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991.
H7[NiV13O38] was synthesized from K7[NiV13O38] using an ion exchange method. Then Pr2H[NiV13O38] was obtained by double decomposition of H7[NiV13O38] with Pr2(CO3)3. The actual amount of praseodymium measured by elemental analysis coincides with the designed amount of praseodymium in Pr2H[NiV13O38]. The i.r. spectra suggested that the [NiV13O38]7– anion did not collapse after the ion exchange and double decomposition. The 51V n.m.r. spectrum of Pr2H[NiV13O38] showed four peaks and their ratio of the relative intensity was 4:4:4:1. This result agrees with the chemical environment of V atoms in the [NiV13O38]7– anion. In vitro antitumor activities of polyoxometalates on several human tumor cells have been investigated using the MTT method. Pr2H[NiV13O38] is the most effective polyoxometalate tested in this study for inhibiting KB cell. Pr2H[NiV13O38] also showed remarkable inhibitory effect on some other tumor cells: HCT, Bel, B16, BCAP and ESCL cells. These results indicate that Pr2H[NiV13O38] is a potent broad spectrum antitumor agent. The structure type of polyoxometalates greatly influences their antitumor activity: the order of structure type for inhibiting KB cell is: [NiV13O38]7–>[Mo7O24]6–>Anderson structure Keggin structure Dawson structure. Moreover, the nature of the polyatom in the polyoxometalates also greatly influences their antitumor activity: the polyatom order for inhibiting KB cell is: V>Mo W. On the other hand, the nature of the counter cation and the heteroatom in the polyoxometalates exerted a relatively small influence on the inhibitory effect against the KB cell, although the praseodymium salt of [NiV13O38]7– showed a higher antitumor activity than its potassium salt. 相似文献
992.
The equation of state (EOS) of Duh and Mier-y-Terán for one Yukawa potential is expanded to two Yukawa potentials to describe the nonidealities of the charged lysozyme and alpha-chymotrypsin solutions. Instead of the classical DLVO theory, the attractive dispersion and double-layer repulsion interactions are represented by two Yukawa potentials, respectively. For the aqueous lysozyme solutions, the only adjustable dispersion energy parameter epsilon/k is regressed and the average deviation is 1.76%. For the aqueous alpha-chymotrypsin solutions, two adjustable parameters (the molecular weight and dispersion energy parameter) are regressed and the average deviation is 7.62%. Some correlation and prediction results are discussed. 相似文献
993.
Nikos G. Tsierkezos 《Journal of solution chemistry》2007,36(10):1301-1310
The reduction of benzophenone (Bzph) in 3-pentanone (PEN), acetone (ACE), N,N-dimethylacetamide (DMA), N,N-dimethylformamide (DMF), tetrahydrofuran (THF), acetonitrile (ACN) and dimethyl sulfoxide (DMSO) with n-tetrabutylammonium hexafluorophosphate (TBAPF6) as background electrolyte was studied using the technique of cyclic voltammetry at the temperature of 263.15 K. The half-wave
potentials (E
1/2) were extracted. The reduction of Bzph occurs in two successive one-electron steps to produce first the free radical anion
Bzph− and then the dianion Bzph2−. The results indicated that the radical anion Bzph− is reoxidized to Bzph in all investigated solvent media whereas the dianion Bzph2− is reoxidized to Bzph− only in THF. The heterogeneous electron-transfer rate constants (k
s
) were evaluated by employing the electrochemical rate equation proposed by Nicholson. The rate of electron transfer for the
Bzph/Bzph− couple was found to be relatively slow in all investigated solvent media. Consequently, the electron-transfer processes can
be recognized as quasi-reversible. The diffusion coefficients (D) of Bzph in the investigated solvent media have been calculated using the modified Randles-Sevcik equation. The effect of
the physical and chemical properties of the solvent medium on the electrochemical behavior of Bzph has been examined. 相似文献
994.
Alcohol sensing membranes coated on overhead transparency films for the continuous monitoring of ethanol, propanol and butanol are presented. Alcohol oxidation catalyzed by alcohol oxidase in conjunction with the fluorescence quenching reaction of oxygen-sensitive dye ion-pair, tris(4,7-diphenyl-1,10-phenanthroline) ruthenium(II) didodecylsulphate was chosen for the determination. Alcohol oxidase was immobilized covalently on a plasticized carboxylated poly(vinyl chloride) membrane and the oxygen-sensitive dye ion-pair was entrapped in the same membrane. The sensing membrane relates oxygen consumption, as a result of enzymatic oxidation, to alcohol concentration. Measurements have been performed in air-saturated alcohol standard solutions of pH 7.0. Storage stability, reproducibility and the effect of pH on sensing membrane performance have been studied in detail. The alcohol sensing membrane proposed here is simple to prepare and has a fairly rapid response time of <1 min. It has been successfully applied to the determination of the ethanol contents in various spirits. 相似文献
995.
996.
Grand canonical Monte Carlo and configurational bias Monte Carlo techniques were employed to simulate the adsorption of binary mixtures of butane isomers and quaternary mixtures in nine zeolites at 300 K. For binary mixtures the results show there is a critical pore size, which is 10-membered-ring about 5.6 Å. The channel sizes of BEA, ISV, MOR and CFI are larger than this critical pore size, they prefer i-butane than n-butane, whereas TON with smaller channel size than critical pore size prefers n-butane than i-butane, but its selectivity decreases with pressure increasing. MFI, MEL and TER prefer i-butane than n-butane at low pressure, but with pressure increasing, the selectivity is reversed. BOG prefers i-butane than n-butane but the selectivity decreased with pressure increasing. It demonstrates that the adsorption and selectivity are controlled by both pore size and pore structure. The n-butane–i-butane–n-pentane–2-methylbutane quaternary mixtures adsorbed in these nine zeolites were studied, and the results show alkane chain length dependence at low pressure, but the adsorption is controlled by pore size and structure with pressure increasing in all the zeolites except for TON and BOG. 相似文献
997.
A. V. Makarycheva-Mikhailova S. I. Selivanov N. A. Bokach V. Yu. Kukushkin P. F. Kelly A. J. L Pombeiro 《Russian Chemical Bulletin》2004,53(8):1681-1685
Reactions of the platinum(IV) nitrile complexes [PtCl4(RCN)2] (R = Me, CH2Ph, Ph) with 1,2- and 1,4-PhS(=NH)C6H4SPh in CH2Cl2 afforded addition products of sulfimides and coordinated nitriles, viz., the [PtCl4{NH=C(R)N=S(Ph)(C6H4SPh)}2] complexes. The latter were isolated in 75—90% yields and characterized by elemental analysis, positive-ion FAB mass spectrometry, IR spectroscopy, and 1H and 13C1H NMR spectroscopy. The temperature dependence of the 1H NMR spectra of the model [PtCl4{NH=C(R)N=SPh2}2] complexes (R = Me, Et) in CD2Cl2 studied in a temperature range from +40 to -70 °C demonstrated that E—Z isomerization of the ligands is a dynamic process in a range from +40 to -10 °C. The activation free energy of this process was calculated.Published in Russian in Izvestiya Akademii Nauk.
Seriya Khimicheskaya, No. 8, pp. 1618–1622, August, 2004. 相似文献
998.
Hu Chuanjiang Duan Chunying Meng Qingjin Liu Yongjiang Lu Changsheng Reng Xiaoming Chen Yijun Cao Mi 《Transition Metal Chemistry》2000,25(2):141-144
The mixed-valence molybdovanadate compound Na2(NH4)4[VIVVV
8Mo)O28] · 10H2O [Vanadata(6-)tetradeca--oxotetra-3-oxodi-6-oxoheptaoxo(oxomolybdate) nonatetrammonium disodium, decahydrate] has been synthesized from sodium molybdate(VI) dihydrate and sodium metavanadate dihydrate in aqueous solution by adding NH2OH · HCl. The molecular structure has been determined by X-ray diffraction and is based on the isopolydecavanadate structure. The molybdate atom is crystallographically disordered over 6MO6 octahedral sites. The e.s.r. spectrum clearly indicates that one vanadium atom has the oxidation number +4. 相似文献
999.
Chiral recognition of di-o-benzoyl-tartaric acid dibutyl ester (T) was achieved in the gas phase by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. In this method two divalent transition metal cations, zinc(II) and copper(II), were used as binding metal ions, and L-tryptophan (A) was used as a chiral reference. Multimeric complexes were readily formed by electrospray ionization of a methanol:water (50:50) solution containing metal ion, L-tryptophan and T. These multimeric complexes included singly charged protonated dimeric [TAH](+), doubly charged copper(II) bound tetrameric [TACu-H](2)(2+) and doubly charged zinc(II) bound tetrameric [TAZn-H](2)(2+), together with other complexes. The mass-selected complex, i.e., [TAH](+), [TACu-H](2)(2+) and [TAZn-H](2)(2+), was used to acquire the second stage mass spectra. The chiral recognition capability of these three complexes was evaluated using the abundance ratios of daughter ion to parent ion. A high degree of chiral recognition ability was observed in [TACu-H](2)(2+) and [TAZn-H](2)(2+). It was found that the type of binding ion played an important role in the chiral recognition. Different binding ions exhibited distinctive dissociation pathways and unique chiral recognition characteristics. The present method is based not only on whole-molecule loss but also on fractional-molecule loss. In addition, the reproducibility of the chiral recognition method was confirmed by several determinations of the abundance ratios of daughter ion to parent ion with a fixed activation energy and with five different activation energies. It was also shown that this chiral recognition method can tolerate acid interference. 相似文献
1000.
Mallet CR Lu Z Fisk R Mazzeo JR Neue UD 《Rapid communications in mass spectrometry : RCM》2003,17(2):163-170
Recently, sample preparation has been considered to be the major cause of bottlenecks during high-throughput analysis. With the assistance of robotic liquid handlers and the 96-well plate format, more samples can be prepared for subsequent liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis. Protein precipitation is still widely used despite potential loss of sensitivity or variable results due to ion suppression. The use of solid-phase extraction (SPE) clearly gives superior results but may not be as cost effective as protein precipitation due to the labor and material costs associated with the process. Here, a novel 96-well SPE plate is described that was designed to minimize the elution volume required for quantitative elution of analytes. The plate is packed with 2 mg of a high-capacity SPE sorbent that allows loading of up to 750 microL of plasma, while the novel design permits elution with as little as 25 microL. Therefore, the plate offers up to a 15-fold increase in sample concentration. The evaporation and reconstitution step that is typically required in SPE is avoided due to the concentrating ability of the plate. Examples of applications in drug discovery/development are shown and results are compared to protein precipitation. Excellent sensitivity and linearity are demonstrated. 相似文献