In all dynamic ensembles (1xqq, 2nr2, 2k39) as well as in the backrub-ensemble (brub), residues I3, V5, I36, I44, I61, and L67 have a very strong preference for a single rotameric state of χ1. In contrast, the MFA results predict prevalence of the same rotamer but with substantial additional excursions into a second rotameric equilibrium position in up to 20% of the cases. These few odd rotamers are sufficient to account for part of the lowering of the (Cγ) order parameters as well as increasing their anisotropy (ηrdc(Cγ)) (see Fig. 2). For the solvent-exposed residues L8 and V70, χ1 samples more than one state in all ensembles. For V70, the same 2-state distribution (tr/g−) of χ1 rotamers is reproduced by all ensembles as well as by the MFA. However, the distribution of L8 predicted from the MFA or from the EROS ensemble includes significant representation of all three rotamers whereas the relaxation-based ensembles include only the tr and g− rotamers. This result suggests the existence of an additional mode of motion in the supra-τc for residue L8.