My expertise and research interests lie in the area of reaction mechanisms involving transition metal chemistry and the importance of transition metal ions in biological systems. I have three projects that contribute to this subfield of inorganic chemistry. Two of these projects focus on the role of chromium ions in biological systems. The third project examines the photochemistry of a model for the active site of the iron-only hydrogenase, an enzyme involved in the oxidation of molecular hydrogen.
Chromium(III) binding proteins
Chromium can exist in many different forms but the most stable and common are chromium (VI) and chromium (III) ions. Chromium (VI) is a particularly dangerous environmental pollutant due to its carcinogenicity and water solubility. Chromium (VI) is a strong oxidizing agent and inside biological systems participates in a string of complex redox reactions. Products of these reactions include chromium (III) DNA complexes, which are often discussed in the literature. My research at SSU has shown that chromium (III) can also form protein complexes after exposure to chromium(VI) . My working hypothesis is that these chromium (III) proteins are formed to prevent chromium (VI) from reacting with DNA, as a possible detoxification mechanism. In order to determine if these chromium (III) protein complexes serve a detoxification role, I have designed experiments to isolate and study the chromium (III) proteins that form in bovine liver after exposures to chromium (VI). In order to understand the function of these metallo-proteins, their structural information must first be determined, which is the long-term goal of my research in this area.
Bacteria can rapidly evolve to tolerate extreme chemical environments. This has become important in bioremediation of polluted soil and water. The chromate reductase project is concerned with studying the mechanisms that some bacteria utilize to live in high chromium (VI) environments. I am particularly interested in bacteria that can reduce toxic chromium (VI) to the less toxic chromium(III) form. This reduction process can only occur through a catalyzed reaction pathway, utilizing a type of enzyme called chromate reductase. My research group at SSU has identified a new bacteria, Pseudomonas Veronii that is capable of reducing chromium (VI), indicating the presence of a chromate reductase. We have performed a partial purification of the enzyme from Pseudomonas Veronii and the initial studies on the enzyme kinetics. The current goal for this project is the complete purification and structural characterization of Pseudomonas Veronii. The long-term goal for this project is to understand the functional role of this enzyme.
Photochemistry of m-(1,3-propanedithiolato)-hexacarbonyldiiron
The focus of this project is the photochemical reactivity of m-(1,3-propanedithiolato)-hexacarbonyldiiron. This compound is a structural and functional model for the active site of iron-only hydrogenase. Iron-only hydrogenase is an enzyme that catalyzes the reversible oxidation of molecular hydrogen and is responsible for most of the bio-processing of hydrogen. The photochemical experiments in this project could lend insight into how bacteria use hydrogen as a fuel.