Hydrogenases are found in a wide-variety of microbes, the two most abundant forms, [FeFe] and [NiFe], are categorized based on metal content of their catalytic sites. We are investigating the structural and functional properties of [FeFe] hydrogenases and their effectiveness as catalysts for application in artificial solar H2 production systems. Modifications to enzymes are performed using a recombinant expression system to test hypotheses regarding proton-transfer and the role of structure in sensitivity to inhibitors. Currently there is little known about the mechanism of how these enzymes couple multi-electron transfer to proton reduction or the process leading to inactivation of the catalytic site by molecular O² and CO. Both native and modified enzymes are being used in combination with a variety of materials for the synthesis and characterization of biohybrid electrodes and nanocomplexes. The basic research objective of these biohybrid investigations is to build understanding on how to achieve stable integration, efficient charge-transfer and catalytic longevity of biocatalysts in non-biological contexts. Applied research efforts include the integration of [FeFe] hydrogenase-material biohybrids with dye-solar cells as model systems for the conversion of solar energy into H₂. Results of investigations on hydrogenase structure-function, biohybrid fabrication and dye-solar cell integration will be presented.

*Research supported by the Department of Energy, Office of Science, Basic Energy Sciences.