“Hairy Surface Layer” Concept of Electrophoresis Combined with Local Fixed Surface Charge Density Isotherms:  Application to Human Erythrocyte Electrophoretic Fingerprinting

Abstract

In order to describe the electrophoretic behavior of “hairy-layer”-coated particles, local charge density isotherms have been combined with considerations of hydrodynamic flow penetration into the layer. An iterative numerical procedure was employed to calculate the electrophoretic mobility as a function of both pH and salt concentration. A major result is that information can be gained regarding the distribution functions of oppositely charged groups from the behavior of the point of zero mobility as a function of pH and salt concentration. The theoretical results were used to reinterprete the electrophoretic behavior of native, neuraminidase-treated and glutaraldehyde-treated human erythrocytes. Theoretical analysis of the experimental data revealed that negative groups had occurred preferentially in the outer regions of the layer. A penetration depth of 1 nm into the 3.5 nm thick hairy layer successfully accounted for the erythrocyte mobility data for all methods of analysis tried. Upon sialic acid removal, alterations of the glycocalyx structure occurred, resulting in possible changes in the fixed charge distribution. It was concluded that intramolecular, as well as intermolecular, electrostatic interactions are important for the structure of the hairy surface layer (glycocalyx). No evidence for the adsorption of small ions was found.

Dielectrophoretic discrimination of bovine red blood cell starvation age by buffer selection and membrane cross-linking

“…To accomplish this aim, further dielectrophoretic optimization was achieved by glutaraldehyde-induced bRBC modification. The addition of glutaraldehyde to bRBCs eliminates positive amino groups from the surface of the cell, 15,16 and destroys the lipid membrane. 17 This procedure cross-links both membrane and interior proteins, producing a network of polyelectrolytes within a particle that exhibits FIG.…”

On the mechanism of stomatocyte–echinocyte transformations of red blood cells: experiment and theoretical model

“…To estimate Γ (1) 1 , we take into account that the phosphatidylserine constitutes 12.5% of the lipids in the inner membrane leaflet [47], and that the average area per lipid in the membrane is about 0.5 nm 2 . Thus we obtain Γ On the outer membrane surface, the surface charge, due to the sialic, acid is estimated to be 0.0198 C/m 2 [48], which corresponds to Γ (2) 1 = 0.124 nm −2 (the negative charge on both inner and outer membrane surfaces is due mostly to carboxylic groups, which are expected to be completely dissociated at the working pH = 7.4). The latter values of Γ (1) 1 and Γ (2) 1 are used in our computations.…”

“…Negatively charged ionizable groups are present at the inner and outer surfaces of the membrane of an erythrocyte [47,48]. It is known that the surface charges give rise to the formation of electric double layers [36,49,50], which have to be present on both sides of the cell membrane.…”

“…Γ (1) 1 is determined by the surface density of the headgroups of the lipid phosphatidylserine in the inner membrane leaflet [47], whereas Γ (2) 1 is mostly due to the sialic acid residues in the glycocalyx [48]. Furthermore, let Γ (1) 2 and Γ (2) 2 be the surface density of the adsorbed counterions, respectively, at the inner and outer membrane surfaces.…”

Structure and Electrical Properties of Polyelectrolyte Multilayers Formed on Anisometric Colloidal Particles

“…Irrespective of the decisive role of the electrostatics in the formation of multilayers, until now only ζ -potential mea-surements have been carried out to obtain valuable information on the electrical properties of the adsorbed polymers and the substrate (16,23,24). The sign reversal of the ζ -potential after deposition of each polymer is evidence of the formation of the multilayer film, but its values have only been used for qualitative comparisons because of the uncertainty in the ζ -potential interpretation (25,26). Möhwald et al (27), for example, realize that coating of colloids with extremely different polyelectrolytes leads to nearly the same values of the ζ -potential.…”