title: Lateral pressure dependence of the phospholipid transmembrane diffusion rate in planar-supported lipid bilayers.
abstract: The dependence of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) flip-flop kinetics on the lateral membrane pressure in a phospholipid bilayer was investigated by sum-frequency vibrational spectroscopy. Planar-supported lipid bilayers were prepared on fused silica supports using the Langmuir-Blodgett/Langmuir-Schaeffer technique, which allows precise control over the lateral surface pressure and packing density of the membrane. The lipid bilayer deposition pressure was varied from 28 to 42 mN/m. The kinetics of lipid flip-flop in these membranes was measured by sum-frequency vibrational spectroscopy at 37 degrees C. An order-of-magnitude difference in the rate constant for lipid translocation (10.9 x 10(-4) s(-1) to 1.03 x 10(-4) s(-1)) was measured for membranes prepared at 28 mN/m and 42 mN/m, respectively. This change in rate results from only a 7.4% change in the packing density of the lipids in the bilayer. From the observed kinetics, the area of activation for native phospholipid flip-flop in a protein-free DPPC planar-supported lipid bilayer was determined to be 73 +/- 12 A(2)/molecule at 37 degrees C. Significance of the observed activation area and potential future applications of the technique to the study of phospholipid flip-flop are discussed.
authors.affiliation: Department of Chemistry, University of Utah, Salt Lake City, Utah, USA.
authors.forename: Timothy C
authors.initials: TC
authors.lastname: Anglin
authors.forename: John C
authors.initials: JC
authors.lastname: Conboy
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D003198:Computer Simulation; D004058:Diffusion; D008051:Lipid Bilayers / Q000737:chemistry*; D008560:Membrane Fluidity; D008956:Models, Chemical; D008958:Models, Molecular
chemical_list: D008051:Lipid Bilayers; D015060:1,2-Dipalmitoylphosphatidylcholine