Structure and Formation of Lipid Tubules

这项研究将确定脂类的分子结构，它们在双层中的堆积，以及这些双层与脂质体相反，自组织成脂管的趋势之间的关系。P.G.de Gennes最近提出的小管形成理论认为，如果脂质双层分子堆积类似于近晶C*液晶，有效的电荷分离可能会导致双分子层卷曲成螺旋和小管。这项拟议的工作将检验这一理论关于小管结晶度的结构假设，以及该理论的定性和定量预测。用于已知和潜在的小管形成脂质系统的技术包括a)相差显微镜和荧光显微镜来研究形态、螺旋性和小管形成的途径，以及b)振动光谱来确定分子在小管中的堆积、有序性、水化和取向。离子强度对微管和螺旋的形成、形态和稳定性的影响将检验该理论的预测。数据将与X射线研究相关联，以开发肾小管双层结构的三维模型。这项研究延续了早些时候通过快速奖励开始的一项研究。脂类是细胞膜的主要结构元素，它们会自发地组织成膜状双层。这位研究人员是一种新结构--脂管的共同发现者，这种结构可以由某些脂双层自发形成。这些小管只有几个分子层厚，具有苏打吸管结构。对这种现象的研究将极大地促进我们对双层内结构作用力的理解，包括活细胞中的膜结构。这项工作发生在物理化学、生物学和工程学的交界处，尽管在这一点上，小管的工程应用仍然是推测的。脂小管具有独特的物理属性组合：它们像晶体和石墨纤维一样坚硬而笔直，但中空，壁极薄；它们也像脂质体一样具有生物相容性。没有其他已知的方法来制造其尺寸、形状和精度的结构。已经证明，它们可以被涂上金属。潜在的应用广泛，从遮蔽(通过它们与电磁辐射的相互作用)到修复脱髓鞘的神经到陶瓷复合材料中的结构元件。

This study will define the relationship between the molecular structure of lipids, their packing in bilayers, and the tendency of those bilayers to self-organize into lipid tubules as opposed to liposomes. A recent theory of tubule formation, proposed by P. G. de Gennes, suggests that if lipid bilayer molecular packing is like that of a smectic C* liquid crystal, effective charge separation could cause bilayer strips to curl into helices and tubules. The proposed work will test the structural assumption of this theory with regard to the crystallinity of tubules, and the theory's qualitative and quantitative predictions. Techniques to be used on known and potential tubule forming lipid systems include a) phase contrast and fluorescence microscopy to study morphology, helicity, and routes to tubule formation, and b) vibrational spectroscopy to determine packing, order, hydration, and orientation of molecules within tubules. The effects of ionic strength on formation, morphology, and stabilities of tubules and helices will test predictions from the theory. Data will be correlated with X-ray studies to develop a three-dimensional model of bilayer structure in tubules. This study continues one begun earlier by an expedited award. Lipids like those which are the principal structural elements of cell membranes spontaneously organize into membrane-like bilayers. The investigator was a co-discoverer of a new structure, lipid tubules, which can form spontaneously out of certain lipid bilayers. The tubules, only a few molecular layers thick, have a soda-straw structure. Study of the phenomenon should significantly advance our understanding of structural forces inside bilayers, including membrane structures in living cells. This work occurs at the interface between physical chemistry, biology, and engineering, though engineering applications of tubules are still speculative at this point. Lipid tubules have a unique combination of physical attributes: they are rigid and straight like crystals and graphite fibers, but are hollow, with extremely thin walls; they are also biocompatible like liposomes. There is no other known method to manufacture structures of their size, shape, and precision. It has already been demonstrated that they can be coated with metals. Potential applications are widespread, from obscuration, (by their interactions with electromagnetic radiation) through repair of demyelinated nerves to structural elements in ceramic composites.