The DSSP program was designed by Wolfgang Kabsch and Chris Sander to standardize secondary structure assignment. DSSP is a database of secondary structure assignments (and much more) for all protein entries in the Protein Data Bank (PDB). DSSP is also the program that calculates DSSP entries from PDB entries. DSSP does not predict secondary structure.
If you use DSSP, please quote these two articles:
1) A series of PDB related databases for everyday needs.
Wouter G Touw, Coos Baakman, Jon Black, Tim AH te Beek, E Krieger, Robbie P Joosten, Gert Vriend.
Nucleic Acids Research 2015 January; 43(Database issue): D364-D368.
2) Dictionary of protein secondary structure: pattern recognition of
hydrogen-bonded and geometrical features.
Kabsch W, Sander C,
Biopolymers. 1983 22 2577-2637.
PMID: 6667333; UI: 84128824.
In 2011 Maarten Hekkelman has written new software that produces the same output as the original DSSP, but that deals better with the many exceptions life the PDB and everything throw at us. And the new software is much faster and easier to maintain in the future too. To not confuse the topic too much, we call this new software DSSP. The original DSSP will be referred to as DSSPold. In 2012 the determination of π-helices (I prefer to call them α-bulges) has been implemented in DSSP strictly following the original description by Kabsch and Sander, but assigning π-helices before α-helices. Output from the new version (2.1.0) therefore deviates a bit from output from the original DSSP (that now is called DSSPold). We believe that the newest DSSP version is ′better′ than all previous versions.
DSSP stores each residue's chain ID under column 12 as a single character. Since mmCIF-based structures can have chain IDs of more than one character, extra columns were required. In 2017, the DSSP format has been extended with two extra row entries, under columns 150-153 and 160-163 of each maximally four characters long. These contain the RCSB-given chain ID and the author-given chain ID respectively, according to the mmCIF file. Column 12 of mmCIF-based DSSP files will hold the RCSB chain ID, unless it is longer than one character, in which case it will be a '>' character instead.
Under ′Download′ you find access to DSSP. The package comes with everyting in, on, and at it (including source code), and it comes under the Boost license.
There is no license agreement or anything like that. If you are a commercial entity, the same rules hold for the new DSSP. So, as of 'now' (Sept 15 2014) DSSP is free of cost and free of license restrictions for everybody.
By the way, DSSP is also part of the Debian and Ubuntu Linux distributions.
We provide a series of DSSP related facilities that are explained partly in these DSSP pages, and partly elsewhere in the PDBfacilities pages.