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Updated: Apr 27, 2026

Author Spotlight: Exploring Intrinsically Disordered Protein Dynamics Through NMR Relaxation Experiments
Published on: November 1, 2024
Continuous wave W- and D-band EPR spectroscopy offer "sweet-spots" for characterizing conformational changes and
Thomas M Casey1, Zhanglong Liu1, Jackie M Esquiaqui1
1Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611, USA.
Abstract:
Site-directed spin labeling (SDSL) electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for characterizing conformational sampling and dynamics in biological macromolecules. Here we demonstrate that nitroxide spectra collected at frequencies higher than X-band (∼9.5 GHz) have sensitivity to the timescale of motion sampled by highly dynamic intrinsically disordered proteins (IDPs). The 68 amino acid protein IA3, was spin-labeled at two distinct sites and a comparison of X-band, Q-band (35 GHz) and W-band (95 GHz) spectra are shown for this protein as it undergoes the helical transition chemically induced by tri-fluoroethanol. Experimental spectra at W-band showed pronounced line shape dispersion corresponding to a change in correlation time from ∼0.3 ns (unstructured) to ∼0.6 ns (α-helical) as indicated by comparison with simulations. Experimental and simulated spectra at X- and Q-bands showed minimal dispersion over this range, illustrating the utility of SDSL EPR at higher frequencies for characterizing structural transitions and dynamics in IDPs.
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