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排序方式: 共有418条查询结果,搜索用时 31 毫秒
411.
通过离子液体氯化1-苄基-3-甲基咪唑(BenzMeIm-Cl)与PtCl2的反应,合成了配合物(BenzMeIm)2[PtCl4],并用元素分析、红外光谱、紫外-可见光谱、1H NMR、13C NMR和单晶X射线衍射对其进行了表征。单晶X射线分析表明,配合物结构属于P21/c空间群,晶胞参数和结构解析参数为:a=0.981 80(5)nm,b=0.861 47(3)nm,c=0.144 332(7)nm,β=92.480(2)°,V=121.96(1)nm3,R1=0.014 4,wR2=0.038 8。 相似文献
412.
Jamal Nasser Elie About-jaudet Noel Collignon 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):171-179
Abstract Cycloalkylphosphonates 2 of different sizes (from cyclopropyl to cycloheptyl) bearing various functional groups Z in a position were synthesized by bis-alkylation of α-functional methylphosphonates 1 and Ω-dibromoalkanes in presence of base. The choice of the basic system is determined by the nature of Z. With powerful electron-withdrawing groups, NaH-THF/DMSO (Method A, for Z=CN, SO2R) or liquid-solid phase transfer process [Method B, for Z=COOR, P(O) (OEt)2] proved to be the more suitable systems. For Z=aryl or SR, lithium diisopropylamide is required to achieve the deprotonation. A wide range of new phosphonates were obtained in high yields on preparative scale. 相似文献
413.
We have described the primary studies on the conductivity and molecular weight of polyaniline in an electric field as it is used in a field effect experimental configuration. We report further studies on doped in-situ deposited polyaniline. First we have chemically synthesized polyaniline by ammonium peroxodisulfate in an acidic solution, with aqueous, organic and emulsion conditions at different times. Next, we measured mass and conductivity and obtained the best time of polymerizations. Then, we repeated these reactions under different electrical fields in constant time and measured mass and conductivity. The polyaniline is characterized by gel permeation chromatography (GPC), UV-visible spectroscopy and electrical conductivity. Polyanilines with high molecular weight are synthesized under electric field M w = (5.2–6.8) × 105, with M w/M n = 2.0–2.5. The UV-visible spectra of polyanilines oxidized by ammonium peroxodisulfate and protonated with dodecylbenzenesulfonic acid (PANi-DBSA), in N-methylpyrolidone (NMP) show a smeared polaron peak shifted into the visible. Electrical conductivity of polyaniline has been studied by four-probe method. The conductivity of the films of emeraldine protonated by DBSA cast from NMP is higher than 500 S/cm under (10 kV/cm2 of potential) electric field and shows an enhanced resistance to ageing. Next, we carried chemical polymerization at the best electric field at different times. Finally, the best time and amount of electric field were determined. Polymers synthesized under an electric field probably have better physical properties regarding the existence of less branching and high electric conductivity. 相似文献
414.
Simultaneous preconcentration of phenol, 2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 2-nitrophenol, 4-nitrophenol, and 2,4-dinitrophenol was improved by using olive wood (OW) washed with ethanol then pyrolyzed at 200 °C as preconcentrating sorbent. Various OW sorbents were prepared by either washing OW (with ethanol, ether, dichloromethane, tetrahydrofuran or n-hexane); or by pyrolysis (at 100, 150, 200, 250 or 300 °C); or by combined pyrolysis/washing. The adsorbents were characterized by elemental analysis, total acidity/basicity, methylene blue relative surface area, point of zero charge, distribution coefficients of the phenols, and sample loading flow rate. It seems that washing and pyrolysis have removed compounds covering the OW pores, which improved the OW porosity and exposed more acidic groups on the OW surface. The pores and the surface acidic groups seem to play major role in phenols sorption. Ethanol-washed OW then pyrolyzed at 200 °C gave the best preconcentration performance towards phenols (300 mg sorbent, 150 mL of the sample (pH 7), and elution with 3 mL of acetonitrile). The method was linear up to 100 μg L−1; limit of quantification: 0.20-0.48 μg L−1. The method could detect phenol and 2,4-dinitrophenol in industrial wastewater with spiked recovery range from 80.2% to 91.4% (±1.1 to 5.5%RSD) for all the phenols. 相似文献
415.
Chevreux G Atmanene C Lopez P Ouazzani J Van Dorsselaer A Badet B Badet-Denisot MA Sanglier-Cianférani S 《Journal of the American Society for Mass Spectrometry》2011,22(3):431-439
Escherichia coli glucosamine-6-phosphate synthase (GlmS) is a dimeric enzyme from the glutamine-dependent amidotransferases family, which
catalyses the conversion of D-fructose-6-phosphate (Fru6P) and glutamine (Gln) into D-glucosamine-6-phosphate (GlcN6P) and
glutamate, respectively. Extensive X-ray crystallography investigations have been reported, highlighting the importance of
the dimeric association to form the sugar active site as well as significant conformational changes of the protein upon substrate
and product binding. In the present work, an approach based on time-resolved noncovalent mass spectrometry has been developed
to study the dynamics of GlmS subunit exchange. Using 14N versus 15N labeled proteins, the kinetics of GlmS subunit exchange was monitored with the wild-type enzyme in the presence of different
substrates and products as well as with the protein bearing a key amino acid mutation specially designed to weaken the dimer
interface. Determination of rate constants of subunit exchange revealed important modifications of the protein dynamics: while
glutamine, glutamate, and K603A mutation accelerates subunit exchange, Fru6P and GlcN6P totally prevent it. These results
are described in light of the available structural information, providing additional useful data for both the characterization
of GlmS catalytic process and the design of new GlmS inhibitors. Finally, time-resolved noncovalent MS can be proposed as
an additional biophysical technique for real-time monitoring of protein dynamics. 相似文献
416.
Matin-Alsadat Mostaan Jamal Davoodi Hadi Alizadeh Mohsen Yarifard 《The European Physical Journal B - Condensed Matter and Complex Systems》2018,91(10):260
In this paper, we study the tensile behavior of cylindrical rutile TiO2 nanowires, employing molecular dynamics (MD) simulation technique. The third-generation charge optimized many-body (COMB3) has been used for interatomic potential modeling. The influence of temperature and nanowire diameter on Young’s modulus is investigated. Our simulations exhibit the anisotropic behavior of Young’s modulus as a function of diameter for different crystallographic orientations. Although our results are in good accord with the existing results in [1 0 0] direction, Young’s modulus adds up monotonically with increasing the cross-sectional diameter of nanowire in [0 0 1] direction. It is found that Young’s modulus of the nanowires are lower (higher) than the bulk value for [0 0 1] ([1 0 0]) direction. Furthermore, simulation results also indicate that Young’s modulus of rutile TiO2 nanowire increases as a function of temperature for a given diameter, unexpectedly. The obtained results may be useful in the field of nanotechnology for optimizing mechanical performance to gain specific applications. 相似文献
417.
Trina Ekawati Tallei Fatimawali Ahmad Akroman Adam Mona M. Elseehy Ahmed M. El-Shehawi Eman A. Mahmoud Adinda Dwi Tania Nurdjannah Jane Niode Diah Kusumawaty Souvia Rahimah Yunus Effendi Rinaldi Idroes Ismail Celik Md. Jamal Hossain Talha Bin Emran 《Molecules (Basel, Switzerland)》2022,27(1)
Before entering the cell, the SARS-CoV-2 spike glycoprotein receptor-binding domain (RBD) binds to the human angiotensin-converting enzyme 2 (hACE2) receptor. Hence, this RBD is a critical target for the development of antiviral agents. Recent studies have discovered that SARS-CoV-2 variants with mutations in the RBD have spread globally. The purpose of this in silico study was to determine the potential of a fruit bromelain-derived peptide. DYGAVNEVK. to inhibit the entry of various SARS-CoV-2 variants into human cells by targeting the hACE binding site within the RBD. Molecular docking analysis revealed that DYGAVNEVK interacts with several critical RBD binding residues responsible for the adhesion of the RBD to hACE2. Moreover, 100 ns MD simulations revealed stable interactions between DYGAVNEVK and RBD variants derived from the trajectory of root-mean-square deviation (RMSD), radius of gyration (Rg), and root-mean-square fluctuation (RMSF) analysis, as well as free binding energy calculations. Overall, our computational results indicate that DYGAVNEVK warrants further investigation as a candidate for preventing SARS-CoV-2 due to its interaction with the RBD of SARS-CoV-2 variants. 相似文献
418.