Department of Physics , McGill University , Montreal , Quebec H3A 2T8 , Canada.
Department of Physics , Case Western Reserve University , Cleveland , Ohio 44106 , United States.
J Am Chem Soc. 2019 May 15;141(19):7751-7757. doi: 10.1021/jacs.8b13349. Epub 2019 May 6.
Biomolecular condensates formed by liquid-liquid phase separation of proteins and nucleic acids have been recently discovered to be prevalent in biology. These dynamic condensates behave like biochemical reaction vessels, but little is known about their structural organization and biophysical properties, which are likely related to condensate size. Thus, it is critical that we study them on scales found in vivo. However, previous in vitro studies of condensate assembly and physical properties have involved condensates up to 1000 times larger than those found in vivo. Here, we apply confinement microscopy to visualize condensates and control their sizes by creating appropriate confinement length scales relevant to the cell environment. We observe anomalous diffusion of probe particles embedded within confined condensates, as well as heterogeneous dynamics in condensates formed from PEG/dextran and in ribonucleoprotein complexes of RNA and the RNA-binding protein Dhh1. We propose that the observed non-Gaussian dynamics indicate a hopping diffusion mechanism inside condensates. We also observe that, for dextran-rich condensates, but not for ribonucleo condensates, probe particle diffusion depends on condensate size.
生物分子凝聚物是由蛋白质和核酸的液-液相分离形成的，最近在生物学中被发现普遍存在。这些动态凝聚物的行为类似于生化反应容器，但它们的结构组织和物理性质知之甚少，而这些性质可能与凝聚物的大小有关。因此，在体内发现的尺度上研究它们是至关重要的。然而，以前关于凝聚物组装和物理性质的体外研究涉及的凝聚物比体内发现的凝聚物大 1000 倍。在这里，我们应用限制显微镜来可视化凝聚物，并通过创建与细胞环境相关的适当限制长度尺度来控制其大小。我们观察到嵌入受限凝聚物中的探针粒子的异常扩散，以及 PEG/dextran 形成的凝聚物和 RNA 与 RNA 结合蛋白 Dhh1 的核糖核蛋白复合物中的异质动力学。我们提出，观察到的非高斯动力学表明凝聚物内部存在跳跃扩散机制。我们还观察到，对于富含 dextran 的凝聚物，但不是对于核糖核凝聚物，探针粒子的扩散取决于凝聚物的大小。
