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

本项目的主要目标是建立细胞表面糖萼的物理模型，以合成和天然糖脂的水分散体和平面双层为基础。作为第一步，我们利用差示扫描量热法（DSC）和小角和广角x射线散射（SAXS/WAXS）表征糖脂分散体的热致性和溶致性相行为作为分子结构的函数。在下一步，我们测量了在气候室中沉积在固体基底上的平面糖脂片的镜面和非镜面（漫射）x射线和中子散射。x射线散射产生具有高空间分辨率的电子密度分布图，而中子散射使我们能够通过选择性氘化（对比变化）来突出“感兴趣的分子”。平面几何结构使我们能够区分镜面和非镜面散射矢量分量，而在气候室中的实验允许精确控制温度和渗透压。对不同渗透压下的扩散散射和膜厚度的定量测量（力-距离关系）使人们能够计算膜的弯曲刚度以及膜间电位。作为目标系统，我们从具有系统结构修饰的合成糖脂开始，并将相同的策略扩展到来自不同细菌突变体的天然糖脂。

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.