Switched-angle spinning applied to bicelles containing phospholipid-associated peptides

Area of Science:

• Structural Biology
• Biophysical Chemistry
• Nuclear Magnetic Resonance Spectroscopy

Background:

• Investigating membrane-bound peptides like leucine-enkephalin is crucial for understanding biological processes.
• Proton NMR spectroscopy of such systems is often limited by anisotropic interactions and proton-proton couplings, reducing spectral resolution.
• Magic-angle sample spinning (MASS) is a technique used to narrow NMR spectral lines by averaging out anisotropic interactions.

Purpose of the Study:

• To investigate the proton NMR spectrum of leucine-enkephalin associated with bicelles.
• To improve spectral resolution for membrane-bound peptides using advanced NMR techniques.
• To correlate high-resolution isotropic spectra with anisotropic spectra for enhanced structural information.

Main Methods:

• Proton Nuclear Magnetic Resonance (NMR) spectroscopy was employed.
• Magic-angle sample spinning (MASS) was utilized to improve spectral resolution.
• Two-dimensional switched-angle spinning (2D SAS) NMR experiments were developed and applied.

Main Results:

• Static sample NMR spectra exhibited limited resolution due to anisotropic interactions and strong proton-proton couplings.
• Magic-angle sample spinning significantly improved spectral resolution.
• 2D SAS NMR experiments successfully correlated high-resolution isotropic spectra with anisotropic spectra, yielding well-resolved spectra.
• Switched-angle spinning techniques allowed for controlled scaling of dipolar interactions by adjusting the angle between the rotor axis and the magnetic field.

Conclusions:

• 2D SAS NMR is a powerful technique for analyzing membrane-bound peptides, combining the benefits of both isotropic and anisotropic spectral information.
• This method enhances structural elucidation of peptides in ordered bicellar phases.
• Switched-angle spinning offers a tunable approach to scaling dipolar interactions in NMR studies.