Department of Chemistry, Imperial College London, London SW7 2AZ, UK.
Institute of Chemical Biology, Imperial College London, London SW7 2AZ, UK.
J R Soc Interface. 2018 Nov 21;15(148):20180610. doi: 10.1098/rsif.2018.0610.
For the past decade, droplet interface bilayers (DIBs) have had an increased prevalence in biomolecular and biophysical literature. However, much of the underlying physics of these platforms is poorly characterized. To further our understanding of these structures, lipid membrane tension on DIB membranes is measured by analysing the equilibrium shape of asymmetric DIBs. To this end, the morphology of DIBs is explored for the first time using confocal laser scanning fluorescence microscopy. The experimental results confirm that, in accordance with theory, the bilayer interface of a volume-asymmetric DIB is curved towards the smaller droplet and a lipid-asymmetric DIB is curved towards the droplet with the higher monolayer surface tension. Moreover, the DIB shape can be exploited to measure complex bilayer surface energies. In this study, the bilayer surface energy of DIBs composed of lipid mixtures of phosphatidylgylcerol (PG) and phosphatidylcholine are shown to increase linearly with PG concentrations up to 25%. The assumption that DIB bilayer area can be geometrically approximated as a spherical cap base is also tested, and it is discovered that the bilayer curvature is negligible for most practical symmetric or asymmetric DIB systems with respect to bilayer area.
在过去的十年中，液滴界面双层（DIB）在生物分子和生物物理文献中越来越受欢迎。然而，这些平台的许多基础物理学特性尚未得到很好的描述。为了进一步了解这些结构，通过分析不对称 DIB 的平衡形状来测量 DIB 膜上的脂质膜张力。为此，首次使用共焦激光扫描荧光显微镜探索 DIB 的形态。实验结果证实，与理论一致，体积不对称 DIB 的双层界面向较小的液滴弯曲，而脂类不对称 DIB 向具有较高单层表面张力的液滴弯曲。此外，DIB 的形状可用于测量复杂的双层表面能。在这项研究中，表明由磷脂酰甘油（PG）和磷脂酰胆碱组成的 DIB 的双层表面能与 PG 浓度呈线性增加，直至 25%。还测试了 DIB 双层面积可以几何近似为球形帽基底的假设，并且发现对于大多数实际的对称或不对称 DIB 系统，相对于双层面积，双层曲率可以忽略不计。
