Carr-Purcell Pulsed Electron Double Resonance with Shaped Inversion Pulses

Area of Science:

• Biophysics
• Structural Biology
• Spectroscopy

Background:

• Pulsed electron paramagnetic resonance (EPR) spectroscopy measures distances between spin labels on macromolecules.
• Existing EPR methods have limited distance measurements (1.5-8 nm) for membrane proteins due to reduced electron spin coherence times.

Purpose of the Study:

• To overcome the limitations of current EPR techniques for distance measurements in membrane proteins.
• To develop a novel pulse sequence for extending the measurable distance range and improving accuracy.

Main Methods:

• Introduction of a new pulse sequence using Carr-Purcell decoupling and shaped inversion pulses.
• The scheme efficiently recouples dipolar interactions, extending the observation time window for electron spins.

Main Results:

• The new method successfully validated on a bis-nitroxide model compound.
• Reliable interprotomer distance measurements up to 6 nm were achieved for the trimeric betaine transporter BetP.
• This extends the accessible distance range beyond the capabilities of existing EPR methods.

Conclusions:

• The developed pump/probe excitation scheme significantly enhances distance determination in membrane protein complexes.
• This advancement allows for more accurate and extended structural analysis of membrane proteins using EPR.