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Search Results (263)

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Keywords = cation bridge

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27 pages, 5041 KiB  
Article
Differential Evolution in Hydrochemical Characteristics Amongst Porous, Fissured and Karst Aquifers in China
by Chengsong Li, Jie Fang, Feisheng Feng, Tingting Yao, Yongping Shan and Wanli Su
Hydrology 2025, 12(7), 175; https://doi.org/10.3390/hydrology12070175 - 1 Jul 2025
Viewed by 385
Abstract
The efficacy of water resource management and protection hinges on a profound understanding of the controlling factors and regulatory mechanisms that shape groundwater chemistry within aquifers. Despite this, our comprehension of how groundwater chemistry and ion sources vary across diverse aquifer types remained [...] Read more.
The efficacy of water resource management and protection hinges on a profound understanding of the controlling factors and regulatory mechanisms that shape groundwater chemistry within aquifers. Despite this, our comprehension of how groundwater chemistry and ion sources vary across diverse aquifer types remained limited. To bridge this gap, our study conducted a detailed hydrochemical and statistical investigation of porous, fissured, and karst aquifers. By applying multivariate statistical techniques, including principal component analysis (PCA) and hierarchical cluster analysis (HCA), the hydrochemical characteristics and main ion sources of each aquifer type, as well as distinct controlling factors and regulation patterns, were determined. Notably, evaporation predominantly affected the hydrochemistry of porous aquifers, whereas mineral dissolution and rock weathering processes played a pivotal role in shaping the groundwater evolution of fissured and karst aquifers. HCO3 and SO42− are the most common anions of all types, while Na+ is dominant in porous and fissured aquifers and Ca2+ is dominant in karst aquifers. The most common hydrochemical types identified were HCO3-Ca·Mg (accounting for approximately 56.84%) and SO4·Cl-Na (constituting approximately 21.75%). PCA results revealed that lateral recharge from fissured aquifers in hilly regions into the groundwater of porous aquifer, and wastewater discharge and agricultural fertilizer application, significantly impact the groundwater chemistry across all three aquifer types. It is worth noting that the dissolution of carbonate minerals, often influenced by human activities, had a profound effect on the hydrochemistry of each aquifer. Conversely, the dissolution of evaporitic minerals affected groundwater chemistry primarily through cation exchange processes. In summary, the hydrochemical characteristics of these aquifer types were predominantly shaped by a complex interplay of mineral dissolution, cation exchange, evaporation, and anthropogenic activities, with notable contributions from fissured aquifer recharge and pollution. These insights were critical for informing national-level strategies for groundwater resource protection and management. Full article
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34 pages, 7701 KiB  
Article
Docking Simulations of G-Protein Coupled Receptors Uncover Crossover Binding Patterns of Diverse Ligands to Angiotensin, Alpha-Adrenergic and Opioid Receptors: Implications for Cardiovascular Disease and Addiction
by Harry Ridgway, Graham J. Moore, Laura Kate Gadanec and John M. Matsoukas
Biomolecules 2025, 15(6), 855; https://doi.org/10.3390/biom15060855 - 11 Jun 2025
Viewed by 1583
Abstract
Recent bioassay studies have unexpectedly supported the high (computationally predicted) binding affinities of angiotensin receptor blockers (ARBs) at α-adrenergic receptors (αARs) in isolated smooth muscle. Computational predictions from ligand docking studies are consistent with very low concentrations of ARBs (e.g., sartans or bisartans) [...] Read more.
Recent bioassay studies have unexpectedly supported the high (computationally predicted) binding affinities of angiotensin receptor blockers (ARBs) at α-adrenergic receptors (αARs) in isolated smooth muscle. Computational predictions from ligand docking studies are consistent with very low concentrations of ARBs (e.g., sartans or bisartans) that partially reduce (20–50%) the contractile response to phenylephrine, suggesting that some ARBs may function as partial inverse agonists at αARs. Virtual ligand screening (docking) and molecular dynamics (MD) simulations were carried out to explore the binding affinities and stabilities of selected non-peptide ligands (e.g., ARBs and small-molecule opioids) for several G-protein coupled receptor (GPCR) types, including angiotensin II (AngII) type 1 receptor (AT1R), α1AR, α2AR, and μ-(µOR) and ժ-opioid receptors (ժOR). Results: All ligands docked preferentially to the binding pocket on the cell surface domain of the GPCR types investigated. Drug binding was characterized by weak interactions (hydrophobic, hydrogen bonding, pi-pi) and stronger ionic and salt-bridge interactions (cation-pi and cation-anion interactions). Ligands specific to each GPCR category showed considerable cross-binding with alternative GPCRs, with small-molecule medications appearing less selective than their peptide or ARB functional equivalents. ARBs that exhibit higher affinities for AT1R also demonstrate higher affinities for µORs and ժORs than opiate ligands, such as fentanyl and naltrexone. Moreover, ARBs had a higher affinity for αARs than either alpha agonists (epinephrine and phenylephrine) or inhibitors (prazosin and doxazosin). MD simulations of membrane-embedded ARB-GPCR complexes proved stable over nanosecond time scales and suggested that some ARBs may behave as agonists or antagonists depending on the GPCR type. Based on the results presented in this and related investigations, we propose that agonists bind to the resting A-site of GPCRs, while inverse agonists occupy the desensitizing D-site, which partial agonists like morphine and fentanyl share, contributing to addiction. ARBs block both AngII and alpha receptors, suggesting that they are more potent antihypertensive drugs than ACE inhibitors. ARBs have the potential to inhibit morphine tolerance and appear to disrupt receptor desensitization processes, potentially by competing at the D-site. Our results suggest the possible therapeutic potential of ARBs in treating methamphetamine and opiate addictions. Full article
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15 pages, 3356 KiB  
Article
Synthesis, Crystal Structure, Characterization, and Hydrophobicity Tests of Bismuth(III)– and Silver(I)–Triammionium Bromide Low-Dimensional Perovskites
by Victor C. Sousa, Bruno Dival and Willian X. C. Oliveira
Compounds 2025, 5(2), 20; https://doi.org/10.3390/compounds5020020 - 4 Jun 2025
Viewed by 782
Abstract
This work describes the synthesis, crystal structure, and hydrophobicity tests of four bismuth(III)– and silver(I)–bromide complexes using the triammonium cations diethylenetriaminonium (H3DETA3+) and N,N,N′,N″,N‴-pentamethyldiethylenetriammonium (H3PMDTA3+). The prepared compounds are the 0D perovskites (H3DETA)[BiBr [...] Read more.
This work describes the synthesis, crystal structure, and hydrophobicity tests of four bismuth(III)– and silver(I)–bromide complexes using the triammonium cations diethylenetriaminonium (H3DETA3+) and N,N,N′,N″,N‴-pentamethyldiethylenetriammonium (H3PMDTA3+). The prepared compounds are the 0D perovskites (H3DETA)[BiBr6] (1), (H3DETA)2[AgBr4]Br3 (2), and (H3PMDTA)[BiBr6] (3), as well as the 1D/2D mixed perovskite with minimum formula (H3PMDTA)[Ag3Br6] (4), being the last three novel materials. Compounds 1 and 3 crystallize in the orthorhombic P212121 space group and are discrete [BiBr6]3− units with the cation surrounding them. In both compounds, the bismuth(III) metal ion is found in a distorted octahedral coordination geometry. Compound 2 crystallizes in the monoclinic P21/c space group, and it is a mixed salt consisting of (H3DETA)[AgBr4] and (H3DETA)Br3, whereas the silver(I) complexes are also isolated. Finally, compound 4, which crystallizes in the orthorhombic space group Pbcn, is a combination of a 2D and 1D silver–bromide perovskite, with the cations filling the voids. The 2D structure has the minimal formula [Ag4Br7]3−, with the 1D coordination polymer [Ag2Br5]3− being both built up by a combination of bromide ions acting as tetrahedra corner and edge-sharing bridging ligands. The silver(I) in 2 and 4 is found in a tetrahedral coordination geometry. All compounds were deposited on pristine FTO glass, resulting in an increase in the contact angle from 22° to 44°, 36°, 62°, and 54° for films of 1, 2, 3, and 4, respectively. Compounds 1 and 3 were also deposited onto Cs2AgBiBr6 film, and the contact angles were observed to be the same as when deposited directly onto the FTO cover glass. Full article
(This article belongs to the Special Issue Feature Papers in Compounds (2025))
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21 pages, 3823 KiB  
Article
Adsorption of Sr2+ from Synthetic Waste Effluents Using Taiwan Zhi-Shin Bentonite
by Yihui Lin, Yuhan Li, Yating Yang and Po-Hsiang Chang
Int. J. Mol. Sci. 2025, 26(11), 5298; https://doi.org/10.3390/ijms26115298 - 30 May 2025
Viewed by 442
Abstract
This study investigated strontium (Sr2+) adsorption by Taiwan Zhi-Shin bentonite (cation exchange capacity (CEC): 80–86 meq 100 g−1) using Sr(NO3)2-simulated nuclear waste. Kinetic analysis revealed pseudo-second-order adsorption kinetics, achieving 95% Sr2+ removal within 5 [...] Read more.
This study investigated strontium (Sr2+) adsorption by Taiwan Zhi-Shin bentonite (cation exchange capacity (CEC): 80–86 meq 100 g−1) using Sr(NO3)2-simulated nuclear waste. Kinetic analysis revealed pseudo-second-order adsorption kinetics, achieving 95% Sr2+ removal within 5 min at pH 9. Isothermal studies showed a maximum capacity of 0.28 mmol g−1 (56 meq 100 g−1) at 15 mmol L−1 Sr2+, accounting for 65–70% CEC and fitting the Freundlich model. Cation exchange was the dominant mechanism (84% contribution), driven by Sr2+ displacing interlayer Ca2+. Alkaline conditions (pH > 9) enhanced adsorption through improved surface charge and electrostatic attraction. Thermodynamic studies demonstrated temperature-dependent behavior: increasing temperature reduced adsorption at 0.01 mM Sr2+ but increased efficiency at 10 mM. Na+ addition suppressed adsorption, aligning with cation exchange mechanisms. Molecular dynamics simulations identified hydrated Ca2+-Sr2+ water bridges interacting with bentonite via hydrogen-bonding networks. The material exhibits rapid kinetics (5 min equilibrium), alkaline pH optimization, and resistance to ion interference, making it suitable for emergency Sr2+ treatment. It shows promise as a cost-effective and good performing adsorbent for radioactive waste solutions. Full article
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25 pages, 6816 KiB  
Article
Mechanisms of Cu2+ Immobilization Using Carbonyl Iron Powder–Biochar Composites for Remediating Acidic Soils from Copper Sulfide Mining Areas
by Shuting Wang, Jinchun Xue, Min He, Xiaojuan Wang and Hui Qi
Sustainability 2025, 17(10), 4281; https://doi.org/10.3390/su17104281 - 8 May 2025
Viewed by 622
Abstract
Soil heavy metal contamination poses critical challenges to ecological sustainability in mining regions, particularly in acidic soils from copper sulfide mines. This study developed a sustainable remediation strategy using a carbonyl iron powder–biochar composite (CIP@BC) derived from agricultural waste (rice husk) and industrial [...] Read more.
Soil heavy metal contamination poses critical challenges to ecological sustainability in mining regions, particularly in acidic soils from copper sulfide mines. This study developed a sustainable remediation strategy using a carbonyl iron powder–biochar composite (CIP@BC) derived from agricultural waste (rice husk) and industrial byproducts. The composite was synthesized through an energy-efficient mechanical grinding method at a 10:1 mass ratio of biochar to carbonyl iron powder, aligning with circular economy principles. Material characterization revealed CIP particles uniformly embedded within biochar’s porous structure, synergistically enhancing surface functionality and redox activity. CIP@BC demonstrated exceptional Cu2+ immobilization capacity (910.5 mg·g−1), achieved through chemisorption and monolayer adsorption mechanisms. Notably, the remediation process concurrently improved key soil health parameters. Soil incubation trials demonstrated that 6% CIP@BC application elevated soil pH from 4.27 to 6.19, reduced total Cu content by 29.43%, and decreased DTPA-extractable Cu by 67.26%. This treatment effectively transformed Cu speciation from bioavailable to residual fractions. Concurrent improvements in electrical conductivity (EC), cation exchange capacity (CEC), soil organic matter (OM), and soil water content (SWC) collectively highlighted the composite’s multifunctional remediation potential. This study bridges environmental remediation with sustainable land management through an innovative waste-to-resource approach that remediates acidic mine soils. The dual functionality of CIP@BC in contaminant immobilization and soil quality restoration provides a scalable solution. Full article
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16 pages, 12510 KiB  
Article
Experimental Investigation on the Improvement of Dredged Sludge Using Air–Booster Vacuum Preloading with Polyacrylamide Addition
by Heng Zhang, Lingfeng Guo and Chongzhi Tu
Materials 2025, 18(9), 2065; https://doi.org/10.3390/ma18092065 - 30 Apr 2025
Viewed by 329
Abstract
Reducing the water content in soft soil is crucial for improving its load-bearing capacity. However, traditional vacuum preloading demonstrates limited effectiveness for dredged sludge due to its high water content and low permeability, resulting in inadequate consolidation and long treatment durations. To address [...] Read more.
Reducing the water content in soft soil is crucial for improving its load-bearing capacity. However, traditional vacuum preloading demonstrates limited effectiveness for dredged sludge due to its high water content and low permeability, resulting in inadequate consolidation and long treatment durations. To address these limitations, this study proposes a new improvement approach that combines pressurized air injection with a polyacrylamide (PAM) addition to enhance vacuum consolidation. Experimental results demonstrated that cationic polyacrylamide (CPAM) exhibited superior performance in improving water discharge efficiency, which promoted the aggregation of fine soil particles and reduced the clogging of drainage channels through adsorption bridging. The incorporation of pressurized air injection further enhanced consolidation efficiency by increasing hydraulic gradients and inducing micro-fractures in soil, thereby improving soil permeability and vacuum pressure transmission. However, excessive CPAM addition or high-pressure air injection was found to compromise the effectiveness of the vacuum preloading treatment due to drainage channel clogging and extensive soil fracturing. The appropriate consolidation performance was achieved with a 0.075% CPAM addition and 20 kPa air pressure injection, demonstrating a 24.5% increase in water discharge mass and a 30.9% improvement in soil shear strength compared to traditional methods. Microstructural analysis revealed a more compacted soil matrix with reduced porosity and enhanced interparticle interactions. These findings provide valuable insights for improving the treatment efficiency of dredged sludge in coastal regions, particularly in the Nansha District of Guangzhou. Full article
(This article belongs to the Section Polymeric Materials)
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18 pages, 3413 KiB  
Article
Coupled Influence of Magnetic Biochar and Solution Chemistries on Retention and Release of Nanoplastics in Porous Media
by Yan Qin, Yan Liang and Yongtao Peng
Int. J. Mol. Sci. 2025, 26(5), 2207; https://doi.org/10.3390/ijms26052207 - 28 Feb 2025
Viewed by 656
Abstract
Magnetic biochar (MBC), as an environmentally friendly material, has been extensively used for the remediation of soil and groundwater contamination. The retention and release of nanoplastics (NPs) with carboxyl (NPs-COOH) or amino functionalization (NPs- NH2) in saturated porous media were investigated [...] Read more.
Magnetic biochar (MBC), as an environmentally friendly material, has been extensively used for the remediation of soil and groundwater contamination. The retention and release of nanoplastics (NPs) with carboxyl (NPs-COOH) or amino functionalization (NPs- NH2) in saturated porous media were investigated under varying conditions of ionic strength (IS), MBC addition, humic acid (HA) concentration, and cation types. The reversible and irreversible retention of NPs was examined by altering the IS, increasing the solution pH, and inducing cation exchange. The results revealed that MBC enhanced the surface roughness of the media, thereby inhibiting NPs’ transport. The HA promoted NPs-NH2 transport more effectively than NPs-COOH due to electrostatic repulsion, steric hindrance, and competition for deposition sites. Under a reduced IS and increased pH, a portion of the retained NPs was released, with NPs-NH2 showing a greater release than NPs-COOH, indicating reversible retention. Additionally, the stronger charge-shielding and cation-bridging effects of Ca2+ significantly enhanced the retention of NPs. Cation exchange resulted in less NPs being released, as most were irreversibly retained in deeper primary minima. However, a small number of retained NPs were remobilized by electrical double layer expansion, surface deprotonation, and cation exchange, indicating reversible retention. These findings provide valuable insights into the fate of NPs in the environment. Full article
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26 pages, 3892 KiB  
Article
Ru(II) Complexes with 3,4-Dimethylphenylhydrazine: Exploring In Vitro Anticancer Activity and Protein Affinities
by Jasmina Dimitrić Marković, Dušan Dimić, Thomas Eichhorn, Dejan Milenković, Aleksandra Pavićević, Dragoslava Đikić, Emilija Živković, Vladan Čokić, Tobias Rüffer and Goran N. Kaluđerović
Biomolecules 2025, 15(3), 350; https://doi.org/10.3390/biom15030350 - 28 Feb 2025
Viewed by 768
Abstract
Two new Ru(II) complexes, mononuclear [RuCl26-p-cymene)(3,4-dmph-κN)] (1) and the binuclear complex [{RuCl(η6-p-cymene)}2(μ-Cl)(μ-3,4-dmph-κ2N,N′)]Cl (2; 3,4-dmph = 3,4-dimethylphenylhydrazine), are synthesized and experimentally [...] Read more.
Two new Ru(II) complexes, mononuclear [RuCl26-p-cymene)(3,4-dmph-κN)] (1) and the binuclear complex [{RuCl(η6-p-cymene)}2(μ-Cl)(μ-3,4-dmph-κ2N,N′)]Cl (2; 3,4-dmph = 3,4-dimethylphenylhydrazine), are synthesized and experimentally and theoretically structurally characterized utilizing 1H and 13C NMR and FTIR spectroscopy, as well as DFT calculations. Degradation product of 2, thus ([{RuCl(η6-p-cymene)}2(μ-Cl)(μ-3,4-dmph-κ2N,N′)][RuCl36-p-cymene)] (2b) was characterized with SC-XRD. In the crystals of 2b, the cationic and anionic parts interact through N-H...Cl hydrogen bridges. The spectrofluorimetric measurements proved the spontaneity of the binding processes of both complexes and HSA. Spin probing EPR measurements implied that 1 and 2 decreased the amount of bound 16-doxylstearate and implicated their potential to bind to HSA more strongly than the spin probe. The cytotoxicity assessment of both complexes against the MDA-MB-231 and MIA PaCa-2 cancer cell lines demonstrated a clear dose-dependent decrease in cell viability and no effect on healthy HS-5 cells. Determination of the malondialdehyde and protein carbonyl concentrations indicated that new complexes could offer protective antioxidant benefits in specific cancer contexts. Gel electrophoresis measurements showed the reduction in MMP9 activity and indicated the potential of 1 in limiting the cancer cells’ invasion. The annexin V/PI apoptotic assay results showed that 1 and 2 exhibit different selectivity towards MIA PaCa-2 and MDA-MB-231 cancer cells. A comparative molecular docking analysis of protein binding, specifically targeting acetylcholinesterase (ACHE), matrix metalloproteinase-9 (MMP-9), and human serum albumin (HSA), demonstrated distinct binding interactions for each complex. Full article
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40 pages, 5920 KiB  
Article
Molecular Recognition of Diaryl Ureas in Their Targeted Proteins—A Data Mining and Quantum Chemical Study
by Majed S. Aljohani and Xiche Hu
Molecules 2025, 30(5), 1007; https://doi.org/10.3390/molecules30051007 - 21 Feb 2025
Viewed by 786
Abstract
Diaryl ureas (DU) are a cornerstone scaffold in organic and medicinal chemistry, celebrated for their unique structural attributes and broad range of biomedical applications. Their therapeutic reach has broadened beyond kinase inhibition in cancer therapy to encompass diverse mechanisms, including modulation of chromatin [...] Read more.
Diaryl ureas (DU) are a cornerstone scaffold in organic and medicinal chemistry, celebrated for their unique structural attributes and broad range of biomedical applications. Their therapeutic reach has broadened beyond kinase inhibition in cancer therapy to encompass diverse mechanisms, including modulation of chromatin remodeling complexes, interference with developmental signaling pathways, and inhibition of stress-activated protein kinases in inflammatory disorders. A critical element in the rational design and optimization of DU-based therapeutics is a detailed understanding of their molecular recognition by target proteins. In this study, we employed a multi-tiered computational approach to investigate the molecular determinants of DU–protein interactions. A large-scale data mining of the Protein Data Bank resulted in an in-house dataset of 158 non-redundant, high-resolution crystal structures of DU–protein complexes. This dataset serves as the basis for a systematic analysis of nonbonded interactions, including hydrogen bonding, salt bridges, π–π stacking, CH-π, cation–π, and XH-π interactions (X = OH, NH, SH). Advanced electronic structure calculations at the B2PLYP/def2-QZVP level are applied to quantify the energetic contributions of these interactions and their roles in molecular recognition of diaryl ureas in their target proteins. The study led to the following findings: central to the molecular recognition of diaryl ureas in proteins are nonbonded π interactions—predominantly CH-π and π–π stacking—that synergize with hydrogen bonding to achieve high binding affinity and specificity. Aromatic R groups in diaryl ureas play a pivotal role by broadening the interaction footprint within hydrophobic protein pockets, enabling energetically favorable and diverse binding modes. Comparative analyses highlight that diaryl ureas with aromatic R groups possess a more extensive and robust interaction profile than those with non-aromatic counterparts, emphasizing the critical importance of nonbonded π interactions in molecular recognition. These findings enhance our understanding of molecular recognition of diaryl ureas in proteins and provide valuable insights for the rational design of diaryl ureas as potent and selective inhibitors of protein kinases and other therapeutically significant proteins. Full article
(This article belongs to the Section Computational and Theoretical Chemistry)
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20 pages, 4322 KiB  
Article
Influence of Tetrabromobisphenol-A on the Fate and Behavior of Zinc Oxide Nanoparticles Affected by Salts, Humic Acid, and Bovine Serum Albumin in Water Systems
by Anwar Ul Haq Khan, Yanju Liu, Ravi Naidu, Cheng Fang and Ho Kyong Shon
Toxics 2025, 13(3), 148; https://doi.org/10.3390/toxics13030148 - 21 Feb 2025
Viewed by 684
Abstract
The environmental release of zinc oxide nanoparticles (ZnO-NPs) may have consequences for ecosystems. The behavior and environmental effects of ZnO-NPs could change due to their interactions with other existing substances. This research explored how the presence of coexisting organic pollutants (like tetrabromobisphenol-A (TBBPA)), [...] Read more.
The environmental release of zinc oxide nanoparticles (ZnO-NPs) may have consequences for ecosystems. The behavior and environmental effects of ZnO-NPs could change due to their interactions with other existing substances. This research explored how the presence of coexisting organic pollutants (like tetrabromobisphenol-A (TBBPA)), electrolytes (such as NaCl and CaCl2), natural organic materials (including humic acid (HA)), and bovine serum albumin (BSA) in simulated water affected the behavior of ZnO-NPs. Various characterization techniques were used to analyze the size, shape, purity, crystallinity, and surface charge of ZnO-NPs following interactions (after one day, one week, two weeks, and three weeks) at pH 7. The findings demonstrated changes in both the size and zeta potential of the ZnO-NPs in isolation and when TBBPA and electrolytes were included in the suspension. The size and surface charge exhibited different variations across fixed concentrations (5 mM) of various electrolytes. HA and BSA contributed to the dispersion of ZnO-NPs by affecting the zeta potential. These dispersion effects were also observed in the presence of TBBPA and salts, attributed to their substantial aliphatic carbon content and complex structures. Potential interaction forces that could explain the adsorption of TBBPA include cation bridging, hydrophobic interactions, hydrogen bonding, electrostatic interactions, and van der Waals forces. The co-occurrence of organic pollutants (TBBPA) and natural organic compounds (HA and BSA) can alter the surface properties and behavior of ZnO-NPs in natural and seawater, aiding in the understanding of the fate and impact of engineered nanoparticles (such as ZnO-NPs) in the environment. Full article
(This article belongs to the Special Issue Environmental Transport and Transformation of Pollutants)
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23 pages, 3460 KiB  
Article
Molecular Determinants for the Binding of the Highly Infectious SARS-CoV-2 Omicron (BA.1) Variant to the Human ACE2 Receptor
by Majed S. Aljohani, Pawan Bhatta and Xiche Hu
Physchem 2025, 5(1), 8; https://doi.org/10.3390/physchem5010008 - 20 Feb 2025
Cited by 1 | Viewed by 1616
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19, continually undergoes mutation, leading to variants with altered pathogenicity and transmissibility. The Omicron variant (B.1.1.529), first identified in South Africa in 2021, has become the dominant strain worldwide. It harbors approximately [...] Read more.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19, continually undergoes mutation, leading to variants with altered pathogenicity and transmissibility. The Omicron variant (B.1.1.529), first identified in South Africa in 2021, has become the dominant strain worldwide. It harbors approximately 50 mutations compared to the original strain, with 15 located in the receptor-binding domain (RBD) of the spike protein that facilitates viral entry via binding to the human angiotensin-converting enzyme 2 (ACE2) receptor. How do these mutated residues modulate the intermolecular interactions and binding affinity between the RBD and ACE2? This is a question of great theoretical importance and practical implication. In this study, we employed quantum chemical calculations at the B2PLYP-D3/def2-TZVP level of theory to investigate the molecular determinants governing Omicron’s ACE2 interaction. Comparative analysis of the Omicron and wild-type RBD–ACE2 interfaces revealed that mutations including S477N, Q493R, Q498R, and N501Y enhance binding through the formation of bifurcated hydrogen bonds, π–π stacking, and cation–π interactions. These favorable interactions counterbalance such destabilizing mutations as K417N, G446S, G496S, and Y505H, which disrupt salt bridges and hydrogen bonds. Additionally, allosteric effects improve the contributions of non-mutated residues (notably A475, Y453, and F486) via structural realignment and novel hydrogen bonding with ACE2 residues such as S19, leading to an overall increase in the electrostatic and π-system interaction energy. In conclusion, our findings provide a mechanistic basis for Omicron’s increased infectivity and offer valuable insights for the development of targeted antiviral therapies. Moreover, from a methodological perspective, we directly calculated mutation-induced binding energy changes at the residue level using advanced quantum chemical methods rather than relying on the indirect decomposition schemes typical of molecular dynamics-based free energy analyses. The strong correlation between calculated energy differences and experimental deep mutational scanning (DMS) data underscores the robustness of the theoretical framework in predicting the effects of RBD mutations on ACE2 binding affinity. This demonstrates the potential of quantum chemical methods as predictive tools for studying mutation-induced changes in protein–protein interactions and guiding rational therapeutic design. Full article
(This article belongs to the Section Theoretical and Computational Chemistry)
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18 pages, 2986 KiB  
Article
Influence of Electrolyte Composition on the Semiconductor–Electrolyte Interface (SEI) Built-In for Enhanced Photoelectrochemical (PEC) Processes
by Bartłomiej Leks, Aleksandra Parzuch, Nabila Nawaz, Justyna Widera-Kalinowska, Krzysztof Bienkowski and Renata Solarska
Molecules 2025, 30(4), 885; https://doi.org/10.3390/molecules30040885 - 14 Feb 2025
Cited by 1 | Viewed by 870
Abstract
The relentless consumption of fossil fuels and soaring CO2 emissions have plunged the world into an energy and environmental crisis. As society grapples with these challenges, the demand for clean, renewable, and sustainable energy solutions has never been more urgent. However, even [...] Read more.
The relentless consumption of fossil fuels and soaring CO2 emissions have plunged the world into an energy and environmental crisis. As society grapples with these challenges, the demand for clean, renewable, and sustainable energy solutions has never been more urgent. However, even though many efforts have been made in this field, there is still room for improvement concerning efficiency, material stability, and catalytic enhancement regarding kinetics and selectivity of photoelectrochemical (PEC) processes. Herein, we provide the experimental proof for the enhancement of the photocurrent efficiency by the critical focus on semiconductor–electrolyte interface (SEI) properties. By tailoring electrolyte composition, researchers can unlock significant improvements in catalytic efficiency and stability, paving the way for advanced PEC technologies. In this study, we investigate the influence of electrolyte composition on SEI properties and its impact on PEC performance. By employing electrolytes enriched with carbonates, borates, sulphates, and alkali cations, we demonstrate their profound role in optimising photoelectrochemical CO2 reduction reaction (CO2RR) efficiency. Central to this work is Cu2O—an affordable, highly promising photocatalyst. While its potential is undeniable, Cu2O’s inherent instability and diverse reduction products, ranging from CH3OH to CO, HCOOH, CH3COOH, and CH3CH2OH, have hindered its widespread adoption in PEC CO2 reduction (CO2RR). Our approach leverages a straightforward yet powerful electrodeposition method, enabling a deeper exploration of SEI dynamics during photocatalysis. Key parameters, such as carbonate concentration, local pH, alkali cation presence, anionic geometry, CO2 solubility, and electrolyte conductivity, are systematically investigated. The findings reveal the formation of a unique “rigid layer” at the photocatalyst surface, driven by specific cation–anion interactions. This rigid layer plays a pivotal role in boosting PEC performance, offering a new perspective on optimising, among other PEC processes, CO2RR catalytic efficiency. This profound study bridges a critical knowledge gap, shedding light on the dual influence of cations and anions on SEI properties and PEC CO2RR. By unravelling these intricate interactions, we provide a roadmap for designing next-generation PEC systems. These insights pave the way for sustainable energy advancements, inspiring innovative strategies to tackle one of the most pressing challenges of our time. Full article
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20 pages, 2441 KiB  
Article
An Investigation into the Factors Influencing the Effectiveness of a Biodegradable Natural Coagulant Derived from Phaseolus vulgaris Seeds and Coagulation Mechanism
by Jelena M. Prodanović, Nataša M. Nastić, Marina B. Šćiban, Dragana V. Lukić, Vesna M. Vasić and Nevena T. Blagojev
Sustainability 2025, 17(4), 1372; https://doi.org/10.3390/su17041372 - 7 Feb 2025
Viewed by 787
Abstract
One of the major criteria for monitoring water and wastewater quality is turbidity, which is most often reduced using chemical coagulants and flocculants, such as alum and iron salts and acrylamide. However, due to their detrimental effects, intensive investigations into natural coagulants and [...] Read more.
One of the major criteria for monitoring water and wastewater quality is turbidity, which is most often reduced using chemical coagulants and flocculants, such as alum and iron salts and acrylamide. However, due to their detrimental effects, intensive investigations into natural coagulants and flocculants have recently been conducted. These coagulants are biodegradable, derived from renewable sources, and do not pose health risks, making them a sustainable solution for water and wastewater treatment. Coagulation and flocculation using natural coagulants is a complex phenomenon influenced by multiple factors. In this study, the impact of the solvent used to extract the natural coagulant from Phaseolus vulgaris seeds on its coagulation effectiveness was examined, along with the effects of pH, the initial turbidity of the treated water, and the applied coagulant dose. The extract obtained using 0.5 mol/L NaCl demonstrated higher coagulation activity compared to the extract obtained with distilled water. Both extracts exhibited improved performance in water with higher initial turbidity (200 NTU) and at the lowest pH tested (pH 6). Under these conditions, the water extract achieved a maximum coagulation activity of 58.4% at a dose of 0.1 mL/L, while the NaCl extract reached an 83.5% turbidity reduction at a dose of 0.4 mL/L. The dominant coagulants in the NaCl extract of Phaseolus vulgaris seeds are anionic polyelectrolytes. In the presence of divalent cations, these coagulants destabilize negatively charged particles through either the bridging mechanism or the sweep coagulation mechanism. Full article
(This article belongs to the Section Environmental Sustainability and Applications)
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48 pages, 12131 KiB  
Review
Review of Layered Transition Metal Oxide Materials for Cathodes in Sodium-Ion Batteries
by Mehdi Ahangari, Meng Zhou and Hongmei Luo
Micromachines 2025, 16(2), 137; https://doi.org/10.3390/mi16020137 - 24 Jan 2025
Cited by 4 | Viewed by 4007
Abstract
The growing interest in sodium-ion batteries (SIBs) is driven by scarcity and the rising costs of lithium, coupled with the urgent need for scalable and sustainable energy storage solutions. Among various cathode materials, layered transition metal oxides have emerged as promising candidates due [...] Read more.
The growing interest in sodium-ion batteries (SIBs) is driven by scarcity and the rising costs of lithium, coupled with the urgent need for scalable and sustainable energy storage solutions. Among various cathode materials, layered transition metal oxides have emerged as promising candidates due to their structural similarity to lithium-ion battery (LIB) counterparts and their potential to deliver high energy density at reduced costs. However, significant challenges remain, including limited capacity at high charge/discharge rates and structural instability during extended cycling. Addressing these issues is critical for advancing SIB technology toward industrial applications, particularly for large-scale energy storage systems. This review provides a comprehensive analysis of layered sodium transition metal oxides, focusing on their structural properties, electrochemical performance, and degradation mechanisms. Special attention is given to the intrinsic and extrinsic factors contributing to their instability, such as structural phase transitions, and cationic/anionic redox behavior. Additionally, recent advancements in material design strategies, including doping, surface modifications, and composite formation, are discussed to highlight the progress toward enhancing the stability and performance of these materials. This work aims to bridge the knowledge gaps and inspire further innovations in the development of high-performance cathodes for sodium-ion batteries. Full article
(This article belongs to the Special Issue Energy Conversion Materials/Devices and Their Applications)
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12 pages, 3093 KiB  
Article
Tetrazenyl-, Imido-, and Azidoaluminate Derivatives of a Sterically Demanding Bis-Silazide Ligand
by Han-Ying Liu, Ryan J. Schwamm, Jakub Kenar, Mary F. Mahon and Michael S. Hill
Inorganics 2025, 13(1), 25; https://doi.org/10.3390/inorganics13010025 - 16 Jan 2025
Viewed by 858
Abstract
The potassium alumanyl [{SiNDipp}AlK]2 (SiNDipp = {CH2SiMe2NDipp}2; Dipp = 2,6-i-Pr2C6H3) reacts with organic azides via reductive N2 elimination. With the less sterically encumbered azides [...] Read more.
The potassium alumanyl [{SiNDipp}AlK]2 (SiNDipp = {CH2SiMe2NDipp}2; Dipp = 2,6-i-Pr2C6H3) reacts with organic azides via reductive N2 elimination. With the less sterically encumbered azides PhN3 and C10H15N3 (1-azidoadamantane), the putative initially formed aluminium imide undergoes facile [2 + 3] cycloaddition to provide the tetrazenylaluminates [{SiNDipp}Al-κ2-N,N′-({N(R)}2N2)]K (R = Ph, C10H15). In contrast, each Al(I) centre of [{SiNDipp}AlK]2 only reacts with a single equivalent of 2,4,6-Me3C6H2N3 to provide the imidoaluminate [{SiNDipp}AlN(2,4,6-Me3C6H2)(K∙C6H6)], which crystallises as a monomer and displays a short Al-N distance of 1.7040(13) Å. Attempts to synthesise the azide [{SiNDipp}AlN3] by reaction of [{SiNDipp}AlI] with an excess of KN3 resulted in exclusive formation of the bis(azido)aluminate [{SiNDipp}Al(N3)2K], which crystallises as an infinite 1-dimensional polymer propagated by μ-(1,3)-N3 bridging interactions between the potassium cations and azide anions. Although the THF-adducted azide [{SiNDipp}AlN3(THF)] may be synthesised and characterised by more stringent control of the reaction stoichiometry, the synthetic viability of this route remains compromised by competitive generation of [{SiNDipp}Al(N3)2K]. Full article
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