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Disulphide bond

(Science: chemistry molecular biology) The s s linkage. A linkage formed between the sh groups of two cysteine moieties either within or between peptide chains.

Each cysteine then becomes a half cystine residue. S s linkages stabilise, but do not determine, secondary structure in proteins. They are easily disrupted by sh groups in an exchange reaction and are not present in cytosolic proteins (cytosol has a high concentration of glutathione that has a free sh residue).