Thermodynamic study of interaction of TSPP, CoTsPc, and FeTsPc with calf thymus DNA

The interaction of two water soluble phthalocyanines, cobalt(II) 4,4 ,4 ,4 -tetrasulfo-phthalocyanine (CoTsPc) and iron(II) 4,4 ,4 ,4 -tetrasulfo-phthalocyanine (FeTsPc), and one water soluble porphyrin, tetra sodium meso-tetrakis(p-sulfophenyl)porphyrin (TSPP), with calf thymus DNA has been studied by UV-Vis spectroscopy at five different temperatures (20, 25, 30, 35, and 40 degrees C). The optical absorption spectra of these materials were analyzed to obtain binding constants and stoichiometries using SQUAD software. The results show that the best fitting corresponds to a 1 : 1 complex model between a base pair of DNA and these materials. All of the studied porphyrin and phthalocyanines showed strong electrolyte effect, and increasing NaCl concentration induced self-aggregation of these materials.