Direct electrochemistry of redox proteins

In a redox enzyme the functional electron transfer center, normally surrounded by an insulating protein matrix, can be electrically connected to an external source of current through a path of fast electron-relaying redox couples. Such “wiring” is achieved through electrostatically or covalently binding to the enzyme-proteins high molecular weight redox polycations having segments anchored to electrodes. With the wired enzymes subsecond response time amperometric biosensors can be built.

Electrical Wiring of Redox Enzymes

Reversible electrochemistry of horse heart cytochrome c (Cc) has been obtained at SnO2 electrodes modified with 12-nm-diameter colloidal Au particles. Previous experiments had demonstrated electrochemical addressability of these particle ensembles; the high current densities and small peak-to-peak separations observed for Cc are indicative of facile electron transfer. In contrast to previously described modified electrodes for Cc, these data were acquired without polishing and without any modification of the Au particle surface. Quasireversible voltammetry was obtained with surfaces comprising monodisperse 36-nm-diameter and polydisperse 6-nm-diameter Au particles, but no voltammetric wave for Cc was seen at surfaces composed of aggregates of 12-nm-diameter or 22-nm-diameter Au particles. These data indicate that nanometer-scale morphology of metals plays a key role in protein electrochemistry, and suggest that isolated, surface-confined colloidal Au particles may be useful building blocks for macroscopic...

Fred M. Hawkridge

Papers

Interfacial electrochemistry of cytochrome c at tin oxide, indium oxide, gold, and platinum electrodes

Spectroelectrochemical Determination of Heterogeneous Electron Transfer Kinetic Parameters