Medulla Tetrapanacis water extract alleviates inflammation and infection by regulating macrophage polarization through MAPK signaling pathway.

Medulla Tetrapanacis (MT) is a commonly used herb to promote lactation and manage mastitis in lactating mothers. However, its anti-inflammatory and anti-bacterial effects are currently unknown. We hypothesized that MT water extract possesses anti-inflammatory and anti-bacterial effects by modulating macrophage polarization to reduce the release of inflammatory mediators and phagocytosis via inactivation of MAPKs pathways. The chemical composition of the MT water extract was analyzed by UPLC-Orbitrap-mass spectrometry. The anti-inflammatory and anti-bacterial properties of the MT water extract were examined using LPS-stimulated inflammation and Staphylococcus aureus infection model in RAW 264.7 cells, respectively. The underlying mechanism of action of the MT water extract was also investigated. We identified eight compounds by UPLC-Orbitrap-mass spectrometry that are abundant within the MT water extract. MT water extract significantly suppressed LPS-induced nitric oxide, TNF-α and IL-6 secretion in RAW 264.7 cells which was accompanied by the promotion of macrophage polarization from pro-inflammatory towards anti-inflammatory phenotypes. MT water extract significantly suppressed the LPS-induced MAPK activation. Finally, MT water extract decreased the phagocytic capacity of the RAW 264.7 cells against S. aureus infection. MT water extract could suppress LPS-induced inflammation by promoting macrophages towards an anti-inflammatory phenotype. In addition, MT also inhibited the growth of S. aureus.

Variables associated with nonresponders to high-frequency (10 kHz) spinal cord stimulation.

INTRODUCTION: The use of spinal cord stimulation (SCS) therapy to treat chronic pain continues to rise. Optimal patient selection remains one of the most important factors for SCS success. However, despite increased utilization and the existence of general indications, predicting which patients will benefit from neuromodulation remains one of the main challenges for this therapy. Therefore, this study aims to identify the variables that may correlate with nonresponders to high-frequency (10 kHz) SCS to distinguish the subset of patients less likely to benefit from this intervention. MATERIALS AND METHODS: This was a retrospective single-center observational study of patients who underwent 10 kHz SCS implant. Patients were divided into nonresponders and responders groups. Demographic data and clinical outcomes were collected at baseline and statistical analysis was performed for all continuous and categorical variables between the two groups to calculate statistically significant differences. RESULTS: The study population comprised of 237 patients, of which 67.51% were responders and 32.49% were nonresponders. There was a statistically significant difference of high levels of kinesiophobia, high self-perceived disability, greater pain intensity, and clinically relevant pain catastrophizing at baseline in the nonresponders compared to the responders. A few variables deemed potentially relevant, such as age, gender, history of spinal surgery, diabetes, alcohol use, tobacco use, psychiatric illness, and opioid utilization at baseline were not statistically significant. CONCLUSION: Our study is the first in the neuromodulation literature to raise awareness to the association of high levels of kinesiophobia preoperatively in nonresponders to 10 kHz SCS therapy. We also found statistically significant differences with greater pain intensity, higher self-perceived disability, and clinically relevant pain catastrophizing at baseline in the nonresponders relative to responders. It may be appropriate to screen for these factors preoperatively to identify patients who are less likely to respond to SCS. If these modifiable risk factors are present, it might be prudent to consider a pre-rehabilitation program with pain neuroscience education to address these factors prior to SCS therapy, to enhance successful outcomes in neuromodulation.

CAM photosynthesis in Bulnesia retama (Zygophyllaceae), a non-succulent desert shrub from South America.

BACKGROUND AND AIMS: Bulnesia retama is a drought-deciduous, xerophytic shrub from arid landscapes of South America. In a survey of carbon isotope ratios (δ13C) in specimens from the field, B. retama exhibited less negative values, indicative of CAM or C4 photosynthesis. Here, we investigate whether B. retama is a C4 or CAM plant. METHODS: Gas-exchange responses to intercellular CO2, diurnal gas-exchange profiles, δ13C and dawn vs. afternoon titratable acidity were measured on leaves and stems of watered and droughted B. retama plants. Leaf and stem cross-sections were imaged to determine whether the tissues exhibited succulent CAM or C4 Kranz anatomy. KEY RESULTS: Field-collected stems and fruits of B. retama exhibited δ13C between -16 and -19 ‰. Plants grown in a glasshouse from field-collected seeds had leaf δ13C values near -31 ‰ and stem δ13C values near -28 ‰. The CO2 response of photosynthesis showed that leaves and stems used C3 photosynthesis during the day, while curvature in the nocturnal response of net CO2 assimilation rate (A) in all stems, coupled with slightly positive rates of A at night, indicated modest CAM function. C4 photosynthesis was absent. Succulence was absent in all tissues, although stems exhibited tight packing of the cortical chlorenchyma in a CAM-like manner. Tissue titratable acidity increased at night in droughted stems. CONCLUSIONS: Bulnesia retama is a weak to modest C3 + CAM plant. This is the first report of CAM in the Zygophyllaceae and the first showing that non-succulent, xerophytic shrubs use CAM. CAM alone in B. retama was too limited to explain less negative δ13C in field-collected plants, but combined with effects of low stomatal and mesophyll conductance it could raise δ13C to observed values between -16 and -19 ‰. Modest CAM activity, particularly during severe drought, could enable B. retama to persist in arid habitats of South America.

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.

Arnicolide D Inhibits Triple Negative Breast Cancer Cell Proliferation by Suppression of Akt/mTOR and STAT3 Signaling Pathways.

Triple-Negative Breast Cancer (TNBC) is a most dangerous breast cancer subtype. The naturally occurring sesquiterpene lactone, arnicolide D (AD), has proven effective against a variety of tumors, however, the inhibitory effects of AD against TNBC and the underlying mechanisms remain unclear. In the present study, two TNBC cell lines (MDA-MB-231 and MDA-MB-468) and an MDA-MB-231 xenograft mouse model were employed to investigate the anti-TNBC effects of AD in vitro and in vivo. Cell viability was assessed by MTT assay. Cell cycle arrest and apoptosis were analyzed by flow cytometry. Protein levels were determined by immunoblotting. In vitro studies demonstrated that AD significantly decreased cell viability, and induced G2/M cell cycle arrest and apoptosis. In vivo assays showed that oral administration of 25 or 50 mg/kg AD for 22 days led to a reduction of tumor weights by 24.7% or 41.0%, without appreciable side effects. Mechanistically, AD inhibited the activation of Akt/mTOR and STAT3 signaling pathways. Based on our findings, AD is a promising candidate for development as an adjunctive therapeutic drug for TNBC.

NMR Applications for Botanical Mixtures: The Use of HSQC Data to Determine Lignan Content in Sambucus williamsii.

Lignans found in the botanical extract of the Traditional Chinese Medicine Sambucus williamsii Hance exhibit protective effects on trabecular bone mass and mechanical strength of cortical bone of ovariectomized rats. A novel approach was adapted using HSQC NMR methods to estimate the total amount of these bioactives in a complex mixture. It was determined that lignans possessing the hydroxy- or oxybenzyl carbon signal were bioactive. These compounds were readily identified and assigned in a defined region of the 13C NMR spectrum at 80-90 ppm and calculated as 10-15% of the lignan-rich fraction of S. williamsii. Comparison of the peak heights of the oxybenzyl-substituted carbon resonance signals of the lignans in the botanical extract was made against those of a standard lignan pinoresinol. The application of this simple and reliable NMR method can be used to estimate amounts of related compounds and chemical families in complex mixtures or botanical extracts and offers measurable scientific evidence in quality processes. This is of particular importance for registration requirements of botanical drugs and in complex mixtures of botanical extracts.

Arnicolide D, from the herb Centipeda minima, Is a Therapeutic Candidate against Nasopharyngeal Carcinoma.

Nasopharyngeal carcinoma (NPC) is a high morbidity and mortality cancer with an obvious racial and geographic bias, particularly endemic to Southeast China. Our previous studies demonstrated that Centipeda minima extract (CME) exhibited anti-cancer effects in human NPC cell lines. Arnicolide C and arnicolide D are sesquiterpene lactones isolated from Centipeda minima. In this study, for the first time, we investigated their anti-NPC effects and further explored the related molecular mechanisms. The effects of both arnicolide C and arnicolide D were tested in NPC cells CNE-1, CNE-2, SUNE-1, HONE1, and C666-1. The results showed that the two compounds inhibited NPC cell viability in a concentration- and time-dependent manner. As the inhibitory effect of arnicolide D was the more pronounced of the two, our following studies focused on this compound. Arnicolide D could induce cell cycle arrest at G2/M, and induce cell apoptosis. The molecular mechanism of cell cycle regulation and apoptosis induction was investigated, and the results showed that arnicolide D could downregulate cyclin D3, cdc2, p-PI3K, p-AKT, p-mTOR, and p-STAT3, and upregulate cleaved PARP, cleaved caspase 9, and Bax. Regulation of cyclin B1, cdk6, and Bcl-2 expression by arnicolide D showed dynamic changes according to dose and time. Taken together, arnicolide D modulated the cell cycle, activated the caspase signaling pathway, and inhibited the PI3K/AKT/mTOR and STAT3 signaling pathways. These findings provide a solid base of evidence for arnicolide D as a lead compound for further development, and act as proof for the viability of drug development from traditional Chinese medicines.

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.

Point-of-care ultrasonography in Canadian anesthesiology residency programs: a national survey of program directors.

PURPOSE: Point-of-care ultrasonography (POCUS) is a useful tool with multiple perioperative applications relevant to the anesthesiologist. Nevertheless, the full scope of POCUS applications has yet to be formally incorporated into Canadian anesthesiology training. The purpose of this study was to determine the current state of POCUS training in Canadian anesthesiology residency programs. METHODS: We conducted a web-based survey of program directors from Royal College-accredited anesthesiology residency programs across Canada. Respondents were asked about POCUS training and assessment strategies at their institution as well as perceived barriers to POCUS education. We also elicited program directors' views on the importance of various POCUS applications as well as future direction of POCUS education within Canadian anesthesiology residency programs. RESULTS: Thirteen of 17 (76%) program directors responded to our survey. All respondents' residency programs provide some training in POCUS-facilitated vascular access, peripheral nerve blocks, neuraxial techniques, and transthoracic echocardiography. Nevertheless, training varies significantly for the other POCUS applications in our survey. The most frequently quoted teaching method employed is informal bedside teaching, followed by structured expert demonstration, hands-on scanning, and didactic lectures. The most frequently quoted barrier to teaching POCUS is the lack of trained staff. The majority of respondents agreed that competence in POCUS is important for graduating anesthesiology residents, and that POCUS should be incorporated into the National Curriculum for Canadian Anesthesiology Residency. CONCLUSION: Point-of-care ultrasonography training within Canadian anesthesiology residency programs is highly variable. Given the importance of POCUS abilities and their relevance to modern anesthesia practice, POCUS training and assessment within Canadian anesthesiology residency programs should be formalized.

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.

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.

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.

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 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.

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.

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.