Effect of the electrostatic interaction on the redox reaction of positively charged cytochrome c adsorbed on the negatively charged surfaces of acid-terminated alkanethiol monolayers on a Au(111) electrode

Shinichiro Imabayashi, Takahiro Mita, Takashi Kakiuchi

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42 Citations (Scopus)

Abstract

The electrochemical properties of cytochrome c (cyt c) adsorbed on mixed self-assembled monolayers (SAMs) of 2-mercaptoethanesulfonate (MES)/2-mercaptoethanol (MED are compared with those on single-component SAMs of MES, MEL, and mercaptopropionic acid (MPA), using cyclic voltammetry and potential-modulated UV-vis reflectance spectroscopy. The rate constant of electron transfer (ET), ket, of cyt c adsorbed on the SAM of MPA decreases from 1450 ± 210 s-1 at pH 7 to 890 ± 100 s-1 at pH 9. In contrast, the value of ket of cyt c on the SAM of MES is pH-independent at 100 ± 15 s-1. Those facts suggest that a large negative charge density on the SAM surface slows down the ET between cyt c and the electrode. The surface charge density of the SAM affects also the amount of electroactive cyt c, Γe, which decreases from 10.0 ±1.0 to 5.3 ± 1.1 pmol cm-2 with increasing pH from 7 to 9 on the SAM of MPA. Similarly, the ket of cyt c adsorbed on the mixed SAMs of MES/MEL sharply decreases from 900 ± 300 s-1 to 110 s-1 as the surface mole fraction of MES increases beyond 0.5, suggesting the presence of a negative surface charge threshold beyond which the rate of ET of cyt c is dramatically lowered. The decrease in the ket on the SAMs at high negative charge densities probably results from the confinement of adsorbed cyt c by the strong electrostatic force to an orientation that is not optimal for the ET reaction.

Original languageEnglish
Pages (from-to)1470-1474
Number of pages5
JournalLangmuir
Volume21
Issue number4
DOIs
Publication statusPublished - 2005 Feb 15
Externally publishedYes

Fingerprint

Redox reactions
cytochromes
Self assembled monolayers
Cytochromes c
Coulomb interactions
Monolayers
Mesna
electrostatics
Proteins
Electrodes
acids
Acids
electrodes
electron transfer
interactions
Charge density
Electrons
Surface charge
Electrostatic force
Mercaptoethanol

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Colloid and Surface Chemistry

Cite this

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title = "Effect of the electrostatic interaction on the redox reaction of positively charged cytochrome c adsorbed on the negatively charged surfaces of acid-terminated alkanethiol monolayers on a Au(111) electrode",
abstract = "The electrochemical properties of cytochrome c (cyt c) adsorbed on mixed self-assembled monolayers (SAMs) of 2-mercaptoethanesulfonate (MES)/2-mercaptoethanol (MED are compared with those on single-component SAMs of MES, MEL, and mercaptopropionic acid (MPA), using cyclic voltammetry and potential-modulated UV-vis reflectance spectroscopy. The rate constant of electron transfer (ET), ket, of cyt c adsorbed on the SAM of MPA decreases from 1450 ± 210 s-1 at pH 7 to 890 ± 100 s-1 at pH 9. In contrast, the value of ket of cyt c on the SAM of MES is pH-independent at 100 ± 15 s-1. Those facts suggest that a large negative charge density on the SAM surface slows down the ET between cyt c and the electrode. The surface charge density of the SAM affects also the amount of electroactive cyt c, Γe, which decreases from 10.0 ±1.0 to 5.3 ± 1.1 pmol cm-2 with increasing pH from 7 to 9 on the SAM of MPA. Similarly, the ket of cyt c adsorbed on the mixed SAMs of MES/MEL sharply decreases from 900 ± 300 s-1 to 110 s-1 as the surface mole fraction of MES increases beyond 0.5, suggesting the presence of a negative surface charge threshold beyond which the rate of ET of cyt c is dramatically lowered. The decrease in the ket on the SAMs at high negative charge densities probably results from the confinement of adsorbed cyt c by the strong electrostatic force to an orientation that is not optimal for the ET reaction.",
author = "Shinichiro Imabayashi and Takahiro Mita and Takashi Kakiuchi",
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T1 - Effect of the electrostatic interaction on the redox reaction of positively charged cytochrome c adsorbed on the negatively charged surfaces of acid-terminated alkanethiol monolayers on a Au(111) electrode

AU - Imabayashi, Shinichiro

AU - Mita, Takahiro

AU - Kakiuchi, Takashi

PY - 2005/2/15

Y1 - 2005/2/15

N2 - The electrochemical properties of cytochrome c (cyt c) adsorbed on mixed self-assembled monolayers (SAMs) of 2-mercaptoethanesulfonate (MES)/2-mercaptoethanol (MED are compared with those on single-component SAMs of MES, MEL, and mercaptopropionic acid (MPA), using cyclic voltammetry and potential-modulated UV-vis reflectance spectroscopy. The rate constant of electron transfer (ET), ket, of cyt c adsorbed on the SAM of MPA decreases from 1450 ± 210 s-1 at pH 7 to 890 ± 100 s-1 at pH 9. In contrast, the value of ket of cyt c on the SAM of MES is pH-independent at 100 ± 15 s-1. Those facts suggest that a large negative charge density on the SAM surface slows down the ET between cyt c and the electrode. The surface charge density of the SAM affects also the amount of electroactive cyt c, Γe, which decreases from 10.0 ±1.0 to 5.3 ± 1.1 pmol cm-2 with increasing pH from 7 to 9 on the SAM of MPA. Similarly, the ket of cyt c adsorbed on the mixed SAMs of MES/MEL sharply decreases from 900 ± 300 s-1 to 110 s-1 as the surface mole fraction of MES increases beyond 0.5, suggesting the presence of a negative surface charge threshold beyond which the rate of ET of cyt c is dramatically lowered. The decrease in the ket on the SAMs at high negative charge densities probably results from the confinement of adsorbed cyt c by the strong electrostatic force to an orientation that is not optimal for the ET reaction.

AB - The electrochemical properties of cytochrome c (cyt c) adsorbed on mixed self-assembled monolayers (SAMs) of 2-mercaptoethanesulfonate (MES)/2-mercaptoethanol (MED are compared with those on single-component SAMs of MES, MEL, and mercaptopropionic acid (MPA), using cyclic voltammetry and potential-modulated UV-vis reflectance spectroscopy. The rate constant of electron transfer (ET), ket, of cyt c adsorbed on the SAM of MPA decreases from 1450 ± 210 s-1 at pH 7 to 890 ± 100 s-1 at pH 9. In contrast, the value of ket of cyt c on the SAM of MES is pH-independent at 100 ± 15 s-1. Those facts suggest that a large negative charge density on the SAM surface slows down the ET between cyt c and the electrode. The surface charge density of the SAM affects also the amount of electroactive cyt c, Γe, which decreases from 10.0 ±1.0 to 5.3 ± 1.1 pmol cm-2 with increasing pH from 7 to 9 on the SAM of MPA. Similarly, the ket of cyt c adsorbed on the mixed SAMs of MES/MEL sharply decreases from 900 ± 300 s-1 to 110 s-1 as the surface mole fraction of MES increases beyond 0.5, suggesting the presence of a negative surface charge threshold beyond which the rate of ET of cyt c is dramatically lowered. The decrease in the ket on the SAMs at high negative charge densities probably results from the confinement of adsorbed cyt c by the strong electrostatic force to an orientation that is not optimal for the ET reaction.

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