Influence of the position of the N-methyl group in tetra-(N-methylpyridyl)porphyrin on the features of its interaction with oligonucleotides. Spectral and thermochemical study.

We studied the influence of the position of the N-methyl group in tetra-(N-methylpyridyl)porphyrin on the features of its interaction with oligonucleotides using experimental physicochemical methods. Spectral methods detecting changes in the photophysical properties of chromophore ligands made it possible to prove the mechanism of binding to poly[d(AT) 2 ] and poly[d(GC) 2 ]. The thermochemical method made it possible to evaluate the structural consequences of ligation of oligonucleotides, and in the case of tetra-(3-N-methyl-pyridyl)porphyrin, to clarify the mechanism of binding to oligonucleotides. The combination of spectral and thermochemical analysis is useful for elucidating the structure of ligand complexes with synthetic and natural DNA. [Display omitted] • Spectral and thermochemical analysis of complexes of cationic ligands with oligonucleotides was carried out. • Changing the position of the N-methyl group of porphyrin changes the nature of its interaction with oligos. • Poly[d(AT) 2 ] and poly[d(GC) 2 ] bind ligands in different ways. • The informativeness of the estimation of the specific heat capacities of solutions in the study of DNA with ligands is shown. • The non-fluorescent EtBr minor groove poly[d(AT) 2 ] complex is AT-specific. [ABSTRACT FROM AUTHOR]