CD spectra of acp3U (A), acb3U (B), cp3U (C), and hb3U (D) (dashed lines) in H2O are compared with U (solid lines) at room temperature. The molar ellipticities were normalized from concentrations of 10, 14, 37, and 17 mM, respectively, based on an extinction coefficient of 1.33 × 104 cm−1 M−1 at 260 nm. Each curve represents the average of five scans.