Illustrated Glossary of Organic Chemistry

Disulfide bridge: A disulfide that links two cysteine residues in a peptide or protein.

A disulfide bridge between two cysteine residues can be formed by oxidation. The process is reversed, and the sulfur-sulfur bond ruptured, by a reduction reaction.

Human insulin, a protein composed of 51 amino acids, includes six cysteine residues and three disulfide bridges (shown in red).