Copolymerization of carbon dioxide and propylene oxide with Ln(CCl3COO)(3)-based catalyst: The role of rare-earth compound in the catalytic system

A highly alternative copolymer of carbon dioxide and propylene oxide was obtained using a lanthanide trichloroacetates-based ternary catalyst. The rare-earth compound in the ternary catalyst was critical to dramatically raise the yield and molecular weight of the copolymer in addition to maintaining a high alternating ratio of the copolymer. (C) 2001 John Wiley & Sons, Inc.

Preparation and properties of a selenium-containing catalytic antibody as type I deiodinase mimic

Conversion of thyroxine (T-4) to 3,5,3'-triiodothyronine is an essential first step in controlling thyroid hormone action. Type I deiodinase (DI) can catalyze the conversion to produce the bulk of serum 3,5,3'-triiodothyronine. Acting as a mimic of DI, a selenium-containing catalytic antibody (Se-4C5) prepared by converting the serine residues of monoclonal antibody 4C5 raised against T4 into selenocysteines, can catalyze the deiodination of T4 with dithiothreitol (DTT) as cosubstrate. The mimic enzyme Se-4C5 exhibited a much greater deiodinase activity than model compound ebselen and another selenium-containing antibody Se-Hp4 against GSH. The coupling of selenocysteine with the combining pocket of antibody 4C5 endowed Se-4C5 with enzymatic activity. To probe the catalytic mechanism of the catalytic antibody, detailed kinetic studies were carried out in this paper. Investigations into the deiodinative reaction revealed the relationship between the initial velocity and substrate concentration. The characteristic parallel Dalziel plots demonstrated that Se-4C5-catalyzed reaction mechanism was ping-pong one, involving at least one covalent enzyme intermediate. The kinetic properties of the catalytic antibody were similar to those of DI, with K-m values for T-4 and DTT of approximately 0.8 muM and 1.8 muM, respectively, and a V-m value of 270 pmol per mg of protein per min. The activity could be sensitively inhibited by 6-propyl-2-thiouracil (PTU) with a K-i value of similar to 120 muM at 2.0 muM T-4 concentration. The PTU inhibition was progressively alleviated with the increasing concentration of added DTT, revealing that PTU was a competitive inhibitor for DTT.

Synthesis of poly(ether ether ketone)s with high content of sodium sulfonate groups as gas dehumidification membrane materials

Sodium sulfonate-functionalized polyether ether ketone)s derived from Bisphenol A with a degree of sulfonation up to 2.0 were synthesized by aromatic nucleophilic polycondensation of various amounts of 5,5-carbonylbis(2-fluorobenzenesulfonate) (1), 4,4'-diflurobenzophenone (2) and Bisphenol A (2). Copolymers showed excellent thermal stability and good mechanical properties. The selectivity of water vapor over nitrogen of membranes prepared from copolymers 3a and 3h was determined to be 3.43 x 10(6) and 1.05 x 10(7), respectively.

A selenium-containing catalytic antibody with type I deiodinase activity

Acting as a mimic of type I deiodinase (DI), a selenium-containing catalytic antibody (Se-4C5) prepared by converting the serine residues of monoclonal antibody 4C5 raised against thyroxine (T-4) into selenocysteines, can catalyze the deiodination of T-4 to 3,5,3'-triiodothyronine (T-3) with dithiothreitol (DTT) as cosubstrate. Investigations into the deiodinative reaction by Se-4C5 revealed the relationship between the initial velocity and substrate concentration was subjected to Michaelis-Menten equation and the reaction mechanism was ping-pong one. The kinetic properties of the catalytic antibody were a little similar to those of DI, with K-m values for T-4 and DTT of approximately 0.8 muM and 1.8 mM, respectively, and V-m value of 270 pmol per mg protein per min. The activity could be sensitively inhibited by PTU with a K-i value of approximately 120 muM at 2.0 muM of T-4 concentration, revealing that PTU was a competitive inhibitor for DTT, (C) 2001 Academic Press.

Studies on the transport of lanthanides ions through the membrane of human erythrocyte in vitro by ICP-MS

A method was developed for the determination of lanthanum in the cytoplasm of human erythrocytes after they were incubated in lanthanum nitrate or citrate solutions. The lanthanum concentration in the cytoplasm of incubated erythrocytes is much higher than that in normal erythrocytes. It is suggested lanthanum can transport through the membrane of erythrocyte in vitro. Solutions containing chelator are unsuitable to be washing buffer in the investigation.

A new kind of potassium sensor based on capacitance measurement of mimic membrane

A novel type of potassium sensor based on the capacitance change of valinomycin-incorporated bilayer supported on a gold electrode has been developed and characterized. The lipid membrane was Formed by painted method and monitored simultaneously by capacitance variation. The capacitance of the electrode-supported membrane was found to be modulated by different concentrations of K+. Investigating the capacitance change allows a simple and specific technique for the measurement of potassium ion in solution. Especially, the homemade capacitance meter is, to our knowledge, used to monitor the bilayer membrane formation and detect K+ for the first time. It has been proved that this capacitance measurement is a very useful technique because it is simple and sensitive compared to the other methods.

Catalytic reduction of NO, by CO on hydrotalcites-derived mixed oxides CoAlM and MgAlM (M = Cr, Mn, Fe, Co, Ni, Cu)

Two series of mixed oxides, CoAlM and MgAlM (M = Cr, Mn, Fe, Co, Ni, Cu), were prepared by calcining their corresponding hydrotalcite-like compounds (HTLc). The ratio of Mg: Al: M (or Co: Al: hi) was 3:1:1. The catalytic activity of all samples for the reaction of NO + CO was investigated. The results showed that the activity of CoAlM was much higher than that of MgAlM. The structure and the property of redox were characterized by XRD and H-2-TPR. The results indicated that only MgO phase was observed after calcining MgAlM hydrotalcites, and the transition metals became more stable. The spinel-like phase appeared in all of CoAlM samples after the calcination, and the transition metals were changed to be more active, and easily reduced. The activities of three series of mixed oxides CoAlCu obtained from different preparation methods, different ratio of Co:Al: Cu and at different calcination temperatures, were studied in detail for proposing the mechanism of reaction. The ability of adsorption of NO and CO were investigated respectively for supporting the mechanism.

Oxidation of NADH by dopamine incorporated in lipid film cast onto a glassy carbon electrode

Stable lipid film was made by casting lipid in chloroform onto a glassy carbon electrode. This model of a biological membrane was used to investigate the oxidation of dihydronicotinamide adenine dinucleotide (NADH) by dopamine. After this electrode had been immersed in dopamine solution for 10 h, it was found that some dopamine had been incorporated in the film. The cyclic voltammogram was obtained for the oxidation of 2.0 X 10(-3) mol 1(-1) NADH with dopamine incorporated in the films. All electrochemical experiments were performed in 0.005 mol 1(-1) phosphate buffer (pH 7.0) containing 0.1 mol 1(-1) NaCl without oxygen. The oxidation current increased gradually with successive sweeps and reached steady state. It was a different phenomenon from previous results. The anodic overpotential was reduced by about 130 mV compared with that obtained at a bare glassy carbon electrode. The diffusion coefficient for 2.0 X 10(-3) mol 1(-1) NADH was 6.7 X 10(-6) cm(2) s(-1). (C) 1999 Elsevier Science S.A. All rights reserved.

A manganese molybdenum phosphate with a tunnel: hydrothermal synthesis, structure and catalytic properties of (NH3CH2CH2NH3)(10-)H3O)(3)(H5O2)Na-2[MnMo12O24(OH)(6)(PO4)(4)(PO3OH)(4)]-[MnMo12O24(OH)(6)(PO4)(6)(PO3OH)(2)] center dot 9H(2)O

A manganese molybdenum phosphate, (NH3CH2CH2NH3)(10)(H3O)(3)(H5O)Na-2[MnMo12O24(OH)(6) (PO4)(4)(PO3OH)(4)][MnMo12O24 (OH)(6)(PO4)(6)(PO3OH)(2)]. 9H(2)O, has been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. The structure of this compound may be considered to be two [Mo6O12(OH)(3)(PO4)(2)(HPO4)(2)](7-) units bonded together by a manganese atom, although several P-O groups are not protonated on account of coordination to a Na+ cation. One-dimensional tunnels were formed in the solid. A probe reaction of the oxidation of acetaldehyde with H2O2 using this compound as catalyst was carried out in a liquid-solid system, showing that the manganese molybdenum phosphate has high catalytic activity in the reaction.

Preparation, characterization of solid solution La4BaCu5-xMnxO13+lambda (x=0-5) and its catalytic activity in the reduction of NO by CO

A series of layered mixed oxides La4BaCu5-xMnxO13+lambda(x = 0-5) was prepared, characterized and used as catalysts for NO+CO reaction. It was found that all the samples were single phase having a structure with five-layered-perovskite. La4BaCu2Mn3O13+lambda showed the highest activity in the title reaction, this could be attributed to the synergetic effect between Cu and Mn. The results of TPR, TPD and excess oxygen investigations confirmed that the Cu ion would be the active center. The displacement of the Cu ion by Mn caused the Cu ion to be more easily reducible and more content of excess oxygen, and it was beneficial to the activity of the catalyst. The reaction mechanism was also proposed.

Preparation, charactreization, and catalytic properties of Co-M-Al (M = transition metal) mixed oxides derived from hydrotalcite-like compound

Hydrotalcite-like compounds (HTLcs) CoMAlCO3, where M stands for Cr, Mn, Ni, Cu, or Fe, were synthesized by coprecipitation. After calcination at 450 degrees C, they became mixed oxides with spinel-like structure. The mixed oxides were characterized by XRD, BET, chemical analysis and the adsorption of NO. The catalytic decomposition of NO and its reduction by CO were studied over these mixed oxides. The study showed that the catalytic activity for removal of NO, was very high. The reaction mechanism is proposed and the effects of d-electrons of the transition metals on catalytic activity are elucidated.

Study on the synthesis of mixed oxide La2CuO4 and the effect on the catalytic activity to catalytic removal of NO

The mixed oxide La2CuO4 was synthesized by four different methods and characterized with XRD, BET, TEM and low angle XRD. The effect of the synthetic method on the crystal structure, crystal size, surface area and catalytic activity to NO - CO reaction were studied. The results showed that the samples derived from different methods exhibited different activity to NO-CO reaction, the reason may be that the concentration and type of oxygen defect were different when the synthetic methods were different.

Catalytic oxidization polymerization of aniline in an H2O2-Fe2+ system

Polyaniline is prepared by chemical polymerization of aniline in an acidic solution using H2O2 as an oxidant and ferrous chloride as a catalyst. A wide variety of synthesis parameters are studied, such as the amount of the catalyst, reaction temperature, reaction time, initial molar ratio of oxidant, monomer and catalyst, and aniline and HCl concentrations. The polymerization of aniline can be initiated by a very small amount of catalyst. The yield and the conductivity of product depend on the initial molar ratio of the oxidant and monomer. The polyaniline with a conductivity of about 10 degrees S/cm and a yield of 60% is prepared under optimum conditions. The process of polymerization was studied by in situ ultraviolet-visible spectroscopy and open-circuit potential technology. Compared to the polymerization process in a (NH4)(2)S2O8 system, the features of the H2O2-Fe2+ system are pointed out, and the chain growth mechanism is proposed. (C) 1999 John Wiley & Sons, Inc.

Catalytic reduction of NO by CO with hydrotalcite derived mixed oxides

Catalysts with spinel structure derived from Hydrotalcite-like Compounds (HTLcs) containing cobalt have been investigated in NO catalytic reduction by Co. It was found that catalysts with spinel structures derived from HTLcs had obviously higher activity than that prepared from general methods. A two-step reaction was observed during the reaction curse: NO was first reduced to N2O by Co, and with the increase of temperature, the N2O was reduced to N-2. The reactivity of the catalysts studied increased with the amount of cobalt-content in the catalyst, and decreased with the calcination temperature. The crystal defect would play an important role in the reaction.

Catalytic combustion of CH4 and CO on La1-xMxMnO3 perovskites

The activities of perovskites depend on compositions and preparation methods. Various perovskites, La1-xMxMnO3 (M=Ag, Sr, Ce, La), have been prepared by two different methods (co-precipitation and spray decomposition). The new preparation method, spray decomposition, produced perovskites of a high surface area of over 10 m(2)/g. The catalytic activities for CH4 and CO oxidation have been studied on a series of catalysts, La1-xMxMnO3. The perovskite-type oxide, La0.7Ag0.3MnO3, shows the highest catalytic activity: the complete conversion of CO and CH4 at 370 and 825 K, respectively. (C) 1999 Elsevier Science B.V. All rights reserved.