Figure 1.

(a) Schematic structure of the (3 + 1) G-quadruplex platform used in this study. Anti and syn guanines are shown in light gray and dark gray, respectively. (b) Chemical schematic of a modified guanine tetrad with a centrally located K⁺ ion. The C8-modified guanine derivative is depicted by a modification group R. (c–g) The chemical schematics of guanine and the guanine derivatives explored in this work: (c) guanine, (d) 8-bromo-guanine, (e) 8-O-methyl-guanine, (f) 8-amino-guanine, and (g) 8-oxo-guanine.