New insights into lung surfactant monolayers using vibrational sum frequency generation spectroscopy

Area of Science:

• Biophysics
• Surface Chemistry
• Materials Science

Background:

• Lung surfactant maintains alveolar stability by reducing surface tension.
• Understanding the molecular behavior of surfactant components is vital for respiratory health.

Purpose of the Study:

• To elucidate the interfacial molecular structure, intermolecular interactions, and dynamic behaviors (relaxation, respreading) of model lung surfactant monolayers.
• To investigate the effects of specific lipids and peptides on surfactant film properties.

Main Methods:

• Utilized vibrational sum frequency generation (VSFG) spectroscopy.
• Employed a Langmuir film balance to form and control model lung surfactant monolayers.
• Studied binary and ternary mixtures of dipalmitoylphosphatidylcholine (DPPC-d62), palmitoyloleoyl-phosphatidylglycerol (POPG), palmitic acid (PA), and tripalmitin.
• Investigated respreading properties of a complex mixture including DPPC-d62, POPG, PA, and KL4 peptide using real-time VSFG.

Main Results:

• Palmitic acid (PA) exhibited a condensing effect on DPPC chains, while POPG showed a fluidizing effect.
• A balance between condensing and fluidizing effects was observed in ternary mixtures.
• Tripalmitin enhanced the film stability and relaxation of DPPC-d62.
• Real-time VSFG revealed DPPC enrichment after compression in a complex lung surfactant mixture.

Conclusions:

• The study provides insights into the complex molecular interactions governing lung surfactant function at the air-water interface.
• Specific lipid compositions significantly influence surfactant film properties, impacting lung mechanics.
• VSFG spectroscopy is a powerful tool for real-time analysis of surfactant dynamics and respreading behavior.