G4 DNA oligonucleotides were synthesized using β-cyanoethylphosphoramidite solid-phase chemistry (Applied Biosystem Expedite 8909), as described previously [36 (link)]. NMR experiments were performed on a Bruker AV-III-500-HD equipped with a BBFO Z-gradient cryoprobe. DNA samples were heated to 95 °C for 5 min, then cooled slowly for G4 formation. For the 1D 1H NMR experiments, samples contained 100–250 μM DNA in an appropriate buffer solution with 10% D2O for the lock. The titrations were performed by adding increasing amounts of the compounds to the DNA samples in solution.
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