Structure and function of surfactant protein B and C in lipid monolayers: A scanning force microscopy study

S. Krol, A. Janshoff, M. Ross, H. J. Galla

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This study focuses on the impact of surfactant protein C and B on lipid monolayers at various surface pressures. The artificial system is composed of the saturated phospholipids dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG) in a molar ratio of 4:1 with 0.2 mol% SP-B and/or 0.4 mol% SP-C. A dominating influence of SP-C on the morphology of lipid monolayers at high surface pressure was found. Even in the presence of both proteins structural peculiarities typical for SP-C were found at elevated pressure employing tapping mode scanning force microscopy of LB-films. Stacked bilayer-protrusions known to be induced by SP-C are visible in films containing SP-C together with SP-B. The findings were corroborated by fluorescence microscopy at the air/water interface and are consistent with the appearance of the corresponding isotherms. In the low pressure regime, however, disc-like protrusions characteristic of SP-B containing films are discernible. Filamentous LE domains with large boundaries arise due to the reduced line tension in the presence of surface active proteins, particularly SP-B. Remarkably, SP-B fluidizes the monolayer to a larger extent than SP-C as revealed by scanning force microscopy images. These findings show that SP-B and SP-C interact independently of each other. Therefore we conclude that SP-C may be responsible for the fast respreading process during the breathing cycle while SP-B removes material from the monolayer in more discrete portions.

Original languageEnglish
Pages (from-to)4586-4593
Number of pages8
JournalPhysical Chemistry Chemical Physics
Issue number20
Publication statusPublished - Oct 15 2000

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Atomic and Molecular Physics, and Optics


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