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Long distance electron transfer in cytochrome c oxidase immobilised on electrodes. A surface enhanced resonance Raman spectroscopic study
Citation key ISI:000235608500011
Author Hrabakova, J and Ataka, K and Heberle, J and Hildebrandt, P and Murgida, D H
Pages 759-766
Year 2006
ISSN 1463-9076
DOI 10.1039/b513379n
Address THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND
Journal Phys. chem. chem. phys
Volume 8
Number 6
Month FEB 14
Publisher ROYAL SOC CHEMISTRY
Abstract Cytochrome c oxidase was tethered to a functionalised Ag electrode via a histidine-tag oil the C-terminus of subunit I or II and embedded in a phospholipid bilayer. The uniformly oriented membrane-bound proteins were studied by surface enhanced resonance Raman spectroscopy (SERRS) that reveals preservation of the native structures of the heme a and heme a(3) sites. On the basis of time-dependent SERRS measurements, the rate constant for the heterogeneous electron transfer to heme a was determined to be 0.002 s(-1) independent of the enzyme orientation and the overpotential. Taking into account that the electrode-to-heme a distance is larger than 50 A, these findings suggest an electron hopping mechanism in which the Cu-A center is not involved. Electrochemical reduction is restricted to heme a whereas electron transfer from heme a to heme a(3), which in solution occurs on the nanosecond time scale, is drastically slowed down. It may be that the network of cooperativities that links intramolecular electron transfer and proton translocation is perturbed in the immobilised enzyme, possibly due to the effect of the interfacial electric field.
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