Molecular dynamics simulations of lung surfactant phospholipid monolayers

Rose, Doyle (2007) Molecular dynamics simulations of lung surfactant phospholipid monolayers. Masters thesis, Memorial University of Newfoundland.

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Abstract

Lung surfactant is a thin layer of lipids and proteins that lines the alveoli of the lungs. It enables breathing by lowering the surface tension at the air / water interface, thus preventing lung collapse during expiration and reducing the work necessary to re-expand the lung. The lipids are believed to be responsible for the reduction in surface tension, but the molecular mechanisms that bring about this reduction are not well understood. -- Molecular dynamics simulations are a means of studying the molecular interactions of the lung surfactant lipids. Molecular dynamics models a complex chemical system using detailed knowledge on the atomic scale. The GROMACS software package was used to model the interactions between the lung surfactant lipids. -- Simulations were performed on monolayers with different lipid compositions and at different packing densities. In tightly packed monolayers some lipids were observed to rise up out of the monolayer. In mixed monolayers there was no preference as to which type of lipid would rise. Tightly packed monolayers had large expansive lateral pressures that led to the calculation of negative surface tensions. Loosely packed monolayers had positive surface tensions that were similar to experimental measurements. Comparison to experiments might not be appropriate for tightly packed monolayers, since the interface between lipids and water was not flat.

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