ELECTRICAL COMMUNICATION OF REDOX PROTEINS BY MEANS OF ELECTRON RELAY-TETHERED POLYMERS IN PHOTOCHEMICAL, ELECTROCHEMICAL AND PHOTOELECTROCHEMICAL SYSTEMS

Redox polymers act as macromolecular interfaces that electrically comm unicate redox centers in proteins with their macroscopic environment. thyl-N'-carboxyalkyl-4,4'-bipyridinium-derivatized polylysine (1) acts as an electron mediator from photoexcited Ru(bpy)3(2+) to the redox e nzyme glutathione reductase (GR). The rate of electron transfer from t he redox polymer to GR is controlled by the chain lengths linking the bipyridinium units to the polymer. Nitrate reductase (NR) immobilized in an crylamide-N-methyl-N'-acrylamido-4,4'-bipyridinium copolymer (4) reveals electrical communication with photoexcited Ru(bpy)3(2+) and s timulates the photoinduced biocatalyze reduction of nitrate (NO3-) to nitrite (NO2-). Electrobiocatalyzed reduction of nitrate to nitrite is accomplished by immobilization of NR in polythiophene-4,4'-bipyridini um associated with an Au electrode. The rate of electrocatalyzed reduc tion of NO3- relates to the bulk concentration of nitrate, and thus th e enzyme electrode acts as a biosensor for NO3-. Photoelectrochemical biocatalyzed reduction of nitrate to nitrite is accomplished by electr ostatic or covalent attachment of NR to a -methyl-N'-propionyl-4,4'-bi pyridinium-derivatized polyethyleneimine associated with semiconductor TiO2 colloids or powders. The polymer acts as electron trap of conduc tion band electrons and electrically communicates the semiconductor ph otocatalyst with nitrate reductase.