This research has been directed at the study of both the enzyme sulfite oxidase and molybdenum model chemistry. A modification of a previously published procedure has been used to purify sulfite oxidase in high yield which is well-suited for experiments requiring prosthetically intact enzyme and which is not contaminated with extraneous heme or with other redox active proteins. Laser flash photolysis was used to study the reaction of photoproduced 5-deazariboflavin, lumiflavin, and riboflavin semiquinone radicals with the redox centers of purified sulfite oxidase. Two distinctly different intramolecular electron transfer processes were observed between the molybdenum and heme sites of the enzyme, and these assignments were supported by flash photolysis studies of the cyanide-inactivated enzyme and the sulfite oxidase heme peptide. Microcoulometric experiments on sulfite oxidase have shown that the enzyme requires the addition of three electrons for complete subunit reduction. Midpoint potentials for the Mo(VI)/Mo(V), Mo(V)/Mo(IV), and Fe(III)/Fe(II) couples have been obtained under varied buffer conditions. The midpoint potentials obtained under High-pH and Low-pH conditions provided a means for reductively titrating the enzyme to the Mo(V) oxidation state for EXAFS studies. EXAFS of sulfite oxidase under High-pH and Low-pH conditions have provided the first example of a structural study of the three accessible oxidation states (Mo(VI), Mo(V), and Mo(IV)). A biologically relevant synthetic model for the formation of the Mo(V) Low-pH form of sulfite oxidase has been developed. The Mo(V) model compound closely resembles the minimum coordination environment for the Mo(V) Low-pH form of sulfite oxidase as determined by EXAFS. Using synchrotron radiation, molybdenum L-edge x-ray absorption spectra have been obtained for a variety of oxomolybdenum(V) compounds which serve as models for sulfite oxidase. An attempt has been made to correlate unique features of the molecules to the observed 2P → 4d electronic transitions.

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xvi, 240 p.; also includes graphics (some col.). Includes bibliographical references (p. 231-240). Available online via OhioLINK's ETD Center

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xv, 172 p.; also includes graphics. Includes bibliographical references (p. 165-172).

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Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 157-184). Also available via the Internet.

Thesis (Ph. D.)--Ohio State University, 2003. / Title from first page of PDF file. Document formatted into pages; contains xvi, 176 p.; also includes graphics (some col.). Includes abstract and vita. Advisor:, Dept. of Biochemistry. Includes bibliographical references (p. 168-176).

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 113-119).

Thesis (M.S.)--The University of North Carolina at Greensboro, 2008. / Directed by Bruce Banks; submitted to the Dept. of Chemistry. Title from PDF t.p. (viewed Jul. 31, 2009). Includes bibliographical references (p. 95-102).

Thesis (Ph.D.) - University of Queensland, 2004. / Includes bibliographical references.

Haemophilus influenzae is a host adapted human mucosal pathogen involved in a variety of acute and chronic respiratory tract infections, including chronic obstructive pulmonary disease and asthma, all of which rely on its ability to efficiently establish continuing interactions with the host. Here we report the characterization of a novel molybdenum enzyme, TorZ/MtsZ that supports interactions of H. influenzae with host cells during growth in oxygen-limited environments. Strains lacking TorZ/MtsZ showed a reduced ability to survive in contact with epithelial cells as shown by immunofluorescence microscopy and adherence/invasion assays. This included a reduction in the ability of the strain to invade human epithelial cells, a trait that could be linked to the persistence of H. influenzae. The observation that in a murine model of H. influenzae infection, strains lacking TorZ/MtsZ were almost undetectable after 72 h of infection, while similar to 3.6 x 10(3) CFU/mL of the wild type strain were measured under the same conditions is consistent with this view. To understand how TorZ/MtsZ mediates this effect we purified and characterized the enzyme, and were able to show that it is an S- and N-oxide reductase with a stereospecificity for S-sulfoxides. The enzyme converts two physiologically relevant sulfoxides, biotin sulfoxide and methionine sulfoxide (MetSO), with the kinetic parameters suggesting that MetSO is the natural substrate of this enzyme. TorZ/MtsZ was unable to repair sulfoxides in oxidized Calmodulin, suggesting that a role in cell metabolism/energy generation and not protein repair is the key function of this enzyme. Phylogenetic analyses showed that H. influenzae TorZ/MtsZ is only distantly related to the Escherichia colt TorZ TMAO reductase, but instead is a representative of a new, previously uncharacterized Glade of molybdenum enzyme that is widely distributed within the Pasteurellaceae family of pathogenic bacteria. It is likely that MtsZ/TorZ has a similar role in supporting host/pathogen interactions in other members of the Pasteurellaceae, which includes both human and animal pathogens.