GRAZING INCIDENCE SAXS ON SUBSTRATE SUPPORTED LIPID MEMBRANES

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 通过在平坦光滑的表面上自组装，可以制备高度排列的脂膜堆叠，形成近晶-C液晶结构，其中水插入由脂类分子形成的双层之间。这种取向膜的样品已被广泛用于集中于沿双层法线的膜结构的衍射实验。在研究脂质-蛋白质相互作用时，观察蛋白质在膜平面上的横向分布也是非常有用的。我们在含有二聚体离子通道Gramiidin的不同厚度的取向磷脂膜上开始了一系列的实验。利用新开发的具有湿度和温度控制的样品室，我们研究了膜内多肽之间的最近邻距离随膜厚度和水化状态的变化。我们发现，随着双层厚度的增加，平均多肽到多肽的距离增加。这种效应归因于由于多肽和脂类之间的疏水不匹配而增加了多肽之间的排斥相互作用。除了同一膜平面内的多肽之间的膜介导相互作用外，我们还发现，在相对湿度为85%的情况下，相邻膜中的多肽开始相互作用，导致多肽在膜堆栈上的偏序。

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. Highly aligned stacks of lipid membranes can be prepared by self assembly on flat smooth surfaces forming a smectic-C liquid crystal structure with water intercalated between the bilayers formed by the lipid molecules. Such samples of aligned membranes have been extensively used for diffraction experiments concentrating on the structure of the membrane along the bilayer normal. In studying lipid-protein interactions it is also highly informative to look at the lateral distribution of the proteins in the membrane plane. We started a series of experiments on aligned phospholipid membranes of different thickness containing the dimeric ion channel Gramicidin. Using the newly developed sample chamber with humidity and temperature control, we investigated the change in the nearest neighbor distance between the peptides inside the membrane as a function of thickness and hydration state of the membrane. We find that the average peptide-to-peptide distance increases with increasing thickness of the bilayer. This effect is attributed to the increased repulsive interaction of the peptides due to the hydrophobic mismatch between the peptide and the lipid. In addition to the membrane mediated interaction between the peptides within the same membrane plane, we found that below a relative air humidity of 85% the peptide in neighboring membranes start to interact with each other leading to a partial ordering of of the peptides across the membrane stack.