MAGNETIC ALIGNMENT OF BINARY MIXTURES OF PHOSPHOLIPIDS

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。 悬浮在水中的长链和短链磷脂的二元混合物自发形成扁平的盘状脂质胶束，即所谓的双分子。这些双细胞悬浮液最有趣的特性之一是，在长链脂类组分的主相变以上的温度下，它们能够在外部磁场的影响下部分定向。这种机制也可以用来宏观地定向与这些双分子相关的蛋白质，尽管目前，观察到磁排列的相的拓扑结构仍然存在争议。这个项目是为了测试这种方法的潜力，利用这种诱导体系中的偏序，利用小角x射线散射来研究膜蛋白相互作用。到目前为止，我们已经成功地测量了不同长链和短链脂类比例的脂双分子的圆盘形状因子。当外加约1T的磁场时，所有被测混合物都在长链脂类主相变上方5℃到10℃的温度下表现出宏观取向。我们还发现，在脂类体系中加入小的二聚体离子通道Graicidin并不显著干扰双分子束，我们能够在这个含有脂类的多肽体系中获得类似质量的磁有序。

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. Binary mixtures of long and short chain phospholipids suspended in water spontaneously form flat disk-like lipid micelles, so-called bicelles. One of the most interesting properties of these bicelle suspensions is their ability to partially orient under the influence of an external magnetic field at temperatures above the main phase transition of the long chain lipid component. This mechanism can be used to macroscopically orient also proteins that are associated with these bicelles, although at present, the topology of the phase where magnetic alignment is observed is still disputed. This project was started to test the potential of this approach to study membrane protein interactions using small angle x-ray scattering taking advantage of this induced partial ordering in the system. So far we have successfully measured the disk form factor of the lipid bicelles for different ratios of long chain to short chain lipids. All mixtures measured exhibited macroscopic orientation at temperatures between 5¿C to 10¿C above the main phase transition of the long chain lipid when subjected to an external magnetic field of about 1 T. We also found that the addition of gramicidin, a small dimeric ion channel, to the lipid system does not significantly disturb the bicelle and we were able to achieve a similar quality of magnetic ordering in this peptide containing lipid system.