Amino acids are organic compounds containing basic amino groups and acidic carboxyl groups. The chemical formula is RCH(NH2)COOH. A compound formed by replacing the hydrogen atom on the carbon atom of carboxylic acid with an amino group.

Amino acid molecules contain two functional groups, amino and carboxyl. Similar to hydroxy acids, amino acids can be divided into α-, β-, γ-, w-, etc. amino acids according to the different positions of the amino groups on the carbon chain. However, the amino acids obtained after protein hydrolysis are all α-amino acids, and There are only twenty-two species, and they are the basic units that make up proteins.

Chemical properties of amino acids:

1. Reactions of amino acids: acylation reaction; reaction with nitrous acid; reaction with aldehyde; sulfonylation reaction; reaction with DNFB; salt-forming reaction .

2. Reaction of carboxyl group The carboxyl group of amino acids, like other carboxylic acids, can undergo acylation, esterification, decarboxylation and salt-forming reactions under certain conditions.

3. Reaction with ninhydrin hydrate: α-amino acid and ninhydrin hydrate are heated in a weakly acidic solution, and undergo oxidative deamination to generate the corresponding α-keto acid, which is further decarboxylated to form an aldehyde. , hydrated ninhydrin is reduced to reduced ninhydrin. In a weakly acidic solution, reduced ninhydrin and the ammonia removed from the amino acid react and condense with another hydrated ninhydrin to form a blue-purple complex.

Proline and hydroxyproline react with ninhydrin to produce yellow substances, and the remaining α-amino acids react with ninhydrin to produce blue-purple substances. This color reaction is often used for the colorimetric determination of α-amino acids and the color development of chromatographic analysis. ?

Reference for the following content: Baidu Encyclopedia-Amino Acids