A structural study of interfacial phospholipid and lung surfactant layers by transmission electron microscopy after Blodgett sampling: influence of surface pressure and temperature.

Monolayer studies of the lung surfactant extract (LSE), dipalmitoyl phosphatidilcholine (DPPC) and dioleyl phosphatidilcholine (DOPC) have been performed in the dynamic condition at various temperatures. These compounds were also studied by differential scanning calorimetry, and the Langmuir Blodgett films were examined by electron microscopy. The combination of these techniques allowed us to describe precisely the collapse process, which was found to be different above and below the transition temperature of the lipids. However, whereas a phase separation for DPPC/DOPC mixtures occurred at all temperatures studied, this separation was observed for LSE only at temperatures lower than that characteristic of the "rigid state" to "liquid-like state" transition temperature. The ability of LSE to rapidly respread upon decompression appears to be due to the formation of piled amorphous aggregates formed during compression of its monolayers.