Hexammineruthenium(III) ion interactions with Z-­DNA

The hexamer duplex d(CGCGCA)·d(TGCGCG) was crystallized with hex­ammineruthenium(III) ions in an orthorhombic space group; the crystals diffracted to 1.54 Å resolution. Strong ion interactions with the adenine base induce a tautomeric shift from the amino to the imino form. Consequently, the A·T base pairing is disrupted. This structural study may be relevant to metal toxicity.