Evaluating side chain prediction accuracy using Hunter in X-ray and NMR structures. (a) Side chain conformations of the barstar structure were modelled using Hunter and compared to those determined in two different X-ray crystal structures. For most buried side chains, conformation predicted with Hunter is in a good agreement with observed conformations in the crystal structures. For a number of exposed residues (circled in the figure) Hunter's side chain conformation is different from those observed in crystal structures; however, their conformations differ also between the structures. (b) Side chains were rebuilt with Hunter starting from the X-ray or NMR structures of barnase (PDB IDs 1A2P and 1FW7, respectively; backbone RMSD between X-ray and NMR structure is 1.07 Å). RMSD between X-ray and NMR - 1.45 Å; X-ray modelled versus NMR modelled - 1.49 Å; X-ray versus NMR modelled - 1.54 Å; X-ray modelled versus NMR, 1.52 Å; X-ray versus X-ray modelled, 0.85 Å; NMR versus NMR modelled - 1.15 Å.