An Off-resonance Rotating Frame Relaxation Experiment for the Investigation of Macromolecular Dynamics Using...

Area of Science:

• Biophysics
• Structural Biology
• Nuclear Magnetic Resonance (NMR) Spectroscopy

Background:

• 15N off-resonance rotating frame relaxation is a key technique for studying protein dynamics.
• Existing methods have limitations in covering all protein residues and chemical shift ranges.
• Understanding internal protein dynamics is crucial for deciphering protein function.

Purpose of the Study:

• To enhance the performance of 15N off-resonance rotating frame relaxation measurements.
• To enable the measurement of relaxation rates for a broader range of protein residues and chemical shifts.
• To develop a more comprehensive method for characterizing protein internal dynamics.

Main Methods:

• Application of simultaneous amplitude and phase-modulated adiabatic radiofrequency (RF) pulses.
• Alignment of nuclear spin magnetization with the off-resonance spin-lock field.
• Utilizing Nuclear Magnetic Resonance (NMR) spectroscopy on the serine protease PB92.

Main Results:

• Achieved improved performance in 15N off-resonance rotating frame relaxation measurements.
• Successfully measured relaxation rates for all non-overlapping residues in PB92, including arginine side chains.
• Covered a wide chemical shift range of 50 ppm, demonstrating broad applicability.
• Simulations confirmed the ability to obtain rates for magnetization vectors at arbitrary angles.

Conclusions:

• The proposed adiabatic RF pulse technique significantly improves 15N off-resonance rotating frame relaxation measurements.
• This method allows for more complete characterization of protein internal dynamics.
• The technique is applicable to large proteins and diverse residue types, expanding NMR's utility in structural biology.