Continuous wave W- and D-Band EPR spectroscopy offer “sweet-spots” for characterizing conformational changes and dynamics in intrinsically disordered proteins

•W- and D-Band line shapes are sensitive to motions in the 0.1–2ns time regime.•These frequencies effectively report on conformational dynamics of IDPs.•W-band spectra reflecting helical formation in IA3 is experimentally demonstrated. Site-directed spin labeling (SDSL) electron paramagnetic resonan...

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Bibliographic Details
Published in:Biochemical and biophysical research communications 2014-07, Vol.450 (1), p.723-728
Main Authors: Casey, Thomas M., Liu, Zhanglong, Esquiaqui, Jackie M., Pirman, Natasha L., Milshteyn, Eugene, Fanucci, Gail E.
Format: Article
Language:English
Subjects:
60 APPLIED LIFE SCIENCES
ABSORPTION SPECTROSCOPY
Algorithms
AMINO ACIDS
COMPARATIVE EVALUATIONS
CONFORMATIONAL CHANGES
CORRELATIONS
ELECTRON SPIN RESONANCE
Electron Spin Resonance Spectroscopy - methods
EPR spectroscopy
GHZ RANGE
High-field EPR
Intrinsically disordered proteins
LABELLING
Multi-frequency EPR
Protein Conformation
PROTEINS
Proteins - chemistry
Proteins - ultrastructure
SENSITIVITY
Site-directed spin-labeling
SPIN
Staining and Labeling - methods
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Summary:•W- and D-Band line shapes are sensitive to motions in the 0.1–2ns time regime.•These frequencies effectively report on conformational dynamics of IDPs.•W-band spectra reflecting helical formation in IA3 is experimentally demonstrated. 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 (∼9.5GHz) 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 (35GHz) and W-band (95GHz) 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 ∼0.3ns (unstructured) to ∼0.6ns (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.
ISSN:0006-291X
1090-2104
DOI:10.1016/j.bbrc.2014.06.045