DNA intercalation and photosensitization by cationic meso substituted porphyrins

Abstract

Several cationic porphyrins are known to bind to DNA by intercalate and outside binding modes. This study identifies the 2 and trans isomers of bis(N-methyl-4-phridiniumyl)diphenyl porphyrln as DNA intercalators based on evidence from a DNA topoisomerase I assay. Moreover, both isomers are shown to be potent photosensitizers of DNA, inducing multiple S1 nuclease sensitive breaks in the phosphodiester backbone. Porphyrin-lnduced photodamage in DNA was also shown to be quantitatively dependent upon ionic strength and to inhibit the action of restriction endonucleases. The results indicate that these porphyrins can be useful probes of DNA structure and have potential as DNA-targeted photosensitizers. © 1992 IRL Press at Oxford University Press.