Figure 1

Schematic representation of a G-tetrad and different conformations of G-quadruplexes; ORTEP views of dptmp and 1.
(a) a G-tetrad consists of four guanines, (b) the wild-type 22-mer crystal with K+ (parallel structure, PDB ID: 1KF1), (c) the modified 20-mer in K+ solution (mixed-type “(3 + 1) hybrid” structure, PDB ID: 2KZD), (d) the wild-type 22-mer in Na+ solution (basket-type “(2 + 2) hybrid” structure, PDB ID: 143D).