Membrane properties of binary and ternary systems of ganglioside GMi/dipalmitoylphosphatidylcholine/dioleoylphosphatidylcholine

摘要

The membrane properties of the ganglioside GMI (GM1 )/dioleoylphosphatidylcholine (DOPC) binary system and GMl/dipalmitoylphos-phatidylcholine (DPPC)/DOPC ternary system were investigated using surface pressure measurements and atomic force microscopy (AFM), and the effect of surface pressure on the properties of the membranes was examined. Mixed GMl/DPPC/DOPC monolayers were deposited on mica using the Langmuir-Blodgett technique for AFM. GM 1 and DOPC were immiscible and phase-separated. The AFM image of the GM1/DOPC (1:1) monolayer showed island-like GMl domains embedded in the DOPC matrix. There was no morphological change on varying surface pressure. The surface pressure-area isotherm of the GMl/DPPC/DOPC (2:9:9) monolayer showed a two-step collapse as in the DPPC/DOPC (1:1) monolayer. The AFM image for the GMl/DPPC/DOPC monolayer showed DPPC and GMl domains in the DOPC matrix, and the DPPC-rich phase containing GMl showed a percolation pattern the same as the GM1/DPPC (1:9) monolayer. The percolation pattern in the GM 1/DPPC/DOPC monolayer changed as the surface pressure was varied. The surface pressure-responsive change in morphology of GMl was affected by the surrounding environment, suggesting that the GMl localized in each organ has a specific role.