Deeper Protein Identification by Using FAIMS in Top-down Proteomics

Field Asymmetric Ion Mobility Spectrometry (FAIMS), when used in proteomics studies, provides superior selectivity, and enables more proteins to be identified by providing additional gas phase separation. Here, we tested the performance of cylindrical FAIMS for the identification and characterization of proteoforms by top-down mass spectrometry of heterogeneous protein mixtures. Combining FAIMS with chromatographic separation resulted in a 62% increase in protein identifications and an 8% increase in proteoform identifications as compared to samples analyzed without FAIMS. This increase was attributable, in part, to improved signal-to-noise for proteoforms with similar retention times. Additionally, our results show that the optimal compensation voltage of any given proteoform was correlated with the molecular weight of the analyte. Collectively these results suggest that the addition of FAIMS can enhance top-down proteomics in both discovery and targeted applications.