Thermodynamic and kinetic aspects of the electron transfer reaction of bovine cytochrome c immobilized on 4-mercaptopyridine and 11-mercapto-1-undecanoic acid films

Abstract

Bovine cytochrome c (cyt c) was adsorbed on a polycrystalline gold electrode coated with 4-mercaptopyridine and 11-mercapto-1-undecanoic acid self-assembled monolayers (SAMs) and the thermodynamics and kinetics of the heterogeneous protein-electrode electron transfer (ET) reaction were determined by cyclic voltammetry. The E°0 values for the immobilized protein were found to be lower than those for the corresponding diffusing species. The thermodynamic parameters for protein reduction (DH 0 rc and DS 0 rc ) indicate that the stabilization of the ferric state due to protein-SAM interaction is enthalpic in origin. The kinetic data suggest that a tunneling mechanism is involved in the ET reaction: the distance between the redox center of the protein and the electrode surface can be efficiently evaluated using the Marcus equation.

Thermodynamics and kinetics of the electron transfer process of spinach plastocyanin adsorbed on a modified gold electrode

“…They are similar to those obtained for the cytochrome c adsorbed on the same SAM [1,58,61] and result to be lower than those for freely diffusing cupredoxins [63][64][65]. A similar effect of protein immobilization on k has been found for cytochrome c [21,[60][61][62] for which the reorganization energy is remarkably affected by the nature of the SAM.…”

“…An analogous E°0 decrease was observed for the positively charged cytochrome c upon [46]. adsorption on À OOC-terminated monolayers, which was attributed to the electrostatic stabilization of the oxidized protein (which bears one more positive charge than the reduced one) brought about by the negatively charged SAM surface [1,4,8,21,47]. Therefore, adsorption of pc is likely to be the result of the interaction between the positively charged lysine residues located near the metal center, opposite to the large acidic patch (Fig.…”

“…Cytochrome c has been the most thoroughly investigated species in this respect: relatively fast electron transfer in nondenaturing conditions has been obtained recently for this species immobilized both covalently and electrostatically on bare or functionalized solid electrodes [1][2][3][4][5][6][7][8][9][10]16,[19][20][21][22][23][24][25][26]. Much less has been done for other ET proteins.…”

On the mechanism of ubiquinone mediated photocurrent generation by a reaction center based photocathode

“…In the present study the working gold electrode was coated with a thin SAM formed from 4-mercaptopyridine (4-MP) [46]. This SAM could be applied through a simple 10 min incubation, as opposed to a 12-24 h process for other organo-sulfur compounds [47], and therefore did not significantly complicate electrode fabrication.…”

Electrodeposition of dendritic gold/silver nanaoparticles on disposable screen‐printed carbon electrode and its application of 4‐mercaptopyridine in in situ electrochemical surface‐enhanced Raman scattering

“…4-Mercaptopyridine has been applied in the field of sensors, optics, and solar cells: for example, a SERS probe in detecting Hg 2+ concentration [4] or a mediator for the charge transfer of cytochrome C. [5] Electrochemical SERS works by probing the transformation of molecular structures in the liquid-solid interface under the influence of an electric field, such as in the oxygen reduction process, the cleavage of carbon-halogen bonds and the charge transfer between protein and self-assembled layers, [6] which performs an important function in the identifying intermediates during reactions and in establishing reaction mechanisms in the field of electrochemical (EC) synthesis or EC catalysis. The prevalent electrodes for in situ EC SERS detection mostly include column electrodes (gold, silver, or copper) or indium tin oxide electrodes.…”