YedY: A Mononuclear Molybdenum Enzyme with a Redox-Active Ligand?

A recent electrochemical investigation suggests that the mononuclear molybdenum enzyme YdeY utilizes redox-active ligands during catalysis.

Combustion Growth of NiFe Layered Double Hydroxide for Efficient and Durable Oxygen Evolution Reaction.

NiFe layered double hydroxide (LDH) with abundant heterostructures represents a state-of-the-art electrocatalyst for the alkaline oxygen evolution reaction (OER). Herein, NiFe LDH/Fe2O3 nanosheet arrays have been fabricated by facile combustion of corrosion-engineered NiFe foam (NFF). The in situ grown, self-supported electrocatalyst exhibited a low overpotential of 248 mV for the OER at 50 mA cm-2, a small Tafel slope of 31 mV dec-1, and excellent durability over 100 h under the industrial benchmarking 500 mA cm-2 current density. A balanced Ni and Fe composition under optimal corrosion and combustion contributed to the desirable electrochemical properties. Comprehensive ex-situ analyses and operando characterizations including Fourier-transformed alternating current voltammetry (FTACV) and in situ Raman demonstrate the beneficial role of modulated interfacial electron transfer, dynamic atomic structural transformation to NiOOH, and the high-valence active metal sites. This study provides a low-cost and easy-to-expand way to synthesize efficient and durable electrocatalysts.

FTacV study of electroactive immobilized enzyme/free substrate reactions: Enzymatic catalysis of epinephrine by a multicopper oxidase from Thermothelomyces thermophila.

In the present work, a kinetic analysis is made concerning the reaction of an electroactive immobilized enzyme with a free substrate, based on a Michaelis-Menten scheme. The proposed kinetic equations are investigated numerically for conditions describing large amplitude fast Fourier transform alternating current voltammetry (FTacV), under different reaction states (transient or steady state for the reaction intermediate as well as quasi or complete reversibility of the electrochemical step). The dependence of two chief observables that occur from the analysis of the results of the method, that is, the maximum of the harmonics and the potential shift of the corresponding dominant peaks, on substrate concentration is presented. The FTacV method is applied experimentally for an immobilized laccase-like multicopper oxidase from Thermothelomyces thermophila, TtLMCO1, and its reaction with epinephrine. From the experimental findings it is shown that the intrinsic characteristics of the system do not lead to the extraction of the desired kinetic data although indications on the relation between the kinetic constants is revealed. Finally, the response of the third harmonic for the first additions of epinephrine at subnanomolarity range can be exploited for the detection of epinephrine at rather low concentrations.

Direct electron transfer of lytic polysaccharide monooxygenases (LPMOs) and determination of their formal potentials by large amplitude Fourier transform alternating current cyclic voltammetry.

MtLPMO9 and FoLPMO9 are two lytic polysaccharide monooxygenases (LPMOs), from the filamentous fungi Thermothelomyces thermophila and Fusarium oxysporum, respectively. In the present study an attempt has been made to achieve direct electron transfer between these enzymes and a glassy carbon electrode by immobilization in Nafion polyelectrolyte. The method used to ascertain the feasibility of direct electron transfer was large amplitude Fourier transform alternating current voltammetry (FTacV) and the formal potentials of these enzymes were determined at different temperatures. The findings of this paper indicate that LPMOs can be studied by direct electron transfer, which could be exploited in the near future for their biochemical characterization.