Persulfide

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In chemistry, persulfide refers to the functional group R-S-S-H. [1] Persulfides are intermediates in the biosynthesis of iron-sulfur proteins [2] and are invoked as precursors to hydrogen sulfide, a signaling molecule.

Contents

Nomenclature

The nomenclature used for organosulfur compounds is often non-systematic. Sometimes persulfides are called hydrodisulfides to further avoid confusion with disulfides with the grouping R-S-S-R, by emphasizing the presence of an H at one end of a disulfide bond.

Properties

Compared to thiols (R-S-H), persulfides are uncommon. They are thermodynamically unstable with respect to loss of elemental sulfur:

RSSH → RSH + 1/8 S8

Nonetheless, persulfides are often kinetically stable.

The S-H bond is both more acidic and more fragile than in thiols. This can be seen in the bond dissociation energy of a typical persulfide, which is 22 kcal/mol weaker than a typical thiol, and the lower pKa of about 6.2 for persulfides compared to 7.5 for thiols. Thus, persulfides exist predominantly in the ionized form at neutral pH. This effect is attributed to the stability of the RSS· radical. [1]

Structure and reactions

The structure of trityl persulfide has been determined by X-ray crystallography. The S-S bond length is 204 picometers and the C-S-S-H dihedral angle is 82°. These parameters are unexceptional. [3] (C6H5)3CSSH behaves as a source of sulfur, illustrated by its reaction with triphenylphosphine to give triphenylphosphine sulfide and triphenylmethanethiol:

(C6H5)3CSSH + P(C6H5)3 → (C6H5)3CSH + SP(C6H5)3

Biosynthetic and catabolic roles

The cofactors 4-thiouridine and thiamine are produced by the action of persulfides. Cystathionase generates the persulfide of cysteine (sometimes called thiocysteine) from cystine.

Persulfides have been invoked as intermediates in the biodegradation of carbon disulfide [4] and mercaptopyruvate.

Related Research Articles

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<span class="mw-page-title-main">Cysteine</span> Proteinogenic amino acid

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In chemistry, a disulfide is a compound containing a R−S−S−R′ functional group or the S2−
2
anion. The linkage is also called an SS-bond or sometimes a disulfide bridge and usually derived from two thiol groups.

<span class="mw-page-title-main">Thiol</span> Any organic compound having a sulfanyl group (–SH)

In organic chemistry, a thiol, or thiol derivative, is any organosulfur compound of the form R−SH, where R represents an alkyl or other organic substituent. The −SH functional group itself is referred to as either a thiol group or a sulfhydryl group, or a sulfanyl group. Thiols are the sulfur analogue of alcohols, and the word is a blend of "thio-" with "alcohol".

<span class="mw-page-title-main">Organic sulfide</span> Organic compound with an –S– group

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<span class="mw-page-title-main">Triphenylphosphine</span> Chemical compound

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In chemistry, a sulfenic acid is an organosulfur compound and oxoacid with the general formula R−S−OH. It is the first member of the family of organosulfur oxoacids, which also include sulfinic acids and sulfonic acids, respectively. The base member of the sulfenic acid series with R = H is hydrogen thioperoxide.

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<span class="mw-page-title-main">Hydrogen disulfide</span> Chemical compound

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<span class="mw-page-title-main">Iron–sulfur cluster biosynthesis</span>

In biochemistry, the iron–sulfur cluster biosynthesis describes the components and processes involved in the biosynthesis of iron–sulfur proteins. The topic is of interest because these proteins are pervasive. The iron sulfur proteins contain iron–sulfur clusters, some with elaborate structures, that feature iron and sulfide centers. One broad biosynthetic task is producing sulfide (S2-), which requires various families of enzymes. Another broad task is affixing the sulfide to iron, which is achieved on scaffolds, which are nonfunctional. Finally these Fe-S cluster is transferred to a target protein, which then become functional.

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<span class="mw-page-title-main">Transition metal thiolate complex</span>

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References

  1. 1 2 Park, Chung-Min; Weerasinghe, Laksiri; Day, Jacob J.; Fukuto, Jon M.; Xian, Ming (2015). "Persulfides: Current knowledge and challenges in chemistry and chemical biology". Molecular BioSystems. 11 (7): 1775–1785. doi:10.1039/c5mb00216h. PMC   4470748 . PMID   25969163.
  2. Lill, Roland (2009). "Function and biogenesis of iron–sulphur proteins". Nature. 460 (7257): 831–838. Bibcode:2009Natur.460..831L. doi:10.1038/nature08301. PMID   19675643.
  3. Bailey, T. Spencer; Zakharov, Lev N.; Pluth, Michael D. (2014). "Understanding Hydrogen Sulfide Storage: Probing Conditions for Sulfide Release from Hydrodisulfides". Journal of the American Chemical Society. 136 (30): 10573–10576. doi:10.1021/ja505371z. PMC   4120993 . PMID   25010540.
  4. Catignani, George L., Robert A. Neal (1975). "Evidence for the formation of a protein bound hydrodisulfide resulting from the microsomal mixed function oxidase catalyzed desulfuration of carbon disulfide". Biochemical and Biophysical Research Communications. 65 (2): 629–636. doi:10.1016/S0006-291X(75)80193-8. PMID   238535.{{cite journal}}: CS1 maint: multiple names: authors list (link)