Localization of Fatty Acyl and Double Bond Positions in Phosphatidylcholines Using a Dual Stage CID Fragmentation Coupled with Ion Mobility Mass Spectrometry |
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Authors: | Jose Castro-Perez Thomas P. Roddy Nico M. M. Nibbering Vinit Shah David G. McLaren Stephen Previs Athula B. Attygalle Kithsiri Herath Zhu Chen Sheng-Ping Wang Lyndon Mitnaul Brian K. Hubbard Rob J. Vreeken Douglas G. Johns Thomas Hankemeier |
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Affiliation: | Department of Atherosclerosis Exploratory Biomarkers, Merck Research Laboratories, 126 E. Lincoln Ave, 80Y-2D7, Rahway, NJ 07065, USA. jose_castro-perez@merck.com |
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Abstract: | A high content molecular fragmentation for the analysis of phosphatidylcholines (PC) was achieved utilizing a two-stage [trap (first generation fragmentation) and transfer (second generation fragmentation)] collision-induced dissociation (CID) in combination with travelling-wave ion mobility spectrometry (TWIMS). The novel aspects of this work reside in the fact that a TWIMS arrangement was used to obtain a high level structural information including location of fatty acyl substituents and double bonds for PCs in plasma, and the presence of alkali metal adduct ions such as [M?+?Li]+ was not required to obtain double bond positions. Elemental compositions for fragment ions were confirmed by accurate mass measurements. A very specific first generation fragment ion m/z 577 (M-phosphoryl choline) from the PC [16:0/18:1 (9Z)] was produced, which by further CID generated acylium ions containing either the fatty acyl 16:0 (C15H31CO+, m/z 239) or 18:1 (9Z) (C17H33CO+, m/z 265) substituent. Subsequent water loss from these acylium ions was key in producing hydrocarbon fragment ions mainly from the α-proximal position of the carbonyl group such as the hydrocarbon ion m/z 67 (+H2C-HC?=?CH-CH?=?CH2). Formation of these ions was of important significance for determining double bonds in the fatty acyl chains. In addition to this, and with the aid of 13C labeled lyso-phosphatidylcholine (LPC) 18:1 (9Z) in the ω-position (methyl) TAP fragmentation produced the ion at m/z 57. And was proven to be derived from the α-proximal (carboxylate) or distant ω-position (methyl) in the LPC. |
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