Cysteine has a thiol group (–SH) in its side chain. When two cysteines are close and become oxidised, their sulphurs join to form an S–S bond: the disulfide bridge. It can form within the same chain, creating a ring, or between two different chains, as in insulin.
Oxytocin and vasopressin are classic examples of peptides with a ring closed by a disulfide. That ring is essential for their activity: if the bridge is broken (reduced), the molecule loses the shape its receptor recognises.
In synthesis, forming the right disulfides is a delicate step. In peptides with several cysteines, mispaired bridges or dimers (two molecules joined together) can appear, impurities with the same or double the mass that analytical control has to rule out.
Peptides with disulfides are sensitive to reducing agents and certain pH changes. Knowing whether a compound has them helps explain its storage requirements and possible impurities.
Related terms
Learn it in depth at the Peptide University
- Chemical modifications: from the natural sequence to the analog · Module 1
- Levels of structure and structure-activity relationship · Module 1
- Antimicrobial peptides of innate immunity · Module 12
- Related impurities and counterions · Module 7
- Chemical degradation: the weak points of the sequence · Module 11
Related catalogue compounds
Definition for educational and scientific purposes. It is not medical advice or a recommendation for use. NeoPeptidos products are sold labelled for research use only (RUO).