In light of the relative advanced fundamental understanding of methanol oxidation over inorganic supported vanadium oxide catalysts relative to V-containing enzymes, there is currently an excellent research opportunity to apply the in situ and operando methodologies developed in the study of vanadium oxide inorganic catalysts to the study of vanadium containing bioinorganic enzyme catalysts. Specifically, the employment of state-of-the-art time resolved in situ and operando spectroscopic methods (Raman, UV-vis, ATR-IR, 51V NMR and quick-XANES/EXAFS) during aqueous oxidation reactions establish the fundamental structure-activity relationships for methanol oxidation by vanadium-containing enzymes. The success of this research program is greatly enhanced by collaboration with the research group of Professor Onal at Middle Eastern technical University (Ankara, Turkey), a leader in density functional theory calculations. The collaboration with Professor Onal is an outgrowth of the recent 6th Eastern Mediterranean Chemical Engineering Conference that was supported by NSF.
Intellectual Merit. The objectives of this research are to (1) establish effective characterization methods and approaches for the study vanadium oxide catalysts in the aqueous phase in the presence of HOOH and CH3OH environments with time resolved in situ and operando spectroscopy studies in the millisecond to minutes time scale (Raman, UV-vis, 51V NMR, EPR, rapid scan ATR-IR and quick-XANES/EXAFS) and (2) apply the advanced methodologies to study the VOx structures, oxidation states, reaction intermediates, mechanism, and kinetics of homogeneous vanadium haloperoxidase as a biocatalyst for the aqueous phase oxidation of methanol. Today, cutting edge catalysis research must combine the latest molecular spectroscopic characterization methodologies under relevant reaction conditions with state-of-the-art density functional theory (DFT). The rather complex V-containing enzymes in aqueous solution possess multiple oxygen functionalities (e.g., terminal V=O bonds, V-O-H bonds, bridging V-O-C bonds and peroxy V-O2 bonds) whose vibrational assignments are not straightforward without the assistance of DFT calculations. It is proposed that DFT calculations are performed on the V-containing enzymes in collaboration with Professor Onal's group at Middle Eastern Technical University (Anakara, Turkey) since only such research will provide molecular level insights into the reaction energetics of the different reaction pathways. Only combination of the molecular spectroscopic insights with the reaction pathways will allow the achievement of molecular structure reactivity relationships that is the ultimate goal of this research program.
Broader Impact. The proposed research program extends the previous gas-solid CH3OH oxidation catalysis studies to liquid phase oxidation of CH3OH and also bridges inorganic catalysis with aqueous bioinorganic catalysis of enzymes. The development of time-resolved in situ and operando spectroscopic methodologies for investigating aqueous phase catalysis of inorganic and bioinorganic catalysts are significantly advanced by this undertaking and have wide reaching implications for numerous aqueous phase catalytic applications. Vanadium bioinorganic enzymes may provide a "green" alternative to traditional inorganic catalysts currently used in oxidation reactions and the new fundamental insights may assist in the development of improved pharmaceuticals, therapeutics, diabetes management and biocatalytic industrial applications. The Lehigh group significantly benefits from exposure to and training by a leading research group performing density functional theory calculations. The Turkish group significantly benefits by exposure to state-of-the-art experimental spectroscopic catalyst characterization methods and integration of theory with experiment.
Vanadium enzyme mimics are being medically investigated for treating humans with diabetes (type 2) and the objective of the research is to develop a fundamental understanding of the reduction-oxidation (redox) mechanism of vanadium enzyme mimics. The approach of this international research program was to combine experimental findings (Lehigh University-USA) and theoretical calculations (Middle Eastern Technical University, Turkey) to discover the fundamental molecular level redox mechanism of vanadium enzyme mimics. The combined experimental and theoretical approach successfully determined the fundamental molecular level reaction steps involved in the redox mechanism of vanadium enzyme mimics. In addition, this work extended characterization techniques typically employed for gas-solid heterogeneous catalysis to aqueous phase vanadium enzyme mimics. The current research demonstrated how conventional approaches to heterogeneous catalysis research can be extended to enzyme catalysis. The research and educational skills of both graduate students have positively developed during the course of this collaborative project. Both participating graduate students were females. The experimental student (Ms. Julie Molinari-Lehigh) was exposed to theoretical approaches and the theoreticican (Ms. D. Gerceker-METU) was exposed to experimental approaches. The informational resources generated about V enzyme mimics can be applied by others in their research on enzyme mimics and educational experiences. Dissemination of the findings have been made via technical presentations, class lectures and journal publications. Ms. Molinari participated in Lehigh's program for local middle school girls that exposed the middle school females to her research program on vanadium enzyme mimics and its findings. This successful international collaboration between Lehigh University and Middle Eastern Technical University is being used as a model collaboration to establish student exchange programs between Lehigh University and Middle Eastern Technical University.
