Capacitance and conductance as tools for the measurement of asymmetric surface potentials and energy barriers of lipid bilayer membranes

摘要: A simple method for the determination of asymmetric surface potentials in lipid bilayers is described. The based on dependence bilayer capacitance transmembrane voltage. measured by rectifying 90° component an applied alternating current signal. superimposed slow triangular wave results a hysteresis-like time course capacitance. center hysteresis figure shifted along voltage axis amount equal to difference dipole plus surfacecharge two sides (capacitance minimization potential). Alternatively, such asymmetry was studied using current-voltage characteristics presence nonactin as carrier. This analysis integrated Nernst-Planck equation, assuming trapezoidal energy barrier and equilibrium reactions. methods gave consistent phosphatidyl serine membranes asymmetrically shielded with calcium. In addition, yields positions corners barrier, found be set 13% this lipid.