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

Abstract

This article is available online at http://www.jlr.org glycerophospholipids (GPs). Numerous accounts have examined the role of GPs in cellular biochemistries including membrane permeability, protein aggregation, and receptor activation ( 1-6 ). MS is a powerful tool for GP structure elucidation and is commonly used in contemporary lipidomics studies in complex biological extracts. MS/MS that uses collision-induced dissociation (CID) is central to most protocols in modern lipidomics and can identify headgroup class, acyl chain length, and degree of acyl chain unsaturation ( 7-11 ). However, there are numerous important structural features of GPs that are not easily discerned by CID, including identifi cation of carbon-carbon double bond position(s), the stereochemistry of carboncarbon double bonds, and the position of substitution of each acyl chain on the glycerol backbone (i.e., sn -position) ( 9, 12, 13 ). The inability to discriminate between snpositional isomers, or even to unequivocally exclude the presence of both isomers, is an impediment to our understanding of the roles of these distinct molecular structures in biological systems.Recent reports point to specifi c arrangements of acyl chains in GPs being responsible for structural interactions that induce specifi c activity. This has been noted particularly in the interactions of GPs toward nuclear receptor proteins. For example, Liu et al. ( 14 )

Mass Spectrometry Imaging with Isomeric Resolution Enabled by Ozone‐Induced Dissociation

“…In the white matter PC(18:1/16:0) represents 31±3 % of the lipid isomer population made up of PC(16:0/18:1) and PC(18:1/16:0) and this increases to 43±2 % in gray matter. Importantly, for such monounsaturated sn ‐positional isomers relative CID/OzID product ion abundances have been demonstrated to reflect absolute isomer populations, and thus these results represent absolute molar fractions 11c. Moreover, we observed an increase of LPC(18:1) relative to LPC(16:0) in the white matter (Figure S3, Supporting Information).…”

Three-dimensional enhanced lipidomics analysis combining UPLC, differential ion mobility spectrometry, and mass spectrometric separation strategies

“…To date, several examples of DMS separation power have been applied to mixtures of tautomers ( 21 ), stereoisomers ( 22 ), and structural isomers ( 23 ); however, this is the fi rst report to apply the technique to lipid profi ling. DMS separates ions based on differences in their mobilities during the high-and lowfi eld portions of an applied asymmetric waveform ( 24 phospholipid classes were separated by ramping the compensation voltage (COV).…”

Oxidative Lipidomics Coming of Age: Advances in Analysis of Oxidized Phospholipids in Physiology and Pathology

“…In contrast, isomeric compounds, which have the same elemental composition but different structures, can only be distinguished by fragmentation, or separated chromatographically (102), or using ion mobility MS. Ion mobility mass spectrometry (IMS) is an increasingly valuable technique for lipid analysis, after the recent introduction of commercial technologies (such as the SynaptÔ mass spectrometer and the SelexIONÔ source). Ion mobility separates ions based on their shape (more correctly on their average collisional crosssection) and has proved particularly useful in lipidomics for distinguishing isobaric lipids from different classes or of different double bond configurations (2,14,56,66,69,93,109). It also has great potential for removing interfering chemical background from the mass spectra, allowing better assignment and more sensitive detection, and has proved particularly useful in mass spectrometric imaging applications (16,52,144).…”