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W Schöpp

Publications and source records attributed to W Schöpp.

At least 19 recordsLinked to original sources
PubMed2001

Estimating long-term population exposure to ozone in urban areas of Europe.

Tropospheric ozone concentrations regarded as harmful for human health are frequently encountered in Central Europe in summertime. Although ozone formation generally results from precursors transported over long distances, in urban areas local effects, such as reactions due to nearby emission sources, play a major role in determining ozone concentrations. Europe-wide mapping and modeling of population exposure to high ozone concentrations is subject to many uncertainties, because small-scale phenomena in urban areas can significantly change ozone levels from those of the surroundings. Currently the integrated assessment modeling of European ozone control strategies is done utilizing the results of large-scale models intended for estimating the rural background ozone levels. This paper presents an initial study on how much local nitrogen oxide (NOx) concentrations can explain variations between large-scale ozone model results and urban ozone measurements, on one hand, and between urban and nearby rural measurements, on the other. The impact of urban NOx concentrations on ozone levels was derived from chemical equations describing the ozone balance. The study investigated the applicability of the method for improving the accuracy of modeled population exposure, which is needed for efficient control strategy development. The method was tested with NOx and ozone measurements from both urban and rural areas in Switzerland and with the ozone predictions of the large-scale photochemical model currently used in designing Europe-wide control strategies for ground-level ozone. The results suggest that urban NOx levels are a significant explanatory factor in differences between urban and nearby rural ozone concentrations and that the phenomenon could be satisfactorily represented with this kind of method. Further research efforts should comprise testing of the method in more locations and analyzing the performance of more widely applicable ways of deriving the initial parameters.

Air Pollutants↗
PubMed1992

Purification of pro- and eukaryotic superoxide dismutases by charge-controlled hydrophobic chromatography.

The process of purifying superoxide dismutases was simplified using charge-controlled hydrophobic chromatography on 10-carboxydecyl Sepharose. In only one chromatographic step following ammonium sulphate precipitation, Fe-containing superoxide dismutase from Pseudomonas putida and Cu,Zn-containing superoxide dismutase from bovine erythrocytes were purified with an overall yield of about 70% to electrophoretic homogeneity. The specific activities of the crystalline enzyme preparations were expressed in McCord and Fridovich units and were 3000 and 3200 U/mg, respectively.

Animals↗
PubMed1989

[Determination of the activity of superoxide dismutase in terms of rea substrate conversion].

On the basis of photochemical generation of O2.- and the tetrazolium/formazan system as indicating reaction an assay for SOD was developed which allows the determination of initial rate velocities of the enzyme. This was achieved by a special apparatus yielding the continuous registration of product formation simultaneously with the photochemical generation of O2.-. The investigation of the indicating reaction revealed that the reduction of nitro blue tetrazolium chloride to formazan is stoichiometrical with respect to riboflavin/methionine generated O2.- above pH 9. On this basis, an activity unit of SOD can be defined as real substrate consumption. One unit of the enzyme causes a decrease in the formation of formazan of 1 mumol/min under defined conditions.

Formazans↗
PubMed1988

Histochemically demonstrable activity of phosphate-activated glutaminase in the postnatally developing rat hippocampus.

Phosphate-activated glutaminase (PAG) mediating the conversion of glutamine to glutamate and ammonia, appears to be the major glutamate metabolizing enzyme in brain. The functional relevance of PAG in postnatally maturing glutamatergic/aspartatergic structures of the rat hippocampus was studied by means of quantitative enzyme histochemistry as an alternative to immunocytochemical techniques. The calibration of the histochemical PAG reaction as well as several control experiments for specificity were carried out to ensure reliability of findings. PAG activity increased markedly during the first weeks of life with a drastic rise between postnatal days 12 and 15. On the other hand, activity of NADH diaphorase involved in the histochemical PAG assay as an auxiliary enzyme, showed a different distribution pattern as well as a different developmental sequence with high levels early in ontogenesis. The topographical and temporal parallelisms of PAG activity to several other parameters which are putatively associated with postnatally maturing glutamatergic/aspartatergic transmission processes, mutually indicate their significance in such a functional context.

Aging↗
PubMed1985

[Characterization and differentiation of fluorescent pseudemonads by substrate utilization studies].

A rapid procedure is described for detecting and differentiating pseudomonads by their ability to degrade substrates with diverse physico-chemical properties, including volatile and non-volatile water-insoluble compounds, strong organic acids and bases, surfactants, disinfectants, and other toxic substances. The bacteria are embedded in an agar medium containing mineral salts and exposed to about 5 mg amounts of six to eight different substrates placed on the surface of an agar plate. After incubation at 25 degrees C for 24 hrs, growth zones around utilizable substrates may be used to differentiate various Pseudomonas strains and species.

Bacteriological Techniques↗
PubMed1976

Kinetics and reaction mechanism of yeast alcohol dehydrogenase with long-chain primary alcohols.

Kinetic studies of yeast alcohol dehydrogenase with NAD+ and ethanol, hexanol or decanol as substrates invariably result in non-linear Lineweaver-Burk plots if the alcohol is the variable substrate. The kinetic coefficients determined from secondary plots are consistent with an 'equilibrium random-order' mechanism for extremely low alcohol concentrations and for all alcohols, the transformation of the ternary complexes being the rate-limiting step of the reaction. This mechanism also applies to long-chain substrates at high concentrations, whereas the rate of the ethanol-NAD+ reaction at high ethanol concentrations is determined by the dissociation of the enzyme-NADH complex. The dissociation constants for the enzyme-NAD+ complex and for the enzyme-alcohol complexes obtained from the kinetic quotients satisfactorily correspond to the dissociation constants obtained by use of other techniques. It is suggested that the non-linear curves may be attributed to a structural change in the enzyme itself, caused by the alcohol.

Albumins↗
PubMed1976

[Kinetic properties of enzymes in particular of yeast alcohol dehydrogenase following their adsorption on polyaminomethylstyrene].

The adsorption of 8 enzymes to polyaminomethylstyrene was studied. While lactate dehydrogenase, alkaline phosphatase and glucose-6-phosphate dehydrogenase exhibit a relatively low affinity to the carrier, alcohol dehydrogenase, glutamate dehydrogenase and urease were found to form stabile complexes with the polymer that are enzymatically active. Adsorbed urease and beta-hydroxybutyrate dehydrogenase, are still active after several weeks; the other preparations lose their activity soon. It can be shown by the example of yeast alcohol dehydrogenase that the activity loss following adsorption is caused possibly by a process of reorientation of already bound enzyme molecules or by the increasing enzyme coverage of the carrier, with the active centres becoming more and more inaccessible for the substrate. During the substrate conversion catalysed by the alcohol dehydrogenase-polyaminomethylstyrene complex, a small amount of the enzyme is again detached from the carrier. The activity rises to a certain extent in the supernatant but drops to zero again. The stability of the adsorbed urease is distinctly increased compared with the dissolved enzyme. For the pH optimum and the KM value there are no differences between the two preparations. Continuous application of polyaminomethylstyrene-bound beta-hydroxybutyrate dehydrogenase and urease, respectively, in a column shows that both preparations have unchanged enzymatic activities even after running times of 5 and 24 days, respectively.

Adsorption↗
PubMed1976

[Enzymatic conversion of tetradecanol in heterogenous phase by yeast-alcohol dehydrogenase].

Alcohol dehydrogenase from yeast converts long-chain primary alcohols not only in the dissolved state, but also at the surface of undissolved particles. Tetradecanol beads with a defined surface can be produced and employed as model substrate. The reaction rate was determined by the proton release accomplished in the reaction. The initial reaction rate depends on the enzyme concentration. The relation is nonlinear (vi = k-[e]0,4); the numerical value of the exponent (n = 0.4) argues in favour of a reaction occurring at the interface. The Lineweaver-Burk plots become linear if the substrate concentrations are based on the molar surface concentrations of the particles. The pH optimum for the reaction at the surface is displaced by 0.25 pH units towards the alkaline region (compared with ethanol as substrate). The activation energy of the reaction with tetradecanol beads as substrate is 30% lower than that for the ethanol oxydation.

Alcohol Oxidoreductases↗
PubMed1975

Separation of dehydrogenases on polyaminomethylstyrene.

The binding of dehydrogenases, especially alcohol dehydrogenase, and other proteins to several ion exchangers and hydrophobic polymers was investigated. Quantitative parameters for the stability of the polymer-protein complexes (obtained form double reciprocal plots) indicate a high but different affinity of many proteins for polyaminomethylstyrene. The chromatography of a mixture of five dehydrogenases and human serum albumin on polyaminomethylstyrene is described.

Alcohol Oxidoreductases↗
PubMed1975

[Kinetic studies on long-chain alcohol turnover by yeast alcohol dehydrogenase within the transition from real solution to emulsion or suspension].

The enzymatic oxidation of hexanol, decanol, and tetradecanol by yeast alcohol dehydrogenase was studied. The enzyme was found to catalyze not only conversion in the real aqueous solution of the substrates, but also at the surface of undissolved substrate particles. The kinetic parameters varied on transition from the real solution to dispersion, in dependence on the chain length of the substrate.

Alcohol Oxidoreductases↗