title: Wiring photosystem I for direct solar hydrogen production.
abstract: The generation of H(2) by the use of solar energy is a promising way to supply humankind's energy needs while simultaneously mitigating environmental concerns that arise due to climate change. The challenge is to find a way to connect a photochemical module that harnesses the sun's energy to a catalytic module that generates H(2) with high quantum yields and rates. In this review, we describe a technology that employs a "molecular wire" to connect a terminal [4Fe-4S] cluster of Photosystem I directly to a catalyst, which can be either a Pt nanoparticle or the distal [4Fe-4S] cluster of an [FeFe]- or [NiFe]-hydrogenase enzyme. The keys to connecting these two moieties are surface-located cysteine residues, which serve as ligands to Fe-S clusters and which can be changed through site-specific mutagenesis to glycine residues, and the use of a molecular wire terminated in sulfhydryl groups to connect the two modules. The sulfhydryl groups at the end of the molecular wire form a direct chemical linkage to a suitable catalyst or can chemically rescue a [4Fe-4S] cluster, thereby generating a strong coordination bond. Specifically, the molecular wire can connect the F(B) iron-sulfur cluster of Photosystem I either to a Pt nanoparticle or, by using the same type of genetic modification, to the differentiated iron atom of the distal [4Fe-4S].(Cys)(3)(Gly) cluster of hydrogenase. When electrons are supplied by a sacrificial donor, this technology forms the cathode of a photochemical half-cell that evolves H(2) when illuminated. If such a device were connected to the anode of a photochemical half-cell that oxidizes water, an in vitro solar energy converter could be realized that generates only O(2) and H(2) in the light. A similar methodology can be used to connect Photosystem I to other redox proteins that have surface-located [4Fe-4S] clusters. The controlled light-driven production of strong reductants by such systems can be used to produce other biofuels or to provide mechanistic insights into enzymes catalyzing multielectron, proton-coupled reactions.
authors: Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors: Carolyn E
authors: CE
authors: Lubner
authors: Rebecca
authors: R
authors: Grimme
authors: Donald A
authors: DA
authors: Bryant
authors: John H
authors: JH
authors: Golbeck
mesh_terms: D001665:Binding Sites; D002384:Catalysis; D006859:Hydrogen / Q000378:metabolism*; D006864:Hydrogenase / Q000737:chemistry / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D045331:Photosystem I Protein Complex / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D013329:Structure-Activity Relationship; D013472:Sunlight
chemical_list: D007506:Iron-Sulfur Proteins; D045331:Photosystem I Protein Complex; D006859:Hydrogen; C043296:nickel-iron hydrogenase; D006864:Hydrogenase