Effect of protein, cholesterol, and phosphatidylglycerol on the surface activity of the lipid-protein complex reconstituted from pig pulmonary surfactant.

Lipid-protein complexes reconstituted from pig surfactant lipids and proteins were investigated for surface adsorption, minimum surface tension, stability index, and surface compressibility. Lipid constituents remained unchanged with procedures for the reconstitution. An apoprotein with a nominal molecular weight of 15,000 daltons significantly accelerated the lipid-protein complex to absorb the air-water interface. A 34,000-dalton apoprotein slightly modified the surface adsorption and the surface activity when it was incorporated into the lipid-protein complex formed from lipids and 15,000-dalton apoprotein. No significant surface adsorption was found in lipid vesicles even with the same lipid constituents as in the lipid-protein complex. In the lipid-protein complex prepared by changing the content of cholesterol and phosphatidylglycerol, cholesterol affected both the minimum surface tension and the surface compressibility while phosphatidylglycerol had little effect on the surface activity of the complex.