Developing Electroanalytical Methods for Enzymology Applications

With support from the Chemical Measurement & Imaging (CMI) program in the Division of Chemistry (CHE) and the Biosensors program in the CBET Division, Professor Shelley Minteer at the University of Utah is developing new electroanalytical tools for investigating enzymes, biological catalysts that play critical roles in the chemistry of life processes but that are also very useful in biotechnology. Biochemists and molecular biologists have keen interest in how enzyme structure controls function. In addition, enzymes have inspired the design of selective catalysts for challenging transformations such as reduction of carbon dioxide to methanol and nitrogen (N2) to ammonia. These attributes have motivated extensive enzymology research over the last couple of decades, prompting interest in developing better analytical tools for investigating enzyme function. The Minteer group is both developing such tools and extending their impact through educational opportunities offered to both college and high school students. For example, Professor Minteer is providing unique high school student research internships to inspire student interest in STEM (science, technology, engineering and mathematics) disciplines. In order to develop new electroanalytical methods for enzymology, it is critical to be able to immobilize enzymes on electrode surfaces in a manner whereby they can undergo direct electron transfer with the electrode without the need for exogenous redox mediators. The Minteer group is utilizing two strategies to enable direct electron transfer: 1) incorporation of non-natural amino acids as orienting tags for conjugation of proteins to electrode surfaces, thereby ensuring that the active site is within tunneling distance of the electrode surface; and 2) "wiring" enzymes to electrode surfaces by incorporating metal-binding peptide sequences that promote in-situ formation of metal nanoparticles within the protein. Bioelectrodes modified by either approach will be used to study both single enzymes and enzyme cascades using new galvanostatic titration methods, with an aim of improved understanding of how the rate of electron injection into the active site of a protein (i.e. nitrogenase) controls the selectivity of the products formed (ammonia versus hydrogen). Additionally, rotating ring-disk electroanalytical chemistry methods are being developed to study substrate channeling and to quantitate the leaking of intermediates to the bulk solution from the supercomplex of an enzyme cascade. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.