Proteomics and Metabolomics File Formats Reference

Proteomics and Metabolomics File Formats Reference

This reference covers file formats specific to proteomics, metabolomics, lipidomics, and related omics workflows.

Mass Spectrometry-Based Proteomics

.mzML - Mass Spectrometry Markup Language

Description: Standard XML format for MS data Typical Data: MS1 and MS2 spectra, retention times, intensities Use Cases: Proteomics, metabolomics pipelines Python Libraries:

• pymzml: pymzml.run.Reader('file.mzML')
• pyteomics.mzml: pyteomics.mzml.read('file.mzML')
• pyopenms: OpenMS Python bindings EDA Approach:
• Scan count and MS level distribution
• Total ion chromatogram (TIC) analysis
• Base peak chromatogram (BPC)
• m/z coverage and resolution
• Retention time range
• Precursor selection patterns
• Data completeness
• Quality control metrics (lock mass, standards)

.mzXML - Legacy MS XML Format

Description: Older XML-based MS format Typical Data: Mass spectra with metadata Use Cases: Legacy proteomics data Python Libraries:

• pyteomics.mzxml
• pymzml: Can read mzXML EDA Approach:
• Similar to mzML
• Format version compatibility
• Conversion quality validation
• Metadata preservation check

.mzIdentML - Peptide Identification Format

Description: PSI standard for peptide identifications Typical Data: Peptide-spectrum matches, proteins, scores Use Cases: Search engine results, proteomics workflows Python Libraries:

• pyteomics.mzid
• pyopenms: MzIdentML support EDA Approach:
• PSM count and score distribution
• FDR calculation and filtering
• Modification analysis
• Missed cleavage statistics
• Protein inference results
• Search parameters validation
• Decoy hit analysis
• Rank-1 vs lower ranks

.pepXML - Trans-Proteomic Pipeline Peptide XML

Description: TPP format for peptide identifications Typical Data: Search results with statistical validation Use Cases: Proteomics database search output Python Libraries:

• pyteomics.pepxml EDA Approach:
• Search engine comparison
• Score distributions (XCorr, expect value, etc.)
• Charge state analysis
• Modification frequencies
• PeptideProphet probabilities
• Protein coverage
• Spectral counting

.protXML - Protein Inference Results

Description: TPP protein-level identifications Typical Data: Protein groups, probabilities, peptides Use Cases: Protein-level analysis Python Libraries:

• pyteomics.protxml EDA Approach:
• Protein group statistics
• Parsimonious protein sets
• ProteinProphet probabilities
• Coverage and peptide count per protein
• Unique vs shared peptides
• Protein molecular weight distribution
• GO term enrichment preparation

.pride.xml - PRIDE XML Format

Description: Proteomics Identifications Database format Typical Data: Complete proteomics experiment data Use Cases: Public data deposition (legacy) Python Libraries:

• pyteomics.pride
• Custom XML parsers EDA Approach:
• Experiment metadata extraction
• Identification completeness
• Cross-linking to spectra
• Protocol information
• Instrument details

.tsv / .csv (Proteomics)

Description: Tab or comma-separated proteomics results Typical Data: Peptide or protein quantification tables Use Cases: MaxQuant, Proteome Discoverer, Skyline output Python Libraries:

• pandas: pd.read_csv() or pd.read_table() EDA Approach:
• Identification counts
• Quantitative value distributions
• Missing value patterns
• Intensity-based analysis
• Label-free quantification assessment
• Isobaric tag ratio analysis
• Coefficient of variation
• Batch effects

.msf - Thermo MSF Database

Description: Proteome Discoverer results database Typical Data: SQLite database with search results Use Cases: Thermo Proteome Discoverer workflows Python Libraries:

• sqlite3: Database access
• Custom MSF parsers EDA Approach:
• Database schema exploration
• Peptide and protein tables
• Score thresholds
• Quantification data
• Processing node information
• Confidence levels

.pdResult - Proteome Discoverer Result

Description: Proteome Discoverer study results Typical Data: Comprehensive search and quantification Use Cases: PD study exports Python Libraries:

• Vendor tools for conversion
• Export to TSV for Python analysis EDA Approach:
• Study design validation
• Result filtering criteria
• Quantitative comparison groups
• Imputation strategies

.pep.xml - Peptide Summary

Description: Compact peptide identification format Typical Data: Peptide sequences, modifications, scores Use Cases: Downstream analysis input Python Libraries:

• pyteomics: XML parsing EDA Approach:
• Unique peptide counting
• PTM site localization
• Retention time predictability
• Charge state preferences

Quantitative Proteomics

.sky - Skyline Document

Description: Skyline targeted proteomics document Typical Data: Transition lists, chromatograms, results Use Cases: Targeted proteomics (SRM/MRM/PRM) Python Libraries:

• skyline: Python API (limited)
• Export to CSV for analysis EDA Approach:
• Transition selection validation
• Chromatographic peak quality
• Interference detection
• Retention time consistency
• Calibration curve assessment
• Replicate correlation
• LOD/LOQ determination

.sky.zip - Zipped Skyline Document

Description: Skyline document with external files Typical Data: Complete Skyline analysis Use Cases: Sharing Skyline projects Python Libraries:

• zipfile: Extract for processing EDA Approach:
• Document structure
• External file references
• Result export and analysis

.wiff - SCIEX WIFF Format

Description: SCIEX instrument data with quantitation Typical Data: LC-MS/MS with MRM transitions Use Cases: SCIEX QTRAP, TripleTOF data Python Libraries:

• Vendor tools (limited Python access)
• Conversion to mzML EDA Approach:
• MRM transition performance
• Dwell time optimization
• Cycle time analysis
• Peak integration quality

.raw (Thermo)

Description: Thermo raw instrument file Typical Data: Full MS data from Orbitrap, Q Exactive Use Cases: Label-free and TMT quantification Python Libraries:

• pymsfilereader: Thermo RawFileReader
• ThermoRawFileParser: Cross-platform CLI EDA Approach:
• MS1 and MS2 acquisition rates
• AGC target and fill times
• Resolution settings
• Isolation window validation
• SPS ion selection (TMT)
• Contamination assessment

.d (Agilent)

Description: Agilent data directory Typical Data: LC-MS and GC-MS data Use Cases: Agilent instrument workflows Python Libraries:

• Community parsers
• Export to mzML EDA Approach:
• Method consistency
• Calibration status
• Sequence run information
• Retention time stability

Metabolomics and Lipidomics

.mzML (Metabolomics)

Description: Standard MS format for metabolomics Typical Data: Full scan MS, targeted MS/MS Use Cases: Untargeted and targeted metabolomics Python Libraries:

• Same as proteomics mzML tools EDA Approach:
• Feature detection quality
• Mass accuracy assessment
• Retention time alignment
• Blank subtraction
• QC sample consistency
• Isotope pattern validation
• Adduct formation analysis
• In-source fragmentation check

.cdf / .netCDF - ANDI-MS

Description: Analytical Data Interchange for MS Typical Data: GC-MS, LC-MS chromatography data Use Cases: Metabolomics, GC-MS workflows Python Libraries:

• netCDF4: Low-level access
• pyopenms: CDF support
• xcms via R integration EDA Approach:
• TIC and extracted ion chromatograms
• Peak detection across samples
• Retention index calculation
• Mass spectral matching
• Library search preparation

.msp - Mass Spectral Format (NIST)

Description: NIST spectral library format Typical Data: Reference mass spectra Use Cases: Metabolite identification, library matching Python Libraries:

• matchms: Spectral matching
• Custom MSP parsers EDA Approach:
• Library coverage
• Metadata completeness (InChI, SMILES)
• Spectral quality metrics
• Collision energy standardization
• Precursor type annotation

.mgf (Metabolomics)

Description: Mascot Generic Format for MS/MS Typical Data: MS/MS spectra for metabolite ID Use Cases: Spectral library searching Python Libraries:

• matchms: Metabolomics spectral analysis
• pyteomics.mgf EDA Approach:
• Spectrum quality filtering
• Precursor isolation purity
• Fragment m/z accuracy
• Neutral loss patterns
• MS/MS completeness

.nmrML - NMR Markup Language

Description: Standard XML format for NMR metabolomics Typical Data: 1D/2D NMR spectra with metadata Use Cases: NMR-based metabolomics Python Libraries:

• nmrml2isa: Format conversion
• Custom XML parsers EDA Approach:
• Spectral quality metrics
• Binning consistency
• Reference compound validation
• pH and temperature effects
• Metabolite identification confidence

.json (Metabolomics)

Description: JSON format for metabolomics results Typical Data: Feature tables, annotations, metadata Use Cases: GNPS, MetaboAnalyst, web tools Python Libraries:

• json: Standard library
• pandas: JSON normalization EDA Approach:
• Feature annotation coverage
• GNPS clustering results
• Molecular networking statistics
• Adduct and in-source fragment linkage
• Putative identification confidence

.txt (Metabolomics Tables)

Description: Tab-delimited feature tables Typical Data: m/z, RT, intensities across samples Use Cases: MZmine, XCMS, MS-DIAL output Python Libraries:

• pandas: Text file reading EDA Approach:
• Feature count and quality
• Missing value imputation
• Data normalization assessment
• Batch correction validation
• PCA and clustering for QC
• Fold change calculations
• Statistical test preparation

.featureXML - OpenMS Feature Format

Description: OpenMS detected features Typical Data: LC-MS features with quality scores Use Cases: OpenMS workflows Python Libraries:

• pyopenms: FeatureXML support EDA Approach:
• Feature detection parameters
• Quality metrics per feature
• Isotope pattern fitting
• Charge state assignment
• FWHM and asymmetry

.consensusXML - OpenMS Consensus Features

Description: Linked features across samples Typical Data: Aligned features with group info Use Cases: Multi-sample LC-MS analysis Python Libraries:

• pyopenms: ConsensusXML reading EDA Approach:
• Feature correspondence quality
• Retention time alignment
• Missing value patterns
• Intensity normalization needs
• Batch-wise feature agreement

.idXML - OpenMS Identification Format

Description: Peptide/metabolite identifications Typical Data: MS/MS identifications with scores Use Cases: OpenMS ID workflows Python Libraries:

• pyopenms: IdXML support EDA Approach:
• Identification rate
• Score distribution
• Spectral match quality
• False discovery assessment
• Annotation transfer validation

Lipidomics-Specific Formats

.lcb - LipidCreator Batch

Description: LipidCreator transition list Typical Data: Lipid transitions for targeted MS Use Cases: Targeted lipidomics Python Libraries:

• Export to CSV for processing EDA Approach:
• Transition coverage per lipid class
• Retention time prediction
• Collision energy optimization
• Class-specific fragmentation patterns

.mzTab - Proteomics/Metabolomics Tabular Format

Description: PSI tabular summary format Typical Data: Protein/peptide/metabolite quantification Use Cases: Publication and data sharing Python Libraries:

• pyteomics.mztab
• pandas for TSV-like structure EDA Approach:
• Data completeness
• Metadata section validation
• Quantification method
• Identification confidence
• Software and parameters
• Quality metrics summary

.csv (LipidSearch, LipidMatch)

Description: Lipid identification results Typical Data: Lipid annotations, grades, intensities Use Cases: Lipidomics software output Python Libraries:

• pandas: CSV reading EDA Approach:
• Lipid class distribution
• Identification grade/confidence
• Fatty acid composition analysis
• Double bond and chain length patterns
• Intensity correlations
• Normalization to internal standards

.sdf (Metabolomics)

Description: Structure data file for metabolites Typical Data: Chemical structures with properties Use Cases: Metabolite database creation Python Libraries:

• RDKit: Chem.SDMolSupplier('file.sdf') EDA Approach:
• Structure validation
• Property calculation (logP, MW, TPSA)
• Molecular formula consistency
• Tautomer enumeration
• Retention time prediction features

.mol (Metabolomics)

Description: Single molecule structure files Typical Data: Metabolite chemical structure Use Cases: Structure-based searches Python Libraries:

• RDKit: Chem.MolFromMolFile('file.mol') EDA Approach:
• Structure correctness
• Stereochemistry validation
• Charge state
• Implicit hydrogen handling

Data Processing and Analysis

.h5 / .hdf5 (Omics)

Description: HDF5 for large omics datasets Typical Data: Feature matrices, spectra, metadata Use Cases: Large-scale studies, cloud computing Python Libraries:

• h5py: HDF5 access
• anndata: For single-cell proteomics EDA Approach:
• Dataset organization
• Chunking and compression
• Metadata structure
• Efficient data access patterns
• Sample and feature annotations

.Rdata / .rds - R Objects

Description: Serialized R analysis objects Typical Data: Processed omics results from R packages Use Cases: xcms, CAMERA, MSnbase workflows Python Libraries:

• pyreadr: pyreadr.read_r('file.Rdata')
• rpy2: R-Python integration EDA Approach:
• Object structure exploration
• Data extraction
• Method parameter review
• Conversion to Python-native formats

.mzTab-M - Metabolomics mzTab

Description: mzTab specific to metabolomics Typical Data: Small molecule quantification Use Cases: Metabolomics data sharing Python Libraries:

• pyteomics.mztab: Can parse mzTab-M EDA Approach:
• Small molecule evidence
• Feature quantification
• Database references (HMDB, KEGG, etc.)
• Adduct and charge annotation
• MS level information

.parquet (Omics)

Description: Columnar storage for large tables Typical Data: Feature matrices, metadata Use Cases: Efficient big data omics Python Libraries:

• pandas: pd.read_parquet()
• pyarrow: Direct parquet access EDA Approach:
• Compression efficiency
• Column-wise statistics
• Partition structure
• Schema validation
• Fast filtering and aggregation

.pkl (Omics Models)

Description: Pickled Python objects Typical Data: ML models, processed data Use Cases: Workflow intermediate storage Python Libraries:

• pickle: Standard serialization
• joblib: Enhanced pickling EDA Approach:
• Object type and structure
• Model parameters
• Feature importance (if ML model)
• Data shapes and types
• Deserialization validation

.zarr (Omics)

Description: Chunked, compressed array storage Typical Data: Multi-dimensional omics data Use Cases: Cloud-optimized analysis Python Libraries:

• zarr: Array storage EDA Approach:
• Chunk optimization
• Compression codecs
• Multi-scale data
• Parallel access patterns
• Metadata annotations