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Thermal Fluctuations Determine the Electron‐Transfer Rates of Cytochrome c in Electrostatic and Covalent Complexes
Author(s) -
Ly Hoang Khoa,
Marti Marcelo A.,
Martin Diego F.,
AlvarezPaggi Damian,
Meister Wiebke,
Kranich Anja,
Weidinger Inez M.,
Hildebrandt Peter,
Murgida Daniel H.
Publication year - 2010
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200900966
Subject(s) - electron transfer , covalent bond , chemical physics , chemistry , thermal , electron , photochemistry , materials science , physics , thermodynamics , organic chemistry , quantum mechanics
The heterogeneous electron‐transfer (ET) reaction of cytochrome c (Cyt‐c) electrostatically or covalently immobilized on electrodes coated with self‐assembled monolayers (SAMs) of ω‐functionalized alkanethiols is analyzed by surface‐enhanced resonance Raman (SERR) spectroscopy and molecular dynamics (MD) simulations. Electrostatically bound Cyt‐c on pure carboxyl‐terminated and mixed carboxyl/hydroxyl‐terminated SAMs reveals the same distance dependence of the rate constants, that is, electron tunneling at long distances and a regime controlled by the protein orientational distribution and dynamics that leads to a nearly distance‐independent rate constant at short distances. Qualitatively, the same behavior is found for covalently bound Cyt‐c, although the apparent ET rates in the plateau region are lower since protein mobility is restricted due to formation of amide bonds between the protein and the SAM. The experimental findings are consistent with the results of MD simulations indicating that thermal fluctuations of the protein and interfacial solvent molecules can effectively modulate the electron tunneling probability.