Effects of Monovalent and Divalent Cations on the Rheology of Entangled DNA

TL;DR

This study explores how different cations influence the flow and deformation behavior of entangled DNA solutions, revealing distinct effects of monovalent and divalent ions on DNA interactions and network formation.

Contribution

It provides new insights into how cation valency and concentration modulate DNA rheology, highlighting the role of ionic bridging and stabilization mechanisms.

Findings

Monovalent cations moderately increase viscoelasticity by stabilizing DNA monomers.

Divalent cations induce complex effects, including DNA-DNA bridging.

Results are relevant for DNA-based materials and biological systems.

Abstract

In this paper we investigate the effects of varying cation valency and concentration on the rheology of entangled lambda DNA solutions. We show that monovalent cations moderately increase the viscoelasticty of the solutions mainly by stabilising linear condensation of lambda DNA ``monomers'' via hybridisation of their sticky ends. On the contrary, divalent cations have a far more complex and dramatic effect on the rheology of the solution and we observe evidence of inter-molecular DNA-DNA bridging by Mg2+. We argue that these results may be interesting in the context of dense solutions of single and double stranded DNA, e.g. in vivo or in biotechnology applications such as DNA origami and DNA hydrogels.