chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...

, a selenosulfide refers to distinct classes of inorganic and

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...

s containing sulfur and selenium. The organic derivatives contain Se-S bonds, whereas the inorganic derivatives are more variable.

Organic selenosulfides

These species are classified as both organosulfur and

organoselenium Organoselenium compounds (or seleno-organic) are chemical compounds containing carbon-to-selenium chemical bonds. Organoselenium chemistry is the corresponding science exploring their properties and reactivity. Selenium belongs with oxygen and sulf ...

compounds. They are hybrids of organic disulfides and organic

diselenide Diselenide may refer to: *Diselane, H-Se-Se-H *Carbon diselenide, CSe2, a yellow-orange oily liquid with pungent odor * Any organic chemical compound with a selenium-selenium bond, R-Se-Se-R **Diphenyl diselenide, (C6H5)–Se–Se–(C6H5) *Metal ...

Preparation, structure, and reactivity

Selenosulfides have been prepared by the reaction of selenyl halides with thiols: : The equilibrium between diselenides and disulfides lies on the left: :RSeSeR + R'SSR' 2 RSeSR' Because of the facility of this equilibrium, many of the best characterized examples of selenosulfides are cyclic, whereby S-Se bonds are stabilized intramolecularly. One example is the 1,8-selenosulfide of

naphthalene Naphthalene is an organic compound with formula . It is the simplest polycyclic aromatic hydrocarbon, and is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromati ...

. The selenium-sulfur bond length is about 220 picometers, the average of a typical S-S and Se-Se bond.

Occurrence

Selenosulfide groups can be found in almost all living organisms as part of various peroxidase enzymes, such as glutathione peroxidase and

thioredoxin reductase Thioredoxin reductases (TR, TrxR) () are enzymes that reduce thioredoxin (Trx). Two classes of thioredoxin reductase have been identified: one class in bacteria and some eukaryotes and one in animals. In bacteria TrxR also catalyzes the reduction ...

. They are formed by the oxidative coupling of

selenocysteine Selenocysteine (symbol Sec or U, in older publications also as Se-Cys) is the 21st proteinogenic amino acid. Selenoproteins contain selenocysteine residues. Selenocysteine is an analogue of the more common cysteine with selenium in place of the s ...

and

cysteine Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the formula . The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile. When present as a deprotonated catalytic residue, sometime ...

residues. This reaction is powered by the decomposition of cellular peroxides, which can be highly damaging and a source of oxidative stress. Selenocysteine has a lower reduction potential than cysteine, making it very suitable for proteins that are involved in

antioxidant Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals. This can lead to polymerization and other chain reactions. They are frequently added to industrial products, such as fuels and lubricant ...

activity. Selenosulfides have been identified in some species of '' Allium'' and in roasted coffee. The mammalian version of the protein

contains a

residue which forms a thioselenide (analogous to a disulfide) upon oxidation.

Inorganic selenosulfides

Some inorganic

selenide sulfide In chemistry, a selenosulfide refers to distinct classes of inorganic compound, inorganic and organic compounds containing sulfur and selenium. The organic derivatives contain Se-S bonds, whereas the inorganic derivatives are more variable. Orga ...

compounds are also known. Simplest is the material

selenium sulfide Selenium sulfide can refer to either of the following: * Selenium disulfide, SeS2 * Selenium hexasulfide, Se2S6 {{Short pages monitor