Membrane Curvature Modeling and Lipid Organization in Supported Lipid Bilayers

Abstract

Membranes in the cell exist in a wide range of shapes and provide for compartmentalization and transport throughout the cell. Curvature plays an important role in this cellular organization and even the organization of lipids within the membrane itself. Supported lipid bilayers (SLB) continue to be an important means of measuring the thermodynamic and mechanical properties of phospholipid membranes, but on some supports, the proximity of the solid surface may modify the behavior of the adsorbed bilayer. To overcome this problem, we use a technique for spin coating lipids on the substrate that creates multilamellar stacks of membranes[1] where the influence of the substrate on upper layers is weakened. The substrates we have used are nanoscopically patterned with steps and these features induce curvature in the membranes that appear to be step-height dependent. This provides a platform for adhesion, mobility and organizational studies. We show that multilamellar SLB on patterned substrates exhibit curvature induced phase separated domain organization and increased lateral lipid mobility. Molecular dynamics of coarse-grained supported lipid bilayers[2] are used to simulate membranes supported on corrugated surfaces and we discuss and compare the behavior with experimental systems. We show that substrate corrugation height, adhesion energy, and mechanical moduli can be controlled to predict adsorbed membrane curvature. Furthermore we model lipid mixtures in the regions of substrate induced curvature to show the relationship between bending energies and phase separation. [1] M.H. Jensen, E.J. Morris, A.C. Simonsen, Domain Shapes, Coarsening, and Random Patterns in Ternary Membranes, Langmuir 23 (2007) 8135-8141. [2] M.I. Hoopes, M. Deserno, M.L. Longo, R. Faller, Coarse-grained modeling of interactions of lipid bilayers with supports, The Journal of Chemical Physics 129 (2008) 175102-175107.