COLL 89 |
| Thomas Heimburg, Heiko Seeger, Agnieszka Hac, and Matthias Fidorra. Membrane Biophysics and Thermodynamics Group, Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100 Copenhagen O, Denmark |
| Biomembranes consist of a large variety of lipids and proteins. The lipid composition is highly variable and differs between various cell types and even between the organelles within one cell type. The reason for this is largely unknown. However, the finding of domains in artificial and biological membranes in the recent years has shed new light on the role of the cooperative behavior of membrane components, since it is now assumed that phase separation processes and domain formation play an important role in communication pathways within the native membranes. Some biological membranes display a lipid chain melting transition very close to the physiological growth temperature. In this transition the elastic constants of the membrane are largely influenced, and dramatic changes in the lateral distribution of molecules within the membrane occur. These changes can be visualized by confocal microscopy and atomic force microscopy. Phase separation phenomena result in very typical changes in heat capacity profiles, which can be understood by statistical thermodynamics simulations. We use these simulations to predict domain formation and to understand the complex diffusion behavior of lipids in membranes. We also study diffusion by fluorescence correlation spectroscopy (FCS), which is an indirect monitor for phase separation processes, because the lateral diffusion constant of lipids and proteins may be very different within different domains. Comparing the FCS results with simulations yields a self consistent picture of fluctuations in membranes, and one can well understand the physical chemistry of the response functions as well as of the lateral distribution of membrane components. In particualar we propose that the large fluctuations at domain boundaries influence the elastic constants, the permeability and relaxation time scales. |
|
Bio-Colloids
8:30 AM-11:30 AM, Monday, March 29, 2004 Marriott -- Grand Ballroom K, Oral
Division of Colloid and Surface Chemistry |