J0102-1-3 Coarse Grained Molecular Dynamics Simulation of Pulmonary Surfactant Monolayer

Abstract

Coarse grained molecular dynamics simulations of pulmonary-surfactant monolayers on a water layer are conducted to understand phase changes of the monolayer under various area per lipid (APL) in the molecular level. The monolayer is modeled by a monolayer comprised by dipalmitoylphosphatidylcholine (DPPC) molecules, which are the major component of human pulmonary surfactant. The area of the system calculated is varied according to APL from 0.40 to 0.80 nm^2/lipid, whereas the system size in the monolayer normal direction is 100 nm. The constant temperature and volume MD calculation is performed in 30 ns for each APL condition. Visual inspection of the hydrophobic-beads packing shows the monolayer calculated is in the lipid-condensed (LC) phase for APL=0.45, in the lipid-expanded (LE) phase for APL=0.70, in the LE and LC coexisting (LE/LC) phase for APL=0.50, and in the LE and the uncovered water layer coexisting (LE/G) phase for APL=0.70. In addition, the monolayer buckles for APL=0.40. The results obtained here agree with available experimental data.