This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The proposed study will investigate the structure of uni-lamellar lipid vesicles. While the structure of stacked lipid membranes (or multi-lamellar vesicles) have long been studied using traditional diffraction techniques, scattering studies from an ensemble of individual 'uncorrelated' lipid vesicles are uncommon and few publications attempt analysis of the so called 'diffuse' scattering. Recently, we have made advances in data collection and analysis of x-ray scattering from uni-lamellar vesicles at the PX beamlines 8.2.1 and 8.2.2. at ALS. Our initial data is very promising and clearly shows scattering from uni-lamellar vesicles. However, our experiments suffer from poor signal to noise and lack of small angle resolution due to the experimental conditions typical for PX beamlines. With the use of BL 4-2 we hope acquire the quality of data, which can be fit to our recently developed vesicle model. Specifically, from one experiment we will determine the average radius of vesicles, the distribution of vesicles sizes and a complete description of the bilayer allowing for asymmetric (inside vs. outside) distribution of lipids and membrane associated molecules. Below is a simulated scattering plot for vesicles of average radius 400 a distribution half-width of 100 and an asymmetric bilayer profile as shown on the right.
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