Collaborative Research: Mechanics and Structural Polymorphism of Bacterial Flagellar Assemblies

该奖项的目标是组装自我限制的结构和材料，这些结构和材料可以根据不断变化的环境条件（如温度、溶液性质或施加的力）进行大规模的结构变化。该项目将利用细菌鞭毛作为基本构建块，鞭毛是一种螺旋聚合物，可作为纳米级弹簧，并表现出在合成材料中不常见的非单调力-延伸关系。为了实现这一目标，该项目将利用实验、计算和理论工具的结合，在三个层次上阐明鞭毛基材料的行为。首先，该项目将描述和模拟单个鞭毛的机制，以及嵌合鞭毛，以实现新的多态开关反应。第二，将是产生，表征和控制吸引的相互作用之间的鞭毛对。最后，这些吸引的相互作用将被用来组装由数千鞭毛组成的鞭毛束或绳。这项研究有望产生具有良好控制力学和结构性能的纳米结构、响应性纤维材料，其中单个单体单位在埃尺度上的构象变化协同级联跨越多个长度尺度，从而在毫米尺寸的材料中产生宏观力学变化。该项目的教育和研究部分将通过扩大REU计划来整合，为参加布兰代斯大学和马萨诸塞大学夏季研究的本科生举办一年一度的“理论与实验”研讨会，让新手研究人员了解软材料理论和实验研究的独特和互补方法。此外，还将与宾夕法尼亚大学设计学院的建筑师、设计师和讲师Jennifer Sabin合作，探索复杂生物聚合物组装图案与最先进的纺织品设计和制造过程之间的关系。

The objective of this award is to assemble self-limited structures and material that undergo large-scale structural changes in response to changing environmental conditions such as temperature, solution properties, or imposed force. As a basic building block the project will utilize bacterial flagella, a helical polymer which acts as a nanoscale spring and exhibits non-monotonic force-extension relationship that is not commonly found in synthetic materials. To achieve the goal the project will utilize a combination of experimental, computational and theoretical tools to elucidate the behavior of flagella based materials at three levels of hierarchy. First, the project will characterize and model the mechanics of individual flagella, as well as chimeric flagella engineered to achieve new polymorphic switching responses. Second, will be to generate, characterize, and control attractive interactions between a pair of flagella. Finally, these same attractive interactions will be used to assemble flagellar bundles or ropes consisting of thousands of flagella. This study holds the promise to generate nano-structured, responsive fibrous materials with well-controlled mechanical and structural properties, in which conformational changes of individual monomeric units at Angstrom scales cooperatively cascade across multiple lengthscales to produce macroscopic mechanical changes in millimeter-sized materials. The educational and research component of this project will be integrated by expanding an REU program to hold an annual "Theory Meets Experiment" symposium for undergraduates participating in summer research at Brandeis and University of Massachusetts, to expose novice researchers to the distinct and complementary methods of theoretical and experimental research in soft materials. In addition, a partnership will be explored with Jennifer Sabin, architect, designer, and lecturer at the University of Pennsylvania School of Design in order to explore the relationship between complex biopolymer assembly motifs and a state-of-the-art textile design and fabrication process.