Search Results (2,778)

In this work, we investigated the incorporation of a fluorescent side group, fluorescein octyl ester (FOE), in benzodithiophene-based donor–acceptor terpolymers as a strategy to modulate excited-state behavior. Three FOE-containing terpolymers (P2-iIa-c), obtained at different polymerization times, were systematically evaluated against an analogous material without the fluorescent pendant unit (P1-iI). Thermal analysis revealed good thermal stability and an increase in glass transition temperature upon FOE incorporation, suggesting restricted segmental mobility and increased conformational constraints within the conjugated backbone. Optical characterization showed distinct absorption spectra with reaction time and shorter fluorescence lifetimes for the FOE-containing materials, consistent with the presence of additional excited-state deactivation pathways and intramolecular energy transfer processes within the terpolymer backbone. An approximate estimation of energy transfer efficiencies (≈60–65%) suggested that such processes may be operative within the system. Cyclic voltammetry measurements showed only minor variations in HOMO and LUMO energy levels between P1-iI and P2-iIa-c series, indicating that the conjugated backbone predominantly determined the frontier orbital energies despite side chain modification. Furthermore, photocurrent measurements from the bilayer device configuration exhibited a systematic increase in photocurrent for the FOE-containing material, supporting the role of excitonic modulation, rather than significant changes in interfacial energetic alignment. These results suggest that fluorescent side chain incorporation provides an effective strategy for regulating exciton dynamics while maintaining the electronic structure of the donor–acceptor terpolymer. Full article

Flavor esters are valuable compounds widely used in the food, beverage, and cosmetics industries for their aroma and flavor-enhancing properties. Traditional methods of obtaining these compounds, such as extraction from natural sources or chemical synthesis, present challenges related to cost and toxicity, respectively. Enzymatic synthesis, particularly using immobilized lipases, offers a sustainable and efficient alternative. This study investigates the application of CRL immobilized on Diaion HP-20 for geranyl butyrate synthesis via esterification of geraniol and butanoic acid using Candida rugosa lipase (CRL) immobilized on Diaion HP-20 (CRL-DHP-20). The immobilization process resulted in a protein loading of 29.6 ± 2.2 mg/g support from an initial 40 mg/g, and the immobilized biocatalyst exhibited a hydrolytic activity of 124.0 ± 2.5 U/g using olive oil emulsion. Reaction conditions were optimized through a central composite design, evaluating the influence of biocatalyst concentration, temperature, and agitation on ester conversion. The optimal conditions (13.4% CRL-DHP-20, 48.2 °C, and 220.1 rpm) led to 85.4% conversion in 360 min. Additionally, CRL-DHP-20 retained 84% of its initial activity after six reaction cycles, indicating good operational stability. These findings highlight the potential of CRL-DHP-20 as an effective and reusable biocatalyst for green synthesis of flavor esters. Full article

Light-triggered hydrogel systems offer precise spatiotemporal control over drug release, yet most existing approaches require direct chemical conjugation of a photocleavable linker to the payload, which risks compromising bioactivity and limits applicability to structurally diverse molecules. Here, we report a gelatin–poly(ethylene glycol) (PEG) hybrid hydrogel crosslinked via strain-promoted azide–alkyne cycloaddition (SPAAC) click chemistry, in which an o-nitrobenzyl photocleavable (PC) linker is incorporated into the PEG crosslinker arm rather than conjugated to the drug. Acetylated gelatin–azide (AGA) was synthesized by sequential azide functionalization and amine capping of gelatin, and four-arm PEG-PC-DBCO (4armPEG-PC-DBCO) was prepared by coupling a PC DBCO-PEG4-NHS ester to four-arm PEG amine. Successful incorporation of the azide, DBCO, and o-nitrobenzyl moieties was confirmed by FT-IR spectroscopy, ¹H NMR spectroscopy, and UV-Vis spectrophotometry. Hydrogel formation under physiological conditions (PBS, 37 °C) without catalysts or initiators was verified by rheological frequency sweep analysis, which confirmed elastic-dominant behavior (G′ > G″). Upon irradiation at 365 nm, the crosslinker was cleaved, and rapid network dissolution was observed both macroscopically and by in situ time sweep rheology. This platform enables on-demand, UV-selective hydrogel degradation independently of payload identity, providing a versatile foundation for future controlled drug release applications and dynamic, on-demand degradable scaffolds for tissue engineering. Full article

This paper presents an investigation into the effect of dissolved gases (DGs) on the insulating properties, such as breakdown strength, of Midel EN 1204 natural ester oil and Poweroil TO 1020 60U mineral oils. The gasses were generated by simulating thermal fault/s at 130 °C, 210 °C, 340 °C, 400 °C, and 450 °C. Dissolved gas analysis (DGA) was conducted according to IEC 60567 to determine the concentrations of H₂, CH₄, C₂H₆, C₂H₄, C₂H₂, and CO in each of the twelve oil samples. Moisture was measured using the Karl Fischer Method according to IEC 60814. The breakdown voltage (BDV) was measured according to IEC 60156. The results show that total dissolved gas concentration and rate of rise increased with fault temperature in both oils. For this relatively short time experiment, the rise in concentration of DGs had minimal effect. The overall BDV 73.7 kV (virgin ester oil BDV) increased to 76.3 kV at 450 °C for natural ester oil, whereas the BDV of mineral oil decreased from 68.7 kV to 63.1 kV. These findings showed that natural ester oil has better insulation stability under thermal stress. Full article

Aims: Globally, cardiovascular disorders represent the foremost contributor to mortality, and elevated arterial pressure constitutes one of their principal risk determinants. Despite the availability of various treatments, optimal blood pressure control is rarely achieved. The present work was undertaken to assess the antihypertensive and vasorelaxant properties of benzaldehyde, a naturally occurring aromatic aldehyde whose role in the regulation of arterial pressure has, to our knowledge, not yet been documented. Materials and Methods: Antihypertensive activity was evaluated in normotensive Wistar rats and in animals rendered hypertensive by chronic administration of Nω-nitro-L-arginine methyl ester (L-NAME). Benzaldehyde was administered orally at doses of 20 and 40 mg/kg under both acute (6 h) and subacute (7-day) treatment protocols. Arterial pressure was recorded non-invasively by means of a tail-cuff plethysmography system. Vasorelaxant activity was examined in vitro using isolated rat aortic rings precontracted with either Epinephrine (EP, 10 μM) or potassium chloride (KCl, 80 mM). Endothelium-dependent and endothelium-independent components were dissected by pre-incubating the rings with selective pharmacological inhibitors. Additionally, the effects of benzaldehyde on both phasic and tonic contractions induced by extracellular Ca²⁺ were assessed in EP-precontracted rings in Ca²⁺-free Krebs solution. Key Findings: In hypertensive animals, benzaldehyde produced a dose-related decrease in both systolic and diastolic arterial pressure. It induced concentration-dependent vasorelaxation in both endothelium-intact and -denuded aortic rings. Relaxation was also observed in KCl-precontracted rings. Vasorelaxant responses were significantly attenuated by Indomethacin, Nifedipine, and 2-Aminoethoxydiphenyl borinate (2-APB). Significance: These findings demonstrate that benzaldehyde lowers blood pressure through both endothelium-dependent and -independent mechanisms. These include activation of the prostacyclin (PGI₂)/cAMP pathway, inhibition of L-type calcium channels, and blockade of store-operated calcium channels (SOCCs). Full article

High-temperature temporary sealing operations require liquid plug materials that can be placed as low-viscosity precursors, converted into mechanically stable networks under reservoir temperature, and subsequently removed after service. Existing epoxy-based sealing systems generally provide high post-curing strength, but the coordination among pumpability, thermally triggered curing, and post-service degradability remains insufficiently addressed. In this work, an epoxidized soybean oil (ESO)-modified epoxy–anhydride liquid plug was designed to regulate these sequential stages within a single material system. The precursor formulation, rheological transition, curing kinetics, mechanical response, network structure, and degradation behavior were evaluated using viscosity monitoring, curing-time tests, DSC, compression testing, DMA, gel fraction and swelling measurements, FTIR, and high-temperature degradation experiments. The optimized precursor exhibited an initial viscosity of 65.4 ± 2.1 mPa·s, remaining below the pumpability threshold of 100 mPa·s before curing. Its curing time was adjustable within 1–10 h at 120–140 °C through temperature and initiator regulation. ESO incorporation produced a non-monotonic mechanical response, with the optimized network reaching a compressive strength of 112.5 ± 3.5 MPa and an elastic modulus of 142.50 ± 5.26 MPa. FTIR and thermal–mechanical analyses supported the formation of an ester-rich epoxy–anhydride network containing both rigid epoxy-derived segments and ESO-derived flexible chains. In the post-service stage, degradation was strongly temperature dependent, with the characteristic unsealing time decreasing from 84 h at 120 °C to 24 h at 130 °C and 18 h at 140 °C. The combined results define a coupled curing–degradation window in which pumpable placement, thermal network formation, load-bearing sealing, and controlled unsealing are temporally separated but structurally connected. Full article

The (3aS, 6aR)-lactone serves as the key chiral intermediate for the synthesis of d-biotin. A promising approach involves the asymmetric hydrolysis of meso-dimethyl ester catalyzed by an esterase to yield the (4S, 5R)-monomethyl ester, which is subsequently reduced and cyclized to afford (3aS, 6aR)-lactone. This study first optimized the fermentation medium and culture conditions for the recombinant E. coli pET21a-EstSIT01 harboring the Microbacterium esterase gene, which exhibits high selectivity for the asymmetric synthesis of (4S, 5R)-monomethyl ester. Under optimal conditions (fermentation medium: glycerol 25 g/L, yeast extract 15 g/L, NaCl 10 g/L, MgSO₄•7H₂O 5 g/L; induction was initiated 2 h post-inoculation at 30 °C and pH 7.2), the enzyme activity increased 5.1-fold compared to the initial level, reaching 1072.7 U/L. Secondly, the reaction conditions for the whole-cell synthesis of (4S, 5R)-monomethyl ester catalyzed by EstSIT01 were optimized. The results indicated that organic solvents adversely affected enzyme stability, while high buffer salt concentration negatively impacted enzyme activity at elevated substrate concentrations. The optimal reaction strategy involved maintaining the pH of the aqueous reaction system at 7.5 by the controlled addition of aqueous ammonia to neutralize the (4S, 5R)-monomethyl ester produced during the reaction. Using 17.5 g/L cells and 200 mM substrate meso-dimethyl ester in deionized water, with the reaction pH mentioned at 7.5, complete conversion (100%) was achieved within 4 h at 30 °C. The space–time yield reached 441.6 g/L/d, exceeding the typical requirement for industrial biotransformation (>100 g/L/d), with 99.1% enantiomeric excess (ee) of (4S, 5R)-monomethyl ester. Finally, (4S, 5R)-monomethyl ester was reduced using sodium borohydride to synthesize (3aS, 6aR)-lactone with an ee value of 98.7%. The overall yield from meso-dimethyl ester to (3aS, 6aR)-lactone was 86.2%. These results demonstrate that this integrated chemo-enzymatic approach constitutes a greener method with promising potential for industrial application. Full article

Temporary plugging and flow diversion in multi-fracture reservoirs require gel particles that can provide stable plugging in dominant fractures while enabling low-residue deplugging after treatment. In this study, ester-bond-cleavable self-degradable gel particles were prepared by aqueous free-radical crosslinking using acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-vinyl-2-pyrrolidone, and polyethylene glycol diacrylate as a hydrolysable crosslinker. An MBAA-crosslinked particle was used as a nondegradable control. FTIR and SEM results confirmed the formation of ester-containing crosslinked networks with tunable morphology. Among the prepared samples, EGP-2 showed a balanced hydration and mechanical response, with an equilibrium swelling ratio of 7.12 g/g at 80 °C and 100,000 mg/L salinity, a storage modulus of 205 Pa at 1 Hz, a compressive stress of 54.2 kPa at 30% strain, and a height recovery ratio of 91.8%. In single-fracture tests, EGP-2 achieved plugging efficiencies of 98.6% and 97.4% in 0.5 and 1.0 mm fractures, respectively, with corresponding erosion retention ratios of 94.1% and 92.6%. In a three-parallel-fracture model, EGP-2 reduced the dominant-fracture flow split ratio from 78.4% to 32.8%, while increasing the combined flow split ratio of the medium and narrow fractures from 21.6% to 67.2%, corresponding to a flow diversion efficiency of 58.2%. After aging at 120 °C for 96 h, EGP-2 exhibited a mass loss ratio of 78.4% and a G′ retention ratio of 25.4%. Subsequent flowback tests showed a flowback ratio of 82.6%, a permeability recovery ratio of 88.7%, and a residue ratio of 10.9%. These results demonstrate that ester-bond-cleavable gel particles can integrate temporary plugging, flow diversion, and controlled deplugging, offering a low-residue strategy for multi-fracture reservoir conformance control. Full article

This study introduced freeze-withering to resolve the conflict in traditional Taiping Kuihong black tea processing, where rolling enhances flavor but damages the integrity of the leaf shape. Using sensory evaluation, high-performance liquid chromatography, and gas chromatography–mass spectrometry, the effects of three freezing treatments (−20 °C, −80 °C, and liquid nitrogen at −196 °C) were analyzed and compared with traditional withering (CK). The results demonstrated that low-temperature treatments better preserved the morphological integrity of ‘two leaves and one bud.’ Compared to the CK group, the −20 °C low-temperature treatment group had a significantly higher proportion of esters among the volatile compounds in Taiping Kuihong black tea. Key floral fragrance components were abundant, while grassy undertones were greatly decreased. Concurrently, this group had the highest levels of theaflavins and TF/TR ratios. The −80 °C treatment was highly effective in preserving thearubigins; however, it resulted in a less complex fragrance profile with a reduced theaflavin level. Liquid nitrogen treatment caused aberrant accumulation of theabrownins, poor aroma harmony, and the lowest theaflavin level. This study indicates that −20 °C freezing withering is the best method for harmonizing the appearance and internal quality of Taiping Kuihong, giving critical evidence for targeted processing of unique black teas. Full article

A recent genome-wide association study showed that the protease proprotein convertase subtilisin/kexin type 6 (PCSK6) is highly expressed in idiopathic pulmonary fibrosis (IPF) lung parenchyma and that its expression is associated with disease progression and worse survival. However, whether PCSK6 plays a role in IPF pathophysiology remains elusive. This study aimed to determine whether PCSK6 contributes to IPF pathophysiology, specifically in the cross-talk between epithelial cells and fibroblasts. A549 epithelial cells were transduced with a PCSK6-GFP or control-mCherry vector. Both proliferation (crystal violet) and cell competition assays showed that PCSK6 promoted cell proliferation. Western blot and PCSK-specific fluorogenic substrate assays showed that A549-PCSK6 conditioned medium (CM) had higher PCSK6 enzyme activity compared to mCherry control A549 CM. Human lung fibroblasts stimulated with PCSK6-CM significantly decreased collagen I protein levels as compared to fibroblasts stimulated with control A549-CM. Matrix-metalloproteinase (MMP) specific fluorogenic substrate assays subsequently showed that A549-PCSK6 CM contained higher MMP activity and that PCSK6 inhibition reduced MMP activity in A549-PCSK6 CM, suggesting that PCSK6 plays a role in the activation of MMPs that may degrade collagen type I. In conclusion, epithelial PCSK6 promotes cell proliferation and decreases collagen deposition by fibroblasts, potentially via MMP activation. These in vitro data suggest that PCSK6 could play a dual role in IPF progression and its actual role in IPF should consequently be elucidated using in vivo/ex vivo models. Full article

In this report, we describe the synthesis of two new celastrol derivatives featuring aryl-substituted 1,2,3-triazole fragments attached to the celastrol scaffold via an ester linkage. The target compounds, incorporating 4-methoxyphenyl and p-tert-butylphenyl groups, were characterized by ¹H and ¹³C NMR spectroscopy, FTIR, UV-Vis, HRMS, melting point determination, and specific rotation measurements. Full article

Chemical recycling of mixed plastic waste can recover hydrocarbon products, but additive-derived non-intentionally added substances (NIASs) and other volatile or extractable residues may affect product quality and safety. In this study, six polyolefin-rich waste streams (P1–P6) were analyzed by analytical pyrolysis coupled with comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (Py–GC×GC–TOF–MS), while three additional consumer-grade plastics (P7–P9) were examined by headspace/solvent-extraction GC–MS and aqueous migration testing to profile volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), and water migrants. Under rapid pyrolysis at 650 °C, the condensable products were dominated by C5–C30 aliphatic hydrocarbons. Polyethylene (PE)-rich feeds produced mainly n-paraffins and α-olefins, whereas polypropylene (PP)-rich feeds produced more branched olefins and modest mono-aromatics. Oxygenated compounds were negligible in non-oxidized feeds, but persisted at low levels in weathered high-density polyethylene (HDPE), consistent with pre-existing oxidation. Antioxidant-derived NIASs, including 2,4-di-tert-butylphenol and an Irganox 1010-related spiro-dione, were detected at trace to low area-fraction levels. VOC/SVOC and migration analyses revealed mainly low-intensity hydrocarbons, esters, antioxidant-related degradation products, caprolactam, and selected plasticizer-related compounds. These results show that relatively clean polyolefin streams can yield hydrocarbon-rich pyrolysates, but oxidized PE and additive-derived NIASs remain important quality-control targets. The GC-based methods used here characterize the volatile, condensable, and readily extractable fraction and do not represent the total contaminant load of the source waste. Full article

This study investigated the use of Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) as a cost-effective analytical approach for screening the bioactivity of green algal extracts. Samples of five Caulerpa species—C. ashmeadii, C. paspaloides, C. cupressoides, C. verticillata, and C. prolifera—were collected from Dzilam, Yucatán, Mexico, across seven seasonal campaigns. Sequential extraction was performed using solvents of increasing polarity: hexane, dichloromethane, acetone, and methanol. After solvent evaporation, extracts were analyzed via ATR-FTIR, and Total Phenolic Content (TPC) and Trolox Equivalent Antioxidant Capacity (TEAC) were quantified. Statistical analysis (PERMANOVA) revealed that the type of solvent accounted for most of the variance (61.6%), while species and collection date contributed minimally. Infrared (IR) band assignments highlighted functional groups associated with lipids, such as terpenes, and carbohydrates. K-means clustering enabled the subdivision of less polar extracts, notably grouping numerous samples from C. verticillata. Classification models comparing full-spectrum and IR band datasets showed that Partial Least Squares Discriminant Analysis (PLS-DA) with full-spectrum data achieved the best performance. TPC showed a positive correlation with absorption at 1730.8 cm⁻¹, which is associated with ester-containing metabolites. Although ATR-FTIR effectively distinguished extraction solvents, it was less sensitive to subtle biological variation among Caulerpa. However, the method remains a practical tool for rapid screening, with spectral data supporting solvent-based classification. Reduction of salt content prior to extraction may minimize interference in both FTIR measurements and biological assays. Full article

Lubricants contain various types of additives, with corrosion and rust inhibitors being some of the most important. Due to the importance of 2,5-Dimercapto-1,3,4-thiadiazole (DMTD) in the field of corrosion inhibitors, we used it as a key intermediate to synthesize a series of 4-thiazolidinone and 4-imidazolidinone derivatives. This work also includes performing the reaction of DMTD with ethyl chloroacetate, which produced the corresponding ester, followed by the conversion into a hydrazide derivative using hydrazine hydrate. The next step is the condensing of the yielded hydrazide with various aromatic aldehydes yielding Schiff bases, which were subjected to cyclization by means of mercapto acetic acid and ethyl glycinate to produce the target 4-thiazolidinone and 4-imidazolidinone derivatives, respectively. FT IR, ¹H NMR, and ¹³C NMR spectroscopies were involved to confirm the structures of these derivatives. The synthesized derivatives have been evaluated as copper corrosion and rust inhibitors for medium lubricants in accordance with ASTM-D130 and ASTM-D665 standards. Interestingly, some lubricant blends of the synthesized derivatives showed good performance as copper corrosion and rust inhibitors. Full article

This study explores the interfacial interactions between a novel collector, S-[2-(hydroxyamino)-2-oxoethyl]-O-octyl-dithiocarbonate ester (EHAOX), and bastnaesite mineral surfaces during selective flotation. Compared to conventional octylhydroxamic acid (OHA), EHAOX demonstrated superior recovery, achieving an over 40% absolute increase in recovery compared to octylhydroxamic acid (OHA) at the same collector concentration (1 × 10⁻⁵ mol/L) and pH 8.0, and selectivity for bastnaesite, attributed to its optimized hydrophobicity (supported by CLogP calculations). Mechanistic studies via zeta potential, UV/vis spectroscopy, and FTIR revealed the formation of a complex composite via chemisorption between EHAOX and Ce³⁺ sites on the bastnaesite surface, with coordination occurring through the sulfur (N-C(=S)) and oxygen (-C(=O)N-OH) functional groups. This selective adsorption minimized EHAOX’s affinity for calcite, highlighting its potential for tailoring composite mineral separation processes. The findings advance the design of functionalized collectors for rare-earth mineral enrichment, with implications for composite material processing in resource recovery. Full article