Observation of Electron Transfer between a Silver Electrode and Putidaredoxin Using Electromodulated Reflectance Spectroscopy

Gaigalas, Adolfas K.; Reipa, Vytas; Vilker, Vincent L.

doi:10.1006/jcis.1996.4651

Cited by 13 publications

(14 citation statements)

References 10 publications

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“…They were deaerated at least 30 min prior to and throughout the experiments by purging nitrogen gas. Putidaredoxin was prepared according to the procedure described in Gaigalas et al 6 and used no later than 24 h after preparation. One milliliter of 160 µM Pdx solution was introduced into 40 mL of buffer for adsorption studies.…”

Section: Methodsmentioning

confidence: 99%

“…3,5,6 Electroreflectance spectroscopy has shown that Pdx retains its characteristic absorption bands while adsorbed on metal electrodes. 6 This property makes it suitable for spectroscopic ellipsometry investigation. Among the questions stimulated in previous protein electrochemistry studies 1,2 were the uncertainty about extent of protein and modifier adsorption with varying electrode potential, together with uncertainty about the structural alterations of the adsorbed layer.…”

Section: Introductionmentioning

confidence: 99%

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Spectroscopic Real-Time Ellipsometry of Putidaredoxin Adsorption on Gold Electrodes

1997

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Adsorption of putidaredoxin (Pdx) on gold electrodes was studied using dynamic spectroscopic ellipsometry and differential capacitance. A method to account for the metal surface optical perturbation during protein adsorption at constant potential is described. The method is based on the concept of the charged transition layer which develops between metal substrate and adsorbate. Transition-layer charge was determined from the differential capacitance and the ellipsometry measurements in buffer solutions. A three-phase (metal substrate/protein film/solution) reflecting surface model was amended with a charged metal transition layer as a fourth phase, which allowed the elucidation of the adsorbed Pdx complex index of refraction spectrum. On the basis of this spectrum, a time dependent protein surface concentration was calculated. For short times, this surface concentration was in good agreement with estimates based on mass transport limited adsorption.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Spectroscopic Real-Time Ellipsometry of Putidaredoxin Adsorption on Gold Electrodes

1997

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“…The above procedure leads to an expression for numerically since linearization was not valid. The ER re-the current density which is a sum of cos(vt) and sin(vt) sponse DR/R, was assumed to be of the form (14) terms. The coefficients of the two terms give the usual expressions for the resistive and capacitive parts of the electrochemical impedance.…”

Section: Introduction Analysismentioning

confidence: 99%

Measurement of Electron Transfer Rates between Adsorbed Azurin and a Gold Electrode Modified with a Hexanethiol Layer

Gaigalas

Niaura

1997

Journal of Colloid and Interface Science

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“…In a previous study of electron transfer between a surface-modified silver electrode and the P450 redox protein putidaredoxin (Pdx), we found that the heterogeneous electron-transfer rate constant determined by ER and CV would be consistent only if the Pdx was in solution. Analysis with a model of immobilized Pdx gave rates which differed by almost 2 orders of magnitude …”

Section: Introductionmentioning

confidence: 99%

Electron Transfer between Surface-Confined Cytochrome c and an N-Acetylcysteine-Modified Gold Electrode

et al. 1998

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Cytochrome c (cyt c) was adsorbed on N-acetylcysteine (NAC)-modified gold electrodes via electrostatic interaction. The cyt c layer exhibited reversible and stable electrochemical redox transformation in 0.01 M phosphate butter, pH 7.4, where the heterogeneous electron transfer (ET) constant k‘het was measured by three techniques: cyclic voltammetry at high sweep rates (CV), electrochemical impedance (EI), and electroreflectance (ER) spectroscopy. In addition, k‘het was also determined from combining sets of simultaneous electrochemical impedance (EI) and electroreflectance (ER) measurements in a new impedance model in which a constant-phase element was used. The negligible shift (−0.023 mV) in the formal potential from the solution value, and the close agreement of the measured distribution around the CV peaks (full-width voltage at half-peak-height, E fwhh = 97 mV) with the theoretical value of 90.6 mV, suggested that the immobilized cyt c is retained at the electrode in the native state. Apparent k‘het values, as determined by each method separately, were as follows: (k‘CV = 920 ± 280 s-1 by CV, k‘EI = 660 ± 200 s-1 by EI, and k‘ER = 2100 ± 300 s-1 by ER as interpreted using previously published methods. ,, In the combined EI/ER measurements, k‘ER was found to increase linearly with the frequency of the ac modulating current and spanned a range from about 400 to 800 s-1, which is close to the interprotein electron-transfer rate constant (800 s-1) measured between cyt c and one of its natural redox partners, cytochrome c peroxidase. It is concluded that further attempts to reconcile these discrepancies in k‘het determinations will require more detailed descriptions of the interfacial elements in the impedance models.

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Observation of Electron Transfer between a Silver Electrode and Putidaredoxin Using Electromodulated Reflectance Spectroscopy

Cited by 13 publications

References 10 publications

Spectroscopic Real-Time Ellipsometry of Putidaredoxin Adsorption on Gold Electrodes

Spectroscopic Real-Time Ellipsometry of Putidaredoxin Adsorption on Gold Electrodes

Measurement of Electron Transfer Rates between Adsorbed Azurin and a Gold Electrode Modified with a Hexanethiol Layer

Electron Transfer between Surface-Confined Cytochrome c and an N-Acetylcysteine-Modified Gold Electrode

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