Nucleic acids have an important range of interactions with Mg. The binding of Mg to DNA and RNA stabilises structure; this can be observed in the increased melting temperature (T) of double-stranded DNA in the presence of Mg. In addition, ribosomes contain large amounts of Mg and the stabilisation provided is essential to the complexation of this ribo-protein. A large number of enzymes involved in the biochemistry of nucleic acids bind Mg for activity, using the ion for both activation and catalysis. Finally, the autocatalysis of many ribozymes (enzymes containing only RNA) is Mg dependent (e.g. the yeast mitochondrial group II self splicing introns).
Magnesium ions can be critical in maintaining the positional integrity of closely clustered phosphate groups. These clusters appear in numerous and distinct parts of the cell nucleus and cytoplasm. For instance, hexahydrated Mg ions bind in the deep major groove and at the outer mouth of A-form nucleic acid duplexes.