Infrared Spectroscopy During Electrocatalytic Turnover Reveals the Ni-L Active Site State During H sub(2) Oxidation by a NiFe Hydrogenase

• Published in: Angewandte Chemie International Edition Vol. 54; no. 24; pp. 7110 - 7113
• Main Authors: Hidalgo, Ricardo, Ash, Philip A, Healy, Adam J, Vincent, Kylie A
• Format: Journal Article
• Language: English
• Published: 01.06.2015
• Subjects: Catalysis; Catalysts; Hydrogenase; Intermetallics; Iron compounds; Nickel; Nickel base alloys; Nickel compounds; Spectra
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201502338

A novel in situ IR spectroscopic approach is demonstrated for the characterization of hydrogenase during catalytic turnover. E. coli hydrogenase1 (Hyd-1) is adsorbed on a high surface-area carbon electrode and subjected to the same electrochemical control and efficient supply of substrate as in protein film electrochemistry during spectral acquisition. The spectra reveal that the active site state known as Ni-L, observed in other NiFe hydrogenases only under illumination or at cryogenic temperatures, can be generated reversibly in the dark at ambient temperature under both turnover and non-turnover conditions. The observation that Ni-L is present at all potentials during turnover under H sub(2) suggests that the final steps in the catalytic cycle of H sub(2) oxidation by Hyd-1 involve sequential proton and electron transfer via Ni-L. A broadly applicable IR spectroscopic technique is presented for addressing electrode-adsorbed redox enzymes under fast catalytic turnover. Protein film IR electrochemistry: A combination of precise electrochemical control with infrared spectral acquisition provides fresh insight into catalytic states of the NiFe hydrogenase active site.