Comment on "Impact of water on the BrO + HO2 gas-phase reaction: mechanism, kinetics and products" by N. T. Tsona, S. Tang and L. Du, Phys. Chem. Chem. Phys., 2019, 21, 20296.

The reaction, BrO + HO2 → HOBr + O2, is exothermic and can produce O2 in both its ground state (X[combining tilde]3∑g-) and its first excited state (ã1Δg). As a result, this reaction can proceed on both a singlet and a triplet potential energy surface. Recently, Tsona, Tang and Du published a paper entitled "Impact of water on the BrO + HO2 gas-phase reaction: mechanism, kinetics and products (Phys. Chem. Chem. Phys. 2019, 21, 20296-203072). The results of this work showed significant differences from those published earlier on this reaction by Chow et al. (Phys. Chem. Chem. Phys. 2016, 18, 30554-30569). Further calculations performed in this present work, combined with higher level calculations published by Chow et al. (Phys. Chem. Chem. Phys. 2016, 18, 30554-30569), demonstrate that the work of Tsona et al. is flawed because the integration grid size used in their lowest singlet and triplet calculations is too small, and a closed-shell wavefunction, rather than an open-shell wavefunction, has been used for the singlet surface. The major conclusion in the work of Tsona et al. that the lowest singlet and triplet channels are barrierless is shown to be incorrect. Also, the computed rate coefficients of Tsona et al. showed a positive temperature dependence, which is inconsistent with the experimentally observed negative temperature dependence, whereas the singlet rate coefficients computed by Chow et al. (Phys. Chem. Chem. Phys. 2016, 18, 30554-30569) showed a negative temperature dependence consistent with experiment.

Schwann cell-specific Pten inactivation reveals essential role of the sympathetic nervous system activity in adipose tissue development.

There is increasing evidence that the sympathetic nervous system (SNS) plays an important role in adipose tissue development. However, the underlying molecular mechanism(s) associated with this remains unclear. SNS innervation of white adipose tissue (WAT) is believed to be necessary and sufficient to elicit WAT lipolysis. In this current study, mice with Schwann cell (SC)-specific inactivation of phosphatase and tensin homolog (Pten) displayed enlarged inguinal white adipose tissue (iWAT). This serendipitous observation implicates the role of SCs in mediating SNS activity associated with mouse adipose tissue development. Mice with SC-specific Pten inactivation displayed enlarged iWAT. Interestingly, the SNS activity in iWAT of SC-specific Pten-deficient mice was reduced as demonstrated by decreased tyrosine hydroxylase (TH) expression level and neurotransmitters, such as norepinephrine (NE) and histamine (H). The lipolysis related protein, phosphorylated hormone sensitive lipase (pHSL), was also decreased. As expected, AKT-associated signaling pathway was hyperactivated and hypothesized to induce enlarged iWAT in SC-specific Pten-deficient mice. Moreover, preliminary experiments using AKT inhibitor AZD5363 treatment ameliorated the enlarged iWAT condition in SC-specific Pten-deficient mice. Taken together, SCs play an essential role in the regulation of SNS activity in iWAT development via the AKT signaling pathway. This novel role of SCs in SNS function allows for better understanding into the genetic mechanisms of peripheral neuropathy associated obesity.

A theoretical study of the addition of CH2OO to hydroxymethyl hydroperoxide and its implications on SO3 formation in the atmosphere.

The reaction of hydroxymethyl hydroperoxide (HMHP, HOCH2OOH) with the simplest Criegee intermediate, CH2OO, has been examined using quantum chemical methods with transition state theory. Geometry optimization and IRC calculations were performed using the M06-2X, MN15-L, and B2PLYP-D3 functionals in conjunction with the aug-cc-pVTZ basis set. Single point energy calculations using QCISD(T) and BD(T) with the same basis set have been performed to determine the energy of reactants, reactive complexes, transition states, and products. Rate coefficients have been obtained using variational transition state theory. The addition of CH2OO on the three different oxygen atoms in HMHP has been considered and the ether oxide forming channel, CH2OO + HOCH2OOH → HOCH2O(O)CH2OOH (channel 2), is the most favorable. The best computed standard enthalpy of reaction (ΔH) and zero-point corrected barrier height are -20.02 and -6.33 kcal mol-1, respectively. The reaction barrier is negative and our results suggest that both the inner and outer transition states contribute to the corresponding overall reactive flux in the tropospheric temperature range (220 K to 320 K). A two-transition state model has been used to obtain reliable rate coefficients at the high-pressure limit. The pressure-dependent rate coefficient calculations using the SS-QRRK theory have shown that this channel is pressure-dependent. Moreover, our investigation has shown that the ether oxide formed may rapidly react with SO2 at 298 K to form SO3, which can, in turn, react with water to form atmospheric H2SO4. A similar calculation has been conducted for the reaction of HMHP with OH, suggesting that the titled reaction may be a significant sink of HMHP. Therefore, the reaction between CH2OO and HOCH2OOH could be an indirect source for generating atmospheric H2SO4, which is crucial to the formation of clouds, and it might relieve global warming.

Dihydrochalcone-derived polyphenols from tea crab apple (Malus hupehensis) and their inhibitory effects on α-glucosidase in vitro.

Three dihydrochalcone-derived polyphenols, huperolides A-C (1-3), along with thirteen known compounds (4-16) were isolated from the leaves of Malus hupehensis, the well-known tea crab apple in China. Their chemical structures were elucidated by extensive spectroscopic analysis including NMR (HSQC, HMBC, 1H-1H COSY and ROESY), HRMS and CD spectra. Huperolide A is a polyphenol with a new type of carbon skeleton, while huperolides B and C are a couple of atropisomers, which were isolated from natural sources for the first time. The antihyperglycemic effects of the isolated compounds were evaluated based on assaying their inhibitory activities against α-glucosidase. As a result, phlorizin (4), 3-hydroxyphloridzin (5), 3-O-coumaroylquinic acid (12) and ß-hydroxypropiovanillone (15) showed significant concentration-dependent inhibitory effects on α-glucosidase. Therefore, those compounds might be responsible for the antihyperglycemic effect of this herb, and are the most promising compounds to lead discovery of drugs against diabetes.

HBx-K130M/V131I Promotes Liver Cancer in Transgenic Mice via AKT/FOXO1 Signaling Pathway and Arachidonic Acid Metabolism.

Chronic hepatitis B viral (HBV) infection remains a high underlying cause for hepatocellular carcinoma (HCC) worldwide, while the genetic mechanisms behind this remain unclear. This study elucidated the mechanisms contributing to tumor development induced by the HBV X (HBx) gene of predominantly Asian genotype B HBV and its common HBx variants. To compare the potential tumorigenic effects of K130M/V131I (Mut) and wild-type (WT) HBx on HCC, the Sleeping Beauty (SB) transposon system was used to deliver HBx Mut and WT into the livers of fumarylacetoacetate hydrolase (Fah)-deficient mice and in the context of transformation related protein 53 (Trp53) deficiency. From our results, HBx Mut had a stronger tumorigenic effect than its WT variant. Also, inflammation, necrosis, and fibrosis were evident in HBx experimental animals. Reduction of forkhead box O1 (FOXO1) with increased phosphorylation of upstream serine/threonine kinase (AKT) was detected under HBx Mut overexpression. Thus, it is proposed that HBx Mut enhances disease progression by reducing FOXO1 via phosphorylation of AKT. At the metabolomic level, HBx altered the expression of genes that participated in arachidonic acid (AA) metabolism, as a result of inflammation via accumulation of proinflammatory factors such as prostaglandins and leukotriene in liver. Taken together, the increased rate of HCC observed in chronic hepatitis B patients with K130M/V131I-mutated X protein, may be due to changes in AA metabolism and AKT/FOXO1 signaling. IMPLICATIONS: Our findings suggested that HBx-K130M/V131I-mutant variant promoted HCC progression by activating AKT/FOXO1 pathway and inducing stronger inflammation in liver via AA metabolism.

A study of the Group 1 metal tetra-aza macrocyclic complexes [M(Me4cyclen)(L)]+ using electronic structure calculations.

Metal-cyclen complexes have a number of important applications. However, the coordination chemistry between metal ions and cyclen-based macrocycles is much less well studied compared to their metal ion-crown ether analogues. This work, which makes a contribution to address this imbalance by studying complex ions of the type [M(Me4cyclen)(L)]+, was initiated by results of an experimental study which prepared some Group 1 metal cyclen complexes, namely [Li(Me4cyclen)(H2O)][BArF] and [Na(Me4cyclen)(THF)][BArF] and obtained their X-ray crystal structures [J. M. Dyke, W. Levason, M. E. Light, D. Pugh, G. Reid, H. Bhakhoa, P. Ramasami, and L. Rhyman, Dalton Trans., 2015, 44, 13853]. The lowest [M(Me4cyclen)(L)]+ minimum energy structures (M = Li, Na, K, and L = H2O, THF, DEE, MeOH, DCM) are studied using density functional theory (DFT) calculations. The geometry of each [M(Me4cyclen)(L)]+ structure and, in particular, the conformation of L are found to be mainly governed by steric hindrance which decreases as the size of the ionic radius increases from Li+ → Na+ → K+. Good agreement of computed geometrical parameters of [Li(Me4cyclen)(H2O)]+ and [Na(Me4cyclen)(THF)]+ with the corresponding geometrical parameters derived from the crystal structures [Li(Me4cyclen)(H2O)]+[BArF]- and [Na(Me4cyclen)(THF)]+[BArF]- is obtained. Bonding analysis indicates that the stability of the [M(Me4cyclen)(L)]+ structures originates mainly from ionic interaction between the Me4cyclen/L ligands and the M+ centres. The experimental observation that [M(Me4cyclen)(L)]+[BArF]- complexes could be prepared in crystalline form for M+ = Li+ and Na+, but that experiments aimed at synthesising the corresponding K+, Rb+, and Cs+ complexes failed resulting in formation of [Me4cyclenH][BArF] is investigated using DFT and explicitly correlated calculations, and explained by considering production of [Me4cyclenH]+ by a hydrolysis reaction, involving traces of water, which competes with [M(Me4cyclen)(L)]+ formation. [Me4cyclenH]+ formation dominates for M+ = K+, Rb+, and Cs+ whereas formation of [M(Me4cyclen)(L)]+ is energetically favoured for M+ = Li+ and Na+. The results indicate that the number and type of ligands, play a key role in stabilising the [M(Me4cyclen)]+ complexes and it is hoped that this work will encourage experimentalists to prepare and characterise other [M(Me4cyclen)(L)]+ complexes.

The Atmospherically Important Reaction of Hydroxyl Radicals with Methyl Nitrate: A Theoretical Study Involving the Calculation of Reaction Mechanisms, Enthalpies, Activation Energies, and Rate Coefficients.

A theoretical study, involving the calculation of reaction enthalpies, activation energies, mechanisms, and rate coefficients, was made of the reaction of hydroxyl radicals with methyl nitrate, an important process for methyl nitrate removal in the earth's atmosphere. Four reaction channels were considered: formation of H2O + CH2ONO2, CH3OOH + NO2, CH3OH + NO3, and CH3O + HNO3. For all channels, geometry optimization and frequency calculations were performed at the M06-2X/6-31+G** level, while relative energies were improved at the UCCSD(T*)-F12/CBS level. The major channel is found to be the H abstraction channel, to give the products H2O + CH2ONO2. The reaction enthalpy (ΔH298 KRX) of this channel is computed as -17.90 kcal mol-1. Although the other reaction channels are also exothermic, their reaction barriers are high (>24 kcal mol-1), and therefore these reactions do not contribute to the overall rate coefficient in the temperature range considered (200-400 K). Pathways via three transition states were identified for the H abstraction channel. Rate coefficients were calculated for these pathways at various levels of variational transition state theory including tunneling. The results obtained are used to distinguish between two sets of experimental rate coefficients, measured in the temperature range of 200-400 K, one of which is approximately an order of magnitude greater than the other. This comparison, as well as the temperature dependence of the computed rate coefficients, shows that the lower experimental values are favored. The implications of the results to atmospheric chemistry are discussed.

Direct Measurements of Unimolecular and Bimolecular Reaction Kinetics of the Criegee Intermediate (CH3)2COO.

The Criegee intermediate acetone oxide, (CH3)2COO, is formed by laser photolysis of 2,2-diiodopropane in the presence of O2 and characterized by synchrotron photoionization mass spectrometry and by cavity ring-down ultraviolet absorption spectroscopy. The rate coefficient of the reaction of the Criegee intermediate with SO2 was measured using photoionization mass spectrometry and pseudo-first-order methods to be (7.3 ± 0.5) × 10-11 cm3 s-1 at 298 K and 4 Torr and (1.5 ± 0.5) × 10-10 cm3 s-1 at 298 K and 10 Torr (He buffer). These values are similar to directly measured rate coefficients of anti-CH3CHOO with SO2, and in good agreement with recent UV absorption measurements. The measurement of this reaction at 293 K and slightly higher pressures (between 10 and 100 Torr) in N2 from cavity ring-down decay of the ultraviolet absorption of (CH3)2COO yielded even larger rate coefficients, in the range (1.84 ± 0.12) × 10-10 to (2.29 ± 0.08) × 10-10 cm3 s-1. Photoionization mass spectrometry measurements with deuterated acetone oxide at 4 Torr show an inverse deuterium kinetic isotope effect, kH/kD = (0.53 ± 0.06), for reactions with SO2, which may be consistent with recent suggestions that the formation of an association complex affects the rate coefficient. The reaction of (CD3)2COO with NO2 has a rate coefficient at 298 K and 4 Torr of (2.1 ± 0.5) × 10-12 cm3 s-1 (measured with photoionization mass spectrometry), again similar to rate for the reaction of anti-CH3CHOO with NO2. Cavity ring-down measurements of the acetone oxide removal without added reagents display a combination of first- and second-order decay kinetics, which can be deconvolved to derive values for both the self-reaction of (CH3)2COO and its unimolecular thermal decay. The inferred unimolecular decay rate coefficient at 293 K, (305 ± 70) s-1, is similar to determinations from ozonolysis. The present measurements confirm the large rate coefficient for reaction of (CH3)2COO with SO2 and the small rate coefficient for its reaction with water. Product measurements of the reactions of (CH3)2COO with NO2 and with SO2 suggest that these reactions may facilitate isomerization to 2-hydroperoxypropene, possibly by subsequent reactions of association products.

Simulation of the photodetachment spectrum of HHfO- using coupled-cluster calculations.

The photodetachment spectrum of HHfO- was simulated using restricted-spin coupled-cluster single-double plus perturbative triple {RCCSD(T)} calculations performed on the ground electronic states of HHfO and HHfO-, employing basis sets of up to quintuple-zeta quality. The computed RCCSD(T) electron affinity of 1.67 ± 0.02 eV at the complete basis set limit, including Hf 5s25p6 core correlation and zero-point energy corrections, agrees well with the experimental value of 1.70 ± 0.05 eV from a recent photodetachment study [X. Li et al., J. Chem. Phys. 136, 154306 (2012)]. For the simulation, Franck-Condon factors were computed which included allowances for anharmonicity and Duschinsky rotation. Comparisons between simulated and experimental spectra confirm the assignments of the molecular carrier and electronic states involved but suggest that the experimental vibrational structure has suffered from poor signal-to-noise ratio. An alternative assignment of the vibrational structure to that suggested in the experimental work is presented.

A theoretical study of the atmospherically important radical-radical reaction BrO + HO2; the product channel O2(a1Δg) + HOBr is formed with the highest rate.

A theoretical study has been made of the BrO + HO2 reaction, a radical-radical reaction which contributes to ozone depletion in the atmosphere via production of HOBr. Reaction enthalpies, activation energies and mechanisms have been determined for five reaction channels. Also rate coefficients have been calculated, in the atmospherically important temperature range 200-400 K, for the two channels with the lowest activation energies, both of which produce HOBr: (R1a) HOBr(X1A') + O2(X3Σ) and (R1b) HOBr(X1A') + O2(a1Δg). The other channels considered are: (R2) BrO + HO2 → HBr + O3, (R3) BrO + HO2 → OBrO + OH and (R4) BrO + HO2 → BrOO + OH. For all channels, geometry optimization and frequency calculations were carried out at the M06-2X/AVDZ level, while relative energies of the stationary points on the reaction surface were improved at a higher level (BD(TQ)/CBS or CCSD(T)/CBS). The computed standard reaction enthalpies (ΔH) for channels (R1a), (R1b), (R2), (R3) and (R4) are -47.5, -25.0, -4.3, 14.9 and 5.9 kcal mol-1, and the corresponding computed activation energies (ΔE) are 2.53, -3.07, 11.83, 35.0 and 37.81 kcal mol-1. These values differ significantly from those obtained in earlier work by Kaltsoyannis and Rowley (Phys. Chem. Chem. Phys., 2002, 4, 419-427), particularly for channel (R1b), and reasons for this are discussed. In particular, the importance of obtaining an open-shell singlet wavefunction, rather than a closed-shell singlet wavefunction, for the transition state of this channel is emphasized. Rate coefficient calculations from computed potential energy surfaces were made for BrO + HO2 for the first time. Although channel (R1a) is the most exothermic, channel (R1b) has the lowest barrier height, which is negative (at -3.07 kcal mol-1). Most rate coefficient calculations were therefore made for (R1b). A two transition state model has been used, involving an outer and an inner transition state. The inner transition state was found to be the major bottleneck of the reaction with the outer transition state having essentially no effect on the overall rate coefficient (k) in the temperature range considered. Studying the entropy, enthalpy and free energy of activation of this channel as a function of temperature shows that the main contributor to the magnitude of ln k at a selected temperature is the entropy term (ΔS#/kB) whereas the temperature dependence of ln k is determined mainly by the enthalpy term (-ΔH#/kBT). This compares with reactions with positive barrier heights where the enthalpy term makes a bigger contribution to ln k. Comparison of the computed rate coefficients with available experimental values shows that the computed values have a negative temperature dependence, as observed experimentally, but are too low by approximately an order of magnitude at any selected temperature in the range 200-400 K.

Simulation of the single-vibronic-level emission spectra of HAsO and DAsO.

The single-vibronic-level (SVL) emission spectra of HAsO and DAsO have been simulated by electronic structure/Franck-Condon factor calculations to confirm the spectral molecular carrier and to investigate the electronic states involved. Various multi-reference (MR) methods, namely, NEVPT2 (n-electron valence state second order perturbation theory), RSPT2-F12 (explicitly correlated Rayleigh-Schrodinger second order perturbation theory), and MRCI-F12 (explicitly correlated multi-reference configuration interaction) were employed to compute the geometries and relative electronic energies for the X̃(1)A(') and Ã(1)A(″) states of HAsO. These are the highest level calculations on these states yet reported. The MRCI-F12 method gives computed T0 (adiabatic transition energy including zero-point energy correction) values, which agree well with the available experimental T0 value much better than previously computed values and values computed with other MR methods in this work. In addition, the potential energy surfaces of the X̃(1)A(') and Ã(1)A(″) states of HAsO were computed using the MRCI-F12 method. Franck-Condon factors between the two states, which include anharmonicity and Duschinsky rotation, were then computed and used to simulate the recently reported SVL emission spectra of HAsO and DAsO [R. Grimminger and D. J. Clouthier, J. Chem. Phys. 135, 184308 (2011)]. Our simulated SVL emission spectra confirm the assignments of the molecular carrier, the electronic states involved, and the vibrational structures observed in the SVL emission spectra but suggest a loss of intensity in the reported experimental spectra at the low emission energy region almost certainly due to a loss of responsivity near the cutoff region (∼800 nm) of the detector used. Computed and experimentally derived re (equilibrium) and/or r0 {the (0,0,0) vibrational level} geometries of the two states of HAsO are discussed.

A Study of H2O2 with Threshold Photoelectron Spectroscopy (TPES) and Electronic Structure Calculations: Redetermination of the First Adiabatic Ionization Energy (AIE).

In this work, hydrogen peroxide has been studied with threshold photoelectron (TPE) spectroscopy and photoelectron (PE) spectroscopy. The TPE spectrum has been recorded in the 10.0-21.0 eV ionization energy region, and the PE spectrum has been recorded at 21.22 eV photon energy. Five bands have been observed which have been assigned on the basis of UCCSD(T)-F12/VQZ-F12 and IP-EOM CCSD calculations. Vibrational structure has only been resolved in the TPE spectrum of the first band, associated with the X̃(2)Bg H2O2(+) ← X̃(1)A H2O2 ionization, on its low energy side. This structure is assigned with the help of harmonic Franck-Condon factor calculations that use the UCCSD(T)-F12a/VQZ-F12 computed adiabatic ionization energy (AIE), and UCCSD(T)-F12a/VQZ-F12 computed equilibrium geometric parameters and harmonic vibrational frequencies for the H2O2 X̃(1)A state and the H2O2(+) X̃(2)Bg state. These calculations show that the main vibrational structure on the leading edge of the first TPE band is in the O-O stretching mode (ω3) and the HOOH deformation mode (ω4), and comparison of the simulated spectrum to the experimental spectrum gives the first AIE of H2O2 as (10.685 ± 0.005) eV and ω4 = (850 ± 30) and ω3 = (1340 ± 30) cm(-1) in the X̃(2)Bg state of H2O2(+). Contributions from ionization of vibrationally excited levels in the torsion mode have been identified in the TPE spectrum of the first band and the need for a vibrationally resolved TPE spectrum from vibrationally cooled molecules, as well as higher level Franck-Condon factors than performed in this work, is emphasized.

Novel cycloartane triterpenoid from Cimicifuga foetida (Sheng ma) induces mitochondrial apoptosis via inhibiting Raf/MEK/ERK pathway and Akt phosphorylation in human breast carcinoma MCF-7 cells.

BACKGROUND: Cycloartane triterpenoids exhibited anticancer effects. This study aims to identify any potential novel anticancer cycloartane triterpenoids from Cimicifuga foetida L. rhizome (Sheng ma) and the mode of actions. METHODS: Cycloartane triterpenoids were isolated from the C. foetida rhizome by a series of column chromatography and identified by IR, MS and NMR. Their anticancer effects on several human cancer cell lines, MCF-7, HepG2, HepG2/ADM, HeLa, and PC3, and normal human mammary epithelial cells MCF10A were investigated by colony formation and MTT assays. Morphological analysis of apoptosis induction was performed by acridine orange/ethidium bromide dual-staining and Hoechst 33258 nuclear staining. The cell-cycle profile and annexin V staining were evaluated by flow cytometry. Apoptosis were investigated by measuring changes in mitochondrial membrane potential and analyzing expression of cell cycle- and apoptosis-related proteins in MCF-7 cells by Western blotting. RESULTS: A novel cycloartane triterpenoid, 25-O-acetyl-7,8-didehydrocimigenol-3-O-ß-d-(2-acetyl)xylopyranoside (ADHC-AXpn), together with the known 7,8-didehydrocimigenol-3-O-ß-d-xylopyranoside (DHC-Xpn) were isolated. MCF-7 growth was significantly inhibited by ADHC-AXpn in a dose- and time-dependent manner (IC50: 27.81 µM at 48 h; P = 0.004 vs. control at 25 µM for 48 h treatment), and ADHC-AXpn was selectively cytotoxic for cancerous cells (MCF-7, HepG2/ADM, HepG2 and HELA cells) based on its higher IC50 values for normal cells MCF10A (IC50: 78.63 µM at 48 h) than for tumor cells. In MCF-7 cells, ADHC-AXpn induced G2/M cell cycle arrest by mediating cyclin-B1, and CDK1 and its phosphorylation; and induced apoptosis through the mitochondrial-mediated apoptotic pathway, with inhibition of Akt activation. As ADHC-AXpn suppressed phosphorylation of ERK1/2, Raf and Akt proteins in MCF-7 cells, its apoptotic effect might be associated with Raf/MEK/ERK signaling and Akt activation. CONCLUSIONS: ADHC-AXpn significantly suppressed the growth of MCF-7 cells, induced mitochondrial apoptosis and cell-cycle arrest, and inhibited Raf/MEK/ERK signaling pathway and Akt phosphorylation.

Reaction between CH3O2 and BrO radicals: a new source of upper troposphere lower stratosphere hydroxyl radicals.

Over the last two decades it has emerged that measured hydroxyl radical levels in the upper troposphere are often underestimated by models, leading to the assertion that there are missing sources. Here we report laboratory studies of the kinetics and products of the reaction between CH3O2 and BrO radicals that shows that this could be an important new source of hydroxyl radicals:BrO + CH3O2 → products (1). The temperature dependent value in Arrhenius form of k(T) is k1 = (2.42­0.72+1.02) × 10­14 exp[(1617 ± 94)/T] cm3 molecule­1 s­1. In addition, CH2OO and HOBr are believed to be the major products. Global model results suggest that the decomposition of H2COO to form OH could lead to an enhancement in OH of up to 20% in mid-latitudes in the upper troposphere and in the lower stratosphere enhancements in OH of 2­9% are inferred from model integrations. In addition, reaction 1 aids conversion of BrO to HOBr and slows polar ozone loss in the lower stratosphere.

A theoretical study of the mechanism of the atmospherically relevant reaction of chlorine atoms with methyl nitrate, and calculation of the reaction rate coefficients at temperatures relevant to the troposphere.

The reaction between atomic chlorine (Cl) and methyl nitrate (CH3ONO2) is significant in the atmosphere, as Cl is a key oxidant, especially in the marine boundary layer, and alkyl nitrates are important nitrogen-containing organic compounds, which are temporary reservoirs of the reactive nitrogen oxides NO, NO2 and NO3 (NOx). Four reaction channels HCl + CH2ONO2, CH3OCl + NO2, CH3Cl + NO3 and CH3O + ClNO2 were considered. The major channel is found to be the H abstraction channel, to give the products HCl + CH2ONO2. For all channels, geometry optimization and frequency calculations were carried out at the M06-2X/6-31+G** level, while relative electronic energies were improved to the UCCSD(T*)-F12/CBS level. The reaction barrier (ΔE(‡)0K) and reaction enthalpy (ΔH(RX)298K) of the H abstraction channel were computed to be 0.61 and -2.30 kcal mol(-1), respectively, at the UCCSD(T*)-F12/CBS//M06-2X/6-31+G** level. Reaction barriers (ΔE(‡)0K) for the other channels are more positive and these pathways do not contribute to the overall reaction rate coefficient in the temperature range considered (200-400 K). Rate coefficients were calculated for the H-abstraction channel at various levels of variational transition state theory (VTST) including tunnelling. Recommended ICVT/SCT rate coefficients in the temperature range 200-400 K are presented for the first time for this reaction. The values obtained in the 200-300 K region are particularly important as they will be valuable for atmospheric modelling calculations involving reactions with methyl nitrate. The implications of the results to atmospheric chemistry are discussed. Also, the enthalpies of formation, ΔHf,298K, of CH3ONO2 and CH2ONO2 were computed to be -29.7 and 19.3 kcal mol(-1), respectively, at the UCCSD(T*)-F12/CBS level.

Petroleum ether extractive of the hips of Rosa multiflora ameliorates collagen-induced arthritis in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: The hip of Rosa multiflora Thunb. (HRM) has been traditionally used as a dietary supplement and a herbal remedy for the treatment of various diseases, including inflammation, osteoarthritis, rheumatoid arthritis and chronic pain, in China. The current study was to evaluate the therapeutic efficacy of the petroleum ether extractive of HRM (PEE) on type II collagen-induced rheumatoid arthritis (CIA) in male Wistar rats. In addition, the anti-inflammatory mechanism(s) of PEE on type II CIA was explored. MATERIALS AND METHODS: Rheumatoid arthritis (RA) was induced by intradermal injection of bovine type II collagen on Day 1 and Day 8. Starting from Day 13, normal rats were treated with vehicle (serving as the control group); the CIA rats were treated with vehicle (CIA group), dexamethasone (0.25mg/kg bw per day, p.o.) (a positive control), lei-gong-teng (LGT: 10mg/kg bw per day, p.o.) (a clinically used Chinese patent medicine in RA therapy) or PEE (12, 36 or 120mg/kg bw per day, p.o.) for 28 days. RESULTS AND CONCLUSIONS: PEE (120mg/kg bw per day) efficiently attenuated the severity of arthritis in the CIA rats by reducing the mean arthritis severity scores and the fore/hind paw swelling as well as reduced histological changes by decreasing the cartilage surface erosion and cartilage proteoglan depletion. PEE׳s therapeutic effect in RA may involve the inhibition of pro-inflammatory cytokines, such as TNF-α, IL-1ß and IL-6, in serum and/or the elevation of the activities of hepatic anti-oxidative enzymes including SOD, CAT and GSH-Px. However, the detailed anti-inflammatory mechanism, the main effective components and the interaction between different ingredients in PEE are still not clear and require more studies.

Prediction of peptide fragment ion mass spectra by data mining techniques.

Accurate prediction of peptide fragment ion mass spectra is one of the critical factors to guarantee confident peptide identification by protein sequence database search in bottom-up proteomics. In an attempt to accurately and comprehensively predict this type of mass spectra, a framework named MS(2)PBPI is proposed. MS(2)PBPI first extracts fragment ions from large-scale MS/MS spectra data sets according to the peptide fragmentation pathways and uses binary trees to divide the obtained bulky data into tens to more than 1000 regions. For each adequate region, stochastic gradient boosting tree regression model is constructed. By constructing hundreds of these models, MS(2)PBPI is able to predict MS/MS spectra for unmodified and modified peptides with reasonable accuracy. Moreover, high consistency between predicted and experimental MS/MS spectra derived from different ion trap instruments with low and high resolving power is achieved. MS(2)PBPI outperforms existing algorithms MassAnalyzer and PeptideART.

Simulation of the single-vibronic-level emission spectrum of HPS.

We have computed the potential energy surfaces of the X¹A' and ùA" states of HPS using the explicitly correlated multi-reference configuration interaction (MRCI-F12) method, and Franck-Condon factors between the two states, which include anharmonicity and Duschinsky rotation, with the aim of testing the assignment of the recently reported single-vibronic-level (SVL) emission spectrum of HPS [R. Grimminger, D. J. Clouthier, R. Tarroni, Z. Wang, and T. J. Sears, J. Chem. Phys. 139, 174306 (2013)]. These are the highest level calculations on these states yet reported. It is concluded that our spectral simulation supports the assignments of the molecular carrier, the electronic states involved and the vibrational structure of the experimental laser induced fluorescence, and SVL emission spectra proposed by Grimminger et al. [J. Chem. Phys. 139, 174306 (2013)]. However, there remain questions unanswered regarding the relative electronic energies of the two states and the geometry of the excited state of HPS.

Rate coefficients of the Cl + CH3C(O)OCH3 → HCl + CH3C(O)OCH2 reaction at different temperatures calculated by transition-state theory with ab initio and density functional theory reaction paths.

The complex relationship of computed rate coefficients (k's) with different ab initio/DFT and TST levels was studied. The MEPs, gradients, and Hessians of the title reaction were computed using the MP2 and DFT methods. Electronic energies were improved to the UCCSD(T)-F12x/CBS level, and k's were calculated at the TST, CVT, and ICVT levels with various tunnelling corrections. Although computed microcanonical and tunnelling effects are small, computed k(TST) values are larger than computed k(TST/ZCT) and k(TST/SCT) values by 3 orders of magnitude at low temperatures, because computed κ((TST/CAG)) values are as small as 6 × 10(-4). In some cases, the maximum of the ΔG/s curves at a certain T is far away from the MEP maximum. This raises the question of the range of s to be considered in a VTST calculation and, of a possible scenario, where no maximum on the ΔG curve can be located and hence a breakdown of VTST occurs. For dual-level direct dynamics calculations, different entropic contributions from different lower levels can lead to computed k's, which differ by more than 1 order of magnitude. Matching computed and experimental k values leads to an empirical barrier of 1.34 kcal mol(-1) for the title reaction.