Pulmonary surfactant adsorbs rapidly to the liquid layer that lines the alveolar air-sacks of the lungs. When compressed by the decreasing alveolar surface during exhalation, the adsorbed films avoid collapse from the air/liquid interface and reduce surface tension to exceptionally low levels. Results with factors that induce surfactant lipids to increase spontaneous curvature, achieved in the absence of applied stress, suggest that adsorption proceeds via a curved rate-limiting structure. Samples with negative spontaneous curvature, with a concave hydrophilic surface, adsorb rapidly, but they also desorb quickly. Prior reports show that by optimizing chain-packing, n-tetradecane (td) can promote the conversion of planar bilayers to the negatively curved cylindrical monolayers of the inverse hexagonal phase without changing spontaneous curvature. The studies here show that td increases the rate of adsorption by the complete set of surfactant lipids without affecting spontaneous curvature, and without promoting desorption of the adsorbed film during compression.
Loney et al. (Sun,) studied this question.