First derivatives of the UV melting profiles of hTel24-NMR (A), ST-DNA (B), p(dA)•2p(dT) (C), p(rA)•p(dT) (D), and p(rA)•2p(rU) (E) in the absence (red) and presence of HXDV (black) or HXLV-AC (green). The melting profiles for the quadruplex formed by hTel24-NMR were acquired at 295 nm, while the melting profiles for the nucleic acid duplexes and triplexes were acquired at 260 nm. For the melting profiles of the triplexes, HG denotes the Hoogsteen transition of the triplex into duplex plus single strand, while WC denotes the Watson-Crick transition of the remaining duplex into single strands.