The Environmental Pollutant NO3• Rapidly Damages Alkene Moieties in Lipids Through Electron Transfer

Abstract

The presence of alkene moieties in fatty acids of (phospho)lipids and cholesterol derivatives makes them highly susceptible to damage by nitrate radicals (NO3•), potentially formed through simultaneous exposure to the environmental air pollutants nitrogen dioxide (NO2•) and ozone (O3). Absolute rate coefficients derived from reactions with simplified model systems range from 4 to 8 × 109 M−1 s−1 in acetonitrile, ranking among the highest determined for NO3• reactions with biomolecules in solution to date. Alkenes featuring an electron‐withdrawing carbonyl substituent also display notable reactivity with k values of (2.5 ± 1.0) × 108 M−1 s−1. Calculations suggest that these reactions are initiated by oxidative electron transfer (ET) involving the C=C bond, followed by recombination of the resulting alkene radical cation with nitrate anion (NO3−) to form the nitrate adduct radical as the kinetically controlled product. Conversely, saturated fatty acid derivatives and cholestanol react with NO3• through hydrogen atom transfer (HAT) with rate coefficients of 106 – 107 M−1 s−1, indicating that biomolecules with a considerable number of non‐ or moderately activated sp3 C–H bonds are also highly susceptible to NO3• attack. These findings underscore the potential health hazards associated with exposure to combined NO2• and O3 gases.