Cations in charge: magnesium ions in RNA folding and catalysis

► Mg2+ is a uniquely suited partner for RNA due to its ability to localize water molecules and pack RNA phosphate groups.
► Current and past work supports the ubiquity of Mg2+, both diffuse and coordinated, in RNA folding and catalysis.
► Review of recent literature reveals inaccuracy in the treatment of RNA-divalent cation interactions in theoretical models.
► A general conceptual framework of cation-RNA interactions is presented, which links thermodynamics and structure.
► Examples of new applications of previous methods and new methods for studying RNA-cation relationships are described.