A view of three different lipid monolayers by atomic force microscopy

Abstract
Lipid monolayers prepared by the Langmuir technique are commonly used as model biomembranes. They have been extensively studied for years with a wide range of techniques, and during the last decade atomic force microscopy (AFM) [1] has emerged as a powerful tool for imaging the structure of the supported lipid films. AFM offers the view at nanometric scale of the transferred monolayers which provides information on the topographical organization of the films [2-41. In the present work we have studied the morphology of three lipid monolayers : zwitterionic DPPC, anionic DPPC : PI (9 : 1, mol : mol) and cationic DPPC : SA. (9 : 1, mol : mol). The structure of these three mixed monolayers transferred on mica is determined by AFM, and compared with the phase properties of the films at the air-water interface.