A Fourier transform infrared spectrometry study of the reactions of phosphatidylcholines with gaseous N2O5 and NO2.

The liquid lining of the alveolar region of the lung contains a surfactant which lowers the surface tension. The major active surface-tension-lowering compounds are phosphatidylcholines, some of which contain unsaturated fatty acid components. In order to determine whether these unsaturated moieties react with the gaseous air pollutant N2O5, which may be present in urban atmospheres at concentrations up to 15 ppb, phosphatidylcholines adsorbed on glass at 25 degrees C were exposed to mixtures of approximately 2 Toor (approximately 2600 ppm) N2O5 in 1 atm of air or argon in the gas phase. Nitronitrates were identified as products of the reactions of N2O5 with beta-oleoyl-gamma-palmitoyl L-alpha-phosphatidylcholine (OPPC) and dioleoyl L-alpha-phosphatidylcholine (DOPC) using Fourier transform infrared (FTIR) spectrometry and in the case of DOPC, fast atom bombardment mass spectrometry. FTIR studies also show that 2 Torr (approximately 2600 ppm) NO2 in 1 atm of air reacts with OPPC and DOPC to give new bands tentatively identified as nitronitrates. Finally, HNO3 was shown to react with OPPC, DOPC, and the saturated dipalmitoyl L-alpha-phosphatidylcholine to give products tentatively identified as nitrate salts and glycerol. These studies suggest that inhaled N2O5, if it reaches the alveolar region, is likely to react with unsaturated C = C groups in surfactant to form nitronitrates.