Fig. 10. Protein motion and secondary structure. Using one set of coordinates from an ensemble of NMR models the continuous DSSP assignment reproduces the segments in proteins that experimentally had a high degree of motion due to thermal fluctuations in water. Figure reproduced from [3] . Protein motion has been independently measured by the order parameter 1-S2, by the tumbling of the N-H backbone bond-vector. 1-S2 is low when the amino acid is fixed as in the protein core and it is high when the residue fluctuates. 1-S2 is shown versus the continuous DSSP assignment grouping helices (GHI) and strands (EB). The points are averages over a window segment of three consecutive residues; the line gives an average of helix/strand assignments.