Morin applied in speciation of aluminium in natural waters and biological samples by reversed-phase high-performance liquid chromatography with fluorescence detection

A reversed-phase high-performance liquid chromatographic method with fluorescence detection for the determination of labile monomeric aluminium has been developed through pre-column complexation using morin as the analytical reagent. The highly fluorescent aluminium-morin complex (excitation wavelength 418 nm, emission wavelength 490 nm) was separated on a Spherisorb ODS 2 column with an eluent consisting of 30% methanol and 70% water (pH 1.0 with perchloric acid). The most remarkable point of this protocol was that only the most toxic aluminium species, that is, free aqua-aluminium ion and its monomeric hydroxo complex ions, selectively respond among various aluminium complexes. This strategy has been successfully applied to direct fractionation of the toxic aluminium in natural waters and biological samples without any pretreatment.     

线性非理想条件下液相色谱柱末端峰形规律

 色谱流出曲线的二阶中心矩μ２和三阶中心矩μ３以及描述峰形非对称程度的偏态系数∑ｋ＝μ３／μ１．５２是反映色谱峰形的重要参数。从液相色谱过程动力学方程出发，运用电子计算机证明了在线性非理想条件下高效液相色谱体系中不同保留值组分在柱末端峰形的分布基本一致的结论。     

Grid‐like Cobalt(II) Layered Complex with an Unprecedented Double 1,2‐Bis(1,2,4‐triazole‐1‐yl)methane Bridges

A novel two‐dimensional cobalt complex, [Co(btrm)₂(dca)]ClO₄ ( 1 , btrm = 1,2‐bis(1,2,4‐triazole‐1‐yl)methane, dca = dicyanamide), was synthesized and characterized. X‐ray diffraction analyses reveal that the title complex crystallizes in the monoclinic space group C2/m with a = 29.507(13)Å, b = 17.804(8) Å, c = 14.709(7) Å, β = 119.916(7)°, Z = 12, and R₁ = 0.0784, wR₂ = 0.2041. The cobalt atom involves a six‐coordinated CoN₆ environment, with a distorted octahedral coordination. Two btrm ligands connect the Co^II atoms with the exodentate nitrogen atoms on the 4‐position of triazole rings to form a sixteen‐membered rhombic grid. The unprecedented double btrm bridges and μ_1,5‐dca bridge connect the cobalt atoms to form a two‐dimensional grid‐like layered structure. The spectroscopic and magnetic properties have also been investigated.     

Selective hydrogenation by Pd nanoparticles embedded in polyelectrolyte multilayers

Alternating adsorption of poly(acrylic acid) and a polyethylenimine-Pd(II) complex on alumina and subsequent reduction of Pd(II) by NaBH4 yield catalytic Pd nanoparticles embedded in multilayer polyelectrolyte films. The polyelectrolytes limit aggregation of the particles and impart catalytic selectivity in the hydrogenation of alpha-substituted unsaturated alcohols by restricting access to catalytic sites. Hydrogenation of allyl alcohol by encapsulated Pd(0) nanoparticles can occur as much as 24-fold faster than hydrogenation of 3-methyl-1-penten-3-ol. Additionally, the nanoparticle/polyelectrolyte system suppresses unwanted substrate isomerization, when compared to a commercial palladium catalyst. Selective diffusion through poly(acrylic acid)/polyethlyenimine membranes suggests that hydrogenation selectivities are due to different rates of diffusion to nanoparticle catalysts. First-order kinetics are also consistent with a diffusion-limited mechanism. Further exploitation of the versatility of polyelectrolyte films should increase selectivity in hydrogenation as well as other reactions.     

Kinetics of the Reaction of Abstracting Hydrogen from Ethylene by Hydrogen Atom

Hydrogen abstraction reaction, H C2H4 --H2 C2H2 was studied by using A initio SCF method. Ge-ometries were fully optimized at SCF level and energies were computed at STO-3G basis set for reactants and transition state. Vibrational analysis was performed thereupon. Finally, the rate constant calculations were carried out at different temperatures for all range of reaction temperature according to Eyring's sbwlute reaction rate theory. The calculated activation energy is 12. 68 kcal/mol, lower than observed value (H. S kcal/mol) by 1. 82 kcal/mol only. The agreement of the calculated rate constants with the experiments is satisfactory.     

Simultaneous determination of lead(II) and cadmium(II) at a diacetyldioxime modified carbon paste electrode by differential pulse stripping voltammetry

A simple and effective chemically modified carbon paste electrode (CMCPE) for the simultaneous determination of lead(II) and cadmium(II) was developed in this work. The electrode was prepared by the addition of diacetyldioxime into a carbon paste mixture. Pb²⁺ and Cd²⁺ were preconcentrated on the surface of the modified electrode by complexing with diacetyldioxime and reduced at a negative potential (−1.10 V). Then the reduced products were oxidized by differential pulse stripping. The fact that two stripping peaks appeared on the voltammograms at the potentials of −0.65 V (Cd²⁺) and −0.91 V (Pb²⁺) demonstrates the possibility of simultaneous determination of Pb²⁺ and Cd²⁺. Under the optimized working conditions, calibration graphs were linear in the concentration ranges of 1.0×10⁻⁷-1.5×10⁻⁵ mol l⁻¹ (Pb²⁺) and 2.5×10⁻⁷-2.5×10⁻⁵ mol l⁻¹ (Cd²⁺), respectively. For 5 min preconcentration, detection limits of 1×10⁻⁸ mol l⁻¹ (Pb²⁺) and 4×10⁻⁸ mol l⁻¹ (Cd²⁺) were obtained at the signal noise ratio (SNR) of 3. To evaluate the reproducibility of the newly developed electrode, the measurements of 5×10⁻⁷ mol l⁻¹ Pb²⁺ and Cd²⁺ were parallel carried out for six times at different electrodes and the relative standard deviations were 2.9% (Pb²⁺) and 3.2% (Cd²⁺), respectively. Interferences by some metals were investigated. Only Ni²⁺ and Hg²⁺ apparently affected the peak currents of Pb²⁺ and Cd²⁺. The diacetyldioxime modified carbon paste electrode was applied to the determination of Pb²⁺ and Cd²⁺ in water samples. The results indicate that this electrode is sensitive and effective for the simultaneous determination of Pb²⁺ and Cd²⁺.     

Multilayer poly(vinyl alcohol)-adsorbed coating on poly(dimethylsiloxane) microfluidic chips for biopolymer separation

A poly(dimethylsiloxane) (PDMS) microfluidic chip surface was modified by multilayer-adsorbed and heat-immobilized poly(vinyl alcohol) (PVA) after oxygen plasma treatment. The reflection absorption infrared spectrum (RAIRS) showed that 88% hydrolyzed PVA adsorbed more strongly than 100% hydrolyzed one on the oxygen plasma-pretreated PDMS surface, and they all had little adsorption on original PDMS surface. Repeating the coating procedure three times was found to produce the most robust and effective coating. PVA coating converted the original PDMS surface from a hydrophobic one into a hydrophilic surface, and suppressed electroosmotic flow (EOF) in the range of pH 3-11. More than 1,000,000 plates/m and baseline resolution were obtained for separation of fluorescently labeled basic proteins (lysozyme, ribonuclease B). Fluorescently labeled acidic proteins (bovine serum albumin, beta-lactoglobulin) and fragments of dsDNA phiX174 RF/HaeIII were also separated satisfactorily in the three-layer 88% PVA-coated PDMS microchip. Good separation of basic proteins was obtained for about 70 consecutive runs.     

A Novel 3‐D Heterobimetallic Cyano‐bridged Coordination Polymer Incorporating Ag···Ag Interaction: [Cu(dien)Ag(CN)2]2[Ag2(CN)3][Ag(CN)2]

A three‐dimensional cyano‐bridged copper(II) complex, [Cu(dien)Ag(CN)₂]₂[Ag₂(CN)₃][Ag(CN)₂] ( 1 ) (dien = diethylenetriamine), has been prepared and characterized by X‐ray crystallography. Complex 1 crystallized in the monoclinic space group P2₁/n with a = 6.988(2), b = 17.615(6), c = 12.564(4) Å, β = 90.790(5)°. The crystal consists of cis‐[Cu(dien)]²⁺ units bridged by [Ag(CN)₂]^— to form a zig‐zag chain. The Ag atoms of the free and bridging [Ag(CN)₂]^— link together to form additional infinite zig‐zag chains with short Ag···Ag distances. The presence of Ag···Ag interactions effectively increases the dimensionality from a 1‐D chain to a 3‐D coordination polymer.     

Calculation of ligand-field and Stark sub-levels in laser crystals Nd~(3+):KY(WO_4)_2 and Nd~(3+):KGd(WO_4)_2

The parameters of ligand field of laser crystal Na~(3+):KY(WO_4)_2 and Nd~(3+):KGd(WO_4)_2are obtained by a scheme which involved intermediate coupling and ligand field interaction.Thecalculated Stark-levels are in good agreement with the experimental values.     

Blue myoglobin reconstituted with an iron porphycene shows extremely high oxygen affinity

Myoglobin will be a good scaffold for engineering a function into proteins. To modulate the physiological function of myoglobin, almost all approaches have been demonstrated by site-directed mutagenesis, however, there are few studies which show a significant improvement in the function. In contrast, we focused on the replacement of heme in the protein with an artificial prosthetic group. Recently, we prepared a novel myoglobin reconstituted with an iron porphycene as a structural isomer of mesoheme. The bluish colored reconstituted myoglobin is relatively stable and the deoxymyoglobin reversibly binds ligands. Interestingly, the O2 affinity of the reconstituted myoglobin, 1.1 x 109 M-1, is a significant 1,400-fold higher than that of the native myoglobin. Furthermore, the unfavorable autoxidation kinetics show 7-fold decrease in rate for the reconstituted myoglobin relative to the native myoglobin, indicating the stable oxy-form against autoxidation. The net results come from the slow dissociation of the O2 ligand in the reconstituted myoglobin, koff = 0.11 s-1, because of the formation of strong hydrogen bond between His64 and negatively charged dioxygen. The present study indicates that the replacement of native heme with an artificially created prosthetic group will give us a unique function into a hemoprotein.