PubMed · 13603322
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D KIRMAN, S W MORGENSTERN, D FELDMAN. 1958. A modified microtechnic for determining chloride.. https://pubmed.ncbi.nlm.nih.gov/13603322/
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We have studied the peroxidase-oxidase reaction catalyzed by human myeloperoxidase in an open system where both substrates-molecular oxygen and NADH-are supplied continuously to the reaction mixture. The reaction shows oscillatory kinetics at pH values around 5, provided that the reaction medium in addition to the enzyme and the substrates also contains an aromatic electron mediator such as melatonin or 4-hydroxybenzoic acid and chloride ions at concentrations >1mM. The experimental findings can be simulated by a detailed model of the reaction. The results are important for our understanding of oxidant production in neutrophils.
In this paper, a simple, flexible, and cost-effective flow-through microdialyzer hyphenated with a miniaturized differential potentiometric detector is proposed for continuous diffusion-controlled sampling of analytes of environmental interest. The analytical performance of the dedicated configuration involving merely a single cellulose regenerated hollow fiber is critically compared with that of commercially available concentric probes commonly exploited for in vivo monitoring of the extracellular space in living tissues and that of large dialysis-based probes furnished with flat membranes. The outstanding feature of the capillary-type design is the ability of adapting the extraction fractions (EF) to the requirements of the assays and flow-through detectors by selection of appropriate membrane length/perfusion rate ratios. Passive sampling under steady-state conditions (EF approximately 100%) has proven feasible for environmentally relevant ions, such as chloride, by perfusing a 3-cm-long capillary with water at a flow rate of 2.0 microL/min. Hence, there is no need for recalibration of the flow setup after implantation of the purpose-made probe. The effect of physical and chemical variables on the diffusive flux is discussed in detail for the various flow-through membrane separation devices assessed. Effective means to attain identical dialysate concentrations of target species under dynamic regime irrespective of the matrix ingredients are also presented. The dedicated microdialyzer features extreme tolerance to high molecular weight interfering matrix compounds (> or =5000 mg/L humic acid) at the 5% interference level, which makes it especially suited for the interference-free potentiometric determination of ionic species in environmental samples containing high levels of organic matter. The potentials of the membrane separation unit were assessed for continuous monitoring of chemical changes in the interstitial/pore water of organic soils via stimulus-response strategies.
Micropatterning of surfaces with several chemicals at different spatial locations usually requires multiple stamping and registration steps. Here, we describe an experimental method based on reaction-diffusion phenomena that allows for simultaneous micropatterning of a substrate with several coloured chemicals. In this method, called wet stamping (WETS), aqueous solutions of two or more inorganic salts are delivered onto a film of dry, ionically doped gelatin from an agarose stamp patterned in bas relief. Once in conformal contact, these salts diffuse into the gelatin, where they react to give deeply coloured precipitates. Separation of colours in the plane of the surface is the consequence of the differences in the diffusion coefficients, the solubility products, and the amounts of different salts delivered from the stamp, and is faithfully reproduced by a theoretical model based on a system of reaction-diffusion partial differential equations. The multicolour micropatterns are useful as non-binary optical elements, and could potentially form the basis of new applications in microseparations and in controlled delivery.