Bilayer membranes containing the ganglioside GM1: models for electrostatic potentials adjacent to biological membranes

Abstract

Although the Gouy-Chapman-Stern theory of the aqueous diffuse double layer describes well the electrostatic potential adjacent to negatively charged phospholipid bilayer membranes, it does not describe adequately the zeta potential of biological membranes: the zeta potential of an erythrocyte is about half the value predicted from the theory by using the known density of negatively charged sialic acid residues. To investigate the factors responsible for this low electrophoretic mobility, we formed membranes from mixtures of the zwitterionic lipid phosphatidylcholine, PC, and the glycolipid galactosyl-N-acetylgalactosaminyl(N-acetylneuraminyl) -galactosylglucosylceramide, GM1. This glycolipid differs from phospholipids in two respects. First, the negative charge on GM1 is located about 1 nm from the surface, which tends to increase the electrophoretic mobility of vesicles. Second, the head group of GM1 contains five sugar groups that exert a hydrodynamic drag, which tends to decrease the mobility of the vesicles. In a decimolar monovalent salt solution, where the Debye length is about 1 nm, the electrophoretic mobility of the PC-GM1 vesicles is about half the mobility of PC-phosphatidylserine or PC-phosphatidylglycerol vesicles of equivalent composition. In addition, conductance measurements with planar bilayer membranes as well as 31P nuclear magnetic resonance and fluorescence measurements with sonicated vesicles indicate that the potential at the surface of PC-GM1 membranes is about half the value measured for PC-phosphatidylserine membranes in a 0.1 M monovalent salt solution.

Influence of Size on Electrokinetic Behavior of Phosphatidylserine and Phosphatidylethanolamine Lipid Vesicles

“…Moreover, sonicated liposomes present a higher polydispersity and are intrinsically less stable because their structure undergoes more changes as a function of time than the extruded liposomes. In MLV liposomes formed by 20% of PS, McDaniel et al (15) reported a zeta potential of Ϫ75 mV, whereas for the same composition we found a value of Ϫ73.9 Ϯ 5.1 mV.…”

Interaction of Basic Drugs with Lipid Bilayers Using Liposome Electrokinetic Chromatography

“…Liposomes consisting of 20% PG or 20% PS also have a similar zeta potential value. Vesicles formed from 5:1 PC:PG or 5:1 PC:PS mixtures have been found to have similar zeta potentials (40,42). This correlation is slightly reduced at low percentages (5%) of anionic lipid, between liposomes composed of PG and PS, with a R 2 value of 0.977 for 17 drugs.…”

“…5. Many detailed discussions on the effect of anionic lipid content on the zeta potential have been published (40)(41)(42). Zeta potentials have been found to have an exponential dependence on the PS content in liposomes (43).…”

The adsorption of Pseudomonas aeruginosa exotoxin A to phospholipid monolayers is controlled by pH and surface potential

“…The local electrical potential at the surface of a phospholipid monolayer containing acidic lipids was calculated according to the Guy-Chapman-Stern (G-C-S) theory (Aveyard and Haydon, 1973), as discussed, for example in Eisenberg et al (1979) and McDaniel et al (1984). Both screening and specific binding of counterions (protons and Na+ ions in our case) were taken into account.…”