Localization of fatty acyl and double bond positions in phosphatidylcholines using a dual stage CID fragmentation coupled with ion mobility mass spectrometry

 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 travellingwave 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.





J.M. Castro-Perez, T.P. Roddy, N.M.M. Nibbering, V. Shah, D.G. McLaren, S. Previs, A.B. Attygalle, K. Herath, Z. Chen, S.P. Wang, R.J. Vreeken, D.G. Johns, T. Hankemeier
Authors from the NMC: 
2011; 22: 1552-1567
Published in: 
Journal of the American Society of Mass Spectrometry
Date of publication: 
September, 2011
Status of the publication: