Reduction In Zeta Potential Research Articles

Inhibition of human red cell sodium and potassium transport by divalent cations.

The influx and efflux of Na and K across the human red cell membrane by the bumetanide-sensitive (Na-K co-transport) and residual (ouabain- and bumetanide-insensitive) routes were inhibited by increasing concentrations of external Mg. Ca, Sr, Ba, Mn and Co also inhibited bumetanide-sensitive and residual K transport. External Mg inhibited choline uptake and the Na-dependent fractions of L-alanine and L-serine uptakes. External Mg reduced the maximal rate (app. Vmax) but not the affinity (app. Km) of the bumetanide-sensitive K and Na influxes when they were measured as functions of external K and Na respectively. The inhibitory effect of Mg was not due to a small reduction in zeta potential since much larger reductions in zeta potential produced by neuraminidase did not affect transport. Internal Mg stimulated the ouabain-sensitive K influx but inhibited the co-transport and residual components of K influx. Bumetanide was a poor co-transport inhibitor in red cells pre-treated with A23187 and EDTA. It was concluded that the inhibitory effects of external Mg were probably not due to changes in the ionic composition of the diffuse double layer adjacent to the cell membrane. Mg and other divalent cations should not be used as 'inert' ionic substitutes in human red cell Na and K transport studies.

Thin double layer approximation for electrophoresis and dielectric response

An earlier thin double layer approximation for the dielectric response of spherical macroions is extended to allow calculation of the electrophoretic mobility and inclusion of convective polarization of the ion atmosphere. Comparison is made with exact numerical results and with other thin double layer approximations. The approximation gives fairly accurate values of the dielectric response at macroion radii down to 50 D lengths, for the range of zeta potentials 0≤ζR≤8, where ζR is the reduced zeta potential and D is the Debye length. The accuracy worsens gradually with decreasing size and increasing zeta potential. Electrophoretic mobility results are considerably better.

Quantitative haemagglutination. 4. Effect of neuraminidase treatment on agglutination by blood group antibodies.

Summary. As sialic acid is removed from red cells by neuraminidase treatment agglutinability measured by the sensitive AutoAnalyzer continuous flow technique increases with anti‐A, ‐B, ‐H, ‐D and ‐c. The increase in agglutinability is related to the amount of sialic acid removed, but the relationship is different for different antibodies. Rather than a simple non‐specific reduction in zeta potential, these results suggest a more complex explanation, probably involving the decrease of ordered water near the surface of the desialated cells.

Deaggregation in Oil-In-Water Emulsions II: Influence of Alcohols and Dioctyl Sodium Sulfosuccinate

The influence of n -butanol, n -hexanol, n -octanol, and dioctyl sodium sulfosuccinate (AOT) on the deaggregation of a 2 per cent hexadecane-in-water emulsion was studied. It was found that n -butanol did not significantly affect the deaggregation rate, n -hexanol depressed deaggregation rate at higher concentrations, and both n -octanol and AOT were capable of inhibiting deaggregation completely at relatively low concentrations. AOT was observed to depress the rate of deaggregation further than equivalent concentrations of NaCl shown previously. These observations were interpreted as further evidence that both reduction of zeta potential and film-film attractions are important to enhancing aggregation in disperse systems.

Investigation of the Sedimentation Behavior of Dispersions

Using a modification of the method of Greiner and Vold, suspension isotherms were obtained for dispersions of zinc oxide, calcium carbonate, and bismuth sub-carbonate in sodium lauryl sulfate, dioctyl sodium sulfosuccinate and sodium-salts of polymerized alkylnaphthalenesulfonic acids (Daxad 11) solutions. For zinc oxide and bismuth subcarbonate systems maximum suspendability was reached at surfactant concentrations somewhat beyond the critical micelle concentration and extended over a relatively short concentration range. In the case of calcium carbonate, limited suspendability was observed with all three surfactants. Previous workers attribute the reduction in suspendability at higher surfactant concentrations to a reduction in zeta potential, thus permitting increased aggregation. Suspension isotherms obtained at constant and varying ionic strengths of sodium chloride indicate that aggregation is facilitated by the presence of excess surfactant through some additional mechanism. Using a modification of the method of Greiner and Vold, suspension isotherms were obtained for dispersions of zinc oxide, calcium carbonate, and bismuth sub-carbonate in sodium lauryl sulfate, dioctyl sodium sulfosuccinate and sodium-salts of polymerized alkylnaphthalenesulfonic acids (Daxad 11) solutions. For zinc oxide and bismuth subcarbonate systems maximum suspendability was reached at surfactant concentrations somewhat beyond the critical micelle concentration and extended over a relatively short concentration range. In the case of calcium carbonate, limited suspendability was observed with all three surfactants. Previous workers attribute the reduction in suspendability at higher surfactant concentrations to a reduction in zeta potential, thus permitting increased aggregation. Suspension isotherms obtained at constant and varying ionic strengths of sodium chloride indicate that aggregation is facilitated by the presence of excess surfactant through some additional mechanism.