A5032182445- Metalloenzymes and iron-sulfur proteins
- Electrocatalysts for Energy Conversion
- Microbial Fuel Cells and Bioremediation
- Metal-Catalyzed Oxygenation Mechanisms
- Hydrogen Storage and Materials
- Ammonia Synthesis and Nitrogen Reduction
- Photosynthetic Processes and Mechanisms
- Catalysis for Biomass Conversion
- Enzyme Catalysis and Immobilization
- Algal biology and biofuel production
- Carbon dioxide utilization in catalysis
- CO2 Reduction Techniques and Catalysts
- Hybrid Renewable Energy Systems
- Advanced battery technologies research
- Microbial Community Ecology and Physiology
- Biochemical Acid Research Studies
- Electrochemical sensors and biosensors
- Porphyrin and Phthalocyanine Chemistry
- Oxidative Organic Chemistry Reactions
- Catalysis and Hydrodesulfurization Studies
- Biocrusts and Microbial Ecology
- Inorganic and Organometallic Chemistry
- Alcohol Consumption and Health Effects
- Microbial metabolism and enzyme function
- Vanadium and Halogenation Chemistry
George Washington University
2025
Kyushu University
2011-2024
Graduate School USA
2018-2021
SPring-8
2017
Konkuk University
2014
Japan Science and Technology Agency
2010-2012
Ibaraki University
2007-2011
Inventec (Taiwan)
2006
The Ohio State University
1999-2001
The University of Tokyo
1997-1998
NAD+ (oxidized form of NAD:nicotinamide adenine dinucleotide)-reducing soluble [NiFe]-hydrogenase (SH) is phylogenetically related to NADH (reduced NAD+):quinone oxidoreductase (complex I), but the geometrical arrangements subunits and Fe-S clusters are unclear. Here, we describe crystal structures SH in oxidized reduced states. The cluster arrangement similar that complex I, orientation not, which supports hypothesis evolved as prebuilt modules. active site includes a six-coordinate Ni,...
The study of hydrogenase enzymes (H2ases) is necessary because their importance to a future hydrogen energy economy. These come in three distinct classes: [NiFe] H2ases, which have propensity toward H2 oxidation; [FeFe] evolution; and [Fe] catalyze H- transfer. Modeling these has so far treated them as different species, understandable given the cores ligand sets natural molecules. Here, we demonstrate, using x-ray analysis nuclear magnetic resonance, infrared, Mössbauer spectroscopies,...
Rubredoxin (Rd) from the moderately thermophilic green sulfur bacterium <i>Chlorobium tepidum</i> was found to function as an electron acceptor for pyruvate ferredoxin oxidoreductase (PFOR). This enzyme, which catalyzes conversion of acetyl-CoA and CO<sub>2</sub>, exhibited absolute dependence upon presence Rd. However, Rd incapable participating in synthase or CO<sub>2</sub> fixation reaction <i>C. PFOR, two different reduced ferredoxins are employed donors. These results suggest a specific...
A hydrogen-oxidizing bacterium strain AH-24 was isolated, which classified in the genus Hydrogenophaga, based on 16S rRNA gene sequence. The isolate possessed a typical yellow pigment of Hydrogenophaga species. Its closest relative pseudoflava, but assimilation profile sugar compounds resembled that no species Hydrogenophaga. optimum temperature and pH for autotrophic growth were, respectively, 33-35 degrees C 7.0. Most hydrogenase activity (benzyl viologen reducing activity) localized...
We report the decomposition of formic acid to hydrogen and carbon dioxide, catalysed by a NiRu complex originally developed as [NiFe]hydrogenase model. This is first example H2 evolution, model, which does not require additional energy.
Cyanobacteria are widely distributed in marine, aquatic, and terrestrial ecosystems, play an important role the global nitrogen cycle. In present study, we examined genome sequence of thermophilic non-heterocystous N2-fixing cyanobacterium, Thermoleptolyngbya sp. O-77 (formerly known as Leptolyngbya O-77) characterized its nitrogenase activity. The this cyanobacterial strain consists a single chromosome containing fixation gene cluster. A phylogenetic analysis indicated that NifH amino acid...
We propose a modified mechanism for the inhibition of [NiFe]hydrogenase ([NiFe]H2ase) by CO. present model study, using NiRu H2ase mimic, that demonstrates (i) CO completely inhibits catalytic cycle compound, (ii) prefers to coordinate RuII center rather than taking an axial position on NiII center, and (iii) is unable displace hydrido ligand from center. combine these studies with reevaluation previous that, under normal circumstances, [NiFe]H2ase complexing FeII
Two distinct ferredoxins, Fd I and II, were isolated purified to homogeneity from photoautotrophically grown Chlorobium tepidum, a moderately thermophilic green sulfur bacterium that assimilates carbon dioxide by the reductive tricarboxylic acid cycle. Both ferredoxins serve crucial role as electron donors for carboxylation, catalyzed key enzyme of this pathway, pyruvate synthase/pyruvate ferredoxin oxidoreductase. The reduction potentials II determined cyclic voltammetry be -514 -584 mV,...
This communication reports the successful merging of chemical properties a natural [NiFe]hydrogenase (Desulfovibrio vulgaris Miyazaki F) and our previously reported [NiRu] hydrogenase-mimic. The catalytic activity both enzyme mimic is almost identical, with exception working pH ranges, this allows us to use them simultaneously in same reaction flask. In such manner, isotope exchange between D(2) H(2)O could be conducted over an extended range (about 2-10) one pot under mild conditions at...
<italic>Citrobacter</italic> sp. S-77 [NiFe]-hydrogenase harbors a standard [4Fe–4S] cluster proximal to the Ni–Fe active site.
The electrochemical reduction of nicotinamide adenine dinucleotide (NAD) using water as a hydrogen source is promising strategy for the efficient and environmentally friendly production active enzymatic cofactor 1,4-NADH, which key further application systems in various industrial fields. However, regeneration 1,4-NADH (NADH-reg) remains major challenge. rate-limiting step conversion oxidized NAD second electron transfer to an radical, formed by NAD+, at large overpotential, whereas other...
Membrane-bound [NiFe]-hydrogenase from Hydrogenophaga sp. AH-24 was purified to homogeneity. The molecular weight estimated as 100+/-10 kDa, consisting of two different subunits (62 and 37 kDa). optimal pH values for H(2) oxidation evolution were 8.0 4.0, respectively, the activity ratio (H(2) oxidation/H(2) evolution) 1.61 x 10(2) at 7.0. temperature 75 degrees C. enzyme quite stable under air atmosphere (the half-life c. 48 h 4 C), which should be important function in aerobic habitat...
We report the first example of characterization a Ru-based peroxide intermediate O2-promoted activation C–H bond pentamethylcyclopentadienyl (Cp*) ligand. The complex activates to form tetramethylfulvene complex. propose proton-coupled electron-transfer (PCET) mechanism based on structures and properties complexes.
Enzymatic reactions involving pyruvate: ferredoxin oxidoreductase and 2-oxoglutarate: from a thermophilic, aerobic, chemolithoautotrophic, hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus TK-6, were investigated as the CO2 exchange reaction fixation using isolated same organism reductant.
Herein, we report the first crystal structure of a monomeric p-semiquinonato d-block complex and its reactivity toward dioxygen, closely associated with biological system an oxygen evolving centre photosystem II.
We present a mechanistic investigation for the activation of H2 and O2, induced by simple ligand effect within [NiFe] models O2-tolerant [NiFe]hydrogenase. Kinetic study reveals Michaelis–Menten type saturation behaviors both O2 activation, which is same behavior as that found in Such caused complexation followed heterolytic cleavage an outer-sphere base, resulting formation hydride species showing hydridic character.