Utschig, L.M.

Chem. Commun. 2015, 51, 10628-10631, 10.1039/c5cc03006d

Long-lived charge separation facilitates photocatalytic H2 production in a mini reaction center/catalyst complex.

Kim, H.M.; Lee, H.S.

Biomacromolecules 2020, 21, 5021-5028, 10.1021/acs.biomac.0c01194

Many natural proteins function in oligomeric forms, which are critical for their sophisticated functions. The construction of protein assemblies has great potential for biosensors, enzyme catalysis, and biomedical applications. In designing protein assemblies, a critical process is to create protein–protein interaction (PPI) networks at defined sites of a target protein. Although a few methods are available for this purpose, most of them are dependent on existing PPIs of natural proteins to some extent. In this report, a metal-chelating amino acid, 2,2′-bipyridylalanine (BPA), was genetically introduced into defined sites of a monomeric protein and used to form protein oligomers. Depending on the number of BPAs introduced into the protein and the species of metal ions (Ni2+ and Cu2+), dimers or oligomers with different oligomerization patterns were formed by complexation with a metal ion. Oligomer sizes could also be controlled by incorporating two BPAs at different locations with varied angles to the center of the protein. When three BPAs were introduced, the monomeric protein formed a large complex with Ni2+. In addition, when Cu2+ was used for complex formation with the protein containing two BPAs, a linear complex was formed. The method proposed in this report is technically simple and generally applicable to various proteins with interesting functions. Therefore, this method would be useful for the design and construction of functional protein assemblies.

Tiede, D.M.; Utschig, L.M.

J. Am. Chem. Soc. 2011, 133, 16334-16337, 10.1021/ja206012r

Solar energy conversion of water into the environmentally clean fuel hydrogen offers one of the best long-term solutions for meeting future energy demands. Nature provides highly evolved, finely tuned molecular machinery for solar energy conversion that exquisitely manages photon capture and conversion processes to drive oxygenic water-splitting and carbon fixation. Herein, we use one of Nature’s specialized energy-converters, the Photosystem I (PSI) protein, to drive hydrogen production from a synthetic molecular catalyst comprised of inexpensive, earth-abundant materials. PSI and a cobaloxime catalyst self-assemble, and the resultant complex rapidly produces hydrogen in aqueous solution upon exposure to visible light. This work establishes a strategy for enhancing photosynthetic efficiency for solar fuel production by augmenting natural photosynthetic systems with synthetically tunable abiotic catalysts.

Tiede, D.M.; Utschig, L.M.

J. Am. Chem. Soc. 2013, 135, 13246-13249, 10.1021/ja405277g

The direct conversion of sunlight into fuel is a promising means for the production of storable renewable energy. Herein, we use Nature’s specialized photosynthetic machinery found in the Photosystem I (PSI) protein to drive solar fuel production from a nickel diphosphine molecular catalyst. Upon exposure to visible light, a self-assembled PSI-[Ni(P2PhN2Ph)2](BF4)2 hybrid generates H2 at a rate 2 orders of magnitude greater than rates reported for photosensitizer/[Ni(P2PhN2Ph)2](BF4)2 systems. The protein environment enables photocatalysis at pH 6.3 in completely aqueous conditions. In addition, we have developed a strategy for incorporating the Ni molecular catalyst with the native acceptor protein of PSI, flavodoxin. Photocatalysis experiments with this modified flavodoxin demonstrate a new mechanism for biohybrid creation that involves protein-directed delivery of a molecular catalyst to the reducing side of Photosystem I for light-driven catalysis. This work further establishes strategies for constructing functional, inexpensive, earth-abundant solar fuel-producing PSI hybrids that use light to rapidly produce hydrogen directly from water.

Birnbaum, E.R.; Darnall, D.W.

J. Biol. Chem. 1970, n/a

The rate of activation of the conversion of trypsinogen to trypsin has been found to be greatly accelerated by the neodymium(III) ion. The similarity of this process to the calcium(II) ion activation suggests that both metal ions bind at identical sites in trypsinogen. The rate of activation in the presence of the neodymium ion is much greater than that of the calcium ion, probably reflecting the increased stability constant of the neodymium-protein complex. In contrast to the calcium ion, however, neodymium(III) can be scrutinized by a variety of spectral and magnetic techniques which should reveal information concerning the calcium ion binding sites in proteins. Since the chemistry and the range of sires of the rare earth metal ions are so similar to that of the calcium ion, it is suggested that generally these ions should make good replacement ions for probing the calcium ion binding sites of proteins and enzymes.

Utschig, L.M.

Chem. Sci. 2016, 7, 7068-7078, 10.1039/c6sc03121h

A series of Ru–protein–Co biohybrids have been prepared using the electron transfer proteins ferredoxin (Fd) and flavodoxin (Fld) as scaffolds for photocatalytic hydrogen production. The light-generated charge separation within these hybrids has been monitored by transient optical and electron paramagnetic resonance spectroscopies. Two distinct electron transfer pathways are observed. The Ru–Fd–Co biohybrid produces up to 650 turnovers of H2 utilizing an oxidative quenching mechanism for Ru(II)* and a sequential electron transfer pathway via the native [2Fe–2S] cluster to generate a Ru(III)–Fd–Co(I) charge separated state that lasts for ∼6 ms. In contrast, a direct electron transfer pathway occurs for the Ru–ApoFld–Co biohybrid, which lacks an internal electron relay, generating Ru(I)–ApoFld–Co(I) charge separated state that persists for ∼800 μs and produces 85 turnovers of H2 by a reductive quenching mechanism for Ru(II)*. This work demonstrates the utility of protein architectures for linking donor and catalytic function via direct or sequential electron transfer pathways to enable stabilized charge separation which facilitates photocatalysis for solar fuel production.