Amino acids )20 standard amino acids 4. Negatively charged groups(2 COO COo 3 2 2 COO 2 COo Aspartate(Asp) Glutamate(Glu 门冬氨酸 谷氨酸 Acidic amino acids-containing two carboxylic groups一、Amino Acids （二）20 standard amino acids Acidic amino acids——containing two carboxylic groups +H3N COO￾H CH2 COO￾Aspartate (Asp) Glutamate(Glu) 门冬氨酸 谷氨酸 +H3N COO￾H CH2 CH2 COO- 4. Negatively charged R groups (2)