Spillane Katelyn M, Ortega-Arroyo Jaime, de Wit Gabrielle, Eggeling Christian, Ewers Helge, Wallace Mark I, Kukura Philipp
Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford , South Parks Road, Oxford OX1 3QZ, United Kingdom.
Nano Lett. 2014 Sep 10;14(9):5390-7. doi: 10.1021/nl502536u. Epub 2014 Aug 27.
The biological functions of the cell membrane are influenced by the mobility of its constituents, which are thought to be strongly affected by nanoscale structure and organization. Interactions with the actin cytoskeleton have been proposed as a potential mechanism with the control of mobility imparted through transmembrane "pickets" or GPI-anchored lipid nanodomains. This hypothesis is based on observations of molecular mobility using various methods, although many of these lack the spatiotemporal resolution required to fully capture all the details of the interaction dynamics. In addition, the validity of certain experimental approaches, particularly single-particle tracking, has been questioned due to a number of potential experimental artifacts. Here, we use interferometric scattering microscopy to track molecules labeled with 20-40 nm scattering gold beads with simultaneous <2 nm spatial and 20 μs temporal precision to investigate the existence and mechanistic origin of anomalous diffusion in bilayer membranes. We use supported lipid bilayers as a model system and demonstrate that the label does not influence time-dependent diffusion in the small particle limit (≤40 nm). By tracking the motion of the ganglioside lipid GM1 bound to the cholera toxin B subunit for different substrates and lipid tail properties, we show that molecular pinning and interleaflet coupling between lipid tail domains on a nanoscopic scale suffice to induce transient immobilization and thereby anomalous subdiffusion on the millisecond time scale.
细胞膜的生物学功能受其组成成分流动性的影响，而这些组成成分被认为会受到纳米级结构和组织的强烈影响。与肌动蛋白细胞骨架的相互作用被认为是一种潜在机制，通过跨膜“栓子”或糖基磷脂酰肌醇（GPI）锚定的脂质纳米域来控制流动性。这一假设基于使用各种方法对分子流动性的观察，尽管其中许多方法缺乏完全捕捉相互作用动力学所有细节所需的时空分辨率。此外，由于一些潜在的实验假象，某些实验方法的有效性，特别是单粒子追踪，受到了质疑。在这里，我们使用干涉散射显微镜来追踪用20 - 40纳米散射金珠标记的分子，同时具有小于2纳米的空间精度和20微秒的时间精度，以研究双层膜中反常扩散的存在及其机制起源。我们使用支持脂质双层作为模型系统，并证明在小颗粒极限（≤40纳米）下，标记不会影响时间依赖性扩散。通过追踪结合在霍乱毒素B亚基上的神经节苷脂GM1在不同底物和脂质尾部性质下的运动，我们表明纳米尺度上脂质尾部结构域之间的分子固定和跨层耦合足以诱导瞬时固定，从而在毫秒时间尺度上产生反常亚扩散。
