TY - JOUR
T1 - DNA binding of iron(II) mixed-ligand complexes containing 1,10- phenanthroline and 4,7-diphenyl-1,10-phenanthroline
AU - Mudasir,
AU - Yoshioka, Naoki
AU - Inoue, Hidenari
N1 - Funding Information:
The first author (M) wishes to thank The Hitachi Scholarship Foundation, Tokyo, Japan, for financial support. This work was supported in part by Grant-in-Aid for Scientific Research No. 10440199 from the Ministry of Education, Science and Culture of the Japanese Government.
PY - 1999/11/30
Y1 - 1999/11/30
N2 - 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.
AB - 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.
KW - 1,10- Phenanthroline
KW - DNA interaction
KW - Iron(II)
KW - Mixed-ligand complex
KW - Thermodynamic parameters
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U2 - 10.1016/S0162-0134(99)00206-8
DO - 10.1016/S0162-0134(99)00206-8
M3 - Article
C2 - 10643662
AN - SCOPUS:0033382809
VL - 77
SP - 239
EP - 247
JO - Journal of Inorganic Biochemistry
JF - Journal of Inorganic Biochemistry
SN - 0162-0134
IS - 3-4
ER -