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In this paper, we examined the effect of adsorbed monovalent ions on the surface charge of liposomal membranes formed from neutral (sphingomyelin), anionic (phosphatidylinositol) lipids mixed in various ratios. The surface charge density of the membrane was determined from electrophoretic mobility measurements at various pHs of solution. A four-quilibria model describing adsorption of ions on the sphingomyelin (SM) membrane and a two-equilibria model describing adsorption of ions on the phosphatidylinositol (PI) membrane was presented. We proposed a mathematical model for characterizing these equilibria. Using these models, together with experimental data of the membrane surface charge density, we determined association constants characterizing the equilibria. The correctness of the proposed model was proven by comparing the theoretical charge variation curves for SM and PI membranes with the experimental date.

We examined the adsorption of Na+, Cl−, H+, and OH− ions on phosphatidylcholine-cardiolipin liposomal membrane surfaces using both experimental and theoretical approaches. The dependence of the membrane surface charge density on the pH of the electrolyte solution was determined using microelectrophoresis. A mathematical model comprising eight equilibria was formulated to describe the adsorption of the electrolyte ions. Combination of this model with experimental surface charge density values enabled the determination of association constants. From the good agreement between the experimental and theoretical data, we can conclude that the assumed model is compatible with the experimental data.

In this study, the influence of pH, electrolyte concentration, and type of ionic species on the electrokinetic properties (zeta potential and electrokinetic charge density) of the acid-activated montmorillonite mineral have been investigated using the microelectrophoresis method. The electrokinetic properties of acid-activated montmorillonite dispersions have been determined in aqueous solutions of mono-, di-, and trivalent salts and divalent heavy metal salts. Zeta potential experiments have been performed to determine the point of zero charge (pzc) and potential determining ions (pdi). The zeta potential values of the acid-activated montmorillonite particles were negative and did not vary significantly within the pH range studied. Acid-activated montmorillonite dispersions do not have point of zero charge (pzc). The valence of the electrolytes has a great influence on the electrokinetic behavior of the suspension. A gradual decrease in the zeta potential (from −25 mV to −5 mV) occurs with the monovalent...

Nanocapsules containing hinokitiol (HKL) were prepared by an emulsion-diffusion method. In an emulsification step in preparing nanocapsules, cetyltrimethylamonium chloride (CTAC) was employed as a cationic emulsifier, Poly(epsilon-caprolactone) (PCL) was use as a wall material and HKL dissolved in octylsalicylate (OS) was used as a core material. The submicron-sized nanoparticle was observed on a TEM. The size ranged 55-234 nm and the mean diameters were 223 nm, which were determined by a dynamic light scattering method. According to the results of pH-dependent microelectrophoresis, the absolute value of the surface potential of the nanocapsules was greater than 20 mV. The nanocapsules were colloidally stable over the pH range of 3-11. The nanocapsules were included in two kinds of preparations, namely shampoo and hair tonic, and the preparations were applied every day for 3 weeks on the clipped backs of 6 week-old mouse (C57BL/6) to investigate the hair growth-promoting effect. The degree of hair growth was evaluated by image-analysing the photographs of the backs and, in parallel, by the histological observation of the formation and the growth of hair or hair bulbs. The results were compared with those of commercially available Minoxidil solution (3%). Phosphate buffered saline was used as a control. The in vivo hair growth-promoting effects of the two preparations were comparable to those of Minoxidil solution. These results are in a good agreement with the histological and structural changes of follicles of the model animals, of which skins were treated with either the testing samples or the control in the same way the experiments of in vivo hair growth promotion were performed.

The relatively new technique of Sedimentation/Steric Field-Flow Fractionation (Sd/St FFF) is a simple, fast, and accurate method for the size separation and characterization of starch granules. In the present work, the Sd/St FFF technique was used for the calculation of the mass ratios of the A-large and B-small granules from barley and wheat starch samples. The mass ratios were obtained from the distribution curves of the starch samples at various pH and ionic strength of the suspending medium, in the presence or the absence of the surfactant FL-70. The influence of the suspension pH and ionic strength on the mass ratios of A- and B-granules is discussed in relation to the zeta potentials of the particles, which were measured by a microelectrophoresis apparatus.

Microelectrophoresis is an important technique for characterizing the surface charge and stability of colloidal dispersions. Zeta potential has been calculated from electrophoretic mobility measurements using capillary cell electrophoresis for more than 50 years. This particular new method for obtaining electrophoretic mobility and zeta potential results improves the resolution compared with previous methods, provides accurate mean mobility and mobility distributions in a single measurement, avoids making multiple measurements at different locations through the capillary cell and eliminates the requirement for measurement at the stationary layer of a capillary cell altogether. M3 is an acronym for “Mixed Mode Measurement”. This new measurement method is a combination of measurements that improve the resolution of mean electrophoretic mobility measurements and provide mobility distribution results that will be described herein. The combination of measurements includes a fast field reversal measure...

Microcapsules were prepared by complex coacervation between gelatin (Type A) and carboxymethylcellulose (CMC). Triclosan (TS) dissolved in octyl salicylate (OS) was used a core material and glutaraldehyde as a crosslinking agent. The microcapsules on the scanning electron micrographs were spherical and exhibited core and shell morphology. The thermograms of freeze-dried microcapsules showed no evidence for the melting of TS, suggesting that TS remained dissolved in the cores of the microcapsules and did not exist as a crystalline solid even after the microcapsules were dried. Microelectrophoresis revealed that the point of zero charge of the microcapsules occured around pH 3.3, far below the isoelectric point of gelatin. This means that along with gelatin, CMC, a negatively charged polymer, constitutes the wall of microcapsules, decreasing the positive charges on the gelatin. The degree of release of TS and OS from the microcapsules in ethanol/water solvents was strongly dependent on the content of the al...

The present work examines the effect of pH on aqueous suspensions of alumina and alumina–kyanite mixtures to assess the influence of kyanite additions on suspension properties. This system is of interest because on heating to temperatures above 1400°C the mineral kyanite (Al2O3 . SiO2 ) reacts to form silica and mullite (3Al2O3 . 2SiO2 ) and as the latter mineral has attractive elevated temperature properties, its incorporation into a common refractory material such as alumina is of importance in the field of technical ceramics. A popular method to produce such materials is to prepare a stable suspension of the components of interest and cast a green compact from the slurry; this compact is subsequently sintered at an appropriate temperature to densify the product. As the solids content of the original suspension influences the final product density, rheological properties are of critical importance. Both microelectrophoresis and rheological techniques suggested that a pH of 3–4 provided optimum s...

The purpose of this study was to determine whether the interfacial properties of emulsifier films could be related to emulsion stability and therefore be used as stability predictors using Bovine serum albumin (BSA) as a model oil-in water (o/w) emulsifier. Soybean o/w emulsions were prepared by ultrasonication, emulsion droplet interfacial charge was determined by microelectrophoresis, droplet size distribution was measured using an Accusizer, and centrifugal stress was studied using an ultracentrifuge. Real time, thermal kinetic, and centrifugal stress accelerated stability tests were performed. Stability data obtained from centrifugal stress tests followed the same trends as real time stability data and these data were in general agreement with stability predictions made based on interfacial properties. The thermal kinetic accelerated tests were not predictive of stability, because emulsion breakdown was rapid and did not allow differentiation between the emulsions. Emulsion stability increased with an increase in emulsifier concentration (emulsions prepared at 2% w/v BSA had not cracked at 60 days, whereas those prepared at 0.1% w/v had cracked-by 30 days), increase in ionic strength (emulsions prepared at an ionic strength of 1 mM had cracked by 60 days, whereas those prepared at an ionic strength of 10 mM had cracked by 90 days), and decrease in temperature (emulsions prepared at 37 and 60 degrees C had cracked by 5 days, whereas those prepared at 5 and 25 degrees C had not cracked at 60 days). There was no significant change in stability for emulsions prepared at pH 5.3 and pH 7.4. The addition of dextran sulfate improved emulsion stability, whereas the addition of acacia decreased stability. Emulsions prepared with BSA alone cracked by 90 days, those prepared with BSA and acacia cracked by 30 days, and those prepared with BSA and dextran sulfate had not cracked at 90 days. Interfacial properties were useful in predicting emulsion stability.

The study was aimed at investigating the role of asphaltenes as stabilizers for totuene-in-water miniemulsions. These miniemulsions were prepared with sodium laurylsulphate and cetyl alcohol. To confirm the amphoteric nature of the asphaltenes: 1) they were adsorbed on fluorite and their electrophoretic mobility was measured using a microelectrophoresis cell and; 2) interfacial tension measurements were carried out using a tensiometer. The experiments reported here use the electrosonic analysis (ESA) method and were carried out on the ESA-8000 Analysis System (Matec) It was experimentally observed that there is a direct relationship between the ESA Potential and the asphaltenes content in the miniemulsions. The pH influence on the ESA Potential of the alphaltenes-containing miniemulsions was investigated as welt A theoretical explanation for both phenomena is provided. To our knowledge, this is the first published attempt to determine the influence of asphaltenes on toluene-in-water emulsions sta...

Measurements of zeta potential (microelectrophoresis) and surface charge (polyelectrolyte titration) were performed on natural rubber latex with the addition of anion-active tensides of the fatty acid type. The negative zeta potential showed a monotonous rise with increasing tenside concentration for decanate, while a maximum was observed for laurate, myristate, and palmitate. The surface charge increased monotonously. A comparison with direct adsorption measurements showed that zeta potential measurements allow a simple determination of optimal tenside concentration, and that the mentioned maximum is related to the saturation concentration of the tenside.

The present study was aimed to identify peculiarities of the polypeptide composition in three morphofunc-tionally different classes of neurons of the rat brainstem: giant multipolar neurons of n. reticularis gigantocellularis, relay sensory neurons of lateral geniculate body and pyramidal neurons of the pyramidal layer of the CA3 – CA4 fields of hippocampus. The method of free hand dissection of neurons and sodium dodecyl sulfate (SDS) slab gel microelectrophoresis in our modifications were used. Polypeptide peculiarities for each class of investigated neurons have been found. Most of these polypeptides belong to the low molecular weight range (8.8–24.3 KD) of the polypeptide spectra and only some of them to the high one (64.6–75.3 KD).

A relationship between Hb Bart's levels in cord blood and the number of alpha-globin genes has been established by screening cord blood samples from 1,075 newborn babies. Diagnosis was made by gene mapping of DNA samples with restriction endonuclease digestion. The presence of Hb Bart's was determined with a discontinuous microelectrophoresis on cellulose acetate at pH 8.34. The establishment of this relationship allows an early diagnosis of alpha-thalassemia by this simple microelectrophoretic procedure.

Alkaline sucrose sedimentation was for a number of years the standard procedure for the measurement of single-strand breaks. Some years ago a number of new techniques with improved sensitivity were introduced. The following techniques are presented and discussed: alkaline unwinding, alkaline filter elution, nucleoid sedimentation, viscoelastometry, microelectrophoresis of single cells, DNA precipitation, pulse field gel electrophoresis, fluctuation spectroscopy and nick translation.

Simplified agarose-coated capillary microelectrophoresis was adapted to the Macrophage Electrophoretic Mobility (MEM) test for cancer detection. Guinea pig alveolar macrophages gave superior reproducibility to peritoneal macrophages. As good or better reproducibility was obtained with cryopreserved, as with fresh macrophages. The electrophoretic mobilities of patients' lymphocytes themselves, after incubation with Encephalitogenic Factor (EF) showed a significant increase in electrophoretic mobility, while in control lymphocytes a decrease occurred. Thus, for the detection of the results of the interaction of EF on human lymphocytes, a direct lymphocyte electrophoretic mobility test may suffice, and guinea pig macrophages may no longer be required at all.

Dilute emulsified particles (≅300 mg•dm-3, da≅8 μm) of heavy oil A were removed in a 50×50mm-square and 0.32m-deep column by flotation using small bubble swarms (da≅80 μm) generated by a rapid depressurization of supersaturated liquid. Pressure at which air was dissolved was varied within 2-4.5×105 Pa. The flotation efficiency is best at 3×105 Pa and decreases at higher pressure in spite of higher bubble holdup, probably because of excessive liquid disturbance. The flotation is also influenced significantly by the chemical species added and their concentrations. A solution of pH 4 shows the best flotation in the pH range investigated (pH 2-10). A microelectrophoresis measurement shows that the zeta potential ξ of both oil particle and bubble shifts from positive to negative with increasing pH through a PZC (point of zero charge, ξ=0) around pH 4 and the best flotation at pH 4 can be explained by the great reduction in repulsive interaction of the electric double layer. Flotation efficiencies are improved in CaCl2 and A1C13 solutions with increasing concentration (10-5-10-2 mol-dm-3) while they decrease [slightly in NaCl solution. This trend is discussed semiquantatively in the light of the variation of zeta potential with concentration.

A method and an apparatus to measure the ξ-potential of bubbles has been developed. The apparatus is of microelectrophoresis type. Small bubbles of 20-40μm in diameter are generated by pressure reduction of a solution containing dissolved air and are introduced into an electrophoresis cell of 0.972 mm thickness. As the movement of the bubbles is followed over 4 seconds in this arrangement, the measurement error due to the rapid rising of the bubbles can be considerably decreased. The bubbles were positively charged in a cationic surfactant solution of cetyltrimethylammonium bromide (CTAB) and the charge decreased with increasing electrolyte concentration in the solution. In an anionic surfactant solution of sodium dodecyl sulfate (SDS), both the bubbles and oil particles were negatively charged. But, by the addition of Al2(SO4)3, the oil particles maintained their negative charge while the charge of the bubbles was changed to positive. The situation of the attaching of oil particles to bubbles was observed photographically.

Vertical fractionation of a mixture of fixed horse and human red blood cells layered over a stabilizing support medium was done to give a valid comparison with proposed space experiments. In particular, the effects of sample thickness and concentration on zone migration rate were investigated. Electrophoretic mobilities of horse and human cells calculated from zone migration rates were compatible with those obtained by microelectrophoresis. Complete cell separation was observed when low power and effective cooling were employed.

The electrokinetic properties exhibited by a lignitic coal, a highly oxidized coal, and an unoxidized eastern Canadian coal together with its associated pyrite were investigated by using the microelectrophoresis technique. Points-of-zero-charge (PZC) of the samples were determined to be at pH values of 2.1,2.8,5.1 and 2.2 respectively. Mechanisms of surface charging on these coals are discussed on the basis of various hypothetical models of the surface compounds. The relationship between surface behaviour of the samples and pH is explained and the implications of the electrokinetic differences between banded ingredients of coals are discussed. Resume Les proprieties electrocinetiques d'un charbon a base de lignite, d'un charbon tres oxyde, d'un charbon non oxyde de l'est du Canada ainsi que sa pyrite ont ete mises en evidence et etudiees a l'aide de la technique de la micro-electrophorese. Les points de charge zero des echantillons ont ete determines a pH 2.1, 2.8,5.1 et 2.2 respectivement. Les me...

The problem in title is analyzed for dilute solutions with no substantial intenonic effects and with the diffusivity and the electrophoretic mobility being related via the Nernst-Einslein equation. The case is considered of only the positive ion reacting at the electrodes, being produced at the anode and consumed at the cathode, With the electroneutrality condition as a first approximation, the equations for the average concentration and the electric field are decoupled and solved analytically. Then the deviation from electroneutrality is calculated in the second approximation via Poisson' s equation. The problem has a steady state if the current is smaller than a certain value. With this analysis and measurements of concentrations at different times, electrophoretic mobilities of the two ions can be calculated. The implications for interpreting measurements in microelectrophoresis and electrophoretic mass transport analysis are discussed

Three different micromethods for studying GABA biochemistry and function at single microdissected GABA-acceptive neuronal membranes are discussed. The basis for such studies is the possibility of obtaining by microdissection single Deiters' neurons from the lateral vestibular nucleus of the rat and the rabbit. From these isolated cells the plasma membrane may be prepared and studied. The first micromethod allows the study of the Na+ independent diffusion of GABA through such a plasma membrane which is postsynaptic to GABA-ergic boutons. A modification of such method allows also the study of the effects of GABA-ergic drugs on Cl- permeability. The second method allows the study by microelectrophoresis in capillaries of GABA catabolism by GABA-T associated with microdissected single Deiters' membranes. The third one was developed in order to study the characteristics of Na+ dependent GABA carrier activity present on such membranes.

The zeta-potentials af silver. silver bramide and silver sulphide have been determined by streaming potential and microelectrophoresis measurements. It is shown that the zela-potential af SIlver bromIde depends on crystal size and can be altered by photolysis. The charge on colloidal silver and silver sulphide is negative at pAg values above 5 O. The effect of adsorbed gelatin an the zeta-potential of the three substances has been examined and the results are discussed in relation to theories of photographic development.