Lamellar stacking split by in-membrane clustering of bulky glycolipids.
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.
Del Favero
E
E
Department of Medical Chemistry, Biochemistry and Biotechnologies, University of Milan, LI.T.A., Via F. lli Cervi 93, 20090 Segrate, Italy.
Raudino
A
A
Brocca
P
P
Motta
S
S
Fragneto
G
G
Corti
M
M
Cantú
L
L
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
D006017:Glycolipids; D008567:Membranes, Artificial; D010743:Phospholipids