Nucleic Acids Research, 1992, Vol. 20, No. 6 1315-1319
© 1992
CHEMISTRY |
DNA intercalation and photosensitization by cationic meso substituted porphyrins
Experimental Biology, Roswell Park Cancer Institute Elm & Carlton Streets, Buffalo, NY 14263, USA 1Biophysics Department, Roswell Park Cancer Institute Elm & Carlton Streets, Buffalo, NY 14263, USA
Received December 4, 1991. Revised February 21, 1992. Accepted February 21, 1992.
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.