pfizer-opensource / cospred

Mass Spectrometry Spectrum Prediction Workflow

CoSpred

Complete MSMS spectrum prediction workflow.

This provide workflow to prepare your own training datasets from raw files and convert them into tensors. These tensors are input for machine learning architecure. The architecture can be build using Tensorflow or Pytorch framework.

Here we are predicting full MSMS spectrum as set of (Mi,Ii) where Mi is the mass of the peak and Ii is the intenisty of the peak. For the BiGRU model, the MSMS spectrum is presented as b/y ion series discribed in original Prosit paper.

Two machine learning architectures were demonstrated.

• Transformer: Predicts full MSMS spectrum using transformer architecture
• BiGRU: Predicts y-, b- ion intensities using BiGRU architecture

Installation

Install all the packages given in conf/requirements_cospred_*.yml in a virtual environment

conda env create -n cospred_gpu_py39 -f conf/requirements_cospred_gpu_py39.yml

Or use the package manager pip to install dependencies specified in the YAML files.

Usage

Configuration

• Main configuration regarding file location and preprocessing parameters could be found and modified in params folder.

• For B/Y ion prediction, training parameters and model setup could be found in JSON files under model_spectra folder. Edit model_construct.py to modify architecture and generate compatible model.json file. Two examples model_byion.json and model_fullspectrum.json were provided.

python model_construct.py

• For transformer based model setup, users could directly modify cospred_model/model/transformerEncoder.py, as well train_transformer module in training_cospred.py.

Data Preprocessing

Database search and pair identification with spectra

• Create PSM file with identified peptides from softwares like Proteome Discoverer corresponding to each rawfiles from the experiment.

Spectrum file format conversion

• Convert rawfiles into mzml and mgf

Msconvert can be run using GUI version of the software on windows computer or can use Docker on linux machine. We recommend to run MSCovert in Windows GUI. At the end, assuming two files were generated, example.mzML and example.mgf. Keep these two files together with example_PSMs.txt got from Proteome Discoverer in the folder data/example.

• OPTION 1: The MGF file doesn't contain sequence information

  • Split the dataset into train and test set. (About 15mins for 300k spectra)

  5000 spectra will be randomly selected for test by default, which could be modified in the script. example_train.mgf and example_test.mgf will be generated from this step. rawfile2hdf_prosit.py (preparing dataset with b/y ion annotation) and rawfile2hdf_cospred.py (preparing dataset for full spectrum representation) are the scripts for this purpose. (About 2 minitues for the example dataset)

  python rawfile2hdf_cospred.py -w split

  • OPTION 1.1: Pair database search result with MGF spectrum, annotate B and Y ion for MSMS spectrum

  Pyteomics is used to parse annotations of y and b ions and their fragments charges from MZML and MGF, and report to annotated MGF files for downstream Prosit application. Note that to parse the input file correctly, you will likely need to adjust regex routine according to the specific MGF format you are using. (About 1 hour for the example dataset)

  python rawfile2hdf_prosit.py -w train
  python rawfile2hdf_prosit.py -w test

  • OPTION 1.2: Pair database search result with MGF spectrum, reformat to full MSMS using bins. (About 2 minitues for the example dataset)

  python rawfile2hdf_cospred.py -w train
  python rawfile2hdf_cospred.py -w test

• OPTION 2: For MGF file with assigned peptide sequence, reformat to full MSMS using bins. Note: you may need to reformat MGF so that peptide sequence representation is compatible for downstream.

python mgf2hdf_cospred.py -w reformat       # Reformat the MGF for CoSpred workflow.
python mgf2hdf_cospred.py -w split_usi      # Split the dataset into train and test set.
python mgf2hdf_cospred.py -w train          # Convert training set into full spectrum bins
python mgf2hdf_cospred.py -w test           # Convert testing set into full spectrum bins

At the end, a few files will be generated. train.hdf5 and test.hdf5 are input files for the following ML modules.

In-house training procedure

training_cospred.py is the script for customized training. Workflows could be selected by arguments, including 1) -t: fine-tuning / continue training the existing model; 2) -f: opt in full MS/MS spectrum model instead of B/Y ions; 3) -c: chucking the input dataset (to prevent memory overflow by large dataset); 4) -p: opt in for BiGRU model instead of Transformer.

Representative training workflows

python training_cospred.py -p   # Training B/Y ion spectrum prediction using BiGRU architecture.
python training_cospred.py      # Training B/Y ion spectrum prediction using Transformer architecture.
python training_cospred.py -pf   # Training full spectrum prediction using BiGRU architecture. 
python training_cospred.py -f   # Training full spectrum prediction using Transformer architecture. 

Inference

Keep the best model under model_spectra folder. Some pre-trained model could be provided upon request. Naming will be like below,

• For B/Y ion, BiGRU model: prosit_byion_[YYYYMMDD]_[HHMMSS]_epoch[integer]_loss[numeric].hdf5
• For full spectrum, BiGRU model: prosit_full_[YYYYMMDD]_[HHMMSS]_epoch[integer]_loss[numeric].hdf5
• For B/Y ion, Transformer model: transformer_byion_[YYYYMMDD]_[HHMMSS]_epoch[integer]_loss[numeric].pt
• For full spectrum, Transformer model: transformer_full_[YYYYMMDD]_[HHMMSS]_epoch[integer]_loss[numeric].pt

With trained models, predict spectrum given peptide sequences from peptidelist_test.csv. Performance evaluation will be executed with -e argument, as long as ground truth test.hdf5 is provided. Performance results will be stored under prediction folder, and the predicted spectra will be stored in peptidelist_pred.msp.

python prediction.py -p   # Predict B/Y ion spectrum prediction using BiGRU architecture.
python prediction.py      # Predict B/Y ion spectrum prediction using Transformer architecture.
python prediction.py -pf   # Predict full spectrum prediction using BiGRU architecture. 
python prediction.py -f   # Predict full spectrum prediction using Transformer architecture. 

Plotting

Predicted spectrum and mirror plot for visual evaluation could be generated by spectra_plot.py. Plots will be stored in prediction/plot folder.

python spectra_plot.py

License

Apache license 2.0

Contact

[email protected]