极性中性氨基酸 OH SH CH2 CH2 COH CH2 H N-C-COO- H N-C-COO H N-C-COO- H N-C-COO H Serine (Ser)S Cysteine (Cys)C Threonine(Thr)T Methionine (Met)M OH NH2 CH2 CH2 HgN- C00 HaN-C-COo- H N-C -C00 Tyrosine (Tyr)Y Tryptophan (Trp)W Asparagine (Asn)N Glutamine (GIn)Q 极性中性氨基酸