Activation and Inactivation of Hydrogenase Function and the Catalytic Cycle:  Spectroelectrochemical Studies

Lacey, Antonio L. De; Fernández, Vı́ctor M.; Rousset, Marc; Cammack, Richard

doi:10.1021/cr0501947

Cited by 437 publications

(487 citation statements)

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“…7 In the high potential regime, the Ni-S state was stable up to +0.6 V although irreversible degradation of the active site occurred at more positive potentials. Thus the RH does not form the oxidised Ni-B state.…”

Section: Methodsmentioning

confidence: 92%

“…The presence of intrinsic CO and CN À ligands at the active sites means that infrared (IR) spectroscopy is a useful method for following electronic and coordination changes during catalysis or inhibition brought about by light triggers, gas exchange or electrochemical control. [6][7][8][9] Solution IR spectroelectrochemical studies interpreted alongside EPR analysis 10 and X-ray crystallographic structures have shaped our understanding of hydrogenase structure and mechanism, distinguishing a range of catalytically active and inactive states of the active site, with subtle variations evident between hydrogenases from different organisms. Most of the IR spectroelectrochemical studies on hydrogenases have been carried out in transmission geometry in an optically transparent thin layer electrochemical (OTTLE) cell originally developed by Moss et al using a gold minigrid working electrode.…”

mentioning

confidence: 99%

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Attenuated total reflectance infrared spectroelectrochemistry at a carbon particle electrode; unmediated redox control of a [NiFe]-hydrogenase solution

Healy

Ash

Lenz

et al. 2013

Phys. Chem. Chem. Phys.

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We report a versatile infrared spectroscopic method for studying redox chemistry of metalloproteins, and demonstrate for the first time electrochemically-induced changes to the active site of the regulatory [NiFe]-hydrogenase from Ralstonia eutropha. A carbon particle network working electrode allows control over a wide potential window without the need for solution mediators.Hydrogenases are able to oxidise or produce H 2 at high turnover frequencies with a low overpotential requirement, and high selectivity for H 2 in the face of other gases. 1 A number of applications of hydrogenases have been explored, including light-driven H 2 production, 2 H 2 fuel cells, 3 and H 2 -supported recycling of the cofactor NADH. 4,5 Hydrogenases capable of functioning in the presence of O 2 are of particular interest for these applications. This impressive catalytic ability, together with the fact that hydrogenase active sites are built from readily available metals (iron, nickel), has inspired studies directed towards a detailed understanding of their chemistry. The presence of intrinsic CO and CN À ligands at the active sites means that infrared (IR) spectroscopy is a useful method for following electronic and coordination changes during catalysis or inhibition brought about by light triggers, gas exchange or electrochemical control. 6-9 Solution IR spectroelectrochemical studies interpreted alongside EPR analysis 10 and X-ray crystallographic structures have shaped our understanding of hydrogenase structure and mechanism, distinguishing a range of catalytically active and inactive states of the active site, with subtle variations evident between hydrogenases from different organisms. Most of the IR spectroelectrochemical studies on hydrogenases have been carried out in transmission geometry in an optically transparent thin layer electrochemical (OTTLE) cell originally developed by Moss et al. using a gold minigrid working electrode. 11 It is usually necessary to include small molecule redox mediators to achieve reasonable rates of electron transfer between the electrode and the hydrogenase; an exception is a study of the unusually small 49 kDa [FeFe]-hydrogenase from Chlamydomonas reinhardtii. 12 An Attenuated Total Reflectance (ATR) geometry opens up more flexible options for choice of working electrode. Rich and co-workers have developed an ATR-IR spectroelectrochemical cell in which a layer of protein coated onto the optical element is in contact with redox which shuttle electrons across the solution interface from a platinum mesh or glassy carbon electrode. 13 An alternative approach used widely for studying metallic surface chemistry, in which a thin metallic layer deposited on an ATR prism serves as the working electrode, has been adapted for biological molecules. 8,14 In this configuration, the protein is immobilised onto the gold electrode layer via a self-assembled alkanethiolate monolayer, and is in efficient solute contact, as demonstrated for reduction of hydrogenases upon introduction of H 2 . 8 Graphitic elect...

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Section: Methodsmentioning

confidence: 92%

mentioning

confidence: 99%

Attenuated total reflectance infrared spectroelectrochemistry at a carbon particle electrode; unmediated redox control of a [NiFe]-hydrogenase solution

Healy

Ash

Lenz

et al. 2013

Phys. Chem. Chem. Phys.

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“…These investigations have addressed various active and inactive forms of the enzyme which can be distinguished on the basis of the frequencies of IR bands arising from active site CO and CN − (De Lacey et al 2007). Slow diffusion of gases through water means that time resolution is necessarily low (many seconds).…”

Section: (B) Gas Exchange or Solute Exchange As A Reaction Triggermentioning

confidence: 99%

Triggered infrared spectroscopy for investigating metalloprotein chemistry

Vincent

2010

Phil. Trans. R. Soc. A.

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Recent developments in infrared (IR) spectroscopic time resolution, sensitivity and sample manipulation make this technique a powerful addition to the suite of complementary approaches for the study of time-resolved chemistry at metal centres within proteins. Application of IR spectroscopy to proteins has often targeted the amide bands as probes for gross structural change. This article focuses on the possibilities arising from recent IR technical developments for studies that monitor localized vibrational oscillators in proteins-native or exogenous ligands such as NO, CO, SCN − or CN − , or genetically or chemically introduced probes with IR-active vibrations. These report on the electronic and coordination state of metals, the kinetics, intermediates and reaction pathways of ligand release, hydrogen-bonding interactions between the protein and IR probe, and the electrostatic character of sites in a protein. Metalloprotein reactions can be triggered by light/dark transitions, an electrochemical step, a change in solute composition or equilibration with a new gas atmosphere, and spectra can be obtained over a range of time domains as far as the sub-picosecond level. We can expect to see IR spectroscopy exploited, alongside other spectroscopies, and crystallography, to elucidate reactions of a wide range of metalloprotein chemistry with relevance to cell metabolism, health and energy catalysis.

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“…Electrochemistry is a very powerful technique that can provide fundamental insights into reaction mechanisms of redox catalysts (23)(24)(25)(26)(27). Conventionally, a catalyst is deposited on a conducting electrode material (e.g., graphite); however, this approach does not allow site isolation of the catalysts.…”

mentioning

confidence: 99%

O ₂ reduction by a functional heme/nonheme bis-iron NOR model complex

Collman

Dey

Yang

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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O2 reactivity of a functional NOR model is investigated by using electrochemistry and spectroscopy. The electrochemical measurements using interdigitated electrodes show very high selectivity for 4e O2 reduction with minimal production of partially reduced oxygen species (PROS) under both fast and slow electron flux. Intermediates trapped at cryogenic temperatures and characterized by using resonance Raman spectroscopy under single-turnover conditions indicate that an initial bridging peroxide intermediate undergoes homolytic OOO bond cleavage generating a trans heme/nonheme bis-ferryl intermediate. This bis ferryl species can oxygenate 2 equivalents of a reactive substrate.C ytochrome c oxidase (CcO) and nitric oxide reductase (NOR) belong to the heme copper oxidase superfamily of enzymes (1, 2). CcO is the terminal enzyme in the respiratory chain of higher organisms, located in their mitochondrial membrane, that reduces O 2 to H 2 O as source of energy. The O 2 reduction process in CcO generates a pH gradient across the bilayer membrane, which provides the driving force for ATP synthesis. The bimetallic active site of CcO has a heme ligated to the protein by a proximal histidine ligand and a distal Cu B site coordinated by 3 histidine ligands ( Fig. 1) (3). In addition to the bimetallic site, there is a conserved tyrosine ligand covalently attached to one of the histidines coordinated to Cu B (4, 5). The NORs are the older member of the family and are found in bacteria using NO 3 Ϫ as source of energy instead of O 2 (2, 6, 7). Although there are no high-resolution crystal structures of NOR, biochemical studies and computer modeling indicate that these enzymes have a histidine-ligated heme, quite like the CcOs, and a distal Fe B , unlike Cu B in CcO, coordinated by 3 histidines ( Fig. 1) (8-10). NORs do not have the conserved tyrosine residue of CcO but have a few conserved key glutamate residues (11,12). Although the NOR enzymes are proposed to have specific proton channels, they are probably not involved in generating proton gradients (13-16).These 2 enzymes exhibit complementary reactivity toward 2 very significant diatomic molecules in nature; O 2 and NO. In eukaryotes CcO (aa 3 type) reduces O 2 to H 2 O and is reversibly but strongly inhibited by [17][18][19][20]. Several other CcOs (ba 3 , caa 3 , cbb 3 ) are reported to exhibit limited (Ͻ1%) NOR activity, i.e., reduce NO to N 2 O (7, 21). On the other hand, NORs that reduce NO to N 2 O are reversibly but strongly inhibited by O 2 , and some of them show modest (Ϸ10%) O 2 reduction activity (12). The parallels in their reactivities toward O 2 and NO and similarities in their secondary structures have led to a hypotheses regarding NOR's and CcO's similar evolutionary origins (6,22).Electrochemistry is a very powerful technique that can provide fundamental insights into reaction mechanisms of redox catalysts (23-27). Conventionally, a catalyst is deposited on a conducting electrode material (e.g., graphite); however, this approach does not allow site isola...

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Activation and Inactivation of Hydrogenase Function and the Catalytic Cycle: Spectroelectrochemical Studies

Cited by 437 publications

References 345 publications

Attenuated total reflectance infrared spectroelectrochemistry at a carbon particle electrode; unmediated redox control of a [NiFe]-hydrogenase solution

Attenuated total reflectance infrared spectroelectrochemistry at a carbon particle electrode; unmediated redox control of a [NiFe]-hydrogenase solution

Triggered infrared spectroscopy for investigating metalloprotein chemistry

O ₂ reduction by a functional heme/nonheme bis-iron NOR model complex

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Activation and Inactivation of Hydrogenase Function and the Catalytic Cycle: Spectroelectrochemical Studies

Cited by 437 publications

References 345 publications

Attenuated total reflectance infrared spectroelectrochemistry at a carbon particle electrode; unmediated redox control of a [NiFe]-hydrogenase solution

Attenuated total reflectance infrared spectroelectrochemistry at a carbon particle electrode; unmediated redox control of a [NiFe]-hydrogenase solution

Triggered infrared spectroscopy for investigating metalloprotein chemistry

O 2 reduction by a functional heme/nonheme bis-iron NOR model complex

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Product

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O ₂ reduction by a functional heme/nonheme bis-iron NOR model complex