Chemistry and Chemical Biology ETDs

Publication Date

Summer 7-15-2020

Abstract

Pyranopterin molybdenum and tungsten enzymes are expressed in numerous organisms from all domains of life. These enzymes catalyze a variety of atom, hydride, and electron transfer reactions. The enzymes are of great importance in the biogeochemical cycles of nitrogen, carbon, and sulfur. In recent years, chemists have investigated applications for some of these enzymes as industrial biocatalysts. The dimethylsulfoxide reductase (DMSOr) enzyme family is the broadest family of pyranopterin Mo enzymes. The first coordination sphere of the Mo or W-containing active site for each member of this family is made up of 4 sulfur donors from the two pyranopterin dithiolenes (PDTs); either a SCys, SeSec or OSer donor from the polypeptide; and for the oxidized form of the enzyme a terminal oxo or sulfido ligand. Although numerous spectroscopic studies have contributed to our understanding of the geometric and electronic structures of reduced (Mo (IV)) and oxidized (Mo (VI)) forms of these enzymes, studies on paramagnetic (Mo (V)) intermediates of the DMSOr family are limited. Remarkably, there is a dearth of detailed studies on synthetic analogs for EPR active forms of DMSOR enzymes. We have now synthesized and characterized new compounds as models of paramagnetic DMSOr enzyme intermediates. Through interpretation of their XAS, EPR, and electronic absorption spectra, in addition to computational results for these model compounds, we have added new insight into the electronic and geometric structures of the respective enzymes. Understanding their geometric and electronic structures also provides insight into the mechanistic details of the corresponding enzymes.

Language

English

Keywords

EPR, XAS, Synthesis of Model Compounds

Document Type

Dissertation

Degree Name

Chemistry

Level of Degree

Doctoral

Department Name

Department of Chemistry and Chemical Biology

First Committee Member (Chair)

Prof. Martin L. Kirk

Second Committee Member

Prof. Abhaya K. Datye

Third Committee Member

Prof. Jeffrey J. Rack

Fourth Committee Member

Prof. Terefe G. Habteyes

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