High-Resolution Ambient MS Imaging of Negative Ions in Positive Ion Mode: Using Dicationic Reagents with the Single-Probe

J Am Soc Mass Spectrom. 2016 Jan;27(1):124-34. doi: 10.1007/s13361-015-1287-7.

Abstract

We have used the Single-probe, a miniaturized sampling device utilizing in-situ surface microextraction for ambient mass spectrometry (MS) analysis, for the high resolution MS imaging (MSI) of negatively charged species in the positive ionization mode. Two dicationic compounds, 1,5-pentanediyl-bis(1-butylpyrrolidinium) difluoride [C5(bpyr)2F2] and 1,3-propanediyl-bis(tripropylphosphonium) difluoride [C3(triprp)2F2], were added into the sampling solvent to form 1+ charged adducts with the negatively charged species extracted from tissues. We were able to detect 526 and 322 negatively charged species this way using [C5(bpyr)2F2] and [C3(triprp)2F2], respectively, including oleic acid, arachidonic acid, and several species of phosphatidic acid, phosphoethanolamine, phosphatidylserine, phosphatidylglycerol, phosphatidylinositol, and others. In conjunction with the identification of the non-adduct cations, we have tentatively identified a total number of 1200 and 828 metabolites from mouse brain sections using [C5(bpyr)2F2] and [C3(triprp)2F2], respectively, through high mass accuracy measurements (mass error <5 ppm); MS/MS analyses were also performed to verify the identity of selected species. In addition to the high mass accuracy measurement, we were able to generate high spatial resolution (~17 μm) MS images of mouse brain sections. Our study demonstrated that utilization of dicationic compounds in the surface microextraction with the Single-probe device can perform high mass and spatial resolution ambient MSI measurements of broader types of compounds in tissues. Other reagents can be potentially used with the Single-probe device for a variety of reactive MSI studies to enable the analysis of species that are previously intractable.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain Chemistry
  • Cations / chemistry
  • Equipment Design
  • Mice
  • Miniaturization / instrumentation*
  • Molecular Imaging / instrumentation
  • Molecular Imaging / methods
  • Spectrometry, Mass, Electrospray Ionization / instrumentation*
  • Spectrometry, Mass, Electrospray Ionization / methods*
  • Tandem Mass Spectrometry / instrumentation
  • Tandem Mass Spectrometry / methods

Substances

  • Cations