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The key terms used within the '''ValidatorDB''' environment are defined below. It is important to establish these terms before moving on to the description of the [[ValidatorDB:Principles | principles]]
on which ''' ValidatorDB''' is built.
We generally use the term ''residue'' to refer to any component of a biomacromolecule or a biomacromolecular complex. Within the
'''ValidatorDB''' environment, a collection of atoms bound by chemical bonds (covalent, coordinative or ionic) can be considered a residue as long as this fact is appropriately indicated in the input PDB file. Specifically, all the atoms that make up a residue should have the same ''residue annotation'' (3-letter code) and ''residue identifier'' (index internal to the PDB file).
We use the term ''ligand'' to refer to a chemical compound which forms a complex with a biomacromolecule (e.g., sugar, drug, heme). Ions can also function as self standing ligands, or they can be part of a residue (such as Fe in heme). In the PDB format, a ligand has its own residue identifier and annotation (3-letter code), and is composed from HETATM records. The '''
ValidatorDB''' term ''residue'' thus fully covers ligands.
It is essential to note that '''ValidatorDB''' contains validation results for all ligands and non-standard residues containing ''7 or more heavy atoms''. These are denoted as ''molecules relevant for validation'', or simply ''molecules''. The reason '''ValidatorDB''' focuses on these types of molecules is that they exhibit high diversity and nontriviality in their structure.
We use the term ''model'' to refer to a particular structure that is known to be correct. This structure will then be used as reference in the validation process. A model is identified by its residue annotation (3-letter code). The origin of the models used by '''ValidatorDB''' is the wwPDB Chemical Component Dictionary (wwPDB CCD).
'''Continue with reading about the [[ValidatorDB:Principles | principles]]
used in ValidatorDB, or return to the [[ValidatorDB:UserManual | Table of contents]].'''