Remember - the PDB contains information on theoretical models as well as experimental structures.
PDBsum - is a very useful resource for obtaining details of stereochemical quality as well as other information not found in the PDB. [2cpk]
The "Geometry" option from the Structure Explorer page and the associated Fold Deviation Score provide some insights.
Consider the example below, again of 2CPK:
The color coding represents deviations from ideality based on the small molecule data for
peptides of Engh and Huber. Blue is closest to ideality, green less so, through to red
which shows extensive deviations as you will discover for yourself in the excercises that
follow.
