Impedance analysis of phosphatidylcholine–cholesterol system in bilayer lipid membranes

Electrochemical impedance spectroscopy was used for the study of two-component lipid membranes. Phosphatidylcholine (lecithin, PC) and cholesterol (Ch) were chosen for the study because they are present in biological membranes and they fulfil essential functions in lively organisms. The theory of equilibrium between components of the membranes has been developed in order to obtain the parameters describing the PCCh complex. The equilibrium between the PC, Ch and PCCh complex on the basis of derived equations was considered and forming the 1:1 complex was proved. The following parameters of the complex were determined: capacitance (C3), conductance (R3−1), area occupied by complex molecule (A3) as well as stability constant of the complex (K).