A molecular approach to rationally constructing specific fluorogenic substrates for the detection of acetylcholinesterase activity in live cells,mice brains and tissues

Acetylcholinesterase (AChE) is an extremely critical hydrolase tightly associated with neurological diseases. Currently, developing specific substrates for imaging AChE activity still remains a great challenge due to the interference from butyrylcholinesterase (BChE) and carboxylesterase (CE). Herein, we propose an approach to designing specific substrates for AChE detection by combining dimethylcarbamate choline with a self-immolative scaffold. The representative P10 can effectively eliminate the interference from CE and BChE. The high specificity of P10 has been proved via imaging AChE activity in cells. Moreover, P10 can also be used to successfully map AChE activity in different regions of a normal mouse brain, which may provide important data for AChE evaluation in clinical studies. Such a rational and effective approach can also provide a solid basis for designing probes with different properties to study AChE in biosystems and another way to design specific substrates for other enzymes.

In this work, a new approach was developed for designing the representative P10 with high selectivity and sensitivity for imaging AChE activity in the cells and normal mouse brain.     

高质量AlPO4-5分子筛单晶的螯合剂法合成与表征

考察了几种螯合剂对AlPO4-5分子筛单晶合成的影响，结果表明，用邻苯二酚，乙酰丙酮，水杨醛为螯合剂可以得到高质量的，尺寸较大的分子筛单晶，其作用机理可能与它们加入到分子筛合成体系中，改变了溶胶中铝的配位数或产生了铝的螯合物有关。     

Quantitative analysis of 23-hydroxybetulinic acid in mouse plasma using electrospray liquid chromatography/mass spectrometry

23-Hydroxybetulinic acid is a newly isolated derivative of betulinic acid. The agent exhibits potential anti-tumor activity and functions in this regard via apoptosis. In support of pharmacokinetic and toxicological evaluations, a new assay based on liquid chromatography/mass spectrometry (LC/MS) was developed for the quantitative analysis of 23-hydroxybetulinic acid. Sample preparation consisted of extraction of the plasma by the addition of methylene chloride followed by centrifugation. Aliquots of the supernatant were analyzed using an isocratic reversed-phase high-performance liquid chromatography (HPLC) system coupled to a negative ion electrospray mass spectrometer. Molecules of 23-hydroxybetulinic acid and the internal standard limonin were detected using selected ion monitoring at m/z 471 and 469, respectively. The limit of detection of 23-hydroxybetulinic acid was 0.05 pg (0.11 fmol) injected on-column (10 pg/mL, 5 microL injection volume), and the limit of quantitation was 10 pg (21.19 fmol, 2 ng/mL, 5 muL injection volume). 23-Hydroxybetulinic acid was stable in plasma samples at -20 degrees C for at least 3 weeks. The intra-day and inter-day coefficients of variation of the assay were 3.0 and 4.8%, respectively. The utility of the assay was demonstrated by measuring 23-hydroxybetulinicacid in mouse plasma following intragastric administration (IG) in vivo. Pharmacokinetic parameters were calculated using the 3P97 pharmacokinetic software package. A two-compartment, first-order model was selected for pharmacokinetic modeling. The result showed that after IG of 200 mg/kg 23-hydroxybetulinic acid, the plasma concentrations reached peaks at 2 h with C(max) of 3.1 microg/mL. The 200 mg/kg 23-hydroxybetulinic acid suspension IG doses were found to have long elimination half-lives of 25.6 h and low bioavailability of 2.3%. No interference was noted due to endogenous substances. These analytical methods should be of value in future studies related to the development and characterization of 23-hydroxybetulinic acid.     

Comparative Studies on the Deactivation and Regeneration of TiO2 Nanoparticles in Three Photocatalytic Oxidation Systems: C7H16, SO2, and C7H16-SO2

Three photocatalytic oxidation (PCO) systems: C₇H₁₆-O₂, SO₂-O₂ and C₇H₁₆-SO₂-O₂ were carried out with the aid of UV-illuminated TiO₂ nanoparticles at room temperature in a batch reactor. In C₇H₁₆-O₂-TiO₂ system, no catalyst deactivation was observed, while for SO₂-O₂-TiO₂ and C₇H₁₆-SO₂-O₂-TiO₂ systems, the photocatalytic activity of used TiO₂ powder showed decreasing and eventually no activity after used consecutively. The reaction products such as sulfur trioxide or sulfuric acid adsorbed onto the surface of TiO₂ catalyst were poisoning species. Photocatalytic activity of the deactivated TiO₂ powder could be regenerated by sonicating treatment with water and methanol for the two systems, respectively.     

Rapid determination of volatile constituents of Michelia alba flowers by gas chromatography-mass spectrometry with solid-phase microextraction

The volatile constituents of Michelia alba flowers, including fresh flowers, frozen flowers and withered flowers, were investigated by GC-MS. The volatiles in a simulated natural environment were sampled by solid-phase microextraction (SPME), with a 100 microm polydimethylsiloxane fiber at 25+/-5 degrees C for 4 h. The fibers were desorbed in a GC injection liner at 250 degrees C for 3 min. With headspace SPME-GC-MS analysis, 61 peaks were separated. The main compounds in headspace of fresh Michelia alba flowers included alpha-myrcene, (S)-limonene, (R)-fenchone, linalool, camphor, caryophyllene, germacrene D, etc., a greater number of compounds than for frozen flowers and withered flowers. At the same time, the biomarkers of fresh flowers were compared with the frozen flowers and withered flowers. In this study, headspace SPME-GC-MS afforded a simple and more sensitive sampling method for fresh Michelia alba flowers and other fresh flowers.     

氨基酸在乙醇/磷酸氢二钾双水相体系中分配行为

研究了5种结构和性质各异的氨基酸(谷氨酸,半胱氨酸,苯丙氨酸,赖氨酸,精氨酸)在亲水性有机溶剂乙醇和磷酸盐溶液形成的乙醇/K2HPO4双水相体系中的分配行为及其影响因素。当双水相体系中乙醇的质量分数从22%增加到30%时,半胱氨酸和苯丙氨酸的分配系数明显增大,其它三种氨基酸的分配系数变化幅度不大;当磷酸盐的质量分数从14%增加到22%时,氨基酸的分配系数的变化均不明显;双水相体系的pH值对氨基酸的分配系数影响较大,当pH增加时,5种氨基酸的分配系数均增加,但是当pH约为9.5时,苯丙氨酸、半胱氨酸的分配系数接近相等但与其它3种氨基酸的分配系数相差较多,当pH为6.0~8.0时,苯丙氨酸的分配系数远远大于另外4种氨基酸。氨基酸的支链结构中含有非极性基团将导致其分配系数的增加。     

Stochastic resonance is applied to quantitative analysis for weak chromatographic signal of glyburide in plasma

Based on the theory of stochastic resonance, a new method carried on the quantitive analysis to weak chromatographic signal of glyburide in plasma, which was embedded in the noise background and the signal-to-noise ratio (SNR) of HPLC-UV is enhanced remarkably. This method enhances the quantification limit to 1 ng ml⁻¹, which is the same as HPLC-MS, and makes it possible to detect the weak signal accurately by HPLC-UV, which was not suitable before. The results showed good recovery and linear range from 1 to 50 ng ml⁻¹ of glyburide in plasma and the method can be used for quantitative analysis of glyburide.     

A modulated dsc study on the in situ polymerization of cyclic butylene terephthalate oligomers

The polymerization of a cyclic butylene terephthalate (CBT) oligomer was studied as a function of temperature (T=200 and 260°C, respectively) by modulated DSC (MDSC). The first heating was followed by cooling after various holding times (5, 15 and 30 min) prior to the second heating which ended always at T=260°C. This allowed us to study the crystallization and melting behavior of the resulting polybutylene terephthalate (PBT), as well. In contrary to the usual belief, the CBT polymerization is exothermic and the related process is superimposed to that of the CBT melting. The melting behavior of the PBT was affected by the polymerization mode (performed below or above the melting temperature of the PBT product) of the CBT. Annealing above the melting temperature of PBT yielded a product featuring double melting. This was attributed to the presence of crystallites with different degrees of perfection. The crystals perfection which occurred via recrystallization/remelting was manifested by a pronounced exothermic peak in the non-reversing trace.     

基于三维静电势参数研究C60溶解性的构效关系

在量子化学从头算基础上,对一系列溶剂化合物分子进行了结构优化和三维静电势参数计算,运用多元线性回归分析和神经网络方法对C60在121种不同溶剂的溶解性与计算的结构参数进行了构效关系研究.用建立起来的QSPR 关系式对15种不同结构类型溶剂进行了预测,并阐述了C60溶质与不同溶剂之间的相互作用,获得了满意的结果.