The interfacial tension of phase-separated biomolecular condensates affects their fusion and multiphase organization, and yet how this important property depends on the composition and interactions of the constituent macromolecules is poorly understood. Here we use molecular dynamics simulations to determine the interfacial tension and phase equilibrium of model condensate-forming systems. The model systems consist of binary mixtures of Lennard-Jones particles or chains of such particles. We refer to the two components as drivers and regulators; the former has stronger self-interactions and hence a higher critical temperature (T_c) for phase separation. In previous work, we have shown that, depending on the relative strengths of driver-regulator and driver-driver interactions, regulators can either promote or suppress phase separation (i.e., increase or decrease T_c). Here we find that the effects of regulators on T_c quantitatively match the effects on interfacial tension (γ). This important finding means that, when a condensate-forming system experiences a change in macromolecular composition or a change in intermolecular interactions (e.g., by mutation or posttranslational modification, or by variation in solvent conditions such as temperature, pH, or salt), the resulting change in T_c can be used to predict the change in γ and vice versa. We also report initial results showing that disparity in intermolecular interactions drives multiphase coexistence. These findings provide much needed guidance for understanding how biomolecular condensates mediate cellular functions.

中文翻译：

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大分子调节剂对生物分子缩合物的相平衡和界面张力具有匹配作用

相分离的生物分子凝聚物的界面张力会影响它们的融合和多相组织，但这一重要性质如何取决于组成大分子的组成和相互作用却知之甚少。在这里，我们使用分子动力学模拟来确定模型冷凝物形成系统的界面张力和相平衡。模型系统由 Lennard-Jones 粒子或此类粒子链的二元混合物组成。我们将这两个组件称为驱动器和调节器；前者具有更强的自相互作用，因此具有更高的临界温度（T _c) 用于相分离。在以前的工作中，我们已经表明，根据驱动器-调节器和驱动器-驱动器相互作用的相对强度，调节器可以促进或抑制相分离（即增加或减少T _c）。在这里，我们发现调节剂对T _c的影响在数量上与对界面张力 ( γ ) 的影响相匹配。这一重要发现意味着，当形成冷凝物的系统经历大分子组成的变化或分子间相互作用的变化（例如，通过突变或翻译后修饰，或通过温度、pH 或盐等溶剂条件的变化）时，导致T _c的变化可用于预测γ的变化，反之亦然。我们还报告了初步结果，表明分子间相互作用的差异推动了多相共存。这些发现为理解生物分子凝聚物如何介导细胞功能提供了急需的指导。