No abstract

Existing instrumental resolving power limitations in ion mobility spectrometry (IMS) often restrict adequate characterization of unresolved or co-eluting chemical isomers. Recently, we introduced a novel chemometric deconvolution approach that utilized post-IM collision-induced dissociation (CID) mass spectrometry (MS) data to extract "pure" IM profiles and construct CID mass spectra of individual components from a mixture containing two IM-overlapped components [J. Am. Soc. Mass Spectrom., 2012, 23, 1873-1884]. In this manuscript we extend the capabilities of the IM-MS deconvolution methodology and demonstrate the utility of energy resolved IM deconvolution for successful characterization of ternary and quaternary isomer mixtures with overlapping IM profiles. Furthermore, we show that the success of IM-MS deconvolution is a collision-energy dependent process where different isomers can be identified at various ion fragmentation collision-energies. Details on how to identify a single collision-energy or suitable collision-energy ranges for successful characterization of isomer mixtures are discussed. To confirm the validity of the proposed approach, deconvoluted IM and MS spectra from IM overlapped analyte mixtures are compared to IM and MS data from individually run mixture components. Criteria for "successful" deconvolution of overlapping IM profiles and extraction of their corresponding pure mass spectra are discussed.

A multimodal workflow for mass spectrometry imaging was developed that combines MALDI imaging with protein identification and quantification by liquid chromatography tandem mass spectrometry (LC-MS/MS). Thin tissue sections were analyzed by MALDI imaging, and the regions of interest (ROI) were identified using a smoothing and edge detection procedure. A midinfrared laser at 3-μm wavelength was used to remove the ROI from the brain tissue section after MALDI mass spectrometry imaging (MALDI MSI). The captured material was processed using a single-pot solidphase-enhanced sample preparation (SP3) method and analyzed by LC-MS/MS using ion mobility (IM) enhanced data independent acquisition (DIA) to identify and quantify proteins; more than 600 proteins were identified. Using a modified database that included isoform and the post-translational modifications chain, loss of the initial methionine, and acetylation, 14 MALDI MSI peaks were identified. Comparison of the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of the identified proteins was achieved through an evolutionary relationships classification system.