Department of Chemistry and Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60607, USA.
J Chem Phys. 2021 Oct 14;155(14):145102. doi: 10.1063/5.0064247.
A theoretical study on the shape dynamics of phase-separated biomolecular droplets is presented, highlighting the importance of condensate viscoelasticity. Previous studies on shape dynamics have modeled biomolecular condensates as purely viscous, but recent data have shown them to be viscoelastic. Here, we present an exact analytical solution for the shape recovery dynamics of deformed biomolecular droplets. The shape recovery of viscous droplets has an exponential time dependence, with the time constant given by the "viscocapillary" ratio, i.e., viscosity over interfacial tension. In contrast, the shape recovery dynamics of viscoelastic droplets is multi-exponential, with shear relaxation yielding additional time constants. During shape recovery, viscoelastic droplets exhibit shear thickening (increase in apparent viscosity) at fast shear relaxation rates but shear thinning (decrease in apparent viscosity) at slow shear relaxation rates. These results highlight the importance of viscoelasticity and expand our understanding of how material properties affect condensate dynamics in general, including aging.
本文对相分离生物分子液滴的形状动力学进行了理论研究，强调了凝聚物粘弹性的重要性。先前关于形状动力学的研究将生物分子凝聚物建模为纯粘性的，但最近的数据表明它们具有粘弹性。在这里，我们提出了一个用于变形生物分子液滴形状恢复动力学的精确解析解。粘性液滴的形状恢复具有指数时间依赖性，时间常数由“粘毛细”比给出，即粘度与界面张力之比。相比之下，粘弹性液滴的形状恢复动力学是多指数的，剪切松弛会产生额外的时间常数。在形状恢复过程中，粘弹性液滴在快速剪切松弛速率下表现出剪切增稠（表观粘度增加），而在缓慢剪切松弛速率下表现出剪切稀化（表观粘度降低）。这些结果强调了粘弹性的重要性，并扩展了我们对材料性质如何影响一般凝聚物动力学（包括老化）的理解。
