[reaction: see text] Novel highly functionalized dipeptide isosters are synthesized via a diastereoselective alkyl/arylation protocol of a glucose-derived (R)-tert-butanesulfinylimine. One of these novel sugar amino acid derivatives, a D-Ala-Ser/Thr isostere, was applied in a peptide synthesis protocol to afford a cyclic tetramer. 相似文献
The crystal structure of the complex 12.calix-[4]-arene dihydroxyphosphonic acid, 12.propane diammonium, 12.ethanol and 40.water molecules is based on dimeric units of the calix, assembled via trigonal units into a hexameric tube of 15 A radius and 16 A depth, further assemby via spanning propane diammonium cations and ethanol molecules forms a channel (40 A), selectively containing all the water molecules. 相似文献
Starch-acrylic acid-co-vinyl sulfonic acid/multiwalled carbon nanotubes (starch-AA-VSA/f-MWCNTs) bionanocomposite was successfully synthesized using gamma radiation for initiate the grafting of AA/VSA on starch in the presence of f-MWCNTs by template polymerization technique. The structural characteristics were confirmed by FTIR, SEM, and TGA. The adsorption behaviors of bionanocomposite toward Eu(III) and Cs(I) were examined using the batch adsorption experiments. Langmuir and Freundlich’s models were used to fit the experimental data of the adsorption isotherms. Kinetic studies showed that the adsorption data followed the pseudo-second-order model. Thermodynamic studies indicated that the reaction was favorable at high temperature and endothermic process.
In this study, CoFe2O4/Sawdust and NiFe2O4/Sawdust magnetic nanocomposites were synthesized using a hydrothermal method, and then characterized using X-ray powder diffraction, Infrared, scanning electron microscopy, Brunauer–Emmett–Teller/Barrett–Joyner–Halenda, and vibrating-sample magnetometer techniques. In this study, unmodified sawdust (US), modified sawdust (MS), unmodified CoFe2O4/sawdust (UCS), modified CoFe2O4/sawdust (MCS), unmodified NiFe2O4/sawdust (UNS), and modified NiFe2O4/Sawdust (MNS) magnetic nanocomposites, which are inexpensive, economical, environmentally friendly absorbents, and have a high selective hydrophobic, were used for the removal of oil from the water surface. The results show that the UCS, MCS, UNS, and MNS magnetic nanocomposites can selectively absorb the oil spreading on the water surface, due to its superhydrophobicity and superoleophilicity, and can be easily collected from water under the influence of a magnetic field. In addition, the results showed that the absorbents reach their equilibrium at the 30-min mark. Among all the absorbents, the MNS magnetic nanocomposite showed the maximum absorption capacity (18.172 g/g) at the 40-min mark. The results of the kinetic studies showed that the second-order kinetic equation with the highest correlation coefficient had the best fit with the experimental results. 相似文献
In this study, we present a versatile and easy procedure for modifying a cobalt ferrite nanoparticle step by step. A new nanocatalyst was prepared via CuII immobilized onto CoFe2O4@HT@Imine. The catalyst was fully characterized by Fourier‐transform infrared (FT‐IR), energy‐dispersive X‐ray spectroscopy (EDX), field emission scanning electron microscopy (FE‐SEM), X‐ray diffraction (XRD), and vibrating sample magnetometer (VSM) analyses. The current procedure as a green protocol offers benefits including a simple operational method, an excellent yield of products, mild reaction conditions, minimum chemical wastes, and short reaction times. Without any significant reduction in the catalytic performance, up to five recyclability cycles of the catalyst were obtained. The optimization results suggest that the best condition in the oxidation of benzyl alcohol derivatives is 0.003 g of the CoFe2O4@HT@Imine‐CuII catalyst, TEMPO, at 70°C under solvent‐free condition and air. 相似文献
We investigate a one-dimensional (1-D) Ising model for finite-site systems. The finite-site free energy and the surface free energy are calculated via the transfer matrix method. We show that, at high magnetic fields, the surface free energy has an asymptotic limit. The absolute surface energy increases when the value of f (the ratio of magnetic field to nearest-neighbor interactions) increases, and for f?≥?10 approaches a constant value. For the values of f?≥?0.2, the finite-site free energy also increases, but slowly. The thermodynamic limit in which physical properties approach the bulk value is also explored. 相似文献
Three new sesquiterpene alcohols, laur‐2‐ene‐3,12‐diol ( 1 ), cuparene‐3,12‐diol ( 2 ), and 8,11‐dihydro‐1‐methoxylaurokamuren‐12‐ol ( 3 ), along with one known diterpene, kahukuen‐10‐ol ( 4 ) have been isolated from the organic extract of the red alga Laurencia obtusa. The chemical structures were elucidated on the basis of spectroscopic analysis. The cytotoxicity of the isolated compounds were evaluated against three cancer cell lines, i.e., KB, HepG2, and MCF‐7. Compound 4 exhibited a wide range of cytotoxic activity against KB, HepG2, and MCF‐7 cell lines with IC50 of 0.100, 0.057, and 0.054 μm, respectively. In addition, 1 showed moderate activities towards KB and MCF‐7 cell lines with IC50 values of 0.171 and 0.184 μM , respectively and 2 exhibited a moderate activity against KB cell line at a concentration of 0.213 μg/ml. On the other hand, compound 3 exhibited no cytotoxic activity against any of the three cell lines. 相似文献
The synthesis of benzylated N2-(4,7,10,13-tetraazatridec-1-yl)-2′-deoxyguanosines 4 was accomplished by a key nucleophilic reaction of the novel unsymmetrical polyamine 2 , with 3′,5′-O-(tetraisopropyldisiloxane-1,3-diyl)-2-chloro-2′-deoxyinosine ( 1 ). 相似文献
Analysis of peroxidase activity by native polyacrylamide gel electrophoresis (PAGE) from a garlic bulb (Allium sativum L) extract showed two major activities (designated POX1 and POX2). The POX2 isoenzyme was purified to homogeneity by ammonium sulfate precipitation, gel filtration, and cation-exchange chromatography. The purified enzyme was found to be monomeric with a molecular mass of 36.5 kDa, as determined by sodium dodecyl sulfate-PAGE. The optimum temperature ranged from 25 to 40 degrees C and optimum pH was about 5.0. The apparent Km values for guaiacol and H2O2 were 9.5 and 2 mM, respectively. POX2 appeared highly stable since 50% of its activity was conserved at 50 degrees C for 5 h. Moreover POX2 was stable over a pH range of 3.5-11.0. Immobilization of POX2 was achieved by covalent binding of the enzyme to an epoxy-Sepharose matrix. The immobilized enzyme showed great stability toward heat and storage when compared with soluble enzyme. These properties permit the use of this enzyme as a biosensor to detect H2O2 in some food components such as milk or its derivatives. 相似文献
We demonstrate the application of an ionic liquid-based ferrofluid to the dispersive solid phase extraction of lead(II) using PAN as the chelator. The ionic liquid contains silica nanoparticles with a magnetic core as the dispersion medium, and its use results in improved stability of the colloidal dispersion and a complete extraction of lead(II) within a few seconds. In addition, there is no need for centrifugation. Specifically, the effect of different variables on the extraction of lead(II) was studied using an experimental design. Lead(II) was quantified by AAS. Under optimized conditions, the calibration graph for lead(II) is linear in the range from 5 to 372 μg L−1, the relative standard deviation is 1.34 % (for n = 7), the limit of detection is 1.66 μg L−1, and the enrichment factor is 200. The maximum adsorption capacity of sorbent was calculated to be 10.7 mg g−1, and adsorption follows a Langmuir isotherm.