Disulphide Bridges

Disulphide bridges are covalent bonds formed between pairs of cysteine residues (forming cystine). These contribute to the tertiary structure of proteins by linking distant regions of a protein. Disulphide bridges may also occur between different peptide chains within a protein, e.g. between the A and B chains of insulin. They are common in extracellular proteins, but less common in intracellular proteins. Strong reducing agents are required to break the disulphide bridges.

Fig 1: Cysteine and Cystine

Fig 1: Disulphide Bridge

Source: Fig 1,  Fig 2, Fig 3,