title: Lamellar stacking split by in-membrane clustering of bulky glycolipids.
abstract: We developed a simple model to investigate the effect of lipid clustering on the local interlayer distance in a cluster of interacting lamellae. The model, based on nonequilibrium thermodynamics and linear stability theories, explores the early stages of the lamella-lamella phase separation process where the lateral diffusion is much faster than the interlamellar lipid exchange. Results indicate, in the early stages, the presence of locally distorted regions with a higher concentration of one lipid component and an anomalous repeat distance. Experimental cases are presented, consisting of multilamellar-oriented depositions of phospholipids containing minority amounts of ganglioside or sphingomyelin under a low-hydration condition. The minority components are known to form domains within the phospholipid bilayer matrix. The low water content inhibits the lipid exchange among nearby lamellae and strengthens lamella-lamella interaction, allowing for a straightforward comparison with the model. Small-angle and wide-angle neutron diffraction experiments were performed in order to detect interlayer distances and local chain order, respectively. Lamellar stacking splitting has been observed for the ganglioside-containing lamellae, induced by in-phase lipid clustering. In excess water and after long equilibration times, these local structures may further evolve, leading to coexisting lamellar phases with different lipid compositions and interlayer distances.
authors.affiliation: Department of Medical Chemistry, Biochemistry and Biotechnologies, University of Milan, LI.T.A., Via F. lli Cervi 93, 20090 Segrate, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Del Favero
authors.forename: A
authors.initials: A
authors.lastname: Raudino
authors.forename: P
authors.initials: P
authors.lastname: Brocca
authors.forename: S
authors.initials: S
authors.lastname: Motta
authors.forename: G
authors.initials: G
authors.lastname: Fragneto
authors.forename: M
authors.initials: M
authors.lastname: Corti
authors.forename: L
authors.initials: L
authors.lastname: Cantú
mesh_terms: D006017:Glycolipids / Q000737:chemistry*; D008567:Membranes, Artificial; D008958:Models, Molecular; D008968:Molecular Conformation; D033363:Neutron Diffraction; D010743:Phospholipids / Q000737:chemistry; D053838:Scattering, Small Angle; D013696:Temperature
chemical_list: D006017:Glycolipids; D008567:Membranes, Artificial; D010743:Phospholipids