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Submitted to: Rapid Communications in Mass Spectrometry
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 1/10/1998 Publication Date: N/A Citation: N/A Interpretive Summary: Phospholipids make up the walls of cells. The types of phospholipids present determine specific characteristics of cells. Thus, it is important to be able to reliably determine the phospholipid compositions of cell extracts. A method is described that used two mass spectrometers for the same sample. One mass spectrometer was used to identify phospholipid types. A second mass spectrometer was operated together with the first to determine amounts of the phospholipid types present. Using two mass spectrometers, we identified types and amounts of phospholipids in the eye lens of pigs for the first time. This method can also be used to identify phospholipids in human plasma extract. Scientists conducting analysis of phospholipids from plants or animals can use this methodology to save time, money and other resources by obtaining data from two instruments at the same time. Technical Abstract: Analysis of phospholipids was performed using a liquid chromatographic separation with two mass spectrometers in parallel providing electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) data simultaneously from a triple quadrupole instrument and a single quadrupole instrument, respectively. The output from UV-Vis and evaporative light scattering detectors were also acquired by the two mass spectrometers, respectively, for four detectors overall. This arrangement was used to identify and calculate area percents for molecular species of dihydrosphingomyelin (DHS) and sphingomyelin (SPM) in commercially available bovine brain SPM, in human plasma extract and in porcine lens extract. Molecular species of phosphatidylethanolamine and its plasmalogen and phosphatidylcholine and its plasmalogen were identified and semiquantitative analysis performed. Commercially available bovine brain SPM was found to contain 11.5% DHS and 88.5% SPM. The only DHS molecular species identified in human plasma was 16:0 DHS, at or below 1% of the sphingolipid content. Porcine lens membranes were found to contain 14.4% DHS and 85.6% SPM. Other findings include: 1) phospholipids were found to undergo dimerization in the electrospray source, giving masses representing combinations of species present; 2) triacylglycerols gave usable mass spectra under electrospray ionization conditions, as well as under APCI-MS conditions; 3) triacylglycerols gave ammonium adducts as base peaks in their APCI mass spectra, this reduced fragmentation and increased the proportions of molecular ions); 4) mass spectra were obtained for phospholipids which underwent both protonation and sodium adduct formation in different chromatographic runs. |
