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Unexpected formation of oxygen-free products and nitrous acid from the ozonolysis of the neonicotinoid nitenpyram.

ABSTRACT: The neonicotinoid nitenpyram (NPM) is a multifunctional nitroenamine [(R1N)(R2N)C=CHNO2] pesticide. As a nitroalkene, it is structurally similar to other emerging contaminants such as the pharmaceuticals ranitidine and nizatidine. Because ozone is a common atmospheric oxidant, such compounds may be oxidized on contact with air to form new products that have different toxicity compared to the parent compounds. Here we show that oxidation of thin solid films of NPM by gas-phase ozone produces unexpected products, the majority of which do not contain oxygen, despite the highly oxidizing reactant. A further surprising finding is the formation of gas-phase nitrous acid (HONO), a species known to be a major photolytic source of the highly reactive hydroxyl radical in air. The results of application of a kinetic multilayer model show that reaction was not restricted to the surface layers but, at sufficiently high ozone concentrations, occurred throughout the film. The rate constant derived for the O3-NPM reaction is 1 × 10-18 cm3?s-1, and the diffusion coefficient of ozone in the thin film is 9 × 10-10 cm2?s-1 These findings highlight the unique chemistry of multifunctional nitroenamines and demonstrate that known chemical mechanisms for individual moieties in such compounds cannot be extrapolated from simple alkenes. This is critical for guiding assessments of the environmental fates and impacts of pesticides and pharmaceuticals, and for providing guidance in designing better future alternatives.

SUBMITTER: Wang W

PROVIDER: S-EPMC7260956 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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Unexpected formation of oxygen-free products and nitrous acid from the ozonolysis of the neonicotinoid nitenpyram.

Wang Weihong W Ezell Michael J MJ Lakey Pascale S J PSJ Aregahegn Kifle Z KZ Shiraiwa Manabu M Finlayson-Pitts Barbara J BJ

Proceedings of the National Academy of Sciences of the United States of America 20200511 21

The neonicotinoid nitenpyram (NPM) is a multifunctional nitroenamine [(R1N)(R2N)C=CHNO2] pesticide. As a nitroalkene, it is structurally similar to other emerging contaminants such as the pharmaceuticals ranitidine and nizatidine. Because ozone is a common atmospheric oxidant, such compounds may be oxidized on contact with air to form new products that have different toxicity compared to the parent compounds. Here we show that oxidation of thin solid films of NPM ...[more]

PMID: 32393627

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Project description:Purpose: Free nitrous acid (FNA) has recently been demonstrated as an antimicrobial agent to a range of microorganisms. However, its antimicrobial mechanism is largely unknown. For this study Desulfovibrio vulgaris Hildenborough was selected to gain a systematic understanding of the antimicrobial mechanism of FNA. Methods: D. vulgaris was grown under anaerobic denitrifying conditions and when FNA was added (4 μg-N/L) growth temporarily stopped. From cultures with and without added FNA, RNA was extracted and the abundance of gene transcripts was detected by sequencing. Transcripts exhibiting ≥1 or ≤-1 fold abundance change in the presence of FNA were designated as differentially expressed. Results:The results imply that FNA exerted multiple antimicrobial effects. Growth of the culture was inhibited by FNA and significant proportions of the cells were killed during the exposure. Respiration by sulfate reduction and lactate oxidation was shut down along with ATP production when exposed to FNA. Correspondingly, decreased transcript levels of genes involved in these metabolic pathways were detected. Detoxification of FNA was evident by nitrite reduction and the genes coding both nitrite reductase (NrfA) and hydroxylamine reductase were highly up regulated. During the FNA induced energy depleted state, there was evidence that D. vulgaris lowered both ribosome activity and protein production. Conditions within the cells were more oxidizing and genes coding for proteins providing resistance to oxidative stress were up regulated. Culture thiol levels increased during the exposure, suggesting that FNA had caused protein structures to alter. Furthermore, genes for motility were up regulated possibly as an attempt to avoid FNA stress. These findings provide new insight for understanding the response of D. vulgaris to FNA exposure. Conclusion: In this study, we performed genome-wide high throughput RNA sequencing (RNA-Seq) analysis on D. vulgaris in the absence and presence of a bacteriostatic-level of FNA (4 μg-N/L). By combining the global activated/suppressed gene profiles and detected physiological responses, we detected the microbial response to FNA exposure and revealed potential antimicrobial mechanisms of FNA on this prevalent model sulfate reducing bacteria.

Project description:The formation of atmospheric cloud droplets due to secondary organic aerosol (SOA) particles is important for quantifying the Earth's radiative balance under future, possibly warmer, climates, yet is only poorly understood. While cloud activation may be parametrized using the surface tension depression that coincides with surfactant partitioning to the gas-droplet interface, the extent to which cloud activation is influenced by both the chemical structure and reactivity of the individual molecules comprising this surfactant pool is largely unknown. We report herein considerable differences in the surface tension depression of aqueous pendant droplets that contain synthetically prepared ozonolysis products derived from α-pinene and β-caryophyllene, the most abundant of the monoterpenes and sesquiterpenes, respectively, that are emitted over the planet's vast forest ecosystems. Oxidation products derived from β-caryophyllene were found to exhibit significantly higher surface activity than those prepared from α-pinene, with the critical supersaturation required for cloud droplet activation reduced by 50% for β-caryophyllene aldehyde at 1 mM. These considerable reductions in the critical supersaturation were found to coincide with free energies of adsorption that exceed ∼25 kJ/mol, or just one hydrogen bond equivalent, depending on the ammonium sulfate and oxidation product concentration in the solution. Additional experiments showed that aldehyde-containing oxidation products exist in equilibrium with hydrated forms in aqueous solution, which may modulate their bulk solubility and surface activity. Equilibration time scales on the order of 10-5 to 10-4 s calculated for micrometer-sized aerosol particles indicate instantaneous surface tension depression in the activation processes leading to cloud formation in the atmosphere. Our findings highlight the underlying importance of molecular structure and reactivity when considering cloud condensation activity in the presence of SOA particles.

Project description:Purpose: Free nitrous acid (FNA) has recently been demonstrated as an antimicrobial agent to a range of microorganisms. However, its antimicrobial mechanism is largely unknown. For this study Pseudomonas aeruginosa PAO1 was selected to gain a systematic understanding of the antimicrobial mechanism of FNA. Methods: PAO1 was grown under anaerobic denitrifying conditions and when FNA was added (0.1 mg-N/L) growth temporarily stopped. From cultures with and without added FNA, RNA was extracted and the abundance of gene transcripts was detected by sequencing. Transcripts exhibiting â¥2.5 or â¤-2.5 fold abundance change in the presence of FNA were designated as differentially expressed. Results:In response to FNA, 167 genes showed increased transcription while 424 exhibited deceased transcript levels. Respiration was likely inhibited as denitrification activity was severely decreased. Genes coding for enzymes of the tricarboxylic acid cycle were down regulated, while highly increased transcripts were detected for pyruvate fermentation, indicating a possible survival response to FNA. Moreover, genes coding ribosomal proteins had significantly decreased transcript levels, implicating that protein biosynthesis was severely inhibited by FNA. Whereas, genes encoding proteins functioning to preserve ribosome units under stressful conditions, were up-regulated during FNA exposure. Conclusion: In this study, we performed genome-wide high throughput RNA sequencing (RNA-Seq) analysis on PAO1 in the absence and presence of a bacteriostatic-level of FNA (0.1 mg N/L). By combining the global activated/suppressed gene profiles and detected physiological responses, we detected the microbial response to FNA exposure and revealed potential antimicrobial mechanisms of FNA on this prevalent opportunistic pathogen and environmentally relevant denitrifier. mRNA profiles of P. aeruginosa PAO1 towards FNA stress were generated by next generation sequencing in triplicate via Illumina 2000.

Project description:Purpose: Free nitrous acid (FNA) has recently been demonstrated as an antimicrobial agent to a range of microorganisms. However, its antimicrobial mechanism is largely unknown. For this study Desulfovibrio vulgaris Hildenborough was selected to gain a systematic understanding of the antimicrobial mechanism of FNA. Methods: D. vulgaris was grown under anaerobic denitrifying conditions and when FNA was added (4 Î¼g-N/L) growth temporarily stopped. From cultures with and without added FNA, RNA was extracted and the abundance of gene transcripts was detected by sequencing. Transcripts exhibiting â¥1 or â¤-1 fold abundance change in the presence of FNA were designated as differentially expressed. Results:The results imply that FNA exerted multiple antimicrobial effects. Growth of the culture was inhibited by FNA and significant proportions of the cells were killed during the exposure. Respiration by sulfate reduction and lactate oxidation was shut down along with ATP production when exposed to FNA. Correspondingly, decreased transcript levels of genes involved in these metabolic pathways were detected. Detoxification of FNA was evident by nitrite reduction and the genes coding both nitrite reductase (NrfA) and hydroxylamine reductase were highly up regulated. During the FNA induced energy depleted state, there was evidence that D. vulgaris lowered both ribosome activity and protein production. Conditions within the cells were more oxidizing and genes coding for proteins providing resistance to oxidative stress were up regulated. Culture thiol levels increased during the exposure, suggesting that FNA had caused protein structures to alter. Furthermore, genes for motility were up regulated possibly as an attempt to avoid FNA stress. These findings provide new insight for understanding the response of D. vulgaris to FNA exposure. Conclusion: In this study, we performed genome-wide high throughput RNA sequencing (RNA-Seq) analysis on D. vulgaris in the absence and presence of a bacteriostatic-level of FNA (4 Î¼g-N/L). By combining the global activated/suppressed gene profiles and detected physiological responses, we detected the microbial response to FNA exposure and revealed potential antimicrobial mechanisms of FNA on this prevalent model sulfate reducing bacteria. mRNA profiles of D. vulgaris Hildenborough towards FNA stress were generated by next generation sequencing in triplicate via Illumina 2000.

Dataset Information

Unexpected formation of oxygen-free products and nitrous acid from the ozonolysis of the neonicotinoid nitenpyram.

Publications

Unexpected formation of oxygen-free products and nitrous acid from the ozonolysis of the neonicotinoid nitenpyram.

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