Fig. 2: Deep sulfatide profiling via QCL-MIR imaging-guided TIMS-MSI in ARSA−/− mouse kidney.
From: Deep MALDI-MS spatial omics guided by quantum cascade laser mid-infrared imaging microscopy
a ISOM (red, 1) and inner medulla/papilla (IMP; green,2) identified as ROIs via QCL-MIR imaging (top) and sulfatide distribution in MSI (sum intensities; bottom). Scale bar, 500 µm. Partly created in BioRender. https://BioRender.com/spcji05. b Overlaid QCL-MIR imaging-guided ion image of I) m/z 778.515 (SM4 34:1;O2[M-H]-; orange), II) m/z 850.572 (SM4 38:1;O3[M-H]-; red), and III) m/z 1052.692 (SM3 42:1;O2[M-H] -; green) within kidney (grey). Mass window ±3 ppm. Subsequently, precursor ions for iprm-PASEF are region-selectively filtered for on-tissue fragmentation analysis to reveal molecular identities. In total, we acquired iprm-PASEF-derived MS2 spectra for 153 sulfatide species of which 33 are considered chimeric. Scale bar, 500 µm. c Separation of even-and odd-chain sulfatides on-tissue: Extracted ion mobilograms and iprm-PASEF isolation windows for SM4 38:2;O3 (black rhombus) and SM4 39:1;O2 (orange dot) acquired with (i) 120 ms (red) and (ii) 480 ms TIMS ramp time (blue). Gaussians describe the data for each molecule (dashed and dotted lines). d Peak intensity ratios within the isolation window (filled areas under curve in (c)) for both sulfatides and ramp time settings. Peak intensity maxima are marked in dotted lines. e Butterfly plot of iprm-PASEF-derived MS2 spectra (top, blue) and conventional on-tissue MS2 without ion mobility separation (bottom, black) for m/z 848.591 (SM4 39:1;O2[M-H]-). Fragments at m/z 568.28, m/z 540.29, and m/z 522.28 refer to the loss of the α-OH-FA. f MS2 fragments observed (green dots) in iprm-PASEF analysis of selected sulfatides (columns). g Venn diagram of sulfatide subclasses identified by 4D-LC-TIMS-MS (blue) and MALDI-TIMS-MSI (purple). h Evaluation of the ground truth concept: Total number of identified sulfatides per subclass out of 156 theoretical sulfatide configurations. Created in BioRender. https://BioRender.com/64y1bin. Source data is provided as a Source Data file.
