A turn-on Schiff base fluorescence sensor for zinc ion

A simple Schiff base type fluorescent receptor 1 was prepared and evaluated for its fluorescence response to heavy metal ions. Receptor 1 exhibits an ‘off-on-type’ mode with high selectivity in the presence of Zn²⁺ ion. The selectivity of 1 for Zn²⁺ is the consequence of combined effects of chelation-enhanced fluorescence (CHEF), CN isomerization, and inhibition of photoinduced electron transfer (PET).     

Promoting immobilization and catalytic activity of horseradish peroxidase on mesoporous silica through template micelles

New concept on the promotion of immobilization and catalytic activity of enzyme on mesoporous silica through template micelles is proposed and realized in this paper. Proper P123 templates are controllable retained in the as-synthesized SBA-15, not only to anchor the horseradish peroxidase (HRP) guest, but also to establish the crowding-like microenvironment around the enzyme. The influence of retaining templates on the pore structure of SBA-15, immobilization, and catalytic activity of HRP is studied, and the possible process of template removal is proposed. Ethanol refluxing of 6 h is conformable to prepare the optimal mesoporous support characterized with the retained templates of about 8%. With the assistance of retained templates in SBA-15, up to 49 mg g(-1) of HRP can be immobilized, 100% more than that on calcined SBA-15. Furthermore, the thermal stability, the resistance of pH variation and denaturing agent urea, and the recycle usage of HRP immobilized are obviously elevated, paving a novel and low-cost route to develop enzyme catalysts.     

Methyl Pothoscandensate,a New ent‐18(4→3)‐Abeokaurane from Pothos scandens

Methyl pothoscandensate ( 1 ), a new molecular skeleton of ent‐18(4→3)‐abeokaurane, along with eight known compounds was isolated from the whole plant of Pothos scandens. The structure of the new compound was established by spectroscopic techniques and confirmed by single‐crystal X‐ray diffraction. The inhibitory activity of selected compounds against porcine respiratory and reproductive syndrome virus (PRRSV) was measured by the cytopathic effect (CPE) method. Compound 1 showed weak effect on PRRSV with an IC₅₀ value of 40.3±8.3 μM (TI=15.7).     

Synthesis and antitumor activity of 1-acetyl-3-(4-phenyl)-4,5-dihydro-2-pyrazoline-5-phenylursolate and 4-chalcone ursolate derivatives

New 4-chalcone ursolate and 1-acetyl-3-(4-phenyl)-4,5-dihydro-2-pyrazoline-5-phenyl ursolate derivatives were synthesized by esterification of UA and chalcone or pyrazoline. The compounds were structurally confirmed by IR, ¹H NMR, ¹³C NMR, and HR-MS spectroscopy. The cytotoxicity of ten derivatives was evaluated against A549, SKOV3, and HepG2 cell lines by MTT assay. The result showed that several compounds were more potent than UA against A549 and SKOV3 cells; however, none of them were more potent than UA against HepG2.     

Neutral mononuclear, dinuclear, tetranuclear d7/d10 metal complexes containing bis-pyrazole/pyridine ligands supported by 2,6-bis(3-pyrazolyl)pyridine: synthesis, structure, spectra, and catalytic activity

A series of novel bis-pyrazole/pyridine complexes, [Zn(2)(HL(1))(2)(μ(2)-SO(4))](2)·EtOH·H(2)O (1), [Co(2)(HL(1))(2)(μ(2)-SO(4))](2)·2DMF·6H(2)O (2), [Zn(4)(HL(1))(4)(μ(4)-SO(4))][OH](2) (3), [Zn(2)(HL(2))(2)(μ(2)-SO(4))]·2H(2)O (4), [Zn(H(2)L(2))(H(2)O)(2)](SO(4))·0.87H(2)O (5) (H(2)L(1) = 2,6-di-(5-phenyl-1H-pyrazol-3-yl)pyridine, H(2)L(2) = 2,6-di-(5-methyl-1H-pyrazol-3-yl)pyridine), were synthesized hydrothermally from the self-assembly of Zn(II) or Co(II) with different types of bipyrazolyl/pyridine derivative ligands. All the complexes were characterized by elemental analysis, IR and UV-vis spectroscopy, powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction. Structural analyses revealed that metal atoms (Zn and Co) in complexes 1-5 are five-coordination modes, forming slightly distorted trigonal bipyramidal geometries. In complexes 1-3, H(2)L(1) ligand connected the two metal centers via the tetradentate fashion, and the same form of connection was found in complex 4 with H(2)L(2) ligand. While in complex 5, H(2)L(2) only connected with one metal center via the tridentate fashion, which was different from those in complexes 1-4. Additionally, there are abundant hydrogen bonding interactions in complexes 1-4. Interestingly, for hydrogen bonding connecting fashions being different, the molecules for the complexes 1 and 4 are held together by the hydrogen bond to form a 1D supramolecular structure, whereas complexes 2 and 3 are a hydrogen bonded dimer. In addition, quantum chemical calculations for 1, 3, and 4, thermal behaviors and photoluminescent properties for 1 and 3-5 were performed and discussed in detail. In the mean time, we found that these complexes had potential catalytic activity for the oxidation reaction of cyclohexane.     

Dual conductance, negative differential resistance, and rectifying behavior in a molecular device modulated by side groups

We investigate the electronic transport properties for a molecular device model constructed by a phenylene ethynylene oligomer molecular with different side groups embedding in a carbon chain between two graphene electrodes. Using the first-principles method, the unusual dual conductance, negative differential resistance (NDR) behavior with large peak to valley ratio, and obvious rectifying performance are numerically observed in such proposed molecular device. The analysis of the molecular projected self-consistent Hamiltonian and the evolution of the frontier molecular orbitals (MOs) as well as transmission coefficients under various external voltage biases gives an inside view of the observed results, which suggests that the dual conductance behavior and rectifying performance are due to the asymmetry distribution of the frontier MOs as well as the corresponding coupling between the molecule and electrodes. But the NDR behavior comes from the conduction orbital being suppressed at certain bias. Interestingly, the conduction properties can be tuned by introducing side groups to the molecule and the rectification as well as the NDR behavior (peak to valley ratio) can be improved by adding different side groups in the device model.     

Rhodium-catalyzed asymmetric conjugate addition of arylboronic acids to nitroalkenes using olefin-sulfoxide ligands

An efficient rhodium/olefin-sulfoxide catalyzed asymmetric conjugate addition of organoboronic acids to a variety of nitroalkenes has been developed, where 2-methoxy-1-naphthyl sulfinyl functionalized olefin ligands have shown to be highly effective and are applicable to a broad scope of aryl, alkyl, and heteroaryl nitroalkenes.     

食品中痕量危害物分析过程污染的来源和控制

食品中危害物分析日趋痕量化,痕量化学分析因其敏感而易受外部环境的影响发生过程污染。通过对食品中痕量危害物检测过程污染实际案例的分析,发现污染的发生主要来自于实验环境、器具、试剂和过程控制等。探讨建立人员培训,方法学考查,实验环境和实验全过程控制等预防食品中痕量危害物化学分析过程污染的制度,并以此提高食品安全分析实验室检测过程预防污染的水平。     

In vitro growth and activity of chondrocytes on three dimensional polycaprolactone/chitosan scaffolds

Porous polycaprolactone/chitosan blend scaffolds with various compositional proportions were prepared using a particulate‐leaching method. The pore parameters of resultant scaffolds were found to be mainly modulated by porogen. The compressive mechanical properties and hydrophilicity of scaffolds were examined by measuring their compressive modulus and stress strength as well as swelling index. Selected chondrocytes isolated from articular cartilage of knee joints of rabbits were seeded on these scaffolds, and further in vitro cultured for various periods. The growth and activity of seeded cells were estimated by counting numbers of cells proliferated on scaffolds and measuring the amounts of proteoglycans and type II collagen synthesized by the seeded cells. It was found that some scaffolds composed of proper component ratios and having appropriate pore parameters exhibited promising characteristics for the adhesion and proliferation of seeded cells while maintaining the phenotype and activity of the cells. Copyright © 2010 John Wiley & Sons, Ltd.     

Capillary electrophoresis‐laser‐induced fluorescence detection of rat brain catecholamines with microwave‐assisted derivatization

In this study, a rapid and sensitive method is described for the catecholamines detection in rat brain. CE with LIF detection for the determination of FITC derivatized catecholamines (dopamine, epinephrine, and norepinephrine) was demonstrated. Conventional water bath and microwave‐assisted derivatization methods were employed and a significant reduction in the derivatization time from 2 h for the conventional water bath at room temperature (ca. 25°C) to 2 min for the microwave‐assisted derivatization was achieved. Online sample concentration of field‐amplified sample stacking (FASS) method was employed to achieve higher sensitivities (the detection limits obtained in the normal injection mode ranged from 2.6 to 4.5 ng L^?1 and in the FASS mode ranged from 22 to 34 pg L^?1). Furthermore, this microwave‐assisted derivatization CE–LIF method successfully determined catecholamines in rat brain with as low as 100 ng L^?1 (FASS mode) to 10 μg L^?1 (normal injection mode). This CE–LIF method provided better detection ability when compared to the best reports on catecholamines analyses.