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Cysteine redox potential

In Figure 4 the effect of prothrombin on the differential capacity of a PS monolayer is presented. The overall capacitance, which is proportional to the out-of-phase (quadrature) ac current, increases upon interaction with the prothrombin. Moreover, a pseudocapacitance peak (at —0.7 V relative to the N-AgCl electrode) characteristic of cystine-cysteine redox potential appears. The peak potential moves as expected toward more... [Pg.123]

A second example is that of an Ala-to-Cys mutation, which causes the fonnation of a rare SH S hydrogen bond between the cysteine and a redox site sulfur and a 50 mV decrease in redox potential (and vice versa) in the bacterial ferredoxins [73]. Here, the side chain contribution of the cysteine is significant however, a backbone shift can also contribute depending on whether the nearby residues allow it to happen. Site-specific mutants have confirmed the redox potential shift [76,77] and the side chain conformation of cysteine but not the backbone shift in the case with crystal structures of both the native and mutant species [78] the latter can be attributed to the specific sequence of the ferre-doxin studied [73]. [Pg.407]

While the redox potentials of Rieske clusters are above -1-100 mV at pH 7, values between 100 and 150 mV have been determined for the redox potentials of Rieske-type clusters (Table XI). Several 4-cysteine coordinated [2Fe-2S] clusters have redox potentials similar to those of Rieske-type clusters, for example, the [2Fe-2S] clusters of the dioxygenase reductases [compilation in (104)]-, therefore, the redox potential is not useful for distinguishing between Rieske-type and ferredoxin-type clusters. [Pg.142]

The third reason for favoring a non-radical pathway is based on studies of a mutant version of the CFeSP. This mutant was generated by changing a cysteine residue to an alanine, which converts the 4Fe-4S cluster of the CFeSP into a 3Fe-4S cluster (14). This mutation causes the redox potential of the 3Fe-4S cluster to increase by about 500 mV. The mutant is incapable of coupling the reduction of the cobalt center to the oxidation of CO by CODH. Correspondingly, it is unable to participate in acetate synthesis from CH3-H4 folate, CO, and CoA unless chemical reductants are present. If mechanism 3 (discussed earlier) is correct, then the methyl transfer from the methylated corrinoid protein to CODH should be crippled. However, this reaction occurred at equal rates with the wild-type protein and the CFeSP variant. We feel that this result rules out the possibility of a radical methyl transfer mechanics and offers strong support for mechanism 1. [Pg.324]

Electrochemical studies performed in the 7 x Cys-Aspl4 D. afri-canus Fdlll indicate that the reduced [3Fe-4S] center can react rapidly with Fe to form a [4Fe-4S] core that must include noncysteinyl coordination (101). The carboxylate side chain of Asp 14 was proposed as the most likely candidate, since this amino acid occupies the cysteine position in the typical sequence of a 8Fe protein as indicated before. The novel [4Fe-4S] cluster with mixed S and O coordination has a midpoint redox potential of 400 mV (88). This novel coordinated state with an oxygen coordination to the iron-sulfur core is a plausible model for a [4Fe-4S] core showing unusual spin states present in complex proteins (113, 114). [Pg.377]

Cysteine, however, is able to strip ca. 50% of the technetium from the labelled protein after 4 hours of incubation [102]. Methods for complexation of antibodies with technetium must be modified for rhenium, because of its lower redox potential and-consequently-its greater tendency to reoxidize [103]. [Pg.98]

Finally, the redox potential of the heterodisulfide CoB-S-S-CoM (22), which was synthesized according to known procedures [49], was measured under the same conditions in phosphate buffer at pH 7. An value of -143 10 mV vs SHE for 22 exhibits a more positive redox potential than typical disulfides such as glutathione and cysteine (E° =-204 6 mV vs SHE and E° =-202 3 mV vs. SHE, resp.). That these deviations are probably due to the presence of sulfonate... [Pg.93]

Cys(StBu) with phosphines only a slight excess of tributylphosphine is required for this purpose. Under these conditions reduction of the diselenide does not occur at all, and subsequent air oxidation of the two cysteine residues at high dilution leads in a highly selective manner to the diselenide- and disulfide-bridged peptides. The selectivity of the disulfide bridging is assured by the complete absence of thiol/diselenide exchange reactions even at alkaline pH values due to the very low reactivity of the diselenide toward mono-thiols as a result of their highly differentiated redox potentials. ... [Pg.220]


See other pages where Cysteine redox potential is mentioned: [Pg.117]    [Pg.117]    [Pg.178]    [Pg.12]    [Pg.13]    [Pg.14]    [Pg.38]    [Pg.348]    [Pg.362]    [Pg.452]    [Pg.453]    [Pg.454]    [Pg.455]    [Pg.457]    [Pg.476]    [Pg.59]    [Pg.70]    [Pg.181]    [Pg.70]    [Pg.53]    [Pg.307]    [Pg.296]    [Pg.148]    [Pg.257]    [Pg.178]    [Pg.214]    [Pg.221]    [Pg.596]    [Pg.602]    [Pg.232]    [Pg.119]    [Pg.142]    [Pg.142]    [Pg.143]    [Pg.152]    [Pg.154]    [Pg.359]    [Pg.110]    [Pg.787]    [Pg.859]    [Pg.723]    [Pg.75]    [Pg.622]    [Pg.629]   
See also in sourсe #XX -- [ Pg.20 ]




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Redox potentials

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