Single-Molecule Imaging Reveals Topology Dependent Mutual Relaxation of Polymer Chains
Maram Abadi, Maged F. Serag, Satoshi Habuchi
Macromolecules 2015, 48, 6263-6271.
Abstract
The motion and relaxation of linear and cyclic polymers under entangled
conditions are investigated by means of a newly developed
single-molecule tracking technique, cumulative-area (CA) tracking. CA
tracking enables simultaneous quantitative characterization of the
diffusion mode, diffusion rate, and relaxation time that have been
impossible with a widely used conventional single-molecule localization
and tracking method, by analyzing cumulative areas occupied by the
moving molecule. Using the novel approach, we investigate the motion and
relaxation of entangled cyclic polymers, which have been an important
but poorly understood question. Fluorescently labeled 42 kbp linear or
cyclic tracer dsDNAs in concentrated solutions of unlabeled linear or
cyclic DNAs are used as model systems. We show that CA tracking can
explicitly distinguish topology-dependent diffusion mode, rate, and
relaxation time, demonstrating that the method provides an invaluable
tool for characterizing topological interaction between the entangled
chains. We further demonstrate that the current models proposed for the
entanglement between cyclic polymers which are based on cyclic chains
moving through an array of fixed obstacles cannot correctly describe the
motion of the cyclic chain under the entangled conditions. Our results
rather suggest the mutual relaxation of the cyclic chains, which
underscore the necessity of developing a new model to describe the
motion of cyclic polymer under the entangled conditions based on the
mutual interaction of the chains.