Elucidating the binding mechanism of 1,4-bis[(3-Piperidino)propanamido]anthracen-9,10-dione (1,4-BPAQ) to human telomeric G-quadruplexes: a multi-technique approach including spectroscopic, calorimetric and molecular docking insights.

Current research suggests that anthraquinone compounds have ability to interact with G4 DNA, leading to its stabilization and potential use as telomerase inhibitors in human cells. In light of this, a series of experiments to investigate the interaction between the compound 1,4-bis[(3-Piperidino)propanamido]anthracen-9,10-dione (1,4-BPAQ) and human telomeric DNA sequences in solutions rich in K and Na solutions was conducted. Employing various biophysical techniques and titration studies, it was observed that the binding of 1,4-BPAQ to G4 sequences resulted in notable changes in absorbance, including hypochromicity followed by hyperchromicity. Furthermore, extensive fluorescence quenching (94%) was accompanied by shifts in absorbance maxima, emission wavelength, and change in ellipticity (at 265 nm and 290 nm) was found in CD spectra. The data analysis indicated possible stoichiometries of 0.5:1 and 1:1 for the drug-quadruplex DNA complexes. Presence of a red shift suggested partial stacking between bases as primary interaction mode. Interestingly, binding affinity values were moderately higher in K-rich solution. In addition, a significant thermal stabilization effect of up to 25 °C in K environment, while no such stabilization was observed in Na solution upon ligand binding. Molecular docking studies revealed similar binding energies across all conformational variations, despite distinct contact patterns between the ligand and three different G4 DNA conformations (2HY9/2JPZ/143D). This research demonstrated the potential anticancer activity of 1,4-BPAQ through MTT assay, with apoptosis activity observed at lower concentrations (IC = 5.25 µM) against HepG2 cancer cells. These structural findings may hold significance in the context of drug development for anti-cancer therapies.