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Structures, spectra, and DNA-binding properties of mixed ligand copper(II) complexes of iminodiacetic acid: The novel role of diimine co-ligands on DNA conformation and hydrolytic and oxidative double strand DNA cleavage
Auteur(s)
Selvakumar, Balaraman
Rajendiran, Venugopal
Maheswari, Palanisamy Uma
Palaniandavar, Mallayan
Date de parution
2006
In
Journal of Solid State Chemistry, Elsevier, 2006/100/3/316-330
Résumé
The coordination geometry around copper(II) in [Cu(imda)(phen)(H<sub>2</sub>O)] (<b>1</b>) (H2imda = iminodiacetic acid, phen = 1,10-phenanthroline) is described as distorted octahedral while those in [Cu(imda)(5,6-dmp)] (<b>2</b>) (5,6-dmp = 5,6-dimethyl-1,10-phenanthroline) and [Cu(imda)(dpq)] (3) (dpq = dipyrido-[3,2-<i>d</i>:2′,3′-<i>f</i>]-quinoxaline) as trigonal bipyramidal distorted square-based pyramidal with the imda anion facially coordinated to copper(II). Absorption spectral (<i>K</i><sub>b</sub>: <b>1</b>, 0.60 ± 0.04 × 10<sup>3</sup>; <b>2</b>, 3.9 ± 0.3 × 10<sup>3</sup>; <b>3</b>, 1.7 ± 0.5 × 10<sup>4</sup> M<sup>−1</sup>) and thermal denaturation studies (Δ<i>T</i><sub>m</sub>: <b>1</b>, 5.70 ± 0.05; <b>2</b>, 5.5 ± 10; <b>3</b>, 10.6 ± 10 °C) and viscosity measurements indicate that <b>3</b> interacts with calf thymus DNA more strongly than <b>1</b> and <b>2</b>. The relative viscosities of DNA bound to <b>1</b> and <b>3</b> increase while that of DNA bound to <b>2</b> decreases indicating formation of kinks or bends and/or conversion of B to A conformation as revealed by the decrease in intensity of the helicity band in the circular dichroism spectrum of DNA. While <b>1</b> and <b>3</b> are bound to DNA through partial intercalation, respectively, of phen ring and the extended planar ring of dpq with DNA base stack, the complex <b>2</b> is involved in groove binding. All the complexes show cleavage of pBR322 supercoiled DNA in the presence of ascorbic acid with the cleavage efficiency varying in the order <b>3</b> > <b>1</b> > <b>2</b>. The highest oxidative DNA cleavage of dpq complex is ascribed to its highest Cu(II)/Cu(I) redox potential. Oxidative cleavage studies using distamycin reveal minor groove binding for the dpq complex but a major groove binding for the phen and 5,6-dmp complexes. Also, all the complexes show hydrolytic DNA cleavage activity in the absence of light or a reducing agent with cleavage efficiency varying in the order <b>1</b> > <b>3</b> > <b>2</b>.
Identifiants
Type de publication
journal article
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