Structural Analysis of Phospholipid Using Hydrogen Abstraction Dissociation and Oxygen Attachment Dissociation in Tandem Mass Spectrometry

Abstract

Gas-phase hydrogen radicals were introduced into a quadrupole ion trap containing singly charged phospholipids to obtain structural fragmentation patterns in tandem mass spectrometry (MS/MS). Saturated and unsaturated phosphatidylcholines were used as a model phospholipid, whose chain-length ranges between 16 and 24. The MS/MS spectrum yielded a continuous series of fragment ions with a mass difference of 14 Da, representing the saturated fatty acyl chains. The fragment ions corresponding to the double-bond position within a single fatty acyl chain showed a characteristic mass difference of 12 Da. The detection of these diagnostic product ions enabled the structural analysis of double-bond isomers of phospholipids. To further investigate the potential of radical-induced dissociation for the isomeric analysis of phospholipids, gas-phase hydroxyl radicals, and triplet oxygen atoms were employed in tandem mass spectrometry. The methylene bridges adjacent to the double-bond positions were selectively dissociated, accompanied by oxidation of the double bonds. Tandem mass spectrometry incorporating multiple radical species facilitates the structural analysis of isomeric phospholipids.

A lipidomic workflow capable of resolving sn- and CC location isomers of phosphatidylcholines

“…Homolytic bond cleavage has been demonstrated for lipid analysis using photons, 35,37 electrons, 38 and radicals. 39 Reid and co-workers, however, showed that it was possible to induce radicaldirected fragmentation from CID of anionic adducts of PC ions, such as methylcarbonate (CH 3 OCO 2 À ) and triuoroacetate…”

“…S5 †). The process is followed by homolytic cleavage of the C-N bond leading to a neutral loss of (CH 3 ) 2 N-CH 2 c. These two losses (120 Da) collectively lead to the formation of an ethyl radical on the remaining lipid anion (C 39 (ref. 43) and forms a double bond between C2 and C3 on the glycerol backbone.…”

Large-scale lipid analysis with C=C location and sn-position isomer resolving power

“…PB reaction converts the C=C to an oxetane which can be preferentially fragmented by low-energy collisioninduced dissociation (CID). Other approaches include ion mobility spectrometry (IMS) 36,37 and alternative gas-phase ion activation [38][39][40][41][42][43][44] . These lipid characterizing methods were also compatible with mass spectrometry imaging (MSI) [45][46][47][48][49][50] .…”

Identification and Evaluation of Biomarkers for Niemann-Pick Disease Type C Based on Chemical Analysis Techniques

“…To obtain further structural information, hydrogen abstraction/attachment dissociation (HAD)-MS/MS analysis was performed [106]. Unlike normal CID conditions, this method can cleave the double bonds in lipids [107]. As a result, product ions at m/z 255.086, 271.113, and 299.100 were obtained, suggesting the presence of the partial structure of N-acyl-phosphocholine-serine.…”