Membrane Structure of Small Unilamellar Vesicles Determined by Small Angle X-Ray Scattering: A Comparison of Full and Local Spectrum Fittings

We determined the membrane structure of small unilamellar vesicles in aqueous solution by using small angle X-ray scattering. The multi-parameter symmetry and asymmetry models were constructed to fit the full spectrum scattering curve to determine the membrane structure. As a comparison, a simple model with one parameter was used to fit the scattering curve around the second peak to obtain the membrane thickness. We used the model membranes composed of saturated and unsaturated lipids with different chain lengths to prepare small unilamellar vesicles in aqueous solution. The X-ray light source in BL13A and BL23A beam lines of NSRRC and home-made temperature controlled cell with Mylar windows will be applied in the measurements. Consequently, the membrane thicknesses extracted from full and local spectrum fittings are consistent and in agreement with reference papers. However, the parameters determined by full spectrum fittings exist discrepancies in different models except for membrane thickness. The result suggests that one parameter fitting of local spectrum should be a simple, reliable and efficient way to determine membrane thickness of unilamellar vesicles in aqueous solution.