Micro- and Nano-Mechanics of Active Biopolymer Networks

该奖项的研究目标是开发新的解析和数值方法，以研究纤维力学和网络结构与半柔性网络的集体弹性性质之间的复杂关系。半柔性网络是刚性聚合物的交联体。它们从根本上不同于更好地理解的聚合物材料，后者是现代合成化学的常见产品。在外加应力作用下，半柔性网络可以在组成纤维的拉伸和弯曲过程中存储弹性能量，而由高度柔性的高分子链组成的传统聚合物网络只在纤维拉伸中存储弹性能量。半柔性网络最常见的例子是活细胞的细胞骨架。坚硬的蛋白质丝(F-肌动蛋白)被交叉连接，形成一个承压框架，使细胞具有机械刚性。最近的实验表明，网络结构和分子马达作用的微小变化可以导致这些F-肌动蛋白网络的弹性发生显着变化。本研究将详细探讨这些网络结构的变化和非平衡稳态(通过分子马达的作用)如何导致网络的大的力学变化。成功完成这项工作的好处之一是更深入地理解建造一类新的轻质、机械可调材料的设计原则。该理论还将解决新的仿生材料设计方法，即通过修改材料的非平衡稳态，利用内源马达的作用来调整机械性能。这样的研究将能够创造出机械性能可以精确控制的新的生物兼容材料。这些材料可能会在促进伤口愈合方面得到应用。最后，这项研究将有助于培养从事物理、生物和工程相结合的学生/博士后。

The research objective of this award is to develop new analytic and numerical approaches to examine the complex relationship of filament mechanics and network structure to the collective elastic properties of semiflexible networks. Semiflexible networks are cross-linked aggregates of stiff polymers. They are fundamentally different from the better understood polymeric materials that are the usual products of modern synthetic chemistry. Under applied stress semiflexible networks can store elastic energy in both the stretching and bending of the constituent filaments, while traditional polymer networks, which are composed of highly flexible polymer chains, store elastic energy only in filament stretching. The most common example of a semiflexible network is found in the cytoskeleton of living cells. There stiff protein filaments (F-actin) are cross-linked to form a stress-bearing framework that gives the cell its mechanical rigidity. Recent experiments have shown that small changes in network architecture and in the action of molecular motors can lead to significant changes the elasticity of these F-actin networks. This research will explore in detail how these changes in network structure and non-equilibrium steady-state (via the action of the molecular motors) leads to large mechanical changes of the network. Among the benefits of the successful completion of this work will be a deeper understanding of the design principles for building a new class of light-weight, mechanically tunable materials. The theory will also address new biomimetic approaches to materials design that use the action of endogenous motors to tune mechanical properties through the modification of the materials non-equilibrium steady-state. Such research will enable the creation of new bio-compatible materials whose mechanical properties can be precisely controlled. These materials may find applications in the promotion of wound healing. Finally, this research will assist the training of students/postdocs working at the interface of the physics, biology, and engineering.