Interaction of Na⁺, K⁺, Mg²⁺ and Ca²⁺ counter cations with RNA

Alkaline and alkaline earth ions, namely Na+, K+, Mg2+ and Ca2+, are critical for the stability, proper folding and functioning of RNA. Moreover, those metal ions help to facilitate macromolecular interactions as well as the formation of supramolecular structures (e.g. the ribosome and the ribozymes). Therefore, identifying the interactions between ions and nucleic acids is a key to the better comprehension of the physical nature and biological functions of those biomolecules. The scope of this review is to highlight the preferential location and binding sites of alkaline and alkaline earth metal ions compensating the negatively charged backbone of nucleic acids and interacting with other electronegative centers, focusing on RNA. We summarize experimental studies from X-ray crystallography and spectroscopic analysis (infrared, Raman and NMR spectroscopies). Computational results obtained with classical and ab initio methods are presented afterwards.