One-step synthesis of PANI/Mn3O4 nanocomposites and evaluation of their electrochemical properties

In this paper, we have developed a simple, facile, and efficient approach to synthesize polyaniline/Mn₃O₄ (PANI/Mn₃O₄) nanocomposites using aniline as a reducer in the presence of KMnO₄ without any additives or templates. The morphology of the composites is characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results demonstrate that the tetrahedral Mn₃O₄ nanoparticles have uniform sizes and are finely dispersed in the PANI matrix. The crystallinity and chemical constituents of the composites are characterized by powder X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR) and UV-vis spectrophotometry. Moreover, cyclic voltammetry (CV) measurements are used to characterize the electrochemical properties of PANI/Mn₃O₄ nanocomposites. The developed materials give a pair of redox peaks and have better operation stability, which indicates that the composites show distinct electrochemical performance. So the PANI/Mn₃O₄ nanocomposites would have potential applications in bioanalysis, biodetection and so on.     

Hadron production at forward rapidity in nuclear collisions at RHIC

The main experimental results obtained by the BRAHMS experiment at Relativistic Heavy Ion Collider (RHIC) for Au+Au collisions at \(\sqrt {s_{NN} } \) =62.4, 200 GeV and d+Au collisions at \(\sqrt {s_{NN} } \) = 200GeV are presented. The m _T spectra and the Gaussian-like rapidity densities of produced pions and kaons in Au+Au central collisions at \(\sqrt {s_{NN} } \) = 200 are GeV shown, and their rapidity densities are compared with results from models. The net-proton yield in the same system is compared with that from AGS and SPS energies to study the high energy collision scenario-transparency and stopping. The rapidity, energy and centrality dependence of the nuclear modification factors in both systems are compared with models to differentiate between the initial and final state effect.     

On-chip chiral separation based on bovine serum albumin-conjugated carbon nanotubes as stationary phase in a microchannel

A novel method of chiral separation based on protein-stationary phase immobilized in a poly(methyl methacrylate) microfluidic chip was developed. BSA conjugated with the shortened carboxylic single-walled carbon nanotubes (SWNTs) was employed as the chiral selector. Successful separation of tryptophan enantiomers was achieved in less than 70 s with a resolution factor of 1.35 utilizing a separation length of 32 mm. This is the first example of chiral separation based on SWNTs-BSA conjugates as stationary phase immobilized in microchip channel. The stability of the stationary phase in the channel was examined by microchip electrophoresis with laser-induced fluorescence detection. Factors that influenced the chiral separation resolution were examined. Under the optimized conditions, the proposed modified chip revealed adequate repeatability concerning run-to-run. These results show that the use of SWNTs-BSA conjugates within microfluidic channels hold great promise for a variety of analytical schemes.     

Unsaturation in binuclear cyclopentadienyliron carbonyls

The binuclear cyclopentadienyliron carbonyls Cp2Fe2(CO)n (n = 4, 3, 2, 1; Cp = eta(5)-C5H5) have been studied by density functional theory (DFT) using the B3LYP and BP86 methods. The trans- and cis-Cp2Fe2(CO)2(mu-CO)2 isomers of Cp2Fe2(CO)4 known experimentally are predicted by DFT methods to be genuine minima with no significant imaginary vibrational frequencies. The energies of these two Cp2Fe2(CO)2(mu-CO)2 structures are very similar, consistent with the experimental observation of an equilibrium between these isomers in solution. An intermediate between the interconversion of the trans- and cis-Cp2Fe2(CO)2(mu-CO)2 dibridged isomers of Cp2Fe2(CO)4 can be the trans unbridged isomer of Cp2Fe2(CO)4 calculated to be 2.3 kcal/mol (B3LYP) or 9.1 kcal/mol (BP86) above the global minimum trans-Cp2Fe2(CO)2(mu-CO)2. For the unsaturated Cp2Fe2(CO)3, the known triplet isomer Cp2Fe2(mu-CO)3 with an Fe=Fe double bond similar to the O=O double bond in O2 is found to be the global minimum. The lowest-energy structure for the even more unsaturated Cp2Fe2(CO)2 is a dibridged structure Cp2Fe2(mu-CO)2, with a short Fe-Fe distance suggestive of the Fe[triple bond]Fe triple bond required to give both Fe atoms the favored 18-electron configuration. Singlet and triplet unbridged structures for Cp2Fe2(CO)2 were also found but at energies considerably higher (20-50 kcal/mol) than that of the global minimum Cp2Fe2(mu-CO)2. The lowest-energy structure for Cp2Fe2(CO) is the triplet unsymmetrically bridged structure Cp2Fe2(mu-CO), with a short Fe-Fe distance (approximately 2.1 A) suggestive of the sigma + 2pi + (2/2)delta Fe[quadruple bond]Fe quadruple bond required to give both Fe atoms the favored 18-electron rare gas configuration.     

Determination of folic acid by capillary electrophoresis with chemiluminescence detection

A rapid and simple method is presented for the determination of folic acid (FA) by capillary electrophoresis (CE) with chemiluminescence (CL) detection. This method was based on enhance effect of FA on the CL reaction between luminol and BrO(-) in alkaline aqueous solution. Optimal separation and determination was obtained with an electrophoretic buffer of 35 mM sodium borate (pH 9.4) containing 0.8 mM luminol, and an oxidizer solution of 1.6 mM NaBrO in 100 mM NaCO(3) buffer solution (pH 12.0). Under the optimal conditions, the determination of FA was achieved in less than 20 min, and the detection limit was 2.0 x 10(-8) M (S/N=3). The relative standard deviations (RSDs) on peak area and migration time were in the 1.5 and 1.1%, respectively. The present CE-CL method was applied to the determination of FA in commercial pharmaceutical tablets, apple juices and human urine.     

Arsenic trioxide targets Hsp60, triggering degradation of p53 and survivin

The mechanisms of action of arsenic trioxide (ATO), a clinically used drug for the treatment of acute promyelocytic leukemia (APL), have been actively studied mainly through characterization of individual putative protein targets. There appear to be no studies at a system level. Herein, we integrate metalloproteomics through a newly developed organoarsenic probe, As-AC (C₂₀H₁₇AsN₄O₃S₂) with quantitative proteomics, allowing 37 arsenic binding and 250 arsenic regulated proteins to be identified in NB4, a human APL cell line. Bioinformatics analysis reveals that ATO disrupts multiple physiological processes, in particular, chaperone-related protein folding and cellular response to stress. Furthermore, we discover heat shock protein 60 (Hsp60) as a vital target of ATO. Through biophysical and cell-based assays, we demonstrate that ATO binds to Hsp60, leading to abolishment of Hsp60 refolding capability. Significantly, the binding of ATO to Hsp60 disrupts the formation of Hsp60-p53 and Hsp60-survivin complexes, resulting in degradation of p53 and survivin. This study provides significant insights into the mechanism of action of ATO at a systemic perspective, and serves as guidance for the rational design of metal-based anticancer drugs.

A highly selective organoarsenic fluorescent probe As-AC and quantitative proteomics were employed to track arsenic-binding and regulating proteins in live leukemia cells. Hsp60 was validated as a new target of ATO.     

Pulsed multi-wavelength excitation using fiber-in-capillary light emitting diode induced fluorescence detection in capillary electrophoresis

A novel instrument was developed using a multi-wavelength pulsed LED array with in-column optic-fiber induced fluorescence detection by capillary electrophoresis. The light from 2 different wavelength LEDs (450 nm and 480 nm) was pulsed for short intervals at high intensity. The beam from each LED was collimated and reshaped with the gradient index (GRIN) lens group to achieve a highly effective coupling between LED light source and an optical fiber. The optical fiber was placed inside the capillary for in-capillary LED-induced fluorescence detection. The advantages of this system were validated by the simultaneous determination of vitamin B2 and fluorescein. Detection limits for vitamin B2 and fluorescein were estimated to be 5 nM and 0.29 nM (S/N = 3), respectively. The relative standard deviations (RSDs, n = 6) of the both compounds for migration time and peak area were better than 0.83%, 2.20% and 1.21%, 2.75%, respectively. The method was applied to the determination of vitamin B2 in commercial tablets and fluorescein in fluorescein sodium injection and the recoveries obtained were in the range of 96.6-102.0% and 99.9-102.8%, respectively. It was also applied to human serum, where the recoveries were found to be in the range of 94.4-97.0% and 92.6-96.4%, respectively. The system has been successfully applied in separation and determination of the both biological samples with acceptable analytical performance.     

1,3-二叔丁基-5,5-二硝基嘧啶烷的合成及反应机理研究

1,3-二叔丁基-5,5-二硝基嘧啶烷(3)是混合炸药含能增塑剂1,3,5,5-四硝基-1,3-二氮杂环环己烷的关键硝化前体. 通过研究3的合成反应机理, 目的是为制备1,3,5,5-四硝基-1,3-二氮杂环环己烷的工艺优化提供理论依据. 以2,2-二硝基-1,3-丙二醇(1)、甲醛和叔丁胺为原料, 通过Mannich缩合反应得到1,3-二叔丁基-5,5-二硝基嘧啶烷. 采用同位素示踪技术以及分离关键中间体对反应机理进行推测. 以氘代甲醛、1和叔丁胺缩合得到氘标记的3, ¹H NMR和MS分析结果表明: 在反应过程中1首先解离生成偕二硝基甲烷和甲醛, 小分子碎片随机组合生成了3. 分离出了关键中间体1-叔丁氨基-2,2-二硝基乙烷. 根据所获得的证据, 推断了3的合成反应机理.     

农药残留与食品安全——由中日间的“毒饺子”事件引发的思考

近年来,农药残留和食品安全问题成为备受关注的研究领域。本文从中日间“毒饺子”事件引发的社会问题,简单介绍了农药与食品安全的关系,概述了甲胺磷农药的结构、性质和致毒机理,介绍了食品中化学农药残留的种类、农药残留污染样品的处理以及减少农药残留污染的对策等内容,并对该领域的发展作了展望。     

Theoretical study of water-assisted hydrolytic deamination mechanism of adenine

The water-assisted hydrolytic deamination mechanism of adenine was studied using density functional method at B3LYP/6-311G(d,p) level. Intrinsic reaction coordinate (IRC) calculations were performed on the transition states to verify whether it is the real transition states that connect the corresponding intermediates. Single-point calculations were carried out on the previous optimized geometries obtained during IRC calculations. The activation energies have also been calculated using G3MP2//B3LYP/6-311G(d,p) method. The water molecules attack the adenine and a tetrahedral intermediate forms. Then, two different intermediates have been obtained through different bond rotations. In pathway a, the second water molecule takes part in the formation of transition state and acts as a bridge to transfer hydrogen atom, while in pathway b, the second water molecule does not involve in the creation of transition state and only acts as a medium. The energy barriers are 23.40 and 37.17 kcal/mol for pathways a and b, respectively. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.