Surface plasmon near-field imaging of very thin microstructured polymer layers

We report on the near-field imaging of microstructured polymer layers deposited on an homogeneous metal thin film on which a surface plasmon mode is excited. The microstructures in the polymer layers are designed by electron beam lithography, and the near-field imaging is performed with a photon scanning tunneling microscope (PSTM). We show that, despite their very small height, the microstructures can be conveniently imaged with a PSTM thanks to the field enhancement at the surface of the metal thin film supporting the surface plasmon. The influence of the illumination conditions on the contrast of the PSTM images is discussed. In particular, we show that both the field enhancement and the near-field intensity distribution around the microstructures depend dramatically upon the illumination conditions, leading to the conclusion that the PSTM is well suited for spatially resolved near-field surface plasmon sensing purposes.     

环己烯和2-甲基戊烯-1在几种Y型分子筛上的吸附量热研究

用SETARAM热流式量热计测定了环己烯和2-甲基戊烯-1于室温下在NaY、CaY、R_EY和HY等几种分子筛上的微分吸附热。我们又用Benson基团加合法计算得到了生成仲碳离子和叔碳离子时的吸附热。根据实验测得的于不同吸附量时环己烯和2-甲基戊烯-1的吸附热之差值, 对它们在上述几种Y型分子筛上的吸附机理进行了讨论。     

Investigation of the luminescent properties of terbium-anthranilate complexes and application to the determination of anthranilic acid derivatives in aqueous solutions

The luminescent properties of terbium complexes with furosemide (FR), flufenamic (FF) acid, tolfenamic (TF) acid and mefenamic (MF) acid have been investigated in aqueous solutions. For all four compounds, complexation occurs when the carboxylic acid of the aminobenzoic group is dissociated and is greatly favoured in the presence of trioctylphosphine oxide as co-ligand and Triton X-100 as surfactant. Under optimum conditions, luminescence of the lanthanide ion is efficiently sensitised and the lifetime of the resonance level of terbium in the complex is ranging between 1 and 1.9 ms, against 0.4 ms for the aqua ion. The sensitivity of the method for the determination of anthranilic acid derivatives is improved by one to two orders of magnitude with respect to that achieved using native fluorescence or terbium-sensitised luminescence in methanol. The limits of detection are 2×10⁻¹⁰, 5×10⁻¹⁰ and 2×10⁻⁹ mol l⁻¹ for flufenamic acid, furosemide and tolfenamic acid, and mefenamic acid, respectively, with within-run RSD values of less than 1%. The method has been applied to the determination of flufenamic acid in spiked calf sera with and without sample pretreatment. Depending on the method and the analyte concentration, the recovery was ranging between 83 and 113% and the lowest concentration attainable in serum samples was close to 1×10⁻⁷ mol l⁻¹.     

Novel dual inhibitors against FP-2 and PfDHFR as potential antimalarial agents: Design,synthesis and biological evaluation

A series of novel 2,4-diaminopyrimidine-modified compounds was designed and synthesized. Compound 14 showed micromolar dual inhibitory effect on both FP-2 and PfDHFR, and potential inhibition to the proliferation of P. falciparum 3D7 strain and chloroquine-resistant P. falciparum Dd2 strain.     

水/硅胶吸附体系的热化学研究

我们用精密自动绝热量热计测定了几种不同吸附水含量的水/硅胶吸附体系在200～320 K温度范围内的热容. 结果表明, 当吸附水含量使表面复盖度(θ)大于1时, 在相应的C_p～T曲线上会出现吸附水的相变峰. 这说明吸附在硅胶表面上的水分子已经形成了聚集态; 而当θ<1时, 由于尚未形成聚集态水, 故没有相变过程出现, 其C_p～T曲线呈光滑状. 这些现象与H_2O/γ-Al_2O_3吸附体系是一致的. 又由于硅胶表面对水分子的吸附力较γ-Al_2O_3的要小, 故在同样的吸附量的C_p～T曲线上, 水/硅胶的峰要比H_2O/γ-Al_2O_3的尖锐, 且蜂温增高的速度要快. 这些都表明, 吸附在硅胶表面上的二维表相水会随吸附量的增加而以较快的趋势接近于体相水. 此外, 由不同含水量的C_p～T曲线外推, 求出了不含吸附水的硅胶在200～300 K范围内的热容.     

Structural characterization of phosphatidylcholines by atmospheric pressure photoionization mass spectrometry

The potential of atmospheric pressure photoionization was investigated for the structural analysis of phosphatidylcholine lipids (PCs). [M+H]+ ions of high abundance were obtained, along with several fragment ions. Three of these dissociation products corresponded to quite unusual fragmentation pathways but allowed the determination of both the nature and the position on the glycerol backbone (sn-1 or sn-2) of the fatty acyl chains. The loss of a methyl group from the choline head was also observed. These results suggest a complex ionization mechanism in APPI. However, this method proved to be very powerful for the rapid structural analysis of PC species without using MS/MS experiments.     

High-performance liquid chromatographic determination of cocaine and benzoylecgonine by direct injection of human blood plasma sample into an alkyl-diol-silica (ADS) precolumn

A column-switching high-performance liquid chromatographic method with UV detection for the determination of cocaine (COC) and benzoylecgonine (BZE) in human blood plasma samples is described. The method uses an alkyl-diol-silica ADS-C18 extraction precolumn. A 50- micro L plasma sample was introduced to the ADS precolumn in order to separate the analytes from proteins and endogenous compounds. The fraction containing COC and BZE was back-flushed and transferred to an Alltech mixed-mode C(18)/cation-exchange analytical column for final separation. The validation of the method revealed quantitative recoveries from 95.0 to 99.0% for COC at three different concentrations (0.5, 1.0 and 2.0 micro g mL(-1)), and from 96.0 to 99.0% for BZE at the same concentration levels with coefficients of variation <4.00% (n=5). The detection limit (signal to noise ratio (S/N)>3) was 0.03 micro g mL(-1) for all the compounds with an injection volume of 50 micro L. However, it was possible to enhance the sensitivity further by injecting larger plasma volumes, up to 200 micro L, at the same optimal conditions. The overlap of sample preparation, analysis and reconditioning of the extraction column, increase the overall sample throughput to 5 samples h(-1). The developed method has been applied to human blood plasma samples from subjects suspected of cocaine abuse.     

Synthesis of sugar-based ethenyl ethers through a vinyl bis-sulfone methodology

The recently devised route to ethenyl ethers—i.e. 1,2-bis(phenylsulfonyl)ethylene (BPSE)-mediated conversion of alcohols into β-alkoxyvinyl sulfones followed by reductive desulfonylation—has been applied in the carbohydrate field to the synthesis of a number of vinyl-functionalised monosaccharides, a number of which had not been prepared via alternative routes.     

Purification and Characterization of an Intracellular β-Glucosidase from Lactobacillus casei ATCC 393

The lactic acid bacterium,Lactobacillus casei, produces an intracellular β-glucosidase when grown on Man-Rogosa-Sharpe (MRS) medium with cellobiose as carbon source. The β-glucosidase activity is produced intracellulary, and no extracellulary activity was detected. The enzyme was purified by ion-exchange chromatography and gel filtration. The molecular mass of the purified intracellular β-glucosidase as estimated by gel filtration was 480 kDa, consisting of six probably identical subunits. The enzyme exhibited optimum activity at 35°C and pH 6.3 with citrate-phosphate buffer. The enzyme was active against soluble glycosides with (1→4)-β configuration and from Lineweaver Burk plots, K_m value of 16 mmol/L was found for β-pNPG. The β-glucosidase was competitively inhibited by glucose, and no glycosyl transferase activity was observed in the presence of ethanol.