Pepitome: Evaluating improved spectral library search for identification complementarity and quality assessment

Surendra Dasari, Matthew C. Chambers, Misti A. Martinez, Kristin L. Carpenter, Amy Joan L. Ham, Lorenzo J. Vega-Montoto, David L. Tabb

Research output: Contribution to journalArticlepeer-review

43 Scopus citations


Spectral libraries have emerged as a viable alternative to protein sequence databases for peptide identification. These libraries contain previously detected peptide sequences and their corresponding tandem mass spectra (MS/MS). Search engines can then identify peptides by comparing experimental MS/MS scans to those in the library. Many of these algorithms employ the dot product score for measuring the quality of a spectrum-spectrum match (SSM). This scoring system does not offer a clear statistical interpretation and ignores fragment ion m/z discrepancies in the scoring. We developed a new spectral library search engine, Pepitome, which employs statistical systems for scoring SSMs. Pepitome outperformed the leading library search tool, SpectraST, when analyzing data sets acquired on three different mass spectrometry platforms. We characterized the reliability of spectral library searches by confirming shotgun proteomics identifications through RNA-Seq data. Applying spectral library and database searches on the same sample revealed their complementary nature. Pepitome identifications enabled the automation of quality analysis and quality control (QA/QC) for shotgun proteomics data acquisition pipelines.

Original languageEnglish (US)
Pages (from-to)1686-1695
Number of pages10
JournalJournal of Proteome Research
Issue number3
StatePublished - Mar 2 2012


  • dot products
  • hypergeometric distribution
  • quality control
  • spectral libraries bioinformatics

ASJC Scopus subject areas

  • Biochemistry
  • Chemistry(all)


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