Peptide sequence tag

A peptide sequence tag is a piece of information about a peptide obtained by tandem mass spectrometry that can be used to identify this peptide in a protein database.^[1][2][3]

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Mass spectrometry

In general, peptides can be identified by fragmenting them in a mass spectrometer. For example, during collision-induced dissociation peptides collide with a gas within the mass spectrometer and break into pieces at their peptide bonds. The resulting fragment ions (called b-ions and y-ions) have mass differences corresponding to the residue masses of the respective amino acids. Thus, a tandem mass spectrum contains partial information about the amino acid sequence of the peptide. The peptide sequence tag approach, developed by Matthias Wilm and Matthias Mann at the EMBL,^[4] uses this information to identify the peptide in a database. Briefly, a couple of masses is extracted from the spectrum in order to obtain the peptide sequence tag. This peptide sequence tag is a unique identifier of a specific peptide and can be used to find it in a database containing all possible peptide sequences.

Peptide fragment notation

  A notation has been developed for indicating peptide fragments that arise from a tandem mass spectrum.^[5] Peptide fragment ions are indicated by a, b, or c if the charge is retained on the N-terminus and by x, y or z if the charge is maintained on the C-terminus. The subscript indicates the number of amino acid residues in the fragment.

See also

• Protein sequence
• Protein mass spectrometry

References