Spectroscopic investigation on the interaction of copper porphyrazines and phthalocyanine with human telomeric G-quadruplex DNA

•Interaction of Cu(PcTs), [Cu(2,3-tmtppa)]4 + and [Cu(3,4-tmtppa)]4 + with telomeric G-quadruplex DNA is investigated.•Interaction of the porphyrazines is stronger than the phthalocyanine.•K+ form of G4 converges to the Na+ form after binding to the porphyrazines.•Porphyrazines could be suitable candidates for investigations about inhibition of telomerase.

The G-quadruplex DNA is a novel target for anticancer drug discovery and many scientific groups are investigating interaction of small molecules with G-quadruplex DNA to discover therapeutic agents for cancer. Here, interaction of a phthalocyanine (Cu(PcTs)) and two tetrapyridinoporphyrazines ([Cu(2,3-tmtppa)]4 + and [Cu(3,4-tmtppa)]4 +) with Na+ and K+ forms of human telomeric G-quadruplex DNA has been investigated by spectroscopic techniques. The results indicated that interaction of the cationic porphyrazines is remarkably stronger than the anionic phthalocyanine and they presumably bind to the G-quadruplex DNA through end-stacking. Fluorescent intercalator displacement assay implied the displacement ability of the complexes with thiazole orange. In addition, circular dichroism spectra of both quadruplex forms converge to the Na+ isoform after binding to the porphyrazines. In conclusion, the porphyrazines as the complexes that bind to the G-quadruplex DNA, could be suitable candidates for further investigations about inhibition of telomerase enzyme.

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