Forming a fluid film like the skin of a soap bubble, lipid molecules are free to move around the membrane laterally -- like couples on a dance floor. At the same time, however, cellular proteins have to interact in a very controlled fashion with the membrane.

Spatially resolved measurements performed by researchers at the University of Illinois at Urbana-Champaign now show that adsorption of macromolecules of different size can modify the mobility of underlying lipids.

"Understanding what controls the lateral mobility of individual lipid molecules might help us better explain how cell membranes function," said Steve Granick, an Illinois professor of materials science and engineering, chemistry and physics, and corresponding author of a paper to be published the week of June 20 in the Online Early Edition of the Proceedings of the National Academy of Sciences. The print version will appear at a later date.

To study lipid mobility, Granick and graduate student Liangfang Zhang first supported a bilayer made of a single type of phospholipid molecule on a planar substrate (separated from the substrate by a thin layer of water several nanometers thick, the lipid molecules were free to move around). This simple bilayer mimicked the much more complex structure of a real cell membrane comprised of hundreds of different lipids and proteins.

Next, the researchers deposited synthetic polymer macromolecules onto the bilayer surface to mimic the roles of membrane-associating proteins. The polymers adsorbed onto the surface, flattening like pancakes and covering hundreds of lipids.

Using a measurement technique called fluorescence correlation spectroscopy, the researchers then recorded lipi
'"/>

Contact: James E. Kloeppel, Physical Sciences Editor
kloeppel@uiuc.edu
217-244-1073
University of Illinois at Urbana-Champaign
20-Jun-2005