Asymmetric synthesis of α-aminophosphonates by means of direct organocatalytic three-component hydrophosphonylation

The direct asymmetric three-component reaction of an aromatic (or cinnamic) aldehyde, an amine and a phosphite was investigated by employing chiral Brønsted acid. In general, modest to good enantioselectivities (31%–87% ee) could be obtained in acceptable isolated yields (61%–91%) for a series of substrates.     

Research progress in synthesis and catalysis of polyoxometalates

Polyoxometalates (POMs) form a large class ofmetal oxide cluster type compounds. Their wealthytopology, physical and chemical properties have at tracted increasing interests. In this paper, based onour group’s research, we review the latest progress inthe synthetic chemistry and catalysis of POMs and in troduce some POMs with novel structure and theirderivatives that emerged in 2002—2004. Most of thecited references come from those published in 2003.Due to POMs’superio…     

Research progress in synthesis and catalysis of polyoxometalates

Recent progress in the synthetic chemistry and catalysis of polyoxometalates (POMs) is reviewed. The novel POMs and their derivatives emerging in nearly three years (2002—2004) are introduced, including POMs with novel structure, POMs-organic hybrid compounds and host-guest complexes. Our review is focused on the elaboration of POMs' supramolecular chemistry.     

非司酮对人早孕期绒毛中PGF2α 合成及表达的影响

目的:通过对比观察米非司酮对人早孕期绒毛中前列腺素合成及表达的影响,探讨米非司酮终止早孕的分子机制.方法:采用免疫组化法检测环加氧酶-2(COX-2)及ELISA法检测前列腺素F2α(PGF2α)在米非司酮药流组与人流对照组(孕7～9周各12例)绒毛中表达的差异,了解米非司酮对人早孕期绒毛前列腺素合成及表达的影响.结果:米非司酮药流组滋养细胞中COX-2的表达较人流对照组明显增加(P＜0.01),其PU值(-x±S)分别为(33.52±9.16,13.42±7.53).米非司酮药流组绒毛中PGF2α的表达较人流对照组明显增加(P＜0.01),其质量浓度值(-x±S)分别为(30.14±8.20,15.01±4.14)ng/mL.结论:米非司酮可产生孕酮撤退效应,导致前列腺素合成酶COX-2水平升高,引起PGF2α合成增加,不利于妊娠的维持.     

Preparation of β-SiC by combustion synthesis in a large-scale reactor

The feasibility of 5 kg β-SiC synthesized in one batch was demonstrated through igniting the mixture of Si, C-black and polytetrafluoroethylene (PTFE) under different nitrogen pressures. The effect of experimental parameters, including the contents of PTFE, nitrogen pressure, preheating, and raw materials distribution forms were investigated. The results show that the products are β-SiC with equiaxed grains. The average grain size is less than 200 nm. The powders loaded loosely promote reaction heat dispersing, resulting in small grains. High purity β-SiC powders are obtained when the PTFE content is as low as 5wt%, which simplifies the process and decreases the cost effectively. The ceramic sintered from the obtained β-SiC powders presents the hardness of 22.20 GPa, the bending strength as high as 715.15 MPa and the fracture toughness of 8.179 MPa·m1/2, which are higher than those of ceramics fabricated with α-SiC produced by combustion synthesis.     

Protein synthesis inhibition in the basolateral nucleus of amygdala facilitates extinction of auditory fear memory

It is known that consolidation of fear conditioning requires de novo protein synthesis in the amygdala. However, there is controversy about the role of protein synthesis in post-retrieval extinction of fear memory. The present study investigated the effect of protein synthesis inhibition (PSI) in the baso- lateral nucleus of amygdala (BLA) on post-retrieval extinction of auditory fear memory. Intra-BLA infu- sion of the protein synthesis inhibitor anisomycin ‘0’ h post-retrieval facilitated the extinction, but was ineffective if the memory was not retrieved. Anisomycin had no effect on the extinction when it was infused 6 h post-retrieval. The present results suggest that there exists a protein-synthesis-dependent mechanism in the BLA that retards extinction of auditory fear memory.     

Ultrasonic synthesis of poly（2-methoxy-5-butoxy） phenylene vinylene

A new method was developed using ultrasonic irradiation to synthesize poly(2-methoxy-5-butoxy) phenylene vinylene from p-methoxy phenol (MOPh) and CH3 (CH2)3Br.Ultrasonic irradiation catalyzes the reactions through three major steps of etherification, bischloromethylation and elimination. Results showed that our ultrasonic irradiation method could significantly enhance production yield and reduce process time of the synthesis compared with reflux agitating method.     

Static synthesis of high-quality MCM-22 zeolite with high SiO2／Al2O3 ratio

We demonstrate a synthesis method to broaden the range of SiO2/Al2O3 ratio (30-100) of high-silica MCM-22 zeolites by prolonging the aging time of the gel before the crystallization. The synthesis conditions such as silica sources, chemical compositions of initial gel and aging time of gel were investigated in detail.High quality MCM-22 products with various morphologies have been synthesized by optimize their synthesis conditions.Our results show that increasing of the aging time can make the gel be homogenization and promote their nucleus formation,which may avoid the formation of impurity phase and thus broaden the range of SiO2/Al2O3 ratio.     

Investigation on the key factors in the hydrothermal synthesis of BN： The way of introducing sodium azide

The way of introducing sodium azide (NaN_3) into the reaction solution played an important role in the preparation of cBN by hydrothermal synthesis method. The results showed that both cBN content and crystalline perfection of the samples improved with increasing R_N value, and pure cBN could be obtained at 300℃ and 10 MPa when R_N increased to 3:1. Here R_N is defined as R_N =NaN_3(I)/NaN_3(II), wherNaN_3(I) denotes the amount of NaN_3 (in molar) that is added into the autoclave at the beginning of threaction process, and NaN_3(II) is the amount of NaN_3 (also in molar) introduced into the autoclave ahigh temperature and high pressure (i.e. 300℃ and 10 MPa). In order to explain the experimental results, a preliminary model was proposed in this paper.     

Investigation on the synthesis mechanism of β-FeSi2 prepared by pulsed laser deposition

The FeSi2 target alloy was fabricated by conventional powder metallurgy technology, and then, β-FeSi2 thin films was successfully prepared by pulsed laser deposition (PLD). X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were used to characterize the structure, composition, and their changes in the process of β-FeSi2 preparation. In addition, a laser sintering process was also employed to prepare FeSi2 alloy. The analysis of radiation heat transfers in different-sized FeSi2 melt indicates that the cooling rate of the melt depends on the size, i.e., the cooling rate of the micron sized melt is 103 times greater than that of the millimeter-sized melt. The product α-FeSi2 by laser sintering and β-FeSi2 by PLD reveals the different phase transition process in crystallization of milli-meter-sized and micron-sized (or submicron-sized) FeSi2 melt. The results of PLD preparation process shows that β-FeSi2 could be pre-pared through a liquid-phase sintering, followed by a rapid cooling.     

Dissociation of NO2 in femtosecond intense fields

The study of molecules in strong laser fields is a challenging topic in molecular science[1―10]. With the advent of short-pulse lasers, the behavior of molecules can be explored on the time scale of vibrational mo-tions. An intense and linearly polarized…     

Morphology controllable synthesis of Pd/CeO2–ZrO2 catalysts and its structure-activity relationship in three-way catalytic performance

CeO₂–ZrO₂ mixed oxides with controlled morphologies(i.e., nanorod, nano-polyhedral and disordered shape)were synthesized through either hydrothermal or coprecipitation method, and the corresponding supported Pd/CeO₂–ZrO₂ catalysts were also prepared by conventional impregnation. The obtained catalysts were subjected to systematic structural/physio-chemical characterizations as well as three-way catalytic performance evaluations.The results showed that ...     

Involvement of Oxidative Stress and Down-Regulation of Bcl-2 in Arachidonic Acid-Induced Apoptosis in HUVECs

0IntroductionAraacicdhi,diosn fiocu ancidd p(reAdAo)m i,naanntelsys eantt itahle p sonl-y2u npsoastiutiroante doff actetl-ylular phospholipids . Normal free AAconcentrationin humanblood ranges from5 .8μmol/Lto 49 .3μmol/L[1].It is re-leased mostlythroughactivation of phospholipase A2by physi-ological and pathological sti muli[2]. Free AAcan be metabo-lizedinto various eicosanoids via specific enzymes such as cy-clooxygenases ( COX) , lipoxygenase and cytochromesP-450[3]. During AA met…     

Effects of H_2O_2 on Oxygen Supply in the Process of DCA Fermentation

IntroductionLong chainα,ω- dicarboxylic acids (DCA ) areversatile chemical intermediates used as rawmaterials for the preparation of perfumes,polymers,and adhesives[1] .Various strains of C.tropicalis are known to produce DCA whencultured with alkanes or fatty acids as the carbonsource[2 ,3] .　During aerobic and viscous fermentation,theoxygen supply is of crucial importance becauseinsufficient oxygen can lead to suboptimalproductivities[4 ] as well as products of low quality.Several meth…     

The synthesis of sphericalcal cium carbonate composite in amphiphilic PS-b-PAA solution and its thermal dynamic characteristic

Spherical calcium carbonate composite is synthesized in the solution of amphiphilic block copolymer of polystyrene(PS) and poly(acrylic acid)(PAA). SEM and XRD measurements show that the diameter of the particulates decreases with the augment of the PS-b-PAA concentration,crystalline in the composite is calcite and its morphology as well as the structure is changed too. TG-DTA together with IR analysis is applied to investigating the thermal dynamic behavior of the composite. The results show that the composite is mainly composed of two phases, that is, the nanocrystalline calcium carbonate and the PS-b-PA-Ca composites. PS phase decomposes first with a large heat release at about 330℃. However, the PAA chains have relatively high thermal stability, probably due to the structural Ca-O bond,and decomposes at above 400℃. Matching opinions are used to explain the possible reasons for the regular as well as the particular characteristics of the composite corresponding to a certain copolymer concentration.     

Unfolding of C2A Domain of Synaptotagmin I in the Presence of Guanidine Hydrochloride

The C2 domain originally referred to the second of four constant structural motifs in protein kinase C (PKC). Now this domain represents a large structural family sharing a homologous dimensional structure in many proteins that play important roles in many organisms. The C2A domain is one of the two C2 domains of synaptotagmin I involved in the Ca^2 regulation of exocytosis. This domain is mostly composed of β-sheet except for a small fraction of α-helix, and therefore provides an ideal model for a protein folding study. In this report, the unfolding equilibrium of the C2A domain in guanidine hydrochloride (GdnHCI) containing solutions has been studied using ultraviolet (UV) difference spectrum, fluorescence spectrum, size exclusion chromatography (SEC), and circular dichroism (CD) spectrum. The results suggest that unfolding of the C2A domain occurs as a two-state process during GdnHCI titration. By examining the changes of both tertiary structure and secondary structure, no intermediates could be detected during this unfolding study. However, it has been found that the native state of the C2A domain has a large hydrophobic surface. This result suggests that as a fragment of a protein, the C2A domain itself may exist in a state with large hydrophobic surface. This hydrophobic surface may be the molecular basis for interaction between domains in the whole protein.Furthermore, the hydrophobic behavior may play a role during the oligomerization of svnaptotagmin.     

Protein tyrosine phosphatases involved in signaling of the ABA-induced H2O2 generation in guard cells of Vicia faba L.

Although protein tyrosine phosphatases (PTPases) play an important role in signal transduction in animal cells, little is known about the function of PTPases in higher plants. Hydrogen peroxide (H2O2) and mitogen-activated protein kinases (MAPKs) are the critical components of ABA signaling pathway in guard cells. PTPase is an important regulator of MAPK, which is believed to mediate ABA-induced H2O2 generation in guard cells of Vicia faba L. Here, we investigate the possible role of PTPases in stomatal movement process. Phenylarsine oxide (PAO), a specific inhibitor of PTPases, could prevent ABA or H2O2-induced stomatal closure of Vicia faba L; furthermore, it could promote opening of the stomata closed by ABA or H2O2. The activity of PTPases can be effectively inhibited by PAO and H2O2. DTT had no effect on the PAO-induced inhibition of PTPases activity, but it could relieve the inhibition of H2O2 on PTPases activity. PAO could also inhibit the ABA-induced H2O2 generation in guard cells of V‘wia faba L. These results suggested that PTPases is a critical signaling component in ABA-induced stomatal closure, and serve as targets for H2O2 lying on the signaling pathways downstream of ABA induced H2O2 generation.     

Hydrothermal synthesis, characterization and nonlinear optical effect of orthorhombic phase Ca2B6O11 · H2O

Hydrothermal treatment of calcium oxide and boric acid mixtures at temperatures between 234 °C and 300 °C has produced a colorless, transparent, orthorhombic compound Ca₂B₆O₁₁ · H₂O. Of the seven known members of the series of hydrated dicalcium hexaborate containing boron-oxygen six-membered ring anionic group (B₃O₈)^-7, only the title compound has been found to have the nonlinear optical effect. The second harmanic generation (SHG) effect of its crystal is larger than that of KH₂PO₄ (KDP). The reflection spectrum has shown that this compound has no absorption in the experimental wavelength range (800–240 nm). Its crystal structure is favorable for generating the nonlinear optical effect.