Elasticity generates indissoluble biomolecular condensates

While biomolecular condensates are often liquid-like, many experiments found that condensates also exhibit solid-like behaviors, making them indissoluble in conditions liquid condensates dissolve. Despite the biological significance of indissoluble condensates to cellular fitness, the mechanisms underlying the indissolubility of solid-like condensates are still unclear. In this work, we study the effects of elasticity on the dissolution of biomolecular condensates. We demonstrate that the bulk stress inside condensates may prevent the condensates from dissolution and obtain a new mechanical equilibrium condition of elastic condensates. Moreover, we theoretically predict a phase diagram of indissolubility for biomolecular condensates and identify a minimum bulk modulus for the condensates to be indissoluble. To verify our theories, we simulate the two-fluid model in which the slow component corresponding to biomolecules generates elastic stress. Our theoretical predictions are nicely confirmed and independent of microscopic details. Our works show that elasticity makes biomolecular condensates less prone to dissolution.