Photo-Driven Hydrogen Evolution by an Artificial Hydrogenase Utilizing the Biotin-Streptavidin Technology

Photocatalytic hydrogen evolution by an artificial hydrogenase based on the biotin-streptavidin technology is reported. A biotinylated cobalt pentapyridyl-based hydrogen evolution catalyst (HEC) was incorporated into different mutants of streptavidin. Catalysis with [Ru(bpy)(3)]Cl-2 as a photosensitizer (PS) and ascorbate as sacrificial electron donor (SED) at different pH values highlighted the impact of close lying amino acids that may act as a proton relay under the reaction conditions (Asp, Arg, Lys). In the presence of a close-lying lysine residue, both, the rates were improved, and the reaction was initiated much faster. The X-ray crystal structure of the artificial hydrogenase reveals a distance of 8.8 angstrom between the closest lying Co-moieties. We thus suggest that the hydrogen evolution mechanism proceeds via a single Co centre. Our findings highlight that streptavidin is a versatile host protein for the assembly of artificial hydrogenases and their activity can be fine-tuned via mutagenesis.