高分子相分离中的幻数--刚性的重要性
Magic numbers in polymer phase separation -- the importance of being rigid
摘要：
细胞具有非膜结合体，其中许多现在被理解为相分离的凝聚物。一类这样的缩合物由两种聚合物物质组成，其中每种聚合物物质由以一对一方式与另一种聚合物的结合位点相互作用的重复结合位点组成。以前的生物学动机的这种双组分系统的建模令人惊讶地发现，相分离抑制的结合位点的数量的某些组合。这种现象，被称为“幻数效应”，如果两种聚合物可以形成完全键合的小低聚物，凭借一种聚合物中的结合位点的数量是另一种聚合物的结合位点数量的整数倍。在这里，我们使用晶格模型模拟和分析计算表明，如果其中一种聚合物具有刚性形状，允许多个不同的键合构象，这种魔数效应可以大大增强。此外，如果一种物质是刚性的，则该效应在两种物质的更大的相对浓度范围内是稳健的。我们的研究结果推进了我们对基于双组分聚合物的相分离的基本物理学的理解，并对生物和合成系统提出了建议。
英文摘要：
Cells possess non-membrane-bound bodies, many of which are now understood as phase-separated condensates. One class of such condensates is composed of two polymer species, where each consists of repeated binding sites that interact in a one-to-one fashion with the binding sites of the other polymer. Previous biologically-motivated modeling of such a two-component system surprisingly revealed that phase separation is suppressed for certain combinations of numbers of binding sites. This phenomenon, dubbed the "magic-number effect", occurs if the two polymers can form fully-bonded small oligomers by virtue of the number of binding sites in one polymer being an integer multiple of the number of binding sites of the other. Here we use lattice-model simulations and analytical calculations to show that this magic-number effect can be greatly enhanced if one of the polymer species has a rigid shape that allows for multiple distinct bonding conformations. Moreover, if one species is rigid, the effect is robust over a much greater range of relative concentrations of the two species. Our findings advance our understanding of the fundamental physics of two-component polymer-based phase-separation and suggest implications for biological and synthetic systems.
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