Mg2+ ion effect on stability of double-stranded popynucleotide formed by polyriboinosinic and polyribocytidilic chains

TL;DR

This study investigates how Mg2+ ions influence the thermal stability of double-stranded polyIpolyC, revealing a complex interaction that affects melting temperature and structural state transitions under near-physiological conditions.

Contribution

It provides new insights into the Mg2+ ion's role in modulating polynucleotide stability and structural transitions, highlighting a critical concentration where behavior changes.

Findings

Mg2+ increases melting temperature (Tm) initially

A critical Mg2+ concentration causes Tm to decrease

Mg2+ induces a structural transition in polyIpolyC

Abstract

Mg2+ effect on the thermal stability of the double-stranded polynucleotide polyIpolyC (IC) under conditions close to physiological ones (0.1M Na+, pH7) was studied by the differential UV spectroscopy. The initial increase of the ion concentration ([Mg2+]) leads to the increase of the melting temperature (Tm) and to the decrease of the absorption hyperchromicity value that is caused by the helix-coil transition (hmax). Mg2+ interacts to p-electrons of hypoxanthine or cytosine rings (cation-p-interaction). When [Mg2+] reaches a critical value of about 10-4 M, Tm decreases and hmax increase to values close to one observed in the absence of magnesium. It is supposed that at [Mg2+]=[Mg2+]cr IC transits into a new structural state. With [Mg2+>[Mg2+]cr Tm increases again and hmax slowly decreases. Key words: polynucleotides, thermal stability, metal ions.