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Monolayer-multilayer transitions in a lung surfactant model: IR reflection-absorption spectroscopy and atomic force
Lin Wang1, Peng Cai, Hans-Joachim Galla
1Department of Chemistry, Newark College of Arts and Sciences, Rutgers University, 73 Warren Street, Newark, NJ 07102, USA. flach@andromeda.rutgers.edu
European Biophysics Journal : EBJ
|January 13, 2005
Summary
Pulmonary surfactant protein C (SP-C) facilitates breathing by forming multilayers. This study reveals SP-C
Area of Science:
- Biophysics
- Materials Science
- Respiratory Physiology
Background:
- Pulmonary surfactant, a complex mixture of lipids and proteins, is crucial for reducing surface tension in the lungs.
- Hydrophobic pulmonary surfactant protein C (SP-C) plays a role in lung mechanics, but its molecular behavior at the air/water interface is not fully understood.
Purpose of the Study:
- To investigate the molecular-level mechanics of SP-C's role in surfactant film transitions.
- To characterize the structural changes of SP-C during monolayer-to-multilayer transitions at the air/water interface.
Main Methods:
- Atomic force microscopy (AFM) on Langmuir-Blodgett films to verify multilayer formation.
- Infrared reflection-absorption spectroscopy (IRRAS) at the air/water interface to analyze SP-C structure and orientation.
Main Results:
- SP-C containing model surfactant films exhibit reversible monolayer-to-multilayer transitions.
- Multilayer formation was dependent on the presence of SP-C.
- IRRAS revealed a significant change in SP-C's helical structure orientation from ~80° tilt in monolayers to a transmembrane orientation in multilayers.
Conclusions:
- SP-C is essential for the formation of surfactant multilayers at the air/water interface.
- The observed change in SP-C helix orientation provides insight into the molecular mechanism of surfactant respreading.
- This study offers the first quantitative measure of SP-C helix orientation in mixed monolayer/multilamellar domains.