Analysis of oxosteroids by nano-electrospray mass spectrometry of their oximes

A method for the analysis of neutral oxosteroids by electrospray mass spectrometry is described. The oxosteroids are converted into their oximes by treatment with hydroxyammonium chloride in aqueous methanol. Intense peaks corresponding to protonated oxime molecules are observed in nano-electrospray mass spectra. The detection limits for the oximes of progesterone, pregnenolone and dehydroepiandrosterone were 2.5, 5 and 25 pg/microL, respectively, approximately 20 times lower than for the underivatised steroids. The signal intensities were proportional to the concentration of the steroids in the range of 500 to 2.5 pg/microL. Fragmentation by collision-induced dissociation (CID) was studied using oximes of 28 model steroids carrying an oxo group at C-3, C-17 or C-20. Some of the steroid oximes were labelled with deuterium or (15)N. Fragment ions were observed which yielded useful structural information. Upon CID, protonated oximes of 3-oxo-Delta(4)-steroids produced abundant ions by cleavage through the B-ring and by loss of the side chain, while protonated oximes of saturated 3-oxosteroids did not give abundant ions by cleavage through the B-ring. Protonated oximes of 20-oxosteroids unsubstituted at C-21, C-17 or C-16 produced a characteristic ion at m/z 86 containing the side chain, C-16 and C-17. Protonated oximes of steroids containing only a 17-oxo group gave fewer ions of diagnostic value. Coupled with the selective isolation of steroid oximes from a biological matrix this method of derivatisation and CID may be used for the analysis of neutral oxosteroids in biological samples.     

Preparation of 5-substituted 3-aminofuran-2-carboxylate esters

[reaction: see text] An efficient method for the preparation of 3-aminofuran-2-carboxylate esters has been developed. This method is based on the reaction of an alpha-cyanoketone with ethyl glyoxylate under Mitsunobu conditions to produce a vinyl ether in good yield. Subsequent treatment of the vinyl ether with sodium hydride afforded the 3-aminofuran. It was also found that a one-pot procedure using the Mitsunobu reaction followed by cyclization afforded the 3-aminofuran in comparable yield. Currently, this method is limited to the synthesis of 5-alkyl-, 5-aryl-, and 4,5-fused bicyclic furans.     

水相锌二次电池正极材料V2O5/C的电化学性能研究

采用溶胶－凝胶法合成了一种V₂O₅/C复合材料.扫描电镜（SEM）和红外光谱（FTIR）分析表明,这是一种外层V₂O₅胶体包覆内层乙炔分子的多孔复合材料.以V₂O₅/C作正极,锌片为负极,Zn(ClO₄)₂溶液为电解质组成水相锌二次电池,采用循环伏安（CV）和电化学阻抗谱（EIS）等方法研究发现:V₂O₅:C质量比为1:1时电极具有最好的电化学性能,电池开路电压达1.64 V; Zn^2＋能分别在1.01 V和1.26 V处分步嵌入V₂O₅/C结构中A、B两种位置,其嵌入电流密度峰值最高可达70 mA•g^－1,并且具有较好的循环充放电性能;在一定放电深度下,V₂O₅/C电极反应速率受Zn^2＋的扩散过程控制.     

脱氢姜黄烯及其类似物的合成

利用苯乙酮及苯乙酮衍生物,经过傅-克乙酰化反应、偶联反应、Wittig烯化反应,合成了脱氢姜黄烯及其类似物.再经选择性催化氢化反应,可分别得到α-姜黄烯、黄根醇甲醚及姜黄氢醌甲醚.     

(XN)4R4簇合物的结构与化学键

用密度泛函理论,在B3LYP/6-311G水平上,对(XN)4R4 (X=C,Si,Ge;R=H,CH3,NH2,OH)及合成的先驱化合物(XN)2R2进行几何构型、电子结构、振动频率和化学反应焓变等进行了研究.结果表明,(RCN)4比(CNR)4更稳定.所有簇合物的零点能EZP值,R=H时最小,R=CH3时最大,R配位原子依次为C、N和O时,EZP值逐渐减小.     

(ClAlNH)n簇合物的结构与稳定性

用量子化学从头算方法（HF／6－31G）和密度泛函理论（DFT）的B3LYP方法，以6－31G标准基组加一个极化函数，对（ClAlNH)n(n=1-10)簇合物的几何构型，电子结构和红外光谱进行了优化，并讨论了聚合反应（ClAlNH)m→(ClAlNH)n的热力学效应，结果表明，（ClAlNH)n系列簇合物的基态稳定结构为Cs(n=1),D2h(n=2),D3h(n=3),Td(n=4),Cs(n=5),D3d(n=6),Cs(n=7),S4(n=8),D3h(n=9),C2h(n=10,n=2,4,6,8,10等偶数对应的（ClAlNH)n簇化合物的结构比n等于奇数量更稳定。     

Retrieving definitional content for ontology development

Ontology construction requires an understanding of the meaning and usage of its encoded concepts. While definitions found in dictionaries or glossaries may be adequate for many concepts, the actual usage in expert writing could be a better source of information for many others. The goal of this paper is to describe an automated procedure for finding definitional content in expert writing. The approach uses machine learning on phrasal features to learn when sentences in a book contain definitional content, as determined by their similarity to glossary definitions provided in the same book. The end result is not a concise definition of a given concept, but for each sentence, a predicted probability that it contains information relevant to a definition. The approach is evaluated automatically for terms with explicit definitions, and manually for terms with no available definition.     

High-energy collision-induced dissociation of oxosteroids derivatised to Girard hydrazones

Neutral oxosteroids have been derivatised with Girard T and P hydrazine reagents to give the corresponding Girard hydrazone quaternary ammonium salts. Both Girard T (GT) and Girard P (GP) hydrazones of oxosteroids give very intense [M](+) ion signals in electrospray (ES) mass spectra and fragment within the ES interface and collision cell to give characteristic fragment ions. GT and GP derivatives give informative high-energy collision-induced dissociation spectra, from which the structure of the precursor oxosteroid can be determined. Both charge-remote and charge-mediated mechanisms are responsible for the formation of the fragment ions at high collision-energy.     

Critical evaluation of spiking of low-grade ore samples in activation analysis for gold and uranium

In applying non-destructive neutron-activation analysis for gold and uranium in spiked low-grade ore samples, the following extrapolated unspiked concentrations were measured: 0.27₈ ± 0.01₅ ppm gold (chemical assay: 0.20₂ ± 0.02₀ ppm gold); 25.1 ± 1.1 ppm uranium (chemical assay value: 19.5 ±2.0 ppm uranium). Different approaches to the fitting of results, and the influence of spiking non-uniformity, are discussed.     

加速剂对化学镀镍层组成与结构的影响

加速剂对化学镀镍层组成与结构的影响方景礼，武勇，韩克平，张敏（南京大学应用化学研究所配位化学国家重点实验室南京２１００９３）关键词化学镀镍，Ｎｉ０Ｐ合金，加速剂，硫脲化学镀镍磷合金具有耐蚀性、可焊性、厚度均匀和硬度高等优点，已得到广泛应用。为提高生产...