Metalloenzymes effect a variety of important chemical transformations, often involving small molecule substrates or products such as molecular oxygen, hydrogen, nitrogen, and water. A diverse array of ions or metal clusters is observed at the active-site cores, but living systems use basic recurring structures that have been modified or tuned for specific purposes. Inorganic chemists are actively involved in the elucidation of the structure, spectroscopy, and mechanism of action of these biological catalysts, in part through a synthetic modeling approach involving biomimetic studies.

https://science.sciencemag.org/content/sci/261/5122/701.full.pdf

Metalloenzymes, structural motifs, and inorganic models

Characteristics and Activities of Sulfate-reducing Bacteria L.L. Barton, F.A. Tomei. Sulfate-reducing Archaea R.K. Thauer, J. Kunow. Taxonomic Relationships E. Stackebrandt, et al. Respiratory Sulfate Reduction J.M. Akagi. Characteristics of Electron Transfer Proteins L. Chen, et al. Solute Transport and Cell Energetics H. Cypionka. Molecular Biology of Redoxactive Metal Proteins from Desulfovibrio W.M.A.M. van Dongen. Ecology of Sulfate-reducing Bacteria G.D. Fauque. Biocorrosion W.A. Hamilton, W. Lee. Control in Industrial Settings T.R. Jack, D.W.S. Westlake. Metabolism of Environmental Contaminants by Mixed and Pure Cultures of Sulfate-reducing Bacteria B.D. Ensley, J.M. Suflita. Index.

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Sulfate-reducing bacteria

The role of the hybrid cluster protein in oxidative stress defense.

A magnetic study of an Fe-chitosan complex and its relevance to other biomolecules.

Iron-sulfur polymetallic centers pose interesting questions on the oxidation state of each metal ion, on the possibility of electron delocalization over the metal ions versus the possibility of existence of equilibria among different localized-valence states, and on the factors determining if, and to what extent, electron delocalization is present. By interpreting the hyperfine coupling of unpaired electrons with 57Fe as well as with 1H, and by analyzing the EPR spectra, the valence distributions of Fe-S polymetallic centers in proteins and model systems are obtained. The systems analyzed here are: [Fe2S2]2+/+, [Fe3S4]+/0, [Fe4S4]3+/2+/+. The understanding of the parameters describing the exchange coupling within pairs of spin vectors, as well as the double exchange coupling, is attempted on the basis of the oxidation states of the various ions. Upon proper scaling of these parameters, we show that it is possible to transfer them from one polymetallic center to another. The electronic properties are tentatively related to the microscopic reduction potentials of each iron in the center.

Boi Hahn Huynh

Papers

Direct spectroscopic evidence for the presence of a 6Fe cluster in an iron-sulfur protein isolated from Desulfovibrio desulfuricans (ATCC 27774)