 |
Journal articles
Charge inversion, condensation and decondensation of DNA and polystyrene sulfonate by polyethylenimine
Abstract : We study the formation and structure of stable electrostatic complexes between polyanions
(DNA and poly(styrene-sulfonate)) and linear polyethylenimine. The charge ratio x of the mixture is
tuned by varying the concentration of the polycation at constant concentration of polyanion. In agreement
with recent theories, dynamic light scattering and electrophoretic mobility measurements show two distinct
regimes of weak and strong complexation. At low polycation concentration, negatively charged small complexes
involving a few polyanion chains are observed first. By further increasing x, these small complexes
condense at a precise charge ratio xc < 1 to form large anionic aggregates. The inversion of the charge
of the condensed complexes coincides with the maximum of complexation and precedes the dissolution
of the aggregates which occurs at a well-defined decondensation threshold xd > 1. Above xd, positively
charged complexes containing again a few overcharged polyanion chains are observed. The macroscopic
phase diagram is qualitatively well corroborated by AFM observation of the complexes. The influence of
entropic effects is probed by varying parameters like concentration, polycation molecular weight and ionic
strength. Structure of stable negatively charged complexes is investigated at higher concentration using
Small Angle Neutron Scattering. In the condensed regime, we observe large soluble bundles with sharp
interfaces where the local structure of the polyanions is preserved.
https://hal-univ-evry.archives-ouvertes.fr/hal-02321710
Contributor : Olek Maciejak <>
Submitted on : Monday, October 21, 2019 - 2:26:21 PM
Last modification on : Friday, April 10, 2020 - 5:17:58 PM
Contributor : Olek Maciejak <>
Submitted on : Monday, October 21, 2019 - 2:26:21 PM
Last modification on : Friday, April 10, 2020 - 5:17:58 PM
Links full text
