Interactions of meso-tetra-(4-N-oxyethylpyridyl) porphyrin, its 3-N analogand their metallocomplexes with duplex DNA

Interactions of meso-tetra-(4-N-oxyethylpyridyl) porphyrin (TOEPyP(4)), its 3-N analog (TOEPyP(3)) and their Co, Cu, Ni, Zn metallocomplexes with dupl ex DNA have been investigated by uv/visible absorbance and circular dichros im spectroscopies. Results reveal the interactions of these complexes with duplex DNA are of two types. (1) External binding of duplex DNA by metallop orphyrins containing Zn and Co, and (2) Binding of duplex DNA both external ly and internally (by intercalation) by porphyrins not containing metals, a nd metalloporphyrins containing Cu and Ni. Results indicate that (4N-oxyeth ylpyridyl) porphyrins intercalate more preferably in the structure of duple x DNA and have weaker external binding than 3N-porphyrins.