The Chemical Entities of Biological Interest (ChEBI) ontology is downloaded weekly from EMBL-EBI at http://www.ebi.ac.uk/chebi/. The data is made available under the Creative Commons License (CC BY 3.0, http://creativecommons.org/licenses/by/3.0/). For more information see: Degtyarenko et al. (2008) ChEBI: a database and ontology for chemical entities of biological interest. Nucleic Acids Res. 36, D344–D350.
A reagent with two reactive groups, usually at opposite ends of the molecule, that are capable of reacting with and thereby forming bridges between macromolecules, principally side chains of amino acids in proteins, allowing the locations of naturally reactive areas within the proteins to be identified.