Exploring the copper(II)-aminotriazole complex-binding sites of human serum albumin

Temperature rise and copper exposure reduce heart mitochondrial reactive oxygen species scavenging capacity

Mitochondria produce and scavenge reactive oxygen species (ROS); however, whether oxidative distress due to exogenous stress arises from excessive production or impaired scavenging remains unclear. We assessed the effect of copper (Cu) and thermal stress on kinetics of ROS (H₂O₂) consumption in mitochondria isolated from fish heart. Mitochondria were energized with succinate, glutamate-malate or palmitoylcarnitine (PC) and incubated with 1-25 μM Cu at 11 (control) and 23 °C. We found that H₂O₂ consumption capacity of heart mitochondria varies with substrate and is additively reduced by temperature rise and Cu. While Cu is a potent inhibitor of H₂O₂ consumption in mitochondria oxidizing glutamate-malate and succinate, mitochondria oxidizing PC are resistant to the inhibitory effect of the metal. Moreover, the sensitivity of H₂O₂ consumption pathways to Cu depend on the substrate and are greatly impaired during oxidation of glutamate-malate. Pharmacological manipulation of mitochondrial antioxidant systems revealed that NADPH-dependent peroxidase systems are the centerpieces of ROS scavenging in heart mitochondria, with the glutathione-dependent pathway being the most prominent while catalase played a minimal role. Surprisingly, Cu is as efficacious in inhibiting thioredoxin-dependent peroxidase pathway as auranofin, a selective inhibitor of thioredoxin reductase. Taken together, our study uncovered unique mechanisms by which Cu alters mitochondrial H₂O₂ homeostasis including its ability to inhibit specific mitochondrial ROS scavenging pathways on a par with conventional inhibitors. Importantly, because of additive inhibitory effect on mitochondrial ROS removal mechanisms, hearts of organisms jointly exposed to Cu and thermal stress are likely at increased risk of oxidative distress.

Mono- and bis-pyrazolophthalazines: Design, synthesis, cytotoxic activity, DNA/HSA binding and molecular docking studies

In an attempt to find new potent cytotoxic compounds, several mono- and bis-pyrazolophthalazines 4a-m and 6a-h were synthesized through an efficient, one-pot, three- and pseudo five-component synthetic approach. All derivatives were evaluated for their in vitro cytotoxic activities against four human cancer cell lines of A549, HepG2, MCF-7, and HT29. Compound 4e showed low toxicity against normal cell lines (MRC-5 and MCF 10A, IC₅₀ > 200 µM) and excellent cytotoxic activity against A549 cell line with IC₅₀ value of 1.25 ± 0.19 µM, which was 1.8 times more potent than doxorubicin (IC₅₀ = 2.31 ± 0.13 µM). In addition, compound 6c exhibited remarkable cytotoxic activity against A549 and MCF-7 cell lines (IC₅₀ = 1.35 ± 0.12 and 0.49 ± 0.01 µM, respectively), more than two-fold higher than that of doxorubicin. The binding properties of the best active mono- and bis-pyrazolophthalazine (4e and 6c) with HSA and DNA were fully evaluated by various techniques including UV-Vis absorption, circular dichroism (CD), Zeta potential and dynamic light scattering analyses indicating interaction of the compounds with the secondary structure of HSA and significant change of DNA conformation, presumably via a groove binding mechanism. Additionally, molecular docking and site-selective binding studies confirmed the fundamental interaction of compounds 4e and 6c with base pairs of DNA. Compounds 4e and 6c showed promising features to be considered as potential lead structures for further studies in cancer therapy.

Bio-affinity of copper(II) complexes with nitrogen and oxygen donor ligands: Synthesis, structural studies and in vitro DNA and HSA interaction of copper(II) complexes

Reported herein the binding affinity between Human Serum Albumin and the DNA binding and cleavage activity of three copper(II) complexes, [Cu(phen)(o-van)ClO₄] (1), [Cu(phen)(gly)]ClO₄ (2) and [Cu(L¹)₂(H₂O)₂] (3) wherein 1 and 2 are synthesized with 1,10-phenanthroline (phen) and co-ligands (o-van: o-vanillin; gly: glycine) and 3 with a ligand 2-hydroxy-3-methoxybenzylidene-4H-1,2,4-triazol-4-amine (H₁L¹). Complex 2 crystallizes in monoclinic (P21/n) space group shows square pyramidal geometry. The complex 3 crystallizes in monoclinic (P21/a) space group. All the three complexes exhibit binding affinity towards the transport protein Human Serum albumin (HSA). Quantitative evaluation of the thermodynamics of interaction and the results obtained from fluorescence spectroscopy suggest that metal coordinated glycynate, o-vanillin and perchlorate groups have a major role to play in the binding process, the latter two being stronger in the binding of complex 1. The coordinated water in complex 3 also plays an important role in the binding, which makes binding of complex 3 with HSA stronger than that of complex 2. Experimental results indicate that the binding affinity of the complexes towards CT-DNA is in the order 1>3>2 implying that complex 1 binds stronger than complex 3 and 2.The DNA cleaving activity of all the three complexes was explored in the presence of reactive oxygen compound, H₂O₂. All the three complexes have primarily shown the DNA cleaving activity.

Hybrid compounds assembled from copper-triazole complexes and phosphomolybdic acid as advanced catalysts for the oxidation of olefins with oxygen

Hybrid compounds of [CuI4(3atrz)₄][PMoVI11Mo^VO₄₀] (1) and [CuI6(3atrz)₆][PMo₁₂O₄₀]₂ (2) are active catalysts for olefin oxidation.