Electrochemical studies on c-type cytochromes at microelectrodes

Santos, Margarida M. Correia dos; Sousa, Patrícia M. Paes de; Gonçalves, Maria Eduarda; Lopes, Helena; Moura, Isabel; Moura, José J. G.

doi:10.1016/s0022-0728(98)00474-4

Cited by 14 publications

(11 citation statements)

References 35 publications

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“…where C cyt c is the concentration of cytochrome c-552 under the membrane, D cyt c is its diffusion coefficient (1.0 9 10 -6 cm 2 s -1 [33]) and A is the electrode surface area (see ''Materials and methods''). Calculations with this equation gave k = (5.6 ± 0.4) 9 10 5 M -1 s -1 at pH 7.0, a value identical to the one obtained with the previous approach (Eq.…”

Section: Resultsmentioning

confidence: 99%

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A new CuZ active form in the catalytic reduction of N2O by nitrous oxide reductase from Pseudomonas nautica

et al. 2010

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The final step of bacterial denitrification, the two-electron reduction of N 2 O to N 2 , is catalyzed by a multicopper enzyme named nitrous oxide reductase. The catalytic centre of this enzyme is a tetranuclear copper site called CuZ, unique in biological systems. The in vitro reconstruction of the activity requires a slow activation in the presence of the artificial electron donor, reduced methyl viologen, necessary to reduce CuZ from the resting nonactive state (1Cu II /3Cu I ) to the fully reduced state (4Cu I ), in contrast to the turnover cycle, which is very fast. In the present work, the direct reaction of the activated form of Pseudomonas nautica nitrous oxide reductase with stoichiometric amounts of N 2 O allowed the identification of a new reactive intermediate of the catalytic centre, CuZ°, in the turnover cycle, characterized by an intense absorption band at 680 nm. Moreover, the first mediated electrochemical study of Ps. nautica nitrous oxide reductase with its physiological electron donor, cytochrome c-552, was performed. The intermolecular electron transfer was analysed by cyclic voltammetry, under catalytic conditions, and a second-order rate constant of (5.5 ± 0.9) 9 10 5 M -1 s -1 was determined. Both the reaction of stoichiometric amounts of substrate and the electrochemical studies show that the active CuZ°species, generated in the absence of reductants, can rearrange to the resting non-active CuZ state. In this light, new aspects of the catalytic and activation/inactivation mechanism of the enzyme are discussed.

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Section: Resultsmentioning

confidence: 99%

“…In the determination of the N 2 O concentration dependence of the catalytic current, 8,17,25,33,48,125 For the direct reaction of the enzyme with substrate, an equimolar amount of N 2 O was added to 35 lM N 2 OR preactivated in 0.1 M Tris-HCl at pH 7.6. The reaction was followed using a TIDAS diode-array spectrophotometer.…”

Section: Electrochemical Methodsmentioning

confidence: 99%

A new CuZ active form in the catalytic reduction of N2O by nitrous oxide reductase from Pseudomonas nautica

et al. 2010

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“…6, 4). This reaction occurs between an OM protein and the electrode and is probably reversible, given the reversibility of electron transfer observed in cytochromes (dos Santos et al , 1999).…”

Section: Extracellular Potential Losses (Eom−eanode)mentioning

confidence: 99%

A kinetic perspective on extracellular electron transfer by anode-respiring bacteria

et al. 2010

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In microbial fuel cells and electrolysis cells (MXCs), anode-respiring bacteria (ARB) oxidize organic substrates to produce electrical current. In order to develop an electrical current, ARB must transfer electrons to a solid anode through extracellular electron transfer (EET). ARB use various EET mechanisms to transfer electrons to the anode, including direct contact through outer-membrane proteins, diffusion of soluble electron shuttles, and electron transport through solid components of the extracellular biofilm matrix. In this review, we perform a novel kinetic analysis of each EET mechanism by analyzing the results available in the literature. Our goal is to evaluate how well each EET mechanism can produce a high current density (> 10 A m(-2)) without a large anode potential loss (less than a few hundred millivolts), which are feasibility goals of MXCs. Direct contact of ARB to the anode cannot achieve high current densities due to the limited number of cells that can come in direct contact with the anode. Slow diffusive flux of electron shuttles at commonly observed concentrations limits current generation and results in high potential losses, as has been observed experimentally. Only electron transport through a solid conductive matrix can explain observations of high current densities and low anode potential losses. Thus, a study of the biological components that create a solid conductive matrix is of critical importance for understanding the function of ARB.

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“…They are known to achieve fast ET with biological redox compounds, including cytochromes [120] and other redox biological mediators [121]. Their high electronic conductivity and low double-layer capacitance limit the residual currents and increase the sensitivity of the electrochemical measurements [122].…”

Section: Gold and Palladiummentioning

confidence: 99%

Behavior of metal ions in bioelectrochemical systems: A review

Dingming

et al. 2015

Journal of Power Sources

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Electrochemical studies on c-type cytochromes at microelectrodes

Cited by 14 publications

References 35 publications

A new CuZ active form in the catalytic reduction of N2O by nitrous oxide reductase from Pseudomonas nautica

A new CuZ active form in the catalytic reduction of N2O by nitrous oxide reductase from Pseudomonas nautica

A kinetic perspective on extracellular electron transfer by anode-respiring bacteria

Behavior of metal ions in bioelectrochemical systems: A review

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