Complexes of cationic non-symmetric porphyrin with synthetic and natural nucleic acids

Porphyrins, owing to their unique physicochemical properties, hold great potential as candidates for the synthesis of new materials and active pharmaceutical drugs. The introduction of functional groups into porphyrin structures enables the creation of novel compounds with finely tuned structural and optical properties, as well as complex-forming abilities. In this study, spectral and thermochemical investigations were conducted to explore the complex formation of 5-[4′-(N-methyl-1″,3″-benzoimidazol-2″-yl)phenyl]-10,15,20-tris-(N-methyl-3′-pyridyl)porphyrin triiodide with synthetic (poly[d(GC)2], poly[d(AT)2]) and natural (ssDNA, ctDNA) nucleic acids. It was observed that the porphyrin forms complexes with poly[d(AT)2] and ssDNA, localized within the major groove of the biopolymer. Additionally, the porphyrin forms multiple intercalation complexes with varying geometries when interacting with poly[d(GC)2] and ctDNA. These findings demonstrate a new potential for enhancing the selective binding of ligands with nucleic acids (NA). Moreover, the study highlights the methodological aspect that establishing the type of formed complexes based on ligands’ electronic absorption spectra, known as “fingerprints,“ may lead to incorrect conclusions.