A multinuclear solid-state NMR study of phospholipid-cholesterol interactions....

Area of Science:

• Biophysics
• Solid-state NMR spectroscopy
• Lipid-cholesterol interactions

Background:

• Cholesterol is a vital component of cell membranes, influencing their fluidity and function.
• Understanding lipid-cholesterol interactions is crucial for deciphering membrane behavior.

Purpose of the Study:

• To investigate the molecular interactions between dipalmitoylphosphatidylcholine (DPPC) and cholesterol (CHOL) in lipid multilayers.
• To assess the capability of multinuclear solid-state NMR techniques in characterizing these interactions and detecting crystalline cholesterol.

Main Methods:

• Multinuclear (1H, 13C, 31P) Magic Angle Spinning Nuclear Magnetic Resonance (MASNMR) and static solid-state 31P NMR were employed.
• DPPC and CHOL multilayers with varying CHOL concentrations (0-65 mol%) were analyzed at different temperatures (25-55°C).
• Chemical shifts, line shapes, and Chemical Shift Anisotropy (CSA) were measured and analyzed.

Main Results:

• Cholesterol significantly altered the 13C chemical shifts and line shapes of DPPC carbonyl carbons.
• Changes in CHOL carbon resonances indicated a dynamic local environment for cholesterol.
• 13C MASNMR detected crystalline monohydrate CHOL in mixtures with >50 mol% CHOL.
• Excess crystalline CHOL, undetectable by other methods, affected the 31P NMR spectra, suggesting interaction with the bilayer interface.

Conclusions:

• Solid-state NMR provides detailed insights into DPPC-CHOL molecular interactions within lipid bilayers.
• 13C MASNMR is a powerful tool for identifying crystalline cholesterol in biological systems, even in submicroscopic forms.
• These findings enhance our understanding of cholesterol's role in membrane structure and dynamics.