Spectroscopic studies on the binding of holmium-1,10-phenanthroline complex with DNA

Fluorescence and absorption spectroscopy, circular dichroism (CD) as well as viscosity experiment have been used to characterize the DNA binding of [Ho(Phen)(2)Cl-3]center dot H2O, where phen stand for 1,10-phanathroline. This complex exhibits the marked decrease in the emission intensity and some hypochromism in UV-Vis spectrum in the presence of DNA. For characterization of the binding mode between the Ho(III) complex and DNA various procedures such as: absorption and emission titration and EB quenching experiments, viscosity measurements, CD study, iodide quenching assay, salt effect and thermodynamical investigation are used. The intrinsic binding constant of [Ho(Phen)(2)Cl-3]center dot H2O with DNA is calculated by UV-Vis and florescence spectroscopy. The value of binding constants in 296, 299 and 303 are 1.99 +/- 0.07 x 10(4), 1.07 +/- 0.09 x 10(4) and 0.84 +/- 0.06 x 10(4), respectively. The thermodynamic studies show that the reaction is entropically driven. The above-mentioned physical measurements indicate that the Ho(III) complex binds to fish salmon DNA, presumably via groove binding mode. (C) 2012 Elsevier B.V. All rights reserved.