Modeling the reaction mechanisms for redox regulation of protein tyrosine phosphatase 1B activity

Protein tyrosine phosphatase 1B (PTP1B) functions by removing the phosphoryl group from tyrosinephosphorylated proteins in insulin signaling and metabolism. The regeneration of the active site involves a sulphenylamide intermediate derived from the intrastrand cross-linking between the catalytic serine and the neighboring backbone nitrogen. Two mechanisms have been proposed for the formation of the sulphenylamide intermediate and the subsequent reactivation of the catalytic site. In the current work, the proposed mechanisms have been investigated by the use of density functional theory calculations. Our results suggest that these two mechanisms have similar overall energy barriers and that the preferred route will be determined by the availability of hydrogen peroxide or other oxidizing reagents.     

心脑血管病患者头发微量元素铜、锌含量调查

调查了心脑血管病患者头发微量元素铜、锌含量，发现患者发现Cu、Zn含量普通遇低于正常值。     

双羟基极性键合固定相在氨基酸分析上的应用

我们曾报道了一类新型双羟基键合固定相(GDSB)的合成,研究表明这类固定相具有键合相浓度高,热和化学稳定性好的特点,可用于性质相似的有机化合物的分离。 本文以GDSB为色谱柱填料,含Cu~(2+)离子和烷基磺酸盐的HAc-NaAc缓冲溶液作流动     

各种氨基酸衍生物在Chirasil—Val固定相上的气相色谱分离

本文叙述氨基酸及其对映体的全氟酰基烷基脂(O-异丙基、-异丁基、-正丁基;N(O,S)-三氟乙酰基,TFA、-七氟丁酰基,HFB)在Chirasil-Val上的洗脱特性。随烷基取代增大,保留时间增加;用HFB代替TFA,对映体的分离因子降低。此外,DL-氨基酸与另丁醇衍生,生成的对映及非对映衍生物在Chirasil-Val上可拆分成四个色谱峰。     

Aerobic oxidation assisted by ligand-free palladium catalysts

Aerobic oxidation of electron-rich benzylic and phenyl allylic alcohols was achieved with high yields with only 0.1 mol.% of Pd(OAc)2 catalyst in the absence of any ligand. This procedure was expected to be valuable for realistic industrial-scale applications from both economic as well as environmental points of view.     

基于Person Ⅶ核函数的支持向量机及其在化学模式分类中的应用

化学模式分类问题通常是非线性的,而且比较复杂,难以用经典统计方法建立分类判别模型。以支持向量机(SVM)构建的分类器具有更好的分类性能。对于非线性分类,SVM通过核函数将其映射到高维特征空间中,然后再进行线性分类。因此,核函数往往是决定SVM非线性分类性能的关键。实际应用时,一般通过选择几种核函数,并对其参数进行优化,然后根据分类器的预测性能来决定,训练过程非常耗时,而且结果难以保证最优。为此,采用一种通用性的核函数,即PersonⅦ核函数(PUKF),它可取代目前常用的几种核函数,可避免SVM非线性分类器训练过程的核函数选择问题。本研究将基于PUKF的SVM分类器应用于两个化学模式分类问题,均取得了较好的结果。对于多类分类,设计了一种子分类器的构造方法,它在分类性能保持较好的情况下,简化了多类分类器结构,大大降低了计算量。     

Study of urinary nucleosides as biological marker in cancer patients analyzed by micellar electrokinetic capillary chromatography

Thirteen normal and modified nucleosides, primarily degradation products of transfer ribonucleic acid (tRNA), were evaluated as potential tumor markers for cancer patients. Their urinary concentrations were determined by means of micellar electrokinetic capillary chromatography (MEKC) in the urine from 54 healthy adults and 70 cancer patients, then quantitatively expressed as a function of creatinine excretion. It was found that urinary nucleosides for cancer patients were on the average significantly higher than those for healthy controls, however, no significant differences were found between male and female or between different ages. Based on 13 urinary nucleoside concentrations, principal component analysis (PCA) could be used to classify 72% of cancer patients from the healthy controls. The present study shows that the precise measurement of urinary nucleosides by MEKC in combining with PCA technique may provide a clinically useful approach for diagnosis of cancer.     

Determination of N-Methylpyrrolidine in Cefepime for Injection by Capillary Electrophoresis with Indirect UV Detection

N-Methylpyrrolidine in cefepime for injection was determined by capillary electrophoresis with indirect UV detection. Best results were achieved with background electrolyte consisting of 10 mM creatinine adjusted to pH 3.8 with formic acid and an applied voltage of 30 kV in a bare fused-silica capillary. Indirect UV detection was performed at a wavelength of 225 nm. The application of a small amount of inlet pressure during the separation assisted the attainment of a stable baseline. The optimized method was validated regarding selectivity, linearity, accuracy, precision, ruggedness, repeatability and detection limits. Careful control of capillary conditioning enabled migration time precision values of <0.2% RSD. The use of an internal standard enabled precision values of <1% RSD to be obtained for peak area ratios.     

Disposable ionic liquid coating for headspace solid-phase microextraction of benzene, toluene, ethylbenzene, and xylenes in paints followed by gas chromatography-flame ionization detection

Solid-phase microextraction (SPME) with a disposable ionic liquid (IL) coating was developed for headspace extraction of benzene, toluene, ethylbenzene, and xylenes (BTEX) in paints. The SPME fiber was coated with IL prior to every extraction, then the analytes were extracted and desorbed on the injection port of gas chromatography, and finally the IL coating on the fiber was washed out with solvents. The coating and washing out of IL from the fiber can be finished in a few minutes. This disposable IL-coated fiber was applied to determine BTEX in water-soluble paints with results in good agreement with that obtained by using commercially available SPME fibers. For all the four studied paints samples, the benzene contents were under the detection limits, but relatively high contents of toluene, ethylbenzene and xylenes (56-271 microg g(-1)) were detected with spiked recoveries in the range of 70-114%. Compared to the widely used commercially available SPME fibers, this proposed disposable IL-coated fiber has much lower cost per determination, comparable reproducibility (RSD < 11%), and no carryover between each determination. Considering that IL possess good extractability for various organic compounds and metals ions, and that task-specific IL can be designed and synthesized for selective extraction of target analytes, this disposable IL coating SPME might has great potential in sample preparation.     

Conformation dependence of electronic structures of poly(ethylene oxide)

The electronic structure of pure poly(ethylene oxide) (PEO) for four different polymeric chain conformations has been studied by Hartree-Fock (HF) and density functional theory (DFT) through the analysis of their valence band photoelectron spectroscopy (VB-PES), X-ray emission spectroscopy (XES), and resonant inelastic X-ray scattering (RIXS). It is shown that the valence band of PEO presents specific conformation dependence, which can be used as a fingerprint of the polymeric structures. The calculated spectra have been compared with experimental results for PEO powder.