Modification of β2 I by glutardialdehydeI by glutardialdehyde

Autoantibodies from patients with antiphospholipid syndrome (APS) recognize an epitope on β₂glycoprotein I (β₂GPI) only when native β₂GPI is adsorbed on surfaces composed of anionic phospholipids or oxidized polystyrene, β₂GPI was modified with the crosslinking agent, glutardialdehyde (GDA), which induced exposure of the anti-β₂GPI epitope at GDA: β₂GPI mol ratios in the range of 500–2000. A second crosslinking agent, dimethyl-suberimidate (DMS), did not expose the epitope, which may be a consequence of its having less tendency than GDA to form intermolecular links. SDS-PAGE experiments demonstrate that GDA does promote extensive intermolecular crosslinking of β₂GPI, and DMS does not. Formaldehyde also reacts with the lysine residues of β₂GPI, but does not expose the epitope. The circular dichroism spectra of native and modified β₂GPI confirm that GDA induces changes in conformation that are qualitatively different from those caused by formaldehyde. These data provide evidence that binding of lysine residues is not a sufficient condition for exposure of the autoepitope, and also support the likelihood that β₂GPI antibodies bind only to aggregates of the protein. Thus, by synthesizing an active holoantigen of β₂GPI, conditions were defined that are necessary for binding of human autoantibodies. The authors also suggest that treatment of phospholipid-binding proteins with chemical agents might provide a strategy to modify their structure and permit exposure of epitopes, resulting in synthetic antigens for therapeutic and diagnostic use.     

Enantiomer separation by CEC——Enantiomer separation by packed-capillary electrochromatography

Three chiral compounds were successfully separated in a short time with two enantiomer separation models on packed-capillary electrochromatography (CEC). (i) 75 μm I.D. capillaries were packed with 5 μm β-cyclodextrin (β-CD) chiral stationary phase (CSP). Effects of voltage, pH and concentration of organic modifier on electroosmotic flow (EOF) and chiral separations were investigated systematically. Enantiomers of a neutral compound (benzoin) and a neutral drug (mephenytoin) were separated within a short time with high efficiency. Efficiency of 32 000 theoretical plates per meter and resolution (R_s) of 1.42 were achieved for enantiomers of benzoin using a βCD packed column with 6.2 cm packed length. Efficiency of 45 000 theoretical plates per meter and R_s of 3.40 were obtained for enantiomers of mephenytoin. Especially, the enantiomer separation of mephenytion was performed in just 3.4 min with R_s of 2.60. (ⅱ) 75 μm I.D. capillary was packed with octadecylsilica particles (ODS). Chiral separat     

CO2 activation by metal−ligand-cooperation mediated by iridium pincer complexes

Abstract

Herein we report the reversible activation of CO₂ by the dearomatized complex [(^tBuPNP*)Ir(COE)] (1) and by the aromatized complex [(^tBuPNP)Ir(C₆H₅)] (2) via metal-ligand cooperation (MLC) (^tBuPN = 2,6-bis-(di-tert-butylphosphinomethyl)pyridine; ^tBuPNP* = deprotonated PNP; COE = cyclooctadiene). The [1,3]-addition of CO₂ to 1 and 2 is reversible at ambient temperature. While the dearomatized complex 1 reacts readily at ambient temperature with CO₂ in THF or benzene, complex 2 reacts with CO₂ upon heating in benzene at 80 °C or at ambient temperature in THF. The novel aromatized complex [(^tBuPNP)IrCl] (10) does not react with CO₂. Based on the reactivity patterns of 1, 2, and 10 with CO₂, we suggest that CO₂ activation via MLC takes place only via the dearomatized species, and that in the case of 2 THF plays a role as a polar solvent in facilitating formation of the dearomatized hydrido phenyl complex intermediate (complex II).     

"Pure by NMR"?

Integration of a (13)C-(1)H satellite peak of a given (12)C-(1)H parent resonance within a quantitative (1)H NMR spectrum and comparison to the minor component represents a simple protocol for the accurate determination of diastereoisomeric ratios of up to 1000:1 (i.e., 99.8% de).     

Molecular-Sieving Membrane by Partitioning the Channels in Ultrafiltration Membrane by In Situ Polymerization

Commercial ultrafiltration membranes have proliferated globally for water treatment. However, their pore sizes are too large to sieve gases. Conjugated microporous polymers (CMPs) feature well-developed microporosity yet are difficult to be fabricated into membranes. Herein, we report a strategy to prepare molecular-sieving membranes by partitioning the mesoscopic channels in water ultrafiltration membrane (PSU) into ultra-micropores by space-confined polymerization of multi-functionalized rigid building units. Nine CMP@PSU membranes were obtained, and their separation performance for H₂/CO₂, H₂/N₂, and H₂/CH₄ pairs surpass the Robeson upper bound and rival against the best of those reported membranes. Furthermore, highly crosslinked skeletons inside the channels result in the structural robustness and transfer into the excellent aging resistance of the CMP@PSU. This strategy may shed light on the design and fabrication of high-performance polymeric gas separation membranes.     

Renewable β-Myrcene Polymerization Initiated by Lutetium Alkyl Complexes Ligated by Imidophosphonamido Ligand

β-Imidophosphonamido ligated lutetium alkyl complex(NPNDipp)Lu(CH2Si Me3)2(THF)(NPNDipp = Ph2P(NC6H3iPr2-2,6)2) with the activation of AliBu3 and [Ph3C][B(C6F5)4] exhibited high catalytic activity, medium syndio-(rr = 66%) but remarkably high 3,4-regioselectivity for the polymerization of β-myrcene(MY). In sharp contrast, high isotactic 3,4-polymyrcene(PMY)(mm = 95%) was obtained by the precursor(NPNEt)Lu(CH2Si Me3)2(THF)(NPNEt = PPh2(NC6H3iPr2-2,6)(NC6H4-Et-2)) with less bulky substituents on the N-aryl ring.     

Asymmetric Syntheses Aided by Biocatalysts

This article summarizes the achievements of the authors‘ group in the area of biocatalyst-catalyzed organic reactions in recent 10 years. A strain of Geotrichum sp. obtained by screeninu is capable of stereoselectlvely reducing a number of carbonyl compounds. In many cases, the stermghemistry is complementary with that obtained by baker‘ s yeast. Therefore, this microorganism provides a useful pathway to the preparation of alcohol eompounds with specific configurations. On the other hand, a nmmber of plant sourees have been screened for oxynitrilases and the hydrocyanation reactions of various arylcarboxalde-hydes have been investigated.A“micro-aqueous reaction system“ was invented,by which a serles of novel optically active cyanohydrins were prepared.On this hasis,a high through-put comtimasous reaction system has been designed.This paper also deseribes examples of the syntheses of bio-active compounds by using the optieally active compounds obtained from the above mentioned catalytic reactions as precursors.     

Glucose biosensor enhanced by nanoparticles

Glucose biosensors have been formed with glucose oxidase (GOD) immobilized in composite immobilization membrane matrix, which is composed of hydrophobic gold, or hydro-philic gold, or hydrophobic silica nanoparticles, or the combination of gold and silica nanoparticles, and polyvinyl butyral (PVB) by a sol-gel method. The experiments show that nanoparticles can significantly enhance the catalytic activity of the immobilization enzyme. The current response can be increased from tens of nanoamperometer (nA) to thousands of nanoamperometer to the same glucose concentration, and the electrodes respond very quickly, to about 1 min. The function of nanoparticles effect on immobilization enzyme has been discussed.     

Ouroboros: Heterocycles closed by dative σ bonds and stabilized by π delocalization

Heteroarenes such as (aza and oxa)borines are increasingly important as synthetic targets and reagents. We map the intramolecular cyclization of saturated heterocyclic chains through dative bonding. A related set of planar unsaturated aza-, oxa-, and fluora-rings that feature dative σ bonding enhanced by π delocalization are identified. The systems have, in general, the formulae A′(CH₂)_mD′ and A′(CH)_mD′, where m?=?3 and 4, and A′ and D′ are acceptor and donor sites, respectively. In each case, the ring isomers, achievable via A′←D' internal coordination (in the manner of Kekulé’s ouroboros), are more stable than chains. Unsaturated aromatic rings examined herein include a oxadiborine with a hypervalent oxygen center and a dioxadiborine. They are isoelectronic with an azaborine, which was synthesized more recently, and benzene.     

Characterization of Galactosyl-neoglycoalbumin by MALDI-TOF-MS

Matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS, model AXIMA CFR ) was used to analyze galactosyl-HSA (human serum albumin) synthesized in our laboratory. It clearly showed that HSA covalently combined with galactoses. Galactosyl-HSA is pure and the ratio of galactosyl residues to protein is 48:1.     

Can crude oils be distinguished by different component distribution obtained by laser desorption ionization mass spectrometry and evaluated by chemometrics?

Fourteen different crude oil samples were analyzed as collected by mass spectrometry. For two of them the results obtained by means of different techniques, i.e. electrospray ionization, atmospheric pressure chemical ionization, laser desorption/ionization, were compared. The latter technique leads to the best results: even if unable to give specific information on heteroatom-containing components, it allows a general view to be obtained of the panorama of the oil composition in terms of molecular weight distribution. The statistical evaluation of the mass spectrometry data by multivariate techniques, such as cluster analysis (Average Linkage) and correspondence analysis, allows evidence for the differences and similarities among the crude oils under study.     

Knoevenagel Condensation Catalysed by Alumina

在Ａｌ２Ｏ３催化下活泼亚甲基化合物和羰基化合物进行克脑文格尔缩合反应，在温和的反应条件下得到较高收率的产物。将超声波辐射应用于该缩合反应使反应速度明显提高。     

Studies of Self-assembled Monolayers Formed by Imidazoline on Iron Surface by SEM and SECM

Self-assembled monolayers (SAMs) formed from organic substances can improve the inhibition of metal corrosion, because uniform and closely packed films formed on the metal surface providing an insulating layer1, 2. SAMs on the iron surface are studied so far because iron is one active metal which is easily corroded in the air. In this paper, SECM and SEM have successfully been applied in the study of SAMs inhibition corrosion for iron. SECM has been used to study the electrochemically a…     

Complexation of inorganic anions by β-cyclodextrin studied by polarography and 1H NMR

Abstract

Complexation of o-chloronitrobenzene with β-cyclodextrin has been studied in 0.1 M aqueous solutions containing PF₆ ^?, ClO₄ ^?, C₂O₄ ^2-, SCN^?, SO₄ ^2- and F^? anions by a polarographic method. Using an equation which takes account of the change in the cyclodextrin concentration due to the simultaneous complexation of the anion, both stability constants have been calculated. Interaction of the ClO₄ ^? anion with β-cyclodextrin has been confirmed by ¹H NMR techniques. It has been found that the ClO₄ ^? anion is trapped in the β-cyclodextrin cavity. The stability constant has been calculated. Results of polarographic and ¹H NMR studies have been compared.     

Ethylene–Norbornene Copolymerization by Rare-Earth Metal Complexes and by Carbon Nanotube-Supported Metallocene Catalysis

E–N copolymerization with a number of half-sandwich rare-earth metal compounds [M(η5-C₅Me₄SiMe₂R)(η1-CH₂SiMe₃)₂(L)] (M = Sc, Y, Lu) has been achieved. Mainly atactic alternating E N copolymers are obtained with all catalytic systems. Interestingly, copolymers arising from [Sc(η5-C₅Me₄SiMe₂C₆F₅)(η¹-CH₂SiMe₃)₂(THF)]/[/[Ph₃C][B(C₆F₅)₄] possess narrower molar mass distributions than those from [Sc(η⁵-C₅Me₄SiMe₃)(η¹-CH₂SiMe₃)₂(THF)] / [Ph₃C][B(C₆F₅)₄]. In addition, homogeneous surface coating of multi-walled carbon nanotubes is accomplished for the first time by in situ E–N copolymerization as catalyzed by rac-Et(Ind)₂ZrCl₂/MMAO-3A anchored onto the carbon nanotube surface. The copolymerization reaction allows for the destructuration of the native nanotube bundles. The relative quantity of E N copolymer can be tuned up as well as the norbornene content in the formed copolymers and accordingly their glass transition temperature. By melt blending with an ethylene-vinyl-co-acetate copolymer (27 wt.-% vinyl acetate comonomer) matrix, high performance polyolefinic nanocomposites are obtained.     

Studies of Self-assembled Monolayers Formed by Imidazofine on Iron Surface by SEM and SECM

The self-assembled monolayers （SAMs） of imidazoline （IM） on the iron surface were characterized by scanning electron microscope （SEM） and scanning electrochemical microscopy （SECM）. The results showed that SAMs were an effective inhibition film for iron.     

Preparation of D-Phenylalanine by Asymmetric Transformation

The method of preparing D-phenylalanine by asymmetric transformation is reported.D-phenylalanine was prepared from DL-phenylalanine by two-step reaction.D-phenylalanine(2S,3S)-tartrate was prepared by heating DL-phenylalanine,salicylaldehyde,and (2S,3S)-tartaric acid in propionic acid;the obtained D-phenylalanine(2S,3S)-tartrate was treated with triethylamine in ethanol giving D-phenylalanine with 98% optical purity in 69% yield.     

Surface Modification of Montmorillonites by Chlorosilanes

Montmorillonite was modified by chlorosilane derivatives (trimethylchlorosilane and tert-butyldimethylchlorosilane)based on the reaction between OH group and chlorosilane,Fourier-transformed infrared spectra(FTIR)confirmed that chlorosilanes did react with the OH groups of montmorillonite.The effect of reaction time and dispersing agents on the intercalation was studied by wide angle X-ray diffraction(WAXD) method.Further experiments proved that there is no reactive OH group on the surface of layers in the interlayer galleries of montmorillonite.The cation exchange capacity(CEC) of montmorillonites was measured.showing that after modification by chlorosilane derivatives,CEC values drastically decreased.The dispersibility measurements of montmorillonites were conducted.which showed that the dispersibility of modified montmorillonites both in H2O and toluene wer improved due to the decrease of attractions of particles and layers.     

β-Peptide coatings by surface-initiated polymerization

Homopolymers of β-lactams can be grown by surface-initiated polymerization. These surface-linked β-peptides are living polymers with the potential to be utilized as tunable, protease-resistant interfaces in multiphase structural composites where the characteristics of the interface influence bulk properties.