The observation that G-quadruplex structures exist in nucleic acid sequences associated with cancers has generated substantial interest in G quadruplexes as potential antineoplastics. The G quadruplex, with planar G tetrads, is an appealing nucleic acid drug target, as the G tetrad is structurally distinct from the Watson-Crick base pair. High-affinity G-quadruplex ligands have begun to show medicinal promise, although the connection between G-quadruplex binding and in vivo activity might not always be obvious. Here, we report a novel, high-affinity, high-selectivity scaffold for G-quadruplex ligands: the azacyanines. We present data on the G-quadruplex and Watson-Crick dsDNA binding affinity of these ligands. Additionally, we present data related to the binding site for these ligands on the G quadruplex formed by the human telomeric DNA repeat in potassium solution
