EAGER Renewal: Bio-Inorganic Chemistry of the Rare Earth Metals: Chemistry Relevant to the Cerium-Dependent Methanol Dehydrogenase

University Of Pennsylvania, Philadelphia PA

Investigators

Abstract

With this award the Chemistry of Life Processes (CLP) program in the Division of Chemistry (CHE) is funding Dr. Eric J. Schelter at the University of Pennsylvania for studies on one of only two known rare earth-containing enzymes. The rare earths are actually metals that are important to many of our modern electrical devices but are rarely, if ever, found in biological systems. The PI is studying an enzyme from a bacterium discovered in acidic volcanic mudpots, found to have rare earth elements as an essential growth requirement. This project is attempting to understand the unique characteristics and reactivity conferred to an enzyme isolated from these bacteria through the presence of cerium, one of the rare earth elements. The results are expanding understanding of new and unusual biochemistry, particularly as it concerns metabolism and energy. Students trained on this project are accruing skills in synthetic bioinorganic chemistry and chemical analysis. Undergraduate and graduate chemistry students from underrepresented groups are also benefiting from support of the project. A growing body of information suggests that rare earth elements play an important role in the global carbon cycle. Rare earth elements can incorporate the active site of a methanol dehydrogenase (MDH), encoded namely by the XoxF gene of M. fumariolicum SoIV, that includes a pyrroloquinoline quinone (PQQ) cofactor. The central hypothesis of this application is that quinolone quinones that replicate the electronic structure of PQQ, developed in the first stage of the project, will similarly induce alcohol dehydrogenation reactivity upon coordination with rare earth element cations in model complexes, and that the strong Lewis acidity of rare earth metal cations enable fast and unique reactivity for rare earth-XoxF-MDH. The overall goals of this proposal are to use a combination of synthesis, electrochemistry, Density Functional Theory (DFT) and high throughput experimentation to elucidate the unique physicochemical characteristics of the rare earth element-XoxF-MDH active site and to test functional model compounds of the active site in the catalytic dehydrogenation of small molecules.