An On‐Tissue Paternò–Büchi Reaction for Localization of Carbon–Carbon Double Bonds in Phospholipids and Glycolipids by Matrix‐Assisted Laser‐Desorption–Ionization Mass‐Spectrometry Imaging

Abstract

Matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) visualizes the distribution of phospho- and glycolipids in tissue sections. However, C=C double-bond (db) positional isomers generally cannot be distinguished. Now an on-tissue Paternò-Büchi (PB) derivatization procedure that exploits benzaldehyde as a MALDI-MSI-compatible reagent is introduced. Laser-induced postionization (MALDI-2) was used to boost the yields of protonated PB products. Collision-induced dissociation of these species generated characteristic ion pairs, indicative of C=C position, for numerous singly and polyunsaturated phospholipids and glycosphingolipids in mouse brain tissue. Several db-positional isomers of phosphatidylcholine and phosphatidylserine species were expressed with highly differential levels in the white and gray matter areas of cerebellum. Our PB-MALDI-MS/MS procedure could help to better understand the physiological role of these db-positional isomers.

Large-scale lipid analysis with C=C location and sn-position isomer resolving power

“…For instance, OzID implemented with matrix-assisted laser desorption ionization (MALDI) MSI revealed altered fractions of phosphatidylcholine (PC) sn-isomers in a tumorous mouse brain 45 . Similarly, MSI based on PB-MS/MS 34,46 and UVPD 47 showed the spatial distribution of lipid C=C location isomers in brain, thyroid, and breast cancer tissues, revealing significant fractional changes of C=C location isomers in cancerous tissues. These studies highlight the significance of developing lipid analysis methods with high structural specificities and their huge potentials in uncovering biological features invisible to conventional lipid profiling.…”

“…Other approaches include ion mobility spectrometry (IMS) 36,37 and alternative gas-phase ion activation [38][39][40][41][42][43][44] . These lipid characterizing methods were also compatible with mass spectrometry imaging (MSI) [45][46][47][48][49][50] . For instance, OzID implemented with matrix-assisted laser desorption ionization (MALDI) MSI revealed altered fractions of phosphatidylcholine (PC) sn-isomers in a tumorous mouse brain 45 .…”

Reshaping Lipid Biochemistry by Pushing Barriers in Structural Lipidomics

“…Bednarik et al. extended the use of PB reactions to MALDI‐MSI . Here a PB derivatization protocol using benzaldehyde was developed that allowed efficient PB reactions to occur on tissue sections while preserving the spatial location of the lipids.…”

“…Here a PB derivatization protocol using benzaldehyde was developed that allowed efficient PB reactions to occur on tissue sections while preserving the spatial location of the lipids. After derivatization, the tissue was studied using post‐ionization‐enhanced MALDI‐MS/MS‐MSI . This enabled the localization and distinction of db‐isomers from a variety of lipid classes, including PC, PS, and hexosylceramides (HexCer) in mouse and pig brain tissues.…”

A Polymer Coating Transfer Enrichment Method for Direct Mass Spectrometry Analysis of Lipids in Biofluid Samples

“…Although it is still very challenging,some MS-based techniques have been developed for identification of C = Cl ocation of lipids. [21] Coupling PCTE with aP B reaction and MS/MS should allow for fast identification of lipid structures in biofluids.T his was realized by mixing acetone with the elution solvent after enrichment. [7] PB-MS/MS has shown good performance in lipid extracts [20] and tissue slices for isomer imaging.…”