Journal of Advanced Ceramics
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2021
·Vol. 10
·期 6
·1317-1325
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IF 6.707
Liu Zetan,Zhao Shiqiang,Yang Tian,Zhou Ji
It is possible to improve the machinability of aluminum nitride-hexagonal boron nitride (AlN-h-BN) ceramics while maintaining high strength and high thermal conductivity. The composite ceramics with 0–30 wt% BN as secondary phase were prepared by hot pressed sintering, using yttrium oxide (Y 2 O 3 ) as sintering aid. The phase composition, density, microstructure, mechanical properties, thermal conductivity, and dielectric properties were investigated. The sintering additives were favorable to purify the grain boundaries and improve densification, reacting with oxide impurities on the surface of raw material powder particles. The optimum BN content improved the flexural strength and fracture toughness of composite ceramics with 475 MPa and 4.86 MPa·m 1/2 , respectively. With increasing the amount of BN, the thermal conductivity and hardness of composites gradually decreased, but the minimum value of thermal conductivity was still 85.6 W·m −1 ·K −1 . The relative dielectric constant and dielectric loss tangent of the samples ranged from 6.8 to 8.3 and from 2.4 × 10 −3 to 6.4 × 10 −3 , respectively, in 22–26 GHz.
研究领域:
材料科学
·
工程学
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DOI
高影响因子
INTERNATIONAL JOURNAL OF ANTIMICROBIAL AGENTS
·
2017
·
IF 4.307
Hong-Yan Luo,Ma-Feng Liu,Ming-Shu Wang,Xin-Xin Zhao,Ren-Yong Jia,Shun Chen,Kun-Feng Sun,Qiao Yang,Ying Wu,Xiao-Yue Chen,Francis Biville,Yuan-Feng Zou,Bo Jing,An-Chun Cheng,De-Kang Zhu
The Gram-negative bacterium Riemerella anatipestifer CH-2 is resistant to lincosamides, having a lincomycin (LCM) minimum inhibitory concentration (MIC) of 128 µg/mL. The G148_1775 gene of R. anatipestifer CH-2, designated lnu (H), encodes a 260-amino acid protein with ≤41% identity to other reported lincosamide nucleotidylyltransferases. Escherichia coli Rosetta TM (DE3) containing the pBAD24- lnu (H) plasmid showed four- and two-fold increases in the MICs of LCM and clindamycin (CLI), respectively. A kinetic assay of the purified Lnu(H) enzyme for LCM and CLI showed that the protein could inactive lincosamides. Mass spectrometry analysis demonstrated that the Lnu(H) enzyme catalysed adenylylation of lincosamides. In addition, an lnu (H) gene deletion strain exhibited 512- and 32-fold decreases in LCM and CLI MICs, respectively. The wild-type level of lincosamide resistance could be restored by complementation with a shuttle plasmid carrying the lnu (H) gene. The transformant R. anatipestifer ATCC 11845 [ lnu (H)] acquired by natural transformation also exhibited high-level lincosamide resistance. Moreover, among 175 R. anatipestifer field isolates, 56 (32.0%) were positive for the lnu (H) gene by PCR. In conclusion, Lnu(H) is a novel lincosamide nucleotidylyltransferase that inactivates LCM and CLI by nucleotidylylation, thus conferring high-level lincosamide resistance to R. anatipestifer CH-2.
研究领域:
微生物学
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分子生物学
·
抗生素抗性研究
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DOI
PubMed
高影响因子
JACS Au
·
2023
·
IF 8
Qi Yang,Xiujuan Gao,Faen Song,Xiaoxing Wang,Tao Zhang,Pan Xiong,Yunxing Bai,Xingchen Liu,Xiaoyan Liu,Junfeng Zhang,Gang Fu,Yisheng Tan,Yizhuo Han,Qingde Zhang
Selective oxidation of C–H bonds under mild conditions is one of the most important and challenging issues in utilization of energy-related molecules. Molybdenum oxide nanostructures containing Mo5+ species are effective for these reactions, but the accurate identification of the structure of active Mo5+ species and the catalytic mechanism remain unclear. Herein, unsaturated penta-coordinated Mo5c5+ with a high fraction in MoOx fabricated by the hydrothermal method were identified as the active sites for low-temperature oxidation of dimethyl ether (DME) by the deep correlation of characterizations, density functional theory calculations, and activity results, giving a methyl formate selectivity of 96.3% and DME conversion of 12.5% at unreported 110 °C. Low-temperature electron spin resonance (ESR) and quasi in situ X-ray photoelectron spectra (XPS) with the designed experiments confirm that the Mo5c5+ species can be formed in situ. Molybdenum located at the pentachronic site is preferable to significantly promote the oxidation of the C–H bond in CH3O* at lower temperatures.
研究领域:
化学
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材料科学
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能源化学
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产品关联
DOI
PubMed
高影响因子
MOLECULES
·
2024
·Vol. 29
·期 12
·2861
·
IF 4.2
Yonghui Sun,Qiyu He,Xucheng Lv,Naizhen Zhang,Wei Yan,Jianghui Sun,Lili Zhuang
Regioselective benzanilide bromination that generates either regioisomer from the same starting material is desirable. Herein, we develop switchable site-selective C(sp2)-H bromination by promoter regulation. This protocol leads to regiodivergent brominated benzanilide starting from the single substrate via selection of promoters. The protocol demonstrates excellent regioselectivity and good tolerance of functional groups with high yields. The utility effectiveness of this method has been well exemplified in the late-stage modification of biologically important molecules.
研究领域:
有机化学
·
药物化学
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DOI
PubMed
高影响因子
Polymer Chemistry
·
2012
·Vol. 3
·期 12
·3330-3339
·
IF 5.321
Cheng-guang Mu,Xiao-dong Fan,Wei Tian,Yang Bai,Zhen Yang,Wei-wei Fan,Heng Chen
We describe the synthesis and self-assembly of a well-defined H-shaped terpolymer in this paper. A block copolymer of poly(ethylene glycol) (PEG) and poly(N,N-dimethylaminoethyl methacrylate) (PDMA), which bears an azido group at the diblock junction (PEG–N3(–PDMA)) was first prepared by atom transfer radical polymerization. Then, an alkynyl-terminated narrow distributed polytetrahydrofuran (PTHF-Alk) was synthesized as another building block via cationic ring opening polymerization. The well-defined H-shaped terpolymer was afforded by clicking PEG–N3(–PDMA) onto both chain-ends of PTHF-Alk. This H-shaped terpolymer can self-assemble into micelles with different sizes and morphologies at various solution pH values. The micellar size also exhibits temperature-dependence at pH 7.4 and 9.2. The variation of size and morphology of the micelles with the solution pH and temperature is ascribed to the pH- and thermo-responsive properties of the PDMA block.
研究领域:
高分子化学
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材料科学
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DOI
高影响因子
Evidence-based Complementary and Alternative Medicine
·
2013
·
IF 1.722
Huiqing Lv,Xiaoping Zhang,XueZhi Chen,Zhijun Xie,Changfeng Hu,Chengping Wen,Kezhi Jiang
Background. Ficus pandurata H. (Moraceae) is widely used in traditional Chinese medicine as a healthy food condiment or a medicine for treatment of various diseases including inflammation. Objective. The purpose of the present study is to investigate the phytochemical compositions and antioxidant and anti-inflammatory activities of crude water (FPW) and ethanolic extracts (FPE) from Ficus pandurata H. Methods. Phytochemical compositions were identified by a high-performance liquid chromatography-electrospray ionization-mass spectrometry method (HPLC-ESI-MS). The antioxidant activities were evaluated by diphenylpicrylhydrazyl (DPPH) and hydroxyl radical assays, and the anti-inflammatory activities were evaluated by paw edema and levels of inflammatory mediator TNF-α and PGE2 in monosodium urate (MSU) crystal-induced rats. Results. Six compounds were identified by HPLC-MS method, and abundance of phenolics was found in FPE. The FPE showed concentration-dependent-significant scavenging of DPPH and hydroxyl radicals with IC50 values 118.4 and 192.9 μg/mL, respectively. The FPE treatment significantly inhibited the paw edema and the production of TNF-α and PGE2 in MSU crystal-induced rats. Conclusion. The FPE exerted stronger antioxidant and anti-inflammatory activities which may be attributed to its high phenolic content.
研究领域:
药理学
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植物化学
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传统医学
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DOI
PubMed
高影响因子
RESOURCES CONSERVATION AND RECYCLING
·
2021
·
IF 10.204
Liming Yang,Genping Yi,Bo Wang,Penghui Shao,Yufa Feng,Yanbiao Liu,Kai Yu,Fuqiang Liu,Lingling Liu,Xubiao Luo,Shenglian Luo
Simultaneous recovery and value-added conversion of hazardous heavy metal ions from complex wastewater sources is of great significance yet challenging. Herein, we demonstrate that highly toxic antimonite Sb(III) could be effectively recovered from antimony (Sb) mine flotation wastewater and converted into high-value-added metallic Sb using a novel facile atomic H* enhanced electrochemical reduction avenue coupled with thermal reduction by H 2 gas. The high production of atomic H* generated from the electrochemical cathode with an optimum reduction potential of –1.2 V vs . Ag/AgCl, which is lower than the Sb(III) reduction potential of –1.0 V, might be attributable to the superior Sb recovery capabilities. Furthermore, the metallic Sb concentration at –1.2 V was 14.43 times greater than at –1.0 V due to the strong reductivity of atomic H*. In addition, Sb(III) removal efficiency was found to be as high as 98.52%, with a metallic Sb recovery rate of up to 1.67 mg min –1 . The efficiency of Sb(III) recovery was demonstrated throughout a wide pH range, with metallic Sb being the main product, independent of the presence of multiple coexisting ions. Economic analysis also indicated that treating Sb mine flotation wastewater per ton may yield a net profit of $40.09. This research contributes to the advancement of an atomic H* enhanced electrochemical technology for high-valued heavy metal recovery from complex heavy metal-polluted wastewater.
研究领域:
环境科学
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冶金工程
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电化学工程
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DOI
高影响因子
SENSORS AND ACTUATORS B-CHEMICAL
·
2020
·
IF 7.1
Kaiwu Zhang,Xuan Wang,Caicheng Long,Jin Xu,Zixin Jiang,Bo Feng,Peng Zhang,Junjie Fei,Taiping Qing
DNA templated fluorescent copper nanoclusters (DNA-CuNCs) have demonstrated enormous potential for biochemical analysis. However, most of them are focused on DNA-related sensing. Here, we designed a hairpin DNA/RNA chimeric chain for the formation of fluorescent CuNCs and further applied it to detect reverse transcription-associated ribonuclease H (RNase H). The DNA/RNA chimera templated copper nanoclusters (DNA/RNA-CuNCs) exhibited similar spectral properties with DNA-CuNCs. In the presence of RNase H, the RNA segment in chimera is hydrolyzed and release short oligonucleotides, which fail to synthsize fluorescent CuNCs. The capabilities for RNase H detection from complex samples and screening of inhibitors were verified. This strategy exhibited high sensitivity for RNase H with a detectable minimum concentration of 5.5 × 10 −4 U mL -1 , which is lower than the developed fluorescent methods. This work will open up new thoughts to design new template for metal nanoclusters and broaden their application in RNA-related sensing.
研究领域:
生物化学
·
分子生物学
·
分析化学
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DOI
高影响因子
ACS Catalysis
·
2024
·
IF 11.3
Zaixiang Xu,Fengcang Zhou,Hanchi Chen,Jianguo Wang
The regeneration of NAD(P)H and its analogues is crucial for biocatalytic processes. However, despite the efficiency of enzymatic catalysis in regenerating NAD(P)H, the sustainability of enzymes is often compromised, particularly under extreme catalytic conditions. Moreover, artificial cofactors may present advantages in certain reactions due to their stability and versatility, yet the substrate specificity of enzymes poses significant challenges to their regeneration through the enzymatic method. Therefore, it is imperative to develop a highly stable regeneration method that can be adapted to both natural and artificial cofactors. In this work, employing potassium-ion-doped carbon nitride (ionCN-0.2) as a catalyst not only achieves high-efficiency photocatalytic regeneration of NAD(P)H, comparable to that of glucose dehydrogenase (GDH), but also a remarkable ability to regenerate nicotinamide analogues. This enhanced performance stems from the tunable negative ζ-potential, which effectively adsorbs the positively charged [Cp*Rh(bpy)H2O]2+ mediator, resulting in enhanced regeneration kinetics of the nicotinamide moiety. The catalyst demonstrates superior performance compared to the reported systems; the optimal regeneration rate reaches 0.55 mmol L–1 gcat–1 min–1 and approaches enzymatic regeneration efficiency. Expanding the reaction conditions to a wider temperature and pH range also confirms the effectiveness and sufficient stability of this photocatalytic system, offering a promising strategy for stable cofactor regeneration in biocatalytic processes.
研究领域:
生物化学
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材料科学
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催化化学
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产品关联
DOI
高影响因子
MICROPOROUS AND MESOPOROUS MATERIALS
·
2024
·
IF 4.8
Tianyu Bai,Jinquan Tao,Yijing Jia,Wenbin Huang,Rongpeng Yao,Xinan Xue,Yasong Zhou,Qiang Wei
In the research of directly synthesizing H-form ZSM-5, ammonium hydroxide is commonly used as an alkali source instead of NaOH to avoid multiple ion exchange steps. However, the volatile nature and the lack of structure-directing effect of ammonium hydroxide limit its application in practical. In this study, n -butylamine (NBA) was used as the main alkali source to directly prepare HZSM-5 zeolites with SiO 2 /Al 2 O 3 ratios ranging from 40 to 300 under traditional hydrothermal conditions. The influence of the amount of NBA, ethanol, seed, and pre-crystallization on the synthesis products was investigated under the condition of SiO 2 /Al 2 O 3 = 80. Theoretical simulation suggested that n -butylamine cations (NBA + ) play the most potent directing role in the formation of the MFI structure but could lead to difficulties in removal during calcination. The addition of ethanol as the zeolite growth modifier (ZGM) could decrease the usage of NBA and reduce the difficulties in calcination, and the addition of seed provided the conditions for initiating crystallization in the system that could not spontaneously nucleate. HZSM-5 with different SiO 2 /Al 2 O 3 ratios were prepared under the optimal crystallization conditions, and the as-synthesized samples exhibited superior textural and acid properties compared to commercial zeolite. Finally, the 1 L scale-up synthesis and MTP reaction were conducted to demonstrate the practicality of this economically and environmentally-friendly synthesis strategy.
研究领域:
材料科学
·
化学工程
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DOI
高影响因子
EUROPEAN JOURNAL OF ORGANIC CHEMISTRY
·
2020
·Vol. 2020
·期 25
·3889-3895
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IF 2.889
Xinpeng Jiang,Zongchen Zhao,Zhifeng Shen,Keda Chen,Liyun Fang,Chuanming Yu
Graphical A metal-free aerobic oxidative C–H sulfenylation of aryl-fused cyclic amines with various thiols was developed with excellent functional compatibility. While flavin I catalyzed the C–H sulfenylation of indolines to afford 3-sulfenylindoles, flavin II enabled transformations resulting in substitution at the position para to the N atom on the aryl ring to obtain 6-sulfenylquinolines. We report an aerobic oxidative C–H sulfenylation of aryl-fused cyclic amines with various thiols catalyzed by flavin/I 2 for the first time. While flavin I catalyzed the C–H sulfenylation of indolines to afford 3-sulfenylindoles, flavin II enabled transformations resulted in substitution at the position para to the N atom on the aryl ring to obtain 6-sulfenylquinolines. The advantages of this metal-free oxidative C–S coupling approach utilizing ambient oxygen as the terminal oxidant were that it was conducted under mild conditions with good atom-efficiency and excellent functional compatibility.
研究领域:
有机化学
·
合成化学
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DOI
高影响因子
Materials Chemistry Frontiers
·
2020
·Vol. 4
·期 4
·1158-1163
·
IF 6.788
Zewen Zhuang,Yu Wang,Zheng Chen,Dingsheng Wang,Chen Chen,Qing Peng,Yadong Li
Densely populated metal atomic site catalysts play a key role in practical catalysis applications. Herein, we report an amorphous nanobox with high-density atomic platinum species which are uniformly dispersed into the ZIF-8 skeleton through cation exchange. During the dispersing process, the ZIF-8 core was gradually etched into the hollow structure though the Kirkendall effect, and a great amount substitutions of Pt with Zn breaks the initial long-range ordered ZIF-8 topology into a distorted skeleton which leads to the significantly unsaturated coordination of atomic Pt species. The high-density atomic Pt nanoboxes exhibit excellent performance in direct C–H bond borylation of arenes which are usually catalyzed by homogeneous complexes. Such high-density atomic site heterogeneous catalysts could serve as a bridge to convert from homogeneous to heterogeneous catalysis.
研究领域:
化学
·
材料科学
·
催化反应
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产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）