Solid-state NMR study of trehalose/1,2-dipalmitoyl-sn-phosphatidylcholine interactions

Area of Science:

• Solid-state NMR spectroscopy
• Biophysics
• Materials Science

Background:

• Trehalose (TRE) is a disaccharide known for its protective effects on biological membranes during dehydration.
• 1,2-dipalmitoyl-sn-phosphatidylcholine (DPPC) is a common phospholipid model for cell membranes.
• Understanding the structural and dynamic properties of TRE/DPPC mixtures is crucial for explaining anhydrobiosis.

Purpose of the Study:

• To investigate the phase behavior and molecular dynamics of dry trehalose/DPPC mixtures using solid-state NMR.
• To characterize the novel phase formed by trehalose and DPPC above the phase transition temperature.
• To elucidate the mechanism by which trehalose protects membranes during dehydration.

Main Methods:

• 31P and 2H solid-state NMR spectroscopy were employed.
• DPPC was specifically labeled at the sn-2 chain (2[7,7-2H2]DPPC) for 2H NMR studies.
• NMR spectral line shapes were analyzed and simulated using molecular dynamics models.

Main Results:

• 31P NMR indicated rigid head groups in both dry DPPC and TRE/DPPC mixtures.
• 2H NMR of DPPC showed two-site jumps, indicative of ordered acyl chains.
• Above the phase transition, TRE/DPPC mixtures exhibited significantly narrowed 2H NMR spectra, requiring a four-site jump model, suggesting highly disordered lipid acyl chains.

Conclusions:

• Dry TRE/DPPC mixtures form a new liquid crystalline-like phase, termed the lambda-phase, above their transition temperature.
• The disordered acyl chain dynamics in the lambda-phase are similar to hydrated lipid L alpha-phases.
• The dynamic properties of this lambda-phase provide insight into the membrane stabilization mechanism in anhydrobiotic organisms.