In-plane and Out-of-plane Structural Ordering of Natural and Synthetic Glycolipid Membranes

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The primary goal of this project is to establish physical models of cell surface glycocalyx, based on aqueous dispersions and planar bilayers of synthetic and natural glycolipids. As the first step, we characterize the thermotropic and lyotropic phase behavior of glycolipid dispersions as functions of molecular structures using differential scanning calorimetry (DSC) and small- and wide-angle x-ray scattering (SAXS/WAXS). In the next step, we measure specular and off-specular (diffuse) x-ray and neutron scattering of planar glycolipid lamellae deposited on solid substrates in a climate chamber. X-ray scattering yields the electron density profile with a high spatial resolution, while neutron scattering allows us to highlight the ¿molecules of interest¿ by selective deuteration (contrast variation). Planar geometry enables us to distinguish the specular and off-specular scattering vector components, while the experiments in a climate chamber allow for the precise control of temperature and osmotic pressure. Quantitative measurements of the diffuse scattering and membrane thickness at various osmotic pressures (force-distance relationships) enable one to calculate the bending rigidity of membranes as well as the intermembrane potential. As target systems, we start from synthetic glycolipids with systematic structural modifications, and extend the same strategy to natural glycolipids from different bacterial mutants.