New Evidence for a Quasi-Simultaneous Proton-Coupled Two-Electron Transfer and Direct Wiring for Glucose Oxidase Captured by the Carbon Nanotube-Polymer Matrix

Systematic cyclic voltammetry (CV) studies of glucose oxidase (GOx) and its cofactor, flavine adenine dinucleotide (FAD), almost similarly captured by the matrix of single-walled carbon nanotube and polymer complex, in turn, deposited on GC electrodes have been performed. The comparative analysis of kinetic data obtained for the FAD and GOx specimens treated through the same Marcus theory-based algorithmic procedure strongly suggests that the GOx species, notwithstanding the deeply buried position of FAD, mechanistically behave virtually in the same manner as isolated FADs (the operationally capable, nearly intact structure of GOx was confirmed by the catalytic activity vs glucose), strongly suggesting that FADs inside GOx are directly wired to the GC electrode, presumably, via almost direct contact of nanotubes with both FADs residing inside each GOx biomolecule (as basically suggested by Guiseppi-Elie, A.; et al. Nanotechnology 2002, 13, 559-564, and shortly supported by a number of valued researchers). Furthermore, the nonadiabatic, quasi-simultaneous two-proton-coupled two-electron transfer/exchange mechanism was concluded from further cross-analysis based on a generalized Marcus theory for the proton-coupled electron transfer (PCET), extra furnished by the first-time temperature-dependent CV studies and a subsequent Arrhenius treatment.