Amperometric response to reducing carbohydrates of an enzyme electrode based on oligosaccharide dehydrogenase. Detection of lactose and α-amylase

A mediated amperometric enzyme electrode, which was constructed by immobilizing oligosacharide dehydrogenase behind a dialysis membrane on the surface of a carbon paste electrode containing p-benzoquinone, showed a current response to d-xylose, d-galactose, d-mannose, lactose, maltose, maltotriose, maltopentaose and maltohexaose. The sensitivity of the current response to these carbohydrates was dependent on the kinetics of the immobilized enzyme reaction and/or the permeation rate of the substrate through the dialysis membrane. Hence the sensitivity could be varied by controlling the amount of the immobilized enzyme and the thickness of the dialysis membrane. The time dependence of the current response ofthe enzyme electrode with a large amount of the immobilized enzyme and a thicker dialysis membrane could be explained by an equation describing diffusion of the substrate in the membrane. The enzyme electrode was used to measure lactose in milk and to assay α-amylase in standard serum.     

Preparation of an amphiphilic resin-supported BINAP ligand and its use for rhodium-catalyzed asymmetric 1,4-addition of phenylboronic acid in water

[reaction: see text] The axially chiral bisphosphine ligand, 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (binap), was supported on a polystyrene-poly(ethylene glycol) copolymer (PS-PEG) resin and was used successfully for the rhodium-catalyzed asymmetric 1,4-addition of phenylboronic acid to alpha,beta-unsaturated ketones in water.     

Direct injection method for quantitation of delta-aminolevulinic acid in urine by high-performance liquid chromatography.

A highly sensitive and simple method for determining delta-aminolevulinic acid (ALA) in urine was established, using direct injection of urine into a high-performance liquid chromatographic column, with fluorometric detection after post-column derivatization with o-phthalaldehyde (OPA). The recovery of ALA was about 100% and ALA was completely separated on an ion exchange column (retention time, 38 min). The detection limit for ALA was 10 pmol (S/N = 2). The mean levels of urinary ALA of 10 healthy volunteers, 4 patients with acute intermittent porphyria, and 2 workers occupationally exposed to lead were 0.76, 5.25, and 23.54 mg/l, respectively. Because of its simplicity, the method is considered to be suitable for routine analysis of urinary ALA in the clinical laboratory.     

478—Theory of Brdička current and the dependence of the current on cobalt ion concentration

An equation of Brdi?ka current and its experimental verification are presented, in which Brdi?ka current is expressed by a function of the surface concentration of protein, the bulk concentration of cobalt ion and two parameters, n_ck_c and k_f/k_d, characterizing the protein-zero-valent cobalt complex which is to catalize the hydrogen evolution, where n_c is the total number of sites on which the complex can be formed in a protein molecule, and k_c and k_d are the (average) constants representing the intrinsic catalytic activity and the lifetime respectively, of the complex.     

Transparent CoAl2O4 hybrid nano pigment by organic ligand-assisted supercritical water

Transparent types of inorganic pigments are important as they can be used in a variety of applications, such as metallic finishing, contrast enhancing luminescent pigments, high-end optical filters, and so on. Currently, the difficulty in producing monodisperse and stable binary metal oxide nano pigments at low temperature hampers the applicability and realization of transparent blue nano pigments. Here, for the first time, we report organic ligand capped CoAl2O4 hybrid transparent nano pigment, which has a particle size less than 8 nm with well-stabilized single nanocrystals, using organic ligand-assisted supercritical water as the reaction medium. The organic ligand capping could effectively inhibit the particle growth and also control the size of nanocrystals. This helps to diminish the scattering effect of the nano blue pigment, realizing a transparent cobalt blue nano pigment without any postheat treatment.     

Rhodium‐Catalyzed Intramolecular Hydroarylation of 1‐Halo‐1‐alkynes: Regioselective Synthesis of Semihydrogenated Aromatic Heterocycles

The regioselective intramolecular hydroarylation of (3‐halo‐2‐propynyl)anilines, (3‐halo‐2‐propynyl) aryl ethers, or (4‐halo‐3‐butynyl) aryl ethers was efficiently catalyzed by Rh₂(OCOCF₃)₄ to give semihydrogenated aromatic heterocycles, such as 4‐halo‐1,2‐dihydroquinolines, 4‐halo‐3‐chromenes, or 4‐(halomethylene)chromans, in good to excellent yields. Some synthetic applications taking advantage of the halo‐substituents of the products are also illustrated.     

Dechlorination of poly(vinylidene chloride) in NaOH/ethylene glycol as a function of NaOH concentration, temperature, and solvent

The wet dechlorination treatment of poly(vinylidene chloride) (PVDC) was evaluated at atmospheric pressure in a solution of NaOH in ethylene glycol (EG), as a function of NaOH concentration, temperature, and solvent. Hydroxide ion from NaOH was required for dechlorination with EG acting solely as a solvent. The wet treatment exhibited significantly enhanced dechlorination efficiency over traditional thermal techniques, with a reaction efficiency as high as 92.8% in 1.0 M NaOH at 190 °C. Dechlorination reactions of PVDC in both NaOH/EG and NaOH/H₂O were expressed by an apparent first-order reaction. At 190 °C, the apparent rate constant in 1.0 M NaOH/EG was approximately 1.4 times larger than in 1.0 M NaOH/H₂O, with an apparent activation energy of 82.8 kJ mol⁻¹, indicating that the reaction proceeded under chemical control. The degree of dechlorination increased with increasing reaction temperature, favouring the elimination of HCl over the hydroxyl substitution of chloride.