Characterization of Phosphatidylcholine Oxidation Products by MALDI MSⁿ

Abstract

Phospholipid oxidation has been implicated in the pathogenesis and progression of numerous age-related and neurodegenerative diseases. Despite these implications, this broad class of biomolecules remains poorly characterized. In this work, the fragmentation patterns of [M + H](+) and [M + Na](+) ions of intact phosphatidylcholine oxidation products (OxPCs) were characterized by matrix-assisted laser desorption/ionization tandem mass spectrometry (MALDI MS(n), n = 2, 3, and 4). MS(2) of both the [M + H](+) and [M + Na](+) ions of short-chain OxPCs yielded product ions related to the PC headgroup and the fatty acid substituents. MS(3) of the [M + Na - N(CH3)3](+) ions yielded fragmentation indicative of the OxPC modification; specifically, a product ion corresponding to the neutral loss of CO2 (NL of 44) was observed for OxPCs containing a terminal carboxylic acid rather than an aldehyde. Furthermore, MS(4) of the [M + Na - HPO4(CH2)2N(CH3)3](+) ions resulted in fragmentation pathways dependent on the sn-2 fatty acid chain length and type of functional group(s). Specifically, CHO-containing OxPCs with palmitic acid esterified to the sn-1 position of the glycerol backbone yielded a NL of 254, 2 u less than the nominal mass of palmitic acid, whereas the analogous terminal COOH-containing OxPCs demonstrated a NL of 256. Finally, the presence of a γ-ketone relative to the terminal carboxyl group resulted in C-C bond cleavages along the sn-2 substituent, providing diagnostic product ions for keto-containing OxPCs. This work illustrates the enhanced selectivity afforded by MS(n) on the linear ion trap and develops a method for the identification of individual products of PC oxidation.

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

“…This means that MALDI is intrinsically less amenable to absolute quantification than ESI. However, procedures for MALDI-MS of phospholipids and oxidized or chlorinated phospholipids have been developed (32,112,122): Recently, MALDI-MS has been applied to a wider range of oxidized phospholipids (26,27,151) and has been used to investigate the fragmentation of cardiolipin by copper in a mouse model of the copper overload condition Wilson's disease (151), as well as demonstrating the occurrence of truncated oxidized PCs in spinal cord tissue of Sprague-Dawley rats (124). It has been argued that MALDI has advantages compared with ESI for biological samples, as it is more tolerant of the presence of salts or detergents, whereas ESI usually requires sample cleanup or the application of LC.…”

“…Until recently, oxidized lipids and phospholipids have been poorly represented in these resources, but as interest in + , a PL known to localize in the gray matter of rat spinal cord), the ions related to the OxPCs appear mostly in the gray matter (outlined in red). Reprinted with permission from Stutts et al (124); Copyright ª 2013 American Chemical Society. To see this illustration in color, the reader is referred to the web version of this article at www.liebertpub.com/ars their analysis and available MS data grow, this is being remedied.…”

LipidPioneer : A Comprehensive User-Generated Exact Mass Template for Lipidomics

“…The mechanisms of formation for lipid oxidation and the most common oxidized lipid species are available in literature. [19–22] …”

Imaging Mass Spectrometry of Diversified Cardiolipin Molecular Species in the Brain

“…Recently, an imaging mass spectrometry study by Stutts et al also utilized FTICR technology for the mapping of oxidized phosphatidylcholine species in spinal cord tissue. 34 While we did not detect any oxidized cardiolipin species from naïve brain tissue sections, our method is directly applicable to brain tissue sections from animals whose brain function has been compromised, such as from traumatic brain injury, an insult which has been shown to result in the production of CL oxidation products. 9 …”