Advancing the Measurement of Lipid Transbilayer Exchange

一个只有两个分子厚的膜包裹着所有的细胞，负责以选择性的方式控制材料进出细胞的通道。我们目前对细胞膜的结构和动力学的了解出现在20世纪70年代初？S。然而，关于这个看似简单的“壳”，我们仍然有很多不知道的东西，它使我们所知的生命成为可能。生物学中的一个中心问题是分子在细胞膜上的运动。这种“易位”在活细胞被病毒感染、抗生素、防腐剂和药物的作用以及细胞的调节和生长方面都很重要。已经有许多研究试图找出这是如何发生的。有很多理论，但没有结论。利用研究人员实验室开发的方法，发明了一种新的分析方法，以选择性地探测脂双层(模型细胞膜)中的脂转移和膜组成。拟议研究的目标是使用这一新工具来解决与膜中分子运动有关的一些中心问题。促进人们对化学、生物、物理和数学的兴趣也是拟议研究的一个组成部分，目前正在努力在犹他大学创建一个创新的科学和数学教育设施，该设施将接触到高中生、大学新生和普通公众，以扩大他们的科学意识和知识。通过这一奖项，化学部的生命过程化学项目资助了犹他大学的约翰·康博伊博士，以揭示脂类在细胞膜上的移动和脂类成分不对称建立之间的复杂相互作用。到目前为止，对细胞系统中膜不对称的实现和维持的机制还没有完全了解，主要是因为很难以非破坏性或非扰动的方式研究膜生物物理现象。有人认为，脂膜的不对称性是由单向脂类转运蛋白与高能的转运障碍共同维持的，这限制了脂类自发性跨膜转运的速度。然而，这种假定的Flppase还没有确定，越来越多的文献证明了磷脂的快速自发移位。利用PI开发的和频振动光谱(SFVS)选择性地探测平面支撑脂质双层(PSLB)中的不对称性，将探索平面支撑脂质双层(PSLB)中脂质成分不对称性与触发器之间的联系。这种新的表面分析方法允许直接检测脂类触发器，而不需要荧光或自旋标记的脂类探针，这可能会改变测量的易位率。这项研究的目的是使用这种表面分析工具来解决有关双层系统中跨双层运动和建立脂质不对称性的一些中心问题。此外，还将探讨脂类触发能量学与脂类不对称性建立之间的耦合关系。这些研究旨在为脂质成分不对称的机制提供物理上的见解。

A membrane, only two molecules thick, surrounds all cells and is responsible for controlling the passage of materials in and out of the cell in a selective manner. Our current understanding of the structure and dynamics of cellular membranes emerged in the early 1970?s. However, there is still much we do not know about this seemingly simple "shell" which makes life as we know it possible. A central issue in biology is the movement of molecules across the cellular membrane. This "translocation" is important in the infection of living cells by viruses, the functioning of antibiotics, antiseptics and drugs, and the regulation and growth of cells. There have been a number of studies attempting to find out just how this happens. There are many theories, but no conclusions. Using methods developed in the investigator's laboratory, a novel analytical approach was invented to selectively probe lipid translocation and membrane composition in a lipid bilayer (model cell membrane). The goal of the proposed research is to use this new tool to address some of the central issues concerning molecular motion in membranes. Facilitating an interest in chemistry, biology, physics and mathematics is also an integral part of the proposed studies, with efforts underway to create an innovative science and math education facility at the University of Utah, which will reach out to high school students, college freshmen and the general public, to expand their awareness and knowledge of science. With this award, the Chemistry of Life Processes Program in the Chemistry Division is funding Dr. John Conboy from the University of Utah to unravel the complex interplay between the movement of lipid species across the cellular membrane and the establishment of lipid compositional asymmetry. A full understanding of the mechanism by which membrane asymmetry is achieved and maintained in cellular systems has not been realized to date; primarily due to the difficulty of studying membrane biophysical phenomena in a non-destructive or non-perturbing fashion. It has been suggested that lipid membrane asymmetry is maintained by unidirectional lipid transporters, in conjunction with a high energetic barrier to translocation which limits the rate at which lipids might spontaneously translocate across the membrane. However, such a putative flippase has yet to be identified, and a growing number of publications demonstrate cases of rapid spontaneous translocation of phospholipids. The connection between lipid compositional asymmetry and flip-flop in planar supported lipid bilayers will be explored using a novel application of sum-frequency vibrational spectroscopy (SFVS) developed by the PI to selectively probe the asymmetry in a planar-supported lipid bilayer (PSLB). This new surface analytical method allows for the direct detection of lipid flip-flop without the need for a fluorescent or spin-labeled lipid probe, which can alter the measured translocation rates. The goal of this research is to use this surface analytical tool to address some of the central issues concerning the transbilayer movement and establishment of lipid asymmetry in bilayer systems. In addition, the coupling of lipid flip-flop energetics to the establishment of lipid asymmetry will also be explored. These studies are aimed at providing physical insight into the mechanism of lipid compositional asymmetry.