1,720,972 research outputs found
ELECTROCHEMICAL SENSORS FOR THE DETERMINATION OF METAL-IONS
No full textAn electrochemical method for the determination of the metal ions Fe3+, Cu2+ and Hg2+ has been developed. It is based on organic chelators changing their electrochemical behaviour as a function of metal ion concentration in solution. Amperometric measurements of the metal ions are performed by cyclic voltammetry using a glassy carbon or a modified carbon paste as working electrodes. Fe3+ is determined in the range 6-60 ppb using two chelators synthesized by the British Technology Group (UK Patent Nos. GB 2118176B and GB 2136807B), Cu2+ is determined in the range 0.35-4 ppm with bis-cyclohexanone oxalyldihydrazone and Hg2+ is determined in the range 20-200 ppm using glyoxal dithiosemicarbazone.[...
A new conducting polymer glucose sensor based on polythianaphthene
No full textA glucose biosensor has been developed by entrapment of glucose oxidase in a polythianaphthene film formed onto a platinum surface. Glucose has been measured by H2O2 detection at +400 mV (vs. SCE). Electrochemical kinetic constants for the enzyme electrode have been calculated and indicated that in the unsaturated region the rate limiting step is the diffusion of the substrate through the polymer. The biosensor exhibited a linear response in the range 0.05-7.4 mmol/L with a response time of 30-60 s and a relative standard deviation of 5.4%. The presence of the film onto the electrode prevents the oxidation of interfering agents such as ascorbic and uric acid. The use of additional polycarbonate membranes onto the electrode surface extended the linearity of the response allowing the probe to be used in blood glucose analysis. The amount of glucose in two control sera was measured using the biosensor. Results correlated well with the glucose nominal values.[...
Oxygen and carbon monoxide binding to myoglobin from the dolphin fish Coryphaena hippurus
No full textProperties of Thermus aquaticus b-NADH oxidase immobilised on various supports
No full textbeta-NADH oxidase purified from Thermus aquaticus was covalently immobilised on various solid supports. The preparations obtained were compared with the soluble enzyme for activity and kinetic properties. Activated glutaryl-PVA was found to be the best support. The immobilised enzyme was less stable at high temperatures than the soluble enzyme. No differences could be detected in the presence of organic solvents.beta-NADH oxidase purified from Thermus aquaticus was covalently immobilised on various solid supports. The preparations obtained were compared with the soluble enzyme for activity and kinetic properties. Activated glutaryl-PVA was found to be the best support. The immobilised enzyme was less stable at high temperatures than the soluble enzyme. No differences could be detected in the presence of organic solvents
Flavin-grafted poly(vinyl alcohol): preparation and properties
No full textAn NAD(P)H oxidase-like activity was found in semisynthetic flavoadducts, prepared from an aldehyde derivative of riboflavin and commercial poly(vinylalcohol) (PVA), previously grafted with aminopropyl side chains. Both water-soluble and water-insoluble beaded preparations were obtained. The products showed a noticeable NAD(P)H oxidase-like activity, converting the nucleotide substrate to its oxidized counterpart NAD(P)(+) at the expense of molecular oxygen, the latter being reduced to hydrogen peroxide. In contrast to some "true" beta-NAD(P)H oxidases, the PVA adducts do not require the presence of additional flavin adenine dinucleotide (FAD) to work; some properties of the flavoadducts were studied that make these flavoadducts good candidates for technological applications. (C) 2002 Wiley Periodicals, Inc
isolation and characterization of a cDNA clone for a novel serine-rich neutrophil protein.
No full textThe primary structure of iron-superoxide dismutase from Photobacterium leiognathi
No full textThe complete amino acid sequence of iron-superoxide dismutase from Photobacterium leiognathi was determined. The sequence was deduced following characterization of the peptides obtained from tryptic, chymotryptic, and Staphylococcus aureus V-8 protease digests of the apoprotein. The amino acid sequence listed below is made up of 193 residues. It is the first complete sequence to be determined for an iron-superoxide dismutase. The iron-superoxide dismutase shows the same order of homology with the manganese-superoxide dismutases as these enzymes show among themselves. No homology was observed with the copper/zinc-containing class of superoxide dismutases
Aspartate aminotranferase from the thermophilic bacterium Thermus aquaticus YT-1. Functional characterisation and stability
No full textAspartate aminotranferase from the thermophilic bacterium Thermus aquaticus has been purified to homogeneity. The enzyme is pyridoxal-5-phosphate dependent and is composed of two subunits having an Mr 44000 each. T. aquaticus AspAT shows a pI of 4.5 and is a thermophilic enzyme exhibiting its maximum activity at 80 degrees C in the pH range 7-8. It is also resistant against denaturation to heat and several chemical agents
The primary structure of human erythrocyte copper/zinc superoxide dismutase: cleavage with Staphylococcus aureus protease, determination of the N-terminal blocking group and location of the disulfide bond
No full textResults obtained after digestion of copper/zinc superoxide dismutase from human erythrocytes with S. aureus protease are described. In particular, peptides soluble in alkaline conditions proved essential for completing the determination of the primary structure of the enzyme; other peptides were important for establishing the amidation state of dicarboxylic amino acid residues and for confirming controversial sequences. The human enzyme is acetylated at the NH2 terminus and contains an intrasubunit disulfide bond connecting half-cystine residues 57 and 146
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