Popitam

Popitam performs automated peptide identification from tandem mass spectrometry (MS/MS) spectra to improve detection of peptides, including those bearing post-translational modifications and mutations.

Key Features:

• Automated Protein Identification: Matches MS/MS data against a peptide sequence database to produce candidate peptide identifications.
• Handling Modifications and Mutations: Accounts for post-translational modifications and sequence mutations when evaluating peptide-spectrum matches.
• Performance with Large Databases: Scales to searches against large genomic databases and is intended to operate on low-quality MS/MS data.
• Structured Spectral Representation: Represents MS/MS spectra using a structured format akin to spectrum graphs used in de novo sequencing software to align theoretical sequences with experimental peaks.
• Bio-Inspired Algorithm (Ant Colony Optimization): Applies an Ant Colony Optimization algorithm to parse the spectrum graph and emphasize relevant regions for each theoretical peptide.
• Correlation Scoring System: Ranks candidate peptides by a correlation score computed after parsing the spectrum graph.

Scientific Applications:

• Proteomics Identification: Identification of proteins and their post-translational modifications from MS/MS experiments.
• Proteogenomics and Mutation Detection: Detection of peptide variants and mutated sequences by searching genomic-scale peptide databases.
• High‑throughput and Large‑scale Studies: Large-database and high-throughput MS/MS analyses where scalability and handling of low-quality spectra are required.
• Modification Discovery and Functional Analysis: Discovery of unknown modifications to support studies of protein function and interactions.

Methodology:

Matches theoretical peptide sequences from a database to a structured representation of MS/MS spectra (spectrum graphs similar to de novo sequencing), parses the spectrum graph with an Ant Colony Optimization algorithm to highlight relevant sections, and generates a ranked list of peptides by correlation score.