Binding of nickel(II) tetrakis(dimethylpyrazolium-4-yl)porphyrin to poly(dG-dC)2 and poly(dA-dT)2

Abstract

The interaction of nickel(II) complex of cationic porphyrins bearing five-membered rings, meso-tetrakis(1,2-dimethylpyrazolium-4-yl)porphyrinatonickel(II) (NiPzP) , with synthetic polynucleotides poly(dG-dC)2 and poly(dA-dT)2 has been characterized by viscometric, visible absorption, CD and MCD spectroscopic, and melting temperature measurements. The nickel(II) complex NiPzP is intercalated into poly(dG-dC)2 but outside bound to the major groove of poly(dA-dT)2. The binding constants of NiPzP to poly(dG-dC)2 and poly(dA-dT)2 are in the order of 106 M-1 and comparable to those of other reported cationic metalloporphyrins. The binding process of NiPzP to poly(dG-dC)2 and poly(dA-dT)2 is endothermic and entropically driven.