ELABORATION AND CHARACTERIZATION OF PHOSPHOLIPID LANGMUIR-BLODGETT-FILMS

In order to model biological membranes, DPPE 2-dihexadecanoyl-sn-glyce ro-3-phosphoethanolamine) and DPPC (1,2-dihexadecanoyl-sn-glycero-3-ph osphocholine) Langmuir-Blodgett (LB) films were deposited on hydrophil ic mica and hydrophobic highly ordered pyrolitic graphite (HOPG), and subsequently characterized by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy(XPS). AFM was used to determine the topogra phy and to monitor the stability of the deposited films in air and und er water at varying experimental parameters. Angle-resolved XPS was us ed to measure the mean thickness and the orientation of the deposit. M onolayer transfer pressure was determined at 40 mN/m with molecular ar ea at 0.42 +/- 0.02 nm(2) for DPPE and 0.55 +/- 0.02 nm(2) for DPPC. N anometric resolution was achieved on DPPE crystal and LB films and all owed the determination of the corresponding lattice constants a = 0.64 +/- 0.03 nm, b = 0.91 +/- 0.07 nm, and c = 5.6 +/- 0.2 nm and a = 0.6 8 +/- 0.02 nm, b = 0.93 +/- 0.05 nm, and c = 5.6 +/- 0.2 nm, respectiv ely. The DPPE monolayer on mica was measured to be 2.7 +/- 0.2 nm thic k and the surface was hydrophobic. The reorganization of DPPE bilayer when going from the water to the air was directly observed to form mon olayer and trilayer domains. On HOPG, the outermost layer of DPPE was partly hydrophilic and partly hydrophobic. Under the same conditions o f deposition, DPPC formed a mixed structure of flat domains and vesicl es. In water, monolayer aliphatic tail ending is less compact and pres ents a higher friction coefficient than polar heads as measured by lat eral force AFM.