Selection criterion	Notes
Substrate/cofactors/catalytic metal ions bound	Important for modeling an active conformation of the target protein.
Highly resolved	Discernible from crystallographic resolution and/or Rfree values.
Few or no synthetic mutations	Sometimes point mutations are necessary to solve structures, if they are near or in the active site this could impact on local conformation.
Few or no unresolved regions	Unresolved regions result in unmodelable portions of the target protein (see step 13d), although this may not be avoidable if they reflect and indicate flexibility of a structural region/loop.