Phase behavior of charged lipid bilayer membranes with added electrolyte

摘要

We investigate the phase behavior of the aqueous solution of charged lipid bilayer membranes forming a lamellar structure in the presence of the added electrolyte. The Goldstein-Leibler model [Phys. Rev. A 40, 1025 (1989)] proposed for neutral lipids is extended by taking into account the screened electrostatic interaction which belongs to the so called intermediate region of the Poisson-Boltzmann theory. We mainly focus on the variation of the phase behavior as the added electrolyte concentration is changed. By decreasing the electrolyte concentration, the electrostatic repulsion between the neighboring membranes becomes stronger. As a result, the maximum equilibrium swelling composition shifts to larger water content, and the lamellar repeat distance increases although the membrane thickness remains almost constant. Our results recover not only the experimentally observed phase diagram for the charged lipid, but also the dependence of the lamellar repeat distance both on the electrolyte concentration and on the lipid composition. Some discussions are provided for the case when the electrostatic interaction is not screened due to the absence of any electrolyte. (C) 2003 American Institute of Physics. [References: 25]