In this work, we study the existence of eigenvalues for a type of non-linear equations and we give some conditions to get positive eigenfunctions. Particularly, we show that under some appropriate conditions, the set of eigenvalues is an interval. 相似文献
Research on Chemical Intermediates - Among the reactive oxygen species, the superoxide anion radical (O 2 ·? ) has a fundamental role in several biological functions. Consequently, its... 相似文献
A planar lens structure based on an array of nanoscale slits in a metallic film is modeled using a waveguide modal technique. The structure is modeled as a one dimensional lens followed by free space propagation. The obtained results are compared to published experimental results as well as numerical simulations using either the finite difference frequency domain or the transmission line method. A good agreement has been obtained with significant simulation time reduction. 相似文献
Ten benzoxazole clubbed 2-pyrrolidinones (11–20) as human monoacylglycerol lipase inhibitors were designed on the criteria fulfilling the structural requirements and on the basis of previously reported inhibitors. The designed, synthesized, and characterized compounds (11–20) were screened against monoacylglycerol lipase (MAGL) in order to find potential inhibitors. Compounds 19 (4-NO2 derivative) and 20 (4-SO2NH2 derivative), with an IC50 value of 8.4 and 7.6 nM, were found most active, respectively. Both of them showed micromolar potency (IC50 value above 50 µM) against a close analogue, fatty acid amide hydrolase (FAAH), therefore considered as selective inhibitors of MAGL. Molecular docking studies of compounds 19 and 20 revealed that carbonyl of 2-pyrrolidinone moiety sited at the oxyanion hole of catalytic site of the enzyme stabilized with three hydrogen bonds (~2 Å) with Ala51, Met123, and Ser122, the amino acid residues responsible for the catalytic function of the enzyme. Remarkably, the physiochemical and pharmacokinetic properties of compounds 19 and 20, computed by QikProp, were found to be in the qualifying range as per the proposed guideline for good orally bioactive CNS drugs. In formalin-induced nociception test, compound 20 reduced the pain response in acute and late stages in a dose-dependent manner. They significantly demonstrated the reduction in pain response, having better potency than the positive control gabapentin (GBP), at 30 mg/kg dose. Compounds 19 and 20 were submitted to NCI, USA, for anticancer activity screening. Compounds 19 (NSC: 778839) and 20 (NSC: 778842) were found to have good anticancer activity on SNB-75 cell line of CNS cancer, exhibiting 35.49 and 31.88% growth inhibition (% GI), respectively. 相似文献
AbstractThe reaction of 3-oxopropanenitriles with phenyl isothiocyanate in DMF containing KOH afforded the corresponding potassium salts. The latter salts were converted into ketene N,S-acetals upon acidification with hydrogen chloride. The reaction of the ketene N,S-acetals with 2-bromo-1-[5-methyl-1-(p-tolyl)-1H-1,2,3-triazol-4-yl]ethan-1-one or 3-(2-bromoacetyl)-2H-chromen-2-one gave novel thiophenes in good yields. Treatment of the ketene N,S-acetals with hydrazonyl halides afforded 1,3,4-thiadiazoles in good yields. The stereochemistry of the synthesized compounds was studied. 相似文献
The kinetics of oxidation of [FeII(phen)2(H2O)2]2+ (phen = 1,10-phenanthroline) by periodate were investigated in aqueous acidic medium at different [H+] over a temperature range of 20–40 °C. The reaction was studied under pseudo-first-order conditions by taking [IO4?] > tenfold over [FeII(phen)2(H2O)22+]. The reaction rate increases with increasing [H+], and the kinetics of oxidation obeyed the following rate law:
The surfactant sodium dodecyl sulfate was found to enhance the rate, whereas cetyltrimethylammonium bromide had little effect. Activation parameters associated with k2 and k3 were calculated. An electron transfer from Fe(II) to I(VII) is identified as the rate-determining step. The I(VI) species thus generated reacts in a fast step with another Fe(II) complex.
A series of hydrazones 5a–i were synthesized by the condensation of hydrazides derived from dichlorophenylacetic acids with different aromatic aldehydes and ketones. Their structures were confirmed by spectroscopic data and elemental analysis. Hydrazones 5a–i were evaluated for α‐glucosidase and urease inhibition activities. Five compounds exhibited potent α‐glucosidase inhibitory potential with IC50 values 8.5 ± 0.3, 22.2 ± 0.78, 32.9 ± 1.5, 34 ± 2.4, and 170.6 ± 7.5 μM, respectively, which are many times better than that of the standard inhibitor acarbose (IC50 = 840 ± 1.73 μM). Furthermore, molecular docking study was performed to explore the binding mode in the active sites of α‐glucosidase and urease enzymes. 相似文献
Using emulsified triacylglycerols, we have shown recently [Mosbah et al., 2007, submitted for publication] that amino acid residue G311 of Staphylococcus xylosus lipase (SXL) is critically involved in substrate selectivity, pH and temperature dependency. Using the monomolecular film technique, we show in the present study that the four single mutants of this residue (G311L, G311W, G311D, and G311K), interact efficiently with egg-phosphatidyl choline (egg-PC) monomolecular films, comparably to the wild-type (G311). A critical surface pressure (pi(c)) of about 25 mN/m was obtained with the SXL wild-type (SXL-WT) and its mutants. These results support our conclusion that the G311 residue is not involved in the interfacial adsorption step of SXL. A kinetic study on the surface pressure dependency, stereoselectivity, and regioselectivity of SXL-WT and its G311 mutants was also performed using optically pure enantiomers of diacylglycerols (1,2-sn-dicaprin and 2,3-sn-dicaprin) and a prochiral isomer (1,3-sn-dicaprin) spread as monomolecular films at the air-water interface. Our results indicated that the mutation of one single residue at position 311 affects critically the catalytic activity, the stereo- and the regioselectivity of SXL. As previously observed with emulsified substrates [Mosbah et al., 2007, submitted for publication] we observed that an increase in the size of the 311 amino acid side chain residue was accompanied by a decrease of lipase activity measured on dicaprin monolayer. We also noticed that the substitution of G311 by a basic or acidic residue (G311K and G311D), induces a significant shift of the pH optimum from 8 to 9.5 or from 8 to 6.5, respectively. 相似文献
A simple ionic liquid-assisted approach for the fabrication of graphene-based nanocomposite is reported. Pd–CuO/rGO and Au–CuO/rGO nanocomposites are successfully fabricated with the assistance of the ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate. The physicochemical features of nanocomposite are systematically characterized by XRD, FT-IR, Raman spectroscopy, XPS, TGA, FESEM, AFM, and HRTEM. Carbon monoxide has been used as a probe molecule to emphasize the performance of the fabricated materials. The results indicate that the incorporation of a little quantity of ionic liquid results in the creation of uniformly dispersed NPs simultaneously with the reduction of graphene oxide (GO) into rGO, which leads to a low-temperature CO oxidation process. Besides, the Au–CuO/rGO catalyst achieved excellent durability in CO oxidation for 14 h, without detectable deactivation. The low-temperature CO oxidation was mainly induced by the synergistic effects between the components of catalysts. The Au or Pd and CuO combination not only generates more interfaces, which is more favorable for the activation of oxygen but also enhances the catalyst reduction behavior. Consequently, a graphene composite catalyst can be considered a potential CO oxidation candidate.