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Nanospray Desorption Electrospray Ionization (nano-DESI) Mass Spectrometry Imaging of Drift Time-Separated Ions
preprintsubmitted on 03.07.2020, 18:27 and posted on 06.07.2020, 10:51 by Daisy Unsihuay, ruichuan yin, Daniela Mesa Sanchez, Yingju Li, Xiaofei Sun, Sudhansu Dey, Julia Laskin
Simultaneous spatial localization and structural characterization of molecules in complex biological samples currently represents an analytical challenge for mass spectrometry imaging (MSI) techniques. In this study, we describe a novel experimental platform, which substantially expands the capabilities and enhances the depth of chemical information obtained in high spatial resolution MSI experiments performed using nanospray desorption electrospray ionization (nano-DESI). Specifically, we designed and constructed a portable nano-DESI MSI platform and coupled it with a drift tube ion mobility spectrometer-mass spectrometer (IM-MS). Separation of biomolecules observed in MSI experiments based on their drift times provides unique molecular descriptors necessary for their identification by comparison with databases. Furthermore, it enables isomer-specific imaging, which is particularly important for unraveling the complexity of biological systems. Imaging of day 4 pregnant mouse uterine sections using the newly developed nano-DESI-IM-MSI system demonstrates rapid isobaric and isomeric separation and reduced chemical noise in MSI experiments. A direct comparison of the performance of the new nano-DESI-MSI platform operated in the MS mode with the more established nano-DESI-Orbitrap platform indicates a comparable performance of these two systems. A spatial resolution of better than ~16 µm and similar molecular coverage was obtained using both platforms. The structural information provided by the ion mobility separation expands the molecular specificity of high-resolution MSI necessary for the detailed understanding of biological systems.