Spectroscopic Studies on the Binding of Kaempferol‐3,7‐α‐L‐rhamnopyranoside to Bovine Serum Albumin

The binding of kaempferol‐3,7‐α‐L‐rhamnopyranoside (KRR) with bovine serum albumin (BSA) was investigated by different spectroscopic methods under simulative physiological conditions. Analysis of ?uorescence quenching data of BSA by KRR at different temperatures using Stern‐Volmer methods revealed the formation of a ground state KRR‐BSA complex with moderate binding constant of the order 10⁴ L·mol^?1. The existence of some metal ions could weaken the binding of KRR on BSA. The changes in the van't Hoff enthalpy (ΔH⁰) and entropy (ΔS⁰) of the interaction were estimated to be ?26.53 kJ·mol^?1 and 3.33 J·mol^?1·K^?1 and both hydrophobic and electrostatic forces contributed to stabilizing the BSA‐KRR complex. According to the F?ster theory of non‐radiation energy transfer, the distance r between the donor (BSA) and the acceptor (KRR) was obtained (r=2.83 nm). Site marker competitive experiments showed that KRR could bind to Site I of BSA. In addition, synchronous fluorescence, UV‐Vis absorption and circular dichroism (CD) results indicated that the KRR binding could cause conformational changes of BSA.     

Simultaneous Detection of Copper,Lead and Zinc on Tin Film/Gold Nanoparticles/Gold Microelectrode by Square Wave Stripping Voltammetry

In this work, three heavy metals (Cu(II), Pb(II) and Zn(II)) in wide potential window were simultaneously detected on tin film/gold nanoparticles/gold microelectrode (Sn/GNPs/gold microelectrode) by the method of square wave stripping voltammetry. The Sn/GNPs/gold microelectrode was fabricated by in situ plating of a Sn film on a gold nanoparticles (GNPs) modified gold microelectrode. The influence of hydrogen overflow on stripping of Zn(II) on the gold microelectrode was reduced by modification of GNPs, which made the stripping potential of target metals shift positively. The interference of sulfhydryl groups was reduced and the selectivity of the microelectrode was improved due to the addition of Sn in the detection solution. After accumulation at ?1.4 V for 300 s in acetate buffer solution (0.1 mol L^?1, pH 4.5), the Sn/GNPs/gold microelectrode revealed a good linear behavior in the examined concentration ranges from 5 to 500 µg L^?1 for Cu(II) and Pb(II), and from 10 to 500 µg L^?1 for Zn(II), with a limit of detection of 2 µg L^?1 for Cu(II), 3 µg L^?1 for Pb(II) and 5 µg L^?1 for Zn(II) (S/N=3). When compared with a Sb/GNPs/gold microelectrode and a Bi/GNPs/gold microelectrode, the Sn/GNPs/gold microelectrode showed the best stripping performance to Cu(II), Pb(II) and Zn(II). As a new type of environment‐friendly electrode, the Sn/GNPs/gold microelectrode has potential applications for detection of heavy metals.     

A molecular dynamics study on permeability of gases through parylene AF8 membranes

The amorphous and crystalline poly‐p‐xylylene (parylene) AF8 membranes are constructed by a novel computational technique, that is, a combined method of NVT + NPT‐molecular dynamics (MD) and gradually reduce the size. The related permeation properties are calculated using Grand Canonical Monte Carlo (GCMC) and NVT‐MD methods. The results show that amorphous and crystalline parylene AF8 membranes have different permeation properties. Compared with amorphous parylene AF8 area, crystalline parylene AF8 membranes provide less walking paths of gases. In parylene AF8 membranes, gases walk front and back among the stable sites for holding the minimal energy. Furthermore, gases walk just along the y axis of crystalline cell, however, randomly in amorphous area. The corresponding permeability coefficients approach the experimental data. Copyright © 2011 John Wiley & Sons, Ltd.     

Binding of Engeletin with Bovine Serum Albumin: Insights from Spectroscopic Investigations

In this paper, several spectroscopic techniques were used to investigate the interaction of engeletin (ELN) with bovine serum albumin (BSA). The analysis of UV–Vis absorption and fluorescence spectra revealed that ELN and BSA formed a static complex ELN–BSA, and ELN quenched the fluorescence of BSA effectively. According to the thermodynamic parameters ΔS ⁰ = 47.27 J·mol⁻¹·K⁻¹ and ΔΗ ⁰ = −10.34 kJ·mol⁻¹, the hydrophobic and hydrogen bond interactions were suggested to be the major interaction forces between ELN and BSA. Raman spectroscopy indicated that the binding of ELN slightly changed the conformations and microenviroment of BSA and decreased the α–helix content of BSA.     

Study on the Failure Factors of Composite Insulation in High-Voltage Storage Capacitors

High-voltage storage capacitors, which have composite insulations of polypropylene film and paper impregnated with oil, are working under charge–discharge mode. The insulations are not only exposed to electrical stress but also to thermal stress. Failure factors of composite insulation in capacitors are analyzed from three aspects: partial discharge (PD), space charge, and thermal factors. In order to investigate the possible influences on the dielectric properties of materials in capacitors, aging tests were conducted on the capacitors. Some parameters were detected in aged capacitors compared with nonaged ones. Experimental results reveal that PD is the key factor leading to the breakdown of the capacitor, space charge is the direct factor that induces the breakdown, and thermal factor just accelerates the degradation process.      

Measurements of the continuum R(uds) and R values in e(+)e(-) annihilation in the energy region between 3.650 and 3.872 GeV

We report measurements of the continuum R(uds) near the center-of-mass energy of 3.70 GeV, the R[uds(c)+psi(3770)](s) and the R(had)(s) values in e(+)e(-) annihilation at 68 energy points in the energy region between 3.650 and 3.872 GeV with the BES-II detector at the BEPC Collider. We obtain the R(uds) for the continuum light hadron (containing u, d, and s quarks) production near the DD threshold to be R(uds)=2.141+/-0.025+/-0.085.     

水溶液中锌电极诱发芳香醛的还原偶联反应

以锌片为电极芳香醛为底物在酸性条件下电合成呐醇,探讨了电流密度、反应时间、盐酸浓度对产率的影响.最佳反应条件如下:电流密度2.4A/dm2,反应时间60min,盐酸用量(5mL)2mol/L,呐醇的产率范围14%～80%.     

铱催化环加成反应的研究进展

过渡金属催化环加成反应是合成单环及多环化合物的重要方法,也是有机化学的研究热点之一.综述了近年来铱催化环加成反应的研究进展,主要包括了[2+2+1],[2+2+2],[4+2],1,3-偶极环加成反应等,及少量关于[3+2+2],[3+2],[5+1]环加成反应的报道,并讨论了部分铱催化环加成反应机理.     

Accurate Quantum Dynamics of the Simplest Isomerization System Involving Double-H Transfer

We perform accurate quantum dynamics calculations on the isomerization of vinylidene-acetylene. Large-scale parallel computations are accomplished by an efficient theoretical scheme developed by our group, in which the basis functions are customized for the double-H transfer process. The \begin{document}$ A_1' $\end{document} and \begin{document}$ B_2'' $\end{document} vinylidene and delocalization states are obtained. The peaks recently observed in the cryo-SEVI spectra are analyzed, and very good agreement for the energy levels is achieved between theory and experiment. The discrepancies of energy levels between our calculations and recent experimental cryo-SEVI spectra are of similar magnitudes to the experimental error bars, or \begin{document}$ \le $\end{document}30 cm\begin{document}$ ^{-1} $\end{document} excluding those involving the excitation of the CCH\begin{document}$ _2 $\end{document} scissor mode. A kind of special state, called the isomerization state, is revealed and reported, which is characterized by large probability densities in both vinylidene and acetylene regions. In addition, several states dominated by vinylidene character are reported for the first time. The present work would contribute to the understanding of the double-H transfer.     

Solvothermal Syntheses and Crystal Structures of Two Thiostannates(IV) [M(tepa)]<Subscript>2</Subscript>(<Emphasis Type="Italic">μ</Emphasis>-Sn<Subscript>2</Subscript>S<Subscript>6</Subscript>) (M = Fe<Superscript>2+</Superscript> and Co<Superscript>2+</Superscript>)

Abstract  

Two new thiostannates [M(tepa)]₂(μ-Sn₂S₆) (tepa = tetraethylenepentamine, M = Fe²⁺ 1 and Co²⁺ 2) were prepared by solvothermal method. Compounds 1 and 2 are isostructural. Both the compounds crystallize in the tetragonal system, space group I41/a (no. 88) with the crystal parameters of 1: a = 25.683(2) ?, b = 25.683(2) ?, c = 9.9860(9) ?, V = 6,586.7(11) ?³, Z = 8, and 2: a = 25.742(3) ?, b = 25.742(3) ?, c = 9.8977(12) ?, V = 6,558.5(14) ?³, Z = 8. The Sn₂S₆ ⁴⁻ anion acts as a bidentate bridging ligand connecting two transition metal complex cations by trans terminal S atoms to form neutral centrosymmetric [M(tepa)]₂(μ-Sn₂S₆) moieties.