Fig. 3

Evidence for rocking motion in cubic-PEG-ub crystals from NERRD NMR measurements. a–c NERRD data of representative amide sites outside the dynamic β-turn region for MPD-ub (black) and cubic-PEG-ub (red). Error bars were obtained from Monte Carlo analysis, described in the Methods section. The solid red lines correspond to a two-state fit of data from 22 amide sites with a common exchange time constant and per-residue-adjustable motional amplitude (all shown in Supplementary Fig. 6). d χ ² value of this fit as a function of the jump time constant. In fitting these NERRD data, we have assumed that protein rocking can be approximated as two-site jump process, which is a crude but justifiable model⁷⁰