Fragmentation data and exact mass searching for isotopes.

IsoMETLIN Metabolite Searching

The isoMETLIN Metabolite Database is a database designed for isotope-based metabolomics. Specifically, isoMETLIN facilitates the identification of metabolites incorporating isotopic labels. isoMETLIN enables users to search all computed isotopologues (>1 million) derived from METLIN on the basis of mass-to-charge values and specified isotopes of interest, such as 13C or 15N.

Tandem Mass Spectrometry

IsoMETLIN contains experimental MS/MS data on isotopomers. These data assist in localizing the position of isotopic labels within a metabolite. From these experimental MS/MS isotopomer spectra, precursor atoms are mapped to fragments. The MS/MS spectra of additional isotopomers have then been computationally generated and included within isoMETLIN.


Created in 2003, METLIN now includes over a million molecules ranging from lipids, steroids, plant & bacteria metabolites, small peptides, carbohydrates, exogenous drugs/metabolites, central carbon metabolites and toxicants. The metabolites and other chemical entities have been individually analyzed to provide experimental MS/MS data.


METLIN fragmentation. METLIN not only provides MS/MS data at multiple collision energies in both positive and negative ionization mode. It also uses the known structure of the metabolite, the elemental composition, and the accurate mass measurement of the fragments to predict the fragment structure.

METLIN Links. METLIN provides links and information for every one of its 960,000 compounds. These include name, systematic name, structure, elemental formula, mass, CAS number, KEGG ID and link, HMDB ID and link, PubChem ID and link, commercial availability and direct search options on the molecule itself.