Tuning the DNA binding and cleavage of bpa Cu(II) complexes by ether tethers with hydroxyl and methoxy groups

Structural Characterization of Zinc(II)/Cobalt(II) Complexes of Chiral N-(Anthracen-9-yl)methyl-N,N-bis(2-picolyl)amine and Evaluation of DNA Photocleavage Activity

We designed and synthesized a chiral ligand N-(anthracen-9-ylmethyl)-1-(pyridin-2-yl)-N-(pyridin-2-ylmethyl)ethanamine (APPE) DNA photocleavage agent to investigate the effects of chirality of bis(2-picolyl)amine on the DNA photocleavage activity of metal complexes. The structures of Zn^II and Co^II complexes in APPE were analyzed via X-ray crystallography and fluorometric titration. APPE formed metal complexes with a 1 : 1 stoichiometry in both the crystalline and solution states. Fluorometric titration was used to show that the Zn^II and Co^II association constants of these complexes (log K_as) were 4.95 and 5.39, respectively. The synthesized complexes were found to cleave pUC19 plasmid DNA when irradiated at 370 nm. The DNA photocleavage activity of the Zn^II complex was higher than that of the Co^II complex. The absolute configuration of the methyl-attached carbon did not affect DNA cleavage activity and, unfortunately, an achiral APPE derivative without the methyl group (ABPM) was found to perform DNA photocleavage more effectively than APPE. One reason for this may be that the methyl group suppressed the structural flexibility of the photosensitizer. These results will be useful for the design of new photoreactive reagents.

Copper(II) Complexes with Tetradentate Piperazine-Based Ligands: DNA Cleavage and Cytotoxicity

Five-coordinate Cu(II) complexes, [Cu(Ln)X]ClO4/PF6, where Ln = piperazine ligands bearing two pyridyl arms and X = ClO4− for Ln = L1 (1-ClO4), L2 (2-ClO4), L3 (3-ClO4), and L6 (6-ClO4) as well as [Cu(Ln)Cl]PF6 for Ln = L1 (1-Cl), L4 (4-Cl), and L5 (5-Cl) have been synthesized and characterized by spectroscopic techniques. The molecular structures of the last two complexes were determined by X-ray crystallography. In aqueous acetonitrile solutions, molar conductivity measurements and UV-VIS spectrophotometric titrations of the complexes revealed the hydrolysis of the complexes to [Cu(Ln)(H2O)]2+ species. The biological activity of the Cu(II) complexes with respect to DNA cleavage and cytotoxicity was investigated. At micromolar concentration within 2 h and pH 7.4, DNA cleavage rate decreased in the order: 1-Cl ≈ 1-ClO4 > 3-ClO4 ≥ 2-ClO4 with cleavage enhancements of up to 23 million. Complexes 4-Cl, 5-Cl, and 6-ClO4 were inactive. In order to elucidate the cleavage mechanism, the cleavage of bis(4-nitrophenyl)phosphate (BNPP) and reactive oxygen species (ROS) quenching studies were conducted. The mechanistic pathway of DNA cleavage depends on the ligand’s skeleton: while an oxidative pathway was preferable for 1-Cl/1-ClO4, DNA cleavage by 2-ClO4 and 3-ClO4 predominantly proceeds via a hydrolytic mechanism. Complexes 1-ClO4, 3-ClO4, and 5-Cl were found to be cytotoxic against A2780 cells (IC50 30–40 µM). In fibroblasts, the IC50 value was much higher for 3-ClO4 with no toxic effect.

Theoretical study on the DNA interaction properties of copper(II) complexes

Theoretical studies on DNA-cleavage and DNA-binding properties of a series of Cu(II) complexes [Cu(bimda)(diimine)] 1-5 have been carried out by density functional theory (DFT). The optimized structures of Cu(II) complexes were docked into parallel, antiparallel and mixed G-quadruplexes, with which the binding energies of complexes 1-5 were obtained. The cytotoxicities of these complexes can be predicted preliminarily by the binding energies. To explore the energy changes of Cu(II) complexes in duplex DNA, the optimized structures of these complexes were docked into the duplex DNA, and the obtained docking models were further optimized using QM/MM method. The DNA-cleavage abilities of complexes 1-5 can be predicted accurately and explained reasonably by the computed intra-molecular reorganization energies of these complexes. This work reported here has implications for the understanding of the interaction Cu(II) complexes with the DNA, which might be helpful for the future directing the design of novel anticancer Cu(II) complexes.

A fluorescence assay for the detection of hydrogen peroxide and hydroxyl radicals generated by metallonucleases

Metal complexes can initiate DNA cleavage by the formation of reactive oxygen species (ROS). A conventional assay to probe for ROS is to add quenchers in a gel electrophoresis experiment. As we show here, such an assay is neither selective nor reliable. Instead, we suggest the use of simple fluorogens, as tested here with several metallonucleases for the detection of H2O2 and HO˙.

De novo design of a hydrolytic DNA cleavage agent, mono nitratobis(phen)cobalt(ii) aqua nitrate complex

Demonstration of DNA intercalation and hydrolytic cleavage by complex1.