Force Distributions in Biopolymer Networks

细胞内生物聚合物网络为活细胞执行许多基本功能。它们稳定细胞结构，通过形成分子马达的轨迹促进定向运输，并使细胞运动。这些网络大多表现出高度非线性的力学响应，这在宏观尺度上得到了很好的研究；然而，关于单个细丝和网络结构的具体特性如何导致非线性的实验知之甚少。在这个项目中，将开发一种方法，在没有和有外部负载的情况下，同时可视化网络结构和通过网络的力分布。网络将使用最近开发的基于光学镊子的3D扫描探针显微镜成像，该显微镜使用小胶体颗粒作为传感器。由于颗粒的尺寸明显小于网络的典型网格尺寸，因此它可以在网络中自由扩散。驱动粒子运动的热作用力提供了一个天然的位置扫描仪。粒子位置之后是一个纳米精度和兆赫带宽的三维位置传感器。从粒子的三维位置直方图中提取网络结构和力分布。该项目将为生物聚合物网络如何从单个细丝的力学中获得高度非线性的力学特性以及这些网络如何分配力提供实验见解。该领域的研究人员将能够改进他们的模型和/或开发新的模型。所提出的活动产生的更广泛的影响将是开发一种新的显微技术，用于成像生物聚合物网络中的纳米结构和力分布。学生将接受最新开发的3D扫描探针显微镜的培训。这些数据对健康相关研究和新型材料的工程设计具有重要意义。此外，该项目是理想的整合研究和教育的本科生，研究生在一个跨学科的领域。

Intracellular biopolymer networks perform many essential functions for living cells. They stabilize the architecture of cells, facilitate directed transport by forming tracks for molecular motors, and enable cell motility. Most of these networks show a highly nonlinear mechanical response that is well studied on the macroscopic scale; however little is known experimentally about how specific properties of the individual filaments and the network architecture contribute to the nonlinearity. In this project a method will be developed for simultaneously visualizing the network architecture and the distribution of forces through the network, without and with an external load. Networks will be imaged with a recently developed 3D scanning probe microscope based on optical tweezers that use a small colloidal particle as a sensor. As the size of the particle is significantly smaller than the typical mesh size of the network, it can diffuse freely through the network. Thermal forces which drive the motion of the particle provide a natural position scanner. The particle position is followed by a 3D position sensor with nanometer precision and megahertz bandwidth. The network structure and force distribution are extracted from 3D position histograms of the particle. This project will provide experimental insight into how biopolymer networks obtain highly nonlinear mechanical properties from the mechanics of individual filaments and how these networks distribute forces. Researchers in the field will be able to refine their models and/or develop new ones. The broader impact resulting from the proposed activity will be the development of a novel microscopic technique for imaging the nanoscopic architecture and force distributions in biopolymer networks. Students will be trained in recently developed 3D scanning probe microscopy. The data will be important for health related research and engineering of novel materials. Additionally, the project is ideal for integrating research and education for undergraduate, and graduate students in an interdisciplinary field.