Submitted to: Rapid Communications in Mass Spectrometry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/4/2002
Publication Date: 10/17/2002
Citation: AL-SAAD, K.A., ZABROUSKOV, V., SIEMS, W.F., KNOWLES, N.R., HANNAN, R.M., HILL, H.H. MATRIX-ASSISTED LASER DESORPTION/IONIZATION TIME-OF-FLIGHT MASS SPECTROMETRY OFLIPIDS: IONIZATION AND PROMPT FRAGMENTATION PATTERNS. RAPID COMMUNICATIONS IN MASS SPECTROMETRY. 2002. v. 16. p. 1-10.
Interpretive Summary: We used a new technology, matrix-assisted laser desorption/ionization (MALDI), to evaluate the breakdown and restructuring of simple and phosphorous containing lipids in plant tissue. This was an effort to determine how these molecules dissembled naturally, and then try to predict what the resultant molecules role would be in the maturing or aging process of the plant or seed. We found that, contrary to previous work published, the lipids formed very predictable products. This work exemplified the use of MALDI as an analytical tool in evaluating lipids from living systems.
Technical Abstract: Ionization and prompt fragmentation pattern of triacylglycerols, phospholipids (PL) and galactolipids were investigated using matrix-assisted laser desorption/ionization (MALDI). Positive ions of non-nitrogen containing lipids appeared only in the sodiated form, while nitrogen containing lipids were detected as both sodiated and protonated adducts. Lipids containing acidic hydroxyls were detected as multiple sodium adducts or deprotonated ions, with the exception of phosphatidylcholine. The positive MALDI spectra of triacylglycerols contained prompt fragments equivalent to the loss of RCOO- from the neutral molecules. Prompt fragment ions [PL- polar head]+ were observed in the positive MALDI spectra of all studied phospholipids except phosphatidylcholines. The latter showed only a minor positive fragment corresponding to the head group itself (m/z 184). Galactolipids did not undergo prompt fragmentation. Post source decay (PSD) was used to examine the source of prompt fragments. PSD fragment patterns indicated that the lipid prompt fragment ions did not originate from observed pseudomolecular ions (sodiated or protonated) and suggested that the prompt fragmentation followed the formation of highly unstable, possibly, protonated parent ions. Pathways leading to formation of prompt fragments ions were proposed.