Structure of Lung-Mimetic Multilamellar Bodies with Lipid Compositions Relevant in Pneumonia*

Pneumonia is the leading cause of death amongst captive dolphins. While the pathology of pneumonia is understood at a macroscopic level, recent results show that changes in material chemistry at the lung-air interface plays an important role in symptoms, though the physical basis is unknown.[1] Healthy lungs are coated by a thin, hydrated biological composite composed primarily of amphiphilic lipids and a small amount of proteins. These self-assemble into liquid-crystalline phases which can reduce the fluid-air interfacial surface energy to near 0. In diseased lungs abnormally high concentrations of cardiolipin, a highly charged and highly unsaturated lipid, and Ca²⁺ can be found. Here we observe using small angle X-ray diffraction (SAXS) that addition of cardiolipin dehydrates the lipid membranes, contrary to predictions of pure electric double layer theory. The physical cause for these effects and the influence of Ca²⁺ is studied using wide angle X-ray diffraction (WAXS) and solid state nuclear magnetic resonance (ssNMR).
[NB Ray et al. Nature Medicine 16, pp. 1120–1127 (2010)]