Fig. 7. : Thermal fluctuations and variations between different NMR models correlate. The single residue rmsd is plotted versus 1-S2, in which S2 is the generalised order parameter for backbone 15N spins. This graph relates thermal fluctuations in solution to the differences between NMR models for the same protein. The rmsd difference between NMR models correlates to the conformational disorder measured by the order parameter (CC=0.69). Note that the semi-quantitative correlation between the variation among NMR models and intra-molecular thermal motions of proteins in solution justifies our assignment evaluation scheme that measures the consistency between assignments for different NMR models. The dark circles are measurement for the following 6 proteins (given by their PDB identifiers): 1cdn [46] , 1d5v [47] , 1e41 [48] , 1fsp [49] , 1vre [50] , and 1xoa [xxx 51]. Open circles highlight the notable exception to the observed correlation for the C-terminus (residue 83-94) of 1d5v [47] . This region is completely disordered in the ensemble of structures; however, the 15N hetero-nuclear NOEs are positive and the measured order parameters are high (S2 Î [0.4:0.8]). Thus, the disorder in the ensemble is likely to be dominated by experimental limitations, rather than thermal motion. All data sets kindly provided by the authors of the respective structures.