ABSTRACT
A method of identification of C=C location and relative quantitation of unsaturated phosphatidylcholine ( PC ) isomers in breast cells by online photochemical reaction-pulsed directed current electrospray-tandem mass spectrometry ( PB-pulsed-dc-ESI-MS/MS) was established with benzophenone ( BP) as a photochemical reactant. The three-phase extraction method was used to extract the lipids in the cells, and then the C=C in the unsaturated PC and the carbonyl in BP were specifically cycled under the irradiation of 254 nm ultraviolet light (Paternò-Büchi, PB reaction). The PB products were ionized and mass-isolated for low-energy collision dissociation through the non-contact pulsed-dc-ESI ionization method. The double bond position and the relative content of the location isomers were obtained from the resulting ions in the MS/MS spectrum. The C=C location of 8 kinds of unsaturated PCs in MCF-7 and MCF-10A was detected, and the relative contents of 4 kinds of C=C location isoforms were analyzed. It was found that the relative abundance of △9 isomer in PC 16:018:1 was not significantly different between the two cells. The relative abundance of△9 isomers in PC 18:018:1 and PC 18:118:1 was slightly different. However, there is a big difference of △9 in LPC 18:1 between the cancer cell and normal cell (56. 0% ± 1. 3% vs. 71. 7% ± 6. 8%). The establishment of such a rapid and easy mass spectrometry method can analyze the C=C location and the relative content of location isomers, and it is expected to be a powerful tool to identify different cell states and different disease states.