The thermal decomposition mechanism of RDX/AP composites: ab initio neural network MD simulations.

A neural network potential (NNP) is developed to investigate the decomposition mechanism of RDX, AP, and their composites. Utilizing an ab initio dataset, the NNP is evaluated in terms of atomic energy and forces, demonstrating strong agreement with ab initio calculations. Numerical stability tests across a range of timesteps reveal excellent stability compared to the state-of-the-art ReaxFF models. Then the thermal decomposition of pure RDX, AP, and RDX/AP composites is performed using NNP to explore the coupling effect between RDX and AP. The results highlight a dual interaction between RDX and AP, i.e., AP accelerates RDX decomposition, particularly at low temperatures, and RDX promotes AP decomposition. Analyzing RDX trajectories at the RDX/AP interface unveils a three-part decomposition mechanism involving N-N bond cleavage, H transfer with AP to form Cl-containing acid, and chain-breaking reactions generating small molecules such as N2, CO, and CO2. The presence of AP enhances H transfer reactions, contributing to its role in promoting RDX decomposition. This work studies the reaction kinetics of RDX/AP composites from the atomic point of view, and can be widely used in the establishment of reaction kinetics models of composite systems with energetic materials.

Determining the mechanical and decomposition properties of high energetic materials (α-RDX, ß-HMX, and ε-CL-20) using a neural network potential.

Molecular simulations of high energetic materials (HEMs) are limited by efficiency and accuracy. Recently, neural network potential (NNP) models have achieved molecular simulations of millions of atoms while maintaining the accuracy of density functional theory (DFT) levels. Herein, an NNP model covering typical HEMs containing C, H, N, and O elements is developed. The mechanical and decomposition properties of 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), hexahydro-1,3,5-trinitro-1,3,5-triazine (HMX), and 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (CL-20) are determined by employing the molecular dynamics (MD) simulations based on the NNP model. The calculated results show that the mechanical properties of α-RDX, ß-HMX, and ε-CL-20 agree with previous experiments and theoretical results, including cell parameters, equations of state, and elastic constants. In the thermal decomposition simulations, it is also found that the initial decomposition reactions of the three crystals are N-NO2 homolysis, corresponding radical intermediates formation, and NO2-induced reactions. This decomposition trajectory is mainly divided into two stages separating from the peak of NO2: pyrolysis and oxidation. Overall, the NNP model for C/H/N/O elements in this work is an alternative reactive force field for RDX, HMX, and CL-20 HEMs, and it opens up new potential for future kinetic study of nitramine explosives.

Multiple evaluations of atmospheric behavior between Criegee intermediates and HCHO: Gas-phase and air-water interface reaction.

Given the high abundance of water in the atmosphere, the reaction of Criegee intermediates (CIs) with (H2O)2 is considered to be the predominant removal pathway for CIs. However, recent experimental findings reported that the reactions of CIs with organic acids and carbonyls are faster than expected. At the same time, the interface behavior between CIs and carbonyls has not been reported so far. Here, the gas-phase and air-water interface behavior between Criegee intermediates and HCHO were explored by adopting high-level quantum chemical calculations and Born-Oppenheimer molecular dynamics (BOMD) simulations. Quantum chemical calculations evidence that the gas-phase reactions of CIs + HCHO are submerged energy or low energy barriers processes. The rate ratios speculate that the HCHO could be not only a significant tropospheric scavenger of CIs, but also an inhibitor in the oxidizing ability of CIs on SOx in dry and highly polluted areas with abundant HCHO concentration. The reactions of CH2OO with HCHO at the droplet's surface follow a loop structure mechanism to produce i) SOZ (), ii) BHMP (HOCH2OOCH2OH), and iii) HMHP (HOCH2OOH). Considering the harsh reaction conditions between CIs and HCHO at the interface (i.e., the two molecules must be sufficiently close to each other), the hydration of CIs is still their main atmospheric loss pathway. These results could help us get a better interpretation of the underlying CIs-aldehydes chemical processes in the global polluted urban atmospheres.

Cytokine-Like 1 Is a Novel Proangiogenic Factor Secreted by and Mediating Functions of Endothelial Progenitor Cells.

RATIONALE: Endothelial colony forming cells (ECFCs) or late blood outgrowth endothelial cells can be isolated from human cord or peripheral blood, display properties of endothelial progenitors, home into ischemic tissues and support neovascularization in ischemic disease models. OBJECTIVE: To assess the functions of CYTL1 (cytokine-like 1), a factor we found preferentially produced by ECFCs, in regard of vessel formation. METHODS AND RESULTS: We show by transcriptomic analysis that ECFCs are distinguished from endothelial cells of the vessel wall by production of high amounts of CYTL1. Modulation of expression demonstrates that the factor confers increased angiogenic sprouting capabilities to ECFCs and can also trigger sprouting of mature endothelial cells. The data further display that CYTL1 can be induced by hypoxia and that it functions largely independent of VEGF-A (vascular endothelial growth factor-A). By recombinant production of CYTL1 we confirm that the peptide is indeed a strong proangiogenic factor and induces sprouting in cellular assays and functional vessel formation in animal models comparable to VEGF-A. Mass spectroscopy corroborates that CYTL1 is specifically O-glycosylated on 2 neighboring threonines in the C-terminal part and this modification is important for its proangiogenic bioactivity. Further analyses show that the factor does not upregulate proinflammatory genes and strongly induces several metallothionein genes encoding anti-inflammatory and antiapoptotic proteins. CONCLUSIONS: We conclude that CYTL1 can mediate proangiogenic functions ascribed to endothelial progenitors such as ECFCs in vivo and may be a candidate to support vessel formation and tissue regeneration in ischemic pathologies.

The Otubain YOD1 Suppresses Aggregation and Activation of the Signaling Adaptor MAVS through Lys63-Linked Deubiquitination.

MAVS is a critical adaptor required for activating an innate antiviral immune response against viral infection. The activation of MAVS requires modification of the Lys63-linked ubiquitination and formation of prion-like aggregates. However, the molecular mechanisms regulating MAVS activity remain largely obscured. In this study, we identified a deubiquitinase YOD1, also known as a member of the ovarian tumor family, as a negative regulator of MAVS activation in both human and murine cells. YOD1 was recruited to mitochondria to interact with MAVS through its UBX and Znf domains after viral infection. Subsequently, YOD1 cleaved the K63-linked ubiquitination and abrogated the formation of prion-like aggregates of MAVS, which led to attenuation of IRF3, P65 activation, and IFN-ß production. Knockdown of YOD1 potentiated IRF3 and P65 activation, IFN-ß production, and antiviral innate immune response to RNA virus. Our findings thus provided, to our knowledge, novel insights into the regulatory cascade of the cellular antiviral response through YOD1-mediated K63-linked deubiquitination and aggregation of MAVS.

The favorable routes for the hydrolysis of CH2OO with (H2O)n (n = 1-4) investigated by global minimum searching combined with quantum chemical methods.

The hydrolysis reaction of CH2OO with water and water clusters is believed to be a dominant sink for the CH2OO intermediate in the atmosphere. However, the favorable route for the hydrolysis of CH2OO with water clusters is still unclear. Here global minimum searching using the Tsinghua Global Minimum program has been introduced to find the most stable geometry of the CH2OO(H2O)n (n = 1-4) complex firstly. Then, based on these stable complexes, favorable hydrolysis of CH2OO with (H2O)n (n = 1-4) has been investigated using the quantum chemical method of CCSD(T)-F12a/cc-pVDZ-F12//B3LYP/6-311+G(2d,2p) and canonical variational transition state theory with small curvature tunneling. The calculated results have revealed that, although the contribution of CH2OO + (H2O)2 is the most obvious in the hydrolysis of CH2OO with (H2O)n (n = 1-4), the hydrolysis of CH2OO with (H2O)3 is not negligible in atmospheric gas-phase chemistry as its rate is close to the rate of the CH2OO + H2O reaction. The calculated results also show that, in a clean atmosphere, the CH2OO + (H2O)n (n = 1-2) reaction competes well with the CH2OO + SO2 reaction at 298 K when the concentrations of (H2O)n (n = 1-2) range from 20% relative humidity (RH) to 100% RH, and SO2 is 2.46 × 1011 molecules per cm3. Meanwhile, when the RH is higher than 40%, it is a new prediction that the CH2OO + (H2O)3 reaction can also compete well with the CH2OO + SO2 reaction at 298 K. Besides, Born-Oppenheimer molecular dynamics simulation results show that all the favorable channels of the CH2OO + (H2O)n (n = 1-3) reaction cannot react on a time scale of 100 ps in the NVT simulation. However, the NVE simulation results show that the CH2OO + (H2O)3 reaction can be finished well at 8.5 ps, indicating that the gas phase reaction of CH2OO + (H2O)3 is not negligible in the atmosphere. Overall, the present results have provided a definitive example of how the favorable hydrolysis of important atmospheric species with (H2O)n (n = 1-4) takes place, which will stimulate one to consider the favorable hydrolysis of water and water clusters with other Criegee intermediates and other important atmospheric species.

Atmospheric Chemistry of CH2OO: The Hydrolysis of CH2OO in Small Clusters of Sulfuric Acid.

The hydrolysis of CH2OO is not only a dominant sink for the CH2OO intermediate in the atmosphere but also a key process in the formation of aerosols. Herein, the reaction mechanism and kinetics for the hydrolysis of CH2OO catalyzed by the precursors of atmospheric aerosols, including H2SO4, H2SO4···H2O, and (H2SO4)2, have been studied theoretically at the CCSD(T)-F12a/cc-pVDZ-F12//B3LYP/6-311+G(2df,2pd) level. The calculated results show that the three catalysts decrease the energy barrier by over 10.3 kcal·mol-1; at the same time, the product formation of HOCH2OOH is more strongly bonded to the three catalysts than to the reactants CH2OO and H2O, revealing that small clusters of sulfuric acid promote the hydrolysis of CH2OO both kinetically and thermodynamically. Kinetic simulations show that the H2SO4-assisted reaction is more favorable than the H2SO4···H2O- (the pseudo-first-order rate constant being 27.9-11.5 times larger) and (H2SO4)2- (between 2.8 × 104 and 3.4 × 105 times larger) catalyzed reactions. Additionally, due to relatively lower concentration of H2SO4, the hydrolysis of CH2OO with H2SO4 cannot compete with the CH2OO + H2O or (H2O)2 reaction within the temperature range of 280-320 K, since its pseudo-first-order rate ratio is smaller by 4-7 or 6-8 orders of magnitude, respectively. However, the present results provide a good example of how small clusters of sulfuric acid catalyze the hydrolysis of an important atmospheric species.

Polyethylene oxide enhances the ductility and toughness of polylactic acid: the role of mesophase.

A lack of understanding of the structure-property relationship of the polylactic acid (PLA)-based polymer composite system makes it a challenge to manufacture products with optimized mechanical performance by precisely regulating the microscopic structure and morphology. Herein, we chose the PLA/polyethylene oxide (PEO) blend as a model to investigate the structural reason for the enhanced ductility and toughness of this kind of material. We have demonstrated that a considerable amount of the PLA mesophases exist in the melt quenched films that display high ductility and toughness, in contrast to the PLA crystals in their counterparts of slowly cooled films that are dominated by brittle fracture. The mesophase formed by melt quenching is attributed to a moderate acceleration of PLA chain mobility due to the plasticizing effect of the flexible PEO. In situ experiments have revealed the further formation of oriented mesophases induced by tensile deformation, which presents a high consistency between the content increase and the tensile stress intensification. We illustrate that the mesophases directly develop into a microfibrillar morphology to transmit the external stress and prevent crack propagation under deformation. This work emphasizes the essential role of the PLA mesophase in acquiring the enhanced ductility and toughness of the PLA/PEO composite films, which may be generalized to other similar PLA-based polymer composite materials.

Clinical and Prognostic Characteristics of 53 Cases of Extracranial Malignant Rhabdoid Tumor in Children. A Single-Institute Experience from 2007 to 2017.

BACKGROUND: The aim of this study is to add to the current knowledge regarding extracranial malignant rhabdoid tumor (MRT), a rare and highly aggressive tumor that occurs most commonly in infants and young children. PATIENTS AND METHODS: A retrospective medical record review was conducted on 53 patients with pathologically confirmed MRT in Beijing Children's Hospital between January 2007 and October 2017. RESULTS: Fifty-three patients were diagnosed with MRT at a median age of 16 months, including 32 cases of malignant rhabdoid tumor of the kidney (MRTK) and 21 cases of extrarenal extracranial rhabdoid tumor (EERT). Fourteen (14/32, 43.75%) patients with MRTK and five (5/21, 23.81%) patients with EERT had metastases at diagnosis, and quite a few number of cases occurred tumor rupture (26.42%). Among the 53 patients, 40 (75.47%) patients died, 10 (18.87%) patients survived, and 3 patients (5.66%) were lost to follow-up. Among the 40 dead patients, 38 patients died from rapid progression of the disease or tumor recurrence, and 2 patients died of severe postoperative complications. Most of the recurrent or relapsed cases (94.11%) occurred within 8 months, with a median time of 76 days after diagnosis. The overall survival rates of 3 years and 5 years for the entire cohort were 23.71% and 18.44%, respectively. After survival analysis, it was clear that a younger age at diagnosis and distant stage patients had relatively poor outcomes. The effect of treatment was the most difficult to analyze because patients were not treated uniformly. Statistically significant differences in survival were noted among patients treated with standard chemotherapy, total resection, and radiotherapy. CONCLUSION: Extracranial MRT is still a highly aggressive tumor in children. Younger patients and those suffering from metastatic disease were most likely to have a poor outcome because of rapid progression or recurrence of the tumor. IMPLICATIONS FOR PRACTICE: This is the largest single-institutional report that investigates the clinical characteristics and outcomes of extracranial malignant rhabdoid tumor (MRT) in China. Our study showed that gross hematuria and tumor rupture were typical characteristics of malignant rhabdoid tumor of the kidney. After survival analysis, it was found that the advanced stage of the tumor and an age ≤12 months at diagnosis were significantly associated with poorer survival. Although extracranial MRT is still a highly aggressive tumor in children, multimodal treatment approach, including chemotherapy, surgery, and radiotherapy, should be employed for this disease.

Atmospheric chemistry of the self-reaction of HO2 radicals: stepwise mechanism versus one-step process in the presence of (H2O)n (n = 1-3) clusters.

The effects of water on radical-radical reactions are of great importance for the elucidation of the atmospheric oxidation process of free radicals. In the present work, the HO2 + HO2 reactions with (H2O)n (n = 1-3) have been investigated using quantum chemical methods and canonical variational transition state theory with small curvature tunneling. We have explored both one-step and stepwise mechanisms, in particular the stepwise mechanism initiated by ring enlargement. The calculated results have revealed that the stepwise mechanism is the dominant one in the HO2 + HO2 reaction that is catalyzed by one water molecule. This is because its pseudo-first-order rate constant (kRWM1') is 3 orders of magnitude larger than that of the corresponding one-step mechanism. Additionally, the value of kRWM1' at 298 K has been found to be 4.3 times larger than that of the rate constant of the HO2 + HO2 reaction (kR1) without catalysts, which is in good agreement with the experimental findings. The calculated results also showed that the stepwise mechanism is still dominant in the (H2O)2 catalyzed reaction due to its higher pseudo-first-order rate constant, which is 3 orders of magnitude larger than that of the corresponding one-step mechanism. On the other hand, the one-step process is much faster than the stepwise mechanism by a factor of 105-106 in the (H2O)3 catalyzed reaction. However, the pseudo-first-order rate constants for the (H2O)2 and (H2O)3-catalyzed reactions are lower than that of the H2O-catalyzed reaction by 3-4 orders of magnitude, which indicates that the water monomer is the most efficient one among all the catalysts of (H2O)n (n = 1-3). The present results have provided a definitive example that water and water clusters have important influences on atmospheric reactions.

IL-35 over-expression increases apoptosis sensitivity and suppresses cell growth in human cancer cells.

Interleukin (IL)-35 is a novel heterodimeric cytokine in the IL-12 family and is composed of two subunits: Epstein-Barr virus-induced gene 3 (EBI3) and IL-12p35. IL-35 is expressed in T regulatory (Treg) cells and contributes to the immune suppression function of these cells. In contrast, we found that both IL-35 subunits were expressed concurrently in most human cancer cell lines compared to normal cell lines. In addition, we found that TNF-α and IFN-γ stimulation led to increased IL-35 expression in human cancer cells. Furthermore, over-expression of IL-35 in human cancer cells suppressed cell growth in vitro, induced cell cycle arrest at the G1 phase, and mediated robust apoptosis induced by serum starvation, TNF-α, and IFN-γ stimulation through the up-regulation of Fas and concurrent down-regulation of cyclinD1, survivin, and Bcl-2 expression. In conclusion, our results reveal a novel functional role for IL-35 in suppressing cancer activity, inhibiting cancer cell growth, and increasing the apoptosis sensitivity of human cancer cells through the regulation of genes related to the cell cycle and apoptosis. Thus, this research provides new insights into IL-35 function and presents a possible target for the development of novel cancer therapies.

Multiple fluorescence response behaviors towards antibiotics and bacteria based on a highly stable Cd-MOF.

The abuse of antibiotics has triggered the rise of drug-resistance bacteria, which has seriously threatened public health globally. As a result, carrying out efficient and accurate antibiotic and bacteria identification are quite significant but challenge. Herein, an unprecedented Cd-MOF-based sensor, [CdL]n [1, H2L = 4-(2-methyl-1H-benzo[d]imidazol-1-yl) isophthalic acid] with multiple fluorescence response behaviours towards antibiotics and bacteria was developed. Single-crystal X-ray diffraction revealed that 1 is a mesomeric 2D bilayer, which is comprised of two opposite chiral mono-layers, each assembled by left-handed or right-handed helixes. More interestingly, 1 represented multiplex detection capability towards antibiotics and bacteria through two detection behaviors: toward nitro-antibiotics and chlortetracycline (CTC) via fluorescent quenching, while toward Staphylococcus albus (S. albus) via fluorescent enhancement. Remarkably, 1 showed a low limit of detection (LOD, 47 CFU/mL) accompanied with specificity in the detection of S. albus compared to other bacteria, such as Staphylococcus aureus, Acinetobacter baumannii, Klebsiella pneumonia, Pseudomonas aeruginosa and Escherichia coli. In addition, the LOD could reach to ppm level for nitro-antibiotics and CTC. Moreover, the practical application of 1 was further reinforced through the detection of nitro-antibiotics and CTC, as well as S. albus in fetal calf serum and river water.

High-yield expression, purification, characterization, and structure determination of tag-free Candida utilis uricase.

We report the successful high-yield expression of Candida utilis uricase in Escherichia coli and the establishment of an efficient three-step protein purification protocol. The purity of the recombinant protein, which was confirmed to be C. utilis uricase by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometer analysis, was >98% and the specific activity was 38.4 IU/mg. Crystals of C. utilis uricase were grown at 18°C using 25% polyethylene glycol 3350 as precipitant. Diffraction by the crystals extends to 1.93 Å resolution, and the crystals belong to the space group P2(1)2(1)2(1) with unit cell parameters a = 69.16 Å, b = 139.31 Å, c = 256.33 Å, and α = ß = γ = 90°. The crystal structure of C. utilis uricase shares a high similarity with other reported structures of the homologous uricases from other species in protein database, demonstrating that the three-dimensional structure of the protein defines critically to the catalytic activities.

DDAH2 suppresses RLR-MAVS-mediated innate antiviral immunity by stimulating nitric oxide-activated, Drp1-induced mitochondrial fission.

The RIG-I-like receptor (RLR) signaling pathway is pivotal for innate immunity against invading viruses, and dysregulation of this molecular cascade has been linked to various diseases. Here, we identified dimethylarginine dimethylaminohydrolase 2 (DDAH2) as a potent regulator of the RLR-mediated antiviral response in human and mouse. Overexpression of DDAH2 attenuated RLR signaling, whereas loss of DDAH2 function enhanced RLR signaling and suppressed viral replication ex vivo and in mice. Upon viral infection, DDAH2 relocated to mitochondria, where it induced the production of nitric oxide (NO) and the activation of dynamin-related protein 1 (Drp1), which promoted mitochondrial fission and blocked the activation of innate immune responses mediated by mitochondrial antiviral signaling (MAVS). TANK-binding kinase 1 (TBK1), a kinase downstream of MAVS, inhibited DDAH2 by phosphorylating DDAH2 at multiple sites. Our study thus identifies a reciprocal inhibitory loop between the DDAH2-NO cascade and the RLR signaling pathway that fine-tunes the antiviral immune response.

Anti-IFN-γ therapy alleviates acute lung injury induced by severe influenza A (H1N1) pdm09 infection in mice.

BACKGROUND/PURPOSE: Severe infection with influenza A (H1N1)pdm09 virus is characterized by acute lung injury. The limited efficacy of anti-viral drugs indicates an urgent need for additional therapies. We have previously reported that neutralization of gamma interferon (IFN-γ) could significantly rescue the thymic atrophy induced by severe influenza A (H1N1)pdm09 infection in BALB/c mice. A deeper investigation was conducted into the influence of neutralizing IFN-γ to the BALB/c mice weight, survival rate, and lung injury. METHODS: The BALB/c mice was infected with severe influenza A (H1N1)pdm09. Monoclonal antibodies against IFN-γ were injected into the abdominal cavities of the mice. After neutralization of IFN-γ occurred in mice infected by severe ∖ influenza A (H1N1)pdm09, observing the influence of neutralizing IFN-γ to the BALB/c mice weight, survival rate, lung injury. RESULT: Our results here showed that anti-IFN-γ therapy alleviated the acute lung injury in this mouse model. Neutralization of IFN-γ led to a significant reduction in the lung microvascular leak and the cellular infiltrate in the lung tissue, and also improved the outcome in mice mortality. Several pro-inflammatory cytokines, including interleukin (IL)-1α, tumor necrosis factor (TNF)-α and granulocyte-colony stimulating factor (G-CSF) in the bronchoalveolar lavage fluid (BALF), and the chemokines including G-CSF, monocyte chemoattractant protein-1 (MCP-1) in serum samples were found to be significantly reduced after anti-IFN-γ treatment. CONCLUSION: These results suggested that IFN-γ plays an important role in acute lung injury induced by severe influenza A (H1N1)pdm09 infection, and monoclonal antibodies against IFN-γ could be useful as a potential therapeutic remedy for future influenza pandemics.

Effect of NH3 and HCOOH on the H2O2 + HO → HO2 + H2O reaction in the troposphere: competition between the one-step and stepwise mechanisms.

The H2O2 + HO → HO2 + H2O reaction is an important reservoir for both radicals of HO and HO2 catalyzing the destruction of O3. Here, this reaction assisted by NH3 and HCOOH catalysts was explored using the CCSD(T)-F12a/cc-pVDZ-F12//M06-2X/aug-cc-pVTZ method and canonical variational transition state theory with small curvature tunneling. Two possible sets of mechanisms, (i) one-step routes and (ii) stepwise processes, are possible. Our results show that in the presence of both NH3 and HCOOH catalysts under relevant atmospheric temperature, mechanism (i) is favored both energetically and kinetically than the corresponding mechanism (ii). At 298 K, the relative rate for mechanism (i) in the presence of NH3 (10, 2900 ppbv) and HCOOH (10 ppbv) is respectively 3-5 and 2-4 orders of magnitude lower than that of the water-catalyzed reaction. This is due to a comparatively lower concentration of NH3 and HCOOH than H2O which indicates the positive water effect under atmospheric conditions. Although NH3 and HCOOH catalysts play a negligible role in the reservoir for both radicals of HO and HO2 catalyzing the destruction of O3, the current study provides a comprehensive example of how acidic and basic catalysts assisted the gas-phase reactions.

Effects of water, ammonia and formic acid on HO2 + Cl reactions under atmospheric conditions: competition between a stepwise route and one elementary step.

Quantum chemical calculations at M06-2X and CCSD(T) levels of theory have been performed to investigate the effects of H2O, NH3, and HCOOH on the HO2 + Cl → HCl + O2 reaction. The results show that catalyzed reactions with three catalysts could proceed through two different mechanisms, namely a stepwise route and one elementary step, where the former reaction is more favorable than the latter. Meanwhile, for the stepwise route, a single hydrogen atom transfer pathway in the presence of all catalysts has more advantages than the respective double hydrogen atom transfer pathway. Then, the relative impacts of catalysts under tropospheric conditions were investigated by considering the temperature dependence of the rate constants and the altitude dependence of catalyst concentrations. The calculated results show that at 0 km altitude, the HO2 + Cl → HCl + O2 reaction with catalysts, such as H2O, NH3, or HCOOH, cannot compete with the reaction without a catalyst, as the effective rate constant with a catalyst is smaller by 2-6 orders of magnitude than the naked reaction within the temperature range 280-320 K. The calculated results also show that at altitudes of 5, 10 and 15 km, the effective rate constant of the HCOOH-catalyzed reaction increases obviously with an increase in altitude. At 15 km altitude, its value is up to 9.63 × 10-11 cm3 per molecule per s, which is close to the corresponding value of the reaction without a catalyst, showing that the contribution of HCOOH to the HO2 + Cl → HCl + O2 reaction cannot be neglected at high altitudes. The new findings in this investigation are not only of great necessity and importance for elucidating the gas-phase reaction of HO2 with Cl in the presence of acidic, neutral and basic catalysts, but are also of great interest for understanding the importance of other types of hydrogen abstraction in the atmosphere.

Catalytic effect of (H2O) n (n = 1-3) clusters on the HO2 + SO2 → HOSO + 3O2 reaction under tropospheric conditions.

The HO2 + SO2 → HOSO + 3O2 reaction, both without a catalyst and with (H2O) n (n = 1-3) as a catalyst, has been investigated using CCSD(T)/CBS//M06-2X/aug-cc-pVTZ methods, and canonical variational transition state theory with small curvature tunneling (CVT/SCT). The calculated results show that H2O exerts the strongest catalytic role in the hydrogen atom transfer processes of HO2 + SO2 → HOSO + 3O2 as compared with (H2O)2 and (H2O)3. In the atmosphere at 0 km altitude within the temperature range of 280.0-320.0 K, the reaction with H2O is dominant, compared with the reaction without a catalyst, with an effective rate constant 2-3 orders of magnitude larger. In addition, at 0 km, it is worth mentioning that the relevance of the HO2 + SO2 → HOSO + 3O2 reaction with H2O depends heavily on its ability to compete with the primary loss mechanism of HO2 radicals (such as the HO2 + HO2 and HO2 + NO3 reactions) and SO2 (such as the SO2 + HO reaction). The calculated results show that the HO2 + SO2 → HOSO + 3O2 reaction with H2O cannot be neglected in the primary loss mechanism of the HO2 radical and SO2. The calculated results also show that for the formation of HOSO and 3O2, the contribution of H2O decreases from 99.98% to 27.27% with an increase in altitude from 0 km to 15 km, due to the lower relative concentration of water. With the altitude increase, the HO2 + SO2 → HOSO + 3O2 reaction with H2O cannot compete with the primary loss mechanism of HO2 radicals. The present results provide new insight into (H2O) n (n = 1-3) catalysts, showing that they not only affect energy barriers, but also have an influence on loss mechanisms. The present findings should have broad implications in computational chemistry and atmospheric chemistry.

Correction: Effects of water, ammonia and formic acid on HO2 + Cl reactions under atmospheric conditions: competition between a stepwise route and one elementary step.

[This corrects the article DOI: 10.1039/C9RA03541A.].

Vγ4+γδT Cells Aggravate Severe H1N1 Influenza Virus Infection-Induced Acute Pulmonary Immunopathological Injury via Secreting Interleukin-17A.

The influenza A (H1N1) pdm09 virus remains a critical global health concern and causes high levels of morbidity and mortality. Severe acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are the major outcomes among severely infected patients. Our previous study found that interleukin (IL)-17A production by humans or mice infected with influenza A (H1N1) pdm09 substantially contributes to ALI and subsequent morbidity and mortality. However, the cell types responsible for IL-17A production during the early stage of severe influenza A (H1N1) pdm09 infection remained unknown. In this study, a mouse model of severe influenza A (H1N1) pdm09 infection was established. Our results show that, in the lungs of infected mice, the percentage of γδT cells, but not the percentages of CD4+Th and CD8+Tc cells, gradually increased and peaked at 3 days post-infection (dpi). Further analysis revealed that the Vγ4+γδT subset, but not the Vγ1+γδT subset, was significantly increased among the γδT cells. At 3 dpi, the virus induced significant increases in IL-17A in the bronchoalveolar lavage fluid (BALF) and serum. IL-17A was predominantly secreted by γδT cells (especially the Vγ4+γδT subset), but not CD4+Th and CD8+Tc cells at the early stage of infection, and IL-1ß and/or IL-23 were sufficient to induce IL-17A production by γδT cells. In addition to secreting IL-17A, γδT cells secreted interferon (IFN)-γ and expressed both an activation-associated molecule, natural killer group 2, member D (NKG2D), and an apoptosis-associated molecule, FasL. Depletion of γδT cells or the Vγ4+γδT subset significantly rescued the virus-induced weight loss and improved the survival rate by decreasing IL-17A secretion and reducing immunopathological injury. This study demonstrated that, by secreting IL-17A, lung Vγ4+γδT cells, at least, in part mediated influenza A (H1N1) pdm09-induced immunopathological injury. This mechanism might serve as a promising new target for the prevention and treatment of ALI induced by influenza A (H1N1) pdm09.