Abstract:
Nuclear magnetoresistance (NMR) studies were carried out to investigate a series of phospholipids in the Lα state. The influences of the acyl length, lipid polar head groups, addition of a cosurfactant, and incorporation of cholesterol were determined in terms of the bilayer viscoelastic properties. The results imply that the concept of elastic deformation of membranes is applicable on the mesoscopic length scale, approaching the molecular dimensions, with quasicoherent nodes on the order of the bilayer hydrocarbon thickness and less.
PMID: 1731924;Abstract:
The stability of two-component liposomes composed of the polymerizable 1,2-bis-[10-(2′,4′-hexadienoyloxy)decanoyl]-sn-glycero-3- phosphatidylcholine (SorbPC) and either a phosphatidylethanolamine (PE) or a phosphatidylcholine (PC) were examined via fluorescence leakage assays. Ultraviolet light exposure of SorbPC-containing liposomes forms poly-SorbPC, which phase separates from the remaining monomeric lipids. If the nonpolymerizable lipids are PE's, then the photoinduced polymerization destabilizes the liposome with loss of aqueous contents. The permeability of the control dioleoylPC/SorbPC membranes was not affected by photopolymerization of SorbPC. The photodestabilization of dioleoylPE/SorbPC (3:1) liposomes required the presence of oligolamellar liposomes. NMR spectroscopy of extended bilayers of dioleoylPE/SorbPC (3:1) showed that the photopolymerization lowers the temperature for the appearance of 31P NMR signals due to the formation of isotropically symmetric lipid structures. These observations suggest the following model for the photoinduced destabilization of liposomes composed of PE/SorbPC: photopolymerization induced phase separation with the formation of enriched domains of PE, which allows the close approach of apposed regions of enriched PE lamellae and permits the formation of an isotropically symmetric structure between the lamellae. The formation of such an interlamellar attachment (ILA) between the lamellae of an oligolamellar liposome provides a permeability pathway for the light-stimulated leakage of entrapped water-soluble reagents. © 1992 American Chemical Society.
