Disulfide Bonds in Peptides

Some peptides contain disulfide bonds — internal “bridges” that lock the molecule into a specific shape. They’re different from the peptide bonds that link the chain. Here’s a simple explainer.

• What they are: bonds between two cysteine amino acids.
• What they do: hold a peptide in a folded, stable shape.
• Different from: the peptide bonds that build the chain.

What a disulfide bond is

The amino acid cysteine has a sulfur-containing side chain. When two cysteines come close, their sulfur atoms can link to form a disulfide bond (an S–S “bridge”). This bridge can connect distant parts of the same chain, pulling the peptide into a defined 3D shape.

Why they matter

• Shape: the bridge stabilizes the peptide’s structure, which can be essential to its function.
• Stability: disulfide-bonded peptides can behave differently in handling and storage.
• Chemistry: these bonds are distinct from the backbone peptide bonds.

For more terms, see the research glossary and the 20 amino acids.