title: Spectroscopic studies on the thermodynamic and thermal denaturation of the ct-DNA binding of methylene blue.
abstract: The ct-DNA binding properties of methylene blue (MB) including binding constant, thermodynamic parameter and thermal denaturation (T(m)) have been systematically studied by spectrophotometric method. The binding of MB to ct-DNA is quite strong as indicated by remarkable hypochromicity, red shift and equilibrium binding constant (K(b)). Van't Hoff plot of 1/T versus lnK(b) suggests that the MB dye binds exothermically to ct-DNA which is characterized by large negative enthalpy and entropy changes. According to polyelectrolyte theory, the charge release (Z) when ct-DNA interacts with MB is +1.09 which corresponds very well to the one positive charge carried by the MB dye. The K(b) at a low concentration of salt is dominated by electrostatic interaction (90%) while that at a high concentration of salt is mostly controlled by non-electrostatic process (85%). However, the stabilization of the DNA binding event in both cases is governed by non-electrostatic process. A moderate stabilization of double helix ct-DNA occurs when the MB dye binds to ct-DNA as indicated by the increase in T(m) of ct-DNA of about 5.5 degrees C in the presence of MB. This suggests that MB dye possibly binds to ct-DNA via electrostatic and intercalation modes.
authors.affiliation: Department of Chemistry, Faculty of Mathematics and Natural Sciences, Gadjah Mada University, Sekip Utara, P.O. Box Bls. 21, Yogyakarta 55281, Indonesia. mudasir@ugm.ac.id
authors.lastname: Mudasir
authors.forename: Endang Tri
authors.initials: ET
authors.lastname: Wahyuni
authors.forename: Daryono H
authors.initials: DH
authors.lastname: Tjahjono
authors.forename: Naoki
authors.initials: N
authors.lastname: Yoshioka
authors.forename: Hidenari
authors.initials: H
authors.lastname: Inoue
mesh_terms: D000818:Animals; D002417:Cattle; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000378:metabolism; D008751:Methylene Blue / Q000737:chemistry* / Q000378:metabolism; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D011485:Protein Binding; D012492:Salts / Q000737:chemistry; D013057:Spectrum Analysis / Q000379:methods; D055672:Static Electricity; D013816:Thermodynamics
chemical_list: D004791:Enzyme Inhibitors; D012492:Salts; D004247:DNA; D008751:Methylene Blue