Disulfide bond

In chemistry, a disulfide bond is a single covalent bond derived from the coupling of thiol groups. The linkage is also called an SS-bond or disulfide bridge. The overall connectivity is therefore C-S-S-C. The terminology is almost exclusively used in biochemistry, bioinorganic and bioorganic chemistry. Formally the connection is called a persulfide, in analogy to a peroxide (R-O-O-R), but this terminology is rare.
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(-S-S-): A covalent linkage between two cysteine residues in different parts of a protein or between two different proteins. Insulin (a small protein having two polypeptide chains), for example, has interchain and intrachain disulfide bonds. HLA molecules also have disulfide bonds. The C282Y mutation removes one of the disulfide bonds in the HLA class I-like HFE protein and abolishes its surface expression.