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Abstract: The complexation reactions between octaazamacrocyclic ligand N,N′,N″,N′″-tetrakis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane (tpmc) and Co2+, Ni2+, Zn2+ and Cu2+ metal cations have been studied conductometrically in acetonitrile and aqueous solutions. The conductance data exhibit different stoichiometry of the complexes in two studied solutions. In most cases 1:1 (ML) complexes were formed while in some cases 2:1 (M2L) complexes are evident. The stability constants of the resulting 1:1 complexes were determined by computer fitting of the conductance/mole ratio data. Theoretical DFT calculations were used to explain metal binding capability of tpmc ligand and the binding sequences were found to follow the order: Cu2+ ≫Ni2+ >Co2+ >Zn2+. The combination of results obtained by this theoretical approach and conductometric study successfully explains sensitivity and selectivity of recently developed tpmc based ISE and could play a guiding role in planning experiments with large macrocyclic ligands. [Copyright &y& Elsevier]

Under simulated physiological conditions, this study investigates the interaction between nutraceutical phycocyanobilin (PCB) and the universal anti-protease protein human alpha-2-macroglobulin (α 2 M). Extensive molecular docking analyses on multiple α2M conformations, spectroscopic techniques, and α2M activity assays were utilized to examine the complex formation. The results revealed that for every protein conformation, two high energy binding sites exist: the first, conformationally independent, at the interface region between two monomer chains and the second, conformationally dependent, in the pocket composed of amino acids from four distinct domains (TED, RBD, CUB, and MG2) of the single protein chain. Spectrofluorimetric measurements indicated a moderate affinity between α 2 M and PCB with a moderately high binding constant of 6.3 × 10 5 M -1 at 25 °C. The binding of PCB to α 2 M resulted in minor changes in the secondary structure content of α 2 M. Furthermore, PCB protected α 2 M from oxidation and preserved its anti-protease activity in the oxidative environment. These findings suggest that PCB binding could indirectly impact the body's response to oxidative stress by influencing α 2 M's role in controlling enzyme activity during the inflammatory process.Communicated by Ramaswamy H. Sarma.

In this paper, three different Zn(II) complexes with ( E )-2-(2-(1-(6-bromopyridin-2-yl)ethylidene)hydrazinyl)- N , N , N -trimethyl-2-oxoethan-1-aminium chloride (HLCl) have been synthesized and characterized by single crystal X-ray diffraction, elemental analysis, IR and NMR spectroscopy. All complexes are mononuclear, with the ligand (L) coordinated in a deprotonated formally neutral zwitterionic form via NNO donor set atoms. Complex 1 forms an octahedral geometry with the composition [ZnL 2 ](BF 4 ) 2 , while complexes 2 [ZnL(NCO) 2 ] and 3 [ZnL(N 3 ) 2 ] form penta-coordinated geometry. Density functional theory (DFT) calculations were performed to enhance our understanding of the structures of the synthesized complexes and the cytotoxic activity of the complexes was tested against five human cancer cell lines (HeLa, A549, MDA-MB-231, K562, LS 174T) and normal human fibroblasts MRC-5. Additionally, antibacterial and antifungal activity of these complexes was tested against a panel of Gram-negative and Gram-positive bacteria, two fungal strains, and a yeast strain. It is noteworthy that all three complexes show selective antifungal activity comparable to that of amphotericin B. Molecular docking analysis predicted that geranylgeranyl pyrophosphate synthase, an enzyme essential for sterol biosynthesis, is the most likely target for inhibition by the tested complexes.

The aim of this work is to study joining Al 2024-T3 alloy plates with different welding procedures. Aluminum alloy AA 2024-T351 is especially used in the aerospace industry. Aluminum plates are welded by the TIG and MIG fusion welding process, as well as by the solid-state welding process, friction stir welding (FSW), which has recently become very important in aluminum and alloy welding. For welding AA2024-T35 with MIG and TIG fusion processes, the filler material ER 4043-AlSi 5 was chosen because of reduced cracking. Different methods were used to evaluate the quality of the produced joints, including macro- and microstructure evaluation, in addition to hardness and tensile tests. The ultimate tensile strength (UTS) of the FSW sample was found to be 80% higher than that of MIG and TIG samples. The average hardness value of the weld zone of metal for the MIG- and TIG-produced AA2024-T3511 butt joints showed a significant decrease compared to the hardness of the base metal AA2024-T351 by 50%, while for FSW joints, in the nugget zone, the hardness is about 10% lower relative to the base metal AA2024-T3511.

Adhesive bonding has proven to be a reliable method of joining materials, and the development of new adhesives has made it possible to use bonding in a variety of applications. This article addresses the challenges of bonding metals such as the aluminum alloy EN AW-5754 and the stainless steel X5CrNi18-10. In this study, the effects of laser cleaning and texturing on the surface properties and strength of two bonded joints were investigated and compared with mechanical preparation (hand sanding with Scotch-Brite and P180 sandpaper). The bonded joints were tested with three different epoxy adhesives. During the tests, the adhesion properties of the bonded surface were determined by measuring the contact angle and assessing the wettability, the surface roughness parameters for the different surface preparations, and the mechanical properties (tensile lap-shear strength). Based on the strength test results, it was found that bonded joints made of stainless steel had 16% to 40% higher strength than aluminum alloys when using the same adhesive and surface preparation. Laser cleaning resulted in maximum shear strength of the aluminum alloy bond, while the most suitable surface preparation for both materials was preparation with P180 sandpaper for all adhesives.

Copper(II) complexes with an α-diimine show a wide variety of biological activities, such as antibacterial, antifungal, antioxidant and anticancer. In this work, we synthesized and structurally characterized two novel Cu(II) complexes with methyl 3-formyl-4-hydroxybenzoate (HL) and α-diimines: 2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen). Crystal structure analysis shows that the formulas of the compounds are [Cu(bipy)(L)(BF 4 )] (1) and [Cu(phen)(L)(H 2 O)](BF 4 )·H 2 O (2), with BF 4 - as a ligand in complex 1, which is rarely coordinated to metals. Both complexes have a square pyramidal geometry, while DFT calculations showed that the most stable structures of complexes 1 and 2 in a water/DMSO mixture are square-planar derivatives [Cu(bipy)(L)] + and [Cu(phen)(L)] + . The antibacterial activity of compounds was evaluated in vitro on four Gram-negative and four Gram-positive bacterial strains. Complex 2 showed greater antibacterial activity towards all bacterial strains comparable to the control compound Amikacin. Complex 2 exerted a strong cytotoxic effect against the tested cancer cell lines (IC 50 values ranging from 0.32 to 0.44 μM). Both complexes caused apoptotic cell death in HeLa cells and a noticeable in vitro antiangiogenic effect. In the concentration range of 5 to 100 μM, the complexes showed the absence of a genotoxic effect and displayed a protective effect against oxidative DNA damage induced by H 2 O 2 in human peripheral blood cells. The interaction between the compounds and calf-thymus DNA was evaluated by diverse techniques suggesting a tight binding, which was also confirmed by molecular docking. In addition, it was found that the complexes bind tightly and reversibly to bovine and human serum albumin.

In this article, cytotoxicity, the mechanisms of cytotoxic activity, genotoxicity, and interaction with DNA and proteins, of two Cu(II) complexes with a salicylaldehyde derivative (4-(diethylamino)salicylaldehyde) and α-diimine (2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen)) are reported. Both Cu(II) complexes performed cytotoxic effects against all tested malignant cell lines. Complexes exerted highest cytotoxicity against HeLa and A375 malignant cell lines. The cytotoxic activity of Cu(II) complex with phen as a α-diimine co-ligand was significantly higher in comparison with cytotoxic activity of Cu(II) complex with bipy. Pretreatment with specific inhibitors of caspase-3, caspase-8 or caspase-9, in order to clear up the mode of cell death triggered by two Cu(II) complexes in HeLa cells, indicated the ability of these complexes to induce apoptosis through activation of target caspases. Cu(II)-phen complex exhibited significant antioxidant activity compared with Cu(II)-bipy complex, and showed a better effect on reducing intracellular ROS levels in HeLa cells. Tested complexes did not display genotoxic potential in human peripheral blood leucocytes, but exhibited an antigenotoxic effect in post-treatment, after H 2 O 2 exposure. The study of the in vitro biological properties regarding their affinity towards CT (calf-thymus) DNA and serum albumins showed that the compounds can intercalate to CT DNA, and bind reversibly and tightly to the albumins. Molecular docking studies of the ability of compounds to bind to biomacromolecules are consistent with in vitro studies., (Copyright © 2022 Elsevier Inc. All rights reserved.)

In this study, β-keto esters as readily available bio-based building blocks were used to decorate the C 60 sphere. Generally, cyclopropanated fullerene derivatives are obtained by the standard Bingel-Hirsch procedure. Herein, omitting the iodine from the reaction mixture and adding TEMPO afforded dihydrofuran fused C 60 fullerene derivatives. The mechanism of the reaction shifted from nucleophilic aliphatic substitution to oxidative [3 + 2] cycloaddition via fullerenyl cations as an intermediate. This mechanism is proposed based on a series of control experiments with radical scavengers. Therefore, dihydrofuran-fused C 60 derivatives were selectively obtained in good yields and their structures were established based on UV-Vis, IR, NMR spectroscopy and mass spectrometry. The electrochemical properties of the synthesized compounds were investigated by cyclic voltammetry. DFT calculations were performed in order to investigate the difference in stability, electronic properties and π-electron delocalization between methano and furano fullerenes., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

In this study, the interaction between clozapine, an atypical antipsychotic drug, and alpha-2-macroglobulin (α 2 M), a multipurpose anti-proteinase, was investigated under simulated (patho) physiological conditions using multiple spectroscopic techniques and molecular modeling. It was found that α 2 M binds clozapine with a moderate affinity (the binding constant of 0.9 × 10 5 M -1 at 37 °C). The preferable binding site for both clozapine's atropisomers was revealed to be a large pocket at the interface of C and D monomer subunits of the protein. Hydrogen bonds and the hydrophobic effect were proposed as dominant forces in complex formation. The binding of clozapine did not induce significant conformational change of the protein, as confirmed by virtually unaltered α 2 M secondary structure and anti-proteinase activity. However, both clozapine and α 2 M shielded each other from the deleterious influence of strong oxidants: sodium hypochlorite and 2,2'-azobis-2-methyl-propanimidamide dihydrochloride (AAPH). Moreover, clozapine in a concentration range that is usually targeted in the plasma during patients' treatment effectively protected the anti-proteinase activity of α 2 M under AAPH-induced free radical overproduction. Our results suggest that the cooperation between α 2 M and clozapine may be a path by which these two molecules synergistically protect neural tissue against injury caused by disturbed proteostasis or oxidative stress., (Copyright © 2021 Elsevier B.V. All rights reserved.)

In order to ensure a quality welded joint, and thus safe operation and high reliability of the welded part or structure achieved by friction stir welding, it is necessary to select the optimal welding parameters. The parameters of friction stir welding significantly affect the structure of the welded joint, and thus the mechanical properties of the welded joint. Investigation of the influence of friction stir welding parameters was performed on 6-mm thick plates of aluminum alloy AA2024 T351. The quality of the welded joint is predominantly influenced by the tool rotation speed n and the welding speed v. In this research, constant tool rotation speed was adopted n = 750 rpm, and the welding speed was varied ( v = 73, 116 and 150 mm/min). By the visual method and radiographic examination, imperfections of the face and roots of the welded specimens were not found. This paper presents the performed experimental tests of the macro and microstructure of welded joints, followed by tests of micro hardness and fracture behavior of Friction Stir Welded AA2024-T351 joints. It can be concluded that the welding speed of v = 116 mm/min is favorable with regard to the fracture behavior of the analysed FSW-joint.

A detailed theoretical investigation of cyclophanes with a divergent set of methods ranging from molecular mechanics through semiempirical to ab initio is presented. Cyclophanes have attracted interest over the years due to their unusual chemistry and increasing applications. There has been previous debate over the effects contributing to the greater stability of more-crowded in isomers of certain cyclophanes, and a higher strain in the out isomer was the prevailing explanation. Application of EDA-NOCV and SAPT analysis has enabled us to distinguish between different effects controlling isomer stability and determine the significance of all effects involved. Our results show that, although strain has a large significance, orbital stabilization within the molecule from the aromatic electron density is crucial. Furthermore, we analysed halogen-substituted cyclophanes in order to further understand these subtle effects.

The state of the tautomeric equilibria of 2(6)-hydroxy-4-methyl-6(2)-oxo-1-(substituted phenyl)-1,2(1,6)-dihydropyridine-3-carbonitriles, 2-PY/6-PY, was evaluated using experimental and theoretical methodology. The experimental data were interpreted with the aid of time-dependent density functional (TD-DFT) method. Electron charge density was obtained by the use of Quantum Theory of Atoms in Molecules, i.e. Bader's analysis. Linear solvation energy relationships (LSER) rationalized solvent influence on tautomeric equilibrium. Linear free energy relationships (LFERs) were applied to the substituent-induced NMR chemical shifts (SCS) using SSP (single substituent parameter) and DSP (dual substituent parameter) model. Theoretical calculations and obtained correlations gave insight into the influence of molecular conformation on the transmission of substituent electronic effects, as well as on different solvent-solute interactions, and the state of tautomeric equilibrium., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Polyphenols, the potent plant secondary metabolites, have beneficial effects on human health, but the mechanism(s) by which these effects are exerted is not well understood. Here, we present the detailed analysis of the interactions between the major green tea catechin, epigallo-catechin 3-gallate (EGCG), and the major dietary protein and allergen, ovalbumin (OVA). We show that EGCG binds to the pocket that partly overlaps with the previously identified IgE-binding region in OVA, and that this interaction induces structural changes in the allergen. Moreover, our ex vivo studies reveal that OVA binds IgE and stimulates degranulation of basophils, and that its uptake by monocytes proceeds at a slower rate in the presence of EGCG. This study provides further evidence in support of the proposed mechanism by which EGCG interactions with the food allergens contribute to its diverse biological activities and may impair antigen uptake by antigen-presenting cells., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

In search for novel biologically active metal based compounds, an evaluation of in vitro cytotoxic, antioxidant, and antimicrobial activity of new Pt(II) complex and its Zn(II), Cu(II), and Co(III) analogues, with NNO tridentately coordinated N-heteroaromatic Schiff base ligand (E)-2-[N'-(1-pyridin-2-yl-ethylidene)hydrazino]acetate, was performed. Investigation of antioxidative properties showed that all of the compounds have strong radical scavenging potencies. The Zn(II) complex showed potent inhibition of DNA cleavage by hydroxyl radical. A cytotoxic action of investigated compounds was evaluated on cultures of human promyelocitic leukaemia (HL-60), human glioma (U251), rat glioma (C6), and mouse melanoma (B16) cell lines. It was shown that binuclear pentacoordinated Zn(II) complex possesses a strong dose-dependent cytotoxic activity, of the same order of magnitude as cisplatin on B16, C6, and U251 cells. Furthermore, Zn(II) complex causes oxidative stress-induced apoptotic death of HL-60 leukemic cells, associated with caspase activation, phosphatidylserine externalization, and DNA fragmentation., (© 2013 Wiley Periodicals, Inc.)

The absorption spectra of twelve 5-arylidene-2,4-thiazolidinediones were recorded in twenty one solvents in the range from 300 to 600 nm. The effect of specific and non-specific solvent-solute interactions on the absorption maxima shifts were evaluated by using the Catalán solvent parameter set. Furthermore, the experimental findings were interpreted with the aid of ab initio MP2 and time-dependent density functional (TD-DFT) methods. It was found that different substituents significantly change the extent of conjugation in the molecules and further affect their intramolecular charge transfer character., (Copyright © 2011 Elsevier B.V. All rights reserved.)