DIRECT MASS-SPECTROMETRIC ANALYSIS OF OZONIDES - APPLICATION TO UNSATURATED GLYCEROPHOSPHOCHOLINE LIPIDS

The reaction of ozone with double bonds present in glycerophosphocholi ne lipids results in formation of ozonides that can be directly analyz ed by mass spectrometry as either positive or negative molecular ion s pecies generated by electrospray ionization, Polyunsaturated fatty acy l groups esterified to the phospholipid yielded a mixture of ozonide s pecies with the maximum number of ozone molecules added equal to the t otal number of double bonds, Ozonide decomposition resulted in omega-a ldehyde and omega-carboxylic acid products as revealed by ESI-MS. Coll isional activation of the ozone adducts for mono- and polyunsaturated phospholipids gave rise to fragment ions indicative of the position of the double bonds in these molecules. The major decomposition pathway for either positive or negative ozonide ion species involved charge re mote fragmentation of the ozonide initiated by homolytic cleavage of t he peroxide bridge followed by rearrangement to form the omega-aldehyd e and omega-carboxylate acyl species. The reaction of ozone with phosp holipids containing polyunsaturated fatty acyl groups is a useful meth od to probe the position of double bonds by electrospray ionization ma ss spectrometry.