Multiphase Kinetic Modeling of Air Pollutant Effects on Protein Modification and Nitrotyrosine Formation in Epithelial Lining Fluid

Exposure to ambient air pollution is a major risk factor for human health. Inhalation of air pollutants can enhance the formation of reactive species in the epithelial lining fluid (ELF) of the respiratory tract and can lead to oxidative stress and oxidative damage. Here, we investigate the chemical modification of proteins by reactive species from air pollution and endogenous biological sources using an extended version of the multiphase chemical kinetic model KM-SUB-ELF 2.0 with a detailed mechanism of protein modification. Fine particulate matter (PM2.5) and nitrogen dioxide (•NO2) act synergistically and increase the formation of nitrotyrosine (Ntyr), a common biomarker of oxidative stress. Ozone (O3) is found to be a burden on the antioxidant defense system but without substantial influence on the Ntyr concentration. In simulations with low levels of air pollution, the Ntyr concentration in the ELF is consistent with the range of literature values for bronchoalveolar lavage fluid from healthy individuals. With high levels of air pollution, however, we obtain strongly elevated Ntyr concentrations. Our model analysis shows how chemical reactions of air pollutants can modify proteins and thus their functionality in the human body, elucidating a molecular pathway that may explain air pollutant effects on human health

Organic Nitrate Contribution to New Particle Formation and Growth in Secondary Organic Aerosols from α‑Pinene Ozonolysis

The chemical kinetics of organic nitrate production during new particle formation and growth of secondary organic aerosols (SOA) were investigated using the short-lived radioactive tracer ¹³N in flow-reactor studies of α-pinene oxidation with ozone. Direct and quantitative measurements of the nitrogen content indicate that organic nitrates accounted for ∼40% of SOA mass during initial particle formation, decreasing to ∼15% upon particle growth to the accumulation-mode size range (>100 nm). Experiments with OH scavengers and kinetic model results suggest that organic peroxy radicals formed by α-pinene reacting with secondary OH from ozonolysis are key intermediates in the organic nitrate formation process. The direct reaction of α-pinene with NO₃ was found to be less important for particle-phase organic nitrate formation. The nitrogen content of SOA particles decreased slightly upon increase of relative humidity up to 80%. The experiments show a tight correlation between organic nitrate content and SOA particle-number concentrations, implying that the condensing organic nitrates are among the extremely low volatility organic compounds (ELVOC) that may play an important role in the nucleation and growth of atmospheric nanoparticles

Secondary Organic Aerosol (SOA) from Nitrate Radical Oxidation of Monoterpenes: Effects of Temperature, Dilution, and Humidity on Aerosol Formation, Mixing, and Evaporation

Nitrate radical (NO₃) oxidation of biogenic volatile organic compounds (BVOC) is important for nighttime secondary organic aerosol (SOA) formation. SOA produced at night may evaporate the following morning due to increasing temperatures or dilution of semivolatile compounds. We isothermally dilute the oxidation products from the limonene+NO₃ reaction at 25 °C and observe negligible evaporation of organic aerosol via dilution. The SOA yields from limonene+NO₃ are approximately constant (∼174%) at 25 °C and range from 81 to 148% at 40 °C. Based on the difference in yields between the two temperatures, we calculated an effective enthalpy of vaporization of 117–237 kJ mol^–1. The aerosol yields at 40 °C can be as much as 50% lower compared to 25 °C. However, when aerosol formed at 25 °C is heated to 40 °C, only about 20% of the aerosol evaporates, which could indicate a resistance to aerosol evaporation. To better understand this, we probe the possibility that SOA from limonene+NO₃ and β-pinene+NO₃ reactions is highly viscous. We demonstrate that particle morphology and evaporation is dependent on whether SOA from limonene is formed before or during the formation of SOA from β-pinene. This difference in particle morphology is present even at high relative humidity (∼70%)

Data for repository_final

The Excelfile provided comprises two data sheets. On the first sheet the calibration data for measurement 2-4 for the 60 sensors are given. On the second sheet, the minimum conductivity value measured in the field without any water present is given. The values are already temperature-corrected

Protein Cross-Linking and Oligomerization through Dityrosine Formation upon Exposure to Ozone

Air pollution is a potential driver for the increasing prevalence of allergic disease, and post-translational modification by air pollutants can enhance the allergenic potential of proteins. Here, the kinetics and mechanism of protein oligomerization upon ozone (O₃) exposure were studied in coated-wall flow tube experiments at environmentally relevant O₃ concentrations, relative humidities and protein phase states (amorphous solid, semisolid, and liquid). We observed the formation of protein dimers, trimers, and higher oligomers, and attribute the cross-linking to the formation of covalent intermolecular dityrosine species. The oligomerization proceeds fast on the surface of protein films. In the bulk material, reaction rates are limited by diffusion depending on phase state and humidity. From the experimental data, we derive a chemical mechanism and rate equations for a kinetic multilayer model of surface and bulk reaction enabling the prediction of oligomer formation. Increasing levels of tropospheric O₃ in the Anthropocene may promote the formation of protein oligomers with enhanced allergenicity and may thus contribute to the increasing prevalence of allergies

Heterogeneous OH Oxidation, Shielding Effects, and Implications for the Atmospheric Fate of Terbuthylazine and Other Pesticides

Terbuthylazine (TBA) is a widely used herbicide, and its heterogeneous reaction with OH radicals is important for assessing its potential to undergo atmospheric long-range transport and to affect the environment and public health. The apparent reaction rate coefficients obtained in different experimental investigations, however, vary by orders of magnitude depending on the applied experimental techniques and conditions. In this study, we used a kinetic multilayer model of aerosol chemistry with reversible surface adsorption and bulk diffusion (KM-SUB) in combination with a Monte Carlo genetic algorithm to simulate the measured decay rates of TBA. Two experimental data sets available from different studies can be described with a consistent set of kinetic parameters resolving the interplay of chemical reaction, mass transport, and shielding effects. Our study suggests that mass transport and shielding effects can substantially extend the atmospheric lifetime of reactive pesticides from a few days to weeks, with strong implications for long-range transport and potential health effects of these substances

Quantitative Efficacy Classification of Ice Recrystallization Inhibition Agents

Experimental investigations of ice recrystallization inhibition (IRI) efficacy have been performed for a large number of different substances, including natural antifreeze proteins (AFP) and antifreeze glycoproteins (AFGP), several synthetic AFGP analogues, as well as synthetic polymers. Here we define IRI efficacy as that concentration at which the ice recrystallization rate is dominated by the IRI compound. The investigated 39 compounds show IRI efficacies from about 2 mmol L^–1 for the least effective compound still showing activity to about 1 nmol L^–1, which corresponds to the highest efficacy found for natural AFGP samples. Hence, the assay employed allows for a quantitative comparison of IRI efficacy over a range of at least 6 orders of magnitude, thereby enabling studies of distinguishing effects induced by even subtle structural variations in AFGP analogues that were synthesized. Our results show that AFGP are by far the most effective IRI agents in our assay, and we surmise that this particular efficacy may be due to their disaccharide moieties. This supposition is supported by the fact that IRI efficacy is strongly reduced for monosaccharide AFGP analogues, as well as for AFGP analogues with acetyl-protected monosaccharide moieties