Elaborating the Atmospheric Transformation of Combined and Free Amino Acids From the Perspective of Observational Studies

Proteinaceous matter (PrM) is a substantial component of bioaerosols. Although numerous studies have examined the characteristics and sources of PrM in the atmosphere, its interactions with atmospheric oxidants remain uncertain. A 1‐year observation of PrM characteristics in PM2.5 was performed in b...

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Published in:Journal of geophysical research. Atmospheres 2024-08, Vol.129 (16), p.n/a
Main Authors: Xu, Yu, Lin, Xi, Sun, Qi‐Bin, Xiao, Hong‐Wei, Xiao, Hao, Xiao, Hua‐Yun
Format: Article
Language:English
Subjects:
Acid resistance
Aerosols
Amino acids
Atmosphere
Bioaerosols
Biosphere
Composition
composition characteristics
Degradation
Glycine
Glycine (amino acid)
Hydroxyl radicals
Liquid phases
Nitrogen compounds
Observational studies
Organic nitrogen
Oxidants
Oxidation
Oxidation resistance
oxidative degradation
Oxidizing agents
Particulate matter
Proline
Protein composition
proteins
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Summary:Proteinaceous matter (PrM) is a substantial component of bioaerosols. Although numerous studies have examined the characteristics and sources of PrM in the atmosphere, its interactions with atmospheric oxidants remain uncertain. A 1‐year observation of PrM characteristics in PM2.5 was performed in both urban Nanchang (eastern China) and suburban Guiyang (southwestern China), respectively. Glycine was the dominant free amino acid (FAA) species in urban Nanchang. In contrast, proline dominated both total free amino acids (FAAs) and total combined amino acids (CAAs) in suburban Guiyang. We found that oxidative degradation can significantly promote the release of FAAs, especially glycine, from CAAs in Nanchang. The controlled experiment on protein oxidation by hydroxyl radical suggested that the contribution of free glycine to the total FAA fraction tended to increase during the oxidative degradation of CAAs, supporting the predominance of glycine in FAAs in Nanchang and most previous observations. The composition of FAAs was mainly influenced by primary sources in suburban Guiyang with weak atmospheric degradation of PrM. These results suggest that the degradation of aerosol PrM by atmospheric oxidants can be responsible for the difference in FAA composition between the biosphere and the atmosphere, and also imply that the oxidative degradation of aerosol PrM may be a potential source of secondary organic nitrogen compounds in aerosols. Thus, this study can improve the current understanding of the composition characteristics of PrM in the biosphere and the atmosphere, as well as the liquid phase reactions of proteinaceous compounds with atmospheric oxidants. Plain Language Summary Proteinaceous matter (PrM) is a ubiquitous component in both the biosphere and the atmosphere, which has seen intense research over years. This study, for the first time, combines a large amount of observational data with controlled experiments to reveal the potential atmospheric transformation of combined and free amino acids. The observed increase in the mass fraction of glycine in the total free amino acids from the biosphere to the atmosphere can be attributed to the fact that glycine has a higher release potential from the oxidative degradation of combined amino acids and is more resistant to further oxidative degradation. The overall results provide field evidence for the strong dependence of free glycine release from aerosol PrM on the hydroxyl radical, likely improving the c
ISSN:2169-897X
2169-8996
DOI:10.1029/2024JD040730