کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5372253 | 1388870 | 2006 | 7 صفحه PDF | دانلود رایگان |
The salt-dependent binding of racemic iron(II) mixed-ligand complex containing 1,10-phenanthroline (phen) and dipyrido[3,2-a:2â²,3â²-c]phenazine (dppz), [Fe(phen)2(dppz)]2+ to calf thymus DNA (ct-DNA) has been characterized by UV-VIS spectrophotometric titration. The equilibrium binding constant (Kb) of the iron(II) complex to ct-DNA decreases with the salt concentration in the solution. The slope, SK = (δlog Kb / δlog [Na2+]) has been found to be 0.49, suggesting that, in addition to intercalation, considerable electrostatic interaction is also involved in the ct-DNA binding of [Fe(phen)2(dppz)]2+. The calculation of non-electrostatic binding constant (Kto) based on polyelectrolyte theory has revealed that the non-electrostatic contribution to the total binding constant (Kb) increases significantly with the increase in [Na+] and reaches 36% at 0.1 M NaCl. On the other hand, the contribution of the non-electrostatic binding free energy (ÎGto) to the total binding free energy change (ÎGo) is considerably large, i.e. 87% at [Na+] = 0.1 M, suggesting that the stabilization of the DNA binding is mostly due to the contribution of non-electrostatic process. Moreover, the effect of specific ligand substitutions on ÎGo has been rigorously evaluated using the quantity ÎÎGto, i.e. the difference in ÎGto relative to that of the parent iron(II) complex, [Fe(phen)3]2+, indicating that each substitution of phen by dip and dppz contributes 7.5 and 17.5 kJ molâ 1, respectively to more favorable ct-DNA binding.
Journal: Biophysical Chemistry - Volume 121, Issue 1, 20 April 2006, Pages 44-50