Nonelectrolyte Diffusion across Lipid Bilayer Systems

Nonelectrolyte diffusion across the red cell membrane provides informat ion about membrane physical characteristics (1), which has been interpreted in the light of comparisons with model lipid bilayer systems such as liposomes (2). The multilamellar structure of the liposomes makes it difficult to obtain absolute permeability coefficients f rom the initial rate of swelling, the usual measure of liposome permeat ion. However, absolute permeability coefficients can be obtained f rom measurements o f diffusion across bilayers. T h o u g h Andreoli et al. (3) repor t that the permeability coefficients of small nonelectrolytes are generally too small to measure across planar bilayers, such measurements have been made by Vreeman (4), Gallucci et al. (5, 6), Lippe et al. (7, 8), and J u n g (9). We have used spherical lipid bilayers, p repared by the method of J u n g (9), to obtain permeability coefficients across single spherical bilayers for a homologous series of monoamides and urea. These permeability coefficients are qualitatively, T H E J O U R N A L o r G E N E R A L P H Y S I O L O G Y V O L U M E 67, 1976 • p a g e s 4 5 6 6 4 5 on Jne 1, 2017 D ow nladed fom Published January 1, 1976