Living cells organize their internal space into dynamic condensates through liquid-liquid phase separation of multivalent proteins in association with cellular nucleic acids. Here we study how variations in nucleic acid (NA)-to-protein stoichiometry modulate the condensed phase organization and fluid dynamics in a model system of multi-component heterotypic condensates. Employing a multi-parametric approach of particle tracking video microscopy and optical-tweezer induced droplet fusion, we show that the interfacial tension, but not viscosity, of protein-NA condensates is controlled by the NA-to-protein ratio across the two-phase regime. In parallel, we utilize fluorescence correlation spectroscopy (FCS) to quantify protein and nucleic acid diffusion in the condensed phase. FCS measurements reveal that the diffusion of the component protein and NA within the condensate core is governed by the viscosity, and hence, also remains insensitive to the changes in NA-to-protein stoichiometry. Collectively, our results provide insights into the regulation of multi-component heterotypic liquid condensates, reflecting how the bulk mixture composition affects their core vs. surface organization and dynamical properties.

中文翻译：

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量化多组分蛋白质-核酸缩合物的粘度和表面张力


活细胞通过与细胞核酸结合的多价蛋白质的液-液相分离，将其内部空间组织成动态凝聚体。在这里，我们研究了核酸（NA）与蛋白质化学计量的变化如何调节多组分异型凝聚物模型系统中的凝聚相组织和流体动力学。采用粒子跟踪视频显微镜和光镊诱导液滴融合的多参数方法，我们表明蛋白质-NA 冷凝物的界面张力（而不是粘度）是由两相中的 NA 与蛋白质的比率控制的。政权。同时，我们利用荧光相关光谱（FCS）来量化凝聚相中的蛋白质和核酸扩散。 FCS 测量表明，凝析核内组分蛋白质和 NA 的扩散受粘度控制，因此对 NA 与蛋白质化学计量的变化也不敏感。总的来说，我们的结果提供了对多组分异型液体冷凝物调节的见解，反映了本体混合物成分如何影响其核心与表面组织和动力学特性。