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At least 1,045 records · Page 58Linked to original sources
PubMed1990

Effect of polyelectrolytes on serine proteinase secretion by Bacillus subtilis.

Addition of polycations with molecular masses of 5-40 kDa as well as Na+, stimulated serine proteinase secretion by Bacillus subtilis cells. Polyanions and higher-molecular-mass polycations (100-200 kDa) were inefficient. The enzyme yields in the presence of polycations or Na+ were equal in magnitude. The results indicate that the cations, apparently counteracting the negative surface charge of the bacterial plasma membrane, cause the desorption of the serine (alkaline) proteinase. The synthesis of the proteinase is inferred to be stopped as the enzyme is bound to the outer surface of the plasma membrane. The desorption of the enzyme thus induces the synthesis of the new portions of proteinase.

Bacillus subtilis↗
PubMed1991

Immobilization of invertase by encapsulation in polyelectrolyte complexes.

Free and polystyrene-bound invertase from Saccharomyces cerevisiae were encapsulated within symplex membranes which were composed of cellulose sulfate as the polymeric anion and poly(dimethyldiallylammonium chloride) as the polymeric cation. The kinetics and the performance of the encapsulated enzyme preparations have been compared to the free enzyme employing the hydrolysis of sucrose. The pH and temperature optima were only slightly affected by the encapsulation. The kinetic constants, however, were changed by the encapsulation as a result of diffusional limitation. Encapsulated invertase showed a high storage stability and a high operational stability if low substrate concentrations were applied. The coimmobilization of invertase with living cells, which are not capable of utilizing sucrose, in the described capsules, opens many possibilities in fermentation technology.

Enzyme Stability↗
PubMed1993

Change in pH during setting of polyelectrolyte dental cements.

The change in pH during setting has been studied for five different glass polyalkenoate (ionomer) cements and for two different zinc polycarboxylate cements using a flat-headed combination electrode on both the fresh cement and on a slurry of the set cement. The results show that the pH of the glass ionomers was slightly lower in the early stages of setting than was the pH of the zinc polycarboxylates and also that the pH of glass ionomers rises more slowly. For anhydrous cements (i.e. those formulated from dried polymer) pH was found to rise quicker than for hydrous cements (i.e. those prepared from aqueous solutions of polymer). Previous workers have assumed that anhydrous cements undergo slower rises in pH than hydrous ones. Our results clearly refute this assumption, and also suggest that the reported pulpal irritation associated with the use of anhydrous glass ionomers may be due to something other than low pH.

Acrylic Resins↗
PubMed1975

Electro-optical studies on synthetic polyelectrolytes. I. Ultraviolet electric dichroism of poly-N-alkylvinylpyridinium bromides in aqueous solution.

The electric dichroism of aqueous solutions of poly-2- and 4-vinylpyridinium bromides has been measured in the 220 to 300 nm region. From the knowledge of the assignments of the absorption bands, the orientation of the pyridinium ring with respect to the macromolecular axis was determined for the poly-N-butyl-4-vinylpyridium bromide. An estimation of the birefringence contribution in the visible region originating from these ultraviolet dichroic bands revealed that the negative birefringence observed mainly arose from electronic transitions at shorter wavelengths.

Mathematics↗
PubMed1976

Thermodynamic properties of polyelectrolyte solutions containing mixtures of monovalent and trivalent counterions.

The osmotic coefficients, heats of dilution, and volume changes on dilution of aqueous solutions containing mixtures of polystyrenesulfonic acid and its lanthanum salt have been determined at 25 degrees C. The curve representing the osmotic coefficient as a function of the equivalent fraction of the acid has a maximum; the corresponding curves for the enthalpy and volume changes on dilution have a sigmoidal shape. Experimental results have been compared with predictions of the theory based on the cell model with cylindrical symmetry. A semiquantitative agreement between theory and experiment has been found.

Electrolytes↗