title: Tandem mass spectrometry of negative ions from choline phospholipid molecular species related to platelet activating factor.
abstract: Fast atom bombardment mass spectrometry of choline phospholipids produces negative ions characteristic of the intact molecule and tandem mass spectrometry of collision-induced decomposition of M-15 anions characterizes both the identity and substituent position of radyl groups. Certain choline phospholipid molecular species which may be of special interest in the generation of platelet activating factor contain a highly unsaturated fatty acyl substituent at sn-2 and an ether radyl group at sn-1; other choline phospholipid molecular species which contain esterified arachidonic acid are of interest as potential sources of arachidonate for eicosanoid biosynthesis. Collisional activated decomposition of 1-hexadecanoyl-2-arachidonoyl-sn-glycero-phosphocholine produce abundant carboxylate anions at m/z 303 (arachidonate) and m/z 255 (hexadecanoate) in a ratio of 3:1, diagnostic for the sn-2 arachidonoyl position. The ether analog, 1-O-hexadecyl-2-arachidonoyl glycerophosphocholine, produces only one collision-induced dissociation ion at m/z 303 and no product ions corresponding to the ether substituent at sn-1. Molecular weight information from the M-15 ion combined with the CID generated carboxylate anions completely characterize these important phospholipids. Precursor ion studies of M-15 anions from glycero-phosphocholine lipids indicate that this ion is derived directly from a unique adduct ion formed by attachment of the molecular species to a matrix alkoxide ion, neutralizing the positive charge of the quaternary choline nitrogen. Decomposition of this adduct ion yields a methylated matrix molecule and the nominal M-15 ion.
authors.affiliation: Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206.
authors.forename: J A
authors.initials: JA
authors.lastname: Zirrolli
authors.forename: K L
authors.initials: KL
authors.lastname: Clay
authors.forename: R C
authors.initials: RC
authors.lastname: Murphy
mesh_terms: D008968:Molecular Conformation; D015394:Molecular Structure; D010742:Phospholipid Ethers / Q000737:chemistry*; D010972:Platelet Activating Factor / Q000031:analogs & derivatives* / Q000737:chemistry*; D016339:Spectrometry, Mass, Fast Atom Bombardment / Q000379:methods; D013329:Structure-Activity Relationship
chemical_list: D010742:Phospholipid Ethers; D010972:Platelet Activating Factor; C043051:1-O-hexadecyl-2-arachidonyl-sn-glycero-3-phosphocholine