Spectroscopic studies on the thermodynamic and thermal denaturation of the ct-DNA binding of methylene blue

Mudasir, Endang Tri Wahyuni, Daryono H. Tjahjono, Naoki Yoshioka, Hidenari Inoue

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53 Citations (Scopus)


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 ln K 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 °C in the presence of MB. This suggests that MB dye possibly binds to ct-DNA via electrostatic and intercalation modes.

Original languageEnglish
Pages (from-to)528-534
Number of pages7
JournalSpectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
Issue number2
Publication statusPublished - 2010 Oct 1


  • Cationic dyes
  • DNA
  • Methylene blue
  • Thermal denaturation
  • Thermodynamic parameter

ASJC Scopus subject areas

  • Analytical Chemistry
  • Atomic and Molecular Physics, and Optics
  • Instrumentation
  • Spectroscopy


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