INTERACTION OF TOEPyP4 PORPHYRIN WITH A FORM OF DNA

Abstract

The peculiarities of binding the water-soluble meso-tetra-(4N-oxyethylpyridyl) porphyrin (TOEPyP4) with B-DNA and A-DNA have been studied by means of UV-VIS spectrophotometry and circular dichroism method. The binding constant (K_b) and stoichiometry (n) were determined based on the absorbance spectra for each DNA–porphyrin complex. The free energy, enthalpy and entropy of binding also were calculated using the values of K_b. A comparative analysis with TOEPyP4–B-DNA complex was performed. The obtained results show that the porphyrin interacts with B-DNA by way of intercalation at low relative concentrations (r = C_porf./C_DNA) and external binding at large values of r, whereas the interaction of TOEPyP4 with A-DNA occurs via the outside binding mode only.