Evidence for metastability in stearoylsphingomyelin bilayers

Area of Science:

• Biophysics
• Materials Science
• Physical Chemistry

Background:

• Phospholipids are key components of biological membranes.
• Sphingomyelin is a unique phospholipid with implications in cellular structure and function.
• Understanding phospholipid phase behavior is crucial for drug delivery and biomaterial design.

Purpose of the Study:

• To investigate the physical properties and phase behavior of aqueous stearoylsphingomyelin dispersions.
• To characterize the gel and liquid-crystalline states of stearoylsphingomyelin.
• To explore the influence of lipophilic substances on stearoylsphingomyelin stability.

Main Methods:

• Differential scanning calorimetry (DSC) for thermal analysis.
• Fluorescence spectroscopy to probe molecular environment.
• X-ray diffraction to determine structural organization.

Main Results:

• Stearoylsphingomyelin exhibits a highly ordered, thermodynamically stable gel phase.
• A reversible transition to a liquid-crystalline state occurs at 57°C.
• A metastable gel forms at 44°C upon cooling, slowly converting to the stable gel.
• Lipophilic substances enhance the stability of the metastable gel phase.

Conclusions:

• Stearoylsphingomyelin possesses distinct and stable gel phases with unique transition kinetics.
• The formation and conversion of metastable and stable gel states are temperature-dependent.
• Lipophilic compounds can modulate the phase stability of stearoylsphingomyelin, with potential applications in formulation science.