A scanning force- and fluorescence light microscopy study of the structure and function of a model pulmonary surfactant |
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Authors: | M Amrein A von Nahmen M Sieber |
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Institution: | Institut für Medizinische Physik und Biophysik, Westf?lische Wilhelms-Universit?t, Robert-Koch-Strasse 31, D-48149 Münster, Germany, DE Institut für Biochemie, Westf?lische Wilhelms-Universit?t, Wilhelm-Klemm-Strasse 2, D-48149 Münster, Germany, DE
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Abstract: | The structure of an artificial pulmonary surfactant was studied by scanning force- and fluorescence light microscopy (SFM,
and FLM, respectively). The surfactant – a mixture of dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylglycerol
(DPPG) and recombinant surfactant-associated protein C (SP-C) – was prepared at the air-water interface of a Langmuir film
balance and imaged by FLM under various states of compression. In order to visualize their topography by SFM, the films were
transferred onto a solid mica support by the Langmuir-Blodgett (LB) technique. We found that a region of high film compressibility
of the spread monolayer close to its equilibrium surface pressure (π=50 mN/m) was due to the exclusion of layered protrusions with each layer 5.5 to 6.5 nm thick. They remained associated with
the monolayer and readily reinserted upon expansion of the film. Comparison with the FLM showed that the protrusions contained
the protein in high concentration. The more the film was compressed, the larger was the number of layers on top of each other.
The protrusions arose from regions of the monolayer with a distinct microstructure that may have been responsible for their
formation. The molecular architecture of the microstructure remains to be elucidated, although some of it can be inferred
from spectroscopic data in combination with the SFM topographical images. We illustrate our current understanding of the film
structure with a molecular model.
Received: 20 September 1996 / Accepted: 22 May 1997 |
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Keywords: | Scanning force microscopy Fluorescence light microscopy Pulmonary surfactant Pulmonary surfactant protein C Monolayer Langmuir-Blodgett technique |
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