Fig 4. Determination of NMR order parameters.
(A) Processes in the pico- to nanosecond time regime can be probed by experiments that monitor the relaxation rates of different spin modes. Relaxation rates at multiple sites in a protein are determined from exponential fits of resonance intensities in a time series. (B) Analysis of the experimental data within the model-free approach separates nanosecond timescale contributions arising from rotational diffusion of the protein as a whole (τc) from (typically) picosecond contributions due to internal bond vector fluctuations, for which amplitudes (S2), timescale (τe), and, if applicable, information on additional motions are obtained.