Binding interaction of Trivalent Praseodymium with Calf Thymus DNA: A Comparative Study

Abstract

The interaction of trivalent praseodymium ion with Calf-Thymus DNA (CT-DNA) has been studied by employing absorption spectroscopy involving 4f-4f transitions. The absorption spectra of Pr(III) exhibits hyperchromism without shifting in wavelength on increasing the amount of CT-DNA thereby inducing the subsequent changes in the oscillator strengths of different 4f-4f bands. The other spectral parameters namely Slator-Condon, nephelauxetic ratio, bonding and covalency parameters were also determined to correlate with the binding of calf-thymus DNA to Pr(III). The binding constant, Kb has been determined and found to be 5.18 x102 M-1. The viscosity of rod-liked DNA was found to be decreased on addition of Pr(III). The absorption and viscosity measurement result suggest the non-intercalative mode of binding between trivalent praseodymium and Calf-thymus DNA. Thermodynamic parameters determined from relevant absorption data further revealed the appearance of hydrophobic interaction in addition to electrostatic mode of binding on negatively charged DNA phosphate backbone that occurs along external DNA double helix.