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Research efforts to develop efficient systems for H2 production encompass a variety of biological and chemical
approaches. For solar-driven H2 production we are investigating an approach that integrates biological catalysts, the
[FeFe] hydrogenases, with a photoelectrochemical cell as a novel bio-hybrid system. Structurally the [FeFe]
hydrogenases consist of an iron-sulfur catalytic site that in some instances is electronically wired to accessory iron-sulfur
clusters proposed to function in electron transfer. The inherent structural complexity of most examples of these enzymes
is compensated by characteristics desired for bio-hybrid systems (i.e., low activation energy, high catalytic activity and
solubility) with the benefit of utilizing abundant, less costly non-precious metals. Redesign and modification of [FeFe]
hydrogenases is being undertaken to reduce complexity and to optimize structural properties for various integration
strategies. The least complex examples of [FeFe] hydrogenase are found in the species of photosynthetic green algae and
are being studied as design models for investigating the effects of structural minimization on substrate transfer, catalytic
activity and oxygen sensitivity. Redesigning hydrogenases for effective use in bio-hybrid systems requires a detailed
understanding of the relationship between structure and catalysis. To achieve better mechanistic understanding of [FeFe]
hydrogenases both structural and dynamic models are being used to identify potential substrate transfer mechanisms
which are tested in an experimental system. Here we report on recent progress of our investigations in the areas of
[FeFe] hydrogenase overexpression, minimization and biochemical characterization.
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