20种氨基酸的结构 COOH COOH HN-C一H HN*一 C-H H-C-OH CHs Threonine (Thr,T) Cysteine(Cys,C) COOH COOH H N+-C-H HC- H'N OH Tyrosine (Tyr,Y) Histidine (His,H) (d)Basic COOH COOH HN-C 一H CH NH Lysine (Lys,K) He'N Arginine (Arg.R)9 20种氨基酸的结构