硅胶催化的选择性去除N-Boc保护基

发现了在回流的甲苯中, 以硅胶为催化剂, 多种N-Boc保护的伯胺、仲胺、氨基酸的氨基都可以迅速脱除Boc. 该方法具有条件温和、操作简便、反应时间短和产率高等优点. 同时, 其它常用的保护基Cbz和Fmoc等在同样的条件下不受影响.     

Simultaneous Determination of Enalapril and Enalaprilat in Human Plasma by LC-MS: Application to a Bioequivalence Study

A rapid, simple and specific liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method has been developed and validated for the simultaneous determination of enalapril and its major active metabolite enalaprilat in human plasma. Benazepril hydrochloride was used as the internal standard. Plasma was deproteinized with acetone and centrifuged. The supernatant was transferred and evaporated to dryness and the residue dissolved in mobile phase. Samples were separated on a C18 column with a mobile phase of methanol–20 mM ammonium acetate (53:47, v/v) containing 0.15% trifluoracetic acid (v/v) with a pH of 3.0. Enalapril, enalaprilat and the internal standard were measured by electrospray positive selective ion monitoring mode. The method was validated over a linear range of 1.56–400 ng mL⁻¹ and the limits of quantification were 1.56 ng mL⁻¹ for both enalapril and enalaprilat using 0.1 mL plasma. Extraction efficiency was more than 84% and recoveries were in range of 93.65–101.17%. The intra-day relative standard deviations (RSD) were less than 8.16 and 7.05% and inter-day RSDs were within 8.42 and 5.72% for enalapril and enalaprilat, respectively. The storage stability of QC samples was investigated under various conditions. The method was successfully applied for the evaluation of the pharmacokinetics and bioequivalence of enalapril and enalaprilat in 20 healthy volunteers after an oral dose of 20 mg enalapril maleate.     

Inorganic speciation of As(III, V), Se(IV, VI) and Sb(III, V) in natural water with GF-AAS using solid phase extraction technology

The paper presents a procedure for the multi-element inorganic speciation of As(III, V), Se(IV, VI) and Sb(III, V) in natural water with GF-AAS using solid phase extraction technology. Total As(III, V), Se(IV, VI) and Sb(III, V) were determined according to the following procedure: titanium dioxide (TiO₂) was used to adsorb inorganic species of As, Se and Sb in sample solution; after filtration, the solid phase was prepared to be slurry for determination. For As(III), Se(IV) and Sb(III), their inorganic species were coprecipitated with Pb-PDC, dissolved in dilute nitric acid, and then determined. The concentrations of As(V), Se(VI) and Sb(V) can be calculated by the difference of the concentrations obtained by the above determinations. For the determination of As(III), Se(IV) and Sb(III), palladium was chosen as a modifier and pyrolysis temperature was 800 °C. Optimum conditions for the coprecipitation were listed for 100 ml of sample solution: pH 3.0, 15 min of stirring time, 40.0 μg l⁻¹ Pb(NO₃)₂ and 150.0 μg l⁻¹ APDC. The proposed method was applied to the determination of trace amounts of As(III, V), Se(IV, VI) and Sb(III, V) in river water and seawater.     

Ni添加对0.4Zr0.1V1.1Mn0.5Cr0.1合金的相结构和电化学性能的影响

本文通过XRD、SEM、EDS研究了Ti_0.4Zr_0.1V_1.1Mn_0.5Cr_0.1Ni_x(x=0，0.2，0.4，0.6，0.8)合金的相结构和电化学性能。该合金系由BCC结构的V基固溶体主相和六方结构的C14 Laves第二相组成，Ni能够促进第二相的生成，Ni含量的增加导致了各相中的化学组成和晶格参数的变化，并通过电化学方法研究了Ni含量对_0.4Zr_0.1V_1.1Mn_0.5Cr_0.1合金电极的最大放电容量、自放电性能、高倍率放电性能、循环稳定性能等的影响。     

C12-2-En-C12•2Br与SDS混合水溶液的胶团化研究

与[C12H25N＋(CH3)2CH2]2•2Br－(简记为C12-2-C12•2Br)/ C12H25SO4Na(SDS)混合水溶液相比,随着联接链上乙氧基团(E)数目增加,[C12H25N＋(CH3)2]2C2H4(OC2H4)n•2Br－(简记为C12-2-En-C12•2Br, n=2,3)与SDS混合水溶液澄清区域明显增大. C12-2-E3-C12•2Br/SDS混合胶团化过程中二组分产生了协同效应,理论预测在澄清区域所能达到的最小临界胶团总浓度(cmcT,min)= 0.0339 mmol•L－1,对应的SDS在溶液体相中的摩尔分数(x2*)=0.447.当水溶液体相中SDS摩尔分数(x2)=0.5时,混合胶团总聚集数(NT)=36,混合胶团中SDS的摩尔分数(x2M)=0.43.     

涂料中甲醛的分光光度测定新方法

在FeCl3存在的盐酸介质中,甲醛与蛋白胨反应生成紫色化合物,最大吸收波长555 nm,甲醛浓度在1~25μg/10 mL范围内,吸光度与浓度成线性关系,线性相关系数r2=0.9997,检出限0.05μg/mL。用本法测定经活性炭脱色的水溶性涂料中的甲醛含量,回收率为96.46%~103.32%,相对标准偏差(n=6)为1.36%~2.09%。     

合成天然产物曲古抑菌素A的新方法

报道了一条组蛋白去乙酰化酶抑制剂曲古抑菌素A的有效合成路线. 通过L-脯氨酸催化对硝基苯甲醛与丙醛的羟醛缩合反应, 高立体选择性地构建了目标分子的手性中心, 羟醛缩合产物的ee值大于99%, anti∶syn＝16∶1. 随后的合成过程中无消旋化现象, 合成的曲古抑菌素A是单一R型异构体, ee值大于99%.     

Nb 掺杂LiFePO4/C 的一步固相合成及电化学性能

用固相法一步合成了Nb掺杂的LiFePO4/C复合材料, 研究了Nb掺杂量对材料电化学性能的影响. 结果表明, Nb掺杂后LiFePO4/C复合材料的电化学性能明显提高. 在0.5C、1C和2C充放电倍率下, 名义成分为Li0.96Nb0.008FePO4/C正极材料的比容量分别为161、148和132 mAh•g−1, 已达到实用化水平. 阻抗谱和循环伏安特性测试显示, Nb掺杂有效地降低了复合材料电极的阻抗和极化, 说明Nb掺杂的主要作用是提高了LiFePO4的电子电导率.     

Synthesis of Novel Nucleoside Analog （3R）-2,3-Dideoxy-3-（N-hydroxy-N-methylamino）-L-arabinofuranosyl Uracil

The synthesis of novel nucleoside analog (3R)-2,3-dideoxy-3-(N-hydroxy-N-methylamino)-L-arabinofuranosyl uracil was studied. A twelve-step synthetic route, started from L-ascorbic acid, was designed, and the final product was obtained in 20.8% yield.     

De novo sequencing of tryptic peptides sulfonated by 4-sulfophenyl isothiocyanate for unambiguous protein identification using post-source decay matrix-assisted laser desorption/ionization mass spectrometry

A simple method of solid-phase derivatization and sequencing of tryptic peptides has been developed for rapid and unambiguous identification of spots on two-dimensional gels using post-source decay (PSD) matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. The proteolytic digests of proteins are chemically modified by 4-sulfophenyl isothiocyanate. The derivatization reaction introduces a negative sulfonic acid group at the N-terminus of a peptide, which can increase the efficiency of PSD fragmentation and enable the selective detection of only a single series of fragment ions (y-ions). This chemically assisted method avoids the limitation of high background normally observed in MALDI-PSD spectra, and makes the spectra easier to interpret and facilitates de novo sequencing of internal fragment. The modification reaction is conducted in C(18) microZipTips to decrease the background and to enhance the signal/noise. Derivatization procedures were optimized for MALDI-PSD to increase the structural information and to obtain a complete peptide sequence even in critical cases. The MALDI-PSD mass spectra of two model peptides and their sulfonated derivatives are compared. For some proteins unambiguous identification could be achieved by MALDI-PSD sequencing of derivatized peptides obtained from in-gel digests of phosphorylase B and proteins of hepatic satellite cells (HSC).