Problem of pattern preservation in lipid monolayers during transfer on solid supports

The problems arising during and after the transfer of lipid monolayers from the water - air interface to solid supports showing two-dimensional domain patterns are discussed. Experiments with Langmuir - Blodgett films (fluorescent probe marked PE) were performed for different speeds of monolayer compression and support pulling. Horizontal lifting was also attempted. As solid supports clean glass cover-slips and Formvarcovered EM grids with evaporated carbon and silicon monoxide layers were used. Experimental methods included fluorescence microscopy, fluorescence recovery after photobleaching (FRAP), phase-contrast electron microscopy, electron diffraction and computer image processing. Experimental procedures for obtaining both solid domains in a fluid environment and fluid domains in a solid environment are demonstrated. The data clearly indicate that flow orientation and shear force deformation of the domain pattern depend on the pulling speed. A theoretical model for the elongation of fluid domains caused by the shear force is developed. FRAP measurements show a very low coefficient of lateral diffusion in the transferred monolayers, even at elevated temperatures, and a low percentage of diffusing species, typically lower than 10% of the total number of fluorescing molecules. Electron diffraction shows a high degree of positional and orientational order in solid domains formed after slow compression. A considerably lower order is found in the monolayers subject to fast expansion after compression.