Fig. 2.

(A) Ten lowest-energy superimposed solution structures of Z-G4. (B) Crystal structure of Z-G4. The electron density corresponds to the final 2mFo-DFc map contoured at 1.0 σ. (C) Ribbon view of the crystal structure of Z-G4. Anti and syn guanine bases are colored in cyan and magenta, respectively; thymine bases are in orange; phosphate backbone are in gray; phosphate oxygens are in red; and O4′ oxygens are in yellow. Potassium ions and water molecules are colored in purple and red, respectively. (D) Schematic structure of Z-G4. Arrows represent the 5′-to-3′ strand progression.