Determining the Structure of Biological Membranes through Adhesive Emulsions

细胞膜将细胞内部的内容物与周围的液体分开。半透膜由脂质双分子层和各种蛋白质组成，这些蛋白质使细胞间的信号传导和控制物质通过膜的交换。脂质和蛋白质之间的相互作用有助于蛋白质在膜上的空间组织。双分子层每个小叶内的相互作用已被广泛研究；这个项目的重点是传单之间的横向相互作用。该项目将开发一种新的实验方法，使用涂有脂质的液滴相互压迫形成合成脂质双层膜。测量相互作用的液滴和膜的某些特性将允许定量地确定横向脂质相互作用的能量学。这项研究的发现将揭示双分子层的两个小叶组成的差异如何影响细胞功能，这可能会激发新的治疗方法来检测和对抗疾病。该项目将为来自多个工程学科的研究生提供参与高度跨学科研究的机会。该项目还将通过佐治亚大学现有的几个项目吸引高中生和本科生，这些项目将加强来自代表性不足群体的学生参与工程研究。虽然脂质亚域在细胞膜上的形成是由于脂质与脂质的横向相互作用，但伴随的脂质亚域的跨膜偶联尚未得到充分的研究。本项目将利用液滴界面双层的流体特性，结合张力测量和电生理学来研究这些现象。纳米液滴涂有有序的脂质单层将被操纵成接触，形成模型脂质双层膜与不同的组成在每个小叶。施加在膜上的电场将产生电压缩和电润湿，使膜同时变薄和膨胀。在此过程中，对膜面积和接触角的目测将提供膜厚度和表观双层张力的准确值，而无需额外校准。电压缩过程中膜张力的变化将反映脂质小叶内部和之间的脂质相互作用。模型筏或脂质子结构域将使用光聚合脂质创建，并且在电压缩期间膜性质的变化将作为这些子结构域在膜小叶之间不对称分布的函数进行跟踪。这种方法将提供由小叶不对称产生的不匹配能量的实验测量，这被假设为驱动脂质结构域的搭配。该项目将为工程研究生提供跨学科培训，重点是电生理学、张力测量学、界面化学、建模和仪器仪表。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The membrane of a cell separates the cell's interior contents from the surrounding fluid. The semi-permeable membrane is composed of a lipid bilayer and various proteins that enable cell-cell signaling and control exchange of material through the membrane. Interactions among lipids and proteins help organize the proteins spatially in the membrane. Interactions within each leaflet of the bilayer have been studied extensively; this project focuses on transverse interactions between the leaflets. The project will develop a new experimental approach that uses lipid-coated droplets pressed against each other to form synthetic lipid bilayer membranes. Measurements of certain characteristics of the interacting droplets and the membrane will allow the energetics of transverse lipid interactions to be determined quantitatively. Findings from this research will show how differences in the compositions of the two leaflets of a bilayer affect cell function, which could inspire new therapeutics to detect and combat disease. The project will provide opportunities for graduate students from several engineering disciplines to participate in highly interdisciplinary research. The project will also engage high school and undergraduate students through several existing programs at the University of Georgia that enhance participation of students from underrepresented groups in engineering research.While the formation of lipid subdomains in cellular membranes due to lateral lipid-lipid interactions is well characterized, the accompanying cross-membrane coupling of lipid subdomains is underexplored. This project will exploit the fluidic properties of droplet interface bilayers to study these phenomena through a combination of tensiometry and electrophysiology. Aqueous nanoliter droplets coated with ordered lipid monolayers will be manipulated into contact to form model lipid bilayer membranes with varying compositions in each leaflet. An imposed electric field across the membrane will produce both electrocompression and electrowetting, causing the membrane to simultaneously thin and expand. Visual measurements of the membrane area and the angle of contact during this process will provide accurate values of the membrane thickness and the apparent bilayer tension without additional calibration. Changes in the membrane tension during electrocompression will reflect lipid-lipid interactions within and between the lipid leaflets. Model rafts or lipid subdomains will be created using photopolymerizable lipids, and changes in the membrane properties during electrocompression will be tracked as a function of the asymmetric distribution of these subdomains between the membrane leaflets. This approach will provide experimental measurements of the mismatch energy generated by leaflet asymmetry, which has been hypothesized to drive collocation of the lipid domains. The project will provide interdisciplinary training for a graduate student in engineering, with emphasis on electrophysiology, tensiometry, interfacial chemistry, modeling, and instrumentation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.