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The spectroscopic studies of pyrococcus furiosus superoxide reductase are detailed. The ability cyanide to bind exogenous ligands to both the ferrous and ferric sites of superoxide reductase is consistent with an inner-sphere catalytic mechanism involving superoxide binding at the ferrous site to yield a ferric-hydroperoxo intermediate.

Resonance Raman spectra and excitation profiles were determined for four distinct forms of Rhodobacter sphaeroides dimethyl sulfoxide reductase as prepared by Mo(VI), dithionite-reduced Mo(IV), dimethyl sulfide reduced Mo(IV) and glycerol-inhibited Mo(V). All the vibrational modes in the 200-1700/cm area of the Mo(VI) and Mo(IV) forms were assigned to vibrations involving atoms in the first or second coordination sphere of the bis-molybdopterin-coordinated Mo active site, the dithiolene chelate rings, or nonresonantly enhanced protein modes.

Electron paramagnetic resonance and variable-temperature magnetic circular dichroism spectroscopies were employed to investigate the redox and electronic behavior of the iron and tungsten centers in the aldehyde ferredoxin oxidoreductases (AOR) isolated from Pyrococcus strain ES-4 (ES-4) and Pyrococcus furiosus (Pf). The results revealed the nonhomogeneity of the tungsten centers and the presence of (4Fe-4S)(sup 2+,+) clusters in both samples.

Electron paramagnetic resonance and electron-nuclear double-resonance spectroscopy of Pyroccocus furiosus reveal 4-Fe ferredoxin that has a cluster anchored to its protein by only three cysteinyl residues. The cluster exhibits S=1/2 and S=3/2 spin states and is easily converted to S=1/2 state in the presence of an excess cyanide ion. Dialysis reverses the reaction and converts the cluster back to its original spin state. Investigations reveal that cyanide bound to monomeric low-spin Fe(III)-containing proteins than cyanide bound to 4Fe-Fds.

Analysis of the interaction of Tl(+) and Cs(+) with (Fe3S4)(super +, O) cluster in Pyrococcus furiosus ferredoxin yields a comparison of the affinities of these two large, polarizable monocovalent cations to ferrodoxin. Various spectroscopic studies characterize the resultant heterometallic clusters. Tl(super +) is incorporated into both the oxidized and reduced clusters to form (TlFe3S4)super(+, 2+), but Cs(super +) incorporations are not observed in both oxidized and reduced forms of the cluster.

The x-ray crystal structure of the S-adenosylmethionine-dependent enzyme MoaA with the substrate guanosine 5'-triphosphate (5'-GTP) was studied to understand the binding of the substrate to the unique iron of one of two 4Fe-4S clusters through either or both the amino and N1 nitrogen nuclei. The results provide insight into the important mechanistic implications of binding-induced tautomerization observed for the guanine base which adopts the enol tautomer as N1 binds to Fe4 and the hydrogen bond with S4 of the 4Fe-4S cluster formed by the 06-H hydroxyl group.

A combination of sulfur K-edge X-ray absorption spectroscopy (XAS) and density functional theory is used to study the structure of superoxide reductase (SOR). The sites with high positive charge in these compounds are found to have higher affinity for binding another anion.

G-protein-coupled receptor (GPCR) microarrays on porous glass surface and functional assays to monitor their activation are studied. The results suggest that functional GPCR microarrays could potentially streamline drug discovery by helping integrate primary screening with selectivity and safety screening, without compromising the essential functional information that is obtained using conventional cell-based assays.

Spectroscopic and redox characterization of the active site of ferredoxin: thioredoxin reductase (FTR) in various forms of the enzyme, including wild-type FTR, point-mutation variants at each of the active-site cysteine residues and stable analogues of the one-electron-reduced FTR-Trx heterodisulfide intermediate are reported. Two-electron-reduced FTR in which the disulfide is reduced to a dithiol contains an unprecedented electron-rich cluster comprising both valence-delocalized and valence-localized Fe(super 2+)Fe(super 3+) pairs.

Spectroscopic studies demonstrate that BioB can accommodate one [4Fe-4S](super ++) cluster per monomer, and provide direct evidence that the [4Fe-4S)(super +) cluster is responsible for reductive cleavage of S-adenosyl-L-methionine (SAM) and is ligated by the cysteines in the C-X3-C-X2-C motif. This suggests a common mechanism of SAM for all enzymes in the radical SAM family.

Ferredoxin:thioredoxin reductase (FTR) plays an important role in the light regulated catalytic properties of enzymes involved in the Calvin cycle. Studies show that both the as-purified and NEM-modified forms of FTR from spinach are investigated by Mossbauer spectroscopy to provide further understanding of the cluster coordination and electronic state.

The mechanism of IscS-directed Fe-S cluster assembly on the IscU scaffold is described using mass spectroscopy. The direct transfer of sulfane sulfur, S(super 0), from the cysteine persulfide on IscS to the cysteine residues on IscU indicates that this reaction constitutes the first step in Fe-S cluster biosynthesis on an IscU scaffold.

Research is presented demonstrating a mechanism for the biosynthesis of Fe-S clusters in which IscU acts as a scaffold for the assembly of [Fe2(mu2-S)2]cores which are IscS-mediated.

A novel type of medium-dependent reversible cluster that includes the A33C form of Pyrococcus furiosus ferredoxin (PfFd) was discovered. The A33C PfFd was prepared and characterized to evaluate the effects of the location of additional free cysteine adjacent to the cluster. The resonance, which was found to be 1.0 +- 0.1 spins/molecule, was similar to that caused by ferricyanide oxidation of wild-type PfFd, thereby pointing to the existence of one {Fe3S4}+ cluster per molecule.

Aerobic and anaerobic ribonucleotide reductases and pyruvate formate-lyase from Escherichia coli can utilize stable protein-based radicals as part of their catalytic cycles. Pyruvate formate-lyase (PFL) is known to need a stable glycyl radical for the rearrangement of pyruvate to formate. Evidence of the presence of an iron-sulfur cluster in PFL activating enzyme (PFL-AE) is reported.

The molybdenum domain of the wild-type and C207S mutant forms of recombinant human sulfite oxidase have been described using the resonance Raman spectra. Mo=O stretching modes have been studied for a biological molybdenum center and results show that only one oxo group exchanges during redox cycling in connection to direct oxo-transfer catalytic process. Both the wild-type and C207S mutant of the molybdenum domain display bands at 1006, 1161 and 1532 cm-1 which are not enhanced with excitation wavelengths > 514 nm but are dominant in the spectra with 488-, 476-, and 457-nm excitation.

The resonance Raman spectra of prismane-type iron-sulphur clusters containing six iron atoms (6Fe-6S) in aerobically purified monomeric proteins isolated from Desulfovibrio vulgaris and Desulfovibrio desulfuricans were studied. The spectra, which revealed the presence of a non-heme Fe=O or monobridged Fe-O-Fe species, suggested that 'at least one of the Fe sites' in the recombinant (6Fe-6S) proteins has a unique oxo moiety.

Electron paramagnetic resonance and variable temperature magnetic circular dichroism studies of the Cys60 Ser mutant of Clostrodium pasteurianum 2Fe ferredoxin provide evidence for a reduced Fe2S2 cluster with a S = 9/2 ground state. Antiferromagnetic exchange interaction within a localized valence (Fe2S2)+ cluster is responsible for the S = 1/2 species and double exchange within a valence-delocalized (Fe2S2)+ cluster is responsible for the S = 9/2 ground state.