| 1. |
- Hola, Katerina, et al.
(författare)
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Carbon Dots and [FeFe] Hydrogenase Biohybrid Assemblies for Efficient Light-Driven Hydrogen Evolution
- 2020
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Ingår i: ACS Catalysis. - : AMER CHEMICAL SOC. - 2155-5435. ; 10:17, s. 9943-9952
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Tidskriftsartikel (refereegranskat)abstract
- Artificial photosynthesis is seen as a path to convert and store solar energy into chemical energy for our society. In this work, highly fluorescent aspartic acid-based carbon dots (CDs) are synthesized and employed as a photosensitizer to drive photocatalytic hydrogen evolution with an [FeFe] hydrogenase (CrHydA1). The direct interaction in CDs from L-aspartic acid (AspCDs)/CrHydA1 self-assembly systems, which is visualized from native gel electrophoresis, has been systematically investigated to understand the electron-transfer dynamics and its impact on photocatalytic efficiency. The study discloses the significant influence of the electrostatic surrounding generated by sacrificial electron donors on the intimate interplay within the oppositely charged subunits of the biohybrid assembly as well as the overall photocatalytic performance. The system reaches an external quantum efficiency of 1.7% at 420 nm and an initial activity of 1.73 mu mol(H-2) mg(-1) (hydrogenase) min(-1) under favorable electrostatic conditions. Owing to the ability of the synthesized AspCDs to operate efficiently under visible light, in contrast to other materials that require UV illumination, the stability of the biohybrid assembly in the presence of a redox mediator extends beyond 1 week.
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| 2. |
- Land, Henrik, et al.
(författare)
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Characterization of a putative sensory [FeFe]-hydrogenase provides new insight into the role of the active site architecture
- 2020
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Ingår i: Chemical Science. - : The Royal Society of Chemistry. - 2041-6539. ; 11:47, s. 12789-12801
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Tidskriftsartikel (refereegranskat)abstract
- [FeFe]-hydrogenases are known for their high rates of hydrogen turnover, and are intensively studied in the context of biotechnological applications. Evolution has generated a plethora of different subclasses with widely different characteristics. The M2e subclass is phylogenetically distinct from previously characterized members of this enzyme family and its biological role is unknown. It features significant differences in domain- and active site architecture, and is most closely related to the putative sensory [FeFe]-hydrogenases. Here we report the first comprehensive biochemical and spectroscopical characterization of an M2e enzyme, derived from Thermoanaerobacter mathranii. As compared to other [FeFe]-hydrogenases characterized to-date, this enzyme displays an increased H2 affinity, higher activation enthalpies for H+/H2 interconversion, and unusual reactivity towards known hydrogenase inhibitors. These properties are related to differences in active site architecture between the M2e [FeFe]-hydrogenase and “prototypical†[FeFe]-hydrogenases. Thus, this study provides new insight into the role of this subclass in hydrogen metabolism and the influence of the active site pocket on the chemistry of the H-cluster.
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| 3. |
- Németh, Brigitta, et al.
(författare)
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[FeFe]-hydrogenase maturation : H-cluster assembly intermediates tracked by electron paramagnetic resonance, infrared, and X-ray absorption spectroscopy
- 2020
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Ingår i: Journal of Biological Inorganic Chemistry. - : Springer Nature. - 0949-8257 .- 1432-1327. ; 25:5, s. 777-788
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Tidskriftsartikel (refereegranskat)abstract
- [FeFe]-hydrogenase enzymes employ a unique organometallic cofactor for efficient and reversible hydrogen conversion. This so-called H-cluster consists of a [4Fe-4S] cubane cysteine linked to a diiron complex coordinated by carbon monoxide and cyanide ligands and an azadithiolate ligand (adt =NH(CH2S)(2)).[FeFe]-hydrogenase apo-protein binding only the [4Fe-4S] sub-complex can be fully activated in vitro by the addition of a synthetic diiron site precursor complex ([2Fe](adt)). Elucidation of the mechanism of cofactor assembly will aid in the design of improved hydrogen processing synthetic catalysts. We combined electron paramagnetic resonance, Fourier-transform infrared, and X-ray absorption spectroscopy to characterize intermediates of H-cluster assembly as initiated by mixing of the apo-protein (HydA1) from the green alga Chlamydomonas reinhardtii with [2Fe](adt). The three methods consistently show rapid formation of a complete H-cluster in the oxidized, CO-inhibited state (Hox-CO) already within seconds after the mixing. Moreover, FTIR spectroscopy support a model in which Hox-CO formation is preceded by a short-lived Hred'-CO-like intermediate. Accumulation of Hox-CO was followed by CO release resulting in the slower conversion to the catalytically active state (Hox) as well as formation of reduced states of the H-cluster. [GRAPHICS] .
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| 4. |
- Németh, Brigitta, et al.
(författare)
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The maturase HydF enables [FeFe] hydrogenase assembly via transient, cofactor-dependent interactions
- 2020
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Ingår i: Journal of Biological Chemistry. - : American Society for Biochemistry and Molecular Biology. - 0021-9258 .- 1083-351X. ; 295:33, s. 11891-11901
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Tidskriftsartikel (refereegranskat)abstract
- [FeFe] hydrogenases have attracted extensive attention in the field of renewable energy research because of their remarkable efficiency for H(2)gas production. H(2)formation is catalyzed by a biologically unique hexanuclear iron cofactor denoted the H-cluster. The assembly of this cofactor requires a dedicated maturation machinery including HydF, a multidomain [4Fe4S] cluster protein with GTPase activity. HydF is responsible for harboring and delivering a precatalyst to the apo-hydrogenase, but the details of this process are not well understood. Here, we utilize gas-phase electrophoretic macromolecule analysis to show that a HydF dimer forms a transient interaction complex with the hydrogenase and that the formation of this complex depends on the cofactor content on HydF. Moreover, Fourier transform infrared, electron paramagnetic resonance, and UV-visible spectroscopy studies of mutants of HydF show that the isolated iron-sulfur cluster domain retains the capacity for binding the precatalyst in a reversible fashion and is capable of activating apo-hydrogenase inin vitroassays. These results demonstrate the central role of the iron-sulfur cluster domain of HydF in the final stages of H-cluster assembly,i.e.in binding and delivering the precatalyst.
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