Formation of Three-Dimensional Protein-Lipid Aggregates in Monolayer Films Induced by Surfactant Protein B

This study focuses on the structural organization of surfactant protein B (SP-B) containing lipid monolayers. 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....

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Bibliographic Details
Published in:Biophysical journal 2000-08, Vol.79 (2), p.904-918
Main Authors: Krol, Silke, Ross, Michaela, Sieber, Manfred, Künneke, Stephanie, Galla, Hans-Joachim, Janshoff, Andreas
Format: Article
Language:English
Subjects:
1,2-Dipalmitoylphosphatidylcholine - chemistry
Animals
Biochemistry
Lipids
Lungs
Microscopy, Atomic Force
Microscopy, Fluorescence
Models, Molecular
Molecular Conformation
Phosphatidylglycerols - chemistry
Protein Conformation
Proteins
Proteolipids - chemistry
Proteolipids - ultrastructure
Pulmonary Surfactants - chemistry
Pulmonary Surfactants - ultrastructure
Swine
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Summary:This study focuses on the structural organization of surfactant protein B (SP-B) containing lipid monolayers. 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. The different “squeeze-out” structures of SP-B were visualized by scanning probe microscopy and compared with structures formed by SP-C. Particularly, the morphology and material properties of mixed monolayers containing 0.2 mol% SP-B in a wide pressure range of 10 to 54 mN/m were investigated revealing that filamentous domain boundaries occur at intermediate surface pressure (15–30 mN/m), while disc-like protrusions prevail at elevated pressure (50–54 mN/m). In contrast, SP-C containing lipid monolayers exhibit large flat protrusions composed of stacked bilayers in the plateau region (app. 52 mN/m) of the pressure-area isotherm. By using different scanning probe techniques (lateral force microscopy, force modulation, phase imaging) it was shown that SP-B is dissolved in the liquid expanded rather than in the liquid condensed phase of the monolayer. Although artificial, the investigation of this system contributes to further understanding of the function of lung surfactant in the alveolus.
ISSN:0006-3495
1542-0086
DOI:10.1016/S0006-3495(00)76346-6