Hamid Dezhampanah - Corresponding Author Address: Hamid Dezhampanah, Laboratory of physical Chemistry, Department of Chemistry, Faculty of science, University of Guilan, P. O. Box ۴۱۳۳۵-۱۹۱۴, rashat ۰۰۹۸, Iran.

Interaction of tetrakis (N, N´,N´´,N´´´-tetramethyl tetra-3,4-pyridino) porphyrazine copper (II) ([Cu (II) 3,4-tmtppa]4+) with calf thymus DNA has been studied in 1mM aqueous phosphate buffer of pH 7.0, by optical absorption spectroscopy. The appearance of hypochromicity of less than 10% and bathochromicity shift of Δ l £ 2 nm in UV-vis spectra of [Cu (II) 3,4-tmtppa]4+, due to interaction with DNA, represent the minor outside groove binding mode without any stack aggregate formation. The thermodynamic of the binding of [Cu (II) 3, 4-tmtppa]4+-DNA also has been studied. The binding constant (K) was obtained by analysis of the optical absorption spectra of the complex at various DNA concentrations using SQUAD software. The value of K was estimated to be 2.34 ´ 105 ± 0.06M-1 at 25˚C. The thermodynamic parameters were calculated by vanُ t Hoff equation. The enthalpy and entropy changes were 41.83 ± 3.28 kJ/mol and 242.08 ± 9.88 J/mol.K at 25˚C, respectively. The results indicate that the process is entropy driven and suggest that hydrophobic interactions are the main driving forces for the complex formation.

calf thymus DNA, resonance light scattering, copper porphyrazine