The molecular organization of bimolecular lipid membranes. A study of the low frequency Maxwell-Wagner impedance dispersion

Theoretical considerations show that the presence of the polar group regions in bimolecular lipid membranes will produce a small (2–3%) dispersion of the bimolecular lipid membrane capacitance at low frequencies (0.1–100 Hz).A dispersion in conductance will also result. Calculations are given of the resolution of phase angle and impendance amplitude required to detect this dispersion and a new measuring technique is described which can achieve this. From the experimental result presented for lecithin bimolecular lipid membranes a determination was made of the individual capacitances and conductances of both the hydrocarbon and polar groups regions. The polar group conductance was found to vary from 700 μΩ^?1 · cm^?2 (in 1 mM KCl) to 2000 μΩ^?1 · cm^?2 (in 1 M KCl).The polar group capacitances were found to be approx.30 μF · cm^?2 and not systematically dependent on the concentration of the external electrolyte.