Alternating electron transfer mechanism in the case of high-performance tetrathiafulvalene–tetracyanoquinodimethane enzymatic electrodes

Transmembrane NADH Oxidation with Tetracyanoquinodimethane

The design of efficient schemes for nicotinamide adenine dinucleotide (NAD) regeneration is essential for the development of enzymatic biotechnological processes in order to sustain continuous production. In line with our motivation for the encapsulation of redox cascades in liposomes to serve as microbioreactors, we developed a straightforward strategy for the interfacial oxidation of entrapped NADH by ferricyanide as an external electron acceptor. Instead of the commonly applied enzymatic regeneration methods, we employed a hydrophobic redox shuttle embedded in the liposome bilayer. Tetracyanoquinodimethane (TCNQ) mediated electron transfer across the membrane and thus allowed us to shortcut and emulate part of the electron transfer chain functionality without the involvement of membrane proteins. To describe the experimental system, we developed a mathematical model which allowed for the determination of rate constants and exhibited handy predictive utility.

Electron Transfer Between Enzymes and Electrodes

Efficient electron transfer between redox enzymes and electrocatalytic surfaces plays a significant role in development of novel energy conversion devices as well as novel reactors for production of commodities and fine chemicals. Major application examples are related to enzymatic fuel cells and electroenzymatic reactors, as well as enzymatic biosensors. The two former applications are still at the level of proof-of-concept, partly due to the low efficiency and obstacles to electron transfer between enzymes and electrodes. This chapter discusses the theoretical backgrounds of enzyme/electrode interactions, including the main mechanisms of electron transfer, as well as thermodynamic and kinetic aspects. Additionally, the main electrochemical methods of study are described for selected examples. Finally, some recent advancements in the preparation of enzyme-modified electrodes as well as electrodes for soluble co-factor regeneration are reviewed. Graphical Abstract.

Combined electrochemical and microscopic study of porous enzymatic electrodes with direct electron transfer mechanism

In the present work electrochemical and microscopic methods have been utilized to get more insight into the complex relationship between the preparation route, structure and activity of porous enzymatic electrodes.