3 years ago

Activation Thermodynamics and H/D Kinetic Isotope Effect of the Hox to HredH+ Transition in [FeFe] Hydrogenase

Activation Thermodynamics and H/D Kinetic Isotope Effect of the Hox to HredH+ Transition in [FeFe] Hydrogenase
Carolyn E. Lubner, Molly B. Wilker, Michael W. Ratzloff, Gordana Dukovic, Katherine A. Brown, Hayden Hamby, Paul W. King, David W. Mulder
Molecular complexes between CdSe nanocrystals and Clostridium acetobutylicum [FeFe] hydrogenase I (CaI) enabled light-driven control of electron transfer for spectroscopic detection of redox intermediates during catalytic proton reduction. Here we address the route of electron transfer from CdSe→CaI and activation thermodynamics of the initial step of proton reduction in CaI. The electron paramagnetic spectroscopy of illuminated CdSe:CaI showed how the CaI accessory FeS cluster chain (F-clusters) functions in electron transfer with CdSe. The Hox→HredH+ reduction step measured by Fourier-transform infrared spectroscopy showed an enthalpy of activation of 19 kJ mol–1 and a ∼2.5-fold kinetic isotope effect. Overall, these results support electron injection from CdSe into CaI involving F-clusters, and that the Hox→HredH+ step of catalytic proton reduction in CaI proceeds by a proton-dependent process.

Publisher URL: http://dx.doi.org/10.1021/jacs.7b04216

DOI: 10.1021/jacs.7b04216

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