Science.gov

Sample records for aromatic polycarboxylic acids

  1. Ambient cure polyimide foams prepared from aromatic polyisocyanates, aromatic polycarboxylic compounds, furfuryl alcohol, and a strong inorganic acid

    NASA Technical Reports Server (NTRS)

    Sawko, Paul M. (Inventor); Riccitiello, Salvatore R. (Inventor); Hamermesh, Charles L. (Inventor)

    1980-01-01

    Flame and temperature resistant polyimide foams are prepared by the reaction of an aromatic dianhydride, e.g., pyromellitic dianhydride, with an aromatic polyisocyanate, e.g., polymethylene polyphenylisocyanate (PAPI) in the presence of an inorganic acid and a lower molecular weight alcohol, e.g., dilute sulfuric acid or phosphoric acid and furfuryl alcohol. The exothermic reaction between the acid and the alcohol provides the heat necessary for the other reactants to polymerize without the application of any external heat. Such mixtures, therefore, are ideally suited for in situ foam formation, especially where the application of heat is not practical or possible.

  2. 40 CFR 721.3110 - Polycarboxylic acid ester (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Polycarboxylic acid ester (generic... Substances § 721.3110 Polycarboxylic acid ester (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a polycarboxylic acid...

  3. 40 CFR 721.3110 - Polycarboxylic acid ester (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Polycarboxylic acid ester (generic... Substances § 721.3110 Polycarboxylic acid ester (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a polycarboxylic acid...

  4. 40 CFR 721.3110 - Polycarboxylic acid ester (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Polycarboxylic acid ester (generic... Substances § 721.3110 Polycarboxylic acid ester (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a polycarboxylic acid...

  5. 40 CFR 721.3110 - Polycarboxylic acid ester (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Polycarboxylic acid ester (generic... Substances § 721.3110 Polycarboxylic acid ester (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a polycarboxylic acid...

  6. 40 CFR 721.6475 - Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alkyl polycarboxylic acids, esters... Significant New Uses for Specific Chemical Substances § 721.6475 Alkyl polycarboxylic acids, esters with... chemical substances identified generically as alkyl polycarboxylic acids, esters with ethoxylated...

  7. 40 CFR 721.6475 - Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkyl polycarboxylic acids, esters... Significant New Uses for Specific Chemical Substances § 721.6475 Alkyl polycarboxylic acids, esters with... chemical substances identified generically as alkyl polycarboxylic acids, esters with ethoxylated...

  8. 40 CFR 721.2086 - Coco acid triamine condensate, polycarboxylic acid salts.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Coco acid triamine condensate... Specific Chemical Substances § 721.2086 Coco acid triamine condensate, polycarboxylic acid salts. (a... coco acid triamine condensate, poly-car-box-ylic acid salts. (PMN P-92-446) is subject to...

  9. 40 CFR 721.2086 - Coco acid triamine condensate, polycarboxylic acid salts.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Coco acid triamine condensate... Specific Chemical Substances § 721.2086 Coco acid triamine condensate, polycarboxylic acid salts. (a... coco acid triamine condensate, poly-car-box-ylic acid salts. (PMN P-92-446) is subject to...

  10. 40 CFR 721.2086 - Coco acid triamine condensate, polycarboxylic acid salts.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Coco acid triamine condensate, polycarboxylic acid salts. 721.2086 Section 721.2086 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.2086 Coco acid triamine condensate, polycarboxylic acid salts....

  11. 40 CFR 721.3620 - Fatty acid amine condensate, polycarboxylic acid salts.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Fatty acid amine condensate, polycarboxylic acid salts. 721.3620 Section 721.3620 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.3620 Fatty acid amine condensate, polycarboxylic acid salts....

  12. 40 CFR 721.3620 - Fatty acid amine condensate, polycarboxylic acid salts.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Fatty acid amine condensate, polycarboxylic acid salts. 721.3620 Section 721.3620 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.3620 Fatty acid amine condensate, polycarboxylic acid salts....

  13. 40 CFR 721.3620 - Fatty acid amine condensate, polycarboxylic acid salts.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Fatty acid amine condensate, polycarboxylic acid salts. 721.3620 Section 721.3620 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.3620 Fatty acid amine condensate, polycarboxylic acid salts....

  14. 40 CFR 721.3620 - Fatty acid amine condensate, polycarboxylic acid salts.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Fatty acid amine condensate, polycarboxylic acid salts. 721.3620 Section 721.3620 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.3620 Fatty acid amine condensate, polycarboxylic acid salts....

  15. 40 CFR 721.2086 - Coco acid triamine condensate, polycarboxylic acid salts.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Coco acid triamine condensate, polycarboxylic acid salts. 721.2086 Section 721.2086 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.2086 Coco acid triamine condensate, polycarboxylic acid salts....

  16. 40 CFR 721.2086 - Coco acid triamine condensate, polycarboxylic acid salts.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Coco acid triamine condensate, polycarboxylic acid salts. 721.2086 Section 721.2086 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.2086 Coco acid triamine condensate, polycarboxylic acid salts....

  17. 40 CFR 721.3620 - Fatty acid amine condensate, polycarboxylic acid salts.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Fatty acid amine condensate, polycarboxylic acid salts. 721.3620 Section 721.3620 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.3620 Fatty acid amine condensate, polycarboxylic acid salts....

  18. Two new luminescent Zn(II) compounds constructed from guanazole and aromatic polycarboxylate ligands

    NASA Astrophysics Data System (ADS)

    Zhao, Haixiang; Dong, Yanli; Liu, Haiping

    2016-02-01

    Two new Zn(II) compounds, namely [(CH3)2NH2]2n[Zn3(bpt)2(datrz)2]n (1) and [(CH3)2NH2)]n[Zn2(bptc)(datrz)]n·n(H2O) (2) (H3bpt = biphenyl-3,4‧,5-tricarboxylic acid, H4bptc = biphenyl-3,3‧,5,5‧-tetracarboxylic acid, Hdatrz = 3,5-diamino-1,2,4-triazole), have been obtained by the self-assemble reactions of Zn(NO3)2, 3,5-diamino-1,2,4-triazole, aromatic polycarboxylate ligands under solvothermal conditions. Single crystal X-ray structural analyses reveal that both compounds display three-dimensional (3D) frameworks. Compound 1 features a trinodal (3, 4, 6)-connected topological network with the point symbol of {4.62}2{4.64.8}{46.64.85}. Compound 2 displays a binodal (4, 6)-connected topological network with the point symbol of {32.62.72}{34.42.64.75}. In addition, the thermal stabilities and luminescent properties of compounds 1 and 2 were also investigated in the solid state at room temperature.

  19. 40 CFR 721.2098 - Aliphatic polycarboxylic acid metal salt (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.2098 Aliphatic polycarboxylic acid metal salt (generic). (a) Chemical... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Aliphatic polycarboxylic acid...

  20. 40 CFR 721.2098 - Aliphatic polycarboxylic acid metal salt (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... salt (generic). 721.2098 Section 721.2098 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.2098 Aliphatic polycarboxylic acid metal salt (generic). (a) Chemical... as an aliphatic polycarboxylic acid metal salt (PMN P-01-7) is subject to reporting under...

  1. 40 CFR 721.2098 - Aliphatic polycarboxylic acid metal salt (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... salt (generic). 721.2098 Section 721.2098 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.2098 Aliphatic polycarboxylic acid metal salt (generic). (a) Chemical... as an aliphatic polycarboxylic acid metal salt (PMN P-01-7) is subject to reporting under...

  2. 40 CFR 721.2098 - Aliphatic polycarboxylic acid metal salt (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... salt (generic). 721.2098 Section 721.2098 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.2098 Aliphatic polycarboxylic acid metal salt (generic). (a) Chemical... as an aliphatic polycarboxylic acid metal salt (PMN P-01-7) is subject to reporting under...

  3. 40 CFR 721.2098 - Aliphatic polycarboxylic acid metal salt (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... salt (generic). 721.2098 Section 721.2098 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.2098 Aliphatic polycarboxylic acid metal salt (generic). (a) Chemical... as an aliphatic polycarboxylic acid metal salt (PMN P-01-7) is subject to reporting under...

  4. Dimensional modulation and magnetic properties of triazole- and bis(triazole)-based copper(II) coordination polymers tuned by aromatic polycarboxylates

    SciTech Connect

    Zhang, Ju-Wen; Zhao, Wei; Lu, Qi-Lin; Luan, Jian; Qu, Yun; Wang, Xiu-Li

    2014-04-01

    Five new metal–organic coordination polymers ([Cu{sub 3}(μ{sub 2}-OH){sub 2}(atrz){sub 2}(nph){sub 2}(H{sub 2}O){sub 2}]·2H{sub 2}O){sub n} (1), ([Cu{sub 2}(μ{sub 3}-OH)(atrz)(1,2,4-btc)]·2H{sub 2}O){sub n} (2), ([Cu{sub 2}(μ{sub 3}-OH)(atrz)(1,2,4-btc)(H{sub 2}O)]·H{sub 2}O){sub n} (3), [Cu(dth){sub 0.5}(nph)(H{sub 2}O)]{sub n} (4) and [Cu(dth)(Hnip){sub 2}]{sub n} (5) [atrz=4-amino-1,2,4-triazole, dth=N,N'-di(4H-1,2,4-triazole)hexanamide, H{sub 2}nph=3-nitrophthalic acid, 1,2,4-H{sub 3}btc=1,2,4-benzenetricarboxylic acid and H{sub 2}nip=5-nitroisophthalic acid] were hydrothermally synthesized and structurally characterized. Polymer 1 shows a one-dimensional (1D) chain. Polymers 2 and 3 exhibit similar tetranuclear Cu{sup II}{sub 4} cluster-based three-dimensional (3D) frameworks with the same components. Polymer 4 possesses a 3D framework with a 4{sup 12}·6{sup 3}-pcu topology. Polymer 5 displays a 3D framework with a 4{sup 4}·6{sup 10}·8-mab topology. The magnetic properties of 1–4 were investigated. - Graphical abstract: Five triazole-based copper(II) polymers modulated by polycarboxylates were synthesized. Bis-triazole-bis-amide ligand and polycarboxylates play important roles in tuning dimensionality of polymers. Magnetic properties of polymers were investigated. - Highlights: • Five triazole- and bis(triazole)-based copper(II) coordination polymers tuned by aromatic polycarboxylates were obtained. • The aromatic polycarboxylates have an important influence on the dimensionality of five polymers. • The magnetic properties of four polymers were investigated.

  5. Separation of aromatic carboxylic acids using quaternary ammonium salts on reversed-phase HPLC. 1. Separation behavior of aromatic carboxylic acids

    SciTech Connect

    Kawamura, K.; Okuwaki, A.; Verheyen, T.; Perry, G.J.

    2006-02-15

    In order to develop separation processes and analytical methods for aromatic carboxylic acids for the coal oxidation products, the separation behavior of aromatic carboxylic acids on a reversed-phase HPLC using eluent containing quaternary ammonium salt has been investigated. The retention mechanism of aromatic carboxylic acids was discussed on the basis of both ion-pair partition model and ion-exchange model. The retention behavior of aromatic carboxylic acids possessing one (or two) carboxylic acid group(s) followed the ion-pair partition model, where linear free energy relationship was observed between the capacity factor and the extraction equilibrium constants of benzoic acid and naphthalene carboxylic acid. Besides, the retention behavior followed ion-exchange model with increasing the number of carboxylic acids, where the capacity factor of benzene polycarboxylic acids is proportional to the association constants between aromatic acids and quaternary ammonium ions calculated on the basis of an electrostatic interaction model.

  6. Black Carbon in Sedimentary Organic Carbon in the Northeast Pacific using the Benzene Polycarboxylic Acid Method

    NASA Astrophysics Data System (ADS)

    Coppola, A. I.; Ziolkowski, L. A.; Druffel, E. R.

    2010-12-01

    Black carbon (BC) in the Northeast Pacific ultrafiltered dissolved organic matter (UDOM) was found to be surprisingly old with a 14C age of 18,000 +/-3,000 14C years (Ziolkowski and Druffel, 2010) using the Benzene Polycarboxylic Acid (BPCA) method, while BC in sedimentary organic carbon (SOC) was found to be 2,400-12,900 14C years older than non-BC SOC (Masiello and Druffel, 1998) with a different method. Using the dichromate-sulfuric acid oxidation method (Wolbach and Anders, 1989), Masiello and Druffel (1998) estimated that 12-31% of SOC in the Northeast Pacific and the Southern Ocean surface sediments was black carbon (BC). However, the dichromate-sulfuric acid oxidation may over-estimate the concentration of BC, because this method is more biased toward modern (char) material (Currie et al., 2002). Alternatively, the BPCA method isolates aromatic components of BC as benzene rings substituted with carboxylic acid groups, and provides structural information about the BC. Recent modifications to the BPCA method by Ziolkowski and Druffel (2009) involve few biases in quantifying BC in the continuum between char and soot in UDOM. Here we use the BPCA method to determine the concentrations and 14C values of BC in sediments from three sites in the Northeast Pacific Ocean. Constraining the difference between non-BC SOC and BC-SOC using the BPCA method allows for a more precise estimate of how much BC is present in the sediments and its 14C age. Presumably, the intermediate reservoir of BC is oceanic dissolved organic carbon (DOC) and is, in part, responsible for DOC’s great 14C age. These results can be utilized to better constrain the oceanic carbon budget as a possible sink of BC. References: Currie, L. A., Benner Jr., B. A., Kessler, J.D., et al (2002), A critical evaluation of interlaboratory data on total, elemental, and isotopic carbon in the carbonaceous particle reference material, nist srm 1649a, J. Res. Natl. Inst. Stand. Technol., 107, 279-298. Masiello, C

  7. Reaction Products of Unsaturated Polycarboxylic Acids and Sodium Hypophosphite for Improved Flame Resistance of Cotton-Containing Materials

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Reaction products of unsaturated polycarboxylic acids and sodium hypophosite were found to improve flame resistance of cellulosic materials as determined by the 45 degree flammability test for apparel textiles. The most effective product was that from the reaction of maleic acid with sodium hypopho...

  8. Calcite crystal growth rate inhibition by polycarboxylic acids

    USGS Publications Warehouse

    Reddy, M.M.; Hoch, A.R.

    2001-01-01

    Calcite crystal growth rates measured in the presence of several polycarboxyclic acids show that tetrahydrofurantetracarboxylic acid (THFTCA) and cyclopentanetetracarboxylic acid (CPTCA) are effective growth rate inhibitors at low solution concentrations (0.01 to 1 mg/L). In contrast, linear polycarbocylic acids (citric acid and tricarballylic acid) had no inhibiting effect on calcite growth rates at concentrations up to 10 mg/L. Calcite crystal growth rate inhibition by cyclic polycarboxyclic acids appears to involve blockage of crystal growth sites on the mineral surface by several carboxylate groups. Growth morphology varied for growth in the absence and in the presence of both THFTCA and CPTCA. More effective growth rate reduction by CPTCA relative to THFTCA suggests that inhibitor carboxylate stereochemical orientation controls calcite surface interaction with carboxylate inhibitors. ?? 20O1 Academic Press.

  9. 40 CFR 721.6477 - Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with maleic...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... with ethoxylated fatty alcohols, reaction products with maleic anhydride. 721.6477 Section 721.6477... SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.6477 Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with...

  10. 40 CFR 721.6477 - Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with maleic...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... with ethoxylated fatty alcohols, reaction products with maleic anhydride. 721.6477 Section 721.6477... SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.6477 Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with...

  11. 40 CFR 721.6477 - Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with maleic...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... with ethoxylated fatty alcohols, reaction products with maleic anhydride. 721.6477 Section 721.6477... SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.6477 Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with...

  12. 40 CFR 721.6477 - Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with maleic...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... with ethoxylated fatty alcohols, reaction products with maleic anhydride. 721.6477 Section 721.6477... SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.6477 Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with...

  13. 40 CFR 721.6477 - Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with maleic...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... with ethoxylated fatty alcohols, reaction products with maleic anhydride. 721.6477 Section 721.6477... SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.6477 Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with...

  14. Effects of acid diffusibility and affinity to cellulose on strength loss of polycarboxylic acid crosslinked fabrics.

    PubMed

    Ji, Bolin; Zhao, Cunyi; Yan, Kelu; Sun, Gang

    2016-06-25

    1,2,3,4-Butanetetracarboxylic acid (BTCA) imparts good anti-wrinkle property to cotton fabrics and results in significant strength loss due to cross-linking and acid degradation of cellulose simultaneously. However, benzophenone-3,3',4,4'- tetracarboxylic acid (BPTCA), an aromatic acid, crosslinks cellulose effectively but causes less strength loss to the products under similar conditions. The difference in damages to cellulose fibers was analyzed by using diffusibility and corresponding affinity of the acids to cellulose fibers, which were estimated by their molecular sizes and Hansen solubility parameters (HSP). Both experimental results and theoretical speculations revealed consistent agreement, indicating that smaller acid molecules could diffuse into cellulose fiber more rapidly and deeply, resulting in more acid degradation. Besides, the aliphatic acid such as BTCA has higher molecular affinity than BPTCA to cellulose, causing additional more degradation of cellulose. Both factors are potential reasons of the observed more severe tensile strength loss of the BTCA treated cotton fabrics. PMID:27083819

  15. Extraneous carbon assessment in ultra-microscale radiocarbon analysis using benzene polycarboxylic acids (BPCA)

    NASA Astrophysics Data System (ADS)

    Hanke, Ulrich M.; McIntyre, Cameron P.; Schmidt, Michael W. I.; Wacker, Lukas; Eglinton, Timothy I.

    2016-04-01

    Measurements of the natural abundance of radiocarbon (14C) concentrations in inorganic and organic carbon-containing materials can be used to investigate their date of origin. Particularly, the biogeochemical cycling of specific compounds in the environment may be investigated applying molecular marker analyses. However, the isolation of specific molecules from environmental matrices requires a complex processing procedure resulting in small sample sizes that often contain less than 30 μg C. Such small samples are sensitive to extraneous carbon (Cex) that is introduced during the purification of the compounds (Shah and Pearson, 2007). We present a thorough radiocarbon blank assessment for benzene polycarboxylic acids (BPCA), a proxy for combustion products that are formed during the oxidative degradation of condensed polyaromatic structures (Wiedemeier et al, in press). The extraneous carbon assessment includes reference material for (1) chemical extraction, (2) preparative liquid chromatography (3) wet chemical oxidation which are subsequently measured with gas ion source AMS (Accelerator Mass Spectrometer, 5-100 μg C). We always use pairs of reference materials, radiocarbon depleted (14Cfossil) and modern (14Cmodern) to determine the fraction modern (F14C) of Cex.Our results include detailed information about the quantification of Cex in radiocarbon molecular marker analysis using BPCA. Error propagation calculations indicate that ultra-microscale samples (20-30 μg) are feasible with uncertainties of less than 10 %. Calculations of the constant contamination reveal important information about the source (F14C) and mass (μg) of Cex (Wacker and Christl, 2011) for each sub procedure. An external correction of compound specific radiocarbon data is essential for robust results that allow for a high degree of confidence in the 14C results. References Shah and Pearson, 2007. Ultra-microscale (5-25μg C) analysis of individual lipids by 14C AMS: Assessment and

  16. Characterization, Quantification and Compound-specific Isotopic Analysis of Pyrogenic Carbon Using Benzene Polycarboxylic Acids (BPCA).

    PubMed

    Wiedemeier, Daniel B; Lang, Susan Q; Gierga, Merle; Abiven, Samuel; Bernasconi, Stefano M; Früh-Green, Gretchen L; Hajdas, Irka; Hanke, Ulrich M; Hilf, Michael D; McIntyre, Cameron P; Scheider, Maximilian P W; Smittenberg, Rienk H; Wacker, Lukas; Wiesenberg, Guido L B; Schmidt, Michael W I

    2016-01-01

    Fire-derived, pyrogenic carbon (PyC), sometimes called black carbon (BC), is the carbonaceous solid residue of biomass and fossil fuel combustion, such as char and soot. PyC is ubiquitous in the environment due to its long persistence, and its abundance might even increase with the projected increase in global wildfire activity and the continued burning of fossil fuel. PyC is also increasingly produced from the industrial pyrolysis of organic wastes, which yields charred soil amendments (biochar). Moreover, the emergence of nanotechnology may also result in the release of PyC-like compounds to the environment. It is thus a high priority to reliably detect, characterize and quantify these charred materials in order to investigate their environmental properties and to understand their role in the carbon cycle. Here, we present the benzene polycarboxylic acid (BPCA) method, which allows the simultaneous assessment of PyC's characteristics, quantity and isotopic composition ((13)C and (14)C) on a molecular level. The method is applicable to a very wide range of environmental sample materials and detects PyC over a broad range of the combustion continuum, i.e., it is sensitive to slightly charred biomass as well as high temperature chars and soot. The BPCA protocol presented here is simple to employ, highly reproducible, as well as easily extendable and modifiable to specific requirements. It thus provides a versatile tool for the investigation of PyC in various disciplines, ranging from archeology and environmental forensics to biochar and carbon cycling research. PMID:27214064

  17. Characterization, Quantification and Compound-specific Isotopic Analysis of Pyrogenic Carbon Using Benzene Polycarboxylic Acids (BPCA)

    PubMed Central

    Wiedemeier, Daniel B.; Lang, Susan Q.; Gierga, Merle; Abiven, Samuel; Bernasconi, Stefano M.; Früh-Green, Gretchen L.; Hajdas, Irka; Hanke, Ulrich M.; Hilf, Michael D.; McIntyre, Cameron P.; Scheider, Maximilian P. W.; Smittenberg, Rienk H.; Wacker, Lukas; Wiesenberg, Guido L. B.; Schmidt, Michael W. I.

    2016-01-01

    Fire-derived, pyrogenic carbon (PyC), sometimes called black carbon (BC), is the carbonaceous solid residue of biomass and fossil fuel combustion, such as char and soot. PyC is ubiquitous in the environment due to its long persistence, and its abundance might even increase with the projected increase in global wildfire activity and the continued burning of fossil fuel. PyC is also increasingly produced from the industrial pyrolysis of organic wastes, which yields charred soil amendments (biochar). Moreover, the emergence of nanotechnology may also result in the release of PyC-like compounds to the environment. It is thus a high priority to reliably detect, characterize and quantify these charred materials in order to investigate their environmental properties and to understand their role in the carbon cycle. Here, we present the benzene polycarboxylic acid (BPCA) method, which allows the simultaneous assessment of PyC's characteristics, quantity and isotopic composition (13C and 14C) on a molecular level. The method is applicable to a very wide range of environmental sample materials and detects PyC over a broad range of the combustion continuum, i.e., it is sensitive to slightly charred biomass as well as high temperature chars and soot. The BPCA protocol presented here is simple to employ, highly reproducible, as well as easily extendable and modifiable to specific requirements. It thus provides a versatile tool for the investigation of PyC in various disciplines, ranging from archeology and environmental forensics to biochar and carbon cycling research. PMID:27214064

  18. Preparation of polyimides from mixtures of monomeric diamines and esters of polycarboxylic acids

    NASA Technical Reports Server (NTRS)

    Serafini, T. T.; Delvigs, P.; Lightsey, G. R. (Inventor)

    1973-01-01

    Polyimides having high thermal and oxidative stability are prepared by the reaction of a mixture of monomers comprising (1) a dialkyl or tetraalkyl ester of an aromatic tetracarboxylic acid; (2) an aromatic diamine; and (3) a monoalkyl or dialkyl ester of a dicarboxylic acid where in the ratio of a:b:c is n:(n+1):2, wherein n has a value from 1 to 20. The mixture of monomers is prepared in a 30 to 70 percent by weight solution of an organic solvent, a substrate impregnated with the solution and heated at 50 to 205 C to remove said solvent and form a low molecular weight prepolymer, and thereafter heated at 275 to 350 C to cure to a high molecular weight polyimide.

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

    PubMed

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

    2014-11-26

    Because of similar properties and very low volatility, isomers of benzene poly(carboxylic acid)s (BPCAs) are very difficult to separate. In this work, we found that isomers of BPCAs could be separated efficiently by quaternary ammonium salts (QASs) via formation of deep eutectic solvents (DESs). Three kinds of QASs were used to separate the isomers of BPCAs, including the isomers of benzene tricarboxylic acids (trimellitic acid, trimesic acid, and hemimellitic acid) and the isomers of benzene dicarboxylic acids (phthalic acid and isophthalic acid). Among the QASs, tetraethylammonium chloride was found to have the best performance, which could completely separate BPCA isomers in methyl ethyl ketone solutions. It was found that the hydrogen bond forming between QAS and BPCA results in the selective separation of BPCA isomers. QAS in DES was regenerated effectively by the antisolvent method, and the regenerated QAS was reused four times with the same high efficiency. PMID:25351281

  20. Calcite growth-rate inhibition by fulvic acids isolated from Big Soda Lake, Nevada, USA, The Suwannee River, Georgia, USA and by polycarboxylic acids

    USGS Publications Warehouse

    Reddy, Michael M.; Leenheer, Jerry

    2011-01-01

    Calcite crystallization rates are characterized using a constant solution composition at 25°C, pH=8.5, and calcite supersaturation (Ω) of 4.5 in the absence and presence of fulvic acids isolated from Big Soda Lake, Nevada (BSLFA), and a fulvic acid from the Suwannee River, Georgia (SRFA). Rates are also measured in the presence and absence of low-molar mass, aliphatic-alicyclic polycarboxylic acids (PCA). BSLFA inhibits calcite crystal-growth rates with increasing BSLFA concentration, suggesting that BSLFA adsorbs at growth sites on the calcite crystal surface. Calcite growth morphology in the presence of BSLFA differed from growth in its absence, supporting an adsorption mechanism of calcite-growth inhibition by BSLFA. Calcite growth-rate inhibition by BSLFA is consistent with a model indicating that polycarboxylic acid molecules present in BSLFA adsorb at growth sites on the calcite crystal surface. In contrast to published results for an unfractionated SRFA, there is dramatic calcite growth inhibition (at a concentration of 1 mg/L) by a SRFA fraction eluted by pH 5 solution from XAD-8 resin, indicating that calcite growth-rate inhibition is related to specific SRFA component fractions. A cyclic PCA, 1, 2, 3, 4, 5, 6-cyclohexane hexacarboxylic acid (CHXHCA) is a strong calcite growth-rate inhibitor at concentrations less than 0.1 mg/L. Two other cyclic PCAs, 1, 1 cyclopentanedicarboxylic acid (CPDCA) and 1, 1 cyclobutanedicarboxylic acid (CBDCA) with the carboxylic acid groups attached to the same ring carbon atom, have no effect on calcite growth rates up to concentrations of 10 mg/L. Organic matter ad-sorbed from the air onto the seed crystals has no effect on the measured calcite crystal-growth rates.

  1. Genetics Home Reference: aromatic l-amino acid decarboxylase deficiency

    MedlinePlus

    ... aromatic l-amino acid decarboxylase deficiency aromatic l-amino acid decarboxylase deficiency Enable Javascript to view the expand/ ... PDF Open All Close All Description Aromatic l-amino acid decarboxylase (AADC) deficiency is an inherited disorder that ...

  2. Vapor pressures of substituted polycarboxylic acids are much lower than previously reported

    NASA Astrophysics Data System (ADS)

    Huisman, A. J.; Krieger, U. K.; Zuend, A.; Marcolli, C.; Peter, T.

    2013-01-01

    The partitioning of compounds between the aerosol and gas phase is a primary focus in the study of the formation and fate of secondary organic aerosol. We present measurements of the vapor pressure of 2-Methylmalonic (isosuccinic) acid, 2-Hydroxymalonic (tartronic) acid, 2-Methylglutaric acid, 3-Hydroxy-3-carboxy-glutaric (citric) acid and 2,3-Dihydroxysuccinic (tartaric) acid which were obtained from the evaporation rate of supersaturated liquid particles levitated in an electrodynamic balance. Our measurements indicate that the pure component liquid vapor pressures at 298.15 K for tartronic, citric and tartaric acids are much lower than the same quantity which was derived from solid state measurements in the only other room temperature measurement of these materials (made by Booth et al., 2010). This strongly suggests that empirical correction terms in vapor pressure estimation models to account for the inexplicably high vapor pressures of these and similar compounds should be revisited, and that due caution should be used when the estimated vapor pressures of these and similar compounds are used as inputs for other studies.

  3. Vapor pressures of substituted polycarboxylic acids are much lower than previously reported

    NASA Astrophysics Data System (ADS)

    Huisman, A. J.; Krieger, U. K.; Zuend, A.; Marcolli, C.; Peter, T.

    2013-07-01

    The partitioning of compounds between the aerosol and gas phase is a primary focus in the study of the formation and fate of secondary organic aerosol. We present measurements of the vapor pressure of 2-methylmalonic (isosuccinic) acid, 2-hydroxymalonic (tartronic) acid, 2-methylglutaric acid, 3-hydroxy-3-carboxy-glutaric (citric) acid and DL-2,3-dihydroxysuccinic (DL-tartaric) acid, which were obtained from the evaporation rate of supersaturated liquid particles levitated in an electrodynamic balance. Our measurements indicate that the pure component liquid vapor pressures at 298.15 K for tartronic, citric and tartaric acids are much lower than the same quantity that was derived from solid state measurements in the only other room temperature measurement of these materials (made by Booth et al., 2010). This strongly suggests that empirical correction terms in a recent vapor pressure estimation model to account for the inexplicably high vapor pressures of these and similar compounds should be revisited, and that due caution should be used when the estimated vapor pressures of these and similar compounds are used as inputs for other studies.

  4. Pyrolysis Mechanisms of Aromatic Carboxylic Acids

    SciTech Connect

    Britt, P.F.; Eskay, T.P.; Buchanan, A.C. III

    1997-12-31

    Although decarboxylation of carboxylic acids is widely used in organic synthesis, there is limited mechanistic information on the uncatalyzed reaction pathways of aromatic carboxylic acids at 300-400 {degrees} C. The pyrolysis mechanisms of 1,2-(3,3-dicarboxyphenyl)ethane, 1,2-(4,4-dicarboxylphenyl)ethane, 1-(3-carboxyphenyl)-2-(4- biphenyl)ethane, and substituted benzoic acids have been investigated at 325-425 {degrees} C neat and diluted in an inert solvent. Decarboxylation is the dominant pyrolysis path. Arrhenius parameters, substituent effects, and deuterium isotope effects are consistent with decarboxylation by an electrophilic aromatic substitution reaction. Pyrolysis of benzoic acid in naphthalene, as a solvent, produces significant amounts of 1- and 2-phenylnaphthalenes. The mechanistic pathways for decarboxylation and arylation with be presented.

  5. Biosynthesis of the Aromatic Amino Acids.

    PubMed

    Pittard, James; Yang, Ji

    2008-09-01

    This chapter describes in detail the genes and proteins of Escherichia coli involved in the biosynthesis and transport of the three aromatic amino acids tyrosine, phenylalanine, and tryptophan. It provides a historical perspective on the elaboration of the various reactions of the common pathway converting erythrose-4-phosphate and phosphoenolpyruvate to chorismate and those of the three terminal pathways converting chorismate to phenylalanine, tyrosine, and tryptophan. The regulation of key reactions by feedback inhibition, attenuation, repression, and activation are also discussed. Two regulatory proteins, TrpR (108 amino acids) and TyrR (513 amino acids), play a major role in transcriptional regulation. The TrpR protein functions only as a dimer which, in the presence of tryptophan, represses the expression of trp operon plus four other genes (the TrpR regulon). The TyrR protein, which can function both as a dimer and as a hexamer, regulates the expression of nine genes constituting the TyrR regulon. TyrR can bind each of the three aromatic amino acids and ATP and under their influence can act as a repressor or activator of gene expression. The various domains of this protein involved in binding the aromatic amino acids and ATP, recognizing DNA binding sites, interacting with the alpha subunit of RNA polymerase, and changing from a monomer to a dimer or a hexamer are all described. There is also an analysis of the various strategies which allow TyrR in conjunction with particular amino acids to differentially affect the expression of individual genes of the TyrR regulon. PMID:26443741

  6. Highly Energetic, Low Sensitivity Aromatic Peroxy Acids.

    PubMed

    Gamage, Nipuni-Dhanesha H; Stiasny, Benedikt; Stierstorfer, Jörg; Martin, Philip D; Klapötke, Thomas M; Winter, Charles H

    2016-02-18

    The synthesis, structure, and energetic materials properties of a series of aromatic peroxy acid compounds are described. Benzene-1,3,5-tris(carboperoxoic) acid is a highly sensitive primary energetic material, with impact and friction sensitivities similar to those of triacetone triperoxide. By contrast, benzene-1,4-bis(carboperoxoic) acid, 4-nitrobenzoperoxoic acid, and 3,5-dinitrobenzoperoxoic acid are much less sensitive, with impact and friction sensitivities close to those of the secondary energetic material 2,4,6-trinitrotoluene. Additionally, the calculated detonation velocities of 3,5-dinitrobenzoperoxoic acid and 2,4,6-trinitrobenzoperoxoic acid exceed that of 2,4,6-trinitrotoluene. The solid-state structure of 3,5-dinitrobenzoperoxoic acid contains intermolecular O-H⋅⋅⋅O hydrogen bonds and numerous N⋅⋅⋅O, C⋅⋅⋅O, and O⋅⋅⋅O close contacts. These attractive lattice interactions may account for the less sensitive nature of 3,5-dinitrobenzoperoxoic acid. PMID:26743434

  7. Synthesis and Characterization of Surface Grafted Poly(N-isopropylacrylamide) and Poly(Carboxylic Acid)– Iron Particles via Atom Transfer Radical Polymerization for Biomedical Applications

    PubMed Central

    Sutrisno, Joko; Fuchs, Alan; Evrensel, Cahit

    2014-01-01

    This research relates to the preparation and characterization of surface grafted poly(N-isopropylacrylamide) and poly(carboxylic acid)–micron-size iron particles via atom transfer radical polymerization (ATRP). The surface grafted polymers–iron particles result in multifunctional materials which can be used in biomedical applications. The functionalities consist of cell targeting, imaging, drug delivery, and immunological response. The multifunctional materials are synthesized in two steps. First, surface grafting is used to place polymer molecules on the iron particles surface. The second step, is conjugation of the bio-molecules onto the polymer backbone. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy were used to confirm the presence of polymers on the iron particles. The thickness of the grafted polymers and glass transition temperature of the surface grafted polymers were determined by transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The covalent bond between grafted polymers and iron particles caused higher glass transition temperature as compared with non-grafted polymers. The ability to target the bio-molecule and provide fluorescent imaging was simulated by conjugation of rat immunoglobulin and fluorescein isothiocyanate (FITC) labeled anti-rat. The fluorescence intensity was determined using flow cytometry and conjugated IgG-FITC anti-rat on iron particles which was imaged using a fluorescence microscopy. PMID:25382869

  8. Strong-acid, carboxyl-group structures in fulvic acid from the Suwannee River, Georgia. 2. Major structures

    USGS Publications Warehouse

    Leenheer, J.A.; Wershaw, R. L.; Reddy, M.M.

    1995-01-01

    Polycarboxylic acid structures that account for the strong-acid characteristics (pKa1 near 2.0) were examined for fulvic acid from the Suwannee River. Studies of model compounds demonstrated that pKa values near 2.0 occur only if the ??-ether or ??-ester groups were in cyclic structures with two to three additional electronegative functional groups (carboxyl, ester, ketone, aromatic groups) at adjacent positions on the ring. Ester linkage removal by alkaline hydrolysis and destruction of ether linkages through cleavage and reduction with hydriodic acid confirmed that the strong carboxyl acidity in fulvic acid was associated with polycarboxylic ??-ether and ??-ester structures. Studies of hypothetical structural models of fulvic acid indicated possible relation of these polycarboxylic structures with the amphiphilic and metal-binding properties of fulvic acid.

  9. How Do Haloarchaea Synthesize Aromatic Amino Acids?

    PubMed Central

    Gulko, Miriam Kolog; Dyall-Smith, Mike; Gonzalez, Orland; Oesterhelt, Dieter

    2014-01-01

    Genomic analysis of H. salinarum indicated that the de novo pathway for aromatic amino acid (AroAA) biosynthesis does not follow the classical pathway but begins from non-classical precursors, as is the case for M. jannaschii. The first two steps in the pathway were predicted to be carried out by genes OE1472F and OE1475F, while the 3rd step follows the canonical pathway involving gene OE1477R. The functions of these genes and their products were tested by biochemical and genetic methods. In this study, we provide evidence that supports the role of proteins OE1472F and OE1475F catalyzing consecutive enzymatic reactions leading to the production of 3-dehydroquinate (DHQ), after which AroAA production proceeds via the canonical pathway starting with the formation of DHS (dehydroshikimate), catalyzed by the product of ORF OE1477R. Nutritional requirements and AroAA uptake studies of the mutants gave results that were consistent with the proposed roles of these ORFs in AroAA biosynthesis. DNA microarray data indicated that the 13 genes of the canonical pathway appear to be utilised for AroAA biosynthesis in H. salinarum, as they are differentially expressed when cells are grown in medium lacking AroAA. PMID:25216252

  10. Affinity labelling enzymes with esters of aromatic sulfonic acids

    DOEpatents

    Wong, Show-Chu; Shaw, Elliott

    1977-01-01

    Novel esters of aromatic sulfonic acids are disclosed. The specific esters are nitrophenyl p- and m-amidinophenylmethanesulfonate. Also disclosed is a method for specific inactivation of the enzyme, thrombin, employing nitrophenyl p-amidinophenylmethanesulfonate.

  11. Dimensional modulation and magnetic properties of triazole- and bis(triazole)-based copper(II) coordination polymers tuned by aromatic polycarboxylates

    NASA Astrophysics Data System (ADS)

    Zhang, Ju-Wen; Zhao, Wei; Lu, Qi-Lin; Luan, Jian; Qu, Yun; Wang, Xiu-Li

    2014-04-01

    Five new metal-organic coordination polymers {[Cu3(μ2-OH)2(atrz)2(nph)2(H2O)2]·2H2O}n (1), {[Cu2(μ3-OH)(atrz)(1,2,4-btc)]·2H2O}n (2), {[Cu2(μ3-OH)(atrz)(1,2,4-btc)(H2O)]·H2O}n (3), [Cu(dth)0.5(nph)(H2O)]n (4) and [Cu(dth)(Hnip)2]n (5) [atrz=4-amino-1,2,4-triazole, dth=N,N'-di(4H-1,2,4-triazole)hexanamide, H2nph=3-nitrophthalic acid, 1,2,4-H3btc=1,2,4-benzenetricarboxylic acid and H2nip=5-nitroisophthalic acid] were hydrothermally synthesized and structurally characterized. Polymer 1 shows a one-dimensional (1D) chain. Polymers 2 and 3 exhibit similar tetranuclear CuII4 cluster-based three-dimensional (3D) frameworks with the same components. Polymer 4 possesses a 3D framework with a 412·63-pcu topology. Polymer 5 displays a 3D framework with a 44·610·8-mab topology. The magnetic properties of 1-4 were investigated.

  12. Mechanistic Investigation into the Decarboxylation of Aromatic Carboxylic Acids

    SciTech Connect

    Britt, P F; Buchanan, III, A C; Eskay, T P; Mungall, W S

    1999-08-22

    It has been proposed that carboxylic acids and carboxylates are major contributors to cross-linking reactions in low-rank coals and inhibit its thermochemical processing. Therefore, the thermolysis of aromatic carboxylic acids was investigated to determine the mechanisms of decarboxylation at temperatures relevant to coal processing, and to determine if decarboxylation leads to cross-linking (i.e., formation of more refractory products). From the thcrmolysis of simple and polymeric coal model compounds containing aromatic carboxylic acids at 250-425 °C, decarboxylation was found to occur primarily by an acid promoted ionic pathway. Carboxylate salts were found to enhance the decarboxylation rate, which is consistent with the proposed cationic mechanism. Thermolysis of the acid in an aromatic solvent, such as naphthalene, produced a small amount of arylated products (~5 mol%)), which constitute a low-temperature cross-link. These arylated products were formed by the rapid decomposition of aromatic anhydrides, which are in equilibrium with the acid. These anhydrides decompose by a free radical induced decomposition pathway to form atyl radicals that can add to aromatic rings to form cross-links or abstract hydrogen. Large amounts of CO were formed in the thennolysis of the anhydrides which is consistent with the induced decomposition pathway. CO was also formed in the thermolysis of the carboxylic acids in aromatic solvents which is consistent with the formation and decomposition of the anhydride. The formation of anhydride linkages and cross-links was found to be very sensitive to the reactions conditions. Hydrogen donor solvents, such as tetralin, and water were found to decrease the formation of arylated products. Silar reaction pathways were also found in the thermolysis of a polymeric model that contained aromatic carboxylic acids. In this case, anhydride formation and decomposition produced an insoluble polymer, while the O-methylated polymer and the non

  13. Flame retardancy and UV protection of cotton based fabrics using nano ZnO and polycarboxylic acids.

    PubMed

    El-Hady, M M Abd; Farouk, A; Sharaf, S

    2013-01-30

    This research mainly deals with a novel flame-retardant and UV-protection for cellulosic fabrics using ZnO nanoparticles. We present the preparation and application of ZnO nanoparticles. The size of the prepared nanoparticles was analysed using dynamic light scattering (DLS). The application of nano ZnO on cellulosic fabrics (cotton 100% and cotton/cotton polyester 65/35%) was achieved by using different polycarboxilic acids (succinic acid [SA] and 1,2,3,4-butane tetracarboxilic acids [BTCA]) with sodium hypophosphite (SHP) as catalyst through conventional pad-dry-cure method. The effect of concentration of SHP on the physical properties, flammability and UV-protection of cross-linked fabrics are investigated. The effect of concentration of zinc oxide nanoparticles and the effect of curing temperature were also investigated. The results revealed the importance of SHP in increasing the flame-redundancy of the treated cellulosic fabrics. PMID:23218312

  14. A novel star-shaped poly(carboxylic acid) for resin-modified glass-ionomer restoratives.

    PubMed

    Weng, Y; Howard, L; Xie, D

    2014-07-01

    We have developed a novel glass-ionomer cement (GIC) system composed of photo-curable star-shaped poly(acrylic acid-co-itaconic acid)s. These polyacids were synthesized via a chain-transfer radical polymerization using a newly synthesized multi-arm chain-transfer agent. The star-shaped polyacids showed significantly lower viscosities in water as compared to the linear polyacids. Due to the lower viscosities, the molecular weight (MW) of the polyacids can be significantly increased for enhancing the mechanical strengths while keeping the ease of mixing and handling. The effects of MW, GM-tethering ratio, P/L ratio, and aging on the compressive properties of the experimental cements were significant. The light-cured experimental cements showed significantly improved mechanical strengths i.e. 49% in yield strength, 41% in modulus, 25% in CS, 20% in DTS, and 36% in FS, higher than commercial Fuji II LC. After aging in water for 1 month, the compressive strength of the novel light-cured experimental cement reached 343 MPa, which was 34% and 42% higher than Fuji II and Fuji II LC, respectively. This one-month aged experimental cement was also 23% higher than itself after one day aging, indicating that aging in water can significantly enhance salt-bridge formation for this novel star-shaped polyacid-comprised GIC. PMID:24865692

  15. Oxidative photodegradation of herbicide fenuron in aqueous solution by natural iron oxide α-Fe2O3, influence of polycarboxylic acids.

    PubMed

    Kribéche, Mohamed El Amine; Mechakra, Hind; Sehili, Tahar; Brosillon, Stephan

    2016-01-01

    The photodegradation of the herbicide fenuron (1,1-dimethyl-3-phenylurea) by using a natural iron oxide (NIO), α-Fe2O3, in aqueous solution at acidic pH has been undertaken. The NIO was characterized by the Raman spectroscopy method. The degradation pathways and the formation of degradation products were studied. A high-pressure mercury lamp and sunlight were employed as light source. Fenuron photodegradation using NIO with oxalic acid followed the pseudo-first-order kinetics, the optimal experimental conditions were [oxalic acid]0 = 10(-3) M and [NIO] = 0.1 g L(-1) at pH 3. A UVA/NIO/oxalic acid system led to a low fenuron half-life (60 min). The results were even better when solar light is used (30 min). The variables studied were the doses of iron oxide, of carboxylic acids, the solution pH and the effect of sunlight irradiation. The effects of four carboxylic acids, oxalic, citric, tartaric and malic acids, on the fenuron photodegradation with NIO have been investigated, oxalic acid was the most effective carboxylic acid used at pH 3. A similar trend was observed for the removal of total organic carbon (TOC), 75% of TOC was removed. The analytical study showed many aromatic intermediates, short-chain carboxylic acids and inorganic ion. PMID:26102217

  16. Amino Acids, Aromatic Compounds, and Carboxylic Acids: How Did They Get Their Common Names?

    ERIC Educational Resources Information Center

    Leung, Sam H.

    2000-01-01

    Surveys the roots of the common names of organic compounds most likely to be encountered by undergraduate organic chemistry students. Includes information for 19 amino acids, 17 aromatic compounds, and 21 carboxylic acids. (WRM)

  17. Decarboxylative homocoupling of (hetero)aromatic carboxylic acids.

    PubMed

    Cornella, Josep; Lahlali, Hicham; Larrosa, Igor

    2010-11-21

    A variety of hetero(aromatic) carboxylic acids are shown to undergo decarboxylative homocoupling, mediated by a Pd/Ag system. This novel methodology for the synthesis of symmetrical biaryls avoids the use of haloarenes and organometallic compounds as starting materials. PMID:20882244

  18. Chlamydia pneumoniae encodes a functional aromatic amino acid hydroxylase

    PubMed Central

    Abromaitis, Stephanie; Hefty, P. Scott; Stephens, Richard S.

    2010-01-01

    Chlamydia pneumoniae is a community-acquired respiratory pathogen that has been associated with the development of atherosclerosis. Analysis of the C. pneumoniae genome identified a gene (Cpn1046) homologous to eukaryotic aromatic amino acid hydroxylases. Aromatic amino acid hydroxylases (AroAA-H) hydroxylate phenylalanine, tyrosine, and tryptophan into tyrosine, dihydroxyphenylalanine (L-DOPA), and 5-hydroxytryptophan, respectively. Sequence analysis of Cpn1046 demonstrated that residues essential for AroAA-H enzymatic function are conserved and that a subset of Chlamydia species contain an AroAA-H homolog. The chlamydial AroAA-H are transcriptionally linked to a putative bacterial membrane transport protein. We determined that recombinant Cpn1046 is able to hydroxylate phenylalanine, tyrosine, and tryptophan with roughly equivalent activity for all three substrates. Cpn1046 is expressed within 24 h of infection, allowing C. pneumoniae to hydroxylae host stores of aromatic amino acids during the period of logarithmic bacterial growth. From these results we can conclude that C. pneumoniae, as well as a subset of other Chlamydia species, encode an AroAA-H that is able to use all three aromatic amino acids as substrates. The maintenance of this gene within a number of Chlamydia suggests that the enzyme may have an important role in shaping the metabolism or overall pathogenesis of these bacteria. PMID:19141112

  19. [Spectrophotometric determination of aromatic amino compounds with J-acid].

    PubMed

    Yin, Xiao-hang; Shi, Wen-jian; Shen, Xin; Ma, Jun-tao; Li, Liang

    2015-01-01

    The problems such as chromogenic reaction selectivity, reaction rate, sensitivity and water-solubility of azo compounds were considered. The molecular structures of coupling components were theoretically designed and screened in the present research The reaction conditions and methods of chromogenic reaction were investigated. J-Acid (2-amino-5-naphthol-7-sulfonic acid) as a coupling reagent to determine aromatic amino compounds was established. In the presence of potassium bromide, at room temperature, nitrite reacted with aromatic amino compounds in the medium of thin hydrochloric acid. Then diazonium salt reacted with J-Acid in the aqueous solution of sodium carbonate, forming coloured azo dye, which had a maximum adsorption at 480 nm. The molar adsorption coeffcients of aniline, 4-aminobenzene sulfonic acid and 1-naphthylamine were 3. 95 X 10(4), 3. 24 X 10(4) and 3. 91 X 10(4) L . mol-1 . cm-1 , respectively. Experimental results showed that common coexisting ions on the surface water did not affect the results of determination. J-Acid of spectrophotometry was used to determine the samples of Shanghai Fu Xing Dao canal. Meanwhile, recovery experiments by standard addition method were done. Experiment results showed that the recoveries of aniline were in the range of 98. 5%-102. 1%, and RSD was 2. 08%. J-Acid is a common organic reagent. It is soluble in water and low volatile, and its toxicity is much lower than N-ethylenediamine. spectrophotometric determination of aromatic amino compounds by J-Acid has the advantage of high sensitivity, good selectivity, simple rapid operation and accurate results, and thus it can be used for the determination of trace aromatic amino compounds in the environmental water. PMID:25993847

  20. The Nature of Intermolecular Interactions Between Aromatic Amino Acid Residues

    SciTech Connect

    Gervasio, Francesco; Chelli, Riccardo; Procacci, Piero; Schettino, Vincenzo

    2002-05-01

    The nature of intermolecular interactions between aromatic amino acid residues has been investigated by a combination of molecular dynamics and ab initio methods. The potential energy surface of various interacting pairs, including tryptophan, phenilalanine, and tyrosine, was scanned for determining all the relevant local minima by a combined molecular dynamics and conjugate gradient methodology with the AMBER force field. For each of these minima, single-point correlated ab initio calculations of the binding energy were performed. The agreement between empirical force field and ab initio binding energies of the minimum energy structures is excellent. Aromatic-aromatic interactions can be rationalized on the basis of electrostatic and van der Waals interactions, whereas charge transfer or polarization phenomena are small for all intermolecular complexes and, particularly, for stacked structures.

  1. 40 CFR 721.9620 - Aromatic sulfonic acid compound with amine.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Aromatic sulfonic acid compound with... Specific Chemical Substances § 721.9620 Aromatic sulfonic acid compound with amine. (a) Chemical substance... aromatic sulfonic acid compound with amine (PMN P-93-832) is subject to reporting under this section...

  2. 40 CFR 721.9620 - Aromatic sulfonic acid compound with amine.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Aromatic sulfonic acid compound with... Specific Chemical Substances § 721.9620 Aromatic sulfonic acid compound with amine. (a) Chemical substance... aromatic sulfonic acid compound with amine (PMN P-93-832) is subject to reporting under this section...

  3. 40 CFR 721.9620 - Aromatic sulfonic acid compound with amine.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Aromatic sulfonic acid compound with... Specific Chemical Substances § 721.9620 Aromatic sulfonic acid compound with amine. (a) Chemical substance... aromatic sulfonic acid compound with amine (PMN P-93-832) is subject to reporting under this section...

  4. 40 CFR 721.9620 - Aromatic sulfonic acid compound with amine.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Aromatic sulfonic acid compound with... Specific Chemical Substances § 721.9620 Aromatic sulfonic acid compound with amine. (a) Chemical substance... aromatic sulfonic acid compound with amine (PMN P-93-832) is subject to reporting under this section...

  5. 40 CFR 721.9620 - Aromatic sulfonic acid compound with amine.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Aromatic sulfonic acid compound with... Specific Chemical Substances § 721.9620 Aromatic sulfonic acid compound with amine. (a) Chemical substance... aromatic sulfonic acid compound with amine (PMN P-93-832) is subject to reporting under this section...

  6. 40 CFR 721.10633 - Aromatic sulfonic acid amino azo dye salts (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Aromatic sulfonic acid amino azo dye... Specific Chemical Substances § 721.10633 Aromatic sulfonic acid amino azo dye salts (generic). (a) Chemical... as aromatic sulfonic acid amino azo dye salts (PMN P-12-276) is subject to reporting under...

  7. 40 CFR 721.10633 - Aromatic sulfonic acid amino azo dye salts (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Aromatic sulfonic acid amino azo dye... Specific Chemical Substances § 721.10633 Aromatic sulfonic acid amino azo dye salts (generic). (a) Chemical... as aromatic sulfonic acid amino azo dye salts (PMN P-12-276) is subject to reporting under...

  8. Propensity of salicylamide and ethenzamide cocrystallization with aromatic carboxylic acids.

    PubMed

    Przybyłek, Maciej; Ziółkowska, Dorota; Mroczyńska, Karina; Cysewski, Piotr

    2016-03-31

    The cocrystallization of salicylamide (2-hydroxybenzamide, SMD) and ethenzamide (2-ethoxybenzamide, EMD) with aromatic carboxylic acids was examined both experimentally and theoretically. The supramolecular synthesis taking advantage of the droplet evaporative crystallization (DEC) technique was combined with powder diffraction and vibrational spectroscopy as the analytical tools. This led to identification of eleven new cocrystals including pharmaceutically relevant coformers such as mono- and dihydroxybenzoic acids. The cocrystallization abilities of SMD and EMD with aromatic carboxylic acids were found to be unexpectedly divers despite high formal similarities of these two benzamides and ability of the R2,2(8) heterosynthon formation. The source of diversities of the cocrystallization landscapes is the difference in the stabilization of possible conformers by adopting alternative intramolecular hydrogen boding patterns. The stronger intramolecular hydrogen bonding the weaker affinity toward intermolecular complexation potential. The substituent effects on R2,2(8) heterosynthon properties are also discussed. PMID:26898408

  9. Isotopic exchange of hydrogen in aromatic amino acids

    SciTech Connect

    Pshenichnikova, A.B.; Karnaukhova, E.N.; Mitsner, B.I.

    1993-10-20

    The kinetics of the isotopic replacement of hydrogen in the aromatic amino acids L-tryptophan, L-tyrosine, and L-phenylalanine in solutions of deuterochloric and deuterosulfuric acids in deuterium oxide were investigated by PMR spectroscopy. The reactions were shown to be of first orders with respect both to the concentration of the substrate and to the activity of the deuterium ion. The isotopic effects of hydrogen and the values of the activation energy of H-D exchange in different positions of the aromatic ring in tryptophan and tyrosine were determined. The effect of properties of the medium on the rate of the isotopic exchange of hydrogen is discussed. 17 refs., 2 figs., 2 tabs.

  10. Chlamydia pneumoniae encodes a functional aromatic amino acid hydroxylase.

    PubMed

    Abromaitis, Stephanie; Hefty, P Scott; Stephens, Richard S

    2009-03-01

    Chlamydia pneumoniae is a community-acquired respiratory pathogen that has been associated with the development of atherosclerosis. Analysis of the C. pneumoniae genome identified a gene (Cpn1046) homologous to eukaryotic aromatic amino acid hydroxylases (AroAA-Hs). AroAA-Hs hydroxylate phenylalanine, tyrosine, and tryptophan into tyrosine, dihydroxyphenylalanine, and 5-hydroxytryptophan, respectively. Sequence analysis of Cpn1046 demonstrated that residues essential for AroAA-H enzymatic function are conserved and that a subset of Chlamydia species contain an AroAA-H homolog. The chlamydial AroAA-Hs are transcriptionally linked to a putative bacterial membrane transport protein. We determined that recombinant Cpn1046 is able to hydroxylate phenylalanine, tyrosine, and tryptophan with roughly equivalent activity for all three substrates. Cpn1046 is expressed within 24 h of infection, allowing C. pneumoniae to hydroxylate host stores of aromatic amino acids during the period of logarithmic bacterial growth. From these results we can conclude that C. pneumoniae, as well as a subset of other Chlamydia species, encode an AroAA-H that is able to use all three aromatic amino acids as substrates. The maintenance of this gene within a number of Chlamydia suggests that the enzyme may have an important role in shaping the metabolism or overall pathogenesis of these bacteria. PMID:19141112

  11. The roles of polycarboxylates in Cr(VI)/sulfite reaction system: Involvement of reactive oxygen species and intramolecular electron transfer.

    PubMed

    Jiang, Bo; Wang, Xianli; Liu, Yukun; Wang, Zhaohui; Zheng, Jingtang; Wu, Mingbo

    2016-03-01

    In this study, the effects of polycarboxylates on both Cr(VI) reduction and S(IV) consumption in Cr(VI)/S(IV) system was investigated in acidic solution. Under aerobic condition, the productions of reactive oxygen species (ROS), i.e., SO4(-) and OH, have been confirmed in S(IV) reducing Cr(VI) process by using electron spin resonance and fluorescence spectrum techniques, leading to the excess consumption of S(IV). However, when polycarboxylates (oxalic, citric, malic and tartaric acid) were present in Cr(VI)/S(IV) system, the affinity of polycarboxylates to CrSO6(2-) can greatly promote the reduction of Cr(VI) via expanding the coordination of Cr(VI) species from tetrahedron to hexahedron. Besides, as alternatives to S(IV), these polycarboxylates can also act as electron donors for Cr(VI) reduction via intramolecular electron transfer reaction, which is dependent on the energies of the highest occupied molecular orbital of these polycarboxylates. Notably, the variant electron donating capacity of these polycarboxylates resulted in different yield of ROS and therefore the oxidation efficiencies of other pollutants, e.g., rhodamine B and As(III). Generally, this study does not only shed light on the mechanism of S(IV) reducing Cr(VI) process mediated by polycarboxylates, but also provides an escalated, cost-effective and green strategy for the remediation of Cr(VI) using sulfite as a reductant. PMID:26610099

  12. Aromatic Amino Acids and Related Substances: Chemistry, Biology, Medicine, and Application

    Technology Transfer Automated Retrieval System (TEKTRAN)

    On the occasion of the "Transdisciplinary International Conference on Aromatic Amino Acids and Related Substances," the organizing committee honors and thanks the expert participants from many areas of aromatic amino acid (AAA)3 research. In this transdisciplinary meeting, "aromatic paradigms" were ...

  13. Influence of quantum dots on the aromaticity of thiosalicylic acid.

    PubMed

    Guan, Qiumei

    2013-12-01

    When ligands are coordinated to quantum dots (QDs), the ring current of the ligand strongly influences the applications of the QDs, for example in solar cell technology. The Raman spectrum of the ligand can be used to probe and identify ions or measure ion concentrations. Here, we investigated, using a theoretical method, the aromaticities and Raman spectra of CdTe, CdSe, and CdS QDs coordinated with thiosalicylic acid ligands. We found that the aromaticity of the benzene ring in free thiosalicylic acid increased when it was used as a QD ligand. The ring currents of the benzene rings in the CdTe-ligand, CdSe-ligand, and CdS-ligand systems were stronger than the ring current of the benzene ring in free thiosalicylic acid; in other words, the QDs influence the ring current--they enhance the electron transfer rate of the benzene ring. We also discovered that the CdTe-ligand and CdSe-ligand systems have stronger ring currents than the CdS-ligand system. The high electronegativity and vacant d orbital of the sulfur atom influence the ring current of the ligand in the CdS-ligand system. Further, the Raman spectrum of free thiosalicylic acid was different from the spectra of the ligands in the QD-ligand systems: the Raman spectra of COO(-) in each QD-ligand system was enhanced compared with that of the COO(-) in free thiosalicylic acid. PMID:23934301

  14. Substituent effects on the energetics and aromaticity of aminomethylbenzoic acids.

    PubMed

    Lima, Carlos F R A C; Gomes, Lígia R; Santos, Luís M N B F

    2007-10-25

    The standard (p0 = 0.1 MPa) molar enthalpies of combustion of six aminomethylbenzoic acids were measured at T = 298.15 K by static bomb calorimetry. With these values, the standard molar enthalpies of formation in the crystalline state were obtained. Combining these results with the standard molar enthalpies of sublimation, the standard molar enthalpies of formation in the gaseous phase were derived. For the 10 possible isomers, the obtained experimental results were compared to and correlated with the relative stability obtained by ab initio calculations at the B3LYP/6-311++G(d,p) level of theory. Seeking a better understanding of the aromatic behavior and energetics of aminomethylbenzoic acids in the gas phase, calculations of NICS values, HOMA indices, and dihedral angles between the aromatic carbon and the amino group, Phi(Ar-NHH), were also performed computationally. The significant differences observed in the energetics, as well as in the NICS values, HOMA indices, and Phi(Ar-NHH) dihedral angles for these 10 isomers suggest a strong dependency on the identity and relative position of the three substituents on the benzene ring. This study points out a marked tendency for a decrease of the ring aromaticity, accompanied by an increase in the respective system stability, as the conjugation between the substituents becomes more extensive. PMID:17914759

  15. A medicated polycarboxylate cement to prevent complications in composite resin therapy

    SciTech Connect

    Okamoto, Y.; Shintani, H.; Yamaki, M. )

    1990-01-01

    Preparative treatment is the preferred method to protect the dentin and pulp from complications in composite resin therapy. This study investigated the in vivo effects of the polycarboxylate cement containing zinc fluoride and tannic acid in composite resin restorations. Scanning electron micrographs established that the composite resin failed to contact the axial wall. The gaps varied from 10 to 60 microns. However, this polycarboxylate cement was shown to provide excellent adaptation to dentin when used as a base and its chemical adhesion allowed it to make close contact with the unetched dentin. The newly developed electron probe x-ray microanalyzer revealed that the in vivo penetration of fluoride and zinc occurred through the dentinal tubules. When this polycarboxylate cement was used, the orifices of dentinal tubules were partially occluded, possibly with the smear layer fixed by tannic acid. In addition, by releasing the components, this polycarboxylate cement adds acid resistance to dentin and increases the resistance of dentin collagen to proteolytic enzymes. As such this polycarboxylate cement offers advantages as a base to composite resin therapy.

  16. Method for continuous production of aromatic carboxylic acid

    SciTech Connect

    Abrams, K.J.

    1988-12-20

    This patent describes a method for the continuous production of an aromatic carboxylic acid product in a pressurized oxidation reactor by liquid-phase, exothermic oxidation of an aromatic alkyl feed with an oxygen-containing gas, in the presence of an aromatic alkyl feed with an oxygen-containing gas, in the presence of an oxidation catalyst and in an aqueous monocarboxylic C/sub 2/ to C/sub 6/ aliphatic acid solvent medium, wherein the heat generated during the course of the oxidation is removed from the reactor by vaporization of a portion of the reaction medium and water, wherein the resulting vapors are condensed in part in a reflux loop externally of the oxidation reactor to produce a condensate and a gaseous phase, and wherein at least a portion of the condensate is returned to the oxidation reactor, the improvement comprising a method for controlling within desired limits the concentration of water in the oxidation reactor, which comprises: partitioning the vapors into a parallel condensate having a relatively lesser water-to-solvent weight ratio and a vapor phase having a relatively greater water-to-solvent weight ratio; returning the partial condensate directly to the oxidation reactor as a direct reflux stream; withdrawing the vapor phase from the reflux loop as a vapor stream; subjecting the withdrawn vapor stream to heat exchange while decreasing the vapor stream pressure to less than the oxidation reactor pressure to thereby produce an aqueous aliphatic acid stream having a water-to-solvent weight ratio greater than that of the direct reflux stream.

  17. Formic-acid-induced depolymerization of oxidized lignin to aromatics

    NASA Astrophysics Data System (ADS)

    Rahimi, Alireza; Ulbrich, Arne; Coon, Joshua J.; Stahl, Shannon S.

    2014-11-01

    Lignin is a heterogeneous aromatic biopolymer that accounts for nearly 30% of the organic carbon on Earth and is one of the few renewable sources of aromatic chemicals. As the most recalcitrant of the three components of lignocellulosic biomass (cellulose, hemicellulose and lignin), lignin has been treated as a waste product in the pulp and paper industry, where it is burned to supply energy and recover pulping chemicals in the operation of paper mills. Extraction of higher value from lignin is increasingly recognized as being crucial to the economic viability of integrated biorefineries. Depolymerization is an important starting point for many lignin valorization strategies, because it could generate valuable aromatic chemicals and/or provide a source of low-molecular-mass feedstocks suitable for downstream processing. Commercial precedents show that certain types of lignin (lignosulphonates) may be converted into vanillin and other marketable products, but new technologies are needed to enhance the lignin value chain. The complex, irregular structure of lignin complicates chemical conversion efforts, and known depolymerization methods typically afford ill-defined products in low yields (that is, less than 10-20wt%). Here we describe a method for the depolymerization of oxidized lignin under mild conditions in aqueous formic acid that results in more than 60wt% yield of low-molecular-mass aromatics. We present the discovery of this facile C-O cleavage method, its application to aspen lignin depolymerization, and mechanistic insights into the reaction. The broader implications of these results for lignin conversion and biomass refining are also considered.

  18. Formic-acid-induced depolymerization of oxidized lignin to aromatics.

    PubMed

    Rahimi, Alireza; Ulbrich, Arne; Coon, Joshua J; Stahl, Shannon S

    2014-11-13

    Lignin is a heterogeneous aromatic biopolymer that accounts for nearly 30% of the organic carbon on Earth and is one of the few renewable sources of aromatic chemicals. As the most recalcitrant of the three components of lignocellulosic biomass (cellulose, hemicellulose and lignin), lignin has been treated as a waste product in the pulp and paper industry, where it is burned to supply energy and recover pulping chemicals in the operation of paper mills. Extraction of higher value from lignin is increasingly recognized as being crucial to the economic viability of integrated biorefineries. Depolymerization is an important starting point for many lignin valorization strategies, because it could generate valuable aromatic chemicals and/or provide a source of low-molecular-mass feedstocks suitable for downstream processing. Commercial precedents show that certain types of lignin (lignosulphonates) may be converted into vanillin and other marketable products, but new technologies are needed to enhance the lignin value chain. The complex, irregular structure of lignin complicates chemical conversion efforts, and known depolymerization methods typically afford ill-defined products in low yields (that is, less than 10-20wt%). Here we describe a method for the depolymerization of oxidized lignin under mild conditions in aqueous formic acid that results in more than 60wt% yield of low-molecular-mass aromatics. We present the discovery of this facile C-O cleavage method, its application to aspen lignin depolymerization, and mechanistic insights into the reaction. The broader implications of these results for lignin conversion and biomass refining are also considered. PMID:25363781

  19. 40 CFR 721.10289 - Hexanedioic acid polymer with aliphatic polyol dihydrogen phosphate aromatic ester (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... aliphatic polyol dihydrogen phosphate aromatic ester (generic). 721.10289 Section 721.10289 Protection of... polymer with aliphatic polyol dihydrogen phosphate aromatic ester (generic). (a) Chemical substance and... acid polymer with aliphatic polyol dihydrogen phosphate aromatic ester (PMN P-11-333) is subject...

  20. 40 CFR 721.10289 - Hexanedioic acid polymer with aliphatic polyol dihydrogen phosphate aromatic ester (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... aliphatic polyol dihydrogen phosphate aromatic ester (generic). 721.10289 Section 721.10289 Protection of... polymer with aliphatic polyol dihydrogen phosphate aromatic ester (generic). (a) Chemical substance and... acid polymer with aliphatic polyol dihydrogen phosphate aromatic ester (PMN P-11-333) is subject...

  1. 40 CFR 721.10289 - Hexanedioic acid polymer with aliphatic polyol dihydrogen phosphate aromatic ester (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... aliphatic polyol dihydrogen phosphate aromatic ester (generic). 721.10289 Section 721.10289 Protection of... polymer with aliphatic polyol dihydrogen phosphate aromatic ester (generic). (a) Chemical substance and... acid polymer with aliphatic polyol dihydrogen phosphate aromatic ester (PMN P-11-333) is subject...

  2. Palladium-catalyzed synthesis of aromatic carboxylic acids with silacarboxylic acids.

    PubMed

    Friis, Stig D; Andersen, Thomas L; Skrydstrup, Troels

    2013-03-15

    Aryl iodides and bromides were easily converted to their corresponding aromatic carboxylic acids via a Pd-catalyzed carbonylation reaction using silacarboxylic acids as an in situ source of carbon monoxide. The reaction conditions were compatible with a wide range of functional groups, and with the aryl iodides, the carbonylation was complete within minutes. The method was adapted to the double and selective isotope labeling of tamibarotene. PMID:23441830

  3. Influence of cryolite on the properties of polycarboxylate cement.

    PubMed

    Bansal, R K; Tewari, U S; Singh, P; Murthy, D V

    1995-02-01

    Zinc oxide, the inorganic component of polycarboxylate cement, was mixed with the filler cryolite (Na3A1F6) in various proportions that ranged from 10% to 50%. These powder combinations were mixed with polyacrylic acid in three powder-to-liquid ratios of 1:1, 1.5:1, and 2:1 (w/w). The physical properties of the resulting cements such as setting time and compressive and diametral tensile strengths were determined. It was observed that the setting time increased with an increase in cryolite content. The compressive and diametral tensile strengths also increased by twofold with a concentration of 20% cryolite. PMID:7722938

  4. Applications of electrochemically-modulated liquid chromatography (EMLC): Separations of aromatic amino acids and polycyclic aromatic hydrocarbons

    SciTech Connect

    Deng, L.

    1998-03-27

    The research in this thesis explores the separation capabilities of a new technique termed electrochemically-modulated liquid chromatography (EMLC). The thesis begins with a general introduction section which provides a literature review of this technique as well as a brief background discussion of the two research projects in each of the next two chapters. The two papers which follow investigate the application of EMLC to the separation of a mixture of aromatic amino acids and of a mixture of polycyclic aromatic hydrocarbons (PAHs). The last section presents general conclusions and summarizes the thesis. References are compiled in the reference section of each chapter. The two papers have been removed for separate processing.

  5. Gene therapy for aromatic L-amino acid decarboxylase deficiency.

    PubMed

    Hwu, Wuh-Liang; Muramatsu, Shin-ichi; Tseng, Sheng-Hong; Tzen, Kai-Yuan; Lee, Ni-Chung; Chien, Yin-Hsiu; Snyder, Richard O; Byrne, Barry J; Tai, Chun-Hwei; Wu, Ruey-Meei

    2012-05-16

    Aromatic L-amino acid decarboxylase (AADC) is required for the synthesis of the neurotransmitters dopamine and serotonin. Children with defects in the AADC gene show compromised development, particularly in motor function. Drug therapy has only marginal effects on some of the symptoms and does not change early childhood mortality. Here, we performed adeno-associated viral vector-mediated gene transfer of the human AADC gene bilaterally into the putamen of four patients 4 to 6 years of age. All of the patients showed improvements in motor performance: One patient was able to stand 16 months after gene transfer, and the other three patients achieved supported sitting 6 to 15 months after gene transfer. Choreic dyskinesia was observed in all patients, but this resolved after several months. Positron emission tomography revealed increased uptake by the putamen of 6-[(18)F]fluorodopa, a tracer for AADC. Cerebrospinal fluid analysis showed increased dopamine and serotonin levels after gene transfer. Thus, gene therapy targeting primary AADC deficiency is well tolerated and leads to improved motor function. PMID:22593174

  6. Polycarboxylic acids as network modifiers for water durability improvement of inorganic-organic hybrid tin-silico-phosphate low-melting glasses

    SciTech Connect

    Menaa, Bouzid . E-mail: bouzidmenaa@noncry.kuicr.kyoto-u.ac.jp; Mizuno, Megumi; Takahashi, Masahide . E-mail: masahide@noncry.kuicr.kyoto-u.ac.jp; Tokuda, Yomei; Yoko, Toshinobu

    2006-02-15

    We investigated the water durability of the inorganic-organic hybrid tin-silico-phosphate glasses Me{sub 2}SiO-SnO-P{sub 2}O{sub 5} (Me designs the organic methyl group) doped with organic acids (salicylic acid (SA), tartaric acid (TA), citric acid (Canada) and butane tetracarboxylic acid (BTCA)) containing one or more of carboxylic groups per molecule. The structure, thermal properties and durability of the final glasses obtained via a non-aqueous acid-base reaction were discussed owing to the nature and the concentration of the acid added. {sup 29}Si magic angle spinning (MAS) NMR and {sup 31}P MAS NMR spectra, respectively, showed clearly a modification of the network in the host glass matrix of the Me{sub 2}SiO-SnO-P{sub 2}O{sub 5} system. The polycondensation enhancement to form -P-O-Si-O-P- linkages (PSP) and the increase of the Q {sup 2} unit (two bridging oxygens per phosphorus atom) over the Q {sup 3} unit (three bridging oxygens per phosphorus atom) as a function of the acid in the order SAacids containing a large number of carboxylic groups per molecule. The presence of carboxylic groups of the acid acting as network modifier may retard the movement of water molecules through the glasses due to the steric hindrance strengthening the PSP connections in a chain-like structure.

  7. Synthesis of novel amphiphilic hyaluronan containing-aromatic fatty acids for fabrication of polymeric micelles.

    PubMed

    Matelová, Alena; Huerta-Angeles, Gloria; Šmejkalová, Daniela; Brůnová, Zdislava; Dušek, Jan; Vícha, Robert; Velebný, Vladimír

    2016-10-20

    Novel hydrophobized hyaluronan (HA) derivatives, containing ω-phenylalkanoic acids (ω-PAA, 4-phenylbutyric acid, 6-phenylhexanoic, 8-phenyloctanoic or 11-tolylundecanoic acids) were prepared by esterification. Mixed anhydrides obtained after reaction of the carboxyl acid moiety and benzoyl chloride were found to be active acylating agents, affording hydrophobized HA in good yield and under mild conditions. The reactivity of the aromatic fatty acids towards esterification has decreased with the increasing length of the aliphatic spacer between the aromatic substituent and carboxylic acid moiety. The novel HA derivatives self-assembled from very low concentrations and were found to be non-cytotoxic. The potential use of ω-phenylalkanoic acids grafted-HA towards drug delivery applications was demonstrated by hydrophobic drugs (resveratrol and retinyl palmitate) encapsulation. The drug loading capacity of the novel HA derivatives was significantly improved most likely because of π⋯π interactions between the micelle core and loaded hydrophobic aromatic compound. PMID:27474668

  8. Acetic acid and aromatics units planned in China

    SciTech Connect

    Alperowicz, N.

    1993-01-27

    The Shanghai Wujing Chemical Complex (SWCC; Shanghai) is proceeding with construction of an acetic acid plant. The 100,000-m.t./year until will use BP Chemicals carbonylation technology, originally developed by Monsanto. John Brown has been selected by China National Technical Import Corp. (CNTIC) to supply the plant, Chinese sources say. The UK contractor, which competed against Mitsui Engineering Shipbuilding (Tokyo) and Lurgi (Frankfurt), has built a similar plant for BP in the UK, although using different technology. The new plant will require 54,000 m.t./year of methanol, which is available onsite. Carbon monoxide will be delivered from a new plant. The acetic acid unit will joint two other acetic plants in China supplied some time ago by Uhde (Dortmund). SWCC is due to be integrated with two adjacent complexes to form Shanghai Pacific Chemical. Meanwhile, four groups are competing to supply a UOP-process aromatics complex for Jilin Chemical Industrial Corp. They are Toyo Engineering, Lurgi, Lucky/Foster Wheeler, and Eurotechnica. The complex will include plants with annual capacities for 115,000 m.t. of benzene, 90,000 m.t. of ortho-xylene, 93,000 m.t. of mixed xylenes, and 20,000 m.t. of toluene. The plants will form part of a $2-billion petrochemical complex based on a 300,000-m.t./year ethylene plant awarded last year to a consortium of Samsung Engineering and Linde. Downstream plants will have annual capacities for 120,000 m.t. of linear low-density polyethylene, 80,000 m.t. of ethylene oxide, 100,000 m.t. of ethylene glycol, 80,000 m.t. of phenol, 100,000 m.t. of acrylonitrile, 20,000 m.t. of sodium cyanide, 40,000 m.t. of phthalic anhydride, 40,000 m.t. of ethylene propylene rubber, 20,000 m.t. of styrene butadiene styrene, and 30,000 m.t. of acrylic fiber.

  9. Applications of FT-IR spectroscopy to the studies of esterification and crosslinking of cellulose by polycarboxylic acids: Part II. The performance of the crosslinked cotton fabrics

    NASA Astrophysics Data System (ADS)

    Wei, Weishu; Yang, Charles Q.

    1998-06-01

    Durable press finishing processes are commonly used in the textile industry to produce wrinkle-free cotton fabrics and garments. A durable press finishing agent forms covalent bands with cellulosic hydroxyl groups, thus crosslinking the cellulose molecules. The crosslinking of cellulose increases wrinkle resistance of the treated cotton fabric and reduces fabric mechanical strength. Wrinkle recovery angle (WRA) and tensile strength are the two most important parameters used to evaluate the performance of the crosslinked cotton fabrics and garments. In this study, we investigated the correlation between WRA and tensile strength on one hand, and the amount of crosslinkages formed by the crosslinking agents including dimethyloldihydroxylethyleneurea (DMDHEU) and 1,2,3,4-butanetetracarboxylic acid (BTCA) determined by FT-IR spectroscopy on the other hand. Linear regression curves between the carbonyl band absorbance, and WRA and tensile strength of the treated cotton fabric were developed. The data indicated that FT-IR spectroscopy is a reliable technique for predicting the performance of durable press finished cotton fabrics, therefore can be used as a convenient instrumental method for quality control in the textile and garment industry.

  10. Efficient Route to Highly Water-Soluble Aromatic Cyclic Hydroxamic Acid Ligands

    SciTech Connect

    Seitz, Michael; Raymond, Kenneth N.

    2008-02-06

    2-Hydroxyisoquinolin-1-one (1,2-HOIQO) is a new member of the important class of aromatic cyclic hydroxamic acid ligands which are widely used in metal sequestering applications and metal chelating therapy. The first general approach for the introduction of substituents at the aromatic ring of the chelating moiety is presented. As a useful derivative, the highly water-soluble sulfonic acid has been synthesized by an efficient route that allows general access to 1,2-HOQIO 3-carboxlic acid amides, which are the most relevant for applications.

  11. Inhibition of barium sulfate deposition by polycarboxylates of various molecular structures

    SciTech Connect

    van der Leeden, M.C.; van Rosmalen, G.M. )

    1990-02-01

    To establish a relationship between the molecular structure of polycarboxylates and their growth-retarding influence on barium sulfate, seeded-suspension-growth experiments were performed at various inhibitor concentrations and pH values. Two types of polycarboxylates with a molecular structure based on their polyacrylic or maleic acid were studied. The molecular structure of these compounds were varied by particle substitution with monomers containing hydroxyl, amide, and sulfonic acid, as well as hydrophobic groups. Hydrophobic groups are detrimental to good inhibitor performance, whereas the introduction of OH, NH {sub 2}, or SO {sub 3} H groups presents opportunities to enhance the inhibitor effectiveness. The sequence in performance of the compounds on barium sulfate was compared with the sequence formerly obtained for calcium sulfate dihydrate.

  12. Interactions of aromatic amino acids with heterocyclic ligand: An IR spectroscopic study

    NASA Astrophysics Data System (ADS)

    Tyunina, E. Yu.; Badelin, V. G.; Tarasova, G. N.

    2015-09-01

    The interactions of L-phenylalanine and L-tryptophan with nicotinic acid and uracyl in an aqueous buffer solution at pH 7.35 were studied by IR spectroscopy. The contributions of various functional groups to the complexation of aromatic amino acids with heterocyclic ligands were determined from the IR spectra of the starting substances and their mixtures.

  13. Comparative effects of oral aromatic and branched-chain amino acids on urine calcium and excretion

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aromatic amino acids (AAAs) bind to the calcium sensor receptor (CaR) but branched-chain amino acids (B-CAAs) do not; by binding to this receptor, AAAs have an increased potential to affect calcium homeostasis. This study was conducted to determine and compare the effects of AAAs and B-CAAs on calci...

  14. Structural and functional characterization of solute binding proteins for aromatic compounds derived from lignin: p-coumaric acid and related aromatic acids.

    PubMed

    Tan, Kemin; Chang, Changsoo; Cuff, Marianne; Osipiuk, Jerzy; Landorf, Elizabeth; Mack, Jamey C; Zerbs, Sarah; Joachimiak, Andrzej; Collart, Frank R

    2013-10-01

    Lignin comprises 15-25% of plant biomass and represents a major environmental carbon source for utilization by soil microorganisms. Access to this energy resource requires the action of fungal and bacterial enzymes to break down the lignin polymer into a complex assortment of aromatic compounds that can be transported into the cells. To improve our understanding of the utilization of lignin by microorganisms, we characterized the molecular properties of solute binding proteins of ATP-binding cassette transporter proteins that interact with these compounds. A combination of functional screens and structural studies characterized the binding specificity of the solute binding proteins for aromatic compounds derived from lignin such as p-coumarate, 3-phenylpropionic acid and compounds with more complex ring substitutions. A ligand screen based on thermal stabilization identified several binding protein clusters that exhibit preferences based on the size or number of aromatic ring substituents. Multiple X-ray crystal structures of protein-ligand complexes for these clusters identified the molecular basis of the binding specificity for the lignin-derived aromatic compounds. The screens and structural data provide new functional assignments for these solute-binding proteins which can be used to infer their transport specificity. This knowledge of the functional roles and molecular binding specificity of these proteins will support the identification of the specific enzymes and regulatory proteins of peripheral pathways that funnel these compounds to central metabolic pathways and will improve the predictive power of sequence-based functional annotation methods for this family of proteins. PMID:23606130

  15. Structural and functional characterization of solute binding proteins for aromatic compounds derived from lignin: p-coumaric acid and related aromatic acids

    PubMed Central

    Tan, Kemin; Chang, Changsoo; Cuff, Marianne; Osipiuk, Jerzy; Landorf, Elizabeth; Mack, Jamey C.; Zerbs, Sarah; Joachimiak, Andrzej; Collart, Frank R.

    2013-01-01

    Lignin comprises 15.25% of plant biomass and represents a major environmental carbon source for utilization by soil microorganisms. Access to this energy resource requires the action of fungal and bacterial enzymes to break down the lignin polymer into a complex assortment of aromatic compounds that can be transported into the cells. To improve our understanding of the utilization of lignin by microorganisms, we characterized the molecular properties of solute binding proteins of ATP.binding cassette transporter proteins that interact with these compounds. A combination of functional screens and structural studies characterized the binding specificity of the solute binding proteins for aromatic compounds derived from lignin such as p-coumarate, 3-phenylpropionic acid and compounds with more complex ring substitutions. A ligand screen based on thermal stabilization identified several binding protein clusters that exhibit preferences based on the size or number of aromatic ring substituents. Multiple X-ray crystal structures of protein-ligand complexes for these clusters identified the molecular basis of the binding specificity for the lignin-derived aromatic compounds. The screens and structural data provide new functional assignments for these solute.binding proteins which can be used to infer their transport specificity. This knowledge of the functional roles and molecular binding specificity of these proteins will support the identification of the specific enzymes and regulatory proteins of peripheral pathways that funnel these compounds to central metabolic pathways and will improve the predictive power of sequence-based functional annotation methods for this family of proteins. PMID:23606130

  16. Evidence for transport intermediates in aromatic amino acid synthesis of non-green tissues

    SciTech Connect

    Leuschner, C.; Schultz, G. )

    1990-05-01

    Quinate (QA) is the predominant pre-aromatic compound formed at high rates in leaves of many plants at the early vegetation stage and transported through the phloem. The transfer of 3-dehydroquinate, 3-dehydroshikimate and (SkA) across the plastidial membranes has been evidenced. The question was whether the rate of QA uptake is comparable to that of the 3 SkA-pathway intermediates. To demonstrate this, /U-{sup 14}C/QA and /U-{sup 14}C/SkA were applied to Brassica rapa roots. Both compounds were uptaken at considerable rates and incorporated into aromatic amino acids (Phe + Tyr + Trp formation, in nmol/g fresh wt x h: applying 145 {mu}mol QA: 21.2; applying 156 {mu}mol Ska: 31.8). Thus, QA is a possible candidate for transport into non-green tissues for aromatic amino acid synthesis.

  17. Secoiridoids and antifungal aromatic acids from Gentiana algida.

    PubMed

    Tan, R X; Wolfender, J L; Ma, W G; Zhang, L X; Hostettmann, K

    1996-01-01

    Fractionation of an aqueous acetone extract of the whole herb of Gentiana algida gave one new [2'-(o,m-dihydroxybenzyl)sweroside] and five known secoiridoids, together with anofinic acid, fomannoxin acid, sitosterol, daucosterol, stigmasterol, oleanolic acid, orientin and gentianose. The structures were determined by spectral methods and a few chemical transformations. Anofinic acid and fomannoxin acid were found to be active against Cladosporium cucumerinum, a plant pathogenic fungus. Preliminary structure-activity studies indicated that the presence of carboxylic moieties in these acids was presumably a precondition for activity, whereas their methyl esters, inactive to the fungus, were active against the human pathogenic yeast Candida albicans. The chemotaxonomic significance of the isolates is discussed briefly. PMID:8588862

  18. Accumulation of polycyclic aromatic hydrocarbons in acid sensitive lakes

    SciTech Connect

    Furlong, E.T.; Cessar, L.R.; Hites, R.A. )

    1987-11-01

    Polycyclic aromatic hydrocarbon concentrations and fluxes were measured in {sup 210}Pb dated sediment cores taken from nine lakes in four regions identified as susceptible to acidification. Calculated PAH accumulations were compared with historic S emissions, accumulation of sedimentary S, and anthropogenic metal accumulations to determine if PAH could be used as an indicator of combustion-derived sulfate deposition. Comparisons between regions indicated that the Adirondacks have a significantly higher burden of PAH than do northern New England, the northern Great Lakes States, and northern Florida. This difference likely results from significant upwind PAH sources to the Adirondack lakes. Detailed investigation of the largest lake in the study set, Big Moose Lake, indicates that PAH may serve as conservative, combustion indicators in large lakes. In this lake, PAH fluxes and concentrations were significantly correlated with historical S emission rates. These data suggest that PAH measured in sediment cores from large lakes can serve as indicators of past combustion production deposition.

  19. Accumulation of polycyclic aromatic hydrocarbons in acid sensitive lakes

    NASA Astrophysics Data System (ADS)

    Furlong, Edward T.; Cessar, Linda Roll; Hites, Ronald A.

    1987-11-01

    Polycyclic aromatic hydrocarbon concentrations and fluxes were measured in 210Pb dated sediment cores taken from nine lakes in four regions identified as susceptible to acidification. Calculated PAH accumulations were compared with historic S emissions, accumulation of sedimentary S and anthropogenic metal accumulations to determine if PAH could be used as an indicator of combustion-derived sulfate deposition. Comparisons between regions indicated that the Adirondacks have a significantly higher burden of PAH than do northern New England, the northern Great Lakes States and northern Florida. This difference likely results from significant upwind PAH sources to the Adirondack lakes. Detailed investigation of the largest lake in the study set, Big Moose Lake, indicates that PAH may serve as conservative, combustion indicators in large lakes. In this lake, PAH fluxes and concentrations were significantly correlated with historical S emission rates. These data suggest that PAH measured in sediment cores from large lakes can serve as indicators of past combustion product deposition.

  20. Activation of Aro80 transcription factor by heat-induced aromatic amino acid influx in Saccharomyces cerevisiae.

    PubMed

    Lee, Kyusung; Sung, Changmin; Kim, Byung-Gee; Hahn, Ji-Sook

    2013-08-16

    In Saccharomyces cerevisiae, transcription of ARO9 and ARO10 genes, involved in the catabolism of aromatic amino acids, is activated by Aro80 transcription factor in response to aromatic amino acids. Here we show that the transcription of ARO9 and ARO10 is also induced by heat shock in an Aro80-dependent manner. However, heat shock-related signaling pathways including PKA, PKC, and HOG pathways are not involved in the heat shock activation of Aro80. We elucidate that heat-induced increase in aromatic amino acid influx can lead to the inducer-dependent activation of Aro80 upon heat shock. Known aromatic amino acid permeases play an insignificant role in the heat-induced expression of ARO9 and ARO10, suggesting that an increase in plasma membrane fluidity might be responsible for the influx of aromatic amino acids during heat shock stress. PMID:23860270

  1. Synthesis and characterization of highly functionalized symmetric aromatic hexa-ol intermediates from oleic acid.

    PubMed

    Song, Dong; Narine, Suresh S

    2008-09-01

    A novel highly functionalized aromatic hexa-ol was synthesized by palladium-catalyzed cyclotrimerization of an alkyne fatty acid ester followed by LAH reduction. This polyol product is a novel monomer made from a renewable lipid raw material for the production of polyurethanes, polyesters and polyamides. PMID:18640106

  2. Environment influences on the aromatic character of nucleobases and amino acids

    PubMed Central

    Szefler, Beata

    2010-01-01

    Geometric (HOMA) and magnetic (NICS) indices of aromaticity were estimated for aromatic rings of amino acids and nucleobases. Cartesian coordinates were taken directly either from PDB files deposited in public databases at the finest resolution available (≤1.5 Å), or from structures resulting from full gradient geometry optimization in a hybrid QM/MM approach. Significant environmental effects imposing alterations of HOMA values were noted for all aromatic rings analysed. Furthermore, even extra fine resolution (≤1.0 Å) is not sufficient for direct estimation of HOMA values based on Cartesian coordinates provided by PDB files. The values of mean bond errors seem to be much higher than the 0.05 Å often reported for PDB files. The use of quantum chemistry geometry optimization is strongly advised; even a simple QM/MM model comprising only the aromatic substructure within the QM region and the rest of biomolecule treated classically within the MM framework proved to be a promising means of describing aromaticity inside native environments. According to the results presented, three consequences of the interaction with the environment can be observed that induce changes in structural and magnetic indices of aromaticity. First, broad ranges of HOMA or NICS values are usually obtained for different conformations of nearest neighborhood. Next, these values and their means can differ significantly from those characterising isolated monomers. The most significant increase in aromaticities is expected for the six-membered rings of guanine, thymine and cytosine. The same trend was also noticed for all amino acids inside proteins but this effect was much smaller, reaching the highest value for the five-membered ring of tryptophan. Explicit water solutions impose similar changes on HOMA and NICS distributions. Thus, environment effects of protein, DNA and even explicit water molecules are non-negligible sources of aromaticity changes appearing in the rings of

  3. Assessing aromaticity and the degree of aromatic condensation of pyrogenic carbon

    NASA Astrophysics Data System (ADS)

    Wiedemeier, D. B.; Abiven, S.; Hockaday, W. C.; Keiluweit, M.; Kleber, M.; Masiello, C. A.; McBeath, A. V.; Nico, P. S.; Pyle, L. A.; Schneider, M. P.; Smernik, R. J.; Wiesenberg, G. L.; Schmidt, M. W.

    2013-12-01

    Fire-derived, pyrogenic carbon (PyC) is a persistent organic carbon fraction in soils because it is relatively resistant against chemical and biological degradation. PyC thus represents a carbon sequestration potential in the global carbon cycle and was also reported to be potentially beneficial for soil fertility. PyC is naturally added to soils during wildfires and anthropogenically in the form of biochar, after organic waste is pyrolyzed. Aromaticity and the degree of aromatic condensation are the two main quality properties of PyC that probably determine its persistence against degradation. Consequently, the two properties largely influence the PyC's carbon sequestration potential as well as the duration, during which it can provide benefits to the soil. Aromaticity and the degree of aromatic condensation of PyC should theoretically be dependent on pyrolysis conditions, such as highest heating temperature or pyrolysis time, and also depend on the feedstock. In this study, we used two different pyrolysis procedures and four different feedstocks to produce four thermosequences of 38 chars in total, with highest heating temperatures ranging from 100 - 1000° C. The chars were then analyzed with an extensive suite of seven different methods: solid state 13C nuclear magnetic resonance (13C NMR), diffuse infrared Fourier transform spectroscopy (DRIFT), synchrotron-based near-edge X-ray absorption fine structure analysis (NEXAFS), benzene polycarboxylic acid analysis (BPCA), lipid analysis, elemental analysis and helium pycnometry. These methods allowed to infer the aromaticity and the degree of aromatic condensation of the differently pyrolyzed materials. Using multivariate statistical methods, aromaticity and the degree of aromatic condensation could successfully be linked to highest heating temperature and other pyrolysis conditions because characteristic patterns of the two aromatic properties could be observed by different methods throughout all four

  4. Transition-Metal-Free Decarboxylative Photoredox Coupling of Carboxylic Acids and Alcohols with Aromatic Nitriles.

    PubMed

    Lipp, Benjamin; Nauth, Alexander M; Opatz, Till

    2016-08-01

    A transition-metal-free protocol for the redox-neutral light-induced decarboxylative coupling of carboxylic acids with (hetero)aromatic nitriles at ambient temperature is presented. A broad scope of acids and nitriles is accepted, and alcohols can be coupled in a similar fashion through their oxalate half esters. Various inexpensive sources of UV light and even sunlight can be used to achieve this C-C bond formation proceeding through a free radical mechanism. PMID:27399619

  5. Steroidal aromatic 'naphthenic acids' in oil sands process-affected water: structural comparisons with environmental estrogens.

    PubMed

    Rowland, Steven J; West, Charles E; Jones, David; Scarlett, Alan G; Frank, Richard A; Hewitt, L Mark

    2011-11-15

    The large volumes, acute toxicity, estrogenicity, and antiandrogenicity of process-affected waters accruing in tailings ponds from the operations of the Alberta oil sands industries pose a significant task for environmental reclamation. Synchronous fluorescence spectra (SFS) suggest that oil sands process-affected water (OSPW) may contain aromatic carboxylic acids, which are among the potentially environmentally important toxicants, but no such acids have yet been identified, limiting interpretations of the results of estrogenicity and other assays. Here we show that multidimensional comprehensive gas chromatography-mass spectrometry (GCxGC-MS) of methyl esters of acids in an OSPW sample produces mass spectra consistent with their assignment as C(19) and C(20) C-ring monoaromatic hydroxy steroid acids, D-ring opened hydroxy and nonhydroxy polyhydrophenanthroic acids with one aromatic and two alicyclic rings and A-ring opened steroidal keto acids. High resolution MS data support the assignment of several of the so-called 'O3' species. When fractions of distilled, esterified, OSPW acid-extractable organics were examined, the putative aromatics were mainly present in a high boiling fraction; when examined by argentation thin layer chromatography, some were present in a fraction with a retardation factor between that of the methyl esters of synthetic monoalicyclic and monoaromatic acids. Ultraviolet absorption spectra of these fractions indicated the presence of benzenoid moieties. SFS of model octahydro- and tetrahydrophenanthroic acids produced emissions at the characteristic excitation wavelengths observed in some OSPW extracts, consistent with the postulations from ultraviolet spectroscopy and mass spectrometry data. We suggest the acids originate from extensive biodegradation of C-ring monoaromatic steroid hydrocarbons and offer a means of differentiating residues at different biodegradation stages in tailings ponds. Structural similarities with estrone and

  6. Acid-catalyzed reactions of a disecondary aromatic diol with alkanols

    SciTech Connect

    Zaitsev, B.A.; Dantsig, L.L.

    1986-07-10

    On heating a disecondary aromatic diol with an alkanol in an aromatic solvent in the presence of an acid catalyst, condensation telomerization takes place with the formation of oligomeric ethers, alcoholysis of which and condensation of hydroxylated intermediate products gives dialkyl ethers of the diol, followed by cleavage of these ethers to give vinyl- and divinylaromatic compounds, and cationic polyaddition of these monomers to give straight-chain unsaturated oligomers, giving mixtures of vinylaromatic compounds and unsaturated straight-chain oligomers. The rate of cleavage of dialkoxy-derivatives of the aromatic diol decreases as the reaction progresses as a result of the increasing concentration of the liberated alkanol, which modifies the activity of the catalyst.

  7. Leaving group activation by aromatic stacking: an alternative to general acid catalysis.

    PubMed

    Versées, Wim; Loverix, Stefan; Vandemeulebroucke, An; Geerlings, Paul; Steyaert, Jan

    2004-04-16

    General acid catalysis is a powerful and widely used strategy in enzymatic nucleophilic displacement reactions. For example, hydrolysis/phosphorolysis of the N-glycosidic bond in nucleosides and nucleotides commonly involves the protonation of the leaving nucleobase concomitant with nucleophilic attack. However, in the nucleoside hydrolase of the parasite Trypanosoma vivax, crystallographic and mutagenesis studies failed to identify a general acid. This enzyme binds the purine base of the substrate between the aromatic side-chains of Trp83 and Trp260. Here, we show via quantum chemical calculations that face-to-face stacking can raise the pKa of a heterocyclic aromatic compound by several units. Site-directed mutagenesis combined with substrate engineering demonstrates that Trp260 catalyzes the cleavage of the glycosidic bond by promoting the protonation of the purine base at N-7, hence functioning as an alternative to general acid catalysis. PMID:15050818

  8. Aliphatic, cyclic, and aromatic organic acids, vitamins, and carbohydrates in soil: a review.

    PubMed

    Vranova, Valerie; Rejsek, Klement; Formanek, Pavel

    2013-01-01

    Organic acids, vitamins, and carbohydrates represent important organic compounds in soil. Aliphatic, cyclic, and aromatic organic acids play important roles in rhizosphere ecology, pedogenesis, food-web interactions, and decontamination of sites polluted by heavy metals and organic pollutants. Carbohydrates in soils can be used to estimate changes of soil organic matter due to management practices, whereas vitamins may play an important role in soil biological and biochemical processes. The aim of this work is to review current knowledge on aliphatic, cyclic, and aromatic organic acids, vitamins, and carbohydrates in soil and to identify directions for future research. Assessments of organic acids (aliphatic, cyclic, and aromatic) and carbohydrates, including their behaviour, have been reported in many works. However, knowledge on the occurrence and behaviour of D-enantiomers of organic acids, which may be abundant in soil, is currently lacking. Also, identification of the impact and mechanisms of environmental factors, such as soil water content, on carbohydrate status within soil organic matter remains to be determined. Finally, the occurrence of vitamins in soil and their role in biological and biochemical soil processes represent an important direction for future research. PMID:24319374

  9. Protein Quantification by Derivatization-Free High-Performance Liquid Chromatography of Aromatic Amino Acids.

    PubMed

    Hesse, Almut; Weller, Michael G

    2016-01-01

    Amino acid analysis is considered to be the gold standard for quantitative peptide and protein analysis. Here, we would like to propose a simple HPLC/UV method based on a reversed-phase separation of the aromatic amino acids tyrosine (Tyr), phenylalanine (Phe), and optionally tryptophan (Trp) without any derivatization. The hydrolysis of the proteins and peptides was performed by an accelerated microwave technique, which needs only 30 minutes. Two internal standard compounds, homotyrosine (HTyr) and 4-fluorophenylalanine (FPhe) were used for calibration. The limit of detection (LOD) was estimated to be 0.05 µM (~10 µg/L) for tyrosine and phenylalanine at 215 nm. The LOD for a protein determination was calculated to be below 16 mg/L (~300 ng BSA absolute). Aromatic amino acid analysis (AAAA) offers excellent accuracy and a precision of about 5% relative standard deviation, including the hydrolysis step. The method was validated with certified reference materials (CRM) of amino acids and of a pure protein (bovine serum albumin, BSA). AAAA can be used for the quantification of aromatic amino acids, isolated peptides or proteins, complex peptide or protein samples, such as serum or milk powder, and peptides or proteins immobilized on solid supports. PMID:27559481

  10. Aliphatic, Cyclic, and Aromatic Organic Acids, Vitamins, and Carbohydrates in Soil: A Review

    PubMed Central

    Vranova, Valerie; Rejsek, Klement; Formanek, Pavel

    2013-01-01

    Organic acids, vitamins, and carbohydrates represent important organic compounds in soil. Aliphatic, cyclic, and aromatic organic acids play important roles in rhizosphere ecology, pedogenesis, food-web interactions, and decontamination of sites polluted by heavy metals and organic pollutants. Carbohydrates in soils can be used to estimate changes of soil organic matter due to management practices, whereas vitamins may play an important role in soil biological and biochemical processes. The aim of this work is to review current knowledge on aliphatic, cyclic, and aromatic organic acids, vitamins, and carbohydrates in soil and to identify directions for future research. Assessments of organic acids (aliphatic, cyclic, and aromatic) and carbohydrates, including their behaviour, have been reported in many works. However, knowledge on the occurrence and behaviour of D-enantiomers of organic acids, which may be abundant in soil, is currently lacking. Also, identification of the impact and mechanisms of environmental factors, such as soil water content, on carbohydrate status within soil organic matter remains to be determined. Finally, the occurrence of vitamins in soil and their role in biological and biochemical soil processes represent an important direction for future research. PMID:24319374

  11. Protein Quantification by Derivatization-Free High-Performance Liquid Chromatography of Aromatic Amino Acids

    PubMed Central

    Hesse, Almut

    2016-01-01

    Amino acid analysis is considered to be the gold standard for quantitative peptide and protein analysis. Here, we would like to propose a simple HPLC/UV method based on a reversed-phase separation of the aromatic amino acids tyrosine (Tyr), phenylalanine (Phe), and optionally tryptophan (Trp) without any derivatization. The hydrolysis of the proteins and peptides was performed by an accelerated microwave technique, which needs only 30 minutes. Two internal standard compounds, homotyrosine (HTyr) and 4-fluorophenylalanine (FPhe) were used for calibration. The limit of detection (LOD) was estimated to be 0.05 µM (~10 µg/L) for tyrosine and phenylalanine at 215 nm. The LOD for a protein determination was calculated to be below 16 mg/L (~300 ng BSA absolute). Aromatic amino acid analysis (AAAA) offers excellent accuracy and a precision of about 5% relative standard deviation, including the hydrolysis step. The method was validated with certified reference materials (CRM) of amino acids and of a pure protein (bovine serum albumin, BSA). AAAA can be used for the quantification of aromatic amino acids, isolated peptides or proteins, complex peptide or protein samples, such as serum or milk powder, and peptides or proteins immobilized on solid supports. PMID:27559481

  12. Probing the Sophisticated Synergistic Allosteric Regulation of Aromatic Amino Acid Biosynthesis in Mycobacterium tuberculosis Using ᴅ-Amino Acids.

    PubMed

    Reichau, Sebastian; Blackmore, Nicola J; Jiao, Wanting; Parker, Emily J

    2016-01-01

    Chirality plays a major role in recognition and interaction of biologically important molecules. The enzyme 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase (DAH7PS) is the first enzyme of the shikimate pathway, which is responsible for the synthesis of aromatic amino acids in bacteria and plants, and a potential target for the development of antibiotics and herbicides. DAH7PS from Mycobacterium tuberculosis (MtuDAH7PS) displays an unprecedented complexity of allosteric regulation, with three interdependent allosteric binding sites and a ternary allosteric response to combinations of the aromatic amino acids l-Trp, l-Phe and l-Tyr. In order to further investigate the intricacies of this system and identify key residues in the allosteric network of MtuDAH7PS, we studied the interaction of MtuDAH7PS with aromatic amino acids that bear the non-natural d-configuration, and showed that the d-amino acids do not elicit an allosteric response. We investigated the binding mode of d-amino acids using X-ray crystallography, site directed mutagenesis and isothermal titration calorimetry. Key differences in the binding mode were identified: in the Phe site, a hydrogen bond between the amino group of the allosteric ligands to the side chain of Asn175 is not established due to the inverted configuration of the ligands. In the Trp site, d-Trp forms no interaction with the main chain carbonyl group of Thr240 and less favourable interactions with Asn237 when compared to the l-Trp binding mode. Investigation of the MtuDAH7PSN175A variant further supports the hypothesis that the lack of key interactions in the binding mode of the aromatic d-amino acids are responsible for the absence of an allosteric response, which gives further insight into which residues of MtuDAH7PS play a key role in the transduction of the allosteric signal. PMID:27128682

  13. Probing the Sophisticated Synergistic Allosteric Regulation of Aromatic Amino Acid Biosynthesis in Mycobacterium tuberculosis Using ᴅ-Amino Acids

    PubMed Central

    Reichau, Sebastian; Blackmore, Nicola J.; Jiao, Wanting; Parker, Emily J.

    2016-01-01

    Chirality plays a major role in recognition and interaction of biologically important molecules. The enzyme 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase (DAH7PS) is the first enzyme of the shikimate pathway, which is responsible for the synthesis of aromatic amino acids in bacteria and plants, and a potential target for the development of antibiotics and herbicides. DAH7PS from Mycobacterium tuberculosis (MtuDAH7PS) displays an unprecedented complexity of allosteric regulation, with three interdependent allosteric binding sites and a ternary allosteric response to combinations of the aromatic amino acids l-Trp, l-Phe and l-Tyr. In order to further investigate the intricacies of this system and identify key residues in the allosteric network of MtuDAH7PS, we studied the interaction of MtuDAH7PS with aromatic amino acids that bear the non-natural d-configuration, and showed that the d-amino acids do not elicit an allosteric response. We investigated the binding mode of d-amino acids using X-ray crystallography, site directed mutagenesis and isothermal titration calorimetry. Key differences in the binding mode were identified: in the Phe site, a hydrogen bond between the amino group of the allosteric ligands to the side chain of Asn175 is not established due to the inverted configuration of the ligands. In the Trp site, d-Trp forms no interaction with the main chain carbonyl group of Thr240 and less favourable interactions with Asn237 when compared to the l-Trp binding mode. Investigation of the MtuDAH7PSN175A variant further supports the hypothesis that the lack of key interactions in the binding mode of the aromatic d-amino acids are responsible for the absence of an allosteric response, which gives further insight into which residues of MtuDAH7PS play a key role in the transduction of the allosteric signal. PMID:27128682

  14. Biochemical Evaluation of the Decarboxylation and Decarboxylation-Deamination Activities of Plant Aromatic Amino Acid Decarboxylases*

    PubMed Central

    Torrens-Spence, Michael P.; Liu, Pingyang; Ding, Haizhen; Harich, Kim; Gillaspy, Glenda; Li, Jianyong

    2013-01-01

    Plant aromatic amino acid decarboxylase (AAAD) enzymes are capable of catalyzing either decarboxylation or decarboxylation-deamination on various combinations of aromatic amino acid substrates. These two different activities result in the production of arylalkylamines and the formation of aromatic acetaldehydes, respectively. Variations in product formation enable individual enzymes to play different physiological functions. Despite these catalytic variations, arylalkylamine and aldehyde synthesizing AAADs are indistinguishable without protein expression and characterization. In this study, extensive biochemical characterization of plant AAADs was performed to identify residues responsible for differentiating decarboxylation AAADs from aldehyde synthase AAADs. Results demonstrated that a tyrosine residue located on a catalytic loop proximal to the active site of plant AAADs is primarily responsible for dictating typical decarboxylase activity, whereas a phenylalanine at the same position is primarily liable for aldehyde synthase activity. Mutagenesis of the active site phenylalanine to tyrosine in Arabidopsis thaliana and Petroselinum crispum aromatic acetaldehyde synthases primarily converts the enzymes activity from decarboxylation-deamination to decarboxylation. The mutation of the active site tyrosine to phenylalanine in the Catharanthus roseus and Papaver somniferum aromatic amino acid decarboxylases changes the enzymes decarboxylation activity to a primarily decarboxylation-deamination activity. Generation of these mutant enzymes enables the production of unusual AAAD enzyme products including indole-3-acetaldehyde, 4-hydroxyphenylacetaldehyde, and phenylethylamine. Our data indicates that the tyrosine and phenylalanine in the catalytic loop region could serve as a signature residue to reliably distinguish plant arylalkylamine and aldehyde synthesizing AAADs. Additionally, the resulting data enables further insights into the mechanistic roles of active site

  15. Aromatic and volatile acid intermediates observed during anaerobic metabolism of lignin-derived oligomers

    SciTech Connect

    Colberg, P.J.; Young, L.Y.

    1985-02-01

    Anaerobic enrichment cultures acclimated for 2 years to use a /sup 14/C-labeled, lignin-derived substrate with a molecular weight of 600 as a sole source of carbon were characterized by capillary and packed column gas chromatography. After acclimation, several of the active methanogenic organisms were inhibited with 2-bromoethanesulfonic acid, which suppressed methane formation and enhanced accumulation of a series of metabolic intermediates. Volatile fatty acids levels in 2-bromoethansulfonic acid-amended cultures were 10 times greater than those in the uninhibited, methane-forming organisms with acetate as the predominant component. Furthermore, in the 2-bromoethanesulfonic acid-amended organisms, almost half of the original substrate carbon was metabolized to 10 monaromatic compounds, with the most appreciable quantities accumulated as cinnamic, benzoic, caffeic, vanillic, and ferulic acids. 2-Bromoethanesulfonic acid seemed to effectively block CH/sub 4/ formation in the anaerobic food chain, resulting in the observed buildup of volatile fatty acids and monoaromatic intermediates. Neither fatty acids nor aromatic compounds were detected in the oligolignol substrate before its metabolism, suggesting that these anaerobic organisms have the ability to mediate the cleavage of the ..beta..-aryl-ether bond, the most common intermonomeric linkage in lignin, with the subsequent release of the observed constituent aromatic monomers.

  16. Influence of Fluorine Atoms and Aromatic Rings on the Acidity of Ethanol

    NASA Astrophysics Data System (ADS)

    Ramírez, Ramsés E.; García-Martínez, Cirilo; Méndez, Francisco

    2009-09-01

    Absolute gas-phase acidities ΔacidG0(OH) and ΔacidG0(CH) were calculated at the B3LYP and MP2 levels using six different standard basis sets for the OH and CH heterolytic bond cleavage of ethanol and twelve derivatives of the type CH3-nFnCHXrOH, where n ranges from zero to three and represents the number of fluorine atoms and r represents hydrogen and the type of aromatic ring, namely: X0 = hydrogen, X1 = phenyl, X2 = 1-naphthyl, and X3 = 9-anthryl. The similarity between calculated and experimental ΔacidG0(OH) values for ethanol (1a), 2-fluoroethanol (1b), 2,2-difluoroethanol (1c), 2,2,2-trifluoroethanol (1d), and 1-phenylethanol (2a) was used to validate the right theoretical method for this study. Substituent partial contributions to hydroxyl-, methylene-, and methine-hydrogen acidities were evaluated by linear combination. Good parameter fittings of the primary and secondary alcohols were obtained and interpreted as additive contribution of the substituent effects. The nonlinear contributions were identified. Calculations prove that fluoroalcohols exhibit C-H acidity, which is usually lower than O-H acidity. In principle, the inversion of this acidity order is possible by the introduction of a large aromatic ring instead to increase the number of fluorine atoms.

  17. Porosity-Acidity Interplay in Hierarchical ZSM-5 Zeolites for Pyrolysis Oil Valorization to Aromatics.

    PubMed

    Puértolas, Begoña; Veses, Alberto; Callén, Maria Soledad; Mitchell, Sharon; García, Tomás; Pérez-Ramírez, Javier

    2015-10-12

    The properties of crude bio-oils attained by the pyrolysis of lignocellulosic biomass can be greatly enhanced by means of catalytic upgrading. Here, we demonstrate an efficient process concept coupling the production of pyrolysis oil from pine wood with a consecutive catalytic upgrading step over hierarchically structured ZSM-5 zeolites to attain aromatic-rich bio-oils. The selective upgrading of these complex mixtures is shown to be tightly connected to the extent of mesopore development and the density of Brønsted acid sites at the mesopore surface. A full product analysis enables elucidation of the impact of mesopore introduction and the acidic properties on the complex reaction network. The preferential occurrence of decarbonylation reactions in hierarchical zeolites versus dehydration transformations in the bulk counterparts is believed to be decisive in promoting increased aromatics formation. PMID:26336806

  18. Relevance of Aromatic Amino Acids for Electron Conduction along Geobacter Pili Protein

    NASA Astrophysics Data System (ADS)

    Adhikari, Ramesh; Malvankar, Nikhil; Tuominen, Mark; Lovley, Derek

    It has been proposed that the charge transport though Geobacter sulfurreducens pili protein occurs through the aromatic amino acids forming helical conducting chain within pili. X-ray studies of pili show that the aromatic amino acids are packed close enough (3-4 Å) for pi-stacking to occur. Conductivity of the pili network increases with lowering temperature indicating metallic-like transport mechanism. However due to the complexity of charge percolation path in 3D network, the intrinsic conductivity of an individual pili was not known. Here, we report transport measurements of individual pili of G. sulfurreducens. The conductivity, similar to that of organic polymers, shows that the pili may have implications in materials research. In addition, the conductivity value is sufficient to explain the respiration rate of the G. sulfurreducens. Further studies of pili from different natural and genetically modified species with varying amount of aromatic amino acid density demonstrate that it can play a decisive role on the magnitude of the conductivity. This research was supported by the Office of Naval Research (ONR) and National Science Foundation (NSF) Center for Hierarchical Manufacturing (CHM). Nikhil S. Malvankar holds a Career Award from the Burroughs Wellcome Fund.

  19. Analysis of aromatic acids by nonaqueous capillary electrophoresis with ionic-liquid electrolytes.

    PubMed

    Lu, Yuanqi; Wang, Dunqing; Kong, Chunyan; Zhong, Hao; Breadmore, Michael C

    2014-12-01

    The separation of six kinds of aromatic acids by CZE with 1-ethyl-3-methylimidazolium chloride (EMIMCl) and 1-ethyl-3-methylimidazolium hydrogen sulfate (EMIMHSO4 ), two kinds of ionic liquids (ILs) as background electrolytes, and acetonitrile as solvent were investigated. The six kinds of aromatic acids can be separated under positive voltage with low IL concentration with either of the two ILs and separation with EMIMHSO4 is better in consideration of peak shapes and separation efficiency. But the migration order is different when the IL is different. Under negative voltage with high IL concentration, the six analytes can be separated with EMIMCl as background electrolytes and the migration order of the analytes is opposite to those with low concentration of EMIMCl as background electrolyte. The separations are based on the combination effects of heteroconjugation between the anions and cations in the ILs and the analytes, of which the heteroconjugation between the anions in the ILs and the analytes plays a dominant role. The heteroconjugation between the anions of the ILs and analytes is proton sensitive and only a very small amount of proticsolvents added into the electrolyte solution can harm the separation. When EMIMCl concentration is high, the heteroconjugation between the IL anions and the proton in the analytes make the effective mobility of the analytes much higher than the EOF and their migration direction reversed. Finally, the six aromatic acids in water samples were analyzed by nonaqueous CE with low concentration of EMIMHSO4 as background electrolytes with satisfactory results. PMID:25141838

  20. OH-radical induced degradation of hydroxybenzoic- and hydroxycinnamic acids and formation of aromatic products—A gamma radiolysis study

    NASA Astrophysics Data System (ADS)

    Krimmel, Birgit; Swoboda, Friederike; Solar, Sonja; Reznicek, Gottfried

    2010-12-01

    The OH-radical induced degradation of hydroxybenzoic acids (HBA), hydroxycinnamic acids (HCiA) and methoxylated derivatives, as well as of chlorogenic acid and rosmarinic acid was studied by gamma radiolysis in aerated aqueous solutions. Primary aromatic products resulting from an OH-radical attachment to the ring (hydroxylation), to the position occupied by the methoxyl group (replacement -OCH 3 by -OH) as well as to the propenoic acid side chain of the cinnamic acids (benzaldehyde formations) were analysed by HPLC-UV and LC-ESI-MS. A comparison of the extent of these processes is given for 3,4-dihydroxybenzoic acid, vanillic acid, isovanillic acid, syringic acid, cinnamic acid, 4-hydroxycinnamic acid, caffeic acid, ferulic acid, isoferulic acid, chlorogenic acid, and rosmarinic acid. For all cinnamic acids and derivatives benzaldehydes were significant oxidation products. With the release of caffeic acid from chlorogenic acid the cleavage of a phenolic glycoside could be demonstrated. Reaction mechanisms are discussed.

  1. Biomolecular Interactions and Biological Responses of Emerging Two-Dimensional Materials and Aromatic Amino Acid Complexes.

    PubMed

    Mallineni, Sai Sunil Kumar; Shannahan, Jonathan; Raghavendra, Achyut J; Rao, Apparao M; Brown, Jared M; Podila, Ramakrishna

    2016-07-01

    The present work experimentally investigates the interaction of aromatic amino acids viz., tyrosine, tryptophan, and phenylalnine with novel two-dimensional (2D) materials including graphene, graphene oxide (GO), and boron nitride (BN). Photoluminescence, micro-Raman spectroscopy, and cyclic voltammetry were employed to investigate the nature of interactions and possible charge transfer between 2D materials and amino acids. Graphene and GO were found to interact strongly with aromatic amino acids through π-π stacking, charge transfer, and H-bonding. Particularly, it was observed that both physi and chemisorption are prominent in the interactions of GO/graphene with phenylalanine and tryptophan while tyrosine exhibited strong chemisorption on graphene and GO. In contrast, BN exhibited little or no interactions, which could be attributed to localized π-electron clouds around N atoms in BN lattice. Lastly, the adsorption of amino acids on 2D materials was observed to considerably change their biological response in terms of reactive oxygen species generation. More importantly, these changes in the biological response followed the same trends observed in the physi and chemisorption measurements. PMID:27281436

  2. Investigation of the gas-phase hydrogen/deuterium exchange behavior of aromatic dicarboxylic acids in a quadrupole ion trap

    NASA Astrophysics Data System (ADS)

    Chipuk, Joseph E.; Brodbelt, Jennifer S.

    2007-11-01

    Gas-phase hydrogen/deuterium (H/D) exchange reactions of four deprotonated aromatic dicarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid and 2,6-naphthalic acid) with D2O were performed in a quadrupole ion trap mass spectrometer. Experimental results showed significant differences in the rate and extent of exchange when the relative position of the carboxylic acid groups varied. Spontaneous and near complete exchange of one aromatic hydrogen atom occurred when the carboxylic acid groups were in the meta-position, whereas no additional exchange was observed for either the ortho- or para-isomers or for the structurally similar naphthalic acid. Computational investigations support the participation of several possible exchange mechanisms with the contribution of each relying heavily on the relative orientation of the acid moieties. A relay mechanism that bridges the deprotonation site and the labile hydrogen site appears to be responsible for the H/D exchange of not only the labile hydrogen atom of isophthalic acid, but also for the formation of a stable carbanion and corresponding subsequent exchange of one aromatic hydrogen atom. The impact of hydrogen bonding on the relay mechanism is demonstrated by the reaction of phthalic acid as the extent and rate of reaction are greatly retarded by the favorable interaction of the two carboxylic acid groups. Finally, a flip-flop mechanism is likely responsible for the exchange of both terephthalic acid and 2,6-naphthalic acid where the reactive sites are too remote for exchange via relay.

  3. Study on the performance of polycarboxylate-based superplasticizers synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization

    NASA Astrophysics Data System (ADS)

    Yu, Binbin; Zeng, Zhong; Ren, Qinyu; Chen, Yang; Liang, Mei; Zou, Huawei

    2016-09-01

    A series of block type polycarboxylate-based superplasticizers (PCs) with different molecular architectures were synthesized with macromonomer butenyl alkylene polyoxyethylene-polyoxypropylene ether (BAPP) and acrylic acid (AA) by reversible addition-fragmentation chain transfer (RAFT) polymerization. Fourier-Transformed Infrared (FTIR) Spectroscopy and dynamic light scattering (DLS) were applied to investigate the PCs' molecular structure. The dispersion capacity of the PCs in cement were also measured, and the results showed that the polycarboxylic dispersing agents prepared by this method were suitable for portlant cement. It was found that the PCs could affect the hydration process, which was performed through retarding the generation of ettringite in the hydrated product. Our studies with X-ray diffraction (XRD), scanning electron microscopy (SEM) and compressive strength measurement of hydrated production were all supporting this conclusion.

  4. Transmembrane aromatic amino acid distribution in P-glycoprotein. A functional role in broad substrate specificity.

    PubMed

    Pawagi, A B; Wang, J; Silverman, M; Reithmeier, R A; Deber, C M

    1994-01-14

    Multidrug resistance (MDR) in cancer cells is associated with overexpression of P-glycoprotein (Pgp), a membrane protein which interacts with structurally diverse hydrophobic molecules of high membrane affinity. In an analysis of the molecular basis for this broad range of substrate specificity, we found that the transmembrane (TM) regions of Pgp are rich in highly conserved aromatic amino acid residues. Computer-generated three-dimensional model structures showed that a typical substrate, rhodamine 123, can intercalate between three to four phenylalanine side-chains in any of several Pgp TM helices with minimal protrusion of the drug into bulk lipid, and that five to six (of the 12 Pgp putative TM segments) helices can facilitate transport through creation of a sterically compatible pore. In contrast to the case for proteins involved in the transport of membrane-impermeable, relatively polar substrates, the "transport path" for Pgp substrates need not be polar, and may involve either an internal channel occupied largely by aromatic side-chains, or external gaps along TM helix-lipid interfaces. Weakly polar interactions between drug cationic sites and Pgp aromatic residues contribute additionally to overall protein/drug binding. The ability of Pgp to recognize and efflux structurally diverse molecules suggests that rather than a unique structure, the Pgp channel may maintain the intrinsic capacity to undergo wide-ranging drug-dependent dynamic reorganization. PMID:7904655

  5. Biomolecular interactions of emerging two-dimensional materials with aromatic amino acids

    NASA Astrophysics Data System (ADS)

    Mallineni, Sai Sunil Kumar; Karakaya, Mehmet; Podila, Ramakrishna; Rao, Apparao

    The present work experimentally investigates the interaction of aromatic amino acids, viz., tyrosine, tryptophan, and phenylalanine with novel two-dimensional (2D) materials including graphene (G), graphene oxide (GO), and boron nitride (BN). Photoluminescence, micro-Raman spectroscopy and cyclic voltammetry were employed to investigate the nature of interactions and possible charge transfer between 2D materials and amino acids. Consistent with previous theoretical studies, graphene and BN were observed to interact with amino acids through π- π interactions. Furthermore, we found that GO exhibits strong interactions with tryptophan and tyrosine as compared to graphene and BN, which we attribute to the formation of H-bonds between tryptophan and GO as shown theoretically in Ref. 2. On the other hand, phenylalanine did not exhibit much difference in interactions with G, GO, and BN. Clemson Nanomaterials Center, Clemson University, Clemson, SC, USA.

  6. An aromatic ion platform for enantioselective Brønsted acid catalysis.

    PubMed

    Gheewala, Chirag D; Collins, Bridget E; Lambert, Tristan H

    2016-02-26

    Chiral acid catalysts are useful for the synthesis of enantioenriched small molecules, but the standard catalysts require laborious and expensive preparations. Here, we describe a chiral Brønsted acid prepared in one step from naturally occurring (-)-menthol and readily available 1,2,3,4,5-pentacarbomethoxycyclopentadiene. Aromatic stabilization serves as a key contributing factor to the potent acidity of the resulting compound, which is shown to catalyze both Mukaiyama-Mannich and oxocarbenium aldol reactions with high efficiency and enantioselectivity. Catalyst loadings as low as 0.01 mole percent and preparative scalability (25 grams) are demonstrated. Alternative amide catalysts are also shown to be promising platforms. In addition to proton catalysis, a chiral anion pathway is demonstrated to be viable with this catalyst system. PMID:26917768

  7. [Ion pair-HPLC of some aromatic amino- and hydroxycarboxylic acids].

    PubMed

    Jira, T; Beyrich, T; Reinhardt, K

    1988-06-01

    Various factors influencing the ion-pair-HPLC separation of some aromatic amino- and hydroxycarbon acids were described and discussed. Distinct effects of the ion pair formation of organic acids with quarternary alkylammonium salts (CTAB) are recognized on condition that the carboxylic group is not blocked by intramolecular H-bonding or partial betain structure. If the carboxylic group is unconnected the retention time increases depending on the pka of the acid with increasing pH if no complete ionization exists. In order to separate similar compounds at low retention time with distinct resolution an organic modifier of suitable strength and high selectivity have to be added to the mobile phase. PMID:3212029

  8. Prediction of Intramolecular Polarization of Aromatic Amino Acids Using Kriging Machine Learning.

    PubMed

    Fletcher, Timothy L; Davie, Stuart J; Popelier, Paul L A

    2014-09-01

    Present computing power enables novel ways of modeling polarization. Here we show that the machine learning method kriging accurately captures the way the electron density of a topological atom responds to a change in the positions of the surrounding atoms. The success of this method is demonstrated on the four aromatic amino acids histidine, phenylalanine, tryptophan, and tyrosine. A new technique of varying training set sizes to vastly reduce training times while maintaining accuracy is described and applied to each amino acid. Each amino acid has its geometry distorted via normal modes of vibration over all local energy minima in the Ramachandran map. These geometries are then used to train the kriging models. Total electrostatic energies predicted by the kriging models for previously unseen geometries are compared to the true energies, yielding mean absolute errors of 2.9, 5.1, 4.2, and 2.8 kJ mol(-1) for histidine, phenylalanine, tryptophan, and tyrosine, respectively. PMID:26588516

  9. Investigating the inclusion properties of aromatic amino acids complexing beta-cyclodextrins in model peptides.

    PubMed

    Caso, Jolanda Valentina; Russo, Luigi; Palmieri, Maddalena; Malgieri, Gaetano; Galdiero, Stefania; Falanga, Annarita; Isernia, Carla; Iacovino, Rosa

    2015-10-01

    Cyclodextrins are commonly used as complexing agents in biological, pharmaceutical, and industrial applications since they have an effect on protein thermal and proteolytic stability, refolding yields, solubility, and taste masking. β-cyclodextrins (β-CD), because of their cavity size are a perfectly suited complexing agent for many common guest moieties. In the case of peptide-cyclodextrin and protein-cyclodextrin host-guest complexes the aromatic amino acids are reported to be the principal responsible of the interaction. For these reasons, we have investigated the inclusion properties of nine designed tripeptides, obtained permuting the position of two L-alanines (Ala, A) with that of one L-tryptophan (Trp, W), L-phenylalanine (Phe, F), or L-tyrosine (Tyr, Y), respectively. Interestingly, the position of the aromatic side-chain in the sequence appears to modulate the β-CD:peptide binding constants, determined via UV-Vis and NMR spectroscopy, which in turn assumes values higher than those reported for the single amino acid. The tripeptides containing a tyrosine showed the highest binding constants, with the central position in the Ac-AYA-NH2 peptide becoming the most favorite for the interaction. A combined NMR and Molecular Docking approach permitted to build detailed complex models, highlighting the stabilizing interactions of the neighboring amino acids backbone atoms with the upper rim of the β-CD. PMID:25985927

  10. Sorption of polar and nonpolar aromatic compounds to two humic acids with varied structural heterogeneity

    SciTech Connect

    Sun, H.Y.; Zhu, D.Q.; Mao, J.D.

    2008-12-15

    The major objective of the present study was to evaluate the correlation between structural nature of humic acids (HAs) and sorption affinity of organic compounds with varied polarity. We compared the sorption behavior of three aromatic compounds-nonpolar phenanthrene (PHEN) and 1,2,4,5-tetrachlorobenzene (TeCB) and highly polar 2,4-dichlorophenol (DCP)-to a solid-phase coal humic acid (CHA) and a soil humic acid (SHA) suspended in aqueous solution. The structural nature of HAs was characterized using elemental analysis, ultraviolet absorbance, diffusive reflectance Fourier-transform infrared, and solid-state C-13 nuclear magnetic resonance. The two tested HAs have very different structural properties: CHA consists primarily of poly(methylene)-rich aliphatics with high aromatic content and some COO/N-C=O but low polarity, while SHA consists of young materials of lignin, carbohydrates, and peptides with high polarity. In response to the structural heterogeneity of HAs, sorption of nonpolar and more hydrophobic solutes (PHEN, TeCB) to CHA is much greater than that to SHA because of the predominance of hydrophobic effects; however, disparities in sorption affinity between the two HAs become smaller for polar and less hydrophobic DCP because of the major role played by polar interactions. The influence of pH on the sorption of different solutes to the two HAs was also discussed. The results of the present work highlight the importance of structural heterogeneity of both solutes and HAs in the sorption process.

  11. Predicting the Sorption of Aromatic Acids to Noncarbonized and Carbonized Sorbents.

    PubMed

    Sigmund, Gabriel; Sun, Huichao; Hofmann, Thilo; Kah, Melanie

    2016-04-01

    Approaches based on the octanol-water partition coefficient are commonly used to describe sorption of neutral organic compounds in environmental systems, but they are not suitable for organic acids, which can dissociate to form anions. We here investigate the applicability of an alternative approach based on the pH-dependent distribution ratio (DOW) to describe sorption of aromatic acids to sorbents representing different degrees of carbonization. Sorption isotherms for four structurally similar acids ((2,4-dichlorophenoxy)acetic acid (2,4-D), 4-chloro-2-15 methylphenoxy)acetic acid (MCPA), 4-(2,4-dichlorophenoxy)butanoic16 acid (2,4-DB), and 5-chloro-2-(2,4-dichlorophenoxy)phenol (triclosan)) were measured for 15 sorbents: fresh and carbonized wood shavings, pig manure, sewage sludge, carbon nanotubes, and activated carbon. Dissociation greatly affected the sorption of all acids. Sorption coefficients measured in the high pH range indicated that sorption of the anions ranged over several orders of magnitude and should not be neglected. Sorption trends for all sorbates and carbonized sorbents could be very well described by a single regression equation that included DOW of the sorbate and the specific surface area of the sorbent (R(2) > 0.89). PMID:26949216

  12. The chemical structure of highly aromatic humic acids in three volcanic ash soils as determined by dipolar dephasing NMR studies

    USGS Publications Warehouse

    Hatcher, P.G.; Schnitzer, M.; Vassallo, A.M.; Wilson, M.A.

    1989-01-01

    Dipolar dephasing 13C NMR studies of three highly aromatic humic acids, one from a modern soil and two from paleosols, have permitted the determination of the degree of aromatic substitution. From these data and the normal solid-state 13C NMR data we have been able to develop a model for the average chemical structure of these humic acids that generally correlates well with permanganate oxidation data. The models depict these humic acids as benzene di- and tricarboxylic acids interconnected by biphenyl linkages. An increasing degree of substitution is observed with increasing geologic age. These structures may be characteristic of the resistant aromatic part of the "core" of humic substances that survives degradation. ?? 1989.

  13. Comments on the Treatment of Aromaticity and Acid-Base Character of Pyridine and Pyrrole in Contemporary Organic Chemistry Textbooks

    NASA Astrophysics Data System (ADS)

    Anderson, Hugh J.; Bauer, Ludwig

    1999-08-01

    Presentations of aromaticity and acid-base character of pyridine and pyrrole in 18 contemporary organic chemistry textbooks were surveyed. Superficially, each of these two monoaza aromatic heterocycles retains an electron pair on its sp2-hybridized ring nitrogen, ostensibly available for neutralization with a proton to form a salt. The two nonbonded electrons in pyridine, in an sp2-hybridized orbital outside the ring, are not interacting with the 6p-electron aromatic sextet and thus are fully available for neutralization to form an N+-H pyridinium cation. However, in pyrrole, the nonbonded electron pair on nitrogen is part of the aromatic 6p- electron sextet and is not available for NH salt formation, since this would generate an aliphatic (highly reactive) diene imminium cation, which would destroy pyrrole's aromaticity. However, electrophilic attack of a proton in an irreversible manner attacks C-2 of pyrrole to form a resonance-stabilized cationic intermediate capable of further transformations. Pyridine is classified correctly as a weak base, while pyrrole in aqueous solutions is classified essentially neutral. In reality, pyrrole is a weak acid, neutralized by strong bases to generate a stable aromatic and highly reactive nucleophilic anion. Most authors fail to stress the acidic property of pyrrole and some organic texts need revision to eliminate some misconceptions and omissions.

  14. CATABOLISM OF AROMATIC BIOGENIC AMINES BY 'PSEUDOMONAS AERUGINOSA' PA01 VIA META CLEAVAGE OF HOMOPROTOCATECHUIC ACID (JOURNAL VERSION)

    EPA Science Inventory

    Pseudomonas aruginosa PA01 catabolized the aromatic amines tyramine and octopamine through 4-hydroxyphenylacetic acid and 3,4-dihydroxyphenylacetic acid (HPA). Meta ring cleavage was mediated by 3-4-dihydroxyphenylacetate 2,3-dioxygenase (HPADO), producing 2-hydroxy-5-carboxymeth...

  15. Polycyclic Aromatic Acids Are Primary Metabolites of Alkyl-PAHs-A Case Study with Nereis diversicolor.

    PubMed

    Malmquist, Linus M V; Selck, Henriette; Jørgensen, Kåre B; Christensen, Jan H

    2015-05-01

    Although concentrations of alkylated polycyclic aromatic hydrocarbons (alkyl-PAHs) in oil-contaminated sediments are higher than those of unsubstituted PAHs, only little attention has been given to metabolism and ecotoxicity of alkyl-PAHs. In this study we demonstrated that metabolism of alkyl-PAHs primarily forms polycyclic aromatic acids (PAAs). We generalize this to other alkyl-PAHs, based on literature and the present study of the metabolism of 1-methylphenanthrene, 3,6-dimethylphenanthrene, and 1-, 2-, 3-, and 6-methylchrysene related to their unsubstituted parent PAHs. Also, we observed that body burdens and production of PAAs was related to the position of the methyl group, showing the same isomer specific preferences as for microbial degradation of alkyl-PAHs. We detected a high production of PAAs, and larger metabolism of alkyl-PAHs than their unsubstituted parent PAHs. We therefore propose that carboxylic acid metabolites of alkyl-PAHs have the potential of constituting a new class of contaminants in marine waters that needs attention in relation to ecological risk assessments. PMID:25827176

  16. Proton induced tautomeric switching in N-rich aromatics with tunable acid-base character

    NASA Astrophysics Data System (ADS)

    Centore, Roberto; Manfredi, Carla; Fusco, Sandra; Maglione, Cira; Carella, Antonio; Capobianco, Amedeo; Peluso, Andrea; Colonna, Daniele; Di Carlo, Aldo

    2015-08-01

    The acid-base properties of selected derivatives of the [1,2,4]triazolo[3,2-c][1,2,4]triazole fused aromatic system have been investigated by UV-vis spectroscopy. Neutral heterobicycles (HL) exhibit amphoteric behavior (they can deliver the N-H proton forming the conjugated base L- and can accept up to two protons, forming the species H2L+ and H3L++) and show an unprecedented tautomeric switching upon protonation, as revealed by single crystal X-ray analysis and confirmed by theoretical calculations. By varying the groups attached at the heterocycle, a remarkable shift of pKai values, up to 5-6 units, is observed. In particular, with strong electron attractor groups at position 7 (e.g. p-nitrophenyl or pentafluorophenyl) the neutral compounds are stronger acids than phenol or p-nitrophenol.

  17. Pyrolysis of simple coal model compounds containing aromatic carboxylic acids: Does decarboxylation lead to cross-linking?

    SciTech Connect

    Eskay, T.P.; Britt, P.F.; Buchanan, A.C.

    1996-10-01

    Recently, a number of studies have shown that the evolution of CO{sub 2} from carboxylate groups is a key indicator of cross-linking reactions in pyrolysis and liquefaction of low rank coals. This result suggests that the thermal decarboxylation may occur by a pathway which initiates retrogressive reactions in the coal polymer. However, the chemistry of the thermal decomposition of aromatic carboxylic acids is not thoroughly understood. To provide insight into the thermal decarboxylation of aromatic carboxylic acids, and the role decarboxylation may play in coal pyrolysis, we have conducted a study of the pyrolysis of several bibenzyls containing aromatic carboxylic acids. The results of our pyrolysis study and the relevance of thermal decarboxylation on coal cross-linking reactions will be discussed.

  18. Enzymatic Acylation of Anthocyanin Isolated from Black Rice with Methyl Aromatic Acid Ester as Donor: Stability of the Acylated Derivatives.

    PubMed

    Yan, Zheng; Li, Chunyang; Zhang, Lixia; Liu, Qin; Ou, Shiyi; Zeng, Xiaoxiong

    2016-02-10

    The enzymatic acylation of anthocyanin from black rice with aromatic acid methyl esters as acyl donors and Candida antarctica lipase B was carried out under reduced pressure. The highest conversion of 91% was obtained with benzoic acid methyl ester as acyl donor; cyanidin 3-(6″-benzoyl)-glucoside, cyanidin 3-(6″-salicyloyl)-glucoside, and cyanidin 3-(6″-cinnamoyl)-glucoside were successfully synthesized. This is the first report on the enzymatic acylation of anthocyanin from black rice with methyl aromatic esters as acyl donors and lipase as biocatalyst. Furthermore, the acylation with aromatic carboxylic acids enhanced both the thermostability and light resistivity of anthocyanin. In particular, cyanidin 3-(6″-cinnamoyl)-glucoside was the most stable among the three acylated anthocyanins synthesized. PMID:26766135

  19. Indole-3-acetic acid biosynthetic pathway and aromatic amino acid aminotransferase activities in Pantoea dispersa strain GPK.

    PubMed

    Kulkarni, G B; Nayak, A S; Sajjan, S S; Oblesha, A; Karegoudar, T B

    2013-05-01

    This investigation deals with the production of IAA by a bacterial isolate Pantoea dispersa strain GPK (PDG) identified by 16S rRNA gene sequence analysis. HPLC and Mass spectral analysis of metabolites from bacterial spent medium revealed that, IAA production by PDG is Trp-dependent and follows indole-3-pyruvic acid (IPyA) pathway. Substrate specificity study of aromatic amino acid aminotransferase (AAT) showed high activities, only when tryptophan (Trp) and α-ketoglutarate (α-kg) were used as substrates. AAT is highly specific for Trp and α-kg as amino group donor and acceptor, respectively. The effect of exogenous IAA on bacterial growth was established. Low concentration of exogenous IAA induced the growth, whereas high concentration decreased the growth of bacterium. PDG treatment significantly increased the root length, shoot length and dry mass of the chickpea and pigeon pea plants. PMID:23448265

  20. Mechanisms of cellular membrane effects of TCDD, selected perfluorinated acids, and polyhalogenated aromatic hydrocarbons. Forecast report

    SciTech Connect

    Rogers-Back, A.

    1985-02-01

    The first six months of the contract have been devoted to examining the effects of perfluorinated acids and polyhalogenated aromatic hydrocarbons on the colony-forming ability of L5178Y cells. Two subclones of this cell line have been utilized. One subclone is designated L5178Y TK+/. The two cell lines differ markedly in their growth characteristics. L5178Y TK+/- cells tend to associate in clumps of cells and are grown in a shaker incubator to produce better cell suspensions. L5178Y TK+/+ cells grow as a single cell suspension without agitation. The toxic response of both cell lines after treatment with the perfluorinated acids (perfluoro-n-decanoic acid) was measured. In summary, the results for the perfluorinated acids with chain length of 9 or 10 indicate that there is some dissociation of colony growth from suspension growth. Medium type does not affect the toxicity. This would imply that these perfluorinated acids are producing toxicity through a membrane interaction. The dissociation appears to occur in the TK+/+ cells at concentrations approximately 20 higher than those previously reported.

  1. Aromatic amino acids as precursors of antimicrobial metabolites in Geotrichum candidum.

    PubMed

    Naz, Saima; Gueguen-Minerbe, Marielle; Cretenet, Marina; Vernoux, Jean-Paul

    2013-07-01

    Geotrichum candidum ATCC 204307 was previously found to generate phenyllactic acid (PLA) and indoleacetic acid (ILA) in complex culture media. In this study, a relationship between concentrations of PLA, ILA, and hydroxy PLA (OH-PLA) and initial concentrations of phenylalanine, tryptophan, and tyrosine, added respectively as unique sources of nitrogen in synthetic medium, was established. Phenylpyruvic acid (PPA), an intermediate compound of PLA metabolism, was able to induce not only PLA but also phenylethyl alcohol (PEA) production when used separately as initial substrate. Under pH, temperature, and salt concentrations used for cheese-making, phenylalanine was found to be the most efficient substrate for antimicrobial metabolite production. In excess of substrate, different yeast strains of Geotrichum candidum, Yarrowia lipolytica, Candida natalensis, and Candida catenulata were shown here to produce 1.6 ± 0.5-5.0 ± 0.2 mM of PLA from phenylalanine, 5.0 ± 0.1-10.9 ± 0.3 mM of ILA from tryptophan, and 1.3 ± 0.3-7.0 ± 0.02 of PLA and 0.1 ± 0.0-2.22 ± 0.09 mM of PEA from PPA. Geotrichum candidum ATCC 204307 was the highest producer. This is the first time these antimicrobial metabolites PLA, OH-PLA, ILA, and PEA are being reported as the reaction products of aromatic amino acids catabolism in G. candidum. PMID:23590565

  2. 4D APSY-HBCB(CG)CDHD experiment for automated assignment of aromatic amino acid side chains in proteins.

    PubMed

    Krähenbühl, Barbara; Hiller, Sebastian; Wider, Gerhard

    2011-11-01

    A four-dimensional (4D) APSY (automated projection spectroscopy)-HBCB(CG)CDHD experiment is presented. This 4D experiment correlates aromatic with aliphatic carbon and proton resonances from the same amino acid side chain of proteins in aqueous solution. It thus allows unambiguous sequence-specific assignment of aromatic amino acid ring signals based on backbone assignments. Compared to conventional 2D approaches, the inclusion of evolution periods on (1)H(β) and (13)C(δ) efficiently removes overlaps, and provides two additional frequencies for consequent automated or manual matching. The experiment was successfully applied to three proteins with molecular weights from 6 to 13 kDa. For the complementation of the assignment of the aromatic resonances, TOCSY- or COSY-based versions of a 4D APSY-HCCH(aro) sequence are proposed. PMID:21947871

  3. Bioactive Compounds Derived from the Yeast Metabolism of Aromatic Amino Acids during Alcoholic Fermentation

    PubMed Central

    Guillamon, Jose Manuel; Torija, Maria Jesus; Beltran, Gemma; Troncoso, Ana M.; Garcia-Parrilla, M. Carmen

    2014-01-01

    Metabolites resulting from nitrogen metabolism in yeast are currently found in some fermented beverages such as wine and beer. Their study has recently attracted the attention of researchers. Some metabolites derived from aromatic amino acids are bioactive compounds that can behave as hormones or even mimic their role in humans and may also act as regulators in yeast. Although the metabolic pathways for their formation are well known, the physiological significance is still far from being understood. The understanding of this relevance will be a key element in managing the production of these compounds under controlled conditions, to offer fermented food with specific enrichment in these compounds or even to use the yeast as nutritional complements. PMID:24895623

  4. Structural studies of aromatic carboxylic acids via computational chemistry and microwave spectroscopy

    NASA Astrophysics Data System (ADS)

    Godfrey, Peter D.; McNaughton, Don

    2013-01-01

    The structures of three simple aromatic carboxylic acids: benzoic, isophthalic, and terephthalic have been investigated using a combination of theoretical high-level quantum chemical calculations and experimental millimeter-wave Stark-modulated free-jet absorption spectroscopy. Rotational and centrifugal distortion constants have been measured for one conformer of each of the species and for its -COOD isotopologue, leading to the experimental determination of the coordinates of the carboxyl hydrogen atom. Consideration of the observed inertial defect is consistent with a planar equilibrium structure for each species. Calculated structures, relative energies, and electric dipole moments, using ab initio methods at the MP2/cc-pVTZ level, are reported for all the lower-energy conformers of each species. The theoretical calculations lead to the unambiguous identification of the conformers involved in the observed microwave spectra. The match between theoretical and spectroscopic measurements was used to gauge the reliability of the quantum chemical structure optimization calculations.

  5. Extended Electron-Transfer in Animal Cryptochromes Mediated by a Tetrad of Aromatic Amino Acids.

    PubMed

    Nohr, Daniel; Franz, Sophie; Rodriguez, Ryan; Paulus, Bernd; Essen, Lars-Oliver; Weber, Stefan; Schleicher, Erik

    2016-07-26

    The cryptochrome/photolyase protein family possesses a conserved triad of tryptophans that may act as a molecular wire to transport electrons from the protein surface to the FAD cofactor for activation and/or signaling-state formation. Members from the animal (and animal-like) cryptochrome subclade use this process in a light-induced fashion in a number of exciting responses, such as the (re-)setting of circadian rhythms or magnetoreception; however, electron-transfer pathways have not been explored in detail yet. Therefore, we present an in-depth time-resolved optical and electron-paramagnetic resonance spectroscopic study of two cryptochromes from Chlamydomonas reinhardtii and Drosophila melanogaster. The results do not only reveal the existence of a fourth, more distant aromatic amino acid that serves as a terminal electron donor in both proteins, but also show that a tyrosine is able to fulfill this very role in Chlamydomonas reinhardtii cryptochrome. Additionally, exchange of the respective fourth aromatic amino acid to redox-inactive phenylalanines still leads to light-induced radical pair formation; however, the lifetimes of these species are drastically reduced from the ms- to the μs-range. The results presented in this study open up a new chapter, to our knowledge, in the diversity of electron-transfer pathways in cryptochromes. Moreover, they could explain unique functions of animal cryptochromes, in particular their potential roles in magnetoreception because magnetic-field effects of light-induced radical pairs strongly depend on distance and orientation parameters. PMID:27463133

  6. Kinetically and thermodynamically stable isomers of thorium chelates of polyaza polycarboxylic macrocycles

    NASA Astrophysics Data System (ADS)

    Jacques, Vincent; Desreux, Jean F.

    1994-10-01

    The solution conformation of the thorium(IV) complexes of two polyaza polycarboxylic macrocycles, DOTA and HEHA (1,4,7,10-tetraazacyclododecane-N, N', N(double prime), N(triple prime)-tetraacetic acid and 1,4,7,10,13,16-hexaazacyclooctadecane-N, N', N(double prime), N(triple prime), N(double prime)(double prime), N(double prime)(triple prime)-hexaacetic acid), was investigated by one- and two-dimensional nuclear magnetic resonance spectroscopy. ThHEHA(2+) forms a kinetically stable topomer of C2 symmetry and a thermodynamically stable topomer of S6 symmetry. Both complexes are assigned an icosahedral geometry. The activation energy for the intermolecular exchange is very high (214 kJ/mol). The behavior of ThHEHA(2+) contrasts with the properties of the other Th(IV) chelates that are known to be fluxional.

  7. Genetic Engineering Activates Biosynthesis of Aromatic Fumaric Acid Amides in the Human Pathogen Aspergillus fumigatus

    PubMed Central

    Kalb, Daniel; Heinekamp, Thorsten; Lackner, Gerald; Scharf, Daniel H.; Dahse, Hans-Martin; Brakhage, Axel A.

    2014-01-01

    The Aspergillus fumigatus nonribosomal peptide synthetase FtpA is among the few of this species whose natural product has remained unknown. Both FtpA adenylation domains were characterized in vitro. Fumaric acid was identified as preferred substrate of the first and both l-tyrosine and l-phenylalanine as preferred substrates of the second adenylation domain. Genetically engineered A. fumigatus strains expressed either ftpA or the regulator gene ftpR, encoded in the same cluster of genes, under the control of the doxycycline-inducible tetracycline-induced transcriptional activation (tet-on) cassette. These strains produced fumaryl-l-tyrosine and fumaryl-l-phenylalanine which were identified by liquid chromatography and high-resolution mass spectrometry. Modeling of the first adenylation domain in silico provided insight into the structural requirements to bind fumaric acid as peptide synthetase substrate. This work adds aromatic fumaric acid amides to the secondary metabolome of the important human pathogen A. fumigatus which was previously not known as a producer of these compounds. PMID:25527545

  8. Dietary supplementation with aromatic amino acids increases protein synthesis in children wHh severe acute malnutrition

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Although 2 earlier studies reported that aromatic amino acid (AAA) supplementation of children with severe acute malnutrition (SAM) improved whole-body protein anabolism during the early postadmission (maintenance) phase of rehabilitation, it is not known whether this positive effect was maintained ...

  9. Enhancing muconic acid production from glucose and lignin-derived aromatic compounds via increased protocatechuate decarboxylase activity

    DOE PAGESBeta

    Johnson, Christopher W.; Salvachua, Davinia; Khanna, Payal; Smith, Holly; Peterson, Darren J.; Beckham, Gregg T.

    2016-04-22

    The conversion of biomass-derived sugars and aromatic molecules to cis,cis-muconic acid (referred to hereafter as muconic acid or muconate) has been of recent interest owing to its facile conversion to adipic acid, an important commodity chemical. Metabolic routes to produce muconate from both sugars and many lignin-derived aromatic compounds require the use of a decarboxylase to convert protocatechuate (PCA, 3,4-dihydroxybenzoate) to catechol (1,2-dihydroxybenzene), two central aromatic intermediates in this pathway. Several studies have identified the PCA decarboxylase as a metabolic bottleneck, causing an accumulation of PCA that subsequently reduces muconate production. A recent study showed that activity of the PCAmore » decarboxylase is enhanced by co-expression of two genetically associated proteins, one of which likely produces a flavin-derived cofactor utilized by the decarboxylase. Using entirely genome-integrated gene expression, we have engineered Pseudomonas putida KT2440-derived strains to produce muconate from either aromatic molecules or sugars and demonstrate in both cases that co-expression of these decarboxylase associated proteins reduces PCA accumulation and enhances muconate production relative to strains expressing the PCA decarboxylase alone. In bioreactor experiments, co-expression increased the specific productivity (mg/g cells/h) of muconate from the aromatic lignin monomer p-coumarate by 50% and resulted in a titer of >15 g/L. In strains engineered to produce muconate from glucose, co-expression more than tripled the titer, yield, productivity, and specific productivity, with the best strain producing 4.92+/-0.48 g/L muconate. Furthermore, this study demonstrates that overcoming the PCA decarboxylase bottleneck can increase muconate yields from biomass-derived sugars and aromatic molecules in industrially relevant strains and cultivation conditions.« less

  10. Long-term carbon stabilization through sorption of dissolved aromatic acids to reactive particles (Invited)

    NASA Astrophysics Data System (ADS)

    Kramer, M. G.; Sanderman, J.; Chadwick, O.; Chorover, J.; Vitousek, P.

    2010-12-01

    Short-range order minerals are highly reactive soil constituents that are found in all soils and in particularly high quantities in volcanic soils. They retain large quantities of soil carbon, thereby acting as a long-term sink for carbon dioxide, but the main source for this carbon accumulation in soil is not yet known. We evaluated the biochemistry of solid and dissolved organic carbon in horizons containing differing short-range ordered mineral concentrations using solid-state 13C nuclear magnetic resonance spectroscopy, stable isotope measurements and soil column leaching experiments across a well-constrained chronosequence of volcanic soils in Hawai’i. Molecular mixing model results, isotopic and elemental measurements, indicate that the oldest and most persistent C stores across the chronosequence are comprised not of highly microbially processed organic matter (e.g. proteins or lipids), but rather of partially oxidized aromatic plant compounds (up to 62% of the total soil C) preserved through chemical bonding to reactive soil minerals via carboxyl-rich functionalities. NMR spectra obtained from deep soil horizons containing an abundance of SRO minerals, showed strong chemical resemblance to that of DOM derived from plant litter. Solublization and high production rates of recalcitrant DOM controlled substantially by microbial activity were observed in the soil column leaching experiments. When the DOM-rich solution derived from organic horizons was leached through mineral soil horizons, the quantity of DOM sorbed was dependent on the abundance of SRO minerals present in the soil. These results suggest that microbial-driven DOM formation derived from plant litter and the subsequent binding of the aromatic acids in the DOM to reactive mineral surfaces is a dominant source for long-term soil carbon stabilization in these soils. This potentially globally significant carbon sink may be unresponsive to climate change over decadal to centennial timescales due to

  11. Thermolysis of a polymer model of aromatic carboxylic acids in low-rank coal

    SciTech Connect

    Mungall, W.S.; Britt, P.F.; Buchanan, A.C. III

    1997-03-01

    To compliment our current investigation into the role that decarboxylation of aromatic carboxylic acids plays in the low-temperature cross-linking of low-rank coals, we are investigating the thermolysis of a polymeric coal model compound to determine if the polymeric network structure of coal can alter the decarboxylation pathways. In this investigation, a bibenzylic polymer, poly-(m-xylylene-co-5-carboxy-m-xylylene), 1, was synthesized containing 2.3 carboxylic acids per 100 carbons, which is similar to that found in Zapp lignite. The pyrolysis of 1 was compared to poly-m-xylylene, 2, and the methyl ester of 1, 3, to determine if the carboxy group enhances cross-linking reactions. The major product from the pyrolysis of 1 at 375{degrees} C or 400{degrees} C for 1 h was a THF insoluble residue (60-75 wt%), while pyrolysis of 2 or the methyl ester of 1 produced only a THF soluble product. The mechanistic pathways leading to cross-linking will be discussed.

  12. Supramolecular aromaticity

    NASA Astrophysics Data System (ADS)

    Karabıyık, Hande; Sevinçek, Resul; Karabıyık, Hasan

    2014-05-01

    We report experimental and theoretical evidences for supramolecular aromaticity as a new concept to be widely used in researches about molecular crystals. CSD survey regarding frequently encountered resonance-assisted H-bonds (RAHBs) in formic acid, formamide, formimidamide, formic acid-formamide, and formamide-formimidamide dimers shows that supramolecular quasirings formed by RAHBs have remarkable electronic delocalization within themselves, which is reminiscent of aromaticity at supramolecular level. This study criticizes and reevaluates the validity of conventional judgment which states that ring systems formed by intermolecular H-bonds cannot be aromatic. Thus, the term aromaticity can be extended to supramolecular systems formed by RAHBs. Supramolecular aromaticity has a multi-fold nature involving both σ- and π-delocalization, and σ-delocalization through RAHBs takes on a task of compensating σ-deficiency within quasirings. Atomic composition in donor-acceptor set of the dimers is descriptive for supramolecular aromaticity. We revised bond-valence parameters for RAHBs and they suggest that hypervalent character of H atoms is more pronounced than their hypovalent character in RAHBs. The σ-delocalized bonding within H-bonded quasirings necessitates hypervalent character of H atoms. Quantum chemical calculations based on adiabatic Hydrogen Atom Transfer (HAT) between the monomers reveal that topological parameters at ring critical points (RCPs) of the quasirings correlate well with Shannon's entropic aromaticity index. The presence of additional LP orbital on O atoms implying more diffused LP-orbitals in donor-acceptor set leads to the formation of resonance-disabling states reducing supramolecular aromaticity of a quasiring and energetic cost of the electron transfer between the monomers. There is a nonignorable electron transfer between the monomers even in the cases where H atoms are close to donor or acceptor atom. NBO analyses have revealed that

  13. Secondary Structures in a Freeze-Dried Lignite Humic Acid Fraction Caused by Hydrogen-Bonding of Acidic Protons with Aromatic Rings.

    PubMed

    Cao, Xiaoyan; Drosos, Marios; Leenheer, Jerry A; Mao, Jingdong

    2016-02-16

    A lignite humic acid (HA) was separated from inorganic and non-HA impurities (i.e., aluminosilicates, metals) and fractionated by a combination of dialysis and XAD-8 resin. Fractionation revealed a more homogeneous structure of lignite HA. New and more specific structural information on the main lignite HA fraction is obtained by solid-state nuclear magnetic resonance (NMR) spectroscopy. Quantitative (13)C multiple cross-polarization (multiCP) NMR indicated oxidized phenyl propane structures derived from lignin. MultiCP experiments, conducted on potassium HA salts titrated to pH 10 and pH 12, revealed shifts consistent with carboxylate and phenolate formation, but structural changes associated with enolate formation from aromatic beta keto acids were not detected. Two-dimensional (1)H-(13)C heteronuclear correlation (2D HETCOR) NMR indicated aryl-aliphatic ketones, aliphatic and aromatic carboxyl groups, phenol, and methoxy phenyl ethers. Acidic protons from carboxyl groups in both the lignite HA fraction and a synthetic HA-like polycondensate were found to be hydrogen-bonded with electron-rich aromatic rings. Our results coupled with published infrared spectra provide evidence for the preferential hydrogen bonding of acidic hydrogens with electron-rich aromatic rings rather than adjacent carbonyl groups. These hydrogen-bonding interactions likely result from stereochemical arrangements in primary structures and folding. PMID:26836017

  14. Interactions of low molecular weight aromatic acids and amino acids with goethite, kaolinite and bentonite with or without organic matter coating

    NASA Astrophysics Data System (ADS)

    Gao, Jiajia; Jansen, Boris; Cerli, Chiara; Kalbitz, Karsten

    2015-04-01

    Interaction of organic matter molecules with the soil's solid phase is a key factor influencing the stabilization of carbon in soils and thus forms a crucial aspect of the global carbon cycle. While subject of much research attention so far, we still have much to learn about such interactions at the molecular level; in particular in the light of competition between different classes of organic molecules and in the presence of previously adsorbed soil organic matter. We studied the interaction of a group of low molecular weight (LMW) aromatic acids (salicylic, syringic, vanillic and ferulic acid) and amino acids (lysine, glutamic, leucine and phenylalanine) on goethite, kaolinite and bentonite with and without previously adsorbed dissolved organic matter (DOM). For this we used batch experiments at pH = 6.0 where some of the organic compounds were positively charged (i.e. lysine) or negatively charged (i.e. glutamic and salicylic acid) while the minerals also displayed positively (i.e. goethite) or negatively charged surfaces (i.e. bentonite). We found much higher sorption of salicylic acid and lysine than other compounds. On the bare minerals we found a great variety of sorption strength, with salicylic acid strongly adsorbed, while syringic, vanillic and ferulic acid showed little or no adsorption. For the amino acids, protonated lysine showed a stronger affinity to negatively charged kaolinite and bentonite than other amino acids. While deprotonated glutamic acid showed the strongest adsorption on goethite. Leucine and phenylalanine showed hardly any adsorption on any of the minerals. When present concurrently, amino acids decreased the sorption of salicylic acid on the three types of mineral, while the presence of LMW aromatic acids increased the sorption of lysine on kaolinite and bentonite and the sorption of glutamic acid on goethite. The presence of previously adsorbed DOM reduced the sorption of salicylic acid and lysine. The results confirm that

  15. Determination of polycyclic aromatic hydrocarbons by four-way parallel factor analysis in presence of humic acid.

    PubMed

    Yang, Ruifang; Zhao, Nanjing; Xiao, Xue; Yu, Shaohui; Liu, Jianguo; Liu, Wenqing

    2016-01-01

    There is not effective method to solve the quenching effect of quencher in fluorescence spectra measurement and recognition of polycyclic aromatic hydrocarbons in aquatic environment. In this work, a four-way dataset combined with four-way parallel factor analysis is used to identify and quantify polycyclic aromatic hydrocarbons in the presence of humic acid, a fluorescent quencher and an ubiquitous substance in aquatic system, through modeling the quenching effect of humic acid by decomposing the four-way dataset into four loading matrices corresponding to relative concentration, excitation spectra, emission spectra and fluorescence quantum yield, respectively. It is found that Phenanthrene, pyrene, anthracene and fluorene can be recognized simultaneously with the similarities all above 0.980 between resolved spectra and reference spectra. Moreover, the concentrations of them ranging from 0 to 8μgL(-1) in the test samples prepared with river water could also be predicted successfully with recovery rate of each polycyclic aromatic hydrocarbon between 100% and 120%, which were higher than those of three-way PARAFAC. These results demonstrate that the combination of four-way dataset with four-way parallel factor analysis could be a promising method to recognize the fluorescence spectra of polycyclic aromatic hydrocarbons in the presence of fluorescent quencher from both qualitative and quantitative perspective. PMID:26233788

  16. Determination of polycyclic aromatic hydrocarbons by four-way parallel factor analysis in presence of humic acid

    NASA Astrophysics Data System (ADS)

    Yang, Ruifang; Zhao, Nanjing; Xiao, Xue; Yu, Shaohui; Liu, Jianguo; Liu, Wenqing

    2016-01-01

    There is not effective method to solve the quenching effect of quencher in fluorescence spectra measurement and recognition of polycyclic aromatic hydrocarbons in aquatic environment. In this work, a four-way dataset combined with four-way parallel factor analysis is used to identify and quantify polycyclic aromatic hydrocarbons in the presence of humic acid, a fluorescent quencher and an ubiquitous substance in aquatic system, through modeling the quenching effect of humic acid by decomposing the four-way dataset into four loading matrices corresponding to relative concentration, excitation spectra, emission spectra and fluorescence quantum yield, respectively. It is found that Phenanthrene, pyrene, anthracene and fluorene can be recognized simultaneously with the similarities all above 0.980 between resolved spectra and reference spectra. Moreover, the concentrations of them ranging from 0 to 8 μg L-1 in the test samples prepared with river water could also be predicted successfully with recovery rate of each polycyclic aromatic hydrocarbon between 100% and 120%, which were higher than those of three-way PARAFAC. These results demonstrate that the combination of four-way dataset with four-way parallel factor analysis could be a promising method to recognize the fluorescence spectra of polycyclic aromatic hydrocarbons in the presence of fluorescent quencher from both qualitative and quantitative perspective.

  17. Synthesis of o-Carboxyarylacrylic Acids by Room Temperature Oxidative Cleavage of Hydroxynaphthalenes and Higher Aromatics with Oxone.

    PubMed

    Parida, Keshaba Nanda; Moorthy, Jarugu Narasimha

    2015-08-21

    A simple procedure for the synthesis of a variety of o-carboxyarylacrylic acids has been developed with Oxone (2KHSO5·KHSO4·K2SO4); the oxidation reaction involves the stirring of methoxy/hydroxy-substituted naphthalenes, phenanthrenes, anthracenes, etc. with Oxone in an acetonitrile-water mixture (1:1, v/v) at rt. Mechanistically, the reaction proceeds via initial oxidation of naphthalene to o-quinone, which undergoes cleavage to the corresponding o-carboxyarylacrylic acid. The higher aromatics are found to yield carboxymethyl lactones derived from the initially formed o-carboxyarylacrylic acids. PMID:26194877

  18. Influence of pH and diluent on the ion-pair solvent extraction of aromatic carboxylic acids using quaternary ammonium salts

    SciTech Connect

    Kawamura, K.; Takahashi, K.; Okuwaki, A.

    2006-07-01

    The influence of pH and diluent on the ion-pair solvent extraction of benzene polycarboxylic acids have been investigated for the separation of the coal oxidation products, which are formed by the treatment with alkaline solutions at high temperatures. Although the extent of the solvent extraction of benzoic acid (1BE) with a quaternary ammonium reagent (tri-n-octylmethylammonium chloride) into chloroform and benzene did not change at a very acidic and alkaline solutions, those of 1,2-benzenedicarboxylic acid (12BE) and trimellitic acid (124BE) somewhat decreased at very low pH and very high pH. The magnitudes of the equilibrium constants (K{sub ex}) of 1BE using a different diluent decreased in the order benzene {gt} carbontetrachloride {gt} 1,2-dichloroethane {gt} cyclohexane {gt} hexane {gt} chloroform {gt} 1-octanol and those of 12BE decreased in the order benzene {gt} cyclohexane {gt} carbontetrachloride {gt} hexane {gt} 1,2-dichloroethane {gt} chloroform. The inspection of the correlation between the values of K{sub ex} and several parameters of the diluent implies that the magnitude of K{sub ex} can be described by using the dielectric constant and the solubility parameter of diluent.

  19. The Antifungal Eugenol Perturbs Dual Aromatic and Branched-Chain Amino Acid Permeases in the Cytoplasmic Membrane of Yeast

    PubMed Central

    Darvishi, Emad; Omidi, Mansoor; Bushehri, Ali Akbar Shahnejat; Golshani, Ashkan; Smith, Myron L.

    2013-01-01

    Eugenol is an aromatic component of clove oil that has therapeutic potential as an antifungal drug, although its mode of action and precise cellular target(s) remain ambiguous. To address this knowledge gap, a chemical-genetic profile analysis of eugenol was done using ∼4700 haploid Saccharomyces cerevisiae gene deletion mutants to reveal 21 deletion mutants with the greatest degree of susceptibility. Cellular roles of deleted genes in the most susceptible mutants indicate that the main targets for eugenol include pathways involved in biosynthesis and transport of aromatic and branched-chain amino acids. Follow-up analyses showed inhibitory effects of eugenol on amino acid permeases in the yeast cytoplasmic membrane. Furthermore, phenotypic suppression analysis revealed that eugenol interferes with two permeases, Tat1p and Gap1p, which are both involved in dual transport of aromatic and branched-chain amino acids through the yeast cytoplasmic membrane. Perturbation of cytoplasmic permeases represents a novel antifungal target and may explain previous observations that exposure to eugenol results in leakage of cell contents. Eugenol exposure may also contribute to amino acid starvation and thus holds promise as an anticancer therapeutic drug. Finally, this study provides further evidence of the usefulness of the yeast Gene Deletion Array approach in uncovering the mode of action of natural health products. PMID:24204588

  20. Aromatic L-amino acid decarboxylase deficiency diagnosed by clinical metabolomic profiling of plasma.

    PubMed

    Atwal, Paldeep S; Donti, Taraka R; Cardon, Aaron L; Bacino, C A; Sun, Qin; Emrick, L; Reid Sutton, V; Elsea, Sarah H

    2015-01-01

    Aromatic L-amino acid decarboxylase (AADC) deficiency is an inborn error of metabolism affecting the biosynthesis of serotonin, dopamine, and catecholamines. We report a case of AADC deficiency that was detected using the Global MAPS platform. This is a novel platform that allows for parallel clinical testing of hundreds of metabolites in a single plasma specimen. It uses a state-of-the-art mass spectrometry platform, and the resulting spectra are compared against a library of ~2500 metabolites. Our patient is now a 4 year old boy initially seen at 11 months of age for developmental delay and hypotonia. Multiple tests had not yielded a diagnosis until exome sequencing revealed compound heterozygous variants of uncertain significance (VUS), c.286G>A (p.G96R) and c.260C>T (p.P87L) in the DDC gene, causal for AADC deficiency. CSF neurotransmitter analysis confirmed the diagnosis with elevated 3-methoxytyrosine (3-O-methyldopa). Metabolomic profiling was performed on plasma and revealed marked elevation in 3-methoxytyrosine (Z-score +6.1) consistent with the diagnosis of AADC deficiency. These results demonstrate that the Global MAPS platform is able to diagnose AADC deficiency from plasma. In summary, we report a novel and less invasive approach to diagnose AADC deficiency using plasma metabolomic profiling. PMID:25956449

  1. Establishment of a yeast platform strain for production of p-coumaric acid through metabolic engineering of aromatic amino acid biosynthesis.

    PubMed

    Rodriguez, Angelica; Kildegaard, Kanchana R; Li, Mingji; Borodina, Irina; Nielsen, Jens

    2015-09-01

    Aromatic amino acids are precursors of numerous plant secondary metabolites with diverse biological functions. Many of these secondary metabolites are already being used as active pharmaceutical or nutraceutical ingredients, and there are numerous exploratory studies of other compounds with promising applications. p-Coumaric acid is derived from aromatic amino acids and, besides being a valuable chemical building block, it serves as precursor for biosynthesis of many secondary metabolites, such as polyphenols, flavonoids, and some polyketides. Here we developed a p-coumaric acid-overproducing Saccharomyces cerevisiae platform strain. First, we reduced by-product formation by knocking out phenylpyruvate decarboxylase ARO10 and pyruvate decarboxylase PDC5. Second, different versions of feedback-resistant DAHP synthase and chorismate mutase were overexpressed. Finally, we identified shikimate kinase as another important flux-controlling step in the aromatic amino acid pathway by overexpressing enzymes from Escherichia coli, homologous to the pentafunctional enzyme Aro1p and to the bifunctional chorismate synthase-flavin reductase Aro2p. The highest titer of p-coumaric acid of 1.93 ± 0.26 g L(-1) was obtained, when overexpressing tyrosine ammonia-lyase TAL from Flavobacterium johnsoniaeu, DAHP synthase ARO4(K229L), chorismate mutase ARO7(G141S) and E. coli shikimate kinase II (aroL) in Δpdc5Δaro10 strain background. To our knowledge this is the highest reported titer of an aromatic compound produced by yeast. The developed S. cerevisiae strain represents an attractive platform host for production of p-coumaric-acid derived secondary metabolites, such as flavonoids, polyphenols, and polyketides. PMID:26292030

  2. Using spin labels to study molecular processes in soils: Covalent binding of aromatic amines to humic acids of soils

    NASA Astrophysics Data System (ADS)

    Aleksandrova, O. N.; Kholodov, V. A.; Perminova, I. V.

    2015-08-01

    Interactions of aliphatic and aromatic amines with soil and humic acids isolated from it are studied by means of spin labels and electron paramagnetic resonance (EPR) spectroscopy. Nitroxyl radicals containing amino groups are used as spin labels. It is found experimentally that aromatic amines are instantaneously converted to the bound state. It is shown that the microareas of their incorporation are characterized by a significant delay in the reduction of the nitroxyl fragment of spin-label molecules, indicating the formation of condensed structures typical of an oxidative binding mechanism. It is concluded that aliphatic amines do not bind to humic acids. It is noted that the studied process allows elucidating the formation of bound xenobiotic residues in soils.

  3. The Hypolipidemic and Anti-Inflammatory Activity of Boronated Aromatic Amino Acids in CF1 Male Mice

    PubMed Central

    Miller, Merrill C.; Sood, A.; Spielvogel, Bernard F.

    1999-01-01

    The boronated aromatic amino acids were shown to be potent hypolipidemic agents in mice lowering both serum cholesterol and triglycerides after 16 days. Selective compounds were as effective as the clinical standards. Furthermore, the compounds were effective anti-inflammatory agents reducing local and central pain as well as suppressing LPS induced endotoxic shock in mice. These agents inhibited lysosomal and proteolytic enzymes of the liver and macrophages as a part of their mechanism of action. PMID:18475910

  4. Formation constants of ternary complexes of some heavy metal ions with N-(2-acetamido)iminodiacetic acid and aliphatic or aromatic acids

    SciTech Connect

    Hamed, M.M.A.; Mahmoud, M.R. . Dept. of Chemistry); Saleh, M.B.; Ahmed, I.T. . Dept. of Chemistry)

    1994-07-01

    N-(2-Acetamido)iminodiacetic acid (H[sub 2]ADA) is considered as one of the biologically important ligands. It is used as a complexing agent in the field of metal ion buffers working at the physiological pH range. Furthermore, it is widely used as an analytical chelating agent for the spectrophotometric determination of metal ions. Solution equilibria of the ternary systems involving La(III), Y(III), Ce(III), and UO[sub 2][sup 2+], N-(2-acetamido)iminodiacetic acid, and some aliphatic or aromatic acids have been investigated potentiometrically. The formation of 1:1:1 mixed ligand complexes is inferred from the potentiometric titration curves. Formation constants of the different binary and ternary complexes formed in such systems were determined at 25 [+-] 0.1 C and [mu] = 0.1 mol dm[sup [minus]3] (KNO[sub 3]). It is deduced that the mixed ligand complexes are more stable than the corresponding binary complexes containing the aliphatic or aromatic acidate moiety. The order of stability of the binary and ternary complexes is investigated and discussed in terms of the nature of both the metal ion and the secondary ligand (aliphatic or aromatic acid).

  5. Reassessment of the Role of Aromatic Amino Acid Hydroxylases and the Effect of Infection by Toxoplasma gondii on Host Dopamine

    PubMed Central

    Wang, Zi T.; Harmon, Steve; O'Malley, Karen L.

    2014-01-01

    Toxoplasma gondii infection has been described previously to cause infected mice to lose their fear of cat urine. This behavioral manipulation has been proposed to involve alterations of host dopamine pathways due to parasite-encoded aromatic amino acid hydroxylases. Here, we report successful knockout and complementation of the aromatic amino acid hydroxylase AAH2 gene, with no observable phenotype in parasite growth or differentiation in vitro and in vivo. Additionally, expression levels of the two aromatic amino acid hydroxylases were negligible both in tachyzoites and in bradyzoites. Finally, we were unable to confirm previously described effects of parasite infection on host dopamine either in vitro or in vivo, even when AAH2 was overexpressed using the BAG1 promoter. Together, these data indicate that AAH enzymes in the parasite do not cause global or regional alterations of dopamine in the host brain, although they may affect this pathway locally. Additionally, our findings suggest alternative roles for the AHH enzymes in T. gondii, since AAH1 is essential for growth in nondopaminergic cells. PMID:25547791

  6. Synthesis, crystal structure and photoluminescence property of Eu/Tb MOFs with mixed polycarboxylate ligands

    NASA Astrophysics Data System (ADS)

    Yang, Lu; Zhang, Sheng; Qu, Xiaoni; Yang, Qi; Liu, Xiangyu; Wei, Qing; Xie, Gang; Chen, Sanping

    2015-11-01

    Lanthanide MOFs, [Eu(TCA)(NDC)·H2O]n (1) and [Tb(TCA)(NDC)·H2O]n (2), have been prepared with the mixed aromatic carboxylate ligands, namely, 4,4‧,4″-tricarboxytriphenylamine (H3TCA) and 1,4-naphthalenedicarboxylate (H2NDC). Single-crystal X-ray diffraction analysis reveals that isomorphic 1 and 2 present pillar-layered 3D framework that Eu/Tb(III) bond with carboxylate in various coordination fashions. Optical investigation indicates that the as-prepared compounds feature characteristic luminescence emission bands of Eu/Tb ions in the visible regions at room temperature. Moreover, compound 2 shows a relatively longer luminescence lifetime (τ=0.342 ms) and significantly enhanced quantum yield (Φoverall=11%) comparing with those of 1 (τ=0.335 ms, Φoverall=0.06%). Two Ln-MOFs (Ln=EuIII, TbIII) with mixed polycarboxylate ligands present different luminescent properties.

  7. Separation of aromatic carboxylic acids using quaternary ammonium salts on reversed-phase HPLC. 2. Application for the analysis of Loy Yang coal oxidation products

    SciTech Connect

    Kawamura, K.; Okuwaki, A.; Verheyen, T.V.; Perry, G.J.

    2006-07-01

    In order to develop separation processes and analytical methods for aromatic carboxylic acids for the coal oxidation products, the separation behavior of aromatic carboxylic acids on a reversed-phase HPLC using eluent containing quaternary ammonium salt was optimized using the solvent gradient method. This method was applied for the analysis of Loy Yang coal oxidation products. It was confirmed that the analytical data using this method were consistent with those determined using gas chromatography.

  8. B···π-aromatic and C-H···B interactions in co-crystals of aromatic amine N-oxides with p-phenylenediboronic acid

    NASA Astrophysics Data System (ADS)

    Sarma, Rupam; Baruah, Jubaraj Bikash

    2009-02-01

    Co-crystals of p-phenylenediboronic acid with four aromatic N-oxides namely pyridine N-oxide, quinoline N, N'-dioxide, isoquinoline N, N'-dioxide and 4,4'-dipyridine N, N'-dioxide are prepared and are structurally characterized. The stacking pattern in each case is found to be different. An interesting stacking effect that, sandwiches the boronic acid groups by pyridine N-oxide rings and associated through η2 and η3 type B-π interactions is presented. In the structures of co-crystals of aromatic amine N-oxides with p-phenylenediboronic acid B···π aromatic and C-H···B interactions are observed.

  9. Pyrolysis of simple coal model compounds containing aromatic carboxylic acids: Does decarboxylation lead to cross-linking?

    SciTech Connect

    Eskay, T.P.; Britt, P.F.; Buchanan, A.C. III

    1996-02-01

    The thermolysis of two aromatic carboxylic acids 1,2-(3,3`-dicarboxyphenyl)ethane (2) have been investigated at 400{degree} C as models of carboxylic acids in low rank coals. The major decomposition pathway observed is decarboxylation, which mainly occurs by an ionic pathway. This decarboxylation route does not lead to any significant amount of coupling or high molecular weight products that would be indicative of cross-linking products in coal. The pyrolysis of 1 and 2 will be investigated under a variety of conditions that better mimic the enviromment found in coal to further delineate the role that decarboxylation plays in coal cross-linking chemistry.

  10. New water soluble phosphonate and polycarboxylate complexants for enhanced f element separations

    SciTech Connect

    Nash, K.L.; Rickert, P.G.; Lessmann, E.P.; Mendoza, M.D.; Feil, J.F.; Sullivan, J.C.

    1994-08-01

    While lipophilic extractant molecules and ion exchange polymeric materials are clearly essential to efficient separation of metal ions by solvent extraction or ion exchange, the most difficult separations often could not be accomplished without the use of water soluble complexants. This report focuses on recent developments in design, synthesis and characterization of phosphonic acid and polycarboxylic acid ligands for enhanced f element separations. Emphasis is on the basic solution chemistry and crystal structures of complexes of the f elements with selected amino-derivatives of methanediphosphonic acid and with tetrahydrofuran-2,3,4,5-tetracarboxylic acid. The former series of compounds exhibit high affinity for lanthanides and actinides in acidic solutions. The latter ligand exhibits an unusual (and very useful) ``anti-selectivity`` for uranyl ion in a solvent extraction process, which permits efficient separation of uranyl from more radioactive components of nuclear wastes. Most of the observed effects can be explained through examination of the structure of the ligand, and comparison of the spectroscopic and thermodynamic parameters for complexation of various metal ions.

  11. Triple-helical collagen hydrogels via covalent aromatic functionalization with 1,3-Phenylenediacetic acid

    PubMed Central

    Tronci, Giuseppe; Doyle, Amanda; Russell, Stephen J.; Wood, David J.

    2016-01-01

    Chemical crosslinking of collagen is a general strategy to reproduce macroscale tissue properties in physiological environment. However, simultaneous control of protein conformation, material properties and biofunctionality is highly challenging with current synthetic strategies. Consequently, the potentially-diverse clinical applications of collagen-based biomaterials cannot be fully realised. In order to establish defined biomacromolecular systems for mineralised tissue applications, type I collagen was functionalised with 1,3-Phenylenediacetic acid (Ph) and investigated at the molecular, macroscopic and functional levels. Preserved triple helix conformation was observed in obtained covalent networks via ATR-FTIR (AIII/A1450 ~ 1) and WAXS, while network crosslinking degree (C: 87-99 mol.-%) could be adjusted based on specific reaction conditions. Decreased swelling ratio (SR: 823-1285 wt.-%) and increased thermo-mechanical (Td: 80-88 °C; E: 28-35 kPa; σmax: 6-8 kPa; εb: 53-58 %) properties were observed compared to state-of-the-art carbodiimide (EDC)-crosslinked collagen controls, likely related to the intermolecular covalent incorporation of the aromatic segment. Ph-crosslinked hydrogels displayed nearly intact material integrity and only a slight mass decrease (MR: 5-11 wt. %) following 1-week incubation in either PBS or simulated body fluid (SBF), in contrast to EDC-crosslinked collagen (MR: 33-58 wt. %). Furthermore, FTIR, SEM and EDS revealed deposition of a calcium-phosphate phase on SBF-retrieved samples, whereby an increased calcium phosphate ratio (Ca/P: 0.84-1.41) was observed in hydrogels with higher Ph content. 72-hour material extracts were well tolerated by L929 mouse fibroblasts, whereby cell confluence and metabolic activity (MTS assay) were comparable to those of cells cultured in cell culture medium (positive control). In light of their controlled structure-function properties, these biocompatible collagen hydrogels represent attractive

  12. Production of Dopamine by Aromatic l-Amino Acid Decarboxylase Cells after Spinal Cord Injury.

    PubMed

    Ren, Li-Qun; Wienecke, Jacob; Hultborn, Hans; Zhang, Mengliang

    2016-06-15

    Aromatic l-amino acid decarboxylase (AADC) cells are widely distributed in the spinal cord, and their functions are largely unknown. We have previously found that AADC cells in the spinal cord could increase their ability to produce serotonin (5-hydroxytryptamine) from 5-hydroxytryptophan after spinal cord injury (SCI). Because AADC is a common enzyme catalyzing 5-hydroxytryptophan to serotonin and l-3,4-dihydroxyphenylalanine (l-dopa) to dopamine (DA), it seems likely that the ability of AADC cells using l-dopa to synthesize DA is also increased. To prove whether or not this is the case, a similar rat sacral SCI model and a similar experimental paradigm were adopted as that which we had used previously. In the chronic SCI rats (> 45 days), no AADC cells expressed DA if there was no exogenous l-dopa application. However, following administration of a peripheral AADC inhibitor (carbidopa) with or without a monoamine oxidase inhibitor (pargyline) co-application, systemic administration of l-dopa resulted in ∼94% of AADC cells becoming DA-immunopositive in the spinal cord below the lesion, whereas in normal or sham-operated rats none or very few of AADC cells became DA-immunopositive with the same treatment. Using tail electromyography, spontaneous tail muscle activity was increased nearly fivefold over the baseline level. When pretreated with a central AADC inhibitor (NSD-1015), further application of l-dopa failed to increase the motoneuron activity although the expression of DA in the AADC cells was not completely inhibited. These findings demonstrate that AADC cells in the spinal cord below the lesion gain the ability to produce DA from its precursor in response to SCI. This ability also enables the AADC cells to produce 5-HT and trace amines, and likely contributes to the development of hyperexcitability. These results might also be implicated for revealing the pathological mechanisms underlying l-dopa-induced dyskinesia in Parkinson's disease. PMID:26830512

  13. The metabolism of aromatic acids by micro-organisms. Metabolic pathways in the fungi

    PubMed Central

    Cain, R. B.; Bilton, R. F.; Darrah, Josephine A.

    1968-01-01

    1. The metabolic pathways of aromatic-ring fission were examined in a range of fungal genera that utilize several compounds related to lignin. 2. Most of the genera, after growth on p-hydroxybenzoate, protocatechuate or compounds that are degraded to the latter (e.g. caffeate, ferulate or vanillate), rapidly oxidized these compounds, but not catechol. 3. Such genera possessed a protocatechuate 3,4-oxygenase and accumulated β-carboxymuconate as the product of protocatechuate oxidation. This enzyme had a high pH optimum in most organisms; the Rhodotorula enzyme was competitively inhibited by catechol. 4. β-Carboxymuconate was converted by all competent fungi into β-carboxymuconolactone, which was isolated and characterized. None of the fungi produced or utilized at significant rates the corresponding bacterial intermediate γ-carboxymuconolactone. 5. The lactonizing enzymes of Rhodotorula and Neurospora crassa had a pH optimum near 5·5 and approximate molecular weights of 19000 and 190000 respectively. 6. The fungi did not degrade the isomeric (+)-muconolactone, γ-carboxymethylenebutanolide or β-oxoadipate enol lactone at significant rates, and thus differ radically from bacteria, where β-oxoadipate enol lactone is the precursor of β-oxoadipate in all strains examined. 7. The end product of β-carboxymuconolactone metabolism by extracts was β-oxoadipate. 8. Evidence for a coenzyme A derivative of β-oxoadipate was found during further metabolism of this keto acid. 9. A few anomalous fungi, after growth on p-hydroxybenzoate, had no protocatechuate 3,4-oxygenase, but possessed all the enzymes of the catechol pathway. Catechol was detected in the growth medium in one instance. 10. A strain of Penicillium sp. formed pyruvate but no β-oxoadipate from protocatechuate, suggesting the existence also of a `meta' type of ring cleavage among fungi. PMID:5691754

  14. Interconversion of biologically important carboxylic acids by radiation

    NASA Technical Reports Server (NTRS)

    Negron-Mendoza, A.; Ponnamperuma, C.

    1978-01-01

    The interconversion of a group of biologically important polycarboxylic acids (acetic, fumaric, malic, malonic, succinic, citric, isocitric, tricarballylic) under gamma-ray or ultraviolet radiation was investigated. The formation of high molecular weight compounds was observed in all cases. Succinic acid was formed in almost all radiolysis experiments. Citric, malonic, and succinic acids appeared to be relatively insensitive to radiation. Interconversion of the polycarboxylic acids studied may have occurred under the effect of radiation in the prebiotic earth.

  15. Infrared and Raman spectra of N-acetyl- L-amino acid methylamides with aromatic side groups

    NASA Astrophysics Data System (ADS)

    Matsuura, Hiroatsu; Hasegawa, Kodo; Miyazawa, Tatsuo

    Infrared and Raman spectra of N-acetyl- L-phenylalanine methylamide, N-acetyl- L-tyrosine methylamide and N-acetyl- L-tryptophan methylamide, as model compounds of aromatic amino acid residues in proteins, were measured in the solid state and in methanol solutions. Vibrational assignments of the spectra were made by utilizing the deuteration effect and by comparison with the spectra of related compounds which include toluene, p-cresol and 3-methylindole. The amide I, III and IV bands were strong in Raman scattering, but other characteristic amide bands were ill-defined. In the Raman spectra of methanol solutions, only the bands due to the aromatic side group vibrations were markedly observed, but those due to the peptide backbone vibrations were very weak, suggesting the coexistence of various molecular conformations in solution.

  16. Rhodium(I)-catalyzed regiospecific dimerization of aromatic acids: two direct C-H bond activations in water.

    PubMed

    Gong, Hang; Zeng, Huiying; Zhou, Feng; Li, Chao-Jun

    2015-05-01

    2,2'-Diaryl acids are key building blocks for some of the most important and high-performance polymers such as polyesters and polyamides (imides), as well as structural motifs of MOFs (metal-organic frameworks) and biological compounds. In this study, a direct, regiospecific and practical dimerization of simple aromatic acids to generate 2,2'-diaryl acids has been discovered, which proceeds through two rhodium-catalyzed C-H activations in water. This reaction can be easily scaled up to gram level by using only 0.4-0.6 mol % of the rhodium catalyst. As a proof-of-concept, the natural product ellagic acid was synthesized in two steps by this method. PMID:25765625

  17. Integration of chemotaxis, transport and catabolism in Pseudomonas putida and identification of the aromatic acid chemoreceptor PcaY.

    PubMed

    Luu, Rita A; Kootstra, Joshua D; Nesteryuk, Vasyl; Brunton, Ceanne N; Parales, Juanito V; Ditty, Jayna L; Parales, Rebecca E

    2015-04-01

    Aromatic and hydroaromatic compounds that are metabolized through the β-ketoadipate catabolic pathway serve as chemoattractants for Pseudomonas putida F1. A screen of P. putida F1 mutants, each lacking one of the genes encoding the 18 putative methyl-accepting chemotaxis proteins (MCPs), revealed that pcaY encodes the MCP required for metabolism-independent chemotaxis to vanillate, vanillin, 4-hydroxybenzoate, benzoate, protocatechuate, quinate, shikimate, as well as 10 substituted benzoates that do not serve as growth substrates for P. putida F1. Chemotaxis was induced during growth on aromatic compounds, and an analysis of a pcaY-lacZ fusion revealed that pcaY is expressed in the presence of β-ketoadipate, a common intermediate in the pathway. pcaY expression also required the transcriptional activator PcaR, indicating that pcaY is a member of the pca regulon, which includes three unlinked gene clusters that encode five enzymes required for the conversion of 4-hydroxybenzoate to tricarboxylic acid cycle intermediates as well as the major facilitator superfamily transport protein PcaK. The 4-hydroxybenzoate permease PcaK was shown to modulate the chemotactic response by facilitating the uptake of 4-hydroxybenzoate, which leads to the accumulation of β-ketoadipate, thereby increasing pcaY expression. The results show that chemotaxis, transport and metabolism of aromatic compounds are intimately linked in P. putida. PMID:25582673

  18. A rare cause of severe diarrhoea diagnosed by urine metabolic screening: aromatic L-amino acid decarboxylase deficiency.

    PubMed

    Lee, L K; Cheung, K M; Cheng, W W; Ko, C H; Lee, Hencher H C; Ching, C K; Mak, Chloe M

    2014-04-01

    A 15-year-old Chinese male with infantile-onset hypotonia, developmental delay, ptosis, and oculogyric episodes presented with a history of chronic diarrhoea since the age of 5 years. At presentation, he had an exacerbation of diarrhoeal symptoms resulting in dehydration and malnutrition with a concurrent severe chest infection. In view of his infantile-onset hypotonia, oculogyric crises, and protracted diarrhoea, an autonomic disturbance related to neurotransmitters was suspected. Urine organic acid profiling was compatible with aromatic L-amino acid decarboxylase deficiency. The diagnosis was confirmed based on cerebrospinal fluid analysis and genetic mutation analysis. The patient was treated with a combination of bromocriptine, selegiline, and pyridoxine; a satisfactory reduction in diarrhoea ensued. Our report highlights the importance of urine organic acid screening in infantile-onset hypotonia, especially when accompanied by oculogyric crises, and severe diarrhoea which could manifest as a result of autonomic disturbance. PMID:24714172

  19. Urinary Metabolomics Reveals Alterations of Aromatic Amino Acid Metabolism of Alzheimer's Disease in the Transgenic CRND8 Mice.

    PubMed

    Tang, Zhi; Liu, Liangfeng; Li, Yongle; Dong, Jiyang; Li, Min; Huang, Jiandong; Lin, Shuhai; Cai, Zongwei

    2016-01-01

    Alzheimer's disease (AD) is a progressive neurodegenerative disorder, with amyloid plaques accumulation as the key feature involved in its pathology. To date, however, the biochemical changes in AD have not been clearly characterized. Here, we present that urinary metabolomics based on high resolution mass spectrometry was employed for delineation of metabolic alterations in transgenic CRND8 mice. In this noninvasive approach, urinary metabolome reveals the biochemical changes in early onset of this AD mouse model. In virtue of comprehensive metabolite profiling and multivariate statistical analysis, a total of 73 differential metabolites of urine sample sets was identified in 12-week and 18-week transgenic mice compared to wild-type littermates, covering perturbations of aromatic amino acid metabolism, the Krebs cycle and one-carbon metabolism. Of particular interest is that divergent tryptophan metabolism, such as upregulation of serotonin pathway while downregulation of kynurenine pathway, was observed. Meanwhile, the accumulation of both N-acetylvanilalanine and 3-methoxytyrosine indicated aromatic L-amino acid decarboxylase deficiency. And the microbial metabolites derived from aromatic amino acid metabolism and drug-like phase II metabolic response via the glycine conjugation reactions were also highlighted, indicating that genetic modification in mouse brain not only alters genotype but also perturbs the gut microbiome. Together, our study demonstrated that the integrative approach employing mass spectrometry-based metabolomics and a transgenic mouse model for AD may provide new evidence for distinct metabolic signatures. The perturbations of metabolic pathways may have far-reaching implications for early diagnosis and intervention in AD. PMID:26825095

  20. Promoters inducible by aromatic amino acids and γ-aminobutyrate (GABA) for metabolic engineering applications in Saccharomyces cerevisiae.

    PubMed

    Kim, Sujin; Lee, Kyusung; Bae, Sang-Jeong; Hahn, Ji-Sook

    2015-03-01

    A wide range of promoters with different strengths and regulatory mechanisms are valuable tools in metabolic engineering and synthetic biology. While there are many constitutive promoters available, the number of inducible promoters is still limited for pathway engineering in Saccharomyces cerevisiae. Here, we constructed aromatic amino-acid-inducible promoters based on the binding sites of Aro80 transcription factor, which is involved in the catabolism of aromatic amino acids through transcriptional activation of ARO9 and ARO10 genes in response to aromatic amino acids. A dynamic range of tryptophan-inducible promoter strengths can be obtained by modulating the number of Aro80 binding sites, plasmid copy numbers, and tryptophan concentrations. Using low and high copy number plasmid vectors and different tryptophan concentrations, a 29-fold range of fluorescence intensities of enhanced green fluorescent protein (EGFP) reporter could be achieved from a synthetic U4C ARO9 promoter, which is composed of four repeats of Aro80 binding half site (CCG) and ARO9 core promoter element. The U4C ARO9 promoter was applied to express alsS and alsD genes from Bacillus subtilis for acetoin production in S. cerevisiae, resulting in a gradual increase in acetoin titers depending on tryptophan concentrations. Furthermore, we demonstrated that γ-aminobutyrate (GABA)-inducible UGA4 promoter, regulated by Uga3, can also be used in metabolic engineering as a dose-dependent inducible promoter. The wide range of controllable expression levels provided by these tryptophan- and GABA-inducible promoters might contribute to fine-tuning gene expression levels and timing for the optimization of pathways in metabolic engineering. PMID:25573467

  1. The role of polycarboxylic acids in calcium phosphate mineralization.

    PubMed

    Tsortos, Achilles; Nancollas, George H

    2002-06-01

    The role of two polyelectrolytes, poly-L-glutamate and poly-L-aspartate, in the growth of calcium phosphate crystal phases, has been investigated at constant supersaturation. Both molecules are strong inhibitors of HAP growth when present in the solution phase but also act as hydroxyapatite and (octacalcium phosphate)-like crystal nucleators when adsorbed on germanium surfaces. The structure of the polymers in solution is presented and various adsorption models are analyzed. A "train-loop" structure of these long, flexible chain polymers on the crystal surface is consistent with all the adsorption (experimental and theoretical), inhibition, and electrophoretic mobility results. PMID:16290647

  2. Chemical and isotopic characterization of fatty acids and polycyclic aromatic hydrocarbons in aerosols - implications for biomass burning

    SciTech Connect

    Ballentine, D.C.

    1995-12-31

    Emissions of organic materials during biomass burning have been suggested to influence the biogeochemical distribution of nutrients in a range of ecosystems. Additionally, some organic components survive pyrolytic processes and are of regional and global biogeochemical significance because they may serve as tracers for transport of biomass burning products. Two classes of compounds that are of interest in determining the transport of these products are polycyclic aromatic hydrocarbons (PAH) and fatty acids. Polycyclic aromatic hydrocarbons are stable to biodegradation and are typically produced during natural and anthropogenic combustion processes. Fatty acids are also stable to atmospheric degradation and have been implicated as useful biomarkers for atmospheric transport. In this study, PAH and fatty acids emitted during controlled low and high temperature burns of sugar cane have been chemically and isotopically characterized using GC/MS and GC/IRMS, respectively. In order to determine if these species are suitable biomarkers for the transport of biomass burning materials, aerosols collected during sugar cane burning in South Africa have been similarly analyzed.

  3. Aromatic/heterocyclic amino acids and the simulated sunlight-ultraviolet inactivation of the Heliothis/Helicoverpa baculovirus

    SciTech Connect

    Ignoffo, C.M.; Garcia, C.

    1995-04-01

    Tryptophan, of five aromatic/heterocyclic amino acids (tyrosine, phenylalanine, proline, histidine) provided significant protection of the Heliothis baculovirus (HzSNPV) from inactivation by simulated ultraviolet (SUV). Fifty percent of SUV protection of HzSNPV with tryptophan or tyrosine was obtained at 0.03 mg/ml and 0.5 mg/ml, respectively. Rates as high as 100.0 mg/ml of phenylalanine, histidine, or proline provided <50% protection. The extent of tryptophan protection was correlated with its absorption in the sunlight UV-B spectra. 16 refs., 2 tabs.

  4. Sequestering ability of polycarboxylic ligands towards dioxouranium(VI).

    PubMed

    Crea, Francesco; Foti, Claudia; Sammartano, Silvio

    2008-05-15

    In this paper we report a comparison on the sequestering ability of some polycarboxylic ligands towards dioxouranium(VI) (UO(2)(2+), uranyl). Ligands taken into account are mono- (acetate), di- (oxalate, malonate, succinate and azelate), tri- (1,2,3-propanetricarboxylate) and hexa-carboxylate (1,2,3,4,5,6-benzenehexacarboxylate). The sequestering ability of polycarboxylic ligands towards UO(2)(2+) was quantified by a new approach expressed by means of a sigmoid Boltzman type equation and of a empirical parameters (pL(50)) which defines the amount of ligand necessary to sequester 50% of the total UO(2)(2+) concentration. A fairly linear correlation was obtained between pL(50) or log K(110) (log K(110) refers to the equilibrium: UO(2)(2+)+L(z-)=UO(2)L((2-z)); L=generic ligand) and the polyanion charges. In order to complete the picture, a tetra-carboxylate ligand (1,2,3,4-butanetetracarboxylate) was studied in NaCl aqueous solutions at 0polycarboxylate systems was modelled by the SIT (specific ion interaction theory) approach and by the Pitzer equations. PMID:18585146

  5. Deletion of the Saccharomyces cerevisiae ARO8 gene, encoding an aromatic amino acid transaminase, enhances phenylethanol production from glucose.

    PubMed

    Romagnoli, Gabriele; Knijnenburg, Theo A; Liti, Gianni; Louis, Edward J; Pronk, Jack T; Daran, Jean-Marc

    2015-01-01

    Phenylethanol has a characteristic rose-like aroma that makes it a popular ingredient in foods, beverages and cosmetics. Microbial production of phenylethanol currently relies on whole-cell bioconversion of phenylalanine with yeasts that harbour an Ehrlich pathway for phenylalanine catabolism. Complete biosynthesis of phenylethanol from a cheap carbon source, such as glucose, provides an economically attractive alternative for phenylalanine bioconversion. In this study, synthetic genetic array (SGA) screening was applied to identify genes involved in regulation of phenylethanol synthesis in Saccharomyces cerevisiae. The screen focused on transcriptional regulation of ARO10, which encodes the major decarboxylase involved in conversion of phenylpyruvate to phenylethanol. A deletion in ARO8, which encodes an aromatic amino acid transaminase, was found to underlie the transcriptional upregulation of ARO10 during growth, with ammonium sulphate as the sole nitrogen source. Physiological characterization revealed that the aro8Δ mutation led to substantial changes in the absolute and relative intracellular concentrations of amino acids. Moreover, deletion of ARO8 led to de novo production of phenylethanol during growth on a glucose synthetic medium with ammonium as the sole nitrogen source. The aro8Δ mutation also stimulated phenylethanol production when combined with other, previously documented, mutations that deregulate aromatic amino acid biosynthesis in S. cerevisiae. The resulting engineered S. cerevisiae strain produced >3 mm phenylethanol from glucose during growth on a simple synthetic medium. The strong impact of a transaminase deletion on intracellular amino acid concentrations opens new possibilities for yeast-based production of amino acid-derived products. PMID:24733517

  6. Self-assembly of short peptides composed of only aliphatic amino acids and a combination of aromatic and aliphatic amino acids.

    PubMed

    Subbalakshmi, Chilukuri; Manorama, Sunkara V; Nagaraj, Ramakrishnan

    2012-05-01

    The morphology of structures formed by the self-assembly of short N-terminal t-butyloxycarbonyl (Boc) and C-terminal methyl ester (OMe) protected and Boc-deprotected hydrophobic peptide esters was investigated. We have observed that Boc-protected peptide esters composed of either only aliphatic hydrophobic amino acids or aliphatic hydrophobic amino acids in combination with aromatic amino acids, formed highly organized structures, when dried from methanol solutions. Transmission and scanning electron microscopic images of the peptides Boc-Ile-Ile-OMe, Boc-Phe-Phe-Phe-Ile-Ile-OMe and Boc-Trp-Ile-Ile-OMe showed nanotubular structures. Removal of the Boc group resulted in disruption of the ability to form tubular structures though spherical aggregates were formed. Both Boc-Leu-Ile-Ile-OMe and H-Leu-Ile-Ile-OMe formed only spherical nanostructures. Dynamic light scattering studies showed that aggregates of varying dimensions were present in solution suggesting that self-assembly into ordered structures is facilitated by aggregation in solution. Fourier transform infrared spectroscopy and circular dichroism spectroscopy data show that although all four of the protected peptides adopt well-defined tertiary structures, upon removal of the Boc group, only H-Phe-Phe-Phe-Ile-Ile-OMe had the ability to adopt β-structure. Our results indicate that hydrophobic interaction is a very important determinant for self-assembly and presence of charged and aromatic amino acids in a peptide is not necessary for self-assembly. PMID:22431418

  7. Electronic Structure, NMR, Spin-Spin Coupling, and Noncovalent Interactions in Aromatic Amino Acid Based Ionic Liquids.

    PubMed

    Rao, Soniya S; Gejji, Shridhar P

    2016-07-21

    Noncovalent interactions accompanying phenylalanine (Phe), tryptophan (Trp), and tyrosine (Tyr) amino acids based ionic liquids (AAILs) composed of 1-methyl-3-butyl-imidazole and its methyl-substituted derivative as cations have been analyzed employing the dispersion corrected density functional theory. It has been shown that cation-anion binding in these bioionic ILs is primarily facilitated through hydrogen bonding in addition to lp---π and CH---π interactions those arising from aromatic moieties which can be probed through (1)H and (13)C NMR spectra calculated from the gauge independent atomic orbital method. Characteristic NMR spin-spin coupling constants across hydrogen bonds of ion pair structures viz., Fermi contact, spin-orbit and spin-dipole terms show strong dependence on mutual orientation of cation with the amino acid anion. The spin-spin coupling mechanism transmits spin polarization via electric field effect originating from lp---π interactions whereas the electron delocalization from lone pair on the carbonyl oxygen to antibonding C-H orbital is facilitated by hydrogen bonding. It has been demonstrated that indirect spin-spin coupling constants across the hydrogen bonds correlate linearly with hydrogen bond distances. The binding energies and dissected nucleus independent chemical shifts (NICS) document mutual reduction of aromaticity of hydrogen bonded ion pairs consequent to localization of π-character. Moreover the nature and type of such noncovalent interactions governing the in-plane and out-of-plane NICS components provide a measure of diatropic and paratropic currents for the aromatic rings of varying size in AAILs. Besides the direction of frequency shifts of characteristic C═O and NH stretching vibrations in the calculated vibrational spectra has been rationalized. PMID:27336283

  8. Investigation of a substrate-specifying residue within Papaver somniferum and Catharanthus roseus aromatic amino acid decarboxylases.

    PubMed

    Torrens-Spence, Michael P; Lazear, Michael; von Guggenberg, Renee; Ding, Haizhen; Li, Jianyong

    2014-10-01

    Plant aromatic amino acid decarboxylases (AAADs) catalyze the decarboxylation of aromatic amino acids with either benzene or indole rings. Because the substrate selectivity of AAADs is intimately related to their physiological functions, primary sequence data and their differentiation could provide significant physiological insights. However, due to general high sequence identity, plant AAAD substrate specificities have been difficult to identify through primary sequence comparison. In this study, bioinformatic approaches were utilized to identify several active site residues within plant AAAD enzymes that may impact substrate specificity. Next a Papaver somniferum tyrosine decarboxylase (TyDC) was selected as a model to verify our putative substrate-dictating residues through mutation. Results indicated that mutagenesis of serine 372 to glycine enables the P. somniferum TyDC to use 5-hydroxytryptophan as a substrate, and reduces the enzyme activity toward 3,4-dihydroxy-L-phenylalanine (dopa). Additionally, the reverse mutation in a Catharanthus roseus tryptophan decarboxylase (TDC) enables the mutant enzyme to utilize tyrosine and dopa as substrates with a reduced affinity toward tryptophan. Molecular modeling and molecular docking of the P. somniferum TyDC and the C. roseus TDC enzymes provided a structural basis to explain alterations in substrate specificity. Identification of an active site residue that impacts substrate selectivity produces a primary sequence identifier that may help differentiate the indolic and phenolic substrate specificities of individual plant AAADs. PMID:25107664

  9. Extraction of Lanthanide and Actinide Ions from Aqueous Mixtures Using a Carboxylic Acid-Functionalized Porous Aromatic Framework

    PubMed Central

    2016-01-01

    Porous aromatic frameworks (PAFs) incorporating a high concentration of acid functional groups possess characteristics that are promising for use in separating lanthanide and actinide metal ions, as required in the treatment of radioactive waste. These materials have been shown to be indefinitely stable to concentrated acids and bases, potentially allowing for multiple adsorption/stripping cycles. Additionally, the PAFs combine exceptional features from MOFs and inorganic/activated carbons giving rise to tunable pore surfaces and maximum chemical stability. Herein, we present a study of the adsorption of selected metal ions, Sr2+, Fe3+, Nd3+, and Am3+, from aqueous solutions employing a carbon-based porous aromatic framework, BPP-7 (Berkeley Porous Polymer-7). This material displays high metal loading capacities together with excellent adsorption selectivity for neodymium over strontium based on Langmuir adsorption isotherms and ideal adsorbed solution theory (IAST) calculations. Based in part upon X-ray absorption spectroscopy studies, the stronger adsorption of neodymium is attributed to multiple metal ion and binding site interactions resulting from the densely functionalized and highly interpenetrated structure of BPP-7. Recyclability and combustibility experiments demonstrate that multiple adsorption/stripping cycles can be completed with minimal degradation of the polymer adsorption capacity. PMID:27163056

  10. Extraction of Lanthanide and Actinide Ions from Aqueous Mixtures Using a Carboxylic Acid-Functionalized Porous Aromatic Framework.

    PubMed

    Demir, Selvan; Brune, Nicholas K; Van Humbeck, Jeffrey F; Mason, Jarad A; Plakhova, Tatiana V; Wang, Shuao; Tian, Guoxin; Minasian, Stefan G; Tyliszczak, Tolek; Yaita, Tsuyoshi; Kobayashi, Tohru; Kalmykov, Stepan N; Shiwaku, Hideaki; Shuh, David K; Long, Jeffrey R

    2016-04-27

    Porous aromatic frameworks (PAFs) incorporating a high concentration of acid functional groups possess characteristics that are promising for use in separating lanthanide and actinide metal ions, as required in the treatment of radioactive waste. These materials have been shown to be indefinitely stable to concentrated acids and bases, potentially allowing for multiple adsorption/stripping cycles. Additionally, the PAFs combine exceptional features from MOFs and inorganic/activated carbons giving rise to tunable pore surfaces and maximum chemical stability. Herein, we present a study of the adsorption of selected metal ions, Sr(2+), Fe(3+), Nd(3+), and Am(3+), from aqueous solutions employing a carbon-based porous aromatic framework, BPP-7 (Berkeley Porous Polymer-7). This material displays high metal loading capacities together with excellent adsorption selectivity for neodymium over strontium based on Langmuir adsorption isotherms and ideal adsorbed solution theory (IAST) calculations. Based in part upon X-ray absorption spectroscopy studies, the stronger adsorption of neodymium is attributed to multiple metal ion and binding site interactions resulting from the densely functionalized and highly interpenetrated structure of BPP-7. Recyclability and combustibility experiments demonstrate that multiple adsorption/stripping cycles can be completed with minimal degradation of the polymer adsorption capacity. PMID:27163056

  11. Interplay of Aro80 and GATA activators in regulation of genes for catabolism of aromatic amino acids in Saccharomyces cerevisiae.

    PubMed

    Lee, Kyusung; Hahn, Ji-Sook

    2013-06-01

    Aro80, a member of the Zn(2)Cys(6) family proteins, activates expression of the ARO9 and ARO10 genes involved in catabolism of aromatic amino acids in response to aromatic amino acids that act as inducers. ARO9 and ARO10 are also under the control of nitrogen catabolite repression, but the direct roles for GATA factors, Gat1 and Gln3, in this regulation have not yet been elucidated. Here, we demonstrate that Aro80 is constitutively bound to its target promoters and activated by inducers at the level of transactivation. Although Aro80 also binds to its own promoter, ARO80 expression is induced only by rapamycin, but not by tryptophan. We show that Aro80 is absolutely required for Gat1 binding to the ARO9, ARO10 and ARO80 promoters upon rapamycin treatment. Gln3 binding to these promoters shows a partial requirement for Aro80. Rapamycin-dependent Gat1 and Gln3 binding to the Aro80 target promoters is not affected by tryptophan availability, suggesting that transactivation activity of Aro80 is not necessary for the recruitment of GATA factors. Rapamycin-dependent induction of Aro80 target genes also requires PP2A phosphatase complex, but not Sit4 phosphatase, acting downstream of TORC1. PMID:23651256

  12. Hydrogen-deuterium exchange of aromatic amines and amides using deuterated trifluoroacetic acid

    PubMed Central

    Giles, Richard; Lee, Amy; Jung, Erica; Kang, Aaron; Jung, Kyung Woon

    2014-01-01

    The H-D exchange of aromatic amines and amides, including pharmaceutically relevant compounds such as acetaminophen and diclofenac, was investigated using CF3COOD as both the sole reaction solvent and source of deuterium label. The described method is amenable to efficient deuterium incorporation for a wide variety of substrates possessing both electron-donating and electron-withdrawing substituents. Best results were seen with less basic anilines and highly activated acetanilides, reflecting the likelihood of different mechanistic pathways. PMID:25641994

  13. A theoretical study on the interaction of aromatic amino acids with graphene and single walled carbon nanotube.

    PubMed

    Rajesh, Chinagandham; Majumder, Chiranjib; Mizuseki, Hiroshi; Kawazoe, Yoshiyuki

    2009-03-28

    In this study we have investigated the interaction of phenylalanine (Phe), histidine (His), tyrosine (Tyr), and tryptophan (Tryp) molecules with graphene and single walled carbon nanotubes (CNTs) with an aim to understand the effect of curvature on the non-covalent interaction. The calculations are performed using density functional theory and the Moller-Plesset second-order perturbation theory (MP2) within linear combination of atomic orbitals-molecular orbital (LCAO-MO) approach. Using these methods, the equilibrium configurations of these complexes were found to be very similar, i.e., the aromatic rings of the amino acids prefer to orient in parallel with respect to the plane of the substrates, which bears the signature of weak pi-pi interactions. The binding strength follows the trend: Hisaromatic motifs of the amino acids. Remarkably, we find excellent correlation between the polarizability and the strength of the interaction; the higher the polarizability, greater is the binding strength. Moreover, we have analyzed the electronic densities of state spectrum before and after adsorption of the amino acid moieties. The results reveal that the Fermi level of the free CNT is red-shifted by the adsorption of the amino acids and the degree of shift is consistent with the trend in polarizability of these molecules. PMID:19334893

  14. Polycyclic aromatic hydrocarbon reaction rates with peroxy-acid treatment: prediction of reactivity using local ionization potential.

    PubMed

    Shoulder, J M; Alderman, N S; Breneman, C M; Nyman, M C

    2013-08-01

    Property-Encoded Surface Translator (PEST) descriptors were found to be correlated with the degradation rates of polycyclic aromatic hydrocarbons (PAHs) by the peroxy-acid process. Reaction rate constants (k) in hr(-1) for nine PAHs (acenaphthene, anthracene, benzo[a]pyrene, benzo[k]fluoranthene, fluoranthene, fluorene, naphthalene, phenanthrene, and pyrene) were determined by a peroxy-acid treatment method that utilized acetic acid, hydrogen peroxide, and a sulphuric acid catalyst to degrade the polyaromatic structures. Molecular properties of the selected nine PAHs were derived from structures optimized at B3LYP/6-31G(d) and HF/6-31G(d) levels of theory. Properties of adiabatic and vertical ionization potential (IP), highest occupied molecular orbitals (HOMO), HOMO/lowest unoccupied molecular orbital (LUMO) gap energies and HOMO/singly occupied molecular orbital (SOMO) gap energies were not correlated with rates of peroxy-acid reaction. PEST descriptors were calculated from B3LYP/6-31G(d) optimized structures and found to have significant levels of correlation with k. PIP Min described the minimum local IP on the surface of the molecule and was found to be related to k. PEST technology appears to be an accurate method in predicting reactivity and could prove to be a valuable asset in building treatment models and in remediation design for PAHs and other organic contaminants in the environment. PMID:23734862

  15. Hydrophobicity, expressivity and aromaticity are the major trends of amino-acid usage in 999 Escherichia coli chromosome-encoded genes.

    PubMed Central

    Lobry, J R; Gautier, C

    1994-01-01

    Multivariate analysis of the amino-acid compositions of 999 chromosome-encoded proteins from Escherichia coli showed that three main factors influence the variability of amino-acid composition. The first factor was correlated with the global hydrophobicity of proteins, and it discriminated integral membrane proteins from the others. The second factor was correlated with gene expressivity, showing a bias in highly expressed genes towards amino-acids having abundant major tRNAs. Just as highly expressed genes have reduced codon diversity in protein coding sequences, so do they have a reduced diversity of amino-acid choice. This showed that translational constraints are important enough to affect the global amino-acid composition of proteins. The third factor was correlated with the aromaticity of proteins, showing that aromatic amino-acid content is highly variable. PMID:8065933

  16. A heteromeric membrane-bound prenyltransferase complex from hop catalyzes three sequential aromatic prenylations in the bitter acid pathway.

    PubMed

    Li, Haoxun; Ban, Zhaonan; Qin, Hao; Ma, Liya; King, Andrew J; Wang, Guodong

    2015-03-01

    Bitter acids (α and β types) account for more than 30% of the fresh weight of hop (Humulus lupulus) glandular trichomes and are well known for their contribution to the bitter taste of beer. These multiprenylated chemicals also show diverse biological activities, some of which have potential benefits to human health. The bitter acid biosynthetic pathway has been investigated extensively, and the genes for the early steps of bitter acid synthesis have been cloned and functionally characterized. However, little is known about the enzyme(s) that catalyze three sequential prenylation steps in the β-bitter acid pathway. Here, we employed a yeast (Saccharomyces cerevisiae) system for the functional identification of aromatic prenyltransferase (PT) genes. Two PT genes (HlPT1L and HlPT2) obtained from a hop trichome-specific complementary DNA library were functionally characterized using this yeast system. Coexpression of codon-optimized PT1L and PT2 in yeast, together with upstream genes, led to the production of bitter acids, but no bitter acids were detected when either of the PT genes was expressed by itself. Stepwise mutation of the aspartate-rich motifs in PT1L and PT2 further revealed the prenylation sequence of these two enzymes in β-bitter acid biosynthesis: PT1L catalyzed only the first prenylation step, and PT2 catalyzed the two subsequent prenylation steps. A metabolon formed through interactions between PT1L and PT2 was demonstrated using a yeast two-hybrid system, reciprocal coimmunoprecipitation, and in vitro biochemical assays. These results provide direct evidence of the involvement of a functional metabolon of membrane-bound prenyltransferases in bitter acid biosynthesis in hop. PMID:25564559

  17. Energetics and kinetics of anaerobic aromatic and fatty acid degradation. Final report

    SciTech Connect

    Michael J. McInerney

    1996-06-24

    The factors that affect the rate and extent of a model aromatic compound, benzoate, in methanogenic environments was studied. Benzoate is degraded to a threshold concentration below which no further substrate degradation occurs. The threshold concentration depended on the substrate concentration and the amount of acetate present. The threshold value was not a function of the kinetic ability of the organism or toxicity of the end products. Rather a minimal Gibb's free energy value may exist where thermodynamic constraints preclude further benzoate degradation. In addition, new bacterial species were isolated and described, that degrade benzoate or reduce iron, cobalt and other metals.

  18. Design, Synthesis, EPR-Studies and Conformational Bias of Novel Spin-Labeled DCC-Analogues for the Highly Regioselective Labeling of Aliphatic and Aromatic Carboxylic Acids.

    PubMed

    Gölz, Jan Philipp; NejatyJahromy, Yaser; Bauer, Mirko; Muhammad, Ashraf; Schnakenburg, Gregor; Grimme, Stefan; Schiemann, Olav; Menche, Dirk

    2016-07-01

    Novel types of spin-labeled N,N'-dicyclohexylcarbodiimides (DCC) are reported that bear a 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO) residue on one side and different aromatic and aliphatic cyclohexyl analogues on the other side of the diimide core. These readily available novel reagents add efficiently to aliphatic and aromatic carboxylic acids, forming two possible spin-labeled amide derivatives with different radical distances of the resulting amide. The addition of aromatic DCC analogues proceeds with excellent selectivity, giving amides where the carboxylic acid is exclusively connected to the aromatic residue, while little or no selectivity was observed for the aliphatic congeners. The usefulness of these adducts in structural studies was demonstrated by EPR (electron paramagnetic resonance) measurements of biradical adducts of biphenyl-4,4'-dicarboxylic acids. These analyses also reveal high degrees of conformational bias for aromatic DCC derivatives, which further underlines the powerfulness of these novel reagents. This observation was further corroborated by quantum chemical calculations, giving a detailed understanding of the structural dynamics, while detailed information on the solid state structure of all novel reagents was obtained by X-ray structure analyses. PMID:27272435

  19. Fenton-like oxidation of small aromatic acids from biomass burning in atmospheric water and in the absence of light: Identification of intermediates and reaction pathways.

    PubMed

    Santos, Patrícia S M; Domingues, M Rosário M; Duarte, Armando C

    2016-07-01

    A previous work showed that the night period is important for the occurrence of Fenton-like oxidation of small aromatic acids from biomass burning in atmospheric waters, which originate new chromophoric compounds apparently more complex than the precursors, although the chemical transformations involved in the process are still unknown. In this work were identified by gas chromatography-mass spectrometry (GC-MS) and by electrospray mass spectrometry (ESI-MS) the organic intermediate compounds formed during the Fenton-like oxidation of three aromatic acids from biomass burning (benzoic, 4-hydroxybenzoic and 3,5-dihydroxybenzoic acids), the same compounds evaluated in the previous study, in water and in the absence of light, which in turns allows to disclose the chemical reaction pathways involved. The oxidation intermediate compounds found for benzoic acid were 2-hydroxybenzoic, 3-hydroxybenzoic, 4-hydroxybenzoic, 2,3-dihydroxybenzoic, 2,5-dihydroxybenzoic, 2,6-dihydroxybenzoic and 3,4-dihydroxybenzoic acids. The oxidation intermediates for 4-hydroxybenzoic acid were 3,4-hydroxybenzoic acid and hydroquinone, while for 3,5-dihydroxybenzoic acid were 2,4,6-trihydroxybenzoic and 3,4,5-trihydroxybenzoic acids, and tetrahydroxybenzene. The results suggested that the hydroxylation of the three small aromatic acids is the main step of Fenton-like oxidation in atmospheric waters during the night, and that the occurrence of decarboxylation is also an important step during the oxidation of the 4-dihydroxybenzoic and 3,5-dihydroxybenzoic acids. In addition, it is important to highlight that the compounds produced are also small aromatic compounds with potential adverse effects on the environment, besides becoming available for further chemical reactions in atmospheric waters. PMID:27088537

  20. Humic acids-based one-step fabrication of SERS substrates for detection of polycyclic aromatic hydrocarbons.

    PubMed

    Qu, Lu-Lu; Li, Yuan-Ting; Li, Da-Wei; Xue, Jin-Qun; Fossey, John S; Long, Yi-Tao

    2013-03-01

    A facile one-step approach to fabricate substrates for surface-enhanced Raman scattering (SERS) detection of polycyclic aromatic hydrocarbons (PAHs) was explored by reduction of silver nitrate with humic acids (HAs). This simple process readily delivers silver nanoparticles (Ag NPs) decorated with HAs (HAs-Ag NPs), and an average diameter of 50 nm. More importantly, it compares favorably to Ag NPs prepared by the usual sodium citrate method, HAs-Ag NPs show excellent SERS activity for PAHs and display a remarkable capacity to absorb aromatic molecules through presumed π-π stacking interactions. Furthermore, the HAs-Ag NPs displayed good SERS stability, possibly due to the fact that HAs form loose coils or networks around the nanoparticles thus preventing aggregation. The investigation of qualitative and quantitative detection of PAHs on HAs-Ag NPs indicate that different PAHs can be distinguished easily from their discriminant SERS peaks, and the SERS responses exhibited a linear dependence on PAH concentrations over two orders of magnitude, with tens of nM detection limits. In addition, the HAs-Ag NPs performed well in the multicomponent analysis of PAH mixtures by the SERS technique without pre-separation. PMID:23340517

  1. Branched-chain and aromatic amino acid catabolism into aroma volatiles in Cucumis melo L. fruit

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The unique aroma of melons (Cucumis melo L., Cucurbitaceae) is composed of many volatile compounds biosynthetically derived from fatty-acids, carotenoids, amino-acids as well as terpenes. Incubation of melon fruit cubes with amino- and a-keto acids led to the enhanced formation of aroma compounds be...

  2. Characterization of novel perylene diimides containing aromatic amino acid side chains.

    PubMed

    Farooqi, Mohammed J; Penick, Mark A; Burch, Jessica; Negrete, George R; Brancaleon, Lorenzo

    2016-01-15

    Perylene diimide derivatives have attracted initial interest as industrial dyes. Recently, much attention has been focused on their strong π-π stacks resulting from the large PDI aromatic core. These PDI stacks have distinct optical properties, and provide informative models that could mimic light-harvesting systems and initial charge transfer typical of photosynthetic systems. The absorption property of PDI derivatives may be tuned from visible to near-infrared region by peripheral substitution. We have studied a new class of PDI derivatives with aryl substituents derived from the side chains of aromatic aminoacids (Tyrosine, Tryptophan and Phenylalanine). We have investigated their absorption and the fluorescence properties in a set of organic solvents and established their different tendencies to aggregate in solution despite their solubility. Most aggregation appears to be unordered. One PDI analogue (the one formed from Tyr) in Methanol, however, appears to form J-type aggregates. Based on our results the compounds appear to be promising for future investigations regarding the interaction of these dyes with biomolecules. PMID:26298679

  3. Solid compounds of europium and terbium with some aromatic carboxylic acids

    SciTech Connect

    Chupakhina, R.A.; Biryulina, V.N.; Kasimova, L.V.; Balakhonov, V.G.

    1986-10-20

    By the reactions of europium and terbium hydroxides with aqueous solutions of benzoic, salicylic, phthalic, and phthalaldehydic acids, compounds were obtained with the compositions: for phthalic acid M/sub 2/L/sub 3/ x 3H/sub 2/O, and for the other acids ML/sub 3/ x 3H/sub 2/O, in which M = Eu/sup 3 +/, Tb/sup 3 +/; L is the anion of the corresponding acid. The compounds of europium and terbium with phthalaldehydric acid were prepared for the first time.

  4. Reduction in uptake by rice and soybean of aromatic arsenicals from diphenylarsinic acid contaminated soil amended with activated charcoal.

    PubMed

    Arao, Tomohito; Maejima, Yuji; Baba, Koji

    2011-10-01

    Activated charcoal (AC) amendment has been suggested as a promising method to immobilize organic contaminants in soil. We performed pot experiments with rice and soybean grown in agricultural soil polluted by aromatic arsenicals (AAs). The most abundant AA in rice grains and soybean seeds was methylphenylarsinic acid (MPAA). MPAA concentration in rice grains was significantly reduced to 2% and 3% in 0.2% AC treated soil compared to untreated soil in the first year of rice cultivation. In the second year, MPAA concentration in rice grains was significantly reduced to 15% in 0.2% AC treated soil compared to untreated soil. MPAA concentration in soybean seeds was significantly reduced to 44% in 0.2% AC treated soil compared to untreated soil. AC amendment was effective in reducing AAs in rice and soybean. PMID:21782301

  5. Distribution of polychlorinated biphenyls, phthalic acid esters, polycyclic aromatic hydrocarbons and organochlorine substances in the Moscow River, Russia.

    PubMed

    Eremina, Natalia; Paschke, Albrecht; Mazlova, Elena A; Schüürmann, Gerrit

    2016-03-01

    The purpose of this study was to investigate the levels of polychlorinated biphenyl (PCB), phthalic acid esters (PAE), polycyclic aromatic hydrocarbons (PAH) and organochlorine substances (OCP) in the Moscow River water. Some studies have reported the occurrence of these substances in the soil of the Moscow region; however, no study has yet established an overview for these compounds in the Moscow River water. In this study the Moscow River water contamination with PAEs, PAHs and OCPs was determined. Obtained results were associated with the resident area located on the river bank, and the possible contamination sources were considered. The obtained data were compared with the data on the contamination of the different world-wide rivers. This research indicates the further study necessity of the Moscow region to cover more contaminated sites and environmental compartments. PMID:26807987

  6. Quantitative determination of polycyclic aromatic hydrocarbon adducts to deoxyribonucleic acid using GC/MS (gas chromatography/mass spectrometry) techniques

    SciTech Connect

    Bean, R.M.; Thomas, B.L.; Chess, E.K.; Pavlovich, J.G.; Springer, D.L.

    1988-02-01

    A direct, specific mass spectrometric method useful for determination of polycyclic aromatic adducts has been developed. Our experiments indicated that overall recoveries from the acid hydrolysis, isolation and derivatization steps will be about 50%. It is apparent that a method even for BaP adducts is not yet complete. The methods described in this paper are provided in detail. Other derivatization techniques are needed that are selective and quantitative, and that will enhance the singal in the mass spectrometer to improve instrument selectivity and sensitivity. In addition to improvements in instrument sensitivity and gas chromatography column performance, there is a great need for procedures for rigorous documentation of organic analytical methods at the picogram level. 12 refs., 2 tabs.

  7. The effect of aromatic amines and phenols in the thiyl-induced reactions of polyunsaturated fatty acids

    NASA Astrophysics Data System (ADS)

    Tartaro Bujak, Ivana; Chatgilialoglu, Chryssostomos; Ferreri, Carla; Valgimigli, Luca; Amorati, Riccardo; Mihaljević, Branka

    2016-07-01

    Thiols are well known for their role in cellular redox homeostasis, while aromatic amines and phenols are the best known classes of chain-breaking antioxidants. On the other hand, thiyl radicals are known to catalyse the double bond isomerization in PUFA. We investigated the role and interplay of 2-mercaptoethanol and diphenylamine in the parallel processes of peroxidation and cis-trans isomerization of linoleic acid (LA) during gamma radiolysis, both in solution and micelles. Both compounds, used alone were able to protect LA from oxidation; however pro-oxidant activity and enhanced isomerization was observed when they were used together, depending on the experimental settings. Instead, α-tocopherol protected LA from both oxidation and isomerization in the presence of thiols under any tested settings. The mechanistic scenario is discussed highlighting the role of diphenylaminyl radicals in promoting thiyl-radical-induced cis-trans isomerization in the presence of oxygen.

  8. Utilization of oriented crystal growth for screening of aromatic carboxylic acids cocrystallization with urea

    NASA Astrophysics Data System (ADS)

    Przybyłek, Maciej; Ziółkowska, Dorota; Kobierski, Mirosław; Mroczyńska, Karina; Cysewski, Piotr

    2016-01-01

    The possibility of molecular complex formation in the solid state of urea with benzoic acid analogues was measured directly on the crystallite films deposited on the glass surface using powder X-ray diffractometry (PXRD). Obtained solid mixtures were also analyzed using Fourier transform infrared spectroscopy (FTIR). The simple droplet evaporation method was found to be efficient, robust, fast and cost-preserving approach for first stage cocrystal screening. Additionally, the application of orientation effect to cocrystal screening simplifies the analysis due to damping of majority of diffraction signals coming from coformers. During validation phase the proposed approach successfully reproduced both positive cases of cocrystallization (urea:salicylic acid and urea:4-hydroxy benzoic acid) as well as pairs of co-formers immiscible in the solid state (urea:benzoic acid and urea:acetylsalicylic acids). Based on validated approach new cocrystals of urea were identified in complexes with 3-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid and 3,5-dihydroxybenzoic acid. In all cases formation of multicomponent crystal phase was confirmed by the appearance of new reflexes on the diffraction patterns and FTIR absorption band shifts of O-H and N-H groups.

  9. Site-directed mutagenesis of tobacco anionic peroxidase: Effect of additional aromatic amino acids on stability and activity.

    PubMed

    Poloznikov, A A; Zakharova, G S; Chubar, T A; Hushpulian, D M; Tishkov, V I; Gazaryan, I G

    2015-08-01

    Tobacco anionic peroxidase (TOP) is known to effectively catalyze luminol oxidation without enhancers, in contrast to horseradish peroxidase (HRP). To pursue structure-activity relationship studies for TOP, two amino acids have been chosen for mutation, namely Thr151, close to the heme plane, and Phe140 at the entrance to the active site pocket. Three mutant forms TOP F140Y, T151W and F140Y/T151W have been expressed in Escherichia coli, and reactivated to yield active enzymes. Single-point mutations introducing additional aromatic amino acid residues at the surface of TOP exhibit a significant effect on the enzyme catalytic activity and stability as judged by the results of steady-state and transient kinetics studies. TOP T151W is up to 4-fold more active towards a number of aromatic substrates including luminol, whereas TOP F140Y is 2-fold more stable against thermal inactivation and 8-fold more stable in the reaction course. These steady-state observations have been rationalized with the help of transient kinetic studies on the enzyme reaction with hydrogen peroxide in a single turnover regime. The stopped-flow data reveal (a) an increased stability of F140Y Compound I towards hydrogen peroxide, and thus, a higher operational stability as compared to the wild-type enzyme, and (b) a lesser leakage of oxidative equivalents from TOP T151W Compound I resulting in the increased catalytic activity. The results obtained show that TOP unique properties can be further improved for practical applications by site-directed mutagenesis. PMID:25957835

  10. Thermal pretreatment of olive mill wastewater for efficient methane production: control of aromatic substances degradation by monitoring cyclohexane carboxylic acid.

    PubMed

    Pontoni, Ludovico; d'Antonio, Giuseppe; Esposito, Giovanni; Fabbricino, Massimiliano; Frunzo, Luigi; Pirozzi, Francesco

    2015-01-01

    Anaerobic digestion is investigated as a sustainable depurative strategy of olive oil mill wastewater (OOMW). The effect of thermal pretreatment on the anaerobic biodegradation of aromatic compounds present in (OMWW) was investigated. The anaerobic degradation of phenolic compounds, well known to be the main concern related to this kind of effluents, was monitored in batch anaerobic tests at a laboratory scale on samples pretreated at mild (80±1 °C), intermediate (90±1 °C) and high temperature (120±1 °C). The obtained results showed an increase of 34% in specific methane production (SMP) for OMWW treated at the lowest temperature and a decrease of 18% for treatment at the highest temperature. These results were related to the different decomposition pathways of the lignocellulosic compounds obtained in the tested conditions. The decomposition pathway was determined by measuring the concentrations of volatile organic acids, phenols, and chemical oxygen demand (COD) versus time. Cyclohexane carboxylic acid (CHCA) production was identified in all the tests with a maximum concentration of around 200 µmol L(-1) in accordance with the phenols degradation, suggesting that anaerobic digestion of aromatic compounds follows the benzoyl-CoA pathway. Accurate monitoring of this compound was proposed as the key element to control the process evolution. The total phenols (TP) and total COD removals were, with SMP, the highest (TP 62.7%-COD 63.2%) at 80 °C and lowest (TP 44.9%-COD 32.2%) at 120 °C. In all cases, thermal pretreatment was able to enhance the TP removal ability (up to 42% increase). PMID:25624137

  11. Effect of Thenardite on the Direct Detection of Aromatic Amino Acids: Implications for the Search for Life in the Solar System

    SciTech Connect

    C. Doc Richardson; Nancy W. Hinman; Jill R. Scott

    2009-10-01

    With the discovery of Na-sulfate minerals on Mars and Europa, recent studies using these minerals have focused on their ability to assist in the detection of bio/organic signatures. This study further investigates the ability of thenardite (Na2SO4) to effectively facilitate the ionization and identification of aromatic amino acids (phenylalanine, tyrosine, and tryptophan) using a technique called geomatrix-assisted laser desorption/ionization (GALDI) in conjunction with a Fourier transform mass spectrometry (FTICR-MS). This technique is based on the ability of a mineral host to facilitate the ionization and detection of bio/organic molecules. Spectra obtained from each aromatic amino acid alone and in combination with thenardite show differences in ionization mechanism and fragmentation patterns. These differences are due to chemical and structural differences between the aromatic side chains of their respective amino acid. Tyrosine and tryptophan when combined with thenardite were observed to undergo cation-attachment ([M+Na]+), due to the high alkali affinity of their aromatic side chains. Subsequent cation substitution of the carboxyl group led to formation double cation-attached peaks ([M-H+Na]Na+). In contrast, phenylalanine mixed with thenardite showed no evidence of Na+ interaction. Understanding how codeposition of amino acids with thenardite can affect the observed mass spectra is important for future exploration missions that are likely to use laser desorption mass spectrometry to search for bio/organic compounds in extraterrestrial environments.

  12. Effect of thenardite on the direct detection of aromatic amino acids: implications for the search for life in the solar system

    NASA Astrophysics Data System (ADS)

    Doc Richardson, C.; Hinman, Nancy W.; Scott, Jill R.

    2009-10-01

    With the discovery of Na-sulphate minerals on Mars and Europa, recent studies using these minerals have focused on their ability to assist in the detection of bio/organic signatures. This study further investigates the ability of thenardite (Na2SO4) to effectively facilitate the ionization and identification of aromatic amino acids (phenylalanine, tyrosine and tryptophan) using a technique called geomatrix-assisted laser desorption/ionization in conjunction with a Fourier transform ion cyclotron resonance mass spectrometry. This technique is based on the ability of a mineral host to facilitate desorption and ionization of bio/organic molecules for detection. Spectra obtained from each aromatic amino acid alone and in combination with thenardite show differences in ionization mechanism and fragmentation patterns. These differences are due to chemical and structural differences between the aromatic side chains of their respective amino acid. Tyrosine and tryptophan when combined with thenardite were observed to undergo cation-attachment ([M+Na]+), due to the high alkali ion affinity of their aromatic side chains. In addition, substitution of the carboxyl group hydrogen by sodium led to formation of [M-H+Na]Na+ peaks. In contrast, phenylalanine mixed with thenardite showed no evidence of Na+ attachment. Understanding how co-deposition of amino acids with thenardite can affect the observed mass spectra is important for future exploration missions that are likely to use laser desorption mass spectrometry to search for bio/organic compounds in extraterrestrial environments.

  13. Nucleophilic Aromatic Substitution.

    ERIC Educational Resources Information Center

    Avila, Walter B.; And Others

    1990-01-01

    Described is a microscale organic chemistry experiment which demonstrates one feasible route in preparing ortho-substituted benzoic acids and provides an example of nucleophilic aromatic substitution chemistry. Experimental procedures and instructor notes for this activity are provided. (CW)

  14. Studies of the developmental toxicity of polycarboxylate dispersing agents.

    PubMed

    Nolen, G A; Monroe, A; Hassall, C D; Iavicoli, J; Jamieson, R A; Daston, G P

    1989-06-01

    Three linear polycarboxylate compounds, two linear polyacrylates (90,000 MW and 4,500 MW) and one linear polyacrylate-maleate copolymer (12,000 MW), were tested for their teratogenic potential in female Sprague Dawley rats. These polymers, which were tested as sodium salts, are used as dispersing agents in detergent formulations at levels of 1-5%. All compounds were administered by gavage during organogenesis (days 6-15 of pregnancy). No adverse effects on development were seen with any of the three compounds at any of the doses tested. The highest dose, and therefore the minimum no-effect dose, for the three linear polymers was 1125 mg/kg/day for the 90,000 MW polyacrylate, 3000 mg/kg/day for the 4,500 MW polyacrylate, and 6670 mg/kg/day for the polyacrylate-maleate copolymer. Based on these data, these compounds are not developmentally toxic, even at very high dose levels. PMID:2598833

  15. Characterisation of calamansi (Citrus microcarpa). Part I: volatiles, aromatic profiles and phenolic acids in the peel.

    PubMed

    Cheong, Mun Wai; Chong, Zhi Soon; Liu, Shao Quan; Zhou, Weibiao; Curran, Philip; Bin Yu

    2012-09-15

    Volatile compounds in the peel of calamansi (Citrus microcarpa) from Malaysia, the Philippines and Vietnam were extracted with dichloromethane and hexane, and then analysed by gas chromatography-mass spectroscopy/flame ionisation detector. Seventy-nine compounds representing >98% of the volatiles were identified. Across the three geographical sources, a relatively small proportion of potent oxygenated compounds was significantly different, exemplified by the highest amount of methyl N-methylanthranilate in Malaysian calamansi peel. Principal component analysis and canonical discriminant analysis were applied to interpret the complex volatile compounds in the calamansi peel extracts, and to verify the discrimination among the different origins. In addition, four common hydroxycinnamic acids (caffeic, p-coumaric, ferulic and sinapic acids) were determined in the methanolic extracts of calamansi peel using ultra-fast liquid chromatography coupled to photodiode array detector. The Philippines calamansi peel contained the highest amount of total phenolic acids. In addition, p-Coumaric acid was the dominant free phenolic acids, whereas ferulic acid was the main bound phenolic acid. PMID:23107679

  16. Method of increasing conversion of a fatty acid to its corresponding dicarboxylic acid

    DOEpatents

    Craft, David L.; Wilson, C. Ron; Eirich, Dudley; Zhang, Yeyan

    2004-09-14

    A nucleic acid sequence including a CYP promoter operably linked to nucleic acid encoding a heterologous protein is provided to increase transcription of the nucleic acid. Expression vectors and host cells containing the nucleic acid sequence are also provided. The methods and compositions described herein are especially useful in the production of polycarboxylic acids by yeast cells.

  17. A method comparison to infer charring temperature, aromaticity and the degree of condensation of pyrogenic carbon

    NASA Astrophysics Data System (ADS)

    Wiedemeier, Daniel; Abiven, Samuel; Hockaday, William; Keiluweit, Marco; Kleber, Markus; Pyle, Lacey; Masiello, Caroline; McBeath, Anna; Nico, Peter; Schneider, Maximilan; Smernik, Ronald; Schmidt, Michael

    2013-04-01

    Fire-derived, pyrogenic carbon (PyC) is a persistent organic carbon fraction with a slow turnover in the environment because it is relatively resistant against chemical and biological degradation. It thus represents an important carbon fraction with a sequestration potential in the global carbon cycle. PyC is naturally produced on a large scale during wildfires and anthropogenically in the form of biochar, when organic waste is pyrolyzed. Aromaticity and the degree of condensation are the two main quality properties of PyC that probably largely determine its persistence against degradation. The two parameters should theoretically be dependent on pyrolysis conditions, such as charring temperature, pyrolysis time or feedstock. In this study, we used four different feedstocks and two different pyrolysis procedures to produce a thermosequence of 40 chars, ranging from 100 - 1000° C. The chars were then analyzed with six different state-of-the-art methods: solid state 13C nuclear magnetic resonance (13C NMR), diffuse infrared Fourier transform spectroscopy (DRIFT), X-ray diffraction (XRD), synchrotron-based near-edge X-ray absorption fine structure analysis (NEXAFS), benzene polycarboxylic acid analysis (BPCA) and pycnometry. They allowed to infer the aromaticity and the degree of condensation of the material. Using multivariate statistical methods, aromaticity and the degree of condensation could successfully be linked to charring temperature because characteristic patterns of the two properties could be observed by different methods throughout the whole thermosequence. Moreover, we show, which methods are most suitable for a quality assessment of PyC and discuss their advantages and limitations.

  18. Interaction of aromatic alcohols, aldehydes and acids with α-hydroxyl-containing carbon-centered radicals: A steady state radiolysis study

    NASA Astrophysics Data System (ADS)

    Samovich, S. N.; Brinkevich, S. D.; Shadyro, O. I.

    2013-01-01

    Benzaldehyde and its derivatives efficaciously oxidize in aqueous solutions α-hydroxyl-containing carbon-centered radicals (α-HCR) of various structures, suppressing thereby the radical recombination and fragmentation reactions. The compounds containing cinnamic moieties are capable of adding α-hydroxyethyl radicals (α-HER) to the carbon-carbon double bonds conjugated with the aromatic system to form molecular products identifiable by mass spectrometry. On radiolysis of aqueous ethanol solutions, reduction of α-HER by aromatic alcohols and acids has been shown to proceed via formation of their adducts with hydrated electron species.

  19. Synergistic selective extraction of actinides(III) over lanthanides from nitric acid using new aromatic diorganyldithiophosphinic acids and neutral organophosphorus compounds

    SciTech Connect

    Modolo, G.; Odoj, R.

    1999-01-01

    New aromatic dithiophosphinic acids (R{sub 2}PSSH) with R = C{sub 6}H{sub 5{sup {minus}}}, ClC{sub 6}H{sub 4{sup {minus}}}, FC{sub 6}H{sub 4{sup {minus}}} and CH{sub 3}C{sub 6}H{sub 4{sup {minus}}} were synthesized, characterized and tested as potential separating agents for trivalent actinides over lanthanides. The extraction of Am(III), Eu(III) and other lanthanides was carried out from nitric acid medium with mixtures of R{sub 2}PSSHs and neutral organophosphorus compounds. There was no detectable extraction when R{sub 2}PSSHs were used alone as extractants for either Am(III) or Eu(III) (D{sub Am,Eu} < 10{sup {minus}3}) under the experimental conditions used in this study. High separation factors (D{sub Am}/D{sub Eu} > 20) with D{sub Am} > 1 were achieved in the nitric acid range 0.1--1 mol/L by means of a synergistic mixture of bis(chlorophenyl)dithiophosphinic acid + tributylphosphate (TBP), trioctylphosphine oxide (TOPO) or tributylphosphine oxide (TBPO). The high radiation resistance (up to 10{sup 6} Gy absorbed {gamma}-doses) of the extractants was also demonstrated.

  20. Eaton's reagent-mediated domino π-cationic arylations of aromatic carboxylic acids to Iasi-red polymethoxylated polycyclic aromatic hydrocarbons: products with unprecedented biological activities as tubulin polymerization inhibitors.

    PubMed

    Ghinet, Alina; Gautret, Philippe; Hijfte, Nathalie Van; Ledé, Bertrand; Hénichart, Jean-Pierre; Bîcu, Elena; Darbost, Ulrich; Rigo, Benoît; Daïch, Adam

    2014-08-01

    A rapid domino π-cationic arylation of aromatic carboxylic acids, mediated by Eaton's reagent, has been developed for the synthesis of Iasi-red polymethoxylated polycyclic aromatic hydrocarbons (PAHs). This route is currently the easiest method to obtain such popular PAH compounds, which bear in addition numerous methoxy groups. The domino process was generalized, the structure of the obtained red products and the mechanism of their formations were elucidated, and some of their photophysical properties were determined. Newly synthesized polymethoxylated-PAHs were tested for their interaction with tubulin polymerization as well as for their cytotoxicity on a panel of NCI-60 human cancer cell lines. Interestingly, one of these rubicene derivatives exhibited remarkable cytotoxicity in vitro, including inhibition of leukemia, colon, melanoma, CNS, and ovarian cancer cell lines with GI50 values in the low nanomolar range (GI50 < 10 nM). PMID:25042333

  1. Quenching of triplet states of aromatic ketones by sulfur-containing amino acids in solution. Evidence for electron transfer

    SciTech Connect

    Marciniak, B.; Bobrowski, K.; Hug, G.L. )

    1993-11-18

    The mechanism for quenching triplet states of benzophenones by sulfur-containing amino acids in water/acetonitrile solution was investigated by laser flash photolysis. The amino acids in the study were methionine, S-methylcysteine, and S-carboxymethylcysteine, and the eight aromatic triplets were those of benzophenone and its derivatives possessing electron-withdrawing or electron-donating groups. The presence of radical ions in the transient spectra and correlations of the quenching rate constants with the free energy change for electron transfer are strong indications that the process involves an electron transfer. These correlations were displayed as Rehm-Weller plots (logarithm of quenching rate vs free energy). Classical theoretical formulations of the Rehm-Weller correlations were used to estimate the intrinsic barriers and the transmission coefficients for the electron-transfer processes. Applying both [open quotes]quadratic[close quotes] Marcus and [open quotes]asymptotic[close quotes] Agmon-Levine free energy relationships led to the values of intrinsic barriers lower than the solvent reorganization energy calculated within the framework of the dielectric continuum model. These relationships also led to low electronic transmission coefficients. The low values of the intrinsic barriers for electron transfer were also obtained using the recently developed Tachiya approach. 58 refs., 5 figs., 2 tabs.

  2. Methanogenic Inhibition by Roxarsone (4-Hydroxy-3-nitrophenylarsonic acid) and Related Aromatic Arsenic Compounds

    PubMed Central

    Sierra-Alvarez, Reyes; Cortinas, Irail; Field, Jim A.

    2009-01-01

    Roxarsone (4-hydroxy-3-nitro-phenylarsonic acid) and p-arsanilic acid (4-aminophenylarsonic acid) are feed additives widely used in the broiler and swine industry. This study evaluated the inhibitory effect of roxarsone, p-arsanilic, and other phenylarsonic compounds on the activity of acetate- and H2-utilizing methanogenic microorganisms. Roxarsone, p-arsanilic, and 4-hydroxy-3-aminophenylarsonic acid (HAPA) inhibited acetoclastic and hydrogenotrophic methanogens when supplemented at concentrations of 1 mM, and their inhibitory effect increased sharply with incubation time. Phenylarsonic acid (1 mM) inhibited acetoclastic but not H2-utilizing methanogens. HAPA, a metabolite from the anaerobic biodegradation of roxarsone, was found to be sensitive to autooxidation by oxygen. The compound (2.6 mM) caused low methanogenic inhibition (only 14.2%) in short-term assays of 12 h when autooxidation was prevented by supplementing HAPA solutions with ascorbate. However, ascorbate-free HAPA solutions underwent spontaneous autooxidation in the presence of oxygen, leading to the formation of highly inhibitory compounds. These results confirm the microbial toxicity of organoarsenic compounds, and they indicate that biotic as well as abiotic transformations can potentially impact the fate and microbial toxicity of these contaminants in the environment. PMID:19889499

  3. Water-Soluble Poly(p-aryleneethynylene)s: A Sensor Array Discriminates Aromatic Carboxylic Acids.

    PubMed

    Han, Jinsong; Wang, Benhua; Bender, Markus; Seehafer, Kai; Bunz, Uwe H F

    2016-08-10

    A chemical tongue consisting of 11 elements (four poly(p-aryleneethynylene)s (PAE) at pH 7 and pH 13, and seven electrostatic complexes formed from oppositely charged poly(p-aryleneethynylene)s at pH 7) discriminate 21 benzoic and phenylacetic acid derivatives in aqueous solution. The mechanism of discrimination is the fluorescence modulation of the PAEs, leading to quenching or fluorescence turn-on. The PAEs alone at both pH values and the tongue, consisting of the complexes only, discriminate the 21 acids with 92% (PAEs at pH 7), 95% (PAEs at pH 13), and 99% (complexes at pH 7) reliability after linear discriminant analysis (LDA). A sensor field with all 14 elements, according to LDA, discriminates all of the 21 acids with 100% accuracy. PMID:27415439

  4. Pretreatment of solid carbonaceous material with dicarboxylic aromatic acids to prevent scale formation

    DOEpatents

    Brunson, Roy J.

    1982-01-01

    Scale formation during the liquefaction of lower ranking coals and similar carbonaceous materials is significantly reduced and/or prevented by pretreatment with a pretreating agent selected from the group consisting of phthalic acid, phthalic anhydride, pyromellitic acid and pyromellitic anhydride. The pretreatment is believed to convert the scale-forming components to the corresponding phthalate and/or pyromellitate prior to liquefaction. The pretreatment is accomplished at a total pressure within the range from about 1 to about 2 atmospheres. Temperature during pretreatment will generally be within the range from about 5.degree. to about 80.degree. C.

  5. Vibrational analysis of amino acids and short peptides in hydrated media. VIII. Amino acids with aromatic side chains: L-phenylalanine, L-tyrosine, and L-tryptophan.

    PubMed

    Hernández, Belén; Pflüger, Fernando; Adenier, Alain; Kruglik, Sergei G; Ghomi, Mahmoud

    2010-11-25

    Four out of the 20 natural α-amino acids (α-AAs) contain aromatic rings in their side chains. In a recent paper (J. Phys. Chem. B 2010, 114, 9072-9083), we have analyzed the structural and vibrational features of l-histidine, one of the potent elements of this series. Here, we report on the three remaining members of this family, i.e., l-phenylalanine, l-tyrosine, and l-tryptophan. Their solution (H(2)O and D(2)O) Raman scattering and Fourier transform infrared absorption attenuated total reflection (FT-IR ATR) spectra were measured at room temperature from the species corresponding to those existing at physiological conditions. Because of the very low water solubility of tyrosine, special attention was paid to avoid any artifact concerning the report of the vibrational spectra corresponding to nondissolved powder of this AA in aqueous solution. Finally, we could obtain for the first time the Raman and FT-IR spectra of tyrosine at very low concentration (2.3 mM) upon long accumulation time. To clarify this point, those vibrational spectra of tyrosine recorded either in the solid phase or in a heterogeneous state, where dissolved and nondissolved species of this AA coexist in aqueous solution, are also provided as Supporting Information . To carry out a discussion on the general geometrical and vibrational behavior of these AAs, we resorted to quantum mechanical calculations at the DFT/B3LYP/6-31++G* level, allowing (i) determination of potential energy surfaces of these AAs in a continuum solvent as a function of the torsion angles χ(1) and χ(2), defining the conformation of each aromatic side chain around C(α)-C(β) and C(β)-C(γ) bonds, respectively; (ii) analysis of geometrical features of the AAs surrounded by clusters of n explicit (n = 5-7) water molecules interacting with the backbone and aromatic rings; and (iii) assignment of the observed vibrational modes by means of the theoretical data provided by the lowest energy conformers of explicitly

  6. Postprandial Levels of Branch Chained and Aromatic Amino Acids Associate with Fasting Glycaemia.

    PubMed

    Ottosson, Filip; Ericson, Ulrika; Almgren, Peter; Nilsson, Jeanette; Magnusson, Martin; Fernandez, Céline; Melander, Olle

    2016-01-01

    High fasting plasma concentrations of isoleucine, phenylalanine, and tyrosine have been associated with increased risk of hyperglycaemia and incidence of type 2 diabetes. Whether these associations are diet or metabolism driven is unknown. We examined how the dietary protein source affects the postprandial circulating profile of these three diabetes associated amino acids (DMAAs) and tested whether the postprandial DMAA profiles are associated with fasting glycaemia. We used a crossover design with twenty-one healthy individuals and four different isocaloric test meals, containing proteins from different dietary sources (dairy, fish, meat, and plants). Analysis of the postprandial DMAAs concentrations was performed using targeted mass spectrometry. A DMAA score was defined as the sum of all the three amino acid concentrations. The postprandial area under the curve (AUC) of all the three amino acids and the DMAA score was significantly greater after intake of the meal with dairy protein compared to intake of the three other meals. The postprandial AUC for the DMAA score and all the three amino acids strongly associated with fasting glucose level and insulin resistance. This indicates the importance of the postprandial kinetics and metabolism of DMAAs in understanding the overall association between DMAAs and glycaemia. PMID:27274867

  7. Selective deuteration of (hetero)aromatic compounds via deutero-decarboxylation of carboxylic acids.

    PubMed

    Grainger, Rachel; Nikmal, Arif; Cornella, Josep; Larrosa, Igor

    2012-04-28

    A practical, mild and highly selective protocol for the monodeuteration of a variety of arenes and heteroarenes is presented. Catalytic amounts of Ag(I) salts in DMSO/D(2)O are shown to facilitate the deutero-decarboxylation of ortho-substituted benzoic and heteroaromatic α-carboxylic acids in high yields with excellent levels of deuterium incorporation. PMID:22418863

  8. One-Pot Synthesis of Arylketones from Aromatic Acids via Palladium-Catalyzed Suzuki Coupling.

    PubMed

    Wu, Hongxiang; Xu, Baiping; Li, Yue; Hong, Fengying; Zhu, Dezhao; Jian, Junsheng; Pu, Xiaoer; Zeng, Zhuo

    2016-04-01

    A palladium-catalyzed one-pot procedure for the synthesis of aryl ketones has been developed. Triazine esters when coupled with aryl boronic acids provided aryl ketones in moderate to excellent yields (up to 95%) in the presence of 1 mol % Pd(PPh3)2Cl2 for 30 min. PMID:26949103

  9. Postprandial Levels of Branch Chained and Aromatic Amino Acids Associate with Fasting Glycaemia

    PubMed Central

    Ottosson, Filip; Ericson, Ulrika; Almgren, Peter; Nilsson, Jeanette; Magnusson, Martin; Fernandez, Céline; Melander, Olle

    2016-01-01

    High fasting plasma concentrations of isoleucine, phenylalanine, and tyrosine have been associated with increased risk of hyperglycaemia and incidence of type 2 diabetes. Whether these associations are diet or metabolism driven is unknown. We examined how the dietary protein source affects the postprandial circulating profile of these three diabetes associated amino acids (DMAAs) and tested whether the postprandial DMAA profiles are associated with fasting glycaemia. We used a crossover design with twenty-one healthy individuals and four different isocaloric test meals, containing proteins from different dietary sources (dairy, fish, meat, and plants). Analysis of the postprandial DMAAs concentrations was performed using targeted mass spectrometry. A DMAA score was defined as the sum of all the three amino acid concentrations. The postprandial area under the curve (AUC) of all the three amino acids and the DMAA score was significantly greater after intake of the meal with dairy protein compared to intake of the three other meals. The postprandial AUC for the DMAA score and all the three amino acids strongly associated with fasting glucose level and insulin resistance. This indicates the importance of the postprandial kinetics and metabolism of DMAAs in understanding the overall association between DMAAs and glycaemia. PMID:27274867

  10. Two new Zn(II) coordination polymers based on mixed pipemidic acid and flexible aromatic dicarboxylic acid ligands: Syntheses, crystal structures and luminescent properties

    NASA Astrophysics Data System (ADS)

    Jia, Yanxia; Zhou, Pingping

    2016-09-01

    Two new Zn(II) coordination polymers, namely [Zn(4,4‧-sdb) (HPPA)]n (1) and [Zn(2,2‧-bpdc)0.5(PPA)]n (2) (4,4‧-H2sdb = 4,4‧-sulfonyldibenzoate, 2,2‧-H2bpdc = 2,2‧-biphenyldicarboxylic acid, HPPA = pipemidic acid) were successfully obtained under hydrothermal conditions. These two compounds were further characterized by single-crystal X-ray diffraction analyses, elemental analyses, powder X-ray diffraction (PXRD) analyses and IR spectra. Compound 1 features a 1D chain structure, which further extended into a 3D supramolecular framework via intermolecular hydrogen bonds and weak van der Waals interactions, and compound 2 features a 3D framework with 6-connected α-Po-type topology. The structural regulation for these two compounds was successfully achieved by changing the flexible aromatic dicarboxylic acid ligand. Moreover, the thermal stabilities and luminescent properties for these two compounds were also investigated.

  11. Comparison of Aromatic Dithiophoshinic and Phosphinic Acid Derivatives for Minor Actinide Extraction

    SciTech Connect

    John R. Klaehn; Dean R. Peterman; Mason K. Harrup; Richard D. Tillotson; Mitchell R. Greenhalgh; Thomas A. Luther; Jack D. Law; Lee M. Daniels

    2008-03-01

    A new extractant for the separation of actinide(III) and lanthanide(III), bis(otrifluoromethylphenyl) phosphinic acid (O-PA) was synthesized. The synthetic route employed mirrors one that was employed to produce the sulfur containing analog bis(otrifluoromethylphenyl) dithiophosphinic acid (S-PA). Multinuclear NMR spectroscopy was used for elementary characterization of the new O-PA derivative. This new O-PA extractant was used to perform Am(III)/Eu(III) separations and the results were directly compared to those obtained in identical separation experiments using S-PA, an extractant that is known to exhibit separation factors of ~100,000 at low pH. The separations data are presented and discussed in terms comparing the nature of the oxygen atom as a donor to that of the sulfur atom in extractants that are otherwise identical.

  12. Energetics and kinetics of anaerobic aromatic and fatty acid degradation. Progress report, March 1992--June 1995

    SciTech Connect

    McInerney M.J.

    1995-06-23

    Factors affecting the rate and extent of benzoate degradation by anaerobic syntrophic consortia were studied. Cocultures of a syntrophic benzoate degrader, strain SB, with a hydrogen/formate-using sulfate reducer degraded benzoate to a threshold that depended on the amount of substrate and acetate present. The benzoate threshold was not a function of the inhibition of benzoate degradation capacity by acetate or the toxicity of the undissociated form of acetate. Rather, a critical or minimal Gibb`s free energy value may exist where thermodynamic constraints preclude further benzoate degradation. A sensitive assay to detect low formate concentrations was developed to measure the formate levels when the benzoate threshold was reached. We showed that increased acetate concentrations, even when hydrogen and formate levels are low, affects the extent of benzoate degradation, implicating the importance of interspecies acetate transfer. In addition to benzoate, various saturated and unsaturated fatty acids, 2-methylbutyrate, and methyl esters of fatty acids supported growth in coculture with a hydrogen-using partner. SB is the only syntrophic bacterium known to use both benzoate and fatty acids. Phylogenetic analysis showed that SB clustered with sulfate reducers in the delta subclass of the Proteobacteria. SB grew well in coculture with Desulfoarculus baarsii, a sulfate reducer that uses formate but not hydrogen. This unequivocally shows that SB can grow by interspecies formate transfer.

  13. The Legionella pneumophila Siderophore Legiobactin Is a Polycarboxylate That Is Identical in Structure to Rhizoferrin

    PubMed Central

    Burnside, Denise M.; Wu, Yuyang; Shafaie, Saman

    2015-01-01

    Legionella pneumophila, the agent of Legionnaires' disease, secretes a siderophore (legiobactin) that promotes bacterial infection of the lung. In past work, we determined that cytoplasmic LbtA (from Legiobactin gene A) promotes synthesis of legiobactin, inner membrane LbtB aids in export of the siderophore, and outer membrane LbtU and inner membrane LbtC help mediate ferrilegiobactin uptake and assimilation. However, the past studies examined legiobactin contained within bacterial culture supernatants. By utilizing high-pressure liquid chromatography that incorporates hydrophilic interaction-based chemistry, we have now purified legiobactin from supernatants of virulent strain 130b that is suitable for detailed chemical analysis. High-resolution mass spectrometry (MS) revealed that the molecular mass of (protonated) legiobactin is 437.140 Da. On the basis of the results obtained from both MS analysis and various forms of nuclear magnetic resonance, we found that legiobactin is composed of two citric acid residues linked by a putrescine bridge and thus is identical in structure to rhizoferrin, a polycarboxylate-type siderophore made by many fungi and several unrelated bacteria. Both purified legiobactin and rhizoferrin obtained from the fungus Cunninghamella elegans were able to promote Fe3+ uptake by wild-type L. pneumophila as well as enhance growth of iron-starved bacteria. These results did not occur with 130b mutants lacking lbtU or lbtC, indicating that both endogenously made legiobactin and exogenously derived rhizoferrin are assimilated by L. pneumophila in an LbtU- and LbtC-dependent manner. PMID:26195554

  14. The Legionella pneumophila Siderophore Legiobactin Is a Polycarboxylate That Is Identical in Structure to Rhizoferrin.

    PubMed

    Burnside, Denise M; Wu, Yuyang; Shafaie, Saman; Cianciotto, Nicholas P

    2015-10-01

    Legionella pneumophila, the agent of Legionnaires' disease, secretes a siderophore (legiobactin) that promotes bacterial infection of the lung. In past work, we determined that cytoplasmic LbtA (from Legiobactin gene A) promotes synthesis of legiobactin, inner membrane LbtB aids in export of the siderophore, and outer membrane LbtU and inner membrane LbtC help mediate ferrilegiobactin uptake and assimilation. However, the past studies examined legiobactin contained within bacterial culture supernatants. By utilizing high-pressure liquid chromatography that incorporates hydrophilic interaction-based chemistry, we have now purified legiobactin from supernatants of virulent strain 130b that is suitable for detailed chemical analysis. High-resolution mass spectrometry (MS) revealed that the molecular mass of (protonated) legiobactin is 437.140 Da. On the basis of the results obtained from both MS analysis and various forms of nuclear magnetic resonance, we found that legiobactin is composed of two citric acid residues linked by a putrescine bridge and thus is identical in structure to rhizoferrin, a polycarboxylate-type siderophore made by many fungi and several unrelated bacteria. Both purified legiobactin and rhizoferrin obtained from the fungus Cunninghamella elegans were able to promote Fe(3+) uptake by wild-type L. pneumophila as well as enhance growth of iron-starved bacteria. These results did not occur with 130b mutants lacking lbtU or lbtC, indicating that both endogenously made legiobactin and exogenously derived rhizoferrin are assimilated by L. pneumophila in an LbtU- and LbtC-dependent manner. PMID:26195554

  15. Syntheses, crystal structures, and properties of four complexes based on polycarboxylate and imidazole ligands

    NASA Astrophysics Data System (ADS)

    Qiao, Rui; Chen, Shui-Sheng; Sheng, Liang-Quan; Yang, Song; Li, Wei-Dong

    2015-08-01

    Four metal-organic coordination polymers [Zn(HL)(H2O)]·4H2O (1), [Zn(HL)(L1)]·4H2O (2), [Cu(HL)(H2O)]·3H2O (3) and [Cu(HL)(L1)]·5H2O (4) were synthesized by reactions of the corresponding metal(II) salts with semirigid polycarboxylate ligand (5-((4-carboxypiperidin-1-yl)methyl)isophthalic acid hydrochloride, H3L·HCl) or auxiliary ligand (1,4-di(1H-imidazol-4-yl)benzene, L1). The structures of the compounds were characterized by elemental analysis, FT-IR spectroscopy and single-crystal X-ray diffraction. The use of auxiliary ligand L1 has great influence on the structures of two pairs of complexes 1, 2 and 3, 4. Complex 1 is a uninodal 3-connected rare 2-fold interpenetrating ZnSc net with a Point (Schlafli) symbol of (103) while 2 is a one-dimensional (1D) ladder structure. Compound 3 features a two-dimensional (2D) honeycomb network with typical 63-hcb topology, while 4 is 2D network with (4, 4) sql topology based on binuclear CuII subunits. The non-covalent bonding interactions such as hydrogen bonds, π···π stacking and C-H···π exist in complexes 1-4, which contributes to stabilize crystal structure and extend the low-dimensional entities into high-dimensional frameworks. And the photoluminescent property of 1 and 2 and gas sorption property of 4 have been investigated.

  16. Trace analysis of oxidized, nitrated, and chlorinated aromatic amino acids by capillary electrophoresis with electroosmotic flow modification allowing large-volume sample stacking.

    PubMed

    Tábi, Tamás; Magyar, Kálmán; Szöko, Eva

    2005-05-01

    A capillary electrophoresis method has been developed for the simultaneous analysis of the oxidized, nitrated, and chlorinated aromatic amino acids, as well as their parent compounds. These modifications of the aromatic amino acids in proteins or free form are induced by the attack of reactive, mainly free radical species generated during cell stress, and these stable products may serve as biomarkers of cell damage. The analytes tyrosine, phenylalanine, dihydroxyphenylalanine, tryptophan, 3-nitrotyrosine, 3-chlorotyrosine, ortho-tyrosine, meta-tyrosine, 3-hydroxyphenylacetic acid (internal standard 1), and alpha-methyltyrosine (internal standard 2) were separated in their anionic forms in alkaline borate buffer. The polyamine spermine was used as electroosmotic flow (EOF) modifier. Adsorbing to the capillary wall, spermine can either suppress or even reverse the EOF depending on its concentration and the pH. The effects of the pH of the separation buffer, the spermine concentration, the temperature, and the applied field strength on the separation were examined. The modified aromatic amino acids are present in biological fluids in a much lower concentration than their parent compounds, thus high detection sensitivity of the analytical method is required. To achieve good detection sensitivity, field-amplified sample stacking of large injection volumes was applied. Omitting polyamine from the sample buffer allowed local reversal of the EOF, thus removal of the low conductivity sample buffer at the capillary inlet. In this way, 100% of the capillary to the detection window could be filled with the sample, and the detection limits achieved for the modified aromatic amino acids were in the range of 2.5-10 nM. PMID:15818575

  17. Advanced Model Compounds for Understanding Acid-Catalyzed Lignin Depolymerization: Identification of Renewable Aromatics and a Lignin-Derived Solvent.

    PubMed

    Lahive, Ciaran W; Deuss, Peter J; Lancefield, Christopher S; Sun, Zhuohua; Cordes, David B; Young, Claire M; Tran, Fanny; Slawin, Alexandra M Z; de Vries, Johannes G; Kamer, Paul C J; Westwood, Nicholas J; Barta, Katalin

    2016-07-20

    The development of fundamentally new approaches for lignin depolymerization is challenged by the complexity of this aromatic biopolymer. While overly simplified model compounds often lack relevance to the chemistry of lignin, the direct use of lignin streams poses significant analytical challenges to methodology development. Ideally, new methods should be tested on model compounds that are complex enough to mirror the structural diversity in lignin but still of sufficiently low molecular weight to enable facile analysis. In this contribution, we present a new class of advanced (β-O-4)-(β-5) dilinkage models that are highly realistic representations of a lignin fragment. Together with selected β-O-4, β-5, and β-β structures, these compounds provide a detailed understanding of the reactivity of various types of lignin linkages in acid catalysis in conjunction with stabilization of reactive intermediates using ethylene glycol. The use of these new models has allowed for identification of novel reaction pathways and intermediates and led to the characterization of new dimeric products in subsequent lignin depolymerization studies. The excellent correlation between model and lignin experiments highlights the relevance of this new class of model compounds for broader use in catalysis studies. Only by understanding the reactivity of the linkages in lignin at this level of detail can fully optimized lignin depolymerization strategies be developed. PMID:27310182

  18. Transcriptome Profiling and Physiological Studies Reveal a Major Role for Aromatic Amino Acids in Mercury Stress Tolerance in Rice Seedlings

    PubMed Central

    Trinh, Ngoc Nam; Huang, Li-Yao; Chen, Ying-Chih; Cheng, Kai-Teng; Huang, Tsai-Lien; Lin, Chung-Yi; Huang, Hao-Jen

    2014-01-01

    Mercury (Hg) is a serious environmental pollution threat to the planet. The accumulation of Hg in plants disrupts many cellular-level functions and inhibits growth and development, but the mechanism is not fully understood. To gain more insight into the cellular response to Hg, we performed a large-scale analysis of the rice transcriptome during Hg stress. Genes induced with short-term exposure represented functional categories of cell-wall formation, chemical detoxification, secondary metabolism, signal transduction and abiotic stress response. Moreover, Hg stress upregulated several genes involved in aromatic amino acids (Phe and Trp) and increased the level of free Phe and Trp content. Exogenous application of Phe and Trp to rice roots enhanced tolerance to Hg and effectively reduced Hg-induced production of reactive oxygen species. Hg induced calcium accumulation and activated mitogen-activated protein kinase. Further characterization of the Hg-responsive genes we identified may be helpful for better understanding the mechanisms of Hg in plants. PMID:24840062

  19. Ascorbic Acid Enhances the Accumulation of Polycyclic Aromatic Hydrocarbons (PAHs) in Roots of Tall Fescue (Festuca arundinacea Schreb.)

    PubMed Central

    Gao, Yanzheng; Li, Hui; Gong, Shuaishuai

    2012-01-01

    Plant contamination by polycyclic aromatic hydrocarbons (PAHs) is crucial to food safety and human health. Enzyme inhibitors are commonly utilized in agriculture to control plant metabolism of organic components. This study revealed that the enzyme inhibitor ascorbic acid (AA) significantly reduced the activities of peroxidase (POD) and polyphenol oxidase (PPO), thus enhancing the potential risks of PAH contamination in tall fescue (Festuca arundinacea Schreb.). POD and PPO enzymes in vitro effectively decomposed naphthalene (NAP), phenanthrene (PHE) and anthracene (ANT). The presence of AA reduced POD and PPO activities in plants, and thus was likely responsible for enhanced PAH accumulation in tall fescue. This conclusion is supported by the significantly enhanced uptake of PHE in plants in the presence of AA, and the positive correlation between enzyme inhibition efficiencies and the rates of metabolism of PHE in tall fescue roots. This study provides a new perspective, that the common application of enzyme inhibitors in agricultural production could increase the accumulation of organic contaminants in plants, hence enhancing risks to food safety and quality. PMID:23185628

  20. Transcriptome profiling and physiological studies reveal a major role for aromatic amino acids in mercury stress tolerance in rice seedlings.

    PubMed

    Chen, Yun-An; Chi, Wen-Chang; Trinh, Ngoc Nam; Huang, Li-Yao; Chen, Ying-Chih; Cheng, Kai-Teng; Huang, Tsai-Lien; Lin, Chung-Yi; Huang, Hao-Jen

    2014-01-01

    Mercury (Hg) is a serious environmental pollution threat to the planet. The accumulation of Hg in plants disrupts many cellular-level functions and inhibits growth and development, but the mechanism is not fully understood. To gain more insight into the cellular response to Hg, we performed a large-scale analysis of the rice transcriptome during Hg stress. Genes induced with short-term exposure represented functional categories of cell-wall formation, chemical detoxification, secondary metabolism, signal transduction and abiotic stress response. Moreover, Hg stress upregulated several genes involved in aromatic amino acids (Phe and Trp) and increased the level of free Phe and Trp content. Exogenous application of Phe and Trp to rice roots enhanced tolerance to Hg and effectively reduced Hg-induced production of reactive oxygen species. Hg induced calcium accumulation and activated mitogen-activated protein kinase. Further characterization of the Hg-responsive genes we identified may be helpful for better understanding the mechanisms of Hg in plants. PMID:24840062

  1. The effect of sorption on the degradation of aromatic acids and bases

    SciTech Connect

    Ainsworth, C.C.; Fredrickson, J.K.; Smith, S.C.

    1992-10-01

    The availability and degradation of selected ionizable organic compounds sorbed to pure mineral phases are discussed. Substrates sorbed to mineral surfaces may or may not be protected from microbial attack; the degree of protection appears to be dependent on the type and cell density of the microorganism involved. The currently available data, however, demonstrate that there is little, if any, consensus on the types of reactions or interactions that facilitate sorbed substrate utilization. Rates of degradation of organic bases and cations that sorb to clay minerals via an exchange reaction are suggested to be directly related to substrate binding intensity and conformation on the clay surface. Similarly, rates of degradation of organic acids sorbed to the surface of oxides are suggested to be related to their interaction with the surface and the type of oxide sorbent. Although the rate-limiting step in microbial utilization of sorbed acids and bases is apparently a desorption process, the rate of desorption is itself linked to the compound's binding intensities on a given sorbent. Thus, as the binding intensities of compounds increase, chemical kinetic reactions, rather than mass-transfer processes, appear to limit the rate of desorption.

  2. The effect of sorption on the degradation of aromatic acids and bases

    SciTech Connect

    Ainsworth, C.C.; Fredrickson, J.K.; Smith, S.C.

    1992-10-01

    The availability and degradation of selected ionizable organic compounds sorbed to pure mineral phases are discussed. Substrates sorbed to mineral surfaces may or may not be protected from microbial attack; the degree of protection appears to be dependent on the type and cell density of the microorganism involved. The currently available data, however, demonstrate that there is little, if any, consensus on the types of reactions or interactions that facilitate sorbed substrate utilization. Rates of degradation of organic bases and cations that sorb to clay minerals via an exchange reaction are suggested to be directly related to substrate binding intensity and conformation on the clay surface. Similarly, rates of degradation of organic acids sorbed to the surface of oxides are suggested to be related to their interaction with the surface and the type of oxide sorbent. Although the rate-limiting step in microbial utilization of sorbed acids and bases is apparently a desorption process, the rate of desorption is itself linked to the compound`s binding intensities on a given sorbent. Thus, as the binding intensities of compounds increase, chemical kinetic reactions, rather than mass-transfer processes, appear to limit the rate of desorption.

  3. Pyrolysis of simple coal model compounds containing aromatic carboxylic acids: Does decarboxylation lead to cross-linking?

    SciTech Connect

    Eskay, T.P.; Britt, P.F.; Buchanan, A.C. III

    1996-12-31

    In recent years, it has been proposed that oxygen functional groups, prevalent in low rank coals, are major actors in retrograde reactions which inhibit their efficient thermochemical processing. In the pyrolysis and liquefaction of low-rank coals, low temperature cross-linking reactions have been correlated with the loss of carboxyl groups and the evolution of CO{sub 2} and H{sub 2}O. Pretreatments such as methylation, demineralization, or ion-exchange of the inorganic cations reduce cross-linking and CO{sub 2} evolution in pyrolysis, while the exchange of Na{sup +}, K{sup +}, Ca{sup ++}, and Ba{sup ++} into demineralized coal increases cross-linking and CO{sub 2} evolution in pyrolysis and liquefaction. These results suggest, in part, that decarboxylation pathways in coal may play an important role in the cross-linking of the coal polymer. However, the reaction pathways associated with the decarboxylation and cross-linking events in low rank coal are currently unknown. Furthermore, it is not known whether the reaction pathway that leads to decarboxylation also leads to cross-linking. Radical recombination or addition reactions have been suggested as being involved in retrograde reactions. However, the involvement of radical pathways in thermal decarboxylation reactions has recently been brought into question by the observation that decarboxylation of benzoic acid derivatives under coal liquefaction conditions yielded only small amounts of aryl-aryl coupling products. Therefore, to gain a better understanding of the role decarboxylation plays in cross-linking reactions in low rank coals, we have studied the pyrolysis of several bibenzyls containing aromatic carboxylic acids. The structures currently under investigation are 1,2-(3,3`-dicarboxyphenyl)ethane (1) and 1,2-(4,4`-dicarboxyphenyl)ethane(2). These compounds are capable of forming reactive free-radical intermediates at ca. 400{degrees}C through homolysis of the weak bibenzylic bonds.

  4. Aromatization of hydrocarbons by oxidative dehydrogenation catalyzed by the mixed addenda heteropoly acid H sub 5 PMo sub 10 V sub 2 O sub 40

    SciTech Connect

    Neumann, R. ); Lissle, M. )

    1989-09-15

    The mixed addenda heteropoly acid H{sub 5}PMo{sub 10}V{sub 2}O{sub 40} dissolved in 1,2-dichloroethane with tetraglyme, forming the (tetraglyme){sub 3}-H{sub 5}PMo{sub 10}V{sub 2}O{sub 40} complex, catalyzes the aromatization of cyclic dienes at moderate temperatures in the presence of molecular oxygen. Dehydrogenations of exocyclic dienes such as limonene show that dehydrogenation is preceded by isomerization to their endocyclic isomers. Aromatization takes place by successive one-electron transfers and proton abstractions from the organic substrate to the heteropoly acid the latter being reoxidized by dioxygen coupled with the formation of water.

  5. Polycyclic aromatic hydrocarbon removal from contaminated soils using fatty acid methyl esters.

    PubMed

    Gong, Zongqiang; Wang, Xiaoguang; Tu, Ying; Wu, Jinbao; Sun, Yifei; Li, Peng

    2010-03-01

    In this study, solubilization of PAHs from a manufactured gas plant (MGP) soil and two artificially spiked soils using fatty acid methyl esters (FAME) was investigated. PAH removals from both the MGP and the spiked soils by FAME, methanol, soybean oil, hydroxypropyl-beta-cyclodextrin, Triton X-100, and Tween 80 were compared. The effect of FAME:MGP soil ratios on PAH removals was also investigated. Results showed that the FAME mixture synthesized by our lab was more efficient than the cyclodextrin and the two surfactants used for PAH removal from the spiked soils with individual PAH concentrations of 200 and 400 mg kg(-1). However, the difference among three PAH removals by the FAME, soybean oil and methanol was not quite pronounced. The FAME synthesized and market biodiesel exhibited better performance for PAH removals (46% and 35% of total PAH) from the weathered contaminated MGP soil when compared with the other agents (0-31%). Individual PAH removals from the weathered MGP soil were much lower than those from the spiked soils. The percentages of total PAH removals from the MGP soil were 59%, 46%, and 51% for the FAME:MGP soil ratios of 1:2, 1:1, and 2:1, respectively. These results showed that the FAME could be a more attractive alternative to conventional surfactants in ex situ washing of PAH-contaminated soils. PMID:20149410

  6. Aromatic D-amino acids act as chemoattractant factors for human leukocytes through a G protein-coupled receptor, GPR109B.

    PubMed

    Irukayama-Tomobe, Yoko; Tanaka, Hirokazu; Yokomizo, Takehiko; Hashidate-Yoshida, Tomomi; Yanagisawa, Masashi; Sakurai, Takeshi

    2009-03-10

    GPR109B (HM74) is a putative G protein-coupled receptor (GPCR) whose cognate ligands have yet to be characterized. GPR109B shows a high degree of sequence similarity to GPR109A, another GPCR that was identified as a high-affinity nicotinic acid (niacin) receptor. However, the affinity of nicotinic acid to GPR109B is very low. In this study, we found that certain aromatic D-amino acids, including D-phenylalanine, D-tryptophan, and the metabolite of the latter, D-kynurenine, decreased the activity of adenylate cyclase in cells transfected with GPR109B cDNA through activation of pertussis toxin (PTX)-sensitive G proteins. These D-amino acids also elicited a transient rise of intracellular Ca(2+) level in cells expressing GPR109B in a PTX-sensitive manner. In contrast, these D-amino acids did not show any effects on cells expressing GPR109A. We found that the GPR109B mRNA is abundantly expressed in human neutrophils. D-phenylalanine and D-tryptophan induced a transient increase of intracellular Ca(2+) level and a reduction of cAMP levels in human neutrophils. Furthermore, knockdown of GPR109B by RNA interference inhibited the D-amino acids-induced decrease of cellular cAMP levels in human neutrophils. These D-amino acids induced chemotactic activity of freshly prepared human neutrophils. We also found that D-phenylalanine and D-tryptophan induced chemotactic responses in Jurkat cells transfected with the GPR109B cDNA but not in mock-transfected Jurkat cells. These results suggest that these aromatic D-amino acids elicit a chemotactic response in human neutrophils via activation of GPR109B. PMID:19237584

  7. Studies on the Simultaneous Formation of Aroma-Active and Toxicologically Relevant Vinyl Aromatics from Free Phenolic Acids during Wheat Beer Brewing.

    PubMed

    Langos, Daniel; Granvogl, Michael

    2016-03-23

    During the brewing process of wheat beer, the desired aroma-active vinyl aromatics 2-methoxy-4-vinylphenol and 4-vinylphenol as well as the undesired and toxicologically relevant styrene are formed from their respective precursors, free ferulic acid, p-coumaric acid, and cinnamic acid, deriving from the malts. Analysis of eight commercial wheat beers revealed high concentrations of 2-methoxy-4-vinylphenol and 4-vinylphenol always in parallel with high concentrations of styrene or low concentrations of the odorants in parallel with low styrene concentrations, suggesting a similar pathway. To better understand the formation of these vinyl aromatics, each process step of wheat beer brewing and the use of different strains of Saccharomyces cerevisiae were evaluated. During wort boiling, only a moderate decarboxylation of free phenolic acids and formation of desired and undesired vinyl aromatics were monitored due to the thermal treatment. In contrast, this reaction mainly occurred enzymatically catalyzed during fermentation with S. cerevisiae strain W68 with normal Pof(+) activity (phenolic off-flavor) resulting in a wheat beer eliciting the typical aroma requested by consumers due to high concentrations of 2-methoxy-4-vinylphenol (1790 μg/L) and 4-vinylphenol (937 μg/L). Unfortunately, also a high concentration of undesired styrene (28.3 μg/L) was observed. Using a special S. cerevisiae strain without Pof(+) activity resulted in a significant styrene reduction (

  8. Syntheses, crystal structures, and properties of four complexes based on polycarboxylate and imidazole ligands

    SciTech Connect

    Qiao, Rui; Chen, Shui-Sheng; Sheng, Liang-Quan; Yang, Song; Li, Wei-Dong

    2015-08-15

    Four metal–organic coordination polymers [Zn(HL)(H{sub 2}O)]·4H{sub 2}O (1), [Zn(HL)(L{sub 1})]·4H{sub 2}O (2), [Cu(HL)(H{sub 2}O)]·3H{sub 2}O (3) and [Cu(HL)(L{sub 1})]·5H{sub 2}O (4) were synthesized by reactions of the corresponding metal(II) salts with semirigid polycarboxylate ligand (5-((4-carboxypiperidin-1-yl)methyl)isophthalic acid hydrochloride, H{sub 3}L·HCl) or auxiliary ligand (1,4-di(1H-imidazol-4-yl)benzene, L{sub 1}). The structures of the compounds were characterized by elemental analysis, FT-IR spectroscopy and single-crystal X-ray diffraction. The use of auxiliary ligand L{sub 1} has great influence on the structures of two pairs of complexes 1, 2 and 3, 4. Complex 1 is a uninodal 3-connected rare 2-fold interpenetrating ZnSc net with a Point (Schlafli) symbol of (10{sup 3}) while 2 is a one-dimensional (1D) ladder structure. Compound 3 features a two-dimensional (2D) honeycomb network with typical 6{sup 3}-hcb topology, while 4 is 2D network with (4, 4) sql topology based on binuclear Cu{sup II} subunits. The non-covalent bonding interactions such as hydrogen bonds, π···π stacking and C–H···π exist in complexes 1–4, which contributes to stabilize crystal structure and extend the low-dimensional entities into high-dimensional frameworks. And the photoluminescent property of 1 and 2 and gas sorption property of 4 have been investigated. - Graphical abstract: Four new coordination polymers have been obtained and their photoluminescent and gas sorption properties have also been investigated. - Highlights: • Two pairs of Zn{sup II}/ Cu{sup II} compounds have been synthesized. • Auxiliary ligand-controlled assembly of the complexes is reported. • The luminescent properties of complexes 1–2 were investigated. • The gas sorption property of 4 has been investigated.

  9. Solid-phase extraction using bis(indolyl)methane-modified silica reinforced with multiwalled carbon nanotubes for the simultaneous determination of flavonoids and aromatic organic acid preservatives.

    PubMed

    Wang, Na; Liao, Yuan; Wang, Jiamin; Tang, Sheng; Shao, Shijun

    2015-12-01

    A novel bis(indolyl)methane-modified silica reinforced with multiwalled carbon nanotubes sorbent for solid-phase extraction was designed and synthesized by chemical immobilization of nitro-substituted 3,3'-bis(indolyl)methane on silica modified with multiwalled carbon nanotubes. Coupled with high-performance liquid chromatography analysis, the extraction properties of the sorbent were evaluated for flavonoids and aromatic organic acid compounds. Under optimum conditions, the sorbent can simultaneously extract five flavonoids and two aromatic organic acid preservatives in aqueous solutions in a single-step solid-phase extraction procedure. Wide linear ranges were obtained with correlation coefficients (R(2) ) ranging from 0.9843 to 0.9976, and the limits of detection were in the range of 0.5-5 μg/L for the compounds tested. Compared with the silica modified with multiwalled carbon nanotubes sorbent and the nitro-substituted 3,3'-bis(indolyl)methane-modified silica sorbent, the developed sorbent exhibited higher extraction efficiency toward the selected analytes. The synergistic effect of nitro-substituted 3,3'-bis(indolyl)methane and multiwalled carbon nanotubes not only improved the surface-to-volume ratio but also enhanced multiple intermolecular interactions, such as hydrogen bonds, π-π, and hydrophobic interactions, between the new sorbent and the selected analytes. The as-established solid-phase extraction with high-performance liquid chromatography and diode array detection method was successfully applied to the simultaneous determination of flavonoids and aromatic organic acid preservatives in grape juices with recoveries ranging from 83.9 to 112% for all the selected analytes. PMID:26529362

  10. Enhanced formation of aromatic amino acids increases fragrance without affecting flower longevity or pigmentation in Petunia × hybrida.

    PubMed

    Oliva, Moran; Ovadia, Rinat; Perl, Avichai; Bar, Einat; Lewinsohn, Efraim; Galili, Gad; Oren-Shamir, Michal

    2015-01-01

    Purple Petunia × hybrida V26 plants accumulate fragrant benzenoid-phenylpropanoid molecules and anthocyanin pigments in their petals. These specialized metabolites are synthesized mainly from the aromatic amino acids phenylalanine. Here, we studied the profile of secondary metabolites of petunia plants, expressing a feedback-insensitive bacterial form of 3-deoxy-di-arabino-heptulosonate 7-phosphate synthase enzyme (AroG*) of the shikimate pathway, as a tool to stimulate the conversion of primary to secondary metabolism via the aromatic amino acids. We focused on specialized metabolites contributing to flower showy traits. The presence of AroG* protein led to increased aromatic amino acid levels in the leaves and high phenylalanine levels in the petals. In addition, the AroG* petals accumulated significantly higher levels of fragrant benzenoid-phenylpropanoid volatiles, without affecting the flowers' lifetime. In contrast, AroG* abundance had no effect on flavonoids and anthocyanins levels. The metabolic profile of all five AroG* lines was comparable, even though two lines produced the transgene in the leaves, but not in the petals. This implies that phenylalanine produced in leaves can be transported through the stem to the flowers and serve as a precursor for formation of fragrant metabolites. Dipping cut petunia stems in labelled phenylalanine solution resulted in production of labelled fragrant volatiles in the flowers. This study emphasizes further the potential of this metabolic engineering approach to stimulate the production of specialized metabolites and enhance the quality of various plant organs. Furthermore, transformation of vegetative tissues with AroG* is sufficient for induced production of specialized metabolites in organs such as the flowers. PMID:25283446