Disulfide linkages formation

In addition to phosphorylation and glycosylation, disulfide linkage formation is another PTM that can be characterized more readily by ETD than by excitation with either photons or low-energy collisions, the latter of which tend not to cleave disulfide bonds present in multiply-protonated polypeptides [133,134]. The rupture... 

A final method of forming disulfide crosslinks between toxins and targeting molecules is the use of S-sulfonate formation using sodium sulfite (Na2SC>3) in the presence of sodium tetrathion-ate (Na2S40g). Tetrathionate reacts with sulfhydryls to form sulfenylthiosulfate intermediates (section 1.1.5.2). These derivatives are reactive toward other thiols to create disulfide linkages... 

Ajoene (Spanish, ajo, garlic), 4,5,9-trithiadodeca-l,6,ll-triene-9-oxide 35 (Scheme 12), an antithrombotic compound with other well-defined physiological properties, is formed from allicin.84 Like allicin, ajoene is a sulfoxide but has two further sulfur atoms in a disulfide linkage. E and Z isomeric forms are possible involving the C=C bond at positions 6 and 7. Ajoene is somewhat more stable than allicin. The formation of ajoene probably involves condensation of 2 molecules of allicin forming a sulfonium salt 33, with elimination of propenesulfenic acid. Elimination of a second molecule of propenesulfenic acid... 

The data for the model compound study strongly supports the tenet of a photolytic bond cleavage of the sulfur-sulfur bond in PATTE polymers (Scheme IV). Combined with the results for PASE, we feel quite confident in postulating the formation of a disulfide linkage upon photolysis of PATE films (Scheme III). 

Insect OBPs are secretory proteins whose only posttranslational modification is the formation of three disulfide bridges [39,45] from six cysteine residues. That six cysteine residues are well conserved in OBPs from species of the same order is a hallmark of these proteins. The disulfide links of OBPs in a few species have been determined by analytical methods, first in the OBPs from B. mori [45,46]. As part of our attempt to get better insight into the structural biology of pheromone-binding proteins, we have determined the disulfide linkages... 

FIGURE 2.19 Chemical cross-linking of polyethylene (PE) chains through formation of disulfide linkages. 

Figure 7.3 Gold-thiolate bonds encourage the adsorption of the bisthiol 5 on the surface of gold in the form of a monolayer (a). The subsequent and spontaneous formation of disulfide linkages promotes the deposition of additional molecules of 5 to produce multilayers (b).

Addition of oxidizing agent to soy flour resulted in a less-puffed or undertexturized extrudates. The extrudate showed rough, discontinuous surface and small dieimeter. This result further proves that the change of disulfide linkages is an essential reaction for texture formation. 

Applications of the TASP approach are then considered for such aspects as four-helical bundles (Section 13.1.2.4.2)J4 The details of structures and synthetic routes for the preparation of the bundles are described. Other chain assemblies and applications are discussed (Section 13.1.2.5) including metal-ion assisted self assemblies, disulfide linkages in the formation of four-helical bundles (Section 13.1.2.5.2), multiple antigenic peptide systems (Section 13.1.2.5.4), and templates constructed from a trialdehyde template by reductive amination to form a three-helical bundle (Section 13.1.2.5.5))5 ... 

Sodium tetrathionate (Na2S406) is a redox compound that under the right conditions can facilitate the formation of disulfide bonds from free sulfhydryls. The tetrathionate anion reacts with a sulfhydryl to create a somewhat stable active intermediate, a sulfenylthiosulfate (Fig. 102). Upon attack of the nucleophilic thiolate anion on this activated species, the thiosulfate (S203 =) leaving group is removed and a disulfide linkage forms (Pihl and Lange, 1962). The reduction of tetrathionate to thiosulfate in vivo was a subject of early study (Theis and Freeland, 1940 Chen et al., 1934). 

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