Efficient electrocatalytic CO2 fixation by nanoconfined enzymes via a C3-to-C4 reaction that is favored over H2 production

Reduction of CO2 and its direct entry into organic chemistry is achieved efficiently and in a highly visible way using a metal oxide electrode in which two enzyme catalysts, one for electrochemically regenerating NADPH, the other for assimilating CO2 and converting pyruvate (C3) to malate (C4) are entrapped within its nanopores. The resulting reversible electrocatalysis is exploited to construct a solar CO2 reduction/water splitting device producing O2 and C4 with high faradaic efficiency

A hydrogen fuel cell for rapid, enzyme-catalysed organic synthesis with continuous monitoring

A one-pot fuel cell for specific, enzyme-catalysed organic synthesis, with continuous monitoring of rate and reaction progress, combines an electrode catalysing rapid, reversible and diffusion-controlled interconversion of NADP+ and NADPH with a Pt electrode catalysing 2H+/H2 interconversion. This Communication demonstrates its performance and characteristics using the reductive amination of 2-oxoglutarate as a test system

A hydrogen fuel cell for rapid, enzyme-catalysed organic synthesis with continuous monitoring

A one-pot fuel cell for specific, enzyme-catalysed organic synthesis, with continuous monitoring of rate and reaction progress, combines an electrode catalysing rapid, reversible and diffusion-controlled interconversion of NADP+ and NADPH with a Pt electrode catalysing 2H+/H2 interconversion. This Communication demonstrates its performance and characteristics using the reductive amination of 2-oxoglutarate as a test system

The value of enzymes in solar fuels research – efficient electrocatalysts through evolution

The reasons for using enzymes as tools for solar fuels research are discussed. Many oxidoreductases, including components of membrane-bound electron-transfer chains in living organisms, are extremely active when directly attached to an electrode, at which they display their inherent catalytic activity as electrical current. Electrocatalytic voltammograms, which show the rate of electron flow at steady-state, provide direct information on enzyme efficiency with regard to optimising use of available energy, a factor that would have driven early evolution. Oxidoreductases have evolved to minimise energy wastage ('overpotential requirement') across electron-transport chains where rate and power must be maximised for a given change in Gibbs energy, in order to perform work such as proton pumping. At the elementary level (uncoupled from work output), redox catalysis by many enzymes operates close to the thermodynamically reversible limit. Examples include efficient and selective electrocatalytic reduction of CO2 to CO or formate - reactions that are very challenging at the chemistry level, yet appear almost reversible when catalysed by enzymes. Experiments also reveal the fleeting existence of reversible four-electron O2 reduction and water oxidation by 'blue' Cu oxidases, another reaction of great importance in realising a future based on renewable energy. Being aware that such enzymes have evolved to approach perfection, chemists are interested to know the minimal active site structure they would need to synthesise in order to mimic their performance

Enzyme-catalysed enantioselective oxidation of alcohols by air exploiting fast electrochemical nicotinamide cycling in electrode nanopores

Enantioselective conversion of alcohols to ketones using air as the oxidant is achieved with high rates and efficiency using an indium tin oxide (ITO) electrode in which an alcohol dehydrogenase and a photosynthetic NADPH recycling enzyme are confined within nanopores. The massive catalytic enhancement arising from nanoconfinement is exploited in an air-driven electrochemical cell, which requires no complicating control features yet allows continuous monitoring of the reaction via the current that flows between anode (ITO: organic chemistry) and cathode (Pt: O2 from air)

Transfer of photosynthetic NADP+/NADPH recycling activity to a porous metal oxide for highly specific, electrochemically-driven organic synthesis

In a discovery of the transfer of chloroplast biosynthesis activity to an inorganic material, ferredoxin-NADP+ reductase (FNR), the pivotal redox flavoenzyme of photosynthetic CO2 assimilation, binds tightly within the pores of indium tin oxide (ITO) to produce an electrode for direct studies of the redox chemistry of the FAD active site, and fast, reversible and diffusion-controlled interconversion of NADP+ and NADPH in solution. The dynamic electrochemical properties of FNR and NADP(H) are thus revealed in a special way that enables facile coupling of selective, enzyme-catalysed organic synthesis to a controllable power source, as demonstrated by efficient synthesis of l-glutamate from 2-oxoglutarate and NH4+

Electrocatalytic volleyball: rapid nanoconfined nicotinamide cycling for organic synthesis in electrode pores

In living cells, redox chains rely on nanoconfinement using tiny enclosures, such as the mitochondrial matrix or chloroplast stroma, to concentrate enzymes and limit distances that nicotinamide cofactors and other metabolites must diffuse. In a chemical analogue exploiting this principle, nicotinamide adenine dinucleotide phosphate (NADPH) and NADP+ are cycled rapidly between ferredoxin-NADP+ reductase and a second enzyme-the pairs being juxtaposed within the 5-100 nm scale pores of an indium tin oxide electrode. The resulting electrode material, denoted (FNR+E2)@ITO/support, can drive and exploit a potentially large number of enzyme-catalysed reactions