Fast atom bombardment and collision-induced dissociation of prostaglandins and thromboxanes: Some examples of charge remote fragmentation.

The mass spectra of products found by collisional activation of selected prostaglandins and thromboxanes were studied by tandem mass spectrometry as barium carboxylate salts and as carboxylate anions. Collision-induced dissociation (CID) of these closed shell ions generated by fast atom bombardment mass spectrometry reveals a wealth of structural information for these hydroxy acids. Decomposition reactions were found to be dependent upon the eicosanoid ring structure and the type of ion being studied, either positive or negative ion. The bariated carboxylate salts undergo reactions by processes that are similar to those previously characterized as charge remote mechanisms in which neutral species are lost as in thermal and photolytic decompositions. The most abundant ion is formed by loss of water from each of the hydroxyl groups present on the prostaglandin or thromboxane structure. For these multifunctionalized eicosanoids, typical patterns of decomposition emerge as characteristic of the oxygen substituents present along the carbon chain of the eicosanoid structure. The structural information obtained from the barium salts along with those from the carboxylate anions is substantially different, yet the structural information from each process is complementary. The CIDs of positive ions (metalated salts) provide structural information concerning the substituents between the carboxyl group and C12 of the eicosanoid structure, whereas the decompositions of the carboxylate anions (negative ion mode) provide data concerning structure alterations of the eicosanoid structure between C15 and C20.

Development of a mass spectrometric method to quantitate platelet activating factor in mouse urine.

Platelet activating factor (PAF) is a lipid mediator of inflammation released by a variety of stimulated inflammatory cells. It may be involved in immune glomerulonephritis. Thus, its measurement in urine could give information on the mechanism of this disease. We present here a method to measure PAF in mouse urine, using gas-liquid chromatography-mass spectrometry (GLC-MS) in the selected ion recording (SIR) mode. Before instrumental analysis, the extracted and purified samples were hydrolyzed and derivatized with pentafluorobenzoyl chloride. Different experimental conditions are presented and discussed to corroborate the analytical findings. PAF levels in mouse urine were 2.08 +/- 0.46 ng/24 h. This procedure might represent a new experimental tool to establish the possible role of PAF as mediator of tissue damage in renal disease.

A fast atom bombardment-mass spectrometric method to quantitate lysophosphatidylserine in rat brain.

A method to quantitate lysophosphatidylserine by fast atom bombardment-mass spectrometry using 1-hexa-decanoyl-sn-glycero-3-phospho-L-serine as internal standard is described. The standard curve is linear with a correlation coefficient r2 = 0.999 from 10 to 1000 ng. This curve has been used to quantitate LPS in rat brain using phosphorus assay as a test control. We found 475 +/- 70 ng of LPS in 1 mg of tissue (n = 3). This method presents advantages due to its sensitivity and its capability to give molecular information of the unmodified compound.