Sulfide bridge

Sulfur Dyes. These dyes are synthesized by heating aromatic amines, phenols, or nitro compounds with sulfur or, more usually, alkah polysulfides. Unlike most other dye types, it is not easy to define a chromogen for the sulfur dyes (qv). It is likely that they consist of macromolecular stmctures of the phenothiazone-thianthrone type (72), in which the sulfur is present as (sulfide) bridging links and thiazine groups (1). 

Peptide containing intra-sulfide bridge at positions 96 and 104. Heme-containing peptide. 

The sequence was confirmed from a separate LC-ESMS/MS analysis. One Hg atom (Mr 200.6) is included in the calculated molecular weight. Peptide containing intra-sulfide bridge at positions 96 and 104. 

Chen, P., Gorelsky, S.I., Ghosh, S. and Solomon, E.I. (2004) NzO reduction by the i4-sulfide-bridged tetranuclear Cuz cluster active site, Angew. Chem. Int. Ed., 43, 4132-4140. 

A-acetylcysteine, a substance that cleaves sulfide bridges, has also been investigated, and although early reports claimed success, later studies showed no effect at all (B23, G10, H14, K39, S15). The differences in observations were probably induced by technical problems in the analysis of Lp(a) in the presence of a substance potent in the cleavage of S-S bonds. 

There are many important mixed valence and fractional formal oxidation state compounds (e.g., Fc304) and complexes of iron. Mixed valence trinuclear /.t-oxo-carboxylato-complexes are dealt with in Section 5.4.5.4.2, polynuclear complexes held together by sulfide bridges in Section 5.4.5.9.2. 

Note 2 A classic example of vulcanization is the crosslinking of c/s-polyisoprene through sulfide bridges in the thermal treatment of natural rubber with sulfur or a sulfur-containing compound. 

From a stereochemical viewpoint, the sulfur extrusion methods12122 using P(NEt2)3 seem to have certain advantages, because chiral centers at alpha carbon atoms are not involved in the lanthionine formation. However, due to the possible formation of ionic intermediates prior to formation of the sulfide bridge, undesired symmetrically substituted or also ste-reochemically undesired lanthionines may inadvertently be formed. Possible solutions to circumvent these problems have also been reported. 23,26 ... 

The sulfur extrusion method 21 has been extensively investigated for the synthesis of threo-3-methyllanthionine 25 however, in this case desulfurization was not used to generate the amino acid (either in free or protected form), but rather to form different sulfide-bridged cyclic peptides as precursors for the total synthesis of nisin (3). Development of synthetic methods in this area was particularly important in respect to the synthesis of nisin, since this lantibiotic contains four // eo-3-methyllanthionine residues. The synthesis proceeded from a protected f/zreo-3-methyl-D-cysteine in the N-terminal position and L-cysteine in the C-terminal position. 

Scheme 11 Postsynthetic Sulfide Bridging of Peptides to Cystathionine Peptides1441...

Insulin is composed of 51 amino acids arranged in two polypeptide chains, designated A and B, which are linked together by two di- sulfide bridges (Figure 23.3A). The insulin molecule also contains an j intramolecular disulfide bridge between amino acid residues of the A chain. Beef insulin differs from human insulin at three amino add positions, whereas pork insulin varies at only one position. 

Two cage phosphorus sulfides may be synthesized by the formation of sulfide bridges through the action of bisririmethyltin) sulfide.1 ... 

There are also interesting complexes with sulfide bridging between gold(I) and tungsten(VI),... 

For both the dipalladium and palladium-platinum complexes the metal-metal bond is unusually reactive and a number of small molecules undergo an insertion reaction with (9) to give (10 equation 8). The corresponding sulfide-bridged dipalladium dimer can be prepared from the reaction of S8 or MeCHCH2S with (9).83 A mixed rhodium-palladium dimer can also be prepared from (9) (see Scheme 6).84... 

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