In-depth structural characterization of phospholipids by pairing solution photochemical reaction with charge inversion ion/ion chemistry
Shotgun lipid analysis based on electrospray ionization-tandem mass spectrometry (ESI-MS/MS) is increasingly used in lipidomic studies. One challenge for the shotgun approach is the discrimination of lipid isomers and isobars. Gas-phase charge inversion via ion/ion reactions has been used as an effective method to identify multiple isomeric/isobaric components in a single MS peak by exploiting the distinctive functionality of different lipid classes. In doing so, fatty acyl chain information can be obtained without recourse to condensed-phase separations or derivatization. This method alone, however, cannot provide carbon–carbon double bond (C=C) location information from fatty acyl chains. Herein, we provide an enhanced method pairing photochemical derivatization of C=C via the Paternò–Büchi reaction with charge inversion ion/ion tandem mass spectrometry. This method was able to provide gas-phase separation of phosphatidylcholines and phosphatidylethanolamines, the fatty acyl compositions, and the C=C location within each fatty acyl chain. We have successfully applied this method to bovine liver lipid extracts and identified 40 molecular species of glycerophospholipids with detailed structural information including head group, fatty acyl composition, and C=C location.
KeywordsLipidomics The Paternò–Büchi reaction Unsaturated lipid Charge inversion Mass spectrometry
This research was supported by the National Institutes of Health (R01GM118484 to Y. X. and GM R37-45372 to S. A. M.) and Sciex.
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Conflict of interest
The authors declare that they have no conflict of interest.
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