Complete 1H and 13C assignments of fluorinated analogs of dehydroepiandrosterone

The complete assignments of all 1H and 13C chemical shifts were made for the fluorinated dehydroepiandrosterone (DHEA) analog fluasterone, 2, and two potential in vivo metabolites 3 and 4. The assignments were made using a combination of one- and two-dimensional NMR techniques (1H, 13C, gDQCOSY, gHSQC, gHMBC). Once the proton chemical shifts were assigned, the stereochemistry of the two hydroxylated analogs was determined using 2D ROESY experiments.     

Determination of 4-aminobutyric acid, aspartate, glutamate and glutamine and their 13C stable-isotopic enrichment in brain tissue by gas chromatography-mass spectrometry

A selected-ion monitoring method was developed for measuring 4-aminobutyric acid, aspartate, glutamate, and glutamine in brain tissue. Natural isotopes of these amino acids and their stable-isotopic enrichment following intravenous infusion of a precursor, [13C]glucose, were quantitated. Frozen mouse brain tissue was homogenized in cold 80% ethanol, and the supernatant, equivalent to 1 mg of wet weight brain tissue, was extracted using solid-phase bonded silica ion-exchange columns. Aspartate and glutamate (dicarboxylic acids) were isolated from strong anion-exchange columns, whereas 4-aminobutyric acid and glutamine (neutral amino acids) were isolated from strong-cation exchange columns. n-Butyl ester pentafluoropropionyl amide derivatives of these amino acids were analyzed by gas chromatography-mass spectrometry using a methane positive chemical ionization mode after gas chromatographic separation on a wide-bore, fused-silica capillary column. The method is applicable to determination of brain concentrations of these amino acids as well as their fluxes following administration of a stable-isotopic tracer.     

相对论平均场理论对Pb同位素位移的研究

运用变形的相对论平均场理论研究了Pb同位素链的基态性质. 对关联的处理采用了BCS方法, 不成对核子的处理运用了“阻塞”法. 计算的结果很好地符合了实验上Pb的平均结合能, 中子分离能, 同位素位移. 接着从原子核的微观结构出发, 比较详细地研究了Pb链同位素位移出现反常扭折这一重要性质的物理机制.