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Dr. Darensbourg
http://www.chem.tamu.edu/rgroup/marcetta/ Our interests lie in the active sites of
enzymes that control organometallic transformations. Our goals are to
produce small-molecule functional models based on known or
spectroscopically implied structures,
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and to explore their chemical and
spectroscopic properties. Ultimately we would like to provide mechanistic
understanding for the synthetic and natural catalytic processes that might
develop useful catalysts sans protein. For example, parallel processes in
nature and in industry exist in the realm of carbon-carbon coupling
reactions as mediated by transition metals. While the metals used in
industrial catalysis are typically rare and expensive, chemistry performed
by the active site of Acetyl CoA Synthase relies on a base metal, nickel.
The core of the site involves two nickel ions, one in a tripeptide which
uses cysteine sulfurs to bridge to the second nickel where the methyl-CO
coupling process takes place. We have developed analogs of this N2S2Ni
site and have characterized them (Figure 3). Biological-like N2S2
ligands, including tripeptides anchored to resins, form hybrid
organometallic/bioinorganic constructs leading to new catalysts. We also
explore the production or uptake of H2 by binuclear [Ni Fe] or [Fe-Fe]
complexes which represent the active sites of hydrogenases as a means of
characterizing these biocatalysts.