Scheme 1.
Influence of the temperature on the formation of (rUG4U)4 and (TGnT)4 quadruplexes in 0.125 M Li+ (green), Na+ (red) and K+ (blue). Canonical quadruplex formation prevails in the temperature ranges indicated by heavy full lines. Strand association results predominantly in kinetically trapped mismatched structures in the temperature ranges indicated by heavy dotted lines. The thin colored lines indicate the temperature ranges where no data are available. The formation of mismatched structure increases with the G tract length, at low temperature and in K+ solution.