Trimethylation Enhancement Using (13)C-Diazomethane ((13)C-TrEnDi): Increased Sensitivity and Selectivity of Phosphatidylethanolamine, Phosphatidylcholine, and Phosphatidylserine Lipids Derived from Complex Biological Samples

Anal Chem. 2016 Jul 19;88(14):6996-7004. doi: 10.1021/acs.analchem.5b04524. Epub 2016 Jun 27.

Abstract

Significant sensitivity enhancements in the tandem mass spectrometry-based analysis of complex mixtures of several phospholipid classes has been achieved via (13)C-TrEnDi. (13)C-TrEnDi-modified phosphatidylethanolamine (PE), phosphatidylserine (PS), and phosphatidylcholine (PC) lipids extracted from HeLa cells demonstrated greater sensitivity via precursor ion scans (PISs) than their unmodified counterparts. Sphingomyelin (SM) species exhibited neither an increased nor decreased sensitivity following modification. The use of isotopically labeled diazomethane enabled the distinction of modified PE and modified PC species that would yield isobaric species with unlabeled diazomethane. (13)C-TrEnDi created a PE-exclusive PIS of m/z 202.1, two PS-exclusive PISs of m/z 148.1 and m/z 261.1, and a PIS of m/z 199.1 for PC species (observed at odd m/z values) and SM species (observed at even m/z values). The standardized average area increase after TrEnDi modification was 10.72-fold for PE species, 2.36-fold for PC, and 1.05-fold for SM species. The sensitivity increase of PS species was not quantifiable, as there were no unmodified PS species identified prior to derivatization. (13)C-TrEnDi allowed for the identification of 4 PE and 7 PS species as well as the identification and quantitation of an additional 4 PE and 4 PS species that were below the limit of detection (LoD) prior to modification. (13)C-TrEnDi also pushed 24 PE and 6 PC lipids over the limit of quantitation (LoQ) that prior to modification were above the LoD only.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carbon Isotopes
  • Diazomethane / chemistry*
  • HeLa Cells
  • Humans
  • Limit of Detection
  • Methylation
  • Phosphatidylcholines / analysis*
  • Phosphatidylcholines / chemistry
  • Phosphatidylcholines / classification
  • Phosphatidylethanolamines / analysis*
  • Phosphatidylethanolamines / chemistry
  • Phosphatidylethanolamines / classification
  • Phosphatidylserines / analysis*
  • Phosphatidylserines / chemistry
  • Phosphatidylserines / classification
  • Sensitivity and Specificity
  • Spectrometry, Mass, Electrospray Ionization / methods

Substances

  • Carbon Isotopes
  • Phosphatidylcholines
  • Phosphatidylethanolamines
  • Phosphatidylserines
  • Diazomethane