Photocatalytic Hydrogen Production and Carbon Dioxide Reduction Catalyzed by an Artificial Cobalt Hemoprotein

Abstract

The covalent insertion of a cobalt heme into the cavity of an artificial protein named alpha Rep (αRep) leads to an artificial cobalt hemoprotein that is active as a catalyst not only for the photo-induced production of H2, but also for the reduction of CO2 in a neutral aqueous solution. This new artificial metalloenzyme has been purified and characterized by Matrix Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS), circular dichroism, and UltraViolet–Visible spectroscopy. Using theoretical experiments, the structure of this biohybrid and the positioning of the residues near the metal complex were examined, which made it possible to complete the coordination of the cobalt ion by an axial glutamine Gln283 ligand. While the Co(III)–porphyrin catalyst alone showed weak catalytic activity for both reactions, 10 times more H2 and four times more CO2 were produced when the Co(III)–porphyrin complex was buried in the hydrophobic cavity of the protein. This study thus provides a solid basis for further improvement of these biohybrids using well-designed modifications of the second and outer coordination sphere by site-directed mutagenesis of the host protein.

Self-Standing Pd-Based Nanostructures for Electrocatalytic CO Oxidation: Do Nanocatalyst Shape and Electrolyte pH Matter?

“…Before the measurements, a CV test was conducted on each electrolyte under continuous purging of N 2 at 200 mV/s for 100 cycles to remove any impurities, followed by measurement at 50 mV/s for 3 cycles to determine the electrochemical active surface area (ECSA). The ECSA was calculated using coulombic charge (Q), Pd loading (m) on the working electrode, and coulombic constant for monolayer of Pd (0.424 mC/cm 2 ) from Equation (4).…”

“…The unavoidable increase in carbon footprint has a wide range of negative impacts on ecosystems and planet earth, so reducing it is essential [1][2][3][4]. The conversion of gases to value-added products [3,[5][6][7][8] and using green energy sources are the main approaches to mitigate carbon footprint [9][10][11][12][13][14].…”

Enzymatic and Bioinspired Systems for Hydrogen Production

“…In a subsequent work, the same authors explored the effect of replacing heme with CoPPIX in Cytochrome b562 [236]. Cofactor substitution afforded a photoactive enzyme (Co-cyt b562), whose activity could be modulated through mutagenesis in the primary Along these lines, Mahy and coworkers recently developed an artificial hydrogenase via insertion of maleimide functionalized CoPPIX into an artificial protein, named αRep (Table 2, entry 30) [237]. This protein has been shown to adopt a closed shell-like conformation hosting a large hydrophobic cavity, which has been previously exploited for the anchoring of catalytic metal complexes.…”

Covalent Molecular Anchoring of Metal-Free Porphyrin on Graphitic Surfaces toward Improved Electrocatalytic Activities in Acidic Medium

“…These intrinsic characteristics have provided great flexibility in engineering and designing surface-terminal functional groups, thereby enhancing the applicability of this class of molecule in electrocatalysis including HER and OER [27,28]. Thus far, metallated porphyrin-based catalysts with a metal center responsible for the catalytic activity have been exclusively investigated for water splitting [26,[29][30][31]. Non-covalent functionalization of electrode surfaces has been employed for designing these types of heterogeneous catalysts [4,29,[32][33][34].…”