Figure 2.

(A) Absorbance properties of compound 4 in the presence of a quadruplex-forming oligonucleotide. The temperature of the sample was fixed at 20°C. Compound 4 (10 µM) was incubated in a 10 mM sodium cacodylate, 0.1 M KCl, pH 7.3 buffer. Increasing amounts of 22A (0.5–14 µM final strand concentration) were added. All titrations were performed in 1 cm pathlength quartz cuvettes. Unbroken line indicates reaction without 22A. (B) Fluorescence properties of compound 4 in the presence of a quadruplex-forming oligonucleotide. Fluorescence titration of 4 (400 nM concentration) by 28G (40 nM–1.8 µM). Excitation was set at 500 nm. The temperature of the sample was fixed at 20°C. Circles indicate emission spectrum of reaction without 28G. (C) Scatchard analysis of the fluorescence-binding data. The points were fitted with a line corresponding to 1:1 binding sites/oligonucleotide and an affinity of 1.15 × 10⁷ M^–1.