柔性生物聚合物壳内宿存纤维的形态发生和自组织
Morphogenesis and self-organization of persistent filaments confined within flexible biopolymeric shells
摘要：
我们系统地探讨了自组装的半柔性聚合物在可变形的球形限制在一个广泛的政权的链刚度，轮廓长度和包装分数通过粗粒度的分子动力学模拟。顺应性，DNA样丝被发现经历了连续的交叉从两个不同的表面有序的四极状态，其特征在于由四面体图案的拓扑缺陷，无论是纵向或横向双极结构，随着聚合物浓度的增加。这些过渡，以及它们涉及的中间安排，可以归因于一个取向润湿现象与微妙的密度和轮廓长度相关的变化，在相应的液晶相的弹性各向异性的组合。相反，刚性的，微管状聚合物的组织证据连续弹性理论的逐步崩溃的链尺寸变得可比的平衡半径的封装膜。在这种情况下，我们观察到一个逐渐的转变，从扁长形，类触体的形态，扁，红细胞样的结构，增加轮廓长度，这是所产生的有序，聚合物和膜屈曲之间的相互作用。我们进一步提供了一些尚未确定的，自组织的国家在这样的封闭系统的刚性非手性细丝，包括自发螺旋近晶组装，多面体和扭曲的斜纹状安排的数字证据。我们的研究结果是量化的，通过引入几个序参量和无监督的学习计划的表面拓扑缺陷的本地化，并与场论的预测，以及经典的弹性理论的薄杆和球壳。
英文摘要：
We systematically explore the self-assembly of semi-flexible polymers in deformable spherical confinement across a wide regime of chain stiffness, contour lengths and packing fractions by means of coarse-grained molecular dynamics simulations. Compliant, DNA-like filaments are found to undergo a continuous crossover from two distinct surface-ordered quadrupolar states, both characterized by tetrahedral patterns of topological defects, to either longitudinal or latitudinal bipolar structures with increasing polymer concentrations. These transitions, along with the intermediary arrangements that they involve, may be attributed to the combination of an orientational wetting phenomenon with subtle density- and contour-length-dependent variations in the elastic anisotropies of the corresponding liquid crystal phases. Conversely, the organization of rigid, microtubule-like polymers evidences a progressive breakdown of continuum elasticity theory as chain dimensions become comparable to the equilibrium radius of the encapsulating membrane. In this case, we observe a gradual shift from prolate, tactoid-like morphologies to oblate, erythrocyte-like structures with increasing contour lengths, which is shown to arise from the interplay between nematic ordering, polymer and membrane buckling. We further provide numerical evidence of a number of yet-unidentified, self-organized states in such confined systems of stiff achiral filaments, including spontaneous spiral smectic assemblies, faceted polyhedral and twisted bundle-like arrangements. Our results are quantified through the introduction of several order parameters and an unsupervised learning scheme for the localization of surface topological defects, and are in excellent agreement with field-theoretical predictions as well as classical elastic theories of thin rods and spherical shells.
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