Comparative Monolayer Investigations of Surface Properties of Negatively Charged Glycosphingolipids from Vertebrates (Gangliosides) and Invertebrates (SGL-II, Lipid IV)

Abstract

The surface properties of four negatively charged glycosphingolipids from vertebrates, the sialo-glycosphingolipids (= gangliosides) GM1, GD1a, GT1b and a sulfo-glycosphingolipid (= sulfatide), and of the two negatively charged glycosphingolipids from lower invertebrates, the glucurono-glycosphingolipid Lipid IV and the aminophosphono-glycosphingolipid SGL-II were investigated in monolayers at the air/water interface. The molecular peculiarities under investigation were surface pressure (pi) and surface potential (delta V) which are described for Lipid IV and SGL-II for the first time. The surface pressure/area isotherms of all glycosphingolipids were typical of a liquid-expanded monolayer and, with the exception of SGL-II, exhibited a phase transition to a liquid-condensed state at surface pressures above 20 mN/m. The surface potential/molecular area data found for gangliosides in the closely packed state at pi = 30 mN/m (GM1: delta V = -17 mV; GD1a: delta V = -35 mV; GT1b: delta V = -39 mV) showed only a slight influence of the additional number of negatively charged residues. For Lipid IV, the surface behavior was very similar to GM1 both possessing one negative group per molecule, whereas in SGL-II also the surface potential data (delta V = +173 mV) were different compared with GD1a both possessing two negative groups per molecule. The addition of Ca2+ condensed the monolayers of all glycolipids and increased the potential in the direction to more positive values, but these findings were less effective in SGL-II films. On the basis of monolayer results presented here, in biological membranes of invertebrates especially Lipid IV might play a similar role as the ganglioside GM1 in vertebrate cells.

Density of GM1 in Nanoclusters Is a Critical Factor in the Formation of a Spherical Assembly of Amyloid β-Protein on Synaptic Plasma Membranes

“…The lipid monolayer prepared using a Langmuir trough was transferred onto POPC-coated mica to generate a reconstituted lipid bilayer (Figure a) . We used the reconstituted lipid bilayer because a stable lipid membrane with cell membrane pressure at 30 mN m –1 could be prepared for AFM study . The lipid bilayer resembles a cell membrane in terms of the lateral distribution of lipid components.…”

“…21 We used the reconstituted lipid bilayer because a stable lipid membrane with cell membrane pressure at 30 mN m −1 could be prepared for AFM study. 26 The lipid bilayer resembles a cell membrane in terms of the lateral distribution of lipid components. The surface topography of the bilayer facilitates imaging of the membrane microdomain at a nanometer scale.…”

Size and Shape of Amyloid Fibrils Induced by Ganglioside Nanoclusters: Role of Sialyl Oligosaccharide in Fibril Formation

“…19 Briefly, a POPC lipid monolayer was prepared at the air−water interface of a Langmuir−Blodgett trough at 25 °C with a subphase of water and transferred to freshly cleaved mica (1 × 1 cm) by horizontal deposition at a surface pressure of 35 mN m −1 (POPC-coated mica, Figure 2A). A second lipid monolayer consisting of ganglioside/SM/chol (molar ratio) was loaded onto the POPCcoated mica by horizontal deposition at a surface pressure of 30 mN m −1 to obtain a lipid bilayer (i.e., ganglioside-containing membrane), 21 which was incubated with a seed-free Aß solution (1−10 μM) for 15 min−72 h at 37 °C to investigate the interaction with Aß. After washing three times with phosphate-buffered saline, the membrane was analyzed by AFM.…”