Study of the interaction of beta-cyclodextrin with phospholipid monolayers by surface pressure measurements and fluorescence microscopy.

The interaction of beta-cyclodextrin (beta-CD) with different lipids has been studied, using Langmuir monolayers kept at constant surface pressure or constant spreading surface. Results show that beta-CD, injected beneath the monolayer, is able to desorb unsaturated palmitoyloleoylphosphatidylcholine (POPC) and sphingomyelin (SM) under specific experimental conditions. In this last case, SM monolayers, labeled with the fluorescent NBD-PC probe, were also observed by fluorescence microscopy, before and after beta-CD injection.

Study of the cholesterol-GM3 ganglioside interaction by surface pressure measurements and fluorescence microscopy.

The nature of the cholesterol/glycolipid interaction in rafts being poorly understood, the interaction of cholesterol with the GM(3) ganglioside has been studied by surface pressure measurements and fluorescence microscopy. Results have been compared to those obtained with sphingomyelin (SM)-cholesterol and palmitoyl-oleoyl-phosphatidylcholine (POPC)-cholesterol monolayers. The analysis of (pi-A) isotherms of mixed monolayers show a condensing effect of cholesterol on GM(3) molecules, in the same range than the effect observed with POPC and higher than the effect on SM.

Spectroscopic study of lysopalmitoylphosphatidylcholine Newton black films.

Lysopalmitoylphosphatidylcholine (LPC) black films have been studied by confocal Raman spectroscopy and their spectra analyzed and compared to their counterparts obtained from LPC in the solid state and aqueous solution. It appears that LPC is able to form stable and highly ordered black films, despite the presence of only one hydrophobic chain in this molecule. A complementary infrared study of LPC Gibbs monolayers suggests that the whole LPC polar head is perpendicular to the air/water interface.

Behavior of GM3 ganglioside in lipid monolayers mimicking rafts or fluid phase in membranes.

We studied the interaction of GM3 ganglioside with sphingomyelin (SM) and palmitoyl-oleoyl-phosphatidylcholine (POPC) in Langmuir monolayers mimicking, respectively, raft and fluid phase of a cellular membrane, by surface pressure measurements and fluorescence microscopy. No difference was observed in the behavior of SM-GM3 and POPC-GM3 monolayers. In both cases, a GM3 threshold concentration has been underlined between 20 and 40 mol%.