Non-monotonic density dependence of the diffusion of DNA fragments in low-salt suspensions

TL;DR

This study reveals that DNA fragment diffusion in low-salt suspensions exhibits a non-monotonic dependence on concentration due to electrostatic and hydrodynamic interactions, highlighting complex behavior in charged polymer solutions.

Contribution

It demonstrates the non-monotonic diffusion behavior of DNA fragments caused by electrostatic and hydrodynamic coupling in low-salt conditions, a novel insight into DNA dynamics.

Findings

Diffusion varies non-monotonically with DNA concentration.

Electrostatic and hydrodynamic interactions are strongly coupled.

Far-field hydrodynamic interactions dominate at large separations.

Abstract

The high linear charge density of 20-base-pair oligomers of DNA is shown to lead to a striking non-monotonic dependence of the long-time self-diffusion on the concentration of the DNA in low-salt conditions. This generic non-monotonic behavior results from both the strong coupling between the electrostatic and solvent-mediated hydrodynamic interactions, and from the renormalization of these electrostatic interactions at large separations, and specifically from the dominance of the far-field hydrodynamic interactions caused by the strong repulsion between the DNA fragments.