Active Matter based on Varying Topologies of DNA

Active soft materials have been widely investigated in recent years. However, using polymer topology as a route to actively alter the viscoelastic properties of a material remains largely unexplored. Here, we confer non-equilibrium dynamics into concentrated DNA solutions by using enzymes to alter the topology of DNA molecules. Specifically, we incorporate restriction endonucleases into concentrated solutions of supercoiled DNA to slowly convert them to linear and relaxed circular topologies. We use particle-tracking microrheology to measure how the viscoelastic properties of the materials change over time during enzymatic activity. We use gel electrophoresis to map the viscoelastic properties to the distribution of topologies of the DNA molecules. We examine the effect of enzyme and DNA concentrations as well as DNA length on the active material properties. Our initial results show that during enzymatic conversion from supercoiled to linear topology, DNA solutions monotonically increase in viscosity. However, the time dependence of this trend is quite noisy due to large non-equilibrium fluctuations in the distribution of DNA topologies.