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Synthesis, Structure, and Phosphatase-Like Activity of a New Trinuclear Gd Complex with the Unsymmetrical Ligand H3L As a Model for Nucleases

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posted on 15.03.2010, 00:00 by Maryene A. Camargo, Ademir Neves, Bruno Szpoganicz, Adailton J. Bortoluzzi, Franciele L. Fischer, Hernán Terenzi, Eduardo E. Castellano
The new trinuclear gadolinium complex [Gd3L2(NO3)2(H2O)4]NO3·8H2O (1) with the unsymmetrical ligand 2-[N-bis-(2-pyridylmethyl)aminomethyl]-4-methyl-6-[N-bis(2-hydroxy-2-oxoethyl)aminomethyl] phenol (H3L) was synthesized and characterized. The new ligand H3L was obtained in good yield. Complex 1 crystallizes in an orthorhombic cell, space group Pcab. Kinetic studies show that complex 1 is highly active in the hydrolysis of the substrate 2,4-bis(dinitrophenyl)phosphate (Km = 4.09 mM, Vmax = 2.68 × 10−2 mM s−1, and kcat = Vmax/[1] = 0.67 s−1). Through a potentiometric study and determination of the kinetic behavior of 1 in acetonitrile/water solution, the species present in solution could be identified, and a trinuclear monohydroxo species appears to be the most prominent catalyst under mild conditions. Complex 1 displays high efficiency in DNA hydrolytic cleavage, and complete kinetic studies were carried out (Km = 4.57 × 10−4 M, kcat = 3.42 h−1, and kcat/Km = 7.48 × 103 M−1 h−1). Studies with a radical scavenger (dimethyl sulfoxide, DMSO) showed that it did not inhibit the activity, indicating the hydrolytic action of 1 in the cleavage of DNA, and studies on the incubation of distamycin with plasmid DNA suggest that 1 is regio-specific, interacting with the minor groove of DNA.

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