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 knowledg e of the structure of these membranes, LB films of a mixture of miscib le and nonmiscible phospholipids were studied by atomic force microsco py (AFM). Mixtures of various compositions were deposited on mica and graphite substrates at various pressures, AFM images showed two coexis ting domains corresponding to the nonmiscible (DPPE-DOPE) phospholipid s with difference in height of about 0.5 nm due to the structural diff erences between the two phospholipids. The area ratios between the two types of domains, measured on AFM images, were consistent with the mo lar fraction and area per molecule at the surface pressure during depo sition. We have also reported on the topography of multilayers of nonm iscible mixtures, In conclusion, AFM allowed us to have a better insig ht into deposition mechanisms and the properties of binary mixtures of phospholipids LB films. (C) 1996 American Vacuum Society.