Soaking Experiments Research Articles

Enhancing the apo protein tyrosine phosphatase non-receptor type 2 crystal soaking strategy through inhibitor-accessible binding sites.

Protein tyrosine phosphatase non-receptor type 2 (PTPN2) has recently been recognized as a promising target for cancer immunotherapy. Despite extensive structural and functional studies of other protein tyrosine phosphatases, there is limited structural understanding of PTPN2. Currently, there are only five published PTPN2 structures and none are truly unbound due to the presence of a mutation, an inhibitor or a loop (related to crystal packing) in the active site. In this report, a novel crystal packing is revealed that resulted in a true apo PTPN2 crystal structure with an unbound active site, allowing the active site to be observed in a native apo state for the first time. Key residues related to accommodation in the active site became identifiable upon comparison with previously published PTPN2 structures. Structures of PTPN2 in complex with an established PTPN1 active-site inhibitor and an allosteric inhibitor were achieved through soaking experiments using these apo PTPN2 crystals. The increased structural understanding of apo PTPN2 and the ability to soak in inhibitors will aid the development of future PTPN2 inhibitors.

Screening of Casuarina equisetifolia rhizosphere-promoting bacteria and their effects on seed germination and seedling growth.

To promote the growth of Casuarina equisetifolia and address the abnormalities in the structure and function of rhizosphere soil microbial community, we isolated eight strains with multiple functions from the root nodules of C. equisetifolia, including nitrogen fixation (N), production of cell wall-degrading enzymes (protease and cellulase), auxin (IAA) production, siderophore production, ammonia (NH3) production, and phosphate solubilization. Among these strains, LB08, LB18, LB19, LB42, LB46, LB63, and LB69 were identified as Paenibacillus species, while LQ10 was identified as a Brucella sp. Results of seed soaking experiments showed that all the eight strains promoted the growth of C. equisetifolia seedlings. Strain LB69 significantly increased the germination rate and seedling vigor by 19.7% and 28.3%, respectively. Strain LQ10 significantly enhanced root length and root vigor by 48.2% and 334.4%, respectively. Strains LB18 and LB42 had the strongest effects on early shoot length and biomass accumulation, with increases of 22.4% and 32.8%, respectively. After seed soaking, the number of isozymes bands of polyphenol oxidase, superoxide dismutase, and peroxidase increased, with some bands showing enhanced intensity and increased diversity of enzyme isoforms, thereby enhancing stress resistance. In summary, the addition of these eight strains promoted plant growth and antioxidant enzyme activity, indicating their potential role as biofertilizers.

Karrikinolide1 (KAR1), a Bioactive Compound from Smoke, Improves the Germination of Morphologically Dormant Apium graveolens L. Seeds by Reducing Indole-3-Acetic Acid (IAA) Levels.

Smoke-water (SW) and Karrikinolide1 (KAR1) release dormancy and improve seed germination in many plant species. Therefore, we tested SW (1:2500 v/v) and KAR1 (10-7 M) to break the morphological dormancy of celery cultivar (Apium graveolens L.). In the first trial, seeds were subjected to a 21-day incubation period at 20 °C with SW and KAR1 applied as single treatments. KAR1 showed significantly improved germination (30.7%) as compared to SW (17.2%) and a water control (14.7%). In seed soaking experiments, SW, KAR1, and gibberellic acid (GA3) treatments showed higher germination percentages than the water control after 3 and 6 h of soaking. However, prolonged soaking (12 h) reduced germination percentages for all treatments, indicating a detrimental effect. Analysis of KAR1 content dynamics in 7-day- and 21-day-old celery seeds indicated its prolonged effects on germination and dormancy alleviation. Phytohormones, including auxins in 7-day-old and cytokinins in 7-day- and 21-day-old celery seedlings, along with their precursors and metabolites, were analyzed using ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) after treatment with KAR1 and SW. The analysis of auxin levels in 7-day-old seeds revealed a negative correlation between seed germination and auxin (indole-3-acetic acid, IAA) content. Notably, it was found that KAR1-treated seeds significantly reduced IAA levels in all treatments. SW and KAR1 did not significantly affect cytokinin levels during celery germination except for N6-Isopentenyladenine. Hence, further research is needed to understand their precise role in celery seed germination. This work will improve our understanding of the role of bioactive compounds from plant-derived smoke and how they regulate hormonal responses and improve germination efficiency in celery.

A novel design of lithium-polymer pouch battery pack with passive thermal management for electric vehicles

This study investigates the thermal characteristics of a lithium polymer pouch battery thermal management system using phase change material (PCM) during the discharge. The research provides a detailed discussion of various factors influencing the system. The novelty aspect of this study involves evaluating thermal changes in the battery at 40 °C through hot soaking experiments comparing with both PCM-integrated modules and without PCM modules. The study further aims to identify the optimal PCM for both normal and high ambient conditions. Thermal parameters, including maximum temperature Tmax, average temperature Taverage and thermal gradient ΔT were evaluated at 25 °C and hot soaking performance at 40 °C temperature during discharge was analysed. Simulation were conducted to compare module behavior, especially at high-temperature conditions. Furthermore, a thorough examination of PCM melting and solid-phase transitions at high temperatures were performed that significantly impact the cooling performance of the PCM system. Our findings reveal that expanded graphite PCMs offers effective thermal performance with observed improvement of 27 %. Therefore, we recommend employing EG26 and EG28 PCMs for real-world application electric vehicle battery pack systems.

Exploring the coordination chemistry of ruthenium complexes with lysozymes: structural and in-solution studies.

This study presents a comprehensive structural analysis of the adducts formed upon the reaction of two Ru(III) complexes [HIsq][trans-RuIIICl4(dmso)(Isq)] (1) and [H2Ind][trans-RuIIICl4(dmso)(HInd)] (2) (where HInd-indazole, Isq-isoquinoline, analogs of NAMI-A) and two Ru(II) complexes, cis-[RuCl2(dmso)4] (c) and trans-[RuCl2(dmso)4] (t), with hen-egg white lysozyme (HEWL). Additionally, the crystal structure of an adduct of human lysozyme (HL) with ruthenium complex, [H2Ind][trans-RuCl4(dmso)(HInd)] was solved. X-ray crystallographic data analysis revealed that all studied Ru complexes, regardless of coordination surroundings and metal center charge, coordinate to the same amino acids (His15, Arg14, and Asp101) of HEWL, losing most of their original ligands. In the case of the 2-HL adduct, two distinct metalation sites: (i) Arg107, Arg113 and (ii) Gln127, Gln129, were identified. Crystallographic data were supported by studies of the interaction of 1 and 2 with HEWL in an aqueous solution. Hydrolytic stability studies revealed that both complexes 1 and 2 liberate the N-heterocyclic ligand under crystallization-like conditions (pH 4.5) as well as under physiological pH conditions, and this process is not significantly affected by the presence of HEWL. A comparative examination of nine crystal structures of Ru complexes with lysozyme, obtained through soaking and co-crystallization experiments, together with in-solution studies of the interaction between 1 and 2 with HEWL, indicates that the hydrolytic release of the N-heterocyclic ligand is one of the critical factors in the interaction between Ru complexes and lysozyme. This understanding is crucial in shedding light on the tendency of Ru complexes to target diverse metalation sites during the formation and in the final forms of the adducts with proteins.

Research on Pitting Corrosion of Microalloyed High-Strength Steel Bars

In this study, a series of soaking experiments were conducted in a simulated marine environment solution to explore the pitting corrosion behavior induced by four types of inclusions in microalloyed steel bars: Al2O3, MnS, Al2O3-(Ti, V, Nb)N, and Al2O3-MnS-(Ti, V, Nb)N. In the early stage of corrosion, due to the high-density lattice distortion zone around the MnS and Al2O3 inclusions, along with the fact that these inclusions are not closely connected with the steel matrix, microcracks can occur leading to the initial corrosion of MnS in the Cl− environment. The corrosion rate of Al2O3 is the second highest after MnS, and clusters of Al2O3 can further accelerate the corrosion rate. The lattice distortion density around (Ti, V, Nb)N precipitates is significantly lower than that around MnS and Al2O3 inclusions. Additionally, (Ti, V, Nb)N is closely connected with the steel matrix without any microvoids. Therefore, (Ti, V, Nb)N is not sufficient to induce pitting corrosion of the matrix. The trend of pitting corrosion induced by the four types of inclusions, Al2O3, MnS, Al2O3-(Ti, V, Nb)N, and Al2O3-MnS-(Ti, V, Nb)N, is as follows: MnS > Al2O3 > Al2O3-MnS-(Ti, V, Nb)N > Al2O3-(Ti, V, Nb)N.

Surface modification of TiNb alloys by hydrothermal-precalcification treatment and its excellent in vitro osteogenic bioactivity

The superb comprehensive mechanical properties of titanium and its alloys make them ideal materials for artificial bone repair. However, the osseointegration between normal tissue and implant is lengthy due to the relatively poor surface osteogenic bioactivity of titanium-based materials. For the sake of accelerating the bone healing process, surface modification for the titanium- based implant is therefore of great necessity. In this paper, the novel [Formula: see text]-typed TiNb alloy with good biocompatibility was modified by a simple hydrothermal-precalcification method. The experimental results demonstrate that these hydrothermally prepared TiNb alloys were coated by a superhydrophilic Nb-doped TiO2 film with a hierarchical micro-nanostructure. After subsequent pre-calcification treatment, calcium and phosphorus species with low content were successfully introduced into the film without morphological change. The simulated body fluid (SBF) soaking experiments show that the TiNb alloy with the two-step surface treatment represented excellent in vitro bioactivity. After incubating in SBF for only 1 day, the TiNb alloy surface was thoroughly coated with a layer of newly formed spherical hydroxyapatite clusters. Comparatively, no obvious hydroxyapatite was deposited on the TiNb alloy surface with the one-step hydrothermal treatment even after five days of incubation in SBF. As a result, the hydrothermal–precalcification treatment is an ideal method to improve the osteogenic bioactivity of TiNb alloy, which can be further extended to surface modification of other titanium-based implant materials.

All-weather anti-icing and de-icing properties of the carbon-based electro@photo-thermal material with adaptive temperature control performance

Photo-thermal anti/de-icing and electro-thermal anti/de-icing have been widely used in the field of anti/de-icing in recent years. The combination of electro@photo-thermal can achieve all-weather anti/de-icing. However, there is no need for anti/de-icing in hot environments, but the photo-thermal conversion does not automatically stop. And the photo-thermal conversion will cause the surface to overheat, seriously affecting the safety and normal operation of the machine, which is a great challenge in practical applications. Based on this, an electro@photo-thermal material with adaptive temperature control performance was proposed in this work. Specifically, the carbon cloth was used as an electro-thermal substrate, and the thermochromic powder mixed with polydimethylsiloxane (PDMS) was used as a photo-thermal component. The photo-thermal conversion experiment shows that when the temperature reaches the threshold temperature, the color of the material can be changed from black to white to reduce the absorption of sunlight, thus avoiding the overheating phenomenon. The anti/de-icing experiment also shows that the material meets the all-weather anti/de-icing requirements. In addition, continuous tape stripping experiments and acid-base soaking experiments also verified the excellent hydrophobicity of the material. The research provides new ideas for all-weather anti/de-icing systems with adaptive temperature control performance.

Chemical and thermal stability of electrospinned polyvinylidene fluoride/graphene composite membranes

The effect of graphene content, spinning flow rate, and distance on the chemical and thermal stability of electrospinned polyvinylidene fluoride (PVDF)/graphene composite membranes was systematically investigated. Long-duration soaking experiments by three typical solution media, diluted hydrochloric acid, dimethyl sulfoxide, and mixed-solution of lithium hexafluorophosphate/methyl ethyl carbonate, were used to evaluate the chemical stability of the selected samples. The relevant results of relative mass change rate all indicate that the chemical stability of PVDF composite materials increases with increasing graphene content as well as flow rate or decreasing distance. Moreover, there is a clear consistency between thermal stability and chemical stability. The results of the thermal shrinkage rate evidence that the thermal stability of the samples could be enhanced by increasing graphene content, flow rate, and decreasing spinning distance.

LifeSoaks: a tool for analyzing solvent channels in protein crystals and obstacles for soaking experiments.

Due to the structural complexity of proteins, their corresponding crystal arrangements generally contain a significant amount of solvent-occupied space. These areas allow a certain degree of intracrystalline protein flexibility and mobility of solutes. Therefore, knowledge of the geometry of solvent-filled channels and cavities is essential whenever the dynamics inside a crystal are of interest. Especially in soaking experiments for structure-based drug design, ligands must be able to traverse the crystal solvent channels and reach the corresponding binding pockets. Unsuccessful screenings are sometimes attributed to the geometry of the crystal packing, but the underlying causes are often difficult to understand. This work presents LifeSoaks, a novel tool for analyzing and visualizing solvent channels in protein crystals. LifeSoaks uses a Voronoi diagram-based periodic channel representation which can be efficiently computed. The size and location of channel bottlenecks, which might hinder molecular diffusion, can be directly derived from this representation. This work presents the calculated bottleneck radii for all crystal structures in the PDB and the analysis of a new, hand-curated data set of structures obtained by soaking experiments. The results indicate that the consideration of bottleneck radii and the visual inspection of channels are beneficial for planning soaking experiments.

Exploring the inhibition of the soluble lytic transglycosylase Cj0843c of Campylobacter jejuni via targeting different sites with different scaffolds.

Bacterial lytic transglycosylases (LTs) contribute to peptidoglycan cell wall metabolism and are potential drug targets to potentiate β-lactam antibiotics to overcome antibiotic resistance. Since LT inhibitor development is underexplored, we probed fifteen N-acetyl-containing heterocycles in a structure-guided fashion for their ability to inhibit and bind to the Campylobacter jejuni LT Cj0843c. Ten GlcNAc analogs were synthesized with substitutions at the C1 position, with two having an additional modification at the C4 or C6 position. Most of the compounds showed weak inhibition of Cj0843c activity. Compounds with alterations at the C4 position, replacing the -OH with a -NH2 , and C6 position, the addition of a -CH3 , yielded improved inhibitory efficacy. All ten GlcNAc analogs were crystallographically analyzed via soaking experiments using Cj0843c crystals and found to bind to the +1 +2 saccharide subsites with one of them additionally binding to the -2 -1 subsite region. We also probed other N-acetyl-containing heterocycles and found that sialidase inhibitors N-acetyl-2,3-dehydro-2-deoxyneuraminic acid and siastatin B inhibited Cj0843c weakly and crystallographically bound to the -2 -1 subsites. Analogs of the former also showed inhibition and crystallographic binding and included zanamivir amine. This latter set of heterocycles positioned their N-acetyl group in the -2 subsite with additional moieties interacting in the -1 subsite. Overall, these results could provide novel opportunities for LT inhibition via exploring different subsites and novel scaffolds. The results also increased our mechanistic understanding of Cj0843c regarding peptidoglycan GlcNAc subsite binding preferences and ligand-dependent modulation of the protonation state of the catalytic E390. This article is protected by copyright. All rights reserved.

3D printing of polylactic acid/boron nitride bone scaffolds: Mechanical properties, biomineralization ability and cell responses

Polylactic acid (PLA) has been widely utilized as a bone scaffold material; however, it exhibits inadequate mechanical performance, biomineralization ability, and cell response, leading to limitations in its practical application. In this study, we utilized boron nitride (BN) nanosheets with favorable mechanical and biological properties to improve the performances of PLA, and prepared PLA/BN composite scaffolds by FDM 3D printing technology. Then, the PLA/BN composite scaffolds with varying BN contents (0–4 wt%) were investigated in terms of microstructure, mechanical performance, biomineralization ability, and cell response. The results showed that the FDM printed PLA/BN scaffolds have an orderly and interconnected porous structure. The mechanical tests showed that the tensile and compression properties (strength and modulus) increased first and then decreased with the content of BN gradually increasing from 0 wt% to 4 wt%, with the optimum mechanical properties occurring at 1 wt%, as an appropriate content of BN could be well-dispersed in the PLA matrix with forming a good interfacial bond, while an excessive content of BN would lead to obvious agglomeration. The simulated body fluid (SBF) soaking experiments showed that BN improved the biomineralization of the PLA scaffold through promoting the formation and deposition of apatite on the scaffold surface by accelerating ion exchange. Besides, an appropriate content of BN promoted the adhesion, proliferation, and osteogenic differentiation of rabbit bone marrow mesenchymal stem cells (BMSCs). These results indicated that BN could be used as a versatile filler for improving the comprehensive performances of polymers, especially for bone tissue engineering.

Bioceramic calcium phosphate-polymer scaffolds: A promising strategy for osteochondral repair and regenerative medicine

The study's objective was to fabricate a porous scaffold with desirable biological and bioactive characteristics, utilizing freeze-drying with polyvinyl alcohol (PVA). Subsequently, compressive strength tests and simulated body fluid (SBF) soaking experiments were performed to assess the mechanical and biological properties of the scaffold. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for analyzing the scaffolds. The findings indicated that an increase in the amount of dicalcium phosphate decreased the porosity of the scaffold from 76% to 64%, raised the compressive strength from 2.48 MPa to 4.8 MPa, and lowered the dissolution rate from 39% to 24%. These changes led to an improvement in the scaffold's chemical bonding and stability. According to micromechanical models, the optimal scaffold composition was found to be 10 wt% of dicalcium phosphate in a polyvinyl alcohol mixture with constant drug content. Moreover, an increase in the dicalcium phosphate content led to an elevation in the drug release percentage due to the reduction in porosity and an increase in the drug release rate. The data were analyzed by using various kinetic models through diagrams generated by a UV device.

The Effect of High-Velocity Air-Fuel WC-12Co Coatings on the Wear and Corrosion Resistance of TC18 Titanium Alloy

TC18 titanium alloy is an essential material for aircraft landing gear. To reveal the wear and corrosion mechanisms of landing gear in service, a WC-12Co coating on a TC18 substrate was prepared by High-Velocity Air-Fuel (HVAF) spraying based on optimized process parameters, and an analysis of the microscopic characterization results for the materials involved was performed. Based on the computational fluid dynamics (CFD) method, the combustion reaction and discrete phase models of HVAF spraying were established. The flame characteristics under compressible turbulence and the flight temperature and velocity of particles were calculated. The effect of the spraying parameters on the flight temperature and velocity of particles was evaluated based on the response surface method (RSM) through multiple groups of orthogonal experiments, and the optimized process parameters were determined. The mass flow rate of reactants was 0.051 kg/s, the oxygen/fuel ratio was 2.83, the mass flow rate of the nitrogen was 0.000325 kg/s, the pressure of oxygen and fuel inlet was 1 MPa, the pressure at the particles inlet was 0.6 MPa and the maximum temperature and velocity of spraying particles were 1572 K and 417 m/s, respectively. The coatings prepared with the optimized process were subjected to the Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS), X-Ray Diffraction (XRD), wear, hardness, artificial seawater soaking and neutral salt spray experiments. The results showed that the mean hardness of the TC18 substrate was 401.2 HV0.3, the mean hardness of the WC-12Co coating was 1121 HV0.3, the friction coefficient between the TC18 substrate and the Si3N4 ceramic ball was 0.55 and the friction coefficient between the WC-12Co coating and the Si3N4 ceramic ball was 0.4. Compared to the TC18 substrate, the hardness of the WC-12Co coating was increased by 720 HV0.3, the friction coefficient with the Si3N4 ceramic ball decreased by 0.11, the corrosion resistance significantly improved and the maximum depth of the corrosion pits was 5 μm. The properties of the TC18 titanium alloy were effectively improved by the WC-12Co coating. The results of this study provide guidance for surface protection technologies of aircraft landing gear.

Experimental study of the effect of CO2 on rock seepage characteristics

The influence of different phase states of CO2 on the seepage characteristics of different rocks is one of the most important factors to enhance shale gas exploitation, such as CO2 fracturing and displacement, and achieve CO2 geological storage. Rock soaking experiments with different CO2 phase states were carried out to compare and analyze the influence of permeability, contact angle, starting pressure gradient and other seepage characteristic parameters of sandstone and shale before and after soaking. Research shows: After soaking in liquid and supercritical CO2, the permeability and contact angle of sandstone and shale increase in varying degrees, and the starting pressure gradient decreases in varying degrees. After soaking in liquid CO2, the permeability of sandstone and shale increased by 1.71% and 12.88% respectively, the contact angle increased by 3.23% and 7.47% respectively, and the starting pressure gradient decreased by 3.02% and 5.88% respectively. After supercritical CO2 immersion, the permeability of sandstone and shale increased by 37.37% and 48.82% respectively, the contact angle increased by 19.27% and 36.80% respectively, and the starting pressure gradient decreased by 35.39% and 39.34% respectively. Compared with sandstone, the seepage characteristics of shale after soaking in liquid and supercritical CO2 have greater changes; Compared with liquid CO2, the seepage characteristics of sandstone and shale change more after supercritical CO2 soaking. With the increase of supercritical CO2 soaking time, the contact angle of sandstone slightly increases, while that of shale obviously increases. Compared with liquid CO2, the change of seepage curves of sandstone and shale after supercritical CO2 soaking is more different.

Examination of the fire performance of wood materials treated with different precautions

This paper aims to discover how organic wood preservatives containing different fungicides and insecticides used to protect wood against fungal and insect pests affect the fire performance and combustion properties of wood materials commonly used in the domestic wood and construction industry. The aim of this article was to investigate the charring depth. From the point of view of the loss of load-bearing capacity of the wood, only the charring depth matters, since the reduction of the load-bearing capacity will be determined by the reduction of the cross section of the wood. We examined the effects of wood preservatives applied to undamaged samples of Scots pine and Norway spruce conditioned under normal climate conditions. The test samples underwent a second treatment application after which we examined the effect of different preservative combinations. Seven treatment mixtures were selected from the organic solvent and water-based wood preservatives available on the domestic market. The soaking experiments demonstrated that the preservative impregnation of Norway spruce differs significantly from that of Scots pine, which affected the comparability of the test results. We have experimentally investigated the moisture content, the loss of mass and we have calculated the char depth. Adhering to the MSZ 9607–1:1983 standard, the Linder method was performed to analyze the wood and wooden-based construction products used in construction. The effect of the different treatment materials was more significantly detectable when analyzing the size of the surface burn patterns. The Scots pine specimens suffered much greater surface burn than the Norway spruce specimens did, regardless of the type of preservative used. The higher body density, resin content (1–10%) and higher initial moisture content of Scots pine caused it to bend and, therefore, to burn better.

Investigation on Polishing the Concave Surface of Zirconia Ceramics with Magnetic Compound Fluid Enhanced by Hydration Reaction

Zirconia ceramics are prominent engineering materials and are widely used in computers, consumer electronics, and the fifth-generation communication industry. However, zirconia ceramics are a typical hard-to-cut material, and the product structures are more complex as the demanding on the industry increases. In this case, the polishing efficiency should be improved for meeting these requirements. To overcome the problem of polishing concave surfaces of zirconia ceramics, a small polishing tool with a magnetic compound fluid (MCF) was invented. The effect of the polishing parameters on the surface roughness and material removal rate was analyzed by an L9(33) orthogonal experiment. The weight ratio of the parameters was also studied based on the experimental results. With the combination of chemical and mechanical functions, the polishing characteristics were further examined. Based on the soaking experiments, the material removal mechanism is discussed. The results are as follows: (1) the optimal polishing parameters were the revolution speed of the MCF carrier nc of 400 rpm, the working gap h of 0.1 mm, the CIP size D of 5 μm for better surface roughness, the revolution speed of the MCF carrier nc of 400 rpm, the working gap h of 0.1 mm, and the CIP size D of 7 μm for a higher material removal rate. The impact degrees on surface roughness and material removal rate were a revolution speed of the MCF carrier of 54% > working gap of 31%> CIP size of 15% and working gap of 40% > revolution speed of the MCF carrier of 32% > and CIP size of 18%, respectively. (2) Surface roughness was rapidly reduced in the first 20 min and tended to be stable in the last 10 min of polishing. A circular polished area was observed on the flat workpiece for studying the typical material removal curve, and the deepest point was found at the fringe of the material removal curve. The concave workpiece was polished successfully, and the best surface roughness Ra reached 1 nm and 1.2 nm. (3) A pH = 10 with a sodium hydroxide (NaOH) solution has a greater performance in hardness reduction. The chemical and mechanical functions were combined to remove material to enhance the polishing efficiency. All in all, the proposed polishing method with a combination of a small MCF polishing tool and hydration reaction was effective for polishing zirconia ceramics.

Investigation of the Mechanism and Effect of Citric Acid-Based Deep Eutectic Solvents Inhibiting Hydration and Expansion of Gas Shale Clay Minerals

This study developed a shale hydration inhibitor using a citric acid-based deep eutectic solvent (Cit-DES) and hexadecylammonium bromide (cetyltrimethylammonium bromide) to aid wellbore instability and collapse caused by drilling of shale gas wells with water-based drilling fluids. Soaking and linear expansion experiments were conducted with Na-bent and Longmaxi formation shale, respectively. The changes in illite interlayer spacing, wettability, and water absorption capacity of shale samples before and after soaking in an inhibitor solution were evaluated, which indicated that the inhibitor reduced shale hydration. The results showed that the inhibitor effectively inhibits the osmotic and surface hydration of the shale. Due to the Cit-DES hydrogen bond, the inhibitor is firmly adsorbed on the shale pore wall and inserted between clay minerals, reducing the shale surface energy, hydrophilicity, and surface potential. The swelling expansion rate of shale inhibitors is only 38.9% compared to a 3% KCl solution. The amount of shale imbibition per unit mass in distilled water is 0.011 g/g. In the inhibitor, the imbibition mass per unit of shale is 0.002 g/g, which is only 23.68% of that in distilled water. The inhibitor is environment-friendly and has a broad application prospect for maintaining shale wellbore stability and preventing wellbore collapse during horizontal shale drilling operations.

Engineering a Highly Regioselective Fungal Peroxygenase for the Synthesis of Hydroxy Fatty Acids.

The hydroxylation of fatty acidsis an appealing reaction in synthetic chemistry, although the lack of selective catalysts hampers its industrial implementation. Here, we have engineered a highly regioselective fungal peroxygenase for thew-1 hydroxylation of fatty acids with quenched stepwise over-oxidation. One single mutationnear the Phe catalytic tripod narrowed the heme cavity, promoting a dramatic shift toward sub-terminal hydroxylation with a drop in the over-oxidation activity. While crystallographic soaking experiments and molecular dynamic simulations shed light on this unique oxidation pattern, the selective biocatalyst was produced byPichia pastorisat 0.4 g/L in a fed-batch bioreactor and used in thepreparative synthesis of 1.4 g of (w-1)-hydroxytetradecanoic acid with 95% regioselectivity and 83%eethrough the (S)-enantiomer.The hydroxylation of fatty acidsis an appealing reaction in synthetic chemistry, although the lack of selective catalysts hampers its industrial implementation. Here, we have engineered a highly regioselective fungal peroxygenase for thew-1 hydroxylation of fatty acids with quenched stepwise over-oxidation. One single mutationnear the Phe catalytic tripod narrowed the heme cavity, promoting a dramatic shift toward sub-terminal hydroxylation with a drop in the over-oxidation activity. While crystallographic soaking experiments and molecular dynamic simulations shed light on this unique oxidation pattern, the selective biocatalyst was produced byPichia pastorisat 0.4 g/L in a fed-batch bioreactor and used in thepreparative synthesis of 1.4 g of (w-1)-hydroxytetradecanoic acid with 95% regioselectivity and 83%eethrough the (S)-enantiomer.

Engineering a Highly Regioselective Fungal Peroxygenase for the Synthesis of Hydroxy Fatty Acids

AbstractThe hydroxylation of fatty acids is an appealing reaction in synthetic chemistry, although the lack of selective catalysts hampers its industrial implementation. In this study, we have engineered a highly regioselective fungal peroxygenase for the ω‐1 hydroxylation of fatty acids with quenched stepwise over‐oxidation. One single mutation near the Phe catalytic tripod narrowed the heme cavity, promoting a dramatic shift toward subterminal hydroxylation with a drop in the over‐oxidation activity. While crystallographic soaking experiments and molecular dynamic simulations shed light on this unique oxidation pattern, the selective biocatalyst was produced by Pichia pastoris at 0.4 g L−1 in a fed‐batch bioreactor and used in the preparative synthesis of 1.4 g of (ω‐1)‐hydroxytetradecanoic acid with 95 % regioselectivity and 83 % ee for the S enantiomer.