Electrostatic and structural properties of the surface of human erythrocytes. I-cell-electrophoretic studies following neuraminidase treatment

Electrostatic interaction between stereocilia: I. Its role in supporting the structure of the hair bundle

This paper provides theoretical estimates for the forces of electrostatic interaction between adjacent stereocilia in auditory and vestibular hair cells. Estimates are given for parameters within the measured physiological range using constraints appropriate for the known geometry of the hair bundle. Stereocilia are assumed to possess an extended, negatively charged surface coat, the glycocalyx. Different charge distribution profiles within the glycocalyx are analysed. It is shown that charged glycocalices on the apical surface of the hair cells can support spatial separation between adjacent stereocilia in the hair bundles through electrostatic repulsion between stereocilia. The charge density profile within the glycocalyx is a crucial parameter. In fact, attraction instead of repulsion between adjacent stereocilia will be observed if the charge of the glycocalyx is concentrated near the membrane of the stereocilia, thereby making this type of charge distribution unlikely. The forces of electrostatic interaction between stereocilia may influence the mechanical properties of the hair bundle and, being strongly non-linear, contribute to the non-linear phenomena that have been recorded from the periphery of the auditory and vestibular systems.

Topo-optical investigations of human erythrocyte glycocalyx conformational changes induced by dextran

Cell surface properties are involved in the aggregation process of red blood cells. Using the topo-optical toluidine blue reaction, conformational changes of the glycocalyx (main component glycophorin A) were found when red blood cells were incubated and fixed in the presence of dextran. Relative differences in optical path as a measure of red blood cell membrane anisotropy decreased in relation to dextran concentration during fixation. These conformational changes could not be detected by electrophoretic measurements. When incubating, fixing and staining red blood cells in the presence of dextran, anisotropy decreased only at low dextran concentrations and increased at rising dextran concentrations. This biphasic course of differences in optical path seems to be due to different effects of dextran superimposing upon each other: a disturbing influence on the spatial order of sialic acid carrying oligosaccharide side chains due to H-bond interaction, and an increase in the size of dye aggregates and suppression of the thermal motion of macromolecules at higher dextran concentrations.

A biophysical model for interaction of cells with a surface coat (glycocalyx). I. Electrostatic interaction profile

A model of the primary stage of cell-cell interaction is assumed, including not only the classical electrostatic and electrodynamic energies in the sense of DLVO theory but also steric interaction energy, the energy of specific and non-specific bonds and the energy due to changes of surface potential. Furthermore, in this paper, we exploit recent advances in the understanding of the structure of the cell surface (glycocalyx), assuming the fixed electrostatic charges (dissociated groups of the glycocalyx), to be space charge densities and the glycocalyx itself to be an adsorption layer. In this first part the profile of the electrostatic potential between two cells is calculated on the basis of the linear Poisson-Boltzmann equation (analytical integration) and discussed in dependence on charge densities of the glycocalyx, the separation distance between cells and the ionic strength of the suspension medium.