PhosCalc

PhosCalc assigns probabilities to potential phosphorylation sites on peptides by comparing theoretical b and y fragment ion masses with experimental mass spectra to support phosphosite identification in proteomics.

Key Features:

• Probabilistic Site Assignment: Uses a probabilistic approach to assign likelihood scores to candidate phosphorylation sites on peptides.
• Theoretical Ion Mass Calculation: Calculates theoretical masses for b and y fragment ions from user-provided peptide sequences.
• Experimental Spectrum Comparison: Matches theoretical b and y ions to experimental mass spectra to identify supported fragment ions.
• Probability Scoring of Site Combinations: Computes probability scores for each combination of phosphorylation sites to rank site assignments.
• Throughput and Scalability: Processes datasets of up to 100 peptides simultaneously and is scalable to larger datasets.
• Validation: Has been validated against manually curated datasets using phosphopeptides derived from bovine beta-casein.

Scientific Applications:

• Phosphosite Localization: Localizing phosphorylation sites within peptides in phosphoproteomics studies.
• High-throughput Phosphopeptide Analysis: Facilitating large-scale analysis and comparison of phosphopeptide datasets.
• Integration into Data-analysis Pipelines: Providing probability-scored site assignments for incorporation into proteomic data-processing workflows.

Methodology:

Generates theoretical masses for b and y ions from peptide sequences across possible phosphorylation site combinations, compares these theoretical masses to experimental mass spectra to identify supported ions, and computes probability scores for each site combination; validation was performed using phosphopeptides derived from bovine beta-casein against manually curated datasets.