Thermodynamic of Interaction between Some Water-Soluble Porphyrins and DNA by Titration Microcalorimetry

Abstract

In the present work, the interaction of three water soluble porphyrins, tetra (p-trimethyle) ammonium<br />phenyl porphyrin iodide (TAPP) as a cationic porphyrin, tetra sodium meso-tetrakis (p-sulphonato<br />phenyle) porphyrin (TSPP) as an anionic porphyrin and manganese tetrakis (p-sulphonato phenyl)<br />porphinato acetate (MnTSPP) as a metal porphyrin, with DNA have been studied by isothermal<br />titration microcalorimetry at 1 mM phosphate buffer, pH 7.0 and 25 °C. The values of binding<br />constant, entropy, enthalpy and Gibbs free energy changes for binding of the first MnTSPP, and first<br />and second TSPP and TAPP molecules were estimated from microcalorimetric data analysis. The<br />results represent that the process is both entropy and enthalpy driven and DNA induces selfaggregation<br />of the porphyrins. The results indicate that both columbic and hydrophobic interactions act<br />as self-aggregation driving forces for the formation of aggregates around DNA.