Improved Electro- and Photocatalytic Water Reduction by Confined Cobalt Catalysts in Streptavidin

Abstract

Incorporation of biotinylated aminopyridine cobalt complexes derived from the triazacyclononane scaffold into the streptavidin protein leads to formation of artificial metalloenzymes for water reduction to hydrogen. The synthesized artificial metalloenzymes have lower overpotential (at the half-peak up to 100 mV) and higher photocatalytic hydrogen evolution activity (up to 14and 10-fold increase in TOF and TON, respectively, at pH 12.5) than the free biotinylated cobalt complexes. 1 H-NMR, EPR and XAS highlight the presence of the metal complexes upon supramolecular attachment to the streptavidin. pHdependent catalytic studies and molecular dynamics (MD) simulations suggest that the increase in the catalytic activity could be induced by the protein residues positioned close to the metal centers. These findings illustrate the ability of the biotin−streptavidin technology to produce artificial metalloproteins for photo-and electrocatalytic hydrogen evolution reaction.

Mimochrome, a metalloporphyrin‐based catalytic Swiss knife†

“…In collaboration with the Bren's group, we have screened the Co-derivative of MC6*a as a potential electrocatalyst for HER. To date, numerous synthetic or protein-based cobalt complexes have been studied for this kind of reactivity [302][303][304][305][306][307]. High overpotential values, low water-solubility, and the need for strong acids as proton sources are the common drawbacks associated with small-sized complexes [308][309][310].…”

Biosynthetic Approaches towards the Design of Artificial Hydrogen‐Evolution Catalysts

“…Biotin‐streptavidin technology has been employed to construct artificial hydrogenases featuring Co and Fe‐Fe cofactors . Biotinylated macrocyclic Co complexes employing pentapyridyl and 1,4‐di(picolyl)‐1,4,7‐triazacyclononane ( H Py 2 tacn) ligands with varying linker lengths have been synthesized followed by investigating the H 2 production activity of protein‐encapsulated cofactors (Figure ). Upon incorporation of the biotinylated pentapyridyl Co complex into streptavidin (Sav), a significant decrease in the activity was observed for photocatalytic H 2 production.…”

Enhanced Photocatalytic Hydrogen Production by Hybrid Streptavidin‐Diiron Catalysts

“…Streptavidin‐based catalysts that interface an organometallic complex with a protein scaffold have been used successfully in particular to impart stereospecificity to a reaction . This approach, however, had been partially successful in the catalysis of proton reduction: incorporation of cobalt catalysts did not enhance activity at neutral pH, although significant effects were observed at high pH when using [Ir(bpy)(ppy) 2 ]PF 6 as photosensitizer and triethanolamine as sacrificial electron donor; these conditions require the use of acetonitrile as co‐solvent . Herein, we chose to explore the incorporation of a different type of hydrogen evolving complex, a biomimetic diiron hexacarbonyl active center.…”

“…[39][40][41][42][43][44] In this system, cobalt catalysts for hydrogen production retained or improved catalytic activity,e specially when probed at high pH. [45,46] Mutations close to the organometallic complex improved pH dependence and initial rates/TON as comparedt ot he naked catalyst. [46] Inspired by these results, we utilizedt he streptavidin-avidin system to stably encapsulate ab iomimetic diiron hexacarbonyl complex,r easoning that the biotin scaffold could stabilizei ts catalytically active state, in analogy to what observed in natural [FeFe] hydrogenases.…”

“…A synthetically convenient strategy to build hybrid metalloproteins is based on the streptavidin‐avidin complex; since its introduction, this strategy has been successfully used to catalyze enantioselective reduction of a variety of organic substrates, indicating that catalysts linked to biotin interact with the protein . In this system, cobalt catalysts for hydrogen production retained or improved catalytic activity, especially when probed at high pH . Mutations close to the organometallic complex improved pH dependence and initial rates/TON as compared to the naked catalyst …”