Salt-induced condensation in actin-DNA mixtures

¹ Department of Materials Science & Engineering, Department of Physics Department of Bioengineering, University of Illinois at Urbana-Champaign Urbana, IL 61801, USA
² Isaac Newton Institute for Mathematical Sciences - Cambridge, CB3 0EH, UK
³ Institute for Advanced Studies in Basic Sciences - Zanjan 45195-159, Iran
⁴ Department of Applied Mathematics, University of Leeds - Leeds LS2 9JT, UK

Corresponding author: gclwong@uiuc.edu

Received: 19 October 2004
Accepted: 24 March 2005

Abstract

Multivalent ions can induce condensation of like-charged polyelectrolytes into compact states, a process that requires different ion valence for different polyelectrolyte species. We have examined the trivalent ion-induced condensation behavior in binary anionic polyelectrolyte mixtures consisting of DNA coils and F-actin rods, and observe a micro-phase separation between the two polyelectrolytes into coexisting finite-sized F-actin bundles and DNA toroids. Further, by increasing the DNA volume fraction in the mixture, condensed F-actin bundles can be completely destabilized, leading to only DNA condensation within the mixture. We examine a number of possible causes and propose a model based on polyelectrolyte competition for ions.