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The key terms used within the '''MotiveValidator''' and '''ValidatorDB''' environment are defined below. It is important to establish these terms before moving on to the description of the [[ValidatorDB:Principles | '''ValidatorDB''' principles]] on which , or [[MotiveValidator:Functionality | '''ValidatorDBMotiveValidator''' is functionality]] on which both validation tools are built.
We generally use the term ''residue'' to refer to any component of a biomacromolecule or a biomacromolecular complex. Within the '''ValidatorDB''' validation 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).
=Non-standard residue=
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 '''ValidatorDBvalidation''' term ''residue'' thus fully covers ligands.
'''ValidatorDB''' uses In the validation, ''molecules'' are used as an umbrella term for ''ligands and non-standard residues''. Therefore, all properties of ligands and non-standard residues are valid for molecules as well (PDB entry of origin, residue annotation, residue identifier, number of heavy atoms, properties assigned after the validation, etc.). Moreover, a single occurrence of a ligand or non-standard residue is also a ''molecule''.
It is essential to note that '''[[ValidatorDB:UserManual | 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:UserManual | 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 both by '''[[MotiveValidator:UserManual | MotiveValidator]] and [[ValidatorDB''' :UserManual | ValidatorDB]] is the wwPDB Chemical Component Dictionary (wwPDB CCD)<ref name="Sen_2014"/>.
=MotifInput motif=The term ''motif'' is used here as a fragment of a biomacromolecule, biomacromolecular complex or ligand, made up ofone or more residues or parts of residues. Specifically, the term ''input motif'' refers to the individual molecule being validated, together with its surroundings (i.e., atoms from neighboring residues, within two bonds of any atom of the validated molecule). Each ''input motif'' in '''ValidatorDB''' is assigned a unique motif identifier during the validation based on its PDB entry of origin. On the other hand, the term ''validated motif'' (or ''validated molecule'') refers strictly to the subset of atoms in the ''input motif'' which were successfully mapped to atoms in the ''model''.  '''Continue with reading about the [[ValidatorDB:Principles | ValidatorDB principles]], [[MotiveValidator:Principles | MotiveValidator functionality]], or return to the [[ValidatorDB:UserManual | ValidatorDB]], or [[MotiveValidator:UserManual | MotiveValidator]] manuals.'''  =References=<references><ref name="Sen_2014">Sen,S., Young,J., Berrisford,J.M., Chen,M., Conroy,M.J., Dutta,S., Di Costanzo,L., Gao,G., Ghosh,S., Hudson,B.P., et al. (2014) [ Small molecule annotation for the Protein Data Bank]. Database (Oxford)., 2014, 1–11.</ref></references>