Kota Divya, Zhou Huan-Xiang
J Phys Chem Lett. 2022 Jun 8:5285-5290. doi: 10.1021/acs.jpclett.2c00824.
Biomolecular condensates inside cells contain dozens to hundreds of macromolecular components and are surrounded by many others. Our computational studies predicted that macromolecular regulators have matching effects on the phase equilibrium and interfacial tension of condensates. Here we validate this prediction experimentally and characterize the effects of macromolecular regulators on other material properties, including viscoelasticity and fusion speed. Local melting due to the heating of a laser beam and turbidity assay both show that Ficoll70 raises the melting temperature of condensates formed by polylysine:heparin mixtures, whereas optical-tweezer measurements reveal parallel increases in interfacial tension. Additional optical-tweezer experiments report elevations in viscosity and shear relaxation time but also fusion speed by Ficoll70. The fusion speed is higher than predicted by modeling the condensates as purely viscous, demonstrating viscoelasticity and shear thinning. These results illustrate the ample opportunities for macromolecular regulators to tune material properties for proper functions of biomolecular condensates.
细胞内的生物分子凝聚物包含数十到数百种大分子成分，并被许多其他成分包围。我们的计算研究预测，大分子调节剂对凝聚物的相平衡和界面张力有匹配效应。在这里，我们通过实验验证了这一预测，并表征了大分子调节剂对其他材料特性的影响，包括粘弹性和融合速度。激光束加热导致的局部熔化和浊度测定均表明，Ficoll70提高了聚赖氨酸：肝素混合物形成的凝聚物的熔化温度，而光镊测量显示界面张力也相应增加。额外的光镊实验表明，Ficoll70还会提高粘度、剪切松弛时间以及融合速度。融合速度高于将凝聚物建模为纯粘性物质时的预测值，这表明凝聚物具有粘弹性和剪切变稀特性。这些结果表明，大分子调节剂有充分的机会来调节材料特性，以使生物分子凝聚物发挥正常功能。
