XmlmmCIF equivalent: 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 sub-categories 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 in 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. XmlmmCIF equivalent: entity/details A description of special aspects of the entity. XmlmmCIF equivalent: entity/formula_weight Formula mass in daltons of the entity. XmlmmCIF equivalent: entity/pdbx_description A description of the entity, with the name of the entity in parenthesis. Maps to PDB compound name. XmlmmCIF equivalent: entity/pdbx_ec Enzyme Commission (EC) number(s) XmlmmCIF equivalent: entity/pdbx_formula_weight_exptl Experimentally determined formula mass in daltons of the entity XmlmmCIF equivalent: entity/pdbx_formula_weight_exptl_meth Method used to determine _entity.pdbx_formula_weight_exptl. XmlmmCIF equivalent: entity/pdbx_fragment Entity fragment description(s). XmlmmCIF equivalent: entity/pdbx_modification Description(s) of any chemical or post-translational modifications XmlmmCIF equivalent: entity/pdbx_mutation Details about any entity mutation(s). XmlmmCIF equivalent: entity/pdbx_number_of_molecules A place holder for the number of molecules of the entity in the entry. XmlmmCIF equivalent: entity/pdbx_parent_entity_id An identifier for the parent entity if this entity is part of a complex entity. For instance a chimeric entity may be decomposed into several independent chemical entities where each component entity was obtained from a different source. XmlmmCIF equivalent: entity/src_method The method by which the sample for the entity was produced. Entities isolated directly from natural sources (tissues, soil samples, etc.) are expected to have further information in the ENTITY_SRC_NAT category. Entities isolated from genetically manipulated sources are expected to have further information in the ENTITY_SRC_GEN category. XmlmmCIF equivalent: entity/target_id The value of _entity.target_id points to a target idenitifier from which this entity was generated. XmlmmCIF equivalent: entity/type Defines the type of the entity. Polymer entities are expected to have corresponding ENTITY_POLY and associated entries. Non-polymer entities are expected to have corresponding CHEM_COMP and associated entries. Water entities are not expected to have corresponding entries in the ENTITY category. XmlmmCIF equivalent: entity/id The value of _entity.id must uniquely identify a record in the ENTITY list. Note that this item need not be a number; it can be any unique identifier.