Photo-induced H2 production by [NiFe]-hydrogenase from T. roseopersicina covalently linked to a Ru(II) photosensitizer

Abstract

The potential of hydrogen as a clean renewable fuel source and the finite reserves of platinum metal to be utilized in hydrogen production catalysts have provided the motivation for the development of non-noble metal-based solutions for catalytic hydrogen production. There are a number of microorganisms that possess highly efficient hydrogen production catalysts termed hydrogenases that generate hydrogen under certain metabolic conditions. Although hydrogenases occur in photosynthetic microorganisms, the oxygen sensitivity of these enzymes represents a significant barrier in directly coupling hydrogen production to oxygenic photosynthesis. To overcome this barrier, there has been considerable interest in identifying or engineering oxygen tolerant hydrogenases or generating mimetic systems that do not rely on oxygen producing photocatalysts. In this work, we demonstrate photo-induced hydrogen production from a stable [NiFe]-hydrogenase coupled to a [Ru(2,2'-bipyridine)(2)(5-amino-1,10-phenanthroline)](2+) photocatalyst. When the Ru(II) complex is covalently attached to the hydrogenase, photocatalytic hydrogen production occurs more efficiently in the presence of a redox mediator than if the Ru(II) complex is simply present in solution. Furthermore, sustained hydrogen production occurs even in the presence of oxygen by presumably creating a local anoxic environment through the reduction of oxygen similar to what is proposed for oxygen tolerant hydrogenases. These results provide a strong proof of concept for engineering photocatalytic hydrogen production in the presence of oxygen using biohybrid mimetic systems.

Ruthenium Imidazophenanthrolinium Complexes with Prolonged Excited‐State Lifetimes

“…[41][42][43][44][45][46] An investigation of intramolecular photocatalysis and a comparison with already known intermolecular systems for photocatalytic water reduction under aerobic conditions is desirable. This would be possible with this type of chromophore owing to the ability of the imidazole unit of the bbip ligand to act as a carbene precursor.…”

Ru(II)-diimine functionalized metalloproteins: From electron transfer studies to light-driven biocatalysis

“…On one hand, the amino group of Ru(bpy) 2 PhenA (PhenA = 5-amino-1,10-phenthroline) can be coupled with the carboxylic acid side chains of aspartic or glutamic acids in the presence of crosslinking carboxydiimide reagents. [27] On the other hand, the amino side chain of lysine residues can react with N-hydrosuccinimide derivatives of the Ru(bpy) 2 (dcbpy) complex (dcbpy = 4,4′-dicarboxy-2,2′-bipyridine)[28] or the isocyanate moiety introduced on a phenanthroline ligand (Table 1, entry 4). [29, 30]…”

“…The direct attachment of a ruthenium photosensitizer to a [NiFe]-hydrogenase (Figure 2B) led to the production of dihydrogen with a rate of 16 nmol of H 2 /min/mg of protein, which corresponds to 592 units/uM of ruthenium photosensitizer. [27] Armstrong et al took on a different approach using a TiO 2 nanoparticle sensitized with a Ru(II) complex bearing phosphonate groups (Figure 2C). [66, 67] In this case, the TiO 2 nanoparticle acts not only as anchor for both the enzyme and the light-harvesting compound but also as an electron mediator in the process.…”

Solar-driven proton and carbon dioxide reduction to fuels — lessons from metalloenzymes

“…A photoenzyme formed by covalently attaching a polypyridine Ru(II) photosensitiser to a [NiFe]-H2ase was reported by Peters and co-workers [43]. The authors used an amine functionality on one of the Ru-ligands to form amide bonds with various carboxylates on the protein surface.…”