Figure 9. Auxiliary information useful for statistical validation of peptide identifications.

While acquired MS/MS spectra are the primary source of information used for peptide identification, auxiliary information available from various stages of the experiment can also be useful for discriminating between true and false identifications. Some auxiliary parameters (e.g., mass accuracy ΔM and the number of tryptic termini NTT) can be used to restrict the set of candidate database peptides during the database search. Alternatively, it can be utilized in the post-database search statistical analysis in addition to the database search score.