NMR-spectroscopic investigation of the complex between tetraazoniapentapheno[6,7-h]pentaphene and quadruplex DNA Tel26

Abstract

The association of organic ligands with nucleic acids is an important event in biology and in medicine because it may affect the regular function of the DNA. In this context, quadruplex DNA (G4-DNA) has gained special attention as a promising drug target. In this contribution, the complex formation between the tetracationic tetraazoniapentapheno[6,7-h]pentaphene and the oligonucleotide Tel26 [d(A₃G₃T₂AG₃T₂AG₃T₂AG₃A₂)], which forms a (3+1) antiparallel/parallel structure (hybrid-1), was investigated by ¹H-NMR spectroscopy. The analysis of the different developments of shifts and line broadening of the imino proton signals of the guanine residues revealed a preferential terminal π stacking of the ligand. Considering accessibility and steric constraints of the possible binding sites it is proposed that the ligand may stack on top of the A3–A9–A21 triplet at one terminal end of the quadruplex, rather than on a G4-quartet.