List of important changes/enhancements to PDB format as found in Contents Guide Version 2.0.
* Columns 71 - 80 now contain data. They previously contained the PDB ID code and record serial number. These items may be generated using scripts available from the PDB.
Changes to ATOM/HETATM Records
* A segment identifier has been added to the coordinate records in columns 73 - 76. This allows unambiguous identification of regions of the chains and the relationship between them by specifying segments of molecules.
* The element symbol and charge now appear in columns 77 - 80 of the coordinate records.
* When temperature factors are provided, the tempFactor field (columns 61 - 66) always contains the isotropic B value, even when ANISOU records are provided.
* Insertion codes (column 27) are now defined as being alphabetic only.
Changes to Other Records
* HELIX records now contain the length of the helix in columns 72 - 76.
* SSBOND records now state the symmetry operation needed to generate one of the residues of the disulfide bond, if necessary.
* Footnotes (FTNOTE) have been dropped.
* In CRYST1 records:
- The full international Hermann-Mauguin symbol is used,
e.g., P 1 21 1 instead of P 21.
- For a rhombohedral space group in the hexagonal setting,
the lattice type symbol used is H.
* A number of record types which previously contained free text have been restructured as follows:
- "Keyword: value" pairs have been introduced in certain records
such as COMPND and SOURCE to allow easier parsing.
- EXPDTA has been expanded and now appears in every PDB coordinate
entry.
- REMARK records have been restructured to allow easier parsing
and to bring more organization to these records.
New Record Types Added
* TITLE
* CAVEAT
* KEYWDS
* MODRES
* DBREF
* SEQADV
* HETNAM
* HETSYN
* LINK
* HYDBND
* SLTBRG
* CISPEP
For details on each of these changes, see the section of the associated record type in this document.