Search Results (2,258)

The large-scale production and utilization of nitrogen-containing compounds have greatly promoted the development of modern agriculture and the chemical industry, but have also resulted in increasingly severe nitrate contamination and an imbalance of the nitrogen cycle. The efficient conversion of nitrate into value-added ammonia not only contributes to pollutant remediation but also provides a promising route for green ammonia synthesis. Owing to its mild reaction conditions, potentially lower environmental impact, and compatibility with renewable electricity, electrocatalytic nitrate reduction to ammonia has attracted considerable attention in recent years. This process involves a multielectron transfer process involving numerous intermediate transformations, and its catalytic performance largely depends on the adsorption and conversion of key intermediates on the catalyst surface, as well as the suppression of the competing hydrogen evolution reaction. This review systematically summarizes recent advances in electrocatalytic nitrate reduction to ammonia, with emphasis on the reaction mechanisms and major reaction pathways, as well as the design strategies, structure–activity relationships, and performance enhancement mechanisms of metal-based, carbon-based, and composite catalysts. In addition, the main challenges in this field, including product selectivity, mass transport, in-situ mechanistic characterization, and long-term stability, are discussed. Finally, the construction of highly efficient catalytic systems and key directions for future research are outlined, with particular emphasis on nitrate valorization and sustainable ammonia synthesis. Full article

We investigate reactive collision dynamics and effective interaction cross-sections using classical trajectory simulations on a reduced-dimensional reactive potential-energy surface containing reactant and product wells separated by an intermediate barrier region. The simulations are performed over a range of collision velocities for which direct scattering, transient trapping, and reactive trajectories coexist within the same interaction landscape. Trajectories are propagated using a velocity-Verlet integration scheme, while reaction probabilities are analyzed as functions of the impact parameter and initial projectile velocity. The calculated probability distributions exhibit strongly localized reactive windows in phase space separated by extended nonreactive regions, indicating pronounced sensitivity of the dynamics to both collision geometry and initial conditions. Probability maps in the (v_x,b) plane reveal a fragmented phase-space structure and highly nonuniform accessibility of the interaction region across the investigated parameter range. The simulations further show substantial variations in the relative importance of reactive, trapped, and back-scattering trajectories with increasing collision velocity, together with non-monotonic behavior of the effective reactive cross-sections. Despite the intentionally reduced dimensionality of the model, the trajectory ensembles reproduce several characteristic features of complex reactive scattering dynamics, including transient trapping, competing dynamical pathways, and broad residence-time distributions. The present results demonstrate that reduced-dimensional classical trajectory approaches can already capture important phase-space mechanisms governing dynamical accessibility and channel competition in reactive molecular collisions. Full article

Biochar has attracted increasing attention in soil remediation due to its porous structure, abundant surface functional groups, and environmental compatibility. Beyond its conventional roles as an adsorbent and soil amendment, biochar has increasingly been recognized as an electron shuttle that mediates electron transfer between electron donors and acceptors, thereby promoting redox reactions involved in pollutant transformation, immobilization, and toxicity mitigation. However, the structural basis, influencing factors, and underlying electron-transfer mechanisms of biochar-mediated processes remain insufficiently integrated. This review summarizes biochar-mediated electron transfer in soil remediation. Three pathways are discussed: direct electron transfer through conductive carbon matrices, indirect electron transfer mediated by redox-active surface functional groups, and composite interfacial electron transfer involving microorganisms, metal oxides, and nanomaterials. By introducing the synergistic effects between biochar and microorganisms, metal oxides, and nanomaterials, the functions of biochar in immobilizing heavy metals and degrading organic pollutants are emphasized. Biochar’s electron-shuttling ability is closely related to aromatic carbon structures, redox-active functional groups, and persistent free radicals, while key factors affecting electron-shuttling performance, including feedstock properties, pyrolysis temperature, pH, coexisting ions, pollutant concentration, and modification strategies, are also discussed. This review offers guidance for the design of biochar-based soil remediation strategies. Full article

The ultrafast photochemical reaction dynamics of a cyclic(alkyl)(amino)carbene–carbon disulfide (CAAC–CS₂) dimer containing two adjacent S–S bonds were investigated using femtosecond time-resolved infrared spectroscopy in combination with multireference electronic structure calculations. Time-resolved vibrational spectra and global kinetic analysis reveal that photoexcitation of the S–S n → σ* transition at 375 nm induces subpicosecond (<0.3 ps) homolytic cleavage of one S–S bond, generating a bis-thiyl diradical intermediate. This intermediate undergoes two competing pathways: recombination to regenerate the parent dimer with a time constant of 5.7–8.5 ps, or secondary cleavage of the remaining S–S bond to yield two CAAC–CS₂ monomers with a time constant of 30–35 ps. Wavelength- and temperature-dependent kinetic measurements demonstrate that the branching between these pathways is governed by excess excitation energy and thermally driven radical-pair fluctuations. Multireference electronic structure calculations support a sequential S–S bond cleavage mechanism, in good agreement with the experimental observations. These findings provide direct spectroscopic evidence for a bis-thiyl diradical intermediate and offer new mechanistic insight into the ultrafast photochemistry of adjacent S–S bonds. Full article

Co-processing organic waste in coal–water slurry (CWS) gasifiers offers high gasification efficiency and robust stabilization of hazardous substances, representing a crucial pathway for waste valorization and low-carbon chemical processing. This review systematically examines the key influencing factors, control strategies, environmental risks, and operational challenges of this technology. We compare the adaptability of various gasifier designs for handling organic waste and propose operational strategies to balance slurryability and gasification performance under complex feedstock conditions. Furthermore, this paper elucidates the mechanisms underlying adverse effects on equipment (e.g., slagging and corrosion) and emission risks induced by problematic waste components, such as high ash, alkali metals, chlorine, and heavy metals. Finally, we highlight future research directions, emphasizing the synergistic management of multi-source wastes, developing multi-scale reaction modeling, and conducting life cycle assessments (LCA) and economic evaluations to advance CWS co-processing toward highly efficient, stable, and low-carbon operations. Full article

Thanks to the rapid development of advanced analytical methods, researchers can now identify new, so far unknown applications for existing drugs. This expanding knowledge about the mechanisms of drug action, including interactions with various molecules and molecular pathways, not only enables more effective use of available therapies but also reduces both the time and cost of developing new therapeutic options. One of the proteins reported to interact with numerous drugs and chemicals is Translationally Controlled Tumor Protein (TCTP). Numerous studies have demonstrated that TCTP plays a crucial role in diverse biological processes, including cell growth, cell cycle regulation, cellular proliferation, allergic reactions, stress response, inhibition of apoptosis, calcium ion binding, interacting with microtubules and actin microfilaments, the progression of various cancers, and tumor reversion. Therefore, this review article aims to compile a list of drugs and substances shown to interact with TCTP and that, given TCTP’s numerous cellular functions, could be repurposed for other therapies. Full article

Background: Colorectal cancers (CRCs) harboring the BRAFV600E (V600E) mutation exhibit aggressive clinical behavior and chemotherapy resistance, yet the underlying mechanisms remain poorly understood. Ferroptosis, which is driven by iron-dependent lipid peroxidation, has emerged as a potential therapeutic vulnerability. This study aimed to explore whether the NF-κB/Lipocalin 2 (LCN2) pathway modulates cisplatin sensitivity through Fenton-reaction-induced ferroptosis in BRAFV600E-overexpressing CRC cells. Methods: BRAF mutation status and the expression of LCN2, PTGS2, and cleaved caspase3 were examined in clinical CRC specimens by immunohistochemistry. The correlations between ferroptosis and apoptosis markers and 5-year survival rate were evaluated in TCGA datasets. CRC cells with LCN2 knockdown/knockout or BRAF/V600E/LCN2 overexpression were established to assess the proliferation, lipid metabolism, iron levels, and NF-κB/LCN2 signaling under cisplatin treatment. In vivo studies were employed with BALB/c xenograft models. Results: V600E-mutant clinical specimens exhibit significantly reduced expression of the ferroptosis marker PTGS2, and the iron metabolism regulators LCN2. Within a KRAS-mutant cellular model, V600E overexpression attenuated cisplatin-induced ferroptosis through suppression of the NF-κB/LCN2 signaling axis, leading to impairment of Fenton-reaction-mediated lipid peroxidation. Restoration of LCN2 expression re-sensitized V600E-overexpressing cells to cisplatin both in vitro and in vivo. Interestingly, inhibition of apoptosis contributes to the resistance of cisplatin induced ferroptosis in V600E overexpression cells, implying a crosstalk between ferroptosis and apoptosis within the therapeutic resistance. Conclusions: Our findings show that the NF-κB/LCN2 axis drives Fenton-reaction-induced ferroptosis to promote the vulnerability of V600E overexpression CRC cells within a KRAS-mutant background to cisplatin. LCN2 restoration partially overcomes V600E overexpression resistance both in vitro and in vivo, suggesting LCN2 as a promising therapeutic target. The crosstalk between ferroptosis and apoptosis may offer potential strategies to overcome chemotherapy resistance of this high-risk CRC subtype. Full article

Background/Objectives: Boronic acid-based proteasome inhibitors (BABPIs) including Bortezomib, Ixazomib, and Delanzomib are clinically relevant anticancer agents whose mechanism of action depends on direct interaction between the boronic acid warhead and the threonine residue at the first position (Thr1), leading to the formation of covalent tetrahedral complex. Although the formation of this complex is well studied, the subsequent behavior of the boronic acid warhead, particularly the possible formation of monoanionic boronate species through deprotonation of one of the two boronic hydroxyl groups, remains unexplored. Therefore, the present study addresses whether the formation of Thr1-OH and a monoanionic boronate species is thermodynamically favorable and which of the two hydroxyl groups is more favorable for deprotonation. Methods: Density Functional Theory (DFT) calculations at the B3LYP/6-311+G(d,p) level, combined with the Polarizable Continuum Model (PCM), were used to study two competing deprotonation pathways for the inhibitors and for a simplified warhead model. To mimic the proteasome environment, reactions were modeled in different polar media—diethyl ether (ε = 4), methanol (ε = 33), and water (ε = 78). Results: Our DFT calculations confirmed that the covalent tetrahedral complex could convert into Thr1-OH and a monoanionic boronate species, representing the deprotonation of one of the boronic hydroxyl groups. Deprotonation via pathway 1 is more favorable than deprotonation via pathway 2 for all inhibitors, especially in polar solvents. Bortezomib demonstrated a strong preference for -OH₁ deprotonation with ∆∆G ≈ −7 kcal·mol⁻¹. In contrast, Ixazomib, Delanzomib, and the simplified warhead model showed smaller ∆∆G values (≈−2 kcal·mol⁻¹), within the method’s uncertainty (±2 kcal·mol⁻¹), suggesting both deprotonation modes under physiological conditions. Conclusions: These results provide comparative thermodynamic insight into the deprotonation behavior of BABPIs, suggesting that the two hydroxyl groups are not equivalent during deprotonation. This finding offers a physicochemical framework that may support the rational design of next-generation BABPIs. Full article

Background/Objectives: Mesoporous silica nanoparticles (MSNs) are widely investigated as nanocarriers for drug delivery, gene transfer, and bioimaging. However, the mechanisms underlying their size-dependent cytotoxicity at the metabolic level remain incompletely understood. This study aimed to determine whether different-sized MSNs induce distinct patterns of subcellular injury and metabolic reprogramming in lung epithelial cells. Methods: A549 cells were exposed to 80 nm and 600 nm MSNs at 50 and 200 μg/mL for 24 h. Ultrastructural changes were examined by transmission electron microscopy (TEM). Intracellular reactive oxygen species (ROS) and Ca²⁺ were measured by 2′,7′-dichlorodihydrofluorescein diacetate (DCFH-DA) and Fluo-4 AM fluorescence, respectively. Inflammatory gene expression (IL1B, IL6, TNFA, HIF1A) was quantified by reverse transcription quantitative polymerase chain reaction (RT-qPCR). Untargeted metabolomics were performed using combined gas chromatography–mass spectrometry (GC-MS) and liquid chromatography–mass spectrometry (LC-MS) platforms, followed by principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), and MetaboAnalyst-based pathway enrichment. Results: TEM revealed distinct size-dependent subcellular distributions: 80 nm MSNs were predominantly associated with mitochondrial abnormalities, including cristae disruption, swelling, and mitophagy-like features, whereas 600 nm MSNs accumulated in endocytic vesicles with membrane disruption. Metabolomic profiling showed that 80 nm MSNs were associated with TCA cycle blockade—characterized by the accumulation of early intermediates (citrate, oxaloacetate) and the depletion of distal intermediates (fumarate, malate)—with compensatory glycolytic activation (increased glyceraldehyde-3-phosphate and pyruvate) and reduced deoxynucleotide pools (dCDP, dUMP). By contrast, 600 nm MSNs triggered broad nucleotide triphosphate accumulation (ATP, CTP, dGTP, dCTP), amino acid depletion, and robust inflammatory activation, including a ~136-fold increase in IL1B expression and HIF1A transcriptional upregulation. PCA and PLS-DA confirmed distinct size-dependent metabolic phenotypes. Conclusions: MSN size strongly influences subcellular targeting—80 nm particles were predominantly associated with mitochondrial injury while 600 nm particles disrupted endocytic vesicles—driving qualitatively distinct patterns of metabolic reprogramming and inflammatory signaling. These findings establish a correlative mechanistic framework linking particle size to organelle-specific injury and provide candidate metabolic markers for nanotoxicological evaluation. Full article

Long-chain n-alkane hydroisomerization is a key catalytic route for upgrading wax-rich, bio-derived, and synthetic hydrocarbon feedstocks into diesel fuels, sustainable aviation fuels, and lubricant base oils with improved low-temperature properties. However, selective hydroisomerization remains challenging because mismatches in the spatial proximity and relative strength of metal and acid sites can prolong the residence time of olefin/carbenium-ion intermediates, thereby promoting over-isomerization to multibranched species, deep cracking, and coke formation. This review summarizes recent advances in zeolite-based bifunctional catalysts for long-chain n-alkane hydroisomerization. The catalytic mechanisms are first discussed, including metal-catalyzed dehydrogenation/hydrogenation, acid-catalyzed skeletal rearrangement, and shape-selective pathways governed by pore-mouth and key-lock effects. Catalyst construction strategies are then outlined, with emphasis on the preparation of zeolite supports and the introduction and localization of metal sites. Subsequently, structure–performance relationships are reviewed from the perspectives of support properties, metal site characteristics, and promoter effects, followed by a concise assessment of catalyst performance with real feedstocks under industrially relevant conditions. Finally, this review provides guidance for the precise design of metal–acid bifunctional hydroisomerization catalysts by highlighting descriptor-guided optimization, spatially regulated metal–acid–pore architectures, multiscale characterization and modeling, and scalable catalyst construction under practical reaction conditions. Full article

Lithium–sulfur (Li-S) batteries, featuring a superior theoretical energy density of 2600 Wh/kg and a high specific capacity of 1675 mAh/g for sulfur cathodes, have emerged as a promising candidate for next-generation, high-energy-density energy storage technologies. Nevertheless, their commercialization has been hindered by some bottlenecks, including the polysulfide (LiPSs) shuttle effect, severe volume expansion, and sluggish reaction kinetics. Density Functional Theory (DFT), serving as an atomic-scale computational tool, offers essential theoretical assistance for clarifying the mechanisms and guiding the precision design of S cathode of Li-S batteries. This review focuses on the role of DFT in the mechanism of polysulfide conversion and the shuttle effect. By simulating the adsorption energy, charge density distribution, and reaction pathways of LiPSs using DFT calculations, the key reaction steps of polysulfide conversion can be clearly identified. In addition, DFT calculations also play a vital role in the inhibition of lithium dendrites and the regulation of the solid-electrolyte interphase (SEI) film. This review suggests that DFT calculations could provide more applications in the development of Li-S batteries. Full article

The consistent increase in atmospheric CO₂ concentration, mostly driven by the global combustion of fossil fuels, is considered one of the primary contributors to the increasing severity of environmental problems, like climate change and global warming. Attending to this issue requires innovative strategies that transform CO₂ into a valuable resource. In this work, we report a sustainable and fully metal-free approach for the synthesis of cyclic carbonates via the direct coupling of CO₂ with epoxides, using natural sugars as readily available, non-toxic organocatalysts in combination with tetrabutylammonium iodide (TBAI) as a cocatalyst. Seven representative mono- and disaccharides were screened, employing styrene oxide as a model substrate under mild reaction conditions (80 °C, 20 bar CO₂, 2 h). Among them, D-xylose exhibited the best catalytic performance. The robustness of this catalytic system was further demonstrated through the efficient transformation of a wide range of terminal, internal, and biomass-derived epoxides into their corresponding cyclic carbonates with high yields and selectivity (up to 99%). Additionally, a set of computational simulations based on density functional theory (DFT) calculations was carried out to gain insight into the atomistic mechanisms involved in this chemical transformation. We identified that the hydroxyl groups of the sugar catalyst play a pivotal role in activating the epoxy ring-opening process, leading to cyclic carbonate formation. This bio-inspired strategy provides a green, cost-effective, and scalable pathway to produce key precursors for organic chemistry, contributing to the development of a circular carbon economy and the advancement of sustainable chemistry. Full article

The research on semiconductor electrocatalysts has developed into an active field of study in the past decade. By constructing heterojunctions, one may efficiently overcome the limitations of semiconductors’ broad band gaps and low conductivity. This work uses a single-step hydrothermal approach to load nitrogen-doped carbon quantum dots onto TiO₂ nanoparticles, resulting in an excellent N−CQDs/TiO₂ catalyst with an Ohmic contact effect for better NORR electrocatalytic performance under ambient circumstances. The ammonia production rate is 4242.24 μg·h⁻¹·mg⁻¹ at an applied potential of −0.90 V vs. RHE (in a 0.10 M K₂SO₄ electrolyte), and the Faradaic efficiency is 88.02%. When compared to the unmodified TiO₂ catalytic performance, the ammonia generation rate doubles, and the Faradaic efficiency increases by 42.90%. A detailed investigation of the microstructure, charge transfer, NO adsorption, and reaction pathways of N−CQDs/TiO₂ was performed using density functional theory (DFT) computations. According to the theoretical results, nitrogen doping creates an uneven charge distribution on carbon quantum dots, enhancing NO adsorption by N−CQDs. The Ohmic contact between N−CQDs and TiO₂ facilitates charge transfer. The ICOHP value is more negative during NO adsorption on N-doped carbon quantum dots, decreasing the N=O interaction and boosting the NORR, according to crystal orbital Hamilton population (COHP) research. We have established the excellent performance and catalytic mechanism of the N−CQDs/TiO₂ catalyst based on these discoveries, giving strong theoretical and experimental evidence for the creation of effective catalysts for nitrogen oxide reduction processes. Full article

Objectives: Coronary artery disease (CAD) remains a leading cause of morbidity and mortality worldwide, yet population-specific evidence regarding the contribution of MIA3 genetic variation in Middle Eastern populations remains limited. This study investigated the association of the MIA3 rs17465637 polymorphism with CAD susceptibility and its relationship with lipid-related phenotypes in a Saudi population. Methods: A case–control study was conducted between June 2020 and August 2022, including 200 patients with angiographically confirmed CAD and 200 age- and sex-matched healthy Saudi controls. Genotyping of rs17465637 was performed using a TaqMan real-time polymerase chain reaction assay. Genotype distributions were evaluated using chi-square analysis under multiple inheritance models. Multivariable logistic regression was subsequently performed to estimate adjusted odds ratios after controlling age, BMI, smoking, physical inactivity, systolic BP, diastolic BP, blood glucose, triglycerides, total cholesterol, LDL-C, and HDL-C. Associations between rs17465637 genotypes and serum lipid parameters were also examined. Results: Genotype frequencies of rs17465637 differed modestly between cases and controls; however, unadjusted comparisons under codominant, dominant, recessive, and allelic inheritance models did not reach statistical significance, and none remained significant after Bonferroni correction. In contrast, multivariable logistic regression demonstrated an independent association between the rs17465637 C allele and CAD after adjustment for conventional cardiovascular risk factors. In genotype–phenotype analyses, carriers of the C allele exhibited higher association with low-density lipoprotein cholesterol concentrations and less favorable lipid profiles than AA homozygotes, supporting a relationship between the variant and lipid metabolism. These findings are consistent with a potential contribution of rs17465637 to CAD susceptibility through lipid-related pathways. Conclusions: Although unadjusted genotype comparisons were not statistically significant after correction for multiple testing, multivariable analysis provides evidence supporting an independent association between the MIA3 rs17465637 variant and CAD susceptibility in this Saudi cohort. The observed associations with adverse lipid profiles further provide evidence linking this specific locus to the molecular mechanisms underlying cardiovascular disease. Replication in larger, multi-center studies incorporating genome-wide ancestry-informative markers and functional investigations is warranted to further minimize the possibility of residual population stratification, confirming these findings and clarifying the biological mechanisms underlying this association. Full article

The increasing global demand for sustainable energy solutions has intensified the need for efficient and environmentally friendly biomass-conversion technologies. Among these, thermochemical processes, such as pyrolysis, gasification, and hydrothermal liquefaction, have emerged as promising pathways for transforming lignocellulosic and other organic waste materials into valuable biofuels and biochemicals. This paper presents a comprehensive evaluation of advanced thermochemical conversion and catalytic conversion methods, focusing on their operational mechanisms, catalytic enhancements, and product yields. The efficiency, environmental impact, and economic feasibility of various thermochemical platforms, including recent developments in catalyst design and process-integration strategies, are compared, and innovative approaches to optimize hydrogen generation, improve carbon efficiency, and minimize undesirable byproducts through tailored reaction conditions and bifunctional catalytic systems are explored. Recent advances as well as the current challenges related to feedstock variability, process scalability, and system sustainability are highlighted. By identifying critical research gaps, this study provides strategic insights aimed at guiding future improvements in thermochemical biomass utilization for clean energy production within a circular economy framework. Full article