Figure 3.

The structure formed under H-DNA/triplex-forming conditions is stable in the presence of K⁺, except when heated. Using CD spectroscopy, the DNA structure annealed under triplex-forming conditions (100 mM Na⁺, 10 mM Mg²⁺) remained unperturbed with increasing concentrations of K⁺ for both the (A) R1 and (D) R2 motifs. When DNA was annealed in the presence of 160 mM K⁺, competing with the triplex-forming conditions (100 mM Na⁺ + 10 mM Mg²⁺), the triplex signature at 210 nm was diminished, (B) R1 and (E) R2. CD spectra of (C) R1 and (F) R2 when annealed under triplex-forming conditions (black) or 110 mM K⁺ (red) alone. The CD spectra obtained in the presence of competing conditions (B and E) approaches that of the signature under 110 mM K⁺ alone (C and F, red).