Structural Transformation of Guanine Coordination Motifs in Water Induced by Metal Ions and Temperature

The transformation effects of metal ions and temperature on the DNA base guanine (G) metal–organic coordination motifs in water have been investigated by scanning tunneling microcopy (STM). The G molecules form an ordered hydrogen-bonded structure at the water–highly oriented pyrolytic graphite interface. The STM observations reveal that the canonical G/9H form can be transformed into the G/(3H,7H) tautomer by increasing the temperature of the G solution to 38.6 °C. Moreover, metal ions bind with G molecules to form G4Fe13+, G3Fe32+, and the heterochiral intermixed G4Na1+ metal–organic networks after the introduction of alkali-metal ions in cellular environment.