Disulfide interactions

The events leading to the macromolecular associations observed with (3-lactoglobulin appear to be mediated by disulfide interactions. The initial solution proposed to reduce thermoinduced aggregation was to remove the Cys 121 and replace it with alanine (Cho et al., 1994). Unfortunately, recombinant protein could not be purified from inclusion bodies. The alternative... 

In this section on mechanism and in the section to follow on structure, the comparisons will show that the relationship between lipoamide dehydrogenase and glutathione reductase is more marked than is the relationship of either to thioredoxin reductase. Thus, in catalysis, lipoamide dehydrogenase and glutathione reductase cycle between the oxidized state and a spectrally characteristic state in which the enzyme has accepted two electrons and these are shared between the FAD and the active center disulfide. This intermediate does not seem to be operative in thioredoxin reductase, and in this enzyme the FAD and disulfide interact in a different way. The oxidized forms of these enzsrmes can then be represented as... 

Carbon disulfide interacts with several organophosphorus compounds including the insecticides malathion and parathion. Metabolism of malathion and parathion requires cytochrome P-450 and is thus inhibited by carbon disulfide (Dalvi and Howell 1978). It is important to note that carbon disulfide would potentiate the toxic effect of compounds that require cytochrome P-450 microsomal metabolism for detoxification. 

A solution contains 3.95 g of carbon disulfide (CS2) and 2.43 g of acetone (CH3COCH3). The vapor pressures at 35 °C of pure carbon disulfide and pure acetone are 515 torr and 332 torr, respectively. Assuming ideal behavior, calculate the vapor pressures of each of the components and the total vapor pressure above the solution. The experimentally measured total vapor pressure of the solution at 35 °C is 645 torr. Is the solution ideal If not, what can you say about the relative strength of carbon disulfide-acetone interactions compared to the acetone-acetone and carbon disulfide-carbon disulfide interactions ... 

Lastly, compare the calculated total pressure for the ideal case to the experimentally measured total pressure. Since the experimentally measured pressure is greater than the calculated pressure, we can conclude that the interactions between the two components are weaker than the interactions between the components themselves. Ptot(exp) = 645 torr Ptot(exp) > Ptot (ideal) The solution is not ideal and shows positive deviations from Raoult s law. Therefore, carbon disulfide-acetone interactions must be weaker than acetone-acetone and carbon disulfide-carbon disulfide interactions. 

Size Isomers. In solution, hGH is a mixture of monomer, dimer, and higher molecular weight oligomers. Furthermore, there are aggregated forms of hGH found in both the pituitary and in the circulation (16,17). The dimeric forms of hGH have been the most carefully studied and there appear to be at least three distinct types of dimer a disulfide dimer connected through interchain disulfide bonds (8) a covalent or irreversible dimer that is detected on sodium dodecylsulfate- (SDS-)polyacrylamide gels (see Electroseparations, Electrophoresis) and is not a disulfide dimer (19,20) and a noncovalent dimer which is easily dissociated into monomeric hGH by treatment with agents that dismpt hydrophobic interactions in proteins (21). In addition, hGH forms a dimeric complex with ( 2). Scatchard analysis has revealed that two ions associate per hGH dimer in a cooperative... 

In addition to the restrictions on their mobiHty caused by steric and polar interactions between chemical groups, the protein molecules in wool fibers are covalentiy cross-linked by disulfide bonds. Permanent setting only occurs if these disulfide bonds are also rearranged to be in equiHbrium with the new shape of the fiber. Disulfide bond rearrangement occurs only at high temperature (>70° C) in wet wool and at even higher temperatures (above 100°C) in... 

The thioredoxin domain (see Figure 2.7) has a central (3 sheet surrounded by a helices. The active part of the molecule is a Pa(3 unit comprising p strands 2 and 3 joined by a helix 2. The redox-active disulfide bridge is at the amino end of this a helix and is formed by a Cys-X-X-Cys motif where X is any residue in DsbA, in thioredoxin, and in other members of this family of redox-active proteins. The a-helical domain of DsbA is positioned so that this disulfide bridge is at the center of a relatively extensive hydrophobic protein surface. Since disulfide bonds in proteins are usually buried in a hydrophobic environment, this hydrophobic surface in DsbA could provide an interaction area for exposed hydrophobic patches on partially folded protein substrates. 

Clostridial neurotoxins are bacterial protein toxins that consist of a heavy and a light chain connected by a disulfide bond and non-covalent interactions. They... 

Conserved sequences that fold into large loops stabilized by three disulfide linkages. The name Kringle comes from the Scandinavian pastry that these structures resemble. They can mediate certain protein-protein interactions. 

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