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Issue 30, 2008
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Electrochemical elucidation on the mechanism of uncoupling caused by hydrophobic weak acids

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Abstract

Uncoupler-mediated cation transport has been investigated by cyclic voltammetry for the ion transfer from one aqueous phase (W1) to another (W2) across a bilayer lipid membrane (BLM) in the presence of typical uncouplers, 3,5-di(tert-butyl)-4-hydroxybenzylidenemalononitril (SF6847) and 2,4-dinitrophenol (DNP). The voltammograms for the ion transfer were in a steady state and exhibited a rotated sigmoidal shape that was almost symmetrical about the origin (0 V, 0 A). The plot of the ion transfer current against pH was a bell-type curve centered on pH ≅ pKa + 1, Ka being the dissociation constant of the uncouplers in the aqueous phase. Taking into account the ion transfer reactions at the W1|BLM and the BLM|W2 interfaces, these properties were well explained by our proposed model which considers that the ion transfer current is attributable to the facilitated transfers of H+ and Na+. The buffer action in the aqueous phase was found to play an important role in the facilitated H+-transfer across the BLM. The nature of the pH-dependence of the ion transfer current was reasonably explained from an electrochemical viewpoint based on the distribution coefficient of the anionic and neutral forms of SF6847, as estimated from its absorption spectra in liposomal membrane. The proposed model is also valuable for understanding the pH-dependence of uncoupling activity in mitochondria in the literature.

Graphical abstract: Electrochemical elucidation on the mechanism of uncoupling caused by hydrophobic weak acids

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Publication details

The article was received on 28 Feb 2008, accepted on 24 Apr 2008 and first published on 12 Jun 2008


Article type: Paper
DOI: 10.1039/B803458C
Citation: Phys. Chem. Chem. Phys., 2008,10, 4449-4455
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    Electrochemical elucidation on the mechanism of uncoupling caused by hydrophobic weak acids

    S. Ozaki, K. Kano and O. Shirai, Phys. Chem. Chem. Phys., 2008, 10, 4449
    DOI: 10.1039/B803458C

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