Sterically Hindered Carboxylates for Modeling Nonheme Iron Proteins

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This award in the Bioinorganic and Organometallic Chemistry Program supports Professors William B. Tolman and Lawrence Que at the University of Minnesota for detailed studies on synthetic models of carboxylate bridged di-iron enzymes, such as ribonucleotide reductase, methane monooxygenase, toluene monooxygenase, and stearoyl ACP desaturase. In this research, sterically bulky carboxylate ligands will be used to control complex nuclearity and coordination number(s), as well as to provide hydrophobic shielding for stabilizing reactive intermediates and influencing redox potentials. Variation of the steric properties of the carboxylates and co-incorporated N-donor ligands will be used to control the structural attributes of the complexes and purposefully access both mono- and diiron complexes. These complexes will serve as precursors of reactive intermediates to be trapped in the reactions with oxygen, superoxide, and peroxides. Transient species and reaction mechanisms for iron-oxygen intermediate formation reactions and interconversions will be assessed by kinetics studies. This work will involve collaborations with E. Munck (Mossbauer, Carnegie-Mellon U) and E. Rybak-Akimova (cryogenic stopped-flow kinetics, Tufts U). The research will elucidate the functioning of nonheme iron enzymes that play central roles in processes of biological and environmental significance. These processes are closely related to catalytic reactions in industry, so that the fundamental knowledge acquired during the course of the research will impact catalysis in a broad sense. Graduate students will be trained in a highly multidisciplinary environment involving the Center for Metals in Biocatalysis at the University of Minnesota.