On-tissue dataset-dependent MALDI-TIMS-MS2 bioimaging

Abstract

Trapped ion mobility spectrometry (TIMS) adds an additional separation dimension to mass spectrometry (MS) imaging, however, the lack of fragmentation spectra (MS2) impedes confident compound annotation in spatial metabolomics. Here, we describe spatial ion mobility-scheduled exhaustive fragmentation (SIMSEF), a dataset-dependent acquisition strategy that augments TIMS-MS imaging datasets with MS2 spectra. The fragmentation experiments are systematically distributed across the sample and scheduled for multiple collision energies per precursor ion. Extendable data processing and evaluation workflows are implemented into the open source software MZmine. The workflow and annotation capabilities are demonstrated on rat brain tissue thin sections, measured by matrix-assisted laser desorption/ionisation (MALDI)-TIMS-MS, where SIMSEF enables on-tissue compound annotation through spectral library matching and rule-based lipid annotation within MZmine and maps the (un)known chemical space by molecular networking. The SIMSEF algorithm and data analysis pipelines are open source and modular to provide a community resource.

Large-Scale Screening of Pharmaceutical Compounds to Explore the Application Space of On-Tissue MALDI and MALDI-2 Mass Spectrometry

“…In future applications, the challenge of isobaric interferences could for instance be mitigated using ultrahigh resolving power mass spectrometry or targeted multireaction monitoring (MRM) approaches. With the increasing availability of instrumentation, such as the employed timsTOF flex MALDI-2, the use of ion mobility separation (IMS) in combination with MALDI-MSI offers particularly high potential to reduce ambiguities in analyte annotation. ,− …”

Hyphenation of Liquid Chromatography and Trapped Ion Mobility – Mass Spectrometry for Characterization of Isomeric Phosphatidylethanolamines with Focus on N-Acylated Species

“…46 This database could then be applied to tissue imaging due to TIMS capability as a postionization technique. 46,52 In this study, a multidimensional approach via HILIC-TIMS-MS/MS is used to investigate regioisomeric PE and LNAPE. The focus is on a comprehensive characterization of LNAPE, including fragmentation behavior in both ionization modes as Figure 1.…”

“…Recently, ion mobility has been used to address various isomeric challenges, including cis/trans isomers or enantiomers in the field of lipids. , A frequently used ion mobility technique in lipidomics is TIMS. , By applying an electric field gradient to a counteracting gas flow, a trapping mechanism is performed, resulting in a high and adjustable mobility resolving power. , This technique is used in conjunction with MS for the direct analysis of isomeric analytes, and can also be combined with chromatographic techniques into a multidimensional approach. , Multidimensional methods are becoming increasingly popular, especially in omics studies, due to their additional selectivity and peak capacity. , Furthermore, mobility-resolved fragmentation can be achieved through parallel accumulation-serial fragmentation (PASEF). ,, Helmer et al already used TIMS in a multidimensional approach to generate a CCS database for the differentiation of regioisomeric PG and BMP . This database could then be applied to tissue imaging due to TIMS capability as a postionization technique. , …”