I need to generate an ensemble of proteins to capture backbone flexibility in docking. I ran relax with thorough flag, but the resultants decoys are not that much different (RMSD ranges fro 0.2 to 0.7). Then I ran Backrub without defining pivot_residue and without resfile. The resultant decoys of Backrub are also similar. Does anyone have suggestions to define pivot_residue? or how can I sample conformational space enough to consider backbone flexibility?