Amino acid profiles of young adults differ by sex, body mass index and insulin resistance.

BACKGROUND AND AIMS: An increase in plasma branched-chain amino acids is associated with a higher risk of developing type 2 diabetes and cardiovascular diseases. However, little is known about the basal plasma amino acid concentrations in young adults. Our aim was to determine the plasma amino acid profiles of young adults and to evaluate how these profiles were modified by sex, body mass index (BMI) and insulin resistance (IR). METHODS AND RESULTS: We performed a transversal study with 608 Mexican young adults aged 19.9 ± 2.4 years who were applicants to the Universidad Autónoma de San Luis Potosí. The subjects underwent a physical examination and provided a clinical history and a blood sample for biochemical, hormonal and amino acid analyses. The women had higher levels of arginine, aspartate and serine and lower levels of α-aminoadipic acid, cysteine, isoleucine, leucine, methionine, proline, tryptophan, tyrosine, urea and valine than the men. The obese subjects had higher levels of alanine, aspartate, cysteine, ornithine, phenylalanine, proline and tyrosine and lower levels of glycine, ornithine and serine than the normal weight subjects. Subjects with IR (defined as HOMA > 2.5) had higher levels of arginine, alanine, aspartate, isoleucine, leucine, phenylalanine, proline, tyrosine, taurine and valine than the subjects without IR. Furthermore, we identified two main groups in the subjects with obesity and/or IR; one group was composed of amino acids that positively correlated with the clinical, biochemical and hormonal parameters, whereas the second group exhibited negative correlations. CONCLUSION: This study demonstrates that young adults with obesity or IR have altered amino acid profiles characterized by an increase in alanine, aspartate, proline and tyrosine and a decrease in glycine.

O2(X³Σg⁻) and O2(a¹Δg) charge exchange with simple ions.

We present theory and experiments which describe charge transfer from the X³Σg⁻ and a(1)Δg states of molecular oxygen and atomic and molecular cations. Included in this work are new experimental results for O2(a(1)Δg) and the cations O(+), CO(+), Ar(+), and N2⁺, and new theory based on complete active space self-consistent field method calculations and an extended Langevin model to calculate rate constants for ground and excited O2 reacting with the atomic ions Ar(+), Kr(+), Xe(+), Cl(+), and Br(+). The T-shaped orientation of the (X - O2)(+) potential surface is used for the calculations, including all the low lying states up to the second singlet state of the oxygen molecule b¹Σ(g)⁺. The calculated rate constants for both O2(X³Σg⁻) and O2(a(1)Δg) show consistent trends with the experimental results, with a significant dependence of rate constant on charge transfer exothermicity that does not depend strongly on the nature of the cation. The comparisons with theory show that partners with exothermicities of about 1 eV have stronger interactions with O2, leading to larger Langevin radii, and also that more of the electronic states are attractive rather than repulsive, leading to larger rate constants. Rate constants for charge transfer involving O2(a(1)Δg) are similar to those for O2(X³Σg⁻) for a given exothermicity ignoring the electronic excitation of the O2(a(1)Δg) state. This means (and the electronic structure calculations support) that the ground and excited states of O2 have about the same attractive interactions with ions.

CONTROL OF VIRAL DISEASES TRANSMITTED IN A PERSISTENT MANNER BY THRIPS IN PEPPER (TOMATO SPOTTED WILT VIRUS).

Tomato spotted wilt disease is caused by Tomato Spotted Wilt Virus (TSWV) (Tospovirus, Bunyaviridae), a virus that severely damages and reduces the yield of many economically important plants worldwide and actually it is a major disease affecting the production of tomato and pepper in Italy. Due to the non-predictive nature of its outbreaks combined with the lack of forecasting, adoption of preventive measures have not always been practical, in fact the disease cycle has proven to be extremely difficult to break because of the wide and often overlapping host range of both the virus and the thrips vectors, which transmit the virus in a persistent, circulative, and propagative manner. Moreover recently, resistance breaking (RB) isolates of TSWV that overcome the resistance conferred by the Tsw gene in different pepper hybrids have been recovered in different locations in Italy and also in Brazil, USA, Spain and Australia, and this occurrence raises the question on the importance of a new approach of integrated pest management for TSWV management, including both control of its insect vector and the induction of the plant's resistance against viral infection. In this perspective, a study was performed in 2012 and 2013 with the purpose of evaluating the efficacy of the insecticide Cyantraniliprole alone or combined with Acibenzolar-S-Methyl (ASM), inducer of systemic acquired resistance, in the control of tomato spotted wilt disease in pepper. The experiment was performed in laboratory, in a thermo-conditioned greenhouse, into separate insect-proof cages and consisted of 5 treatments and 2 applications (plus a pre-transplant application for treatments were ASM was used. Variables were the mode of application of ASM in pre-transplant (by foliar or by drench) and the duration of the exposure time of the treated plants to viruliferous insects. Pepper cv. Corno di Toro, devoid of any resistance to TSWV, was used. Plants were observed daily to record any symptom induced by TSWV and/or of phytotoxicity. The possible TSWV infection was verified by DAS-ELISA using antisera supplied by Agdia Biofords. It was shown that the combination of ASM and Cyantraniliprole allowed the best control of TSWV transmission by thrips and of the development of the infection in treated pepper plants, regardless of the exposure time to thrips infestation. The application via drench of the combination seems to be the most effective. The efficacy of Cyantraniliprole used alone was comparable to that obtained with its combination with ASM only when plants were exposed to viruliferous insects for 24 h after product application, and the effectiveness of protection decreased with increasing time of exposure to viruliferous thrips. Treatment with ASM alone determined a good protection to plants regardless of the length of the exposure timing to viruliferous insects, with a smaller number of infected plants and milder symptoms compared to the check. Results of our current experiments raise the interesting possibility to combine in one product an insecticide and a non-specific (to various biotic and abiotic stresses) resistance inducer, particularly against diseases caused by viruses, and offer great opportunity for the integrated pest management (IPM) strategy for the control of pepper diseases.

Tanshinone VI inhibits the expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1.

This study investigated the possible antitumor mechanisms of action of Tanshinone VI, one of the components of Salvia miltiorrhiza Bunge, which is used in traditional Chinese herbal medicine. To this end, the expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1), were evaluated in-vitroin tumor necrosis factor-alpha (TNF-alpha)-stimulated endothelial cells, with, or without the addition of Tanshinone VI (10, 20, 30, or 40 mM) in the culture medium; the effects of Tanshinone VI on angiogenesis was also evaluated with an epithelial cell tube formation assay and its toxicity was evaluated with a colorimetric (MTT) cell viability assay. The results showed that the up-regulation of ICAM-1 and VCAM-1 induced by TNF-alpha was dose-dependently inhibited by Tanshinone VI, with restoration of control levels at the dose of 40 mM; Tanshinone VI also had a remarkable anti-angiogenesis effect, already at the dose of 10 mM, while none of the doses tested had significant effects on cell viability. These results indicate that the antitumor properties of Tanshinone VI can be ascribed to the inhibition of cell adhesion, due to blockage of the up-regulation of cell adhesion molecules, with the consequent inhibition of metastases formation and/or angiogenesis. The lack of toxic effects at the dosage used makes Tanshinone VI a good candidate for its therapeutic use in humans.

Resistance breaking tomato spotted wilt virus isolates on resistant pepper varieties in Italy.

In spring 2012, resistance breaking (RB) isolates of tomato spotted wilt virus (TSWV) that overcome the resistance conferred by the Tsw gene in different pepper hybrids have been recovered in different locations in southern Italy (Campania and Apulia regions) in protected cultivation, about one month after transplant. The percentage of symptomatic plants was 5-10% and, only in particular cases of advanced stage of cultivation, it reached 30-50% at the end of cycle. All TSWV isolates induced similar systemic symptoms in all resistant infected pepper hybrids: yellowing or browning of apical leaves, which later become necrotic, long necrotic streakson stems, extending to the terminal shoots, complete necrosis of younger fruits and large necrotic streaks and spots on fruits formed after infection. On ripe fruits, yellow spots with concentric rings or necrotic streaks could be observed. Leaf extracts of these samples were tested in ELISA for the detection of TSWV, Cucumber mosaic virus (CMV), Tobacco mosaic virus (TMV), Tomato mosaic virus (ToMV), Impatiens necrotic spot virus (INSV), Potato virus Y (PVY), Alfalfa mosaic virus (AMV), Pepper mild mottle virus (PMMoV) and Pepper Mottle Virus (PepMoV). Only TSWV was detected in all the field samples tested. The correspondent virus isolates were inoculated mechanically and by Frankliniella occidentalis on to a set of different pepper and tomato hybrids, as well as on some herbaceous test plants, in order to investigate for their ability to overcome the resistance genes Tsw and Sw5, respectively. Tomato hybrids carrying the Sw5 gene were uninfected by all RB isolates, whereas all resistant pepper hybrids became systemically infected. RB isolates did not differ noticeably in transmission efficiency when they were tested with the thrips F. occidentalis. Obtained results demonstrate that evolved strains of TSWV have emerged, that they are able to overcome the Tsw resistance gene in pepper plants experimentally inoculated both by mechanical infection and by the vector F. accidentalis. Moreover, evolved strains, here indicated as TSWV-RB-PI (Pepper, Italy), are not able to infect tomato plants carrying the Sw5 gene, confirming that distinct viral gene products control the outcome of infection in plants carrying Sw5 and Tsw. The simultaneous presence of evolved TSWV strains, showing the same biological characteristics (such as host range and symptomatology on different hosts) in two geographic areas of southern Italy, very far each other, let us hypothesize a unique focus of infection. Only subsequently, infected plants, through trade of plant material, have been diffused in locations so far apart. Further molecular studies are underway to assess the possible correlation between the different isolates in different geographical areas.

Inhibition of long-term potentiation by CuZn superoxide dismutase injection in rat dentate gyrus: involvement of muscarinic M1 receptor.

Long-term potentiation (LTP) and long-term depression represent important processes that modulate synaptic transmission that carries out a key role in neural mechanisms of memory. Many studies give strong evidences on a role of the reactive oxygen species in the induction of LTP in CA1 region of hippocampal slices that was inhibited by adding the scavenger enzyme superoxide dismutase (SOD1). Previous data showed that SOD1 is secreted by many cellular lines, including neuroblastoma SK-N-BE cells through microvesicles by an ATP-dependent mechanism; moreover, it has been shown that SOD1 interacts with human neuroblastoma cell membranes increasing intracellular calcium levels via a phospholipase C-protein kinase C pathway activation. The aim of this study was to investigate the effect of intracerebral injection of SOD1 or the inactive form of enzyme (ApoSOD) on the modulation of synaptic transmission in dentate gyrus of the hippocampus in urethane anesthetized rats. The results of the present research showed that intracerebral injection of SOD1 and ApoSOD in the dentate gyrus of the rat hippocampal formation inhibits LTP induced by high-frequency stimulation of the perforant path. This result cannot be only explained by the dismutation of oxygen radical induced by SOD1 since also ApoSOD, that lacks the enzymatic activity, carries out the same inhibitory effect on LTP induction.

Electron attachment to C7F14, thermal detachment from C7F14(-), the electron affinity of C7F14, and neutralization of C7F14(-) by Ar+.

Rate coefficients and branching fractions have been measured for electron attachment to perfluoromethylcyclohexane, C(7)F(14), along with thermal detachment rate coefficients for C(7)F(14)(-), from 300 to 630 K, using a flowing-afterglow Langmuir-probe apparatus. The attachment rate coefficient at room temperature is 4.5 ± 1.2 × 10(-8) cm(3) s(-1) and increases with temperature at a rate described by an activation energy of 50 ± 25 meV. Thermal electron detachment is negligible at room temperature, but measurable at 600 K and above, reaching 2300 ± 1300 s(-1) at 630 K. Analysis of the attachment-detachment equilibrium yields EA(C(7)F(14)) = 1.02 ± 0.06 eV, in agreement with the literature value while more than halving the uncertainty. Implications of the measurement for the electron affinity of SF(6) are discussed. The dominant product of electron attachment is the parent anion, but C(6)F(11)(-) and C(7)F(13)(-) are also observed at very low levels (<0.1%) at room temperature and increase in importance as the temperature is increased, reaching ~10% each at 630 K. In the course of this work we have also measured rate coefficients for the neutralization of C(7)F(14)(-) by Ar(+) at 300, 400, and 500 K: 4.8, 3.5, and 3.1 × 10(-8) cm(3) s(-1), respectively, with uncertainties of ±5 × 10(-9) cm(3) s(-1).

Electron attachment to fluorocarbon radicals.

Thermal electron attachment rate constants for a series of small fluorocarbon radicals (CF(2), C(2)F(3), 1-C(3)F(7), 2-C(3)F(7), C(3)F(5), CF(3)O) were measured from 300 to 600 K using the variable electron and neutral density attachment mass spectrometry method. With the exception of CF(2), for which no attachment was observed, all species exclusively underwent dissociative attachment to yield F(-). The magnitude and temperature dependences of the rate constants varied significantly between species; however, attachment was in all cases inefficient, never exceeding 2% of the calculated collisional value. The data are interpreted and extrapolated to conditions inaccessible to the experiment using a kinetic modeling approach to the electron attachment process.

Behavior of rate coefficients for ion-ion mutual neutralization, 300-550 K.

Rate coefficients k(MN) have been measured for a number of anion neutralization reactions with Ar(+) and Kr(+) over the temperature range 300-550 K. For the first time, the data set includes anions of radicals and other short-lived species. In the present paper, we review these results and make note of correlations with reduced mass, electron binding energy of the anion (equivalent to the electron affinity of the corresponding neutral), and temperature, and compare with expectations from absorbing sphere models. An intriguing result is that the data for diatomic anions neutralized by Ar(+) and Kr(+) have k(MN) values close to 3 × 10(-8) cm(3) s(-1) at 300 K, a figure which is lower than those for all of the polyatomic anions at 300 K except for SF(5)(-) + Kr(+). For the polyatomic anions studied here, neutralized by Ar(+) and Kr(+), the reduced mass dependence agrees with theory, on average, but we find a stronger temperature dependence of T(-0.9) than expected from the theoretical E(-0.5) energy dependence of the rate coefficient at thermal energies. The k(MN) show a weak dependence on the electron binding energy of the anion for the polyatomic species studied.

Kinetics of electron attachment to OH and HNO3 and mutual neutralization of Ar+ with NO2(-) and NO3(-) at 300 and 500 K.

The electron attachment rate constant to nitric acid (HNO(3)) has been measured in a flowing afterglow-Langmuir probe (FALP) apparatus at 300 and 500 K using three independent methods: the traditional FALP technique of monitoring electron depletion, "one-gas" VENDAMS (variable electron and neutral density attachment mass spectrometry), and "two-gas" VENDAMS. The three measurements are in agreement with a 300 K weighted average of 1.4 ± 0.3 × 10(-7) cm(3) s(-1), 2 to 10 times higher than previously reported values. Attachment is primarily dissociative yielding NO(2)(-) as previously reported, but for the first time a small endothermic channel to produce OH(-) was also observed at 500 K. From the one-gas VENDAMS data, associative attachment to the OH produced in the primary attachment was found to occur with an effective two body rate constant of 1.2±(0.7) (3)×10(-11) cm(3) s(-1) at 300 K, the first reported rate constant for this radical species. Finally, ion-ion neutralization rate constants of NO(2)(-) and NO(3)(-) with Ar(+) were determined to be 5.2±(2.5) (1.5) × 10(-8) and 4.5 ± 2.5 × 10(-8) cm(3) s(-1) at 300 K, respectively.

Electron attachment to 14 halogenated alkenes and alkanes, 300-600 K.

Thermal electron attachment to 14 alkenes and alkanes with bromine, fluorine, and iodine substituents has been studied over the temperature range 300-600 K using a flowing-afterglow Langmuir-probe apparatus. Rate coefficients and anion products are reported, most for the first time. Among these were 3 isomers of C(3)F(5)Br and the 2 isomers of C(3)F(7)I. Four dibromide compounds were studied, all of which yield Br(2)(-) product in addition to Br(-) product. The results are analyzed using a statistical kinetic modeling approach, which is able to reproduce both attachment rate coefficients and product branching ratios within experimental uncertainty. The kinetic modeling indicates that factor of 2 differences in attachment rate coefficients to the isomeric species can be explained by subtle variations in the potential surfaces.

O2(a1Δg) + Mg, Fe, and Ca: experimental kinetics and formulation of a weak collision, multiwell master equation with spin-hopping.

The first excited electronic state of molecular oxygen, O(2)(a(1)Δ(g)), is formed in the upper atmosphere by the photolysis of O(3). Its lifetime is over 70 min above 75 km, so that during the day its concentration is about 30 times greater than that of O(3). In order to explore its potential reactivity with atmospheric constituents produced by meteoric ablation, the reactions of Mg, Fe, and Ca with O(2)(a) were studied in a fast flow tube, where the metal atoms were produced either by thermal evaporation (Ca and Mg) or by pulsed laser ablation of a metal target (Fe), and detected by laser induced fluorescence spectroscopy. O(2)(a) was produced by bubbling a flow of Cl(2) through chilled alkaline H(2)O(2), and its absolute concentration determined from its optical emission at 1270 nm (O(2)(a(1)Δ(g) - X(3)Σ(g) (-)). The following results were obtained at 296 K: k(Mg + O(2)(a) + N(2) → MgO(2) + N(2)) = (1.8 ± 0.2) × 10(-30) cm(6) molecule(-2) s(-1); k(Fe + O(2)(a) → FeO + O) = (1.1 ± 0.1) × 10(-13) cm(3) molecule(-1) s(-1); k(Ca + O(2)(a) + N(2) → CaO(2) + N(2)) = (2.9 ± 0.2) × 10(-28) cm(6) molecule(-2) s(-1); and k(Ca + O(2)(a) → CaO + O) = (2.7 ± 1.0) × 10(-12) cm(3) molecule(-1) s(-1). The total uncertainty in these rate coefficients, which mostly arises from the systematic uncertainty in the O(2)(a) concentration, is estimated to be ±40%. Mg + O(2)(a) occurs exclusively by association on the singlet surface, producing MgO(2)((1)A(1)), with a pressure dependent rate coefficient. Fe + O(2)(a), on the other hand, shows pressure independent kinetics. FeO + O is produced with a probability of only ∼0.1%. There is no evidence for an association complex, suggesting that this reaction proceeds mostly by near-resonant electronic energy transfer to Fe(a(5)F) + O(2)(X). The reaction of Ca + O(2)(a) occurs in an intermediate regime with two competing pressure dependent channels: (1) a recombination to produce CaO(2)((1)A(1)), and (2) a singlet∕triplet non-adiabatic hopping channel leading to CaO + O((3)P). In order to interpret the Ca + O(2)(a) results, we utilized density functional theory along with multireference and explicitly correlated CCSD(T)-F12 electronic structure calculations to examine the lowest lying singlet and triplet surfaces. In addition to mapping stationary points, we used a genetic algorithm to locate minimum energy crossing points between the two surfaces. Simulations of the Ca + O(2)(a) kinetics were then carried out using a combination of both standard and non-adiabatic Rice-Ramsperger-Kassel-Marcus (RRKM) theory implemented within a weak collision, multiwell master equation model. In terms of atmospheric significance, only in the case of Ca does reaction with O(2)(a) compete with O(3) during the daytime between 85 and 110 km.

Dissociative electron attachment to C2F5 radicals.

Dissociative electron attachment to the reactive C(2)F(5) molecular radical has been investigated with two complimentary experimental methods; a single collision beam experiment and a new flowing afterglow Langmuir probe technique. The beam results show that F(-) is formed close to zero electron energy in dissociative electron attachment to C(2)F(5). The afterglow measurements also show that F(-) is formed in collisions between electrons and C(2)F(5) molecules with rate constants of 3.7 × 10(-9) cm(3) s(-1) to 4.7 × 10(-9) cm(3) s(-1) at temperatures of 300-600 K. The rate constant increases slowly with increasing temperature, but the rise observed is smaller than the experimental uncertainty of 35%.

Electron-catalyzed mutual neutralization of various anions with Ar+: evidence of a new plasma process.

The mutual neutralization of anions with Ar+ has been studied by variable electron and neutral density attachment mass spectrometry. Evidence of a previously unobserved plasma loss process, electron-catalyzed mutual neutralization (ECMN), e.g., SF6-+Ar+ + e-→neutrals + e-, is reported. Results for 10 species suggest that ECMN occurs generally and significantly affects the total ion-loss rate in plasmas with electron densities exceeding 10(10) cm-3. ECMN is discussed in the context of other known three-body plasma processes, the mechanisms for which appear insufficient to explain the observed effect. A mechanism for ECMN involving an incident electron facilitating energy transfer to the internal modes of the anion is proposed.

Reaction of HOD+ with NO2: effects of OD and OH stretching, bending, and collision energy on reactions on the singlet and triplet potential surfaces.

Integral cross sections and product recoil velocity distributions were measured for the reaction of HOD(+) with NO(2), in which the HOD(+) reactant was prepared in its ground state and with mode-selective excitation in the 001 (OH stretch), 100 (OD stretch), and 010 (bend) modes. In addition, we measured the 300 K thermal kinetics in a selected ion flow tube reactor and report product branching ratios different from previous measurements. Reaction is found to occur on both the singlet and triplet surfaces with near-unit efficiency. At 300 K, the product branching indicates that triplet → singlet transitions occur in about 60% of triplet-coupled collisions, which we attribute to long interaction times mediated by complexes on the triplet surface. Because the collision times are much shorter in the beam experiments, the product distributions show no signs of such transitions. The dominant product on the singlet surface is charge transfer. Reactions on the triplet surface lead to NO(+), NO(2)H(+), and NO(2)D(+). There is also charge transfer, producing NO(2)(+) (a(3)B(2)); however, this triplet NO(2)(+) mostly predissociates. The NO(2)H(+)/NO(2)D(+) cross sections peak at low collision energies and are insignificant above ~1 eV due to OH/OD loss from the nascent product ions. The effects of HOD(+) vibration are mode-specific. Vibration inhibits charge transfer, with the largest effect from the bend. The NO(2)H(+)/NO(2)D(+) channels are also vibrationally inhibited, and the mode dependence reveals how energy in different reactant modes couples to the internal energy of the product ions.

Electron attachment to POCl3. III. Measurement and kinetic modeling of branching fractions.

Electron attachment to POCl(3) was studied in the bath gas He over the pressure range 0.4-3.1 Torr and the temperature range 300-1210 K. Branching fractions of POCl(3)(-), POCl(2)(-), Cl(-), and Cl(2)(-) were measured. The results are analyzed by kinetic modeling, using electron attachment theory for the characterization of the nonthermal energy distribution of the excited POCl(3)(-∗) anions formed and chemical activation-type unimolecular rate theory for the subsequent competition between collisional stabilization of POCl(3)(-∗) and its dissociation to various dissociation products. Primary and secondary dissociations and∕or thermal dissociations of the anions are identified. The measured branching fractions are found to be consistent with the modeling results based on molecular parameters obtained from quantum-chemical calculations.

Kinetics of electron attachment to SF3CN, SF3C6F5, and SF3 and mutual neutralization of Ar+ with CN- and C6F5(-).

The additions of two sulfur fluoride derivatives (SF(3)C(6)F(5) and SF(3)CN) to a flowing afterglow were studied by variable electron and neutral density mass spectrometry. Data collection and analysis were complicated by the high reactivity of the neutral species. Both species readily dissociatively attach thermal electrons at 300 K to yield SF(3) + X(-) (X = C(6)F(5), CN). Attachment to SF(3)C(6)F(5) also results in SF(3)(-) + C(6)F(5) as a minor product channel. The determined electron attachment rate constants were 1(-0.6) (+1) × 10(-7) cm(3) s(-1) for SF(3)C(6)F(5), a lower limit of 1 × 10(-8) cm(3) s(-1) for SF(3)CN, and 4 ± 3 × 10(-9) cm(3) s(-1) for SF(3). Mutual neutralization rate constants of C(6)F(5)(-) and CN(-) with Ar(+) at 300 K were determined to be 5.5(-1.6) (+1.0) × 10(-8) and 3.0 ± 1 × 10(-8) cm(3) s(-1), respectively.

Ion chemistry of VX surrogates and ion energetics properties of VX: new suggestions for VX chemical ionization mass spectrometry detection.

Room temperature rate constants and product ion branching ratios have been measured for the reactions of numerous positive and negative ions with VX chemical warfare agent surrogates representing the amine (triethylamine) and organophosphonate (diethyl methythiomethylphosphonate (DEMTMP)) portions of VX. The measurements have been supplemented by theoretical calculations of the proton affinity, fluoride affinity, and ionization potential of VX and the simulants. The results show that many proton transfer reactions are rapid and that the proton affinity of VX is near the top of the scale. Many proton transfer agents should detect VX selectively and sensitively in chemical ionization mass spectrometers. Charge transfer with NO(+) should also be sensitive and selective since the ionization potential of VX is small. The surrogate studies confirm these trends. Limits of detection for commercial and research grade CIMS instruments are estimated at 80 pptv and 5 ppqv, respectively.

Reexamination of the quenching of NO(+) vibrations by O(2)(a (1)Delta(g)).

The quenching of vibrationally excited NO(+) by O(2)(a (1)Delta(g)) has been examined using the monitor ion technique and chemical generation of O(2)(a (1)Delta(g)). In contrast to previous results which showed that the rate constant was much larger than for ground state O(2), this study finds that the rate constant for quenching is below the detection limit (<10(-11) cm(3) s(-1)) of this experiment. The previous experiments produced O(2)(a (1)Delta(g)) in a discharge, which would also produces O atoms. We found that the monitor ion CH(3)I(+) reacts with O atoms to produce CHIOH(+). This is the likely cause of error in the previous experiments.

Survey of the reactivity of O(2)(a (1)Delta(g)) with negative ions.

The reactivity of O(2)(a (1)Delta(g)) was studied with a series of anions, including (-)CH(2)CN, (-)CH(2)NO(2), (-)CH(2)C(O)H, CH(3)C(O)CH(2)(-), C(2)H(5)O(-), (CH(3))(2)CHO(-), CF(3)CH(2)O(-), CF(3)(-), HC(2)(-), HCCO(-), HC(O)O(-), CH(3)C(O)O(-), CH(3)OC(O)CH(2)(-), and HS(-). Reaction rate constants and product ion branching ratios were measured. All of the carbanions react through a common pathway to produce their major products. O(2)(a) adds across a bond at the site of the negative charge, resulting in the cleavage of this bond and the O=O bond. Oxyanions react through a hydride transfer to produce their major products. Proton transfer within these product ion-dipole complexes can occur, where the final branching ratios reflect the basicity of the resulting anions. Several of these anions (CF(3)(-), HC(2)(-), CH(3)OC(O)CH(2)(-)) were also found to undergo several sequential reactions within a single encounter. These three basic types of mechanisms are supported by calculations; a potential energy diagram for each type of reaction has been calculated. Additionally, six of these reactions had been qualitatively studied before; our results are in agreement with previous data.