On the origin of the dynamic Stokes shift of Laurdan molecules in lipid membranes

Frequency-resolved time correlated single photon counting experiments have been performed to investigate the time scales and molecular mechanisms for solvation dynamics of 6-dodecanoyl-2-dimethylaminonaphthalene (Laurdan) embedded in liquid-crystalline bilayers of unilamellar dimyristoyl-phosphatidylcholine (DMPC) vesicles. The reconstructed fluorescence spectra as a function of time exhibit a pronounced double-exponential Stokes shift, which is strongly correlated with the rotational diffusion dynamics of the chromophore as evidenced by experiments on transient fluorescence depolarization.     

基于LFHB 理论模型关联和预测醇+惰性溶剂的1H NMR 化学位移

运用含氢键缔合的格子流体状态方程(LFHB), 仅用一个参数关联了一元醇-惰性溶剂共17个体系29套1H NMR化学位移数据. 并且用关联参数成功预测了不同温度下丁醇+环己烷的化学位移. 所得结果与化学缔合理论的结果进行了比较. 对于某些体系在稀浓度范围LFHB的计算氢键缔合度要低于化学缔合理论的结果. 并且分析了LFHB理论中的物理参数和化学参数对于缔合度计算的不同影响.     

同位素稀释-超高效液相色谱-线性离子阱串联质谱分析谷物及其制品中呕吐毒素及其衍生物和代谢物

建立了谷物及其制品中脱氧雪腐镰刀菌烯醇、3-乙酰脱氧雪腐镰刀菌烯醇、15-乙酰脱氧雪腐镰刀菌烯醇、去环氧脱氧雪腐镰刀菌烯醇的同位素稀释-超高效液相色谱-线性离子阱串联质谱( UHPLC-QTRAP-MS/MS)定性确证和定量测定方法。样品经乙腈-水(84：16, V/V)混合溶液提取,乙腈饱和的正己烷除脂,HLB固相萃取柱净化,Waters Atlantis? T3色谱柱分离,以乙腈-0.02%氨水溶液为流动相进行梯度洗脱,在负离子模式下,采用多反应监测( MRM)-信息依赖性采集( IDA)-增强子离子扫描( EPI)模式检测,在线EPI谱库定性分析,同位素内标定量,在1~300μg/L 浓度范围内,4种目标物的线性相关系数均大于0.999,检出限为0.1μg/kg,定量限为0.3μg/kg,添加5,50和200μg/kg的3个浓度水平,4种目标物的平均回收率均在81.3%~101.7%之间,相对标准偏差均小于5%,将该技术应用于FAPAS阳性玉米质控样品和5种代表性的样品进行测试,结果表明,本方法简单、准确、快速,适用于谷物及其制品中呕吐毒素及其衍生物和代谢物的快速确证和定量测定。     

Characterization of the active phase of NiMo/Al2O3 hydrodesulfurization catalysts

The active phase of the NiMo/Al₂O₃ catalyst for hydrodesulfurization reactions has been investigated in this work. Special attention has been focused on the effect of the order of metal impregnation on the formation of the active phase in the reaction. The Mo and Ni oxides and their sulfides on the alumina were investigated by XPS and DRS analyses. The Ni-Mo oxides or precursor of the active phase which are chemically bonded between Mo and Ni were also confirmed from the binding energy shifts of the XPS peaks. The amount of Ni-Mo oxides was determined after the formation of metal oxides during calcination. The Ni-Mo sulfide (active phase) was then induced through sulfidation. It was important that Mo should be located at the tetrahedral sites on the alumina with a high Mo dispersion. These results indicated that there are two important factors in preparing highly efficient Ni-Mo catalysts; one is that Mo should be located at the tetrahedral coordination on Al₂O₃ in high dispersion (Mo/Al₂O₃) and the other is that the Ni species should be supported on MoAl₂O₄ to form Ni-Mo oxides which change into the Ni-Mo sulfide active sites by sulfidation.     

Improved design of a DFB Raman fibre laser

A Raman fibre laser based on phase shifted DFB structures is modelled for the first time. Using parameters of realistic devices, the model predicts low-threshold and highly-efficient laser output. The change of position and width of the phase shift were found to have a substantial impact on laser performance.     

α-Funktionelle 2-Methylphenylphosphane, 2-(HE?CH2)?C6H4?PH2 (E = O,NR, PH). II. Komplexbildungsverhalten mit den Metallcarbonylen des Cr,Mo, W

α-Functionalized 2-Methyl Phenylphosphines, 2-(HE? CH₂)? C₆H₄? PH₂ (E = O, NR, PH) II. Coordination Behaviour with Metal Carbonyles of Cr, Mo, W The preparation of different carbonyl substituted coordination compounds (M: Cr, Mo, W) of the phosphines 2-(HE? CH₂)C₆H₄? PH₂ (E = O, NPh, PH) is described. In one case, after deprotonation of a PH₂ group a phosphine/phosphide migration of a W(CO)₅ fragment is detected.     

On the possibility of suppression of the self-frequency shift of the cnoidal waves in the medium with delayed nonlinear response by bandwidth-limited amplification

We both theoretically and numerically investigate conditions of the stable balance between competing processes of the Raman self-frequency shift and bandwidth-limited amplification of the periodical cnoidal waves. The dependencies of the initial wave form-factor and frequency shift necessary for the stable balance on the parameter describing degree of localisation of the wave energy are presented.     

关于算子的超等距膨胀

本文研究了算子可超等距膨胀的条件，证明了超等距可膨胀算子有非平凡的不变子空间，并在一定条件下对Ｂｅｒｇｍａｎ空间的乘法算子Ｍｆ１，Ｍｆ２，…；Ｍｆｋ，Ｍｆ，证明了的充分必要条件是ｆ１＝ｆ２＝…＝ｆｋ＝ｆ＝常数．这里ｋ＞２．     

Dynamics ofLens culinaris agglutinin studied by red-edge excitation spectra and anisotropy measurements of 2-p-toluidinylnaphthalene-6-sulfonate (TNS) and of tryptophan residues

The fluorescence of 2-p-toluidinylnaphthalene-6-sulfonate bound toLens culinaris agglutinin and of the Trp residues of the protein was investigated. Red-edge excitation spectra and steady-state anisotropy as a function of temperature indicate that the TNS is bound rigidly. Red-edge excitation spectra, steady-state anisotropy as a function of sucrose and anisotropy decay experiments performed on Trp residues fluorescence prove that the internal fluorophore presents residual motion independent of the global rotation of the protein. Fluorescence anisotropy decay allows to calculate the rotational correlation time (351 ps) of this local motion. Quenching resolved emission anisotropy with iodide gives values equal to 0.257 and 0.112 for the anisotropies of the buried and the surface Trp residues, respectively. This result indicates that the Trp residues present at the surface of the protein have important local motions compared to those embedded in the protein matrix. The results obtained from TNS and Trp residues indicate that the agglutinin has different dynamic domains.     

NMR determination of pKa values of indoloquinoline alkaloids

Malaria is one of the most serious global health problems. Isolating new therapeutic agents with potential antimalarial activity from natural sources or preparing such agents either semisynthetically or synthetically is one strategy for solving the problem of resistance constantly evolving to the drugs currently in use. For alkaloids, the acid–base dissociation constant, pK_a, is an important characteristic, thought to be associated with biological activity. In this contribution, pK_a values for several indoloquinoline alkaloids were determined by using ¹H NMR spectroscopy in a mixture of solvents. The data were recalculated for water solutions using the correction factors reported previously. The structural dependence of the pK_a values for cryptolepine and its isomers neocryptolepine, isocryptolepine and isoneocryptolepine as well as some substituted neocryptolepine derivatives is discussed. Copyright © 2009 John Wiley & Sons, Ltd.