Heteronuclear Adiabatic Relaxation Dispersion (HARD) for Quantitative Analysis of Conformational Dynamics in Proteins

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Heteronuclear Adiabatic Relaxation Dispersion (HARD) for Quantitative Analysis of Conformational Dynamics in Proteins


Publication year: 2012
Source:Journal of Magnetic Resonance

Nathaniel J. Traaseth, Fa-An Chao, Larry R. Masterson, Silvia Mangia, Michael Garwood, Shalom Michaeli, Burckhard Seelig, Gianluigi Veglia

NMR relaxation methods probe biomolecular motions over a wide range of timescales. In particular, the rotating frame spin-lock R1? and Carr-Purcell-Meiboom-Gill (CPMG) R2 experiments are commonly used to characterize ?sec-msec dynamics, which play a critical role in enzyme folding and catalysis. In an effort to complement these approaches, we introduced the heteronuclear adiabatic relaxation dispersion (HARD) method, where dispersion in rotating frame relaxation rate constants (longitudinal R1? and transverse R2?) is created by modulating the shape and duration of adiabatic full passage (AFP) pulses. Previously, we showed the ability of the HARD method to detect chemical exchange dynamics in the fast exchange regime (exchange rate constants: kex ~ 104 - 105 s-1). In this article, we compare the performance of the HARD method for two soluble proteins (ubiquitin and 10C RNA ligase), showing its sensitivity to slower exchange processes. An advantage of the HARD method is its nominal dependence on the applied radio frequency field, which can be leveraged to modulate the dispersion in the relaxation rate constants. In addition, we also include product operator simulations to define the dynamic range of adiabatic R1? and R2? that is valid under all exchange regimes. We conclude from both experimental observations and simulations that this method is highly complementary to CPMG-based and rotating frame spin-lock R1? experiments to probe conformational exchange dynamics for biomolecules. Finally, this approach is germane to several NMR-active nuclei, where relaxation rates are frequency-offset independent.
Graphical Abstract

Graphical abstract Highlights

? Heteronuclear Adiabatic Relaxation Dispersion (HARD) detect fast and slow conformational dynamics. ? Adiabatic relaxation can be interpreted quantitatively. ? HARD method is complementary to CPMG and rotating frame spin-lock R1? relaxation Measurements.





Source: Journal of Magnetic Resonance