Design and synthesis of models for copper enzymes in denitrifying bacteria

University Of Oklahoma Norman Campus, Norman OK

Investigators

Abstract

This award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports research by Professor Robert P. Houser at the University of Oklahoma to model the copper-containing metalloenzymes nitrite reductase (NiR) and nitrous oxide reductase (N2OR) by using small molecule copper complexes that mimic their structures, spectroscopic features, and functions of the enzymes. Complexes that model the structure and function of the two copper sites in NiR will be synthesized using pyridyl amide ligands that contain functional groups, which mimic histidine and cysteine. The electrochemical properties of the model complexes will be characterized to learn about the electron transfer process that occurs in NiR. Reactivity with nitrite will be investigated and characterized to gain insight into the catalytic reaction in NiR. The active site of N2OR, which catalyzes the reduction of nitrous oxide to dinitrogen, contains an unusual copper cluster, CuZ, which contains four copper ions bridged by a sulfide anion. Complexes that model the CuZ site will be synthesized and characterized structurally and spectroscopically in order to compare and interpret the CuZ site in the enzyme. These studies will contribute to the understanding of the roles of NiR and N2OR in the global nitrogen cycle. N2O is a potent greenhouse gas despite its relatively low atmospheric concentration and is a catalyst of stratospheric ozone decay via decomposition to nitric oxide, which is a pollutant and is an important component of photochemical smog. Additional broader impacts stem from the education of young scientists, including postdoctoral researchers, graduate students and undergraduates, who will trained in modern synthetic inorganic chemistry and bioinorganic chemistry.