透射型表面电离源的研制

以镍或铂等高功函数金属网为电离材料制成了间接加热式球形表面电离器，用于溅射型负离子源中，正铯离子流达到ｍＡ级，被溅射的负离子流（如Ｐ）分析后可达５０－６０μＡ。透气的电离表面增加了铯蒸汽的流量，避免了流动缓慢区的形成，并减少了污染。     

Conformational changes of Mal d 2, a thaumatin-like apple allergen,induced by food processing

Mal d 2, a thaumatin-like protein from apple was previously described to react to almost 75% of the apple allergic patient sera. Based on the molecular structure of this protein, the present study focused on the conformational stability of Mal d 2 in relation to in vitro IgE-binding under different physico-chemical conditions and proteolysis. The structural integrity of Mal d 2 was monitored using SDS–PAGE, Western blotting using polyclonal antibodies and human sera, fluorescence spectrometry and circular dichroism. Results confirmed the stability of Mal d 2. However, Mal d 2 was reactive to human serum IgEs mainly after reduction of disulphide bridges fixing the α-helical domain II. Contrary to previous assumptions, the current findings suggest that the allergenic epitopes of Mal d 2 are hidden inside the protein structure and none of the rigorous conditions applied in industrial juice processing or digestive proteolysis enhance or reduce the binding to IgE molecules.     

Structural identification of a new acetildenafil analogue from pre-mixed bulk powder intended as a dietary supplement

An analogue of acetildenafil was detected in an extract of pre-mixed bulk powder. To our knowledge, the powder was destined to be encapsulated and sold as a dietary supplement. The structure was identified by NMR, HR-ESI-MS, ESI-MSⁿ and FTIR analyses. Owing to the inclusion of a hydroxyl group in acetildenafil, the detected compound was called 'hydroxyacetildenafil'. With increasing use of dietary supplements marketed for penile erectile dysfunction, the detection of analogues of sexual performance enhancers is important and timely.     

A study of Si-L and O-K ELNES in plant material: SiO2, Ca- and Zn-silicate in Minuartia

The formation of vacuolar precipitates containing silicon and calcium, as well as the accumulation of metal-silicates in cell walls of Minuartia has been investigated by electron microscopy, energy-dispersive X-ray analysis and electron spectroscopic imaging. The bond state of the elements concerned is examined by analysing energy-loss near-edge structures (ELNES), particularly the Si-L_2,3 and the O-K ELNES. Experimental ELNES results are compared with local densities of unoccupied states calculated by molecular orbital methods and results of XANES calculations.     

Calibration of Electret-Based Integral Radon Monitors Using NIST Polyethylene-Encapsulated 226Ra/222Rn Emanation (PERE) Standards

The recently developed ²²²Rn emanation standards that are based on polyethylene-encapsulated ²²⁶Ra solutions were employed for a first field-measurement application test to demonstrate their efficacy in calibrating passive integral radon monitors. The performance of the capsules was evaluated with respect to the calibration needs of electret ionization chambers (E-PERM^®, Rad Elec Inc.). The encapsulated standards emanate well-characterized and known quantities of ²²²Rn, and were used in two different-sized, relatively-small, accumulation vessels (about 3.6 L and 10 L) which also contained the deployed electret monitors under test. Calculated integral ²²²Rn activities from the capsules over various accumulation times were compared to the averaged electret responses. Evaluations were made with four encapsulated standards ranging in ²²⁶Ra activity from approximately 15 Bq to 540 Bq (with ²²²Rn emanation fractions of 0.888); over accumulation times from 1 d to 33 d; and with four different types of E-PERM detectors that were independently calibrated. The ratio of the electret chamber response E_Rn to the integral ²²²Rn activity I_Rn was constant (within statistical variations) over the variables of the specific capsule used, the accumulation volume, accumulation time, and detector type. The results clearly demonstrated the practicality and suitability of the encapsulated standards for providing a simple and readily-available calibration for those measurement applications. However, the mean ratio E_Rn/I_Rn was approximately 0.91, suggesting a possible systematic bias in the extant E-PERM calibrations. This 9 % systematic difference was verified by an independent test of the E-PERM calibration based on measurements with the NIST radon-in-water standard generator.     

甘遂炮制的电喷雾质谱研究

应用电喷雾质谱(ESI-MS)技术,根据甘遂中巨大戟二萜醇型化合物在质谱中离子强度的变化情况,采用正交实验法,优化甘遂药材醋炒和醋烘两种炮制工艺的最佳炮制条件,并提出醋烘法的炮制工艺。实验结果表明:醋炒最佳炮制条件为30%醋量,闷制24h,100℃炒25min;醋烘最佳炮制条件为30%醋量,闷制24h,110℃烘40min。     

纺织品中致癌性芳香胺的质谱成像

表面解析常压化学电离串联质谱(SDAPCI-MSn)可以在无需样品预处理的条件下直接检测纺织品中存在的致癌性邻甲苯胺。在此基础上,分别以质子化邻甲苯胺(m/z108)及其特征峰碎片离子(m/z91)为探针,对穿过的衣服袖口进行二维质谱扫描,用不同颜色表示袖口上芳香胺信号强度的高低,在无损衣服的情况下获得该袖口上邻甲苯胺的质谱影像,从分子层次上对衣袖中邻甲苯胺的分布进行可视化表达,所成像图的空间分辨率达0.2mm2,对了解致癌性芳香胺在纺织品中的分布具有重要意义。