Solvent accessibility
Neglecting the two alanines and the Cγ for I44 which have unusually large order parameters, a correlation between the side chain solvent-accessibility and the side chain mobility can be observed (Fig. 3a). The correlation coefficient between solvent-accessibility and (CC) order parameters is r = −0.501. The side chains which are more solvent-accessible show a tendency to be more mobile.
Fig. 3 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