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Laboratoire d'Electrochimie Moleculaire, LEM, Paris

UMR CNRS - Université Paris Diderot - Paris France

Master Frontiers in Chemistry | UFR de Chimie - Université Paris Diderot - Paris 7 CNRS - Institut de chimie Université de Paris Master Chimie Sorbonne Paris Cité UFR de Chimie - Université Paris Diderot - Paris 7 CNRS - Institut de chimie
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Université Paris Diderot
Université de Paris CNRS, Centre National de la Recherche Scientifique

Le LEM - Publications: Abstracts

Publication 645

Langmuir 25, 6532-6542, 2009.
DOI: 10.1021/la900062y

Characterization of the Electron Transfer of a Ferrocene Redox Probe and a Histidine-Tagged Hemoprotein Specifically Bound to a Nitrilotriacetic-Terminated Self-Assembled Monolayer

Veronique Balland, Sophie Leconte, and Benoît Limoges

Laboratoire d’Electrochimie Moléculaire, Université Paris Diderot, UMRCNRS 7591, 15 rue Jean-Antoine de Baïf, 75205 Paris Cedex 13, France, and Chimie Biologie des Membranes et Nano-objets, Université Bordeaux1, UMR CNRS 5248, 2 rue Robert d’Escarpit, 33607 Pessac, France


We report the selective, controlled binding of a model redox probe, 1,1′-bis(N-imidazolylmethyl)ferrocene (Fc-Im2), and a small redox hemoprotein, histidine-tagged recombinant human neuroglobin (hNb), at the surface of metal electrodes (gold and SER-active silver) modified by a self-assembled monolayer (SAM) of a nitrilotriacetic(NTA)-terminated thiol. The resulting SAMs were characterized by cyclic voltammetry and surface-enhanced resonance Raman (SERR) spectroscopy coupled to electrochemistry. Once specifically bounded to the Ni(II)−NTA-modified gold electrode, nearly ideal cyclic voltammetric behavior with relatively fast electron-transfer (ET) communication through the SAM was determined for the Fc-Im2 redox probe. However, no direct electron transfer could be evidenced for the hNb redox protein under the same conditions. This outcome was different from the result obtained during SERR experiments coupled to electrochemistry in which a direct electrochemical conversion of hNb immobilized on a Ni(II)−NTA-modified SER-active Ag electrode was observed. The SERR spectra of the immobilized hNb was the same as the resonance Raman spectra of the protein in homogeneous solution, allowing us to conclude that the native structure of hNb was retained upon immobilization and that the direct ET was not the result of some partial or complete protein denaturation. The long-range ET rate constant (kET) through the SAM was determined by time-resolved SERR spectroscopy. A value of kET = 0.12 s−1 was obtained, which is within the predicted range of a fully nonadiabatic ET through a SAM thickness of ~26 Å and close to the values previously determined for analogous small redox proteins at similar long-range ET distances. A SERR spectroelectrochemical titration of the immobilized hNb was also carried out, showing both an apparent standard potential (E0′) negatively shifted by 100 mV compared with hNb in solution and a gentle slope in the titration curve. These results suggest a range of chemical environments in the surroundings of the redox protein and a variety of interactions with the NTA-terminated SAM. The influence of protein immobilization on E0′ is discussed together with the long-range ET rate constant and molecular orientation of the surface-immobilized hNb.

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