The Proteomics Standards Initiative (PSI) aims to define community standards for data representation in proteomics to facilitate data comparison, exchange and verification. For detailed information on all PSI activities, please see the home page. The protein modification workgroup focuses on developing a concensus nomenclature and provide an ontology reconciling in a hierarchical representation the complementary descriptions of residue modifications.

The protein modification ontology (PSI-MOD) is available in OBO format or in OBO.xml.

A spreadsheet containing the mapping of the descriptive labels used in various databases and search engines, the concensus list of proposed short name for protein modifications established by collaborative effort of mass spectrometry community, and the proposed rules and recommendations for this nomenclature are available here. These short names are included in the ontology as synonyms of the corresponding terms.