College Park, Maryland      June 6 - 10 , 2004

M3-B3 (2:15 PM): Determining lipid structure by neutron reflection

M. Mihailescu, S. White (University of California at Irvine), N. Berk, C. Majkrzak (NIST Center for Neutron Research)

Multilamellar lipid membranes from the Glycero-Phosphocholine category, deposited on solid substrate were analyzed in reflection geometry, under low hydration conditions, i.e. 0 to 95% relative humidity. The new Advanced Neutron Diffractometer/ Reflectometer built and operated since September 2003, under the "Cold Neutrons for Biology and Technology" project, was employed for these investigations. The high quality of the data permitted reconstruction of the scattering length density profile of the lipid along the normal to the multi-bilayer plane, and allowed for a direct comparison with models published previously [King & White 1986]. Contrast variation by replacing H2O vapor with D2O, in the sample ambiental chamber, allows for the determination of the water distribution around the lipid head-group [Wiener & White 1991]. Moreover, the degree of lipid packing order is explored, by varying number of double bonds per lipid acyl chain. The position and extensions of the double bonds are assessed. Functional data analysis methods can be used to asses statistical uncertainties of the measured profiles.

[1] G. I. King and S. H. White, Biophys. J. 49 : 1047 (1986)
[2] M. C. Wiener , G. I. King and S. H. White, Biophys. J. 60 : 568 (1991)

Acknowledgments: Research supported through Grant No.NIH-RR14812 from the National Center for Research and Resources, and the University of California at Irvine

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