Sliding Window Adduct Removal Method (SWARM) for Enhanced Electrospray Ionization Mass Spectrometry Binding Data

Area of Science:

• Analytical Chemistry
• Biochemistry
• Structural Biology

Background:

• Electrospray ionization mass spectrometry (ESI-MS) is crucial for identifying protein-ligand interactions.
• Non-specific adduct formation complicates ESI-MS data analysis, hindering accurate affinity measurements.
• Spectral overlap from adducts can obscure ligand identification and lead to errors.

Purpose of the Study:

• To present a novel method, SWARM, for quantitative correction of ESI mass spectra.
• To address signal overlap caused by adducts in low-to-moderate resolution ESI-MS.
• To improve the accuracy of ligand identification and affinity measurements in complex biological mixtures.

Main Methods:

• Developed the sliding window adduct removal method (SWARM).
• Utilized the statistical nature of adduct formation and assumed identical adduct distributions for protein species.
• Implemented stepwise subtraction of adduct signals using a reference species (free protein).

Main Results:

• SWARM effectively corrects ESI mass spectra for adduct-related signal overlap.
• The method's assumption of identical adduct distributions was supported by experimental data.
• Demonstrated successful application of SWARM to protein-oligosaccharide and ligand-glycan interaction data.

Conclusions:

• SWARM provides a straightforward and quantitative approach to correct ESI-MS spectra.
• This method enhances the reliability of ligand identification and affinity measurements.
• SWARM is valuable for analyzing complex screening libraries in drug discovery and chemical biology.