H2 has been proposed as the ideal fuel to meet the worlds energetic requirements, but a scalable H2 production system is currently unavailable. Hydrogenases (H2ase), and in particular [FeFe] h2ases, provide a tantalizing model for a H2 production catalyst. Despite considerable effort devoted to unraveling the mechanistic details of the [FeFe] h2ase catalytic cycle, there remains several questions in the field concerning this process. The lack of cohesion in the field highlights the need for a fresh approach to studying this enzyme. We hypothesized that a hybrid system composed of a nanorod, electron shuttle and [FeFe] h2ase, would afford control over this enzyme through photo-initiated turnover via rapid reduction of the active site. By illuminating a sample containing these components, we can rapidly inject electrons into the system triggering turnover as h2ase is reduced. Such a system has allowed us to utilize time-resolved spectroscopic techniques for the observation of catalytically relevant intermediates on sub-millisecond timescales. The CO ligands bound to the active site are excellent reporters for the redox state of the active-site and so serve as convenient spectroscopic handles for time-resolved measurements. With this technique we measured the formation rates of intermediate states giving us insight into the catalytic mechanism of this enzyme. With the results of this study we present the first catalytic cycle modeled exclusively on kinetic measurements made under sub-turnover conditions. By taking advantage of the light sensitivity of nanorods we have developed a system for giving us precise control over enzyme turnover and can observe catalytically active states of [FeFe] h2ase on the microsecond timescale.

Nanorod-enzyme conjugates for photoinduced turnover of [FeFe] hydrogenase

2019 Spring National Meeting

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