Structure elucidation and biomimetic synthesis of hostasinine A, a new benzylphenethylamine alkaloid from Hosta plantaginea

Hostasinine A (1), a benzylphenethylamine alkaloid with an unprecedented skeleton featuring a C-4-C-6 linkage and a nitrone moiety, was isolated from Hosta plantaginea. Its structure was established on the basis of spectroscopic data, and was further confirmed by single-crystal X-ray diffraction. The alkaloid was postulated biogenetically from haemanthidine via N-oxidation and aza-aldol-type condensation and was synthesized biomimetically. The inhibitory activities of 1 on acetylcholinesterase (AChE) and two tumor cell lines (K562 and A549) were also evaluated.     

Study of a new derivatizing reagent that improves the analysis of amino acids by HPLC with fluorescence detection: application to hydrolyzed rape bee pollen

A simple and sensitive method for evaluating the chemical compositions of protein amino acids, including cystine (Cys)₂ and tryptophane (Try) has been developed, based on the use of a sensitive labeling reagent 2-(11H-benzo[α]-carbazol-11-yl) ethyl chloroformate (BCEC–Cl) along with fluorescence detection. The chromophore of the 1,2-benzo-3,4-dihydrocarbazole-ethyl chloroformate (BCEOC-Cl) molecule was replaced with the 2-(11H-benzo[α]-carbazol-11-yl) ethyl functional group, yielding the sensitive fluorescence molecule BCEC–Cl. The new reagent BCEC–Cl could then be substituted for labeling reagents commonly used in amino acid derivatization. The BCEC–amino acid derivatives exhibited very high detection sensitivities, particularly in the cases of (Cys)₂ and Try, which cannot be determined using traditional labeling reagents such as 9-fluorenyl methylchloroformate (FMOC-Cl) and ortho-phthaldialdehyde (OPA). The fluorescence detection intensities for the BCEC derivatives were compared to those obtained when using FMOC-Cl and BCEOC-Cl as labeling reagents. The ratios I _BCEC/I _BCEOC = 1.17–3.57, I _BCEC/I _FMOC = 1.13–8.21, and UV_BCEC/UV_BCEOC = 1.67–4.90 (where I is the fluorescence intensity and UV is the ultraviolet absorbance). Derivative separation was optimized on a Hypersil BDS C₁₈ column. The detection limits calculated from 1.0 pmol injections, at a signal-to-noise ratio of 3, ranged from 7.2 fmol for Try to 8.4 fmol for (Cys)₂. Excellent linear responses were observed, with coefficients of >0.9994. When coupled with high-performance liquid chromatography, the method established here allowed the development of a highly sensitive and specific method for the quantitative analysis of trace levels of amino acids including (Cys)₂ and Try from bee-collected pollen (bee pollen) samples.     

2-[2-(7H-二苯并[a,g]咔唑)-乙氧基]-乙基氯甲酸酯对脂肪胺类化合物的荧光标记及质谱鉴定

利用新型荧光标记试剂2-[2-(7H-二苯并[a,g]咔唑-乙氧基)-乙基氯甲酸酯作为柱前衍生化试剂, 在Eclipse XDB-C8反相色谱柱上,采用梯度洗脱,实现了12种脂肪胺类化合物完全基线分离.检测最佳激发和发射波长分别为300和400 nm.通过荧光检测及离子阱大气压化学电离源(APCI Source)正离子模式实现了在线的柱后质谱鉴定.对土壤中脂肪胺类化合物的测定快速、准确,具有良好的重现性.荧光定量检测的回归系数大于0.9991; 检出限为10.1～0.3 fmol.     

β-二酮、邻菲罗啉分别与铕和铽三元配合物的合成及发光性能研究

为了寻找新的发光材料并研究β-二酮对稀土配合物发光性能的影响, 我们合成了一个新的β-二酮配体: 1-苯 基-3-(对苯乙炔苯基)-1,3-丙二酮(HPPP), 并用HPPP、邻菲罗啉(phen)分别与Eu(III)和Tb(III)反应, 合成了两个新的三元稀土配合物: Eu(PPP)3phen和Tb(PPP)3phen, 通过红外光谱、化学分析、元素分析对三元稀土配合物的组成和结构进行了表征. 研究了配合物的荧光性质, 发现β-二酮配体对配合物的发光有较大影响, 通过量子化学计算对实验结果进行了解释.     

Calorimetric Studies on Enthalpy Relaxation in Maltitol Glass Transition Based on Phenomenological Models

To investigate the enthalpy relaxation behavior of maltitol glass system, differential scanning calorimetry (DSC) was used to obtain the specific heat capacity[C_p(T)] near the glass transition temperature(T_g) at different coo- ling rates ranged between 1 and 20 K/min. Three phenomenological models of enthalpy relaxation, Tool-Narayanaswamy-Moynihan(TNM) model, Adam-Gibbs-Vogel(AGV) model and Gómez Ribelles(GR) model, were used to simulate the experimental data. The models’ parameters were obtained via a curve-fitting method. The results indicate that TNM and AGV models gave the almost identical prediction powers and can reproduce the curves of experimental C_p(T) very well. However, the prediction power of GR model evolved from configurational entropyapproach is not so good as those of TNM and AGV models. In particular, the metastable limit state parameter(δ) introduced by Gómez Ribelles has insignificant effect on the enthalpy relaxation of the small molecular hydrogen-bonding glass system.     

NaA分子筛膜蒸汽渗透促进丙烯酸/乙醇的酯化反应

以对甲苯磺酸为催化剂,利用亲水性NaA分子筛膜蒸汽渗透过程,选择性地将丙烯酸和乙醇酯化反应产物中的水原位分离出反应器,打破反应平衡限制,使反应不断向右进行,反应15 h丙烯酸转化率达到100%。     

乙烯的实验室制备及性质检验的实验改进

在采用乙稀利为原料制备纯净乙烯的研究基础上,从药品配置、实验操作和装置优化等方面对乙烯的实验室制备及性质检验进行了科学改进,希望对高中化学教学有一定的启示作用。     

An experimental investigation of tribological performance of triangular textures in water lubrication regime

Surface texturing has been considered as an effective approach to improve the tribological performances.Based on the consideration of enhancing the tribological performance,the experiments are carried out to investigate tribological performance of triangular textures in water lubrication.The textures are generated by the Nd:YAG laser marking system,with an area density of 20%and a depth of 7 m and are distributed uniformly on the surface of the SiC rings.Compared with the circular textures,the triangular textures have obvious tribological anisotropy.The triangular textures in clockwise direction show the best friction reduction effect among the three textures.The friction reduction mechanisms of the triangular textures in clockwise direction are also analyzed and discussed.     

Effects of carbon sources and carbon contents on the electrochemical properties of LiFePO4/C cathode material

LiFePO₄/C composites are prepared by using two types of carbon source: one using polymer (PAALi) and the other using sucrose. The physical characteristics of LiFePO₄/C composites are investigated by X-ray diffraction), scanning electron microscopy, BET, laser particle analyzer, and Raman spectroscopy. Their electrochemical properties are characterized by cyclic voltammograms, constant current charge–discharge, and electrochemical impedance spectra. These analyses indicate that the carbon source and carbon content have a great effect on the physical and electrochemical performances of LiFePO₄/C composites. An ideal carbon source and appropriate carbon content can effectively increase the lithium-ion diffusion coefficient and exchange current density, decrease the charge transfer resistance (R _ct), and enhance the electrochemical performances of LiFePO₄/C composite. The results show that PAALi is a better carbon source for the synthesis of LiFePO₄/C composites. When the carbon content is 4.11 wt.% (the molar ratio of PAALi/Li₂C₂O₄ was 2:1), as-prepared LiFePO₄/C composite shows the best combination between electrochemical performances and tap density.