Dynamic Exclusion Weighting Strategy Evaluation

dynamic-exclusion-weighting-strategy-evaluation

Summary

Evaluate how weighted dynamic exclusion fragmentation strategies (e.g., WeightedDEWController) compare to baseline TopN acquisition in LC-MS/MS by running parallel simulations through the ViMMS framework and measuring coverage and intensity metrics on the resulting mzML and EvaluationData outputs.

When to use

You have prototyped a novel data-dependent acquisition strategy that uses dynamic exclusion with intensity or ROI weighting, and you need to quantitatively compare its MS/MS coverage and intensity performance against a simpler baseline (TopN) before testing on real instrumentation. Use this when you have a virtual chemical mixture, a candidate controller implementation, and access to ViMMS Environment simulation.

When NOT to use

• You do not have a working implementation of your candidate controller ready to run in ViMMS — use this skill only after validation that your controller class instantiates and runs without errors.
• Your goal is to evaluate a single acquisition strategy in isolation, not to compare strategies — the skill is specifically designed for comparative evaluation.
• Input chemicals are not representative of your target analyte set (e.g., generated from a different m/z range or database than intended) — results will not transfer to real data.

Inputs

• chemical_mixture (list of Chemical objects with m/z, RT, intensity, MS levels)
• IndependentMassSpectrometer instance (polarity, chemicals)
• WeightedDEWController instance (strategy parameters: use_weighteddew_exclusion, isolation_width, N, mz_tol, rt_tol, min_ms1_intensity)
• TopNController instance (baseline parameters: N, isolation_width, polarity)
• Environment simulation parameters (min_time, max_time)

Outputs

• mzML files (one per controller, containing all scans with acquisition metadata)
• EvaluationData pickle objects (one per controller, with times_fragmented_summary, cumulative intensity, scan-level statistics)
• comparative metrics (e.g., fragmentation coverage %, total intensity acquired, ROI completeness)

How to apply

Instantiate two parallel simulation runs in ViMMS: one using your experimental WeightedDEWController with parameters like use_weighteddew_exclusion=True, isolation_width, N (number of precursors), mz_tol, rt_tol, and min_ms1_intensity (e.g., 1.75E5), and a second using a TopNController baseline with identical chemical input and acquisition window. Run both through an Environment with save_eval=True to capture EvaluationData pickles and mzML output. Load both pickled EvaluationData objects and compare times_fragmented_summary (fragmentation coverage) and cumulative intensity metrics using evaluate_simulated_env(). Differences in coverage and intensity distributions directly indicate whether the weighting scheme improves or degrades acquisition performance relative to the baseline.

Related tools

• ViMMS (Core simulation framework: instantiate Environment, WeightedDEWController, IndependentMassSpectrometer; execute env.run() to drive the acquisition loop; export mzML and evaluate_simulated_env() to compare metrics.) — https://github.com/glasgowcompbio/vimms
• Python (Host language for instantiating controllers, running Environment loops, loading EvaluationData pickles, and computing comparative metrics.)
• Poetry (Dependency and environment manager for ViMMS installation and development setup.) — https://python-poetry.org/
• OpenMS (Post-processing of mzML output to compute fragmentation coverage metrics using external peak-picking and spectral matching.)

Examples

from vimms.Common import POSITIVE; from vimms.ChemicalSamplers import UniformMZFormulaSampler; from vimms.MassSpectrometer import IndependentMassSpectrometer; from vimms.Controllers import WeightedDEWController, TopNController; from vimms.Environment import Environment; sampler = UniformMZFormulaSampler(100, 500); chemicals = sampler.sample(100); ms = IndependentMassSpectrometer(POSITIVE, chemicals); dew_ctrl = WeightedDEWController(POSITIVE, N=3, mz_tol=10, rt_tol=15, min_ms1_intensity=1.75E5, use_weighteddew_exclusion=True); env_dew = Environment(ms, dew_ctrl, min_time=0, max_time=1440, save_eval=True); env_dew.run(); env_dew.write_mzML('dew_output.mzML')

Evaluation signals

• Both controller runs complete without runtime errors and produce valid mzML files with identical scan count structure.
• EvaluationData pickle files load successfully and contain non-empty times_fragmented_summary and cumulative intensity arrays for both controllers.
• Fragmentation coverage (times_fragmented_summary) and intensity metrics are numerically comparable (same units, overlapping range) between the two controller results.
• The weighted controller shows measurably different (higher or lower) coverage or intensity than the baseline TopN controller, confirming that the weighting scheme is being applied during acquisition decisions.
• Peak-picking and spectral matching (if using OpenMS) yield consistent ROI completeness and matching confidence scores across both controller outputs.

Limitations

• Virtual simulation does not capture instrument-specific artifacts (e.g., quadrupole transmission efficiency, thermal noise, detector saturation) that may alter ranking in real MS/MS acquisition.
• Comparison depends critically on identical chemical mixture input and identical acquisition window (min_time, max_time); mismatched parameters will confound results.
• EvaluationData metrics rely on accurate peak-picking parameters (MZMine settings); different MZMine configurations may yield different coverage conclusions from the same mzML.
• WeightedDEWController performance is sensitive to parameter choices (isolation_width, mz_tol, rt_tol, min_ms1_intensity); results may not generalize to different thresholds or biological contexts.

Evidence

• [other] The ViMMS framework supports toggling WeightedDEW exclusion as an alternative to TopN fragmentation strategies, enabling comparative evaluation through captured EvaluationData pickles and mzML output.: "The ViMMS framework supports toggling WeightedDEW exclusion as an alternative to TopN fragmentation strategies, enabling comparative evaluation through captured EvaluationData pickles and mzML output."
• [other] Create a WeightedDEWController instance with use_weighteddew_exclusion=True, setting isolation_width=1, N=3, mz_tol=10, rt_tol=15, and min_ms1_intensity=1.75E5.: "Create a WeightedDEWController instance with use_weighteddew_exclusion=True, setting isolation_width=1, N=3, mz_tol=10, rt_tol=15, and min_ms1_intensity=1.75E5."
• [other] Execute env.run() to drive the simulation loop and capture all scans with exclusion-weighted acquisition decisions.: "Execute env.run() to drive the simulation loop and capture all scans with exclusion-weighted acquisition decisions."
• [other] Load the pickled EvaluationData object and compute coverage and intensity metrics using evaluate_simulated_env(), comparing times_fragmented_summary and cumulative intensity against the baseline TopN result.: "Load the pickled EvaluationData object and compute coverage and intensity metrics using evaluate_simulated_env(), comparing times_fragmented_summary and cumulative intensity against the baseline TopN"
• [readme] a flexible and modular framework designed to simulate fragmentation strategies in tandem mass spectrometry-based metabolomics: "a flexible and modular framework designed to simulate fragmentation strategies in tandem mass spectrometry-based metabolomics"
• [other] When running an Environment you can enable the save_eval flag: "When running an Environment you can enable the save_eval flag"