Collaborative Research: Dynamics of Circular Macromolecules (DNA): From Single Molecules to Highly Entangled States

PI：McKenna，Gregory B. /Schroeder，Charles/安德森，RaeProposal Number：1603943/1604038/1603925该提案的目标是探索形成大环的聚合物分子的行为，而不是通常的线性聚合物分子。这样的聚合物，例如DNA分子，在加工或在溶液中流动时，其行为方式与线性分子不同，因为链中没有末端。这项工作的结果可以导致改进的聚合物材料，详细了解生物分子的行为和DNA测序的新技术。圆形聚合物是一种迷人的材料，几十年来一直激励着聚合物理论家和实验学家。由于没有链端，环形链的动力学与线性链有根本的不同。尽管最近的进展，但是，环状拓扑结构对聚合物动力学的影响仍然是该领域中一个关键的未解决的问题。在这项提案中，PI准备通过制备单分散且具有高拓扑纯度的环状和线性DNA分子，在我们的理解方面取得重大进展。该团队拥有合成和表征环状和线性DNA的专业知识，并将在比以前更广泛的浓度和分子量范围内研究这些材料的流变行为。提出了一种综合的方法，将包括宏观和微观流变学，单分子聚合物动力学和DNA合成，提供新的信息，线性和环状DNA的动力学。除了为理解它们的圆形对应物提供一个出发点之外，对线性纠缠DNA的平行研究将提供前所未有的数据，使用完全单分散的DNA样本直接测试爬行理论的预测，例如在极高的纠缠密度下的爬行行为的交叉。除了研究生的参与，教育活动提出了在所有三个合作机构，从代表性不足的少数民族学生参与得克萨斯理工大学，在伊利诺伊州和本科生参与大学圣地亚哥，主要是本科院校的高中教师参与。

PI: McKenna, Gregory B. / Schroeder, Charles / Anderson, RaeProposal Number: 1603943/ 1604038 / 1603925 The goal of this proposal is to explore the behavior of polymer molecules that form large ring, instead of the usual linear polymer molecules. Such polymers, example of which can be the DNA molecule, behave in a different way than linear molecules when processed or when they flow in a solution, because there are not ends in the chains. Results of this work can lead to improved polymer materials, to understanding in detail the behavior of bio-molecules and to new technologies for DNA sequencing. Circular polymers are fascinating materials that have inspired polymer theorists and experimentalists for decades. The dynamics of circular chains differ fundamentally from their linear counterparts due to the absence of chain ends. Despite recent progress, however, the effects of circular topology on polymer dynamics remain a key unresolved problem in the field. In this proposal, the PIs are poised to make major progress in our understanding by preparing circular and linear DNA molecules that are monodisperse and of high topological purity. The assembled team has the expertise to synthesize and characterize circular and linear DNA, and will study the rheological behavior of these materials over a wider range of concentrations and molecular weights than previously achieved. A comprehensive approach is proposed that will include macroscopic and micro-rheology, single molecule polymer dynamics, and DNA synthesis, to provide new information regarding the dynamics of linear and circular DNA. Beyond providing a point of departure for understanding their circular counterparts, the parallel study of linear entangled DNA will provide unprecedented data using perfectly monodisperse DNA samples to directly test predictions from reptation theory, such as the cross-over to reptative behavior at extremely high entanglement densities. In addition to graduate student participation, educational activities are proposed in all three collaborating institutions, ranging from underrepresented minority student involvement at Texas Tech, to high school teacher engagement at Illinois and undergraduate student participation at the U of San Diego, a mainly undergraduate institution.