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1

Density functional theory study of the oligomerization of carboxylic acids.  

PubMed

We present a density functional theory [M06-2X/6-31+G(d,p)] study of the structures and free energies of formation of oligomers of four carboxylic acids (formic acid, acetic acid, tetrolic acid, and benzoic acid) in water, chloroform, and carbon tetrachloride. Solvation effects were treated using the SMD continuum solvation model. The low-lying energy structures of molecular complexes were located by adopting an efficient search procedure to probe the potential energy surfaces of the oligomers of carboxylic acids (CA)n (n = 2-6). The free energies of the isomers of (CA)n in solution were determined as the sum of the electronic energy, vibrational-rotational-translational gas-phase contribution, and solvation free energy. The assessment of the computational protocol adopted in this study with respect to the dimerization of acetic acid, (AA)2, and formic acid, (FA)2, located new isomers of (AA)2 and (FA)2 and gave dimerization constants in good agreement with the experimental values. The calculation of the self-association of acetic acid, tetrolic acid, and benzoic acid shows the following: (i) Classic carboxylic dimers are the most stable isomer of (CA)2 in both the gas phase and solution. (ii) Trimers of carboxylic acid are stable in apolar aprotic solvents. (iii) Molecular clusters consisting of two interacting classic carboxylic dimers (CA)4,(D+D) are the most stable type of tetramers, but their formation from the self-association of classic carboxylic dimers is highly unfavorable. (iv) For acetic acid and tetrolic acid the reactions (CA)2 + 2CA ? (CA)4,(D+D) and (CA)3 + CA ? (CA)4,(D+D) are exoergonic, but these aggregation pathways go through unstable clusters that could hinder the formation of tetrameric species. (v) For tetrolic acid the prenucleation species that are more likely to form in solution are dimeric and trimeric structures that have encoded structural motifs resembling the ? and ? solid forms of tetrolic acid. (vi) Stable tetramers of benzoic acid could form in carbon tetrachloride from the aggregation of trimers and monomers. (vii) Higher order clusters such as acetic acid pentamers and tetrolic acid hexamers are highly unstable in all solvation environments. PMID:25357019

Di Tommaso, Devis; Watson, Ken L

2014-11-20

2

5,6-dihydroxyindole-2-carboxylic acid (DHICA): a First Principles Density-Functional Study  

E-print Network

We report first principles density functional calculations for 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and several reduced forms. DHICA and 5,6-dihydroxyindole (DHI) are believed to be the basic building blocks of the eumelanins. Our results show that carboxylation has a significant effect on the physical properties of the molecules. In particular, the relative stabilities and the HOMO-LUMO gaps (calculated with the $\\Delta$SCF method) of the various redox forms are strongly affected. We predict that, in contrast to DHI, the density of unpaired electrons, and hence the ESR signal, in DHICA is negligibly small.

B. J. Powell

2004-08-24

3

Carboxylic acid sorption regeneration process  

DOEpatents

Carboxylic acids are sorbed from aqueous feedstocks into an organic liquid phase or onto a solid adsorbent. The acids are freed from the sorbent phase by treating it with aqueous alkylamine thus forming an alkylammonium carboxylate which is dewatered and decomposed to the desired carboxylic acid and the alkylamine.

King, C. Judson (Kensington, CA); Poole, Loree J. (Baton Rouge, LA)

1995-01-01

4

Carboxylic acid sorption regeneration process  

DOEpatents

Carboxylic acids are sorbed from aqueous feedstocks into an organic liquid phase or onto a solid adsorbent. The acids are freed from the sorbent phase by treating it with aqueous alkylamine thus forming an alkylammonium carboxylate which is dewatered and decomposed to the desired carboxylic acid and the alkylamine. 10 figs.

King, C.J.; Poole, L.J.

1995-05-02

5

Carboxyl-terminal disulfide bond of acid sphingomyelinase is critical for its secretion and enzymatic function.  

PubMed

The human acid sphingomyelinase (ASM, EC 3.1.4.12), a lysosomal and secretory protein coded by the sphingomyelin phosphodiesterase 1 (SMPD-1) gene, catalyzes the degradation of sphingomyelin (SM) to ceramide and phosphorylcholine. We examined the structural-functional properties of its carboxyl-terminus (amino acids 462-629), which harbors approximately 1/3 of all mutations discovered in the SMPD-1 gene. We created four naturally occurring mutants (DeltaR608, R496L, G577A, and Y537H) and five serial carboxyl-terminal deletion mutants (N620, N590, N570, N510, and N490). Transient transfection of the His/V5-tagged wild-type and mutant recombinant ASM in Chinese hamster ovary cells showed that all the mutants were normally expressed. Nonetheless, none of them, except the smallest deletion mutant N620 that preserved all post-translational modifications, were found capable of secretion to the medium. Furthermore, only the N620 conserved functional integrity (100% activity of the wild type); all other mutants completely lost the ability to catalyze SM hydrolysis. Importantly, cell surface biotinylation revealed that mutant DeltaR608 transfected CHO cells and fibroblasts from a compound heterozygous Niemann-Pick disease type B (NPD-B) patient (DeltaR608 and R441X) have defective translocation to the plasma membrane. Furthermore, we demonstrated that the DeltaR608 and N590 were trapped in the endoplasmic reticulum (ER) quality control checkpoint in contrast to the wild-type lysosomal localization. Interestingly, while the steady-state levels of ubiquitination were minimal for the wild-type ASM, a significant amount of Lys63-linked polyubiquitinated DeltaR608 and N590 could be purified by S5a-affinity chromatography, indicating an important misfolding in the carboxyl-terminal mutants. Altogether, we provide evidence that the carboxyl-terminus of the ASM is crucial for its protein structure, which in turns dictates the enzymatic function and secretion. PMID:18052040

Lee, Ching Yin; Tamura, Taku; Rabah, Nadia; Lee, Dong-Young Donna; Ruel, Isabelle; Hafiane, Anouar; Iatan, Iulia; Nyholt, Dana; Laporte, Frédéric; Lazure, Claude; Wada, Ikuo; Krimbou, Larbi; Genest, Jacques

2007-12-25

6

Solid phase extraction of petroleum carboxylic acids using a functionalized alumina as stationary phase.  

PubMed

Petroleum essentially consists of a mixture of organic compounds, mainly containing carbon and hydrogen, and, in minor quantities, compounds with nitrogen, sulphur, and oxygen. Some of these compounds, such as naphthenic acids, can cause corrosion in pipes and equipment used in processing plants. Considering that the methods of separation or clean up the target compounds in low concentrations and in complex matrix use large amounts of solvents or stationary phases, is necessary to study new methodologies that consume smaller amounts of solvent and stationary phases to identify the acid components present in complex matrix, such as crude oil samples. The proposed study aimed to recover acid compounds using the solid phase extraction method, employing different types of commercial stationary ion exchange phases (SAX and NH(2)) and new phase alumina functionalized with 1,4-bis(n-propyl)diazoniabicyclo[2.2.2]octane chloride silsesquioxane (Dab-Al(2)O(3)), synthesized in this work. Carboxylic acids were used as standard mixture in the solid phase extraction for further calculation of recovery yield. Then, the real sample (petroleum) was fractionated into saturates, aromatics, resins, and asphaltenes, and the resin fraction of petroleum (B1) was eluted through stationary ion exchange phases. The stationary phase synthesized in this work showed an efficiency of ion exchange comparable to that of the commercial stationary phases. PMID:22589166

de Conto, Juliana Faccin; Nascimento, Juciara dos Santos; de Souza, Driele Maiara Borges; da Costa, Luiz Pereira; Egues, Silvia Maria da Silva; Freitas, Lisiane Dos Santos; Benvenutti, Edilson Valmir

2012-04-01

7

Carboxylic Acid Unknowns and Titration 90 CARBOXYLIC ACID UNKNOWN  

E-print Network

Carboxylic Acid Unknowns and Titration 90 CARBOXYLIC ACID UNKNOWN A. Solubility Tests: Water, NaHCO3, and NaOH Test the solubility of your acid first in neutral water, in NaOH/H2O, and in NaHCO3 to 30 drops. Swirl/mix well. Use of small stir bar helps. · Water Test: Only acids with small numbers

Jasperse, Craig P.

8

Synthesis of novel functional polyolefin containing carboxylic acid via Friedel–Crafts acylation reaction  

Microsoft Academic Search

The strong polar group, carboxylic acid, has triumphantly been introduced into ethylene and allylbenzene copolymers without obvious degradation or crosslinking via Friedel–Crafts (F–C) acylation reaction with glutaric anhydride (GA), succinic anhydride (SA) and phthalic anhydride (PA) in the presence of anhydrous aluminum chloride in carbon disulfide. Some important reaction parameters were examined in order to optimize the acylation process. In

Yi Zheng; Yanguo Li; Li Pan; Yuesheng Li

2007-01-01

9

Synthesis, characterization, and bioactivity of carboxylic acid-functionalized titanium dioxide nanobelts  

PubMed Central

Background Surface modification strategies to reduce engineered nanomaterial (ENM) bioactivity have been used successfully in carbon nanotubes. This study examined the toxicity and inflammatory potential for two surface modifications (humic acid and carboxylation) on titanium nanobelts (TNB). Methods The in vitro exposure models include C57BL/6 alveolar macrophages (AM) and transformed human THP-1 cells exposed to TNB for 24 hrs in culture. Cell death and NLRP3 inflammasome activation (IL-1? release) were monitored. Short term (4 and 24 hr) in vivo studies in C57BL/6, BALB/c and IL-1R null mice evaluated inflammation and cytokine release, and cytokine release from ex vivo cultured AM. Results Both in vitro cell models suggest that the humic acid modification does not significantly affect TNB bioactivity, while carboxylation reduced both toxicity and NLRP3 inflammasome activation. In addition, short term in vivo exposures in both C57BL/6 and IL-1R null mouse strains demonstrated decreased markers of inflammation, supporting the in vitro finding that carboxylation is effective in reducing bioactivity. TNB instillations in IL-1R null mice demonstrated the critical role of IL-1? in initiation of TNB-induced lung inflammation. Neutrophils were completely absent in the lungs of IL-1R null mice instilled with TNB for 24 hrs. However, the cytokine content of the IL-1R null mice lung lavage samples indicated that other inflammatory agents, IL-6 and TNF-? were constitutively elevated indicating a potential compensatory inflammatory mechanism in the absence of IL-1 receptors. Conclusions Taken together, the data suggests that carboxylation, but not humic acid modification of TNB reduces, but does not totally eliminate bioactivity of TNB, which is consistent with previous studies of other long aspect ratio nanomaterials such as carbon nanotubes. PMID:25179214

2014-01-01

10

Detection of a CO and NH3 gas mixture using carboxylic acid-functionalized single-walled carbon nanotubes  

PubMed Central

Carbon nanotubes (CNT) are extremely sensitive to environmental gases. However, detection of mixture gas is still a challenge. Here, we report that 10 ppm of carbon monoxide (CO) and ammonia (NH3) can be electrically detected using a carboxylic acid-functionalized single-walled carbon nanotubes (C-SWCNT). CO and NH3 gases were mixed carefully with the same concentrations of 10 ppm. Our sensor showed faster response to the CO gas than the NH3 gas. The sensing properties and effect of carboxylic acid group were demonstrated, and C-SWCNT sensors with good repeatability and fast responses over a range of concentrations may be used as a simple and effective detection method of CO and NH3 mixture gas. PMID:23286690

2013-01-01

11

Cyclopentane-1,3-dione: A Novel Isostere for the Carboxylic Acid Functional Group. Application to the Design of Potent Thromboxane (A2)-Receptor Antagonists  

PubMed Central

Cyclopentane-1,3-diones are known to exhibit pKa values typically in the range of carboxylic acids. To explore the potential of the cyclopentane-1,3-dione unit as a carboxylic acid isostere, the physical-chemical properties of representative congeners were examined and compared with similar derivatives bearing carboxylic acid or tetrazole residues. These studies suggested that cyclopentane-1,3-diones may effectively substitute for the carboxylic acid functional group. To demonstrate the use of the cyclopentane-1,3-dione isostere in drug-design, derivatives of a known thromboxane-A2 prostanoid (TP) receptor antagonist, 3-(3-(2-(4-chlorophenylsulfonamido)ethyl)-phenyl)propanoic acid (12), were synthesized and evaluated in both functional and radioligand-binding assays. A series of mono- and di-substituted cyclopentane-1,3-dione derivatives (41–45) were identified that exhibit nM IC50 and Kd values similar to 12. Collectively, these studies demonstrate that the cyclopentane-1,3-dione moiety comprises a novel isostere of the carboxylic acid functional group. Given the combination of the relatively strong acidity, tunable lipophilicity, and versatility of the structure, the cyclopentane-1,3-dione moiety may constitute a valuable addition to the palette of carboxylic acid isosteres. PMID:21863799

Ballatore, Carlo; Soper, James; Piscitelli, Francesco; James, Michael; Huang, Longchuan; Atasoylu, Onur; Huryn, Donna M.; Trojanowski, John Q.; Lee, Virginia M.-Y.; Brunden, Kurt R.; Smith, Amos B.

2011-01-01

12

Molecular Structure of Cyclopropane carboxylic acid  

NSDL National Science Digital Library

Cyclopropane carboxylic acid is a clear liquid used as an intermediate for agrochemicals, pharmaceuticals, and other organic synthesis such as for the applications of electronics, chemicals, polymer additives, coatings, adhesives, surfactants, and other applications. Also, derivatives of cyclopropane-carboxylic acid are used against parasites in plants and animals. For example, the alkynyl esters of cyclopropane-carboxylic acid are used as pesticides. Similarly, cyclopropane carboxylic acid esters containing a polyhalogenated substituent are used as fungicides.

2003-04-11

13

Peptide Coupling between Amino Acids and the Carboxylic Acid of a Functionalized Chlorido-gold(I)-phosphane.  

PubMed

We have developed a protocol for the direct coupling between methyl ester protected amino acids and the chlorido-gold(I)-phosphane (p-HOOC(C6H4)PPh2)AuCl. By applying the EDC·HCl/NHS strategy (EDC·HCl = N-ethyl-N'-(3-(dimethylamino)propyl)carbodiimide hydrochloride, NHS = N-hydroxysuccinimide), the methyl esters of l-phenylalanine, glycine, l-leucine, l-alanine, and l-methionine are coupled with the carboxylic acid of the gold complex in moderate to good yields (62-88%). All amino acid tagged gold complexes were characterized by (1)H and (13)C NMR spectroscopy and high-resolution mass spectrometry. As corroborated by measurement of the angle of optical rotation, no racemization occurred during the reaction. The molecular structure of the leucine derivative was determined by single-crystal X-ray diffraction. In the course of developing an efficient coupling protocol, the acyl chlorides (p-Cl(O)C(C6H4)PPh2)AuX (X = Cl, Br) were also prepared and characterized. PMID:25203269

Kriechbaum, Margit; List, Manuela; Himmelsbach, Markus; Redhammer, Günther J; Monkowius, Uwe

2014-10-01

14

Structural Synergism in Functionalized Polymers: New Catalysts for Transacylation Reactions of Derivatives of Carboxylic and Phosphoric Acids.  

National Technical Information Service (NTIS)

This project has focused on the development of new highly-efficient, selective catalysts for widely-used commercial and biological reactions of carboxylic and phosphoric acids and their derivatives. The first phase of the project included the design and s...

M. Zeldin, W. K. Fife

1991-01-01

15

Recovery of carboxylic acids produced by fermentation.  

PubMed

Carboxylic acids such as citric, lactic, succinic and itaconic acids are useful products and are obtained on large scale by fermentation. This review describes the options for recovering these and other fermentative carboxylic acids. After cell removal, often a primary recovery step is performed, using liquid-liquid extraction, adsorption, precipitation or conventional electrodialysis. If the carboxylate is formed rather than the carboxylic acid, the recovery process involves a step for removing the cation of the formed carboxylate. Then, bipolar electrodialysis and thermal methods for salt splitting can prevent that waste inorganic salts are co-produced. Final carboxylic acid purification requires either distillation or crystallization, usually involving evaporation of water. Process steps can often be combined synergistically. In-situ removal of carboxylic acid by extraction during fermentation is the most popular approach. Recovery of the extractant can easily lead to waste inorganic salt formation, which counteracts the advantage of the in-situ removal. For industrial production, various recovery principles and configurations are used, because the fermentation conditions and physical properties of specific carboxylic acids differ. PMID:24751382

López-Garzón, Camilo S; Straathof, Adrie J J

2014-01-01

16

Activation of carboxylic acids in asymmetric organocatalysis.  

PubMed

Organocatalysis, catalysis using small organic molecules, has recently evolved into a general approach for asymmetric synthesis, complementing both metal catalysis and biocatalysis. Its success relies to a large extent upon the introduction of novel and generic activation modes. Remarkably though, while carboxylic acids have been used as catalyst directing groups in supramolecular transition-metal catalysis, a general and well-defined activation mode for this useful and abundant substance class is still lacking. Herein we propose the heterodimeric association of carboxylic acids with chiral phosphoric acid catalysts as a new activation principle for organocatalysis. This self-assembly increases both the acidity of the phosphoric acid catalyst and the reactivity of the carboxylic acid. To illustrate this principle, we apply our concept in a general and highly enantioselective catalytic aziridine-opening reaction with carboxylic acids as nucleophiles. PMID:24888674

Monaco, Mattia Riccardo; Poladura, Belén; Diaz de Los Bernardos, Miriam; Leutzsch, Markus; Goddard, Richard; List, Benjamin

2014-07-01

17

Modeling the hydrolysis of perfluorinated compounds containing carboxylic and phosphoric acid ester functions and sulfonamide groups  

Microsoft Academic Search

Temperature-dependent rate constants were estimated for the acid- and base-catalyzed and neutral hydrolysis reactions of perfluorinated telomer acrylates (FTAcrs) and phosphate esters (FTPEs), and the SN1 and SN2 hydrolysis reactions of fluorotelomer iodides (FTIs). Under some environmental conditions, hydrolysis of monomeric FTAcrs could be rapid (half-lives of several years in marine systems and as low as several days in some

Sierra Rayne; Kaya Forest

2010-01-01

18

Carboxylic acid accelerated formation of diesters  

DOEpatents

This invention pertains to accelerating the rate of formation of 1,1-dicarboxylic esters from the reaction of an aldehyde with a carboxylic acid anhydride or a ketene in the presence of a non-iodide containing a strong Bronsted acid catalyst by the addition of a carboxylic acid at about one bar pressure and between about 0.degree. and 80.degree. C. in the substantial absence of a hydrogenation or carbonylation catalyst.

Tustin, Gerald Charles (Kingsport, TN); Dickson, Todd Jay (Kingsport, TN)

1998-01-01

19

Adsorption of a carboxylic acid-functionalized aminoxyl radical onto SiO?.  

PubMed

Silicon wafers both without and with silicon(IV) oxide surface coverage were covered with benzene solutions of stable organic radical 3-(N-tert-butyl-N-aminoxyl)benzoic acid (mNBA). X-ray photoelectron spectroscopy supported the presence of the radical on both surface-cleaned (oxide-reduced) and oxide-covered surfaces. Optical waveguide spectroscopy showed that the radical retained its structure while adsorbed to the surface of the wafers, without noticeable decomposition. AFM and MFM imaging showed that the radical formed blocky particles with a change in rms roughness from 0.3 nm premodification to 1.7 nm postmodification on the surface-cleaned silicon. Similar experiments using oxide-coated silicon showed that the radical adsorbed to form much smoother layers, with a small change in rms roughness from 0.2 to 0.3 nm. Contact angle measurements of water on the premodified and postmodified samples showed a large, hydrophobic change in the silicon oxide surface but only a modest change in the surface-cleaned silicon surface. Samples of mNBA adsorbed onto silica gel showed strong electron-spin resonance signals from the aminoxyl spin, even years after production. The results demonstrate the prospects for treating and coating oxide-covered silicon wafers and silicon oxide-coated particles with a paramagnetically active organic substrate, without major chemical modification of the pretreatment surface; the resulting organic spin sites can be stable for years. PMID:24684264

Murata, Hidenori; Baskett, Martha; Nishide, Hiroyuki; Lahti, Paul M

2014-04-15

20

Extraction of carboxylic acids by amine extractants  

Microsoft Academic Search

This work examines the chemistry of solvent extraction by long-chain amines for recovery of carboxylic acids from dilute aqueous solution. Long-chain amines act as complexing agents with the acid, which facilitates distribution of the acid into the organic phase. The complexation is reversible, allowing for recovery of the acid from the organic phase and regeneration of the extractant. Batch extraction

Janet Ayako Tamada; C. J. King

1989-01-01

21

Nitric Acid Dehydration Using Perfluoro Carboxylate and Mixed Sulfonate/Carboxylate Membranes  

SciTech Connect

Perfluoro ionomer membranes are tetrafluoro ethylene-based materials with microheterogeneous structures consisting of a hydrophobic polymer backbone and a hydrophilic side-chain cluster region. Due to the ionomer cluster morphology, these films exhibit unique transport properties. Recent investigations with perfluoro sulfonate and perfluoro sulfonate/carboxylate composite polymers have demonstrated their value in the dehydration of nitric acid and they show potential as an alternative to conventional, energy intensive unit operations in the concentration of acid feeds. As a result, investigations were conducted to determine the feasibility of using pure perfluoro carboxylate and mixed perfluoro sulfonate/carboxylate films for the dehydration of nitric acid because of the speculation of improved water selectivity of the carboxylate pendant chain. During the first phase of these investigations the effort was focused on generating a thin, solution cast perfluoro carboxylate ionomer film, to evaluate the general, chemical and physical characteristics of the polymer, and to assess the material's aqueous transport performance (flux and nitrate separation efficiencies) in pervaporation and high-pressure environments. Results demonstrated that generating robust solution-cast films was difficult yet a number of membranes survived high trans-membrane pressures up to 700 psig. General characterization of the solution cast product showed reduced ion exchange capacities when compared with thicker, ''as received'' perfluoro carboxylate and similar sulfonate films. Small angle x-ray scattering analysis results suggested that the solution cast carboxylate films contained a small fraction of sulfonate terminated side-chains. Aqueous transport experimentation showed that permeate fluxes for both pure water and nitric acid were approximately two orders of magnitude smaller for the carboxylate solution cast membranes when compared to their sulfonate counterparts of similar thickness (Nafion{trademark} 111). Additionally, nitric acid separation efficiencies ({alpha}) were approximately one order of magnitude higher for the carboxylate solution cast films when compared to Nafion{trademark} 111. The second phase of our work included the generation of thin carboxylate films made by the chemical synthesis perfluoro sulfonate and mixed sulfonate/carboxylate polymers from a perfluoro sulfonyl fluoride precursor, the characterization of the newly generated material, and a study of the transport characteristics of these membranes. Transport studies consisted of the dehydration of nitric acid feeds by pervaporation. In addition, the initial hypothesis was expanded to include demonstration that transmembrane flux and separation efficiencies are a function of the ratio between sulfonate and carboxylate terminated side chains of the perfluoro ionomer. Investigations demonstrated the ability to generate in- house films with varying sulfonate/carboxylate concentrations from commercially available perfluoro sulfonyl fluoride material, and showed that the converted films could be characterized using Fourier transform infrared (FTIR) and x-ray fluorescence (XRF) spectroscopy. Finally, the mixed films where subjected to nitric acid dehydration transport tests and a relationship was found to exist between sulfonate/carboxylate pendant chain ratio and both flux and water separation capability. In summary, experimental results confirmed that, when compared to Nafion 111{trademark}, the mixed film's bulk fluxes decrease by approximately three orders of magnitude and the water separation factor increases by as much as two orders of magnitude as the carboxylate side-chain content was increased from 0 (pure sulfonate film) to 53 mole%, supporting the hypothesis given for this effort. It was observed that the water selectivity improved for both the solution cast perfluoro carboxylate and mixed perfluoro sulfonate/carboxylate films when judged against similar perfluoro sulfonate materials. Of great benefit was that during the investigation a number of research tools w

R.L. Ames

2004-09-01

22

Molecular level computational studies of polyethylene and polyacrylonitrile composites containing single walled carbon nanotubes: effect of carboxylic acid functionalization on nanotube-polymer interfacial properties  

PubMed Central

Molecular dynamics (MD) and molecular mechanics (MM) methods have been used to investigate additive-polymer interfacial properties in single walled carbon nanotube (SWNT)—polyethylene and SWNT—polyacrylonitrile composites. Properties such as the interfacial shear stress and bonding energy are similar for the two composites. In contrast, functionalizing the SWNT with carboxylic acid groups leads to an increase in these properties, with a larger increase for the polar polyacrylonitrile composite. Increasing the percentage of carbon atoms that were functionalized from 1 to 5% also leads to an increase in the interfacial properties. In addition, the interfacial properties depend on the location of the functional groups on the SWNT wall.

Haghighatpanah, Shayesteh; Bohlen, Martin; Bolton, Kim

2014-01-01

23

Direct conversion of carboxylate salts to carboxylic acids via reactive extraction  

E-print Network

-molecular-weight tertiary amine and carbon dioxide to precipitate calcium carbonate. In a distillation column, the Biomass Acid Springing Route 2 Mixed Carboxylic Acids Pretreatment Fermentation Dewater Reactive Extraction Carboxylate Salts Solution Thermal... makes it possible to extract carboxylic acids from the aqueous phase into high-molecular-weight tertiary amine (tri- n-octylamine). Through the physical solubility of the solute in the extractant phase, the carboxylic acids form acid-amine complexes...

Xu, Xin

2008-10-10

24

Vibrational coupling in carboxylic acid dimers  

NASA Astrophysics Data System (ADS)

The vibrational level splitting in the ground electronic state of carboxylic acid dimers mediated by the doubly hydrogen-bonded networks are investigated using pure and mixed dimers of benzoic acid with formic acid as molecular prototypes. Within the 0-2000-cm-1 range, the frequencies for the fundamental and combination vibrations of the two dimers are experimentally measured by using dispersed fluorescence spectroscopy in a supersonic jet expansion. Density-functional-theory calculations predict that most of the dimer vibrations are essentially in-phase and out-of-phase combinations of the monomer modes, and many of such combinations show significantly large splitting in vibrational frequencies. The infrared spectrum of the jet-cooled benzoic acid dimer, reported recently by Bakker et al. [J. Chem. Phys. 119, 11180 (2003)], has been used along with the dispersed fluorescence spectra to analyze the coupled g-u vibrational levels. Assignments of the dispersed fluorescence spectra of the mixed dimer are suggested by comparing the vibronic features with those in the homodimer spectrum and the predictions of density-functional-theory calculation. The fluorescence spectra measured by excitations of the low-lying single vibronic levels of the mixed dimer reveal that the hydrogen-bond vibrations are extensively mixed with the ring modes in the S1 surface.

Nandi, Chayan K.; Hazra, Montu K.; Chakraborty, Tapas

2005-09-01

25

Unique phenolic carboxylic acids from Sanguisorba minor.  

PubMed

The unique phenolic carboxylic acids, 4,8-dimethoxy-7-hydroxy-2-oxo-2H-1-benzopyran-5,6-dicarboxylic acid and 2-(4-carboxy-3-methoxystyryl)-2-methoxysuccinic acid were isolated and identified from the whole Sanguisorba minor plant. The known phenolics, gallic acid; ellagic acid; quercetin-3-O-(6"-galloylglucose); beta-glucogallin; 2,3-hexahydroxydiphenoyl-(alpha/beta)-glucose; 1-galloyl-2,3-hexahydroxydiphenoyl-alpha-glucose together with its beta-isomer were also characterized. Structures were established by conventional methods of analysis and confirmed by NMR and ESI-MS spectral analysis. PMID:12770593

Ayoub, Nahla A

2003-06-01

26

Photoinduced biochemical activity of fullerene carboxylic acid  

Microsoft Academic Search

Here we report the preparation of a water-miscible fullerene carboxylic acid (2) and its biological activity-cytotoxicity and G-selective DNA cleaving ability. What is truly remarkable is that the biological activity of Cââ was observed only under irradiation with visible light and not in the dark, suggesting that fullerenes may serve as useful photosensitive biochemical probes. We have found, for the

Hidetoshi Tokuyama; Shigeru Yamago; Eiichi Nakamura; Takashi Shiraki; Yukio Sugiura

1993-01-01

27

Probing pH-dependent functional elements in proteins: modification of carboxylic acid pairs in Trichoderma reesei cellobiohydrolase Cel6A.  

PubMed

Two carboxylic acid side chains can, depending on their geometry and environment, share a proton in a hydrogen bond and form a carboxyl-carboxylate pair. In the Trichoderma reesei cellobiohydrolase Cel6A structure, five carboxyl-carboxylate pairs are observed. One of these pairs (D175-D221) is involved in catalysis, and three other pairs are found in, or close to the two surface loops covering the active site tunnel of the catalytic domain. To stabilize Cel6A at alkaline pH values, where deprotonation of the carboxylic acids leads to repulsion of their side chains, we designed two mutant enzymes. In the first mutant, one carboxyl-carboxylate pair (E107-E399) was replaced by a corresponding amide-carboxylate pair (Q107-E399), and in the second mutant, all three carboxyl-carboxylate pairs (E107-E399, D170-E184, and D366-D419) were mutated in a similar manner. The unfolding studies using both intrinsic tryptophan fluorescence and far-ultraviolet circular dichroism spectroscopy at different pH values demonstrate that the unfolding temperature (T(m)) of both mutants has changed, resulting in destabilization of the mutant enzymes at acidic pH and stabilization at alkaline pH. The effect of stabilization seems additive, as a Cel6A triple mutant is the most stable enzyme variant. This increased stability is also reflected in the 2- or 4-fold increased half-life of the two mutants at alkaline pH, while the catalytic rate on cellotetraose (at t = 0) has not changed. Increased operational stability at alkaline pH was also observed on insoluble cellulosic substrates. Local conformational changes are suggested to take place in the active site loops of Cel6A wild-type enzyme at elevated pHs (pH 7), affecting to the end-product spectrum on insoluble cellulose. The triple mutant does not show such pH-dependent behavior. Overall, our results demonstrate that carboxyl-carboxylate pair engineering is a useful tool to alter pH-dependent protein behavior. PMID:12939137

Wohlfahrt, Gerd; Pellikka, Tarmo; Boer, Harry; Teeri, Tuula T; Koivula, Anu

2003-09-01

28

Pd/light-accelerated atom-transfer carbonylation of alkyl iodides: applications in multicomponent coupling processes leading to functionalized carboxylic acid derivatives.  

PubMed

The atom-transfer carbonylation reaction of various alkyl iodides thereby leading to carboxylic acid esters was effectively accelerated by the addition of transition-metal catalysts under photoirradiation conditions. By using a combined Pd/h? reaction system, vicinal C-functionalization of alkenes was attained in which ?-substituted iodoalkanes, alkenes, carbon monoxide, and alcohols were coupled to give functionalized esters. When alkenyl alcohols were used as acceptor alkenes, three-component coupling reactions, which were accompanied by intramolecular esterification, proceeded to give lactones. Pd-dimer complex [Pd(2)(CNMe)(6)][PF(6)](2), which is known to undergo homolysis under photoirradiation conditions, worked quite well as a catalyst in these three- or four-component coupling reactions. In this metal/radical hybrid system, both Pd radicals and acyl radicals are key players and a stereochemical study confirmed the carbonylation step proceeded through a radical carbonylation mechanism. PMID:22733719

Fusano, Akira; Sumino, Shuhei; Nishitani, Satoshi; Inouye, Takaya; Morimoto, Keisuke; Fukuyama, Takahide; Ryu, Ilhyong

2012-07-23

29

4-methylene-2-octyl-5-oxotetrahydrofuran-3-carboxylic acid (C75), an inhibitor of fatty-acid synthase, suppresses the mitochondrial fatty acid synthesis pathway and impairs mitochondrial function.  

PubMed

4-Methylene-2-octyl-5-oxotetrahydrofuran-3-carboxylic acid (C75) is a synthetic fatty-acid synthase (FASN) inhibitor with potential therapeutic effects in several cancer models. Human mitochondrial ?-ketoacyl-acyl carrier protein synthase (HsmtKAS) is a key enzyme in the newly discovered mitochondrial fatty acid synthesis pathway that can produce the substrate for lipoic acid (LA) synthesis. HsmtKAS shares conserved catalytic domains with FASN, which are responsible for binding to C75. In our study, we explored the possible effect of C75 on HsmtKAS and mitochondrial function. C75 treatment decreased LA content, impaired mitochondrial function, increased reactive oxygen species content, and reduced cell viability. HsmtKAS but not FASN knockdown had an effect that was similar to C75 treatment. In addition, an LA supplement efficiently inhibited C75-induced mitochondrial dysfunction and oxidative stress. Overexpression of HsmtKAS showed cellular protection against low dose C75 addition, whereas there was no protective effect upon high dose C75 addition. In summary, the mitochondrial fatty acid synthesis pathway has a vital role in mitochondrial function. Besides FASN, C75 might also inhibit HsmtKAS, thereby reducing LA production, impairing mitochondrial function, and potentially having toxic effects. LA supplements sufficiently ameliorated the toxicity of C75, showing that a combination of C75 and LA may be a reliable cancer treatment. PMID:24784139

Chen, Cong; Han, Xiao; Zou, Xuan; Li, Yuan; Yang, Liang; Cao, Ke; Xu, Jie; Long, Jiangang; Liu, Jiankang; Feng, Zhihui

2014-06-13

30

Electrosynthesis and comparative studies on carboxyl-functionalized polythiophene derivatives  

Microsoft Academic Search

Electrochemical synthesis of a novel carboxylic acid functionalized polythiophene – poly(3-thiophene-butyric-acid), PTBA – has been realized. Its morphology, electrochemical, spectral and conducting properties have been compared to those of poly(3-thiophene-acetic-acid), PTAA, which is widely used to immobilise both bioactive molecules and inorganic nanoparticles. According to scanning electron microscopic (SEM) images, the difference in the real and geometric surface area of

Péter S. Tóth; Csaba Janáky; Zoltán Hiezl; Csaba Visy

2011-01-01

31

Carboxylic Acid Esters as Substrates of Cholinesterases  

NASA Astrophysics Data System (ADS)

Data on the kinetics of the hydrolysis of various carboxylic acid esters by two main types of cholinesterases — acetylcholinesterase from human erythrocytes and butyrylcholinesterase from horse blood serum — are surveyed. It is shown that the rate of enzyme hydrolysis depends significantly on the structure of the acyl part of the ester molecule, the nature of the ester heteroatom, the structure of the alcohol component, and particularly the structure of the onium group. Esters based on natural products are of special interest as specific substrates of these enzymes. The role of the productive and non-productive sorption of the substrates in enzyme catalysis is demonstrated. The bibliography includes 81 references.

Brestkin, A. P.; Rozengart, E. V.; Abduvakhabov, A. A.; Sadykov, A. A.

1983-10-01

32

Hypervalent Iodine Iodinative Decarboxylation Of Cubyl And Homocubyl Carboxylic Acids  

NASA Astrophysics Data System (ADS)

The hypervalent iodine oxidative decarboxylation of homocubyl and cubyl mono- and di-carboxylic acids is reported; the carboxylic acid is treated with PhI(OAc)2CC14-I2 under irradiation conditions and 80-90% of the derived iodo compound is obtained. Systematic functionalization of cubane is an important synthetic goal. The two main methods of cubane synthesis involve sequential Favorskii ring contractions to yield first a homocubyl carboxylic acid, and theh after a second Favorskii reaction, a 1,41,2 or 1,33 cubyl dicarboxylic acid. As a consequence of this synthetic procedure the carboxy group is a logical starting functionality for subsequent synthetic transformation in the cubyl ring system. The carboxy group has been converted ,into a nitro group in the synthesis of 1,4-dinitrocubane4 and halogenodecarboxylation has been effected.596 In a basically different approach Eaton et al., used ortho-lithiation of the der td carboxamide etc a site for ortho-iodination.7 Introduction of an iodo group onto the cubyl system is especially desirable because hypervalent iodine synthetic methodology may be employed in order to effect displacement reactions. This scheme has been successfully applied by Eaton et al.8 in tim cubyl system for R-IC12+ R-C1 R-I(OAC)2+ R-OAc where R=1- iodo-2-N,N-di-isopropylcarbox-amido-5-methylcubane.

Moriarty, Robert M.; Khosrowshahi, Jaffar S.; Dalecki, Tomasz

1988-05-01

33

Extraction of carboxylic acids by amine extractants  

SciTech Connect

This work examines the chemistry of solvent extraction by long-chain amines for recovery of carboxylic acids from dilute aqueous solution. Long-chain amines act as complexing agents with the acid, which facilitates distribution of the acid into the organic phase. The complexation is reversible, allowing for recovery of the acid from the organic phase and regeneration of the extractant. Batch extraction experiments were performed to study the complexation of acetic, lactic, succinic, malonic, fumaric, and maleic acids with Alamine 336, an aliphatic, tertiary amine extractant, dissolved in various diluents. Results were interpreted by a ''chemical'' model, in which stoichiometric ratios of acid and amine molecules are assumed to form complexes in the solvent phase. From fitting of the extraction data, the stoichiometry of complexes formed and the corresponding equilibrium constants were obtained. The results of the model were combined with infrared spectroscopic experiments and results of past studies to analyze the chemical interactions that are responsible for extraction behavior. The information from the equilibrium studies was used to develop guidelines for large-scale staged extraction and regeneration schemes. A novel scheme, in which the diluent composition is shifted between extraction and regeneration, was developed which could achieve both high solute recovery and high product concentration. 169 refs., 57 figs., 15 tabs.

Tamada, Janet Ayako; King, C.J.

1989-01-01

34

Photoinduced biochemical activity of fullerene carboxylic acid  

SciTech Connect

Here we report the preparation of a water-miscible fullerene carboxylic acid (2) and its biological activity-cytotoxicity and G-selective DNA cleaving ability. What is truly remarkable is that the biological activity of C{sub 60} was observed only under irradiation with visible light and not in the dark, suggesting that fullerenes may serve as useful photosensitive biochemical probes. We have found, for the first time, that even low-energy visible light is surfficient to induce biological activity in fullerene derivatives. Among the numerous implications of the present findings, the most exciting prospect includes the use of fullerene derivatives for photodynamic therapy. 18 refs., 2 figs., 1 tab.

Tokuyama, Hidetoshi; Yamago, Shigeru; Nakamura, Eiichi [Tokyo Inst. of Technology (Japan); Shiraki, Takashi; Sugiura, Yukio [Kyoto Univ. (Japan)

1993-08-25

35

Characterization and diagenesis of strong-acid carboxyl groups in humic substances  

USGS Publications Warehouse

A small fraction of carboxylic acid functional groups in humic substances are exceptionally acidic with pKa values as low as 0.5. A review of acid-group theory eliminated most models and explanations for these exceptionally acidic carboxyl groups. These acidic carboxyl groups in Suwannee River fulvic acid were enriched by a 2-stage fractionation process and the fractions were characterized by elemental, molecular-weight, and titrimetric analyses, and by infrared and 13C- and 1H-nuclear magnetic resonance spectrometry. An average structural model of the most acidic fraction derived from the characterization data indicated a high density of carboxyl groups clustered on oxygen-heterocycle alicyclic rings. Intramolecular H-bonding between adjacent carboxyl groups in these ring structures enhanced stabilization of the carboxylate anion which results in low pKa1 values. The standard, tetrahydrofuran tetracarboxylic acid, was shown to have similar acidity characteristics to the highly acidic fulvic acid fraction. The end products of 3 known diagenetic pathways for the formation of humic substances were shown to result in carboxyl groups clustered on oxygen-heterocycle alicyclic rings.

Leenheer, J. A.; Wershaw, R. L.; Brown, G. K.; Reddy, M. M.

2003-01-01

36

MICROBIAL TRANSFORMATION OF ESTERS OF CHLORINATED CARBOXYLIC ACIDS  

EPA Science Inventory

Two groups of compounds were selected for microbial transformation studies. In the first group were carboxylic acid esters having a fixed aromatic moiety and an increasing length of the alkyl component. Ethyl esters of chlorine-substituted carboxylic acids were in the second grou...

37

Preparation of .alpha.,.beta.-unsaturated carboxylic acids and esters  

DOEpatents

Disclosed is a process for the preparation of .alpha.,.beta.-unsaturated carboxylic acids and esters thereof which comprises contacting formaldehyde or a source of formaldehyde with a carboxylic acid, ester or anhydride in the presence of a catalyst comprising an oxide of niobium.

Gogate, Makarand Ratnakar (Durham, NC); Spivey, James Jerry (Cary, NC); Zoeller, Joseph Robert (Kingsport, TN)

1998-01-01

38

Short-Chain Carboxylic-Acid-Stimulated, PMN-Mediated Gingival Inflammation  

Microsoft Academic Search

This communication reviews the effects of short-chain carboxylic acids on human cells of importance to the periodontium. The central hypothesis is that these acids can alter both cell function and gene expression, and thus contribute to the initiation and prolongation of gingival inflammation.Short-chain carboxylic acids [CH3-(CH2)x-COOH, x < 3] are metabolic intermediates with a broad range of apparently paradoxical biological

Richard Niederman; Jie Zhang; Shelby Kashket

1997-01-01

39

Phytotoxicity of low-weight carboxylic acids.  

PubMed

Presence of low-weight carboxylic acids (LWCAs) can be the reason for phytotoxicity of green manures, treated bio-waste or digestates from biogas production applied to soils. As the phytotoxic concentrations of LWCA are poorly known, this work presents data on six acids (C(1)C(6): formic, acetic, propionic, butyric, valeric, and caproic). Phytotoxicity was measured in acute (72 or 120 h) and subchronic (21 d) assays for seed germination, seedling elongation, and plant growth for garden cress Lepidium sativum and ryegrass Lolium multiflorum. The dose-response relationship was modeled using Weibull model. Results showed a trend that toxicity of LWCA increases with the length of the carbon chain, formic acid (C(1)) being the least and caproic acid (C(6)) the most toxic. EC50 values in the acute seed germination of cress ranged between 1.9 and 4.2mM and for ryegrass between 1.8 and 6.4mM. In subchronic assays EC50 values for germination were in a range from 11 to 46mMkg(-1)dm for cress, and from 18 to 127 mM kg(-1) dm for ryegrass. EC50 values for early seedling growth of cress based on acute assays ranged from 0.7 to 2.3mM and that of ryegrass from 1.2 to 1.8mM. Range of EC50 values for shoot biomass of cress was between 8 and 40 mM kg(-1) dm and of ryegrass between 12 and 93 mM kg(-1) dm. PMID:22440635

Himanen, Marina; Prochazka, Petr; Hänninen, Kari; Oikari, Aimo

2012-07-01

40

Calixarene based chiral solvating agents for ?-hydroxy carboxylic acids  

NASA Astrophysics Data System (ADS)

Novel chiral calix[4]arene derivatives functionalized at the lower rim have been prepared from the reaction of p-tert-butylcalix[4]arene diamine derivative with N-Phthaloyl-L-phenylalanine or (2S)-2-((benzyloxy)carbonyl)amino)-3-hydroxypropanoic acid or (2S,3R)-2-((benzyloxy)carbonyl)amino-3-hydroxybutanoic acid in 63-81% yield. The structures of these receptors were characterized by FTIR, 1H, 13C and 2D COSY NMR spectroscopy. The enantioselective recognition of these receptors towards the enantiomers of racemic carboxylic acids was studied by 1H NMR spectroscopy. The molar ratios of the chiral compounds with each of the enantiomers of guests were determined by using Job plots. The Job plots indicate that the hosts form 1:2 instantaneous complexes with all guests. The receptors exhibited different chiral recognition abilities toward the enantiomers of racemic guests. NMR studies demonstrated that the receptors function as highly effective chiral shift reagents for determining the enantiomeric purity of a series of carboxylic acids.

Bozkurt, Selahattin

2013-09-01

41

High-throughput aided synthesis of the porous metal-organic framework-type aluminum pyromellitate, MIL-121, with extra carboxylic acid functionalization.  

PubMed

A new porous metal-organic framework (MOF)-type aluminum pyromellitate (MIL-121 or Al(OH)[H(2)btec]·(guest), (guest = H(2)O, H(4)btec = pyromellitic acid) has been isolated by using a high-throughput synthesis method under hydrothermal conditions. Its structure was determined from powder X-ray diffraction analysis using synchrotron radiation (Soleil, France) and exhibits a network closely related to that of the MIL-53 series. It is a three-dimensional (3D) framework containing one-dimensional (1D) channels delimited by infinite trans-connected aluminum-centered octahedra AlO(4)(OH)(2) linked through the pyromellitate ligand. Here the organic ligand acts as tetradendate linker via two of the carboxylate groups. The two others remain non-bonded in their protonated form, and this constitutes a rare case of the occurrence of both bonding and non-bonding organic functionalities of the MOF family. The non-coordinated -COOH groups points toward the channels to get them an open form configuration. Within the tunnels are located unreacted pyromellitic acid and water species, which are evacuated upon heating, and a porous MIL-121 phase is obtained with a Brunauer-Emmett-Teller (BET) surface area of 162 m(2) g(-1). MIL-121 has been characterized by IR, thermogravimetry (TG) analyses, and solid state NMR spectroscopy employing a couple of two-dimensional (2D) techniques such as (1)H-(1)H SQ-DQ BABA, (1)H-(1)H SQ-SQ RFDR, (27)Al{(1)H} CPHETCOR and (27)Al MQMAS. PMID:20923169

Volkringer, Christophe; Loiseau, Thierry; Guillou, Nathalie; Férey, Gérard; Haouas, Mohamed; Taulelle, Francis; Elkaim, Erik; Stock, Norbert

2010-11-01

42

Microtribological properties of molecularly thin carboxylic acid functionalized imidazolium ionic liquid film on single-crystal silicon  

NASA Astrophysics Data System (ADS)

A series of 1-alkyl-3-ethylcarboxylic acid imidazolium chloride ([AEImi][Cl]) ionic liquids was synthesized and evaluated as a new kind of lubricant for microelectromechanical system (MEMS). In this research, novel molecular thin ionic liquid films (ILs) with various bonding percentages were prepared with different annealing temperatures and times. Film wettability was determined by measurement of contact angle and thickness with the ellipsometric method. The chemical composition, structure and morphology were characterized by the means of multi-technique X-ray photoelectron spectrometric, and atomic force microscopic analysis, respectively. The nano- and microtribological properties of the ionic liquid film were investigated. The morphologies of wear tracks of IL films were examined using a 3D non-contact profilometer. The influence of chain length on friction in nano-scale, and the effect of bonding percentage and sliding frequency on friction coefficient, carry-bearing capacity and durability in micro-scale were studied. Data are compared to the perfluoropolyether lubricant Z Dol. The [AEImi][Cl] ionic liquid films with appropriate bonding percentage exhibited comparable load-bearing capacity and durability than Z Dol 3800 at thickness level of several nanometers. Therefore, the [AEImi][Cl] ionic liquid film shows strong potential applications involving the lubrication and protection of MEMS.

Mo, Yufei; Yu, Bo; Zhao, Wenjie; Bai, Mingwu

2008-12-01

43

Preparation of {alpha}, {beta}-unsaturated carboxylic acids and anhydrides  

DOEpatents

Disclosed is a process for the preparation of {alpha},{beta}-unsaturated carboxylic acids and anhydrides thereof which comprises contacting formaldehyde or a source of formaldehyde with a carboxylic anhydride in the presence of a catalyst comprising mixed oxides of vanadium, phosphorus and, optionally, a third component selected from titanium, aluminum or, preferably silicon.

Spivey, J.J.; Gogate, M.R.; Zoeller, J.R.; Tustin, G.C.

1998-01-20

44

Preparation of .alpha., .beta.-unsaturated carboxylic acids and anhydrides  

DOEpatents

Disclosed is a process for the preparation of .alpha.,.beta.-unsaturated carboxylic acids and anhydrides thereof which comprises contacting formaldehyde or a source of formaldehyde with a carboxylic anhydride in the presence of a catalyst comprising mixed oxides of vanadium, phosphorus and, optionally, a third component selected from titanium, aluminum or, preferably silicon.

Spivey, James Jerry (Cary, NC); Gogate, Makarand Ratnakav (Durham, NC); Zoeller, Joseph Robert (Kingsport, TN); Tustin, Gerald Charles (Kingsport, TN)

1998-01-01

45

The protonation state of small carboxylic acids at the water surface from photoelectron spectroscopy.  

PubMed

We report highly surface sensitive core-level photoelectron spectra of small carboxylic acids (formic, acetic and butyric acid) and their respective carboxylate conjugate base forms (formate, acetate and butyrate) in aqueous solution. The relative surface propensity of the carboxylic acids and carboxylates is obtained by monitoring their respective C1s signal intensities from a solution in which their bulk concentrations are equal. All the acids are found to be enriched at the surface relative to the corresponding carboxylates. By monitoring the PE signals of acetic acid and acetate as a function of total concentration, we find that the protonation of acetic acid is nearly complete in the interface layer. This is in agreement with literature surface tension data, from which it is inferred that the acids are enriched at the surface while (sodium) formate and acetate, but not butyrate, are depleted. For butyric acid, we conclude that the carboxylate form co-exists with the acid in the interface layer. The free energy cost of replacing an adsorbed butyric acid molecule with a butyrate ion at 1.0 M concentration is estimated to be >5 kJ mol(-1). By comparing concentration dependent surface excess data with the evolution of the corresponding photoemission signals it is furthermore possible to draw conclusions about how the distribution of molecules that contribute to the excess is altered with bulk concentration. PMID:21633751

Ottosson, Niklas; Wernersson, Erik; Söderström, Johan; Pokapanich, Wandared; Kaufmann, Susanna; Svensson, Svante; Persson, Ingmar; Ohrwall, Gunnar; Björneholm, Olle

2011-07-14

46

Water-enhanced solubility of carboxylic acids in organic solvents and its applications to extraction processes  

SciTech Connect

The solubilities of carboxylic acids in certain organic solvents increase remarkably with an increasing amount of water in the organic phase. This phenomenon leads to a novel extract regeneration process in which the co-extracted water is selectively removed from an extract, and the carboxylic acid precipitates. This approach is potentially advantageous compared to other regeneration processes because it removes a minor component of the extract in order to achieve a large recovery of acid from the extract. Carboxylic acids of interest include adipic acid, fumaric acid, and succinic acid because of their low to moderate solubilities in organic solvents. Solvents were screened for an increase in acid solubility with increased water concentration in the organic phase. Most Lewis-base solvents were found to exhibit this increased solubility phenomena. Solvents that have a carbonyl functional group showed a very large increase in acid solubility. 71 refs., 52 figs., 38 tabs.

Starr, J.N.; King, C.J.

1991-11-01

47

Lactam carboxylic acids, their method of preparation and use  

SciTech Connect

This invention relates to hydrocarbyl lactam-carboxylic acids prepared by a reaction of a hydrocarbyl succinic anhydride with an imine and their use as corrosion inhibitors in crankcase lubricant compositions.

Schlicht, R.C.

1980-04-01

48

Direct esterification of ammonium salts of carboxylic acids  

DOEpatents

A non-catalytic process for producing esters, the process comprising reacting an ammonium salt of a carboxylic acid with an alcohol and removing ammonia from the reaction mixture. Selectivities for the desired ester product can exceed 95 percent.

Halpern, Yuval (Skokie, IL)

2003-06-24

49

ESTIMATION OF CARBOXYLIC ACID ESTER HYDROLYSIS RATE CONSTANTS  

EPA Science Inventory

SPARC chemical reactivity models were extended to calculate hydrolysis rate constants for carboxylic acid esters from molecular structure. The energy differences between the initial state and the transition state for a molecule of interest are factored into internal and external...

50

40 CFR 721.10529 - Cobalt iron manganese oxide, carboxylic acid-modified (generic).  

Code of Federal Regulations, 2013 CFR

... 2013-07-01 false Cobalt iron manganese oxide, carboxylic acid-modified...Substances § 721.10529 Cobalt iron manganese oxide, carboxylic acid-modified...identified generically as cobalt iron manganese oxide, carboxylic...

2013-07-01

51

40 CFR 721.10529 - Cobalt iron manganese oxide, carboxylic acid-modified (generic).  

... 2014-07-01 false Cobalt iron manganese oxide, carboxylic acid-modified...Substances § 721.10529 Cobalt iron manganese oxide, carboxylic acid-modified...identified generically as cobalt iron manganese oxide, carboxylic...

2014-07-01

52

Protease stabilization by carboxylic acid salts: Relative efficiencies and mechanisms  

Microsoft Academic Search

s  Kinetic studies are presented on the inhibition of proteolysis by carboxylic acid salts on the synthetic substrate succinyl\\u000a ala-ala-pro-phe-para nitroanilide. The inhibition of proteolysis\\/autodigestion is shown to be the major factor in the stabilization\\u000a of a detergent protease [i.e., Maxatase (subtilisin Carlsberg)] in an unbuilt, liquid, heavy duty laundry formulation. The\\u000a inhibition of autodigestion by a carboxylic acid salt as

Michael C. Crossin

1989-01-01

53

Carboxylic acid functionalization prevents the translocation of multi-walled carbon nanotubes at predicted environmentally relevant concentrations into targeted organs of nematode Caenorhabditis elegans  

NASA Astrophysics Data System (ADS)

Carboxyl (-COOH) surface modified multi-walled carbon nanotubes (MWCNTs-COOH) can be used for targeted delivery of drugs and imaging. However, whether MWCNTs-COOH at environmentally relevant concentrations exert certain toxic effects on multicellular organisms and the underlying mechanisms are still largely unclear. In the present study, we applied the nematode Caenorhabditis elegans to evaluate the properties of MWCNTs-COOH at environmentally relevant concentrations by comparing the effects of MWCNTs and MWCNTs-COOH exposure on C. elegans from L1-larvae to adult at concentrations of 0.001-1000 ?g L-1. Exposure to MWCNTs could potentially damage the intestine (primary targeted organ) at concentrations greater than 0.1 ?g L-1 and functions of neurons and reproductive organ (secondary targeted organs) at concentrations greater than 0.001 ?g L-1. Carboxyl modification prevented the toxicity of MWCNTs on the primary and the secondary targeted organs at concentrations less than 100 ?g L-1, suggesting that carboxyl modification can effectively prevent the adverse effects of MWCNTs at environmentally relevant concentrations. After exposure, MWCNTs-COOH (1 mg L-1) were translocated into the spermatheca and embryos in the body through the primary targeted organs. However, MWCNTs-COOH (10 ?g L-1) were not observed in spermatheca and embryos in the body of nematodes. Moreover, relatively high concentrations of MWCNTs-COOH exposed nematodes might have a hyper-permeable intestinal barrier, whereas MWCNTs-COOH at environmentally relevant concentrations effectively sustained the normally permeable state for the intestinal barrier. Therefore, we elucidated the cellular basis of carboxyl modification to prevent toxicity of MWCNTs at environmentally relevant concentrations. Our data highlights the key role of biological barriers in the primary targeted organs to block toxicity formation from MWCNTs, which will be useful for the design of effective prevention strategies against MWCNTs toxicity.Carboxyl (-COOH) surface modified multi-walled carbon nanotubes (MWCNTs-COOH) can be used for targeted delivery of drugs and imaging. However, whether MWCNTs-COOH at environmentally relevant concentrations exert certain toxic effects on multicellular organisms and the underlying mechanisms are still largely unclear. In the present study, we applied the nematode Caenorhabditis elegans to evaluate the properties of MWCNTs-COOH at environmentally relevant concentrations by comparing the effects of MWCNTs and MWCNTs-COOH exposure on C. elegans from L1-larvae to adult at concentrations of 0.001-1000 ?g L-1. Exposure to MWCNTs could potentially damage the intestine (primary targeted organ) at concentrations greater than 0.1 ?g L-1 and functions of neurons and reproductive organ (secondary targeted organs) at concentrations greater than 0.001 ?g L-1. Carboxyl modification prevented the toxicity of MWCNTs on the primary and the secondary targeted organs at concentrations less than 100 ?g L-1, suggesting that carboxyl modification can effectively prevent the adverse effects of MWCNTs at environmentally relevant concentrations. After exposure, MWCNTs-COOH (1 mg L-1) were translocated into the spermatheca and embryos in the body through the primary targeted organs. However, MWCNTs-COOH (10 ?g L-1) were not observed in spermatheca and embryos in the body of nematodes. Moreover, relatively high concentrations of MWCNTs-COOH exposed nematodes might have a hyper-permeable intestinal barrier, whereas MWCNTs-COOH at environmentally relevant concentrations effectively sustained the normally permeable state for the intestinal barrier. Therefore, we elucidated the cellular basis of carboxyl modification to prevent toxicity of MWCNTs at environmentally relevant concentrations. Our data highlights the key role of biological barriers in the primary targeted organs to block toxicity formation from MWCNTs, which will be useful for the design of effective prevention strategies against MWCNTs toxicity. Electronic supplementary information (ESI) available. See DOI: 10

Nouara, Abdelli; Wu, Qiuli; Li, Yinxia; Tang, Meng; Wang, Haifang; Zhao, Yuliang; Wang, Dayong

2013-06-01

54

Solvent extraction of rare-earth metals by carboxylic acids  

SciTech Connect

The solvent extraction of the trivalent lanthanides and yttrium from nitrate media by solutions of carboxylic acids in xylene has been studied. Commercially available carboxylic acids such as Versatic 10 and naphthenic acids were used, as well as model compounds of known structure, such as 2-ethylhexanoic and 3-cyclohexylpropanoic acids. In a few cases, extraction of the metals from sulphate and chloride solutions was also investigated. The dependence of the extraction properties of the carboxylic acids on the atomic number of the lanthanide shows a definite relationship to the steric bulk of the carboxylic acid molecule quantified by means of the steric parameter, E{sub s}{prime} of the substituent alkyl group. The stoichiometries of the extracted complexes for representative light (La), middle (Gd) and heavy (Lu) rare-earth metals were investigated by the slope-analysis technique for a sterically hindered acid (Versatic 10 acid; -E{prime}{sub s} = 3.83) and an acid with low steric hindrance (3-cyclohexylpropanoic acid; -E{prime}{sub s} = 0.28). 14 refs., 13 figs., 3 tabs.

Preez, A.C. du; Preston, J.S. [Mintek, Randburg (South Africa)

1992-04-01

55

Azetidine2-carboxylic acid in the food chain  

Microsoft Academic Search

Azetidine-2-carboxylic acid (Aze) 1 is a non-protein amino acid present in sugar beets and in table beets (Beta vulgaris). It is readily misincorporated into proteins in place of proline 2 in many species, including humans, and causes numerous toxic effects as well as congenital malformations. Its role in the pathogenesis of disease in humans has remained unexplored. Sugar beet agriculture,

Edward Rubenstein; Theresa McLaughlin; Richard C. Winant; Agustin Sanchez; Michael Eckart; Karolina M. Krasinska; Allis Chien

2009-01-01

56

Complex formation between benzene carboxylic acids and ?-cyclodextrin  

NASA Astrophysics Data System (ADS)

Complex formation between benzene carboxylic acids and ?-cyclodextrin in aqueous solutions at 290 300 K was studied using UV spectroscopy. The formation of 1:1 supramolecular inclusion compounds ?-cyclodextrin-benzene and ?-cyclodextrin-salicylic acid was found. Stability constants (Ks) of the complexes and thermodynamic parameters for formation of the inclusion compounds (?G, ?H, and ?S) were calculated.

Belyakova, L. A.; Lyashenko, D. Yu.

2008-05-01

57

Structural Basis for Substrate Recognition in the Salicylic Acid Carboxyl Methyltransferase Family  

PubMed Central

Recently, a novel family of methyltransferases was identified in plants. Some members of this newly discovered and recently characterized methyltransferase family catalyze the formation of small-molecule methyl esters using S-adenosyl-l-Met (SAM) as a methyl donor and carboxylic acid–bearing substrates as methyl acceptors. These enzymes include SAMT (SAM:salicylic acid carboxyl methyltransferase), BAMT (SAM:benzoic acid carboxyl methyltransferase), and JMT (SAM:jasmonic acid carboxyl methyltransferase). Moreover, other members of this family of plant methyltransferases have been found to catalyze the N-methylation of caffeine precursors. The 3.0-Å crystal structure of Clarkia breweri SAMT in complex with the substrate salicylic acid and the demethylated product S-adenosyl-l-homocysteine reveals a protein structure that possesses a helical active site capping domain and a unique dimerization interface. In addition, the chemical determinants responsible for the selection of salicylic acid demonstrate the structural basis for facile variations of substrate selectivity among functionally characterized plant carboxyl-directed and nitrogen-directed methyltransferases and a growing set of related proteins that have yet to be examined biochemically. Using the three-dimensional structure of SAMT as a guide, we examined the substrate specificity of SAMT by site-directed mutagenesis and activity assays against 12 carboxyl-containing small molecules. Moreover, the utility of structural information for the functional characterization of this large family of plant methyltransferases was demonstrated by the discovery of an Arabidopsis methyltransferase that is specific for the carboxyl-bearing phytohormone indole-3-acetic acid. PMID:12897246

Zubieta, Chloe; Ross, Jeannine R.; Koscheski, Paul; Yang, Yue; Pichersky, Eran; Noel, Joseph P.

2003-01-01

58

Amide Bond Formation via Reversible, Carboxylic Acid-Promoted Lactone Aminolysis  

E-print Network

A rapid carboxylic acid-promoted lactone aminolysis is reported. A number of carboxylic acids were found to promote this amide bond-forming transformation, with aliphatic acids being the most efficient. This reaction is ...

Foley, Megan A.

59

“ Nafion”-functionalized mesoporous MCM-41 silica shows high activity and selectivity for carboxylic acid esterification and Friedel–Crafts acylation reactions  

Microsoft Academic Search

Hybrid organic–inorganic MCM-41 silicas functionalized with perfluoroalkylsulfonic acid groups analogous to that of Nafion were prepared in a simple single step by a condensation reaction between surface silanol groups of the mesoporous silicas and 1,2,2-trifluoro-2-hydroxy-1-trifluoromethyl-ethane sulfonic acid Beta-sultone. The catalysts showed very high activity for the esterification of long-chain fatty acids with ethanol and high-molecular-weight alcohols with essentially complete selectivity

Mercedes Alvaro; Avelino Corma; Debasish Das; Vicente Fornés; Hermenegildo García

2005-01-01

60

Effect of carbon chain length on esterification of carboxylic acids with methanol using acid catalysis  

Microsoft Academic Search

This paper reports on an investigation into the impact of carboxylic acid chain length on the kinetics of liquid-phase acid-catalyzed esterification. Using sulfuric acid and a commercial Nafion\\/silica composite solid acid catalyst (SAC-13), initial kinetics were measured for the reactions of a series of linear chain carboxylic acids (acetic, propionic, butyric, hexanoic, and caprylic acid) with methanol at 60?°C. It

Yijun Liu; Edgar Lotero; James G. Goodwin

2006-01-01

61

Sucrose phosphorylases catalyze transglycosylation reactions on carboxylic acid compounds  

Microsoft Academic Search

Two sucrose phosphorylases were employed for glycosylation of carboxylic acid compounds. Streptococcus mutans sucrose phosphorylase showed remarkable transglycosylating activity, especially under acidic conditions. Leuconostoc mesenteroides sucrose phosphorylase exhibited very weak transglycosylating activity. Three main products were detected from the reaction\\u000a mixture using benzoic acid and sucrose as an acceptor and a donor molecule, respectively. These compounds were identified\\u000a as 1-O-benzoyl

Kazuhisa Sugimoto; Koji Nomura; Hiromi Nishiura; Kohji Ohdan; Takahisa Nishimura; Hideo Hayashi; Takashi Kuriki

2008-01-01

62

Carboxylic Acids as Indicators of Parent Body Conditions  

NASA Astrophysics Data System (ADS)

Alpha-hydroxy and alpha-amino carboxylic acids found on the Murchison meteorite are deuterium enriched [1]. It is postulated that they arose from a common interstellar source: the reaction of carbonyl compounds in an aqueous mixture containing HCN and NH3. Carbonyl compounds react with HCN to form alph-hydroxy nitriles, RR'CO + HCN <--> RR'C(OH)CN. If ammonia is also present, the alpha-hydroxy nitriles will exist in equilibirum with the alpha-amino nitriles, RR'C(OH)CN +NH3 .<--> RRCNH2CN + H2O. Both nitriles are hydrolyzed by water to form carboxylic acids: RR'C(OH)CN + H2O --> RR'C(OH)CO2H and RR'C(NH2)CN + H2O --> RR'C(NH2)CO2H. Carbonyl compounds observed in the interstellar medium have been shown to be deuterium enriched [2]. The combined alpha-amino acids found on Murchison have deltaD = +1751 o/oo while the combined alpha-hydroxy acids have deltaD = +573. o/oo [1]. This large discrepancy in deltaD values does not preclude common precursors for the alpha-amino acids and the alpha-hydroxy acids. Different relative amounts of specific alpha-amino and alpha-hydroxy acids could lead to quite different combined D/H ratios. If the alpha-hydroxy acids lose significantly more deuterium during synthesis than the alpha-amino acids or if they have a higher rate of H/D exchange with liquid water than alpha-amino acids, the alpha-hydroxy acids would be isotopically lighter than the alpha-amino acids, because the water responsible for the aqueous alteration of the Murchison parent body was deuterium depleted with deltaD = -100. o/oo [3]. To determine between these alternative mechanisms we measured the rates of hydrogen-deuterium exchange of glycolic acid (the alpha-hydroxy analog of glycine), lactic acid (the alpha-hydroxy analog of alanine), and alpha-hydroxy isobutyric acid have been measured in D2O as a function of pH, temperature and the presence of Allende or Murchison minerals. No detectable H/D exchange was observed. Glycine subjected to similar conditons exchanged as much as 80% of its carbon-bonded deuterium, and alanine 43% [4]. Evidently, the relative deuterium content of the alpha-amino acids and alpha-hydroxy acids found on the Murchison meteorite was not determined by H/D exchange with water. In order to determine if deuterium retention is less for alpha-hydroxy acids than it is for alpha-amino carboxylic acids during synthesis a solution was prepared containing: KCN, 0.005M; NH4Cl, 0.002 M; CD2O, 0.0007M; CD3CDO, 0.0008 M; and (CD3)2CO 0.0006 M, and divided into aliquots which were maintained at 263 K and at 295 K. At the end of one month the carbonyls, alpha-amino acids and alpha-hydroxy acids were separated from the mixture and their deuterium content determined from their mass spectra (see Table 1). The retention of deuterium during synthesis varies significantly between the alpha-hydroxy acids and the alpha-amino acids with common precursors. Only comparisons of D/H ratios of specific acids with a postulated common precursor are meaningful. References: [1] Cronin J. R. et al. (1993) GCA, 57, 4745-4752. [2] Zinner E. (1988) in Meteorites and the Early Solar System (J. R. Kerridge and M. S. Matthews, eds.), 956-983, Univ. of Arizona. [3] Robert F. and Epstein S. (1982) GCA, 46, 81-95. [4] Lerner N. R. (1995) GCA, 59, 1623-1631. Table 1 shows D/(D+H) of carbon-bonded hydrogen in compounds separated after one month from a simulated meteorite solution.

Lerner, N. R.

1995-09-01

63

?-Functionalization of Carboxylic Anhydrides with ?-Alkyl Substituents through Carbene Organocatalysis.  

PubMed

The first NHC-catalyzed functionalization of carboxylic anhydrides is described. In this reaction, the ??carbon behaves as a nucleophilic carbon and undergoes asymmetric reactions with electrophiles. Anhydrides with challenging ?-alkyl substituents work effectively. PMID:25284248

Jin, Zhichao; Chen, Shaojin; Wang, Yuhuang; Zheng, Pengcheng; Yang, Song; Chi, Yonggui Robin

2014-12-01

64

Recovery of carboxylic acids at pH greater than pK{sub a}  

Microsoft Academic Search

Economics of producing carboxylic acids by fermentation is often dominated, not by the fermentation cost, but by the cost of recovering and purifying the acids from dilute aqueous solutions. Experiments were performed to measure uptakes of lactic and succinic acids as functions of pH by basic polymeric sorbents; sorbent regeneration was also tested. Performance at pH > pK{sub a} and

Tung

1993-01-01

65

Functionality Distribution of Carboxyl and Hydroxyl-Terminated Polybutadiene  

Microsoft Academic Search

Elurion from silica gel was used to fractionate liquid polymers according to the number of chemically reactive groups per molecule (the functionality). Methods are presented for the functionality fractionation of high and low functionality carboxyl-terminated polybutadiene (CTPB). Results are also given on the fractionation of low functionality hydroxyl-terminated polybutadiene (HTPB) and of high functionality HTPB using a new elution series

M. S. Chang; D. M. French; P. L. Rogers

1973-01-01

66

Lewis acid-catalyzed Friedel–Crafts acylation reaction using carboxylic acids as acylating agents  

Microsoft Academic Search

Rare-earth metal Lewis acids, in particular Eu(NTf2)3, were found to be efficient catalysts for Friedel–Crafts acylation reaction using aliphatic as well as aromatic carboxylic acids as acylating agents at high temperature.

Masato Kawamura; Dong-Mei Cui; Teruyuki Hayashi; Shigeru Shimada

2003-01-01

67

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

ERIC Educational Resources Information Center

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)

Leung, Sam H.

2000-01-01

68

Extraction chemistry of fermentation product carboxylic acids.  

PubMed

Within the framework of a program aiming to improve the existing extractive recovery technology of fermentation products, the state of the art is critically reviewed. The acids under consideration are propionic, lactic, pyruvic, succinic, fumaric, maleic, malic, itaconic, tartaric, citric, and isocitric, all obtained by the aerobic fermentation of glucose via the glycolytic pathway and glyoxylate bypass. With no exception, it is the undissociated monomeric acid that is extracted into carbon-bonded and phosphorus-bonded oxygen donor extractants. In the organic phase, the acids are usually dimerized. The extractive transfer process obeys the Nernst law, and the measured partition coefficients range from about 0.003 for aliphatic hydrocarbons to about 2 to 3 for aliphatic alcohols and ketones to about 10 or more for organophosphates. Equally high distribution ratios are measured when long-chain tertiary amines are employed as extractants, forming bulky salts preferentially soluble in the organic phase. PMID:18555324

Kertes, A S; King, C J

1986-02-01

69

Dissociation Constants of Carboxylic Acids in Formamide  

Microsoft Academic Search

IT has already been shown1,2 that the dissociation constants Ka of formic and acetic acid are lower in formamide than in water although the dielectric constant of the former is much larger than that of the latter. The variation of Ka with temperature may, in both solvents, be described by a reduced curve proposed by Earned and Embree3: Here theta

M. Mandel; P. DECROLY

1964-01-01

70

40 CFR 721.2088 - Carboxylic acids, (C6-C9) branched and linear.  

Code of Federal Regulations, 2010 CFR

...Carboxylic acids, (C6-C9) branched and linear. 721.2088 Section 721.2088 ...Carboxylic acids, (C6-C9) branched and linear. (a) Chemical substances and significant...carboxylic acids, (C6-C9) branched and linear (PMNs P-93-313, 314, 315,...

2010-07-01

71

Toxicity of perfluorinated carboxylic acids for aquatic organisms  

PubMed Central

Toxicity of perfluorinated carboxylic acids with carbon chain C8 to C12 were tested with oligochaeta Tubifex tubifex. Toxicity was evaluated as the exposure time ET50 from onset of damage of the oligochaeta in saturated aqueous solutions. The ET50 fluctuated between 25 and 257 minutes. No statistically significant difference was found among the C8, C9 and C12 acids (ET50 between 143 and 257 minutes with large standard deviation). The acids with carbon chain C10 and C11 induced the effect significantly quicker (25 to 47 minutes). No acute toxicity measured in the three-minute test was observed in any case. PMID:21217876

Tichy, Milon; Valigurova, Radka; Cabala, Radomir; Uzlova, Rut; Rucki, Marian

2010-01-01

72

Toxicity of perfluorinated carboxylic acids for aquatic organisms.  

PubMed

Toxicity of perfluorinated carboxylic acids with carbon chain C(8) to C(12) were tested with oligochaeta Tubifex tubifex. Toxicity was evaluated as the exposure time ET(50) from onset of damage of the oligochaeta in saturated aqueous solutions. The ET(50) fluctuated between 25 and 257 minutes. No statistically significant difference was found among the C(8), C(9) and C(12) acids (ET(50) between 143 and 257 minutes with large standard deviation). The acids with carbon chain C(10) and C(11) induced the effect significantly quicker (25 to 47 minutes). No acute toxicity measured in the three-minute test was observed in any case. PMID:21217876

Tichý, Milo?; Valigurová, Radka; Cabala, Radomír; Uzlová, Rut; Rucki, Marián

2010-06-01

73

Direct preparation of nitriles from carboxylic acids in continuous flow.  

PubMed

A continuous-flow protocol for the preparation of organic nitriles from carboxylic acids has been developed. The method is based on the acid-nitrile exchange reaction with acetonitrile, used as the solvent, and takes place without any catalyst or additives under the high-temperature/high-pressure conditions employed. At 350 °C and 65 bar, where acetonitrile is in its supercritical state, the transformation of benzoic acid to benzonitrile requires 25 min. The protocol has been tested for a variety of nitriles, including aromatic and aliphatic substrates. PMID:24066706

Cantillo, David; Kappe, C Oliver

2013-10-18

74

Transcriptomic Analysis of Carboxylic Acid Challenge in Escherichia coli: Beyond Membrane Damage  

PubMed Central

Carboxylic acids are an attractive biorenewable chemical. Enormous progress has been made in engineering microbes for production of these compounds though titers remain lower than desired. Here we used transcriptome analysis of Escherichia coli during exogenous challenge with octanoic acid (C8) at pH 7.0 to probe mechanisms of toxicity. This analysis highlights the intracellular acidification and membrane damage caused by C8 challenge. Network component analysis identified transcription factors with altered activity including GadE, the activator of the glutamate-dependent acid resistance system (AR2) and Lrp, the amino acid biosynthesis regulator. The intracellular acidification was quantified during exogenous challenge, but was not observed in a carboxylic acid producing strain, though this may be due to lower titers than those used in our exogenous challenge studies. We developed a framework for predicting the proton motive force during adaptation to strong inorganic acids and carboxylic acids. This model predicts that inorganic acid challenge is mitigated by cation accumulation, but that carboxylic acid challenge inverts the proton motive force and requires anion accumulation. Utilization of native acid resistance systems was not useful in terms of supporting growth or alleviating intracellular acidification. AR2 was found to be non-functional, possibly due to membrane damage. We proposed that interaction of Lrp and C8 resulted in repression of amino acid biosynthesis. However, this hypothesis was not supported by perturbation of lrp expression or amino acid supplementation. E. coli strains were also engineered for altered cyclopropane fatty acid content in the membrane, which had a dramatic effect on membrane properties, though C8 tolerance was not increased. We conclude that achieving higher production titers requires circumventing the membrane damage. As higher titers are achieved, acidification may become problematic. PMID:24586888

Royce, Liam A.; Boggess, Erin; Fu, Yao; Liu, Ping; Shanks, Jacqueline V.; Dickerson, Julie; Jarboe, Laura R.

2014-01-01

75

Electrocarboxylation: towards sustainable and efficient synthesis of valuable carboxylic acids  

PubMed Central

Summary The near-unlimited availability of CO2 has stimulated a growing research effort in creating value-added products from this greenhouse gas. This paper presents the trends on the most important methods used in the electrochemical synthesis of carboxylic acids from carbon dioxide. An overview is given of different substrate groups which form carboxylic acids upon CO2 fixation, including mechanistic considerations. While most work focuses on the electrocarboxylation of substrates with sacrificial anodes, this review considers the possibilities and challenges of implementing other synthetic methodologies. In view of potential industrial application, the choice of reactor setup, electrode type and reaction pathway has a large influence on the sustainability and efficiency of the process. PMID:25383120

Matthessen, Roman; Fransaer, Jan; Binnemans, Koen

2014-01-01

76

Polythermal solubility of fullerenes in higher isomeric carboxylic acids  

Microsoft Academic Search

The solubility of individual fullerenes C60 and C70 and a fullerene mixture enriched in higher fullerenes (C60 38.8, C70 33.0, C76–78 5.6, C84 8.6, C90 2.6, and C96 3.3%) in higher isomeric carboxylic acids was studied within the 20–80C temperature range; the corresponding solubility\\u000a polytherms are presented.

K. N. Semenov; O. V. Arapov; A. K. Pyartman; V. A. Keskinov; V. V. Lishchuk; N. A. Charykov; N. I. Alekseev

2007-01-01

77

Functionalized carboxyl nanoparticles enhance mucus dispersion and hydration  

NASA Astrophysics Data System (ADS)

Luminal accumulation of viscous, poorly hydrated, and less transportable mucus has been associated with altered mucus rheology and reduced mucociliary clearance. These symptoms are some of the cardinal clinical manifestations found throughout major respiratory diseases as well as gastrointestinal and digestive disorders. Applications of current mucolytics may yield short-term improvements but are continuously challenged by undesirable side-effects. While nanoparticles (NPs) can interact with mucin polymers, whether functionalized NPs can rectify mucus rheology is unknown. Herein, we report that carboxyl-functionalized NPs (24 nm and 120 nm) dramatically reduced mucin gel size and accelerated mucin matrix hydration rate (diffusivity). Our results suggest that carboxyl-functionalized NPs disperse mucin gels possibly by enhancing network hydration. This report highlights the prospective usages of carboxyl-functionalized NPs as a novel mucus dispersant or mucolytic agent in adjusting mucus rheological properties and improving mucociliary transport to relieve clinical symptoms of patients suffering from relevant diseases.

Chen, Eric Y.; Daley, David; Wang, Yung-Chen; Garnica, Maria; Chen, Chi-Shuo; Chin, Wei-Chun

2012-01-01

78

Approaches for regeneration of amine-carboxylic acid extracts  

SciTech Connect

Extraction processes based on reversible chemical complexation can be useful for separation of polar organics from dilute solution. Tertiary amines are effective extractants for the recovery of carboxylic acids from aqueous solution. The regeneration of aminecarboxylic acid extracts is an important step which strongly influences the economic viability of the separation process. Several regeneration methods are critically reviewed, and the factors that affect swing regeneration processes, including temperature-swing, diluent composition-swing and pH-swing with a volatile base are discussed. Interest in this area comes from interest in treatment of waste streams, particularly in petrochemical and fermentation manufacture.

Dai, Y.; King, C.J.

1995-07-01

79

Alpha-cycloPNA: 1-aminocylopentane-1-carboxylic acid-derived peptide nucleic acid.  

PubMed

All four diastereoisomers of 3-thymine-1-((t)butoxycarbonyl)aminocyclopentane-1-carboxylic acid have been synthesised from (S)-dimethyl malate and thymine monomer 12 has been incorporated into an alpha-cycloPNA oligomer. PMID:14565416

Howarth, Nicola M; Wakelin, Laurence P G; Walker, David M

2003-01-01

80

Functionalization of poly-SNS-anchored carboxylic acid with Lys and PAMAM: surface modifications for biomolecule immobilization/stabilization and bio-sensing applications.  

PubMed

Poly(2-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl) (SNS) acetic acid) was electrochemically deposited on graphite electrodes and functionalized with lysine (Lys) amino acid and poly(amidoamine) derivatives (PAMAM G2 and PAMAM G4) to investigate their matrix properties for biosensor applications. Glucose oxidase (GOx) was immobilized onto the modified surface as the model enzyme. X-Ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to report the surface properties of the matrices in each step of the biosensor construction. The biosensors were characterized in terms of their operational and storage stabilities and the kinetic parameters (K(app)(m) and I(max)). Three new glucose biosensors revealed good stability, featuring low detection limits (19.0 ?M, 3.47 ?M and 2.93 ?M for lysine-, PAMAM G2- and PAMAM G4-functionalized electrodes, respectively) and prolonged the shelf lives (4, 5, and 6 weeks for Lys-, PAMAM G2- and PAMAM G4-modified electrodes, respectively). The proposed biosensors were tested for glucose detection on real human blood serum samples. PMID:22832474

Demirci, Sema; Emre, Fatma Bilge; Ekiz, Fulya; O?uzkaya, Funda; Timur, Suna; Tanyeli, Cihangir; Toppare, Levent

2012-09-21

81

Differences in Cytocompatibility Between MWCNTs and Carboxylic Functionalized MWCNTs  

NASA Astrophysics Data System (ADS)

Influence of carboxylic functionalization on the cytocompatibility of multiwalled carbon nanotubes (MWCNTs) was investigated in this work. Water contact angle assay showed that the surface of MWCNTs-containing carboxyl (MWCNTs-COOH) became much more hydrophilic compared with pure MWCNTs. In cell-adhesion assays, two cell lines, mouse fibroblast cells (L929) and human umbilical vein endothelial cells (EAHY926) were used to assess the cytocompatibility of materials. The MWCNTs-COOH displayed the improved cell proliferation, viability and adhesion due to the enhanced wettability, indicating their superior cytocompatibility over MWCNTs. The existence of carboxyl groups should be benefit to the adhesion and growth of both cells, which implied that MWCNTs-COOH were helpful for seeding both cells and could be used as the functional surface for the adhesion and growth of cells.

Zhang, Yiteng; Li, Dejun; Zhao, Mengli; Guo, Meixian; Deng, Xiangyun; Gu, Hanqing; Wan, Rongxin

2013-02-01

82

THE SOLVENT EXTRACTION OF RARE-EARTH METALS BY CARBOXYLIC ACIDS  

Microsoft Academic Search

The solvent extraction of the trivalent lanthanides and yttrium from nitrate media by solutions of carboxylic acids in xylene has been studied. Commercially available carboxylic acids such as Versatic 10 and naphthenic acids were used, as well as model compounds of known structure, such as 2-ethylhexanoic and 3-cyclohexylpropanoic acids. In a few cases, extraction of the metals from sulphate and

A. C. du Preez; J. S. Preston

1992-01-01

83

Fluorescent carboxylic and phosphonic acids: comparative photophysics from solution to organic nanoparticles.  

PubMed

Phosphonic and carboxylic fluorescent nanoparticles have been fabricated by direct reprecipitation in water. Their fluorescence properties strongly differ from those of the corresponding esters where strong H-bonding formation is prohibited. Comparative experiments between the two acid derivatives, differing only in their acid functions while keeping the same alkyl chain, have evidenced the peculiar behavior of the phosphonic acid derivative compared to its carboxylic analog. A dramatic emission quenching for the phosphonic acid in aprotic toluene could be observed while a fivefold increase in the fluorescence signal was observed for molecules assembled as nanoparticles. Such properties have been attributed on the theoretical basis to the formation of folded conformers in solution, leading to deactivation of the radiative excited state through intramolecular H-bonding. These studies evidence for the first time through time-resolved fluorescence measurements the stronger H-donating character of phosphonic acids compared to the carboxylic ones, and provide information on the degree of structural heterogeneity within the nanoparticles. They should pave the way for the rational fabrication of chelating acid fluorophores, able to complex metal oxides to yield stiff hybrid magnetofluorescent nanoparticles which are attracting considerable attention in the growing fields of bimodal imaging and vectorization applications. PMID:23799511

Faucon, Adrien; Lenk, Romaric; Hémez, Julie; Gautron, Eric; Jacquemin, Denis; Le Questel, Jean-Yves; Graton, Jérôme; Brosseau, Arnaud; Ishow, Eléna

2013-08-14

84

Carboxylic acids in high elevation Alpine glacier snow  

NASA Astrophysics Data System (ADS)

Fresh-snow samples were collected on an event basis on the Glacier de la Girose (3360 m above sea level (asl)) in the southern French Alps, during winters and early springs 1990 and 1991. In addition, a 13-m firn core was recovered in 1991 at the Col du Dôme (4250 m asl), a cold glacier in the northern French Alps, offering the complete seasonal record of alpine precipitation during 3.5 years. All samples were analyzed for total formate and acetate and for major ions using ion chromatography. The acidity-alkalinity was accurately measured using a titration technique. An almost perfect ion balance was achieved for this data set. In absence of Saharan dust transport, the high alpine snow is slightly acid (H+ ˜ 2-20 ?Eq L-1). HCOOT and CH3COOT are generally present in alpine acid snow at very low concentrations: 0.3-0.6 ?Eq L-1 in winter (January to February) and 0.6-2 ?Eq L-1 in early spring (March to April). At Col du Dôme, total acetate concentrations of ˜1 ?Eq L-1 are observed in summer. It remains unclear from our results what the major sources of carboxylic acids are, and in particular of acetic acid, in the wintertime continental free troposphere, while it appears that formic and acetic acids are presumably mainly derived from natural sources in spring and summer. The total contribution of formic and acetic acids to free acidity is, on average, less than 15-20%. Contrary to major ions which are present in wider concentration ranges and show large variations from one snowfall to the other, HCOOT and CH3COOT are surprisingly stable in acid alpine snow. The only significant deviation of HCOOT and CH3COOT from their mean values (up to 9 and 5 ?Eq L-1, respectively) are observed in case of Saharan dust transport, when precipitation pH is shifted from acid toward alkaline conditions. These observations suggest a pH partitioning effect between the aqueous and gas phases, formic and acetic acids being dissolved and neutralized as salts in alkaline cloudwater droplets. On a global scale, the scavenging by alkaline mineral dust could represent an important deposition process of carboxylic acids.

Maupetit, FrançOis; Delmas, Robert J.

1994-08-01

85

Crystal structure and photoluminescence of 7-( N, N?-diethylamino)-coumarin-3-carboxylic acid  

Microsoft Academic Search

The structure of 7-(N,N?-diethylamino)-coumarin-3-carboxylic acid (DCCA) was verified by single crystal X-ray crystallography. The UV–vis absorption and fluorescence of DCCA were discussed. The compound exhibits strong blue emission under ultraviolet light excitation. The molecular structure of DCCA was optimized using density function theory (DFT) at B3LYP\\/6-31G level, showing that the optimized geometers parameters are in good agreement with experiment data.

Hui Zhang; Tianzhi Yu; Yuling Zhao; Duowang Fan; Lili Chen; Yongqing Qiu; Long Qian; Kai Zhang; Changhui Yang

2008-01-01

86

Integrated process for preparing a carboxylic acid from an alkane  

DOEpatents

The present invention relates to an integrated process for producing unsaturated carboxylic acids from the corresponding C.sub.2-C.sub.4 alkane. The process begins with performance of thermally integrated dehydrogenation reactions which convert a C.sub.2-C.sub.4 alkane to its corresponding C.sub.2-C.sub.4 alkene, and which involve exothermically converting a portion of an alkane to its corresponding alkene by oxidative dehydrogenation in an exothermic reaction zone, in the presence of oxygen and a suitable catalyst, and then feeding the products of the exothermic reaction zone to an endothermic reaction zone wherein at least a portion of the remaining unconverted alkane is endothermically dehydrogenated to form an additional quantity of the same corresponding alkene, in the presence of carbon dioxide and an other suitable catalyst. The alkene products of the thermally integrated dehydrogenation reactions are then provided to a catalytic vapor phase partial oxidation process for conversion of the alkene to the corresponding unsaturated carboxylic acid or nitrile. Unreacted alkene and carbon dioxide are recovered from the oxidation product stream and recycled back to the thermally integrated dehydrogenation reactions.

Benderly, Abraham (Elkins Park, PA); Chadda, Nitin (Radnor, PA); Sevon, Douglass (Fairless Hills, PA)

2011-12-20

87

Group Type Analysis of Carboxylic Acids Formed by Degradation of i-Dodecane and Kerosene with Nitric Acid  

Microsoft Academic Search

Quantitative analysis of carboxylic acids formed by diluent degradation with nitric acid was investigated by group type analysis.Based on Beer-Lambert's law and alkaline titration, the apparent molar extinction coefficient (E max) for C=0 stretching vibration (vc=0: 1,694 cm) of carboxylic acids in degraded diluents was determined to be 620±20 mole·\\/·cm. Using this value, the concentrations of carboxylic acids formed under

Ken OHWADA

1967-01-01

88

Azetidine-2-carboxylic acid in the food chain.  

PubMed

Azetidine-2-carboxylic acid (Aze) 1 is a non-protein amino acid present in sugar beets and in table beets (Beta vulgaris). It is readily misincorporated into proteins in place of proline 2 in many species, including humans, and causes numerous toxic effects as well as congenital malformations. Its role in the pathogenesis of disease in humans has remained unexplored. Sugar beet agriculture, especially in the Northern Hemisphere, has become widespread during the past 150 years, and now accounts for nearly 30% of the world's supply of sucrose. Sugar beet byproducts are also used as a dietary supplement for livestock. Therefore, this study was undertaken as an initial survey to identify Aze-containing links in the food chain. Herein, we report the presence of Aze 1 in three sugar beet byproducts that are fed to farm animals: sugar beet molasses, shredded sugar beet pulp, and pelleted sugar beet pulp. PMID:19101705

Rubenstein, Edward; McLaughlin, Theresa; Winant, Richard C; Sanchez, Agustin; Eckart, Michael; Krasinska, Karolina M; Chien, Allis

2009-01-01

89

Regiocontrolled intramolecular cyclizations of carboxylic acids to carbon-carbon triple bonds promoted by acid or base catalyst.  

PubMed

We systematically investigated, for the first time, the relationship between regioselectivity and acid/base effects in the cyclization reactions between carboxylic acids and carbon-carbon triple bonds. We found novel acid- and base-promoted cyclizations to selectively give isocoumarin or pyran-2(2H)-one and phthalide or furan-2(5H)-one skeletons, respectively, and established a catalytic version of regioselective heterocyclic ring synthesis. Density functional theory calculations and application to a short route to thunberginol A were also described. [reaction: see text]. PMID:17107061

Uchiyama, Masanobu; Ozawa, Hiroki; Takuma, Kazuya; Matsumoto, Yotaro; Yonehara, Mitsuhiro; Hiroya, Kou; Sakamoto, Takao

2006-11-23

90

Pancreatic Function in Carboxyl-Ester Lipase Knockout Mice  

Microsoft Academic Search

Background\\/Aims:CEL-MODY is a monogenic form of diabetes and exocrine pancreatic insufficiency due to mutations in the carboxyl-ester lipase (CEL) gene. We aimed to investigate endocrine and exocrine pancreatic function in CEL knockout mice (CELKO). Methods: A knockout mouse model with global targeted deletion of CEL was investigated physiologically and histopathologically, and compared to littermate control CEL+\\/+ mice at 7 and

Mette Vesterhus; Helge Ræder; Amarnath J. Kurpad; Dan Kawamori; Anders Molven; Rohit N. Kulkarni; C. Ronald Kahn; Pål Rasmus Njølstad

2010-01-01

91

Alkali-catalyzed low temperature wet crosslinking of plant proteins using carboxylic acids.  

PubMed

We report the development of a new method of alkali-catalyzed low temperature wet crosslinking of plant proteins to improve their breaking tenacity without using high temperatures or phosphorus-containing catalysts used in conventional poly(carboxylic acid) crosslinking of cellulose and proteins. Carboxylic acids are preferred over aldehyde-containing crosslinkers for crosslinking proteins and cellulose because of their low toxicity and cost and ability to improve the desired properties of the materials. However, current knowledge in carboxylic acid crosslinking of proteins and cellulose requires the use of carboxylic acids with at least three carboxylic groups, toxic phosphorous-containing catalysts and curing at high temperatures (150-185 degrees C). The use of high temperatures and low pH in conventional carboxylic acid crosslinking has been reported to cause substantial strength loss and/or undesired changes in the properties of the crosslinked materials. In this research, gliadin, soy protein, and zein fibers have been crosslinked with malic acid, citric acid, and butanetetracarboxylic acid to improve the tenacity of the fibers without using high temperatures and phosphorus-containing catalysts. The new method of wet crosslinking using carboxylic acids containing two or more carboxylic groups will be useful to crosslink proteins for various industrial applications. PMID:19224570

Reddy, Narendra; Li, Ying; Yang, Yiqi

2009-01-01

92

Recovery of Carboxylic Acids from Fermentation Broth via Acid Springing  

E-print Network

ix LIST OF FIGURES FIGURE Page 1-1 Oil consumption of the United States and other countries ......................... 1 1-2... MixAlco process overview ......................................................................... 5 1-3 Acid springing process .............................................................................. 7 2-1 Projected dimensions of 0...

Dong, Jipeng

2010-01-14

93

FORMATION OF ALIPHATIC CARBOXYLIC ACIDS DURING ALKALINE PULPING OF MULI BAMBOO  

Microsoft Academic Search

A study on the formation of aliphatic carboxylic acids, i.e., formic and acetic acids and various hydroxy monocarboxylic and dicarboxylic acids, during soda-AQ, kraft, and kraft-AQ pulping of muli bamboo (Melocanna baccifera) was carried out. Detailed gas chromatographic analyses revealed that the most abundant hydroxy carboxylic acids were 2-hydroxybutanoic, lactic, glucoisosaccharinic, glycolic, xyloisosaccharinic, 3,4-dideoxypentonic, and 3-deoxypentonic acids. The presence of

Zhinan Feng; Raimo Alén; Klaus Niemelä

2002-01-01

94

Reduced receptor binding by a human interferon-. gamma. fragment lacking 11 carboxyl-terminal amino acids  

SciTech Connect

Treatment of recombinant human (/sup 125/I)-labeled interferon-..gamma..(IFN-..gamma..) with either 1) the arginine-specific proteases clostripain or submaxillaris protease or 2) the broadly specific enzyme pronase produced a stable fragment with m.w. of 15,500. Structural analysis showed that the cleavage occurred between residues 129 and 130 and thus produced a fragment lacking only 11 carboxyl-terminal amino acids. The fragmented and untreated molecules showed identical amino-terminal amino acid sequences and were equally reactive with either polyclonal or monoclonal anti-IFN-..gamma... IFN-..gamma.. lacking carboxyl-terminal amino acids displayed a 1000- to 2000-fold reduction in its capacity to bind to cellular IFN-..gamma.. receptors at 4/sup 0/C. Functionally the fragment showed a 50-fold reduction in its ability to induce antiviral activity in fibroblasts and a 10-fold reduction in its ability to induce Fc receptors on the human histiocytic lymphoma cell line U937. These results thus suggest that the carboxyl terminus of human IFN-..gamma.. contributes significantly to the formation of the receptor-binding site of the molecule.

Leinikki, P.O.; Calderon, J.; Luquette, M.H.; Schreiber, R.D.

1987-11-15

95

Hydrogen bonding and the ultrafast time response in carboxylic acids  

NASA Astrophysics Data System (ADS)

We present a preliminary study of Rayleigh-wing results performed on two carboxylic acids, namely formic acid (HCOOH) and acetic acid (CH 3COOH) at T = 18°C. The obtained data are compared with those deduced from two derivatives (methyl formate, HCOOCH 3 and methyl acetate, CH 3COOCH 3) in which the OH active sites for the interactions have been substituted with the non-interacting CH 3 methyl group. This study allowed us to enter in detail the dynamic contribution to the wing in the picosecond time domain. Recently the Reverse Monte Carlo method and X-ray and neutron diffraction have determined that short branching chains are formed for the stronger acid. In the case of CH 3COOH, due to its steric hindrance, the closed dimeric species are favoured at lower temperature and they tend to open when the temperature increases, as indicated by the Kirkwood correlation factor. The optical response for the two acids has shown the presence of a zero-frequency Lorentzian band plus a definite librational shoulder, and an exponential collision induced contribution. This behaviour is peculiar for H-bonded associated liquids and verifies the Keys and Kivelson's model very well. In the case of the non-associated isomorphous liquids a reorientational Lorentzian band and a Gaussian contribution connected to inertial effects, also zero-frequency centred, fit the spectral wing, together with a vibrational band centred at ? ? 300 cm -1. Furthermore, a preliminary study of the OH stretching region vs. temperature for the acetic acid, allowed us to obtain information about the aggregative processes existing in this system.

Crupi, V.; Magazu', S.; Maisano, G.; Majolino, D.; Migliardo, P.; Musolino, A. M.

1996-07-01

96

Electron mobility enhancement in ZnO thin films via surface modification by carboxylic acids  

E-print Network

Electron mobility enhancement in ZnO thin films via surface modification by carboxylic acids Josef://apl.aip.org/authors #12;Electron mobility enhancement in ZnO thin films via surface modification by carboxylic acids Josef-temperature solution processing,1 and has high transpar- ency in the visible spectrum.2 Production of ZnO thin films

Evans, Paul G.

97

Structure and function studies on enzymes with a catalytic carboxyl group(s): from ribonuclease T1 to carboxyl peptidases  

PubMed Central

A group of enzymes, mostly hydrolases or certain transferases, utilize one or a few side-chain carboxyl groups of Asp and/or Glu as part of the catalytic machinery at their active sites. This review follows mainly the trail of studies performed by the author and his colleagues on the structure and function of such enzymes, starting from ribonuclease T1, then extending to three major types of carboxyl peptidases including aspartic peptidases, glutamic peptidases and serine-carboxyl peptidases. PMID:23759941

TAKAHASHI, Kenji

2013-01-01

98

Hydration of simple carboxylic acids from infrared spectra of HDO and theoretical calculations.  

PubMed

The hydration of carboxylic acids in dilute aqueous solutions is important for our understanding of their functioning in the biochemical context. Here we apply vibrational spectra of HDO isotopically diluted in H(2)O to study this phenomenon, using the difference spectra method for analysis and interpretation of the results. The spectra of HDO affected by formic, acetic, and propionic acid display characteristic component bands, significantly red-shifted from the bulk HDO band position. The appearance of these component bands is linked with isotopic substitution on the carboxylic acid molecule, which forms a short and strong hydrogen bond with a water molecule. Additionally, a charge separation due to the proton transfer in the neutral form of the complex leading to a contact ion pair formation may be inferred from the affected HDO spectra. Apart from the contraction of the principal acid-water hydrogen bond, it results in other major structural changes in the hydration shell, as revealed by density functional theory (DFT) calculations of optimal geometries of aqueous clusters of the studied acids. PMID:21466173

Smiechowski, Maciej; Goj?o, Emilia; Stangret, Janusz

2011-04-28

99

Regeneration of carboxylic acid-laden basic sorbents by leaching with a volatile base in an organic solvent  

DOEpatents

Carboxylic acids are sorbed from aqueous feedstocks onto a solid adsorbent. The acids are freed from the sorbent phase by treating it with an organic solution of alkylamine thus forming an alkylamine/carboxylic acid complex which is decomposed with improved efficiency to the desired carboxylic acid and the alkylamine. Carbon dioxide addition can be used to improve the adsorption or the carboxylic acids by the solid phase sorbent.

King, C. Judson (Kensington, CA); Husson, Scott M. (Berkeley, CA)

1999-01-01

100

Enhancing the enzymatic hydrolysis of lignocellulosic biomass by increasing the carboxylic acid content of the associated lignin.  

PubMed

To assess the effects that the physical and chemical properties of lignin might have on the enzymatic hydrolysis of pretreated lignocellulosic substrates, protease treated lignin (PTL) and cellulolytic enzyme lignin (CEL) fractions, isolated from steam and organosolv pretreated corn stover, poplar, and lodgepole pine, were prepared and characterized. The adsorption of cellulases to the isolated lignin preparations corresponded to a Langmuir adsorption isotherm. It was apparent that, rather than the physical properties of the isolated lignin, the carboxylic acid functionality of the isolated lignin, as determined by FTIR and NMR spectroscopy, had much more of an influence when lignin was added to typical hydrolysis of pure cellulose (Avicel). An increase in the carboxylic content of the lignin preparation resulted in an increased hydrolysis yield. These results suggested that the carboxylic acids within the lignin partially alleviate non-productive binding of cellulases to lignin. To try to confirm this possible mechanism, dehydrogenative polymers (DHP) of monolignols were synthesized from coniferyl alcohol (CA) and ferulic acid (FA), and these model compounds were added to a typical enzymatic hydrolysis of Avicel. The DHP from FA, which was enriched in carboxylic acid groups compared with the DHP from CA, adsorbed a lower mount of cellulases and did not decrease hydrolysis yields when compared to the DHP from CA, which decreased the hydrolysis of Avicel by 8.4%. Thus, increasing the carboxylic acid content of the lignin seemed to significantly decrease the non-productive binding of cellulases and consequently increased the enzymatic hydrolysis of the cellulose. PMID:21246506

Nakagame, Seiji; Chandra, Richard P; Kadla, John F; Saddler, Jack N

2011-03-01

101

Multiple-acid equilibria in adsorption of carboxylic acids from dilute aqueous solution  

SciTech Connect

Equilibria were measured for adsorption of carboxylic acids from aqueous, binary-acid mixtures of lactic and succinic acids and acetic and formic acids onto basic polymeric sorbents. The experimentally determined adsorption isotherms compared well with model predictions, confirming that simple extensions from adsorption of individual acids apply. Fixed-bed studies were carried out that establish the efficacy of chromatographic fractionation of lactic and succinic acids using basic polymeric sorbents. Finally, sequential thermal and solvent regeneration of lactic and acetic acid-laden sorbents was investigated as a method to fractionate among coadsorbed volatile and nonvolatile acids. Essentially complete removal of the acetic acid from the acid-laden sorbent was achieved by vaporization under the conditions used; a small amount of loss of lactic acid (about 11%) was observed.

Husson, S.M.; King, C.J. [Lawrence Berkeley National Lab., CA (United States)] [Lawrence Berkeley National Lab., CA (United States)

1999-02-01

102

Friedel–Crafts acylation reaction using carboxylic acids as acylating agents  

Microsoft Academic Search

Dehydrative Friedel–Crafts acylation reaction of aromatic compounds with carboxylic acids as acylating agents was investigated in the presence of Lewis acid- or Brønsted acid-catalyst. Various metal triflates and bis(trifluoromethanesulfonyl)amides showed catalytic activity at high temperature, among which Eu(NTf2)3 proved to be the most effective and efficiently catalyzed the acylation reaction of alkyl- and alkoxybenzenes with aliphatic and aromatic carboxylic acids

Masato Kawamura; Dong-Mei Cui; Shigeru Shimada

2006-01-01

103

Heat capacity, saturation vapor pressure, and thermodynamic functions of ethyl esters of C3-C5 and C18 carboxylic acids  

NASA Astrophysics Data System (ADS)

The heat capacities of ethyl propanoate (EPr), ethyl n-pentanoate (EPen), and ethyl n-octadecanoate (ethyl stearate, ESt) were measured by vacuum adiabatic calorimetry in the temperature range of 6 to 373 K. Triple point temperatures, fusion enthalpies and entropies, and purity of the samples of the sub-stances under study were determined. The saturation vapor pressures for EPr and EPen were determined by comparative ebulliometry in an atmospheric pressure range of 4.0 to 101.7 kPa. The normal boiling points and vaporization enthalpies vs. temperature were obtained. The standard thermodynamic functions ( S, H, and G) were calculated for the condensed and ideal gas states on the basis of the experimental data. The vapor pressures of the atmospheric range were extrapolated to entire ranges of the liquid phases of EPr and EPen using the principle of corresponding states and the combined processing of pT parameters and low-temperature differences in the heat capacities of an ideal gas and liquid.

Agafonova, L. E.; Varushchenko, R. M.; Druzhinina, A. I.; Polyakova, O. V.; Kolesov, Yu. S.

2011-09-01

104

Influence of cyclic dimer formation on the phase behavior of carboxylic acids.  

PubMed

A new thermodynamic approach based on the Sear and Jackson association theory for doubly bonded dimers [Mol. Phys.1994, 82, 1033] is proposed to describe the thermodynamic properties of carboxylic acids. The new model is able to simultaneously represent the vapor pressures, saturated densities, and vaporization enthalpies of the shortest acids and is in a much better agreement with experimental data than other approaches that do no consider the formation of cyclic dimers. The new model is applied to mixtures of carboxylic acids with nonassociating compounds, and a very good description of the vapor-liquid equilibria in mixtures of alkanes + carboxylic acids is obtained. PMID:22676442

Janecek, Jiri; Paricaud, Patrice

2012-07-12

105

Recovery of carboxylic acids at pH greater than pK{sub a}  

SciTech Connect

Economics of producing carboxylic acids by fermentation is often dominated, not by the fermentation cost, but by the cost of recovering and purifying the acids from dilute aqueous solutions. Experiments were performed to measure uptakes of lactic and succinic acids as functions of pH by basic polymeric sorbents; sorbent regeneration was also tested. Performance at pH > pK{sub a} and regenerability depend on sorbent basicity; apparent pK{sub a} and monomer pK{sub a} can be used to predict sorbent performance. Two basic amine extractants, Alamine 336 and Amberlite LA-2, in were also studied; they are able to sustain capacity to higher pH in diluents that stabilize the acid-amine complex through H bonding. Secondary amines perform better than tert-amines in diluents that solvate the additional proton. Competitive sulfate and phosphate, an interference in fermentation, are taken up by sorbents more strongly than by extractants. The third step in the proposed fermentation process, the cracking of the trimethylammonium (TMA) carboxylate, was also examined. Because lactic acid is more soluble and tends to self-esterify, simple thermal cracking does not remove all TMA; a more promising approach is to esterify the TMA lactate by reaction with an alcohol.

Tung, L.A.

1993-08-01

106

Regeneration of carboxylic acid-amine extracts by back-extraction with an aqueous solution of a volatile amine  

Microsoft Academic Search

Tertiar amines are effective extractants for the recovery of carboxylic acids from aqueous solution. An approach for regeneration and product recovery from such extracts is to back-extract the carboxylic acid with a water-soluble, volatile tertiary amine, such as trimethylamine. The resulting trimethylammonium carboxylate solution can be concentrated and thermally decomposed, yielding the product acid and the volatile amine for recycle.

I. J. Poole; C. Judson King

1991-01-01

107

3922 J. Org. Chem. 1990,55, 3922-3926 Diiodosilane. 3.' Direct Synthesis of Acyl Iodides from Carboxylic Acids,  

E-print Network

Carboxylic Acids, Esters, Lactones, Acyl Chlorides, and Anhydrides E. Keinan* and M. Sahai' Department from variety of carboxylic acid derivatives, such as carboxylic acids,esters,lactones,anhydrides halides have also served as useful precursors for acyl iodides. Acetic anhydride, for instance

Keinan, Ehud

108

Polycarboxylation of carbon nanofibers under Friedel-Crafts condition: A simple route to direct binding of carboxylic functionalities to graphitic ?-system  

NASA Astrophysics Data System (ADS)

The functionalization of carbon nanofibers (CNFs) with oxalyl chloride, via Friedel-Crafts reaction in the presence of aluminum chloride, was first demonstrated as an efficient way to introduce carboxyl groups onto the nanofiber sidewalls. Octa-aminophenylsilsesquioxane (OASQ) was then covalently attached to the carboxylated nanocarbon CNF-(COOH)n through amide linkage. Taking into account the nature of the electrophilic aromatic substitution, this chemical functionalization may involve formation of conjugated carboxylic acid moiety. Structural analysis combined with electron microscopy observation of the robust octasilsesquioxane species show that carboxyl groups are uniformly distributed on the nanofibers surface.

Wu, Jiancheng; Cai, Hualun; Xu, Kai; Fu, Zien; Liu, Xin; Chen, Mingcai; Zhang, Xiuju

2012-11-01

109

Crystal structure and photoluminescence of 7-( N, N'-diethylamino)-coumarin-3-carboxylic acid  

NASA Astrophysics Data System (ADS)

The structure of 7-( N, N'-diethylamino)-coumarin-3-carboxylic acid (DCCA) was verified by single crystal X-ray crystallography. The UV-vis absorption and fluorescence of DCCA were discussed. The compound exhibits strong blue emission under ultraviolet light excitation. The molecular structure of DCCA was optimized using density function theory (DFT) at B3LYP/6-31G level, showing that the optimized geometers parameters are in good agreement with experiment data. In addition, the HOMO and LUMO levels of DCCA were deduced.

Zhang, Hui; Yu, Tianzhi; Zhao, Yuling; Fan, Duowang; Chen, Lili; Qiu, Yongqing; Qian, Long; Zhang, Kai; Yang, Changhui

2008-04-01

110

Crystal structure and photoluminescence of 7-(N,N'-diethylamino)-coumarin-3-carboxylic acid.  

PubMed

The structure of 7-(N,N'-diethylamino)-coumarin-3-carboxylic acid (DCCA) was verified by single crystal X-ray crystallography. The UV-vis absorption and fluorescence of DCCA were discussed. The compound exhibits strong blue emission under ultraviolet light excitation. The molecular structure of DCCA was optimized using density function theory (DFT) at B3LYP/6-31G level, showing that the optimized geometers parameters are in good agreement with experiment data. In addition, the HOMO and LUMO levels of DCCA were deduced. PMID:17656149

Zhang, Hui; Yu, Tianzhi; Zhao, Yuling; Fan, Duowang; Chen, Lili; Qiu, Yongqing; Qian, Long; Zhang, Kai; Yang, Changhui

2008-04-01

111

The first general method for alpha-trifluoromethylation of carboxylic acids using BrF3.  

PubMed

2-Carbomethoxy-1,1-bis(methylsulfide)-1-alkenes, easily made from carboxylic acids, CS(2) and MeI, were treated with BrF(3) producing eventually the desired alpha-trifluoromethyl carboxylate derivatives--RCH(CF(3))COOR'--in good yields. PMID:14973624

Hagooly, Aviv; Rozen, Shlomo

2004-03-01

112

Water Sorption to Hydroxyl and Carboxylic Acid Groups in Carboxymethylcellulose (CMC) Studied with NIR-spectroscopy  

Microsoft Academic Search

In carbohydrate systems which contain polar groups such as hydroxyl and carboxylic acid groups, water molecules are adsorbed in a specific way which varies with the type of polar group. Near infrared Spectroscopy (NIR) combined with multivariate statistical analysis was used to study the interactions between water molecules and carboxymethylated cellulose (CMC) with various degrees of substitution of the carboxylic

Jesper Berthold; Ralf J. O. Olsson; Lennart Salmén

1998-01-01

113

Photophysics of indole-2-carboxylic acid (I2C) and indole-5-carboxylic acid (I5C): heavy atom effect.  

PubMed

In this study the effect of carboxylic group substitution in the 2 and 5 position of indole ring on the photophysics of the parent indole chromophore has been studied. The photophysical parameters crucial in triplet state decay mechanism of aqueous indole-2-carboxylic acid (I2C) and indole-5-carboxylic acid (I5C) have been determined applying our previously proposed methodology based on the heavy atom effect and fluorescence and phosphorescence decay kinetics [Kowalska-Baron et al., 2012]. The determined time-resolved phosphorescence spectra of I2C and I5C are red-shifted as compared to that of the parent indole. This red-shift was especially evident in the case of I2C and may indicate the possibility of hydrogen bonded complex formation incorporating carbonyl CO, the NH group of I2C and, possibly, surrounding water molecules. The possibility of the excited state charge transfer process and the subsequent electronic charge redistribution in such a hydrogen bonded complex may also be postulated. The resulting stabilization of the I2C triplet state is manifested by its relatively long phosphorescence lifetime in aqueous solution (912 ?s). The relatively short phosphorescence lifetime of I5C (56 ?s) may be the consequence of more effective ground-state quenching of I5 C triplet state. This hypothesis may be strengthened by the significantly larger value of the determined rate constant of I5C triplet state quenching by its ground-state (4.4 × 10(8)M(-1)s(-1)) as compared to that for indole (6.8 × 10(7)M(-1)s(-1)) and I2C (2.3 × 10(7)M(-1)s(-1)). The determined bimolecular rate constant for triplet state quenching by iodide [Formula: see text] is equal to 1 × 10(4)M(-1)s(-1); 6 × 10(3)M(-1)s(-1) and 2.7 × 10(4)M(-1)s(-1) for indole, I2 C and I5 C, respectively. In order to obtain a better insight into iodide quenching of I2C and I5C triplet states in aqueous solution, the temperature dependence of the bimolecular rate constants for iodide quenching of the triplet states has been expressed in Arrhenius form. The linearity of the obtained Arrhenius plots clearly indicated the existence of one temperature-dependent non-radiative process for the de-excitation of I2C and I5C triplet state in the presence of iodide. This process may be attributed to the solute-quenching by iodide and, most probably, proceeds via reversibly formed exciplex. The activation energies obtained from linear Arrhenius plots (1.89 kcal/mol for I5 C; 2.55 kcal/mol for I2 C) are smaller as compared to that for diffusion controlled reactions in aqueous solution (about 4 kcal/mol), which may indicate the great importance of the electrostatic interactions between solute and iodide ions in lowering the energy barrier needed for the formation of the triplet-quencher complex. Based on the theoretical predictions (at the DFT(CAM-B3LYP)/6-31+G(d,p) level of theory) and careful analysis of the obtained FTIR spectra it may be concluded that in the solid state I2 C and I5 C molecules form associates by intermolecular NH · · · OC and OH · · · OC hydrogen bonding interactions, whereas the existence of intramolecular NH · · · OC interactions in the solid state of I2C and I5C is highly unlikely. PMID:23933843

Kowalska-Baron, Agnieszka; Ga??cki, Krystian; Wysocki, Stanis?aw

2013-12-01

114

Novel Regenerated Solvent Extraction Processes for the Recovery of Carboxylic Acids or Ammonia from Aqueous Solutions Part I. Regeneration of Amine-Carboxylic Acid Extracts  

SciTech Connect

Two novel regenerated solvent extraction processes are examined. The first process has the potential to reduce the energy costs inherent in the recovery of low-volatility carboxylic acids from dilute aqueous solutions. The second process has the potential for reducing the energy costs required for separate recovery of ammonia and acid gases (e.g. CO{sub 2} and H{sub 2}S) from industrial sour waters. The recovery of carboxylic acids from dilute aqueous solution can be achieved by extraction with tertiary amines. An approach for regeneration and product recovery from such extracts is to back-extract the carboxylic acid with a water-soluble, volatile tertiary amine, such as trimethylamine. The resulting trimethylammonium carboxylate solution can be concentrated and thermally decomposed, yielding the product acid and the volatile amine for recycle. Experimental work was performed with lactic acid, succinic acid, and fumaric acid. Equilibrium data show near-stoichiometric recovery of the carboxylic acids from an organic solution of Alamine 336 into aqueous solutions of trimethylamine. For fumaric and succinic acids, partial evaporation of the aqueous back extract decomposes the carboxylate and yields the acid product in crystalline form. The decomposition of aqueous solutions of trimethylammonium lactates was not carried out to completion, due to the high water solubility of lactic acid and the tendency of the acid to self-associate. The separate recovery of ammonia and acid gases from sour waters can be achieved by combining steam-stripping of the acid gases with simultaneous removal of ammonia by extraction with a liquid cation exchanger. The use of di-2,4,4-trimethylpentyl phosphinic acid as the liquid cation exchanger is explored in this work. Batch extraction experiments were carried out to measure the equilibrium distribution ratio of ammonia between an aqueous buffer solution and an organic solution of the phosphinic acid (0.2N) in Norpar 12. The concentration-based distribution ratios increase from 0.11 to 0.46 as the aqueous phase pH increases from 7.18 to 8.15. Regeneration of the organic extractant solution was carried out by stripping at elevated temperatures to remove the ammonia, with 99% recovery of the ammonia being obtained at 125 C.

Poole, L.J.; King, C.J.

1990-03-01

115

Biological Roles and Therapeutic Potential of Hydroxy-Carboxylic Acid Receptors  

PubMed Central

In the recent past, deorphanization studies have described intermediates of energy metabolism to activate G protein-coupled receptors and to thereby regulate metabolic functions. GPR81, GPR109A, and GPR109B, formerly known as the nicotinic acid receptor family, are encoded by clustered genes and share a high degree of sequence homology. Recently, hydroxy-carboxylic acids were identified as endogenous ligands of GPR81, GPR109A, and GPR109B, and therefore these receptors have been placed into a novel receptor family of hydroxy-carboxylic acid (HCA) receptors. The HCA1 receptor (GPR81) is activated by the glycolytic metabolite 2-hydroxy-propionic acid (lactate), the HCA2 receptor is activated by the ketone body 3-hydroxy-butyric acid, and the HCA3 receptor (GPR109B) is a receptor for the ?-oxidation intermediate 3-hydroxy-octanoic acid. While HCA1 and HCA2 receptors are present in most mammalian species, the HCA3 receptor is exclusively found in humans and higher primates. HCA receptors are expressed in adipose tissue and mediate anti-lipolytic effects in adipocytes through Gi-type G protein-dependent inhibition of adenylyl cyclase. HCA2 and HCA3 inhibit lipolysis during conditions of increased ?-oxidation such as prolonged fasting, whereas HCA1 mediates the anti-lipolytic effects of insulin in the fed state. As HCA2 is a receptor for the established anti-dyslipidemic drug nicotinic acid, HCA1 and HCA3 also represent promising drug targets and several synthetic ligands for HCA receptors have been developed. In this article, we will summarize the deorphanization and pharmacological characterization of HCA receptors. Moreover, we will discuss recent progress in elucidating the physiological and pathophysiological role to further evaluate the therapeutic potential of the HCA receptor family for the treatment of metabolic disease. PMID:22654812

Ahmed, Kashan

2011-01-01

116

The effect of carboxylic acid anions on the stability of framework mineral grains in petroleum reservoirs  

SciTech Connect

This paper presents experimental and empirical evidence to show that carboxylic acid anions (CAA's) are a major diagenetic control on first-cycle basins in Jurassic-to-Pleistocene reservoirs in the 80-to-120{degrees}C thermal window.

MacGowan, D.B.; Surdam, R.C.; Ewing, R.E. (Wyoming Univ., Laramie, WY (USA))

1990-06-01

117

Simple coupling chemistry linking carboxyl-containing organic molecules to silicon oxide surfaces under acidic conditions.  

PubMed

The coupling chemistry of carboxymethylated amylose with organo-silanized silicon oxide surfaces at pH 7.4 and 2.0 was investigated using atomic force microscopy (AFM) based single-molecule force spectroscopy. At close to neutral pH, carbodiimide activation of a carboxylic acid affords formation of an amide bond with an amino surface linker. At pH 2.0, no activation with carbodiimide was required to anchor carboxymethylated amylose between an AFM tip and a glass substrate. At the same time, the mean bond rupture force f(r) dropped from 1.65 ± 0.37 nN at pH 7.4 to 1.39 ± 0.30 nN at pH 2.0 without carbodiimide, indicating that a different link to the surface can be formed at low pH. The coupling mechanism at pH 2.0 was elucidated by a series of experiments, in which the surface was functionalized with four different organosilanes, each containing characteristic functional groups. The results are rationalized with an acid-catalyzed ester condensation between a carboxyl group and a free, unreacted silanol group in the surface anchor or on the surface. PMID:20822126

Schmidt, Sebastian W; Christ, Timo; Glockner, Christian; Beyer, Martin K; Clausen-Schaumann, Hauke

2010-10-01

118

Synthesis of crambescin B carboxylic acid, a potent inhibitor of voltage-gated sodium channels.  

PubMed

The stereocontrolled synthesis of a racemic carboxylic acid of crambescin B, a marine alkaloid, is described. The synthesis features two highly stereoselective reactions: (I) palladium-catalyzed hydroxymethylation of an alkynyl aziridine having an N-guanidino group and (II) cascade bromocyclization providing a spiro-hemiaminal structure. The cell-based colorimetric assay showed that the synthesized carboxylic acid exhibited a potent inhibitory activity on voltage-gated sodium channels. PMID:24216693

Nakazaki, Atsuo; Ishikawa, Yuki; Sawayama, Yusuke; Yotsu-Yamashita, Mari; Nishikawa, Toshio

2014-01-01

119

Direct Catalytic Anti-Markovnikov Addition of Carboxylic Acids to Alkenes  

PubMed Central

A direct catalytic anti-Markovnikov addition of carboxylic acids to alkenes is reported. The catalyst system is comprised of the Fukuzumi acridinium photooxidant (1) and a substoichiometric quantity of a hydrogen atom donor. Oxidizable olefins such as styrenes, trisubstituted aliphatic alkenes, and enamides can be employed along with a variety of carboxylic acids to afford the anti-Markovnikov addition adducts exclusively. A deuterium-labeling experiment lends insight to the potential mechanism. PMID:23808532

Perkowski, Andrew J.

2013-01-01

120

The conversion of corn stover and pig manure to carboxylic acids with the MixAlco process  

E-print Network

The MixAlco process, developed by Dr. Mark T. Holtzapple, uses anaerobic fermentation to convert waste biomass into carboxylate salts which can then be manipulated into carboxylic acids, ketones and alcohols. This project focuses on the application...

Black, Amanda Spring

2013-02-22

121

Studies on technetium and some carboxylic and hydroxamic acids  

Microsoft Academic Search

Interactions between technetium and salicylic acid, oxalic acid, gentisic acid, dipicolinic acid, pyridine-2,5-dicarboxylic acid, salicylhydroxamic acid, dipicolindihydroxamic acid and 5-methoxycarbonyl-2-pyridinehydroxamic acid are described. The complexation reactions have been investigated (pH, , stability, stoichiometry) and the results obtained have been comparatively evaluated.

F. Grases; G. Far; J. G. March

1985-01-01

122

Carboxylic acids in secondary aerosols from oxidation of cyclic monoterpenes by ozone  

SciTech Connect

A series of smog chamber experiments have been conducted in which five cyclic monoterpenes were oxidized by ozone. The evolved secondary aerosol was analyzed by GC-MS and HPLC-MS for nonvolatile polar oxidation products with emphasis on the identification of carboxylic acids. Three classes of compounds were determined at concentration levels corresponding to low percentage molar yields: i.e., dicarboxylic acids, oxocarboxylic acids, and hydroxyketocarboxylic acids. Carboxylic acids are highly polar and have lower vapor pressures than their corresponding aldehydes and may thus play an important role in secondary organic aerosol formation processes. The most abundant carboxylic acids were the following: cis-pinic acid AB1(cis-3-carboxy-2,2-dimethylcyclobutylethanoic acid) from {alpha} and {beta}-pinene; cis-pinonic acid A3 (cis-3-acetyl-2,2-dimethylcyclobutylethanoic acid) and cis-10-hydroxypinonic acid Ab6 (cis-2,2-dimethyl-3-hydroxyacetylcyclobutyl-ethanoic acid) from {alpha}-pinene and {beta}-pinene; cis-3-caric acid C1 (cis-2,2-dimethyl-1,3-cyclopropyldiethanoic acid), cis-3-caronic acid C3 (2,2-dimethyl-3-(2-oxopropyl)cyclopropanylethanoic acid), and cis-10-hydroxy-3-caronic acid C6 (cis-2,2-dimethyl-3(hydroxy-2-oxopropyl)cyclopropanylethanoic acid) from 3-carene; cis-sabinic acid S1 (cis-2-carboxy-1-isopropylcyclopropylethanoic acid) from sabinene; limonic acid L1 (3-isopropenylhexanedioic acid), limononic acid L3 (3-isopropenyl-6-oxo-heptanoic acid), 7-hydroxy-limononic acid L6 (3-isopropenyl-7-hydroxy-6-oxoheptanoic acid), and 7-hydroxylimononic acid Lg{prime} (7-hydroxy-3-isopropenyl-6-oxoheptanoic acid) from limonene.

Glasius, M.; Lahaniati, M.; Calogirou, A.; Di Bella, D.; Jensen, N.R.; Hjorth, J.; Kotzias, D.; Larsen, B.R.

2000-03-15

123

Adsorption of water vapor and carbon dioxide at carboxylic functional groups on the surface of coal  

Microsoft Academic Search

The adsorption of water vapor and carbon dioxide at room temperature in relation to carboxylic functional groups on the surfaces of 20 different types of coal was examined.The carboxylic functional groups on the surface of coal may be considered the preferential sites of adsorption when compared with the other groups. The adsorption of water vapor and carbon dioxide was found

J Nishino

2001-01-01

124

Measuring the concentration of carboxylic acid groups in torrefied spruce wood.  

PubMed

Torrefaction is moderate thermal treatment (?200-300°C) to improve the energy density, handling and storage properties of biomass fuels. In biomass, carboxylic sites are partially responsible for its hygroscopic. These sites are degraded to varying extents during torrefaction. In this paper, we apply methylene blue sorption and potentiometric titration to measure the concentration of carboxylic acid groups in spruce wood torrefied for 30min at temperatures between 180 and 300°C. The results from both methods were applicable and the values agreed well. A decrease in the equilibrium moisture content at different humidity was also measured for the torrefied wood samples, which is in good agreement with the decrease in carboxylic acid sites. Thus both methods offer a means of directly measuring the decomposition of carboxylic groups in biomass during torrefaction as a valuable parameter in evaluating the extent of torrefaction which provides new information to the chemical changes occurring during torrefaction. PMID:22940339

Khazraie Shoulaifar, Tooran; Demartini, Nikolai; Ivaska, Ari; Fardim, Pedro; Hupa, Mikko

2012-11-01

125

Adsorption of pesticidal compounds bearing a single carboxyl functional group and biogenic amines by humic fraction-immobilized silica gel.  

PubMed

Fractions collected from humic acids under acidic and basic conditions were immobilized on silica gel and used as adsorbents for a variety of agricultural pesticide compounds bearing a single carboxyl functional group and biogenic amines in acetonitrile. Among these compounds examined under the same conditions, the percentage of adsorption varies considerably from 0 to almost 100%. The percentage is found to be highly related to the structure of the analyte and the type of functional group attached to it. The adsorption, better performed on adsorbent immobilized with the fraction collected under acidic conditions, is believed to result from the reversible interaction between the functional moieties of the analyte and humic acids (e.g., amino or carboxyl group of analyte vs carboxyl group of humic acids, etc.) as no adsorption is observed under the same conditions for analytes that are derivatives of alcohol, amide, and ester. Given the nature of the analyte, the time needed to reach the maximum percent of adsorption decreases as the amount of adsorbent is increased. Also, the longer the time that has elapsed, the higher the percentage of analyte adsorbed, thus indicating that the adsorption process is surface-oriented. Factors such as the acidic or basic origin of the additive in the liquid phase of the matrix also affect the percentage of analyte adsorbed. PMID:23521499

Chen, Cheng-Sheng; Chen, Shushi

2013-04-17

126

Discovery of a Novel Series of CRTH2 (DP2) Receptor Antagonists Devoid of Carboxylic Acids.  

PubMed

Antagonism of the CRTH2 receptor represents a very attractive target for a variety of allergic diseases. Most CRTH2 antagonists known to date possess a carboxylic acid moiety, which is essential for binding. However, potential acid metabolites O-acyl glucuronides might be linked to idiosynchratic toxicity in humans. In this communication, we describe a new series of compounds that lack the carboxylic acid moiety. Compounds with high affinity (K i < 10 nM) for the receptor have been identified. Subsequent optimization succeeded in reducing the high metabolic clearance of the first compounds in human and rat liver microsomes. At the same time, inhibition of the CYP isoforms was optimized, giving rise to stable compounds with an acceptable CYP inhibition profile (IC50 CYP2C9 and 2C19 > 1 ?M). Taken together, these data show that compounds devoid of carboxylic acid groups could represent an interesting alternative to current CRTH2 antagonists in development. PMID:24900284

Crosignani, Stefano; Jorand-Lebrun, Catherine; Campbell, Gordon; Prêtre, Adeline; Grippi-Vallotton, Tania; Quattropani, Anna; Bouscary-Desforges, Gwenaelle; Bombrun, Agnes; Missotten, Marc; Humbert, Yves; Frémaux, Christèle; Pâquet, Mikaël; El Harkani, Kamel; Bradshaw, Charles G; Cleva, Christophe; Abla, Nada; Daff, Hamina; Schott, Olivier; Pittet, Pierre-André; Arrighi, Jean-François; Gaudet, Marilène; Johnson, Zoë

2011-12-01

127

Carboxylic acids in crystallization of macromolecules: learning from successful crystallization experiments.  

PubMed

The production of macromolecular crystals suitable for structural analysis is one of the most important and limiting steps in the structure determination process. Often, preliminary crystallization trials are performed using hundreds of empirically selected conditions. Carboxylic acids and/or their salts are one of the most popular components of these empirically derived crystallization conditions. Our findings indicate that almost 40 % of entries deposited to the Protein Data Bank (PDB) reporting crystallization conditions contain at least one carboxylic acid. In order to analyze the role of carboxylic acids in macromolecular crystallization, a large-scale analysis of the successful crystallization experiments reported to the PDB was performed. The PDB is currently the largest source of crystallization data, however it is not easily searchable. These complications are due to a combination of a free text format, which is used to capture information on the crystallization experiments, and the inconsistent naming of chemicals used in crystallization experiments. Despite these difficulties, our approach allows for the extraction of over 47,000 crystallization conditions from the PDB. Initially, the selected conditions were investigated to determine which carboxylic acids or their salts are most often present in crystallization solutions. From this group, selected sets of crystallization conditions were analyzed in detail, assessing parameters such as concentration, pH, and precipitant used. Our findings will lead to the design of new crystallization screens focused around carboxylic acids. PMID:24452510

Offermann, Lesa R; He, John Z; Mank, Nicholas J; Booth, William T; Chruszcz, Maksymilian

2014-03-01

128

A novel derivatization reagent possessing a bromoquinolinium structure for biological carboxylic acids in HPLC-ESI-MS/MS.  

PubMed

A novel bromoquinolinium reagent, i.e. 1-(3-aminopropyl)-3-bromoquinolinium bromide (APBQ), was synthesized for the analysis of carboxylic acids. A simple and practical precolumn derivatization procedure using the APBQ in RP chromatography and MS (HPLC-MS) has been developed using bile acids and free fatty acids, as the representative carboxylic acids in biological samples. The APBQ efficiently reacted with carboxylic acids at 60°C for 60 min in the presence of N,N-dicyclohexylcarbodiimide and pyridine as the activation reagents. Because the APBQ possesses a bromine atom in the structure, the identification of a series of carboxylic acids was easily achieved due to the characteristic bromine isotope pattern in the mass spectra. The APBQ also has a quaternary amine structure, thus the positively charged derivatives are predominate for the highly sensitive detection of carboxylic acids. The APBQ was successfully applied to the selective determination of biological carboxylic acids in human plasma. The bile acids (chenodeoxycholic acid and deoxycholic acid) and several saturated (stearic acid and palmitic acid) and unsaturated free fatty acids (oleic acid and linoleic acid) were reasonably determined by HPLC-MS under the proposed procedure. Based on the results of analyses of human plasma and saliva, the proposed procedure using APBQ seems to be applicable for the qualitative and quantitative analyses of a series of carboxylic acids in biological samples. PMID:23568887

Mochizuki, Yuko; Inagaki, Shinsuke; Suzuki, Mayu; Min, Jun Zhe; Inoue, Koichi; Todoroki, Kenichiro; Toyo'oka, Toshimasa

2013-06-01

129

S-Adenosyl-L-Methionine:Salicylic Acid Carboxyl Methyltransferase, an Enzyme Involved in Floral Scent  

E-print Network

S-Adenosyl-L-Methionine:Salicylic Acid Carboxyl Methyltransferase, an Enzyme Involved in Floral Arbor, Michigan 48109 Received February 10, 1998, and in revised form April 14, 1999 S-Adenosyl-L-methionine:salicylic compound in C. breweri, from salicylic acid and S-adenosyl-L-methionine (SAM). The native en- zyme

Pichersky, Eran

130

Chelation ion chromatography of metal ions using high performance substrates dynamically modified with heterocyclic carboxylic acids  

Microsoft Academic Search

This study shows that stable high efficiency metal chelating substrates can be formed from neutral stationary phases by dynamically loading with low molecular weight complexing agents present in the mobile phase. Three complexing pyridine carboxylic acids, namely, picolinic, dipicolinic and quinaldic acids were used to dynamically coat both a C18silica gel and a polystyrene resin and the separation performance compared

M. J Shaw; S. J Hill; P Jones

1999-01-01

131

Novel 5-substituted benzyloxy-2-arylbenzofuran-3-carboxylic acids as calcium activated chloride channel inhibitors.  

PubMed

Transmembrane protein 16A (TMEM16A) channels are recently discovered membrane proteins that functions as a calcium activated chloride channel (CaCC). CaCCs are major regulators of various physiological processes, such as sensory transduction, epithelial secretion, smooth muscle contraction and oocyte fertilization. Thirty novel 5-substituted benzyloxy-2-arylbenzofuran-3-carboxylic acids (B01-B30) were synthesized and evaluated for their TMEM16A inhibitory activity by using short circuit current measurements in Fischer rat thyroid (FRT) cells expressing human TMEM16A. IC(50) values were calculated using YFP fluorescence plate reader assay. Final compounds, having free carboxylic group displayed significant inhibition. Eight of the novel compounds B02, B13, B21, B23, B25, B27, B28, B29 exhibit excellent CaCCs inhibition with IC(50) value <6 ?M, with compound B25 exhibiting the lowest IC(50) value of 2.8 ± 1.3 ?M. None of the tested ester analogs of final benzofuran derivatives displayed TMEM16A/CaCCs inhibition. PMID:22739085

Kumar, Satish; Namkung, Wan; Verkman, A S; Sharma, Pawan K

2012-07-15

132

Photoelectron spectra of some antibiotic building blocks: 2-azetidinone and thiazolidine-carboxylic acid.  

PubMed

X-ray photoelectron spectra of the core and valence levels of the fundamental building blocks of ?-lactam antibiotics have been investigated and compared with theoretical calculations. The spectra of the compounds 2-azetidinone and the 2- and 4-isomers of thiazolidine-carboxylic acid are interpreted in the light of theoretical calculations. The spectra of the two isomers of thiazolidine-carboxylic acid are rather similar, as expected, but show clear effects due to isomerization. Both isomers are analogues of proline, which is well-known to populate several low energy conformers in the gas phase. We have investigated the low energy conformers of thiazolidine-4-carboxylic acid theoretically in more detail and find some spectroscopic evidence that multiple conformers may be present. The measured valence levels are assigned for all three compounds, and the character of the frontier orbitals is identified and analyzed. PMID:22799571

Ahmed, Marawan; Ganesan, Aravindhan; Wang, Feng; Feyer, Vitaliy; Plekan, Oksana; Prince, Kevin C

2012-08-23

133

Evidence for 1-(Malonylamino)cyclopropane-1Carboxylic Acid Being the Major Conjugate of Aminocyclopropane-1- Carboxylic Acid in Tomato Fruit1  

Microsoft Academic Search

Tomato (Lycopersicon esculentum Miller) fruit discs fed with (2,3-14C)1-aminocyclopropane-1-carboxylic acid (ACC) formed 1-malonyl-ACC (MACC) as the major conjugate of ACC in fruit throughout all ripening stages, from immature-green through the red-ripe stage. Another conjugate of ACC, g-glutamyl-ACC (GACC), was formed only in mature-green fruit in an amount about 10% of that of MACC; conjugation of ACC into GACC was not

Galen Peiser; Shang Fa Yang

134

Hydrogen bonds in 1:1 complex of piperidine-3-carboxylic acid with salicylic acid  

NASA Astrophysics Data System (ADS)

The 1:1 complex between the zwitterionic piperidinium-3-carboxylate (P3C) and salicylic acid (SAL), P3C·SAL, has been characterized by single crystal X-ray analysis, FTIR and NMR spectroscopy, and by DFT calculations. The crystals are orthorhombic, space group Pbca, with a = 11.6477(7), b = 9.1754(6), c = 23.5833(12) Å. An O sbnd H⋯O bridge (2.537(1) Å) links the SAL and P3C moieties. The proton in this H bond is located closer to the salicylic carboxylate group. In the P3C moiety, the piperidine ring adopts the chair conformation, and the carboxylate group is in the axial orientation and is stabilized by an intramolecular N +sbnd H⋯O hydrogen bond of 2.847(1) Å. In the crystal packing, two P3C·SAL units form a centrosymmetric dimer through a pair of intermolecular N +sbnd H⋯O bonds of 2.801(1) Å. The dimers form a zigzag chain linked via another N +sbnd H⋯O bond (2.799(1) Å). In the structures of the monomeric [P3C·SAL] and dimeric [(P3C·SAL) 2] species optimized by B3LYP/6-31G(d,p) calculations, both the inter- and intra-molecular hydrogen bonds are shorter than in the crystal. The FTIR spectrum shows a broad absorption in the 3100-2400 cm -1 region attributed to ?NH and ?OH vibrations. The broad absorption in the 1500-600 cm -1 region is attributed to the O sbnd H·O hydrogen bonds. The 1H and 13C NMR spectra have been analyzed to elucidate the structure of the P3C·SAL complex in solution. The GIAO magnetic isotropic shielding tensors have been used to predict the 1H and 13C chemical shifts in DMSO solution.

Bartoszak-Adamska, El?bieta; Dega-Szafran, Zofia; Krociak, Magdalena; Jaskolski, Mariusz; Szafran, Miros?aw

2009-02-01

135

Isothiocoumarin-3-carboxylic acid derivatives: synthesis, anticancer and antitrypanosomal activity evaluation.  

PubMed

A series of new isothiocoumarin-3-carboxylic acids derivatives had been obtained based on the 5-arylidenerhodanines hydrolysis. Anticancer activity screening allowed identification of 7,8-dimethoxy-1-oxo-1H-isothiochromene-3-carboxylic acid (4-phenylthiazol-2-yl)-amide (30) with the highest level of antimitotic activity (GI50NCI-H322M/NSC Lung Cancer = 1.28 ?M). Evaluation of the antitrypanosomal activity against Trypanosoma brucei brucei showed that investigated compounds did not exhibit significant antiparasitic effects. Additionally, the most pharmacologically attractive compounds were non-toxic and well tolerated by the experimental animals. PMID:24530491

Kaminskyy, Danylo; Kryshchyshyn, Anna; Nektegayev, Ihor; Vasylenko, Olexandr; Grellier, Philippe; Lesyk, Roman

2014-03-21

136

Nucleosides of 4-methylthio-1,2,3-triazol-5-yl-carboxylic acid derivatives  

SciTech Connect

2-..beta..-D-Ribofuranosyl-4-methylthio-5-methoxycarbonyl-1,2,3-triazole was obtained by fusing 4-methylthio-5-methoxycarbonyl-1,2,3-triazole together with tetraacyl-D-ribofuranose, followed by deacylation, and its amide and hydrazide were prepared. The structures of the new nucleosides were established by converting them into known 2-nucleosides of 1,2,3-triazol-4-yl-carboxylic acid derivatives. By comparing PMR spectra with previously reported PMR spectra for the isomeric 1- and 2-nucleosides of 1,2,3-triazol-4-yl-carboxylic acid derivatives, the synthesized nucleosides could be assigned to 2-substituted triazoles.

Shingarova, I.D.; Yartseva, I.V.; Preobrazhenskaya, M.N.

1987-08-01

137

Regeneration of carboxylic acid-amine extracts by back-extraction with an aqueous solution of a volatile amine  

SciTech Connect

Tertiar amines are effective extractants for the recovery of carboxylic acids from aqueous solution. An approach for regeneration and product recovery from such extracts is to back-extract the carboxylic acid with a water-soluble, volatile tertiary amine, such as trimethylamine. The resulting trimethylammonium carboxylate solution can be concentrated and thermally decomposed, yielding the product acid and the volatile amine for recycle. In this paper, equilibrium data are presented that show near-stoichiometric recovery of carboxylic acids for amine extracts. For rumaric and succinic acids, partial evaporation of the aqueous back-extract decomposes the carboxylate and yields the acid product in crystalline form. The decomposition of aqueous solutions of trimethylammonium lactates stops short of forming the acid product, because of its greater water solubility and tendency for self-association. Methods of further purifying the crystals are evaluated along the processing implications of the results.

Poole, I.J.; King, C.J. (Dept. of Chemical Engineering and Lawrence Berkeley Lab., Univ. of California, Berkeley, CA (US))

1991-05-01

138

The Dechlorination of Pentachlorophenol by Zerovalent Iron in Presence of Carboxylic Acids  

Microsoft Academic Search

The dechlorination of pentachlorophenol (PCP) by zerovalent iron (Fe0) in presence of low molecular weight carboxylic acids was investigated. The experimental results showed that oxalic acid\\u000a was advantaged among the selected acids for the dechlorination of PCP. The lower pH value and the higher dosage of Fe0 were favorable for the enhancement of dechlorination efficiency. With their strong complexing and

Meifang Hou; Hongfu Wan; Qixing Zhou; Xinming Liu; Wei Luo; Yanning Fan

2009-01-01

139

Oxidation of heterocyclic and aromatic aldehydes to the corresponding carboxylic acids by Acetobacter and Serratia strains  

Microsoft Academic Search

Conversion of heterocyclic and aromatic aldehydes to the corresponding carboxylic acids was carried out using Acetobacter rancens IFO3297, A. pasteurianus IFO13753 and Serratia liquefaciens LF14. IFO3297 produced 110g 2-furoic acid l-1 from furfural with a 95% molar yield. 5-Hydroxymethyl-2-furancarboxylic acid was produced from the corresponding aldehyde by using whole cells LF14. IFO13753 and LF14 both converted isophthalaldehyde, 2,5-furandicarbaldehyde, 2,5-thiophenedicarbaldehyde and

Koichi Mitsukura; Yukihide Sato; Toyokazu Yoshida; Toru Nagasawa

2005-01-01

140

Low molecular weight carboxylic acids in an urban atmosphere: Winter measurements in São Paulo City, Brazil  

Microsoft Academic Search

Atmospheric gas and particle-phase carboxylic acids were measured during July 1996, Winter, in an urban area of São Paulo, a highly polluted Latin American city. Ion chromatography and capillary electrophoresis techniques were used to determine the species. As oxalic (36.2±21.4%), pyruvic (15.0±7.9%), ?-hydroxy-butyric (9.15±9.00%) and glycolic (3.55±2.26%) acids were determined in aerosol particles, formic and acetic acids were determined both

Silvia R. Souza; Pérola C. Vasconcellos; Lilian R. F. Carvalho

1999-01-01

141

Interconversion of biologically important carboxylic acids by radiation  

NASA Technical Reports Server (NTRS)

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.

Negron-Mendoza, A.; Ponnamperuma, C.

1978-01-01

142

Difference in Amounts between Titratable Acid and Total Carboxylic Acids Produced by Oral Streptococci during Sugar Metabolism  

Microsoft Academic Search

The acid produced by the resting cells of Streptococcus mutans NCTC 10449 and HS 6 and S. sanguis ATCC 10556 during sugar metabolism was estimated with a pH-stat and a carboxylic acid analyzer. Lactic, formic, acetic, pyruvic, and carbonic acids were detected in the reaction mixtures, but propionic, citric, succinic, iso-butyric, butyric, iso-valeric, and valeric acids were not detected. The

Y. Iwami; S. Hata; N. Takahashi; T. Yamada

1989-01-01

143

Templating route for mesostructured calcium phosphates with carboxylic acid- and amine-type surfactants.  

PubMed

Mesostructured calcium phosphates constructed by ionic frameworks were synthesized using carboxylic acid- and amine-type surfactants in mixed solvent systems of ethanol and water. A lamellar mesostructured calcium phosphate was prepared using palmitic acid as an anionic surfactant, as in the case using n-alkylamines. A wormhole-like mesostructured calcium phosphate can be obtained using dicarboxyl N-lauroyl- l-glutamic acid, whose headgroup is larger than that of palmitic acid. Similar mesostructured product was obtained using 4-dodecyldiethylenetriamine with a large headgroup containing two primary amine groups. Interactions of carboxyl and primary amino groups in the surfactant molecules with inorganic species are quite important for the formation of mesostructured calcium phosphates. The Ca/P molar ratio of mesostructured calcium phosphates was strongly affected by the molecular structure of surfactants containing carboxyl and primary amino groups. Ca-rich materials can be obtained using carboxylic acid-type surfactants (Ca/P approximately 1.7) rather than amine-type surfactants (Ca/P approximately 1.0). PMID:18947246

Ikawa, Nobuaki; Hori, Hideki; Kimura, Tatsuo; Oumi, Yasunori; Sano, Tsuneji

2008-11-18

144

Cofactor balance by nicotinamide nucleotide transhydrogenase (NNT) coordinates reductive carboxylation and glucose catabolism in the tricarboxylic acid (TCA) cycle.  

PubMed

Cancer and proliferating cells exhibit an increased demand for glutamine-derived carbons to support anabolic processes. In addition, reductive carboxylation of ?-ketoglutarate by isocitrate dehydrogenase 1 (IDH1) and 2 (IDH2) was recently shown to be a major source of citrate synthesis from glutamine. The role of NAD(P)H/NAD(P)(+) cofactors in coordinating glucose and glutamine utilization in the tricarboxylic acid (TCA) cycle is not well understood, with the source(s) of NADPH for the reductive carboxylation reaction remaining unexplored. Nicotinamide nucleotide transhydrogenase (NNT) is a mitochondrial enzyme that transfers reducing equivalents from NADH to NADPH. Here, we show that knockdown of NNT inhibits the contribution of glutamine to the TCA cycle and activates glucose catabolism in SkMel5 melanoma cells. The increase in glucose oxidation partially occurred through pyruvate carboxylase and rendered NNT knockdown cells more sensitive to glucose deprivation. Importantly, knocking down NNT inhibits reductive carboxylation in SkMel5 and 786-O renal carcinoma cells. Overexpression of NNT is sufficient to stimulate glutamine oxidation and reductive carboxylation, whereas it inhibits glucose catabolism in the TCA cycle. These observations are supported by an impairment of the NAD(P)H/NAD(P)(+) ratios. Our findings underscore the role of NNT in regulating central carbon metabolism via redox balance, calling for other mechanisms that coordinate substrate preference to maintain a functional TCA cycle. PMID:23504317

Gameiro, Paulo A; Laviolette, Laura A; Kelleher, Joanne K; Iliopoulos, Othon; Stephanopoulos, Gregory

2013-05-01

145

Preferential Interaction of Na+ over K+ to Carboxylate-functionalized Silver Nanoparticles  

EPA Science Inventory

Elucidating mechanistic interactions between specific ions (Na+/ K+) and nanoparticle surfaces to alter particle stability in polar media has received little attention. We investigated relative preferential binding of Na+ and K+ to carboxylate-functionalized silver nanoparticles ...

146

Three closely related dibenzazepine carboxylic acids: hydrogen-bonded aggregation in one, two and three dimensions.  

PubMed

In the structure of (6R*,11R*)-5-acetyl-11-ethyl-6,11-dihydro-5H-dibenzo[b,e]azepine-6-carboxylic acid, C19H19NO3, (I), the molecules are linked into sheets by a combination of O-H...O and C-H...O hydrogen bonds; in the structure of the monomethyl analogue (6RS,11SR)-5-acetyl-11-ethyl-2-methyl-6,11-dihydro-5H-dibenzo[b,e]azepine-6-carboxylic acid, C20H21NO3, (II), the molecules are linked into simple C(7) chains by O-H...O hydrogen bonds; and in the structure of the dimethyl analogue (6RS,11SR)-5-acetyl-11-ethyl-1,3-dimethyl-6,11-dihydro-5H-dibenzo[b,e]azepine-6-carboxylic acid, C21H23NO3, (III), a combination of O-H...O, C-H...O and C-H...?(arene) hydrogen bonds links the molecules into a three-dimensional framework structure. None of these structures exhibits the R2(2)(8) dimer motif characteristic of simple carboxylic acids. PMID:24594729

Sanabría, Carlos M; Palma, Alirio; Cobo, Justo; Glidewell, Christopher

2014-03-01

147

Qualitative identification of carboxylic acids, boronic acids, and amines using cruciform fluorophores.  

PubMed

Molecular cruciforms are X-shaped systems in which two conjugation axes intersect at a central core. If one axis of these molecules is substituted with electron-donors, and the other with electron-acceptors, cruciforms' HOMO will localize along the electron-rich and LUMO along the electron-poor axis. This spatial isolation of cruciforms' frontier molecular orbitals (FMOs) is essential to their use as sensors, since analyte binding to the cruciform invariably changes its HOMO-LUMO gap and the associated optical properties. Using this principle, Bunz and Miljani? groups developed 1,4-distyryl-2,5-bis(arylethynyl)benzene and benzobisoxazole cruciforms, respectively, which act as fluorescent sensors for metal ions, carboxylic acids, boronic acids, phenols, amines, and anions. The emission colors observed when these cruciform are mixed with analytes are highly sensitive to the details of analyte's structure and - because of cruciforms' charge-separated excited states - to the solvent in which emission is observed. Structurally closely related species can be qualitatively distinguished within several analyte classes: (a) carboxylic acids; (b) boronic acids, and (c) metals. Using a hybrid sensing system composed from benzobisoxazole cruciforms and boronic acid additives, we were also able to discern among structurally similar: (d) small organic and inorganic anions, (e) amines, and (f) phenols. The method used for this qualitative distinction is exceedingly simple. Dilute solutions (typically 10(-6) M) of cruciforms in several off-the-shelf solvents are placed in UV/Vis vials. Then, analytes of interest are added, either directly as solids or in concentrated solution. Fluorescence changes occur virtually instantaneously and can be recorded through standard digital photography using a semi-professional digital camera in a dark room. With minimal graphic manipulation, representative cut-outs of emission color photographs can be arranged into panels which permit quick naked-eye distinction among analytes. For quantification purposes, Red/Green/Blue values can be extracted from these photographs and the obtained numeric data can be statistically processed. PMID:23995878

Schwaebel, Thimon; Lirag, Rio Carlo; Davey, Evan A; Lim, Jaebum; Bunz, Uwe H F; Miljani?, Ognjen Š

2013-01-01

148

Group composition of carboxylic acids from West Siberian crude oils  

Microsoft Academic Search

with alkali [i]~ The physical and chemical properties of the crude oils from which the petroleum acids were obtained are listed in Table i, along with the results from chromatographic separation of the extracts into fractions of neutral substances, phenol, and carboxyiic acids. The deviation between results of parallel analyses was no greater than 15% (relative), and the losses in

N. I. Zhil'tsov; V. A. Ershov; G. I. Samokhvalova

1982-01-01

149

[Analysis of aliphatic carboxylic acids in anaerobic digestion process waters by ion-exclusion chromatography].  

PubMed

The analysis of seven aliphatic carboxylic acids (formic, acetic, propionic, iso-butyric, n-butyric, iso-valeric and n-valeric acid) in anaerobic digestion process waters for biogas production was examined by ion-exclusion chromatography with dilute acidic eluents (benzoic acid, perfluorobutyric acid (PFBA) and sulfuric acid) and non-suppressed conductivity/ultraviolet (UV) detection. The columns used were a styrene/divinylbenzene-based strongly acidic cation-exchange resin column (TSKgel SCX) and a polymethacrylate-based weakly acidic cation-exchange resin column (TSKgel Super IC-A/C). Good separation was performed on the TSKgel SCX in shorter retention times. For the TSKgel Super IC-A/C, peak shape of the acids was sharp and symmetrical in spite of longer retention times. In addition, the mutual separation of the acids was good except for iso- and n-butyric acids. The better separation and good detection was achieved by using the two columns (TSKgel SCX and TSKgel Super IC-A/C connected in series), lower concentrations of PFBA and sulfuric acid as eluents, non-suppressed conductivity detection and UV detection at 210 nm. This analysis was applied to anaerobic digestion process waters. The chromatograms with conductivity detection were relatively simpler compared with those of UV detection. The use of two columns with different selectivities for the aliphatic carboxylic acids and the two detection modes was effective for the determination and identification of the analytes in anaerobic digestion process waters containing complex matrices. PMID:22799193

Ito, Kazuaki; Sakamoto, Jun; Nagaoka, Kazuya; Takayama, Yohichi; Kanahori, Takashi; Sunahara, Hiroshi; Hayashi, Tsuneo; Sato, Shinji; Hirokawa, Takeshi; Tanaka, Kazuhiko

2012-04-01

150

Determination of polyfluoroalkyl phosphoric acid diesters, perfluoroalkyl phosphonic acids, perfluoroalkyl phosphinic acids, perfluoroalkyl carboxylic acids, and perfluoroalkane sulfonic acids in lake trout from the Great Lakes region.  

PubMed

A comprehensive method to extract perfluoroalkyl carboxylic acids, perfluoroalkane sulfonic acids, perfluoroalkyl phosphonic acids, perfluoroalkyl phosphinic acids, and polyfluoroalkyl phosphoric acid diesters simultaneously from fish samples has been developed. The recoveries of target compounds ranged from 78 % to 121 %. The new method was used to analyze lake trout (Salvelinus namaycush) from the Great Lakes region. The results showed that the total perfluoroalkane sulfonate concentrations ranged from 0.1 to 145 ng/g (wet weight) with perfluorooctane sulfonate (PFOS) as the dominant contaminant. Concentrations in fish between lakes were in the order of Lakes Ontario ? Erie > Huron > Superior ? Nipigon. The total perfluoroalkyl carboxylic acid concentrations ranged from 0.2 to 18.2 ng/g wet weight. The aggregate mean perfluorooctanoic acid (PFOA) concentration in fish across all lakes was 0.045 ± 0.023 ng/g. Mean concentrations of PFOA were not significantly different (p > 0.1) among the five lakes. Perfluoroalkyl phosphinic acids were detected in lake trout from Lake Ontario, Lake Erie, and Lake Huron with concentration ranging from non-detect (ND) to 0.032 ng/g. Polyfluoroalkyl phosphoric acid diesters were detected only in lake trout from Lake Huron, at levels similar to perfluorooctanoic acid. PMID:22722738

Guo, Rui; Reiner, Eric J; Bhavsar, Satyendra P; Helm, Paul A; Mabury, Scott A; Braekevelt, Eric; Tittlemier, Sheryl A

2012-11-01

151

Preparation and Characterization of Poly(methyl methacrylate)-functionalized Carboxyl Multi-walled Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

An in situ polymerization process was used to prepare poly (methyl methacrylate) (PMMA)-functionalized carboxyl multi-walled carbon nanotubes using carboxylate carbon nanotubes and methyl methacrylate as reactants and benzoyl peroxide as an initiator agent. The functionalized multi-walled carbon nanotubes were characterized using transmission electron microscope, scanning electron microscope, nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermogravimetric analysis and Raman. The results indicate that the PMMA chains are covalently linked with the surface of carboxylate carbon nanotubes. The surface morphology is controlled by the content of carboxylate carbon nanotubes in the reactants. The PMMA functionalized multi-walled carbon nanotubes are soluble in deuterated chloroform. The storage modulus and tan? magnitude increase as the content of CCNTs increases up to 0.3%.

Meng, Qing-jie; Zhang, Xing-xiang; Bai, Shi-he; Wang, Xue-chen

2007-12-01

152

Alumino-rhenium-sulphide catalysts in hydrogenation of carboxylic acids  

SciTech Connect

Alumino-rhenium sulfide catalysts containing 1.5, 5 and 8% rhenium are active in hydrogenation of mono-, dicarboxylic acids (isobutyric, valeric, pelargonic and succinic) and a fraction of synthetic fatty acids to corresponding alcohols at 210 to 270/sup 0/C and a partial pressure of hydrogen of 25 MPa. These catalysts appear to be more selective and are more stable than other well-known oxide catalysts. 2 tables.

Ryashentseva, M.A.; Minachev, Kh.M.; Yunusov, M.P.; Serodzhev, A.T.

1982-01-01

153

Electrochemical properties of polyolefin nonwoven fabric modified with carboxylic acid group for battery separator  

Microsoft Academic Search

Carboxylic acid group was introduced by radiation-induced grafting of acrylic acid (AAc) onto polyolefine nonwoven fabric (PNF), wherein the PNF comprises at least about 60% of a polyethylene having a melting temperature at ~132°C and no more than about 40% of a second polypropylene having a lower melting temperature at ~162°C, for a battery separator. The AAc-grafted PNF was characterized

S.-H. Choi; H.-J. Kang; E.-N. Ryu; K.-P. Lee

2001-01-01

154

Introduction of carboxylic acid group to polypropylene fabric for battery separator  

Microsoft Academic Search

Carboxylic acid group was introduced by radiation-induced grafting of acrylic acid (AAc) onto a polypropylene (PP) nonwoven\\u000a fabric for a battery separator. The AAc-grafted PP nonwoven fabric was characterized by IR, SEM, and TGA. The wetting speed,\\u000a electrolyte retention, electrical resistance, and tensile strength were evaluated after grafting of AAc. It was found that\\u000a the wetting speed, electrolyte retention, thickness,

Seong-Ho Choi; Young Chang Nho

1999-01-01

155

Electrochemical properties of polyolefin nonwoven fabric modified with carboxylic acid group for battery separator  

Microsoft Academic Search

Carboxylic acid group was introduced by radiation-induced grafting of acrylic acid (AAc) onto polyolefine nonwoven fabric (PNF), wherein the PNF comprises at least about 60% of a polyethylene having a melting temperature at ?132°C and no more than about 40% of a second polypropylene having a lower melting temperature at ?162°C, for a battery separator. The AAc-grafted PNF was characterized

Seong-Ho Choi; Hae-Jeong Kang; Eun-Nyoung Ryu; Kwang-Pill Lee

2001-01-01

156

5-Substituted-1 H-tetrazoles as carboxylic acid isosteres: medicinal chemistry and synthetic methods  

Microsoft Academic Search

5-Substituted-1H-tetrazoles (RCN4H) are often used as metabolism-resistant isosteric replacements for carboxylic acids (RCO2H) in SAR-driven medicinal chemistry analogue syntheses. This review provides a brief summary of the medicinal chemistry of tetrazolic acids and highlights some examples of tetrazole-containing drug substances in the current literature. A survey of representative literature procedures for the preparation of 5-substituted-1H-tetrazoles, focusing on preparations from aryl

R. Jason Herr

2002-01-01

157

Predicting Liquid–Liquid Equilibria of Amine Extraction of Carboxylic Acid Through Solvation Energy Relation  

Microsoft Academic Search

Long?chain, aliphatic tertiary amines (e.g., Alamine 336 or 308) dissolved in suitable organic solvents are known to be effective extractants for carboxylic acids. A log?basis approach SERAS (solvation energy relation for amine systems) has been proposed to estimate the properties and liquid–liquid equilibria (LLE) of amine\\/diluent\\/organic acid associated systems containing protic and nonprotic components. The model combines the solvatochromic parameters

Aynur Senol; Umur Dramur

2004-01-01

158

Liquid chromatography of carboxylic acids using potentiometric detection with a tungsten oxide electrode  

Microsoft Academic Search

A tungsten oxide electrode was evaluated for potentiometric detection of carboxylic acids separated using various liquid Chromatographic methods, such as reversed-phase, ion-interaction and ion-exclusion. The separation of formic, acetic, propionic and butyric acids was performed using reversed-phase chromatography with 10% methanol\\/water solution at pH 6.0 as the eluent. The calibration plots were linear in the range 0.5–3.0 mmol, and the

ZuLiang Chen; Peter W. Alexander; Paul R. Haddad

1997-01-01

159

Derivatization of carboxylic acids with 9-bromomethylacridine using micellar phase-transfer catalysis  

Microsoft Academic Search

Micellar phase-transfer catalysis (MPTC) offers the opportunity to derivatize carboxylic acids directly in an aqueous matrix without prior extraction of the acids into a suitable aprotic solvent. The currently developed MPTC system consists of a non-ionic surfactant, Arkopal N-130, an ion-pair agent, tetrakis-(decyl)-ammonium bromide, and a novel fluorescence reagent, 9-bromomethylacridine. The MPTC system can be applied to the derivatization of

F. A. L. van der Horst; M. H. Post; J. J. M. Holthuis; U. A. Th. Brinkman

1989-01-01

160

Robust carboxylic acid-terminated organic thin films and nanoparticle protectants generated from bidentate alkanethiols.  

PubMed

A new carboxylic acid-terminated alkanethiol having bidentate character, 16-(3,5-bis(mercaptomethyl)phenoxy)hexadecanoic acid (BMPHA), was designed as an absorbate and protectant to form thermally stable carboxylic acid-terminated organic thin films on flat gold and nanoparticles, respectively. The structural features of the organic thin films derived from BMPHA were characterized by ellipsometry, X-ray photoelectron spectroscopy (XPS), and polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), and compared to those derived from mercaptohexadecanoic acid (MHA) and 16-(4-(mercaptomethyl)phenoxy)hexadecanoic acid (MMPHA). This study demonstrates that films derived from BMPHA are less densely packed than films derived from MHA and MMPHA. However, the results of solution-phase thermal desorption tests revealed that the carboxylic acid-terminated films generated from BMPHA exhibit an enhanced thermal stability compared to those generated from MHA and MMPHA. Furthermore, as a nanoparticle protectant, BMPHA can be used to stabilize large gold nanoparticles (~45 nm diameter) in solution, and BMPHA-protected gold nanoparticles exhibited a high thermal stability in solution thermolysis studies. PMID:23855957

Lee, Han Ju; Jamison, Andrew C; Yuan, Yuehua; Li, Chien-Hung; Rittikulsittichai, Supachai; Rusakova, Irene; Lee, T Randall

2013-08-20

161

1-aminocyclopropane-1-carboxylic acid (ACC) in plants: more than just the precursor of ethylene!  

PubMed Central

Ethylene is a simple two carbon atom molecule with profound effects on plants. There are quite a few review papers covering all aspects of ethylene biology in plants, including its biosynthesis, signaling and physiology. This is merely a logical consequence of the fascinating and pleiotropic nature of this gaseous plant hormone. Its biochemical precursor, 1-aminocyclopropane-1-carboxylic acid (ACC) is also a fairly simple molecule, but perhaps its role in plant biology is seriously underestimated. This triangularly shaped amino acid has many more features than just being the precursor of the lead-role player ethylene. For example, ACC can be conjugated to three different derivatives, but their biological role remains vague. ACC can also be metabolized by bacteria using ACC-deaminase, favoring plant growth and lowering stress susceptibility. ACC is also subjected to a sophisticated transport mechanism to ensure local and long-distance ethylene responses. Last but not least, there are now a few exciting studies where ACC has been reported to function as a signal itself, independently from ethylene. This review puts ACC in the spotlight, not to give it the lead-role, but to create a picture of the stunning co-production of the hormone and its precursor.

Van de Poel, Bram; Van Der Straeten, Dominique

2014-01-01

162

ANALYSIS OF AIRBORNE CARBOXYLIC ACIDS AND PHENOLS AS THEIR PENTAFLUOROBENZYL DERIVATIVES: GAS CHROMATOGRAPHY/ION TRAP MASS SPECTROMETRY WITH A NOVEL CHEMICAL IONIZATION REAGENT, PFBOH. (R826247)  

EPA Science Inventory

The complex photochemical transformations of biogenic hydrocarbons such as isoprene and of anthropogenic hydrocarbons such as aromatics are an important source of carboxylic acids in the troposphere. The identification of unknown carboxylic acids can be difficul...

163

Oxidation of heterocyclic and aromatic aldehydes to the corresponding carboxylic acids by Acetobacter and Serratia strains.  

PubMed

Conversion of heterocyclic and aromatic aldehydes to the corresponding carboxylic acids was carried out using Acetobacter rancens IFO3297, A. pasteurianus IFO13753 and Serratia liquefaciens LF14. IFO3297 produced 110 g 2-furoic acid l(-1) from furfural with a 95% molar yield. 5-Hydroxymethyl-2-furancarboxylic acid was produced from the corresponding aldehyde by using whole cells LF14. IFO13753 and LF14 both converted isophthalaldehyde, 2,5-furandicarbaldehyde, 2,5-thiophenedicarbaldehyde and 2,2' biphenyldicarbaldehyde to the corresponding formylcarboxylic acid with 86-91% molar yields. PMID:15604813

Mitsukura, Koichi; Sato, Yukihide; Yoshida, Toyokazu; Nagasawa, Toru

2004-11-01

164

Mechanism of carboxylic acid photooxidation in atmospheric aqueous phase: Formation, fate and reactivity  

NASA Astrophysics Data System (ADS)

In the first part of the work, we investigated the reactivity toward photogenerated hydroxyl radicals (rad OH) of seven monocarboxylic acids and six dicarboxylic acids found in natural cloud water. This leads to the proposition of a schematic degradation pathway linking glutaric acid (C5) to complete mineralization into CO2. We report a detailed mechanism on the succinic acid reactivity toward rad OH leading to the formation of malonic, glyoxylic and consequently oxalic acids and a comparison with reported pathways proposed by the CAPRAM (Chemical Aqueous Phase RAdical Mechanism) is discussed. We also investigated the photooxidation of formic acid under atmospherically relevant conditions leading to the possible formation of oxalic acid via radical mediated recombination. The second part focuses on the polychromatic irradiation (closed to solar irradiation) of a collected cloud aqueous phase showing that irradiation of cloud water leads to the formation of both formic and acetic acids. Carboxylic acid formation increases in the presence of photogenerated hydroxyl radicals from hydrogen peroxide, showing that photooxidation could play a key role in the formation of carboxylic acids under atmospherically relevant conditions.

Charbouillot, Tiffany; Gorini, Sophie; Voyard, Guillaume; Parazols, Marius; Brigante, Marcello; Deguillaume, Laurent; Delort, Anne-Marie; Mailhot, Gilles

2012-09-01

165

Water chemical ionization mass spectrometry of aldehydes, ketones esters, and carboxylic acids  

SciTech Connect

Chemical ionization mass spectrometry (CI) of aliphatic and aromatic carbonyl compounds using water as the reagent gas provides intense pseudomolecular ions and class-specific fragmentation patterns that can be used to identify aliphatic aldehydes, ketones, carboxylic acids, and esters. The length of ester acyl and alkyl groups can easily be determined on the basis of loss of alcohols from the protonated parent. Water CI provides for an approximately 200:1 selectivity of carbonyl species over alkanes. No reagent ions are detected above 55 amu, allowing species as small as acetone, propanal, acetic acid, and methyl formate to be identified. When deuterate water was used as the reagent, only the carboxylic acids and ..beta..-diketones showed significant H/D exchange. The use of water CI to identify carbonyl compounds in a wastewater from the supercritical water extraction of lignite coal, in lemon oil, and in whiskey volatiles is discussed.

Hawthorne, S.B.; Miller, D.J.

1986-11-01

166

Stereospecific Biohydroxylations of Protected Carboxylic Acids with Cunninghamella blakesleeana  

PubMed Central

Cunninghamella blakesleeana DSM 1906 was found to be an efficient biocatalyst for the biotransformation of cycloalkylcarboxylic acids into hydroxy and oxo derivatives. When cultivated in submerged culture, the fungus grew in pellets. In comparison with malt extract-glucose-peptone-yeast extract medium (medium E), Czapek-Dox medium was found to reduce pellet size. Cycloalkylcarboxylic acids were protected against microbial degradation by chemical transformation into 2-cycloalkyl-1,3-benzoxazoles. The transformations of protected cyclopentyl-, cyclohexyl-, cycloheptyl-, and cyclooctylcarboxylic acids by C. blakesleeana were investigated. The biotransformations were performed in medium E by using an aerated, stirred-tank bioreactor. The transformation of 2-cyclopentyl-1,3-benzoxazole yielded (1S,3S)-3-(benz-1,3-oxazol-2-yl)cyclopentan-1-ol as the main product. The main by-product was (1R)-3-(benz-1,3-oxazol-2-yl)cyclopentan-1-one, and 2-(benz-1,3-oxazol-2-yl)cyclopentan-1-ol was also obtained in small amounts. During the experiment, the enantiomeric excess of the main product increased up to 64%. 2-Cyclohexyl-1,3-benzoxazole was hydroxylated to 4-(benz-1,3-oxazol-2-yl)cyclohexan-1-ol. 2-Cycloheptyl-1,3-benzoxazole and 2-cyclooctyl-1,3-benzoxazole were transformed into several alcohols and ketones, all in low yields (2 to 19%). PMID:16535367

Kreiner, M.; Braunegg, G.; de Raadt, A.; Griengl, H.; Kopper, I.; Petsch, M.; Plachota, P.; Schoo, N.; Weber, H.; Zeiser, A.

1996-01-01

167

Effect of carboxylic acid of periodic mesoporous organosilicas on the fructose-to-5-hydroxymethylfurfural conversion in dimethylsulfoxide systems  

NASA Astrophysics Data System (ADS)

This manuscript presents the preparation and catalytic application of highly ordered benzene bridged periodic mesoporous organosilicas (PMOs) functionalized with carboxylic acid (-COOH) group at varied density. The COOH-functionalized PMOs were synthesized by one-step condensation of 1,4-bis (triethoxysilyl) benzene and carboxylic group containing organosilane carboxyethylsilanetriol sodium salt using Brij-76 as the template. The obtained materials were characterized by a mean of methods including powder X-ray diffraction, nitrogen adsorption-desorption, scanning- and transmission electron microscopy, and 13C solid-state nuclear magnetic resonance measurements. The potentials of the obtained PMO materials with ordered mesopores were examined as solid catalysts for the chemical conversion of fructose to 5-hydroxymethylfurfural (HMF) in an organic solvent. The results showed that COOH-functionalized PMO with 10% COOH loading exhibited best results for the fructose to HMF conversion and selectivity. The high surface area, the adequate density acid functional group, and the strength of the PMO materials contributing to a promising catalytic ability were observed.

Dutta, Saikat; Kao, Hsien-Ming; Wu, Kevin C.-W.

2014-11-01

168

Acid monolayer functionalized iron oxide nanoparticle catalysts  

NASA Astrophysics Data System (ADS)

Superparamagnetic iron oxide nanoparticle functionalization is an area of intensely active research, with applications across disciplines such as biomedical science and heterogeneous catalysis. This work demonstrates the functionalization of iron oxide nanoparticles with a quasi-monolayer of 11-sulfoundecanoic acid, 10-phosphono-1-decanesulfonic acid, and 11-aminoundecanoic acid. The carboxylic and phosphonic moieties form bonds to the iron oxide particle core, while the sulfonic acid groups face outward where they are available for catalysis. The particles were characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), potentiometric titration, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectrometry (XPS), and dynamic light scattering (DLS). The sulfonic acid functionalized particles were used to catalyze the hydrolysis of sucrose at 80° and starch at 130°, showing a higher activity per acid site than the traditional solid acid catalyst Amberlyst-15, and comparing well against results reported in the literature for sulfonic acid functionalized mesoporous silicas. In sucrose catalysis reactions, the phosphonic-sulfonic nanoparticles (PSNPs) were seen to be incompletely recovered by an external magnetic field, while the carboxylic-sulfonic nanoparticles (CSNPs) showed a trend of increasing activity over the first four recycle runs. Between the two sulfonic ligands, the phosphonates produced a more tightly packed monolayer, which corresponded to a higher sulfonic acid loading, lower agglomeration, lower recoverability through application of an external magnetic field, and higher activity per acid site for the hydrolysis of starch. Functionalizations with 11-aminoundecanoic acid resulted in some amine groups binding to the surfaces of iron oxide nanoparticles. This amine binding is commonly ignored in iron oxide nanoparticle syntheses and functionalizations for biomedical and catalytic applications, affecting understandings of surface charge and other material properties.

Ikenberry, Myles

169

Substituent R-effects on the core-electron excitation spectra of hydrogen-bonded carboxylic-acid (R-COOH) clusters: Comparison between acetic-acid and formic-acid clusters  

NASA Astrophysics Data System (ADS)

Core-excitation spectra observed for small acetic-acid (AcA) clusters have been interpreted with density functional theory calculations. By comparison of O1s(CO/OH)???(CO) bands between formic-acid (FA) and AcA clusters, larger band-shifts were identified in AcA clusters. Substituent R-effects on these bands are examined in terms of geometrical parameters and acid-base properties of constituent carboxylic-acids (R-COOH). Since small carboxylic-acid clusters comprise a centrosymmetric dimer-unit with resonance-assisted hydrogen-bonds (RAHBs), cooperative ?-electron delocalization characterized by ?-conjugated Cdbnd O/C-O bond equalization plays an important role in intermolecular interactions. The larger band-shifts for AcA clusters result from increased ?-electron delocalization in the constituent molecules relative to FA clusters.

Tabayashi, K.; Takahashi, O.; Namatame, H.; Taniguchi, M.

2013-02-01

170

Pyrolysis of coal model compounds containing aromatic carboxylic acids: The role of carboxylic acids in cross-linking reactions in low-rank coal  

SciTech Connect

The pyrolysis of 1-(3-carboxyphenyl)-2(4-biphenyl)ethane (1) diluted in 10-fold excess of naphthalene has been studied at 400 {degrees}C to investigate whether decarboxylation of aromatic carboxylic acids can lead to cross-linked products. The dominant mechanism for decarboxylation was found to be an acid-promoted ionic pathway that does not lead to cross-linking. However, a small amount of cross-linked products (i.e. naphthalene grafted onto decarboxylated 1) were formed. The yields of the cross-linked products were found to be decreased in the presence of a hydrogen donor solvent, tetralin, suggesting that these products were formed by a free-radical pathway. The mechanism for the formation of cross-linked products was proposed to occur from the formation and decomposition of anhydrides of 1 during pyrolysis.

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

1997-06-01

171

The interaction of carboxylic acids with aluminium oxides: journeying from a basic understanding of alumina nanoparticles to water treatment for industrial and humanitarian applications.  

PubMed

Carboxylic acids are found to react with aluminium oxides via a topotactic reaction such that the carboxylate acts as a bridging ligand. This reaction allows for carboxylate-functionalized alumina nanoparticles to be prepared directly from boehmite (AlOOH). Understanding the structural relationship between molecular and surface species allows for the rationalization/prediction of suitable alternative ligands as well as alternative oxide surfaces. The identity of the carboxylate substituent controls the pH stability of a nanoparticle as well as the porosity and processability of ceramics prepared by thermolysis. Through the choice of functional groups on the carboxylic acid the properties of the alumina surface or alumina nanoparticle can be tailored. For example, the solubility/miscibility of nanoparticles can be tuned to the solvent/matrix, and the wettability to be varied from hydrophobic to super hydrophilic. The choice Zwitter ionic substituents on alumina micro-/ultra-filtration membranes are found to enhance the flux and limit fouling while allowing for the facile separation of organic compounds from water. Examples are presented of purification of frac and flow-back water from oil well production as well as providing drinking water from contaminated sources in underdeveloped regions. PMID:24728503

Barron, Andrew R

2014-06-14

172

Transferable force field for carboxylate esters: application to fatty acid methylic ester phase equilibria prediction.  

PubMed

In this work, a new transferable united-atoms force field for carboxylate esters is proposed. All Lennard-Jones parameters are reused from previous parametrizations of the AUA4 force field, and only a unique set of partial electrostatic charges is introduced for the ester chemical function. Various short alkyl-chain esters (methyl acetate, ethyl acetate, methyl propionate, ethyl propionate) and two fatty acid methylic esters (methyl oleate and methyl palmitate) are studied. Using this new force field in Monte Carlo simulations, we show that various pure compound properties are accurately predicted: saturated liquid densities, vapor pressures, vaporization enthalpies, critical properties, liquid-vapor surface tensions. Furthermore, a good accuracy is also obtained in the prediction of binary mixture pressure-composition diagrams, without introducing empirical binary interaction parameters. This highlights the transferability of the proposed force field and gives the opportunity to simulate mixtures of industrial interest: a demonstration is performed through the simulation of the methyl oleate + methanol mixture involved in the purification sections of biodiesel production processes. PMID:22369235

Ferrando, Nicolas; Lachet, Véronique; Boutin, Anne

2012-03-15

173

Immunocytolocalization of 1-aminocyclopropane-1-carboxylic acid oxidase in tomato and apple fruit  

Microsoft Academic Search

The subcellular localization of 1-aminocyclopropane-1-carboxylic acid oxidase (ACC oxidase), an enzyme involved in the biosynthesis of ethylene, has been studied in ripening fruits of tomato (Lycopersicum esculentum Mill.). Two types of antibody have been raised against (i) a synthetic peptide derived from the reconstructed pTOM13 clone (pRC13), a tomato cDNA encoding ACC oxidase, and considered as a suitable epitope by

Cesar Rombaldi; Jean-Marc Lelièvre; Alain Latché; Michel Petitprez; Mondher Bouzayen; Jean-Claude Pech

1994-01-01

174

Saturation vapor pressures and vaporization enthalpies of esters of ethylene glycol and lower carboxylic acids  

NASA Astrophysics Data System (ADS)

Saturation vapor pressures and vaporization enthalpies of ethylene glycol and C1-C5 carboxylic acid disubstituted esters of normal and branched structures are determined by the transfer method in the temperature range of 295 to 327 K. Dependences of vaporization enthalpies versus the number of carbon atoms in a molecule and the retention indices are determined. An analysis of existing calculation schemes is given to help predict the vaporization enthalpy of the compounds under study.

Maslakova, A. S.; Krasnykh, E. L.; Levanova, S. V.

2011-10-01

175

Amperometric study of the inhibitory effect of carboxylic acids on tyrosinase  

Microsoft Academic Search

A tyrosinase-modified Pt electrode, based on physical entrapment of the enzyme in agar–agar gel, was constructed and used to investigate the inhibitory effect of six carboxylic acids. At an applied potential of ?50mV versus saturated calomel electrode (SCE), the bioelectrode develops a fast, steady state response, linearly correlated with the phenol concentration up to 10mg\\/l, with a sensitivity of 3.7nAl\\/mg.

Sarmiza Elena Stanca; Ionel Catalin Popescu

2004-01-01

176

Design and synthesis of lactam-thiophene carboxylic acids as potent hepatitis C virus polymerase inhibitors.  

PubMed

Herein we report the successful incorporation of a lactam as an amide replacement in the design of hepatitis C virus NS5B Site II thiophene carboxylic acid inhibitors. Optimizing potency in a replicon assay and minimizing potential risk for CYP3A4 induction led to the discovery of inhibitor 22a. This lead compound has a favorable pharmacokinetic profile in rats and dogs. PMID:24986660

Barnes-Seeman, David; Boiselle, Carri; Capacci-Daniel, Christina; Chopra, Rajiv; Hoffmaster, Keith; Jones, Christopher T; Kato, Mitsunori; Lin, Kai; Ma, Sue; Pan, Guoyu; Shu, Lei; Wang, Jianling; Whiteman, Leah; Xu, Mei; Zheng, Rui; Fu, Jiping

2014-08-15

177

Differential expression of two 1-aminocyclopropane-1-carboxylic acid oxidase genes in broccoli after harvest  

Microsoft Academic Search

Broccoli (Brassica oleracea 1.) floral tissues rapidly differen- tiate and grow before harvest and then senesce rapidly after harvest. Associated with this postharvest deterioration is an in- crease in ethylene production by florets. Two cDNA clones having high nucleotide identity to sequences encoding 1 -amino- cyclopropane-1 -carboxylic acid (ACC) oxidase were isolated from senescing florets. The cDNAs, ACC 0x7 and

Barry J. Pogson; Christopher C. Downs; Kevin M. Davies

1995-01-01

178

Retention behaviours and separation of carboxylic acids by ion-exchange chromatography  

Microsoft Academic Search

The use of high-performance suppressed ion chromatography for the separation of aliphatic carboxylic acids has become an attractive and viable method during the past years. This paper summarises and critically concludes that some new results have been achieved in separation and detection of low-molecular-mass organic anions. Theoretical and practical considerations of ion-exchange selectivity to control retention behaviour are presented. The

Peter Hajós; L??via Nagy

1998-01-01

179

Process for the generation of .alpha., .beta.-unsaturated carboxylic acids and esters using niobium catalyst  

DOEpatents

A process using a niobium catalyst includes the step of reacting an ester or carboxylic acid with oxygen and an alcohol in the presence a niobium catalyst to respectively produce an .alpha.,.beta.-unsaturated ester or carboxylic acid. Methanol may be used as the alcohol, and the ester or carboxylic acid may be passed over the niobium catalyst in a vapor stream containing oxygen and methanol. Alternatively, the process using a niobium catalyst may involve the step of reacting an ester and oxygen in the presence the niobium catalyst to produce an .alpha.,.beta.-unsaturated carboxylic acid. In this case the ester may be a methyl ester. In either case, niobium oxide may be used as the niobium catalyst with the niobium oxide being present on a support. The support may be an oxide selected from the group consisting of silicon oxide, aluminum oxide, titanium oxide and mixtures thereof. The catalyst may be formed by reacting niobium fluoride with the oxide serving as the support. The niobium catalyst may contain elemental niobium within the range of 1 wt % to 70 wt %, and more preferably within the range of 10 wt % to 30 wt %. The process may be operated at a temperature from 150 to 450.degree. C. and preferably from 250 to 350.degree. C. The process may be operated at a pressure from 0.1 to 15 atm. absolute and preferably from 0.5-5 atm. absolute. The flow rate of reactants may be from 10 to 10,000 L/kg.sub.(cat) /h, and preferably from 100 to 1,000 L/kg.sub.(cat) /h.

Gogate, Makarand Ratnakav (Durham, NC); Spivey, James Jerome (Cary, NC); Zoeller, Joseph Robert (Kingsport, TN)

1999-01-01

180

Investigation of pyridine carboxylic acids in CM2 carbonaceous chondrites: Potential precursor molecules for ancient coenzymes  

NASA Astrophysics Data System (ADS)

The distribution and abundances of pyridine carboxylic acids (including nicotinic acid) in eight CM2 carbonaceous chondrites (ALH 85013, DOM 03183, DOM 08003, EET 96016, LAP 02333, LAP 02336, LEW 85311, and WIS 91600) were investigated by liquid chromatography coupled to UV detection and high resolution Orbitrap mass spectrometry. We find that pyridine monocarboxylic acids are prevalent in CM2-type chondrites and their abundance negatively correlates with the degree of pre-terrestrial aqueous alteration that the meteorite parent body experienced. We also report the first detection of pyridine dicarboxylic acids in carbonaceous chondrites. Additionally, we carried out laboratory studies of proton-irradiated pyridine in carbon dioxide-rich ices (a 1:1 mixture) to serve as a model of the interstellar ice chemistry that may have led to the synthesis of pyridine carboxylic acids. Analysis of the irradiated ice residue shows that a comparable suite of pyridine mono- and dicarboxylic acids was produced, although aqueous alteration may still play a role in the synthesis (and ultimate yield) of these compounds in carbonaceous meteorites. Nicotinic acid is a precursor to nicotinamide adenine dinucleotide, a likely ancient molecule used in cellular metabolism in all of life, and its common occurrence in CM2 chondrites may indicate that meteorites may have been a source of molecules for the emergence of more complex coenzymes on the early Earth.

Smith, Karen E.; Callahan, Michael P.; Gerakines, Perry A.; Dworkin, Jason P.; House, Christopher H.

2014-07-01

181

Evaluation of toxic effects of several carboxylic acids on bacterial growth by toxicodynamic modelling  

PubMed Central

Background Effects of organic acids on microbial fermentation are commonly tested in investigations about metabolic behaviour of bacteria. However, they typically provide only descriptive information without modelling the influence of acid concentrations on bacterial kinetics. Results We developed and applied a mathematical model (secondary model) to capture the toxicological effects of those chemicals on kinetic parameters that define the growth of bacteria in batch cultures. Thus, dose-response kinetics were performed with different bacteria (Leuconostoc mesenteroides, Carnobacterium pisicola, Escherichia coli, Bacillus subtilis and Listonella anguillarum) exposed at increasing concentrations of individual carboxylic acids (formic, acetic, propionic, butyric and lactic). In all bioassays the acids affected the maximum bacterial load (Xm) and the maximum growth rate (vm) but only in specific cases the lag phase (?) was modified. Significance of the parameters was always high and in all fermentations the toxicodynamic equation was statistically consistent and had good predictability. The differences between D and L-lactic acid effects were significant for the growth of E. coli, L. mesenteroides and C. piscicola. In addition, a global parameter (EC50,?) was used to compare toxic effects and provided a realistic characterization of antimicrobial agents using a single value. Conclusions The effect of several organic acids on the growth of different bacteria was accurately studied and perfectly characterized by a bivariate equation which combines the basis of dose-response theory with microbial growth kinetics (secondary model). The toxicity of carboxylic acids was lower with the increase of the molecular weight of these chemicals. PMID:22118421

2011-01-01

182

Investigation of Pyridine Carboxylic Acids in CM2 Carbonaceous Chondrites: Potential Precursor Molecules for Ancient Coenzymes  

NASA Technical Reports Server (NTRS)

The distribution and abundances of pyridine carboxylic acids (including nicotinic acid) in eight CM2 carbonaceous chondrites (ALH 85013, DOM 03183, DOM 08003, EET 96016, LAP 02333, LAP 02336, LEW 85311, and WIS 91600) were investigated by liquid chromatography coupled to UV detection and high resolution Orbitrap mass spectrometry. We find that pyridine monocarboxylic acids are prevalent in CM2-type chondrites and their abundance negatively correlates with the degree of pre-terrestrial aqueous alteration that the meteorite parent body experienced. We lso report the first detection of pyridine dicarboxylic acids in carbonaceous chondrites. Additionally, we carried out laboratory studies of proton-irradiated pyridine in carbon dioxide-rich ices (a 1:1 mixture) to serve as a model of the interstellar ice chemistry that may have led to the synthesis of pyridine carboxylic acids. Analysis of the irradiated ice residue shows that a comparable suite of pyridine mono- and dicarboxylic acids was produced, although aqueous alteration may still play a role in the synthesis (and ultimate yield) of these compounds in carbonaceous meteorites. Nicotinic acid is a precursor to nicotinamide adenine dinucleotide, a likely ancient molecule used in cellular metabolism in all of life, and its common occurrence in CM2 chondrites may indicate that meteorites may have been a source of molecules for the emergence of more complex coenzymes on the early Earth.

Smith, Karen E.; Callahan, Michael P.; Gerakines, Perry A.; Dworkin, Jason P.; House, Christopher H.

2014-01-01

183

Pyridine and pyridine carboxylic acids as guests in a bidimensional hydrogen bond structure analyzed by scanning tunneling microscopy  

NASA Astrophysics Data System (ADS)

2-Mercaptopyrimidine (2MPy) forms a stable two-dimensional network on Au(1 1 1). The 2MPy dimeric structure forms chains separated by narrow channels that can trap a variety of molecules such as oligopyridines and arenes. In this work, the 2MPy structure was used to intercalate pyridine and its acid derivatives, specifically, picolinic acid, dipicolinic acid, niconitic acid and isonicotinic acid. Pyridine and the pyridine carboxylic acids were intercalated into the thiol structure in a 2:1 stoichiometry. The STM contrast of the carboxylic group varies with its position on the pyridine ring and with the tunneling parameters employed to acquire the images.

Pinheiro, L. S.; Temperini, M. L. A.

2007-04-01

184

Benzene carboxylic acid derivatized graphene oxide nanosheets on natural zeolites as effective adsorbents for cationic dye removal.  

PubMed

Graphene oxide (GO) nanosheets were grafted to acid-treated natural clinoptilolite-rich zeolite powders followed by a coupling reaction with a diazonium salt (4-carboxybenzenediazoniumtetrafluoroborate) to the GO surface. Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA) revealed successful grafting of GO nanosheets onto the zeolite surface. The application of the adsorbents for the adsorption of rhodamine B from aqueous solutions was then demonstrated. After reaching adsorption equilibrium the maximum adsorption capacities were shown to be 50.25, 55.56 and 67.56 mg g(-1) for pristine natural zeolite, GO grafted zeolite (GO-zeolite) and benzene carboxylic acid derivatized GO-zeolite powders, respectively. The adsorption behavior was fitted to a Langmuir isotherm and shown to follow a pseudo-second-order reaction model. Further, a relationship between surface functional groups, pH and adsorption efficiency was established. Results indicate that benzene carboxylic acid derivatized GO-zeolite powders are environmentally favorable adsorbents for the removal of cationic dyes from aqueous solutions. PMID:23778259

Yu, Yang; Murthy, Bandaru N; Shapter, Joseph G; Constantopoulos, Kristina T; Voelcker, Nicolas H; Ellis, Amanda V

2013-09-15

185

Potential Correlation between Carboxylic Acid Metabolites in Biomphalaria alexandrina Snails after Exposure to Schistosoma mansoni Infection  

PubMed Central

Carboxylic acids play an important role in both aerobic and anaerobic metabolic pathways of both the snail and the parasite. Monitoring the effects of infection by schistosome on Biomphalaria alexandrina carboxylic acids metabolic profiles represents a promising additional source of information about the state of metabolic system. We separated and quantified pyruvic, fumaric, malic, oxalic, and acetic acids using ion-suppression reversed-phase high performance liquid chromatography (HPLC) to detect correlations between these acids in both hemolymph and digestive gland gonad complex (DGG's) samples in a total of 300 B. alexandrina snails (150 infected and 150 controls) at different stages of infection. The results showed that the majority of metabolite pairs did not show significant correlations. However, some high correlations were found between the studied acids within the control group but not in other groups. More striking was the existence of reversed correlations between the same acids at different stages of infection. Some possible explanations of the underlying mechanisms were discussed. Ultimately, however, further data are required for resolving the responsible regulatory events. These findings highlight the potential of metabolomics as a novel approach for fundamental investigations of host-pathogen interactions as well as disease surveillance and control. PMID:22711922

Abou Elseoud, Salwa M. F.; Ezz El Din, Hayam M.; Abdel Al, Hala; Mossalem, Hanan; Elleboudy, Noha

2012-01-01

186

Floral benzenoid carboxyl methyltransferases: From in vitro to in planta function  

PubMed Central

Benzenoid carboxyl methyltransferases synthesize methyl esters (e.g., methyl benzoate and methyl salicylate), which are constituents of aromas and scents of many plant species and play important roles in plant communication with the surrounding environment. Within the past five years, eleven such carboxyl methyltransferases were isolated and most of them were comprehensively investigated at the biochemical, molecular and structural level. Two types of enzymes can be distinguished according to their substrate preferences: the SAMT-type enzymes isolated from Clarkia breweri, Stephanotis floribunda, Antirrhinum majus, Hoya carnosa, and Petunia hybrida, which have a higher catalytic efficiency and preference for salicylic acid, while BAMT-type enzymes from A. majus, Arabidopsis thaliana, Arabidopsis lyrata, and Nicotiana suaveolens prefer benzoic acid. The elucidation of C. breweri SAMT’s three-dimensional structure allowed a detailed modelling of the active sites of the carboxyl methyltransferases and revealed that the SAM binding pocket is highly conserved among these enzymes while the methyl acceptor binding site exhibits some variability, allowing a classification into SAMT-type and BAMT-type enzymes. The analysis of expression patterns coupled with biochemical characterization showed that these carboxyl methyltransferases are involved either in floral scent biosynthesis or in plant defense responses. While the latter can be induced by biotic or abiotic stress, the genes responsible for floral scent synthesis exhibit developmental and rhythmic expression pattern. The nature of the product and efficiency of its formation in planta depend on the availability of substrates, the catalytic efficiency of the enzyme toward benzoic acid and/or salicylic acid, and the transcriptional, translational, and post-translational regulation at the enzyme level. The biochemical properties of benzenoid carboxyl methyltransferases suggest that the genes involved in plant defenses might represent the ancestor for the presently existing floral genes which during evolution gained different expression profiles and encoded enzymes with the ability to accept structurally similar substrates. PMID:15946712

Effmert, Uta; Saschenbrecker, Sandra; Ross, Jeannine; Negre, Florence; Fraser, Chris M.; Noel, Joseph P.; Dudareva, Natalia; Piechulla, Birgit

2010-01-01

187

Radiation-induced crosslinks between carboxylic acids and compounds of biological interest.  

PubMed

Various carboxylic acids having short carbon chains (10(-4) or 5 X 10(-4) M) mixed with serum albumin or DNA (1 mg/ml) were irradiated in phosphate buffer solution (10(-3) M, pH 7.0) with 60Co gamma rays. Maleic acid and nicotinic acid showed high binding activity resulting from having an unsaturated double bond and an aromatic ring, respectively. Sodium salts of C18 fatty acids (0.5 mg/ml) such as stearate, oleate, linoleate, and linolenate were also irradiated in the presence of amino acids or nucleobases (10(-4) or 5 X 10(-4) M) in the same buffer solution. The binding yield increased with the increase in the number of double bonds indicating participation of double bonds in the binding. PMID:3952268

Yamamoto, O

1986-02-01

188

Migration of (hydroxy)carboxylic acids in coelectroosmotic capillary electrophoresis. Influence of the electrolyte composition.  

PubMed

This work focused on the way several electrolyte components could affect the electroosmotic flow and the capillary electrophoretic migration of aliphatic or aromatic (hydroxy)carboxylic acids. The effects exerted by the electroosmotic flow modifier, hexadecyltrimethylammonium bromide, the addition of metal salt to the electrolyte and the absorbance provider (chromophore) used for indirect detection were investigated. A retention of the organic acids was demonstrated. Its magnitude was shown to depend on the amount of cationic surfactant adsorbed onto the capillary walls. The addition of sodium nitrate led to a remobilization of all the acids except glycolic acid. Moreover, the presence of the chromophore was shown to influence mainly the migration of the glycolic acid. PMID:11878281

Martin-Jouet, M; Hagège, A; Leroy, M J F

2002-02-01

189

A Novel Aromatic Carboxylic Acid Inactivates Luciferase by Acylation of an Enzymatically Active Regulatory Lysine Residue  

PubMed Central

Firefly luciferase (Luc) is widely used as a reporter enzyme in cell-based assays for gene expression. A novel aromatic carboxylic acid, F-53, reported here for the first time, substantially inhibited the enzymatic activity of Luc in a Luc reporter screening. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and tandem mass spectrometry (MS/MS) analyses showed that F-53 modifies Luc at lysine-529 via amidation of the F-53 carboxyl group. The lysine-529 residue of Luc, which plays a regulatory catalytic role, can be acetylated. Luc also has a long-chain fatty acyl-CoA synthase activity. An in vitro assay that involved both recombinant Luc and mouse liver microsomes identified F-53-CoA as the reactive form produced from F-53. However, whereas the inhibitory effect of F-53 is observed in Hela cells that transiently expressed Luc, it is not observed in an in vitro assay that involves recombinant Luc alone. Therefore, insights into the activities of certain mammalian transferases can be translated to better understand the acylation by F-53. The insights from this study about the novel inhibitory modification mechanism might help not only to avoid misinterpretation of the results of Luc-based reporter screening assays but also to explain the pharmacological and toxicological effects of carboxylic acid-containing drugs. PMID:24066181

Nakagomi, Madoka; Fujimaki, Nobuko; Ito, Ai; Toda, Takahiro; Fukasawa, Hiroshi; Shudo, Koichi; Tomita, Ryoichi

2013-01-01

190

Investigating the photostability of carboxylic acids exposed to Mars surface ultraviolet radiation conditions.  

PubMed

The detection and identification of organic molecules on Mars are of primary importance to establish the existence of a possible ancient prebiotic chemistry or even biological activity. The harsh environmental conditions at the surface of Mars could explain why the Viking probes-the only efforts, to date, to search for organics on Mars-detected no organic matter. To investigate the nature, abundance, and stability of organic molecules that could survive such environmental conditions, we developed a series of experiments that simulate martian surface environmental conditions. Here, we present results with regard to the impact of solar UV radiation on various carboxylic acids, such as mellitic acid, which are of astrobiological interest to the study of Mars. Our results show that at least one carboxylic acid, mellitic acid, could produce a resistant compound-benzenehexacarboxylic acid-trianhydride (C(12)O(9))-when exposed to martian surface radiation conditions. The formation of such products could contribute to the presence of organic matter in the martian regolith, which should be considered a primary target for in situ molecular analyses during future surface missions. PMID:19663761

Stalport, F; Coll, P; Szopa, C; Cottin, H; Raulin, F

2009-01-01

191

Purification, properties and partial amino-acid sequence of 1-aminocyclopropane-1-carboxylic acid oxidase from apple fruits  

Microsoft Academic Search

The enzyme which converts 1-aminocyclo-propane-1-carboxylic acid (ACC) into ethylene, ACC oxidase, has been isolated from apple fruits (Malus x domestica Borkh. cv. Golden Delicious), and for the first time stabilized in vitro by 1,10-phenanthroline and purified 170-fold to homogeneity in a five-step procedure. The sodium dodecyl sulfate-denatured and native proteins have similar molecular weights (approx. 40 kDa) indicating that the

Eve Dupille; César Rombaldi; Jean-Marc Lelièvre; Jean-Claude Cleyet-Marel; Jean-Claude Pech; Alain Latché

1993-01-01

192

Contributions of low molecular weight carboxylic acids to aerosols and wet deposition in a natural subtropical broad-leaved forest environment  

NASA Astrophysics Data System (ADS)

The carboxylic acid component of autumn aerosol and wet deposition (fog water and rainwater) in a broad-leaved forest in central Taiwan was investigated. High levels of low molecular weight carboxylic acids (LMWCAs) were noted in all deposition types. Acetic acid, oxalic acid and formic acid were the most prevalent carboxylic acids, together accounting for 72.2% (fog water), 86.7% (rain water), 77.2% (PM2.5) and 88.3% (PM2.5-10) of total carboxylic acid. The forest fog water contained 2453.9 ± 1030.5 ng mL-1 of carboxylic acid, 2.71 times more than was contained in forest rainwater. In PM, most carboxylic acid existed in the fine PM2.5 aerosol (576.6 ± 254.1 ng m-3 or 6.28 times more than was contained in PM2.5-10. Most carboxylic acids in PM had higher concentrations during the day. Pyruvic acid concentration was higher during the night (2.97 times), however, owing to its rapid photodegradation during the day. Citric acid accounted for 9.1% of the total carboxylic acid in fog water compared with just 1.8% in rainwater, confirming its origin from emissions from leaves. Raman spectroscopy was used to observe the photochemical conversion of citric acid into intermediate products and this observation confirmed that the carboxylic acids identified in the forest dry and wet depositions originated directly from biological emissions in the forest environment.

Tsai, Ying I.; Kuo, Su-Ching

2013-12-01

193

FT-IR, FT-Raman spectra and quantum mechanical study of piperidine-3-carboxylic acid and its tautomers, isomers  

NASA Astrophysics Data System (ADS)

The mid-IR, far-IR, and Raman spectra of piperidine-3-carboxylic acid were measured and interpreted with support of the MP2 and B3LYP/6-311++G(d, p) calculated harmonic vibrational spectra. 10 stable piperidine-3-carboxylic acid tautomers/isomers were found after B3LYP, calculations. The experimental absorption bands of carboxylate (COO-) group show that the free piperidine-3-carboxylic acid molecule exists in zwitterionic form and the most stable tautomer (NAT-1) can be stabilized by an intramolecular N-H...O hydrogen bond. All vibrational frequencies of NAT-1 assigned in detail with the help of total energy distribution (TED). The experimental vibrational wave numbers were compared with the calculated data.

Yurdakul, ?enay; Ya?ayan, Nefise Çi?dem; Bado?lu, Serdar

2014-06-01

194

Five organic salts assembled from carboxylic acids and bis-imidazole derivatives through collective noncovalent interactions  

NASA Astrophysics Data System (ADS)

Five multicomponent crystals of bis(imidazole) derivatives have been prepared with 5-nitrosalicylic acid, 5-sulfosalicylic acid, and phthalic acid. The five crystalline forms reported are organic salts of which the crystal structures have all been determined by X-ray diffraction. The results presented herein indicate that the strength and directionality of the N sbnd H⋯O, O sbnd H⋯O, and N sbnd H⋯N hydrogen bonds (ionic or neutral) between carboxylic acids and ditopic imidazoles are sufficient to bring about the formation of binary organic salts. All supramolecular architectures of the organic salts 1- 5 involve extensive O sbnd H⋯O, and N sbnd H⋯O hydrogen bonds as well as other noncovalent interactions. The role of weak and strong noncovalent interactions in the crystal packing is ascertained. These noncovalent interactions combined, all the complexes displayed 3D framework structure.

Jin, Shouwen; Guo, Jianzhong; Liu, Li; Wang, Daqi

2011-10-01

195

An easy and efficient method for the production of carboxylic acids and aldehydes by microbial oxidation of primary alcohols  

Microsoft Academic Search

An easy and efficient methodology for obtaining aldehydes or carboxylic acids by oxidation of the corresponding primary alcohols with acetic acid bacteria is reported. When the biotransformation is performed in water the acids are obtained; aldehydes can be accumulated by using a water\\/isooctane two-liquid phase system.

Raffaella Gandolfi; Nicola Ferrara; Francesco Molinari

2001-01-01

196

Secondary porosity revisited: The chemistry of feldspar dissolution by carboxylic acids and anions  

SciTech Connect

Carboxylic acids in subsurface waters have been proposed as agents for dissolving feldspars and complexing aluminum to create secondary porosity in sandstones. Previously published experimental work indicated high aluminum mobility in the presence of carboxylic acid solutions. In order to further evaluate aluminum mobility, alkali feldspar dissolution experiments were run at 100C and 300 bars in the presence of mono- and dicarboxylic acids and their anions. Experimental results imply that under reservoir conditions, aluminum-organic anion complexes are insignificant for acetate and propionate and possibly significant for oxalate and malonate. Propionate appeared to inhibit alkali feldspar dissolution and, hence, may retard aluminum mobility. Dissolution of feldspar in the presence of oxalic and acetic acid can be explained by enhanced dissolution kinetics and greater aluminum mobility under low-pH conditions. The general absence of such low-pH fluids in subsurface reservoirs makes this an unlikely mechanism for creating secondary porosity. Also, the thermal instability of oxalate and malonate limits their aluminum-complexing potential in reservoirs at temperatures above 100C.

Stoessell, R.K. (Univ. of New Orleans, LA (United States)); Pittman, E.D. (Univ. of Tulsa, OK (United States))

1990-12-01

197

Theoretical and experimental studies on the electronic, optical, and structural properties of poly-pyrrole-2-carboxylic acid films  

NASA Astrophysics Data System (ADS)

A theoretical approach is used here to explain experimental results obtained from the electrosynthesis of polypyrrole-2-carboxylic acid (PPY-2-COOH) films in nonaqueous medium. An analysis of the Fukui function (reactivity index) indicates that the monomer (pyrrole-2-carboxylic acid, PY-2-COOH), and dimers and trimers are oxidized in the C4 or C5 positions of the heterocyclic ring of the PY-2-COOH structure. After calculating the heat of formation using semiempirical Austin Model 1 post-Hartree-Fock parameterization for dimer species, both C4 and C5 positions adjacent to the aromatic rings of PPY-2-COOH were considered the most susceptible ones to oxidative coupling reactions. The ZINDO-S/CI semiempirical method was used to simulate the electronic transitions typically seen in the UV-VIS-NIR range in monomer and oligomers with different conjugation lengths. The use of an electrochemical quartz crystal microbalance provides sufficient information to propose a polymerization mechanism of PY-2-COOH based on molecular modeling and experimental results.

Foschini, Mauricio; Silva, Hugo Santos; Silva, Raigna A.; Marletta, Alexandre; Gonçalves, Débora

2013-11-01

198

Design, synthesis and biological activity of thiazolidine-4-carboxylic acid derivatives as novel influenza neuraminidase inhibitors.  

PubMed

A series of thiazolidine-4-carboxylic acid derivatives were synthesized and evaluated for their ability to inhibit neuraminidase (NA) of influenza A virus. All the compounds were synthesized in good yields starting from commercially available l-cysteine hydrochloride using a suitable synthetic strategy. These compounds showed moderate inhibitory activity against influenza A neuraminidase. The most potent compound of this series is compound 4f (IC(50)=0.14 ?M), which is about sevenfold less potent than oseltamivir and could be used to design novel influenza NA inhibitors that exhibit increased activity based on thiazolidine ring. PMID:21382719

Liu, Yu; Jing, Fanbo; Xu, Yingying; Xie, Yuanchao; Shi, Fangyuan; Fang, Hao; Li, Minyong; Xu, Wenfang

2011-04-01

199

Palladacycle-catalyzed decarboxylative coupling of alkynyl carboxylic acids with aryl chlorides under air.  

PubMed

A highly efficient and practical protocol for palladacycle-catalyzed decarboxylative coupling of alkynyl carboxylic acids with aryl chlorides was developed. The reaction could proceed smoothly in air within 3 h under optimized reaction conditions (1 mol % of palladacycle, 4 mol % of Xphos, 2.0 equiv of K2CO3 in xylene/H2O), affording the corresponding internal alkynes in mostly good to excellent yields. Remarkably, this result represents the first successful examples of this type of decarboxylative cross-coupling using electron-poor, electron-neutral and even inactive sterically hindered electron-rich aryl chlorides as the starting materials. PMID:23573947

Li, Xiang; Yang, Fan; Wu, Yangjie

2013-05-01

200

Polymer-supported triazenes as smart reagents for the alkylation of carboxylic acids.  

PubMed

Starting from polystyrene, a simple four-step synthesis of polymer-supported alkyltriazenes (alkyl=Me, Et, benzyl) is described. With this synthesis, a loading capacity of 2.2 mmol g(-1) can be reached. The most prominent application of these polymer-supported reagents is the rapid, highly selective and high-yielding esterification of carboxylic acids, which involves a simple "mix and filter off" procedure at room temperature. If stored in a refrigerator, these reagents are stable for many months and they can be recycled several times. PMID:12794900

Erb, Bernhard; Kucma, Jean-Philippe; Mourey, Sandrine; Struber, Fritz

2003-06-01

201

Polymer-Sensitized Solar Cells Using Polythiophene Derivatives with Directly Attached Carboxylic Acid Groups  

NASA Astrophysics Data System (ADS)

Polythiophene derivatives with carboxylic acid groups directly attached to the thiophene rings were synthesized for polymer-sensitized solar cells (PSSCs). The polymer layer densely and uniformly covering the surface of the TiO2 particle in the photoanode of the PSSCs allows excitons to diffuse to the polymer/TiO2 interface efficiently. The PSSCs yielded a maximum incident photon-to-current conversion efficiency of about 80% at 480 nm and the open-circuit voltage (VOC) values but also short-circuit current density (JSC) values increased with decreasing hydrolysis ratio of the polymer.

Akitsu, Kenta; Kubo, Takaya; Uchida, Satoshi; Segawa, Hiroshi; Otani, Naoki; Tomura, Misayo; Tamura, Takayuki; Matsumura, Mitsunobu

2012-10-01

202

Acid-functionalized nanoparticles for biomass hydrolysis  

NASA Astrophysics Data System (ADS)

Cellulosic ethanol is a renewable source of energy. Lignocellulosic biomass is a complex material composed mainly of cellulose, hemicellulose, and lignin. Biomass pretreatment is a required step to make sugar polymers liable to hydrolysis. Mineral acids are commonly used for biomass pretreatment. Using acid catalysts that can be recovered and reused could make the process economically more attractive. The overall goal of this dissertation is the development of a recyclable nanocatalyst for the hydrolysis of biomass sugars. Cobalt iron oxide nanoparticles (CoFe2O4) were synthesized to provide a magnetic core that could be separated from reaction using a magnetic field and modified to carry acid functional groups. X-ray diffraction (XRD) confirmed the crystal structure was that of cobalt spinel ferrite. CoFe2O4 were covered with silica which served as linker for the acid functions. Silica-coated nanoparticles were functionalized with three different acid functions: perfluoropropyl-sulfonic acid, carboxylic acid, and propyl-sulfonic acid. Transmission electron microscope (TEM) images were analyzed to obtain particle size distributions of the nanoparticles. Total carbon, nitrogen, and sulfur were quantified using an elemental analyzer. Fourier transform infra-red spectra confirmed the presence of sulfonic and carboxylic acid functions and ion-exchange titrations accounted for the total amount of catalytic acid sites per nanoparticle mass. These nanoparticles were evaluated for their performance to hydrolyze the beta-1,4 glycosidic bond of the cellobiose molecule. Propyl-sulfonic (PS) and perfluoropropyl-sulfonic (PFS) acid functionalized nanoparticles catalyzed the hydrolysis of cellobiose significantly better than the control. PS and PFS were also evaluated for their capacity to solubilize wheat straw hemicelluloses and performed better than the control. Although PFS nanoparticles were stronger acid catalysts, the acid functions leached out of the nanoparticle during the catalytic reactions. PS nanoparticles were further evaluated for the pretreatment of corn stover in order to increase digestibility of the biomass. The pretreatment was carried out at three different catalyst load and temperature levels. At 180°C, the total glucose yield was linearly correlated to the catalyst load. A maximum glucose yield of 90% and 58% of the hemicellulose sugars were obtained at this temperature.

Pena Duque, Leidy Eugenia

203

Reactivity of ferrate(V) with carboxylic acids: A pre-mix pulse radiolysis study  

NASA Astrophysics Data System (ADS)

Rates of reduction of ferrate(VI) to ferrate(V) by a number of organic acid and ester radicals (monocarboxylic acids, dicarboxylic acids, amino acids, malonic acid esters), generated by the pulse radiolysis technique, vary from 10 7-10 9 dm 3 mol -1 s -1. The rate at which these radicals reduce ferrate(VI) depends upon the nature of the substituents at the ?-carbon atom and decrease in the order ?- C-NH 2>?-C-OH>?-C-H.A similar dependence upon the ?-C-groups(s) has been observed for the oxidation of the parent organic acid by ferrate(V), for which the rate constants vary from 10 1-10 6 dm 3 mol -1 s -1. An oxidation mechanism is being proposed in which ferrate(V) oxidizes the carboxylic acid by a two-electron process. The rate of the oxidation process is dependent on the protonation of ferrate(V). For example, in the oxidation of gluconic acid with H 2Fe VO 4-/HF eVO 42-; k 10(H 2Fe VO 4- + gluconate) = 1.1 × 10 6 dm 3 mol -1 s -1 and k 11(HFe VO 42- + gluconate) = 2.0 × 10 5dm 3 mol -1 s -1. The oxidation mechanisms for malate and asparate by OH radicals and ferrate(V) are compared.

Bielski, Benon H. J.; Sharma, Virender K.; Czapski, Gidon

1994-11-01

204

Carboxylic Acids as Biomarkers of Biomphalaria alexandrina Snails Infected with Schistosoma mansoni  

PubMed Central

Biomphalaria alexandrina snails play an indispensable role in transmission of schistosomiasis. Infection rates in field populations of snails are routinely determined by cercarial shedding neglecting prepatent snail infections, because of lack of a suitable method for diagnosis. The present study aimed at separation and quantification of oxalic, malic, acetic, pyruvic, and fumaric acids using ion-suppression reversed-phase high performance liquid chromatography (HPLC) to test the potentiality of these acids to be used as diagnostic and therapeutic biomarkers. The assay was done in both hemolymph and digestive gland-gonad complex (DGG) samples in a total of 300 B. alexandrina snails. All of the studied acids in both the hemolymph and tissue samples except for the fumaric acid in hemolymph appeared to be good diagnostic biomarkers as they provide not only a good discrimination between the infected snails from the control but also between the studied stages of infection from each other. The most sensitive discriminating acid was malic acid in hemolymph samples as it showed the highest F-ratio. Using the Z-score, malic acid was found to be a good potential therapeutic biomarker in the prepatency stage, oxalic acid and acetic acid in the stage of patency, and malic acid and acetic acid at 2 weeks after patency. Quantification of carboxylic acids, using HPLC strategy, was fast, easy, and accurate in prediction of infected and uninfected snails and possibly to detect the stage of infection. It seems also useful for detection of the most suitable acids to be used as drug targets. PMID:20585528

Abou Elseoud, Salwa M. F.; Ezz El Din, Hayam M.; Abdel Al, Hala; Mossalem, Hanan; Elleboudy, Noha

2010-01-01

205

The amino acid sequences of the carboxyl termini of human and mouse hepatic lipase influence cell surface association  

Microsoft Academic Search

Human hepatic lipase (hHL) mainly exists cell sur- face bound, whereas mouse HL (mHL) circulates in the blood stream. Studies have suggested that the carboxyl terminus of HL mediates cell surface binding. We prepared recombinant hHL, mHL, and chimeric proteins (hHLmt and mHLht) in which the carboxyl terminal 70 amino acids of hHL were ex- changed with the corresponding sequence

Robert J. Brown; Joshua R. Schultz; Kerry W. S. Ko; John S. Hill; Tanya A. Ramsamy; Ann L. White; Daniel L. Sparks; Zemin Yao

2003-01-01

206

Separation of aliphatic carboxylic acids and benzenecarboxylic acids by ion-exclusion chromatography with various cation-exchange resin columns and sulfuric acid as eluent.  

PubMed

The application of various hydrophilic cation-exchange resins for high-performance liquid chromatography (sulfonated silica gel: TSKgel SP-2SW, carboxylated silica gel: TSKgel CM-2SW, sulfonated polymethacrylate resin: TSKgel SP-5PW, carboxylated polymethacrylate resins: TSKgel CM-5PW and TSKgel OA-Pak A) as stationary phases in ion-exclusion chromatography for C1-C7 aliphatic carboxylic acids (formic, acetic, propionic, butyric, isovaleric, valeric, isocaproic, caproic, 2-methylhexanoic and heptanoic acids) and benzenecarboxylic acids (pyromellitic, trimellitic, hemimellitic, o-phthalic, m-phthalic, p-phthalic, benzoic, salicylic acids and phenol) was carried out using diluted sulfuric acid as the eluent. Silica-based cation-exchange resins (TSKgel SP-2SW and TSKgel CM-2SW) were very suitable for the ion-exclusion chromatographic separation of these benzenecarboxylic acids. Excellent simultaneous separation of these benzenecarboxylic acids was achieved on a TSKgel SP-2SW column (150 x 6 mm I.D.) in 17 min using a 2.5 mM sulfuric acid at pH 2.4 as the eluent. Polymethacrylate-based cation-exchange resins (TSKgel SP-5PW, TSKgel CM-5PW and TSKgel OA-Pak A) acted as advanced stationary phases for the ion-exclusion chromatographic separation of these C1-C7 aliphatic carboxylic acids. Excellent simultaneous separation of these C1-C7 acids was achieved on a TSKgel CM-5PW column (150 x 6 mm I.D.) in 32 min using a 0.05 mM sulfuric acid at pH 4.0 as the eluent. PMID:12830883

Ohta, Kazutoku; Ohashi, Masayoshi; Jin, Ji-Ye; Takeuchi, Toyohide; Fujimoto, Chuzo; Choi, Seong-Ho; Ryoo, Jae-Jeong; Lee, Kwang-Pill

2003-05-16

207

Observation of multiple, identical binding sites in the exchange of carboxylic acid ligands with CdS nanocrystals.  

PubMed

We study ligand exchange between the carboxylic acid group and 5.0 nm oleic-acid capped CdS nanocrystals (NCs) using fluorescence resonance energy transfer (FRET). This is the first measurement of the initial binding events between cadmium chalcogenide NCs and carboxylic acid groups. The binding behavior can be described as an interaction between a ligand with single binding group and a substrate with multiple, identical binding sites. Assuming Poissonian binding statistics, our model fits both steady-state and time-resolved photoluminescence (SSPL and TRPL, respectively) data well. A modified Langmuir isotherm reveals that a CdS nanoparticle has an average of 3.0 new carboxylic acid ligands and binding constant, Ka, of 3.4 × 10(5) M(-1). PMID:24810426

Li, Xin; Nichols, Valerie M; Zhou, Dapeng; Lim, Cynthia; Pau, George Shu Heng; Bardeen, Christopher J; Tang, Ming L

2014-06-11

208

Recent studies on lonidamine, the lead compound of the antispermatogenic indazol-carboxylic acids.  

PubMed

Lonidamine (LND) or [1-(2,4-dichlorobenzyl)-1H-indazole-3-carboxylic acid] is an anticancer and an antispermatogenic drug whose mechanism of action is still incompletely understood. LND is effective against a number of tumors, including head, neck and breast cancers, probably because of the inhibition of mitochondrial electron transport and the enzyme hexokinase and to the induction of apoptosis. Instead, the antispermatogenic activity of LND appeared to be related not only to its energolytic activity but also to other effects activities such as the inhibition of specific chloride channels in the epididymis and the disruption of the inter-Sertoli-germ cell junctions, leading to premature release of germ cells. In addition, we recently reported that, in the rat, LND at the dose of 100 mg/Kg b.w. p.o., a fully active but well tolerated dose, caused specific changes of the testicular and epididymal macroglobulins (alpha(2)-macroglobulin, alpha(1) inhibitor-3 and alpha(1)-macroglobulin). Further studies are needed to elucidate the mechanism of action of LND, the lead compound of an interesting class of antispermatogenic drugs based on the core structure of 1-(2,4-dichlorobenzyl)-indazole-3-carboxylic acid. PMID:12020777

Gatto, Maria Teresa; Tita, Beatrice; Artico, Marco; Saso, Luciano

2002-04-01

209

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

SciTech Connect

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.

Mungall, W.S. [Hope College, Holland, MI (United States). Dept. of Chemistry; Britt, P.F.; Buchanan, A.C. III [Oak Ridge National Lab., TN (United States)

1997-03-01

210

Rules governing vapor-phase extraction of carboxylic acids and phenols from aqueous solutions  

NASA Astrophysics Data System (ADS)

The influence of the molecular structure of the components to be extracted and the type of the extractant used on the effectiveness of vapor-phase extraction from water was studied for the example of low-molecular-weight carboxylic acids C2-C6 and phenols. Extraction parameters were found to depend on the length of the analyte molecule and its polarity. The experimental data and correlations observed substantiated the validity of the suggested mechanism of vapor-phase extraction. Changes in the Gibbs energy of extraction equilibrium as the length of the analyte molecule (in the homologous series of organic acids C2-C6) and molecule polarity (for the example of cresol isomers) increased were evaluated.

Bekhterev, V. N.

2008-06-01

211

Charge transport and structural dynamics in carboxylic-acid-based deep eutectic mixtures.  

PubMed

Charge transport and structural dynamics in the 1:2 mol ratio mixture of lidocaine and decanoic acid (LID-DA), a model deep eutectic mixture (DEM), have been characterized over a wide temperature range using broad-band dielectric spectroscopy and depolarized dynamic light scattering. Additionally, Fourier transform infrared spectroscopy measurements were performed to assess the degree of proton transfer between the neutral parent molecules. From our detailed analysis of the dielectric spectra, we have determined that this carboxylic-acid-based DEM is approximately 25% ionic at room temperature. Furthermore, we have found that the characteristic diffusion rate of mobile charge carriers is practically identical to the rate of structural relaxation at all measured temperatures, indicating that fast proton transport does not occur in LID-DA. Our results demonstrate that while LID-DA exhibits the thermal characteristics of a DEM, its charge transport properties resemble those of a protic ionic liquid. PMID:25025600

Griffin, Philip J; Cosby, Tyler; Holt, Adam P; Benson, Roberto S; Sangoro, Joshua R

2014-08-01

212

Synthesis and evaluation of novel dental monomer with branched carboxyl acid group.  

PubMed

To enhance the water miscibility and increase the mechanical properties of dentin adhesives, a new glycerol-based monomer with vinyl and carboxylic acid, 4-((1,3-bis(methacryloyloxy)propan-2-yl)oxy)-2-methylene-4-oxobutanoic acid (BMPMOB), was synthesized and characterized. Dentin adhesive formulations containing 2-hydroxyethyl methacrylate (HEMA), 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy) phenyl]propane (BisGMA), and BMPMOB were characterized with regard to real-time photopolymerization behavior, water sorption, dynamic mechanical analysis, and microscale three-dimensional internal morphologies and compared with HEMA/BisGMA controls. The experimental adhesive copolymers showed higher glass transition temperature and rubbery moduli, as well as improved water miscibility compared to the controls. The enhanced properties of the adhesive copolymers indicated that BMPMOB is a promising comonomer for dental restorative materials. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 1473-1484, 2014. PMID:24596134

Song, Linyong; Ye, Qiang; Ge, Xueping; Misra, Anil; Laurence, Jennifer S; Berrie, Cynthia L; Spencer, Paulette

2014-10-01

213

Experimental alkali feldspar dissolution at 100 degree C by carboxylic acids and their anions  

SciTech Connect

Feldspar dissolution will enhance sandstone porosity if the released aluminum can be transported away in the subsurface waters. Carboxylic acids have been proposed to provide hydrogen ions to promote dissolution and anions to complex aqueous aluminum to keep it in solution. However, the hydrogen ions should react quickly following acid generation in source beds, leaving monocarboxylic anions with lesser amounts of dicarboxylic acids and their anions on feldspar dissolution and the apparent complexing of aluminum in solution. Two-week dissolution experiments of alkali feldspar were run at 100{degree}C and 300 bars in acetic acid, oxalic acid, and sodium salt solutions of chloride, acetate, propionate, oxalate, and malonate. Extrapolation of the results, to reservoir conditions during sandstone diagenesis, implies that concentrations of aluminum-organic complexes are not significant for acetate and propionate and are possibly significant for oxalate and malonate, depending upon fluid compositions. Propionate appeared to inhibit feldspar dissolution and hence might decrease secondary porosity formation. Increases in aluminum concentrations in the presence of oxalic and acetic acid solutions appear to be due to enhanced dissolution kinetics and greater aluminum solubility under low-pH conditions. Such low-pH fluids are generally absent in subsurface reservoirs, making this an unlikely mechanism for enhancing porosity. Furthermore, the observed thermal instability of oxalate and malonate anions explains their general low concentrations in subsurface fluids which limits their aluminum complexing potential in reservoirs during late diagenesis.

Stoessell, R.K. (Univ. of New Orleans, LA (USA)); Pittman, E.D. (Univ. of Tulsa, OK (USA))

1990-05-01

214

Radiation-initiated emulsion copolymerization of styrene and carboxylic acid monomers. [Gamma radiation  

SciTech Connect

The emulsion copolymerization of styrene and carboxylic acid monomers such as acrylic, methacrylic, and itaconic acids (AAc, MAAc, IAc) was studied by using /sup 60/Co ..gamma..-rays as initiator and sodium dodecylsulfate as emulsifier. The polymerization behavior of these acid monomers was followed by simultaneous conductometric and potentiometric titrations for a latex sample taken in polymerization. The polymerization rate of these acid monomers increases in the following order of hydrophobicity: IAc < AAc < MAAc; this suggests that their polymerization sites are mainly the surface and/or subsurface regions of latex particles. The copolymerization rate of styrene and acid monomer increases with an increase in the acid monomer content for AAc and MAAc, whereas for IAc the rate decreases. The particle sizes determined by the stopped-flow method reveal that this variation of copolymerization rate cannot be explained by the number of growing particles and should be attributed to another factor; for instance, the transfer rate of styrene molecules from oil droplets to growing particles.

Egusa, S.; Makuuchi, K.

1982-03-01

215

Conformational characterization of the 1-aminocyclobutane-1-carboxylic acid residue in model peptides.  

PubMed

A series of N- and C-protected, monodispersed homo-oligopeptides (to the dodecamer level) from the small-ring alicyclic C alpha, alpha-dialkylated glycine 1-aminocyclobutane-1-carboxylic acid (Ac4c) and two Ala/Ac4c tripeptides were synthesized by solution methods and fully characterized. The conformational preferences of all the model peptides were determined in deuterochloroform solution by FT-IR absorption and 1H-NMR. The molecular structures of the amino acid derivatives Z-Ac4c-OH and Z2-Ac4c-OH, the tripeptides Z-(Ac4c)3-OtBu, Z-Ac4c-(L-Ala)2-OMe and Z-L-Ala-Ac4c-L-Ala-OMe, and the tetrapeptide Z-(Ac4c)4-OtBu were determined in the crystal state by X-ray diffraction. The average geometry of the cyclobutyl moiety of the Ac4c residue was assessed and the tau(N-C alpha-C') bond angle was found to be significantly expanded from the regular tetrahedral value. The conformational data are strongly in favour of the conclusion that the Ac4c residue is an effective beta-turn and helix former. A comparison with the structural propensities of alpha-aminoisobutyric acid, the prototype of C alpha, alpha-dialkylated glycines, and the other extensively investigated members of the family of 1-aminocycloalkane-1-carboxylic acids (Acnc, with n = 3, 5-8) is made and the implications for the use of the Ac4c residue in conformationally constrained peptide analogues are briefly examined. PMID:9230476

Gatos, M; Formaggio, F; Crisma, M; Toniolo, C; Bonora, G M; Benedetti, Z; Di Blasio, B; Iacovino, R; Santini, A; Saviano, M; Kamphuis, J

1997-01-01

216

Influence of cyclic dimer formation on the phase behavior of carboxylic acids. II. Cross-associating systems.  

PubMed

The doubly bonded dimer association scheme (DBD) proposed by Sear and Jackson is extended to mixtures exhibiting both self- and cross-associations. The PC-SAFT equation of state is combined with the new DBD association contribution to describe the vapor-liquid equilibria of binary mixtures of carboxylic acids + associating compounds (water, alcohols, and carboxylic acids). The effect of doubly bonded dimers on the phase behavior in such systems is less important than in mixtures of carboxylic acids with nonassociating compounds, due to the cross-associations that compete with the formation of DBDs. Nevertheless, a clear improvement in the description of vapor-liquid coexistence curves is achieved over the classical 2B association model, particularly for the dew point curves. PMID:23806104

Jane?ek, Ji?í; Paricaud, Patrice

2013-08-15

217

Enzymes involved in a novel anaerobic cyclohexane carboxylic Acid degradation pathway.  

PubMed

The anaerobic degradation of cyclohexane carboxylic acid (CHC) has so far been studied only in Rhodopseudomonas palustris, in which CHC is activated to cyclohexanoyl coenzyme A (cyclohexanoyl-CoA [CHCoA]) and then dehydrogenated to cyclohex-1-ene-1-carboxyl-CoA (CHeneCoA). This intermediate is further degraded by reactions of the R. palustris-specific benzoyl-CoA degradation pathway of aromatic compounds. However, CHeneCoA is not an intermediate in the degradation of aromatic compounds in all other known anaerobic bacteria; consequently, degradation of CHC was mostly unknown in anaerobic bacteria. We identified a previously unknown CHC degradation pathway in the Fe(III)-reducing Geobacter metallireducens by determining the following CHC-induced in vitro activities: (i) the activation of CHC to CHCoA by a succinyl-CoA:CHC CoA transferase, (ii) the 1,2-dehydrogenation of CHCoA to CHeneCoA by CHCoA dehydrogenase, and (iii) the unusual 1,4-dehydrogenation of CHeneCoA to cyclohex-1,5-diene-1-carboxyl-CoA. This last represents a previously unknown joint intermediate of the CHC and aromatic compound degradation pathway in bacteria other than R. palustris. The enzymes catalyzing the three reactions were purified and characterized as specific enzymes after heterologous expression of the encoding genes. Quantitative reverse transcription-PCR revealed that expression of these genes was highly induced during growth with CHC but not with benzoate. The newly identified CHC degradation pathway is suggested to be present in nearly all CHC-degrading anaerobic bacteria, including denitrifying, Fe(III)-reducing, sulfate-reducing, and fermenting bacteria. Remarkably, all three CHC degradation pathways always link CHC catabolism to the catabolic pathways of aromatic compounds. We propose that the capacity to use CHC as a carbon source evolved from already-existing aromatic compound degradation pathways. PMID:25112478

Kung, Johannes W; Meier, Anne-Katrin; Mergelsberg, Mario; Boll, Matthias

2014-10-15

218

Ascorbic acid absorption in Crohn's disease. Studies using L-(carboxyl-/sup 14/C)ascorbic acid  

SciTech Connect

Total body pool and intestinal absorption of ascorbic acid were studied in 12 patients undergoing operation for Crohn's disease (six with fistulae and six without) and in six control patients undergoing operation for reasons other than Crohn's disease. L-(carboxyl-/sup 14/C)Ascorbic acid, 0.19-0.40 megabecquerels (MBq), was given orally. After a period of equilibration, the labeled ascorbic acid was flushed out of the patient's body tissues using large doses of unlabeled ascorbic acid. Intestinal absorption of ascorbic acid, assessed from the total cumulative urinary /sup 14/C recovery, was found to be similar in patients with fistulizing Crohn's disease (73.9 +/- 8.45%), those without fistulas (72.8 +/- 11.53%), and in controls (80.3 +/- 8.11%). Total body pools of ascorbic acid, calculated using the plasma /sup 14/C decay curves, were similar in patients with Crohn's disease with fistulas (17.1 +/- 5.91 mg/kg), patients without fistulas (9.6 +/- 3.58 mg/kg), and in controls (13.3 +/- 4.28 mg/kg). The results indicate that ascorbic acid absorption is normal in patients with both fistulizing and nonfistulizing Crohn's disease. The results suggest that routine supplements of vitamin C are not necessary unless oral ascorbic acid intake is low.

Pettit, S.H.; Shaffer, J.L.; Johns, C.W.; Bennett, R.J.; Irving, M.H.

1989-04-01

219

Synthesis of functional poly(ester-andydride)s based on succinic acid  

Microsoft Academic Search

This paper describes the three-step synthesis and characteristics of succinic acid based functional poly(ester-anhydride)s bearing allyl groups in side chains. Firstly, carboxyl terminated functional oligoesters with molecular weight in the range of 300–1000 were obtained by melt condensation of allyl glycidyl ether with an excess of succinic acid. Secondly, carboxyl end groups of the macromer obtained were converted to mixed

Katarzyna Jaszcz; Jan ?ukaszczyk; Monika ?miga-Matuszowicz

2008-01-01

220

Catalytic wet air oxidation of carboxylic acids on TiO{sub 2}-supported ruthenium catalysts  

SciTech Connect

The total oxidation of aqueous solutions of carboxylic acids by air was studied in a slurry reactor over the temperature range 180--100 C and oxygen partial pressure of 0.3--1.8 MPa in the presence of a 2.8%Ru/TiO{sub 2} catalyst. The influence of various parameters is presented: the catalytic wet air oxidation of succinic acid is 0 order with respect to succinic acid; the order with respect to oxygen pressure is 0.4, and the activation energy is ca. 125 kJ/mol. It was found that acetic acid, which is one of the intermediates, and CO{sub 2} have no retarding effect on the total organic carbon abatement rate of succinic acid. Substitution of one hydrogen atom of the methyl group in acetic acid by Cl, OH, or NH{sub 2} gives an increase of the oxidation rate. However, it was proposed that the low activity of acetic acid oxidation is due not only to the difficulty to oxidize the methyl group, but also to the low adsorption coefficient of acetic acid on ruthenium surface. Inorganic salts, such as sodium chloride, only slightly decrease the oxidation rate of acetic acid. The absence of metal ions (Ru, Ti) in the effluents after reaction and the absence of particle sintering indicate also a high stability of the catalyst under the conditions employed. The catalyst can be recycled without loss of activity after the second run. The activity becomes stable after the attainment of a steady-state coverage of the Ru particles by oxygen. The study of the effect of reduction-oxidation treatments of the catalyst showed that the activity depends on the oxidation state of the surface.

Beziat, J.C.; Besson, M.; Gallezot, P. [CNRS, Villeurbanne (France). Inst. de Recherches sur la Catalyse] [CNRS, Villeurbanne (France). Inst. de Recherches sur la Catalyse; Durecu, S. [TREDI, Vandoeuvre-les-Nancy (France). Dept. Recherche] [TREDI, Vandoeuvre-les-Nancy (France). Dept. Recherche

1999-02-15

221

Comparison of unimolecular decomposition pathways for carboxylic acids of relevance to biofuels.  

PubMed

Quantum mechanical molecular modeling is used [M06-2X/6-311++G(2df,p)] to compare activation energies and rate constants for unimolecular decomposition pathways of saturated and unsaturated carboxylic acids that are important in the production of biofuels and that are models for plant and algae-derived intermediates. Dehydration and decarboxylation reactions are considered. The barrier heights to decarboxylation and dehydration are similar in magnitude for saturated acids (?71 kcal mol(-1)), with an approximate 1:1 [H2O]/[CO2] branching ratio over the temperature range studied (500-2000 K). ?,?-Unsaturation lowers the barrier to decarboxylation between 2.2 and 12.2 kcal mol(-1) while increasing the barriers to dehydration by ?3 kcal mol(-1). The branching ratio, as a result, is an order of magnitude smaller, [H2O]/[CO2] = 0.07. For some ?,?-unsaturated acids, six-center transition states are available for dehydration, with barrier heights of ?35.0 kcal mol(-1). The branching ratio for these acids can be as high as 370:1. ?,?-Unsaturation results in a small lowering in the barrier height to decarboxylation (?70.0 kcal mol(-1)). ?,?-Unsaturation also leads to a lowering in the dehydration pathway from 1.7 to 5.1 kcal mol(-1). These results are discussed with respect to predicted kinetic values for acids of importance in biofuels production. PMID:24295398

Clark, Jared M; Nimlos, Mark R; Robichaud, David J

2014-01-01

222

Highly Versatile Catalytic Hydrogenation of Carboxylic and Carbonic Acid Derivatives using a Ru-Triphos Complex: Molecular Control over Selectivity and Substrate Scope.  

PubMed

The complex [Ru(Triphos)(TMM)] (Triphos = 1,1,1-tris(diphenylphosphinomethyl)ethane, TMM = trimethylene methane) provides an efficient catalytic system for the hydrogenation of a broad range of challenging functionalities encompassing carboxylic esters, amides, carboxylic acids, carbonates, and urea derivatives. The key control factor for this unique substrate scope results from selective activation to generate either the neutral species [Ru(Triphos)(Solvent)H2] or the cationic intermediate [Ru(Triphos)(Solvent)(H)(H2)](+) in the presence of an acid additive. Multinuclear NMR spectroscopic studies demonstrated together with DFT investigations that the neutral species generally provides lower energy pathways for the multistep reduction cascades comprising hydrogen transfer to C?O groups and C-O bond cleavage. Carboxylic esters, lactones, anhydrides, secondary amides, and carboxylic acids were hydrogenated in good to excellent yields under these conditions. The formation of the catalytically inactive complexes [Ru(Triphos)(CO)H2] and [Ru(Triphos)(?-H)]2 was identified as major deactivation pathways. The former complex results from substrate-dependent decarbonylation and constitutes a major limitation for the substrate scope under the neutral conditions. The deactivation via the carbonyl complex can be suppressed by addition of catalytic amounts of acids comprising non-coordinating anions such as HNTf2 (bis(trifluoromethane)sulfonimide). Although the corresponding cationic cycle shows higher overall barriers of activation, it provides a powerful hydrogenation pathway at elevated temperatures, enabling the selective reduction of primary amides, carbonates, and ureas in high yields. Thus, the complex [Ru(Triphos)(TMM)] provides a unique platform for the rational selection of reaction conditions for the selective hydrogenation of challenging functional groups and opens novel synthetic pathways for the utilization of renewable carbon sources. PMID:25208046

Vom Stein, Thorsten; Meuresch, Markus; Limper, Dominik; Schmitz, Marc; Hölscher, Markus; Coetzee, Jacorien; Cole-Hamilton, David J; Klankermayer, Jürgen; Leitner, Walter

2014-09-24

223

ABIOTIC FORMATION OF CARBOXYLIC ACIDS (RCOOH) IN INTERSTELLAR AND SOLAR SYSTEM MODEL ICES  

SciTech Connect

The present laboratory study simulated the abiotic formation of carboxylic acids (RCOOH) in interstellar and solar system model ices of carbon dioxide (CO{sub 2})-hydrocarbon mix C{sub n} H{sub 2n+2} (n = 1-6). The pristine model ices were irradiated at 10 K under contamination-free, ultrahigh vacuum conditions with energetic electrons generated in the track of galactic cosmic-ray particles. The chemical processing of the ices was monitored by a Fourier transform infrared spectrometer and a quadrupole mass spectrometer during the irradiation phase and subsequent warm-up phases on line and in situ in order to extract qualitative (carriers) and quantitative (rate constants and yields) information on the newly synthesized species. Carboxylic acids were identified to be the main carrier, together with carbon monoxide (CO) and a trace of formyl (HCO) and hydroxycarbonyl (HOCO) radicals at 10 K. The upper limit of acid column density at 10 K was estimated as much as (1.2 {+-} 0.1) x 10{sup 17} molecules cm{sup -2} at doses of 17 {+-} 2 eV molecule{sup -1}, or the yield of 39% {+-} 4% from the initial column density of carbon dioxide. The temporal column density profiles of the products were then numerically fit using two independent kinetic schemes of reaction mechanisms. Finally, we transfer this laboratory simulation to star-forming regions of the interstellar medium, wherein cosmic-ray-induced processing of icy grains at temperatures as low as 10 K could contribute to the current level of chemical complexity as evidenced in astronomical observations and in extracts of carbonaceous meteorites.

Kim, Y. S.; Kaiser, R. I., E-mail: ralfk@hawaii.ed [Department of Chemistry, University of Hawaii at Manoa, Honolulu, HI 96822 (United States)

2010-12-10

224

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

SciTech Connect

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.

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

1996-02-01

225

IV. -Amino Acids: carboxyl and amino groups bonded to -Carbo n A. Acid/Base properties  

E-print Network

Carbohydrate) Nucleotide Oligonucleotide Nucleic Acid Amino Acid Peptid e Polypeptide Protein #12;Table 5. Peptides contain relatively few amino acids linked by peptide bonds: dipeptide, tripeptide, tetrapeptide Structure (1°) sequence of amino acids connected by peptide bonds 2. Secondary Structure (2°) local

Frey, Terry

226

Surface Patterning of Benzene Carboxylic Acids on Graphite: Influence of structure, solvent, and concentration on molecular self-assembly  

NASA Astrophysics Data System (ADS)

Scanning tunneling microscopy (STM) was used to investigate the molecular self-assembly of four different benzene carboxylic acid derivatives at the liquid/graphite interface: pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid), trimellitic acid (1,2,4-benzenetricarboxylic acid), trimesic acid (1,3,5-benzenetricarboxylic acid), and 1,3,5-benzenetriacetic acid. A range of two dimensional networks are observed that depend sensitively on the number of carboxylic acids present, the nature of the solvent, and the solution concentration. We will describe our recent efforts to determine (a) the preferential two-dimensional structure(s) for each benzene carboxylic acid at the liquid/graphite interface, (b) the thermodynamic and kinetic factors influencing self-assembly (or lack thereof), (c) the role solvent plays in the assembly, (e) the effect of in situ versus ex situ dilution on surface packing density, and (f) the temporal evolution of the self-assembled monolayer. Results of computational analysis of analog molecules and model monolayer films will also be presented to aid assignment of network structures and to provide a qualitative picture of surface adsorption and network formation.

Florio, Gina; Stiso, Kimberly; Campanelli, Joseph; Dessources, Kimberly; Folkes, Trudi

2012-02-01

227

Transition metal ion-assisted photochemical generation of alkyl halides and hydrocarbons from carboxylic acids  

SciTech Connect

Near-UV photolysis of aqueous solutions of propionic acid and aqueous Fe3+ in the absence of oxygen generates a mixture of hydrocarbons (ethane, ethylene and butane), carbon dioxide, and Fe2+. The reaction becomes mildly catalytic (about five turnovers) in the presence of oxygen which converts a portion of alkyl radicals to oxidizing intermediates that reoxidize Fe2+. The photochemistry in the presence of halide ions (X? = Cl?, Br?) generates ethyl halides via halogen atom abstraction from FeXn3?n by ethyl radicals. Near-quantitative yields of C2H5X are obtained at ?0.05 M X?. Competition experiments with Co(NH3)5Br2+ provided kinetic data for the reaction of ethyl radicals with FeCl2+ (k = (4.0 ± 0.5) × 106 M?1 s?1) and with FeBr2+ (k = (3.0 ± 0.5) × 107 M?1 s?1). Photochemical decarboxylation of propionic acid in the presence of Cu2+ generates ethylene and Cu+. Longer-chain acids also yield alpha olefins as exclusive products. These reactions become catalytic under constant purge with oxygen which plays a dual role. It reoxidizes Cu+ to Cu2+, and removes gaseous olefins to prevent accumulation of Cu+(olefin) complexes and depletion of Cu2+. The results underscore the profound effect that the choice of metal ions, the medium, and reaction conditions exert on the photochemistry of carboxylic acids.

Carraher, Jack; Pestovsky, Oleg; Bakac, Andreja

2012-03-14

228

Effects of carboxylic acids on the rheological properties of crumb rubber modified asphalt  

SciTech Connect

The Federal mandate of 1991-1995 on the use of scrap tires in Federal roadway construction sparked a major interest in gaining a fundamental understanding of the behavior of rubber in asphalt. This study is a systematic elucidation of what chemistry controls the final crumb rubber modified asphalt (CRMA) product quality. We discovered that the type and total acid content in the asphalt are the most influential chemical factors that determine the changes in the important roadway properties of shear modulus (G*) and loss angle ({delta}) of CRMA. Low acid (<0.005 m/L) asphalts were modified with three types of carboxylic acid and each made into CRMA using typical field mixing conditions of 1 hour at 175{degrees}C. Rheological measurements were then made at various storage times up to 192 hours following storage at both 156 and 200{degrees}C. We found the changes in CRMA theological properties correspond to the acid type spiked into the asphalt.

Tauer, J.E.; Robertson, R.E. [Western Research Institute, Laramie, WY (United States)

1996-12-31

229

Toxicokinetics of seven perfluoroalkyl sulfonic and carboxylic acids in pigs fed a contaminated diet.  

PubMed

The transfer of a mixture of perfluoroalkyl acids (PFAAs) from contaminated feed into the edible tissues of 24 fattening pigs was investigated. Four perfluoroalkyl sulfonic (PFSAs) and three perfluoroalkyl carboxylic acids (PFCAs) were quantifiable in feed, plasma, edible tissues, and urine. As percentages of unexcreted PFAA, the substances accumulated in plasma (up to 51%), fat, and muscle tissues (collectively, meat 40-49%), liver (under 7%), and kidney (under 2%) for most substances. An exception was perfluorooctanesulfonic acid (PFOS), with lower affinity for plasma (23%) and higher for liver (35%). A toxicokinetic model is developed to quantify the absorption, distribution, and excretion of PFAAs and to calculate elimination half-lives. Perfluorohexanoic acid (PFHxA), a PFCA, had the shortest half-life at 4.1 days. PFSAs are eliminated more slowly (e.g., half-life of 634 days for PFOS). PFAAs in pigs exhibit longer elimination half-lives than in most organisms reported in the literature, but still shorter than in humans. PMID:24892814

Numata, Jorge; Kowalczyk, Janine; Adolphs, Julian; Ehlers, Susan; Schafft, Helmut; Fuerst, Peter; Müller-Graf, Christine; Lahrssen-Wiederholt, Monika; Greiner, Matthias

2014-07-16

230

Omega-3 carboxylic acids (epanova(®)): a review of its use in patients with severe hypertriglyceridemia.  

PubMed

Omega-3 carboxylic acids (Epanova(®)) [OM3-CA] is the first free fatty acid form of long-chain marine omega-3 fatty acids (eicosapentaenoic acid and docosahexaenoic acid being the most abundant) to be approved by the US FDA as an adjunct to diet to lower triglyceride levels in patients with severe hypertriglyceridemia (?500 mg/dL). Oral OM3-CA has greater bioavailability than ethyl ester forms of omega-3 and, unlike omega-3 acid ethyl esters, does not require co-ingestion of a high-fat meal, as it does not need pancreatic enzyme activity for absorption. In the 12-week EpanoVa fOr Lowering Very high triglyceridEs (EVOLVE) trial, OM3-CA 2 or 4 g/day significantly reduced serum triglyceride levels relative to placebo. Other lipid parameters, including non-high-density lipoprotein cholesterol (non-HDL-C), total cholesterol, and very low-density lipoprotein cholesterol (VLDL-C) levels, were also reduced significantly with OM3-CA relative to placebo. Low-density lipoprotein cholesterol levels were increased significantly with OM3-CA relative to placebo; however, these increases were not accompanied by increases in the circulating concentrations of non-HDL-C, VLDL-C, or apolipoprotein B. OM3-CA was generally well tolerated in this study, with most adverse events being of mild or moderate severity. Although additional comparative data are needed to position OM3-CA with respect to other formulations of omega-3 fatty acids, current evidence suggests that OM3-CA is a useful addition to the treatment options available for patients with severe hypertriglyceridemia. PMID:25234378

Blair, Hannah A; Dhillon, Sohita

2014-10-01

231

Growth behavior of L-pyrrolidone-2-carboxylic acid (L-PCA) single crystals  

NASA Astrophysics Data System (ADS)

Growth conditions to prepare large single crystals of L-pyrrolidone-2-carboxylic acid (L-PCA), a novel nonlinear optical organic material, have been intensively studied with an attempt for fabrication in optical devices. L-PCA single crystals of good optical quality having dimensions of typically ~ 2.5 × 1.5 ×1.5 cm 3 were grown from aqueous solutions with seed crystals by a slow cooling method. They are chemically stable because molecules are hydrogen bonded to form three-dimensional networks in the crystal state. Further growth conditions to obtain large single crystals in a shorter time have been investigated by considering both mass balance equations and the kinetics for crystal growth. It was found that increasing the cooling rate in the later periods of crystal growth is advantageous for the purpose. The largest crystal was 17.5 g in weight, which was prepared in 6 days.

Kitazawa, Manabu; Takahashi, Mitsuo; Matsuoka, Masakuni

1994-08-01

232

Atomic layer deposition of aluminum oxide on carboxylic acid-terminated self-assembled monolayers.  

PubMed

In situ infrared absorption spectroscopy is used to monitor atomic layer deposition (ALD) of aluminum oxide (Al2O3) on carboxylic acid-terminated self-assembled monolayers (SAMs), Si(111)-(CH2)10-COOH (or COOH-SAMs), directly grafted on silicon (111) at approximately 100 degrees C. The quality of resulting Al2O3 films is comparable to Al2O3 on SiO2. Both the SAM film and the Si/SAM interface remain chemically stable during growth and upon post annealing to 400 degrees C, suggesting that the tight packing of the alkyl chains and COOH-SAM head groups presents a diffusion barrier and promotes ordered nucleation for ALD. PMID:19140733

Li, Meng; Dai, Min; Chabal, Yves J

2009-02-17

233

Synthesis and antihyperglycemic evaluation of new 2-hydrazolyl-4-thiazolidinone-5-carboxylic acids having pyrazolyl pharmacophores.  

PubMed

In the search of new antihyperglycemic agents and following rational approach of drug designing here new 2-hydrazolyl-4-thiazolidinone-5-carboxylic acids (4a-g) with pyrazolyl pharmacophore have been synthesized via thia Michael addition reaction of 1-((3-(4-substituted phenyl)-1-phenyl-1H-pyrazol-4-yl)methylene)thiosemicarbazides (3a-g) with maleic anhydride. The required precursors, (3a-g) were obtained by condensing known 3-(4-substituted phenyl)-1-phenyl-1H-pyrazole-4-carbaldehydes (1a-g) with thiosemicarbazide in ethanol. The newly synthesized compounds (4a-g) have been evaluated for the antihyperglycemic activity in sucrose loaded rat model and among these compounds 4d, 4f and 4g have displayed significant antihyperglycemic activity. PMID:24813740

Bhosle, Manisha R; Mali, Jyotirling R; Pal, Savita; Srivastava, Arvind K; Mane, Ramrao A

2014-06-15

234

Carboxyl Group (?CO2 H) Functionalized Coordination Polymer Nanoparticles as Efficient Platforms for Drug Delivery.  

PubMed

Functionalization of nanoparticles can significantly influence their properties and potential applications. Although researchers can now functionalize metal, metal oxide, and organic polymer nanoparticles with a high degree of precision, controlled surface functionalization of nanoscale coordination polymer particles (CPPs) has remained a significant challenge. The lack of methodology is perhaps one of the greatest roadblocks to the advancement of CPPs into high added-value drug delivery applications. Here, we report having achieved this goal through a stepwise formation and functionalization protocol. We fabricated robust nanoparticles with enhanced thermal and colloidal stabilities by incorporation of carboxyl groups and these surface carboxyl groups could be subsequently functionalized through well-known peptide coupling reactions. The set of chemistries that we employed as proof-of-concept enabled a plethora of new functional improvements for the application of CPPs as drug delivery carriers, including enhanced colloidal stabilities and the incorporation of additional functional groups such as polyethylene glycol (PEG) or fluorescent dyes that enabled tracking of their cellular uptake. Finally, we ascertained the cytotoxicity of the new CPP nanoparticles loaded with camptothecin to human breast adenocarcinoma (MCF-7). Efflux measurements show that the encapsulation of camptothecin enhances the potency of the drug 6.5-fold and increases the drug retention within the cell. PMID:25284328

Novio, Fernando; Lorenzo, Julia; Nador, Fabiana; Wnuk, Karolina; Ruiz-Molina, Daniel

2014-11-17

235

Indolyl carboxylic acids by condensation of indoles with alpha-keto acids.  

PubMed

The novel indole derivatives 2,2-bis(3,3'-indolyl)propionic acid (1); 1,1,1,-tris(3,3',3"-indolyl)ethane (2); and 2,2-bis(3, 3'-indolyl)isocaproic acid (3) were isolated from solvent extracts of indole-supplemented supernatants of Escherichia coli and corynebacteria. The compounds were also obtained by chemical synthesis: compounds 1 and 2 from indole and pyruvic acid and compound 3 from indole and alpha-ketoisocaproic acid, following incubation at 37 degrees C in aqueous medium. Tryptophan and pyruvic acid gave the novel 2-(2-tryptophanyl)lactic acid (4). The condensation reaction between indoles and alpha-keto acids was of general nature, and the mild reaction conditions suggested it may proceed in vivo. Examples for endogenous occurrence may be the neuro-degenerative diseases phenylketonuria and maple syrup urine disease, both characterized by elevated blood levels of alpha-keto acids. PMID:10843566

Garbe, T R; Kobayashi, M; Shimizu, N; Takesue, N; Ozawa, M; Yukawa, H

2000-05-01

236

Short-chain carboxylic acids from gray catbird (Dumetella carolinensis) uropygial secretions vary with testosterone levels and photoperiod.  

PubMed

The uropygial gland of birds produces secretions that are important in maintaining the health and structural integrity of feathers. Non-volatile components of uropygial secretions are believed to serve a number of functions including waterproofing and conditioning the feathers. Volatile components have been characterized in fewer species, but are particularly interesting because of their potential importance in olfactory interactions within and across species. We used solid-phase microextraction headspace sampling with gas chromatography-mass spectrometry to detect and identify volatiles in uropygial secretions of gray catbirds (Dumetella carolinensis), a North American migratory bird. We consistently detected the following carboxylic acids: acetic, propanoic, 2-methylpropanoic, butanoic, and 3-methylbutanoic. We tested for the effect of lengthened photoperiod and/or exogenous testosterone on volatile signal strength and found a negative effect of lengthened photoperiod on the signal strength of propanoic, 2-methylpropanoic, and butanoic acids, suggesting a trade-off between their production and heightened night-time activity associated with lengthened photoperiod. Signal strength of propanoic and 2-methylpropanoic acids was lower in birds treated with exogenous testosterone than in birds treated with placebos. Sex did not affect signal strength of any of the volatile compounds. PMID:20346408

Whelan, Rebecca J; Levin, Tera C; Owen, Jennifer C; Garvin, Mary C

2010-07-01

237

Derivatization of carboxylic acids with 4-APEBA for detection by positive-ion LC-ESI–MS(\\/MS) applied for the analysis of prostanoids and NSAID in urine  

Microsoft Academic Search

In order to develop a generic positive ionization ESI LC–MS method for a variety of interesting substance classes, a new derivatization strategy for carboxylic acids was developed. The carboxylic acid group is labeled with the bromine containing 4-APEBA reagent based on carbodiimide chemistry. The derivatization reaction can be carried out under aqueous conditions, thereby greatly simplifying sample preparation. In this

A. Kretschmer; M. Giera; M. Wijtmans; L. de Vries; H. Lingeman; H. Irth; W. M. A. Niessen

2011-01-01

238

Organocatalytic Lewis base functionalisation of carboxylic acids, esters and anhydrides via C1-ammonium or azolium enolates.  

PubMed

This tutorial review highlights the organocatalytic Lewis base functionalisation of carboxylic acids, esters and anhydrides via C1-ammonium/azolium enolates. The generation and synthetic utility of these powerful intermediates is highlighted through their application in various methodologies including aldol-lactonisations, Michael-lactonisations/lactamisations and [2,3]-rearrangements. PMID:24867308

Morrill, Louis C; Smith, Andrew D

2014-09-01

239

[3 + 2] Cycloaddition reactions of thioisatin with thiazolidine-2-carboxylic acid: a versatile route to new heterocyclic scaffolds  

PubMed Central

A facile synthesis of azabicycloadducts is described by 1,3-dipolar cycloaddition reactions of thioisatin with thiazolidine-2-carboxylic acid in the presence of various electron rich and electron deficient dipolarophiles. Theoritical calculations have been performed to study the regioselectivity of products. The geometrical and energetic properties have been analyzed for the different reactants, transition states and cycloadducts formed. PMID:22373364

2011-01-01

240

Polyvalent-metal salts of heteropolyacid as efficient heterogeneous catalysts for Friedel–Crafts acylation of arenes with carboxylic acids  

Microsoft Academic Search

Polyvalent-metal (Ti4+, Fe3+, Sn4+, Bi3+, Ru3+) salts of dodecatungstophosphate act as effective heterogeneous catalysts for Friedel–Crafts acylation of aromatics with carboxylic acids. The Fe3+ salt shows high yields and the highest turnover number (2500) reported to date and can be reused without loss of activity, providing one of the greenest route to aromatic ketones.

Ken-ichi Shimizu; Kenjiro Niimi; Atsushi Satsuma

2008-01-01

241

Mild, efficient Friedel-Crafts acylations from carboxylic acids using cyanuric chloride and AlCl3.  

PubMed

A mild method for Friedel-Crafts acylation with aromatic and aliphatic carboxylic acids using cyanuric chloride, pyridine, and AlCl(3) was developed. Both inter- and intramolecular acylations were achieved at room temperature in high yield and in very short reaction times. PMID:18512929

Kangani, Cyrous O; Day, Billy W

2008-07-01

242

Gold(I)-Catalyzed Intermolecular Addition of Phenols and Carboxylic Acids to Cai-Guang Yang and Chuan He*  

E-print Network

Gold(I)-Catalyzed Intermolecular Addition of Phenols and Carboxylic Acids to Olefins Cai-Guang Yang 60637 Received January 20, 2005; E-mail: chuanhe@uchicago.edu Gold-catalyzed reactions have emerged as important synthetic methods.1 Cationic gold(I) and gold(III) show exceptional activities to activate alkynes

He, Chuan

243

Synthesis and structure-activity relationship of 4-quinolone-3-carboxylic acid based inhibitors of glycogen synthase kinase-3?.  

PubMed

The synthesis, GSK-3? inhibitory activity, and anti-microbial activity of bicyclic and tricyclic derivatives of the 5,7-diamino-6-fluoro-4-quinolone-3-carboxylic acid scaffold were studied. Kinase selectivity profiling indicated that members of this class were potent and highly selective GSK-3 inhibitors. PMID:21873061

Cociorva, Oana M; Li, Bei; Nomanbhoy, Tyzoon; Li, Qiang; Nakamura, Ayako; Nakamura, Kai; Nomura, Masahiro; Okada, Kyoko; Seto, Shigeki; Yumoto, Kazuhiro; Liyanage, Marek; Zhang, Melissa C; Aban, Arwin; Leen, Brandon; Szardenings, Anna Katrin; Rosenblum, Jonathan S; Kozarich, John W; Kohno, Yasushi; Shreder, Kevin R

2011-10-01

244

Novel Antiphytopathogenic Compound 2-Heptyl-5-Hexylfuran-3-Carboxylic Acid, Produced by Newly Isolated Pseudomonas sp. Strain SJT25 ?†  

PubMed Central

Pseudomonas sp. strain SJT25, which strongly antagonizes plant pathogens, was isolated from rice rhizosphere soil by a bioactivity-guided approach. A novel antiphytopathogenic compound was isolated from the fermentation broth of Pseudomonas sp. SJT25 and identified as 2-heptyl-5-hexylfuran-3-carboxylic acid. This compound showed antimicrobial activities both in vitro and in vivo. PMID:21742907

Wang, Xiao-Ying; Xu, Yu-Quan; Lin, Shuang-Jun; Liu, Zhen-Zhen; Zhong, Jian-Jiang

2011-01-01

245

Determination of oseltamivir carboxylic acid in human serum by solid phase extraction and high performance liquid chromatography with UV detection  

Microsoft Academic Search

This study was aimed at developing a fast and sensitive method for determination of oseltamivir carboxylic acid (OCA), the active moiety of anti-influenza agent, oseltamivir phosphate, in human serum by high performance liquid chromatography and UV detection. The analyte and an internal standard (vanillin) were extracted from human serum by a solid phase extraction (SPE) procedure. Chromatographic separation was achieved

Gholamreza Bahrami; Bahareh Mohammadi; Amir Kiani

2008-01-01

246

EFFECTS OF CARBOXYLIC ACIDS ON LIQUID-PHASE ADSORPTION OF ETHANOL AND WATER BY HIGH-SILICA ZSM-5  

EPA Science Inventory

Adsorption isotherms were measured for each compound adsorbed on commercially available ZSM-5 (Si/Al = 140) powder from binary and ternary liquid mixtures of ethanol, carboxylic acids, and water at room temperature. The amounts adsorbed were measured using a recently developed t...

247

Novel and facile selective reduction of carboxylic acid with a samarium diiodide–lanthanide triflate–methanol–base system  

Microsoft Academic Search

The facile selective reduction of carboxylic acids in the presence of an aldehyde or that bearing a formyl group proceeded smoothly with a samarium diiodide–lanthanide triflate–methanol–base system at room temperature to give the corresponding alcohols in good to almost quantitative yield.

Yasuko Kamochi; Tadahiro Kudo

2000-01-01

248

Long-term trends of mono-carboxylic acids in Antarctica: comparison of changes in sources and  

E-print Network

Long-term trends of mono-carboxylic acids in Antarctica: comparison of changes in sources that include the great climatic changes of the past. Data are from two Antarctic deep ice cores recovered, the main source of acetate deposited over the EDC does not seem to have changed significantly over the past

Paris-Sud XI, Université de

249

Addition of carboxylic acids modifies phosphate sorption on soil and boehmite surfaces: A solution chemistry and XANES spectroscopy study  

Microsoft Academic Search

Soil acidification is a globally significant agricultural issue, as the plant availability of phosphorus (P) is decreased through increased P sorption onto aluminium (Al) hydroxides and other solid phase binding sites. X-ray absorption near edge structure (XANES) spectroscopy generated new information on the speciation of Al and P in the presence of carboxylic acids on soil and boehmite (?-AlOOH) surfaces.

C. R. Schefe; P. Kappen; L. Zuin; P. J. Pigram; C. Christensen

2009-01-01

250

Anodic coupling of carboxylic acids to electron-rich double bonds: A surprising non-Kolbe pathway to lactones  

PubMed Central

Summary Carboxylic acids have been electro-oxidatively coupled to electron-rich olefins to form lactones. Kolbe decarboxylation does not appear to be a significant competing pathway. Experimental results indicate that oxidation occurs at the olefin and that the reaction proceeds through a radical cation intermediate. PMID:24062822

Perkins, Robert J; Xu, Hai-Chao; Campbell, John M

2013-01-01

251

Alkaline battery containing a separator of a cross-linked copolymer of vinyl alcohol and unsaturated carboxylic acid  

NASA Technical Reports Server (NTRS)

A battery separator for an alkaline battery is described. The separator comprises a cross linked copolymer of vinyl alcohol units and unsaturated carboxylic acid units. The cross linked copolymer is insoluble in water, has excellent zincate diffusion and oxygen gas barrier properties and a low electrical resistivity. Cross linking with a polyaldehyde cross linking agent is preferred.

Hsu, L. C.; Philipp, W. H.; Sheibley, D. W.; Gonzalez-Sanabria, O. D. (inventors)

1985-01-01

252

Dissociative Binding of Carboxylic Acid Ligand on Nanoceria Surface in Aqueous Solution: A Joint in Situ Spectroscopic Characterization and First-Principles Study  

SciTech Connect

Carboxylic acid is a common ligand anchoring group to functionalize nanoparticle surfaces. Its binding structures and mechanisms as a function of the oxidation states of metal oxide nanoparticle surfaces are not well characterized experimentally. We present an in situ sum frequency generation vibrational spectroscopy (SFG-VS) study on the binding of deuterated acetic acid on ceria nanoparticles in the aqueous solution. In the SFG experiment, ceria nanoparticles were deposited on the flat surface of a CaF2 hemisphere in contact with acetic acid solutions. While the ceria nanoparticle deprotonated the acetic acid, the CaF2 surface could not. Thus, the binding of the deprotonated acetic acid on ceria can be selectively probed. SFG spectra revealed that the binding modes of the carboxylate group depend on the oxidation states of the ceria surfaces. SFG polarization analysis suggested that the bidentate chelating and bridging binding modes co-exist on the reduced ceria surfaces, while the oxidized ceria surfaces are dominated by the bidentate bridging mode. The direct spectroscopic evidence helps to clarify the binding structures and mechanisms on the ceria nanoparticles. Furthermore, the middle-infrared (IR) transparent CaF2 and its chemical inertness make CaF2 and similar substrate materials good candidates for direct SFG-VS measurement of nanoparticle surface reactions and binding chem-istry.

Lu, Zhou; Karakoti, Ajay S.; Velarde Ruiz Esparza, Luis A.; Wang, Weina; Yang, Ping; Thevuthasan, Suntharampillai; Wang, Hongfei

2013-11-21

253

Unusual stable isotope ratios in amino acid and carboxylic acid extracts from the Murchison meteorite  

NASA Technical Reports Server (NTRS)

The isotopic composition of hydrogen, nitrogen, and carbon in amino acid and monocarboxylic acid extracts from the Murchison meteorite has been determined. The unusually high D/H and N-15/N-14 ratios in the amino acid fraction are uniquely characteristic of known interstellar organic materials. The delta D value of the monocarboxylic acid fraction is lower but still consistent with an interstellar origin. These results confirm the extraterrestrial origin of both classes of compound and provide the first evidence suggesting a direct relationship between the massive organosynthesis occurring in interstellar clouds and the presence of prebiotic compounds in primitive planetary bodies.

Epstein, S.; Krishnamurthy, R. V.; Cronin, J. R.; Pizzarello, S.; Yuen, G. U.

1987-01-01

254

Catalytic activity of salenCo(III)OAc complex in the reaction of addition of carboxylic acids to terminal epoxides  

Microsoft Academic Search

The catalytic activity and regioselectivity were studied of the salenCo(III)OAc complex in the reaction of addition of aliphatic carboxylic acids to a series of terminal epoxides (epichlorohydrin, 1,2-epoxybutane, propylene oxide, tert-butyl glycidyl ether and 2,3-epoxypropyl phenyl ether). The reduction in the activity in the order: acetic > acrylic > methacrylic acid was found. The regioselectivity of the addition was independent

Agnieszka Bukowska; Wiktor Bukowski; Jaros?aw Noworól

2005-01-01

255

Perfluorinated carboxylic acids in directly fluorinated high-density polyethylene material.  

PubMed

Perfluorinated carboxylic acids (PFCAs) are ubiquitous in the environment and have been detected in human blood worldwide. One potential route is direct exposure to PFCAs through contact with polymers that have been fluorinated through a process referred to as direct fluorination. PFCAs are hypothesized to be reaction byproducts of direct fluorination when trace amounts of oxygen are present. The objective of this research was to investigate whether PFCAs could be measured in directly fluorinated high-density polyethylene (HDPE) bottles. PFCAs were quantified using Soxhlet extraction with methanol, followed by LC-MS/MS analysis. Total concentrations of PFCAs ranged from 8.5 ± 0.53 to 113 ± 2.5 ng/bottle (1 L), with the short-chain PFCAs, perfluoropropanoic, perfluorobutanoic, perfluoropentanoic, and perfluorohexanoic acids, being the dominant congeners observed. Relative PFCA concentrations varied depending on fluorination level. Structural isomers were detected using (19)F NMR and are hypothesized to have formed during the fluorination process; NMR data revealed the linear isomer typically comprised 55% of the examined sample. Internally branched, isopropyl branched, and t-butyl PFCA isomers of varying chain length were also identified. Electrochemical fluorination was previously thought to be the only source of branched PFCA isomers. The observation here of branched isomers suggests direct fluorination may be an additional source of exposure to these chemicals. The purpose of this study was to measure PFCAs in directly fluorinated material, serving as a previously unidentified source contributing to the environmental load of PFCAs, with potential for human exposure. PMID:21688793

Rand, Amy A; Mabury, Scott A

2011-10-01

256

New strategy of efficient inhibition of cancer cells by carborane carboxylic acid-CdTe nanocomposites.  

PubMed

Nanoconjugates composed of drug molecules encapsulated in quantum dots (QDs) attract enormous attention due to their promising bioimaging and biomedical applications. Here, the anticancer efficiency of potential pharmacophore agents (o-carborane (Cb), o-carborane-C-carboxylic acid (Cbac1), and o-carborane-C(1)C(2)-dicarboxylic acid (Cbac2) coupling with cadmium telluride QDs capped with cysteamine (CA-CdTe QDs)) have been explored. Compared with free CA-CdTe QDs, the composites consisting of Cbac1/Cbac2 and safe-dosage QDs can greatly improve the inhibition efficiency toward SMMC-7721 hepatocellular carcinoma cells with the aid of our real-time cell bioelectronic sensing system and the MTT assay. The enhanced cytotoxicity correlates with increased intracellular reactive oxygen species generation and cell apoptosis. Confocal laser scanning fluorescent microscopy shows improved cellular uptake and drug distribution of the Cbac1/Cbac2-CdTe QDs nanoconjugates. This work raises the possibility that the carborane pharmacophore in combination with QDs or other anticancer drugs may be viable for efficient cancer diagnosis and chemotherapy. PMID:22094121

Wu, Chunhui; Shi, Lixin; Li, Qingning; Jiang, Hui; Selke, Matthias; Yan, Hong; Wang, Xuemei

2012-08-01

257

Potamogeton pectinatus Is Constitutively Incapable of Synthesizing Ethylene and Lacks 1-Aminocyclopropane-1-Carboxylic Acid Oxidase.  

PubMed

A highly sensitive laser-driven photoacoustic detector responsive to [less than or equal to]2.1 nmol m-3 ethylene (50 parts per trillion [v/v]) was used for ethylene analysis. Dark-grown plants of Potamogeton pectinatus L. growing from small tubers made no ethylene. Exposure of shoots to white light, wounding, submergence in water followed by desubmergence, partial oxygen shortage, indole acetic acid, or carbon dioxide failed to induce ethylene production, although clear effects were observed in Pisum sativum L. Some ethylene was released after applying high concentrations of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC; 10 mol m-3) to P. pectinatus, but the amount was trivial compared with that released by P. sativum. More endogenous ACC was found in P. pectinatus than in P. sativum. Considerable ACC oxidase activity was present in tissue extracts of P. sativum. However, no ACC oxidase activity was found in P. pectinatus, indicating that this is where ethylene production is arrested. PMID:12226336

Summers, J. E.; Voesenek, LACJ.; Blom, CWPM.; Lewis, M. J.; Jackson, M. B.

1996-07-01

258

Potamogeton pectinatus Is Constitutively Incapable of Synthesizing Ethylene and Lacks 1-Aminocyclopropane-1-Carboxylic Acid Oxidase.  

PubMed Central

A highly sensitive laser-driven photoacoustic detector responsive to [less than or equal to]2.1 nmol m-3 ethylene (50 parts per trillion [v/v]) was used for ethylene analysis. Dark-grown plants of Potamogeton pectinatus L. growing from small tubers made no ethylene. Exposure of shoots to white light, wounding, submergence in water followed by desubmergence, partial oxygen shortage, indole acetic acid, or carbon dioxide failed to induce ethylene production, although clear effects were observed in Pisum sativum L. Some ethylene was released after applying high concentrations of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC; 10 mol m-3) to P. pectinatus, but the amount was trivial compared with that released by P. sativum. More endogenous ACC was found in P. pectinatus than in P. sativum. Considerable ACC oxidase activity was present in tissue extracts of P. sativum. However, no ACC oxidase activity was found in P. pectinatus, indicating that this is where ethylene production is arrested. PMID:12226336

Summers, J. E.; Voesenek, LACJ.; Blom, CWPM.; Lewis, M. J.; Jackson, M. B.

1996-01-01

259

Analysis of structure-cytotoxicity in vitro relationship (SAR) for perfluorinated carboxylic acids.  

PubMed

Perfluorinated carboxylic acids (PFAs) represent derivatives of naturally occurring compounds and have been widely used in various industrial fields for decades. They are known to be environmentally persistent. Thus far numerous reports have been focused on reproductive toxicity of PFAs in animals but few studies have been carried out on toxicity towards human cells. Viability tests were performed here at varying time-exposures on C6-C18 PFAs with human colon carcinoma (HCT116) cells. These cells were found earlier as the most useful line for in vitro assays. A chain length-EC50 dependence has been clearly observed. Estimated values of EC50 decreased with elongation of fluorocarbon chain (PFHxA > PFHpA > PFOA > PFNA > PFDA > PFDoA > PFTeDA). Further elongation (C16 and C18) did not deepen the effect but even partially reversed it. The effect was intensified after longer exposure (72 h); at relatively low 40 microM PFTeDA, the viability decreased to approximately 50%. It seems that PFAs are not acutely toxic at the cellular level. Even so, however, they can trigger cell apoptosis, which is prominent in the case of myristic acid perfluorinated analogue. PMID:17572060

Kleszczy?ski, Konrad; Gardzielewski, Pawe?; Mulkiewicz, Ewa; Stepnowski, Piotr; Sk?adanowski, Andrzej C

2007-09-01

260

Carboxylic acid-grafted mesoporous material and its high catalytic activity in one-pot three-component coupling reaction  

NASA Astrophysics Data System (ADS)

A new carboxylic acid functionalized mesoporous organic polymer has been synthesized via in situ radical polymerization of divinylbenzene and acrylic acid using a mesoporous silica as a seed during the polymerization process under solvothermal conditions. The mesoporous material MPDVAA-1 has been thoroughly characterized employing powder XRD, solid state 13C cross polarization magic angle spinning-nuclear magnetic resonance, FT-IR spectroscopy, N2 sorption, HR-TEM, and NH3 temperature programmed desorption-thermal conductivity detector (TPD-TCD) analysis to understand its porosity, chemical environment, bonding, and surface properties. The mesoporous polymer was used as a catalyst for a three comp onent Biginelli condensation between various aldehydes, ?-keto esters, and urea/thioureas to give 3,4-dihydropyrimidine-2(1H)-ones. The reactions were carried out under conventional heating as well as solvent-free microwave irradiation of solid components, and in both the cases, the mesoporous polymer MPDVAA-1 proved to be a powerful, robust, and reusable catalyst with high catalytic efficiency.

Gomes, Ruth; Dutta, Saikat; Bhaumik, Asim

2014-11-01

261

Evaluation of the acute toxicity of perfluorinated carboxylic acids using eukaryotic cell lines, bacteria and enzymatic assays.  

PubMed

The acute biological activity of a homologous series of perfluorinated carboxylic acids - perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA) - was studied. To analyze the potential risk of the perfluorinated acids to humans and the environment, different in vitro toxicity test systems were employed. The cytotoxicity of the chemicals towards two different types of mammalian cell lines and one marine bacteria was investigated. The viability of cells from the promyelocytic leukemia rat cell line (IPC-81) and the rat glioma cell line (C6) was assayed calorimetrically with WST-1 reagent. The evaluation was combined with the Vibrio fischeri acute bioluminescence inhibition assay. The biological activity of the compounds was also determined at the molecular level with acetylcholinesterase and glutathione reductase inhibition assays. This is the first report of the effects of perfluorinated acids on the activity of purified enzymes. The results show these compounds have a very low acute biological activity. The observed effective concentrations lie in the millimole range, which is well above probable intracellular concentrations. A relationship was found between the toxicity of the perfluorinated carboxylic acids and the perfluorocarbon chain length: in every test system applied, the longer the perfluorocarbon chain, the more toxic was the acid. The lowest effective concentrations were thus recorded for perfluorononanoic and perfluorodecanoic acids. PMID:21783770

Mulkiewicz, E; Jastorff, B; Sk?adanowski, A C; Kleszczy?ski, K; Stepnowski, P

2007-05-01

262

Metabolomic Analysis of Key Central Carbon Metabolism Carboxylic Acids as Their 3-Nitrophenylhydrazones by UPLC/ESI-MS  

PubMed Central

Multiple hydroxy-, keto-, di-, and tri-carboxylic acids are among the cellular metabolites of central carbon metabolism (CCM). Sensitive and reliable analysis of these carboxylates is important for many biological and cell engineering studies. In this work, we examined 3-nitrophenylhydrazine as a derivatizing reagent and optimized the reaction conditions for the measurement of ten CCM related carboxylic compounds, including glycolate, lactate, malate, fumarate, succinate, citrate, isocitrate, pyruvate, oxaloacetate, and ?-ketoglutarate as their 3-nitrophenylhydrazones using LC/MS with electrospray ionization. With the derivatization protocol which we have developed, and using negative-ion multiple reaction monitoring on a triple-quadrupole instrument, all of the carboxylates showed good linearity within a dynamic range of ca. 200 to more than 2000. The on-column limits of detection and quantitation were from high femtomoles to low picomoles. The analytical accuracies for eight of the ten analytes were determined to be between 89.5 to 114.8% (CV?7.4%, n=6). Using a quadrupole time-of-flight instrument, the isotopic distribution patterns of these carboxylates, extracted from a 13C-labeled mouse heart, were successfully determined by UPLC/MS with full-mass detection, indicating the possible utility of this analytical method for metabolic flux analysis. In summary, this work demonstrates an efficient chemical derivatization LC/MS method for metabolomic analysis of these key CCM intermediates in a biological matrix. PMID:23580203

Han, Jun; Gagnon, Susannah; Eckle, Tobias; Borchers, Christoph H.

2014-01-01

263

Qualitative analysis of some carboxylic acids by ion-exclusion chromatography with atmospheric pressure chemical ionization mass spectrometric detection.  

PubMed

A simple, selective and sensitive method for the determination of carboxylic acids has been developed. A mixture of formic, acetic, propionic, valeric, isovaleric, isobutyric, and isocaproic acids has been separated on a polymethacrylate-based weak acidic cation-exchange resin (TSK gel OA pak-A) based on an ion-exclusion chromatographic mechanism with detection using UV-photodiode array, conductivity and atmospheric pressure chemical ionization mass spectrometry (APCI-MS). A mobile phase consisting of 0.85 mM benzoic acid in 10% aqueous methanol (pH 3.89) was used to separate the above carboxylic acids in about 40 min. For LC-MS, the APCI interface was used in the negative ionization mode. Linear plots of peak area versus concentration were obtained over the range 1-30 mM (r2=0.9982) and 1-30 mM (r2=0.9958) for conductimetric and MS detection, respectively. The detection limits of the target carboxylic acids calculated at S/N=3 ranged from 0.078 to 2.3 microM for conductimetric and photometric detection and from 0.66 to 3.82 microM for ion-exclusion chromatography-APCI-MS. The reproducibility of retention times was 0.12-0.16% relative standard deviation for ion-exclusion chromatography and 1.21-2.5% for ion-exclusion chromatography-APCI-MS. The method was applied to the determination of carboxylic acids in red wine, white wine, apple vinegar, and Japanese rice wine. PMID:12108651

Helale, Murad I H; Tanaka, Kazuhiko; Taoda, Hiroshi; Hu, Wenzhi; Hasebe, Kiyoshi; Haddad, Paul R

2002-05-17

264

Reaction Kinetics for the Biocatalytic Conversion of Phenazine-1-Carboxylic Acid to 2-Hydroxyphenazine  

PubMed Central

The phenazine derivative 2-hydroxyphenazine (2-OH-PHZ) plays an important role in the biocontrol of plant diseases, and exhibits stronger bacteriostatic and fungistatic activity than phenazine-1-carboxylic acid (PCA) toward some pathogens. PhzO has been shown to be responsible for the conversion of PCA to 2-OH-PHZ, however the kinetics of the reaction have not been systematically studied. Further, the yield of 2-OH-PHZ in fermentation culture is quite low and enhancement in our understanding of the reaction kinetics may contribute to improvements in large-scale, high-yield production of 2-OH-PHZ for biological control and other applications. In this study we confirmed previous reports that free PCA is converted to 2-hydroxy-phenazine-1-carboxylic acid (2-OH-PCA) by the action of a single enzyme PhzO, and particularly demonstrate that this reaction is dependent on NADP(H) and Fe3+. Fe3+ enhanced the conversion from PCA to 2-OH-PHZ and 28°C was a optimum temperature for the conversion. However, PCA added in excess to the culture inhibited the production of 2-OH-PHZ. 2-OH-PCA was extracted and purified from the broth, and it was confirmed that the decarboxylation of 2-OH-PCA could occur without the involvement of any enzyme. A kinetic analysis of the conversion of 2-OH-PCA to 2-OH-PHZ in the absence of enzyme and under different temperatures and pHs in vitro, revealed that the conversion followed first-order reaction kinetics. In the fermentation, the concentration of 2-OH-PCA increased to about 90 mg/L within a red precipitate fraction, as compared to 37 mg/L within the supernatant. The results of this study elucidate the reaction kinetics involved in the biosynthesis of 2-OH-PHZ and provide insights into in vitro methods to enhance yields of 2-OH-PHZ. PMID:24905009

Chen, Mingmin; Cao, Hongxia; Peng, Huasong; Hu, Hongbo; Wang, Wei; Zhang, Xuehong

2014-01-01

265

Discrimination of fresh fruit juices by a fluorescent sensor array for carboxylic acids based on molecularly imprinted titania.  

PubMed

Design of chemical sensor arrays that can discriminate real-world samples has been highly attractive in recent years. Herein a fluorescent indicator-displacement sensor array for discrimination of fresh fruit juices was developed. By coupling the unique high affinity of titania to electron-donating anions and the cross-reactivity of molecularly imprinted materials to structurally similar species, a small array was fabricated using only one rhodamine-based fluorescent dye and three synthesized materials. Citric, malic, succinic and tartaric acids were chosen as indices. The recognition mechanism was investigated by spectrofluorimetric titration using a non-linear Langmuir-type adsorption model. The proposed method was applied to discriminate thirteen fruit juices through their carboxylic acid contents. Principal component analysis of the data clearly grouped the thirteen juices with the first principal component owning 98.2% of the total variation. The comparison of the sensor array with HPLC determination of the carboxylic acids was finally made. PMID:25038646

Tan, Jin; Li, Rong; Jiang, Zi-Tao

2014-12-15

266

Selective extraction and recovery of cytochrome c by liquid-liquid extraction using a calix[6]arene carboxylic acid derivative.  

PubMed

Recently, we reported that a calix[6]arene carboxylic acid derivative can selectively extract the lysine-rich protein cytochrome c by interacting with amino groups on the protein surface. In the present article, quantitative extraction and recovery of cytochrome c using this calix[6]arene carboxylic acid derivative are described. Both adjustment of the pH under acidic conditions and addition of an alcohol are necessary to strip the extracted protein from an organic solution to an aqueous solution. Separation of cytochrome c and lysozyme using the calix[6]arene was achieved under the optimal conditions. In the forward extraction stage, 93% of the cytochrome c was extracted, while lysozyme remained in the solution. In the subsequent stripping stage, the extracted cytochrome c was quantitatively recovered in an aqueous solution. Finally, separation of these proteins, which have similar molecular weights and isoelectric points, was accomplished. PMID:16042454

Oshima, Tatsuya; Higuchi, Hiroaki; Ohto, Keisuke; Inoue, Katsutoshi; Goto, Masahiro

2005-08-01

267

Reaction of carboxylic acids with vinyl ethers under solvent-free conditions using molecular iodine as a catalyst.  

PubMed

The reaction of vinyl ethers with carboxylic acids using iodine as a catalyst under solvent-free conditions was investigated. The reaction of saturated carboxylic acids with vinyl ethers gave the corresponding esters. Mechanistic studies revealed the production of the adduct of the vinyl ether with the carboxylic acid, which then rearranged to form the ester. At low temperatures, the reaction of 2-(1-hydroxycyclohexyl)acetic acid (1) and butyl vinyl ether yielded a butyl ester. However, at a reaction temperature of 80°C, both the esterification and the elimination of a water molecule occurred, yielding the unsaturated butyl ester butyl 2-cyclohexenylacetate. The reaction of 2-((1S,2S,4R)-2-hydroxy-1,7,7-trimethylbicyclo[2.2.1]heptan-2-yl)acetic acid (12) with butyl vinyl ether at low temperatures resulted in a mixture of four compounds. However, similar to the high-temperature (>60°C) reaction of 1, the esterification was accompanied by the elimination of a water molecule to give the unsaturated butyl ester (E)-butyl 2-((1S,4R)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ylidene)acetate. While a ?-hydrogen was abstracted to form the endo-type double bond in the reaction of 1, an ?-hydrogen was abstracted to form the exo-type double bond in the reaction of 12. PMID:23357815

Hanzawa, Yohko; Kasashima, Yoshio; Hashimoto, Kahoko; Sasaki, Tatsuhiro; Tomisaki, Keita; Mino, Takashi; Sakamoto, Masami; Fujita, Tsutomu

2013-01-01

268

Action of picolinic acid and structurally related pyridine carboxylic acids on quinolinic acid-induced cortical cholinergic damage  

Microsoft Academic Search

Picolinic acid, a pyridine monocarboxylic acid derived from tryptophan metabolism by the kynurenine pathway, was shown to block cortical cholinergic neurotoxicity induced by quinolinic acid (QUIN), a pyridine dicarboxylic acid yielded by the same pathway. This study examined the specificity of the anti-toxic effect of picolinic acid by comparing its effect with several structurally related mono- and dicarboxylic acids, and

J. Cockhill; K. Jhamandas; R. J. Boegman; R. J. Beninger

1992-01-01

269

Oxidation of benzene with hydrogen peroxide catalyzed with ferrocene in the presence of pyrazine carboxylic acid  

NASA Astrophysics Data System (ADS)

It is found that ferrocene in the presence of small amounts of pyrazine carboxylic acid (PCA) effectively catalyzes the oxidation of benzene to phenol with hydrogen peroxide. Two main differences upon the oxidation of two different substrates, i.e., cyclohexane and benzene, with the same H2O2-ferrocene-PCA catalytic system are revealed: the rates of benzene oxidation and hydrogen peroxide decomposition are several times lower than the rate of cyclohexane oxidation at close concentrations of both substrates, and the rate constant ratios for the reactions of oxidizing particles with benzene and acetonitrile are significantly lower than would be expected for reactions involving free hydroxyl radicals. The overall rate of hydrogen peroxide decomposition, including both the catalase and oxidase routes, is lower in the presence of benzene than in the presence of cyclohexane. It is suggested on the grounds of these data that a catalytically active particle different from the one generated in the absence of benzene is formed in the presence of benzene. This particle catalyzes hydrogen peroxide decomposition less efficiently than the initial complex and generates a dissimilar oxidizing particle that exhibits higher selectivity. It is shown that reactivity of the system at higher concentrations of benzene differs from that of an initial system not containing an aromatic component with the capability of ?-coordination with metal ions.

Shul'pina, L. S.; Durova, E. L.; Kozlov, Yu. N.; Kudinov, A. R.; Strelkova, T. V.; Shul'pin, G. B.

2013-12-01

270

Ethylene-Enhanced 1-Aminocyclopropane-1-carboxylic Acid Synthase Activity in Ripening Apples.  

PubMed

Apples (Malus sylvestris Mill, cv Golden Delicious) were treated before harvest with aminoethoxyvinylglycine (AVG). AVG is presumed to reversibly inhibit 1-aminocyclopropane-1-carboxylic acid (ACC) activity, but not the formation of ACC synthase. AVG treatment effectively blocked initiation of autocatalytic ethylene production and ripening of harvested apples. Exogenous ethylene induced extractable ACC synthase activity and ripening in AVG-treated apples. Removal of exogenous ethylene caused a rapid decline in ACC synthase activity and in CO(2) production. The results with ripened, AVG-treated apples indicate (a) a dose-response relationship between ethylene and enhancement of ACC synthase activity with a half-maximal response at approximately 0.8 mul/l ethylene; (b) reversal of ethylene-enhanced ACC synthase activity by CO(2); (c) enhancement of ACC synthase activity by the ethylene-activity analog propylene.Induction of ACC synthase activity, autocatalytic ethylene production, and ripening of preclimacteric apples not treated with AVG were delayed by 6 and 10% CO(2), but not by 1.25% CO(2). However, each of these CO(2) concentrations reduced the rate of increase of ACC synthase activity. PMID:16663569

Bufler, G

1984-05-01

271

Tolerance of transgenic canola expressing 1-aminocyclopropane-1-carboxylic acid deaminase to growth inhibition by nickel.  

PubMed

Plant growth-promoting bacteria are useful to phytoremediation strategies in that they confer advantages to plants in contaminated soil. When plant growth-promoting bacteria contain the enzyme 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, the bacterial cell acts as a sink for ACC, the immediate biosynthetic precursor of the plant growth regulator ethylene thereby lowering plant ethylene levels and decreasing the negative effects of various environmental stresses. In an effort to gain the advantages provided by bacterial ACC deaminase in the phytoremediation of metals from the environment two transgenic canola lines with the gene for this enzyme were generated and tested. In these transgenic canola plants, expression of the ACC deaminase gene is driven by either tandem constitutive cauliflower mosaic virus (CaMV) 35S promoters or the root specific rolD promoter from Agrobacterium rhizogenes. Following the growth of transgenic and non-transformed canola in nickel contaminated soil, it was observed that the rolD plants demonstrate significantly increased tolerance to nickel compared to the non-transformed control plants. PMID:16023358

Stearns, Jennifer C; Shah, Saleh; Greenberg, Bruce M; Dixon, D George; Glick, Bernard R

2005-07-01

272

Photochromic properties of a water-soluble methyl carboxylic acid indolylfulgimide.  

PubMed

Photochromic fulgides and fulgimides have been identified as promising materials for applications in optical memory media, optical switches, and sensors. For applications in humid environments or biological systems, hydrolytic stability is crucial. A new photochromic methyl carboxylic acid indolylfulgimide was synthesized to improve hydrolytic stability in aqueous solution. The UV-vis spectra, extinction coefficient, thermal stability, and photochemical stability of the fulgimide were characterized in 50 mM sodium phosphate buffer (pH 7.4). The open and closed forms were both stable in buffer. At 37 °C after 500 h, the open forms of the fulgimide showed no degradation within experimental error (1-2%) by (1)H NMR and 2.3% decomposition by UV-vis spectroscopy. The closed form degraded 22% and 11% after 500 h at 37 °C in buffer by UV-vis and (1)H NMR data, respectively. In addition, the fulgimide cycled back and forth between the open and closed forms 80 times before degrading by 20% in buffer. The methyl group at the bridging position of the fulgimide significantly increased the thermal stability by overcoming the rapid hydrolysis of the trifluoromethyl group. PMID:21380459

Chen, Xi; Islamova, Nadezhda I; Robles, Rachel V; Lees, Watson J

2011-06-01

273

Generation and characterization of isolates of Peronophythora litchii resistant to carboxylic acid amide fungicides.  

PubMed

Four isolates of Peronophythora litchii with resistance to carboxylic acid amide (CAA) fungicides were selected on fungicide-amended agar. These isolates had various levels of resistance, as evidenced by their resistance factor (RF), which is the 50% effective concentration (EC(50)) value of a particular isolate divided by that of the wild-type parent. RF values to dimethomorph for the four isolates were 15, 24, 141, and >1,500. Resistance was stable for two isolates, while the EC(50) values decreased for the other two after repeated subculturing on fungicide-free medium. Cross-resistance occurred with all CAAs tested here (dimethomorph, mandipropamid, flumorph, and pyrimorph), but not with strobilurins (azoxystrobin and famoxadone) or other fungicides (metalaxyl, cymoxanil, and mancozeb). Studies on fitness parameters (mycelial growth, sporulation, spore germination, zoospore formation, aggressiveness, and temperature tolerance) in the parent wild-type and resistant isolates demonstrated that penalties in different parameters may be associated with CAA resistance, depending on the isolate. These studies show that Peronophythora litchii is able to express CAA resistance under laboratory conditions but it is not known if resistant strains could become established in the field and sensitivity monitoring studies are recommended. PMID:20373974

Wang, Hancheng; Sun, Haiyan; Stammler, Gerd; Ma, Jianxia; Zhou, Mingguo

2010-05-01

274

Carboxylic acids affect induction, development and quality of potato ( Solanum tuberosum L.) microtubers grown in vitro from single-node explants  

Microsoft Academic Search

The role of three carboxylic acids with increasing alkyl-chain length, viz., formic, acetic and propionic acids in microtuberization was investigated in three potato (Solanum tuberosum L.) genotypes in vitro. Different concentrations of these carboxylic acids (0.0, 1.5, 3.0, 4.5 and 6.0 mM) were supplemented in microtuber induction medium, which was based on MS medium containing 8% sucrose, and their efficacy for

Sushruti Sharma; A. Chanemougasoundharam; Debabrata Sarkar; Suman K. Pandey

2004-01-01

275

Carboxylic and dicarboxylic acids extracted from crushed magnesium oxide single crystals  

NASA Technical Reports Server (NTRS)

Carboxylic and dicarboxylic acids (glycolic, oxalic, malonic and succinic) have been extracted with tetrahydrofuran (THF) and H2O from large synthetic MgO crystals, crushed to a medium fine powder. The extracts were characterized by infrared spectroscopy and 1H-NMR. The THF extracts were derivatized with tert-butyldimethylsilyl (t-BDMS) for GC-MS analysis. A single crystal separated from the extract was used for an x-ray structure analysis, giving the monoclinic unit cell, space group P21/c with ao = 5.543 A, bo = 8.845 A, co = 5.086 A, and beta = 91.9 degrees, consistent with beta-succinic acid, HOOC(CH2)COOH. The amount of extracted acids is estimated to be of the order of 0.1 to 0.5 mg g-1 MgO. The MgO crystals from which these organic acids were extracted grew from the 2860 degrees C hot melt, saturated with CO/CO2 and H2O, thereby incorporating small amounts of the gaseous components to form a solid solution (ss) with MgO. Upon cooling, the ss becomes supersaturated, causing solute carbon and other solute species to segregate not only to the surface but also internally, to dislocations and subgrain boundaries. The organic acids extracted from the MgO crystals after crushing appear to derive from these segregated solutes that formed C-C, C-H and C-O bonds along dislocations and other defects in the MgO structure, leading to entities that can generically be described as (HxCyOz)n-. The processes underlying the formation of these precursors are fundamental in nature and expected to be operational in any minerals, preferentially those with dense structures, that crystallized in H2O-CO2-laden environments. This opens the possibility that common magmatic and metamorphic rocks when weathering at the surface of a tectonically active planet like Earth may be an important source of abiogenically formed complex organic compounds.

Freund, F.; Gupta, A. D.; Kumar, D.

1999-01-01

276

Carboxylic and Dicarboxylic Acids Extracted from Crushed Magnesium Oxide Single Crystals  

NASA Technical Reports Server (NTRS)

Carboxylic and dicarboxylic acids (glycolic, oxalic, malonic and succinic) have been extracted with tetrahydrofuran (THE) and H2O from large synthetic MgO crystals, crushed to a medium fine powder. The extracts were characterized by infrared spectroscopy and (sup 1)H-NMR (Nuclear Magnetic Resonance). The THF extracts were derivatized with tert-butyldimethylsilyl (t-BDMS) for GC-MS (Gas Chromatography - Mass Spectroscopy) analysis. A single crystal separated from the extract was used for an x-ray structure analysis, giving the monoclinic unit cell, space group P2(sub 1)/c with a(sub o) = 5.543 A, b(sub o) = 8.845 A, c(sub o) = 5.086 A, and beta = 91.9 degrees, consistent with beta-succinic acid, HOOC(CH2)COOH. The amount of extracted acids is estimated to be of the order of 0.1 to 0.5 mg/g MgO. The MgO crystals from which these organic acids were extracted grew from the 2360 C hot melt, saturated with CO/CO2 and H2O, thereby incorporating small amounts of the gaseous components to form a solid solution (ss) with MgO. Upon cooling, the ss becomes supersaturated, causing solute carbon and other solute species to segregate not only to the surface but also internally, to dislocations and subgrain boundaries. The organic acids extracted from the MgO crystals after crushing appear to derive from these segregated solutes that formed C-C, C-H, and C-O bonds along dislocations and other defects in the MgO structure, leading to entities that can generically be described as (HxCyOz)(sup n-). The processes underlying the formation of these precursors are fundamental in nature and expected to be operational in any minerals, preferentially those with dense structures, that crystallized in H2O-CO2-laden environments. This opens the possibility that common magmatic and metamorphic rocks when weathering at the surface of a tectonically active planet like Earth may be an important source of abiogenically formed complex organic compounds.

Freund, Friedemann; Gupta, Alka D.; Kumar, Devendra; DeVincenzi, Donald (Technical Monitor)

1998-01-01

277

Further derivatives of 4-benzoyl-1,5-diphenyl-1 H -pyrazole-3-carboxylic acid and their antibacterial activities  

Microsoft Academic Search

Compound 4, 5, 6, 7, and 8 were synthesized from 4-benzoyl-1,5-diphenyl-1H-pyrazole-3-carboxylic acid 1 as a starting material. The pyrazolo[4,3-d]oxazinone 4 was obtained from direct reaction of the acid 1 with hydroxylamine hydrochloride. Acid chloride 2 was converted easily into the new derivatives consisting of 1-(4-benzoyl-1,5-diphenyl-1H-pyrazol-3-oyl)-sulfamide 5 and 3,4-dibenzoyl-1,5-diphenyl-1H-pyrazole 6. The nitrile derivative 7 was obtained by dehydration of the amide

?shak Bildirici; Ahmet ?ener; ?srafil Tozlu

2007-01-01

278

Presence of tetrahydro-?-carboline-3-carboxylic acids in foods by gas chromatography—mass spectrometry as their N-methoxycarbonyl methyl ester derivatives  

Microsoft Academic Search

Various tetrahydro-?-carboline-3-carboxylic acids (TH?C-3-COOH) are identified in commercial foods and drinks by GC-MS. Positive identification of 1-methyl-1,2,3,4-tetrahydro-?-carboline-3-carboxylic acid (MTCA) is demonstrated in soy and tobasco sauces, wine, beer, wine vinegar, cider, orange juice, toasted bread, blue cheese and yoghurt. 1,2,3,4-Tetrahydro-?-carboline-3-carboxylic acid (THCA) occurs in toasted bread, beer, cider, wine vinegar, soy and tobasco sauce, orange juice and blue cheese. MTCA

T. Herraiz; F. Sanchez

1997-01-01

279

Distinct pathways of ERK1/2 activation by hydroxy-carboxylic acid receptor-1.  

PubMed

Mechanistic investigations have shown that, upon agonist activation, hydroxy-carboxylic acid receptor-1(HCA1) couples to a Gi protein and inhibits adenylate cyclase activity, leading to inhibition of liberation of free fatty acid. However, the underlying molecular mechanisms for HCA1 signaling remain largely unknown. Using CHO-K1 cells stably expressing HCA1, and L6 cells, which endogenously express rat HCA1 receptors, we found that activation of ERK1/2 by HCA1 was rapid, peaking at 5 min, and was significantly blocked by pertussis toxin. Furthermore, time course experiments with different kinase inhibitors demonstrated that HCA1 induced ERK1/2 activation via the extracellular Ca2+, PKC and IGF-I receptor transactivation-dependent pathways. In addition, we observed that pretreated the cells with M119K, an inhibitor of G?? subunit-dependent signaling, effectively attenuated the ERK1/2 activation triggered by HCA1, suggesting a critical role for ??-subunits in HCA1-activated ERK1/2 phosphorylation. Furthermore, the present results also indicated that the arrestin2/3 were not required for ERK1/2 activation. In conclusion, our findings demonstrate that upon binding to agonist, HCA1 receptors initially activate Gi, leading to dissociation of the G?? subunit from activated Gi, and subsequently induce ERK1/2 activation via two distinct pathways: one PKC-dependent pathway and the other IGF-IR transactivation-dependent pathway. Our results provide the first in-depth evidence that defines the molecular mechanism of HCA1-mediated ERK1/2 activation. PMID:24671202

Li, Guo; Wang, Hui-qian; Wang, Li-hui; Chen, Ru-ping; Liu, Jun-ping

2014-01-01

280

Distinct Pathways of ERK1/2 Activation by Hydroxy-Carboxylic Acid Receptor-1  

PubMed Central

Mechanistic investigations have shown that, upon agonist activation, hydroxy-carboxylic acid receptor-1(HCA1) couples to a Gi protein and inhibits adenylate cyclase activity, leading to inhibition of liberation of free fatty acid. However, the underlying molecular mechanisms for HCA1 signaling remain largely unknown. Using CHO-K1 cells stably expressing HCA1, and L6 cells, which endogenously express rat HCA1 receptors, we found that activation of ERK1/2 by HCA1 was rapid, peaking at 5 min, and was significantly blocked by pertussis toxin. Furthermore, time course experiments with different kinase inhibitors demonstrated that HCA1 induced ERK1/2 activation via the extracellular Ca2+, PKC and IGF-I receptor transactivation-dependent pathways. In addition, we observed that pretreated the cells with M119K, an inhibitor of G?? subunit-dependent signaling, effectively attenuated the ERK1/2 activation triggered by HCA1, suggesting a critical role for ??-subunits in HCA1-activated ERK1/2 phosphorylation. Furthermore, the present results also indicated that the arrestin2/3 were not required for ERK1/2 activation. In conclusion, our findings demonstrate that upon binding to agonist, HCA1 receptors initially activate Gi, leading to dissociation of the G?? subunit from activated Gi, and subsequently induce ERK1/2 activation via two distinct pathways: one PKC-dependent pathway and the other IGF-IR transactivation-dependent pathway. Our results provide the first in-depth evidence that defines the molecular mechanism of HCA1-mediated ERK1/2 activation. PMID:24671202

Li, Guo; Wang, Hui-qian; Wang, Li-hui; Chen, Ru-ping; Liu, Jun-ping

2014-01-01

281

Friction force microscopy of alkylphosphonic acid and carboxylic acids adsorbed on the native oxide of aluminum.  

PubMed

Monolayers of alkylphosphonic acids (APA) and alkylcarboxylic acids (ACA) on magnetron-sputtered aluminum films have been investigated by friction force microscopy (FFM), contact angle measurement, and polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS). Clear evidence has been provided from PM-IRRAS that friction coefficients, determined from FFM data, may be correlated directly with variations in adsorbate molecular structure. The friction coefficient increased with the length of the adsorbate molecule, but reached a limiting value when the alkyl chain of the adsorbate contained eight carbons in the case of APA or 12 carbons in the case of ACA. For a given alkyl chain length, APA monolayers yielded coefficients of friction that were similar to those of monolayers of alkylthiols of the same length, but smaller than those of ACA. These data indicate that APA monolayers are better ordered than ACA monolayers. These inferences were supported by PM-IRRAS data, which enabled the density of gauche defects to be estimated and correlated with variations in the coefficient of friction. PMID:17042539

Foster, Trevor T; Alexander, Morgan R; Leggett, Graham J; McAlpine, Eoghan

2006-10-24

282

Spectrofluorimetric determination of 3-methylflavone-8-carboxylic acid, the main active metabolite of flavoxate hydrochloride in human urine.  

PubMed

A simple, sensitive and selective spectrofluorimetric method has been developed for the determination of 3-methylflavone-8-carboxylic acid as the main active metabolite of flavoxate hydrochloride in human urine. The proposed method was based on the measurement of the native fluorescence of the metabolite in methanol at an emission wavelength 390 nm, upon excitation at 338 nm. Moreover, the urinary excretion pattern has been calculated using the proposed method. Taking the advantage that 3-methylflavone-8-carboxylic acid is also the alkaline degradate, the proposed method was applied to in vitro determination of flavoxate hydrochloride in tablets dosage form via the measurement of its corresponding degradate. The method was validated in accordance with the ICH requirements and statistically compared to the official method with no significant difference in performance. PMID:25004902

Zaazaa, Hala E; Mohamed, Afaf O; Hawwam, Maha A; Abdelkawy, Mohamed

2015-01-01

283

14,15-Epoxyeicosa-5,8,11-trienoic Acid (14,15-EET) surrogates: carboxylate modifications.  

PubMed

The cytochrome P450 eicosanoid 14,15-epoxyeicosa-5,8,11-trienoic acid (14,15-EET) is a powerful endogenous autacoid that has been ascribed an impressive array of physiologic functions including regulation of blood pressure. Because 14,15-EET is chemically and metabolically labile, structurally related surrogates containing epoxide bioisosteres were introduced and have become useful in vitro pharmacologic tools but are not suitable for in vivo applications. A new generation of EET mimics incorporating modifications to the carboxylate were prepared and evaluated for vasorelaxation and inhibition of soluble epoxide hydrolase (sEH). Tetrazole 19 (ED50 0.18 ?M) and oxadiazole-5-thione 25 (ED50 0.36 ?M) were 12- and 6-fold more potent, respectively, than 14,15-EET as vasorelaxants; on the other hand, their ability to block sEH differed substantially, i.e., 11 vs >500 nM. These data will expedite the development of potent and specific in vivo drug candidates. PMID:25119815

Falck, John R; Koduru, Sreenivasulu Reddy; Mohapatra, Seetaram; Manne, Rajkumar; Atcha, Raju; Manthati, Vijaya L; Capdevila, Jorge H; Christian, Sarah; Imig, John D; Campbell, William B

2014-08-28

284

Successful computer guided planned synthesis of (4R)-thiazolidine carboxylic acid and its 2-substituted analogues as urease inhibitors.  

PubMed

By using internal combinatorial library we were able to identify (4R)-thiazolidines carboxylic acid and its 2-substituted analogs as active inhibitors of urease. Molecular modeling and virtual screening were utilized to find out potential compounds. Computational techniques were employed at database of 90,000 ligands and selected the structure representing the low energy conformations, Grid and FlexX docking algorithms were used and the top binding ligands were synthesized and screened in wet-lab. PMID:16710811

Khan, Khalid Mohammed; Ullah, Zia; Lodhi, Muhammad Arif; Ali, Muhammad; Choudhary, Muhammad Iqbal; Rahman, Atta Ur; Haq, Zaheer Ul

2006-05-01

285

Effect of 1-(2,4-dichlorobenzyl)-indazole-3-carboxylic acid on sperm tails in rhesus monkeys.  

PubMed

Large numbers of spermatozoa with bent or coiled tails were found in the ejaculates of rhesus monkeys treated with 1-(2,4-dichlorobenzyl-indazole-3-carboxylic acid (DICA) (50 or 500 mg/kg for various periods). The defect appeared only in spermatozoa in the cauda epididymidis and consisted of axoneme disarrangement and loss of the fibre doublets. The coil was completely enclosed in a membrane. PMID:416207

Lobl, T J; Mathews, J

1978-03-01

286

Amides of 4-hydroxy-8-methanesulfonylamino-quinoline-2-carboxylic acid as zinc-dependent inhibitors of Lp-PLA?.  

PubMed

AX10479, the phenyl amide of 4-hydroxy-8-methanesulfonylamino-quinoline-2-carboxylic acid, was identified as a Zn(2+)-dependent, 27nM inhibitor of human plasma Lp-PLA(2). Structure-activity relationship studies focused on the AX10479 2-phenylamide group identified equipotent cycloaliphatic amides, an enantioselective preference for chiral amides, and phenyl substitution patterns (e.g., 2-methyl-3-fluoro) that increased potency. PMID:23333209

Hu, Yi; Lin, Emme C K; Pham, Lan M; Cajica, Julia; Amantea, Christopher M; Okerberg, Eric; Brown, Heidi E; Fraser, Allister; Du, Lingling; Kohno, Yasushi; Ishiyama, Junichi; Kozarich, John W; Shreder, Kevin R

2013-03-01

287

Synergistic rhodium(II) carboxylate and brønsted acid catalyzed multicomponent reactions of enalcarbenoids: direct synthesis of ?-pyrrolylbenzylamines.  

PubMed

The design of a synergistic rhodium(II) carboxylate and BINOL phosphoric acid catalyzed efficient multicomponent reaction of enaldiazo compounds, arylamines, and aryl aldehydes leading to the first transition-metal-catalyzed direct synthesis of valuable ?-pyrrolylbenzylamines is disclosed. The reaction is proposed to involve a transient ammonium ylide of a new class of electrophilic rhodium enalcarbenoid, its regioselective Mannich reaction, and a cyclocondensation cascade. The methodology was used in a highly diastereoselective synthesis of a binaphthyl based chiral pyrrole. PMID:24988365

Dawande, Sudam Ganpat; Kanchupalli, Vinaykumar; Lad, Bapurao Sudam; Rai, Jyoti; Katukojvala, Sreenivas

2014-07-18

288

Nutritional factors regulating growth and accumulation of phenazine 1-carboxylic acid by Pseudomonas fluorescens 2-79  

Microsoft Academic Search

Pseudomonas fluorescens strain 2-79 (NRRL B-15 132) is a biocontrol agent of take-all of wheat caused by the fungus Gaeumannomyces graminis var. tritici. Strain 2-79 produces the antibiotic phenazine 1-carboxylic acid, which acts as the primary mechanism of disease suppression. As a first step toward designing efficient methods of mass producing and formulating this biocontrol agent, the regulation of growth

Patricia J. Slininger; Mark A. Jackson

1992-01-01

289

A Seven-Gene Locus for Synthesis of Phenazine1Carboxylic Acid by Pseudomonas fluorescens 2-79  

Microsoft Academic Search

Pseudomonas fluorescens 2-79 produces the broad-spectrum antibiotic phenazine-1-carboxylic acid (PCA), which is active against a variety of fungal root pathogens. In this study, seven genes designated phzABCDEFG that are sufficient for synthesis of PCA were localized within a 6.8-kb BglII-XbaI fragment from the phenazine biosynthesis locus of strain 2-79. Polypeptides corresponding to all phz genes were identified by analysis of

DMITRI V. MAVRODI; VLADIMIR N. KSENZENKO; ROBERT F. BONSALL; R. JAMES COOK; ALEXANDER M. BORONIN; LINDA S. THOMASHOW

1998-01-01

290

Anaerobic degradation of trans -cinnamate and ?-phenylalkane carboxylic acids by the photosynthetic bacterium Rhodopseudomonas palustris : evidence for a ?-oxidation mechanism  

Microsoft Academic Search

The mechanism responsible for the initial steps in the anaerobic degradation of trans-cinnamate and ?-phenylalkane carboxylates by the purple non-sulphur photosynthetic bacterium Rhodopseudomonas palustris was investigated. Phenylacetate did not support growth and there was a marked CO2 dependence for growth on acids with greater side-chain lengths. Here, CO2 was presumably acting as a redox sink for the disposal of excess

Douglas J. E. Elder; Philip Morgan; David J. Kelly

1992-01-01

291

4Hydroxy3-methyl-6-phenylbenzofuran-2-carboxylic acid ethyl ester derivatives as potent anti-tumor agents  

Microsoft Academic Search

Based on the structure of 4-hydroxy-3-methyl-6-phenylbenzofuran-2-carboxylic acid ethyl ester (1), which exhibits selective cytotoxicity against a tumorigenic cell line, (2,4-dimethoxyphenyl)-(4-hydroxy-3-methyl-6-phenylbenzofuran-2-yl)-methanone (18m) was designed and synthesized as a biologically stable derivative containing no ester group. Although the potency of 18m was almost the same as our initial hit compound 1, 18m is expected to last longer in the human body as

Ichiro Hayakawa; Rieko Shioya; Toshinori Agatsuma; Hidehiko Furukawa; Shunji Naruto; Yuichi Sugano

2004-01-01

292

Structure of six anhydrous molecular salts assembled from noncovalent associations between carboxylic acids and bis-N-imidazoles  

NASA Astrophysics Data System (ADS)

Six crystalline organic acid-base adducts derived from bis(N-imidazolyl) and carboxylic acids (3,5-dinitrobenzoic acid, 5-nitrosalicylic acid, 3,5-dinitrosalicylic acid, and phthalic acid) were prepared and characterized by X-ray diffraction analysis, IR, mp, and elemental analysis. The six compounds are all organic salts. In salts 1, 2, 4, 5, and 6 the corresponding bis(imidazole) derivatives are diprotonated, while in 3, the corresponding bis(imidazole) derivative is only monoprotonated. All supramolecular architectures of the salts 1-6 involve extensive Nsbnd H⋯O, Osbnd H⋯O, CH⋯O, and CH2⋯O hydrogen bonds as well as other noncovalent interactions. The role of weak and strong noncovalent interactions in the crystal packing is ascertained. All the salts displayed 3D framework structures under the cooperation of these weak interactions. The results presented herein indicate that the strength and directionality of the N+sbnd H⋯O-, Osbnd H⋯O, and Nsbnd H⋯N hydrogen bonds between carboxylic acids and ditopic imidazoles are sufficient to bring about the formation of binary organic salts.

Jin, Shouwen; Guo, Ming; Wang, Daqi

2012-08-01

293

Metabolism of cyclohexane carboxylic acid by the photosynthetic bacterium Rhodopseudomonas palustris  

Microsoft Academic Search

Cyclohexane carboxylate supported relatively rapid growth (doubling times 7–8 h) ofRhodopseudomonas palustris under oxic or photosynthetic conditions, but did not serve as a substrate for either of the known aromatic CoA ligases. A\\u000a CoA ligase that thioesterifies cyclohexane carboxylate was partially purified and did not cross react immunologically with\\u000a the two CoA ligases purified previously from this bacterium. Crude extracts

Jan Küver; Yuhong Xu; Jane Gibson

1995-01-01

294

Acid zeta function and ajoint acid zeta function  

E-print Network

In this paper we set up the theory of acid zeta function and ajoint acid zeta function, based on the theory, we point out a reason to doubt the truth of the Riemann hypothesis and also as a consequence, we give out some new RH equivalences.

Jining Gao

2010-03-16

295

Parahydrogen-induced polarization of carboxylic acids: a pilot study of valproic acid and related structures.  

PubMed

Parahydrogen-induced polarization (PHIP) is a promising new tool for medical applications of MR, including MRI. The PHIP technique can be used to transfer high non-Boltzmann polarization, derived from parahydrogen, to isotopes with a low natural abundance or low gyromagnetic ratio (e.g. (13)C), thus improving the signal-to-noise ratio by several orders of magnitude. A few molecules acting as metabolic sensors have already been hyperpolarized with PHIP, but the direct hyperpolarization of drugs used to treat neurological disorders has not been accomplished until now. Here, we report on the first successful hyperpolarization of valproate (valproic acid, VPA), an important and commonly used antiepileptic drug. Hyperpolarization was confirmed by detecting the corresponding signal patterns in the (1)H NMR spectrum. To identify the optimal experimental conditions for the conversion of an appropriate VPA precursor, structurally related molecules with different side chains were analyzed in different solvents using various catalytic systems. The presented results include hyperpolarized (13)C NMR spectra and proton images of related systems, confirming their applicability for MR studies. PHIP-based polarization enhancement may provide a new MR technique to monitor the spatial distribution of valproate in brain tissue and to analyze metabolic pathways after valproate administration. PMID:24812006

Lego, Denise; Plaumann, Markus; Trantzschel, Thomas; Bargon, Joachim; Scheich, Henning; Buntkowsky, Gerd; Gutmann, Torsten; Sauer, Grit; Bernarding, Johannes; Bommerich, Ute

2014-07-01

296

Tf 2O as a rapid and efficient promoter for the dehydrative Friedel–Crafts acylation of aromatic compounds with carboxylic acids  

Microsoft Academic Search

The Friedel–Crafts acylation of aromatic compounds with carboxylic acids was investigated in the presence of Tf2O. The reaction was carried out efficiently and very rapidly under mild reaction conditions without the need of any catalyst.

Mohammd Mehdi Khodaei; Abdolhamid Alizadeh; Ehsan Nazari

2007-01-01

297

40 CFR 180.426 - 2-[4,5-Dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinoline carboxylic acid...  

Code of Federal Regulations, 2011 CFR

...imidazol-2-yl]-3-quinoline carboxylic acid; tolerance for residues. A tolerance is established for residues of the herbicide 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H -imidazol-2-yl]-3-quinoline...

2011-07-01

298

40 CFR 180.426 - 2-[4,5-Dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinoline carboxylic acid...  

Code of Federal Regulations, 2013 CFR

...imidazol-2-yl]-3-quinoline carboxylic acid; tolerance for residues. A tolerance is established for residues of the herbicide 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H -imidazol-2-yl]-3-quinoline...

2013-07-01

299

ESTIMATION OF HYDROLYSIS RATE CONSTANTS OF CARBOXYLIC ACID ESTER AND PHOSPHATE ESTER COMPOUNDS IN AQUEOUS SYSTEMS FROM MOLECULAR STRUCTURE BY SPARC  

EPA Science Inventory

SPARC (SPARC Performs Automated Reasoning in Chemistry) chemical reactivity models were extended to calculate hydrolysis rate constants for carboxylic acid ester and phosphate ester compounds in aqueous non- aqueous and systems strictly from molecular structure. The energy diffe...

300

Intermolecular C-O Addition of Carboxylic Acids to Arynes: Synthesis of o-Hydroxyaryl Ketones, Xanthones, 4-Chromanones, and Flavones  

PubMed Central

An efficient and simple route to biologically and pharmaceutically important o-hydroxyaryl ketones, xanthones, 4-chromanones, and flavones has been developed utilizing readily available carboxylic acids and commercially available o-(trimethylsilyl)aryl triflates. PMID:23520410

Dubrovskiy, Anton V.

2013-01-01

301

THE ANTIMUTAGENICITY OF 2-SUBSTITUTED SELENAZOLIDINE-4-(R)-CARBOXYLIC ACIDS.  

PubMed Central

Selenium can have cancer chemopreventive activity, although the mechanism of action has not been well defined. Selenazolidine-4-(R)-carboxylic acids (SCAs) were devised as prodrugs of L-selenocysteine, to provide selenium in a form and at a concentration commensurate with cancer chemopreventive activity. In the present study, a series of selenazolidines has been evaluated in the Salmonella typhimurium TA98 tester strain and all were found to possess antimutagenic activity. There was little difference between the seven selenazolidines in their effectiveness against either benzo[a]pyrene (B[a]P) or 3,6-bis(dimethylamino)acridine (acridine orange), agents which differ in their requirement for mammalian enzyme bioactivation for mutagenicity. Antimutagenic activity against acridine orange was dependent on selenazolidine concentration, and EC50 values were in the 5 –10 ?M range. At 25 ?M, the concentration tested in common for the two mutagens, the selenazolidines were more effective antimutagens against acridine orange than against B[a]P, with reductions in mutant frequency ranging from 54–71% for B[a]P and 79–93% for acridine orange. Efficacy against B[a]P was not enhanced when the concentration was increased to 50 ?M. The similarity in efficacy among the selenazolidines against B[a]P mutagenicity, contrasted with inter-compound differences in their ability to inhibit S9 CYP1A activity. The CYP1A Ki values ranged from a low of 63 ?M (2-[2'-hydroxyphenyl]SCA) to a high of 1.1 mM (2-cyclohexylSCA), but all were above the concentration required to inhibit mutagenicity by 50%. Thus, all the SCAs possess antimutagenic activity against both B[a]P and acridine orange, the efficacy varies little between the individual selenazolidines, and for B[a]P, the efficacy is not proportional to the inhibitory effect on the mutagen bioactivating enzyme. PMID:17166761

El-Sayed, Wael M.; Hussin, Warda A; Franklin, Michael R.

2007-01-01

302

Papain adulteration in 11-nor-Delta9-tetrahydrocannabinol- 9-carboxylic acid-positive urine samples.  

PubMed

The adulteration of urine samples is an ongoing problem in forensic drug-testing laboratories, even in the military where the practice of observed collections is performed. These adulterants are used to produce a false-negative result when samples are analyzed for drugs of abuse. It has been reported that papain, a cysteine protease, could be successfully used as a urine adulterant, altering the concentration of 11-nor-Delta9-tetrahydrocannabinol-9- carboxylic acid (THCCOOH) in urine samples. The current study analyzes the effects of latex papain (Sigma, 10 mg/mL) and Lawry's Adolph's Meat Tenderizer (papain is an active ingredient, 10 mg/mL) on immunoassays (FPIA, EMIT, KIMS) and gas chromatography-mass spectrometry (GC-MS) analysis for biological samples. The samples were analyzed initially between 2 and 4 h and then at 1-, 3-, 7-, and 10-day time intervals after the addition of papain. A decrease in response averaged over the course of the study was observed with FPIA (Abbott, 22%) and EMIT (Syva) Dade Behring, 26%, Microgenics, 10%) screening assays by the addition of latex papain to the samples. An increase in response was found using the KIMS (Roche) assay (156% increase). In addition, the GC-MS results (27% decrease) demonstrate that papain affects both the screening and confirmation assays. The addition of meat tenderizer caused decrease in the FPIA (Abbott, 11%) screening assay and GC-MS results (22%) similar to the latex papain while having varied results on the other screening assays. This study confirms papain could be a potential problem for urine drug-testing programs. PMID:18652751

Larson, Scott J; Holler, Justin M; Magluilo, Joseph; Dunkley, Christopher S; Jacobs, Aaron

2008-01-01

303

Friedel–Crafts acylation of aromatic compounds with carboxylic acids in the presence of P 2O 5\\/SiO 2 under heterogeneous conditions  

Microsoft Academic Search

A convenient and efficient procedure for the Friedel–Crafts acylation of aromatic compounds with carboxylic acids in the presence of P2O5\\/SiO2 is described. Both aromatic and aliphatic carboxylic acids reacted easily to afford the corresponding aromatic ketones. The use of non-toxic and inexpensive materials, simple and clean work-up, short reaction times and good yields of the products are the advantages of

Amin Zarei; Abdol R. Hajipour; Leila Khazdooz

2008-01-01

304

A comparison of the conversion of 1-amino-2-ethylcyclopropane-1-carboxylic acid stereoisomers to 1-butene by pea epicotyls and by a cell-free system  

Microsoft Academic Search

The characteristics of the conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene by pea (Pisum sativum L.) epicotyls and by pea epicotyl enzyme are compared. Of the four stereoisomers of 1-amino-2-ethylcyclopropane-1-carboxylic acid (AEC), only (1R,2S)-AEC is preferentially converted to 1-butene in pea epicotyls. This conversion is inhibited by ACC, indicating that butene production from (1R,2S)-AEC and ethylene production from ACC are

Thomas A. McKeon; Shang Fa Yang

1984-01-01

305

Laccase-mediator system for alcohol oxidation to carbonyls or carboxylic acids: toward a sustainable synthesis of profens.  

PubMed

By combining two green and efficient catalysts, such as the commercially available enzyme laccase from Trametes versicolor and the stable free radical 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), the oxidation in water of some primary alcohols to the corresponding carboxylic acids or aldehydes and of selected secondary alcohols to ketones can be accomplished. The range of applicability of bio-oxidation is widened by applying the optimized protocol to the oxidation of enantiomerically pure 2-arylpropanols (profenols) into the corresponding 2-arylpropionic acids (profens), in high yields and with complete retention of configuration. PMID:25044433

Galletti, Paola; Pori, Matteo; Funiciello, Federica; Soldati, Roberto; Ballardini, Alberto; Giacomini, Daria

2014-09-01

306

New Samarium(III), Gadolinium(III), and Dysprosium(III) Complexes of Coumarin-3-Carboxylic Acid as Antiproliferative Agents  

PubMed Central

New complexes of samarium(III), gadolinium(III), and dysprosium(III) with coumarin-3-carboxylic acid (HCCA) were prepared by the reaction of the ligand with respective metal nitrates in ethanol. The structures of the final complexes were determined by means of physicochemical data, elemental analysis, IR and Raman spectra. The metal-ligand binding mode in the new Ln(III) complexes of coumarin-3-carboxylic acid was elucidated. The vibrational study gave evidence for bidentate coordination of CCA? to Ln(III) ions through the carbonylic oxygen and the carboxylic oxygen atoms. The complexes were tested for antiproliferative activitiy on the chronic myeloid leukemia-derived K-562, overexpressing the BCR-ABL fusion protein. Cytotoxicity towards tumor cells was determined for a broad concentration range. The samarium salt exerted a very weak antiproliferative effect on these cells. This is in contrast to the lanthanide complexes, especially samarium complex, which exhibited potent antiproliferative activity. The present study confirms our previous observations that the lanthanide complexes of coumarins exhibit antiproliferative activity towards K-562 cell line. PMID:18274603

Kostova, Irena; Momekov, Georgi; Stancheva, Peya

2007-01-01

307

Biosynthesis of 1-aminocyclopropane-1-carboxylic acid and ethylene from delta-aminolevulinic acid in ripening tomato fruits  

SciTech Connect

A new pathway for ethylene (C/sub 2/H/sub 4/) biosynthesis, which utilizes delta-aminolevulinic acid (ALA) as a precursor of 1-aminocyclopropane-1-carboxylic acid (ACC), the immediate precursor of C/sub 2/H/sub 4/, is presented. ALA enhanced ACC accumulation to 410% and C/sub 2/H/sub 4/ production to 232% of the control. The C/sub 2/H/sub 4/ production rate varied with the ALA concentration and the stage of tomato fruit development. As the ALA concentration increased from zero to 40 mM, the C/sub 2/H/sub 4/ production rate increased. Both treated and untreated pericarp discs from fruits at the pink stage of development yielded the largest C/sub 2/H/sub 4/ production rate. Radioactivity from (2,3-/sup 3/H)ALA was detected in both ACC and C/sub 2/H/sub 4/, and radioactivity from (4-/sup 14/C)ALA was detected in ACC and CO/sub 2/ but not in C/sub 2/H/sub 4/. However, radioactivity from (5-/sup 14/C)ALA was detected in CO/sub 2/, and its amount was greater than that obtained from (4-/sup 14/C)ALA. Neither ACC nor C/sub 2/H/sub 4/ showed any radioactivity when (5-/sup 14/C)ALA was supplied to the fruit discs. In addition, when (2,3-/sup 3/H)ALA or (4-/sup 14/C)ALA was supplied to the fruit discs, radioactivity was detected in other metabolites such as fumarate, succinate, malate, glutamate, glutamine, ..cap alpha..-ketoglutarate, and methionine, but the amount of radioactivity was insignificant as compared with the amount of radioactivity found in C/sub 2/H/sub 4/ and ACC.

El-Rayes, D.E.D.A.

1987-01-01

308

Halogen-induced organic aerosol (XOA) formation and decarboxylation of carboxylic acids by reactive halogen species - a time-resolved aerosol flow-reactor study  

NASA Astrophysics Data System (ADS)

Reactive halogen species (RHS) are released to the atmosphere from various sources like photo-activated sea-salt aerosol and salt lakes. Recent studies (Cai et al., 2006 and 2008, Ofner et al., 2012) indicate that RHS are able to interact with SOA precursors similarly to common atmospheric oxidizing gases like OH radicals and ozone. The reaction of RHS with SOA precursors like terpenes forms so-called halogen-induced organic aerosol (XOA). On the other hand, RHS are also able to change the composition of functional groups, e.g. to initiate the decarboxylation of carboxylic acids (Ofner et al., 2012). The present study uses a 50 cm aerosol flow-reactor, equipped with a solar simulator to investigate the time-resolved evolution and transformation of vibrational features in the mid-infrared region. The aerosol flow-reactor is coupled to a home-made multi-reflection cell (Ofner et al., 2010), integrated into a Bruker IFS 113v FTIR spectrometer. The reactor is operated with an inlet feed (organic compound) and a surrounding feed (reactive halogen species). The moveable inlet of the flow reactor allows us to vary reaction times between a few seconds and up to about 3 minutes. Saturated vapours of different SOA precursors and carboxylic acids were fed into the flow reactor using the moveable inlet. The surrounding feed inside the flow reactor was a mixture of zero air with molecular chlorine as the precursor for the formation of reactive halogen species. Using this setup, the formation of halogen-induced organic aerosol could be monitored with a high time resolution using FTIR spectroscopy. XOA formation is characterized by hydrogen-atom abstraction, carbon-chlorine bond formation and later, even formation of carboxylic acids. Several changes of the entire structure of the organic precursor, caused by the reaction of RHS, are visible. While XOA formation is a very fast process, the decarboxylation of carboxylic acids, induced by RHS is rather slow. However, XOA formation from aliphatic or aromatic precursors is coupled to the formation of carboxylic acids by saturation of reactive radical sites with oxygen, but carboxylic acids themselves can be destroyed by RHS, leading to further fragmentation of the carbon structure. References Cai, X., and Griffin, R. J.: Secondary aerosol formation from the oxidation of biogenic hydrocarbons by chlorine atoms, J. Geophys. Res., 111, D14206/14201-D14206/14214, 2006. Cai, X., Ziemba, L. D., and Griffin, R. J.: Secondary aerosol formation from the oxidation of toluene by chlorine atoms, Atmos. Environ., 42, 7348-7359, 2008. Ofner, J., Krüger, H.-U., and Zetzsch, C.: Circular multireflection cell for optical spectroscopy, Appl. Opt., 49, 5001-5004, 2010. Ofner, J., Balzer, N., Buxmann, J., Grothe, H., Schmitt-Kopplin, Ph., Platt, U., and Zetzsch, C.: Halogenation processes of secondary organic aerosol and implications on halogen release mechanisms, Atmos. Chem. Phys., 12, 5787-5806, 2012.

Ofner, Johannes; Zetzsch, Cornelius

2013-04-01

309

catena-Poly[[di-aqua-bis-(?3-5-carboxyl-ato-1H-pyrazole-3-carb-oxy-lic acid-?(3) O (3):O (3);O (5))dilithium(I)] monohydrate].  

PubMed

The basic structural unit of the title polymeric ribbon, {[Li2(C5H3N2O2)2(H2O)2]·H2O} n , is a centrosymmetric dinuclear complex in which the two Li(I) ions are bridged by two carboxyl-ato O atoms, to generate a centrosymmetric Li2O2 core. These are connected into a chain along [01-1] by carboxylic acid-carbonyl-O bonds. The tetra-hedral coordination of the Li(I) cation is completed by an aqua ligand. The carboxylic acid is involved in an intra-ribbon hydrogen bond. A solvate water molecule showing positional (50:50) disorder is observed. Polymeric ribbons along [01-1] are connected by O-H?O, N-H?O and O-H?N hydrogen bonds into a three-dimensional architecture. PMID:24454029

Starosta, Wojciech; Leciejewicz, Janusz

2013-10-12

310

catena-Poly[[di-aqua-bis-(?3-5-carboxyl-ato-1H-pyrazole-3-carb-oxy-lic acid-?3 O 3:O 3;O 5)dilithium(I)] monohydrate  

PubMed Central

The basic structural unit of the title polymeric ribbon, {[Li2(C5H3N2O2)2(H2O)2]·H2O}n, is a centrosymmetric dinuclear complex in which the two LiI ions are bridged by two carboxyl­ato O atoms, to generate a centrosymmetric Li2O2 core. These are connected into a chain along [01-1] by carboxylic acid–carbonyl-O bonds. The tetra­hedral coordination of the LiI cation is completed by an aqua ligand. The carboxylic acid is involved in an intra-ribbon hydrogen bond. A solvate water molecule showing positional (50:50) disorder is observed. Polymeric ribbons along [01-1] are connected by O—H?O, N—H?O and O—H?N hydrogen bonds into a three-dimensional architecture. PMID:24454029

Starosta, Wojciech; Leciejewicz, Janusz

2013-01-01

311

Floral benzenoid carboxyl methyltransferases: From in vitro to in planta function  

Microsoft Academic Search

Benzenoid carboxyl methyltransferases synthesize methyl esters (e.g., methyl benzoate and methyl salicylate), which are constituents of aromas and scents of many plant species and play important roles in plant communication with the surrounding environment. Within the past five years, eleven such carboxyl methyltransferases were isolated and most of them were comprehensively investigated at the biochemical, molecular and structural level. Two

Uta Effmert; Sandra Saschenbrecker; Jeannine Ross; Florence Negre; Chris M. Fraser; Joseph P. Noel; Natalia Dudareva; Birgit Piechulla

2005-01-01

312

Floral Benzenoid Carboxyl Methyltransferases: From in Vitro to in Planta Function  

Microsoft Academic Search

Benzenoid carboxyl methyltransferases synthesize methyl esters (e.g., methyl benzoate and methyl salicylate), which are constituents of aromas and scents of many plant species and play important roles in plant communication with the surrounding environment. Within the past five years, eleven such carboxyl methyltransferases were isolated and most of them were comprehensively investigated at the biochemical, molecular and structural level. Two

Uta Effmert; Sandra Saschenbrecker; Jeannine Ross; Florence Negre; Chris M. Fraser; Joseph P. Noel; Natalia Dudareva; Birgit Piechulla

2005-01-01

313

Carboxylic acids in PM 2.5 over Pinus morrisonicola forest and related photoreaction mechanisms identified via Raman spectroscopy  

NASA Astrophysics Data System (ADS)

The PM 2.5 aerosol from within an area of Pinus morrisonicola Hayata in Taiwan was collected and analyzed for its low molecular weight carboxylic acid (LMWCAs) content. Oxalic acid was the major LMWCA in the aerosol, followed by acetic, tartaric and maleic acids. This differs significantly from the LMWCA composition of PM 2.5 aerosol reported for a southern Taiwan suburban region (oxalic > succinic > malonic) [Atmospheric Environment 42, 6836-6850 (2008)]. P. morrisonicola Hayata emits oxalic, malic and formic acids and yet there was an abundance of maleic and tartaric acids in the PM 2.5 forest aerosol, indicating that tartaric acid is derived from the transformation of other P. morrisonicola Hayata emissions. Raman spectroscopy was applied and 28 species of LMWCAs and inorganic species were identified. The photochemical mechanisms of maleic and tartaric acids were studied and it was found that the abundant tartaric acid in forest aerosol is most probably the photochemical product from reactions of maleic acid. Furthermore, tartaric acid is photochemically transformed into formic acid and ultimately into CO 2.

Kuo, Su-Ching; Tsai, Ying I.; Tsai, Cheng-Hsien; Hsieh, Li-Ying

2011-12-01

314

Fabrication of carboxylic functionalized superparamagnetic mesoporous silica microspheres and their application for removal basic dye pollutants from water  

Microsoft Academic Search

Superparamagnetic mesoporous silica microspheres embedded with a silica-coated superparamagnetic iron oxide nanoparticles core and mesoporous silica shell have been prepared using stearyltrimethyl ammonium bromide (STAB) as surfactant template. The superparamagnetic mesoporous silica microspheres then were modified with anhydride functionalized silane to graft carboxylic groups and developed for removing basic dye pollutants, e.g., Methylene Blue (MB) and Acridine Orange (AO) from

Xucheng Fu; Xing Chen; Jin Wang; Jinhuai Liu

2011-01-01

315

Ion-exclusion chromatographic separations of C1-C6 aliphatic carboxylic acids on a sulfonated styrene-divinylbenzene co-polymer resin column with 5-methylhexanoic acid as eluent.  

PubMed

The application of C7 aliphatic carboxylic acids (heptanoic, 2-methylhexanoic, 5-methylhexanoic and 2,2-dimethyl-n-valeric acids) as eluents in ion-exclusion chromatography with conductimetric detection for C1-C6 aliphatic carboxylic acids (formic, acetic, propionic, isobutyric, butyric, isovaleric, valeric, isocaproic and caproic acids) was carried out using a highly sulfonated styrene-divinylbenzene co-polymer resin (TSKgel SCX) in the H+ form as a stationary phase. When using 0.05 mM sulfuric acid at pH 4.0 as the eluent, peak shapes of hydrophobic carboxylic acids (isovaleric, valeric, isocaproic and caproic acids) were tailed strongly. In contrast, when using 1 mM these C7 carboxylic acids at pH ca. 4 as the eluents, although system peaks (vacant peaks) corresponding to these C7 carboxylic acids appeared, peak shapes of these hydrophobic acids were improved drastically. Excellent simultaneous separation and relatively high sensitive conductimetric detection for these C1-C6 aliphatic carboxylic acids were achieved in 25 min on the TSKgel SCX column (150 x 6 mm I.D.) using 1 mM 5-methylhexanoic acid at pH 4.0 as the eluent. PMID:12830882

Ohta, Kazutoku; Towata, Atsuya; Ohashi, Masayoshi

2003-05-16

316

Bidentate Structures of Acetic Acid on Ge(100): The Role of Carboxyl Oxygen Eunkyung Hwang,, Do Hwan Kim,,, Yun Jeong Hwang, Ansoon Kim,  

E-print Network

Bidentate Structures of Acetic Acid on Ge(100): The Role of Carboxyl Oxygen Eunkyung Hwang,,§ Do structures of acetic acid on the Ge(100) surface at room temperature have been investigated by using both of acetic acid to acetate on the Ge(100) surface occurs through dissociation of the O-H bond

Kim, Sehun

317

Perfluoroalkyl sulfonic and carboxylic acids: A critical review of physicochemical properties, levels and patterns in waters and wastewaters, and treatment methods  

Microsoft Academic Search

Perfluorinated acids (PFAs) are an emerging class of environmental contaminants present in various environmental and biological matrices. Two major PFA subclasses are the perfluorinated sulfonic acids (PFSAs) and carboxylic acids (PFCAs). The physicochemical properties and partitioning behavior for the linear PFA members are poorly understood and widely debated. Even less is known about the numerous branched congeners with varying perfluoroalkyl

Sierra Rayne; Kaya Forest

2009-01-01

318

2-hydroxy-1-oxo-1,2-dihydroisoquinoline-3-carboxylic acid with inbuilt ?-N-hydroxy-?-keto-acid pharmacophore as HCV NS5B polymerase inhibitors.  

PubMed

The inbuilt 2-N-hydroxy-1-oxo-3-carboxylic acid of isoquinolone was designed as pyrophosphate mimic for hepatitis C NS5B polymerase. Various 2-hydroxy-1-oxo-1,2-dihydroisoquinoline-3-carboxylic acid derivatives 11a-p were synthesized and evaluated as HCV NS5B polymerase inhibitors. Compound 11c exhibited moderate inhibitory potency based on the inorganic pyrophosphate generation (IC?? = 9.5 ?M) and based on NTP incorporation by NS5B enzyme (IC?? = 5.9 ?M). Compound 11c demonstrated antiviral activity (EC?? = 15.7 ?M) and good selectivity in HCV genotype 1b replicon Ava.5 cells. Compound 11c reduced the interaction of NTP to NS5B polymerase. Docking model showed that 11c situated in similar orientation to the bound uridine triphosphate in the active site of NS5B polymerase. As a result, 2-hydroxy-1-oxo-1,2-dihydroisoquinoline-3-carboxylic acid was disclosed as a novel inbuilt ?-N-Hydroxy-?-keto-acid pharmacophore for HCV NS5B polymerase inhibitors. PMID:22204334

Deore, R R; Chen, G S; Chen, C-S; Chang, P-T; Chuang, M-H; Chern, T-R; Wang, H-C; Chern, J-W

2012-01-01

319

Molecular Models of Reactants and Products from an Asymmetric Synthesis of a Chiral Carboxylic Acid  

NSDL National Science Digital Library

Our JCE Featured Molecules for this month come from the paper by Thomas E. Smith, David P. Richardson, George A. Truran, Katherine Belecki, and Megumi Onishi (1). The authors describe the use of a chiral auxiliary, 4-benzyl-2-oxazolidinone, in the synthesis of a chiral carboxylic acid. The majority of the molecules used in the experiment, together with several of the pharmaceuticals mentioned in the paper, have been added to our molecule collection. In many instances multiple enantiomeric and diastereomeric forms of the molecules have been included. This experiment could easily be extended to incorporate various aspects of computation for use in an advanced organic or integrated laboratory. Here are some possible exercises using the R and S forms of the 4-benzyl-2-oxazolidinone as the authors point out that both forms are available commercially. Calculation of the optimized structures and energies of the enantiomers at the HF/631-G(d) level using Gaussian03 (2) produces the results shown in Table 1. Evaluation of the vibrational frequencies results in no imaginary frequencies and the 66 real frequencies are identical for the two forms. Examination of the computed IR spectra also shows them to be identical. Additionally, the Raman and NMR spectra can be calculated for the enantiomers and compared to experimental values and spectral patterns. A tool that is becoming increasingly important for assigning absolute configuration is vibrational circular dichroism (VCD). Although the vibrational spectra of an enantiomeric pair are identical, the VCD spectra show opposite signs, as shown in Figure 1. One can imagine a synthesis, using an unknown enantiomer of the chiral auxiliary, followed by calculations of the electronic and vibrational properties of all of the intermediates and the product, and determination of absolute configuration of reactants and products by comparison of experimental and computed VCD spectra. Using a viewer capable of displaying two molecules that can be moved independently, students could more easily visualize the origin of the enantiomeric preference in the reaction between the chelated enolate and allyl iodide.

320

Acid-base-controlled stereoselective metalation of overhanging carboxylic acid porphyrins: consequences for the formation of heterobimetallic complexes.  

PubMed

Overhanging carboxylic acid porphyrins have revealed promising ditopic ligands offering a new entry in the field of supramolecular coordination chemistry of porphyrinoids. Notably, the adjunction of a so-called hanging-atop (HAT) Pb(II) cation to regular Pb(II) porphyrin complexes allowed a stereoselective incorporation of the N-core bound cation, and an allosterically controlled Newton's cradle-like motion of the two Pb(II) ions also emerged from such bimetallic complexes. In this contribution, we have extended this work to other ligands and metal ions, aiming at understanding the parameters that control the HAT Pb(II) coordination. The nature of the N-core bound metal ion (Zn(II), Cd(II)), the influence of the deprotonation state of the overhanging COOH group and the presence of a neutral ligand on the opposite side (exogenous or intramolecular), have been examined through (1)H NMR spectroscopic experiments with the help of radiocrystallographic structures and DFT calculations. Single and bis-strap ligands have been considered. They all incorporate a COOH group hung over the N-core on one side. For the bis-strap ligands, either an ester or an amide group has been introduced on the other side. In the presence of a base, the mononuclear Zn(II) or Cd(II) complexes incorporate the carbonyl of the overhanging carboxylate as apical ligand, decreasing its availability for the binding of a HAT Pb(II). An allosteric effector (e.g., 4-dimethylaminopyridine (DMAP), in the case of a single-strap ligand) or an intramolecular ligand (e.g., an amide group), strong enough to compete with the carbonyl of the hung COO(-), is required to switch the N-core bound cation to the opposite side with concomitant release of the COO(-), thereby allowing HAT Pb(II) complexation. In the absence of a base, Zn(II) or Cd(II) binds preferentially the carbonyl of the intramolecular ester or amide groups in apical position rather than that of the COOH. This better preorganization, with the overhanging COOH fully available, is responsible for a stronger binding of the HAT Pb(II). Thus, either allosteric or acid-base control is achieved through stereoselective metalation of Zn(II) or Cd(II). In the latter case, according to the deprotonation state of the COOH group, the best electron-donating ligand is located on one or the other side of the porphyrin (COO(-)>CONHR>COOR>COOH): the lower affinity of COOH for Zn(II) and Cd(II), the higher for a HAT Pb(II). These insights provide new opportunities for the elaboration of innovative bimetallic molecular switches. PMID:23813639

Le Gac, Stéphane; Najjari, Btissam; Dorcet, Vincent; Roisnel, Thierry; Fusaro, Luca; Luhmer, Michel; Furet, Eric; Halet, Jean-François; Boitrel, Bernard

2013-08-12

321

Structure-activity relationships on the odor detectability of homologous carboxylic acids by humans  

PubMed Central

We measured concentration detection functions for the odor detectability of the homologs: formic, acetic, butyric, hexanoic, and octanoic acids. Subjects (14 ? n ? 18) comprised young (19–37 years), healthy, nonsmoker, and normosmic participants from both genders. Vapors were delivered by air dilution olfactometry, using a three-alternative forced-choice procedure against carbon-filtered air, and an ascending concentration approach. Delivered concentrations were established by gas chromatography (flame ionization detector) in parallel with testing. Group and individual olfactory functions were modeled by a sigmoid (logistic) equation from which two parameters are calculated: C, the odor detection threshold (ODT) and D, the steepness of the function. Thresholds declined with carbon chain length along formic, acetic, and butyric acid where they reached a minimum (ODTs = 514, 5.2, and 0.26 ppb by volume, respectively). Then, they increased for hexanoic (1.0 ppb) and octanoic (0.86 ppb) acid. Odor thresholds and interindividual differences in olfactory acuity among these young, normosmic participants were lower than traditionally thought and reported. No significant effects of gender on odor detectability were observed. The finding of an optimum molecular size for odor potency along homologs confirms a prediction made by a model of ODTs based on a solvation equation. We discuss the mechanistic implications of this model for the process of olfactory detection. Electronic supplementary material The online version of this article (doi:10.1007/s00221-010-2430-0) contains supplementary material, which is available to authorized users. PMID:20931179

Abraham, Michael H.

2010-01-01

322

Di-?-aqua-bis­[aqua­(5-carboxyl­ato-1H-1,2,3-triazole-4-carb­oxy­lic acid-?2 N 3,O 4)lithium  

PubMed Central

The crystal structure of the title compound, [Li2(C4H2N3O4)2(H2O)4], contains centrosymmetric dinuclear mol­ecules in which two LiI ions are bridged by two water O atoms. The metal ion is coordinated by one N,O-bidentate ligand and three water O atoms (one of them is symmetry generated), with one of the bridging water O atoms in the apical position of a distorted square pyramid. The carboxyl­ate group that participates in coordination to the metal ion remains protonated; the other is deprotonated and coordination inactive. An intra­molecular O—H?O hydrogen bond between carboxyl­ate groups is observed. In the crystal, dimers are linked by O—H?O, O—H?N and N—H?O hydrogen bonds, generating a three-dimensional network. PMID:24427005

Starosta, Wojciech; Leciejewicz, Janusz

2013-01-01

323

Trace Amounts of Furan-2-Carboxylic Acids Determine the Quality of Solid Agar Plates for Bacterial Culture  

PubMed Central

Background Many investigators have recognised that a significant proportion of environmental bacteria exist in a viable but non-culturable state on agar plates, and some researchers have also noticed that some of such bacteria clearly recover their growth on matrices other than agar. However, the reason why agar is unsuitable for the growth of some bacteria has not been addressed. Methodology/Principal Findings According to the guide of a bioassay for swarming inhibition, we identified 5-hydroxymethylfuran-2-carboxylic acid (5-HMFA) and furan-2-carboxylic acid (FA) as factors that inhibit bacterial swarming and likely inhibit extracellular polysaccharide production on agar. The furan-2-carboxylic acids 5-HMFA and FA effectively inhibited the swarming and swimming of several environmental bacteria at concentrations of 1.8 and 2.3 µg L?1 (13 and 21 nmol L?1), respectively, which are equivalent to the concentrations of these compounds in 0.3% agar. On Luria-Bertani (LB) plates containing 1.0% agar that had been previously washed with MeOH, a mixture of 5-HMFA and FA in amounts equivalent to their original concentrations in the unwashed agar repressed the swarming of Escherichia coli K12 strain W3110, a representative swarming bacterium. Conclusions/Significance Agar that contains trace amounts of 5-HMFA and FA inhibits the proliferation of some slow-growing or difficult-to-culture bacteria on the plates, but it is useful for single colony isolation due to the ease of identification of swarmable bacteria as the non-swarmed colonies. PMID:22848437

Hara, Shintaro; Isoda, Reika; Tahvanainen, Teemu; Hashidoko, Yasuyuki

2012-01-01

324

Analysis of carboxyl tail function in the skeletal muscle Cl- channel hClC-1.  

PubMed

Human ClC-1 (skeletal muscle Cl- channel) has a long cytoplasmic C-tail (carboxyl tail), containing two CBS (cystathionine beta-synthase) domains, which is very important for channel function. We have now investigated its significance further, using deletion and alanine-scanning mutagenesis, split channels, GST (glutathione transferase)-pull-down and whole-cell patch-clamping. In tagged split-channel experiments, we have demonstrated strong binding between an N-terminal membrane-resident fragment (terminating mid-C-tail at Ser(720) and containing CBS1) and its complement (containing CBS2). This interaction is not affected by deletion of some sequences, suggested previously to be important, particularly in channel gating. Contact between CBS1 and CBS2, however, may make a major contribution to assembly of functional channels from such co-expressed complements, although the possibility that C-tail fragments could, in addition, bind to other parts of the membrane-resident component has not been eliminated. We now show such an interaction between a membrane-resident component terminating at Ser(720) (but with CBS1 deleted) and a complete C-tail beginning at Leu(598). Channel function is rescued in patch-clamped HEK-293T (human embryonic kidney) cells co-expressing these same fragments. From our own results and those of others, we conclude that the CBS1-CBS2 interaction is not sufficient, in itself, for channel assembly, but rather that this might normally assist in bringing some part of the CBS2/C-tail region into appropriate proximity with the membrane-resident portion of the protein. Previously conflicting and anomalous results can now be explained by an hypothesis that, for split channels to be functional, at least one membrane-resident component must include a plasma membrane trafficking signal between Leu(665) and Lys(680). PMID:18321245

Ma, Linlin; Rychkov, Grigori Y; Hughes, Bernard P; Bretag, Allan H

2008-07-01

325

Synthesis of novel derivatives of 4-pyridine carboxylic acid hydrazide and their activity on central nervous system.  

PubMed

Six novel derivatives (2-7) of 4-Pyridine carboxylic acid hydrazide (PCH) were synthesized by treating this lead molecule with substituted arylsulphonyl and benzoyl chlorides. The molecular structures of the newly derived products were characterized by the help of UV Visible, IR, FAB, 1HNMR spectroscopy and CHN analysis. During the preliminary pharmacological screening, it was observed that the synthesized compounds induced noticeable changes on motor activity of the animals. Interesting structure activity relationship was also observed among the synthesized molecules. Because of the interesting affect on motor activity, the newly synthesized derivatives can further be evaluated for their effects on CNS. PMID:25176234

Naeem, Sabahat; Akhtar, Shamim; Mushtaq, Nousheen; Kamil, Arfa; Zafar, Shaista; Anwar, Sana; Arif, Muhammad

2014-09-01

326

Selective conversion of alcohols in water to carboxylic acids by in situ generated ruthenium trans dihydrido carbonyl PNP complexes.  

PubMed

In this work, we present a mild method for direct conversion of primary alcohols into carboxylic acids with the use of water as an oxygen source. Applying a ruthenium dihydrogen based dehydrogenation catalyst for this cause, we investigated the effect of water on the catalytic dehydrogenation process of alcohols. Using 1 mol% of the catalyst we report up to high yields. Moreover, we isolated key intermediates which most likely play a role in the catalytic cycle. One of the intermediates was identified as a trans dihydrido carbonyl complex which is generated in situ in the catalytic process. PMID:25019331

Choi, Jong-Hoo; Heim, Leo E; Ahrens, Mike; Prechtl, Martin H G

2014-11-01

327

Decarboxylative palladium(II)-catalyzed synthesis of aryl amidines from aryl carboxylic acids: development and mechanistic investigation.  

PubMed

A fast and convenient synthesis of aryl amidines starting from carboxylic acids and cyanamides is reported. The reaction was achieved by palladium(II)-catalysis in a one-step microwave protocol using [Pd(O2 CCF3 )2 ], 6-methyl-2,2'-bipyridyl and trifluoroacetic acid (TFA) in N-methylpyrrolidinone (NMP), providing the corresponding aryl amidines in moderate to excellent yields. The protocol is very robust with regards to the cyanamide coupling partner but requires electron-rich ortho-substituted aryl carboxylic acids. Mechanistic insight was provided by a DFT investigation and direct ESI-MS studies of the reaction. The results of the DFT study correlated well with the experimental findings and, together with the ESI-MS study, support the suggested mechanism. Furthermore, a scale-out (scale-up) was performed with a non-resonant microwave continuous-flow system, achieving a maximum throughput of 11?mmol?h(-1) by using a glass reactor with an inner diameter of 3?mm at a flow rate of 1?mL?min(-1) . PMID:23983102

Rydfjord, Jonas; Svensson, Fredrik; Trejos, Alejandro; Sjöberg, Per J R; Sköld, Christian; Sävmarker, Jonas; Odell, Luke R; Larhed, Mats

2013-10-01

328

Phosphorylation of tomato 1-aminocyclopropane-1-carboxylic acid synthase, LE-ACS2, at the C-terminal region.  

PubMed

1-aminocyclopropane-1-carboxylic acid synthase is a key enzyme in the ethylene biosynthesis pathway. Recent studies raise the possibility that 1-aminocyclopropane-1-carboxylic acid synthase (ACS) is regulated not only transcriptionally but also post-translationally. To elucidate post-translational ACS regulation, we analyzed the modification of LE-ACS2 protein, a wound-inducible isozyme in the ACS family, in tomato fruit (Lycopersicon esculentum L.) using an anti-LE-ACS2 antibody. We detected phosphorylated LE-ACS2 at 55-kDa using immunoprecipitation from an extract of wounded fruit fed with [32P]inorganic phosphate. Analysis of LE-ACS2 phosphoamino acids indicated that serine residue(s) were phosphorylated. In vitro phosphorylation analyses using site-directed mutagenesis of recombinant LE-ACS2 as a substrate demonstrate that serine 460 located at the C-terminal region of ACS is phosphorylated. During tomato ripening stages, expression of both LE-ACS2 and LE-ACS4 mRNA increased. LE-ACS4, however, was not phosphorylated in vitro. These results suggest that ACS isozymes have different post-translational regulatory mechanisms, such as phosphorylation. PMID:11375393

Tatsuki, M; Mori, H

2001-07-27

329

Preparation and chiro-optical characterization of polyaniline doped with (+) or (-)-2-pyrrolidone-5-carboxylic acid (PCA).  

PubMed

Optically active polyaniline (PANI) salts were readily generated in solution via the enantioselective acid doping of neutral emeraldine base (EB) form of PANI with either (+) or (-)-2-pyrrolidone-5-carboxylic acid (PCA) in dimethylsulfoxide (DMSO) and dimethylformamide (DMF) solvents. Strong mirror imaged circular dichroism (CD) spectra were obtained for the deep green polymer solutions obtained with (+) or (-) PCA, suggesting that the acid doping is enantioselective, with one helical screw of the polymer chain being preferentially produced depending on the nature of enantiomer. It was observed that molar concentration of PCA as well as nature of solvent plays a very important role in the generation of optically active PANI. The generated optically active PANI did not show any loss of optical activity up to 200 h. PMID:21384436

Dubey, Rama; Dutta, Dhiraj; Shami, Trilok Chand; Rao, Kandepudi Udaya Bhasker

2011-04-01

330

Selected Functionality Changes of ?-Lactoglobulin upon Esterification of Side-Chain Carboxyl Groups  

Microsoft Academic Search

Free carboxyl groups of bovine ~34actoglobulin were esterified with meth- anol, ethanol, and n-butanol. The modified proteins showed increased positive charge as the number of ionizable carboxyl groups was reduced. The methyl, ethyl, and butyl esters of ~-lactoglobulin showed enhanced surface activity, determined with surface and interfacial tension measurements at an air\\/water and oil\\/ water interface, respectively. The methyl ester

Margaret I. Halpin; T. Richardson

1985-01-01

331

Efficient access to (1 H)-isoindolin-1-one-3-carboxylic acid derivatives by orthopalladation and carbonylation of methyl arylglycinate substrates  

Microsoft Academic Search

The orthopalladation of methyl arylglycinate derivatives has been studied. The reaction proceeds efficiently for different electron-withdrawing and electron-releasing substituents at the aryl ring. The carbonylation of the orthopalladated complexes affords, in a single step, substituted (1H)-isoindolin-1-one-3-carboxylates. These compounds constitute valuable synthetic intermediates and can be transformed diastereoselectively into octahydroisoindole-1-carboxylic acid derivatives, an important scaffold in the synthesis of many biologically

Sonia Nieto; Francisco J. Sayago; Pedro Laborda; Tatiana Soler; Carlos Cativiela; Esteban P. Urriolabeitia

2011-01-01

332

Permeation of Aromatic Carboxylic Acids across Lipid Bilayers: The pH-Partition Hypothesis Revisited  

Microsoft Academic Search

According to the pH-partition hypothesis the charged species of organic compounds do not contribute to lipid bilayer permeation as they generally show negligible partitioning into n-octanol. With this assumption, membrane permeation is related to the molar fraction of the neutral species at a particular pH. A recently developed permeation assay permits us to directly determine pH-dependent permeation of aromatic carboxylic

Anita V. Thomae; Heidi Wunderli-Allenspach; Stefanie D. Krämer

2005-01-01

333

Synthesis of 1-piperideine-6-carboxylic acid produced by L-lysine-epsilon-aminotransferase from the Streptomyces clavuligerus gene expressed in Escherichia coli.  

PubMed

The gene (lat) encoding L-lysine epsilon-aminotransferase (LAT) in Streptomyces clavuligerus was cloned and expressed in Escherichia coli. Nucleotide sequence analysis of lat predicted a single open reading frame (ORF) of 1371 bp, encoding a polypeptide of 457 amino acids with calculated molecular mass of 49.89 kDa. S. clavuligerus LAT was grouped into aminotransferase subfamily II of alpha family on the basis of sequence homology. A model system composed of the recombinant LAT in phosphate buffer was set up to study the biosynthesis of 2-acetyltetrahydropyridine. Lysine was found to be transformed to 1-piperideine-6-carboxylic acid. 2-Acetyltetrahydropyridine was characterized from the mixture of 1-piperideine-6-carboxylic acid and methylglyoxal. For the first time, we demonstrated that the L-lysine epsilon-aminotransferase is responsible for the formation of 1-piperideine-6-carboxylic acid, which may react with methylglyoxal to generate the acylated N-heterocyclic odorant 2-acetyltetrahydropyridine. PMID:17288446

Wu, Mei-Li; Chen, Jun-Hao; Ho, Chi-Tang; Huang, Tzou-Chi

2007-03-01

334

Investigation of acid sites in a zeotypic giant pores chromium(III) carboxylate.  

PubMed

A study of the zeotypic giant pores chromium(III) tricarboxylate Cr(III)3OF(x)(OH)(1-x)(H2O)2 x {C6H3-(CO2)3}2 x nH2O (MIL-100) has been performed. First, its thermal behavior, studied by X-ray thermodiffractometry and infrared spectroscopy, indicates that the departure of water occurs without any pore contraction and no loss in crystallinity, which confirms the robustness of the framework. In a second step, IR spectroscopy has shown the presence of three distinct types of hydroxy groups depending on the outgassing conditions; first, at high temperatures (573 K), only Cr-OH groups with a medium Brønsted acidity are present; at lower temperatures, two types of Cr-H2O terminal groups are observed; and at room temperature, their relatively high Brønsted acidity allows them to combine with H-bonded water molecules. Finally, a CO sorption study has revealed that at least three Lewis acid sites are present in MIL-100 and that fluorine atoms are located on a terminal position on the trimers of octahedra. A first result of grafting of methanol molecules acting as basic organic molecules on the chromium sites has also been shown, opening the way for a postsynthesis functionalization of MIL-100. PMID:16522102

Vimont, Alexandre; Goupil, Jean-Michel; Lavalley, Jean-Claude; Daturi, Marco; Surblé, Suzy; Serre, Christian; Millange, Franck; Férey, Gerard; Audebrand, Nathalie

2006-03-15

335

Investigation of the role of aromatic carboxylic acids in cross-linking processes in low-rank coals  

SciTech Connect

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. It is not clearly understood how decarboxylation leads to cross-linking beyond the suggestion that decarboxylation could be a radical process that involves radical recombination or radical addition reactions. We have recently conducted a study of the pyrolysis of 1,2-(3,3{prime}-dicarboxyphenyl)ethane (1) and 1,2-(4,4{prime}-dicarboxyphenyl)ethane (2) and found that decarboxylation occurs readily between 350-425 {degrees}C with no evidence of coupling products or products representative of cross-links. We proposed that decarboxylation occurred primarily by an acid-promoted cationic pathway, and the source of acid was a second carboxylic acid. The decarboxylation of 1 and 2 was investigated in diphenyl ether and naphthalene as inert diluents. In each solvent, the rate of decarboxylation dropped by roughly a factor of 2 upon dilution from the neat liquid to ca. 0.4 mole fraction of acid, but further dilution had no effect on the rate. This could be a consequence of hydrogen bonding or an intramolecular protonation. Molecular mechanics calculations indicated that 1 and 2 can adopt an appropriate conformation for internal proton transfer from a carboxy group on one ring to the second aryl ring without a significant energy penalty. In addition, the dicarboxylic acid could internally hydrogen bond, which may further complicate the reaction mechanism. Therefore, we have conducted a study of the pyrolysis of a monocarboxybibenzyl, 1-(3-carboxyphenyl)-2-(4-biphenyl)ethane (3), to determine if decarboxylation occurs by an ionic pathway in the absence of intramolecular pathways.

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

1997-03-01

336

Synthesis, structure and structure-activity relationship analysis of 3-tert-butoxycarbonyl-2-arylthiazolidine-4-carboxylic acid derivatives as potential antibacterial agents.  

PubMed

Nine 2-arylthiazolidine-4-carboxylic acid derivatives and nine 3-tert-butoxycarbonyl-2-arylthiazolidine-4-carboxylic acid derivatives were synthesized to screen for their antibacterial activities. Compounds 5, 14-18 were first reported. Their chemical structures were clearly determined by (1)H NMR, (13)C NMR, ESI mass spectra and elemental analyses, coupled with one selected single-crystal structure. All the compounds were assayed for antibacterial activities against two Gram-positive bacterial strains (Bacillus subtilis ATCC 6633 and Staphylococcus aureus ATCC 6538) and two Gram-negative bacterial strains (Escherichia coli ATCC 35218 and Pseudomonas aeruginosa ATCC 13525) by MTT method. Most of the 3-tert-butoxycarbonyl-2-arylthiazolidine-4-carboxylic acid derivatives exhibited better antibacterial activities against the four bacterial strains than relative 2-arylthiazolidine-4-carboxylic acid derivatives. Compound (2RS,4R)-3-(tert-butoxycarbonyl)-2-(5-fluoro-2-hydroxyphenyl)thiazolidine-4-carboxylic acid (14) showed powerful antibacterial activities against P. aeruginosa with IC(50) value of 0.195 microg/mL, which was superior to the positive controls Penicillin G and Kanamycin B, respectively. On the basis of the biological results, structure-activity relationships were discussed. PMID:19423200

Song, Zhong-Cheng; Ma, Gao-Yuan; Lv, Peng-Cheng; Li, Huan-Qiu; Xiao, Zhu-Ping; Zhu, Hai-Liang

2009-10-01

337

Functional carboxyl groups in the red cell anion exchange protein. Modification with an impermeant carbodiimide  

PubMed Central

Anion exchange in human red blood cell membranes was inactivated using the impermeant carbodiimide 1-ethyl-3-(4-azonia-4,4-dimethylpentyl)- carbodiimide (EAC). The inactivation time course was biphasic: at 30 mM EAC, approximately 50% of the exchange capacity was inactivated within approximately 15 min; this was followed by a phase in which irreversible exchange inactivation was approximately 100-fold slower. The rate and extent of inactivation was enhanced in the presence of the nucleophile tyrosine ethyl ester (TEE), suggesting that the inactivation is the result of carboxyl group modification. Inactivation (to a maximum of 10% residual exchange activity) was also enhanced by the reversible inhibitor of anion exchange 4,4'-dinitrostilbene-2,2'- disulfonate (DNDS) at concentrations that were 10(3)-10(4) times higher than those necessary for inhibition of anion exchange. The extracellular binding site for stilbenedisulfonates is essentially intact after carbodiimide modification: the irreversible inhibitor of anion exchange 4,4'-diisothiocyanostilbene-2,2'-disulfonate (DIDS) eliminated (most of) the residual exchange activity: DNDS inhibited the residual (DIDS-sensitive) Cl- at concentrations similar to those that inhibit Cl- exchange of unmodified membranes: and Cl- efflux is activated by extracellular Cl-, with half-maximal activation at approximately 3 mM Cl-, which is similar to the value for unmodified membranes. But the residual anion exchange function after maximum inactivation is insensitive to changes of extra- and intracellular pH between pH 5 and 7. The titratable group with a pKa of approximately 5.4, which must be deprotonated for normal function of the native anion exchanger, thus appears to be lost after EAC modification. PMID:2738575

1989-01-01

338

Synthesis, characterization, theoretical study and biological activities of oxovanadium (IV) complexes with 2-thiophene carboxylic acid hydrazide.  

PubMed

Oxovanadium (IV) complexes (1)-(3) have been synthesized by treating 2-thiophene carboxylic acid hydrazide with VOSO4?xH2O and VCl3(THF)3 in different M/L ratios. These complexes have been characterized by elemental analysis, UV-vis, FT-IR and mass spectrometry. The FT-IR data predicts the bidentate nature of the ligand which is also confirmed by semi-empirical study. Mass spectrometric data shows that molecular ion peak is only observed for 2-thiophene carboxylic acid hydrazide. The ESP map and thermodynamic parameters shows the presence of partial charge on atoms and stability of synthesized oxovanadium complexes, respectively. DNA binding study of complexes (1)-(3) was carried out by UV-vis and cyclic voltammetric methods which suggests the intercalative binding mode of the complexes with DNA. Cytotoxicity was checked by brine shrimp lethality assay and complex (1) showed greater cytotoxicity towards Artemia salina as compared to free ligand. Immuno-modulatory activity data shows that hydrazide ligand was more active as compared to oxovanadium complexes and standard drug. Complex (2) shows significant urease inhibition activity. The ligand and synthesized complexes were found inactive against all tested bacterial and fungal strains. PMID:24844618

Jabeen, Mudassir; Ali, Saqib; Shahzadi, Saira; Sharma, Saroj K; Qanungo, Kushal

2014-07-01

339

Design, synthesis and biological evaluation of 2-(substituted phenyl)thiazolidine-4-carboxylic acid derivatives as novel tyrosinase inhibitors.  

PubMed

Herein we describe the design, synthesis and biological activities of 2-(substituted phenyl)thiazolidine-4-carboxylic acid derivatives as novel tyrosinase inhibitors. The target compounds 2a-2j were designed and synthesized from the structural characteristics of N-phenylthiourea, tyrosinase inhibitor and tyrosine, and l-DOPA, the natural substrates of tyrosinase. Among them, (2R/S,4R)-2-(2,4-dimethoxyphenyl)thiazolidine-4-carboxylic acid (2g) caused the greatest inhibition 66.47% at 20 ?M of l-DOPA oxidase activity of mushroom tyrosinase. Kinetic analysis of tyrosinase inhibition revealed that 2g is a competitive inhibitor. We predicted the tertiary structure of tyrosinase, and simulated the docking of mushroom tyrosinase with 2g. These results suggest that the binding affinity of 2g with tyrosinase is high. Also, 2g effectively inhibited tyrosinase activity and reduced melanin levels in B16 cells treated with ?-MSH. These data strongly suggest that 2g can suppress the production of melanin via the inhibition of tyrosinase activity. PMID:21945595

Ha, Young Mi; Park, Yun Jung; Lee, Ji Yeon; Park, Daeui; Choi, Yeon Ja; Lee, Eun Kyeong; Kim, Ji Min; Kim, Jin-Ah; Park, Ji Young; Lee, Hye Jin; Moon, Hyung Ryong; Chung, Hae Young

2012-02-01

340

Speciation of aqueous Ni(II)-carboxylate and Ni(II)-fulvic acid solutions: Combined ATR-FTIR and XAFS analysis  

NASA Astrophysics Data System (ADS)

Aqueous solutions containing Ni(II) and a series of structurally related carboxylic acids were analyzed using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and Ni K-edge X-ray absorption fine structure spectroscopy (XAFS). XAFS spectra were also collected for solutions containing Ni 2+ and chelating ligands (ethylenediaminetetraacetic acid, nitrilotriacetic acid (NTA)) as well as soil fulvic acid. Limited spectral changes are observed for aqueous Ni(II) complexes with monocarboxylates (formate, acetate) and long-chain polycarboxylates (succinate, tricarballylate), where individual donor groups are separated by multiple bridging methylene groups. These spectral changes indicate weak interactions between Ni(II) and carboxylates, and the trends are similar to some earlier reports for crystalline Ni(II)-acetate solids, for which X-ray crystallography studies have indicated monodentate Ni(II)-carboxylate coordination. Nonetheless, electrostatic or outer-sphere coordination cannot be ruled out for these complexes. However, spectral changes observed for short-chain dicarboxylates (oxalate, malonate) and carboxylates that contain an alcohol donor group adjacent to one of the carboxylate groups (lactate, malate, citrate) demonstrate inner-sphere metal coordination by multiple donor groups. XAFS spectral fits of Ni(II) solutions containing soil fulvic acid are consistent with inner-sphere Ni(II) coordination by one or more carboxylate groups, but spectra are noisy and outer-sphere modes of coordination cannot be ruled out. These molecular studies refine our understanding of the interactions between carboxylates and weakly complexing divalent transition metals, such as Ni(II).

Strathmann, Timothy J.; Myneni, Satish C. B.

2004-09-01

341

Carboxylic acid sorption on synthetic clays in sea water: In vitro experiments and implications for organo-clay behaviour under marine conditions  

Microsoft Academic Search

In order to investigate the role of clay minerals in organic matter preservation, the fixation of pure organic compounds on two synthetic low charge and high charge saponites was investigated in laboratory experiments simulating marine water conditions. The clays were exposed to four carboxylic acids: pentadecanoic, docosanoic, 5?-cholanic acid and ursolic, dissolved in treated natural sea water. Characterization of the

Sylvain Drouin; Mohammed Boussafir; Jean-Louis Robert; Patrick Alberic; Aude Durand

2010-01-01

342

Photometric determination of carboxylic acid impurities in polymers and organic liquids with the use of the ion pair of trinonyloctadecylammonium and Bromothymol Blue as the colored reagent  

Microsoft Academic Search

A method was proposed for the photometric determination of carboxylic acid impurities in polyvinylchloride, food and machine oils, and other samples. The method is based on the interaction of the acid groups of the sample with the ion pair of Bromothymol Blue and the trinonyloctadecylammonium cation in the binary solvent toluene-tetrahydrofuran. The method is highly sensitive and reproducible and was

E. M. Rakhman’ko; V. V. Zhilko; V. V. Egorov

2005-01-01

343

THz and mid-IR spectroscopy of interstellar ice analogs: methyl and carboxylic acid groups.  

PubMed

A fundamental problem in astrochemistry concerns the synthesis and survival of complex organic molecules (COMs) throughout the process of star and planet formation. While it is generally accepted that most complex molecules and prebiotic species form in the solid phase on icy grain particles, a complete understanding of the formation pathways is still largely lacking. To take full advantage of the enormous number of available THz observations (e.g., Herschel Space Observatory, SOFIA, and ALMA), laboratory analogs must be studied systematically. Here, we present the THz (0.3-7.5 THz; 10-250 cm(-1)) and mid-IR (400-4000 cm(-1)) spectra of astrophysically-relevant species that share the same functional groups, including formic acid (HCOOH) and acetic acid (CH3COOH), and acetaldehyde (CH3CHO) and acetone ((CH3)2CO), compared to more abundant interstellar molecules such as water (H2O), methanol (CH3OH), and carbon monoxide (CO). A suite of pure and mixed binary ices are discussed. The effects on the spectra due to the composition and the structure of the ice at different temperatures are shown. Our results demonstrate that THz spectra are sensitive to reversible and irreversible transformations within the ice caused by thermal processing, suggesting that THz spectra can be used to study the composition, structure, and thermal history of interstellar ices. Moreover, the THz spectrum of an individual species depends on the functional group(s) within that molecule. Thus, future THz studies of different functional groups will help in characterizing the chemistry and physics of the interstellar medium (ISM). PMID:25302394

Ioppolo, S; McGuire, B A; Allodi, M A; Blake, G A

2014-01-01

344

Ion-exclusion chromatographic behavior of aliphatic carboxylic acids and benzenecarboxylic acids on a sulfonated styrene--divinylbenzene co-polymer resin column with sulfuric acid containing various alcohols as eluent.  

PubMed

The addition of C1-C7 alcohols (methanol, ethanol, propanol, butanol, heptanol, hexanol and heptanol) to dilute sulfuric acid as eluent in ion-exclusion chromatography using a highly sulfonated styrene-divinylbenzene co-polymer resin (TSKgel SCX) in the H+ form as the stationary phase was carried out for the simultaneous separations of both (a) C1-C7 aliphatic carboxylic acids (formic, acetic, propionic, isobutyric, butyric, isovaleric, valeric, 2-methylvaleric, isocaproic, caproic, 2,2-dimethyl-n-valeric, 2-methylhexanoic, 5-methylhexanoic and heptanoic acids) and (b) benzenecarboxylic acids (pyromellitic, hemimellitic, trimellitic, o-phthalic, m-phthalic, p-phthalic, benzoic and salicylic acids and phenol). Heptanol was the most effective modifier in ion-exclusion chromatography for the improvement of peak shapes and a reduction in retention volumes for higher aliphatic carboxylic acids and benzenecarboxylic acids. Excellent simultaneous separation and relatively highly sensitive conductimetric detection for these C1-C7 aliphatic carboxylic acids were achieved on the TSKgel SCX column (150 x 6 mm I.D.) in 30 min using 0.5 mM sulfuric acid containing 0.025% heptanol as eluent. Excellent simultaneous separation and highly sensitive UV detection at 200 nm for these benzenecarboxylic acids were also achieved on the TSKgel SCX column in 30 min using 5 mM sulfuric acid containing 0.075% heptanol as eluent. PMID:12830881

Ohta, Kazutoku; Towata, Atsuya; Ohashi, Masayoshi

2003-05-16

345

Oxadiazolyl-pyridines and perfluoroalkyl-carboxylic acids as building blocks for protic ionic liquids: crossing the thin line between ionic and hydrogen bonded materials.  

PubMed

A series of 18 samples has been prepared in order to obtain fluorinated materials as Protic Ionic Liquids (PILs). These were synthesized by appropriately mixing 1,2,4-oxadiazoles derivatised with two pyridines, or one pyridine and a fluorinated chain, and perfluoroalkyl-carboxylic acids, either mono- or dicarboxylic, leading to symmetric and non-symmetric materials. Many of them showed low melting points. However, the possibility of classifying the synthesized materials as PILs is discussed in terms of effective ionicity of the systems by the combination of Density Functional Theory (DFT) calculation and IR spectroscopy. The important outcome of our investigation is that the complete proton transfer reaction cannot be taken for granted. The thermal behaviour of the new fluorinated materials was also studied by Differential Scanning Calorimetry (DSC) and Thermogravimetric analysis (TGA). PMID:23001030

Pibiri, I; Pace, A; Buscemi, S; Causin, V; Rastrelli, F; Saielli, G

2012-11-01

346

Electrochemical quartz crystal microbalance study of covalent tethering of carboxylated thiol to polyaniline for electrocatalyzed oxidation of ascorbic acid in neutral aqueous solution.  

PubMed

The electrochemical quartz crystal microbalance (EQCM) was used to study the electrosyntheses and electrochemical properties of two kinds of polyaniline (PANI)-thiol composite films in aqueous solutions, which were prepared by covalent binding of a thiol to the oxidized forms of PANI (PANI(post)-thiol, protocol A), and electropolymerization of aniline in the presence of a thiol (PANI(poly)-thiol, protocol B), respectively. The thiols involved were mercaptosuccinic acid (MSA), thioglycolic acid (TGA) and beta-mercaptoethanol (ME). The PANI(post)-thiol binding processes were monitored in situ with the EQCM, giving molar binding ratios (r, thiol vs. aniline unit of the polymer) of ca. 0.50 at saturation for these thiols. Both PANI(post)-thiol and PANI(poly)-thiol composite films from the carboxylated thiols showed a controllable electroactivity of the PANI moiety in neutral even weakly alkaline phosphate buffer solutions (PBS), with maximum electroactivity roughly at r = 0.11 for PANI(post)-MSA or at r = 0.21 for PANI(post)-TGA. The PANI-thiol interaction was also supported by experiments of scanning electron microscopy, electrochemical surface plasmon resonance, Fourier transform infrared spectroscopy and ultraviolet-visible spectroscopy, and the interaction mechanism is briefly discussed. The PANI(post)-thiol and PANI(poly)-thiol composite films from the carboxylated thiols effectively electrocatalyzed the oxidation of ascorbic acid in pH = 7.3 PBS, and the PANI(post)-thiol exhibited electrocatalytic activity higher than the relevant PANI(poly)-thiol under our experimental conditions. The covalent anchoring of anionic thiol groups on the PANI backbone to prepare electroactive PANI in neutral solutions is conceptually new and may be extended to the development of new functional materials from many other conducting polymers and thiols for wide applications in catalysis, biosensing, molecular electronics, and so on. PMID:19812825

Su, Zhaohong; Huang, Jinhua; Xie, Qingji; Fang, Zhengfa; Zhou, Cong; Zhou, Qingmei; Yao, Shouzhuo

2009-10-28

347

Conformational characterization of peptides rich in the cycloaliphatic C alpha,alpha-disubstituted glycine 1-aminocyclononane-1-carboxylic acid.  

PubMed

A series of N- and C-protected, monodispersed homo-oligopeptides (to the pentamer level) from the cycloaliphatic C alpha,alpha-dialkylated glycine 1-aminocyclononane-1-carboxylic acid (Ac9c) and two Ala/Ac9c tripeptides have been synthesized by solution methods and fully characterized. The conformational preferences of all the model peptides were determined in deuterochloroform solution by FT-IR absorption and 1H-NMR. The molecular structures of the amino acid derivatives mCIAc-Ac9c-OH and Z-Ac9c-OtBu, the dipeptide pBrBz-(Ac9c)2-OtBu, the tetrapeptide Z-(Ac9c)4-OtBu, and the pentapeptide Z-(Ac9c)5-OtBu were determined in the crystal state by X-ray diffraction. Based on this information, the average geometry and the preferred conformation for the cyclononyl moiety of the Ac9c residue have been assessed. The backbone conformational data are strongly in favour of the conclusion that the Ac9c residue is a strong beta-turn and helix former. A comparison with the structural propensity of alpha-aminoisobutyric acid, the prototype of C alpha,alpha-dialkylated glycines, and the other extensively investigated members of the family of 1-aminocycloalkane-1-carboxylic acids (Acnc, with n = 3-8) is made and the implications for the use of the Ac9c residue in conformationally constrained analogues of bioactive peptides are briefly examined. PMID:9391912

Gatos, M; Formaggio, F; Crisma, M; Valle, G; Toniolo, C; Bonora, G M; Saviano, M; Iacovino, R; Menchise, V; Galdiero, S; Pedone, C; Benedetti, E

1997-01-01

348

Oxorhenium(V) complexes of quinoline and isoquinoline carboxylic acids--synthesis, structural characterization and catalytic application in epoxidation reactions.  

PubMed

Six novel oxorhenium(V) complexes incorporating quinoline and isoquinoline carboxylic acid derivatives were prepared in good yields. Relying on the experimental conditions, compounds with two chelate ligands [ReOCl(iqc)2]·MeOH (1), [ReO(OMe)(iqc)2] (2), [ReO(OMe)(mqc)2] (3) and [ReO(OMe)(8-qc)2] (4) and compounds incorporating one bidentate ligand [ReOCl2(iqc)(PPh3)] (5) and [ReOCl2(mqc)(PPh3)] (6) were synthesized (iqcH = isoquinoline-1-carboxylic acid, mqcH = 4-methoxy-2-quinolinecarboxylic acid and 8-qcH = 8-quinolinecarboxylic acid). The reported compounds were characterized by spectroscopic methods and single crystal X-ray diffraction analysis. In compounds 1 and 2, one chelate ligand occupies an axial and an equatorial position, while the other one occupies two equatorial positions, forming a cis-(N,N) isomer. In turn, complexes 3 and 4 show a rare ligand arrangement with two trans-N, trans-O chelate ligands in the equatorial plane and a linear axial [O=Re-OMe] unit. The complexes with one chelate ligand 5 and 6 are cis-(Cl,Cl)-isomers. All compounds were tested as potential catalysts in the epoxidation of cyclooctene with 3 equiv. of tert-butylhydroperoxide. The yield of cyclooctane oxide varies between 16 and 68% (50 °C, 24 h), and the catalytic competency of compounds 1-6 was discussed with regard to the structure of each complex. PMID:23640402

Machura, Barbara; Wolff, Mariusz; Benoist, Eric; Schachner, Jörg A; Mösch-Zanetti, Nadia C

2013-06-28

349

Effect of Carboxylic Functional Group Functionalized on Carbon Nanotubes Surface on the Removal of Lead from Water  

PubMed Central

The adsorption mechanism of the removal of lead from water by using carboxylic functional group (COOH) functionalized on the surface of carbon nanotubes was investigated. Four independent variables including pH, CNTs dosage, contact time, and agitation speed were carried out to determine the influence of these parameters on the adsorption capacity of the lead from water. The morphology of the synthesized multiwall carbon nanotubes (MWCNTs) was characterized by using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) in order to measure the diameter and the length of the CNTs. The diameters of the carbon nanotubes were varied from 20 to 40?nm with average diameter at 24?nm and 10 micrometer in length. Results of the study showed that 100% of lead was removed by using COOH-MCNTs at pH 7, 150?rpm, and 2 hours. These high removal efficiencies were likely attributed to the strong affinity of lead to the physical and chemical properties of the CNTs. The adsorption isotherms plots were well fitted with experimental data. PMID:21350599

Atieh, Muataz Ali; Bakather, Omer Yehya; Al-Tawbini, Bassam; Bukhari, Alaadin A.; Abuilaiwi, Faraj Ahmad; Fettouhi, Mohamed B.

2010-01-01

350

Novel Regenerated Solvent Extraction Processes for the Recovery of Carboxylic Acids or Ammonia from Aqueous Solutions Part II. Recovery of Ammonia from Sour Waters  

SciTech Connect

Two novel regenerated solvent extraction processes are examined. The first process has the potential to reduce the energy costs inherent in the recovery of low-volatility carboxylic acids from dilute aqueous solutions. The second process has the potential for reducing the energy costs required for separate recovery of ammonia and acid gases (e.g. CO{sub 2} and H{sub 2}S) from industrial sour waters. The recovery of carboxylic acids from dilute aqueous solution can be achieved by extraction with tertiary amines. An approach for regeneration and product recovery from such extracts is to back-extract the carboxylic acid with a water-soluble, volatile tertiary amine, such as trimethylamine. The resulting trimethylammonium carboxylate solution can be concentrated and thermally decomposed, yielding the product acid and the volatile amine for recycle. Experimental work was performed with lactic acid, SUCCiOlC acid, and fumaric acid. Equilibrium data show near-stoichiometric recovery of the carboxylic acids from an organic solution of Alamine 336 into aqueous solutions of trimethylamine. For fumaric and succinic acids, partial evaporation of the aqueous back extract decomposes the carboxylate and yields the acid product in crystalline form. The decomposition of aqueous solutions of trimethylammonium lactates was not carried out to completion, due to the high water solubility of lactic acid and the tendency of the acid to self-associate. The separate recovery of ammonia and acid gases from sour waters can be achieved by combining steam-stripping of the acid gases with simultaneous removal of ammonia by extraction with a liquid cation exchanger. The use of di-2,4,4-trimethylpentyl phosphinic acid as the liquid cation exchanger is explored in this work. Batch extraction experiments were carried out to measure the equilibrium distribution ratio of ammonia between an aqueous buffer solution and an organic solution of the phosphinic acid (0.2N) in Norpar 12. The concentration-based distribution ratios increase from 0.11 to 0.46 as the aqueous phase pH increases from 7.18 to 8.15. Regeneration of the organic extractant solution was carried out by stripping at elevated temperatures to remove the ammonia, with 99% recovery of the ammonia being obtained at 125 C.

Poole, L.J.; King, C.J.

1990-03-01

351

QSTR studies regarding the ECOSAR toxicity of benzene-carboxylic acid' esters to fathead minnow fish (Pimephales promelas).  

PubMed

The present work employs 152 benzene-carboxylic acid' esters having computed the toxicity within the range [2.251, 10.222] for fathead minnow fish (Pimephales promelas). Calibration set includes many pairs having very similar chemical structure, size, shape and hydrophilicity, but very different value of ECOSAR toxicity or vice versa. The QSTR study, which uses all esters as calibration set, emphasized a large percent (16.2%) of outliers. In this QSTR study most of the estimated values of toxicity for outliers are much lower than ECOSAR toxicity. The LogP and some aromaticity descriptors are predictors. The best QSTR for esters having low value (< 5.5) of ECOSAR toxicity and the best QSTR for esters having high value (> 5.5) of ECOSAR toxicity are obtained when the number of outliers is very small. These QSTRs are different enough and highlight opposite influences of certain descriptors on toxicity. The results emphasize two possibilities: (a) the esters having low value of ECOSAR toxicity and the esters having high value of ECOSAR toxicity are included in two different classes from the point of view of structure-toxicity relationship and/or (b) many high values of ECOSAR toxicity are wrong. By comparison, a QSTR using experimental values of toxicity against rats for 37 benzene-carboxylic esters included in the same database gives good correlation experimental/computed values of toxicity, the number of outliers is null and the result of validation test is good. PMID:24724900

Tarko, Laszlo; Putz, Mihai V; Ionascu, Cosmin; Putz, Ana-Maria

2014-01-01

352

Crystal structures of (2R,4R)-2-(polyhydroxyalkyl)-1,3-thiazolidine-4-carboxylic acids: condensation products of l-cysteine with d-hexoses.  

PubMed

We report herein the first crystal structures of (4-carboxy-1,3-thiazolidin-2-yl)pentitols [2-(polyhydroxyalkyl)thiazolidine-4-carboxylic acids], condensation products of l-cysteine with d-galactose and d-mannose: 2-(d-galacto-pentahydroxypentyl)thiazolidine-4-carboxylic acid hydrate, Gal-Cys·H(2)O (1), and 2-(d-manno-pentahydroxypentyl)thiazolidine-4-carboxylic acid hydrate, Man-Cys·H(2)O (2). In 1 and 2 the compounds crystallize as zwitterions, with the carboxylic groups deprotonated and the thiazolidine N atoms protonated. The sugar moiety and carboxylate group are in a cis configuration relative to the thiazolidinium ring, which adopts different conformation: twisted (T) on C(?)-S in 1, and S-puckered envelope (E) in 2. The carbon chain of the galactosyl/mannosyl moiety remains in an extended zig-zag conformation. The orientation of the sugar O2 atom with respect to the thiazolidinium S and N atoms is trans-gauche in 1 and gauche-gauche in 2. The molecular conformation is stabilized by the intramolecular N-H?O(Cys) contacts in both 1 and 2 and by the additional N-H?O(Man) interaction in 2. The crystal packing of orthorhombic 1 and monoclinic 2 is determined mainly by N/O/C-H?O hydrogen bonds forming ribbons linked to each other by direct and water-mediated O/C-H?O/S contacts. PMID:21129733

Tarnawski, Miros?aw; Slepokura, Katarzyna; Lis, Tadeusz

2011-01-01

353

S-Adenosyl- l-Methionine:Salicylic Acid Carboxyl Methyltransferase, an Enzyme Involved in Floral Scent Production and Plant Defense, Represents a New Class of Plant Methyltransferases  

Microsoft Academic Search

S-Adenosyl-l-methionine:salicylic acid carboxyl methyltransferase (SAMT) was partially purified from petals of the annual California plant Clarkia breweri. SAMT catalyzes the formation of methylsalicylate, an important floral scent compound in C. breweri, from salicylic acid and S-adenosyl-l-methionine (SAM). The native enzyme is a dimer with a subunit molecular weight of 40.3 kDa, and it has a Km for salicylic acid of

Jeannine R. Ross; Kyoung Hee Nam; John C. D'Auria; Eran Pichersky

1999-01-01

354

Precolumn fluorescence tagging reagent for carboxylic acids in high-performance liquid chromatography: 4-substituted-7-aminoalkylamino-2,1,3-benzoxadiazoles.  

PubMed

Four new 2,1,3-benzoxadiazole amine reagents having different functional groups at the 4- and 7-positions, [4-nitro-7-N-piperazino-2,1,3-benzoxadiazole (NBD-PZ), 4-(N,N-dimethylaminosulphonyl)-7-N-piperazino-2,1,3-benzoxad iazole (DBD-PZ), 4-(N,N-dimethylaminosulphonyl)-7-N-cadaverino-2,1,3-benzoxad iazole (DBD-CD) and ammonium 7-N-piperazino-2,1,3-benzoxadiazole-4-sulphonate (SBD-PZ)] were synthesized as fluorogenic tagging reagents for carboxylic acids in high-performance liquid chromatography. The reagents, except SBD-PZ, reacted with carboxylic acid at room temperature in the presence of activation agents to produce fluorescent adducts. The maximum wavelengths of arachidic acid tagged with DBD-PZ, DBD-CD and NBD-PZ were 569 nm (excitation, 440 nm), 561 nm (excitation, 437 nm) and 541 nm (excitation, 470 nm), respectively. Among various activation agents tested [diethyl phosphorocyanidate (DEPC), diphenyl phosphoroyl azide (DPPA), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)-pyridine, 2.2'-dipyridyl disulphide-triphenylphosphine (Mukaiyama A) and 2-chloro-1-methylpyridinium iodide-triethylamine (Mukaiyama B)], DEPC and Mukaiyama A were more effective than the others. When the piperazino reagents (DBD-PZ and NBD-PZ) were used as the tagging reagents, the derivatization reaction in the presence of Mukaiyama A was faster than that in the presence of DEPC. Although the reaction in the presence of Mukaiyama A was completed after 30 min, an unknown peak derived from the activation agent appeared on the chromatograms. The fluorescence peak intensities were compared in the presence of DEPC. The order of the fluorescence peak areas obtained after reaction for 6 h in the presence of DEPC was DBD-PZ greater than DBD-CD greater than NBD-PZ. Thirteen saturated free fatty acids (FFAs) derivatized with DBD-PZ (or DBD-CD) and DEPC (or Mukaiyama A) in acetonitrile were separated completely by linear gradient elution on a reversed-phase ODS column. Eight drugs (ibuprofen, indomethacin, dinoprost, prostaglandin E1, dehydrocholic acid, ursodesoxycholic acid, hydrocartisone succinate and prednisolone succinate) were also tagged with DBD-PZ in the presence of DEPC and separated by isocratic elution. The detection limits (signal-to-noise ratio = 3) of FFAs tagged with DBD-PZ were in the range 3.2-4.7 fmol, whereas those of drugs were in the range 3.9-14 fmol. PMID:1818086

Toyo'oka, T; Ishibashi, M; Takeda, Y; Nakashima, K; Akiyama, S; Uzu, S; Imai, K

1991-12-27

355

Spectroscopic and physicochemical behavior of magnesium phthalocyanine derivatives mono-substituted with a carboxylic acid group  

NASA Astrophysics Data System (ADS)

This work reports on the synthesis of novel unsymmetrically substituted magnesium phthalocyanine complexes containing one carboxyl group. The physicochemical behavior of these complexes were compared with those of their unmetallated and zinc counterparts. The MgPcs showed interesting absorption spectra with [8,15,22-Tris-(naphtho)-4,5-(3-carboxy-1,2-dioxyphenyl)phthalocyaninato]magnesium (II) showing a large split in the Q band whereas [8,15,22-Tris-(naphtho)-2-(carboxy) phthalocyaninato]magnesium(II) presented only a small splitting. The magnesium phthalocyanine derivatives displayed higher fluorescence quantum yields compared to unmetallated and zinc phthalocyanine counterparts. The latter gave admirable triplet and singlet oxygen quantum yields. These molecules can distinctly be employed in the field of photodynamic therapy in combination with fluorescence imaging.

Nombona, Nolwazi; Chidawanyika, Wadzanai; Nyokong, Tebello

2012-03-01

356

ANALYSIS OF PERFLUORINATED CARBOXYLIC ACIDS IN SOILS: DETECTION AND QUANTITATION ISSUES AT LOW CONCENTRATIONS  

EPA Science Inventory

Methods were developed for the extraction from soil, identification, confirmation and quantitation by LC/MS/MS of trace levels of perfluorinated octanoic acid (PFOA), perfluorinated nonanoic acid (PFNA) and perfluorinated decanoic acid (PFDA). Whereas PFOA, PFNA and PFDA all can...

357

Predictions of the Fluorine NMR Chemical Shifts of Perfluorinated Carboxylic Acids, CnF2n+1COOH (n = 6-8)  

NASA Astrophysics Data System (ADS)

Perfluorinated carboxylic acids (PFCAs) are a class of persistent environmental pollutants. Commercially available PFCAs are mixtures of linear and branched isomers, possibly with impurities. Different isomers have different physical and chemical properties and toxicities. However, little is known about the properties and the finer details of the structures of the individual branched isomers. Full geometry optimizations for the linear n-alkane (C6-C27) PFCAs indicated that all have helical structures. The helical angle increases slightly with increasing chain length, from 16.3° in C6F13COOH to 17.0° in C27F55COOH. This study predicts 19F NMR parameters for 69 linear and branched isomers of the perfluoro carboxylic acids C6F13COOH, C7F15COOH, and C8F17COOH. B3LYP-GIAO/6-31++G(d,p)//B3LYP/6-31G(d,p) was used for the NMR calculations with analysis of the chemical shifts by the natural bond orbital method. The predictions of the 19F chemical shifts revealed the differences among the CF3, CF2, and CF groups. In general, the absolute values for the chemical shifts for the CF3 group are smaller than 90 ppm, for the CF larger than 160 ppm, and for the CF2 between 110 and 130 ppm. The chemical shifts of the branched isomers are smaller in magnitude than the linear ones. The decrease is correlated with the steric hindrance of the CF3 groups, the more hindered the CF3, the greater the decrease in the 19F chemical shifts. The predicted 19F chemical shifts are similar to those for analogous perfluoro compounds with other terminal functional groups such as -SO3H or -SO3NH2CH2CH3.

Liu, Zizhong; Goddard, John D.

2009-10-01

358

New Derivatives of 3,4-Dihydroisoquinoline-3-carboxylic Acid with Free-Radical Scavenging, D-Amino Acid Oxidase, Acetylcholinesterase and Butyrylcholinesterase Inhibitory Activity.  

PubMed

A series of 3,4-dihydroisoquinoline-3-carboxylic acid derivatives were synthesised and tested for their free-radical scavenging activity using 2,2-diphenyl-1-picrylhydrazyl radical (DPPH·), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical (ABTS·+), superoxide anion radical (O2·-) and nitric oxide radical (·NO) assays. We also studied d-amino acid oxidase (DAAO), acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitory activity. Almost each of newly synthesised compounds exhibited radical scavenging capabilities. Moreover, several compounds showed moderate inhibitory activities against DAAO, AChE and BuChE. Compounds with significant free-radical scavenging activity may be potential candidates for therapeutics used in oxidative-stress-related diseases. PMID:25271427

Solecka, Jolanta; Gu?piel, Adam; Postek, Magdalena; Ziemska, Joanna; Kaw?cki, Robert; L?czycka, Katarzyna; Osior, Agnieszka; Pietrzak, Bart?omiej; Pypowski, Krzysztof; Wyrzykowska, Agata

2014-01-01

359

Solid compounds of europium and terbium with some aromatic carboxylic acids  

SciTech Connect

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.

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

1986-10-20

360

Functional Reconstitution of the Integral Membrane Enzyme, Isoprenylcysteine Carboxyl Methyltransferase, in Synthetic Bolalipid Membrane Vesicles†  

PubMed Central

Three bipolar archaeal-type diglycerophosphocholine tetraether lipids (a.k.a., bolalipids) have been prepared to determine 1) the influence of molecular structure on the physical properties of bolalipid membranes and 2) their impact on the functional reconstitution of Ste14p, a membrane-associated isoprenylcysteine carboxyl methyltransferase from Saccharomyces cerevisiae. The three bolalipids synthesized were: C20BAS, C32BAS, and C32phytBAS. These bolalipid structures differ in that the C20BAS derivative has a short sn-1 glyceryl diether C20H40 transmembrane alkyl chain and two ether-linked sn-2 n-decyl chains, whereas the C32BAS and C32phytBAS derivatives have a longer sn-1 diether C32H64 membrane-spanning chain and two ether-linked sn-2 n-hexadecyl or phytanyl chains, respectively. Differential scanning calorimetry and temperature-dependent 31P NMR was used to determine the gel-to-liquid crystalline phase transition temperatures of the bolalipids (C32BAS Tm > 85 °C; C32phytBAS Tm = 14 °C; C20BAS Tm = 17°C). The bolalipid lateral diffusion coefficients, determined by fluorescence recovery after photobleaching at 20 °C, were 1.5 × 10?8 and 1.8 × 10?9 cm2/s for C20BAS and C32phytBAS, respectively. The mobility of C32BAS could not be measured at this temperature. Ste14p activity was monitored by an in vitro methyltransferase assay in reconstituted vesicle dispersions composed of DMPC, C20BAS:E. coli polar lipid, C20BAS:POPC, C32phytBAS:E. coli polar lipid, and C32phytBAS:POPC. Ste14p activity was lost in vesicles composed of 75–100 mol% C20BAS and 0–100 mol% C32BAS, but retained in vesicles with 0–50 mol% C20BAS and 0–100 mol% C32phytBAS. Confocal immunofluorescence microscopy confirmed the presence of Ste14p in 100 mol% C20BAS and 100 mol% C32phytBAS vesicle dispersions, even though the lamellar liquid crystalline phase thickness of C20BAS is only 32 Å. Since Ste14p activity was not affected by either the gel to liquid-crystal phase transition temperature of the lipid or the temperature of the assay, the low activity observed in 75–100 mol% C20BAS membranes can be attributed to hydrophobic mismatch between this bolalipid and the hydrophobic surface of Ste14p. PMID:17144661

Febo-Ayala, Wilma; Morera-Felix, Shakira L.

2008-01-01

361

A new extraction technique for in situ analyses of amino and carboxylic acids on Mars by gas chromatography mass spectrometry  

NASA Astrophysics Data System (ADS)

In order to target key organic compounds in the Martian regolith using gas chromatography mass spectrometry (GC-MS), we have developed a new extraction procedure coupled with chemical derivatization. This new technique was tested on a Mars analog soil sample collected from the Atacama Desert in Chile. We found that amino and carboxylic acids can be extracted from the Atacama soil in a 1:1 mixture of isopropanol and water after ultrasonic treatment for 30 min. The extracted organic compounds were then derivatized in a single-step reaction using N-methyl- N-( tert-butyldimethylsilyl)-trifluoroacetamide (MTBSTFA) as the silylating agent in order to transform these compounds into volatile species that can then be detected by GC-MS. We are currently developing a miniaturized reaction cell suited for spaceflight, where both organic extraction and chemical derivatization processes can take place in a single step.

Buch, A.; Glavin, D. P.; Sternberg, R.; Szopa, C.; Rodier, C.; Navarro-González, R.; Raulin, F.; Cabane, M.; Mahaffy, P. R.

2006-12-01

362

pH effect on molecular size exclusion of polyacrylonitrile ultrafiltration membranes having carboxylic acid groups  

Microsoft Academic Search

Polyacrylonitrile copolymer membranes with filtration performance controlled by pH were prepared by phase inversion technique. The pH sensitive molecular sieve effect on transport of macromolecular solute was compared in both copolymer membranes having acrylic acid (AA) and methacrylic acid (MA) segments. The water permeation rate through the membranes was remarkably decreased by the surrounding pH change from acid to alkali

Mangala S. Oak; Takaomi Kobayashi; Hong Ying Wang; Takahiro Fukaya; Nobuyuki Fujii

1997-01-01

363

Simple and Efficient Procedure for the Friedel–Crafts Acylation of Aromatic Compounds with Carboxylic Acids in the Presence of P2O5\\/AL2O3 Under Heterogeneous Conditions  

Microsoft Academic Search

An efficient and chemoselective method for the Friedel–Crafts acylation of aromatic compounds using P2O5\\/Al2O3 and carboxylic acids. Both aromatic and aliphatic carboxylic acids reacted easily to afford the corresponding aromatic ketones in good yields.

Abdol R. Hajipour; Amin Zarei; Leila Khazdooz; Arnold E. Ruoho

2009-01-01

364

Solvent-free Friedel–Crafts acylation of aromatic compounds with carboxylic acids in the presence of trifluoroacetic anhydride and aluminum dodecatungstophosphate  

Microsoft Academic Search

The stable and non-hygroscopic aluminum dodecatungstophosphate (AlPW12O40), was found to be an effective catalyst (3 mol%) for the solvent-free Friedel–Crafts acylation of aromatic compounds with carboxylic acids in the presence of trifluoroacetic anhydride under mild reaction conditions.

Habib Firouzabadi; Nasser Iranpoor; Farhad Nowrouzi

2003-01-01

365

Carboxylic acid sorption on synthetic clays in marine water: in vitro experiments and implications for organo-clay behaviour under marine conditions  

E-print Network

molecules connected to clay surfaces by van der Waals interactions. The high stability of the bonds formed materials. Keywords: organic molecules, carboxylic acids, clays, sorption, organic matter, preservation to investigate the role of clay minerals in organic matter preservation, the fixation of pure organic compounds

366

THERMAL DESORPTION MASS SPECTROMETRIC ANALYSIS OF ORGANIC AEROSOL FORMED FROM REACTIONS OF 1-TETRADECENE AND O3 IN THE PRESENCE OF ALCOHOLS AND CARBOXYLIC ACIDS. (R826235)  

EPA Science Inventory

The chemistry of secondary organic aerosol formation from reactions of 1-tetradecene and O3 in dry air in the presence of excess alcohols and carboxylic acids was investigated in an environmental chamber using a thermal desorption particle beam mass spec...

367

Concise synthesis of 2,4-disubstituted thiazoles from ?-azido disulfides and carboxylic acids or anhydrides: asymmetric synthesis of cystothiazole C.  

PubMed

A novel and efficient method for the one-pot synthesis of 2,4-disubstituted thiazoles from carboxylic acids or anhydrides is presented. Based on this new method, the total synthesis of the bis-2,4-disubstituted bis(thiazoles) natural product cystothiazole C is also presented. PMID:25223403

Liu, Yi; Sun, Xue; Zhang, Xing; Liu, Jun; Du, Yuguo

2014-10-01

368

Synthesis of 1-(Substituted Phenylcarbonyl/sulfonylamino)-1,2,3,6-tetrahydropyridine-5-carboxylic acid diethylamides as Potential Anti-inflammatory Agents  

PubMed Central

Fifteen novel 1-(substituted phenylcarbonyl/sulfonylamino)-1,2,3,6-tetrahydro- pyridine-5-carboxylic acid diethylamide (7, 15) were synthesized in fair to good yields via sodium borohydride reduction of the corresponding 1-(substituted phenylcarbonyl/ sulfonylimino)-3-diethylcarbamoyl pyridinium ylides (6, 14) in absolute ethanol. PMID:20721309

Gangapuram, Madhavi

2010-01-01

369

One pot direct synthesis of amides or oxazolines from carboxylic acids using Deoxo-Fluor reagent  

PubMed Central

A mild and highly efficient one pot–one step condensation and/or condensation–cyclization of various acids to amides and/or oxazolines using Deoxo-Fluor reagents is described. Parallel syntheses of various free fatty acids with 2-amino-2, 2-dimethyl-1-propanol resulted with excellent yields. PMID:16755305

Kangani, Cyrous O.; Kelley, David E.

2006-01-01

370

Long-chain carboxylic acids in pyrolysates of Green River kerogen  

NASA Technical Reports Server (NTRS)

Long-chain fatty acids (C10-C32), as well as C14-C21 isoprenoid acids (except for C18), have been identified in anhydrous and hydrous pyrolyses products of Green River kerogen (200-400 degrees C, 2-1000 hr). These kerogen-released fatty acids are characterized by a strong even/odd predominance (CPI: 4.8-10.2) with a maximum at C16 followed by lesser amounts of C18 and C22 acids. This distribution is different from that of unbound and bound geolipids extracted from Green River shale. The unbound fatty acids show a weak even/odd predominance (CPI: 1.64) with a maximum at C14, and bound fatty acids display an even/odd predominance (CPI: 2.8) with maxima at C18 and C30. These results suggest that fatty acids were incorporated into kerogen during sedimentation and early diagenesis and were protected from microbial and chemical changes over geological periods of time. Total quantities of fatty acids produced during heating of the kerogen ranged from 0.71 to 3.2 mg/g kerogen. Highest concentrations were obtained when kerogen was heated with water for 100 hr at 300 degrees C. Generally, their amounts did not decrease under hydrous conditions with increase in temperature or heating time, suggesting that significant decarboxylation did not occur under the pyrolysis conditions used, although hydrocarbons were extensively generated.

Kawamura, K.; Tannenbaum, E.; Huizinga, B. J.; Kaplan, I. R.

1986-01-01

371

Rapid degradation of Pseudomonas fluorescens 1-aminocyclopropane-1-carboxylic acid deaminase proteins expressed in transgenic Arabidopsis.  

PubMed

1-Aminocyclopropane-1-carboxylate (ACC) deaminase is commonly produced by plant growth-promoting rhizobacteria (PGPR) and has been suggested to facilitate the growth and stress tolerance of hosts via a reduction in levels of ethylene. However, the regulatory mechanism of ACC deaminase (AcdS) protein within host plant cells is largely unknown. Here, we demonstrated beneficial effects and post-translational modification of PGPR-originated AcdS proteins in plants. Compared with the wild-type, transgenic Arabidopsis expressing the Pseudomonas fluorescens acdS (PfacdS) gene displayed increased root elongation and reduced sensitivity to 10 ?M exogenous ACC, an ethylene precursor. Arabidopsis expressing PfacdS also showed increased tolerance to high salinity (150 mM NaCl). PfAcdS proteins accumulated in transgenic Arabidopsis were rapidly degraded, which was potentially mediated by the 26S proteasome pathway. The degradation of PfAcdS was alleviated in the presence of exogenous ACC. In conclusion, our data suggest that the plant growth-promoting effects of bacterial AcdS proteins are potentially modulated via protein turnover inside the host plant cells. Such post-translational modification plays a physiological role in the mutualistic interactions between microorganisms and plants in the rhizospheric and/or endospheric niche. PMID:24801274

Kim, Kangmin; Park, Sung-Hee; Chae, Jong-Chan; Soh, Byoung Yul; Lee, Kui-Jae

2014-06-01

372

Contents of carboxylic acids and two phenolics and antioxidant activity of dried portuguese wild edible mushrooms.  

PubMed

The organic acids and phenolics compositions of nine wild edible mushrooms species (Suillus bellini, Tricholomopsis rutilans, Hygrophorus agathosmus, Amanita rubescens, Russula cyanoxantha, Boletus edulis, Tricholoma equestre, Suillus luteus, and Suillus granulatus) were determined by HPLC-UV and HPLC-DAD, respectively. The antioxidant potential of these species was also assessed by using the DPPH* scavenging assay. The results showed that all of the species presented a profile composed of at least five organic acids: oxalic, citric, malic, quinic, and fumaric acids. In a general way, the pair of malic plus quinic acids were the major compounds. Only very small amounts of two phenolic compounds were found in some of the analyzed species: p-hydroxybenzoic acid (in A. rubescens, R. cyanoxantha, and T. equestre) and quercetin (in S. luteus and S. granulatus). All of the species exhibited a concentration-dependent scavenging ability against DPPH*. T. rutilans revealed the highest antioxidant capacity. PMID:17061830

Ribeiro, Barbara; Rangel, Joana; Valentão, Patrícia; Baptista, Paula; Seabra, Rosa M; Andrade, Paula B

2006-11-01

373

Linear and cyclic aliphatic carboxamides of the Murchison meteorite: Hydrolyzable derivatives of amino acids and other carboxylic acids  

NASA Astrophysics Data System (ADS)

Analyses of fractionated aqueous extracts of the Murchison meteorite by gas chromatographymass spectrometry after silylation with N-methyl-N ( tert-butyldimethylsilyl) trifluoroacetamide have revealed an extensive series of linear and cyclic aliphatic amides. These include monocarboxylic acid amides, dicarboxylic acid monoamides, hydroxy acid amides, lactams, carboxy lactams, lactims, N-acetyl amino acids, and substituted hydantoins. Numerous isomers and homologues through at least C 8 were observed in all cases, except for the N-acetyl amino acids and hydantoins. Carboxy lactams, lactams, hydantoins, and N-acetyl amino acids are converted to amino acids by acid hydrolysis, thus, these compounds qualitatively account for the earlier observation of acid-labile amino acid precursors in meteoritic extracts. Laboratory studies of the spontaneous decomposition of N-carbamyl-?-amino acids and their dehydration products, the 5-substituted hydantoins, have led to the recognition of a series of aqueous phase reactions by which amino acids and cyanic acid/cyanate ion in the primitive parent body might have given rise to several of the observed classes of amides, as well as to monocarboxylic acids, dicarboxylic acids, and hydroxy acids. A previously undescribed reaction of 5-substituted hydantoins with cyanic acid/cyanate ion to give carboxamides of the 5-substituent groups was observed in the course of these studies. The presence of an extensive suite of amides in a CM chondrite appears to be consistent with the interstellar-parent body formation hypothesis for the organic compounds of these meteorites. The presence of carboxy lactams and lactams along with free amino acids suggests the possibility of further chemical evolution of meteorite amino acids by thermal polymerization. The cyclic amides, given their potential for hydrogen-bonded pair formation, might be considered candidate bases for a primitive sequence coding system.

Cooper, G. W.; Cronin, J. R.

1995-03-01

374

Functional Role of Aspartic Acid27 in Dihydrofolate Reductase Revealed by Mutagenesis  

Microsoft Academic Search

The crystal structures and enzymic properties of two mutant dihydrofolate reductases (Escherichia coli) were studied in order to clarify the functional role of an invariant carboxylic acid (aspartic acid at position 27) at the substrate binding site. One mutation, constructed by oligonucleotide-directed mutagenesis, replaces Asp27 with asparagine; the other is a primary-site revertant to Ser27. The only structural perturbations involve

Elizabeth E. Howell; Jesus E. Villafranca; Mark S. Warren; Stuart J. Oatley; Joseph Kraut

1986-01-01

375

Effects of oxidizing adulterants on detection of 11-nor-delta9-THC-9-carboxylic acid in urine.  

PubMed

Bleach, nitrite, chromate, and hydrogen peroxide-peroxidase are effective urine adulterants used by the illicit drug users to conceal marijuana-positive results. Methods for detecting nitrite and chromate are available. Effects of other oxidizing agents that could possibly be used as adulterants and are difficult to detect or measure are presented in this report. Urine samples containing 40 ng/mL of 11-nor-delta9-THC-9-carboxylic acid (THC-acid) were treated with 10 mmol/L of commonly available oxidizing agents. Effects of horseradish peroxidase of activity 10 unit/mL and extracts from 2.5 g of red radish (Raphanus sativus, Radicula group), horseradish (Armoracia rusticana), Japanese radish (Raphanus sativus, Daikon group), and black mustard seeds (Brassica nigra), all with 10 mmol/L of hydrogen peroxide, were also examined. After 5 min, 16 h and 48 h of exposure at room temperature (23 degrees C) the specimens were tested by a gas chromatographic-mass spectrometric method for THC-acid. A control group treated with sodium hydrosulfite to reduce the oxidants, was also tested to investigate the effect of oxidizing agents on THC-acid in the extraction method. THC-acid was lost completely in the extraction method when treated with chromate, nitrite, oxone, and hydrogen peroxide/ferrous ammonium sulfate (Fenton's reagent). Some losses were also observed with persulfate and periodate (up to 25%). These oxidants, and other oxidizing agents like permanganate, periodate, peroxidase, and extracts from red radish, horseradish, Japanese radish and black mustard seeds destroyed most of the THC-acid (> 94%) within 48 h of exposure. Chlorate, perchlorate, iodate, and oxychloride under these conditions showed little or no effect. Complete loss was observed when THC-acid was exposed to 50 mmol/L of oxychloride for 48 h. Several oxidizing adulterants that are difficult to test by the present urine adulterant testing methods showed considerable effects on the destruction of THC-acid. The time and temperature for these effects were similar to those used by most laboratories to collect and test specimens. In several cases, the loss of THC-acid was > 94%. PMID:12423000

Paul, Buddha D; Jacobs, Aaron

2002-10-01

376

Degradation of carboxylic acids on Y 2O 3 surface under UV light. Synergism by semiconductors  

NASA Astrophysics Data System (ADS)

Under UV light formic, oxalic, acetic and citric acids undergo degradation on the surface of Y 2O 3, an insulator. The oxidation of oxalic acid displays first-order kinetics with a linear dependence on light intensity. The photonic efficiency is lower with UV-A light than with UV-C light. While particulate TiO 2, ZnO, CuO, Bi 2O 3 and Nb 2O 5 individually photocatalyze the oxidation, each semiconductor when present along with Y 2O 3 shows synergism, indicating interparticle electron-jump from oxalic acid-adsorbed Y 2O 3 to the band gap-excited semiconductor on collision. The ease of photodegradation of the acids on Y 2O 3 is as follows: formic>oxalic>acetic>citric.

Karunakaran, C.; Dhanalakshmi, R.; Anilkumar, P.

2009-03-01

377

Empirical method for consideration of solvent effect on the dissociation constants of carboxylic acids  

Microsoft Academic Search

An empirical method was used to calculate 363 dissociation constants of 33 benzoic and acetic acid derivatives in 11 solvents.\\u000a The relative error in the calculations did not exceed 9.5%, and the average error was no higher than 3%. The calculated values\\u000a were compared with those obtained by quantum-chemical and other methods for determination of acid dissociation constants in\\u000a different

Yu. E. Zevatskii; D. V. Samoilov

2008-01-01

378

Formation of carboxamides by direct condensation of carboxylic acids and amines in alcohols using a new alcohol- and water-soluble condensing agent: DMT-MM  

Microsoft Academic Search

Selective formation of carboxamides in an alcohol or water by an exceptionally convenient one-step procedure in which a condensing agent is simply added to a mixture of acids and amines has been achieved successfully by using a new condensing agent, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM). Activation of carboxylic acids by DMT-MM in the presence of amines and subsequent aminolysis of the resulting

Munetaka Kunishima; Chiho Kawachi; Kazuhito Hioki; Keiji Terao; Shohei Tani

2001-01-01

379

Promotion of tomato ( Lycopersicon esculentum Mill.) plant growth by rhizosphere competent 1-aminocyclopropane-1-carboxylic acid deaminase-producing streptomycete actinomycetes  

Microsoft Academic Search

The ability of streptomycete actinomycetes to promote growth of tomato through the production of 1-aminocyclopropane-1-carboxylic\\u000a acid (ACC) deaminase was evaluated under gnotobiotic and greenhouse conditions. To achieve this, 64 isolates of Streptomyces spp. obtained from a tomato rhizosphere in the United Arab Emirates were initially selected for their ability to produce\\u000a ACC deaminase as well as indole-3-acetic acid (IAA) and

Khaled A. El-Tarabily

2008-01-01

380

Permeability and toxicity characteristics of L-cysteine and 2-methyl-thiazolidine-4-carboxylic acid in Caco-2 cells.  

PubMed

Acetaldehyde is a known mutagenic substance and has been classified as a group-one carcinogen by the WHO. It is possible to bind acetaldehyde locally in the gastrointestinal (GI) tract with the semi-essential amino acid l-cysteine, which reacts covalently with acetaldehyde and forms compound 2-methyl-thiozolidine-4-carboxylic acid (MTCA). The Caco-2 cell line was used to determine the permeation of l-cysteine and MTCA, as well as the possible cell toxicity of both substances. Neither of the substances permeated through the Caco-2 cells at the concentrations used in this study, and only the highest concentration of MTCA affected the viability of the cells in the MTT (3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide) test. These results showed that when l-cysteine is administered in formulations releasing it locally in the lower parts of GI tract, it is not absorbed but can react with acetaldehyde, and that neither l-cysteine nor MTCA is harmful to the cells when present locally in the upper parts of GI tract. This study also shows that MTCA is sensitive at a lower pH of 5.5. Since stable MTCA is desired in different parts of the GI tract, this observation raises concern over the influence of lower pH on l-cysteine-containing product ability to bind and eliminate carcinogenic acetaldehyde. PMID:22356486

Kartal-Hodzic, Alma; Marvola, Tuuli; Schmitt, Mechthild; Harju, Kirsi; Peltoniemi, Marikki; Sivén, Mia

2013-01-01

381

Mononuclear metal complexes of organic carboxylic acid derivatives: Synthesis, spectroscopic characterization, thermal investigation and antimicrobial activity  

NASA Astrophysics Data System (ADS)

Two Schiff base ligands bearing organic acid moiety, vis., N-(2-thienylmethylidene)-2-amino-4-chlorobenzoic acid (HL 1) and N-(2-hydroxybenzylidene)-2-amino-4-chlorobenzoic acid (H 2L 2) have been synthesized by the interaction of 2-thiophenecarboxaldehyde and 2-hydroxybenzaldehyde with 2-amino-4-chlorobenzoic acid. Co(II), Ni(II), Cu(II) and Zn(II) complexes of these ligands have been prepared. They are characterized on the basis of analytical data, molar conductance, IR, 1H NMR, UV-vis, mass spectra, magnetic measurements, thermal analysis and X-ray powder diffraction technique. The molar conductance data reveal that these complexes are non-electrolytes. The ligands are coordinated to the metal ions in a terdentate manner with ONO/ONS donor sites of the carbonyl oxygen, azomethine nitrogen and phenolic oxygen or thiophenic sulphur. An octahedral structure is proposed for the prepared metal complexes and some ligand field parameters ( Dq, B and ?) in addition to CFSE were calculated. The thermal stability of the metal complexes is evaluated. The Schiff base ligands and their metal complexes have been tested against four species of bacteria as well as four species of fungi and the results have been compared with some known antibiotics.

Abd El-Wahab, Zeinab H.

2007-05-01

382

Highly effective copper-catalyzed decarboxylative coupling of aryl halides with alkynyl carboxylic acids.  

PubMed

We have developed a highly effective copper-catalyzed decarboxylative coupling of alkynylcarboxylic acids with various aryl and alkyl halides at 2 mol% loading of copper. This method is simple, economical and practical for the synthesis of disubstituted alkyne compounds. PMID:21904730

Qu, Xiaoming; Li, Tingyi; Sun, Peng; Zhu, Yan; Yang, Hailong; Mao, Jincheng

2011-10-21

383

[Investigation of protonation and complex formation processes of some new polyamino carboxylic acids].  

PubMed

The medicinal chemistry often needs chemical compound with special properties. The preparation of compounds with special properties generally needs 10-20 steps of preparation and the final product is available in small amount. The characterisation of this kinds of compounds needs special methods and procedures for investigation. This kind of method has been developed and used for characterisation of some new polyaminopolycarboxylic acid derivatives. Protolytic equilibrium of 2,2',2",2'"-[terpyridine-6,6"diyl)bis(methylenenitrilo)]tetrakisacetic acid and 3,5-bis[6'-bis (N,N-bis(carboxymethyl)aminomethyl]-2'-pyridyl)-1H,2, 4-triazole was investigated by pH-metric and spectrophotometric methods. The pK values of the aromatic nitrogen atoms were estimated. Complexation of Eu(III)ion with both ligands are studied by spectrophotometric method. Composition(ML2) and stability of complexes were determined. PMID:11379022

Hargitai, J; Labádi, I; Harri, L

2000-01-01

384

Actions of a proline analogue, L-thiazolidine-4-carboxylic acid (T4C), on Trypanosoma cruzi.  

PubMed

It is well established that L-proline has several roles in the biology of trypanosomatids. In Trypanosoma cruzi, the etiological agent of Chagas' disease, this amino acid is involved in energy metabolism, differentiation processes and resistance to osmotic stress. In this study, we analyzed the effects of interfering with L-proline metabolism on the viability and on other aspects of the T. cruzi life cycle using the proline analogue L- thiazolidine-4-carboxylic acid (T4C). The growth of epimastigotes was evaluated using different concentrations of T4C in standard culture conditions and at high temperature or acidic pH. We also evaluated possible interactions of this analogue with stress conditions such as those produced by nutrient starvation and oxidative stress. T4C showed a dose-response effect on epimastigote growth (IC(50) = 0.89+/-0.02 mM at 28 degrees C), and the inhibitory effect of this analogue was synergistic (p<0.05) with temperature (0.54+/-0.01 mM at 37 degrees C). T4C significantly diminished parasite survival (p<0.05) in combination with nutrient starvation and oxidative stress conditions. Pre-incubation of the parasites with L-proline resulted in a protective effect against oxidative stress, but this was not seen in the presence of the drug. Finally, the trypomastigote bursting from infected mammalian cells was evaluated and found to be inhibited by up to 56% when cells were treated with non-toxic concentrations of T4C (between 1 and 10 mM). All these data together suggest that T4C could be an interesting therapeutic drug if combined with others that affect, for example, oxidative stress. The data also support the participation of proline metabolism in the resistance to oxidative stress. PMID:19229347

Magdaleno, Anahí; Ahn, Il-Young; Paes, Lisvane Silva; Silber, Ariel M

2009-01-01

385

Actions of a Proline Analogue, L-Thiazolidine-4-Carboxylic Acid (T4C), on Trypanosoma cruzi  

PubMed Central

It is well established that L-proline has several roles in the biology of trypanosomatids. In Trypanosoma cruzi, the etiological agent of Chagas' disease, this amino acid is involved in energy metabolism, differentiation processes and resistance to osmotic stress. In this study, we analyzed the effects of interfering with L-proline metabolism on the viability and on other aspects of the T. cruzi life cycle using the proline analogue L- thiazolidine-4-carboxylic acid (T4C). The growth of epimastigotes was evaluated using different concentrations of T4C in standard culture conditions and at high temperature or acidic pH. We also evaluated possible interactions of this analogue with stress conditions such as those produced by nutrient starvation and oxidative stress. T4C showed a dose-response effect on epimastigote growth (IC50?=?0.89±0.02 mM at 28°C), and the inhibitory effect of this analogue was synergistic (p<0.05) with temperature (0.54±0.01 mM at 37°C). T4C significantly diminished parasite survival (p<0.05) in combination with nutrient starvation and oxidative stress conditions. Pre-incubation of the parasites with L-proline resulted in a protective effect against oxidative stress, but this was not seen in the presence of the drug. Finally, the trypomastigote bursting from infected mammalian cells was evaluated and found to be inhibited by up to 56% when cells were treated with non-toxic concentrations of T4C (between 1 and 10 mM). All these data together suggest that T4C could be an interesting therapeutic drug if combined with others that affect, for example, oxidative stress. The data also support the participation of proline metabolism in the resistance to oxidative stress. PMID:19229347

Magdaleno, Anahi; Ahn, Il-Young; Paes, Lisvane Silva; Silber, Ariel M.

2009-01-01

386

Organocatalytic Michael addition-lactonisation of carboxylic acids using ?,?-unsaturated trichloromethyl ketones as ?,?-unsaturated ester equivalents.  

PubMed

Isothiourea HBTM-2.1 catalyses the Michael addition-lactonisation of 2-aryl and 2-alkenylacetic acids and ?,?-unsaturated trichloromethyl ketones. Ring-opening of the resulting dihydropyranones and subsequent alcoholysis of the CCl3 ketone with an excess of methanol gives a range of diesters in high diastereo- and enantioselectivity (up to 95?:?5 dr and >99% ee). Sequential addition of two different nucleophiles to a dihydropyranone gives the corresponding differentially substituted diacid derivative. PMID:25285662

Morrill, Louis C; Stark, Daniel G; Taylor, James E; Smith, Siobhan R; Squires, James A; D'Hollander, Agathe C A; Simal, Carmen; Shapland, Peter; O'Riordan, Timothy J C; Smith, Andrew D

2014-10-21

387

Potamogeton pectinatus is constitutively incapable of synthesizing ethylene and lacks 1-aminocyclopropane-1-carboxylic acid oxidase  

Microsoft Academic Search

A highly sensitive laser-driven photoacoustic detector respon- sive to 52.1 nmol m-3 ethylene (50 parts per trillion (v\\/v)) was used for ethylene analysis. Dark-grown plants of Potamogeton pectinatus 1. growing from small tubers made no ethylene. Ex- posure of shoots to white light, wounding, submergence in water followed by desubmergence, partia1 oxygen shortage, indole ace- tic acid, or carbon dioxide

J. E. Summers; L. A. C. J. Voesenek; C. W. P. M. Blom; M. J. Lewis; M. B. Jackson

1996-01-01

388

Conformation of the umifenovir cation in the molecular and crystal structures of four carboxylic acid salts  

NASA Astrophysics Data System (ADS)

The umifenovir salts of maleic, salicylic, glutaric, and gentisic acid as well as the chloroform solvate of the salicylate were prepared. Single crystals of the five compounds were obtained and their molecular and crystal structures determined by X-ray diffraction. In each structure the conformation of phenyl ring with respect to the indole group of the umifenovir moiety is different. The water solubility and melting points of the studied umifenovir salts have been determined.

Orola, Liana; Sarcevica, Inese; Kons, Artis; Actins, Andris; Veidis, Mikelis V.

2014-01-01

389

Variable-temperature powder X-ray diffraction of aromatic carboxylic acid and carboxamide cocrystals.  

PubMed

The effect of temperature on the cocrystallization of benzoic acid (BA), pentafluorobenzoic acid (FBA), benzamide (BAm), and pentafluorobenzamide (FBAm) is examined in the solid state. BA and FBA formed a 1:1 complex 1 at ambient temperature by grinding with a mortar and pestle. Grinding FBA and BAm together resulted in partial conversion into the 1:1 adduct 2 at 28 degrees C and complete transformation into the product cocrystal at 78 degrees C. Further heating (80-100 degrees C) and then cooling to room temperature gave a different powder pattern from that of 2. BAm and FBAm hardly reacted at ambient temperature, but they afforded the 1:1 cocrystal 3 by melt cocrystallization at 110-115 degrees C. Both BA+FBAm (4) and BA+BAm (5) reacted to give new crystalline phases upon heating, but the structures of these products could not be determined owing to a lack of diffraction-quality single crystals. The stronger COOH and CONH2 hydrogen-bonding groups of FBA and FBAm yielded the equimolar cocrystal 6 at room temperature, and heating of these solids to 90-100 degrees C gave a new crystalline phase. The X-ray crystal structures of 1, 2, 3, and 6 are sustained by the acid-acid/amide-amide homosynthons or acid-amide heterosynthon, with additional stabilization from phenyl-perfluorophenyl stacking in 1 and 3. The temperature required for complete transformation into the cocrystal was monitored by in situ variable-temperature powder X-ray diffraction (VT-PXRD), and formation of the cocrystal was confirmed by matching the experimental peak profile with the simulated diffraction pattern. The reactivity of H-bonding groups and the temperature for cocrystallization are in good agreement with the donor and acceptor strengths of the COOH and CONH2 groups. It was necessary to determine the exact temperature range for quantitative cocrystallization in each case because excessive heating caused undesirable phase transitions. PMID:17441188

Reddy, L Sreenivas; Bhatt, Prashant M; Banerjee, Rahul; Nangia, Ashwini; Kruger, Gert J

2007-04-01

390

Different geometrical arrangements in carboxylate coordination polymers of flexible dicarboxylic acid  

SciTech Connect

Dicarboxylate coordination polymers (1-5) of Mn(II), Ni(II), Cu(II), Zn(II) and Cd(II), respectively, derived from (7-carboxymethoxy-naphthalen-2-yloxy)-acetic acid (L{sub 1}H{sub 2}) are synthesized and characterized. Depending on the coordination sites around the metal centers and coordination mode of the ligand, dimensionality of these polymers varies. The dicarboxylates adopt three spatial orientations: in-plane linear coordination, out-of-plane cis coordination and out-of-plane trans coordination mode. Both the cis and trans out-of-plane coordination modes are found to exist only if the ancillary ligand pyridine is coordinated to the metal ion. When the aquoligand coordinates the in-plane linear coordination mode of L{sub 1} predominates. The coordination polymers 4 and 5 show photoluminescence in solution. The dicarboxylate of (5-carboxymethoxy-naphthalen-1-yloxy)-acetic acid (L{sub 2}H{sub 2}) does not form coordination polymer under ambient conditions, but prefers to remain as uncoordinated anion providing hydrophobic confinement to hexa-aquometal(II) cation. Compound 3 crystallizes in P2{sub 1} space group and it shows broadband ultra-violet fluorescence centered at 352.9 nm on focusing 632.8 nm He:Ne laser. - Graphical abstract: Different geometrical arrangements in coordination polymers derived from (7-carboxymethoxy-naphthalen-2-yloxy)-acetic acid of metal ions Mn(II), Ni(II), Cu(II), Zn(II) and Cd(II) are presented. The (5-carboxymethoxy-naphthalen-1-yloxy)-acetic acid led to hexa-aquo cadmium(II) dicarboxylate. Highlights: > Structural and spectroscopic characterizations of five dicarboxylate coordination polymers of (7-carboxymethoxy-naphthalen-2-yloxy)-acetic acid with different metal ions are presented. > Different geometrical arrangements of coordination polymers stabilized in solid state are described. > Photoluminescence properties of the polymers are shown. > NLO property of a copper coordination polymer is described.

Deka, Himangshu; Sarma, Rupam [Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781 039, Assam (India); Kumari, Satchi; Khare, Alika [Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781 039, Assam (India); Baruah, Jubaraj B., E-mail: juba@iitg.ernet.in [Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781 039, Assam (India)

2011-07-15

391

Analysis of 11-nor-?9 -tetrahydrocannabinol-9-carboxylic acid and its glucuronide in urine by capillary electrophoresis/mass spectrometry.  

PubMed

?(9) -Tetrahydrocannabinol is the primary psychoactive component in cannabis, one of the most commonly used illicit drugs in the world. This paper describes a simple and rapid method for direct analysis of major metabolites of ?(9) -tetrahydrocannabinol; 11-nor-?(9) -tetrahydrocannabinol-9-carboxylic acid and its glucuronide in urine by capillary electrophoresis/mass spectrometry. The only pretreatment needed for a urine sample was dilution with methanol containing an internal standard and centrifugation. Electrophoresis was carried out in an untreated fused-silica capillary (50 µm i.d. × 85 cm) filled with 40 m m ammonium formate (pH 6.4). An analysis could be completed within 10 min. For both compounds, the assay was linear over the range 0.1-10 µg/mL in urine with correlation coefficients (r(2) )?>0.99 and the limit of detection was 0.5 pg (10 nL injection). The detection yields and reproducibilities were determined at three different concentrations (0.1, 0.5 and 2 µg/mL in urine). The mean detection yields were 60-99%. The intra- and inter-day relative standard deviations of migration times were 0.063-0.19 and 0.18-0.36%, and those of peak areas were 4.2-18 and 5.9-25%, respectively. The proposed method successfully analyzed the urine samples of cannabis users. PMID:22419476

Iwamuro, Yoshiaki; Iio-Ishimaru, Reiko; Chinaka, Satoshi; Takayama, Nariaki; Hayakawa, Kazuichi

2012-11-01

392

Establishment of the measurement uncertainty of 11-nor-D9-tetrahydrocannabinol-9-carboxylic acid in hair.  

PubMed

The quantitative analysis of 11-nor-D(9)-tetrahydrocannabinol-9-carboxylic acid (THCCOOH) in hair requires a sensitive method to detect a low-pg level. Before applying the method to real hair samples, the method was validated; in this study, we examined the uncertainty obtained from around the cut-off level of THCCOOH in hair. We calculated the measurement uncertainty (MU) of THCCOOH in hair as follows: specification of the measurand, identification of parameters using "cause and effect" diagrams, quantification of the uncertainty contributions using three factors, the uncertainty of weighing the hair sample, the uncertainty from calibrators and the calibration curve, and the uncertainty of the method precision. Finally, we calculated the degrees of freedom and the expanded uncertainty (EU). The concentration of THCCOOH in the hair sample with its EU was (0.60 ± 0.1) × 10(-4)ng/mg. The relative uncertainty percent for the measurand 0.60 × 10(-4)ng was 9.13%. In this study, we also selected different concentrations of THCCOOH in real hair samples and then calculated the EU, the relative standard uncertainty (RSU) of the concentration of THCCOOH in the test sample [u(r)(c0)], the relative uncertainty percent, and the effective degree of freedom (v(eff)). When the concentrations of THCCOOH approached the cut-off level, u(r)(c0) and the relative uncertainty percent increased but absolute EU and v(eff) decreased. PMID:21194857

Han, Eunyoung; Yang, Wonkyung; Lee, Sooyeun; Kim, Eunmi; In, Sangwhan; Choi, Hwakyung; Lee, Sangki; Chung, Heesun; Song, Joon Myong

2011-03-20

393

Dependence of in vivo ethylene production rate on 1-aminocyclopropane-1-carboxylic Acid content and oxygen concentrations.  

PubMed

1-Aminocyclopropane-1-carboxylic acid (ACC) is aerobically oxidized in plant tissues to form ethylene by ethylene-forming enzyme (EFE). The effect of substrate (ACC and oxygen) concentrations on ethylene production rate by plant tissues was investigated. The K(m) value for O(2) in ethylene production varied greatly depending on the internal ACC content. When ACC levels in the tissue were low (below its K(m) value), the concentration of O(2) giving half-maximal ethylene production rate ([S](0.5)) ranged between 5 and 7%, and was similar among different tissues. As the concentration of ACC was increased (greater than its K(m) value), [S](0.5) for O(2) decreased markedly. In contrast, the K(m) value for ACC was not much dependent on O(2) concentration, but varied greatly among different plant tissues, ranging from 8 micromolar in apple (Malus sylvestris Mill.) tissue to 120 micromolar in etiolated wheat (Triticum aestivum) leaf. Such a great variation was thought to be due to the different compartmentation of ACC within the cells in different tissues. These kinetic data are consistent with the view that EFE follows an ordered binding mechanism in which EFE binds first to O(2) and then to ACC. PMID:16666347

Yip, W K; Jiao, X Z; Yang, S F

1988-11-01

394

The Cytotoxicity of Benzaldehyde Nitrogen Mustard-2-Pyridine Carboxylic Acid Hydrazone Being Involved in Topoisomerase II? Inhibition  

PubMed Central

The antitumor property of iron chelators and aromatic nitrogen mustard derivatives has been well documented. Combination of the two pharmacophores in one molecule in drug designation is worth to be explored. We reported previously the syntheses and preliminary cytotoxicity evaluation of benzaldehyde nitrogen mustard pyridine carboxyl acid hydrazones (BNMPH) as extended study, more tumor cell lines (IC50 for HepG2: 26.1 ± 3.5??M , HCT-116: 57.5 ± 5.3??M, K562: 48.2 ± 4.0??M, and PC-12: 19.4 ± 2.2??M) were used to investigate its cytotoxicity and potential mechanism. In vitro experimental data showed that the BNMPH chelating Fe2+ caused a large number of ROS formations which led to DNA cleavage, and this was further supported by comet assay, implying that ROS might be involved in the cytotoxicity of BNMPH. The ROS induced changes of apoptosis related genes, but the TFR1 and NDRG1 metastatic genes were not obviously regulated, prompting that BNMPH might not be able to deprive Fe2+ of ribonucleotide reductase. The BNMPH induced S phase arrest was different from that of iron chelators (G1) and alkylating agents (G2). BNMPH also exhibited its inhibition of human topoisomerase II?. Those revealed that the cytotoxic mechanism of the BNMPH could stem from both the topoisomerase II inhibition, ROS generation and DNA alkylation. PMID:24995306

Fu, Yun; Zhou, Sufeng; Liu, Youxun; Yang, Yingli; Sun, Xingzhi; Li, Changzheng

2014-01-01

395

Saponin Biosynthesis in Saponaria vaccaria. cDNAs Encoding ?-Amyrin Synthase and a Triterpene Carboxylic Acid Glucosyltransferase1[OA  

PubMed Central

Saponaria vaccaria (Caryophyllaceae), a soapwort, known in western Canada as cowcockle, contains bioactive oleanane-type saponins similar to those found in soapbark tree (Quillaja saponaria; Rosaceae). To improve our understanding of the biosynthesis of these saponins, a combined polymerase chain reaction and expressed sequence tag approach was taken to identify the genes involved. A cDNA encoding a ?-amyrin synthase (SvBS) was isolated by reverse transcription-polymerase chain reaction and characterized by expression in yeast (Saccharomyces cerevisiae). The SvBS gene is predominantly expressed in leaves. A S. vaccaria developing seed expressed sequence tag collection was developed and used for the isolation of a full-length cDNA bearing sequence similarity to ester-forming glycosyltransferases. The gene product of the cDNA, classified as UGT74M1, was expressed in Escherichia coli, purified, and identified as a triterpene carboxylic acid glucosyltransferase. UGT74M1 is expressed in roots and leaves and appears to be involved in monodesmoside biosynthesis in S. vaccaria. PMID:17172290

Meesapyodsuk, Dauenpen; Balsevich, John; Reed, Darwin W.; Covello, Patrick S.

2007-01-01

396

Synthesis of acid-functionalized composite via surface deposition of acid-containing amorphous carbon  

NASA Astrophysics Data System (ADS)

A synthetic procedure, including two steps: a hydrothermal treatment using H2SO4 solution and a thermal treatment with concentrated H2SO4 in Teflon-lined stainless autoclaves was developed to synthesize acid-functionalized composite. In this process, the carbonization of glucose which contributed to the formation of carbon species with acid functional groups occurred on the silica surface. The resultant composite, investigated by powder XRD, low temperature N2 sorption and TEM, possessed well-defined mesostructure. And it was determined by XPS that amorphous carbon was deposited at the silica surface of SBA-15. The presence of multi-functional groups in the composite was confirmed by FT-IR results. Furthermore, carboxylic and sulfonic groups could be incorporated into the composite material via the covalent bond. The composite was employed as the catalyst for the acetalization of carbonyl compounds. It was suggested that acid sites were well dispersed, which was responsible for the good performance in the catalytic test. According to these facts, a synthesis route for mesostructured composite with acid functional groups has been proposed.

Du, Bin; Zhang, Xuan; Lou, Lan-Lan; Dong, Yanling; Liu, Gaixia; Liu, Shuangxi

2012-07-01

397

Polar organic marker compounds in atmospheric aerosol in the Po Valley during the Supersito campaigns - Part 1: Low molecular weight carboxylic acids in cold seasons  

NASA Astrophysics Data System (ADS)

In the framework of the “Supersito” project, three intensive experimental campaigns were conducted in the Po Valley (Northern Italy) in cold seasons, such as late autumn, pre-winter and deep-winter, over three years from 2011 to 2013. As a part of a study on polar marker compounds, including carboxylic acids, sugar derivatives and lignin phenols, the present study reports a detailed discussion on the atmospheric concentrations of 14 low molecular weight carboxylic acids, mainly dicarboxylic and oxo-hydroxy carboxylic acids, as relevant markers of primary and secondary organic aerosols. PM2.5 samples were collected in two monitoring sites, representing urban and rural background stations. The total quantities of carboxylic acids were 262, 167 and 249 ng m-3 at the urban site and 308, 115, 248 ng m-3 at the rural site in pre-winter, fall and deep-winter, respectively. These high concentrations can be explained by the large human emission sources in the urbanized region, combined with the stagnant atmospheric conditions during the cold seasons that accumulate the organic precursors and accelerate the secondary atmospheric reactions. The distribution profiles of the investigated markers suggest the dominant contributions of primary anthropogenic sources, such as traffic, domestic heating and biomass burning. These results are confirmed by comparison with additional emission tracers, such as anhydro-saccharides for biomass burning and fatty acids originated from different anthropogenic sources. In addition, some secondary constituents were detected in both sites, as produced by in situ photo-chemical reactions from both biogenic (e.g. pinonic acid) and anthropogenic precursors (e.g. phthalic and adipic acids). The impact of different sources from human activities was elucidated by investigating the week pattern of carboxylic and fatty acid concentrations. The weekly trends of analytes during the warmer campaign (fall 2012; mean temperature: 12 °C) may be related to emissions from motor vehicle traffic and industrial activities. Otherwise, the random pattern of the markers suggests the prevalent contribution of primary emissions from residential heating in the colder deep-winter (mean temperature: 5 °C).

Pietrogrande, Maria Chiara; Bacco, Dimitri; Visentin, Marco; Ferrari, Silvia; Poluzzi, Vanes

2014-04-01

398

(CF3CO)2O/CF3SO3H-mediated synthesis of 1,3-diketones from carboxylic acids and aromatic ketones  

PubMed Central

Summary A very simple and convenient reaction for 1,3-diketone preparation from carboxylic acids and aromatic ketones in TFAA/TfOH system is described. When the ?-phenylpropionic acids were used as starting materials, they initially gave 1-indanones and then underwent further acylation with the formation of 2-(?-phenylpropionyl)-1-indanones as the main reaction products. In addition, the application of the proposed protocol allowed for the synthesis of selected polysubstituted pyrazoles in a one-pot procedure directly from acids and ketones. PMID:25298794

Kim, JungKeun; Shokova, Elvira; Tafeenko, Victor

2014-01-01

399

A simple colorimetric chemosensor bearing a carboxylic acid group with high selectivity for CN-  

NASA Astrophysics Data System (ADS)

A new simple ‘naked eye' chemosensor 1 (sodium (E)-2-((2-(3-hydroxy-2-naphthoyl)hydrazono)methyl)benzoate) has been synthesized for detection of CN- in a mixture of DMF/H2O (9:1). The sensor 1 comprises of a naphthoic hydrazide as efficient hydrogen bonding donor group and a benzoic acid as the moiety with the water solubility. The receptor 1 showed high selectivity toward cyanide ions in a 1:1 stoichiometric manner, which induces a fast color change from colorless to yellow for CN- over other anions. Therefore, receptor 1 could be useful for cyanide detection in aqueous environment, displaying a high distinguishable selectivity from hydrogen bonded anions and being clearly visible to the naked eye.

Park, Gyeong Jin; Choi, Ye Won; Lee, Dongkuk; Kim, Cheal

2014-11-01

400

Atmospheric oxidation of polyfluorinated amides: historical source of perfluorinated carboxylic acids to the environment.  

PubMed

Polyfluorinated amides (PFAMs) are a class of fluorinated compounds which were produced as unintentional byproducts in the electrochemical fluorination process used for polyfluorinated sulfonamide synthesis in 1947-2002. To investigate the historical potential of PFAMs as an atmospheric perfluorinated acid (PFCA) source we studied N-ethylperfluorobutyramide (EtFBA) as a surrogate for longer chained PFAMs. Smog chamber relative rate techniques were used to measure bimolecular rate coefficients for reactions of EtFBA with chlorine atoms and hydroxyl radicals. It was found kCl = (2.08 ± 0.15) × 10(-11) cm(3) molecule(-1) s(-1) and kOH = (2.65 ± 0.50) × 10(-12) cm(3) molecule(-1) s(-1) and the atmospheric lifetime of EtFBA with respect to reaction with OH was estimated to be approximately 4.4 days. Offline sampling with both GC-MS and LC-MS/MS techniques was used to determine the products and hence a plausible pathway of atmospheric oxidation of EtFBA. Three primary oxidation products were observed by GC-MS, the N-dealkylation product C3F7C(O)NH2 and two carbonyl products, probably C3F7C(O)N(H)C(O)CH3 and C3F7C(O)N(H)CH2CHO. These primary products react further to give perfluorocarboxylic acids (PFCAs) as detected by LC-MS/MS, suggesting that eight carbon PFAMs were a historical source of PFCAs to remote regions, including the Canadian Arctic. PMID:23586598

Jackson, Derek A; Wallington, Timothy J; Mabury, Scott A

2013-05-01

401

Structure of the PLP Degradative Enzyme 2-Methyl-3-hydroxypyridine-5-carboxylic acid Oxygenase from Mesorhizobium loti MAFF303099 and its Mechanistic Implications†‡  

PubMed Central

A vitamin B6 degradative pathway has recently been identified and characterized in Mesorhizobium loti MAFF303099. One of the enzymes on this pathway, 2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase (MHPCO), is a flavin-dependent enzyme and catalyzes the oxidative ring opening of 2-methyl-3-hydroxypyridine-5-carboxylic acid to form E-2-acetaminomethylene succinate. The gene for this enzyme has been cloned and the corresponding protein has been overexpressed in Escherichia coli and purified. The crystal structure of MHPCO has been solved to 2.1 Å using SAD phasing with and without the substrate MHPC bound. These crystal structures provide insight into the reaction mechanism and suggest roles for active site residues in the catalysis of a novel oxidative ring-opening reaction. PMID:19317437

McCulloch, Kathryn M.; Mukherjee, Tathagata; Begley, Tadhg P.; Ealick, Steven E.

2009-01-01

402

Light- and temperature-entrained circadian regulation of activity and mRNA accumulation of 1-aminocyclopropane-1-carboxylic acid oxidase in Stellaria longipes.  

PubMed

Stem and leaf tissues of Stellaria longipes Goldie (prairie ecotype) exhibit circadian rhythmicity in the activity and mRNA abundance for 1-aminocyclopropane-1-carboxylic acid oxidase (EC 1.4.3). The steady-state mRNA levels and enzymatic activity levels fluctuated with a period of approximately 24 h and reached their maxima by the middle of the light phase and minima by the middle of the dark phase. The oscillations showed damping under constant light, constant dark and constant temperature conditions, indicating that the rhythm is entrained by an external signal. The results indicate that light/dark cycles have greater entraining effects than temperature cycles. A 15-min red light pulse, but not a blue light pulse, could reset rhythm in continuous darkness, suggesting the possible role of a red-light signal transduction pathway in the circadian regulation of 1-aminocyclopropane-1-carboxylic acid oxidase. PMID:8771799

Kathiresan, A; Reid, D M; Chinnappa, C C

1996-01-01

403

Regio- and stereoselective synthesis of ferrocene-containing ?-iodoallylic esters and ethers from the iodofunctionalization of ferrocenylallene with carboxylic acids, phenols, and alcohols.  

PubMed

The iodofunctionalization of ferrocenylallene with carboxylic acids, phenols, and alcohols is described. The reaction proceeds smoothly in the presence of molecule iodine as a halonium promoter and using various carboxylic acids, phenols, and alcohols as nucleophiles to give the corresponding ferrocene-containing ?-iodoallylic ester and ether products in moderate to high yields and with high regio- and stereoselectivities. It can be envisaged that the regio- and stereoselectivity of this reaction may be controlled by the steric effect of the bulky ferrocene group. The presence of the C-I bond in the corresponding products makes these molecules highly attractive from a synthetic point of view, as it provides an opportunity for further transformations. Thus, palladium-catalyzed Heck coupling, Suzuki coupling, Sonogashira coupling, and copper-catalyzed click reactions were carried out successfully. PMID:24855998

Chen, Shufeng; Zhang, Hongli; Yan, Qing; Wang, Chenjun; Han, Fei; Zhang, Kaixin; Zhao, Haiying; Li, Baoguo

2014-06-20

404

Structure of the PLP Degradative Enzyme 2-Methyl-3-hydroxypyridine-5-carboxylic Acid Oxygenase from Mesorhizobium loti MAFF303099 and Its Mechanistic Implications  

SciTech Connect

A vitamin B{sub 6} degradative pathway has recently been identified and characterized in Mesorhizobium loti MAFF303099. One of the enzymes on this pathway, 2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase (MHPCO), is a flavin-dependent enzyme and catalyzes the oxidative ring-opening of 2-methyl-3-hydroxypyridine-5-carboxylic acid to form E-2-(acetamino-methylene)succinate. The gene for this enzyme has been cloned, and the corresponding protein has been overexpressed in Escherichia coli and purified. The crystal structure of MHPCO has been solved to 2.1 {angstrom} using SAD phasing with and without the substrate MHPC bound. These crystal structures provide insight into the reaction mechanism and suggest roles for active site residues in the catalysis of a novel oxidative ring-opening reaction.

McCulloch, Kathryn M.; Mukherjee, Tathagata; Begley, Tadhg P.; Ealick, Steven E.; Cornell

2009-06-12

405

Electronic structure, novel synthesis, and O-H...O and C-H...O interactions in two 6-oxopiperidine-2-carboxylic acid derivatives.  

PubMed

Molecules of (S)-6-oxo-1-(thiophen-2-ylmethyl)piperidine-2-carboxylic acid, C11H13NO3S, crystallize as single enantiomers in the space group P21 and the thiophene ring is disordered over two positions, while (S)-6-oxo-1-(thiophen-3-ylmethyl)piperidine-2-carboxylic acid, C11H13NO3S, crystallizes as a single enantiomer in the space group P212121. Their absolute configurations were confirmed by anomalous dispersion effects in diffraction measurements on the crystals. The molecules of each compound are linked by a combination of strong O-H...O hydrogen bonds and weak C-H...O interactions, resulting in two- and three-dimensional networks, respectively, in the crystal structures. PMID:25093366

Vrábel, Viktor; Sivý, Július; Šafá?, Peter; Marchalín, Štefan

2014-08-15

406

Hybrid nanoparticles for drug delivery and bioimaging: mesoporous silica nanoparticles functionalized with carboxyl groups and a near-infrared fluorescent dye.  

PubMed

The development of a drug delivery system with fluorescent biolabels is important in anti-cancer drug delivery application due to the potential for simultaneous diagnosis and treatment of diseases. Here, we reported the synthesis and multiple functionalization of mesoporous silica nanoparticle (MSN) for bioimaging and controlled drug release. After the functionalization with carboxyl group, the nanoparticles exhibited much better dispersity and stability in aqueous solution than MSN. Furthermore, a substantial doxorubicin (DOX) loading level was achieved and DOX-loaded nanoparticles exhibited noticeable pH-sensitive behavior with accelerated release of DOX in acidic environment. Compared with native DOX-MSN, DOX-MSN/COOH-Cy5 exhibited enhanced intracellular uptake efficacy and stronger effect on killing tumor cells. Meanwhile, it was observed that the MSN/COOH-Cy5 was able to locate in the cytoplasm of MCF-7 cells and could accumulate in tumor tissues for a long period of time. Overall, the functional nanoparticle could potentially be used for simultaneous controlled drug release and near-infrared fluorescent bioimaging. PMID:23394807

Xie, Meng; Shi, Hui; Ma, Kun; Shen, Haijun; Li, Bo; Shen, Song; Wang, Xinshi; Jin, Yi

2013-04-01

407

Single wall carbon nanotube/bis carboxylic acid-ICG as a sensitive contrast agent for in vivo tumor imaging in photoacoustic tomography  

NASA Astrophysics Data System (ADS)

In this study, we present a novel photoacoustic contrast agent which is based on bis-carboxylic acid derivative of Indocyanine green (ICG) covalently conjugated to single-wall carbon nanotubes (ICG/SWCNT). Covalently attaching ICG to the functionalized SWCNT provides a more robust system that delivers much more ICG to the tumor site. The detection sensitivity of the new contrast agent in mouse tumor model is demonstrated in vivo by our custom built photoacoustic imaging system. PAT summation signal is defined to show the long-term light absorption of tumor areas in ICG injected mice and ICG/SWCNT injected mice. It is shown that ICG is able to provide 33% enhancement at approximately 20 minutes peak response time referred to pre-injection PAT summation level, while ICG/SWCNT provides 128% enhancement at 80 minutes and even higher enhancement of 196% at the end point of experiments (120 minutes on average). Additionally, the ICG/SWCNT enhancement was mainly observed at the tumor periphery as confirmed by fluorescence images of the tumor samples. This feature is highly valuable in guiding surgeons to assess tumor boundaries and dimensions in vivo and improve surgical resection of tumors for achieving clean tumor margins.

Zanganeh, Saeid; Li, Hai; Kumavor, Patrick; Alqasemi, Umar; Aguirre, Andres; Mohammad, Innus; Stanford, Courtney; Smith, Michael B.; Zhu, Quing

2013-03-01

408

Structural characterization of a dipeptide compound with immunostimulant activity: 3-(5-thioxo-L-prolyl)-L-thiazolidine-4-carboxylic acid.  

PubMed

The structural characteristics of an immunostimulating agent (3-(5-thioxo-L-prolyl)-L-thiazolidine-4-carboxylic acid) have been established using a combination of 1H and 13C NMR spectroscopy, molecular mechanic calculations (in vacuo and in solution) and X-ray crystallographic analyses. Conformational calculations and NMR spectra identify two classes of conformers, cis and trans, around the peptide bond between the rings, while in the solid state only the cis form has been found. PMID:13679183

Artali, R; Bombieri, G; Meneghetti, F; Nava, D; Ragg, E; Stradi, R

2003-09-01

409

Transgenic pigs as bioreactors: a comparison of gamma-carboxylation of glutamic acid in recombinant human protein C and factor IX by the mammary gland  

Microsoft Academic Search

The mammary gland of transgenic livestock can be used as a bioreactor for producing complex therapeutic proteins. However, the capacity for making a given post-translational modification upon any given polypeptide is uncertain. For example, the efficiency of gamma-carboxylation of glutamic acid in the amino terminal regions of recombinant human protein C (rhPC) and recombinant human Factor IX (rhFIX) is different

Kevin E Van Cott; Stephen P Butler; Christopher G Russell; Anu Subramanian; Henryk Lubon; F. C Gwazdauskas; James Knight; William N Drohan; William H Velander

1999-01-01

410

High-performance liquid chromatographic determination of inactive carboxylic acid metabolite of clopidogrel in human serum: Application to a bioequivalence study  

Microsoft Academic Search

A sensitive and rapid method is described for determination of clopidogrel carboxylic acid (CCA), the inactive metabolite of anti platelet agent, clopidogrel, in human serum. The analytical procedure involves liquid–liquid extraction of the analyte and an internal standard (phenytoin) with ethyl acetate. A mobile phase consisting of 0.05M phosphate buffer containing triethylamine (0.5mL\\/L; pH 5.7) and acetonitrile (56:44 v\\/v) was

Gholamreza Bahrami; Bahareh Mohammadi; Sajjad Sisakhtnezhad

2008-01-01

411

Improved growth performance of the mangrove Avicennia marina seedlings using a 1-aminocyclopropane-1-carboxylic acid deaminase-producing isolate of Pseudoalteromonas maricaloris  

Microsoft Academic Search

Out of 62 bacterial isolates obtained from the mangrove Avicennia\\u000a marina rhizosphere that grows along the Abu Dhabi coast, United Arab Emirates (UAE), an isolate of Pseudoalteromonas maricaloris (Wild type strain) (WT) produced relatively high levels of 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase in vitro.\\u000a Application of this WT strain under greenhouse conditions to A. marina seedlings significantly (P P in planta endogenous plant

Khaled A. El-Tarabily; Tarek Youssef

412

5Ethynyl1-?- d-ribofuranosyl-1 H-[1,2,3]triazole-4-carboxylic acid amide (ETCAR) and its analogues: Synthesis and cytotoxic properties  

Microsoft Academic Search

Efficient Pd(0)-catalysed synthesis of 5-alkynyl-1-?-d-ribofuranosyl-1H-[1,2,3]triazole-4-carboxylic acid amide depends on the presence of different protecting groups of the ribose moiety. Peracetylated 5-iodo substrate (15) couples with terminal alkynes or trimethyl-[(tributylstannyl)ethynyl]silane in 50–71% and 72% yield (ETCAR), respectively, although its hydrodehalogenation to 19 is noticeable. On the other hand, hydrodehalogenation of acetonide (16) predominates over coupling with terminal alkyne and slightly decreases

Tomasz Ostrowski; Piotr Januszczyk; Marcin Cieslak; Julia Kazmierczak-Baranska; Barbara Nawrot; Elzbieta Bartoszak-Adamska; Joanna Zeidler

2011-01-01

413

Ethylene promotes ethylene biosynthesis during pea seed germination by positive feedback regulation of 1-aminocyclo-propane-1-carboxylic acid oxidase  

Microsoft Academic Search

.  ?Increased ethylene evolution accompanies seed germination of many species including Pisum sativum L., but only a little is known about the regulation of the ethylene biosynthetic pathway in different seed tissues. Biosynthesis\\u000a of the direct ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), the expression of ACC oxidase (ACO), and ethylene\\u000a production were investigated in the cotyledons and embryonic axis of germinating pea

Luciana Petruzzelli; Immacolata Coraggio; Gerhard Leubner-Metzger

2000-01-01

414

Improved taxol yield by aromatic carboxylic acid and amino acid feeding to cell cultures of taxus cuspidata.  

PubMed

Cell culture of Taxus cuspidata represents an alternative to whole plant extraction as a source of taxol and related taxanes. Feeding phenylalanine to callus cultures was previously shown to result in increased taxol yields, probably due to the involvement of this amino acid as a precursor for the N-benzoylphenylisoserine side chain of taxol. Inthis study, we have examined the effect of various concentrations of phenylalanine, benzoic acid, N-benzoylglycine, serine, glycine, alanine, and 3-amino-3-phenyl-propionic acid on taxol accumulation in 2-year-old cell suspensions of Taxus cuspidata, cell line FCL1F, and in developing callus cultures of T. cuspidata. All compounds tested were included in media at stationary phase (suspensions) or after the period of fastest growth (calli). Alanine and 3-amino-3-phenyl-propionicacid were tested only in callus cultures and did not affect taxol accumulation. Significant increases or trends toward increases in taxol accumulationin callus and suspensions were observed in the presence of phenylalanine, benzoic acid, N-benzoylglycine, serine, and glycine. The greatest increases in taxol accumulation were observed in the presence of various concentrations of phenylalanine (1 mM for callus; 0.05, 0.1, and 0.2 mM for suspensions) and benzoic acid (0.2 and 1 mM for callus and 0.05, 0.1, and 0.2 mM for suspensions). Increases in taxol yields of cell suspensions in the presence of the most effective precursors brought taxol amounts at stationary phase from 2 mug . g(-1) to approximately 10 mug . g(-1) of the extracted dry weight. The results are discussed in termsof possible implications to taxol biosynthesis and in terms of practical applications to large-scale cell culture systems for the production ofthis drug. (c) 1994 John Wiley & Sons, Inc. PMID:18618915

Fett-Neto, A G; Melanson, S J; Nicholson, S A; Pennington, J J; Dicosmo, F

1994-10-01

415

Retention indices, relative response factors, and mass spectra of trifluoroethyl and heptafluorobutyl esters of carboxylic acids determined by capillary GC/MS  

SciTech Connect

The GC/MS characteristics of carboxylic acid esters prepared from fluorine-containing alcohols were compared to those of methyl esters. The GC retention of 2,2,2-trifluoroethyl (TFE) esters was less than, and 2,2,3,3,4,4,4-heptafluoro-1-butyl (HFB) esters approximately equivalent to that of methyl esters. The peak shape of both TFE and HFB esters was slightly superior to that of methyl esters. Mass spectra of TFE and HFB aliphatic esters show significantly more intense molecular and key fragment ions than those of methyl esters. Also, owing to their significantly higher molecular weights, TFE or HFB ester molecular ions and most fragment ions of interest occur at significantly higher m/z values than most potential interfering ions. The GC retention indices, relative GC/MS total ion current response factors, and 70 eV electron impact mass spectra of about 70 TFE and 70 HFB carboxylic acid esters are reported. Results from analysis of a TFE/HFB esterified petroleum carboxylic acid concentrate are discussed in detail. 26 refs., 17 figs., 3 tabs.

Yu, S.K.-T.; Vrana, R.P.; Green, J.B.

1990-11-01

416

Theoretical and experimental studies on the carbon-nanotube surface oxidation by nitric acid: interplay between functionalization and vacancy enlargement.  

PubMed

The nitric acid oxidation of multiwalled carbon nanotubes leading to surface carboxylic groups has been investigated both experimentally and theoretically. The experimental results show that such a reaction involves the initial rapid formation of carbonyl groups, which are then transformed into phenol or