Objetivo THE ADVANTAGE OF USING ELECTRICITY IN COMBINATION WITH OXIDATION-REDUCTION ENZYMES IS THE LOW COSTS AND CLEAN FORM OF THIS POWER. A DIRECT ELECTRON TRANSFER BETWEEN AN ELECTRODE AND A REDOX ENZYME IS, HOWEVER, VERY INEFFICIENT. REDOX MEDIATORS OR CONDUCTING POLYMERS CAN HELP TO BRIDGE THIS TRANSFER. AFTER IMMOBILISATION, THESE REACTIONS CAN TAKE PLACE WITHOUT CONTAMINATING THE PRODUCTS WITH THE USUAL REDOX MEDIATORS AND AT THE SAME TIME THE PRODUCTS CAN BE EASILY SEPARATED. THESE SYSTEMS CAN THEREFORE BE USED FOR ELECTRO-ENZYMATIC, STEREOSPECIFIC REDUCTION REACTIONS AT A PREPARATIVE SCALE AND IN, FOR EXAMPLE, AMPEROMETRIC BIOSENSORS FOR ANALYTICAL PURPOSES. The model of bioelectrochemical reactions calculates the current and concentration of species as a function of time for bioelectrochemical reactions at a flat electrode surface. In this model the mathematical equations describing chronoamperometric experiments are used without further approximation or simplification.In order to apply redox biocatalysts in an economic way, electrodes of electrochemcial cells should be useful as a source or sink for electrons. However, enzymes are usually not able to exchange electrons directly with electrodes and need in general very expensive biological electron carriers, which are also not able to exchange electrons with electrodes.Enzymes have been found which react with simple artificial and cheap electron carriers which can be oxidised or reduced on electrodes. The enzymes are enoate reductase (ER) and a viologen dependent nicotinamide adenine dinucleotide (phosphate) oxidoreductase (VAPOR). VAPOR enables the use of a large number of nicotinamide adenine dinucleotide (phosphate) dependent oxidoreductases for preparative scale synthesis via electrochemical mediator regeneration. Bifunctional mediators have been synthesized and their suitability as spacers and molecular wires has been tested. Enzyme kinetic parameters of ER, lipodehydrogenase and VAPOR with viologens and cobalt cage complexes and rate constants by electrochemical measurements have been determined. The new mediators were immobilized on carbon electrodes and enzymes were immobilized on the mediator carrying electrode. In order to optimize such systems, mathematical modelling was successfully developed.Covalent coimmobilization of bifunctional mediators and enzyme (VAPOR) on carbon electrodes led to protein monolayers or multilayers doped with mediator molecules acting as electron relays and molecular wires between the electrode and the enzyme layer. These completely immobilized systems are the first in which electrons reach the active centre of the enzyme directly. This is different from the known case of mediated diffusion controlled homogenous catalysis. So far, these new systems produced up to 3.5 nmol h{-1} cm{-2} of reduced nicotinamide adenine dinucleotide. Immobilized on carbon felt (750 m{2} inner surface/m{2} macroscopic area) a current density of 1A m{-2} of m acroscopic area could be expected. Optimization of the systems is in progress. One of the main drawbacks is that the mediators either showed insufficient long term stability during the production process or that the long term stability was sufficient but the electron transfer rate from the mediator to the mediator to the enzyme was too low.THE OBJECTIVE OF THIS PROJECT IS TO DRIVE, FOR PREPARATIVE PURPOSES, THE ENZYME CATALYSED ELECTROCHEMICAL REDUCTION OF ENOATES, 2-OXOCARBOXYLATES AND NAD(P)+, RESPECTIVELY, BY EITHER CORRESPONDING ENZYME-REDOX MEDIATOR MODIFIED ELECTRODES OR CORRESPONDING CONDUCTING POLYMER MODIFIED ELECTRODES. THE ENZYMES STUDIED WILL BE ENOATE- AND 2-OXOCARBOXYLATE REDUCTASE AS WELL AS THE VIOLOGEN DEPENDENT NAD(P) OXIDOREDUCTASE. THE RECOVERY AND STABILITY OF THESE ENZYMES WILL BE TESTED AFTER ENTRAPMENT IN CONDUCTING POLYMERS. THE IMMOBILISATION OF THE ENZYMES AT ELECTRODE SURFACES IN THE PRESENCE OF REDOX MEDIATORS WILL BE WORKED OUT BY THE MUENCHEN GROUP, AFTER WHICH THE DELFT GROUP WILL DO THE SCALING UP OF THIS SYSTEM. NEXT TO THIS ELECTROENZYMATIC CELLS WILL BE CONSTRUCTED WITH SPECIAL ATTENTION TO THE SOURCE OF CARBON AND THE DESIGN OF THE WORKING ELECTRODE. FINALLY THE MOST OPTIMAL COMBINATION, WAY OF IMMOBILISATION, SOURCE OF CARBON AND ELECTRODE DESIGN WILL BE TESTED AND THE FEASIBILITY OF THIS SYSTEM IN ORGANIC SOLVENTS STUDIED. Ámbito científico natural scienceschemical scienceselectrochemistrynatural scienceschemical sciencespolymer sciencesnatural scienceschemical sciencescatalysisbiocatalysisnatural sciencesbiological sciencesbiochemistrybiomoleculesproteinsenzymesnatural sciencesmathematicsapplied mathematicsmathematical model Programa(s) FP1-BAP - Multiannual research action programme (EEC) in the field of biotechnology (BAP), 1985-1989 Tema(s) Data not available Convocatoria de propuestas Data not available Régimen de financiación CSC - Cost-sharing contracts Coordinador TNO Aportación de la UE Sin datos Dirección J.V. STOLBERGLAAN 148 2595 CL DEN HAAG Países Bajos Ver en el mapa Coste total Sin datos Participantes (1) Ordenar alfabéticamente Ordenar por aportación de la UE Ampliar todo Contraer todo Technische Universitaet Muenchen Alemania Aportación de la UE Sin datos Dirección Lichtenbergstrasse 4 85748 Garching Ver en el mapa Enlaces Sitio web Opens in new window Coste total Sin datos
