The role of the gel double left right arrow liquid-crystalline phase transition in the lung surfactant cycle

Lipid polymorphism plays an important role in the lung surfactant cycle. A better understanding of the influence of phase transitions on the formation of a lipid film from dispersions of vesicles will help to describe the mec hanism of action of lung surfactant. The surface pressure (or tension) of d ispersions of DPPC, DMPC, and DPPE unilamellar vesicles was studied as a fu nction of temperature. These aggregates rapidly fuse with a clean air-water interface when the system is at their phase transition temperature (T-m), showing a direct correlation between phase transition and film formation. B ased on these results, an explanation on how fluid aggregates in the alveol ar subphase can form a rigid monolayer at the alveolar interface is propose d. (C) 2001 Elsevier Science B.V. All rights reserved.