Permeability Characteristics of Lipid Bilayers from Lipoic Acid Derived Phosphatidylcholines: Comparison of Monomeric, Cross-Linked and Non-Cross-Linked Polymerized Membranes

Article abstract of DOI:10.1021/ja00230a030

Polymerized and monomeric forms of large unilamellar liposomes (ca. 1000-Angstroem diameter) have been prepared from a cross-linkable phospholipid, 1,2-bis<12-(lipoyloxy)dodecanoyl>-sn-glycero-3-phosphocholine (1), a non-cross-linkable analogue, 1-palmitoyl-2-<12-(lipoyloxy)dodecanoyl>-sn-glycero-3-phosphocholine (2), and certain mixtures of 1 and 2.On the basis of efflux measurements, membranes derived from monomeric 2 were found to be less permeable toward captured <(14)C>sucrose than those prepared from monomeric 1; increasing the mole percentage of 2 in mixed bilayers resulted in decreased permeability.While homopolymerization of liposomal 2 significantly increased bilayer permeability, analogous homopolymerization of 1 significantly decreased membrane permeability.Increasing the mole percentage of 1 in mixed polymerized liposomes resulted in a reduction in bilayer permeability.The trends that have been observed for the monomeric bilayers are interpreted in terms of the relative packing efficiency of 1 and 2.A "polymer boundary" hypothesis is used to account for the permeability behavior of polymerized analogues.