Figure 1.

Chemical structure of telomestatin and folding pattern of the three G-quadruplexes studied here. [TG₄T]₄ adopts a parallel fold and can incorporate three ammonium ions between its four G-quartets [21], the 4-repeat telomeric sequence (T₂AG₃)₄ adopts an intramolecular antiparallel fold in ammonium acetate and incorporates up to two ammonium ions [22], and the Pu22myc promoter sequence GAG₃TG₄AG₃TG₄A₂G adopts a predominantly parallel fold in ammonium acetate and incorporates two ammonium ions [23].