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.