Fractionation of phosphopeptides on strong anion‐exchange capillary trap column for large‐scale phosphoproteome analysis of microgram samples

It is one of the key issues to develop powerful fractionating method to increase the identification of the low‐abundance phosphopeptides. In this study, a semi‐online 2‐D LC separation strategy based on three‐step fractionation of the enriched peptides on strong anion‐exchange trap column was developed. It was demonstrated that the sensitivity and phosphoproteome coverage obtained by this fractionating method with strong anion‐exchange trap column is much higher than those by the conventional methods based on C18 trap column. In addition, when the same amount of sample was loaded, the number of identified phosphopeptides had increased 108%. Combination of this three‐step fractionation method with RPLC‐MS/MS analysis by 300 min RP‐gradient separation was applied to phosphoproteome analysis of human liver proteins, and 853 unique phosphopeptides was positively identified from 500 μg tryptic digest of human liver proteins. After three cycles' consecutive analyses, 1554 unique phosphopeptides and 1566 phosphorylated sites were totally identified from 735 phosphorylated proteins at a false discovery rate of <1% in about 54 h of analysis time.     

Simultaneous sampling of volatile and non-volatile analytes in beer for fast fingerprinting by extractive electrospray ionization mass spectrometry

By gently bubbling nitrogen gas through beer, an effervescent beverage, both volatile and non-volatile compounds can be simultaneously sampled in the form of aerosol. This allows for fast (within seconds) fingerprinting by extractive electrospray ionization mass spectrometry (EESI-MS) in both negative and positive ion mode, without the need for any sample pre-treatment such as degassing and dilution. Trace analytes such as volatile esters (e.g., ethyl acetate and isoamyl acetate), free fatty acids (e.g., caproic acid, caprylic acid, and capric acid), semi/non-volatile organic/inorganic acids (e.g., lactic acid), and various amino acids, commonly present in beer at the low parts per million or at sub-ppm levels, were detected and identified based on tandem MS data. Furthermore, the appearance of solvent cluster ions in the mass spectra gives insight into the sampling and ionization mechanisms: aerosol droplets containing semi/non-volatile substances are thought to be generated via bubble bursting at the surface of the liquid; these neutral aerosol droplets then collide with the charged primary electrospray ionization droplets, followed by analyte extraction, desolvation, ionization, and MS detection. With principal component analysis, several beer samples were successfully differentiated. Therefore, the present study successfully extends the applicability of EESI-MS to the direct analysis of complex liquid samples with high gas content.

Evolution of the solvent polarity in an electrospray plume

Solvent polarity plays an important role in electrospray ionization-mass spectrometry (ESI-MS), one of the most widely used analytical methods for biochemistry. To have a comprehensive understanding of how solvent polarity affects ESI-MS measurements, we systematically investigated the polarity change in the ESI plume formed from an ethanol solution using laser-induced fluorescence (LIF) spectroscopy. Two solvatochromic dyes (i.e., dyes whose fluorescence emission is sensitive to solvent polarity), Nile red and DCM (4-dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran), were used as probes. The peak emission wavelengths of these two dyes exhibited significant red shifts (8–12 nm) when the measuring spot was moved away from the spray tip and in radial direction in the plume, indicating a dramatic polarity change during shrinking of the droplets. The emission intensities were also measured with a polarity-insensitive dye as a reference. The results are consistent with the peak wavelength measurements. Two key mechanisms responsible for the change of solvent polarity in the plume were considered, water entrainment from the surrounding air and solvent evaporation. Furthermore, quantitative analysis of the solvent polarity change was performed by using the Lippert-Mataga polarity parameter Δf. The value of Δf reached 0.305–0.307 at the periphery of the ESI plume, which means that the solvent polarity in the smaller droplet is close to that of a mixture of 30% water and 70% ethanol (Δf = 0.307), even though the bulk solvent was ethanol containing less than 1% water as an impurity.     

多元电解质溶液表面张力的新型预测方程

将半理想溶液理论和Butler方程相结合建立了预测多元电解质溶液表面张力的新型线性预测方程.新方程可由二元系数据预测多元系的表面张力数据,而不涉及任何多元交互作用参数.利用不同温度下24个混合电解质溶液的表面张力数据对新方程进行了系统检验.结果表明新方程可利用298.15K时二元系的渗透压系数和不同温度下二元系的表面张力数据预测不同温度下高浓度的多元系的表面张力数据,且预测结果与实验数据符合得很好,并且预测结果普遍优于基于Pitzer方程的表面张力模型.     

Synthesis, characterization and applications of vinylsilafluorene copolymers: New host materials for electroluminescent devices

Vinylsilafluorene (VSiF) was successfully synthesized and copolymerized with vinylcarbazole and methyl methacrylate via free radical copolymerization for the first time. The synthesis, photophysical properties, computational modeling studies, and organic light-emitting devices of the VSiF copolymers were presented. The good coordinated photoluminescent (PL) spectra with the absorption of blue light-emitting materials and the high energy band-gap of the VSiF copolymers were observed. Higher triplet band gap (³ E _g) to host the blue phosphorescent emitters and better HOMO and LUMO than PVK for electron and hole injection and transportation of the VSiF model compounds were revealed by density functional theory (DFT) calculations. The preliminary device results in applications of these copolymers as host materials for green phosphorescent emitters demonstrate the copolymers of VSiF and vinylcarbazole have comparable device performance of polyvinylcarazole (PVK), suggesting a bright future of VSiF as building blocks for host materials.     

(4R)-5,5-二甲基-4-苄硫甲基-2-噁唑烷酮的合成

以价廉易得的天然L-半胱氨酸为原料,经巯基保护、酯化、氨基保护、格氏反应及环化等5步反应,合成了一个新的手性助剂(4R)-5,5-二甲基-4-苄硫甲基-2-噁唑烷酮,总收率31%.产物结构经IR,~1H NMR,~(13)C NMR及MS表征.     

聚丙烯酰胺凝胶电泳前活性染料与蛋白质共价染色的条件探索

采用聚丙烯酰胺凝胶电泳前染色法,考察了多种类型活性染料与牛血清白蛋白共价染色的条件.实验发现,活性蓝KN-R型标记效果最佳,其优化标记条件为: pH 10.0, 60 ℃, 50 min,蛋白检出限达200 ng,重复性和测试范围内的定量性较好,可在电泳时直接实时观测,作为蛋白标示剂有一定的应用前景.     

真空蒸馏预富集-电感耦合等离子体发射光谱法测定铂

建立了真空蒸馏预富集-电感耦合等离子体发射光谱法测定铅试样中微量铂的方法.在真空条件下,利用Pb和Pt在较高温度下蒸汽压的差别进行分离,富集后的铂溶解制成溶液后进行电感耦合等离子体发射光谱检测,实现了真空密闭回收铅.针对试样的特点,对真空蒸馏方法理论上的可行性进行研究.结果表明:在蒸馏温度为1250 K,真空度为30 Pa,蒸馏时间为3 h条件下,铂的富集分离效果最好,可富集至99.01%以上.线性范围为0.023～20 mg/L,检出限(3σ)为0.0069 mg/L,对样品测定的相对标准偏差为1.7%(n=6).用本方法对样品中加入的铂标准溶液进行了测定,回收率为99.8%～103.0%.本方法简便快速、无污染,已应用于废电路板贵金属冶余物料中铂的测定.     

高效液相色谱的4种商品手性柱对38种手性化合物的拆分研究

采用纤维素-三(3,5-二甲基苯基氨基甲酸酯)涂敷型手性固定相(Chiralcel OD柱)、直链淀粉-三(3,5-二甲基苯基氨基甲酸酯)涂敷型手性固定相(Chiralpak AD柱)、直链淀粉-三(3,5-二甲基苯基氨基甲酸酯)键合型手性固定相(Chiralpak IA柱)和Pirkle型的(S,S)-Whelk-01手性固定相对38种外消旋体化合物进行手性拆分。实验结果表明,4种固定相的手性识别能力为:OD>AD>IA>(S,S)-Whelk-01,OD固定相的手性识别率达到60%,并且它们之间的手性识别性能还具有一定的互补性。本研究对4种常用手性固定相的拆分能力进行了对比,为拆分手性化合物时有的放矢地选择手性固定相提供了参考。