Mass Spectrometry Imaging of Glycosphingolipid C═C Position Isomers by On-tissue Capture-Epoxidation on a Diselenide-Functionalized Covalent Organic Framework

onto slides for tissue thaw-mounting, on-tissue capture-epoxidation was completed within 5 min. With a two-step ambient liquid extraction MS/MS imaging workflow, epoxidized phospholipids and glycosphingolipids on tissue were imaged separately in each step. Compared with the conventional method, this strategy substantially improved the lipid coverage of isomer-differentiated MSI by 7-fold in brain tissue, especially for glycolipids or sphingolipids (27 vs 0). This work illuminates the inaccessible spatial landscape of glycosphingolipid C═C isomers, opening new avenues for understanding their roles in brain function and disease.