作为蛋白质基本构件的氨基酸,除具有羧基外还有氨基,所以是一种两性电解质,既能进行酸性解离,又能进行碱性解离。例如甘氨酸,未解离前是以两性离子形式H_3~+NCH_2COO~-存在,在不同的P~H值环境下,进行如下两种不同的解离:即在氢离子浓度较低的碱性环境下,它基本上是放出质子,呈负离子状态,在氢离子浓度较高的酸性环境下,它基本上吸收质子,呈正离子状态,只有在氢离子浓度适中时,它才主要以两性离子(或中性分子)状态存在。上面之所以加上“基本上”,“主要”,是因为不管 Amino acids, which are basic components of proteins, have an amino group in addition to a carboxyl group and are therefore ampholytes, which are capable of both acidic and alkaline dissociation. For example, glycine, before being dissociated, exists in the form of zwitterions H_3 ~ + NCH_2COO ~ -. Under different P ~ H conditions, two different dissociations occur: in the basic environment with lower hydrogen ion concentration , It basically releases protons in the negative ion state, which absorbs substantially protons in a positive ion state under a high hydrogen ion concentration. It is positive only when the hydrogen ion concentration is moderate, and it mainly takes zwitterions (or Neutral molecules) state exists. The reason for adding “basically”, “main” is because no matter