinevalerianic acid. 



/NH 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 /3-imidazole-a-aminopropionic acid. 



CH 



^ \ 

 N NH 



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



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



CH 2 CH 2 



CH 2 CH . COOH 



\ / 

 NH 



17. Oxyproline, or oxypyrrolidine carboxylic acid. 



C 5 H 9 N0 3 



18. Tryptophane, C n H 12 N 2 O 2 , or j8-indole-o-aminopropionic acid. 



C CH 2 . CH(NH 2 ) . COOH 



/ \ 



C 6 H 4 CH 



\ / 

 NH 



