Figure 1.

(A) An ideal structure of an unmodified DNA three-way junction (3WJ) motif. Drawn based on a crystal structure (PDB ID: 1DRG) reported by Baldwin et al. (B) Construction of a DNA three-way junction motif bridged by a metal complex. (C) Molecular design of bipyridine (bpy)-modified nucleotides. (D) The structure of a representative metal complex formed at the core of the 3WJ. (E,F) Base sequences of DNA strands forming metal-bridged 3WJs. U represents U_bpy-1 or U_bpy-2. C represents C_bpy. (G) Melting temperatures of the 3WJs in the absence and in the presence of Ni^II ions. [Ni^II]/[3WJ] = 1.1 (for C_bpy) or 1.0 (for the others). Note that the measurement conditions were slightly different form each other. For the details, see the original papers (Duprey et al., 2013; Stubinitzky et al., 2014; Takezawa et al., 2016). (H) Proposed structure of the Ni^II(bpy)₃ complex at the core of the U_bpy-1-containing 3WJ. Only Λ-isomer is shown. Reproduced from a literature (Duprey et al., 2013) with permission from Wiley-VCH.