Understanding How Coacervates Drive Reversible Small Molecule Reactions to Promote Molecular Complexity
Understanding How Coacervates Drive Reversible Small Molecule Reactions to Promote Molecular Complexity
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DOI：
10.1021/acs.langmuir.1c02231
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发表时间：
2021-12-14
期刊：
影响因子：
3.9
通讯作者：
Schroeder, Charles M.
中科院分区：
文献类型：
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作者：
Jacobs, Michael, I;Jira, Edward R.;Schroeder, Charles M.
液-液相分离的凝聚液滴产生的无膜隔室在细胞的空间组织和反应性中起着重要作用。由于其分子密集的性质和隔离生物分子的能力，凝聚液滴为酶促反应动力学和反应机制创造了独特的环境，这与散装溶液明显不同。在这项工作中，我们采用实验和定量建模相结合的方法来了解凝聚液滴如何促进可逆的小分子反应化学。特别地，我们研究了在一系列条件下聚丙烯酸-聚乙二醇凝聚液滴中产生不稳定荧光亚胺的模型缩合反应。在平衡状态下，凝聚液滴中的亚胺生成物浓度约为散装溶液中的140倍，这是由于反应物和生成物优先分配到凝聚液滴中，并且凝聚液滴中的反应平衡常数约为溶液中的3倍。建立了反应扩散模型，定量地描述了竞争反应和分配平衡如何控制凝聚液滴内亚胺产物的空间分布。总的来说，我们的研究结果表明，区隔化稳定了动力学不稳定的反应产物，与散装溶液相比，这使得凝聚液滴中的反应物浓度更高。总的来说，这些结果提高了对生物分子凝聚体如何促进涉及不稳定反应中间体的多步骤反应途径的理解，并表明凝聚体如何提供潜在的非生物机制来促进分子复杂性。
Liquid-liquid phase-separated coacervate droplets give rise to membraneless compartments that play an important role in the spatial organization and reactivity in cells. Due to their molecularly crowded nature and ability to sequester biomolecules, coacervate droplets create distinct environments for enzymatic reaction kinetics and reaction mechanisms that markedly differ from bulk solution. In this work, we use a combination of experiments and quantitative modeling to understand how coacervate droplets promote reversible small molecule reaction chemistry. In particular, we study a model condensation reaction generating an unstable fluorescent imine in polyacrylic acid-polyethylene glycol coacervate droplets over a range of conditions. At equilibrium, the concentration of the imine product in coacervate droplets is approximately 140-fold larger than that in bulk solution, which arises due to preferential partitioning of reactants and products into coacervate droplets and a reaction equilibrium constant that is roughly threefold larger in coacervate droplets than in solution. A reaction-diffusion model is developed to quantitatively describe how competing reaction and partitioning equilibria govern the spatial distribution of the imine product inside coacervate droplets. Overall, our results show that compartmentalization stabilizes kinetically labile reaction products, which enables larger reactant concentrations in coacervate droplets compared to bulk solution. Broadly, these results provide an improved understanding of how biomolecular condensates promote multistep reaction pathways involving unstable reaction intermediates and suggest how coacervates provide a potential abiotic mechanism to promote molecular complexity.