Metrabase schema. The database tables are grouped according to their context. There are four main tables: ‘activities’, ‘compounds’, ‘proteins’ and ‘refs’. Chemical structures and proteins are stored in the ‘compounds’ and ‘proteins’ tables respectively. Interactions between chemical compounds and proteins are stored in the ‘activities’ table, while the ‘refs’ table contains the publications’ citation information (bibliographic fields). An entity relationship diagram showing all the database fields is provided for download along with the database.