Potassium Ion Transport by Valinomycin across a Hg-Supported Lipid Bilayer

• Published in: Journal of the American Chemical Society 2005-09, Vol.127 (38), p.13316-13323
• Main Authors: Becucci, Lucia, Moncelli, Maria Rosa, Naumann, Renate, Guidelli, Rolando
• Format: Article
• Language: English
• Subjects: Artificial membranes and reconstituted systems; Biological and medical sciences; Chemistry; Colloidal state and disperse state; Electric Conductivity; Electrochemistry; Electrodes; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; General and physical chemistry; Ionophores - chemistry; Lipid Bilayers - chemistry; Membrane physicochemistry; Membranes; Mercury - chemistry; Molecular biophysics; Potassium - chemistry; Valinomycin - chemistry
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja052920t

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 × 10-2 to 1 × 105 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.