Microsecond Protein Dynamics from Combined Bloch-McConnell and Near-Rotary-Resonance R_1p Relaxation-Dispersion MAS...

Area of Science:

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

Background:

• Protein dynamics on microsecond-to-millisecond (μs-ms) timescales are crucial for understanding protein function.
• Magic-angle-spinning (MAS) NMR is a powerful technique for studying these dynamics.

Purpose of the Study:

• To develop and apply a joint analysis of rotating-frame relaxation dispersion experiments in different radio-frequency (RF) field strength regimes.
• To gain comprehensive insight into protein motion, including geometric amplitudes, chemical-shift changes, populations, and exchange kinetics.

Main Methods:

• Utilizing Bloch-McConnell-type relaxation dispersion at low RF field strengths to observe isotropic-chemical-shift fluctuations.
• Employing Near-Rotary-Resonance Relaxation Dispersion (NERRD) near rotary resonance conditions to study bond angle fluctuations.
• Performing numerical simulations to illustrate the effects and parameter extraction potential.
• Applying the methodology to study conformational exchange in microcrystalline ubiquitin.

Main Results:

• Demonstrated the ability to extract detailed motion parameters by combining low and high RF field strength relaxation dispersion data.
• Successfully applied the joint analysis to a known conformational exchange process in ubiquitin.
• Validated the potential of the integrated approach for comprehensive dynamic analysis.

Conclusions:

• Joint analysis of different RF field strength regimes in MAS NMR relaxation dispersion offers a more complete picture of protein dynamics.
• This integrated methodology enhances the characterization of molecular motion, including kinetics and conformational landscapes.
• The study provides a robust framework for investigating μs-ms protein dynamics in complex systems.