Relative Yields Of Products Research Articles

Stability calculations for Eu@C74 isomers

AbstractDensity functional theory (DFT) calculations are reported for Eu@C74, where the considered C74 cage is either the IPR (isolated pentagon rule) species or two cages with a pentagon–pentagon junction. Their relative thermodynamic production yields are evaluated using the DFT calculated terms and it is shown that the IPR‐based Eu@C74 endohedral prevails at relevant temperatures in agreement with observation, however, isolation of a minor isomer should be possible.

Ratio quantification of gene dosage by Agilent 2100 Bioanalyzer for detection of somatic gene deletions

We applied the Agilent 2100 Bioanalyzer, a microfluidics-based electrophoresis instrument, and introduced an accurate and consistent parameter, the relative product yield ratio (ROY), to detect somatic gene deletions in tumor cells. Briefly for such purpose, the Agilent 2100 Bioanalyzer quantified the ROY of a target gene to an endogenous internal control, both of which were initially co-amplified by Robust-Dosage PCR (RD- PCR). Herein, we extensively validated this approach. We first tested the effect of well positions on the Agilent DNA chip. We found that no matter which wells the samples were loaded in, the ROY was consistent with coefficient of variation (CV) < 2%. Then we tested the effect of product concentrations that varied 8-fold, and the ROY was also consistent with CV < 3.5%. Furthermore, we applied this approach to identify six somatic KRAS deletions in non-small cell lung cancer patients, confirming our previous findings. Thus, the Agilent 2100 Bioanalyzer is simple, accurate, quick, and ultimately able to replace conventional gel electrophoresis for the detection of somatic gene deletions.

Gas diffusion electrodes for methanol electrooxidation studied by a new DEMS configuration: Influence of the diffusion layer

A novel differential electrochemical mass spectrometry (DEMS) cell has been developed to study gas diffusion electrodes (GDEs) used in fuel cells under operating conditions. In this way, catalytic and diffusion properties of the electrodes can be evaluated at the same time. Moreover, DEMS, allows the detection of volatile and gaseous products and intermediates generated in the electrochemical reactions with good sensitivity. In this way, CO2 conversion efficiencies are evaluated during alcohol oxidation reaction. In the present communication, the electrochemical behaviour towards hydrogen evolution and CO and alcohol electrooxidation at different platinum-based catalysts has been studied using the new DEMS cell configuration. The relative yields of CO2 and by-side products during methanol oxidation have been evaluated to determine the CO2 conversion efficiency. In addition, the diffusional properties of diverse GDEs have been considered.

O(3P) + CO2 Collisions at Hyperthermal Energies: Dynamics of Nonreactive Scattering, Oxygen Isotope Exchange, and Oxygen-Atom Abstraction

The dynamics of O((3)P) + CO(2) collisions at hyperthermal energies were investigated experimentally and theoretically. Crossed-molecular-beams experiments at <E(coll)> = 98.8 kcal mol(-1) were performed with isotopically labeled (12)C(18)O(2) to distinguish products of nonreactive scattering from those of reactive scattering. The following product channels were observed: elastic and inelastic scattering ((16)O((3)P) + (12)C(18)O(2)), isotope exchange ((18)O + (16)O(12)C(18)O), and oxygen-atom abstraction ((18)O(16)O + (12)C(18)O). Stationary points on the two lowest triplet potential energy surfaces of the O((3)P) + CO(2) system were characterized at the CCSD(T)/aug-cc-pVTZ level of theory and by means of W4 theory, which represents an approximation to the relativistic basis set limit, full-configuration-interaction (FCI) energy. The calculations predict a planar CO(3)(C(2v), (3)A'') intermediate that lies 16.3 kcal mol(-1) (W4 FCI excluding zero point energy) above reactants and is approached by a C(2v) transition state with energy 24.08 kcal mol(-1). Quasi-classical trajectory (QCT) calculations with collision energies in the range 23-150 kcal mol(-1) were performed at the B3LYP/6-311G(d) and BMK/6-311G(d) levels. Both reactive channels observed in the experiment were predicted by these calculations. In the isotope exchange reaction, the experimental center-of-mass (c.m.) angular distribution, T(θ(c.m.)), of the (16)O(12)C(18)O products peaked along the initial CO(2) direction (backward relative to the direction of the reagent O atoms), with a smaller isotropic component. The product translational energy distribution, P(E(T)), had a relatively low average of <E(T)> = 35 kcal mol(-1), indicating that the (16)O(12)C(18)O products were formed with substantial internal energy. The QCT calculations give c.m. P(E(T)) and T(θ(c.m.)) distributions and a relative product yield that agree qualitatively with the experimental results, and the trajectories indicate that exchange occurs through a short-lived CO(3)* intermediate. A low yield for the abstraction reaction was seen in both the experiment and the theory. Experimentally, a fast and weak (16)O(18)O product signal from an abstraction reaction was observed, which could only be detected in the forward direction. A small number of QCT trajectories leading to abstraction were observed to occur primarily via a transient CO(3) intermediate, albeit only at high collision energies (149 kcal mol(-1)). The oxygen isotope exchange mechanism for CO(2) in collisions with ground state O atoms is a newly discovered pathway through which oxygen isotopes may be cycled in the upper atmosphere, where O((3)P) atoms with hyperthermal translational energies can be generated by photodissociation of O(3) and O(2).

Calculations of Metallofullerene Yields

The paper reports computations for Mg@C74, Ca@C74, Sr@C74, Ba@C74, and all lanthanoids, based on encapsulation into the only C 74 IPR (isolated pentagon rule) cage, and for Al@C 82 , Sc@C82, Y@C82 and La@C82 based on encapsulation into the IPR C2v C82 cage. Their structural and energetic characteristics are used for evaluations of the relative production yields, employing the encapsulation Gibbs-energy terms and saturated metal pressures. It is moreover shown that the encapsulation potential-energy changes in such series can be well related to the mere ionization potentials of the free metal atoms.

Calculated relative yields for Sc2S@C82 and Y2S@C82

The paper reports computations for a newly observed class of the mixed, sulfur-containing X2S@C82 metallofullerenes, namely for X = Sc and Y, based on encapsulation into the Cs and C3v C82 isolated pentagon rule cages. Their structural, vibrational, and energetic characteristics from the density-functional-theory calculations with the standard 6-31G* and LanL2DZ basis sets are used for the evaluations of the relative production yields. The encapsulation Gibbs energy terms from the partition functions combined with the observed saturated metal pressures are employed. A model scheme is used dealing with the XS template gas-phase presence. The computations predict that Sc2S@C82 should be produced in considerably larger amounts than Y2S@C82 which is in agreement with available observations. The yield order originates in the fact that both energetics and saturated metal pressure favor Sc over Y.

Effect of humidity on the composition of isoprene photooxidation secondary organic aerosol

Abstract. The effect of relative humidity (RH) on the composition and concentrations of gas-phase products and secondary organic aerosol (SOA) generated from the photooxidation of isoprene under high-NOx conditions was investigated. Experiments were performed with hydrogen peroxide as the OH precursor and in the absence of seed aerosol. The relative yields of most gas-phase products were the same regardless of initial water vapor concentration with exception of hydroxyacetone and glycolaldehyde, which were considerably affected by RH. A significant change was observed in the SOA composition, with many unique condensed-phase products formed under humid (90 % RH) vs. dry (&lt;2 % RH) conditions, without any detectable effect on the rate and extent of the SOA mass growth. There is a 40 % reduction in the number and relative abundance of distinct particle-phase nitrogen-containing organic compounds (NOC) detected by high resolution mass spectrometry. The suppression of condensation reactions, which produce water as a product, is the most important chemical effect of the increased RH. For example, the total signal from oligomeric esters of 2-methylglyceric acid was reduced by about 60 % under humid conditions and the maximum oligomer chain lengths were reduced by 7–11 carbons. Oligomers formed by addition mechanisms, without direct involvement of water, also decreased at elevated RH but to a much smaller extent. The observed reduction in the extent of condensation-type oligomerization at high RH may have substantial impact on the phase characteristics and hygroscopicity of the isoprene aerosol. The reduction in the amount of organic nitrates in the particle phase has implications for understanding the budget of NOC compounds.

Synthesis, Singlet Oxygen Photogeneration and DNA Photocleavage of Porphyrins with Nitrogen Heterocycle Tails

Eight novel compounds were prepared by reaction of 5-(bromo- propoxyphenyl)-10,15,20-triphenylporphyrin with oxazole thiols, 1,3,4-oxadiazole thiols and 1,3,4-thiadiazole thiols, and their structures confirmed by UV-vis, IR, 1H-NMR, MS and elemental analysis. The assessment of indirectly measured 1O2 production rates against 5,10,15,20-tetraphenyl porphyrin (H2TPP) were described and the relative singlet oxygen production yields were: porphyrin 5 > porphyrins 1, 3, 4, 6-8, H2TPP > porphyrin 2. Porphyrin 4 and porphyrin 7 showed substantial photocleavage activities toward DNA, with over 75% cleavage observed at 40 µM. It suggested that these those porphyrins with nitrogen heterocycle tails are potential photosensitive agents.

The Mechanism of the Acid‐Catalyzed Benzidine Rearrangement of Hydrazobenzene: A Theoretical Study

AbstractThe acid‐catalyzed benzidine rearrangement of hydrazobenzene yields p‐benzidine and diphenyline as the main products and some other secondary products such as o‐benzidine, o‐semidine and p‐semidine. Several reaction mechanisms have been proposed for this rearrangement, but none fully describes it. In this work we present the results of an unrestricted DFT(M06‐2X) study in which the benzidine rearrangement of the hydrazobenzene is fully described. Some relevant points were also analyzed with the CASSCF and CASPT2 methods. Our theoretical approach properly describes the electronic structure of all species along the reaction pathway. The rearrangement of the hydrazobenzene has been found to take place through a multi‐step mechanism in which complexes with dication diradical character similar to those proposed by Dewar play a key role. For the first time, the kinetic isotope effects have been calculated and were found to be in good agreement with the experimental findings. The relative yields of the main products were also correctly estimated. Finally, an explanation of the general acid catalysis observed in some experiments is offered.

Metallofullerene Series: Free-Metal Ionization-Potential Control of the Production Yields

The paper reports computations for Al@C 82 , Sc@C 82 , Y@C 82 and La@C 82 based on encapsulation into the IPR (isolated pentagon rule) C 2 υ C 82 cage and also on Mg@C 74 , Ca@C 74 , Sr@C 74 and Ba@C 74 based on encapsulation into the only C 74 IPR cage. Their structural and energetic characteristics are used for evaluations of the relative production yields, employing the encapsulation Gibbs-energy terms and saturated metal pressures. It is shown that the results can be well re- lated to the ionization potentials of the free metal atoms.

Structural and bonding features of Z@C82 (Z=Al, Sc, Y, La) endohedrals

The paper reports computations for Al@C$_{82}$, Sc@C$_{82}$, Y@C$_{82}$ and La@C$_{82}$ based on encapsulation into the IPR (isolated pentagon rule) $C_{2v}$ C$_{82}$ cage. Their structural and bonding features are also used for evaluations of the relative production yields, employing the encapsulation Gibbs-energy terms and saturated metal pressures. The results can be well related to the ionization potentials of the free metal atoms.

13C-selective infrared multiple photon dissociation of β-propiolactone by a free electron laser

The irradiation of a free electron laser at Tokyo University of Science (FEL-TUS) to β-propiolactone molecules in the gas phase has efficiently induced the infrared multiple photon dissociation of the compound in the wavenumber regions of 1000–1100 and 1700–2000 cm −1. The products were carbon dioxide and ethylene at equal amounts, where carbon dioxide was enriched with 13C under selected irradiation conditions. The relative yields of products and the selectivity of 13C were examined under various experimental conditions; the maximum 13C atom fraction of 59% was achieved when 2.5 Torr β-propiolactone was irradiated by FEL pulses at 1750 cm −1 with a fluence of 5.8 J cm −2. One of the reasons of this high selectivity is a large isotope shift of ∼47 cm −1 for the C O stretching vibration around 1880 cm −1, which is larger than the energy resolution of FEL-TUS. Another possible factor may be a shorter micropulse interval (∼350 ps) of FEL-TUS than the collisional frequency of β-propiolactone molecules in the gas phase, which prevents the collisional energy transfer from 13C molecules to 12C molecules during successive micropulses.

Computed stabilities in metallofullerene series: Al@C82, Sc@C82, Y@C82, and La@C82

AbstractThis article reports computations for Al@C82, Sc@C82, Y@C82, and La@C82 based on encapsulation into the IPR (isolated pentagon rule) C2v C82 cage. Their structural and bonding features are also used for evaluations of the relative production yields, employing the encapsulation Gibbs‐energy terms and saturated metal pressures. The results can be well related to the ionization potentials of the free metal atoms and thus also rationalized. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011

Intramolecular Conversion of Pentaaquahydroperoxidochromium(III) Ion to Aqueous Chromium(V): Potential Source of Carcinogenic Forms of Chromium in Aerobic Organisms

The decomposition of the title compound (H(2)O)(5)CrOOH(2+) (hereafter Cr(aq)OOH(2+)) in acidic aqueous solutions is kinetically complex and generates mixtures of products (Cr(aq)(3+), HCrO(4)(-), H(2)O(2), and O(2)). Relative yields of individual products vary greatly with reaction conditions and initial concentrations of Cr(aq)OOH(2+). At pH 5.5 in the presence of O(2), the reaction was complete in less than a minute and generated chromate in about 70% yield. These findings, in addition to poor reproducibility of kinetic data, are indicative of the involvement of one or more reactive intermediates that consume additional amounts of Cr(aq)OOH(2+) in post-rate-determining steps. The kinetics were simplified in the presence of H(2)O(2) or ABTS(2-), both of which are capable of scavenging strongly oxidizing intermediates. The measured rate constant in 0.10 M HClO(4) at low O(2) concentrations (≤0.03 mM) was independent of the concentration of the scavengers and was, within error, the same for ABTS(2-), k = 4.9 (±0.2) × 10(-4) s(-1), and H(2)O(2), k = 5.3 (±0.7) × 10(-4) s(-1). At a constant ionic strength of 1.0 M, the reaction in the presence of either H(2)O(2) or ABTS(2-) obeyed a two-term rate law, k(obs)/s(-1) = 6.7 (±0.7) × 10(-4) + 7.6 (±1.1) × 10(-4) [H(+)]. Both in the presence and absence of ABTS(2-) as the scavenger, the yields of H(2)O(2) increased with increasing [H(+)]. These results are discussed in terms of a dual-pathway mechanism for the decay of Cr(aq)OOH(2+). The H(+)-catalyzed path leads to the dissociation of H(2)O(2) from Cr(III), while in the H(+)-independent reaction, Cr(aq)OOH(2+) is transformed to Cr(V). Both scavengers rapidly remove Cr(V) and simplify both the kinetics and products.

Prediction of wheat response to an application of phosphorus under field conditions using diffusive gradients in thin-films (DGT) and extraction methods

The ability of the Diffusive Gradients in Thin Films (DGT) technique and two other established testing methods (Colwell, resin) to predict wheat responsiveness to applied P from 35 field trials across southern Australia was investigated. Regression analysis of relative early dry matter production and grain yield responses demonstrated that the DGT method predicted plant responsiveness to applied P more accurately than Colwell P and resin P at sites where maximum yields were reached with P rates used (20 out of 35). The measured concentration in soils at the DGT surface, CDGT, explained 74% of the variation in response for both early dry matter and grain, compared to 7% for early dry matter and 35% for grain using the resin P method. No significant relationships could be obtained for Colwell P although modifying the Colwell test data using Phosphorus Buffering Index resulted in a correct response prediction for 11 of the 20 field sites compared to 18 for DGT and 14 for resin P. These observations suggest that the DGT technique can assess plant available P in soils with significantly greater accuracy than traditional soil P testing methods. The critical P threshold, expressed as CDGT, was 255 μg L−1 for early dry matter and 66 μg L−1 for grain.

Photochemistry of Adsorbed Nitrate on Aluminum Oxide Particle Surfaces

Nitrogen oxides, including nitrogen dioxide and nitric acid, react with mineral dust particles in the atmosphere to yield adsorbed nitrate. Although nitrate ion is a well-known chromophore in natural waters, little is known about the surface photochemistry of nitrate adsorbed on mineral particles. In this study, nitrate adsorbed on aluminum oxide, a model system for mineral dust aerosol, is irradiated with broadband light (lambda > 300 nm) as a function of relative humidity (RH) in the presence of molecular oxygen. Upon irradiation, the nitrate ion readily undergoes photolysis to yield nitrogen-containing gas-phase products including NO(2), NO, and N(2)O, with NO being the major product. The relative ratio and product yields of these gas-phase products change with RH, with N(2)O production being highest at the higher relative humidities. Furthermore, an efficient dark reaction readily converts the major NO product into NO(2) during post-irradiation. Photochemical processes on mineral dust aerosol surfaces have the potential to impact the chemical balance of the atmosphere, yet little is known about these processes. In this study, the impact that adsorbed nitrate photochemistry may have on the renoxification of the atmosphere is discussed.

Establishment of a Cryopreservation Method for the Industrial Use ofD-Amino Acid Oxidase-OverexpressingEscherichia coli

A cryopreservation condition for D-amino acid oxidase (DAAO)-overexpressing Escherichia coli (E. coli BL21(DE3)/pET-DAAO) was established. Ten percent was the optimum concentration of glycerol as a cryoprotectant, and its diffusion into stationary phase cells was superior to that into log cells. The results also showed that rather than fast cooling, a slow cooling method was appropriate to our recombinant E. coli. In addition, 15 min was the best equilibration period, at which higher than 90% of recovery rates were maintained at all test points. Most importantly, the relative recovery rates, product yield, and fermentation pattern of the cell banks (CBs) constructed according to our cryopreservation method did not change over 12 months, confirming that our method not only permits exceptional cryopreservation, but offers prolonged productivity. Taken together, our results demonstrating a cryopreservation method for E. coli BL21(DE3)/pET-DAAO provide insight into an improvement in the industrial production of DAAO.

Effect of ferroelectric polarization on the adsorption and reaction of ethanol on BaTiO 3

The effect of ferroelectric polarization on the adsorption and reaction of ethanol on BaTiO 3 was studied using temperature-programmed desorption (TPD). Consistent with previous studies for methanol, the reactive sticking coefficient for ethanol on the surfaces of the ferroelectric, tetragonal phase of BaTiO 3 was found to be dependent on the orientation of the ferroelectric domains with a higher sticking coefficient on the c + surface relative to the c − surface. TPD peak shapes and the relative product yields were also found to be polarization dependent suggesting that ferroelectric polarization may affect the intrinsic reactivity of the surface.

Photoisomerization Reactions of Cyclopropene and 1,3,3-Trimethylcyclopropene: A Theoretical Study.

The mechanisms of the photochemical isomerization reactions were investigated theoretically using two model systems, cyclopropene and 1,3,3-trimethylcyclopropene with the CASSCF/6-311G(d) (six-electron/six-orbital active space) and MP2-CAS/6-311G(d,p)/CASSCF/6-311G(d) methods. The structures of the conical intersections, which play a decisive role in such photorearrangements, were obtained. The intermediates and transition structures of the ground states were also calculated to assist in providing a qualitative explanation of the reaction pathways. Our model investigations suggest that the preferred reaction route for both cyclopropene and 1,3,3-trimethylcyclopropene is as follows: reactant → Franck-Condon region → local minimum → transition state → conical intersection → local intermediate → transition state → photoproduct. The theoretical findings suggest that the conical intersection mechanism found in this work gives a good explanation and supports the experimental observations. We also investigated the thermal (dark) reaction mechanisms for the hydrogen migration reactions. Again, all the relative yields of final products predicted based on the present work are in good agreement with the available experimental findings.

Computational screening of metallofullerenes for nanoscience: Sr@C74

Density-functional theory calculations are presented for Sr@C74 where C74 is either the isolated pentagon rule (IPR) cage or two cages with a pentagon–pentagon junction. Their relative thermodynamic production yields are evaluated using the calculated terms and it is shown that the IPR-based endohedral prevails at relevant temperatures. The encapsulation Gibbs energy is also combined with the saturated metal pressure as the combined term allows for evaluation of the relative production yields in a metallofullerene series.