a Methyl group order parameters measured from RDCs in ubiquitin are plotted against side chain solvent-exposure parameters calculated with Molmol (Koradi et al. 1996) on pdb:1ubi structure. The straight line represents the correlation between the two parameters (r = −0.501). b Influence of the number of torsion angles from the backbone to the methyl carbon on its measured order parameter. Mean values are 1.24, 0.52, and 0.25 for χ1-, χ1χ2- and χ1χ2χ3-dependent methyl groups. c Order parameters as a function of the angle between the average axial orientation predicted from MFA and from X-ray structure pdb:1ubi for methyl groups