Conformational change of ternary copper(II) complexes of cationic Schiff-bases and N-heteroaromatic amines induced by intercalative binding to DNA

Biological activity of mixed chelate copper(II) complexes, with substituted diimine and tridentate Schiff bases (NNO) and their hydrogenated derivatives as secondary ligands: Casiopeína's fourth generation

We synthesize and characterize nine copper(II) compounds. Four with general formula [Cu(NNO)(NO₃)] and five mixed chelates [Cu(NNO)(N-N)]⁺, where NNO corresponds to asymmetric salen ligands (E)-2-((2-(methylamino)ethylimino)methyl)phenolate (L1) and (E)-3-((2-(methylamino)ethylimino)methyl)naphthalenolate (LN1); and their hydrogenated derivatives 2-((2-(methylamino)ethylamino)methyl)phenolate (LH1) and 3-((2-(methylamino)ethylamino)methyl)naphthalenolate (LNH1); and N-N correspond to 4,4'-dimethyl-2,2'-bipiridyne(dmbpy) or 1,10-phenanthroline (phen). Using EPR, the geometries of the compounds in solution in DMSO were assigned, [Cu(LN1)(NO₃)] and [Cu(LNH1)(NO₃)] a square-planar, [Cu(L1)(NO₃)], [Cu(LH1)(NO₃)], [Cu(L1)(dmby)]⁺ and [Cu(LH1)(dmby)]⁺ a square-based pyramid; and [Cu(LN1)(dmby)]⁺, [Cu(LNH1)(dmby)]⁺ and [Cu(L1)(phen)]⁺ and elongated octahedral. By X-ray it was observed that [Cu(L1)(dmby)]⁺ and. [Cu(LN1)(dmby)]⁺ presented a square-based pyramidal, and [Cu(LN1)(NO₃)]⁺ a square-planar geometry. The electrochemical study showed that copper reduction process is a quasi-reversible system, where the complexes with hydrogenated ligands were less oxidizing. The cytotoxicity of the complexes was tested by MTT assay, all the compounds showed biological activity in HeLa cell line, the mixed compounds were the more active ones. Naphthalene moiety, imine hydrogenation and aromatic diimine coordination, increased biological activity. A structure-activity relationships were found: Log(IC₅₀) =  - 1.01(E_pc) - 0.35(Conjugated Rings) + 0.87, for Schiff base complexes and Log(IC₅₀) = 0.078(E_pc) - 0.32(Conjugated Rings) + 1.94, for hydrogenated complexes; the less oxidizing species with a great number of conjugated rings presented the best biological activity. Complexes-DNA binding constants were obtained by uv-vis studies using CT-DNA, the results suggested that the complexes can interact through the grooves, except the phenanthroline mixed complex that intercalate with DNA. Gel electrophoresis study with pBR 322 showed that compounds can produce changes in the form of DNA and some complexes can cleave DNA in the presence of H₂O₂.

Interaction of DNA with Simple and Mixed Ligand Copper(II) Complexes of 1,10-Phenanthrolines as Studied by DNA-Fiber EPR Spectroscopy

The interaction of simple and ternary Cu(II) complexes of 1,10-phenanthrolines with DNA has been studied extensively because of their various interesting and important functions such as DNA cleavage activity, cytotoxicity towards cancer cells, and DNA based asymmetric catalysis. Such functions are closely related to the DNA binding modes of the complexes such as intercalation, groove binding, and electrostatic surface binding. A variety of spectroscopic methods have been used to study the DNA binding mode of the Cu(II) complexes. Of all these methods, DNA-fiber electron paramagnetic resonance (EPR) spectroscopy affords unique information on the DNA binding structures of the complexes. In this review we summarize the results of our DNA-fiber EPR studies on the DNA binding structure of the complexes and discuss them together with the data accumulated by using other measurements.

DNA/BSA binding, DNA cleavage and electrochemical properties of new multidentate copper(ii) complexes

A new series of multidentate copper(ii) complexes [Cu(L¹⁻⁵)](ClO₄) (1–5) were synthesized and characterized for their DNA/BSA binding, DNA cleavage, cytotoxic properties and antimicrobial activities.

DNA/RNA binding and anticancer/antimicrobial activities of polymer-copper(II) complexes

Water soluble polymer-copper(II) complexes with various degrees of coordination in the polymer chain were synthesized and characterized by elemental analysis, IR, UV-visible and EPR spectra. The DNA/RNA binding behavior of these polymer-copper(II) complexes was examined by UV-visible absorption, emission and circular dichroism spectroscopic methods, and cyclic voltammetry techniques. The binding of the polymer-copper(II) complexes with DNA/RNA was mainly through intercalation but some amount of electrostatic interaction was also observed. This binding capacity increased with the degree of coordination of the complexes. The polymer-copper(II) complex having the highest degree of coordination was subjected to analysis of cytotoxic and antimicrobial properties. The cytotoxicity study indicated that the polymer-copper(II) complexes affected the viability of MCF-7 mammary carcinoma cells, and the cells responded to the treatment with mostly through apoptosis although a few cells succumbed to necrosis. The antimicrobial screening showed activity against some human pathogens.

Two novel copper complexes of 2,2'-bipyridine: evaluation of the DNA binding and cytotoxic activity

Two novel copper-2,2'-bipyridine complexes [Cu(SAL)(2,2'-bipy)ClO4]2 (1) and [Cu(μ2-O)(2,2'-bipy)NO3]2 (2) (HSAL=salicylaldehyde) were synthesized and characterized by X-ray single-crystal diffraction, elemental analysis and IR spectra. The interactions of the complexes with salmon sperm DNA were investigated by viscosity analysis, UV, fluorescence and circular dichroism (CD) spectroscopic techniques. Absorption spectral (Kb=3.00×10(5)M(-1) (1), 3.49×10(5)M(-1)(2)), emission spectral ((Ksv) 3.33×10(4)M(-1) (1), 3.40×10(4)M(-1) (2)), and viscosity measurements reveal that 1 and 2 interact with DNA through intercalation. In fluorimetric studies, the enthalpy (ΔH>0) and entropy (ΔS>0) changes of the reactions between the Cu (II) complexes with DNA demonstrate hydrophobic interactions. In addition, CD study indicates the Cu (II) complexes cause a more B-like to a more A-like conformational change upon binding DNA. All the experimental results show that the interaction mode of the two complexes was greatly affected by the coordination environments of Cu (II) centers. Their in vitro cytotoxicity towards five selected tumor cell lines HepG-2, HeLa, NCI-H460, MCF-7 and HL-60 has been evaluated by MTT method, and 2 exhibits higher growth inhibition of the selected cell lines at concentration of 50 μM, this result is identical with their DNA binding ability order.