Cyanomethanimine Isomers in Cold Interstellar Clouds: Insights from Electronic Structure and Kinetic Calculations

NASA Astrophysics Data System (ADS)

Vazart, Fanny; Latouche, Camille; Skouteris, Dimitrios; Balucani, Nadia; Barone, Vincenzo

2015-09-01

New insights into the formation of interstellar cyanomethanimine, a species of great relevance in prebiotic chemistry, are provided by electronic structure and kinetic calculations for the reaction CN + CH2 = NH. This reaction is a facile formation route of Z,E-C-cyanomethanimine, even under the extreme conditions of density and temperature typical of cold interstellar clouds. E-C-cyanomethanimine has been recently identified in Sgr B2(N) in the Green Bank Telescope (GBT) PRIMOS survey by P. Zaleski et al. and no efficient formation routes have been envisaged so far. The rate coefficient expression for the reaction channel leading to the observed isomer E-C-cyanomethanimine is 3.15 × 10-10 × (T/300)0.152 × e(-0.0948/T). According to the present study, the more stable Z-C-cyanomethanimine isomer is formed with a slightly larger yield (4.59 × 10-10 × (T/300)0.153 × e(-0.0871/T). As the detection of E-isomer is favored due to its larger dipole moment, the missing detection of the Z-isomer can be due to the sensitivity limit of the GBT PRIMOS survey and the detection of the Z-isomer should be attempted with more sensitive instrumentation. The CN + CH2 = NH reaction can also play a role in the chemistry of the upper atmosphere of Titan where the cyanomethanimine products can contribute to the buildup of the observed nitrogen-rich organic aerosols that cover the moon.

Treatment of isomers in nucleosynthesis codes

NASA Astrophysics Data System (ADS)

Reifarth, René; Fiebiger, Stefan; Göbel, Kathrin; Heftrich, Tanja; Kausch, Tanja; Köppchen, Christoph; Kurtulgil, Deniz; Langer, Christoph; Thomas, Benedikt; Weigand, Mario

2018-03-01

The decay properties of long-lived excited states (isomers) can have a significant impact on the destruction channels of isotopes under stellar conditions. In sufficiently hot environments, the population of isomers can be altered via thermal excitation or de-excitation. If the corresponding lifetimes are of the same order of magnitude as the typical time scales of the environment, the isomers have to be treated explicitly. We present a general approach to the treatment of isomers in stellar nucleosynthesis codes and discuss a few illustrative examples. The corresponding code is available online at http://exp-astro.de/isomers/.

Separation behavior of octadecadienoic acid isomers and identification of cis- and trans-isomers using gas chromatography.

PubMed

Shibamoto, Shigeaki; Gooley, Andrew; Yamamoto, Kouhei

2015-01-01

Using a strongly polar cyanopropyl capillary column we have investigated the gas chromatography (GC) separation behaviors of 24 octadecadienoic acid methyl ester (18:2ME) isomers compared against saturated methyl stearate (18:0ME) and arachidic acid methyl ester (20:0ME), and the dependency on the GC column temperature. The 24 isomers were obtained by performing cis-to trans-isomerization of six regioisomers: five of the 18:2ME isomers were prepared by the partial reduction of methyl α-linolenate and methyl γ-linolenate C18 trienoic acids with different double bond positions, whereas the sixth isomer, 18:2ME (c5, c9), was obtained from a raw constituent fatty acid methyl ester (FAME) sample extracted from Japanese yew seeds. There are no reference standards commercially available for 18:2ME isomers, and in elucidating the elution order of these isomers this study should help the future identification of cis- and trans-type of 18:2ME. We also report the identification method of cis- and trans-type of FAME using equivalent chain lengths and attempt the identification of cis- and trans-type of 18:2ME isomers from partially hydrogenated canola oil.

Isomer spectroscopy of neutron-rich 168Tb 103

DOE PAGES

Gurgi, L. A.; Regan, P. H.; Söderström, P. -A.; ...

2016-12-29

In-flight fission of a 345 MeV per nucleon 238U primary beam on a 2 mm thick 9Be target has been used to produce and study the decays of a range of neutron-rich nuclei centred around the doubly mid-shell nucleus 170Dy at the RIBF Facility, RIKEN, Japan. The produced secondary fragments of interest were identified event-by-event using the BigRIPS separator. The fragments were implanted into the WAS3ABI position sensitive silicon active stopper which allowed pixelated correlations between implants and their subsequent β-decay. Discrete γ-ray transitions emitted following decays from either metastable states or excited states populated following beta decay were identifiedmore » using the 84 coaxial high-purity germanium (HPGe) detectors of the EURICA spectrometer, which was complemented by 18 additional cerium-doped lanthanum bromide (LaBr 3) fast-timing scintillation detectors from the FATIMA collaboration. This paper presents the internal decay of a metastable isomeric excited state in the odd-odd nucleus 168Tb, which corresponds to a single proton-neutron hole configuration in the valence maximum nucleus 170Dy. These data represent the first information on excited states in this nucleus, which is the most neutron-rich odd-odd isotope of terbium (Z = 65) studied to date. Here, Nilsson configurations associated with an axially symmetric, prolate-deformed nucleus are proposed for the 168Tb ground state the observed isomeric state by comparison with Blocked BCS-Nilsson calculations.« less

Isomer spectroscopy of neutron-rich 168Tb103

NASA Astrophysics Data System (ADS)

Gurgi, L. A.; Regan, P. H.; Söderström, P.-A.; Watanabe, H.; Walker, P. M.; Podolyák, Zs.; Nishimura, S.; Berry, T. A.; Doornenbal, P.; Lorusso, G.; Isobe, T.; Baba, H.; Xu, Z. Y.; Sakurai, H.; Sumikama, T.; Catford, W. N.; Bruce, A. M.; Browne, F.; Lane, G. J.; Kondev, F. G.; Odahara, A.; Wu, J.; Liu, H. L.; Xu, F. R.; Korkulu, Z.; Lee, P.; Liu, J. J.; Phong, V. H.; Yag, A.; Zhang, G. X.; Alharbi, T.; Carroll, R. J.; Chae, K. Y.; Dombradi, Zs.; Estrade, A.; Fukuda, N.; Griffin, C.; Ideguchi, E.; Inabe, N.; Kanaoka, H.; Kojouharov, I.; Kubo, T.; Kubono, S.; Kurz, N.; Kuti, I.; Lalkovski, S.; Lee, E. J.; Lee, C. S.; Lotay, G.; Moon, C.-B.; Nishizuka, I.; Nita, C. R.; Patel, Z.; Roberts, O. J.; Schaffner, H.; Shand, C. M.; Suzuki, H.; Takeda, H.; Terashima, S.; Vajta, Zs.; Yoshida, S.; Valiente-Dòbon, J. J.

2017-11-01

In-flight fission of a 345 MeV per nucleon 238U primary beam on a 2 mm thick 9Be target has been used to produce and study the decays of a range of neutron-rich nuclei centred around the doubly mid-shell nucleus 170Dy at the RIBF Facility, RIKEN, Japan. The produced secondary fragments of interest were identified event-by-event using the BigRIPS separator. The fragments were implanted into the WAS3ABI position sensitive silicon active stopper which allowed pixelated correlations between implants and their subsequent β-decay. Discrete γ-ray transitions emitted following decays from either metastable states or excited states populated following beta decay were identified using the 84 coaxial high-purity germanium (HPGe) detectors of the EURICA spectrometer, which was complemented by 18 additional cerium-doped lanthanum bromide (LaBr3) fast-timing scintillation detectors from the FATIMA collaboration. This paper presents the internal decay of a metastable isomeric excited state in the odd-odd nucleus 168Tb, which corresponds to a single proton-neutron hole configuration in the valence maximum nucleus 170Dy. These data represent the first information on excited states in this nucleus, which is the most neutron-rich odd-odd isotope of terbium (Z=65) studied to date. Nilsson configurations associated with an axially symmetric, prolate-deformed nucleus are proposed for the 168Tb ground state the observed isomeric state by comparison with Blocked BCS-Nilsson calculations.

Conjugated linoleic acid-rich soy oil triacylglycerol identification.

PubMed

Lall, Rahul K; Proctor, Andrew; Jain, Vishal P; Lay, Jackson O

2009-03-11

Conjugated linoleic acid (CLA)-rich soy oil has been produced by soy oil linoleic acid (LA) photoisomerization, but CLA-rich oil triacylglycerol (TAG) characterization was not described. Therefore, the objectives were to identify and quantify new TAG fractions in CLA-rich oil by nonaqueous reversed-phase high-performance liquid chromatography (NARP-HPLC). Analytical NARP-HPLC with an acetonitrile/dichloromethane (ACN/DCM) gradient and an evaporating light scattering detector/ultraviolet (ELSD/UV) detector was used. New TAG peaks from LA-containing TAGs were observed. The LnLL, LLL, LLO, and LLP (Ln, linolenic; L, linoleic; O, oleic; and P, palmitic) peaks reduced after isomerization with an increase in adjacent peaks that coeluted with LnLnO, LnLO, LnOO, and LnPP. The newly formed peaks were wider than those of the original oil and absorbed at 233 nm, suggesting the possibility of various CLA containing TAGs. The HPLC profile showed five fractions of mixed TAGs, and fatty acid analysis showed that CLA isomers were found predominately in fractions 2 and 3, which originally contained most LA. The CLA isomers were 70-80% trans,trans and 20-30% cis,trans and trans,cis.

Can honey bees discriminate between floral-fragrance isomers?

PubMed

Aguiar, João Marcelo Robazzi Bignelli Valente; Roselino, Ana Carolina; Sazima, Marlies; Giurfa, Martin

2018-05-24

Many flowering plants present variable complex fragrances, which usually include different isomers of the same molecule. As fragrance is an essential cue for flower recognition by pollinators, we ask if honey bees discriminate between floral-fragrance isomers in an appetitive context. We used the olfactory conditioning of the proboscis extension response (PER), which allows training a restrained bee to an odor paired with sucrose solution. Bees were trained under an absolute (a single odorant rewarded) or a differential conditioning regime (a rewarded vs. a non-rewarded odorant) using four different pairs of isomers. One hour after training, discrimination and generalization between pairs of isomers were tested. Bees trained under absolute conditioning exhibited high generalization between isomers and discriminated only one out of four isomer pairs; after differential conditioning, they learned to differentiate between two out of four pairs of isomers but in all cases generalization responses to the non-rewarding isomer remained high. Adding an aversive taste to the non-rewarded isomer facilitated discrimination of isomers that otherwise seemed non-discriminable, but generalization remained high. Although honey bees discriminated isomers under certain conditions, they achieved the task with difficulty and tended to generalize between them, thus showing that these molecules were perceptually similar to them. We conclude that the presence of isomers within floral fragrances might not necessarily contribute to a dramatic extent to floral odor diversity. © 2018. Published by The Company of Biologists Ltd.

Preferential polymerization and adsorption of L-optical isomers of amino acids relative to D-optical isomers on kaolinite templates.

NASA Technical Reports Server (NTRS)

Jackson, T. A.

1971-01-01

Experiments on the polymerization of the L- and D-optical isomers of aspartic acid and serine using kaolinite as a catalyst showed that the L-optical isomers were polymerized at a much higher rate than the D-optical isomers; racemic (DL-) mixtures were polymerized at an intermediate rate. The peptides formed from the L-monomers were preferentially adsorbed by the clay. In the absence of kaolinite, no significant or consistent difference in the behavior of the L- and D-optical isomers was observed. In experiments on the adsorption of L- and D-phenylalanine by kaolinite, the L-optical isomer was preferentially adsorbed.

Electronic and spectroscopic characterizations of SNP isomers

NASA Astrophysics Data System (ADS)

Trabelsi, Tarek; Al Mogren, Muneerah Mogren; Hochlaf, Majdi; Francisco, Joseph S.

2018-02-01

High-level ab initio electronic structure calculations were performed to characterize SNP isomers. In addition to the known linear SNP, cyc-PSN, and linear SPN isomers, we identified a fourth isomer, linear PSN, which is located ˜2.4 eV above the linear SNP isomer. The low-lying singlet and triplet electronic states of the linear SNP and SPN isomers were investigated using a multi-reference configuration interaction method and large basis set. Several bound electronic states were identified. However, their upper rovibrational levels were predicted to pre-dissociate, leading to S + PN, P + NS products, and multi-step pathways were discovered. For the ground states, a set of spectroscopic parameters were derived using standard and explicitly correlated coupled-cluster methods in conjunction with augmented correlation-consistent basis sets extrapolated to the complete basis set limit. We also considered scalar and core-valence effects. For linear isomers, the rovibrational spectra were deduced after generation of their 3D-potential energy surfaces along the stretching and bending coordinates and variational treatments of the nuclear motions.

CYANOMETHANIMINE ISOMERS IN COLD INTERSTELLAR CLOUDS: INSIGHTS FROM ELECTRONIC STRUCTURE AND KINETIC CALCULATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vazart, Fanny; Latouche, Camille; Skouteris, Dimitrios

2015-09-10

New insights into the formation of interstellar cyanomethanimine, a species of great relevance in prebiotic chemistry, are provided by electronic structure and kinetic calculations for the reaction CN + CH{sub 2} = NH. This reaction is a facile formation route of Z,E-C-cyanomethanimine, even under the extreme conditions of density and temperature typical of cold interstellar clouds. E-C-cyanomethanimine has been recently identified in Sgr B2(N) in the Green Bank Telescope (GBT) PRIMOS survey by P. Zaleski et al. and no efficient formation routes have been envisaged so far. The rate coefficient expression for the reaction channel leading to the observed isomermore » E-C-cyanomethanimine is 3.15 × 10-10 × (T/300){sup 0.152} × e{sup (−0.0948/T)}. According to the present study, the more stable Z-C-cyanomethanimine isomer is formed with a slightly larger yield (4.59 × 10{sup −10} × (T/300){sup 0.153} × e{sup (−0.0871/T)}. As the detection of E-isomer is favored due to its larger dipole moment, the missing detection of the Z-isomer can be due to the sensitivity limit of the GBT PRIMOS survey and the detection of the Z-isomer should be attempted with more sensitive instrumentation. The CN + CH{sub 2} = NH reaction can also play a role in the chemistry of the upper atmosphere of Titan where the cyanomethanimine products can contribute to the buildup of the observed nitrogen-rich organic aerosols that cover the moon.« less

Design of micro-second pulsed laser mode for ophthalmological CW self-raman laser

NASA Astrophysics Data System (ADS)

Mota, Alessandro D.; Rossi, Giuliano; Ortega, Tiago A.; Costal, Glauco Z.; Fontes, Yuri C.; Yasuoka, Fatima M. M.; Stefani, Mario A.; de Castro N., Jarbas C.; Paiva, Maria S. V.

2011-02-01

This work presents the mechanisms adopted for the design of micro-second pulsed laser mode for a CW Self-Raman laser cavity in 586nm and 4W output power. The new technique for retina disease treatment discharges laser pulses on the retina tissue, in laser sequences of 200 μs pulse duration at each 2ms. This operation mode requires the laser to discharge fast electric pulses, making the system control velocity of the electronic system cavity vital. The control procedures to keep the laser output power stable and the laser head behavior in micro-second pulse mode are presented.

Pulsed Electron Beam Water Radiolysis for Sub-Microsecond Hydroxyl Radical Protein Footprinting

PubMed Central

Watson, Caroline; Janik, Ireneusz; Zhuang, Tiandi; Charvátová, Olga; Woods, Robert J.; Sharp, Joshua S.

2009-01-01

Hydroxyl radical footprinting is a valuable technique for studying protein structure, but care must be taken to ensure that the protein does not unfold during the labeling process due to oxidative damage. Footprinting methods based on sub-microsecond laser photolysis of peroxide that complete the labeling process faster than the protein can unfold have been recently described; however, the mere presence of large amounts of hydrogen peroxide can also cause uncontrolled oxidation and minor conformational changes. We have developed a novel method for sub-microsecond hydroxyl radical protein footprinting using a pulsed electron beam from a 2 MeV Van de Graaff electron accelerator to generate a high concentration of hydroxyl radicals by radiolysis of water. The amount of oxidation can be controlled by buffer composition, pulsewidth, dose, and dissolved nitrous oxide gas in the sample. Our results with ubiquitin and β-lactoglobulin A demonstrate that one sub-microsecond electron beam pulse produces extensive protein surface modifications. Highly reactive residues that are buried within the protein structure are not oxidized, indicating that the protein retains its folded structure during the labeling process. Time-resolved spectroscopy indicates that the major part of protein oxidation is complete in a timescale shorter than that of large scale protein motions. PMID:19265387

Microsecond switchable thermal antenna

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ben-Abdallah, Philippe, E-mail: pba@institutoptique.fr; Benisty, Henri; Besbes, Mondher

2014-07-21

We propose a thermal antenna that can be actively switched on and off at the microsecond scale by means of a phase transition of a metal-insulator material, the vanadium dioxide (VO{sub 2}). This thermal source is made of a periodically patterned tunable VO{sub 2} nanolayer, which support a surface phonon-polariton in the infrared range in their crystalline phase. Using electrodes properly registered with respect to the pattern, the VO{sub 2} phase transition can be locally triggered by ohmic heating so that the surface phonon-polariton can be diffracted by the induced grating, producing a highly directional thermal emission. Conversely, when heatingmore » less, the VO{sub 2} layers cool down below the transition temperature, the surface phonon-polariton cannot be diffracted anymore so that thermal emission is inhibited. This switchable antenna could find broad applications in the domain of active thermal coatings or in those of infrared spectroscopy and sensing.« less

High efficiency laser-assisted H - charge exchange for microsecond duration beams

DOE PAGES

Cousineau, Sarah; Rakhman, Abdurahim; Kay, Martin; ...

2017-12-26

Laser-assisted stripping is a novel approach to H - charge exchange that overcomes long-standing limitations associated with the traditional, foil-based method of producing high-intensity, time-structured beams of protons. This paper reports on the first successful demonstration of the laser stripping technique for microsecond duration beams. The experiment represents a factor of 1000 increase in the stripped pulse duration compared with the previous proof-of-principle demonstration. The central theme of the experiment is the implementation of methods to reduce the required average laser power such that high efficiency stripping can be accomplished for microsecond duration beams using conventional laser technology. In conclusion,more » the experiment was performed on the Spallation Neutron Source 1 GeV H - beam using a 1 MW peak power UV laser and resulted in ~95% stripping efficiency.« less

High efficiency laser-assisted H - charge exchange for microsecond duration beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cousineau, Sarah; Rakhman, Abdurahim; Kay, Martin

Laser-assisted stripping is a novel approach to H - charge exchange that overcomes long-standing limitations associated with the traditional, foil-based method of producing high-intensity, time-structured beams of protons. This paper reports on the first successful demonstration of the laser stripping technique for microsecond duration beams. The experiment represents a factor of 1000 increase in the stripped pulse duration compared with the previous proof-of-principle demonstration. The central theme of the experiment is the implementation of methods to reduce the required average laser power such that high efficiency stripping can be accomplished for microsecond duration beams using conventional laser technology. In conclusion,more » the experiment was performed on the Spallation Neutron Source 1 GeV H - beam using a 1 MW peak power UV laser and resulted in ~95% stripping efficiency.« less

Radargrams Indicating Ice-Rich Subsurface Deposit

NASA Image and Video Library

2016-11-22

These two images show data acquired by the Shallow Radar (SHARAD) instrument while passing over two ground tracks in a part of Mars' Utopia Planitia region where the orbiting, ground-penetrating radar detected subsurface deposits rich in water ice. The instrument on NASA's Mars Reconnaissance Orbiter emits radio waves and times their echo off of radio-reflective surfaces and interfaces on Mars. The white arrows indicate a subsurface reflector interpreted as the bottom of the ice-rich deposit. The deposit is about as large in area as the state of New Mexico and contains about as much water as Lake Superior. The horizontal scale bar indicates 40 kilometers (25 miles) along the ground track of the radar, as flown by the orbiter overhead. The vertical scale bar indicates a return time of one microsecond for the reflected radio signal, equivalent to a distance of about 90 meters (295 feet). http://photojournal.jpl.nasa.gov/catalog/PIA21137

Slightly uneven electric field trigatron employed in tens of microseconds charging time.

PubMed

Lin, Jiajin; Yang, Jianhua; Zhang, Jiande; Zhang, Huibo; Yang, Xiao

2014-09-01

To solve the issue of operation instability for the trigatron switch in the application of tens of microseconds or even less charging time, a novel trigatron spark gap with slightly uneven electric field was presented. Compared with the conventional trigatron, the novel trigatron was constructed with an obvious field enhancement on the edge of the opposite electrode. The selection of the field enhancement was analyzed based on the theory introduced by Martin. A low voltage trigatron model was constructed and tested on the tens of microseconds charging time platform. The results show that the character of relative range was improved while the trigger character still held a high level. This slightly uneven electric field typed trigatron is willing to be employed in the Tesla transformer - pulse forming line system.

Enumerating Substituted Benzene Isomers of Tree-Like Chemical Graphs.

PubMed

Li, Jinghui; Nagamochi, Hiroshi; Akutsu, Tatsuya

2018-01-01

Enumeration of chemical structures is useful for drug design, which is one of the main targets of computational biology and bioinformatics. A chemical graph with no other cycles than benzene rings is called tree-like, and becomes a tree possibly with multiple edges if we contract each benzene ring into a single virtual atom of valence 6. All tree-like chemical graphs with a given tree representation are called the substituted benzene isomers of . When we replace each virtual atom in with a benzene ring to obtain a substituted benzene isomer, distinct isomers of are caused by the difference in arrangements of atom groups around a benzene ring. In this paper, we propose an efficient algorithm that enumerates all substituted benzene isomers of a given tree representation . Our algorithm first counts the number of all the isomers of the tree representation by a dynamic programming method. To enumerate all the isomers, for each , our algorithm then generates the th isomer by backtracking the counting phase of the dynamic programming. We also implemented our algorithm for computational experiments.

Analysis, toxicity, occurrence and biodegradation of nonylphenol isomers: a review.

PubMed

Lu, Zhijiang; Gan, Jay

2014-12-01

Over the last two decades, nonylphenols (NPs) have become to be known as a priority hazardous substance due primarily to its estrogenicity and ubiquitous occurrence in the environment. Nonylphenols are commonly treated as a single compound in the evaluation of their environmental occurrence, fate and transport, treatment or toxicity. However, technical nonylphenols (tNPs) are in fact a mixture of more than 100 isomers and congeners. Recent studies showed that some of these isomers behaved significantly differently in occurrence, estrogenicity and biodegradability. The most estrogenic isomer was about 2 to 4 times more active than tNP. Moreover, the half lives of the most recalcitrant isomers were about 3 to 4 times as long as those of readily-biodegradable isomers. Negligence of NP's isomer specificity may result in inaccurate assessment of its ecological and health effects. In this review, we summarized the recent publications on the analysis, occurrence, toxicity and biodegradation of NP at the isomer level and highlighted future research needs to improve our understanding of isomer-specificity of NP. Copyright © 2014. Published by Elsevier Ltd.

Microsecond MD Simulations of Nano-patterned Polymer Brushes on Self-Assembled Monolayers

NASA Astrophysics Data System (ADS)

Buie, Creighton; Qiu, Liming; Cheng, Kwan; Park, Soyeun

2010-03-01

Nano-patterned polymer brushes end-grafted onto self-assembled monolayers have gained increasing research interests due to their unique thermodynamic properties and their chemical and biomedical applications in colloids, biosensing and tissue engineering. So far, the interactions between the polymer brushes with the surrounding environments such as the floor and solvent at the nanometer length scale and microsecond time scale are still difficult to obtained experimentally and computationally. Using a Coarse-Grained MD approach, polymer brushes of different monomeric lengths, grafting density and hydrophobicity of the monomers grafted on self-assembled monolayers and in explicit solvent were studied. Molecular level information, such as lateral diffusion, transverse height and volume contour of the brushes, were calculated from our microsecond-MD simulations. Our results demonstrated the significance of the hydration of the polymer in controlling the conformational arrangement of the polymer brushes.

Failures of fractional crystallization: ordered co-crystals of isomers and near isomers.

PubMed

Kelley, Steven P; Fábián, László; Brock, Carolyn Pratt

2011-02-01

A list of 270 structures of ordered co-crystals of isomers, near isomers and molecules that are almost the same has been compiled. Searches for structures containing isomers could be automated by the use of IUPAC International Chemical Identifier (InChI™) strings but searches for co-crystals of very similar molecules were more labor intensive. Compounds in which the heteromolecular A···B interactions are clearly better than the average of the homomolecular A···A and B···B interactions were excluded. The two largest structural classes found include co-crystals of configurational diastereomers and of quasienantiomers (or quasiracemates). These two groups overlap. There are 114 co-crystals of diastereomers and the same number of quasiracemates, with 71 structures being counted in both groups; together the groups account for 157 structures or 58% of the total. The large number of quasiracemates is strong evidence for inversion symmetry being very favorable for crystal packing. Co-crystallization of two diastereomers is especially likely if a 1,1 switch of a methyl group and an H atom, or of an inversion of a [2.2.1] or [2.2.2] cage, in one of the diastereomers would make the two molecules enantiomers.

Isolation and spectral characterization of thermally generated multi-Z-isomers of lycopene and the theoretically preferred pathway to di-Z-isomers.

PubMed

Honda, Masaki; Kudo, Tatsuya; Kuwa, Takahiro; Higashiura, Takuma; Fukaya, Tetsuya; Inoue, Yoshinori; Kitamura, Chitoshi; Takehara, Munenori

2017-02-01

Lycopene has a large number of geometric isomers caused by E/Z isomerization at arbitrary sites within the 11 conjugated double bonds, offering varying characteristics related to features such as antioxidant capacity and bioavailability. However, the geometric structures of only a few lycopene Z-isomers have been thoroughly identified from natural sources. In this study, seven multi-Z-isomers of lycopene, (9Z,13'Z)-, (5Z,13Z,9'Z)-, (9Z,9'Z)-, (5Z,13'Z)-, (5Z,9'Z)-, (5Z,9Z,5'Z)-, and (5Z,9Z)-lycopene, were obtained from tomato samples by thermal isomerization, and then isolated by elaborate chromatography, and fully assigned using proton nuclear magnetic resonance. Moreover, the theoretically preferred pathway from (all-E)-lycopene to di-Z-isomers was examined with a computational approach using a Gaussian program. Fine-tuning of the HPLC separation conditions led to the discovery of novel multi-Z-isomers, and whose formation was supported by advanced theoretical calculations.

Microsecond time-scale kinetics of transient biochemical reactions

PubMed Central

Mitić, Sandra; Strampraad, Marc J. F.; de Vries, Simon

2017-01-01

To afford mechanistic studies in enzyme kinetics and protein folding in the microsecond time domain we have developed a continuous-flow microsecond time-scale mixing instrument with an unprecedented dead-time of 3.8 ± 0.3 μs. The instrument employs a micro-mixer with a mixing time of 2.7 μs integrated with a 30 mm long flow-cell of 109 μm optical path length constructed from two parallel sheets of silver foil; it produces ultraviolet-visible spectra that are linear in absorbance up to 3.5 with a spectral resolution of 0.4 nm. Each spectrum corresponds to a different reaction time determined by the distance from the mixer outlet, and by the fluid flow rate. The reaction progress is monitored in steps of 0.35 μs for a total duration of ~600 μs. As a proof of principle the instrument was used to study spontaneous protein refolding of pH-denatured cytochrome c. Three folding intermediates were determined: after a novel, extremely rapid initial phase with τ = 4.7 μs, presumably reflecting histidine re-binding to the iron, refolding proceeds with time constants of 83 μs and 345 μs to a coordinatively saturated low-spin iron form in quasi steady state. The time-resolution specifications of our spectrometer for the first time open up the general possibility for comparison of real data and molecular dynamics calculations of biomacromolecules on overlapping time scales. PMID:28973014

Structure-biodegradability relationship of nonylphenol isomers during biological wastewater treatment process.

PubMed

Hao, Ruixia; Li, Jianbing; Zhou, Yuwen; Cheng, Shuiyuan; Zhang, Yi

2009-05-01

The relationship between nonylphenol (NP) isomer structure and its biodegradability within the wastewater treatment process of sequencing batch reactor (SBR) was investigated. The GC-MS method was used for detecting the NP isomers existing in the SBR influent, activated sludge and effluent. Fifteen NP isomers were detected in the influent, with significant biodegradability variations being observed among these isomers. It was found that the NP isomers associated with retention time of 10.553, 10.646, 10.774, and 10.906 min in the GC-MS analysis showed higher biodegradability, while the isomers with retention time of 10.475, 10.800, and 10.857 min illustrated lower biodegradability. Through analyzing the mass spectrograms, the chemical structures of four selected NP isomers in the wastewater were further deduced. The higher correlation coefficients of 0.9421 and 0.9085 were observed between the NP isomer biodegradation rates and the molecular connectivity indexes with the order of two and four, respectively. Such correlation analysis indicated that a more complex side branch structure (such as a larger side carbon-chain branch or more branches in the nonyl) of NP isomer would lead to lower biodegradability, and a longer nonyl chain of the isomer would result in a higher biodegradability.

Isomer spectroscopy of neutron-rich $$^{165,167}$$Tb

DOE PAGES

Gurgi, L. A.; Regan, P. H.; Soderstrom, P. -A.; ...

2017-01-01

We present information on the excited states in the prolate-deformed, neutron-rich nuclei 165,167Tb 100,102. The nuclei of interest were synthesised following in-flight fission of a 345 MeV per nucleon 238U primary beam on a 2 mm 9Be target at the Radioactive Ion-Beam Factory (RIBF), RIKEN, Japan. The exotic nuclei were separated and identified event-by-event using the BigRIPS separator, with discrete energy gamma-ray decays from isomeric states with half-lives in the μs regime measured using the EURICA gamma-ray spectrometer. Metastable-state decays are identified in 165Tb and 167Tb and interpreted as arising from hindered E1 decay from the 72 –[523] single quasi-protonmore » Nilsson configuration to rotational states built on the 32 –[411] single quasi-proton ground state. Lastly, these data correspond to the first spectroscopic information in the heaviest, odd-A terbium isotopes reported to date and provide information on proton Nilsson configurations which reside close to the Fermi surface as the 170Dy doubly-midshell nucleus is approached.« less

Use of microsecond current prepulse for dramatic improvements of wire array Z-pinch implosion

NASA Astrophysics Data System (ADS)

Calamy, H.; Lassalle, F.; Loyen, A.; Zucchini, F.; Chittenden, J. P.; Hamann, F.; Maury, P.; Georges, A.; Bedoch, J. P.; Morell, A.

2008-01-01

The Sphinx machine [F. Lassalle et al., "Status on the SPHINX machine based on the 1microsecond LTD technology"] based on microsecond linear transformer driver (LTD) technology is used to implode an aluminium wire array with an outer diameter up to 140mm and maximum current from 3.5to5MA. 700to800ns implosion Z-pinch experiments are performed on this driver essentially with aluminium. Best results obtained before the improvement described in this paper were 1-3TW radial total power, 100-300kJ total yield, and 20-30kJ energy above 1keV. An auxiliary generator was added to the Sphinx machine in order to allow a multi microsecond current to be injected through the wire array load before the start of the main current. Amplitude and duration of this current prepulse are adjustable, with maxima ˜10kA and 50μs. This prepulse dramatically changes the ablation phase leading to an improvement of the axial homogeneity of both the implosion and the final radiating column. Total power was multiplied by a factor of 6, total yield by a factor of 2.5 with a reproducible behavior. This paper presents experimental results, magnetohydrodynamic simulations, and analysis of the effect of such a long current prepulse.

Kinetics of photoirradiation-induced synthesis of soy oil-conjugated linoleic acid isomers.

PubMed

Jain, Vishal P; Proctor, Andrew

2007-02-07

Photoirradiation of soy oil with UV/visible light has been shown to produce significant amounts of trans,trans conjugated linoleic acid (CLA) isomers through conversion of various synthesized intermediate cis,trans isomers. The objective of this study was to determine the kinetics of CLA isomers synthesis to better understand the production of various isomers. Soy oil was irradiated with UV/visible light for 144 h in the presence of an iodine catalyst and CLA isomers analyzed by gas chromatography (GC). Arrhenius plots were developed for the conversion of soy oil linoleic acid (A) to form cis-, trans/trans-, cis-CLA (B), conversion of cis-, trans/trans-, cis-CLA to form trans,trans-CLA (C) with respect to B, and formation of trans,trans-CLA isomers with respect to C. The kinetics of consumption of linoleic acid (LA) to form cis-, trans/trans-, cis-CLA was found to be of second-order with a rate constant of 9.01 x 10-7 L/mol s. The rate of formation of cis-, trans/trans-, cis-CLA isomers depends on the rate of formation from LA and its rate of consumption to form trans,trans-CLA isomers. The conversion of cis-, trans/trans-, cis-CLA isomers to trans,trans-CLA isomers was found to be of first-order with a rate constant of 2.75 x 10-6 s-1. However, the formation of thermodynamically stable trans,trans-CLA isomers (C) with respect to C was found to be a zero-order reaction with a rate constant of 10.66 x 10-7 mol/L s. The consumption of LA was found to be the rate-determining step in the CLA isomers formation reaction mechanism. The findings provide a better understanding of the mechanism of CLA isomers synthesis by photoirradiation and the factors controlling the ratio of various isomers.

Isolating isomers of perfluorocarboxylates in polar bears (Ursus maritimus) from two geographical locations.

PubMed

De Silva, Amila O; Mabury, Scott A

2004-12-15

The source of involatile, anthropogenic perfluorocarboxylate anions (PFCAs) in biota from remote regions is of heightened interest due to the persistence, toxicity, and bioaccumulation of these materials. Large-scale production of fluorinated compounds is carried out primarily by one of two methods: electrochemical fluorination (ECF) and telomerization. Products of the two processes may be distinguished based on constitutional isomer pattern as ECF products are characteristically comprised of a variety of constitutional isomers. The objective of this research was to develop a method for identifying the constitutional isomer profile of PFCAs in environmental samples and to apply the method to polar bear livers from two different locations. Resolution of constitutional isomers of derivatized PFCAs (8-13 carbons) was accomplished via GC-MS. Seven isomers of an authentic ECF perfluorooctanoate (PFOA) standard were separated. The linear isomer comprised 78% of this standard. Isomer profiles of PFCAs in liver samples of 15 polar bears (Ursus maritimus) from the Canadian Arctic and eastern Greenland were determined by GC-MS. The PFOA isomer pattern in Greenland polar bear samples showed a variety of branched isomers while only the linear PFOA isomer was determined in Canadian samples. Samples of both locations had primarily (>99%) linear isomers of perfluorononanoate and perfluorotridecanoate. Branched isomers of perfluorodecanoate, perfluoroundecanoate, and perfluorododecanoate were determined in the polar bear samples. Unlike the PFOA isomer signature, only a single branched isomer peak on the chromatograms was observed for these longer chain PFCAs. The presence of branched isomers suggests some contribution from ECF sources. However, in comparison to the amount of branched isomers in the ECF PFOA standard, such minor percentages of branched PFCAs may suggest additional input from an exclusively linear isomer source.

Anaerobic Degradation of Phthalate Isomers by Methanogenic Consortia

PubMed Central

Kleerebezem, Robbert; Pol, Look W. Hulshoff; Lettinga, Gatze

1999-01-01

Three methanogenic enrichment cultures, grown on ortho-phthalate, iso-phthalate, or terephthalate were obtained from digested sewage sludge or methanogenic granular sludge. Cultures grown on one of the phthalate isomers were not capable of degrading the other phthalate isomers. All three cultures had the ability to degrade benzoate. Maximum specific growth rates (μSmax) and biomass yields (YXtotS) of the mixed cultures were determined by using both the phthalate isomers and benzoate as substrates. Comparable values for these parameters were found for all three cultures. Values for μSmax and YXtotS were higher for growth on benzoate compared to the phthalate isomers. Based on measured and estimated values for the microbial yield of the methanogens in the mixed culture, specific yields for the phthalate and benzoate fermenting organisms were calculated. A kinetic model, involving three microbial species, was developed to predict intermediate acetate and hydrogen accumulation and the final production of methane. Values for the ratio of the concentrations of methanogenic organisms, versus the phthalate isomer and benzoate fermenting organisms, and apparent half-saturation constants (KS) for the methanogens were calculated. By using this combination of measured and estimated parameter values, a reasonable description of intermediate accumulation and methane formation was obtained, with the initial concentration of phthalate fermenting organisms being the only variable. The energetic efficiency for growth of the fermenting organisms on the phthalate isomers was calculated to be significantly smaller than for growth on benzoate. PMID:10049876

40 CFR 721.10564 - Mixed amino diaryl sulfone isomers (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Mixed amino diaryl sulfone isomers... Specific Chemical Substances § 721.10564 Mixed amino diaryl sulfone isomers (generic). (a) Chemical... as mixed amino diaryl sulfone isomers (PMN P-08-39) is subject to reporting under this section for...

40 CFR 721.10564 - Mixed amino diaryl sulfone isomers (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Mixed amino diaryl sulfone isomers... Specific Chemical Substances § 721.10564 Mixed amino diaryl sulfone isomers (generic). (a) Chemical... as mixed amino diaryl sulfone isomers (PMN P-08-39) is subject to reporting under this section for...

Differential Degradation of Nonylphenol Isomers by Sphingomonas xenophaga Bayram

PubMed Central

Gabriel, Frédéric L. P.; Giger, Walter; Guenther, Klaus; Kohler, Hans-Peter E.

2005-01-01

Sphingomonas xenophaga Bayram, isolated from the activated sludge of a municipal wastewater treatment plant, was able to utilize 4-(1-ethyl-1,4-dimethylpentyl)phenol, one of the main isomers of technical nonylphenol mixtures, as a sole carbon and energy source. The isolate degraded 1 mg of 4-(1-ethyl-1,4-dimethylpentyl)phenol/ml in minimal medium within 1 week. Growth experiments with five nonylphenol isomers showed that the three isomers with quaternary benzylic carbon atoms [(1,1,2,4-tetramethylpentyl)phenol, 4-(1-ethyl-1,4-dimethylpentyl)phenol, and 4-(1,1-dimethylheptyl)phenol] served as growth substrates, whereas the isomers containing one or two hydrogen atoms in the benzylic position [4-(1-methyloctyl)phenol and 4-n-nonylphenol] did not. However, when the isomers were incubated as a mixture, all were degraded to a certain degree. Differential degradation was clearly evident, as isomers with more highly branched alkyl side chains were degraded much faster than the others. Furthermore, the C9 alcohols 2,3,5-trimethylhexan-2-ol, 3,6-dimethylheptan-3-ol, and 2-methyloctan-2-ol, derived from the three nonylphenol isomers with quaternary benzylic carbon atoms, were detected in the culture fluid by gas chromatography-mass spectrometry, but no analogous metabolites could be found originating from 4-(1-methyloctyl)phenol and 4-n-nonylphenol. We propose that 4-(1-methyloctyl)phenol and 4-n-nonylphenol were cometabolically transformed in the growth experiments with the mixture but that, unlike the other isomers, they did not participate in the reactions leading to the detachment of the alkyl moiety. This hypothesis was corroborated by the observed accumulation in the culture fluid of an as yet unidentified metabolite derived from 4-(1-methyloctyl)phenol. PMID:15746308

Identification of (2-aminopropyl)indole positional isomers in forensic samples.

PubMed

Scott, Kenneth R; Power, John D; McDermott, Seán D; O'Brien, John E; Talbot, Brian N; Barry, Michael G; Kavanagh, Pierce V

2014-01-01

In 2012, 5-(2-aminopropyl)indole (5-API, 5-IT) was reported by Norwegian authorities to the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) via the Early Warning System (EWS). The 3- isomer, 3-(2-aminopropyl)indole (3-API, AMT, alpha-methyltryptamine), has been available on the recreational drugs market for a somewhat longer time, having first been reported to the EMCDDA by Finnish authorities in 2001. Both isomers are available from online vendors of 'legal highs'. Recently, three forensic drug cases (two tablets and one powder) were presented for routine analysis and the active constituent was tentatively identified as an API isomer. The six positional isomers (2-, 3-, 4-, 5-, 6- and 7-(2-aminopropyl)indoles) were synthesized and analyses by a combination gas chromatography-mass spectrometry (GC-MS), and liquid chromatography-mass spectrometry (LC-MS) showed that these could be readily discriminated thus facilitating the identification of 3-API in the tablets and 5-API in the powder. With exception of 5- and 6-APIs, which co-eluted, it was found possible to separate the isomers by GC without derivatization. LC separation also proved to be a feasible method for the discrimination of the isomers. Although the 2- and 7- isomers were not fully resolved by LC, it was found possible to distinguish them using their product ion spectra as the 2- isomer produced the m/z 132 fragment ion formed by loss of vinylamine, whereas the 7- isomer formed m/z 158 through loss of methylamine. In the synthesis 2-API, a novel tricyclic by-product was formed in an annulation reaction where the reaction solvent, tetrahydrofuran, was incorporated into the molecule. Copyright © 2013 John Wiley & Sons, Ltd.

An Isomer-Specific Approach to Endocrine-Disrupting Nonylphenol in Infant Food.

PubMed

Günther, Klaus; Räcker, Torsten; Böhme, Roswitha

2017-02-15

Nonylphenols (NPs) are persistent endocrine disruptors that are priority hazardous substances of the European Union Water Framework Directive. Their presence in the environment has caused growing concern regarding their impact on human health. Recent studies have shown that nonylphenol is ubiquitous in commercially available foodstuffs and is also present in human blood. The isomer distribution of 4-nonylphenol was analyzed by gas chromatography - mass spectrometry in 44 samples of infant food. Our study shows that the distribution of nonylphenol isomers is dependent on the foodstuff analyzed. Although some isomer groups prevail, different distributions are frequent. Variations are even found in the same food group. Nonylphenol is a complex mixture of isomers, and the estrogenic potentials of each of these isomers are very different. Consequently, to determine the potential toxicological impact of NP in food, an isomer-specific approach is necessary.

Molecular structure of uranium carbides: Isomers of UC3

NASA Astrophysics Data System (ADS)

Zalazar, M. Fernanda; Rayón, Víctor M.; Largo, Antonio

2013-03-01

In this article, the most relevant isomers of uranium tricarbide are studied through quantum chemical methods. It is found that the most stable isomer has a fan geometry in which the uranium atom is bonded to a quasilinear C3 unit. Both, a rhombic and a ring CU(C2) structures are found about 104-125 kJ/mol higher in energy. Other possible isomers including linear geometries are located even higher. For each structure, we provide predictions for those molecular properties (vibrational frequencies, IR intensities, dipole moments) that could eventually help in their experimental detection. We also discuss the possible routes for the formation of the different UC3 isomers as well as the bonding situation by means of a topological analysis of the electron density.

Molecular structure of uranium carbides: isomers of UC3.

PubMed

Zalazar, M Fernanda; Rayón, Víctor M; Largo, Antonio

2013-03-21

In this article, the most relevant isomers of uranium tricarbide are studied through quantum chemical methods. It is found that the most stable isomer has a fan geometry in which the uranium atom is bonded to a quasilinear C3 unit. Both, a rhombic and a ring CU(C2) structures are found about 104-125 kJ/mol higher in energy. Other possible isomers including linear geometries are located even higher. For each structure, we provide predictions for those molecular properties (vibrational frequencies, IR intensities, dipole moments) that could eventually help in their experimental detection. We also discuss the possible routes for the formation of the different UC3 isomers as well as the bonding situation by means of a topological analysis of the electron density.

Enhanced bioavailability of lycopene when consumed as cis-isomers from tangerine compared to red tomato juice, a randomized, cross-over clinical trial

PubMed Central

Cooperstone, Jessica L.; Ralston, Robin A.; Riedl, Ken M.; Haufe, Thomas C.; Schweiggert, Ralf M.; King, Samantha A.; Timmers, Cynthia D.; Francis, David M.; Lesinski, Gregory B.; Clinton, Steven K.; Schwartz, Steven J.

2015-01-01

Scope Tangerine tomatoes (Solanum lycopersicum) are rich in tetra-cis-lycopene resulting from natural variation in carotenoid isomerase. Our objective was to compare the bioavailability of lycopene from tangerine to red tomato juice, and elucidate physical deposition forms of these isomers in tomatoes by light and electron microscopy. Methods and results Following a randomized crossover design, subjects (n=11, 6M/5F) consumed two meals delivering 10 mg lycopene from tangerine (94% cis) or red tomato juice (10% cis). Blood was sampled over 12 hours and triglyceride-rich lipoprotein fractions of plasma (TRLs) were isolated and analyzed using HPLC-DAD-MS/MS. Lycopene was crystalline in red tomato chromoplasts and globular in tangerine tomatoes. With tangerine tomato juice we observed a marked 8.5-fold increase in lycopene bioavailability compared to red tomato juice (P<0.001). Fractional absorption was 47.70 ± 8.81% from tangerine and 4.98 ± 1.92% from red tomato juices. Large heterogeneity was observed among subjects. Conclusions Lycopene is markedly more bioavailable from tangerine than from red tomato juice, consistent with a predominance of cis-lycopene isomers and presence in chromoplasts in a lipid dissolved globular state. These results justify using tangerine tomatoes as a lycopene source in studies examining the potential health benefits of lycopene-rich foods. PMID:25620547

Enhanced bioavailability of lycopene when consumed as cis-isomers from tangerine compared to red tomato juice, a randomized, cross-over clinical trial.

PubMed

Cooperstone, Jessica L; Ralston, Robin A; Riedl, Ken M; Haufe, Thomas C; Schweiggert, Ralf M; King, Samantha A; Timmers, Cynthia D; Francis, David M; Lesinski, Gregory B; Clinton, Steven K; Schwartz, Steven J

2015-04-01

Tangerine tomatoes (Solanum lycopersicum) are rich in tetra-cis-lycopene resulting from natural variation in carotenoid isomerase. Our objective was to compare the bioavailability of lycopene from tangerine to red tomato juice, and elucidate physical deposition forms of these isomers in tomatoes by light and electron microscopy. Following a randomized cross-over design, subjects (n = 11, 6 M/5 F) consumed two meals delivering 10 mg lycopene from tangerine (94% cis) or red tomato juice (10% cis). Blood was sampled over 12 h and triglyceride-rich lipoprotein fractions of plasma were isolated and analyzed using HPLC-DAD-MS/MS. Lycopene was crystalline in red tomato chromoplasts and globular in tangerine tomatoes. With tangerine tomato juice we observed a marked 8.5-fold increase in lycopene bioavailability compared to red tomato juice (p < 0.001). Fractional absorption was 47.70 ± 8.81% from tangerine and 4.98 ± 1.92% from red tomato juices. Large heterogeneity was observed among subjects. Lycopene is markedly more bioavailable from tangerine than from red tomato juice, consistent with a predominance of cis-lycopene isomers and presence in chromoplasts in a lipid dissolved globular state. These results justify using tangerine tomatoes as a lycopene source in studies examining the potential health benefits of lycopene-rich foods. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

27 CFR 21.120 - Nitropropane, mixed isomers of.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Nitropropane, mixed isomers of. 21.120 Section 21.120 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE... Denaturants § 21.120 Nitropropane, mixed isomers of. (a) Nitropropane content. A minimum of 94 percent by...

27 CFR 21.120 - Nitropropane, mixed isomers of.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 27 Alcohol, Tobacco Products and Firearms 1 2014-04-01 2014-04-01 false Nitropropane, mixed isomers of. 21.120 Section 21.120 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE... Denaturants § 21.120 Nitropropane, mixed isomers of. (a) Nitropropane content. A minimum of 94 percent by...

27 CFR 21.120 - Nitropropane, mixed isomers of.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Nitropropane, mixed isomers of. 21.120 Section 21.120 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE... Denaturants § 21.120 Nitropropane, mixed isomers of. (a) Nitropropane content. A minimum of 94 percent by...

27 CFR 21.120 - Nitropropane, mixed isomers of.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 27 Alcohol, Tobacco Products and Firearms 1 2013-04-01 2013-04-01 false Nitropropane, mixed isomers of. 21.120 Section 21.120 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE... Denaturants § 21.120 Nitropropane, mixed isomers of. (a) Nitropropane content. A minimum of 94 percent by...

27 CFR 21.120 - Nitropropane, mixed isomers of.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Nitropropane, mixed isomers of. 21.120 Section 21.120 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE... Denaturants § 21.120 Nitropropane, mixed isomers of. (a) Nitropropane content. A minimum of 94 percent by...

Distribution of hexadecenoic, octadecenoic and octadecadienoic acid isomers in human tissue lipids.

PubMed

Adlof, R O; Emken, E A

1986-09-01

The trans 16:1, 18:1 and 18:2 fatty acid composition of various human organ lipids was studied to determine if isomers accumulated in specific tissues. "Trans" isomers are defined as those fatty acids containing one or more trans double bonds. Adipose, kidney, brain, heart and liver tissue lipids were analyzed. Gas chromatography with a 100-SP2560 capillary column was used to characterize the various positional and/or geometrical isomers. The distribution of trans 16:1 and 18:1 isomers ranged from 0.3% in the brain to 4.0% in adipose tissue, while trans 18:2 isomers ranged from 0.0% in the brain to 0.4% in adipose tissue. No trans 18:3 isomers were detected. Positional isomer ratios for cis 16:1 (delta 9 vs delta 7) and cis 18:1 (delta 11 vs delta 9) were also determined. Since these ratios are reproducible from one individual to the next, they might be useful for diagnosis of human metabolic disorders.

Ablation of steel by microsecond pulse trains

NASA Astrophysics Data System (ADS)

Windeler, Matthew Karl Ross

Laser micromachining is an important material processing technique used in industry and medicine to produce parts with high precision. Control of the material removal process is imperative to obtain the desired part with minimal thermal damage to the surrounding material. Longer pulsed lasers, with pulse durations of milli- and microseconds, are used primarily for laser through-cutting and welding. In this work, a two-pulse sequence using microsecond pulse durations is demonstrated to achieve consistent material removal during percussion drilling when the delay between the pulses is properly defined. The light-matter interaction moves from a regime of surface morphology changes to melt and vapour ejection. Inline coherent imaging (ICI), a broadband, spatially-coherent imaging technique, is used to monitor the ablation process. The pulse parameter space is explored and the key regimes are determined. Material removal is observed when the pulse delay is on the order of the pulse duration. ICI is also used to directly observe the ablation process. Melt dynamics are characterized by monitoring surface changes during and after laser processing at several positions in and around the interaction region. Ablation is enhanced when the melt has time to flow back into the hole before the interaction with the second pulse begins. A phenomenological model is developed to understand the relationship between material removal and pulse delay. Based on melt refilling the interaction region, described by logistic growth, and heat loss, described by exponential decay, the model is fit to several datasets. The fit parameters reflect the pulse energies and durations used in the ablation experiments. For pulse durations of 50 us with pulse energies of 7.32 mJ +/- 0.09 mJ, the logisitic growth component of the model reaches half maximum after 8.3 mus +/- 1.1 us and the exponential decays with a rate of 64 mus +/- 15 us. The phenomenological model offers an interpretation of the material

Wire Array Z-pinches on Sphinx Machine: Experimental Results and Relevant Points of Microsecond Implosion Physics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Calamy, H.; Hamann, F.; Lassalle, F.

Centre d'Etudes de Gramat (France) has developed an efficient long implosion time (800 ns) Aluminum plasma radiation source (PRS). Based on the LTD technology, the SPHINX facility is developed as a 1-3MJ, 1{mu}s rise time, 4-10 MA current driver. In this paper, it was used in 1MJ, 4MA configuration to drive Aluminum nested wire arrays Z-pinches with K-shell yield up to 20 kJ and a FWHM of the x-ray pulse of about 50 ns. We present latest SPHINX experiments and some of the main physic issues of the microsecond regime. Experimental setup and results are described with the aim ofmore » giving trends that have been obtained. The main features of microsecond implosion of wire arrays can be analyzed thanks to same methods and theories as used for faster Z-pinches. The effect of load polarity was examined. The stability of the implosion , one of the critical point of microsecond wire arrays due to the load dimensions imposed by the time scale, is tackled. A simple scaling from 100 ns Z-pinch results to 800 ns ones gives good results and the use of nested arrays improves dramatically the implosion quality and the Kshell yield of the load. However, additional effects such as the impact of the return current can geometry on the implosion have to be taken into account on our loads. Axial inhomogeneity of the implosion the origin of which is not yet well understood occurs in some shots and impacts the radiation output. The shape of the radiative pulse is discussed and compared with the homogeneity of the implosion. Numerical 2D R-Z and R-{theta} simulations are used to highlight some experimental results and understand the plasma conditions during these microsecond wire arrays implosions.« less

Wire Array Z-pinches on Sphinx Machine: Experimental Results and Relevant Points of Microsecond Implosion Physics

NASA Astrophysics Data System (ADS)

Calamy, H.; Hamann, F.; Lassalle, F.; Bayol, F.; Mangeant, C.; Morell, A.; Huet, D.; Bedoch, J. P.; Chittenden, J. P.; Lebedev, S. V.; Jennings, C. A.; Bland, S. N.

2006-01-01

Centre d'Etudes de Gramat (France) has developed an efficient long implosion time (800 ns) Aluminum plasma radiation source (PRS). Based on the LTD technology, the SPHINX facility is developed as a 1-3MJ, 1μs rise time, 4-10 MA current driver. In this paper, it was used in 1MJ, 4MA configuration to drive Aluminum nested wire arrays Z-pinches with K-shell yield up to 20 kJ and a FWHM of the x-ray pulse of about 50 ns. We present latest SPHINX experiments and some of the main physic issues of the microsecond regime. Experimental setup and results are described with the aim of giving trends that have been obtained. The main features of microsecond implosion of wire arrays can be analyzed thanks to same methods and theories as used for faster Z-pinches. The effect of load polarity was examined. The stability of the implosion , one of the critical point of microsecond wire arrays due to the load dimensions imposed by the time scale, is tackled. A simple scaling from 100 ns Z-pinch results to 800 ns ones gives good results and the use of nested arrays improves dramatically the implosion quality and the Kshell yield of the load. However, additional effects such as the impact of the return current can geometry on the implosion have to be taken into account on our loads. Axial inhomogeneity of the implosion the origin of which is not yet well understood occurs in some shots and impacts the radiation output. The shape of the radiative pulse is discussed and compared with the homogeneity of the implosion. Numerical 2D R-Z and R-θ simulations are used to highlight some experimental results and understand the plasma conditions during these microsecond wire arrays implosions.

Homochiral Asymmetric Triacylglycerol Isomers in Egg Yolk.

PubMed

Nagai, Toshiharu; Ishikawa, Keiko; Yoshinaga, Kazuaki; Yoshida, Akihiko; Beppu, Fumiaki; Gotoh, Naohiro

2017-12-01

The composition of triacylglycerol (TAG) positional isomer (-PI) and enantiomer (-E) in immature chicken egg yolk, mature chicken yolk, and chicken meat was examined. POO (consisting of one palmitic acid (P) and two oleic acids (Os)), PPO (consisting of two Ps and one O), and PPL (consisting of two Ps and one linoleic acid (L)) were treated as representative TAG molecular species in all the analytical samples because P, O, and L were the major fatty acids comprising egg and chicken meat. sn-POO (binding P at sn-1 position) was predominant in egg yolks, while sn-OOP and sn-OPO were present in chicken meat. This difference was ascribed to the different roles of these isomers as nutrients, because TAG in egg yolk is important for new born organisms and TAG in chicken meat is used for fat accumulation. The compositions of the TAG isomers in PPO and PPL in egg yolk were similar, and O and L did not bind at the sn-1 position. In contrast, all the isomers of PPO and PPL were found in chicken meat. These results imply that the TAG structure could be modified so that the nutrient requirement is fulfilled in egg yolk and chicken meat.

Substitution effects on the absorption spectra of nitrophenolate isomers.

PubMed

Wanko, Marius; Houmøller, Jørgen; Støchkel, Kristian; Suhr Kirketerp, Maj-Britt; Petersen, Michael Åxman; Nielsen, Mogens Brøndsted; Nielsen, Steen Brøndsted; Rubio, Angel

2012-10-05

Charge-transfer excitations highly depend on the electronic coupling between the donor and acceptor groups. Nitrophenolates are simple examples of charge-transfer systems where the degree of coupling differs between ortho, meta and para isomers. Here we report the absorption spectra of the isolated anions in vacuo to avoid the complications of solvent effects. Gas-phase action spectroscopy was done with two different setups, an electrostatic ion storage ring and an accelerator mass spectrometer. The results are interpreted on the basis of CC2 quantum chemical calculations. We identified absorption maxima at 393, 532, and 399 nm for the para, meta, and ortho isomer, respectively, with the charge-transfer transition into the lowest excited singlet state. In the meta isomer, this π-π* transition is strongly redshifted and its oscillator strength reduced, which is related to the pronounced charge-transfer character, as a consequence of the topology of the conjugated π-system. Each isomer's different charge distribution in the ground state leads to a very different solvent shift, which in acetonitrile is bathochromic for the para and ortho, but hypsochromic for the meta isomer.

Actual ratios of triacylglycerol positional isomers and enantiomers comprising saturated fatty acids and highly unsaturated fatty acids in fishes and marine mammals.

PubMed

Nagai, Toshiharu; Matsumoto, Yumiko; Jiang, Yanying; Ishikawa, Keiko; Wakatabe, Tokuhisa; Mizobe, Hoyo; Yoshinaga, Kazuaki; Kojima, Koichi; Kuroda, Ikuma; Saito, Tadao; Beppu, Fumiaki; Gotoh, Naohiro

2013-01-01

It has been previously shown that the positional isomers of triacylglycerol (TAG) containing palmitic acid (P) and highly unsaturated fatty acids (HUFAs) such as DHA (D) and EPA (E) vary between fishes and marine mammals. However, it has not yet been understood why in marine mammals HUFAs are located only at the α position when two palmitic acid chains combine, and not in fishes. In order to gain further understanding of the biosynthetic pathways involved in the formation of these asymmetric TAGs, we investigated whether the HUFA in the TAG of marine mammals exists predominantly at the sn-1 or sn-3 position. We examined the TAG positional isomers and enantiomers in marine organisms in detail. As a result, while PDP and PEP were not detected, sn-PPD and sn-PPE were found in abundance in marine mammals. For fishes, on the other hand, PDP, PEP, sn-PPD, and sn-PPE were all identified. In the case of TAGs that contain two HUFAs and one palmitic acid, marine mammals were rich in DPD and EPE whereas fishes were rich in sn-PDD and sn-PEE.

Enantioselective separation of defined endocrine-disrupting nonylphenol isomers.

PubMed

Acir, Ismail-Hakki; Wüst, Matthias; Guenther, Klaus

2016-08-01

Nonylphenol is in the focus of worldwide endocrine-disrupter research and accounted for as a priority hazardous substance of the Water Framework Directive of the European Union. Technical nonylphenol consists of a very complex mixture of isomers and enantiomers. As estrogenic effect and degradation behavior in environmental processes of single nonylphenols are heavily dependent on the structure of the nonyl side chain, it is absolutely necessary to consider the nonylphenol problem from an isomer and enantiomer-specific viewpoint. In this study, an enantiomer-specific separation of eight defined synthesized nonylphenol isomers by five different special chiral cyclodextrin columns was performed underivatized and after methylation, silylation, and acylation. This work demonstrates that three columns out of the investigated five show an excellent separation behavior for the studied different nonylphenol isomers and can be used for the enantiomer-specific determination of nonylphenols in food, other biological matrices, and environmental samples in the future. Graphical abstract Enantiomeric pair of 4-NP170 (4-[1-ethyl-1,3,3-trimethylbutyl]phenol).

The interstellar chemistry of H2C3O isomers

PubMed Central

Loison, Jean-Christophe; Agúndez, Marcelino; Marcelino, Núria; Wakelam, Valentine; Hickson, Kevin M.; Cernicharo, José; Gerin, Maryvonne; Roueff, Evelyne; Guélin, Michel

2016-01-01

We present the detection of two H2C3O isomers, propynal and cyclopropenone, toward various starless cores and molecular clouds, together with upper limits for the third isomer propadienone. We review the processes controlling the abundances of H2C3O isomers in interstellar media showing that the reactions involved are gas-phase ones. We show that the abundances of these species are controlled by kinetic rather than thermodynamic effects. PMID:27013768

Evaluation of electrical conductivity of Cu and Al through sub microsecond underwater electrical wire explosion

NASA Astrophysics Data System (ADS)

Sheftman, D.; Shafer, D.; Efimov, S.; Krasik, Ya. E.

2012-03-01

Sub-microsecond timescale underwater electrical wire explosions using Cu and Al materials have been conducted. Current and voltage waveforms and time-resolved streak images of the discharge channel, coupled to 1D magneto-hydrodynamic simulations, have been used to determine the electrical conductivity of the metals for the range of conditions between hot liquid metal and strongly coupled non-ideal plasma, in the temperature range of 10-60 KK. The results of these studies showed that the conductivity values obtained are typically lower than those corresponding to modern theoretical electrical conductivity models and provide a transition between the conductivity values obtained in microsecond time scale explosions and those obtained in nanosecond time scale wire explosions. In addition, the measured wire expansion shows good agreement with equation of state tables.

Transient isomers in the photodissociation of bromoiodomethane

NASA Astrophysics Data System (ADS)

Marcellini, Moreno; Nasedkin, Alexandr; Zietz, Burkhard; Petersson, Jonas; Vincent, Jonathan; Palazzetti, Federico; Malmerberg, Erik; Kong, Qingyu; Wulff, Michael; van der Spoel, David; Neutze, Richard; Davidsson, Jan

2018-04-01

The photochemistry of halomethanes is fascinating for the complex cascade reactions toward either the parent or newly synthesized molecules. Here, we address the structural rearrangement of photodissociated CH2IBr in methanol and cyclohexane, probed by time-resolved X-ray scattering in liquid solution. Upon selective laser cleavage of the C-I bond, we follow the reaction cascade of the two geminate geometrical isomers, CH2I-Br and CH2Br-I. Both meta-stable isomers decay on different time scales, mediated by solvent interaction, toward the original parent molecule. We observe the internal rearrangement of CH2Br-I to CH2I-Br in cyclohexane by extending the time window up to 3 μs. We track the photoproduct kinetics of CH2Br-I in methanol solution where only one isomer is observed. The effect of the polarity of solvent on the geminate recombination pathways is discussed.

Nuclear isomer suitable for gamma ray laser

NASA Technical Reports Server (NTRS)

Jha, S.

1979-01-01

The operation of gamma ray lasers (gasers) are studied. It is assumed that the nuclear isomers mentioned in previously published papers have inherent limitations. It is further assumed that the judicious use of Bormann effect or the application of the total external reflection of low energy gamma radiation at grazing angle of incidence may permit the use of a gaser crystal sufficiently long to achieve observable stimulated emission. It is suggested that a long lived 0(+) isomer decaying by low energy gamma ray emission to a short lived 2(+) excited nuclear state would be an attractive gaser candidate. It is also suggested that the nuclear isomer be incorporated in a matrix of refractory material having an electrostatic field gradient whose principal axis lies along the length of the medium. This results in the preferential transmission of electric quadrupole radiation along the length of the medium.

High-K isomers and rotational structures in {sup 174}W

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tandel, S.K.; Chowdhury, P.; Seabury, E.H.

2006-04-15

High-spin states in {sup 174}W (Z = 74) have been populated using the reaction {sup 128}Te({sup 50}Ti, 4n){sup 174}W at beam energies of 215 and 225 MeV. The Gammasphere array was used to detect the {gamma} rays emitted by the evaporation residues. Four previously known collective band structures have been extended, and 16 new rotational sequences observed. Two are built upon isomeric states, one corresponding to a two-quasiparticle K = 8 isomer, the other to a four-quasiparticle K = 12 isomer, with the latter exhibiting strong K-violating {delta}K=12 decays to the ground state band. Nucleonic configurations for the two- andmore » four-quasiparticle excitations are proposed, and Woods-Saxon cranking calculations are presented to understand the rotational structures. Decay mechanisms of multi-quasiparticle K isomers are discussed in terms of the prevalent phenomenological models, with special emphasis on {gamma}-tunneling calculations. Surprisingly, the latter underpredict the decay hindrance for the K = 12 isomer by three orders of magnitude, unlike all other isomer decays in this mass region.« less

Effectiveness of Iron Ethylenediamine-N,N'-bis(hydroxyphenylacetic) Acid (o,o-EDDHA/Fe3+) Formulations with Different Ratios of Meso and d,l-Racemic Isomers as Iron Fertilizers.

PubMed

Alcañiz, Sara; Jordá, Juana D; Cerdán, Mar

2017-01-18

Two o,o-EDDHA/Fe 3+ formulations (meso, 93.5% w/w of meso isomer; and d,l-racemic, 91.3% w/w of d,l-racemic mixture) were prepared, and their efficacy to avoid or to relieve iron deficiency in Fe-sufficient and Fe-deficient tomato plants grown on hydroponic solution was compared with that of the current o,o-EDDHA/Fe 3+ formulations (50% of meso and d,l-racemic isomers). The effectiveness of the three o,o-EDDHA/Fe 3+ formulations was different depending on the iron nutritional status of plants. The three o,o-EDDHA/Fe 3+ formulations tested were effective in preventing iron chlorosis in healthy plants. However, the higher the meso concentration in the formulations, the higher the effectiveness in the recovery of iron chlorotic plants from iron deficiency. Accordingly, o,o-EDDHA/Fe 3+ formulations rich in meso isomer are recommended in hydroponic systems.

Isomer Shift and Magnetic Moment of the Long-Lived 1/2^{+} Isomer in _{30}^{79}Zn_{49}: Signature of Shape Coexistence near ^{78}Ni.

PubMed

Yang, X F; Wraith, C; Xie, L; Babcock, C; Billowes, J; Bissell, M L; Blaum, K; Cheal, B; Flanagan, K T; Garcia Ruiz, R F; Gins, W; Gorges, C; Grob, L K; Heylen, H; Kaufmann, S; Kowalska, M; Kraemer, J; Malbrunot-Ettenauer, S; Neugart, R; Neyens, G; Nörtershäuser, W; Papuga, J; Sánchez, R; Yordanov, D T

2016-05-06

Collinear laser spectroscopy is performed on the _{30}^{79}Zn_{49} isotope at ISOLDE-CERN. The existence of a long-lived isomer with a few hundred milliseconds half-life is confirmed, and the nuclear spins and moments of the ground and isomeric states in ^{79}Zn as well as the isomer shift are measured. From the observed hyperfine structures, spins I=9/2 and I=1/2 are firmly assigned to the ground and isomeric states. The magnetic moment μ (^{79}Zn)=-1.1866(10)μ_{N}, confirms the spin-parity 9/2^{+} with a νg_{9/2}^{-1} shell-model configuration, in excellent agreement with the prediction from large scale shell-model theories. The magnetic moment μ (^{79m}Zn)=-1.0180(12)μ_{N} supports a positive parity for the isomer, with a wave function dominated by a 2h-1p neutron excitation across the N=50 shell gap. The large isomer shift reveals an increase of the intruder isomer mean square charge radius with respect to that of the ground state, δ⟨r_{c}^{2}⟩^{79,79m}=+0.204(6)  fm^{2}, providing first evidence of shape coexistence.

Population and decay of a Kπ=8- two-quasineutron isomer in 244Pu

NASA Astrophysics Data System (ADS)

Hota, S. S.; Tandel, S. K.; Chowdhury, P.; Ahmad, I.; Carpenter, M. P.; Chiara, C. J.; Greene, J. P.; Hoffman, C. R.; Jackson, E. G.; Janssens, R. V. F.; Kay, B. P.; Khoo, T. L.; Kondev, F. G.; Lakshmi, S.; Lalkovski, S.; Lauritsen, T.; Lister, C. J.; McCutchan, E. A.; Moran, K.; Peterson, D.; Shirwadkar, U.; Seweryniak, D.; Stefanescu, I.; Toh, Y.; Zhu, S.

2016-08-01

The decay of a Kπ=8- isomer in 244Pu and the collective band structures populating the isomer were studied using deep inelastic excitations with 47Ti and 208Pb beams, respectively. Precise measurements of M 1 /E 2 branching ratios in the band confirm a 9 /2-[734] ν⊗7 /2+[624] ν configuration assignment for the isomer, validating the systematics of Kπ=8- , two-quasineutron isomers observed in even-Z , N =150 isotones. These isomers around the deformed shell gap at N =152 provide critical benchmarks for theoretical predictions of single-particle energies in this gateway region to superheavy nuclei.

Separation and conversion dynamics of nuclear-spin isomers of gaseous methanol

PubMed Central

Sun, Zhen-Dong; Ge, Meihua; Zheng, Yujun

2015-01-01

All symmetrical molecules with non-zero nuclear spin exist in nature as nuclear-spin isomers (NSIs). However, owing to the lack of experimental information, knowledge is rare about interconversions of NSIs of gaseous molecules with torsional symmetry. Here we report our separation and conversion observations on NSI-torsion-specific transition systems of gaseous methanol from a light-induced drift experiment involving partially spatial separation of the ortho and para isomers. We find that vibrationally excited molecules of the methanol spin isomer have a smaller collision cross-section than their ground-state counterparts. Interconversion of the enriched ortho isomer with the para isomer, which is generally considered improbable, has been quantitatively studied by sensitive detections of the spectral intensities. Rather counterintuitively, this reveals that the interconversion is inhibited with increasing pressure. Our results suggest that the spin conversion mechanism in methanol is via a quantum relaxation process with the quantum Zeno effect induced by molecular collisions. PMID:25880882

Using Multiorder Time-Correlation Functions (TCFs) To Elucidate Biomolecular Reaction Pathways from Microsecond Single-Molecule Fluorescence Experiments.

PubMed

Phelps, Carey; Israels, Brett; Marsh, Morgan C; von Hippel, Peter H; Marcus, Andrew H

2016-12-29

Recent advances in single-molecule fluorescence imaging have made it possible to perform measurements on microsecond time scales. Such experiments have the potential to reveal detailed information about the conformational changes in biological macromolecules, including the reaction pathways and dynamics of the rearrangements involved in processes, such as sequence-specific DNA "breathing" and the assembly of protein-nucleic acid complexes. Because microsecond-resolved single-molecule trajectories often involve "sparse" data, that is, they contain relatively few data points per unit time, they cannot be easily analyzed using the standard protocols that were developed for single-molecule experiments carried out with tens-of-millisecond time resolution and high "data density." Here, we describe a generalized approach, based on time-correlation functions, to obtain kinetic information from microsecond-resolved single-molecule fluorescence measurements. This approach can be used to identify short-lived intermediates that lie on reaction pathways connecting relatively long-lived reactant and product states. As a concrete illustration of the potential of this methodology for analyzing specific macromolecular systems, we accompany the theoretical presentation with the description of a specific biologically relevant example drawn from studies of reaction mechanisms of the assembly of the single-stranded DNA binding protein of the T4 bacteriophage replication complex onto a model DNA replication fork.

Study on Separation of Structural Isomer with Magneto-Archimedes method

NASA Astrophysics Data System (ADS)

Kobayashi, T.; Mori, T.; Akiyama, Y.; Mishima, F.; Nishijima, S.

2017-09-01

Organic compounds are refined by separating their structural isomers, however each separation method has some problems. For example, distillation consumes large energy. In order to solve these problems, new separation method is needed. Considering organic compounds are diamagnetic, we focused on magneto-Archimedes method. With this method, particle mixture dispersed in a paramagnetic medium can be separated in a magnetic field due to the difference of the density and magnetic susceptibility of the particles. In this study, we succeeded in separating isomers of phthalic acid as an example of structural isomer using MnCl2 solution as the paramagnetic medium. In order to use magneto-Archimedes method for separating materials for food or medicine, we proposed harmless medium using oxygen and fluorocarbon instead of MnCl2 aqueous solution. As a result, the possibility of separating every structural isomer was shown.

Isomer-Specific Binding Affinity of Perfluorooctanesulfonate (PFOS) and Perfluorooctanoate (PFOA) to Serum Proteins.

PubMed

Beesoon, Sanjay; Martin, Jonathan W

2015-05-05

Perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) are among the most prominent contaminants in human serum, and these were historically manufactured as technical mixtures of linear and branched isomers. The isomers display unique pharmacokinetics in humans and in animal models, but molecular mechanisms underlying isomer-specific PFOS and PFOA disposition have not previously been studied. Here, ultrafiltration devices were used to examine (i) the dissociation constants (Kd) of individual PFOS and PFOA isomers with human serum albumin (HSA) and (ii) relative binding affinity of isomers in technical mixtures spiked to whole calf serum and human serum. Measurement of HSA Kd's demonstrated that linear PFOS (Kd=8(±4)×10(-8) M) was much more tightly bound than branched PFOS isomers (Kd range from 8(±1)×10(-5) M to 4(±2)×10(-4) M). Similarly, linear PFOA (Kd=1(±0.9)×10(-4) M) was more strongly bound to HSA compared to branched PFOA isomers (Kd range from 4(±2)×10(-4) M to 3(±2)×10(-4) M). The higher binding affinities of linear PFOS and PFOA to total serum protein were confirmed when both calf serum and human serum were spiked with technical mixtures. Overall, these data provide a mechanistic explanation for the longer biological half-life of PFOS in humans, compared to PFOA, and for the higher transplacental transfer efficiencies and renal clearance of branched PFOS and PFOA isomers, compared to the respective linear isomer.

Short-lived isomers in 192Po and 194Po

NASA Astrophysics Data System (ADS)

Andel, B.; Andreyev, A. N.; Antalic, S.; Heßberger, F. P.; Ackermann, D.; Hofmann, S.; Huyse, M.; Kalaninová, Z.; Kindler, B.; Kojouharov, I.; Kuusiniemi, P.; Lommel, B.; Nishio, K.; Page, R. D.; Sulignano, B.; Van Duppen, P.

2016-06-01

Isomeric states in 194Po and 192Po were studied at the velocity filter SHIP. The isotopes were produced in the fusion-evaporation reactions 141Pr(56Fe, p 2 n )194Po and 144Sm(51V, p 2 n )192Po . Several new γ -ray transitions were attributed to the isomers and γ -γ coincidences for both isomers were studied for the first time. The 459-keV transition earlier, tentatively proposed as de-exciting the isomeric level in 194Po, was replaced by a new 248-keV transition, and the spin of this isomer was reassigned from (11-) to (10-). The de-excitation of the (11-) isomeric level in 192Po by the 154-keV transition was confirmed and a parallel de-excitation by a 733-keV (E 3 ) transition to (8+) level of the ground-state band was suggested. Moreover, side feeding to the (4+) level of the ground-state band was proposed. The paper also discusses strengths of transitions de-exciting 11- isomers in neighboring Po and Pb isotopes.

Analyzing ion distributions around DNA: sequence-dependence of potassium ion distributions from microsecond molecular dynamics

PubMed Central

Pasi, Marco; Maddocks, John H.; Lavery, Richard

2015-01-01

Microsecond molecular dynamics simulations of B-DNA oligomers carried out in an aqueous environment with a physiological salt concentration enable us to perform a detailed analysis of how potassium ions interact with the double helix. The oligomers studied contain all 136 distinct tetranucleotides and we are thus able to make a comprehensive analysis of base sequence effects. Using a recently developed curvilinear helicoidal coordinate method we are able to analyze the details of ion populations and densities within the major and minor grooves and in the space surrounding DNA. The results show higher ion populations than have typically been observed in earlier studies and sequence effects that go beyond the nature of individual base pairs or base pair steps. We also show that, in some special cases, ion distributions converge very slowly and, on a microsecond timescale, do not reflect the symmetry of the corresponding base sequence. PMID:25662221

Selectivity of hexaphenylbenzene-based hydrocarbon stationary phase with propeller-like conformation for aromatic and aliphatic isomers.

PubMed

Yang, Yinhui; Chang, Zhengfeng; Yang, Xiaohong; Qi, Meiling; Wang, Jinliang

2018-08-03

Herein we report a propeller-like hexaphenylbenzene-based hydrocarbon material (denoted as BT) as the stationary phase for capillary gas chromatography (GC). The statically-coated BT capillary column showed a high column efficiency of 4340 plates m -1 and weak polarity. Owing to its unique conformation, π-electron toroidal delocalization and intrinsic microporosity, the BT stationary phase exhibited interesting selectivity for aromatic compounds over alkanes. Compared with the graphene (G) column, the BT column showed much prolonged retention and high selectivity for aromatic isomers, especially methylnaphthalenes, dimethylnaphthalenes and phenanthrene/anthracene, mainly because of its propeller-like conformation with rich intercalation effects. Moreover, it exhibited good column repeatability (intra-day, inter-day) and reproducibility (between-column) with RSD values on the retention times less than 0.08% for intra-day, 0.32% for inter-day and 3.8% for between-column, respectively. Also, it showed good potential for determination of minor isomer impurities in real samples. To the best of our knowledge, this work presents the first example of employing an neat aromatic hydrocarbon material as the GC stationary phase with high selectivity for analytes of a wide ranging polarity. Copyright © 2018 Elsevier B.V. All rights reserved.

Parallel line raster eliminates ambiguities in reading timing of pulses less than 500 microseconds apart

NASA Technical Reports Server (NTRS)

Horne, A. P.

1966-01-01

Parallel horizontal line raster is used for precision timing of events occurring less than 500 microseconds apart for observation of hypervelocity phenomena. The raster uses a staircase vertical deflection and eliminates ambiguities in reading timing of pulses close to the end of each line.

Distribution of perfluorooctane sulfonate isomers and predicted risk of thyroid hormonal perturbation in drinking water.

PubMed

Yu, Nanyang; Wang, Xiaoxiang; Zhang, Beibei; Yang, Jingping; Li, Meiying; Li, Jun; Shi, Wei; Wei, Si; Yu, Hongxia

2015-06-01

We documented the distribution of seven perfluorooctane sulfonate (PFOS) isomers in drinking water in Jiangsu Province, China. Compared to the 30% proportion of branched PFOS in technical PFOS, the levels of branched PFOS in drinking water increased to 31.8%-44.6% of total PFOS. Because of previous risk assessment without considering the PFOS isomer profile and the toxicity of individual PFOS isomers, here we performed a new health risk assessment of PFOS for thyroid hormonal perturbation in drinking water with the contribution from individual PFOS isomers. The risk quotients (RQs) of individual PFOS isomers indicated that linear PFOS contributed most to the risk among all the target PFOS isomers (83.0%-90.2% of the total PFOS RQ), and that risk from 6m-PFOS (5.2%-11.9% of the total PFOS RQ) was higher than that from other branched PFOS isomers. We found that the risks associated with PFOS in drinking water would be overestimated by 10.0%-91.7% if contributions from individual PFOS isomers were not considered. The results revealed that the PFOS isomer profile and the toxicity of individual PFOS isomers were important factors in health risk assessment of PFOS and should be considered in the future risk assessments. Copyright © 2015 Elsevier Ltd. All rights reserved.

[Cytotoxicity of lysomustine and its isomers, and their potential use for selection of cells].

PubMed

Rozov, F N; Grinenko, T S; Levit, G L; Grishakov, A N; Beliavskiĭ, A V; Krasnov, V P

2011-01-01

N epsilon-Nitroso-N epsilon- [N'-(2-chloroethyl)carbamoyl]-L-lysine (I) and N epsilon- [N'-(2-chloroethyl)-N'-nitrosocarbamoyl]-L-lysine (II), the isomers being the constituents of antitumor agent Lysomustine, were obtained by RFHPLC. The study of cytotoxicity of the above compounds against K562 cells showed that the lesions induced by isomer (II) produce a significant cytotoxic effect but can be efficiently repaired by the action of MGMT (O6-methylaguanine DNA methyltransferase). Under similar conditions, the lesions induced by isomer (I) produce substantially smaller effect but are weakly if at all repairable by MGMT. The effects of a clinically approved agent Lysomustine, which is the mixture of isomers (I) and (II), are similar to those of isomer (II). The results obtained point to a different chemical nature of DNA lesions induced by two Lysomustine isomers. Our data indicate that Lysomustine and its isomer (II) can be used for in vitro selection of cells expressing MGMT.

An Unusual Conformational Isomer of Verrucosidin Backbone from a Hydrothermal Vent Fungus, Penicillium sp. Y-50-10.

PubMed

Pan, Chengqian; Shi, Yutong; Auckloo, Bibi Nazia; Chen, Xuegang; Chen, Chen-Tung Arthur; Tao, Xinyi; Wu, Bin

2016-08-18

A new verrucosidin derivative, methyl isoverrucosidinol (1), was isolated from the marine fungus Penicillium sp. Y-50-10, dwelling in sulfur rich sediment in the Kueishantao hydrothermal vents off Taiwan. The structure was established by spectroscopic means including HRMS and 2D-NMR spectroscopic analysis. The absolute configuration was defined mainly by comparison of quantum chemical TDDFT calculated and experimental ECD spectra. Among hitherto known compounds with a verrucosidine backbone isolated from natural resource, compound 1 represents the first example of a new conformational isomer of its skeleton, exhibiting antibiotic activity against Bacillus subtilis with MIC value 32 μg/mL.

Computational Screening of Nanoporous Materials for Hexane and Heptane Isomer Separation

DOE PAGES

Chung, Yongchul G.; Bai, Peng; Haranczyk, Maciej; ...

2017-07-05

Computational high-throughput screening was carried out to assess a large number of experimentally reported metal–organic frameworks (MOFs) and zeolites for their utility in hexane isomer separation. Through the paper, we identified many MOFs and zeolites with high selectivity (S L+M > 10) for the group of n-hexane, 2-methylpentane, and 3-methylpentane (linear and monobranched isomers) versus 2,2-dimethylbutane and 2,3-dimethylbutane (dibranched isomers). This group of selective sorbents includes VICDOC (Fe 2(BDP) 3), a MOF with triangular pores that is known to exhibit high isomer selectivity and capacity. For three of these structures, the adsorption isotherms for a 10-component mixture of hexane andmore » heptane isomers were calculated. Subsequent simulations of column breakthrough curves showed that the DEYVUA MOF exhibits a longer process cycle time than VICDOC MOF or MRE zeolite, which are previously reported, high-performing materials, illustrating the importance of capacity in designing MOFs for practical applications. Among the identified candidates, we synthesized and characterized a MOF in a new copper form with high predicted adsorbent capacity (q L+M > 1.2 mol/L) and moderately high selectivity (S L+M ≈ 10). In conclusion, we examined the role of pore shape in hexane isomer separations, especially of triangular-shaped pores. We show through the potential energy surface and three-dimensional siting analyses that linear alkanes do not populate the corners of narrow triangular channels and that structures with nontriangular pores can efficiently separate hexane isomers. Detailed thermodynamic analysis illustrates how differences in the free energy of adsorption contribute to shape-selective separation in nanoporous materials.« less

Computational Screening of Nanoporous Materials for Hexane and Heptane Isomer Separation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chung, Yongchul G.; Bai, Peng; Haranczyk, Maciej

Computational high-throughput screening was carried out to assess a large number of experimentally reported metal–organic frameworks (MOFs) and zeolites for their utility in hexane isomer separation. Through the paper, we identified many MOFs and zeolites with high selectivity (S L+M > 10) for the group of n-hexane, 2-methylpentane, and 3-methylpentane (linear and monobranched isomers) versus 2,2-dimethylbutane and 2,3-dimethylbutane (dibranched isomers). This group of selective sorbents includes VICDOC (Fe 2(BDP) 3), a MOF with triangular pores that is known to exhibit high isomer selectivity and capacity. For three of these structures, the adsorption isotherms for a 10-component mixture of hexane andmore » heptane isomers were calculated. Subsequent simulations of column breakthrough curves showed that the DEYVUA MOF exhibits a longer process cycle time than VICDOC MOF or MRE zeolite, which are previously reported, high-performing materials, illustrating the importance of capacity in designing MOFs for practical applications. Among the identified candidates, we synthesized and characterized a MOF in a new copper form with high predicted adsorbent capacity (q L+M > 1.2 mol/L) and moderately high selectivity (S L+M ≈ 10). In conclusion, we examined the role of pore shape in hexane isomer separations, especially of triangular-shaped pores. We show through the potential energy surface and three-dimensional siting analyses that linear alkanes do not populate the corners of narrow triangular channels and that structures with nontriangular pores can efficiently separate hexane isomers. Detailed thermodynamic analysis illustrates how differences in the free energy of adsorption contribute to shape-selective separation in nanoporous materials.« less

New isomer and decay half-life of {sup 115}Ru

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurpeta, J.; Plochocki, A.; Rissanen, J.

2010-12-15

Exotic, neutron-rich nuclei of mass A=115 produced in proton-induced fission of {sup 238}U were extracted using the IGISOL mass separator. The beam of isobars was transferred to the JYFLTRAP Penning trap system for further separation to the isotopic level. Monoisotopic samples of {sup 115}Ru nuclei were used for {gamma}and {beta} coincidence spectroscopy. In {sup 115}Ru we have observed excited levels, including an isomer with a half-life of 76(6) ms and (7/2{sup -}) spin and parity. The first excited 61.7-keV level in {sup 115}Ru with spins and parity (3/2{sup +}) may correspond to an oblate 3/2{sup +}[431] Nilsson orbital. A half-lifemore » of 318(19) ms for the {beta}{sup -} decay of the (1/2{sup +}) ground state in {sup 115}Ru has been firmly established in two independent measurements, a value which is significantly shorter than that previously reported.« less

Fac and mer isomers of Ru(II) tris(pyrazolyl-pyridine) complexes as models for the vertices of coordination cages: structural characterisation and hydrogen-bonding characteristics.

PubMed

Metherell, Alexander J; Cullen, William; Stephenson, Andrew; Hunter, Christopher A; Ward, Michael D

2014-01-07

We have prepared a series of mononuclear fac and mer isomers of Ru(II) complexes containing chelating pyrazolyl-pyridine ligands, to examine their differing ability to act as hydrogen-bond donors in MeCN. This was prompted by our earlier observation that octanuclear cube-like coordination cages that contain these types of metal vertex can bind guests such as isoquinoline-N-oxide (K = 2100 M(-1) in MeCN), with a significant contribution to binding being a hydrogen-bonding interaction between the electron-rich atom of the guest and a hydrogen-bond donor site on the internal surface of the cage formed by a convergent set of CH2 protons close to a 2+ metal centre. Starting with [Ru(L(H))3](2+) [L(H) = 3-(2-pyridyl)-1H-pyrazole] the geometric isomers were separated by virtue of the fact that the fac isomer forms a Cu(I) adduct which the mer isomer does not. Alkylation of the pyrazolyl NH group with methyl iodide or benzyl bromide afforded [Ru(L(Me))3](2+) and [Ru(L(bz))3](2+) respectively, each as their fac and mer isomers; all were structurally characterised. In the fac isomers the convergent group of pendant -CH2R or -CH3 protons defines a hydrogen-bond donor pocket; in the mer isomer these protons do not converge and any hydrogen-bonding involving these protons is expected to be weaker. For both [Ru(L(Me))3](2+) and [Ru(L(bz))3](2+), NMR titrations with isoquinoline-N-oxide in MeCN revealed weak 1 : 1 binding (K ≈ 1 M(-1)) between the guest and the fac isomer of the complex that was absent with the mer isomer, confirming a difference in the hydrogen-bond donor capabilities of these complexes associated with their differing geometries. The weak binding compared to the cage however occurs because of competition from the anions, which are free to form ion-pairs with the mononuclear complex cations in a way that does not happen in the cage complexes. We conclude that (i) the presence of fac tris-chelate sites in the cage to act as hydrogen-bond donors, and (ii

Decay and Fission Hindrance of Two- and Four-Quasiparticle K Isomers in Rf 254

DOE Office of Scientific and Technical Information (OSTI.GOV)

David, H. M.; Chen, J.; Seweryniak, D.

2015-09-01

Two isomers decaying by electromagnetic transitions with half-lives of 4.7(1.1) and 247 ( 73 ) μ s have been discovered in the heavy 254 Rf nucleus. The observation of the shorter-lived isomer was made possible by a novel application of a digital data acquisition system. The isomers were interpreted as the K π = 8 - , ν 2 ( 7 / 2 + [ 624 ] , 9 / 2 - [ 734 ] ) two-quasineutron and the K π = 1 6 + , 8 - ν 2 ( 7 / 2 + [ 624 ] , 9more » / 2 - [ 734 ] ) Ⓧ 8 - π 2 ( 7 / 2 -[ 514 ] , 9 / 2 + [ 624 ] ) four-quasiparticle configurations, respectively. Surprisingly, the lifetime of the two-quasiparticle isomer is more than 4 orders of magnitude shorter than what has been observed for analogous isomers in the lighter N = 150 isotones. The four-quasiparticle isomer is longer lived than the 254 Rf ground state that decays exclusively by spontaneous fission with a half-life of 23.2 ( 1.1 ) μ s . The absence of sizable fission branches from either of the isomers implies unprecedented fission hindrance relative to the ground state.« less

Decay and Fission Hindrance of Two- and Four-Quasiparticle K Isomers in ^{254}Rf.

PubMed

David, H M; Chen, J; Seweryniak, D; Kondev, F G; Gates, J M; Gregorich, K E; Ahmad, I; Albers, M; Alcorta, M; Back, B B; Baartman, B; Bertone, P F; Bernstein, L A; Campbell, C M; Carpenter, M P; Chiara, C J; Clark, R M; Cromaz, M; Doherty, D T; Dracoulis, G D; Esker, N E; Fallon, P; Gothe, O R; Greene, J P; Greenlees, P T; Hartley, D J; Hauschild, K; Hoffman, C R; Hota, S S; Janssens, R V F; Khoo, T L; Konki, J; Kwarsick, J T; Lauritsen, T; Macchiavelli, A O; Mudder, P R; Nair, C; Qiu, Y; Rissanen, J; Rogers, A M; Ruotsalainen, P; Savard, G; Stolze, S; Wiens, A; Zhu, S

2015-09-25

Two isomers decaying by electromagnetic transitions with half-lives of 4.7(1.1) and 247(73) μs have been discovered in the heavy ^{254}Rf nucleus. The observation of the shorter-lived isomer was made possible by a novel application of a digital data acquisition system. The isomers were interpreted as the K^{π}=8^{-}, ν^{2}(7/2^{+}[624],9/2^{-}[734]) two-quasineutron and the K^{π}=16^{+}, 8^{-}ν^{2}(7/2^{+}[624],9/2^{-}[734])⊗8^{-}π^{2}(7/2^{-}[514],9/2^{+}[624]) four-quasiparticle configurations, respectively. Surprisingly, the lifetime of the two-quasiparticle isomer is more than 4 orders of magnitude shorter than what has been observed for analogous isomers in the lighter N=150 isotones. The four-quasiparticle isomer is longer lived than the ^{254}Rf ground state that decays exclusively by spontaneous fission with a half-life of 23.2(1.1) μs. The absence of sizable fission branches from either of the isomers implies unprecedented fission hindrance relative to the ground state.

Formation of melatonin and its isomer during bread dough fermentation and effect of baking.

PubMed

Yılmaz, Cemile; Kocadağlı, Tolgahan; Gökmen, Vural

2014-04-02

Melatonin is produced mainly by the pineal gland in vertebrates. Also, melatonin and its isomer are found in foods. Investigating the formation of melatonin and its isomer is of importance during bread dough fermentation and its degradation during baking since bread is widely consumed in high amounts. Formation of melatonin was not significant during dough fermentation. The melatonin isomer content of nonfermented dough was found to be 4.02 ng/g and increased up to 16.71 ng/g during fermentation. Lower amounts of isomer in crumb and crust than dough showed that the thermal process caused a remarkable degree of degradation in melatonin isomer. At the end of the 180 min fermentation Trp decreased by 58%. The results revealed for the first time the formation of a melatonin isomer in bread dough during yeast fermentation.

Feeding of Rh and Ag isomers in fast-neutron-induced reactions

DOE PAGES

Fotiades, Nikolaos; Devlin, Matthew James; Nelson, Ronald Owen; ...

2016-10-17

In (n,n') reactions on stable Ir and Au isotopes in the mass A=190 region, the experimentally established feeding of the isomers relative to the feeding of the corresponding ground states increases with increasing neutron energy, up to the neutron energy where the (n,2n) reaction channel opens up, and then decreases. In order to check for similar behavior in the mass A=100 region, the feeding of isomers and ground states in fast-neutron-induced reactions on stable isotopes in this mass region was studied. This is of especial interest for Rh which can be used as a radiochemical detector. Here, excited states weremore » studied using the (n,n'γ), (n,2nγ), and (n,3nγ) reactions on 103Rh and 109Ag. A germanium detector array for γ-ray detection and the broad-spectrum pulsed neutron source of the Los Alamos Neutron Science Center's Weapons Neutron Research facility were used for the measurement. The energy of the incident neutrons was determined using the time-of-flight technique. Absolute partial γ-ray cross sections were measured for 57 transitions feeding isomers and ground states in 101,102,103Rh and 107,108,109Ag. The feeding of the isomers was found to be very similar in the corresponding reaction channels and it is compared to the feeding determined for the ground states. In conclusion, the opening of reaction channels at higher neutron energies removes angular momentum from the residual nucleus and reduces the population of the higher-spin isomers relative to the feeding of the lower-spin ground states. Similar behavior was observed in the mass A=190 region in the feeding of higher-spin isomers, but the reverse behavior was observed in 176Lu with a lower-spin isomer and a higher-spin ground state.« less

Feeding of Rh and Ag isomers in fast-neutron-induced reactions

NASA Astrophysics Data System (ADS)

Fotiades, N.; Devlin, M.; Nelson, R. O.; Kawano, T.; Carroll, J. J.

2016-10-01

Background: In (n ,n' ) reactions on stable Ir and Au isotopes in the mass A =190 region, the experimentally established feeding of the isomers relative to the feeding of the corresponding ground states increases with increasing neutron energy, up to the neutron energy where the (n ,2 n ) reaction channel opens up, and then decreases. Purpose: In order to check for similar behavior in the mass A =100 region, the feeding of isomers and ground states in fast-neutron-induced reactions on stable isotopes in this mass region was studied. This is of especial interest for Rh which can be used as a radiochemical detector. Methods: Excited states were studied using the (n ,n'γ ), (n ,2 n γ ), and (n ,3 n γ ) reactions on 103Rh and 109Ag. A germanium detector array for γ -ray detection and the broad-spectrum pulsed neutron source of the Los Alamos Neutron Science Center's Weapons Neutron Research facility were used for the measurement. The energy of the incident neutrons was determined using the time-of-flight technique. Results: Absolute partial γ -ray cross sections were measured for 57 transitions feeding isomers and ground states in 101,102,103Rh and 107,108,109Ag. The feeding of the isomers was found to be very similar in the corresponding reaction channels and it is compared to the feeding determined for the ground states. Conclusions: The opening of reaction channels at higher neutron energies removes angular momentum from the residual nucleus and reduces the population of the higher-spin isomers relative to the feeding of the lower-spin ground states. Similar behavior was observed in the mass A =190 region in the feeding of higher-spin isomers, but the reverse behavior was observed in 176Lu with a lower-spin isomer and a higher-spin ground state.

Feeding of Rh and Ag isomers in fast-neutron-induced reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fotiades, Nikolaos; Devlin, Matthew James; Nelson, Ronald Owen

In (n,n') reactions on stable Ir and Au isotopes in the mass A=190 region, the experimentally established feeding of the isomers relative to the feeding of the corresponding ground states increases with increasing neutron energy, up to the neutron energy where the (n,2n) reaction channel opens up, and then decreases. In order to check for similar behavior in the mass A=100 region, the feeding of isomers and ground states in fast-neutron-induced reactions on stable isotopes in this mass region was studied. This is of especial interest for Rh which can be used as a radiochemical detector. Here, excited states weremore » studied using the (n,n'γ), (n,2nγ), and (n,3nγ) reactions on 103Rh and 109Ag. A germanium detector array for γ-ray detection and the broad-spectrum pulsed neutron source of the Los Alamos Neutron Science Center's Weapons Neutron Research facility were used for the measurement. The energy of the incident neutrons was determined using the time-of-flight technique. Absolute partial γ-ray cross sections were measured for 57 transitions feeding isomers and ground states in 101,102,103Rh and 107,108,109Ag. The feeding of the isomers was found to be very similar in the corresponding reaction channels and it is compared to the feeding determined for the ground states. In conclusion, the opening of reaction channels at higher neutron energies removes angular momentum from the residual nucleus and reduces the population of the higher-spin isomers relative to the feeding of the lower-spin ground states. Similar behavior was observed in the mass A=190 region in the feeding of higher-spin isomers, but the reverse behavior was observed in 176Lu with a lower-spin isomer and a higher-spin ground state.« less

Differences in Dihydrotetrabenazine Isomer Concentrations Following Administration of Tetrabenazine and Valbenazine.

PubMed

Skor, Heather; Smith, Evan B; Loewen, Gordon; O'Brien, Christopher F; Grigoriadis, Dimitri E; Bozigian, Haig

2017-09-01

Tetrabenazine (TBZ) activity is thought to result from four isomeric dihydrotetrabenazine (HTBZ) metabolites ([+]-α-HTBZ, [-]-α-HTBZ, [+]-β-HTBZ, [-]-β-HTBZ). Each isomer has a unique profile of vesicular monoamine transporter 2 (VMAT2) inhibition and off-target binding. Previously published data only report total isomer (α) and (β) concentrations. We developed a method to quantify the individual HTBZ isomers in samples from patients with Huntington's disease receiving TBZ. For comparison, concentrations of [+]-α-HTBZ, the single active metabolite shared by valbenazine (VBZ) and TBZ, were determined in samples from patients with tardive dyskinesia receiving VBZ. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for quantitation of the four individual HTBZ isomers. Concentrations were determined in serum from patients with Huntington's disease administered TBZ and plasma from patients with tardive dyskinesia administered VBZ once daily. In patients administered TBZ, [-]-α-HTBZ and [+]-β-HTBZ were the most abundant HTBZ isomers while [-]-β-HTBZ and [+]-α-HTBZ were present as minor metabolites. Only [+]-α-HTBZ was observed in patients administered VBZ. Based on relative abundance and potency, [+]-β-HTBZ appears to be the primary contributor to VMAT2 inhibition by TBZ, a finding in contrast with the generally held assertion that [+]-α-HTBZ is the major contributor. [-]-α-HTBZ, the other abundant TBZ metabolite, has much lower VMAT2 inhibitory potency than [+]-β-HTBZ, but increased affinity for other CNS targets, which may contribute to off-target effects of TBZ. In contrast, pharmacological activity for VBZ is derived primarily from [+]-α-HTBZ. Individual HTBZ isomer concentrations provide a more clinically relevant endpoint for assessing on- and off-target effects of TBZ than total isomer concentrations.

LAS bioconcentration is isomer specific

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tolls, J.; Haller, M.; Graaf, I. de

1995-12-31

The authors measured parent compound specific bioconcentration data for linear alkylbenzene sulfonates in Pimephales promelas. They did so by using cold, custom synthesized sulfophenyl alkanes. They observed that, within homologous series of isomers, the uptake rate constants (k{sub 1}) and the bioconcentration factor (BCF) increase with increasing number of carbon atoms in the alkyl chain (n{sub C-atoms}). In contrast, the elimination rate constant k{sub 2} appears to be independent of the alkyl chain length. Regressions of log BCF vs n{sub C-atoms} yielded different slopes for the homologous groups of the 5- and the 2-sulfophenyl alkane isomers. Regression of all logmore » BCF-data vs log 1/CMC yielded a good description of the data. However, when regressing the data for both homologous series separately again very different slopes are obtained. The results therefore indicate that hydrophobicity-bioconcentration relationships may be different for different homologous groups of sulfophenyl alkanes.« less

Five isomers of C 60 generated in microwave plasma of chloroform

NASA Astrophysics Data System (ADS)

Xie, Su-Yuan; Deng, Shun-Liu; Huang, Rong-Bin; Yu, La-Jia; Zheng, Lan-Sun

2001-08-01

In addition to Ih symmetry buckminsterfullerene, four other isomers of C 60 were generated in a microwave plasma of chloroform. The newly observed isomers, separated and identified by a high performance liquid chromatography coupled with mass spectrometry (HPLC-MS), were found to be stable at room temperature but transform to buckminsterfullerene when heated. With regards to the generation of various fully chlorinated carbon clusters as well as the C 60 isomers, which may be attributed to the rapidly cooling of the synthetic reaction, a modified Pentagon Road scheme is suggested for fullerene formation.

Characterization of the Antinociceptive Effects of the Individual Isomers of Methadone Following Acute and Chronic Administration

PubMed Central

Morgan, Richard W.; Nicholson, Katherine L.

2011-01-01

Methadone is a long-acting opioid used in the treatment of various pain states and substitution therapy in heroin addiction. Extensive behavioral characterization has been carried out utilizing the racemate, but limited investigation has been performed with the individual isomers. While the l-isomer is a potent opioid agonist, the d-isomer has weak μ opioid activity and has also been shown to possess N-methyl-d-aspartate (NMDA) antagonist properties in vitro. The acute antinociceptive effects of the isomers were evaluated in rats using a warm water tail withdrawal procedure at two stimulus intensities (50° and 55° C). Increasing dose ratios of d- to l-methadone were administered chronically to determine the ability of the d-isomer to modulate antinociceptive tolerance to the l-isomer. Acutely, both l- (0.1-5.6 mg/kg, sc) and d- (3.0-56.0 mg/kg, sc) methadone produced antinociception though the efficacy of the d-isomer was limited at 55° C. These effects were dose-dependently blocked by naltrexone (0.01-1.0 mg/kg, sc). Administered chronically, d-methadone (1.7-10 mg/kg, sc) dose-dependently blocked tolerance development to the l-isomer (1.7 mg/kg, sc). These findings support the antinociceptive effects of the isomers being opioid receptor mediated with the l-isomer functioning as a full efficacy agonist whereas the d-isomer appears to have lower efficacy. The ability of nonracemic doses of the d-isomer to prevent tolerance development to the l-isomer may be attributed to partial μ agonist activity however NMDA antagonist activity cannot be discounted. PMID:21836464

Drug delivery with microsecond laser pulses into gelatin.

PubMed

Shangguan, H; Casperson, L W; Shearin, A; Gregory, K W; Prahl, S A

1996-07-01

Photo acoustic drug delivery is a technique for localized drug delivery by laser-induced hydrodynamic pressure following cavitation bubble expansion and collapse. Photoacoustic drug delivery was investigated on gelatin-based thrombus models with planar and cylindrical geometries by use of one microsecond laser pulses. Solutions of a hydrophobic dye in mineral oil permitted monitoring of delivered colored oil into clear gelatin-based thrombus models. Cavitation bubble development and photoacoustic drug delivery were visualized with flash photography. This study demonstrated that cavitation is the governing mechanism for photoacoustic drug delivery, and the deepest penetration of colored oil in gels followed the bubble collapse. Spatial distribution measurements revealed that colored oil could be driven a few millimeters into the gels in both axial and radial directions, and the penetration was less than 500 µm when the gelatin structure was not fractured.

Mass measurements of neutron-rich indium isotopes toward the N =82 shell closure

NASA Astrophysics Data System (ADS)

Babcock, C.; Klawitter, R.; Leistenschneider, E.; Lascar, D.; Barquest, B. R.; Finlay, A.; Foster, M.; Gallant, A. T.; Hunt, P.; Kootte, B.; Lan, Y.; Paul, S. F.; Phan, M. L.; Reiter, M. P.; Schultz, B.; Short, D.; Andreoiu, C.; Brodeur, M.; Dillmann, I.; Gwinner, G.; Kwiatkowski, A. A.; Leach, K. G.; Dilling, J.

2018-02-01

Precise mass measurements of the neutron-rich In-130125 isotopes have been performed with the TITAN Penning trap mass spectrometer. TITAN's electron beam ion trap was used to charge breed the ions to charge state q =13 + thus providing the necessary resolving power to measure not only the ground states but also isomeric states at each mass number. In this paper, the properties of the ground states are investigated through a series of mass differentials, highlighting trends in the indium isotopic chain as compared to its proton-magic neighbor, tin (Z =50 ). In addition, the energies of the indium isomers are presented. The (8-) level in 128In is found to be 78 keV lower than previously thought and the (21 /2- ) isomer in 127In is shown to be lower than the literature value by more than 150 keV.

Gaussian and linear deconvolution of LC-MS/MS chromatograms of the eight aminobutyric acid isomers

PubMed Central

Vemula, Harika; Kitase, Yukiko; Ayon, Navid J.; Bonewald, Lynda; Gutheil, William G.

2016-01-01

Isomeric molecules present a challenge for analytical resolution and quantification, even with MS-based detection. The eight-aminobutyric acid (ABA) isomers are of interest for their various biological activities, particularly γ-aminobutyric acid (GABA) and the d- and l-isomers of β-aminoisobutyric acid (β-AIBA; BAIBA). This study aimed to investigate LC-MS/MS-based resolution of these ABA isomers as their Marfey's (Mar) reagent derivatives. HPLC was able to separate three Mar-ABA isomers l-β-ABA (l-BABA), and l- and d-α-ABA (AABA) completely, with three isomers (GABA, and d/l-BAIBA) in one chromatographic cluster, and two isomers (α-AIBA (AAIBA) and d-BABA) in a second cluster. Partially separated cluster components were deconvoluted using Gaussian peak fitting except for GABA and d-BAIBA. MS/MS detection of Marfey's derivatized ABA isomers provided six MS/MS fragments, with substantially different intensity profiles between structural isomers. This allowed linear deconvolution of ABA isomer peaks. Combining HPLC separation with linear and Gaussian deconvolution allowed resolution of all eight ABA isomers. Application to human serum found a substantial level of l-AABA (13 μM), an intermediate level of l-BAIBA (0.8 μM), and low but detectable levels (<0.2 μM) of GABA, l-BABA, AAIBA, d-BAIBA, and d-AABA. This approach should be useful for LC-MS/MS deconvolution of other challenging groups of isomeric molecules. PMID:27771391

Isomer-delayed gamma-ray spectroscopy of neutron-rich 166Tb

NASA Astrophysics Data System (ADS)

Gurgi, L. A.; Regan, P. H.; Söderström, P.-A.; Watanabe, H.; Walker, P. M.; Podolyák, Zs.; Nishimura, S.; Berry, T. A.; Doornenbal, P.; Lorusso, G.; Isobe, T.; Baba, H.; Xu, Z. Y.; Sakurai, H.; Sumikama, T.; Catford, W. N.; Bruce, A. M.; Browne, F.; Lane, G. J.; Kondev, F. G.; Odahara, A.; Wu, J.; Liu, H. L.; Xu, F. R.; Korkulu, Z.; Lee, P.; Liu, J. J.; Phong, V. H.; Yagi, A.; Zhang, G. X.; Alharbi, T.; Carroll, R. J.; Chae, K. Y.; Dombradi, Zs.; Estrade, A.; Fukuda, N.; Griffin, C.; Ideguchi, E.; Inabe, N.; Kanaoka, H.; Kojouharov, I.; Kubo, T.; Kubono, S.; Kurz, N.; Kuti, I.; Lalkovski, S.; Lee, E. J.; Lee, C. S.; Lotay, G.; Moon, C. B.; Nishizuka, I.; Nita, C. R.; Patel, Z.; Roberts, O. J.; Schaffner, H.; Shand, C. M.; Suzuki, H.; Takeda, H.; Terashima, S.; Vajta, Zs.; Kanaya, S.; Valiente-Dobòn, J. J.

2017-09-01

This short paper presents the identification of a metastable, isomeric-state decay in the neutron-rich odd-odd, prolate-deformed nucleus 166Tb. The nucleus of interest was formed using the in-flight fission of a 345 MeV per nucleon 238U primary beam at the RIBF facility, RIKEN, Japan. Gamma-ray transitions decaying from the observed isomeric states in 166Tb were identified using the EURICA gamma-ray spectrometer, positioned at the final focus of the BigRIPS fragments separator. The current work identifies a single discrete gamma-ray transition of energy 119 keV which de-excites an isomeric state in 166Tb with a measured half-life of 3.5(4) μs. The multipolarity assignment for this transition is an electric dipole and is made on the basis internal conversion and decay lifetime arguments. Possible two quasi-particle Nilsson configurations for the initial and final states which are linked by this transition in 166Tb are made on the basis of comparison with Blocked BCS Nilsson calculations, with the predicted ground state configuration for this nucleus arising from the coupling of the v(1-/2)?[521] and ? π(3+/2) Nilsson orbitals.

40 CFR 180.1073 - Isomate-M; exemption from the requirement of a tolerance.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 24 2011-07-01 2011-07-01 false Isomate-M; exemption from the... Exemptions From Tolerances § 180.1073 Isomate-M; exemption from the requirement of a tolerance. The oriental fruit moth pheromone (Isomate-M) (Z-8-dodecen-l-yl acetate, E-8-dodecen-l-yl acetate, Z-8-dodecen-l-ol...

40 CFR 180.1073 - Isomate-M; exemption from the requirement of a tolerance.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Isomate-M; exemption from the... Exemptions From Tolerances § 180.1073 Isomate-M; exemption from the requirement of a tolerance. The oriental fruit moth pheromone (Isomate-M) (Z-8-dodecen-l-yl acetate, E-8-dodecen-l-yl acetate, Z-8-dodecen-l-ol...

Stereospecific Synthesis of the Geometrical Isomers of a Natural Product

ERIC Educational Resources Information Center

Grove, T.; DiLella, D.; Volker, E.

2006-01-01

Stereospecific synthesis of a geometrical isomer is not a common topic for the introductory organic chemistry laboratory. We have developed and tested an experiment for the synthesis of (Z) and (E) isomers that has been performed successfully by undergraduate students. The experiment is presented to the students as a puzzle in which they must…

Energetics of the S 2 state spin isomers of the oxygen-evolving complex of Photosystem II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vinyard, David J.; Khan, Sahr; Askerka, Mikhail

Here, the S 2 redox intermediate of the oxygen-evolving complex in Photosystem II is present as two spin isomers. The S = 1/2 isomer gives rise to a multiline EPR signal at g = 2, while the S = 5/2 isomer exhibits a broad EPR signal at g = 4.1. The electronic structures of these isomers are known, but their role in the catalytic cycle of water oxidation remains unclear. We show that formation of the S = 1/2 state from the S = 5/2 state is exergonic at temperatures above 160 K. However, the S = 1/2 isomer decaysmore » to S 1 more slowly than the S = 5/2 isomer. These differences support the hypotheses that the S 3 state is formed via the S 2 state S = 5/2 isomer and that the stabilized S 2 state S = 1/2 isomer plays a role in minimizing S 2Q A- decay in light-limiting conditions.« less

Energetics of the S 2 state spin isomers of the oxygen-evolving complex of Photosystem II

DOE PAGES

Vinyard, David J.; Khan, Sahr; Askerka, Mikhail; ...

2017-01-12

Here, the S 2 redox intermediate of the oxygen-evolving complex in Photosystem II is present as two spin isomers. The S = 1/2 isomer gives rise to a multiline EPR signal at g = 2, while the S = 5/2 isomer exhibits a broad EPR signal at g = 4.1. The electronic structures of these isomers are known, but their role in the catalytic cycle of water oxidation remains unclear. We show that formation of the S = 1/2 state from the S = 5/2 state is exergonic at temperatures above 160 K. However, the S = 1/2 isomer decaysmore » to S 1 more slowly than the S = 5/2 isomer. These differences support the hypotheses that the S 3 state is formed via the S 2 state S = 5/2 isomer and that the stabilized S 2 state S = 1/2 isomer plays a role in minimizing S 2Q A- decay in light-limiting conditions.« less

Solvation effect on isomer stability and electronic structures of protonated serotonin

NASA Astrophysics Data System (ADS)

Omidyan, Reza; Amanollahi, Zohreh; Azimi, Gholamhassan

2017-07-01

Microsolvation effect on geometry and transition energies of protonated serotonin has been investigated by MP2 and CC2 quantum chemical methods. Also, conductor-like screening model, implemented recently in the MP2 and ADC(2) methods, was examined to address the bulk water environment's effect on the isomer stability and electronic transition energies of protonated serotonin. It has been predicted that the dipole moment of gas phase isomers plays the main role on the isomer stabilization in water solution and electronic transition shifts. Also, both red- and blue-shift effects have been predicted to take place on electronic transition energies, upon hydration.

An Unusual Conformational Isomer of Verrucosidin Backbone from a Hydrothermal Vent Fungus, Penicillium sp. Y-50-10

PubMed Central

Pan, Chengqian; Shi, Yutong; Auckloo, Bibi Nazia; Chen, Xuegang; Chen, Chen-Tung Arthur; Tao, Xinyi; Wu, Bin

2016-01-01

A new verrucosidin derivative, methyl isoverrucosidinol (1), was isolated from the marine fungus Penicillium sp. Y-50-10, dwelling in sulfur rich sediment in the Kueishantao hydrothermal vents off Taiwan. The structure was established by spectroscopic means including HRMS and 2D-NMR spectroscopic analysis. The absolute configuration was defined mainly by comparison of quantum chemical TDDFT calculated and experimental ECD spectra. Among hitherto known compounds with a verrucosidine backbone isolated from natural resource, compound 1 represents the first example of a new conformational isomer of its skeleton, exhibiting antibiotic activity against Bacillus subtilis with MIC value 32 μg/mL. PMID:27548192

Isomer-delayed gamma-ray spectroscopy of neutron-rich 166Tb

DOE PAGES

Gurgi, L. A.; Regan, P. H.; Söderström, P. -A.; ...

2017-09-13

Here, this short paper presents the identification of a metastable, isomeric-state decay in the neutron-rich odd-odd, prolate-deformed nucleus 166Tb. The nucleus of interest was formed using the in-flight fission of a 345 MeV per nucleon 238U primary beam at the RIBF facility, RIKEN, Japan. Gamma-ray transitions decaying from the observed isomeric states in 166Tb were identified using the EURICA gamma-ray spectrometer, positioned at the final focus of the BigRIPS fragments separator. The current work identifies a single discrete gamma-ray transition of energy 119 keV which de-excites an isomeric state in 166Tb with a measured half-life of 3.5(4) μs. The multipolaritymore » assignment for this transition is an electric dipole and is made on the basis internal conversion and decay lifetime arguments. Possible two quasi-particle Nilsson configurations for the initial and final states which are linked by this transition in 166Tb are made on the basis of comparison with Blocked BCS Nilsson calculations, with the predicted ground state configuration for this nucleus arising from the coupling of the v(1-/2)[521] and π(3+/2) Nilsson orbitals.« less

Measurements of Short-Lived Fission Isomers

NASA Astrophysics Data System (ADS)

Finch, Sean; Bhike, Megha; Howell, Calvin; Krishichayan, Fnu; Tornow, Werner

2016-09-01

Fission yields of the short lived isomers 134mTe (T1 / 2 = 162 ns) and 136mXe (T1 / 2 = 2 . 95 μs) were measured for 235U and 238U. The isomers were detected by the γ rays associated with the decay of the isomeric states using high-purity germanium detectors. Fission was induced using both monoenergetic γ rays and neutrons. At TUNL's High-Intensity Gamma-ray Source (HI γS), γ rays of 9 and 11 MeV were produced . Monoenergetic 8 MeV neutrons were produced at TUNL's tandem accelerator laboratory. Both beams were pulsed to allow for precise time-gated spectroscopy of both prompt and delayed γ rays following fission. This technique offers a non-destructive probe of special nuclear materials that is sensitive to the isotopic identity of the fissile material.

Development of a microsecond X-ray protein footprinting facility at the Advanced Light Source.

PubMed

Gupta, Sayan; Celestre, Richard; Petzold, Christopher J; Chance, Mark R; Ralston, Corie

2014-07-01

X-ray footprinting (XF) is an important structural biology tool used to determine macromolecular conformations and dynamics of both nucleic acids and proteins in solution on a wide range of timescales. With the impending shut-down of the National Synchrotron Light Source, it is ever more important that this tool continues to be developed at other synchrotron facilities to accommodate XF users. Toward this end, a collaborative XF program has been initiated at the Advanced Light Source using the white-light bending-magnet beamlines 5.3.1 and 3.2.1. Accessibility of the microsecond time regime for protein footprinting is demonstrated at beamline 5.3.1 using the high flux density provided by a focusing mirror in combination with a micro-capillary flow cell. It is further reported that, by saturating samples with nitrous oxide, the radiolytic labeling efficiency is increased and the imprints of bound versus bulk water can be distinguished. These results both demonstrate the suitability of the Advanced Light Source as a second home for the XF experiment, and pave the way for obtaining high-quality structural data on complex protein samples and dynamics information on the microsecond timescale.

Drug delivery with microsecond laser pulses into gelatin

NASA Astrophysics Data System (ADS)

Shangguan, Hanqun; Casperson, Lee W.; Shearin, Alan; Gregory, Kenton W.; Prahl, Scott A.

1996-07-01

Photoacoustic drug delivery is a technique for localized drug delivery by laser-induced hydrodynamic pressure following cavitation bubble expansion and collapse. Photoacoustic drug delivery was investigated on gelatin-based thrombus models with planar and cylindrical geometries by use of one microsecond laser pulses. Solutions of a hydrophobic dye in mineral oil permitted monitoring of delivered colored oil into clear gelatin-based thrombus models. Cavitation bubble development and photoacoustic drug delivery were visualized with flash photography. This study demonstrated that cavitation is the governing mechanism for photoacoustic drug delivery, and the deepest penetration of colored oil in gels followed the bubble collapse. Spatial distribution measurements revealed that colored oil could be driven a few millimeters into the gels in both axial and radial directions, and the penetration was less than 500 mu m when the gelatin structure was not fractured. localized drug delivery, cavitation bubble, laser thrombolysis.

Population and decay of a K π = 8 – two-quasineutron isomer in Pu 244

DOE PAGES

Hota, S. S.; Tandel, S. K.; Chowdhury, P.; ...

2016-08-22

Here, the decay of a K π = 8 – isomer in 244Pu and the collective band structures populating the isomer were studied using deep inelastic excitations with 47Ti and 208Pb beams, respectively. Precise measurements of M1/E2 branching ratios in the band confirm a 9/2 –[734] νⓍ7/2 +[624] ν configuration assignment for the isomer, validating the systematics of K π = 8 –, two-quasineutron isomers observed in even-Z, N = 150 isotones. These isomers around the deformed shell gap at N = 152 provide critical benchmarks for theoretical predictions of single-particle energies in this gateway region to superheavy nuclei.

Population and decay of a K π = 8 – two-quasineutron isomer in Pu 244

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hota, S. S.; Tandel, S. K.; Chowdhury, P.

Here, the decay of a K π = 8 – isomer in 244Pu and the collective band structures populating the isomer were studied using deep inelastic excitations with 47Ti and 208Pb beams, respectively. Precise measurements of M1/E2 branching ratios in the band confirm a 9/2 –[734] νⓍ7/2 +[624] ν configuration assignment for the isomer, validating the systematics of K π = 8 –, two-quasineutron isomers observed in even-Z, N = 150 isotones. These isomers around the deformed shell gap at N = 152 provide critical benchmarks for theoretical predictions of single-particle energies in this gateway region to superheavy nuclei.

Lipid and glycolipid isomer analyses using ultra-high resolution ion mobility spectrometry separations

DOE PAGES

Wojcik, Roza; Webb, Ian K.; Deng, Liulin; ...

2017-01-18

Understanding the biological mechanisms related to lipids and glycolipids is challenging due to the vast number of possible isomers. Mass spectrometry (MS) measurements are currently the dominant approach for studying and providing detailed information on lipid and glycolipid structures. However, difficulties in distinguishing many structural isomers (e.g. distinct acyl chain positions, double bond locations, as well as glycan isomers) inhibit the understanding of their biological roles. Here we utilized ultra-high resolution ion mobility spectrometry (IMS) separations based upon the use of traveling waves in a serpentine long path length multi-pass Structures for Lossless Manipulations (SLIM) to enhance isomer resolution. Themore » multi-pass arrangement allowed separations ranging from ~16 m (1 pass) to ~470 m (32 passes) to be investigated for the distinction of lipids and glycolipids with extremely small structural differences. Lastly, these ultra-high resolution SLIM IMS-MS analyses provide a foundation for exploring and better understanding isomer specific biological and disease processes.« less

Structures of cage, prism, and book isomers of water hexamer from broadband rotational spectroscopy.

PubMed

Pérez, Cristóbal; Muckle, Matt T; Zaleski, Daniel P; Seifert, Nathan A; Temelso, Berhane; Shields, George C; Kisiel, Zbigniew; Pate, Brooks H

2012-05-18

Theory predicts the water hexamer to be the smallest water cluster with a three-dimensional hydrogen-bonding network as its minimum energy structure. There are several possible low-energy isomers, and calculations with different methods and basis sets assign them different relative stabilities. Previous experimental work has provided evidence for the cage, book, and cyclic isomers, but no experiment has identified multiple coexisting structures. Here, we report that broadband rotational spectroscopy in a pulsed supersonic expansion unambiguously identifies all three isomers; we determined their oxygen framework structures by means of oxygen-18-substituted water (H(2)(18)O). Relative isomer populations at different expansion conditions establish that the cage isomer is the minimum energy structure. Rotational spectra consistent with predicted heptamer and nonamer structures have also been identified.

The Creation and Destruction of Hf-178m2 Isomer by Neutron Interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsu, Hsiao-Hua; Talbert, Willard L.; Ward, Tom

The property of the isomer state in 178m2Hf was an interesting topic in nuclear structure studies during the time period 1970 to 1980. The state at 2.446 MeV with spin and parity K π = 16 +, has a half-life of 31 years. The isomer is described as a four-quasi-particle state. The K forbidden deexcitatiion by gamma emission is the reason for long half-life. During 1980, the isomer became a troublesome issue for radiation safety workers, because this isomer can also be produced in the first wall of a fussion reactor containing tungsten and also in a tungsten beam stopmore » of a high-energy accelerator.« less

Surfactant mediated enhanced biodegradation of hexachlorocyclohexane (HCH) isomers by Sphingomonas sp. NM05.

PubMed

Manickam, Natesan; Bajaj, Abhay; Saini, Harvinder S; Shanker, Rishi

2012-09-01

Environmental biodegradation of several chlorinated pesticides is limited by their low solubility and sorption to soil surfaces. To mitigate this problem we quantified the effect of three biosurfactant viz., rhamnolipid, sophorolipid and trehalose-containing lipid on the dissolution, bioavailability, and biodegradation of HCH-isomers in liquid culture and in contaminated soil. The effect of biosurfactants was evaluated through the critical micelle concentration (CMC) value as determined for each isomer. The surfactant increased the solubilization of HCH isomers by 3-9 folds with rhamnolipid and sophorolipid being more effective and showing maximum solubilization of HCH isomers at 40 μg/mL, compared to trehalose-containing lipid showing peak solubilization at 60 μg/mL. The degradation of HCH isomers by Sphingomonas sp. NM05 in surfactant-amended liquid mineral salts medium showed 30% enhancement in 2 days as compared to degradation in 10 days in the absence of surfactant. HCH-spiked soil slurry incubated with surfactant also showed around 30-50% enhanced degradation of HCH which was comparable to the corresponding batch culture experiments. Among the three surfactants, sophorolipid offered highest solubilization and enhanced degradation of HCH isomers both in liquid medium and soil culture. The results of this study suggest the effectiveness of surfactants in improving HCH degradation by increased bioaccessibility.

Structural isomers of C2N(+) - A selected-ion flow tube study

NASA Technical Reports Server (NTRS)

Knight, J. S.; Petrie, S. A. H.; Freeman, C. G.; Mcewan, M. J.; Mclean, A. D.

1988-01-01

Reactivities of the structural isomers CCN(+) and CNC(+) were examined in a selected-ion flow tube at 300 + or - 5 K. The less reactive CNC(+) isomer was identified as the product of the reactions of C(+) + HCN and C(+) + C2N2; in these reactions only CNC(+) can be produced because of energy constraints. Rate coefficients and branching ratios are reported for the reactions of each isomer with H2, CH4, NH3, H2O, C2H2, HCN, N2, O2, N2O, and CO2. Ab initio calculations are presented for CCN(+) and CNC(+); a saddle point for the reaction CCN(+) yielding CNC(+) is calculated to be 195 kJ/mol above CNC(+). The results provide evidence that the more reactive CCN(+) isomer is unlikely to be present in measurable densities in interstellar clouds.

Low-energy electron collisions with C{sub 4}H{sub 6} isomers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lopes, A.R.; Bettega, M.H.F.; Lima, M.A.P.

2004-01-01

We report integral, differential, and momentum-transfer cross sections for elastic scattering of low-energy electrons by C{sub 4}H{sub 6} isomers, namely, 1,3-butadiene, 2-butyne, and cyclobutene. We use the Schwinger multichannel method with pseudopotentials [M. H. F. Bettega, L. G. Ferreira, and M. A. P. Lima, Phys. Rev. A 47, 1111 (1993)] at the static-exchange approximation to compute the cross sections for energies from 10 to 60 eV. In particular, we discuss the isomer effect, reported by experimental studies for isomers of C{sub 3}H{sub 4} and C{sub 4}H{sub 6}. We also calculate the total ionization cross section using the binary-encounter-Bethe model formore » 2-butyne and 1,3-butadiene, and estimate the inelastic cross section for these two isomers.« less

Identification of absolute geometries of cis and trans molecular isomers by Coulomb Explosion Imaging.

PubMed

Ablikim, Utuq; Bomme, Cédric; Xiong, Hui; Savelyev, Evgeny; Obaid, Razib; Kaderiya, Balram; Augustin, Sven; Schnorr, Kirsten; Dumitriu, Ileana; Osipov, Timur; Bilodeau, René; Kilcoyne, David; Kumarappan, Vinod; Rudenko, Artem; Berrah, Nora; Rolles, Daniel

2016-12-02

An experimental route to identify and separate geometric isomers by means of coincident Coulomb explosion imaging is presented, allowing isomer-resolved photoionization studies on isomerically mixed samples. We demonstrate the technique on cis/trans 1,2-dibromoethene (C 2 H 2 Br 2 ). The momentum correlation between the bromine ions in a three-body fragmentation process induced by bromine 3d inner-shell photoionization is used to identify the cis and trans structures of the isomers. The experimentally determined momentum correlations and the isomer-resolved fragment-ion kinetic energies are matched closely by a classical Coulomb explosion model.

Identification of absolute geometries of cis and trans molecular isomers by Coulomb Explosion Imaging

PubMed Central

Ablikim, Utuq; Bomme, Cédric; Xiong, Hui; Savelyev, Evgeny; Obaid, Razib; Kaderiya, Balram; Augustin, Sven; Schnorr, Kirsten; Dumitriu, Ileana; Osipov, Timur; Bilodeau, René; Kilcoyne, David; Kumarappan, Vinod; Rudenko, Artem; Berrah, Nora; Rolles, Daniel

2016-01-01

An experimental route to identify and separate geometric isomers by means of coincident Coulomb explosion imaging is presented, allowing isomer-resolved photoionization studies on isomerically mixed samples. We demonstrate the technique on cis/trans 1,2-dibromoethene (C2H2Br2). The momentum correlation between the bromine ions in a three-body fragmentation process induced by bromine 3d inner-shell photoionization is used to identify the cis and trans structures of the isomers. The experimentally determined momentum correlations and the isomer-resolved fragment-ion kinetic energies are matched closely by a classical Coulomb explosion model. PMID:27910943

Identification of absolute geometries of cis and trans molecular isomers by Coulomb Explosion Imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ablikim, Utuq; Bomme, Cédric; Xiong, Hui

An experimental route to identify and separate geometric isomers by means of coincident Coulomb explosion imaging is presented, allowing isomer-resolved photoionization studies on isomerically mixed samples. We demonstrate the technique on cis/trans 1,2-dibromoethene (C 2H 2Br 2). The momentum correlation between the bromine ions in a three-body fragmentation process induced by bromine 3d inner-shell photoionization is used to identify the cis and trans structures of the isomers. Lastly, the experimentally determined momentum correlations and the isomer-resolved fragment-ion kinetic energies are matched closely by a classical Coulomb explosion model.

Identification of absolute geometries of cis and trans molecular isomers by Coulomb Explosion Imaging

DOE PAGES

Ablikim, Utuq; Bomme, Cédric; Xiong, Hui; ...

2016-12-02

An experimental route to identify and separate geometric isomers by means of coincident Coulomb explosion imaging is presented, allowing isomer-resolved photoionization studies on isomerically mixed samples. We demonstrate the technique on cis/trans 1,2-dibromoethene (C 2H 2Br 2). The momentum correlation between the bromine ions in a three-body fragmentation process induced by bromine 3d inner-shell photoionization is used to identify the cis and trans structures of the isomers. Lastly, the experimentally determined momentum correlations and the isomer-resolved fragment-ion kinetic energies are matched closely by a classical Coulomb explosion model.

C5H9N isomers: pointers to possible branched chain interstellar molecules

NASA Astrophysics Data System (ADS)

Etim, Emmanuel E.; Gorai, Prasanta; Das, Ankan; Arunan, Elangannan

2017-04-01

The astronomical observation of isopropyl cyanide further stresses the link between the chemical composition of the interstellar medium (ISM) and molecular composition of the meteorites in which there is a dominance of branched chain amino acids as compared to the straight. However, observations of more branched chain molecules in ISM will firmly establish this link. In the light of this, we have considered C5H9N isomeric group in which the next higher member of the alkyl cyanide and other branched chain isomers belong. High-level quantum chemical calculations have been employed in estimating accurate energies of these isomers. From the results, the only isomer of the group that has been astronomically searched, n-butyl cyanide is not the most stable isomer and therefore, which might explain why its search could only yield upper limits of its column density without a successful detection. Rather, the two most stable isomers of the group are the branched chain isomers; tert-butylnitrile and isobutyl cyanide. Based on the rotational constants of these isomers, it is found that the expected intensity of tert-butylnitrile is the maximum among this isomeric group. Thus, this is proposed as the most probable candidate for astronomical observation. A simple LTE (local thermodynamic equilibrium) modelling has also been carried out to check the possibility of detecting tert-butyl cyanide in the millimetre-wave region. Contribution to the Topical Issue "Low-Energy Interactions related to Atmospheric and Extreme Conditions", edited by S. Ptasinska, M. Smialek-Telega, A. Milosavljevic and B. Sivaraman.

Biological activity of cannabichromene, its homologs and isomers.

PubMed

Turner, C E; Elsohly, M A

1981-01-01

Cannabichromene (CBC) is one of four major cannabinoids in Cannabis sativa L. and is the second most abundant cannabinoid in drug-type cannabis. Cannabichromene and some of its homologs, analogs, and isomers were evaluated for antiinflammatory, antibacterial, and antifungal activity. Antiinflammatory activity was evaluated by the carrageenan-induced rat paw edema and the erythrocyte membrane stabilization method. In both tests, CBC was superior to phenylbutazone. Antibacterial activity of CBC and its isomers and homologs was evaluated using gram-positive, gram-negative, and acid-fast bacteria. Antifungal activity was evaluated using yeast-like and filamentous fungi and a dermatophyte. Antibacterial activity was strong, and the antifungal activity was mild to moderate.

Observation of the 2+ isomer in 52Co

NASA Astrophysics Data System (ADS)

Orrigo, S. E. A.; Rubio, B.; Gelletly, W.; Blank, B.; Fujita, Y.; Giovinazzo, J.; Agramunt, J.; Algora, A.; Ascher, P.; Bilgier, B.; Cáceres, L.; Cakirli, R. B.; de France, G.; Ganioǧlu, E.; Gerbaux, M.; Grévy, S.; Kamalou, O.; Kozer, H. C.; Kucuk, L.; Kurtukian-Nieto, T.; Molina, F.; Popescu, L.; Rogers, A. M.; Susoy, G.; Stodel, C.; Suzuki, T.; Tamii, A.; Thomas, J. C.

2016-10-01

We report the first observation of the 2+ isomer in 52Co, produced in the β decay of the 0+, 52Ni ground state. We have observed three γ rays at 849, 1910, and 5185 keV characterizing the β de-excitation of the isomer. We have measured a half-life of 102(6) ms for the isomeric state. The Fermi and Gamow-Teller transition strengths for the β decay of Com52 to 52Fe have been determined. We also add new information on the β decay of the 6+, 52Co ground state, for which we have measured a half-life of 112(3) ms.

Roles of the tyrosine isomers meta-tyrosine and ortho-tyrosine in oxidative stress.

PubMed

Ipson, Brett R; Fisher, Alfred L

2016-05-01

The damage to cellular components by reactive oxygen species, termed oxidative stress, both increases with age and likely contributes to age-related diseases including Alzheimer's disease, atherosclerosis, diabetes, and cataract formation. In the setting of oxidative stress, hydroxyl radicals can oxidize the benzyl ring of the amino acid phenylalanine, which then produces the abnormal tyrosine isomers meta-tyrosine or ortho-tyrosine. While elevations in m-tyrosine and o-tyrosine concentrations have been used as a biological marker of oxidative stress, there is emerging evidence from bacterial, plant, and mammalian studies demonstrating that these isomers, particularly m-tyrosine, directly produce adverse effects to cells and tissues. These new findings suggest that the abnormal tyrosine isomers could in fact represent mediators of the effects of oxidative stress. Consequently the accumulation of m- and o-tyrosine may disrupt cellular homeostasis and contribute to disease pathogenesis, and as result, effective defenses against oxidative stress can encompass not only the elimination of reactive oxygen species but also the metabolism and ultimately the removal of the abnormal tyrosine isomers from the cellular amino acid pool. Future research in this area is needed to clarify the biologic mechanisms by which the tyrosine isomers damage cells and disrupt the function of tissues and organs and to identify the metabolic pathways involved in removing the accumulated isomers after exposure to oxidative stress. Published by Elsevier B.V.

Roles of the tyrosine isomers meta-tyrosine and ortho-tyrosine in oxidative stress

PubMed Central

Ipson, Brett R.; Fisher, Alfred L.

2016-01-01

The damage to cellular components by reactive oxygen species, termed oxidative stress, both increases with age and likely contributes to age-related diseases including Alzheimer’s disease, atherosclerosis, diabetes, and cataract formation. In the setting of oxidative stress, hydroxyl radicals can oxidize the benzyl ring of the amino acid phenylalanine, which then produces the abnormal tyrosine isomers meta-tyrosine or ortho-tyrosine. While elevations in m-tyrosine and o-tyrosine concentrations have been used as a biological marker of oxidative stress, there is emerging evidence from bacterial, plant, and mammalian studies demonstrating that these isomers, particularly m-tyrosine, directly produce adverse effects to cells and tissues. These new findings suggest that the abnormal tyrosine isomers could in fact represent mediators of the effects of oxidative stress. Consequently the accumulation of m- and o-tyrosine may disrupt cellular homeostasis and contribute to disease pathogenesis, and as result, effective defenses against oxidative stress can encompass not only the elimination of reactive oxygen species but also the metabolism and ultimately the removal of the abnormal tyrosine isomers from the cellular amino acid pool. Future research in this area is needed to clarify the biologic mechanisms by which the tyrosine isomers damage cells and disrupt the function of tissues and organs, and to identify the metabolic pathways involved in removing the accumulated isomers after exposure to oxidative stress. PMID:27039887

Identification of the isomers using principal component analysis (PCA) method

NASA Astrophysics Data System (ADS)

Kepceoǧlu, Abdullah; Gündoǧdu, Yasemin; Ledingham, Kenneth William David; Kilic, Hamdi Sukur

2016-03-01

In this work, we have carried out a detailed statistical analysis for experimental data of mass spectra from xylene isomers. Principle Component Analysis (PCA) was used to identify the isomers which cannot be distinguished using conventional statistical methods for interpretation of their mass spectra. Experiments have been carried out using a linear TOF-MS coupled to a femtosecond laser system as an energy source for the ionisation processes. We have performed experiments and collected data which has been analysed and interpreted using PCA as a multivariate analysis of these spectra. This demonstrates the strength of the method to get an insight for distinguishing the isomers which cannot be identified using conventional mass analysis obtained through dissociative ionisation processes on these molecules. The PCA results dependending on the laser pulse energy and the background pressure in the spectrometers have been presented in this work.

Theoretical and experimental NMR study of protopine hydrochloride isomers.

PubMed

Tousek, Jaromír; Malináková, Katerina; Dostál, Jirí; Marek, Radek

2005-07-01

The 1H and 13C NMR chemical shifts of cis- and trans-protopinium salts were measured and calculated. The calculations of the chemical shifts consisted of conformational analysis, geometry optimization (RHF/6-31G** method) and shielding constants calculations (B3LYP/6-31G** method). Based on the results of the quantum chemical calculations, two sets of experimental chemical shifts were assigned to the particular isomers. According to the experimental results, the trans-isomer is more stable and its population is approximately 68%. Copyright 2005 John Wiley & Sons, Ltd

The influence of isomer purity on trap states and performance of organic thin-film transistors.

PubMed

Diemer, Peter J; Hayes, Jacori; Welchman, Evan; Hallani, Rawad; Pookpanratana, Sujitra J; Hacker, Christina A; Richter, Curt A; Anthony, John E; Thonhauser, Timo; Jurchescu, Oana D

2017-01-01

Organic field-effect transistor (OFET) performance is dictated by its composition and geometry, as well as the quality of the organic semiconductor (OSC) film, which strongly depends on purity and microstructure. When present, impurities and defects give rise to trap states in the bandgap of the OSC, lowering device performance. Here, 2,8-difluoro-5,11-bis(triethylsilylethynyl)-anthradithiophene is used as a model system to study the mechanism responsible for performance degradation in OFETs due to isomer coexistence. The density of trapping states is evaluated through temperature dependent current-voltage measurements, and it is discovered that OFETs containing a mixture of syn - and anti -isomers exhibit a discrete trapping state detected as a peak located at ~ 0.4 eV above the valence-band edge, which is absent in the samples fabricated on single-isomer films. Ultraviolet photoelectron spectroscopy measurements and density functional theory calculations do not point to a significant difference in electronic band structure between individual isomers. Instead, it is proposed that the dipole moment of the syn -isomer present in the host crystal of the anti -isomer locally polarizes the neighboring molecules, inducing energetic disorder. The isomers can be separated by applying gentle mechanical vibrations during film crystallization, as confirmed by the suppression of the peak and improvement in device performance.

A debranching enzyme IsoM of Corallococcus sp. strain EGB with potential in starch processing.

PubMed

Li, Zhoukun; Ji, Kai; Zhou, Jie; Ye, Xianfeng; Wang, Ting; Luo, Xue; Huang, Yan; Cao, Hui; Cui, Zhongli; Kong, Yi

2017-12-01

Interest in use of resistant starch and maltooligosaccharides as functional foods and biopreservatives has grown in recent years. In this research, a novel debranching enzyme IsoM from Corallococcus sp. strain EGB was identified and expressed in P. pastoris GS115. Sequence alignments showed that IsoM was typical isoamylase with the specific activity up to 70,600U/mg, which belongs to glycoside hydrolase family 13 (GH 13). Enzymatic reaction pattern demonstrated that IsoM has high debranching efficiency against α-1,6-glycosidic bond of branched starch, and exhibited no activity towards α-1,4-glycosidic bond. The potential application of IsoM in starch processing was determined. IsoM was a potential candidate for the production of RS (70.9%) from raw starch, which was comparable with the commercial pullulanase (Promozyme ® D2). IsoM also improved the maltohexaose yield in combination with maltohexaose-producing α-amylase AmyM (KM114206), the maltohexaose yield was improved by 63.3% compared with 21.9% improvement of Promozyme ® D2. The results of RS production and combination with other amylases suggesting that IsoM is a potential candidate for the efficient conversion of starch. Copyright © 2017. Published by Elsevier B.V.

Virtual libraries of tetrapyrrole macrocycles. Combinatorics, isomers, product distributions, and data mining.

PubMed

Taniguchi, Masahiko; Du, Hai; Lindsey, Jonathan S

2011-09-26

A software program (PorphyrinViLiGe) has been developed to enumerate the type and relative amounts of substituted tetrapyrrole macrocycles in a virtual library formed by one of four different classes of reactions. The classes include (1) 4-fold reaction of n disubstituted heterocycles (e.g., pyrroles or diiminoisoindolines) to form β-substituted porphyrins, β-substituted tetraazaporphyrins, or α- or β-substituted phthalocyanines; (2) combination of m aminoketones and n diones to form m × n pyrroles, which upon 4-fold reaction give β-substituted porphyrins; (3) derivatization of an 8-point tetrapyrrole scaffold with n reagents, and (4) 4-fold reaction of n aldehydes and pyrrole to form meso-substituted porphyrins. The program accommodates variable ratios of reactants, reversible or irreversible reaction (reaction classes 1 and 2), and degenerate modes of formation. Pólya's theorem (for enumeration of cyclic entities) has also been implemented and provides validation for reaction classes 3 and 4. The output includes the number and identity of distinct reaction-accessible substituent combinations, the number and identity of isomers thereof, and the theoretical mass spectrum. Provisions for data mining enable assessment of the number of products having a chosen pattern of substituents. Examples include derivatization of an octa-substituted phthalocyanine with eight reagents to afford a library of 2,099,728 members (yet only 6435 distinct substituent combinations) and reversible reaction of six distinct disubstituted pyrroles to afford 2649 members (yet only 126 distinct substituent combinations). In general, libraries of substituted tetrapyrrole macrocycles occupy a synthetically accessible region of chemical space that is rich in isomers (>99% or 95% for the two examples, respectively).

[TLC-FT-SERS study on a pair of optic isomers in ephedra].

PubMed

Wang, Yuan; Zhang, Jin-zhi; Ma, Xin-yong

2004-11-01

A new method for analyzing the ingredients of a pair of optic isomers in ephedra, nor-ephedrine and nor-pseudo-ephedrine, using hyphenated high-efficiency thin layer chromatography (TLC) and surface-enhanced Raman spectroscopy (SERS) techniques, is reported. The results show that the characteristic spectral bands of nor-ephedrine and nor-pseudo-ephedrine can be obtained from the TLC spot with 8 microg sample of about 2.0 mm in diameter. The difference between the SERS and solid spectra was found. Spectral bands at 1004 cm(-1) and 1605 cm(-1) were found greatly enhanced. Molecule was absorbed in surface silver sol by pi electrons in ring. Under similar experimental conditions the spectral information of Levo-nor-ephedrine ramifications TLC-SERS is rich with strong credibility, whereas dextral-nor-ephedrine ramifications show a relatively strong fluorescence backdrop with less spectral information and weak credibility. The effective combination of TLC and SERS can be used to analyse the chemical ingredients with high sensitivity.

Revealing the structure of isolated peptides: IR-IR predissociation spectroscopy of protonated triglycine isomers

NASA Astrophysics Data System (ADS)

Voss, Jonathan M.; Fischer, Kaitlyn C.; Garand, Etienne

2018-05-01

We report an isomer specific IR-IR double resonance study of the mass-selected protonated triglycine peptide. Comparison of experimental spectra with calculations reveals the presence of two isomers, with protonation occurring at either the terminal amine site or one of the amide oxygen sites. The amine protonated isomer identified in our experiment contains an atypical cis amide configuration as well as a more typical trans amide. The amide protonated peptide, on the other hand, contains two trans amide moieties. Both isomers are found to be the lowest energy structures for their respective protonation site, but it is unclear, from experiments and calculations, which one is the global minimum. The presence of both in our experiments likely points to kinetic trapping of a higher energy structure. Finally, the observed frequencies of the Nsbnd H and Osbnd H stretch vibrations are used to estimate the hydrogen-bond strengths present in each isomer, accounting for the relative stabilities of these structures.

Revealing the structure of isolated peptides: IR-IR predissociation spectroscopy of protonated triglycine isomers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Voss, Jonathan M.; Fischer, Kaitlyn C.; Garand, Etienne

Here, we report an isomer specific IR-IR double resonance study of the mass-selected protonated triglycine peptide. Comparison of experimental spectra with calculations reveals the presence of two isomers, with protonation occurring at either the terminal amine site or one of the amide oxygen sites. The amine protonated isomer identified in our experiment contains an atypical cis amide configuration as well as a more typical trans amide. The amide protonated peptide, on the other hand, contains two trans amide moieties. Both isomers are found to be the lowest energy structures for their respective protonation site, but it is unclear, from experimentsmore » and calculations, which one is the global minimum. The presence of both in our experiments likely points to kinetic trapping of a higher energy structure. Lastly, the observed frequencies of the NH and OH stretch vibrations are used to estimate the hydrogen-bond strengths present in each isomer, accounting for the relative stabilities of these structures.« less

Revealing the structure of isolated peptides: IR-IR predissociation spectroscopy of protonated triglycine isomers

DOE PAGES

Voss, Jonathan M.; Fischer, Kaitlyn C.; Garand, Etienne

2018-03-08

Here, we report an isomer specific IR-IR double resonance study of the mass-selected protonated triglycine peptide. Comparison of experimental spectra with calculations reveals the presence of two isomers, with protonation occurring at either the terminal amine site or one of the amide oxygen sites. The amine protonated isomer identified in our experiment contains an atypical cis amide configuration as well as a more typical trans amide. The amide protonated peptide, on the other hand, contains two trans amide moieties. Both isomers are found to be the lowest energy structures for their respective protonation site, but it is unclear, from experimentsmore » and calculations, which one is the global minimum. The presence of both in our experiments likely points to kinetic trapping of a higher energy structure. Lastly, the observed frequencies of the NH and OH stretch vibrations are used to estimate the hydrogen-bond strengths present in each isomer, accounting for the relative stabilities of these structures.« less

Resolution and Assignment of Differential Ion Mobility Spectra of Sarcosine and Isomers.

PubMed

Berthias, Francis; Maatoug, Belkis; Glish, Gary L; Moussa, Fathi; Maitre, Philippe

2018-04-01

Due to their central role in biochemical processes, fast separation and identification of amino acids (AA) is of importance in many areas of the biomedical field including the diagnosis and monitoring of inborn errors of metabolism and biomarker discovery. Due to the large number of AA together with their isomers and isobars, common methods of AA analysis are tedious and time-consuming because they include a chromatographic separation step requiring pre- or post-column derivatization. Here, we propose a rapid method of separation and identification of sarcosine, a biomarker candidate of prostate cancer, from isomers using differential ion mobility spectrometry (DIMS) interfaced with a tandem mass spectrometer (MS/MS) instrument. Baseline separation of protonated sarcosine from α- and β-alanine isomers can be easily achieved. Identification of DIMS peak is performed using an isomer-specific activation mode where DIMS- and mass-selected ions are irradiated at selected wavenumbers allowing for the specific fragmentation via an infrared multiple photon dissociation (IRMPD) process. Two orthogonal methods to MS/MS are thus added, where the MS/MS(IRMPD) is nothing but an isomer-specific multiple reaction monitoring (MRM) method. The identification relies on the comparison of DIMS-MS/MS(IRMPD) chromatograms recorded at different wavenumbers. Based on the comparison of IR spectra of the three isomers, it is shown that specific depletion of the two protonated α- and β-alanine can be achieved, thus allowing for clear identification of the sarcosine peak. It is also demonstrated that DIMS-MS/MS(IRMPD) spectra in the carboxylic C=O stretching region allow for the resolution of overlapping DIMS peaks. Graphical Abstract ᅟ.

Terahertz Spectroscopy and Solid-State Density Functional Theory Calculations of Cyanobenzaldehyde Isomers.

PubMed

Dash, Jyotirmayee; Ray, Shaumik; Nallappan, Kathirvel; Kaware, Vaibhav; Basutkar, Nitin; Gonnade, Rajesh G; Ambade, Ashootosh V; Joshi, Kavita; Pesala, Bala

2015-07-23

Spectral signatures in the terahertz (THz) frequency region are mainly due to bulk vibrations of the molecules. These resonances are highly sensitive to the relative position of atoms in a molecule as well as the crystal packing arrangement. To understand the variation of THz resonances, THz spectra (2-10 THz) of three structural isomers: 2-, 3-, and 4-cyanobenzaldehyde have been studied. THz spectra obtained from Fourier transform infrared (FTIR) spectrometry of these isomers show that the resonances are distinctly different especially below 5 THz. For understanding the intermolecular interactions due to hydrogen bonds, four molecule cluster simulations of each of the isomers have been carried out using the B3LYP density functional with the 6-31G(d,p) basis set in Gaussian09 software and the compliance constants are obtained. However, to understand the exact reason behind the observed resonances, simulation of each isomer considering the full crystal structure is essential. The crystal structure of each isomer has been determined using X-ray diffraction (XRD) analysis for carrying out crystal structure simulations. Density functional theory (DFT) simulations using CRYSTAL14 software, utilizing the hybrid density functional B3LYP, have been carried out to understand the vibrational modes. The bond lengths and bond angles from the optimized structures are compared with the XRD results in terms of root-mean-square-deviation (RMSD) values. Very low RMSD values confirm the overall accuracy of the results. The simulations are able to predict most of the spectral features exhibited by the isomers. The results show that low frequency modes (<3 THz) are mediated through hydrogen bonds and are dominated by intermolecular vibrations.

Resolution and Assignment of Differential Ion Mobility Spectra of Sarcosine and Isomers

NASA Astrophysics Data System (ADS)

Berthias, Francis; Maatoug, Belkis; Glish, Gary L.; Moussa, Fathi; Maitre, Philippe

2018-02-01

Due to their central role in biochemical processes, fast separation and identification of amino acids (AA) is of importance in many areas of the biomedical field including the diagnosis and monitoring of inborn errors of metabolism and biomarker discovery. Due to the large number of AA together with their isomers and isobars, common methods of AA analysis are tedious and time-consuming because they include a chromatographic separation step requiring pre- or post-column derivatization. Here, we propose a rapid method of separation and identification of sarcosine, a biomarker candidate of prostate cancer, from isomers using differential ion mobility spectrometry (DIMS) interfaced with a tandem mass spectrometer (MS/MS) instrument. Baseline separation of protonated sarcosine from α- and β-alanine isomers can be easily achieved. Identification of DIMS peak is performed using an isomer-specific activation mode where DIMS- and mass-selected ions are irradiated at selected wavenumbers allowing for the specific fragmentation via an infrared multiple photon dissociation (IRMPD) process. Two orthogonal methods to MS/MS are thus added, where the MS/MS(IRMPD) is nothing but an isomer-specific multiple reaction monitoring (MRM) method. The identification relies on the comparison of DIMS-MS/MS(IRMPD) chromatograms recorded at different wavenumbers. Based on the comparison of IR spectra of the three isomers, it is shown that specific depletion of the two protonated α- and β-alanine can be achieved, thus allowing for clear identification of the sarcosine peak. It is also demonstrated that DIMS-MS/MS(IRMPD) spectra in the carboxylic C=O stretching region allow for the resolution of overlapping DIMS peaks. [Figure not available: see fulltext.

Coulomb excitation of the 242mAm isomer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayes, A; Cline, D; Moody, K

2006-10-24

The {sup 242m}Am isomer, a well-known candidate for photo-depopulation research, has been studied in this first ever Coulomb excitation of a nearly pure ({approx} 98%) isomer target. Thirty new states, including a new rotational band built on a K{sup {pi}} = 6{sup -} state have been identified. Strong K-mixing results in nearly equal populations of the K{sup {pi}} = 5{sup -} and 6{sup -} states. Newly identified states have been assigned to the K{sup {pi}} = 3{sup -} rotational band, the lowest states of which are known to decay into the ground-state band. Implications regarding K-mixing and Coulomb excitation pathsmore » to the ground state are discussed.« less

Theoretical studies of possible toroidal high-spin isomers in the light-mass region

DOE PAGES

Staszczak, A.; Wong, Cheuk-Yin

2016-05-11

We review our theoretical knowledge of possible toroidal high-spin isomers in the light mass region in 28≤A≤52 obtained previously in cranked Skyrme-Hartree-Fock calculations. We report additional toroidal high-spin isomers in 56Ni with I=114ℏ and 140ℏ, which follow the same (multi-particle) (multi-hole) systematics as other toroidal high-spin isomers. We examine the production of these exotic nuclei by fusion of various projectiles on 20Ne or 28Si as an active target in time-projection-chamber (TPC) experiments.

From microseconds to seconds and minutes—time computation in insect hearing

PubMed Central

Hartbauer, Manfred; Römer, Heiner

2014-01-01

The computation of time in the auditory system of insects is of relevance at rather different time scales, covering a large range from microseconds to several minutes. At the one end of this range, only a few microseconds of interaural time differences are available for directional hearing, due to the small distance between the ears, usually considered too small to be processed reliably by simple nervous systems. Synapses of interneurons in the afferent auditory pathway are, however, very sensitive to a time difference of only 1–2 ms provided by the latency shift of afferent activity with changing sound direction. At a much larger time scale of several tens of milliseconds to seconds, time processing is important in the context species recognition, but also for those insects where males produce acoustic signals within choruses, and the temporal relationship between song elements strongly deviates from a random distribution. In these situations, some species exhibit a more or less strict phase relationship of song elements, based on phase response properties of their song oscillator. Here we review evidence on how this may influence mate choice decisions. In the same dimension of some tens of milliseconds we find species of katydids with a duetting communication scheme, where one sex only performs phonotaxis to the other sex if the acoustic response falls within a very short time window after its own call. Such time windows show some features unique to insects, and although its neuronal implementation is unknown so far, the similarity with time processing for target range detection in bat echolocation will be discussed. Finally, the time scale being processed must be extended into the range of many minutes, since some acoustic insects produce singing bouts lasting quite long, and female preferences may be based on total signaling time. PMID:24782783

Laboratory data base for isomer-specific determination of polychlorinated biphenyls

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwartz, T.R.; Campbell, R.D.; Stalling, D.L.

1984-07-01

A computer-assisted technique for quantitative determination of polychlorinated biphenyl isomers is described. PCB isomers were identified by use of a retention index system with n-alkyl trichloroacetates as retention index marker compounds. A laboratory data base system was developed to aid in editing and quantitation of data generated from capillary gas chromatographic data. Data base management was provided by computer programs written in DSM-11 (Digital Standard MUMPS) for the PDP-11 family of computers. 13 references, 4 figures, 2 tables.

Trans- and cis-octadecenoic acid isomers in the hump and milk lipids from Camelus dromedarius.

PubMed

Wolff, R L; Precht, D; Nasser, B; El Kebbaj, M S

2001-10-01

The distribution profiles of individual trans- as well as cis-18:1 isomers from the fat prepared from the hump adipose tissue and the milk from Camelus dromedarius (the single-humped Arabian species) are described. Gas-liquid chromatography on two capillary columns with different polarities and lengths were used for this purpose in combination with argentation thin-layer chromatography. A comparison of the profiles established is made with that of true ruminant fats. In the fats from the dromedarius as well as from true ruminants, the trans-18:1 isomers have their ethylenic bonds in all positions between delta4 and delta16. The prominent trans isomer is the 11-18:1 (vaccenic) acid in all species, and the complete distribution profiles are quite similar. Concerning the cis isomers, the prominent isomer is oleic acid, followed by cis-vaccenic acid, as in true ruminant fats. Other cis isomers encompass the delta6-8 and the delta12 to delta15 isomers. Camelidae (suborder Tylopoda) and Bovidae (suborder Ruminantia) have evolved independently since the Eocene, that is for approximately 50 million years. Despite this considerable period, and the profound differences in anatomy, morphology, physiology, ecological and dietary habits between the extant species of these suborders, the rumen microflora has continued to synthesize the same trans- and cis-octadecenoic acid isomers, in comparable proportions, at least as deduced from their composition profiles. We conclude that the trans-18:1 acid profile is not intrinsically species-dependent, but it can be affected by the nature and the proportions of dietary unsaturated fatty acids that themselves depend on the feed, and that may be species-specific.

Aqueous phase partitioning of hexachlorocyclohexane (HCH) isomers by biosurfactant produced by Pseudomonas aeruginosa WH-2.

PubMed

Sharma, Suman; Singh, Partapbir; Raj, Mayil; Chadha, Bhupinder Singh; Saini, Harvinder Singh

2009-11-15

The different isomers of technical-grade hexachlorocyclohexane (t-HCH) including the insecticidal gamma-isomer, commonly known as lindane, have been reported to be toxic, carcinogenic and endocrine disrupters. The spatial arrangements of the chlorine atoms on different isomers and low aqueous phase solubility contribute to their persistence in environment, beta-HCH being the most resistance to transformation. The biosurfactant preparation of Pseudomonas aeruginosa isolate WH-2 was evaluated for its ability to improve the aqueous phase partitioning of different isomers of HCH-muck. Further, the ability of biosurfactant preparation to emulsify HCH and n-hexadecane was checked under different conditions, usually characteristic of sites contaminated with pollutants viz. wide range of pH, temperature, and salinity. The data obtained from this study will be helpful in designing suitable bioremediation strategies for huge stock piles of HCH-muck and sites polluted by reckless use/disposal of HCH-isomers.

New isomer in 96Y marking the onset of deformation at N = 57

NASA Astrophysics Data System (ADS)

Iskra, Ł. W.; Fornal, B.; Leoni, S.; Bocchi, G.; Petrovici, A.; Porzio, C.; Blanc, A.; De France, G.; Jentschel, M.; Köster, U.; Mutti, P.; Régis, J.-M.; Simpson, G.; Soldner, T.; Ur, C. A.; Urban, W.; Bazzacco, D.; Benzoni, G.; Bottoni, S.; Bruce, A.; Cieplicka-Oryńczak, N.; Crespi, F. C. L.; Fraile, L. M.; Korten, W.; Kröll, T.; Lalkovski, S.; Márginean, N.; Michelagnoli, C.; Melon, B.; Mengoni, D.; Million, B.; Nannini, A.; Napoli, D.; Podolyák, Zs.; Regan, P. H.; Szpak, B.

2017-01-01

The level scheme of 96Y was significantly extended and a new 201 ns isomer was located at 1655 keV excitation energy, with spin-parity assignment of 5± or 6-. The isomer decays to spherical low-spin structure by transitions with large hindrance and is fed by a short cascade which resembles the beginning of a rotational band. This is in analogy with the feeding and decay pattern of the 4- isomer in 98Y, here confirmed, by lifetime analysis, as a bandhead of a rotational structure with sizable deformation. It is suggested that the new isomer in 96Y arises from a shape change between deformed and spherical configurations, which indicates the appearance of deformation already at N = 57 in the yttrium chain. The experimental findings for 96Y are strengthened by theoretical calculations based on the complex Excited Vampir model.

Linear and branched perfluorooctane sulfonate (PFOS) isomer patterns differ among several tissues and blood of polar bears.

PubMed

Greaves, Alana K; Letcher, Robert J

2013-09-01

Perfluorooctane sulfonate (PFOS) is a globally distributed persistent organic pollutant that has been found to bioaccumulate and biomagnify in aquatic food webs. Although principally in its linear isomeric configuration, 21-35% of the PFOS manufactured via electrochemical fluorination is produced as a branched structural isomer. PFOS isomer patterns were investigated in multiple tissues of polar bears (Ursus maritimus) from East Greenland. The liver (n = 9), blood (n = 19), brain (n = 16), muscle (n = 5), and adipose (n = 5) were analyzed for linear PFOS (n-PFOS), as well as multiple mono- and di-trifluoromethyl-substituted branched isomers. n-PFOS accounted for 93.0 ± 0.5% of Σ-PFOS isomer concentrations in the liver, whereas the proportion was significantly lower (p<0.05) in the blood (85.4 ± 0.5%). Branched isomers were quantifiable in the liver and blood, but not in the brain, muscle, or adipose. In both the liver and blood, 6-perfluoromethylheptane sulfonate (P6MHpS) was the dominant branched isomer (2.61 ± 0.10%, and 3.26 ± 0.13% of Σ-PFOS concentrations, respectively). No di-trifluoromethyl-substituted isomers were detectable in any of the tissues analyzed. These tissue-specific isomer patterns suggest isomer-specific pharmacokinetics, perhaps due to differences in protein affinities, and thus differences in protein interactions, as well transport, absorption, and/or metabolism in the body. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

Anaerobic biotransformation of hexachlorocyclohexane isomers by Dehalococcoides species and an enrichment culture.

PubMed

Bashir, Safdar; Kuntze, Kevin; Vogt, Carsten; Nijenhuis, Ivonne

2018-06-18

The biotransformation of hexachlorocyclohexane isomers (HCH) by two Dehalococcoides mccartyi strains (195 and BTF08) and an enrichment culture was investigated and compared to conversion by the obligate anaerobic strain Clostridium pasteurianum strain DSMZ 525. The D. mccartyi strains preferentially transformed γ-HCH over α-HCH and δ-HCH isomers while β-HCH biotransformation was not significant. In case of the enrichment culture, γ-HCH was preferentially transformed over the δ-HCH, β-HCH and α-HCH isomers. Major observed metabolites in both cases were tetrachlorocyclohexene and as end products monochlorobenzene (MCB) and benzene. Dechlorination of the γ-HCH isomer was linked to an increase in cell numbers for strain 195. γ-HCH transformation was linked to considerable carbon stable isotope fractionation with the enrichment factor ε c  = - 5.5 ± 0.8‰ for D. mccartyi strain 195, ε c  = - 3.1 ± 0.4‰ for the enrichment culture and ε c  = - 4.1 ± 0.6‰ for co-metabolic transformation by C. pasteurianum.

Effect of thermal treatment and light irradiation on the stability of lycopene with high Z-isomers content.

PubMed

Murakami, Kazuya; Honda, Masaki; Takemura, Ryota; Fukaya, Tetsuya; Wahyudiono; Kanda, Hideki; Goto, Motonobu

2018-06-01

The stability of lycopene with high Z-isomers content during thermal treatment and light irradiation was investigated. Purified (all-E)-lycopene was thermally isomerized to the Z-isomers in dichloromethane (CH 2 Cl 2 ) at 50 °C for 24 h. The total content of the Z-isomers of lycopene reached 56.1%. Then, the mixture of lycopene isomers was stored in the dark at 4, 25, and 40 °C for 30 days, and under light irradiation using a fluorescent light at 4 °C for 336 h. The degradation rate of lycopene during thermal treatment rose with increasing temperature and the activation energy for decomposition of the mixture of lycopene isomers was calculated to be 71.0 kJ mol -1 . The degradation rate of lycopene isomers was almost the same under thermal treatment. On the other hand, during light irradiation, isomerization was promoted rather than decomposition, i.e. (9Z)- and (13Z)-lycopene converted to the (all-E)-isomer. Copyright © 2018 Elsevier Ltd. All rights reserved.

Physical chemistry and membrane properties of two phosphatidylinositol bisphosphate isomers.

PubMed

Slochower, David R; Wang, Yu-Hsiu; Radhakrishnan, Ravi; Janmey, Paul A

2015-05-21

The most highly charged phospholipids, polyphosphoinositides, are often involved in signaling pathways that originate at cell-cell and cell-matrix contacts, and different isomers of polyphosphoinositides have distinct biological functions that cannot be explained by separate highly specific protein ligand binding sites [Lemmon, Nat. Rev. Mol. Cell Biol., 2008, 9, 99-111]. PtdIns(3,5)P2 is a low abundance phosphoinositide localized to cytoplasmic-facing membrane surfaces, with relatively few known ligands, yet PtdIns(3,5)P2 plays a key role in controlling membrane trafficking events and cellular stress responses that cannot be duplicated by other phosphoinositides [Dove et al., Nature, 1997, 390, 187-192; Michell, FEBS J., 2013, 280, 6281-6294]. Here we show that PtdIns(3,5)P2 is structurally distinct from PtdIns(4,5)P2 and other more common phospholipids, with unique physical chemistry. Using multiscale molecular dynamics techniques on the quantum level, single molecule, and in bilayer settings, we found that the negative charge of PtdIns(3,5)P2 is spread over a larger area, compared to PtdIns(4,5)P2, leading to a decreased ability to bind divalent ions. Additionally, our results match well with experimental data characterizing the cluster forming potential of these isomers in the presence of Ca(2+) [Wang et al., J. Am. Chem. Soc., 2012, 134, 3387-3395; van den Bogaart et al., Nature, 2011, 479, 552-555]. Our results demonstrate that the different cellular roles of PtdIns(4,5)P2 and PtdIns(3,5)P2in vivo are not simply determined by their localization by enzymes that produce or degrade them, but also by their molecular size, ability to chelate ions, and the partial dehydration of those ions, which might affect the ability of PtdIns(3,5)P2 and PtdIns(4,5)P2 to form phosphoinositide-rich clusters in vitro and in vivo.

Three-quasiparticle isomer in 173Ta and the excitation energy dependence of K -forbidden transition rates

NASA Astrophysics Data System (ADS)

Wood, R. T.; Walker, P. M.; Lane, G. J.; Carroll, R. J.; Cullen, D. M.; Dracoulis, G. D.; Hota, S. S.; Kibédi, T.; Palalani, N.; Podolyák, Zs.; Reed, M. W.; Schiffl, K.; Wright, A. M.

2017-05-01

Using the 168Er(10B,5 n ) reaction at a beam energy of 68 MeV, new data have been obtained for the population and decay of a T1 /2=148 ns, Kπ=21 /2- three-quasiparticle isomer at 1717 keV in 173Ta. Revised decay energies and intensities have been determined, together with newly observed members of a rotational band associated with the isomer. By comparison with other isomers in the A ≈180 deformed region, the 173Ta isomer properties help to specify the key degrees of freedom that determine K -forbidden transition rates. In particular, when all three quasiparticles are of the same nucleon type, there is a strong dependence of the E 2 reduced hindrance factor on the isomer excitation energy.

Mutual diffusion coefficients of heptane isomers in nitrogen: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Chae, Kyungchan; Violi, Angela

2011-01-01

The accurate knowledge of transport properties of pure and mixture fluids is essential for the design of various chemical and mechanical systems that include fluxes of mass, momentum, and energy. In this study we determine the mutual diffusion coefficients of mixtures composed of heptane isomers and nitrogen using molecular dynamics (MD) simulations with fully atomistic intermolecular potential parameters, in conjunction with the Green-Kubo formula. The computed results were compared with the values obtained using the Chapman-Enskog (C-E) equation with Lennard-Jones (LJ) potential parameters derived from the correlations of state values: MD simulations predict a maximum difference of 6% among isomers while the C-E equation presents that of 3% in the mutual diffusion coefficients in the temperature range 500-1000 K. The comparison of two approaches implies that the corresponding state principle can be applied to the models, which are only weakly affected by the anisotropy of the interaction potentials and the large uncertainty will be included in its application for complex polyatomic molecules. The MD simulations successfully address the pure effects of molecular structure among isomers on mutual diffusion coefficients by revealing that the differences of the total mutual diffusion coefficients for the six mixtures are caused mainly by heptane isomers. The cross interaction potential parameters, collision diameter σ _{12}, and potential energy well depth \\varepsilon _{12} of heptane isomers and nitrogen mixtures were also computed from the mutual diffusion coefficients.

Tamoxifen metabolite isomer separation and quantification by liquid chromatography-tandem mass spectrometry.

PubMed

Jaremko, Malgorzata; Kasai, Yumi; Barginear, Myra F; Raptis, George; Desnick, Robert J; Yu, Chunli

2010-12-15

Tamoxifen (Tam), the antiestrogen used to treat estrogen receptor-positive breast cancer is a pro-drug that is converted to its major active metabolites, endoxifen and 4-hydroxy-tamoxifen (4-OH-Tam) by various biotransformation enzymes of which cytochrome P450-2D6 (CYP2D6) is key. The usual Tam dose is 20 mg daily; however, the plasma active metabolite concentrations vary due to common genetic variants encoding the biotransformation enzymes and environmental factors (e.g., concomitant drugs) that inhibit these enzymes. Effective treatment depends on adequate Tam conversion to its active isomers. To monitor metabolite plasma levels, a novel liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to separate and quantitate Tam, N-desmethyl-tamoxifen (ND-Tam), and tamoxifen-N-oxide (Tam-N-oxide), and the E, Z, and Z' isomers of endoxifen and 4-OH-Tam. Known standards were used to identify each metabolite/isomer. Quantitation of these metabolites in plasma was linear from 0.6 to 2000 nM. Intra- and inter-assay reproducibilities were 0.2-8.4% and 0.6-6.3%, respectively. Accuracy determined by spike experiments with known standards was 86-103%. Endoxifen, 4-OH-Tam, and their isomers were stable in fresh frozen plasma for ≥6 months. This method provides the first sensitive, specific, accurate, and reproducible quantitation of Tam and its metabolite isomers for monitoring Tam-treated breast cancer patients.

Low-energy electron scattering from C{sub 4}H{sub 9}OH isomers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bettega, M. H. F.; Winstead, C.; McKoy, V.

2010-12-15

We present differential, integral, and momentum-transfer cross sections for elastic scattering of low-energy electrons by three butanol isomers, isobutanol, t-butanol, and 2-butanol. Our results were calculated with the Schwinger multichannel method in the static-exchange plus polarization approximation for collision energies from 1 to 50 eV. The present results are compared with previous calculations and measurements for the remaining C{sub 4}H{sub 9}OH isomer, n-butanol [Khakoo et al., Phys. Rev. A 78, 062714 (2008)]. Distinctive behavior is observed in the differential cross sections at collision energies between 5 and 10 eV. In particular, whereas n-butanol exhibits an f-wave scattering pattern, the othermore » isomers exhibit d-wave behavior. A similar pattern is found in the related alkanes when comparing straight-chain versus branched isomers. We discuss the possible connection of this behavior to shape resonances that influence the scattering.« less

Prospects for measuring the 229Th isomer energy using a metallic magnetic microcalorimeter.

PubMed

Kazakov, G A; Schauer, V; Schwestka, J; Stellmer, S P; Sterba, J H; Fleischmann, A; Gastaldo, L; Pabinger, A; Enss, C; Schumm, T

2014-01-21

The Thorium-229 isotope features a nuclear isomer state with an extremely low energy. The currently most accepted energy value, 7.8±0.5 eV, was obtained from an indirect measurement using a NASA x-ray microcalorimeter with an instrumental resolution 26 eV. We study, how state-of-the-art magnetic metallic microcalorimeters with an energy resolution down to a few eV can be used to measure the isomer energy. In particular, resolving the 29.18 keV doublet in the γ-spectrum following the α-decay of Uranium-233, corresponding to the decay into the ground and isomer state, allows to measure the isomer transition energy without additional theoretical input parameters, and increase the energy accuracy. We study the possibility of resolving the 29.18 keV line as a doublet and the dependence of the attainable precision of the energy measurement on the signal and background count rates and the instrumental resolution.

Prospects for measuring the 229Th isomer energy using a metallic magnetic microcalorimeter☆

PubMed Central

Kazakov, G.A.; Schauer, V.; Schwestka, J.; Stellmer, S.P.; Sterba, J.H.; Fleischmann, A.; Gastaldo, L.; Pabinger, A.; Enss, C.; Schumm, T.

2014-01-01

The Thorium-229 isotope features a nuclear isomer state with an extremely low energy. The currently most accepted energy value, 7.8±0.5 eV, was obtained from an indirect measurement using a NASA x-ray microcalorimeter with an instrumental resolution 26 eV. We study, how state-of-the-art magnetic metallic microcalorimeters with an energy resolution down to a few eV can be used to measure the isomer energy. In particular, resolving the 29.18 keV doublet in the γ-spectrum following the α-decay of Uranium-233, corresponding to the decay into the ground and isomer state, allows to measure the isomer transition energy without additional theoretical input parameters, and increase the energy accuracy. We study the possibility of resolving the 29.18 keV line as a doublet and the dependence of the attainable precision of the energy measurement on the signal and background count rates and the instrumental resolution. PMID:25844000

A chiral HPLC method for the simultaneous separation of configurational isomers of the predominant cis/trans forms of astaxanthin.

PubMed

Abu-Lafi, S; Turujman, S A

1997-01-01

We report an HPLC method that allows the simultaneous separation of configurational isomers of the predominant cis/trans forms of astaxanthin. The configurational isomers of the all-trans-, and most of the configurational isomers of the 9-cis-, 13-cis- and 15-cis-astaxanthin were separated on a Sumichiral OA-2000 column, which is manufactured and packed in Japan with a Pirkle covalent D-phenylglycine chiral stationary phase (CSP). The large separation of the cis isomers from the all-trans isomers that we report here ensure the suitability of this method for the routine determination of the ratio of the configurational isomers of all-trans-astaxanthin.

40 CFR 180.157 - Methyl 3-[(dimethoxyphos-phinyl) oxy]butenoate, alpha and beta isomers; tolerances for residues.

Code of Federal Regulations, 2010 CFR

2010-07-01

...]butenoate, alpha and beta isomers; tolerances for residues. 180.157 Section 180.157 Protection of...]butenoate, alpha and beta isomers; tolerances for residues. (a) General. Tolerances are established for residues of the insecticide methyl 3-[(dimethoxyphosphinyl)oxy]butenoate, alpha and beta isomers, in or on...

40 CFR 180.157 - Methyl 3-[(dimethoxyphos-phinyl) oxy]butenoate, alpha and beta isomers; tolerances for residues.

Code of Federal Regulations, 2011 CFR

2011-07-01

...]butenoate, alpha and beta isomers; tolerances for residues. 180.157 Section 180.157 Protection of...]butenoate, alpha and beta isomers; tolerances for residues. (a) General. Tolerances are established for residues of the insecticide methyl 3-[(dimethoxyphosphinyl)oxy]butenoate, alpha and beta isomers, in or on...

Quantitative Analysis of the Distribution of cis-Eicosenoic Acid Positional Isomers in Marine Fishes from the Indian Ocean.

PubMed

Senarath, Samanthika; Yoshinaga, Kazuaki; Nagai, Toshiharu; Yoshida, Akihiko; Beppu, Fumiaki; Jayasinghe, Chamila; Devadawson, Chandravathany; Gotoh, Naohiro

2017-02-01

This study investigated the occurrence and distribution of cis-eicosenoic acid (c-20:1) positional isomers in fishes from the Indian Ocean and compared to those from the Pacific and Atlantic Ocean. Lipids were extracted from the edible part of the fish and then methylated. The eicosenoic acid methyl ester fraction was separated from total fatty acid methyl esters by reversed-phase HPLC and quantitatively analyzed using a GC-FID fitted with the SLB-IL111 highly polar GC column. c14-20:1 was used as an internal standard. The results indicated that the highest levels of c-20:1 positional isomers were found in fishes from the Pacific Ocean (saury, 166.95±12.4 mg/g of oil), followed by the Atlantic Ocean (capelin, 162.7±3.5 mg/g of oil), and lastly in fishes from the Indian Ocean (goatfish, 34.39 mg/g of oil). With only a few exceptions, the most abundant 20:1 positional isomer found in fishes of the Indian and Atlantic Ocean was the c11-20:1 isomer (>50%) followed by the c13-20:1 isomer (<25%). Unusually, the c7-20:1 isomer was predominantly found in a few fishes such as the tooth ponyfish, longface emperor, and commerson's sole. The c9, c5, and c15-20:1 isomers were the least occurring in fishes from the Indian and Atlantic Ocean. In contrast, the c9-20:1 isomer was the principal isomer identified in fishes from the Pacific Ocean. The results revealed that the content and distribution of c-20:1 positional isomers varied among fishes in different oceans. The data presented in the current study are the first to report on the distribution of c-20:1 positional isomers in fishes from the Indian Ocean.

Microsecond-scale electric field pulses in cloud lightning discharges

NASA Technical Reports Server (NTRS)

Villanueva, Y.; Rakov, V. A.; Uman, M. A.; Brook, M.

1994-01-01

From wideband electric field records acquired using a 12-bit digitizing system with a 500-ns sampling interval, microsecond-scale pulses in different stages of cloud flashes in Florida and New Mexico are analyzed. Pulse occurrence statistics and waveshape characteristics are presented. The larger pulses tend to occur early in the flash, confirming the results of Bils et al. (1988) and in contrast with the three-stage representation of cloud-discharge electric fields suggested by Kitagawa and Brook (1960). Possible explanations for the discrepancy are discussed. The tendency for the larger pulses to occur early in the cloud flash suggests that they are related to the initial in-cloud channel formation processes and contradicts the common view found in the atmospheric radio-noise literature that the main sources of VLF/LF electromagnetic radiation in cloud flashes are the K processes which occur in the final, or J type, part of the cloud discharge.

Two New Isomers of Palmityl-4-hydroxycinnamate from Flowers of Taraxacum Species.

PubMed

Dudáš, Matej; Vilková, Mária; Béres, Tibor; Repcák, Miroslav; Mártonfi, Pavol

2016-06-01

Two isomers, (Z)- and (E)-palmityl 4-hydroxycinnamate [hexadecyl(2Z)-3-(4-hydroxyphenyl)prop-2-enoate and hexadecyl(2E)-3-(4-hydroxyphenyl)prop-2-enoate] were isolated for the first time from ligulate flowers of Taraxacum linearisquameum Soest (sect. Taraxacum). The highest amount of these compounds was detected in pollen grains; 0.26 mg/100 mg DW of the (E)-isomer and 0.096 mg/100 mg DW of the (Z)-isomer. The structures of these compounds were elucidated by a combination of HPLC-ESI-Qtof-MS and 1D and 2D NMR spectroscopy. Their presence was confirmed in other species of Taraxacum, but they were not found in the male - sterile triploid agamospermous taxon T. parnassicum.

Accurate ab initio Quartic Force Fields of Cyclic and Bent HC2N Isomers

NASA Technical Reports Server (NTRS)

Inostroza, Natalia; Huang, Xinchuan; Lee, Timothy J.

2012-01-01

Highly correlated ab initio quartic force field (QFFs) are used to calculate the equilibrium structures and predict the spectroscopic parameters of three HC2N isomers. Specifically, the ground state quasilinear triplet and the lowest cyclic and bent singlet isomers are included in the present study. Extensive treatment of correlation effects were included using the singles and doubles coupled-cluster method that includes a perturbational estimate of the effects of connected triple excitations, denoted CCSD(T). Dunning s correlation-consistent basis sets cc-pVXZ, X=3,4,5, were used, and a three-point formula for extrapolation to the one-particle basis set limit was used. Core-correlation and scalar relativistic corrections were also included to yield highly accurate QFFs. The QFFs were used together with second-order perturbation theory (with proper treatment of Fermi resonances) and variational methods to solve the nuclear Schr dinger equation. The quasilinear nature of the triplet isomer is problematic, and it is concluded that a QFF is not adequate to describe properly all of the fundamental vibrational frequencies and spectroscopic constants (though some constants not dependent on the bending motion are well reproduced by perturbation theory). On the other hand, this procedure (a QFF together with either perturbation theory or variational methods) leads to highly accurate fundamental vibrational frequencies and spectroscopic constants for the cyclic and bent singlet isomers of HC2N. All three isomers possess significant dipole moments, 3.05D, 3.06D, and 1.71D, for the quasilinear triplet, the cyclic singlet, and the bent singlet isomers, respectively. It is concluded that the spectroscopic constants determined for the cyclic and bent singlet isomers are the most accurate available, and it is hoped that these will be useful in the interpretation of high-resolution astronomical observations or laboratory experiments.

Artificial maturation of an immature sulfur- and organic matter-rich limestone from the Ghareb Formation, Jordan

USGS Publications Warehouse

Koopmans, M.P.; Rijpstra, W.I.C.; De Leeuw, J. W.; Lewan, M.D.; Damste, J.S.S.

1998-01-01

An immature (Ro=0.39%), S-rich (S(org)/C = 0.07), organic matter-rich (19.6 wt. % TOC) limestone from the Ghareb Formation (Upper Cretaceous) in Jordan was artificially matured by hydrous pyrolysis (200, 220 ..., 300??C; 72 h) to study the effect of progressive diagenesis and early catagenesis on the amounts and distributions of hydrocarbons, organic sulfur compounds and S-rich geomacromolecules. The use of internal standards allowed the determination of absolute amounts. With increasing thermal maturation, large amounts of alkanes and alkylthiophenes with predominantly linear carbon skeletons are generated from the kerogen. The alkylthiophene isomer distributions do not change significantly with increasing thermal maturation, indicating the applicability of alkylthiophenes as biomarkers at relatively high levels of thermal maturity. For a given carbon skeleton, the saturated hydrocarbon, alkylthiophenes and alkylbenzo[b]thiophenes are stable forms at relatively high temperatures, whereas the alkylsulfides are not stable. The large amount of alkylthiophenes produced relative to the alkanes may be explained by the large number of monosulfide links per carbon skeleton. These results are in good agreement with those obtained previously for an artificial maturation series of an immature S-rich sample from the Gessoso-solfifera Formation.An immature (Ro = 0.39%), S-rich (Sorg/C = 0.07), organic matter-rich (19.6 wt.% TOC) limestone from the Ghareb Formation (Upper Cretaceous) in Jordan was artificially matured by hydrous pyrolysis (200, 220, ..., 300??C; 72 h) to study the effect of progressive diagenesis and early catagenesis on the amounts and distributions of hydrocarbons, organic sulfur compounds and S-rich geomacromolecules. The use of internal standards allowed the determination of absolute amounts. With increasing thermal maturation, large amounts of alkanes and alkylthiophenes with predominantly linear carbon skeletons are generated from the kerogen. The

Determination of ortho-cresyl phosphate isomers of tricresyl phosphate used in aircraft turbine engine oils by gas chromatography and mass spectrometry.

PubMed

De Nola, G; Kibby, J; Mazurek, W

2008-07-25

Tricresyl phosphate (TCP) is used as an anti-wear additive in aircraft turbine engine oil. Concerns about its toxicity are largely based on the tri-o-cresyl phosphate isomer content. However, the presence of other and more toxic isomers has been previously suggested. In this work, the structural isomers of TCP have been determined by two methods (experimental and semi-theoretical). First, the TCP isomers were separated by gas chromatography (GC) and identified by mass spectrometry (MS). Second, after base cleavage of TCP, GC was used to quantify the cresol precursors. These results were used to calculate the TCP isomer distribution based on the assumption of a statistical distribution of the TCP isomers. The results from the two determinations showed reasonable agreement for three of the four oils studied. The o-cresyl isomers were found to be present almost exclusively as the more toxic mono-o-cresyl isomers in the concentration range 13-150 mg/L. The ability to analyse for the mono-o-cresyl isomers allows the toxicity of TCP to be based on the latter isomers rather than on the less toxic tri-o-cresyl phosphate isomer.

Isomeric discrimination of synthetic cannabinoids by GC-EI-MS: 1-adamantyl and 2-adamantyl isomers of N-adamantyl carboxamides.

PubMed

Asada, Akiko; Doi, Takahiro; Tagami, Takaomi; Takeda, Akihiro; Sawabe, Yoshiyuki

2017-03-01

N-(1-adamantyl)-1-pentyl-1H-indazole-3-carboxamide (APINACA) and N-(1-adamantyl)-1-pentyl-1H-indole-3-carboxamide (APICA) are carboxamide-type synthetic cannabinoids comprising indazole/indole-3-carboxylic acid and adamantan-1-amine moieties. However, in the case of compounds like APINACA or APICA, adamantyl positional isomers exist, wherein either adamantan-1-amine or adamantan-2-amine is present. These adamantyl positional isomers have not been reported in previous studies, and no analytical data are available. To avoid misidentification of adamantyl carboxamide-type synthetic cannabinoids, it is important to develop methods to discriminate these adamantyl positional isomers. In this study, we report the analytical characterization by gas chromatography-electron ionization-mass spectrometry (GC-EI-MS). For providing analytical standards, we synthesized eight carboxamide-type synthetic cannabinoids (APINACA 2-adamantyl isomer, APICA 2-adamantyl isomer, 5 F-APINACA 2-adamantyl isomer, 5 F-APICA 2-adamantyl isomer, 5Cl-APINACA, 5Cl-APINACA 2-adamantyl isomer, adamantyl-THPINACA, 2-adamantyl-THPINACA) and purchased four 1-adamantyl derivatives (APINACA, APICA, 5 F-APINACA, 5 F-APICA). Although the retention times of the isomers are similar, 1-adamantyl carboxamides can be clearly discriminated from their 2-adamantyl isomers based on their different fragmentation patterns in the EI-MS spectra. Specifically, EI-MS spectra for adamantylindazole carboxamides showed remarkable differences between the 1-adamantyl and 2-adamantyl isomers. On the other hand, EI-MS spectra for adamantylindole carboxamides were similar, but the diagnostic ions of the 2-adamantyl isomers were observed. The method described herein was applicable to all compounds tested in this study and is expected to be of use for isomeric differentiation between other untested adamantyl carboxamide-type synthetic cannabinoids. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley

Naturally Occurring Structural Isomers in Serum IgA1 O-Glycosylation

PubMed Central

Takahashi, Kazuo; Smith, Archer D.; Poulsen, Knud; Kilian, Mogens; Julian, Bruce A.; Mestecky, Jiri; Novak, Jan; Renfrow, Matthew B.

2013-01-01

IgA is the most abundantly produced antibody and plays an important role in the mucosal immune system. Human IgA is represented by two isotypes, IgA1 and IgA2. The major structural difference between these two subclasses is the presence of nine potential sites of O-glycosylation in the hinge region between the first and second constant region domains of the heavy chain. Thr225, Thr228, Ser230, Ser232 and Thr236 have been identified as the predominant sites of O-glycan attachment. The range and distribution of O-glycan chains at each site within the context of adjacent sites in this clustered region create a complex heterogeneity of surface epitopes that is incompletely defined. We previously described the analysis of IgA1 O-glycan heterogeneity by use of high resolution LC/MS and electron capture dissociation tandem MS to unambiguously localize all amino acid attachment sites in IgA1 (Ale) myeloma protein. Here, we report the identification and elucidation of IgA1 O-glycopeptide structural isomers that occur based on amino acid position of the attached glycans (positional isomers) and the structure of the O-glycan chains at individual sites (glycan isomers). These isomers are present in a model IgA1 (Mce1) myeloma protein and occur naturally in normal human serum IgA1. Variable O-glycan chains attached to Ser230, Thr233 or Thr236 produce the predominant positional isomers, including O-glycans composed of a single GalNAc residue. These findings represent the first definitive identification of structural isomeric IgA1 O-glycoforms, define the single-site heterogeneity for all O-glycan sites in a single sample, and have implications for defining epitopes based on clustered O-glycan variability. PMID:22067045

Isomer Profiles of Perfluorochemicals in Matched Maternal, Cord, and House Dust Samples: Manufacturing Sources and Transplacental Transfer

PubMed Central

Beesoon, Sanjay; Webster, Glenys M.; Shoeib, Mahiba; Harner, Tom; Benskin, Jonathan P.

2011-01-01

Background: Perfluorochemicals (PFCs) are detectable in the general population and in the human environment, including house dust. Sources are not well characterized, but isomer patterns should enable differentiation of historical and contemporary manufacturing sources. Isomer-specific maternal–fetal transfer of PFCs has not been examined despite known developmental toxicity of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) in rodents. Objectives: We elucidated relative contributions of electrochemical (phased out in 2001) and telomer (contemporary) PFCs in dust and measured how transplacental transfer efficiency (TTE; based on a comparison of maternal and cord sera concentrations) is affected by perfluorinated chain length and isomer branching pattern. Methods: We analyzed matching samples of house dust (n = 18), maternal sera (n = 20), and umbilical cord sera (n = 20) by isomer-specific high-performance liquid chromatography tandem mass spectrometry. Results: PFOA isomer signatures revealed that telomer sources accounted for 0–95% of total PFOA in house dust (median, 31%). This may partly explain why serum PFOA concentrations are not declining in some countries despite the phase-out of electrochemical PFOA. TTE data indicate that total branched isomers crossed the placenta more efficiently than did linear isomers for both PFOS (p < 0.01) and PFOA (p = 0.02) and that placental transfer of branched isomers of PFOS increased as the branching point moved closer to the sulfonate (SO3–) end of the molecule. Conclusions: Results suggest that humans are exposed to telomer PFOA, but larger studies that also account for dietary sources should be conducted. The exposure profile of PFOS and PFOA isomers can differ between the mother and fetus—an important consideration for perinatal epidemiology studies of PFCs. PMID:21757419

Astropulse: A Search for Microsecond Transient Radio Signals Using Distributed Computing. I. Methodology

NASA Astrophysics Data System (ADS)

Von Korff, J.; Demorest, P.; Heien, E.; Korpela, E.; Werthimer, D.; Cobb, J.; Lebofsky, M.; Anderson, D.; Bankay, B.; Siemion, A.

2013-04-01

We are performing a transient, microsecond timescale radio sky survey, called "Astropulse," using the Arecibo telescope. Astropulse searches for brief (0.4 μs to 204.8 μs ), wideband (relative to its 2.5 MHz bandwidth) radio pulses centered at 1420 MHz. Astropulse is a commensal (piggyback) survey, and scans the sky between declinations of -1.°33 and 38.°03. We obtained 1540 hr of data in each of seven beams of the ALFA receiver, with two polarizations per beam. The data are one-bit complex sampled at the Nyquist limit of 0.4 μs per sample. Examination of timescales on the order of microseconds is possible because we used coherent dedispersion, a technique that has frequently been used for targeted observations, but has never been associated with a radio sky survey. The more usual technique, incoherent dedispersion, cannot resolve signals below a minimum timescale which depends on the signal's dispersion measure (DM) and frequency. However, coherent dedispersion requires more intensive computation than incoherent dedispersion. The required processing power was provided by BOINC, the Berkeley Open Infrastructure for Network Computing. BOINC is a distributed computing system, allowing us to utilize hundreds of thousands of volunteers' computers to perform the necessary calculations for coherent dedispersion. Astrophysical events that might produce brief radio pulses include giant pulses from pulsars, rotating radio transients, exploding primordial black holes, or new sources yet to be imagined. Radio frequency interference and noise contaminate the data; these are mitigated by a number of techniques including multi-polarization correlation, DM repetition detection, and frequency profiling.

Photocatalytic production and processing of conjugated linoleic acid-rich soy oil.

PubMed

Jain, Vishal P; Proctor, Andrew

2006-07-26

Daily intake of conjugated linoleic acid (CLA), an anticarcinogenic, antiatherosclerotic, antimutagenic agent, and antioxidant, from dairy and meat products is substantially less than estimated required values. The objective of this study was to obtain CLA-rich soybean oil by a customized photochemical reaction system with an iodine catalyst and evaluate the effect of processing on iodine and iodo compounds after adsorption. After 144 h of irradiation, a total CLA yield of 24% (w/w) total oil was obtained with 0.15% (w/w) iodine. Trans,trans isomers (17.5%) formed the majority of the total yield and are also associated with health benefits. The isomers cis-9,trans-11 and trans-10,cis-12 CLA, associated with maximum health benefits, formed approximately 3.5% of the total oil. This amount is quite significant considering that total CLA obtained from dairy sources is only 0.6%. ATR-FTIR, 1H NMR, and GC-MS analyses indicated the absence of peroxide and aldehyde protons, providing evidence that secondary lipid oxidation products were not formed during the photochemical reaction. Adsorption processing vastly reduced the iodine and iodocompounds without CLA loss. Photocatalysis significantly increased the levels of CLA in soybean oil.

Glass transition dynamics and boiling temperatures of molecular liquids and their isomers.

PubMed

Wang, Li-Min; Richert, Ranko

2007-03-29

The relation between a dynamic and a thermodynamic temperature, glass transition Tg and boiling point Tb, is investigated for various glass-forming liquids, with emphasis on monohydroxy alcohols. As is well known, Tb and Tg are positively correlated across a large variety of liquids. However, we found that the same quantities show a negative correlation within an isomeric series, i.e., Tb decreases with increasing Tg for different isomers of the same chemical formula. For the alcohol series, CnH2n+1OH with 3 < or = n < or = 10, a master curve of the negative Tg - Tb correlation is obtained if the temperatures are normalized to the respective values of the n-alkanols. This Tg - Tb dependence of isomeric liquids is linked to entropic effects and responsible for much of the scatter of the correlation observed for a large number of molecular organic glass-formers with 45 < Tg < 250 K. Dielectric relaxation is measured for three groups of isomers: (a) 3-methoxyl-1-butanol and 2-iso-propoxyethanol, (b) 1,4-, 1,2-, and 2,4-pentanediol, and (c) di-n- and di-iso-butyl phthalate. Two key parameters of the dynamics, fragility m and stretching exponent beta, are found to be indistinguishable within isomers of moderately different Tgs. Larger fragility differences are readily expected with pronounced structural change, but no systematic trend is observed within an isomer series. The results provide a useful tool for assessing Tg, m, and beta for marginal glass formers on the basis of their isomers.

Application of terahertz spectroscopy and theoretical calculation in dimethylurea isomers investigation

NASA Astrophysics Data System (ADS)

Zhao, Yonghong; Li, Zhi; Liu, Jianjun; Chen, Tao; Zhang, Huo; Qin, Binyi; Wu, Yifang

2018-03-01

The characteristic absorption spectra of two structural isomers of dimethylurea(DMU) in 0.6-1.8 THz region have been measured using terahertz time-domain spectroscopy (THZ-TDS) at room temperature. Significant differences have been found between their terahertz spectra and implied that the THZ-TDS is an effective means of identifying structural isomers. To simulate their spectra, calculations on single molecule and cluster of 1,1-DMU and 1,3-DMU were performed, and we found that the cluster calculations using DFT-D3 method are better to predict the experimental spectra. Using the normal mode as displacements in redundant internal coordinates and the GaussView program, most observed THz vibrational modes are assigned to bending and rocking modes related to the intermolecular hydrogen bonding interactions, and twisting mode of ethyl groups. The different spectral features of two isomers mainly arise from different intermolecular hydrogen bonds resulting from different atom arrangements in molecules and different molecule arrangements in crystals. Using the reduced-density-gradient (RDG) analysis, the positions and types of intermolecular hydrogen bonding interactions in 1,1-DMU and 1,3-DMU crystals are visualized. Therefore, we can confirm that THz-TDS can be used as an effective means for the recognition of structural isomers and detection of intermolecular hydrogen bonding interactions in these crystals.

Differentiating Positional Isomers of Nucleoside Modifications by Higher-Energy Collisional Dissociation Mass Spectrometry (HCD MS)

NASA Astrophysics Data System (ADS)

Jora, Manasses; Burns, Andrew P.; Ross, Robert L.; Lobue, Peter A.; Zhao, Ruoxia; Palumbo, Cody M.; Beal, Peter A.; Addepalli, Balasubrahmanyam; Limbach, Patrick A.

2018-06-01

The analytical identification of positional isomers (e.g., 3-, N 4-, 5-methylcytidine) within the > 160 different post-transcriptional modifications found in RNA can be challenging. Conventional liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) approaches rely on chromatographic separation for accurate identification because the collision-induced dissociation (CID) mass spectra of these isomers nearly exclusively yield identical nucleobase ions (BH2 +) from the same molecular ion (MH+). Here, we have explored higher-energy collisional dissociation (HCD) as an alternative fragmentation technique to generate more informative product ions that can be used to differentiate positional isomers. LC-MS/MS of modified nucleosides characterized using HCD led to the creation of structure- and HCD energy-specific fragmentation patterns that generated unique fingerprints, which can be used to identify individual positional isomers even when they cannot be separated chromatographically. While particularly useful for identifying positional isomers, the fingerprinting capabilities enabled by HCD also offer the potential to generate HPLC-independent spectral libraries for the rapid analysis of modified ribonucleosides. [Figure not available: see fulltext.

Long-lived K isomer and enhanced γ vibration in the neutron-rich nucleus 172Dy: Collectivity beyond double midshell

NASA Astrophysics Data System (ADS)

Watanabe, H.; Zhang, G. X.; Yoshida, K.; Walker, P. M.; Liu, J. J.; Wu, J.; Regan, P. H.; Söderström, P.-A.; Kanaoka, H.; Korkulu, Z.; Lee, P. S.; Nishimura, S.; Yagi, A.; Ahn, D. S.; Alharbi, T.; Baba, H.; Browne, F.; Bruce, A. M.; Carroll, R. J.; Chae, K. Y.; Dombradi, Zs.; Doornenbal, P.; Estrade, A.; Fukuda, N.; Griffin, C.; Ideguchi, E.; Inabe, N.; Isobe, T.; Kanaya, S.; Kojouharov, I.; Kondev, F. G.; Kubo, T.; Kubono, S.; Kurz, N.; Kuti, I.; Lalkovski, S.; Lane, G. J.; Lee, C. S.; Lee, E. J.; Lorusso, G.; Lotay, G.; Moon, C.-B.; Nishizuka, I.; Nita, C. R.; Odahara, A.; Patel, Z.; Phong, V. H.; Podolyák, Zs.; Roberts, O. J.; Sakurai, H.; Schaffner, H.; Shand, C. M.; Shimizu, Y.; Sumikama, T.; Suzuki, H.; Takeda, H.; Terashima, S.; Vajta, Zs.; Valiente-Dóbon, J. J.; Xu, Z. Y.

2016-09-01

The level structure of 172Dy has been investigated for the first time by means of decay spectroscopy following in-flight fission of a 238U beam. A long-lived isomeric state with T1/2 = 0.71 (5) s and Kπ =8- has been identified at 1278 keV, which decays to the ground-state and γ-vibrational bands through hindered electromagnetic transitions, as well as to the daughter nucleus 172Ho via allowed β decays. The robust nature of the Kπ =8- isomer and the ground-state rotational band reveals an axially-symmetric structure for this nucleus. Meanwhile, the γ-vibrational levels have been identified at unusually low excitation energy compared to the neighboring well-deformed nuclei, indicating the significance of the microscopic effect on the non-axial collectivity in this doubly mid-shell region. The underlying mechanism of enhanced γ vibration is discussed in comparison with the deformed Quasiparticle Random-Phase Approximation based on a Skyrme energy-density functional.

Fingerprints of Both Watson-Crick and Hoogsteen Isomers of the Isolated (Cytosine-Guanine)H+ Pair.

PubMed

Cruz-Ortiz, Andrés F; Rossa, Maximiliano; Berthias, Francis; Berdakin, Matías; Maitre, Philippe; Pino, Gustavo A

2017-11-16

 Gas phase protonated guanine-cytosine (CGH + ) pair was generated using an electrospray ionization source from solutions at two different pH (5.8 and 3.2). Consistent evidence from MS/MS fragmentation patterns and differential ion mobility spectra (DIMS) point toward the presence of two isomers of the CGH + pair, whose relative populations depend strongly on the pH of the solution. Gas phase infrared multiphoton dissociation (IRMPD) spectroscopy in the 900-1900 cm -1 spectral range further confirms that the Watson-Crick isomer is preferentially produced (91%) at pH = 5.8, while the Hoogsteen isomer predominates (66%) at pH = 3.2). These fingerprint signatures are expected to be useful for the development of new analytical methodologies and to trigger isomer selective photochemical studies of protonated DNA base pairs.

Preparation, Separation, and Conformational Analysis of Differentially Sulfated Heparin Octasaccharide Isomers using Ion Mobility Mass Spectrometry

PubMed Central

Seo, Youjin; Andaya, Armann; Leary, Julie A.

2012-01-01

Heparin is a linear sulfated polysaccharide widely used in medicine because of its anticoagulant properties. The various sulfation and/or acetylation patterns on heparin impart different degrees of conformational change around the glycosidic bonds and subsequently alter its function as an anticoagulant, anticancer, or antiviral drug. Characterization of these structures is important for eventual elucidation of its function but presents itself as an analytical challenge due to the inherent heterogeneity of the carbohydrates. Heparin octasaccharide structural isomers of various sulfation patterns were investigated using ion mobility mass spectrometry (IMMS). In addition to distinguishing the isomers, we report the preparation and tandem mass spectrometry analysis for multiple sulfated or acetylated oligosaccharides. Herein, our data indicate that heparin octasaccharide isomers were separated based on their structural conformations in the ion mobility cell. Subsequent to this separation, isomers were further distinguished using product ions resulting from tandem mass spectrometry. Overall, IMMS analysis was used to successfully characterize and separate individual isomers and subsequently measure their conformations. PMID:22283665

Why Is Benzene Unique? Screening Magnetic Properties of C6 H6 Isomers.

PubMed

Janda, Tomáš; Foroutan-Nejad, Cina

2018-05-25

Magnetic properties are commonly used to identify new aromatic molecules because it is generally believed that magnetization and energetic stability are correlated. To verify the potential correlation between the energy and magnetic response properties, we examined a set of 198 isomers of C 6 H 6 . The energy and magnetic properties of these molecules can be directly compared with no need to invoke any arbitrary reference state because the studied systems are all isomers. Benzene is the global minimum on the potential energy surface of C 6 H 6 , 35 kcal mol -1 lower in energy than the second most stable isomer, fulvene. Unlike its electronic energy, isotropic magnetizability of benzene is slightly lower than the average magnetizability of its isomers. Altogether, 44 isomers of C 6 H 6 were identified to have more negative magnetic susceptibility than benzene but were between 67.0 to 168.6 kcal mol -1 higher in energy than benzene. However, benzene is unique in two ways. Analyzing the paramagnetic contribution to the magnetic susceptibility as originally suggested by Bilde and Hansen (Mol. Phys., 1997, 92, 237) revealed that 53 molecules have lower paramagnetic susceptibility than benzene but among monocyclic systems benzene has the least paramagnetic susceptibility. Furthermore, benzene has the largest out-of-plane magnetic susceptibility that originates from the strongest ring current among all studied species. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Search of the energetic gamma-ray experiment telescope (EGRET) data for high-energy gamma-ray microsecond bursts

NASA Technical Reports Server (NTRS)

Fichtel, C. E.; Bertsch, D. L.; Dingus, B. L.; Esposito, J. A.; Hartman, R. C.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.; Lin, Y. C.; Mattox, J. R.

1994-01-01

Hawking (1974) and Page & Hawking (1976) investigated theoretically the possibility of detecting high-energy gamma rays produced by the quantum-mechanical decay of a small black hole created in the early universe. They concluded that, at the very end of the life of the small black hole, it would radiate a burst of gamma rays peaked near 250 MeV with a total energy of about 10(exp 34) ergs in the order of a microsecond or less. The characteristics of a black hole are determined by laws of physics beyond the range of current particle accelerators; hence, the search for these short bursts of high-energy gamma rays provides at least the possibility of being the first test of this region of physics. The Compton Observatory Energetic Gamma-Ray Experiment Telescope (EGRET) has the capability of detecting directly the gamma rays from such bursts at a much fainter level than SAS 2, and a search of the EGRET data has led to an upper limit of 5 x 10(exp -2) black hole decays per cu pc per yr, placing constraints on this and other theories predicting microsecond high-energy gamma-ray bursts.

CIS-TRANS ISOMERS OF VITAMIN A AND RETINENE IN THE RHODOPSIN SYSTEM

PubMed Central

Hubbard, Ruth; Wald, George

1952-01-01

Vitamin A and retinene, the carotenoid precursors of rhodopsin, occur in a variety of molecular shapes, cis-trans isomers of one another. For the synthesis of rhodopsin a specific cis isomer of vitamin A is needed. Ordinary crystalline vitamin A, as also the commercial synthetic product, both primarily all-trans, are ineffective. The main site of isomer specificity is the coupling of retinene with opsin. It is this reaction that requires a specific cis isomer of retinene. The oxidation of vitamin A to retinene by the alcohol dehydrogenase-cozymase system displays only a low degree of isomer specificity. Five isomers of retinene have been isolated in crystalline condition: all-trans; three apparently mono-cis forms, neoretinenes a and b and isoretinene a; and one apparently di-cis isomer, isoretinene b. Neoretinenes a and b were first isolated in our laboratory, and isoretinenes a and b in the Organic Research Laboratory of Distillation Products Industries. Each of these substances is converted to an equilibrium mixture of stereoisomers on simple exposure to light. For this reaction, light is required which retinene can absorb; i.e., blue, violet, or ultraviolet light. Yellow, orange, or red light has little effect. The single geometrical isomers of retinene must therefore be protected from low wave length radiation if their isomerization is to be avoided. By incubation with opsin in the dark, the capacity of each of the retinene isomers to synthesize rhodopsin was examined. All-trans retinene and neoretinene a are inactive. Neoretinene b yields rhodopsin indistinguishable from that extracted from the dark-adapted retina (λmax· 500 mµ). Isoretinene a yields a similar light-sensitive pigment, isorhodopsin, the absorption spectrum of which is displaced toward shorter wave lengths (λmax· 487 mµ). Isoretinene b appears to be inactive, but isomerizes preferentially to isoretinene a, which in the presence of opsin is removed to form isorhodopsin before the

Home cooking and ingredient synergism improve lycopene isomer production in Sofrito.

PubMed

Rinaldi de Alvarenga, José Fernando; Tran, Camilla; Hurtado-Barroso, Sara; Martinez-Huélamo, Miriam; Illan, Montserrat; Lamuela-Raventos, Rosa M

2017-09-01

There has been increasing interest in tomato products rich in lycopene Z-isomers since these carotenoids present greater bioavailability and antioxidant capacity than the all-E lycopene form. Intrinsic food properties as well as processing and the interaction between dietary components can all influence the content, type and bioavailability of carotenoids. The aim of this study was to evaluate whether carotenoid content and isomerization in tomato-based Mediterranean sofrito is affected by the process of home cooking and the presence of other ingredients such as extra virgin olive oil, onion and garlic. We used a full factorial design to clarify the contribution of each ingredient to the carotenoid composition of sofrito and to determine whether this can be improved by the cooking time and ingredient synergism. Cooking time and onion content were associated with a higher production of 5-Z-lycopene, 9-Z-lycopene and 13-Z-lycopene in sofrito. Onion proved to be the most interesting ingredient in the sofrito formulation due to their enhancing effect on lycopene isomerization. The use of onion combined with an adequate processing time may improve the bioavailability of lycopene in tomato products. Copyright © 2017 Elsevier Ltd. All rights reserved.

Observation of a new high-spin isomer in {sup 94}Pd

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brock, T. S.; Nara Singh, B. S.; Wadsworth, R.

2010-12-15

A second {gamma}-decaying high-spin isomeric state, with a half-life of 197(22)ns, has been identified in the N=Z+2 nuclide {sup 94}Pd as part of a stopped-beam Rare Isotope Spectroscopic INvestigation at GSI (RISING) experiment. Weisskopf estimates were used to establish a tentative spin/parity of 19{sup -}, corresponding to the maximum possible spin of a negative parity state in the restricted (p{sub 1/2}, g{sub 9/2}) model space of empirical shell model calculations. The reproduction of the E3 decay properties of the isomer required an extension of the model space to include the f{sub 5/2} and p{sub 3/2} orbitals using the CD-Bonn potential.more » This is the first time that such an extension has been required for a high-spin isomer in the vicinity of {sup 100}Sn and reveals the importance of such orbits for understanding the decay properties of high-spin isomers in this region. However, despite the need for the extended model space for the E3 decay, the dominant configuration for the 19{sup -} state remains ({pi}p{sub 1/2}{sup -1}g{sub 9/2}{sup -3}){sub 11} x ({nu}g{sub 9/2}{sup -2}){sub 8}. The half-life of the known, 14{sup +}, isomer was remeasured and yielded a value of 499(13) ns.« less

Separation of the isomers of benzene poly(carboxylic acid)s by quaternary ammonium salt via formation of deep eutectic solvents.

PubMed

Hou, Yucui; Li, Jian; Ren, Shuhang; Niu, Muge; Wu, Weize

2014-11-26

Because of similar properties and very low volatility, isomers of benzene poly(carboxylic acid)s (BPCAs) are very difficult to separate. In this work, we found that isomers of BPCAs could be separated efficiently by quaternary ammonium salts (QASs) via formation of deep eutectic solvents (DESs). Three kinds of QASs were used to separate the isomers of BPCAs, including the isomers of benzene tricarboxylic acids (trimellitic acid, trimesic acid, and hemimellitic acid) and the isomers of benzene dicarboxylic acids (phthalic acid and isophthalic acid). Among the QASs, tetraethylammonium chloride was found to have the best performance, which could completely separate BPCA isomers in methyl ethyl ketone solutions. It was found that the hydrogen bond forming between QAS and BPCA results in the selective separation of BPCA isomers. QAS in DES was regenerated effectively by the antisolvent method, and the regenerated QAS was reused four times with the same high efficiency.

ASTROPULSE: A SEARCH FOR MICROSECOND TRANSIENT RADIO SIGNALS USING DISTRIBUTED COMPUTING. I. METHODOLOGY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Von Korff, J.; Heien, E.; Korpela, E.

We are performing a transient, microsecond timescale radio sky survey, called 'Astropulse', using the Arecibo telescope. Astropulse searches for brief (0.4 {mu}s to 204.8 {mu}s ), wideband (relative to its 2.5 MHz bandwidth) radio pulses centered at 1420 MHz. Astropulse is a commensal (piggyback) survey, and scans the sky between declinations of -1. Degree-Sign 33 and 38. Degree-Sign 03. We obtained 1540 hr of data in each of seven beams of the ALFA receiver, with two polarizations per beam. The data are one-bit complex sampled at the Nyquist limit of 0.4 {mu}s per sample. Examination of timescales on the ordermore » of microseconds is possible because we used coherent dedispersion, a technique that has frequently been used for targeted observations, but has never been associated with a radio sky survey. The more usual technique, incoherent dedispersion, cannot resolve signals below a minimum timescale which depends on the signal's dispersion measure (DM) and frequency. However, coherent dedispersion requires more intensive computation than incoherent dedispersion. The required processing power was provided by BOINC, the Berkeley Open Infrastructure for Network Computing. BOINC is a distributed computing system, allowing us to utilize hundreds of thousands of volunteers' computers to perform the necessary calculations for coherent dedispersion. Astrophysical events that might produce brief radio pulses include giant pulses from pulsars, rotating radio transients, exploding primordial black holes, or new sources yet to be imagined. Radio frequency interference and noise contaminate the data; these are mitigated by a number of techniques including multi-polarization correlation, DM repetition detection, and frequency profiling.« less

Interstellar Isomers: The Importance of Bonding Energy Differences

NASA Technical Reports Server (NTRS)

Remijan, Anthony J.; Hollis, J. M.; Lovas, F. J.; Plusquellic, D. F.; Jewell, P. R.

2005-01-01

We present strong detections of methyl cyanide (CH3CN), vinyl cyanide (CH2CHCN), ethyl cyanide (CH3CH2CN) and cyanodiacetylene (HC4CN) molecules with the Green Bank Telescope (GBT) toward the Sgr B2(N) molecular cloud. Attempts to detect the corresponding isocyanide isomers were only successful in the case of methyl isocyanide (CH3NC) for its J(sub K) = 1(sub 0) - 0(sub 0) transition, which is the first interstellar report of this line. To determine the spatial distribution of CH3NC, we used archival Berkeley-Illinois-Maryland Association (BIMA) array data for the J(sub K) = 1(sub 0) - 0(sub 0) transitions but no emission was detected. From ab initio calculations, the bonding energy difference between the cyanide and isocyanide molecules is greater than 8500 per centimeter (greater than 12,000 K). Thus, cyanides are the more stable isomers and would likely be formed more preferentially over their isocyanide counterparts. That we detect CH3NC emission with a single antenna (Gaussian beamsize(omega(sub B))=1723 arcsec(sup 2)) but not with an interferometer (omega(sub b)=192 arcsec(sup 2)), strongly suggests that CH3NC has a widespread spatial distribution toward the Sgr B2(N) region. Other investigators have shown that CH3CN is present both in the LMH hot core of Sgr B2(N) and in the surrounding medium, while we have shown that CH3NC appears to be deficient in the LMH hot core. Thus, largescale, non-thermal processes in the surrounding medium may account for the conversion of CH3CN to CH3NC while the LMH hot core, which is dominated by thermal processes, does not produce a significant amount of CH3NC. Ice analog experiments by other investigators have shown that radiation bombardment of CH3CN can produce CH3NC, thus supporting our observations. We conclude that isomers separated by such large bonding energy differences are distributed in different interstellar environments, making the evaluation of column density ratios between such isomers irrelevant unless it can

Communication: Gas-phase structural isomer identification by Coulomb explosion of aligned molecules

NASA Astrophysics Data System (ADS)

Burt, Michael; Amini, Kasra; Lee, Jason W. L.; Christiansen, Lars; Johansen, Rasmus R.; Kobayashi, Yuki; Pickering, James D.; Vallance, Claire; Brouard, Mark; Stapelfeldt, Henrik

2018-03-01

The gas-phase structures of four difluoroiodobenzene and two dihydroxybromobenzene isomers were identified by correlating the emission angles of atomic fragment ions created, following femtosecond laser-induced Coulomb explosion. The structural determinations were facilitated by confining the most polarizable axis of each molecule to the detection plane prior to the Coulomb explosion event using one-dimensional laser-induced adiabatic alignment. For a molecular target consisting of two difluoroiodobenzene isomers, each constituent structure could additionally be singled out and distinguished.

Separation of cis and trans geometric isomers by Coulomb explosion imaging

NASA Astrophysics Data System (ADS)

Ablikim, Utuq; Kaderiya, B.; Kumarapan, V.; Rudenko, A.; Rolles, D.; Bomme, C.; Savelyev, E.; Xiong, H.; Berrah, N.; Kilcoyne, D.

2016-05-01

Isomers, i.e. molecules with the same chemical formula but different chemical structure, play an important role in many biological processes. Recently, it was shown that it is possible to identify different isomers of a chiral molecule by Coulomb explosion imaging. Here, we show that by imaging the Coulomb explosion of C2 H2 Br2 molecules after inner-shell photoionization, we are able to separate a mixture of cis and trans structures using the momentum correlation between ionic fragments measured in coincidence. Furthermore, we used this capability to investigate the isomer-selective photoionization and fragmentation dynamics of C2 H2 Br2 after Br (3d) ionization. Coulomb explosion simulation results for momentum correlation as well as kinetic energies match closely the experimental results. This project is supported by the DOE, Office of Science, BES, Division of Chemical, Geological and Biological Sciences under Award Number DE-FG02-86ER13491 (U.A., B.K., V.K., A.R., D.R.) and Award Number DE-SC0012376 (H.X., N.B.).

Facial and meridional isomers of holmium-nitrate N-tert-butylacetamide complexes

NASA Astrophysics Data System (ADS)

Chang, Ye-Di; Xue, Jun-Hui; Kang, Xiao-Yan; Yang, Li-Min; Li, Wei-Hong; Xu, Yi-Zhuang; Zhao, Guo-Zhong; Zhang, Gao-Hui; Liu, Ke-Xin; Chen, Jia-Er; Wu, Jin-Guang

2018-06-01

Two Ho(C6H13NO)3(NO3)3 complexes formed by holmium nitrate and N-tert-butylacetamide (NtBA) (Ho-NtBA(I) in a Cc space group, and Ho-NtBA(II) in a P21/c space group) are reported here to investigate the coordination of lanthanide ions with amide groups. Using X-ray single crystal diffraction, FTIR, Raman, FIR and THz methods the structures of the two complexes were identified, in which Ho3+ is 9-coordinated to three carbonyl oxygen atoms provided by three NtBA ligands and three bidentate nitrate ions to form the "facial" and "meridional" isomers. Their FTIR and Raman spectra indicate the formation of two holmium complexes, the variations of NtBA after holmium coordination and the spectra are similar for the isomers in some extent. Their FIR and THz spectroscopic results show the coordination of holmium ions and THz maybe more sensitive to isomers. The results demonstrate the coordination behaviors of holmium ions and NtBA ligand.

Isomer Information from Ion Mobility Separation of High-Mannose Glycan Fragments.

PubMed

Harvey, David J; Seabright, Gemma E; Vasiljevic, Snezana; Crispin, Max; Struwe, Weston B

2018-05-01

Extracted arrival time distributions of negative ion CID-derived fragments produced prior to traveling-wave ion mobility separation were evaluated for their ability to provide structural information on N-linked glycans. Fragmentation of high-mannose glycans released from several glycoproteins, including those from viral sources, provided over 50 fragments, many of which gave unique collisional cross-sections and provided additional information used to assign structural isomers. For example, cross-ring fragments arising from cleavage of the reducing terminal GlcNAc residue on Man 8 GlcNAc 2 isomers have unique collision cross-sections enabling isomers to be differentiated in mixtures. Specific fragment collision cross-sections enabled identification of glycans, the antennae of which terminated in the antigenic α-galactose residue, and ions defining the composition of the 6-antenna of several of the glycans were also found to have different cross-sections from isomeric ions produced in the same spectra. Potential mechanisms for the formation of the various ions are discussed and the estimated collisional cross-sections are tabulated. Graphical Abstract ᅟ.

Isomer Information from Ion Mobility Separation of High-Mannose Glycan Fragments

NASA Astrophysics Data System (ADS)

Harvey, David J.; Seabright, Gemma E.; Vasiljevic, Snezana; Crispin, Max; Struwe, Weston B.

2018-05-01

Extracted arrival time distributions of negative ion CID-derived fragments produced prior to traveling-wave ion mobility separation were evaluated for their ability to provide structural information on N-linked glycans. Fragmentation of high-mannose glycans released from several glycoproteins, including those from viral sources, provided over 50 fragments, many of which gave unique collisional cross-sections and provided additional information used to assign structural isomers. For example, cross-ring fragments arising from cleavage of the reducing terminal GlcNAc residue on Man8GlcNAc2 isomers have unique collision cross-sections enabling isomers to be differentiated in mixtures. Specific fragment collision cross-sections enabled identification of glycans, the antennae of which terminated in the antigenic α-galactose residue, and ions defining the composition of the 6-antenna of several of the glycans were also found to have different cross-sections from isomeric ions produced in the same spectra. Potential mechanisms for the formation of the various ions are discussed and the estimated collisional cross-sections are tabulated. [Figure not available: see fulltext.

Differential Potency of 2,6-Dimethylcyclohexanol Isomers for Positive Modulation of GABAA Receptor Currents.

PubMed

Chowdhury, Luvana; Croft, Celine J; Goel, Shikha; Zaman, Naina; Tai, Angela C-S; Walch, Erin M; Smith, Kelly; Page, Alexandra; Shea, Kevin M; Hall, C Dennis; Jishkariani, D; Pillai, Girinath G; Hall, Adam C

2016-06-01

GABAA receptors meet all of the pharmacological requirements necessary to be considered important targets for the action of general anesthetic agents in the mammalian brain. In the following patch-clamp study, the relative modulatory effects of 2,6-dimethylcyclohexanol diastereomers were investigated on human GABAA (α1β3γ2s) receptor currents stably expressed in human embryonic kidney cells. Cis,cis-, trans,trans-, and cis,trans-isomers were isolated from commercially available 2,6-dimethylcyclohexanol and were tested for positive modulation of submaximal GABA responses. For example, the addition of 30 μM cis,cis-isomer resulted in an approximately 2- to 3-fold enhancement of the EC20 GABA current. Coapplications of 30 μM 2,6-dimethylcyclohexanol isomers produced a range of positive enhancements of control GABA responses with a rank order for positive modulation: cis,cis > trans,trans ≥ mixture of isomers > > cis,trans-isomer. In molecular modeling studies, the three cyclohexanol isomers bound with the highest binding energies to a pocket within transmembrane helices M1 and M2 of the β3 subunit through hydrogen-bonding interactions with a glutamine at the 224 position and a tyrosine at the 220 position. The energies for binding to and hydrogen-bond lengths within this pocket corresponded with the relative potencies of the agents for positive modulation of GABAA receptor currents (cis,cis > trans,trans > cis,trans-2,6-dimethylcyclohexanol). In conclusion, the stereochemical configuration within the dimethylcyclohexanols is an important molecular feature in conferring positive modulation of GABAA receptor activity and for binding to the receptor, a consideration that needs to be taken into account when designing novel anesthetics with enhanced therapeutic indices. Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.

Excitation of the 229 m Th nuclear isomer via resonance conversion in ionized atoms

NASA Astrophysics Data System (ADS)

Karpeshin, F. F.; Trzhaskovskaya, M. B.

2015-09-01

Pressing problems concerning the optical pumping of the 7.6-eV 229 m Th nuclear isomer, which is a candidate for a new nuclear optical reference point for frequencies, are examined. Physics behind the mechanism of the two-photon optical pumping of the isomer is considered. It is shown that, irrespective of the pumping scheme, a dominant contribution comes, in accord with what was proven earlier for the 3.5-eV isomer, from the resonance 8 s-7 s transition. Details of an optimum experimental scheme are discussed. It is shown that, after isomer excitation, the atom involved remains with a high probability in an excited state at an energy of about 0.5 eV rather than in the ground state, the required energy of the two photons being equal to the energy of the nuclear level plus the energy of the lowest 7 s state of the atom. The estimated pumping time is about 1.5 s in the case where the field strength of each laser is 1 V/cm.

Isomer profiles of perfluoroalkyl substances in water and soil surrounding a chinese fluorochemical manufacturing park.

PubMed

Jin, Hangbiao; Zhang, Yifeng; Zhu, Lingyan; Martin, Jonathan W

2015-04-21

Despite that China is the largest global manufacturer of perfluoroalkyl substances (PFASs), the manufacturing methods and isomer purity of these chemicals are generally unknown. Here, sampling was conducted around a major fluorochemical manufacturing park in China in 2012, including soil and water collection inside the park, including from a wastewater treatment plant (WWTP), as well as in surrounding rivers and soil (∼15 km radius). Perfluoroalkyl sulfonates (PFSAs) were lower than perfluoroalkyl carboxylates (PFCAs) in all samples, and short-chain (C4-C6) PFCAs were predominant. Perfluoroalkyl phosphonates and phosphate diesters were occasionally detected, but at low detection frequency. Branched isomers of perfluorobutanesulfonate (PFBS) are reported for the first time, accounting for 15-27% of total PFBS in water. An enrichment of isopropyl-PFOA (28%) was found in WWTP influent, suggesting its manufacturing primarily by isopropyl telomerization. More numerous branched isomers were observed for the longer C9-C13 PFCAs (e.g., C12 PFCA had 16 branched isomers), including high proportions of one major branched isomer (likely isopropyl), possibly as impurities from isopropyl-PFOA manufacturing. Overall, short-chain perfluorinated acids were the predominant PFASs being released, but PFOA was still a major chemical in use at this site, primarily from isopropyl telomerization.

Cooling rate and stress relaxation in silica melts and glasses via microsecond molecular dyanmics

DOE PAGES

Lane, J. Matthew D.

2015-07-22

We have conducted extremely long molecular dynamics simulations of glasses to microsecond times, which close the gap between experimental and atomistic simulation time scales by two to three orders of magnitude. The static, thermal, and structural properties of silica glass are reported for glass cooling rates down to 5×10 9 K/s and viscoelastic response in silica melts and glasses are studied over nine decades of time. We finally present results from relaxation of hydrostatic compressive stress in silica and show that time-temperature superposition holds in these systems for temperatures from 3500 to 1000 K.

Recording of Terahertz Pulses of Microsecond Duration Using the Thermoacoustic Effect

NASA Astrophysics Data System (ADS)

Andreev, V. G.; Vdovin, V. A.; Kalynov, Yu. K.

2014-01-01

We consider the possibility of using a thermoacoustic detector (TAD) for recording of high-power pulse radiation at frequencies of 0.55, 0.68, and 0.87 THz. Electromagnetic wave is transformed into an acoustic wave in a structure consisting of a 10-nm thick chromium film deposited on a quartz substrate and a layer of the immersion liquid that is in contact with the film. It is shown that for the pulse of microsecond duration (3-10 μs) the waveform detected by the thermoacoustic detector is matched with high accuracy to the derivative of the terahertz pulse profile. For recording of electromagnetic radiation in the 0.5-0.9 THz frequency range it is possible to employ the simplified design of TAD, in which a transparent quartz substrate is in contact with a layer of water or ethanol.

Measurement of conjugated linoleic acid (CLA) in CLA-rich soy oil by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR).

PubMed

Kadamne, Jeta V; Jain, Vishal P; Saleh, Mohammed; Proctor, Andrew

2009-11-25

Conjugated linoleic acid (CLA) isomers in oils are currently measured as fatty acid methyl esters by a gas chromatography-flame ionization detector (GC-FID) technique, which requires approximately 2 h to complete the analysis. Hence, we aim to develop a method to rapidly determine CLA isomers in CLA-rich soy oil. Soy oil with 0.38-25.11% total CLA was obtained by photo-isomerization of 96 soy oil samples for 24 h. A sample was withdrawn at 30 min intervals with repeated processing using a second batch of oil. Six replicates of GC-FID fatty acid analysis were conducted for each oil sample. The oil samples were scanned using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and the spectrum was collected. Calibration models were developed using partial least-squares (PLS-1) regression using Unscrambler software. Models were validated using a full cross-validation technique and tested using samples that were not included in the calibration sample set. Measured and predicted total CLA, trans,trans CLA isomers, total mono trans CLA isomers, trans-10,cis-12 CLA, trans-9,cis-11 CLA and cis-10,trans-12 CLA, and cis-9,trans-11 CLA had cross-validated coefficients of determinations (R2v) of 0.97, 0.98, 0.97, 0.98, 0.97, and 0.99 and corresponding root-mean-square error of validation (RMSEV) of 1.14, 0.69, 0.27, 0.07, 0.14, and 0.07% CLA, respectively. The ATR-FTIR technique is a rapid and less expensive method for determining CLA isomers in linoleic acid photo-isomerized soy oil than GC-FID.

Isolation of rotational isomers and developments derived therefrom

PubMed Central

ŌKI, Michinori

2010-01-01

Isolation of rotational isomer models of ethane-type molecules is described. We could experimentally prove that, if rotational isomers whose molecular shape was chiral, the molecule could be optically active, even though it did not carry an asymmetric carbon atom. As an extension, other types of stereochemically fundamental and optically active molecules were isolated and their absolute stereochemistry was determined. One example is the model of meso-tartaric acid, for which optical inactivity had been attributed to internal compensation but is now explained as follows. On dissolution of meso-tartaric acid in a solvent, the molecule gives two kinds of conformers, one of which is a Ci molecule and the other is a C1 molecule. Although the latter is intrinsically optically active, the optical activity is cancelled by its enantiomer. The theory of internal compensation is recommended to be abandoned. As an extension to another area, some reactions of conformers are also discussed. PMID:21084771

Stereoselective bioaccumulation of syn- and anti-Dechlorane plus isomers in different tissues of common carp (Cyprinus carpio).

PubMed

Tang, Bin; Luo, Xiao-Jun; Huang, Chen-Chen; Sun, Run-Xia; Wang, Tao; Zeng, Yan-Hong; Mai, Bi-Xian

2018-03-01

Common carps (Cyprinus carpio) were exposed to syn- and anti-Dechlorane Plus (DP) isomers to investigate absorption, tissue distribution, and stereoselective bioaccumulation of DP isomers. The absorption efficiencies of anti-DP in the gastrointestinal system were higher than those of syn-DP. A linear accumulation was found for both isomers in all fish tissues except for serum; and the liver and gill exhibited the highest and lowest DP assimilation efficiency, respectively. The elimination of DP isomers in all tissues followed first-order kinetics, with the fastest depuration rate occurring in the liver and serum. The biomagnification factors (BMFs) of both isomers were less than one in all tissues, except for serum. Anti-DP was preferably accumulated in the liver, gill, and serum, whereas syn-DP was selectively accumulated in the carcass and gastrointestinal tract. As a whole, fish did not show selective accumulation of the syn- or anti-DP isomer in the uptake stage, whereas a selective accumulation of syn-DP in fish was observed during the depuration period, which could be due to a selective excretion of anti-DP. Metabolism cannot be ruled out as a possible reason considering the high f anti values and the high elimination rate of DPs in the liver. Copyright © 2017 Elsevier B.V. All rights reserved.

Isomer profiling of perfluorinated substances as a tool for source tracking: a review of early findings and future applications.

PubMed

Benskin, Jonathan P; De Silva, Amila O; Martin, Jonathan W

2010-01-01

The two major manufacturing techniques for perfluorochemicals can be distinguished based on the isomeric profile of their products. ECF (major use from 1950s to 2002) results in a product containing both linear and branched isomers, while telomerization (major use from 2002 to present) typically yields an isomerically pure, linear product. Among the most important question today, which has implication for future regulation of these chemicals, is to what extent human and environmental exposure is from historical products (i.e., ECF) versus currently manufactured fluorochemicals (i.e., telomer). Perfluoroalkyl-chain branching can also affect the physical and chemical properties of these chemicals, which may influence their environmental transport and degradation, partitioning, bioaccumulation, pharmacokinetics, and toxicity. Unless perfluorinated substances are considered as individual isomers, much of this information will be overlooked or missed altogether, which could potentially lead to inaccuracies in human and environmental risk assessments. In this review, we have highlighted novel findings, current knowledge gaps, and areas for improvement based on early experiments on the disposition of PFA and PFA-precursor isomers in the environment. We have also emphasized the wealth of information that can potentially be gleaned from future work in this area, which renders routine adoption of isomer-specific methodologies an attractive and logical next step in the progression of fluorochemicals analysis. However, despite vast improvements in recent years, a fast and comprehensive method capable of separating all major PFA and PFA-precursor isomers, while removing interferences is still required before these methods becomes routine in most labs. Purified and characterized standards of PFOA and PFOS that have isomer profiles consistent with those of historically produced (i.e., 3M) PFOS and PFOA are also required. The limited data available on PFA isomer profiles that

Rapid In Situ Profiling of Lipid C═C Location Isomers in Tissue Using Ambient Mass Spectrometry with Photochemical Reactions.

PubMed

Tang, Fei; Guo, Chengan; Ma, Xiaoxiao; Zhang, Jian; Su, Yuan; Tian, Ran; Shi, Riyi; Xia, Yu; Wang, Xiaohao; Ouyang, Zheng

2018-05-01

Rapid and in situ profiling of lipids using ambient mass spectrometry (AMS) techniques has great potential for clinical diagnosis, biological studies, and biomarker discovery. In this study, the online photochemical reaction involving carbon-carbon double bonds was coupled with a surface sampling technique to develop a direct tissue-analysis method with specificity to lipid C═C isomers. This method enabled the in situ analysis of lipids from the surface of various tissues or tissue sections, which allowed the structural characterization of lipid isomers within 2 min. Under optimized reaction conditions, we have established a method for the relative quantitation of lipid C═C location isomers by comparing the abundances of the diagnostic ions arising from each isomer, which has been proven effective through the established linear relationship ( R 2 = 0.999) between molar ratio and diagnostic ion ratio of the FA 18:1 C═C location isomers. This method was then used for the rapid profiling of unsaturated lipid C═C isomers in the sections of rat brain, lung, liver, spleen, and kidney, as well as in normal and diseased rat tissues. Quantitative information on FA 18:1 and PC 16:0-18:1 C═C isomers was obtained, and significant differences were observed between different samples. To the best of our knowledge, this is the first study to report the direct analysis of lipid C═C isomers in tissues using AMS. Our results demonstrated that this method can serve as a rapid analytical approach for the profiling of unsaturated lipid C═C isomers in biological tissues and should contribute to functional lipidomics and clinical diagnosis.

Computational Docking of the Isomers of Nonylphenol to the Ligand Binding Domain of the Estrogen Receptor

EPA Science Inventory

Nonylphenols are environmentally persistent endocrine disrupting chemicals. They exist in the environment as complex mixtures containing many nonylphenol isomers. Environmental mixtures of nonylphenols, along with a few single isomers have been tested for their capacity to inte...

On the Relative Stability of Cumulenone and Aldehyde Isomers: when we HEAT345(Q) Things UP

NASA Astrophysics Data System (ADS)

Lee, Kelvin; McCarthy, Michael C.; Stanton, John F.

2017-06-01

Isomers of H_2C_{2n+1}O are examples of complex organic molecules that are either known or proposed to exist in the interstellar medium. For the smallest of these chains (H_2C_3O) only two of three isomers are observed in space: propynal (HC(O)CCH) and cyclopropenone (c-C_3H_2O), while evidence for the remaining isomer propadienone (H_2C_3O) is currently lacking. Potentially, this behaviour may be rationalised by a thermodynamic argument: several studies have provided quantum chemical calculations in an effort to determine the relative thermodynamic stability between these three isomers. An early study by Radom, at the SCF/6-31G** level ranked HC(O)CCH as the thermodynamic minimum, followed by H_2C_3O, and c-C_3H_2O. The most recent determination by Karton and Talbi, using W2-F12 theory, places H_2C_3O as the lowest energy isomer; 2.5 kJ mol^{-1} lower than the HC(O)CCH form. In an attempt to resolve this long-standing ambiguity, we were motivated to provide high level calculations based on the HEAT protocol. In this talk, we will discuss the relative stability of H_2C_3O and H_2C_5O isomers, along with their sulfur analogues, as revealed by HEAT345(Q) theory.

Properties of γ -decaying isomers and isomeric ratios in the 100Sn region

NASA Astrophysics Data System (ADS)

Park, J.; Krücken, R.; Lubos, D.; Gernhäuser, R.; Lewitowicz, M.; Nishimura, S.; Ahn, D. S.; Baba, H.; Blank, B.; Blazhev, A.; Boutachkov, P.; Browne, F.; Čeliković, I.; de France, G.; Doornenbal, P.; Faestermann, T.; Fang, Y.; Fukuda, N.; Giovinazzo, J.; Goel, N.; Górska, M.; Grawe, H.; Ilieva, S.; Inabe, N.; Isobe, T.; Jungclaus, A.; Kameda, D.; Kim, G. D.; Kim, Y.-K.; Kojouharov, I.; Kubo, T.; Kurz, N.; Lorusso, G.; Moschner, K.; Murai, D.; Nishizuka, I.; Patel, Z.; Rajabali, M. M.; Rice, S.; Sakurai, H.; Schaffner, H.; Shimizu, Y.; Sinclair, L.; Söderström, P.-A.; Steiger, K.; Sumikama, T.; Suzuki, H.; Takeda, H.; Wang, Z.; Watanabe, H.; Wu, J.; Xu, Z. Y.

2017-10-01

Half-lives and energies of γ rays emitted in the decay of isomeric states of nuclei in the vicinity of the doubly magic 100Sn were measured in a decay spectroscopy experiment at Rikagaku Kenkyusho (The Institute of Physical and Chemical Research) of Japan Nishina Center. The measured half-lives, some with improved precision, are consistent with literature values. Three new results include a 55-keV E 2 γ ray from a new (4+) isomer with T1 /2=0.23 (6 ) μ s in 92Rh, a 44-keV E 2 γ ray from the (15+) isomer in 96Ag, and T1 /2(6+) =13 (2 ) ns in 98Cd. Shell-model calculations of electromagnetic transition strengths in the (p1 /2,g9 /2) model space agree with the experimental results. In addition, experimental isomeric ratios were compared to the theoretical predictions derived with an abrasion-ablation model and the sharp cutoff model. The results agreed within a factor of 2 for most isomers. From the nonobservation of time-delayed γ rays in 100Sn, new constraints on the T1 /2, γ -ray energy, and internal conversion coefficients are proposed for the hypothetical isomer in 100Sn.

Fundamental Issues Related to the Origin of Melatonin and Melatonin Isomers during Evolution: Relation to Their Biological Functions

PubMed Central

Tan, Dun-Xian; Zheng, Xiaodong; Kong, Jin; Manchester, Lucien C.; Hardeland, Ruediger; Kim, Seok Joong; Xu, Xiaoying; Reiter, Russel J.

2014-01-01

Melatonin and melatonin isomers exist and/or coexist in living organisms including yeasts, bacteria and plants. The levels of melatonin isomers are significantly higher than that of melatonin in some plants and in several fermented products such as in wine and bread. Currently, there are no reports documenting the presence of melatonin isomers in vertebrates. From an evolutionary point of view, it is unlikely that melatonin isomers do not exist in vertebrates. On the other hand, large quantities of the microbial flora exist in the gut of the vertebrates. These microorganisms frequently exchange materials with the host. Melatonin isomers, which are produced by these organisms inevitably enter the host’s system. The origins of melatonin and its isomers can be traced back to photosynthetic bacteria and other primitive unicellular organisms. Since some of these bacteria are believed to be the precursors of mitochondria and chloroplasts these cellular organelles may be the primary sites of melatonin production in animals or in plants, respectively. Phylogenic analysis based on its rate-limiting synthetic enzyme, serotonin N-acetyltransferase (SNAT), indicates its multiple origins during evolution. Therefore, it is likely that melatonin and its isomer are also present in the domain of archaea, which perhaps require these molecules to protect them against hostile environments including extremely high or low temperature. Evidence indicates that the initial and primary function of melatonin and its isomers was to serve as the first-line of defence against oxidative stress and all other functions were acquired during evolution either by the process of adoption or by the extension of its antioxidative capacity. PMID:25207599

Synthesis and isolation of one isomer of C{sub 60}H{sub 6}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meier, M.S.; Weedon, B.R.; Spielmann, H.P.

1996-11-20

A reaction is reported that produces C{sub 60}H{sub 6} with essentially no contamination by adjacent oxidation states. The compound is formed as one dominant isomer and one minor isomer, and the assignment is reported of the structure of the major isomer through a comparison of its C-H coupled {sup 13}C NMR spectrum with that of 1, 2-C{sub 60}H{sub 2}. Isolation of the major C{sub 60}H{sub 6} band was accomplished by HPLC using a preparative Buckyclutcher column and an automated injector/fraction collector. Analysis of the fraction containing 1 (a cranberry-colored solution when concentrated) by Buckyclutcher and C{sub 18} HPCL in severalmore » different solvent systems has failed to produce evidence of more than one component. The typical isolated yield is 35%. 15 refs., 3 figs.« less

Identification Of Fatty Acid Isomers By Gas Chromatography / Matrix Isolation / Fourier Transform Infrared Spectroscopy

NASA Astrophysics Data System (ADS)

Mossoba, Magdi M.; McDonald, Richard E.; Chen, Jo-Yun T.; Page, Samuel W.

1989-12-01

Geometric and positional isomers of fatty acid methyl esters (FAME) derived from hydrogenated soybean oil and margarines were separated by silver nitrate-thin layer chromatography (AgNO3-TLC) followed by capillary gas chromatography (GC) and identified by matrix isolation / Fourier transform infrared (MI/FTIR) spectroscopyi,2. Because of the high specificity of the MI technique, it was possible to distinguish between different 18-carbon aliphatic chains of FAME positional isomers with cis or trans configuration, and to determine their degree of unsaturation. For the first time mid-IR spectra were observed for methylene-interrupted or isolated trans, trans or cis/ trans C18 FAME positional isomers. These spectra could be readily differentiated based on unique MI/FTIR spectral characteristics.

Comparative study for elastic electron collisions on C{sub 2}N{sub 2} isomers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michelin, S. E.; Falck, A. S.; Mazon, K. T.

2006-08-15

In this work, we present a theoretical study on elastic electron collisions with the four C{sub 2}N{sub 2} isomers. More specifically, calculated differential, integral, and momentum transfer cross sections are reported in the 1-100 eV energy range. Calculations are performed at both the static-exchange-absorption and the static-exchange-polarization-absorption levels. The iterative Schwinger variational method combined with the distorted wave approximation is used to solve the scattering equations. Our study reveals an interesting trend of the calculated cross sections for the four isomers. In particular, strong isomer effect is seen at low incident energies. Also, we have identified a shape resonance whichmore » leads to a depression in the calculated partial integral cross section.« less

Investigation of cis-trans isomer dependent dermatotoxicokinetics of UV filter ethylhexyl methoxycinnamate through stratum corneum in vivo.

PubMed

Sharma, Anežka; Bányiová, Katarína; Vrana, Branislav; Justan, Ivan; Čupr, Pavel

2017-11-01

2-Ethylhexyl methoxycinnamate (EHMC) is one of the most used ultraviolet filters in personal care products. It undergoes cis/trans isomerization in sunlight, and there is limited toxicological understanding of the effects of the cis-isomer. It is known that two geometric isomers of one compound can have different physico-chemical properties and effects. However, there are no studies focusing on toxicokinetics of EHMC isomerization products to compare their potential difference in dermal exposure to cis-EHMC and trans-EHMC due to the difference in their dermatotoxicokinetics. In this study, dermal absorption of the parental trans-EHMC and its cis isomer was studied. A commercially available sunscreen lotion containing trans-EHMC and spiked with laboratory-prepared cis-EHMC was locally applied on the forearm skin of two volunteers. After 8 h of skin exposure, the stratum corneum (SC) layer was removed by tape stripping. The removed thickness of the SC was determined spectrophotometrically using a total protein assay. The concentration of both isomers in the removed SC was measured by HPLC-DAD. A new diffusion and permeability coefficient of both EHMC isomers in SC were determined by Fick's second law of diffusion in vivo. The difference in dermatotoxicokinetic parameters between the two isomers was not statistically significant. However, separate toxicological studies of isomeric forms and the determination of their dermatotoxicokinetic parameters are crucial for refinement of human risk assessment.

Activation of Reactive MALDI Adduct Ions Enables Differentiation of Dihydroxylated Vitamin D Isomers

NASA Astrophysics Data System (ADS)

Qi, Yulin; Müller, Miriam J.; Volmer, Dietrich A.

2017-12-01

Vitamin D compounds are secosteroids, which are best known for their role in bone health. More recent studies have shown that vitamin D metabolites and catabolites such as dihydroxylated species (e.g., 1,25- and 24,25-dihydroxyvitamin D3) play key roles in the pathologies of various diseases. Identification of these isomers by mass spectrometry is challenging and currently relies on liquid chromatography, as the isomers exhibit virtually identical product ion spectra under collision induced dissociation conditions. Here, we developed a simple MALDI-CID method that utilizes ion activation of reactive analyte/matrix adducts to distinguish isomeric dihydroxyvitamin D3 species, without the need for chromatography separation or chemical derivatization techniques. Specifically, reactive 1,5-diaminonaphthalene adducts of dihydroxyvitamin D3 compounds formed during MADI were activated and specific cleavages in the secosteroid's backbone structure were achieved that produced isomer-diagnostic fragment ions. [Figure not available: see fulltext.

Occurrence of positional isomers of octadecenoic and hexadecenoic acids in human depot fat.

PubMed

Jacob, J; Grimmer, G

1967-07-01

Positional isomers of hexadecenoic aud octadecenoic acids of human adipose tissue have been separated by gas-liquid chromatography and their amounts determined by oxidative cleavage (MnO(4) and IO(4)). The following isomeric octadecenoic acids were present: 7-octadecenoic acid (0.4%), 8- (1.9%), 9- (73.0%), 10- (2.5%), 11- (19.0%) and 12- (3.2%). The hexadecenoic acids have also been shown to be a mixture of positional isomers, in which the cis-9-isomer predominates. 10-Hexadecenoic and 12-octadecenoic acids could conceivably be precursors of linoleic acid. The following branched fatty acids have also been determined in human depot fat: 13-methyltetradecanoic, 12-methyltetradecanoic, 14-methylpentadecanoic, 14-methylhexadecanoic, and 16-methylheptadecanoic acid. They were present in percentages of 0.02-0.6% and their identification rests solely on comparison of their gas-liquid chromatographic retention times with those of synthetic compounds.

Providing theoretical data for detection of four formamidic acid isomers in astrophysical media

NASA Astrophysics Data System (ADS)

Vichietti, R. M.; da Silva, A. B. F.; Haiduke, R. L. A.

2018-03-01

We present a theoretical study, so that molecular data (geometrical parameters, vibrational frequencies, infrared intensities, electronic energies, enthalpies, and Gibbs energies) of four formamidic acid (FA) isomers (labeled here as FA1, FA2, FA3, and FA4) and formamide (HCONH2) are obtained from CCSD/cc-pVTZ, CCSD/aug-cc-pVTZ, CCSD/cc-pVQZ, and CCSD(T)/cc-pVTZ calculations. Furthermore, on the basis of insufficient or even lacking theoretical and experimental results in the literature, we employed the aforementioned theory levels to determine benchmark values of dipole moments and rotational constants for these four FA isomers in order to contribute for their detection in astrophysical environments. Besides, we provide for the first time data about forward and reverse rate constants (200-4000 K) and Arrhenius' parameters for each interconversion reaction between pairs of FA isomers as well as for the tautomeric process involving FA4 and formamide, which were calculated from a Complete Basis Set (CBS) extrapolation equation obtained at CCSD/cc-pVTZ optimized geometries. Our kinetic analysis indicated a faster interconversion between the FA structures in comparison with the FA4 ↔ HCONH2 process, suggesting that these isomers could co-exist in astrophysical media. Finally, we estimated that these isomers may be detected with relative abundances, [FAx]/[HCONH2] (x = 1, 2, 3, and 4), between ∼0.01 and ∼0.1% in astrophysical sources at chemical equilibrium conditions and temperatures around 1000 K. However, these ratios can become as high as ∼1, ∼3, and ∼5%, respectively, in hotter regions with temperatures around 2000, 3000, and 4000 K (expected, for example, in massive star-forming regions).

Metabolism of a- and y-hexabromocyclododecane and enantioselective fractions of a-, ß-, y-isomers in mice

USDA-ARS?s Scientific Manuscript database

Commercial HBCD is a mixture of three major isomers, a, ß, and ', with the '-diastereoisomer predominating (>70%). Thus, the prevalence of the a-isomer as an environmental contaminant must be explained by either different pharmacokinetics, or by isomerization of the '-diastereoisomer. a- and '-[14...

Excitation of the {sup 229m}Th nuclear isomer via resonance conversion in ionized atoms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karpeshin, F. F., E-mail: fkarpeshin@gmail.com; Trzhaskovskaya, M. B.

2015-09-15

Pressing problems concerning the optical pumping of the 7.6-eV {sup 229m}Th nuclear isomer, which is a candidate for a new nuclear optical reference point for frequencies, are examined. Physics behind the mechanism of the two-photon optical pumping of the isomer is considered. It is shown that, irrespective of the pumping scheme, a dominant contribution comes, in accord with what was proven earlier for the 3.5-eV isomer, from the resonance 8s–7s transition. Details of an optimum experimental scheme are discussed. It is shown that, after isomer excitation, the atom involved remains with a high probability in an excited state at anmore » energy of about 0.5 eV rather than in the ground state, the required energy of the two photons being equal to the energy of the nuclear level plus the energy of the lowest 7s state of the atom. The estimated pumping time is about 1.5 s in the case where the field strength of each laser is 1 V/cm.« less

Discovery and identification of a series of alkyl decalin isomers in petroleum geological samples.

PubMed

Wang, Huitong; Zhang, Shuichang; Weng, Na; Zhang, Bin; Zhu, Guangyou; Liu, Lingyan

2015-07-07

The comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC × GC/TOFMS) has been used to characterize a crude oil and a source rock extract sample. During the process, a series of pairwise components between monocyclic alkanes and mono-aromatics have been discovered. After tentative assignments of decahydronaphthalene isomers, a series of alkyl decalin isomers have been synthesized and used for identification and validation of these petroleum compounds. From both the MS and chromatography information, these pairwise compounds were identified as 2-alkyl-decahydronaphthalenes and 1-alkyl-decahydronaphthalenes. The polarity of 1-alkyl-decahydronaphthalenes was stronger. Their long chain alkyl substituent groups may be due to bacterial transformation or different oil cracking events. This systematic profiling of alkyl-decahydronaphthalene isomers provides further understanding and recognition of these potential petroleum biomarkers.

Tautomeric preferences of the cis and trans isomers of axitinib

NASA Astrophysics Data System (ADS)

Mirzaei, M. Saeed; Taherpour, Avat Arman

2018-05-01

The tautomeric preferences of axitinib, a potent anticancer drug, as tyrosine kinase inhibitor have been investigated using quantum chemical calculations and docking methods. The energy differences between the two tautomers of trans-isomer are around 4 and 3 kcal mol-1 in vacuo and water, respectively, and for its cis-isomer (major photochemical isomerization product) this equilibrium reversed completely in favour of the second tautomer (not considered previously), which is about 7-8 kcal mol-1 more stable in both gas and aqueous media. The results indicate a very high activation energy for proton exchange for both [1,2] and [1,5] H-shift (around 50 kcal mol-1) in the gas phase, but inclusion of protic solvents (e.g. water) decrease this barrier to around 14 and 35 kcal mol-1 for the both hydrogen shift processes, respectively. In order to have better insight about the electronic structure of axitinib tautomers, the NBO, HOMO-LUMO, NICS and molecular electrostatic potential surfaces (MESP) calculations have been carried out. Docking investigations on the two more stable tautomers revealed that binding of the trans isomer of tautomer I to the active site of the receptor is the most favourable in the terms of energy and structure. This more stability could be attributed to the more hydrogen bonding of this tautomer with the protein residues in comparison to the second tautomer.

The interstellar chemistry of C3H and C3H2 isomers

PubMed Central

Loison, Jean-Christophe; Agúndez, Marcelino; Wakelam, Valentine; Roueff, Evelyne; Gratier, Pierre; Marcelino, Núria; Nuñez Reyes, Dianailys; Cernicharo, José; Gerin, Maryvonne

2017-01-01

We report the detection of linear and cyclic isomers of C3H and C3H2 towards various starless cores and review the corresponding chemical pathways involving neutral (C3Hx with x=1,2) and ionic (C3Hx+ with x = 1,2,3) isomers. We highlight the role of the branching ratio of electronic Dissociative Recombination (DR) reactions of C3H2+ and C3H3+ isomers showing that the statistical treatment of the relaxation of C3H* and C3H2* produced in these DR reactions may explain the relative c,l-C3H and c,l-C3H2 abundances. We have also introduced in the model the third isomer of C3H2 (HCCCH). The observed cyclic-to-linear C3H2 ratio vary from 110 ± 30 for molecular clouds with a total density around 1×104 molecules.cm-3 to 30 ± 10 for molecular clouds with a total density around 4×105 molecules.cm-3, a trend well reproduced with our updated model. The higher ratio for low molecular cloud densities is mainly determined by the importance of the H + l-C3H2 → H + c-C3H2 and H + t-C3H2 → H + c-C3H2 isomerization reactions. PMID:29142332

The interstellar chemistry of C3H and C3H2 isomers

NASA Astrophysics Data System (ADS)

Loison, Jean-Christophe; Agúndez, Marcelino; Wakelam, Valentine; Roueff, Evelyne; Gratier, Pierre; Marcelino, Núria; Reyes, Dianailys Nuñez; Cernicharo, José; Gerin, Maryvonne

2017-10-01

We report the detection of linear and cyclic isomers of C3H and C3H2 towards various starless cores and review the corresponding chemical pathways involving neutral (C3Hx with x = 1,2) and ionic (C3Hx+ with x = 1,2,3) isomers. We highlight the role of the branching ratio of electronic dissociative recombination (DR) reactions of C3H2+ and C3H3+ isomers, showing that the statistical treatment of the relaxation of C3H* and C3H2* produced in these DR reactions may explain the relative c,l-C3H and c,l-C3H2 abundances. We have also introduced in the model the third isomer of C3H2 (HCCCH). The observed cyclic-to-linear C3H2 ratio varies from 110 ± 30 for molecular clouds with a total density of about 1 × 104 molecules cm-3 to 30 ± 10 for molecular clouds with a total density of about 4 × 105 molecules cm-3, a trend well reproduced with our updated model. The higher ratio for molecular clouds with low densities is determined mainly by the importance of the H + l-C3H2 → H + c-C3H2 and H + t-C3H2 → H + c-C3H2 isomerization reactions.

Hexadecenoic fatty acid isomers: a chemical biology approach for human plasma biomarker development.

PubMed

Sansone, Anna; Melchiorre, Michele; Chatgilialoglu, Chryssostomos; Ferreri, Carla

2013-11-18

Hexadecenoic fatty acids are monounsaturated lipid components, which are interesting targets of plasma lipidomic studies and biomarker development. The main positional isomers, palmitoleic (9-cis-16:1) and sapienic acids (6-cis-16:1), have an endogenous origin from palmitic acid, the former being recognized as a component of adipose tissue with signaling activity, whereas the latter is mainly reported as a component of sebum. The trans 16:1 isomers are attributed so far to dietary sources of industrial and dairy fats, whereas the endogenous formation due to the free radical-mediated isomerization can represent an emerging, yet unexplored, pathway connected to cellular stress. Herein, we report a chemical biology approach for the development of hexadecenoic fatty acids as plasma biomarkers, with the first synthesis of 6-trans-16:1 and the efficient analytical setup with unambiguous assignment of 16:1 double bond position and geometry, which was applied to human commercial LDL and plasma cholesteryl esters. Sapienic acid was identified together with its geometrical trans isomer for the first time. The quantitation of hexadecenoic fatty acid isomers evidenced their different levels in the two lipid classes and LDL fractions, making us foresee interesting applications to the metabolic evaluation of fatty acid pathways. These findings open new perspectives for plasma lipidomics involving monounsaturated fatty acids, highlighting future developments for their evaluation in different health conditions including free radical stress.

High-spin yrast structure of 204Hg from the decay of a four-hole, 22+ isomer

NASA Astrophysics Data System (ADS)

Wrzesiński, J.; Lane, G. J.; Maier, K. H.; Janssens, R. V. F.; Dracoulis, G. D.; Broda, R.; Byrne, A. P.; Carpenter, M. P.; Clark, R. M.; Cromaz, M.; Fornal, B.; Lauritsen, T.; Macchiavelli, A. O.; Rejmund, M.; Szpak, B.; Vetter, K.; Zhu, S.

2015-10-01

A high-spin isomer with τ >700 ns has been found in 204Hg , populated in reactions of 1360-MeV 208Pb and 330-MeV 48Ca beams with a thick 238U target and a 1450-MeV 208Pb beam on a thick 208Pb target. The observed γ -ray decay of the isomer has established the yrast states below it, including another isomer with τ =33 (3 ) ns. The experimental results are compared with shell-model calculations that include four holes in the configuration space between 132Sn and 208Pb . The available spectroscopic information, including transition strengths, total conversion, and angular correlation coefficients, together with the observed agreement with the calculations, allows spin, parity, and configuration assignments to be proposed for the experimental states. The τ >700 ns isomer is the 22+ state of maximum spin available from the alignment of the four valence holes with the configuration π h11/2 -2ν i13/2 -2 .

Electron impact elastic and excitation cross-sections of the isomers of C4F6 molecule for plasma modeling

NASA Astrophysics Data System (ADS)

Gupta, Dhanoj; Song, Mi-Young; Baluja, K. L.; Choi, Heechol; Yoon, Jung-Sik

2018-06-01

We report the calculations of elastic (along with its symmetry components) and electronic excitation cross sections by electron impact of the three isomers of C4F6, namely, hexafluoro-1,3-butadiene (1,3-C4F6), hexafluoro-2-butyne (2-C4F6), and hexafluorocyclobutene (c-C4F6) belonging to the point groups C2, D3d, and C2v, respectively, using the R-matrix approach. The electron energy range is from 0.01 eV to 12 eV. We have employed the cc-pVTZ basis set for C and F atoms to generate self-consistent field molecular orbitals to construct the target states for all the isomers included in our calculations. All the target states are constructed by including correlation effects in a configuration interaction (CI) approach. The target properties such as vertical excitation energies and dipole moment of all the isomers are in reasonable agreement with the literature values. Differences in the cross sections of these isomers are strongly influenced by the effect of correlation and polarization effects and their geometrical extent. We have included the ground state and many excited states of each isomer in the trial wave function of the entire scattering system. The resulting elastic cross sections are compared with the available experimental results. The agreement is reasonably good for energies above 5 eV. The shape resonances detected at 2.57, 2.95, and 3.20 eV for c-C4F6, 1,3-C4F6, and 2-C4F6 isomers are associated with the negative anion formation of C3F3- as observed in the mass spectrometry experiments. We have also performed 1-state CI calculation for all the isomers that include only the correlated ground state. The position of resonances shifts to lower energies as the number of target states is increased compared to 1-state calculation for all the isomers. The elastic cross section for 2-C4F6 isomer is larger than the other isomers because of its larger spatial extent. The present cross section data are important for plasma simulation and modeling, especially

Temporal evolution of atmosphere pressure plasma jets driven by microsecond pulses with positive and negative polarities

NASA Astrophysics Data System (ADS)

Shao, Tao; Yang, Wenjin; Zhang, Cheng; Fang, Zhi; Zhou, Yixiao; Schamiloglu, Edl

2014-09-01

Current-voltage characteristics, discharge images, and optical spectra of atmospheric pressure plasma jets (APPJs) are studied using a microsecond pulse length generator producing repetitive output pulses with different polarities. The experimental results show that the APPJs excited by the pulses with positive polarity have longer plume, faster propagation speed, higher power, and more excited species, such as \\text{N}2 , O, He, \\text{N}2+ , than that with the negatively excited APPJs. The images taken using an intensified charge-coupled device show that the APPJs excited by pulses with positive polarity are characterized by a bullet-like structure, while the APPJs excited by pulses with negative polarity are continuous. The propagation speed of the APPJs driven by a microsecond pulse length generator is about tens of km/s, which is similar to the APPJs driven by a kHz frequency sinusoidal voltage source. The analysis shows that the space charge accumulation effect plays an important role during the discharge. The transient enhanced electric field induced by the accumulated ions between the needle-like electrode and the nozzle in the APPJs excited by pulses with negative polarity enhances electron field emission from the cathode, which is illustrated by the bright line on the time-integrated images. This makes the shape of the APPJ excited using pulses with negative polarity different from the bullet-like shape of the APPJs excited by pulses with positive polarity.

In vitro interaction study of retinoic acid isomers with telmisartan and amlodipine by equilibrium dialysis method using UV spectroscopy

NASA Astrophysics Data System (ADS)

Varghese, Susheel John; Johny, Sojimol K.; Paul, David; Ravi, Thengungal Kochupappy

2011-07-01

The in vitro protein binding of retinoic acid isomers (isotretinoin and tretinoin) and the antihypertensive drugs (amlodipine and telmisartan) was studied by equilibrium dialysis method. In this study, free fraction of drugs and the % of binding of drugs in the mixture to bovine serum albumin (BSA) were calculated. The influence of retinoic acid isomers on the % of protein binding of telmisartan and amlodipine at physiological pH (7.4) and temperature (37 ± 0.5 °C) was also evaluated. The in vitro displacement interaction study of drugs telmisartan and amlodipine on retinoic acid isomers and also interaction of retinoic acid isomers on telmisartan and amlodipine were carried out.

Visualizing the Role of Molecular Orbitals in Charge Transport through Individual Diarylethene Isomers

PubMed Central

2016-01-01

Diarylethene molecules are prototype molecular switches with their two isomeric forms exhibiting strikingly different conductance, while maintaining similar length. We employed low-temperature scanning tunneling microscopy (STM) to resolve the energy and the spatial extend of the molecular orbitals of the open and closed isomers when lying on a Au(111) surface. We find an intriguing difference in the extension of the respective HOMOs and a peculiar energy splitting of the formerly degenerate LUMO of the open isomer. We then lift the two isomers with the tip of the STM and measure the current through the individual molecules. By a simple analytical model of the transport, we show that the previously determined orbital characteristics are essential ingredients for the complete understanding of the transport properties. We also succeeded in switching the suspended molecules by the current, while switching the ones which are in direct contact to the surface occurs nonlocally with the help of the electric field of the tip. PMID:27775886

Self-Assembly of Mesoscale Isomers: The Role of Pathways and Degrees of Freedom

PubMed Central

Pandey, Shivendra; Johnson, Daniel; Kaplan, Ryan; Klobusicky, Joseph; Menon, Govind; Gracias, David H.

2014-01-01

The spontaneous self-organization of conformational isomers from identical precursors is of fundamental importance in chemistry. Since the precursors are identical, it is the multi-unit interactions, characteristics of the intermediates, and assembly pathways that determine the final conformation. Here, we use geometric path sampling and a mesoscale experimental model to investigate the self-assembly of a model polyhedral system, an octahedron, that forms two isomers. We compute the set of all possible assembly pathways and analyze the degrees of freedom or rigidity of intermediates. Consequently, by manipulating the degrees of freedom of a precursor, we were able to experimentally enrich the formation of one isomer over the other. Our results suggest a new approach to direct pathways in both natural and synthetic self-assembly using simple geometric criteria. We also compare the process of folding and unfolding in this model with a geometric model for cyclohexane, a well-known molecule with chair and boat conformations. PMID:25299051

Evidences and perspectives in the utilization of CLNA isomers as bioactive compounds in foods.

PubMed

Fontes, Ana L; Pimentel, Lígia L; Simões, Catarina D; Gomes, Ana M P; Rodríguez-Alcalá, Luís M

2017-08-13

Conjugated alpha linolenic acid (CLNA) isomers are promising lipids owing to their similarities with conjugated linoleic acid (CLA) but exerting their bioactivity at lower doses; some isomers also belong to omega 3 family. This review aims to summarize the state of the art about the utilization of CLNA as a functional ingredient. Indeed, in vitro and in vivo studies reported that CLNA exerted anticancer, anti-inflammatory, anti-obese, and antioxidant activities. However, CLNA has not been tested in humans. These compounds are naturally present in meat and milk fat from ruminants but the highest concentrations are found in vegetable oils. Their incorporation in foodstuffs is one of the most effective strategies to elaborate CLNA-enriched products together with the microbiological production. Lactobacilli, propionibacteria, and bifidobacteria strains have been assayed to produce CLNA isomers but at the current moment there are not high CLNA concentration products elaborated using these strains. Furthermore, it is known that CLNA isomers are highly prone to oxidation when compared with linoleic acid and CLA, but the possible effects of elaboration and storage on high CLNA productsare unknown.The utilization of CLNA as a functional compound still remains a challenge and requires more research to address all of its technological and bioactivity aspects.

Infrared spectroscopy of the methanol cation and its methylene-oxonium isomer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mosley, J. D.; Young, J. W.; Duncan, M. A., E-mail: mccoy@chemistry.ohio-state.edu, E-mail: maduncan@uga.edu

2015-03-21

The carbenium ion with nominal formula [C,H{sub 4},O]{sup +} is produced from methanol or ethylene glycol in a pulsed-discharge supersonic expansion source. The ion is mass selected, and its infrared spectrum is measured from 2000 to 4000 cm{sup −1} using laser photodissociation spectroscopy and the method of rare gas atom tagging. Computational chemistry predicts two isomers, the methanol and methylene-oxonium cations. Predicted vibrational spectra based on scaled harmonic and reduced dimensional treatments are compared to the experimental spectra. The methanol cation is the only isomer produced when methanol is used as a precursor. When ethylene glycol is used as themore » precursor, methylene-oxonium is produced in addition to the methanol cation. Theoretical results at the CCSD(T)/cc-pVTZ level show that methylene-oxonium is lower in energy than methanol cation by 6.4 kcal/mol, and is in fact the global minimum isomer on the [C,H{sub 4},O]{sup +} potential surface. Methanol cation is trapped behind an isomerization barrier in our source, providing a convenient method to produce and characterize this transient species. Analysis of the spectrum of the methanol cation provides evidence for strong CH stretch vibration/torsion coupling in this molecular ion.« less

High Spin Isomers and Super Heavy Elements (SHE) Synthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Popescu, Domitian G.

2010-04-30

To get closer to the SHE-Island the new radioactive beams are proposed for future fusion reaction. We suggest something different: to use the advantage of High Spin Isomer States, by tacking into account the importance of the G (spin-isospin cupling) suggested by Ripka 1.

In vitro interaction study of retinoic acid isomers with telmisartan and amlodipine by equilibrium dialysis method using UV spectroscopy.

PubMed

Varghese, Susheel John; Johny, Sojimol K; Paul, David; Ravi, Thengungal Kochupappy

2011-07-01

The in vitro protein binding of retinoic acid isomers (isotretinoin and tretinoin) and the antihypertensive drugs (amlodipine and telmisartan) was studied by equilibrium dialysis method. In this study, free fraction of drugs and the % of binding of drugs in the mixture to bovine serum albumin (BSA) were calculated. The influence of retinoic acid isomers on the % of protein binding of telmisartan and amlodipine at physiological pH (7.4) and temperature (37±0.5°C) was also evaluated. The in vitro displacement interaction study of drugs telmisartan and amlodipine on retinoic acid isomers and also interaction of retinoic acid isomers on telmisartan and amlodipine were carried out. Copyright © 2011 Elsevier B.V. All rights reserved.

Clomiphene and Its Isomers Block Ebola Virus Particle Entry and Infection with Similar Potency: Potential Therapeutic Implications

PubMed Central

Nelson, Elizabeth A.; Barnes, Alyson B.; Wiehle, Ronald D.; Fontenot, Gregory K.; Hoenen, Thomas; White, Judith M.

2016-01-01

The 2014 outbreak of Ebola virus (EBOV) in Western Africa highlighted the need for anti-EBOV therapeutics. Clomiphene is a U.S. Food and Drug Administration (FDA)-approved drug that blocks EBOV entry and infection in cells and significantly protects EBOV-challenged mice. As provided, clomiphene is, approximately, a 60:40 mixture of two stereoisomers, enclomiphene and zuclomiphene. The pharmacokinetic properties of the two isomers vary, but both accumulate in the eye and male reproductive tract, tissues in which EBOV can persist. Here we compared the ability of clomiphene and its isomers to inhibit EBOV using viral-like particle (VLP) entry and transcription/replication-competent VLP (trVLP) assays. Clomiphene and its isomers inhibited the entry and infection of VLPs and trVLPs with similar potencies. This was demonstrated with VLPs bearing the glycoproteins from three filoviruses (EBOV Mayinga, EBOV Makona, and Marburg virus) and in two cell lines (293T/17 and Vero E6). Visual problems have been noted in EBOV survivors, and viral RNA has been isolated from semen up to nine months post-infection. Since the clomiphene isomers accumulate in these affected tissues, clomiphene or one of its isomers warrants consideration as an anti-EBOV agent, for example, to potentially help ameliorate symptoms in EBOV survivors. PMID:27490565

A comparative study of the infrared and Raman spectra of aniline and o-, m-, p-phenylenediamine isomers.

PubMed

Badawi, Hassan M; Förner, Wolfgang; Ali, Shaikh A

2013-08-01

The structural stabilities of o-, m- and p-phenylenediamine (PDA) isomers were investigated by DFT-B3LYP and ab initio MP2 calculations with the 6-311G(**) basis set. From the calculations the three isomers were predicted to exist predominantly in an anti (transoid) structure. In the o-isomer, the syn (cisoid) form is calculated to turn to the anti (transoid) form with the two HNCC torsional angles of about 44 and 10° and the NH2 inversion barrier of 3-4 kcal/mol. The CCNH torsional angles in the m-PDA and p-PDA isomers were calculated to be about 25-26° as compared to 20° in aniline. A comparison of the Raman spectra of the three PDA-s with those of aniline shows the high sensitivity of the ring breathing mode to the nature of substituents in the aniline ring. The vibrational wavenumbers were computed at the DFT-B3LYP for aniline and the o-, m- and p-PDA isomers for the purpose of comparison. Complete vibrational assignments were made on the basis of normal coordinate analyses and potential energy distributions for aniline and the o-, m- and p-PDA molecules. Copyright © 2013 Elsevier B.V. All rights reserved.

Clomiphene and Its Isomers Block Ebola Virus Particle Entry and Infection with Similar Potency: Potential Therapeutic Implications.

PubMed

Nelson, Elizabeth A; Barnes, Alyson B; Wiehle, Ronald D; Fontenot, Gregory K; Hoenen, Thomas; White, Judith M

2016-08-02

The 2014 outbreak of Ebola virus (EBOV) in Western Africa highlighted the need for anti-EBOV therapeutics. Clomiphene is a U.S. Food and Drug Administration (FDA)-approved drug that blocks EBOV entry and infection in cells and significantly protects EBOV-challenged mice. As provided, clomiphene is, approximately, a 60:40 mixture of two stereoisomers, enclomiphene and zuclomiphene. The pharmacokinetic properties of the two isomers vary, but both accumulate in the eye and male reproductive tract, tissues in which EBOV can persist. Here we compared the ability of clomiphene and its isomers to inhibit EBOV using viral-like particle (VLP) entry and transcription/replication-competent VLP (trVLP) assays. Clomiphene and its isomers inhibited the entry and infection of VLPs and trVLPs with similar potencies. This was demonstrated with VLPs bearing the glycoproteins from three filoviruses (EBOV Mayinga, EBOV Makona, and Marburg virus) and in two cell lines (293T/17 and Vero E6). Visual problems have been noted in EBOV survivors, and viral RNA has been isolated from semen up to nine months post-infection. Since the clomiphene isomers accumulate in these affected tissues, clomiphene or one of its isomers warrants consideration as an anti-EBOV agent, for example, to potentially help ameliorate symptoms in EBOV survivors.

Chromatographic peak deconvolution of constitutional isomers by multiple-reaction-monitoring mass spectrometry.

PubMed

Trapp, Oliver

2010-02-12

Highly efficient and sophisticated separation techniques are available to analyze complex compound mixtures with superior sensitivities and selectivities often enhanced by a 2nd dimension, e.g. a separation technique or spectroscopic and spectrometric techniques. For enantioselective separations numerous chiral stationary phases (CSPs) exist to cover a broad range of chiral compounds. Despite these advances enantioselective separations can become very challenging for mixtures of stereolabile constitutional isomers, because the on-column interconversion can lead to completely overlapping peak profiles. Typically, multidimensional separation techniques, e.g. multidimensional GC (MDGC), using an achiral 1st separation dimension and transferring selected analytes to a chiral 2nd separation are the method of choice to approach such problems. However, this procedure is very time consuming and only predefined sections of peaks can be transferred by column switching to the second dimension. Here we demonstrate for stereolabile 1,2-dialkylated diaziridines a technique to experimentally deconvolute overlapping gas chromatographic elution profiles of constitutional isomers based on multiple-reaction-monitoring MS (MRM-MS). The here presented technique takes advantage of different fragmentation probabilities and pathways to isolate the elution profile of configurational isomers. Copyright 2009 Elsevier B.V. All rights reserved.

Ab initio correlated study of the Al13H- anion: Isomers, their kinetic stability and vertical detachment energies

NASA Astrophysics Data System (ADS)

Moc, Jerzy

2012-01-01

We report correlated ab initio calculations for the Al13H- cluster anion isomers, their kinetic stability and vertical detachment energies (VDEs). Of the two most energetically favored anion structures involving H atom in terminal and threefold bridged sites of the icosahedral Al13-, the higher energy ‘threefold bridged' isomer is shown to be of low kinetic stability. Our results are consistent with the recent photoelectron spectroscopy (PE) study of Grubisic et al. who observed two distinct Al13H- isomers, one of them identified as ‘metastable'. The VDE energies computed at the CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVDZ level for the ‘terminal' and ‘threefold bridged' Al13H- isomers of 3.21 and 2.32 eV are in good agreement with those determined in the PE study.

Microsecond Molecular Dynamics Simulations of Lipid Mixing

PubMed Central

2015-01-01

Molecular dynamics (MD) simulations of membranes are often hindered by the slow lateral diffusion of lipids and the limited time scale of MD. In order to study the dynamics of mixing and characterize the lateral distribution of lipids in converged mixtures, we report microsecond-long all-atom MD simulations performed on the special-purpose machine Anton. Two types of mixed bilayers, POPE:POPG (3:1) and POPC:cholesterol (2:1), as well as a pure POPC bilayer, were each simulated for up to 2 μs. These simulations show that POPE:POPG and POPC:cholesterol are each fully miscible at the simulated conditions, with the final states of the mixed bilayers similar to a random mixture. By simulating three POPE:POPG bilayers at different NaCl concentrations (0, 0.15, and 1 M), we also examined the effect of salt concentration on lipid mixing. While an increase in NaCl concentration is shown to affect the area per lipid, tail order, and lipid lateral diffusion, the final states of mixing remain unaltered, which is explained by the largely uniform increase in Na+ ions around POPE and POPG. Direct measurement of water permeation reveals that the POPE:POPG bilayer with 1 M NaCl has reduced water permeability compared with those at zero or low salt concentration. Our calculations provide a benchmark to estimate the convergence time scale of all-atom MD simulations of lipid mixing. Additionally, equilibrated structures of POPE:POPG and POPC:cholesterol, which are frequently used to mimic bacterial and mammalian membranes, respectively, can be used as starting points of simulations involving these membranes. PMID:25237736

Pronounced photosensitivity of molecular [Ru(bpy)2(OSO)]+ solutions based on two photoinduced linkage isomers.

PubMed

Dieckmann, Volker; Eicke, Sebastian; Rack, Jeffrey J; Woike, Theo; Imlau, Mirco

2009-08-17

Photosensitive properties of [Ru(bpy)(2)(OSO)] PF(6) dissolved in propylene carbonate originating from photoinduced linkage isomerism have been studied by temperature and exposure dependent transmission and UV/Vis absorption spectroscopy. An exceeding photochromic photosensitivity of S = (63 +/- 10) x 10(3) cm l J(-1) mol(-1) is determined. It is attributed to a maximum population of 100% molecules in the photoinduced isomers, a unique absorption cross section per molecule and a very low light exposure of Q(0) = (0.25 +/- 0.03) Ws cm(-2) for isomerism. Relaxation studies of O-bonded to S-bonded isomers at different temperatures verify the existence of two distinct structures of linkage isomers determined by the activation energies of E(A,1) = (0.76 +/- 0.08) eV and E(A,2) = (1.00 +/- 0.14) eV.

Novel synthesis and characterization of five isomers of (C(70))(2) fullerene dimers.

PubMed

Forman, Grant S; Tagmatarchis, Nikos; Shinohara, Hisanori

2002-01-16

The synthesis and characterization of dimers and polymers, wherein two or more cages are linked, represent an important frontier in the chemistry of fullerene derivatives. A simple and novel method that requires no special apparatus has been developed for the dimerization of [70]fullerene to (C70)2. Upon grinding [70]fullerene in a mortar and pestle in the presence of K2CO3, five structural isomers of (C70)2 have been produced. These isomers are separated from one another via high performance liquid chromatography and are characterized by 13C NMR, UV-vis-NIR absorption and mass spectroscopy.

Production of isotopes and isomers with irradiation of Z = 47–50 targets by 23-MeV bremsstrahlung

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karamian, S. A., E-mail: karamian@nrmail.jinr.ru; Carroll, J. J.; Aksenov, N. V.

2015-09-15

The irradiations of Ag to Sn targets by bremsstrahlung generated with 23-MeV electron beams are performed at the MT-25 microtron. Gamma spectra of the induced activities have been measured and the yields of all detected radionuclides and isomers are carefully measured and analyzed. A regular dependence of yields versus changed reaction threshold is confirmed. Many isomers are detected and the suppression of the production probability is observed with growing product spin. Special peculiarities for the isomer-to-ground state ratios were deduced for the {sup 106m}Ag, {sup 108m}Ag, {sup 113m}In, {sup 115m}In, and {sup 123m}Sn isomers. The production of such nuclides asmore » {sup 108m}Ag, {sup 115m}In, {sup 117g}In, and {sup 113m}Cd is of interest for applications, especially when economic methods are available.« less

Isomer Energy Source for Space Propulsion Systems

DTIC Science & Technology

2004-03-01

1,590 Engine F/W (no shield) 3.4 5.0 20.0 A similar core design replacing the fission fuel with the isomer 178Hfm2 is the starting point for this...particles interact and collide with other atoms in the fuel material, reactor core , or coolant, their energy can be transferred to thermal energy...thrust (44). The program produced several reactors that made it all the way through the testing stages of development . The reactors used uranium-235

Differential adsorption of CHON isomers at interstellar grain surfaces

NASA Astrophysics Data System (ADS)

Lattelais, M.; Pauzat, F.; Ellinger, Y.; Ceccarelli, C.

2015-06-01

Context. The CHON generic chemical formula covers different isomers such as isocyanic acid (HNCO), cyanic acid (HOCN), fulminic acid (HCNO), and isofulminic acid (HONC); the first three have been identified in a large variety of environments in the interstellar medium (ISM). Several phenomena could be at the origin of the observed abundances, such as different pathways of formation and destruction involving gas phase reactions with different possible activation barriers and/or surface processes depending on the local temperature and the nature of the support. Aims: The scope of this article is to shed some light on the interaction of the CHON isomers with interstellar grains as a function of the nature of the surface and to determine the corresponding adsorption energies in order to find whether this phenomenon could play a role in the abundances observed in the ISM. Methods: The question was addressed by means of numerical simulations using first principle periodic density functional theory (DFT) to represent the grain support as a solid of infinite dimension. Results: Regardless of the nature of the model surface (water ice, graphene, silica), two different classes of isomers were identified: weakly bound (HNCO and HCNO) and strongly bound (HOCN and HONC), with the adsorption energies of the latter group being about twice those of the former. The range of the adsorption energies is (from highest to lowest) HOCN > HONC > HNCO > HCNO. They are totally disconnected from the relative stabilities, which range from HNCO > HOCN > HCNO > HONC. Conclusions: The possibility of hydrogen bonding is the discriminating factor in the trapping of CHON species on grain surfaces. Whatever the environment, differential adsorption is effective and its contribution to the molecular abundances should not be ignored. The theoretical adsorption energies provided here could be profitably used for a more realistic modeling of molecule-surfaces interactions.

Anaerobic degradation of hexachlorocyclohexane isomers in liquid and soil slurry systems.

PubMed

Quintero, Juan Carlos; Moreira, Maria Teresa; Feijoo, Gumersindo; Lema, Juan M

2005-10-01

Gamma-hexachlorocyclohexane (gamma-HCH or lindane), one of the most commonly used insecticides, has been mainly used in agriculture. Organochloride compounds are known to be highly toxic and persistent, causing serious water and soil pollution. The objective of the present study is the evaluation of the anaerobic degradation of alpha-, beta-, gamma-, delta-HCH in liquid and slurry cultures. The slurry system with anaerobic sludge appears as an effective alternative in the detoxification of polluted soils with HCH, as total degradation of the four isomers was attained. While alpha- and gamma-HCH disappeared after 20-40d, the most recalcitrant isomers: beta- and delta-HCH were only degraded after 102d. Intermediate metabolites of HCH degradation as pentachlorocyclohexane (PCCH), tetrachlorocyclohexene (TCCH), tri-, di- and mono-chlorobenzenes were observed during degradation time.

Simulating the Thermal Response of High Explosives on Time Scales of Days to Microseconds

NASA Astrophysics Data System (ADS)

Yoh, Jack J.; McClelland, Matthew A.

2004-07-01

We present an overview of computational techniques for simulating the thermal cookoff of high explosives using a multi-physics hydrodynamics code, ALE3D. Recent improvements to the code have aided our computational capability in modeling the response of energetic materials systems exposed to extreme thermal environments, such as fires. We consider an idealized model process for a confined explosive involving the transition from slow heating to rapid deflagration in which the time scale changes from days to hundreds of microseconds. The heating stage involves thermal expansion and decomposition according to an Arrhenius kinetics model while a pressure-dependent burn model is employed during the explosive phase. We describe and demonstrate the numerical strategies employed to make the transition from slow to fast dynamics.

Photo-Induced depopulation of the 180mTa isomer

NASA Astrophysics Data System (ADS)

Bhike, Megha; Krishichayan, Fnu; Tornow, W.

2015-10-01

The 180mTa nucleus is the rarest isotope in the universe, existing only in an isomeric state at 77.2 keV (Jπ = 9-) with half-life of greater than 7.1 ×1015 years. The stellar production of this high-spin isomer has been a challenging astrophysical problem. Cross-section measurements for the depopulation of the 180mTa isomer with monoenergetic photon beams of energies 2.5 and 3.1 MeV have been carried out at the HI γS facility. The activated Ta foils of natural abundance and containing 14.4 mg of 180mTa were γ-ray counted at TUNL's low background facility using a 13% planar HPGe detector. A 8'' ×12'' NaI detector in combination with the standard HI γS scintillator paddle system was employed for absolute photon-flux determination. Preliminary results will be discussed, and measurements at lower energies are planned. This work was supported by the U.S. DOE under Grant NO. DE-FG02-97ER41033.

Theoretical infrared and electronic absorption spectra of C16H10 isomers, their ions and doubly ions

NASA Astrophysics Data System (ADS)

Naganathappa, Mahadevappa; Chaudhari, Ajay

2012-09-01

Polycyclic aromatic hydrocarbons (PAHs) or PAH-related molecules are considered to be responsible for the unidentified infrared (UIR) emission features at 3.3, 6.2, 7.7, 8.6 and 11.2 μm. However, the exact identification of PAH or PAH-related molecules is difficult. There have been several investigations on the spectroscopic characterization of PAH molecules. But none of them compared the spectra of isomers of PAHs, which might have help in the identification of the UIR emission features. This work presents the infrared and electronic absorption spectra of isomers of C16H10. The aim of the present work is to compare infrared and electronic absorption spectra of four isomers of C16H10 PAH viz. pyrene, aceanthrylene, acephenanthrylene and fluoranthene, their ions and doubly ions. We also compare the spectra of pyrene in the gas-phase and in H2O ice. We have used the density functional theory with B3LYP exchange and correlation functional and 6-311++g** basis set to study the infrared spectra. The time-dependent density functional theory (TDDFT) has been used to obtain the electronic absorption spectra. Significant difference in the CC stretching, CH in-plane bending and CH out-of-plane bending vibration modes is observed for the isomers of C16H10 whereas there is no large difference in the CH stretching vibration band. A significant change in the vibrational band is observed for pyrene in H2O ice compared to gas-phase pyrene. Though isomers of C16H10 PAH have the same number of carbon and hydrogen atoms, their spectroscopic characteristics are different. This study should help in identifying the isomers of C16H10, their ions and doubly cation in the interstellar medium.

Portable, Battery Operated Capillary Electrophoresis with Optical Isomer Resolution Integrated with Ionization Source for Mass Spectrometry

NASA Astrophysics Data System (ADS)

Moini, Mehdi; Rollman, Christopher M.

2016-03-01

We introduce a battery operated capillary electrophoresis electrospray ionization (CE/ESI) source for mass spectrometry with optical isomer separation capability. The source fits in front of low or high resolution mass spectrometers similar to a nanospray source with about the same weight and size. The source has two high voltage power supplies (±25 kV HVPS) capable of operating in forward or reverse polarity modes and powered by a 12 V rechargeable lithium ion battery with operation time of ~10 h. In ultrafast CE mode, in which short narrow capillaries (≤15 μm i.d., 15-25 cm long) and field gradients ≥1000 V/cm are used, peak widths at the base are <1 s wide. Under these conditions, the source provides high resolution separation, including optical isomer resolution in ~1 min. Using a low resolution mass spectrometer (LTQ Velos) with a scan time of 0.07 s/scan, baseline separation of amino acids and their optical isomers were achieved in ~1 min. Moreover, bovine serum albumin (BSA) was analyzed in ~1 min with 56% coverage using the data-dependent MS/MS. Using a high resolution mass spectrometer (Thermo Orbitrap Elite) with 15,000 resolution, the fastest scan time achieved was 0.15 s, which was adequate for CE-MS analysis when optical isomer separation is not required or when the optical isomers were well separated. Figures of merit including a detection limit of 2 fmol and linear dynamic range of two orders of magnitude were achieved for amino acids.

Varicella zoster virus DNA exists as two isomers.

PubMed Central

Ecker, J R; Hyman, R W

1982-01-01

Fragments of varicella zoster virus DNA produced by EcoRI endonuclease cleavage were cloned in vector pACYC 184 and those produced by HindIII cleavage were cloned in pBR322. Restriction enzyme cleavage maps established by double digestion and blot hybridization showed that varicella zoster virus DNA has a Mr of 80 +/- 3 x 10(6) and exists as a population of two isomers. Images PMID:6275385

Binding Energy Calculation of Patchouli Alcohol Isomer Cyclooxygenase Complexes Suggested as COX-1/COX-2 Selective Inhibitor

PubMed Central

Mahdi, Chanif; Nurdiana, Nurdiana; Kikuchi, Takheshi; Fatchiyah, Fatchiyah

2014-01-01

To understand the structural features that dictate the selectivity of the two isoforms of the prostaglandin H2 synthase (PGHS/COX), the three-dimensional (3D) structure of COX-1/COX-2 was assessed by means of binding energy calculation of virtual molecular dynamic with using ligand alpha-Patchouli alcohol isomers. Molecular interaction studies with COX-1 and COX-2 were done using the molecular docking tools by Hex 8.0. Interactions were further visualized by using Discovery Studio Client 3.5 software tool. The binding energy of molecular interaction was calculated by AMBER12 and Virtual Molecular Dynamic 1.9.1 software. The analysis of the alpha-Patchouli alcohol isomer compounds showed that all alpha-Patchouli alcohol isomers were suggested as inhibitor of COX-1 and COX-2. Collectively, the scoring binding energy calculation (with PBSA Model Solvent) of alpha-Patchouli alcohol isomer compounds (CID442384, CID6432585, CID3080622, CID10955174, and CID56928117) was suggested as candidate for a selective COX-1 inhibitor and CID521903 as nonselective COX-1/COX-2. PMID:25484897

Structure and spectroscopic properties of neutral and cationic tetratomic [C,H,N,Zn] isomers: A theoretical study

NASA Astrophysics Data System (ADS)

Redondo, Pilar; Largo, Antonio; Vega-Vega, Álvaro; Barrientos, Carmen

2015-05-01

The structure and spectroscopic parameters of the most relevant [C,H,N,Zn] isomers have been studied employing high-level quantum chemical methods. For each isomer, we provide predictions for their molecular structure, thermodynamic stabilities as well as vibrational and rotational spectroscopic parameters which could eventually help in their experimental detection. In addition, we have carried out a detailed study of the bonding situations by means of a topological analysis of the electron density in the framework of the Bader's quantum theory of atoms in molecules. The analysis of the relative stabilities and spectroscopic parameters suggests two linear isomers of the neutral [C,H,N,Zn] composition, namely, cyanidehydridezinc HZnCN (1Σ) and hydrideisocyanidezinc HZnNC (1Σ), as possible candidates for experimental detections. For the cationic [C,H,N,Zn]+ composition, the most stable isomers are the ion-molecule complexes arising from the direct interaction of the zinc cation with either the nitrogen or carbon atom of either hydrogen cyanide or hydrogen isocyanide, namely, HCNZn+ (2Σ) and HCNZn+ (2Σ).

Structural analysis of conjugated linoleic acid produced by Lactobacillus plantarum, and factors affecting isomer production.

PubMed

Kishino, Shigenobu; Ogawa, Jun; Ando, Akinori; Iwashita, Takashi; Fujita, Tsuyoshi; Kawashima, Hiroshi; Shimizu, Sakayu

2003-01-01

An isomer of the conjugated linoleic acid (CLA) produced from linoleic acid by Lactobacillus plantarum was identified as cis-9,trans-11-octadecadienoic acid by proton nuclear magnetic resonance spectroscopy. Together with earlier results, we concluded that the bacterium produces two CLA isomers, cis-9,trans-11- and trans-9,trans-11-octadecadienoic acid from linoleic acid. The addition of L-serine, glucose, AgNO3, or NaCl to the reaction mixture reduced production of the latter.

Revisiting shape selectivity in liquid chromatography for polycyclic aromatic hydrocarbons (PAHs) - six-ring and seven-ring Cata-condensed PAH isomers of molecular mass 328 Da and 378 Da.

PubMed

Oña-Ruales, Jorge O; Sander, Lane C; Wilson, Walter B; Wise, Stephen A

2018-01-01

The relationship of reversed-phase liquid chromatography (RPLC) retention on a polymeric C 18 stationary phase and the shape of polycyclic aromatic hydrocarbons (PAHs) was investigated for three-ring to seven-ring cata-condensed isomers. We report the first RPLC separation for six-ring and seven-ring cata-condensed PAH isomers. Correlations of LC retention and shape parameters (length-to-breath ratio, L/B and thickness, T) were investigated for 2 three-ring isomers (molecular mass 178 Da), 5 four-ring isomers (molecular mass 228 Da), 11 five-ring isomers (molecular mass 278 Da), 17 six-ring isomers (molecular mass 328 Da), and 20 seven-ring isomers (molecular mass 378 Da). Significant linear correlations were found for all isomer groups (r = 0.71 to 0.94). Nonplanarity of the PAH isomers was found to influence retention (i.e., nonplanar isomers eluting earlier than expected based on L/B) and linear correlations of retention vs. T for isomer groups containing nonplanar isomers were significant (r = 0.71 to 0.86). Graphical abstract.

Level Structure Above the T1/2 = 2 . 0 ×105 yr Isomer in 186Re

NASA Astrophysics Data System (ADS)

Matters, D. A.; McClory, J. W.; Kondev, F. G.; Carpenter, M. P.; Carroll, J. J.; Chiara, C. J.; Lane, G. J.; Kibédi, T.; Ideguchi, E.; Fang, Y.; Watanabe, H.; E435 Cagra Collaboration

2016-03-01

The level structure above the Kπ = (8+) , 149-keV isomer in 186Re is largely undeveloped. The isomer could play a role in the s-process nucleosynthesis of 187Os and 187Re and affect the accuracy of the Re-Os cosmochronometer. An experiment was conducted at the Research Center for Nuclear Physics (RCNP) at Osaka University, Japan, using the Clover Array Gamma-ray spectrometer at RCNP/RIBF for Advanced research (CAGRA) to measure γ-ray coincidences from (d , 2 n) reactions on an enriched 186W target. The γ - γ coincidence data obtained from the CAGRA array were analyzed along with data from a similar experiment performed in 2006 at the Australian National University. A preliminary analysis of the data reveals several new levels and transitions feeding the 186mRe isomer.

Electronic single-molecule identification of carbohydrate isomers by recognition tunnelling

NASA Astrophysics Data System (ADS)

Im, Jongone; Biswas, Sovan; Liu, Hao; Zhao, Yanan; Sen, Suman; Biswas, Sudipta; Ashcroft, Brian; Borges, Chad; Wang, Xu; Lindsay, Stuart; Zhang, Peiming

2016-12-01

Carbohydrates are one of the four main building blocks of life, and are categorized as monosaccharides (sugars), oligosaccharides and polysaccharides. Each sugar can exist in two alternative anomers (in which a hydroxy group at C-1 takes different orientations) and each pair of sugars can form different epimers (isomers around the stereocentres connecting the sugars). This leads to a vast combinatorial complexity, intractable to mass spectrometry and requiring large amounts of sample for NMR characterization. Combining measurements of collision cross section with mass spectrometry (IM-MS) helps, but many isomers are still difficult to separate. Here, we show that recognition tunnelling (RT) can classify many anomers and epimers via the current fluctuations they produce when captured in a tunnel junction functionalized with recognition molecules. Most importantly, RT is a nanoscale technique utilizing sub-picomole quantities of analyte. If integrated into a nanopore, RT would provide a unique approach to sequencing linear polysaccharides.

Structural Identification of 19 Purified Isomers of the OPV Acceptor Material bisPCBM by 13C NMR and UV-Vis Absorption Spectroscopy and High-Performance Liquid Chromatography.

PubMed

Liu, Tong; Abrahams, Isaac; Dennis, T John S

2018-04-26

The molecular structures of 19 purified isomers of bis-phenyl-C 62 -butyric acid methyl ester were identified by a combination of 13 C NMR and UV-vis absorption spectroscopies and high-performance liquid chromatography (HPLC) retention time analysis. All 19 isomers are dicyclopropafullerenes (none are homofullerenes). There were seven isomers with C 1 molecular point-group symmetry, four with C s , six with C 2 , one with C 2 v , and one with C 2 h symmetry. The C 2 h , C 2 v , and all five nonequatorial C 1 isomers were unambiguously assigned to their respective HPLC fractions. For the other 12 isomers, the 13 C NMR and UV-vis spectra placed them in six groups of two same-symmetry isomers. On the basis of the widely spaced HPLC retention times of the two isomers within each of these six groups, and the empirical inverse correlation between retention time and addend spacing, each isomer was assigned to its corresponding HPLC fraction. In addition, the missing trans-1 isomer was found, purified, and characterized.

Axial plasma jet characterization on a microsecond x-pinch

NASA Astrophysics Data System (ADS)

Jaar, G. S.; Appartaim, R. K.

2018-06-01

The jets produced on a microsecond x-pinch (quarter period T1/4 ˜ 1 μs, dI/dt ˜ 0.35 kA/ns) have been studied through light-field schlieren imaging and optical framing photographs across 4 different materials: Al, Ti, Mo, and W. The axial velocity of the jets was measured and exhibited no dependence on atomic number (Z) of the wire material. There may be a dependence on another factor(s), namely, the current rise rate. The average axial jet velocity across all four materials was measured to be 2.9 ± 0.5 × 106 cm/s. The average jet diameter and the average radial jet expansion rate displayed inverse relationships with Z, which may be attributed to radiative cooling and inertia. Asymmetry between the anode and cathode jet behavior was observed and is thought to be caused by electron beam activity. The mean divergence angle of the jet was found to vary with wire material and correlated inversely with the thermal conductivity of the cold wire. Optical images indicated a two-layer structure in Al jets which may be caused by standing shocks and resemble phenomena observed in astrophysical jet formation and collimation. Kinks in the jets have also been observed which may be caused by m = 1 MHD instability modes or by the interaction of the jet with the electrode plasma.

Sequence and Solution Effects on the Prevalence of d-Isomers Produced by Deamidation

PubMed Central

2017-01-01

Deamidation of asparagine is a spontaneous and irreversible post-translational modification associated with a growing list of human diseases. While pervasive, deamidation is often overlooked because it represents a relatively minor chemical change. Structural and functional characterization of this modification is complicated because deamidation of asparagine yields four isomeric forms of Asp. Herein, radical directed dissociation (RDD), in conjunction with mass spectrometry, is used to identify and quantify all four isomers in a series of model peptides that were subjected to various deamidation conditions. Although primary sequence significantly influences the rate of deamidation, it has little impact on the relative proportions of the product isomers. Furthermore, the addition of ammonia can be used to increase the rate of deamidation without significantly perturbing isomer populations. Conversely, external factors such as buffer conditions and temperature alter product distributions but exhibit less dramatic effects on the deamidation rate. Strikingly, the common laboratory and biologically significant bicarbonate buffer is found to strongly promote racemization, yielding increased amounts of d-Asp and d-isoAsp. These outcomes following deamidation have broad implications in human aging and should be considered during the development of protein-based therapeutics. PMID:28984444

Chemical Simulations of Prebiotic Molecules: Interstellar Ethanimine Isomers

NASA Astrophysics Data System (ADS)

Quan, Donghui; Herbst, Eric; Corby, Joanna F.; Durr, Allison; Hassel, George

2016-06-01

The E- and Z-isomers of ethanimine (CH3CHNH) were recently detected toward the star-forming region Sagittarius (Sgr) B2(N) using the Green Bank Telescope PRIMOS cm-wave spectral data, and imaged by the Australia Telescope Compact Array. Ethanimine is not reported in the hot cores of Sgr B2, but only in gas that absorbs at +64 and +82 km s-1 in the foreground of continuum emission generated by H II regions. The ethanimine isomers can serve as precursors of the amino acid alanine and may play important roles in forming biological molecules in the interstellar medium. Here we present a study of the chemistry of ethanimine using a gas-grain simulation based on rate equations, with both isothermal and warm-up conditions. In addition, the density, kinetic temperature, and cosmic ray ionization rate have been varied. For a variety of physical conditions in the warm-up models for Sgr B2(N) and environs, the simulations show reasonable agreement with observationally obtained abundances. Isothermal models of translucent clouds along the same line of sight yield much lower abundances, so that ethanimine would be much more difficult to detect in these sources despite the fact that other complex molecules have been detected there.

Isomer-specific determination of 4-nonylphenols using comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry.

PubMed

Eganhouse, Robert P; Pontolillo, James; Gaines, Richard B; Frysinger, Glenn S; Gabriel, Frédéric L P; Kohler, Hans-Peter E; Giger, Walter; Barber, Larry B

2009-12-15

Technical nonylphenol (tNP), used for industrial production of nonylphenol polyethoxylate surfactants, is a complex mixture of C(3-10)-phenols. The major components, 4-nonylphenols, are weak endocrine disruptors whose estrogenicities vary according to the structure of the branched nonyl group. Thus, accurate risk assessment requires isomer-specific determination of 4-NPs. Comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC x GC/ToFMS) was used to characterize tNP samples obtained from seven commercial suppliers. Under optimal chromatographic conditions, 153-204 alkylphenol peaks, 59-66 of which were identified as 4-NPs, were detected. The 4-NPs comprised approximately 86-94% of tNP, with 2-NPs and decylphenols making up approximately 2-9% and approximately 2-5%, respectively. The tNP products were analyzed for eight synthetic 4-NP isomers, and results were compared with published data based on GC/MS analysis. Significant differences were found among the products and between two samples from a single supplier. The enhanced resolution of GC x GC coupled with fast mass spectral data acquisition by ToFMS facilitated identification of all major 4-NP isomers and a number of previously unrecognized components. Analysis of tNP altered by the bacterium, Sphingobium xenophagum Bayram, revealed several persistent 4-NPs whose structures and estrogenicities are presently unknown. The potential of this technology for isomer-specific determination of 4-NP isomers in environmental matrices is demonstrated using samples of wastewater-contaminated groundwater and municipal wastewater.

Isomer-specific determination of 4-nonylphenols using comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry

USGS Publications Warehouse

Eganhouse, R.P.; Pontolillo, J.; Gaines, R.B.; Frysinger, G.S.; Gabriel, F.L.P.; Kohler, H.-P.E.; Giger, W.; Barber, L.B.

2009-01-01

Technical nonylphenol (tNP), used for industrial production of nonylphenol polyethoxylate surfactants, is a complex mixture of C3-10-phenols. The major components, 4-nonylphenols, are weak endocrine disruptors whose estrogenicities vary according to the structure of the branched nonyl group. Thus, accurate risk assessment requires isomer-specific determination of 4-NPs. Comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC x GC/ ToFMS) was used to characterize tNP samples obtained from seven commercial suppliers. Under optimal chromatographic conditions, 153-204 alkylphenol peaks, 59-66 of which were identified as 4-NPs, were detected. The 4-NPs comprised ???86-94% of tNP, with 2-NPs and decylphenols making up???2-9%and???2-5%, respectively. The tNP products were analyzed for eight synthetic 4-NP isomers, and results were compared with published data based on GC/ MS analysis. Significant differences were found among the products and between two samples from a single supplier. The enhanced resolution of GC x GC coupled with fast mass spectral data acquisition by ToFMS facilitated identification of all major 4-NP isomers and a number of previously unrecognized components. Analysis of tNP altered by the bacterium, Sphingobium xenophagum Bayram, revealed several persistent 4-NPs whose structures and estrogenicities are presently unknown. The potential of this technology for isomer-specific determination of 4-NP isomers in environmental matrices is demonstrated using samples of wastewatercontaminated groundwater and municipal wastewater. ?? 2009 American Chemical Society.

Electrical control of calcium oscillations in mesenchymal stem cells using microsecond pulsed electric fields.

PubMed

Hanna, Hanna; Andre, Franck M; Mir, Lluis M

2017-04-20

Human mesenchymal stem cells are promising tools for regenerative medicine due to their ability to differentiate into many cellular types such as osteocytes, chondrocytes and adipocytes amongst many other cell types. These cells present spontaneous calcium oscillations implicating calcium channels and pumps of the plasma membrane and the endoplasmic reticulum. These oscillations regulate many basic functions in the cell such as proliferation and differentiation. Therefore, the possibility to mimic or regulate these oscillations might be useful to regulate mesenchymal stem cells biological functions. One or several electric pulses of 100 μs were used to induce Ca 2+ spikes caused by the penetration of Ca 2+ from the extracellular medium, through the transiently electropermeabilized plasma membrane, in human adipose mesenchymal stem cells from several donors. Attached cells were preloaded with Fluo-4 AM and exposed to the electric pulse(s) under the fluorescence microscope. Viability was also checked. According to the pulse(s) electric field amplitude, it is possible to generate a supplementary calcium spike with properties close to those of calcium spontaneous oscillations, or, on the contrary, to inhibit the spontaneous calcium oscillations for a very long time compared to the pulse duration. Through that inhibition of the oscillations, Ca 2+ oscillations of desired amplitude and frequency could then be imposed on the cells using subsequent electric pulses. None of the pulses used here, even those with the highest amplitude, caused a loss of cell viability. An easy way to control Ca 2+ oscillations in mesenchymal stem cells, through their cancellation or the addition of supplementary Ca 2+ spikes, is reported here. Indeed, the direct link between the microsecond electric pulse(s) delivery and the occurrence/cancellation of cytosolic Ca 2+ spikes allowed us to mimic and regulate the Ca 2+ oscillations in these cells. Since microsecond electric pulse delivery

Fission and Properties of Neutron-Rich Nuclei

NASA Astrophysics Data System (ADS)

Hamilton, Joseph H.; Ramayya, A. V.; Carter, H. K.

2008-08-01

Opening session. Nuclear processes in stellar explosions / M. Wiescher. In-beam [symbol]-ray spectroscopy of neutron-rich nuclei at NSCL / A. Gade -- Nuclear structure I. Shell-model structure of neutron-rich nuclei beyond [symbol]Sn / A. Covello ... [et al.]. Shell structure and evolution of collectivity in nuclei above the [symbol]Sn core / S. Sarkar and M. S. Sarkar. Heavy-ion fusion using density-constrained TDHF / A. S. Umar and V. E. Oberacker. Towards an extended microscopic theory for upper-fp shell nuclei / K. P. Drumev. Properties of the Zr and Pb isotopes near the drip-line / V. N. Tarasov ... [et al.]. Identification of high spin states in [symbol] Cs nuclei and shell model calculations / K. Li ... [et al.]. Recent measurements of spherical and deformed isomers using the Lohengrin fission-fragment spectrometer / G. S. Simpson ... [et al.] -- Nuclear structure II. Nuclear structure investigation with rare isotope spectroscopic investigations at GSI / P. Boutachkov. Exploring the evolution of the shell structures by means of deep inelastic reactions / G. de Anaelis. Probing shell closures in neutron-rich nuclei / R. Krücken for the S277 and REX-ISOLDEMINIBALL collaborations. Structure of Fe isotopes at the limits of the pf-shell / N. Hoteling ... [et al.]. Spectroscopy of K isomers in shell-stabilized trans-fermium nuclei / S. K. Tandel ... [et al.] -- Radioactive ion beam facilities. SPIRAL2 at GANIL: a world leading ISOL facility for the next decade / S. Gales. New physics at the International Facility for Antiproton and Ion Research (FAIR) next to GSI / I. Augustin ... [et al.]. Radioactive beams from a high powered ISOL system / A. C. Shotter. RlKEN RT beam factory / T. Motobayashi. NSCL - ongoing activities and future perspectives / C. K. Gelbke. Rare isotope beams at Argonne / W. F. Henning. HRIBF: scientific highlights and future prospects / J. R. Beene. Radioactive ion beam research done in Dubna / G. M. Ter-Akopian ... [et al.] -- Fission I

CuCl2 for the isolation of a broad array of endohedral fullerenes containing metallic, metallic carbide, metallic nitride, and metallic oxide clusters, and separation of their structural isomers.

PubMed

Stevenson, Steven; Rottinger, Khristina A

2013-08-19

A typical arc-synthesis generates many types of fullerenes and endohedrals. Resulting soot extracts contain a complex mixture of >50 types of fullerenes, metallofullerenes, and their structural isomers. Prior to application development, novel separation methods are required to fractionate this rich array of metallic, metallic carbide, metallic nitride, and metallic oxide endohedrals, all of which can be present in a single, soot extract. Herein, we report the discovery of CuCl2 as a Lewis acid that will selectively precipitate only the more reactive members of each of these endohedral families. The more reactive Sc4O2@Ih-C80, Sc3C2@Ih-C80, and Sc3N@D3h-C78 endohedrals are quickly removed from extracts to greatly decrease the number of endohedrals present in a sample. Experiments indicate that enrichment factors of several orders of magnitude can be achieved within minutes of reaction time. CuCl2 also has sufficient selectivity to resolve and separate structural isomers, as demonstrated with Er2@C82 (isomer I, Cs(6)-C82 versus isomer III). The selective complexation of CuCl2 with fullerenes can be correlated to their first oxidation potential. We estimate a significantly lower threshold of precipitation for CuCl2 (<0.19 V) compared to stronger Lewis acids. Fullerenes and metallofullerenes having first oxidation potentials above 0.19 V tend to remain unreacted in solution. In contrast, species with first oxidation potentials below 0.19 V (vs Fc/Fc(+)) precipitate via complexation, and are easily decomplexed. CuCl2 is compared to Lewis acids having higher precipitation thresholds (e.g., FeCl3) in our goal to predict a priori which endohedrals would remain in solution versus which endohedral species would complex and precipitate. The ability to predict endohedral precipitation a priori is beneficial to the design of purification strategies for metallofullerenes.

SEPARATION OF ISOMERS OF NONYLPHENOL AND SELECT NONPHENYL POLYETHOXYLATES BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY ON A GRAPHITIC CARBON COLUMN

EPA Science Inventory

p-Nonylphenol (NP) is ubiquitous degradation product of nonylphenol polyethoxylate (NPE) surfactants and has been reported to be an endocrine disrupter. It is composed of numerous structural isomers resulting from ;the various branching patterns of the C-9 group. Twenty-two isome...

A combined experimental and computational thermodynamic study of difluoronitrobenzene isomers.

PubMed

Ribeiro da Silva, Manuel A V; Monte, Manuel J S; Lobo Ferreira, Ana I M C; Oliveira, Juliana A S A; Cimas, Álvaro

2010-10-14

This work reports the experimental and computational thermochemical study performed on three difluorinated nitrobenzene isomers: 2,4-difluoronitrobenzene (2,4-DFNB), 2,5-difluoronitrobenzene (2,5-DFNB), and 3,4-difluoronitrobenzene (3,4-DFNB). The standard (p° = 0.1 MPa) molar enthalpies of formation in the liquid phase of these compounds were derived from the standard molar energies of combustion, in oxygen, at T = 298.15 K, measured by rotating bomb combustion calorimetry. A static method was used to perform the vapor pressure study of the referred compounds allowing the construction of the phase diagrams and determination of the respective triple point coordinates, as well as the standard molar enthalpies of vaporization, sublimation, and fusion for two of the isomers (2,4-DFNB and 3,4-DFNB). For 2,5-difluoronitrobenzene, only liquid vapor pressures were measured enabling the determination of the standard molar enthalpies of vaporization. Combining the thermodynamic parameters of the compounds studied, the following standard (p° = 0.1 MPa) molar enthalpies of formation in the gaseous phase, at T = 298.15 K, were derived: Δ(f)H(m)° (2,4-DFNB, g) = -(296.3 ± 1.8) kJ · mol⁻¹, Δ(f)H(m)° (2,5-DFNB, g) = -(288.2 ± 2.1) kJ · mol⁻¹, and Δ(f)H(m)° (3,4-DFNB, g) = -(302.4 ± 2.1) kJ · mol⁻¹. Using the empirical scheme developed by Cox, several approaches were evaluated in order to identify the best method for estimating the standard molar gas phase enthalpies of formation of these compounds. The estimated values were compared to the ones obtained experimentally, and the approach providing the best comparison with experiment was used to estimate the thermodynamic behavior of the other difluorinated nitrobenzene isomers not included in this study. Additionally, the enthalpies of formation of these compounds along with the enthalpies of formation of the other isomers not studied experimentally, i.e., 2,3-DFNB, 2,6-DFNB, and 3,5-DFNB, were estimated

Influence of photoisomers in bilirubin determinations on Kodak Ektachem and Hitachi analysers in neonatal specimens study of the contribution of structural and configurational isomers.

PubMed

Gulian, J M; Dalmasso, C; Millet, V; Unal, D; Charrel, M

1995-08-01

We compared data obtained with the Kodak Ektachem and Hitachi 717 Analysers and HPLC from 83 neonates under phototherapy. Total bilirubin values determined with the Kodak and Hitachi are in good agreement, but we observed a large discrepancy in the results for conjugated (Kodak) and direct (Hitachi) bilirubin. HPLC revealed that all the samples contained configurational isomers, while only 7.7% and 30.8% contained conjugated bilirubin and structural isomers, respectively. We developed a device for the specific and quantitative production of configurational or structural isomers, by irradiation with blue or green light. In vitro, total bilirubin values are coherent for the routine analysers in the presence of configurational or structural isomers. With configurational isomers, unconjugated bilirubin (Kodak) is lower than total bilirubin (Kodak), and conjugated bilirubin (Kodak) is always equal to zero, so the apparatus gives a false positive response for delta bilirubin. In contrast, the direct bilirubin (Hitachi) is constant. Furthermore, in the presence of structural isomers, unconjugated bilirubin (Kodak) is unexpectedly higher than total bilirubin (Kodak), conjugated bilirubin (Kodak) is proportional to the quantity of these isomers, and direct bilirubin (Hitachi) is constant. The contribution of photoisomers in bilirubin measurements is discussed.

Topologically guided tuning of Zr-MOF pore structures for highly selective separation of C6 alkane isomers

DOE PAGES

Wang, Hao; Dong, Xinglong; Lin, Junzhong; ...

2018-05-01

As an alternative technology to energy intensive distillations, adsorptive separation by porous solids offers lower energy cost and higher efficiency. Herein we report a topology-directed design and synthesis of a series of Zr-based metal-organic frameworks with optimized pore structure for efficient separation of C6 alkane isomers, a critical step in the petroleum refining process to produce gasoline with high octane rating. Zr 6O 4(OH) 4(bptc) 3 adsorbs a large amount of n-hexane but excluding branched isomers. The n-hexane uptake is ~70% higher than that of a benchmark adsorbent, zeolite-5A. A derivative structure, Zr 6O 4(OH) 8(H 2O) 4(abtc) 2, ismore » capable of discriminating all three C6 isomers and yielding a high separation factor for 3-methylpentane over 2,3-dimethylbutane. This property is critical for producing gasoline with further improved quality. Multicomponent breakthrough experiments provide a quantitative measure of the capability of these materials for separation of C6 alkane isomers. A detailed structural analysis reveals the unique topology, connectivity and relationship of these compounds.« less

Resolving Structural Isomers of Monosaccharide Methyl Glycosides Using Drift Tube and Traveling Wave Ion Mobility Mass Spectrometry

PubMed Central

Li, Hongli; Giles, Kevin; Bendiak, Brad; Kaplan, Kimberly; Siems, William F.; Hill, Herbert H.

2013-01-01

Monosaccharide structural isomers including sixteen methyl-D-glycopyranosides and four methyl-N-acetylhexosamines were subjected to ion mobility measurements by electrospray ion mobility mass spectrometry. Two ion mobility-MS systems were employed: atmospheric pressure drift tube ion mobility time-of-flight mass spectrometry and a Synapt G2 HDMS system which incorporates a low pressure traveling wave ion mobility separator. All the compounds were investigated as [M+Na]+ ions in the positive mode. A majority of the monosaccharide structural isomers exhibited different mobility drift times in either system, depending on differences in their anomeric and stereochemical configurations. In general, drift time patterns (relative drift times of isomers) matched between the two instruments. Higher resolving power was observed using the atmospheric pressure drift tube. Collision cross section values of monosaccharide structural isomers were directly calculated from the atmospheric pressure ion mobility experiments and a collision cross section calibration curve was made for the traveling wave ion mobility instrument. Overall, it was demonstrated that ion mobility-mass spectrometry using either drift tube or traveling wave ion mobility is a valuable technique for resolving subtle variations in stereochemistry among the sodium adducts of monosaccharide methyl glycosides. PMID:22339760

Topologically guided tuning of Zr-MOF pore structures for highly selective separation of C6 alkane isomers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hao; Dong, Xinglong; Lin, Junzhong

As an alternative technology to energy intensive distillations, adsorptive separation by porous solids offers lower energy cost and higher efficiency. Herein we report a topology-directed design and synthesis of a series of Zr-based metal-organic frameworks with optimized pore structure for efficient separation of C6 alkane isomers, a critical step in the petroleum refining process to produce gasoline with high octane rating. Zr 6O 4(OH) 4(bptc) 3 adsorbs a large amount of n-hexane but excluding branched isomers. The n-hexane uptake is ~70% higher than that of a benchmark adsorbent, zeolite-5A. A derivative structure, Zr 6O 4(OH) 8(H 2O) 4(abtc) 2, ismore » capable of discriminating all three C6 isomers and yielding a high separation factor for 3-methylpentane over 2,3-dimethylbutane. This property is critical for producing gasoline with further improved quality. Multicomponent breakthrough experiments provide a quantitative measure of the capability of these materials for separation of C6 alkane isomers. A detailed structural analysis reveals the unique topology, connectivity and relationship of these compounds.« less

Dietary supplementation with long-chain monounsaturated fatty acid isomers decreases atherosclerosis and alters lipoprotein proteomes in LDLr-/- mice.

PubMed

Yang, Zhi-Hong; Gordon, Scott M; Sviridov, Denis; Wang, Shuibang; Danner, Robert L; Pryor, Milton; Vaisman, Boris; Shichijo, Yuka; Doisaki, Nobushige; Remaley, Alan T

2017-07-01

Concentrated fish oils, containing a mixture of long-chain monounsaturated fatty acids (LCMUFA) with aliphatic chains longer than 18 C atoms (i.e., C20:1 and C22:1), have been shown to attenuate atherosclerosis development in mouse models. It is not clear, however, how individual LCMUFA isomers may act on atherosclerosis. In the present study, we used saury fish oil-derived concentrates enriched in either C20:1 or C22:1 isomer fractions to investigate their individual effect on atherosclerosis and lipoprotein metabolism. LDLR-deficient (LDLr -/- ) mice were fed a Western diet supplemented with 5% (w/w) of either C20:1 or C22:1 concentrate for 12 wk. Compared to the control Western diet with no supplement, both LCMUFA isomers increased hepatic levels of LCMUFA by 2∼3-fold (p < 0.05), and decreased atherosclerotic lesion areas by more than 40% (p < 0.05), although there were no major differences in plasma lipoproteins or hepatic lipid content. Both LCMUFA isomers significantly decreased plasma CRP levels, improved Abca1-dependent cholesterol efflux capacity of apoB-depleted plasma, and enhanced Ppar transcriptional activities in HepG2 cells. LC-MS/MS proteomic analysis of lipoproteins (HDL, LDL and VLDL) revealed that both LCMUFA isomer diets resulted in similar potentially beneficial alterations in proteins involved in complement activation, blood coagulation, and lipid metabolism. Several lipoprotein proteome changes were significantly correlated with atherosclerotic plaque reduction. Dietary supplementation with the LCMUFA isomers C20:1 or C22:1 was equally effective in reducing atherosclerosis in LDLr -/- mice and this may partly occur through activation of the Ppar signaling pathways and favorable alterations in the proteome of lipoproteins. Published by Elsevier B.V.

Improved synthesis and characterization of saturated branched-chain fatty acid isomers

USDA-ARS?s Scientific Manuscript database

The development of viable technologies for producing green products from renewable fats and oils is highly desirable since such materials can serve as replacements for non-renewable and poorly biodegradable petroleum-based products. Mixtures of saturated branched-chain fatty acid isomers (sbc-FAs),...

A new formulation of Gamma Delta Tocotrienol has superior bioavailability compared to existing Tocotrienol-Rich Fraction in healthy human subjects.

PubMed

Meganathan, Puvaneswari; Jabir, Rafid Salim; Fuang, Ho Gwo; Bhoo-Pathy, Nirmala; Choudhury, Roma Basu; Taib, Nur Aishah; Nesaretnam, Kalanithi; Chik, Zamri

2015-09-01

Gamma and delta tocotrienols are isomers of Vitamin E with established potency in pre-clinical anti-cancer research. This single-dose, randomized, crossover study aimed to compare the safety and bioavailability of a new formulation of Gamma Delta Tocotrienol (GDT) in comparison with the existing Tocotrienol-rich Fraction (TRF) in terms of gamma and delta isomers in healthy volunteers. Subjects were given either two 300 mg GDT (450 mg γ-T3 and 150 mg δ-T3) capsules or four 200 mg TRF (451.2 mg γ-T3 &102.72 mg δ-T3) capsules and blood samples were taken at several time points over 24 hours. Plasma tocotrienol concentrations were determined using HPLC method. The 90% CI for gamma and delta tocotrienols for the ratio of log-transformation of GDT/TRF for Cmax and AUC0-∞ (values were anti-logged and expressed as a percentage) were beyond the bioequivalence limits (106.21-195.46, 154.11-195.93 and 52.35-99.66, 74.82-89.44 respectively). The Wilcoxon Signed Rank Test for Tmax did not show any significant difference between GDT and TRF for both isomers (p > 0.05). No adverse events were reported during the entire period of study. GDT was found not bioequivalent to TRF, in terms of AUC and Cmax. Gamma tocotrienol in GDT showed superior bioavailability whilst delta tocotrienol showed less bioavailability compared to TRF.

Nuclear States with Abnormally Large Radii (size Isomers)

NASA Astrophysics Data System (ADS)

Ogloblin, A. A.; Demyanova, A. S.; Danilov, A. N.; Belyaeva, T. L.; Goncharov, S. A.

2015-06-01

Application of the methods of measuring the radii of the short-lived excited states (Modified diffraction model MDM, Inelastic nuclear rainbow scattering method INRS, Asymptotic normalization coefficients method ANC) to the analysis of some nuclear reactions provide evidence of existing in 9Be, 11B, 12C, 13C the excited states whose radii exceed those of the corresponding ground states by ~ 30%. Two types of structure of these "size isomers" were identified: neutron halo an α-clusters.

Tuning zinc coordination architectures by benzenedicarboxylate position isomers and bis(triazole)

NASA Astrophysics Data System (ADS)

Peng, Yan-fen; Li, Ke; Zhao, Shan; Han, Shan-shan; Li, Bao-long; Li, Hai-Yan

2015-08-01

Three position isomers 1,2-, 1,3-, 1,4-benzenedicarboxylate and 1,4-bis(1,2,4-triazol-4-yl)benzene were used to assembly zinc(II) coordination polymers {[Zn2(btx)0.5(1,2-bdc)2(H2O)]·H2O}n (1), {[Zn(btx)(1,3-bdc)]·2H2O·(DMF)}n (2) and {[Zn(btx)(1,4-bdc)]·3H2O}n (3). 1 is a (3,4,4,4)-connected two-dimensional network with point symbol (42·6)(44·62)(43·62·8)(42·6·103). 2 shows a two-dimensional (4,4) network. 3 exhibits a 5-fold interpenetrated three-dimensional diamondoid network. The structural versatility shows that the structures of coordination polymers can be tuned by the position isomers ligands. The luminescence and thermal stability were investigated.

An extensive ab initio study of the structures, vibrational spectra, quadratic force fields, and relative energetics of three isomers of Cl2O2

NASA Technical Reports Server (NTRS)

Lee, Timothy J.; Rohlfing, Celeste MCM.; Rice, Julia E.

1992-01-01

Quantum mechanical computational methods are employed for an ab initio investigation of: (1) the molecular properties of the lowest isomers of the ClO dimer; and (2) predicted molecular and thermochemical properties. Techniques employed include electron correlation and particularly singles and doubles coupled-cluster (CCSD) theory with or without perturbational estimates of the effects of connected triple excitations. The isomers ClOClO and ClClO2 are found to have higher energies than the ClOOCl isomer, and the theoretical vibrational frequencies of the isomers are well correlated with experimental data. Experimental values of the heat of formation for the isomers are also compared with calculations based on an isodesmic reaction with Cl2O, H2O, and HOOH.

Lipophilicity of potent porphyrin-based antioxidants. Comparison of ortho and meta isomers of Mn(III) N-alkylpyridylporphyrins

PubMed Central

Kos, Ivan; Rebouças, Júlio S.; DeFreitas-Silva, Gilson; Salvemini, Daniela; Vujaskovic, Zeljko; Dewhirst, Mark W.; Spasojevic, Ivan; Batinic-Haberle, Ines

2009-01-01

Mn(III) N-alkylpyridylporphyrins are among the most potent known SOD mimics and catalytic peroxynitrite scavengers, and modulators of redox-based cellular transcriptional activity. In addition to their intrinsic antioxidant capacity, bioavailability plays major role in their in vivo efficacy. While of identical antioxidant capacity, lipophilic MnTnHex-2-PyP is up to 120-fold more efficient in reducing oxidative stress injuries than hydrophilic MnTE-2-PyP. Due to limitations of analytical nature, porphyrin lipophilicity has been often estimated by thin-layer chromatographic Rf parameter, instead of the standard n-octanol/water partition coefficient, POW. Herein we used a new methodological approach to finally describe the MnP lipophilicity, by the conventional log POW means, for a series of biologically active ortho and meta isomers of Mn(III) N-alkylpyridylporphyrins. Three new porphyrins (MnTnBu-3-PyP, MnTnHex-3-PyP and MnTnHep-2-PyP) were synthesized to strengthen the conclusions. The log POW was linearly related to Rf and to the number of carbons in the alkyl chain (nC) for both isomer series; the meta isomers being 10-fold more lipophilic than the analogous ortho porphyrins. Increasing the length of the alkyl chain for 1 carbon atom increases the log POW value ~ 1 log unit with both isomers. Dramatic ~4 and ~5 orders of magnitude increase in lipophilicity of ortho isomers by extending pyridyl alkyl chains from 2 (MnTE-2-PyP, log POW = −6.25) to 6 (MnTnHex-2-PyP, log POW = −2.29) and 8 carbon atoms (MnTnOct-2-PyP, log POW = −0.77) parallels the increased efficacy in several oxidative-stress injury models, particularly those of the central nervous system where transport across the blood-brain barrier is critical. Although meta isomers are only slightly less potent SOD mimics and antioxidants than their ortho analogues, their higher lipophilicity and smaller bulkiness may lead to a higher cellular uptake and overall similar effectiveness in vivo. PMID

Shell-model states with seniority ν = 3 , 5, and 7 in odd- A neutron-rich Sn isotopes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iskra, Ł. W.; Broda, R.; Janssens, R. V. F.

2016-01-01

Excited states with seniority ν=3, 5, and 7 have been investigated in odd neutron-rich Sn119,121,123,125 isotopes produced by fusion-fission of 6.9-MeV/ACa48 beams with Pb208 and U238 targets and by fission of a U238 target bombarded with 6.7-MeV/ANi64 beams. Level schemes have been established up to high spin and excitation energies in excess of 6 MeV, based on multifold gamma-ray coincidence relationships measured with the Gammasphere array. In the analysis, the presence of isomers was exploited to identify gamma rays and propose transition placements using prompt and delayed coincidence techniques. Gamma decays of the known 27/2- isomers were expanded by identifyingmore » new deexcitation paths feeding 23/2+ long-lived states and 21/2+ levels. Competing branches in the decay of 23/2- states toward two 19/2- levels were delineated as well. In Sn119, a new 23/2+ isomer was identified, while a similar 23/2+ long-lived state, proposed earlier in Sn121, has now been confirmed. In both cases, isomeric half-lives were determined with good precision. In the range of ν=3 excitations, the observed transitions linking the various states enabled one to propose with confidence spin-parity assignments for all the observed states. Above the 27/2- isomers, an elaborate structure of negative-parity levels was established reaching the (39/2-), ν=7 states, with tentative spin-parity assignments based on the observed deexcitation paths as well as on general yrast population arguments. In all the isotopes under investigation, strongly populated sequences of positive-parity (35/2+), (31/2+), and (27/2+) states were established, feeding the 23/2+ isomers via cascades of three transitions. In the Sn121,123 isotopes, these sequences also enabled the delineation of higher-lying levels, up to (43/2+) states. In Sn123, a short half-life was determined for the (35/2+) state. Shell-model calculations were carried out for all the odd Sn isotopes, from Sn129 down to Sn119, and the results

α decay of high-K isomers in 270Ds and 266Hs in a superfluid tunneling model

NASA Astrophysics Data System (ADS)

Clark, R. M.; Rudolph, D.

2018-02-01

We use the superfluid tunneling model (STM) to calculate the half-lives of ground-state α decays of even-even superheavy nuclei (SHN) with Z ≥100 . The experimental data are reproduced to accuracies comparable to other contemporary models of α decay of SHN. We apply the STM to the case of the α decaying high-K isomers identified in the decay chains of 270Ds. By accounting for the α -decay Q values, Qα, the angular momentum difference between initial and final states, L, and a reduction in the pairing gap, Δ, we are able to reproduce the observed α decay of the isomers, including the unusual competition between L ≈10 and L ≈0 α branches seen for the K isomer in 270Ds(Z =110 ) .

Surface physicochemical properties and decay of the low-lying isomer in the 229Th nucleus

NASA Astrophysics Data System (ADS)

Borisyuk, P. V.; Kurel'chuk, U. N.; Vasil'ev, O. S.; Troyan, V. I.; Lebedinskii, Yu Yu; Tkalya, E. V.

2018-05-01

The effect of the 229Th nucleus proximity to the CsI surface on the decay probability of its anomalously low lying isomeric level is studied. Results of experimental and theoretical studies show that the CsI surface does not produce chemical bonding with Th and does not noticeably change its valence shells. Hence, it is an optimal substrate for measuring the probability of the 229Th isomer state decay via internal electron conversion. The half-life of the 229Thm isomer in the thorium atom is calculated for neutral chemical environment.

Translesion synthesis across the (6-4) photoproduct and its Dewar valence isomer by the Y-family and engineered DNA polymerases.

PubMed

Yamamoto, Junpei; Loakes, David; Masutani, Chikahide; Simmyo, Shizu; Urabe, Kumiko; Hanaoka, Fumio; Holliger, Philipp; Iwai, Shigenori

2008-01-01

We analyzed the translesion synthesis across the UV-induced lesions, the (6-4) photoproduct and its Dewar valence isomer, by using human DNA polymerases eta and iota in vitro. The primer extension experiments revealed that pol eta tended to incorporate dG opposite the 3' component of both lesions, but the incorporation efficiency for the Dewar isomer was higher than that for the (6-4) photoproduct. On the other hand, pol iota was likely to incorporate dA opposite the 3' components of the (6-4) photoproduct and its Dewar isomer with a similar efficiency. Elongation after the incorporation opposite the UV lesions was not observed for these Y-family polymerases. We further analyzed the bypass ability of an engineered polymerase developed from Thermus DNA polymerase for the amplification of ancient DNA. This polymerase could bypass the Dewar isomer more efficiently than the (6-4) photoproduct.

Comparative study of hypocholesterolemic and hypolipidemic effects of conjugated linolenic acid isomers against induced biochemical perturbations and aberration in erythrocyte membrane fluidity.

PubMed

Saha, Siddhartha S; Chakraborty, Anirban; Ghosh, Santinath; Ghosh, Mahua

2012-06-01

The purpose of the study was to evaluate hypolipidemic and hypocholesterolemic activities of conjugated linolenic acid (CLnA) isomers, present in bitter gourd and snake gourd seed, in terms of amelioration of plasma lipid profile, lipoprotein oxidation and erythrocyte membrane fluidity after oral administration. Male albino rats were divided into six groups. Group 1 was control, and others were induced with oxidative stress by oral gavage of sodium arsenite (Sa). Group 2 was kept as treated control, and groups 3-6 were further treated with different oral doses of seed oils to maintaining definite concentration of CLnA isomers (0.5 and 1.0% of total lipid for each CLnA isomer). CLnA isomers normalized cholesterol, LDL-cholesterol, HDL-cholesterol and triglyceride contents in plasma and body weight of experimental rats and decreased cholesterol synthesis by reducing hepatic HMG-CoA reductase activity. Administration of Sa caused alteration in erythrocyte membrane fluidity due to increase in cholesterol and decrease in phospholipid content. Tissue cholesterol and lipid contents were also increased by Sa administration. These altered parameters were reversed by experimental oil administration. Protective effect of CLnA isomers on erythrocyte morphology was observed by atomic force microscopy (AFM). Fatty acid composition of erythrocyte membrane showed decrease in polyunsaturated fatty acid (PUFA) and increase in arachidonic acid content after Sa administration, which was normalized with the treatment of these oils. Supplementation of CLnA isomers restored erythrocyte membrane (EM) lipid peroxidation and lipoprotein oxidation. CLnA isomers, present in vegetable oils, showed potent hypolipidemic and hypocholesterolemic activities against biochemical perturbations.

Role of chirality in peptide-induced formation of cholesterol-rich domains

PubMed Central

2005-01-01

The chiral specificity of the interactions of peptides that induce the formation of cholesterol-rich domains has not been extensively investigated. Both the peptide and most lipids are chiral, so there is a possibility that interactions between peptide and lipid could require chiral recognition. On the other hand, in our models with small peptides, the extent of folding of the peptide to form a specific binding pocket is limited. We have determined that replacing cholesterol with its enantiomer, ent-cholesterol, alters the modulation of lipid organization by peptides. The phase-transition properties of SOPC (1-stearoyl-2-oleoylphosphatidylcholine):cholesterol [in a 6:4 ratio with 0.2 mol% PtdIns(4,5)P2] are not significantly altered when ent-cholesterol replaces cholesterol. However, in the presence of 10 mol% of a 19-amino-acid, N-terminally myristoylated fragment (myristoyl-GGKLSKKKKGYNVNDEKAK-amide) of the protein NAP-22 (neuronal axonal membrane protein), the lipid mixture containing cholesterol undergoes separation into cholesterol-rich and cholesterol-depleted domains. This does not occur when ent-cholesterol replaces cholesterol. In another example, when N-acetyl-Leu-Trp-Tyr-Ile-Lys-amide (N-acetyl-LWYIK-amide) is added to SOPC:cholesterol (7:3 ratio), there is a marked increase in the transition enthalpy of the phospholipid, indicating separation of a cholesterol-depleted domain of SOPC. This phenomenon completely disappears when ent-cholesterol replaces cholesterol. The all-D-isomer of N-acetyl-LWYIK-amide also induces the formation of cholesterol-rich domains with natural cholesterol, but does so to a lesser extent with ent-cholesterol. Thus specific peptide chirality is not required for interaction with cholesterol-containing membranes. However, a specific chirality of membrane lipids is required for peptide-induced formation of cholesterol-rich domains. PMID:15929726

Identification, Tissue Distribution, and Bioaccumulation Potential of Cyclic Perfluorinated Sulfonic Acids Isomers in an Airport Impacted Ecosystem.

PubMed

Wang, Yuan; Vestergren, Robin; Shi, Yali; Cao, Dong; Xu, Lin; Cai, Yaqi; Zhao, Xiaoli; Wu, Fengchang

2016-10-18

The use of cyclic perfluoroalkyl acids as anticorrosive agents in hydraulic fluids remains a poorly characterized source of organofluorine compounds to the environment. Here, we investigated the presence of perfluoroethylenecyclohexanesulfonate (PFECHS) isomers in environmental samples for the first time using a combination of high resolution and tandem mass spectrometry. Five distinct peaks attributed to different isomers of PFECHS and perfluoropropylcyclopentanesulfonate (PFPCPeS) were identified in environmental samples. The sum of PFECHS and PFPCPeS isomers displayed logarithmically decreasing spatial trends in water (1.04-324 ng/L) and sediment samples (Isomer-specific differences in the tissue/blood distribution ratios and BAF whole-body indicate that ring structure and position of the sulfonic acid group affect the bioaccumulation potential of cyclic perfluoroalkyl acids. Based on the high mobility and moderate bioaccumulation potential of cyclic perfluorinated acids it is suggested that contamination of aquifers used for drinking water around airports may be a hitherto overlooked problem for this novel class of contaminants.

Evaluation of sub-microsecond recovery resonators for In Vivo Electron Paramagnetic Resonance Imaging

PubMed Central

F, Hyodo; S, Subramanian; N, Devasahayam; R, Murugesan; K, Matsumoto; JB, Mitchell; MC, Krishna

2008-01-01

Time-domain (TD) electron paramagnetic resonance (EPR) imaging at 300 MHz for in vivo applications requires resonators with recovery times less than 1 microsecond after pulsed excitation to reliably capture the rapidly decaying free induction decay (FID). In this study, we tested the suitability of the Litz foil coil resonator (LCR), commonly used in MRI, for in vivo EPR/EPRI applications in the TD mode and compared with parallel coil resonator (PCR). In TD mode, the sensitivity of LCR was lower than that of the PCR. However, in continuous wave (CW) mode, the LCR showed better sensitivity. The RF homogeneity was similar in both the resonators. The axis of the RF magnetic field is transverse to the cylindrical axis of the LCR, making the resonator and the magnet co-axial. Therefore, the loading of animals, and placing of the anesthesia nose cone and temperature monitors was more convenient in the LCR compared to the PCR whose axis is perpendicular to the magnet axis. PMID:18042414

Three-dimensional multispectral hand-held optoacoustic imaging with microsecond-level delayed laser pulses

NASA Astrophysics Data System (ADS)

Deán-Ben, X. L.; Bay, Erwin; Razansky, Daniel

2015-03-01

Three-dimensional hand-held optoacoustic imaging comes with important advantages that prompt the clinical translation of this modality, with applications envisioned in cardiovascular and peripheral vascular disease, disorders of the lymphatic system, breast cancer, arthritis or inflammation. Of particular importance is the multispectral acquisition of data by exciting the tissue at several wavelengths, which enables functional imaging applications. However, multispectral imaging of entire three-dimensional regions is significantly challenged by motion artefacts in concurrent acquisitions at different wavelengths. A method based on acquisition of volumetric datasets having a microsecond-level delay between pulses at different wavelengths is described in this work. This method can avoid image artefacts imposed by a scanning velocity greater than 2 m/s, thus, does not only facilitate imaging influenced by respiratory, cardiac or other intrinsic fast movements in living tissues, but can achieve artifact-free imaging in the presence of more significant motion, e.g., abrupt displacements during handheld-mode operation in a clinical environment.

An UPLC-MS/MS method for separation and accurate quantification of tamoxifen and its metabolites isomers.

PubMed

Arellano, Cécile; Allal, Ben; Goubaa, Anwar; Roché, Henri; Chatelut, Etienne

2014-11-01

A selective and accurate analytical method is needed to quantify tamoxifen and its phase I metabolites in a prospective clinical protocol, for evaluation of pharmacokinetic parameters of tamoxifen and its metabolites in adjuvant treatment of breast cancer. The selectivity of the analytical method is a fundamental criteria to allow the quantification of the main active metabolites (Z)-isomers from (Z)'-isomers. An UPLC-MS/MS method was developed and validated for the quantification of (Z)-tamoxifen, (Z)-endoxifen, (E)-endoxifen, Z'-endoxifen, (Z)'-endoxifen, (Z)-4-hydroxytamoxifen, (Z)-4'-hydroxytamoxifen, N-desmethyl tamoxifen, and tamoxifen-N-oxide. The validation range was set between 0.5ng/mL and 125ng/mL for 4-hydroxytamoxifen and endoxifen isomers, and between 12.5ng/mL and 300ng/mL for tamoxifen, tamoxifen N-desmethyl and tamoxifen-N-oxide. The application to patient plasma samples was performed. Copyright © 2014 Elsevier B.V. All rights reserved.

Discrimination of Isomers of Released N- and O-Glycans Using Diagnostic Product Ions in Negative Ion PGC-LC-ESI-MS/MS

NASA Astrophysics Data System (ADS)

Ashwood, Christopher; Lin, Chi-Hung; Thaysen-Andersen, Morten; Packer, Nicolle H.

2018-03-01

Profiling cellular protein glycosylation is challenging due to the presence of highly similar glycan structures that play diverse roles in cellular physiology. As the anomericity and the exact linkage type of a single glycosidic bond can influence glycan function, there is a demand for improved and automated methods to confirm detailed structural features and to discriminate between structurally similar isomers, overcoming a significant bottleneck in the analysis of data generated by glycomics experiments. We used porous graphitized carbon-LC-ESI-MS/MS to separate and detect released N- and O-glycan isomers from mammalian model glycoproteins using negative mode resonance activation CID-MS/MS. By interrogating similar fragment spectra from closely related glycan isomers that differ only in arm position and sialyl linkage, product fragment ions for discrimination between these features were discovered. Using the Skyline software, at least two diagnostic fragment ions of high specificity were validated for automated discrimination of sialylation and arm position in N-glycan structures, and sialylation in O-glycan structures, complementing existing structural diagnostic ions. These diagnostic ions were shown to be useful for isomer discrimination using both linear and 3D ion trap mass spectrometers when analyzing complex glycan mixtures from cell lysates. Skyline was found to serve as a useful tool for automated assessment of glycan isomer discrimination. This platform-independent workflow can potentially be extended to automate the characterization and quantitation of other challenging glycan isomers. [Figure not available: see fulltext.

Evaluation of Enhanced Comprehensive 2-D Gas Chromatography-Time-Of-Flight Mass Spectrometry for the Separation of Recalcitrant Polychlorinated Biphenyl Isomers

EPA Science Inventory

The separation of some recalcitrant polychlorinated biphenyl (PCB) isomers in extracts from environmental compartments has been a daunting task for environmental chemists. Summed quantitation values for coeluting PCB isomers are often reported. This composite data obscures the ac...

Metabolomics of hexachlorocyclohexane (HCH) transformation: ratio of LinA to LinB determines metabolic fate of HCH isomers.

PubMed

Geueke, Birgit; Garg, Nidhi; Ghosh, Sneha; Fleischmann, Thomas; Holliger, Christof; Lal, Rup; Kohler, Hans-Peter E

2013-04-01

Although the production and use of technical hexachlorocyclohexane (HCH) and lindane (the purified insecticidal isomer γ-HCH) are prohibited in most countries, residual concentrations still constitute an immense environmental burden. Many studies describe the mineralization of γ-HCH by bacterial strains under aerobic conditions. However, the metabolic fate of the other HCH isomers is not well known. In this study, we investigated the transformation of α-, β-, γ-, δ-, ε-HCH, and a heptachlorocyclohexane isomer in the presence of varying ratios of the two enzymes that initiate γ-HCH degradation, a dehydrochlorinase (LinA) and a haloalkane dehalogenase (LinB). Each substrate yielded a unique metabolic profile that was strongly dependent on the enzyme ratio. Comparison of these results to those of in vivo experiments with different bacterial isolates showed that HCH transformation in the tested strains was highly optimized towards productive metabolism of γ-HCH and that under these conditions other HCH-isomers were metabolized to mixtures of dehydrochlorinated and hydroxylated side-products. In view of these results, bioremediation efforts need very careful planning and toxicities of accumulating metabolites need to be evaluated. © 2012 Society for Applied Microbiology and Blackwell Publishing Ltd.

Graphene-ZIF8 composite material as stationary phase for high-resolution gas chromatographic separations of aliphatic and aromatic isomers.

PubMed

Yang, Xiaohong; Li, Changxia; Qi, Meiling; Qu, Liangti

2016-08-19

This work presents the separation performance of graphene-ZIF8 (G-Z) composite material as stationary phase for capillary gas chromatography (GC). The G-Z stationary phase achieved high column efficiency of 5000 plates/m determined by n-dodecane (k=1.22) at 120°C and showed weakly polar nature. Importantly, it exhibited high selectivity and resolving capability for branched alkane isomers and aromatic positional isomers, showing clear advantages over the reported neat graphene and ZIF8. In addition, it attained high resolution for geometric cis-/trans-isomers. The G-Z column exhibited good column thermal stability up to 300°C and column repeatability with RSD values of retention times in the range of 0.01-0.19% for intra-day, 0.05-0.88% for inter-day and 0.66-5.6% for between-column, respectively, Moreover, the G-Z column was employed for the determination of minor impurity isomers in real reagent samples, which demonstrates its promising potential in GC applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Hierarchical Biomolecular Dynamics: Picosecond Hydrogen Bonding Regulates Microsecond Conformational Transitions.

PubMed

Buchenberg, Sebastian; Schaudinnus, Norbert; Stock, Gerhard

2015-03-10

Biomolecules exhibit structural dynamics on a number of time scales, including picosecond (ps) motions of a few atoms, nanosecond (ns) local conformational transitions, and microsecond (μs) global conformational rearrangements. Despite this substantial separation of time scales, fast and slow degrees of freedom appear to be coupled in a nonlinear manner; for example, there is theoretical and experimental evidence that fast structural fluctuations are required for slow functional motion to happen. To elucidate a microscopic mechanism of this multiscale behavior, Aib peptide is adopted as a simple model system. Combining extensive molecular dynamics simulations with principal component analysis techniques, a hierarchy of (at least) three tiers of the molecule's free energy landscape is discovered. They correspond to chiral left- to right-handed transitions of the entire peptide that happen on a μs time scale, conformational transitions of individual residues that take about 1 ns, and the opening and closing of structure-stabilizing hydrogen bonds that occur within tens of ps and are triggered by sub-ps structural fluctuations. Providing a simple mechanism of hierarchical dynamics, fast hydrogen bond dynamics is found to be a prerequisite for the ns local conformational transitions, which in turn are a prerequisite for the slow global conformational rearrangement of the peptide. As a consequence of the hierarchical coupling, the various processes exhibit a similar temperature behavior which may be interpreted as a dynamic transition.

Quantum-Chemical ab initio Calculations on the Three Isomers of Diborabenzene (C4H4B2)

NASA Astrophysics Data System (ADS)

Singh, Jaswinder; Wang, Yuekui; Raabe, Gerhard

2010-01-01

Quantum-chemical ab initio calculations up to the ZPE+CCSD(T)/aug-cc-pVTZ//MP2/6- 311++G** level were performed on three possible structural isomers of diborabenzene (C4H4B2). All three molecules were found to be local minima on the C4H4B2 energy surface and to have closed shell singlet ground states. While the ground states of the 1,3- and 1,4-isomer are planar and of C2v and D2h symmetry, respectively, 1,2-diborabenzene is non-planar with a C2 axis passing through the center of the BB bond and the middle of the opposite carbon-carbon bond as the only symmetry element. The energetically most favourable 1,3-diborabenzene was found to be about 19 and 36 kcal/mol lower in energy than the 1,2- and the 1,4-isomer. Planar 1,3- and 1,4-diborabenzene have three doubly occupied π orbitals while non-planar 1,2-diborabenzene has also three doubly occupied orbitals which can be derived from the π orbitals of its 3.7 kcal/mol energetically less favourable planar form ("π-like" orbitals). The lowest unoccupied orbitals of all three isomers have σ symmetry with large coefficients at the two boron atoms. These orbitals are lower in energy than the lowest unoccupied molecular orbitals (LUMOs) of e. g. benzene and pyridine and might cause pronounced acceptor properties which could be one of the reasons for the elusiveness of the title compounds. The results of bond separation reactions show that cyclic conjugation stabilizes all three diborabenzenes relative to their isolated fragments. The most effective stabilization energy of about 24 kcal/mol was found for the energetically lowest 1,3-isomer. This value amounts to approximately one third of the experimental value for the bond separation energy of pyridine. In all cases the energetically lowest triplet states are significantly (16 - 24 kcal/mol) higher in energy than the singlet ground states. Also among the triplets the 1,3-isomer is the energetically most fabourable species.

Synthesis of protected 2-pyrrolylalanine for peptide chemistry and examination of its influence on prolyl amide isomer equilibrium.

PubMed

Dörr, Aurélie A; Lubell, William D

2012-08-03

Protected enantiopure 2-pyrrolylalanine was synthesized for application in peptide science as an electron-rich arylalanine (histidine) analog with π-donor capability. (2S)-N-(Boc)-N'-(Phenylsulfonyl)-, (2S)-N,N'-bis-(phenylsulfonyl)-, and (2S)-N,N'-bis-(Boc)-3-(2-pyrrolyl)alanines (10, 3, and 14, respectively) were made in 13-17% overall yields and six to seven steps from oxazolidine β-methyl ester 4. Homoallylic ketone 5 was prepared by a copper-catalyzed cascade addition of vinylmagnesium bromide to ester 4 and converted to pyrrolyl amino alcohol 7 by olefin oxidation and Paal-Knorr condensation. Protecting group shuffle and oxidation of the primary alcohol enabled the synthesis of pyrrolylalanines. The bis-Boc analog 14 proved useful in peptide chemistry and was employed to make N-acetyl-pyrrolylalaninyl-proline N''-methylamide 25. A study of the influence of the pyrrole moiety on the prolyl amide isomer equilibrium of 25 using (1)H NMR spectroscopy in chloroform, DMSO, and water demonstrated that the pyrrolylalanine peptide exhibited behavior and conformations different from those of other arylalanine analogs.

Simultaneous biodegradation of three mononitrophenol isomers by a tailor-made microbial consortium immobilized in sequential batch reactors.

PubMed

Fu, H; Zhang, J-J; Xu, Y; Chao, H-J; Zhou, N-Y

2017-03-01

The ortho-nitrophenol (ONP)-utilizing Alcaligenes sp. strain NyZ215, meta-nitrophenol (MNP)-utilizing Cupriavidus necator JMP134 and para-nitrophenol (PNP)-utilizing Pseudomonas sp. strain WBC-3 were assembled as a consortium to degrade three nitrophenol isomers in sequential batch reactors. Pilot test was conducted in flasks to demonstrate that a mixture of three mononitrophenols at 0·5 mol l -1 each could be mineralized by this microbial consortium within 84 h. Interestingly, neither ONP nor MNP was degraded until PNP was almost consumed by strain WBC-3. By immobilizing this consortium into polyurethane cubes, all three mononitrophenols were continuously degraded in lab-scale sequential reactors for six batch cycles over 18 days. Total concentrations of ONP, MMP and PNP that were degraded were 2·8, 1·5 and 2·3 mol l -1 during this time course respectively. Quantitative real-time PCR analysis showed that each member in the microbial consortium was relatively stable during the entire degradation process. This study provides a novel approach to treat polluted water, particularly with a mixture of co-existing isomers. Nitroaromatic compounds are readily spread in the environment and pose great potential toxicity concerns. Here, we report the simultaneous degradation of three isomers of mononitrophenol in a single system by employing a consortium of three bacteria, both in flasks and lab-scale sequential batch reactors. The results demonstrate that simultaneous biodegradation of three mononitrophenol isomers can be achieved by a tailor-made microbial consortium immobilized in sequential batch reactors, providing a pilot study for a novel approach for the bioremediation of mixed pollutants, especially isomers present in wastewater. © 2016 The Society for Applied Microbiology.

A new formulation of Gamma Delta Tocotrienol has superior bioavailability compared to existing Tocotrienol-Rich Fraction in healthy human subjects

PubMed Central

Meganathan, Puvaneswari; Jabir, Rafid Salim; Fuang, Ho Gwo; Bhoo-Pathy, Nirmala; Choudhury, Roma Basu; Taib, Nur Aishah; Nesaretnam, Kalanithi; Chik, Zamri

2015-01-01

Gamma and delta tocotrienols are isomers of Vitamin E with established potency in pre-clinical anti-cancer research. This single-dose, randomized, crossover study aimed to compare the safety and bioavailability of a new formulation of Gamma Delta Tocotrienol (GDT) in comparison with the existing Tocotrienol-rich Fraction (TRF) in terms of gamma and delta isomers in healthy volunteers. Subjects were given either two 300 mg GDT (450 mg γ-T3 and 150 mg δ-T3) capsules or four 200 mg TRF (451.2 mg γ-T3 & 102.72 mg δ-T3) capsules and blood samples were taken at several time points over 24 hours. Plasma tocotrienol concentrations were determined using HPLC method. The 90% CI for gamma and delta tocotrienols for the ratio of log-transformation of GDT/TRF for Cmax and AUC0–∞ (values were anti-logged and expressed as a percentage) were beyond the bioequivalence limits (106.21–195.46, 154.11–195.93 and 52.35–99.66, 74.82–89.44 respectively). The Wilcoxon Signed Rank Test for Tmax did not show any significant difference between GDT and TRF for both isomers (p > 0.05). No adverse events were reported during the entire period of study. GDT was found not bioequivalent to TRF, in terms of AUC and Cmax. Gamma tocotrienol in GDT showed superior bioavailability whilst delta tocotrienol showed less bioavailability compared to TRF. PMID:26323969

Time- and isomer-resolved measurements of sequential addition of acetylene to the propargyl radical

DOE PAGES

Savee, John D.; Selby, Talitha M.; Welz, Oliver; ...

2015-10-06

Soot formation in combustion is a complex process in which polycyclic aromatic hydrocarbons (PAHs) are believed to play a critical role. Recent works concluded that three consecutive additions of acetylene (C 2H 2) to propargyl (C 3H 3) create a facile route to the PAH indene (C 9H 8). However, the isomeric forms of C 5H 5 and C 7H 7 intermediates in this reaction sequence are not known. We directly investigate these intermediates using time- and isomer-resolved experiments. Both the resonance stabilized vinylpropargyl ( vp-C 5H 5) and 2,4-cyclopentadienyl ( c-C 5H 5) radical isomers of C 5H 5more » are produced, with substantially different intensities at 800 K vs 1000 K. In agreement with literature master equation calculations, we find that c-C 5H 5 + C 2H 2 produces only the tropyl isomer of C 7H 7 ( tp-C 7H 7) below 1000 K, and that tp-C 7H 7 + C 2H 2 terminates the reaction sequence yielding C 9H 8 (indene) + H. Lastly, this work demonstrates a pathway for PAH formation that does not proceed through benzene.« less

Nuclear states with anomalously large radius (size isomers)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ogloblin, A. A.; Demyanova, A. S., E-mail: a.s.demyanova@bk.ru; Danilov, A. N.

2016-07-15

Methods of determination of the nuclear excited state radii are discussed together with the recently obtained data on the states of some light nuclei having abnormally large radii (size isomers). It is shown that such states include excited neutron-halo states in {sup 9}Be, {sup 11}Be, and {sup 13}C and some alpha-cluster states in {sup 12}C, {sup 11}B, and {sup 13}C. Among the latter ones, there is the well-known Hoyle state in {sup 12}C—the structure of this state exhibit rudimentary features of alpha-particle states.

PBPK modeling of the cis- and trans-permethrin isomers and their major urinary metabolites in rats

DOE Office of Scientific and Technical Information (OSTI.GOV)

Willemin, Marie-Emilie; Sorbonne University, Université de Technologie de Compiègne, CNRS, UMR 7338 Biomechanics and Bioengineering, Centre de recherche Royallieu CS 60319,60203 Compiègnee Cedex; Desmots, Sophie

2016-03-01

Permethrin, a pyrethroid insecticide, is suspected to induce neuronal and hormonal disturbances in humans. The widespread exposure of the populations has been confirmed by the detection of the urinary metabolites of permethrin in biomonitoring studies. Permethrin is a chiral molecule presenting two forms, the cis and the trans isomers. Because in vitro studies indicated a metabolic interaction between the trans and cis isomers of permethrin, we adapted and calibrated a PBPK model for trans- and cis-permethrin separately in rats. The model also describes the toxicokinetics of three urinary metabolites, cis- and trans-3-(2,2 dichlorovinyl)-2,2-dimethyl-(1-cyclopropane) carboxylic acid (cis- and trans-DCCA), 3-phenoxybenzoic acidmore » (3-PBA) and 4′OH-phenoxybenzoic acid (4′-OH-PBA). In vivo experiments performed in Sprague–Dawley rats were used to calibrate the PBPK model in a Bayesian framework. The model captured well the toxicokinetics of permethrin isomers and their metabolites including the rapid absorption, the accumulation in fat, the extensive metabolism of the parent compounds, and the rapid elimination of metabolites in urine. Average hepatic clearances in rats were estimated to be 2.4 and 5.7 L/h/kg for cis- and trans-permethrin, respectively. High concentrations of the metabolite 4′-OH-PBA were measured in urine compared to cis- and trans-DCCA and 3-PBA. The confidence in the extended PBPK model was then confirmed by good predictions of published experimental data obtained using the isomers mixture. The extended PBPK model could be extrapolated to humans to predict the internal dose of exposure to permethrin from biomonitoring data in urine. - Highlights: • A PBPK model of isomers of permethrin and its urinary metabolites was developed. • A quantitative link was established for permethrin and its biomarkers of exposure. • The bayesian framework allows getting confidence interval on the estimated parameters. • The PBPK model can be

An isomer-specific study of solid nitromethane decomposition pathways - Detection of aci-nitromethane (H2CNO(OH)) and nitrosomethanol (HOCH2NO) intermediates

NASA Astrophysics Data System (ADS)

Maksyutenko, Pavlo; Förstel, Marko; Crandall, Parker; Sun, Bing-Jian; Wu, Mei-Hung; Chang, Agnes H. H.; Kaiser, Ralf I.

2016-08-01

An isomer specific study of energetic electron exposed nitromethane ices was performed via photoionization - reflectron time of flight mass spectrometry (PI-ReTOF-MS) of the subliming products employing tunable vacuum ultraviolet light for ionization. Supported by electronic structure calculations, nitromethane (CH3NO2) was found to isomerize to methyl nitrite (CH3ONO) and also via hydrogen migration to the hitherto elusive aci-nitromethane isomer (H2CNO(OH)). The latter isomerizes to nitrosomethanol (HOCH2NO) through hydroxyl group (OH) migration, and, probably, ring closure to the cyclic 2-hydroxy-oxaziridine isomer (c-H2CON(OH)) as well. The importance of hydrogen migrations was also verified via the nitrosomethane (CH3NO) - formaldehyde oxime isomer (CH2NOH) pair.

UV-induced bond modifications in thymine and thymine dideoxynucleotide: structural elucidation of isomers by differential mobility mass spectrometry.

PubMed

St-Jacques, Antony; Anichina, Janna; Schneider, Bradley B; Covey, Thomas R; Bohme, Diethard K

2010-07-15

Differential mobility spectrometry has been applied to reveal the occurrence of isomerization of thymine nucleobase and of thymine dideoxynucleotide d(5'-TT-3') due to bond redisposition induced by UV irradiation at 254 nm of frozen aqueous solutions of these molecules. Collision-induced dissociation (CID) spectra of electrosprayed photoproducts of the thymine solution suggest the presence of two isomers (the so-called cyclobutane and 6,4-photoproducts) in addition to the proton-bound thymine dimer, and these were separated using differential mobility spectrometry/mass spectrometry (DMS/MS) techniques with water as the modifier. Similar experiments with d(5'-TT-3') revealed the formation of a new isomer of deprotonated thymine dideoxynucleotide upon UV irradiation that was easily distinguished using DMS/MS with isopropanol as the modifier. The results reinforce the usefulness of DMS/MS in isomer separation.

Occurrence and biological activity of palmitoleic acid isomers in phagocytic cells.

PubMed

Astudillo, Alma M; Meana, Clara; Guijas, Carlos; Pereira, Laura; Lebrero, Patricia; Balboa, María A; Balsinde, Jesús

2018-02-01

Recent studies have highlighted the role of palmitoleic acid [16:1 n-7 ( cis -9-hexadecenoic acid)] as a lipid hormone that coordinates cross-talk between liver and adipose tissue and exerts anti-inflammatory protective effects on hepatic steatosis and insulin signaling in murine models of metabolic disease. More recently, a 16:1 n-7 isomer, cis -7-hexadecenoic acid (16:1 n-9 ), that also possesses marked anti-inflammatory effects, has been described in human circulating monocytes and monocyte-derived macrophages. By using gas chromatographic/mass spectrometric analyses of dimethyl disulfide derivatives of fatty acyl methyl esters, we describe in this study the presence of a third 16:1 isomer, sapienic acid [16:1 n-10 (6- cis -hexadecenoic acid)], in phagocytic cells. Cellular levels of 16:1 n-10 appear to depend not only on the cellular content of linoleic acid, but also on the expression level of fatty acid desaturase 2, thus revealing a complex regulation both at the enzyme level, via fatty acid substrate competition, and directly at the gene level. However, unlike 16:1 n-7 and 16:1 n-9 , 16:1 n-10 levels are not regulated by the activation state of the cell. Moreover, while 16:1 n-7 and 16:1 n-9 manifest strong anti-inflammatory activity when added to the cells at low concentrations (10 μM), notably higher concentrations of 16:1 n-10 are required to observe a comparable effect. Collectively, these results suggest the presence in phagocytic cells of an unexpected variety of 16:1 isomers, which can be distinguished on the basis of their biological activity and cellular regulation. Copyright © 2018 by the American Society for Biochemistry and Molecular Biology, Inc.

Response of Dendroctonus mexicanus (Hopkins) to two optical isomers of verbenone

Treesearch

Vicente Diaz-Nunez; Guillermo Sanchez-Martinez; Nancy E. Gillette

2006-01-01

Given the need for diminishing the use of pesticides in natural environments, in this research we investigated the efficacy of two optical isomers of verbenone (4, 6, 6-trimethylbicyclo[3.1.1] hepto-3-en-e-1) as controls of the attack of Dendroctonus mexicanus (Hopkins) (Coleoptera: Curculionidae: Scolytinae).Two experiments were established in the...

Using One's Hands for Naming Optical Isomers and Other Stereochemical Positions.

ERIC Educational Resources Information Center

Mezl, Vasek A.

1996-01-01

Presents a method that allows students to use their hands to obtain the stereochemistry of chiral centers without redrawing the structure. Discusses the use of the model in: determining the configurations of amino acids, determining if sugars are D or L isomers, the sequence rule procedure, prochirality, naming the sides of trigonal carbons, and…

Isomer beam elastic scattering: 26mAl(p, p) for astrophysics

NASA Astrophysics Data System (ADS)

Kahl, D.; Shimizu, H.; Yamaguchi, H.; Abe, K.; Beliuskina, O.; Cha, S. M.; Chae, K. Y.; Chen, A. A.; Ge, Z.; Hayakawa, S.; Imai, N.; Iwasa, N.; Kim, A.; Kim, D. H.; Kim, M. J.; Kubono, S.; Kwag, M. S.; Liang, J.; Moon, J. Y.; Nishimura, S.; Oka, S.; Park, S. Y.; Psaltis, A.; Teranishi, T.; Ueno, Y.; Yang, L.

2018-01-01

The advent of radioactive ground-state beams some three decades ago ultimately sparked a revolution in our understanding of nuclear physics. However, studies with radioactive isomer beams are sparse and have often required sophisticated apparatuses coupled with the technologies of ground-state beams due to typical mass differences on the order of hundreds of keV and vastly different lifetimes for isomers. We present an application of a isomeric beam of 26mAl to one of the most famous observables in nuclear astrophysics: galactic 26Al. The characteristic decay of 26Al in the Galaxy was the first such specific radioactivity to be observed originating from outside the Earth some four decades ago. We present a newly-developed, novel technique to probe the structure of low-spin states in 27Si. Using the Center for Nuclear Study low-energy radioisotope beam separator (CRIB), we report on the measurement of 26mAl proton resonant elastic scattering conducted with a thick target in inverse kinematics. The preliminary results of this on-going study are presented.

Elastic scattering of low-energy electrons by C{sub 3}H{sub 4} isomers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lopes, A.R.; Bettega, M.H.F.

2003-03-01

We report integral, differential, and momentum-transfer cross sections for elastic scattering of low-energy electrons by the C{sub 3}H{sub 4} isomers allene, propyne, and cyclopropene, which belong to the D{sub 2d}, C{sub 3v}, and C{sub 2v} groups, respectively. We use the Schwinger multichannel method with pseudopotentials [Bettega et al., Phys. Rev. A 47, 1111 (1993)] at the static-exchange approximation to compute the cross sections for energies up to 40 eV. We compare our results with available experimental results and find very good agreement. Our results confirm the existence of the shape resonances in the cross sections of allene and propyne, andmore » the isomer effect, both reported by the experimental studies.« less

Profiling of the molecular weight and structural isomer abundance of macroalgae-derived phlorotannins.

PubMed

Heffernan, Natalie; Brunton, Nigel P; FitzGerald, Richard J; Smyth, Thomas J

2015-01-16

Phlorotannins are a group of complex polymers of phloroglucinol (1,3,5-trihydroxybenzene) unique to macroalgae. These phenolic compounds are integral structural components of the cell wall in brown algae, but also play many secondary ecological roles such as protection from UV radiation and defense against grazing. This study employed Ultra Performance Liquid Chromatography (UPLC) with tandem mass spectrometry to investigate isomeric complexity and observed differences in phlorotannins derived from macroalgae harvested off the Irish coast (Fucus serratus, Fucus vesiculosus, Himanthalia elongata and Cystoseira nodicaulis). Antioxidant activity and total phenolic content assays were used as an index for producing phlorotannin fractions, enriched using molecular weight cut-off dialysis with subsequent flash chromatography to profile phlorotannin isomers in these macroalgae. These fractions were profiled using UPLC-MS with multiple reaction monitoring (MRM) and the level of isomerization for specific molecular weight phlorotannins between 3 and 16 monomers were determined. The majority of the low molecular weight (LMW) phlorotannins were found to have a molecular weight range equivalent to 4-12 monomers of phloroglucinol. The level of isomerization within the individual macroalgal species differed, resulting in substantially different numbers of phlorotannin isomers for particular molecular weights. F. vesiculosus had the highest number of isomers of 61 at one specific molecular mass, corresponding to 12 phloroglucinol units (PGUs). These results highlight the complex nature of these extracts and emphasize the challenges involved in structural elucidation of these compounds.

Profiling of the Molecular Weight and Structural Isomer Abundance of Macroalgae-Derived Phlorotannins

PubMed Central

Heffernan, Natalie; Brunton, Nigel P.; FitzGerald, Richard J.; Smyth, Thomas J.

2015-01-01

Phlorotannins are a group of complex polymers of phloroglucinol (1,3,5-trihydroxybenzene) unique to macroalgae. These phenolic compounds are integral structural components of the cell wall in brown algae, but also play many secondary ecological roles such as protection from UV radiation and defense against grazing. This study employed Ultra Performance Liquid Chromatography (UPLC) with tandem mass spectrometry to investigate isomeric complexity and observed differences in phlorotannins derived from macroalgae harvested off the Irish coast (Fucus serratus, Fucus vesiculosus, Himanthalia elongata and Cystoseira nodicaulis). Antioxidant activity and total phenolic content assays were used as an index for producing phlorotannin fractions, enriched using molecular weight cut-off dialysis with subsequent flash chromatography to profile phlorotannin isomers in these macroalgae. These fractions were profiled using UPLC-MS with multiple reaction monitoring (MRM) and the level of isomerization for specific molecular weight phlorotannins between 3 and 16 monomers were determined. The majority of the low molecular weight (LMW) phlorotannins were found to have a molecular weight range equivalent to 4–12 monomers of phloroglucinol. The level of isomerization within the individual macroalgal species differed, resulting in substantially different numbers of phlorotannin isomers for particular molecular weights. F. vesiculosus had the highest number of isomers of 61 at one specific molecular mass, corresponding to 12 phloroglucinol units (PGUs). These results highlight the complex nature of these extracts and emphasize the challenges involved in structural elucidation of these compounds. PMID:25603345

Experimental and computational investigation of the thermochemistry of the six isomers of dichloroaniline.

PubMed

Ribeiro da Silva, Manuel A V; Amaral, Luísa M P F; Gomes, José R B

2006-07-27

The standard (p(o) = 0.1 MPa) molar enthalpies of formation of 2,3-, 2,4-, 2,5-, 2,6-, 3,4- and 3,5-dichloroanilines were derived from the standard molar energies of combustion, in oxygen, to yield CO(2)(g), N(2)(g) and HCl.600H(2)O(l), at T = 298.15 K, measured by rotating bomb combustion calorimetry. The Calvet high-temperature vacuum sublimation technique was used to measure the enthalpies of sublimation of the six isomers. These two thermodynamic parameters yielded the standard molar enthalpies of formation of the six isomers of dichloroaniline, in the gaseous phase, at T = 298.15 K. The gas-phase enthalpies of formation were also estimated by G3MP2B3 calculations, which were further extended to the computation of gas-phase acidities, proton affinities, and ionization enthalpies.

Fe uptake from meso and D,L-racemic Fe(o,o-EDDHA) isomers by strategy I and II plants.

PubMed

Cerdán, Mar; Alcañiz, Sara; Juárez, Margarita; Jordá, Juana D; Bermúdez, Dolores

2006-02-22

One of the most efficient fertilizers to correct Fe deficiency in calcareous soils and waters with high bicarbonate content is based on ferric ethylenediamine-N,N'-bis(o-hydroxyphenylacetic) acid [Fe(o,o-EDDHA)]. Fe(o,o-EDDHA) forms two groups of geometric isomers known as meso and D,L-racemic. To determine the Fe uptake from meso and D,L-racemic Fe(o,o-EDDHA), four iron-efficient plants, two plants representative of strategy I (tomato and pepper) and two plants representative of strategy II (wheat and oats), were grown in hydroponic culture. Results indicated that strategy II plants took up iron from both Fe(o,o-EDDHA) isomers equally. However, strategy I plants took mainly the iron associated with the meso form (the lowest stability isomer).

Safety assessment of a natural tomato oleoresin containing high amounts of Z-isomers of lycopene prepared with supercritical carbon dioxide.

PubMed

Honda, Masaki; Higashiura, Takuma; Fukaya, Tetsuya

2017-02-01

Z-isomers of lycopene, which are abundantly present in processed tomato products, are more bioavailable than (all-E)-lycopene found predominantly in raw tomatoes. Despite extensive studies on the bioavailability and biological activities of Z-isomers of lycopene, detailed studies on their safety and toxicology are limited. The geno-, acute and subacute toxicities of tomato oleoresin that contained high amounts of lycopene Z-isomers (10.9% lycopene with 66.3% Z-isomer content) and had been prepared with supercritical carbon dioxide were investigated. The oleoresin was non-mutagenic in the Ames test with and without metabolic activation (S9 mix). The medial lethal dose (LD 50 ) of the oleoresin in rats, as determined by a single-dose oral test, was more than 5000 mg kg body weight -1 (bw) [361 mg (Z)-lycopene kg bw -1 ]. In the 4-week repeated-dose oral toxicity test, rats were administered oleoresin at 4500 mg kg -1 day -1 [325 mg (Z)-lycopene kg bw -1 day -1 ]. There were no clinically significant changes with respect to vital signs, physical examination outcomes and laboratory test values during the test period. Based on our findings and as supported by its long history of consumption, tomato oleoresin that contains high amounts of Z-isomers of lycopene prepared with supercritical carbon dioxide can be considered as safe for human consumption. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Microsecond Electron Beam Source with Electron Energy Up to 400 Kev and Plasma Anode

NASA Astrophysics Data System (ADS)

Abdullin, É. N.; Basov, G. F.; Shershnev, S.

2017-12-01

A new high-power source of electrons with plasma anode for producing high-current microsecond electron beams with electron energy up to 400 keV has been developed, manufactured, and put in operation. To increase the cross section and pulse current duration of the beam, a multipoint explosive emission cathode is used in the electron beam source, and the beam is formed in an applied external guiding magnetic field. The Marx generator with vacuum insulation is used as a high-voltage source. Electron beams with electron energy up to 300-400 keV, current of 5-15 kA, duration of 1.5-3 μs, energy up to 4 kJ, and cross section up to 150 cm2 have been produced. The operating modes of the electron beam source are realized in which the applied voltage is influenced weakly on the current. The possibility of source application for melting of metal surfaces is demonstrated.

Microsecond gain-switched master oscillator power amplifier (1958 nm) with high pulse energy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ke Yin; Weiqiang Yang; Bin Zhang

2014-02-28

An all-fibre master oscillator power amplifier (MOPA) emitting high-energy pulses at 1958 nm is presented. The seed laser is a microsecond gain-switched thulium-doped fibre laser (TDFL) pumped with a commercial 1550-nm pulsed fibre laser. The TDFL operates at a repetition rate f in the range of 10 to 100 kHz. The two-stage thulium-doped fibre amplifier is built to scale the energy of the pulses generated by the seed laser. The maximum output pulse energy higher than 0.5 mJ at 10 kHz is achieved which is comparable with the theoretical maximum extractable pulse energy. The slope efficiency of the second stagemore » amplifier with respect to the pump power is 30.4% at f = 10 kHz. The wavelength of the output pulse laser is centred near 1958 nm at a spectral width of 0.25 nm after amplification. Neither nonlinear effects nor significant amplified spontaneous emission (ASE) is observed in the amplification experiments. (lasers)« less

Spectroscopic and computational study of a new isomer of salinomycin

NASA Astrophysics Data System (ADS)

Pankiewicz, Radosław

2013-09-01

A new derivative of polyether ionophore salinomycin was obtained as a result of a rearrangement catalysed by sulphuric acid in two-phase medium of water/methylene chloride solution. The new isomer was fully characterized by multinuclear 2D NMR, NOESY and MALDI-TOF. The properties of the new compound were additionally study by semiempirical (PM5) and DFT (B3LYP) methods. A potential mechanism of the rearrangement was also proposed.

Tailorable PC71 BM Isomers: Using the Most Prevalent Electron Acceptor to Obtain High-Performance Polymer Solar Cells.

PubMed

Zhan, Xin-Xing; Zhang, Xin; Dai, Si-Min; Li, Shu-Hui; Lu, Xu-Zhai; Deng, Lin-Long; Xie, Su-Yuan; Huang, Rong-Bin; Zheng, Lan-Sun

2016-12-23

Despite being widely used as electron acceptor in polymer solar cells, commercially available PC 71 BM (phenyl-C 71 -butyric acid methyl ester) usually has a "random" composition of mixed regioisomers or stereoisomers. Here PC 71 BM has been isolated into three typical isomers, α-, β 1 - and β 2 -PC 71 BM, to establish the isomer-dependent photovoltaic performance on changing the ternary composition of α-, β 1 - and β 2 -PC 71 BM. Mixing the isomers in a ratio of α/β 1 /β 2 =8:1:1 resulted in the best power conversion efficiency (PCE) of 7.67 % for the polymer solar cells with PTB7:PC 71 BM as photoactive layer (PTB7=poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl

The sim Operon Facilitates the Transport and Metabolism of Sucrose Isomers in Lactobacillus casei ATCC 334▿

PubMed Central

Thompson, John; Jakubovics, Nicholas; Abraham, Bindu; Hess, Sonja; Pikis, Andreas

2008-01-01

Inspection of the genome sequence of Lactobacillus casei ATCC 334 revealed two operons that might dissimilate the five isomers of sucrose. To test this hypothesis, cells of L. casei ATCC 334 were grown in a defined medium supplemented with various sugars, including each of the five isomeric disaccharides. Extracts prepared from cells grown on the sucrose isomers contained high levels of two polypeptides with Mrs of ∼50,000 and ∼17,500. Neither protein was present in cells grown on glucose, maltose or sucrose. Proteomic, enzymatic, and Western blot analyses identified the ∼50-kDa protein as an NAD+- and metal ion-dependent phospho-α-glucosidase. The oligomeric enzyme was purified, and a catalytic mechanism is proposed. The smaller polypeptide represented an EIIA component of the phosphoenolpyruvate-dependent sugar phosphotransferase system. Phospho-α-glucosidase and EIIA are encoded by genes at the LSEI_0369 (simA) and LSEI_0374 (simF) loci, respectively, in a block of seven genes comprising the sucrose isomer metabolism (sim) operon. Northern blot analyses provided evidence that three mRNA transcripts were up-regulated during logarithmic growth of L. casei ATCC 334 on sucrose isomers. Internal simA and simF gene probes hybridized to ∼1.5- and ∼1.3-kb transcripts, respectively. A 6.8-kb mRNA transcript was detected by both probes, which was indicative of cotranscription of the entire sim operon. PMID:18310337

Levitation effect in zeolites: Quasielastic neutron scattering and molecular dynamics study of pentane isomers in zeolite NaY.

PubMed

Borah, Bhaskar J; Jobic, H; Yashonath, S

2010-04-14

We report the quasielastic neutron scattering (QENS) and molecular dynamics (MD) investigations into diffusion of pentane isomers in zeolite NaY. The molecular cross section perpendicular to the long molecular axis varies for the three isomers while the mass and the isomer-zeolite interaction remains essentially unchanged. Both QENS and MD results show that the branched isomers neopentane and isopentane have higher self-diffusivities as compared with n-pentane at 300 K in NaY zeolite. This result provides direct experimental evidence for the existence of nonmonotonic, anomalous dependence of self-diffusivity on molecular diameter known as the levitation effect. The energetic barrier at the bottleneck derived from MD simulations exists for n-pentane which lies in the linear regime while no such barrier is seen for neopentane which is located clearly in the anomalous regime. Activation energy is in the order E(a)(n-pentane)>E(a)(isopentane)>E(a)(neopentane) consistent with the predictions of the levitation effect. In the liquid phase, it is seen that D(n-pentane)>D(isopentane)>D(neopentane) and E(a)(n-pentane)isomer has a higher diffusivity as compared with the linear analog is at variation from what is normally seen.

Levitation effect in zeolites: Quasielastic neutron scattering and molecular dynamics study of pentane isomers in zeolite NaY

NASA Astrophysics Data System (ADS)

Borah, Bhaskar J.; Jobic, H.; Yashonath, S.

2010-04-01

We report the quasielastic neutron scattering (QENS) and molecular dynamics (MD) investigations into diffusion of pentane isomers in zeolite NaY. The molecular cross section perpendicular to the long molecular axis varies for the three isomers while the mass and the isomer-zeolite interaction remains essentially unchanged. Both QENS and MD results show that the branched isomers neopentane and isopentane have higher self-diffusivities as compared with n-pentane at 300 K in NaY zeolite. This result provides direct experimental evidence for the existence of nonmonotonic, anomalous dependence of self-diffusivity on molecular diameter known as the levitation effect. The energetic barrier at the bottleneck derived from MD simulations exists for n-pentane which lies in the linear regime while no such barrier is seen for neopentane which is located clearly in the anomalous regime. Activation energy is in the order Ea(n-pentane)>Ea(isopentane)>Ea(neopentane) consistent with the predictions of the levitation effect. In the liquid phase, it is seen that D(n-pentane)>D(isopentane)>D(neopentane) and Ea(n-pentane)isomer has a higher diffusivity as compared with the linear analog is at variation from what is normally seen.

Nonadiabatic dynamics simulation of photoisomerization mechanism of the second stablest isomer of N-salicilydenemethylfurylamine

NASA Astrophysics Data System (ADS)

Gao, Aihua; Li, Jianpeng; Wang, Dehua; Ma, Xiaoguang; Wang, Meishan

2018-02-01

The photoisomerization processes of the second stablest isomer in the aromatic Schiff base, N-salicilydenemethylfurylamine, in the gas phase have been studied by static electronic structure calculations and surface-hopping dynamics simulations based on the Zhu-Nakamura theory. Various stable structures are obtained in the optimization because of different orientations of methyl-furyl part with respect to the salicylaldimine part and different orientations of hydroxy group with respect to the benzene ring. Upon photoexcitation into the first excited state, bond isomerization in the salicylaldimine part is completely suppressed until the strong excited-state hydrogen bond is broken. The decay pathway involves two excited-state minima, one in cis-enol form and the other in cis-keto form. After the excited-state proton transfer, twists of bonds lead to a conical intersection between the ground and excited states. After internal conversion around a conical intersection, the molecule is stabilized in cis- or trans-keto form. If the reverse hydrogen transfer process occurs in the ground state, the molecule will finally end up in the cis-enol region. The cis-keto and trans-keto isomers are observed as photoproducts. According to our full-dimensional nonadiabatic dynamics simulations, we find the excited-state intramolecular proton transfer and torsions of three single bonds in the chain to be responsible for photoisomerization of the second stablest isomer of N-salicilydenemethylfurylamine.

Application of new nuclear de-excitation model of PHITS for prediction of isomer yield and prompt gamma-ray production

NASA Astrophysics Data System (ADS)

Ogawa, Tatsuhiko; Hashimoto, Shintaro; Sato, Tatsuhiko; Niita, Koji

2014-06-01

A new nuclear de-excitation model, intended for accurate simulation of isomeric transition of excited nuclei, was incorporated into PHITS and applied to various situations to clarify the impact of the model. The case studies show that precise treatment of gamma de-excitation and consideration for isomer production are important for various applications such as detector performance prediction, radiation shielding calculations and the estimation of radioactive inventory including isomers.

Shapes displayed with durations in the microsecond range do not obey Bloch's law of temporal summation

PubMed Central

Greene, Ernest; Ogden, R. Todd

2013-01-01

Shape patterns were displayed with simultaneous brief flashes from a light-emitting diode array. Flash durations in the microsecond range and luminous intensities were adjusted to vary the degree of successful shape recognition. Four experiments were conducted to test whether Bloch's law would apply in this task. Bloch's law holds that for very brief flashes the perceptual threshold is determined by the total number of photons being delivered, i.e., there is reciprocity of intensity and duration. The present results did not find that effectiveness of flashes was based on the total quantity of photons, as predicted by Bloch's law. Additionally, the evidence points to a visual mechanism that has ultra-high temporal precision that either registers the rate of photon flux or the duration of flashes. PMID:24349700

Molecular structure of the trans and cis isomers of metal-free phthalocyanine studied by gas-phase electron diffraction and high-level quantum chemical calculations: NH tautomerization and calculated vibrational frequencies.

PubMed

Strenalyuk, Tatyana; Samdal, Svein; Volden, Hans Vidar

2008-05-29

The molecular structure of the trans isomer of metal-free phthalocyanine (H2Pc) is determined using the gas electron diffraction (GED) method and high-level quantum chemical calculations. B3LYP calculations employing the basis sets 6-31G**, 6-311++G**, and cc-pVTZ give two tautomeric isomers for the inner H atoms, a trans isomer having D2h symmetry and a cis isomer having C2v symmetry. The trans isomer is calculated to be 41.6 (B3LYP/6-311++G**, zero-point corrected) and 37.3 kJ/mol (B3LYP/cc-pVTZ, not zero-point corrected) more stable than the cis isomer. However, Hartree-Fock (HF) calculations using different basis sets predict that cis is preferred and that trans does not exist as a stable form of the molecule. The equilibrium composition in the gas phase at 471 degrees C (the temperature of the GED experiment) calculated at the B3LYP/6-311++G** level is 99.8% trans and 0.2% cis. This is in very good agreement with the GED data, which indicate that the mole fraction of the cis isomer is close to zero. The transition states for two mechanisms of the NH tautomerization have been characterized. A concerted mechanism where the two H atoms move simultaneously yields a transition state of D2h symmetry and an energy barrier of 95.8 kJ/mol. A two-step mechanism where a trans isomer is converted to a cis isomer, which is converted into another trans isomer, proceeds via two transition states of C(s) symmetry and an energy barrier of 64.2 kJ/mol according to the B3LYP/6-311++G** calculation. The molecular geometry determined from GED is in very good agreement with the geometry obtained from the quantum chemical calculations. Vibrational frequencies, IR, and Raman intensities have been calculated using B3LYP/6-311++G**. These calculations indicate that the molecule is rather flexible with six vibrational frequencies in the range of 20-84 cm(-1) for the trans isomer. The cis isomer might be detected by infrared matrix spectroscopy since the N-H stretching frequencies are

[Investigation on simultaneous determination of dihydroxybenzene isomers in water samples using multi-walled carbon nanotube modified screen-printed electrode].

PubMed

Li, Yuan-Ting; Li, Da-Wei; Song, Wei; Long, Yi-Tao

2011-02-01

A disposable electrode, multi-walled carbon nanotube modified screen printed electrode (MWCNT/SPE), had been fabricated using screen printing technology and drop-coating method to determine dihydroxybenzene isomers (hydroquinone, catechol and resorcinol). The cyclic voltammetry behavior of dihydroxybenzene isomers had been investigated with the MWCNT/SPE. The results reveal that MWCNT/SPE, which shows a strong electrocatalytic activity for the oxidation of dihydroxybenzenes, can entirely separate the oxidation peaks of them. According to differential pulse voltammetry tests, the peak currents of dihydroxybenzene isomers are linear to their concentrations at the range of 8.20 x 10(-6) -1.00 x 10(-3), 8.20 x 10(-6) -1.00 x 10(-3) and 1.64 x 10(-5) -1.16 x 10(-3) mol x L(-1), with the detection limits of 4.34 x 10(-6), 3.42 x 10(-6) and 6.70 x 10(-6) mol x L(-1) for hydroquinone, catechol and resorcinol, respectively. For the determination of dihydroxybenzene isomers in water samples, the value of recovery found by standard addition method was in the range of 96.2%-104.9%. These results indicate MWCNT/SPE can be applied to rapid in-situ determination of dihydroxybenzenes-polluted water samples.

Identification of Spilled Oil from the MV Marathassa (Vancouver, Canada 2015) Using Alkyl PAH Isomer Ratios.

PubMed

Morales-Caselles, Carmen; Yunker, Mark B; Ross, Peter S

2017-07-01

On the morning of April 9, 2015, citizens in Vancouver (British Columbia, Canada) awoke to the sight and smell of oil on the shores of popular downtown beaches. Because the oil also had spread over the shallow seawater intakes for the Vancouver Aquarium, a preliminary screening of samples was performed as a prompt, first response to assess the risks to the Aquarium collection and guide the emergency operational response. A subsequent, more detailed examination for the presence of spilled oil in sediment, biota and water samples from the Vancouver Harbour region was then conducted based on the analysis of a large suite of alkanes, petroleum biomarkers, parent polycyclic aromatic hydrocarbons (PAHs) and alkyl PAH isomers. Most of the commonly applied biomarker ratios exhibit similar values for the spilled oil, Alberta oil (the main petroleum source for British Columbia), and pre-spill and un-oiled sediment samples. In contrast, alkyl PAH isomer ratios showed a clear distinction between the spilled oil and pre-spill samples, with the largest differences shown by isomers of the methyl fluoranthene/pyrene alkyl PAH series. This novel use of alkyl PAH isomers for fingerprinting petroleum helped to confirm the grain carrier MV Marathassa as the source of the oil that affected beach and mussel samples to document definitively the spread of the oil and to establish which samples contained a mix of the oil and hydrocarbons linked to historical activities. Finally, an initial evaluation of the biological risks of the MV Marathassa oil spill in Vancouver Harbour showed that oiled beach sediments had priority parent PAH concentrations that are likely to harm marine life.

AN ISOMER PREDICTION MODEL FOR PCNS, PCDD/FS, AND PCBS FROM MUNICIPAL WASTE INCINERATORS

EPA Science Inventory

Isomer patterns of polychlorinated naphthalenes (PCNs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated biphenyls (PCBs) from municipal waste incinerators (MWIs) were predicted by a model based on dechlorination kinetics from the most-chlorinated species. Successfu...

Complete Hexose Isomer Identification with Mass Spectrometry

NASA Astrophysics Data System (ADS)

Nagy, Gabe; Pohl, Nicola L. B.

2015-04-01

The first analytical method is presented for the identification and absolute configuration determination of all 24 aldohexose and 2-ketohexose isomers, including the D and L enantiomers for allose, altrose, galactose, glucose, gulose, idose, mannose, talose, fructose, psicose, sorbose, and tagatose. Two unique fixed ligand kinetic method combinations were discovered to create significant enough energetic differences to achieve chiral discrimination among all 24 hexoses. Each of these 24 hexoses yields unique ratios of a specific pair of fragment ions that allows for simultaneous determination of identification and absolute configuration. This mass spectrometric-based methodology can be readily employed for accurate identification of any isolated monosaccharide from an unknown biological source. This work provides a key step towards the goal of complete de novo carbohydrate analysis.

227 Views of RNA: Is RNA Unique in Its Chemical Isomer Space?

PubMed Central

Meringer, Markus; Goodwin, Jay

2015-01-01

Abstract Ribonucleic acid (RNA) is one of the two nucleic acids used by extant biochemistry and plays a central role as the intermediary carrier of genetic information in transcription and translation. If RNA was involved in the origin of life, it should have a facile prebiotic synthesis. A wide variety of such syntheses have been explored. However, to date no one-pot reaction has been shown capable of yielding RNA monomers from likely prebiotically abundant starting materials, though this does not rule out the possibility that simpler, more easily prebiotically accessible nucleic acids may have preceded RNA. Given structural constraints, such as the ability to form complementary base pairs and a linear covalent polymer, a variety of structural isomers of RNA could potentially function as genetic platforms. By using structure-generation software, all the potential structural isomers of the ribosides (BC5H9O4, where B is nucleobase), as well as a set of simpler minimal analogues derived from them, that can potentially serve as monomeric building blocks of nucleic acid–like molecules are enumerated. Molecules are selected based on their likely stability under biochemically relevant conditions (e.g., moderate pH and temperature) and the presence of at least two functional groups allowing the monomers to be incorporated into linear polymers. The resulting structures are then evaluated by using molecular descriptors typically applied in quantitative structure–property relationship (QSPR) studies and predicted physicochemical properties. Several databases have been queried to determine whether any of the computed isomers had been synthesized previously. Very few of the molecules that emerge from this structure set have been previously described. We conclude that ribonucleosides may have competed with a multitude of alternative structures whose potential proto-biochemical roles and abiotic syntheses remain to be explored. Key Words: Evolution—Chemical evolution�

Pilot-scale production of conjugated linoleic acid-rich soy oil by photoirradiation.

PubMed

Jain, V P; Proctor, A; Lall, R

2008-05-01

Conjugated linoleic acid (CLA) is found naturally in dairy and beef products at levels of 0.2% to 2% of the total fat. A more concentrated source of dietary CLA, low in saturated fat, would be highly desirable to obtain optimum CLA levels of about 3 g/d. We recently reported photoisomerization of soy oil with iodine catalysis to be a simple way of producing CLA in laboratory without high-energy input or expensive enzymes and microorganisms. However, a long irradiation time of 144 h has been a limitation for this technique to be of practical value. The objectives of this study were to build a pilot plant unit to rapidly produce high-CLA soy oil by photoirradiation and optimize the processing parameters to obtain high-CLA soy oil. Degassed oil with dissolved-iodine catalyst was irradiated by UV lamps in an illuminated laminar flow unit (ILFU). The ILFU consists of 2 borosilicate glass plates in a silicone lined stainless steel frame. The static mode of operation yielded 5.7% of total CLA isomers and performed twice as well than the continuous mode with 2.5% of total CLA. Irradiating oil in a static mode with reflective surfaces increased the CLA yields 3-fold to 16.4%. About 22% of total CLA isomers can be rapidly produced from soy oil linoleic acid with 0.35% iodine catalyst in a 0.5-cm-thick oil layer maintained at 48 degrees C for 12 h. The peroxide value and GC-MS analysis did not identify any volatile compounds characteristic of lipid oxidation. This study is a definitive step toward the commercialization of large-scale production of CLA-rich soy oil.

New decay modes of the high-spin isomer of 124Cs

NASA Astrophysics Data System (ADS)

Radich, A. J.; Garrett, P. E.; Andreoiu, C.; Ball, G. C.; Bianco, L.; Bildstein, V.; Chagnon-Lessard, S.; Cross, D. S.; Demand, G. A.; Diaz Varela, A.; Dunlop, R.; Finlay, P.; Garnsworthy, A. B.; Hackman, G.; Hadinia, B.; Jigmeddorj, B.; Laffoley, A. T.; Leach, K. G.; McGee, E.; Michetti-Wilson, J.; Orce, J. N.; Rajabali, M. M.; Rand, E. T.; Starosta, K.; Sumithrarachchi, C. S.; Svensson, C. E.; Triambak, S.; Wang, Z. M.; Williams, S. J.; Wong, J.; Wood, J. L.; Yates, S. W.

2017-09-01

A new β+/EC branch of 0.11± 0.02% from the (7)+ isomer of 124Cs was identified in a measurement of the decay of 124Cs using the 8π spectrometer at TRIUMF. Combinations of γ-γ, γ-e-, and e--e- coincidence data were used to further investigate the isomeric decay. Six new transitions were observed and their branching ratios were measured.

New transitions and feeding of the Jπ=(8+) isomer in 186Re

NASA Astrophysics Data System (ADS)

Matters, D. A.; Fotiades, N.; Carroll, J. J.; Chiara, C. J.; McClory, J. W.; Kawano, T.; Nelson, R. O.; Devlin, M.

2015-11-01

The spallation neutron source at the Los Alamos Neutron Science Center Weapons Neutron Research facility was used to populate excited states in 186Re via (n ,2 n γ ) reactions on an enriched 187Re target. Gamma rays were detected with the GErmanium Array for Neutron Induced Excitations spectrometer, a Compton-suppressed array of 18 HPGe detectors. Incident neutron energies were determined by the time-of-flight technique and used to obtain γ -ray excitation functions for the purpose of identifying γ rays by reaction channel. Analysis of the singles γ -ray spectrum gated on the neutron energy range 10 ≤En≤25 MeV resulted in five transitions and one level added to the 186Re level scheme. The additions include the placement of three γ rays at 266.7, 381.2, and 647.7 keV which have been identified as feeding the 2.0 ×105yr , Jπ=(8+) isomer and yield an improved value of 148.2 (5 )keV for the isomer energy. These transitions may have astrophysical implications related to the use of the Re-Os cosmochronometer.

Kinetic properties of the human liver cytosolic aldehyde dehydrogenase for retinal isomers.

PubMed

Bhat, P V; Samaha, H

1999-01-15

Retinoic acid exerts pleiotropic effects by acting through two families of nuclear receptors, RAR and RXR. All-trans and 9-cis retinoic acid bind RARs, whereas 9-cis retinoic acid binds and activates only the RXRs. To understand the role of human liver cytosolic aldehyde dehydrogenase (ALDH1) in retinoic acid synthesis, we examined the ability of ALDH 1 to catalyze the oxidation of the naturally occurring retinal isomers. ALDH1 catalyzed the oxidation of all-trans, 9-cis, and 13-cis retinal with equal efficiency. However, the affinity to all-trans retinal (Km = 2.2 microM) was twofold higher than to 9-cis (Km = 5.5 microM) and 13-cis (Km = 4.6 microM) retinal. All-trans retinol was a potent inhibitor of ALDH1 activity, and inhibited all-trans retinal oxidation uncompetitively. Comparison of the kinetic properties of ALDH1 for retinal isomers with those of previously reported rat kidney retinal dehydrogenase showed distinct differences, suggesting that ALDH1 may play a different role in retinal metabolism in liver.

Chemical variation in Piper aduncum and biological properties of its dillapiole-rich essential oil.

PubMed

de Almeida, Roseli R P; Souto, Raimundo N P; Bastos, Cleber N; da Silva, Milton H L; Maia, José G S

2009-09-01

The essential oils of the specimens of Piper aduncum that occur in deforested areas of Brazilian Amazon, North Brazil, are rich in dillapiole (35-90%), a derivative of phenylpropene, to which are attributed biological properties. On the other hand, the oils of the specimens with occurrence in the Atlantic Forest, and Northeastern and Southeastern Brazil, do not contain dillapiole, but only terpene compounds such as (E)-nerolidol and linalool. One specimen existing in the Amazon was hydrodistilled. The obtained oil was fractioned on a silica chromatographic column, resulting in fractions rich in dillapiole (95.0-98.9%) utilized for analyses by GC and GC/MS, structural characterization by NMR, confirmation of their biological properties, and to obtain the isomer isodillapiole. Dillapiole showed a fungicide action against the fungus Clinipellis perniciosa (witches' broom) by inhibition of its basidiospores, in concentrations ranging from 0.6 to 1.0 ppm. The larvicide and insecticide actions of dillapiole were tested against the larvae and the adult insects of Anopheles marajoara and Aedes aegypti (malaria and dengue mosquitoes), resulting in mortality of the larvae (48 h, 100%) at a concentration of 100 ppm, and mortality of the insects (30 min, 100%) at a concentration of 600 ppm. The isomeric isodillapiole showed no significant activity in the same biological tests.

Effect of food processing on degradation of hexachlorocyclohexane and its isomers in milk

PubMed Central

Singh, Sujatha; Nelapati, Krishnaiah

2017-01-01

Aim: To study the effect of different food processing techniques on the degradation of organochlorine compounds (α, β, ɣ and δ hexachlorocyclohexane isomers (HCH)) residues in both natural and fortified samples of milk. Materials and Methods: Raw milk samples are collected from the local areas of Hyderabad, India. Naturally and fortified milk samples (HCH) were subjected to various food processing techniques, pasteurization (63ºC for ½ h), sterilization (121ºC for 15 min) and boiling for 5 min and analyzed by gas chromatography with electron capture detector using quick, easy, cheap, effective, rugged and safe method for multiresidue analysis of pesticides in milk with slight modification. Results: The final mean residual concentration of pesticide in milk after heat processing and percentage of degradation were calculated with respective treatments. Conclusion: Heat treatments are highly effective on reduction of mean residual concentration of HCH in milk. In which Sterilization and boiling proved to be more effective in degradation of HCH isomers. PMID:28435187

Effect of food processing on degradation of hexachlorocyclohexane and its isomers in milk.

PubMed

Singh, Sujatha; Nelapati, Krishnaiah

2017-03-01

To study the effect of different food processing techniques on the degradation of organochlorine compounds (α, β, ɣ and δ hexachlorocyclohexane isomers (HCH)) residues in both natural and fortified samples of milk. Raw milk samples are collected from the local areas of Hyderabad, India. Naturally and fortified milk samples (HCH) were subjected to various food processing techniques, pasteurization (63ºC for ½ h), sterilization (121ºC for 15 min) and boiling for 5 min and analyzed by gas chromatography with electron capture detector using quick, easy, cheap, effective, rugged and safe method for multiresidue analysis of pesticides in milk with slight modification. The final mean residual concentration of pesticide in milk after heat processing and percentage of degradation were calculated with respective treatments. Heat treatments are highly effective on reduction of mean residual concentration of HCH in milk. In which Sterilization and boiling proved to be more effective in degradation of HCH isomers.

E 5 decay from the J π = 11 / 2 - isomer in Ba 137

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moran, K.; McCutchan, E. A.; Lister, C. J.

2014-10-01

A new gamma-decay branch has been found from the well-known 661.659(3)-keV J(pi) = 11/2(-), T-1/2 = 2.552(1) min isomer in Ba-137 which is populated in the beta decay of Cs-137. The new 377.9(3)-keV gamma ray connects the isomer to the low-lying 283.5 keV, J(pi) = 1/2(-) state. It is of near-pure E5 character. The decay has a gamma branching ratio (Br-gamma = Gamma(gamma)/Gamma(tot)) of 1.12(9) x 10(-7). The new decay has a B(E5) of 0.71(6) W.u. [ B(E5) down arrow= 6.5(6) x 10(5) e(2) fm(10)], a value consistent with other "single-particle" E5 decays in the region. The new decay branchmore » is of topical interest, as it competes with the much-sought "two-photon" second-order electromagnetic decay from this state.« less

Determination of nonylphenol isomers in landfill leachate and municipal wastewater using steam distillation extraction coupled with comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry.

PubMed

Zhang, Caixiang; Eganhouse, Robert P; Pontolillo, James; Cozzarelli, Isabelle M; Wang, Yanxin

2012-03-23

4-Nonylphenols (4-NPs) are known endocrine disruptors and by-products of the microbial degradation of nonylphenol polyethoxylate surfactants. One of the challenges to understanding the toxic effects of nonylphenols is the large number of isomers that may exist in environmental samples. In order to attribute toxic effects to specific compounds, a method is needed for the separation and quantitation of individual nonylphenol isomers. The pre-concentration methods of solvent sublimation, solid-phase extraction or liquid-liquid extraction prior to chromatographic analysis can be problematic because of co-extraction of thousands of compounds typically found in complex matrices such as municipal wastewater or landfill leachate. In the present study, steam distillation extraction (SDE) was found to be an effective pre-concentration method for extraction of 4-NPs from leachate and wastewater, and comprehensive two-dimensional gas chromatography (GC×GC) coupled with fast mass spectral data acquisition by time-of-flight mass spectrometry (ToFMS) enhanced the resolution and identification of 4-NP isomers. Concentrations of eight 4-NP isomers were determined in leachate from landfill cells of different age and wastewater influent and effluent samples. 4-NP isomers were about 3 times more abundant in leachate from the younger cell than the older one, whereas concentrations in wastewater effluent were either below detection limits or <1% of influent concentrations. 4-NP isomer distribution patterns were found to have been altered following release to the environment. This is believed to reflect isomer-specific degradation and accumulation of 4-NPs in the aquatic environment. Copyright © 2012 Elsevier B.V. All rights reserved.

Determination of nonylphenol isomers in landfill leachate and municipal wastewater using steam distillation extraction coupled with comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry

USGS Publications Warehouse

Zhang, Caixiang; Eganhouse, Robert P.; Pontolillo, James; Cozzarelli, Isabelle M.; Wang, Yanxin

2012-01-01

4-Nonylphenols (4-NPs) are known endocrine disruptors and by-products of the microbial degradation of nonylphenol polyethoxylate surfactants. One of the challenges to understanding the toxic effects of nonylphenols is the large number of isomers that may exist in environmental samples. In order to attribute toxic effects to specific compounds, a method is needed for the separation and quantitation of individual nonylphenol isomers. The pre-concentration methods of solvent sublimation, solid-phase extraction or liquid–liquid extraction prior to chromatographic analysis can be problematic because of co-extraction of thousands of compounds typically found in complex matrices such as municipal wastewater or landfill leachate. In the present study, steam distillation extraction (SDE) was found to be an effective pre-concentration method for extraction of 4-NPs from leachate and wastewater, and comprehensive two-dimensional gas chromatography (GC × GC) coupled with fast mass spectral data acquisition by time-of-flight mass spectrometry (ToFMS) enhanced the resolution and identification of 4-NP isomers. Concentrations of eight 4-NP isomers were determined in leachate from landfill cells of different age and wastewater influent and effluent samples. 4-NP isomers were about 3 times more abundant in leachate from the younger cell than the older one, whereas concentrations in wastewater effluent were either below detection limits or <1% of influent concentrations. 4-NP isomer distribution patterns were found to have been altered following release to the environment. This is believed to reflect isomer-specific degradation and accumulation of 4-NPs in the aquatic environment.

Novel opioid cyclic tetrapeptides: Trp isomers of CJ-15,208 exhibit distinct opioid receptor agonism and short-acting κ opioid receptor antagonism.

PubMed

Ross, Nicolette C; Reilley, Kate J; Murray, Thomas F; Aldrich, Jane V; McLaughlin, Jay P

2012-02-01

The κ opioid receptor antagonists demonstrate potential for maintaining abstinence from psychostimulant abuse, but existing non-peptide κ-receptor selective antagonists show exceptionally long activity. We hypothesized that the L- and D-Trp isomers of CJ-15,208, a natural cyclic tetrapeptide reported to be a κ-receptor antagonist in vitro, would demonstrate short-acting, dose-dependent antagonism in vivo, preventing reinstatement of cocaine-seeking behaviour. Affinity, selectivity and efficacy of the L-Trp and D-Trp isomers for opioid receptors were assessed in vitro in radioligand and GTPγS binding assays. Opioid receptor agonist and antagonist activities were characterized in vivo following i.c.v. administration with the 55°C warm water tail-withdrawal assay. The D-Trp isomer, which demonstrated primarily κ-receptor selective antagonist activity, was further evaluated for its prevention of stress- and drug-induced reinstatement of extinguished cocaine conditioned place preference (CPP). The two isomers showed similar affinity and selectivity for κ receptors (K(i)  30-35 nM) as well as κ receptor antagonism in vitro. As expected, the D-Trp cyclic tetrapeptide exhibited minimal agonist activity and induced dose-dependent κ-receptor selective antagonism lasting less than 18 h in vivo. Pretreatment with this peptide prevented stress-, but not cocaine-induced, reinstatement of extinguished cocaine CPP. In contrast, the L-Trp cyclic tetrapeptide unexpectedly demonstrated mixed opioid agonist/antagonist activity. The L-Trp and the D-Trp isomers of CJ-15,208 demonstrate stereospecific opioid activity in vivo. The relatively brief κ opioid receptor antagonism, coupled with the prevention of stress-induced reinstatement of extinguished cocaine-seeking behaviour, suggests the D-Trp isomer could be used therapeutically to maintain abstinence from psychostimulant abuse. © 2011 The Authors. British Journal of Pharmacology © 2011 The British Pharmacological

IsoMS: automated processing of LC-MS data generated by a chemical isotope labeling metabolomics platform.

PubMed

Zhou, Ruokun; Tseng, Chiao-Li; Huan, Tao; Li, Liang

2014-05-20

A chemical isotope labeling or isotope coded derivatization (ICD) metabolomics platform uses a chemical derivatization method to introduce a mass tag to all of the metabolites having a common functional group (e.g., amine), followed by LC-MS analysis of the labeled metabolites. To apply this platform to metabolomics studies involving quantitative analysis of different groups of samples, automated data processing is required. Herein, we report a data processing method based on the use of a mass spectral feature unique to the chemical labeling approach, i.e., any differential-isotope-labeled metabolites are detected as peak pairs with a fixed mass difference in a mass spectrum. A software tool, IsoMS, has been developed to process the raw data generated from one or multiple LC-MS runs by peak picking, peak pairing, peak-pair filtering, and peak-pair intensity ratio calculation. The same peak pairs detected from multiple samples are then aligned to produce a CSV file that contains the metabolite information and peak ratios relative to a control (e.g., a pooled sample). This file can be readily exported for further data and statistical analysis, which is illustrated in an example of comparing the metabolomes of human urine samples collected before and after drinking coffee. To demonstrate that this method is reliable for data processing, five (13)C2-/(12)C2-dansyl labeled metabolite standards were analyzed by LC-MS. IsoMS was able to detect these metabolites correctly. In addition, in the analysis of a (13)C2-/(12)C2-dansyl labeled human urine, IsoMS detected 2044 peak pairs, and manual inspection of these peak pairs found 90 false peak pairs, representing a false positive rate of 4.4%. IsoMS for Windows running R is freely available for noncommercial use from www.mycompoundid.org/IsoMS.

Linear and branched perfluorooctane sulfonate isomers in technical product and environmental samples by in-port derivatization-gas chromatography-mass spectrometry.

PubMed

Chu, Shaogang; Letcher, Robert J

2009-06-01

Perfluorooctane sulfonate (PFOS) is found globally as an environmental contaminant and is highly bioaccumulative in exposed biota including humans. However, there is a dearth of environmental information on the isomeric profile of PFOS, especially in biological samples, which requires suitable analysis methods for the identification and quantification of ultratrace amounts. In the present study, a novel method was developed that incorporates clean up by solid-phase extraction (SPE) WAX cartridges and in-port derivatization-gas chromatography-mass spectrometry (GC/MS) to identify and quantitatively determine linear PFOS (L-PFOS) and branched (monotrifluoromethyl and bistrifluoromethyl) isomers in PFOS technical product and in environmentally relevant biological samples. Tetrabutylammonium hydroxide (TBAH) was used for derivatization via an in situ pyrolytic alkylation reaction that occurred in the GC injector and generated butyl PFOS isomer derivatives. In addition to L-PFOS, ten branched PFOS isomers were identified in the technical product. The environmental relevance of branched PFOS isomers in addition to L-PFOS was evidenced by the presence of six branched and L-PFOS in representative herring gull and double-crested cormorant egg, and polar bear liver and plasma samples from the Great Lakes and Arctic, respectively. For all PFOS isomers in the technical product and biota samples the method demonstrated high sensitivity with the limit of detection (LOD) ranging from 0.05 to 0.25 ng/mL, with exception of L-PFOS where the LOD was 1.46 ng/mL. For the biotic samples, the method detection limits (MDLs) were slightly higher than the LODs and ranged from 0.09 to 0.46 ng/g wet weight (w.w.) with exception of L-PFOS (MDL = 6.87 ng/g w.w.).

Simple Preparation and NMR Analysis of mer and fac Isomers of Tris(1,1,1-trifluoro-2,4-pentanedionato)cobalt(III). An Experiment for the Inorganic Chemistry Laboratory

NASA Astrophysics Data System (ADS)

Jensen, Ashley W.; O'Brien, Brian A.

2001-07-01

A one-step procedure for the preparation of tris(1,1,1-trifluoro-2,4-pentanedionato)cobalt(III) from hydrated cobalt(II) carbonate and 10% hydrogen peroxide, in which tert-butyl alcohol is used as a component of the solvent, is described. The procedure is short, simple, and less hazardous than procedures reported in the literature, and the starting materials are readily available and inexpensive. The product is a mixture of mer and fac isomers that can be separated by silica gel chromatography with toluene as the eluent. Thin-layer chromatography is used to obtain a collective class sample of each isomer for 1H, 13C, and 19F NMR analysis. The NMR analyses clearly illustrate the threefold rotational symmetry of the fac isomer and the lack of symmetry of the mer isomer. Detailed NMR data are provided for each isomer.

IR and Raman spectra of nitroanthracene isomers: substitional effects based on density functional theory study.

PubMed

Alparone, Andrea; Librando, Vito

2012-04-01

Structure, IR and Raman spectra of 1-, 2- and 9-nitroanthracene isomers (1-NA, 2-NA and 9-NA) were calculated and analyzed through density functional theory computations using the B3LYP functional with the 6-311+G** basis set. Steric and π-conjugative effects determine the characteristic ONCC dihedral angles, which vary from 0° (2-NA) to 28-29° (1-NA) and 59° (9-NA), influencing the relative order of stability along the series 9-NA<1-NA<2-NA. The spectral regions at wavenumber values>3000 cm(-1) and <1000 cm(-1) little depend on the substituent position. The Raman and IR intensity values of the characteristic symmetric nitro group stretching transition, appearing between 1310 and 1345 cm(-1), are rather sensitive to the position of the substituent, decreasing regularly on passing from the planar to the NO2-rotated isomers (9-NA<1-NA<2-NA). In the medium-energy spectral region (1000-1700 cm(-1)), the number and the relative position of the strongest Raman bands are of potential utility to discriminate the NA isomers. Structural and spectroscopic results suggest that the unknown mutagenic activity of 1-NA is expected to be between that of 9-NA and 2-NA. Copyright © 2011 Elsevier B.V. All rights reserved.

Dehydrogenation reactions of cyclic C(2)B(2)N(2)H(12) and C(4)BNH(12) isomers.

PubMed

Matus, Myrna H; Liu, Shih-Yuan; Dixon, David A

2010-02-25

The energetics for different dehydrogenation pathways of C(2)B(2)N(2)H(12) and C(4)BNH(12) cycles were calculated at the B3LYP/DGDZVP2 and G3(MP2) levels with additional calculations at the CCSD(T)/complete basis set level. The heats of formation of the different isomers were calculated from the G3(MP2) relative energies and the heats of formation of the most stable isomers of c-C(2)B(2)N(2)H(6), c-C(2)B(2)N(2)H(12), and c-C(4)BNH(12) at the CCSD(T)/CBS including additional corrections together with the previously reported value for c-C(4)BNH(6). Different isomers were analyzed for c-C(2)B(2)N(2)H(x) and c-C(4)BNH(x) (x = 6 and 12), and the most stable cyclic structures were those with C-C-B-N-B-N and C-C-C-C-B-N sequences, respectively. The energetics for the stepwise loss of three H(2) were predicted, and the most feasible thermodynamic pathways were found. Dehydrogenation of the lowest energy c-C(2)B(2)N(2)H(12) isomer (6-H(12)) is almost thermoneutral with DeltaH(3dehydro) = 3.4 kcal/mol at the CCSD(T)/CBS level and -0.6 kcal/mol at the G3(MP2) level at 298 K. Dehydrogenation of the lowest energy c-C(4)BNH(12) isomer (7-H(12)) is endothermic with DeltaH(3dehydro) = 27.9 kcal/mol at the CCSD(T)/CBS level and 23.5 kcal/mol at the G3(MP2) level at 298 K. Dehydrogenation across the B-N bond is more favorable as opposed to dehydrogenation across the B-C, N-C, and C-C bonds. Resonance stabilization energies in relation to that of benzene are reported as are NICS NMR chemical shifts for correlating with the potential aromatic character of the rings.

Ortho-para spin isomers of the protons in the methylene group--possible implications for protein structure.

PubMed

Shinitzky, Meir; Elitzur, Avshalom C

2006-09-01

The two hydrogen atoms attached to the carbon in the methylene group are of two different spin configurations, similar to those in the case of water: ortho, where the two proton spins are parallel to each other, and para, where they are antiparallel. The ortho configuration has three degenerate states, while the para configuration is singular, leading to a statistical ratio of these isomers 3:1 ortho/para. Such spin isomers are present in glycine and most chiral amino acids where they may induce broadening of structural zones, a possibility which remains to be assessed. The implications of this neglected possibility could be far-reaching, in particular with respect to protein structure and the origins of biochirality.

Development of the Los Alamos continuous high average-power microsecond pulser ion accelerator

NASA Astrophysics Data System (ADS)

Bitteker, L. J.; Wood, B. P.; Davis, H. A.; Waganaar, W. J.; Boyd, I. D.; Lovberg, R. H.

2000-10-01

The continuous high average-power microsecond pulser (CHAMP) ion accelerator is being constructed at Los Alamos National Laboratory. Progress on the testing of the CHAMP diode is discussed. A direct simulation Monte Carlo computer code is used to investigate the puffed gas fill of the CHAMP anode. High plenum pressures and low plenum volumes are found to be desirable for effective gas puffs. The typical gas fill time is 150-180 μs from initiation of valve operation to end of fill. Results of anode plasma production at three stages of development are discussed. Plasma properties are monitored with electric and magnetic field probes. From this data, the near coil plasma density under nominal conditions is found to be on the order of 1×1016 cm-3. Large error is associated with this calculation due to inconsistencies between tests and the limitations of the instrumentation used. The diode insulating magnetic field is observed to result in lower density plasma with a more diffuse structure than for the cases when the insulating field is not applied. The importance of these differences in plasma quality on the beam production is yet to be determined.

The crystal structures of two isomers of 5-(phenyl-iso-thia-zol-yl)-1,3,4-oxa-thia-zol-2-one.

PubMed

Zhu, Shuguang; Schriver, Melbourne J; Hendsbee, Arthur D; Masuda, Jason D

2017-11-01

The syntheses and crystal structures of two isomers of phenyl iso-thia-zolyl oxa-thia-zolone, C 11 H 6 N 2 O 2 S 2 , are described [systematic names: 5-(3-phenyl-iso-thia-zol-5-yl)-1,3,4-oxa-thia-zol-2-one, (I), and 5-(3-phenyl-iso-thia-zol-4-yl)-1,3,4-oxa-thia-zol-2-one, (II)]. There are two almost planar (r.m.s. deviations = 0.032 and 0.063 Å) mol-ecules of isomer (I) in the asymmetric unit, which form centrosymmetric tetra-mers linked by strong S⋯N [3.072 (2) Å] and S⋯O contacts [3.089 (1) Å]. The tetra-mers are π-stacked parallel to the a -axis direction. The single mol-ecule in the asymmetric unit of isomer (II) is twisted into a non-planar conformation by steric repulsion [dihedral angles between the central iso-thia-zolyl ring and the pendant oxa-thia-zolone and phenyl rings are 13.27 (6) and 61.18 (7)°, respectively], which disrupts the π-conjugation between the heteroaromatic iso-thia-zoloyl ring and the non-aromatic oxa-thia-zolone heterocycle. In the crystal of isomer (II), the strong S⋯O [3.020 (1) Å] and S⋯C contacts [3.299 (2) Å] and the non-planar structure of the mol-ecule lead to a form of π-stacking not observed in isomer (I) or other oxa-thia-zolone derivatives.

Inositol Pentakisphosphate Isomers Bind PH Domains with Varying Specificity and Inhibit Phosphoinositide Interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

S Jackson; S Al-Saigh; C Schultz

2011-12-31

PH domains represent one of the most common domains in the human proteome. These domains are recognized as important mediators of protein-phosphoinositide and protein-protein interactions. Phosphoinositides are lipid components of the membrane that function as signaling molecules by targeting proteins to their sites of action. Phosphoinositide based signaling pathways govern a diverse range of important cellular processes including membrane remodeling, differentiation, proliferation and survival. Myo-Inositol phosphates are soluble signaling molecules that are structurally similar to the head groups of phosphoinositides. These molecules have been proposed to function, at least in part, by regulating PH domain-phosphoinositide interactions. Given the structural similaritymore » of inositol phosphates we were interested in examining the specificity of PH domains towards the family of myo-inositol pentakisphosphate isomers. In work reported here we demonstrate that the C-terminal PH domain of pleckstrin possesses the specificity required to discriminate between different myo-inositol pentakisphosphate isomers. The structural basis for this specificity was determined using high-resolution crystal structures. Moreover, we show that while the PH domain of Grp1 does not possess this high degree of specificity, the PH domain of protein kinase B does. These results demonstrate that some PH domains possess enough specificity to discriminate between myo-inositol pentakisphosphate isomers allowing for these molecules to differentially regulate interactions with phosphoinositides. Furthermore, this work contributes to the growing body of evidence supporting myo-inositol phosphates as regulators of important PH domain-phosphoinositide interactions. Finally, in addition to expanding our knowledge of cellular signaling, these results provide a basis for developing tools to probe biological pathway.« less

Analysis of the isomer ratios of polymethylated-DOTA complexes and the implications on protein structural studies

PubMed Central

Opina, Ana Christina L.; Strickland, Madeleine; Lee, Yong-Sok; Tjandra, Nico; Byrd, R. Andrew; Swenson, Rolf E.; Vasalatiy, Olga

2016-01-01

A rigidified and symmetrical polymethylated 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) ligand bearing four SSSS methyl groups in both the tetraaza ring and the acetate arms (SSSS-SSSS-M4DOTMA) was prepared. The isomer ratio of SSSS-SSSS-M4DOTMA complexed with a series of lanthanide ions was carefully investigated using RP-HPLC and NMR. A square antiprismatic (SAP) configuration was exclusively observed for the early lanthanides, while the twisted square antiprismatic (TSAP) geometry was preferred as the lanthanide ion size decreases. The late lanthanides preferentially adopted the TSAP geometry. One of the pendant arms was modified with a pyridyl disulfide group (SSSS-SSSS-M8SPy) for cysteine attachment and displayed a similar isomer trend as the parent compound, Ln-SSSS-SSSS-M4DOTMA. Covalent attachment to the ubiquitin S57C mutant showed resonances whose intensities are in agreement with the isomeric population observed by HPLC. Furthermore, the NOE experiments combined with quantum chemical calculations have unequivocally demonstrated that the SAP of Pr-SSSS-SSSS-M4DOTMA and Pr-SSSS-SSSS-M8SPy, as well as the TSAP of Yb-SSSS-SSSS-M8SPy are more stable than their corresponding isomers. PMID:26857249

Separation of Opiate Isomers Using Electrospray Ionization and Paper Spray Coupled to High-Field Asymmetric Waveform Ion Mobility Spectrometry

NASA Astrophysics Data System (ADS)

Manicke, Nicholas E.; Belford, Michael

2015-05-01

One limitation in the growing field of ambient or direct analysis methods is reduced selectivity caused by the elimination of chromatographic separations prior to mass spectrometric analysis. We explored the use of high-field asymmetric waveform ion mobility spectrometry (FAIMS), an ambient pressure ion mobility technique, to separate the closely related opiate isomers of morphine, hydromorphone, and norcodeine. These isomers cannot be distinguished by tandem mass spectrometry. Separation prior to MS analysis is, therefore, required to distinguish these compounds, which are important in clinical chemistry and toxicology. FAIMS was coupled to a triple quadrupole mass spectrometer, and ionization was performed using either a pneumatically assisted heated electrospray ionization source (H-ESI) or paper spray, a direct analysis method that has been applied to the direct analysis of dried blood spots and other complex samples. We found that FAIMS was capable of separating the three opiate structural isomers using both H-ESI and paper spray as the ionization source.

Streptomyces sp. is a powerful biotechnological tool for the biodegradation of HCH isomers: biochemical and molecular basis.

PubMed

Cuozzo, S A; Sineli, P E; Davila Costa, J; Tortella, G

2018-08-01

Actinobacteria are well-known degraders of toxic materials that have the ability to tolerate and remove organochloride pesticides; thus, they are used for bioremediation. The biodegradation of organochlorines by actinobacteria has been demonstrated in pure and mixed cultures with the concomitant production of metabolic intermediates including γ-pentachlorocyclohexene (γ-PCCH); 1,3,4,6-tetrachloro-1,4-cyclohexadiene (1,4-TCDN); 1,2-dichlorobenzene (1,2-DCB), 1,3-dichlorobenzene (1,3-DCB), or 1,4-dichlorobenzene (1,4-DCB); 1,2,3-trichlorobenzene (1,2,3-TCB), 1,2,4-trichlorobenzene (1,2,4-TCB), or 1,3,5-trichlorobenzene (1,3,5-TCB); 1,3-DCB; and 1,2-DCB. Chromatography coupled to mass spectrometric detection, especially GC-MS, is typically used to determine HCH-isomer metabolites. The important enzymes involved in HCH isomer degradation metabolic pathways include hexachlorocyclohexane dehydrochlorinase (LinA), haloalkane dehalogenase (LinB), and alcohol dehydrogenase (LinC). The metabolic versatility of these enzymes is known. Advances have been made in the identification of actinobacterial haloalkane dehydrogenase, which is encoded by linB. This knowledge will permit future improvements in biodegradation processes using Actinobacteria. The enzymatic and genetic characterizations of the molecular mechanisms involved in these processes have not been fully elucidated, necessitating further studies. New advances in this area suggest promising results. The scope of this paper encompasses the following: (i) the aerobic degradation pathways of hexachlorocyclohexane (HCH) isomers; (ii) the important genes and enzymes involved in the metabolic pathways of HCH isomer degradation; and (iii) the identification and quantification of intermediate metabolites through gas chromatography coupled to mass spectrometry (GC-MS).

Stable isomers and electronic, vibrational, and optical properties of WS2 nano-clusters: A first-principles study

NASA Astrophysics Data System (ADS)

Hafizi, Roohollah; Hashemifar, S. Javad; Alaei, Mojtaba; Jangrouei, MohammadReza; Akbarzadeh, Hadi

2016-12-01

In this paper, we employ an evolutionary algorithm along with the full-potential density functional theory (DFT) computations to perform a comprehensive search for the stable structures of stoichiometric (WS2)n nano-clusters (n = 1 - 9), within three different exchange-correlation functionals. Our results suggest that n = 5 and 8 are possible candidates for the low temperature magic sizes of WS2 nano-clusters while at temperatures above 500 Kelvin, n = 7 exhibits a comparable relative stability with n = 8. The electronic properties and energy gap of the lowest energy isomers were computed within several schemes, including semilocal Perdew-Burke-Ernzerhof and Becke-Lee-Yang-Parr functionals, hybrid B3LYP functional, many body based DFT+GW approach, ΔSCF method, and time dependent DFT calculations. Vibrational spectra of the lowest lying isomers, computed by the force constant method, are used to address IR spectra and thermal free energy of the clusters. Time dependent density functional calculation in a real time domain is applied to determine the full absorption spectra and optical gap of the lowest energy isomers of the WS2 nano-clusters.

Enhancing glycan isomer separations with metal ions and positive and negative polarity ion mobility spectrometry-mass spectrometry analyses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Xueyun; Zhang, Xing; Schocker, Nathaniel S.

Glycomics has become an increasingly important field of research since glycans play critical roles in biology processes ranging from molecular recognition and signaling to cellular communication. Glycans often conjugate with other biomolecules such as proteins and lipids, and alter their properties and functions, so understanding the effect glycans have on cellular systems is essential. However the analysis of glycans is extremely difficult due to their complexity and structural diversity (i.e., the number and identity of monomer units, and configuration of their glycosidic linkages and connectivities). In this work, we coupled ion mobility spectrometry with mass spectrometry (IMS-MS) to characterize glycanmore » standards and biologically important isomers of synthetic αGal-containing O-glycans including glycotopes of the protozoan parasite Trypanosoma cruzi, which is the causative agent of Chagas disease. IMS-MS results showed significant differences for the glycan structural isomers when analyzed in positive and negative polarity and complexed with different metal cations. These results suggest specific metal ions or ion polarities could be used to target and baseline separate glycan isomers of interest with IMS-MS.« less

The Dewar Isomer of 1,2-Dihydro-1,2-azaborinines: Isolation, Fragmentation, and Energy Storage.

PubMed

Edel, Klara; Yang, Xinyu; Ishibashi, Jacob S A; Lamm, Ashley N; Maichle-Mössmer, Cäcilia; Giustra, Zachary X; Liu, Shih-Yuan; Bettinger, Holger F

2018-05-04

The photochemistry of 1,2-dihydro-1,2-azaborinine derivatives was studied under matrix isolation conditions and in solution. Photoisomerization occurs exclusively to the Dewar valence isomers upon irradiation with UV light (>280 nm) with high quantum yield (46 %). Further photolysis with UV light (254 nm) results in the formation of cyclobutadiene and an iminoborane derivative. The thermal electrocyclic ring-opening reaction of the Dewar valence isomer back to the 1,2-dihydro-1-tert-butyldimethylsilyl-2-mesityl-1,2-azaborinine has an activation barrier of (27.0±1.2) kcal mol -1 . In the presence of the Wilkinson catalyst, the ring opening occurs rapidly and exothermically (ΔH=(-48±1) kcal mol -1 ) at room temperature. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of cis- and trans-octadecenoic acid positional isomers in edible fat and oil using gas chromatography-flame ionisation detector equipped with highly polar ionic liquid capillary column.

PubMed

Yoshinaga, Kazuaki; Asanuma, Masaharu; Mizobe, Hoyo; Kojima, Koichi; Nagai, Toshiharu; Beppu, Fumiaki; Gotoh, Naohiro

2014-10-01

In this study, the characterisation of all cis- and trans-octadecenoic acid (C18:1) positional isomers in partially hydrogenated vegetable oil (PHVO) and milk fat, which contain several cis- and trans-C18:1 positional isomers, was achieved by gas chromatography-flame ionisation detector equipped with a highly polar ionic liquid capillary column (SLB-IL111). Prior to analysis, the cis- and trans-C18:1 fractions in PHVO and milk fat were separated using a silver-ion cartridge. The resolution of all cis-C18:1 positional isomers was successfully accomplished at the optimal isothermal column temperature of 120 °C. Similarly, the positional isomers of trans-C18:1, except for trans-6-C18:1 and trans-7-C18:1, were separated at 120 °C. The resolution of trans-6-C18:1 and trans-7-C18:1 isomers was made possible by increasing the column temperature to 160 °C. This analytical method is suitable for determining the cis- and trans-C18:1 positional isomers in edible fats and oils. Copyright © 2014 Elsevier Ltd. All rights reserved.

Melting behavior of nanometer sized gold isomers

NASA Astrophysics Data System (ADS)

Liu, H. B.; Ascencio, J. A.; Perez-Alvarez, M.; Yacaman, M. J.

2001-09-01

In the present work, the melting behavior of nanometer sized gold isomers was studied using a tight-binding potential with a second momentum approximation. The cases of cuboctahedra, icosahedra, Bagley decahedra, Marks decahedra and star-like decahedra were considered. We calculated the temperature dependence of the total energy and volume during melting and the melting point for different types and sizes of clusters. In addition, the structural evolutions of the nanosized clusters during the melting transition were monitored and revealed. It is found that the melting process has three characteristic time periods for the intermediate nanosized clusters. The whole process includes surface disordering and reordering, followed by surface melting and a final rapid overall melting. This is a new observation, which it is in contrast with previous reports where surface melting is the dominant step.

Table of superdeformed nuclear bands and fission isomers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Firestone, R.B.; Singh, B.

A minimum in the second potential well of deformed nuclei was predicted and the associated shell gaps are illustrated in the harmonic oscillator potential shell energy surface calculations shown in this report. A strong superdeformed minimum in {sup 152}Dy was predicted for {beta}{sub 2}-0.65. Subsequently, a discrete set of {gamma}-ray transitions in {sup 152}DY was observed and, assigned to the predicted superdeformed band. Extensive research at several laboratories has since focused on searching for other mass regions of large deformation. A new generation of {gamma}-ray detector arrays is already producing a wealth of information about the mechanisms for feeding andmore » deexciting superdeformed bands. These bands have been found in three distinct regions near A=l30, 150, and 190. This research extends upon previous work in the actinide region near A=240 where fission isomers were identified and also associated with the second potential well. Quadrupole moment measurements for selected cases in each mass region are consistent with assigning the bands to excitations in the second local minimum. As part of our committment to maintain nuclear structure data as current as possible in the Evaluated Nuclear Structure Reference File (ENSDF) and the Table of Isotopes, we have updated the information on superdeformed nuclear bands. As of April 1994, we have complied data from 86 superdeformed bands and 46 fission isomers identified in 73 nuclides for this report. For each nuclide there is a complete level table listing both normal and superdeformed band assignments; level energy, spin, parity, half-life, magneto moments, decay branchings; and the energies, final levels, relative intensities, multipolarities, and mixing ratios for transitions deexciting each level. Mass excess, decay energies, and proton and neutron separation energies are also provided from the evaluation of Audi and Wapstra.« less

Identification of (2-aminopropyl)benzofuran (APB) phenyl ring positional isomers in internet purchased products.

PubMed

Stanczuk, Andrzej; Morris, Noreen; Gardner, Elizabeth A; Kavanagh, Pierce

2013-04-01

5-(2-Aminopropyl)benzofuran (5-APB), a 'research chemical' that was first reported by UK authorities to the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) in 2010, is anecdotally reported to produce a combination of stimulant and entactogenic effects. More recently, in 2011, 6-(2-aminopropyl)benzofuran (6-APB) was identified by Hungarian authorities. To confirm positional isomer identity in Internet purchased products, 4- 5- 6- and 7-APBs were synthesized and found to be separable by gas chromatography (as heptafluorobutyramide derivatives) and liquid chromatography. The analyses of products purchased from online vendors of 'research chemicals' identified the presence of 5- or 6-APBs. These findings were further confirmed by liquid chromatography-mass spectrometry and (1) H nuclear magnetic resonance spectroscopy. In products containing 6-APB, the 4- positional isomer was also identified and this may have arisen during the manufacturing process. Copyright © 2013 John Wiley & Sons, Ltd.

A new approach to highly sensitive determination of retinoic acid isomers by preconcentration with CdSe quantum dots.

PubMed

Torabi, Behzad; Shemirani, Farzaneh

2014-03-01

Unusual amounts of retinoic acid (RA) isomers play an important role in abnormal morphological development of mammals; such as rat embryos. Each isomer of RA has a unique function in first steps of embryonic life. In the current study, a new method for preconcentration and simultaneous determination of all-trans retinoic acid, 13-cis retinoic acid, 9-cis retinoic acid and 9,13-di-cis retinoic acid in rat whole rudimentary embryo culture (RWEC) has been developed. RA isomers were extracted from samples by conjugation to appropriate amount of surface modified CdSe quantum dots (QDs) prior to HPLC/UV determination. In order to quickly release of the analytes with unchanged form, separated RA-QD conjugation were irradiated by intensive near infrared wavelength (NIR). Low energy NIR irradiation results in maintaining the primary forms of RA isomers during the release. The conjugation and release mechanisms were described and experimental parameters were investigated in detail. Under optimized conditions, the method was linear in the range of 0.040-34.600 pmol g(-1) for all-trans RA (R(2)=0.9996), 0.070-34.200 pmol g(-1) for 13-cis RA (R(2)=0.9992), 0.050-35.300 pmol g(-1) for 9,13-di-cis RA (R(2)=0.9998) and 0.050-32.900 pmol g(-1) for 9-cis RA (R(2)=0.9990). The present method can be useful for retinoic acid monitoring in clinical studies. © 2013 Published by Elsevier B.V.

Accurate thermochemistry and spectroscopy of the oxygen-protonated sulfur dioxide isomers.

PubMed

Puzzarini, Cristina

2011-12-28

Despite the promising relevance of protonated sulfur dioxide in astrophysical and atmospheric fields, its thermochemical and spectroscopic characterization is very limited. High-level quantum-chemical calculations have shown that the most stable isomer is the cis oxygen-protonated sulfur dioxide, HOSO(+), while the trans form is about 2 kcal mol(-1) less stable; even less stable (by about 42 kcal mol(-1)) is the S-protonated isomer [V. Lattanzi et al., J. Chem. Phys., 2010, 133, 194305]. The enthalpy of formation for the cis- and trans-HOSO(+) is presented, based on the well tested HEAT protocol [A. Tajti et al., J. Chem. Phys., 2004, 121, 11599]. Systematically extrapolated ab initio energies, accounting for electron correlation through coupled cluster theory, including up to single, double, triple and quadruple excitations, have been corrected for core-electron correlation, anharmonic zero-point vibrational energy, diagonal Born-Oppenheimer and scalar relativistic effects. As a byproduct, proton affinity of sulfur dioxide and atomization energies have also been obtained at the same levels of theory. Vibrational and rotational spectroscopic properties have been investigated by means of composite schemes that allow us to account for truncation of basis set as well as core correlation. Where available, for both thermochemistry and spectroscopy, very good agreement with experimental data has been observed.

Anti-Leishmania and cytotoxic activities of perillaldehyde epoxide synthetic positional isomers.

PubMed

Keesen, Tatjana Souza Lima; da Silva, Larisse Virgolino; da Câmara Rocha, Juliana; Andrade, Luciana Nalone; Lima, Tamires Cardoso; de Sousa, Damião Pergentino

2018-03-13

Leishmaniasis belongs to a complex of zoonotic disease caused by protozoa of the genus Leishmania and is considered a major public health problem. Several essential oil chemical components have inhibitory effect against protozoa, including Leishmania donovani. Thus, the aim of this study was to evaluate for the first time the anti-Leishmania activity of two p-menthane monoterpene isomers (EPER-1: perillaldehyde 1,2-epoxide and EPER-2: perillaldehyde 8,9-epoxide) against L. donovani promastigotes as well as evaluating cytotoxic effect on mononuclear peripheral blood cells. Results of anti-Leishmania assay revealed that EPER-2 (IC 50  = 3.8 μg.mL -1 ) was 16-fold more potent than its isomer EPER-1 (IC 50  = 64.6 μg.mL -1 ). In contrast to PBMC cells, EPER-2 was not cytotoxic (IC 50  > 400 μg.mL -1 ) when compared to positive control. These data suggest that the disposition of epoxide group into the p-menthane skeleton affects the anti-Leishmania activity, being that the presence of the exocyclic epoxide group considerably increased potency. Thus, it was possible to observe that the location of the epoxide group into the p-menthane skeleton resulted in different potencies.

Monopole-driven shell evolution below the doubly magic nucleus 132Sn explored with the long-lived isomer in 126Pd.

PubMed

Watanabe, H; Lorusso, G; Nishimura, S; Otsuka, T; Ogawa, K; Xu, Z Y; Sumikama, T; Söderström, P-A; Doornenbal, P; Li, Z; Browne, F; Gey, G; Jung, H S; Taprogge, J; Vajta, Zs; Wu, J; Yagi, A; Baba, H; Benzoni, G; Chae, K Y; Crespi, F C L; Fukuda, N; Gernhäuser, R; Inabe, N; Isobe, T; Jungclaus, A; Kameda, D; Kim, G D; Kim, Y K; Kojouharov, I; Kondev, F G; Kubo, T; Kurz, N; Kwon, Y K; Lane, G J; Moon, C-B; Montaner-Pizá, A; Moschner, K; Naqvi, F; Niikura, M; Nishibata, H; Nishimura, D; Odahara, A; Orlandi, R; Patel, Z; Podolyák, Zs; Sakurai, H; Schaffner, H; Simpson, G S; Steiger, K; Suzuki, H; Takeda, H; Wendt, A; Yoshinaga, K

2014-07-25

A new isomer with a half-life of 23.0(8) ms has been identified at 2406 keV in (126)Pd and is proposed to have a spin and parity of 10(+) with a maximally aligned configuration comprising two neutron holes in the 1h(11/2) orbit. In addition to an internal-decay branch through a hindered electric octupole transition, β decay from the long-lived isomer was observed to populate excited states at high spins in (126)Ag. The smaller energy difference between the 10(+) and 7(-) isomers in (126)Pd than in the heavier N=80 isotones can be interpreted as being ascribed to the monopole shift of the 1h(11/2) neutron orbit. The effects of the monopole interaction on the evolution of single-neutron energies below (132)Sn are discussed in terms of the central and tensor forces.

The fingerprint nature of PCDD in iron ore sinter strand emissions, the effect of suppressants and alternative fuels, and the potential for comparison with the isomer profile of PCDF.

PubMed

Ooi, Tze C; Thompson, Dennis; Anderson, David R; Fisher, Ray

2018-01-01

It has been previously shown that the isomer profile of PCDF emissions from iron ore sinter plant only varies within limits even when suppressants or alternative fuels are added, to the extent that it can be said to have a 'fingerprint'. The isomer profiles of PCDD from tetra- to hexacholrodibenzo-p-dioxin from the same samples examined for PCDF emissions have been obtained, and show the same tendency for a 'fingerprint ' isomer distribution to occur. Occasional exceptionally high isomer abundances are observed, but these are uncommon. The potential for comparison of the abundances of PCDF and PCDD isomers with similar chlorination patterns to determine whether the same formation process is involved has been examined. It is found that co-elutions prevent extensive comparisons irrespective of whether the SP2331 or DB5ms column is used in the analyses for separation of isomers to provide the results used for comparisons, although they allow limited results to be obtained. It is suggested that analyses using the two chromatography columns to analyse the same sample in parallel could provide more resolution of the isomer profiles for use in comparisons. A pilot study using samples analysed using each column is limited because of detailed differences in the emissions profiles, but demonstrates that greater resolution is possible if the two columns are used to analyse one sample. Copyright © 2017 Elsevier Ltd. All rights reserved.

Mechanism for odd-electron anion generation of dihydroxybenzoic acid isomers in matrix-assisted laser desorption/ionization mass spectrometry with density functional theory calculations.

PubMed

Yamagaki, Tohru; Takeuchi, Michika; Watanabe, Takehiro; Sugahara, Kohtaro; Takeuchi, Takae

2016-12-30

Proton and radical are transferred between matrices and matrix and analyte in matrix-assisted laser desorption/ionization (MALDI) and these transfers drive ionization of analytes. The odd-electron anion [M-2H] •- was generated in dihydroxybenzoic acids (DHBs) and the ion abundance of the 2,5-DHB was the highest among six DHB isomers. We were interested in the mechanism of the ion generation of the odd-electron anion. The observed [M-2H] •- and [M-3H] - ions, which were generated with the hydrogen radical removed from the phenolic hydroxyl groups (OH) in DHB isomers, were analyzed using negative-ion MALDI-MS. The enthalpy for ion generation and their stable structures were calculated using the density functional theory (DFT) calculation program Gaussian 09 with the B3LYP functional and the 6-31+G(d) basis set. The number of observed [M-2H] •- and [M-3H] - ions of the DHB isomers was dependent on the positions of the phenolic OH groups in the DHB isomers because the carboxy group interacts with the ortho OH group due to neighboring group participation, as confirmed from the stable structures of the [M-2H] •- anions calculated with the Gaussian 09 program. The DHB isomers were placed into three categories according to the number of the ions. Odd-electron anions ([M-2H] •- ) and [M-2H • -H] - ([M-3H] - ) ions were generated from DHB isomers due to removal of the hydrogen radical from the phenolic groups. The enthalpy for ion generation revealed that ion formation proceeds via a two-step pathway through the [M-M] - ion as an intermediate. © 2016 The Authors. Rapid Communications in Mass Spectrometry Published by John Wiley & Sons Ltd. © 2016 The Authors. Rapid Communications in Mass Spectrometry Published by John Wiley & Sons Ltd.

In vitro neurotoxic hazard characterization of different tricresyl phosphate (TCP) isomers and mixtures.

PubMed

Duarte, Daniel J; Rutten, Joost M M; van den Berg, Martin; Westerink, Remco H S

2017-03-01

Exposure to tricresyl phosphates (TCPs), via for example contaminated cabin air, has been associated with health effects including the so-called aerotoxic syndrome. While TCP neurotoxicity is mainly attributed to ortho-isomers like tri-ortho-cresyl phosphate (ToCP), recent exposure and risk assessments indicate that ToCP levels in cabin air are very low. However, the neurotoxic potential of non-ortho TCP isomers and TCP mixtures is largely unknown. We therefore measured effects of exposure (up to 48h) to different TCP isomers, mixtures and the metabolite of ToCP (CBDP: cresyl saligenin phosphate) on cell viability and mitochondrial activity, spontaneous neuronal electrical activity, and neurite outgrowth in primary rat cortical neurons. The results demonstrate that exposure to TCPs (24-48h, up to 10μM) increases mitochondrial activity, without affecting cell viability. Effects of acute TCP exposure (30min) on neuronal electrical activity are limited. However, electrical activity is markedly decreased for the majority of TCPs (10μM) following 48h exposure. Additional preliminary data indicate that exposure to TCPs (48h, 10μM) did not affect the number of neurites per cell or average neurite length, except for TmCP and the analytical TCP mixture (Sigma) that induced a reduction of average neurite length. The combined neurotoxicity data demonstrate that the different TCPs, including ToCP, are roughly equipotent and a clear structure-activity relation is not apparent for the studied endpoints. The no-observed-effect-concentrations (1μM) are well above current exposure levels indicating limited neurotoxic health risk, although exposures may have been higher in the past. Moreover, prolonged and/or repeated exposure to TCPs may exacerbate the observed neurotoxic effects, which argues for additional research. Copyright © 2016 Elsevier B.V. All rights reserved.

Zwitterionic-hydrophilic interaction capillary liquid chromatography coupled to tandem mass spectrometry for the characterization of human alpha-acid-glycoprotein N-glycan isomers.

PubMed

Mancera-Arteu, Montserrat; Giménez, Estela; Barbosa, José; Peracaula, Rosa; Sanz-Nebot, Victòria

2017-10-23

In this work, a μZIC-HILIC-MS/MS methodology was established in negative ion mode for the characterization of glycan isomers. The possibility to separate the glycan isomers by the μZIC-HILIC strategy coupled to a high resolution tandem mass spectrometry detection permitted us to obtain valuable information about each glycan structure. The most important diagnostic ion fragments previously described to characterize structural features of glycans, were evaluated in this study using hAGP as model glycoprotein. The assignation of hAGP glycan isomers performed in our previous work using the GRIL strategy in combination with exoglycosidase digestion [1] was used in this paper to confirm or discard some ion fragments reported in the literature and delve into the structural characterization of glycan isomers. Sialic acid as well as fucose linkage-type glycan isomers were assigned using this approach and daughter ions with higher diagnostic value were determined. The location of α2-3/α2-6 sialic acids on antennas and a deeper characterization of several highly sialylated tri- and tetraantennary glycans was also possible using the established MS/MS method. Moreover, relying on the characterization performed in Ref. [1], core and antenna fucosylation were differentiated in this work using specific ion fragments obtained in the tandem mass spectra. This methodology was also applied to hAGP purified from control and pathological serum samples, which corroborated its robustness and its potential for finding novel glycan-based biomarkers in patho-glycomic studies. Copyright © 2017 Elsevier B.V. All rights reserved.

The Influence of Interfaces on Properties of Thin-Film Inorganic Structural Isomers Containing SnSe-NbSe2 Subunits.

PubMed

Alemayehu, Matti B; Falmbigl, Matthias; Ta, Kim; Johnson, David C

2015-04-28

Inorganic isomers ([SnSe]1+δ)m(NbSe2)n([SnSe]1+δ)p(NbSe2)q([SnSe]1+δ)r(NbSe2)s where m, n, p, q, r, and s are integers and m + p + r = n + q + s = 4 were prepared using the modulated elemental reactant technique. This series of all six possible isomers provides an opportunity to study the influence of interface density on properties while maintaining the same unit cell size and composition. As expected, all six compounds were observed to have the same atomic compositions and an almost constant c-axis lattice parameter of ≈4.90(5) nm, with a slight trend in the c-axis lattice parameter correlated with the different number of interfaces in the isomers: two, four and six. The structures of the constituents in the ab-plane were independent of one another, confirming the nonepitaxial relationship between them. The temperature dependent electrical resistivities revealed metallic behavior for all the six compounds. Surprisingly, the electrical resistivity at room temperature decreases with increasing number of interfaces. Hall measurements suggest this results from changes in carrier concentration, which increases with increasing thickness of the thickest SnSe block in the isomer. Carrier mobility scales with the thickness of the thickest NbSe2 block due to increased interfacial scattering as the NbSe2 blocks become thinner. The observed behavior suggests that the two constituents serve different purposes with respect to electrical transport. SnSe acts as a charge donor and NbSe2 acts as the charge transport layer. This separation of function suggests that such heterostructures can be designed to optimize performance through choice of constituent, layer thickness, and layer sequence. A simplistic model, which predicts the properties of the complex isomers from a weighted sum of the properties of building blocks, was developed. A theoretical model is needed to predict the optimal compound for specific properties among the many potential compounds that can be prepared.

Quantification of the Influence of Extracellular Laccase and Intracellular Reactions on the Isomer-Specific Biotransformation of the Xenoestrogen Technical Nonylphenol by the Aquatic Hyphomycete Clavariopsis aquatica▿

PubMed Central

Martin, Claudia; Corvini, Philippe F. X.; Vinken, Ralph; Junghanns, Charles; Krauss, Gudrun; Schlosser, Dietmar

2009-01-01

The aquatic hyphomycete Clavariopsis aquatica was used to quantify the effects of extracellular laccase and intracellular reactions on the isomer-specific biotransformation of technical nonylphenol (t-NP). In laccase-producing cultures, maximal removal rates of t-NP and the isomer 4-(1-ethyl-1,4-dimethylpentyl)phenol (NP112) were about 1.6- and 2.4-fold higher, respectively, than in laccase-lacking cultures. The selective suppression of either laccase or intracellular reactions resulted in essentially comparable maximal removal rates for both compounds. Evidence for an unspecific oxidation of t-NP isomers was consistently obtained from laccase-expressing fungal cultures when intracellular biotransformation was suppressed and from reaction mixtures containing isolated laccase. This observation contrasts with the selective degradation of t-NP isomers by bacteria and should prevent the enrichment of highly estrogenic isomers in remaining t-NP. In contrast with laccase reactions, intracellular fungal biotransformation caused a significant shift in the isomeric composition of remaining t-NP. As a result, certain t-NP constituents related to more estrogenic isomers were less efficiently degraded than others. In contrast to bacterial degradation via ipso-hydroxylation, the substitution pattern of the quaternary α-carbon of t-NP isomers does not seem to be very important for intracellular transformation in C. aquatica. As-yet-unknown intracellular enzymes are obviously induced by nonylphenols. Mass spectral data of the metabolites resulting from the intracellular oxidation of t-NP, NP112, and 4-(1-ethyl-1,3-dimethylpentyl)phenol indicate nonyl chain hydroxylation, further oxidation into keto or aldehyde compounds, and the subsequent formation of carboxylic acid derivatives. Further metabolites suggest nonyl chain desaturation and methylation of carboxylic acids. The phenolic moieties of the nonylphenols remained unchanged. PMID:19429559

Hydrogen atom transfer reactions in thiophenol: photogeneration of two new thione isomers.

PubMed

Reva, Igor; Nowak, Maciej J; Lapinski, Leszek; Fausto, Rui

2015-02-21

Photoisomerization reactions of monomeric thiophenol have been investigated for the compound isolated in low-temperature argon matrices. The initial thiophenol population consists exclusively of the thermodynamically most stable thiol form. Phototransformations were induced by irradiation of the matrices with narrowband tunable UV light. Irradiation at λ > 290 nm did not induce any changes in isolated thiophenol molecules. Upon irradiation at 290-285 nm, the initial thiol form of thiophenol converted into its thione isomer, cyclohexa-2,4-diene-1-thione. This conversion occurs by transfer of an H atom from the SH group to a carbon atom at the ortho position of the ring. Subsequent irradiation at longer wavelengths (300-427 nm) demonstrated that this UV-induced hydrogen-atom transfer is photoreversible. Moreover, upon irradiation at 400-425 nm, the cyclohexa-2,4-diene-1-thione product converts, by transfer of a hydrogen atom from the ortho to para position, into another thione isomer, cyclohexa-2,5-diene-1-thione. The latter thione isomer is also photoreactive and is consumed if irradiated at λ < 332 nm. The obtained results clearly show that H-atom-transfer isomerization reactions dominate the unimolecular photochemistry of thiophenol confined in a solid argon matrix. A set of low-intensity infrared bands, observed in the spectra of UV irradiated thiophenol, indicates the presence of a phenylthiyl radical with an H- atom detached from the SH group. Alongside the H-atom-transfer and H-atom-detachment processes, the ring-opening photoreaction occurred in cyclohexa-2,4-diene-1-thione by the cleavage of the C-C bond at the alpha position with respect to the thiocarbonyl C[double bond, length as m-dash]S group. The resulting open-ring conjugated thioketene adopts several isomeric forms, differing by orientations around single and double bonds. The species photogenerated upon UV irradiation of thiophenol were identified by comparison of their experimental infrared

The role of core excitations in the structure and decay of the 16 + spin-gap isomer in 96Cd

DOE PAGES

Davies, Paul John; Grawe, H.; Moschner, K.; ...

2017-02-14

The first evidence for β -delayed proton emission from the 16 + spin gap isomer in 96Cd is presented. The data were obtained from the Rare Isotope Beam Factory, at the RIKEN Nishina Center, using the BigRIPS spectrometer and the EURICA decay station. βp branching ratios for the ground state and 16 + isomer have been extracted along with more precise lifetimes for these states and the lifetime for the ground state decay of 95Cd. Large scale shell model (LSSM) calculations have been performed and WKB estimates made for ℓ=0,2,4 proton emission from three resonance-like states in 96Ag, that aremore » populated by the β decay of the isomer, and the results compared to the new data. The calculations suggest that ℓ=2 proton emission from the resonance states, which reside ~5 MeV above the proton separation energy, dominates the proton decay. Finally, the results highlight the importance of core-excited wavefunction components for the 16 + state.« less

Optimization of the extraction of the p-menthadienol isomers and aristolone contained in the essential oil from Elyonurus hensii using a 23 full factorial design.

PubMed

Loumouamou, Aubin Nestor; Bikindou, Kévin; Bitemou, Ernest; Chalard, Pierre; Silou, Thomas; Figueredo, Gilles

2017-05-01

The aim of this study was to optimize the extraction of p -menthadienol isomers and aristolone from the essential oil of Elyonurus hensii by hydrodistillation. The study of the seasonal variation in the chemical composition has shown that the plant material has been subject to a natural selection regarding the biosynthesis of the p -menthadienol isomers: during periods of water stress, the extracts are rich in cis and trans-p -mentha-1(7),8-dien-2-ol and poor in cis and trans-p -mentha-2,8-dien-1-ol. Regarding the modeling, eight experiments were carried out by considering three easily interpretable factors (the extraction duration, the residual water content and the state of the division of the plant material). The average yield was 1.33% for the aerial part and 0.74% for the roots. The residual water content is the most important factor, which significantly influences the average yield of the essential oil and the content of the major constituents. Regarding the aerial part, a low residual water content of the plant material varies the essential oil yield (from 0.40% to 2.11%) and the content of cis and trans - p -mentha-2.8-dien-1-ol (from 15.87% to 23.24%). At the root level, the samples that have a very low residual water content provide extracts richer in aristolone. The combined effects of the extraction duration, the state of division, and the residual water content influence greatly the extraction of aristolone (from 36.68% to 54.55%). However, these interactions are more complex and difficult to assess.

Sequence-specific backbone resonance assignments and microsecond timescale molecular dynamics simulation of human eosinophil-derived neurotoxin.

PubMed

Gagné, Donald; Narayanan, Chitra; Bafna, Khushboo; Charest, Laurie-Anne; Agarwal, Pratul K; Doucet, Nicolas

2017-10-01

Eight active canonical members of the pancreatic-like ribonuclease A (RNase A) superfamily have been identified in human. All structural homologs share similar RNA-degrading functions, while also cumulating other various biological activities in different tissues. The functional homologs eosinophil-derived neurotoxin (EDN, or RNase 2) and eosinophil cationic protein (ECP, or RNase 3) are known to be expressed and secreted by eosinophils in response to infection, and have thus been postulated to play an important role in host defense and inflammatory response. We recently initiated the biophysical and dynamical investigation of several vertebrate RNase homologs and observed that clustering residue dynamics appear to be linked with the phylogeny and biological specificity of several members. Here we report the 1 H, 13 C and 15 N backbone resonance assignments of human EDN (RNase 2) and its molecular dynamics simulation on the microsecond timescale, providing means to pursue this comparative atomic-scale functional and dynamical analysis by NMR and computation over multiple time frames.

Strategies to distinguish new synthetic cannabinoid FUBIMINA (BIM-2201) intake from its isomer THJ-2201: metabolism of FUBIMINA in human hepatocytes.

PubMed

Diao, Xingxing; Scheidweiler, Karl B; Wohlfarth, Ariane; Zhu, Mingshe; Pang, Shaokun; Huestis, Marilyn A

Since 2013, a new drugs-of-abuse trend attempts to bypass drug legislation by marketing isomers of scheduled synthetic cannabinoids (SCs), e.g., FUBIMINA (BIM-2201) and THJ-2201. It is much more challenging to confirm a specific isomer's intake and distinguish it from its structural analog because the isomers and their major metabolites usually have identical molecular weights and display the same product ions. Here, we investigated isomers FUBIMINA and THJ-2201 and propose strategies to distinguish their consumption. THJ-2201 was scheduled in the US, Japan, and Europe; however, FUBIMINA is easily available on the Internet. We previously investigated THJ-2201 metabolism in human hepatocytes, but human FUBIMINA metabolism is unknown. We aim to characterize FUBIMINA metabolism in human hepatocytes, recommend optimal metabolites to confirm its consumption, and propose strategies to distinguish between intakes of FUBIMINA and THJ-2201. FUBIMINA (10 μM) was incubated in human hepatocytes for 3 h, and metabolites were characterized with high-resolution mass spectrometry (HR-MS). We identified 35 metabolites generated by oxidative defluorination, further carboxylation, hydroxylation, dihydrodiol formation, glucuronidation, and their combinations. We recommend 5'-OH-BIM-018 (M34), BIM-018 pentanoic acid (M33), and BIM-018 pentanoic acid dihydrodiol (M7) as FUBIMINA specific metabolites. THJ-2201 produced specific metabolite markers 5'-OH-THJ-018 (F26), THJ-018 pentanoic acid (F25), and hydroxylated THJ-2201 (F13). Optimized chromatographic conditions to achieve different retention times and careful selection of specific product ion spectra enabled differentiation of isomeric metabolites, in this case FUBIMINA from THJ-2201. Our HR-MS approach should be applicable for differentiating future isomeric SCs, which is especially important when different isomers have different legal status.

An ab initio study of the electronic structure and relative stability of the halogenated thiophosphorus compounds SPX (X = Cl, F, Br) and their isomers

NASA Astrophysics Data System (ADS)

Nowek, Andrzej; Richardson, Rhonda; Babinec, Peter; Leszczyński, Jerzy

1997-12-01

The electronic structure and relative stability of the halogenated thiophosphorus compounds SPCl, SPF, and SPBr and their isomers ClSP, FSP, and BrSP were investigated using ab initio post-Hartree-Fock methods. Molecular geometries of all these structures together with the transition states between isomers, have been optimized at the SCF, MP2, and CCSD levels. Single-point CCSD(T) and MP4 calculations have been performed at the optimal CCSD and MP2 geometries. All calculations have been done using the standard 6-311G(2d) basis set. Harmonic vibrational frequencies and IR intensities for all species were calculated at the correlated levels, and they are in good agreement with the available data from matrix-isolated IR spectroscopy. Because the isomers ClSP, FSP, and BrSP have not yet been experimentally observed, we extended our study by calculating of equilibrium constants of isomerization using Eyring transition state theory, and we have found that at sufficiently high temperatures (≈ 1000 K) the equilibrium constants are large enough for the possible detection of these isomers.

The Synthesis and X-ray Structural Characterization of mer and fac isomers of the Technetium(I) Nitrosyl Complex [TcCl(2)(NO)(PNPpr)].

PubMed

Nicholson, T L; Mahmood, A; Refosco, F; Tisato, F; Müller, P; Jones, A G

2009-08-01

The nitrosyl complex H[TcNOCl(4)] reacts with the tridentate ligand bis[(2-diphenylphosphino)propyl]amine (PNPpr) to yield a mixture of the mer or fac isomers of [TcCl(2)(NO)(PNPpr)]. In acetonitrile, where the ligand is freely soluble, reaction occurs at room temperature to yield mostly the mer isomer with the linear nitrosyl ligand cis to the amine ligand; and the phosphine ligands arranged in a mutually trans orientation. The reaction in methanol requires reflux to dissolve the lipophilic ligand and generates the fac isomer of [TcCl2(NO)(PNPpr)] as the major product, with the tridentate ligand in a facial arrangement, leaving the chlorides and nitrosyl ligand in the remaining facial sites. The steric bulk of the tridentate ligand's diphenylphophino- moieties results in a significant distortion from octahedral geometry, with the P-Tc-P bond angle expanded to 99.48(4)°. The infrared spectra display absorptions from these nitrosyl ligands in the 1700 and 1800 cm(-1) regions for the fac and mer isomers respectively. The ESI(+) mass spectra each display the parent ion at 647 m/z.

Single-channel recordings of RyR1 at microsecond resolution in CMOS-suspended membranes.

PubMed

Hartel, Andreas J W; Ong, Peijie; Schroeder, Indra; Giese, M Hunter; Shekar, Siddharth; Clarke, Oliver B; Zalk, Ran; Marks, Andrew R; Hendrickson, Wayne A; Shepard, Kenneth L

2018-02-20

Single-channel recordings are widely used to explore functional properties of ion channels. Typically, such recordings are performed at bandwidths of less than 10 kHz because of signal-to-noise considerations, limiting the temporal resolution available for studying fast gating dynamics to greater than 100 µs. Here we present experimental methods that directly integrate suspended lipid bilayers with high-bandwidth, low-noise transimpedance amplifiers based on complementary metal-oxide-semiconductor (CMOS) integrated circuits (IC) technology to achieve bandwidths in excess of 500 kHz and microsecond temporal resolution. We use this CMOS-integrated bilayer system to study the type 1 ryanodine receptor (RyR1), a Ca 2+ -activated intracellular Ca 2+ -release channel located on the sarcoplasmic reticulum. We are able to distinguish multiple closed states not evident with lower bandwidth recordings, suggesting the presence of an additional Ca 2+ binding site, distinct from the site responsible for activation. An extended beta distribution analysis of our high-bandwidth data can be used to infer closed state flicker events as fast as 35 ns. These events are in the range of single-file ion translocations.

Correction to Account for the Isomer of 87Y in the 87Y Radiochemical Diagnostic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayes-Sterbenz, Anna Catherine; Jungman, Gerard

Here we summarize the need to correct inventories of 87Y reported by the Los Alamos weapons radiochemistry team. The need for a correction arises from the fact that a 13.37 hour isomer of 87Y, that is strongly populated through (n, 2n) reactions on 88Y and isomers of 88Y, has not been included in the experimental analyses of NTS data. Inventories of 87Y reported by LANL’s weapons radiochemistry team should be multiplied by a correction factor that is numerically close to 0.9. Alternatively, the user could increase simulated values of 87Y by 1.1 for comparison with the original method for reportingmore » NTS values. If the inventories in question were directly reported by LLNL’s radiochemistry team, care must be taken to determine whether or not the correction factor has already been applied.« less

Evaluation of D-isomers of 4-borono-2-18F-fluoro-phenylalanine and O-11C-methyl-tyrosine as brain tumor imaging agents: a comparative PET study with their L-isomers in rat brain glioma.

PubMed

Kanazawa, Masakatsu; Nishiyama, Shingo; Hashimoto, Fumio; Kakiuchi, Takeharu; Tsukada, Hideo

2018-06-13

The potential of the D-isomerization of 4-borono-2- 18 F-fluoro-phenylalanine ( 18 F-FBPA) to improve its target tumor to non-target normal brain tissue ratio (TBR) was evaluated in rat brain glioma and compared with those of L- and D- 11 C-methyl-tyrosine ( 11 C-CMT). The L- or D-isomer of 18 F-FBPA was injected into rats through the tail vein, and their whole body kinetics and distributions were assessed using the tissue dissection method up to 90 min after the injection. The kinetics of L- and D- 18 F-FBPA or L- and D- 11 C-CMT in the C-6 glioma-inoculated rat brain were measured for 90 or 60 min, respectively, using high-resolution animal PET, and their TBRs were assessed. Tissue dissection analyses showed that D- 18 F-FBPA uptake was significantly lower than that of L- 18 F-FBPA in the brain and abdominal organs, except for the kidney and bladder, reflecting the faster elimination rate of D- 18 F-FBPA than L- 18 F-FBPA from the blood to the urinary tract. PET imaging using 18 F-FBPA revealed that although the brain uptake of D- 18 F-FBPA was significantly lower than that of L- 18 F-FBPA, the TBR of the D-isomer improved to 6.93 from 1.45 for the L-isomer. Similar results were obtained with PET imaging using 11 C-CMT with a smaller improvement in TBR to 1.75 for D- 11 C-CMT from 1.33 for L- 11 C-CMT. The present results indicate that D- 18 F-FBPA is a better brain tumor imaging agent with higher TBR than its original L-isomer and previously reported tyrosine-based PET imaging agents. This improved TBR of D- 18 F-FBPA without any pre-treatments, such as tentative blood-brain barrier disruption using hyperosmotic agents or sonication, suggests that the D-isomerization of BPA results in the more selective accumulation of 10 B in tumor cells that is more effective and less toxic than conventional L-BPA.

Performance of some DFT functionals with dispersion on modeling of the translational isomers of a solvent-switchable [2]rotaxane

NASA Astrophysics Data System (ADS)

Ivanov, Petko

2016-03-01

The balances of interactions were studied by computational methods in the translational isomers of a solvent switchable fullerene-stoppered [2]rotaxane (1) manifesting unexpected behavior, namely that due to favorable dispersion interactions the fullerene stopper becomes the second station upon change of the solvent. For comparison, another system, a pH switchable molecular shuttle (2), was also examined as an example of prevailing electrostatic interactions. Tested for 1 were five global hybrid Generalized Gradient Approximation functionals (B3LYP, B3LYP-D3, B3LYP-D3BJ, PBEh1PBE and APFD), one long-range corrected, range-separated functional with D2 empirical dispersion correction, ωB97XD, the Zhao-Truhlar's hybrid meta-GGA functional M06 with double the amount of nonlocal exchange (2X), and a pure functional, B97, with the Grimme's D3BJ dispersion (B97D3). The molecular mechanics method qualitatively correctly reproduced the behavior of the [2]rotaxanes, whereas the DFT models, except for M06-2X to some extent, failed in the case of significant dispersion interactions with participation of the fulleropyrrolidine stopper (rotaxane 1). Unexpectedly, the benzylic amide macrocycle tends to adopt preferentially 'boat'-like conformation in most of the cases. Four hydrogen bonds interconnect the axle with the wheel for the translational isomer with the macroring at the succinamide station (station II), whereas the number of hydrogen bonds vary for the isomer with the macroring at the fulleropyrrolidine stopper (station I) depending of the computational model used. The B3LYP and the PBEh1PBE results show strong preference of station II in the gas phase and in the model solvent DMSO. After including empirical dispersion correction, the translational isomer with the macroring at station I has the lower energy with B3LYP, both in the gas phase and in DMSO. The same result, but with higher preference of station I, was estimated with APFD, ωB97XD and B97D3. Only M06-2X

Efficacy of Fe(o,o-EDDHA) and Fe(o,p-EDDHA) isomers in supplying Fe to strategy I plants differs in nutrient solution and calcareous soil.

PubMed

Rojas, Carmen L; Romera, Francisco J; Alcántara, Esteban; Pérez-Vicente, Rafael; Sariego, Cristina; Garcaí-Alonso, J Ignacio; Boned, Javier; Marti, Gabriel

2008-11-26

The FeEDDHA [iron(3+) ethylenediamine di(o-hydroxyphenylacetic) acid] is one of the most efficient iron chelates employed in the correction of iron clorosis in calcareous soils. FeEDDHA presents different positional isomers: the ortho-ortho (o,o), the ortho-para (o,p), and the para-para (p,p). Of these isomers, the p,p cannot chelate Fe in soil solution in a wide range of pH values, while both o,o and o,p can. The objective of this work was to compare the efficiency of both isomers (o,o and o,p) to provide Fe to two Strategy I plants (tomato and peach) in nutrient solution (pH approximately 6.0), as well as in calcareous soil (pH approximately 8.4; CALCIXEREPT). For this, chelates of both o,o-EDDHA and o,p-EDDHA with 57Fe (a nonradioactive isotope of Fe) were used, where the 57Fe acts as a tracer. The results obtained showed that the o,o isomer is capable of providing sufficient Fe to plants in both nutrient solution and calcareous soil. However, the o,p isomer is capable of providing sufficient Fe to plants in nutrient solution but not in calcareous soil.

Estrogenic effects of nonylphenol and octylphenol isomers in vitro by recombinant yeast assay (RYA) and in vivo with early life stages of zebrafish.

PubMed

Puy-Azurmendi, E; Olivares, A; Vallejo, A; Ortiz-Zarragoitia, M; Piña, B; Zuloaga, O; Cajaraville, M P

2014-01-01

Commercial OP and NP are complex isomer mixtures that can be individually present in the environment, showing different estrogenic potencies. The aims of this study were to establish the estrogenic potency of some AP isomers in comparison to the commercial NP (cNP) mixture in vitro and to investigate in vivo their possible effects during the embryo and larval development of zebrafish. An in vitro estrogen receptor-based recombinant yeast assay was used to test the estrogenicity of specific AP isomers (22-OP, 33-OP, 22-NP, 33-NP and 363-NP) and cNP. The EC₅₀ was in the range of 0.6-7.7 mg/L. Both OP isomers and 363-NP exhibited higher estrogenic activity than cNP. For in vivo experiments, one-day postfertilisation (dpf) embryos were exposed to cNP (50, 250 and 500 μg/L), 363-NP and 33-OP (50 μg/L), 17β-estradiol (100 ng/L) and DMSO (0.01% v/v) for 4weeks. After exposure fish were maintained for 2 weeks in clean water in order to evaluate a possible recovery. Fish of groups exposed to cNP and 363-NP were the last to hatch. Histological alterations were not observed after 7, 28 or 42 dpf. Exposure to 33-OP increased transcriptional levels of erα, vtg and cyp19a1b genes. However, transcriptional response in E2 exposure was observed at later stages and with higher fold induction levels. Exposure to cNP decreased levels of erα whereas increased levels of rxrγ and cyp19a1b. Exposure to 363-NP did not cause changes in transcriptional levels of studied genes. The differences in response of the OP isomer compared to the NP isomer in zebrafish could be related to the rapid decay in concentration of the latter. Copyright © 2013 Elsevier B.V. All rights reserved.

Identification of geometrical isomers and comparison of different isomeric samples of astaxanthin.

PubMed

Qiu, Dan; Wu, Yue-Chan; Zhu, Wen-Li; Yin, Hong; Yi, Long-Tao

2012-09-01

A high-performance liquid chromatographic (HPLC) analysis system for isomeric astaxanthin was developed. The separation system consisted of a C(30) column and an elution system of methanol/MTBE/water/dichloromethane (77:13:8:2, v/v/v/v). Using the combination of HPLC diode array detector and HPLC atmospheric pressure chemical ionization mass spectrometry, 11 geometrical isomers and 4 epoxides of astaxanthin were successfully identified. Referred to crystal, only isomerization with different degrees was found for solvent dissolving and iodine catalysis, while melting of astaxanthin caused isomerization, slight oxidation, and more noticeable polymerization confirmed by gel permeation chromatography. Chemical changes in isomeric samples all caused a decrease in UV content. The vibrational spectra (infrared and Raman) showed that epoxide was the only new functional group generated for melting. Changes of several key bands and formations of new bands were found in iodine catalysis and melting samples because of isomerization. Practical Application:  Eleven geometrical isomers and 4 epoxides, which were normally generated for solvent dissolving, iodine catalysis, and melting of astaxanthin, have been identified by C(30) -HPLC-MS technology. Furthermore, different samples were measured by gel permeation chromatography, UV, infrared, and Raman, based on the analysis of messages, the effect of each processing was well understood. © 2012 Institute of Food Technologists®

Estimating human exposure to PFOS isomers and PFCA homologues: the relative importance of direct and indirect (precursor) exposure.

PubMed

Gebbink, Wouter A; Berger, Urs; Cousins, Ian T

2015-01-01

Contributions of direct and indirect (via precursors) pathways of human exposure to perfluorooctane sulfonic acid (PFOS) isomers and perfluoroalkyl carboxylic acids (PFCAs) are estimated using a Scenario-Based Risk Assessment (SceBRA) modelling approach. Monitoring data published since 2008 (including samples from 2007) are used. The estimated daily exposures (resulting from both direct and precursor intake) for the general adult population are highest for PFOS and perfluorooctanoic acid (PFOA), followed by perfluorohexanoic acid (PFHxA) and perfluorodecanoic acid (PFDA), while lower daily exposures are estimated for perfluorobutanoic acid (PFBA) and perfluorododecanoic acid (PFDoDA). The precursor contributions to the individual perfluoroalkyl acid (PFAA) daily exposures are estimated to be 11-33% for PFOS, 0.1-2.5% for PFBA, 3.7-34% for PFHxA, 13-64% for PFOA, 5.2-66% for PFDA, and 0.7-25% for PFDoDA (ranges represent estimated precursor contributions in a low- and high-exposure scenario). For PFOS, direct intake via diet is the major exposure pathway regardless of exposure scenario. For PFCAs, the dominant exposure pathway is dependent on perfluoroalkyl chain length and exposure scenario. Modelled PFOS and PFOA concentrations in human serum using the estimated intakes from an intermediate-exposure scenario are in agreement with measured concentrations in different populations. The isomer pattern of PFOS resulting from total intakes (direct and via precursors) is estimated to be enriched with linear PFOS (84%) relative to technical PFOS (70% linear). This finding appears to be contradictory to the observed enrichment of branched PFOS isomers in recent human serum monitoring studies and suggests that either external exposure is not fully understood (e.g. there are unknown precursors, missing or poorly quantified exposure pathways) and/or that there is an incomplete understanding of the isomer-specific human pharmacokinetic processes of PFOS, its precursors and

Infrared detection of (H 2O) 20 isomers of exceptional stability: A drop-like and a face-sharing pentagonal prism cluster

DOE PAGES

Pradzynski, Christoph C.; Dierking, Christoph W.; Zurheide, Florian; ...

2014-09-01

Water clusters containing fully coordinated water molecules are model systems that mimic the local environment of the condensed phase. Present knowledge about the water cluster size regime in which the transition from the allsurface to the fully solvated water molecules occurs is mainly based on theoretical predictions in lieu of the absence of precisely size resolved experimental measurements. Here, we report size and isomer selective infrared (IR) spectra of (H 2O) 20 clusters tagged with a sodium atom by employing IR excitation modulated photoionization spectroscopy. The observed absorption patterns in the OH stretching ”fingerprint” region are consistent with the theoreticallymore » predicted spectra of two structurally distinct isomers: A drop-like cluster with a fully coordinated (interior) water and an edge-sharing pentagonal prism cluster in which all atoms are on the surface. The observed isomers show exceptional stability and are predicted to be nearly isoenergetic.« less

Kinetics and selectivity of permanganate chemiluminescence: a study of hydroxyl and amino disubstituted benzene positional isomers.

PubMed

Slezak, Teo; Smith, Zoe M; Adcock, Jacqui L; Hindson, Christopher M; Barnett, Neil W; Nesterenko, Pavel N; Francis, Paul S

2011-11-30

Examination of the chemiluminescence reactions of dihydroxybenzenes, aminophenols and phenylenediamines with acidic potassium permanganate has provided a new understanding of the relationships between analyte structure, reaction conditions, kinetics of the light-producing pathway and emission intensity, with broad implications for this widely utilised chemiluminescence detection system. Using a permanganate reagent prepared in a polyphosphate solution and adjusted to pH 2.5, large differences in the rate of reaction with different positional isomers were observed, with the meta-substituted forms reacting far slower and therefore exhibiting much lower chemiluminescence intensities in flow analysis systems. The preliminary partial reduction of permanganate to form significant concentrations of Mn(III) increased the rate of reaction with all analytes tested, resulting in comparable or (in the case of aminophenol and phenylenediamine) even greater emission intensities for the meta-isomers, demonstrating the opportunity to tune the selectivity of the reagent towards certain classes of compound or even specific positional isomers of the same compound. Using more acidic permanganate reagents, in which polyphosphates are not required, the discrepancy between the chemiluminescence intensities was still observed, but was less prominent due to the generally faster rates of reaction. The enhancement of these chemiluminescence reactions by on-line addition of formic acid or formaldehyde can in part also be attributed to the generation of significant pools of the key Mn(III) precursor to the emitting species. Copyright © 2011 Elsevier B.V. All rights reserved.

Evidence for two interconverting protein isomers in the methotrexate complex of dihydrofolate reductase from Escherichia coli

DOE Office of Scientific and Technical Information (OSTI.GOV)

Falzone, C.J.; Benkovic, S.J.; Wright, P.E.

1991-02-26

Two-dimensional {sup 1}H NMR methods and a knowledge of the X-ray crystal structure have been used to make resonance assignments for the amino acid side chains of dihydrofolate reductase from Escherichia coli complexed with methotrexate. The H7 proton on the pteridine ring of methotrexate was found to have NOEs to the methyl protons of Leu-28 which were assigned by using the L28F mutant. These NOEs indicated that the orientation of the methotrexate pteridine ring is similar in both solution and crystal structures. During the initial assignment process, it became evident that many of the resonances in this complex, unlike thosemore » of the folate complex, are severally broadened or doubled. The observation of two distinct sets of resonances in a ratio of approximately 2:1 was attributed to the presence of two protein isomers. Many of the side chains with clearly doubled resonances were located in the {beta}-sheet and the active site. Preliminary studies on the apoprotein also revealed doubled resonances in the absence of the inhibitor, indicating the existence of the protein isomers prior to methotrexate binding. In contrast to the methotrexate complex, the binary complex with folate and the ternary MTX-NADPH-DHFR complex presented a single enzyme form. These results are proposed to reflect the ability of folate and NADPH to bind predominantly to one protein isomer.« less

Interactions between major chlorogenic acid isomers and chemical changes in coffee brew that affect antioxidant activities.

PubMed

Liang, Ningjian; Xue, Wei; Kennepohl, Pierre; Kitts, David D

2016-12-15

Coffee bean source and roasting conditions significantly (p<0.05) affected the content of chlorogenic acid (CGA) isomers, several indices of browning and subsequent antioxidant values. Principal component analysis was used to interpret the correlations between physiochemical and antioxidant parameters of coffee. CGA isomer content was positively correlated (p<0.001) to capacity of coffee to reduce nitric oxide and scavenge Frémy's salt. Indices of browning in roasted coffee were positively correlated (p<0.001) to ABTS and TEMPO radical scavenging capacity, respectively. Only the CGA content of coffee corresponded to intracellular antioxidant capacity measured in Caco-2 intestinal cells. This study concluded that the intracellular antioxidant capacity that best describes potential health benefits of coffee positively corresponds best with CGA content. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

The 75As(n,2n) Cross Sections into the 74As Isomer and Ground State

DOE Office of Scientific and Technical Information (OSTI.GOV)

Younes, W; Garrett, P E; Becker, J A

2003-06-30

The {sup 75}As(n, 2n) cross section for the population of the T{sub 1/2} = 26.8-ns isomer at E{sub x} = 259.3 keV in {sup 74}As has been measured as a function of incident neutron energy, from threshold to E{sub n} = 20 MeV. The cross section was measured using the GEANIE spectrometer at LANSCE/WNR. For convenience, the {sup 75}As(n, 2n) population cross section for the {sup 74}As ground state has been deduced as the difference between the previously-known (n, 2n) reaction cross section and the newly measured {sup 75}As(n, 2n){sup 74}As{sup m} cross section. The (n, 2n) reaction, ground-state, andmore » isomer population cross sections are tabulated in this paper.« less

Determination of (4-methylcyclohexyl)methanol isomers by heated purge-and-trap GC/MS in water samples from the 2014 Elk River, West Virginia, chemical spill

USGS Publications Warehouse

Foreman, William T.; Rose, Donna L.; Chambers, Douglas B.; Crain, Angela S.; Murtagh, Lucinda K.; Thakellapalli, Haresh; Wang, Kung K.

2015-01-01

A heated purge-and-trap gas chromatography/mass spectrometry method was used to determine the cis- and trans-isomers of (4-methylcyclohexyl)methanol (4-MCHM), the reported major component of the Crude MCHM/Dowanol™ PPh glycol ether material spilled into the Elk River upriver from Charleston, West Virginia, on January 9, 2014. The trans-isomer eluted first and method detection limits were 0.16-μg L−1trans-, 0.28-μg L−1cis-, and 0.4-μg L−1 Total (total response of isomers) 4-MCHM. Estimated concentrations in the spill source material were 491-g L−1trans- and 277-g L−1cis-4-MCHM, the sum constituting 84% of the source material assuming its density equaled 4-MCHM. Elk River samples collected ⩽ 3.2 km downriver from the spill on January 15 had low (⩽2.9 μg L−1 Total) 4-MCHM concentrations, whereas the isomers were not detected in samples collected 2 d earlier at the same sites. Similar 4-MCHM concentrations (range 4.2–5.5 μg L−1 Total) occurred for samples of the Ohio River at Louisville, Kentucky, on January 17, ∼630 km downriver from the spill. Total 4-MCHM concentrations in Charleston, WV, office tap water decreased from 129 μg L−1 on January 27 to 2.2 μg L−1on February 3, but remained detectable in tap samples through final collection on February 25 indicating some persistence of 4-MCHM within the water distribution system. One isomer of methyl 4-methylcyclohexanecarboxylate was detected in all Ohio River and tap water samples, and both isomers were detected in the source material spilled.

Synthesis, characterization, and in-vitro antitumor activity of the polyethylene glycol (350 and 1000) succinate derivatives of the tocopherol and tocotrienol isomers of Vitamin E

PubMed Central

Abu-Fayyad, Ahmed; Nazzal, Sami

2017-01-01

Vitamin E refers to a group of saturated tocopherol (T) isomers and the biologically more active unsaturated tocotrienol (T3) isomers. PEGylated α-tocopherol, commercially known as Vitamin E TPGS, has been used as an emulsifier and therapeutic agent for children with vitamin E deficiency. Limited information, however, is available about the PEG conjugates of the tocotrienol isomers of vitamin E. The current work was therefore undertaken to synthesize and characterize the water soluble polyethylene glycol (PEG 350 and 1000) derivatives of T and T3. Yield and the identity of the synthesized products were confirmed by 1H NMR, mass spectroscopy, HPLC, and thermal analysis. The self-assembly of the PEGylated vitamin E isomers in water at critical micelle concentrations (CMC) was further confirmed by size, zeta, and Cryo-TEM image analysis. While stable at pH 7.4, PEG conjugates were found to rapidly hydrolyze at pH 1.2. Our data showed that PEGylated T3 isomers were significantly more active as inhibitors for P-glycoprotein than PEGylated T. The in vitro cytotoxicity of the conjugates was also tested against a large panel of normal and tumorigenic cells. Of the conjugates, γ-T3PGS 1000 and δ-T3PGS 1000 were found to have the least toxicity against non-tumorigenic breast and pancreatic cell lines, which may be advantageous for its use as functional excipients in drug delivery. The results from the current work have demonstrated the feasibility of synthesizing PEGylated conjugates of vitamin E isomers and highlighted the potential use of these conjugates in drug delivery as functional and safer excipients especially for γ-T3PGS 1000 and δ-T3PGS 1000 conjugate. PMID:28093324

Synthesis, characterization, and in-vitro antitumor activity of the polyethylene glycol (350 and 1000) succinate derivatives of the tocopherol and tocotrienol isomers of Vitamin E.

PubMed

Abu-Fayyad, Ahmed; Nazzal, Sami

2017-03-15

Vitamin E refers to a group of saturated tocopherol (T) isomers and the biologically more active unsaturated tocotrienol (T 3 ) isomers. PEGylated α-tocopherol, commercially known as Vitamin E TPGS, has been used as an emulsifier and therapeutic agent for children with vitamin E deficiency. Limited information, however, is available about the PEG conjugates of the tocotrienol isomers of vitamin E. The current work was therefore undertaken to synthesize and characterize the water soluble polyethylene glycol (PEG 350 and 1000) derivatives of T and T 3 . Yield and the identity of the synthesized products were confirmed by 1 H NMR, mass spectroscopy, HPLC, and thermal analysis. The self-assembly of the PEGylated vitamin E isomers in water at critical micelle concentrations (CMC) was further confirmed by size, zeta, and Cryo-TEM image analysis. While stable at pH 7.4, PEG conjugates were found to rapidly hydrolyze at pH 1.2. Our data showed that PEGylated T 3 isomers were significantly more active as inhibitors for P-glycoprotein than PEGylated T. The in vitro cytotoxicity of the conjugates was also tested against a large panel of normal and tumorigenic cells. Of the conjugates, γ-T 3 PGS 1000 and δ-T 3 PGS 1000 were found to have the least toxicity against non-tumorigenic breast and pancreatic cell lines, which may be advantageous for its use as functional excipients in drug delivery. The results from the current work have demonstrated the feasibility of synthesizing PEGylated conjugates of vitamin E isomers and highlighted the potential use of these conjugates in drug delivery as functional and safer excipients especially for γ-T 3 PGS 1000 and δ-T 3 PGS 1000 conjugate. Copyright © 2017 Elsevier B.V. All rights reserved.

Ultra-performance liquid chromatographic separation of geometric isomers of carotenoids and antioxidant activities of 20 tomato cultivars and breeding lines.

PubMed

Li, Hongyan; Deng, Zeyuan; Liu, Ronghua; Loewen, Steven; Tsao, Rong

2012-05-01

All-trans-lutein, lycopene, β-carotene and their 22 cis-isomers in 20 tomato breeding were separated and identified by a rapid and sensitive UPLC method using a 1.7μm C18 column and a new gradient mobile phase based on methanol-MTBE-water in 15 min. All-trans-carotenoids were predominant, but 9-cis, 13-cis-lutein, 5-cis, 9-cis, 13-cis, 15-cis, di-cis-lycopene, 9-cis, 13-cis, 15-cis and di-cis-β-carotene were also found. The cis-isomers were identified using absorption around 330nm and the Q-ratio. The total antioxidant activities as evaluated by PCL and DPPH assays were found to correlate well with the total carotenoid content, but not with the individual carotenoid or its different isomers. This paper provides an efficient analytical method for obtaining a complete picture of carotenoids in tomatoes. It can be a valuable tool for plant breeders, food processors and researchers in developing designer tomatoes and tomato-products with unique carotenoid compositions, and functional properties. Copyright © 2011 Elsevier Ltd. All rights reserved.

Analyses of barley spike mutant waxes identify alkenes, cyclopropanes and internally branched alkanes with dominating isomers at carbon 9.

PubMed

von Wettstein-Knowles, Penny

2007-01-01

About 15% of the epidermal wax on Hordeum vulgare cv. Bonus barley spikes is n-alkanes. Longer homologues are greatly reduced in the eceriferum mutants, cer-a(6), cer-e(8), cer-n(26), cer-n(53), cer-n(985), cer-x(60), cer-yc(135) and cer-yl(187). Simultaneously hydrocarbons accounting for only traces in the wild-type become prominent in the mutants, although their chain-length distributions remain unchanged. Accordingly several new hydrocarbon series were identified. The two major ones were C(23)-C(35)cis monoenoic alkenes (the major 9-ene isomer was part of a homologous series including 11, 13 and 15-enes), and the novel C(27)-C(31) cyclopropanes (the ring carbons of major isomers were 9,10 and 11,12 with lesser amounts of 13,14). Three minor series included 2- and 3-methylalkanes plus C(25)-C(33) internally branched alkanes (methyls on carbons 9, 11, 13, 15 or 17; shorter homologues dominated by the 9 isomer, longer homologues by 11, 13 or 15 isomers). Acyl chains destined for spike waxes are synthesized via acyl and polyketide elongase systems plus associated reductive and decarbonylative/decarboxylative enzyme systems. Both elongation systems are defective in synthesizing C(32) acyl chains in all nine mutants. The similarities in the position of the chemical groups (primarily on carbon 9, secondarily on carbon 11) of the alkenes, cyclopropanes and internally branched methyl alkanes imply an origin from a common, hitherto unrecognized associated pathway in barley, designated the enoic pathway. The elongation system leading to the enoic derived hydrocarbons differs from the known elongation systems by inclusion of a mechanism for introducing a double bond.

High-spin structures in 132Xe and 133Xe and evidence for isomers along the N =79 isotones

NASA Astrophysics Data System (ADS)

Vogt, A.; Siciliano, M.; Birkenbach, B.; Reiter, P.; Hadyńska-Klek, K.; Wheldon, C.; Valiente-Dobón, J. J.; Teruya, E.; Yoshinaga, N.; Arnswald, K.; Bazzacco, D.; Blazhev, A.; Bracco, A.; Bruyneel, B.; Chakrawarthy, R. S.; Chapman, R.; Cline, D.; Corradi, L.; Crespi, F. C. L.; Cromaz, M.; de Angelis, G.; Eberth, J.; Fallon, P.; Farnea, E.; Fioretto, E.; Fransen, C.; Freeman, S. J.; Fu, B.; Gadea, A.; Gelletly, W.; Giaz, A.; Görgen, A.; Gottardo, A.; Hayes, A. B.; Hess, H.; Hetzenegger, R.; Hirsch, R.; Hua, H.; John, P. R.; Jolie, J.; Jungclaus, A.; Karayonchev, V.; Kaya, L.; Korten, W.; Lee, I. Y.; Leoni, S.; Liang, X.; Lunardi, S.; Macchiavelli, A. O.; Menegazzo, R.; Mengoni, D.; Michelagnoli, C.; Mijatović, T.; Montagnoli, G.; Montanari, D.; Müller-Gatermann, C.; Napoli, D.; Pearson, C. J.; Podolyák, Zs.; Pollarolo, G.; Pullia, A.; Queiser, M.; Recchia, F.; Regan, P. H.; Régis, J.-M.; Saed-Samii, N.; Şahin, E.; Scarlassara, F.; Seidlitz, M.; Siebeck, B.; Sletten, G.; Smith, J. F.; Söderström, P.-A.; Stefanini, A. M.; Stezowski, O.; Szilner, S.; Szpak, B.; Teng, R.; Ur, C.; Warner, D. D.; Wolf, K.; Wu, C. Y.; Zell, K. O.

2017-08-01

The transitional nuclei 132Xe and 133Xe are investigated after multinucleon-transfer (MNT) and fusion-evaporation reactions. Both nuclei are populated (i) in 136Xe+208Pb MNT reactions employing the high-resolution Advanced GAmma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA, (ii) in the 136Xe+198Pt MNT reaction employing the GAMMASPHERE spectrometer in combination with the gas-detector array CHICO, and (iii) as an evaporation residue after a 130Te(α ,x n )134 -x nXe fusion-evaporation reaction employing the HORUS γ -ray array at the University of Cologne. The high-spin level schemes are considerably extended above the Jπ=(7-) and (10+) isomers in 132Xe and above the 11 /2- isomer in 133Xe. The results are compared to the high-spin systematics of the Z =54 as well as the N =78 and N =79 chains. Furthermore, evidence is found for a long-lived (T1 /2≫1 μ s ) isomer in 133Xe which closes a gap along the N =79 isotones. Shell-model calculations employing the SN100PN and PQM130 effective interactions reproduce the experimental findings and provide guidance to the interpretation of the observed high-spin features.

High-spin structures in Xe 132 and Xe 133 and evidence for isomers along the N = 79 isotones

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vogt, A.; Siciliano, M.; Birkenbach, B.

In this study, the transitional nuclei 132Xe and 133Xe are investigated after multinucleon-transfer (MNT) and fusion-evaporation reactions. Both nuclei are populated (i) in 136Xe + 208Pb MNT reactions employing the high-resolution Advanced GAmma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA, (ii) in the 136Xe + 198Pt MNT reaction employing the GAMMASPHERE spectrometer in combination with the gas-detector array CHICO, and (iii) as an evaporation residue after a 130Te (α,xn) 134-xnXe fusion-evaporation reaction employing the HORUS γ -ray array at the University of Cologne. The high-spin level schemes are considerably extended above the J π = (7 -) andmore » (10 +) isomers in 132Xe and above the 11/2 - isomer in 133Xe. The results are compared to the high-spin systematics of the Z = 54 as well as the N = 78 and N = 79 chains. Furthermore, evidence is found for a long-lived (T 1/2 » 1 μs) isomer in 133Xe which closes a gap along the N = 79 isotones. Finally, shell-model calculations employing the SN100PN and PQM130 effective interactions reproduce the experimental findings and provide guidance to the interpretation of the observed high-spin features.« less

High-spin structures in Xe 132 and Xe 133 and evidence for isomers along the N = 79 isotones

DOE PAGES

Vogt, A.; Siciliano, M.; Birkenbach, B.; ...

2017-08-24

In this study, the transitional nuclei 132Xe and 133Xe are investigated after multinucleon-transfer (MNT) and fusion-evaporation reactions. Both nuclei are populated (i) in 136Xe + 208Pb MNT reactions employing the high-resolution Advanced GAmma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA, (ii) in the 136Xe + 198Pt MNT reaction employing the GAMMASPHERE spectrometer in combination with the gas-detector array CHICO, and (iii) as an evaporation residue after a 130Te (α,xn) 134-xnXe fusion-evaporation reaction employing the HORUS γ -ray array at the University of Cologne. The high-spin level schemes are considerably extended above the J π = (7 -) andmore » (10 +) isomers in 132Xe and above the 11/2 - isomer in 133Xe. The results are compared to the high-spin systematics of the Z = 54 as well as the N = 78 and N = 79 chains. Furthermore, evidence is found for a long-lived (T 1/2 » 1 μs) isomer in 133Xe which closes a gap along the N = 79 isotones. Finally, shell-model calculations employing the SN100PN and PQM130 effective interactions reproduce the experimental findings and provide guidance to the interpretation of the observed high-spin features.« less

Determination of the D and L isomers of some protein amino acids present in soils

NASA Technical Reports Server (NTRS)

Pollock, G. E.; Cheng, C.-N.; Cronin, S. E.

1977-01-01

The D and L isomers of some protein amino acids present in soils were measured by using a gas chromatographic technique. The results of two processing procedures were compared to determine the better method. Results of the comparison indicated that the determination of D and L percentages requires amino acid purification if one is to obtain accurate data. It was found that very significant amounts of D-alanine, D-aspartic acid, and D-glutamic acid were present in the contemporary soils studied. Valine, isoleucine, leucine, proline, and phenylalanine generally contained only a trace to very small amounts of the D isomer. It is probable that the D-amino acids from the alanine, aspartic, and glutamic acids are contributed to the soil primarily via microorganisms. The finding of very significant quantities of some D-amino acids (about 5-16%) in present-day soils may alert some investigators of geological sediments to a possible problem in using amino acid racemization as an age-dating technique.

Hindered rotation and nuclear spin isomers separation of molecularly chemisorbed H2 on Pd(210)

NASA Astrophysics Data System (ADS)

Arguelles, Elvis F.; Kasai, Hideaki

2018-03-01

We investigated the hindered rotation and nuclear spin isomer separation of H2 on Pd(210) for various pre-adsorbed atomic hydrogen coverages (Θ), by total energy calculations based on density functional theory. Our results revealed that H2 is in the molecularly chemisorbed state and the adsorption is characterized by a highly anisotropic potential energy surface. Further, we found that J = 1 degenerate level splitting is insensitive to the increase in Θ from 1 to 2 ML. This is due to the comparable potential strengths hindering/restricting the polar rotations in both coverages. On a fully H passivated (3 ML) Pd(210), H2 is in a weakly physisorbed state with a negligible potential anisotropy. Our findings suggest that the activation barrier for polar rotational motion does not strongly depend on the adsorption energy but rather on the surface-molecule bond. The estimated rotational state desorption energies show a separation of ortho and para isomers by around 7.0 meV.

Separation of Cis-Trans Phospholipid Isomers using Reversed Phase LC with High Resolution MS Detection

PubMed Central

Bird, Susan S.; Marur, Vasant R.; Stavrovskaya, Irina G.; Kristal, Bruce S.

2012-01-01

The increased presence of synthetic trans fatty acids into western diets has been shown to have deleterious effects on physiology and raising an individual’s risk of developing metabolic disease, cardiovascular disease, and stroke. The importance of these fatty acids for health and the diversity of their (patho) physiological effects suggest that not only should the free trans fatty acids be studied, but that monitoring the presence of these fats into the side-chains of biological lipids, such as glycerophospholipids, is also essential. We developed a high resolution LC-MS method that quantitatively monitors the major lipid classes found in biospecimens in an efficient, sensitive and robust manner while also characterizing individual lipid side-chains through the use of HCD fragmentation and chromatographic alignment. We herein show how this previously described reversed phase method can baseline separate the cis-trans isomers of phosphatidylglycerol and phosphatidylcholine (PC) with two 18:1 side chains, in both positive and negative mode, as neat solutions and when spiked into a biological matrix. Endogenous PC (18:1/18:1) cis and PC (18:1/18:1) trans isomers were examined in mitochondrial and serum profiling studies, where rats were fed diets enriched in either trans 18:1 fatty acids, or cis 18:1 fatty acids. In this study, we determined the cis:trans isomer ratios of PC (18:1/18:1) and related this ratio to dietary composition. This generalized LC-MS method enables the monitoring of trans fats in biological lipids in the context of a non-targeted method, allowing for relative quantitation and enhanced identification of unknown lipids in complex matrices. PMID:22656324

Unraveling Unprecedented Charge Carrier Mobility through Structure Property Relationship of Four Isomers of Didodecyl[1]benzothieno[3,2-b][1]benzothiophene.

PubMed

Tsutsui, Yusuke; Schweicher, Guillaume; Chattopadhyay, Basab; Sakurai, Tsuneaki; Arlin, Jean-Baptiste; Ruzié, Christian; Aliev, Almaz; Ciesielski, Artur; Colella, Silvia; Kennedy, Alan R; Lemaur, Vincent; Olivier, Yoann; Hadji, Rachid; Sanguinet, Lionel; Castet, Frédéric; Osella, Silvio; Dudenko, Dmytro; Beljonne, David; Cornil, Jérôme; Samorì, Paolo; Seki, Shu; Geerts, Yves H

2016-09-01

The structural and electronic properties of four isomers of didodecyl[1]-benzothieno[3,2-b][1]benzothiophene (C12-BTBT) have been investigated. Results show the strong impact of the molecular packing on charge carrier transport and electronic polarization properties. Field-induced time-resolved microwave conductivity measurements unravel an unprecedented high average interfacial mobility of 170 cm(2) V(-1) s(-1) for the 2,7-isomer, holding great promise for the field of organic electronics. © 2016 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Striking differences in properties of geometric isomers of [Ir(tpy)(ppy)H](+): Experimental and computational studies on their hydricities, interaction with CO 2, and photochemistry

DOE PAGES

Garg, Komal; Fujita, Etsuko; Matsubara, Yasuo; ...

2015-11-16

Here, we prepared two geometric isomers of [Ir(tpy)(ppy)H] +, previously proposed as a key intermediate in the photochemical reduction of CO 2 to CO, and characterized their notably different ground- and excited-state interactions with CO 2 and their hydricities using experimental and computational methods. Only one isomer, C-trans-[Ir(tpy)(ppy)H] +, reacts with CO 2 to generate the formato complex in the ground state, consistent with its calculated hydricity. Under photocatalytic conditions in CH 3CN/TEOA, a common reactive C-trans-[Ir(tpy)(ppy)] 0 species, irrespective of the starting isomer or monodentate ligand (such as hydride or Cl), reacts with CO 2 and produces CO withmore » the same catalytic efficiency.« less

Free energy surface of the Michaelis complex of lactate dehydrogenase: a network analysis of microsecond simulations.

PubMed

Pan, Xiaoliang; Schwartz, Steven D

2015-04-30

It has long been recognized that the structure of a protein creates a hierarchy of conformations interconverting on multiple time scales. The conformational heterogeneity of the Michaelis complex is of particular interest in the context of enzymatic catalysis in which the reactant is usually represented by a single conformation of the enzyme/substrate complex. Lactate dehydrogenase (LDH) catalyzes the interconversion of pyruvate and lactate with concomitant interconversion of two forms of the cofactor nicotinamide adenine dinucleotide (NADH and NAD(+)). Recent experimental results suggest that multiple substates exist within the Michaelis complex of LDH, and they show a strong variance in their propensity toward the on-enzyme chemical step. In this study, microsecond-scale all-atom molecular dynamics simulations were performed on LDH to explore the free energy landscape of the Michaelis complex, and network analysis was used to characterize the distribution of the conformations. Our results provide a detailed view of the kinetic network of the Michaelis complex and the structures of the substates at atomistic scales. They also shed light on the complete picture of the catalytic mechanism of LDH.

Optical isomer separation of potential analgesic drug candidates by using capillary electrophoresis.

PubMed

Ferrara, G; Santagati, N A; Aturki, Z; Fanali, S

1999-09-01

Using cyclodextrin capillary zone electrophoresis (CD-CZE), baseline separation of synthetic potential analgesic drug diastereoisomer candidates 6,11-dimethyl-1,2,3,4,5,6-hexahydro-3-[(2'-methoxycarbonyl-2'-phenylc yclopropyl)methyl]-2,6-methano-3-benzazocin-8-ol (MPCB) and 6,11-dimethyl-1,2,3,4,5,6-hexahydro-3-[[2'-methoxycarbonyl-2'(4-chloroph enyl)cyclopropyl]methyl]-2,6-methano-3-benzazocin-8-ol (CCB) was achieved. Among the cyclodextrins tested (hydroxypropyl-, carboxymethyl- and sulfobutyl-beta-cyclodextrin (HP-beta-CD, CM-beta-CD and SBE-beta-CD)) SBE-beta-CD was found to be the most effective complexing agent, allowing good optical isomer separation. Resolution was also influenced by the CD concentration, pH of the buffer and presence of organic modifier in the background electrolyte. The optimum experimental conditions for the separation of studied analgesic drugs were found using 25 mM borate buffer at pH 9 containing 40 mM of SBE-beta-CD and 20% v/v of methanol. Using the above-mentioned background electrolyte, it was also possible to separate, in the same run, the enantiomers of normetazocine (NMZ) as well as the optical isomers of (+/-)-cis-2-chloromethyl-1-phenyl cyclopropancarboxylic acid methyl ester (PCE) or (+/-)-cis-2-chloromethyl-1-(4-chlorophenyl)cyclopropancarboxylic acid methyl ester (CPCE) reagents used in the synthesis of the studied analgesic drugs).

Stability and electronic spectra of C76N2 isomers

PubMed Central

Teng, Qi-wen; Wu, Shi

2005-01-01

Study of geometries of 16 possible isomers for C76N2 based on C78(C 2v) by intermediate neglect of differential overlap (INDO) series of methods indicated that the most stable geometry 25,78-C76N2 where two nitrogen atoms substitute two apexes C(25) and C(78) near the shortest X axis and Y axis formed by two hexagons and a pentagon. Electronic structures and spectra of C76N2 were investigated. The reason for the red-shift for absorptions of C76N2 compared with that of C78(C 2v) is discussed. PMID:15909352

Isomer-specific vibronic structure of the 9-, 1-, and 2-anthracenyl radicals via slow photoelectron velocity-map imaging

PubMed Central

DeVine, Jessalyn A.; Levine, Daniel S.; Kim, Jongjin B.; Neumark, Daniel M.

2016-01-01

Polycyclic aromatic hydrocarbons, in various charge and protonation states, are key compounds relevant to combustion chemistry and astrochemistry. Here, we probe the vibrational and electronic spectroscopy of gas-phase 9-, 1-, and 2-anthracenyl radicals (C14H9) by photodetachment of the corresponding cryogenically cooled anions via slow photoelectron velocity-map imaging (cryo-SEVI). The use of a newly designed velocity-map imaging lens in combination with ion cooling yields photoelectron spectra with <2 cm−1 resolution. Isomer selection of the anions is achieved using gas-phase synthesis techniques, resulting in observation and interpretation of detailed vibronic structure of the ground and lowest excited states for the three anthracenyl radical isomers. The ground-state bands yield electron affinities and vibrational frequencies for several Franck–Condon active modes of the 9-, 1-, and 2-anthracenyl radicals; term energies of the first excited states of these species are also measured. Spectra are interpreted through comparison with ab initio quantum chemistry calculations, Franck–Condon simulations, and calculations of threshold photodetachment cross sections and anisotropies. Experimental measures of the subtle differences in energetics and relative stabilities of these radical isomers are of interest from the perspective of fundamental physical organic chemistry and aid in understanding their behavior and reactivity in interstellar and combustion environments. Additionally, spectroscopic characterization of these species in the laboratory is essential for their potential identification in astrochemical data. PMID:26792521

Formation of toxic 2-nonyl-p-benzoquinones from α-tertiary 4-nonylphenol isomers during microbial metabolism of technical nonylphenol.

PubMed

Gabriel, Frédéric L P; Mora, Mauricio Arrieta; Kolvenbach, Boris A; Corvini, Philippe F X; Kohler, Hans-Peter E

2012-06-05

In many environmental compartments, microbial degradation of α-quaternary nonylphenols proceeds along an ipso-substitution pathway. It has been reported that technical nonylphenol contains, besides α-quaternary nonylphenols, minor amounts of various α-H, α-methyl substituted tertiary isomers. Here, we show that potentially toxic metabolites of such minor components are formed during ipso-degradation of technical nonylphenol by Sphingobium xenophagum Bayram, a strain isolated from activated sewage sludge. Small but significant amounts of nonylphenols were converted to the corresponding nonylhydroquinones, which in the presence of air oxygen oxidized to the corresponding nonyl-p-benzoquinones-yielding a complex mixture of potentially toxic metabolites. Through reduction with ascorbic acid and subsequent analysis by gas chromatography-mass spectrometry, we were able to characterize this unique metabolic fingerprint and to show that its components originated for the most part from α-tertiary nonylphenol isomers. Furthermore, our results indicate that the metabolites mixture also contained several α, β-dehydrogenated derivatives of nonyl-p-benzoquinones that originated by hydroxylation induced rearrangement, and subsequent ring and side chain oxidation from α-tertiary nonylphenol isomers. We predict that in nonylphenol polluted natural systems, in which microbial ipso-degradation is prominent, 2-alkylquinone metabolites will be produced and will contribute to the overall toxicity of the remaining material.

Bioaccessibility, Cellular Uptake, and Transport of Astaxanthin Isomers and their Antioxidative Effects in Human Intestinal Epithelial Caco-2 Cells.

PubMed

Yang, Cheng; Zhang, Hua; Liu, Ronghua; Zhu, Honghui; Zhang, Lianfu; Tsao, Rong

2017-11-29

The bioaccessibility, bioavailability, and antioxidative activities of three astaxanthin geometric isomers were investigated using an in vitro digestion model and human intestinal Caco-2 cells. This study demonstrated that the trans-cis isomerization of all-E-astaxanthin and the cis-trans isomerization of Z-astaxanthins could happen both during in vitro gastrointestinal digestion and cellular uptake processes. 13Z-Astaxanthin showed higher bioaccessibility than 9Z- and all-E-astaxanthins during in vitro digestion, and 9Z-astaxanthin exhibited higher transport efficiency than all-E- and 13Z-astaxanthins. These might explain why 13Z- and 9Z-astaxanthins are found at higher concentrations in human plasma than all-E-astaxanthin in reported studies. All three astaxanthin isomers were effective in maintaining cellular redox homeostasis as seen in the antioxidant enzyme (CAT, SOD) activities ; 9Z- and 13Z- astaxanthins exhibited a higher protective effect than all-E-astaxanthin against oxidative stress as demonstrated by the lower cellular uptake of Z-astaxanthins and lower secretion and gene expression of the pro-inflammatory cytokine IL-8 in Caco-2 cells treated with H 2 O 2 . We conclude, for the first time, that Z-astaxanthin isomers may play a more important role in preventing oxidative stress induced intestinal diseases.

Bilirubin isomer distribution in jaundiced neonates during phototherapy with LED light centered at 497 nm (turquoise) vs. 459 nm (blue).

PubMed

Ebbesen, Finn; Madsen, Poul H; Vandborg, Pernille K; Jakobsen, Lasse H; Trydal, Torleif; Vreman, Hendrik J

2016-10-01

Phototherapy using blue light is the treatment of choice worldwide for neonatal hyperbilirubinemia. However, treatment with turquoise light may be a desirable alternative. Therefore, the aim of this randomized, controlled study was to compare the bilirubin isomer distribution in serum of jaundiced neonates after 24 h of therapy with narrow-band (LED) light centered at 497 nm (turquoise) vs. 459 nm (blue), of essentially equal irradiance. Eighty-three neonates (≥33 wk gestational age) with uncomplicated hyperbilirubinemia were included in the study. Forty neonates were exposed to light centered at 497 nm and 43 infants with light centered at 459 nm. Irradiances were 5.2 × 10(15) and 5.1 × 10(15) photons/cm(2)/s, respectively. After 24 h of treatment no significant differences in serum concentrations of total bilirubin isomers and Z,Z-bilirubin were observed between the 2 groups. Interestingly, concentrations of Z,E-bilirubin, and thus also total bilirubin isomers formed during therapy, were highest for infants receiving light centered at 459 nm, while the concentration of E,Z-bilirubin was highest for those receiving light centered at 497 nm. No significant difference was found between concentrations of E,Z-lumirubin. Therapy with LED light centered at 497 nm vs. 459 nm, applied with equal irradiance on the infants, resulted in a different distribution of bilirubin isomers in serum.

Changes in plasma and oral mucosal lycopene isomer concentrations in healthy adults consuming standard servings of processed tomato products.

PubMed

Allen, Charlotte M; Schwartz, Steven J; Craft, Neal E; Giovannucci, Edward L; De Groff, Valerie L; Clinton, Steven K

2003-01-01

The consumption of tomato products is associated with a reduced risk of cardiovascular disease and several cancers. It is hypothesized that lycopene, the major carotenoid in tomato products, may mediate this relationship. We designed a study to examine changes in plasma and buccal mucosal cell (BMC) lycopene concentrations in healthy adults consuming standard daily servings of processed tomato products: spaghetti sauce, tomato soup, or vegetable juice. Thirty-six healthy subjects consumed a lycopene-free diet for 2 wk and were then assigned to one of three (n = 12) intervention groups consuming daily, single servings of sauce (21 mg lycopene per (1/2) cup), soup (12 mg lycopene per 1 cup), or juice (17 mg lycopene per 8 oz) for 4 wk. Fasting blood and BMC samples were evaluated by high-performance liquid chromatography analysis for carotenoids and lycopene isomers. Total plasma lycopene concentrations (Mean +/- SEM) decreased from 1.05 +/- 0.07 to 0.54 +/- 0.05 micromol/l (49%, P < 0.0001) during the 2-wk washout period. Following intervention, plasma lycopene concentrations increased significantly for those consuming sauce, soup, and juice (compared with washout baseline) to 2.08 (192%, P < 0.0001), 0.91 (122%, P < 0.0001), and 0.99 (92%, P < 0.0001) micromol/l, respectively. Plasma isomer concentrations show a 61:39 ratio of cis:all-trans at the start of the study. During the 2-wk washout the decrease in plasma all-trans-lycopene was greater than that for pooled cis isomers (70:30 cis:trans ratio, P < 0.001). After 2 wk of dietary intervention isomer ratios returned to those observed at the start of the study. Total BMC lycopene concentrations did not significantly change during the brief washout. During the 4-wk intervention period, BMC total lycopene concentrations increased (P < 0.005) by 165, 42, and 48% nmol/mg protein for those consuming sauce, soup, and juice, respectively. This study demonstrates that plasma lycopene decreases by 50% after approximately 2

Toward the laboratory identification of the not-so-simple NS2 neutral and anion isomers

NASA Astrophysics Data System (ADS)

Fortenberry, Ryan C.; Thackston, Russell; Francisco, Joseph S.; Lee, Timothy J.

2017-08-01

The NS2 radical is a simple arrangement of atoms with a complex electronic structure. This molecule was first reported by Hassanzadeh and Andrew's group [J. Am. Chem. Soc. 114, 83 (1992)] through Ar matrix isolation experiments. In the quarter century since this seminal work was published, almost nothing has been reported about nitrogen disulfide even though NS2 is isovalent with the common NO2. The present study aims to shed new insight into possible challenges with the characterization of this radical. No less than three potential energy surfaces all intersect in the C2v region of the SNS radical isomer. A type-C Renner-Teller molecule is present for the linear 2Πu state where the potential energy surface is fully contained within the 2.05 kcal/mol lower energy X ˜ 2A1 state. A C2v, 1 2B1 state is present in this same region, but a double excitation is required to access this state from the X ˜ 2A1 state of SNS. Additionally, a 1 2A' NSS isomer is also present but with notable differences in the geometry from the global minimum. Consequently, the rovibronic spectrum of these NS2 isomers is quite complicated. While the present theory and previous Ar matrix experiments agree well on isotopic shifts, they differ notably for the absolute fundamental vibrational frequency transitions. These differences are likely a combination of matrix shifts and issues associated with the neglect of non-adiabatic coupling in the computations. In either case, it is clear that high-resolution gas phase experimental observations will be complicated to sort. The present computations should aid in their analysis.

Cytotoxicity and apoptotic activities of alpha-, gamma- and delta-tocotrienol isomers on human cancer cells.

PubMed

Lim, Su-Wen; Loh, Hwei-San; Ting, Kang-Nee; Bradshaw, Tracey D; Zeenathul, Nazariah A

2014-12-06

Tocotrienols, especially the gamma isomer was discovered to possess cytotoxic effects associated with the induction of apoptosis in numerous cancers. Individual tocotrienol isomers are believed to induce dissimilar apoptotic mechanisms in different cancer types. This study was aimed to compare the cytotoxic potency of alpha-, gamma- and delta-tocotrienols, and to explore their resultant apoptotic mechanisms in human lung adenocarcinoma A549 and glioblastoma U87MG cells which are scarcely researched. The cytotoxic effects of alpha-, gamma- and delta-tocotrienols in both A549 and U87MG cancer cells were first determined at the cell viability and morphological aspects. DNA damage types were then identified by comet assay and flow cytometric study was carried out to support the incidence of apoptosis. The involvements of caspase-8, Bid, Bax and mitochondrial membrane permeability (MMP) in the execution of apoptosis were further expounded. All tocotrienols inhibited the growth of A549 and U87MG cancer cells in a concentration- and time-dependent manner. These treated cancer cells demonstrated some hallmarks of apoptotic morphologies, apoptosis was further confirmed by cell accumulation at the pre-G1 stage. All tocotrienols induced only double strand DNA breaks (DSBs) and no single strand DNA breaks (SSBs) in both treated cancer cells. Activation of caspase-8 leading to increased levels of Bid and Bax as well as cytochrome c release attributed by the disruption of mitochondrial membrane permeability in both A549 and U87MG cells were evident. This study has shown that delta-tocotrienol, in all experimental approaches, possessed a higher efficacy (shorter induction period) and effectiveness (higher induction rate) in the execution of apoptosis in both A549 and U87MG cancer cells as compared to alpha- and gamma-tocotrienols. Tocotrienols in particular the delta isomer can be an alternative chemotherapeutic agent for treating lung and brain cancers.

Repellent activity of catmint, Nepeta cataria, and iridoid nepetalactone isomers against Afro-tropical mosquitoes, ixodid ticks and red poultry mites.

PubMed

Birkett, Michael A; Hassanali, Ahmed; Hoglund, Solveig; Pettersson, Jan; Pickett, John A

2011-01-01

The repellent activity of the essential oil of the catmint plant, Nepeta cataria (Lamiaceae), and the main iridoid compounds (4aS,7S,7aR) and (4aS,7S,7aS)-nepetalactone, was assessed against (i) major Afro-tropical pathogen vector mosquitoes, i.e. the malaria mosquito, Anopheles gambiae s.s. and the Southern house mosquito, Culex quinquefasciatus, using a World Health Organisation (WHO)-approved topical application bioassay (ii) the brown ear tick, Rhipicephalus appendiculatus, using a climbing repellency assay, and (iii) the red poultry mite, Dermanyssus gallinae, using field trapping experiments. Gas chromatography (GC) and coupled GC-mass spectrometry (GC-MS) analysis of two N. cataria chemotypes (A and B) used in the repellency assays showed that (4aS,7S,7aR) and (4aS,7S,7aS)-nepetalactone were present in different proportions, with one of the oils (from chemotype A) being dominated by the (4aS,7S,7aR) isomer (91.95% by GC), and the other oil (from chemotype B) containing the two (4aS,7S,7aR) and (4aS,7S,7aS) isomers in 16.98% and 69.83% (by GC), respectively. The sesquiterpene hydrocarbon (E)-(1R,9S)-caryophyllene was identified as the only other major component in the oils (8.05% and 13.19% by GC, respectively). Using the topical application bioassay, the oils showed high repellent activity (chemotype A RD(50)=0.081 mg cm(-2) and chemotype B RD(50)=0.091 mg cm(-2)) for An. gambiae comparable with the synthetic repellent DEET (RD(50)=0.12 mg cm(-2)), whilst for Cx. quinquefasciatus, lower repellent activity was recorded (chemotype A RD(50)=0.34 mg cm(-2) and chemotype B RD(50)=0.074 mg cm(-2)). Further repellency testing against An. gambiae using the purified (4aS,7S,7aR) and (4aS,7S,7aS)-nepetalactone isomers revealed overall lower repellent activity, compared to the chemotype A and B oils. Testing of binary mixtures of the (4aS,7S,7aR) and (4aS,7S,7aS) isomers across a range of ratios, but all at the same overall dose (0.1 mg), revealed not only a

Theoretical IR spectra of the diketene molecule, its isomers and their mono- and disulphur analogues

NASA Astrophysics Data System (ADS)

Rode, J. E.; Dobrowolski, J. Cz; Jamróz, M. H.; Borowiak, M. A.

2001-05-01

Theoretical infrared spectra of diketene (4-methylene-2-oxetanone), its 3- and 2-methylene isomers and their mono- and disulphur analogues were calculated at the MP2/6-311++G ∗∗ level. The effect of methylene and sulphur substitution on the IR spectra is discussed in terms of potential energy distribution (PED) analysis.

Determination of melatonin and its isomer in foods by liquid chromatography tandem mass spectrometry.

PubMed

Kocadağlı, Tolgahan; Yılmaz, Cemile; Gökmen, Vural

2014-06-15

This study aimed to develop a reliable analytical method for the determination of melatonin and its isomers in various food products. The method entails ethanol extraction of solid samples (or dilution of liquid samples) prior to liquid chromatography coupled to triple quadruple mass spectrometry (LC-MS/MS) analysis of target analytes. The method was in-house validated and successfully applied to various food matrices. Recovery of melatonin from different matrices were found to be 86.0 ± 3.6%, 76.9 ± 5.4%, 98.6 ± 6.4%, and 67.0 ± 4.5% for beer, walnut, tomato and sour cherry samples, respectively. No melatonin could be detected in black and green tea, sour cherry, sour cherry concentrate, kefir (a fermented milk drink) and red wine while the highest amount of melatonin (341.7 ± 29.3 pg/g) was detected in crumb. The highest amounts of melatonin isomer were detected in yeast-fermented foods such as 170.7 ± 29.9 ng/ml in red wine, 14.3 ± 0.48 ng/ml in beer, and 15.7 ± 1.4 ng/g in bread crumb. Copyright © 2013 Elsevier Ltd. All rights reserved.

Accessible silanol sites - beneficial for the RP-HPLC separation of constitutional and diastereomeric azaspirovesamicol isomers.

PubMed

Wenzel, Barbara; Fischer, Steffen; Brust, Peter; Steinbach, Jörg

2010-12-10

Different RP-HPLC columns (phenyl, conventional ODS, cross-linked C(18) and special end-capped C(8) and C(18) phases) were used to investigate the separation of four basic ionizable isomers. Using ACN/20mM NH(4)OAc aq., a separation was observed exclusively on RP columns with higher silanol activity at unusual high ACN concentration, indicating cation-exchange as main retention mechanism. Using MeOH/20mM NH(4)OAc aq., another separation at low MeOH concentrations was observed on both, RP columns with higher as well as RP columns with lower silanol activity, which is mainly based on hydrophobic interactions. The isomers were also separated on a bare silica column at higher MeOH content using NH(4)OAc. Since cation-exchange governs this retention, the elution order was different compared to the RP phases. A strong retention on the silica column was observed in ACN, which could be attributed to partition processes as additional retention mechanism. Copyright © 2010 Elsevier B.V. All rights reserved.

Selective Reduction of Dinitrotoluene Isomers by Ascorbate Ion. Relative Rates in Homogeneous Solution.

DTIC Science & Technology

1978-02-01

abatement Ascorbic acid TNT process Purification of dinitrotoluenes Specification grade TNT 20. ABST RACT ( C f~~.. se reverse .f ~~ If nse,ee s’ d...inexpensive carbohydrates, such that the resulting mixture , upon subsequent nitra tion , would yield specification grade TNT. Using ascorbic acid as a... acid solution, the undesired DNT isomers were considerably reduced, whereas the desired 2,4- and 2,6-DNT’s were virtually unaffected . 2 UNCLASSIFIED

An all-solid-state microsecond-range quasi-square pulse generator based on fractional-turn ratio saturable pulse transformer and anti-resonance network.

PubMed

Chen, Rong; Yang, Jianhua; Cheng, Xinbing; Pan, Zilong

2017-03-01

High voltage pulse generators are widely applied in a number of fields. Defense and industrial applications stimulated intense interests in the area of pulsed power technology towards the system with high power, high repetition rate, solid state characteristics, and compact structure. An all-solid-state microsecond-range quasi-square pulse generator based on a fractional-turn ratio saturable pulse transformer and anti-resonance network is proposed in this paper. This generator consists of a charging system, a step-up system, and a modulating system. In this generator, the fractional-turn ratio saturable pulse transformer is the key component since it acts as a step-up transformer and a main switch during the working process. Demonstrative experiments show that if the primary storage capacitors are charged to 400 V, a quasi-square pulse with amplitude of about 29 kV can be achieved on a 3500 Ω resistive load, as well as the pulse duration (full width at half maximum) of about 1.3 μs. Preliminary repetition rate experiments are also carried out, which indicate that this pulse generator could work stably with the repetition rates of 30 Hz and 50 Hz. It can be concluded that this kind of all-solid-state microsecond-range quasi-square pulse generator can not only lower both the operating voltage of the primary windings and the saturable inductance of the secondary windings, thus ideally realizing the magnetic switch function of the fractional-turn ratio saturable pulse transformer, but also achieve a quasi-square pulse with high quality and fixed flat top after the modulation of a two-section anti-resonance network. This generator can be applied in areas of large power microwave sources, sterilization, disinfection, and wastewater treatment.

Species richness of arbuscular mycorrhizal fungi: associations with grassland plant richness and biomass.

PubMed

Hiiesalu, Inga; Pärtel, Meelis; Davison, John; Gerhold, Pille; Metsis, Madis; Moora, Mari; Öpik, Maarja; Vasar, Martti; Zobel, Martin; Wilson, Scott D

2014-07-01

Although experiments show a positive association between vascular plant and arbuscular mycorrhizal fungal (AMF) species richness, evidence from natural ecosystems is scarce. Furthermore, there is little knowledge about how AMF richness varies with belowground plant richness and biomass. We examined relationships among AMF richness, above- and belowground plant richness, and plant root and shoot biomass in a native North American grassland. Root-colonizing AMF richness and belowground plant richness were detected from the same bulk root samples by 454-sequencing of the AMF SSU rRNA and plant trnL genes. In total we detected 63 AMF taxa. Plant richness was 1.5 times greater belowground than aboveground. AMF richness was significantly positively correlated with plant species richness, and more strongly with below- than aboveground plant richness. Belowground plant richness was positively correlated with belowground plant biomass and total plant biomass, whereas aboveground plant richness was positively correlated only with belowground plant biomass. By contrast, AMF richness was negatively correlated with belowground and total plant biomass. Our results indicate that AMF richness and plant belowground richness are more strongly related with each other and with plant community biomass than with the plant aboveground richness measures that have been almost exclusively considered to date. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

The near-UV absorber OSSO and its isomers.

PubMed

Wu, Zhuang; Wan, Huabin; Xu, Jian; Lu, Bo; Lu, Yan; Eckhardt, André K; Schreiner, Peter R; Xie, Changjian; Guo, Hua; Zeng, Xiaoqing

2018-05-01

Disulfur dioxide, OSSO, has been proposed as the enigmatic "near-UV absorber" in the yellowish atmosphere of Venus. However, the fundamentally important spectroscopic properties and photochemistry of OSSO are scarcely documented. By either condensing gaseous SO or 266 laser photolysis of an S2O2 complex in Ar or N2 at 15 K, syn-OSSO, anti-OSSO, and cyclic OS([double bond, length as m-dash]O)S were identified by IR and UV/Vis spectroscopy for the first time. The observed absorptions (λmax) for OSSO at 517 and 390 nm coincide with the near-UV absorption (320-400 nm) found in the Venus clouds by photometric measurements with the Pioneer Venus orbiter. Subsequent UV light irradiation (365 nm) depletes syn-OSSO and anti-OSSO and yields a fourth isomer, syn-OSOS, with concomitant dissociation into SO2 and elemental sulfur.

Lifetime Measurement of the 229Th nuclear isomer

NASA Astrophysics Data System (ADS)

Seiferle, Benedict; von der Wense, Lars; Thirolf, Peter G.

2017-01-01

The first excited isomeric state of 229Th possesses the lowest energy among all known excited nuclear states. The expected energy is accessible with today's laser technology and in principle allows for a direct optical laser excitation of the nucleus. The isomer decays via three channels to its ground state (internal conversion, γ decay, and bound internal conversion), whose strengths depend on the charge state of Thm229 . We report on the measurement of the internal-conversion decay half-life of neutral Thm229 . A half-life of 7 ±1 μ s has been measured, which is in the range of theoretical predictions and, based on the theoretically expected lifetime of ≈1 04 s of the photonic decay channel, gives further support for an internal conversion coefficient of ≈1 09, thus constraining the strength of a radiative branch in the presence of internal conversion.

[Atomic/ionic fluorescence in microwave plasma torch discharge excited by high current microsecond pulsed hollow cathode lamp-europium atomic/ionic fluorescence spectrometry].

PubMed

Gong, Z; Liang, F; Yang, P; Jin, Q; Huang, B

1999-06-01

Eu atomic and ionic fluorescence spectrometry in microwave plasma torch discharge excited by high current microsecond pulsed hollow cathode lamp (HCMP HCL-MPT AFS/IFS) was studied. Operating conditions were optimized. The best detection limits for AFS and IFS obtained with a desolvated ultrasonic nebulization system were 42.0 ng/mL for Eu I 462.7 nm and 21.8 ng/mL for Eu II 381.97 nm, respectively, both were better than those given by the instruction manual of a Baird ICP AFS-2000 spectrometer using pneumatic concentric nebulizer with desolvation for AFS, but were significantly higher than those obtained by using the Baird spectrometer with a mini-monochromator and a ultrasonic nebulzer system.

Application of Attenuated Total Reflectance-Fourier Transformed Infrared (ATR-FTIR) Spectroscopy To Determine the Chlorogenic Acid Isomer Profile and Antioxidant Capacity of Coffee Beans.

PubMed

Liang, Ningjian; Lu, Xiaonan; Hu, Yaxi; Kitts, David D

2016-01-27

The chlorogenic acid isomer profile and antioxidant activity of both green and roasted coffee beans are reported herein using ATR-FTIR spectroscopy combined with chemometric analyses. High-performance liquid chromatography (HPLC) quantified different chlorogenic acid isomer contents for reference, whereas ORAC, ABTS, and DPPH were used to determine the antioxidant activity of the same coffee bean extracts. FTIR spectral data and reference data of 42 coffee bean samples were processed to build optimized PLSR models, and 18 samples were used for external validation of constructed PLSR models. In total, six PLSR models were constructed for six chlorogenic acid isomers to predict content, with three PLSR models constructed to forecast the free radical scavenging activities, obtained using different chemical assays. In conclusion, FTIR spectroscopy, coupled with PLSR, serves as a reliable, nondestructive, and rapid analytical method to quantify chlorogenic acids and to assess different free radical-scavenging capacities in coffee beans.

One-microsecond molecular dynamics simulation of channel gating in a nicotinic receptor homologue

PubMed Central

Nury, Hugues; Poitevin, Frédéric; Van Renterghem, Catherine; Changeux, Jean-Pierre; Corringer, Pierre-Jean; Delarue, Marc; Baaden, Marc

2010-01-01

Recently discovered bacterial homologues of eukaryotic pentameric ligand-gated ion channels, such as the Gloeobacter violaceus receptor (GLIC), are increasingly used as structural and functional models of signal transduction in the nervous system. Here we present a one-microsecond-long molecular dynamics simulation of the GLIC channel pH stimulated gating mechanism. The crystal structure of GLIC obtained at acidic pH in an open-channel form is equilibrated in a membrane environment and then instantly set to neutral pH. The simulation shows a channel closure that rapidly takes place at the level of the hydrophobic furrow and a progressively increasing quaternary twist. Two major events are captured during the simulation. They are initiated by local but large fluctuations in the pore, taking place at the top of the M2 helix, followed by a global tertiary relaxation. The two-step transition of the first subunit starts within the first 50 ns of the simulation and is followed at 450 ns by its immediate neighbor in the pentamer, which proceeds with a similar scenario. This observation suggests a possible two-step domino-like tertiary mechanism that takes place between adjacent subunits. In addition, the dynamical properties of GLIC described here offer an interpretation of the paradoxical properties of a permeable A13′F mutant whose crystal structure determined at 3.15 Å shows a pore too narrow to conduct ions. PMID:20308576

FAST TRACK COMMUNICATION: Contrasting characteristics of sub-microsecond pulsed atmospheric air and atmospheric pressure helium-oxygen glow discharges

NASA Astrophysics Data System (ADS)

Walsh, J. L.; Liu, D. X.; Iza, F.; Rong, M. Z.; Kong, M. G.

2010-01-01

Glow discharges in air are often considered to be the ultimate low-temperature atmospheric pressure plasmas for numerous chamber-free applications. This is due to the ubiquitous presence of air and the perceived abundance of reactive oxygen and nitrogen species in air plasmas. In this paper, sub-microsecond pulsed atmospheric air plasmas are shown to produce a low concentration of excited oxygen atoms but an abundance of excited nitrogen species, UV photons and ozone molecules. This contrasts sharply with the efficient production of excited oxygen atoms in comparable helium-oxygen discharges. Relevant reaction chemistry analysed with a global model suggests that collisional excitation of O2 by helium metastables is significantly more efficient than electron dissociative excitation of O2, electron excitation of O and ion-ion recombination. These results suggest different practical uses of the two oxygen-containing atmospheric discharges, with air plasmas being well suited for nitrogen and UV based chemistry and He-O2 plasmas for excited atomic oxygen based chemistry.

Assigning Peptide Disulfide Linkage Pattern Among Regio-Isomers via Methoxy Addition to Disulfide and Tandem Mass Spectrometry

NASA Astrophysics Data System (ADS)

Durand, Kirt L.; Tan, Lei; Stinson, Craig A.; Love-Nkansah, Chasity B.; Ma, Xiaoxiao; Xia, Yu

2017-06-01

Pinpointing disulfide linkage pattern is critical in the characterization of proteins and peptides consisting of multiple disulfide bonds. Herein, we report a method based on coupling online disulfide modification and tandem mass spectrometry (MS/MS) to distinguish peptide disulfide regio-isomers. Such a method relies on a new disulfide bond cleavage reaction in solution, involving methanol as a reactant and 254 nm ultraviolet (UV) irradiation. This reaction leads to selective cleavage of a disulfide bond and formation of sulfenic methyl ester (-SOCH3) at one cysteine residue and a thiol (-SH) at the other. Under low energy collision-induced dissociation (CID), cysteine sulfenic methyl ester motif produces a signature methanol loss (-32 Da), allowing its identification from other possible isomeric structures such as S-hydroxylmethyl (-SCH2OH) and methyl sulfoxide (-S(O)-CH3). Since disulfide bond can be selectively cleaved and modified upon methoxy addition, subsequent MS2 CID of the methoxy addition product provides enhanced sequence coverage as demonstrated by the analysis of bovine insulin. More importantly, this reaction does not induce disulfide scrambling, likely due to the fact that radical intermediates are not involved in the process. An approach based on methoxy addition followed by MS3 CID has been developed for assigning disulfide linkage patterns in peptide disulfide regio-isomers. This methodology was successfully applied to characterizing peptide systems having two disulfide bonds and three disulfide linkage isomers: side-by-side, overlapped, and looped-within-a-loop configurations. [Figure not available: see fulltext.

Isomer-dependent fragmentation dynamics of inner-shell photoionized difluoroiodobenzene

DOE PAGES

Ablikim, Utuq; Bomme, Cédric; Savelyev, Evgeny; ...

2017-05-11

The fragmentation dynamics of 2,6- and 3,5-difluoroiodobenzene after iodine 4d inner-shell photoionization with soft X-rays are studied using coincident electron and ion momentum imaging. By analyzing the momentum correlation between iodine and fluorine cations in three-fold ion coincidence events, we can distinguish the two isomers experimentally. Classical Coulomb explosion simulations are in overall agreement with the experimentally determined fragment ion kinetic energies and momentum correlations and point toward different fragmentation mechanisms and time scales. Finally, while most three-body fragmentation channels show clear evidence for sequential fragmentation on a time scale larger than the rotational period of the fragments, the breakupmore » into iodine and fluorine cations and a third charged co-fragment appears to occur within several hundred femtoseconds.« less

Communication: "Position" does matter: The photofragmentation of the nitroimidazole isomers

NASA Astrophysics Data System (ADS)

Bolognesi, P.; Casavola, A. R.; Cartoni, A.; Richter, R.; Markus, P.; Borocci, S.; Chiarinelli, J.; Tošić, S.; Sa'adeh, H.; Masič, M.; Marinković, B. P.; Prince, K. C.; Avaldi, L.

2016-11-01

A combined experimental and theoretical approach has been used to disentangle the fundamental mechanisms of the fragmentation of the three isomers of nitroimidazole induced by vacuum ultra-violet (VUV) radiation, namely, 4-, 5-, and 2-nitroimidazole. The results of mass spectrometry as well as photoelectron-photoion coincidence spectroscopy display striking differences in the radiation-induced decomposition of the different nitroimidazole radical cations. Based on density functional theory (DFT) calculations, a model is proposed which fully explains such differences, and reveals the subtle fragmentation mechanisms leading to the release of neutral species like NO, CO, and HCN. Such species have a profound impact in biological media and may play a fundamental role in radiosensitising mechanisms during radiotherapy.

In vitro human metabolism of permethrin isomers alone or as a mixture and the formation of the major metabolites in cryopreserved primary hepatocytes.

PubMed

Willemin, M-E; Kadar, A; de Sousa, G; Leclerc, E; Rahmani, R; Brochot, C

2015-06-01

In vitro metabolism of permethrin, a pyrethroid insecticide, was assessed in primary human hepatocytes. In vitro kinetic experiments were performed to estimate the Michaelis-Menten parameters and the clearances or formation rates of the permethrin isomers (cis- and trans-) and three metabolites, cis- and trans-3-(2,2 dichlorovinyl)-2,2-dimethyl-(1-cyclopropane) carboxylic acid (cis- and trans-DCCA) and 3-phenoxybenzoic acid (3-PBA). Non-specific binding and the activity of the enzymes involved in permethrin's metabolism (cytochromes P450 and carboxylesterases) were quantified. Trans-permethrin was cleared more rapidly than cis-permethrin with a 2.6-factor (25.7±0.6 and 10.1±0.3 μL/min/10(6) cells respectively). A 3-factor was observed between the formation rates of DCCA and 3-PBA obtained from trans- and cis-permethrin. For both isomers, the rate of formation of DCCA was higher than the one of 3-PBA. The metabolism of the isomers in mixture was also quantified. The co-incubation of isomers at different ratios showed the low inhibitory potential of cis- and trans-permethrin on each other. The estimates of the clearances and the formation rates in the co-incubation condition did not differ from the estimates obtained with a separate incubation. These metabolic parameters may be integrated in physiologically based pharmacokinetic (PBPK) models to predict the fate of permethrin and metabolites in the human body. Copyright © 2015 Elsevier Ltd. All rights reserved.

Isomer-specific vibronic structure of the 9-, 1-, and 2-anthracenyl radicals via slow photoelectron velocity-map imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weichman, Marissa L.; DeVine, Jessalyn A.; Levine, Daniel S.

Polycyclic aromatic hydrocarbons, in various charge and protonation states, are key compounds relevant to combustion chemistry and astrochemistry. In this paper, we probe the vibrational and electronic spectroscopy of gas-phase 9-, 1-, and 2-anthracenyl radicals (C 14H 9) by photodetachment of the corresponding cryogenically cooled anions via slow photoelectron velocity-map imaging (cryo-SEVI). The use of a newly designed velocity-map imaging lens in combination with ion cooling yields photoelectron spectra with <2 cm -1 resolution. Isomer selection of the anions is achieved using gas-phase synthesis techniques, resulting in observation and interpretation of detailed vibronic structure of the ground and lowest excitedmore » states for the three anthracenyl radical isomers. The ground-state bands yield electron affinities and vibrational frequencies for several Franck–Condon active modes of the 9-, 1-, and 2-anthracenyl radicals; term energies of the first excited states of these species are also measured. Spectra are interpreted through comparison with ab initio quantum chemistry calculations, Franck–Condon simulations, and calculations of threshold photodetachment cross sections and anisotropies. Experimental measures of the subtle differences in energetics and relative stabilities of these radical isomers are of interest from the perspective of fundamental physical organic chemistry and aid in understanding their behavior and reactivity in interstellar and combustion environments. Finally and additionally, spectroscopic characterization of these species in the laboratory is essential for their potential identification in astrochemical data.« less

Isomer-specific vibronic structure of the 9-, 1-, and 2-anthracenyl radicals via slow photoelectron velocity-map imaging

DOE PAGES

Weichman, Marissa L.; DeVine, Jessalyn A.; Levine, Daniel S.; ...

2016-01-20

Polycyclic aromatic hydrocarbons, in various charge and protonation states, are key compounds relevant to combustion chemistry and astrochemistry. In this paper, we probe the vibrational and electronic spectroscopy of gas-phase 9-, 1-, and 2-anthracenyl radicals (C 14H 9) by photodetachment of the corresponding cryogenically cooled anions via slow photoelectron velocity-map imaging (cryo-SEVI). The use of a newly designed velocity-map imaging lens in combination with ion cooling yields photoelectron spectra with <2 cm -1 resolution. Isomer selection of the anions is achieved using gas-phase synthesis techniques, resulting in observation and interpretation of detailed vibronic structure of the ground and lowest excitedmore » states for the three anthracenyl radical isomers. The ground-state bands yield electron affinities and vibrational frequencies for several Franck–Condon active modes of the 9-, 1-, and 2-anthracenyl radicals; term energies of the first excited states of these species are also measured. Spectra are interpreted through comparison with ab initio quantum chemistry calculations, Franck–Condon simulations, and calculations of threshold photodetachment cross sections and anisotropies. Experimental measures of the subtle differences in energetics and relative stabilities of these radical isomers are of interest from the perspective of fundamental physical organic chemistry and aid in understanding their behavior and reactivity in interstellar and combustion environments. Finally and additionally, spectroscopic characterization of these species in the laboratory is essential for their potential identification in astrochemical data.« less

X2Y2 isomers: tuning structure and relative stability through electronegativity differences (X = H, Li, Na, F, Cl, Br, I; Y = O, S, Se, Te).

PubMed

El-Hamdi, Majid; Poater, Jordi; Bickelhaupt, F Matthias; Solà, Miquel

2013-03-04

We have studied the XYYX and X2YY isomers of the X2Y2 species (X = H, Li, Na, F, Cl, Br, I; Y = O, S, Se, Te) using density functional theory at the ZORA-BP86/QZ4P level. Our computations show that, over the entire range of our model systems, the XYYX isomers are more stable than the X2YY forms except for X = F and Y = S and Te, for which the F2SS and F2TeTe isomers are slightly more stable. Our results also point out that the Y-Y bond length can be tuned quite generally through the X-Y electronegativity difference. The mechanism behind this electronic tuning is the population or depopulation of the π* in the YY fragment.

Probing microsecond time scale dynamics in proteins by methyl (1)H Carr-Purcell-Meiboom-Gill relaxation dispersion NMR measurements. Application to activation of the signaling protein NtrC(r).

PubMed

Otten, Renee; Villali, Janice; Kern, Dorothee; Mulder, Frans A A

2010-12-01

To study microsecond processes by relaxation dispersion NMR spectroscopy, low power deposition and short pulses are crucial and encourage the development of experiments that employ (1)H Carr-Purcell-Meiboom-Gill (CPMG) pulse trains. Herein, a method is described for the comprehensive study of microsecond to millisecond time scale dynamics of methyl groups in proteins, exploiting their high abundance and favorable relaxation properties. In our approach, protein samples are produced using [(1)H, (13)C]-d-glucose in ∼100% D(2)O, which yields CHD(2) methyl groups for alanine, valine, threonine, isoleucine, leucine, and methionine residues with high abundance, in an otherwise largely deuterated background. Methyl groups in such samples can be sequence-specifically assigned to near completion, using (13)C TOCSY NMR spectroscopy, as was recently demonstrated (Otten, R.; et al. J. Am. Chem. Soc. 2010, 132, 2952-2960). In this Article, NMR pulse schemes are presented to measure (1)H CPMG relaxation dispersion profiles for CHD(2) methyl groups, in a vein similar to that of backbone relaxation experiments. Because of the high deuteration level of methyl-bearing side chains, artifacts arising from proton scalar coupling during the CPMG pulse train are negligible, with the exception of Ile-δ1 and Thr-γ2 methyl groups, and a pulse scheme is described to remove the artifacts for those residues. Strong (13)C scalar coupling effects, observed for several leucine residues, are removed by alternative biochemical and NMR approaches. The methodology is applied to the transcriptional activator NtrC(r), for which an inactive/active state transition was previously measured and the motions in the microsecond time range were estimated through a combination of backbone (15)N CPMG dispersion NMR spectroscopy and a collection of experiments to determine the exchange-free component to the transverse relaxation rate. Exchange contributions to the (1)H line width were detected for 21 methyl

Total Synthesis of Biselyngbyolide B and Its C21-C22 Z-Isomer.

PubMed

Kämmler, Lena; Maier, Martin E

2018-04-20

Investigations toward the synthesis of the 18-membered macrolactone biselyngbyolide B (2) from a C1-C13 and a C14-C23 fragment are described. As a key reaction in the synthesis of the C1-C13 fragment, we used an asymmetric propargylation of chiral vinylketene silyl N, O-acetal 12. Access to a C14-C23 fragment featuring a skipped diene and a sensitive allyl alcohol function was initially attempted via reductive fragmentation of a pyran template. However, this ring opening on iodide 32 with t-BuLi led to dienynol 33 with a 21 Z double bond. With a silyl protecting group at 3-OH and by implementing an intramolecular Stille coupling for macrolactonization, the 21 Z-isomer of biselyngbyolide B (47) was obtained. For preparation of a C14-C23 fragment with the 21 E-configuration, a cross-coupling of vinylstannane 48 with 4-bromocrotonate (49) set the configuration of the two double bonds. Biselyngbyolide B (2) was then accessed by an intramolecular Heck coupling. In preliminary biological cytotoxicity assays, 2 turned out to be active, whereas the 21 Z-isomer 47 was much less active. The 3-OMEM analogue 40 was devoid of activity. These results support the notion that the side chain with the correct configuration is relevant for binding to the Ca 2+ -ATPase and the biological activity.

Isomer depletion as experimental evidence of nuclear excitation by electron capture

NASA Astrophysics Data System (ADS)

Chiara, C. J.; Carroll, J. J.; Carpenter, M. P.; Greene, J. P.; Hartley, D. J.; Janssens, R. V. F.; Lane, G. J.; Marsh, J. C.; Matters, D. A.; Polasik, M.; Rzadkiewicz, J.; Seweryniak, D.; Zhu, S.; Bottoni, S.; Hayes, A. B.; Karamian, S. A.

2018-02-01

The atomic nucleus and its electrons are often thought of as independent systems that are held together in the atom by their mutual attraction. Their interaction, however, leads to other important effects, such as providing an additional decay mode for excited nuclear states, whereby the nucleus releases energy by ejecting an atomic electron instead of by emitting a γ-ray. This ‘internal conversion’ has been known for about a hundred years and can be used to study nuclei and their interaction with their electrons. In the inverse process—nuclear excitation by electron capture (NEEC)—a free electron is captured into an atomic vacancy and can excite the nucleus to a higher-energy state, provided that the kinetic energy of the free electron plus the magnitude of its binding energy once captured matches the nuclear energy difference between the two states. NEEC was predicted in 1976 and has not hitherto been observed. Here we report evidence of NEEC in molybdenum-93 and determine the probability and cross-section for the process in a beam-based experimental scenario. Our results provide a standard for the assessment of theoretical models relevant to NEEC, which predict cross-sections that span many orders of magnitude. The greatest practical effect of the NEEC process may be on the survival of nuclei in stellar environments, in which it could excite isomers (that is, long-lived nuclear states) to shorter-lived states. Such excitations may reduce the abundance of the isotope after its production. This is an example of ‘isomer depletion’, which has been investigated previously through other reactions, but is used here to obtain evidence for NEEC.

Analysis of co-eluted isomers of high-molecular weight polycyclic aromatic hydrocarbons in high performance liquid chromatography fractions via solid-phase nanoextraction and time-resolved Shpol'skii spectroscopy.

PubMed

Wilson, Walter B; Campiglia, Andres D

2011-09-28

We present an accurate method for the determination of isomers of high-molecular weight polycyclic aromatic hydrocarbons co-eluted in HPLC fractions. The feasibility of this approach is demonstrated with two isomers of molecular weight 302 with identical mass fragmentation patterns, namely dibenzo[a,i]pyrene and naphtho[2,3-a]pyrene. Qualitative and quantitative analysis is carried out via laser-excited time-resolved Shpol'skii spectroscopy at liquid helium temperature. Unambiguous identification of co-eluted isomers is based on their characteristic 4.2 K line-narrowed spectra in n-octane as well as their fluorescence lifetimes. Pre-concentration of HPLC fractions prior to spectroscopic analysis is performed with the aid of gold nanoparticles via an environmentally friendly procedure. In addition to the two co-eluted isomers, the analytical figures of merit of the entire procedure were evaluated with dibenzo[a,l]pyrene, dibenzo[a,h]pyrene and dibenzo[a,e]pyrene. The analytical recoveries from drinking water samples varied between 98.2±5.5 (dibenzo[a,l]pyrene) and 102.7±3.2% (dibenzo[a,i]pyrene). The limits of detection ranged from 51.1 ng L(-1) (naphtho[2,3-a]pyrene) to 154 ng L(-1) (dibenzo[a,e]pyrene). The excellent analytical figures of merit associated to its HPLC compatibility makes this approach an attractive alternative for the analysis of co-eluted isomers with identical mass spectra. Copyright © 2011 Elsevier B.V. All rights reserved.

Methyl-perfluoroheptene-ethers (CH3OC7F13): measured OH radical reaction rate coefficients for several isomers and enantiomers and their atmospheric lifetimes and global warming potentials.

PubMed

Jubb, Aaron M; Gierczak, Tomasz; Baasandorj, Munkhbayar; Waterland, Robert L; Burkholder, James B

2014-05-06

Mixtures of methyl-perfluoroheptene-ethers (CH3OC7F13, MPHEs) are currently in use as replacements for perfluorinated alkanes (PFCs) and poly-ether heat transfer fluids, which are persistent greenhouse gases with lifetimes >1000 years. At present, the atmospheric processing and environmental impact from the use of MPHEs is unknown. In this work, rate coefficients at 296 K for the gas-phase reaction of the OH radical with six key isomers (including stereoisomers and enantiomers) of MPHEs used commercially were measured using a relative rate method. Rate coefficients for the six MPHE isomers ranged from ∼ 0.1 to 2.9 × 10(-12) cm(3) molecule(-1) s(-1) with a strong stereoisomer and -OCH3 group position dependence; the (E)-stereoisomers with the -OCH3 group in an α- position relative to the double bond had the greatest reactivity. Rate coefficients measured for the d3-MPHE isomer analogues showed decreased reactivity consistent with a minor contribution of H atom abstraction from the -OCH3 group to the overall reactivity. Estimated atmospheric lifetimes for the MPHE isomers range from days to months. Atmospheric lifetimes, radiative efficiencies, and global warming potentials for these short-lived MPHE isomers were estimated based on the measured OH rate coefficients along with measured and theoretically calculated MPHE infrared absorption spectra. Our results highlight the importance of quantifying the atmospheric impact of individual components in an isomeric mixture.

Selected Reaction Monitoring to Differentiate and Relatively Quantitate Isomers of Sulfated and Unsulfated Core 1 O-Glycans from Salivary MUC7 Protein in Rheumatoid Arthritis*

PubMed Central

Flowers, Sarah A.; Ali, Liaqat; Lane, Catherine S.; Olin, Magnus; Karlsson, Niclas G.

2013-01-01

Rheumatoid arthritis is a common and debilitating systemic inflammatory condition affecting up to 1% of the world's population. This study aimed to investigate the immunological significance of O-glycans in chronic arthritis at a local and systemic level. O-Glycans released from synovial glycoproteins during acute and chronic arthritic conditions were compared and immune-reactive glycans identified. The sulfated core 1 O-glycan (Galβ1–3GalNAcol) was immune reactive, showing a different isomeric profile in the two conditions. From acute reactive arthritis, three isomers could be sequenced, but in patients with chronic rheumatoid arthritis, only a single 3-Gal sulfate-linked isomer could be identified. The systemic significance of this glycan epitope was investigated using the salivary mucin MUC7 in patients with rheumatoid arthritis and normal controls. To analyze this low abundance glycan, a selected reaction monitoring (SRM) method was developed to differentiate and relatively quantitate the core 1 O-glycan and the sulfated core 1 O-glycan Gal- and GalNAc-linked isomers. The acquisition of highly sensitive full scan linear ion trap MS/MS spectra in addition to quantitative SRM data allowed the 3- and 6-linked Gal isomers to be differentiated. The method was used to relatively quantitate the core 1 glycans from MUC7 to identify any systemic changes in this carbohydrate epitope. A statistically significant increase in sulfation was identified in salivary MUC7 from rheumatoid arthritis patients. This suggests a potential role for this epitope in chronic inflammation. This study was able to develop an SRM approach to specifically identify and relatively quantitate sulfated core 1 isomers and the unsulfated structure. The expansion of this method may afford an avenue for the high throughput investigation of O-glycans. PMID:23457413

Enantioselective Reduction of Citral Isomers in NCR Ene Reductase: Analysis of an Active-Site Mutant Library.

PubMed

Kress, Nico; Rapp, Johanna; Hauer, Bernhard

2017-04-18

A deeper understanding of the >99 % S-selective reduction of both isomers of citral catalyzed by NCR ene reductase was achieved by active-site mutational studies and docking simulation. Though structurally similar, the E/Z isomers of citral showed a significantly varying selectivity response to introduced mutations. Although it was possible to invert (E)-citral reduction enantioselectivity to ee 46 % (R) by introducing mutation W66A, for (Z)-citral it remained ≥88 % (S) for all single-residue variants. Residue 66 seems to act as a lever for opposite binding modes. This was underlined by a W66A-based double-mutant library that enhanced the (E)-citral derived enantioselectivity to 63 % (R) and significantly lowered the S selectivity for (Z)-citral to 44 % (S). Formation of (R)-citronellal from an (E/Z)-citral mixture is a desire in industrial (-)-menthol synthesis. Our findings pave the way for a rational enzyme engineering solution. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Crystal chemistry and oxidation state of Fe-rich prehnite from a hydrothermally altered dolerite

NASA Astrophysics Data System (ADS)

Nagashima, Mariko; Iwasa, Kiyoka; Akasaka, Masahide

2018-04-01

Fe-rich prehnite, Ca2(Al,Fe)(AlSi3)O10(OH)2, in a hydrothermally altered dolerite sill from Mitsu, Shimane Peninsula, Japan, was studied using 57Fe Mössbauer spectroscopy and X-ray Rietveld method to determine the oxidation state and distribution of Fe within the prehnite and to clarify its structural properties. Prehnite shows two modes of occurrence: a druse and vein mineral (prehnite I) associated with Fe-rich pumpellyite and laumontite and a replacement of primary plagioclase (prehnite II). The Fe contents of prehnite I and II are 0.33-0.44 and 0.01-0.46 Fe3+ atoms per formula unit, respectively. The Mössbauer spectrum of prehnite II consists of one doublet with isomer shift ( IS) = 0.364 mm/s and quadrupole splitting ( QS) = 0.284 mm/s assigned to Fe3+ at the octahedral M site. In contrast, the Mössbauer spectrum of prehnite I consists of two doublets assigned to Fe3+ at the M site ( IS = 0.369 mm/s and QS = 0.299 mm/s) and Fe2+ at the seven coordinated A site ( IS = 1.05 and QS = 2.78 mm/s). According to X-ray Rietveld refinements with Pmna and Pma2 space groups, the fitting with Pma2 gave more reduced reliability factors than those using Pmna for both specimens, implying ordering of Al and Si at the tetrahedral T2 sites. Determined T2-O bond lengths at the Al-rich and Si-rich T2 sites, 1.71-1.72 and 1.62-1.64 Å, respectively, also indicate the ordered arrangement of Al and Si at the T2 sites. Refined site occupancies at the A and M sites are represented as A (Ca0.993(9)Fe2 + 0.007) M (Al0.666(6)Fe3 + 0.334) for prehnite I, and A Ca1.0 M (Al0.865(5)Fe3 + 0.135) for prehnite II, respectively. The existence of Fe2+ in the A site filling Ca deficiency in prehnite I is consistent with the result from the Mössbauer analysis.

Distribution and fate of HCH isomers and DDT metabolites in a tropical environment-case study Cameron Highlands-Malaysia.

PubMed

Saadati, Naghmeh; Abdullah, Md Pauzi; Zakaria, Zuriati; Rezayi, Majid; Hosseinizare, Nader

2012-11-07

The serious impact effects of persistent organic pollutants such as organochlorine pesticides, especially dichlorodiphenyltrichloroethane family (DDTs) and hexachlorocyclohexane isomers (HCHs) have been causing widespread concern, despite effective control on their manufacturing, agricultural and vector practices. In that, in addition to the previous global limitations on DDTs usage, α-HCH, β-HCH and lindane have also became an on-going topic of global relevance based on the latest Stockholm Convention list on 10th of May 2009. Concentrations of dichlorodiphenyltrichloroethane family (DDTs) and hexachlorocyclohexane isomers (HCHs) were determined by GC-ECD in Cameron Highlands, the main vegetables and flowers farming area in Malaysia as an agricultural tropical environment. A total of 112 surface water and sediment samples at eight points were collected along the main rivers in the area namely Telom and Bertam in the dry and wet seasons of 2011. Total concentration of HCH isomers ranged from not detected to 25.03 ng/L in the water (mean of 5.55 ±6.0 ng/L), while, it ranged from 0.002 to 59.17 ng/g (mean of 8.06±9.39 ng/g) in the sediment. Total concentration of DDT and its metabolites in the water samples varied from not detected to 8.0 ng/L (mean of 0.90±1.66 ng/g), whereas, it was in the range of 0.025 to 23.24 ng/g (mean of 2.55±4.0 ng/g) in the surface sediment samples. The ratio of HCHs and DDTs composition indicated an obvious historical usage and new inputs of these pesticides. Among alpha, beta, gamma and delta isomers of HCH, gamma was the most dominant component in the sediment and water as well. Some seasonal variations in the level of selected pesticides were noted. The results illustrate distribution, behaviour and fate of HCHs, and DDTs have closely connected with topological and meteorological properties of the area beyond their chemical characterizations. The features of environmental circumstances exceed one or more of these characters in

40 CFR 180.449 - Avermectin B1 and its delta-8,9-isomer; tolerances for residues.

Code of Federal Regulations, 2012 CFR

2012-07-01

...-isomer in or on the following commodities: Commodity Parts per million Almond, hulls 0.10 Apple 0.020 Apple, wet pomace 0.10 Avocado 0.020 Bean, dry, seed 0.01 Cattle, fat 0.03 Cattle, meat 0.02 Cattle..., undelinted seed 0.005 Food products in food handling establishments (other than those already covered by...

Versatile Indolocarbazole-Isomer Derivatives as Highly Emissive Emitters and Ideal Hosts for Thermally Activated Delayed Fluorescent OLEDs with Alleviated Efficiency Roll-Off.

PubMed

Zhang, Dongdong; Song, Xiaozeng; Cai, Minghan; Kaji, Hironori; Duan, Lian

2018-02-01

Maintaining high efficiency at high brightness levels is an exigent challenge for real-world applications of thermally activated delayed fluorescent organic light-emitting diodes (TADF-OLEDs). Here, versatile indolocarbazole-isomer derivatives are developed as highly emissive emitters and ideal hosts for TADF-OLEDs to alleviate efficiency roll-off. It is observed that photophysical and electronic properties of these compounds can be well modulated by varying the indolocarbazole isomers. A photoluminescence quantum yield (η PL ) approaching unity and a maximum external quantum efficiency (EQE max ) of 25.1% are obtained for the emitter with indolo[3,2-a]carbazolyl subunit. Remarkably, record-high EQE/power efficiency of 26.2%/69.7 lm W -1 at the brightness level of 5000 cd m -2 with a voltage of only 3.74 V are also obtained using the same isomer as the host in a green TADF-OLED. It is evident that TADF hosts with high η PL values, fast reverse intersystem crossing processes, and balanced charge transport properties may open the path toward roll-off-free TADF-OLEDs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Lanthanum-mediated dehydrogenation of butenes: Spectroscopy and formation of La(C4H6) isomers

NASA Astrophysics Data System (ADS)

Cao, Wenjin; Hewage, Dilrukshi; Yang, Dong-Sheng

2018-01-01

La atom reactions with 1-butene, 2-butene, and isobutene are carried out in a laser-vaporization molecular beam source. The three reactions yield the same La-hydrocarbon products from the dehydrogenation and carbon-carbon bond cleavage and coupling of the butenes. The dehydrogenated species La(C4H6) is the major product, which is characterized with mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical computations. The MATI spectrum of La(C4H6) produced from the La+1-butene reaction exhibits two band systems, whereas the MATI spectra produced from the La+2-butene and isobutene reactions display only a single band system. Each of these spectra shows a strong origin band and several vibrational progressions. The two band systems from the spectrum of the 1-butene reaction are assigned to the ionization of two isomers: La[C(CH2)3] (Iso A) and La(CH2CHCHCH2) (Iso B), and the single band system from the spectra of the 2-butene and isobutene reactions is attributed to Iso B and Iso A, respectively. The ground electronic states are 2A1 (C3v) for Iso A and 2A' (Cs) for Iso B. The ionization of the doublet state of each isomer removes a La 6s-based electron and leads to the 1A1 ion of Iso A and the 1A' ion of Iso B. The formation of both isomers consists of La addition to the C=C double bond, La insertion into two C(sp3)—H bonds, and H2 elimination. In addition to these steps, the formation of Iso A from the La+1-butene reaction may involve the isomerization of 1-butene to isobutene prior to the C—H bond activation, whereas the formation of Iso B from the La+trans-2-butene reaction may include the trans- to cis-butene isomerization after the C—H bond activation.

Toroidal high-spin isomers in the nucleus 304120

NASA Astrophysics Data System (ADS)

Staszczak, A.; Wong, Cheuk-Yin; Kosior, A.

2017-05-01

Background: Strongly deformed oblate superheavy nuclei form an intriguing region where the toroidal nuclear structures may bifurcate from the oblate spheroidal shape. The bifurcation may be facilitated when the nucleus is endowed with a large angular moment about the symmetry axis with I =Iz . The toroidal high-K isomeric states at their local energy minima can be theoretically predicted using the cranked self-consistent Skyrme-Hartree-Fock method. Purpose: We use the cranked Skyrme-Hartree-Fock method to predict the properties of the toroidal high-spin isomers in the superheavy nucleus 120304184. Method: Our method consists of three steps: First, we use the deformation-constrained Skyrme-Hartree-Fock-Bogoliubov approach to search for the nuclear density distributions with toroidal shapes. Next, using these toroidal distributions as starting configurations, we apply an additional cranking constraint of a large angular momentum I =Iz about the symmetry z axis and search for the energy minima of the system as a function of the deformation. In the last step, if a local energy minimum with I =Iz is found, we perform at this point the cranked symmetry- and deformation-unconstrained Skyrme-Hartree-Fock calculations to locate a stable toroidal high-spin isomeric state in free convergence. Results: We have theoretically located two toroidal high-spin isomeric states of 120304184 with an angular momentum I =Iz=81 ℏ (proton 2p-2h, neutron 4p-4h excitation) and I =Iz=208 ℏ (proton 5p-5h, neutron 8p-8h) at the quadrupole moment deformations Q20=-297.7 b and Q20=-300.8 b with energies 79.2 and 101.6 MeV above the spherical ground state, respectively. The nuclear density distributions of the toroidal high-spin isomers 120304184(Iz=81 ℏ and 208 ℏ ) have the maximum density close to the nuclear matter density, 0.16 fm-3, and a torus major to minor radius aspect ratio R /d =3.25 . Conclusions: We demonstrate that aligned angular momenta of Iz=81 ℏ and 208 ℏ arising from

Evaluation of electrical conductivity and equations of state of non-ideal plasma through microsecond timescale underwater electrical wire explosion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheftman, D.; Krasik, Ya. E.

2011-09-15

Experimental and simulation results of underwater electrical Cu, Al, and W wire explosions in the microsecond timescale are presented. It was shown that the electrical conductivity results for Cu and Al agree well with modified Lee-More and quantum molecular dynamic models for temperatures above 10 kK. The equation of state (EOS) values based on SESAME tables for Cu and Al were slightly modified for intermediate temperatures in order to obtain fitting between experimental and simulated exploding wire radial expansion. Also, it was shown that the electrical conductivity results and the EOS evaluation differ significantly from the results obtained in nanosecondmore » timescale experiments. Finally, it was found that underwater electrical W wire explosion is characterized by the appearance of non-uniformities along the z-axis of the wire. This phenomena adds uncertainty to the possibility of applying this type of experiments for evaluation of the electrical conductivity and EOS of W.« less

Applications of Group Theory: Infrared and Raman Spectra of the Isomers of 1,2-Dichloroethylene: A Physical Experiment

ERIC Educational Resources Information Center

Craig, Norman C.; Lacuesta, Nanette N.

2004-01-01

A study of the vibrational spectroscopy of the cis and trans isomers of 1,2-dichloroethylene provides an excellent opportunity to learn the applications group theory in laboratories. The necessity of using infrared (IR) spectroscopy and Raman spectroscopy in making full vibrational assignments is illustrated.

Theoretical and experimental vibrational spectroscopy study on rotational isomer of 4-phenylbutylamine

NASA Astrophysics Data System (ADS)

Ünal, A.; Okur, M.

2017-02-01

The possible four stable rotational isomers of 4-phenylbutylamine (4PBA) molecule were experimentally and theoretically studied by vibrational spectroscopy. The FT-IR (4000-400 cm-1) and Raman (3700-60 cm-1) spectra of 4PBA were recorded at room temperature in liquid phase. The complete vibrational wavenumbers and corresponding vibrational assignments of 4PBA molecule were discussed assisted with B3LYP/6-311++G(d,p) level of theory along with scaled quantum mechanics force field (SQM-FF) method. Results from experimental and theoretical data the most stable form of 4PBA molecule was obtained.

Photoionization of three isomers of the C9H7 radical.

PubMed

Hemberger, Patrick; Steinbauer, Michael; Schneider, Michael; Fischer, Ingo; Johnson, Melanie; Bodi, Andras; Gerber, Thomas

2010-04-15

Three resonance-stabilized radicals, 1-indenyl (Ind), 1-phenylpropargyl (1PPR), and 3-phenylpropargyl (3PPR), all isomers of the composition C(9)H(7), were generated by jet flash pyrolysis. Their photoionization was examined by VUV synchrotron radiation. The mass spectra show a clean and efficient radical generation when the pyrolysis is turned on. To study the photoionization, photoion yield measurements and threshold photoionization spectroscopy techniques were applied. We determined adiabatic ionization energies (IE(ad)) of 7.53 eV for Ind, 7.20 eV for 3PPR, and 7.4 eV for 1PPR. Ab initio calculations show no major change in geometry upon ionization, in agreement with ionization from a nonbonding molecular orbital. The IEs were also computed and are in agreement with the measured ones. The difference in the IE might allow a distinction of the three isomers in flames. In the indenyl spectrum, an excited a(+) (3)B(2) state of the cation was identified at 8.10 eV, which shows a low-energy vibrational progression of 61 meV. Furthermore, we have examined the dissociative photoionization of the precursors. The indenyl precursor, 1-indenyl bromide, undergoes dissociative photoionization to Ind(+). An appearance energy (AE(0K)) of 10.2 eV was obtained from fitting the experimental breakdown diagram. A binding energy of 1.8 eV can thus be determined for the C-Br bond in 1-indenyl bromide. The phenylpropargyl precursors 1PPBr (1-phenylpropargyl bromide/3-phenyl-3-bromopropyne) and 3PPBr (3-phenylpropargyl bromide/1-phenyl-3-bromopropyne) also lose a bromine atom upon dissociative photoionization. Approximate appearance energies of 9.8 eV for 3PPBr and 9.3 eV for 1PPBr have been determined.

Investigation of Isomer-specific Sinks of Isoprene Oxidation Products in varying NOx Environments

NASA Astrophysics Data System (ADS)

Vasquez, K.; Allen, H.; Xu, L.; Nölscher, A. C.; Praske, E.; Bates, K. H.; Crounse, J. D.; Wennberg, P. O.

2017-12-01

Isoprene is the dominant non-methane hydrocarbon emitted into the atmosphere. Its large emissions and rapid rate coefficient with OH leads to a large role in the oxidative chemistry of the atmosphere. This is primarily due to the formation of its six isomeric isoprene peroxy radicals (ISOPO2) whose individual fates are critical in controlling local and regional concentrations of important atmospheric species. Though much insight has been gained about ISOPO2 chemistry through the observation of isoprene's oxidation products, our inability to distinguish between the individual isomers of these compounds have limited our ability to diagnose the photochemistry and its impact on secondary organic aerosol, NOx and tropospheric ozone. We have developed a field-hardened high resolution chemical ionization mass spectrometer coupled with a low-pressure gas chromatograph (GC-CIMS) that is capable of observing in situ isomer distributions of a wide range of atmospheric species. Its first deployment during the PROPHET 2016 campaign yielded promising results, providing insights into the atmospheric fate of species such as the isoprene hydroxy nitrates (ISOPN) in a low NOx environment. During summer 2017, deployment of the GC-CIMS at the Caltech campus in Pasadena, CA provided a valuable contrast to the PROPHET data set, showing the isomeric distributions of oxidation products in a high NOx, urban environment. Together these two data sets allow us to better understand the drivers of isoprene chemistry and lead to more quantitative description of isoprene oxidative chemistry.

THE DIFFERENTIAL HEPATOTOXICITY AND CYTOCHROME P450 RESPONSE OF F344 RATS TO THE THREE ISOMERS OF DICHLOROBENZENE

EPA Science Inventory

The acute hepatotoxicity and response of hepatic cytochrome P450 to treatment with the three isomers of dichlorobenzene (DCB) have been investigated. The objectives were to estimate toxic thresholds and to further e1ucidate the role of cytochrome P450 in the metabolism and toxici...

Differentiation of closely related isomers: application of data mining techniques in conjunction with variable wavelength infrared multiple photon dissociation mass spectrometry for identification of glucose-containing disaccharide ions.

PubMed

Stefan, Sarah E; Ehsan, Mohammad; Pearson, Wright L; Aksenov, Alexander; Boginski, Vladimir; Bendiak, Brad; Eyler, John R

2011-11-15

Data mining algorithms have been used to analyze the infrared multiple photon dissociation (IRMPD) patterns of gas-phase lithiated disaccharide isomers irradiated with either a line-tunable CO(2) laser or a free electron laser (FEL). The IR fragmentation patterns over the wavelength range of 9.2-10.6 μm have been shown in earlier work to correlate uniquely with the asymmetry at the anomeric carbon in each disaccharide. Application of data mining approaches for data analysis allowed unambiguous determination of the anomeric carbon configurations for each disaccharide isomer pair using fragmentation data at a single wavelength. In addition, the linkage positions were easily assigned. This combination of wavelength-selective IRMPD and data mining offers a powerful and convenient tool for differentiation of structurally closely related isomers, including those of gas-phase carbohydrate complexes.

Photocrystallographic structure determination of a new geometric isomer of [Ru(NH3)4(H2O)(eta1-OSO)][MeC6H4SO3]2.

PubMed

Bowes, Katharine F; Cole, Jacqueline M; Husheer, Shamus L G; Raithby, Paul R; Savarese, Teresa L; Sparkes, Hazel A; Teat, Simon J; Warren, John E

2006-06-21

The structure of a new metastable geometric isomer of [Ru(NH3)4(H2O)(SO2)][MeC6H4SO3]2 in which the SO2 group is coordinated through a single oxygen in an eta1-OSO bonding mode has been determined at 13 K; the new isomer was obtained as a 36% component of the structure within a single crystal upon irradiation using a tungsten lamp.

Microsecond Simulations of DNA and Ion Transport in Nanopores with Novel Ion-Ion and Ion-Nucleotides Effective Potentials

PubMed Central

De Biase, Pablo M.; Markosyan, Suren; Noskov, Sergei

2014-01-01

We developed a novel scheme based on the Grand-Canonical Monte-Carlo/Brownian Dynamics (GCMC/BD) simulations and have extended it to studies of ion currents across three nanopores with the potential for ssDNA sequencing: solid-state nanopore Si3N4, α-hemolysin, and E111N/M113Y/K147N mutant. To describe nucleotide-specific ion dynamics compatible with ssDNA coarse-grained model, we used the Inverse Monte-Carlo protocol, which maps the relevant ion-nucleotide distribution functions from an all-atom MD simulations. Combined with the previously developed simulation platform for Brownian Dynamic (BD) simulations of ion transport, it allows for microsecond- and millisecond-long simulations of ssDNA dynamics in nanopore with a conductance computation accuracy that equals or exceeds that of all-atom MD simulations. In spite of the simplifications, the protocol produces results that agree with the results of previous studies on ion conductance across open channels and provide direct correlations with experimentally measured blockade currents and ion conductances that have been estimated from all-atom MD simulations. PMID:24738152

Determination of unsaturation grade and trans isomers generated during thermal oxidation of edible oils and fats by FTIR

NASA Astrophysics Data System (ADS)

Moya Moreno, M. C. M.; Mendoza Olivares, D.; Amézquita López, F. J.; Gimeno Adelantado, J. V.; Bosch Reig, F.

1999-05-01

The oxidative deterioration of culinary oils and fats during episodes of heating associated with normal usage (80°C-300°C, 20-40 min) was monitored by FTIR spectroscopy. The thermal oxidation of polyunsaturated fatty acids during heating was studied by the determination of unsaturation percentage and trans isomers at various temperatures and heating times. Oils frequently used in food frying such as olive oil, sunflower oil, corn oil and seeds oil (sunflower, safflower and canola seed), and lard were studied. The Absorbance Correction Method is proposed to correct the spectral interference and allows the analytic use of signal which would not be initially valid for quantitative analysis. The results show that there is a decrease in unsaturation and an increase in trans isomers starting at 150°C and becomes more pronounced at temperatures around 250°C. This variation in unsaturation grade and conformation provides evidence of the transformation of essential polyunsaturated fatty acids and subsequent decrease in the oils' nutritional value.

A High Accuracy Measurement of the Nuclear Decay of 235mU and Search for the Nuclear Decay of 229mTh

NASA Astrophysics Data System (ADS)

Ponce, Francisco

Among all nuclear decays, there exist two isomeric states with very low-energy that belong to . {229}Th (7.8 ± 0.5 eV) and . {235}U (76.8 ± 0.5 eV) . Of particular interest is . {229}Th, because the decay energy is in the ultraviolet, and therefore in the range of modern tunable lasers. The isomer can potentially be used as the basis for a nuclear clock that is expected to be two orders of magnitude more precise than atomic clocks. However, the . {229m}Th nuclear decay energy is not sufficiently well known to design the necessary laser system for a nuclear clock. This work describes the development of a new technique using superconducting tunnel junction (STJ) detectors to directly measure the nuclear decay of low-energy isomers with a high level of accuracy. The strength of the technique is demonstrated by measuring the decay energy of the . {235}U isomer at 76.737 ± 0.018 eV. Over an order of magnitude more accurate than the current literature value. The technique is then applied to detect the transition in . {229m}Th directly and measure its energy with comparable accuracy. These experiments are unsuccessful and are discussed in light of the recent measurement of the . {229m}Th half-life of 7 ± \\SI{1}{\\micro\\second}.

Low-temperature kinetic measurements of microsecond freeze-hyperquench (MHQ) cytochrome oxidase monitored by UV-visible spectroscopy with a newly designed cuvette.

PubMed

Wiertz, F G M; de Vries, S

2006-02-01

A special cuvette was designed to measure optical changes of MHQ (microsecond freeze-hyperquench) powder samples at temperatures below approx. 250 K. Reduced cytochrome c oxidase from Paracoccus denitrificans was reacted with O(2) for 100 micros, frozen as a powder and transferred to the cuvette. Subsequently, cytochrome oxidase was allowed to react further following stepwise increments of the temperature from 100 K up to 250 K while recording spectra between 300 and 700 nm. The temperature was raised only when no further changes in the spectra could be detected. The experiment yielded spectra of the A, P(M), F and O intermediate states. This demonstrated that the catalytic cycle of cytochrome oxidase at low temperature is similar to that at room temperature and so verifies the suitability of this method for the study of enzymes with high catalytic-centre activity.

Probing the Methyl Torsional Barriers of the E and Z Isomers of Butadienyl Acetate by Microwave Spectroscopy

NASA Astrophysics Data System (ADS)

Jabri, Atef; Nguyen, Ha Vinh Lam; Kleiner, Isabelle; Van, Vinh; Stahl, Wolfgang

2016-06-01

The Fourier transform microwave spectra of the E and the Z isomer of butadienyl acetate have been measured in the frequency range from 2 to 26.5 GHz under molecular beam conditions. The most stable conformer of each isomer, in which all heavy atoms are located in a symmetry plane, was identified after analyzing the spectrum by comparison with results from quantum chemical calculations. The barrier to internal rotation of the acetyl methyl group was found to be 149.1822(20) cm-1 and 150.2128(48) cm-1 for the E and the Z isomer, respectively, which are similar to that of vinyl acetate. A comparison between two theoretical approaches treating internal rotations, the rho axis method (using the program BELGI-Cs) and combined axis method (using the program XIAM), is also performed. Since several years we study the barriers to internal rotation of the acetyl methyl group in acetates, CH3-COOR. Currently, we assume that all acetates can be divided into three classes. Class I contains α,β saturated acetates, where the torsional barrier is always close to 100 cm-1. Examples are a series of alkyl acetates such as methyl acetate and ethyl acetate. Class II contains α,β-unsaturated acetates where the C=C double bond is located in the COO plane. This is the case of vinyl acetate and butadienyl acetate. Finally, in class III with isopropenyl acetate and phenyl acetate as two representatives, α,β-unsaturated acetates, in which the double bond is not located in the COO plane, are collected. There, we observed a barrier height around 135 cm-1. This observation will be discussed in details. B. Velino, A. Maris, S. Melandri, W. Caminati, J. Mol. Spectrosc. 2009, 256, 228 H. V. L. Nguyen, A. Jabri, V. Van, and W. Stahl, J. Phys. Chem. A, 2014, 118, 12130.

Analysis of deformation of aluminum plates under the influence of nano- and microsecond laser pulses

NASA Astrophysics Data System (ADS)

Jach, K.; Świerczyński, R.; Ostrowski, R.; Rycyk, A.; CzyŻ, K.; Strzelec, M.; Sarzyński, A.

2017-10-01

The paper presents numerical modeling of interaction of strong laser radiation with conventional aluminum sheets, similar to those used in military technology. The theoretical model uses equations of continuum mechanics (equations of hydrodynamics and the equations of mechanics of solid bodies in a cylindrical coordinates r, z), enriched with equations describing the typical effects of high temperature, such as absorption of laser radiation within the Al shield, electronic and radiative thermal conductivity, and energy loss on phase transitions (melting, evaporation, ionization). Semiempirical equations of state were used to describe the properties of material in the conditions of large deformation and the Johnson-Cook's model. The equations were solved using the method of free points developed by one of the authors. Two kinds od laser pulses were considered: microsecond pulse with duration of 200 μs and a low peak power of 10 kW/cm2 (CW laser), and nanosecond pulse with duration of 10 ns and high peak power of 5 GW/cm2 (pulsed laser). The aim of this study was to determine the shapes and temperatures of Al plates under the influence of these pulses for the comparison of the numerical results with future experiments and to verify the possibility to determine the distribution of the energy density of the laser beam on the basis of the plate deformation.

[Microsecond Pulsed Hollow Cathode Lamp as Enhanced Excitation Source of Hydride Generation Atomic Fluorescence Spectrometry].

PubMed

Zhang, Shuo

2015-09-01

The spectral, electrical and atomic fluorescence characteristics of As, Se, Sb and Pb hollow cathode lamps (HCLs) powered by a laboratory-built high current microsecond pulse (HCMP) power supply were studied, and the feasibility of using HCMP-HCLs as the excitation source of hydride generation atomic fluorescence spectrometry (HG-AFS) was evaluated. Under the HCMP power supply mode, the As, Se, Sb, Pb HCLs can maintain stable glow discharge at frequency of 100~1000 Hz, pulse width of 4.0~20 μs and pulse current up to 4.0 A. Relationship between the intensity of characteristic emission lines and HCMP power supply parameters, such as pulse current, power supply voltage, pulse width and frequency, was studied in detail. Compared with the conventional pulsed (CP) HCLs used in commercial AFS instruments, HCMP-HCLs have a narrower pulse width and much stronger pulse current. Under the optimized HCMP power supply parameters, the intensity of atomic emission lines of As, Se, Sb HCLs had sharp enhancement and that indicated their capacity of being a novel HG-AFS excitation source. However, the attenuation of atomic lines and enhancement of ionic lines negated such feasibility of HCMP-Pb HCL. Then the HG-AFS analytical capability of using the HCMP-As/Se/Sb HCLs excitation source was established and results showed that the HCMP-HCL is a promising excitation source for HG-AFS.

Isomer pattern and elimination of dioxins in workers exposed at a municipal waste incineration plant

PubMed Central

YAMAMOTO, Kenya; KUDO, Mitsuhiro; ARITO, Heihachiro; OGAWA, Yasutaka; TAKATA, Tsutomu

2015-01-01

The aim of this study was to clarify patterns of serum concentrations of dioxins in the employees of a waste incineration plant and to estimate elimination rates and half-lives of serum dioxin isomers, and the maximum serum concentrations of dioxin isomers at the time of plant shutdown. Sixteen subjects participating 3 times or more in annual health examinations during an 8-yr period from 2000 to 2007 were recruited for this study. Serum concentrations of dioxins expressed as TEQ/g lipid decreased gradually after plant shutdown with the highest decrease observed in polychlorinated dibenzofurans (PCDFs) followed by polychlorinated deibenzo-p-dioxins (PCDDs) and then coplanar PCBs. The serum toxic equivalency (TEQ) concentrations of PCDF and PCDD congeners in the employees were higher than those in the general population survey by the Ministry of the Environment, Japan, whereas the serum concentrations of coplanar PCBs were similar to those in the general population. The estimated half-lives and elimination rates of PCDDs and PCDFs in the highly exposed workers increased compared with the moderately exposed workers. The estimated geometric mean serum concentrations of PCDDs, PCDFs and total dioxins at the time of plant shutdown were 35, 53 and 107 pg TEQ/g lipid, respectively. PMID:26118856

Prediction, Refinement and Persistency of Transmembrane Helix Dimers in Lipid Bilayers using Implicit and Explicit Solvent/Lipid Representations: Microsecond Molecular Dynamics Simulations of ErbB1/B2 and EphA1

PubMed Central

Zhang, Liqun; Sodt, Alexander J.; Venable, Richard M.; Pastor, Richard W.; Buck, Matthias

2012-01-01

All-atom simulations are carried out on ErbB1/B2 and EphA1 transmembrane helix dimers in lipid bilayers starting from their solution/DMPC bicelle NMR structures. Over the course of microsecond trajectories, the structures remain in close proximity to the initial configuration and satisfy the great majority of experimental tertiary contact restraints. These results further validate CHARMM protein/lipid force fields and simulation protocols on Anton. Separately, dimer conformations are generated using replica exchange in conjunction with an implicit solvent and lipid representation. The implicit model requires further improvement, and this study investigates whether lengthy all-atom molecular dynamics simulations can alleviate the shortcomings of the initial conditions. The simulations correct many of the deficiencies. For example excessive helix twisting is eliminated over a period of hundreds of nanoseconds. The helix tilt, crossing angles and dimer contacts approximate those of the NMR derived structure, although the detailed contact surface remains off-set for one of two helices in both systems. Hence, even microsecond simulations are not long enough for extensive helix rotations. The alternate structures can be rationalized with reference to interaction motifs and may represent still sought after receptor states that are important in ErbB1/B2 and EphA1 signaling. PMID:23042146

Discrimination of nuclear spin isomers exploiting the excited state dynamics of a quinodimethane derivative

DOE Office of Scientific and Technical Information (OSTI.GOV)

Obaid, Rana; Faculty of Pharmacy, Al-Quds University, Abu Dis, Palestine; Kinzel, Daniel

2014-10-28

Despite the concept of nuclear spin isomers (NSIs) exists since the early days of quantum mechanics, only few approaches have been suggested to separate different NSIs. Here, a method is proposed to discriminate different NSIs of a quinodimethane derivative using its electronic excited state dynamics. After electronic excitation by a laser field with femtosecond time duration, a difference in the behavior of several quantum mechanical operators can be observed. A pump-probe experimental approach for separating these different NSIs is then proposed.

The effect of meta coupling on colour purity, quantum yield, and exciton utilizing efficiency in deep-blue emitters from phenanthroimidazole isomers.

PubMed

Wang, Zhiming; Li, Xueying; Zhang, Wanyu; Zhang, Shitong; Li, Hui; Yu, Zhenqiang; Chen, Yanming; Lu, Ping; Chen, Ping

2015-12-21

meta-Coupling isomers usually exhibit bluer emission than do the para-isomers, but the loss of efficiency with respect to photoluminescence (PL) and electroluminescence (EL) is an inevitable result in most cases, particularly for deep blue emitters. In this study, three blue emitting isomers, 4,4'-bis(1-phenyl-phenanthro[9,10-d]imidazol-2-yl)biphenyl (BPPI), 3,4'-bis(1-phenyl-phenanthro[9,10-d]-imidazol-2-yl)biphenyl (L-BPPI) and 3,3'-bis(1-phenyl-phenanthro[9,10-d]-imidazol-2-yl)biphenyl (Z-BPPI), were chosen as model compounds to investigate the essential reason behind the meta-coupling effect due to their different coupling forms, viz. para-para, para-meta, and meta-meta, respectively, in similar dimeric phenanthroimidazole frameworks. A combination of detailed photophysical data, device performance and DFT calculations for the excited state provided valuable information. In particular, the relationship between certain key parameters in calculations as well as PL or EL properties was confirmed, such as oscillator strength and quantum yield, among others, which could effectively reduce the issues related to synthesis and characterisation using prior computer simulations. Good agreement was observed in the results obtained from calculation and experiments, and it was concluded that meta-tuning barely realised improvement in EL, unless some special excited states formed or an exciton conversion channel appeared, as in the case of reverse intersystem crossing.

Distribution and fate of HCH isomers and DDT metabolites in a tropical environment–case study Cameron Highlands–Malaysia

PubMed Central

2012-01-01

Background The serious impact effects of persistent organic pollutants such as organochlorine pesticides, especially dichlorodiphenyltrichloroethane family (DDTs) and hexachlorocyclohexane isomers (HCHs) have been causing widespread concern, despite effective control on their manufacturing, agricultural and vector practices. In that, in addition to the previous global limitations on DDTs usage, α-HCH, β-HCH and lindane have also became an on-going topic of global relevance based on the latest Stockholm Convention list on 10th of May 2009. Concentrations of dichlorodiphenyltrichloroethane family (DDTs) and hexachlorocyclohexane isomers (HCHs) were determined by GC-ECD in Cameron Highlands, the main vegetables and flowers farming area in Malaysia as an agricultural tropical environment. A total of 112 surface water and sediment samples at eight points were collected along the main rivers in the area namely Telom and Bertam in the dry and wet seasons of 2011. Results Total concentration of HCH isomers ranged from not detected to 25.03 ng/L in the water (mean of 5.55 ±6.0 ng/L), while, it ranged from 0.002 to 59.17 ng/g (mean of 8.06±9.39 ng/g) in the sediment. Total concentration of DDT and its metabolites in the water samples varied from not detected to 8.0 ng/L (mean of 0.90±1.66 ng/g), whereas, it was in the range of 0.025 to 23.24 ng/g (mean of 2.55±4.0 ng/g) in the surface sediment samples. The ratio of HCHs and DDTs composition indicated an obvious historical usage and new inputs of these pesticides. Among alpha, beta, gamma and delta isomers of HCH, gamma was the most dominant component in the sediment and water as well. Some seasonal variations in the level of selected pesticides were noted. Conclusions The results illustrate distribution, behaviour and fate of HCHs, and DDTs have closely connected with topological and meteorological properties of the area beyond their chemical characterizations. The features of environmental circumstances exceed one or

Mapping and quantifying isomer sets of hydrocarbons (≥ C12) in diesel exhaust, lubricating oil and diesel fuel samples using GC × GC-ToF-MS

NASA Astrophysics Data System (ADS)

Alam, Mohammed S.; Zeraati-Rezaei, Soheil; Liang, Zhirong; Stark, Christopher; Xu, Hongming; MacKenzie, A. Rob; Harrison, Roy M.

2018-05-01

Airborne particles and vapours, like many other environmental samples including water, soils and sediments, contain complex mixtures of hydrocarbons, often deriving from crude oil either before or after fractionation into fuels, lubricants and feedstocks. Comprehensive 2D gas chromatography time-of-flight mass spectrometry (GC × GC-ToF-MS), offers a very powerful technique that separates and identifies many compounds in complicated hydrocarbon mixtures. However, quantification and identification of individual constituents at high ionization energies would require hundreds of expensive (when available) standards for calibration. Although the precise chemical structure of hydrocarbons does matter for their environmental impact and fate, strong similarities can be expected for compounds having very similar chemical structures and carbon numbers. There is, therefore, a clear benefit in an analytical technique which is specific enough to separate different classes of compounds and to distinguish homologous series while avoiding the need to handle each isomer individually. Varying EI (electron impact) ionization mass spectrometry significantly enhances the identification of individual isomers and homologous compound groups, which we refer to as isomer sets. Advances are reported in mapping and quantifying isomer sets of hydrocarbons (≥ C12) in diesel fuel, lubricating oil and diesel exhaust emissions. By using this analysis we report mass closures of ca. 90 and 75 % for diesel fuel and lubricating oil, and identify 85 and 75 % of the total ion current for gas- and particulate-phase diesel exhaust emissions.

Determination of fucoxanthin isomers in microalgae (Isochrysis sp.) by high-performance liquid chromatography coupled with diode-array detector multistage mass spectrometry coupled with positive electrospray ionization.

PubMed

Crupi, Pasquale; Toci, Aline Theodore; Mangini, Silvio; Wrubl, Federico; Rodolfi, Liliana; Tredici, Mario R; Coletta, Antonio; Antonacci, Donato

2013-05-15

Due to their health benefits, there is growing interest in the production and use of carotenoids from natural sources, e.g. microalgae. To date, only Haematococcus pluvialis and Dunaliella, that accumulate, respectively, astaxanthin and β-carotene in large quantities, are grown commercially. However, interest is also being focused on other xanthophylls, such as (all-E)-fucoxanthin characterized by anti-obesity and anti-carcinogenic effects. In this regard, rigorous chemical and analytical techniques following preparative isolation of components are needed to unequivocally identify individual carotenoids in microalgae. The carotenoid profile of Isochrysis sp. biomass, produced in closed photobioreactors, was determined by reversed-phase C30 (RP-30) high-performance liquid chromatography coupled with diode-array detector mass spectrometry using positive electrospray ionization (HPLC/DAD-MS/ESI(+) ) analysis. Additionally, multistage mass spectrometry (MS(n) ) analyses, together with fine structures of the UV-vis spectra, were used to differentiate structural and geometrical isomers. This technique allowed the simultaneous determination of geometrical, isomers of fucoxanthin (all-E-fucoxanthin, 13Z-, 13'Z- and 9'Z-fucoxanthin), diatoxanthin and 5,8-epoxydiadinoxanthin diasteroisomers (R/S). The analyzed extracts contained fucoxanthin isomers as the major carotenoids and, in particular, (all-E)-fucoxanthin was the main geometrical isomer (~85%) found at a concentration of 17 mg/g of the lyophilized biomass. Considering the high content of fucoxanthin in Isochrysis sp. biomass, the microalga could be proposed as a source of this compound for nutraceutical and pharmaceutical applications. Copyright © 2013 John Wiley & Sons, Ltd.

Energy and Spectroscopic Characterization of the Isomers of C4H3-, C6H3-, and C6H5-

NASA Technical Reports Server (NTRS)

Wright, Danielle; Bera, Partha P.; Lee, Timothy J.

2015-01-01

Organic and inorganic molecules, neutral and ions have been observed in the interstellar medium. A few anions of organic molecules have also been observed recently. The Cassini spacecraft in the upper atmosphere of Titan has observed anions of large organic molecules. In this project we have studied the physical and spectroscopic properties of C4H3-, C6H3-, and C6H5-. We have optimized the geometrical structures of all low-lying isomers of the anions, calculated rotational, and harmonic vibrational frequencies of the anions mentioned above using the B3LYP density functional along with the augmented correlation consistent polar valence triple zeta (aug-cc-pVTZ) basis set. We have found many low-lying isomers on the potential energy surface of these anions.

Rich catalytic injection

DOEpatents

Veninger, Albert [Coventry, CT

2008-12-30

A gas turbine engine includes a compressor, a rich catalytic injector, a combustor, and a turbine. The rich catalytic injector includes a rich catalytic device, a mixing zone, and an injection assembly. The injection assembly provides an interface between the mixing zone and the combustor. The injection assembly can inject diffusion fuel into the combustor, provides flame aerodynamic stabilization in the combustor, and may include an ignition device.

Differential behavior of amino-imino constitutional isomers in nonlinear optical processes.

PubMed

Latorre, Sonia; Moreira, Ibério de P R; Villacampa, Belén; Julià, Lluís; Velasco, Dolores; Bofill, Josep Maria; López-Calahorra, Francisco

2010-03-15

A detailed study of the "blocked" amino-imino tautomers derived from N-acridine-substituted 2-aminobenzothiazole--and their effect on the nonlinear optical response--is presented. The synthesis, characterization, and nonlinear optical properties of these frozen tautomers, namely, N-methyl-N-(2-nitroacridin-6-yl)-2-aminobenzothia-zole and 3-methyl-N-(7-nitroacridin-3-yl)-2-iminobenzothiazole, are reported. A theoretical model based on valence-bond theory is also proposed and used to analyze the effects of the nuclear configuration corresponding to each frozen tautomer structure. In the present case, the aromatic form and the allylic-anion-like system of the -N-C-N- group inherent to each isomer are crucial for understanding and analyzing the different responses of each "blocked" tautomer.

A simple HPLC method for the comprehensive analysis of cis/trans (Z/E) geometrical isomers of carotenoids for nutritional studies

USDA-ARS?s Scientific Manuscript database

Geometrical isomers of carotenoids behave differently in aspects like stability towards oxidants, bioavailability, vitamin A activity and specificity for enzymes. The availability of HPLC methods for their detailed profiling is therefore advisable to expand our knowledge on their metabolism and biol...

GAS CHROMATOGRAPHIC/MASS SPECTROMETRIC APPROACH FOR ISOMER-SPECIFIC ENVIRONMENTAL MONITORING OF THE 1700 BROMO-, CHLORO-, AND BROMOCHLORO-DIBENZO-P-DIOXINS

EPA Science Inventory

A combined approach using gas chromatographic retention indices and mass spectrometric characteristics has been elaborated for the isomer-specific identification of the 1700 bromo-, chloro- and bromochloro-dioxins which may be found in the environment. ver 100 dioxins were synthe...

An In Silico Study on the Isomers of Pentacene: The Case for Air-Stable and Alternative C22H14 Acenes for Organic Electronics.

PubMed

Jones, Leighton; Lin, Long

2017-04-13

Pentacene is one of the most investigated candidates for organic thin film transistor (OTFT) applications over the last few decades even though it unstable in air (E g = 1.80 eV), owing in part to its planar nature and high charge-transfer mobilities as both a single crystal (35 cm 2 V -1 s -1 ) and as a thin-film (3.0 cm 2 V -1 s -1 ). Until now, picene is the only isomer of pentacene to be investigated for organic electronic applications, due to its greater stability (E g = 4.21 eV) and high-charge transfer mobility (3.0 cm 2 V -1 s -1 ); even benefiting from oxygen doping. In the present study, a total of 12 fused-ring isomers (including pentacene, picene and ten other structures) of the formula C 22 H 14 were analyzed and investigated for their electronic and optical properties for worth in OTFT applications. We screened several pure and hybrid DFT functionals against the experimental frontier molecular orbitals (FMOs) of pentacene, then deployed Marcus Theory, Koopmans' Theorem and Green's function with the P3 electron propagator variant, for the internal hole reorganization energy, the hole transfer integral (via the "splitting-in-dimer method" at d = 3.0, 3.5, and 4.0 Å), the charge transfer rate constant, and vertical ionization energies. Using these as a basis, we studied pentacene's isomers and found that the four nonplanar structures, namely, benzo[g]chrysene (3), naphtho[c]phenanthrene (7), benzo[c]chrysene (11) and dibenzo[c,c']phenthrene (12), are (I) more stable than pentacene, by up to 2 eV, and (II) have relatively similar ionization energies (7.5-7.6 eV) to those of picene's experimental value (7.51 eV). The largest charge transfer rates at 3.5 Å dimer separations were given by the isomers benzo[b]chrysene 4, naphtha[c]phenanthrene 7, dibenzo[a,c]anthracene 8 and benzo[a]tetracene 10 and found to be 2.92, 1.72, 1.30, and 3.09 × 10 14 s -1 respectively. In comparison to that of pentacene (K CT = 3.97 × 10 14 s -1 ), these unusual isomers are

A theoretical study of the hydrogen bonding between the vic-, cis- and trans-C 2H 2F 2 isomers and hydrogen fluoride

NASA Astrophysics Data System (ADS)

Rusu, Victor H.; da Silva, João Bosco P.; Ramos, Mozart N.

2009-04-01

MP2/6-31++G(d,p) and B3LYP/6-31++G(d,p) theoretical calculations have been employed to investigate the hydrogen bonding formation involving the vic-, cis- and trans-C 2H 2F 2 isomers and hydrogen fluoride. Our calculations have revealed for each isomer the preferential existence of two possible hydrogen-bonded complexes: a non-cyclic complex and a cyclic complex. For all the three isomers the binding energies for the non-cyclic and cyclic hydrogen complexes are essentially equal using both the MP2 and B3LYP calculations, being that the cyclic structure is slightly more stable. For instance, the binding energies including BSSE and ZPE corrections for the non-cyclic and cyclic structures of cis-C 2H 2F···HF are 8.7 and 9.0 kJ mol -1, respectively, using B3LYP calculations. The cyclic complex formation reduces the polarity, in contrast to what occurs with the non-cyclic complex. This result is more accentuated in vic-C 2H 2F 2···HF. In this latter, Δ μ(cyclic) is -3.07 D, whereas Δ μ(non-cyclic) is +1.92 D using B3LYP calculations. Their corresponding MP2 values are +0.44 D and -1.89 D, respectively. As expected, the complexation produces an H sbnd F stretching frequency downward shift, whereas its IR intensity is enhanced. On the other hand, the vibrational modes of the vic-, cis- and trans-C 2H 2F 2 isomers are little affected by complexation. The new vibrational modes due to hydrogen bonding formation show several interesting features, in particular the HF bending modes which are pure rotations in the free molecule.

Ab initio studies of ClOx reactions. VII. Isomers of Cl2O3 and their roles in the ClO+OClO reaction

NASA Astrophysics Data System (ADS)

Zhu, R. S.; Lin, M. C.

2003-05-01

The mechanism for the reaction ClO+OClO has been investigated by ab initio molecular orbital and transition state theory calculations. Nine stable isomers of Cl2O3 (including optical isomers) are located at the B3LYP/6-311+G(3df ) level. The transition states between pairs of isomers are explored and the stability of the isomers and their dissociation mechanisms are discussed. The relative stability predicted by the modified Gaussian-2 (G2M) method at the G2M//B3LYP/6-311+G(3df ) level is ClOCl(O)O>ClOOOCl(C2)>ClOOOCl(Cs)>ClClO3(C3v)>cyc-ClOOCl(O)>ClOOClO. The formation of ClOCl(O)O is dominant at low temperatures, taking place barrierlessly with the second and third order rate constant, k1∞=3.0×10-10 cm3molecule-1 s-1 and k10=1.1×10-17 T-5.5 exp(-398/T) cm6 molecule-2 s-1 in the temperature range of 200-400 K for N2 as the third-body. Over 500 K, formation of ClOO+ClO becomes dominant and ClOCl+1O2 is also competitive. Their overall rate constants can be given by kClOO=1.0×10-22 T2.8 exp(-78/T) and kClOCl=9.6×10-22 T2.4 exp(-1670/T)cm3 molecule-1 s-1, respectively, in the temperature range of 500-2500 K.

Determination of astaxanthin and astaxanthin esters in the microalgae Haematococcus pluvialis by LC-(APCI)MS and characterization of predominant carotenoid isomers by NMR spectroscopy.

PubMed

Holtin, Karsten; Kuehnle, Maximilian; Rehbein, Jens; Schuler, Paul; Nicholson, Graeme; Albert, Klaus

2009-11-01

The oily product ZANTHIN consists of natural astaxanthin, which is manufactured from the microalgae Haematococcus pluvialis by supercritical CO(2) extraction. An HPLC method was developed to separate all of the components of the complex astaxanthin extract using a C(30) column. The separation resulted in different isomers of astaxanthin accompanied by two other carotenoids. The main component consisted of astaxanthin singly esterified with several different fatty acids. C18:3, C18:2, C18:1 and C16:0 were identified as the most commonly occurring fatty acids. Doubly esterified astaxanthin was also found, although in lower concentrations compared to singly esterified astaxanthin. After performing a detailed fatty acid analysis by GC-MS, the peaks from the extract were assigned via HPLC-MS. A trans to cis transmutation of the all-trans compound was performed by thermal treatment in order to obtain an enrichment of cis isomers as the basis for unambiguous identification via NMR experiments. The all-trans as well as the 9- and 13-cis isomers of astaxanthin were characterized in detail by UV/Vis, (1)H, and (1)H,(1)H COSY NMR spectroscopy.

Identification of isomers and control of ionization and dissociation processes using dual-mass-spectrometer scheme and genetic algorithm optimization

NASA Astrophysics Data System (ADS)

Chen, Zhou; Tong, Qiu-Nan; Zhang, Cong-Cong; Hu, Zhan

2015-04-01

Identification of acetone and its two isomers, and the control of their ionization and dissociation processes are performed using a dual-mass-spectrometer scheme. The scheme employs two sets of time of flight mass spectrometers to simultaneously acquire the mass spectra of two different molecules under the irradiation of identically shaped femtosecond laser pulses. The optimal laser pulses are found using closed-loop learning method based on a genetic algorithm. Compared with the mass spectra of the two isomers that are obtained with the transform limited pulse, those obtained under the irradiation of the optimal laser pulse show large differences and the various reaction pathways of the two molecules are selectively controlled. The experimental results demonstrate that the scheme is quite effective and useful in studies of two molecules having common mass peaks, which makes a traditional single mass spectrometer unfeasible. Project supported by the National Basic Research Program of China (Grant No. 2013CB922200) and the National Natural Science Foundation of China (Grant No. 11374124).

Isolation of (S)-(+)-naproxene from Musa acuminata. Inhibitory effect of naproxene and its 7-methoxy isomer on constitutive COX-1 and inducible COX-2.

PubMed

Abad, T; McNaughton-Smith, G; Fletcher, W Q; Echeverri, F; Diaz-Peñate, R; Tabraue, C; Ruiz de Galarreta, C M; López-Blanco, F; Luis, J G

2000-06-01

The isolation and characterisation of (S)-(+)-6-methoxy-alpha-methyl-2-naphthaleneacetic acid, a well known synthetic non-steroidal anti-inflammatory drug (naproxene), from a natural source is described for the first time. We evaluated the ability of naproxene and its 7-methoxy isomer to abrogate constitutive COX-1 and inducible COX-2 activity in human A549 cells. Naproxene inhibited COX-1 (IC50 = 3.42 microM) and COX-2 (IC50 = 1.53 microM), whereas the 7-methoxy isomer had no appreciable effect on COX-1 (IC50 > 100 microM) but also abrogated the activity of COX-2 enzyme (IC50 = 14.42 microM).

Structural isomers of polyfluorinated di- and tri-alkylated phosphate ester surfactants present in industrial blends and in microwave popcorn bags.

PubMed

Trier, Xenia; Nielsen, Nikoline Juul; Christensen, Jan H

2011-09-01

In this study, we provide strategies for detecting and quantifying the structural isomers of polyfluorinated di- and tri-alkyl surfactants (PFAS) by mass spectrometry (MS). We specifically investigate polyfluorinated dialkylated phosphate ester surfactants (x:2/y:2 diPAPS, (F(CF(2))( x )CH(2)CH(2)O-P(O)(O)(-)-OCH(2)CH(2)(CF(2))( y )F)) and their thioether analogues (x:2/y:2 S-diPAPS, F(CF(2))( x )CH(2)CH(2)SCH(2)-C[CH(2)O)(2)P(O)(O)(-)]-CH(2)SCH(2)CH(2)(CF(2))( y )F), which are used for industrial applications, such as oil- and water-repellent coatings on paper and board. DiPAPS have been found in human blood and are metabolised to the persistent perfluoroalkyl carboxylic acids (PFCA) in rats. A microwave popcorn bag extract was analysed by ultrahigh-pressure liquid chromatography coupled to a negative electrospray ionisation-quadrupole time-of-flight MS. The extract contained S-diPAPS, diPAPS and trialkylated (triPAPS) impurities. TriPAPS were also present in industrial and synthetic diPAPS standards, and were verified with an 8:2/8:2/8:2 triPAPS standard. The eight elemental compositions (m/z's) of diPAPS in the extract represent 19 precursor ion structures, and the six S-diPAPS m/z's represent at least 13 structures. The diPAPS had [M-H](-) precursor ions of m/z 789, 889,…1,489 and the S-diPAPS of m/z 921, 1,021,…1,421, corresponding to fluorinated chains from C(6-18). Each m/z appeared as one to three chromatographic peaks of structural isomers, where, e.g. m/z 1,189 was present as 10:2/10:2, 8:2/12:2 and 6:2/14:2 diPAPS. The isomers formed different products ions, thus only half of the m/z 1,189 diPAPS concentration was measured with one precursor ion > product ion transition. In general, knowledge about structural isomers of poly-alkylated PFAS is needed for the estimation of types and amounts of perfluorinated degradation products, such as PFCA from diPAPS.

Solid and solution NMR studies of the complexation of Ag + with the trans isomer of captopril: Biological activities of this high blood pressure drug along with its Ag + complex

NASA Astrophysics Data System (ADS)

Isab, Anvarhusein A.; Wazeer, Mohamed I. M.

2006-09-01

Complexation of Ag + with captopril, 1-[(2 S)-3-mercapto-2-methylpropionyl]- L-proline, has been studied by 1H and 13C-NMR spectroscopy. The equilibrium constants for the trans to cis isomers of captopril bound to Ag + were measured by 1H NMR spectroscopy. It is observed that the trans isomer of the drug binds more strongly to Ag + between pH 5 and 8, as shown by the broadening of the trans isomer's resonances in 13C NMR spectra on complexation. A monodentate complexation of the trans captopril with Ag + via the thiol site is proposed based on the solid-state NMR and IR data. A superior antimicrobial activity is exhibited by the Cap-Ag(I) complex compared to captopril ligand itself against Heterotrotropic Plate Counts (HPC), Pseudomonas aeruginosa and Fecal streptococcus bacteria.

241Am (n,gamma) isomer ratio measurement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bond, Evelyn M; Vieira, David J; Moody, Walter A

The objective of this project is to improve the accuracy of the {sup 242}Cm/{sup 241}Am radiochemistry ratio. We have performed an activation experiment to measure the {sup 241}Am(n,{gamma}) cross section leading to either the ground state of {sup 242g}Am (t{sub 1/2} = 16 hr) which decays to {sup 242}Cm (t{sub 1/2} = 163 d) or the long-lived isomer {sup 242m}Am (t{sub 1/2} = 141 yr). This experiment will develop a new set of americium cross section evaluations that can be used with a measured {sup 242}Cm/{sup 241}Am radiochemical measurement for nuclear forensic purposes. This measurement is necessary to interpret themore » {sup 242}Cm/{sup 241}Am ratio because a good measurement of this neutron capture isomer ratio for {sup 241}Am does not exist. The targets were prepared in 2007 from {sup 241}Am purified from LANL stocks. Gold was added to the purified {sup 241}Am as an internal neutron fluence monitor. These targets were placed into a holder, packaged, and shipped to Forschungszentrum Karlsruhe, where they were irradiated at their Van de Graff facility in February 2008. One target was irradiated with {approx}25 keV quasimonoenergetic neutrons produced by the {sup 7}Li(p,n) reaction for 3 days and a second target was also irradiated for 3 days with {approx}500 keV neutrons. Because it will be necessary to separate the {sup 242}Cm from the {sup 241}Am in order to measure the amount of {sup 242}Cm by alpha spectrometry, research into methods for americium/curium separations were conducted concurrently. We found that anion exchange chromatography in methanol/nitric acid solutions produced good separations that could be completed in one day resulting in a sample with no residue. The samples were returned from Germany in July 2009 and were counted by gamma spectrometry. Chemical separations have commenced on the blank sample. Each sample will be spiked with {sup 244}Cm, dissolved and digested in nitric acid solutions. One third of each sample will be processed at a

Selective identification of specialized pro-resolving lipid mediators from their biosynthetic double di-oxygenation isomers.

PubMed

Hansen, Trond V; Dalli, Jesmond; Serhan, Charles N

The n-3 polyunsaturated fatty acids are substrates for lipoxygenases and cyclooxygenases. During inflammatory processes, these enzymes form several distinct families of oxygenated polyunsaturated fatty acids coined specialized pro-resolving lipid mediators. Structural elucidation of these natural products using LC-MS/MS based metabololipidomics with the pico- to nanogram amounts of biosynthetic material available have been performed. The specialized pro-resolving lipid mediators display stereospecific and potent anti-inflammatory and pro-resolving actions. Most often the different families among these mediators are chemically characterized by two or three chiral, secondary alcohols, separated by either an E,E,Z -triene or an E,Z,E,E -tetraenemoiety. The lipoxygenases also form other oxygenated polyunsaturated natural products, coined double di-oxygenation products, that are constitutional isomers of the protectin and maresin families of specialized pro-resolving lipid mediators. Very often these products exhibit similar chromatographic properties and mass spectrometrical fragment ions as the pro-resolving mediators. In addition, the double di-oxygenation products are sometimes formed in larger amounts than the specialized pro-resolving lipid mediators. Thus, it is not always possible to distinguish between the specialized pro-resolving mediators and their double di-oxygenation isomers in biological systems, using LC/MS-based techniques. Herein, a convenient and easy-to-use protocol to meet this challenge is presented.

Enantio-selective optrode for optical isomers of biologically active amines using a new lipophilic aromatic carrier

NASA Astrophysics Data System (ADS)

He, Huarui; Uray, Georg; Wolfbeis, Otto S.

1991-09-01

This paper presents a method for optically sensing enantiomers (optical isomers) of biological amines such as norephedrine, and drugs such as the (Beta) -blocker propranolol. It is based on the use of a new lipophilic aromatic ammonium ion carrier (DODD) and a highly fluorescent lipophilic proton carrier (DZ 49) dissolved in a pvc membrane. Recognition of one of the enantiomers is accomplished by specific interaction of the amine with the optically active lipophilic substrate in a pvc membrane. The amine, which is present as an ammonium ion at physiological pH, is carried into the pvc membranes. Simultaneously, a proton is released from the proton carrier (a lipophilic xanthene dye) that thereby undergoes a change in both color and fluorescence intensity. The sensors respond to three analytes in the concentration range from 0.01 to 10 mM for propranolol, 0.3 to 100 mM for norephedrine, and 1 to 100 mM for 1-phenylethylamine. The selectivity coefficients (Kopt) are 0.8, 0.7, and 0.8 for propranolol, norephedrine,a nd 1-phenylethylamine, respectively. It is of potential utility for specifically recognizing one out of several isomers, in particular bioactive amines, where one form usually is active only. The carrier showed stronger affinity for compounds which contain naphthyl rather than phenyl substituents.

A validated LC method for determination of 2,3-dichlorobenzoic acid and its associated regio isomers.

PubMed

Krishnaiah, Ch; Sri, Khagga Bhavya

2012-05-01

A simple, selective and sensitive gradient reversed-phase liquid chromatography method has been developed for the separation and determination of 2,3-dichlorobenzoic acid, which is an intermediate of the lamotrizine drug substance, and its regio isomers. The separation was achieved on a reversed-phase United States Pharmacopeia L1 (C-18) column using 0.01 M ammonium acetate buffer at pH 2.5 and methanol (50:50 v/v) mixture as mobile phase A and a methanol and water mixture (80:20 v/v) as mobile phase B in a gradient elution at flow rate 1.2 mL/min with ultraviolet detection at 210 nm. The method is found to be selective, precise, linear, accurate and robust. It was used for quality assurance and monitoring the synthetic reactions involved in the process development of lamotrizine. The method is found to be simple, rapid, specific and reliable for the determination of unreacted levels of raw materials and isomers in reaction mixtures and finished product lamotrizine. The method was fully validated as per International Conference of Harmonization guidelines and results from validation confirm that the method is highly suitable for its intended purpose. © The Author [2012]. Published by Oxford University Press. All rights reserved.

Occurrence, fluxes and sources of perfluoroalkyl substances with isomer analysis in the snow of northern China.

PubMed

Shan, Guoqiang; Chen, Xinwei; Zhu, Lingyan

2015-12-15

In this study, perfluoroalkyl substances (PFASs) and the isomers of perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS) were analyzed in fresh snow samples collected from 19 cities in northern China, 2013. The levels of total PFASs in the snow samples were 33.5-229 ng/L, suggesting heavy atmospheric pollution of PFASs in northern China. PFOA (9.08-107 ng/L), PFOS (3.52-54.3 ng/L), perfluoroheptanoate (PFHpA) (3.66-44.8 ng/L), and perfluorohexanoate (PFHxA) (3.21-23.6 ng/L) were predominant with a summed contribution of 82% to the total PFASs. The particulate matters (PMs) associated PFASs contributed 21.5-56.2% to the total PFASs in the snow, suggesting PMs are vital for the transport and deposition of airborne PFASs. Partitioning of PFASs between PM and dissolved phases was dependent on the carbon chain length and end functional groups. Isomer profiles of PFOA and PFOS in the snow were in agreement with the signature of the historical 3M electrochemical fluorination (ECF) products, suggesting that the ECF products were still produced and used in China. Further source analysis showed that the airborne PFASs in urban area were mainly due to direct release rather than degradation of their precursors. Copyright © 2015 Elsevier B.V. All rights reserved.

Separation of porphyrin-based photosensitizer isomers by laser-induced fluorescence capillary electrophoresis.

PubMed

Peng, Xuejun; Sternberg, Ethan; Dolphin, David

2005-10-01

Methods for the separation of photosensitizer isomers, such as benzoporphyrin derivative monoacid, benzoporphyrin ethyl monoacid, 2-[1-hexyloxyethyl]-2-devinylpyropheophorbide-a, diethyleneglycol diester benzoporphyrin derivative, tin ethyl etiopurpurin, and phthalocyanine tetrasulfonate, have been systematically developed by CE. Detection was accomplished by UV absorption at 214 nm or by LIF with excitation at 442/488 nm and emission at 690 nm. The effects of three major experimental parameters of buffer types, organic solvents, and surfactant additives are described. The optimized separation conditions were determined so as to provide satisfactory separation efficiency and analysis time. The methods are shown to be suitable for the separation and determination of porphyrin and phthalocyanines regioisomers, diastereoisomers, and enantiomers.

Physical and biological mechanisms of nanosecond- and microsecond-pulsed FE-DBD plasma interaction with biological objects

NASA Astrophysics Data System (ADS)

Dobrynin, Danil

2013-09-01

Mechanisms of plasma interaction with living tissues and cells can be quite complex, owing to the complexity of both the plasma and the tissue. Thus, unification of all the mechanisms under one umbrella might not be possible. Here, analysis of interaction of floating electrode dielectric barrier discharge (FE-DBD) with living tissues and cells is presented and biological and physical mechanisms are discussed. In physical mechanisms, charged species are identified as the major contributors to the desired effect and a mechanism of this interaction is proposed. Biological mechanisms are also addressed and a hypothesis of plasma selectivity and its effects is offered. Spatially uniform nanosecond and sub-nanosecond short-pulsed dielectric barrier discharge plasmas are gaining popularity in biological and medical applications due to their increased uniformity, lower plasma temperature, lower surface power density, and higher concentration of the active species produced. In this presentation we will compare microsecond pulsed plasmas with nanosecond driven systems and their applications in biology and medicine with specific focus on wound healing and tissue regeneration. Transition from negative to positive streamer will be discussed with proposed hypothesis of uniformity mechanisms of positive streamer and the reduced dependence on morphology and surface chemistry of the second electrode (human body) being treated. Uniform plasma offers a more uniform delivery of active species to the tissue/surface being treated thus leading to better control over the biological results.

Microsecond Unfolding Kinetics of Sheep Prion Protein Reveals an Intermediate that Correlates with Susceptibility to Classical Scrapie

PubMed Central

Chen, Kai-Chun; Xu, Ming; Wedemeyer, William J.; Roder, Heinrich

2011-01-01

The microsecond folding and unfolding kinetics of ovine prion proteins (ovPrP) were measured under various solution conditions. A fragment comprising residues 94–233 of the full-length ovPrP was studied for four variants with differing susceptibilities to classical scrapie in sheep. The observed biexponential unfolding kinetics of ovPrP provides evidence for an intermediate species. However, in contrast to previous results for human PrP, there is no evidence for an intermediate under refolding conditions. Global analysis of the kinetic data, based on a sequential three-state mechanism, quantitatively accounts for all folding and unfolding data as a function of denaturant concentration. The simulations predict that an intermediate accumulates under both folding and unfolding conditions, but is observable only in unfolding experiments because the intermediate is optically indistinguishable from the native state. The relative population of intermediates in two ovPrP variants, both transiently and under destabilizing equilibrium conditions, correlates with their propensities for classical scrapie. The variant susceptible to classical scrapie has a larger population of the intermediate state than the resistant variant. Thus, the susceptible variant should be favored to undergo the PrPC to PrPSc conversion and oligomerization. PMID:21889460

Peptide kinetics from picoseconds to microseconds using boxed molecular dynamics: Power law rate coefficients in cyclisation reactions

NASA Astrophysics Data System (ADS)

Shalashilin, Dmitrii V.; Beddard, Godfrey S.; Paci, Emanuele; Glowacki, David R.

2012-10-01

Molecular dynamics (MD) methods are increasingly widespread, but simulation of rare events in complex molecular systems remains a challenge. We recently introduced the boxed molecular dynamics (BXD) method, which accelerates rare events, and simultaneously provides both kinetic and thermodynamic information. We illustrate how the BXD method may be used to obtain high-resolution kinetic data from explicit MD simulations, spanning picoseconds to microseconds. The method is applied to investigate the loop formation dynamics and kinetics of cyclisation for a range of polypeptides, and recovers a power law dependence of the instantaneous rate coefficient over six orders of magnitude in time, in good agreement with experimental observations. Analysis of our BXD results shows that this power law behaviour arises when there is a broad and nearly uniform spectrum of reaction rate coefficients. For the systems investigated in this work, where the free energy surfaces have relatively small barriers, the kinetics is very sensitive to the initial conditions: strongly non-equilibrium conditions give rise to power law kinetics, while equilibrium initial conditions result in a rate coefficient with only a weak dependence on time. These results suggest that BXD may offer us a powerful and general algorithm for describing kinetics and thermodynamics in chemical and biochemical systems.

Predictive coupled-cluster isomer orderings for some Si{sub n}C{sub m} (m, n ≤ 12) clusters: A pragmatic comparison between DFT and complete basis limit coupled-cluster benchmarks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Byrd, Jason N., E-mail: byrd.jason@ensco.com; ENSCO, Inc., 4849 North Wickham Road, Melbourne, Florida 32940; Lutz, Jesse J., E-mail: jesse.lutz.ctr@afit.edu

The accurate determination of the preferred Si{sub 12}C{sub 12} isomer is important to guide experimental efforts directed towards synthesizing SiC nano-wires and related polymer structures which are anticipated to be highly efficient exciton materials for the opto-electronic devices. In order to definitively identify preferred isomeric structures for silicon carbon nano-clusters, highly accurate geometries, energies, and harmonic zero point energies have been computed using coupled-cluster theory with systematic extrapolation to the complete basis limit for set of silicon carbon clusters ranging in size from SiC{sub 3} to Si{sub 12}C{sub 12}. It is found that post-MBPT(2) correlation energy plays a significant rolemore » in obtaining converged relative isomer energies, suggesting that predictions using low rung density functional methods will not have adequate accuracy. Utilizing the best composite coupled-cluster energy that is still computationally feasible, entailing a 3-4 SCF and coupled-cluster theory with singles and doubles extrapolation with triple-ζ (T) correlation, the closo Si{sub 12}C{sub 12} isomer is identified to be the preferred isomer in the support of previous calculations [X. F. Duan and L. W. Burggraf, J. Chem. Phys. 142, 034303 (2015)]. Additionally we have investigated more pragmatic approaches to obtaining accurate silicon carbide isomer energies, including the use of frozen natural orbital coupled-cluster theory and several rungs of standard and double-hybrid density functional theory. Frozen natural orbitals as a way to compute post-MBPT(2) correlation energy are found to be an excellent balance between efficiency and accuracy.« less

Isomer-delayed γ -ray spectroscopy of A =159 -164 midshell nuclei and the variation of K -forbidden E 1 transition hindrance factors

NASA Astrophysics Data System (ADS)

Patel, Z.; Walker, P. M.; Podolyák, Zs.; Regan, P. H.; Berry, T. A.; Söderström, P.-A.; Watanabe, H.; Ideguchi, E.; Simpson, G. S.; Nishimura, S.; Wu, Q.; Xu, F. R.; Browne, F.; Doornenbal, P.; Lorusso, G.; Rice, S.; Sinclair, L.; Sumikama, T.; Wu, J.; Xu, Z. Y.; Aoi, N.; Baba, H.; Bello Garrote, F. L.; Benzoni, G.; Daido, R.; Dombrádi, Zs.; Fang, Y.; Fukuda, N.; Gey, G.; Go, S.; Gottardo, A.; Inabe, N.; Isobe, T.; Kameda, D.; Kobayashi, K.; Kobayashi, M.; Komatsubara, T.; Kojouharov, I.; Kubo, T.; Kurz, N.; Kuti, I.; Li, Z.; Matsushita, M.; Michimasa, S.; Moon, C.-B.; Nishibata, H.; Nishizuka, I.; Odahara, A.; Şahin, E.; Sakurai, H.; Schaffner, H.; Suzuki, H.; Takeda, H.; Tanaka, M.; Taprogge, J.; Vajta, Zs.; Yagi, A.; Yokoyama, R.

2017-09-01

Excited states have been studied in 159Sm, 161Sm, 162Sm (Z =62 ), 163Eu (Z =63 ), and 164Gd (Z =64 ), populated by isomeric decay following 238U projectile fission at RIBF, RIKEN. The isomer half-lives range from 50 ns to 2.6 μ s . In comparison with other published data, revised interpretations are proposed for 159Sm and 163Eu. The first data for excited states in 161Sm are presented, where a 2.6-μ s isomer is assigned a three-quasiparticle, Kπ=17 /2- structure. The interpretation is supported by multi-quasiparticle Nilsson-BCS calculations, including the blocking of pairing correlations. A consistent set of reduced E 1 hindrance factors is obtained. Limited evidence is also reported for isomeric decay in 163Sm, 164Eu, and 165Eu.

Doubly magic 208Pb: High-spin states, isomers, and E 3 collectivity in the yrast decay

NASA Astrophysics Data System (ADS)

Broda, R.; Janssens, R. V. F.; Iskra, Ł. W.; Wrzesinski, J.; Fornal, B.; Carpenter, M. P.; Chiara, C. J.; Cieplicka-Oryńczak, N.; Hoffman, C. R.; Kondev, F. G.; Królas, W.; Lauritsen, T.; Podolyak, Zs.; Seweryniak, D.; Shand, C. M.; Szpak, B.; Walters, W. B.; Zhu, S.; Brown, B. A.

2017-06-01

Yrast and near-yrast levels up to spin values in excess of I =30 ℏ have been delineated in the doubly magic 208Pb nucleus following deep-inelastic reactions involving 208Pb targets and, mostly, 430-MeV 48Ca and 1440-MeV 208Pb beams. The level scheme was established up to an excitation energy of 16.4 MeV, based on multifold γ-ray coincidence relationships measured with the Gammasphere array. Below the well-known, 0.5-μs 10+ isomer, ten new transitions were added to earlier work. The delineation of the higher parts of the level sequence benefited from analyses involving a number of prompt- and delayed-coincidence conditions. Three new isomeric states were established along the yrast line with Iπ=20- (10 342 keV), 23+ (11 361 keV), and 28- (13 675 keV), and respective half-lives of 22(3), 12.7(2), and 60(6) ns. Gamma transitions were also identified preceding in time the 28- isomer; however, only a few could be placed in the level scheme and no firm spin-parity quantum numbers could be proposed. In contrast, for most states below this 28- isomer, firm spin-parity values were assigned, based on total electron-conversion coefficients, deduced for low-energy (<500 keV ) transitions from γ-intensity balances, and on measured γ-ray angular distributions. The latter also enabled the quantitative determination of mixing ratios. The transition probabilities extracted for all isomeric transitions in 208Pb have been reviewed and discussed in terms of the intrinsic structure of the initial and final levels involved. Particular emphasis was placed on the many observed E 3 transitions as they often exhibit significant enhancements in strength [of the order of tens of Weisskopf units (W.u.)] comparable to the one seen for the neutron j15 /2→g9 /2 E 3 transition in 209Pb. In this context, the enhancement of the 725-keV E 3 transition (56 W.u.) associated with the decay of the highest-lying 28- isomer observed in this work remains particularly challenging to explain. Large

Hexabromocyclododecane Flame Retardant Isomers in Sediments from Detroit River and Lake Erie of the Laurentian Great Lakes of North America.

PubMed

Letcher, Robert J; Lu, Zhe; Chu, Shaogang; Haffner, G Douglas; Drouillard, Ken; Marvin, Christopher H; Ciborowski, Jan J H

2015-07-01

Sediments collected in 2004 from along the Detroit River (n = 19) and across all of Lake Erie (n = 18) were analyzed for isomers of the flame retardant chemical, hexabromocyclododecane (HBCD), using liquid chromatography-tandem mass spectrometry. Sediment samples had ΣHBCD concentrations ranging from not detected to 1.6 ng/g d.w. γ-HBCD (56 %-100 % of ΣHBCDs) was the predominate isomer, observed in 7 of 19 samples from the Detroit River and 6 of 18 samples from Lake Erie (all within the western basin). α-HBCD was found in 4 Detroit River and 2 Lake Erie western basin sites, while β-HBCD was only in two Detroit River samples. High ΣHBCD concentrations (>100 ng/g d.w.) were found in two sludge samples from two Windsor, ON, wastewater treatment plants that feed into the Detroit River upstream. HBCD contamination into the Detroit River is a major input vector into Lake Erie and with an apparent sediment dilution effect moving towards the eastern basin.

Products from the Oxidation of Linear Isomers of Hexene

PubMed Central

Battin-Leclerc, Frédérique; Rodriguez, Anne; Husson, Benoit; Herbinet, Olivier; Glaude, Pierre-Alexandre; Wang, Zhandong; Cheng, Zhanjun; Qi, Fei

2014-01-01

The experimental study of the oxidation of the three linear isomers of hexene was performed in a quartz isothermal jet-stirred reactor (JSR) at temperatures ranging from 500 to 1100 K including the negative temperature coefficient (NTC) zone, at quasi-atmospheric pressure (1.07 bar), at a residence time of 2 s and with dilute stoichiometric mixtures. The fuel and reaction product mole fractions were measured using online gas chromatography. In the case of 1-hexene, the JSR has also been coupled through a molecular-beam sampling system to a reflectron time-of-flight mass spectrometer combined with tunable synchrotron vacuum ultraviolet photoionization. A difference of reactivity between the three fuels which varies with the temperature range has been observed and is discussed according to the changes in the possible reaction pathways when the double bond is displaced. An enhanced importance of the reactions via the Waddington mechanism and of those of allylic radicals with HO2 radicals can be noted for 2- and 3-hexenes compared to 1-hexene. PMID:24400665

Distribution pathways of hexachlorocyclohexane isomers in a soil-plant-air system. A case study with Cynara scolymus L. and Erica sp. plants grown in a contaminated site.

PubMed

Pereira, R Calvelo; Monterroso, C; Macías, F; Camps-Arbestain, M

2008-09-01

This study focuses on the main routes of distribution and accumulation of different hexachlorocyclohexane (HCH) isomers (mainly alpha-, beta-, gamma- and delta-HCH) in a soil-plant-air system. A field assay was carried out with two plant species, Cynara scolymus L. and Erica sp., which were planted either: (i) directly in the HCH-contaminated soil; or (ii) in pots filled with uncontaminated soil, which were placed in the HCH-contaminated soil. Both plant species accumulated HCH in their tissues, with relatively higher accumulation in above-ground biomass than in roots. The beta-HCH isomer was the main isomer in all plant tissues. Adsorption of HCH by the roots from contaminated soil (soil-->root pathway) and adsorption through the aerial biomass from either the surrounding air, following volatilization of the contaminant (soil-->air-->shoot pathway), and/or contact with air-suspended particles contaminated with HCH (soil particles-->shoot pathway) were the main mechanisms of accumulation. These results may have important implications for the use of plants for reducing the transfer of contaminants via the atmosphere.

[Atomic/ionic fluorescence in microwave plasma torch discharge with excitation of high current and microsecond pulsed hollow cathode lamp: Ca atomic/ionic fluorescence spectrometry].

PubMed

Gong, Zhen-bin; Liang, Feng; Yang, Peng-yuan; Jin, Qin-han; Huang, Ben-li

2002-02-01

A system of atomic and ionic fluorescence spectrometry in microwave plasma torch (MPT) discharge excited by high current microsecond pulsed hollow cathode lamp (HCMP HCL) has been developed. The operation conditions for Ca atomic and ionic fluorescence spectrometry have been optimized. Compared with atomic fluorescence spectrometry (AFS) in argon microwave induced plasma (MIP) and MPT with the excitation of direct current and conventional pulsed HCL, the system with HCMP HCL excitation can improve AFS and ionic fluorescence spectrometry (IFS) detection limits in MPT atomizer and ionizer. Detection limits (3 sigma) with HCMP HCL-MPT-AFS/IFS are 10.1 ng.mL-1 for Ca I 422.7 nm, 14.6 ng.mL-1 for Ca II 393.4 nm, and 37.4 ng.mL-1 for Ca II 396.8 nm, respectively.

Concomitant tumor resistance: the role of tyrosine isomers in the mechanisms of metastases control.

PubMed

Ruggiero, Raúl A; Bruzzo, Juan; Chiarella, Paula; Bustuoabad, Oscar D; Meiss, Roberto P; Pasqualini, Christiane D

2012-03-01

Concomitant tumor resistance (CR) is a phenomenon in which a tumor-bearing host is resistant to the growth of secondary tumor implants and metastasis. Although previous studies indicated that T-cell-dependent processes mediate CR in hosts bearing immunogenic small tumors, manifestations of CR induced by immunogenic and nonimmunogenic large tumors have been associated with an elusive serum factor. In a recently published study, we identified this factor as meta-tyrosine and ortho-tyrosine, 2 isomers of tyrosine that would not be present in normal proteins. In 3 different murine models of cancer that generate CR, both meta- and ortho-tyrosine inhibited tumor growth. Additionally, we showed that both isoforms of tyrosine blocked metastasis in a fourth model that does not generate CR but is sensitive to CR induced by other tumors. Mechanistic studies showed that the antitumor effects of the tyrosine isomers were mediated in part by early inhibition of the MAP/ERK pathway and inactivation of STAT3, potentially driving tumor cells into a state of dormancy in G(0)-phase. Other mechanisms, putatively involving the activation of an intra-S-phase checkpoint, would also inhibit tumor proliferation by accumulating cells in S-phase. By revealing a molecular basis for the classical phenomenon of CR, our findings may stimulate new generalized approaches to limit the development of metastases that arise after resection of primary tumors or after other stressors that may promote the escape of metastases from dormancy, an issue that is of pivotal importance to oncologists and their patients.

A theoretical study on the geometry and spectroscopic properties of ground-state and local minima isomers of (CuS)n=2-6 clusters

NASA Astrophysics Data System (ADS)

Luque-Ceballos, Jonathan C.; Posada-Borbón, Alvaro; Herrera-Urbina, Ronaldo; Aceves, R.; Juárez-Sánchez, J. Octavio; Posada-Amarillas, Alvaro

2018-03-01

Spectroscopic properties of gas-phase copper sulfide clusters (CuS)n (n = 2-6) are calculated using Density Functional Theory (DFT) and time-dependent (TD) DFT approaches. The energy landscape of the potential energy surface is explored through a basin-hopping DFT methodology. Ground-state and low-lying isomer structures are obtained. The global search was performed at the B3PW91/SDD level of theory. Normal modes are calculated to validate the existence of optimal cluster structures. Energetic properties are obtained for the ground-state and isomer clusters and their relative energies are evaluated for probing isomerization. This is a few tenths of an eV, except for (CuS)2 cluster, which presents energy differences of ∼1 eV. Notable differences in the infrared spectra exist between the ground-state and first isomer structures, even for the (CuS)5 cluster, which has in both configurations a core copper pyramid. TDDFT provides the simulated absorption spectrum, presenting a theoretical description of optical absorption bands in terms of electronic excitations in the UV and visible regions. Results exhibit a significant dependence of the calculated UV/vis spectra on clusters size and shape regarding the ground state structures. Optical absorption is strong in the UV region, and weak or forbidden in the visible region of the spectrum.