Wu Tingting, King Matthew R, Qiu Yuanxin, Farag Mina, Pappu Rohit V, Lew Matthew D
Department of Electrical and Systems Engineering, Washington University in St. Louis, James F. McKelvey School of Engineering, Washington University in St. Louis; St. Louis, MO 63130, USA.
Center for Biomolecular Condensates, James F. McKelvey School of Engineering, Washington University in St. Louis; St. Louis, MO 63130, USA.
bioRxiv. 2024 Oct 7:2023.01.26.525727. doi: 10.1101/2023.01.26.525727.
Biomolecular condensates are viscoelastic materials. Simulations predict that fluid-like condensations are defined by spatially inhomogeneous organization of the underlying molecules. Here, we test these predictions using single-fluorogen tracking and super-resolution imaging. Specifically, we leverage the localization and orientational preferences of freely diffusing fluorogens and the solvatochromic effect whereby specific fluorogens are turned on in response to condensate microenvironments. We deployed three different fluorogens to probe the microenvironments and molecular organization of different protein-based condensates. The spatiotemporal resolution and environmental sensitivity afforded by single-fluorogen imaging shows that the internal environments of condensates are more hydrophobic than coexisting dilute phases. Molecules within condensates are organized in a spatially inhomogeneous manner, and this gives rise to slow-moving nanoscale molecular clusters that coexist with fast-moving molecules. Fluorogens that localize preferentially to the interface help us map their distinct features. Our findings provide a structural and dynamical basis for the viscoelasticity of condensates.
生物分子凝聚物是粘弹性材料。模拟预测，类流体凝聚物由基础分子的空间不均匀组织所定义。在此，我们使用单荧光团追踪和超分辨率成像来检验这些预测。具体而言，我们利用自由扩散荧光团的定位和取向偏好以及溶剂化显色效应，即特定荧光团会响应凝聚物微环境而被激活。我们部署了三种不同的荧光团来探测不同蛋白质基凝聚物的微环境和分子组织。单荧光团成像所提供的时空分辨率和环境敏感性表明，凝聚物的内部环境比共存的稀相更疏水。凝聚物中的分子以空间不均匀的方式组织，这导致了与快速移动分子共存的缓慢移动的纳米级分子簇。优先定位于界面的荧光团帮助我们描绘出它们的独特特征。我们的研究结果为凝聚物的粘弹性提供了结构和动力学基础。
