Grazing incidence neutron scattering investigations of lateral phase separation in oriented mixed lipid bilayers
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Date
2012-07-25
Journal Title
Journal ISSN
Volume Title
Publisher
Saha Institue of Nuclear Physics
Abstract
Since they were first proposed more than a decade ago, lipid rafts have been shown to carry out essential roles within plasma membranes. At a fundamental level, lipid rafts represent a demixing or phase separation of different components within the membrane. Mixtures of saturated and
unsaturated lipids are thought to undergo phase separation due to energetic cost of hydrophobic packing, and that the addition of a hybrid lipid containing both saturated and unsaturated tails may stabilise domains in well defined sizes by lowering the interfacial free energy between the unsaturated and saturated phases (Figure 1). By selectively deuterating lipid species, surface heterogeneity of scattering length densities due to the presence of lipids domains can be probed with off-specular grazing incidence neutron scattering.
We examined mixed lipid systems of deuterated saturated lipid (DPPC), hydrogenated hybrid lipid (POPC) and a hydrogenated unsaturated lipid (DOPC) using grazing incidence neutron scattering measurements on the BIOREF reflectometer (Helmholtz-Zentrum Berlin fur Materialien und Energie GmbH, Berlin, Germany). Simultaneous in situ infrared spectroscopy was employed to study phase transitions and phase separation of the lipids. Specular and off-specular scattering was recorded using a two-dimensional area detector and time-of—flight data. Repeat spacings of the lipid bilayers from specular scattering showed distinct phase separation behavior of these systems at 30 °C when compared to 55 °C. These changes are correlated to changes in the smectic length scale of the lipid bilayer and the characteristic height-height correlation function determined from the Fourier transform of the decay of the integrated intensity of the Bragg sheets as a function of qll3.
Description
Physical copy held by ANSTO Library at DDC: 539.758/30
Keywords
Scattering, Neutrons, Lipids, Separation processes, Spectroscopy, Fourier transformation, Infrared spectrometers
Citation
Kent, B., Bryant, G., Hunt, T., Kreuzer, M., Strobl, M. & Garvey, C. J. (2012). Grazing incidence neutron scattering investigations of lateral phase separation in oriented mixed lipid bilayers. Paper presented to SXNS12, 12th International Conference on Surface X-Ray and Neutron Scattering, 25-28 July 2012, Kolkata, India, (pp. 43).