Evaluation of products upon the reaction of hypohalous acid with unsaturated phosphatidylcholines

Myeloperoxidase released from stimulated neutrophils is able to produce hypochlorous and hypobromous acids. The composition of the reaction products of the interaction of hypohalous acid with double bonds of phosphatidylcholines was analysed by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry using reagents enriched in 16O, 18O, 35Cl, 37Cl, 79Br, or 81Br. Two different types of products were assigned according to the mass spectra. First, chlorohydrins as well as bromohydrins were formed whereby the oxygen introduced was derived from water as shown by using H2 16O or H2 18O. In the second product a hydrogen atom was replaced by a halogen. This was clearly evidenced by different mass shifts using chlorine or bromine isotopes and the lack of any effects by oxygen isotopes. These results are consistent with the view that two principal possibilities of stabilisation of pi-complexes formed after binding of Cl(+) or Br(+) to the pi-system of the double bond exist.