222 Biological Chemistry. 



5. /soleucine, a-amino-/?-methyl-/^ethylpropionic acid 



CH 3X 



>CH-CH(NH 2 )-COOH 

 C 2 H/ 



6. Phenylalanine, /3-phenyl-a-aminopropionic acid 



CeHs-CE^ CH(NH 2 ) COOH 



7. Tyrosine, f$-p hydroxyphenyl-a-aimnopropionic acid 



OH C 6 H 4 .CH 2 -CH(NH 2 ) COOH 



8. Serine, /?-hydroxy-a-aminopropionic acid 



OH CHa CH(NH 2 ) COOH 



9. Cystine, a sulphur derivative of a-aminopropionic acid, of 

 the formula 



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



B. Monoamino-dicarboxylic Acids. 



10. Aspartic, or aminosuccinic acid 



CH^COOH 



11. Glutamic, or a-aminoglutaric acid 



HOOC CH 2 -CH, CH(NH 2 )-COOH 



C. Diamino-monocarboxylic Acids. 



12. Arginine 



/NH, 



HN = C 



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



13. Lysine HaN CH, CH 2 -CH 2 CH 2 .CH(NH 2 )-COOH 



D. Heterocyclic Compounds (compounds containing 

 rings other than that of benzene). 



14. Histidine, /3-iminazole-a-aminopropionic acid 



