GRAZING INCIDENCE SAXS ON SUBSTRATE SUPPORTED LIPID MEMBRANES

该子项目是利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得主要资金， 因此可以在其他CRISP条目中表示。列出的机构是 中心，不一定是研究者的机构。 高度对齐的脂质膜堆叠可以通过在平坦光滑表面上自组装来制备，形成近晶-C液晶结构，其中水插在由脂质分子形成的双层之间。这种取向膜的样品已被广泛用于衍射实验，集中在沿沿着双层法线的膜的结构上。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。我们开始了一系列的实验排列磷脂膜的不同厚度含有二聚体离子通道短杆菌肽。使用新开发的具有湿度和温度控制的样品室，我们研究了膜内的肽之间的最近邻距离作为膜的厚度和水合状态的函数的变化。我们发现，平均肽到肽的距离增加的双层厚度。这种效应归因于肽与脂质之间的疏水性错配导致肽的排斥相互作用增加。除了相同膜平面内的肽之间的膜介导的相互作用之外，我们发现，在85%的相对空气湿度以下，相邻膜中的肽开始彼此相互作用，导致跨膜堆叠的肽的部分排序。

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.