Baroji Younes F, Oddershede Lene B, Seyed Reihani Seyed Nader, Bendix Poul M
Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100, Copenhagen, Denmark.
Eur Biophys J. 2014 Dec;43(12):595-602. doi: 10.1007/s00249-014-0989-2. Epub 2014 Sep 26.
Membrane nanotubes, ubiquitous in cellular systems, adopt a spectrum of curvatures and shapes that are dictated by their intrinsic physical characteristics as well as their interactions with the local cellular environment. A high bending flexibility is needed in the crowded cytoplasm where tubes often need to bend significantly in the axial direction at sub-micron length scales. We find the stiffness of spontaneously formed membrane nanotubes by measuring the persistence length of reconstituted membrane nanotubes freely suspended in solution and imaged by fluorescence microscopy. By quantifying the tube diameter we demonstrate for the first time that the persistence length scales linearly with radius. Although most tubes are uni-lamellar, the predicted linear scaling between tube radius and persistence length allows us to identify tubes that spontaneously form as multilamellar structures upon hydration. We provide the first experimental evidence that illumination of lipid fluorophores can have a profound effect on the lipid bilayer which we sensitively detect as a continuous change in the tube persistence length with time. The novel assay and methodology here presented has potential for quantification of the structural reinforcement of membrane tubes by scaffolding proteins.
膜纳米管在细胞系统中普遍存在，其曲率和形状各异，这由其内在物理特性以及与局部细胞环境的相互作用所决定。在拥挤的细胞质中，膜纳米管需要很高的弯曲灵活性，因为在亚微米长度尺度下，纳米管常常需要在轴向大幅弯曲。我们通过测量自由悬浮于溶液中并用荧光显微镜成像的重构膜纳米管的持久长度，来确定自发形成的膜纳米管的刚度。通过量化管径，我们首次证明持久长度与半径呈线性比例关系。尽管大多数纳米管是单分子层的，但预测的管径与持久长度之间的线性比例关系使我们能够识别出在水合作用下自发形成多层结构的纳米管。我们首次提供了实验证据，证明脂质荧光团的光照会对脂质双层产生深远影响，我们能灵敏地检测到这一影响表现为纳米管持久长度随时间的持续变化。本文介绍的新型检测方法和技术有潜力用于量化支架蛋白对膜纳米管结构的增强作用。
