Nucleic Acids Research, 1985, Vol. 13, No. 1 167-184
© 1985
Articles |
A comparative study of the interaction of 5,10,15,20-tetrakis (N-methylpyridinium-4-yl)porphyrin and its zinc complex with DNA using fluorescence spectroscopy and topoisomerisation
Department of Chemistry, University of Dublin, Trinity College Dublin 2, Ireland Department of Genetics, University of Dublin, Trinity College Dublin 2, Ireland
Received October 26, 1984. Revised December 7, 1984. Accepted December 7, 1984.
Binding of 5,10,15,20-tetrakis(N-methylpyridiniutn-4-yl)porphyrin (H2TMPyP4+) and its zinc complex (ZnTMPyP4+) to DNA is demonstrated by their coelectrophoresis and by absorption and fluorescence spectroscopic methods. Topoisoinerisation of pBR322 DNA shows that H2TMPyP4+ unwinds DNA as efficiently as ethidium bromide showing that it intercalates at many sites. ZnTMPyP4+ may cause limited unwinding. Marked changes in the fluorescence spectra of the porphyrins are found in the presence of DNA. The fluorescence intensity of either H or ZnTMPyP4+ is enhanced in the presence of poly (d(AT)), whereas in the presence of poly (d(GC)) the fluorescence intensity of ZnTMPyP4+ is only slightly affected and that of H2TMPyP4+ markedly reduced. Both the porphyrins photosensitise the cleavage of DNA in aerated solution upon visible light irradiation.