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Sample records for acid isomers present

  1. 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.

  2. Electropolymerization mechanisms of hydroxyphenylacetic acid isomers

    NASA Astrophysics Data System (ADS)

    Rodrigues, Luciano P.; Ferreira, Deusmaque C.; Sonoda, Milton Taidi; Madurro, Ana Graci B.; Abrahão, Odonírio; Madurro, João M.

    2014-08-01

    Three different films of conducting polymers with free carboxylic functional groups were obtained from 2,3 and 4-hydroxyphenylacetic acid isomers (HPA) and the respective electropolymerization mechanisms were elucidated by DFT calculations. The different properties observed at these new material characterizations, obtained by means of cyclic voltammetry on graphite, are in agreement with theoretical interpretation presented for each reaction mechanisms, which involves the different radical cation coupling and formation of aromatic polyethers with free carboxyl groups, characterized by FTIR spectrometry and electrochemical tests. The computational chemistry analysis of the radical cations spin densities and partial atomic charges variation during the monomer oxidations, indicates the most probably reactive sites for their coupling, allowing the proposition of HPA electropolymerization mechanisms. The poly(2-HPA) had the largest yield in the electropolymerization reaction and the lowest electron transfer. The poly(4-HPA) displayed the lowest yield and the largest electron transfer coefficient, with poly(3-HPA) presenting intermediate values between the former two. Therefore, poly(3-HPA) is a very promising polymer for the platform development for electronic systems, which require materials with good electronic conductivity allied to intrinsic flexibility of polymeric materials.

  3. Two methods for the separation of monounsaturated octadecenoic acid isomers.

    PubMed

    Villegas, C; Zhao, Y; Curtis, J M

    2010-01-29

    The identification and quantification of complex mixtures of cis and trans octadecenoic (18:1) fatty acid isomers presents a major challenge for conventional one-dimensional GC/FID analysis of their methyl esters. We have compared the use of two methods to achieve optimized separations of positional and geometrical octadecenoic fatty acid isomers-comprehensive two-dimensional gas chromatography (GCxGC), and silver ion high performance liquid chromatography interfaced to atmospheric pressure photoionization (APPI) mass spectrometry. Nine isomers of octadecenoic acid methyl ester were well separated on a single silver ion column with a mobile phase of 0.018% acetonitrile and 0.18% isopropanol in hexane. Reproducible retention times were obtained with relative standard deviations of around 1% over 5 injections. The extra selectivity and reproducibility afforded by APPI-MS, together with the wide separation of cis and trans isomers by silver ion chromatography, resulted in a promising method for measurement of octadecenoic acid FAME. The GCxGC separation was performed using various column combinations, and optimal separation was obtained by coupling an ionic liquid column (Supelco SLB-IL100 [1,9-di(3-vinyl-imidazolium) nonane bis(trifluoromethyl) sulfonyl imidate]) in the first dimension with a SGE BPX50 (50% phenyl polysilphenylene-siloxane) in the second dimension. These methods have been applied to the analysis of octadecenoic acid in milk and beef fat. PMID:20022011

  4. Trans fatty acid isomers in human health and in the food industry.

    PubMed

    Valenzuela, A; Morgado, N

    1999-01-01

    Trans fatty acids are unsaturated fatty acids with at least one double bond in the trans configuration. These fatty acids occur naturally in dairy and other natural fats and in some plants. However, industrial hydrogenation of vegetable or marine oils is largely the main source of trans fatty acids in our diet. The metabolic effect of trans isomers are today a matter of controversy generating diverse extreme positions in light of biochemical, nutritional, and epidemiological studies. Trans fatty acids also have been implicated in the etiology of various metabolic and functional disorders, but the main concern about its health effects arose because the structural similarity of these isomers to saturated fatty acids, the lack of specific metabolic functions, and its competition with essential fatty acids. The ingestion of trans fatty acids increases low density lipoprotein (LDL) to a degree similar to that of saturated fats, but it also reduces high density lipoproteins (HDL), therefore trans isomers are considered more atherogenic than saturated fatty acids. Trans isomers increase lipoprotein(a), a non-dietary-related risk of atherogenesis, to levels higher than the corresponding chain-length saturated fatty acid. There is little evidence that trans fatty acids are related to cancer risk at any of the major cancer sites. Considerable improvement has been obtained with respect to the metabolic effect of trans fatty acids due the development of analytical procedures to evaluate the different isomers in both biological and food samples. The oleochemical food industries have developed several strategies to reduce the trans content of hydrogenated oils, and now margarine and other hydrogenated-derived products containing low trans or virtually zero trans are available and can be obtained in the retail market. The present review provides an outline of the present status of trans fatty acids including origin, analytical procedures, estimated ingestion, metabolic effects

  5. Chromatographic selectivity study of 4-fluorophenylacetic acid positional isomers separation.

    PubMed

    Chasse, Tyson; Wenslow, Robert; Bereznitski, Yuri

    2007-07-13

    Unique properties of the fluorine atom stimulate widespread use and development of new organofluorine compounds in agrochemistry, biotechnology and pharmacology applications. However, relatively few synthetic methods exhibit a high degree of fluorination selectivity, which ultimately results in the presence of structurally related fluorinated isomers in the synthetic product. This outcome is undesirable from a pharmaceutical perspective as positional isomers possess different reactivity, biological activity and toxicity as compared to the desired product. It is advantageous to control positional isomers in the early stages of the synthetic process, as rejection and analysis of these isomers will likely become more difficult in later stages. The current work reports the development of a chromatographic analysis of 2- and 3-fluorophenylacetic acid positional isomer impurities in 4-fluorophenylacetic acid (4-FPAA), a building block in the synthesis of an active pharmaceutical ingredient. The method is employed as a part of a Quality by Design Approach to control purity of the starting material in order to eliminate the presence of undesirable positional isomers in the final drug substance. During method development, a wide range of chromatographic conditions and structurally related positional isomer probe molecules were exploited in an effort to gain insight into the specifics of the separation mechanism. For the systems studied it was shown that the choice of organic modifier played a key role in achieving acceptable separation. Further studies encompassed investigation of temperature influence on retention and selectivity of the FPAA isomers separation. Thermodynamic analysis of these data showed that the selectivity of the 2- and 4- fluorophenylacetic acids separation was dominated by an enthalpic process, while the selectivity of the 4- and 3-fluorophenylacetic acids separation was exclusively entropy driven (Delta(DeltaH degrees approximately 0). Studies of

  6. The Immunomodulatory Activity of Jacaric Acid, a Conjugated Linolenic Acid Isomer, on Murine Peritoneal Macrophages.

    PubMed

    Liu, Wai Nam; Leung, Kwok Nam

    2015-01-01

    This study aims at demonstrating the immunomodulatory property of jacaric acid, a conjugated linolenic acid (CLNA) isomer that is present in jacaranda seed oil, on murine peritoneal macrophages. Our results showed that jacaric acid exhibited no significant cytotoxicity on the thioglycollate-elicited murine peritoneal macrophages as revealed by the neutral red uptake assay, but markedly increased their cytostatic activity on the T-cell lymphoma MBL-2 cells as measured by the fluorometric CyQuant® NF Cell Proliferation Assay Kit. Flow cytometric analysis indicated that jacaric acid could enhance the endocytic activity of macrophages and elevated their intracellular production of superoxide anion. Moreover, jacaric acid-treated macrophages showed an increase in the production of nitric oxide which was accompanied by an increase in the expression level of inducible nitric oxide synthase protein. In addition, the secretion of several pro-inflammatory cytokines, including interferon-γ, interleukin-1β and tumor necrosis factor-α, was up-regulated. Collectively, our results indicated that the naturally-occurring CLNA isomer, jacaric acid, could exhibit immunomodulating activity on the murine peritoneal macrophages in vitro, suggesting that this CLNA isomer may act as an immunopotentiator which can be exploited for the treatment of some immunological disorders with minimal toxicity and fewer side effects.

  7. The Immunomodulatory Activity of Jacaric Acid, a Conjugated Linolenic Acid Isomer, on Murine Peritoneal Macrophages

    PubMed Central

    Liu, Wai Nam; Leung, Kwok Nam

    2015-01-01

    This study aims at demonstrating the immunomodulatory property of jacaric acid, a conjugated linolenic acid (CLNA) isomer that is present in jacaranda seed oil, on murine peritoneal macrophages. Our results showed that jacaric acid exhibited no significant cytotoxicity on the thioglycollate-elicited murine peritoneal macrophages as revealed by the neutral red uptake assay, but markedly increased their cytostatic activity on the T-cell lymphoma MBL-2 cells as measured by the fluorometric CyQuant® NF Cell Proliferation Assay Kit. Flow cytometric analysis indicated that jacaric acid could enhance the endocytic activity of macrophages and elevated their intracellular production of superoxide anion. Moreover, jacaric acid-treated macrophages showed an increase in the production of nitric oxide which was accompanied by an increase in the expression level of inducible nitric oxide synthase protein. In addition, the secretion of several pro-inflammatory cytokines, including interferon-γ, interleukin-1β and tumor necrosis factor-α, was up-regulated. Collectively, our results indicated that the naturally-occurring CLNA isomer, jacaric acid, could exhibit immunomodulating activity on the murine peritoneal macrophages in vitro, suggesting that this CLNA isomer may act as an immunopotentiator which can be exploited for the treatment of some immunological disorders with minimal toxicity and fewer side effects. PMID:26629697

  8. Hydroxybenzoic acid isomers and the cardiovascular system

    PubMed Central

    2014-01-01

    Today we are beginning to understand how phytochemicals can influence metabolism, cellular signaling and gene expression. The hydroxybenzoic acids are related to salicylic acid and salicin, the first compounds isolated that have a pharmacological activity. In this review we examine how a number of hydroxyphenolics have the potential to ameliorate cardiovascular problems related to aging such as hypertension, atherosclerosis and dyslipidemia. The compounds focused upon include 2,3-dihydroxybenzoic acid (Pyrocatechuic acid), 2,5-dihydroxybenzoic acid (Gentisic acid), 3,4-dihydroxybenzoic acid (Protocatechuic acid), 3,5-dihydroxybenzoic acid (α-Resorcylic acid) and 3-monohydroxybenzoic acid. The latter two compounds activate the hydroxycarboxylic acid receptors with a consequence there is a reduction in adipocyte lipolysis with potential improvements of blood lipid profiles. Several of the other compounds can activate the Nrf2 signaling pathway that increases the expression of antioxidant enzymes, thereby decreasing oxidative stress and associated problems such as endothelial dysfunction that leads to hypertension as well as decreasing generalized inflammation that can lead to problems such as atherosclerosis. It has been known for many years that increased consumption of fruits and vegetables promotes health. We are beginning to understand how specific phytochemicals are responsible for such therapeutic effects. Hippocrates’ dictum of ‘Let food be your medicine and medicine your food’ can now be experimentally tested and the results of such experiments will enhance the ability of nutritionists to devise specific health-promoting diets. PMID:24943896

  9. Hydroxybenzoic acid isomers and the cardiovascular system.

    PubMed

    Juurlink, Bernhard H J; Azouz, Haya J; Aldalati, Alaa M Z; AlTinawi, Basmah M H; Ganguly, Paul

    2014-01-01

    Today we are beginning to understand how phytochemicals can influence metabolism, cellular signaling and gene expression. The hydroxybenzoic acids are related to salicylic acid and salicin, the first compounds isolated that have a pharmacological activity. In this review we examine how a number of hydroxyphenolics have the potential to ameliorate cardiovascular problems related to aging such as hypertension, atherosclerosis and dyslipidemia. The compounds focused upon include 2,3-dihydroxybenzoic acid (Pyrocatechuic acid), 2,5-dihydroxybenzoic acid (Gentisic acid), 3,4-dihydroxybenzoic acid (Protocatechuic acid), 3,5-dihydroxybenzoic acid (α-Resorcylic acid) and 3-monohydroxybenzoic acid. The latter two compounds activate the hydroxycarboxylic acid receptors with a consequence there is a reduction in adipocyte lipolysis with potential improvements of blood lipid profiles. Several of the other compounds can activate the Nrf2 signaling pathway that increases the expression of antioxidant enzymes, thereby decreasing oxidative stress and associated problems such as endothelial dysfunction that leads to hypertension as well as decreasing generalized inflammation that can lead to problems such as atherosclerosis. It has been known for many years that increased consumption of fruits and vegetables promotes health. We are beginning to understand how specific phytochemicals are responsible for such therapeutic effects. Hippocrates' dictum of 'Let food be your medicine and medicine your food' can now be experimentally tested and the results of such experiments will enhance the ability of nutritionists to devise specific health-promoting diets. PMID:24943896

  10. [Determination of dimethylbenzoic acid isomers in urine by gas chromatography].

    PubMed

    Kostrzewski, P; Wiaderna-Brycht, A; Czerski, B

    1994-01-01

    Trimethylobenzene (TMB) is a main ingredient of many organic solvents used in industry. In Farbasol (Polish trade name of the solvent) TMB occurs as a mixture of three isomers: pseudocumene (1, 2, 4-TMB) 30%; mesitylene (1, 3, 5-TMB) 15%; hemimellitene (1,2,3-TMB) 5%. As it is known in human organism, TMB is metabolized mainly to dimethylbenzoic (DMBA) and dimethylhippuric (DMHA) acids, and some authors suggest, that the acids excreted in urine can be biological indicators of exposure to TMB. This study was aimed at developing the method of determination of DMBA isomers in urine. Biological material was hydrolyzed with sodium hydroxide and next extracted with diethyl ether. DMBA concentration in urine was determined by gas chromatography using a variant of quantitative analysis with internal standard (5-methyl-2-isopropylphenol, thymol). Analytical parameters of the developed method of determination of DMBA isomers in urine such as linearity, precision, reproducibility, stability (192 days, when urine samples stored at-18 degrees C), detectability limit (400 micrograms/dm3) have been fully compatible with the requirements of biological monitoring. In order to confirm the presence of DMBA isomers in urine, four volunteers were exposed (8 hours) to Farbasol in toxicological chamber. The TMB concentration in the air, determined by means of gas chromatograph (HP 5890), amounted to 100 mg/m3 (MAC value in Poland). In urine samples collected 2,3-; 2,4-; 2,5-; 2,6-; 3,4-; 3,5-dimethylbenzoic acids were identified by means of GC/MSD.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8170375

  11. Fuel properties of heptadecene isomers prepared via tandem isomerization-decarboxylation of oleic acid

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Heptadecene isomers were prepared via tandem isomerization-decarboxylation of oleic acid using catalytic triruthenium dodecacarbonyl [Ru3(CO)12]. Chromatographic and spectroscopic characterization of the isolated heptadecene mixture indicated that it consisted of 96% internal isomers and 4% aromatic...

  12. Are conjugated linolenic acid isomers an alternative to conjugated linoleic acid isomers in obesity prevention?

    PubMed

    Miranda, Jonatan; Arias, Noemi; Fernández-Quintela, Alfredo; del Puy Portillo, María

    2014-04-01

    Despite its benefits, conjugated linoleic acid (CLA) may cause side effects after long-term administration. Because of this and the controversial efficacy of CLA in humans, alternative biomolecules that may be used as functional ingredients have been studied in recent years. Thus, conjugated linolenic acid (CLNA) has been reported to be a potential anti-obesity molecule which may have additional positive effects related to obesity. According to the results reported in obesity, CLNA needs to be given at higher doses than CLA to be effective. However, because of the few studies conducted so far, it is still difficult to reach clear conclusions about the potential use of these CLNAs in obesity and its related changes (insulin resistance, dyslipidemia, or inflammation).

  13. Enhanced isomer purity of lactic acid from the non-sterile fermentation of kitchen wastes.

    PubMed

    Zhang, Bo; He, Pin-Jing; Ye, Ning-Fang; Shao, Li-Ming

    2008-03-01

    In order to improve the purity of lactic acid isomers, the effects of pH, temperature, fermentation time and their interactions on l(+) or d(-)-lactic acid production were evaluated during lactic acid fermentation of the non-sterile kitchen wastes. The results showed that l(+)-lactic acid was the main isomeric form. The isomer purity was much higher at acidic or alkalic pH (non-controlled pH, pH 5 and pH 8) than neutral pH (pH 6 and pH 7). Increasing the fermentation temperature from 35 degrees C to 45 degrees C at pH 7 enhanced the isomer purity from 60:40 to 83:17. The optimal fermentation time for the purity of lactic acid isomers was found to depend on the corresponding pH and temperature. From the response surface analysis, the optimized combination of pH and temperature could obviously increase the l(+)-isomer concentration. It is confirmed that the variation of the isomer purity with pH, temperature and fermentation time change resulted from the substitution of microbial community composition. The lactic acid bacteria and Clostridium sp. dominated the fermentation of non-sterile kitchen wastes, and the emergence and disappearance of lactic acid bacteria which produced l(+)-isomer and Clostridium sp. resulted in the variations of the isomer purity. PMID:17376675

  14. 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.

  15. Identification, quantitative determination, and antioxidative activities of chlorogenic acid isomers in prune (Prunus domestica L. ).

    PubMed

    Nakatani, N; Kayano, S; Kikuzaki, H; Sumino, K; Katagiri, K; Mitani, T

    2000-11-01

    Neochlorogenic acid (3-CQA) and cryptochlorogenic acid (4-CQA), isolated from prune (Prunus domestica L.), were identified by NMR and MS analyses. In addition, the quantity of chlorogenic acid isomers in prune were measured by HPLC. These isomers, 3-CQA, 4-CQA, and chlorogenic acid (5-CQA), were contained in the ratio 78.7:18. 4:3.9, respectively. 4-CQA was identified and quantified in prune for the first time, and relatively high amounts of this isomer were characteristic. Antioxidative activities of the chlorogenic acid isomers, such as scavenging activity on superoxide anion radicals and inhibitory effect against oxidation of methyl linoleate, were also evaluated. Each isomer showed antioxidative activities which were almost the same.

  16. Fuel properties of heptadecene isomers prepared via tandem isomerization-decarboxylation of oleic acid

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Heptadecene isomers were prepared via tandem isomerization-decarboxylation of oleic acid using catalytic triruthenium dodecacarbonyl [Ru3(CO)12]. Chromatographic and spectroscopic characterization of the isolated heptadecene mixture indicated that it consisted of 96% internal trans isomers and 4% ar...

  17. Advances in research on cis-9, trans-11 conjugated linoleic acid: a major functional conjugated linoleic acid isomer.

    PubMed

    Wang, Tao; Lee, Hong Gu

    2015-01-01

    Conjugated linoleic acid (CLA) consists of a group of positional and geometric conjugated isomers of linoleic acid. Since the identification of CLA as a factor that can inhibit mutagenesis and carcinogenesis, thousands of studies have been conducted in the last several decades. Among the many isomers discovered, cis-9, trans-11 CLA is the most intensively studied because of its multiple, isomer-specific effects in humans and animals. This paper provides an overview of the available data on cis-9, trans-11 CLA, including its isomer-specific effects, biosynthesis, in vivo/in vitro research models, quantification, and the factors influencing its content in ruminant products.

  18. Identification and quantitation of unsaturated fatty acid isomers by electrospray ionization tandem mass spectrometry: a shotgun lipidomics approach.

    PubMed

    Yang, Kui; Zhao, Zhongdan; Gross, Richard W; Han, Xianlin

    2011-06-01

    Identification and quantification of unsaturated fatty acid (FA) isomers in a biological system are significant in the study of lipid metabolism and catabolism, membrane biophysics, and pathogenesis of diseases but are challenging in lipidomics. We developed a novel approach for identification and quantitation of unsaturated FA isomers by exploiting two facts: (1) unsaturated FA anions yield fragment ion(s) from loss of CO(2) or H(2)O from the anions upon collision-induced dissociation; and (2) the fragment ions yielded from discrete FA isomers have distinct profiles of the fragment ion intensity vs. collision conditions. These distinct profiles likely result from the differential interactions of the negative charge of the fragment ion with the electron clouds of the double bonds due to their different distances in discrete FA isomers. The novel approach was also extended to analyze the double bond isomers of FA chains present in phospholipids by multistage tandem mass spectrometry. Collectively, we developed a new approach for identification and quantification of the double bond isomers of endogenous FA species or FA chains present in intact phospholipid species. We believe that this approach should further advance the lipidomic power for identification of the biochemical mechanisms underlying metabolic diseases.

  19. Structure/effect studies of fatty acid isomers as skin penetration enhancers and skin irritants.

    PubMed

    Aungst, B J

    1989-03-01

    Comparisons were made of branched vs unbranched saturated fatty acids and cis vs trans unsaturated fatty acids as skin penetration enhancers and primary skin irritants. Skin penetration studies used naloxone base as the diffusant, propylene glycol as the vehicle, and human skin. Maximum naloxone flux was with C9-12-branched and unbranched fatty acids. For C5-14 fatty acids, branched and unbranched isomers had similar effects. One branched C18 fatty acid isomer (C16-branched isostearic acid) was more effective in enhancing skin penetration than a differently branched (C2-branched isostearic acid) or unbranched C18 isomer (stearic acid). There was no significant difference between cis and trans unsaturated C16-18 fatty acid isomers in their effects on naloxone flux, and all unsaturated fatty acids were more effective enhancers than the corresponding saturated isomers. Several of these fatty acid/propylene glycol vehicles were evaluated in a rabbit primary skin irritation test. Irritation indices were poorly correlated with the effectiveness of the vehicles in enhancing naloxone flux. It was possible to enhance naloxone skin penetration greatly with a vehicle with only minimal skin irritation potential.

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

    PubMed

    Jain, Vishal P; Proctor, Andrew

    2007-02-01

    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.

  1. C18-unsaturated branched-chain fatty acid isomers: characterization and physical properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Iso-oleic acid is a mixture of C18-unsaturated branched-chain fatty acid isomers with a methyl group on various positions of the alkyl chain, which is the product of the skeletal isomerization reaction of oleic acid and is the intermediate used to make isostearic acid (C18-saturated branched-chain f...

  2. Trans and positional ethylenic bonds in two dominant isomers of eicosapentaenoic acid from the freshwater sponge Baicalospongia bacillifera.

    PubMed

    Imbs, Andrey B; Rodkina, Svetlana A

    2005-09-01

    Reinvestigation of the current FA composition of the regional freshwater sponge Baicalospongia bacillifera showed that the main measured isomer of EPA (14% of the total FA now detected) is, in fact, an unusual 5Z,8Z,11Z,14Z,18E-EPA. Two other isomers of this acid also present were identified as a novel 5Z,8Z,11Z,15Z,18E-EPA and the common methylene-interrupted 5Z,8Z,11Z,14Z,17Z-EPA (usually written simply as EPA). Isolation of these acids as their methyl ester derivatives was accomplished with the use of a combination of silver-ion column chromatography and HPLC. The structure of the two new compounds was deduced from GC-MS and detailed NMR data. Partial hydrazine reduction of all three isolated EPA esters followed by separation of cis/trans isomers of the resulting monoenoic acids and GC-MS analysis of their dimethyl disulfide adducts were used for determination of the configuration and position of the double bonds. We may assume that the sponge B. bacillifera cannot receive these unusual EPA isomers directly from food sources (e.g., algal diatoms), and accordingly restructuring of ordinary EPA to novel acids may take place in the sponge tissue.

  3. Trans fatty acid isomers and the trans-9/trans-11 index in fat containing foods

    PubMed Central

    Kuhnt, Katrin; Baehr, Melanie; Rohrer, Carsten; Jahreis, Gerhard

    2011-01-01

    To determine trans fatty acid (TFA) distribution of contemporary foods, especially regarding individual trans octadecenoic acids (trans C18:1), 339 German foods of six categories (semi-solid fats, deep-fried potato products, bakery products, confectioneries, instant products and butter) were analysed using two GC methods. Results showed a high variation of TFA content between and within the categories containing between 0 and 40.5% of FAME except in butter, which is a source of natural TFA. The mean TFA values were below 2.0% of FAME, however, bakery products contained 4.5% and butter fat 3.2%, respectively. In addition, the distribution of individual trans C18:1 differed. In samples containing ruminant fat (butter and various confectioneries), vaccenic acid (t11-C18:1, t11) predominated, while in foods containing industrially hydrogenated fats, elaidic acid (trans-9, t9-) and t10-C18:1 were the major trans isomers.. This was reflected by a low t9/t11 index of 0.3 and 0.5 in butter and ruminant fat containing confectioneries, respectively, whilst the highest index was observed in shortenings and deep-fried potato products at 5.2 and 6.8, respectively. In conclusion, the TFA content of foods available on the German market is generally declining, but substantial variations are present. The t9/t11 index could be used as an indicator to determine ruminant fat. Practical applications: A number of studies provide evidence that a high TFA intake, particularly of industrial origin, adversely affects human health. The TFA content of foods could be reduced due to the introduction of several mandatory regulations and modifications regarding the hydrogenation process of oils. The most abundant dietary TFA are the isomers of trans C18:1. Unfortunately, the differentiation of these isomers is not yet very common, though the trans C18:1 profile differs depending on its origin (bacterial hydrogenation in the rumen or industrial hydrogenation). To date, data for TFA content

  4. Electrochemical discrimination of phthalic acid among three phthalic acid isomers based on an N-butylaminomethyl-ferrocene derivative.

    PubMed

    Yoon, Jisoo; Jadhav, Jyoti Ramesh; Kim, Jun Myung; Cheong, Minserk; Kim, Hong-Seok; Kim, Joohoon

    2014-07-21

    A chemosensor compound (1) consisting of a central ferrocene with two butylaminomethyl arms showed unexpected facile electrochemical oxidation of the secondary amines in proximity to the ferrocene, which was utilized for electrochemical discrimination of phthalic acid selectively over two other isomers, isophthalic acid and terephthalic acid.

  5. Food sources of individual plasma phospholipid trans fatty acid isomers: the Cardiovascular Health Study12345

    PubMed Central

    King, Irena B; Lemaitre, Rozenn N; Rimm, Eric B; Sacks, Frank; Song, Xiaoling; Siscovick, David S; Mozaffarian, Dariush

    2010-01-01

    Background: The overall consumption of trans fatty acids (TFAs) increases the risk of coronary artery disease. However, multiple TFA isomers exist, each with potentially different health effects. Different food sources of these specific TFA isomers are not well established. Objective: Our objective was to determine the major independent food sources of specific TFA isomers. Design: We investigated relations of major potential food sources of TFAs, as assessed by serial food-frequency questionnaires, with 10 plasma phospholipid TFA isomers [5 trans (t-) 18:1, 3 t-18:2, and 2 t-16:1] in 3330 older adults in the Cardiovascular Health Study, a community-based multicenter cohort. Stepwise regression was used to identify independent major food sources of individual plasma phospholipid TFA isomers, which were adjusted for demographic, lifestyle, and dietary factors. Results: All 5 t-18:1 isomers were similarly associated with foods commonly made with partially hydrogenated vegetable oils (PHVOs), including biscuits (0.51 higher SD of total 18:1 fatty acid concentrations per serving/d, P < 0.01), chips and/or popcorn (0.33 higher SD per serving/d, P = 0.02), margarine (0.32 higher SD per serving/d, P < 0.001), fried foods (0.32 higher SD per serving/d, P = 0.04), and bakery foods (0.23 higher SD per serving/d, P = 0.02). Each of the t-18:2 isomers were associated only with bakery foods (0.50 higher SD of total 18:2 fatty acid concentrations per serving/d, P < 0.001). Ruminant foods were major correlates of t-16:1n−7, including red meats (0.72 higher SD per serving/d, P < 0.001), butter (0.43 higher SD per serving/d, P < 0.001), and higher-fat dairy (0.37 higher SD per serving/d, P < 0.001). In contrast, t-16:1n−9 were derived mainly from margarine (0.31 higher SD per serving/d, P < 0.001). Conclusions: t-18:1 Isomers are similarly derived from multiple PHVO-containing foods. In contrast, t-18:2 and t-16:1n−9 isomers are derived from more-specific types of PHVO

  6. Calculating the acidity constants of homologues and isomers of organic acids by means of recurrence relations

    NASA Astrophysics Data System (ADS)

    Zenkevich, I. G.

    2013-06-01

    It is noted that the p K a values of organic acids can be calculated using the unique recurrence relation p K a( n + 1) = ap K a( n) + b from the p K a values of other (usually the simplest and, consequently, better characterized) homologues of the same series. It is shown that this relation is valid within two taxonomic groups: insertion homologues of the ω-substituted acids X(CH2) n CO2H ( n ≥ 1) and isomers that differ in the position of substituents X in their alkyl fragments, k-X(C n H2 n )CO2H ( n ≥ 1, 1 ≤ k ≤ n + 1). It is concluded that this algorithm is a consequence of the unique mathematical properties of recurrence relations.

  7. Methyl-branched poly(hydroxyalkanoate) biosynthesis from 13- methyltetradecanoic acid and mixed isostearic acid isomer substrates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pseudomonas resinovorans, a known medium-chain-length (mcl-) poly(hydroxyalkanoate) (PHA) producer, was grown on 13-methyltetradecanoic acid (13-MTDA) and a mixture of isostearic acid (IA) isomers to produce methyl-branched mcl-PHA polymers. Shake flask experiments revealed polymer productivities (...

  8. Screening of multicomponent crystals of L-tryptophan with three isomers of pyridinedicarboxylic acids

    NASA Astrophysics Data System (ADS)

    Das, Babulal

    2016-08-01

    Multicomponent crystallization of L-tryptophan with three different isomers of pyridinedicarboxylic acids, namely, 2,3-pyridinedicarboxylic acid (2,3-PDA), 2,5-pyridinedicarboxylic acid (2,5-PDA) and 2,6-pyridinedicarboxylic acid (2,6-PDA), were screened using conventional solution cocrystallization technique. Whereas the new phases derived from the amino acid with 2,3-PDA or 2,5-PDA were analyzed using powder X-ray diffraction and thermal analysis techniques, the crystalline phase synthesized from 2,6-substituted isomer was further characterized by single crystal X-ray diffraction. Structural analysis revealed that the amino acid exists in the zwitterionic form interacting with the neutral 2,6-PDA by strong intermolecular hydrogen bonding. The components in the co-crystal self-assemble leading to a three dimensional hydrogen bonded closed packed network structure. Isothermal calorimetric titration showed that among the three isomers, 2,6-PDA showed relatively strong binding interaction towards the amino acid in water at 298 K. All the crystals exhibit marginal quenching of fluorescence properties of L-tryptophan in the solid state.

  9. Human tissue lipids: occurrence of fatty acid isomers from dietary hydrogenated oils.

    PubMed

    Ohlrogge, J B; Emken, E A; Gulley, R M

    1981-08-01

    Hydrogenation of vegetable oils produces fatty acids with unusual structures having trans double bonds and double bonds in new positions of the acyl chain. This study was designed to determine which of these fatty acid isomers are incorporated or accumulated in humans during long-term dietary consumption of hydrogenated fats. The double bond position and configuration of the octadecenoate fraction of total lipids extracted from human heart, brain, liver, aorta, and adipose tissue were determined. The level of trans octadecenoate in the tissues as determined by both direct gas-liquid chromatography (GLC) and by GLC after silver nitrate thin-layer chromatography ranged between 0.4 and 5.0%, with an average of 2.7%. Tissues were found to contain trans-octadecenoic isomers having double bonds between the 6 and 15 positions, whereas cis double bonds were found to occur between the 6 and 14 positions. The distribution of double bonds in adipose tissue correlated very closely with the composition of dietary hydrogenated fat. Thus, essentially all of the unusual octadecenoic fatty acid isomers that are produced during vegetable oil hydrogenation are incorporated into human tissue. However, in contrast to results of short-term (1-6 months) feeding studies of animals, our results suggest that long-term (20-60 years) consumption of hydrogenated fats by humans does not lead to substantial preferential accumulation of positional isomers in human tissue total lipids.

  10. Isomer-specific regulation of differentiating pig preadipocytes by conjugated linoleic acids.

    PubMed

    Brandebourg, T D; Hu, C Y

    2005-09-01

    Conjugated linoleic acids are a group of geometric and positional isomers of linoleic acid that decrease body fat in growing animals by a poorly understood mechanism. The objective of this study was to investigate the isomer-specific effect of CLA on the proliferation and differentiation of pig preadipocytes in primary culture. The effect of CLA on preadipocyte proliferation was determined using cleavage of the tetrazolium salt, WST-1, as a marker for proliferation. Preadipocyte number was decreased in a dose-dependent fashion by trans-12,cis-10 CLA (P < 0.05). No other fatty acid affected preadipocyte number. Differentiation was monitored on d 10 after induction morphologically, enzymatically, and by measuring the mRNA abundance of key adipogenic transcription factors. Both a crude CLA preparation containing a mixture of CLA isomers (CLA-mix) and the pure trans-10,cis-12 CLA isomer inhibited glycerol-3-phosphate dehydrogenase (GPDH) activity in a dose-dependent fashion, with trans-10,cis-12 CLA being more potent (P < 0.01) than the CLA-mix. Cis-9,trans-11 CLA failed to decrease GPDH activity; however, increasing concentrations of cis-9,trans-11 CLA tended to blunt the inhibitory effect of trans-10,cis-12 CLA on GPDH activity (P < 0.09), suggesting that cis-9,trans-11 CLA may antagonize the action of trans-10,cis-12 CLA in porcine adipocytes. Finally, the isomer-specific effect of CLA on adipogenic transcription factor gene expression was investigated. Trans-10,cis-12 CLA decreased expression of peroxisome proliferator-activated receptor gamma (PPAR gamma; P < 0.01) and sterol regulatory element-binding protein-1c (SREBP-1c; P < 0.05) mRNA, while failing to alter the expression of CCAAT/enhancer binding protein alpha (C/EBPalpha) mRNA. Interestingly, both the CLA-mix and the trans-10,cis-12 CLA isomer increased the mRNA abundance of chicken ovalbumin upstream promoter transcription factor 1 (COUP-TF; P < 0.002). No other fatty acid affected COUP-TF mRNA levels

  11. Two Isomers of Protonated Isocyanic Acid: Evidence for an Ion-Molecule Pathway for HNCO ↔ HOCN Isomerization.

    PubMed

    Lattanzi, Valerio; Thorwirth, Sven; Gottlieb, Carl A; McCarthy, Michael C

    2012-12-01

    Ion-molecule reactions are thought to play a crucial role in the formation of metastable isomers, but relatively few protonated intermediates beyond HNCH(+) have been characterized at high spectral resolution. We present here laboratory measurements of the rotational spectra of protonated isocyanic acid in two isomeric forms, the ground state H2NCO(+) with C2v symmetry and a low-lying bent chain HNCOH(+), guided by coupled cluster calculations of their molecular structure. Somewhat surprisingly, HNCOH(+) is found to be more abundant than H2NCO(+), even though this metastable isomer is calculated to lie approximately 15-20 kcal/mol higher in energy. In the same way that HCNH(+) serves as a key intermediate in ion-molecule reactions that form HNC via dissociative electron recombination in cold dense interstellar molecular clouds, HNCOH(+) may play an analogous role in the conversion of HNCO to HOCN.

  12. Two Isomers of Protonated Isocyanic Acid: Evidence for an Ion-Molecule Pathway for HNCO-HOCN Isomerization

    NASA Astrophysics Data System (ADS)

    Lattanzi, V.; Thorwirth, S.; Gottlieb, C. A.; McCarthy, M. C.

    2012-11-01

    Ion-molecule reactions are thought to play a crucial role in the formation of metastable isomers, but relatively few protonated intermediates beyond HNCH+ have been characterized at high spectral resolution. We present here laboratory measurements of the rotational spectra of protonated isocyanic acid in two isomeric forms, the ground state H2NCO+ with C2v symmetry and a low-lying bent chain HNCOH+, guided by coupled cluster calculations of their molecular structure. Somewhat surprisingly, HNCOH+ is found to be more abundant than H2NCO+, even though this metastable isomer is calculated to lie approximately 15-20 kcal/mol higher in energy. In the same way that HCNH+ serves as a key intermediate in ion-molecule reactions that form HNC via dissociative electron recombination in cold dense interstellar molecular clouds, HNCOH+ may play an analogous role in the conversion of HNCO to HOCN.

  13. Two Isomers of Protonated Isocyanic Acid: Evidence for an Ion-Molecule Pathway for HNCO ↔ HOCN Isomerization.

    PubMed

    Lattanzi, Valerio; Thorwirth, Sven; Gottlieb, Carl A; McCarthy, Michael C

    2012-12-01

    Ion-molecule reactions are thought to play a crucial role in the formation of metastable isomers, but relatively few protonated intermediates beyond HNCH(+) have been characterized at high spectral resolution. We present here laboratory measurements of the rotational spectra of protonated isocyanic acid in two isomeric forms, the ground state H2NCO(+) with C2v symmetry and a low-lying bent chain HNCOH(+), guided by coupled cluster calculations of their molecular structure. Somewhat surprisingly, HNCOH(+) is found to be more abundant than H2NCO(+), even though this metastable isomer is calculated to lie approximately 15-20 kcal/mol higher in energy. In the same way that HCNH(+) serves as a key intermediate in ion-molecule reactions that form HNC via dissociative electron recombination in cold dense interstellar molecular clouds, HNCOH(+) may play an analogous role in the conversion of HNCO to HOCN. PMID:26290966

  14. The role of alkoxy radicals in the heterogeneous reaction of two structural isomers of dimethylsuccinic acid.

    PubMed

    Cheng, Chiu Tung; Chan, Man Nin; Wilson, Kevin R

    2015-10-14

    A key challenge in understanding the transformation chemistry of organic aerosols is to quantify how changes in molecular structure alter heterogeneous reaction mechanisms. Here we use two model systems to investigate how the relative locations of branched methyl groups control the heterogeneous reaction of OH with two isomers of dimethylsuccinic acid (C6H10O4). 2,2-Dimethylsuccinic acid (2,2-DMSA) and 2,3-dimethylsuccinic acid (2,3-DMSA) differ only in the location of the two branched methyl groups, thus enabling a closer inspection of how the distribution of carbon reaction sites impacts the chemical evolution of the aerosol. The heterogeneous reaction of OH with 2,3-DMSA (reactive OH uptake coefficient, γ = 0.99 ± 0.16) is found to be ∼2 times faster than that of 2,2-DMSA (γ = 0.41 ± 0.07), which is attributed to the larger stability of the tertiary alkyl radical produced by the initial OH abstraction reaction. While changes in the average aerosol oxidation state (OSC) and the carbon number (NC) are similar for both isomers upon reaction, significant differences are observed in the underlying molecular distribution of reaction products. The reaction of OH with the 2,3-DMSA isomer produces two major reaction products: a product containing a new alcohol functional group (C6H10O5) formed by intermolecular hydrogen abstraction and a C5 compound formed via carbon-carbon (C-C) bond scission. Both of these reaction products are explained by the formation and subsequent reaction of a tertiary alkoxy radical. In contrast, the OH reaction with the 2,2-DMSA isomer forms four dominant reaction products, the majority of which are C5 scission products. The difference in the quantity of C-C bond scission products for these two isomers is unexpected since decomposition is assumed to be favored for the isomer with the most tertiary carbon sites (i.e. 2,3-DMSA). For both isomers, there is a much larger abundance of C6 alcohol relative to C6 ketone products, which suggests

  15. Differential developmental toxicity of naphthoic acid isomers in medaka (Oryzias latipes) embryos

    PubMed Central

    Carney, Michael W.; Erwin, Kyle; Hardman, Ron; Yuen, Bonny; Volz, David C.; Hinton, David E.; Kullman, Seth W.

    2013-01-01

    Polycyclic aromatic hydrocarbons (PAHs) are widespread persistent pollutants that readily undergo biotic and abiotic conversion to numerous transformation products in rivers, lakes and estuarine sediments. Here we characterize the developmental toxicity of four PAH transformation products each structural isomers of hydroxynaphthoic acid: 1H2NA, 2H1NA, 2H3NA, and 6H2NA. Medaka fish (Oryzias latipes) embryos and eleutheroembryos were used to determine toxicity. A 96-well micro-plate format was used to establish a robust, statistically significant platform for assessment of early life stages. Individual naphthoic acid isomers demonstrated a rank order of toxicity with 1H2NA > 2H1NA > 2H3NA > 6H2NA being more toxic. Abnormalities of circulatory system were most pronounced including pericardial edema and tube heart. To determine if HNA isomers were AhR ligands, spatial-temporal expression and activity of CYP1A was measured via in vivo EROD assessments. qPCR measurement of CYP1A induction proved different between isomers dosed at respective concentrations affecting 50% of exposed individuals (EC50s). In vitro, all ANH isomers transactivated mouse AhR using a medaka CYP1A promoter specific reporter assay. Circulatory abnormalities followed P450 induction and response was consistent with PAH toxicity. A 96-well micro-plates proved suitable as exposure chambers and provided statistically sound evaluations as well as efficient toxicity screens. Our results demonstrate the use of medaka embryos for toxicity analysis thereby achieving REACH objectives for the reduction of adult animal testing in toxicity evaluations. PMID:18433798

  16. Formation of isomers of anionic hemiesters of sugars and carbonic acid in aqueous medium.

    PubMed

    Dos Santos, Vagner B; Vidal, Denis T R; Francisco, Kelliton J M; Ducati, Lucas C; do Lago, Claudimir L

    2016-06-16

    Hemiesters of carbonic acid can be freely formed in aqueous media containing HCO3(-)/CO2 and mono- or poly-hydroxy compounds. Herein, (13)C NMR spectroscopy was used to identify isomers formed in aqueous solutions of glycerol (a prototype compound) and seven carbohydrates, as well as to estimate the equilibrium constant of formation (Keq). Although both isomers are formed, glycerol 1-carbonate corresponds to 90% of the product. While fructose and ribose form an indistinct mixture of isomers, the anomers of d-glucopyranose 6-carbonate correspond to 74% of the eight isomers of glucose carbonate that were detected. The values of Keq for the disaccharides sucrose (4.3) and maltose (4.2) are about twice the values for the monosaccharides glucose (2.0) and fructose (2.3). Ribose (Keq = 0.89)-the only sugar without a significant concentration of a species containing a -CH2OH group in an aqueous solution-resulted in the smallest Keq. On the basis of the Keq value and the concentrations of HCO3(-) and glucose in blood, one can anticipate a concentration of 2-4 µmol L(-1) for glucose 6-carbonate, which corresponds to ca. of 10% of its phosphate counterpart (glucose 6-phosphate).

  17. Effect of cooking methods on fatty acids, conjugated isomers of linoleic acid and nutritional quality of beef intramuscular fat.

    PubMed

    Alfaia, Cristina M M; Alves, Susana P; Lopes, Anabela F; Fernandes, Maria J E; Costa, Ana S H; Fontes, Carlos M G A; Castro, Matilde L F; Bessa, Rui J B; Prates, José A M

    2010-04-01

    The effect of boiling, microwaving and grilling on the composition and nutritional quality of beef intramuscular fat from cattle fed with two diets was investigated. Longissimus lumborum muscle from 15 Alentejano young bulls fed on concentrate or pasture was analyzed. Cooking losses and, consequently, total lipids, increased directly with the cooking time and internal temperature reached by meat (microwaving>boiling>grilling). The major changes in fatty acid composition, which implicated 16 out of 34 fatty acids, resulted in higher percentages in cooked beef of SFA and MUFA and lower proportions of PUFA, relative to raw meat, while conjugated linoleic acid (CLA) isomers revealed a great stability to thermal processes. Heating decreased the PUFA/SFA ratio of meat but did not change its n-6/n-3 index. Thermal procedures induced only slight oxidative changes in meat immediately after treatment but hardly affected the true retention values of its individual fatty acids (72-168%), including CLA isomers (81-128%).

  18. Increase of geometrical and positional fatty acid isomers in dark meat from broilers fed heated oils.

    PubMed

    Bou, R; Tres, R Codony A; Baucells, M D; Guardiola, F

    2005-12-01

    Oxidation of polyunsaturated fatty acids leads to primary and secondary oxidation products. Compounds and amounts of these products vary, depending on the oxidative conditions. Because these oxidation products have different absorption and biological effects, we performed 2 different heating treatments on sunflower oil. The first was heating the oil at 190 to 195 degrees C for 28 h (i.e., very oxidized oil), and the other was heating at 60 degrees C for 12 d (i.e., peroxidized oil). In the frame of this study, we compared the fatty acid composition of a refined sunflower oil (fresh oil), peroxidized oil, very oxidized oil, and a mixture (1:1) of fresh and very oxidized oil (i.e., oxidized oil). Oil fatty acid compositions were affected by the heating treatments. In addition, different fatty acid isomers were formed during heating at 190 to 195 degrees C, and significant differences were found between their contents in the sunflower oils. We also studied the effect of feeding broilers with these oils and Zn and tocopherol supplements on the fatty acid composition of their raw dark meat. Various trans fatty acid isomers increased in dark meat from broilers fed oxidized and very oxidized oils. In addition, discriminant analysis showed that ditrans-conjugated linoleic acid content was able to distinguish dark chicken meat from chickens fed sunflower oils heated at 190 to 195 degrees C.

  19. Micellar and sub-micellar ultra-high performance liquid chromatography of hydroxybenzoic acid and phthalic acid positional isomers.

    PubMed

    Fasciano, Jennifer M; Danielson, Neil D

    2016-03-18

    Micellar liquid chromatography (MLC) has been used primarily for the separation of neutral analytes of varying polarities, most commonly phenols and polyaromatic hydrocarbons, but does not seem to have been used to study aromatic hydroxy acids in detail. We have studied the separation of hydroxybenzoic acid mixtures, including monohydroxybenzoic and dihydroxybenzoic acid positional isomers by MLC. Sodium dodecylsulfate (SDS) is investigated as the modifying surfactant on a C18 ultra-high performance liquid chromatography (UHPLC) column (100 × 2.1mm, 1.8 μm). The addition of only SDS (no organic solvent) to the mobile phase reduced the influence of hydrophobic interactions while improving the retention times, resolution, and peak shapes, even at concentrations below the critical micellization concentration (CMC). The UHPLC separation of 7 hydroxybenzoic acids, including 6 dihydroxybenzoic acid positional isomers and one trihydroxybenzoic acid, is achieved with high efficiency using 0.1% SDS in 1.84 mM sulfuric acid (pH 2.43) mobile phase, in less than 6 min with a flow rate of 0.3 mL min(-1), and in less than four min with a flow rate of 0.7 mL min(-1). Six monohydroxybenzoic acid isomers are also effectively separated by MLC, using a 0.5% SDS mobile phase modifier, in less than 20 min with a flow rate of 0.3 mL min(-1), and in less than 14 min with a flow rate of 0.7 mL min(-1). The 3 phthalic acid isomers could be separated using a similar mobile phase and flow rates in less than 6 and 4 min. Solute-micelle equilibrium constants and partition coefficients are calculated for 6 monohydroxybenzoic acids based on a plot of MLC retention factor vs. mobile phase micelle concentration. All aromatic acid isomers studied can be classified as binding solutes in the MLC retention mechanism. Less effective separations are observed with shorter chain surfactants, leading to higher retention times and poor peak shapes. It is concluded that increasing chain length led to more

  20. 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. PMID:27451179

  1. Isomer-specific trophic transfer of perfluorocarboxylic acids in the marine food web of Liaodong Bay, North China.

    PubMed

    Zhang, Zhong; Peng, Hui; Wan, Yi; Hu, Jianying

    2015-02-01

    Trophic transfers of perfluorocarboxylic acids (PFCAs) have been well studied in aquatic food webs; however, most studies examined PFCAs as single compounds without differentiating isomers. In this study, an in-port derivatization GC-MS method was used to determine PFCA (perfluorooctanoic acid, PFOA; perfluorononanoic acid, PFNA; perfluorodecanoate acid, PFDA; perfluoroundecanoate acid, PFUnDA; perfluorododecanoate acid, PFDoDA; perfluorotridecanoate acid, PFTriDA, and perfluorotetradecanoate acid, PFTeDA) structural isomers in 11 marine species including benthic invertebrates, fishes, and gulls collected in November 2006 from Liaodong Bay in China. The total concentrations of linear PFCAs were 0.35-1.10, 0.93-2.61, and 2.13-2.69 ng/g ww, and the corresponding percentages of branched PFCAs to linear PFCAs were 6.6-15.5%, 4.2-9.9%, and 4.5-6.0% in invertebrates, fishes, and birds, respectively. Except for linear PFOA, significant positive relationships were found between the concentrations of all the target linear PFCAs and trophic levels, and the trophic magnification factors (TMFs) ranged from 1.90 to 4.88. Positive correlations between the concentrations of branched PFCAs isomers and trophic levels were also observed but were without statistical significance. The relatively high biomagnification of linear isomers of PFCAs would lead to low percentages of branched PFCAs to total PFCAs in organisms at high trophic levels. This study for the first time clarified isomer-specific trophic transfers of PFCAs in a marine food web.

  2. Photophysics of Fe(III) complexes with fluorosalicylic acid isomers in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Pozdnyakov, Ivan P.; Melnikov, Alexey A.; Šípoš, Rastislav; Chekalin, Sergey V.; Šima, Jozef

    2016-09-01

    Transient absorption spectroscopy is used to study photophysical processes of 1:1 Fe(III) complexes with all four fluorosalicylic acid isomers (Fe-FSAs) in aqueous solutions. Excited states of Fe-FSAs decay to the ground electronic state with two time constants. The faster process is interpreted as internal conversion to the vibrationally hot electronic ground state and the slower one - as a combination of vibrational cooling and solvation of the ground state. The results obtained for Fe-FSAs and other previously investigated Fe(III) salicylato compounds allow us to reveal the main cause of photochemical stability of the complexes upon charge transfer band excitation.

  3. Differential accumulation and elimination behavior of perfluoroalkyl Acid isomers in occupational workers in a manufactory in China.

    PubMed

    Gao, Yan; Fu, Jianjie; Cao, Huiming; Wang, Yawei; Zhang, Aiqian; Liang, Yong; Wang, Thanh; Zhao, Chunyan; Jiang, Guibin

    2015-06-01

    In this study, serum and urine samples were collected from 36 occupational workers in a fluorochemical manufacturing plant in China from 2008 to 2012 to evaluate the body burden and possible elimination of linear and branched perfluoroalkyl acids (PFAAs). Indoor dust, total suspended particles (TSP), diet, and drinking water samples were also collected to trace the occupational exposure pathway to PFAA isomers. The geometric mean concentrations of perfluorooctanesulfonate (PFOS), perfluorooctanoate (PFOA), and perfluorohexanesulfonate (PFHxS) isomers in the serum were 1386, 371, and 863 ng mL(-1), respectively. The linear isomer of PFOS, PFOA, and PFHxS was the most predominant PFAA in the serum, with mean proportions of 63.3, 91.1, and 92.7% respectively, which were higher than the proportions in urine. The most important exposure routes to PFAA isomers in the occupational workers were considered to be the intake of indoor dust and TSP. A renal clearance estimation indicated that branched PFAA isomers had a higher renal clearance rate than did the corresponding linear isomers. Molecular docking modeling implied that linear PFOS (n-PFOS) had a stronger interaction with human serum albumin (HSA) than branched isomers did, which could decrease the proportion of n-PFOS in the blood of humans via the transport of HSA.

  4. Cyclodextrin and its complexation for resolution of isomers using diffusion ordered spectroscopy

    NASA Astrophysics Data System (ADS)

    Chaudhari, Sachin R.; Srinivasa; Suryaprakash, N.

    2013-02-01

    Diffusion ordered spectroscopy (DOSY) generally fails to separate the peaks pertaining to isomeric species possessing identical molecular weights and similar hydrodynamic radii. The present study demonstrates the resolution of isomers using α/β-cyclodextrin as a co-solute by Matrix Assisted Diffusion Ordered Spectroscopy. The resolution of isomers has been achieved by measuring the significant differences in the diffusion rates between the positional isomers of aminobenzoic acids, benzenedicarboxylic acids and between the cis, trans isomers, fumaric acid and maleic acid.

  5. The 10t,12c isomer of conjugated linoleic acid inhibits fatty acid synthase expression and enzyme activity in human breast, colon, and prostate cancer cells.

    PubMed

    Lau, Dominic S Y; Archer, Michael C

    2010-01-01

    The objective of this study was to determine whether downregulation of fatty acid synthase (FAS) expression and/or inhibition of its activity by the two major CLA isomers, 10t,12c and 9c,11t CLA, could contribute to their inhibitory effect on the growth of human breast (MCF-7), colon (HT-29) and prostate (LNCaP) cancer cell lines. We first confirmed and extended the results of others showing that the inhibitory action of CLA on proliferation is dependent on the cell type as well as the structure of the isomer, the 10,12 isomer being a more potent inhibitor than the 9,11 isomer in the concentration range 25-100 microM. By Western analysis, we showed that 10,12 CLA downregulated FAS expression in all of the cell lines in a concentration-dependent manner, but the 9,11 isomer had no effect. Both isomers inhibited FAS enzyme activity, but 10,12 CLA was again more potent than the 9,11 isomer. Our results suggest that downregulation of FAS by 10,12 CLA, but not by the 9,11 isomer, as well as inhibition of FAS enzyme activity by both isomers, may contribute to growth inhibition of cancer cells but only at relatively high concentrations.

  6. Gene characterized for membrane desaturase that produces (E)-11 isomers of mono- and diunsaturated fatty acids.

    PubMed

    Liu, Weitian; Jiao, Hongmei; Murray, Nancy C; O'Connor, Marion; Roelofs, Wendell L

    2002-01-22

    Moth species have evolved integral membrane desaturases that exhibit a wide diversity in substrate specificity, as well as in regiospecificity and stereospecificity of the unsaturated products. We report here the cloning and expression of a single desaturase from the sex pheromone gland of the light brown apple moth, Epiphyas postvittana, that makes E11 isomers of monounsaturated (E11-16 and E11-14) fatty acids and a diunsaturated (E9,E11-14) fatty acid. In the pheromone gland, the monoene precursor is made available by beta oxidation of E11-16 acid with a subsequent two-carbon loss to E9-14 acid. A functional assay using a baculovirus expression system required addition of myristic acid and E9-14 acid precursors to demonstrate the unusual regiospecificity and stereospecificity of this desaturase. The amino acid sequence of this desaturase has approximately 61% identity to that of Z11-desaturases from two other insect species, and only approximately 48% identity to the metabolic Z9-desaturases in those species. A pheromone-gland Z9-desaturase gene also was found with the light brown apple moth that differed in its deduced amino acid sequence (66% identity) with the metabolic Z9-desaturase from fat body in this species. PMID:11805319

  7. MALDI mechanism of dihydroxybenzoic acid isomers: desorption of neutral matrix and analyte.

    PubMed

    Liang, Chi Wei; Lee, Chih Hao; Lin, Yu-Jiun; Lee, Yuan Tseh; Ni, Chi Kung

    2013-05-01

    Angular resolved velocity distributions of laser desorbed neutral matrices (dihydroxybenzoic acids, DHB) and analytes (tryptophan) embedded in these matrices were investigated at 322 nm by a modified crossed molecular beam apparatus. Desorbed ions generated from MALDI were measured by a time-of-flight mass spectrometer. Desorptions of neutral matrix and analyte from 2,3-DHB, 2,4-DHB, 2,5-DHB, 2,6-DHB, and 3,5--DHB at 322 nm have similar properties, but the ion intensities are in the order 2,3DHB ≅ 2,6-DHB > 2,5-DHB ≅ 2,4-DHB > 3,5-DHB. It indicates that the combination of various parameters related to neutral species, including absorption coefficient, sublimation energy, contact of analyte and matrix in crystal, and plume dynamics of desorbed species are not crucial in the determination of MALDI process for DHB isomers. The difference of matrix activity of DHB isomers at this wavelength must result from the other properties, like the excited state lifetime, proton affinity, gas-phase basicity, acidity, ionization energy, or the other properties related to the primary reactions in ion generation.

  8. Beef conjugated linoleic acid isomers reduce human cancer cell growth even when associated with other beef fatty acids.

    PubMed

    De La Torre, Anne; Debiton, Eric; Juanéda, Pierre; Durand, Denys; Chardigny, Jean-Michel; Barthomeuf, Chantal; Bauchart, Dominique; Gruffat, Dominique

    2006-02-01

    Although many data are available concerning anticarcinogenic effects of industrial conjugated linoleic acid (CLA), few studies have reported the antitumour properties of CLA mixtures originating from ruminant products. The aim of the present study was to investigate the in vitro antiproliferative effects of beef CLA mixtures on breast, lung, colon, melanoma and ovarian human cancer cell lines. For this purpose, four fatty acid (FA) extracts prepared from beef lipid and varying in their CLA composition, their corresponding purified CLA-enriched fractions, and mixtures of pure synthetic CLA, the composition of which reproduced that of the four selected beef samples, were tested on cancer cell lines. Cancer cells were exposed for 48 h to medium containing 100 microm-FA and their proliferation was determined by quantifying cellular DNA content (Hoechst 33342 dye). Compared with cells incubated without FA, the number of cancer cells was reduced from 25 to 67 % (P<0.0001) following FA treatment. Antiproliferative effects of CLA mixtures varied in magnitude according to the source of FA, the CLA composition and the cell lines. CLA mixtures naturally present in beef inhibited the proliferation of human cancer cell lines, a high content in cis-trans isomers allowing the most important antiproliferative effect. Beef total FA exhibited a greater growth-inhibitory activity than their corresponding CLA-enriched fractions. These results suggested that either beef FA other than beef CLA could possess antiproliferative properties and/or the existence of complementary effects of non-conjugated FA and CLA, which could favour the antiproliferative properties of beef total FA. PMID:16469152

  9. Beef conjugated linoleic acid isomers reduce human cancer cell growth even when associated with other beef fatty acids.

    PubMed

    De La Torre, Anne; Debiton, Eric; Juanéda, Pierre; Durand, Denys; Chardigny, Jean-Michel; Barthomeuf, Chantal; Bauchart, Dominique; Gruffat, Dominique

    2006-02-01

    Although many data are available concerning anticarcinogenic effects of industrial conjugated linoleic acid (CLA), few studies have reported the antitumour properties of CLA mixtures originating from ruminant products. The aim of the present study was to investigate the in vitro antiproliferative effects of beef CLA mixtures on breast, lung, colon, melanoma and ovarian human cancer cell lines. For this purpose, four fatty acid (FA) extracts prepared from beef lipid and varying in their CLA composition, their corresponding purified CLA-enriched fractions, and mixtures of pure synthetic CLA, the composition of which reproduced that of the four selected beef samples, were tested on cancer cell lines. Cancer cells were exposed for 48 h to medium containing 100 microm-FA and their proliferation was determined by quantifying cellular DNA content (Hoechst 33342 dye). Compared with cells incubated without FA, the number of cancer cells was reduced from 25 to 67 % (P<0.0001) following FA treatment. Antiproliferative effects of CLA mixtures varied in magnitude according to the source of FA, the CLA composition and the cell lines. CLA mixtures naturally present in beef inhibited the proliferation of human cancer cell lines, a high content in cis-trans isomers allowing the most important antiproliferative effect. Beef total FA exhibited a greater growth-inhibitory activity than their corresponding CLA-enriched fractions. These results suggested that either beef FA other than beef CLA could possess antiproliferative properties and/or the existence of complementary effects of non-conjugated FA and CLA, which could favour the antiproliferative properties of beef total FA.

  10. Multispectroscopic and docking studies on the binding of chlorogenic acid isomers to human serum albumin: Effects of esteryl position on affinity.

    PubMed

    Tang, Bin; Huang, Yanmei; Ma, Xiangling; Liao, Xiaoxiang; Wang, Qing; Xiong, Xinnuo; Li, Hui

    2016-12-01

    Structural differences among various dietary polyphenols affect their absorption, metabolism, and bioactivities. In this work, chlorogenic acid (CA) and its two positional isomers, neochlorogenic acid (NCA) and cryptochlorogenic acid (CCA), were investigated for their binding reactions with human serum albumin (HSA) using fluorescence, ultraviolet-visible, Fourier transform infrared and circular dichroism spectroscopies, as well as molecular docking. All three isomers were bound to HSA at Sudlow's site I and affected the protein secondary structure. CCA presented the strongest ability of hydrogen-bond formation, and both CA and NCA generated more electrostatic interactions with HSA. The albumin-binding capacity of these compounds decreased in the order CCA>NCA>CA. The compound with 4-esteryl structure showed higher binding affinity and larger conformational changes to HSA than that with 3- or 5-esteryl structures. These comparative studies on structure-affinity relationship contributed to the structural modification and design of phenolic food additives or new polyphenol-like drugs. PMID:27374553

  11. Analysis of a series of chlorogenic acid isomers using differential ion mobility and tandem mass spectrometry.

    PubMed

    Willems, Jamie L; Khamis, Mona M; Mohammed Saeid, Waleed; Purves, Randy W; Katselis, George; Low, Nicholas H; El-Aneed, Anas

    2016-08-24

    Chlorogenic acids are among the most abundant phenolics found in the human diet. Of these, the mono-caffeoylquinic acids are the predominant phenolics found in fruits, such as apples and pears, and products derived from them. In this research, a comprehensive study of the electrospray ionization (ESI) tandem mass spectrometric (MS/MS) dissociation behavior of the three most common mono-caffeoylquinic acids, namely 5-O-caffeoylquinic acid (5-CQA), 3-O-caffeoylquinic acid (3-CQA) and 4-O-caffeoylquinic acid (4-CQA), were determined using both positive and negative ionization. All proposed structures of the observed product ions were confirmed with second-generation MS(3) experiments. Similarities and differences between the dissociation pathways in the positive and negative ion modes are discussed, confirming the proposed structures and the established MS/MS fingerprints. MS/MS dissociation was primarily driven via the cleavage of the ester bond linking the quinic acid moiety to the caffeic acid moiety within tested molecules. Despite being structural isomers with the same m/z values and dissociation behaviors, the MS/MS data in the negative ion mode was able to differentiate the three isomers based on ion intensity for the major product ions, observed at m/z 191, 179 and 173. This differentiation was consistent among various MS instruments. In addition, ESI coupled with high-field asymmetric waveform ion mobility spectrometry-mass spectrometry (ESI-FAIMS-MS) was employed for the separation of these compounds for the first time. By combining MS/MS data and differential ion mobility, a method for the separation and identification of mono-caffeoylquinic in apple/pear juice samples was developed with a run time of less than 1 min. It is envisaged that this methodology could be used to identify pure juices based on their chlorogenic acid profile (i.e., metabolomics), and could also be used to detect juice-to-juice adulteration (e.g., apple juice addition to pear juice).

  12. Analysis of a series of chlorogenic acid isomers using differential ion mobility and tandem mass spectrometry.

    PubMed

    Willems, Jamie L; Khamis, Mona M; Mohammed Saeid, Waleed; Purves, Randy W; Katselis, George; Low, Nicholas H; El-Aneed, Anas

    2016-08-24

    Chlorogenic acids are among the most abundant phenolics found in the human diet. Of these, the mono-caffeoylquinic acids are the predominant phenolics found in fruits, such as apples and pears, and products derived from them. In this research, a comprehensive study of the electrospray ionization (ESI) tandem mass spectrometric (MS/MS) dissociation behavior of the three most common mono-caffeoylquinic acids, namely 5-O-caffeoylquinic acid (5-CQA), 3-O-caffeoylquinic acid (3-CQA) and 4-O-caffeoylquinic acid (4-CQA), were determined using both positive and negative ionization. All proposed structures of the observed product ions were confirmed with second-generation MS(3) experiments. Similarities and differences between the dissociation pathways in the positive and negative ion modes are discussed, confirming the proposed structures and the established MS/MS fingerprints. MS/MS dissociation was primarily driven via the cleavage of the ester bond linking the quinic acid moiety to the caffeic acid moiety within tested molecules. Despite being structural isomers with the same m/z values and dissociation behaviors, the MS/MS data in the negative ion mode was able to differentiate the three isomers based on ion intensity for the major product ions, observed at m/z 191, 179 and 173. This differentiation was consistent among various MS instruments. In addition, ESI coupled with high-field asymmetric waveform ion mobility spectrometry-mass spectrometry (ESI-FAIMS-MS) was employed for the separation of these compounds for the first time. By combining MS/MS data and differential ion mobility, a method for the separation and identification of mono-caffeoylquinic in apple/pear juice samples was developed with a run time of less than 1 min. It is envisaged that this methodology could be used to identify pure juices based on their chlorogenic acid profile (i.e., metabolomics), and could also be used to detect juice-to-juice adulteration (e.g., apple juice addition to pear juice

  13. Biological and Chemical Properties of the Epidioxide Isomer of Abscisic Acid and its Rearrangement Products

    PubMed Central

    Sondheimer, Ernest; Michniewicz, Barbara M.; Powell, Loyd E.

    1969-01-01

    The growth inhibitory activity of the epidioxide (II), a precursor in the synthesis of abscisic acid (ABA), has been confirmed with additional assay systems. Under physiological conditions the epidioxide is rearranged to give ABA and an isomer of ABA which has probably the structure V. This major product has very low, if any, biological activity. The biological activity of the epidioxide is explained by its partial conversion (about 20%) to ABA. The reaction rate was enhanced by heavy metal ions and decreased by EDTA. At pH 12.5, the decomposition of the epidioxide is slower than it is near neutrality and ABA is the predominant product. In the biological systems studied the activity of the epidioxide can be accounted for by nonenzymatic conversion to ABA. PMID:16657047

  14. Fatty acid profile of Canadian dairy products with special attention to the trans-octadecenoic acid and conjugated linoleic acid isomers.

    PubMed

    Mendis, Sanjaya; Cruz-Hernandez, Cristina; Ratnayake, Walisundera M N

    2008-01-01

    Current scientific evidence indicates that consumption of industrial trans fatty acids (TFA) produced via partial hydrogenation of vegetable oils increases the risk of coronary heart disease. However, some studies have suggested that ruminant TFA, especially vaccenic acid (VA or 11t-18:1) and rumenic acid (RA or 9c,11t-18:2), which is a conjugated linoleic acid (CLA) isomer, may have potential beneficial health effects for humans. To date, no concerted effort has been made to provide detailed isomer composition of ruminant TFA and CLA of Canadian dairy products, information that is required to properly assess their nutritional impacts. To this end, we analyzed the fatty acid profile of popular brands of commercial cheese (n = 17), butter (n = 12), milk (n = 8), and cream (n = 4) sold in retail stores in Ottawa, Canada, in 2006-2007 by silver nitrate thin-layer chromatography and gas liquid chromatography. The average total TFA content of cheese, butter, milk, and cream samples were 5.6, 5.8, 5.8, and 5.5% of total fatty acids, respectively. VA was the major trans-octadecenoic acid (18:1) isomer in all the Canadian dairy samples with average levels of (as % total trans-18:1) 33.9% in cheese, 35.6% in butter, 31.0% milk, and 30.1% in cream. The different dairy products contained very similar levels of CLA, which ranged from 0.5 to 0.9% of total fat. RA was the major CLA isomer of all the dairy products, accounting for 82.4-83.2% of total CLA. There were no significant differences (P > 0.05) in the fatty acid profile between the 4 different dairy groups, which suggests lack of processing effects on the fatty acid profile of dairy fat.

  15. Identification of enriched conjugated linoleic acid isomers in cultures of ruminal microorganisms after dosing with 1-(13)C-linoleic acid.

    PubMed

    Lee, Yong-Jae; Jenkins, Thomas C

    2011-08-01

    Most studies of linoleic acid biohydrogenation propose that it converts to stearic acid through the production of cis-9 trans-11 CLA and trans-11 C18:1. However, several other CLA have been identified in ruminai contents, suggesting additional pathways may exist. To explore this possibility, this research investigated the linoleic acid biohydrogenation pathway to identify CLA isomers in cultures of ruminai microorganisms after dosing with a (13)C stable isotope. The (13)C enrichment was calculated as [(M+1/M)×100] in labeled minus unlabeled cultures. After 48 h incubation, significant (13)C enrichment was observed in seven CLA isomers, indicating their formation from linoleic acid. All enriched CLA isomers had double bonds in either the 9,11 or 10,12 position except for trans-9 cis-11 CLA. The cis-9 trans-11 CLA exhibited the highest enrichment (30.65%), followed by enrichments from 21.06 to 23.08% for trans-10 cis-12, cis-10 trans-12, trans-9 trans-11, and trans-10 trans-12 CLA. The remaining two CLA (cis-9 cis-11 and cis-10 cis-12 CLA) exhibited enrichments of 18.38 and 19.29%, respectively. The results of this study verified the formation of cis-9 trans-11 and trans-10 cis-12 CLA isomers from linoleic acid biohydrogenation. An additional five CLA isomers also contained carbons originating from linoleic acid, indicating that pathways of linoleic acid biohydrogenation are more complex than previously described.

  16. Colorimetric and fluorometric discrimination of geometrical isomers (maleic acid vs fumaric acid) with real-time detection of maleic acid in solution and food additives.

    PubMed

    Samanta, Soham; Kar, Chirantan; Das, Gopal

    2015-09-01

    Heterobis imine Schiff base probe L is able to discriminate geometrical isomers (maleic acid vs fumaric acid) through sharp colorimetric as well as fluorogenic responses even conspicuous with the naked eye. Colorimetric as well as fluorogenic sensing of maleic acid among various carboxylic acids was also demonstrated in ethanol-buffer medium. Sensing behavior of L was corroborated by (1)H NMR spectra, mass spectrometry, and theoretical calculations. Subsequently sensing behavior of L was used to probe maleic acid in starch rich food samples.

  17. Colorimetric and fluorometric discrimination of geometrical isomers (maleic acid vs fumaric acid) with real-time detection of maleic acid in solution and food additives.

    PubMed

    Samanta, Soham; Kar, Chirantan; Das, Gopal

    2015-09-01

    Heterobis imine Schiff base probe L is able to discriminate geometrical isomers (maleic acid vs fumaric acid) through sharp colorimetric as well as fluorogenic responses even conspicuous with the naked eye. Colorimetric as well as fluorogenic sensing of maleic acid among various carboxylic acids was also demonstrated in ethanol-buffer medium. Sensing behavior of L was corroborated by (1)H NMR spectra, mass spectrometry, and theoretical calculations. Subsequently sensing behavior of L was used to probe maleic acid in starch rich food samples. PMID:26246182

  18. Interstellar isomers

    NASA Technical Reports Server (NTRS)

    Defrees, D.; Mclean, D.; Herbst, E.

    1986-01-01

    Both observational and theoretical studies of molecular clouds are hindered by many difficulties. One way to partially circumvent the difficulties of characterizing the chemistry within these objects is to study the relative abundances of isomers which are synthesized from a common set of precursors. Unfortunately, only one such system has been confirmed, the HCN/HNC pair of isomers. While the basic outlines of its chemistry have been known for some years, there are still many aspects of the chemistry which are unclear. Another potential pair of isomers is HCO+/HOC+; HCO+ is an abundant instellar molecule and a tentative identification of HOC+ has been made in Sgr B2. This identification is being challenged, however, based on theoretical and laboratory evidence that HOC+ reacts with H2. Another potential pair of interstellar isomers is methyl cyanide (CH3CN, acetonitrile) and methyl isocyanide (CH3NC). The cyanide is well known, however the isocyanide has yet to be observed despite theoretical predictions that appreciable quantities should be present.

  19. Regiospecific Distribution of trans-Octadecenoic Acid Positional Isomers in Triacylglycerols of Partially Hydrogenated Vegetable Oil and Ruminant Fat.

    PubMed

    Yoshinaga, Kazuaki; Kawamura, Yoshinori; Kitayama, Takashi; Nagai, Toshiharu; Mizobe, Hoyo; Kojima, Koichi; Watanabe, Yomi; Sato, Shinichi; Beppu, Fumiaki; Gotoh, Naohiro

    2015-01-01

    It is revealed that binding position of fatty acid in triacylglycerol (TAG) deeply relates to the expression of its function. Therefore, we investigated the binding positions of individual trans-octadecenoic acid (trans-C18:1) positional isomers, known as unhealthy fatty acids, on TAG in partially hydrogenated canola oil (PHCO), milk fat (MF), and beef tallow (BT). The analysis was carried out by the sn-1(3)-selective transesterification of Candida antarctica Lipase B and by using a highly polar ionic liquid capillary column for gas chromatography-flame ionization detection. Trans-9-C18:1, the major trans-C18:1 positional isomer, was selectively located at the sn-2 position of TAG in PHCO, although considerable amounts of trans-9-C18:1 were also esterified at the sn-1(3) position. Meanwhile, trans-11-C18:1, the major isomer in MF and BT, was preferentially located at the sn-1(3) position. These results revealed that the binding position of trans-C18:1 positional isomer varies between various fats and oils.

  20. Regiospecific Distribution of trans-Octadecenoic Acid Positional Isomers in Triacylglycerols of Partially Hydrogenated Vegetable Oil and Ruminant Fat.

    PubMed

    Yoshinaga, Kazuaki; Kawamura, Yoshinori; Kitayama, Takashi; Nagai, Toshiharu; Mizobe, Hoyo; Kojima, Koichi; Watanabe, Yomi; Sato, Shinichi; Beppu, Fumiaki; Gotoh, Naohiro

    2015-01-01

    It is revealed that binding position of fatty acid in triacylglycerol (TAG) deeply relates to the expression of its function. Therefore, we investigated the binding positions of individual trans-octadecenoic acid (trans-C18:1) positional isomers, known as unhealthy fatty acids, on TAG in partially hydrogenated canola oil (PHCO), milk fat (MF), and beef tallow (BT). The analysis was carried out by the sn-1(3)-selective transesterification of Candida antarctica Lipase B and by using a highly polar ionic liquid capillary column for gas chromatography-flame ionization detection. Trans-9-C18:1, the major trans-C18:1 positional isomer, was selectively located at the sn-2 position of TAG in PHCO, although considerable amounts of trans-9-C18:1 were also esterified at the sn-1(3) position. Meanwhile, trans-11-C18:1, the major isomer in MF and BT, was preferentially located at the sn-1(3) position. These results revealed that the binding position of trans-C18:1 positional isomer varies between various fats and oils. PMID:26028327

  1. Heterogeneous OH Oxidation of Two Structure Isomers of Dimethylsuccinic Acid Aerosol: Reactivity and Oxidation Products

    NASA Astrophysics Data System (ADS)

    Chan, M. N.; Cheng, C. T.; Wilson, K. R.

    2014-12-01

    Organic aerosol contribute a significant mass fraction of ambient aerosol carbon and can continuously undergo oxidation by colliding with gas phase OH radicals. Although heterogeneous oxidation plays a significant role in the chemical transformation of organic aerosol, the effect of molecular structure on the reactivity and oxidation products remains unclear. We investigate the effect of branched methyl groups on the reactivity of two dimethylsuccinic acids (2,2-dimethylsuccinic acid (2,2-DMSA) and 2,3-dimethylsuccinic acid (2,3-DMSA)) toward gas phase OH radicals in an atmospheric pressure aerosol flow tube reactor. The oxidation products formed upon oxidation is characterized in real time by the Direct Analysis in Real Time (DART), an ambient soft ionization source. The 2,2-DMSA and 2,3-DMSA are structural isomers with the same oxidation state (OSC = -0.33) and carbon number (NC = 6), but different branching characteristics (2,2-DMSA has one secondary carbon and 2,3-DMSA has two tertiary carbons). The difference in molecular distribution of oxidation products observed in these two structural isomers would allow one to assess the sensitivity of kinetics and chemistry to the position of branched methyl group in the DMSA upon oxidation. We observe that the reactivity of 2,3-DMSA toward OH radicals is about 2 times faster than that of 2,2-DMSA. This difference in OH reactivity may attribute to the stability of the carbon-centered radical generated after hydrogen abstraction because an alkyl radical formed from the hydrogen abstraction on a tertiary carbon in 2,3-DMSA is more stable than on a secondary carbon in 2,2-DMSA. For both 2,2-DMSA and 2,3-DMSA, the molecular distribution and evolution of oxidation products is characterized by a predominance of functionalization products at the early oxidation stages. When the oxidation further proceeds, the fragmentation becomes more favorable and the oxidation mainly leads to the reduction of the carbon chain length through

  2. Contents of conjugated linoleic acid isomers in ruminant-derived foods and estimation of their contribution to daily intake in Portugal.

    PubMed

    Martins, Susana V; Lopes, Paula A; Alfaia, Cristina M; Ribeiro, Verónica S; Guerreiro, Teresa V; Fontes, Carlos M G A; Castro, Matilde F; Soveral, Graça; Prates, José A M

    2007-12-01

    The present study provides a detailed overview of the contents of conjugated linoleic acid (CLA) isomers in the most consumed Portuguese CLA-rich foods (milk, butter, yoghurt, cheese, beef and lamb meat), by using silver ion-HPLC. In addition, the contribution of these ruminant-derived foods to the daily intake of CLA isomers was estimated based on Portuguese consumption habits. The total CLA concentration in milk and dairy products ranged from 4.00 mg/g fat in yoghurt to 7.22 mg/g fat in butter, and, regarding meats, from 4.45 mg/g fat in intensively produced beef to 11.29 mg/g fat in lamb meat. The predominant CLA isomers identified in these products were cis-9, trans-11 (59.89-79.21 %) and trans-7, cis-9 (8.04-20.20 %). The average estimated total CLA intake for the Portuguese population was 73.70 mg/d. Milk and cheese are probably the two products with the highest contribution to the final CLA intake, as a result of their high fat content and consumption values. The results also suggested that cis-9, trans-11 and trans-7, cis-9 are the isomers most represented, with, respectively, 76.10 and 12.56 % of the total CLA intake. Being the first detailed report on the contents of total and individual CLA isomers in Portuguese commercial ruminant-derived foods, we further discuss the implication of the results for diet characteristics and human health.

  3. Hydroxyalkylation of phenol to bisphenol F over heteropolyacid catalysts: The effect of catalyst acid strength on isomer distribution and kinetics.

    PubMed

    Wu, Xianzhang; Liu, Yutang; Liu, Ran; Wang, Longlu; Lu, Yanbing; Xia, Xinnian

    2016-11-01

    Hydroxyalkylation of phenol with formaldehyde to bisphenol F over heteropolyacid impregnated on clay was investigated. These catalysts displayed excellent catalytic performance for this reaction, especially that the effects of acid sites on the isomer distribution are obvious. Various solid catalysts were prepared by impregnating heteropolyacid on different kind of clay matrices, and their chemical compositions, textural properties, and acid strength of the heteropolyacid catalysts were characterized by EDX, BET, NH3-TPD, XRD, and FT-IR. Moreover, the effects of acid sites and reaction temperature on the yield and 4,4'-isomer distribution were launched by comparing the data obtained from the two kinds of catalysts. Furthermore, the kinetics of the hydroxyalkylation of phenol to BPF was established.

  4. Hydroxyalkylation of phenol to bisphenol F over heteropolyacid catalysts: The effect of catalyst acid strength on isomer distribution and kinetics.

    PubMed

    Wu, Xianzhang; Liu, Yutang; Liu, Ran; Wang, Longlu; Lu, Yanbing; Xia, Xinnian

    2016-11-01

    Hydroxyalkylation of phenol with formaldehyde to bisphenol F over heteropolyacid impregnated on clay was investigated. These catalysts displayed excellent catalytic performance for this reaction, especially that the effects of acid sites on the isomer distribution are obvious. Various solid catalysts were prepared by impregnating heteropolyacid on different kind of clay matrices, and their chemical compositions, textural properties, and acid strength of the heteropolyacid catalysts were characterized by EDX, BET, NH3-TPD, XRD, and FT-IR. Moreover, the effects of acid sites and reaction temperature on the yield and 4,4'-isomer distribution were launched by comparing the data obtained from the two kinds of catalysts. Furthermore, the kinetics of the hydroxyalkylation of phenol to BPF was established. PMID:27451037

  5. Analysis of histidine and urocanic acid isomers by reversed-phase high-performance liquid chromatography.

    PubMed

    Hermann, K; Abeck, D

    2001-01-01

    The qualitative separation performance of a C18, C8 and C4 reversed-phase column was investigated for the separation of histidine and its metabolites histamine, 1-methyihistamine and trans- and cis-urocanic acid. Trans- and cis-urocanic acid were baseline separated from their precursor histidine on all three columns using isocratic elution with a mobile phase composed of 0.01 M aqueous TEAP pH 3.0 and acetonitrile at a ratio of 98:2 (v/v). However, histidine was not separated from histamine and 1-methyihistamine. Selecting the C8 column and introducing 0.005 M of the ion pairing reagent 1-octanesulfonic acid sodium salt into the aqueous solution and acetonitrile at a ratio of 90:10 (v/v), significantly improved the separation. The separation was also followed by a change in the retention times and the order of elution. The sequence of elution was histidine, cis-urocanic acid, trans-urocanic acid, histamine and 1-methylhistamine with retention times of 5.58 +/- 0.07, 7.03 +/- 0.15, 7.92 +/- 0.18, 18.77 +/- 0.24 and 20.79 +/- 0.21 min (mean +/- SD; n=5). The separation on the C8 column in the presence of the ion-pairing reagent was further improved with gradient elution that resulted in a reduction in the retention times and elution volumes of histamine and 1-methylhistamine. The detection limits of histidine and trans-urocanic acid at a wavelength of 210 nm and an injection volume of 0.05 ml were 5 x 10(-8) mol l(-1) (n=3). The kinetic of the in-vitro conversion of trans- into the cis-isomer after UV irradiation was depending on the time of exposure and the energy of the light source. UVB light induced a significantly faster conversion than UVA light. TUCA and cUCA samples kept at -25 degrees C were stable for up to 50 weeks. Samples, eluted from human skin showed various concentrations of histidine and trans- and cis-urocanic acid with an average of 1.69 +/- 0.33 x 10(-5) mol l(-1), 1.17 +/- 0.43 x 10(-5) mol l(-1) and 1.67 +/- 0.33 x 10(-5) mol l(-1), respectively

  6. Synthesis of hydroxytyrosol, 2-hydroxyphenylacetic acid, and 3-hydroxyphenylacetic acid by differential conversion of tyrosol isomers using Serratia marcescens strain.

    PubMed

    Allouche, Noureddine; Sayadi, Sami

    2005-08-10

    We investigated to develop an effective procedure to produce the potentially high-added-value phenolic compounds through bioconversion of tyrosol isomers. A soil bacterium, designated Serratia marcescens strain, was isolated on the basis of its ability to grow on p-tyrosol (4-hydroxyphenylethanol) as a sole source of carbon and energy. During growth on p-tyrosol, Ser. marcescens strain was capable of promoting the formation of hydroxytyrosol. To achieve maximal hydroxytyrosol yield, the growth state of the culture utilized for p-tyrosol conversion as well as the amount of p-tyrosol that was treated were optimized. The optimal yield of hydroxytyrosol (80%) was obtained by Ser. marcescens growing cells after a 7-h incubation using 2 g/L of p-tyrosol added at the end of the exponential phase to a culture pregrown on 1 g/L of p-tyrosol. Furthermore, the substrate specificity of the developed biosynthesis was investigated using m-tyrosol (3-hydroxyphenylethanol) and o-tyrosol (2-hydroxyphenylethanol) as substrates. Ser. marcescens strain transformed completely m-tyrosol and o-tyrosol into 3-hydroxyphenylacetic acid and 2-hydroxyphenylacetic acid, respectively, via the oxidation of the side chain carbon of the treated substrates. This proposed procedure is an alternative approach to obtain hydroxytyrosol, 2-hydroxyphenylacetic acid, and 3-hydroxyphenylacetic acid in an environmentally friendly way which could encourage their use as alternatives in the search for replacement of synthetic food additives.

  7. Biotransformations of 2-hydroxy-2-(ethoxyphenylphosphinyl)acetic acid and the determination of the absolute configuration of all isomers.

    PubMed

    Majewska, Paulina

    2015-08-01

    2-Hydroxy-2-(ethoxyphenylphosphinyl)acetic acid, a new type of organophosphorus compound possessing two stereogenic centers, was investigated. Racemic 2-butyryloxy-2-(ethoxyphenylphosphinyl)acetic acid was synthesized and hydrolyzed using four bacterial species as biocatalysts. In all cases the reaction was more or less stereoselective and isomers bearing a phosphorus atom with an (SP)-configuration were hydrolyzed preferentially. The observed (1)H and (31)P NMR chemical shifts of Mosher esters of 2-hydroxy-2-(ethoxyphenylphosphinyl)acetic acid were correlated with the configurations of both stereogenic centers of all four stereoisomers.

  8. Temporal changes (1997-2012) of perfluoroalkyl acids and selected precursors (including isomers) in Swedish human serum.

    PubMed

    Gebbink, Wouter A; Glynn, Anders; Berger, Urs

    2015-04-01

    Concentrations (including isomer patterns) and temporal changes (1997-2012) of perfluoroalkyl acids (PFAAs) and selected perfluorooctane sulfonate (PFOS) and perfluoroalkyl carboxylic acid (PFCA) precursors were determined in serum samples from Swedish women. Perfluorooctane sulfonamide (FOSA) and perfluorooctane sulfonamidoacetic acid (FOSAA), as well as its N-methyl and N-ethyl derivatives (MeFOSAA and EtFOSAA) were consistently detected. Highest PFOS precursor concentrations were found for EtFOSAA (before year 2000) or MeFOSAA and FOSAA (after 2000). Disappearance half-lives for all PFOS precursors were shorter compared to PFOS. 4:2/6:2 and 6:2/6:2 polyfluoroalkyl phosphate diesters (diPAPs) were detected in <60% of the samples, whereas 6:2/8:2 and 8:2/8:2 diPAPs were detected in >60% of the samples, but showed no significant change in concentrations over time. Linear and sum-branched isomers were quantified separately for three PFAAs and three precursors. Significant changes between 1997 and 2012 in the % linear isomer were observed for PFOA and FOSA (increase) and PFOS (decrease).

  9. Estimated pKa values for the environmentally relevant C1 through C8 perfluorinated sulfonic acid isomers.

    PubMed

    Rayne, Sierra; Forest, Kaya

    2016-10-14

    In order to estimate isomer-specific acidity constants (pKa) for the perfluorinated sulfonic acid (PFSA) environmental contaminants, the parameterization method 6 (PM6) pKa prediction method was extensively validated against a wide range of carbon oxyacids and related sulfonic/sulfinic acids. Excellent pKa prediction performance was observed for the carbon oxyacids using the PM6 method, but this approach was found to have a severe positive bias for sulfonic/sulfinic acids. To overcome this obstacle, a correlation was developed between non-adjusted PM6 pKa values and the corresponding experimentally obtained/estimated acidity constants for a range of representative alkyl, aryl and halogen-substituted sulfonic acids. Application of this correction to the PM6 values allows for extension of this computational method to a new acid functional group. When used to estimate isomer-specific pKa values for the C1 through C8 PFSAs, the modified PM6 approach suggests an adjusted pKa range from -5.3 to -9.0, indicating that all members of this class of well-known environmental contaminants will be effectively completely dissociated in aquatic systems.

  10. Estimated pKa values for the environmentally relevant C1 through C8 perfluorinated sulfonic acid isomers.

    PubMed

    Rayne, Sierra; Forest, Kaya

    2016-10-14

    In order to estimate isomer-specific acidity constants (pKa) for the perfluorinated sulfonic acid (PFSA) environmental contaminants, the parameterization method 6 (PM6) pKa prediction method was extensively validated against a wide range of carbon oxyacids and related sulfonic/sulfinic acids. Excellent pKa prediction performance was observed for the carbon oxyacids using the PM6 method, but this approach was found to have a severe positive bias for sulfonic/sulfinic acids. To overcome this obstacle, a correlation was developed between non-adjusted PM6 pKa values and the corresponding experimentally obtained/estimated acidity constants for a range of representative alkyl, aryl and halogen-substituted sulfonic acids. Application of this correction to the PM6 values allows for extension of this computational method to a new acid functional group. When used to estimate isomer-specific pKa values for the C1 through C8 PFSAs, the modified PM6 approach suggests an adjusted pKa range from -5.3 to -9.0, indicating that all members of this class of well-known environmental contaminants will be effectively completely dissociated in aquatic systems. PMID:27389973

  11. Isomers of various species of 1-hydroxy-2-pyridinone-6-carboxylic acid, their proton dissociation and complexes with Cr(III) and Zn(II)

    NASA Astrophysics Data System (ADS)

    Thipyapong, Khajadpai; Ruangpornvisuti, Vithaya

    2008-11-01

    Isomers of 1-hydroxy-2-pyridinone-6-carboxylic acid (6-carboxy-1,2-HOPO), their deprotonated species and complexes with chromium and zinc were theoretically investigated by density functional theory calculations. Free energy of activation, energetics, thermodynamic properties and equilibrium constants of interconversion reactions of their isomers were determined. Measured acid-dissociation constants of the 6-carboxy-1,2-HOPO obtained from potentiometric titration method were compared with the computed constants which were derived from the density functional theory method. Two isomers of each 6-carboxy-1,2-HOPO complexes with chromium and with zinc were found.

  12. Perfluorinated acid isomer profiling in water and quantitative assessment of manufacturing source.

    PubMed

    Benskin, Jonathan P; Yeung, Leo W Y; Yamashita, Nobuyoshi; Taniyasu, Sachi; Lam, Paul K S; Martin, Jonathan W

    2010-12-01

    A method for isomer profiling of perfluorinated compounds (PFCs) in water was developed and applied to quantitatively assess the contributions from electrochemical (ECF) and telomer manufacturing processes around source regions of North America, Asia, and Europe. With the exception of 3 sites in Japan, over 80% of total perfluorooctanoate (PFOA, C(7)F(15)COO(-)) was from ECF, with the balance attributable to strictly linear (presumably telomer) manufacturing source(s). Comparing PFOA isomer profiles in samples from China, with PFOA obtained from a local Chinese manufacturer, indicated <3% difference in overall branched isomer content; thus, exclusive contribution from local ECF production cannot be ruled out. In Tokyo Bay, ECF, linear-telomer, and isopropyl-telomer sources contributed to 33%, 53%, and 14% of total PFOA, respectively. Perfluorooctane sulfonate (PFOS, C(8)F(17)SO(3)(-)) isomer profiles were enriched in branched content (i.e., >50% branched) in the Mississippi River but in all other locations were similar or only slightly enriched in branched content relative to historical ECF PFOS. Isomer profiles of other PFCs are also reported. Overall, these data suggest that, with the exception of Tokyo Bay, ECF manufacturing has contributed to the bulk of contamination around these source regions, but other sources are significant, and remote sites should be monitored.

  13. Power optimization in logic isomers

    NASA Technical Reports Server (NTRS)

    Panwar, Ramesh; Rennels, David; Alkalaj, Leon

    1993-01-01

    Logic isomers are labeled, 2-isomorphic graphs that implement the same logic function. Logic isomers may have significantly different power requirements even though they have the same number of transistors in the implementation. The power requirements of the isomers depend on the transition activity of the input signals. The power requirements of isomorphic graph isomers of n-input NAND and NOR gates are shown. Choosing the less power-consuming isomer instead of the others can yield significant power savings. Experimental results on a ripple-carry adder are presented to show that the implementation using the least power-consuming isomers requires approximately 10 percent less power than the implementation using the most power-consuming isomers. Simulations of other random logic designs also confirm that designs using less power-consuming isomers can reduce the logic power demand by approximately 10 percent as compared to designs using more power-consuming isomers.

  14. Hexadecenoic Fatty Acid Isomers in Human Blood Lipids and Their Relevance for the Interpretation of Lipidomic Profiles

    PubMed Central

    Sansone, Anna; Tolika, Evanthia; Louka, Maria; Sunda, Valentina; Deplano, Simone; Melchiorre, Michele; Anagnostopoulos, Dimitrios; Chatgilialoglu, Chryssostomos; Formisano, Cesare; Di Micco, Rosa; Faraone Mennella, Maria Rosaria; Ferreri, Carla

    2016-01-01

    Monounsaturated fatty acids (MUFA) are emerging health biomarkers, and in particular the ratio between palmitoleic acid (9cis-16:1) and palmitic acid (16:0) affords the delta-9 desaturase index that is increased in obesity. Recently, other positional and geometrical MUFA isomers belonging to the hexadecenoic family (C16 MUFA) were found in circulating lipids, such as sapienic acid (6cis-16:1), palmitelaidic acid (9trans-16:1) and 6trans-16:1. In this work we report: i) the identification of sapienic acid as component of human erythrocyte membrane phospholipids with significant increase in morbidly obese patients (n = 50) compared with age-matched lean controls (n = 50); and ii) the first comparison of erythrocyte membrane phospholipids (PL) and plasma cholesteryl esters (CE) in morbidly obese patients highlighting that some of their fatty acid levels have opposite trends: increases of both palmitic and sapienic acids with the decrease of linoleic acid (9cis,12cis-18:2, omega-6) in red blood cell (RBC) membrane PL were reversed in plasma CE, whereas the increase of palmitoleic acid was similar in both lipid species. Consequentially, desaturase enzymatic indexes gave different results, depending on the lipid class used for the fatty acid content. The fatty acid profile of morbidly obese subjects also showed significant increases of stearic acid (C18:0) and C20 omega-6, as well as decreases of oleic acid (9cis-18:1) and docosahexaenoic acid (C22:6 omega-3) as compared with lean healthy controls. Trans monounsaturated and polyunsaturated fatty acids were also measured and found significantly increased in both lipid classes of morbidly obese subjects. These results highlight the C16 MUFA isomers as emerging metabolic marker provided that the assignment of the double bond position and geometry is correctly performed, thus identifying the corresponding lipidomic pathway. Since RBC membrane PL and plasma CE have different fatty acid trends, caution must also be used in the

  15. Screening of urocanic acid isomers in human basal and squamous cell carcinoma tumors compared with tumor periphery and healthy skin.

    PubMed

    Decara, Juan Manuel; Aguilera, José; Abdala, Roberto; Sánchez, Purificación; Figueroa, Félix L; Herrera, Enrique

    2008-10-01

    Trans-urocanic acid is a major chromophore for ultraviolet (UV) radiation in human epidermis. The UV induces photoisomerization of trans-urocanic acid (tUCA) form to cis-urocanic acid (cUCA) and has been reported as an important mediator in the immunosuppression induced by UV. This immunomodulation has been recognized as an important factor related to skin cancer development. This is the first time that UCA isomers have been measured in epidermis of skin biopsies from patients with squamous cell carcinoma (SCC) and with basal cell carcinoma (BCC) and compared with the tumor periphery and biopsies of healthy photoexposed and non-photoexposed skin as controls. The UCA isomers were separated and quantified by high performance liquid chromatography. Analysis of UCA in healthy skin showed significant increase in total UCA content in non-photoexposed body sites compared with highly exposed skins. In contrast, the percentage of cUCA was higher in photoexposed body sites. Maximal levels of cUCA were found in cheek, forehead and forearm and lower levels in abdomen and thigh. No differences were found in total UCA concentration between the tumor samples and healthy photoexposed skin. However, differences were found in relation between isomers. Higher levels of cUCA were detected in SCC biopsies (44% of total UCA) compared with samples of BCC and that of healthy photoexposed skin (30%). These results suggest that the UV radiation exposure, a main factor in development of SCC can be mediated, apart from direct effect to cells (DNA damage), by immunosuppression pathways mediated by high production of cUCA. PMID:18312386

  16. Isolation of isochlorogenic acid isomers in flower buds of Lonicera japonica by high-speed counter-current chromatography and preparative high performance liquid chromatography.

    PubMed

    Guo, Wei; Wang, Liang; Gao, Yan; Zhao, Bonian; Wang, Daijie; Duan, Wenjuan; Yu, Zongyuan

    2015-02-15

    An efficient method was established by HSCCC combined with prep-HPLC for separating isochlorogenic acid isomers from flower buds of Lonicera japonica. The partially purified sample from the methanol extract of flower buds of L. japonica by silica gel column was separated by HSCCC to result in a fraction containing two isochlorogenic acid isomers. The fraction was further isolated by prep-HPLC to yield isochlorogenic acid A and isochlorogenic acid C with purities of 98% and 96%, and the total recoveries at 80.1% and 79.8%, respectively. The chemical structures of isochlorogenic acid isomers were confirmed by electrospray ionization mass spectrometry (ESI-MS) and (1)H nuclear magnetic resonance (NMR).

  17. Determination of histidine and urocanic acid isomers in the human skin by high-performance capillary electrophoresis.

    PubMed

    Hermann, K; Abeck, D

    2000-11-10

    Histidine was baseline separated from histamine, 1-methylhistamine and cis- and trans-urocanic acid using high-performance capillary electrophoresis (HPCE) on a fused-silica column (50 cm x 75 microm) with 0.05 M NaH2PO4 buffer, pH 5.0, and 12 kV. The detection limit of histidine, trans- and cis-urocanic acid was 10(-6) M at a wavelength of 214 nm. The detection limit of the urocanic acid isomers was slightly enhanced to 5 x 10(-7) M at 267 nm. The transformation of the trans-urocanic acid standard in vitro into the cis-isomer was dependent on the time of exposure and the energy of the light source. UVB light induced a significantly faster conversion than UVA light. The HPCE method was used for the characterization and measurement of histidine and urocanic acid in human skin eluates. The concentrations of histidine, trans- or cis-urocanic acid in ethanol washes from the skin of healthy, non-allergic volunteers were 2.22+/-0.40 x 10(-5) 0.96+/-0.26 x 10(-5) and 1.04+/-0.30 x 10(-5) M, respectively, (mean+/-SEM, n=8). The results obtained by HPCE correlated well with data obtained by HPLC. Correlation coefficients of r2=0.981, r2=0.814 and r2=0.956 were found for histidine, trans- and cis-urocanic acid, respectively.

  18. 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. PMID:26725502

  19. 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.

  20. Three 2D Ag(I)-framework isomers with helical structures controlled by the chirality of camphor-10-sulfonic acid.

    PubMed

    Guo, Peng

    2011-02-28

    Three 2D Ag(I)-framework isomers were constructed from enantiopure camphor-10-sulfonic acids or racemic camphor-10-sulfonic acids, together with achiral 4-aminobenzoic acids. In complex 1, (+)-camphor-10-sulfonic acids bridge the single left-handed helices that are made up of Ag ions and 4-aminobenzoic acids, generating a homochiral 2D layer. In such a structure, the interweaving of triple left-handed homohelices was also found. It is worth noting that the helicity of complex 2 could be controlled by the handedness of the camphor-10-sulfonic acid. In complex 2, there are right-handed helical structures, including single right-handed and triple right-handed helical structures connected by (-)-camphor-10-sulfonic acids. For a comparative study, (±)-camphor-10-sulfonic acids were utilized to synthesize complex 3, in which equal numbers of right-handed or left-handed double-helical chains are created. All the complexes were characterized by single-crystal X-ray structure determination, powder X-ray diffraction, IR, TGA and element analysis. Circular dichroism spectra of complexes 1 and 2 were been studied to confirm the fact that enantiopure bridging ligands do not racemize. PMID:21264423

  1. Three 2D Ag(I)-framework isomers with helical structures controlled by the chirality of camphor-10-sulfonic acid.

    PubMed

    Guo, Peng

    2011-02-28

    Three 2D Ag(I)-framework isomers were constructed from enantiopure camphor-10-sulfonic acids or racemic camphor-10-sulfonic acids, together with achiral 4-aminobenzoic acids. In complex 1, (+)-camphor-10-sulfonic acids bridge the single left-handed helices that are made up of Ag ions and 4-aminobenzoic acids, generating a homochiral 2D layer. In such a structure, the interweaving of triple left-handed homohelices was also found. It is worth noting that the helicity of complex 2 could be controlled by the handedness of the camphor-10-sulfonic acid. In complex 2, there are right-handed helical structures, including single right-handed and triple right-handed helical structures connected by (-)-camphor-10-sulfonic acids. For a comparative study, (±)-camphor-10-sulfonic acids were utilized to synthesize complex 3, in which equal numbers of right-handed or left-handed double-helical chains are created. All the complexes were characterized by single-crystal X-ray structure determination, powder X-ray diffraction, IR, TGA and element analysis. Circular dichroism spectra of complexes 1 and 2 were been studied to confirm the fact that enantiopure bridging ligands do not racemize.

  2. Comparative Cytotoxicity and Sperm Motility Using a Computer-Aided Sperm Analysis System (CASA) for Isomers of Phthalic Acid, a Common Final Metabolite of Phthalates.

    PubMed

    Kwack, Seung Jun; Lee, Byung-Mu

    2015-01-01

    The general population is exposed to phthalates through consumer products, diet, and medical devices. Phthalic acid (PA) is a common final metabolite of phthalates, and its isomers include isophthalic acid (IPA), terephthalic acid (TPA), and phthalaldehyde (o-phthalic acid, OPA). The purpose of this study was to investigate whether PA and PA isomers exert reproductive toxicity, including altered sperm movement. In vitro cell viability assays were comparatively performed using Sertoli and liver cell lines. In animal experiments, PA or PA isomers (10, 100, or 1000 mg/kg) were administered orally to Sprague-Dawley (SD) rats, and semen samples were analyzed by computer-aided sperm analysis (CASA). PA treatment produced a significant effect on curvilinear velocity (VCL), straight-line velocity (VSL), mean velocity or average path velocity (VAP), amplitude of lateral head displacement (ALH), and frequency of head displacement or beat cross-frequency (BCF), whereas IPA, TPA, and OPA induced no marked effects. In vitro cell viability assays showed that mouse normal testis cells (TM4) and human testis cancer cells (NTERA 2 cl. D1) were more sensitive to PA and OPA than mouse liver normal cells (NCTC clone 1469) and human fetal liver cells (FL 62891). Our study suggests that PA and PA isomers specifically produced significant in vitro and in vivo reproductive toxicity, particularly sperm toxicity and testis cell cytotoxicity. Of the isomers examined, PA appeared to be the most toxic and may serve as a surrogate biomarker for reproductive toxicity following mixed exposure to phthalates.

  3. Frying stability of high oleic sunflower oils as affected by composition of tocopherol isomers and linoleic acid content.

    PubMed

    Aladedunye, Felix; Przybylski, Roman

    2013-12-01

    The influence of linoleic acid content and tocopherol isomeric composition on the frying performance of high oleic sunflower oil was evaluated during a 14-day restaurant style frying operation. At equal linoleic acid content, no significant difference was observed between high oleic sunflower oil containing only α-tocopherol and the sample containing a mixture of α-, γ-, and δ-isomers as measured by the amount of total polar components, oligomers, anisidine value, and free fatty acids. On the contrary, at similar tocopherol isomeric composition, high oleic sunflower oil containing lower amount of linoleic acid showed superior frying stability compared to the sample with a higher content of linoleic acid, suggesting that the frying performance of high oleic sunflower oil is dictated primarily by the level of linoleic acid, with the tocopherol isomeric composition of the oil having no significant influence. In all oil samples, the loss of γ-tocopherol was higher than the corresponding loss of α-tocopherol. PMID:23870970

  4. Determination of Exposure to the Alternaria Mycotoxin Tenuazonic Acid and Its Isomer allo-Tenuazonic Acid in a German Population by Stable Isotope Dilution HPLC-MS(3).

    PubMed

    Hövelmann, Yannick; Hickert, Sebastian; Cramer, Benedikt; Humpf, Hans-Ulrich

    2016-08-31

    The content of the Alternaria toxin tenuazonic acid and its isomer allo-tenuazonic acid was quantitated in urine of a German cohort (n = 48) using a newly developed and successfully validated solid phase extraction based stable isotope dilution HPLC-MS(3) method. Tenuazonic acid was detected in all of the samples and quantifiable in 97.9% of these samples in a range of 0.16-44.4 ng/mL (average = 6.58 ng/mL) or 0.07-63.8 ng/mg creatinine (average = 8.13 ng/mg creatinine). allo-Tenuazonic acid was for the first time detected in human urine (95.8% of the samples positive) and quantitated in 68.8% of the samples in a range of 0.11-5.72 ng/mL (average = 1.25 ng/mL) or 0.08-10.1 ng/mg creatinine (average = 1.52 ng/mg creatinine), representing 3.40-25.0% of the sum of both isomers (average = 12.4%). Food-frequency questionnaires were used to document food consumption of study participants to correlate mycotoxin exposure to nutritional habits. Although no statistically significant correlation between consumption of a specific food and urinary excretion of tenuazonic acid could be determined, a trend regarding elevated intake of cereal products and higher excretion of tenuazonic acid was evident. On the basis of these results, a provisional mean daily intake (PDI) for both tenuazonic acid and allo-tenuazonic acid was calculated, being 0.183 and 0.025 μg/kg body weight, respectively. A combined mean PDI for both isomers amounts to 0.208 μg/kg body weight with the highest individual PDI for one of the participants (1.582 μg/kg body weight) slightly exceeding the threshold of toxicological concern assumed for tenuazonic acid by the European Food Safety Authority of 1.500 μg/kg body weight. This is the first study to investigate the tenuazonic acid content in human urine of a larger sample cohort enabling the calculation of PDIs for tenuazonic acid and allo-tenuazonic acid. PMID:27452834

  5. Synthesis of framework isomer MOFs containing zinc and 4-tetrazolyl benzenecarboxylic acid via a structure directing solvothermal approach

    DOE PAGES

    Ordonez, Carlos; Kinnibrugh, Tiffany L.; Xu, Hongwu; Lindline, Jennifer; Timofeeva, Tatiana; Wei, Qiang

    2015-04-02

    The solvothermal synthesis of framework isomers was carried out using the hybrid carboxylate and tetrazolate functional ligand, 4-tetrazolyl benzenecarboxylic acid (H₂TBC, TBC = 4-tetrazolyl benzenecarboxylate) and zinc. H₂TBC was also synthesized with the solvothermal approach, and is referred herein as structure 1. Using single-crystal X-ray diffraction, we found that the tetrazolate groups of TBC show an unusual “opposite-on” coordination mode with zinc. Three previously characterized metal-organic frameworks (MOFs) were obtained by systematically changing the solvents of the H₂TBC-Zn reaction, (1) ZnTBC, 2, which has a non-porous structure; (2) Zn₂(TBC)₂(H2O), 3, which has an amphiphilic pore structure and (3) Zn₂(TBC)₂{guest}, 4,more » which is porous and has channels containing uncoordinated N heteroatoms. Fluorescence spectra of 4 reveal a strong blue emission mainly from the TBC ligands.« less

  6. Synthesis of framework isomer MOFs containing zinc and 4-tetrazolyl benzenecarboxylic acid via a structure directing solvothermal approach

    SciTech Connect

    Ordonez, Carlos; Kinnibrugh, Tiffany L.; Xu, Hongwu; Lindline, Jennifer; Timofeeva, Tatiana; Wei, Qiang

    2015-04-02

    The solvothermal synthesis of framework isomers was carried out using the hybrid carboxylate and tetrazolate functional ligand, 4-tetrazolyl benzenecarboxylic acid (H₂TBC, TBC = 4-tetrazolyl benzenecarboxylate) and zinc. H₂TBC was also synthesized with the solvothermal approach, and is referred herein as structure 1. Using single-crystal X-ray diffraction, we found that the tetrazolate groups of TBC show an unusual “opposite-on” coordination mode with zinc. Three previously characterized metal-organic frameworks (MOFs) were obtained by systematically changing the solvents of the H₂TBC-Zn reaction, (1) ZnTBC, 2, which has a non-porous structure; (2) Zn₂(TBC)₂(H2O), 3, which has an amphiphilic pore structure and (3) Zn₂(TBC)₂{guest}, 4, which is porous and has channels containing uncoordinated N heteroatoms. Fluorescence spectra of 4 reveal a strong blue emission mainly from the TBC ligands.

  7. The conjugated linoleic acid isomer trans-9,trans-11 is a dietary occurring agonist of liver X receptor {alpha}

    SciTech Connect

    Ecker, Josef; Liebisch, Gerhard; Patsch, Wolfgang; Schmitz, Gerd

    2009-10-30

    Conjugated linoleic acid (CLA) isomers are dietary fatty acids that modulate gene expression in many cell types. We have previously reported that specifically trans-9,trans-11 (t9,t11)-CLA induces expression of genes involved in lipid metabolism of human macrophages. To elucidate the molecular mechanism underlying this transcriptional activation, we asked whether t9,t11-CLA affects activity of liver X receptor (LXR) {alpha}, a major regulator of macrophage lipid metabolism. Here we show that t9,t11-CLA is a regulator of LXR{alpha}. We further demonstrate that the CLA isomer induces expression of direct LXR{alpha} target genes in human primary macrophages. Knockdown of LXR{alpha} with RNA interference in THP-1 cells inhibited t9,t11-CLA mediated activation of LXR{alpha} including its target genes. To evaluate the effective concentration range of t9,t11-CLA, human primary macrophages were treated with various doses of CLA and well known natural and synthetic LXR agonists and mRNA expression of ABCA1 and ABCG1 was analyzed. Incubation of human macrophages with 10 {mu}M t9,t11-CLA led to a significant modulation of ABCA1 and ABCG1 transcription and caused enhanced cholesterol efflux to high density lipoproteins and apolipoprotein AI. In summary, these data show that t9,t11-CLA is an agonist of LXR{alpha} in human macrophages and that its effects on macrophage lipid metabolism can be attributed to transcriptional regulations associated with this nuclear receptor.

  8. Identification of a dicaffeoylquinic acid isomer from Arctium lappa with a potent anti-ulcer activity.

    PubMed

    Carlotto, Juliane; da Silva, Luisa M; Dartora, Nessana; Maria-Ferreira, Daniele; Sabry, Diego de A; Filho, Arquimedes P S; de Paula Werner, Maria F; Sassaki, Guilherme L; Gorin, Philip A J; Iacomini, Marcello; Cipriani, Thales R; de Souza, Lauro M

    2015-04-01

    Leaves of Arctium lappa contain several mono- and dicaffeoylquinic acids, as evaluated by liquid chromatography-mass spectrometry. In order to investigate the protection on gastric mucosa against ulcers, rats were treated with fractions from leaf extract prior to ethanol-induced ulcers. The original fraction obtained as ethanol soluble fraction from hot aqueous extract was able to protect de gastric mucosa, and this effect was retained in the ethyl acetate fraction, obtained from liquid/liquid fractionation. The main compound in this fraction was isolated and chemically characterized by nuclear magnetic resonance and mass spectrometry, assisted by isopropylidene derivatization which gave rise a mass increment of 40 units. Therefore, the underivatized compound that had m/z 515.119 [M-H](-) was shifted to m/z 555.151, being confirmed as 1,3-O-dicaffeoylquinic acid, which presented an ED50 of 57 µg kg(-1) on gastric protection, lesser than the therapeutic concentration of omeprazole (40 mg kg(-1)). PMID:25640125

  9. Perfluoroalkyl acids (PFAAs) with isomer analysis in the commercial PFOS and PFOA products in China.

    PubMed

    Jiang, Weiwei; Zhang, Yifeng; Yang, Liping; Chu, Xiaolong; Zhu, Lingyan

    2015-05-01

    Perfluoroalkyl acids (PFAAs) have been widely used in consumer and industrial products for decades and are widely detected in the environment and humans all over the world. The information on the isomeric profiles of commercial products is important to identify the manufacturing origins of PFAAs in the environment. For the first time, the PFAA compositions and isomeric profiles of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) were reported in three PFOS and five PFOA commercial products manufactured in China. The purity of the three PFOS products was 76.7-80.6%. The major impurity in the PFOS products is PFOA, which contributes more than 10%. Other impurities include perfluorohexanesulfonate (PFHxS), perfluorohexanoate (PFHxA) and perfluoroheptanoate acids (PFHpA). The percentage of linear PFOS (n-PFOS) in the three products was 66.2-71.9%, similar to that in the product manufactured by 3M (70.3%). The purity of the five PFOA products was relatively high (94.0-95.8%), and the major impurity was PFOS (2.06-3.09%). The percentage of n-PFOA in the five PFOA products was 76.4-77.9%, which was similar to that in the 3M PFOA (78%). Although it is widely accepted that telomerization is currently the predominant manufacturing method for PFOA, yielding an isomerically pure and linear product, the results in the present study suggest that electrochemical fluorination is still used by some manufacturers in China.

  10. Identification of a dicaffeoylquinic acid isomer from Arctium lappa with a potent anti-ulcer activity.

    PubMed

    Carlotto, Juliane; da Silva, Luisa M; Dartora, Nessana; Maria-Ferreira, Daniele; Sabry, Diego de A; Filho, Arquimedes P S; de Paula Werner, Maria F; Sassaki, Guilherme L; Gorin, Philip A J; Iacomini, Marcello; Cipriani, Thales R; de Souza, Lauro M

    2015-04-01

    Leaves of Arctium lappa contain several mono- and dicaffeoylquinic acids, as evaluated by liquid chromatography-mass spectrometry. In order to investigate the protection on gastric mucosa against ulcers, rats were treated with fractions from leaf extract prior to ethanol-induced ulcers. The original fraction obtained as ethanol soluble fraction from hot aqueous extract was able to protect de gastric mucosa, and this effect was retained in the ethyl acetate fraction, obtained from liquid/liquid fractionation. The main compound in this fraction was isolated and chemically characterized by nuclear magnetic resonance and mass spectrometry, assisted by isopropylidene derivatization which gave rise a mass increment of 40 units. Therefore, the underivatized compound that had m/z 515.119 [M-H](-) was shifted to m/z 555.151, being confirmed as 1,3-O-dicaffeoylquinic acid, which presented an ED50 of 57 µg kg(-1) on gastric protection, lesser than the therapeutic concentration of omeprazole (40 mg kg(-1)).

  11. Temporal trends of perfluoroalkane sulfonic acids and their sulfonamide-based precursors in herring from the Swedish west coast 1991-2011 including isomer-specific considerations.

    PubMed

    Ullah, Shahid; Huber, Sandra; Bignert, Anders; Berger, Urs

    2014-04-01

    A method was developed for simultaneous analysis of perfluoroalkane sulfonic acids (PFSAs) and their sulfonamide-based precursors (perfluoroalkane sulfonamidoacetic acids (FASAAs), sulfonamides (FASAs), and sulfonamidoethanols (FASEs)) in fish muscle. Extraction was performed with acetonitrile followed by a clean-up and fractionation step and instrumental analysis by UPLC/MS/MS and GC/MS. Time trends of PFSAs and their precursors in herring muscle samples originating from the Kattegat at the west coast of Sweden were investigated covering the years 1991-2011. The following analytes were detected, all with decreasing or unchanged trends between 1991 and 2011: Perfluorobutane sulfonic acid (PFBS, below the method detection limit (acid (PFHxS, 9-38pg/g), perfluorooctane sulfonic acid (PFOS, 240-930pg/g), perfluorodecane sulfonic acid (PFDS, acid (MeFOSAA and EtFOSAA, 2-39 and 2-31pg/g, respectively) and perfluorooctane sulfonamide (FOSA, 78-920pg/g). The highest concentrations were found for PFOS and FOSA around the turn of the century. Shorter disappearance half-lives were observed for precursors compared to PFSAs. Assuming that these trend differences are representative for fish consumed by the general Swedish population, this observation suggests that the relative contribution of precursors to total human exposure to PFOS via fish intake has decreased in Sweden over the study period. PFOS precursors in fish may have constituted a significant indirect exposure pathway for PFOS in the 1990s. Isomer-specific analysis of PFOS and FOSA revealed <10% relative contributions of branched isomers to total PFOS and total FOSA. Furthermore, the percentage branched isomers decreased over time for both compounds. These findings are contrary to patterns and temporal trends of PFOS isomers commonly found in human serum. In combination with literature data on isomer patterns

  12. Selective microbial degradation of saturated methyl branched chain fatty acid isomers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Three strains of Pseudomonas bacteria were screened for their capabilities of degrading chemically synthesized saturated branched-chain fatty acids (sbc-FAs). Mixtures of sbc-FAs with the methyl-branch located at various locales along the fatty acid were used as a carbon feedstock in shake-flask cu...

  13. Two new antioxidant malonated caffeoylquinic acid isomers in fruits of wild eggplant relatives

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fruits of both the cultivated eggplant species Solanum melongena and its wild relative Solanum incanum have a high content of hydroxycinnamic acid conjugates, which along with other phenylpropanoids are implicated in the human health benefits of various fruits and vegetables. Monocaffeoylquinic acid...

  14. Estimating successive pKa values of polyprotic acids from ab initio molecular dynamics using metadynamics: the dissociation of phthalic acid and its isomers.

    PubMed

    Tummanapelli, Anil Kumar; Vasudevan, Sukumaran

    2015-03-01

    Estimation of the dissociation constant, or pKa, of weak acids continues to be a central goal in theoretical chemistry. Here we show that ab initio Car-Parrinello molecular dynamics simulations in conjunction with metadynamics calculations of the free energy profile of the dissociation reaction can provide reasonable estimates of the successive pKa values of polyprotic acids. We use the distance-dependent coordination number of the protons bound to the hydroxyl oxygen of the carboxylic group as the collective variable to explore the free energy profile of the dissociation process. Water molecules, sufficient to complete three hydration shells surrounding the acid molecule, were included explicitly in the computation procedure. Two distinct minima corresponding to the dissociated and un-dissociated states of the acid are observed and the difference in their free energy values provides the estimate for pKa, the acid dissociation constant. We show that the method predicts the pKa value of benzoic acid in good agreement with experiment and then show using phthalic acid (benzene dicarboxylic acid) as a test system that both the first and second pKa values as well, as the subtle difference in their values for different isomers can be predicted in reasonable agreement with experimental data. PMID:25652329

  15. Estimating successive pKa values of polyprotic acids from ab initio molecular dynamics using metadynamics: the dissociation of phthalic acid and its isomers.

    PubMed

    Tummanapelli, Anil Kumar; Vasudevan, Sukumaran

    2015-03-01

    Estimation of the dissociation constant, or pKa, of weak acids continues to be a central goal in theoretical chemistry. Here we show that ab initio Car-Parrinello molecular dynamics simulations in conjunction with metadynamics calculations of the free energy profile of the dissociation reaction can provide reasonable estimates of the successive pKa values of polyprotic acids. We use the distance-dependent coordination number of the protons bound to the hydroxyl oxygen of the carboxylic group as the collective variable to explore the free energy profile of the dissociation process. Water molecules, sufficient to complete three hydration shells surrounding the acid molecule, were included explicitly in the computation procedure. Two distinct minima corresponding to the dissociated and un-dissociated states of the acid are observed and the difference in their free energy values provides the estimate for pKa, the acid dissociation constant. We show that the method predicts the pKa value of benzoic acid in good agreement with experiment and then show using phthalic acid (benzene dicarboxylic acid) as a test system that both the first and second pKa values as well, as the subtle difference in their values for different isomers can be predicted in reasonable agreement with experimental data.

  16. Effect of feeding on conjugated cis delta 9, trans delta 11-octadecadienoic acid and other isomers of linoleic acid in bovine milk fats.

    PubMed

    Precht, D; Molkentin, J

    1997-12-01

    Almost 2000 bovine milk fats were analysed by gas chromatography to investigate the influence of typical barn and pasture feeding of cows on trans-C18:2 isomers (with at least one trans double bond) including the conjugated linoleic acid cis delta9, trans delta11 (c9,t11) as well as the cis delta9, cis delta12 linoleic acid. Moreover, small cow herds were used to determine the influence of pasture Feeding with young and older grass as well as the impact of an energy deficit or the variation of quantity and technical treatment of fed rape-seed on the content of C18:2 isomers in milk fat. The contents of trans-C18:2 (w/o c9,t11) and c9,t11 in 1756 milk fats on average amounted to 0.63% resp. 0.75%. These contents increased from barn feeding, in winter with 0.46% resp. 0.45% over the transiton period in spring and late autumn with 0.66% resp. 0.76% to pasture feeding in summer with 0.87% resp. 1.20%. Milk fat samples from bulk milk obtained weekly during one year from 4 large West German milk collection areas confirmed and completed the data found for the 1756 milk fats. The percentage of linoleic acid with a mean value of 1.24 (n = 1756) varied irregularly during the different feeding periods. The content of the conjugated linoleic acid c9,t11 could be raised considerably up to triple the normal amount by different changes in feeding. However, the content of trans-C18:1 fatty acids was strongly increased as well, respectively.

  17. Effect of feeding on conjugated cis delta 9, trans delta 11-octadecadienoic acid and other isomers of linoleic acid in bovine milk fats.

    PubMed

    Precht, D; Molkentin, J

    1997-12-01

    Almost 2000 bovine milk fats were analysed by gas chromatography to investigate the influence of typical barn and pasture feeding of cows on trans-C18:2 isomers (with at least one trans double bond) including the conjugated linoleic acid cis delta9, trans delta11 (c9,t11) as well as the cis delta9, cis delta12 linoleic acid. Moreover, small cow herds were used to determine the influence of pasture Feeding with young and older grass as well as the impact of an energy deficit or the variation of quantity and technical treatment of fed rape-seed on the content of C18:2 isomers in milk fat. The contents of trans-C18:2 (w/o c9,t11) and c9,t11 in 1756 milk fats on average amounted to 0.63% resp. 0.75%. These contents increased from barn feeding, in winter with 0.46% resp. 0.45% over the transiton period in spring and late autumn with 0.66% resp. 0.76% to pasture feeding in summer with 0.87% resp. 1.20%. Milk fat samples from bulk milk obtained weekly during one year from 4 large West German milk collection areas confirmed and completed the data found for the 1756 milk fats. The percentage of linoleic acid with a mean value of 1.24 (n = 1756) varied irregularly during the different feeding periods. The content of the conjugated linoleic acid c9,t11 could be raised considerably up to triple the normal amount by different changes in feeding. However, the content of trans-C18:1 fatty acids was strongly increased as well, respectively. PMID:9499182

  18. Isomers/enantiomers of perfluorocarboxylic acids: Method development and detection in environmental samples

    EPA Science Inventory

    Perfluoroalkyl substances are globally distributed in both urban and remote settings, and routinely are detected in wildlife, humans, and the environment. One of the most prominent and routinely detected perfluoroalkyl substances is perfluorooctanoic acid (PFOA), which has been s...

  19. The effects of conjugated linoleic acid isomers cis-9,trans-11 and trans-10,cis-12 on in vitro bovine embryo production and cryopreservation.

    PubMed

    Absalón-Medina, V A; Bedford-Guaus, S J; Gilbert, R O; Siqueira, L C; Esposito, G; Schneider, A; Cheong, S H; Butler, W R

    2014-10-01

    Conjugated linoleic acid (CLA) isomers can affect the lipid profile and signaling of cells and thereby alter their function. A total of 5,700 bovine oocytes were used in a structured series of experiments to test the effects of CLA cis-9,trans-11 and CLA trans-10,cis-12 in vitro. In experiment 1, high doses of each CLA isomer during in vitro maturation (IVM) were compared with high or low doses during the entire in vitro culture (IVC) of parthenogenetic embryos. High doses of the CLA isomers ranged from 50 to 200 μM and low doses were 15 and 25 μM. In experiment 2, the low doses of each CLA isomer were tested during IVM/IVC on embryos produced by in vitro fertilization (IVF). Experiment 3 compared the effects of 15 μM doses of each CLA isomer during IVM or IVC of IVF embryos. In experiment 4, post-rewarming survival rates and blastomere counts were assessed for embryos supplemented with each CLA isomer during IVM or for 36 h before vitrification. In experiment 1, when either CLA isomer was provided only during IVM, we observed no effects on overall rates of maturation, cleavage, or blastocysts (92.2 ± 1.6%, 78.3 ± 4.1%, and 28.9 ± 5.1%, respectively). However, high doses of each CLA isomer, but not low doses, during the entire embryo culture period decreased blastocyst rates (5-20%) in a dose-dependent manner. Cleavage rates improved with 15 or 50 μM CLA trans-10,cis-12. Progesterone concentrations in maturation media were significantly increased by high doses of each CLA isomer compared with control, but low doses of CLA isomers had no effect. In experiment 2 with IVF embryos, low doses of each CLA isomer did not alter cleavage rates (average 84.9 ± 1.9%) and only 25 μM CLA trans-10,cis-12 during IVC reduced blastocyst rates below those of controls (25.5 ± 2.1 vs. 38.2 ± 2.3%). The lipid content of embryos was increased and relative expression of the BIRC5 (baculoviral IAP repeat containing 5) gene was depressed by CLA trans-10,cis-12. In experiment 3

  20. Measurement of Internal Acyl Migration Reaction Kinetics Using Directly Coupled HPLC-NMR:  Application for the Positional Isomers of Synthetic (2-Fluorobenzoyl)-d-glucopyranuronic Acid.

    PubMed

    Sidelmann, U G; Hansen, S H; Gavaghan, C; Carless, H A; Lindon, J C; Farrant, R D; Wilson, I D; Nicholson, J K

    1996-08-01

    Ester glucuronides (1-O-acyl-β-d-glucopyranuronates) of many drugs may undergo internal acyl migration reactions, resulting in the formation of new positional isomers with both α- and β-anomers. We illustrate here a novel approach for the direct investigation of the acyl migration kinetics of ester glucuronides and show the application with respect to the isomers of synthetic (2-fluorobenzoyl)-d-glucopyranuronic acid. Individual isomers were separated from an equilibrium mixture containing the β-1-O-acyl, α- and β-2-O-acyl, α- and β-3-O-acyl, and α- and β-4-O-acyl isomers at pH 7.4 in 20 mM phosphate buffer. The interconverting isomers were separated using reversed-phase HPLC and pumped directly into a dedicated on-line NMR flow probe in a 600 MHz NMR spectrometer. The flow was stopped with each isomer in the NMR flow probe, and sequential NMR spectra were collected at 25 °C, allowing direct measurement of the production of positional isomers from each selectively isolated glucuronide isomer. All of the positional isomers and anomers were characterized, and relative quantities determined, and a kinetic model describing the rearrangement reactions was constructed. The acyl migration reaction kinetics were simulated using a theoretical approach using nine first-order rate constants determined for the acyl migration reactions and six first-order rate constants describing the mutarotation each of the 2-, 3-, and 4-positional isomers. The rate constants (in h(-)(1)) for the rearrangement reactions of the 2-fluorobenzoyl glucuronide isomers were as follows:  β-1-O-acyl, 0.29 ± 0.01; α-2-O-acyl, 0.11 ± 0.01; β-2-O-acyl, 0.07 ± 0.01; α-3-O-acyl, 0.10 ± 0.01; β-3-O-acyl, 0.09 ± 0.01; α-4-O-acyl, 0.09 ± 0.01; and β-4-O-acyl, 0.06 ± 0.01. The α- and β-anomerization rates were estimated on the basis of the kinetics model; the anomerization rates of the 4-O-acyl isomers were additionally determined experimentally using directly coupled HPLC-NMR. The

  1. Isomer-sensitive deboronation in reductive aminations of aryl boronic acids

    DOE PAGES

    Jones, Brad Howard; Wheeler, David R.; Wheeler, Jill S.; Miller, Lance Lee; Alam, Todd M.; Spoerke, Erik David

    2015-09-05

    Deboronation is observed during the reductive amination of formylphenylboronic acid (FPBA) to the amine termini and side chains of peptides. This deboronation is sensitive to the isomerism of the boronic acid (BA), with ortho-FPBA yielding complete deboronation in the preparation of an N-terminally-modified dipeptide. The observed behavior is also clearly mediated by the chemical identity of the amine substrate. These results reveal a previously undocumented subtlety of BA functionalization and highlight the importance of thorough spectroscopic characterization in the preparation of peptide and small molecule BAs.

  2. Isomer-sensitive deboronation in reductive aminations of aryl boronic acids

    SciTech Connect

    Jones, Brad Howard; Wheeler, David R.; Wheeler, Jill S.; Miller, Lance Lee; Alam, Todd M.; Spoerke, Erik David

    2015-09-05

    Deboronation is observed during the reductive amination of formylphenylboronic acid (FPBA) to the amine termini and side chains of peptides. This deboronation is sensitive to the isomerism of the boronic acid (BA), with ortho-FPBA yielding complete deboronation in the preparation of an N-terminally-modified dipeptide. The observed behavior is also clearly mediated by the chemical identity of the amine substrate. These results reveal a previously undocumented subtlety of BA functionalization and highlight the importance of thorough spectroscopic characterization in the preparation of peptide and small molecule BAs.

  3. Atlas of Nuclear Isomers

    SciTech Connect

    Jain, Ashok Kumar; Maheshwari, Bhoomika; Garg, Swati; Patial, Monika; Singh, Balraj

    2015-09-15

    We present an atlas of nuclear isomers containing the experimental data for the isomers with a half-life ≥ 10 ns together with their various properties such as excitation-energy, half-life, decay mode(s), spin-parity, energies and multipolarities of emitted gamma transitions, etc. The ENSDF database complemented by the XUNDL database has been extensively used in extracting the relevant data. Recent literature from primary nuclear physics journals, and the NSR bibliographic database have been searched to ensure that the compiled data Table is as complete and current as possible. The data from NUBASE-12 have also been checked for completeness, but as far as possible original references have been cited. Many interesting systematic features of nuclear isomers emerge, some of them new; these are discussed and presented in various graphs and figures. The cutoff date for the extraction of data from the literature is August 15, 2015.

  4. Gas-Phase Formation Rates of Nitric Acid and Its Isomers Under Urban Conditions

    NASA Technical Reports Server (NTRS)

    Okumura, M.; Mollner, A. K.; Fry, J. L.; Feng, L.

    2005-01-01

    Ozone formation in urban smog is controlled by a complex set of reactions which includes radical production from photochemical processes, catalytic cycles which convert NO to NO2, and termination steps that tie up reactive intermediates in long-lived reservoirs. The reaction OH + NO2 + M -4 HONO2 + M (la) is a key termination step because it transforms two short-lived reactive intermediates, OH and NO2, into relatively long-lived nitric acid. Under certain conditions (low VOC/NOx), ozone production in polluted urban airsheds can be highly sensitive to this reaction, but the rate parameters are not well constrained. This report summarizes the results of new laboratory studies of the OH + NO2 + M reaction including direct determination of the overall rate constant and branching ratio for the two reaction channels under atmospherically relevant conditions.

  5. Synthesis of an Isomer of the Decalinoyltetramic Acid Methiosetin by a Stereocontrolled IMDA Reaction of a Metal-Chelated 3-Trienoyltetramate.

    PubMed

    Winterer, Markus; Kempf, Karl; Schobert, Rainer

    2016-09-01

    An isomer of the 3-decalinoyltetramic acid methiosetin was synthesized for the first time. The decalin moiety was established by a late-stage intramolecular Diels-Alder cyclization catalyzed by Me2AlCl or La(OTf)3. Its high diastereoselectivity arose from stereoinduction by a well-defined metal O,O-chelate complex of the 3-acyltetramic acid moiety. The nature of the metal and the bulkiness of the residues at the tetramic acid chelator are decisive for the stereochemical outcome.

  6. Synthesis of an Isomer of the Decalinoyltetramic Acid Methiosetin by a Stereocontrolled IMDA Reaction of a Metal-Chelated 3-Trienoyltetramate.

    PubMed

    Winterer, Markus; Kempf, Karl; Schobert, Rainer

    2016-09-01

    An isomer of the 3-decalinoyltetramic acid methiosetin was synthesized for the first time. The decalin moiety was established by a late-stage intramolecular Diels-Alder cyclization catalyzed by Me2AlCl or La(OTf)3. Its high diastereoselectivity arose from stereoinduction by a well-defined metal O,O-chelate complex of the 3-acyltetramic acid moiety. The nature of the metal and the bulkiness of the residues at the tetramic acid chelator are decisive for the stereochemical outcome. PMID:27551958

  7. Conjugated linoleic acids modulate UVR-induced IL-8 and PGE2 in human skin cells: potential of CLA isomers in nutritional photoprotection.

    PubMed

    Storey, Amy; Rogers, Julia S; McArdle, Francis; Jackson, Malcolm J; Rhodes, Lesley E

    2007-06-01

    Conjugated linoleic acids (CLA), derivatives of linoleic acid found in food products, inhibit chemically induced skin cancers in mice. However, their potential photoprotective properties remain unexplored. We examined whether CLA may modulate ultraviolet radiation (UVR)-induced secretion of interleukin (IL)-8 and prostaglandin E2 (PGE(2)), mediators implicated in UVR-induced inflammation and carcinogenesis, in human skin cells. Since tumour necrosis factor (TNF)-alpha is an early mediator of UVR effects, we also examined influence of CLA on TNF-alpha-induced mediator release. HaCaT keratinocytes were supplemented with CLA isomers cis-9-trans-11 (c9,t11-CLA; > or =90%), trans-10-cis-12 (t10,c12-CLA; > or =90%) or all trans-trans isomers (tt-CLA; 23.7%) in tetrahydrofuran/fetal calf serum (THF/FCS) or THF/FCS control. Supplementation of keratinocytes with c9,t11-CLA reduced Ultraviolet B(UVB)-induced IL-8 from 37 113 +/- 2903 pg/ng protein in control cells to 14 167 +/- 2063 pg/ng protein (P < 0.001). Similarly, t10,c12-CLA reduced UVB-induced IL-8 to 9786 +/- 1291.5 pg/ng protein (P < 0.001). Additionally, t10,c12-CLA and tt-CLA inhibited TNF-alpha-induced IL-8 from 11 669 +/- 1692 pg/ng protein in control cells to 5540 +/- 191 (P < 0.001) and 8082 +/- 1298 pg/ng (P < 0.01) protein, respectively. UVB-induced PGE(2) release was reduced by tt-CLA supplementation, from 4.8 +/- 1.2 to 1.6 +/- 0.8 pg/mg protein (P < 0.01), but increased by t10,c12-CLA to 8.8 +/- 1 pg/mg protein (P < 0.001). Influence of CLA on UVB-induced PGE(2) release was further explored in CCD922SK dermal fibroblasts. CLA isomers reduced UVB-induced PGE(2) in fibroblasts, reaching significance with c9,t11-CLA (98 +/- 5 falling to 0 pg/mg protein, P < 0.05). Hence, CLA isomers differentially modulate UVB effects on skin cells in vitro. CLA-containing foods have potential in photoprotection; the cutaneous effects of individual isomers warrant clinical study.

  8. Extent and mechanism of solvation and partitioning of isomers of substituted benzoic acids: a thermodynamic study in the solid state and in solution.

    PubMed

    Perlovich, German L; Volkova, Tatyana V; Manin, Alex N; Bauer-Brandl, Annette

    2008-09-01

    Temperature dependency of saturated vapour pressure and thermochemical characteristics of fusion processes for 2-, 3- and 4-methoxybenzoic acids (anisic acids) were measured and thermodynamic functions of sublimation, fusion, and evaporation calculated. A new approach to split specific and nonspecific energetic terms in the crystal lattice was developed. For methoxybenzoic acid isomers as well as for a number of analogous molecules, a parameter describing molecular packing density by the ratio of free volume of the molecules in the crystal lattice and van der Waals molecular volume is defined. Its relationship to Gibbs energy of sublimation and to the respective melting points was analysed. Temperature dependencies of solubility in buffers with pH 2.0 and 7.4, n-octanol and n-hexane were measured. The thermodynamic functions of solubility, solvation and transfer processes were deduced. Concentration dependence of partition coefficients for the outlined isomers was measured. Specific and nonspecific solvation terms were distinguished using the transfer from the 'inert' n-hexane to the other solvents. Comparison analysis of specific and nonspecific interactions in the solid state and in solution was carried out. A diagram enabling analysis of the mechanism of the partitioning process was applied. It was found that position of substituents essentially affects the mechanism of partitioning in buffer pH 2.0, however, at pH 7.4, the mechanism is independent of the position of the substituent. PMID:18200548

  9. Decomposition of dinitrotoluene isomers and 2,4,6-trinitrotoluene in spent acid from toluene nitration process by ozonation and photo-ozonation.

    PubMed

    Chen, Wen-Shing; Juan, Chien-Neng; Wei, Kuo-Ming

    2007-08-17

    Ozone and UV/O3 were employed to mineralize dinitrotoluene (DNT) isomers and 2,4,6-trinitrotoluene (TNT) in spent acid from toluene nitration process. The oxidative degradation tests were carried out to elucidate the influence of various operating variables on the performance of mineralization of total organic compounds (TOC) in spent acid, including reaction temperature, intensity of UV (254 nm) irradiation, dosage of ozone and concentration of sulfuric acid. It is remarkable that the nearly complete mineralization of organic compounds can be achieved by ozonation combined with UV irradiation. Nevertheless, the hydroxyl radicals (*OH) would not be generated by either ozone decomposition or photolysis of ozone under the experimental condition of this study. According to the spectra identified by gas chromatograph/mass spectrometer (GC/MS) and further confirmed by gas chromatograph/flame ionization detector (GC/FID), the multiple oxidation pathways of DNT isomers are given, which include o-, m-, p-mononitrotoluene (MNT) and 1,3-dinitrobenzene, respectively. In addition, oxidative degradation of 2,4,6-TNT leads to a 1,3,5-trinitrobenzene intermediate. PMID:17257749

  10. Decomposition of dinitrotoluene isomers and 2,4,6-trinitrotoluene in spent acid from toluene nitration process by ozonation and photo-ozonation.

    PubMed

    Chen, Wen-Shing; Juan, Chien-Neng; Wei, Kuo-Ming

    2007-08-17

    Ozone and UV/O3 were employed to mineralize dinitrotoluene (DNT) isomers and 2,4,6-trinitrotoluene (TNT) in spent acid from toluene nitration process. The oxidative degradation tests were carried out to elucidate the influence of various operating variables on the performance of mineralization of total organic compounds (TOC) in spent acid, including reaction temperature, intensity of UV (254 nm) irradiation, dosage of ozone and concentration of sulfuric acid. It is remarkable that the nearly complete mineralization of organic compounds can be achieved by ozonation combined with UV irradiation. Nevertheless, the hydroxyl radicals (*OH) would not be generated by either ozone decomposition or photolysis of ozone under the experimental condition of this study. According to the spectra identified by gas chromatograph/mass spectrometer (GC/MS) and further confirmed by gas chromatograph/flame ionization detector (GC/FID), the multiple oxidation pathways of DNT isomers are given, which include o-, m-, p-mononitrotoluene (MNT) and 1,3-dinitrobenzene, respectively. In addition, oxidative degradation of 2,4,6-TNT leads to a 1,3,5-trinitrobenzene intermediate.

  11. The Eskimo diet. Prophylactic effects ascribed to the balanced presence of natural cis unsaturated fatty acids and to the absence of unnatural trans and cis isomers of unsaturated fatty acids.

    PubMed

    Booyens, J; Louwrens, C C; Katzeff, I E

    1986-12-01

    In addition to the well recognised roles of eicosapentaenoic acid and possibly docosahexaenoic acid, there are two other major important, but unrecognised, features of the traditional Eskimo staple diet namely that it contains the unsaturated fatty acids (UFA) cis oleic, cis linoleic and cis alpha-linolenic as well as their respective C20 and C22 metabolites in physiologically optimal concentrations and, it is virtually totally devoid of unnatural and potentially hazardous trans and cis isomers of these fatty acids. Large quantities of unnatural trans and cis isomers of UFA are found in the Western diet as partially hydrogenated UFA in many foods. These isomers are formed during the manufacture of margarines and related compounds, as food contaminants during excessive heating of cooking oils for deep-frying and other excessive heat-requiring mass food preparation procedures and it is suggested, as the result of excessive feeding with an unnatural diet of ruminants and non-ruminants for increased meat and/or milk production and of poultry for increased egg and/or meat production. These isomers have been shown to display potentially hazardous metabolic effects which include the competitive inhibition of UFA metabolism at various steps and have been causally implicated in the etiology of ischemic heart disease and cancer. It is suggested that the myth of the safety of trans fatty acids arises from misinterpretation of the observation that increasing dietary cis linoleic acid reduces the toxic effects of trans UFA. It is suggested that the decrease of 20% in the ischemic heart disease mortality in the USA during the past two decades is directly related to a shift in the dietary ratio of unnatural trans and cis UFA isomers: cis linoleic acid in favour of the latter. It is predicted that this ratio will be found to correlate with ischemic heart disease patterns in other countries. Eskimos consume the bulk of their food frozen, raw or dried, seldom boiled, but never deep

  12. Abundances of Triacylglycerol Positional Isomers and Enantiomers Comprised of a Dipalmitoylglycerol Backbone and Short- or Medium-chain Fatty Acids in Bovine Milk Fat.

    PubMed

    Nagai, Toshiharu; Watanabe, Natsuko; Yoshinaga, Kazuaki; Mizobe, Hoyo; Kojima, Koichi; Kuroda, Ikuma; Odanaka, Yuki; Saito, Tadao; Beppu, Fumiaki; Gotoh, Naohiro

    2015-01-01

    Bovine milk fat (BMF) is composed of triacylglycerols (TAG) rich in palmitic acid (P), oleic acid (O), and short-chain or medium-chain fatty acids (SCFAs or MCFAs). The composition and binding positions of the fatty acids on the glycerol backbone determine their physical and nutritional properties. SCFAs and MCFAs are known to characteristically bind to the sn-3 position of the TAGs in BMF; however, there are very few non-destructive analyses of TAG enantiomers binding the fatty acids at this position. We previously reported a method to resolve the enantiomers of TAGs, binding both long-chain saturated fatty acid and unsaturated fatty acid at the sn-1 and 3 positions, in palm oil, fish oil, and marine mammal oil using chiral HPLC. Here, we further developed a method to resolve several TAG enantiomers containing a dipalmitoyl (PP) glycerol backbone and one SCFA (or MCFA) in BMF. We revealed that the predominant TAG structure in BMF was homochiral, such as 1,2-dipalmitoyl-3-butyroyl-sn-glycerol. This is the first quantitative determination of many TAG enantiomers, which bind to a SCFA or MCFA, in BMF was evaluated simultaneously. Furthermore, the results indicated that the amount ratios of the positional isomers and enantiomers of TAGs consisting of a dipalmitoyl (PP) glycerol backbone and SCFA (or MCFA), resembled the whole TAG structures containing the other diacylglycerol backbones consisting of P, O, myristic acid, and/or stearic acid in BMF. PMID:26329769

  13. A novel derivatization-based liquid chromatography tandem mass spectrometry method for quantitative characterization of naphthenic acid isomer profiles in environmental waters.

    PubMed

    Woudneh, Million B; Coreen Hamilton, M; Benskin, Jonathan P; Wang, Guanghui; McEachern, Preston; Cosgrove, John R

    2013-06-01

    A method for quantitative characterization of naphthenic acid (NA) isomer groups by carbon number and extent of cyclization was developed and validated with water samples from northern Alberta. Following solid phase extraction, NAs undergo derivatization with N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide (EDC) allowing detection by positive electrospray ionization tandem mass spectrometry (+ESI)-MS/MS. NA-EDC derivatives produce a common product ion by MS/MS, regardless of structure of the starting NA. Thus, approximately constant relative response factors (RRFs) were assumed for the various isomer groups that elute at a given point in the elution gradient (supported by calculated RRFs for individual model NAs), facilitating quantification using a single standard (1-pyrenebutyric acid). To reduce the impact of major background fatty acids on NA data, the method employed an optimized liquid chromatography method that separated straight chain (Z=0) analytes from other NAs. Method validation was performed at two spiking levels (7.72μg and 38.6μg total refined Merichem per 500mL of reagent water) and good accuracy (mean recoveries of 82.4±2.5% and 93.0±2.6%, respectively; range ~50-130%) and precision (<17% RSD) were achieved at both spiking levels for all 60 NA isomer groups. The method also performed well in an independent method comparison study in which method accuracy values of 107%, 120%, and 121% were obtained for 2 spiked reagent waters (1mg/L and 50mg/L NAs) and spiked Athabasca River water (0.035mg/L NAs), respectively. Application of the method to samples from northern Alberta revealed that NA concentrations decreased in the order: process water (52.8mg/L)>tailings pond water (30.6mg/L)>well water (0.086mg/L)>surface water (0.007mg/L), and that samples were distinguishable by NA isomer profile using Principal components analysis.

  14. High-Throughput Analysis of Methylmalonic Acid in Serum, Plasma, and Urine by LC-MS/MS. Method for Analyzing Isomers Without Chromatographic Separation.

    PubMed

    Kushnir, Mark M; Nelson, Gordon J; Frank, Elizabeth L; Rockwood, Alan L

    2016-01-01

    Measurement of methylmalonic acid (MMA) plays an important role in the diagnosis of vitamin B12 deficiency. Vitamin B12 is an essential cofactor for the enzymatic carbon rearrangement of methylmalonyl-CoA (MMA-CoA) to succinyl-CoA (SA-CoA), and the lack of vitamin B12 leads to elevated concentrations of MMA. Presence of succinic acid (SA) complicates the analysis because mass spectra of MMA and SA are indistinguishable, when analyzed in negative ion mode and the peaks are difficult to resolve chromatographically. We developed a method for the selective analysis of MMA that exploits the significant difference in fragmentation patterns of di-butyl derivatives of the isomers MMA and SA in a tandem mass spectrometer when analyzed in positive ion mode. Tandem mass spectra of di-butyl derivatives of MMA and SA are very distinct; this allows selective analysis of MMA in the presence of SA. The instrumental analysis is performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) in positive ion mode, which is, in combination with selective extraction of acidic compounds, is highly selective for organic acids with multiple carboxyl groups (dicarboxylic, tricarboxylic, etc.). In this method organic acids with a single carboxyl group are virtually undetectable in the mass spectrometer; the only organic acid, other than MMA, that is detected by this method is its isomer, SA. Quantitative measurement of MMA in this method is performed using a deconvolution algorithm, which mathematically resolves the signal corresponding to MMA and does not require chromatographic resolution of the MMA and SA peaks. Because of its high selectivity, the method utilizes isocratic chromatographic separation; reconditioning and re-equilibration of the chromatographic column between injections is unnecessary. The above features of the method allow high-throughput analysis of MMA with analysis cycle time of 1 min. PMID:26602128

  15. High-Throughput Analysis of Methylmalonic Acid in Serum, Plasma, and Urine by LC-MS/MS. Method for Analyzing Isomers Without Chromatographic Separation.

    PubMed

    Kushnir, Mark M; Nelson, Gordon J; Frank, Elizabeth L; Rockwood, Alan L

    2016-01-01

    Measurement of methylmalonic acid (MMA) plays an important role in the diagnosis of vitamin B12 deficiency. Vitamin B12 is an essential cofactor for the enzymatic carbon rearrangement of methylmalonyl-CoA (MMA-CoA) to succinyl-CoA (SA-CoA), and the lack of vitamin B12 leads to elevated concentrations of MMA. Presence of succinic acid (SA) complicates the analysis because mass spectra of MMA and SA are indistinguishable, when analyzed in negative ion mode and the peaks are difficult to resolve chromatographically. We developed a method for the selective analysis of MMA that exploits the significant difference in fragmentation patterns of di-butyl derivatives of the isomers MMA and SA in a tandem mass spectrometer when analyzed in positive ion mode. Tandem mass spectra of di-butyl derivatives of MMA and SA are very distinct; this allows selective analysis of MMA in the presence of SA. The instrumental analysis is performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) in positive ion mode, which is, in combination with selective extraction of acidic compounds, is highly selective for organic acids with multiple carboxyl groups (dicarboxylic, tricarboxylic, etc.). In this method organic acids with a single carboxyl group are virtually undetectable in the mass spectrometer; the only organic acid, other than MMA, that is detected by this method is its isomer, SA. Quantitative measurement of MMA in this method is performed using a deconvolution algorithm, which mathematically resolves the signal corresponding to MMA and does not require chromatographic resolution of the MMA and SA peaks. Because of its high selectivity, the method utilizes isocratic chromatographic separation; reconditioning and re-equilibration of the chromatographic column between injections is unnecessary. The above features of the method allow high-throughput analysis of MMA with analysis cycle time of 1 min.

  16. Modelling Study of Interstellar Ethanimine Isomers

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    Ethanimine (CH3CHNH) , including both the E- and Z- isomers, were detected towards the star-forming region Sgr B2(N) using the GBT PRIMOS data (Loomis et al 2013), and were recently imaged by the ACTA (Corby et al. 2015). These aldimines can serve as precursors of biological molecules such as amino acids thus are considered prebiotic molecules in interstellar medium. In this study, we present chemical simulations of ethanimine with various physical conditions. From models for Sgr B2(N) and environs, calculated ethanimine abundances show reasonable agreement with observed values, while the translucent cloud models yield much lower abundances. These results agree with locations suggested by observations that ethanimine isomers were detected in the foreground of the shells of the hot core.

  17. Moderate doses of conjugated linoleic acid isomers mix contribute to lowering body fat content maintaining insulin sensitivity and a noninflammatory pattern in adipose tissue in mice.

    PubMed

    Parra, Pilar; Serra, Francisca; Palou, Andreu

    2010-02-01

    Conjugated linoleic acid (CLA) modulates body composition, especially by reducing adipose tissue. However, despite the increasing knowledge about CLA's beneficial effects on obesity management, the mechanism of action is not yet fully understood. Furthermore, in some human studies fat loss is accompanied by impairment in insulin sensitivity, especially when using the trans-10,cis-12 isomer. The aim of this work was to study the effects of moderate doses of CLA on body fat deposition, cytokine profile and inflammatory markers in mice. Mice were orally treated with a mixture of CLA isomers, cis-9,trans-11 and trans-10,cis-12 (50:50), for 35 days with doses of CLA1 (0.15 g CLA/kg body weight) and CLA2 (0.5 g CLA/kg body weight). CLA had discrete effects on body weight but caused a clear reduction in fat mass (retroperitoneal and mesenteric as the most sensitive depots), although no other tissue weights were affected. Glucose and insulin were not altered by CLA treatment, and maintenance of glucose homeostasis was observed even under insulin overload. The study of gene expression (Emr1, MCP-1, IL-6, TNFalpha, PPARgamma2 and iNOS) either in adipocytes and/or in the stromal vascular fraction indicated that CLA does not lead to the infiltration of macrophages in adipose tissue or to the induction of expression of pro-inflammatory cytokines. The use of a mixture of both isomers, as well as moderate doses of CLA, is able to induce a reduction of fat gain without an impairment of adipose tissue function while preserving insulin sensitivity.

  18. Identification of the geometrical isomers of α-linolenic acid using gas chromatography/mass spectrometry with a binary decision tree.

    PubMed

    Hejazi, Leila; Hibbert, David Brynn; Ebrahimi, Diako

    2011-01-30

    Gas chromatography, using a highly polar column, low energy (30 eV) electron ionization mass spectrometry and multivariate curve resolution, are combined to obtain the mass spectra of all eight geometrical isomers of α-linolenic acid. A step by step Student's t-test is performed on the m/z 50-294 to identify the m/z by which the geometries of the double bonds could be discriminated. The most intense peak discriminates between cis (m/z 79) and trans (m/z 95) at the central (carbon 12) position. The configuration at carbon 15 is then distinguished by m/z 68 and 236, and finally the geometry at carbon 9 is determined by m/z 93, 173, 191 and 236. A three-question binary tree is developed based on the normalized intensities of these ions by which the identity of any given isomer of α-linolenic is accurately determined. Application of Bayes theorem to data from independent samples shows that the complete configuration is determined correctly with a minimum probability of 87%.

  19. 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.

  20. Dachtal Isomers and Acidic Herbicides and Pesticides in Eggs of Osprey (Pandion haliaetus) from the Seattle and Everett Areas, Washington, U.S.A

    USGS Publications Warehouse

    Chu, S.; Henny, Charles J.; Kaiser, James L.; Drouillard, K.G.; Haffner, G.D.; Letcher, R.J.

    2007-01-01

    Current-use chlorophenoxy herbicides including 2,4-dichlorophenoxyacetic acid, dicamba, triclopyr, dicamba, dimethyl tetrachloroterephthalate (DCPA or dacthal), and the metabolite of pyrethroids, 3-phenoxybenzoic acid (3-PBA), and the fungicide, chlorothalonil, were investigated in the eggs of osprey (Pandion haliaetus) that were collected from 15 sites from five study areas Puget Sound/Seattle area of Washington State, USA. DCPA differs from acidic chlorophenoxy herbicides, and is not readily hydrolyzed to free acid or acid metabolites, and thus we developed a new method. Of the 12 chlorophenoxy herbicides and chlorothalonil analyzed only DCPA could be quantified at six of these sites (2.0 to 10.3 pg/g fresh weight). However, higher levels (6.9 to 85.5 pg/g fresh weight) of the unexpected DCPA structural isomer, dimethyl tetrachlorophthalate (diMe-TCP) were quantified in eggs from all sites. diMe-TCP concentrations tended to be higher in eggs from the Everett Harbor area. As diMe-TCP is not an industrial product, and not commercially available, the source of diMe-TCP is unclear. Regardless, these findings indicate that DCPA and diMe-TCP can be accumulated in the food chain of fish-eating osprey, and transferred in ovo to eggs, and thus may be of concern to the health of the developing chick and the general reproductive health of this osprey population.

  1. Influence of Vaginal Bacteria and d- and l-Lactic Acid Isomers on Vaginal Extracellular Matrix Metalloproteinase Inducer: Implications for Protection against Upper Genital Tract Infections

    PubMed Central

    Witkin, Steven S.; Mendes-Soares, Helena; Linhares, Iara M.; Jayaram, Aswathi; Ledger, William J.; Forney, Larry J.

    2013-01-01

    ABSTRACT We evaluated levels of vaginal extracellular matrix metalloproteinase inducer (EMMPRIN) and matrix metalloproteinase (MMP-8) in vaginal secretions in relation to the composition of vaginal bacterial communities and d- and l-lactic acid levels. The composition of vaginal bacterial communities in 46 women was determined by pyrosequencing the V1 to V3 region of 16S rRNA genes. Lactobacilli were dominant in 71.3% of the women, followed by Gardnerella (17.4%), Streptococcus (8.7%), and Enterococcus (2.2%). Of the lactobacillus-dominated communities, 51.5% were dominated by Lactobacillus crispatus, 36.4% by Lactobacillus iners, and 6.1% each by Lactobacillus gasseri and Lactobacillus jensenii. Concentrations of l-lactic acid were slightly higher in lactobacillus-dominated vaginal samples, but most differences were not statistically significant. d-Lactic acid levels were higher in samples containing L. crispatus than in those with L. iners (P < 0.0001) or Gardnerella (P = 0.0002). The relative proportion of d-lactic acid in vaginal communities dominated by species of lactobacilli was in concordance with the proportions found in axenic cultures of the various species grown in vitro. Levels of l-lactic acid (P < 0.0001) and the ratio of l-lactic acid to d-lactic acid (P = 0.0060), but not concentrations of d-lactic acid, were also correlated with EMMPRIN concentrations. Moreover, vaginal concentrations of EMMPRIN and MMP-8 levels were highly correlated (P < 0.0001). Taken together, the data suggest the relative proportion of l- to d-lactic acid isomers in the vagina may influence the extent of local EMMPRIN production and subsequent induction of MMP-8. The expression of these proteins may help determine the ability of bacteria to transverse the cervix and initiate upper genital tract infections. PMID:23919998

  2. Methods for analysis of conjugated linoleic acids and trans-18:1 isomers in dairy fats by using a combination of gas chromatography, silver-ion thin-layer chromatography/gas chromatography, and silver-ion liquid chromatography.

    PubMed

    Cruz-Hernandez, Cristina; Deng, Zeyuan; Zhou, Jianqiang; Hill, Arthur R; Yurawecz, Martin P; Delmonte, Pierluigi; Mossoba, Magdi M; Dugan, Michael E R; Kramer, John K G

    2004-01-01

    Conjugated linoleic acids (CLA) are octadecadienoic acids (18:2) that have a conjugated double-bond system. Interest in these compounds has expanded since CLA were found to be associated with a number of physiological and pathological responses such as cancer, metastases, atherosclerosis, diabetes, immunity, and body fat/protein composition. The main sources of these conjugated fatty acids are dairy fats. Rumen bacteria convert polyunsaturated fatty acids, especially linoleic and linolenic acids, to CLA and numerous trans- containing mono- and diunsaturated fatty acids. It has been established that an additional route of CLA synthesis in ruminants and monogastric animals, including humans, occurs via delta9 desaturation of the trans-18:1 isomers. To date, a total of 6 positional CLA isomers have been found in dairy fats, each occurring in 4 geometric forms (cis,trans; trans,cis; cis,cis; and trans,trans) for a total of 24. All of these CLA isomers can be resolved only by a combination of gas chromatography (GC), using 100 m highly polar capillary columns, and silver-ion liquid chromatography, using 3 of these 25 cm columns in series. Complete analysis of all the trans-18:1 isomers requires prior isolation of trans monoenes by silver-ion thin-layer chromatography (TLC), followed by GC analysis using the same 100 m capillary columns operated at low temperatures starting from 120 degrees C. These analytical techniques are required to assess the purity of commercial CLA preparations, because their purity will affect the interpretation of any physiological and/or biochemical response obtained. Prior assessment of CLA preparations by TLC is also recommended to determine the presence of any other impurities. The availability of pure CLA isomers will permit the evaluation and analysis of individual CLA isomers for their nutritional and biological activity in model systems, animals, and humans. These techniques are also essential to evaluate dairy fats for their content of

  3. Total lipids of Sarda sheep meat that include the fatty acid and alkenyl composition and the CLA and trans-18:1 isomers.

    PubMed

    Santercole, Viviana; Mazzette, Rina; De Santis, Enrico P L; Banni, Sebastiano; Goonewardene, Laki; Kramer, John K G

    2007-04-01

    The total lipids of the longissimus dorsi muscle were analyzed from commercial adult Sarda sheep in Sardina taken from local abattoirs, and in the subsequent year from three local farms in the Sassari region that provided some information on the amount and type of supplements fed to the pasture-fed sheep. The complete lipid analysis of sheep meat included the fatty acids from O-acyl and N-acyl lipids, including the trans- and conjugated linoleic acid (CLA) isomers and the alk-1-enyl ethers from the plasmalogenic lipids. This analysis required the use of a combination of acid- and base-catalyzed methylation procedures, the former to quantitate the O-acyl, N-acyl and alkenyl ethers, and the latter to determine the content of CLA isomers and their metabolites. A combination of gas chromatographic and silver-ion separation techniques was necessary to quantitate all of the meat lipid constituents, which included a prior separation of the trans-octadecenoic acids (18:1) and a separation of fatty acid methyl esters and the dimethylacetals (DMAs) from the acyl and alk-1-enyl ethers, respectively. The alk-1-enyl moieties of the DMAs were analyzed as their stable cyclic acetals. In general, about half of the meat lipids were triacylglycerols, even though excess fat was trimmed from the meat. The higher fat content in the meat appears to be related to the older age of these animals. The variation in the trans-18:1 and CLA isomer profiles of the Sarda sheep obtained from the abattoirs was much greater than in the profiles from the sheep from the three selected farms. Higher levels of 10t-18:1, 7t9c-18:2, 9t11c-18:2 and 10t12c-18:2 were observed in the commercial sheep meat, which reflected the poorer quality diets of these sheep compared to those from the three farms, which consistently showed higher levels of 11t-18:1, 9c11t-18:2 and 11t13c-18:2. In the second study, sheep were provided with supplements during the spring and summer grazing season, which contributed to higher

  4. Development and Optimization of an UPLC-QTOF-MS/MS Method Based on an In-Source Collision Induced Dissociation Approach for Comprehensive Discrimination of Chlorogenic Acids Isomers from Momordica Plant Species.

    PubMed

    Madala, N E; Tugizimana, F; Steenkamp, P A

    2014-01-01

    Chlorogenic acids (CGA) have been profiled in the leaves of Momordica balsamina, Momordica charantia, and Momordica foetida. All three species were found to contain the trans and cis isomers of 4-acyl para-coumaroylquinic acid (pCoQA), caffeoylquinic acid (CQA), and feruloylquinic acid (FQA). To the best of our knowledge, this is the first report of pCoQA and FQA and their cis isomers in these Momordica species. These profiles were obtained by a newly developed UPLC-qTOF-MS method based on the in-source collision induced dissociation (ISCID) method optimized to mimic the MS(2) and MS(3) fragmentation of an ion trap-based MS. The presence of the cis isomers is believed to be due to high UV exposure of these plants. Furthermore, the absence of the 3-acyl and 5-acyl CGA molecules points to a metabolic mark that is unusual and represents a very interesting biochemical phenotype of these species. Our optimized ISCID method was also shown to be able to distinguish between the geometrical isomers of all three forms of CGA, a phenomenon previously deemed impossible with other common mass spectrometry systems used for CGA analyses.

  5. Development and Optimization of an UPLC-QTOF-MS/MS Method Based on an In-Source Collision Induced Dissociation Approach for Comprehensive Discrimination of Chlorogenic Acids Isomers from Momordica Plant Species

    PubMed Central

    Madala, N. E.; Tugizimana, F.; Steenkamp, P. A.

    2014-01-01

    Chlorogenic acids (CGA) have been profiled in the leaves of Momordica balsamina, Momordica charantia, and Momordica foetida. All three species were found to contain the trans and cis isomers of 4-acyl para-coumaroylquinic acid (pCoQA), caffeoylquinic acid (CQA), and feruloylquinic acid (FQA). To the best of our knowledge, this is the first report of pCoQA and FQA and their cis isomers in these Momordica species. These profiles were obtained by a newly developed UPLC-qTOF-MS method based on the in-source collision induced dissociation (ISCID) method optimized to mimic the MS2 and MS3 fragmentation of an ion trap-based MS. The presence of the cis isomers is believed to be due to high UV exposure of these plants. Furthermore, the absence of the 3-acyl and 5-acyl CGA molecules points to a metabolic mark that is unusual and represents a very interesting biochemical phenotype of these species. Our optimized ISCID method was also shown to be able to distinguish between the geometrical isomers of all three forms of CGA, a phenomenon previously deemed impossible with other common mass spectrometry systems used for CGA analyses. PMID:25295221

  6. High spin isomer beam line at RIKEN

    SciTech Connect

    Kishida, T.; Ideguchi, E.; Wu, H.Y.

    1996-12-31

    Nuclear high spin states have been the subject of extensive experimental and theoretical studies. For the production of high spin states, fusion reactions are usually used. The orbital angular momentum brought in the reaction is changed into the nuclear spin of the compound nucleus. However, the maximum induced angular momentum is limited in this mechanism by the maximum impact parameter of the fusion reaction and by the competition with fission reactions. It is, therefore, difficult to populate very high spin states, and as a result, large {gamma}-detector arrays have been developed in order to detect subtle signals from such very high spin states. The use of high spin isomers in the fusion reactions can break this limitation because the high spin isomers have their intrinsic angular momentum, which can bring the additional angular momentum without increasing the excitation energy. There are two methods to use the high spin isomers for secondary reactions: the use of the high spin isomers as a target and that as a beam. A high spin isomer target has already been developed and used for several experiments. But this method has an inevitable shortcoming that only {open_quotes}long-lived{close_quotes} isomers can be used for a target: {sup 178}Hf{sup m2} (16{sup +}) with a half-life of 31 years in the present case. By developing a high spin isomer beam, the authors can utilize various short-lived isomers with a short half-life around 1 {mu}s. The high spin isomer beam line of RIKEN Accelerator Facility is a unique apparatus in the world which provides a high spin isomer as a secondary beam. The combination of fusion-evaporation reaction and inverse kinematics are used to produce high spin isomer beams; in particular, the adoption of `inverse kinematics` is essential to use short-lived isomers as a beam.

  7. A tandem mass spectrometric study of bile acids: interpretation of fragmentation pathways and differentiation of steroid isomers.

    PubMed

    Qiao, Xue; Ye, Min; Liu, Chun-fang; Yang, Wen-zhi; Miao, Wen-juan; Dong, Jing; Guo, De-an

    2012-02-01

    Bile acids are steroids with a pentanoic acid substituent at C-17. They are the terminal products of cholesterol excretion, and play critical physiological roles in human and animals. Bile acids are easy to detect but difficult to identify by using mass spectrometry due to their poly-ring structure and various hydroxylation patterns. In this study, fragmentation pathways of 18 free and conjugated bile acids were interpreted by using tandem mass spectrometry. The analyses were conducted on ion trap and triple quadrupole mass spectrometers. Upon collision-induced dissociation, the conjugated bile acids could cleave into glycine or taurine related fragments, together with the steroid skeleton. Fragmentations of free bile acids were further elucidated, especially by atmospheric pressure chemical ionization mass spectrometry in positive ion mode. Aside from universally observed neutral losses, eliminations occurred on bile acid carbon rings were proposed for the first time. Moreover, four isomeric 5β-cholanic acid hydroxyl derivatives (3α,6α-, 3α,7β-, 3α,7α-, and 3α,12α-) were differentiated using electrospray ionization in negative ion mode: 3α,7β-OH substituent inclined to eliminate H(2)O and CH(2)O(2) groups; 3α,6α-OH substituent preferred neutral loss of two H(2)O molecules; 3α,12α-OH substituent apt to lose the carboxyl in the form of CO(2) molecule; and 3α,7α-OH substituent exhibited no further fragmentation after dehydration. This study provided specific interpretation for mass spectra of bile acids. The results could contribute to bile acid analyses, especially in clinical assays and metabonomic studies.

  8. Separation of fatty acids or methyl esters including positional and geometric isomers by alumina argentation thin-layer chromatography.

    PubMed

    Breuer, B; Stuhlfauth, T; Fock, H P

    1987-07-01

    This paper describes novel and rapid thin-layer chromatography procedures for the analysis of fatty acids and methyl esters using silver-impregnated alumina sheets. These techniques are known in most laboratories, and the equipment is readily available. The fatty acid method allows a separation of petroselinic (C18:1 delta 6c), oleic (C18:1 delta 9c), elaidic (C18:1 delta 9t), erucic (C22:1 delta 13c), and brassidic acids (C22:1 delta 13t), and the methyl ester method gives an excellent resolution with respect to the number, configuration, and position of the unsaturated centers. Sufficient separation for the subsequent ozonolysis and chromatographic quantification of isomeric C18 and C22 fatty acid methyl esters is obtained with both methods.

  9. Effects of synthetic retinoids and retinoic acid isomers on the expression of alkaline phosphatase in F9 teratocarcinoma cells.

    PubMed

    Gianni, M; Zanotta, S; Terao, M; Garattini, S; Garattini, E

    1993-10-15

    Expression of ALP in F9 teratocarcinoma cells is induced by all-trans retinoic acid (ATRA) (Gianni' et al., Biochem. J. 274: 673-678, 1991). The specific ligand for retinoic acid related receptors (RXRs), 9-cis retinoic acid (9-cis RA), and three synthetic analogs binding to the alpha, beta and gamma forms of the retinoic acid receptors (RARs), AM580, CD2019, and CD437, were used to study their effects on alkaline phosphatase (ALP) enzymatic activity and mRNA levels. At concentrations close to the Kd for their respective receptors, 9-cis RA, AM580 (the RAR alpha agonist) and CD437 (the RAR gamma agonist) clearly upregulate the expression of the ALP gene, whereas the effect of CD2019 (the RAR beta agonist) is very modest. A specific inhibitor of the RAR alpha, Ro 41-5253, completely blocks the induction of ALP triggered by AM580, while it has minor effects on the upregulation caused by ATRA, 9-cis RA, CD437 and CD2019. The induction of ALP observed with the various retinoids is inhibited by the contemporaneous treatment with dibutyryl cAMP. The levels of the RAR alpha and gamma transcripts are unaltered, while RAR beta mRNAs are induced by ATRA, AM580, CD437 and to a lower extent by 9-cis RA and CD2019.

  10. Differentiation of Positional Isomers of Hybrid Peptides Containing Repeats of β-Nucleoside Derived Amino Acid (β-Nda-) and L-Amino Acids by Positive and Negative Ion Electrospray Ionization Tandem Mass Spectrometry (ESI-MS n )

    NASA Astrophysics Data System (ADS)

    Raju, B.; Ramesh, M.; Srinivas, R.; Chandrasekhar, S.; Kiranmai, N.; Sarma, V. U. M.

    2011-04-01

    A new class of positional isomeric pairs of -Boc protected oligopeptides comprised of alternating nucleoside derived β-amino acid (β-Nda-) and L-amino acid residues (alanine, valine, and phenylalanine) have been differentiated by both positive and negative ion electrospray ionization ion-trap tandem mass spectrometry (ESI-MS n ). The protonated dipeptide positional isomers with β-Nda- at the N-terminus lose CH3OH, NH3, and C2H4O2, whereas these processes are absent for the peptides with L-amino acids at the N-terminus. Instead, the presence of L-amino acids at the N-terminus results in characteristic retro-Mannich reaction involving elimination of imine. A good correlation has been observed between the conformational structure of the peptides and the abundance of y{n/+} and b{n/+} ions in MS n spectra. In the case of tetrapeptide isomers that are reported to form helical structures in solution phase, no y{n/+} and b{n/+} ions are observed when the corresponding amide -NH- participates in the helical structures. In contrast, significant y{n/+} and b{n/+} ions are formed when the amide -NH- is not involved in the H-bonding. In the case of tetra- and hexapeptides, it is observed that abundant b{n/+} ions are formed, presumably with stable oxazolone structures when the C-terminus of the b{n/+} ions possessed L-amino acid and the β-Nda- at the C-terminus appears to prevent the cyclization process leading to the absence of corresponding b{n/+} ions.

  11. Recent trends in the fatty acid composition of German sunflower margarines, shortenings and cooking fats with emphasis on individual C16:1, C18:1, C18:2, C18:3 and C20:1 trans isomers.

    PubMed

    Precht, D; Molkentin, J

    2000-08-01

    In some countries the content of trans fatty acids (TFA) in margarines has strongly decreased as a result of the continuous discussion on their disadvantages regarding aspects of nutritional physiology. However, still in 1994 almost 1/3 of total fatty acids in part of German sunflower margarines, shortenings and cooking fats comprised these unfavourable TFA. In the present study the main interest was laid on trans-C16:1, trans-C18:1, trans-C20:1, trans-C18:2 and trans-C18:3 fatty acids and particularly their individual isomers, as negative metabolic activity of TFA possibly might only be attributable to certain isomers. By combining argentation thin-layer chromatography with gas chromatography using a 100-m capillary column (CP-Sil 88) trans fatty acid contents were determined in nearly all German brands of sunflower margarines (SFM; n = 9) and of cooking fats and shortenings (CFS; n = 10). Concerning the above-mentioned groups of isomers mean TFA contents of 0.01, 4.88, 0.00, 0.45 and 0.03% for SFM as well as of 0.01, 5.02, 0.03, 0.70 and 0.17% for CFS were established, respectively. The re-evaluation of samples from 1994 and 1996 exhibited that the total TFA content (sum of all mentioned isomers) in SFM decreased from 21.77% (range: 13.78-26.29; n = 11) to 5.37% (1.98-6.15%; n = 9) between 1994 and 1999. Also the total TFA content in CFS on average strongly decreased from 11.77% (0.08-33.63; n = 16) in 1994 and 12.52% (1.61-26.79%; n = 7) in 1996 to 5.91% (0.43-19.72%; n = 10) in 1999. However, even the newest CFS samples partly exhibited relative high TFA contents. In addition to the total TFA contents all positional isomers of trans-C18:1, trans-C18:2 and trans-C18:3 in SFM and CFS were quantified and compared between different years. The conjugated linoleic acid (cis delta 9, trans delta 11) occurred only in small amounts of 0.03% and 0.02% in current SFM and CFS.

  12. Direct resolution of optically active isomers on chiral packings containing ergoline skeletons. 5. Enantioseparation of amino Acid derivatives.

    PubMed

    Messina, A; Girelli, A M; Flieger, M; Sinibaldi, M; Sedmera, P; Cvak, L

    1996-04-01

    A new procedure for ergot alkaloid-based chiral stationary phase preparation is described. Synthesis is based on bonding the allyl derivative of terguride to mercaptopropylsilanized silica gel. The packing exhibits higher content of chiral selector, stability, reproducibility, and enantioselectivity toward amino acids compared to that previously studied. The chromatographic behavior of amino acids with different side chains and substituent groups is investigated in order to obtain a deeper insight into the enantiodiscriminative mechanism as well as to determine the limitations and strengths of terguride as a chiral selector for this class of compounds. A variety of factors, including mobile phase parameters such as pH, ionic strength, content and nature of organic modifier, and temperature, are examined.

  13. Pharmacodynamic and pharmacokinetic analysis of CNS-active constitutional isomers of valnoctamide and sec-butylpropylacetamide--Amide derivatives of valproic acid.

    PubMed

    Mawasi, Hafiz; Shekh-Ahmad, Tawfeeq; Finnell, Richard H; Wlodarczyk, Bogdan J; Bialer, Meir

    2015-05-01

    Valnoctamide (VCD) and sec-butylpropylacetamide (SPD) are CNS-active closely related amide derivatives of valproic acid with unique anticonvulsant activity. This study evaluated how small chemical changes affect the pharmacodynamics (PD; anticonvulsant activity and teratogenicity) and pharmacokinetics (PK) of three constitutional isomers of SPD [sec-butylisopropylacetamide (SID) and tert-butylisopropylacetamide (TID)] and of VCD [tert-butylethylacetamide (TED)]. The anticonvulsant activity of SID, TID, and TED was comparatively evaluated in several rodent anticonvulsant models. The PK-PD relationship of SID, TID, and TED was evaluated in rats, and their teratogenicity was evaluated in a mouse strain highly susceptible to teratogen-induced neural tube defects (NTDs). sec-Butylisopropylacetamide and TID have a similar PK profile to SPD which may contribute to their similar anticonvulsant activity. tert-Butylethylacetamide had a better PK profile than VCD (and SPD); however, this did not lead to a superior anticonvulsant activity. sec-Butylisopropylacetamide and TED did not cause NTDs at doses 4-7 times higher than their anticonvulsant ED50 values. In rats, SID, TID (ip), and TED exhibited a broad spectrum of anticonvulsant activity. However, combined anticonvulsant analysis in mice and rats shows SID as the most potent compound with similar activity to that of SPD, demonstrating that substitution of the isobutyl moiety in the SPD or VCD molecule by tert-butyl as well as a propyl-to-isopropyl replacement in the SPD molecule did not majorly affect the anticonvulsant activity.

  14. Rapid determination of retinoic acid and its main isomers in plasma by second-order high-performance liquid chromatography data modeling.

    PubMed

    Teglia, Carla M; Cámara, María S; Goicoechea, Héctor C

    2014-12-01

    This paper reports the development of a method based on high-performance liquid chromatography (HPLC) coupled to second-order data modeling with multivariate curve resolution-alternating least-squares (MCR-ALS) for quantification of retinoic acid and its main isomers in plasma in only 5.5 min. The compounds retinoic acid (RA), 13-cis-retinoic acid, 9-cis-retinoic acid, and 9,13-di-cis-retinoic acid were partially separated by use of a Poroshell 120 EC-C18 (3.0 mm × 30 mm, 2.7 μm particle size) column. Overlapping not only among the target analytes but also with the plasma interferents was resolved by exploiting the second-order advantage of the multi-way calibration. A validation study led to the following results: trueness with recoveries of 98.5-105.9 % for RA, 95.7-110.1 % for 13-cis-RA, 97.1-110.8 % for 9-cis-RA, and 99.5-110.9 % for 9,13-di-cis-RA; repeatability with RSD of 3.5-3.1 % for RA, 3.5-1.5 % for 13-cis-RA, 4.6-2.7 % for 9-cis-RA, and 5.2-2.7 % for 9,13-di-cis-RA (low and high levels); and intermediate precision (inter-day precision) with RSD of 3.8-3.0 % for RA, 2.9-2.4 % for 13-cis-RA, 3.6-3.2 % for 9,13-di-cis-RA, and 3.2-2.9 % for 9-cis-RA (low and high levels). In addition, a robustness study revealed the method was suitable for monitoring patients with dermatological diseases treated with pharmaceutical products containing RA and 13-cis-RA.

  15. Ultrasensitive analysis of lysergic acid diethylamide and its C-8 isomer in hair by capillary zone electrophoresis in combination with a stacking technique and laser induced fluorescence detection.

    PubMed

    Airado-Rodríguez, Diego; Cruces-Blanco, Carmen; García-Campaña, Ana M

    2015-03-25

    This article deals with the development and validation of a novel capillary zone electrophoresis (CZE) with laser induced fluorescence detection method for the analysis of lysergic acid diethylamide (LSD) and its isomer iso-LSD in hair samples. The separation of both analytes has been achieved in less than 13 min in a 72-cm effective length capillary with 75-μm internal diameter. As running buffer 25 mM citrate, pH 6.0 has been employed and separation temperature and voltage of 20 °C and 13 kV respectively, were applied. Field amplified sample injection (FASI) has been employed for on-line sample preconcentration, using ultrapure water containing 117 μM H3PO4 as optimum injection medium. Injection voltage and time have been optimized by means of experimental design, obtaining values of 7 kV and 15s, respectively. Methylergonovine has been employed as internal standard in order to compensate irreproducibility from electrokinetic injection. The analytical method has been applied to hair samples, previous extraction of the target analytes by ultrasound assisted solid-liquid extraction at 40 °C for 2.5 h, employing acetonitrile as extracting solvent. Linear responses were found for LSD and iso-LSD in matrix-matched calibrations from around 0.400 up to 50.0 pg mg(-1). LODs (3 S/N) in the order of 0.100 pg mg(-1) were calculated for both analytes, obtaining satisfactory recovery percentages for this kind of sample.

  16. Ultrasensitive analysis of lysergic acid diethylamide and its C-8 isomer in hair by capillary zone electrophoresis in combination with a stacking technique and laser induced fluorescence detection.

    PubMed

    Airado-Rodríguez, Diego; Cruces-Blanco, Carmen; García-Campaña, Ana M

    2015-03-25

    This article deals with the development and validation of a novel capillary zone electrophoresis (CZE) with laser induced fluorescence detection method for the analysis of lysergic acid diethylamide (LSD) and its isomer iso-LSD in hair samples. The separation of both analytes has been achieved in less than 13 min in a 72-cm effective length capillary with 75-μm internal diameter. As running buffer 25 mM citrate, pH 6.0 has been employed and separation temperature and voltage of 20 °C and 13 kV respectively, were applied. Field amplified sample injection (FASI) has been employed for on-line sample preconcentration, using ultrapure water containing 117 μM H3PO4 as optimum injection medium. Injection voltage and time have been optimized by means of experimental design, obtaining values of 7 kV and 15s, respectively. Methylergonovine has been employed as internal standard in order to compensate irreproducibility from electrokinetic injection. The analytical method has been applied to hair samples, previous extraction of the target analytes by ultrasound assisted solid-liquid extraction at 40 °C for 2.5 h, employing acetonitrile as extracting solvent. Linear responses were found for LSD and iso-LSD in matrix-matched calibrations from around 0.400 up to 50.0 pg mg(-1). LODs (3 S/N) in the order of 0.100 pg mg(-1) were calculated for both analytes, obtaining satisfactory recovery percentages for this kind of sample. PMID:25732697

  17. 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…

  18. Rapeseed or linseed in grass-based diets: effects on conjugated linoleic and conjugated linolenic acid isomers in milk fat from Holstein cows over 2 consecutive lactations.

    PubMed

    Lerch, S; Shingfield, K J; Ferlay, A; Vanhatalo, A; Chilliard, Y

    2012-12-01

    Changes in the distribution of conjugated linoleic (CLA) and conjugated linolenic (CLnA) acid isomers in milk from Holstein cows in response to 4 different oilseed supplements rich in either cis-9 18:1 or 18:3n-3 were determined over 2 consecutive lactations in 58 and 35 cows during the first and second years, respectively. For the first 5 wk of the first lactation, all cows were fed the same diet. Thereafter, cows received 1 of 5 treatments for 2 consecutive lactations, including the prepartum period. Treatments comprised the basal diet with no additional lipid, or supplements of extruded linseeds (EL), extruded rapeseeds (ER), cold-pressed fat-rich rapeseed meal, or whole unprocessed rapeseeds to provide 2.5 to 3.0% of additional oil in diet dry matter. During indoor periods, cows were housed and received a mixture (3:1, wt/wt) of grass silage and hay, whereas cows were at pasture during outdoor periods. Over the entire study, EL resulted in the enrichment of ∆11,13 CLA, ∆12,14 CLA, trans-9,trans-11 CLA, trans-13,trans-15 CLA, ∆9,11,15 CLnA, and cis-9,trans-11,trans-13 CLnA (identified for the first time in bovine milk fat) in milk fat, whereas ER and cold-pressed fat-rich rapeseed meal in particular, increased milk fat trans-7,cis-9 CLA concentration. With the exception of the first indoor period, whole unprocessed rapeseeds decreased cis-9,trans-11 CLA, trans-9,cis-11 CLA, and trans-10,trans-12 CLA abundance. During the second indoor period, EL increased milk trans-9,cis-11 CLA and trans-10,cis-12 CLA concentrations, but the increases in cis-9,trans-11 CLA, cis-12,trans-14 CLA, trans-11,cis-13 CLA, and cis-9,trans-11,cis-15 CLnA concentrations to EL and ER were lower for the second than first indoor period. In contrast to the indoor periods, EL and ER decreased milk cis-9,trans-11 CLA, trans-9,cis-11 CLA, and trans-10,cis-12 CLA concentrations at pasture. The extent of changes in the relative distribution and abundance of CLA and CLnA isomers in milk fat

  19. C18:1, C18:2 and C18:3 trans and cis fatty acid isomers including conjugated cis delta 9, trans delta 11 linoleic acid (CLA) as well as total fat composition of German human milk lipids.

    PubMed

    Precht, D; Molkentin, J

    1999-08-01

    In particular with respect to infant nutrition knowledge of the current contents of trans fatty acids (TFA) and of conjugated linoleic acid (CLA in human milk lipids is of interest. After pre-separation by Ag-TLC 11 trans-C18:1 isomers could be quantified by GC with a mean total content of 2.40 +/- 0.60 wt% in samples from 40 German women. For the positional isomers t4, t5, t6-8, t9, t10, t11, t12, t13, t14, t15 and t16 contents of 0.02, 0.02, 0.21, 0.37, 0.32, 0.68, 0.23, 0.15, 0.18, 0.09 and 0.14 wt% were established, with vaccenic acid being the predominant isomer. Further, small trans-C14:1 and trans-C16:1 contents of 0.08% and 0.15% on average were found. As the trans-C18:1 isomers also the trans-C16:1 isomers of human milk lipids could for the first time be baseline-resolved by GC to a great extent. Moreover, besides a mean CLA (c9,t11) content of 0.40 +/- 0.09% further 6 cis/trans isomers of linoleic acid with a total content of 1.07 +/- 0.56% on average (w/o CLA) were determined. Further, 4 trans isomers of alpha-linolenic acid could be baseline-resolved exhibiting a total content of 0.11%. Altogether German human milk lipids on average were found to contain 3.81 +/- 0.97% TFA with a range of 2.38-6.03%. Direct connections between the dietary intake of trans-C18:1 isomers and the composition of human milk lipids could be established. The major fatty acids exhibited the following contents (wt%): C4: 0.16, C6: 0.18, C8: 0.06, C10: 0.58, C12: 3.12, C14: 6.43, C16: 25.28, C18: 7.41, C18: 1 (total): 33.67, C18: 2 (total): 10.63 and alpha-C18: 3:0.87.

  20. Fatty Acids Present in the Lipopolysaccharide of Rhizobium trifolii

    PubMed Central

    Russa, R.; Lorkiewicz, Z.

    1974-01-01

    Approximately 70% of the fatty acids recovered after acid or alkaline hydrolysis of the lipopolysaccharide of Rhizobium trifolii were hydroxy fatty acids identified as hydroxymyristic and hydroxypalmitic acids. Palmitic acid was the only saturated fatty acid found in the lipopolysaccharide of R. trifolii. Octadecenoic and a small amount of hexadecenoic acids were also identified. The results of BF3 methanolysis and hydroxylaminolysis suggest that hydroxypalmitic acid is N-acyl bound. PMID:4852028

  1. Energetic and Structural Study of Diphenylpyridine Isomers

    NASA Astrophysics Data System (ADS)

    Rocha, Marisa A. A.; Gomes, Lígia R.; Low, John N.; Santos, Luís M. N. B. F.

    2009-09-01

    The energetic and structural study of three diphenylpyridine isomers is presented in detail. The three isomers, 2,6-, 2,5-, and 3,5-diphenylpyridines, were synthesized via Suzuki-Miyaura methodology based on palladium catalysis, and the crystal structures of the isomers were obtained by X-ray diffraction. The relative energetic stabilities in the condensed and gaseous phases as well as volatilities and structures of the three studied isomers were evaluated, regarding the position of the phenyl groups relative to the nitrogen atom of the pyridine ring. The temperature, standard molar enthalpies, and entropies of fusion were measured and derived by differential scanning calorimetry. The vapor pressures of the considered isomers were determined by a static apparatus based on a MKS capacitance diaphragm manometer. The standard molar enthalpies, entropies, and Gibbs energies of sublimation, at T = 298.15 K, were derived, and the phase diagram near the triple point coordinates were determined for all isomers. The standard (p° = 0.1 MPa) molar enthalpies of combustion of all crystalline isomers were determined, at T = 298.15 K, by static bomb combustion calorimetry. The standard molar enthalpies of formation, in the crystalline and gaseous phases, at T = 298.15 K, were derived. The experimental results for the energetics in the gaseous phase of the three compounds were compared and assessed with the values obtained by ab initio calculations at different levels of theory (DFT and MP2) showing that, at this level of theory, the computational methods underestimate the energetic stability, in the gaseous phase, for these molecules. In order to understand the aromaticity in the central ring of each isomer, calculations of NICS (B3LYP/6-311G++(d,p) level of theory) values on the pyridine ring were also performed.

  2. Vaccenic acid and trans fatty acid isomers from partially hydrogenated oil both adversely affect LDL cholesterol: a double-blind, randomized controlled trial

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Evidence of the adverse effects of industrially-produced trans fatty acids (iTFA) on risk of cardiovascular disease is consistent and well documented in the scientific literature; however, the cardiovascular effects of naturally-occurring TFA synthesized in ruminant animals (rTFA), such as vaccenic ...

  3. SERS Quantification of Entacapone Isomers

    NASA Astrophysics Data System (ADS)

    Marković, Marina; Biljan, Tomislav

    2010-08-01

    Raman spectroscopy, due to its non-destructive character and speed, has found widespread use in pharmaceutical applications [1]. It is also being used for quantifying various isomer mixtures, best known being the quantification of xylene isomers [2-3]. Solid-state isomer quantification of entacapone was earlier reported [4]. Here, we report quantification of isomer mixture of an active pharmaceutical substance, in solution, by SERS.

  4. A rapid method for the determination of perfluoroalkyl substances including structural isomers of perfluorooctane sulfonic acid in human serum using 96-well plates and column-switching ultra-high performance liquid chromatography tandem mass spectrometry.

    PubMed

    Salihovic, Samira; Kärrman, Anna; Lindström, Gunilla; Lind, P Monica; Lind, Lars; van Bavel, Bert

    2013-08-30

    To facilitate high-throughput analysis suitable for large epidemiological studies we developed an automated column-switching ultra-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for determination of perfluorocarboxylic acids (PFCAs; C5, C6, C7, C8, C9, C10, C11, C12, and C13), perfluoroalkyl sulfonic acids (PFSAs; C4, C6, C8, and C10), perfluorooctane sulfonamide (PFOSA), and five groups of structural perfluorooctane sulfonic acid (PFOS) isomers in human serum or plasma. The analytical procedure involves rapid protein precipitation using 96-well plates followed by an automated sample clean-up using an on-line trap column removing many potentially interfering sample components while through the mobile phase gradient the target analytes are eluted onto the analytical column for further separation and subsequent mass detection. The method was linear (R(2)<0.995) at concentrations ranging from 0.01 to 60ngmL(-1) with method detection limits ranging between 0.01 and 0.17ngmL(-1) depending on the analyte. The developed method was precise, with repeatability (n=7) and reproducibility (n=103) coefficients of variation between 2% and 20% for most compounds including PFOS (2% and 8%) and its structural isomers (2-6% and 4-8%). The method was in conformity with a standard reference material. The column-switching HPLC-MS/MS method has been successfully applied for the determination of perfluoroalkyl substances including structural PFOS isomers in human plasma from an epidemiological study.

  5. The interstellar chemistry of H2C3O isomers

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    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.

  6. 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

  7. The proportion of lycopene isomers in human plasma is modulated by lycopene isomer profile in the meal but not by lycopene preparation.

    PubMed

    Richelle, Myriam; Lambelet, Pierre; Rytz, Andreas; Tavazzi, Isabelle; Mermoud, Anne-France; Juhel, Christine; Borel, Patrick; Bortlik, Karlheinz

    2012-05-01

    Dietary lycopene consists mostly of the (all-E) isomer. Upon absorption, (all-E) lycopene undergoes isomerisation into various (Z)-isomers. Because these isomers offer potentially better health benefits than the (all-E) isomer, the aim of the present study was to investigate if the profile of lycopene isomers in intestinal lipoproteins is affected by the profile of lycopene isomers in the meal and by the tomato preparation. Six postprandial, crossover tests were performed in healthy men. Three meals provided about 70 % of the lycopene as (Z)-isomers, either mainly as 5-(Z) or 13-(Z), or as a mixture of 9-(Z) and 13-(Z) lycopene, while three tomato preparations provided lycopene mainly as the (all-E) isomer. Consumption of the 5-(Z) lycopene-rich meal led to a high (60 %) proportion of this isomer in TAG-rich lipoproteins (TRL), indicating a good absorption and/or a low intestinal conversion of this isomer. By contrast, consumption of meals rich in 9-(Z) and 13-(Z) lycopene isomers resulted in a low level of these isomers but high amounts of the 5-(Z) and (all-E) isomers in TRL. This indicates that the 9-(Z) and 13-(Z) isomers were less absorbed or were converted into 5-(Z) and (all-E) isomers. Dietary (Z)-lycopene isomers were, therefore, differently isomerised and released in TRL during their intestinal absorption in men. Consuming the three meals rich in (all-E) lycopene resulted in similar proportions of lycopene isomers in TRL: 60 % (all-E), 20 % 5-(Z), 9 % 13-(Z), 2 % 9-(Z) and 9 % unidentified (Z)-isomers. These results show that the tomato preparation has no impact on the lycopene isomerisation occurring during absorption in humans.

  8. Pentachlorodibenzo-p-dioxin isomer differentiation by capillary gas chromatography fourier transform infrared spectroscopy

    SciTech Connect

    Grainger, J.; Reddy, V.V.; Patterson, D.G. Jr. )

    1988-09-01

    Analysis of polychlorinated dibenzo-p-dioxin (PCDD) isomers has been the focus of a number of recent investigations due to the extreme toxicities of specific laterally tetrachlorinated isomers. These investigations have primarily been directed toward 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), the most toxic PCDD isomer and toward isomer differentiation of TCDD isomers as a group. With the exception of pentachlorodibenzo-p-dioxin (PnCDD) isomer specific determinations based on calculated retention indices, isomer differentiation of the 14 PnCDD isomers has not been reported although 1,2,3,7,8-PnCDD is nearly as toxic as 2,3,7,8-TCDD. Chromatographically independent methods for PCDD isomer assignment have been reported by x-ray powder diffraction, proton nuclear magnetic resonance ({sup 1}H NMR), gas chromatography/matrix isolation Fourier transform infrared (MI/FTIR) spectroscopy, diffuse reflectance infrared Fourier transformation (DRIFT) spectroscopy and gas chromatography/Fourier transform infrared (GC/FTIR) spectroscopy. Although TCDD isomer assignments by the various methods are substantially in agreement, some differences are yet to be resolved. Vapor-phase reference infrared spectra are presented for the 14 PnCDD isomers. These spectra were recorded from low (< 10) microgram quantities for each isomer. The spectrum of each isomer is unique, allowing for positive isomer identification and individual group frequency absorption characteristics as a function of isomer structure.

  9. Simultaneous ozonation kinetics of phenolic acids present in wastewaters

    SciTech Connect

    Benitez, F.J.; Beltran-Heredia, J.; Acero, J.L.; Pinilla, M.L.

    1996-12-31

    Among the several chemical processes conducted for the removal of organic matter present in wastewaters coming from some agro-industrial plants (wine distilleries, olive oil mills, etc), the oxidation by ozone has shown a great effectiveness in the destruction of specially refractory pollutants: it is demonstrated that the biodegradability of those wastewaters increases aflcer an ozonation pretreatment. Their great pollutant character is imputed to the presence of some organic compounds, like phenols and polyphenols, which are toxic and inhibit the latter biological treatments. In this research, a competitive kinetic procedure reported by Clurol and Nekouinaini is applied to determine the degradation rate constants by ozone of several phenolic acids which are present in the wastewaters from the olive oil obtaining process. The resulting kinetic expressions for the ozonation reactions are useful for the successful design and operation of ozone reactors in water and wastewaters treatment plants.

  10. Influence of the cis-9, cis-12 and cis-15 double bond position in octadecenoic acid (18:1) isomers on the rat FADS2-catalyzed Δ6-desaturation.

    PubMed

    Rioux, Vincent; Choque, Benjamin; Ezanno, Hélène; Duby, Cécile; Catheline, Daniel; Legrand, Philippe

    2015-04-01

    Oleic (cis9-18:1), linoleic (cis9,cis12-18:2) and α-linolenic (cis9,cis12,cis15-18:3) acids are well described substrates of the Δ6-desaturase encoded by the mammalian fatty acid desaturase 2 (FADS2) gene. In addition, at least 9 other very structurally different fatty acids have been shown to be Δ6- or even Δ8-desaturated by the FADS2 protein. A better characterization of the substrate specificity of this enzyme is therefore needed. By using commercial cis9-18:1 and chemically synthesized cis12- and cis15-18:1 (sharing the n-6 double bond with 18:2 n-6 and the n-3 double bond with 18:3 n-3, respectively), we tried to decrypt the fatty acid structure driving the FADS2 substrate affinity. We first showed that both recombinant and native rat FADS2 were able to Δ6-desaturate not only the cis9- but also the cis12- and cis15-18:1 isomers. Next, the inhibitory effect of increasing concentrations of each 18:1 isomer was investigated in vitro on the Δ6-desaturation of α-linolenic acid. At equimolar inhibitor/substrate ratio (60 μM), the cis9-18:1 exhibited a significantly higher inhibition (25%) than the cis12- (8%) and cis15-18:1 (5%). This study shows that a single cis double bond in 12- or 15-position in 18:1 is enough to make them low Δ6-desaturable substrates. If a preexisting cis9-double bond is not absolutely required for the Δ6-desaturation of octadecenoic acids, its presence is however crucial to explain the higher enzyme affinity. Compared with oleic acid, the additional presence of a cis12-double bond in linoleic acid increased its inhibitory effect on the Δ6-desaturation of α-linolenic acid at low concentration (30 μM) but not at higher concentrations (60 and 120 μM). In this classification of the decreasing impact of the double bond when it comes closer to the methyl end of octadecenoic acids, the cis11-18:1 (cis-vaccenic acid) should be considered apart since it is itself not Δ6-desaturated but still a good competitive inhibitor of the

  11. 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…

  12. GAS-GRAIN MODELING OF ISOCYANIC ACID (HNCO), CYANIC ACID (HOCN), FULMINIC ACID (HCNO), AND ISOFULMINIC ACID (HONC) IN ASSORTED INTERSTELLAR ENVIRONMENTS

    SciTech Connect

    Quan Donghui; Herbst, Eric; Osamura, Yoshihiro; Roueff, Evelyne

    2010-12-20

    Isocyanic acid (HNCO) is a well-known interstellar molecule. Evidence also exists for the presence of two of its metastable isomers in the interstellar medium: HCNO (fulminic acid) and HOCN (cyanic acid). Fulminic acid has been detected toward cold and lukewarm sources, while cyanic acid has been detected both in these sources and in warm sources in the Galactic Center. Gas-phase models can reproduce the abundances of the isomers in cold sources, but overproduce HCNO in the Galactic Center. Here we present a detailed study of a gas-grain model that contains these three isomers, plus a fourth isomer, isofulminic acid (HONC), for four types of sources: hot cores, the warm envelopes of hot cores, lukewarm corinos, and cold cores. The current model is partially able to rationalize the abundances of HNCO, HOCN, and HCNO in cold and warm sources. Predictions for HONC in all environments are also made.

  13. Polymerization of the E and Z Isomers of Bis-(Triethoxysilyl)-2-Butene

    SciTech Connect

    Carpenter, J.P. Dorhout, K.; Loy, D.A.; Shaltout, R.M.; Shea, K.J.

    1999-05-11

    We have synthesized the Z and E isomers of 1,4-bis(triethoxysilyl)-2- butene and polymerized them under acid and base catalyzed sol-gel conditions. As expected the E system formed crosslinked, insoluble gels. The Z isomer, by nature of its geometry, formed high molecular weight, soluble polymeric products under acidic conditions. We were able to prepare and isolate both the cyclic disilsesquioxane monomer, and its dimer. Comparison of their spectral characterization with that of the soluble polymers suggests that the cyclics are present within the polymers. lle synthesis of a dimer likely present at some early stage of the polymerization suggests that we may be able to control the reaction and form rigid polymers with controllable tacticity. In addition, most of the gels were found to be non-porous indicating that the gels were, in fact, more compliant than ethenylene-bridged polysilsesquioxanes leading to collapse of pores during drying.

  14. Comparison of suppression of mutagenicity of benzo(a)pyrene among methylsulfonyl polychlorinated biphenyl isomers

    SciTech Connect

    Kiyohara, Chikako; Hirohata, Tomio; Omura, Minoru; Masuda, Yoshito

    1992-06-01

    Methylsulfonyl (MSF) derivatives of polychlorinated biphenyls (PCBs) were first identified in fat from seals in the Baltic. Since then, a number of these substances have been demonstrated in animals. They were also isolated from the excreta of mice and rats treated with tri-, tetra-, penta- or hexachlorobiphenyls. Studies on the metabolic fates of several structurally defined chlorobiphenyls in mice showed that, in addition to the hydroxy species that were considered to be major metabolites of PCBs, sulfur-containing compounds were formed by the mercapturic acid pathway from PCB arene oxide. The accumulations of some MSF-PCB isomers have been evidenced not only in the mice experimentally ingested with certain PCBs but also in a human being accidentally exposed to PCBs. Even health people were found to have MSF-PCB isomers at concentrations as high as those of PCBs. It is noteworthy that some MSF-PCB isomers have been demonstrated to be toxic for rats and mice. Moreover, our preliminary study indicated that some MSF-PCB isomers have an inhibitory potency against the aryl hydrocarbon hydroxylase (AHH) activity, a well-known drug-metabolizing enzyme, in cultured human lymphoblastoid cells. These effects of MSF-PCB isomers seemed comparable to those of the well known 7,8-benzoflavone (7,8-BF), which inhibits chemical carcinogenesis. In the present study, we studied the effect of 11 MSF-PCB isomers and 7,8-BF on the mutagenicity of benzo(a)pyrene (BP) using Salmonella strains TA98 and TA100 in the Ames assay. In addition, the relationship between the results of Ames assay and the AHH assay was investigated. 17 refs., 3 tabs.

  15. Naturally occurring structural isomers in serum IgA1 o-glycosylation.

    PubMed

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

    2012-02-01

    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. Thr(225), Thr(228), Ser(230), Ser(232) and Thr(236) 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 Ser(230), Thr(233) or Thr(236) 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.

  16. Intravenous infusion of L-isomers of phenylalanine and tryptophan stimulate gastric acid secretion at physiologic plasma concentrations in normal subjects and after parietal cell vagotomy.

    PubMed Central

    McArthur, K E; Isenberg, J I; Hogan, D L; Dreier, S J

    1983-01-01

    To determine whether intravenous infusion of individual amino acids stimulated gastric acid secretion in man, graded doses of phenylalanine, tryptophan, glycine, alanine, histidine, and NaCl control were infused on separate days in nine healthy subjects. Intravenous infusion of phenylalanine and tryptophan significantly stimulated gastric acid secretion to 50 and 52%, respectively, of the acid secretory response to intragastric peptone. Intravenous alanine and histidine were without effect, whereas glycine produced a slight response. Serum gastrin concentrations did not significantly change during intravenous amino acid infusion, except in response to 0.1 M phenylalanine. However, the increase in serum gastrin occurred 2 h after acid secretion had significantly increased in response to the 0.025 M phenylalanine infusion. Plasma amino acid concentrations were measured during intravenous amino acid infusion and in response to a steak meal in five of the subjects. At a time when acid secretion was significantly increased during intravenous infusion of phenylalanine and tryptophan, plasma amino acids were similar to, or less than, that observed after the steak meal, suggesting that circulating levels of these three amino acids have a physiologic effect on gastric secretion in man. Intravenous infusion of a combination of graded doses of phenylalanine plus a continuous infusion of 0.01 M tryptophan shifted the dose-response curve to the left and resulted in a significantly greater response than to either amino acid alone. In five subjects with parietal cell vagotomy, intravenous phenylalanine and tryptophan stimulated acid secretion, whereas histidine was without effect, similar to normal subjects. These studies indicate that intravenous infusion of small amounts of phenylalanine (0.025 M, 3.1 mmol/h) and tryptophan (0.01 M, 1.25 mmol/h) stimulated gastric acid secretion at plasma concentrations similar to those observed after a steak meal, suggesting a physiologic role

  17. A glycoprotein binding retinoids and fatty acids is present in Drosophila.

    PubMed

    Duncan, T; Kutty, G; Chader, G J; Wiggert, B

    1994-07-01

    In the search for a possible Drosophila melanogaster homolog of interphotoreceptor retinoid-binding protein (IRBP), a approximately 140-kDa retinoid- and fatty acid-binding glycoprotein found in vertebrates, the 110,000 g supernatant fraction prepared from homogenates of fly heads was analyzed for the presence of proteins capable of binding radiolabeled retinol and palmitic acid. A soluble protein, which binds concanavalin A and has a retention time on size-exclusion high-performance liquid chromatography identical to that of purified bovine IRBP, was identified as binding both ligands. As assessed by fluorescence titration, the protein fraction obtained by concanavalin A-Sepharose affinity chromatography and size-exclusion chromatography of fly head supernatant had apparent dissociation constants of 2.9 x 10(-7) +/- 0.6 M for all-trans retinol, with the number (n) of independent ligand binding sites per protein molecule = 2, and 3.5 x 10(-7) +/- 0.1 M for 16-[9-anthroyloxy] palmitic acid with n = 7. High-performance liquid chromatography of hexane extracts of this protein fraction resolved several peaks with polarity and relative retention times similar, but not identical to all-trans retinol and retinal and their 9-, 11-, and 13-cis isomers. Gas chromatography/mass spectrometry analysis of fatty acid methyl esters prepared following lipid extraction of the protein identified lauric, myristic, palmitic, palmitoleic, and oleic acids as being covalently bound. Laurate, myristate, palmitate, and stearate were noncovalently bound. The apparent molecular mass of the Drosophila protein as assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and silver staining of the retinoid- and fatty acid-binding peak obtained by hydrophobic interaction chromatography of the size-exclusion fraction was approximately 70 kDa. PMID:8031123

  18. Phytanic acid alpha-oxidase deficiency (Refsum disease) presenting in infancy.

    PubMed

    Herbert, M A; Clayton, P T

    1994-01-01

    This report describes a patient with high serum phytanic acid concentration due to phytanic acid alpha-oxidase deficiency (classical Refsum disease). He presented unusually early, hypotonia and developmental delay being apparent by 7 months. A generalized peroxisomal disorder (so-called 'infantile Refsum disease') was excluded by analyses of pristanic acid, very long-chain fatty acids, bile acids and plasmalogen synthesis. The early presentation raises the possibility of in utero exposure to phytanate.

  19. Fatty acid composition, including CLA's isomers and cholesterol content of m. longissimus lumborum and m. semimebranosus of Katahdin, Suffolk, Katahdin x Suffolk, and Suffolk x Katahdin lambs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lipids in meat products have important human health implications. Muscle tissues from Katahdin (KK), Suffolk (SS), Katahdin x Suffolk (KS), and Suffolk x Katahdin (SS) lambs were analyzed to determine the effect of breed-type on muscle fatty acid composition, including conjugated linoleic acid (CLA)...

  20. Trans-9-octadecenoic acid is biologically neutral and does not regulate the low density lipoprotein receptor as the cis isomer does in the hamster.

    PubMed

    Woollett, L A; Daumerie, C M; Dietschy, J M

    1994-09-01

    The concentration of cholesterol carried in low density lipoproteins (LDL-C) is primarily determined by the rate at which LDL-C is produced (Jt) and the rate at which the liver takes up this particle through receptor-dependent transport (Jm). The accumulation of specific dietary fatty acids in the liver profoundly alters these kinetic parameters and will either increase hepatic receptor activity or further suppress Jm, depending upon the particular fatty acid that enriches the various lipid pools. This study tests the thesis that the cellular effects of each fatty acid are determined by the ability of that lipid to act as an effective substrate for cholesteryl ester formation by examining the metabolic effects of either cis-9-octadecenoic acid (18:1(9c)), the preferred substrate for esterification, or trans-9-octadecenoic acid (18:1(9t)), a poor substrate for this reaction. When fed to hamsters for 30 days, the steady-state concentration of cholesteryl esters was markedly increased by the 18:1(9c), as compared to the 18:1(9t), compound. In animals receiving the 18:1(9c) fatty acid, hepatic receptor activity was significantly increased, LDL-C production was suppressed, and the steady-state LDL-C concentration was reduced. In contrast, the 18:1(9t) fatty acid did not significantly alter Jm, Jt, or the plasma LDL-C level from those values found in the control animals fed an isocaloric amount of a biologically neutral fatty acid, octanoic acid. Despite these different effects on the parameters of LDL metabolism, neither the cis nor trans fatty acid altered net cholesterol delivery to the liver from de novo sterol synthesis in any tissue in the body or from uptake of dietary cholesterol across the intestine. Therefore, these studies provide strong support for the thesis that fatty acids exert regulatory effects on hepatic LDL receptor activity by altering the distribution of cholesterol in the hepatocyte between a putative regulatory pool and the inert pool of

  1. How are the Concepts and Theories of Acid Base Reactions Presented? Chemistry in Textbooks and as Presented by Teachers

    NASA Astrophysics Data System (ADS)

    Furió-Más, Carlos; Calatayud, María Luisa; Guisasola, Jenaro; Furió-Gómez, Cristina

    2005-09-01

    This paper investigates the views of science and scientific activity that can be found in chemistry textbooks and heard from teachers when acid base reactions are introduced to grade 12 and university chemistry students. First, the main macroscopic and microscopic conceptual models are developed. Second, we attempt to show how the existence of views of science in textbooks and of chemistry teachers contributes to an impoverished image of chemistry. A varied design has been elaborated to analyse some epistemological deficiencies in teaching acid base reactions. Textbooks have been analysed and teachers have been interviewed. The results obtained show that the teaching process does not emphasize the macroscopic presentation of acids and bases. Macroscopic and microscopic conceptual models involved in the explanation of acid base processes are mixed in textbooks and by teachers. Furthermore, the non-problematic introduction of concepts, such as the hydrolysis concept, and the linear, cumulative view of acid base theories (Arrhenius and Brönsted) were detected.

  2. 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.

  3. 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.

  4. Isomer-specific biodegradation of nonylphenol in river sediments and structure-biodegradability relationship.

    PubMed

    Lu, Zhijiang; Gan, Jay

    2014-01-21

    Nonylphenol (NP), a well-known environmental estrogen with numerous isomers, is frequently found in surface water and sediments. Recent studies showed that NP isomers exhibited different estrogenicity. However, at present little information is available on its isomer-specific degradation in the bed sediment, which is the primary sink of NP in surface aquatic systems. In this study, we investigated the biodegradability of 19 NP isomers in two river sediments under oxic and anoxic conditions. Under oxic conditions, the half-lives of NP isomers in an upper river sediment ranged from 0.9 to 13.2 d. Under reduced conditions, the persistence of NP isomers generally increased, with negligible dissipation under strongly reduced conditions. In the well-aerated sediment, NP isomers with short side chain and/or bulky α-substituents were found to be more recalcitrant to degradation. Moreover, when a total of 57 molecular descriptors were examined, the degree of branching as quantified by IDWbar was found to result in the best linear correlation with half-lives of NP isomers (R(2) = 0.88). These results indicated that the isomer-specificity of NP in environmental processes should be considered, and that simple molecular descriptors may be used to identify the more recalcitrant isomers, thus allowing prioritization in the evaluation of environmental fate and risks of NP isomers.

  5. Carotenoids and their isomers: color pigments in fruits and vegetables.

    PubMed

    Khoo, Hock-Eng; Prasad, K Nagendra; Kong, Kin-Weng; Jiang, Yueming; Ismail, Amin

    2011-02-18

    Fruits and vegetables are colorful pigment-containing food sources. Owing to their nutritional benefits and phytochemicals, they are considered as 'functional food ingredients'. Carotenoids are some of the most vital colored phytochemicals, occurring as all-trans and cis-isomers, and accounting for the brilliant colors of a variety of fruits and vegetables. Carotenoids extensively studied in this regard include β-carotene, lycopene, lutein and zeaxanthin. Coloration of fruits and vegetables depends on their growth maturity, concentration of carotenoid isomers, and food processing methods. This article focuses more on several carotenoids and their isomers present in different fruits and vegetables along with their concentrations. Carotenoids and their geometric isomers also play an important role in protecting cells from oxidation and cellular damages.

  6. An α-acetoxy-tirucallic acid isomer inhibits Akt/mTOR signaling and induces oxidative stress in prostate cancer cells.

    PubMed

    El Gaafary, Menna; Büchele, Berthold; Syrovets, Tatiana; Agnolet, Sara; Schneider, Bernd; Schmidt, Christoph Q; Simmet, Thomas

    2015-01-01

    Here we provide evidence that αATA(8,24) (3α-acetyloxy-tir-8,24-dien-21-oic acid) inhibits Akt/mammalian target of rapamycin (mTOR) signaling. αATA(8,24) and other tirucallic acids were isolated from the acetylated extract of the oleo gum resin of Boswellia serrata to chemical homogeneity. Compared with related tirucallic acids, αATA(8,24) was the most potent inhibitor of the proliferation of androgen-insensitive prostate cancer cells in vitro and in vivo, in prostate cancer xenografted onto chick chorioallantoic membranes. αATA(8,24) induced loss of cell membrane asymmetry, caspase-3 activation, and DNA fragmentation in vitro and in vivo. These effects were selective for cancer cells, because αATA(8,24) exerted no overt toxic effects on peripheral blood mononuclear cells or the chick embryo. At the molecular level, αATA(8,24) inhibited the Akt1 kinase activity. Prior to all biochemical signs of cellular dysfunction, αATA(8,24) induced inhibition of the Akt downstream target mTOR as indicated by dephosphorylation of S6K1. This event was followed by decreased expression of cell cycle regulators, such as cyclin D1, cyclin E, and cyclin B1, as well as cyclin-dependent kinases CDK4 and CDK2 and phosphoretinoblastoma protein, which led to inhibition of the cell-cycle progression. In agreement with the mTOR inhibition, αATA(8,24) and rapamycin increased the volume of acidic vesicular organelles. In contrast to rapamycin, αATA(8,24) destabilized lysosomal and mitochondrial membranes and induced reactive oxygen species production in cancer cells. The ability of αATA(8,24) to inhibit Akt/mTOR signaling and to induce simultaneously oxidative stress could be exploited for the development of novel antitumor therapeutics with a lower profile of toxic side effects.

  7. Polymerization of the cis- and trans-isomers of bis(triethoxysilyl)-2-butene and comparison of their structural properties

    SciTech Connect

    Shaltout, R.M.; Loy, D.A.; Carpenter, J.P.; Dorhout, K.; Shea, K.J.

    1998-09-01

    The cis and trans isomers of bis-(triethoxysilyl)-2-butene were polymerized by the sol-gel method under various conditions. The trans isomer formed gels under all conditions. The cis isomer formed gels only under basic conditions. Under acidic conditions it formed soluble resins of molecular weight ranging from 88,000 to 180,000 Daltons. Solid state and solution {sup 29}Si NMR revealed that the trans isomer formed condensed gels, and that the resins formed by the cis isomer contained cyclic monomers and/or ordered oligomers.

  8. Nuclear isomers: structures and applications

    SciTech Connect

    Sun Yang; Wiescher, Michael; Aprahamian, Ani; Fisker, Jacob

    2006-03-13

    Isomeric states in the nuclei along the rapid proton capture process path are studied by the projected shell model. Emphasis is given to two waiting point nuclei 68Se and 72Kr that are characterized by shape coexistence. Energy surface calculations indicate that the ground state of these nuclei corresponds to an oblate-deformed minimum, while the lowest state at the prolate-deformed minimum can be considered as a shape isomer. Due to occupation of the orbitals with large K-components, states built upon two-quasiparticle excitations at the oblate-deformed minimum may form high K-isomers. The impact of the isomer states on isotopic abundance in X-ray bursts is studied in a multi-mass-zone X-ray burst model by assuming an upper-lower limit approach.

  9. Characterization of diacylglycerol isomers in edible oils using gas chromatography-ion trap electron ionization mass spectrometry.

    PubMed

    Zhu, Hanjiang; Clegg, Michael S; Shoemaker, Charles F; Wang, Selina C

    2013-08-23

    Verifying the authenticity of edible oils is of international concern. A new quality control standard for olive oil has been proposed that relates the ratio of 1,2-diacylglycerol (DAG) to 1,3-DAG to sensory aspects of olive oil. DAGs and their isomers are difficult to quantitate and characterize by Flame Ionization Gas Chromatography (GC-FID) due to the lack of suitable standards. Mass detectors offer the advantage of providing structural detail to the eluding DAG(s), thus removing ambiguity to the identification of both resolved and unresolved DAGs in GC chromatograms. In this study, a GC Electron Ionization Mass Spectrometry (GC-EI-MS) method was developed to determine the fatty acid composition and molecular structure of trimethylsilyl (TMS) derivatized DAGs present in edible oils. Twenty-two species of DAG isomers were identified in refined coconut oil and unrefined olive oil utilizing signature fragment ions, [M-15](+), [M-89](+), [M-RCO2](+), [RCO2+58](+) and [M-RCO2CH2](+). The [M-RCO2CH2](+) ion is considered the key diagnostic ion to distinguish between DAG positional isomers. MS/MS spectra of [M-RCO2](+) and [M-15](+) ions obtained from commercial standards containing both 1,2- and 1,3-DAG isomers were used as a model system to confirm the identification of DAG isomers in natural products. Furthermore, a number of reaction mechanisms are proposed to explain the formation of the most abundant mass fragments of DAGs and their isomers.

  10. An α-acetoxy-tirucallic acid isomer inhibits Akt/mTOR signaling and induces oxidative stress in prostate cancer cells.

    PubMed

    El Gaafary, Menna; Büchele, Berthold; Syrovets, Tatiana; Agnolet, Sara; Schneider, Bernd; Schmidt, Christoph Q; Simmet, Thomas

    2015-01-01

    Here we provide evidence that αATA(8,24) (3α-acetyloxy-tir-8,24-dien-21-oic acid) inhibits Akt/mammalian target of rapamycin (mTOR) signaling. αATA(8,24) and other tirucallic acids were isolated from the acetylated extract of the oleo gum resin of Boswellia serrata to chemical homogeneity. Compared with related tirucallic acids, αATA(8,24) was the most potent inhibitor of the proliferation of androgen-insensitive prostate cancer cells in vitro and in vivo, in prostate cancer xenografted onto chick chorioallantoic membranes. αATA(8,24) induced loss of cell membrane asymmetry, caspase-3 activation, and DNA fragmentation in vitro and in vivo. These effects were selective for cancer cells, because αATA(8,24) exerted no overt toxic effects on peripheral blood mononuclear cells or the chick embryo. At the molecular level, αATA(8,24) inhibited the Akt1 kinase activity. Prior to all biochemical signs of cellular dysfunction, αATA(8,24) induced inhibition of the Akt downstream target mTOR as indicated by dephosphorylation of S6K1. This event was followed by decreased expression of cell cycle regulators, such as cyclin D1, cyclin E, and cyclin B1, as well as cyclin-dependent kinases CDK4 and CDK2 and phosphoretinoblastoma protein, which led to inhibition of the cell-cycle progression. In agreement with the mTOR inhibition, αATA(8,24) and rapamycin increased the volume of acidic vesicular organelles. In contrast to rapamycin, αATA(8,24) destabilized lysosomal and mitochondrial membranes and induced reactive oxygen species production in cancer cells. The ability of αATA(8,24) to inhibit Akt/mTOR signaling and to induce simultaneously oxidative stress could be exploited for the development of novel antitumor therapeutics with a lower profile of toxic side effects. PMID:25316122

  11. Characterization of 18:1 and 18:2 isomers produced during microbial biohydrogenation of unsaturated fatty acids from canola and soya bean oil in the rumen of lactating cows.

    PubMed

    Loor, J J; Bandara, A B P A; Herbein, J H

    2002-12-01

    Ruminal production of biohydrogenation intermediates in response to unsaturated oils was assessed using 24 Jersey cows fed a control diet or the control diet supplemented at 35 g/kg dry matter (DM) with canola, soya bean, or a mixture of equal amounts of canola plus soya bean oil for 4-weeks. Total fatty acid content averaged 63 or 35 g/kg DM for oil-supplemented diets or control. Oleic acid accounted for 6, 29, 21 or 12 g/kg DM in the control, canola, mixture, or soya bean oil diet, respectively. Linoleic acid averaged 17, 19, 26, or 33 g/kg DM and linolenic acid 5, 5, 6 or 8 g/kg DM for control, canola, mixture, or soya bean oil. Concentrations of cis12-, trans11-, trans13+14, and trans15-18:1 were 0.81, 2.99, 2.24, and 0.73 mg/g rumen fluid, respectively, in response to soya bean oil and were 126, 90, 45, and 38% greater compared with other diets. Trans11cis15-, cis9trans11- and cis9 cis11-18:2 also were greater when soya bean oil (0.30, 0.34 and 0.01 mg/g, respectively) was fed compared with other treatments (0.12, 0.21 and 0.004 mg/g, respectively). Feeding canola oil resulted in greater concentrations of trans4-, trans5-, trans6+7+8-, trans9- and trans10-18:1 (0.20, 0.25, 0.87, 0.39 and 0.70 mg/g, respectively) compared with other diets (0.09, 0.15, 0.36, 0.20 and 0.46 mg/g, respectively). Trans10cis12-18:2 concentration did not differ as a result of diet and averaged 0.002 mg/g rumen contents. The pattern of 18:1 and 18:2 isomers formed during ruminal biohydrogenation depends greatly on dietary profile of unsaturated fatty acids.

  12. Past and Present Insights on Alpha-linolenic Acid and the Omega-3 Fatty Acid Family.

    PubMed

    Stark, Aliza H; Reifen, Ram; Crawford, Michael A

    2016-10-25

    Alpha-linolenic acid (ALA) is the parent essential fatty acid of the omega-3 family. This family includes docosahexaenoic acid (DHA), which has been conserved in neural signaling systems in the cephalopods, fish, amphibian, reptiles, birds, mammals, primates, and humans. This extreme conservation, in spite of wide genomic changes of over 500 million years, testifies to the uniqueness of this molecule in the brain and affirms the importance of omega-3 fatty acids. While DHA and its close precursor, eicosapentaenoic acids (EPA), have received much attention by the research community, ALA, as the precursor of both, has been considered of little interest. There are many papers on ALA requirements in experimental animals. Unlike humans, rats and mice can readily convert ALA to EPA and DHA, so it is unclear whether the effect is solely due to the conversion products or to ALA itself. The intrinsic role of ALA has yet to be defined. This paper will discuss both recent and historical findings related to this distinctive group of fatty acids, and will highlight the physiological significance of the omega-3 family.

  13. Retinoic acid isomers up-regulate ATP binding cassette A1 and G1 and cholesterol efflux in rat astrocytes: implications for their therapeutic and teratogenic effects.

    PubMed

    Chen, Jing; Costa, Lucio G; Guizzetti, Marina

    2011-09-01

    Recent studies suggest that retinoids may be effective in the treatment of Alzheimer's disease, although exposure to an excess of retinoids during gestation causes teratogenesis. Cholesterol is essential for brain development, but high levels of cholesterol have been associated with Alzheimer's disease. We hypothesized that retinoic acid may affect cholesterol homeostasis in rat astrocytes, which regulate cholesterol distribution in the brain, through the up-regulation of cholesterol transporters ATP binding cassette (Abc)a1 and Abcg1. Tretinoin, 13-cis retinoic acid (13-cis-RA), 9-cis-RA, and the selective retinoid X receptor (RXR) agonist methoprene significantly increased cholesterol efflux induced by cholesterol acceptors and protein levels of Abca1 by 2.3- (± 0.25), 3.6- (± 0.42), 4.1- (± 0.5), and 1.75- (± 0.43) fold, respectively, and Abcg1 by 2.1- (± 0.26), 2.2- (± 0.33), 2.5- (± 0.23), and 2.2- (± 0.21) fold, respectively. 13-cis-RA and 9-cis-RA also significantly increased mRNA levels of Abca1 (maximal induction 7.3 ± 0.42 and 2.7 ± 0.17, respectively) and Abcg1 (maximal induction 2.0 ± 0.18 and 1.8 ± 0.09, respectively), and the levels of membrane-bound Abca1 (2.5 ± 0.3 and 2.5 ± 0.40-fold increase, respectively), whereas they significantly decreased intracellular cholesterol content without affecting cholesterol synthesis. The effect of 9-cis-RA on cholesterol homeostasis in astrocytes can be ascribed to the activation of RXR, whereas the effects of 13-cis-RA and tretinoin were independent of either RXRs or retinoic acid receptors. These findings suggest that retinoids affect cholesterol homeostasis in astrocytes and that this effect may be involved in both their therapeutic and teratogenic actions.

  14. Synthesis of isomers of 18F-labelled amino acid radiopharmaceutical: position 2- and 3-L-18F-alpha-methyltyrosine using a separation and purification system.

    PubMed

    Tomiyoshi, K; Amed, K; Muhammad, S; Higuchi, T; Inoue, T; Endo, K; Yang, D

    1997-02-01

    To diagnose cancers with radiolabelled amino acid using positron emission tomography, we have constructed a separation and purification system for the production of L-18F-alpha-methyltyrosine (L-18FAmT). This system could provide radioprotection and consistent production of L-18FAmT. L-18FAmT was synthesized and purified and the efficiency of the system was examined. The radiochemical yield of L-18FAmT was 20.3 +/- 5.1% (n = 5) based on the radioactivity trapped in the reaction vessel. The radiochemical purity was greater than 99.4 +/- 0.3% (n = 5). The radiochemical stability in phosphate-buffered saline and human plasma was examined and little decomposition was observed by HPLC analysis. Our results indicate that the separation and purification system gave simple and quick synthesis of L-18FAmT with a large reduction in radiation exposure and consistent production of L-18FAmT.

  15. Process for recovering 4,4 prime dihydroxydiphenyl sulfone from an isomer mixture

    SciTech Connect

    Zemlanicky, F.; Cooker, B.

    1991-03-19

    This patent describes a process for the recovery of 4,4{prime}-bisphenol sulfone from an isomer mixture comprising 4,4{prime}-bisphenol sulfone and 2,4{prime}-bisphenol sulfone. It comprises dissolving the isomer mixture in a basic aqueous solution comprising about one mole of base per mole of the mixture of 4,4{prime}-bisphenol sulfone and 2,4{prime}-bisphenol sulfone to form a basic isomer solution and adding acid to the isomer solution in an amount of from about 0.85 to 0.95 mole per mole of the 4,4{prime}-bisphenol sulfone wherein the acid is added in an amount sufficient to cause selective precipitation of crystals of 4,4{prime}-bisphenol sulfone yet in an amount less than sufficient to neutralize the isomer solution and removing the crystals of 4,4{prime}-bisphenol from the aqueous solution.

  16. Evidence for two interconverting protein isomers in the methotrexate complex of dihydrofolate reductase from Escherichia coli

    SciTech Connect

    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 those 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.

  17. Preferential hydrophobic interactions are responsible for a preference of D-amino acids in the aminoacylation of 5'-AMP with hydrophobic amino acids

    NASA Technical Reports Server (NTRS)

    Lacey, J. C. Jr; Wickramasinghe, N. S.; Sabatini, R. S.

    1992-01-01

    We have studied the chemistry of aminoacyl AMP to model reactions at the 3' terminus of aminoacyl tRNA for the purpose of understanding the origin of protein synthesis. The present studies relate to the D, L preference in the esterification of 5'-AMP. All N-acetyl amino acids we studied showed faster reaction of the D-isomer, with a generally decreasing preference for D-isomer as the hydrophobicity of the amino acid decreased. The beta-branched amino acids, Ile and Val, showed an extreme preference for D-isomer. Ac-Leu, the gamma-branched amino acid, showed a slightly low D/L ratio relative to its hydrophobicity. The molecular basis for these preferences for D-isomer is understandable in the light of our previous studies and seems to be due to preferential hydrophobic interaction of the D-isomer with adenine. The preference for hydrophobic D-amino acids can be decreased by addition of an organic solvent to the reaction medium. Conversely, peptidylation with Ac-PhePhe shows a preference for the LL isomer over the DD isomer.

  18. Identification and estimation of the levo isomer in raw materials and finished products containing atropine and/or hyoscyamine.

    PubMed

    Cieri, Ugo R

    2005-01-01

    The belladonna alkaloids atropine sulfate and hyoscyamine sulfate, occasionally used as anticholinergic and antimuscarinic agents, have identical molecular formulas but different stereo configurations. Hyoscyamine sulfate contains almost 100% of the levo isomer, whereas atropine sulfate is composed of equal parts of dextro and levo isomers. It is believed that the therapeutic properties of these alkaloids are due exclusively or primarily to the levo isomer. Currently available methods determine only the total amount of atropine (hyoscyamine) sulfate. A method has been developed and is reported for the identification and estimation of the levo and dextro isomers of atropine and hyoscyamine. Reference solutions are prepared in methanol at the following weights per 100 mL: 8.0 mg atropine sulfate; 4.0 mg hyoscyamine sulfate; 7.0 mg scopolamine hydrobromide; and 10.0 mg homatropine methylbromide. Samples of raw materials are similarly prepared in methanol, commercial products are also extracted or diluted with methanol, and solutions are filtered. Liquid chromatography is used for separations on a 25 cm Chirobiotic T2 column. The mobile phase is prepared by mixing 3.0 mL acetic acid and 2.0 mL triethylamine with 1000 mL methanol. The injection volume is 100 or 200 microL; the flow rate is about 0.35 mL/min. Fluorescence detection is at 255 nm excitation and 285 nm emission. Scopolamine hydrobromide and hyoscyamine eluted after 20 and 60 min, respectively. Atropine sulfate generated 2 peaks after 60 and 65 min. Homatropine methylbromide also produced 2 peaks after 70 and 85 min. Samples tested in this study included raw materials and commercial tablets or injections containing belladonna alkaloids. In all cases, the percentage calculated was that of the levo isomer relative to the total amount of atropine (hyoscyamine) present.

  19. Metastable isomers - A new class of interstellar molecules

    NASA Technical Reports Server (NTRS)

    Green, S.; Herbst, E.

    1979-01-01

    The abundances of a variety of metastable isomers of small organic molecules, analogous to HNC/HCN, in dense interstellar clouds are considered. These metastable species, some of which are thought to exist as intermediates in laboratory organic chemical reactions, are of considerable interest to chemists. Current ideas of gas-phase, ion-molecule chemistry are utilized to demonstrate that such metastable species should often be present in dense clouds in sufficient abundance to be observed. Unfortunately, the spectral constants of metastable isomers have rarely been determined in the laboratory, and quantum chemical calculations of a varying degree of accuracy must be utilized; results are included of some new quantum chemical calculations. The interstellar chemistry and expected microwave spectra of a representative sample of possibly important interstellar metastable isomers are discussed.

  20. 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.

  1. Binary homogeneous nucleation of octane isomers

    NASA Astrophysics Data System (ADS)

    Doster, George Jay

    The measurement of the binary homogeneous nucleation of i-octane and n-octane (2,2,4-trimethylpentane) has been performed with a Wilson cloud chamber. This system of octane isomers has been chosen because it exhibits the desirable properties of a nearly ideal system. The octanes are non-polar, do not hydrogen bond, and have a low heat of mixing. The results from this experiment are presented and compared to the binary classical nucleation theory, the diffuse interface theory, and the binary scaled nucleation theory. The data from this experiment includes 3 mixtures of the octane isomers in mole fraction ratios of 1:1, 1:3, and 3:1 along with results from the pure octanes. Nucleation rates from approximately 100 to 50,000 cm3s and nucleation temperatures of 215 K to 260 K are included. This wide range of data is an effort to create a collection of data to which modified or new nucleation theories may be compared.

  2. New high spin isomers obtained in thermal fission

    SciTech Connect

    Fogelberg, B.; Mach, H.; Gausemel, H.; Omtvedt, J. P.; Mezilev, K. A.

    1998-10-26

    The product nuclei following fission often are initially highly excited and have high angular momenta. As a consequence, there is a substantial probability for the population of isomeric yrast traps in the vicinity of closed shells. The excitation energies and decay properties of such isomers give important formation regarding the shell structure and interaction energies. Recent experiments at the OSIRIS mass separator have revealed a number of isomers in the {sup 132}Sn region having angular momenta exceeding 10 units. A brief presentation is given of some experimental results and their interpretation.

  3. On the calculation of Mössbauer isomer shift.

    PubMed

    Filatov, Michael

    2007-08-28

    A quantum chemical computational scheme for the calculation of isomer shift in Mossbauer spectroscopy is suggested. Within the described scheme, the isomer shift is treated as a derivative of the total electronic energy with respect to the radius of a finite nucleus. The explicit use of a finite nucleus model in the calculations enables one to incorporate straightforwardly the effects of relativity and electron correlation. The results of benchmark calculations carried out for several iron complexes as well as for a number of atoms and atomic ions are presented and compared with the available experimental and theoretical data. PMID:17764223

  4. Interconversion of diborane(4) isomers

    NASA Technical Reports Server (NTRS)

    Stanton, John F.; Gauss, Juergen; Bartlett, Rodney J.; Helgaker, Trygve; Jorgensen, Poul; Jensen, Hans J. A.; Taylor, Peter R.

    1992-01-01

    Highly correlated electronic structure computations using many-body perturbation theory and coupled-cluster gradient techniques are used to study the reaction pathway that links the two forms (C2u and D2d) of diborane(4). The results obtained indicate that a low-energy pathway exists for interconversion of the two low-lying isomers of diborane(4). The proposed mechanism consists of a single concerted but nonsynchronous rotation of the BH2 groups. The pathway first follows an idealized reaction coordinate which preserves C2 symmetry, but then bifurcates at a branch point, leading to two equivalent transition states which lack nontrivial elements of symmetry.

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

    PubMed

    Willemin, Marie-Emilie; Desmots, Sophie; Le Grand, Rozenn; Lestremau, François; Zeman, Florence A; Leclerc, Eric; Moesch, Christian; Brochot, Céline

    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 acid (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.

  6. 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

  7. Improved HRGC separation of cis, trans CLA isomers as Diels-Alder adducts of alkyl esters.

    PubMed

    Blasi, F; Giua, L; Lombardi, G; Codini, M; Simonetti, M S; Damiani, P; Cossignani, L

    2011-05-01

    This paper reports the separation of four isomers of conjugated linoleic acid (CLA), c,t/t,c-8,10; c,t/t,c-9,11; c,t/t,c-10,12; c,t/t,c-11,13, after reaction of esterification with aliphatic alcohols of different chain length and adduct formation with 4-methyl-1,2,4-triazoline-3,5-dione (MTAD). The high resolution gas chromatographic analyses were carried out using a simple 50-m cyanopropyl polysiloxane capillary column both with a flame ionization detector and a mass spectrometer. The resolution between the two pair of isomers: c,t/t,c-9,11 and c,t/t,c-10,12 and between c,t/t,c-10,12 and c,t/t,c-11,13 isomers were good for all the investigated alkyl esters and increased with the chain length of alcohol esterified to carboxylic moiety of CLA isomers. The most interesting result was relative to the c,t/t,c-8,10 and c,t/t,c-9,11 isomers, critical pair of isomers also when analyzed with a 120-m cyanopropyl polysiloxane capillary column; their resolution also increased from methyl to hexyl esters of CLA isomers and reached an acceptable value (0.8) in the case of hexyl esters. The best resolutions of the four considered CLA isomers were obtained with the hexyl esters of MTAD adducts of the isomers, without excessive analysis time. This method was useful and simple to evaluate the profile of the four main c,t isomers in commercial CLA samples.

  8. Ozonation kinetics of phenolic acids present in wastewaters from olive oil mills

    SciTech Connect

    Benitez, F.J.; Beltran-Heredia, J.; Acero, J.L.; Pinilla, M.L.

    1997-03-01

    A kinetic study of the degradation by ozone of eight phenolic acids present in wastewaters from olive oil mills has been performed by using a competition kinetic method. The selected phenolic acids are: caffeic, p-coumaric, syringic, vanillic, 3,4,5-trimethoxybenzoic, veratric, p-hydroxy-benzoic, and protocatechuic. The influence of the operating variables (temperature, pH, and ozone partial pressure in the gas stream) is established, and the stoichiometric ratios for the individual direct reactions between ozone and each acid are determined. Once the reaction rate constants are evaluated, they are correlated as a function of temperature and pH into kinetic expressions which are provided for every phenolic acid. The global process occurs in the fast and pseudo-first-order kinetic regime of absorption, a condition required by the competition model to be used.

  9. 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.

  10. Complete hexose isomer identification with mass spectrometry.

    PubMed

    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.

  11. Gas chromatography of volatile fatty acids. Method involving separation from biological material by vacuum distillation.

    PubMed

    Tyler, J E; Dibdin, G H

    1975-02-19

    A method is described for the quantitation of C2-C5 volatile fatty acids present in biological tissues. It involved recovery of the acids from their biological matrix by vacuum micro-distillation at room temperature, followed by gas phase separation of aqueous solutions on orthophosphoric acid-modified Phasepak Q columns. The subsequent gas chromatographic procedure resolved iso from normal isomers and showed a linear response for each volatile acid over the range 10-400 ng. There was no evidence of ghosting, isomer peak broadening, or peak tailing. Relative molar response values were shown to be linear with carbon number for all the volatile fatty acids studied.

  12. Reversed Phase High-Performance Liquid Chromatographic Ultra-violet (Photo Diode Array) Quantification of Oleanolic Acid and its Isomer Ursolic Acid for Phytochemical Comparison and Pharmacological Evaluation of Four Leucas Species Used in Ayurveda

    PubMed Central

    Shukla, Pushpendra Kumar; Misra, Ankita; Srivastava, Sharad; Rawat, Ajay K. S.

    2016-01-01

    Content: Different Leucas species are well known as “Dronpushpi,” a well-known herb of Ayurveda, used in the treatment of various ailments. Objective: Evaluation of four industrially important Leucas species for their in vitro antidiabetic potential and radical scavenging effect along with high-performance liquid chromatographic quantification of the bioactive triterpenes. Materials and Methods: The quantification of triterpenes was carried out on C-18 column with acetonitrile and water (90:10) as the solvent system at a detection wavelength of 210 nm. In vitro antidiabetic activity was evaluated by α-amylase inhibition assay based on starch–iodine and 3,5 dinitrosalicylic acid (DNS) method. Antioxidant activity was calculated by five different models, namely total phenolic and total flavonoid content, free radical scavenging activity by 1-1-diphenyl-2-pic-rylhydrazyl (DPPH), ferric-reducing power assay, and the total antioxidant capacity. Results: Maximum concentration of oleanolic acid was found in Leucas cristata, followed by Leucas mollissima, Leucas Aspera, and Leucas biflora. Ursolic acid was highest in L. mollissima and then in L. biflora, L. cristata, and L. aspera, respectively. In in vitro antidiabetic activity, IC50 of L. aspera (1.56 ± 0.01 mg/ml) and L. mollissima (0.75 ± 0.005 mg/ml) were found to be highest in DNS and iodine starch assay. IC50 in DPPH assay ranges from 0.6 ± 0.011 to 1.68 ± 0.011 mg/ml. Antioxidant capacity follows the order; L. aspera > L. mollissima > L. biflora > L. cristata. Conclusion: Promising activities were observed in targeted species, thus L. mollissima, L. biflora, and L. cristata can be used alternatively as a substitute to L. aspera. SUMMARY Physicochemical parameters are within the limit as per the Ayurvedic Pharmacopoeia of IndiaMaximum concentration of oleanolic acid was found in Leucas cristata; however, ursolic acid was highest in Leucas mollissimaIn vitro antidiabetic activity of Leucas aspera and L

  13. Applications for biotechnology: present and future improvements in lactic acid bacteria.

    PubMed

    McKay, L L; Baldwin, K A

    1990-09-01

    The lactic acid bacteria are involved in the manufacture of fermented foods from raw agricultural materials such as milk, meat, vegetables, and cereals. These fermented foods are a significant part of the food processing industry and are often prepared using selected strains that have the ability to produce desired products or changes efficiently. The application of genetic engineering technology to improve existing strains or develop novel strains for these fermentations is an active research area world-wide. As knowledge about the genetics and physiology of lactic acid bacteria accumulates, it becomes possible to genetically construct strains with characteristics shaped for specific purposes. Examples of present and future applications of biotechnology to lactic acid bacteria to improve product quality are described. Studies of the basic biology of these bacteria are being actively conducted and must be continued, in order for the food fermentation industry to reap the benefits of biotechnology.

  14. Hydrofluoric acid exposure: a case report and review on the clinical presentation and management.

    PubMed

    Strausburg, Matthew; Travers, Jeffrey; Mousdicas, Nico

    2012-01-01

    Exposure to hydrofluoric acid can cause severe skin damage via both corrosive and chemical means. Dermatologists should be aware of the various clinical presentations and knowledgeable of how to manage such patients. A case of a man with exposure of the hands after use of a consumer product containing hydrofluoric acid is presented. The presentation may vary depending on the concentration and duration of exposure. Patients experiencing exposure are at risk of serious complications, including death, resulting from electrolyte abnormalities. Information regarding the source of exposure will allow the physician to better predict the patient's course. The use of immediate flushing with water and the use of topical calcium gluconate can prevent extensive damage to the area of exposure and potentially fatal complications that may occur. More extensive burns may necessitate more invasive therapies. The treatment and the management and monitoring of such cases will allow for more optimal outcomes.

  15. Studies of multi-quasiparticle k-isomers in rare-earth and trans-fermium nuclei.

    SciTech Connect

    Kondev, F. G.; Dracoulis, G. D.; Khoo, T. L.; Lane, G. J.; Byrne, A. P.; Kibedi, T.; Ahmad, I.; Carpenter, M. P.; Janssens, R. V. F.; Lauritzen, T.; Lister, C. J.; Seweryniak, D.; Zhu, S.; Chowdhury, P.; Tandel, S. K.; Australian National Univ.; Univ. of Massachusetts Lowell

    2007-01-01

    Nuclear K-isomers play an important role in understanding the structure of deformed axially symmetric nuclei. Examples are presented of recent studies in the rare-earth region (A {approx} 180) using deep-inelastic and multi-nucleon transfer reactions, and in the trans-fermium region (A {approx} 250) using fusion-evaporation reactions. A specific two-level mixing scenario is invoked to explain the unusual decay of the K{sup {pi}} = 13{sup +} isomer in {sup 174}Lu. The identification of 2- and 4-quasiparticle isomers in {sup 254}No is discussed and predictions of similar isomers in neighboring No and Rf nuclei are presented.

  16. 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.

  17. The optical nature of methylsuccinic acid in human urine

    NASA Technical Reports Server (NTRS)

    Zeitman, B.; Lawless, J. G.

    1975-01-01

    Methylsuccinic acid was isolated from human urine, derivatized as the di-S-(+)-2-butyl ester, and analyzed using a gas chromatographic system capable of separating the enantiomers of the derivative. The R-(+)-isomer was found to be present. Methylsuccinic acid is potentially important as a criterion for abiogenicity, having been obtained as a racemic mixture from sources known to be abiotic.

  18. Utilization of Lactate Isomers by Propionibacterium freudenreichii subsp. shermanii: Regulatory Role for Intracellular Pyruvate

    PubMed Central

    Crow, Vaughan L.

    1986-01-01

    Five strains of Propionibacterium freudenreichii subsp. shermanii utilized the l-(+) isomer of lactate at a faster rate than they did the d-(−) isomer when grown with a mixture of lactate isomers under a variety of conditions. ATCC 9614, grown anaerobically in defined medium containing 160 mM dl-lactate, utilized only 4 and 15% of the d-(−)-lactate by the time 50 and 90%, respectively, of the l-(+)-lactate was used. The intracellular pyruvate concentration was high (>100 mM) in the initial stages of lactate utilization, when either dl-lactate or the l-(+) isomer was the starting substrate. The concentration of this intermediate dropped during dl-lactate fermentation such that when only d-(−)-lactate remained, the concentration was <20 mM. When only the d-(−) isomer was initially present, a similar relatively low concentration of intracellular pyruvate was present, even at the start of lactate utilization. The NAD+-independent lactate dehydrogenase activities in extracts showed different kinetic properties with regard to pyruvate inhibition, depending upon the lactate isomer present. Pyruvate gave a competitive inhibitor pattern with l-(+)-lactate and a mixed-type inhibitor pattern with d-(−)-lactate. It is suggested that these properties of the lactate dehydrogenases and the intracellular pyruvate concentrations explain the preferential use of the l-(+) isomer. PMID:16347134

  19. How are the Concepts and Theories of Acid-Base Reactions Presented? Chemistry in Textbooks and as Presented by Teachers

    ERIC Educational Resources Information Center

    Furio-Mas, Carlos; Calatayud, Maria Luisa; Guisasola, Jenaro; Furio-Gomez, Cristina

    2005-01-01

    This paper investigates the views of science and scientific activity that can be found in chemistry textbooks and heard from teachers when acid-base reactions are introduced to grade 12 and university chemistry students. First, the main macroscopic and microscopic conceptual models are developed. Second, we attempt to show how the existence of…

  20. High-resolution separation performance of poly(caprolactone)diol for challenging isomers of xylenes, phenols and anilines by capillary gas chromatography.

    PubMed

    Peng, Jianlin; Zhang, Yan; Yang, Xiaohong; Qi, Meiling

    2016-09-30

    Efficient separation of xylenes, phenols and anilines is a big issue in chemical and petroleum industries. This work presents the first example of employing poly (caprolactone) diol (PCL-Diol) as stationary phase for high-resolution gas chromatographic (GC) separations of these tough isomer mixtures. It showed medium polarity and stronger H-bonding basicity than H-bonding acidity. Impressively, PCL-Diol column exhibited extremely high resolving capability for the isomer mixtures of xylenes, cresols/xylenols, and toluidines/xylidines with good peak shapes. Moreover, it exhibited preferential retention for analytes of a linear alkyl chain, suggesting its shape fitting selectivity for specific analytes. In addition, its separation performance has good repeatability with RSD values on retention times below 0.01% for run to run (n=6), 0.67-0.80% for day to day (n=4) and 3.2-4.4% for column to column (n=4) repeatability, respectively. Furthermore, it was applied for the determination of isomer impurities in real samples, showing good potential for practical use. This work demonstrates the advantageous high-resolution separation performance for challenging isomers and shows its promising future of PCL-Diol-based materials in separation science. PMID:27608617

  1. Determination by GC×GC of fatty acid and conjugated linoleic acid (CLA) isomer profiles in six selected tissues of lambs fed on pasture or on indoor diets with and without rumen-protected CLA.

    PubMed

    Pellattiero, Erika; Cecchinato, Alessio; Tagliapietra, Franco; Schiavon, Stefano; Bittante, Giovanni

    2015-01-28

    In this study GC×GC was used to study the effects of pasture, hay, concentrate (indoor), and indoor plus 8 g/day of a rumen-protected conjugated linoleic acid (indoor-CLA) diets on the detailed fatty acid (FA) profiles of six tissues (muscles, fatty tissues, and liver) collected from 36 lambs. This powerful technique allowed the quantification of 128 FAs, of which 21 SFAs, 16 MUFAs, 19 PUFAs were identified by reference standards. The diets had similar, but not identical, effects on FA profiles (g/100 g FA) in the various tissues, as both indoor diets reduced total PUFAs (from 8.91 ± 6.27 to 8.06 ± 5.97; p < 0.05) and n-3 PUFAs (from 2.70 ± 2.37 to 1.50 ± 1.69; p < 0.01) and increased n-6 PUFA (from 3.76 ± 2.46 to 4.58 ± 3.42; p < 0.01), branched (from 2.37 ± 2.05 to 3.23 ± 0.54; p < 0.01), odd-chain FAs (from 5.88 ± 5.33 to 7.07 ± 1.51; p < 0.01) compared to pasture. Indoor-CLA increased CLAc9,t11 (from 0.42 ± 0.13 to 0.53 ± 0.19; p < 0.01), CLAt10,c12 (from 0.07 ± 0.06 to 0.12 ± 0.22; p < 0.05), and CLAc11,t13 (from 0.02 ± 0.04 to 0.05 ± 0.04; p < 0.05) compared to indoor. PMID:25525905

  2. Isomer-specific combustion chemistry in allene and propyne flames

    SciTech Connect

    Hansen, Nils; Miller, James A.; Westmoreland, Phillip R.; Kasper, Tina; Kohse-Hoeinghaus, Katharina; Wang, Juan; Cool, Terrill A.

    2009-11-15

    A combined experimental and modeling study is performed to clarify the isomer-specific combustion chemistry in flames fueled by the C{sub 3}H{sub 4} isomers allene and propyne. To this end, mole fraction profiles of several flame species in stoichiometric allene (propyne)/O{sub 2}/Ar flames are analyzed by means of a chemical kinetic model. The premixed flames are stabilized on a flat-flame burner under a reduced pressure of 25 Torr (=33.3 mbar). Quantitative species profiles are determined by flame-sampling molecular-beam mass spectrometry, and the isomer-specific flame compositions are unraveled by employing photoionization with tunable vacuum-ultraviolet synchrotron radiation. The temperature profiles are measured by OH laser-induced fluorescence. Experimental and modeled mole fraction profiles of selected flame species are discussed with respect to the isomer-specific combustion chemistry in both flames. The emphasis is put on main reaction pathways of fuel consumption, of allene and propyne isomerization, and of isomer-specific formation of C{sub 6} aromatic species. The present model includes the latest theoretical rate coefficients for reactions on a C{sub 3}H{sub 5} potential [J.A. Miller, J.P. Senosiain, S.J. Klippenstein, Y. Georgievskii, J. Phys. Chem. A 112 (2008) 9429-9438] and for the propargyl recombination reactions [Y. Georgievskii, S.J. Klippenstein, J.A. Miller, Phys. Chem. Chem. Phys. 9 (2007) 4259-4268]. Larger peak mole fractions of propargyl, allyl, and benzene are observed in the allene flame than in the propyne flame. In these flames virtually all of the benzene is formed by the propargyl recombination reaction. (author)

  3. Kinetics of Non-Catalytic Esterification of Free Fatty Acids Present in Jatropha Oil.

    PubMed

    Prasanna Rani, Karna Narayana; Ramana Neeharika, Tulasi Sri Venkata; Kumar, Thella Prathap; Satyavathi, Bankupalli; Sailu, Chintha

    2016-05-01

    Non-catalytic esterfication of free fatty acids (FFA) present in vegetable oils is an alternative pretreatment process for the biodiesel production. Biodiesel, consists of long-chain fatty acid methyl esters (FAME) and is obtained from renewable sources such as vegetable oils or animal fat. This study presents kinetics of thermal esterification of free fatty acids present in jatropha oil with methanol. The effect of process parameters like reaction time (1-5 h), temperature (170-190°C) and oil to methanol ratio (1:3-1:5) at constant pressure was investigated. The optimal conditions were found to be oil to methanol ratio of 1:4, 190°C, at 27.1 bar and 5 h which gave a maximum conversion of 95.1%. A second order kinetic model for both forward and backward reactions was proposed to study the reaction system. A good agreement was observed between the experimental data and the model values. The activation energy for forward reaction and the heat of reaction were found to be 36.364 Kcal/mol and 1.74 Kcal/mol respectively.

  4. Kinetics of Non-Catalytic Esterification of Free Fatty Acids Present in Jatropha Oil.

    PubMed

    Prasanna Rani, Karna Narayana; Ramana Neeharika, Tulasi Sri Venkata; Kumar, Thella Prathap; Satyavathi, Bankupalli; Sailu, Chintha

    2016-05-01

    Non-catalytic esterfication of free fatty acids (FFA) present in vegetable oils is an alternative pretreatment process for the biodiesel production. Biodiesel, consists of long-chain fatty acid methyl esters (FAME) and is obtained from renewable sources such as vegetable oils or animal fat. This study presents kinetics of thermal esterification of free fatty acids present in jatropha oil with methanol. The effect of process parameters like reaction time (1-5 h), temperature (170-190°C) and oil to methanol ratio (1:3-1:5) at constant pressure was investigated. The optimal conditions were found to be oil to methanol ratio of 1:4, 190°C, at 27.1 bar and 5 h which gave a maximum conversion of 95.1%. A second order kinetic model for both forward and backward reactions was proposed to study the reaction system. A good agreement was observed between the experimental data and the model values. The activation energy for forward reaction and the heat of reaction were found to be 36.364 Kcal/mol and 1.74 Kcal/mol respectively. PMID:27086997

  5. Highly Stable trans-Cyclooctene Amino Acids for Live-Cell Labeling.

    PubMed

    Hoffmann, Jan-Erik; Plass, Tilman; Nikić, Ivana; Aramburu, Iker Valle; Koehler, Christine; Gillandt, Hartmut; Lemke, Edward A; Schultz, Carsten

    2015-08-24

    trans-Cyclooctene groups incorporated into proteins via non-canonical amino acids (ncAAs) are emerging as specific handles for bioorthogonal chemistry. Here, we present a highly improved synthetic access to the axially and the equatorially linked trans-cyclooct-2-ene isomers (1 a,b). We further show that the axially connected isomer has a half-life about 10 times higher than the equatorial isomer and reacts with tetrazines much faster, as determined by stopped-flow experiments. The improved properties resulted in different labeling performance of the insulin receptor on the surface of intact cells.

  6. 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.

  7. Follow-up of the delta4 to delta16 trans-18:1 isomer profile and content in French processed foods containing partially hydrogenated vegetable oils during the period 1995-1999. Analytical and nutritional implications.

    PubMed

    Wolff, R L; Combe, N A; Destaillats, F; Boué, C; Precht, D; Molkentin, J; Entressangles, B

    2000-08-01

    America. Differences occur in the total intake of trans-18:1 acids, but most important, in individual trans-18:1 isomer intake, with a particular increase of the delta6-delta8 to delta10 isomers with increasing consumption of PHVO. It is inferred from the present and earlier data that direct GLC of fatty acids is a faulty procedure that results (i) in variable underestimates of total trans-18:1 acids, (ii) in a loss of information as regards the assessment of individual isomeric trans-18:1 acids, and (iii) in the impossibility of comparing data obtained from human tissues if the relative contribution of dietary PHVO and ruminant fats is not known.

  8. Lipophilic caffeic and ferulic acid derivatives presenting cytotoxicity against human breast cancer cells.

    PubMed

    Serafim, Teresa L; Carvalho, Filipa S; Marques, Maria P M; Calheiros, Rita; Silva, Tiago; Garrido, Jorge; Milhazes, Nuno; Borges, Fernanda; Roleira, Fernanda; Silva, Elisiaario T; Holy, Jon; Oliveira, Paulo J

    2011-05-16

    In the present work, lipophilic caffeic and ferulic acid derivatives were synthesized, and their cytotoxicity on cultured breast cancer cells was compared. A total of six compounds were initially evaluated: caffeic acid (CA), hexyl caffeate (HC), caffeoylhexylamide (HCA), ferulic acid (FA), hexyl ferulate (HF), and feruloylhexylamide (HFA). Cell proliferation, cell cycle progression, and apoptotic signaling were investigated in three human breast cancer cell lines, including estrogen-sensitive (MCF-7) and insensitive (MDA-MB-231 and HS578T). Furthermore, direct mitochondrial effects of parent and modified compounds were investigated by using isolated liver mitochondria. The results indicated that although the parent compounds presented no cytotoxicity, the new compounds inhibited cell proliferation and induced cell cycle alterations and cell death, with a predominant effect on MCF-7 cells. Interestingly, cell cycle data indicates that effects on nontumor BJ fibroblasts were predominantly cytostatic and not cytotoxic. The parent compounds and derivatives also promoted direct alterations on hepatic mitochondrial bioenergetics, although the most unexpected and never before reported one was that FA induces the mitochondrial permeability transition. The results show that the new caffeic and ferulic acid lipophilic derivatives show increased cytotoxicity toward human breast cancer cell lines, although the magnitude and type of effects appear to be dependent on the cell type. Mitochondrial data had no direct correspondence with effects on intact cells suggesting that this organelle may not be a critical component of the cellular effects observed. The data provide a rational approach to the design of effective cytotoxic lipophilic hydroxycinnamic derivatives that in the future could be profitably applied for chemopreventive and/or chemotherapeutic purposes.

  9. Isomer effects on polyimide properties

    NASA Technical Reports Server (NTRS)

    Stump, B. L.

    1974-01-01

    The polymerization of 2,4'-methylene-dianiline with benzophenone tetracarboxylic acid dianhydride yields high molecular weight polyamic acid. Polyimide is formed when films of the polyamic acid are cured between 200 - 300 C. A lower molecular weight polyamic acid is obtained from 2,2'-MDA with BTDA, but it appears that a lowering of the reaction temperature will yield high molecular weight polymer. Evaluation of these polymers is underway. Continued efforts to synthesize 2,3'- MDA and 2,3'-diaminobenzophenone have met with little success.

  10. Identification of RNA sequence isomer by isotope labeling and LC-MS/MS.

    PubMed

    Li, Siwei; Limbach, Patrick A

    2014-11-01

    Recently, we developed a method for modified ribonucleic acid (RNA) analysis based on the comparative analysis of RNA digests (CARD). Within this CARD approach, sequence or modification differences between two samples are identified through differential isotopic labeling of two samples. Components present in both samples will each be labeled, yielding doublets in the CARD mass spectrum. Components unique to only one sample should be detected as singlets. A limitation of the prior singlet identification strategy occurs when the two samples contain components of unique sequence but identical base composition. At the first stage of mass spectrometry, these sequence isomers cannot be differentiated and would appear as doublets rather than singlets. However, underlying sequence differences should be detectable by collision-induced dissociation tandem mass spectrometry (CID MS/MS), as y-type product ions will retain the original enzymatically incorporated isotope label. Here, we determine appropriate instrumental conditions that enable CID MS/MS of isotopically labeled ribonuclease T1 (RNase T1) digestion products such that the original isotope label is maintained in the product ion mass spectrum. Next, we demonstrate how y-type product ions can be used to differentiate singlets and doublets from isomer sequences. We were then able to extend the utility of this approach by using CID MS/MS for the confirmation of an expected RNase T1 digestion product within the CARD analysis of an Escherichia coli mutant strain even in the presence of interfering and overlapping digestion products from other transfer RNAs.

  11. Search for the isomers of C2H3NO and C2H3NS in the Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Etim, Emmanuel; Chakrabarti, Sandip Kumar; Das, Ankan; Gorai, Prasanta; Arunan, Elangannan

    2016-07-01

    With about 40% of all the known interstellar and circumstellar molecules having their isomeric analogues as known astromolecules, isomerism remains one of the leading themes in interstellar chemistry. In this regard, the recent detection of methyl isocyanate (with a number of isomeric analogues) in the Sgr B2(N) giant molecular cloud opens a new window for the possible astronomical detection of other C_2H_3NO isomers. The present work looks at the possibility of detecting other isomers of methyl isocyanate by considering different factors such as thermodynamic stability of the different isomers with respect to the Energy, Stability and Abundance (ESA) relationship, effect of interstellar hydrogen bonding with respect to the formation these isomers on the surface of the interstellar dust grains, possible formation routes for these isomers, spectroscopic parameters for potential astromolecules among these isomers, chemical modeling among other studies. The same studies are repeated for the C_2H_3NS isomers which are the isoelectroninc analogues of the C_2H_3NO isomers taking into account the unique chemistry of S and O-containing interstellar molecular species. Among the C_2H_3NS isomers, methyl isothiocyanate remains the most potential candidate for astronomical observation.

  12. 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.

  13. Structural isomers of C2N+: a selected-ion flow tube study.

    PubMed

    Knight, J S; Petrie, S A; Freeman, C G; McEwan, M J; McLean, A D; DeFrees, D J

    1988-01-01

    Reactivities of the structural isomers CCN+ and CNC+ were examined in a selected-ion flow tube at 300 +/- 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+ --> CNC+ is calculated to be 195 kJ mol-1 above the CNC+. The results provide evidence that the more reactive CCN+ isomer is unlikely to be present in measurable densities in interstellar clouds.

  14. Accumulation of D- vs. L-isomers of alanine and leucine in rat prostatic adenocarcinoma

    SciTech Connect

    Conti, P.S.; Schmall, B.; Bigler, R.E.; Zanzonico, P.B.; Kleinert, E.; Whitmore, W.F. Jr.

    1985-05-01

    It has been reported that tumor tissue may accumulate some D-amino acids preferentially over the L-isomers. In order to investigate the potential use of carbon-11 labeled amino acid isomers for in vivo tumor studies with positron emission tomography in patients, the tissue distributions of alanine and leucine, substrates for the A-type and L-type amino acid transport systems, respectively, were studied in Copenhagen rates bearing the Dunning R3327G prostatic adenocarcinoma. The authors have previously reported differences in the accumulation of A-type vs. L-type amino acids in rat prostatic adenocarcinoma and normal tissues. All compounds were labeled with C-14 in the carboxyl position with specific activities of 30.0-56.6 mCi/mmol. Higher levels of C-14 activity (Relative Concentration (RC)=dpm found per gm tissue + dpm inject per gm animal mass) were observed in tumor tissue using D-alanine (0.71) compared to L- (0.21) or DL-alanine (0.27) at 45 min post-injection. While tumor/prostate and tumor/liver ratios were above 2 for all three substrates, tumor/blood and tumor/muscle were above one for only the D-isomer. Comparisons made with D-, L-, and DL-leucine also demonstrated a higher level of RC in tumor tissue with the D-isomer (0.84) vs. the L-(0.66) and DL-leucine (0.63). In this case, however, tumor/blood, tumor/prostate, and tumor/muscle ratios were above one for all three substrates, while tumor/liver ratios were below one. These results support the observation of a preferential accumulation of D-amino acids in tumor tissue over the natural L-isomers. Observed differences in the accumulation of the isomers in normal tissues are discussed.

  15. Isomer-specific accumulation of perfluorooctane sulfonate in the liver of chicken embryos exposed in ovo to a technical mixture.

    PubMed

    O'Brien, Jason M; Kennedy, Sean W; Chu, Shaogang; Letcher, Robert J

    2011-01-01

    Prior to its recent phaseout, perfluorooctane sulfonate (PFOS) was produced by electrochemical fluorination processes, which yielded technical mixtures composed of linear isomer (∼65-79%) and several branched isomers (∼21-35%). Because PFOS can biomagnify in wildlife, birds that occupy higher trophic levels are at increased risk of exposure. We hypothesized that the pharmacokinetic properties of PFOS are isomer-specific in developing chicken (Gallus gallus domesticus) embryos exposed to technical grade PFOS (T-PFOS). In the present study, T-PFOS was composed of 62.7% linear isomer (L-PFOS), and 37.3% branched isomer, including six mono(trifluoromethyl)-branched isomers and four bis(trifluoromethyl)-branched isomers. Concentrations of 0.1, 5, or 100 µg/g of T-PFOS were injected into the air cell of chicken eggs prior to incubation. After pipping, compared with T-PFOS, the PFOS isomer profile in embryonic liver tissue for the 0.1 µg/g dose group showed 21% enrichment in the proportion of L-PFOS with a corresponding decrease in the proportion of branched isomers. Not all branched isomers were discriminated against at equal rates. The proportion of two mono(trifluoromethyl)-branched isomers and three bis(trifluoromethyl)-branched isomers decreased to a greater degree than other branched isomers. In contrast, the mono-branched isomer, P6MHpS, was overrepresented in the low-dose group. In the higher dose groups, L-PFOS was still enriched but only by approximately 10%, which indicated a dose-dependent change in isomer composition relative to T-PFOS. These results show that accumulation of PFOS in chicken embryo livers is dependent on the presence and position of branches on the alkyl backbone. This supports the hypothesis that the pharmacokinetics of PFOS are isomer-specific in biota, and may help explain why wildlife PFOS burdens are dominated by L-PFOS relative to T-PFOS mixtures.

  16. Theoretical characterisation of the SSO, cyclic SOS and SOS isomers

    NASA Astrophysics Data System (ADS)

    Denis, Pablo A.

    2010-01-01

    The SSO, cyclic SOS and open SOS isomers have been investigated, employing the CCSD(T) methodology and the cc-pV(X + d)Z X = 3, 4, 5, 6 basis sets. The anharmonic force fields have been calculated to predict the fundamental vibrational frequencies, rotational constants, vibration-rotation corrections, anharmonic corrections to zero-point energies, and structural parameters. At the CCSD(T)/CBS limit and including corrections for scalar relativistic effects, complete quadruple excitations, spin-orbit and core-valence correlation effects, the estimated enthalpies of formation are -13.9 ± 1, 32.1 ± 1, and -51.2 ± 1 kcal/mol, for SSO, cyclic-SOS and open-SOS, respectively. Finally, it was found that the asymmetric SO stretch of the open and cyclic SOS isomers are located in a nearly identical position and it is likely that SOS also maybe present in the surface of Io.

  17. Shape Isomers - a Key to Fission Barriers

    NASA Astrophysics Data System (ADS)

    Oberstedt, S.; Hambsch, F.-J.; Kornilov, N.; Lövestam, G.; Oberstedt, A.; Gawrys, M.

    2008-04-01

    Quantitative predictions of fission product yields are relevant for the reliable operation of different modern nuclear applications. This concerns the realistic characterizations of the radio-toxicity of the fuel elements after the envisaged extended irradiation, as well as sub-critical assemblies, where the number of delayed neutrons from minor actinides is determined by the characteristic emission yields of the corresponding so-called pre-cursor isotopes. However, to be able to make more reliable quantitative predictions of fission characteristics requires the better understanding of the fission process itself. For this purpose a better knowledge about the distinct structure of the nuclear energy landscape around the fission barrier is indispensable. In particular, the question should be answered, whether the fission barrier is either double- or triple-humped or even multi-humped as been proposed within the multi-modal neck rupture model. Despite quite some effort based on different experimental techniques and theoretical approaches, this question remains still unanswered. There is still no consistent picture of the fission barrier available and hence, different sets of barrier parameters are in use, unable to describe the different observed phenomena in a coherent way. With the systematic investigation of shape isomer population, its decay modes as well as the branching ratio, precise information can be obtained to resolve the puzzling situation. The experimental approach will be discussed and results from first experiments presented.

  18. High-harmonic spectroscopy of molecular isomers

    SciTech Connect

    Wong, M. C. H.; Brichta, J.-P.; Bhardwaj, V. R.; Spanner, M.; Patchkovskii, S.

    2011-11-15

    We demonstrate that high-order-harmonic generation (HHG) spectroscopy can be used to probe stereoisomers of randomly oriented 1,2-dichloroethylene (C{sub 2}H{sub 2}Cl{sub 2}) and 2-butene (C{sub 4}H{sub 8}). The high-harmonic spectra of these isomers are distinguishable over a range of laser intensities and wavelengths. Time-dependent numerical calculations of angle-dependent ionization yields for 1,2-dichloroethylene suggest that the harmonic spectra of molecular isomers reflect differences in their strong-field ionization. The subcycle ionization yields for the cis isomer are an order of magnitude higher than those for the trans isomer. The sensitivity in discrimination of the harmonic spectra of cis- and trans- isomers is greater than 8 and 5 for 1,2-dichloroethylene and 2-butene, respectively. We show that HHG spectroscopy cannot differentiate the harmonic spectra of the two enantiomers of the chiral molecule propylene oxide (C{sub 3}H{sub 6}O).

  19. 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.

  20. Isomer Energy Differences for the C4H3 and C4H5 Isomers UsingDiffusion Monte Carlo

    SciTech Connect

    Domin, D.; Lester Jr., W.A.; Whitesides, R.; Frenklach, M.

    2007-12-01

    A new diffusion Monte Carlo study is performed on the isomers of C{sub 4}H{sub 3} and C{sub 4}H{sub 5} emulating the methodology of a previous study [Int. J. Chem. Kinetics 33, 808 (2001)]. Using the same trial wave function form of the previous study, substantially different isomerization energies were found owing to the use of larger walker populations in the present work. The energy differences between the E and I isomers of C{sub 4}H{sub 3} were found to be 10.5 {+-} 0.5 kcal/mol and for C{sub 4}H{sub 5}, 9.7 {+-} 0.6 kcal/mol. These results are in reasonable accord with recent MRCI and CCSD(T) findings.

  1. Disentangling the Contribution of Multiple Isomers to the Infrared Spectrum of the Protonated Water Heptamer.

    PubMed

    Heine, Nadja; Fagiani, Matias R; Asmis, Knut R

    2015-06-18

    We use infrared/infrared double-resonance population labeling (IR(2)MS(2)) spectroscopy in the spectral region of the free and hydrogen-bonded OH stretching fundamentals (2880-3850 cm(-1)) to identify the number and to isolate the vibrational signatures of individual isomers contributing to the gas-phase IR spectra of the cryogenically cooled protonated water clusters H(+)(H2O)n·H2/D2 with n = 7-10. For n = 7, four isomers are identified and assigned. Surprisingly, the IR(2)MS(2) spectra of the protonated water octa-, nona-, and decamer show no evidence for multiple isomers. The present spectra support the prediction that the quasi-2D to 3D structural transition occurs in between n = 8 and 9 in the cold cluster regime. However, the same models have difficulty explaining the remarkable size dependence of the isomer population reported here.

  2. An isomer-specific high-energy collision-induced dissociation MS/MS database for forensic applications: a proof-of-concept on chemical warfare agent markers.

    PubMed

    Subramaniam, Raja; Östin, Anders; Nygren, Yvonne; Juhlin, Lars; Nilsson, Calle; Åstot, Crister

    2011-09-01

    Spectra database search has become the most popular technique for the identification of unknown chemicals, minimizing the need for authentic reference chemicals. In the present study, an isomer-specific high-energy collision-induced dissociation (CID) MS/MS spectra database of 12 isomeric O-hexyl methylphosphonic acids (degradation markers of nerve agents) was created. Phosphonate anions were produced by the electrospray ionization of phosphonic acids or negative-ion chemical ionization of their fluorinated derivatives and were analysed in a hybrid magnetic-sector-time-of-flight tandem mass spectrometer. A centre-of-mass energy (E(com)) of 65 eV led to an optimal sequential carbon-carbon bond breakage, which was interpreted in terms of charge remote fragmentation. The proposed mechanism is discussed in comparison with the routinely used low-energy CID MS/MS. Even-mass (odd-electron) charge remote fragmentation ion series were diagnostic of the O-alkyl chain structure and can be used to interpret unknown spectra. Together with the odd-mass ion series, they formed highly reproducible, isomer-specific spectra that gave significantly higher database matches and probability factors (by 1.5 times) than did the EI MS spectra of the trimethylsilyl derivatives of the same isomers. In addition, ionization by negative-ion chemical ionization and electrospray ionization resulted in similar spectra, which further highlights the general potential of the high-energy CID MS/MS technique. PMID:21915956

  3. K isomers as probes of nuclear structure

    SciTech Connect

    Tandel, S. K.

    2014-08-14

    K isomers are studied in Pu and Cm isotopes, and also in Hf and W nuclei. Many high-K states, several of which are isomeric, are identified. Lifetime measurements spanning the ns-s range have been performed, and decay paths of isomers established. Rotational bands built on high-K states are also identified in many cases. Isomer decays are considerably hindered in many instances, both in the A≈180 and 250 regions indicating that K is an approximately conserved quantum number. High-K states become the favored excitation mode at high spins in the A≈180 region. The energies of the 2-quasiparticle high-K states in Cm isotopes suggest the presence of a deformed subshell gap at N=152.

  4. 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.

  5. Diffusion studies of dihydroxybenzene isomers in water-alcohol systems.

    PubMed

    Codling, Dale J; Zheng, Gang; Stait-Gardner, Tim; Yang, Shu; Nilsson, Mathias; Price, William S

    2013-03-01

    Nuclear magnetic resonance diffusion studies can be used to identify different compounds in a mixture. However, because the diffusion coefficient is primarily dependent on the effective hydrodynamic radius, it is particularly difficult to resolve compounds with similar size and structure, such as isomers, on the basis of diffusion. Differential solution interactions between species in certain solutions can afford possibilities for separation. In the present study, the self-diffusion of the three isomers of dihydroxybenzene (i.e., (1,2-) catechol, (1,3-) resorcinol, and (1,4-) hydroquinone) was studied in water, aqueous monohydric alcohols (i.e., ethanol, 1-propanol, tert-butanol), and aqueous ethylene glycol. These systems allowed the effects of isomerism and differential solvent interactions on diffusion to be examined. It was found that, while in aqueous solution these isomers had the same diffusion coefficient, in water-monohydric alcohol systems the diffusion coefficient of catechol differed from those of resorcinol and hydroquinone. The separation was found to increase at higher concentrations of monohydric alcohols. The underlying chemical reasons for these differences were investigated.

  6. A Novel Method for Presenting the Amino Acids in an Introductory Biochemistry Course.

    ERIC Educational Resources Information Center

    Kuehl, LeRoy

    1978-01-01

    Introduces an approach to teaching amino acids that employs the use of a poem containing information on the structure and properties of amino acids, and of slides illustrating the poem. Student response to the method was positive. (MA)

  7. An Assessment of Nuclear Isomers as an Energy Storage Medium

    SciTech Connect

    Hartouni, E P

    2008-12-08

    Nuclear Isomers have been suggested as a potential high energy density medium that might be used to store energy. This talk assesses the state of the science supporting key elements of using nuclear isomers in energy storage applications. The focus is on the nuclear isomer {sup 178m2}Hf which has been most widely suggested for energy storage applications. However, the science issues apply to all nuclear isomer. The assessment addresses the production of the nuclear isomer, and inducing the release of the isomer. Also discussed are novel speculations on photon and/or neutron chain reactions, both as a 'pure' material as well as mixed with other materials.

  8. An Assessment of Nuclear Isomers as an Energy Storage Medium

    SciTech Connect

    Hartouni, Edward P.

    2009-03-16

    Nuclear Isomers have been suggested as a potential high energy density medium that might be used to store energy. This talk assesses the state of the science supporting key elements of using nuclear isomers in energy storage applications. The focus is on the nuclear isomer {sup 178m2}Hf which has been most widely suggested for energy storage applications. However, the science issues apply to all nuclear isomer. The assessment addresses the production of the nuclear isomer, and inducing the release of the isomer. Also discussed are novel speculations on photon and/or neutron chain reactions, both as a 'pure' material as well as mixed with other materials.

  9. New Millisecond Isomer Lifetime Measurements at LANSCE

    SciTech Connect

    Devlin, M. Nelson, R.O.; Fotiades, N.; O'Donnell, J.M.

    2014-06-15

    New half-life measurements have been made of the millisecond isomers {sup 71m}Ge, {sup 114m2}I, {sup 208m}Bi, {sup 88m1}Y, {sup 88m2}Y, and {sup 75m}As populated in neutron-induced reactions. These measurements were made using the unique time structure of the LANSCE/WNR neutron source, by observing the γ-ray decays of the isomers during the time between the LANSCE proton macropulses. Two different LANSCE proton beam time structures were used. The GEANIE array of HPGe detectors was used to detect the γ-ray decays.

  10. 'Melatonin isomer' in wine is not an isomer of the melatonin but tryptophan-ethylester.

    PubMed

    Gardana, Claudio; Iriti, Marcello; Stuknytė, Milda; De Noni, Ivano; Simonetti, Paolo

    2014-11-01

    Melatonin is a neurohormone, chronobiotic, and antioxidant compound found in wine and deriving directly from grapes and/or synthesized by yeast during alcoholic fermentation. In addition, a melatonin isomer has been detected in different foods, wine among them. The special interest for melatonin isomer related to the fact that it was found in greater quantities than melatonin and probably shares some of its biological properties. Despite this, its chemical structure has not yet been defined; although some researchers hypothesize, it could be melatonin with the ethylacetamide group shifted into position N1. Thus, the aim of our study was to identify the structures of the melatonin isomer. For this purpose, melatonin and melatonin isomer in Syrah wine were separated chromatographically by a sub-2 μm particle column and detected by tandem mass spectrometry. The sample was then purified and concentrated by solid-phase extraction, hydrolyzed with alkali or esterase, and substrates and products quantified by UPLC-MS/MS. Moreover, melatonin, melatonin isomer, and their product ions were evaluated by high-resolution mass spectrometry. The amount of melatonin isomer and melatonin in the wine was 84 ± 4 and 3 ± 0 ng/mL, respectively. In the solutions, containing diluted alkali or esterase, melatonin isomer was hydrolyzed in about 8 min. Correspondingly, tryptophan was detected, and its amount increased and reached the maximum concentration in about 8 min. Melatonin concentration was not affected by diluted alkali or esterase. The fragmentation pattern of melatonin isomer was different from that of melatonin but comparable to that of tryptophan-ethylester. Finally, the so-called melatonin isomer identity was verified by cochromatography with authentic standard of tryptophan-ethylester.

  11. Isomer Tagging with a Dual Multi-Wire Proportional Counter and a Differential Plunger

    SciTech Connect

    Cullen, D. M.; Mason, P. J. R.; Khan, S.; Kishada, A. M.; Varley, B. J.; Rigby, S. V.; Scholey, C.; Greenlees, P.; Rahkila, P.; Jones, P. M.; Julin, R.; Juutinen, S.; Leino, M.; Leppaenen, A. P.; Nyman, M.; Uusitalo, J.; Grahn, T.; Pakarinen, J.; Nieminen, P.

    2008-05-12

    This report details the status of an experimental research programme which has studied isomeric states in the mass 130-160 region of the nuclear chart. Several new isomers have been established and characterised near the proton drip line using a recoil isomer tagging technique at the University of Jyvaeskylae, Finland. The latest experiments have been performed with a modified setup where the standard GREAT focal-plane double-sided silicon-strip detector was changed to a dual multi-wire proportional-counter arrangement. This new setup has improved capability for short-lived isomer studies where large focal-plane rates can be tolerated. The results of key recent experiments for nuclei situated above ({sup 153}Yb, {sup 152}Tm) and below ({sup 144}Ho, {sup 142}Tb) the N = 82 shell gap were presented. These studies have charted the evolution of isomeric states across the neutron shell from K-Isomers at N = 74, to shape isomers at N = 77 and shell-model isomers at N = 82, 83. The excitation energies for some of the lowest-lying excited states in these isomeric nuclei show behaviour which is characteristic of an X(5) symmetry falling midway between the limits expected for pure vibrational and rotational behaviour. The future prospects for studies of these nuclei were discussed using an isomer-tagged differential-plunger setup. This technique will be capable of establishing the deformation of the states above the isomers and will aid in determining whether their behaviour is indeed well described by the X(5) symmetry limit.

  12. Isomer Studies for Nuclei near the Proton Drip Line in the Mass 130-160 Region

    SciTech Connect

    Cullen, D. M.; Mason, P. J. R.; Khan, S.; Kishada, A. M.; Varley, B. J.; Rigby, S. V.; Scholey, C.; Greenlees, P.; Rahkila, P.; Jones, P. M.; Julin, R.; Juutinen, S.; Leino, M.; Leppaenen, A. P.; Nyman, M.; Uusitalo, J.; Grahn, T.; Nieminen, P.; Pakarinen, J.

    2007-11-30

    This report details the status of an experimental research programme which has studied isomeric states in the mass 130-160 region of the nuclear chart. Several new isomers have been established and characterised near the proton drip line using a recoil isomer tagging technique at the University of Jyvaeskylae, Finland. The latest experiments have been performed with a modified setup where the standard GREAT focal-plane double-sided silicon-strip detector was changed to a dual multi-wire proportional-counter arrangement. This new setup has improved capability for short-lived isomer studies where high focal-plane rates can be tolerated. The results of key recent experiments for nuclei situated above ({sup 153}Yb,{sup 152}Tm) and below ({sup 136}Pm,{sup 142}Tb) the N = 82 shell gap were presented along with an interpretation for the isomers. Finally, the future prospects of the technique, using an isomer-tagged differential-plunger setup, were discussed. This technique will be capable of establishing the deformation of the states above the isomers and will aid in the process of assigning underlying single-particle configurations to the isomeric states.

  13. Dietary fatty acids modulate antigen presentation to hepatic NKT cells in nonalcoholic fatty liver disease[S

    PubMed Central

    Hua, Jing; Ma, Xiong; Webb, Tonya; Potter, James J.; Oelke, Mathias; Li, Zhiping

    2010-01-01

    Dietary fatty acids are major contributors to the development and progression of insulin resistance and nonalcoholic fatty liver disease (NAFLD). Dietary fatty acids also alter hepatic NKT cells that are activated by antigens presented by CD1d. In the current study, we examine the mechanism of dietary fatty acid induced hepatic NKT cell deficiency and its causal relationship to insulin resistance and NAFLD. We discover that dietary saturated fatty acids (SFA) or monounsaturated fatty acids (MUFA), but not polyunsaturated fatty acids (PUFA), cause hepatic NKT cell depletion with increased apoptosis. Dietary SFA or MUFA also impair hepatocyte presentation of endogenous, but not exogenous, antigen to NKT cells, indicating alterations of the endogenous antigen processing or presenting pathway. In vitro treatment of normal hepatocytes with fatty acids also demonstrates impaired ability of CD1d to present endogenous antigen by dietary fatty acids. Furthermore, dietary SFA and MUFA activate the NFκB signaling pathway and lead to insulin resistance and hepatic steatosis. In conclusion, both dietary SFA and MUFA alter endogenous antigen presentation to hepatic NKT cells and contribute to NKT cell depletion, leading to further activation of inflammatory signaling, insulin resistance, and hepatic steatosis. PMID:20185414

  14. FT-Raman spectroscopy of structural isomers of Pt(II) complex PtCl2(PEt3)2

    NASA Astrophysics Data System (ADS)

    Bhatt, Himal; Deo, M. N.; Vishwakarma, S. R.; Bajaj, Naini; Sharma, Surinder M.

    2015-06-01

    We report here the detailed spectroscopic aspects of the structural isomers of Pt(II) complex PtCl2(P(C2H5)3)2 using FT-Raman spectroscopy. A comparison of the structural contraction instigated by lowering the temperature up to liquid nitrogen temperature in the cis and trans isomers has been presented. The lattice region lying in the far infrared region upto 50cm-1 has been analyzed in detail to probe the structural modifications. It was found that the ambient temperature lower symmetry structure of the cis isomer is preserved at low temperatures. The trans isomer, stabilizing in a high symmetry structure at room temperature, transforms to a low symmetry structure on lowering the temperature, which can be attributed to a loss of inversion symmetry of the trans isomer.

  15. Introduction of Branching Degrees of Octane Isomers.

    PubMed

    Perdih, Anton

    2016-01-01

    The concept of branching degrees is introduced. In the case of octane isomers it is derived from the values of a set of their physicochemical properties, calculating for each isomer the average of the normalized values and these averages are defined as branching degrees of octane isomers. The sequence of these branching degrees of octane isomers does not differ much from the »regular« one defined earlier. 2,2-Dimethylhexane appears to be less branched than 3,4-dimethylhexane and 3-ethyl, 2-methylpentane, whereas 2,3,4-trimethylpentane appears to be less branched than 3-ethyl, 3-methylpentane. While the increasing number of branches gives rise to increasing branching degrees, the peripheral position of branches and the separation between branches decreases the value of the branching degree. The central position of branches increases it. A bigger branch increases it more than a smaller one. The quantification of these structural features and their correlations with few indices is given as well. PMID:27333567

  16. Introduction of Branching Degrees of Octane Isomers.

    PubMed

    Perdih, Anton

    2016-01-01

    The concept of branching degrees is introduced. In the case of octane isomers it is derived from the values of a set of their physicochemical properties, calculating for each isomer the average of the normalized values and these averages are defined as branching degrees of octane isomers. The sequence of these branching degrees of octane isomers does not differ much from the »regular« one defined earlier. 2,2-Dimethylhexane appears to be less branched than 3,4-dimethylhexane and 3-ethyl, 2-methylpentane, whereas 2,3,4-trimethylpentane appears to be less branched than 3-ethyl, 3-methylpentane. While the increasing number of branches gives rise to increasing branching degrees, the peripheral position of branches and the separation between branches decreases the value of the branching degree. The central position of branches increases it. A bigger branch increases it more than a smaller one. The quantification of these structural features and their correlations with few indices is given as well.

  17. Ototoxicity of the three xylene isomers in the rat.

    PubMed

    Maguin, Katy; Lataye, Robert; Campo, Pierre; Cossec, Benoît; Burgart, Manuella; Waniusiow, Delphine

    2006-01-01

    Numerous experiments have shown that the aromatic solvents can affect the auditory system in the rat, the cochlea being targeted first. Solvents differ in cochleotoxic potency: for example, styrene is more ototoxic than toluene or xylenes. The goal of this study was to determine the relative ototoxicity of the three isomers of xylene (o-, m- or p-xylene). Moreover, by dosing with the two urinary metabolites of xylene, methylhippuric (MHAs) and mercapturic acids (MBAs), this study points toward a causal relationship between the cochleotoxic effects and potential reactive intermediates arising from the biotransformation of the parent molecules. Separate groups of rats were exposed by inhalation to one isomer following this schedule: 1800 ppm, 6 h/d, 5 d/wk for 3 wk. Auditory thresholds were determined with brainstem-auditory evoked potentials. Morphological analysis of the organ of Corti was performed by counting both sensory and spiral ganglion cells. Among the three isomers, only p-xylene was cochleotoxic. A 39-dB permanent threshold shift was obtained over the tested frequencies range from 8 to 20 kHz. Whereas outer hair cells were largely injured, no significant morphological change was observed within spiral ganglia. The concentrations of urinary p-, o- or m-MHA were greater (p-MHA: 33.2 g/g; o-MHA: 7.8 g/g; m-MHA: 20.4 g/g) than those obtained for MBAs (p-MBA: 0.04 g/g; o-MBA: 6.2 g/g; m-MBA: 0.03 g/g). Besides, there is a large difference between o-MBA (6.2 g/g) and p-MBA (0.04 g/g). As a result, since the cysteine conjugates are not determinant in the ototoxic process of xylenes, the location of the methyl groups around the benzene nucleus could play a key role. PMID:17045780

  18. Peroxy and cyclic isomers of NO2 and NO2(-)

    NASA Astrophysics Data System (ADS)

    Meredith, Cynthia; Davy, Randall D.; Quelch, Geoffrey E.; Schaefer, Henry F., III

    1991-01-01

    Results are reported from ab initio theoretical calculations on possible isomers of NO2 and NO2(-), both of interest for studies of atmospheric chemistry and synthetic fuels. The techniques applied are discussed, and the results are presented in extensive tables. Minima corresponding to the C2v open chain, the Cs peroxy, and the C2v ring forms of both NO2 and NO2(-) are located. The electron affinity of NOO(-) is estimated as 2.11 eV on the basis of the present calculations and experimental results on ONO(-) obtained by Herbst et al. (1974).

  19. The combustion kinetics of octane isomers

    SciTech Connect

    Burcat, A. . Faculty of Aerospace Engineering); Pitz, W.J.; Westbrook, C.K. )

    1990-03-29

    Shock tube experiments provide conditions for testing kinetic models that are unique, since this is the only common environment in which initiation reactions, primarily the unimolecular decompositions of the fuel, play an important role. At least two factors are known to be very important, the fuel molecule size and its precise structure. Iso-octane has an octane number of 100, which reflects the relative difficulty with which iso-octanes/air mixtures ignite. Conversely, C{sub 8}H{sub 18}, the straight chain n-octane, ignites very easily, with an octane number of approximately zero. The present work addresses the importance of fuel structure for large hydrocarbon fuels, by comparing the ignition of isomers of octane under shock tube conditions. Ignition delay times were performed with n-octane, a linear chain molecular with only primary and secondary C-H bonds, 2-3-4-trimethyl-pentane has a highly branched molecule and contains only primary and tertiary C-H bonds, and iso-octane a molecule which includes a mixture of primary, secondary, and tertiary C-H bonds. Also 1-octene, a simple straight chain alkene was included. The experiments were run in a single pulse stainless steel shock tube. 475 shocks were performed. They were spread as follows: (1) 164 experiments with 1-octene (C{sub 8}H{sub 16}). (2) 137 experiments with 2,2,4 tri-methyl pentane. (3) 30 experiments with 2,3,4 tri-methyl pentane. (4) 144 experiments with n-octane. 3 refs.

  20. Isomer discrimination of polycyclic aromatic hydrocarbons in the Murchison meteorite by resonant ionization

    NASA Astrophysics Data System (ADS)

    Callahan, Michael P.; Abo-Riziq, Ali; Crews, Bridgit; Grace, Louis; de Vries, Mattanjah S.

    2008-12-01

    We have used two-color resonant two-photon ionization (2C-R2PI) mass spectrometry to discriminate between isomers of polycyclic aromatic hydrocarbons in the Murchison meteorite. We measured the 2C-R2PI spectra of chrysene and triphenylene seeded in a supersonic jet by laser desorption. Since each isomer differs in its R2PI spectrum, we can distinguish between isomers using wavelength dependent ionization and mass spectrometry. We found both chrysene and triphenylene in sublimates from carbonaceous residue obtained by acid demineralization of the Murchison meteorite. Their R2PI mass spectra show only the molecular ion, even though these samples contain a complex inventory of organic molecules.

  1. 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.

  2. High-K isomers: some of the questions

    NASA Astrophysics Data System (ADS)

    Walker, P. M.

    2016-09-01

    High-K isomers exemplify the coexistence of individual-particle and collective motion in atomic nuclei. Here, the topic is briefly outlined, and some open questions are discussed. These include violations of the K quantum number; the high-spin limit to K isomerism; the fission stability of K isomers; possibilities for manipulation and control of K-isomer decay rates; and access to K isomers in neutron-rich nuclei.

  3. Excitation of nuclear isomers by X rays from laser plasma

    SciTech Connect

    Andreev, Aleksandr A; Karpeshin, F; Trzhaskovskaya, M B; Platonov, Konstantin Yu; Rozhdestvenskii, Yu V

    2010-06-23

    The possibility of obtaining isomer nuclei is studied by the example of the molybdenum isomer {sup 93}Mo upon irradiation of a niobium {sup 93}Nb target by {approx}50-J, 100-fs laser pulses. It is shown that the modern laser technique allows production of isomer nuclei by accelerated protons and radiative de-excitation of isomer nuclear states by thermal or line X-rays from laser plasma. (interaction of laser radiation with matter. laser plasma)

  4. Systems Pharmacology Modeling Predicts Delayed Presentation and Species Differences in Bile Acid-Mediated Troglitazone Hepatotoxicity

    PubMed Central

    Yang, Kyunghee; Woodhead, Jeffrey L; Watkins, Paul B; Howell, Brett A; Brouwer, Kim LR

    2014-01-01

    Troglitazone (TGZ) caused delayed, life-threatening drug-induced liver injury (DILI) in some patients, but was not hepatotoxic in rats. This study investigated altered bile acid (BA) homeostasis as a mechanism of TGZ hepatotoxicity using a systems pharmacology model incorporating drug/metabolite disposition, BA physiology/pathophysiology, hepatocyte life cycle, and liver injury biomarkers. In the simulated human population, TGZ (200–600mg/day×6months) resulted in delayed increases in serum ALT>3× ULN in 0.3–5.1% of the population with concomitant bilirubin elevations>2× ULN in 0.3–3.6%. In contrast, pioglitazone (15–45mg/day×6months) did not elicit hepatotoxicity, consistent with clinical data. TGZ was not hepatotoxic in the simulated rat population. In summary, mechanistic modeling based only on BA effects accurately predicted the incidence, delayed presentation, and species differences in TGZ hepatotoxicity, and the relative liver safety of pioglitazone. Systems pharmacology models integrating physiology and experimental data can evaluate DILI mechanisms and may be useful to predict hepatotoxic potential of drug candidates. PMID:25068506

  5. C68 fullerene isomers, anions, and their metallofullerenes: charge-stabilizing different isomers.

    PubMed

    Chen, De-Li; Tian, Wei Quan; Feng, Ji-Kang; Sun, Chia-Chung

    2008-02-22

    The complete set of 6332 classical isomers of the fullerene C(68) as well as several non-classical isomers is investigated by PM3, and the data for some of the more stable isomers are refined by the DFT-based methods HCTH and B3LYP. C(2):0112 possesses the lowest energy of all the neutral isomers and it prevails in a wide range of temperatures. Among the fullerene ions modeled, C(68) (2-), C(68) (4-) and C(68) (6-), the isomers C(68) (2-)(C(s):0064), C(68) (4-)(C(2v):0008), and C(68) (6-)(D(3):0009) respectively, are predicted to be the most stable. This reveals that the pentagon adjacency penalty rule (PAPR) does not necessarily apply to the charged fullerene cages. The vertical electron affinities of the neutral C(s):0064, C(2v):0008, and D(3):0009 isomers are 3.41, 3.29, and 3.10 eV, respectively, suggesting that they are good electron acceptors. The predicted complexation energy, that is, the adiabatic binding energy between the cage and encapsulated cluster, of Sc(2)C(2)@C(68)(C(2v):0008) is -6.95 eV, thus greatly releasing the strain of its parent fullerene (C(2v):0008). Essentially, C(68) fullerene isomers are charge-stabilized. Thus, inducing charge facilitates the isolation of the different isomers. Further investigations show that the steric effect of the encaged cluster should also be an important factor to stabilize the C(68) fullerenes effectively.

  6. Unique odd-chain polyenoic phospholipid fatty acids present in chytrid fungi.

    PubMed

    Akinwole, Philips O; Lefevre, Emilie; Powell, Martha J; Findlay, Robert H

    2014-09-01

    Chytrid fungi are ubiquitous components of aquatic and terrestrial ecosystems yet they remain understudied. To investigate the use of phospholipid fatty acids as phenotypic characteristics in taxonomic studies and biomarkers for ecological studies, 18 chytrid fungi isolated from soil to freshwater samples were grown in defined media and their phospholipid fatty acid profile determined. Gas chromatographic/mass spectral analysis indicated the presence of fatty acids typically associated with fungi, such as 16:1(n-7), 16:0, 18:2(n-6), 18:3(n-3) 18:1(n-9), and 18:0, as well as, a number of odd-chain length fatty acids, including two polyunsaturated C-17 fatty acids. Conversion to their 3-pyridylcarbinol ester facilitated GC-MS determination of double-bond positions and these fatty acid were identified as 6,9-17:2 [17:2(n-8)] and 6,9,12-17:3 [17:3(n-5)]. To the best of our knowledge, this is the first report of polyunsaturated C-17 fatty acids isolated from the phospholipids of chytrid fungi. Cluster analysis of PLFA profiles showed sufficient correlation with chytrid phylogeny to warrant inclusion of lipid analysis in species descriptions and the presence of several phospholipid fatty acids of restricted phylogenetic distributions suggests their usefulness as biomarkers for ecological studies. PMID:25119485

  7. Teichoic acid is the major polysaccharide present in the Listeria monocytogenes biofilm matrix.

    PubMed

    Brauge, Thomas; Sadovskaya, Irina; Faille, Christine; Benezech, Thierry; Maes, Emmanuel; Guerardel, Yann; Midelet-Bourdin, Graziella

    2016-01-01

    The aim of this study was to characterize the Listeria monocytogenes biofilm and particularly the nature of the carbohydrates in the biofilm extracellular matrix and culture supernatant versus to cell wall carbohydrates. Listeria monocytogenes serotype 1/2a and 4b strains were able to form complex biofilms embedded in an extracellular matrix. The soluble carbohydrates from biofilm extracellular matrix and culture supernatant were identified as teichoic acids, structurally identical to cell wall teichoic acids. In addition, the DSS 1130 BFA2 strain had a serotype 1/2a teichoic acid lacking N-acetyl glucosamine glycosylation due to a mutation in the lmo2550 gene. Consequently, we hypothesized that the extracellular teichoic acids in L. monocytogenes biofilms have the same origin as cell wall teichoic acid.

  8. Photodynamics of potent antioxidants: ferulic and caffeic acids.

    PubMed

    Horbury, Michael D; Baker, Lewis A; Quan, Wen-Dong; Greenough, Simon E; Stavros, Vasilios G

    2016-07-14

    The dynamics of ferulic acid (3-(4-hydroxy-3-methoxyphenyl)-2-propenoic acid) and caffeic acid (3-(3,4-dihydroxyphenyl)-2-propenoic acid) in acetonitrile, dioxane and water at pH 2.2 following photoexcitation to the first excited singlet state are reported. These hydroxycinnamic acids display both strong ultraviolet absorption and potent antioxidant activity, making them promising sunscreen components. Ferulic and caffeic acids have previously been shown to undergo trans-cis photoisomerization via irradiation studies, yet time-resolved measurements were unable to observe formation of the cis-isomer. In the present study, we are able to observe the formation of the cis-isomer as well as provide timescales of relaxation following initial photoexcitation. PMID:27310931

  9. Ultrafast time-resolved absorption spectroscopy of geometric isomers of carotenoids

    NASA Astrophysics Data System (ADS)

    Niedzwiedzki, Dariusz M.; Sandberg, Daniel J.; Cong, Hong; Sandberg, Megan N.; Gibson, George N.; Birge, Robert R.; Frank, Harry A.

    2009-02-01

    The structures of a number of stereoisomers of carotenoids have been revealed in three-dimensional X-ray crystallographic investigations of pigment-protein complexes from photosynthetic organisms. Despite these structural elucidations, the reason for the presence of stereoisomers in these systems is not well understood. An important unresolved issue is whether the natural selection of geometric isomers of carotenoids in photosynthetic pigment-protein complexes is determined by the structure of the protein binding site or by the need for the organism to accomplish a specific physiological task. The association of cis isomers of a carotenoid with reaction centers and trans isomers of the same carotenoid with light-harvesting pigment-protein complexes has led to the hypothesis that the stereoisomers play distinctly different physiological roles. A systematic investigation of the photophysics and photochemistry of purified, stable geometric isomers of carotenoids is needed to understand if a relationship between stereochemistry and biological function exists. In this work we present a comparative study of the spectroscopy and excited state dynamics of cis and trans isomers of three different open-chain carotenoids in solution. The molecules are neurosporene ( n = 9), spheroidene ( n = 10), and spirilloxanthin ( n = 13), where n is the number of conjugated π-electron double bonds. The spectroscopic experiments were carried out on geometric isomers of the carotenoids purified by high performance liquid chromatography (HPLC) and then frozen to 77 K to inhibit isomerization. The spectral data taken at 77 K provide a high resolution view of the spectroscopic differences between geometric isomers. The kinetic data reveal that the lifetime of the lowest excited singlet state of a cis-isomer is consistently shorter than that of its corresponding all- trans counterpart despite the fact that the excited state energy of the cis molecule is typically higher than that of the trans

  10. Search for a ''3.5-eV isomer'' in {sup 229}Th in a hollow-cathode electric discharge

    SciTech Connect

    Inamura, T. T.; Haba, H.

    2009-03-15

    A hollow-cathode electric discharge, a well-established source in optical spectroscopy, was used to populate the ''3.5-eV isomer'' in {sup 229}Th with use of nuclear excitation by electron transition (NEET). The radiochemically purest {sup 229}Th sample was loaded into the hollow cathode in which the electric discharge excited the {sup 229}Th to atomic states some of which could be expected to lie close to the excitation energy of the sought isomer. Although there remain some uncertainties, our experiments indicate that the isomer was populated by NEET and its {alpha} decay observed after switching off the electric discharge with a corresponding isomer half-life 1 min < or approx. T{sub 1/2}{sup m} < or approx. 3 min. From the present NEET condition, the isomer appears to lie between 3 eV and 7 eV. The probability of the isomer population by NEET is discussed.

  11. INVESTIGATING THE MINIMUM ENERGY PRINCIPLE IN SEARCHES FOR NEW MOLECULAR SPECIES—THE CASE OF H{sub 2}C{sub 3}O ISOMERS

    SciTech Connect

    Loomis, Ryan A.; McGuire, Brett A.; Remijan, Anthony J.; Shingledecker, Christopher; Johnson, Chelen H.; Blair, Samantha; Robertson, Amy

    2015-01-20

    Recently, Lattelais et al. have interpreted aggregated observations of molecular isomers to suggest that there exists a ''minimum energy principle'', such that molecular formation will favor more stable molecular isomers for thermodynamic reasons. To test the predictive power of this principle, we have fully characterized the spectra of the three isomers of C{sub 3}H{sub 2}O toward the well-known molecular region Sgr B2(N). Evidence for the detection of the isomers cyclopropenone (c-C{sub 3}H{sub 2}O) and propynal (HCCCHO) is presented, along with evidence for the non-detection of the lowest zero-point energy isomer, propadienone (CH{sub 2}CCO). We interpret these observations as evidence that chemical formation pathways, which may be under kinetic control, have a more pronounced effect on final isomer abundances than thermodynamic effects such as the minimum energy principle.

  12. [Determination of trans fatty acid C18:1, C18:2 and C18:3 isomers in milk fat by silver ion solid phase extraction-gas chromatography].

    PubMed

    Rui, Li; Xu, Xiaomin; Li, Yali; Song, Guoliang; Han, Jianlong; Ren, Yiping

    2010-12-01

    A method for the determination of trans fatty acids C18:1, C18:2 and C18:3 in milk fat was developed by silver ion solid phase extraction-gas chromatography (Ag+ -SPE/GC). The fatty acid methyl esters derived from total milk fat were loaded onto an Ag+ -SPE cartridge, and then eluted with 9 mL of toluene-hexane (5:95, v/v), 8 mL of toluene-hexane (17:83, v/v), 6 mL of toluene-ethyl acetate (17:83, v/v) and 10 mL of toluene-ethyl acetate (30:70, v/v) in sequence. The fraction from each step was analyzed by GC. The average recoveries of trans fatty acids ranged from 88.4% to 107.2% with the relative standard deviations (RSDs) from 1.2% to 11.9% except trans linolenic acid with the recoveries from 69.9% to 101.0% and the RSDs from 11.0% to 18.1%. Comparing with the traditional methods, the developed approach can avoid the interference of cis and saturated fatty acids. The method was successfully applied to analyze dairy products. Satisfactory results were shown.

  13. K Isomer in {sup 252}No

    SciTech Connect

    Sulignano, B.; Theisen, Ch.; Drouart, A.; Goergen, A.; Korten, W.; Obertelli, A.; Ackermann, D.; Hessberger, F. P.; Hofmann, S.; Antalic, S.; Venhart, M.; Dorvaux, O.; Piot, J.; Greenlees, P. T.; Jakobsson, U.; Jones, P.; Julin, R.; Juutinen, S.

    2010-04-30

    In this paper we discuss the discovery of an isomeric state in {sup 252}No and a recent experiment studying the rotational band built upon this isomeric state. Results from the later experiment help to assign the structure of the isomer on the basis of purely experimental data, and to disentangle between different theoretical interpretations. Comparison with similar states in {sup 250}Fm and {sup 254}No provides important information and helps the development of self -consistent theories.

  14. 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.

  15. Isomer effects on polyimide properties

    NASA Technical Reports Server (NTRS)

    Stump, B. L.

    1978-01-01

    Thermally stable polyimide polymers were prepared. Parameters explored include asymmetry of substitution, addition of alkyl substituents to an aromatic ring, and an increase in the number of aromatic rings present in the diamine monomer. It is shown that the use of an asymmetrical diamine in the preparation of a polyimide produces a polymer with a markedly lowered glass transition temperature. This is achieved with little or no sacrifice of thermal stability. An alternate approach taken was to prepare imide monomers which are capable of addition-type polymerization.

  16. 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

  17. Experimental investigation of the low temperature oxidation of the five isomers of hexane.

    PubMed

    Wang, Zhandong; Herbinet, Olivier; Cheng, Zhanjun; Husson, Benoit; Fournet, René; Qi, Fei; Battin-Leclerc, Frédérique

    2014-07-31

    The low-temperature oxidation of the five hexane isomers (n-hexane, 2-methyl-pentane, 3-methyl-pentane, 2,2-dimethylbutane, and 2,3-dimethylbutane) was studied in a jet-stirred reactor (JSR) at atmospheric pressure under stoichiometric conditions between 550 and 1000 K. The evolution of reactant and product mole fraction profiles were recorded as a function of the temperature using two analytical methods: gas chromatography and synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). Experimental data obtained with both methods were in good agreement for the five fuels. These data were used to compare the reactivity and the nature of the reaction products and their distribution. At low temperature (below 800 K), n-hexane was the most reactive isomer. The two methyl-pentane isomers have about the same reactivity, which was lower than that of n-hexane. 2,2-Dimethylbutane was less reactive than the two methyl-pentane isomers, and 2,3-dimethylbutane was the least reactive isomer. These observations are in good agreement with research octane numbers given in the literature. Cyclic ethers with rings including 3, 4, 5, and 6 atoms have been identified and quantified for the five fuels. While the cyclic ether distribution was notably more detailed than in other literature of JSR studies of branched alkane oxidation, some oxiranes were missing among the cyclic ethers expected from methyl-pentanes. Using SVUV-PIMS, the formation of C2-C3 monocarboxylic acids, ketohydroperoxides, and species with two carbonyl groups have also been observed, supporting their possible formation from branched reactants. This is in line with what was previously experimentally demonstrated from linear fuels. Possible structures and ways of decomposition of the most probable ketohydroperoxides were discussed. Above 800 K, all five isomers have about the same reactivity, with a larger formation from branched alkanes of some unsaturated species, such as allene and propyne, which

  18. Label-free direct surface-enhanced Raman scattering (SERS) of nucleic acids (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Guerrini, Luca; Morla-Folch, Judit; Gisbert-Quilis, Patricia; Xie, Hainan; Alvarez-Puebla, Ramon

    2016-03-01

    Recently, plasmonic-based biosensing has experienced an unprecedented level of attention, with a particular focus on the nucleic acid detection, offering efficient solutions to engineer simple, fast, highly sensitive sensing platforms while overcoming important limitations of PCR and microarray techniques. In the broad field of plasmonics, surface-enhanced Raman scattering (SERS) spectroscopy has arisen as a powerful analytical tool for detection and structural characterization of biomolecules. Today applications of SERS to nucleic acid analysis largely rely on indirect strategies, which have been demonstrated very effective for pure sensing purposes but completely dismiss the exquisite structural information provided by the direct acquisition of the biomolecular vibrational fingerprint. Contrarily, direct label-free SERS of nucleic acid shows an outstanding potential in terms of chemical-specific information which, however, remained largely unexpressed mainly because of the inherent poor spectral reproducibility and/or limited sensitivity. To address these limitations, we developed a fast and affordable high-throughput screening direct SERS method for gaining detailed genomic information on nucleic acids (DNA and RNA) and for the characterization and quantitative recognition of DNA interactions with exogenous agents. The simple strategy relies on the electrostatic adhesion of DNA/RNA onto positively-charged silver colloids that promotes the nanoparticle aggregation into stable clusters yielding intense and reproducible SERS spectra at picogram level (i.e. the analysis can be performed without the necessity of amplification steps thus providing realistic direct information of the nucleic acid in its native state). We anticipate this method to gain a vast impact and set of applications in different fields, including medical diagnostics, genomic screening, drug discovery, forensic science and even molecular electronics.

  19. Silica sol assisted chromatographic NMR spectroscopy for resolution of trans- and cis-isomers

    NASA Astrophysics Data System (ADS)

    Yang, Ying; Wu, Rui; Huang, Shaohua; Bai, Zhengwu

    2016-04-01

    Chromatographic NMR spectroscopy can separate the mixtures of species with significantly different molecular size, but generally fails for isomeric species. Herein, we reported the resolution of trans- and cis-isomers and their structural analogue, which are different in molecular shapes, but similar in mass, were greatly enhanced in the presence of silica sol. The mixtures of maleic acid, fumaric acid and succinic acid, and the mixtures of trans- and cis-1,2-cyclohexanedicarboxylic acids, were distinguished by virtue of their different degrees of interaction with silica sol. Moreover, we found mixed solvents could improve the spectral resolution of DOSY spectra of mixtures.

  20. Silica sol assisted chromatographic NMR spectroscopy for resolution of trans- and cis-isomers.

    PubMed

    Yang, Ying; Wu, Rui; Huang, Shaohua; Bai, Zhengwu

    2016-04-01

    Chromatographic NMR spectroscopy can separate the mixtures of species with significantly different molecular size, but generally fails for isomeric species. Herein, we reported the resolution of trans- and cis-isomers and their structural analogue, which are different in molecular shapes, but similar in mass, were greatly enhanced in the presence of silica sol. The mixtures of maleic acid, fumaric acid and succinic acid, and the mixtures of trans- and cis-1,2-cyclohexanedicarboxylic acids, were distinguished by virtue of their different degrees of interaction with silica sol. Moreover, we found mixed solvents could improve the spectral resolution of DOSY spectra of mixtures. PMID:26942864

  1. 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. PMID:23952569

  2. The Oak Ridge Isobar and Isomer Separator and Spectrometer (ORISS)

    NASA Astrophysics Data System (ADS)

    Piechaczek, Andreas; Batchelder, J. C.; Carter, H. K.; Reed, C. A.; Yair, O.; Shchepunov, V.; Zganjar, E. F.; Blalock, A.; Berridge, S.; Todd, R.; Armstrong, G.; Omoumi, K.; Fleury, A. R.; Hu, Y.

    2011-04-01

    ORISS is an electrostatic high-resolution isobar and isomer spectrometer and separator to provide pure beams for decay spectroscopy of exotic nuclei. It consists of an RFQ, low emittance, ion cooler and buncher, a multi-pass time-of-flight spectrometer, and a time-of-flight detector to register time-of-flight spectra, or a Bradbury Nielsen (BN) gate to physically separate isobars and isomers of interest. Presently, ORISS uses an off-line ion source. Ion bunches as short as 8 ns FWHM have been produced in the buncher, and a BN gate with transition times open/closed of 15 ns was built. These results of individual component tests together with ion optical calculations predict a mass resolving power of 400,000 and transmission of 50% for the completed system. In the future, radioactive ions from the Holifield Radioactive Ion Beam Facility at ORNL will be injected. Results of first test measurements of the complete off-line system will be presented.

  3. Effects of Bond Location on the Ignition and Reaction Pathways of trans-Hexene Isomers.

    PubMed

    Wagnon, Scott W; Barraza-Botet, Cesar L; Wooldridge, Margaret S

    2015-07-16

    Chemical structure and bond location are well-known to impact combustion reactivity. The current work presents new experimental autoignition and speciation data on the three trans-hexene isomers (1-hexene, trans-2-hexene, and trans-3-hexene), which describe the effects of the location of the carbon-carbon double bond. Experiments were conducted with the University of Michigan rapid compression facility to determine ignition delay times from pressure time histories. Stoichiometric (ϕ = 1.0) mixtures at dilution levels of buffer gas:O2 = 7.5 (mole basis) were investigated at an average pressure of 11 atm and temperatures from 837 to 1086 K. Fast gas sampling and gas chromatography were also used to quantitatively measure 13 stable intermediate species formed during the ignition delay period of each isomer at a temperature of ∼900 K. The measured ignition delay times and species measurements were in good agreement with previous experimental studies at overlapping conditions. The results were modeled using a gasoline surrogate reaction mechanism from Lawrence Livermore National Laboratory, which contains a submechanism for the trans-hexene isomers. The model predictions captured the overall autoignition characteristics of the hexene isomers well (within a factor of 2), as well as the time histories of several of the intermediate species (e.g., propene). However, there were discrepancies between the model predictions and the experimental data for some species, particularly for the 3-hexene isomer.

  4. Elucidation of Drug Metabolite Structural Isomers Using Molecular Modeling Coupled with Ion Mobility Mass Spectrometry.

    PubMed

    Reading, Eamonn; Munoz-Muriedas, Jordi; Roberts, Andrew D; Dear, Gordon J; Robinson, Carol V; Beaumont, Claire

    2016-02-16

    Ion mobility-mass spectrometry (IM-MS) in combination with molecular modeling offers the potential for small molecule structural isomer identification by measurement of their gas phase collision cross sections (CCSs). Successful application of this approach to drug metabolite identification would facilitate resource reduction, including animal usage, and may benefit other areas of pharmaceutical structural characterization including impurity profiling and degradation chemistry. However, the conformational behavior of drug molecules and their metabolites in the gas phase is poorly understood. Here the gas phase conformational space of drug and drug-like molecules has been investigated as well as the influence of protonation and adduct formation on the conformations of drug metabolite structural isomers. The use of CCSs, measured from IM-MS and molecular modeling information, for the structural identification of drug metabolites has also been critically assessed. Detection of structural isomers of drug metabolites using IM-MS is demonstrated and, in addition, a molecular modeling approach has been developed offering rapid conformational searching and energy assessment of candidate structures which agree with experimental CCSs. Here it is illustrated that isomers must possess markedly dissimilar CCS values for structural differentiation, the existence and extent of CCS differences being ionization state and molecule dependent. The results present that IM-MS and molecular modeling can inform on the identity of drug metabolites and highlight the limitations of this approach in differentiating structural isomers. PMID:26752623

  5. Survey of perfluoroalkyl acids (PFAAs) and their precursors present in Japanese consumer products.

    PubMed

    Ye, Feng; Zushi, Yasuyuki; Masunaga, Shigeki

    2015-05-01

    Perfluoroalkyl acids (PFAAs) and their precursors have been used in various consumer products. However, limited information regarding their occurrence and concentration levels in products is available. In this study, we investigated 18 PFAAs and 14 PFAA precursors in various categories of consumer products purchased in Japan. Relatively high total concentrations of PFAAs and their precursors were found in sprays for fabrics and textiles (acid (PFOS), N-methyl perfluorooctane sulfonamidoethanol (MeFOSE) was detected in a higher frequency (8%) and in greater concentrations (acids (PFCAs) (carbon chain length⩾7) were also detected in greater concentrations than short chain PFCAs (⩽6). This result suggests that consumer products are one of the important sources of long-chain PFCAs in the environment.

  6. Nuclear isomers as ultra-high-energy-density materials

    NASA Astrophysics Data System (ADS)

    Poppe, C. H.; Weiss, M. S.; Anderson, J. D.

    1992-04-01

    Nuclear isomers are metastable states of atomic nuclei which release their energy in a prompt burst of electromagnetic radiation. Two kinds of nuclear isomers are known to exist: spin isomers and shape isomers. There is evidence for at least 27 different fissionless shape isomers in isotopes of mercury, lead, and thallium, in agreement with theoretical predictions. Three potential mechanisms for releasing the stored isomeric energy are neutron catalysis, laser-electron-nuclear coupling, and Stark-shift-induced mixing. While shape isomers are believed to hold the most promise for radioactivity-free, ultra-high-energy-density materials, spin isomers can be used as surrogates for developing the release mechanisms. It is proposed to undertake shell-model calculations for the nuclear levels in vicinity of the (sup 178)Hf spin isomer, in order to estimate the efficacy of neutron catalysis. It is also proposed to use the toroidal electron spectrometer to measure the conversion electrons from laser-induced transitions in (sup 229)Th. The final mechanism, Stark-shift-induced mixing of atomic and nuclear levels, would also be studied theoretically. Finally, isomer production is considered briefly, including the possibility of shape isomers in fission products from radwaste or nuclear explosions.

  7. 21 CFR 184.1061 - Lactic acid.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ....1061 Lactic acid. (a) Lactic acid (C3H6O3, CAS Reg. Nos.: dl mixture, 598-82-3; l-isomer, 79-33-4; d-isomer, 10326-41-7), the chemical 2-hydroxypropanoic acid, occurs naturally in several foods. It...

  8. Perfluorooctane sulfonate toxicity, isomer-specific accumulation, and maternal transfer in zebrafish (Danio rerio) and rainbow trout (Oncorhynchus mykiss).

    PubMed

    Sharpe, Rainie L; Benskin, Jonathan P; Laarman, Anne H; Macleod, Sherri L; Martin, Jonathan W; Wong, Charles S; Goss, Greg G

    2010-09-01

    Perfluorooctane sulfonate (PFOS; C(8)F(17)SO(3) (-)) bioaccumulation and toxicity have been demonstrated in both aquatic and terrestrial organisms. The majority of investigations have examined total PFOS concentrations in wildlife and in toxicity testing, but isomer-specific monitoring studies are less common, and no laboratory-based study of PFOS isomer accumulation in fish has been reported. The present study examined accumulation and maternal transfer of PFOS isomers in zebrafish and tissue-specific accumulation of PFOS isomers in trout parr. A median lethal dose (LC50) of 22.2 and 2.5 mg/L was calculated for adult zebrafish and trout parr, respectively. A two-week PFOS exposure resulted in tissue-specific PFOS accumulation in trout, with maximum concentrations identified in the liver tissue (>50 microg/g). Prior exposure to PFOS as alevin did not affect the accumulation of PFOS in tissues later in life. In both species, accumulation of branched PFOS isomers generally occurred to a lesser extent than linear PFOS, which may explain the relative deficiency of branched PFOS isomers in some aquatic species in the field. Analysis of exposed trout tissues indicated that isomer discrimination may occur at the level of elimination or uptake and elimination processes in the kidney or gill, respectively. When zebrafish underwent a reproductive cycle in the presence of PFOS, approximately 10% (wt) of the adult PFOS body burden was transferred to the developing embryos, resulting in a higher total PFOS concentration in eggs (116 +/- 13.3 microg/g) than in the parent fish (72.1 +/- 7.6 microg/g). The isomer profile in eggs was not significantly different from that of adults, suggesting that the maternal transfer of branched and linear PFOS isomers in fish is largely nonisomer specific.

  9. 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.

  10. Conformational preferences and synthesis of isomers Z and E of oxazole-dehydrophenylalanine.

    PubMed

    Staś, Monika; Bujak, Maciej; Broda, Małgorzata A; Siodłak, Dawid

    2016-05-01

    Dehydrophenylalanine, ΔPhe, is the most commonly studied α,β-dehydroamino acid. In nature, further modifications of the α,β-dehydroamino acids were found, for example, replacement of the C-terminal amide group by oxazole ring. The conformational properties of oxazole-dehydrophenylalanine residue (ΔPhe-Ozl), both isomers Z and E, were investigated. To determine all possible conformations, theoretical calculations were performed using Ac-(Z/E)-ΔPhe-Ozl(4-Me) model compounds at M06-2X/6-31++G(d,p) level of theory. Ac-(Z/E)-ΔPhe-Ozl-4-COOEt compounds were synthesized and the conformational preferences of each isomer, Z and E, were investigated using FTIR and NMR-NOE in solutions of increasing polarity (CHCl3 , DMSO-d6). The solid-state low-temperature structures of Ac-(Z)-ΔPhe-Ozl-4-COOEt and its intermediate analog Ac-(Z)-ΔPhe-Ozn(4-OH)-4-COOEt were also determined. In a weakly polar environment, the ΔPhe-Ozl residue has a tendency to adopt the conformation β2 with the calculated φ and ψ angles of -127° and 0° for the isomer Z and -170° and 26° for the isomer E. The increase of environment polarity favors the helical conformation α and the beta-turn like conformation β, but the conformation β2 seems to be still accessible. The (E)-ΔPhe-Ozl residue can be obtained from the isomer Z in photoisomerization reaction. However, hydroxyl-oxazoline-dehydrophenylalanine ΔPhe-Ozn(4-OH) decomposes in such conditions. Alternatively, (E)-ΔPhe-NH2 can be applied as a substrate in the Hantzsch reaction. © 2016 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 283-294, 2016. PMID:27061820

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

    PubMed

    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. PMID:26644308

  12. Conformational preferences and synthesis of isomers Z and E of oxazole-dehydrophenylalanine.

    PubMed

    Staś, Monika; Bujak, Maciej; Broda, Małgorzata A; Siodłak, Dawid

    2016-05-01

    Dehydrophenylalanine, ΔPhe, is the most commonly studied α,β-dehydroamino acid. In nature, further modifications of the α,β-dehydroamino acids were found, for example, replacement of the C-terminal amide group by oxazole ring. The conformational properties of oxazole-dehydrophenylalanine residue (ΔPhe-Ozl), both isomers Z and E, were investigated. To determine all possible conformations, theoretical calculations were performed using Ac-(Z/E)-ΔPhe-Ozl(4-Me) model compounds at M06-2X/6-31++G(d,p) level of theory. Ac-(Z/E)-ΔPhe-Ozl-4-COOEt compounds were synthesized and the conformational preferences of each isomer, Z and E, were investigated using FTIR and NMR-NOE in solutions of increasing polarity (CHCl3 , DMSO-d6). The solid-state low-temperature structures of Ac-(Z)-ΔPhe-Ozl-4-COOEt and its intermediate analog Ac-(Z)-ΔPhe-Ozn(4-OH)-4-COOEt were also determined. In a weakly polar environment, the ΔPhe-Ozl residue has a tendency to adopt the conformation β2 with the calculated φ and ψ angles of -127° and 0° for the isomer Z and -170° and 26° for the isomer E. The increase of environment polarity favors the helical conformation α and the beta-turn like conformation β, but the conformation β2 seems to be still accessible. The (E)-ΔPhe-Ozl residue can be obtained from the isomer Z in photoisomerization reaction. However, hydroxyl-oxazoline-dehydrophenylalanine ΔPhe-Ozn(4-OH) decomposes in such conditions. Alternatively, (E)-ΔPhe-NH2 can be applied as a substrate in the Hantzsch reaction. © 2016 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 283-294, 2016.

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

    SciTech Connect

    Michelin, S. E.; Falck, A. S.; Mazon, K. T.; Piacentini, J. J.; Scopel, M. A.; Silva, L. S. S. da; Oliveira, H. L.; Fujimoto, M. M.; Iga, I.; Lee, M.-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 which leads to a depression in the calculated partial integral cross section.

  14. Systematic analysis of reactivities and fragmentation of glutathione and its isomer GluCysGly.

    PubMed

    Feng, Shan; Zheng, Xiaoyan; Wang, Dong; Gong, Yiyi; Wang, Qingtao; Deng, Haiteng

    2014-09-18

    Glutathione (GSH) is the most abundant tripeptide in human cells and plays an important role in protecting cells' integrity against oxidative stress. GSH has an unusual amide linkage formed between the γ-carboxylic group of the glutamic acid in its side-chain and the amine group of cysteine residue. In the present study, we have compared reactivities of GSH to its isomer GluCysGly (ECG), which has a regular amide bond formed between the α-carboxylic group of glutamic acid and the amine group of cysteine residue. The fragmentation pattern of GSH ions in the gas phase is different from that of ECG ions, showing that the loss of H2O is the major dissociation pathway in ECG fragmentation. This is consistent with the dissociation pathway predicted by density functional calculation. Formation of GSSG from oxidation of GSH is faster than that of ECG disulfide, and the gas phase fragmentation pattern of GSSG is different from that of ECG disulfide. GSH and ECG display similar rates in nucleophilic aromatic substitution when reacting with 1-chloro-2,4-dinitrobenzene (CDNB). However, in the presence of glutathione S-transferases (GST), substitution of CDNB by GSH is 10 times faster than that by ECG. GSH and ECG also show differences in clustering patterns in the gas phase. Taken together, our results shed light on understanding effects of unique boding structure in GSH on its stability and reactivities.

  15. Gamma-ray spectroscopy of the ^238U shape isomer.

    NASA Astrophysics Data System (ADS)

    Hauschild, K.; Bauer, R. W.; Becker, J. A.; Bernstein, L. A.; Britt, H. C.; Younes, W.; Fotiades, N.

    1997-04-01

    The γ--rays de--exciting the fission isomers ^236U and ^238U are very different despite similar excitation energies, lifetimes and low--lying yrast structures. The predominant γ--ray decay branch for ^236U^m is a 1.783 MeV E1 transition (J. Schirmer, et al., Phys. Rev. Lett. 63), 2196 (1989); and Refs. therein., while ^238U^m is depopulated by a 2.513 MeV E2 γ-ray (J. Kantele, et al., Phys. Rev. C 29), 1693 (1984); and Refs. therein.. Approximately 65% of the γ--branch de-exciting ^238U^m remains to be identified. To determine the multipolarity of the remaining γ-branch out of ^238U^m we used the Gammasphere array at LBNL and the ^238U(d,pn) reaction at Ed = 20 MeV. A search for excited states in the 2^nd well has also been conducted. Preliminary results will be presented, and the γ--decay of the shape isomers discussed in context with the recent A ~190 SD decay--out results (T. L. Khoo, et al., Phys. Rev. Lett. 76), 1583 (1996); A. Lopez-Martens, et al., Phys. Lett. B380, 18 (1996); K. Hauschild, et al., submitted to Phys. Rev. C (1996)..

  16. Calculations of long-lived isomer production in neutron reactions

    SciTech Connect

    Chadwick, M.B.; Young, P.G.

    1991-01-01

    We present theoretical calculations for the production of the long-lived isomers: {sup 121m}Sn (11/2-, 55 yr), {sup 166m}Ho(7-, 1200 yr), {sup 184m}Re(8+, 165 d), {sup 186m}Re(8+, 2{times}10{sup 5} yr), {sup 178m}Hf(16+, 31 yr), {sup 179m}Hf(25/2-, 25 d), {sup 192m}Ir(9+, 241 yr), all which pose potential radiation activation problems in nuclear fusion reactors if produced in 14-MeV neutron-induced reactions. We consider mainly (n,2n) production modes, but also (n,n{sup {prime}}) and (n,{gamma}) where necessary, and compare our results both with experimental data (where available) and systematics. We also investigate the dependence of the isomeric cross section ratio on incident neutron energy for the isomers under consideration. The statistical Hauser-Feshbach plus preequilibrium code GNASH was used for the calculations. Where discrete state experimental information was lacking, rotational band members above the isomeric state, which can be justified theoretically but have not been experimentally resolved, were reconstructed. 16 refs., 9 figs., 6 tabs.

  17. Firefighters' exposure to perfluoroalkyl acids and 2-butoxyethanol present in firefighting foams.

    PubMed

    Laitinen, Juha Ari; Koponen, Jani; Koikkalainen, Janne; Kiviranta, Hannu

    2014-12-01

    The aim of this study was to assess eight firefighters' exposure to Sthamex 3% AFFF (aqueous film forming foam) in the simulation of aircraft accidents at Oulu airport in Finland. Study was conducted in 2010 before limitation for the use of PFOA and PFOS in AFFFs. Due to prospective limitation also eight commercially available AFFFs were evaluated from occupational and environmental point of view to find substitutive AFFFs for future. The firefighters' exposure to twelve perfluoroalkyl acids (PFAS) was analyzed in order to observe the signs of accumulation during three consecutive training sessions. The firefighters' short-term exposure to 2-butoxyethanol (EGBE) was analyzed by urinalysis of 2-butoxyacetic acid (2-BAA). For the background information also the concentration of PFAS in used AFFF-liquid was analyzed. Fire fighters' serum PFHxS and PFNA concentrations seemed to increase during the three training sessions although they were not the main PFAS in used AFFF. The statistical significance for the elevations was not able to test due to limited size of test group. In two training sessions, the average urinary excretions of 2-BAA exceeded the reference limit of the occupationally unexposed population. In the evaluations of the firefighting foams, non-fluorine based products were favored and the alcohol resistance properties of foams were recommended for consideration due to the increasing use of biofuels.

  18. Firefighters' exposure to perfluoroalkyl acids and 2-butoxyethanol present in firefighting foams.

    PubMed

    Laitinen, Juha Ari; Koponen, Jani; Koikkalainen, Janne; Kiviranta, Hannu

    2014-12-01

    The aim of this study was to assess eight firefighters' exposure to Sthamex 3% AFFF (aqueous film forming foam) in the simulation of aircraft accidents at Oulu airport in Finland. Study was conducted in 2010 before limitation for the use of PFOA and PFOS in AFFFs. Due to prospective limitation also eight commercially available AFFFs were evaluated from occupational and environmental point of view to find substitutive AFFFs for future. The firefighters' exposure to twelve perfluoroalkyl acids (PFAS) was analyzed in order to observe the signs of accumulation during three consecutive training sessions. The firefighters' short-term exposure to 2-butoxyethanol (EGBE) was analyzed by urinalysis of 2-butoxyacetic acid (2-BAA). For the background information also the concentration of PFAS in used AFFF-liquid was analyzed. Fire fighters' serum PFHxS and PFNA concentrations seemed to increase during the three training sessions although they were not the main PFAS in used AFFF. The statistical significance for the elevations was not able to test due to limited size of test group. In two training sessions, the average urinary excretions of 2-BAA exceeded the reference limit of the occupationally unexposed population. In the evaluations of the firefighting foams, non-fluorine based products were favored and the alcohol resistance properties of foams were recommended for consideration due to the increasing use of biofuels. PMID:25447453

  19. Identification of 4-deoxythreonic acid present in human urine by combining HPLC and NMR techniques

    PubMed Central

    Appiah-Amponsah, Emmanuel; Shanaiah, Narasimhamurthy; Nagana Gowda, G. A.; Owusu-Sarfo, Kwadwo; Ye, Tao; Raftery, Daniel

    2010-01-01

    The 1H NMR spectrum of urine exhibits a large number of detectable and quantifiable metabolites and hence urine metabolite profiling is potentially useful for the study of systems biology and the discovery of biomarkers for drug development or clinical applications. While a number of metabolites (50–100) are readily detectable in urine by NMR, a much larger number is potentially available if lower concentration species can be detected unambiguously. Lower concentration metabolites are thought to be more specific to certain disease states and thus it is important to detect these metabolites with certainty. We report the identification of 4-deoxythreonic acid, a relatively low concentration endogenous metabolite that has not been previously identified in the 1H NMR spectrum of human urine. The complimentary use of HPLC and NMR spectroscopy facilitated the unequivocal and non-invasive identification of the molecule in urine which is complicated by extensive peak overlap and multiple, similar resonances from other metabolites such as 3-hydroxybutanoic acid. High-resolution detection and good sensitivity were achieved by the combination of multiple chromatographic fraction collection, sample pre-concentration, and the use of a cryogenically cooled NMR probe. PMID:19615840

  20. Acid rain monitoring in East-Central Florida from 1977 to present

    NASA Technical Reports Server (NTRS)

    Madsen, B. C.; Kheoh, T.; Hinkle, C. R.; Dreschel, T. W.

    1990-01-01

    Rainfall has been collected on the University of Central Florida campus and at the Kennedy Space Center over a 12 year period. The chemical composition has been determined and summarized by monthly, annual periods, and for the entire 12 year period at both locations. The weighted average pH at each site is 4.58; however, annual weighted average pH has been equal to or above the 12 year average during six of the past eight years. Nitrate concentrations have increased slightly during recent years while excess sulfate concentrations have remained below the 12 year weighted average during six of the past seven years. Stepwise regression suggests that sulfate, nitrate, ammonium ion and calcium play major roles in the description of rainwater acidity. Annual acid deposition and annual rainfall have varied from 20 to 50 meg/(m(exp 2) year) and 100 to 180 cm/year, respectively. Sea salt comprises at least 25 percent of the total ionic composition.

  1. Isomer ratio measurements as a probe of the dynamics of breakup and incomplete fusion

    SciTech Connect

    Gasques, L. R.; Dasgupta, M.; Hinde, D. J.; Peatey, T.; Diaz-Torres, A.; Newton, J. O.

    2006-12-15

    The incomplete fusion mechanism following breakup of {sup 6,7}Li and {sup 9}Be projectiles incident on targets of {sup 209}Bi and {sup 208}Pb is investigated through isomer ratio measurements for the {sup 212}At and {sup 211}Po products. The phenomenological analysis presented in this paper indicates that incomplete fusion brings relatively more angular momentum into the system than equivalent reactions with a direct beam of the fused fragment. This is attributed to the trajectories of breakup fragments. Calculations with a 3D classical trajectory model support this. Isomer ratio measurements for incomplete fusion reactions can provide a test of new theoretical models of breakup and fusion.

  2. On the possible biological relevance of HSNO isomers: a computational investigation.

    PubMed

    Ivanova, Lena V; Anton, Becka J; Timerghazin, Qadir K

    2014-05-14

    Thionitrous acid (HSNO), the smallest S-nitrosothiol, has been identified as a potential biologically active molecule that connects the biochemistries of two important gasotransmitters, nitric oxide (NO) and hydrogen sulfide (H2S). Here, we computationally explore possible isomerization reactions of HSNO that may occur under physiological conditions using high-level coupled-cluster as well as density functional theory and composite CBS-QB3 methodology calculations. Gas-phase calculations show that the formation of the tautomeric form HONS and the Y-isomer SN(H)O is thermodynamically feasible, as they are energetically close, within ∼6 kcal mol(-1), to HSNO, while the recently proposed three-membered ring isomer is not thermodynamically or kinetically accessible. The gas-phase intramolecular proton-transfer reactions required for HSNO isomerization into HONS and SN(H)O are predicted to have prohibitively high reaction barriers, 30-50 kcal mol(-1). However, the polar aqueous environment and water-assisted proton shuttle should decrease these barriers to ∼9 kcal mol(-1), which makes these two isomers kinetically accessible under physiological conditions. Our calculations also support the possibility of an aqueous reaction between the Y-isomer SN(H)O and H2S leading to biologically active nitroxyl HNO. These results suggest that the formation of HSNO in biological milieu can lead to various derivative species with their own, possibly biologically relevant, activity.

  3. Lactones 42. Stereoselective enzymatic/microbial synthesis of optically active isomers of whisky lactone.

    PubMed

    Boratyński, Filip; Smuga, Małgorzata; Wawrzeńczyk, Czesław

    2013-11-01

    Two different methods, enzyme-mediated reactions and biotrasformations with microorganisms, were applied to obtain optically pure cis- and trans-isomers of whisky lactone 4a and 4b. In the first method, eight alcohol dehydrogenases were investigated as biocatalysts to enantioselective oxidation of racemic erythro- and threo-3-methyloctane-1,4-diols (1a and 1b). Oxidation processes with three of them, alcohol dehydrogenases isolated from horse liver (HLADH) as well as recombinant from Escherichia coli and primary alcohol dehydrogenase (PADH I), were characterized by the highest degree of conversion with moderate enantioselectivity (ee=27-82%) of the reaction. In all enzymatic reactions enantiomerically enriched not naturally occurring isomers of trans-(-)-(4R,5S)-4b or cis-(+)-(4R,5R)-4a were formed preferentially. In the second strategy, based on microbial lactonization of γ-oxoacids, naturally occurring opposite isomers of whisky lactones were obtained. Trans-(+)-(4S,5R)-isomer (ee=99%) of whisky lactone 4b was stereoselectively formed as the only product of biotransformations of 3-methyl-4-oxooctanoic acid (5) catalyzed by Didimospheria igniaria KCH6651, Laetiporus sulphurens AM525, Chaetomium sp.1 KCH6670 and Saccharomyces cerevisiae AM464. Biotransformation of γ-oxoacid 5, in the culture of Beauveria bassiana AM278 and Pycnidiella resinae KCH50 afforded a mixtures of trans-(+)-(4S,5R)-4b with enantiomeric excess ee=99% and cis-(-)-(4S,5S)-4a with enantiomeric excesses ee=77% and ee=45% respectively.

  4. Glycolaldehyde, methyl formate and acetic acid adsorption and thermal desorption from interstellar ices

    NASA Astrophysics Data System (ADS)

    Burke, Daren J.; Puletti, Fabrizio; Brown, Wendy A.; Woods, Paul M.; Viti, Serena; Slater, Ben

    2015-02-01

    We have undertaken a detailed investigation of the adsorption, desorption and thermal processing of the astrobiologically significant isomers glycolaldehyde, acetic acid and methyl formate. Here, we present the results of laboratory infrared and temperature programmed desorption (TPD) studies of the three isomers from model interstellar ices adsorbed on a carbonaceous dust grain analogue surface. Laboratory infrared data show that the isomers can be clearly distinguished on the basis of their infrared spectra, which has implications for observations of interstellar ice spectra. Laboratory TPD data also show that the three isomers can be distinguished on the basis of their thermal desorption behaviour. In particular, TPD data show that the isomers cannot be treated the same way in astrophysical models of desorption. The desorption of glycolaldehyde and acetic acid from water-dominated ices is very similar, with desorption being mainly dictated by water ice. However, methyl formate also desorbs from the surface of the ice, as a pure desorption feature, and therefore desorbs at a lower temperature than the other two isomers. This is more clearly indicated by models of the desorption on astrophysical time-scales corresponding to the heating rate of 25 and 5 M⊙ stars. For a 25 M⊙ star, our model shows that a proportion of the methyl formate can be found in the gas phase at earlier times compared to glycolaldehyde and acetic acid. This has implications for the observation and detection of these molecules, and potentially explains why methyl formate has been observed in a wider range of astrophysical environments than the other two isomers.

  5. Identification and quantitation of lipid C=C location isomers: A shotgun lipidomics approach enabled by photochemical reaction

    PubMed Central

    Ma, Xiaoxiao; Chong, Leelyn; Tian, Ran; Shi, Riyi; Hu, Tony Y.; Ouyang, Zheng; Xia, Yu

    2016-01-01

    The field of lipidomics has been significantly advanced by mass spectrometric analysis. The distinction and quantitation of the unsaturated lipid isomers, however, remain a long-standing challenge. In this study, we have developed an analytical tool for both identification and quantitation of lipid C=C location isomers from complex mixtures using online Paternò–Büchi reaction coupled with tandem mass spectrometry (MS/MS). The potential of this method has been demonstrated with an implementation into shotgun lipid analysis of animal tissues. Among 96 of the unsaturated fatty acids and glycerophospholipids identified from rat brain tissue, 50% of them were found as mixtures of C=C location isomers; for the first time, to our knowledge, the quantitative information of lipid C=C isomers from a broad range of classes was obtained. This method also enabled facile cross-tissue examinations, which revealed significant changes in C=C location isomer compositions of a series of fatty acids and glycerophospholipid (GP) species between the normal and cancerous tissues. PMID:26903636

  6. cis-Isomers of Cytokinins Predominate in Chickpea Seeds throughout Their Development1

    PubMed Central

    Emery, Robert Joseph Neil; Leport, Laurent; Barton, Joanne Edith; Turner, Neil Clifford; Atkins, Craig Anthony

    1998-01-01

    Trans-isomers of cytokinins (CK) are thought to predominate and have greater biological activity than corresponding cis-isomers in higher plants. However, this study demonstrates a system within which the predominant CK are cis-isomers. CK were measured at four developmental stages in developing chickpea (Cicer arietinum L. cultivar Kaniva) seeds by gas chromatography-mass spectrometry. Concentrations were highest at an early endospermic fluid stage and fell considerably when the cotyledons expanded. The cis-isomers of zeatin nucleotide ([9R-MP]Z), zeatin riboside ([9R]Z), and zeatin (Z) were present in greater concentrations than those of corresponding trans-isomers: (trans)[9R-MP]Z, (trans)[9R]Z, (trans)Z, or dihydrozeatin riboside. Dihydrozeatin, dihydrozeatin nucleotide, and the isopentenyl-type CK concentrations were either low or not detectable. Root xylem exudates also contained predominantly cis-isomers of [9R-MP]Z and [9R]Z. Identities of (cis)[9R]Z and (cis)Z were confirmed by comparison of ion ratios and retention indices, and a full spectrum was obtained for (cis)[9R]Z. Tissues were extracted under conditions that minimized the possibility of RNase hydrolysis of tRNA following tissue disruption, being a significant source of the cis-CK. Since no isomerization of (trans)[2H]CK internal standards occurred, it is unlikely that the cis-CK resulted from enzymic or nonenzymic isomerization during extraction. Although quantities of total CK varied, similar CK profiles were found among three different chickpea cultivars and between adequately watered and water-stressed plants. Developing chickpea seeds will be a useful system for investigating the activity of cis-CK or determining the origin and metabolism of free CK. PMID:9701607

  7. Unprecedented χ isomers of single-side triol-functionalized Anderson polyoxometalates and their proton-controlled isomer transformation.

    PubMed

    Zhang, Jiangwei; Liu, Zhenhua; Huang, Yichao; zhang, Jin; Hao, Jian; Wei, Yongge

    2015-06-01

    The μ2-O atom in Anderson polyoxometalates was regioselectively activated by the introduction of protons, which, upon functionalization with triol ligands, could afford a series of unique χ isomers of the organically-derived Anderson cluster {[RCC(CH2O)3]MMo6O18(OH)3}(3-). Herein proton-controlled isomer transformation between the δ and χ isomer was observed by using the fingerprint region in the IR spectra and (13)C NMR spectra.

  8. Acid rain monitoring in Florida from 1978 to the present and evaluation of trends in rainwater composition

    SciTech Connect

    Madsen, B.C.; Dreschel, T.W.

    1996-12-31

    The occurrence of acid rain has prompted extensive research and monitoring activities which began in the U.S. during the late 1970`s. In the mid 1970`s the National Aeronautics and Space Administration (NASA) funded an extensive environmental monitoring program which included a substantial acid rain monitoring component. Results from that study and subsequent activities have been summarized in previous reports. One site from the original network has remained in continuous operation to the present time. That site is located on the campus of the University of Central Florida (UCF) near Orlando. The site provides the longest continuous record of rainwater composition data of any site ever operated in the state of Florida. In addition several sites that operate as part of the National Atmospheric Deposition (NADP) network continue in operation. Observations from the UCF site and the NADP sites document substantial changes in rainwater composition and acid deposition.

  9. The truth about the lower plasma concentration of the (-)-isomer after racemic doxazosin administration in rats: Stereoselective inhibition of the (-)-isomer by the (+)-isomer at CYP3A.

    PubMed

    Kong, Dezhi; Li, Qing; Zhang, Panpan; Zhang, Wei; Zhen, Yaqin; Ren, Leiming

    2015-09-18

    Doxazosin (DOX), a long-lasting α1-adrenoceptor antagonist, is used clinically as a racemate that consists of two optical isomers. In humans and rats, following oral administration of racemic DOX [(±)-DOX], the plasma concentration of the (-)-isomer is lower than that of the (+)-isomer, but the mechanism for this interaction is not known. In this study, a chiral HPLC with fluorescence detection was used to measure the drug concentrations for analysis of the stereoselective metabolism of DOX in in vivo and in vitro experiments. We found that the plasma levels of the (-)-isomer were significantly lower than those of the (+)-enantiomer following i.v. administration of (±)-DOX to the rats and that the depletion rate constant (kdep) of (-)-DOX (0.0107±0.0007L/min) was significantly larger than that of (+)-DOX (kdep 0.0088±0.0005L/min) (p<0.05) when (±)-DOX was incubated with rat liver microsomes (RLMs). However, (-)-DOX was not depleted faster than (+)-DOX following their separate incubation with RLMs. The metabolism of (-)- or (+)-isomer in RLMs was catalysed by CYP3A because the depletion of the compounds was inhibited by ketoconazole (a potent CYP3A-selective inhibitor) similarly. More importantly, the kdep of (+)-DOX in the 1.0/2.0 and 0.5/2.5 (+)-DOX/(-)-DOX mixtures was significantly lower than that of (-)-DOX in the 1.0/2.0 and 0.5/2.5 (-)-DOX/(+)-DOX mixtures (p<0.05). In conclusion, although (-)-DOX is not depleted faster than (+)-DOX when only a single isomer of DOX is incubated with rat liver microsomes, it is depleted much faster than (+)-DOX when a mixture of the two isomers was used, suggesting a prominent and stereoselective inhibition of the (-)-isomer over the (+)-isomer at the CYP3A enzyme.

  10. Isoaspartic acid is present at specific sites in myelin basic protein from multiple sclerosis patients: could this represent a trigger for disease onset?

    PubMed

    Friedrich, Michael G; Hancock, Sarah E; Raftery, Mark J; Truscott, Roger J W

    2016-01-01

    Multiple sclerosis (MS) is associated with breakdown of the myelin sheath that coats neurons in the central nervous system. The cause of MS is not known, although the pathogenesis involves destruction of myelin by the immune system. It was the aim of this study to examine the abundant myelin protein, myelin basic protein (MBP), to determine if there are sites of modification that may be characteristic for MS. MBP from the cerebellum was examined from controls and MS patients across the age range using mass spectrometry and amino acid analysis. Amino acid racemization data indicated that myelin basic protein is long-lived and proteomic analysis of MBP showed it to be highly modified. A common modification of MBP was racemization of Asp and this was significantly greater in MS patients. In long-lived proteins, L-Asp and L-Asn can racemize to three other isomers, D-isoAsp, L-isoAsp and D-Asp and this is significant because isoAsp formation in peptides renders them immunogenic.Proteomic analysis revealed widespread modifications of MBP with two surface regions that are altered in MS. In particular, isoAsp was significantly elevated at these sites in MS patients. The generation of isoAsp could be responsible for eliciting an immune response to modified MBP and therefore be implicated in the etiology of MS. PMID:27519525

  11. Isoaspartic acid is present at specific sites in myelin basic protein from multiple sclerosis patients: could this represent a trigger for disease onset?

    PubMed

    Friedrich, Michael G; Hancock, Sarah E; Raftery, Mark J; Truscott, Roger J W

    2016-08-12

    Multiple sclerosis (MS) is associated with breakdown of the myelin sheath that coats neurons in the central nervous system. The cause of MS is not known, although the pathogenesis involves destruction of myelin by the immune system. It was the aim of this study to examine the abundant myelin protein, myelin basic protein (MBP), to determine if there are sites of modification that may be characteristic for MS. MBP from the cerebellum was examined from controls and MS patients across the age range using mass spectrometry and amino acid analysis. Amino acid racemization data indicated that myelin basic protein is long-lived and proteomic analysis of MBP showed it to be highly modified. A common modification of MBP was racemization of Asp and this was significantly greater in MS patients. In long-lived proteins, L-Asp and L-Asn can racemize to three other isomers, D-isoAsp, L-isoAsp and D-Asp and this is significant because isoAsp formation in peptides renders them immunogenic.Proteomic analysis revealed widespread modifications of MBP with two surface regions that are altered in MS. In particular, isoAsp was significantly elevated at these sites in MS patients. The generation of isoAsp could be responsible for eliciting an immune response to modified MBP and therefore be implicated in the etiology of MS.

  12. 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

  13. 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...

  14. 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...

  15. 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...

  16. 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...

  17. 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...

  18. pH dependence of Anabaena sensory rhodopsin: retinal isomer composition, rate of dark adaptation, and photochemistry.

    PubMed

    Rozin, Rinat; Wand, Amir; Jung, Kwang-Hwan; Ruhman, Sanford; Sheves, Mordechai

    2014-07-31

    Microbial rhodopsins are photoactive proteins, and their binding site can accommodate either all-trans or 13-cis retinal chromophore. The pH dependence of isomeric composition, dark-adaptation rate, and primary events of Anabaena sensory rhodopsin (ASR), a microbial rhodopsin discovered a decade ago, are presented. The main findings are: (a) Two pKa values of 6.5 and 4.0 assigned to two different protein residues are observed using spectroscopic titration experiments for both ground-state retinal isomers: all-trans, 15-anti (AT) and 13-cis, 15-syn (13C). The protonation states of these protein residues affect the absorption spectrum of the pigment and most probably the isomerization process of the retinal chromophore. An additional pKa value of 8.5 is observed only for 13C-ASR. (b) The isomeric composition of ASR is determined over a wide pH range and found to be almost pH-independent in the dark (>96% AT isomer) but highly pH-dependent in the light-adapted form. (c) The kinetics of dark adaptation is recorded over a wide pH range, showing that the thermal isomerization from 13C to AT retinal occurs much faster at high pH rather than under acidic conditions. (d) Primary photochemical events of ASR at pH 5 are recorded using VIS hyperspectral pump-probe spectroscopy with <100 fs resolution and compared with the previously recorded results at pH 7.5. For AT-ASR, these are shown to be almost pH-independent. However, photochemistry of 13C-ASR is pH-dependent and slowed down in acidic environments.

  19. Lutein and Zeaxanthin Isomers in Eye Health and Disease.

    PubMed

    Mares, Julie

    2016-07-17

    Current evidence suggests lutein and its isomers play important roles in ocular development in utero and throughout the life span, in vision performance in young and later adulthood, and in lowering risk for the development of common age-related eye diseases in older age. These xanthophyll (oxygen-containing) carotenoids are found in a wide variety of vegetables and fruits, and they are present in especially high concentrations in leafy green vegetables. Additionally, egg yolks and human milk appear to be bioavailable sources. The prevalence of lutein, zeaxanthin, and meso-zeaxanthin in supplements is increasing. Setting optimal and safe ranges of intake requires additional research, particularly in pregnant and lactating women. Accumulating evidence about variable interindividual response to dietary intake of these carotenoids, based on genetic or metabolic influences, suggests that there may be subgroups that benefit from higher levels of intake and/or alternate strategies to improve lutein and zeaxanthin status. PMID:27431371

  20. Isomer ratio calculations using modeled discrete levels

    SciTech Connect

    Gardner, M.A.; Gardner, D.G.; Hoff, R.W.

    1984-10-16

    Isomer ratio calculations were made for the reactions: /sup 175/Lu(n,..gamma..)/sup 176m,g/Lu, /sup 175/Lu(n,2n)/sup 174m,g/Lu, /sup 237/Np(n,2n)/sup 236m,g/Np, /sup 241/Am(n,..gamma..)/sup 242m,g/Am, and /sup 243/Am(n,..gamma..)/sup 244m,g/Am using modeled level structures in the deformed, odd-odd product nuclei. The hundreds of discrete levels and their gamma-ray branching ratios provided by the modeling are necessary to achieve agreement with experiment. Many rotational bands must be included in order to obtain a sufficiently representative selection of K quantum numbers. The levels of each band must be extended to appropriately high values of angular momentum.

  1. Isomer Spectroscopy of the Heaviest Elements

    NASA Astrophysics Data System (ADS)

    Clark, Roderick

    2009-05-01

    A new generation of experiments on the structure and properties of the heaviest elements is being performed in laboratories around the world. These studies are addressing fundamental questions such as the maximum mass and charge that a nucleus can attain. Long-lived high-K isomers are found in the region of prolate-deformed trans-fermium nuclei and by studying their decay one can learn about the single-particle structure, pairing correlations, and excitation modes of the heaviest nuclei. Recent decay spectroscopy experiments using the Berkeley Gas-Filled Separator (BGS) at the 88-Inch Cyclotron of the Lawrence Berkeley National Laboratory have yielded a wealth of detailed new information on many nuclei in the trans-fermium region. I will discuss these new results and their implications.

  2. Laboratory detection of the elusive HSCO+ isomer.

    PubMed

    McCarthy, M C; Thaddeus, P

    2007-12-14

    The rotational spectrum of protonated carbonyl sulfide, HSCO(+), has now been detected in the centimeter-wave band in a molecular beam by Fourier transform microwave spectroscopy. Rotational and centrifugal distortion constants have been determined from transitions in the K(a)=0 ladder of the normal isotopic species, and DSCO(+) and H(34)SCO(+). HSCO(+) is systematically more abundant by a factor of three than HOCS(+), the isomer obtained by attaching the H(+) to the other end of the molecule, which ab initio calculations long predicted to be higher in energy by 4-5 kcalmol. Because HSCO(+) is comparable in polarity to HOCS(+) and is apparently more stable and because OCS is widely distributed in astronomical sources, HSCO(+) is a good candidate for detection with radio telescopes. PMID:18081381

  3. Nuclear structure and depletion of nuclear isomers using electron linacs

    SciTech Connect

    Carroll, J. J.; Litz, M. S.; Henriquez, S. L.; Burns, D. A.; Netherton, K. A.; Pereira, N. R.; Karamian, S. A.

    2013-04-19

    Long-lived nuclear excited states (isomers) have proven important to understanding nuclear structure. With some isomers having half-lives of decades or longer, and intrinsic energy densities reaching 10{sup 12} J/kg, they have also been suggested for a wide range of applications. The ability to effectively transfer a population of nuclei from an isomer to shorter-lived levels will determine the feasibility of any applications. Here is described a first demonstration of the induced depletion of a population of the 438 year isomer of {sup 108}Ag to its 2.38 min ground state, using 6 MeV bremsstrahlung from a modified medical electron linac. The experiment suggests refinements to be implemented in the future and how a similar approach might be applied to study induced depletion of the 1200 year isomer of {sup 166}Ho.

  4. Energetics and Vibrational Analysis of Methyl Salicylate Isomers

    NASA Astrophysics Data System (ADS)

    Massaro, Richard D.; Dai, Yafei; Blaisten-Barojas, Estela

    2009-08-01

    Energetics and vibrational analysis study of six isomers of methyl salicylate in their singlet ground state and first excited triple state is put forward in this work at the density functional theory level and large basis sets. The ketoB isomer is the lowest energy isomer, followed by its rotamer ketoA. For both ketoB and ketoA their enolized tautomers are found to be stable as well as their open forms that lack the internal hydrogen bond. The calculated vibrational spectra are in excellent agreement with IR experiments of methyl salicylate in the vapor phase. It is demonstrated that solvent effects have a weak influence on the stability of these isomers. The ionization reaction from ketoB to ketoA shows a high barrier of 0.67 eV ensuring that thermal and chemical equilibria yield systems containing mostly the ketoB isomer at normal conditions.

  5. Isolation and Characterization of Alfalfa-Nodulating Rhizobia Present in Acidic Soils of Central Argentina and Uruguay

    PubMed Central

    del Papa, María F.; Balagué, Laura J.; Sowinski, Susana Castro; Wegener, Caren; Segundo, Eduardo; Abarca, Francisco Martínez; Toro, Nicolás; Niehaus, Karsten; Pühler, Alfred; Aguilar, O. Mario; Martínez-Drets, Gloria; Lagares, Antonio

    1999-01-01

    We describe the isolation and characterization of alfalfa-nodulating rhizobia from acid soils of different locations in Central Argentina and Uruguay. A collection of 465 isolates was assembled, and the rhizobia were characterized for acid tolerance. Growth tests revealed the existence of 15 acid-tolerant (AT) isolates which were able to grow at pH 5.0 and formed nodules in alfalfa with a low rate of nitrogen fixation. Analysis of those isolates, including partial sequencing of the genes encoding 16S rRNA and genomic PCR-fingerprinting with MBOREP1 and BOXC1 primers, demonstrated that the new isolates share a genetic background closely related to that of the previously reported Rhizobium sp. Or191 recovered from an acid soil in Oregon (B. D. Eardly, J. P. Young, and R. K. Selander, Appl. Environ. Microbiol. 58:1809–1815, 1992). Growth curves, melanin production, temperature tolerance, and megaplasmid profiles of the AT isolates were all coincident with these characteristics in strain Or191. In addition to the ability of all of these strains to nodulate alfalfa (Medicago sativa) inefficiently, the AT isolates also nodulated the common bean and Leucaena leucocephala, showing an extended host range for nodulation of legumes. In alfalfa, the time course of nodule formation by the AT isolate LPU 83 showed a continued nodulation restricted to the emerging secondary roots, which was probably related to the low rate of nitrogen fixation by the largely ineffective nodules. Results demonstrate the complexity of the rhizobial populations present in the acidic soils represented by a main group of N2-fixing rhizobia and a second group of ineffective and less-predominant isolates related to the AT strain Or191. PMID:10103231

  6. 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. PMID:16854047

  7. 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.

  8. Inoculation of Pichia kudriavzevii RB1 degrades the organic acids present in raw compost material and accelerates composting.

    PubMed

    Nakasaki, Kiyohiko; Araya, Shogo; Mimoto, Hiroshi

    2013-09-01

    In this study, the yeast strain Pichia kudriavzevii RB1 was used as an inoculum to accelerate organic matter degradation of rabbit food with added organic acids, which was used as a model food waste for composting. The RB1 strain rapidly degraded the organic acids present in the raw compost material, leading to an increase in pH beyond the neutral level, within 2 days. Both mesophilic and thermophilic bacteria proliferated faster in the compost with RB1 inoculation than in that without inoculation. Although the yeast died with the increase in compost temperature, it affected the early stages of composting prior to the thermophilic stage and accelerated the composting process by 2 days by eliminating the initial lag phase seen in the growth of other microorganisms. Moreover, populations of Bacillus thermoamylovorans, Bacillus foraminis, and Bacillus coagulans became dominant during the thermophilic stages of both composting with and without RB1 inoculation. PMID:23886646

  9. Identification/quantification of free and bound phenolic acids in peel and pulp of apples (Malus domestica) using high resolution mass spectrometry (HRMS).

    PubMed

    Lee, Jihyun; Chan, Bronte Lee Shan; Mitchell, Alyson E

    2017-01-15

    Free and bound phenolic acids were measured in the pulp and peel of four varieties of apples using high resolution mass spectrometry. Twenty-five phenolic acids were identified and included: 8 hydroxybenzoic acids, 11 hydroxycinnamic acids, 5 hydroxyphenylacetic acids, and 1 hydoxyphenylpropanoic acid. Several phenolics are tentatively identified for the first time in apples and include: methyl gallate, ethyl gallate, hydroxy phenyl acetic acid, three phenylacetic acid isomers, 3-(4-hydroxyphenyl)propionic acid, and homoveratric acid. With exception of chlorogenic and caffeic acid, most phenolic acids were quantified for the first time in apples. Significant varietal differences (p<0.05) were observed in both peel and pulp. The levels of total phenolic acids were higher in the pulp as compared to apple peel (dry weight) in all varieties. Coumaroylquinic, protocatechuic, 4-hydroxybenzoic, vanillic and t-ferulic acids were present in free forms. With exception of chlorogenic acid, all other phenolic acids were present only as bound forms.

  10. Infrared spectroscopy of the acetyl cation and its protonated ketene isomer

    SciTech Connect

    Mosley, J. D.; Young, J. W.; Duncan, M. A.

    2014-07-14

    [C{sub 2},H{sub 3},O]{sup +} ions are generated with a pulsed discharge in a supersonic expansion containing methyl acetate or acetone. These ions are mass selected and their infrared spectra are recorded via laser photodissociation and the method of argon tagging. Computational chemistry is employed to investigate structural isomers and their spectra. The acetyl cation (CH{sub 3}CO{sup +}) is the global minimum and protonated ketene (CH{sub 2}COH{sup +}) is the next lowest energy isomer (+176.2 kJ/mol). When methyl acetate is employed as the precursor, the infrared spectrum reveals that only the acetyl cation is formed. Partially resolved rotational structure reveals rotation about the C{sub 3} axis. When acetone is used as the precursor, acetyl is still the most abundant cation, but there is also a minor component of protonated ketene. Computations reveal a significant barrier to interconversion between the two isomers (+221 kJ/mol), indicating that protonated ketene must be obtained via kinetic trapping. Both isomers may be present in interstellar environments, and their implications for astrochemistry are discussed.

  11. Lack of selective developmental toxicity of three butanol isomers administered by inhalation to rats.

    PubMed

    Nelson, B K; Brightwell, W S; Khan, A; Burg, J R; Goad, P T

    1989-04-01

    As part of an ongoing study of the developmental toxicology of industrial alcohols, this report presents the results of the teratology assessments of 1-butanol, 2-butanol, and t-butanol administered by inhalation to rats. Groups of approximately 15 Sprague-Dawley rats were exposed at 8000, 6000, 3500, or 0 ppm 1-butanol, 7000, 5000, 3500, or 0 ppm 2-butanol, or 5000, 3500, 2000, or 0 ppm t-butanol for 7 hr/day on Gestation Days 1-19 (sperm = 0). In each case, the highest concentration was selected to produce maternal toxicity. Dams were sacrificed on Gestation Day 20, and fetuses were individually weighed, tagged, and examined for external malformations. One-half of the fetuses were stained and examined for skeletal abnormalities, and the other half were examined for visceral defects using the Wilson technique. For each butanol isomer examined, the highest concentration (and the intermediate in some cases) was maternally toxic, as manifest by reduced weight gain and feed intake. Even at a maternally toxic dose, and in spite of a dose-dependent reduction in fetal weights for each isomer, the only teratogenicity observed was a slight increase in skeletal malformations (primarily rudimentary cervical ribs), seen with the highest concentration of 1-butanol. Thus, although teratogenicity was observed at 8000 ppm 1-butanol, and developmental toxicity was observed with each of the butyl alcohol isomers studied, concentrations 50 times the current permissible exposure limits for these three butanol isomers do not produce teratogenicity in rats.

  12. Toward the laboratory identification of [O,N,S,S] isomers: Implications for biological NO chemistry

    NASA Astrophysics Data System (ADS)

    Ayari, Tarek; Jaidane, Nejm-Eddine; Al Mogren, Muneerah Mogren; Francisco, Joseph S.; Hochlaf, Majdi

    2016-06-01

    Benchmark ab initio calculations are performed to investigate the stable isomers of [O,N,S,S]. These computations are carried out using coupled cluster (RCCSD(T)) and explicitly correlated coupled cluster methods (RCCSD(T)-F12). In addition to the already known cis isomer of SSNO, nine other stable forms are predicted. The most stable isomer is cis-OSNS. Nine structures are chain bent-bent with relatively large dipole moments which make them detectable, as cis-SSNO, by infrared, far-infrared, and microwave spectroscopies. We found also a C2v isomer (NS2O). Since these species are strongly suggested to play an important role as intermediates during the bioactive reaction products of the NO/H2S interaction, the rotational and vibrational spectroscopic parameters are presented to help aid the in vivo identification and assignment of these spectra. Results from this work show that [O,N,S,S] may play key roles during nitric oxide transport and deliver in biological media, as well as, provide an explanation for the weak characteristic of disulfide bridges within proteins.

  13. Orally administered rosmarinic acid is present as the conjugated and/or methylated forms in plasma, and is degraded and metabolized to conjugated forms of caffeic acid, ferulic acid and m-coumaric acid.

    PubMed

    Baba, Seigo; Osakabe, Naomi; Natsume, Midori; Terao, Junji

    2004-05-28

    Rosmarinic acid (RA) is contained in various Lamiaceae herbs used commonly as culinary herbs. Although RA has various potent physiological actions, little is known on its bioavailability. We therefore investigated the absorption and metabolism of orally administered RA in rats. After being deprived of food for 12 h, RA (50 mg/kg body weight) or deionized water was administered orally to rats. Blood samples were collected from a cannula inserted in the femoral artery before and at designated time intervals after administration of RA. Urine excreted within 0 to 8 h and 8 to 18 h post-administration was also collected. RA and its related metabolites in plasma and urine were measured by LC-MS after treatment with sulfatase and/or beta-glucuronidase. RA, mono-methylated RA (methyl-RA) and m-coumaric acid (COA) were detected in plasma, with peak concentrations being reached at 0.5, 1 and 8 h after RA administration, respectively. RA, methyl-RA, caffeic acid (CAA), ferulic acid (FA) and COA were detected in urine after RA administration. These components in plasma and urine were present predominantly as conjugated forms such as glucuronide or sulfate. The percentage of the original oral dose of RA excreted in the urine within 18 h of administration as free and conjugated forms was 0.44 +/- 0.21% for RA, 1.60 +/- 0.74% for methyl-RA, 1.06 +/- 0.35% for CAA, 1.70 +/- 0.45% for FA and 0.67 +/- 0.29% for COA. Approximately 83% of the total amount of these metabolites was excreted in the period 8 to 18 h after RA administration. These results suggest that RA was absorbed and metabolized as conjugated and/or methylated forms, and that the majority of RA absorbed was degraded into conjugated and/or methylated forms of CAA, FA and COA before being excreted gradually in the urine. PMID:15120569

  14. Profiles of fatty acids and 7-O-acyl okadaic acid esters in bivalves: can bacteria be involved in acyl esterification of okadaic acid?

    PubMed

    Vale, Paulo

    2010-01-01

    The presence of 7-O-acyl okadaic acid (OA) esters was studied by LC-MS in the digestive glands of blue mussel (Mytilus galloprovincialis) and common cockle (Cerastoderma edule) from Albufeira lagoon, located 20km south of Lisbon. The profile of free and total fatty acids (FA) was analysed using a similar LC separation with a reversed phase C8 column and mass spectrometry detection. In mussel the free FA profile was reflected in the FA esterified to OA, being palmitic acid for instance the most abundant in both cases. In cockle, 7-O-acyl esters with palmitic acid were almost absent and esters with a C16:0 isomer were dominant, followed by esters with C15:1 and C15:0. The cockle free FA profile was similar to mussel, and in accordance with literature findings in bivalves. After hydrolysis, a major difference in the FA profile occurred in both species, presenting a high percentage of a C16:0 isomer. The isomer found in general lipids and bound to OA seemed to be related, presenting similar relative retention times (RRT) to C16:0, differing from expected RRT of monomethyl-branched isomers (iso- or anteiso-). A tentative identification was made with the multimethyl-branched isoprenoid, 4,8,12-trimethyltridecanoic acid (TMTD). TMTD is a product of phytol degradation. This was also suspected when the proportion of this compound in relation to palmitic acid was reduced in vivo in mussels fed a chlorophyll-free diet. Extensive esterification of OA by, among others, phytol-degrading bacteria is discussed as a plausible hypothesis in cockle, but not in mussel, due to the relatively high specific proportion of odd-numbered and branched FA.

  15. Removal of co-present chromate and arsenate by zero-valent iron in groundwater with humic acid and bicarbonate.

    PubMed

    Liu, Tongzhou; Rao, Pinhua; Mak, Mark S H; Wang, Peng; Lo, Irene M C

    2009-05-01

    The interactions of co-present Cr(VI) and As(V), and the influences of humic acid and bicarbonate in the process of Cr(VI) and As(V) removal by Fe(0) were investigated in a batch setting using simulated groundwater with 5 mM NaCl, 1 mM Na(2)SO(4), and 0.8 mM CaCl(2) as background electrolytes at an initial pH value of 7. Cr(VI) and As(V) were observed to be subject to different impacts induced by co-existing As(V) or Cr(VI), humic acid and bicarbonate, originating from their distinct removal mechanisms by Fe(0). Cr(VI) removal is a reduction-dominated process, whereas As(V) removal principally involves adsorption onto iron corrosion products. Experimental results showed that Cr(VI) removal was not affected by the presence of As(V) and humic acid. However, As(V) removal appeared to be inhibited by co-present Cr(VI). When the Cr(VI) concentration was 2, 5, and 10 mg/L, in the absence of humic acid and bicarbonate, As(V) removal rate constants were decreased by 27.9%, 49.0%, and 61.2%, respectively, which probably resulted from competition between Cr(VI) and As(V) for adsorption sites of the iron corrosion products. Furthermore, the presence of humic acid significantly varied As(V) removal kinetics by delaying the formation and aggregation of iron hydroxides due to the formation of soluble Fe-humate complexes and stably dispersed fine iron hydroxides colloids. In the presence of bicarbonate, both Cr(VI) and As(V) removal was increased and the inhibitory effect of Cr(VI) on As(V) removal was suppressed, resulting from the buffering effects and the promoted iron corrosion induced by bicarbonate, and the formation of CaCO(3) in solution, which enhanced As(V) adsorption. PMID:19321187

  16. Quantification of the ratio of positional isomer dilinoleoyl-oleoyl glycerols in vegetable oils.

    PubMed

    Jakab, A; Jablonkai, I; Forgács, E

    2003-01-01

    The distribution of fatty acids in a triacylglycerol is of great importance from nutritional, biochemical, quality and technological points of view. The ratio of triacylglycerol positional isomers containing two linoleic acid (18:2) and one oleic acid (18:1) moieties--namely, 1(3),2-dilinoleoyl-3(1)-oleoyl glycerol (LLO) and 1,3-dilinoleoyl-2-oleoyl glycerol (LOL)--were quantified in grape seed, olive, pumpkin seed, soybean, sunflower and wheat germ oils by high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (HPLC/APCI-MS) in selected ion monitoring (SIM) mode. Relative LOL contents (LOL/(LLO+LOL)) of the oils were calculated from the mass abundances of the [LL]+ and [LO]+ diacylglycerol fragment ions ([M+H-RCOOH]+) using a calibration curve. The calibration curve of the relative diacylglycerol mass abundances was measured in SIM mode. The relative LOL contents were found to be relatively consistent for each oil variety. The relative LOL content in grape seed, sunflower, pumpkin seed, soybean and wheat germ oils accounted for 44.2 +/- 2.6, 26.8 +/- 3.2, 16.7 +/- 4.6, 15.9 +/- 2.9 and 13.9 +/- 4.3%, respectively. Only olive oils contained practically 100% of the LLO isomer. These results indicate that the unsaturated fatty acids such as linoleic and oleic acids have 'non-random' distribution patterns in various oils.

  17. Separation and identification of indene–C70 bisadduct isomers

    PubMed Central

    Zhang, Bolong; Subbiah, Jegadesan; Jones, David J

    2016-01-01

    Summary Following an initial work on the isolation of a single geometric isomer from an indene–C70 bisadduct (IC70BA) mixture, we report the full fractionation and identification of the bisadduct species in the material. Eleven fractions of IC70BA isomers were separated by high-performance liquid chromatography. A number of fractions contained relatively pure isomer species and their configuration were deduced using a variety of analytical techniques including 1H and 13C NMR and UV–vis spectroscopy. The electrochemical properties and the organic solar cell device performance were investigated for fractions where a reasonable quantity of sample could be isolated. PMID:27340480

  18. Detection of Actinides via Nuclear Isomer De-Excitation

    SciTech Connect

    Francy, Christopher J.

    2009-07-01

    This dissertation discusses a data collection experiment within the Actinide Isomer Identification project (AID). The AID project is the investigation of an active interrogation technique that utilizes nuclear isomer production, with the goal of assisting in the interdiction of illicit nuclear materials. In an attempt to find and characterize isomers belonging to 235U and its fission fragments, a 232Th target was bombarded with a monoenergetic 6Li ion beam, operating at 45 MeV.

  19. Raman spectroscopic analysis of isomers of biliverdin dimethyl ester.

    PubMed

    Matysik, J; Hildebrandt, P; Smit, K; Mark, F; Gärtner, W; Braslavsky, S E; Schaffner, K; Schrader, B

    1997-06-01

    The constitutional isomers of biliverdin dimethyl ester, IX alpha and XIII alpha, were studied by resonance Raman spectroscopy. The far-reaching spectral similarities suggest that despite the different substitution patterns, the compositions of the normal modes are closely related. This conclusion does not hold only for the parent state (ZZZ, sss configuration) but also for the configurational isomers which were obtained upon double-bond photoisomerization. Based on a comparison of the resonance Raman spectra, a EZZ configuration is proposed for one of the two photoisomers of biliverdin dimethyl ester IX alpha, while a ZZE, ssa configuration has been assigned previously to the second isomer. PMID:9226559

  20. The impact of technical cashew nut shell liquid on thermally-induced trans isomers in edible oils.

    PubMed

    Guo, Qin; Wang, Feng; He, Fan; Ha, Yi-Ming; Li, Qing-Peng; Jin, Jing; Deng, Zhao-Xuan

    2016-03-01

    The effects of technical cashew nut shell liquid (TCNSL) on the trans isomerization of edible oils during heating are investigated. Edible oils were subjected to thermal treatment at various heating times and temperatures. Our results show that the addition of TCNSL to edible oils at the appropriate concentration during heating suppresses trans fatty acid formation and induces formation of conjugated linoleic acid (CLA) isomers. A concentration of 0.2 % TCNSL demonstrates the best ability to inhibit formation of trans-oleic acid, trans-linoleic acid, and trans-linolenic acid isomers as well as increase the formation of 9 t,11 t-CLA and 10 t,12 t-CLA isomers. Our analysis indicates that the presence of 0.2 % TCNSL in corn oil does not significantly reduce the acid value, but may significantly lower the peroxide value. TCNSL is also observed to have better function compared to Vitamin E (VE) and tertiary butylhydroquinone (TBHQ), indicating that it may be considered an effective additive in edible oils. PMID:27570273

  1. The impact of technical cashew nut shell liquid on thermally-induced trans isomers in edible oils.

    PubMed

    Guo, Qin; Wang, Feng; He, Fan; Ha, Yi-Ming; Li, Qing-Peng; Jin, Jing; Deng, Zhao-Xuan

    2016-03-01

    The effects of technical cashew nut shell liquid (TCNSL) on the trans isomerization of edible oils during heating are investigated. Edible oils were subjected to thermal treatment at various heating times and temperatures. Our results show that the addition of TCNSL to edible oils at the appropriate concentration during heating suppresses trans fatty acid formation and induces formation of conjugated linoleic acid (CLA) isomers. A concentration of 0.2 % TCNSL demonstrates the best ability to inhibit formation of trans-oleic acid, trans-linoleic acid, and trans-linolenic acid isomers as well as increase the formation of 9 t,11 t-CLA and 10 t,12 t-CLA isomers. Our analysis indicates that the presence of 0.2 % TCNSL in corn oil does not significantly reduce the acid value, but may significantly lower the peroxide value. TCNSL is also observed to have better function compared to Vitamin E (VE) and tertiary butylhydroquinone (TBHQ), indicating that it may be considered an effective additive in edible oils.

  2. Probing ground and low-lying excited states for HIO2 isomers

    NASA Astrophysics Data System (ADS)

    de Souza, Gabriel L. C.; Brown, Alex

    2014-12-01

    We present a computational study on HIO2 molecules. Ground state properties such as equilibrium structures, relative energetics, vibrational frequencies, and infrared intensities were obtained for all the isomers at the coupled-cluster with single and double excitations as well as perturbative inclusion of triples (CCSD(T)) level of theory with the aug-cc-pVTZ-PP basis set and ECP-28-PP effective core potential for iodine and the aug-cc-pVTZ basis set for hydrogen and oxygen atoms. The HOIO structure is confirmed as the lowest energy isomer. The relative energies are shown to be HOIO < HOOI < HI(O)O. The HO(O)I isomer is only stable at the density functional theory (DFT) level of theory. The transition states determined show interconversion of the isomers is possible. In order to facilitate future experimental identification, vibrational frequencies are also determined for all corresponding deuterated species. Vertical excitation energies for the three lowest-lying singlet and triplet excited states were determined using the configuration interaction singles, time-dependent density functional theory (TD-DFT)/B3LYP, TD-DFT/G96PW91, and equation of motion-CCSD approaches with the LANL2DZ basis set plus effective core potential for iodine and the aug-cc-pVTZ basis set for hydrogen and oxygen atoms. It is shown that HOIO and HOOI isomers have excited states accessible at solar wavelengths (<4.0 eV) but these states have very small oscillator strengths (<2 × 10-3).

  3. Probing ground and low-lying excited states for HIO2 isomers.

    PubMed

    de Souza, Gabriel L C; Brown, Alex

    2014-12-21

    We present a computational study on HIO2 molecules. Ground state properties such as equilibrium structures, relative energetics, vibrational frequencies, and infrared intensities were obtained for all the isomers at the coupled-cluster with single and double excitations as well as perturbative inclusion of triples (CCSD(T)) level of theory with the aug-cc-pVTZ-PP basis set and ECP-28-PP effective core potential for iodine and the aug-cc-pVTZ basis set for hydrogen and oxygen atoms. The HOIO structure is confirmed as the lowest energy isomer. The relative energies are shown to be HOIO < HOOI < HI(O)O. The HO(O)I isomer is only stable at the density functional theory (DFT) level of theory. The transition states determined show interconversion of the isomers is possible. In order to facilitate future experimental identification, vibrational frequencies are also determined for all corresponding deuterated species. Vertical excitation energies for the three lowest-lying singlet and triplet excited states were determined using the configuration interaction singles, time-dependent density functional theory (TD-DFT)/B3LYP, TD-DFT/G96PW91, and equation of motion-CCSD approaches with the LANL2DZ basis set plus effective core potential for iodine and the aug-cc-pVTZ basis set for hydrogen and oxygen atoms. It is shown that HOIO and HOOI isomers have excited states accessible at solar wavelengths (<4.0 eV) but these states have very small oscillator strengths (<2 × 10(-3)). PMID:25527931

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

    SciTech Connect

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

    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 isomer 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.

  5. Probing ground and low-lying excited states for HIO{sub 2} isomers

    SciTech Connect

    Souza, Gabriel L. C. de; Brown, Alex

    2014-12-21

    We present a computational study on HIO{sub 2} molecules. Ground state properties such as equilibrium structures, relative energetics, vibrational frequencies, and infrared intensities were obtained for all the isomers at the coupled-cluster with single and double excitations as well as perturbative inclusion of triples (CCSD(T)) level of theory with the aug-cc-pVTZ-PP basis set and ECP-28-PP effective core potential for iodine and the aug-cc-pVTZ basis set for hydrogen and oxygen atoms. The HOIO structure is confirmed as the lowest energy isomer. The relative energies are shown to be HOIO < HOOI < HI(O)O. The HO(O)I isomer is only stable at the density functional theory (DFT) level of theory. The transition states determined show interconversion of the isomers is possible. In order to facilitate future experimental identification, vibrational frequencies are also determined for all corresponding deuterated species. Vertical excitation energies for the three lowest-lying singlet and triplet excited states were determined using the configuration interaction singles, time-dependent density functional theory (TD-DFT)/B3LYP, TD-DFT/G96PW91, and equation of motion-CCSD approaches with the LANL2DZ basis set plus effective core potential for iodine and the aug-cc-pVTZ basis set for hydrogen and oxygen atoms. It is shown that HOIO and HOOI isomers have excited states accessible at solar wavelengths (<4.0 eV) but these states have very small oscillator strengths (<2 × 10{sup −3})

  6. Time-resolved cryogenic modulation reveals isomer interconversion profiles in dynamic chromatography.

    PubMed

    Mariott, P; Trapp, O; Shellie, R; Schurig, V G

    2001-06-01

    The dynamic chromatographic study of interconversion of E and Z forms of oximes has been investigated by using a novel cryogenic modulation method in a two-dimensional gas chromatographic array. The primary column is a conventional capillary GC column on which the molecular interconversion proceeds. In this case, the molecular dynamical process leads to a peak profile describing the kinetics and thermodynamics of the interconverting molecules during its chromatographic elution. Thus an interconversion region intercedes the elution of the individual stereoisomers of the reaction. Since the molecules are isomers, classical molecular identification methods such as gas chromatography-mass spectrometry are unable to study the individual instantaneous amounts of each of the compounds. Hence the infinitesimal profiles of interconversion along the entire column have never been experimentally observed; rather the total profile is normally subjected to mathematical modelling studies in order to match experiment with theory, and to gain the kinetic parameters of the process. In the present study, an instantaneous ratio of the individual isomers can be found during the chromatographic elution by direct measurement. This is achieved by using a cryogenic zone focussing process, with rapid longitudinal modulation of a cold trap and continual pulsing of collected zones into a fast-analysis high-resolution capillary column on which isomer interconversion is minimized. The data can be displayed as a two-dimensional contour plot to demonstrate the individual isomer profiles. The two-dimensional analysis also allows easy measurement of the peak ratios of the two isomers which is an indicator of the extent of interconversion that has taken place. Two model systems, acetaldoxime and butyraldoxime, were chosen to illustrate the use of the cryogenic modulation procedure. It is anticipated that the procedure could be applied to other molecules which exhibit gas-phase isomerizations or

  7. An experimental and kinetic modeling study of the oxidation of the four isomers of butanol.

    PubMed

    Moss, Jeffrey T; Berkowitz, Andrew M; Oehlschlaeger, Matthew A; Biet, Joffrey; Warth, Valérie; Glaude, Pierre-Alexandre; Battin-Leclerc, Frédérique

    2008-10-30

    Butanol, an alcohol which can be produced from biomass sources, has received recent interest as an alternative to gasoline for use in spark ignition engines and as a possible blending compound with fossil diesel or biodiesel. Therefore, the autoignition of the four isomers of butanol (1-butanol, 2-butanol, iso-butanol, and tert-butanol) has been experimentally studied at high temperatures in a shock tube, and a kinetic mechanism for description of their high-temperature oxidation has been developed. Ignition delay times for butanol/oxygen/argon mixtures have been measured behind reflected shock waves at temperatures and pressures ranging from approximately 1200 to 1800 K and 1 to 4 bar. Electronically excited OH emission and pressure measurements were used to determine ignition-delay times. The influence of temperature, pressure, and mixture composition on ignition delay has been characterized. A detailed kinetic mechanism has been developed to describe the oxidation of the butanol isomers and validated by comparison to the shock-tube measurements. Reaction flux and sensitivity analysis illustrates the relative importance of the three competing classes of consumption reactions during the oxidation of the four butanol isomers: dehydration, unimolecular decomposition, and H-atom abstraction. Kinetic modeling indicates that the consumption of 1-butanol and iso-butanol, the most reactive isomers, takes place primarily by H-atom abstraction resulting in the formation of radicals, the decomposition of which yields highly reactive branching agents, H atoms and OH radicals. Conversely, the consumption of tert-butanol and 2-butanol, the least reactive isomers, takes place primarily via dehydration, resulting in the formation of alkenes, which lead to resonance stabilized radicals with very low reactivity. To our knowledge, the ignition-delay measurements and oxidation mechanism presented here for 2-butanol, iso-butanol, and tert-butanol are the first of their kind.

  8. Differential adsorption of complex organic molecules isomers at interstellar ice surfaces

    NASA Astrophysics Data System (ADS)

    Lattelais, M.; Bertin, M.; Mokrane, H.; Romanzin, C.; Michaut, X.; Jeseck, P.; Fillion, J.-H.; Chaabouni, H.; Congiu, E.; Dulieu, F.; Baouche, S.; Lemaire, J.-L.; Pauzat, , F.; Pilmé, J.; Minot, C.; Ellinger, Y.

    2011-08-01

    Context. Over 20 of the ~150 different species detected in the interstellar and circumstellar media have also been identified in icy environments. For most of the species observed so far in the interstellar medium (ISM), the most abundant isomer of a given generic chemical formula is the most stable one (minimum energy principle - MEP) with few exceptions such as, for example, CH3COOH/HCOOCH3 and CH3CH2OH/CH3OCH3, whose formation is thought to occur on the icy mantles of interstellar grains. Aims: We investigate whether differences found in the compositions of molecular ices and the surrounding gas phase could originate from differences between the adsorption of one isomer from that of another at the ice surface. Methods: We performed a coherent and concerted theoretical/experimental study of the adsorption energies of the four molecules mentioned above, i.e. acetic acid (AA)/methyl formate (MF) and ethanol (EtOH)/dimethyl ether (DME) on the surface of water ice at low temperature. The question was first addressed theoretically at LCT using solid state periodic density functional theory (DFT) to represent the organized solid support. The experimental determination of the ice/molecule interaction energies was then carried out independently by two teams at LPMAA and LERMA/LAMAp using temperature programmed desorption (TPD) under an ultra-high vacuum (UHV) between 70 and 160 K. Results: For each pair of isomers, theory and experiments both agree that the most stable isomer (AA or EtOH) interacts more efficiently with the water ice than the higher energy isomer (MF or DME). This differential adsorption can be clearly seen in the different desorption temperatures of the isomers. It is not related to their intrinsic stability but instead to both AA and EtOH producing more and stronger hydrogen bonds with the ice surface. Conclusions: We show that hydrogen bonding may play an important role in the release of organic species from grains and propose that, depending on the

  9. Isomer spectroscopy of {sup 127}Cd

    SciTech Connect

    Naqvi, F.; Gorska, M.; Grawe, H.; Beck, T.; Doornenbal, P.; Geissel, H.; Gerl, J.; Kojouharov, I.; Kurz, N.; Montes, F.; Prokopowicz, W.; Schaffner, H.; Tashenov, S.; Wollersheim, H. J.; Caceres, L.; Jungclaus, A.; Pfuetzner, M.; Werner-Malento, E.; Nowacki, F.; Sieja, K.

    2010-09-15

    The spin and configurational structure of excited states of {sup 127}Cd, the two-proton and three-neutron hole neighbor of {sup 132}Sn, has been studied. An isomeric state with a half-life of 17.5(3) {mu}s was populated in the fragmentation of a {sup 136}Xe beam on a {sup 9}Be target at a beam energy of 750 MeV/u. Time distributions of the delayed {gamma} transitions and {gamma}{gamma} coincidence relations were exploited to construct a decay scheme. The observed yrast (19/2){sup +} isomer is proposed to have dominant configurations of {nu}(h{sub 11/2}{sup -3}){pi}(g{sub 9/2}{sup -1},p{sub 1/2}{sup -1}), {nu}(h{sub 11/2}{sup -2}d{sub 3/2}{sup -1}){pi}(g{sub 9/2}{sup -2}), and {nu}(h{sub 11/2}{sup -2},s{sub 1/2}{sup -1}){pi}(g{sub 9/2}{sup -2}) and to decay by two competing stretched M2 and E3 transitions. Experimental results are compared with the isotone {sup 129}Sn. The new information provides input for the proton-neutron interaction and the evolution of neutron hole energies in nuclei around the doubly magic {sup 132}Sn core.

  10. Acute Generalized Exanthematous Pustulosis Induced by Amoxicillin/Clavulanic Acid: Report of a Case Presenting With Generalized Lymphadenopathy.

    PubMed

    Syrigou, Ekaterini; Grapsa, Dimitra; Charpidou, Andriani; Syrigos, Konstantinos

    2015-01-01

    Drug-induced acute generalized exanthematous pustulosis is a rare pustular skin reaction, most commonly triggered by antibiotics. Although its diagnosis is based primarily on the presence of specific clinical and histopathologic features, additional in vivo (patch testing) or in vitro testing may be required, especially in atypical cases, to more accurately determine the causative agent. The authors report a histologically confirmed case of acute generalized exanthematous pustulosis that was induced by amoxicillin/clavulanic acid, as documented by subsequent patch testing, and presented with generalized painful lymphadenopathy, mimicking an acute infectious process. This is a very rare and diagnostically challenging clinical presentation of acute generalized exanthematous pustulosis, which has been reported, to the best of our knowledge, only once previously.

  11. Crystal Structure of the 11-cis Isomer of Pharaonis Halorhodopsin: Structural Constraints on Interconversions among Different Isomeric States.

    PubMed

    Chan, Siu Kit; Kawaguchi, Haruki; Kubo, Hiroki; Murakami, Midori; Ihara, Kunio; Maki, Kosuke; Kouyama, Tsutomu

    2016-07-26

    Like other microbial rhodopsins, the light driven chloride pump halorhodopsin from Natronomonas pharaonis (pHR) contains a mixture of all-trans/15-anti and 13-cis/15-syn isomers in the dark adapted state. A recent crystallographic study of the reaction states of pHR has shown that reaction states with 13-cis/15-syn retinal occur in the anion pumping cycle that is initiated by excitation of the all-trans isomer. In this study, we investigated interconversions among different isomeric states of pHR in the absence of chloride ions. The illumination of chloride free pHR with red light caused a large blue shift in the absorption maximum of the retinal visible band. During this "red adaptation", the content of the 11-cis isomer increased significantly, while the molar ratio of the 13-cis isomer to the all-trans isomer remained unchanged. The results suggest that the thermally activated interconversion between the 13-cis and the all-trans isomers is very rapid. Diffraction data from red adapted crystals showed that accommodation of the retinal chromophore with the 11-cis/15-syn configuration was achieved without a large change in the retinal binding pocket. The measurement of absorption kinetics under illumination showed that the 11-cis isomer, with a λmax at 565 nm, was generated upon excitation of a red-shifted species (λmax = 625 nm) that was present as a minor component in the dark adapted state. It is possible that this red-shifted species mimics an O-like reaction state with 13-cis/15-syn retinal, which was hypothesized to occur at a late stage of the anion pumping cycle.

  12. 227 Views of RNA: Is RNA Unique in Its Chemical Isomer Space?

    PubMed

    Cleaves, H James; Meringer, Markus; Goodwin, Jay

    2015-07-01

    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.

  13. Characterization of charge isomers of yeast phosphoglycerate kinase. Evidence for intracellular differences.

    PubMed

    Arvidsson, L; Schierbeck, B; Larsson-Raźnikiewicz, M

    1976-01-01

    Three electrophoretic components of phosphoglycerate kinase have been isolated from baker's yeast. The isoionic point of the major component is 7.18 at 10 degrees C. Corresponding values for the minor ones are 6.91 and 7.48, respectively. There is a difference of one charge-unit between the isomers 1 and 2, and between the isomers 2 and 3. The release of component 3 from the yeast cells appears in contrast to the isomers 1 and 2 to be promoted by an organic solvent, thus suggesting this component to be bound to the cell-membrane. The amino-terminal amino acid residue appears to be N-acetylated serine in each of the three cases. The carboxyl-terminal ends seem to be identical also with -(Ala, Leu, Val, Lys)- Ala-Lys as the ultimate sequence. From the circular dichroism spectra the contents of alpha-helix and beta-structure were estimated to 15 and 40-50%, respectively. Factors have been determined for transformation and comparison of the specific activities as determined under the various conditions used at different laboratories.

  14. Enhanced Raman spectroscopic study of rotational isomers on metal surfaces

    NASA Technical Reports Server (NTRS)

    Loo, B. H.; Lee, Y. G.; Frazier, D. O.

    1986-01-01

    Surfaced-enhanced Raman spectroscopy has been used to study rotational isomers of succinonitrile and N-methyl-thioacetamide on Cu and Ag surfaces. Both the gauche and trans conformers of succinonitrile are found to chemisorb on the metal surface. The doubly degenerate nu(C-triple bond-N) in the free molecules is removed when succinonitrile adsorbs on copper, which indicates that the two (C-triple bond-N) groups are no longer chemically equivalent. Both conformers are found to coordinate to the copper surface through the pi system of one of the two (C-triple bond-N) groups. In the case of N-methyl-thioacetamide, the population of the cis isomer is greatly increased on Cu and Ag surfaces. This is probably due to surface-induced cis-trans isomerization, in which the predominant trans isomer is converted to the cis isomer.

  15. Simple Nuclear Structure in Cd-129111 from Atomic Isomer Shifts

    NASA Astrophysics Data System (ADS)

    Yordanov, D. T.; Balabanski, D. L.; Bissell, M. L.; Blaum, K.; Budinčević, I.; Cheal, B.; Flanagan, K.; Frömmgen, N.; Georgiev, G.; Geppert, Ch.; Hammen, M.; Kowalska, M.; Kreim, K.; Krieger, A.; Meng, J.; Neugart, R.; Neyens, G.; Nörtershäuser, W.; Rajabali, M. M.; Papuga, J.; Schmidt, S.; Zhao, P. W.

    2016-01-01

    Isomer shifts have been determined in 111-129>Cd by high-resolution laser spectroscopy at CERN-ISOLDE. The corresponding mean square charge-radii changes, from the 1 /2+ and the 3 /2+ ground states to the 11 /2- isomers, have been found to follow a distinct parabolic dependence as a function of the atomic mass number. Since the isomers have been previously associated with simplicity due to the linear mass dependence of their quadrupole moments, the regularity of the isomer shifts suggests a higher order of symmetry affecting the ground states in addition. A comprehensive description assuming nuclear deformation is found to accurately reproduce the radii differences in conjunction with the known quadrupole moments. This intuitive interpretation is supported by covariant density functional theory.

  16. 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.

  17. Nonperipheral Tetrakis(dibutylamino)phthalocyanines. New Types of 1,8,15,22-Tetrakis(substituted)phthalocyanine Isomers.

    PubMed

    Chen, Yuxiang; Fang, Wenjuan; Wang, Kang; Liu, Wei; Jiang, Jianzhuang

    2016-09-19

    Cyclic tetramerization of 3-(dibutylamino)phthalonitrile in refluxing n-pentanol in the presence of magnesium pentanoate afforded the four regioisomer-containing nonperipheral 1,8-/11,15-/18,22-/25-tetrakis(dibutylamino)phthalocyaninato magnesium complexes with the 1,8,15,22-tetrakis(dibutylamino)phthalocyanine isomer Mg{Pc[α-N(C4H9)2]4-C4} (2). This, in combination with its much superior crystallinity over the remaining three isomers, renders the easy isolation of 2 only through two simple recrystallizations from THF and methanol. Treatment of 2 with trifluoroacetic acid induced the isolation of metal-free 1,8,15,22-tetrakis(dibutylamino)phthalocyanine, H2{Pc[α-N(C4H9)2]4-C4} (1), which further reacted with M(OAc)2·nH2O (M = Ni, Zn) in refluxing n-pentanol, giving the 1,8,15,22-tetrakis(dibutylamino)phthalocyaninato metal complexes M{Pc[α-N(C4H9)2]4-C4} (M = Ni (3), Zn (4)). The full series of four 1,8,15,22-tetrakis(dibutylamino)phthalocyanine isomeric compounds have been characterized by a series of spectroscopic methods and single-crystal X-ray diffraction analyses. Obviously, the present result provides a simple and effective pathway for the synthesis and isolation of novel 1,8,15,22-tetrakis(dibutylamino)phthalocyanine isomeric derivatives, providing one step forward toward completing bis(alkyl)amino-incorporated phthalocyanine species.

  18. Nonperipheral Tetrakis(dibutylamino)phthalocyanines. New Types of 1,8,15,22-Tetrakis(substituted)phthalocyanine Isomers.

    PubMed

    Chen, Yuxiang; Fang, Wenjuan; Wang, Kang; Liu, Wei; Jiang, Jianzhuang

    2016-09-19

    Cyclic tetramerization of 3-(dibutylamino)phthalonitrile in refluxing n-pentanol in the presence of magnesium pentanoate afforded the four regioisomer-containing nonperipheral 1,8-/11,15-/18,22-/25-tetrakis(dibutylamino)phthalocyaninato magnesium complexes with the 1,8,15,22-tetrakis(dibutylamino)phthalocyanine isomer Mg{Pc[α-N(C4H9)2]4-C4} (2). This, in combination with its much superior crystallinity over the remaining three isomers, renders the easy isolation of 2 only through two simple recrystallizations from THF and methanol. Treatment of 2 with trifluoroacetic acid induced the isolation of metal-free 1,8,15,22-tetrakis(dibutylamino)phthalocyanine, H2{Pc[α-N(C4H9)2]4-C4} (1), which further reacted with M(OAc)2·nH2O (M = Ni, Zn) in refluxing n-pentanol, giving the 1,8,15,22-tetrakis(dibutylamino)phthalocyaninato metal complexes M{Pc[α-N(C4H9)2]4-C4} (M = Ni (3), Zn (4)). The full series of four 1,8,15,22-tetrakis(dibutylamino)phthalocyanine isomeric compounds have been characterized by a series of spectroscopic methods and single-crystal X-ray diffraction analyses. Obviously, the present result provides a simple and effective pathway for the synthesis and isolation of novel 1,8,15,22-tetrakis(dibutylamino)phthalocyanine isomeric derivatives, providing one step forward toward completing bis(alkyl)amino-incorporated phthalocyanine species. PMID:27580413

  19. Rapid survey of four Asp isomers in disease-related proteins by LC-MS combined with commercial enzymes.

    PubMed

    Maeda, Hiroki; Takata, Takumi; Fujii, Norihiko; Sakaue, Hiroaki; Nirasawa, Satoru; Takahashi, Saori; Sasaki, Hiroshi; Fujii, Noriko

    2015-01-01

    Until relatively recently, it was considered that D-amino acids were excluded from living systems except for the cell wall of microorganisms. However, D-aspartate residues have now been detected in long-lived proteins from various tissues of elderly humans. Formation of D-aspartate in proteins induces aggregation and loss of function, leading to age-related disorders such as cataracts and Alzheimer disease. A recent study used LC-MS to analyze isomers of Asp residues in proteins precisely without complex purification of the proteins. However, to identify the four Asp isomers (Lα, Lβ, Dβ, and Dα) on the chromatogram, it was necessary to synthesize reference peptides containing the four different Asp isomers as standards. Here, we describe a method for rapidly and comprehensively identifying Asp isomers in proteins using a combination of LC-MS and commercial enzymes without synthesizing reference peptides. The protein sample is treated with trypsin, trypsin plus Asp-N, trypsin plus PIMT, trypsin plus paenidase, and the resulting peptides are applied to LC-MS. Because Asp-N hydrolyzes peptide bonds on the N-terminus of only Lα-Asp residues, it differentiates peptides containing Lα-Asp from those containing the other three isomers. Similarly, PIMT recognizes only peptides containing Lβ-Asp residues, and paenidase internally cleaves the C-terminus of Dα-Asp residues. This approach was successfully applied to the analysis of all tryptic peptides in aged lens. The comprehensive quantitative data of Asp isomer formation in age-related proteins obtained via this method might be used as biomarkers of age-related disease.

  20. Synthesis of dibenzylamino-1-methylcyclohexanol and dibenzylamino-1-trifluoromethylcyclohexanol isomers.

    PubMed

    Jones, D Heulyn; Bresciani, Stefano; Tellam, James P; Wojno, Justyna; Cooper, Anthony W J; Kennedy, Alan R; Tomkinson, Nicholas C O

    2016-01-01

    The isomers of dibenzylamino-1-methylcyclohexan-1-ol and dibenzylamino-1-trifluoromethylcyclohexan-1-ol have been prepared. The stereochemistry of these compounds was unequivocally assigned through a combination of NMR spectroscopy and single crystal X-ray analysis. The cis-isomer of 3-N,N-dibenzylamino-1-trifluoromethylcyclohexanol and its derivatives display an unusual conformational behaviour in both solution-phase and the solid-state, where the amino group usually adopts an axial conformation. PMID:26468867

  1. 21 CFR 184.1061 - Lactic acid.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Lactic acid. 184.1061 Section 184.1061 Food and... Substances Affirmed as GRAS § 184.1061 Lactic acid. (a) Lactic acid (C3H6O3, CAS Reg. Nos.: dl mixture, 598-82-3; l-isomer, 79-33-4; d-isomer, 10326-41-7), the chemical 2-hydroxypropanoic acid,...

  2. 21 CFR 184.1061 - Lactic acid.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Lactic acid. 184.1061 Section 184.1061 Food and... Substances Affirmed as GRAS § 184.1061 Lactic acid. (a) Lactic acid (C3H6O3, CAS Reg. Nos.: dl mixture, 598-82-3; l-isomer, 79-33-4; d-isomer, 10326-41-7), the chemical 2-hydroxypropanoic acid,...

  3. 21 CFR 184.1061 - Lactic acid.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Lactic acid. 184.1061 Section 184.1061 Food and... Substances Affirmed as GRAS § 184.1061 Lactic acid. (a) Lactic acid (C3H6O3, CAS Reg. Nos.: dl mixture, 598-82-3; l-isomer, 79-33-4; d-isomer, 10326-41-7), the chemical 2-hydroxypropanoic acid,...

  4. 21 CFR 184.1061 - Lactic acid.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Lactic acid. 184.1061 Section 184.1061 Food and... Substances Affirmed as GRAS § 184.1061 Lactic acid. (a) Lactic acid (C3H6O3, CAS Reg. Nos.: dl mixture, 598-82-3; l-isomer, 79-33-4; d-isomer, 10326-41-7), the chemical 2-hydroxypropanoic acid,...

  5. Changes in Dehydrodiferulic Acids and Peroxidase Activity against Ferulic Acid Associated with Cell Walls during Growth of Pinus pinaster Hypocotyl.

    PubMed Central

    Sanchez, M.; Pena, M. J.; Revilla, G.; Zarra, I.

    1996-01-01

    Hydroxycinnamic acids associated with hypocotyl cell walls of dark-grown seedlings of Pinus pinaster Aiton were extracted with 1 N NaOH and identified by gas chromatography-mass spectrometry. The main hydroxycinnamic acid found was ferulic acid. Diferulic acid dehydrodimers were also found, with the 8,8-coupled isomer (compound 11) being the dehydrodiferulate present in the highest amount. However, the 5,5-coupled isomer, commonly referred to referred to as diferulic acid, was not detected. Two truxillic acids, 4-4[prime]-dihydroxy-3-3[prime]-dimethoxy-[alpha]-truxillic acids I and II, were tentatively identified. The 8,8-coupled dehydrodiferulic acid (compound 11) was the phenolic acid that showed the most conspicuous changes with hypocotyl age as well as along the hypocotyl axis. Peroxidase activity against ferulic acid was found in the apoplastic fluid as well as being ionically and covalently bound to the cell walls. The peroxidase activity increased with hypocotyl age as well as from the subapical toward the basal region of the hypocotyls. A key role in the cell-wall stiffening of 8,8 but not 5,5 dimerization of ferulic acid catalyzed by cell-wall peroxidases is proposed. PMID:12226339

  6. Measurements of single nucleotide electronic states as nanoelectronic fingerprints for identification of DNA nucleobases, their protonated and unprotonated states, isomers, and tautomers.

    PubMed

    Ribot, Josep Casamada; Chatterjee, Anushree; Nagpal, Prashant

    2015-04-16

    Several nanoelectronic techniques have been explored to distinguish the sequence of nucleic acids in DNA macromolecules. Identification of unique electronic signatures using nanopore conductance, tunneling spectroscopy, or other nanoelectronic techniques depends on electronic states of the DNA nucleotides. While several experimental and computational studies have focused on interaction of nucleobases with different substrates, the effect of nucleic acid biochemistry on its electronic properties has been largely unexplored. Here, we present correlated measurements of frontier molecular orbitals and higher-order electronic states for four DNA nucleobases (adenine, cytosine, thymine, and guanine), and first-principle quantum chemical density functional theoretical (DFT) computations. Using different pH conditions in our experiments, we show that small changes in the biochemical state of these nucleic acids strongly affect the intrinsic electronic structure, measured using scanning tunneling spectroscopy (STS). In our experimental measurements and computations, significant differences were observed between the position of frontier orbitals and higher-energy states between protonated and unprotonated nucleic acids, isomers, and different keto-enol tautomer's formed in these nucleotides, leading to their facile identification. Furthermore, we show unique "electronic fingerprints" for all nucleotides (A, G, T, C) using STS, with most distinct states identified at acidic pH. These results can have important implications for identification of nucleic acid sequences in DNA molecules using a high-throughput nanoelectronic identification technique.

  7. Theoretical investigation of C56 fullerene isomers and related compounds

    NASA Astrophysics Data System (ADS)

    Chen, De-Li; Tian, Wei Quan; Feng, Ji-Kang; Sun, Chia-Chung

    2008-01-01

    All the 924 classical isomers of fullerene C56 have been investigated by PM3, and some most stable isomers are refined with HCTH/3-21G and B3LYP /6-31G(d) methods. D2:003 with the least number of adjacent pentagons is predicted to be the most stable isomer at B3LYP /6-31G(d) level, while Cs:022 and C2:049 possess nearly degenerate energies with relative energies of 0.03 and 3.90kcal/mol, respectively. However, as to dianionic C562- fullerene, C2v:011 is predicted to be the most stable isomer. Investigations also show that the encapsulation of Ca atom in C56 fullerene is exothermic and the metallofullerenes Ca@C56 can be described as Ca2+@C562-. The computed relative stabilities show that the D2:003 behaves more thermodynamically stable than other isomers in a wide temperature interval, and C2v:011 should also be an important component. The electronic isomerization of C56 (C2v:011) and C50 (D5h:002) indicates that this phenomenon might be rather general in fullerenes and causes different properties, thus bringing about new possible applications of fullerenes. The static second-order hyperpolarizabilities of the three most stable isomers are slightly larger than that of C60.

  8. Site-specific protein glycosylation analysis with glycan isomer differentiation.

    PubMed

    Hua, Serenus; Nwosu, Charles C; Strum, John S; Seipert, Richard R; An, Hyun Joo; Zivkovic, Angela M; German, J Bruce; Lebrilla, Carlito B

    2012-05-01

    Glycosylation is one of the most common yet diverse post-translational modifications. Information on glycan heterogeneity and glycosite occupancy is increasingly recognized as crucial to understanding glycoprotein structure and function. Yet, no approach currently exists with which to holistically consider both the proteomic and glycomic aspects of a system. Here, we developed a novel method of comprehensive glycosite profiling using nanoflow liquid chromatography/mass spectrometry (nano-LC/MS) that shows glycan isomer-specific differentiation on specific sites. Glycoproteins were digested by controlled non-specific proteolysis in order to produce informative glycopeptides. High-resolution, isomer-sensitive chromatographic separation of the glycopeptides was achieved using microfluidic chip-based capillaries packed with graphitized carbon. Integrated LC/MS/MS not only confirmed glycopeptide composition but also differentiated glycan and peptide isomers and yielded structural information on both the glycan and peptide moieties. Our analysis identified at least 13 distinct glycans (including isomers) corresponding to five compositions at the single N-glycosylation site on bovine ribonuclease B, 59 distinct glycans at five N-glycosylation sites on bovine lactoferrin, 13 distinct glycans at one N-glycosylation site on four subclasses of human immunoglobulin G, and 20 distinct glycans at five O-glycosylation sites on bovine κ-casein. Porous graphitized carbon provided effective separation of glycopeptide isomers. The integration of nano-LC with MS and MS/MS of non-specifically cleaved glycopeptides allows quantitative, isomer-sensitive, and site-specific glycoprotein analysis.

  9. Isomer Research: Energy Release Validation, Production, and Applications

    SciTech Connect

    Becker, J A; Rundberg, B

    2003-04-10

    The goal of this applied nuclear isomer research program is the search for, discovery of, and practical application of a new type of high energy density material (HEDM). Nuclear isomers could yield an energy source with a specific energy as much as a hundred thousand times as great as that of chemical fuels. There would be enormous payoffs to the Department of Energy and to the country as a whole if such energy sources could be identified and applied to a range of civilian and defense applications. Despite the potential payoff, efforts in applied isomer research have been rather limited and sporadic. Basic research on nuclear isomers dates back to their discovery in 1935 with occasional hints to tantalize interest in HEDM. In most cases, these hints were refuted following careful examination by other groups. The isomer research area is rich with possibilities: we prioritized several areas likely to be the most rewarding and fruitful for initial experimental investigation because these areas directly bear on important issues: Can the energy stored in nuclear isomers be released on demand? Is the size of the atomic-nuclear mixing matrix element large enough to be useful? Under what circumstances? Can we initiate quantal collective release of isomeric energy from a Moessbauer crystal?

  10. Unraveling the origin of the relative stabilities of group 14 M2N2(2+) (M, N = C, Si, Ge, Sn, and Pb) isomer clusters.

    PubMed

    Díaz-Cervantes, Erik; Poater, Jordi; Robles, Juvencio; Swart, Marcel; Solà, Miquel

    2013-10-10

    We analyze the molecular structure, relative stability, and aromaticity of the lowest-lying isomers of group 14 M2N2(2+) (M and N = C, Si, and Ge) clusters. We use the gradient embedded genetic algorithm to make an exhaustive search for all possible isomers. Group 14 M2N2(2+) clusters are isoelectronic with the previously studied group 13 M2N2(2-) (M and N = B, Al, and Ga) clusters that includes Al4(2-), the archetypal all-metal aromatic molecule. In the two groups of clusters, the cyclic isomers present both σ- and π-aromaticity. However, at variance with group 13 M2N2(2-) clusters, the linear isomer of group 14 M2N2(2+) is the most stable for two of the clusters (C2Si2(2+) and C2Ge2(2+)) , and it is isoenergetic with the cyclic D(4h) isomer in the case of C4(2+). Energy decomposition analyses of the lowest-lying isomers and the calculated magnetic- and electronic-based aromaticity criteria of the cyclic isomers help to understand the nature of the bonding and the origin of the stability of the global minima. Finally, for completeness, we have also analyzed the structure and stability of the heavier Sn and Pb group 14 M2N2(2+) analogues.

  11. 241Am (n,gamma) isomer ratio measurement

    SciTech Connect

    Bond, Evelyn M; Vieira, David J; Moody, Walter A; Slemmons, Alice K

    2011-01-05

    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 the {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 time

  12. Tautomeric conversion, vibrational spectra, and density functional studies on peripheral sulfur derivatives of benzothiazole and benzothiazoline isomers

    NASA Astrophysics Data System (ADS)

    Altun, Ahmet; Kuliyev, Eziz; Aghatabay, Naz M.

    2016-01-01

    The room temperature structural (tautomerism, dimerization, conformational preference, geometry parameters) and vibrational spectral (IR and Raman) analyses have been performed on benzothiazoline (benzothiazoline-2-thione, 3-methyl-benzothiazoline-2-thione) and benzothiazole [2-mercaptobenzothiazole, 2-methylthiobenzothiazole, and bis(benzothiazole-2-ylthio)ethane] derivatives at the B3LYP/6-311++G∗∗ level of theory. Although the keto to enol transition barriers are too high over the most stable benzothiazoline isomers, vibrational spectral analyses reveal some major bands of benzothiazole isomers in the present room temperature experimental FT-IR and FT-Raman specta. Therefore, benzothiazole isomers exist at rare amounts in the powdered samples that are mainly composed of benzothiazoline isomers. The benzothiazole isomers have two stable conformations due to the orientation of their SH and SCH3 moieties. The energetic and vibrational spectral analyses suggest that the benzothiazoline-2-thione molecules can be stabilized further through the NH⋯S intermolecular hydrogen bonds in solid phase. All observed fundamental vibrational bands of the molecules have been assigned based on the calculated mode frequencies and IR/Raman intensities. The mode assignments have been expressed in terms of internal coordinates and their percent potential energy distributions. The effects of substitution at the nitrogen and peripheral sulfur atoms have been analyzed for the geometries and vibrational bands of the molecules.

  13. Up- and down-regulation of beta-adrenoreceptors in rat cerebral cortex following exposure to isomers of hexachlorocyclohexane

    SciTech Connect

    Stark, L.; Hollinger, M.; Joy, R.

    1986-03-01

    The authors have shown that the gamma (lindane) and beta isomers of hexachlorocyclohexane (HCH) have opposite effects on the kindling model of epilepsy (gamma facilitates, beta retards kindling acquisition). In the present study the authors determined the effects of these two isomers on ..beta..-adrenoreceptors in rat brain using /sup 3/H-dihydroalprenolol as the ligand following 10 days treatment with 10 mg/kg p.o. of isomers or corn oil. Results showed a statistically significant decrease in the number of ..beta..-adrenoreceptors in cortical tissue taken from lindane treated rats. In contrast, there was a significant increase in the number of ..beta..-adreno receptors in cortical tissue taken from beta-HCH treated rats. Neither treatment caused a significant change in Kd. It is concluded that the ..beta..-adrenoreceptor system in rat brain is differentially affected by the isomers of HCH. Since the kindling model of epilepsy is sensitive to modulation in adrenergic function, this system may be involved in the pro- and anticonvulsant effects of these HCH isomers on kindling acquisition.

  14. Ion-neutral collisional cross sections of carbohydrate isomers as divalent cation adducts and their electron transfer products.

    PubMed

    Huang, Yuting; Dodds, Eric D

    2015-10-21

    As the gravity of glycoscience continues to amass, a commensurate demand for rapid, sensitive, and structurally comprehensive glycoanalytical tools has arisen. Among the most elusive but desirable analytical capabilities is the ability to expeditiously and unambiguously detect, distinguish, and resolve carbohydrates that differ only in their constitutional isomerism and/or stereoisomerism. While ion mobility spectrometry (IMS) has proven a highly promising tool for such analyses, the facility of this method to discriminate larger oligosaccharides is still somewhat limited. In an effort to expand the capabilities of IMS to discriminate among carbohydrate isomers, the present investigation was focused on IMS studies of four trisaccharide isomers, four pentasaccharide isomers, and two hexasaccharide isomers, each as group II metal ion adducts and their corresponding gas-phase electron transfer (ET) products. These studies were also evaluated in the context of previously investigated group I metal ion adducts of the same saccharides. The orientationally averaged ion-neutral collisional cross sections (CCSs) of the various carbohydrate/metal ion adducts were found to be dependent on the structures of specific carbohydrate isomers, sensitive to the electronic characteristics of the bound cation, and responsive to the attachment of an additional electron (in the case of divalent metal ion adducts). Overall, these results underscore the utility of metal ions for probing carbohydrate structure in concert with IMS, and the capacity of gas-phase ion chemistry to expand the menu of such probes.

  15. Ion-neutral collisional cross sections of carbohydrate isomers as divalent cation adducts and their electron transfer products.

    PubMed

    Huang, Yuting; Dodds, Eric D

    2015-10-21

    As the gravity of glycoscience continues to amass, a commensurate demand for rapid, sensitive, and structurally comprehensive glycoanalytical tools has arisen. Among the most elusive but desirable analytical capabilities is the ability to expeditiously and unambiguously detect, distinguish, and resolve carbohydrates that differ only in their constitutional isomerism and/or stereoisomerism. While ion mobility spectrometry (IMS) has proven a highly promising tool for such analyses, the facility of this method to discriminate larger oligosaccharides is still somewhat limited. In an effort to expand the capabilities of IMS to discriminate among carbohydrate isomers, the present investigation was focused on IMS studies of four trisaccharide isomers, four pentasaccharide isomers, and two hexasaccharide isomers, each as group II metal ion adducts and their corresponding gas-phase electron transfer (ET) products. These studies were also evaluated in the context of previously investigated group I metal ion adducts of the same saccharides. The orientationally averaged ion-neutral collisional cross sections (CCSs) of the various carbohydrate/metal ion adducts were found to be dependent on the structures of specific carbohydrate isomers, sensitive to the electronic characteristics of the bound cation, and responsive to the attachment of an additional electron (in the case of divalent metal ion adducts). Overall, these results underscore the utility of metal ions for probing carbohydrate structure in concert with IMS, and the capacity of gas-phase ion chemistry to expand the menu of such probes. PMID:26225371

  16. High-K isomers in {sup 176}W and mechanisms of K-violation

    SciTech Connect

    Crowell, B.; Janssens, R.V.F.; Blumenthal, D.J.

    1995-08-01

    K-isomers are states in deformed nuclei whose {gamma}-decay is hindered by selection rules involving K, the projection of the angular momentum along the axis of symmetry of the nucleus. Previous work with the Argonne Notre Dame BGO Array delineated the existence of two K-isomers in {sup 176}W, one of which had a very unusual pattern of decay. A short description of this work was published as a letter, and a more complete account is being readied for submission. These results provided evidence that quantum-mechanical fluctuations in the nuclear shape may be responsible for some of the observed K-violating transitions. In addition, hints were present in the data of the existence of another K-isomer with an even higher in. An experiment was performed in September 1994 to observe this isomer, using the reaction {sup 50}Ti({sup 130}Te,4n), and a technique in which recoiling {sup 176}W nuclei were created 17-cm upstream of the center of the array and caught on a Pb catcher foil at the center. Intense ({approximately} 3 pnA) beams of {sup 130}Te were supplied by the ECR source using a new sputtering technique. The recoil-shadow geometry was highly successful at removing the background from non-isomeric decays, allowing the weakly populated K-isomers to be detected cleanly. In addition, the availability of pulsed beams from ATLAS and the timing data from the BGO array provided a second technique for isolating the decays of interest, by selecting events in which a given number of BGO detectors fired between beam pulses. This method was used in the previous experiment, and was also applied in this experiment as a second level of selection. As a result, gamma-ray transitions were detected in the present experiment with intensities as small as {approximately} 0.02 % of the {sup 176}W reaction channel. The existence of the new isomer was confirmed, and a partial level-scheme was constructed.

  17. PARTICLE-HOLE NATURE OF THE LIGHT HIGH-SPIN TOROIDAL ISOMERS

    SciTech Connect

    Staszczak, A.; Wong, Cheuk-Yin

    2015-01-01

    Nuclei under non-collective rotation with a large angular momentum above some threshold can assume a toroidal shape. In our previous work, we showed by using cranked Skyrme Hartree Fock approach that even even, N = Z, high-K, toroidal isomeric states may have general occurrences for light nuclei with 28 < A < 52. We present here some additional results and systematics on the particle-hole nature of these high-spin toroidal isomers.

  18. Frequency Patterns of T-Cell Exposed Amino Acid Motifs in Immunoglobulin Heavy Chain Peptides Presented by MHCs

    PubMed Central

    Bremel, Robert D.; Homan, E. Jane

    2014-01-01

    Immunoglobulins are highly diverse protein sequences that are processed and presented to T-cells by B-cells and other antigen presenting cells. We examined a large dataset of immunoglobulin heavy chain variable regions (IGHV) to assess the diversity of T-cell exposed motifs (TCEMs). TCEM comprise those amino acids in a MHC-bound peptide, which face outwards, surrounded by the MHC histotope, and which engage the T-cell receptor. Within IGHV there is a distinct pattern of predicted MHC class II binding and a very high frequency of re-use of the TCEMs. The re-use frequency indicates that only a limited number of different cognate T-cells are required to engage many different clonal B-cells. The amino acids in each outward-facing TCEM are intercalated with the amino acids of inward-facing MHC groove-exposed motifs (GEM). Different GEM may have differing, allele-specific, MHC binding affinities. The intercalation of TCEM and GEM in a peptide allows for a vast combinatorial repertoire of epitopes, each eliciting a different response. Outcome of T-cell receptor binding is determined by overall signal strength, which is a function of the number of responding T-cells and the duration of engagement. Hence, the frequency of TCEM re-use appears to be an important determinant of whether a T-cell response is stimulatory or suppressive. The frequency distribution of TCEMs implies that somatic hypermutation is followed by T-cell clonal expansion that develops along repeated pathways. The observations of TCEM and GEM derived from immunoglobulins suggest a relatively simple, yet powerful, mechanism to correlate T-cell polyspecificity, through re-use of TCEMs, with a very high degree of specificity achieved by combination with a diversity of GEMs. The frequency profile of TCEMs also points to an economical mechanism for maintaining T-cell memory, recall, and self-discrimination based on an endogenously generated profile of motifs. PMID:25389426

  19. 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

  20. Cytochromes P450 catalyze both steps of the major pathway of clopidogrel bioactivation, whereas paraoxonase catalyzes the formation of a minor thiol metabolite isomer.

    PubMed

    Dansette, Patrick M; Rosi, Julien; Bertho, Gildas; Mansuy, Daniel

    2012-02-20

    The mechanism generally admitted for the bioactivation of the antithrombotic prodrug, clopidogrel, is its two-step enzymatic conversion into a biologically active thiol metabolite. The first step is a classical cytochrome P450 (P450)-dependent monooxygenation of its thiophene ring leading to 2-oxo-clopidogrel, a thiolactone metabolite. The second step was described as a P450-dependent oxidative opening of the thiolactone ring of 2-oxo-clopidogrel, with intermediate formation of a reactive sulfenic acid metabolite that is eventually reduced to the corresponding thiol 4b. A very recent paper published in Nat. Med. (Bouman et al., (2011) 17, 110) reported that the second step of clopidogrel bioactivation was not catalyzed by P450 enzymes but by paraoxonase-1(PON-1) and that PON-1 was a major determinant of clopidogrel efficacy. The results described in the present article show that there are two metabolic pathways for the opening of the thiolactone ring of 2-oxo-clopidogrel. The major one, that was previously described, results from a P450-dependent redox bioactivation of 2-oxo-clopidogrel and leads to 4b cis, two previously reported thiol diastereomers bearing an exocyclic double bond. The second, minor one, results from a hydrolysis of 2-oxo-clopidogrel, which seems to be dependent on PON-1, and leads to an isomer of 4b cis, 4b "endo", in which the double bond has migrated from an exocyclic to an endocyclic position in the piperidine ring. These results were obtained from a detailed study of the metabolism of 2-oxo-clopidogrel by human liver microsomes and human sera and analysis by HPLC-MS under conditions allowing a complete separation of the thiol metabolite isomers, either as such or after derivatization with 3'-methoxy phenacyl bromide or N-ethyl maleimide (NEM). These results also show that the major bioactive thiol isomer found in the plasma of clopidogrel-treated patients derives from 2-oxo-clopidogrel by the P450-dependent pathway. Finally, chemical

  1. Ab initio molecular orbital studies of low-energy, metastable isomers of the ubiquitous cyclopropenylidene. [in interstellar space

    NASA Technical Reports Server (NTRS)

    Defrees, D. J.; Mclean, A. D.

    1986-01-01

    The discovery of cyclopropenylidene in space suggests that other C3H2 isomers may be present, and a tentative detection of one such isomer, propargylene (HCCCH), has been reported. Ab initio molecular orbital theory has been used to characterize five low-lying, metastable isomers of cyclopropenylidene. Extended calculations including the electron correlation energy, show that the lowest in energy is singlet propadienylidene, followed by propargylene; the singlet and triplet of the latter are too close in energy to allow an assignment of the ground state; triplet propadienylidene is at a significantly higher energy. Rotational frequencies computed to an expected accuracy of + or - 1 -2 percent do not confirm the tentative detection of propargylene in space, although the discrepancy between theory and the observation is not so great as to unequivocally rule out this possibility.

  2. High-K isomers in transactinide nuclei close to N = 162

    SciTech Connect

    Prassa, V. Nikšić, T.; Vretenar, D.; Lu, Bing-Nan; Ackermann, D.

    2015-10-15

    Transactinide nuclei around neutron number N = 162 display axially deformed equilibrium shapes, as shown in our previous analysis [1] of constrained mean-field energy surfaces and collective excitation spectra. In the present study we are particularly interested in the occurrence of high-K isomers in the axially deformed isotopes of Rf (Z = 104), Sg (Z = 106), Hs (Z = 108), and Ds (Z = 110), with neutron number N = 160 − 166 and the effect of the N=162 closure on the structure and distribution of two-quasiparticle (2qp) states. The evolution of high-K isomers is analysed in a self-consistent axially-symmetric relativistic Hartree-Bogoliubov calculation using the blocking approximation with time-reversal symmetry breaking.

  3. Identification of an {alpha}-decaying (9{sup -}) isomer in {sup 216}Fr

    SciTech Connect

    Kurcewicz, J.; Karny, M.; Korgul, A.; Kurcewicz, W.; Kurpeta, J.; Lewandowski, S.; Majorkiewicz, P.; Plochocki, A.; Wojtasiewicz, A.; Czarnacki, W.; Kasztelan, M.; Kisielinski, M.; Penttilae, H.; Roussiere, B.; Steczkiewicz, O.

    2007-11-15

    The {alpha} decay of the trans-lead isotopes {sup 212}At, {sup 216}Fr, and {sup 220}Ac was investigated by using mass-separated sources and analog as well as digital signal processing. By measuring {alpha}-{alpha} time correlations evidence was obtained for the occurrence of an {alpha}-decaying (9{sup -}) isomer in {sup 216}Fr. The {alpha}-decay energy and half-life amount to 9000(5) keV and 850(30) ns, respectively. The excitation energy of the isomer is compared with shell-model predictions for the high-spin members of the {pi}(h{sub 9/2}){nu}(g{sub 9/2}) multiplet, and the relevance of the new data concerning the search for reflection asymmetry is presented.

  4. Quantitative analysis of positional isomers of triacylglycerols via electrospray ionization tandem mass spectrometry of sodiated adducts.

    PubMed

    Herrera, Lisandra Cubero; Potvin, Michael A; Melanson, Jeremy E

    2010-09-01

    Herein we report a reversed-phase high-performance liquid chromatography tandem mass spectrometry (RP-HPLC/MS/MS) method for the analysis of positional isomers of triacylglycerols (TAGs) in vegetable oils. The fragmentation behavior of [M + X](+) ions (X = NH(4), Li, Na or Ag) was studied on a quadrupole-time-of-flight (Q-TOF) mass spectrometer under low-energy collision-induced dissociation (CID) conditions. Mass spectra that were dependent on the X(+) ion and the nature and position of the acyl substituents were observed for four pairs of 'AAB/ABA'-type TAGs, namely PPO/POP, OOP/OPO, LLO/LOL and OOL/OLO (where P is 16:0, palmitic acid; O is 18:1, oleic acid; and L is 18:2, linoleic acid). For the majority of [M + X](+) adducts, the loss of the fatty acid in the outer positions (sn-1 or sn-3) was favored over the loss in the central position (sn-2), which enabled the determination of the fractional abundance of the isomers. Ratios of the intensity of fragment ions at various AAB/ABA compositions produced linear calibration curves with positive slopes, comparable to those obtained traditionally by ESI-MS/MS of [M + NH(4)](+) adducts. The only exceptions were the [M + Ag](+) adducts of the PPO/POP system, which produced calibration curves with negative slopes. Sodium adducts provided the most consistent level of isomeric discrimination for the TAGs studied and also offered the most convenience in that they required no additive to the mobile phase. Therefore, calibration curve data derived from [M + Na](+) adducts were applied to the quantification of TAG regioisomers in sunflower and olive oils. The regiospecific analysis showed that palmitic acid was typically located at positions sn-1 or sn-3, whereas unsaturated fatty acids, oleic and linoleic acids were mostly found at the sn-2 position. PMID:20814981

  5. Unstable Isomer of C90 Fullerene Isolated as Chloro Derivatives, C90 (1)Cl10/12.

    PubMed

    Chilingarov, Norbert S; Troyanov, Sergey I

    2016-07-01

    High-temperature chlorination of C90 -containing fullerene fraction resulted in the isolation and X-ray structural characterization of C90 (1)Cl10/12 , the first derivatives of a relatively unstable isomer D5h -C90 (1) with a nanotubular shape. In the crystal structure, three isomers of both C90 (1)Cl10 and C90 (1)Cl12 with similar chlorination patterns co-crystallize in the same crystallographic site. Thus, in contrast to the previous reports, D5h -C90 (1) is present, though with a low abundance, in the fullerene soot produced by arc-discharge method with undoped graphite rods. PMID:27311795

  6. (1) H NMR analysis of O-methyl-inositol isomers: a joint experimental and theoretical study.

    PubMed

    De Almeida, Mauro V; Couri, Mara Rubia C; De Assis, João Vitor; Anconi, Cleber P A; Dos Santos, Hélio F; De Almeida, Wagner B

    2012-09-01

    Density functional theory (DFT) calculations of (1) H NMR chemical shifts for l-quebrachitol isomers were performed using the B3LYP functional employing the 6-31G(d,p) and 6-311 + G(2d,p) basis sets. The effect of the solvent on the B3LYP-calculated NMR spectrum was accounted for using the polarizable continuum model. Comparison is made with experimental (1) H NMR spectroscopic data, which shed light on the average uncertainty present in DFT calculations of chemical shifts and showed that the best match between experimental and theoretical B3LYP (1) H NMR profiles is a good strategy to assign the molecular structure present in the sample handled in the experimental measurements. Among four plausible O-methyl-inositol isomers, the l-quebrachitol 2a structure was unambiguously assigned based only on the comparative analysis of experimental and theoretical (1) H NMR chemical shift data. The B3LYP infrared (IR) spectrum was also calculated for the four isomers and compared with the experimental data, with analysis of the theoretical IR profiles corroborating assignment of the 2a structure. Therefore, it is confirmed in this study that a combined experimental/DFT spectroscopic investigation is a powerful tool in structural/conformational analysis studies. PMID:22865668

  7. (1) H NMR analysis of O-methyl-inositol isomers: a joint experimental and theoretical study.

    PubMed

    De Almeida, Mauro V; Couri, Mara Rubia C; De Assis, João Vitor; Anconi, Cleber P A; Dos Santos, Hélio F; De Almeida, Wagner B

    2012-09-01

    Density functional theory (DFT) calculations of (1) H NMR chemical shifts for l-quebrachitol isomers were performed using the B3LYP functional employing the 6-31G(d,p) and 6-311 + G(2d,p) basis sets. The effect of the solvent on the B3LYP-calculated NMR spectrum was accounted for using the polarizable continuum model. Comparison is made with experimental (1) H NMR spectroscopic data, which shed light on the average uncertainty present in DFT calculations of chemical shifts and showed that the best match between experimental and theoretical B3LYP (1) H NMR profiles is a good strategy to assign the molecular structure present in the sample handled in the experimental measurements. Among four plausible O-methyl-inositol isomers, the l-quebrachitol 2a structure was unambiguously assigned based only on the comparative analysis of experimental and theoretical (1) H NMR chemical shift data. The B3LYP infrared (IR) spectrum was also calculated for the four isomers and compared with the experimental data, with analysis of the theoretical IR profiles corroborating assignment of the 2a structure. Therefore, it is confirmed in this study that a combined experimental/DFT spectroscopic investigation is a powerful tool in structural/conformational analysis studies.

  8. Quantification of Structural Isomers via Mode-Selective Irmpd

    NASA Astrophysics Data System (ADS)

    Polfer, Nicolas C.

    2016-06-01

    Mixtures of structural isomers can pose a challenge for vibrational ion spectroscopy. In cases where particular structures display diagnostic vibrations, these structures can be selectively "burned away". In ion traps, the ion population can be subjected to multiple laser shots, in order to fully deplete a particular structure, in effect allowing a quantification of this structure. Protonated para-amino benzoic acid (PABA) serves as an illustrative example. PABA is known to preferentially exist in the N-protonated (N-prot) form in solution, but in the gas phase it is energetically favorable in the O-protonated (O-prot) form. As shown in Figure 1, the N-prot structure can be kinetically trapped in the gas phase when sprayed from non-protic solvent, whereas the O-prot structure is obtained when sprayed from protic solvents, analogous to results by others [1,2]. y parking the light source on the diagnostic 3440 wn mode, the percentage of the O-prot structure can be determined, and by default the remainder is assumed to adopt the N-prot structure. It will be shown that the relative percentages of O-prot vs N-prot are highly dependent on the solvent mixture, going from close to 0% O-prot in non-protic solvents, to 99% in protic solvents. Surprisingly, water behaves much more like a non-protic solvent than methanol. It is observed that the capillary temperature, which aids droplet desolvation by black-body radiation in the ESI source, is critical to promote the appearance of O-prot structures. These results are consistent with the picture that a protic bridge mechanism is at play to facilitate proton transfer, and thus allow conversion from N-prot to O-prot, but that this mechanism is subject to appreciable kinetic barriers on the timescale of solvent evaporation. 1. J. Phys. Chem. A 2011, 115, 7625. 2. Anal. Chem. 2012, 84, 7857.

  9. Incorporation mechanisms of a branched nonylphenol isomer in soil-derived organo-clay complexes during a 180-day experiment.

    PubMed

    Riefer, Patrick; Klausmeyer, Timm; Adams, Alina; Schmidt, Burkhard; Schäffer, Andreas; Schwarzbauer, Jan

    2013-07-01

    The incorporation process of a defined (13)C- and (14)C-labeled nonylphenol isomer (4-(3,5-dimethylhept-3-yl)phenol) into soil-derived organo-clay complexes was investigated. Isolated organo-clay complexes were separated into humic subfractions. Noninvasive ((13)C-CP/MAS NMR) and invasive methods (sequential chemical degradation, pyrolysis) were applied to obtain detailed information about the mode of incorporation, chemical structure, and change of the incorporation character of nonextractable residues in course of incubation. (13)C-CP/MAS NMR measurements of humic acids revealed an increasing incorporation of phenolic compounds during the experimental time which was referred to residues of the introduced (13)C-labeled NP isomer. Detailed investigations by means of sequential chemical degradation indicated a predominant incorporation of nonextractable NP isomer residues via reversible ester (amide) bonds. In course of time, the amount of releasable compounds decreased, pointing to altering processes which affected the mode of incorporation. BBr3-treatment, RuO4 oxidation, and thermochemolysis released only low portions of nonextractable radioactivity giving evidence of strongly incorporated residues. With the comprehensive application of complementary methods (e.g., humic matter fractionation, (13)C-CP/MAS NMR, sequential chemical degradation) it was possible to provide a comparatively detailed insight into the incorporation behavior of the applied NP isomer. PMID:23713749

  10. Incorporation mechanisms of a branched nonylphenol isomer in soil-derived organo-clay complexes during a 180-day experiment.

    PubMed

    Riefer, Patrick; Klausmeyer, Timm; Adams, Alina; Schmidt, Burkhard; Schäffer, Andreas; Schwarzbauer, Jan

    2013-07-01

    The incorporation process of a defined (13)C- and (14)C-labeled nonylphenol isomer (4-(3,5-dimethylhept-3-yl)phenol) into soil-derived organo-clay complexes was investigated. Isolated organo-clay complexes were separated into humic subfractions. Noninvasive ((13)C-CP/MAS NMR) and invasive methods (sequential chemical degradation, pyrolysis) were applied to obtain detailed information about the mode of incorporation, chemical structure, and change of the incorporation character of nonextractable residues in course of incubation. (13)C-CP/MAS NMR measurements of humic acids revealed an increasing incorporation of phenolic compounds during the experimental time which was referred to residues of the introduced (13)C-labeled NP isomer. Detailed investigations by means of sequential chemical degradation indicated a predominant incorporation of nonextractable NP isomer residues via reversible ester (amide) bonds. In course of time, the amount of releasable compounds decreased, pointing to altering processes which affected the mode of incorporation. BBr3-treatment, RuO4 oxidation, and thermochemolysis released only low portions of nonextractable radioactivity giving evidence of strongly incorporated residues. With the comprehensive application of complementary methods (e.g., humic matter fractionation, (13)C-CP/MAS NMR, sequential chemical degradation) it was possible to provide a comparatively detailed insight into the incorporation behavior of the applied NP isomer.

  11. A Promising Raman Spectroscopy Technique for the Investigation of trans and cis Cholesteryl Ester Isomers in Biological Samples.

    PubMed

    Melchiorre, Michele; Ferreri, Carla; Tinti, Anna; Chatgilialoglu, Chryssostomos; Torreggiani, Armida

    2015-05-01

    Lipid geometry is an important issue in biology and medicine. The cis-trans geometry conversion of double bonds in lipids is an endogenous process that can be mediated by sulfur-centered free radicals. Trans isomers of polyunsaturated fatty acids can be used as biological markers of free radical stress, and their presence in biological samples can be determined by synthesis and characterization of appropriate reference compounds. Fractions of plasma lipids, such as cholesteryl linoleate and arachidonate esters, are interesting targets because of their connection with membrane phospholipid turnover and their roles in cardiovascular health. In this context, Raman spectroscopy can provide a useful contribution, since Raman analysis can be performed directly on the lipid extracts without any derivatization reaction, is nondestructive, and can rapidly supply biochemical information. This study focused on the build up of Raman spectral libraries of different cis and trans isomers of cholesteryl esters to be used as references for the examination of complex biological samples and to facilitate isomer recognition. Unsaturated cholesteryl esters obtained by chemical synthesis and with different alkyl chain lengths, double bond numbers, or both, were analyzed. The potential of Raman analysis for trans isomer detection in biological samples was successfully tested on some cholesteryl ester lipid fractions from human serum. The data suggest promising applications of Raman spectroscopy in metabolomics and lipidomics.

  12. 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

  13. Precursor anion states in dissociative electron attachment to chlorophenol isomers

    NASA Astrophysics Data System (ADS)

    Kossoski, F.; Varella, M. T. do N.

    2016-07-01

    We report a theoretical study on low-energy (<10 eV) elastic electron scattering from chlorophenol isomers, namely, para-chlorophenol (pCP), meta-chlorophenol (mCP), and ortho-chlorophenol (oCP). The calculations were performed with the Schwinger multichannel method with pseudopotentials, and analysis of the computed integral cross sections and virtual orbitals revealed one σCCl ∗ , one σOH ∗ , and three π∗ shape resonances. We show that electron capture into the two lower lying π∗ orbitals initiates dissociative processes that lead to the elimination of the chloride ion, accounting for the two overlapping peaks where this fragment was observed. Despite the relatively small differences on the energetics of the π∗ resonances, a major isomeric effect was found on their corresponding autodetachment lifetimes, which accounts for the observed increasing cross sections in the progression pCP < mCP < oCP. In particular, dissociation from the π1 ∗ anion of pCP is largely suppressed because of the unfavorable mixing with the σCCl ∗ state. We found the intramolecular hydrogen bond present in oCP to have the opposite effects of stabilizing the σCCl ∗ resonance and destabilizing the σOH ∗ resonance. We also suggest that the hydrogen abstraction observed in chlorophenols and phenol actually takes place by a mechanism in which the incoming electron is directly attached to the dissociative σOH ∗ orbital.

  14. Electronic spectra of C4H3Cl+ isomers

    NASA Astrophysics Data System (ADS)

    Chakrabarty, S.; Rudnev, V.; Fulara, J.; Dietsche, R.; Nagy, A.; Garkusha, I.; Mazzotti, F. J.; Rice, C. A.; Maier, J. P.

    2012-12-01

    Two experimental methods were applied to identify the structure and electronic transitions of C4H3Cl+ isomers. The first is a direct absorption technique where mass-selected ions are embedded in 6 K neon matrices using a mass-selected ion beam and absorption spectra of different C4H3Cl+ isomers were thus observed. The second is a gas phase method on ions which have been collisional cooled with cryogenic helium inside of a 22-pole ion trap. The c-type (1)2 A‧ ← X 2 A″ electronic transition of a C4H3Cl+ isomer could then be measured by a one-colour, two-photon technique at 20 and 50 K in the gas phase. The two sets of data, complemented by calculated excitation energies, allowed the assignment of particular isomers. Rotational structure in the gas phase spectra was resolved for C4H3 35Cl+ and C4H3 37Cl+ isomers of cis-1-chlorobutenynylium. The analysis leads to the spectroscopic constants: T 00 = 19 184.680(5), ? , ? , ? , ? , ? and ? (all in cm-1).

  15. 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

    2012-10-01

    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.

  16. Confusion between protectin D1 (PD1) and its isomer protectin DX (PDX). An overview on the dihydroxy-docosatrienes described to date.

    PubMed

    Balas, Laurence; Guichardant, Michel; Durand, Thierry; Lagarde, Michel

    2014-04-01

    There is currently a growing interest in docosahexaenoic acid (DHA) oxygenated metabolites. Among them, protectin D1 (PD1), an endogenous dihydroxylated and non-cyclic docosatriene made through lipoxygenation and hydrolysis of an epoxide intermediate, shows appealing biological effects. However, with the present paper we wish to point out that results are sometimes assigned to PD1 while they are indeed related to its isomer protectin DX (PDX) made through double lipoxygenation only. These misleading conclusions urge us to review herein the structural/chemical and biological differences in the docosatrienes reported to date in the literature i.e. PD1, the related PD1n-3 DPA, AT-NPD1, maresin 1 (MaR1) and MaR1n-3 DPA, as well as their poxytrin analogs such as PDX, and some synthetic diastereoisomers. Hopefully, this will avoid further mistakes and confusion in the future.

  17. Behavioral and electrophysiological responses of Aedes albopictus to certain acids and alcohols present in human skin emanations.

    PubMed

    Guha, Lopamudra; Seenivasagan, T; Iqbal, S Thanvir; Agrawal, O P; Parashar, B D

    2014-10-01

    Human skin emanations attract hungry female mosquitoes toward their host for blood feeding. In this study, we report the flight orientation and electroantennogram response of Aedes albopictus females to certain unsaturated acids and alcohols found in human skin. In the Y-tube olfactometer, odors of lactic acid and 2-methyl-3-pentanol attracted 54-65% of Ae. albopictus females at all doses in a dose-dependent manner. However, at the highest dose (10(-2) g), the acids repelled 40-45% females. Attractancy (ca. 62-68%) at lower doses and repellency (ca. 30-45%) at higher doses were recorded for 3-methyl-3-pentanol and 1-octen-3-ol, while 5-hexen-1-ol, cis-2-hexen-1-ol, and trans 2-hexen-1-ol odor repelled ca. 55-65% of Ae. albopictus females at all doses. Antenna of female Ae. albopictus exhibited a dose-dependent EAG response up to 10(-3) g of L-lactic acid, trans-2-methyl-2-pentenoic acid, 2-octenoic acid, trans-2-hexen-1-ol and 1-octen-3-ol stimulations; however, the highest dose (10(-2) g) caused a little decline in the EAG response. EAG response of 9-10-fold was elicited by lactic acid, 2-octenoic acid, trans-2-hexenoic acid, and 3-methyl-3-pentanol, while cis-2-hexen-1-ol and trans-2-methyl pentenoic acid elicited 1-5-fold responses compared to solvent control. A blend of attractive compounds could be utilized in odor-baited trap for surveillance and repellent molecules with suitable formulation could be used to reduce the biting menace of mosquitoes.

  18. Behavioral and electrophysiological responses of Aedes albopictus to certain acids and alcohols present in human skin emanations.

    PubMed

    Guha, Lopamudra; Seenivasagan, T; Iqbal, S Thanvir; Agrawal, O P; Parashar, B D

    2014-10-01

    Human skin emanations attract hungry female mosquitoes toward their host for blood feeding. In this study, we report the flight orientation and electroantennogram response of Aedes albopictus females to certain unsaturated acids and alcohols found in human skin. In the Y-tube olfactometer, odors of lactic acid and 2-methyl-3-pentanol attracted 54-65% of Ae. albopictus females at all doses in a dose-dependent manner. However, at the highest dose (10(-2) g), the acids repelled 40-45% females. Attractancy (ca. 62-68%) at lower doses and repellency (ca. 30-45%) at higher doses were recorded for 3-methyl-3-pentanol and 1-octen-3-ol, while 5-hexen-1-ol, cis-2-hexen-1-ol, and trans 2-hexen-1-ol odor repelled ca. 55-65% of Ae. albopictus females at all doses. Antenna of female Ae. albopictus exhibited a dose-dependent EAG response up to 10(-3) g of L-lactic acid, trans-2-methyl-2-pentenoic acid, 2-octenoic acid, trans-2-hexen-1-ol and 1-octen-3-ol stimulations; however, the highest dose (10(-2) g) caused a little decline in the EAG response. EAG response of 9-10-fold was elicited by lactic acid, 2-octenoic acid, trans-2-hexenoic acid, and 3-methyl-3-pentanol, while cis-2-hexen-1-ol and trans-2-methyl pentenoic acid elicited 1-5-fold responses compared to solvent control. A blend of attractive compounds could be utilized in odor-baited trap for surveillance and repellent molecules with suitable formulation could be used to reduce the biting menace of mosquitoes. PMID:25049052

  19. Escherichia coli cyclophilin B binds a highly distorted form of trans-prolyl peptide isomer.

    PubMed

    Konno, Michiko; Sano, Yumi; Okudaira, Kayoko; Kawaguchi, Yoko; Yamagishi-Ohmori, Yoko; Fushinobu, Shinya; Matsuzawa, Hiroshi

    2004-09-01

    Cyclophilins facilitate the peptidyl-prolyl isomerization of a trans-isomer to a cis-isomer in the refolding process of unfolded proteins to recover the natural folding state with cis-proline conformation. To date, only short peptides with a cis-form proline have been observed in complexes of human and Escherichia coli proteins of cyclophilin A, which is present in cytoplasm. The crystal structures analyzed in this study show two complexes in which peptides having a trans-form proline, i.e. succinyl-Ala-trans-Pro-Ala-p-nitroanilide and acetyl-Ala-Ala-trans-Pro-Ala-amidomethylcoumarin, are bound on a K163T mutant of Escherichia coli cyclophilin B, the preprotein of which has a signal sequence. Comparison with cis-form peptides bound to cyclophilin A reveals that in any case the proline ring is inserted into the hydrophobic pocket and a hydrogen bond between CO of Pro and Neta2 of Arg is formed to fix the peptide. On the other hand, in the cis-isomer, the formation of two hydrogen bonds of NH and CO of Ala preceding Pro with the protein fixes the peptide, whereas in the trans-isomer formation of a hydrogen bond between CO preceding Ala-Pro and His47 Nepsilon2 via a mediating water molecule allows the large distortion in the orientation of Ala of Ala-Pro. Although loss of double bond character of the amide bond of Ala-Pro is essential to the isomerization pathway occurring by rotating around its bond, these peptides have forms impossible to undergo proton transfer from the guanidyl group of Arg to the prolyl N atom, which induces loss of double bond character.

  20. Low and High Temperature Combustion Chemistry of Butanol Isomers in Premixed Flames and Autoignition Systems

    SciTech Connect

    Sarathy, S M; Pitz, W J; Westbrook, C K; Mehl, M; Yasunaga, K; Curran, H J; Tsujimura, T; Osswald, P; Kohse-Hoinghaus, K

    2010-12-12

    Butanol is a fuel that has been proposed as a bio-derived alternative to conventional petroleum derived fuels. The structural isomer in traditional 'bio-butanol' fuel is n-butanol, but newer conversion technologies produce iso-butanol as a fuel. In order to better understand the combustion chemistry of bio-butanol, this study presents a comprehensive chemical kinetic model for all the four isomers of butanol (e.g., 1-, 2-, iso- and tert-butanol). The proposed model includes detailed high temperature and low temperature reaction pathways. In this study, the primary experimental validation target for the model is premixed flat low-pressure flame species profiles obtained using molecular beam mass spectrometry (MBMS). The model is also validated against previously published data for premixed flame velocity and n-butanol rapid compression machine and shock tube ignition delay. The agreement with these data sets is reasonably good. The dominant reaction pathways at the various pressures and temperatures studied are elucidated. At low temperature conditions, we found that the reaction of alphahydroxybutyl with O{sub 2} was important in controlling the reactivity of the system, and for correctly predicting C{sub 4} aldehyde profiles in low pressure premixed flames. Enol-keto isomerization reactions assisted by HO{sub 2} were also found to be important in converting enols to aldehydes and ketones in the low pressure premixed flames. In the paper, we describe how the structural features of the four different butanol isomers lead to differences in the combustion properties of each isomer.

  1. Spectroscopy of {sup 144}Ho using recoil-isomer tagging

    SciTech Connect

    Mason, P. J. R; Cullen, D. M.; Scholey, C.; Greenlees, P. T.; Jakobsson, U.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Leino, M.; Nyman, M.; Peura, P.; Puurunen, A.; Rahkila, P.; Ruotsalainen, P.; Sorri, J.; Saren, J.; Uusitalo, J.; Xu, F. R.

    2010-02-15

    Excited states in the proton-unbound odd-odd nucleus {sup 144}Ho have been populated using the {sup 92}Mo({sup 54}Fe,pn){sup 144}Ho reaction and studied using the recoil-isomer-tagging technique. The alignment properties and signature splitting of the rotational band above the I{sup p}i=(8{sup +}){sup 144m}Ho isomer have been analyzed and the isomer confirmed to have a pih{sub 11/2} x nuh{sub 11/2} two-quasiparticle configuration. The configuration-constrained blocking method has been used to calculate the shapes of the ground and isomeric states, which are both predicted to have triaxial nuclear shapes with |gamma|approx =24 deg.

  2. FY2010 Annual Report for the Actinide Isomer Detection Project

    SciTech Connect

    Warren, Glen A.; Francy, Christopher J.; Ressler, Jennifer J.; Erikson, Luke E.; Miller, Erin A.; Hatarik, R.

    2011-01-01

    This project seeks to identify a new signature for actinide element detection in active interrogation. This technique works by exciting and identifying long-lived nuclear excited states (isomers) in the actinide isotopes and/or primary fission products. Observation of isomers in the fission products will provide a signature for fissile material. For the actinide isomers, the decay time and energy of the isomeric state is unique to a particular isotope, providing an unambiguous signature for Special Nuclear Materials (SNM). Future work will include a follow-up measurement scheduled for December 2010 at LBNL. Lessons learned from the July 2010 measurements will be incorporated into these new measurements. Analysis of both the July and December experiments will be completed in a few months. A research paper to be submitted to a peer-reviewed journal will be drafted if the conclusions from the measurements warrant publication.

  3. Effects of butanol isomers on dipalmitoylphosphatidylcholine bilayer membranes.

    PubMed

    Reeves, Megan D; Schawel, Adam K; Wang, Weidong; Dea, Phoebe

    2007-06-01

    Differential scanning calorimetry and (31)P-NMR were used to study the effects of butanol isomers on the thermotropic phase behavior of dipalmitoylphosphatidylcholine (DPPC) bilayers. The threshold concentration for the onset of interdigitation for each isomer was determined by the disappearance of the pretransition and the onset of a large hysteresis between the heating and cooling scans of the gel-to-liquid main transition. The threshold concentration was found to correlate with increased solubility of the isomers in the aqueous phase, led by tert-butanol. However, as the solution concentration of tert-butanol increased, there was an abrupt shrinking of the hysteresis, initially with well-resolved shoulder peaks indicating mixed phases. The eventual disappearance of the shoulder peaks was correlated with a breakdown of the multilamellar structure identified using (31)P-NMR.

  4. Cationic Methylene-Pyrene Isomers and Isomerization Pathways: Finite Temperature Theoretical Studies.

    PubMed

    Rapacioli, Mathias; Simon, Aude; Marshall, Charlotte C M; Cuny, Jérôme; Kokkin, Damian; Spiegelman, Fernand; Joblin, Christine

    2015-12-24

    This paper provides spectral characterizations of the two isomers of the 1-methylenepyrene cation, namely, the 1-pyrenemethylium and a pyrene-like isomer owing a tropylium cycle. Both are possible photodissociation products of the 1-methylpyrene cation and were proposed as potential contributors to the diffuse interstellar bands. In that respect, vibrational and electronic spectra are computed for the optimized structures at the density functional theory (DFT) and time-dependent (TD-)DFT levels. Finite temperature effects on these spectra are estimated from molecular dynamics simulations within the density functional-based tight-binding (DFTB) and TD-DFTB frameworks, these methods being first benchmarked against DFT and TD-DFT calculations. The computed spectra allow discrimination of the two isomers. When the temperature increases, bands are observed to redshift and merge. The isomerization mechanism is investigated with the metadynamics technique, a biased dynamics scheme allowing to probe reaction mechanisms with high energy barriers by investigating the free energy surface at various temperatures. Four pathways with similar barrier heights (3.5-4 eV) are found, showing that the interconversion process would only occur in interstellar clouds under photoactivation. The present study opens the way to simulations on larger methyl- and methylenePAHs of astrophysical interest and their experimental investigation.

  5. Cationic Methylene-Pyrene Isomers and Isomerization Pathways: Finite Temperature Theoretical Studies.

    PubMed

    Rapacioli, Mathias; Simon, Aude; Marshall, Charlotte C M; Cuny, Jérôme; Kokkin, Damian; Spiegelman, Fernand; Joblin, Christine

    2015-12-24

    This paper provides spectral characterizations of the two isomers of the 1-methylenepyrene cation, namely, the 1-pyrenemethylium and a pyrene-like isomer owing a tropylium cycle. Both are possible photodissociation products of the 1-methylpyrene cation and were proposed as potential contributors to the diffuse interstellar bands. In that respect, vibrational and electronic spectra are computed for the optimized structures at the density functional theory (DFT) and time-dependent (TD-)DFT levels. Finite temperature effects on these spectra are estimated from molecular dynamics simulations within the density functional-based tight-binding (DFTB) and TD-DFTB frameworks, these methods being first benchmarked against DFT and TD-DFT calculations. The computed spectra allow discrimination of the two isomers. When the temperature increases, bands are observed to redshift and merge. The isomerization mechanism is investigated with the metadynamics technique, a biased dynamics scheme allowing to probe reaction mechanisms with high energy barriers by investigating the free energy surface at various temperatures. Four pathways with similar barrier heights (3.5-4 eV) are found, showing that the interconversion process would only occur in interstellar clouds under photoactivation. The present study opens the way to simulations on larger methyl- and methylenePAHs of astrophysical interest and their experimental investigation. PMID:26600076

  6. Thermal decomposition of 1-pentanol and its isomers: a theoretical study.

    PubMed

    Zhao, Long; Ye, Lili; Zhang, Feng; Zhang, Lidong

    2012-09-20

    Pentanol is one of the promising "next generation" alcohol fuels with high energy density and low hygroscopicity. In the present work, dominant reaction channels of thermal decomposition of three isomers of pentanol: 1-pentanol, 2-methyl-1-butanol, and 3-methyl-1-butanol were investigated by CBS-QB3 calculations. Subsequently, the temperature- and pressure-dependent rate constants for these channels were computed by RRKM/master equation simulations. The difference between the thermal decomposition behavior of pentanol and butanol were discussed, while butanol as another potential alternative alcohol fuel has been extensively studied both experimentally and theoretically. Rate constants of barrierless bond dissociation reactions of pentanol isomers were treated by the variational transition state theory. The comparison between various channels revealed that the entropies of variational transition states significantly impact the rate constants of pentanol decomposition reactions. This work provides sound quality kinetic data for major decomposition channels of three pentanol isomers in the temperature range of 800-2000 K with pressure varying from 7.6 to 7.6 × 10(4) Torr, which might be valuable for developing detailed kinetic models for pentanol combustion.

  7. Oxidation and combustion of the n-hexene isomers: a wide range kinetic modeling study

    SciTech Connect

    Mehl, M; Vanhove, G; Pitz, W J; Ranzi, E

    2008-03-12

    A detailed chemical kinetic mechanism has been developed to study the oxidation of the straight-chain isomers of hexene over a wide range of operating conditions. The main features of this detailed kinetic mechanism, which includes both high and low temperature reaction pathways, are presented and discussed with special emphasis on the main classes of reactions involved in alkene oxidation. Simulation results have been compared with experimental data over a wide range of operating conditions including shock tube, jet stirred reactor and rapid compression machine. The different reactivities of the three isomers have been successfully predicted by the model. Isomerization reactions of the hexenyl radicals were found to play a significant role in the chemistry and interactions of the three n-hexene isomers. A comparative reaction flux analysis is used to verify and discuss the fundamental role of the double bond position in the isomerization reactions of alkenyl radicals, as well as the impact of the allylic site in the low and high temperature mechanism of fuel oxidation.

  8. Oxidation and combustion of the n-hexene isomers: A wide range kinetic modeling study

    SciTech Connect

    Mehl, Marco; Pitz, William J.; Vanhove, Guillaume; Ranzi, Eliseo

    2008-12-15

    A detailed chemical kinetic mechanism has been developed to study the oxidation of the straight-chain isomers of hexene over a wide range of operating conditions. The main features of this detailed kinetic mechanism, which includes both high and low temperature reaction pathways, are presented and discussed with special emphasis on the main classes of reactions involved in alkene oxidation. Simulation results have been compared with experimental data over a wide range of operating conditions including shock tube, jet stirred reactor and rapid compression machine. The different reactivities of the three isomers have been successfully predicted by the model. Isomerization reactions of the hexenyl radicals were found to play a significant role in the chemistry and interactions of the three n-hexene isomers. A comparative reaction flux analysis is used to verify and discuss the fundamental role of the double bond position in the isomerization reactions of alkenyl radicals, as well as the impact of the allylic site in the low and high temperature mechanism of fuel oxidation. (author)

  9. Investigation of a recently detected 11-nor-9-carboxy-Δ(9)-tetrahydrocannabinol isomer: Studies on the degradation of 11-nor-9-carboxy-Δ(9)-tetrahydrocannabinol glucuronide.

    PubMed

    Hanisch, Stephanie; Paulke, Alexander; Toennes, Stefan W

    2016-09-10

    An isomer of the tetrahydrocannabinol (THC) metabolite 11-nor-9-carboxy-Δ(9)-THC (THCCOOH) had been detected in blood of cannabis users. The present study was initiated to elucidate whether the labile metabolite THCCOOH-glucuronide could be the precursor. THCCOOH-glucuronide was incubated in human serum and albumin (HSA) solution at various temperatures (-18, 4.5, 22 and 37°C) and pH values (pH 7.4 and 8.3) for seven days in the presence or absence of the esterase inhibitor sodium fluoride. Analysis of incubation samples was performed using LC-MS/MS. Marked degradation of THCCOOH-glucuronide was observed at 37°C. It was found that not only THCCOOH, but also the isomer is a degradation product of THCCOOH-glucuronide and its in-vivo production is assumed. Degradation to THCCOOH and the isomer occurred at alkaline pH, in the presence of fluoride-sensitive esterases and of HSA alone. To inhibit isomer formation during sample storage, refrigeration and controlling of the pH are recommended. However, THCCOOH and the isomer exhibit similar properties during incubations in serum, but differ in their interaction with HSA. The present study confirmed the nature of the isomer as degradation product of the abundant THC metabolite THCCOOH-glucuronide. Serum albumin and esterases are obviously involved. The isomer is formed not only during storage, but also under physiological conditions, suggesting that it can be considered an in-vivo metabolite. However, the chemical structure of the isomer remains unknown and further research is necessary.

  10. Investigation of a recently detected 11-nor-9-carboxy-Δ(9)-tetrahydrocannabinol isomer: Studies on the degradation of 11-nor-9-carboxy-Δ(9)-tetrahydrocannabinol glucuronide.

    PubMed

    Hanisch, Stephanie; Paulke, Alexander; Toennes, Stefan W

    2016-09-10

    An isomer of the tetrahydrocannabinol (THC) metabolite 11-nor-9-carboxy-Δ(9)-THC (THCCOOH) had been detected in blood of cannabis users. The present study was initiated to elucidate whether the labile metabolite THCCOOH-glucuronide could be the precursor. THCCOOH-glucuronide was incubated in human serum and albumin (HSA) solution at various temperatures (-18, 4.5, 22 and 37°C) and pH values (pH 7.4 and 8.3) for seven days in the presence or absence of the esterase inhibitor sodium fluoride. Analysis of incubation samples was performed using LC-MS/MS. Marked degradation of THCCOOH-glucuronide was observed at 37°C. It was found that not only THCCOOH, but also the isomer is a degradation product of THCCOOH-glucuronide and its in-vivo production is assumed. Degradation to THCCOOH and the isomer occurred at alkaline pH, in the presence of fluoride-sensitive esterases and of HSA alone. To inhibit isomer formation during sample storage, refrigeration and controlling of the pH are recommended. However, THCCOOH and the isomer exhibit similar properties during incubations in serum, but differ in their interaction with HSA. The present study confirmed the nature of the isomer as degradation product of the abundant THC metabolite THCCOOH-glucuronide. Serum albumin and esterases are obviously involved. The isomer is formed not only during storage, but also under physiological conditions, suggesting that it can be considered an in-vivo metabolite. However, the chemical structure of the isomer remains unknown and further research is necessary. PMID:27448313

  11. 2-Methyl-aspartic acid monohydrate.

    PubMed

    Brewer, Greg; Burton, Aaron S; Dworkin, Jason P; Butcher, Ray J

    2013-11-30

    The title compound, C5H9NO4·H2O, is an isomer of the α-amino acid glutamic acid that crystallizes from water in its zwitterionic form as a monohydrate. It is not one of the 20 proteinogenic α-amino acids that are used in living systems and differs from the natural amino acids in that it has an α-methyl group rather than an α-H atom. In the crystal, an O-H⋯O hydrogen bond is present between the acid and water mol-ecules while extensive N-H⋯O and O-H⋯O hydrogen bonds link the components into a three-dimensional array. PMID:24454270

  12. Anaerobic degradation of phthalate isomers by methanogenic consortia

    SciTech Connect

    Kleerebezem, R.; Pol, L.W.H.; Lettinga, G.

    1999-03-01

    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 ({mu}{sub S}{sup max}) and biomass yields (Y{sub X{sub tot}S}) 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 {mu}{sub X}{sup max} and Y{sub X{sub tot}S} 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 (K{sub S}) 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.

  13. K = 6+ Isomers in Hf, yb and W Nuclei

    NASA Astrophysics Data System (ADS)

    Rath, Aswini Kumar; Walker, P. M.; Praharaj, C. R.; Xu, F. R.

    Using deformed Hartree-Fock and angular momentum projection (PHF) technique we try to understand the intrinsic structure and the systematics in the life times of K = 6+ isomers in the Hf isotopes (in 172-178Hf nuclei) and N = 104 Yb, Hf and W isotones. The band structure in 172Hf is reasonably well reproduced. The variation in the B(E2;2+ → 0+) values in the Hf isotopes as well as N = 104 isotones are well reproduced. The calculated K-forbidden E2 transition probabilities from the isomer bandheads to the 4+ yrast states qualitatively explain the variation of the lifetimes with N and Z.

  14. Quantum-chemical study of C 84 fulleren isomers

    NASA Astrophysics Data System (ADS)

    Bakowies, Dirk; Kolb, Matthias; Thiel, Walter; Richard, Sabine; Ahlrichs, Reinhart; Kappes, Manfred M.

    1992-12-01

    Semiempirical and ab initio SCF calculations are reported for the C 84 fullerenes with isolated pentagons. The optimized geometries and relative stabilities are discussed. All methods applied predict two nearly isoenergetic structures with D 2 and D 2d symmetry to be the most stable of the 24 isomers considered, which is consistent with the experimental observed 13C-NMR spectrum. Infrared spectra are predicted for these D 2 and D 2d isomers. The semiempirical results (MNDO, AM1, PM3) for the geometries and relative energies are in excellent agreement with the ab initio predictions at the split-valence SCF level.

  15. Differentiation of optical isomers through enhanced weak-field interactions

    NASA Technical Reports Server (NTRS)

    Aronowitz, S.

    1980-01-01

    The influence of weak field interaction terms due to the cooperative effects which arise from a macroscopic assemblage of interacting sites is studied. Differential adsorption of optical isomers onto an achiral surface is predicted to occur if the surface was continuous and sufficiently large. However, the quantity of discontinuous crystal surfaces did not enhance the percentage of differentiation and thus the procedure of using large quantities of small particles was not a viable technique for obtaining a detectable differentiation of optical isomers on an achiral surface.

  16. 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).

  17. Characterization of epoxydecenal isomers as potent odorants in black tea (Dimbula) infusion.

    PubMed

    Kumazawa, Kenji; Wada, Yoshiyuki; Masuda, Hideki

    2006-06-28

    In a black tea (Dimbula) infusion, the potent "sweet and/or juicy" odorants were identified as the cis- and trans-4,5-epoxy-(E)-2-decenals by comparison of their gas chromatography retention indices, mass spectra, and odor quality to those of the actual synthetic compounds. Of the two odorants, cis-4,5-epoxy-(E)-2-decenal has been identified for the first time in the black tea. On the basis of the aroma extract dilution analysis on the flavor distillate obtained using the solvent-assisted flavor evaporation technique from the black tea infusion, these isomers showed higher flavor dilution (FD) factors. The FD factors and concentrations of these odorants in the black tea infusion were observed to be much higher than those from Japanese green tea. In addition, the model studies showed that these odorants were generated from linoleic acid and its hydroperoxides by heating, but the generated amounts of these odorants from linoleic acid were much less than those of its hydroperoxides. It can be assumed from these results that the withering and fermentation, which are characteristic processes during the manufacturing of the black tea, which includes the enzymatic reaction such as lipoxygenase, is one of the most important factors for the formation of the epoxydecenal isomers.

  18. Exotic SiO2H2 Isomers: Theory and Experiment Working in Harmony.

    PubMed

    McCarthy, Michael C; Gauss, Jürgen

    2016-05-19

    Replacing carbon with silicon can result in dramatic and unanticipated changes in isomeric stability, as the well-studied CO2H2 and the essentially unknown SiO2H2 systems illustrate. Guided by coupled-cluster calculations, three SiO2H2 isomers have been detected and spectroscopically characterized in a molecular beam discharge source using rotational spectroscopy. The cis,trans conformer of dihydroxysilylene HOSiOH, the ground-state isomer, and the high-energy, metastable dioxasilirane c-H2SiO2 are abundantly produced in a dilute SiH4/O2 electrical discharge, enabling precise structural determinations of both by a combination of isotopic measurements and calculated vibrational corrections. The isotopic studies also provide insight into their formation route, suggesting that c-H2SiO2 is formed promptly in the expansion but that cis,trans-HOSiOH is likely formed by secondary reactions following formation of the most stable dissociation pair, SiO + H2O. Although less abundant, the rotational spectrum of trans-silanoic acid, the silicon analogue of formic acid, HSi(O)OH, has also been observed. PMID:27139016

  19. Characterization of epoxydecenal isomers as potent odorants in black tea (Dimbula) infusion.

    PubMed

    Kumazawa, Kenji; Wada, Yoshiyuki; Masuda, Hideki

    2006-06-28

    In a black tea (Dimbula) infusion, the potent "sweet and/or juicy" odorants were identified as the cis- and trans-4,5-epoxy-(E)-2-decenals by comparison of their gas chromatography retention indices, mass spectra, and odor quality to those of the actual synthetic compounds. Of the two odorants, cis-4,5-epoxy-(E)-2-decenal has been identified for the first time in the black tea. On the basis of the aroma extract dilution analysis on the flavor distillate obtained using the solvent-assisted flavor evaporation technique from the black tea infusion, these isomers showed higher flavor dilution (FD) factors. The FD factors and concentrations of these odorants in the black tea infusion were observed to be much higher than those from Japanese green tea. In addition, the model studies showed that these odorants were generated from linoleic acid and its hydroperoxides by heating, but the generated amounts of these odorants from linoleic acid were much less than those of its hydroperoxides. It can be assumed from these results that the withering and fermentation, which are characteristic processes during the manufacturing of the black tea, which includes the enzymatic reaction such as lipoxygenase, is one of the most important factors for the formation of the epoxydecenal isomers. PMID:16787030

  20. Multifunctional Hyaluronic Acid and Chondroitin Sulfate Nanoparticles: Impact of Glycosaminoglycan Presentation on Receptor Mediated Cellular Uptake and Immune Activation.

    PubMed

    Oommen, Oommen P; Duehrkop, Claudia; Nilsson, Bo; Hilborn, Jöns; Varghese, Oommen P

    2016-08-17

    Hyaluronic acid (HA) and chondroitin sulfate (CS) polymers are extensively used for various biomedical applications, such as for tissue engineering, drug delivery, and gene delivery. Although both these biopolymers are known to target cell surface CD44 receptors, their relative cellular targeting properties and immune activation potential have never been evaluated. In this article, we present the synthesis and characterization of novel self-assembled supramolecular HA and CS nanoparticles (NPs). These NPs were developed using fluorescein as a hydrophobic component that induced amphiphilicity in biopolymers and also efficiently stabilized anticancer drug doxorubicin (DOX) promoting a near zero-order drug release. The cellular uptake and cytotoxicity studies of these NPs in different human cancer lines, namely, human colorectal carcinoma cell line HCT116 and human breast cancer cell line MCF-7 demonstrated dose dependent cytotoxicity. Interestingly, both NPs showed CD44 dependent cellular uptake with the CS-DOX NP displaying higher dose-dependent cytotoxicity than the HA-DOX NP in different mammalian cells tested. Immunological evaluation of these nanocarriers in an ex vivo human whole blood model revealed that unlike unmodified polymers, the HA NP and CS NP surprisingly showed platelet aggregation and thrombin-antithrombin complex formation at high concentrations (0.8 mg/mL). We also observed a clear difference in early- and late-stage complement activation (C3a and sC5b-9) with CS and CS NP triggering significant complement activation at high concentrations (0.08-0.8 mg/mL), unlike HA and HA NP. These results offer new insight into designing glycosaminoglycan-based NPs and understanding their hematological responses and targeting ability. PMID:27468113

  1. The spectroscopy and photochemistry of quinioline structural isomers: (E)- and (Z)-phenylvinylnitrile

    SciTech Connect

    Mehta-Hurt, Deepali N.; Korn, Joseph A.; Navotnaya, Polina; Parobek, Alexander P.; Clayton, Rachel M.; Zwier, Timothy S.

    2015-08-21

    In Titan’s atmosphere, photochemical pathways that lead to nitrogen heteroaromatics may incorporate photoisomerization of their structural isomers as a final step. (E)- and (Z)-phenylvinylnitrile ((E)- and (Z)-PVN, C{sub 6}H{sub 5} —CH=CHCN) are structural isomers of quinoline that themselves possess extensive absorptions in the ultraviolet, and thus may engage in such photoisomerization pathways. The present study explores the vibronic spectroscopy and photo-induced isomerization of gas-phase (E)- and (Z)-PVN in the 33,600-35,850 cm{sup −1} region under jet-cooled conditions. The S{sub 0}-S{sub 1} origins for (E)- and (Z)-PVN have been identified at 33 827 cm{sup −1} and 33 707 cm{sup −1}, respectively. Isomer-specific UV-UV hole-burning and UV depletion spectra reveal sharp vibronic structure that extends over almost 2000 cm{sup −1}, with thresholds for fast non-radiative decay identified by a comparison between hole-burning and UV depletion spectra. Dispersed fluorescence spectra of the two isomers enable the assignment of many low frequency transitions in both molecules, aided by harmonic frequency calculations (B3LYP/6-311++G(d,p)) and a comparison with the established spectroscopy of phenylvinylacetylene, the ethynyl counterpart to PVN. Both isomers are proven to be planar in both the S{sub 0} ground and S{sub 1} electronic excited states. (E)-PVN exhibits extensive Duschinsky mixing involving out-of-plane modes whose frequencies and character change significantly in the ππ{sup ∗} transition, which modulates the degree of single- and double-bond character along the vinylnitrile substituent. This same mixing is much less evident in (Z)-PVN. The spectroscopic characterization of (E)- and (Z)-PVN served as the basis for photoisomerization experiments using ultraviolet hole-filling spectroscopy carried out in a reaction tube affixed to the pulsed valve. Successful interconversion between (E) and (Z)-PVN was demonstrated via ultraviolet hole

  2. The spectroscopy and photochemistry of quinioline structural isomers: (E)- and (Z)-phenylvinylnitrile

    NASA Astrophysics Data System (ADS)

    Mehta-Hurt, Deepali N.; Korn, Joseph A.; Navotnaya, Polina; Parobek, Alexander P.; Clayton, Rachel M.; Zwier, Timothy S.

    2015-08-01

    In Titan's atmosphere, photochemical pathways that lead to nitrogen heteroaromatics may incorporate photoisomerization of their structural isomers as a final step. (E)- and (Z)-phenylvinylnitrile ((E)- and (Z)-PVN, C6H5 —CH=CHCN) are structural isomers of quinoline that themselves possess extensive absorptions in the ultraviolet, and thus may engage in such photoisomerization pathways. The present study explores the vibronic spectroscopy and photo-induced isomerization of gas-phase (E)- and (Z)-PVN in the 33,600-35,850 cm-1 region under jet-cooled conditions. The S0-S1 origins for (E)- and (Z)-PVN have been identified at 33 827 cm-1 and 33 707 cm-1, respectively. Isomer-specific UV-UV hole-burning and UV depletion spectra reveal sharp vibronic structure that extends over almost 2000 cm-1, with thresholds for fast non-radiative decay identified by a comparison between hole-burning and UV depletion spectra. Dispersed fluorescence spectra of the two isomers enable the assignment of many low frequency transitions in both molecules, aided by harmonic frequency calculations (B3LYP/6-311++G(d,p)) and a comparison with the established spectroscopy of phenylvinylacetylene, the ethynyl counterpart to PVN. Both isomers are proven to be planar in both the S0 ground and S1 electronic excited states. (E)-PVN exhibits extensive Duschinsky mixing involving out-of-plane modes whose frequencies and character change significantly in the ππ∗ transition, which modulates the degree of single- and double-bond character along the vinylnitrile substituent. This same mixing is much less evident in (Z)-PVN. The spectroscopic characterization of (E)- and (Z)-PVN served as the basis for photoisomerization experiments using ultraviolet hole-filling spectroscopy carried out in a reaction tube affixed to the pulsed valve. Successful interconversion between (E) and (Z)-PVN was demonstrated via ultraviolet hole-filling experiments. Photoexcitation of (E)- and (Z)-PVN at their respective S0-S1

  3. DNA-decorated carbon nanotube-based FETs as ultrasensitive chemical sensors: Discrimination of homologues, structural isomers, and optical isomers

    NASA Astrophysics Data System (ADS)

    Khamis, S. M.; Jones, R. A.; Johnson, A. T. C.; Preti, G.; Kwak, J.; Gelperin, A.

    2012-06-01

    We have explored the abilities of all-electronic DNA-carbon nanotube (DNA-NT) vapor sensors to discriminate very similar classes of molecules. We screened hundreds of DNA-NT devices against a panel of compounds chosen because of their similarities. We demonstrated that DNA-NT vapor sensors readily discriminate between series of chemical homologues that differ by single methyl groups. DNA-NT devices also discriminate among structural isomers and optical isomers, a trait common in biological olfactory systems, but only recently demonstrated for electronic FET based chemical sensors.

  4. Characterization of Nα-Fmoc-protected dipeptide isomers by electrospray ionization tandem mass spectrometry (ESI-MS(n)): effect of protecting group on fragmentation of dipeptides.

    PubMed

    Ramesh, M; Raju, B; Srinivas, R; Sureshbabu, V V; Vishwanatha, T M; Hemantha, H P

    2011-07-30

    A series of positional isomeric pairs of Fmoc-protected dipeptides, Fmoc-Gly-Xxx-OY/Fmoc-Xxx-Gly-OY (Xxx=Ala, Val, Leu, Phe) and Fmoc-Ala-Xxx-OY/Fmoc-Xxx-Ala-OY (Xxx=Leu, Phe) (Fmoc=[(9-fluorenylmethyl)oxy]carbonyl) and Y=CH(3)/H), have been characterized and differentiated by both positive and negative ion electrospray ionization ion-trap tandem mass spectrometry (ESI-IT-MS(n)). In contrast to the behavior of reported unprotected dipeptide isomers which mainly produce y(1)(+) and/or a(1)(+) ions, the protonated Fmoc-Xxx-Gly-OY, Fmoc-Ala-Xxx-OY and Fmoc-Xxx-Ala-OY yield significant b(1)(+) ions. These ions are formed, presumably with stable protonated aziridinone structures. However, the peptides with Gly- at the N-terminus do not form b(1)(+) ions. The [M+H](+) ions of all the peptides undergo a McLafferty-type rearrangement followed by loss of CO(2) to form [M+H-Fmoc+H](+). The MS(3) collision-induced dissociation (CID) of these ions helps distinguish the pairs of isomeric dipeptides studied in this work. Further, negative ion MS(3) CID has also been found to be useful for differentiating these isomeric peptide acids. The MS(3) of [M-H-Fmoc+H](-) of isomeric peptide acids produce c(1)(-), z(1)(-) and y(1)(-) ions. Thus the present study of Fmoc-protected peptides provides additional information on mass spectral characterization of the dipeptides and distinguishes the positional isomers.

  5. Crystal and electronic structures of tris[4,4,4-Trifluoro-1-(2-X)-1,3-butanedionato]iron(III) isomers (X = thienyl or furyl): An X-ray and computational study

    NASA Astrophysics Data System (ADS)

    Conradie, Marrigje M.; van Rooyen, Petrus H.; Conradie, Jeanet

    2013-12-01

    DFT calculations showed that [Fe(acac)3] (where acac = acetylacetonato) is high-spin, with a negative D3 distortion from the octahedral ligand field. Calculations further showed that, although both the fac and mer isomers of complexes [Fe(CF3COCHCOR)3], where R = C4H3S or C4H3O, can exist, the mer isomers are energetically favoured in both complexes. The structure of the major mer isomer of [Fe(CF3COCHCOC4H3S)3] has been published previously, while the crystal structure of the minor fac isomer of [Fe(CF3COCHCOC4H3S)3] is presented in this study. The structure of the mer isomer of [Fe(CF3COCHCOC4H3O)3], in agreement with DFT calculations, showed that the furyl substituent pointed towards the CF3 group in a syn orientation.

  6. Identification of a shape isomer in 235U.

    PubMed

    Oberstedt, A; Oberstedt, S; Gawrys, M; Kornilov, N

    2007-07-27

    The shape isomer in 235U has been searched for in a neutron-induced fission experiment on 234U, which was performed at the isomer spectrometer NEPTUNE of the EC-JRC IRMM. A neutron source, with a tunable pulse frequency in the Hz to kHz range and its individually adjustable neutron pulse width in connection with an appropriate detector system turned out to be the ideal instrument to perform an isomer search, when decay half-lives above 100 micros are expected. From the delayed fission events observed for two different NEPTUNE settings and at mean incident neutron energies En=0.95 and 1.27 MeV the isomeric fission half-life could be determined to be T1/2=(3.6+/-1.8) ms. The corresponding cross section was determined to sigmaif=(10+/-8) microb. With these results an experimental confirmation for the existence of a superdeformed shape isomer in odd-uranium isotopes is given for the first time. PMID:17678355

  7. 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.

  8. Isomers of 3-(4-nitrophenyl)acrolein oxime

    SciTech Connect

    Leitis, L.Ya.; Liepin'sh, E.E.; Yansone, D.P.; Dreibante, I.I.; Shimanskaya, M.V.; Maslii, L.K.; Nikol'skaya, G.S.

    1986-06-10

    The Z and E isomers of 3-(4-nitrophenyl)acrolein oxime were obtained and characterized. The assignment was made on the basis of the geminal hetero constants /sup 2/J(/sup 15/N = C-/sup 1/H) and /sup 2/J(/sup 15/N = C-/sup 13/C).

  9. Electronic Structure Mediated Vibrational Coherence in Methyl Acetophenone Isomers

    NASA Astrophysics Data System (ADS)

    Konar, Arkaprabha; Shu, Yinan; Lozovoy, Vadim; Levine, Benjamin; Dantus, Marcos

    2014-05-01

    The role of ground and excited state electronic structures in influencing the vibrational coherences in gas phase polyatomic molecules has been a hot topic for quite some time. Here we explore the time resolved dynamics of acetophenone and its methyl substituted isomer when excited by intense 800nm femtosecond pump and probe pulses. The parent ion yield show 500 fs modulations that die down within 3ps. Similar modulations having the same timescales in the parent ion yield are also observed for the p-methyl isomer. The o-methyl isomer however shows longer 1ps modulations. Interestingly enough no oscillations are observed for the meta isomer. Quantum chemical calculations at the CASSCF/6-311G level of theory predicts that upon excitation the neutral ground state is planar and the energy spacing between the levels is very small. Preliminary calculations also predict torsional motion coupled to electronic modulations on the D0 state and further calculations are being performed to ascertain the involvement of the D1 and D2 states. This could help us better understand the electronic effect of substitution on a benzene ring.

  10. Electronic Structure Mediated Vibrational Coherence in Methyl Acetophenone Isomers

    NASA Astrophysics Data System (ADS)

    Konar, Arkaprabha; Shu, Yinan; Levine, Benjamin; Lozovoy, Vadim; Dantus, Marcos

    2014-03-01

    The role of ground and excited state electronic structures in influencing the vibrational coherences in gas phase polyatomic molecules has been a hot topic for quite some time. Here we explore the time resolved dynamics of acetophenone and its methyl substituted isomer when excited by intense 800nm femtosecond pump and probe pulses. The parent ion yield show 500 fs modulations that die down within 3ps. Similar modulations having the same timescales in the parent ion yield are also observed for the p-methyl isomer. The o-methyl isomer however shows longer 1ps modulations. Interestingly enough no oscillations are observed for the meta isomer. Quantum chemical calculations at the CASSCF/6-311G level of theory predicts that upon excitation the neutral ground state is planar and the energy spacing between the levels is very small. Preliminary calculations also predict torsional motion coupled to electronic modulations on the D0 state and further calculations are being performed to ascertain the involvement of the D1 and D2 states. This could help us better understand the electronic effect of substitution on a benzene ring.

  11. Density functional theory study of the oligomerization of carboxylic acids.

    PubMed

    Di Tommaso, Devis; Watson, Ken L

    2014-11-20

    We present a density functional theory [M06-2X/6-31+G(d,p)] study of the structures and free energies of formation of oligomers of four carboxylic acids (formic acid, acetic acid, tetrolic acid, and benzoic acid) in water, chloroform, and carbon tetrachloride. Solvation effects were treated using the SMD continuum solvation model. The low-lying energy structures of molecular complexes were located by adopting an efficient search procedure to probe the potential energy surfaces of the oligomers of carboxylic acids (CA)n (n = 2-6). The free energies of the isomers of (CA)n in solution were determined as the sum of the electronic energy, vibrational-rotational-translational gas-phase contribution, and solvation free energy. The assessment of the computational protocol adopted in this study with respect to the dimerization of acetic acid, (AA)2, and formic acid, (FA)2, located new isomers of (AA)2 and (FA)2 and gave dimerization constants in good agreement with the experimental values. The calculation of the self-association of acetic acid, tetrolic acid, and benzoic acid shows the following: (i) Classic carboxylic dimers are the most stable isomer of (CA)2 in both the gas phase and solution. (ii) Trimers of carboxylic acid are stable in apolar aprotic solvents. (iii) Molecular clusters consisting of two interacting classic carboxylic dimers (CA)4,(D+D) are the most stable type of tetramers, but their formation from the self-association of classic carboxylic dimers is highly unfavorable. (iv) For acetic acid and tetrolic acid the reactions (CA)2 + 2CA → (CA)4,(D+D) and (CA)3 + CA → (CA)4,(D+D) are exoergonic, but these aggregation pathways go through unstable clusters that could hinder the formation of tetrameric species. (v) For tetrolic acid the prenucleation species that are more likely to form in solution are dimeric and trimeric structures that have encoded structural motifs resembling the α and β solid forms of tetrolic acid. (vi) Stable tetramers of

  12. Diffusion ordered spectroscopy for resolution of double bonded cis, trans-isomers

    NASA Astrophysics Data System (ADS)

    Chaudhari, Sachin Rama; Suryaprakash, N.

    2012-06-01

    NMR spectroscopic separation of double bonded cis- and trans-isomers, that have different molecular shapes but identical mass have been carried out using Diffusion Ordered Spectroscopy (DOSY). The mixtures of fumaric acid and maleic acid, that have similar hydrodynamic radii, have resolved been 'on the basis of their diffusion coefficients arising due to their different tendencies to associate with micelles or reverse micelles. Sodium dodecyl sulfate (SDS) and Dioctyl sulfosuccinate sodium salt (AOT) have been used as the media to mimic the chromatographic conditions, modify the average mobility and to achieve differential diffusion rates. The best separation of the components has been achieved by Dioctyl sulfosuccinate sodium salt (AOT) in D2O solution.

  13. FY2011 Annual Report for the Actinide Isomer Detection Project

    SciTech Connect

    Warren, Glen A.; Francy, Christopher J.; Ressler, Jennifer J.; Erikson, Luke E.; Tatishvili, Gocha; Hatarik, R.

    2011-10-01

    This project seeks to identify a new signature for actinide element detection in active interrogation. This technique works by exciting and identifying long-lived nuclear excited states (isomers) in the actinide isotopes and/or primary fission products. Observation of isomers in the fission products will provide a signature for fissile material. For the actinide isomers, the decay time and energy of the isomeric state is unique to a particular isotope, providing an unambiguous signature for SNM. This project entails isomer identification and characterization and neutron population studies. This document summarizes activities from its third year - completion of the isomer identification characterization experiments and initialization of the neutron population experiments. The population and decay of the isomeric state in 235U remain elusive, although a number of candidate gamma rays have been identified. In the course of the experiments, a number of fission fragment isomers were populated and measured [Ressler 2010]. The decays from these isomers may also provide a suitable signature for the presence of fissile material. Several measurements were conducted throughout this project. This report focuses on the results of an experiment conducted collaboratively by PNNL, LLNL and LBNL in December 2010 at LBNL. The measurement involved measuring the gamma-rays emitted from an HEU target when bombarded with 11 MeV neutrons. This report discussed the analysis and resulting conclusions from those measurements. There was one strong candidate, at 1204 keV, of an isomeric signature of 235U. The half-life of the state is estimated to be 9.3 {mu}s. The measured time dependence fits the decay time structure very well. Other possible explanations for the 1204-keV state were investigated, but they could not explain the gamma ray. Unfortunately, the relatively limited statistics of the measurement limit, and the lack of understanding of some of the systematic of the experiment, limit

  14. 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...

  15. Vibronic Spectroscopy of a Structural Isomer of Quinoline: -

    NASA Astrophysics Data System (ADS)

    Mehta-Hurt, Deepali N.; Korn, Joseph A.; Zwier, Timothy S.

    2013-06-01

    This talk will present results of a gas phase, jet-cooled vibronic spectroscopy study of (Z)-phenylvinylnitrile ((Z)-C_6H_5-CH=CH-C=N, (Z)-PVN). With a substituent locked into a cis conformation with respect to the aromatic ring, (Z)-PVN is postulated to be a molecule with an ideal functionality to isomerize to quinoline upon photoexcitation. As such, (Z)-PVN is particularly relevant to Titan's nitrile-containing atmosphere, where much of the chemistry is photochemically driven. As a first step towards such photochemical studies, a fluorescence excitation spectrum of a mixture of (E)- and (Z)-PVN was collected spanning the range 33,300-35,580 cm^{-1} (300.0-281.0 nm). Previous investigations in the Zwier group pertaining to the vibronic spectroscopy of (E)-PVN allowed for the identification of peaks in the (E)- and (Z)-PVN composite spectrum that were solely due to (Z)-PVN, and the S_0-S_1 origin of (Z)-PVN was identified as a dominant band that occurs at 33,706 cm^{-1}. For additional confirmation, ultraviolet depletion spectroscopy (UVD) was used to obtain an isomer specific spectrum of (Z)-PVN as well as search for non-radiative transitions. Dispersed fluorescence spectra that characterize the vibronic activity have also been acquired. A comparison between the vibronic spectroscopy of (Z)-PVN with both (E)-PVN and (Z)-phenylvinylacetylene ((Z)-PVA), the hydrocarbon analog of (Z)-PVN, will be made in this talk.

  16. Precursor anion states in dissociative electron attachment to chlorophenol isomers.

    PubMed

    Kossoski, F; Varella, M T do N

    2016-07-28

    We report a theoretical study on low-energy (<10 eV) elastic electron scattering from chlorophenol isomers, namely, para-chlorophenol (pCP), meta-chlorophenol (mCP), and ortho-chlorophenol (oCP). The calculations were performed with the Schwinger multichannel method with pseudopotentials, and analysis of the computed integral cross sections and virtual orbitals revealed one σCCl (∗), one σOH (∗), and three π(∗) shape resonances. We show that electron capture into the two lower lying π(∗) orbitals initiates dissociative processes that lead to the elimination of the chloride ion, accounting for the two overlapping peaks where this fragment was observed. Despite the relatively small differences on the energetics of the π(∗) resonances, a major isomeric effect was found on their corresponding autodetachment lifetimes, which accounts for the observed increasing cross sections in the progression pCP < mCP < oCP. In particular, dissociation from the π1 (∗) anion of pCP is largely suppressed because of the unfavorable mixing with the σCCl (∗) state. We found the intramolecular hydrogen bond present in oCP to have the opposite effects of stabilizing the σCCl (∗) resonance and destabilizing the σOH (∗) resonance. We also suggest that the hydrogen abstraction observed in chlorophenols and phenol actually takes place by a mechanism in which the incoming electron is directly attached to the dissociative σOH (∗) orbital. PMID:27475364

  17. 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). PMID:16478264

  18. WAViS server for handling, visualization and presentation of multiple alignments of nucleotide or amino acids sequences.

    PubMed

    Zika, Radek; Paces, Jan; Pavlícek, Adam; Paces, Václav

    2004-07-01

    Web Alignment Visualization Server contains a set of web-tools designed for quick generation of publication-quality color figures of multiple alignments of nucleotide or amino acids sequences. It can be used for identification of conserved regions and gaps within many sequences using only common web browsers. The server is accessible at http://wavis.img.cas.cz.

  19. Preliminary Results: Release Of Metals From Acid-Mine Drainage Contaminated Streambed Sediments Under Anaerobic Conditions (Presentation)

    EPA Science Inventory

    Many miles of streams in the western U.S. are contaminated with acid-mine drainage (AMD) from abandoned metal mines. Treatment of these streams may include removal of the existing sediments, with subsequent burial (e.g., in a repository). Burial of previously aerobic sediments ma...

  20. Unexpected Changes in the Population of Coordination Isomers for the Lanthanide Ion Complexes of DOTMA-Tetraglycinate.

    PubMed

    Kumas, Cemile; Fernando, W Shirangi; Zhao, Piyu; Regueiro-Figueroa, Martín; Kiefer, Garry E; Martins, André F; Platas-Iglesias, Carlos; Sherry, A Dean

    2016-09-19

    Lanthanide complexes with DOTA-tetraglycinate (DOTA-(gly)4) heavily favor the square antiprismatic (SAP) coordination isomer in aqueous solution, a structural feature that has made them useful as water-based paraCEST agents. In an effort to create amide-based paraCEST agents with rapid water exchange rates, we prepared the analogous tetraglycinate complexes with DOTMA, a ligand known to favor the twisted square antiprismatic (TSAP) coordination structures. Unexpectedly, NMR investigations show that the LnDOTMA-(gly)4 complexes, like the LnDOTA-(gly)4 complexes, also favor the SAP isomers in solution. This observation led to density functional theory (DFT) calculations in order to identify the energy terms that favor the SAP structures in lanthanide complexes formed with macrocyclic DOTA- and DOTMA-tetraamide ligands. The DFT calculations revealed that, regardless the nature of the ligand, the TSAP isomers present more negative hydration energies than the SAP counterparts. The extent to which the TSAP isomer is stabilized varies, however, depending on the ligand structure, resulting in different isomeric populations in solution. PMID:27603690

  1. 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...

  2. Isomer-specific biodegradation of nonylphenol in an activated sludge bioreactor and structure-biodegradability relationship.

    PubMed

    Lu, Zhijiang; Reif, Rubén; Gan, Jay

    2015-01-01

    Nonylphenol (NP), one of the priority hazardous substances, is in fact a mixture of numerous isomers. It is inconclusive whether or not biodegradation during wastewater treatment process is isomer-specific, leading to the environmental release of NP in different isomer profiles. In this study, we evaluated the isomer selectivity of 19 NP isomers in a laboratory-scale continuous flow conventional activated sludge bioreactor under various operational conditions. The removal efficiency of NP isomers ranged from 90 to 99%, depending on the operational conditions and isomer structures. Isomer selective biodegradation resulted in the increase of composition of recalcitrant isomers, such as, NP₁₉₃a/b, NP₁₁₀a and NP₁₉₄ in the effluent. Moreover, biodegradability was related to the bulkiness of α-substituents and followed α-dimethyl > α-ethyl-α-methyl > α-methyl-α-n-propyl > α-iso-propyl-α-methyl. Steric effect index, a quantitative descriptor of steric hindrance, was linearly correlated with residues of NP isomers in the effluent (R² = 0.76). Decrease of temperature to 10 °C decreased the overall biodegradability and also enhanced the relative enrichment of recalcitrant isomers. These findings suggest that isomer compositions of NP entering the environment may be different from those in technical mixtures and that isomeric selectivity should be taken into account to better understand the occurrence, fate, and ecological risks of NP.

  3. 40 CFR 180.418 - Cypermethrin and an isomer zeta-cypermethrin; tolerances for residues.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 24 2011-07-01 2011-07-01 false Cypermethrin and an isomer zeta... FOOD Specific Tolerances § 180.418 Cypermethrin and an isomer zeta-cypermethrin; tolerances for... (±))(cis-trans 3-(2,2-dichloroethenyl)-2,2 dimethylcyclopropanecarboxylate and its inactive R-isomers in...

  4. 40 CFR 180.418 - Cypermethrin and an isomer zeta-cypermethrin; tolerances for residues.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Cypermethrin and an isomer zeta... FOOD Specific Tolerances § 180.418 Cypermethrin and an isomer zeta-cypermethrin; tolerances for... (±))(cis-trans 3-(2,2-dichloroethenyl)-2,2 dimethylcyclopropanecarboxylate and its inactive R-isomers in...

  5. 40 CFR 180.418 - Cypermethrin and an isomer zeta-cypermethrin; tolerances for residues.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 25 2012-07-01 2012-07-01 false Cypermethrin and an isomer zeta... FOOD Specific Tolerances § 180.418 Cypermethrin and an isomer zeta-cypermethrin; tolerances for... (±))(cis-trans 3-(2,2-dichloroethenyl)-2,2 dimethylcyclopropanecarboxylate and its inactive R-isomers in...

  6. 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...

  7. Isomer-specific biodegradation of nonylphenol in an activated sludge bioreactor and structure-biodegradability relationship.

    PubMed

    Lu, Zhijiang; Reif, Rubén; Gan, Jay

    2015-01-01

    Nonylphenol (NP), one of the priority hazardous substances, is in fact a mixture of numerous isomers. It is inconclusive whether or not biodegradation during wastewater treatment process is isomer-specific, leading to the environmental release of NP in different isomer profiles. In this study, we evaluated the isomer selectivity of 19 NP isomers in a laboratory-scale continuous flow conventional activated sludge bioreactor under various operational conditions. The removal efficiency of NP isomers ranged from 90 to 99%, depending on the operational conditions and isomer structures. Isomer selective biodegradation resulted in the increase of composition of recalcitrant isomers, such as, NP₁₉₃a/b, NP₁₁₀a and NP₁₉₄ in the effluent. Moreover, biodegradability was related to the bulkiness of α-substituents and followed α-dimethyl > α-ethyl-α-methyl > α-methyl-α-n-propyl > α-iso-propyl-α-methyl. Steric effect index, a quantitative descriptor of steric hindrance, was linearly correlated with residues of NP isomers in the effluent (R² = 0.76). Decrease of temperature to 10 °C decreased the overall biodegradability and also enhanced the relative enrichment of recalcitrant isomers. These findings suggest that isomer compositions of NP entering the environment may be different from those in technical mixtures and that isomeric selectivity should be taken into account to better understand the occurrence, fate, and ecological risks of NP. PMID:25462736

  8. Effect of storage and cooking on beta-carotene isomers in carrots ( Daucus carota L. cv. 'Stefano').

    PubMed

    Imsic, Michael; Winkler, Sonja; Tomkins, Bruce; Jones, Rod

    2010-04-28

    Carrots are one of the highest dietary sources of beta-carotene and are naturally high in the (all-E)-beta-carotene isomer, which has higher bioavailability, provitamin A activity, and antioxidant capacity compared to Z (cis) isomers. The objectives of the present study were to investigate the effects of storage temperature, time, and cooking (boiling for 15 min) on the levels of carotene isomers in 'Stefano' carrots. Storing carrots at either 4 degrees C to simulate long-term storage or 20 degrees C to simulate marketing practices resulted in increases in (all-E)-beta-carotene of 20.3% after 3 days at 4 degrees C and 34.4% after 14 days at 20 degrees C, respectively. The levels of Z isomers in raw carrots were low with (13Z)-beta-carotene and (9Z)-beta-carotene accounting for less that 1.8% of the total beta-carotene present. Levels of (9Z)-beta-carotene decreased during storage at either temperature, whereas storage at 4 degrees C resulted in a 109% increase in (13Z)-beta-carotene after 56 days. Cooking significantly increased the levels of (13Z)-beta-carotene and (9Z)-beta-carotene and resulted in the production of (15Z)-beta-carotene, which was absent in raw carrots. Storage at 4 degrees C for 15 days or more prior to cooking reduced the susceptibility of (all-E)-beta-carotene to thermal isomerization during cooking, resulting in lower levels of all three Z-beta-carotene isomers being generated, while storage at 20 degrees C for up to 21 days resulted in significantly higher levels of (all-E)-beta-carotene before and after cooking but had no effect on Z-isomer production during cooking. Consequently, we conclude that, for the greatest health benefit, fresh carrots can be stored for up to 21 days at 20 degrees C or at 4 degrees C for up to 56 days without significant reduction in (all-E)-beta-carotene and should be consumed raw or boiled for less than 15 min to limit Z-beta-carotene isomer formation.

  9. Analysis of positional isomers of hydroxylated aromatic cytokinins by micellar electrokinetic chromatography.

    PubMed

    Ge, Liya; Yong, Jean Wan Hong; Tan, Swee Ngin; Yang, Xin Hao; Ong, Eng Shi

    2005-05-01

    A micellar electrokinetic chromatography (MEKC) method was developed for the separation of six positional isomers of hydroxylated aromatic cytokinins (topolin and topolin riboside), including ortho-topolin, meta-topolin, para-topolin, ortho-topolin riboside, meta-topolin riboside, and para-topolin riboside. Optimum resolution and analysis time (ca. 20 min) for the six aromatic cytokinin standards were achieved with a running buffer at pH 8.0 consisting of 20 mM boric acid, 50 mM sodium dodecyl sulfate (SDS), and 20% v/v methanol. The method has good reproducibility and has been successfully applied to detect the presence of a putative ortho-topolin in coconut water extract sample purified using C(18) and mixed-mode solid-phase extraction (SPE) columns. Other advantages of this MEKC method are short analysis time, low solvent consumption, and separation of positional isomers which could be achieved by a simple aqueous buffer system without the use of expensive chromatographic columns. In addition, a high-performance liquid chromatography (HPLC) method with baseline separation of the six topolin and topolin riboside standards was developed for the confirmation of the endogenous ortho-topolin in coconut water sample. Finally, the presence of ortho-topolin was further confirmed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) based on its characteristic fragmentation pattern. PMID:15800967

  10. A unique enzyme of acetic acid bacteria, PQQ-dependent alcohol dehydrogenase, is also present in Frateuria aurantia.

    PubMed

    Trček, Janja; Matsushita, Kazunobu

    2013-08-01

    A membrane-bound, pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenase (ADH) was purified from Frateuria aurantia LMG 1558(T). Although F. aurantia belongs to a group of γ-Proteobacteria, the characteristics of its PQQ-ADH were similar to the enzyme characteristics of the typical high-acetic acid-resistant bacterium Gluconacetobacter europaeus from the group of α-Proteobacteria. The PQQ-dependent ADH was solubilized from the membranes and purified after anionic, cationic, and affinity chromatography with specific activity of 117 U/mg. The purified enzyme was estimated to be composed of two subunits of ca. 72 and 45 kDa, as judged by SDS-polyacrylamide gel electrophoresis. The purified enzyme had maximum activity at pH 4.5 and showed the highest substrate specificity to ethanol, isoamyl alcohol, 1-butanol, and 1-propanol. The deduced sequences of cloned genes adhA and adhB encoding subunits I and II of PQQ-ADH showed 80 % amino acid (AA) identity to AdhA and 68 % AA identity to AdhB of Ga. europaeus V3 (LMG 18494). Because of the high similarity between genes encoding subunits I and II of PQQ-ADH and its homologous genes found in a distantly related taxonomic group of acetic acid bacteria, the results suggest the possibility of horizontal gene transfer between these two groups of genera.

  11. Double Bond Position Plays an Important Role in Delta-9 Desaturation and Lipogenic Properties of Trans 18:1 Isomers in Mouse Adipocytes.

    PubMed

    Vahmani, P; Meadus, W J; Mapiye, C; Duff, P; Rolland, D C; Dugan, M E R

    2015-12-01

    The objective of this research was to study the delta-9 desaturation of individual trans (t) fatty acids that can be found in ruminant fat or partially hydrogenated vegetable oils (PHVO) and determine their effects on lipogenic gene expression in adipocytes. It was hypothesized that delta-9 desaturation and lipogenic properties of t-18:1 isomers depend on the position of double bond. Differentiated 3T3-L1 adipocytes were treated with 200 µM of t6-18:1, t9-18:1, t11-18:1, t13-18:1 or t16-18:1, cis (c)-9 18:1 or bovine serum albumin (BSA) vehicle control for 48 h. Cells were then harvested for fatty acid and gene expression analyses using gas chromatography and quantitative PCR respectively. Among t-18:1 isomers, t13-18:1 and t11-8:1 had the greatest percent delta-9 desaturation (44 and 41 % respectively) followed by t16-18:1 and t6-18:1 (32 and 17 % respectively), while c9-18:1 and t9-18:1 did not undergo delta-9 desaturation. Trans9-18:1 up-regulated (P < 0.05) the expression of lipogenic genes including fatty acid synthase and stearoyl-CoA desaturase-1 (P < 0.05), whereas the expression of these genes were not affected with other t-18:1 isomers (P > 0.05). Consistent with gene expression results, t9-18:1 increased the de novo lipogenic index (16:0/18:2n-6) compared with control cells and increased delta-9 desaturation index (c9-16:1/18:0) compared to other t-18:1 isomers (P < 0.05). The current study provides further evidence that the predominant trans fatty acid in PHVO (t9-18:1) has isomer specific lipogenic properties. PMID:26476931

  12. Double Bond Position Plays an Important Role in Delta-9 Desaturation and Lipogenic Properties of Trans 18:1 Isomers in Mouse Adipocytes.

    PubMed

    Vahmani, P; Meadus, W J; Mapiye, C; Duff, P; Rolland, D C; Dugan, M E R

    2015-12-01

    The objective of this research was to study the delta-9 desaturation of individual trans (t) fatty acids that can be found in ruminant fat or partially hydrogenated vegetable oils (PHVO) and determine their effects on lipogenic gene expression in adipocytes. It was hypothesized that delta-9 desaturation and lipogenic properties of t-18:1 isomers depend on the position of double bond. Differentiated 3T3-L1 adipocytes were treated with 200 µM of t6-18:1, t9-18:1, t11-18:1, t13-18:1 or t16-18:1, cis (c)-9 18:1 or bovine serum albumin (BSA) vehicle control for 48 h. Cells were then harvested for fatty acid and gene expression analyses using gas chromatography and quantitative PCR respectively. Among t-18:1 isomers, t13-18:1 and t11-8:1 had the greatest percent delta-9 desaturation (44 and 41 % respectively) followed by t16-18:1 and t6-18:1 (32 and 17 % respectively), while c9-18:1 and t9-18:1 did not undergo delta-9 desaturation. Trans9-18:1 up-regulated (P < 0.05) the expression of lipogenic genes including fatty acid synthase and stearoyl-CoA desaturase-1 (P < 0.05), whereas the expression of these genes were not affected with other t-18:1 isomers (P > 0.05). Consistent with gene expression results, t9-18:1 increased the de novo lipogenic index (16:0/18:2n-6) compared with control cells and increased delta-9 desaturation index (c9-16:1/18:0) compared to other t-18:1 isomers (P < 0.05). The current study provides further evidence that the predominant trans fatty acid in PHVO (t9-18:1) has isomer specific lipogenic properties.

  13. Comparative effects of phenylenebis(methylene)selenocyanate isomers on xenobiotic metabolizing enzymes in organs of female CD rats.

    PubMed

    Sohn, O S; Fiala, E S; Upadhyaya, P; Chae, Y H; El-Bayoumy, K

    1999-04-01

    present study demonstrates that individual XSC isomers are capable of modulating specific phase I and/or phase II enzymes involved in the activation and/or detoxification of chemical carcinogens, and provides some mechanistic basis for the cancer chemopreventive efficacy of these organoselenium compounds at the stage of tumor initiation.

  14. Changes in PCDD/PCDF formation processes during instationary phases of combustor operation--exemplified by the use of Cl4DD isomer patterns.

    PubMed

    Neuer-Etscheidt, K; Orasche, J; Nordsieck, H; Streibel, T; Zimmermann, R; Kettrup, A

    2007-04-01

    In this paper results of various measurement campaigns at different municipal waste incineration (MWI) plants concerning the change of the PCDD/PCDF isomer distribution in the crude gas during transiently impaired combustion conditions are presented. The focus is on the Cl4DD isomer distributions exemplarily for all other homologue groups to demonstrate the change in PCDD/PCDF formation mechanism at transient combustion conditions. Additionally to crude gas samples, at one plant filter and boiler ash were investigated simultaneously to determine if there is any difference in the isomer distribution between the matrices. For the ash from an electrostatic precipitator (ESP ash), the boiler ash and the corresponding crude gas sample, nearly identical changes in the Cl4DD isomer distribution under transient combustion conditions in relation to the normal operation process could be detected. By comparing the Cl4DD isomer distributions from different incineration plants (two municipal waste incinerators and one little incinerator burning wood chips for heating domestic household) under transient combustion conditions, in all cases the 1,3,6,8- and 1,3,7,9-Cl4DD were dominating the isomer distribution, whereas under normal operation other isomers were predominant. Obviously PCDD/PCDF formation mechanisms under transient combustion conditions are independent from the type of incinerator and of the burned fuel, respectively. Data sets were analyzed with respect to the possible reaction mechanism via chlorophenols and a good correlation of 2,4,6-trichlorophenol during the second phase of a start-up process and during a CO experiment was found. To get more detailed information about possible formation mechanisms, at one plant the dependence of the PCDD/PCDF isomer distribution on the different matrices was studied. Separate analysis of fly ash collected at the boiler exit, subsequent gas phase, ESP ash and boiler ash under normal operation conditions showed that, apart from

  15. Calculated yield of isomer depletion due to NEEC for {sup 93m}Mo recoils

    SciTech Connect

    Karamian, S. A.; Carroll, J. J.

    2012-11-15

    In the present work, quantitative calculations were carried out for production and depletion of the {sup 93m}Mo isomer in a relatively simple experiment using {sup 91}Zr beam ions. Such studies could be arranged at existing and operating accelerator facilities, e.g. at GSI or in JINR. The {sup 93m}Mo nuclei produced in a He gas target due to the {sup 4}He({sup 91}Zr, 2n) reaction will recoil into a gas stopper with a high velocity, being then depleted due to NEEC in highly-ionized species.

  16. 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.

  17. 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. PMID:19924899

  18. Positron emission tomographic investigations of central muscarinic cholinergic receptors with three isomers of [76Br]BrQNP.

    PubMed

    Strijckmans, V; Bottlaender, M; Luo, H; Ottaviani, M; McPherson, D W; Loc'h, C; Fuseau, C; Knapp, F F; Mazière, B

    1997-05-01

    We studied the potential of three radiobrominated isomers of BrQNP, (Z(-,-)-[76Br]BrQNP, E(-,-)-[76Br]BrQNP and E(-,+)-[76Br]BrQNP), as suitable radioligands for imaging of central muscarinic cholinergic receptors in the human brain. These radioligands were stereospecifically prepared by electrophilic radiobromodestannylation of the respective tributylstannyl precursors using no-carrier-added [76Br]BrNH4 and peracetic acid. Preliminary pharmacological characterizations were determined by biodistribution, autoradiography, competition, displacement and metabolite studies in rats. The (-,-)-configuration presented important specific uptakes in brain muscarinic cholinergic receptor (mAChR)-rich structures and in heart, low metabolization rates and an apparent M2 selectivity. The (-,+)-configuration revealed more rapid clearance, lower uptake, a higher metabolization rate and an apparent M1 selectivity. Reversibility of the binding was confirmed for the three radiotracers. Positron emission tomography in the living baboon brain revealed high and rapid uptake in the brain and accumulation in the mAChR-rich structures studied. At 30 min p.i., the E(-,-)-radiotracer reached a plateau in cortex, pons and thalamus with concentrations of 29%, 24% and 19% ID/l, respectively. Z(-,-)-[76Br]BrQNP also accumulated in these structures, reaching a maximal uptake (27% ID/l) in the cortex 2 h p.i. At 5 min p.i. a plateau (17% ID/l) was only observed in the cortex for the E(-, +)-[76Br]BrQNP; by contrast, the other structures showed slow washout. After 3 weeks, the (-,-)-radiotracers were studied in the same baboon pretreated with dexetimide (1 mg/kg), a well-known muscarinic antagonist. In all the mAChR structures, the highly reduced uptake observed after this preloading step indicates that these radiotracers specifically bind to muscarinic receptors. Z(-, -)-[76Br]BrQNP, which is displaced in higher amounts from M2 mAChR-enriched structures, reveals an M2 affinity. The two isomers

  19. Cis and Trans Isomers of Cycloalkenes

    ERIC Educational Resources Information Center

    Barrows, Susan E.; Eberlein, Thomas H.

    2005-01-01

    A study investigates the strain in medium-sized cycloalkenes and the geometric and electronic distortions through which alkenes can relieve that strain. Literature data is summarized and results are presented with the aim of providing a concise reference for those interested in addressing the topic in an introductory organic chemistry curriculum.

  20. 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.

  1. Olfaction Presentation System Using Odor Scanner and Odor-Emitting Apparatus Coupled with Chemical Capsules of Alginic Acid Polymer

    NASA Astrophysics Data System (ADS)

    Sakairi, Minoru; Nishimura, Ayako; Suzuki, Daisuke

    For the purpose of the application of odor to information technology, we have developed an odor-emitting apparatus coupled with chemical capsules made of alginic acid polymer. This apparatus consists of a chemical capsule cartridge including chemical capsules of odor ingredients, valves to control odor emission, and a temperature control unit. Different odors can be easily emitted by using the apparatus. We have developed an integrated system of vision, audio and olfactory information in which odor strength can be controlled coinciding with on-screen moving images based on analytical results from the odor scanner.

  2. Characterization of geometric isomers of Norbornene end-capped imides

    NASA Technical Reports Server (NTRS)

    Young, P. R.; Chang, A. C.

    1983-01-01

    Three geometric isomers from the thermal isomerization of methylene-4,4' bis(endo-N-phenylbicyclo/2.2.1/hept-2-ene-5,6-di carboximide) (I) were chromatographically separated and isolated in order to investigate the thermal cure of norbornene end-capped imide oligomers, which display considerable promise for use in various aerospace adhesive and composite applications. Endo-endo (I), endo-exo (II), and exo-exo (III) configurations were assigned to each compound based on the results of NMR spectroscopy. Several chromatographic, spectroscopic, and thermal techniques were then used to characterize these three isomers which serve as model compounds for norbornene end-capped polyimides. It was found that each compound thermally isomerized to an equilibrium mixture of all three compounds prior to cure. It is proposed that these compounds react by different mechanisms in air and nitrogen.

  3. Spectroscopic studies of the several isomers of UO3

    NASA Astrophysics Data System (ADS)

    Sweet, Lucas E.; Reilly, Dallas D.; Abrecht, David G.; Buck, Edgar C.; Meier, David E.; Su, Yin-Fong; Brauer, Carolyn S.; Schwantes, Jon M.; Tonkyn, Russell G.; Szecsody, James E.; Blake, Thomas A.; Johnson, Timothy J.

    2013-10-01

    Uranium trioxide is known to adopt seven different structural forms. While these structural forms have been well characterized using x-ray or neutron diffraction techniques, little work has been done to characterize their spectroscopic properties, particularly of the pure phases. Since the structural isomers of UO3 all have similar thermodynamic stabilities and most tend to hydrolyze under open atmospheric conditions, mixtures of UO3 phases and the hydrolysis products are common. Much effort went into isolating pure phases of UO3. Utilizing x-ray diffraction as a sample identification check, UV/Vis/NIR spectroscopic signatures of α-UO3, β-UO3, γ-UO3 and α-UO2(OH)2 products were obtained. The spectra of the pure phases can now be used to characterize typical samples of UO3, which are often mixtures of isomers.

  4. Spectroscopic Studies of the Several Isomers of UO3

    SciTech Connect

    Sweet, Lucas E.; Reilly, Dallas D.; Abrecht, David G.; Buck, Edgar C.; Meier, David E.; Su, Yin-Fong; Brauer, Carolyn S.; Schwantes, Jon M.; Tonkyn, Russell G.; Szecsody, James E.; Blake, Thomas A.; Johnson, Timothy J.

    2013-09-26

    Uranium trioxide is known to adopt seven different structural forms. While these structural forms have been well characterized using x-ray or neutron diffraction techniques, little work has been done to characterize their spectroscopic properties, particularly of the pure phases. Since the structural isomers of UO3 all have similar thermodynamic stabilities and most tend to hydrolyze under open atmospheric conditions, mixtures of UO3 phases and the hydrolysis products are common. Much effort went into isolating pure phases of UO3. Utilizing x-ray diffraction as a sample identification check, UV/Vis/NIR spectroscopic signatures of α-UO3, β-UO3, γ-UO3 and UO2(OH)2 products were obtained. The spectra of the pure phases can now be used to characterize typical samples of UO3, which are often mixtures of isomers.

  5. [Beaded molecule imprinted polymer for stereo isomer separation].

    PubMed

    Meng, Z; Wang, J; Zhou, L; Wang, Q; Zhu, D

    1999-07-01

    Beaded molecule imprinted polymer (MIP) was made by suspension polymerization. Particles with the size of 50-70 microns in diameter were collected and evaluated in HPLC mode to separate stereo isomers. Stereo isomers cinchonine and cinchonidine were successfully discriminated with selectivity factor of 2.89 and resolution factor of 0.76. Stereo selectivity of the MIP was found to come from both the interaction between the analyte and carboxyl group on the MIP and the similarity between the stereo structure of imprinted molecule and the MIP. The thermal analysis results showed that the MIP had high thermal stability with initial thermal decomposition temperature of 320 degrees C. The pore volume of the MIP was 0.1849 mL/g, the specific surface area was 126.84 sqm/g and the average pore diameter was 5.8 nanometer. Scanning electron microscopy showed that MIP had perfect spherical morphology.

  6. Mobilities of Li(+)-attached butanol isomers in He gas.

    PubMed

    Takahashi, K; Saito, K; Koizumi, T; Matoba, S; Kojima, T M; Tanuma, H; Shiromaru, H

    2013-08-28

    Mobilities of Li(+)-attached butanol isomers, (n-BuOH)Li(+), (s-BuOH)Li(+), (i-BuOH)Li(+), and (t-BuOH)Li(+), in helium gas were measured over a range of reduced electric fields (E/N = 25-96 Td) at room temperature. Arrival time measurements accurately identified small differences in the measured mobilities of the isomer ions. At low E/N (≤30 Td, corresponding to a mean collision energy ε≤0.05 eV), (n-BuOH)Li(+) showed a mobility about 1.5% greater than that of the other ions, but at high E/N (≥75 Td, ε≥0.1 eV) its mobility was about 1.1% less.

  7. Density Functional Exploration of C4H3N Isomers.

    PubMed

    Custer, Thomas; Szczepaniak, Urszula; Gronowski, Marcin; Fabisiewicz, Emilia; Couturier-Tamburelli, Isabelle; Kołos, Robert

    2016-07-28

    Molecules having C4H3N stoichiometry are of astrophysical interest. Two of these, methylcyanoacetylene (CH3C3N) and its structural isomer allenyl cyanide (H2CCCHN), have been observed in interstellar space, while several more have been examined in laboratories. Here we describe, for a broad range of C4H3N isomers, density functional calculations (B3LYP/aug-cc-pVTZ) of molecular parameters including the energetics, geometries, rotational constants, electric dipole moments, polarizabilities, vibrational IR frequencies, IR absorption intensities, and Raman activities. Singlet-triplet splittings as well as singlet vertical electronic excitation energies are given for selected species. The identification of less stable C4H3N molecules, generated in ongoing spectroscopic experiments, relies heavily on these quantum chemical predictions. PMID:27341606

  8. Positional isomer differentiation of synthetic cannabinoid JWH-081 by GC-MS/MS.

    PubMed

    Kusano, Maiko; Zaitsu, Kei; Nakayama, Hiroshi; Nakajima, Junichi; Hisatsune, Kazuaki; Moriyasu, Takako; Matsuta, Shuntaro; Katagi, Munehiro; Tsuchihashi, Hitoshi; Ishii, Akira

    2015-03-01

    Like many new designer drugs of abuse, synthetic cannabinoids (SC) have structural or positional isomers which may or may not all be regulated under law. Differences in acute toxicity may exist between isomers which impose further burden in the fields of forensic toxicology, medicine and legislation. Isomer differentiation therefore becomes crucial from these standpoints as new designer drugs continuously emerge with just minor positional modifications to their preexisting analogs. The aim of this study was to differentiate the positional isomers of JWH-081. Purchased standard compounds of JWH-081 and its positional isomers were analyzed by gas chromatography-electron ionization-mass spectrometry (GC-EI-MS) first in scan mode to investigate those isomers who could be differentiated by EI scan spectra. Isomers with identical or near-identical EI spectra were further subjected to GC-tandem mass spectrometry (MS/MS) analysis with appropriate precursor ions. EI scan was able to distinguish 3 of the 7 isomers: 2-methoxy, 7-methoxy and 8-methoxy. The remaining isomers exhibited near-identical spectra; hence, MS/MS was performed by selecting m/z 185 and 157 as precursor ions. 3-Methoxy and 5-methoxy isomers produced characteristic product ions that enabled the differentiation between them. Product ion spectrum of 6-methoxy isomer resembled that of JWH-081; however, the relative ion intensities were clearly different from one another. The combination of EI scan and MS/MS allowed for the regioisomeric differentiation of the targeted compounds in this study.

  9. Condensations of single DNA molecules induced by heptaplatin and its chiral isomer

    SciTech Connect

    Zhang, Hong-Yan; Liu, Yu-Ru; Li, Wei; Li, Hui; Dou, Shuo-Xing; Xie, Ping; Wang, Wei-Chi; Wang, Peng-Ye

    2014-08-15

    Heptaplatin is a third-generation platinum antitumor drug. It has a chiral isomer. We studied the interactions between the two isomers and DNA by using magnetic tweezers and atomic force microscopy (AFM) to investigate the effect of chiralities of the isomers on the interactions. We found that the extension curves and average condensation rates of DNA molecules incubated with heptaplatin were nearly the same as those incubated with its chiral isomer. In addition, the structures of DNA molecules incubated with heptaplatin were also similar to those incubated with its chiral isomer. These results indicate the difference in chirality of the two isomers does not induce different interactions of the isomers with DNA. Our study may facilitate the understanding of interactions of platinum complexes with DNA and the design of new antitumor platinum complexes.

  10. Characterization and performance of short cationic antimicrobial peptide isomers.

    PubMed

    Juba, Melanie; Porter, Devin; Dean, Scott; Gillmor, Susan; Bishop, Barney

    2013-07-01

    Cationic antimicrobial peptides (CAMPs) represent an ancient defense mechanism against invading bacteria, with peptides such as the cathelicidins being essential elements of vertebrate innate immunity. CAMPs are typically associated with broad-spectrum antimicrobial potency and limited bacterial resistance. The cathelicidin identified from the elapid snake Naja atra (NA-CATH) contains a semi-conserved repeated 11-residue motif (ATRA motif) with a sequence pattern consistent with formation of an amphipathic helical conformation. Short peptide amides (ATRA-1, -1A, -1P, and -2) generated based on the pair of ATRA motifs in NA-CATH exhibited varied antimicrobial potencies. The small size of the ATRA peptides, coupled with their varied antimicrobial performances, make them interesting models to study the impact various physico-chemical properties have on antimicrobial performance in helical CAMPs. Accordingly, the D- and L-enantiomers of the peptide ATRA-1A, which in earlier studies had shown both good antimicrobial performance and strong helical character, were investigated in order to assess the impact peptide stereochemistry has on antimicrobial performance and interaction with chiral membranes. The ATRA-1A isomers exhibit varied potencies against four bacterial strains, and their conformational properties in the presence of mixed zwitterionic/anionic liposomes are influenced by anionic lipid content. These studies reveal subtle differences in the properties of the peptide isomers. Differences are also seen in the abilities of the ATRA-1A isomers to induce liposome fusion/aggregation, bilayer rearrangement and lysing through turbidity studies and fluorescence microscopy. The similarities and differences in the properties of the ATRA-1A isomers could aid in efforts to develop D-peptide-based therapeutics using high-performing L-peptides as templates.

  11. Thermodynamics of finite magnetic two-isomer systems

    NASA Astrophysics Data System (ADS)

    Borrmann, Peter; Stamerjohanns, Heinrich; Hilf, Eberhard R.; Jund, Philippe; Kim, Seong Gon; Tománek, David

    1999-12-01

    We use Monte Carlo simulations to investigate the thermodynamical behavior of aggregates consisting of few superparamagnetic particles in a colloidal suspension. The potential energy surface of this classical two-isomer system with a stable and a metastable "ring" and "chain" configuration is tunable by an external magnetic field and temperature. We determine the complex "phase diagram" of this system and analyze thermodynamically the nature of the transition between the ring and the chain "phase."

  12. Flame Propagation of Butanol Isomers/Air Mixtures

    SciTech Connect

    Veloo, Peter S.; Egolfopoulos, Fokion N.

    2011-01-01

    An experimental and computational study was conducted on the propagation of flames of saturated butanol isomers. The experiments were performed in the counterflow configuration under atmospheric pressure, unburned mixture temperature of 343 K, and for a wide range of equivalence ratios. The experiments were simulated using a recent kinetic model for the four isomers of butanol. Results indicate that n-butanol/air flames propagate somewhat faster than both sec-butanol/air and iso-butanol/air flames, and that tert-butanol/air flames propagate notably slower compared to the other three isomers. Reaction path analysis of tert-butanol/air flames revealed that iso-butene is a major intermediate, which subsequently reacts to form the resonantly stable iso-butenyl radical retarding thus the overall reactivity of tert-butanol/air flames relatively to the other three isomers. Through sensitivity analysis, it was determined that the mass burning rates of sec-butanol/air and iso-butanol/air flames are sensitive largely to hydrogen, carbon monoxide, and C{sub 1}–C{sub 2} hydrocarbon kinetics and not to fuel-specific reactions similarly to n-butanol/air flames. However, for tert-butanol/air flames notable sensitivity to fuel-specific reactions exists. While the numerical results predicted closely the experimental data for n-butanol/air and sec-butanol/air flames, they overpredicted and underpredicted the laminar flame speeds for iso-butanol/air and tert-butanol/air flames respectively. It was demonstrated further that the underprediction of the laminar flame speeds of tert-butanol/air flames by the model was most likely due to deficiencies of the C{sub 4}-alkene kinetics.

  13. 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.

  14. 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.

  15. Influence on Levels of Information as Presented by Different Technologies on Students' Understanding of Acid, Base, and pH Concepts.

    ERIC Educational Resources Information Center

    Nakhleh, Mary B.; Krajcik, Joseph S.

    1994-01-01

    Involves secondary students in a study designed to allow investigation into how different levels of information presented by various technologies (chemical indicators, pH meters, and microcomputer-based laboratories-MBLs) affected students' understanding of acid, base, and pH concepts. Results showed that students using MBLs exhibited a greater…

  16. Distribution of Polyunsaturated Fatty Acids in Bacteria Present in Intestines of Deep-Sea Fish and Shallow-Sea Poikilothermic Animals

    PubMed Central

    Yano, Y.; Nakayama, A.; Yoshida, K.

    1997-01-01

    The lipid and fatty acid compositions in nine obligate and facultative barophilic bacteria isolated from the intestinal contents of seven deep-sea fish were determined. Phospholipid compositions were simple, with phosphatidylethanolamine and phosphatidylglycerol predominating in all strains. Docosahexaenoic acid (DHA; 22:6n-3), which has not been reported in procaryotes except for deep-sea bacteria, was found to be present in eight strains at a level of 8.1 to 21.5% of total fatty acids. In the other strain, eicosapentaenoic acid (EPA; 20:5n-3) was present at a level of 31.5% of total fatty acids. Other fatty acids observed in all strains were typical of marine gram-negative bacteria. Subcultures from pouches prepared from intestinal contents of five deep-sea fish by the most-probable-number (MPN) method were analyzed for fatty acids, and all subcultures contained DHA and/or EPA. Accordingly, viable cell counts of bacteria containing DHA and EPA were estimated at a maximum of 1.3 x 10(sup8) and 2.4 x 10(sup8) cells per ml, respectively, and accounted for 14 and 30%, respectively, of the total cell counts in the intestinal contents of the deep-sea fish. In the case of 10 shallow-sea poikilothermic animals having bacterial populations of 1.1 x 10(sup6) to 1.9 x 10(sup9) CFU per ml in intestinal contents, no DHA was found in the 112 isolates examined, while production of EPA was found in 40 isolates from cold- and temperate-sea samples. These results suggest that DHA and EPA are involved in some adaptations of bacteria to low temperature and high pressure. PMID:16535638

  17. 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.

  18. A Rapid Compression Machine Modelling Study of the Heptane Isomers

    SciTech Connect

    Silke, E J; Curran, H J; Simmie, J M; Pitz, W J; Westbrook, C K

    2005-05-10

    Previously we have reported on the combustion behavior of all nine isomers of heptane in a rapid compression machine (RCM) with stoichiometric fuel and ''air'' mixtures at a compressed gas pressure of 15 atm. The dependence of autoignition delay times on molecular structure was illustrated. Here, we report some additional experimental work that was performed in order to address unusual results regarding significant differences in the ignition delay times recorded at the same fuel and oxygen composition, but with different fractions of nitrogen and argon diluent gases. Moreover, we have begun to simulate these experiments with detailed chemical kinetic mechanisms. These mechanisms are based on previous studies of other alkane molecules, in particular, n-heptane and iso-octane. We have focused our attention on n-heptane in order to systematically redevelop the chemistry and thermochemistry for this C{sub 7} isomer with the intention of extending our greater knowledge gained to the other eight isomers. The addition of new reaction types, that were not included previously, has had a significant impact on the simulations, particularly at low temperatures.

  19. On the Ionization Energies of C4H3 Isomers

    SciTech Connect

    Kaiser, Ralf I.; Mebel, Alexander; Kostko, Oleg; Ahmed, Musahid

    2009-09-16

    We have conducted a combined experimental and theoretical study on the formation of distinct isomers of resonantly stabilized free radicals, C4H3, which are important intermediates in the formation of polycyclic aromatic hydrocarbons in combustion flames and possibly in the interstellar medium. Our study utilized laser ablation of graphite in combination with seeding the ablated species in neat methylacetylene gas which also acted as a reagent. Photoionization efficiency (PIE) curves were recorded of the C4H3 isomers at the Advanced Light Source from 8.0 to 10.3 eV. The experimental PIE curve was compared with theoretical ones suggesting the formation of four C4H3 radicals: two acyclic structures i-C4H3 [1] and E/Z-n-C4H3 [2E/2Z]and two cyclic isomers 3 and 4. These molecules are likely formed via an initial addition of ground state carbon atoms to the carbon-carbon triple bond of the methylacetylene molecule followed by isomerization via hydrogen migrations and ring opening and emission of atomic hydrogen from these intermediates.

  20. Synthesis of lucifensin by native chemical ligation and characteristics of its isomer having different disulfide bridge pattern.

    PubMed

    Stanchev, Stancho; Zawada, Zbigniew; Monincová, Lenka; Bednárová, Lucie; Slaninová, Jiřina; Fučík, Vladimír; Čeřovský, Václav

    2014-09-01

    The antimicrobial 40-amino-acid-peptide lucifensin was synthesized by native chemical ligation (NCL) using N-acylbenzimidazolinone (Nbz) as a linker group. NCL is a method in which a peptide bond between two discreet peptide chains is created. This method has been applied to the synthesis of long peptides and proteins when solid-phase synthesis is imcompatible. Two models of ligation were developed: [15+25] Ala-Cys and [19+21] His-Cys. The [19+21] His-Cys method gives lower yield because of the lower stability of 18-peptide-His-Nbz-CONH2 peptide, as suggested by density functional theory calculation. Acetamidomethyl-deprotection and subsequent oxidation of the ligated linear lucifensin gave a mixture of lucifensin isomers, which differed in the location of their disulfide bridges only. The dominant isomer showed unnatural pairing of cysteines [C1-6], [C3-5], and [C2-4], which limits its ability to form α-helical structure. The activity of isomeric lucifensin toward Bacillus subtilis, Staphylococcus aureus, and Micrococcus luteus was lower than that of the natural lucifensin. The desired product native lucifensin was prepared from this isomer using a one-pot reduction with dithiotreitol and subsequent air oxidation in slightly alkaline medium.

  1. 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

  2. Isolation and characterization of an amino acid-selective channel protein present in the chloroplastic outer envelope membrane

    PubMed Central

    Pohlmeyer, Kai; Soll, Jürgen; Steinkamp, Thomas; Hinnah, Silke; Wagner, Richard

    1997-01-01

    The reconstituted pea chloroplastic outer envelope protein of 16 kDa (OEP16) forms a slightly cation-selective, high-conductance channel with a conductance of Λ = 1,2 nS (in 1 M KCl). The open probability of OEP16 channel is highest at 0 mV (Popen = 0.8), decreasing exponentially with higher potentials. Transport studies using reconstituted recombinant OEP16 protein show that the OEP16 channel is selective for amino acids but excludes triosephosphates or uncharged sugars. Crosslinking indicates that OEP16 forms a homodimer in the membrane. According to its primary sequence and predicted secondary structure, OEP16 shows neither sequence nor structural homologies to classical porins. The results indicate that the intermembrane space between the two envelope membranes might not be as freely accessible as previously thought. PMID:9256512

  3. Selectivity issues in targeted metabolomics: Separation of phosphorylated carbohydrate isomers by mixed-mode hydrophilic interaction/weak anion exchange chromatography.

    PubMed

    Hinterwirth, Helmut; Lämmerhofer, Michael; Preinerstorfer, Beatrix; Gargano, Andrea; Reischl, Roland; Bicker, Wolfgang; Trapp, Oliver; Brecker, Lothar; Lindner, Wolfgang

    2010-11-01

    Phosphorylated carbohydrates are important intracellular metabolites and thus of prime interest in metabolomics research. Complications in their analysis arise from the existence of structural isomers that do have similar fragmentation patterns in MS/MS and are hard to resolve chromatographically. Herein, we present selective methods for the liquid chromatographic separation of sugar phosphates, such as hexose and pentose phosphates, 2- and 3-phosphoglycerate, dihydroxyacetone phosphate and glyceraldehyde 3-phosphate, as well as glucosamine 1- and 6-phosphate utilizing mixed-mode chromatography with reversed-phase/weak anion-exchangers and a charged aerosol detector. The best results were obtained when the reversed-phase/weak anion-exchanger column was operated under hydrophilic interaction liquid chromatography elution conditions. The effects of various chromatographic parameters were examined and are discussed on the basis of a simple stoichiometric displacement model for explaining ion-exchange processes. Employed acidic conditions have led to the complete separation of α- and β-anomers of glucose 6-phosphate at low temperature. The anomers coeluted in a single peak at elevated temperatures (>40°C) (peak coalescence), while at intermediate temperatures on-column interconversion with a plateau in-between resolved anomer peaks was observed with apparent reaction rate constants between 0.1 and 27.8×10(-4) s(-1). Dynamic HPLC under specified conditions enabled to investigate mutarotation of phosphorylated carbohydrates, their interconversion kinetics, and energy barriers for interconversion. A complex mixture of six hexose phosphate structural isomers could be resolved almost completely.

  4. Cyclic Versus Linear Isomers Produced by Reaction of the Methylidyne Radical (CH) with Small Unsaturated Hydrocarbons

    SciTech Connect

    Goulay, Fabien; Trevitt, Adam J.; Meloni, Giovanni; Selby, Talitha M.; Osborn, David L.; Taatjes, Craig A.; Vereecken, Luc; Leone, Stephen R.

    2008-12-05

    The reactions of the methylidyne radical (CH) with ethylene, acetylene, allene, and methylacetylene are studied at room temperature using tunable vacuum ultraviolet (VUV) photoionization and time-resolved mass spectrometry. The CH radicals are prepared by 248 nm multiphoton photolysis of CHBr3 at 298 K and react with the selected hydrocarbon in a helium gas flow. Analysis of photoionization efficiency versus VUV photon wavelength permits isomer-specific detection of the reaction products and allows estimation of the reaction product branching ratios. The reactions proceed by either CH insertion or addition followed by H atom elimination from the intermediate adduct. In the CH + C2H4 reaction the C3H5 intermediate decays by H atom loss to yield 70(+-8)percent allene, 30(+-8)percent methylacetylene and less than 10percent cyclopropene, in agreement with previous RRKM results. In the CH + acetylene reaction, detection of mainly the cyclic C3H2 isomer is contrary to a previous RRKM calculation that predicted linear triplet propargylene to be 90percent of the total H-atom co-products. High-level CBS-APNO quantum calculations and RRKM calculation for the CH + C2H2 reaction presented in this manuscript predict a higher contribution of the cyclic C3H2 (27.0percent) versus triplet propargylene (63.5percent) than these earlier predictions. Extensive calculations on the C3H3 and C3H2D system combined with experimental isotope ratios for the CD + C2H2 reaction indicate that H-atom assisted isomerization in the present experiments is responsible for the discrepancy between the RRKM calculations and the experimental results. Cyclic isomers are also found to represent 30(+-6)percent of the detected products in the case of CH + methylacetylene, together with 33(+-6)percent 1,2,3-butatriene and 37(+-6)percent vinylacetylene. The CH + allene reaction gives 23(+-5)percent 1,2,3-butatriene and 77(+-5)percent vinylacetylene, whereas cyclic isomers are produced below the detection limit

  5. Influence of Lβ-, Dα- and Dβ-Asp isomers of the Asp-76 residue on the properties of αA-crystallin 70-88 peptide.

    PubMed

    Fujii, Noriko; Fujii, Norihiko; Kida, Masashi; Kinouchi, Tadatoshi

    2010-11-01

    Proteins have been considered to consist exclusively of L-amino acids in living tissues. However, our previous studies showed that two specific aspartyl (Asp) residues in αA- and αB-crystallins from human eye lenses invert to the D-isomers to a high degree during aging. The reaction is also accompanied by isomerization into a form containing β-Asp (isoaspartate) residues. The appearance of D- and β-Asp in a protein potentially induces large changes to the higher order structure of the protein as well as to its function. However, it remains unclear whether the formation of the Asp isomer is the direct trigger of the change to the higher order structure and function. In this study, in order to clarify the effect of the inversion to D-isomers in a protein, we synthesized peptides corresponding to the 70-88 (KFVIFLDVKHFSPEDLTVK) fragment of human αA-crystallin and its corresponding diastereoisomers in which Lα-Asp was replaced with Lβ-Asp, Dα-Asp, and Dβ-Asp at position 76 and compared their biochemical properties with that of normal peptide. The peptides containing abnormal isomers (Lβ-Asp, Dα-Asp, and Dβ-Asp residues, respectively) were more hydrophilic than the normal peptide (containing Lα-Asp), lost β-sheet structure and changed to random structures. The normal peptide promoted the aggregation of insulin while the other three isomers suppressed the aggregation of insulin. This is the first evidence that a single substitution of an Asp isomer in a peptide induces a large change to the properties of the peptide.

  6. Feeding of the 1 1/2- isomers in stable Ir and Au isotopes

    SciTech Connect

    Fotiadis, Nikolaos; Nelson, Ronald O; Devlin, Matthew; Holloway, Shannon T; Kawano, Toshihiko; Talou, Patrick; Chadwick, Mark B; Becker, John A; Garrett, Paul E

    2008-01-01

    Excited states were studied and absolute partial {gamma}-ray cross sections were measured using the ({eta}, {eta}'{gamma}) reaction in {sup 191}Ir, {sup 193}Ir and {sup 197}Au. A Compton-suppressed germanium-detector array (GEANIE) for {gamma}-ray spectroscopy and the broad-spectrum pulsed neutron source of the Los Alamos Neutron Science Center's WNR facility were used for the measurement. The energy of the incident neutrons was determined using the time-of-flight technique. Absolute partial {gamma}-ray cross sections were measured up to incident neutron energy of 20 MeV for several transitions feeding directly the 1 1/2- isomers and ground states in {sup 191}Ir, {sup 193}Ir and {sup 197}Au. The feeding of the 1 1/2- isomers, which originate from the odd proton occupying the h{sub 1 1/2} orbital, was found for the three targets to be very similar and increasing relative to the feeding of the corresponding ground state with increasing neutron energy up to E{sub n} {approx} 10 MeV. Above this neutron energy the opening of the (n, 2{sub n}) reaction channel strongly affects the population of the isomers and leads to a decrease of their relative population compared to the population of the ground states. The experimental results are compared with theoretical predictions from the GNASH reaction model calculation implementing a version of the spin distribution for the pre-equilibrium reaction piece with either a compound nucleus spin distribution (CN-GNASH) or a Feshbach-Kerman-Koonin (FKK-GNASH) quantum mechanical spin distribution. The effects of the spin cutoff parameter values on the population of states are examined. Evidence is presented that FKK-GNASH provides a description of the experimental data that mitigates the need for adjustment of the level density parameter to fit the data.

  7. Supplementation with CLA: isomer incorporation into serum lipids and effect on body fat of women.

    PubMed

    Petridou, Anatoli; Mougios, Vassilis; Sagredos, Angelos

    2003-08-01

    Animal studies have suggested that CLA, a natural component of meat and dairy products, may confer beneficial effects on health. However, human studies using supplementation with CLA have produced contradictory results. The aim of the present study was to further investigate the effect of CLA supplementation on human body fat, serum leptin, and serum lipids, as well as the incorporation of CLA isomers into serum lipids classes. Sixteen young healthy nonobese sedentary women received 2.1 g of CLA (divided equally between the cis,trans-9,11 and trans,cis-10,12 isomers) daily for 45 d and placebo for 45 d in a randomized double-blind crossover design. Body fat was estimated (by measurement of skinfold thickness at 10 sites), and blood was sampled at the beginning, middle, and end of the entire intervention period; an additional blood sample was obtained 2 wk thereafter. No significant differences in energy, carbohydrate, lipid, or protein intake existed between the CLA and placebo intake periods. No significant differences were found in body fat or serum leptin, TAG, total cholesterol, HDL-cholesterol, and alanine aminotransferase between CLA and placebo. The CLA isomer content of serum TAG, phospholipids, and total lipids increased 2-5 times with CLA supplementation (P < 0.05). In contrast, the CLA content of cholesteryl esters did not change significantly. The period of 2 wk after the end of CLA supplementation was sufficient for its washout from serum lipids. These data indicate that supplementation with 2.1 g of CLA daily for 45 d increased its levels in blood but had no effect on body composition or the lipidemic profile of nonobese women.

  8. Electric and magnetic properties of the four most stable CHNO isomers from ab initio CCSD(T) studies.

    PubMed

    Mladenović, Mirjana; Elhiyani, Mohamed; Lewerenz, Marius

    2009-07-21

    Electric and magnetic properties obtained from CCSD(T)/(aug-)cc-pCVXZ (X = T, Q, or 5) electronic structure calculations are reported for isocyanic acid, HNCO, cyanic acid, HOCN, fulminic acid, HCNO, and isofulminic acid, HONC, in their ground electronic states. Comparison of the theoretical results with the available experimentally derived values shows very satisfactory agreement. The new data should be helpful for the identification of these molecules due to characteristic hyperfine structure patterns in their microwave spectra. A brief discussion of the electronic structure properties, based on the electric field gradients, Mulliken population analysis of the total electron density, and molecular orbitals, is provided for the four CHNO isomers and the related HCN/HNC system. PMID:19624192

  9. Clinical vampirism. A presentation of 3 cases and a re-evaluation of Haigh, the 'acid-bath murderer'.

    PubMed

    Hemphill, R E; Zabow, T

    1983-02-19

    Clinical vampirism is named after the mythical vampire, and is a recognizable, although rare, clinical entity characterized by periodic compulsive blood-drinking, affinity with the dead and uncertain identity. It is hypothetically the expression of an inherited archaic myth, the act of taking blood being a ritual that gives temporary relief. From ancient times vampirists have given substance to belief in the existence of supernatural vampires. Four vampirists, including Haigh, the 'acid-bath murderer', are described. From childhood they cut themselves, drank their own, exogenous human or animal blood to relieve a craving, dreamed of blood-shed, associated with the dead, and had a changing identity. They were intelligent, with no family mental or social pathology. Some self-cutters are auto-vampirists; females are not likely to assault others for blood, but males are potentially dangerous. Vampirism may be a cause of unpredictable repeated assault and murder, and should be looked for in violent criminals who are self-mutilators. No specific treatment is known.

  10. Association between Human Plasma Chondroitin Sulfate Isomers and Carotid Atherosclerotic Plaques.

    PubMed

    Zinellu, Elisabetta; Lepedda, Antonio Junior; Cigliano, Antonio; Pisanu, Salvatore; Zinellu, Angelo; Carru, Ciriaco; Bacciu, Pietro Paolo; Piredda, Franco; Guarino, Anna; Spirito, Rita; Formato, Marilena

    2012-01-01

    Several studies have evidenced variations in plasma glycosaminoglycans content in physiological and pathological conditions. In normal human plasma GAGs are present mainly as undersulfated chondroitin sulfate (CS). The aim of the present study was to evaluate possible correlations between plasma CS level/structure and the presence/typology of carotid atherosclerotic lesion. Plasma CS was purified from 46 control subjects and 47 patients undergoing carotid endarterectomy showing either a soft or a hard plaque. The concentration and structural characteristics of plasma CS were assessed by capillary electrophoresis of constituent unsaturated fluorophore-labeled disaccharides. Results showed that the concentration of total CS isomers was increased by 21.4% (P < 0.01) in plasma of patients, due to a significant increase of undersulfated CS. Consequently, in patients the plasma CS charge density was significantly reduced with respect to that of controls. After sorting for plaque typology, we found that patients with soft plaques and those with hard ones differently contribute to the observed changes. In plasma from patients with soft plaques, the increase in CS content was not associated with modifications of its sulfation pattern. On the contrary, the presence of hard plaques was associated with CS sulfation pattern modifications in presence of quite normal total CS isomers levels. These results suggest that the plasma CS content and structure could be related to the presence and the typology of atherosclerotic plaque and could provide a useful diagnostic tool, as well as information on the molecular mechanisms responsible for plaque instability.

  11. 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. PMID:25813491

  12. 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.

  13. Trace analysis of total naphthenic acids in aqueous environmental matrices by liquid chromatography/mass spectrometry-quadrupole time of flight mass spectrometry direct injection.

    PubMed

    Brunswick, Pamela; Shang, Dayue; van Aggelen, Graham; Hindle, Ralph; Hewitt, L Mark; Frank, Richard A; Haberl, Maxine; Kim, Marcus

    2015-07-31

    A rapid and sensitive liquid chromatography quadrupole time of flight method has been established for the determination of total naphthenic acid concentrations in aqueous samples. This is the first methodology that has been adopted for routine, high resolution, high throughput analysis of total naphthenic acids at trace levels in unprocessed samples. A calibration range from 0.02 to 1.0μgmL(-1) total Merichem naphthenic acids was validated and demonstrated excellent accuracy (97-111% recovery) and precision (1.9% RSD at 0.02μgmL(-1)). Quantitative validation was also demonstrated in a non-commercial oil sands process water (OSPW) acid extractable organics (AEOs) fraction containing a higher percentage of polycarboxylic acid isomers than the Merichem technical mix. The chromatographic method showed good calibration linearity of ≥0.999 RSQ to 0.005μgmL(-1) total naphthenic acids with a precision <3.1% RSD and a calculated detection limit of 0.0004μgmL(-1) employing Merichem technical mix reference material. The method is well suited to monitoring naturally occurring and industrially derived naphthenic acids (and other AEOs) present in surface and ground waters in the vicinity of mining developments. The advantage of the current method is its direct application to unprocessed environmental samples and to examine natural naphthenic acid isomer profiles. It is noted that where the isomer profile of samples differs from that of the reference material, results should be considered semi-quantitative due to the lack of matching isomer content. The fingerprint profile of naphthenic acids is known to be transitory during aging and the present method has the ability to adapt to monitoring of these changes in naphthenic acid content. The method's total ion scan approach allows for data previously collected to be examined retrospectively for specific analyte mass ions of interest. A list of potential naphthenic acid isomers that decrease in response with aging is proposed

  14. Relationship between Menthiafolic Acid and Wine Lactone in Wine.

    PubMed

    Giaccio, Joanne; Curtin, Chris D; Sefton, Mark A; Taylor, Dennis K

    2015-09-23

    Menthiafolic acid (6-hydroxy-2,6-dimethylocta-2,7-dienoic acid, 2a) was quantified by GC-MS in 28 white wines, 4 Shiraz wines, and for the first time in 6 white grape juice samples. Menthiafolic acid was detected in all but one of the wine samples at concentrations ranging from 26 to 342 μg/L and in the juice samples from 16 to 236 μg/L. Various model fermentation experiments showed that some menthiafolic acid in wine could be generated from the grape-derived menthiafolic acid glucose ester (2b) during alcoholic and malolactic fermentation. Samples containing high concentrations of menthiafolic acid were also analyzed by enantioselective GC-MS and were shown to contain this compound in predominantly the (S)-configuration. Enantioselective analysis of wine lactone (1) in one of these samples, a four-year-old Chardonnay wine showed, for the first time, the presence of the 3R,3aR,7aS isomer of wine lactone (1b), which is the enantiomer of the form previously reported as the sole isomer present in young wine samples. The weakly odorous 3R,3aR,7aS 1b form comprised 69% of the total wine lactone in the sample. On the basis of the enantioselectivity of the hydrolytic conversion of menthiafolic acid to wine lactone at pH 3.0 determined previously and the relative proportions of (R)- and (S)-menthiafolic acid in the Chardonnay wine, the predicted ratio of wine lactone enantiomers that would be formed from hydrolysis at ambient temperature of the menthiafolic acid present in this wine was close to the ratio measured, which was consistent with menthiafolic acid being the major or sole precursor to wine lactone in this sample. PMID:26321591

  15. Relationship between Menthiafolic Acid and Wine Lactone in Wine.

    PubMed

    Giaccio, Joanne; Curtin, Chris D; Sefton, Mark A; Taylor, Dennis K

    2015-09-23

    Menthiafolic acid (6-hydroxy-2,6-dimethylocta-2,7-dienoic acid, 2a) was quantified by GC-MS in 28 white wines, 4 Shiraz wines, and for the first time in 6 white grape juice samples. Menthiafolic acid was detected in all but one of the wine samples at concentrations ranging from 26 to 342 μg/L and in the juice samples from 16 to 236 μg/L. Various model fermentation experiments showed that some menthiafolic acid in wine could be generated from the grape-derived menthiafolic acid glucose ester (2b) during alcoholic and malolactic fermentation. Samples containing high concentrations of menthiafolic acid were also analyzed by enantioselective GC-MS and were shown to contain this compound in predominantly the (S)-configuration. Enantioselective analysis of wine lactone (1) in one of these samples, a four-year-old Chardonnay wine showed, for the first time, the presence of the 3R,3aR,7aS isomer of wine lactone (1b), which is the enantiomer of the form previously reported as the sole isomer present in young wine samples. The weakly odorous 3R,3aR,7aS 1b form comprised 69% of the total wine lactone in the sample. On the basis of the enantioselectivity of the hydrolytic conversion of menthiafolic acid to wine lactone at pH 3.0 determined previously and the relative proportions of (R)- and (S)-menthiafolic acid in the Chardonnay wine, the predicted ratio of wine lactone enantiomers that would be formed from hydrolysis at ambient temperature of the menthiafolic acid present in this wine was close to the ratio measured, which was consistent with menthiafolic acid being the major or sole precursor to wine lactone in this sample.

  16. Infrared detection of (H2O)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; Forck, Richard M.; Buck, Udo; Zeuch, Thomas; Xantheas, Sotiris S.

    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 (H2O)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 theoretically predicted spectramore » 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

  17. 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

    presented qualitatively correct behavior for the relative stability of the two translational isomers, namely, slight preference of station II for the isolated molecule and higher relative energy of the same isomer with the model solvent DMSO. The electrostatic interactions in 2 have the decisive contribution both when the macroring is positioned at the dipeptide residue for the neutral form, and at the N-benzylalanine fragment after protonation, and the observed behavior of the [2]rotaxane is correctly reproduced by the methods used.

  18. First- and second-electron affinities of C{sub 60} and C{sub 70} isomers

    SciTech Connect

    Zettergren, Henning; Alcami, Manuel; Martin, Fernando

    2007-10-15

    We present density functional theory calculations of C{sub 60}{sup q-} and C{sub 70}{sup q-} (q=0-2) isomers that contain zero to three pairs of adjacent pentagons. The first- and second-electron affinities for the archetype structures of C{sub 60} and C{sub 70} are close to the experimental results, while isomers with pentagon adjacencies have significantly higher values. The results are rationalized in view of the numbers and locations of pentagon adjacencies in the fullerene cages and the spherical aromaticity for the magic number C{sub 70}{sup 2-} with a closed (l=5) electronic shell in the spherical gas model.

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

    PubMed

    Yılmaz, Cemile; Kocadağlı, Tolgahan; Gökmen, Vural

    2014-04-01

    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.

  20. The absolute configurations of hydroxy fatty acids from the royal jelly of honeybees (Apis mellifera).

    PubMed

    Kodai, Tetsuya; Nakatani, Takafumi; Noda, Naoki

    2011-03-01

    9-Hydroxy-2E-decenoic acid (9-HDA) is a precursor of the queen-produced substance, 9-oxo-2E-decenoic acid (9-ODA), which has various important functions and roles for caste maintenance in honeybee colonies (Apis mellifera). 9-HDA in royal jelly is considered to be a metabolite of 9-ODA produced by worker bees, and it is fed back to the queen who then transforms it into 9-ODA. Recently we found that 9-HDA is present in royal jelly as a mixture of optical isomers (R:S, 2:1). The finding leads us to suspect that chiral fatty acids in royal jelly are precursors of semiochemicals. Rather than looking for semiochemicals in the mandibular glands of the queen bee, this study involves the search for precursors of pheromones from large quantities of royal jelly. Seven chiral hydroxy fatty acids, 9,10-dihydroxy-2E-decenoic, 4,10-dihydroxy-2E-decenoic, 4,9-dihydroxy-2E-decenoic, 3-hydroxydecanoic, 3,9-dihydroxydecanoic, 3,11-dihydroxydodecanoic, and 3,10-dihydroxydecanoic acids were isolated. The absolute configurations of these acids were determined using the modified Mosher's method, and it was revealed that, similar to 9-HDA, five acids are present in royal jelly as mixtures of optical isomers.

  1. Identification of chiral drug isomers by capillary electrophoresis.

    PubMed

    Fanali, S

    1996-05-31

    Separation of optical isomers of compounds of pharmaceutical interest by capillary electrophoretic techniques is reviewed. The direct and indirect separation method, as well as the main resolution mechanisms and the parameters influencing the stereoselectivity are discussed considering capillary zone electrophoresis, micellar electrokinetic chromatography, isotachophoresis and electrochromatography. Several chiral selectors have been successfully used in CE for chiral separation, including cyclodextrins and their derivatives, modified crown-ethers, proteins, antibiotics, linear saccharides and chiral surfactants. Only applications in the pharmaceutical field with the most important experimental conditions are summarised in the Tables reported in this paper. The chiral analyses of drugs in real samples like biological fluids or pharmaceutical formulations are also reported.

  2. Identification of a high-spin isomer in Mo99

    NASA Astrophysics Data System (ADS)

    Jones, G. A.; Regan, P. H.; Walker, P. M.; Podolyák, Zs.; Stevenson, P. D.; Carpenter, M. P.; Carroll, J. J.; Chakrawarthy, R. S.; Chowdhury, P.; Garnsworthy, A. B.; Janssens, R. V. F.; Khoo, T. L.; Kondev, F. G.; Lane, G. J.; Liu, Z.; Seweryniak, D.; Thompson, N. J.; Zhu, S.; Williams, S. J.

    2007-10-01

    A previously unreported isomer has been identified in Mo99 at an excitation energy of Ex=3010 keV, decaying with a half-life of T1/2=8(2) ns. The nucleus of interest was produced following fusion-fission reactions between a thick Al27 target frame and a Hf178 beam at a laboratory energy of 1150 MeV. This isomeric state is interpreted as an energetically favored, maximally aligned configuration of νh(11)/(2)⊗π(g(9)/(2))2.

  3. Production of the 178m2Hf isomer using a 4.5-GeV electron accelerator

    NASA Astrophysics Data System (ADS)

    Karamian, S. A.; Carroll, J. J.; Adam, J.; Demekhina, N. A.

    2004-09-01

    High-productivity methods are required for the accumulation of long-lived isomers in amounts that are sufficient for the creation of experimental targets. A tantalum sample was activated with the Yerevan synchrotron using 4.5-GeV bremsstrahlung and the presence of 178m2Hf was detected with good statistical accuracy by γ-activity measurements. The integrated and mean cross-section values were deduced from the experiment. The isomer-to-ground-state ratio was then estimated and compared with that known for the p+ Ta reaction studied at 660 MeV. In the present experiment, both converter and target were relatively thin for better definition of the experimental conditions. However, an assembly designed for high-productivity irradiations should be thick and then the converter can also serve as the target sample when irradiated with a high-energy electron beam. The optimization of the isomer production was solved analytically and the largest estimated yield was determined as calibrated to the experimental yield. The maximum yield of 178m2Hf was found to be of about 3×109 nuclei/s using an electron beam current of 100 μA. This is lower than the yield achieved with proton beams, although for a practical comparison the total cost and radiation safety conditions should be considered. The present results provide a basis for numerical estimations.

  4. Electrons From A 0.3s Isomer In 254No

    SciTech Connect

    Mukherjee, G.; Khoo, T.L.; Blinstrup, R.; Seweryniak, D.; Ahmad, I.; Carpenter, M.P.; Davids, C.N.; Greene, J.P.; Hammond, N.J.; Janssens, R.V.F.; Kondev, F.G.; Lauritsen, T.; Lister, C.J.; Moore, E.F.; Sinha, S.; Butler, P.A.; Herzberg, R.D.; Ikin, P.J.C.; Jones, G.D.; Chowdhury, P.

    2005-04-05

    We have detected the electrons accompanying the decay of a long-lived isomer in 254No, which was produced with the 208Pb(48Ca,2n) reaction. Time and spatial correlations of A = 254 evaporation residues, isomeric electrons and ground-state {alpha}-particles confirmed the existence of the isomer. The measured electron sum-energy spectrum favors a K{pi} = 7- assignment for the isomer.

  5. A family of single-isomer, dicationic cyclodextrin chiral selectors for capillary electrophoresis: mono-6(A)-ammonium-6(C)-butylimidazolium-β-cyclodextrin chlorides.

    PubMed

    Dai, Yun; Wang, Shuye; Zhou, Jie; Tang, Jian; Tang, Weihua

    2013-03-01

    The first member of the single-isomer, dicationic cyclodextrin (CD) family, 6(A)-ammonium-6(C)-butylimidazolium-β-cyclodextrin chlorides (AMBIMCD), has been synthesized, analytically characterized, and used to separate a variety of acidic enantiomers and amino acids by CE. Starting from mono-6(A)-azido-β-cyclodextrin, the cationic imidazolium and ammonium moieties were subsequently introduced onto primary ring of β-cyclodextrin via nucleophilic addition and Staudinger reaction. The analytically pure AC regio-isomer CD was further obtained via column chromatography. This dicationic CD exhibited excellent enantioselectivities for selected analytes at concentration as low as 0.5 mM, which were even better than those of its mono-imidazolium or ammonium-substitued counterpart CDs at 10 equivalent concentrations. The effective mobilities of all studied analytes were found to decrease with the concentration of AMBIMCD. Inclusion complexation in combination with eletrostatic interactions seemed to account for the enhanced chiral discrimination process.

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

    PubMed

    Beesoon, Sanjay; Martin, Jonathan W

    2015-05-01

    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.

  7. Individual CLA Isomers, c9t11 and t10c12, Prevent Excess Liver Glycogen Storage and Inhibit Lipogenic Genes Expression Induced by High-Fructose Diet in Rats.

    PubMed

    Maslak, Edyta; Buczek, Elzbieta; Szumny, Antoni; Szczepnski, Wojciech; Franczyk-Zarow, Magdalena; Kopec, Aneta; Chlopicki, Stefan; Leszczynska, Teresa; Kostogrys, Renata B

    2015-01-01

    This study assessed the effects of individual conjugated linoleic acid isomers, c9t11-CLA and t10c12-CLA, on nonalcoholic fatty liver disease (NAFLD) and systemic endothelial dysfunction in rats fed for four weeks with control or high-fructose diet. The high-fructose diet hampered body weight gain (without influencing food intake), increased liver weight and glycogen storage in hepatocytes, upregulated expression of fatty acid synthase (FAS) and stearoyl-CoA desaturase-1 (SCD-1), and increased saturated fatty acid (SFA) content in the liver. Both CLA isomers prevented excessive accumulation of glycogen in the liver. Specifically, t10c12-CLA decreased concentration of serum triacylglycerols and LDL + VLDL cholesterol, increased HDL cholesterol, and affected liver lipid content and fatty acid composition by downregulation of liver SCD-1 and FAS expression. In turn, the c9t11-CLA decreased LDL+VLDL cholesterol in the control group and downregulated liver expression of FAS without significant effects on liver weight, lipid content, and fatty acid composition. In summary, feeding rats with a high-fructose diet resulted in increased liver glycogen storage, indicating the induction of gluconeogenesis despite simultaneous upregulation of genes involved in de novo lipogenesis. Although both CLA isomers (c9t11 and t10c12) display hepatoprotective activity, the hypolipemic action of the t10c12-CLA isomer proved to be more pronounced than that of c9t11-CLA.

  8. A strategy for the separation of diterpenoid isomers from the root of Aralia continentalis by countercurrent chromatography: The distribution ratio as a substitute for the partition coefficient and a three-phase solvent system.

    PubMed

    Lee, Kyoung Jin; Song, Kwang Ho; Choi, Wonmin; Kim, Yeong Shik

    2015-08-01

    Aralia continentalis (Araliaceae) is widely used as a medicinal plant in East Asia. Previous studies have indicated that diterpenoid isomers (kaurenoic acid, continentalic acid, and ent-continentalic acid) are the major bioactive compounds of this plant. A new strategy was developed to alleviate difficulties in the separation of these isomers from this plant. A three-phase solvent system was applied to separate the isomers, and furthermore, the distribution ratio (Kc) was introduced as a substitute for the partition coefficient (KD). For compounds exhibiting a single equilibrium, their distributions in two immiscible phases were only affected by the partition coefficient of each solute. However, compounds that have a dissociating functional group (e.g., -COOH) are involved in two types of equilibrium in the two-phase system. In this case, the partitioning behaviors of the solutes are greatly affected by the pH of the solution. A mathematical prediction was applied for adjusting the solutions to the proper pH values. To prevent non-used phase (medium phase) waste, both the stationary phase (upper phase) and mobile phase (lower phase) were prepared on-demand without pre-saturation with the application of (1)H NMR. Each fraction obtained was collected and dried, yielding the following diterpenoid isomers from the 50mg injected sample: kaurenoic acid (19.7mg, yield: 39%) and ent-continentalic acid (21.3mg, yield: 42%).

  9. Role of Tyrosine Isomers in Acute and Chronic Diseases Leading to Oxidative Stress - A Review

    PubMed Central

    Molnár, Gergő A.; Kun, Szilárd; Sélley, Eszter; Kertész, Melinda; Szélig, Lívia; Csontos, Csaba; Böddi, Katalin; Bogár, Lajos; Miseta, Attila; Wittmann, István

    2016-01-01

    Oxidative stress plays a major role in the pathogenesis of a variety of acute and chronic diseases. Measurement of the oxidative stress-related end products may be performed, e.g. that of structural isomers of the physiological para-tyrosine, namely meta- and ortho-tyrosine, that are oxidized derivatives of phenylalanine. Recent data suggest that in sepsis, serum level of meta-tyrosine increases, which peaks on the 2nd and 3rd days (p<0.05 vs. controls), and the kinetics follows the intensity of the systemic inflammation correlating with serum procalcitonin levels. In a similar study subset, urinary meta-tyrosine excretion correlated with both need of daily insulin dose and the insulin-glucose product in non-diabetic septic cases (p<0.01 for both). Using linear regression model, meta-tyrosine excretion, urinary meta-tyrosine/para-tyrosine, urinary ortho-tyrosine/para-tyrosine and urinary (meta- + ortho-tyrosine)/para-tyrosine proved to be markers of carbohydrate homeostasis. In a chronic rodent model, we tried to compensate the abnormal tyrosine isomers using para-tyrosine, the physiological amino acid. Rats were fed a standard high cholesterol-diet, and were given para-tyrosine or vehicle orally. High-cholesterol feeding lead to a significant increase in aortic wall meta-tyrosine content and a decreased vasorelaxation of the aorta to insulin and the glucagon-like peptide-1 analogue, liraglutide, that both could be prevented by administration of para-tyrosine. Concluding, these data suggest that meta- and ortho-tyrosine are potential markers of oxidative stress in acute diseases related to oxidative stress, and may also interfere with insulin action in septic humans. Competition of meta- and ortho-tyrosine by supplementation of para-tyrosine may exert a protective role in oxidative stress-related diseases. PMID:26785996

  10. Determination of benzoic acid, chlorobenzoic acids and chlorendic acid in water

    SciTech Connect

    Dietz, E.A.; Cortellucci, N.J.; Singley, K.F. )

    1993-01-01

    To characterize and conduct treatment studies of a landfill leachate an analysis procedure was required to determine concentrations of benzoic acid, the three isomers of chlorobenzoic acid and chlorendic acid. The title compounds were isolated from acidified (pH 1) water by extraction with methyl t-butyl ether. Analytes were concentrated by back-extracting the ether with 0.1 N sodium hydroxide which was separated and acidified. This solution was analyzed by C[sub 18] reversed-phase HPLC with water/acetonitrile/acetic acid eluent and UV detection at 222 nm. The method has detection limits of 200 [mu]g/L for chlorendic acid and 100 [mu]g/L for benzoic acid and each isomer of chlorobenzoic acid. Validation studies with water which was fortified with the analytes at concentrations ranging from one to ten times detection limits resulted in average recoveries of >95%.

  11. The prenucleosome, a stable conformational isomer of the nucleosome

    PubMed Central

    Fei, Jia; Torigoe, Sharon E.; Brown, Christopher R.; Khuong, Mai T.; Kassavetis, George A.; Boeger, Hinrich; Kadonaga, James T.

    2015-01-01

    Chromatin comprises nucleosomes as well as nonnucleosomal histone–DNA particles. Prenucleosomes are rapidly formed histone–DNA particles that can be converted into canonical nucleosomes by a motor protein such as ACF. Here we show that the prenucleosome is a stable conformational isomer of the nucleosome. It consists of a histone octamer associated with ∼80 base pair (bp) of DNA, which is located at a position that corresponds to the central 80 bp of a nucleosome core particle. Monomeric prenucleosomes with free flanking DNA do not spontaneously fold into nucleosomes but can be converted into canonical nucleosomes by an ATP-driven motor protein such as ACF or Chd1. In addition, histone H3K56, which is located at the DNA entry and exit points of a canonical nucleosome, is specifically acetylated by p300 in prenucleosomes relative to nucleosomes. Prenucleosomes assembled in vitro exhibit properties that are strikingly similar to those of nonnucleosomal histone–DNA particles in the upstream region of active promoters in vivo. These findings suggest that the prenucleosome, the only known stable conformational isomer of the nucleosome, is related to nonnucleosomal histone–DNA species in the cell. PMID:26680301

  12. The prenucleosome, a stable conformational isomer of the nucleosome.

    PubMed

    Fei, Jia; Torigoe, Sharon E; Brown, Christopher R; Khuong, Mai T; Kassavetis, George A; Boeger, Hinrich; Kadonaga, James T

    2015-12-15

    Chromatin comprises nucleosomes as well as nonnucleosomal histone-DNA particles. Prenucleosomes are rapidly formed histone-DNA particles that can be converted into canonical nucleosomes by a motor protein such as ACF. Here we show that the prenucleosome is a stable conformational isomer of the nucleosome. It consists of a histone octamer associated with ∼ 80 base pair (bp) of DNA, which is located at a position that corresponds to the central 80 bp of a nucleosome core particle. Monomeric prenucleosomes with free flanking DNA do not spontaneously fold into nucleosomes but can be converted into canonical nucleosomes by an ATP-driven motor protein such as ACF or Chd1. In addition, histone H3K56, which is located at the DNA entry and exit points of a canonical nucleosome, is specifically acetylated by p300 in prenucleosomes relative to nucleosomes. Prenucleosomes assembled in vitro exhibit properties that are strikingly similar to those of nonnucleosomal histone-DNA particles in the upstream region of active promoters in vivo. These findings suggest that the prenucleosome, the only known stable conformational isomer of the nucleosome, is related to nonnucleosomal histone-DNA species in the cell.

  13. Observation of new K isomers among neutron-rich rare earth nuclei produced by in-flight fission of 345 MeV/nucleon 238U

    NASA Astrophysics Data System (ADS)

    Kameda, Daisuke; Kubo, Toshiyuki; BigRIPS new isotope Collaboration

    2014-09-01

    We have performed search for new K isomers for a wide range of neutron-rich rare earth nuclei using the BigRIPS separator at RIKEN RIBF. The rare earth nuclei were produced by in-flight fission of a 238U beam at 345 MeV/nucleon, and isomeric gamma rays were detected using four clover-type germanium detectors. As a result, we have observed a total of 25 new microsecond isomers: 158 m , 159 m , 160 mNd, 158 m , 159 m , 161 mPm, 160 m , 161 m , 162 mSm, 163 m , 164 mEu, 162 m , 164 m , 165 m , 166 mGd, 164 m , 165 m , 166 m , 167 m , 168 mTb, 167 m , 168 m , 169 m , 170 mDy, and 171mHo, and obtained a wealth of spectroscopic information on these nuclei. The nuclei in this region are predicted to be well deformed with a prolate shape, and Kisomers are expected to appear due to the K hindrance. In the present measurement, as anticipated, many of the observed new isomers have been interpreted as a K isomer, because we could identify some gamma rays which belong to the grand-state rotational band being fed by isomeric transitions. The systematics of known K isomers, such as those in neighboring higher- Zisotones, also help and support the interpretation of isomerism. Here we will report on the details of the experimental results and discuss the possible configurations of deformed orbits for the observed new K isomers.

  14. The acetyl bromide method is faster, simpler and presents best recovery of lignin in different herbaceous tissues than Klason and thioglycolic acid methods.

    PubMed

    Moreira-Vilar, Flavia Carolina; Siqueira-Soares, Rita de Cássia; Finger-Teixeira, Aline; de Oliveira, Dyoni Matias; Ferro, Ana Paula; da Rocha, George Jackson; Ferrarese, Maria de Lourdes L; dos Santos, Wanderley Dantas; Ferrarese-Filho, Osvaldo

    2014-01-01

    We compared the amount of lignin as determined by the three most traditional methods for lignin measurement in three tissues (sugarcane bagasse, soybean roots and soybean seed coat) contrasting for lignin amount and composition. Although all methods presented high reproducibility, major inconsistencies among them were found. The amount of lignin determined by thioglycolic acid method was severely lower than that provided by the other methods (up to 95%) in all tissues analyzed. Klason method was quite similar to acetyl bromide in tissues containing higher amounts of lignin, but presented lower recovery of lignin in the less lignified tissue. To investigate the causes of the inconsistencies observed, we determined the monomer composition of all plant materials, but found no correlation. We found that the low recovery of lignin presented by the thioglycolic acid method were due losses of lignin in the residues disposed throughout the procedures. The production of furfurals by acetyl bromide method does not explain the differences observed. The acetyl bromide method is the simplest and fastest among the methods evaluated presenting similar or best recovery of lignin in all the tissues assessed.

  15. Photoactivation of Long-Lived Isomers and its Relevance to Nuclear Structure Physics, γ-LASER Schemes, and Nucleosynthesis

    NASA Astrophysics Data System (ADS)

    Kneissl, U.

    2003-06-01

    Results are presented from experiments recently performed at the well-established bremsstrahlung facilities of the 4.3 MV Stuttgart DYNAMITRON accelerator. The surprisingly strong population of spin isomers in odd-mass nulclei near shell closures in photo-induced reactions have been studied by photoactivation and Nuclear Resonance Fluorescence (NRF) experiments on 113, 115In (Z=49), 87Sr (N=49), and in 135,137Ba (N=79, 81). The generation of a population inversion of low-lying excited nuclear levels by feeding from higher-lying photo-excited states could be demonstrated for the first time by NRF experiments on 103Rh. Such an inversion is the precondition for possible γ-ray laser schemes. The puzzling nucleosynthesis of nature's rarest isotope 180Ta was studied by measuring the depopulation of the quasistable isomer in 180Ta (Jπ = 9-, t1/2 ≥ 1015 yr) by resonant photoabsorption. The new results indicate a dramatic acceleration of the isomer decay to the short-lived Jπ = 9+ ground state (t1/2 = 8.1 h) under stellar s-process conditions. The astrophysical consequences and nuclear structure effects are discussed.

  16. Reductive dechlorination of α-, β-, γ-, and δ-hexachlorocyclohexane isomers with hydroxocobalamin, in soil slurry systems.

    PubMed

    Rodríguez-Garrido, B; Lú-Chau, T A; Feijoo, G; Macías, F; Monterrroso, M C

    2010-09-15

    The present study was carried out to test the viability of a method of reductive dehalogenation of α-, β-, γ-, and δ-hexachlorocyclohexane (HCH) in soil slurry systems. The soil slurries were maintained under anaerobic conditions, with titanium(III) citrate as a reducing agent and hydroxocobalamin (vitamin B(12a)) as a catalyzing agent. Experiments were carried out with two soil samples with markedly different characteristics (particularly regarding organic matter content), at a small scale and larger reactor scale. HCH concentration was monitored throughout the 24 h duration of the tests. In the low organic matter soil HCH isomers degraded rapidly, in both the small scale and reactor systems, and undetectable levels (<0.5%) were reached within 5 h. However, complete degradation of HCH isomers was not achieved in soil with high organic matter content, and there were differences between the results obtained in the small scale and reactor systems. In the small scale system, the levels of degradation reached 93, 88, 94, and 91%, for α-, β-, γ-, and δ-HCH, respectively, and the nondegraded HCH was sorbed in the soil. In the reactor system, the reaction stopped after two hours (no more than 65% of any of the isomers was degraded). PMID:20715766

  17. Sources and Bioactive Properties of Conjugated Dietary Fatty Acids.

    PubMed

    Hennessy, Alan A; Ross, Paul R; Fitzgerald, Gerald F; Stanton, Catherine

    2016-04-01

    The group of conjugated fatty acids known as conjugated linoleic acid (CLA) isomers have been extensively studied with regard to their bioactive potential in treating some of the most prominent human health malignancies. However, CLA isomers are not the only group of potentially bioactive conjugated fatty acids currently undergoing study. In this regard, isomers of conjugated α-linolenic acid, conjugated nonadecadienoic acid and conjugated eicosapentaenoic acid, to name but a few, have undergone experimental assessment. These studies have indicated many of these conjugated fatty acid isomers commonly possess anti-carcinogenic, anti-adipogenic, anti-inflammatory and immune modulating properties, a number of which will be discussed in this review. The mechanisms through which these bioactivities are mediated have not yet been fully elucidated. However, existing evidence indicates that these fatty acids may play a role in modulating the expression of several oncogenes, cell cycle regulators, and genes associated with energy metabolism. Despite such bioactive potential, interest in these conjugated fatty acids has remained low relative to the CLA isomers. This may be partly attributed to the relatively recent emergence of these fatty acids as bioactives, but also due to a lack of awareness regarding sources from which they can be produced. In this review, we will also highlight the common sources of these conjugated fatty acids, including plants, algae, microbes and chemosynthesis. PMID:26968402

  18. 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.

  19. Keto-acids in Carbonaceous Meteorites

    NASA Technical Reports Server (NTRS)

    Cooper, G.; Chang, P. M.; Dugas, A.; Byrd, A.; Chang, P. M.; Washington, N.

    2005-01-01

    The Murchison and Murray meteorites are the best-characterized carbonaceous meteorites with respect to organic chemistry and are generally used as references for organic compounds in extraterrestrial material. Among the classes of organic compounds found in these meteorites are amino acids, carboxylic acids, hydroxy acids, purines, and pyrimidines. Such compounds, important in contemporary biochemistry, are thought to have been delivered to the early Earth in asteroids and comets and may have played a role in early life and/or the origin of life. Absent among (today's) critically important biological compounds reported in carbonaceous meteorites are keto acids, i.e., pyruvic acid, acetoacetic acid, and higher homologs. These compounds are key intermediates in such critical processes as glycolysis and the citric acid cycle. In this study several individual meteoritic keto acids were identified by gas chromatography-mass spectrometry (GC-MS) (see figure below). All compounds were identified as their trimethylsilyl (TMS), isopropyl ester (ISP), and tert-butyldimethylsilyl (tBDMS) derivatives. In general, the compounds follow the abiotic synthesis pattern of other known meteorite classes of organic compounds [1,2]: a general decrease in abundance with increasing carbon number within a class of compounds and many, if not all, possible isomers present at a given carbon number. The majority of the shown compounds was positively identified by comparison of their mass spectra to commercially available standards or synthesized standards.

  20. Effect of phospholipid-based formulations of Boswellia serrata extract on the solubility, permeability, and absorption of the individual boswellic acid constituents present.

    PubMed

    Hüsch, Jan; Gerbeth, Kathleen; Fricker, Gert; Setzer, Constanze; Zirkel, Jürgen; Rebmann, Herbert; Schubert-Zsilavecz, Manfred; Abdel-Tawab, Mona

    2012-10-26

    Boswellia serrata gum resin extracts are used widely for the treatment of inflammatory diseases. However, very low concentrations in the plasma and brain were observed for the boswellic acids (1-6, the active constituents of B. serrata). The present study investigated the effect of phospholipids alone and in combination with common co-surfactants (e.g., Tween 80, vitamin E-TPGS, pluronic f127) on the solubility of 1-6 in physiologically relevant media and on the permeability in the Caco-2 cell model. Because of the high lipophilicity of 1-6, the permeability experiments were adapted to physiological conditions using modified fasted state simulated intestinal fluid as apical (donor) medium and 4% bovine serum albumin in the basolateral (receiver) compartment. A formulation composed of extract/phospholipid/pluronic f127 (1:1:1 w/w/w) increased the solubility of 1-6 up to 54 times compared with the nonformulated extract and exhibited the highest mass net flux in the permeability tests. The oral administration of this formulation to rats (240 mg/kg) resulted in 26 and 14 times higher plasma levels for 11-keto-β-boswellic acid (1) and acetyl-11-keto-β-boswellic acid (2), respectively. In the brain, five times higher levels for 2 compared to the nonformulated extract were determined 8 h after oral administration.