In the present work, the interaction of three water soluble porphyrins, tetra (p-trimethyle) ammoniumphenyl porphyrin iodide (TAPP) as a cationic porphyrin, tetra sodium meso-tetrakis (p-sulphonatophenyle) porphyrin (TSPP) as an anionic porphyrin and manganese tetrakis (p-sulphonato phenyl)porphinato acetate (MnTSPP) as a metal porphyrin, with DNA have been studied by isothermaltitration microc...