Ozone and nitrogen dioxide mediated protein multiphase reactions under ultraviolet radiation conditions

Proteins in aerosols can undergo multiphase reactions when exposed to air pollutants like ozone (O₃) and nitrogen dioxide (NO₂), posing adverse impacts on the environment and human health. The influence of radiation on the reactions has not been thoroughly studied and the reaction mechanism remains unclear. We coated bovine serum albumin (BSA) in a flow tube and exposed it to different combinations of O₃ and NO₂ under dark and ultraviolet (UV) radiation conditions. The results showed that O₃ could significantly promote the degradation, nitration and oligomerization of BSA, indicating that O₃ is the primary driver of the multiphase reactions. We found that UV enhanced protein degradation after exposure to NO₂ and O₃. Meanwhile, UV also enhanced the nitration and oligomerization of protein by NO₂. When exposed to NO₂ and O₃, the effects of nitration and oligomerization on tyrosine residues of BSA were also investigated. Nitrated tyrosine (NTyr) levels were always higher than those of cross-linked tyrosine (DiTyr), highlighting the dominance of nitration in modification reactions. However, the negative influence of UV radiation on protein nitration and oligomerization of BSA was observed in our exposure experiment. We propose that UV radiation-induced degradation may be an important factor to suppress nitration and oligomerization via the breakage of nitrated and oligomerized protein products. This work provides the dataset and knowledge by laboratory exposure to emphasize the possible role of radiation in the multiphase reactions of proteins in the atmosphere, which will help to gain a better understanding of reaction mechanisms.