Interaction of Monoheteryl Substituted Cationic Porphyrins with Synthetic Nucleic Acids

The complex formation of monoheteryl-substituted tricationic porphyrins with representative polynucleotides (poly[d(GC)2] and poly[d(AT)2]) was studied. It has been spectrally established that the studied porphyrins form intercalation complexes of different geometry with poly[d(GC)2]: 1) intercalation between the nitrogenous bases of the porphyrin macroring; 2) intercalation between the nitrogenous bases of the monoheteryl substituent. The studied porphyrins form complexes with the poly[d(AT)2] groove. The DSC method was used to analyse the temperature dependences of the specific heat capacities of solutions of the initial reagents and complexes of porphyrins with poly[d(GC)2] and poly[d(AT)2]; it was found that the proportion of structural changes in the analysed solution associated with intercalation significantly exceeds the similar value during the formation of the complex in the groove of the nucleic acid. The results obtained demonstrate a new potential opportunity to increase the selectivity of binding of ligands to nucleic acids.