Disülfid

Disülfid, known in English as disulfide, refers to a functional group or class of compounds characterized by a bond between two sulfur atoms, S–S, that links two organic fragments. The general structural motif is R–S–S–R′, and disulfides can be formed from thiol precursors or as part of larger molecular frameworks.

Formation and structure. The S–S bond forms by oxidation of thiol groups (R–SH) to yield R–S–S–R′. In biology, disulfide bonds are common in proteins and can be intramolecular (within a single polypeptide) or intermolecular (between two polypeptides). Their formation is favored in oxidizing cellular environments, such as the endoplasmic reticulum, and is often facilitated by enzymes such as protein disulfide isomerase (PDI).

Reactions and properties. Disulfide bonds can be reduced back to thiols by reducing agents such as dithiothreitol (DTT) or beta-mercaptoethanol, and they participate in thiol-disulfide exchange reactions that allow rearrangement of disulfide linkages. This dynamic chemistry underpins protein folding, stability, and regulation in many biological systems. Disulfides also occur as discrete compounds, or as crosslinks in polymers, where they can influence material properties.

Occurrence and applications. In biochemistry, disulfide bonds stabilize protein tertiary and quaternary structures and can control activity through redox changes. In chemistry and materials science, disulfides serve as crosslinkers and reagents; well-known examples include diaryl and dialkyl disulfides used in synthesis and catalysis. In cosmetic and hair-treatment contexts, disulfide chemistry is exploited to reversibly modify keratin structures during processes such as perming and setting.

See also: disulfide bond, thiol, oxidation, reduction.