DNA Binding Studies of Novel Copper(II) Complexes Containing l-Tryptophan as Chiral Auxiliary:  In Vitro Antitumor Activity of Cu−Sn₂ Complex in Human Neuroblastoma Cells

Abstract

Novel trinuclear complexes C23H31N6O6CuSn2Cl5 [1], C23H31N6O6CuZr2Cl5 [2], C23H31N6O6ZnSn2Cl5 [3], and C23H31N6O6ZnZr2Cl5 [4] were synthesized and characterized by spectroscopic (IR, 1H, 13C, 2D COSY, and 119Sn NMR, EPR, UV-vis, ESI-MS) and analytical methods. In complexes 1-4, the geometry of copper and zinc metal ions were described as square-based pyramidal with l-tryptophan coordinated to copper/zinc via carboxylate group while Sn/Zr was present in the hexacoordinate environment. The interaction of 1 and 2 with calf thymus DNA in Tris buffer was studied by electronic absorption titration, luminescence titration, cyclic voltammetry, circular dichroism, and viscometric measurements. The emission quenching of these complexes by [Fe(CN)6]4- depressed greatly when bound to DNA. Observed changes in the circular dichoric spectra of DNA in presence of 1 and 2 support the strong binding of complexes with DNA. The relative specific viscosity of DNA bound to 1 and 2 decreased, indicating that the complexes bind to DNA via covalent binding. The results reveal that the extent of DNA binding of 1 was greater than that of 2. To evaluate the mechanistic pathway of DNA inhibition, counting experiments and MTT assay were employed to assess the induction of apoptosis by 1. Western blot analysis of whole cell lysates and mitochondrial fractions with Bcl-2 and p-53 family proteins and caspase-3 colorimetry assay were also carried out on a human neuroblastoma cell line SY5Y.

Synthesis, Characterization, and Evaluation of Antimicrobial and Antifertility Efficacy of Heterobimetallic Complexes of Copper (II)

“…The primary amine exhibits a band at higher frequency than that of the corresponding secondary amine. In case of Journal of Chemistry 5 mononuclear complex, a broad and strong band is observed for ](N-H) in the range of 3218-3255 cm −1 which swings over to lower frequency region in case of bimetallic complexes [8] evidently specifying the formation of bond between group 14 metal and nitrogen, while bands due to (N-H) appear in the region of 1529-1540 cm −1 with no evident change after chelation [9]. Aromatic ring (C=C) stretching appears at 1645, 1529, and 1453 cm The far IR spectra show a distinct band at 315 cm −1 attributed to (Cu-Cl) band [11].…”

Synthesis, Crystal Structure, DNA-binding Properties and Antioxidant Activities of a Lutetium(III) Complex with the Bis(N-salicylidene)-3- oxapentane-1,5-diamine Ligand

“…Hydrodynamic measurements that are sensitive to changes in DNA length are regarded as the least ambiguous and most critical tests of a binding model in solution in the absence of crystallographic data [25,26]. In classical intercalation, the DNA helix lengthens as base pairs are separated to accommodate the bound complex, leading to increased DNA viscosity, whereas a partial, non-classical complex intercalation causes a bend (or kink) of the DNA helix and reduces its effective length and thereby its viscosity [27].…”

Synthesis, Characterization, and Biological Studies of Binuclear Copper(II) Complexes of (2E)-2-(2-Hydroxy-3-Methoxybenzylidene)-4N-Substituted Hydrazinecarbothioamides

“…It has been found that intercalation or electrostatic interaction between the metal complex and DNA leads to hypochromism, whereas hyperchromism indicates the breakdown of the secondary structure of DNA [41]. The absorption titrations have been employed to ascertain the DNA binding strength of complexes by monitoring the changes in the absorption intensity of the ligand-centered bands around 317-322 nm.…”