Inversion of DNA charge by a positive polymer via fractionalization of the polymer charge

TL;DR

This paper demonstrates that charge inversion of DNA by polyelectrolytes occurs through fractionalization of the polymer charge into defects, a process that reduces self-energy and enables inversion even in worst-case neutral scenarios.

Contribution

It introduces the fractionalization mechanism as a novel explanation for DNA charge inversion, applicable to both linear and nonlinear polymers, and explores its universality across different systems.

Findings

Charge inversion occurs even when DNA is neutralized by PE charges.

Fractionalization of polymer charge reduces self-energy and causes inversion.

Mechanism applies to linear and nonlinear polymers, including dendrimers.

Abstract

Charge inversion of a DNA double helix by an oppositely charged flexible polyelectrolyte (PE) is widely used for gene delivery. It is considered here in terms of discrete charges of DNA. We concentrate on the worst scenario case when in the neutral state of the DNA-PE complex, each of the DNA charges is locally compensated by a PE charge and show that charge inversion exists even in this case. When an additional PE molecule is adsorbed by DNA, its charge gets fractionalized into monomer charges of defects (tails and arches) on the background of the perfectly neutralized DNA. These charges spread all over the DNA eliminating the self-energy of PE. Fractionalization leads to a substantial charge inversion of DNA. We show that fractionalization mechanism charge inversion works also for nonlinear polymers such as dendrimers. Remarkably, such fractionalization happens for adsorption of both PE or dendrimers on a two-dimensional charged lattice, as well. Relation of fractionalization to other mechanisms of charge inversion is discussed.