Membrane properties of mixed ganglioside GM1/phosphatidylcholine monolayers

The interaction between ganglioside GM1 (GM1) and L-alpha-dipalmitoylphosphatidylcholine (DPPC) in mixed monolayers was investigated using surface pressure measurements and atomic force microscopy (AFM), and the effects of GM1, surface pressure and temperature on the properties of the membranes were examined. Mixed GM1/DPPC monolayers were deposited on mica using the Langmuir-Blodgett (LB) technique for AFM. GM1 and DPPC were miscible below the 0.2 mole fraction of GM1 and there was attractive interaction between GM1 and DPPC. The AFM images for the GMI/DPPC monolayers (X-GM1 < 0.2) at 30mN m(-1) and 25degreesC indicated a percolation pattern which means a micro phase separation: namely, the mixed film composed of GM I and DPPC phase-separated from the DPPC liquid-condensed film. The AFM images for the mixed monolayers at 33 mN m(-1) indicated a specific morphology when the surface pressure was varied from 30 to 40 mN m(-1). The percolation pattern in the AFM image at 25degreesC came to be destroyed with increasing temperature and completely disappeared at 45degreesC. The change in the morphology of mixed GM1/DPPC monolayers on varying the surface pressure and temperature is thought to be related to signal transduction and a preventive mechanism against viral infections in the human body. (C) 2003 Elsevier B.V. All rights reserved.