Cobalt(III), nickel(II) and ruthenium(II) complexes of 1,10-phenanthroline family of ligands: DNA binding and photocleavage studies

Abstract

DNA binding and photocleavage characteristics of a series of mixedligand complexes of the type [M(phen) 2 LL] n+ (where M = Co(III), Ni(II) or Ru(II), LL = 1,10-phenanthroline (phen), phenanthroline-dione (phen-dione) or dipyridophenazine (dppz) and n = 3 or 2) have been investigated in detail. Various physico-chemical and biochemical techniques including UV/Visible, fluorescence and viscometric titration, thermal denaturation, and differential pulse voltammetry have been employed to probe the details of DNA binding by these complexes; intrinsic binding constants (K b) have been estimated under a similar set of experimental conditions. Analysis of the results suggests that intercalative ability of the coordinated ligands varies as dppz > phen > phen-dione in this series of complexes. While the Co(II) and Ru(II) complexes investigated in this study effect photocleavage of the supercoiled pBR 322 DNA, the corresponding Ni(II) complexes are found to be inactive under similar experimental conditions. Results of detailed investigations carried out inquiring into the mechanistic aspects of DNA photocleavage by [Co(phen) 2 (dppz)] 3+ have also been reported.

DNA Binding by a New Metallointercalator that Contains a Proflavine Group Bearing a Hanging Chelating Unit

“…1 H and 13 C NMR spectra were recorded at 298 K on a Varian Unity 300 MHz instrument. In 1 H NMR spectra peak positions are reported relative to HOD at d = 4.75 ppm (D 2 O) or to TMS (CD 3 OD, CDCl 3 ), while in 13 C spectra peak positions are reported relative to 1,4-dioxane at d = 67.2 ppm (D 2 O) or TMS (CD 3 OD, CDCl 3 ). In the pH-metric titrations, small amounts of 0.01 m NaOD or DCl were added to adjust the pD.…”

“…[10] In this context, bifunctional molecules that bear both an aromatic moiety and a separate metal-complexing centre appear to be of particular interest. [11][12][13] The aromatic residue provides an anchor for the molecule on the polymer chain by intercalation, whereas the metal centre might intercalate as well, or it might interact with the polymeric backbone thereby exerting its function. [14] Barton and co-workers [15] have synthesised special metallointercalators with diverse functions, from luminescent probes for DNA [16] to structural probes for RNA.…”

Supramolecular assembly and DNA cleavage activity of a nickel(II) complex

“…Ellipsoids are drawn at 30% probability level -0.14, 0.16 [22]. The value of i pc /m 1/2 remained almost constant when the scan rate was varied between 50 and 150 mVÁ s -1 , indicating that this process is controlled by diffusion [23]. The cathodic and anodic peak currents appearing at half-wave potentials at different scan rates were almost equal, with peakpeak separation between the corresponding anodic and cathodic peaks of ca.…”

Binding Studies and Effect of Light on the Conductance of Intercalated Curcumin into DNA

“…By monitoring the change in absorbance with increasing concentration of curcumin, the intrinsic binding constant can be evaluated by Eq. (1) [19,20]. The intrinsic binding constant, K b was determined form the plot of [Cur]/(ε a -ε f ) vs [Cur] according to the equation (1) where [Cur] is the concentration of curcumin, є a , the apparent extinction coefficient is obtained by calculating A obsd /[DNA], є f corresponds to the extinction coefficient of the DNA in its free form and є b refers to the extinction coefficient of the curcumin-DNA complex in the fully bound form.…”