pH Effect of the Sphingomyelin Membrane Interfacial Tension

Abstract

The effect of pH on the interfacial tension of a sphingomyelin membrane in aqueous solution has been studied. Three models describing H(+) and OH(-) ion adsorption on the bilayer lipid surface are presented. In models I and II, the membrane surface is continuous, with uniformly distributed functional groups as centers of H(+) and OH(-) ion adsorption. In model III, the membrane surface is composed of lipid molecules, with and without adsorbed H(+) and OH(-) ions. The contribution of each individual lipid molecule to the overall interfacial tension of the bilayer was assumed to be additive in models I and II. In model III, the Gibbs isotherm was used to describe adsorption of H(+) and OH(-) ions at the bilayer surface. Theoretical equations are derived to describe the interfacial tension as a function of pH for all three models. Maximum interfacial tension was observed experimentally at the isoelectric point.

Cell membrane modulation as adjuvant in cancer therapy

“…Finally, as the inner leaflet typically consists of negatively charged lipids as PS, in non-transformed cells, acidic pH decreases repulsion between polar groups and surface tension giving a less packaged membrane [19, 73, 74]. A slight increase in alkalinity, as happens in resistant cells, shields the negative charges, attenuates repulsion between polar groups and therefore increases packing.…”

“…A slight increase in alkalinity, as happens in resistant cells, shields the negative charges, attenuates repulsion between polar groups and therefore increases packing. Taken together, the interplay between the alkaline nature of the cytoplasm of MDR cells and the makeup of the cell membrane results in a more dense packing of lipids enhancing rigidity of the membrane resulting in poor chemotherapeutic drug penetration of these cells [19, 73, 74]. …”

Biophysics of cell membrane lipids in cancer drug resistance: Implications for drug transport and drug delivery with nanoparticles

“…As the inner leaflet typically consists of negatively charged lipids, such as PS, and these lipids might also be organized in clusters, a slight increase in alkalinity would shield their negative charges and decrease the electrostatic repulsion between polar groups. Therefore, acidic pH is more likely to be central in abolishing the physical repulsion between lipids, thus decreasing surface tension [74–76], which suggests that the sensitive cells with acidic cytoplasm will tend to have cell membranes with less packing density. The alkaline nature of the cytoplasm in resistant cells facilitates increased packing of lipids, which in turn affects the intracellular accumulation of drugs.…”

Friction on charged and neutral soft natural matter surfaces

“…The two natural surfaces charged with the same sign and sliding against one another require better understanding [1][2][3][4]. Due to this, using the lamellar repulsion model, the strong dependence of the friction from both the cartilage surface charge density and the surface wettability [1,5] is supporting (cartilage/cartilage) friction.…”