Amino acids (一) Configuration COOH COOH H2N-TH ■■■ H→NH 2 R R L-ac-amino acid D-ac-amino acid When R*H, a-C is a chiral carbon, there are two stereoisomers(D and L-aamino acid) The amino acids in protein molecules are the L-a-amino acids 20 standard amino acids in proteins一、Amino Acids （一）Configuration H2N H COOH R H NH2 COOH R L-α-amino acid D-α-amino acid • When R ≠ H, α-C is a chiral carbon, there are two stereoisomers (D and L- α- amino acid) • The amino acids in protein molecules are the L- α - amino acids. • 20 standard amino acids in proteins