Synergistic Effect of Ammonia and Methylamine on Nucleation in the Earth’s Atmosphere. A Theoretical Study

Ammonia and amines are important common trace atmospheric species that can enhance new particle formation (NPF) in the Earth’s atmosphere. However, the synergistic effect of these two bases involving nucleation is still lacking. We studied the most stable geometric structures and thermodynamics of quaternary (NH3)­(CH3NH2)­(H2SO4)m(H2O)n (m = 1–3, n = 0–4) clusters at the PW91PW91/6-311++G­(3df,3pd) level of theory for the first time. We find that the proton transfer from H2SO4 molecule to CH3NH2 molecule is easier than to NH3 molecule in the free or hydrated H2SO4-base clusters, and thus leads to the stability. The energetically favorable formation of the (NH3)­(CH3NH2)­(H2SO4)m(H2O)n (n = 0–4) clusters, by hydration or attachment of base or substitution of ammonia by methylamine at 298.15 K, indicate that ammonia and methylamine together could enhance the stabilization of small binary clusters. At low RH and an ambient temperature of 298.15 K, the concentration of total hydrated (NH3)­(CH3NH2)­(H2SO4)2 clusters could reach that of total hydrated (NH3)­(H2SO4)2 clusters, which is the most stable ammonia-containing cluster. These results indicate that the synergistic effect of NH3 and CH3NH2 might be important in forming the initial cluster with sulfuric acid and subsequently growth process. In addition, the evaporation rates of (NH3)­(CH3NH2)­(H2SO4)­(H2O), (NH3)­(CH3NH2)­(H2SO4)2 and (NH3)­(CH3NH2)­(H2SO4)3 clusters, three relative abundant clusters in (NH3)­(CH3NH2)­(H2SO4)m(H2O)n system, were calculated. We find the stability increases with the increasing number of H2SO4 molecules

Surface-Cross-linked Protein-like Single-Chain Nanoparticle Globules Unexpectedly Stabilized with a Low Cross-linking Degree

Single-chain nanoparticles (SCNPs) are an emerging new nanomaterial with promising potential for exhibiting compactly collapsed globular nanostructures and associated functions, like proteins. However, the state-of-the-art synthesis approaches often result in SCNPs with diverse morphologies and loosely packed characteristics, even with an ample presence of cross-linkers, resembling sparse structures found in intrinsically disordered proteins. Herein, we present a facile strategy to fabricate protein-like compact SCNP globules using a low content of solvophilic photoreactive agents in a single-component poor solvent via flow photochemistry. Photoreactive agents in our system serve a dual purpose: acting as stabilizing agents that decorate the surface of the precollapsed precursor globules in the poor solvent and cross-linking with neighboring segments in situ upon UV irradiation on the globule surfaces. These cross-linked globules become effectively locked and remain stable when transferred into a good solvent. Computer simulations demonstrate that surface cross-linking reactions primarily occur between cross-linkers and neighboring monomers positioned at long contour distances along the chain backbone. This mechanism locks up the precollapsed protein-like SCNP globules with high efficiency; an extremely low cross-linker content of 1.6 mol % can result in an obvious reduction in molecular size. Small-angle X-ray scattering (SAXS) measurements also confirm the formation of compactly collapsed globule structures. Moreover, by varying the UV irradiation time, the degree of collapse in the SCNPs can be precisely controlled. The residual cross-linkers on the surface render the formed SCNPs reactive, thus allowing for further polymerization into hierarchical multifunctional self-assembly structures

Properties and Atmospheric Implication of Methylamine–Sulfuric Acid–Water Clusters

The presence of amines can increase aerosol formation rates. Most studies have been devoted to dimethylamine as the representative of amine; however, there have been a few works devoted to methylamine. In this study, theoretical calculations are performed on CH₃NH₂(H₂SO₄)_<i>m</i>(H₂O)_<i>n</i> (<i>m</i> = 0–3, <i>n</i> = 0–3) clusters. In addition to the structures and energetics, we focused on determining the following characteristics: (1) the growth mechanism, (2) the hydrate distributions and the influences of humidity and temperature, (3) Rayleigh scattering properties. We explored the cluster growth mechanism from a thermodynamics aspect by calculating the Gibbs free energy of adding a water or sulfuric acid molecule step by step at three atmospherically relevant temperatures. The relative ease of the reaction at each step is discussed. From the analysis of hydrate distributions, we find that CH₃NH₂(H₂SO₄)­(H₂O)₂, CH₃NH₂(H₂SO₄)₂, and CH₃NH₂(H₂SO₄)₃ are most likely to exist in the atmosphere. The general trend of hydration in all cases is more extensive with the growing relative humidity (RH), whereas the distributions do not significantly change with the temperature. Analysis of the Rayleigh scattering properties showed that both H₂SO₄ and H₂O molecules could increase the Rayleigh scattering intensities and isotropic mean polarizabilities, with greater influence by the sulfuric acid molecules. This work sheds light on the mechanism for further research on new particle formation (NPF) containing methylamine in the atmosphere

Physisorption of Poly(ethylene glycol) on Inorganic Nanoparticles

Poly­(ethylene glycol) (PEG) is the most widely used polymer to decorate inorganic nanoparticles (NPs) by the “grafting-to” method for antifouling properties. PEG also shows diverse supramolecular interactions with nanoparticle surfaces and polar molecules, suggesting that the physisorption between PEG chains and NPs cannot be ignored in the “grafting-to” process. However, the effect of physisorption of PEG to NPs on the process of chemisorption has been rarely studied. Herein, we report that unfunctionalized PEG is physically adsorbed on various NPs by polyvalent supramolecular interactions, adopting “loop-and-train-tail” conformations. We investigated the effect of molecular weight of PEG and ligands of the NPs on the conformation of PEG chains by experimental methods and simulation. It is demonstrated that the physisorption of PEG on NPs can facilitate the chemisorption in the initial stages but delays it in the later stages during the “grafting-to” process. This work provides a deeper understanding of the conformation of physisorbed PEG on NPs and the relationship between physisorption and chemisorption

Real-Time Dissection of the Exosome Pathway for Influenza Virus Infection

Exosomes play an important role in the spread of viral infections and immune escape. However, the exact ability and mechanisms by which exosomes produced during viral infections (vExos) infect host cells are still not fully understood. In this study, we developed a dual-color exosome labeling strategy that simultaneously labels the external and internal structures of exosomes with quantum dots to enable in situ monitoring of the transport process of vExos in live cells using the single-particle tracking technique. Our finding revealed that vExos contains the complete influenza A virus (IAV) genome and viral ribonucleoprotein complexes (vRNPs) proteins but lacks viral envelope proteins. Notably, these vExos have the ability to infect cells and produce progeny viruses. We also found that vExos are transported in three stages, slow–fast–slow, and move to the perinuclear region via microfilaments and microtubules. About 30% of internalized vExos shed the external membrane and release the internal vRNPs into the cytoplasm by fusion with endolysosomes. This study suggested that vExos plays a supporting role in IAV infection by assisting with IAV propagation in a virus-independent manner. It emphasizes the need to consider the infectious potential of vExos and draws attention to the potential risk of exosomes produced by viral infections

Real-Time Dissection of the Exosome Pathway for Influenza Virus Infection

Exosomes play an important role in the spread of viral infections and immune escape. However, the exact ability and mechanisms by which exosomes produced during viral infections (vExos) infect host cells are still not fully understood. In this study, we developed a dual-color exosome labeling strategy that simultaneously labels the external and internal structures of exosomes with quantum dots to enable in situ monitoring of the transport process of vExos in live cells using the single-particle tracking technique. Our finding revealed that vExos contains the complete influenza A virus (IAV) genome and viral ribonucleoprotein complexes (vRNPs) proteins but lacks viral envelope proteins. Notably, these vExos have the ability to infect cells and produce progeny viruses. We also found that vExos are transported in three stages, slow–fast–slow, and move to the perinuclear region via microfilaments and microtubules. About 30% of internalized vExos shed the external membrane and release the internal vRNPs into the cytoplasm by fusion with endolysosomes. This study suggested that vExos plays a supporting role in IAV infection by assisting with IAV propagation in a virus-independent manner. It emphasizes the need to consider the infectious potential of vExos and draws attention to the potential risk of exosomes produced by viral infections

Real-Time Dissection of the Exosome Pathway for Influenza Virus Infection

Exosomes play an important role in the spread of viral infections and immune escape. However, the exact ability and mechanisms by which exosomes produced during viral infections (vExos) infect host cells are still not fully understood. In this study, we developed a dual-color exosome labeling strategy that simultaneously labels the external and internal structures of exosomes with quantum dots to enable in situ monitoring of the transport process of vExos in live cells using the single-particle tracking technique. Our finding revealed that vExos contains the complete influenza A virus (IAV) genome and viral ribonucleoprotein complexes (vRNPs) proteins but lacks viral envelope proteins. Notably, these vExos have the ability to infect cells and produce progeny viruses. We also found that vExos are transported in three stages, slow–fast–slow, and move to the perinuclear region via microfilaments and microtubules. About 30% of internalized vExos shed the external membrane and release the internal vRNPs into the cytoplasm by fusion with endolysosomes. This study suggested that vExos plays a supporting role in IAV infection by assisting with IAV propagation in a virus-independent manner. It emphasizes the need to consider the infectious potential of vExos and draws attention to the potential risk of exosomes produced by viral infections

Bidirectional Interaction of Alanine with Sulfuric Acid in the Presence of Water and the Atmospheric Implication

Amino acids are recognized as important components of atmospheric aerosols, which impact on the Earth’s climate directly and indirectly. However, much remains unknown about the initial events of nucleation. In this work, the interaction of alanine [NH₂CH­(CH₃)­COOH or Ala], one of the most abundant amino acids in the atmosphere, with sulfuric acid (SA) and water (W) has been investigated at the M06-2X/6-311++G­(3df, 3pd) level of theory. We have studied thermodynamics of the hydrated (Ala)­(SA) core system with up to four water molecules. We found that Ala, with one amino group and one carboxyl group, can interact with H₂SO₄ and H₂O in two directions and that it has a high cluster stabilizing effect similar to that of ammonia, which is one of the key nucleation precursor. The corresponding Gibbs free energies of the (Ala)­(SA)­(W)_<i>n</i> (<i>n</i> = 0–4) clusters formation at 298.15 K predicted that Ala can contribute to the stabilization of small binary clusters. Our results showed that the hydrate distribution is temperature-dependent and that a higher humidity and temperature can contribute to the formation of hydrated clusters

Synergistic Adsorption–Photocatalysis based on Magnetic Metal–Organic Framework Nanoplatforms for Organic Pollutant Removal

Organic pollutant control is a highly significant global concern regarding human health and environmental remediation. Designing highly efficient photocatalysts for use in the removal of organic pollutants in the environment has attracted great interest in recent years. Here, a class of metal–organic framework nanoplatforms based on Fe3O4@UiO-66 with versatile combination modes are designed and synthesized for the effective detoxification of aflatoxin B1 (AFB1), one of the high-risk mycotoxins. The composite systems achieved efficient adsorption and photodegradation of AFB1, benefiting from UiO-66’s porous structure and Fe3O4’s catalytic enhancement. A high AFB1 degradation rate of up to 90% is obtained upon using these hybrid materials. The abundant hydroxyl-free radicals produced during the photocatalytic process drive the disruption of the AFB1 structure and thereby reduce its toxicity. In addition, SL- and LS-Fe3O4@UiO-66 catalysts can be facilely recycled, maintaining more than 80% of the catalytic capacity after three cycles. Moreover, these magnetic nanocatalysts have also demonstrated excellent generalizability, achieving over 90% removal of several organic contaminants including pesticides and dyes in solution