In order to better solve the problem of electromagnetic pollution in the civil building cement, to improve the absorption capacity of magnesium oxysulfide cement based materials, and to better use ...sulfur oxide magnesium cement foamed sheet for improvement of electromagnetic industry, this paper uses the excellent microwave absorbing properties of ferrite and the modified sulfur oxide magnesium cement foam board, and discusses the microwave absorbing performance, aiming at improving the electromagnetic pollution in daily life. The effects of ferrite and silicon carbide doping on microwave absorption properties of modified magnesium oxysulfate cement were studied. At the same time, the wave absorbing properties of the corresponding samples were detected by bow method, and the causes of the corresponding phenomena were analyzed by scanning electron microscopy (SEM). The results show that the lowest reflectance of the material is −17.9 dB at 34.1 GHz and the average reflectance of the whole band is −15.9 dB under the target frequency band of 26.5–40 GHz. Under the action of external magnetic field, the absorbing particles are affected by magnetization force, magnetic dipole and resistance coupling, and play the absorbing effect in the cement base solidified completely in the electromagnetic field environment. The lowest reflectance is −17.3dB at 36.4GHz and the average reflectance is −14.3dB for the whole band.
In order to better understand the thermodynamic properties of magnesium oxysulfate (MOS) cement, pure reagent was analyzed to prepare magnesium sulfide cement, non-isothermal kinetics calculation of ...the main hydration products was also carried out, and the conversion process of magnesium sulfide cement 517 phase at different temperatures was investigated. Composition of magnesium sulfide cement prepared was measured by XRD technique, and decomposed by a comprehensive thermal analyzer, and DSC curves of magnesium sulfide cement under different temperature rising rates were processed by Kinssinger method and Dolye-Ozawa method. According to the TG-DSC curves of magnesium sulfide cement, the thermal decomposition reaction process can be divided into five stages under normal conditions. The DSC curve was processed by Kinssinger method and Dolye-Ozawa method, and the kinetic analysis was carried out to calculate the 517 phase activation energy of magnesium sulfide cement. The three stages correspond to different activation energies. Therefore, flame retardant mechanism and thermal decomposition mechanism of magnesium sulfide cement based materials are deduced.
Cortex Dictamni is extensively used as an herbal medicine worldwide, but is believed to induce hepatotoxicity and even causes mortality in many Asian and European countries. As the most abundant ...furoquinoline alkaloid ingredient of Cortex Dictamni, dictamnine (DIC) can be metabolically activated by CYP3A to an epoxide metabolite, which possesses the potential to induce hepatotoxicity by covalent binding with proteins. As yet, the hepatotoxicity of DIC and the role played by metabolic activation remain unknown. Here, we found that DIC caused acute liver injury in a time- and dose-dependent manner in mice. The hepatic and urinary DIC epoxide intermediates were observed in DIC-treated mice. Ketoconazole, a CYP3A inhibitor, significantly reduced the hepatotoxicity of DIC and inhibited the formation of reactive metabolites of DIC. Moreover, treatment with 2,3-dihydro-DIC, a DIC analog synthesized by selective reduction of the furan moiety, produced no hepatotoxicity in mice, and no reactive metabolite was formed, suggesting a structural necessity of furan moiety in DIC hepatotoxicity. A time course of gradual hepatic glutathione consumption was observed in DIC-treated mice, while depletion of hepatic glutathione by L-buthionine-S,R-sulfoximine enhanced the hepatotoxicity of DIC. Collectively, this study demonstrates that DIC induces acute hepatocellular injury in mice, and that metabolic activation of furan plays a crucial role in DIC-induced hepatotoxicity.
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•Dictamnine exhibits dose- and time-dependent hepatotoxicity in mice.•Dictamnine causes hepatocyte necrosis in liver centrilobular portion (zone 3).•CYP3A mediated epoxide metabolite is responsible for dictamnine hepatotoxicity.•Furan ring is an essential moiety for dictamnine hepatotoxicity.
A facile and practical palladium-catalyzed nucleophilic substitution/C–H activation/aromatization cascade reaction has been developed. A range of 6-unsubstituted phenanthridines could be obtained in ...moderate to good yields (31–85%) with readily prepared N-Ms arylamines and commercially available 2-bromobenzyl bromide derivatives as starting materials. The potential application of the protocol was also demonstrated by the expeditious synthesis of the natural alkaloid trisphaeridine.
Chiral methyl mandelates are useful synthons in organic transformation and pharmaceutical synthesis. Green synthesis of these valuable compounds by direct C–H activating oxidative hydroxylation has ...attracted keen interest. Described herein is achieving the stereoselective and efficient bio-hydroxylation of methyl 2-phenylacetates to the chiral methyl mandelates by directed evolution of the cytochrome P450DA hydroxylase. In the present study, a new colorimetric high-throughput screening assay was successfully developed based on a dual-enzyme cascade for the engineering of the P450DA's hydroxylation activity. Several beneficial variants with enhanced bio-hydroxylation activity were created by combining random mutagenesis and site-saturated/directed mutagenesis strategies. Whole-cell bio-hydroxylation of various methyl 2-phenylacetates using the best septuplet-mutant P450DA-11 yielded the corresponding chiral methyl mandelates in up to 92% isolated yields and >99% ee.
The cytochrome P450DA hydroxylase was evolved to increase bio-hydroxylation activity toward methyl 2-phenylacetate by developing a new colorimetric high-throughput screening assay. Various chiral methyl mandelates were synthesized via the engineered P450DA-catalyzed stereoselective bio-hydroxylation. Display omitted
•Two Pseudomonas plecoglossicida strains were screened from soil.•Regio- and stereoselective oxidation of benzylic C–H bonds while N–H bond was unreacted.•(R)-THQL and (R)-TBAL were obtained by ...direct hydroxylation.
Two whole-cell biocatalysts were found to have C–H oxidation activity with high R-enantioselectivity on 1,2,3,4-tetrahydroquinoline (THQ) and 2,3,4,5-tetrahydro-1H-benzobazepine (TBA). R-1,2,3,4-tetrahydroquinolin-4-ol ((R)-THQL) and R-2,3,4,5-tetrahydro-1H-benzobazepin-5-ol ((R)-TBAL) were smoothly obtained with 82% yield in 99% e.e. and 99% yield in 98% e.e., respectively.
•Nano Fe3O4/CMC/SA can exert the advantages of nano Fe3O4 and SA. It has an important research value for immobilized enzyme.•In this study, α-amylase was selected as a simulation object to ...manufacture an immobilized enzyme (SM/CMC/CA/α-Amy).•Immobilization increased 4.67 times to catalytic activity, slowed down release rate and improved reusable performance.•The stabilities of pH, thermal and storage for SM/CMC/CA/α-Amy were improved remarkably.•All these results indicated that SM/CMC/SA was an ideal carrier for immobilizing enzyme.
In order to improve catalytic activity, increase recycling times, reduce use cost for enzyme, superparamagnetic carboxymethyl chitosan/sodium alginate nanosphere (SM/CMC/SA) has been synthesized via an improved hydrothermal method, molecular self-assembly technology, electrostatic interaction and amide linkage. Its mean diameter was 65nm, zeta potential was −36.9mV and BET was 53.8m2/g. α-Amylase was selected as a simulation object to manufacture an immobilized enzyme (SM/CMC/CA/α-Amy), and its catalytic activity, release behavior, reusability and stability were researched. Immobilization increased 4.67 times to catalytic activity, slowed down release rate and improved reusable performance. SM/CMC/CA/α-Amy showed higher activity over a wider pH range, especially in strong acidic and alkaline environments. The thermal stability and storage stability were improved remarkably too. All these results indicated that SM/CMC/SA was an ideal carrier for immobilizing enzyme.
A biocatalytic approach towards a range of 4‐aryloxazolidinones is developed using a halohydrin dehalogenase from Ilumatobacter coccineus (HheG) as biocatalyst. The method is based on the ...HheG‐catalyzed α‐position regioselective ring‐opening of styrene oxide derivatives with cyanate as a nucleophile, producing the corresponding 4‐aryloxazolidinones in moderate to good yields. Synthesis of enantiopure 4‐aryloxazolidinones is also achievable using chiral epoxide materials.
A novel and simple spectrophotometric method is developed for the determination of nitrite in water by using the self-coupling diazotization reagent 2-amino-6-chlorobenzoic acid and UV light ...illumination. The method only involves one reagent and one step, which can be easily applied to the determination of nitrite and tolerates many foreign anions' effects under acidic conditions.
An efficient biocatalytic approach for enantio‐ and regioselective ring‐opening of styrene oxides with cyanate was developed by using the halohydrin dehalogenase HheC from Agrobacterium radiobacter ...AD1, generating the corresponding chiral 5‐aryl‐2‐oxazolidinones in up to 47% yield and 90% ee. Additionally, the origin of enantioselectivity and regioselectivity of the HheC‐catalyzed cyanate‐mediated ring‐opening process was uncovered by single enantiomer bioconversions and molecular docking study.
