Colloidal diffusion and viscoelasticity in blended solutions of supercoiled, ring and linear DNA

DNA, which has been widely studied as a model polymer system, naturally exists in different topological forms including linear, relaxed circular (ring) and supercoiled. While the reptation model can be used to understand molecular transport and interactions in systems of entangled linear polymers, it is far less successful in describing the dynamics of entangled supercoiled or ring polymers. The properties of entangled polymer blends of different topologies and polymer solutions near the critical entanglement concentration are also still poorly understood. Here, we address these problems by creating blended solutions of (1) entangled linear and ring DNA of varying blend ratios and (2) supercoiled and ring DNA of varying overall concentrations from the semidilute to entangled regime. We use particle-tracking methods to measure the diffusion of colloids embedded in these solutions as well as the corresponding linear viscoelastic properties. We reveal previously unobserved and unpredicted dependences of transport and viscoelasticity on the ratio of linear to ring DNA in blends as well as the overall solution concentration.