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Issue 6, 2006
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Long distance electron transfer in cytochrome c oxidase immobilised on electrodes. A surface enhanced resonance Raman spectroscopic study

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Abstract

Cytochrome c oxidase was tethered to a functionalised Ag electrode via a histidine-tag on 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 a3 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 Å, these findings suggest an electron hopping mechanism in which the CuA center is not involved. Electrochemical reduction is restricted to heme a whereas electron transfer from heme a to heme a3, 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.

Graphical abstract: Long distance electron transfer in cytochrome c oxidase immobilised on electrodes. A surface enhanced resonance Raman spectroscopic study

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Article information


Submitted
06 May 2005
Accepted
09 Dec 2005
First published
20 Dec 2005

Phys. Chem. Chem. Phys., 2006,8, 759-766
Article type
Paper

Long distance electron transfer in cytochrome c oxidase immobilised on electrodes. A surface enhanced resonance Raman spectroscopic study

J. Hrabakova, K. Ataka, J. Heberle, P. Hildebrandt and D. H. Murgida, Phys. Chem. Chem. Phys., 2006, 8, 759
DOI: 10.1039/B513379N

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