PubMed · 5746050
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A Masse. [Should Moore prostheses be cemented?].. https://pubmed.ncbi.nlm.nih.gov/5746050/
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The aim of this study was to investigate possible interactions between a polymeric emulsifier and a non-ionic surfactant, with a view of achieving better understanding of emulsion stabilisation mechanisms. The polymeric emulsifier used was acrylates/C10-30 alkyl acrylate crosspolymer (Pemulen TR-2(R)), while Polyoxyethylene 20 sorbitan mono-oleate (Polysorbate 80) has been chosen as a model surfactant. Both materials were used within the concentration range relevant for their practical application. A 0.2%w/w aqueous dispersion of polymeric emulsifier, containing various amounts of surfactant (from 0.01 to 1.0% w/w) was used throughout the study. Interfacial aspects of the proposed polymer/surfactant interactions were analysed by means of surface tension measurements. Changes in the network structure of the test dispersions were quantified by continuous shear rheometry, supported by the texture analysis. To analyse the influence of hydrophobic alkyl groups present on the Pemulen TR-2(R) chains, an unmodified, hydrophilic polyacrylic acid polymer, Carbopol 934P(R), was assessed under the same conditions. The results obtained by both surface tension and rheological studies have revealed large differences in behaviour of the two polymers in the presence of the model surfactant. Pemulen TR-2(R) was shown to desorb the surfactant from the surface, within the whole concentration range studied. Furthermore, an increase in viscosity and texture profile parameters with increasing Polysorbate 80 concentration up to 0.3% w/w was evident in the case of Pemulen TR-2(R) dispersions. This was followed by a decrease in the gel network strength at higher surfactant concentrations. On the other hand, Carbopol 934P(R) has shown no signs of surfactant desorption and only small changes in the network structure with the increasing concentration of surfactant. It is shown in this study that an interaction between a polymeric emulsifier Pemulen TR-2(R) and a non-ionic surfactant Polysorbate 80 does occur in their aqueous dispersion, and that it is: (a) hydrophobic in nature; (b) concentration-dependent; and (c) has an impact on the rheological properties of dispersion.
Phanerochaete chrysosporium, grown on cellulose, produced a cellobiose-dependent dehydrogenase which reduced both ferric iron and molecular oxygen, resulting in the generation of the hydroxyl radical. The hydroxyl radical was detected in reaction mixtures with and without the addition of exogenous H2O2. The purified reductase and the fungus grown under nonligninolytic conditions that promote the production of the reductase were able to depolymerize an insoluble polyacrylate polymer. When oxalate, a secondary metabolite of P. chrysosporium, was used as the iron chelator, it was oxidized by the hydroxyl radical to form the carboxylate anion radical, a strong reductant. Under these reductive conditions, the enzyme was shown to catalyze the reduction of bromotrichloromethane to the trichloromethyl radical. We propose that these oxidative and reductive mechanisms may contribute to the degradation of a wide range of environmental pollutants by fungi which produce this enzyme.
Investigations of fluorescence lifetimes of the dye 6-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]hexanoic acid (NBD-HA) and of DNA M13 primers labeled with NBD-HA, Cy3, rhodamine green and 4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene++ +-3-propionic acid (BODIPY-FL) dyes in polyacrylamide gels of various degrees of crosslinking and different crosslinkers, and in a cellulose sieving buffer with different organic modifiers, are described. The dependence of fluorescence lifetime on gel matrix and on experimental conditions was studied in order to identify which factors may be important for optimization of multiplex fluorescence lifetime detection. Lifetimes were determined in both batch solution and on-the-fly, on-column in CE. Results show that lifetimes of the primer-attached dyes remain constant in gels of different composition. Additionally, multiexponential fluorescence decays are observed for primer-attached dyes in batch solutions of the cellulose sieving buffers but are reduced to monoexponential decays when measured on-the-fly, on-column in CE. Lifetime detectability can be improved by addition of an organic modifier to the gel matrix.