The interaction of $\mathrm{Аg}$-containing porphyrins with DNA at high ionic strength

UV-VIS spectrophotometry and circular dichroism (CD) methods were applied to study the binding of DNA with three novel $\mathrm{Аg}$-containing porphyrins meso-tetra($4N$-allylpyridyl) $(\mathrm{AgTAlPyP4})$, meso-tetra($4$N-butylpyridyl) $(\mathrm{AgTButPyP4})$ and meso-tetra($4N$-oxyethylpyridyl) $(\mathrm{AgTOEtPyP4})$ at high ionic strength. The binding constant $K_b$ and stoichiometry n were determined from binding isotherms for each ligand–DNA complex. The Gibbs free energy, enthalpy and entropy of binding also were calculated using the values of Kb. Obtained results show that these porphyrins associate with the duplex DNA via outside binding mode.