Study of interaction between kaempferol-Eu3+ complex and DNA with the use of the Neutral Red dye as a fluorescence probe

The interaction between kaempferol-Eu3+ complex and calf thymus DNA was investigated in physiological buffer (pH 7.4) using the Neutral Red (NR) dye as a spectral probe by UV-vis absorption and fluorescence spectroscopy, as well as viscosity measurements and DNA melting techniques. The results indicated that kaempferol-Eu3+ Complex can bind to DNA and the major binding mode is intercalative binding. The binding constants K and number of binding sites n of kaempferol-Eu3+ complex with DNA Were obtained by fluorescence quenching method. The thermodynamic parameters (Delta H-theta, Delta S-theta and Delta G(theta)) were calculated from the fluorescence data measured at three different temperatures, which showed that the binding of kaempferol-Eu3+ complex to DNA was driven mainly by hydrophobic interaction. Furthermore, the alternative least squares (ALS) method was applied to resolve a complex two-way array of the absorption spectra data, which provided simultaneously the concentration information for the three reaction components, NR, kaempferol-Eu3+ and DNA-NR. This ALS analysis indicated that the intercalation of the kaempferol-Eu3+ complex into the DNA proceeds by exchanging with the NR probe. (C) 2009 Elsevier B.V. All rights reserved.