Fig. 3.

Structure of the dG(TGGAA)₂C duplex. (A) Ribbon representation of the duplex structure (Left) and a schematic of important interactions between the two strands (Right). The two strands are colored in gray (G1 to C12, from top to bottom) and yellow (G13 to C24, from bottom to top). Guanines are in green, thymines are in purple, cytosines are in cyan, and adenines are in red. Close-up view of the molecular structure of the dG(TGGAA)₂C at the (B) G1 to A6 and (C) G13 to A18 terminal base pair steps. Water molecules and Co(II) ions are shown as light blue and pink balls, respectively. The dashed line represents direct hydrogen bonds and coordinated bonds. (D) Structural detail of the Co(II) (or water)–DNA interactions. (E) Structural detail of the interactions involving hydrogen bonds of mismatched G:A pairs with and without water stabilization.