α-碳原子都是手性碳原子，几乎为L型

Amphiphiles are reflected in the amino and carboxyl groups

Isoelectric point: adjust the pH of the medium. Amino acids exist in the form of dipolar ions (inner salts) with a net charge of 0 and do not move in the electric field. The pH at this point is called the isoelectric point and is recorded as pI.

Solubility is minimum at the isoelectric point and easy to precipitate

Reaction with nitrous acid (quantitative determination)

Reacts with formaldehyde

Alkylation

Oxidative deamination reaction

α-Amino acid reacts with ninhydrin under alkaline conditions to form a blue-purple substance.

Proline and hydroxyproline produce yellow color

The dehydration and condensation of two amino acids to form an amide bond is called a peptide bond

N-terminus and C-terminus