Local mobility in lipid domains of supported bilayers characterized by atomic force microscopy and fluorescence correlation spectroscopy

¹ Sandia National Laboratories
² University of New Mexico

^* To whom correspondence should be addressed. E-mail: aburns{at}sandia.gov.

Submitted on January 28, 2005
Revised on March 18, 2005
Accepted on 29 April 2005

	Abstract

Fluorescence correlation spectroscopy (FCS) is used to examine mobility of labeled probes at specific sites in supported bilayers consisting of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid domains in 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). Those sites are mapped beforehand with simultaneous atomic force microscopy (AFM) and submicron confocal fluorescence imaging, allowing characterization of probe partitioning between gel DPPC and disordered liquid DOPC domains with corresponding topography of domain structure. We thus examine the relative partitioning and mobility in gel and disordered liquid phases for headgroup- and tailgroup-labeled GM1 ganglioside probes, and for headgroup- and tailgroup-labeled phospholipid probes. For the GM1 probes, large differences in mobility between fluid and gel domains are observed; whereas, unexpected mobility is observed in submicron gel domains for the phospholipid probes. We attribute the latter to domain heterogeneities that could be induced by the probe. Furthermore, fits to the FCS data for the phospholipid probes in the DOPC fluid phase require two components (fast and slow). Although proximity to the glass substrate may be a factor, local distortion of the probe by the fluorophore could also be important. Overall, we observe non-ideal aspects of phospholipid probe mobility and partitioning that may not be restricted to supported bilayers.

Key Words: atomic force, bilayer, diffusion, membrane, rafts

This article has been cited by other articles:

				J. R. Unruh and E. Gratton Analysis of Molecular Concentration and Brightness from Fluorescence Fluctuation Data with an Electron Multiplied CCD Camera Biophys. J., December 1, 2008; 95(11): 5385 - 5398. [Abstract] [Full Text] [PDF]

				S. Hebbar, E. Lee, M. Manna, S. Steinert, G. S. Kumar, M. Wenk, T. Wohland, and R. Kraut A fluorescent sphingolipid binding domain peptide probe interacts with sphingolipids and cholesterol-dependent raft domains J. Lipid Res., May 1, 2008; 49(5): 1077 - 1089. [Abstract] [Full Text] [PDF]

				M. J. Higgins, M. Polcik, T. Fukuma, J. E. Sader, Y. Nakayama, and S. P. Jarvis Structured Water Layers Adjacent to Biological Membranes Biophys. J., October 1, 2006; 91(7): 2532 - 2542. [Abstract] [Full Text] [PDF]

				D. J. Frankel, J. R. Pfeiffer, Z. Surviladze, A. E. Johnson, J. M. Oliver, B. S. Wilson, and A. R. Burns Revealing the Topography of Cellular Membrane Domains by Combined Atomic Force Microscopy/Fluorescence Imaging Biophys. J., April 1, 2006; 90(7): 2404 - 2413. [Abstract] [Full Text] [PDF]

				J. E. Shaw, R. F. Epand, R. M. Epand, Z. Li, R. Bittman, and C. M. Yip Correlated Fluorescence-Atomic Force Microscopy of Membrane Domains: Structure of Fluorescence Probes Determines Lipid Localization Biophys. J., March 15, 2006; 90(6): 2170 - 2178. [Abstract] [Full Text] [PDF]