Neutron diffraction studies of the bilayer membrane structure of lipopolysaccharides extracted from pseudomonas aeruginosa

BIOL 139

Thomas Abraham, Thomas.Abraham@nrc.gc.ca1, Sarah Schooling2, Mu Ping Nieh1, Terry J. Beveridge, tjb@uoguelph.ca3, and John Katsaras, John.Katsaras@nrc.gc.ca1. (1) NRC-Canadian Neutron Beam Centre, National research Council of Canada, Chalk River Lab., Bldg 459, Stn 18, Chalk River, ON K0J 1J0, Canada, (2) Department of Molecular and Cellular Biology, University of Guelph, Ontario, Canada, Guelph, ON NG 2W1, Canada, (3) Department of Cellular and Molecular Biology, University of Guelph, 50 Stone Road, Guelph, ON N1G 2W1, Canada
Lipopolysaccharides (LPS) are the major macromolecular component making up the cell envelope of Gram-negative bacteria. LPS controls the bacteria's surface properties and plays a crucial role in regulating the permeability of their outer membrane. Here, we report of neutron diffraction studies performed on aligned, self assembled LPS multibilayers isolated from Psedimonous aeruginosa. Temperature scans have been conducted at various levels of hydration, and the phases (i.e., with increasing temperature they are gel, transition and liqid crystalline) adopted by the LPS along with their corresponding transition temperatures, have been identified. All three bilayers exhibit similar lamellar repeat spacings and from the construction of one-dimensional scattering length density profiles we can unequivocally state that, irrespective of bilayer phase water penetrates the hydrocarbon region, up to and including the center of the bilayer. It was also observed that because of LPS' chemical heterogeneity, the transition from gel to the liquid crystalline bilayers was continuous and not abrupt as commonly observed in single component lipid systems.
 

Chemistry and Metabolism
4:30 PM-6:30 PM, Tuesday, 12 September 2006 Moscone Center -- Hall D, Poster

Division of Biological Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006