Hydrolytic Cleavage of DNA by Ternary Amino Acid Schiff Base Copper(II) Complexes Having Planar Heterocyclic Ligands

Reddy, Pattubala AN and Nethaji, Munirathinam and Chakravarty, Akhil R (2004) Hydrolytic Cleavage of DNA by Ternary Amino Acid Schiff Base Copper(II) Complexes Having Planar Heterocyclic Ligands. In: European Journal of Inorganic Chemistry, 2004 (7). pp. 1440-1446.

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Abstract

The ternary copper(II) complexes [Cu(salgly)L] (L = phen, 1; dpq, 2), [Cu(salala)L] (L = phen, 3; dpq, 4) and [Cu(salphe)L] (L = phen, 5; dpq, 6), where salgly, salala and salphe are tridentate Schiff-base ligands derived from the condensation of salicylaldehyde with glycine, L-alanine and L-phenylalanine, respectively, are prepared and their nuclease activity studied (phen, 1,10-phenanthroline; dpq, dipyridoquinoxaline). The crystal structure of 3 displays a distorted square-pyramidal (4+1) coordination geometry in which the ONO-donor Schiff base is bonded to the metal atom in the basal plane. The chelating phen ligand displays an axial-equatorial mode of bonding. The complexes exhibit a d-d band near 670nm and a charge transfer band near 370nm in methanol. The one-electron paramagnetic complexes display axial EPR spectra in DMF glass at 77K, indicating a ${d_{x2-y2}} ^1$ ground state. The complexes are redox-active and exhibit a quasi-reversible CuII/CuI couple in DMF at approximately -0.6 V vs. SCE. They show catalytic activity in the oxidation of ascorbic acid by molecular oxygen. The ability of the complexes to bind calf thymus (CT) DNA follows the order: 2 \approx 4 \approx 6 > 1 \approx 3 \approx 5. Complexes 1-6 show oxidative DNA cleavage activity in the presence of mercaptopropionic acid as a reducing agent. All the complexes show hydrolytic cleavage activity in the absence of light or any reducing agent. The oxidative and hydrolytic DNA cleavage efficiencies follow the order: 2 \approx 4 \approx 6 > 1 \approx 3 \approx 5. The dpq complexes, which have a greater DNA binding ability, display enhanced nuclease activity than their phen analogues. The hydrolytic DNA cleavage rate of 1.8 h-1, observed for 2, is significantly high relative to most of the known copper-based synthetic hydrolases. Mechanistic pathways involved in the nuclease activity of the complexes are discussed.

Item Type:	Journal Article
Publication:	European Journal of Inorganic Chemistry
Publisher:	WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Additional Information:	The copyright belongs to WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Keywords:	copper;synthetic hydrolase;x ray diffraction;schiff bases;phenanthroline bases
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	25 Nov 2005
Last Modified:	19 Sep 2010 04:21
URI:	http://eprints.iisc.ac.in/id/eprint/4063

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