Two ligands with guanidinium/ammonium groups were synthesized and their copper complexes, [Cu(L1)Cl2](ClO4)2.H2O (1) and [Cu(L2)Cl2](ClO4)2 (2) (L1 = 5,5'-di[1-(guanidyl)methyl]-2,2'-bipyridyl cation and L2 = 5,5'-di[1-(amino)methyl]-2,2'-bipyridyl cation), were prepared to serve as nuclease mimics. X-Ray analysis revealed that Cu(II) ion in 1 has a planar square CuN2Cl2-configuration. The shortest distance between the nitrogen of guanidinium and copper atoms is 6.5408(5) A, which is coincident with that of adjacent phosphodiesters in DNA (ca. 6 A). In the absence of reducing agent, supercoiled plasmid DNA cleavage by the complexes were performed and their hydrolytic mechanisms were demonstrated with radical scavengers and T4 ligase. The pseudo-Michaelis-Menten kinetic parameters (kcat, KM) were calculated to be 4.42 h(-1), 7.46 x 10(-5) M for 1, and 4.21 h(-1), 1.07 x 10(-4) M for 2, respectively. The result shows that their cleavage efficiency is about 10-fold higher than the simple analogue [Cu(bipy)Cl2] (3) (0.50 h(-1), 3.5 x 10(-4) M). The pH dependence of DNA cleavage by 1 and its hydroxide species in solution indicates that mononuclear [Cu(L1)(OH)(H2O)]3+ ion is the active species. Highly effective DNA cleavage ability of is attributed to the effective cooperation of the metal moiety and two guanidinium pendants with the phosphodiester backbone of nucleic acid. 相似文献
Monodisperse Fe3O4 and FeO nanocrystals (NCs) with different sizes (from 10 nm to 50 nm) and different shapes (cube, sphere, and ellipsoid) were synthesized by simply adjusting reaction temperature or molar ratio of Fe/oleic acid (OA) during the decomposition of FeO(OH) in noncoordinating solvent. The concentration of OA affected the nucleation and growth of NCs by improving the chemical reaction driving force during the syntheses of different types of iron oxide NCs. It has been found that the reaction temperature influenced the reaction activity between FeO(OH) and OA. The structure of Fe oleate complexes was studied using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy (TEM) were used for structural and chemical characterization of as-prepared iron oxide NCs. 相似文献
A supramolecular inclusion complex, [Zn(L1)(H2O)2(beta-CD)](ClO4)2.9.5 H2O (1) was synthesized and characterized structurally and its first-order active species for hydrolysis of esters, [Zn(L1)(H2O)(OH)(beta-CD)](ClO4) (2), was isolated (L1=4-(4'-tert-butylbenzyl)diethylenetriamine; beta-CD=beta-cyclodextrin). The apparent inclusion stability constant of the host and the guest measured in aqueous solution was (5.91+/-0.03)x10(3) for 1. The measured values of the first- and second-order pK(a) values of coordinated water molecules were 8.20+/-0.08 and 10.44+/-0.08, respectively, and were assigned to water molecules occupying the plane and remaining axial positions in a distorted trigonal bipyramid of the [Zn(L1)(H2O)2(beta-CD)]2+ sphere according to the structural analysis of [Zn(L2)(H2O)}2(mu-OH)](ClO4)3 (3) (L2=4-benzyldiethylenetriamine). p-Nitrophenyl acetate (pNA) hydrolysis catalyzed by 1 at pH 7.5-9.1 and 25.0+/-0.1 degrees C exhibited a first-order reaction with various concentrations of pNA and 1, but the pH profile did not indicate saturated kinetic behavior. Second-order rate constants of 0.59 and 24.0 M(-1) s(-1) were calculated for [Zn(L1)(H2O)(OH)(beta-CD)]+ and [Zn(L1)(OH)2(beta-CD)], respectively; the latter exhibited a potent catalytic activity relative to the reported mononuclear and polynuclear Zn(II) species. 相似文献
Summary Carbon nanotube supported Pd, Ru and Pd-Ru catalysts have been prepared and tested with the hydrogenation of cinnamaldehyde
as a probe reaction. It has been found that the cinnamaldehyde conversion and the selectivity towards the hydrogenation of
C=O bond over Pd-Ru/PCNT catalyst could reach 56.6% and 79.1%, respectively, at 120oC and 5.0 MPa, which is better than Pd/PCNT and Ru/PCNT catalysts under the same reaction conditions. It is assumed that the
better performance of Pd-Ru/PCNT catalyst for cinnamaldehyde hydrogenation may be due to the synergic effect of Pd and Ru
metals or the promoting effect of Ru metal. 相似文献
Using the techniques proposed in [3], we prove that two nonconstant meromorphic functions f and g on ? must be linked by a quasi-Möbius transformation if they share some pairs of small functions with more precise truncated multiplicities, which improve and extend the results of Duc Quang Si. 相似文献
Fragment-imprinted microspheres (FIMs) were prepared by suspension polymerization. 2,6-Dichloropyrimidine was used as the template molecule instead of sulfonamides, methacrylic acid and styrene were the mixed functional monomers, ethylene dimethacrylate was the crosslinking agent, and azodiisobutyronitrile was the initiator. The optimum conditions were obtained by an orthogonal experiment. The maximum adsorption was obtained under the optimum conditions. The adsorption by FIMs was 7.02 mg g−1, whereas the adsorption by non-FIMs was 5.41 mg g−1. A method for the simultaneous determination of five sulfonamides from milk samples by fragment imprinted-solid phase extraction coupled with HPLC was developed. The recoveries for the five sulfonamide extractions were 89.7–97.6 % with relative standard deviations of 1.79–3.02 %, indicating the suitability of the prepared FIMs for sulfonamide extraction.