The redox potentials of the two-iron plant algal ferredoxins. An electrostatic model

The two-iron–sulphur co-ordination centre in plant and algal ferredoxins is considered as a collection of charged ions whose net negative charge is twice that of the one-iron–sulphur protein rubredoxin. Calculation of the electrostatic free-energy changes for reduction of the two types of proteins indicates that the redox potential of the two-iron–sulphur proteins should be more negative than that of the one-iron–sulphur protein and that in biological systems the ferredoxins should function as one-electron transfer proteins.

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Modulation of redox potential in electron transfer proteins: Effects of complex formation on the active site microenvironment of cytochrome b5

Faraday Discussions ◽

10.1039/b001520m ◽

2000 ◽

Vol 116 ◽

pp. 221-234 ◽

Cited By ~ 17

Author(s):

Marc Wirtz ◽

Vaheh Oganesyan ◽

Xuejun Zhang ◽

Joe Studer ◽

Mario Rivera

Keyword(s):

Electron Transfer ◽

Complex Formation ◽

Redox Potential ◽

Active Site ◽

Cytochrome B5 ◽

Electron Transfer Proteins

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THE COUPLED REDOX POTENTIAL OF THE LACTATE-ENZYME-PYRUVATE SYSTEM

The Journal of General Physiology ◽

10.1085/jgp.16.6.961 ◽

1933 ◽

Vol 16 (6) ◽

pp. 961-976 ◽

Cited By ~ 9

Author(s):

J. Percy Baumberger ◽

J. J. Jürgensen ◽

Kathleen Bardwell

Keyword(s):

Free Energy ◽

Lactic Acid ◽

Redox Potential ◽

Pyruvic Acid ◽

Standard Free Energy ◽

Redox Potentials ◽

Lactic Acid Dehydrogenase ◽

Acid Dehydrogenase ◽

Free Energy Of Formation ◽

Energy Of Formation

1. The term "coupled redox potential" is defined. 2. The system lactic ion See PDF for Equation pyruvic ion + 2H+ + 2e is shown to be reversible (when the enzyme is lactic acid dehydrogenase) and its coupled redox potential between pH 5.2 and 7.2 at 32°C. is: See PDF for Equation 3. The free energy of the reaction: lactic ion (1m) → pyruvic ion (1m) = -ΔF = –14,572. 4. The standard free energy of formation (ΔF298) of pyruvic acid (l) is estimated at –108,127. This is merely an approximation as some necessary data are lacking. 5. The importance of coupled redox potentials as a factor in the regulation of the equilibrium of metabolites is indicated.

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Metal ion and ligand dependency of the redox behaviour of some first row transition metal dithiocarbamates

Australian Journal of Chemistry ◽

10.1071/ch9732533 ◽

1973 ◽

Vol 26 (11) ◽

pp. 2533 ◽

Cited By ~ 61

Author(s):

R Chant ◽

AR Hendrickson ◽

RL Martin ◽

NM Rohde

Keyword(s):

Transition Metal ◽

Redox Potential ◽

Metal Ion ◽

Electron Configuration ◽

Redox Potentials ◽

Redox Behaviour ◽

Reduction Processes ◽

Metal Dithiocarbamates ◽

The One ◽

Marked Dependence

The one-electron oxidation and reduction processes for some 80 dithiocarbamates of Cr, Mn, Fe, Co, Ni, and Cu reveal a marked dependence of redox potential on the metal 3dn electron configuration. For all the complexes examined, the relative ordering of the redox potentials with the dithiocarbamate substituents is remarkably consistent for both oxidation and reduction processes.

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Geobacter sulfurreducens inner membrane cytochrome CbcBA controls electron transfer and growth yield near the energetic limit of respiration

10.1101/2021.04.15.440034 ◽

2021 ◽

Author(s):

Komal Joshi ◽

Chi Ho Chan ◽

Daniel R. Bond

Keyword(s):

Electron Transfer ◽

Redox Potential ◽

Growth Yield ◽

Growth Efficiency ◽

Geobacter Sulfurreducens ◽

Redox Potentials ◽

Hydrogen Electrode ◽

Highly Expressed Genes ◽

Reducing Bacteria ◽

Transfer Chain

AbstractGeobacter sulfurreducens utilizes extracellular electron acceptors such as Mn(IV), Fe(III), syntrophic partners, and electrodes that vary from +0.4 to −0.3 V vs. Standard Hydrogen Electrode (SHE), representing a potential energy span that should require a highly branched electron transfer chain. Here we describe CbcBA, a bc-type cytochrome essential near the thermodynamic limit of respiration when acetate is the electron donor. Mutants lacking cbcBA ceased Fe(III) reduction at −0.21 V vs. SHE, could not transfer electrons to electrodes between −0.21 and −0.28 V, and could not reduce the final 10% – 35% of Fe(III) minerals. As redox potential decreased during Fe(III) reduction, cbcBA was induced with the aid of the regulator BccR to become one of the most highly expressed genes in G. sulfurreducens. Growth yield (CFU/mM Fe(II)) was 112% of WT in ΔcbcBA, and deletion of cbcL (a different bc-cytochrome essential near −0.15 V) in ΔcbcBA increased yield to 220%. Together with ImcH, which is required at high redox potentials, CbcBA represents a third cytoplasmic membrane oxidoreductase in G. sulfurreducens. This expanding list shows how these important metal-reducing bacteria may constantly sense redox potential to adjust growth efficiency in changing environments.

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Oxidation of Structural Ferrous Iron in Vermiculites: I. Oxidation by Fe3+

Clay Minerals ◽

10.1180/claymin.1988.023.3.03 ◽

1988 ◽

Vol 23 (3) ◽

pp. 261-270 ◽

Cited By ~ 1

Author(s):

H. Graf ◽

V. Reichenbach ◽

B. Beyme

Keyword(s):

Hydrogen Peroxide ◽

Electron Transfer ◽

Redox Potential ◽

Cation Exchange ◽

Ferrous Iron ◽

Activity Ratio ◽

Redox Potentials ◽

Interlayer Cation ◽

Pt Electrode ◽

Coupled Reactions

AbstractVermiculite prepared from biotite by interlayer cation exchange was reacted with solutions exhibiting redox potentials between 625 and 765 mV. The redox potential was controlled by the Fe2+/Fe3+ activity ratio, measured with a Pt electrode, and kept constant by addition of hydrogen peroxide to balance electron transfer from structural Fe2+ to Fe3+ in solution. Oxidation of structural Fe2+ was followed by Eh-stat titration and the rate of oxidation was shown to depend on the amount of Fe3+ penetrating into interlayer positions. Consequently, it was affected not only by the redox potential, but also by the activity between Fe3+ and all other cations present in solution or in an exchangeable state. Oxidation and cation exchange are coupled reactions. In contrast to the redox potential in solution, the effective redox potential controlling the oxidation of structural Fe2+ was increased by preferential sorption of the Fe3+ ion.

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Geothrix fermentans Secretes Two Different Redox-Active Compounds To Utilize Electron Acceptors across a Wide Range of Redox Potentials

Applied and Environmental Microbiology ◽

10.1128/aem.01460-12 ◽

2012 ◽

Vol 78 (19) ◽

pp. 6987-6995 ◽

Cited By ~ 44

Author(s):

Misha G. Mehta-Kolte ◽

Daniel R. Bond

Keyword(s):

Electron Transfer ◽

Redox Potential ◽

Electron Acceptor ◽

Extracellular Electron Transfer ◽

Redox Potentials ◽

Active Compounds ◽

Content Type ◽

Electron Shuttles ◽

Redox Active ◽

Geothrix Fermentans

ABSTRACTThe current understanding of dissimilatory metal reduction is based primarily on isolates from the proteobacterial generaGeobacterandShewanella. However, environments undergoing active Fe(III) reduction often harbor less-well-studied phyla that are equally abundant. In this work, electrochemical techniques were used to analyze respiratory electron transfer by the only known Fe(III)-reducing representative of theAcidobacteria,Geothrix fermentans. In contrast to previously characterized metal-reducing bacteria, which typically reach maximal rates of respiration at electron acceptor potentials of 0 V versus standard hydrogen electrode (SHE),G. fermentansrequired potentials as high as 0.55 V to respire at its maximum rate. In addition,G. fermentanssecreted two different soluble redox-active electron shuttles with separate redox potentials (−0.2 V and 0.3 V). The compound with the lower midpoint potential, responsible for 20 to 30% of electron transfer activity, was riboflavin. The behavior of the higher-potential compound was consistent with hydrophilic UV-fluorescent molecules previously found inG. fermentanssupernatants. Both electron shuttles were also produced when cultures were grown with Fe(III), but not when fumarate was the electron acceptor. This study reveals thatGeothrixis able to take advantage of higher-redox-potential environments, demonstrates that secretion of flavin-based shuttles is not confined toShewanella, and points to the existence of high-potential-redox-active compounds involved in extracellular electron transfer. Based on differences between the respiratory strategies ofGeothrixandGeobacter, these two groups of bacteria could exist in distinctive environmental niches defined by redox potential.

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Computational studies of redox potentials of electron transfer proteins

Simulation and theory of electrostatic interactions in solution ◽

10.1063/1.1301541 ◽

1999 ◽

Cited By ~ 3

Author(s):

Toshiko Ichiye

Keyword(s):

Electron Transfer ◽

Computational Studies ◽

Redox Potentials ◽

Electron Transfer Proteins

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Outer-sphere electron-transfer reactions of ascorbate anions

Australian Journal of Chemistry ◽

10.1071/ch9821133 ◽

1982 ◽

Vol 35 (6) ◽

pp. 1133 ◽

Cited By ~ 143

Author(s):

NH Williams ◽

JK Yandell

Keyword(s):

Aqueous Solution ◽

Electron Transfer ◽

Exchange Rate ◽

Ionic Strength ◽

Rate Constants ◽

Outer Sphere ◽

The Self ◽

Transfer Reactions ◽

Redox Potentials ◽

The One

Rate constants for the one-electron oxidation of ascorbate dianion (A2-) by bis(terpyridine)cobalt(III)ion (8.5 × 106 dm3 mol-1 s-1) and pentaammine(pyridine)ruthenium(III) ion (6.0 × 109 dm3 mol-1 s-1), and of the monoanion (HA-) by tetraammine (bipyridine)ruthenium(III)ion (2.1 × 105 dm3 mol-1s-1) have been determined in aqueous solution at 25�C and ionic strength 0.1 (NaNO3 or NaClO4). It is shown that these rate constants, and other published rate constants for oxidation of HA- and A2-, are consistent with the Marcus cross relation, on the assumption that the self-exchange rate constants for both the HA-/HA and A2-/A-couples are 106 dm3 mol-1 s-1. One electron redox potentials for the ascorbate/dehydroascorbate system have been derived from scattered literature data.

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