Disulfide structures

The photochemical behavior of a number of substituted derivatives of thiochroman-4-one 1-oxides has been examined by Still and coworkers192-194. These authors also report that rearrangement to cyclic sulfenates, with subsequent reaction by homolysis of the S—O bond, appears to be a particularly favorable process. For example, ultraviolet irradiation of a solution of 8-methylthiochroman-4-one 1-oxide (133) in benzene for 24h afforded a single crystalline product which was assigned the disulfide structure 134 (equation 54). More recently, Kobayashi and Mutai195 have also suggested a sulfoxide-sulfenate rearrangement for the photochemical conversion of 2,5-diphenyl-l,4-dithiin 1-oxide (135) to the 1,3-dithiole derivatives 136 and 137 (equation 55). 

Although the occurrence of six conserved cysteine residues, the spacing patterns of these residues, and possibly the pattern of disulfide structures are hallmarks of OBPs, the six-cysteine criterion alone is not sufficient to classify a certain protein as an olfactory protein [ 16]. It is important to demonstrate that an OBP is expressed only (or predominantly) in olfactory tissues. Evidence for their ability to bind odorants is also desirable, but not sine qua non. One of these criteria alone would not be enough to define a given protein as an OBP. For example, bovine serum albumin (BSA) binds to insect pheromones (Leal, unpublished data) and yet it is not an OBP because it not expressed in insect olfactory tissues. Conversely, a protein specific to antennae is not necessarily an OBP. There are other proteins that may be expressed in antennae but not in control tissues. Non-OBPs specifically accumulated in insect antennae have been previously detected (Ishida and Leal, unpublished data). Also, a glu-tathione-S-transferase has been reported to be expressed specifically in antennae of M. sexta [52]. 

Qi J., Wu J., Somkuti G.A., and Watson J.T. (2001), Determination of the disulfide structure of sillucin, a highly knotted, cysteine-rich peptide, by cyanylation/cleavage mass mapping, Biochemistry 40, 4531 -538. 

Captax (Structure 15.21) is used to the extent of 1% with hevea rubber and accounts for the major part of the over 30,000 t of accelerators used annually in the United States. Other accelerators widely used include 2-mercaptobenzothiazole sulfenamide (Santocure Structure 15.22), used for the vulcanization of SBR dithiocarbamates and thiuram disulfides. Thiuram disulfide (Structure 15.23) is a member of a group called ultra-accelerators, which allow the curing of rubber at moderate temperatures and may be used in the absence of sulfur. 

When air oxidation of the reduced p-conotoxin GIIIB (18) was carried out in 0.1 M NHtOAc buffer (pH 7.5) at 0.01 mM peptide concentration and at 10 °C, three major products, isomers 15,16, and 17 were produced after 40 hours in a ratio of 1 4 3 (Figure 2). 86 The disulfide structures of each isomer were determined by enzymatic digestion followed by amino acid analyses, mass spectrometry, sequence analyses, as well as by the synthetic approach (Scheme 10). 

Title Novel Sulfur-containing Phenolic Resin, Process for Preparing the Same, Phenol Derivatives Having Thioether Structure or Disulfide Structure, Process for Preparing the Same and Epoxy Resin Composition Adhesive... 

The reaction has been extended to the synthesis of the analogous 3-alkylthio heterocycles (123) from the appropriate dithiobiurets (122).132 1-Substituted 2,4-dithiobiurets (125), unlike their monothio-biuret analogs (118), are unsuitable as precursors of 1,2,4-thiadiazoles, since in any oxidation the two thiol groups may be expected to react preferentially, resulting in the formation of cyclic disulfides (126). The formulation of such oxidation products as 1,2,4-thiadiazoles has indeed been discussed by Bambas1 however, the available evidence133 favors the cyclic disulfide structure.134... 

Isothiocyanate oxide hydrobromides,164 however, all show the characteristic absorption in the imino region their cyclic disulfide structure (153) is thus indicated, presupposing the isomerization 153— 152 (R = alkyl) on liberation of the free base. When a rearrangement of this type can occur readily, it seems reasonable that the dithiazolidine form (153), incorporating the basic alkylimino group, would be the more stable in the presence of acid. 

The oxidation of dithiobiuret and its homologs yields the so-called thiurets (for asummary, see ref. 134), for which a 1,2,4-dithiazolidine structure (319 and 320) is generally accepted. Their formulation as 3-thiono-l,2,4-thiadiazolidines (317 and 318) has been discussed,1 but the weight of the available evidence supports the cyclic disulfide structure (319 and 320)184 originally proposed.188... 

Leal W. S., Nikonova L. and Peng G. (1999) Disulfide structure of the pheromone binding protein from the silkworm moth, Bombyx mori. FEBS Letters. 468, 85-90. 

Therapeutic Function Alcohol deterrent Chemical Name Tetraethylthioperoxydicarbonic diamide Common Name Tetraethyl thiuram disulfide Structural Formula ... 

Holmgren, A. 1995. Thioredoxin structure and mechanism Conformational changes on oxidation of the active-site sulfhydryls to a disulfide. Structure 3 239-243. 

The lack of reversibility, and the presence of precipitation, makes thermodynamic analysis of aFGF particularly challenging. Precipitation in the presence of DTT indicates that precipitation is not dependent upon the formation of mixed disulfides. Structural analysis of human aFGF (17) shows that the three free cysteine residues are located at solvent inaccessible positions (figure 4). Thus, formation of mixed disulfides would be expected to destabilize the protein because a) structural changes would be required to expose the cysteines for oxidation and b) covalent adducts of the cysteine residues would have to be tolerated within the packing constraints of the interior of the protein for the native state to be adopted. 

Relaxin, lGF-1, and IGF-II are all structurally homologous to proinsulin and contain the characteristic 3-disulfide structure of insulin. The IGF-I receptor structure resembles that of the insulin receptor (Fig. 11-11) and also that of the epidermal growth factor (EGF) receptor. ... 

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