Reactions of dinitrogen pentoxide and nitrogen dioxide with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine.

The reactions of gaseous dinitrogen pentoxide (N2O5) and nitrogen dioxide (NO2) with 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphocholine (POPC) coated on the inside surface of a glass reaction cell were studied at 298 K. Unsaturated phosphatidylcholines are significant components of pulmonary surfactant in the alveolar region of the lung and hence serve as a simple model to examine reactions of pulmonary surfactant with these oxidant air pollutants. Using high-performance liquid chromatography (HPLC), Fourier transform infrared and fast atom bombardment mass spectroscopy, the major products of reactions of POPC with N2O5 and NO2 were separated and identified. In the POPC-N2O5 reaction using either air or helium as a buffer gas, the nitronitrate, vinyl nitro and allylic nitro derivatives, as well as a small amount of the trans-isomer of the starting material, were obtained. The nature of the products obtained from the POPC-NO2 reaction depends on the concentration of NO2 as well as whether air is present. At low NO2 concentrations (PNO2/N2O4 less than or equal to 3.8 Torr) in air or in helium, the trans-isomer of POPC was formed almost exclusively. At higher NO2 concentrations (PNO2/N2O4 greater than or equal to 20 Torr) in helium, the dinitro, vinyl nitro and nitro alcohol derivatives were formed. In the presence of air (or 24% 18O2 in helium), a nitronitrate and a dinitronitrate were additional products. Mechanisms for the formation of the observed products and implications for the inhalation of oxides of nitrogen are discussed.