聚四氟乙烯毛细管在线富集分离痕量钌(Ⅲ)及荧光测定

利用碱性条件下聚四氟乙烯毛细管(PTFEtube)对钌-邻菲罗啉具有富集作用,建立了单道流动注射在线富集分离及检测痕量钌的荧光分析法。本方法考察了毛细管壁、流速、pH值、温度及掩蔽剂EDTA、干扰离子等因素对富集效果的影响。当浓缩液pH值为11.8,邻菲罗啉浓度为1×10-4mol/L,浓缩和洗脱速度为3.8mL/min及EDTA的浓度为2×10-2mol/L时,获得最佳结果。在优化的实验条件下,该方法在0~50ng/L范围内呈良好的线性关系,检出限为0.8ng/L(S/N=3);RSD=2.1%(n=3)。     

Site-specific vibrational dynamics of the CD3zeta membrane peptide using heterodyned two-dimensional infrared photon echo spectroscopy

Heterodyned two-dimensional infrared (2D IR) spectroscopy has been used to study the amide I vibrational dynamics of a 27-residue peptide in lipid vesicles that encompasses the transmembrane domain of the T-cell receptor CD3zeta. Using 1-(13)C[Double Bond](18)O isotope labeling, the amide I mode of the 49-Leucine residue was spectroscopically isolated and the homogeneous and inhomogeneous linewidths of this mode were measured by fitting the 2D IR spectrum collected with a photon echo pulse sequence. The pure dephasing and inhomogeneous linewidths are 2 and 32 cm(-1), respectively. The population relaxation time of the amide I band was measured with a transient grating, and it contributes 9 cm(-1) to the linewidth. Comparison of the 49-Leucine amide I mode and the amide I band of the entire CD3zeta peptide reveals that the vibrational dynamics are not uniform along the length of the peptide. Possible origins for the large amount of inhomogeneity present at the 49-Leucine site are discussed.     

Fabrication of interconnected 1D molecular lines along and across the dimer rows on the Si(100)-(2 x 1)-H surface through the radical chain reaction

To realize nanoscale wiring in two dimensions (2D), the fabrication of interconnected one-dimensional (1D) molecular lines through the radical chain reaction of alkene molecules (CH2=CH-R) on the H-terminated Si(100)-(2 x 1) surface have been investigated using scanning tunneling microscopy (STM) at 300 K. By the judicious choice of R in the CH2=CH-R molecule and by creating a dangling bond (DB) at a desired point using the STM tip, the perpendicularly connected allyl mercaptan (ALM) and styrene lines have been fabricated on the Si(100)-(2 x 1)-H surface. The continuous growth of the styrene line at the end DB of a growing ALM line (or vice versa) does not occur, perhaps, due to steric hindrance or/and interaction between adsorbed molecules.     

Discovery of a potent small molecule IL-2 inhibitor through fragment assembly

Using a site-directed fragment discovery method called tethering, we have identified a 60 nM small molecule antagonist of a cytokine/receptor interaction (IL-2/IL2Ralpha) with cell-based activity. Starting with a low micromolar hit, we employed a combination of tethering, structural biology, and computational analysis to design a focused set of 20 compounds. Eight of these compounds were at least 5-fold more active than the original hit. One of these compounds showed a 50-fold enhancement and represents the highest affinity inhibitor reported against this protein-protein target class. This method of coupling selected fragments with a low micromolar hit shows great potential for generating high-affinity lead compounds.     

Complex-radical terpolymerization of phenanthrene,maleic anhydride,and trans-stilbene

The radical terpolymerization of the donor-acceptor-donor monomer system, phenanthrene (P)—maleic anhydride (M)—trans-stilbene (S), was studied. These monomers are known to be nonhomopolymerizable. The terpolymerization was carried out in p-dioxane and/or toluene at 70°C in the presence of benzoyl peroxide used as the initiator. P and S were found to form charge transfer complexes (CTC) with M in p-dioxane at 35°C. The results obtained are discussed in terms of the free monomer and complex propagation models. It is shown that terpolymerization is carried out at a stage close to binary copolymerization of two complexomers. The reactivity ratio of P … M and S … M complexes was estimated by the Kelen-Tüdös method. Absorbance ratios at 1770 cm^?1 (v_C=0 of anhydride group), 764 cm^?1 (δ_CH in monosubstituted benzene of S), and 820 cm^?1 (δ_CH in disubstituted benzene of P) as a function of terpolymer composition were established. P—M—S terpolymers are shown to have high thermal stabilities. © 1995 John Wiley & Sons, Inc.     

Direct determination of trace aluminum with quercetin by reversed-phase high performance liquid chromatography

The determination of trace levels of aluminum by high performance liquid chromatography (HPLC) with spectrophotometric detection using quercetin, a bioactive substance as a pre-column reagent, is developed in this paper. The Al-quercetin chelate was separated on a reversed-phase ODS column with a mobile phase consisting of 70% water (pH 1.0 with perchloric acid) and 30% methanol, and detected at its maximum of 415 nm. The response was linear over the 1.0×10⁻⁷ to 8.0×10⁻⁵ M concentration range with a detection limit of 5.0×10⁻⁸ M and a relative standard deviation of 1.0% at the 5×10⁻⁶ M level. The analysis was free from common ions except iron, which could be successfully screened by 1,10-phenanthroline. This method has been employed to the determination of Al in environmental and biological samples. Moreover, direct speciation of labile monomeric Al, the toxic form of Al, in natural water by the present technique was explored. The coordination ratio of Al complex with quercetin was also elucidated by HPLC combined with molar ratio method. Only a 1:1 complex was formed. Because quercetin exists in body, a preliminary thinking of in vivo determination of Al is provided in this study.     

Selective chain reaction of acetone leading to the successive growth of mutually perpendicular molecular lines on the si(100)-(2 x 1)-H surface

The successive growth of mutually perpendicular molecular lines from one dangling-bond (DB) site on the Si(100)-(2 x 1)-H surface has been realized through a substrate-mediated chain reaction at 300 K. Among various molecules, acetone molecules undergo the most facile chain reaction with a DB site, which proceeds selectively on the Si(100)-(2 x 1)-H surface, resulting in only single molecular lines in the parallel-row (parallel to the dimer row) direction. The smaller size and higher reactivity of acetone molecules enable us to successively grow a parallel-row acetone line from the end of a cross-row (perpendicular to the dimer row) allylmercaptan line simply by changing the feed of gas molecules into the reaction chamber. Since the length of a molecular line is controlled by the number of gas molecules impinged, it is possible to turn a chain reaction from the cross-row direction to the parallel-row direction at any desired point on the surface. The reaction path of the adsorbing molecules is discussed. The present study provides a new means of fabricating mutually perpendicular molecular lines through a chain reaction initiating at a preselected DB site on the Si(100)-(2 x 1) surface.     

Electric Conductivity of α-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Suspensions in Carbonate and Carbonate-Chloride Melts

The temperature dependence of the specific electric conductivity of suspensions based on carbonate and carbonate-chloride melts immobilized with α-Al₂O₃ powder was studied. For carbonate-chloride melts immobilized with α-Al₂O₃, the decrease in the specific electric conductivity considerably exceeded the effect associated with a decrease in the volume fraction of charge carriers. The Raman spectroscopy and Xray diffraction analysis showed that there was no chemical interaction of α-Al₂O₃ with the carbonate and carbonate-chloride melt that could lead to the formation of additional nonconducting phases in these systems in the temperature range under study.     

Thermal analysis of the oxide–chloride systems GdCl3–Gd2O3 and GdCl3–KCl–Gd2O3

Journal of Thermal Analysis and Calorimetry - The thermal analysis of the oxide–chloride systems GdCl3–Gd2O3 and GdCl3–KCl–Gd2O3 with the Gd2O3 content up to...