Prentice et al. (2018). International Journal of Mass Spectrometry. doi: 10.1016/j.ijms.2018.06.006
…erica, MA). Rat brain was purchased from Pel-Freez Biologicals (Rogers, AR). Transverse sections of flash-frozen rat brain tissue were cut at 10 m thickness using a cryostat (CryoStar NX70 Cryostat (Thermo Scientific, Waltham, MA) and thaw mounted onto indium tin oxide (ITO) coated glass slides. A custom-built sublimation apparatus was used to apply a DHB matrix layer (120ºC at <70 mTorr for 7
Abstract
Tandem mass spectrometry (MS/MS) is often used to identify lipids in matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS) workflows. The molecular specificity afforded by MS/MS is crucial on MALDI time-of-flight (TOF) platforms that generally lack high resolution accurate mass measurement capabilities. Unfortunately, imaging MS/MS workflows generally only monitor a single precursor ion over the imaged area, limiting the throughput of this methodology. Herein, we demonstrate that multiple TOF/TOF events performed in each laser shot can be used to improve the throughput of imaging MS/MS. This is shown to enable the simultaneous identification of multiple phosphatidylcholine lipids in rat brain tissue. Uniquely, the separation in time achieved for the precursor ions in the TOF-1 region of the instrument is maintained for the fragment ions as they are analyzed in TOF-2, allowing for the differentiation of fragment ions of the exact same <i>m/z</i> derived from different precursor ions (<i>e.g.,</i> the <i>m/z</i> 163 fragment ion from precursor ion <i>m/z</i> 772.5 is easily distinguished from the <i>m/z</i> 163 fragment ion from precursor ion <i>m/z</i> 826.5). This multiplexed imaging MS/MS approach allows for the acquisition of complete fragment ion spectra for multiple precursor ions per laser shot.