Quantitative analysis of lysophosphatidic acid by time-of-flight mass spectrometry using a phosphate-capture molecule

Lysophosphatidic acid (LPA) is a lipid mediator that may play an important role in wound healing, embryonic development, and progression of cancer. Here, we report a procedure for the quantification of LPA by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The method is based on a characteristic mass shift with total charge change (from -2 to +1) of the phosphate species due to 1:1 complexation of LPA(2-) with a dinuclear zinc (II) complex {1,3-bis[bis(pyridin-2-ylmethyl)amino]propan-2-olato dizinc(II) complex; Zn2L3+} at physiological pH. The monocationic complex [LPA(2-)-Zn2L3+](+) was detected in the positive mode, in which no other signal of cation adducts of LPA(2-) was observed. The detection limit of 18:1 LFA by this method was 0.1 pmol on a sample plate. The intensity ratio of [LPA(2-)-Zn2L3+](+) against an internal standard [17:0 LPA(2-)-Zn2L3+](+) increased linearly with their molar ratio. Based on the relative intensities of complex ions, we determined the amounts of LPA homologs in an egg white by this method; the results obtained were in good agreement with those by gas liquid chromatography.jlr This sensitive and convenient procedure for LPA-specific detection is useful for the quantification of LPA homologs occurring in biological materials.