Order parameters were measured (Lee et al. 1999) from 2H relaxation on selectively 2H-labeled ubiquitin under conditions very similar to ours in concentration, composition and temperature. As for the RDC-based order parameters, the relaxation-based order parameters, (CC) [subscript LS for Lipari-Szabo, in reference to (Lipari and Szabo 1982)], reflect motional fluctuations of the methyl axial CC bond relative to an external reference frame, but with the important difference that the time scale sampled by these motions is strictly faster than the correlation time (τc) of ubiquitin corresponding to about 4 ns. Since RDC-based order parameters are additionally susceptible to the motions over time scales 5–6 orders of magnitude slower than τc, it is generally expected that the condition:10 will be respected for every methyl group, in a similar fashion than what has been described for backbone amide groups when comparing relaxation and RDC-dynamics data (Lakomek et al. 2005, 2006, 2008a, 2008b; Lange et al. 2008; Meiler et al. 2000, 2001). It is however, noteworthy to mention that, whereas the overall scaling  of amide order parameters, (NH), strictly depends on the corresponding condition ( within the experimental error), no additional scaling is used here for the methyl groups, since the alignment tensor is predetermined from the amide order parameters (which already include this condition).