Detection of Sphingomyelin Clusters by Raman Spectroscopy

Area of Science:

• Biophysics
• Lipidomics
• Spectroscopy

Background:

• Sphingomyelin (SM) is a crucial sphingolipid forming lipid domains with cholesterol (Chol) in mammalian cell membranes.
• Understanding SM-Chol interactions is vital for cell membrane structure and function.

Purpose of the Study:

• To identify a characteristic Raman spectroscopic signature for SM.
• To investigate the influence of hydration and cholesterol on this SM signature.
• To explore the utility of this signature for examining SM membrane distribution.

Main Methods:

• Molecular-dynamics simulations
• Density functional theory calculations
• Experimental Raman spectroscopy

Main Results:

• A characteristic Raman band at ~1643 cm⁻¹ was identified as the amide I of SM clusters.
• This amide I band is sensitive to SM hydration and the presence of cholesterol.
• Ceramide phosphoethanolamine (CerPE) also shows an amide I band, but it is unaffected by cholesterol, unlike SM.

Conclusions:

• The identified amide I Raman band serves as a sensitive probe for SM membrane distribution.
• The methyl groups in SM's phosphocholine moiety are critical for its interaction with cholesterol.
• This spectroscopic approach provides new insights into lipid-cholesterol interactions in membranes.