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Elucidating electrokinetic stability by which surface charges regulate toxins interaction with erythrocytes is crucial for understanding the cell functionality. Electrokinetic properties of human erythrocytes upon treatment of Vipoxin, phospholipase A2 (PLA2) and Vipoxin acidic component (VAC), isolated from Vipera ammodytes meridionalis venom were studied using particle microelectrophoresis. PLA2 and Vipoxin treatments alter the osmotic fragility of erythrocyte membranes. The increased stability of cells upon viper toxins is presented by the increased zeta potential of erythrocytes before sedimentation of cells during electric field applied preventing the aggregation of cells. Lipid peroxidation of low dose toxin-treated erythrocytes shows reduced LP products compared to untreated cells. The apparent proton efflux and conductivity assays are performed and the effectiveness PLA2 > Vipoxin>VAC is discussed. The reported results open perspectives to a further investigation of the electrokinetic properties of the membrane after viper toxins treatment to shed light on the molecular mechanisms driving the mechanisms of inflammation and neurodegenerative diseases

The effect of delipidation on the electric surface properties of purple membranes was investigated by electric light scattering and microelectrophoresis. Natural membrane lipids were partially removed (approximately 75% of the phospholipids are extracted) from purple membrane using mild treatment with the zwitterionic bile salt 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate. Partial delipidation of purple membrane fragments causes: (i) a strong reduction of the permanent dipole moment from 6.10 X 10 −24 Cm for native to 0.56 X 10 −24 Cm for delipidated purple membranes, and (ii) a two-fold decrease in the electric polarizability. The ionic strength effect on the electric surface properties of delipidated purple membranes confirms the electrokinetic nature of a part of the membrane charge asymmetry. The contribution of the native membrane lipids to the electro-optically observed permanent dipole moment, i.e. to the membrane charge asymmetry, of purple membrane is demonstrated.

The electrophoretic mobility of microbial cell surfaces can be analysed in terms of a so-called soft layer model, in which the electrophoretic mobility is described as originating from the potentials over the surface charge layer and the membrane fixed charges. Often, the polyelectrolyte layer deforms under the influence of ionic strength variations. In the soft layer analysis of electrophoretic mobilities this is expressed in the softness 1/lambda. Here, we determined the softness of two oral streptococcal strains, S. salivarius HE and HBC12 from particulate microelectrophoresis in KCl solutions of varying ionic strength. Electron microscopy of negatively-stained organisms and X-ray photoelectron spectroscopy showed that strain HE had several classes of proteinaceous fibrils with lengths up to 178 nm on its outermost surface, while variant HBC12 had a bald, peptidoglycan-rich outer surface. The fibrillated strain HE appeared as relatively soft (1/lambda equals 1.4 nm) from analysis of its electrophoretic mobility, while the bald variant HBC12 was hard (1/lambda equals 0.7 nm) due to its comparatively rigid, peptidoglycan-rich outer surface, characteristic to Gram-positive bacteria. The presence of proteinaceous fibrils on strain HE slightly shielded the membrane fixed charges on HBC12. (C) 1998 Elsevier Science B.V. AU rights reserved.

Model membranes (liposomes) of egg yolk phosphatidylcholine were exposed to the charged (cationic) form of amphiphilic drugs (procaine, tetracaine, metroprolol, alprenolol and propranolol). Drug analysis by ultraviolet light absorption of the bulk solution after centrifugation separation was used to determine the amount of drug bound to the membranes. Microelectrophoresis was employed to measure the change in the zeta-potential after drug adsorption. Binding constants were derived by simulating the experimental curves with a theoretical model which considers the electrostatic effects (Gouy-Chapman theory). Analogous experiments were carried out for the adsorption of Eu3+. Metal analysis was made by three different methods. Good agreement between the centrifugation and electrophoresis experiments was obtained for reasonable positions of the plane of shear relative to the positional plane of the bound ions. Displacement of Eu3+ from vesicles upon addition of drug cations was followed by 31P-NMR. The competition experiments were numerically simulated. The Eu3+ binding was assumed to obey a mass action type equilibrium, whereas the drug binding was described by a Henry's law partition. The binding constants for the drugs in the competition experiments followed the same order as in the absence of Eu3+. However, the numerical values had to be reduced. The effect of anions was studied.