Simple Synthetic Receptors for Aspirin

Shallow methylene‐bridged cavitands appended with simple H‐bond donor/acceptor groups are shown to bind aspirin. The structural features needed in a synthetic receptor for aspirin binding are defined.     

新型中性载体硫氰酸根离子选择电极研究

系统研究了新型Schiff碱[N,N'-双-(4-苯偶氮水杨醛)缩邻苯二胺]过渡金属配合物的阴离子响应行为.实验结果表明,配合物中心金属原子的结构与电极的响应行为之间有非常密切的构效关系,其中Mn(Ⅱ)的配合物对硫氰酸根有优良的电位响应性能和选择性,该电极的线性范围为0.14.3×10^-6mol/L,斜率为-58.0mV/dec.,其反Hofmeister选择性次序为SCN^->I^->Sal^->PhCO₂^->ClO₄^->NO₂^->Br^->Ac^->NO₃^->Cl^-.通过交流阻抗和膜相中荷电离子的添加实验证实,该电极对阴离子的响应系中性载体作用机制.该电极具有读数稳定,选择性和重现性好等优点,可直接应用于废水中硫氰酸盐的测定.     

Correlation of counterions with rodlike macroions as assessed by anomalous small-angle X-ray scattering

We consider the analysis of a rodlike synthetic polyelectrolyte in solution by anomalous small-angle X-ray scattering (ASAXS) in order to elucidate the correlation of the counterions with the highly charged macroion. ASAXS can be applied to these systems because the absorption edge of typical counterions, for example, bromine or iodine ions can be attained by synchrotron radiation. Model calculations using the Poisson–Boltzmann cell model show that ASAXS furnishes two terms caused by the anomalous dispersion of the counterions. The leading terms is a cross-term between the ordinary scattering amplitude of the polyelectrolyte and the real part of the scattering length f ′ of the counterions. A second term refers solely to the anomalous contribution of the counterions, i.e., to f ′ and f ′′ ( f ′′: imaginary part of scattering length). Preliminary data obtained from rodlike synthetic macroions having iodine counterions corroborate the theoretical deductions. They demonstrate that ASAXS is capable of furnishing information that is not available by the ordinary SAXS experiment. Received: 11 December 2000/Accepted: 22 February 2001     

Synchronization dynamics of chemically coupled cells with activator–inhibitor pathways

Systems of interacting cells containing an activator–inhibitor pathway, regulating naturally in their inner parts their end-product concentrations through a sequence of biochemical reactions with feedback-loops: an end-product inhibition of the first substrate, and an autocatalytic activation of the end-product through an allosteric enzyme-mediated reaction are investigated. The individual cells are considered to be identical and are described by nonlinear differential equations recently proposed following the concerted transition model. The chemical and electrical coupling types, realized by exchange of metabolites across concentration of the cells are used in order to analyze the onset of phase and complete synchronization in the biochemical system. It is found that depending on the coupling nature and the range of coupling strength, cells enter into different synchronization regimes going from low-quality to high-quality synchronization. The synchronization manifold's stability is analyzed. The results are supported by numerical simulations using indicators such as the conditional Lyapunov exponents and the rate of change of the Lyapunov function. The results indicate that the system cannot completely synchronize under the single action of the chemical coupling. The combined effect of both chemical and electrical couplings is found to be of capital importance in the onset of complete synchronization and high quality synchronization.     

QS540LA电池板测试仪辅助工艺设备的研制

QS540LA电池测试仪辅助工艺设备的研制,改善了国内电池组件测试系统的自动化现状,提高了相关企业的生产效率,减轻了劳动强度,降低了有效生产成本,解决了国内光伏配套设备的国际接轨问题。     

二甲醚电氧化及其阳极催化剂研究

Anode electro-catalysts for direct dimethyl-ether fuel cell (DDFC), Pt/C, PtRu/C (1∶1) and PtSn/C (3∶2), were prepared by chemical impregnation-reduction method with formaldehyde as the reductant. DME electro-oxidation and adsorption at Pt electrode and Pt electro-catalysts were investigated by Cyclic Voltammetry(CV), Quasi-steady state polarization and Gas Chromatography(GC). CV showed that there were two current peaks of DME electro-oxidation at Pt electrode around 0.8V (vs RHE); DME was adsorbed at Pt electrode more weakly and slowly than oxygen, methanol, even hydrogen; the onset potential of DME oxidation was 50mV less than that of methanol, and DME peak potential 110 mV lower, thus more advantageous for using in fuel cells than methanol. GC showed that small amount of HCHO was generated during DME electro-oxidation. The mechanism of DME electro-oxidation was proposed. Among the three electro-catalysts (Pt/C, PtRu/C and PtSn/C), Pt alloy catalysts, especially PtRu/C, showed a higher performance toward DME electro-oxidation, as in the case of methanol. Temperature experiments showed that both DME electro-oxidation and adsorption on Pt and Pt alloy catalysts were favored with increased temperature.     

葡萄糖在碳纳米管/纳米TiO2膜载Pt复合电极上的电催化氧化

用电化学循环伏安法和计时电位法研究了葡萄糖在碳纳米管／纳米TiO2膜载Pt(CNT／nano-TiO2／Pt)复合电极上的电催化氧化,结果表明,在碱性介质中CNT／nano-TiO2／Pt复合电极对葡萄糖的电氧化具有高催化活性,葡萄糖氧化峰电流密度高达13mA／cm^2,比铂电极上的增大一倍;复合电极性能稳定,抗中毒能力强,不易发生氧化振荡,是葡萄糖燃料电池和葡萄糖传感器的高活性催化电极。     

In Cellulo Generation of Fluorescent Probes for Live-Cell Imaging of Cylooxygenase-2

Live-cell imaging with fluorescent probes is an essential tool in chemical biology to visualize the dynamics of biological processes in real-time. Intracellular disease biomarker imaging remains a formidable challenge due to the intrinsic limitations of conventional fluorescent probes and the complex nature of cells. This work reports the in cellulo assembly of a fluorescent probe to image cyclooxygenase-2 (COX-2). We developed celecoxib-azide derivative 14 , possessing favorable biophysical properties and excellent COX-2 selectivity profile. In cellulo strain-promoted fluorogenic click chemistry of COX-2-engaged compound 14 with non/weakly-fluorescent compounds 11 and 17 formed fluorescent probes 15 and 18 for the detection of COX-2 in living cells. Competitive binding studies, biophysical, and comprehensive computational analyses were used to describe protein-ligand interactions. The reported new chemical toolbox enables precise visualization and tracking of COX-2 in live cells with superior sensitivity in the visible range.     

The Effect of Oleic Acid Emulsification using SPE on Fluorite and Dolomite Flotation**

Collector OA, oleic acid, is widely used industrially for fluorite flotation. Low selectivity, dispersibility and collecting capability of the OA collector are always observed. In this study, compared with flotation of dolomite, a collector mixture of OA and SPE (styrylphenol polyoxyethylene ether) demonstrated significantly better performances for the fluorite. An optimal mass ratio 4 : 1 OA : SPE was found, and the recovery of fluorite was increased from over 85 % to more than 94 % compared with pure OA. Furthermore, the dosage of the collector agent was reduced from 50 mg mL⁻¹ to 20 mg mL⁻¹, which did not negatively impact the recovery of dolomite. The results from the contact angle tests indicated that SPE selectively increased the surface hydrophobicity of fluorite but had little effect on dolomite. Besides, zeta potential measurements and IR analyses revealed that the addition of SPE led to strong chemical adsorption on the surface of fluorite, resulting in a significant difference in the flotation performances of the two minerals. Therefore, SPE-emulsified OA is corroborated to prompt more selectivity and collecting capability on flotation of fluorite over dolomite.     

Protective Effect of Ferulic Acid against Hydrogen Peroxide Induced Apoptosis in PC12 Cells

Ferulic Acid (FA) is a highly abundant phenolic phytochemical which is present in plant tissues. FA has biological effects on physiological and pathological processes due to its anti-apoptotic and anti-oxidative properties, however, the detailed mechanism(s) of function is poorly understood. We have identified FA as a molecule that inhibits apoptosis induced by hydrogen peroxide (H₂O₂) or actinomycin D (ActD) in rat pheochromocytoma, PC12 cell. We also found that FA reduces H₂O₂-induced reactive oxygen species (ROS) production in PC12 cell, thereby acting as an anti-oxidant. Then, we analyzed FA-mediated signaling responses in rat pheochromocytoma, PC12 cells using antibody arrays for phosphokinase and apoptosis related proteins. This FA signaling pathway in PC12 cells includes inactivation of pro-apoptotic proteins, SMAC/Diablo and Bad. In addition, FA attenuates the cell injury by H₂O₂ through the inhibition of phosphorylation of the extracellular signal-regulated kinase (ERK). Importantly, we find that FA restores expression levels of brain-derived neurotrophic factor (BDNF), a key neuroprotective effector, in H₂O₂-treated PC12 cells. As a possible mechanism, FA increases BDNF by regulating microRNA-10b expression following H₂O₂ stimulation. Taken together, FA has broad biological effects as a neuroprotective modulator to regulate the expression of phosphokinases, apoptosis-related proteins and microRNAs against oxidative stress in PC12 cells.