Characterization of mixed miscible and nonmiscible phospholipid Langmuir-Blodgett films by atomic force microscopy

Langmuir-Blodgett (LB) phospholipid films have proved to be efficient models for biological membranes. In order to acquire a better knowledge of the structure of these membranes, LB films of a mixture of miscible and nonmiscible phospholipids were studied by atomic force microscopy (AFM). Mixtures of various compositions were deposited on mica and graphite substrates at various pressures, AFM images showed two coexisting domains corresponding to the nonmiscible (DPPE-DOPE) phospholipids with difference in height of about 0.5 nm due to the structural differences between the two phospholipids. The area ratios between the two types of domains, measured on AFM images, were consistent with the molar fraction and area per molecule at the surface pressure during deposition. We have also reported on the topography of multilayers of nonmiscible mixtures, In conclusion, AFM allowed us to have a better insight into deposition mechanisms and the properties of binary mixtures of phospholipids LB films. (C) 1996 American Vacuum Society.