[论文解读] Physics of Solutions and Networks of Semiflexible Macromolecules and the Control of Cell Function

Erwin Frey, Klaus Kroy+1 more|arXiv (Cornell University)|Aug 3, 1998

Cellular Mechanics and Interactions参考文献 6被引用 7

一句话总结

本文研究了细胞环境中半柔性生物聚合物（如肌动蛋白丝和微管）的物理特性，强调其机械与动态特性源于弹性和热涨落之间的平衡。通过统计力学和模拟方法，作者表明细胞骨架网络展现出对维持细胞形态和运动至关重要的独特机械响应，揭示了一类具有涌现生物功能的新型软物质系统。

ABSTRACT

Living cells are soft bodies of a characteristic form, but endowed with a capacity for a steady turnover of their structures. Both of these material properties, i.e. recovery of the shape after an external stress has been imposed and dynamic structural reorganization, are essential for many cellular phenomena. Examples are mechanical properties of tissue, cell motility, cell growth and division, and active intracellular transport. Numerous experiments in vivo and in vitro have shown that the structural element responsible for the extraordinary mechanical and dynamical properties of eukaryotic cells is the cytoskeleton, a three-dimensional assembly of protein fibers such as actin filaments and microtubules. In addition to those biopolymers various proteins with structural and regulatory functions have a major influence on the mechanical properties. At the relevant length-scales (a few microns at most) the building blocks of these biomaterials are very different from conventional polymeric material. In contrast to flexible polymers the persistence length is of the same order of magnitude as their total contour length or even larger. This implies that the physics of such a system is determined by a subtle interplay between energetic and entropic contributions. We review our present understanding of the physics of biopolymers using concepts from macromolecular and statistical physics complemented by computer simulation. These systems open up a new field of soft condensed matter research, which to date is only poorly understood but has a great potential for interesting new physical phenomena.

研究动机与目标

• 理解真核细胞中半柔性生物聚合物的机械与动态行为，特别是其与细胞形态和运动的关系。
• 识别弹性与热涨落之间的相互作用如何决定细胞骨架网络的物理特性。
• 弥合软凝聚 matter 物理学概念与活细胞中实验观测之间的鸿沟。
• 探讨结构蛋白和调节因子如何调控细胞骨架网络的机械响应。
• 建立一个理论与计算框架，用于研究生物系统中活跃的动态生物材料。

提出的方法

• 应用统计力学，对持久长度与 contour 长度相近的半柔性聚合物进行建模。
• 采用蠕虫状链（WLC）模型描述聚合物构象中的弹性与熵贡献。
• 在单根纤维机械分析中引入热涨落与弯曲刚度。
• 开发网络模型，以模拟交联半柔性纤维的集体机械响应。
• 整合计算机模拟，探索致密细胞骨架网络的涌现机械特性。
• 结合连续介质弹性理论与标度论证，描述在外力作用下网络层面的行为。

实验结果

研究问题

• RQ1 半柔性生物聚合物（如肌动蛋白丝）如何促进细胞骨架的机械稳定性和动态重塑？
• RQ2 热涨落与弯曲刚度在决定单根纤维机械响应中的作用是什么？
• RQ3 交联蛋白与网络结构如何影响细胞骨架网络的黏弹性特性？
• RQ4 半柔性聚合物的物理特性如何使细胞功能（如运动与分裂）成为可能？
• RQ5 在致密、活跃的半柔性纤维网络中，会涌现出哪些在柔性聚合物中不存在的物理现象？

主要发现

• 由于弯曲弹性与热涨落之间的竞争，半柔性生物聚合物表现出独特的机械响应，导致非高斯涨落与长程关联。
• 当持久长度与或大于 contour 长度时，系统表现出刚性但可弯曲的机械行为，与柔性聚合物显著不同。
• 细胞骨架网络由于半柔性纤维的几何约束与交联作用，表现出非线性弹性响应并增强抗变形能力。
• 热涨落显著影响单根纤维的机械稳定性，尤其在与细胞结构相关的微米尺度长度上。
• 理论建模与模拟表明，网络力学由纤维刚度、交联密度与热噪声之间的微妙平衡所主导。
• 本研究识别出一类新型软物质系统——活跃的半柔性生物聚合物网络——其涌现的物理现象支撑着关键的细胞功能。