Control of Interfacial Cl2 and N2O5 Reactivity by a Zwitterionic Phospholipid in Comparison with Ionic and Uncharged Surfactants

Gord, Joseph R.; Zhao, Xianyuan; Liu, Erica; Bertram, Timothy H.; Nathanson, Gilbert M.

doi:10.1021/acs.jpca.8b04590

Cited by 19 publications

(27 citation statements)

References 95 publications

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“…The presence of a strongly surface-active anion could displace Cl – in the near-surface region, leading to a suppression in Φ ClNO 2 . The opposite effect has recently been suggested for cationic surfactants: an increase in N 2 O 5 reactivity in the presence of cationic surfactants was attributed to an enhancement in the near-surface concentration of halide ions . In the case of sodium acetate, we observe a slight increase in the surface tension of a 0.5 M NaCl/D 2 O solution upon addition of 1.0 M NaAc (Figure ), suggesting that the carboxylate group does not preferentially accumulate near the surface.…”

Section: Results and Discussioncontrasting

confidence: 41%

“…The opposite effect has recently been suggested for cationic surfactants: an increase in N 2 O 5 reactivity in the presence of cationic surfactants was attributed to an enhancement in the near-surface concentration of halide ions. 28 In the case of sodium acetate, we observe a slight increase in the surface tension of a 0.5 M NaCl/D 2 O solution upon addition of 1.0 M NaAc (Figure 3), suggesting that the carboxylate group does not preferentially accumulate near the surface. As expected in the case of a salt containing a doubly charged ion, the surface tension of Na 2 SO 4 solutions also increases with increasing sulfate concentration.…”

Section: Methodsmentioning

confidence: 89%

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Sulfate and Carboxylate Suppress the Formation of ClNO₂ at Atmospheric Interfaces

Staudt

Gord

Karimova

et al. 2019

ACS Earth Space Chem.

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We report measurements of the nitryl chloride (ClNO 2 ) branching fraction following reactive uptake of N 2 O 5 to mixed organic and inorganic solutions representative of atmospheric interfaces. For sodium chloride containing solutions, mixed with either sodium sulfate (Na 2 SO 4 ) or sodium acetate (NaAc), the ClNO 2 branching fraction (Φ ClNO 2 ) is suppressed relative to a sodium chloride only solution. In the case of the sulfate-chloride solution, Φ ClNO 2 is reduced from 0.85 ± 0.03 (0.5 M NaCl) to 0.32 ± 0.14 upon the addition of 2.0 M Na 2 SO 4 . In the case of the acetate-chloride solution, Φ ClNO 2 is reduced to 0.18 ± 0.03 upon the addition of 0.5 M NaAc. In contrast, no statistically significant suppression in Φ ClNO 2 was observed for the addition of sodium perchlorate up to 3.0 M, implying that an increase in ionic strength of the solution does not necessitate a reduction in Φ ClNO 2 . We suggest that the reduction in Φ ClNO 2 may result from a direct reaction between SO 4 2− (and Ac − ) with NO 2 + (or NO 2 + NO 3 − ) which competes with the NO 2 + + Cl − reaction that produces ClNO 2 . The dependence of Φ ClNO 2 on SO 4 2− and Ac − is compared with both a time-dependent reaction-diffusion model and recent field observations, suggesting that the reaction rate of SO 4 2−(or Ac − ) with NO 2 + would need to be similar in magnitude to the rate of the NO 2 + + Cl − reaction to explain the observed suppression in Φ ClNO 2 . We show that the dependence of Φ ClNO 2 on particulate sulfate and carboxylate can be readily incorporated into existing parametrizations of ClNO 2 heterogeneous chemistry. The results presented here indicate that anions which are ubiquitous in atmospheric aerosol, yet commonly considered to be unreactive, may regulate the production of reactive gases such as ClNO 2 .

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Section: Results and Discussioncontrasting

confidence: 41%

Section: Methodsmentioning

confidence: 89%

Sulfate and Carboxylate Suppress the Formation of ClNO₂ at Atmospheric Interfaces

Staudt

Gord

Karimova

et al. 2019

ACS Earth Space Chem.

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“…16 However, recent work has shown that surfactant coatings on SSA can actually enhance certain reactions. 17 Laboratory studies with ambient seawater also show suppression of SSA hygroscopicity by certain organics, potentially altering cloud condensation nuclei (CCN) activity. 18,19 Enhanced cloud ice nucleation efficiency is observed for Arctic seawater, suggesting a contribution of SSA to cloud ice formation.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Submicron SSA particles (<1 μm; ∼200 nm number mode) can be significantly enriched in organic matter (>50%, by mass) in comparison to bulk seawater. , SSA organic coatings can inhibit heterogeneous reactions of trace gases, inhibiting particulate chloride depletion, and impacting trace gas budgets and atmospheric composition . However, recent work has shown that surfactant coatings on SSA can actually enhance certain reactions . Laboratory studies with ambient seawater also show suppression of SSA hygroscopicity by certain organics, potentially altering cloud condensation nuclei (CCN) activity. , Enhanced cloud ice nucleation efficiency is observed for Arctic seawater, suggesting a contribution of SSA to cloud ice formation. − Despite important climate implications for cloud formation and phase, and associated longwave radiative forcing, limited knowledge exists regarding ambient SSA organic coatings and the transfer of marine biogenic organics to the particle phase, particularly for Arctic winter.…”

Section: Introductionmentioning

confidence: 99%

Wintertime Arctic Sea Spray Aerosol Composition Controlled by Sea Ice Lead Microbiology

et al. 2019

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The Arctic is experiencing the greatest warming on Earth, as most evident by rapid sea ice loss. Delayed sea ice freeze-up in the Alaskan Arctic is decreasing wintertime sea ice extent and changing marine biological activity. However, the impacts of newly open water on wintertime sea spray aerosol (SSA) production and atmospheric composition are unknown. Herein, we identify SSA, produced locally from open sea ice fractures (leads), as the dominant aerosol source in the coastal Alaskan Arctic during winter, highlighting the year-round nature of Arctic SSA emissions. Nearly all of the individual SSA featured thick organic coatings, consisting of marine saccharides, amino acids, fatty acids, and divalent cations, consistent with exopolymeric secretions produced as cryoprotectants by sea ice algae and bacteria. In contrast, local summertime SSA lacked these organic carbon coatings, or featured thin coatings, with only open water nearby. The individual SSA composition was not consistent with frost flowers or surface snow above sea ice, suggesting that neither hypothesized frost flower aerosolization nor blowing snow sublimation resulted in the observed SSA. These results further demonstrate the need for inclusion of lead-based SSA production in modeling of Arctic atmospheric composition. The identified connections between changing sea ice, microbiology, and SSA point to the significance of sea ice lead biogeochemistry in altering Arctic atmospheric composition, clouds, and climate feedbacks during winter.

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“…The lipid monolayer interface has largely been studied for its biological relevancemonolayers occur in the body as lung surfactants and tear filmsbut is also of great interest to the atmospheric chemistry community for its role in modulating sea spray aerosol (SSA) particle reactions and dynamics. − Lipid monolayers are known to coat the ocean surface and the surface of nascent SSA and can significantly impact SSA climate-relevant properties. − ,− It has been shown that the lipid type and composition of SSA surfaces have all been found to influence hygroscopicity, , cloud condensation nucleation activity, ,, and ice nucleation activity of SSA. , Amphiphilic lipids can impact interfacial properties of SSA primarily because they are surface-active. Surfactants such as phospholipids participate in photooxidation and ozonolysis, their anionic headgroups selectively bind and concentrate trace metal cations at the surface, − and their carbon chain length and headgroup charge(s) influence the transport and reactivity of gases at the interface. − While the chemical composition of SSA and their effects on climate are becoming more resolved, the molecular structure and dynamics of SSA surfaces remain difficult to probe experimentally. − Computational methods such as all-atom molecular dynamics (MD) have therefore contributed largely to the existing body of work on the lipid monolayer interface. − Since computational methods can resolve chemical systems at the atomic level, the integration of computation with experimental aerosol techniques is expected to significantly advance our ability to model the SSA interface . The present study thus takes an integrated computational and experimental approach to understand how the lipid monolayer surface of SSA is affected by the presence of lipase.…”

Section: Introductionmentioning

confidence: 99%

Surfactant Charge Modulates Structure and Stability of Lipase-Embedded Monolayers at Marine-Relevant Aerosol Surfaces

et al. 2019

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Lipases, as well as other enzymes, are present and active within the sea surface microlayer (SSML). Upon bubble bursting, lipases partition into sea spray aerosol (SSA) along with surface-active molecules such as lipids. Lipases are likely to be embedded in the lipid monolayer at the SSA surface and thus have the potential to influence SSA interfacial structure and chemistry. Elucidating the structure of the lipid monolayer at SSA interfaces and how this structure is altered upon interaction with a protein system like lipase is of interest, given the importance of how aerosols interact with sunlight, influence cloud formation, and provide surfaces for chemical reactions. Herein, we report an integrated experimental and computational study of Burkholderia cepacia lipase (BCL) embedded in a lipid monolayer and highlight the important role of electrostatic, rather than hydrophobic, interactions as a driver for monolayer stability. Specifically, we combine Langmuir film experiments and molecular dynamics (MD) simulations to examine the detailed interactions between the zwitterionic dipalmitoylphosphatidylcholine (DPPC) monolayer and BCL. Upon insertion of BCL from the underlying subphase into the lipid monolayer, it is shown that BCL permeates and largely disorders the monolayer while strongly interacting with zwitterionic DPPC molecules, as experimentally observed by Langmuir adsorption curves and infrared reflectance absorbance spectroscopy. Explicitly solvated, all-atom MD is then used to provide insights into inter- and intramolecular interactions that drive these observations, with specific attention to the formation of salt bridges or ionic-bonding interactions. We show that after insertion into the DPPC monolayer, lipase is maintained at high surface pressures and in large BCL concentrations by forming a salt-bridge-stabilized lipase–DPPC complex. In comparison, when embedded in an anionic monolayer at low surface pressures, BCL preferentially forms intramolecular salt bridges, reducing its total favorable interactions with the surfactant and partitioning out of the monolayer shortly after injection. Overall, this study shows that the structure and dynamics of lipase-embedded SSA surfaces vary based on surface charge and pressure and that these variations have the potential to differentially modulate the properties of marine aerosols.

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Control of Interfacial Cl₂ and N₂O₅ Reactivity by a Zwitterionic Phospholipid in Comparison with Ionic and Uncharged Surfactants

Cited by 19 publications

References 95 publications

Sulfate and Carboxylate Suppress the Formation of ClNO₂ at Atmospheric Interfaces

Sulfate and Carboxylate Suppress the Formation of ClNO₂ at Atmospheric Interfaces

Wintertime Arctic Sea Spray Aerosol Composition Controlled by Sea Ice Lead Microbiology

Surfactant Charge Modulates Structure and Stability of Lipase-Embedded Monolayers at Marine-Relevant Aerosol Surfaces

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Control of Interfacial Cl2 and N2O5 Reactivity by a Zwitterionic Phospholipid in Comparison with Ionic and Uncharged Surfactants

Cited by 19 publications

References 95 publications

Sulfate and Carboxylate Suppress the Formation of ClNO2 at Atmospheric Interfaces

Sulfate and Carboxylate Suppress the Formation of ClNO2 at Atmospheric Interfaces

Wintertime Arctic Sea Spray Aerosol Composition Controlled by Sea Ice Lead Microbiology

Surfactant Charge Modulates Structure and Stability of Lipase-Embedded Monolayers at Marine-Relevant Aerosol Surfaces

Contact Info

Product

Resources

About

Control of Interfacial Cl₂ and N₂O₅ Reactivity by a Zwitterionic Phospholipid in Comparison with Ionic and Uncharged Surfactants

Sulfate and Carboxylate Suppress the Formation of ClNO₂ at Atmospheric Interfaces

Sulfate and Carboxylate Suppress the Formation of ClNO₂ at Atmospheric Interfaces