A super-swelled lamellar lipid system

Lipid bilayers are an integral structure found in myriad biological systems. Sometimes lipid bilayers stack to make a lamellar phase, in which bilayers are separated by water layers with thicknesses determined by intermolecular interactions such as undulation repulsion, attractive van der Waals forces, and in the case of charged lipids, double layer forces. Water layers in charged lipid systems have demonstrated swelling abilities up to 30 nm, but soft (low bending rigidity) bilayers usually lose periodicity approaching these values due to higher undulation force effects [1]. Here we report a simple lipid system of low-bending-rigidity lipid doped with small amounts of charged lipid that forms a previously undocumented super-swelled lamellar phase with layer spacings upwards of 80 nm at low dilution. These results differ from previous studies into similar systems, and defy currently held theories of maximum lamellar spacings for soft membranes. The formulated lipid systems were characterized with confocal fluorescence microscopy, cryogenic TEM, and ultra-small angle X-ray scattering.

References: [1] A. Steiner et al. (2012) Langmuir. DOI: 10.1021/la203540p