Data on secondary structures and ligand interactions of G-rich oligonucleotides that defy the classical formula for G4 motifs.

The data provided in this article are related to the research article "The expanding repertoire of G4 DNA structures" [1]. Secondary structures of G-rich oligonucleotides (ONs) that represent "imperfect" G-quadruplex (G4) motifs, i.e., contain truncated or interrupted G-runs, were analyzed by optical methods. Presented data on ON structures include circular dichroism (CD) spectra, thermal difference spectra (TDS) and UV -melting curves of the ONs; and rotational relaxation times (RRT) of ethidium bromide (EtBr) complexes with the ONs. TDS, CD spectra and UV-melting curves can be used to characterize the topologies and thermal stabilities of the ON structures. RRTs are roughly proportional to the hydrodynamic volumes of the complexes and thus can be used to distinguish between inter- and intramolecular ON structures. Presented data on ON interactions with small molecules include fluorescence emission spectra of the G4 sensor thioflavin T (ThT) in complexes with the ONs, and CD-melting curves of the ONs in the presence of G4-stabilizing ligands N-methylmesoporphyrin IX (NMM) and pyridostatin (PDS). These data should be useful for comparative analyses of classical G4s and "defective"G4s, such as quadruplexes with vacancies or bulges.