Crystallographic Information Framework

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Protein Data Bank exchange dictionary (pdbx) version 1.0521

Category ENTITY



   Data items in the ENTITY category record details (such as
   chemical composition, name and source) about the molecular
   entities that are present in the crystallographic structure.

   Items in the various ENTITY subcategories provide a full
   chemical description of these molecular entities.

   Entities are of three types:  polymer, non-polymer and water.
   Note that the water category includes only water;  ordered
   solvent such as sulfate ion or acetone would be described as
   individual non-polymer entities.

   The ENTITY category is specific to macromolecular CIF
   applications and replaces the function of the CHEMICAL category
   in the CIF core.

   It is important to remember that the ENTITY data are not the
   result of the crystallographic experiment;  those results are
   represented by the ATOM_SITE data items. ENTITY data items
   describe the chemistry of the molecules under investigation
   and can most usefully be thought of as the ideal groups to which
   the structure is restrained or constrained during refinement.

   It is also important to remember that entities do not correspond
   directly to the enumeration of the contents of the asymmetric
   unit. Entities are described only once, even in those structures
   that contain multiple observations of an entity. The
   STRUCT_ASYM data items, which reference the entity list,
   describe and label the contents of the asymmetric unit.


Example 1 - based on PDB entry 5HVP and laboratory records for the structure corresponding to PDB entry 5HVP.
     1 polymer      10916
    ;              The enzymatically competent form of HIV
                   protease is a dimer. This entity
                   corresponds to one monomer of an active dimer.
     2 non-polymer '762'  .
     3 water        18    .

Category groups:
Category key:

Mandatory category: no