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911.
Based on the theory of stochastic resonance, a new method carried on the quantitive analysis to weak chromatographic signal of glyburide in plasma, which was embedded in the noise background and the signal-to-noise ratio (SNR) of HPLC-UV is enhanced remarkably. This method enhances the quantification limit to 1 ng ml−1, which is the same as HPLC-MS, and makes it possible to detect the weak signal accurately by HPLC-UV, which was not suitable before. The results showed good recovery and linear range from 1 to 50 ng ml−1 of glyburide in plasma and the method can be used for quantitative analysis of glyburide. 相似文献
912.
本文用差热分析法系统地研究了La掺杂对Al-Si共晶合金、亚共晶、超共晶的动态凝固过程的影响。结果表明,La促使α(Al)成核,使体系中初晶α(Al)的析出温度比AJ-Si二元合金中Al初晶的实际析出温度明显提高;La对初晶Si的成核和长大起抑制作用,使超共晶中初晶Si相析出温度较二元合金中的Si初晶的实际析出温度明显降低。 相似文献
913.
锆助剂对低温液相合成甲醇用铜铬硅催化剂性能的影响 总被引:3,自引:2,他引:3
考察了含锆的铜铬硅催化剂低温液相合成甲醇性能,并进行了BET、TPR-H2、TPD-H2、TPD-CO、XRD和XPS表征。结果表明,锆作为结构助剂及电子助剂对催化剂在低温液相合成甲醇反应中具有显著的促进作用,反应活性可提高32.25 %。锆助剂能有效提高催化剂的比表面积,促进催化剂中铜铬组分的分散及表面富集。ZrO2加入在催化剂表面产生的Cu+与催化活性的改善密切相关,Zr4+、Cr3+、Cu+可形成复合中心,为价态的稳定性提供微环境,在H2活化及C O键的断裂等反应步骤中起重要作用。 相似文献
914.
Jian-zhang?Li Bin?Xu Shen-Xin?Li Wei?Zeng Sheng-ying?QinEmail author 《Transition Metal Chemistry》2005,30(6):669-676
Four manganese(III) complexes (MnL1Cl, MnL2Cl, MnL42Cl, MnL52Cl) with a crowned salicylaldimine Schiff base ligand have been synthesized and employed as models to mimic hydrolase in the hydrolysis of p-nitrophenyl picolinate (PNPP). The kinetics and mechanism of catalytic PNPP hydrolysis have been investigated. The kinetic mathematical model of PNPP cleavage catalyzed by these complexes has been proposed. The effects of the ligand structure and crown ether ring in complexes, and the reactive temperature on the rate of catalytic PNPP hydrolysis have been also examined. The results show that compared with the crown-free analogous MnL3Cl and MnL62Cl, the crowned Schiff base manganese(III) complexes, MnL1Cl, MnL2Cl, MnL42Cl and MnL52Cl, exhibit more high catalytic activity, which follow the order: MnL1Cl >MnL2Cl >MnL42Cl >MnL52Cl >MnL3Cl >MnL62Cl; the pseudo-first-order-rate (kobs) for the PNPP hydrolysis catalyzed by the complex MnL1Cl containing three crown ether rings is highest among six complexes and is 1.81 times that of MnL3Cl, 1.49 × 103 times that of spontaneous hydrolysis of PNPP, respectively, at pH = 7.00, [S] = 2.0 × 10−4 mol dm−3. 相似文献
915.
A ligand-exchange capillary electrophoresis was explored, with L-ornithine as the ligand and copper(II) as the central ion. Its applicability was demonstrated with underivatized and dansyl amino acids, a dipeptide, and drugs with amino alcohol structure. The enantioselectivity was found to be strongly dependent on pH and copper(II)-L-Orn complex concentration. Due to the adsorption of the positively charged species onto the capillary inner walls, the chiral separation selectivity is very high while the efficiency is relatively low. Permanent 1,3-propanediamine-coated capillaries show an improved separation efficiency and theoretical plate numbers increasing from 10(4) to 10(5). Similar phenomena were observed when sodium dodecyl sulfate (SDS) micelles were added to the copper(II) complex solution. The poor separation efficiency of chiral compounds in uncoated capillaries may result from the low rate of the ligand-exchange reactions, and the high enantioselectivity may derive from the complexing process in the adsorbed phase. 相似文献
916.
Multistep purification of an antifreeze protein from Ammopiptanthus mongolicus by chromatographic and electrophoretic methods 总被引:2,自引:0,他引:2
Antifreeze proteins (AFPs) are known as thermal hysteresis proteins, which can depress the freezing points of the solution by noncolligative effects, but do not affect the melting points. Although some AFPs have been found in some plants, the identity of most proteins remains unclear, owing to insufficient quantity and quality to characterize them. In this report, we describe the purification of an AFP from the winter leaves of Ammopiptanthus mongolicus using a combination of column chromatography and gel electrophoresis. After homogenization in ascorbate-acid-containing Tris buffers (pH 7.4) the soluble proteins are captured by (diethylamino)ethyl-cellulose 52 material. An elution with 0.1-0.3M KCl leads to a crude active fraction. The crude fraction is further purified on a Superdex 75 prep-grade column and finally a Poros 20HP2 column. A complex, consisting of two proteins with relative molecular masses of 34,700 and 37,100, respectively, in sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, is obtained by this protein purification protocol. The recovery of two proteins from the gel is carried out by electrophoresis. The purified protein, with a molecular mass of 37,100, shows thermal hysteresis activity (THA) and can modify the normal growth of ice crystals. The THA of this purified antifreeze protein is 0.24 degrees C at the concentration of 5 mg/mL. 相似文献
917.
918.
IntroductionItiswellknownthatmetallocenesactivatedwithmethylaluminoxane (MAO)arehighlyactivehomogeneousZiegler Nattacatalyststhatproducepolyolefinwithcon trolledstereoregularityandnarrowmolecularweightdistri bution ,1 4 however,themolecularweightofthepolym… 相似文献
919.
In the reaction of methane and carbon dioxide to C2 hydrocabons under non-equilibrium plasma, methane conversion was decreased,but selectivity of C2 hydroxarbons was increased when using La2O3/γ-Al2O3 as catalyst. So the yield of C2 hydrocarbons was higher than using plasma alone. The synergism of La2O3/γ-Al2O3 and plasma gave methane conversion of 24.9% and C2 yield of 18.1%. The distribution of C2 hydrocarbons changed when Pd-La2O3/γ-Al2O3 was used as catalyst,the major C2 product was ethylene. 相似文献
920.
The reaction of Pt2Ru4(CO)18, 1 with 1,8-bis(phenylethynyl)naphthalene, 2 has yielded two metal carbonyl cluster complexes: Ru2(CO)6[-
2-C10H6C4Ph2], 3 (60% yield) and Ru2Pt(CO)6[-
2-C10H6C4Ph2]2, 4 (8% yield). Both compounds were characterized by a single crystal X-ray diffraction analysis. Both products were formed as a result of fragmentation of the Pt2Ru4 cluster of 1. Compound 3 contains two ruthenium atoms. They are bridged by a tricyclic C10H6C4Ph2 ligand formed by the coupling of the two -carbon atoms of the alkyne groups. The -carbon atoms of the alkynes are -bonded to one of the ruthenium atoms to form a metallacycle and this entire group is -bonded to the second ruthenium atom. Compound 4 contains two ruthenium atoms with a platinum atom between them. This molecule contains two tricyclic C10H6C4Ph2 ligands similar to that in 3, and two metallacycles formed by coordination of the -carbon atoms of both ligands to the platinum atom. One ligand is -bonded to each of the ruthenium atoms. 相似文献