Potassium ion transport by valinomycin across a Hg-supported lipid bilayer.
A biomimetic membrane consisting of a lipid bilayer tethered to a mercury electrode via a hydrophilic spacer was investigated in aqueous KCl by potential-step chronocoulometry and electrochemical impedance spectroscopy, both in the absence and in the presence of the ionophore valinomycin. Impedance spectra, recorded from 1 x 10(-2) to 1 x 10(5) Hz over a potential range of 0.8 V, are satisfactorily fitted to a series of four RC meshes, which are straightforwardly related to the different substructural elements of the biomimetic membrane. The frequency-independent resistances and conductances of both the lipid bilayer and the hydrophilic spacer show a maximum when plotted against the applied potential. This behavior is interpreted on the basis of a general approximate approach that applies the concepts of impedance spectroscopy to a model of the electrified interphase and to the kinetics of potassium ion transport assisted by valinomycin across the lipid bilayer.
Becucci
Lucia
L
Department of Chemistry, Florence University, 50019 Sesto Fiorentino, Florence, Italy.
Moncelli
Maria Rosa
MR
Naumann
Renate
R
Guidelli
Rolando
R
D004553:Electric Conductivity; D004563:Electrochemistry; D004566:Electrodes; D007476:Ionophores / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry*; D008628:Mercury / Q000737:chemistry*; D011188:Potassium / Q000737:chemistry*; D014634:Valinomycin / Q000737:chemistry*
D007476:Ionophores; D008051:Lipid Bilayers; D014634:Valinomycin; D008628:Mercury; D011188:Potassium