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 compound used to form the matrix for MALDI (matrix-assisted laser desorption/ionization) mass spectrometry. MALDI matrix materials are crystalline compounds with a fairly low molecular weight, so as to allow facile vaporization, have strong absorption at UV or IR wavelengths (to rapidly and efficiently absorb laser irradiation), generally contain polar groups (enabling them to be used in aqueous solutions) and are frequently acidic (so assisting ionisation of the compound being studied, which is contained within the matrix material).