Disulfide

Disulfide

3D structure of cystine, a common disulfide.

A disulfide is a functional group with the structure R-S-S-R', where R and R' are organic groups. The linkage is also called a disulfide bridge or disulfide bond. Disulfides are important in the structure and function of many proteins and enzymes.

Structure and Properties

Disulfide bonds are formed by the oxidation of two thiol groups, resulting in the linkage of two sulfur atoms. This bond is relatively stable and can significantly influence the tertiary and quaternary structure of proteins.

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Schematic representation of disulfide bridges in proteins.

The disulfide bond is a covalent bond, and its formation is a reversible process. The bond can be broken by reduction, converting the disulfide back to two thiol groups.

Biological Significance

Disulfide bonds play a crucial role in the folding and stability of proteins. They are often found in extracellular proteins, where they help maintain the protein's structure in the oxidizing environment outside the cell.

Cystine

Skeletal structure of cystine.

Cystine is a dimeric amino acid formed by the oxidation of two cysteine molecules, linked by a disulfide bond. It is a key structural component in many proteins, including keratin and insulin.

Lipoic Acid

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3D structure of lipoic acid.

Lipoic acid is a cofactor for enzymatic reactions and contains a disulfide bond that is essential for its biological activity. It plays a role in the pyruvate dehydrogenase complex and other dehydrogenase complexes.

Chemical Reactions

Disulfides can undergo various chemical reactions, including reduction to thiols and exchange reactions with other thiols.

Thiol-Disulfide Exchange

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Illustration of thiol-disulfide exchange reaction.

Thiol-disulfide exchange is a common reaction where a thiol group attacks a disulfide bond, resulting in the formation of a new disulfide and a new thiol. This reaction is important in redox biology and protein folding.

Industrial and Environmental Aspects

Disulfides are also found in various industrial and environmental contexts. For example, carbon disulfide is used as a solvent and in the production of rayon and cellophane.

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3D structure of carbon disulfide.

Mineralogy

Disulfide bonds are present in some minerals, such as molybdenite, which contains molybdenum disulfide (MoS₂).

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3D structure of molybdenite.

Related Pages

• Thiol
• Cysteine
• Protein folding
• Redox