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15N CPMG Relaxation Dispersion for the Investigation of Protein Conformational Dynamics on the µs-ms Timescale
Published on: April 19, 2021
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Bumps on the Road: The Way to Clean Relaxation Dispersion Magic-Angle Spinning NMR
Ben P Tatman1, Vidhyalakshmi Sridharan2, Motilal Uttarkabat2
1Institute of Science and Technology Austria, Am Campus 1, 3400 Klosterneuburg, Austria.
Journal of the American Chemical Society
|August 1, 2025
Summary
Bloch-McConnell Relaxation Dispersion (BMRD) Nuclear Magnetic Resonance (NMR) studies of protein dynamics in solid states are often confounded by artifacts. Applying continuous wave (CW) decoupling suppresses these artifacts, enabling accurate measurements even in fully protonated proteins.
Area of Science:
- Solid-state Nuclear Magnetic Resonance (NMR) Spectroscopy
- Biomolecular Dynamics
- Protein Structure and Function
Background:
- Microsecond-to-millisecond motions are crucial for biomolecular functions like enzymatic activity and ligand binding.
- Bloch-McConnell Relaxation Dispersion (BMRD) Nuclear Magnetic Resonance (NMR) spectroscopy is vital for studying these dynamics.
- Solid-state BMRD is challenging due to complex spin dynamics from dipolar couplings, often requiring high deuteration.
Purpose of the Study:
- To identify and address artifacts in solid-state 15N R1ρ BMRD profiles.
- To enable accurate and quantitative measurements of microsecond protein dynamics in the solid state.
- To expand the applicability of BMRD to less deuterated or fully protonated protein samples.
Main Methods:
- Investigated artifactual "bumps" in 15N R1ρ BMRD profiles under fast magic-angle spinning (MAS) and high deuteration.
- Identified the artifacts originating from a second-order three-spin Mixed Rotational and Rotary Resonance (MIRROR) recoupling condition.
- Implemented low-power continuous wave (CW) decoupling during the 15N spin-lock to suppress MIRROR conditions.
Main Results:
- Artifactual bumps were found to be common in solid-state 15N R1ρ BMRD, confounding quantitative analysis of microsecond dynamics.
- The MIRROR recoupling condition was identified as the source of these artifacts.
- Application of CW decoupling effectively suppressed the MIRROR artifacts.
- Quantitative microsecond exchange measurements were enabled in solid-state BMRD.
- Accurate BMRD measurements were achieved even in fully protonated proteins at 100 kHz MAS.
Conclusions:
- Artifacts from MIRROR recoupling significantly hinder quantitative solid-state BMRD studies.
- Simultaneous CW decoupling during the 15N spin-lock is a robust method to suppress these artifacts.
- This technique significantly broadens the scope of microsecond dynamics measurements in solid-state MAS NMR, including for fully protonated samples.
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