Affiliations: Laboratory of Physical Chemistry, Department of Chemistry, Faculty of Science, University of Guilan, Rasht, Iran | Department of Biological Sciences, Institute for Advanced Studies in Basic Sciences, Zanjan, Iran
Note: [] Corresponding author: Hamid Dezhampanah, Laboratory of Physical Chemistry, Department of Chemistry, Faculty of Science, University of Guilan, P.O. Box 41335-1914, Rashat 0098, Iran. Tel.: +98 131 32436305; Fax: +98 131 3233262; E-mails: h.dpanah@guilan.ac.ir, h_dpanah@yahoo.com.
Abstract: The calf thymus deoxyribonucleic acid (ct-DNA) binding properties of methylene blue (MB) including binding constant and thermodynamic parameter have been systematically studied by UV-vis absorption and fluorescence spectroscopy. The binding constant and stoichiometry were determined by analysis of optical absorption spectra of the MB dye at various ct-DNA concentrations using SQUAD software. The binding of MB to ct-DNA is quite strong as indicated by remarkable hypochromicity, red shift and equilibrium binding constant (Kb). Van't Hoff plot of 1/T versus ln Kb suggests that the MB dye binds exothermically to ct-DNA which is characterized by large negative enthalpy and entropy changes. The static mode of fluorescence quenching of MB by ct-DNA indicates the formation of a ground-state complex. The results showed that the MB molecule could intercalate into the double helix of the DNA.
