26 UNITY AND DIVERSITY IN BIOCHEMISTRY 



Table VI 

 NH2 



a-amino acids | 



(R-CH— COOH) 



(Symbols indicating the nature of the radical R : aliphatic (Al), aromatic (Ar), 

 heterocyclic (He), acidic (A), basic (B), neutral (N), polar (P), feebly polar (FP), 

 non-polar (NP), ionic (I), feebly ionic (FI), non-ionic (NI).) 



L (+) Alanine (Ala), a-aminopropionic acid 



NH2 



R = methyl (Al, N, NP, NI) CH3-CH-COOH 



L (+) Arginine (Arg), a-amino-S-guanido-w-valeric acid 



R = tu-guanido-n-propyl (Al, B, P, I) 



NHa 



5 Y P «l 



CH2-CH2-CH2-CH-COOH 



I 

 NH 



/ 



C=NH 



\ 



NH2 



L ( — ) Aspartic acid (Asp), a-aminosuccinic acid 



NH2 



R = carboxymethyl (Al, A, P, I) HOOC— CH2— CH— COOH 



L (— ) Cysteine (CySH), a-amino-/3-thiolpropionic acid 



NH2 



I 

 R = thiomethyl (Al, N, P, FI) HS-CH2— CH-COOH 



L (— ) Cystine (CyS), j3, jS'-dithio-bis (a-aminopropionic acid) 



NH2 



R = dimethyldisulphide (Al, N, NP, NI) S-CH2-CH-COOH 



NH2 

 S— CH2-CH— COOH 



L (-|-) Glutamic acid (Glu), a-aminoglutaric acid 



NH2 



I 

 R = carboxyethyl (Al, A, P, I) HOOC— CHo—CHo—CH— COOH 



