Assessing Roles of Cations in G-Quadruplex-Based Nanowires by NMR

G-quadruplexes are uncanonical DNA structures exhibiting promising characteristics for designing DNA-based nanomaterial and nanodevices. The present NMR study addresses the role of cations, the requiring factor for G-quadruplex formation, in long G-quadruplexes. We investigated d(TG(8)T)(4) and its interactions with (NH4+)-N-15 ions, which provided insights into cation localization within a model of G-quadruplex-based nanowire exhibiting eight stacked G-quartets. All interquartet cavities along the central channel were completely occupied by cations. Determined cation exchange rates demonstrated that (NH4+)-N-15 ions move faster from the binding site between two G-quartets, both composed of all guanine residues in an antiglycesidic conformation with respect to the binding site between all-syn/all-anti G-quartets. These results not only extend previous findings from calculated models of long G-quadruplexes and experimental studies on shorter G-quadruplexes but also establish correlation of kinetics of cation movement with the mode of G-quartet stacking, a potentially valuable relation for understanding G-quadruplex-type specific electronic properties.