Characterization of acyl chain position in unsaturated phosphatidylcholines using differential mobility-mass spectrometry

J Lipid Res. 2014 Aug;55(8):1668-77. doi: 10.1194/jlr.M046995. Epub 2014 Jun 17.

Abstract

Glycerophospholipids (GPs) that differ in the relative position of the two fatty acyl chains on the glycerol backbone (i.e., sn-positional isomers) can have distinct physicochemical properties. The unambiguous assignment of acyl chain position to an individual GP represents a significant analytical challenge. Here we describe a workflow where phosphatidylcholines (PCs) are subjected to ESI for characterization by a combination of differential mobility spectrometry and MS (DMS-MS). When infused as a mixture, ions formed from silver adduction of each phospholipid isomer {e.g., [PC (16:0/18:1) + Ag](+) and [PC (18:1/16:0) + Ag](+)} are transmitted through the DMS device at discrete compensation voltages. Varying their relative amounts allows facile and unambiguous assignment of the sn-positions of the fatty acyl chains for each isomer. Integration of the well-resolved ion populations provides a rapid method (< 3 min) for relative quantification of these lipid isomers. The DMS-MS results show excellent agreement with established, but time-consuming, enzymatic approaches and also provide superior accuracy to methods that rely on MS alone. The advantages of this DMS-MS method in identification and quantification of GP isomer populations is demonstrated by direct analysis of complex biological extracts without any prior fractionation.

Keywords: differential mobility spectrometry; lipid isomers; mass spectrometry; sn-positional isomers.

MeSH terms

  • Mass Spectrometry / methods*
  • Phosphatidylcholines / analysis*

Substances

  • Phosphatidylcholines