COLLABORATIVE RESEARCH: Dynamics of Circular Macromolecules (DNA): From Single Molecule to Highly Entangled States

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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.