Search Results (174)

A new approach to the synthesis of a nanosized and hierarchical titanosilicate, TS-1, is presented. Instead of using specific solid or additional mesoporous templates or individual additives to slow down the hydrolysis of titanium alkoxides, it is proposed that the titanosilicate TS-1 can be obtained from gels synthesized with hydrolysis catalysts (HNO₃ and tetrapropylammonium hydroxide). When nitric acid catalyzes tetraethyl orthosilicate (TEOS) hydrolysis, the resulting crystalline TS-1 that can be obtained has uniform particle sizes (150–180 nm), is anatase-free, and contains up to 46–67% of mesopores. When a base catalyst is applied, the obtained material’s features are opposite. Moreover, acid-promoted TS-1 samples catalyze cyclohexene H₂O₂-oxidation via a heterolytic route to the cyclohexane epoxide with 67% selectivity, which is non-typical. Full article

Spruce beetle (Dendroctonus rufipennis (Kirby)) is a major cause of spruce (Picea spp.) mortality in western North America. We synthesized the literature on the chemical ecology of spruce beetle, focusing on efforts to reduce host tree losses. This literature dates back to the mid-20th century and focuses on spruce beetle populations in Alaska, U.S., western Canada, and the central and southern Rocky Mountains, U.S. Spruce beetle aggregation pheromone components include frontalin (1,5-dimethyl-6,8-dioxabicyclo[3.2.1]octane), seudenol (3-methyl-2-cyclohexen-1-ol), MCOL (1-methyl-2-cyclohexen-1-ol), and verbenene (4-methylene-6,6-dimethylbicyclo[3.1.1]hept-2-ene). The attraction of spruce beetle to one aggregation pheromone component is enhanced by the co-release of other aggregation pheromones and host compounds (e.g., α-pinene). Several baits that attract spruce beetles are commercially available and are used for survey and detection, population suppression, snag creation, and experimental purposes. The antiaggregation pheromone is MCH (3-methyl-2-cyclohexen-1-one), which has been evaluated for reducing colonization of felled spruce since the 1970s. Beginning in the early 2000s, MCH has been evaluated for protecting live, standing spruce from colonization by and mortality attributed to spruce beetle. With a few exceptions, significant reductions in levels of spruce beetle colonization and/or spruce mortality were reported. More recent efforts have combined MCH with other repellents (e.g., nonhost compounds) in hope of increasing levels of tree protection. Today, several formulations of MCH are registered for tree protection purposes in the U.S. and Canada. Full article

Background: Rose processing faces critical challenges in preserving bioactive compounds and aroma profiles during thermal treatments, particularly given the growing demand for natural ingredients in the food and cosmetic industries. Methods: Using widely targeted metabolomics, we first characterized volatile profiles of four major commercial cultivars (Hetian, Damask, Bulgarian, and Fenghua; n = 6 replicates per cultivar), identifying terpenoids as dominant components (p < 0.05). Subsequent thermal optimization focused on Hetian rose, where WGCNA and K-means analyses revealed temperature-dependent dynamics (40–55 °C, triplicate drying trials per temperature). Results: Hetian rose exhibited significantly higher accumulation (p < 0.05) of a unique sesquiterpene marker, 4-(1,5-dimethyl-1,4-hexadienyl)-1-methyl-cyclohexene. Systematic drying optimization identified 50 °C as the thermal threshold for optimal color, bioactive retention, and sensory quality. Mechanistic analysis identified 193 temperature-responsive metabolites (VIP > 1, FC < 0.25 or >4, p < 0.01), with terpenoid biosynthesis (MVA/MEP pathways) and esterification dynamics emerging as critical control points. Conclusions: This study establishes the first cultivar-specific processing framework for roses, demonstrating that metabolic signature-guided drying improves product quality. The findings advance our understanding of thermal impacts on aroma biochemistry while providing actionable protocols for natural product industries. Full article

In recent years, the incidence of acute and chronic inflammatory diseases has increased significantly worldwide, intensifying the search for new therapeutic agents, especially anti-inflammatory drugs. Therefore, the aim of this work was to synthesize, biologically assess, and explore the structure–activity relationships of new compounds containing the cyclohex-1-ene-1-carboxylic acid moiety. Six new derivatives, 2a–2f, were synthesized through the reaction of amidrazones 1a–1f with 3,4,5,6-tetrahydrophthalic anhydride. Their toxicity was evaluated in cultures of human peripheral blood mononuclear cells (PBMCs). Additionally, their antiproliferative properties and effects on the synthesis of TNF-α, IL-6, IL-10, and IL-1β were assessed in mitogen-stimulated PBMCs. The antimicrobial activity of derivatives 2a–2f was determined by measuring the minimal inhibitory concentration (MIC) values against five bacterial strains—Staphylococcus aureus, Mycobacterium smegmatis, Escherichia coli, Yersinia enterocolitica, and Klebsiella pneumoniae—and the fungal strain Candida albicans. All compounds demonstrated antiproliferative activity, with derivatives 2a, 2d, and 2f at a concentration of 100 µg/mL being more effective than ibuprofen. Compound 2f strongly inhibited the secretion of TNF-α by approximately 66–81% at all studied doses (10, 50, and 100 µg/mL). Derivative 2b significantly reduced the release of cytokines, including TNF-α, IL-6, and IL-10, at a high dose (by approximately 92–99%). Compound 2c exhibited bacteriostatic activity against S. aureus and M. smegmatis, while derivative 2b selectively inhibited the growth of Y. enterocolitica (MIC = 64 µg/mL). Some structure–activity relationships were established for the studied compounds. Full article

Ru–Zn catalysts exhibit excellent catalytic performance for the selective hydrogenation of benzene to cyclohexene and has been utilized in industrial production. However, the structure–performance relationship between Ru–Zn catalysts and benzene hydrogenation remains lacking. In this work, we focused on the evolution of Ru–Zn nanoparticles with size and Ru/Zn ratio. The structures of Ru nanoparticles and Ru–Zn bimetallic nanoparticles with different sizes were determined by the minima-hopping global optimization method in combination with density functional theory and high-dimensional neural network potential. Furthermore, we propose the growth mechanism for Ru nanoparticles and evolution processes for Ru–Zn bimetallic nanoparticles. Additionally, we analyzed the structural stability, electronic properties, and adsorption properties of Zn atoms. This work provides valuable reference and guidance for future theoretical research and applications. Full article

This study presents a structurally tunable Au-based solid polymer electrolyte (SPE) membrane electrode with significantly enhanced performance in organic hydrogenation reactions. Compared to a Pt-based counterpart, the Au-based electrode achieved a 277% increase in cyclohexane yield and a 4.8% reduction in hydrogen evolution during cyclohexene hydrogenation, demonstrating superior catalytic selectivity and energy efficiency. The improved performance is attributed to synergistic optimization of the electrode’s nanostructure and electronic properties. The Au-based electrode exhibited a 215% increase in specific surface area (SSA) relative to its initial state, along with a markedly enhanced electrochemical active surface area (ECSA). These enhancements stem from its mesoporous architecture, lattice contraction, and high density of zero-dimensional defects. X-ray photoelectron spectroscopy (XPS) revealed a negative shift in Au4f binding energy, a positive shift in Ni⁰ peaks, and an increased concentration of oxygen vacancies (Ov), indicating favorable modulation of the surface electronic structure. This reconstruction promotes H* adsorption and accelerates the hydrogenation reaction, serving as a key mechanism for catalytic enhancement. The core innovation of this work lies in the coordinated engineering of nanoscale structure and surface electronic states, enabling concurrent improvements in reaction rate, selectivity, and energy efficiency. These findings offer valuable guidance for designing noble metal-based membrane electrodes in advanced hydrogen energy conversion and storage systems. Full article

The selective adsorption and separation of benzene from structurally similar six-membered hydrocarbons and fluorocarbons remain a significant challenge due to their comparable physical properties. In this study, we investigated the molecular recognition and separation properties of a perfluorinated triketonate Cu(II) complex (1) as a Nonporous Adaptive Crystal (NAC). In addition to the previously reported benzene (2)-encapsulated crystal of 1•(2)₃, we report here the crystal structures of guest-free 1 and cyclohexene (3)-encapsulated 1•(O)₂•3, where (O)₂ represents two water molecules. Single-crystal analysis demonstrated that 1 selectively encapsulates 2 while excluding other hydrocarbons, including 3, cyclohexane (4), trifluorobenzene (5), and hexafluorobenzene (6). Gas adsorption experiments confirmed this high affinity for 2, as reflected in its preferential adsorption behavior in mixed solvent and vapor environments. The molecular selectivity of 1 was attributed to strong π-hole···π and metal···π interactions, which favor electron-rich aromatic guests. Additionally, crystallization experiments in competitive solvent systems consistently led to the formation of 1•(2)₃, reinforcing the high selectivity of 1 for 2. These findings highlight the unique molecular recognition capabilities of NACs, providing valuable insights into the rational design of advanced molecular separation materials for industrial applications involving aromatic hydrocarbons. Hirshfeld surface analysis revealed that the contribution of F···F interactions to crystal packing decreased upon guest recognition (48.8% in 1, 34.2% in 1•(O)₂•3, and 22.2% in 1•(2)₃), while the contribution of F···H/H···F interactions increased (8.6% in 1, 22.2% in 1•(O)₂•3, and 35.4% in 1•(2)₃). Regarding Cu interactions, the self-assembled columnar structure of 1 results in close contacts at the coordination sites, including Cu···Cu (0.1%), Cu···O (0.7%), and Cu···C (1.3%). However, in the guest-incorporated structures 1•(O)₂•3 and 1•(2)₃, the Cu···Cu contribution disappears; instead, 1•(O)₂•3 exhibits a significant increase in Cu···O interactions (1.2%), corresponding to water coordination, while 1•(2)₃ shows an increase in Cu···C interactions (1.5%), indicative of the metal···π interactions of benzene. Full article

Menaquinone-7 (MK-7) plays a crucial role in preventing fractures and certain cardiovascular diseases and is one of the essential vitamins in the human body. In this study, a strain of Bacillus subtilis that produces MK-7 was isolated from commercially available natto fermentation agents, with an MK-7 titer of 75 mg/L. It was named L-5. Firstly, by employing Atmospheric and Room Temperature Plasma (ARTP) mutagenesis technology and protoplast fusion techniques, mutants resistant to 1-hydroxy-2-naphthoic acid (HNA) and diphenylamine (DPA) were obtained, with the titer of MK-7 reaching 196 mg/L. It was named R-8. Based on whole-genome sequencing technology, four mutants involved in the MK-7 synthesis pathway of strain L-5 were identified: 2-succinyl-5-enol-pyruvate-6-hydroxy-3-cyclohexen-1-carboxylic acid, MenD (S249L); (1,4)-dihydroxy-2-naphthalic acid-heptaisoprenyltransferase, MenA (S196L); 1-deoxy-D-xylose-5-phosphate synthetase, Dxs (N60D, Q185H); and hydroxy acid reductive isomerase, Dxr (Q351K). The overexpression of these mutants led to increases in MK-7 production of 19 mg/L, 20 mg/L, 17 mg/L, and 16 mg/L, respectively, compared to the unmutated genes. These mutations have been shown to be effective. To further enhance the production of MK-7, the mutants menD (S249L), menA (S196L), Dxs (N60D, Q185H), and Dxr (Q351K) were co-expressed. The final titer of MK-7 reached 239 mg/L. This study provides theoretical support for the future genetic modification of key enzymes in the MK-7 biosynthetic pathway. Full article

There is a lack of theoretical evidence regarding the transformation of the aroma of Pu-erh tea (raw tea) during long-term storage. In this study, we comprehensively investigate the aroma characteristics of Pu-erh tea (raw tea) from the same manufacturer, stored for different storage times (7–21 years). Sensory evaluation and qualitative and quantitative analysis of volatile substances were performed on the experimental samples. The results showed that the aroma of Pu-erh tea (raw tea) changed from fruity/floral to smoky and fragrance during the storage process. A total of 290 volatiles were identified by HS-SPME/GC×GC-Q-TOF-MS. The key substances for the fruity/floral aroma are fenchene, (E)-1,2,3-trimethyl-4-propenyl-Naphthalene, (+/−-theaspirane, and decanal, and the key substances for the smoky aroma were 2-ethyl-Furan, camphene, 1-methyl-4-(1-methylethenyl)-Benzene, and cis-β-Ocimene. The key aroma substances for the fragrance aroma are 1-methyl-4-(1-methylethylidene)-Cyclohexene, α-Terpinene, trans-β-Ocimene, (E,E)-2,4-Heptadienal, octanal, 2,5-Dimethoxyethylbenzene, 2,4-Dimethylanisole, 1,2,3-Trimethoxybenzene, and 3,4-Dimethoxytoluene. This study helps us to understand further the aroma changes of Pu-erh tea (raw tea) during long-term storage. Full article

In order to improve the dielectric properties of existing thermosetting resins, taking advantage of reactive fillers is a simple and feasible option. In this paper, we synthesized a new double epoxycyclohexane double-decker silsesquioxane (DEDDSQ), in which the structure of aliphatic epoxy resin introduced into DDSQ successfully, and the resulting structure of DEDDESQ is confirmed by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) spectroscopy, and mass spectrometry (MS). Cyanate ester resin was selected as the case study for the application of DEDDSQ as reactive fillers. A CE/E51/DEDDSQ nanocomposite was fabricated by incorporating a small proportion of E51 resin and DEDDSQ into cyanate ester resin to enhance its comprehensive properties. X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS) analyses demonstrated that DEDDSQ dispersed uniformly within the resin matrix. Dynamic mechanical analysis (DMA) demonstrated that the CE/E51/8.0DEDDSQ nanocomposites exhibit excellent thermal properties. The glass transition temperature (T_g) of the nanocomposite was measured to be 264 °C, indicating its excellent thermal stability. Dielectric property measurements showed that the addition of DEDDSQ reduced the dielectric constant of the cyanate ester resin, with the CE/E51/8.0DEPOSS nanocomposite exhibiting a dielectric constant of 2.47 at 1 MHz. Full article

One-component or bifunctional organocatalysts are some of the most capable compounds to perform the synthesis of cyclic carbonates from epoxides and carbon dioxide (CO₂) since the presence of a co-catalyst is not required. In this study, we designed, synthesized, and evaluated five halogenated compounds as bifunctional organocatalysts for this catalytic transformation. Among them, 1,3-dimethylimidazolium iodide (1) exhibited the highest catalytic efficiency, enabling the synthesis of a broad range of monosubstituted cyclic carbonates with diverse functional groups under mild conditions (80 °C, 20 bar CO₂) within 1 h, using only 1 mol% catalyst loading. Remarkably, this organocatalyst also facilitated the synthesis of five internal cyclic carbonates and a carvone-derived exo-cyclic carbonate, which was obtained for the first time without the use of a metal catalyst, under more demanding conditions. A mechanistic proposal was developed through a combination of ¹H-NMR studies and density functional theory (DFT) simulations. Styrene oxide and cyclohexene oxide were used as model substrates to investigate the reaction pathway, which was computed using an optimized climbing-image nudged elastic band (CI-NEB) method. The results revealed the critical role of 1,3-dimethylimidazolium iodide in key reaction steps, particularly in facilitating the epoxy ring opening process. These findings highlight the potential use of bifunctional compounds as efficient and versatile catalysts for CO₂ valorization. Full article

Partial hydrogenation of benzene is the main approach to cyclohexene synthesis in industry. Here, the reaction mechanisms of benzene hydrogenation on Pd-Zn bimetallic catalysts were studied using density functional theory, with the aim of understanding the effect of different Pd/Zn ratios on catalytic activity and cyclohexene selectivity. Three different surfaces, Pd(111), Pd₄Zn₁(111), and Pd₂Zn₁(111), were considered as catalyst models. It was found that increasing the Zn concentration decreases the hydrogenation energy barriers while also hindering the reverse reactions. These findings are corroborated by microkinetic simulations and also indicate that cyclohexene selectivity increases with higher Zn concentration but at the expense of reaction activity, which decreases due to the weaker C₆H₆* and H* adsorption strength in systems with high Zn concentration. The hydrogen coverage has a significant effect on the reaction activity, degree of rate control coefficient, and apparent activation energy as well. For the high hydrogen coverage situations, C₆H₉ hydrogenation is the rate-controlling step on H₁.₀/Pd(111) at all considered temperatures, but the degree of rate control for the C₆H₁₁ hydrogenation step significantly increases at high temperatures. For H₀.₈/Pd₄Zn₁(111), the rate-controlling step changes from C₆H₇ hydrogenation to C₆H₉ hydrogenation with increasing temperature, and for H₀.₆₇/Pd₂Zn₁(111), it changes from C₆H₇ and C₆H₈ hydrogenation to C₆H₁₀ hydrogenation. Full article

Bimetallic (Ta/Ti, V, Co, Nb) mesoporous MCM-41 nanoparticles were obtained by direct synthesis and hydrothermal treatment. The obtained mesoporous materials were characterized by XRD, XRF, N₂ adsorption/desorption, SEM, TEM, XPS, Raman, UV-Vis, and PL spectroscopy. A more significant effect was observed on the mesoporous structure, typically for MCM-41, and on optic properties if the second metal (Ti, Co) did not belong to the same Vb group with Ta as V and Nb. The XPS showed for the TaTi-MCM-41 sample that framework titanium is the major component. The new nanoparticles obtained were used as catalysts for oxidation with hydrogen peroxide of olefinic compounds (1,4 cyclohexadiene, cyclohexene, styrene) and photodegradation of organic pollutants (phenol, methyl orange) from water. The results showed improvementsin activity and selectivity in oxidation reactions by the addition of the second metal to the Ta-MCM-41 catalyst. The slow addition of H₂O₂ was also beneficial for the selectivity of epoxide products and the stability of the catalysts. The band gap energy values decreased in the presence of the second metal, and the band edge diagram evidenced positive potential for all the conduction bands of the bimetallic samples. The highestlevels of photocatalytic degradation were obtained for the samples with TaTi and TaV. Full article

Enzymes capable of processing a variety of compounds enable plants to adapt to diverse environmental conditions. PRISEs (progesterone-5β-reductase/iridoid synthase-like enzymes), examples of such substrate-promiscuous enzymes, are involved in iridoid and cardenolide pathways and demonstrate notable substrate promiscuity by reducing the activated C=C double bonds of plant-borne and exogenous 1,4-enones. In this study, we identified PRISE genes in Plantago media (PmdP5βR1) and Plantago lanceolata (PlP5βR1), and the corresponding enzymes were determined to share a sequence identity of 95%. Despite the high sequence identity, recombinant expressed PmdP5βR1 was 70 times more efficient than PlP5βR1 for converting progesterone. In order to investigate the underlying reasons for this significant discrepancy, we focused on specific residues located near the substrate-binding pocket and adjacent to the conserved phenylalanine “clamp”. This clamp describes two phenylalanines influencing substrate preferences by facilitating the binding of smaller substrates, such as 2-cyclohexen-1-one, while hindering larger ones, such as progesterone. Using structural analysis based on templates PDB ID: 5MLH and 6GSD from PRISE of Plantago major, along with in silico docking, we identified positions 156 and 346 as hot spots. In PlP5βR1 amino acid residues, A156 and F346 seem to be responsible for the diminished ability to reduce progesterone. Moreover, the double mutant PlP5βR_F156L_A346L, which contains the corresponding amino acids from PmdP5βR1, showed a 15-fold increase in progesterone 5β-reduction. Notably, this modification did not significantly alter the enzyme’s ability to convert other substrates, such as 8-oxogeranial, 2-cyclohexen-1-one, and methyl vinyl ketone. Hence, a rational enzyme design by reducing the number of hotspots selectively, specifically improved the substrate preference of PlP5βR1 for progesterone. Full article

Due to the importance of biaryls as natural products, drugs, agrochemicals, dyes, or organic electronic materials, a green alternative biaryl synthesis has been developed based on easy-to-prepare and cheap copper(I)-exchanged zeolite catalysts. Cu^I-USY proved to efficiently catalyze the direct homocoupling of either phenols or aryl boronic acids under simple and practical conditions. The Cu^I-USY-catalyzed oxidative homocoupling of phenols could conveniently be performed under air either in warm methanol or water with good to high yields. In methanol, a small amount of Cs₂CO₃ was required, while none was necessary in water. The homocoupling of aryl boronic acids was best performed also in warm methanol, without an additive. These mild conditions showed good functional-group tolerance, leading to a variety of substituted (hetero)biaryls (28 examples). The heterogeneous Cu^I-USY catalyst could readily be recovered and reused. Interestingly, the homocoupling of vinyl boronic acids was successfully coupled to a Diels–Alder reaction, even in a one-pot process, allowing access to highly functionalized cyclohexenes. Full article