CD spectra of C-rich telomeric DNA circles having the sizes 36, 42, 48, 54, and 60 nt (A–E), at low (pH = 5.0; closed triangles) and high (pH = 7.0; open circles) pH. The measurements were carried out in buffered solution (10 mM PIPES, pH 7.0 or 50 mM NaOAc, pH 5.0) at 1 μM concentration.