Acidic Properties Research Articles

Effect of microwave irradiation on the synthesis of zeolite with ferrierite structure: Study of acid and catalytic properties

Ferrierite zeolite (FER) was synthesized under microwave conditions while varying the microwave exposure time from 6 to 12 h. For comparison, commercial FER and a FER zeolite synthesized by the conventional hydrothermal synthesis (72 h) were studied. The structure, texture, and acidic properties of the samples were investigated by XRD, low-temperature N2 adsorption, ICP-AES, SEM, and DRIFT spectroscopy using adsorption of CO, CD3CN and pyridine as probe molecules. The catalytic characteristics of the obtained zeolites were studied in the cyclocondensation reaction of 1,2-phenylenediamine and acetone to produce 1,5-benzodiazepine. The activity of the zeolites in this reaction was found to increase with increasing microwave exposure time. The FER-MW sample synthesized in 12 h showed the best results.

Investigation of the Anti-diabetic and Anti-lipid Peroxidative Properties of Gallic Acid in Diabetic Rats

Diabetes mellitus is a chronic non-communicable disease that occurs due to insulin deficiency or reduced function in the body. Therefore, the scientific investigation of herbal plants and their effectiveness is essential. It has been shown that gallic acid has hypoglycemic properties. In this study, the anti-diabetic and anti-lipid peroxidation properties of gallic acid were investigated. For this purpose, Streptozotocin was injected intraperitoneally into male rats at a dose of 60 mg/kg to induce type I diabetes. Seven days after Streptozotocin injection, blood samples were taken and rats with serum glucose levels higher than 250 mg/dL were considered diabetic. The rats were divided into 4 groups. Two groups of diabetic rats received either water or gallic acid at a dose of 40 mg/kg, and two groups of normal rats received either water or gallic acid at 40 mg/kg dose. The treatment period for all groups was 8 weeks. After the end of the period, blood samples were taken from the rats under fasting conditions. The collected blood samples were analyzed for serum biochemical factors (glucose, cholesterol, triglycerides, High-density lipoprotein, and creatinine) using spectrophotometry with the respective kits, and the level of lipid peroxidation in red blood cells was measured. The administration of gallic acid at a dose of 40 mg/kg (8 weeks) significantly reduced serum levels of glucose, triglycerides, cholesterol, alanine aminotransferase, aspartate aminotransferase, very low-density lipoprotein, low-density lipoprotein, and creatinine, while significantly increasing serum levels of high-density lipoprotein. Additionally, the level of Malondialdehyde in red blood cells was decreased in the diabetic group receiving gallic acid compared to the diabetic control group, and in normal rats receiving gallic acid at a dose of 40 mg/kg (8 weeks), it had no significant effect on serum factors and had no toxicity.

Effects of additives (NaCl, citric acid, and ethanol) on the cooking quality and sensory quality of vermicelli produced from freeze–thaw‐dehydrated whole potato powder

SummaryTo conform to the trend of whole‐food diets in recent years, whole potato powder has been used for the processing of extruded vermicelli. The effects of different additives, such as NaCl, citric acid and ethanol, on the cooking quality and sensory quality of whole potato vermicelli obtained via twin‐screw extrusion were investigated. The colour, gelatinisation properties, water absorption, cooking loss, texture profile analysis, scanning electron microscopy analysis and correlation analysis of the whole potato vermicelli were determined and discussed. The brightness of the whole potato vermicelli increased from 52.0 to 55.4 at 1% NaCl addition and increased from 52.0 to 54.9 at 0.8% citric acid addition, and the water absorption of the whole potato vermicelli increased from 83.1% to 159.1% at 0.4% citric acid addition and increased from 83.1% to 258.9% at 8% ethanol addition. The cooking loss of the whole potato vermicelli decreased from 5.3% to 5.1% at 8% ethanol addition, indicating that ethanol could improve the cooking quality of whole potato vermicelli. The texture properties of the whole potato vermicelli decreased with the addition of ethanol, and the ΔH of the whole potato vermicelli decreased from 3.7 to 1.8 J g−1 at 0.8% citric acid addition and decreased from 3.7 to 1.5 J g−1 at 8% ethanol addition, respectively. Moreover, the addition of ethanol was negatively correlated with the max force, break distance, stretching work, hardness, adhesiveness and chewiness of the whole potato vermicelli. The addition of NaCl was positively correlated with the peak gelatinisation temperature. All three additives affected the microstructure of the whole potato vermicelli, including roughening the cross section and increasing the number of pores. In this study, NaCl improved the gelatinisation properties of whole potato vermicelli, citric acid and ethanol improved the water absorption of the whole potato vermicelli, and citric acid improved the anti‐browning effects of the whole potato vermicelli.

Investigation on Tensile Properties of Polylactide-Nanoclay (PLA/ MMT) Surface Modification Nanocomposites

Polylactic acid (PLA) has gained significant attention as an environmentally friendly biopolymer, but its limited mechanical properties have hindered broader applications. Nanoparticles such as montmorillonite (MMT) offer a promising approach to address this limitation. The intercalation of MMT with polymer chains can significantly impact the mechanical properties of the nanocomposites. Hence, this paper investigated the effect of surface-modified montmorillonite (MMT) nanoparticles on the mechanical properties of polylactic acid (PLA) nanocomposites. The acetylation process of MMT was carried out followed by neutralisation process with NaOH. PLA granules and acetylated-modified MMT were mixed, crushed into granular form, and moulded. The effect of varying concentrations of modified MMTs on the tensile strength, elongation at break, and maximum force of PLA/MMT nanocomposites was evaluated using the ASTM D638 standard. FTIR results showed shifts in peak intensities in regions 2750 cm-1- 2810 cm-1 led to changes in the aliphatic and aromatic regions, which confirmed the presence of acetylation. Controlled surface modification improved interfacial interactions and load distribution, enhancing overall mechanical performance. The incorporation of surface-modified MMT in PLA/MMT nanocomposite increased the maximum force, Young's modulus, elongation at breaks and tensile strength. PLA/1wt% MMT and the PLA/7wt% MMT compositions exhibited good mechanical properties. However, the PLA/5 wt% MMT blendis deemed more suitable for food applications, such as disposable cups, plates, and cutleries, due to its lower elongation point. In conclusion, the hydrophilic properties of MMT and the hydrophobic properties of PLA are compatible due to the synergistic effects during surface modification which enhance the overall performance of the nanocomposites.

Impact of organic acid molecular length and structure on rock oil-wetting rapidity and stability

The oil-wetting properties of organic acids play a crucial role in various industrial applications, including enhanced oil recovery, oil spill remediation, surface modification, and so on. This study investigated the impact of organic acid molecular length and structure on oil-wetting rapidity and stability on sandstone and carbonate. Model oils prepared by dissolving organic acids in n-decane, and crude oil, were used as the oil phase. Their oil-wetting behavior was evaluated by contact angle values. The maximum molecular length of each organic acid was approximated based on its molecular structure. Our results indicate that organic acids change wettability much faster in carbonate rock than in sandstone. Longer organic acid molecules exhibit enhanced oil-wetting potential due to increased hydrophobic interactions with oil phases. Water film does not have a long-term impact on the oil-wetting process by organic acid on Indiana limestone. However, the existence of a water film largely inhibited the oil-wetting process for Indiana limestone in crude oil, and for Berea sandstone in crude and model oil. Furthermore, molecular structure, such as the presence of functional groups, significantly influences oil-wetting properties. Organic acids with an aromatic ring demonstrated a more stable oil-wetness against wettability alteration induced by surfactant treatment. Gemini surfactants with benzene ring(s) in the spacer removed aromatic organic acid more efficiently than surfactants without benzene ring. Overall, this study provides insights into the design and optimization of organic acids for applications requiring effective oil-wetting and oil-wetness stability, as well as the designing of surfactant structures with higher oil removal efficiency.

Determination of Cytotoxic and Apoptotic Properties of Lobaric Acid, a Secondary Metabolite of Lichen and Investigation of Its Theoretical Potential

In this study, we aimed to elucidate some of the mechanisms of cell death induced by lobaric acid in A549 (human lung cancer) cells. For this purpose, the effects of cytotoxic concentrations on p53 and caspase-3 gene expressions were investigated. A549 cells were treated with varying concentrations of lobaric acid (12.5, 25, 50, and 100 µg/ml) for 48 hours and then their viability was evaluated and p53 and caspase-3 mRNA expressions were determined at statistically cytotoxic concentrations of 12.5, 50, and 100 µg/ml. According to beta-actin, it was determined that the increase in lobaric acid concentration revealed an upward trend in p53 and caspase-3 mRNA expressions. Furthermore, quantum chemical parameters such as frontier molecular orbitals, band gap energy and ionization potential, electronic affinity, chemical softness, chemical potential, electrophilicity index and chemical hardness were analyzed. Furthermore, molecular docking was performed to identify the binding sites and the binding behavior of lobaric acid to some target proteins (P53, Caspase-3 and Bcl-2).

Impact of Multi-Factor Features on Protein Secondary Structure Prediction.

Protein secondary structure prediction (PSSP) plays a crucial role in resolving protein functions and properties. Significant progress has been made in this field in recent years, and the use of a variety of protein-related features, including amino acid sequences, position-specific score matrices (PSSM), amino acid properties, and secondary structure trend factors, to improve prediction accuracy is an important technical route for it. However, a comprehensive evaluation of the impact of these factor features in secondary structure prediction is lacking in the current work. This study quantitatively analyzes the impact of several major factors on secondary structure prediction models using a more explanatory four-class machine learning approach. The applicability of each factor in the different types of methods, the extent to which the different methods work on each factor, and the evaluation of the effect of multi-factor combinations are explored in detail. Through experiments and analyses, it was found that PSSM performs best in methods with strong high-dimensional features and complex feature extraction capabilities, while amino acid sequences, although performing poorly overall, perform relatively well in methods with strong linear processing capabilities. Also, the combination of amino acid properties and trend factors significantly improved the prediction performance. This study provides empirical evidence for future researchers to optimize multi-factor feature combinations and apply them to protein secondary structure prediction models, which is beneficial in further optimizing the use of these factors to enhance the performance of protein secondary structure prediction models.

Enhancing the mechanical properties of polylactic acid (PLA) composite films using Pueraria lobata root microcrystalline cellulose

To enhance the mechanical properties of polylactic acid (PLA) material, the PLA-based composite films are prepared by using Pueraria lobata (Willd.) Ohwi root microcrystalline cellulose (PRMCC) treated with 3-aminopropyl triethoxysilane (KH550) silane coupling agent as the dispersed phase through solvent casting method. The effects of the concentrations of PRMCC and KH550 as well as the KH550 pretreating condition (ethanol concentration) on the tensile properties of PLA-based composite films are investigated. The PLA-based composite film treated with 5 wt% PRMCC and 18 wt% KH550 (pretreated by 90 % EtOH) exhibits the greatest performance. Its elongation at break value is detected to be 4.0 %, 1.6 times as large as that of pure PLA film. The water absorption of the as-prepared PLA-based composite film is reduced from 0.49 % of the unmodified PLA/PRMCC film to 0.12 %. Moreover, the modified PLA-based composite film has a hydrophobic surface and exhibits good thermal stability. Compared with pure PLA film, the modified PLA-based composite film exhibits improved UV shielding performance with acceptable transparency. Furthermore, after adding poly(butylene adipate-co-terephthalate) (PBAT) to the composite system, the elongation at break of the PLA-based composite film is up to 7.2 %. This research can provide theoretical guidance for enhancing the performance of PLA products.

Efficient Hydrodeoxygenation of Lignin-Derived Phenolic Compounds over Bifunctional Catalyst Comprising H4PMo11VO40 Coupled with Ni/C.

In the catalytic transformation of bio-oil into liquid fuels having alkanes via hydrodeoxygenation (HDO), the acid and metal sites in the catalyst are pivotal for promoting the HDO of lignin-derived phenolic compounds. This study introduces a novel bifunctional catalyst comprising phosphomolybdenum-vanadium heteropolyacids (H4PMo11VO40) coupled with Ni/C. The HDO reaction of the model compound guaiacol was carried out under reaction conditions of 230 °C, revealing the superior performance of H4PMo11VO40 with Ni/C catalysts compared to the conventional acids, even at low dosage. The Keggin structure of H4PMo11VO40 provided a solid catalyst with strong acidic and redox properties, alongside advantages such as ease of synthesis, cost-effectiveness, and tunable acid and redox properties at the molecular level. Characterization of Ni/C and the prepared acid demonstrated favorable pore structure with a mesopore volume of 0.281 cm3/g and an average pore size of 3.404 nm, facilitating uniform distribution and catalytic activity of Ni-metal. Incorporating acid enhances the acidic sites, fostering synergistic interactions between metal and acidic sites within the catalyst, thereby significantly enhancing HDO performance. Guaiacol conversion at 230 °C reached 100 %, with a cyclohexane selectivity of 89.3 %. This study offers a promising avenue for the conversion and upgrading of lignin-derived phenolic compounds.

Catalyst Accessibility and Acidity in the Hydrocracking of HDPE: A Comparative Study of H-USY, H-ZSM-5, and MCM-41 Modified with Ga and Al.

Plastic pollution is a critical environmental issue due to the widespread use of plastic materials and their long degradation time. Hydrocracking (HDC) offers a promising solution to manage plastic waste by converting it into valuable products, namely chemicals or fuels. This work aims to investigates the effect of catalyst accessibility and acidity on the HDC reaction of high density polyethylene (HDPE). Therefore, a variety of materials with significant differences in both textural and acidic properties were tested as catalysts. These include H-USY and H-ZSM.5 zeolites with various Si/Al molar ratios (H-USY: Si/Al = 2.9, 15, 30 and 40; H-ZSM-5: Si/Al = 11.5, 40, 500) and mesostructured MCM-41 materials modified with Ga and Al, also with different Si/metal ratios (Si/Al = 16 and 30; Si/Ga = 63 and 82). Thermogravimetric analysis under hydrogen atmosphere was used as a preliminary screening tool to evaluate the potential of the various catalysts for this application in terms of energy requirements. In addition, batch autoclave reactor experiments (T = 300 °C, PH2 = 20 bar, t = 60 min) were conducted to obtain further information on conversion, product yields and product distribution for the most promising systems. The results show that the catalytic performance in HDPE hydrocracking is determined by a balance between the acidity of the catalyst and its structural accessibility. Accordingly, for catalyst series where the structural and textural properties do not vary with the Si/Al ratio, there is a clear correlation of the HDPE degradation temperature and of the HDPE conversion with the Si/metal ratio (which relates to the acidic properties). In contrast, for catalyst series where the structural and textural properties vary with the Si/Al ratio, no consistent trend is observed and the catalytic performance is determined by a balance between the acidic and textural properties. The product distribution was also found to be influenced by the physical and chemical properties of the catalyst. Catalysts with strong acidity and smaller pores were observed to favor the formation of lighter hydrocarbons. In addition to the textural and acidic properties of the catalyst, the role of coke formation should not be neglected to ensure a comprehensive analysis of the catalytic performance.

Species-specific model based on sequence and structural information for ubiquitination sites prediction

Ubiquitination is a common post-translational modification of proteins in eukaryotic cells, and it is also a significant method of regulating protein biological function. Computational methods for predicting ubiquitination sites can serve as a cost-effective and time-saving alternative to experimental methods. Existing computational methods often build classifiers based on protein sequence information, physical and chemical properties of amino acids, evolutionary information, and structural parameters. However, structural information about most proteins cannot be found in existing databases directly. The features of proteins differ among species, and some species have small amounts of ubiquitinated proteins. Therefore, it is necessary to develop species-specific models that can be applied to datasets with small sample sizes. To solve these problems, we propose a species-specific model (SSUbi) based on a capsule network, which integrates proteins’ sequence and structural information. In this model, the feature extraction module is composed of two sub-modules that extract multi-dimensional features from sequence and structural information respectively. In the submodule, the convolution operation is used to extract encoding dimension features, and the channel attention mechanism is used to extract feature map dimension features. After integrating the multi-dimensional features from both types of information, the species-specific capsule network further converts the features into capsule vectors and classifies species-specific ubiquitination sites. The experimental results show that SSUbi can effectively improve the prediction performance of species with small sample sizes and outperform other models.

Highly Efficient Carbonylation of Propylene Oxide into β‐Butyrolactone Catalyzed over Co‐Al Bimetallic Species†

AbstractRational designation of the catalyst for efficient atom‐economic conversion of propylene oxide (PO) and carbon monoxide (CO) into β‐butyrolactone is of current significance. By employing the O,N,O‐tridentate ligands R1,R2LH2 (1–4), the aluminium compounds (R1,R2LAlCl)2 (R1,R2=H,H (5), tBu,tBu (6), Cl,Cl (7), Br,Br (8)) and the derived anion‐cation pairs [H,HLAl(THF)3]+[Co(CO)4]− (9) and [(R1,R2LAl)2Cl(THF)2]+[Co(CO)4]− (R1,R2=tBu,tBu (10), Cl,Cl (11), Br,Br (12)) as well as the aluminium‐cobalt bimetallic cluster compounds [(R1,R2LAl)2Cl(THF)][Co3(CO)10] (R1,R2=tBu,tBu (13), Cl,Cl (14), Br,Br (15)) were prepared. Compounds 9–12 efficiently catalyzed the PO carbonylation into β‐butyrolactone to achieve up 93.4–98.9 % yields while 13–15 gained 95.2–99.0 % yields all at 25 °C and 0.1 MPa CO pressure. The Lewis acidic property of the aluminium compounds 5–8 was investigated. The kinetic of the catalytic reaction using compound 10 was studied. The cooperatively catalytic reaction mechanism by the Co−Al bimetallic species is proposed.

Sensing the structural and conformational properties of single-stranded nucleic acids using electrometry and molecular simulations

Inferring the 3D structure and conformation of disordered biomolecules, e.g., single stranded nucleic acids (ssNAs), remains challenging due to their conformational heterogeneity in solution. Here, we use escape-time electrometry (ETe) to measure with sub elementary-charge precision the effective electrical charge in solution of short to medium chain length ssNAs in the range of 5–60 bases. We compare measurements of molecular effective charge with theoretically calculated values for simulated molecular conformations obtained from Molecular Dynamics simulations using a variety of forcefield descriptions. We demonstrate that the measured effective charge captures subtle differences in molecular structure in various nucleic acid homopolymers of identical length, and also that the experimental measurements can find agreement with computed values derived from coarse-grained molecular structure descriptions such as oxDNA, as well next generation ssNA force fields. We further show that comparing the measured effective charge with calculations for a rigid, charged rod—the simplest model of a nucleic acid—yields estimates of molecular structural dimensions such as linear charge spacings that capture molecular structural trends observed using high resolution structural analysis methods such as X-ray scattering. By sensitively probing the effective charge of a molecule, electrometry provides a powerful dimension supporting inferences of molecular structural and conformational properties, as well as the validation of biomolecular structural models. The overall approach holds promise for a high throughput, microscopy-based biomolecular analytical approach offering rapid screening and inference of molecular 3D conformation, and operating at the single molecule level in solution.

Efficient cascade reactions involving esterification, hydrogen transfer, and lactonization for biomass conversion using MOF/Metal oxide composites as heterogeneous catalysts

Development of heterogeneous catalysts with both Brønsted and Lewis acid properties has proved to be promising and useful because they offer an efficient way to cascade reactions. In this study, we present the synthesis pathway and efficacy evaluation of new composites which combined by sulfonic acid functional group modified TiO2 and MIL-101, analyzing their structure-performance correlation as heterogeneous catalysts in cascade reactions involving esterification, hydrogen transfer, and lactonization. These composites possess an open porous structure (MOF and porous TiO2), as well as active sites including Lewis acid (unsaturated coordination metal), Lewis base (Ti-OH), and Brønsted acid (-SO3H). The role of these active sites and the synergies between them were investigated through the esterification of levulinic acid and the direct synthesis of γ-valerolactone from levulinic acid and furfural under cascade reactions. The composites exhibit a 100% ethyl levulinate (EL) yield at 120°C for 6 hours, with γ-valerolactone yields reaching up to 94.5% (160 °C, 9 h) and 89.5% (160 °C, 16 h) from levulinic acid and furfural, respectively. This synergistic effect of Lewis acid/base and Brønsted acid ensures efficient esterification. The presence of a sulfonic acid group promotes the lactonization reaction, while the Meerwein-Ponndorf-Verley reduction is facilitated by the dual Cr sites located adjacent to each other in the secondary building unit of MIL-101(Cr). Moreover, the double-porous structure of porous TiO2 and MIL-101(Cr) effectively guarantees the efficient mass transfer of reactants and intermediates, leading to enhanced synergistic effects that promote more efficient reaction conversion.

Teaching protein structure and function through molecular visualization.

The function of proteins is governed by their three-dimensional structure. This structure is determined by the chemical characteristics and atomic interactions of amino acids. Students of biochemistry, with a particular focus on protein chemistry, benefit from looking at protein structures and understanding how proteins are built and fold. Due to their three-dimensional nature, static two-dimensional representations in textbooks can be limiting to student learning. Here, we developed a series of tutorials that introduce students to molecular graphics software. The students are challenged to apply the software to look at proteins and to get a deeper understanding of how amino acid properties are linked to structure. We also familiarize students with some of the latest tools in computational structural biology. Students performed the tutorials with visual enthusiasm and reported general satisfaction in being able to visualize theoretical concepts learned during lectures. We further stimulated student engagement by allowing space for self-exploration. We share the tutorial instructions for other teachers to build on them, and we also offer suggestions for further improvement based on student feedback. In summary, we present a series of tutorials aimed at students of an advanced course in protein biochemistry to enable them to explore the universe of protein structures and how those relate to function.

Croconic Acid Integrated Zwitterionic Conjugated Porous Polymer for Effective Iodine Adsorption.

Given the rapid growth of the nuclear sector, effective treatment of radioactive iodine is critical. Herein, we report the synthesis and the iodine adsorption properties of croconic acid (CTPB) and squaric acid (STPB) containing π-conjugated novel zwitterionic conjugated porous polymers (CPPs). The CPPs have been synthesized through a condensation reaction of tris(4-aminophenyl)benzene with croconic acid or squaric acid in high yields (~95%). The ionic nature of the polymers promoted high iodine/polyiodide vapour adsorption capacity of up to 4.6 g/g for CTPB and 3.5 g/g for STPB under ambient pressure at 80 °C. The zwitterionic framework (croconic acid or squaric acid units) coupled with the aromatic units is expected to effectively capture molecular iodine (I2) and polyiodides (I3- and I5-). The iodine adsorption properties of the polymers have been studied using Fourier-Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Brauner-Emmett-Teller (BET) analysis, and Raman Spectroscopy. Besides this work, there are only three ionic units for effective iodine adsorption. This work demonstrates the importance of zwitterionic units in the porous network reported for iodine adsorption and separation.

Anti-neoplastic Properties of Boswellic Acids and their Novel Semi-synthetic Analogs: In vitro, In vivo and Clinical Evidence

Introduction: Recently, Boswellia gum resin extract has been shown to exhibit therapeutic properties against multiple inflammatory illnesses, comprising arthritis, asthma, diabetes, inflammatory bowel disease, and different malignancies. There are growing shreds of evidence that Boswellia extracts and their phytoconstituents could be used in adjuvant and combinatorial chemotherapeutic approaches for the management and prevention of cancer. Aim: The principal objective of this comprehensive investigation is to offer up-to-date and in-depth insights into the anticancer potential of boswellic acids along with their semisynthetic analog that are novel and preventive/therapeutic substitutes for the management of cancer and inflammatory diseases due to their strong potential. Materials and Methods: In the course of this review, a comprehensive compilation of In-vitro, Invivo, and clinical evidence on the antineoplastic potential of boswellic acids was assembled through systematic computerized searches utilizing platforms such as Google Scholar, PubMed, Sci-Hub, and Research Gate. Result: Boswellic acids, the key compounds found in the resin of nearly all the species of the Boswellia plant, have been reported to exhibit therapeutic effects by modulating various targets in different disease conditions. Moreover, semisynthetic derivatives of boswellic acids show strong cytotoxic effects, particularly those with cyanoenone moieties, endoperoxides, and hybrids, which exhibit enhanced potency. Conclusion: In this review, we have sincerely highlighted the effectiveness of novel boswellic acids as alternative preventive and therapeutic agents for the treatment of cancer and inflammatory conditions. Their strong anticancer potential could provide a basis for promising future direction to develop potent anticancer drugs for human malignancies.

Effect of Acid Properties of Fluorinated Beta and ZSM-5 Zeolites Used as Supports of Ni Catalysts for the Catalytic Hydrodeoxygenation of Guaiacol

Commercial NH4-Beta and Na-ZSM-5 zeolites were fluorinated with different amounts of NH4F and using different procedures (room temperature, conventional refluxing, microwave refluxing). Samples were characterized by XRD, N2 physisorption, FTIR, 1H NMR, SEM-EDS, and TGA of adsorbed cyclohexylamine. An increase in the concentration of NH4F led to fluorinated zeolites with higher surface areas and slightly lower amounts of Brønsted acid sites due to some dealumination. Fluorination by conventional or microwave refluxing at shorter times did not dealuminate ZSM-5, resulting in the formation of higher particle sizes. Ni/fluorinated beta catalysts were more active than Ni/fluorinated ZSM-5 catalysts for the hydrodeoxygenation of guaiacol at 180 °C and 15 bar of H2 for 1 h due to their higher amount of acid sites. The appropriate proportion of metallic and Brønsted acid centers allowed for the selective obtention of cyclohexane (58%) for the Ni supported on beta fluorinated with NH4F 0.1 M catalyst. The combination of this fluorinated beta to a Ni/ordered mesoporous carbon catalyst significantly boosted its selectivity to cyclohexane from 0 to 65%. Fluorinated ZSM-5 samples, although having stronger Brønsted acid sites, as observed by 1H NMR, they had lower amounts, leading to higher selectivity to cyclohexanol when used as catalytic supports.

Post-translational modifications in the Protein Data Bank.

Proteins frequently undergo covalent modification at the post-translational level, which involves the covalent attachment of chemical groups onto amino acids. This can entail the singular or multiple addition of small groups, such as phosphorylation; long-chain modifications, such as glycosylation; small proteins, such as ubiquitination; as well as the interconversion of chemical groups, such as the formation of pyroglutamic acid. These post-translational modifications (PTMs) are essential for the normal functioning of cells, as they can alter the physicochemical properties of amino acids and therefore influence enzymatic activity, protein localization, protein-protein interactions and protein stability. Despite their inherent importance, accurately depicting PTMs in experimental studies of protein structures often poses a challenge. This review highlights the role of PTMs in protein structures, as well as the prevalence of PTMs in the Protein Data Bank, directing the reader to accurately built examples suitable for use as a modelling reference.

Machine learning approaches for assessing stability in acid-crude oil emulsions: application to mitigate formation damage

The stability of acid-crude oil emulsion poses manifold issues in the oil industry. Experimentally evaluating this phenomenon may be costly and time-consuming. In contrast, machine learning models have proven effective in predicting and evaluating various phenomena. This research is the first of its kind to assess the stability of acid-crude oil emulsion, employing various classification machine learning models. For this purpose, a data set consisting of 249 experimental data points belonging to 11 different crude oil samples was collected. Three tree-based models, namely decision tree (DT), random forest (RF), and categorical boosting (CatBoost), as well as three artificial neural network models, namely radial basis function (RBF), multi-layer perceptron (MLP) and convolutional neural network (CNN), were developed based on the properties of crude oil, acid, and protective additive. The CatBoost model obtained the highest accuracy with 0.9687, followed closely by the CNN model with 0.9673. In addition, confusion matrix findings showed the superiority of the CatBoost model. Finally, by applying the SHapley Additive exPlanations (SHAP) method to analyze the impact of input parameters, it was found that the crude oil viscosity has the most significant effect on the model's output with the mean absolute SHAP value of 0.88.