Interaction of water-soluble bridged porphyrin with DNA

Abstract

A water-soluble porphyrin dimer (Por Dimer) containing eight positive charges, bridged by 4,4′-dicarboxy-2,2′-bipyridine, has been synthesized. With Meso-tetrakis(N-methyl-pyridium-4-yl)porphyrin (H₂TMPyP) as the reference compound, the water-soluble porphyrin dimer was investigated for its interaction with DNA by absorption, fluorescence, and circular dichroism (CD) spectroscopy. The apparent affinity binding constant (K_app = 1.2 × 10⁶) of Por Dimer binding to CT DNA was measured by a competition method with ethidium bromide (EB) (that of H₂TMPyP was 6.9 × 10⁶). The cleavage ability of Por Dimer to pBR322 plasmid DNA was studied by gel electrophoresis. The results suggest that the binding modes of Por Dimer were complex and involve both intercalation and outside binding.

Keywords

porphyrin dimmer / DNA / the apparent affinity binding constant / photocleavage