Effect of magnesium ions on dielectric relaxation in semidilute DNA aqueous solutions

TL;DR

This study investigates how magnesium ions influence the dielectric relaxation and stability of semidilute DNA solutions, revealing enhanced electrostatic screening and increased double-stranded DNA stability compared to sodium ions.

Contribution

It provides new insights into Mg2+ interactions with DNA, showing their similar effects to Na+ but with increased stabilization of the double helix.

Findings

Mg2+ enhances electrostatic screening in DNA solutions

No denaturation bubbles detected at low DNA concentrations with Mg2+

Mg2+ increases stability of double-stranded DNA

Abstract

The effect of magnesium ion Mg2+ on the dielectric relaxation of semidilute DNA aqueous solutions has been studied by means of dielectric spectroscopy in the 100 Hz-100 MHz frequency range. De Gennes-Pfeuty-Dobrynin semidilute solution correlation length is the pertinent fundamental length scale for sufficiently low concentration of added salt, describing the collective properties of Mg-DNA solutions. No relaxation fingerprint of the DNA denaturation bubbles, leading to exposed hydrophobic core scaling, was detected at low DNA concentrations, thus indicating an increased stability of the double-stranded conformation in Mg-DNA solutions as compared to the case of Na-DNA solutions. Some changes are detected in the behavior of the fundamental length scale pertaining to the single molecule DNA properties, reflecting modified electrostatic screening effects of the Odijk-Skolnick-Fixman type. All results consistently demonstrate that Mg2+ ions interact with DNA in a similar way as Na1+ ions do, their effect being mostly describable through an enhanced screening.