Determination of Permeability and Transbilayer Diffusion Coefficient across Lipid Bilayers of Liposomes by Using Capillary Electrophoresis with Moment Analysis Theory

A method was developed for experimental determination of the transbilayer diffusion coefficient (D_tb) of solute molecules across lipid bilayers of liposomes. It consists of two steps, i.e., experimental determination of lipid membrane permeability and calculation of D_tb. At first, lipid membrane permeability is determined by analyzing elution peak profiles measured by liposome electrokinetic chromatography (LEKC), in which liposomes themselves are used as pseudostationary phases. Then, the value of D_tb is calculated from that of the lipid membrane permeability on the basis of solubility diffusion theory. The moment analysis method with LEKC experiments is effective for understanding the characteristics and mechanism of transverse solute diffusion across lipid bilayers because a wide range of values of transbilayer diffusion coefficient can be determined by the method under various conditions. It was considered how the value of D_tb is correlated with the number of carbon atoms in the alkyl chains of the phospholipids.