COLL 369 |
| Marjorie L. Longo1, Timothy V. Ratto2, Wan-chen Lin3, and Craig Blanchette3. (1) Department of Chemical Engineering and Materials Science, U. C. Davis, 1 Shields Ave, Davis, CA 95616, (2) Biophysics Graduate Group, University of California, Davis, Currently at Lawrence Livermore National Lab, (3) Biophysics Graduate Group, University of California, Davis |
| We have constructed a well-characterized model membrane system to better understand how nanometer-scale obstacles in cell membranes obstruct diffusion and for use in controlling the valency, mobility, and spacing of mobile or immobile ligands at the nanometer scale. For these studies, we utilize supported bilayers composed of mixtures of 1,2-dilauroylphosphotidylcholine (DLPC) and 1,2 distearoylphosphotidylcholine (DSPC) or a gel phase lipid ligand. Because these lipids are immiscible and phase separate at room temperature, a novel quenching technique allowed us to construct fluid DLPC bilayers containing small (~50 nm) disk-shaped gel-phase domains of DSPC or the ligand. Our experimental setup enabled us to determine (by atomic force microscopy) domain characterize such as size, shape, degree of transbilayer coupling, and area fraction, followed immediately by a determination of the obstacle-dependent diffusion coefficient (by fluorescence recovery after photobleaching) or protein binding (by total internal reflection fluorescence). Our diffusion data is used to validate and determine parameters in theories developed to explain diffusion coefficient measurements in cellular membranes. Lateral obstructed diffusion was found to be dependent on obstacle area fraction, size, and geometry. We find that at solid-phase area fraction between ~35% and 70% (the percolation threshold), diffusion is anomalous at short times and becomes normal at longer times as predicted by Monte Carlo simulations. In addition to these insights with respect to obstructed diffusion in lipid bilayers, we have gained insight into how phases in lipid bilayers become coupled and uncoupled across the lipid bilayer. |
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Surface and Colloid Chemistry Award Symposium Honoring Joseph Zasadzinski
8:10 AM-12:10 PM, Wednesday, March 31, 2004 Marriott -- Orange County 3, Oral
Division of Colloid and Surface Chemistry |