Translational diffusion in charged phospholipid bilayer membranes

The dielectric permittivity spectra of colloidal solutions of highly charged liposomes were analyzed. They showed two dispersion regions around 25 and <300 MHz, which are attributed to rotational diffusion of the zwitterionic phospholipid molecules, and to the diffusion of the counterion atmosphere along the liposome surface, respectively. The lateral self-diffusion coefficient was obtained from the dielectric relaxation time of the zwitterionic phospholipid. The coefficient was determined in un-deionized samples subjected to processes of 40 and 72 h deionization. The study found that the counterions, which were condensed over the liposome surface, facilitated the lateral diffusion of phospholipids within the bilayer.