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.     

Room temperature deposition of nanocrystalline cadmium peroxide thin film by electrochemical route

Nanocrystalline cadmium peroxide thin film has been electrodeposited on indium doped tin oxide glass substrate from aqueous solution at room temperature. The grain size of the nanocrystals of the film is estimated from XRD and is about 14 nm. The deposits are decomposed at 228 °C by formation of CdO, releasing plentiful heat at same time. The band-gap of the nanocrystalline CdO film made from decomposition of electrodeposited CdO₂ is around 2.4 eV.     

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.     

Synthesis of indeno-fused derivatives of quinolizinium salts, imidazo[1,2-a]pyridine, pyrido[1,2-a]indole, and 4h-quinolizin-4-one via benzannulated enyne-allenes

The benzannulated enediynyl propargylic alcohol 8 was prepared from 1-bromo-2-iodobenzene by two consecutive Sonogashira cross-coupling reactions. The subsequent transformation to mesylate 9 followed by treatment with 4-substituted pyridines 10 then furnished the benzannulated enediynes 11. On exposure of 11 to triethylamine, the indeno-fused quinolizinium salts 15 were produced in quantitative yield. Presumably the reaction proceeded through a 1,3-prototropic rearrangement to form the benzannulated enyne-allenes 12, which then underwent either a concerted Diels-Alder reaction or a two-step process involving a Schmittel cyclization reaction to form biradical 13 followed by an intramolecular radical-radical coupling to afford 14. A subsequent prototropic rearrangement then produced 15. Similarly, 21a and 21b were produced from 19a and 19b, respectively. The use of the Sonogashira reaction for cross-coupling between 1-iodo-2-(phenylethynyl)benzene (7) and 1-(2-propynyl)-1H-imidazole (25) followed by treatment of the resulting adduct with potassium tert-butoxide gave the indeno-fused imidazo[1,2-a]pyridine 24 in 98% yield. Similarly, the indeno-fused pyrido[1,2-a]indole 32 and 4H-quinolizin-4-one 35 were obtained by starting from 7 for cross-coupling with 1-(2-propynyl)-1H-indole (30) and 1-(2-propynyl)-2(1H)-pyridinone (33), respectively, followed by treatment with potassium tert-butoxide.     

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.     

Multistep purification of an antifreeze protein from Ammopiptanthus mongolicus by chromatographic and electrophoretic methods

Antifreeze proteins (AFPs) are known as thermal hysteresis proteins, which can depress the freezing points of the solution by noncolligative effects, but do not affect the melting points. Although some AFPs have been found in some plants, the identity of most proteins remains unclear, owing to insufficient quantity and quality to characterize them. In this report, we describe the purification of an AFP from the winter leaves of Ammopiptanthus mongolicus using a combination of column chromatography and gel electrophoresis. After homogenization in ascorbate-acid-containing Tris buffers (pH 7.4) the soluble proteins are captured by (diethylamino)ethyl-cellulose 52 material. An elution with 0.1-0.3M KCl leads to a crude active fraction. The crude fraction is further purified on a Superdex 75 prep-grade column and finally a Poros 20HP2 column. A complex, consisting of two proteins with relative molecular masses of 34,700 and 37,100, respectively, in sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, is obtained by this protein purification protocol. The recovery of two proteins from the gel is carried out by electrophoresis. The purified protein, with a molecular mass of 37,100, shows thermal hysteresis activity (THA) and can modify the normal growth of ice crystals. The THA of this purified antifreeze protein is 0.24 degrees C at the concentration of 5 mg/mL.