Ligand Complexes Research Articles

Organotin(IV) complexes of tridentate (ONO) hydrazone ligands: synthesis, spectral characterization, antituberculosis, antimicrobial, anti-inflammatory, molecular docking and cytotoxicity studies.

Infectious diseases have a significant impact in the historical trajectory of humanity, exerting profound influence on societies, driving advancements in medical science, and significantly impacting individuals on a worldwide scale. Consequently, this research endeavours to identify potent agents combatting tuberculosis, inflammation, and microbial deformities. The investigation focuses on hydrazones (1,2) endowed eight organotin(IV) complexes, where hydrazones were derived from 2-acetyl-1H-indene-1,3(2H)-dione and 2-phenoxypropanehydrazide/2-(2,4-dichlorophenoxy)propanehydrazide. All compounds underwent thorough characterization utilizing a variety of spectral and analytical techniques including, multinuclear NMR, FT-IR, HRMS, UV-Vis, SEM-EDAX, TGA, XRD, molar conductance measurements, establishing the pentacoordinated environment around tin(IV) ion with tridentate (ONO) mode of chelation of hydrazones. Powder XRD revealed the ligand's crystalline and complexes' semi-crystalline nature, while thermal analysis indicated two-step decomposition leaving tin oxide residue. In vitro evaluations utilize microplate alamar blue assay for assessing anti-tuberculosis activity, serial dilution technique for antimicrobial efficacy, and bovine serum albumin method for evaluating anti-inflammatory properties. The complexes exhibited higher biological activities than their respective ligands and the activity of the complexes follow the order: Ph2SnL1-2 > Bu2SnL1-2 > Et2SnL1-2 > Me2SnL1-2. Among them, phenyl complex (10) [Ph2SnL2] displays superior efficacy against TB dysfunction (MIC: 0.0180 ± 0.009μmol/mL) and also demonstrates exceptional potency in combating inflammation (IC50: 7.27 ± 0.04μM), and microbial (MIC: 0.0045μmol/mL) infections, comparable to standard drugs. Additionally, cytotoxicity testing against vero cell line revealed decreased toxicity at lower concentrations, and attenuated by chelation. Phenyl complex (10) [Ph2SnL2] shows promising cytotoxicity at 3.12µg/mL (19.29 ± 0.09%). Further, The diphenyltin(IV) complex (10), identified as the most effective against TB, shows stronger binding to key 3PTY protein residues (-42.2kJ/mol) compared to ligand (2) (-33.4kJ/mol), correlating with its superior anti-tuberculosis potency in biological assays. This comprehensive approach aims to actively contribute to ongoing initiatives addressing infectious diseases, thereby advancing global health and overall well-being.

The partitioning of TCR repertoires by thymic selection.

αβ T cells are critical components of the adaptive immune system; they maintain tissue and immune homeostasis during health, provide sterilizing immunity after pathogen infection, and are capable of eliminating transformed tumor cells. Fundamental to these distinct functions is the ligand specificity of the unique antigen receptor expressed on each mature T cell (TCR), which endows lymphocytes with the ability to behave in a cell-autonomous, disease context-specific manner. Clone-specific behavioral properties are initially established during T cell development when thymocytes use TCR recognition of major histocompatibility complex (MHC) and MHC-like ligands to instruct survival versus death and to differentiate into a plethora of inflammatory and regulatory T cell lineages. Here, we review the ligand specificity of the preselection thymocyte repertoire and argue that developmental stage-specific alterations in TCR signaling control cross-reactivity and foreign versus self-specificity of T cell sublineages.

Green synthesis of thiazole bis-imines as fluorometric sensor for determination of lead in environmental, biological, and food samples

In this work, we describe for the first time the synthesis of a thiazole bis-imine fluorometric sensor for the selective determination of Pb2+ in environmental, biological, and food samples. The novel molecules were obtained through a multicomponent reaction using a green and environmentally sustainable methodology. Synthesized chemical sensors were characterized using spectroscopic techniques to structural elucidation, including UV–Vis, FTIR-ATR, 1H and 13C NMR. One of these sensors exhibited remarkable selectivity for the Pb2+ ion at pH 3, forming a stable 1:1 (metal:ligand) complex. Additionally, the reaction conditions for complex formation were optimized, resulting in a method with a linear range of 0.667–10 μg L−1 and a detection limit of 0.18 μg L−1. Furthermore, method validation reinforced its reliability, showing low relative standard deviation in both intra-day and inter-day analyses. Recovery experiments ranged from 83.53 % to 119.10 %. This study represents a significant and innovative advancement in the development of rapid, sensitive, and alternative methods for the detection of potentially toxic metals in a wide range of samples employing a green multicomponent reaction of thiazole bis-imines.

High-Valence Mn MOF Inspired by Laccase Mediators Enables Versatile Nature-Mimicking Catalysis.

In nature, active Mn3+ -ligand complexes produced by laccase catalyzed oxidation can act as the low-molecular mass, diffusible redox mediators to oxidize the phenolic substrates overcoming the limitations of natural enzymes. Learning from the metal-ligand coordination of natural functional units, high-valence Mn metal-organic framework (Mn MOF) is constructed to simulate the catalysis in natural mediator system. Benefiting from the characteristics of nanoscale size, rich metal coordination unsaturated sites, and mixed valence state dominated by Mn(III), Nano Mn(III)-TP exhibits superior laccase-mimicking activity, whose Vmax (maximal reaction rate) is much higher than that of natural laccase. Referring to natural systems, relevant free radical experiments prove that the material induces the production of active oxygen species with the assistance of carboxylic acid, and active oxygen species further oxidize phenolic substrates. Based on its robust performances, the primary oxidative degradation of an emerging pollutant triclosan (TCS) is creatively applied, an important antiasthmatic medicine terbutaline sulfate (TBT) detection, and the synthesis of non-toxic and black near-natural dyes for dyeing. By simulating the essential mediators of natural enzymatic catalysis, an Mn MOF-based material that demonstrates multiple novel applications is successfully developed, which introduces a new reliable strategy for achieving versatile nature-mimicking catalysis.

Water oxidation through electrocatalytic process using cobalt and nickel complexes of thiazole Schiff-base ligands

Ni(OAc)2.4H2O and CoCl2.6H2O reacted with thiazole ligands, HL and HL' (where HL= (E)-2-(((4-phenylthiazol-2-yl)imino)methyl)phenol and HL'= (Z)-2-(2-benzylidenehydrazinyl)-4-phenylthiazole, in ethanol to create new mononuclear Co(II) and Ni(II) complexes, CoL2, NiL2, CoL'2, and NiL'2 (1-4). X-ray diffraction analysis, spectroscopic, and electrochemical methods were used to study the complexes. A carbon paste electrode that had been modified by complexes 1-4 was used as the working electrode in a three-electrode setup to test the complexes' ability in water oxidation reaction at pH 13. The linear sweep voltammetry (LSV) curves showed that complexes 3 and 2 have much greater activity and only require the overpotential of 570 and 690 mV ʋs. RHE at a current density of 10 mA/cm2 with Tafel slopes of 86.92 and 94.19 mVdec−1 respectively in an alkaline solution. In addition, the amperometry tests exhibited brilliant stability for water oxidation by CPE-complex 3 and CPE-complex 2 under electrochemical conditions at pH 13. Although X-ray diffraction patterns did not display a crystalline structure, the scanning electron microscopy images displayed that cobalt oxide and nickel oxide in an alkaline condition are proper catalysts for water oxidation reaction on the surface of the modified electrode.

Group 7 carbonyl complexes of a PNN-heteroscorpionate ligand.

A series of rhenium and manganese carbonyl complexes of a heteroscorpionate ligand with an atypical N2P-donor set has been prepared to better understand their electronic and CO releasing properties. Thus, the ligand, pz2TTP, with an a,a-bis(pyrazol-1-yl)tolyl group decorated with an ortho-situated di(p-tolyl)phosphanyl reacts with carbonyl group 17 reagents to give [fac-(κ2NP-pz2TTP)Re(CO)3Br], 1, and [fac-(κ3N2P-pz2TTP)M(CO)3](OTf = O3SCF3), 2-M (M = Re, Mn), if care is taken during the preparation of the manganeses derivative. When heated in CH3CN, 2-Mn slowly transforms to [fac,cis-(κ3N2P-pz2TTP)Mn(CO)2(NCCH3)](OTf), 3-Mn. In contrast, the corresponding 3-Re can only be prepared from 2-Re using Me3NO; pure 3-Mn can also be prepared by this method. Experimental and density functional calculations at the M06L/Def2-TZVP/PCM(CH3CN) level show that the replacement of a carbonyl with an acetonitrile solvent decreases the oxidation potential by around 0.8 V per carbonyl released, making decarbonylated species potent reductants. At the same time, the electronic spectrum broadens and undergoes a red-shift, making dicarbonyl complexes more susceptible to photo-initiated decarbonylation reactions than tricarbonyls. When 2-Mn or 3-Mn are irradiated in with 390 nm LED light in aerated solutions, [trans-Mn(pz2TTP = O)2](OTf)2, 4, along with insoluble manganese oxides are rapidly formed.

The Synthesis of Melamine Cored Schiff Bases and Investigation of Heteronuclear Metal Complexes

In this study, 2,4,6-triamino-s-triazine (melamine) is the starting material. The condensation reaction of melamine and 4-hydroxybenzaldehyde resulted in the formation of the monopodal Schiff base. An oxygen-bridged monopodal complex of [(Fe(III)Salophen)Cl] ligand complex with monopodal Schiff base ligand was then obtained. Tripodal Schiff base ligand was obtained by condensing 2-hydroxybenzaldehyde with a monopodal complex and this ligand in some transition metal complexes were synthesized. As a result, the ligand and complexes of this ligand were isolated, as well as elemental analyses, FT-IR, 1H-NMR, TGA and magnetic susceptibility measurements of the obtained compounds were taken to elucidate their structures.

A Novel Synthesis of Substituted Benzo[1,2,4]Oxadiazine Derivatives Via Copper‐Catalyzed Intermolecular O‐Arylation of 2‐Iodoaniline and N‐Hydroxyimidoyl Chloride

AbstractIn this work, a rapid and direct route for the synthesis of benzo[1,2,4]oxadiazine derivatives through a copper iodide‐catalyzed intermolecular O‐arylation of 2‐iodoaniline and N‐hydroxyimidoyl chloride has been investigated. The reaction is fast and simple at room temperature and takes place in a reasonable amount of time. No complex ligands or special equipment are required. The use of cheap and available raw materials and catalysts, without column chromatography, performing the reaction in 4 hours, and good efficiency (72–86 %) are notable features of this protocol. The synthesized product is often found in drugs and other bioactive molecules.

Antithrombin regulates neutrophil activities through the stimulation of C-type lectin family 1A

It has been suggested that a serine proteinase inhibitor, antithrombin (AT), exerts anti-inflammatory effects on different types of cells, independent of thrombin inhibition. In the present study, we aimed to identify a specific receptor for antithrombin by a screening method using a transmembrane tethered-AT ligand expressed on HEK293T cells together with the co-expression of candidate receptors, followed by the immunoprecipitation of a complex of AT ligand with a receptor. We identified C-type lectin family 1A (CLEC1A) as a receptor for AT. We confirmed the binding of AT to the extracellular domain of CLEC1A using surface plasmon resonance. Recombinant as well as native AT concentration-dependently induced the rounding of purified human neutrophils in shape, associated with the suppression of spontaneous ROS production in vitro but argatroban did not, indicating the independence of AT effects on thrombin inhibition. Native AT maintained the passage of neutrophils through the artificial microcapillaries. Both AT also enhanced the phagocytosis of pHrodo-labeled E.coli and prolonged the viability of the neutrophils. The cellular effects of AT were similar to those of HRG which has the same CLEC1A as a receptor, and were partially inhibited by the addition of anti-CLEC1A antibody to the incubation media. These results suggested that CLEC1A is a novel receptor for AT and the stimulation of CLEC1A by AT at least in part mediates the important functional changes of human neutrophils.

Synthesis and characterization of Bis(imino)phosphine [NPN] ligands and their copper(I) halide complexes

A series of four new bis(imino)phosphine [NPN] ligands PhP(C6H4-2-HC = NAr)2 (Ar = 4-OMeC6H4 (L1, 1), 4-ClC6H4 (L2, 2), 4-BrC6H4 (L3, 3), 2,6-iPr2C6H3 (L4, 4)) were synthesized and structurally characterized. Their reactions with Cu(I) halides CuX (X = Cl, Br, I) were explored for the assembly of coordination complexes LnCuX, and the effects of substituent (Ar) and anion (X) were also investigated in a comparative manner. It was found that the reaction of methoxy substituted L1 (Ar = 4-OMeC6H) with CuX gave the mononuclear Cu(I) complexes L1CuX (X = Cl (1a), Br (1b), I (1c)) with isostructural feature. In contrast, when halogen-substituted ligands L2-3 (4-ClC6H4, 4-BrC6H4) were applied, their reactions with CuCl afforded the formation of tetranuclear dimer [Ln(CuCl)2]2 (n = 2 (2a), 3 (3a)) bridged by the Cu2Cl2 square, regardless of the composition of the reactants. On the other hand, reactions of L2-3 with CuBr and CuI generated the mononuclear Cu(I) complexes LnCuX (n = 2, X = Br (2b), I (2c); n = 3, X = Br (3b), I (3c)) again. In all these cases above, L1-3 ligands played the tridentate role by biting the copper(I) centers through NPN sites. When the bulky L4 (Ar = 2,6-iPr2C6H3) was involved, the binuclear dimer (L4CuI)2 (4c) bridged by iodide anions was obtained, where each L4 ligand coordinated the copper center using the bidentate P^N mode with another imino arm pendant. In further exploration, 1,10-o-phenanthroline (denoted as phen) was introduced to produce the heteroleptic complex L1CuCl(phen) (1d), where both imino arms in L4 were pendent. The obtained ligand (L1-4) and Cu(I) complexes were characterized by melting point, elemental analysis, FT-IR, UV–Vis, NMR, and single crystal X-ray diffraction.

Gel-type resin loaded with nano-hydrated ferric oxide for the removal of anions from papermaking wastewater

The main anions in papermaking wastewater are sulfate and chloride. In this paper, a strongly basic gel-type anion exchange resin (201×7) loaded with 20 ~ 200nm hydrated ferric oxide was prepared by dispersion impregnation with ethanol. The modified resin enhances the ability to remove sulfate by complexation of ligands to cause sulfate to form outer and inner sphere complexes on hydrated ferric oxide. The modified resin was dependent on acidic conditions, and the maximum exchange capacity for sulfate was enhanced by 14.2% under the optimal pH, exchange time, and ion concentration conditions. Competitive exchange experiments showed that the removal effect of the modified resin on chloride was almost unchanged under different chloride, sulfate ratios, and the degree of improvement of the removal effect on sulfate decreased from 9.5 ~ 5.5% with the increase of chloride ratio. The removal of sulfate by the modified resin was consistent with the proposed secondary kinetics and Langmuir adsorption model. In addition, the modified resin maintained 88% reuse after four desorption-adsorption cycles and achieved a regeneration rate of 93.1% after was eluted with HCl and reloaded with hydrated ferric oxide. The expected removal effect was well achieved when the resin was applied to the actual wastewater treatment. The above results indicate that the hydrated ferric oxide modification can improve the ability of the 201×7 resin to remove sulfate from water, and is a promising method for removing anions from papermaking wastewater.

Design, Synthesis, Biological Evaluation, and In Silico Study of N‐(Pyridin‐2/3‐yl)alkanamide Derivatives as Quorum Sensing Inhibitors Against Pseudomonas aeruginosa

AbstractThe effectiveness of treating bacterial infections is seriously jeopardized by the emergence of bacterial resistance to chemical therapy. The development of biofilm in bacteria is one of the main causes of resistance to antimicrobial drugs. By developing new antibiofilm medications, quorum sensing (QS) inhibitor was developed as an alternate therapy. QS inhibition, which focuses on the QS signaling pathway, obstructs cell–cell communication. The aim of this work is to develop newer QS inhibitors against Pseudomonas aeruginosa. N‐(Pyridin‐2/3‐yl)alkanamide derivatives were designed as QS inhibitors, and these designed molecules were synthesized. QS inhibitor activity was evaluated for the synthesized compounds (3a–l, 4a–h). The highest QS inhibitor activities for compounds 3k, 4a, and 4c were 11.66 ± 0.11, 14.66 ± 0.15, and 10.66 ± 0.05 mm, respectively. Subsequent molecular docking analyses exhibited moderate to good binding affinity values between −7.1 and −9.3 kcal/mol. Using the in silico method, the physicochemical characteristics of these prepared compounds were examined. Additionally, molecular dynamic simulation was employed to gain a deeper comprehension of stability of the protein and ligand complexes of compounds 3k, 4a, and 4c. The overall findings of the study indicated that N‐(pyridin‐2/3‐yl)alkanamide derivatives might be significant for the development of newer QS inhibitors.

Investigation of the homonuclear and polynuclear complexes of FeIII of pentadentate dipodal s-triazine Schiff base ligand

An efficient synthesis of a new class of “Dipodal s-triazine Schiff base ligand” has been developed based on high-yielding amines substitutions of 2-vinyl-4,6-diamino-1,3,5-triazine (acryloguanamine) (VDAT) by salicylaldehyde. A new compound characterized by a dipodal s-triazine pentadentate Schiff base with 2-vinyl-4,6-N,N’-bis(2,4-dihydroxybenzylidine)-1,3,5-triazine [VDAT24] has been developed. The obtained [VDAT24] was polymerized to obtain poly(2-vinyl-4,6-N,N’-bis(2,4-dihydroxybenzylidine)-1,3,5-triazine) [PVDAT24]. Subsequently, s-Triazine-centered Fe(III) homonuclear complexes [VDAT24Fe], and polynuclear complexes [PVDAT24Fe] were obtained derived. As a result, the ligand obtained by elemental analysis, ICP-AES, TGA, FTIR, 1H NMR and 13C NMR. Isolated ligand complex, FTIR, TGA, and were illuminated structures on the magnetic susceptibility. The resulting two different polymeric ligands and certain complexes of FTIR, TGA, and Ostwald Viscometer elucidated the structures of magnetic susceptibility.

Mixed ligand complex: Synthesis, characterization, and investigation of biomedical activity

تحضيرمركب جديد, تم تحضير معقد النحاس الجديد عن طريق تفاعل CuCl2.2H2O مع الميلاتونين وأحد الأحماض الأمينية (L-cysteine) بنسبة مولية (M:L1:L2) (1:1:1), وتم تشخيص المعقد بواسطة طرق طيفية تتضمن الأشعة تحت الحمراء (FT-IR) والرنين النووي المغناطيسي للبروتون (1H-NMR) والتحليل الحراري (TG) والامتصاص الذري اللهبي (AAS)، وتحليل العناصرالدقيق (CHNS)، وكذلك قياس درجة الانصهار (m.p) وتقديرمحتوى الكلوريد. من معطيات الطرق الطيفية المشاراليها آنفا تشيرالى أن الشكل الهندسي المقترح للمعقد هو ثماني السطوح. أظهرت قياسات التوصيل الكهربائي والمغناطيسية بأن معقد النحاس غيرالكتروليتي وذي صفة بارامغناطيسية. تم فحص فعالية تركيز المعقد المحضر كعامل مضاد للبكتيريا من نوع Escherichia coli (G­)و Staphylococcus aureus (G+) ومضاد للفطريات (fungus Candida) حيث اظهر المعقد فعالية افضل من الليكاندين وتم اختبارخاصيته كمضاد للسرطان.

Synthesis of metal(II) acetate complexes with a heterocyclic azo dye ligand: Characterization, geometrical molecular structures, antioxidant, biological activities, DNA binding and molecular docking studies

A series of Cu(II), Co(II), Ni(II), Mn(II), and UO2(II) complexes have been prepared from the ligand 4-(2’,4’-dihydroxybenzaldehyde phenylazo)antipyrine (H2L). FT-IR spectra demonstrated that the ligand under investigation behaves as a bi-and tridentate centre ligand through the phenolic oxygen of aldehydic, azo nitrogen atoms and carbonyl oxygen of antipyrine and forms a stable five- and six-membered chelating ring. From the X-ray crystallographic analysis (XRD) patterns of the ligand and complexes showed the polycrystalline phases are indicated by the multiple diffraction peaks in the 1igand and its complex (5). The HOMO‒LUMO energy gaps (∆E) were used to create theoretical models for the structure and confirmation barriers in molecular systems for the ligand (H2L) and metal complexes. It was found that the Cu(II), Co(II), Ni(II), and Mn(II) complexes have lower values for HOMO‒LUMO energy gaps (∆E), indicating that they are more stable than the 1igand. The biological activities of ligand (H2L) and its metal complexes showed that ligand was stronger antimicrobial and antioxidant agent than its metal complexes. 50 µg/ml H2L caused inhibition zones ranged from 13 to 20 mm against the tested bacteria and 13 to 16 against fungi. In addition, the present study tested metal (II) acetate complexes with a heterocyclic azodye ligand for their application in the textile industry as antimicrobial dyed fabrics. All obtained results confirmed the possibility of using the prepared compounds in different industrial applications. The 1igand (H2L) and its metal complexes showed moderate to strong antimicrobial activities in agar well diffusion, MIC, and antioxidant tests. Ligand and its metal complexes revealed inhibition zones against all tested microbes ranged between 6 to 24 mm. The MIC values of ligand and its metal complexes were recorded at 20 to 30 μg/ml and 30 to 145 μg/ml, respectively. 50 µg/ml of 1igand and its metal complexes was enough to complete inhibit Gram negative E. coli moreover they could inhibit the multidrug resistant bacteria K. pneumoniae and Pseudomonas sp. By molecular docking study, it was found that the complex (1) showed the highest and better binding affinity (-8.38874 and -7.74442 kcal/mol) than other 1igand (H2L) and complexes (2–5) for the breast cancer (3HB5) protein central activity and the colon cancer (2HQ6) protein central activity.

Transition metal complexes of benzimidazole-based ligands: Synthesis, characterization, biological, and catecholase activities

Heterocyclic ligands 5a and 5b and their metal complexes (1–10) and (11–20) respectively, were synthesized and characterized by mass spectrometry, FT-IR, ESR, 1H, 13C NMR and UV–visible spectroscopy. In vitro antifungal activity of the heterocyclic analogs 5a, 5b and metal complexes (1–20) was evaluated against the fungal strains: Candida albicans, Candida glabrata, and Candida tropicalis., The results showed that Fe(III) 2 and Co(II) complex 13 display considerable antifungal activity with MIC values of 350, 375 and 435 μg/mL and 450, 455, and 455 μg/mL against C. albicans, C. glabrata, and C. tropicalis, respectively. Promising 5a, 5b, Fe(III) 2, and Co(II) complex 13 show groove binding mode with Ct-DNA, which has been confirmed by several techniques, including UV–visible, fluorescence spectroscopy, and cyclic voltammetry. PDB ID: 1BNA was used for the molecular docking investigation of the heterocyclic analogs 5a and 5b. The active Fe(III) complex 2 and Co(II) complex 13 are effectively catalyzed for the oxidation of catechol in acetonitrile to its corresponding quinone with turnover number 5.44 × 104 and 9.78 × 104 h−1, respectively with first order that follow Michaelis-Menten enzymatic kinetics. The pharmacokinetics properties of the all compounds showed good oral bioavailability. Antioxidant potential of ligands 5a, 5b, Fe(III) 2 and Co(II) complex 13 was further approximated through DPPH free radical and H2O2 with remarkable antioxidant activity.

Syntheses, characterization and antibacterial activity of mononuclear and dinuclear copper(II) complexes containing a hydrazone ligand

An aroylhydrazone compound (HL) was prepared and explored as a ligand (HL = N’-(2-hydroxy-4-methoxybenzylidene)-3-hydroxy-4-methoxybenzohydrazide). Reaction of the aroylhydrazone ligand with copper bromide and copper chloride afforded two new copper(II) complexes, [Cu2Br2L2] (1) and [CuL(DMF)]Cl (2), respectively. The aroylhydrazone ligand and copper complexes were characterized by CHN elemental analyses and infrared spectroscopy. Structures were further confirmed by single crystal X-ray diffraction experiments. The aroylhydrazone compound coordinates to Cu atoms through its phenolate oxygen, imino nitrogen and carbonyl oxygen. The Cu atom in 1 adopts a square pyramidal coordination, with three donor atoms of one L and one phenolate oxygen of a second L in the basal plane, and with one Br ligand at the apical position. The Cu atom in 2 is square pyramidal, with three donor atoms of one L and one oxygen of a DMF ligand in the basal plane, and with one Cl ligand at the apical position. Crystal structures of the aroylhydrazone and the copper complexes are stabilized by hydrogen bonds. The complexes possess antibacterial activities against B. subtilis, S. aureus and E. coli.

Carbohydrate-Binding Mechanism of the Coagulant Lectin from Moringa oleifera Seeds (cMoL) Is Related to the Dimeric Protein Structure

This study characterized the binding mechanisms of the lectin cMoL (from Moringa oleifera seeds) to carbohydrates using spectroscopy and molecular dynamics (MD). The interaction with carbohydrates was studied by evaluating lectin fluorescence emission after titration with glucose or galactose (2.0–11 mM). The Stern–Volmer constant (Ksv), binding constant (Ka), Gibbs free energy (∆G), and Hill coefficient were calculated. After the urea-induced denaturation of cMoL, evaluations were performed using fluorescence spectroscopy, circular dichroism (CD), and hemagglutinating activity (HA) evaluations. The MD simulations were performed using the Amber 20 package. The decrease in Ksv revealed that cMoL interacts with carbohydrates via a static mechanism. The cMoL bound carbohydrates spontaneously (ΔG < 0) and presented a Ka on the order of 102, with high selectivity for glucose. Protein–ligand complexes were stabilized by hydrogen bonds and hydrophobic interactions. The Hill parameter (h~2) indicated that the binding occurs through the cMoL dimer. The loss of HA at urea concentrations at which the fluorescence and CD spectra indicated protein monomerization confirmed these results. The MD simulations revealed that glucose bound to the large cavity formed between the monomers. In conclusion, the biotechnological application of cMoL lectin requires specific methods or media to improve its dimeric protein structure.

Adsorption and Catalytic Reduction of Nitrogen Oxides (NO, N2O) on Disulfide Cluster Complexes of Cobalt and Iron-A Density Functional Study.

The reactivity of nitrogen oxide, NO, as a ligand in complexes with [Fe2-S2] and [Co2-S2] non-planar rhombic cores is examined by density functional theory (DFT). The cobalt-containing nitrosyl complexes are less stable than the iron complexes because the Co-S bonds in the [Co2-S2] core are weakened upon NO coordination. Various positions of NO were examined, including its binding to sulfur centers. The release of NO molecules can be monitored photochemically. The ability of NO to form a (NO)2 dimer provides a favorable route of electrochemical reduction, as protonation significantly stabilizes the dimeric species over the monomers. The quasilinear dimer ONNO, with trans-orientation of oxygen atoms, gains higher stability under protonation and reduction via proton-electron transfer. The first two reduction steps lead to an N2O intermediate, whose reduction is more energy demanding: in the two latter reaction steps the highest energy barrier for Co2S2(CO)6 is 109 kJ mol-1, and for Fe2S2(CO)6, it is 133 kJ mol-1. Again, the presence of favorable light absorption bands allows for a photochemical route to overcome these energy barriers. All elementary steps are exothermic, and the final products are molecular nitrogen and water.

Antimicrobial Activity of Anionic Bis(N-Heterocyclic Carbene) Silver Complexes

The antimicrobial properties of a series of anionic bis(carbene) silver complexes Na3[Ag(NHCR)2] were investigated (2a–2g and 2c′, where NHCR is a 2,2′-(imidazol-2-ylidene)dicarboxylate-type N-heterocyclic carbene). The complexes were synthesized by the interaction of imidazolium dicarboxylate compounds with silver oxide in the presence of aqueous sodium hydroxide. Complexes 2f,g were characterized analytically and spectroscopically, and the ligand precursor 1f and complexes 2c and 2g were structurally identified by X-ray diffraction methods. The anions of 2c and 2g, [Ag(NHCR)2]3−, showed a typical linear disposition of Ccarbene-Ag-Ccarbene atoms and an uncommonly eclipsed conformation of carbene ligands. The antimicrobial properties of complexes 2a–g, which contains chiral (2b–2e and 2c′) and non-chiral derivatives (2a,f,g), were evaluated against Gram-negative bacteria, Escherichia coli and Pseudomonas aeruginosa, and a Gram-positive bacterium, Staphylococcus aureus. From the observed values of the minimal inhibitory concentration and minimal bactericidal concentration, complexes 2a and 2b showed the best antimicrobial activity against all strains. An interesting chirality–antimicrobial relationship was found, and eutomer 2c′ showed better activity than its enantiomer 2c against the three bacteria. Furthermore, these complexes were investigated experimentally and theoretically by 109Ag nuclear magnetic resonance, and the electronic and steric characteristics of the dianionic carbene ligands were also examined.