Sum-Frequency Vibrational Spectroscopy Study of Membrane Asymmetry and the Transbilayer Movement of Lipids

犹他州大学的John Conboy教授得到了分析和表面化学项目的支持，通过对模型脂质双层进行非线性表面特异性和频振动光谱测量来探测脂质物质在细胞膜上的运动。脂质的跨双层运动，也称为脂质翻转或易位，是分子生物学中的一个基本重要问题，几十年来一直吸引着生物学家和化学家的兴趣。通常，脂质翻转已经通过核磁共振光谱（NMR）、电子自旋共振光谱和荧光光谱技术与模型膜系统（例如囊泡和平面支撑的脂质双层）研究。为了进行NMR或荧光测量，脂质必须被自旋标记或荧光标记。标记过程将改变脂质的物理性质，因此被认为是这些技术的缺点。在这项工作中，PI正在使用一种新的方法来研究不需要标记的脂质跨双层运动。此外，可以实现跨双层运动的实时监测。PI正在研究全氘脂质在平面膜中的触发器的各种特性，例如其活化能，其对侧压的依赖性，脂质结构和膜成分的影响。特别是，胆固醇和选定的膜活性肽对磷脂触发器的影响正在解决。这项研究的新发现可能会对分子和细胞生物学产生重大影响。 此外，考虑到支持的双层在纳米技术和其他领域的相关性越来越大，该提案提供了一个非常强大的和原始的方法来研究和优化这些膜的各种应用。

Professor John Conboy of the University of Utah is supported by the Analytical and Surface Chemistry Program to probe the movement of lipid species across cellular membranes by performing non-linear surface specific sum-frequency vibrational spectroscopy measurements on model lipid bilayers. The transbilayer movement of lipid, also known as lipid flip-flop or translocation, is a fundamentally important issue in molecular biology and has attracted interest among biologists and chemists for decades. Typically, lipid flip-flop has been investigated by nuclear magnetic spectroscopy (NMR), electron spin resonance spectroscopy and fluorescence spectroscopic techniques with model membrane systems such as vesicles and planar-supported lipid bilayers. To perform NMR or fluorescence measurements, lipids must be either spin-labeled or fluorescence-labeled. The labeling process will modify lipid physical properties and therefore has been considered as the drawback of these techniques. In this work, the PI is using a novel methodology to investigate lipid transbilayer movement that does not require the labeling. In addition, real-time monitoring of transbilayer movement can be attained. The PI is studying various properties of the flip-flop of perdeuterated lipids in planar membranes such as its activation energy, its dependence on lateral pressure, the effect of lipid structure and of membrane composition. In particular, the influence of cholesterol and selected membrane-active peptides on phospholipid flip-flop is being addressed. New findings drawn from the research could have a significant impact in molecular and cellular biology. Further, taking into account the increasing relevance of supported bilayers in nanotechnology and other fields, the proposal provides a very powerful and original approach to study and to optimize those films for various applications.