Hg Complexes Research Articles

Antifungal, antibacterial and DNA binding profile of three novel Zn(II), Cd(II) and Hg(II) complexes of a pyrazole-based Schiff-base ligand: Synthesis, crystal structures, DFT studies and spectroscopic investigation

Three new mononuclear Zn(II), Cd(II) and Hg(II) complexes, [Zn(MPAFA)3](ClO4)2 (1), [Cd(MPAFA)3](ClO4)2 (2) and [Hg(MPAFA)Cl2] (3) of a pyrazole based ‘NN’ bidentate Schiff-base ligand, N-(furan-2-ylmethyl)-1-(5-methyl-1H-pyrazol-3-yl)methanimine, (MPAFA) (L) were synthesized and characterized by elemental analyses, conductance, IR, NMR (1H and 13C), UV-Vis and fluorescence spectral techniques. Molar conductance measurements identified both 1 and 2 as 1:2 electrolytes, while 3 as a non-electrolyte. Single crystal X-ray diffraction studies recognized complexes 1 and 2 as distorted octahedral species with a N6 donor set. The presence of strong non-covalent interactions, such as intramolecular hydrogen bonding and π···π stacking within the complex molecules has been found to contribute to the enhanced stability of the complexes. In absence of single crystal, the structural feature of complex 3 has been confirmed by DFT studies and it has been found to adopt a distorted square-planar geometry with a N2Cl2 coordination. DFT calculations have also been conducted for 1 and 2. The TD-DFT absorption spectral studies supported the experimental results, indicating that the simulated peaks aligned reasonably well with the experimentally resolved peaks. Furthermore, the ligand and all its complexes exhibited effective antifungal activity against Colletotrichum siamense (AP1) and Fusarium equisetum (F.E) fungi. They also displayed promising antibacterial activity against both the gram-negative bacterium Klebsiella sp. (KS) and the gram-positive bacterium Methicillin-resistant Staphylococcus aureus (MRSA). The binding interactions of 1, 2 and 3 with calf-thymus DNA (CT-DNA) have also been studied using a combination of UV-Vis and fluorescence spectroscopic methods.

Mercury Speciation and Stable Isotopes in Emperor Penguins: First Evidence for Biochemical Demethylation of Methylmercury to Mercury-Dithiolate and Mercury-Tetraselenolate Complexes

Apex marine predators, such as toothed whales and large petrels and albatrosses, ingest mercury (Hg) primarily in the form of methylmercury (MeHg) via prey consumption, which they detoxify as tiemannite (HgSe). However, it remains unclear how lower trophic level marine predators, termed mesopredators, with elevated Hg concentrations detoxify MeHg and what chemical species are formed. To address this need, we used high energy-resolution X-ray absorption near edge structure spectroscopy paired with nitrogen (N) and Hg stable isotopes to identify the chemical forms of Hg, Hg sources, and species-specific δ202Hg isotopic values in emperor penguin, a mesopredator feeding primarily on Antarctic silverfish. The penguin liver contains variable proportions of MeHg and two main inorganic Hg complexes (IHg), Hg-dithiolate (Hg(SR)2) and Hg-tetraselenolate (Hg(Sec)4), each characterized by specific isotopic values (δ202MeHg = 0.3 ± 0.2‰, δ202Hg(SR)2 = −1.6 ± 0.2‰, δ202Hg(Sec)4 = −2.0 ± 0.1‰). Using δ15N as a tracer of food source, we show that Hg(SR)2 is likely not obtained through dietary intake, but rather is present as a biochemical demethylation product. Furthermore, on average, female penguins transferred Hg to the egg strictly as MeHg in the egg albumen but as mixtures of MeHg and IHg in the membrane (89% and 11%, respectively) and yolk (32% MeHg and 68% Hg(Sec)4). Despite IHg species in eggs, MeHg is still the main species quantitatively transferred by the mother to the chick because of the disproportionate mass of the MeHg-rich albumen compared to the yolk. This work highlights the transformation of MeHg to Hg(SR)2 during demethylation for the first time in multicellular organisms, but further work is needed to understand the formation of Hg(SR)2 in the presence of relatively abundant Se biomolecules in lower trophic level predator species.

Asymmetric tridentate Schiff base ligand based mononuclear Zn(II) and Hg(II) complexes: Synthesis, structure, spectroscopic studies, thermal studies, and DFT calculation

Two novel mononuclear metal(II) complexes with an asymmetric tridentate Schiff base ligand, and azide/chloride anions, namely [ZnL(N3)2] (1) and [HgL(Cl)2] (2) (L = (pyridin-2yl)methylimino)-2-ethylpyridine), have been synthesized and structurally characterized by elemental analysis, single crystal X-ray crystallography, FT-IR, NMR, UV–vis electronic absorption spectroscopic analysis. The metal in both the complexes displays a pentacoordination environment realized by the tridentate Schiff base and counter anions. The coordination geometry of Zn in complex 1 is in between a trigonal bipyramidal and square pyramidal, whereas Hg in complex 2 shows a distorted square pyramidal. Theoretical DFT/TD-DFT calculation data performed using B3LYP functional with LanL2MB basis set, compared with values of experimental measurements, have shown a reasonable accord. The thermal stability of both complexes has been studied.

Experimental and computational evaluation of anti-malarial and antioxidant potential of transition metal (II) complexes with tridentate schiff base derived from pyrrolopyrimidine.

In the twenty-first century, we are experiencing persistent waves of diverse pathogen variations, contributing significantly to global illness and death rates. Within this varied spectrum of illnesses, malaria and oxidative damage emerge as prominent obstacles that have persistently affected human health. The motivation for exploring the antioxidant potential of transition metal (II) complexes with tridentate Schiff base ligands is driven by the need for effective treatments against malaria and oxidative stress-related conditions. Both malaria and oxidative damage are significant global health concerns. Transition metal complexes can potentially offer enhanced anti-malarial and antioxidant activities, providing a dual benefit. To explore the aforementioned facts and examine the therapeutic potential, the previously synthesized pyrrolopyrimidinehydrazide-3-chlorobenzaldehyde, such as HPPHmCB ligand(1)andtheirMn(II),Fe(II),Co(II),Ni(II), Pd(II),Cu(II),Zn(II),Cd(II),Hg(II)complexes(2-10) of benzaldehydes and pyrrolopyrimidinehydrazide were proposed for in vitro anti-malarial and antioxidant investigation. These compounds were assessed for their anti-malarial efficacy against Plasmodium falciparum using a micro assay protocol, with IC50 values indicating the concentration required to inhibit parasite maturation by 50%. The Hg(II) complex displays pronounced antimalarial activity with an IC50 value of 1.98 ± 0.08µM, closely aligning with the efficacy of quinine, whereas Zn(II), Cu(II), Pd(II) complexes demonstrates most significant anti-malarial activity, with IC50 values close to the reference compound quinine. The antioxidant activity of the compounds was evaluated using the DPPH assay, with several metal complexes such as Cu(II)and Zn(II) showing strong potential in neutralizing oxidative stress. Furthermore, molecular docking simulations were conducted to explore the binding interactions of the compounds with PfNDH2, providing insights into their pharmacological potential. The study also examined the electronic properties, solubility, and potential hepatotoxicity of the compounds. The findings suggest that the metal complexes could be promising candidates for further development as anti-malarial agents, offering enhanced potency compared to the base compound.

Terrestrial input and biological processes drive varying mineral/organic matrix-related mercury sequestration and deposition in the East Siberian Arctic Shelf

Thawing Arctic permafrost is releasing massive amounts of terrestrial mercury (Hg) into the Arctic shelf, which is expected to form a Hg sink in sediments. Here we analyzed the coupling roles of terrestrial input and biological processes in varying mineral/organic matrix-related Hg sequestration and deposition on the East Siberian Arctic shelf (ESAS), using Pearson and partial correlation analysis. Results show that the occurrence of Hg in the Laptev Sea under the Lena River-dominated input exhibits strong correlations with the organic carbon (OC) content and sediment specific surface area. This indicates that the prolonged riverine loading processes facilitate Hg sequestration by organic/mineral matrices and these land-derived mineral-OC-Hg complexes remain stable during cross-shelf transportation. By contrast, the comparative samples with coastal erosion-dominated Hg input in the western East Siberian Sea shows limited Hg complexation, primarily due to the absence of regulation by riverine processes and/or the high sedimentation rates. The correlations between Hg and OC source proxies (δ13C and lignin) indicate that these matrix-free Hg could be more readily sequestrated by the marine OC, which facilitates its deposition via the biological pump. While unexpectedly low Hg abundance in the Chukchi Sea may indicate that the effective biological scavenging of Hg sequestration could be constrained by insufficient terrestrial Hg input. Our findings of the matrix-related Hg sequestration by mineral and/or OC association in this study may shed light on the biogeochemical cycle of Hg in the Arctic aquatic regime, which could reduce the methylmercury formation in water column, and the methylation within sediments needs further exploration.

Synthetic and theoretical study on novel N-ylidic complexes of mercury as new antibacterial agents

The novel structure of Hg(II) complexes including the pyridinium ylide C5H5NCHC(O)C6H4-m-Br (Y) were synthesized and reported in this study. In the first step, the pyridinium salt C5H5NCH2C(O)C6H4-m-Br (S) was produced by reacting 2,3′-dibromoactophenone and pyridine. then, treatment of S with K2CO3 gave the related pyridinium ylide Y. Finally, the reaction of Y with HgX2 and Hg(NO3)2·H2O leads to the formation of novel binuclear [HgY2][HgX4] (X=Cl (1); X=Br (2); X=I (3)) and polymeric [HgY(NO3)2]n (4) complexes. The structure of complex 2 was also determined by X-ray diffraction analysis. The obtained analyses proved the coordination through the ylidic carbon to metallic center. Additionally, Natural Bond Orbital (NBO), Energy Decomposition Analysis (EDA), and EDA-NOCV studies are also used to investigate the nature of metal–ligand bonding in the complexes. Finally, the antibacterial activity of 1–4 was also examined against Gram positive and negative represented significant levels of inhibitory potency respected to used standards.

Heteronuclear Complexes of Hg(II) and Zn(II) with Sodium Monensinate as a Ligand.

The commercial veterinary antibiotic sodium monensinate (MonNa) binds mercury(II) or zinc(II) cations as thiocyanate [Hg(MonNa)2(SCN)2] (1) or isothiocyanate [Zn(MonNa)2(NCS)2] (2) neutral coordination compounds. The structure and physicochemical properties of 1 and 2 were evaluated by the methods of single crystal and/or powder X-ray diffraction, infrared, nuclear magnetic resonance, X-ray photoelectron spectroscopies, and electrospray-mass spectrometry. The primary cores of the two complexes comprise HgS2O2 (1) and ZnN2O2 (2) coordination motifs, respectively, due to the ambidentate binding modes of the SCN-ligands. The directly bound oxygen atoms originate from the carboxylate function of the parent antibiotic. Sodium cations remain in the hydrophilic cavity of monensin and cannot be replaced by the competing divalent metal ions. Zinc(II) binding does not influence the monensin efficacy in the case of Bacillus cereus and Staphylococcus aureus whereas the antimicrobial assay reveals the potential of complex 2 as a therapeutic candidate for the treatment of infections caused by Bacillus subtilis, Kocuria rhizophila, and Staphylococcus saprophyticus.

Bioinspired Hg2+-sensing fluorogenic probe based on amino acid–functionalized rhodamine

Inspired by the suitability of rhodamine spirolactam switching for superresolution imaging and fluorescent probe development, we herein synthesized rhodamine-based probes with sulfur-bearing amine and amino acid moieties and screened their abilities to respond to Hg2+ in the presence of other metal ions. The probe based on S-methylcysteine methyl ester–substituted rhodamine 6G (Rho6G-6) was identified as optimal because of its straightforward synthesis and rapid, selective, and sensitive (detection limit = 8 × 10–9 M) response to Hg2+ manifested by absorption spectrum and emission color changes. The complexation of Hg2+ by Rho6G-6 was examined by absorbance and fluorescence analyses, electrospray ionization–mass spectrometry, and 1H nuclear magnetic resonance (NMR) titration experiments. Furthermore, the practical applicability of the above probe was demonstrated by naked-eye colorimetric Hg2+ detection using paper test strips and the fluorescence-based qualitative mapping of the Hg2+ distribution in living HeLa cells and the organs of live mice. Thus, unlike other probe design strategies, the use of flexible S-methyl amino acids for Hg2+ binding provides new opportunities and strategies for photopromoting the ring switching of the rhodamine spirothiolactam.

Synthesis, Thermogravimetric and Spectroscopic Characterizations of New Tetraazamacrocyclic Schiff Base Ligand and Some Metal Complexes

In the present study, metal complexes of Mn(II), Ni(II), Co(II), Cu(II) and Hg(II) were synthesized using new Tetraazamacrocyclic Schiff Base (5E,8E,14E,17E)-6,8,15,17-tetramethyl-1,2,3,4,4a,7,9a,10,11,12,13,13a,16,18a-tetradecahydrodibenzo [b,i][1,4,8,11]tetraazacyclotetradecine (L) derived from 1,2-diamino cyclo hexane with the acetyl acetone. Compounds have been exanimated and confirmed by fourier-transform infrared (FT-IR), ultraviolet-visible (UV-visible), proton nuclear magnetic resonance (1HNMR), carbon nuclear magnetic resonance (13CNMR), microelemental analyses (CHN), thermal analysis (TG), conductivity and magnetic susceptibility. The propose geometry for all complexes [MLCl2] structures were octahedral. Thermogravimetric of cobalt complex was carried out in two steps by fission into several small aggregates.

Synergistic exploration of antimicrobial potency, cytotoxicity, and molecular mechanisms: A tripartite investigation integrating in vitro, in vivo, and in silico approaches for pyrimidine‐based metal (II) complexes

We synthesized and characterized bioactive metal (II) complexes from a pyrimidine‐based Schiff base ligand, 4‐[2‐(4‐chlorobenzylidene) hydrazinyl]‐7H‐pyrrolo[2,3‐d]pyrimidine. Through thorough elemental analysis and various physicochemical techniques, we characterized both the ligand and its Zn(II), Cd(II), and Hg(II) complexes. Coordination of the metallic ion was established via nitrogen atoms from the ligand's pyrrolo and pyrimidine rings, yielding tetrahedral complexes of the type [M(PPHpCB)2]. These complexes are identified as non‐electrolytes due to their low molar conductance. Furthermore, we investigated the coordination behavior of the pyrimidine‐based Schiff base ligand (HPPHpCB) with metal ions through comprehensive spectroscopic analysis. 1H NMR spectral data showed bonding between HPPHpCB and metal ions, while UV spectra confirmed intra‐ligand and ligand‐to‐metal charge transfer transitions, indicating coordination through nitrogen atoms. The determination of tetrahedral geometry for metal complexes confirmed their diamagnetic properties. Analysis using 13C NMR and electrospray ionization mass spectra (ESI‐MS) revealed variations in chemical shifts, confirming successful complex formation and elucidating structural modifications, electronic interactions, and metal–ligand coordination modes. Moreover, evaluation of in vitro antimicrobial activities using the minimum inhibitory concentration (MIC) approach revealed significant antibacterial and antifungal activities for Hg(II) and Cd(II) complexes, respectively. The Hg(II) complex displayed superior antioxidant activity, while Zn(II) and Cd(II) complexes also demonstrated considerable potential. In vivo, cytotoxicity assessments against Artemia salina provided insights into the cytotoxic properties of ligands and metal complexes. Computational techniques suggested their potential in combating infectious ailments. Overall, our study establishes the synthesis, characterization, and multifaceted biological activities of metal (II) complexes derived from the pyrimidine‐based Schiff base ligand, highlighting their promising role in combating various infectious diseases.

Fluorine-doped g-C3N5 quantum dots for detection of heavy metal ions

Heavy metal contamination is toxic at low concentrations and leads to considerable environmental and health issues. Detection of heavy metal ions by photoluminescence quenching attracts significant attention. This study demonstrates the synthesis of fluorine-doped triazole-based g-C3N5 quantum dots (FQDs) with reduced photoluminescence emission intensities and enhanced excited charge lifetimes. The excited electrons of these FQDs are withdrawn by fluorine ions with high electronegativity, thereby inhibiting photoluminescence emission. FQDs are used for the detection of Fe2+, Fe3+, and Hg2+ ions through photoluminescence (PL) quenching, and the excited electrons are transferred between the F-doped QDs and these transition metal ions, reducing the PL emission. The LOD (limit of detection) values of Fe2+ and Hg2+ ions for CNQD were 0.423 and 0.438 ppm, respectively, whereas 3FQD exhibited an LOD value of 0.262 ppm for Fe2+, and 10FQD had an LOD value of 0.218 ppm for Hg2+ ions. Computational calculations suggest that the divalent cations contribute considerably to the lowest unoccupied molecular orbitals (LUMOs) of C3N5-Fe2+, C3N5-Zn2+, and C3N5Hg2+, and the low-lying excitations of these C3N5−M2+ (M = Fe and Hg) complexes show strong charge transfer features. Most of the excited electrons are situated around the Fe2+ and Hg2+ ions in the C3N5-Fe2+ and C3N5Hg2+ complexes. As a result, Fe2+ and Hg2+ ions induce extensive PL quenching of the triazole-based C3N5 QDs.

Pd(II), Pt(II), Zn(II), Cd(II) and Hg(II) complexes of the newly prepared 1,2-benzo- isothiazol-3(2H)-dithiocarbamate (BIT-DTC) ligand

In the current work, we report the synthesis and characterization of new dithiocarbamate complexes derived from 1,2-benzoisothiazol-3(2H)-one (BitH). The ligand was synthesized by treating the BitH with carbon disulfide in a basic solution. The NMR technique confirmed the preparation of the ligand. The treatment of the Bit-dtcNa with the metal salt’s solution afforded the complexes of the type [M(Bit-dtc)2]; M = Zn, Cd, Hg, Pd, and Pt. The complexes were characterized via FT-IR and 1H-NMR techniques. The Zn, Pd, and Pt complexes were investigated theoretically, and some of their quantum properties were determined. These parameters include HOMO-LUMO energies, electron affinity, ionization potential, chemical hardness, dipole moment and the total energies of the optimized structures. Moreover, the surface structure of Zn and Hg complexes were investigated by SEM and XRD techniques. The SEM pattern showed a cubic structures for the Zn complex while the Hg complex appeared as a nano rods structure. The calculated average particle sizes for Zn and Hg complexes were 23 and 26 nm, respectively. KEY WORDS: Dithiocarbamate, 1,2-Benzoisothiazol-3(2H)-one, DFT, SEM, XRD Bull. Chem. Soc. Ethiop. 2024, 38(3), 889-899. DOI: https://dx.doi.org/10.4314/bcse.v38i4.6

Synthesis, Characterization, and Biological Evaluation of New Hg(II) Complexes of (2-(2-(2-chlorobenzylidene)hydrazineyl)benzothiazole with Phosphine Ligands

The Synthesis of new Hg(II) complexes of (2-(2-(2-chlorobenzylidene) hydrazinyl)benzothiazole) (CHB) with phosphine ligands (dppm, dppe, dppp, and dppb) were synthesized, resulting in complexes with the following formulas: [Hg2(CHB)2(µ-dppm)2]Cl4 or [Hg2(CHB)2(µ-phosphine)Cl2]Cl2 (where the phosphines are dppe, dppp and dppb). The suggested geometry around the metal ion is tetrahedral, with the (CHB) ligand acting as a bidentate ligand through the N atoms, while the phosphine ligands act as bidentate bridging ligands through the P atoms. The prepared complexes were characterized various analytical techniques including molar conductivity, infrared spectra, 31P{1H}-NMR, 1H-NMR, and 13C-NMR spectra. Additionally, the biological effectiveness of these complexes was evaluated against four types of bacteria, namely Streptococcus faecalis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, has been assessed. Some of the complexes exhibited an inhibition level in the range of (5-10 mm) at the minimum inhibitory concentration indicating potential antibacteria properties.

DNA binding, potential anticancer, antioxidant and molecular docking simulations of some isonicotinohydrazide metal complexes with the impact of high energy γ-rays irradiation doses: Synthesis and structural characterization

This work focuses on the preparation and characterization of some VO(II), Co(II), Cu(II), Zn(II) and Hg(II) complexes (1–5) of N'-(2-aminobenzoyl)isonicotinohydrazide ligand (HL). The compounds were characterized using various analytical and spectral tools. The resulting powder samples of the as prepared complexes (3,5) were exposed to two gamma ray doses up to 150 and 200 kGy from highly-energetic 60Co γ-irradiation (hereafter referred to as (3F,5F) at dose value of 150 kGy and (3F*,5F*) at dose value of 200 kGy). The impact of γ-irradiation on the possible structural changes of these samples after gamma irradiation was studied. The ligand and as prepared Cu(II) (3), Hg(II) (5) and their γ-irradiated (3F,5F) and (3F*,5F*) samples were tested for free radical scavenging activity using the DPPH assay. The DNA cleavage activity using supercoiled plasmid DNA (calf thymus ct-DNA) was explored. The tested ligand (HL) and complexes (3,5) showed excellent DNA binding. Additionally, the in vitro antitumor activity of (HL) and its Cu(II) (3) and Hg(II) (5) complexes was scrutinized against the human breast carcinoma (MCF-7), human hepatocarcinoma (Hep-G2) cell lines and kidney epithelial normal cells extracted from African green monkey kidney (Vero) to investigate the potential safety towards the normal cells. Also, docking simulation was done on the active site of 4FM9 and 1H7K protein for liver cancer and breast cancer cell line, respectively and showed excellent results.

Algal-derived dissolved organic matter accelerates mercury methylation under cyanobacterial blooms in the sediment of eutrophic lakes

Mercury (Hg), especially in the form of methylmercury (MeHg), poses a significant threat to both organisms and the environment due to its extreme toxicity. While methylation process of Hg in sediments has been extensively studied, recognition of its associated risks and mechanisms during cyanobacterial blooms remains limited. This study investigated the distribution characteristics of Hg and MeHg in sediments of Taihu Lake, China. The concentration of Hg and MeHg varied within the range of 96.0–212.0 ng g−1 and 0.1–0.5 ng g−1, respectively. Higher ecological risks of Hg were found in algal-dominated regions compared to macrophyte areas. The significant correlations observed between Hg, MeHg, and algal-derived dissolved organic matter (ADOM) components C1 and C2 in algal-dominated regions indicate a close association between ADOM components and the Hg methylation process. These components are involved in the absorption or complexation of Hg, participate in redox reactions, and modulate microbial activity. The dsrB gene in sulfate-reducing bacteria (SRB) was found to accelerate the metabolic pathways of Hg methylation. These findings indicate that ADOM could enhance the methylation process of Hg during cyanobacterial blooms, which warrants attention.

Synthesis and characterizations of Hg (II) Complex of Macrocyclic complexes compounds Tetradecahydrodibenzo hexaazacyclooctadecine with HgX2 (X= Cl, Br) by Hirshfeld analysis and antimicrobial activity

This study examines the synthesis and characterization of a macrocyclic complex molecule having the general formula [M-LX2], where M =Hg (II) with schiff base Tetradecahydrodibenzo hexaazacyclooctadecine ligands. Resulted from the interaction between mercury and the diethyl triamine and benzene- 1, 2 diol in an ethanolic solution. Schiff base and its novel mercury (II) Complexes were studied vibrational in the solid state using spectral, 1H-NMR, IR, UV, and antimicrobial activity approaches. We were able to establish the coordination mode of the metal in complexes by comparing the changes in the ligands' and complexes' FT-IR and UV-Visible spectra.
 Keywords: MERCURY (II), Schiff bases, IR, 1H-NMR, PXRD Spectroscopy.

Design and Synthesis of Pyridine Bis-Hydrazone Metal Complexes of Co(II), Cu(II), and Hg(II): Spectral, Gaussian, Electrochemical, Biological, Drug-Likeness and Molecular Docking Investigations

A bis-hydrazone ligand (H2DS) was synthesized via condensation of pyridine-2,6-dicarbohydrazide with salicylaldehyde and utilized to prepare a new series of Cu(II), Co(II), and Hg(II) metal chelates. All the prepared chelates were investigated using various assistive spectroscopic and microscopic tools including (1H, 13C -NMR, IR, UV–visible, ESR, XRD, EDX, SEM, and MS), elemental analysis, magnetic susceptibility, and thermal (TG/DTA) analysis. Furthermore, all of the previous structural investigations weresupported with theoretical studies based on DFT theory where the molecular modeling of the geometrically optimized structures was constructed through Gaussian 09 software. Various energy components such as (EBinding, EHOMO, and ELUMO) besides MEP (Molecular electrostatic potential), bond parameters (bond angle and bond length), dipole moment, and molecular chemical parameters were derived from the computational calculations. Moreover, the redox behavior of Cu(II) with/without the ligand (H2DS) was investigated using cyclic voltammetry. This technique is utilized to study the effect of the chelating agent on the attitude of the copper species in the solution universe. The impact of interaction is proved by changing in the potential of reduction/oxidation peaks alongside evaluating of both kinetic and thermodynamic stability. The produced hydrazone and its chelates were screened for antimicrobial activities (Escherichia coli, Staphylococcus aureus, and Candida albicans), antioxidant activities (DPPH and TAC), and cell viability MTT assay. Finally, the degree ofefficiency of the binding that occurs between the different protein receptors and the ligandwas estimated by molecular docking where the results showed a strong relationship with the biological investigations.

Investigation of the simulated microgravity impact on heavy metal biosorption by Saccharomyces cerevisiae.

Heavy metals are one of the most dangerous environmental pollutions, and their elimination is one of the health system's priorities. Microorganisms have been introduced as a safe absorber of such pollution and this ability is related to the characteristics of their surface layers. There are reports about some bacteria's increment of cell envelope thickness in space conditions. Therefore, this study investigated SMG effect on heavy metals biosorption using Saccharomyces (S.) cerevisiae. Furthermore, the stability of complex, isotherm, and kinetic absorption models has been investigated. The results showed that the SMG positively affected the biosorption of mercury (Hg) 97% and lead (Pb) 72.5% by S. cerevisiae. In contrast, it did not affect cadmium (Cd) and arsenic (As) biosorption. In gastrointestinal conditions, Hg, Cd, and As-yeast complexes were stable, and their biosorption increased. In the case of the Pb-yeast complex, in simulated gastric exposure, the binding decreased at first but increased again in simulated intestinal exposure in both SMG and normal gravity (NG). The metals' biosorption by yeast followed the pseudo-second-order kinetic and the Langmuir isotherm models for all metals (As) matched with Langmuir and Freundlich. The current research results demonstrate that microgravity provides desirable conditions for heavy metal biosorption by S. cerevisiae. Furthermore, the biosorbent-heavy metal complex remains stable after simulated gastrointestinal conditions. Altogether, the results of this study could be considered in detoxifying food and beverage industries and maintaining astronauts' health.

Elimination of methylmercury production potential in excessive sludge in wastewater treatment plants by sulfur addition

Mercury ions (Hg(II)) in wastewater can accumulate and transform into the highly neurotoxic methylmercury (MeHg) in activated sludge. The release of MeHg can have severe environmental consequences, making the treatment of MeHg-contaminated sludge a pressing concern. In this study, we found that all the collected activated sludge samples, from different wastewater treatment plants in four cities, had the potential for Hg methylation. The Hg-methylating capacity reached a maximum level of 0.70–0.92 μg/g volatile suspended solids after 48 h of exposure to 5 μg/L Hg(II) and showed an average MeHg production rate of 4.8±0.5%. Accordingly, a sludge treatment method involving the addition of elemental sulfur (S0) for a short-term or long-term duration (3 or 180 days, respectively) was proposed. The results demonstrated that this treatment approach effectively mitigated and potentially eliminated MeHg formation by simultaneously reducing Hg bioavailability and Hg-methylating bioactivity. We found that bioavailable Hg(II) ions were converted to a secondary phase similar to insoluble HgS after S0 addition treatment, leading to a decrease in Hg bioavailability in sludge. The enhancement of Hg and extracellular polymeric substances (EPS) complexation via the increasing amount of thiol groups in EPS also reduced the Hg bioavailability after the long-term treatment. Furthermore, the long-term S0 addition significantly reduced the abundance of Hg-methylators with hgcA gene and promoted the growth of Hg-reducers with merA gene, which ensured the complete elimination of MeHg production potential of the excessive activated sludge. Our findings demonstrated that the proposed S0-addition sludge treatment is a promising and safe biotechnology for treating Hg-contaminated sludge. This approach has the potential to contribute significantly to the mitigation of MeHg pollution within environmental contexts.

Construction of a supramolecular antibacterial material based on water-soluble pillar[5]arene and a zwitterionic guest molecule.

A new antibacterial system (HG) based on the host-guest chemistry between pillar[5]arene and a zwitterionic guest was fabricated. The HG complex displayed excellent antibacterial and biofilm formation inhibition and dispersal activities against E. coli, S. aureus and MRSA.