Direct analysis by electrospray ionization tandem mass spectrometry of mixtures of phosphatidyldiacylglycerols from Lactobacillus

Electrospray ionization followed by collision-induced dissociation in a qua drupole ion trap mass spectrometer of mixtures of deprotonated phosphatidyl diacylglycerols afforded a group of three diagnostic ions of convenient abu ndance for each phosphatidyldiacylglycerol (PG) present in the mixture, Thu s, it was possible to determine unmistakably the identity and substitution positions (sn-1 or sn-2) for both acyl groups of each PG present in the mix ture, The method also allows the study of isomeric mixtures of PG and mixtu res containing minor amounts of some PG from crude extracts of Lactobacillu s acidophillus, The present results improve those of previous studies using fast atom bombardment and electrospray ionization tanden mass spectrometry , in which it was reported that it was possible to differentiate the identi ty and position of the sn-2 acyl substituent only by the presence of one io n, with variable abundance. Copyright (C) 2000 John Wiley & Sons, Ltd.