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Job RC, Bruice TC. Iron-sulfur clusters II: Kinetics of ligand exchange studied on a water-soluble Fe(4)S(4)(SR)(4) cluster. Proc Natl Acad Sci U S A. 1975;72(7):2478-82doi: 10.1073/pnas.72.7.2478.
Job, R. C., & Bruice, T. C. (1975). Iron-sulfur clusters II: Kinetics of ligand exchange studied on a water-soluble Fe(4)S(4)(SR)(4) cluster. Proceedings of the National Academy of Sciences of the United States of America, 72(7), 2478-82. https://doi.org/10.1073/pnas.72.7.2478
Job, R C, and Bruice, T C. "Iron-sulfur clusters II: Kinetics of ligand exchange studied on a water-soluble Fe(4)S(4)(SR)(4) cluster." Proceedings of the National Academy of Sciences of the United States of America vol. 72,7 (1975): 2478-82. doi: https://doi.org/10.1073/pnas.72.7.2478
Job RC, Bruice TC. Iron-sulfur clusters II: Kinetics of ligand exchange studied on a water-soluble Fe(4)S(4)(SR)(4) cluster. Proc Natl Acad Sci U S A. 1975 Jul;72(7):2478-82. doi: 10.1073/pnas.72.7.2478. PMID: 16592256; PMCID: PMC432790.
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Proc Natl Acad Sci U S A. 1975 Jul;72(7):2478-82. doi: 10.1073/pnas.72.7.2478.

Iron-sulfur clusters II: Kinetics of ligand exchange studied on a water-soluble Fe(4)S(4)(SR)(4) cluster.

Proceedings of the National Academy of Sciences of the United States of America

R C Job, T C Bruice

Affiliations

  1. Department of Chemistry, University of California, Santa Barbara, Calif. 93106.

PMID: 16592256 PMCID: PMC432790 DOI: 10.1073/pnas.72.7.2478

Abstract

The water-soluble tetranuclear iron-sulfur cluster ion Fe(4)S(4)(SCH(2)CH(2)CO(2) (-))(4) (6-) (II) has been prepared. The stability of II in water is sufficient to allow the spectrotitrimetric determination of the pK(a) of its Fe(4)S(4) core as 7.4. In our hands the one-electron reductions of compounds I [Fe(4)S(4)(SR)(4) (2-), R = alkyl or aryl,] are thermodynamically irreversible with associated E(1/2) values greater than those for one-electron reduction of ferredoxins. In contrast, the one-electron reduction of II is thermodynamically reversible and the associated potential (-0.58 V versus hydrogen electrode) approaches closely that of the ferredoxins. The kinetics for ligand exchange of II as a function of pH and thiol concentration are in accord with four reversible mercaptan/lyate species exchange reactions followed by product formation via specific acid and base catalysis. Preliminary experiments indicate the nucleophilic order towards II to be Cl(-) [unk] Br(-) < HO(-) < CN(-).

References

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