Amperometric tyrosinase biosensor based on a sol-gel-derived titanium oxide-copolymer composite matrix for detection of phenolic compounds

A new type of tyrosinase biosensor was developed for the detection of phenolic compounds, based on the immobilization of tyrosinase in a sol-gel-derived composite matrix that is composed of titanium oxide sol and a grafting copolymer of poly(vinyl alcohol) with 4-vinylpyridine. Tyrosinase entrapped in the composite matrix can retain its activity to a large extent owing to the good biocompatibility of the matrix. The parameters of the fabrication process and the variables of the experimental conditions for the enzyme electrode were optimized. The resulting sensor exhibited a fast response (20 s), high sensitivity (145.5 muA mmol(-1) 1) and good storage stability. A detection limit of 0.5 muM catechol was obtained at a signal-to-noise ratio of 3.

Synthesis and characterization of a new layered zinc phosphate: (C3H4N2)(3)Zn-4(HPO4)(PO4)(2) with imidazole coordinating to Zn atoms

A new two-dimensional hybrid zinc phosphate with electro-neutral open-framework has been hydrothermally synthesized by using imidazole as a structure-directing agent, whose structure is characterized with 3-, 4-, 5, and 12-ring layers and coordination bonds between imidazole groups and zinc atoms, resulting in primary building units of ZnO2N2 and ZnO3N.

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.

A nickel molybdenum phosphate with tunnel: Hydrothermal synthesis and structure of (NH3CH2CH2NH3)(4)center dot(NH3CH2CH2NH2)center dot Na center dot[Ni2Mo12O30(PO4)(HPO4)(4)(H2PO4)(3)]center dot 6H(2)O

A nickel molybdenum phosphate, (NH3CH2CH2NH3)(4).(NH3CH2CH2NH2). Na .[Ni2Mo12O30(PO4)(HPO4)(4)(H2PO4)(3)]. 6H(2)O, invoicing molybdenum present in V oxidation, has been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. Deep brown-red crystals are formed in the triclinic system, space group P (1) over bar, a = 12,011(2), b = 14,612(3), c = 21.252(4) Angstrom, alpha = 80.54(2)degrees, beta = 83.10(2)degrees, gamma = 76.29(2)degrees, V = 3561.4(12) Angstrom(3), Z = 2, lambda(MoK alpha) = 0.71073 Angstrom (R(F) = 0.0529 for 9880 reflections), Data mere collected on a Siemens P4 diffractometer at 20 degrees C in the range of 1.75 degrees < theta < 23.02 degrees using the omega-scan technique. The structure was solved by direct methods using the program SHELXTL-93 and refined with the method of fun-matrix least-squares on F-2. The structure of the title compound may be considered to be two [Mo6O15(HPO4)(H2PO4)(3)](5-) units bonded together with a nickel atom, although several P-O groups are not protonated on account of coordination with a Na+ cation, The one-dimensional tunnels were formed in the solid of the title compound. A probe reaction of the oxidation of acetaldehyde with H2O2 using the title compound as catalyst was carried out in a liquid- solid system, showing that the title compound had high catalytic activity in the reaction, (C) 1999 Academic Press.

Binuclear lanthanide complexes as catalysts for the hydrolysis of double-stranded DNA

The efficient cleavage of plasmid DNA ( pCAT) by binuclear lanthanide complexes was investigated. At 37 degrees C and neutral pH, both Ho23+L and Er23+L promoted 100% conversion of supercoiled plasmid to the nicked circular form and linear form in 1 h. The corresponding saturation kinetics curve of cleavage of pCAT plasmid by binuclear lanthanide complexes showed the expected increase with catalyst concentration. (C) 1999 Elsevier Science S.A. All rights reserved.

Hydrothermal synthesis and structural characterization of a mixed-valence molybdenum (IV,VI) arsenate (III): Ni(H2NCH2CH2NH2)(3)[((MoO6)-O-IV)(Mo6O18)-O-VI((As3O3)-O-III)(2)]H2O

A novel mixed-valence molybdenum(IV, VI) arsenate(III), Ni(H2NCH2CH2NH2)(3)[((MoO6)-O-IV)(Mo6O18)-O-VI((As3O3)-O-III)(2)]H2O, hydrothermally synthesized and characterized by single-crystal X-ray diffraction and thermogravimetric analysis. The polyanion cage derives from the Anderson structure, in which the central octahedron was filled up by molybdenum(IV) and it was capped on both sides by a novel As3O63- cyclo-triarsenate(III). The title compound had a high catalytic activity for the oxidation of benzaldehyde to benzoic acid using H2O2 as oxidant in a liquid-solid biphase system. (C) 1999 Elsevier Science B.V. All rights reserved.

Crystal structure and drawing-induced polymorphism in poly(aryl ether ether ketone). IV

A new crystal modification induced by strain and denoted as form II exists alongside the dominant form I structure in the uniaxially oriented poly(ether ether ketone) (PEEK) and the related polymers. The crystal structure of form II for PEEK is also found to possess a two-chain orthorhombic packing with unit cell parameters of a equal to 0.475 nm, b equal to 1.060 nm, and c equal to 1.086 nm. More extended and flattened chain conformation of form II relative to that of form I is expected to account for an 8% increase in c-axis dimension, which is attributed to the extensional deformation fixed in situ through strain-induced crystallization during uniaxial drawing. Annealing experiments suggest that form II is thermodynamically metastable and can be transformed into more stable form I by chain relaxation and reorganization at elevated temperature without external tension. This strain-induced polymorphism exists universally in the poly(aryl ether ketone) family. (C) 1999 John Wiley & Sons, Inc.

Enzymatic degradation of poly(epsilon-caprolactone)/poly(DL-lactide) blends in phosphate buffer solution

Blend films of poly(epsilon-caprolactone) (PCL) and poly(DL-lactide) (PDLLA) with 0.5 weight fraction of PCL were prepared by means of solution casting and their degradation behavior was studied in phosphate buffer solution containing Pseudomonas (PS) lipase. Enzymatic degradation of the blend films occurred continuously within the first 6 days and finally stopped when the film weight loss reached 50%, showing that only PCL in the blends degraded under the action of PS lipase in the buffer solution. These results indicate the selectivity of PS lipase on the promotion of degradation for PCL and PDLLA. The thermal properties and morphology of the blend films were investigated by differential scanning calorimetry, wide-angle X-ray diffraction and scanning electron microscopy (SEM). The morphology resulting from aggregate structures of PCL in the blends was destroyed in the enzymatic degradation process, as observed by SEM. These results confirm again the enzymatic degradation of PCL in the blends in the presence of PS lipase. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.

A ferric molybdenum phosphate with a tunnel: hydrothermal synthesis and structure of (NH3CH2CH2NH3)(2)center dot(NH3CH2CH2NH2)(3)center dot Na center dot[Fe2Mo12O30(PO4)(HPO4)(4)(H2PO4)(3)]center dot 7H(2)O

A new ferric molybdenum phosphate containing a tunnel structure and crystallographically different clusters has been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. A probe reaction of the oxidation of acetaldehyde with H2O2 using the tide compound as catalyst was carried out in a liquid-solid system, showing that the title compound had high catalytic activity in the reaction. (C) 1998 Elsevier Science S.A. All rights reserved.

Recovery of Ce(IV) and Th(IV) from rare earths(III) with Cyanex 923

Solvent extraction of Ce(IV), Th(IV) with Cyanex 923 in n-hexane from sulphuric acid medium was studied with the dependence of the extraction on acidity and temperature being investigated. The Ce(IV) and Th(IV) extraction mechanism was proposed by slope analysis and the IR spectra of purified Cyanex 923 saturated with Ce(IV) were employed to determine the composition of the Ce(IV) complex. The equilibrium constant and thermodynamic functions of Th(IV) extraction were calculated and the characteristics of the stripping of Ce(IV), Th(IV) from the loaded organic phase were studied. (C) 1998 Elsevier Science B.V. All rights reserved.

Lanthanide binuclear macrocyclic complexes as synthetic enzymes for the cleavage of DNA

Lanthanide binuclear complexes can accelerate the cleavage of pUC19 plasmid DNA, yielding predominantly linear form. The saturation kinetics of the cleavage of pUC19 was studied. The observed rates with lanthanide binuclear complexes showed the expected increase with the catalyst concentration. The rate of cleavage is greater than that of lanthanide ions alone. (C) 1998 Elsevier Science B.V. All rights reserved.

Electrocatalytic oxidation of methanol at the titanium oxide electrode modified with Pt microparticles

The electrocatalytic oxidation of methanol at the Titanium oxide (TiOx, x<2) film modified with Pt microparticles has been studied. The results show that the modified electrodes exhibit a significant electrocatalytic activity and good stability for the oxidation of methanol. Under the optimal conditions, the peak current density at 0.58 V for the oxidation of methanol in the positive-going sweep is about 526 mA/cm(2) at the scan rate of 5 mV/s in 0.5 mol/L CH3OH and 0.5 mol/L H2SO4 solution and the over potential of the methanol oxidation at the modified electrode increases about 30 similar to 40 mV after 70 minutes at the current density of 100 mA/cm(2) and 50 mA/cm(2). The enhanced electrocatalytic activity and good stability are ascribed to the high dispersion of Pt microparticles in and on the TiOx film and the synergistic effect between Pt microparticles and TiOx.

Separation of Ce(IV) and RE(III) with hollow fiber membrane-based extraction

Separation of Ce(IV) and RE(III) was investigated by hollow fiber membrane-based extraction with contercurrent recirculating operation. The mass transfer coefficients of Ce(IV) and RE(III) and the effective factors to them were tested. The results show the mass transfer coefficient of Ce(IV) is larger than that of RE(III), and their mass transfer mechanism is different. The mass transfer of Ce(IV) was controlled by the resistance in water critical layer due to its more rapid interfacial reaction rate and larger distribution coefficient, which was different from RE(III) mass transfer with a slow interfacial reaction rate and small distribution coefficient. Ce(IV) was separated from the mixed solution of Ce(IV) and RE(III) by means of the difference of their mass transfer rates.

Bulk modulus of ternary chalcopyrite A(I)B(III)C(2)(VI) and A(II)B(IV)C(2)(V) semiconductors

Based on the complex crystal chemical bond theory, the formula of Liu and Cohen's, which is only suitable for one type of bond, has been extended to calculate the bulk modulus of ternary chalcopyrite A(I)B(III)C(2)(VI) and A(II)B(IV)C(2)(V) which contains two types of bonds. The calculated results are in fair agreement with the previous theoretical values reported and experimental values. (C) 1998 Elsevier Science Ltd. All rights reserved.