DNA binding of iron(II) mixed-ligand complexes containing 1,10- phenanthroline and 4,7-diphenyl-1,10-phenanthroline

Mudasir, Naoki Yoshioka, Hidenari Inoue

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125 Citations (Scopus)


Absorption spectroscopy and circular dichroism (CD) have been used to characterize the DNA binding of [Fe(phen)3]2+, [Fe(phen)2(DIP)]2+ and [Fe(phen)(DIP)2]2+ where phen and DIP stand for 1,10-phenanthroline and 4,7-diphenyl-1,10-phenanthroline, respectively. Both [Fe(phen)3]2+ and [Fe(phen)2(DIP)]2+ bind weakly to calf thymus DNA (CT-DNA) in an electrostatic mode, while [Fe(phen)(DIP)2]2+ binds more strongly to CT- DNA, possibly in an intercalation mode. The hypochromicity, red shift and K(b) increase in the order [Fe(phen)3]2+ < [Fe(phen)2(DIP)]2+ < [Fe(phen)(DIP)2]2+ in accordance with the increase in size and hydrophobicity of the iron(II) complexes. The thermodynamic parameters obtained suggest that the DNA binding of both [Fe(phen)3]2+ and [Fe(phen)2(DIP)]2+ is entropically driven, while that of [Fe(phen)(DIP)2]2+ is enthalpically driven. A strong CD spectrum in the UV and visible region develops upon addition of CT-DNA into the racemate solution of each iron(II) complex (Pfeiffer effect). This has revealed that a shift in diastereomeric inversion equilibrium takes place in the solution to yield an excess of one of the DNA-complex diastereomers. The striking resemblance of the CD spectral profiles to those of the pure Δ-enantiomer indicates that the Δ-enantiomer of the iron(II) complexes is preferentially bound to CT-DNA. The mechanism of the development of Pfeiffer CD is proposed on the basis of kinetic studies on the DNA binding of the racemic iron(II) complexes.

Original languageEnglish
Pages (from-to)239-247
Number of pages9
JournalJournal of Inorganic Biochemistry
Issue number3-4
Publication statusPublished - 1999 Nov 30


  • 1,10- Phenanthroline
  • DNA interaction
  • Iron(II)
  • Mixed-ligand complex
  • Thermodynamic parameters

ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry


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