On the Use of Impedance Spectroscopy for Studying Bilayer Lipid Membranes

ALCIRA ESTELA VALLEJO; CLAUDIO ALFREDO GERVASI

Advances in planar lipid bilayers and liposomes

Año: 2006; p. 331 - 353

Different methods for supporting lipid bilayers onto conductive electrodes have proved useful to model biological membrane processes. The methods arousing greatest interest involve covalent attachment on gold substrates and noncovalent self-organization on metallic supports and semiconductor electrodes. IS applied to study these supported lipid bilayers was critically analyzed. In this chapter we have described the established ways to apply IS in structural characterization studies of supported lipid bilayers, with a particular focus on the strengths of the method as well as on its weaknesses. A word of caution was expressed concerning the use of equivalent circuit modeling under certain experimental conditions. Full capabilities of IS were demonstrated in relation to ion permeation studies. The use of identifiability and distinguishability concepts was stressed, since this analysis provides a way to select experimental methods according to the structural properties of theoretical models. Accordingly, impedance experiments should be designed so as to allow discrimination between various postulated mechanisms. An example of a globally identifiable mechanism was introduced and this mechanism was used to derive rate parameters of the system from impedance data. Equations for the impedance and for the steady-state polarization curves can be satisfactorily fitted to the experimental results in order to generate the set of kinetic parameters that best describe the experiments.