Editing Protein Data Bank (section)

==File format==
{{main|Protein Data Bank (file format)}}
The file format initially used by the PDB was called the PDB file format. The original format was restricted by the width of [[computer punch card]]s to 80 characters per line. Around 1996, the "macromolecular Crystallographic Information file" format, mmCIF, which is an extension of the [[Crystallographic Information File|CIF format]] was phased in. mmCIF became the standard format for the PDB archive in 2014.<ref>{{cite web|url=https://www.wwpdb.org/documentation/file-formats-and-the-pdb |title=wwPDB: File Formats and the PDB |website=wwpdb.org |access-date=April 1, 2020}}</ref> In 2019, the wwPDB announced that depositions for crystallographic methods would only be accepted in mmCIF format.<ref>{{cite web|url=https://www.wwpdb.org/news/news?year=2019#5d17c1ceea7d0653b99c87e2|title=wwPDB: 2019 News|last=wwPDB.org|website=wwpdb.org}}</ref>

An [[XML]] version of PDB, called PDBML, was described in 2005.<ref>{{cite journal |date=April 2005 | title = PDBML: the representation of archival macromolecular structure data in XML | journal = Bioinformatics | volume = 21 | issue = 7 | pages = 988–992 | doi = 10.1093/bioinformatics/bti082 | pmid = 15509603 |vauthors=Westbrook J, Ito N, Nakamura H, Henrick K, Berman HM | doi-access = free }}</ref>
The structure files can be downloaded in any of these three formats, though an increasing number of structures do not fit the legacy PDB format. Individual files are easily downloaded into graphics packages from Internet [[URL]]s:
* For PDB format files, use, e.g., <code><nowiki>http://www.pdb.org/pdb/files/4hhb.pdb.gz</nowiki></code> or <code><nowiki>http://pdbe.org/download/4hhb</nowiki></code>
* For PDBML (XML) files, use, e.g., <code><nowiki>http://www.pdb.org/pdb/files/4hhb.xml.gz</nowiki></code> or <code><nowiki>http://pdbe.org/pdbml/4hhb</nowiki></code>
The "<code>4hhb</code>" is the PDB identifier. Each structure published in PDB receives a four-character alphanumeric identifier, its PDB ID. (This is not a unique identifier for biomolecules, because several structures for the same molecule&mdash;in different environments or conformations&mdash;may be contained in PDB with different PDB IDs.)