Figure 4.

The interior structures along the central axis of the octaplex (G1-I-lowK). A schematic diagram of the I-motif of G-quartet (a), and its local structures, the stacked double G₅-quartets (b), water-mediated A₄-assembly (c), four G₃ residues paired with the A₆ residues of the anti-parallel strands (d), four ^IC₂ residues paired with the G₇ residues of the anti-parallel strands (e) and four G₁ residues paired with the C₈ residues of the anti-parallel strands (f). At both ends of the octaplex, phospahte groups are gathered around the center. Arrows colored in red and dark blue represent 5′–3′ directions of DNA strands. Light blue and gray spheres represent potassium cations and water oxygen atoms, respectively. Broken lines indicate possible hydrogen bonds.