scholarly journals Generating single metalloprotein crystals in well-defined redox states: electrochemical control combined with infrared imaging of a NiFe hydrogenase crystal

2017 ◽  
Vol 53 (43) ◽  
pp. 5858-5861 ◽  
Author(s):  
P. A. Ash ◽  
S. B. Carr ◽  
H. A. Reeve ◽  
A. Skorupskaitė ◽  
J. S. Rowbotham ◽  
...  
Keyword(s):  
Redox State ◽  
Infrared Imaging ◽  
Redox States ◽  
Infrared Microspectroscopy ◽  
Electrochemical Control

We manipulate and verify the redox state of single metalloprotein crystals by combining electrochemical control with synchrotron infrared microspectroscopy.

scholarly journals The redox state of free nicotinamide–adenine dinucleotide phosphate in the cytoplasm of rat liver

1969 ◽  
Vol 115 (4) ◽  
pp. 609-619 ◽  
Author(s):  
R. L. Veech ◽  
L. V. Eggleston ◽  
H. A. Krebs
Keyword(s):  
Malic Enzyme ◽  
Redox State ◽  
Carbohydrate Diet ◽  
Redox States ◽  
Low Carbohydrate Diet ◽  
A Value ◽  
Low Carbohydrate ◽  
Sucrose Diet ◽  
High Sucrose Diet ◽  
High Sucrose

1. The concentrations of the oxidized and reduced substrates of the ‘malic’ enzyme (EC 1.1.1.40) and isocitrate dehydrogenase (EC 1.1.1.42) were measured in freeze-clamped rat livers. By assuming that the reactants of these dehydrogenase systems are at equilibrium in the cytoplasm the [free NADP+]/[free NADPH] ratio was calculated. The justification of the assumption is discussed. 2. The values of this ratio obtained under different nutritional conditions (well-fed, 48hr.-starved, fed with a low-carbohydrate diet, fed with a high-sucrose diet) were all of the same order of magnitude although characteristic changes occurred on varying the diet. The value of the ratio fell on starvation and on feeding with the low-carbohydrate diet and rose slightly on feeding with the high-sucrose diet. 3. The mean values of the ratio were calculated to be between 0·001 and 0·015, which is about 100000 times lower than the values of the cytoplasmic [free NAD+]/[free NADH] ratio. 4. The differences in the redox state of the two nicotinamide–adenine dinucleotide couples can be explained on a simple physicochemical basis. The differences are the result of equilibria that are determined by the equilibrium constants of a number of highly active readily reversible dehydrogenases and transaminases and the concentrations of the substrates and products of these enzymes. 5. The decisive feature is the fact that the NAD and NADP couples share substrates. This sharing provides a link between the redox states of the two couples. 6. The application of the method of calculation to data published by Kraupp, Adler-Kastner, Niessner & Plank (1967), Goldberg, Passonneau & Lowry (1966) and Kauffman, Brown, Passonneau & Lowry (1968) shows that the redox states of the NAD and NADP couples in cardiac-muscle cytoplasm and in mouse-brain cytoplasm are of the same order as those in rat liver. 7. The determination of the equilibrium constant at 38°, pH7·0 and I 0·25 (required for the calculation of the [free NADP+]/[free NADPH] ratio), gave a value of 3·44×10−2m for the ‘malic’ enzyme (with CO2 rather than HCO3− as the reactant) and a value of 1·98×10−2m−1 for glutathione reductase.

scholarly journals Cellular Redox State Acts as Switch to Determine the Direction of NNT-Catalyzed Reaction in Cystic Fibrosis Cells

2021 ◽  
Vol 22 (2) ◽  
pp. 967
Author(s):  
Maria Favia ◽  
Anna Atlante
Keyword(s):  
Cystic Fibrosis ◽  
Redox State ◽  
Molecular Mechanisms ◽  
Activity Level ◽  
Cellular Redox ◽  
Redox States ◽  
Mitochondrial Ros ◽  
New Information ◽  
Cellular Dysfunction ◽  
Cellular Redox State

The redox states of NAD and NADP are linked to each other in the mitochondria thanks to the enzyme nicotinamide nucleotide transhydrogenase (NNT) which, by utilizing the mitochondrial membrane potential (mΔΨ), catalyzes the transfer of redox potential between these two coenzymes, reducing one at the expense of the oxidation of the other. In order to define NNT reaction direction in CF cells, NNT activity under different redox states of cell has been investigated. Using spectrophotometric and western blotting techniques, the presence, abundance and activity level of NNT were determined. In parallel, the levels of NADPH and NADH as well as of mitochondrial and cellular ROS were also quantified. CF cells showed a 70% increase in protein expression compared to the Wt sample; however, regarding NNT activity, it was surprisingly lower in CF cells than healthy cells (about 30%). The cellular redox state, together with the low mΔΨ, pushes to drive NNT reverse reaction, at the expense of its antioxidant potential, thus consuming NADPH to support NADH production. At the same time, the reduced NNT activity prevents the NADH, produced by the reaction, from causing an explosion of ROS by the damaged respiratory chain, in accordance with the reduced level of mitochondrial ROS in NNT-loss cells. This new information on cellular bioenergetics represents an important building block for further understanding the molecular mechanisms responsible for cellular dysfunction in cystic fibrosis.

scholarly journals The effect of haem ligands on the redox states of the hexa-haem nitrite reductase from Wolinella succinogenes

1990 ◽  
Vol 271 (1) ◽  
pp. 253-257 ◽  
Author(s):  
R S Blackmore ◽  
P M A Gadsby ◽  
C Greenwood ◽  
A J Thomson
Keyword(s):  
Ligand Binding ◽  
Nitrite Reductase ◽  
Active Site ◽  
Redox State ◽  
Stopped Flow ◽  
Ligand Binding Site ◽  
Wolinella Succinogenes ◽  
Redox States ◽  
Cyanide Binding

The nitrite reductase of Wolinella succinogenes containing six covalently bound haem groups has one haem group that will not reduce fully in the presence of excess Na2S2O4. The effect of the extrinsic ligands CO and cyanide on the redox state of this haem was studied by e.p.r. and magnetic c.d. spectroscopy. It was found that both ligands increased the extent of reduction of this haem group, and that in the case of CO binding the level of reduction was correlated with the extent of CO saturation of the enzyme. Stopped-flow studies of the effect of cyanide binding on the rate of dithionite reduction showed that the rate of reduction of the ligand-binding site was increased in the presence of cyanide. This suggests that reduction of the haem groups at the active site is thermodynamically unfavourable in the absence of an extrinsic ligand. The role of the ‘non-reducing’ haem group and the effect of ligands on this centre and on the rate of reduction are discussed in relation to the reduction of nitrite by this enzyme.

Highly water-soluble three-redox state organic dyes as bifunctional analytes

2016 ◽  
Vol 9 (11) ◽  
pp. 3521-3530 ◽  
Author(s):  
Javier Carretero-González ◽  
Elizabeth Castillo-Martínez ◽  
Michel Armand
Keyword(s):  
Redox State ◽  
Organic Dyes ◽  
Water Soluble ◽  
Redox States ◽  
Redox Flow Batteries ◽  
Flow Batteries

Common organic dyes show three stable redox states, offering an alternative to questionable vanadium for the implementation of redox-flow batteries.

scholarly journals First-Principles Study on Redox Magnetism and Electrochromism of Cyclometalated Triarylamine-Core Triruthenium Complex

Crystals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 57
Author(s):  
Lin Li ◽  
Yue Wang ◽  
Meng-Yang Chen ◽  
Jian Zhang ◽  
Jian-Quan Liang ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Spin Density ◽  
First Principles ◽  
Density Functional ◽  
Redox State ◽  
Visible Region ◽  
Geometric Optimization ◽  
Energy Splitting ◽  
Redox States ◽  
Spin Electronic

Spin electronic states and optical properties of a circular ruthenium (Ru) terpyridine complex with a triarylamine core (CTTC) are theoretically investigated by first-principles calculations within an all-electron numerical orbital scheme based on spin density functional theory (SDFT), which demonstrate five well-defined redox states for electrochromic functions. Atomic structure of CTTC molecule is obtained by geometric optimization, and its electronic structure with a decreasing semiconductor band-gap exhibits five consecutive single-electron redox states of Ru-coordinated centers. Except for CTTC in (Ru)3+4 redox state exhibiting a net spin of 2.25 (ћ/2), the other redox states are almost zero in total spin. Density distribution and energy-splitting of spin states indicate that the ferromagnetic coupling of Ru cations coordinating with terpyridine/triarylamine ligands originates dominantly from the spin polarization of Ru 4d-orbitals coordinated by N- and C-2p electrons of triarylamine. CTTC molecule in each redox state represents a well-discriminated absorption in visible region, with the highest characteristic peaks locating at 24.2, 20.2, 21.3, and 19.3/21.7 (103 cm−1) and a manifold of peaks at 13.4~25.3 (103 cm−1) for +2~+6 redox states, respectively. Theoretical electronic structure and optics of CTTC complex are used to evaluate the underlying physical mechanism of realizing a multi-color visible electrochromism by four couples of redox pairs, which is suggested to be applied for monitoring electrical information.

scholarly journals High-spatial-resolution mapping of superhydrophobic cicada wing surface chemistry using infrared microspectroscopy and infrared imaging at two synchrotron beamlines

2013 ◽  
Vol 20 (3) ◽  
pp. 482-489 ◽  
Author(s):  
Mark J. Tobin ◽  
Ljiljana Puskar ◽  
Jafar Hasan ◽  
Hayden K. Webb ◽  
Carol J. Hirschmugl ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Spatial Resolution ◽  
Infrared Imaging ◽  
Antibacterial Properties ◽  
Significant Degree ◽  
Distribution Maps ◽  
Infrared Microspectroscopy ◽  
Aerodynamic Properties ◽  
Industry Applications ◽  
Chemical Distribution

The wings of some insects, such as cicadae, have been reported to possess a number of interesting and unusual qualities such as superhydrophobicity, anisotropic wetting and antibacterial properties. Here, the chemical composition of the wings of the Clanger cicada (Psaltoda claripennis) were characterized using infrared (IR) microspectroscopy. In addition, the data generated from two separate synchrotron IR facilities, the Australian Synchrotron Infrared Microspectroscopy beamline (AS-IRM) and the Synchrotron Radiation Center (SRC), University of Wisconsin-Madison, IRENI beamline, were analysed and compared. Characteristic peaks in the IR spectra of the wings were assigned primarily to aliphatic hydrocarbon and amide functionalities, which were considered to be an indication of the presence of waxy and proteinaceous components, respectively, in good agreement with the literature. Chemical distribution maps showed that, while the protein component was homogeneously distributed, a significant degree of heterogeneity was observed in the distribution of the waxy component, which may contribute to the self-cleaning and aerodynamic properties of the cicada wing. When comparing the data generated from the two beamlines, it was determined that the SRC IRENI beamline was capable of producing higher-spatial-resolution distribution images in a shorter time than was achievable at the AS-IRM beamline, but that spectral noise levels per pixel were considerably lower on the AS-IRM beamline, resulting in more favourable data where the detection of weak absorbances is required. The data generated by the two complementary synchrotron IR methods on the chemical composition of cicada wings will be immensely useful in understanding their unusual properties with a view to reproducing their characteristics in, for example, industry applications.

scholarly journals Tuning Redox State and Ionic Transfers of Mg/Fe-Layered Double Hydroxide Nanosheets by Electrochemical and Electrogravimetric Methods

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1832
Author(s):  
Elise Duquesne ◽  
Stéphanie Betelu ◽  
Alain Seron ◽  
Ioannis Ignatiadis ◽  
Hubert Perrot ◽  
...  
Keyword(s):  
Layered Double Hydroxide ◽  
Redox State ◽  
Quartz Crystal ◽  
Interlayer Space ◽  
Zero Point ◽  
Electrochemical Quartz Crystal Microbalance ◽  
Net Charge ◽  
Electrochemical Control ◽  
Ph Increase ◽  
Double Hydroxide

Studying the electrogravimetric behavior of Mg/Fe-layered double hydroxide (LDH) nanoparticles with an electrochemical quartz crystal microbalance demonstrates its pseudocapacitance properties of mix cation and anion exchanger. The electrochemical control of the oxidation state of iron constituting the layered sheets allowed anion intercalation/deintercalation into the LDH interlayer space. Concomitantly, in agreement with the pH of zero point of net charge of the Mg/Fe-LDH, the interfacial pH increase via catalyzed hydrogen evolution reaction allows cation electroadsorption onto the external surfaces of the nanoplatelets.

Copper Systematics in Arc Magmas and Implications for Crust-Mantle Differentiation

Science ◽  
2012 ◽  
Vol 336 (6077) ◽  
pp. 64-68 ◽  
Author(s):  
Cin-Ty A. Lee ◽  
Peter Luffi ◽  
Emily J. Chin ◽  
Romain Bouchet ◽  
Rajdeep Dasgupta ◽  
...  
Keyword(s):  
Continental Crust ◽  
Redox State ◽  
Building Blocks ◽  
Magmatic Differentiation ◽  
Redox States ◽  
Cu Content ◽  
Arc Magmas ◽  
Reducing Conditions ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

Arc magmas are important building blocks of the continental crust. Because many arc lavas are oxidized, continent formation is thought to be associated with oxidizing conditions. On the basis of copper’s (Cu’s) affinity for reduced sulfur phases, we tracked the redox state of arc magmas from mantle source to emplacement in the crust. Primary arc and mid-ocean ridge basalts have identical Cu contents, indicating that the redox states of primitive arc magmas are indistinguishable from that of mid-ocean ridge basalts. During magmatic differentiation, the Cu content of most arc magmas decreases markedly because of sulfide segregation. Because a similar depletion in Cu characterizes global continental crust, the formation of sulfide-bearing cumulates under reducing conditions may be a critical step in continent formation.

scholarly journals Electronic control of redox reactions inside Escherichia coli using a genetic module

PLoS ONE ◽  
2021 ◽  
Vol 16 (11) ◽  
pp. e0258380
Author(s):  
Moshe Baruch ◽  
Sara Tejedor-Sanz ◽  
Lin Su ◽  
Caroline M. Ajo-Franklin
Keyword(s):  
Escherichia Coli ◽  
Redox State ◽  
Shewanella Oneidensis ◽  
Biological Processes ◽  
Electronic Control ◽  
Electron Transfer Pathway ◽  
External Electrode ◽  
Current Consumption ◽  
Genetic Module ◽  
Electrochemical Control

Microorganisms regulate the redox state of different biomolecules to precisely control biological processes. These processes can be modulated by electrochemically coupling intracellular biomolecules to an external electrode, but current approaches afford only limited control and specificity. Here we describe specific electrochemical control of the reduction of intracellular biomolecules in Escherichia coli through introduction of a heterologous electron transfer pathway. E. coli expressing cymAmtrCAB from Shewanella oneidensis MR-1 consumed electrons directly from a cathode when fumarate or nitrate, both intracellular electron acceptors, were present. The fumarate-triggered current consumption occurred only when fumarate reductase was present, indicating all the electrons passed through this enzyme. Moreover, CymAMtrCAB-expressing E. coli used current to stoichiometrically reduce nitrate. Thus, our work introduces a modular genetic tool to reduce a specific intracellular redox molecule with an electrode, opening the possibility of electronically controlling biological processes such as biosynthesis and growth in any microorganism.

scholarly journals The redox state of the nicotinamide–adenine dinucleotides in rat liver homogenates

1968 ◽  
Vol 108 (4) ◽  
pp. 513-520 ◽  
Author(s):  
H. A. Krebs ◽  
T. Gascoyne
Keyword(s):  
Rat Liver ◽  
Redox State ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Redox States ◽  
Cell Compartments ◽  
Dehydrogenase System ◽  
Liver Homogenates ◽  
Saline Medium ◽  
Pyruvate Ratio

1. The redox state of the NAD couple of rat liver mitochondria, as measured by the [β-hydroxybutyrate]/[acetoacetate] ratio, rapidly changed in the direction of oxidation during the preparation of homogenates in a saline medium. The value of the [β-hydroxybutyrate]/[acetoacetate] ratio fell from 2·3 to 0·15 in 10min. EDTA diminished the fall and succinate prevented it. 2. The redox state of the rat liver cytoplasm, as measured by the [lactate]/[pyruvate] ratio, changed slightly in the direction of reduction during the preparation of homogenate. This was prevented by succinate. 3. In unsupplemented homogenates the differences in the redox states of mitochondria and cytoplasm decreased. Succinate and EDTA together maintained the differences within the physiological range. A measure of the ability of the mitochondria to maintain different redox states in mitochondria and cytoplasm is the value of the expression [lactate][acetoacetate]/[pyruvate][β-hydroxybutyrate]. If there are no differences in the redox states of the NAD in the two cell compartments the value of the expression is 444 at 37°. The value in the intact rat liver is between 4·7 and 21. 4. α-Oxoglutarate or glutamate were still more effective than succinate in maintaining high [β-hydroxybutyrate]/[acetoacetate] ratios in the homogenates because these substrates supply a reducing agent of NAD+ and, through succinate, an inhibitor of the oxidation of NADH. 5. When supplemented with α-oxoglutarate and EDTA, homogenates readily adjust the redox state of the β-hydroxybutyrate dehydrogenase system after it has been upset by the addition of either acetoacetate or β-hydroxybutyrate. 6. Amytal and rotenone raised the value of the [β-hydroxybutyrate]/[acetoacetate] ratio. This is taken to indicate that the reduction of acetoacetate in the homogenates was not an energy-linked process. 7. 2,4-Dinitrophenol shifted the [β-hydroxybutyrate]/[acetoacetate] ratio in the presence of succinate in favour of oxidation because it inhibited the oxidation of succinate and accelerated the oxidation of NADH. 8. Rotenone increased the rate of ketone-body formation of liver homogenates, though it decreased the rate of oxygen uptake.

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