Silk is a protein fiber, also known as silk fibroin. It is a nitrogen-containing polymer compound, the single base of its macromolecule is alpha amino acid. The general structural formula of α amino acids is RCH (NH2) COOH. Because its amino group is located on the α carbon atom next to the carboxyl group or carboxylic acid, it is called α amino acid. According to the general structural formula of silk fibroin molecules, the side groups connected to different peptide groups in the entire macromolecular chain are different, which is an important feature of natural protein fibers.
There are 18 kinds of amino acids that make up silk fibroin. The content of silk fibroin accounts for about 70%-80% of silk. Among them, glycine (gly), alanine (ala) and serine (ser) account for about 80% of the total composition.
