Abstract

Zero-Mode Waveguide Spectroelectrochemistry of Single Oxidoreductase Enzyme Molecules

Paul Bohn, Arthur J. Schmitt Professor of Chemical and Biomolecular Engineering and Professor of Chemistry and Biochemistry, University of Notre Dame

Single electron transfer events in both immobilized and freely diffusing redox-active enzymes can be imaged with facility using electrochemical zero-mode waveguide (E-ZMW) arrays. These bimodal nanoelectrochemical-nanophotonic nanopore arrays are composed of high density zeptoliter-volume recessed dual-ring electrode nanopores. Thus, they provide a link between single electron-transfer events and light emission in fluorigenic redox reactions, such as those involving flavin-containing enzymes, i.e. flavoenzymes. The bimodal optical-electrochemical functionality of the E-ZMW makes it possible to perform single molecule spectroelectrochemical measurements under conditions where the enzyme is potential controlled and optically-coupled, while the enzyme substrate is generated in situ electrochemically at a nearby second working electrode.   Thus, the E-ZMW makes it possible to study single enzyme turnover events in an environment where both confinement and molecular crowding may be controlled.  The ability to combine electrochemical and spectroscopic measurements at the single molecule level is a new tool for the characterization of reaction dynamics.