Tethered Phospholipid Bilayer Membranes

Abstract

Abstract In this study, we discuss applications of the electrochemical impedance (EI) response of tethered bilayer membranes (tBLMs) in protein (peptide)/phospholipid membrane interaction studies. Because of highly asymmetric geometry, tBLMs exhibit unique EI response, which cannot be modeled by simple equivalent circuits consisting of capacitors and resistors. Special functions describe the characteristic features of EI spectra. They take into account the structural and the dielectric properties of the tBLMs. The analysis of the EI response provides the theoretical background for the utility of tBLMs as bioanalytical sensors for the membrane-damaging agents, such as pore-forming toxins. We demonstrate that the magnitude and frequency of the minimum of the negative of the phase as well as the modulus of impedance are the parameters indicative of the extent of the membrane damage and may be used to estimate the defect density in bilayers. The precision of such estimates is highly dependent on the knowledge of the physical properties of the submembrane reservoir separating phospholipid bilayer and solid surface. Clustering of the defects affects the EI response in a unique way, which may be used for the qualitative analysis of protein–membrane interactions.