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1

Gas-Phase Reactivity of Carboxylic Acid Functional Groups with Carbodiimides  

NASA Astrophysics Data System (ADS)

Gas-phase modification of carboxylic acid functionalities is performed via ion/ion reactions with carbodiimide reagents [ N-cyclohexyl- N'-(2-morpholinoethyl)carbodiimide (CMC) and [3-(3-Ethylcarbodiimide-1-yl)propyl]trimethylaminium (ECPT)]. Gas-phase ion/ion covalent chemistry requires the formation of a long-lived complex. In this instance, the complex is stabilized by an electrostatic interaction between the fixed charge quaternary ammonium group of the carbodiimide reagent cation and the analyte dianion. Subsequent activation results in characteristic loss of an isocyanate derivative from one side of the carbodiimide functionality, a signature for this covalent chemistry. The resulting amide bond is formed on the analyte at the site of the original carboxylic acid. Reactions involving analytes that do not contain available carboxylic acid groups (e.g., they have been converted to sodium salts) or reagents that do not have the carbodiimide functionality do not undergo a covalent reaction. This chemistry is demonstrated using PAMAM generation 0.5 dendrimer, ethylenediaminetetraacetic acid (EDTA), and the model peptide DGAILDGAILD. This work demonstrates the selective gas-phase covalent modification of carboxylic acid functionalities.

Prentice, Boone M.; Gilbert, Joshua D.; Stutzman, John R.; Forrest, William P.; McLuckey, Scott A.

2013-01-01

2

Adsorption reactions of carboxylic acid functional groups on sodium aluminoborosilicate glass fiber surfaces.  

PubMed

Multicomponent silicate glasses are ubiquitous in modern society as evidenced by their inclusion in applications ranging from building materials and microelectronics to biomedical implants. Of particular interest in this study is the interface between multicomponent silicate glasses and adhesive polymers. These polymeric systems often possess a variety of different organic functional groups. In this study, we selected acetic acid as a probe molecule representative of the carboxylic acid functional group found in many adhesives. We have used Fourier transform infrared spectroscopy (FT-IR) and NMR to study the interaction of acetic acid with the surface of sodium aluminoborosilicate continuous glass fibers. Methods were developed that enable analyses to be carried out without damaging or altering the pristine as drawn fiber surface. While dosing the surface of fumed silica with acetic acid resulted in the formation of silyl ester groups, analogous dosing of sodium aluminoborosilicate glass fibers resulted in the formation of carboxylate species, principally coordinated to sodium, while silyl ester groups were not observed. PMID:21038910

Stapleton, Joshua J; Suchy, Daniel L; Banerjee, Joy; Mueller, Karl T; Pantano, Carlo G

2010-11-01

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

Preparation of non-covalently functionalized graphene using 9-anthracene carboxylic acid.  

PubMed

A simple way of achieving stable aqueous dispersion of graphene by non-covalent functionalization using 9-anthracene carboxylic acid has been successfully accomplished. Unlike in chemically reduced graphene, the C-sp(2) network of the graphene remains undistorted and therefore of superior quality. The non-covalent functionalization facilitates the exfoliation of graphite layers in a polarity controlled combination of media. A detailed exfoliation mechanism is proposed based on the controlled experiment and is supported by the data from UV-vis spectroscopy, transmission electron microscopy, and x-ray diffraction studies. Formation of monolayer graphene has been confirmed from Raman spectroscopy. The graphene based ultracapacitor shows a high value of specific capacitance (148 F g(-1)). PMID:21911926

Bose, Saswata; Kuila, Tapas; Mishra, Ananta Kumar; Kim, Nam Hoon; Lee, Joong Hee

2011-09-12

5

Carboxylic acid functional group analysis using constant neutral loss scanning-mass spectrometry  

Microsoft Academic Search

The present study describes the development of a new analytical technique for the functional group determination of the carboxylic moiety using atmospheric pressure chemical ionization-mass spectrometry (APCI-MS\\/MS) operated in the constant neutral loss scanning (CNLS) mode. Carboxylic groups were first derivatized into their corresponding methyl esters by reacting with BF3\\/methanol mix and the reaction mixture was then directly injected into

Julien Dron; Gregory Eyglunent; Brice Temime-Roussel; Nicolas Marchand; Henri Wortham

2007-01-01

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

Catalytic properties of carboxylic acid functionalized-polymer microsphere-stabilized gold metallic colloids.  

PubMed

Polymer-microsphere-stabilized gold metallic colloids have been prepared by a novel strategy of simple and convenient reduction of the metallic salt through the stabilization of the active carboxylic acid group on the gel and surface layer of the microsphere. The nature of the interaction between the carboxylic acid and Au nanoparticles was studied in detail by XPS. Preliminary results indicate that polymer-microsphere-stabilized gold colloids are active catalysts for the reduction of 4-nitrophenol to 4-aminophenol with sodium borohydride as reductant. The catalytic properties of the stabilized catalyst for recycling were also investigated. PMID:17007867

Liu, Wei; Yang, Xinlin; Huang, Wenqiang

2006-09-27

8

Absolute p K a determination for carboxylic acids using density functional theory and the polarizable continuum model  

Microsoft Academic Search

The absolute pKas of eight carboxylic acids have been computed using a Born–Haber cycle, the most recent experimental value for the proton solvation energy and completely ab initio structures, energies, and harmonic frequencies of acids and conjugated bases both in vacuo and in aqueous solution. The proton affinities computed by the PBE0 hybrid functional are in very good agreement with

Gloria A. A. Saracino; Roberto Improta; Vincenzo Barone

2003-01-01

9

Computation of large systems with an economic basis set: a density functional study on proton-bound carboxylic acid clusters  

Microsoft Academic Search

We show that first-principle calculations with an economic basis set can predict reliable geometric structures and accurate vibrational frequencies for small proton-bound carboxylic acid clusters. This leads to the potential of using limited computational resources to study large molecular systems. Further applications using density functional (DFT) theory on a series of proton-bound formic and acetic acid clusters have found reasonable

R. Q Zhang; N. B Wong; S. T Lee; R. S Zhu; K. L Han

2000-01-01

10

Density functional theory study of the mechanism of the acid-catalyzed decarboxylation of pyrrole-2-carboxylic acid and mesitoic acid  

Microsoft Academic Search

The mechanisms of the acid-catalyzed decarboxylation of pyrrole-2-carboxylic acid and mesitoic acid have been investigated\\u000a based on density functional theory calculations at the B3LYP\\/6-311G (d, p) level. A polarizable continuum model (PCM) has\\u000a been established in order to evaluate the effects of solvents on these reactions. The results of the calculations indicate\\u000a that the first step of the acid-catalyzed decarboxylation

XingHui Zhang; ZhiYuan Geng; YongCheng Wang

2011-01-01

11

Synergistic effect of self-assembled carboxylic acid-functionalized carbon nanotubes and carbon fiber for improved electro-activated polymeric shape-memory nanocomposite  

NASA Astrophysics Data System (ADS)

The present work studies the synergistic effect of self-assembled carboxylic acid-functionalized carbon nanotube (CNT) and carbon fiber on the electrical property and electro-activated recovery behavior of shape memory polymer (SMP) nanocomposites. The combination of CNT and carbon fiber results in improved electrical conductivity in the SMP nanocomposites. Carboxylic acid-functionalized CNTs are grafted onto the carbon fibers and then self-assembled by deposition to significantly enhance the reliability of the bonding between carbon fiber and SMP via van der Waals and covalent crosslink. Furthermore, the self-assembled carboxylic acid-functionalized CNTs and carbon fibers enable the SMP nanocomposites for Joule heating triggered shape recovery.

Lu, Haibao; Min Huang, Wei

2013-06-01

12

Functionalization of cyclo-olefin polymer substrates by plasma oxidation: stable film containing carboxylic acid groups for capturing biorecognition elements.  

PubMed

Many current designs in biomedical diagnostics devices are based on the use of low cost, disposable, easy-to-fabricate chips made of plastic material, typically a cyclo-olefin polymer (COP). Low autofluorescence properties of such material, among others, make it ideal substrate for fluorescence-based applications. Functionalization of this plastic substrate for biomolecule attachment is therefore of great importance and the quality of films produced on such surface have often a significant influence on the performance of the device. In this communication we discuss the surface chemistry and some other characteristics of hydrophilic films, containing carboxylic acid functional groups, formed by plasma oxidation of COP and also films containing cross-linked, polymerized acryclic acid produced by sequential deposition of tetraorthosilicate and acrylic acid by plasma enhanced chemical vapor deposition (PECVD). Immobilization of labeled, single stranded DNA revealed high binding capacity for both coatings. To our best knowledge, this is the first example of direct immobilization of biomolecules on just plasma oxidized COP. Furthermore, more sophisticated treatment of the oxidized plastic substrate by PECVD with other organic precursors increased the binding capacity by some 40% than that of just plasma oxidized COP. The carboxy functionalized surfaces, due to the negative charge of the carboxy groups, showed very positive trends towards increasing the signal to noise ratio when charged biomolecules such as DNA, are used. PMID:20728322

Gubala, Vladimir; Le, Nam Cao Hoai; Gandhiraman, Ram Prasad; Coyle, Conor; Daniels, Stephen; Williams, David E

2010-08-03

13

New Chemistry with Old Functional Groups: On the Reaction of Isonitriles with Carboxylic Acids - A Route to Various Amide Types  

PubMed Central

Thermolysis of isonitriles with carboxylic acids provides, in one step, N-formyl imides (see, for example 8 + 19 ? 21). The resultant N-formyl group can be converted to N-H, NCH2OH or NCH3. This chemistry allows for a new route for synthesizing ?-N (asparagine) linked glycosyl amino acids.

Li, Xuechen; Danishefsky, Samuel J.

2008-01-01

14

Aqueous infrared carboxylate absorbances: Aliphatic di-acids  

USGS Publications Warehouse

Aqueous attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra of 18 aliphatic di-carboxylic acids are reported as a function of pH. The spectra show isosbestic points and intensity changes which indicate that Beer's law is obeyed, and peak frequencies lie within previously reported ranges for aqueous carboxylates and pure carboxylic acids. Intensity sharing from the symmetric carboxylate stretch is evident in many cases, so that bands which are nominally due to alkyl groups show increased intensity at higher pH. The asymmetric stretch of the HA- species is linearly related to the microscopic acidity constant of the H2A species, with ??pK 2 intervening atoms). The results suggest that aqueous ATR-FTIR may be able to estimate 'intrinsic' pKa values of carboxylic acids, in addition to providing quantitative estimates of ionization. ?? 1998 Elsevier Science B.V. All rights reserved.

Cabaniss, S. E.; Leenheer, J. A.; McVey, I. F.

1998-01-01

15

Method of Preparing Polyfluorinated Aromatic Carboxylic Acids.  

National Technical Information Service (NTIS)

The method of obtaining polyfluorinated aromatic carboxylic acids by treating aromatic fluorinated hydrocarbons with fuming nitric acid with heating and separation of the whole product by known means is distinguished by the fact that in order to simplify ...

S. A. Mazalov V. I. Goloven

1970-01-01

16

Chromatographic separations of aromatic carboxylic acids  

Microsoft Academic Search

The purpose of this review is to present methods of chromatographic analysis of aromatic carboxylic acids. The separation, identification and quantitative analysis of aromatic carboxylic acids are necessary because of their importance as non-steroid antiphlogistic drugs, semi-products of biosynthesis of aromatic amino-acids in plants (phenolic acids), metabolites of numerous toxic substances, drugs and catecholamines. HPLC separation of ionic samples tends

Monika Waksmundzka-Hajnos

1998-01-01

17

Compression in encapsulated carboxylic acid homodimers  

NASA Astrophysics Data System (ADS)

A density functional theory study has been carried out on five carboxylic acid homodimers, free and encapsulated, in order to study the effect of encapsulation or compression. Attractive interactions between the guests and the walls of the capsules stabilize encapsulation even in cases of severe confinement where formation of dimers is unfavorable. Larger hydrogen bonds are calculated for the encapsulated than the isolated dimers except for the case of the bulkiest dimer considered, where encapsulation leads to shortening of the hydrogen bond. Shorter hydrogen-bond lengths with increasing size of the encapsulated dimers are calculated, in agreement with experimental work.

Tzeli, Demeter; Petsalakis, Ioannis D.; Theodorakopoulos, Giannoula

2013-06-01

18

Poly(3-hydroxyalkanoate)s Functionalized with Carboxylic Acid Groups in the Side Chain  

Microsoft Academic Search

Biodegradable polyesters represent an important class of materials, and one subset of these polymers are the bacterially produced poly(3-hydroxyalkanoate)s (PHA), a bacterially produced material. These polymers are very hydrophobic, and chemical methods to increase their hydrophilicity will ultimately lead to new applications. Many copolymers of PHA are known that contain simple, nonpolar functionality in the side chain, and we explored

Dannon J. Stigers; Gregory N. Tew

2003-01-01

19

A Functionally Diverse Enzyme Superfamily that Abstracts the alpha Protons of Carboxylic Acids  

Microsoft Academic Search

Mandelate racemase and muconate lactonizing enzyme are structurally homologous but catalyze different reactions, each initiated by proton abstraction from carbon. The structural similarity to mandelate racemase of a previously unidentified gene product was used to deduce its function as a galactonate dehydratase. In this enzyme superfamily that has evolved to catalyze proton abstraction from carbon, three variations of homologous active

Patricia Clement Babbitt; Gregory T. Mrachko; Miriam Sarah Hasson; Gjalt W. Huisman; Roberto Kolter; Dagmar Ringe; Gregory A. Petsko; George L. Kenyon; John A. Gerlt

1995-01-01

20

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 and 80 C in the substantial absence of a hydrogenation or carbonylation catalyst.

Tustin, G.C.; Dickson, T.J.

1998-04-28

21

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

22

In vitro pollen functionality of attacin-transgenic “Royal Gala” apple plants and apples transformed with 1-aminocyclopropane-1-carboxylic acid synthase (ACS)-antisense vector  

Microsoft Academic Search

To assess pollen functionality of transgenic apple trees, in vitro pollen germination and tube growth were evaluated. Flowers of transgenic “Royal Gala” apple lines containing attacin E gene to confer resistance to fire blight (Erwinia amylovora), or antisense 1-aminocyclopropane-1-carboxylic acid synthase (ACS) construct to improve fruit storage life, were collected, and pollen was harvested. Amongst the 19 transgenic lines, pollen from

K. Ko; S. K. Brown; J. L. Norelli; G. Hrazdina; H. S. Aldwinckle

2010-01-01

23

Self-assembled thiol monolayers with carboxylic acid functionality: Measuring pH-dependent phase transitions with the quartz crystal microbalance  

SciTech Connect

The resonant frequency of the quartz crystal microbalance (QCM) coated with self-assembled thiol monolayers with carboxylic acid functionality is measured while the pH of the aqueous solvent is changed in this paper. Increased tensile stress with increasing pH activity partially contributed to the QCM response, but the major contribution was due to changes in the viscoelastic properties of the hydrodynamic layer in contact with the QCM. 28 refs., 3 figs.

Wang, J.; Frostman, L.M.; Ward, M.D. [Univ. of Minnesota, Minneapolis, MN (United States)]|[Center for Interfacial Engineering, Minneapolis, MN (United States)

1992-06-25

24

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

25

Metabolism of Cyclohexane Carboxylic Acid by Alcaligenes Strain W1  

PubMed Central

Thirty-three microorganisms capable of growth with cyclohexane carboxylate as the sole source of carbon were isolated from mud, water, and soil samples from the Aberystwyth area. Preliminary screening and whole-cell oxidation studies suggested that, with one exception, all of the strains metabolized the growth substrate by beta-oxidation of the coenzyme A ester. This single distinctive strain, able to oxidize rapidly trans-4-hydroxycyclohexane carboxylate, 4-ketocyclohexane carboxylate, p-hydroxybenzoate, and protocatechuate when grown with cyclohexane carboxylate, was classified as a strain of Alcaligenes and given the number W1. Enzymes capable of converting cyclohexane carboxylate to p-hydroxybenzoate were induced by growth with the alicyclic acid and included the first unambiguous specimen of a cyclohexane carboxylate hydroxylase. Because it is a very fragile protein, attempts to stabilize the cyclohexane carboxylate hydroxylase so that a purification procedure could be developed have consistently failed. In limited studies with crude cell extracts, we found that hydroxylation occurred at the 4 position, probably yielding the trans isomer of 4-hydroxycyclohexane carboxylate. Simultaneous measurement of oxygen consumption and reduced nicotinamide adenine dinucleotide oxidation, coupled with an assessment of reactant stoichiometry, showed the enzyme to be a mixed-function oxygenase. Mass spectral analysis enabled the conversion of cyclohexane carboxylate to p-hydroxybenzoate by cell extracts to be established unequivocally, and all of our data were consistent with the pathway: cyclohexane carboxylate ? trans-4-hydroxycyclohexane carboxylate ? 4-ketocyclohexane carboxylate ? p-hydroxybenzoate. The further metabolism of p-hydroxybenzoate proceeded by meta fission and by the oxidative branch of the 2-hydroxy-4-carboxymuconic semialde-hyde-cleaving pathway.

Taylor, David G.; Trudgill, Peter W.

1978-01-01

26

Carboxylic acid (bio)isosteres in drug design.  

PubMed

The carboxylic acid functional group can be an important constituent of a pharmacophore, however, the presence of this moiety can also be responsible for significant drawbacks, including metabolic instability, toxicity, as well as limited passive diffusion across biological membranes. To avoid some of these shortcomings while retaining the desired attributes of the carboxylic acid moiety, medicinal chemists often investigate the use of carboxylic acid (bio)isosteres. The same type of strategy can also be effective for a variety other purposes, for example, to increase the selectivity of a biologically active compound or to create new intellectual property. Several carboxylic acid isosteres have been reported, however, the outcome of any isosteric replacement cannot be readily predicted as this strategy is generally found to be dependent upon the particular context (i.e., the characteristic properties of the drug and the drug-target). As a result, screening of a panel of isosteres is typically required. In this context, the discovery and development of novel carboxylic acid surrogates that could complement the existing palette of isosteres remains an important area of research. The goal of this Minireview is to provide an overview of the most commonly employed carboxylic acid (bio)isosteres and to present representative examples demonstrating the use and utility of each isostere in drug design. PMID:23361977

Ballatore, Carlo; Huryn, Donna M; Smith, Amos B

2013-01-29

27

Decarboxylative etherification of aromatic carboxylic acids.  

PubMed

Decarboxylative Chan-Evans-Lam-type couplings are presented as a new strategy for the regiospecific construction of diaryl and alkyl aryl ethers starting from easily available aromatic carboxylic acids. They allow converting various aromatic carboxylate salts into the corresponding aryl ethers by reaction with alkyl orthosilicates or aryl borates, under aerobic conditions in the presence of silver carbonate as the decarboxylation catalyst and copper acetate as the cross-coupling catalyst. PMID:22681310

Bhadra, Sukalyan; Dzik, Wojciech I; Goossen, Lukas J

2012-06-08

28

Synthesis, Aqueous Reactivity, and Biological Evaluation of Carboxylic Acid Ester-Functionalized Platinum-Acridine Hybrid Anticancer Agents  

PubMed Central

The synthesis of platinum–acridine hybrid agents containing carboxylic acid ester groups is described. The most active derivatives and the unmodified parent compounds showed up to 6-fold higher activity in ovarian cancer (OVCAR-3) and breast cancer (MCF-7, MDA-MB-23) cell lines than cisplatin. Inhibition of cell proliferation at nanomolar concentrations was observed in pancreatic (PANC-1) and non-small cell lung cancer cells (NSCLC, NCI-H460) of 80- and 150-fold, respectively. Introduction of the ester groups did not affect the cytotoxic properties of the hybrids, which form the same monofunctional–intercalative DNA adducts as the parent compounds, as demonstrated in a plasmid unwinding assay. In-line high-performance liquid chromatography and electrospray mass spectrometry (LC-ESMS) shows that the ester moieties undergo platinum-mediated hydrolysis in a chloride concentration-dependent manner to form carboxylate chelates. Potential applications of the chloride-sensitive ester hydrolysis as a self-immolative release mechanism for tumor-selective delivery of platinum–acridines are discussed.

Graham, Leigh A.; Suryadi, Jimmy; West, Tiffany K.; Kucera, Gregory L.; Bierbach, Ulrich

2012-01-01

29

Synthesis, aqueous reactivity, and biological evaluation of carboxylic acid ester-functionalized platinum-acridine hybrid anticancer agents.  

PubMed

The synthesis of platinum-acridine hybrid agents containing carboxylic acid ester groups is described. The most active derivatives and the unmodified parent compounds showed up to 6-fold higher activity in ovarian cancer (OVCAR-3) and breast cancer (MCF-7, MDA-MB-231) cell lines than cisplatin. Inhibition of cell proliferation at nanomolar concentrations was observed in pancreatic (PANC-1) and nonsmall cell lung cancer cells (NSCLC, NCI-H460) of 80- and 150-fold, respectively. Introduction of the ester groups did not affect the cytotoxic properties of the hybrids, which form the same monofunctional-intercalative DNA adducts as the parent compounds, as demonstrated in a plasmid unwinding assay. In-line high-performance liquid chromatography and electrospray mass spectrometry (LC-ESMS) shows that the ester moieties undergo platinum-mediated hydrolysis in a chloride concentration-dependent manner to form carboxylate chelates. Potential applications of the chloride-sensitive ester hydrolysis as a self-immolative release mechanism for tumor-selective delivery of platinum-acridines are discussed. PMID:22871158

Graham, Leigh A; Suryadi, Jimmy; West, Tiffany K; Kucera, Gregory L; Bierbach, Ulrich

2012-08-17

30

Ozone-driven photochemical formation of carboxylic acid groups from alkane groups  

Microsoft Academic Search

Carboxylic acids are ubiquitous in atmospheric particles, and they play an important role in the physical and chemical properties of aerosol particles. During measurements in coastal California in the summer of 2009, carboxylic acid functional groups were highly associated with trajectories from an industrial region with high organic mass (OM), likely from fossil fuel combustion emissions. The concentration of carboxylic

S. Liu; D. A. Day; J. E. Shields; L. M. Russell

2011-01-01

31

Mild Conversion of ?-Diketones and ?-Ketoesters to Carboxylic Acids  

PubMed Central

A mild protocol for the conversion of ?-ketoesters and ?-diketones to carboxylic acids using CAN in CH3CN is described. The method is compatible with a number of functional groups, and can generate carboxylic acids under neutral conditions at room temperature. The reaction is fast and general, providing an alternative method to the commonly used malonic ester acid preparation. Initial mechanistic studies show that initial oxidation of the enol form of the ?-dicarbonyl initiates the reaction. The presence of nitrate as an oxidant ligand or as an additive is critical for success of the reaction.

Zhang, Yang; Jiao, Jingliang

2013-01-01

32

Oleic acid-based gemini surfactants with carboxylic acid headgroups.  

PubMed

Anionic gemini surfactants with carboxylic acid headgroups have been synthesized from oleic acid. The hydrocarbon chain is covalently bound to the terminal carbonyl group of oleic acid via an ester bond, and the carboxylic acid headgroups are introduced to the cis double bond of oleic acid via disuccinyl units. The surfactants exhibit pH-dependent protonation-deprotonation behavior in aqueous solutions. In alkaline solutions (pH 9 in the presence of 10 mmol dm(-3) NaCl as the background electrolyte), the surfactants can lower the surface tension as well as form molecular assemblies, even in the region of low surfactant concentrations. Under acidic (pH 3) or neutral (pH 6-7) conditions, the surfactants are intrinsically insoluble in aqueous media and form a monolayer at the air/water interface. In this study, we have investigated physicochemical properties such as the function of the hydrocarbon chain length by means of static surface tension, pyrene fluorescence, dynamic light scattering, surface pressure-area isotherms, and infrared external reflection measurements. PMID:21768742

Sakai, Kenichi; Umemoto, Naoki; Matsuda, Wataru; Takamatsu, Yuichiro; Matsumoto, Mutsuyoshi; Sakai, Hideki; Abe, Masahiko

2011-01-01

33

The impact of carboxylic acids on ice nucleation  

NASA Astrophysics Data System (ADS)

Ice nucleation is a process which is not fully understood yet. Especially the influence of carboxylic acids has to be investigated. As shown by Pratt et al.[1] carboxylic acids are present in the troposphere and their influence on cloud formation is still unknown. Recent studies showed that pure soot aerosol is unable to nucleate ice and citric acid suppresses the nucleation to a certain extent in laboratory models.[2], [3] Therefore it is consequent to further investigate organic acids with different molecular masses and functional groups. Starting with oxalic acid as the smallest carboxylic acid, several other carboxylic acids with different molecular masses and functional groups have been investigated. Every sample has been observed by ESEM, XRD and optical Microscopy. The same preparation procedure has been applied to all samples to gain comparable results and reveal trends on nucleation abilities. [1] Pratt et al. "In situ detection of biological particles in cloud ice-crystals" Nature Geoscience, 2, 398-401, 2009 [2] O.Möhler et al., Meteorol.Z.14, 477, 2005 [3] B.J. Murray "Inhibition of ice crystallization in highly viscous aqueous organic acid droplets." Atmos.Chem.Phys., 8, 5423-5433, 2008

Weiss, F.; Baloh, P.; Grothe, H.

2012-04-01

34

Pyrolysis Mechanisms of Aromatic Carboxylic Acids  

SciTech Connect

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

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

1997-12-31

35

Decarboxylation of pyrrole-2-carboxylic acid: A DFT investigation  

NASA Astrophysics Data System (ADS)

Decarboxylation is normally a dissociative process, commonly catalyzed by proton or enzymes. The decarboxylation mechanism of pyrrole-2-carboxylic acid involves the addition of water to the carboxyl group, and the C-C bond cleavage leading to the protonated carbonic acid. The direct decarboxylation and decarboxylation aided with water were also investigated to consider the functions of proton and water. Our calculations with G AUSSIAN 03 package show that, with the assistance of H 3O +, the potential energy of the C-C rupture decreases significantly to 9.77 kcal/mol, and the total energy barrier decreases to 33.99 kcal/mol.

Cheng, Xueli; Wang, Jinhu; Tang, Ke; Liu, Yongjun; Liu, Chengbu

2010-08-01

36

Communication: The ionization spectroscopy of mixed carboxylic acid dimers  

NASA Astrophysics Data System (ADS)

We report mass analyzed threshold ionization spectroscopy of supersonically cooled gas phase carboxylic complexes with 9-hydroxy-9-fluorenecarboxylic acid (9HFCA), an analog of glycolic acid. The vibrationally resolved cation spectrum for the 9HFCA complex with formic acid allows accurate determination of its ionization potential (IP), 64 374 +/- 8 cm-1. This is 545 cm-1 smaller than the IP of 9HFCA monomer. The IPs of 9HFCA complexes with acetic acid and benzoic acid shift by -1133 cm-1 and -1438 cm-1, respectively. Density functional calculations confirm that Cs symmetry is maintained upon ionization of the 9HFCA monomer and its acid complexes, in contrast to the drastic geometric rearrangement attending ionization in complexes of 9-fluorene carboxylic acid. We suggest that the marginal geometry changes and small IP shifts are primarily due to the collective interactions among one intramolecular and two intermolecular hydrogen bonds in the dimer.

Yang, Zhijun; Gu, Quanli; Trindle, Carl O.; Knee, J. L.

2013-10-01

37

Communication: The ionization spectroscopy of mixed carboxylic acid dimers.  

PubMed

We report mass analyzed threshold ionization spectroscopy of supersonically cooled gas phase carboxylic complexes with 9-hydroxy-9-fluorenecarboxylic acid (9HFCA), an analog of glycolic acid. The vibrationally resolved cation spectrum for the 9HFCA complex with formic acid allows accurate determination of its ionization potential (IP), 64?374 ± 8 cm(-1). This is 545 cm(-1) smaller than the IP of 9HFCA monomer. The IPs of 9HFCA complexes with acetic acid and benzoic acid shift by -1133 cm(-1) and -1438 cm(-1), respectively. Density functional calculations confirm that Cs symmetry is maintained upon ionization of the 9HFCA monomer and its acid complexes, in contrast to the drastic geometric rearrangement attending ionization in complexes of 9-fluorene carboxylic acid. We suggest that the marginal geometry changes and small IP shifts are primarily due to the collective interactions among one intramolecular and two intermolecular hydrogen bonds in the dimer. PMID:24160490

Yang, Zhijun; Gu, Quanli; Trindle, Carl O; Knee, J L

2013-10-21

38

Comparison of silatrane, phosphonic acid, and carboxylic acid functional groups for attachment of porphyrin sensitizers to TiO2 in photoelectrochemical cells.  

PubMed

A tetra-arylporphyrin dye was functionalized with three different anchoring groups used to attach molecules to metal oxide surfaces. The physical, photophysical and electrochemical properties of the derivatized porphyrins were studied, and the dyes were then linked to mesoporous TiO2. The anchoring groups were ?-vinyl groups bearing either a carboxylate, a phosphonate or a siloxy moiety. The siloxy linkages were made by treatment of the metal oxide with a silatrane derivative of the porphyrin. The surface binding and lability of the anchored molecules were studied, and dye performance was compared in a dye-sensitized solar cell (DSSC). Transient absorption spectroscopy was used to study charge recombination processes. At comparable surface concentration, the porphyrin showed comparable performance in the DSSC, regardless of the linker. However, the total surface coverage achievable with the carboxylate was about twice that obtainable with the other two linkers, and this led to higher current densities for the carboxylate DSSC. On the other hand, the carboxylate-linked dyes were readily leached from the metal oxide surface under alkaline conditions. The phosphonates were considerably less labile, and the siloxy-linked porphyrins were most resistant to leaching from the surface. The use of silatrane proved to be a practical and convenient way to introduce the siloxy linkages, which can confer greatly increased stability on dye-sensitized electrodes with photoelectrochemical performance comparable to that of the other linkers. PMID:23959453

Brennan, Bradley J; Llansola Portolés, Manuel J; Liddell, Paul A; Moore, Thomas A; Moore, Ana L; Gust, Devens

2013-08-20

39

The Conversion of Carboxylic Acids to Ketones: A Repeated Discovery  

ERIC Educational Resources Information Center

|The conversion of carboxylic acids to ketones is a useful chemical transformation with a long history. Several chemists have claimed that they discovered the conversion of carboxylic acids to ketones yet in fact the reaction is actually known for centuries.|

Nicholson, John W.; Wilson, Alan D.

2004-01-01

40

The Conversion of Carboxylic Acids to Ketones: A Repeated Discovery  

ERIC Educational Resources Information Center

The conversion of carboxylic acids to ketones is a useful chemical transformation with a long history. Several chemists have claimed that they discovered the conversion of carboxylic acids to ketones yet in fact the reaction is actually known for centuries.

Nicholson, John W.; Wilson, Alan D.

2004-01-01

41

Experimental and theoretical studies on the functionalization reactions of 4-benzoyl-1,5-diphenyl-1 H -pyrazole-3-carboxylic acid and-acid chloride with various aminophenols  

Microsoft Academic Search

The 1H-pyrazole-3-carboxylic acid 1 was converted via reactions of its acid chloride 2 with various aminophenol derivatives 3a--d into the corresponding N-(hydroxyphenyl)-1H-pyrazole-3-carboxamides 4a--d, respectively, in good yields (34–53%). The reactions of 1 or 2 with 3 in benzene or toluene for 5–7 h with no catalytic amounts of base lead to the formation of the products 4. The structures of all

Ismail Y?ld?r?m; Fatma Kandemirli

2006-01-01

42

Chemistry and reactivity of carboxylic acid-containing surfaces  

Microsoft Academic Search

Polymer surface modification techniques, such as corona, plasma, and ultraviolet treatments, promote adhesion to polymer surfaces through introduction of specific functional groups that interact with subsequent coating layers. Carboxylic acid groups formed during corona and plasma treatments may play a significant role in adhesion promotion, so such groups have been chosen for model surface chemistry studies. Thin films (<30 nm)

C. A. Fleischer; W. P. McKenna; G. Apai

1996-01-01

43

Decarboxylation via addition of water to a carboxyl group: acid catalysis of pyrrole-2-carboxylic acid.  

PubMed

The decarboxylation of pyrrole-2-carboxylic acid is subject to acid catalysis in strongly acidic solutions. Protonation of the pyrrole ring at C2 produces a potentially low-energy carbanion leaving group. Carbon dioxide formation is suppressed by the requisite formation of its high-energy conjugate acid. As a result, decarboxylation must proceed via an associative mechanism through the addition of water to the carboxyl group of the protonated reactant, leading to the formation of pyrrole and protonated carbonic acid, which rapidly dissociates into H(3)O(+) and carbon dioxide. PMID:19645466

Mundle, Scott O C; Kluger, Ronald

2009-08-26

44

Fermentation of corn stover to carboxylic acids.  

PubMed

This article describes countercurrent fermentation to anaerobically convert corn stover and pig manure to mixed carboxylic acids using a mixed culture of mesophilic microorganisms. Corn stover was pretreated with lime to increase digestibility. The Continuum Particle Distribution Model (CPDM) was used to simulate continuous fermentors based on data collected from batch experiments. This model saves considerable time in determining optimum operating conditions. For 80% corn stover/20% pig manure, the highest total carboxylic acid productivity was 1.81 g/(L of liquid. d) at a concentration of 21.4 g total acid/L. The highest total acid selectivity, yield, and conversion were 0.714 g total acid/g volatile solids (VS) digested, 0.550 g total acid/g VS fed, and 0.770 g VS digested/g VS fed, respectively, at a concentration of 16.0 g total acid/L. CPDM predicted the acid concentration and conversion within 13.4 and 11.6%, respectively. PMID:12768625

Thanakoses, Piyarat; Black, Amanda S; Holtzapple, Mark T

2003-07-20

45

Color enhancing effect of carboxylic acids on anthocyanins  

Microsoft Academic Search

The color enhancing effect of aromatic and aliphatic carboxylic acids on anthocyanin-glucosides was investigated in this work. The color of black rice anthocyanin-rich fraction was successfully improved after the addition of aromatic acids (p-coumaric acid, ferulic acid, and sinapic acid), aliphatic acid (lipoic acid) and tannic acid (as a complex acid). The addition of carboxylic acids showed an enhancing and

Robert Yawadio; Naofumi Morita

2007-01-01

46

Arginine of retinoic acid receptor ? which coordinates with the carboxyl group of retinoic acid functions independent of the amino acid residues responsible for retinoic acid receptor subtype ligand specificity  

Microsoft Academic Search

The biological actions of retinoic acid (RA) are mediated by retinoic acid receptors (RAR?, RAR?, and RAR?) and retinoid X receptors (RXR?, RXR?, and RXR?). Consistent with the X-ray crystal structures of RAR? and RAR?, site-directed mutagenesis studies have demonstrated the importance of a conserved Arg residue (?Arg276, ?Arg269, and ?Arg278) for coordination with the carboxyl group of RA. However,

Zeng-Ping Zhang; Juliet M Hutcheson; Helen C Poynton; Jerome L Gabriel; Kenneth J Soprano; Dianne Robert Soprano

2003-01-01

47

Ozone-driven daytime formation of secondary organic aerosol containing carboxylic acid groups and alkane groups  

Microsoft Academic Search

Carboxylic acids are present in substantial quantities in atmospheric particles, and they play an important role in the physical and chemical properties of aerosol particles. During measurements in coastal California in the summer of 2009, carboxylic acid functional groups were exclusively associated with a fossil fuel combustion factor derived from factor analysis of Fourier transform infrared spectroscopic measurements and closely

S. Liu; D. A. Day; J. E. Shields; L. M. Russell

2011-01-01

48

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

49

Soluble, High Molecular Weight Polysilsesquioxanes with Carboxylate Functionalities  

SciTech Connect

Trialkoxysilyl-containing monomers of the type (RO){sub 3}Si(CH{sub 2}){sub 3}C(O)OtBu (R = Me, Et) were prepared by hydrosilation of the corresponding vinylic tert-butyl esters CH{sub 3}CHCH{sub 2}C(O)OtBu. Acid- or base-catalyzed polymerization of the monomers leads to very high molecular weight polymers with relatively narrow polydispersities. The polymerization results in complete condensation of the alkoxy groups while the tert-butyl ester functionality remains fully intact. Partial or full deprotection of the tert-butyl group can easily be achieved to yield the corresponding carboxylic acid polymers. The ester and carboxylic acid functionalities of these new materials allow for their potential use in a variety of applications such as scavenging of heavy metals.

RAHIMIAN,KAMYAR; LOY,DOUGLAS A.; WHEELER,DAVID R.

2000-07-14

50

Synthesis of mono functional carboxylic acid poly(methyl methacrylate) in aqueous medium using sur-iniferter. Application to the synthesis of graft copolymers polyethylene- g-poly(methyl methacrylate) and the compatibilization of LDPE\\/PVDF blends  

Microsoft Academic Search

Carboxylic acid mono functional poly(methyl methacrylate) was prepared by emulsion photopolymerization using 4-diethylthiocarbamoylsulfanylmethyl benzoic acid (DTBA) as sur-iniferter agent. DTBA is efficient to obtain mono functional polymers with a linear evolution of Mn vs. monomer conversion up to 60%. Beyond 60% monomer conversion, Mn decreases drastically and addition of a supplementary surfactant seems to disturb the effect of sur-iniferter. Secondly,

J. Kwak; P. Lacroix-Desmazes; J. J. Robin; B. Boutevin; N. Torres

2003-01-01

51

Functional analysis of Kluyveromyces lactis carboxylic acids permeases: heterologous expression of KlJEN1 and KlJEN2 genes  

Microsoft Academic Search

The present work describes a detailed physiological and molecular characterization of the mechanisms of transport of carboxylic\\u000a acids in Kluyveromyces lactis. This yeast species presents two homologue genes to JEN1 of Saccharomyces cerevisiae: KlJEN1 encodes a monocarboxylate permease and KlJEN2 encodes a dicarboxylic acid permease. In the strain K.\\u000a lactis GG1888, expression of these genes does not require an inducer

Odília Queirós; Leonor Pereira; Sandra Paiva; Pedro Moradas-Ferreira; Margarida Casal

2007-01-01

52

Selective esterification of non-conjugated carboxylic acids in the presence of conjugated or aromatic carboxylic acids over active carbon supported methanesulfonic acid  

Microsoft Academic Search

Non-conjugated carboxylic acids are selectively esterified in good yields in the presence of conjugated or aromatic carboxylic\\u000a acids by stirring over active carbon supported methanesulfonic acid in dichloromethane at room temperature.

ZeWang Feng; XinQi Zhao; Hua Bi

2008-01-01

53

Synthesis of highly lipophilic crown ether carboxylic acids  

SciTech Connect

Synthetic routes to eight highly lipophilic crown ether carboxylic acids are described. Structural variations within this series of crown ether carboxylic acids include changes in the crown ether cavity size, the lipophilic group attachment site, and the basicity of the crown ether oxygens.

Bartsch, R.A.; Liu, Y.; Kang, S.I.; Son, B.; Heo, G.S.; Hipes, P.G.; Bills, L.J.

1983-01-01

54

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, M.R.; Spivey, J.J.; Zoeller, J.R.

1998-09-15

55

MULTIVALENT CARBOXYLIC ACIDS TO MODIFY THE PROPERTIES OF ZEIN  

Technology Transfer Automated Retrieval System (TEKTRAN)

Carboxylic acids having more than one carboxylic acid moiety have been evaluated in zein melt formulations produced in a torque rheometer. These reagents are effective plasticizers for zein, lowering zein viscosity and delaying the onset of rapid viscosity increase. These reagents have been shown ...

56

Boron-containing amino carboxylic acid compounds and uses thereof  

DOEpatents

Novel compounds which are useful for boron neutron capture therapy (BNCT) are disclosed. The compounds comprise a stable boron-containing group and an aminocycloalkane carboxylic acid group or a boronated acyclic hydrocarbon-linked amino carboxylic acid. Methods for synthesis of the compounds and for use of the compounds in BNCT are disclosed.

Kabalka, George W. (Knoxville, TN); Srivastava, Rajiv R. (Knoxville, TN)

2000-03-14

57

Ozone-driven photochemical formation of carboxylic acid groups from alkane groups  

NASA Astrophysics Data System (ADS)

Carboxylic acids are ubiquitous in atmospheric particles, and they play an important role in the physical and chemical properties of aerosol particles. During measurements in coastal California in the summer of 2009, carboxylic acid functional groups were highly associated with trajectories from an industrial region with high organic mass (OM), likely from fossil fuel combustion emissions. The concentration of carboxylic acid groups peaked during daytime, suggesting a photochemical secondary formation mechanism. This daytime increase in concentration was tightly correlated with O3 mixing ratio, indicating O3 was the likely driver in acid formation. Based on the diurnal cycles of carboxylic acid and alkane groups, the covariation of carboxylic acid groups with O3, and the composition of the Combustion factor resulted from the factor analyses, gas-phase alkane oxidation by OH radicals to form dihyfrofuran followed by further oxidation of dihydrofuran by O3 is the likely acid formation mechanism. Using the multi-day average of the daytime increase of carboxylic acid group concentrations and m/z 44-based Aged Combustion factor, we estimated the lower-bound contributions of secondary organic aerosol (SOA) formed in 12-h daytime of processing in a single day to be 30% of the carboxylic acid groups and 25-45% of the Combustion factor concentration. These unique ambient observations of photochemically-driven acid formation suggest that gas-phase alkanes might be important sources of SOA formation in this coastal region.

Liu, S.; Day, D. A.; Shields, J. E.; Russell, L. M.

2011-03-01

58

Strong-acid, carboxyl-group structures in fulvic acid from the Suwannee River, Georgia. 1. Minor structures  

USGS Publications Warehouse

An investigation of the strong-acid characteristics (pKa 3.0 or less) of fulvic acid from the Suwannee River, Georgia, was conducted. Quantitative determinations were made for amino acid and sulfur-containing acid structures, oxalate half-ester structures, malonic acid structures, keto acid structures, and aromatic carboxyl-group structures. These determinations were made by using a variety of spectrometric (13C-nuclear magnetic resonance, infrared, and ultraviolet spectrometry) and titrimetric characterizations on fulvic acid or fulvic acid samples that were chemically derivatized to indicate certain functional groups. Only keto acid and aromatic carboxyl-group structures contributed significantly to the strong-acid characteristics of the fulvic acid; these structures accounted for 43% of the strong-acid acidity. The remaining 57% of the strong acids are aliphatic carboxyl groups in unusual and/or complex configurations for which limited model compound data are available.

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

1995-01-01

59

Corrosion inhibition of steel in concrete by carboxylic acids  

SciTech Connect

Water soluble carboxylic acids have been used as corrosion inhibitors. They remain largely soluble after curing in cement for up to 90d. Corrosion current measurements are presented showing malonic acid, a dicarboxylic acid, to be a very effective corrosion inhibitor even in the presence of 2.5 wt % chloride. Unfortunately, it has an initial retarding effect on the set of Portland cement. The investigation suggests that corrosion inhibitors based on carboxylic acids remain a fruitful field of investigation.

Sagoe-Crentsil, K.K.; Glasser, F.P. (Univ. of Aberdeen, Old Aberdeen (United Kingdom). Dept. of Chemistry); Yilmaz, V.T. (Ondokuz Mayis Univ., Samsun (Turkey))

1993-11-01

60

Influence of biodegradation on crude oil acidity and carboxylic acid composition  

Microsoft Academic Search

Quantitative analysis of separated carboxylic acid fractions of 33 crude oils from the UK, Italy and California, showed that the carboxylic acid fraction is a major factor responsible for the acidity in these oils. It was apparent that biodegradation is the main process that produces high concentrations of carboxylic acids in these crude oils with the extent of biodegradation, as

W Meredith; S.-J Kelland; D. M Jones

2000-01-01

61

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

2012-03-21

62

40 CFR 721.4663 - Fluorinated carboxylic acid alkali metal salts.  

Code of Federal Regulations, 2010 CFR

... false Fluorinated carboxylic acid alkali metal salts. 721.4663 Section...4663 Fluorinated carboxylic acid alkali metal salts. (a) Chemical...identified as fluorinated carboxylic acid alkali metal salts (PMNs...

2010-07-01

63

40 CFR 721.4663 - Fluorinated carboxylic acid alkali metal salts.  

Code of Federal Regulations, 2010 CFR

... false Fluorinated carboxylic acid alkali metal salts. 721.4663 Section...4663 Fluorinated carboxylic acid alkali metal salts. (a) Chemical...identified as fluorinated carboxylic acid alkali metal salts (PMNs...

2009-07-01

64

40 CFR 721.4663 - Fluorinated carboxylic acid alkali metal salts.  

Code of Federal Regulations, 2013 CFR

... false Fluorinated carboxylic acid alkali metal salts. 721.4663 Section...4663 Fluorinated carboxylic acid alkali metal salts. (a) Chemical...identified as fluorinated carboxylic acid alkali metal salts (PMNs...

2013-07-01

65

Functionalization of cyclo-olefin polymer substrates by plasma oxidation: Stable film containing carboxylic acid groups for capturing biorecognition elements  

Microsoft Academic Search

Many current designs in biomedical diagnostics devices are based on the use of low cost, disposable, easy-to-fabricate chips made of plastic material, typically a cyclo-olefin polymer (COP). Low autofluorescence properties of such material, among others, make it ideal substrate for fluorescence-based applications. Functionalization of this plastic substrate for biomolecule attachment is therefore of great importance and the quality of films

Vladimir Gubala; Nam Cao Hoai Le; Ram Prasad Gandhiraman; Conor Coyle; Stephen Daniels; David E. Williams

2010-01-01

66

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

67

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

2011-06-01

68

Carboxyl Methylation of Small GTPases and Endothelial Cell Function  

Microsoft Academic Search

Posttranslational modifications of small GTPases regulate enzyme activity and subcellular localization, resulting in altered\\u000a cellular functions. The role of small-GTPase carboxyl methylation in modulating endothelial functions is not well understood.\\u000a In our study, we have used cultured endothelial cells to assess the effects of inhibition of carboxyl methylation on endothelial\\u000a cell function. We have found that isoprenylcysteine carboxyl methyltransferase (ICMT)

Sharon Rounds; Elizabeth O. Harrington; Qing Lu

69

Olfactory sensitivity and odor structure-activity relationships for aliphatic carboxylic acids in CD-1 mice.  

PubMed

Using a conditioning paradigm, the olfactory sensitivity of CD-1 mice for a homologous series of aliphatic n-carboxylic acids (ethanoic acid to n-octanoic acid) and several of their isomeric forms was investigated. With all 14 odorants, the animals significantly discriminated concentrations as low as 0.03 ppm (parts per million) from the solvent, and with four odorants the best-scoring animals even detected concentrations as low as 3 ppt (parts per trillion). Analysis of odor structure-activity relationships showed that the correlation between olfactory detection thresholds of the mice for the unbranched carboxylic acids and carbon chain length can best be described as a U-shaped function with the lowest threshold values at n-butanoic acid. A significant positive correlation between olfactory detection thresholds and carbon chain length of the carboxylic acids with their branching next to the functional carboxyl group was found. In contrast, no such correlation was found for carboxylic acids with their branching at the distal end of the carbon chain relative to the functional carboxyl group. Finally, a significant correlation was found between olfactory detection thresholds and the position of the branching of the carboxylic acids. Across-species comparisons suggest that mice are more sensitive for short-chained (C(2) to C(4)) aliphatic n-carboxylic acids than other mammalian species, but not for longer-chained ones (C(5) to C(8)). Further comparisons suggest that odor structure-activity relationships are both substance class- and species-specific. PMID:22479594

Can Güven, Selçuk; Laska, Matthias

2012-03-30

70

Chemo-enzymatic epoxidation of unsaturated carboxylic acids  

Microsoft Academic Search

Unsaturated carboxylic acids are converted to percarboxylic acids catalyzed by an immobilized lipase from Candida antarctica (Novozym 435R). These unsaturated percarboxylic acids are only intermediates and epoxidize themselves in good yields and almost without consecutive reactions. The mechanism of the oxygen-transfer is found to be predominantly intermolecular and the formation of the percarboxylic acids proceeds via two different catalytic reactions.

Siegfried Warwel; Mark Rüsch gen. Klaas

1995-01-01

71

Intermolecular C-O Addition of Carboxylic Acids to Arynes  

PubMed Central

A novel, efficient and expedient route to biologically and pharmaceutically important o-hydroxyaryl ketones, xanthones, 4-chromanones and flavones has been developed starting from readily available carboxylic acids and commercially available o-(trimethylsilyl)aryl triflates.

Dubrovskiy, Anton V.; Larock, Richard C.

2010-01-01

72

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

PubMed

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. PMID:23722228

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

2013-05-30

73

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

74

Separation of certain carboxylic acids utilizing cation exchange membranes  

DOEpatents

A method of substantially separating monofunctional lower carboxylic acids from a liquid mixture containing the acids wherein the pH of the mixture is adjusted to a value in the range of from about 1 to about 5 to form protonated acids. The mixture is heated to an elevated temperature not greater than about 100/sup 0/C and brought in contact with one side of a perfluorinated cation exchange membrane having sulfonate or carboxylate groups or mixtures thereof with the mixture containing the protonated acids. A pressure gradient can be established across the membrane with the mixture being under higher pressure, so that protonated monofunctional lower carboxylic acids pass through the membrane at a substantially faster rate than the remainder of the mixture thereby substantially separating the acids from the mixture.

Chum, H.L.; Sopher, D.W.

1983-05-09

75

Separation of certain carboxylic acids utilizing cation exchange membranes  

DOEpatents

A method of substantially separating monofunctional lower carboxylic acids from a liquid mixture containing the acids wherein the pH of the mixture is adjusted to a value in the range of from about 1 to about 5 to form protonated acids. The mixture is heated to an elevated temperature not greater than about 100.degree. C. and brought in contact with one side of a perfluorinated cation exchange membrane having sulfonate or carboxylate groups or mixtures thereof with the mixture containing the protonated acids. A pressure gradient can be established across the membrane with the mixture being under higher pressure, so that protonated monofunctional lower carboxylic acids pass through the membrane at a substantially faster rate than the remainder of the mixture thereby substantially separating the acids from the mixture.

Chum, Helena L. (Arvada, CO); Sopher, David W. (Maarssenbroek, NL)

1984-01-01

76

Corrosion inhibition of steel in concrete by carboxylic acids  

Microsoft Academic Search

Water soluble carboxylic acids have been used as corrosion inhibitors. They remain largely soluble after curing in cement for up to 90d. Corrosion current measurements are presented showing malonic acid, a dicarboxylic acid, to be a very effective corrosion inhibitor even in the presence of 2.5 wt % chloride. Unfortunately, it has an initial retarding effect on the set of

K. K. Sagoe-Crentsil; F. P. Glasser; V. T. Yilmaz

1993-01-01

77

Separation of certain carboxylic acids utilizing cation exchange membranes  

Microsoft Academic Search

A method of substantially separating monofunctional lower carboxylic acids from a liquid mixture containing the acids wherein the pH of the mixture is adjusted to a value in the range of from about 1 to about 5 to form protonated acids. The mixture is heated to an elevated temperature not greater than about 100.degree. C. and brought in contact with

Helena L. Chum; David W. Sopher

1984-01-01

78

Separation of certain carboxylic acids utilizing cation exchange membranes  

Microsoft Academic Search

A method is described for substantially separating monofunctional lower carboxylic acids from a liquid mixture containing the acids wherein the pH of the mixture is adjusted to a value in the range of from about 1 to about 5 to form protonated acids. The mixture is heated to an elevated temperature not greater than about 100 C and brought in

H. L. Chum; D. W. Sopher

1984-01-01

79

One-step hydrothermal synthesis of carboxyl-functionalized upconversion phosphors for bioapplications.  

PubMed

In this paper, we report a facile one-step hydrothermal method to synthesize phase-, size-, and shape-controlled carboxyl-functionalized rare-earth fluorescence upconversion phosphors by using a small-molecule binary acid, such as malonic acid, oxalic acid, succinic acid, or tartaric acid as capping agent. The crystals, from nano- to microstructures with diverse shapes that include nanospheres, microrods, hexagonal prisms, microtubes, microdisks, polygonal columns, and hexagonal tablets, can be obtained with different reaction times, reaction temperatures, molar ratios of capping agent to sodium hydroxide, and by varying the binary acids. Fourier transform infrared, thermogravimetric analysis, and upconversion luminescence spectra measurements indicate that the synthesized NaYF(4):Yb/Er products with hydrophilic carboxyl-functionalized surface offer efficient upconversion luminescent performance. Furthermore, the antibody/secondary antibody conjugation can be realized by the carboxyl-functionalized surfaces of the upconversion phosphors, thus indicating the potential bioapplications of these kinds of materials. PMID:22996059

Yang, Jianping; Shen, Dengke; Li, Xiaomin; Li, Wei; Fang, Yin; Wei, Yong; Yao, Chi; Tu, Bo; Zhang, Fan; Zhao, Dongyuan

2012-09-20

80

Functional group induced excited state intramolecular proton transfer process in 4-amino-2-methylsulfanyl-pyrimidine-5-carboxylic acid ethyl ester: a combined spectroscopic and density functional theory study.  

PubMed

The molecule methyl-2-aminonicotinate (2-MAN) does not exhibit excited state intramolecular proton transfer (ESIPT), but its derivative 4-amino-2-methylsulfanyl-pyrimidine-5-carboxylic acid ethyl ester (AMPCE), widely used in the preparation of pyrimidopyrimidines as a protein kinase inhibitor, does exhibit ESIPT. Increasing acidic and basic character at the proton donor and proton acceptor sites by adding functional groups is found to be responsible for the large Stokes shifted ESIPT emission (?? = 12?706 cm(-1)) in AMPCE. The photophysics of AMPCE have been explored on the basis of steady state and time resolved spectral measurements, quantum yield calculation with variation of polarity, as well as hydrogen bonding ability of solvents. Experimental findings have been correlated with the calculated structure and potential energy surfaces based on the intramolecular proton transfer model obtained by density functional theory (DFT). Properties based on the calculated excited state surfaces generated in vacuo and methanol solvent using time dependent density functional theory (TDDFT) and time dependent density functional theory polarized continuum model (TDDFT-PCM), respectively, show good agreement with the experimental findings. HOMO and LUMO diagrams also support the favorable ESIPT process in the first excited state potential energy surface. PMID:23719759

Jana, Sankar; Dalapati, Sasanka; Guchhait, Nikhil

2013-08-14

81

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

82

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

SciTech Connect

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

Kawamura, K.; Okuwaki, A.; Verheyen, T.; Perry, G.J. [Tohoku University, Miyagi (Japan). Graduate School of Environmental Studies

2006-02-15

83

Antiradical and Antioxidant Activity of Biologically Active Carboxylic Acids  

Microsoft Academic Search

The antioxidant and antiradical activity of a series of biologically active carboxylic acids were studied, their effectiveness series were constructed, and optimal concentrations for inhibition of active oxygen formation were found. It is shown that the mechanism of the antioxidant action of these acids can be studied by their effect on different stages of oxygen reduction.

V. F. Gromovaya; G. S. Shapoval; I. E. Mironyuk

2002-01-01

84

Dissolving Carboxylic Acids and Primary Amines on the Overhead Projector  

ERIC Educational Resources Information Center

|Liquid carboxylic acids (or primary amines) with limited solubility in water are dissolved by addition of aqueous sodium hydroxide (or hydrochloric acid) on the stage of an overhead projector using simple glassware and very small quantities of chemicals. This effective and colorful demonstration can be used to accompany discussions of the…

Solomon, Sally D.; Rutkowsky, Susan A.

2010-01-01

85

Inhibition of palmito ( Acanthophoenix rubra) polyphenol oxidase by carboxylic acids  

Microsoft Academic Search

The inhibition of palmito (Acanthophoenix rubra) polyphenol oxidase (PPO) is reported. Recently, two forms of palmito PPO were partially purified by hydrophobic chromatography. Inhibitory effects of various carboxylic acids on these two forms have been studied. Both forms showed identical behaviour towards the inhibitors studied. Cinnamic acid was found to have the greatest inhibitory effect (Ki = 0·06 mM). When

Christine Robert; Claude Rouch; Frédéric Cadet

1997-01-01

86

The role of carboxylic acids in TALSQueak separations  

SciTech Connect

Recent reports have indicated TALSPEAK-type separations chemistry can be improved through the replacement of bis-2-ethyl(hexyl) phosphoric acid (HDEHP) and diethylenetriamine-N,N,N,N,N-pentaacetic acid (DTPA) with the weaker reagents 2-ethyl(hexyl) phosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) and N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid (HEDTA), respectively. This modified TALSPEAK has been provided with an adjusted acronym of TALSQueak (Trivalent Actinide Lanthanide Separation using Quicker Extractants and Aqueous Komplexes). Among several benefits, TALSQueak chemistry provides more rapid phase transfer kinetics, is less reliant on carboxylic acids to mediate lanthanide extraction and allows a simplified thermodynamic description of the separations process that generally requires only parameters available in the literature to describe metal transfer. This manuscript focuses on the role of carboxylic acids in aqueous ternary (M-HEDTA-carboxylate) complexes, americium/lanthanide separations, and extraction kinetics. Spectrophotometry (UV-vis) of the Nd hypersensitive band indicates the presence of aqueous ternary species (K111 = 1.83 {+-} 0.01 at 1.0 M ionic strength, Nd(HEDTA) + Lac <-> Nd(HEDTA)Lac). Varying the carboxylic acid does not have a significant impact on Ln/Am separations or extraction kinetics. TALSqueak separations come to equilibrium in five minutes at the conventional operational pH of 3.6 using only 0.1 M total lactate or citrate.

Braley, Jenifer C.; Carter, Jennifer C.; Sinkov, Sergey I.; Nash, Ken L.; Lumetta, Gregg J.

2012-04-13

87

IR Study of the Adsorption of Carboxylic Acids on the Surface of Goethite and Haematite Immersed in Carbon Tetrachloride.  

National Technical Information Service (NTIS)

The extent of adsorption of carboxylic acids on the surface of goethite and hematite has been studied. Eight different carboxylic acids (acetic acid, propionic acid butyric acid, hexanoic acid, 2-ethyl hexanoic acid, decanoic acid and lauric acid) were se...

A. Ara

1984-01-01

88

Separation of certain carboxylic acids utilizing cation exchange membranes  

Microsoft Academic Search

A method of substantially separating monofunctional lower carboxylic acids from a liquid mixture containing the acids wherein the pH of the mixture is adjusted to a value in the range of from about 1 to about 5 to form protonated acids. The mixture is heated to an elevated temperature not greater than about 100°C and brought in contact with one

H. L. Chum; D. W. Sopher

1983-01-01

89

More on Effects Controlling Carboxylic Acidity.  

ERIC Educational Resources Information Center

Gas phase acidity data shown are offered to writers of elementary organic chemistry texts for replacement of the aqueous phase data that are universally used. Relative acidities in the gas phase are controlled virtually exclusively by enthalpic factors. Structural-energetic explanations of acidic trends can therefore be used. (SK)

Schwartz, Lowell M.

1981-01-01

90

Atmospheric carboxylic acids in southern California  

SciTech Connect

Intensive measurements of organic acids, inorganic acids, aldehydes and peroxyacetyl nitrate (PAN) in urban air were carried out at a Southern California smog receptor site, Glendora, CA, August 12-22, 1986. The objective of this project was to augment the data base regarding organic acids in urban air and to assess their role with emphasis on ambient levels, diurnal variations, phase distribution, emissions, in-situ formation and removal. The relative abundance of organic acids and inorganic acids was determined for the first time from simultaneous measurements carried out during this study.

Van Neste, A.; Williams, E.L. II; Grosjean, D. (DGA, Inc., Ventura, CA (USA))

1988-09-01

91

Prediction of phase equilibrium and hydration free energy of carboxylic acids by Monte Carlo simulations.  

PubMed

In this work, a new transferable united-atom force field has been developed to predict phase equilibrium and hydration free energy of carboxylic acids. To take advantage of the transferability of the AUA4 force field, all Lennard-Jones parameters of groups involved in the carboxylic acid chemical function are reused from previous parametrizations of this force field. Only a unique set of partial electrostatic charges is proposed to reproduce the experimental gas phase dipole moment, saturated liquid densities and vapor pressures. Phase equilibrium properties of various pure carboxylic acids (acetic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid) and one diacid (1,5-pentanedioic) are studied through Monte Carlo simulations in the Gibbs ensemble. A good accuracy is obtained for pure compound saturated liquid densities and vapor pressures (average deviation of 2% and 6%, respectively), as well as for critical points. The vaporization enthalpy is, however, poorly predicted for short acids, probably due to a limitation of the force field to correctly describe the significant dimerization in the vapor phase. Pressure-composition diagrams for two binary mixtures (acetic acid + n-butane and propanoic acid + pentanoic acid) are also computed with a good accuracy, showing the transferability of the proposed force field to mixtures. Hydration free energies are calculated for three carboxylic acids using thermodynamic integration. A systematic overestimation of around 10 kJ/mol is observed compared to experimental data. This new force field parametrized only on saturated equilibrium properties appears insufficient to reach an acceptable precision for this property, and only relative hydration free energies between two carboxylic acids can be correctly predicted. This highlights the limitation of the transferability feature of force fields to properties not included in the parametrization database. PMID:23697338

Ferrando, Nicolas; Gedik, Ibrahim; Lachet, Véronique; Pigeon, Laurent; Lugo, Rafael

2013-06-03

92

The ground-state tunneling splitting of various carboxylic acid dimers  

Microsoft Academic Search

Carboxylic acid dimers in gas phase reveal ground-state tunneling splittings due to a double proton transfer between the two subunits. In this study we apply a recently developed accurate semiclassical method to determine the ground-state tunneling splittings of eight different carboxylic acid derivative dimers (formic acid, benzoic acid, carbamic acid, fluoro formic acid, carbonic acid, glyoxylic acid, acrylic acid, and

Christofer S. Tautermann; Andreas F. Voegele; Klaus R. Liedl

2004-01-01

93

Synthesis and hypoglycemic evaluation of substituted pyrazole-4-carboxylic acids  

Microsoft Academic Search

The synthesis and in vivo activities of a series of substituted pyrazole-4-carboxylic acids as hypoglycemic agents are described. Modelization of some potent compounds, comparatively to the metformine, presents certain analogies permitting to predict the design of some novel antidiabetic drugs.

Bertrand Cottineau; Patrick Toto; Christophe Marot; Aline Pipaud; Jacques Chenault

2002-01-01

94

Chemolithoautotrophy and mixotrophy in the thiophene-2-carboxylic acid-utilizing xanthobacter tagetidis  

PubMed

Xanthobacter tagetidis grew as a chemolithotrophic autotroph on thiosulfate and other inorganic sulfur compounds, as a heterotroph on thiophene-2-carboxylic acid, acetic acid and alpha-ketoglutaric acid, and as a mixotroph on thiosulfate in combination with thiophene-2-carboxylic acid and/or acetic acid. Autotrophic growth on one-carbon organosulfur compounds, and intermediates in their oxidation are also reported. Thiosulfate enhanced the growth yields in mixotrophic cultures, presumably by acting as a supplementary energy source, since ribulose bisphosphate carboxylase was only active in thiosulfate-grown cells and was not detected in mixotrophic cultures using thiosulfate with thiophene-2-carboxylic acid. Bacteria grown on thiophene-2-carboxylic acid also oxidized sulfide, thiosulfate and tetrathionate, indicating these as possible sulfur intermediates in thiophene-2-carboxylic acid degradation. Thiosulfate and tetrathionate were oxidized completely to sulfate and, consequently, did not accumulate as products of thiophene-2-carboxylic acid oxidation in growing cultures. Km and Vmax values for the oxidation of thiosulfate, tetrathionate or sulfide were 13 &mgr;M and 83 nmol O2 min-1 (mg dry wt.)-1, respectively; thiosulfate and tetrathionate became autoinhibitory at concentrations above 100 &mgr;M. The true growth yield (Ymax) on thiophene-2-carboxylic acid was estimated from chemostat cultures (at dilution rates of 0.034-0.094 h-1) to be 112.2 g mol-1, with a maintenance coefficient (m) of 0.3 mmol thiophene-2-carboxylic acid (g dry wt.)-1 h-1, and the maximum specific growth rate (&mgr;max) was 0.116 h-1. Growth in chemostat culture at a dilution rate of 0. 041 h-1 indicated growth yields [g dry wt. (mol substrate)-1] of 8.1 g (mol thiosulfate)-1, 60.9 g (mol thiophene-2-carboxylic acid)-1, and 17.5 g (mol acetic acid)-1, with additive yields for growth on mixtures of these substrates. At a dilution rate of 0.034 h-1, yields of 57.8 g (mol alpha-ketoglutaric acid)-1 and 60.7 g (mol thiophene-2-carboxylic acid)-1 indicated some additional energy conservation from oxidation of the thiophene-sulfur. SDS-PAGE of cell-free preparations indicated a polypeptide (Mr, 21.0 kDa) specific to growth on thiophene-2-carboxylic acid for which no function can yet be ascribed: no metabolism of thiophene-2-carboxylic acid by cell-free extracts was detected. It was shown that X. tagetidis exhibits a remarkable degree of metabolic versatility and is representative of facultatively methylotrophic and chemolithotrophic autotrophs that contribute significantly to the turnover of simple inorganic and organic sulfur compounds (including substituted thiophenes) in the natural environment. PMID:9477260

Padden; Kelly; Wood

1998-03-01

95

Influence of carboxyl group on the acid hydrolysis of cellulose  

Microsoft Academic Search

Cellulose isolated from wood is more susceptible than cotton cellulose to homogeneous hydrolysis in phosphoric acid. The influence\\u000a of carboxyl group introduction at the C6 position on the hydrolysis rate of cellulose in 82.5% phosphoric acid was studied\\u000a as a model of the oxidation of cellulose during pulping. The rate constant of hydrolysis for dissolving pulp was larger than\\u000a that

Shuichi Hirosawa; Kazuya Minato; Fumiaki Nakatsubo

2001-01-01

96

Thiazolidinone Amides, Thiazolidine Carboxylic Acid Amides, Methods of Making, and Uses Thereof.  

National Technical Information Service (NTIS)

Substituted thiazolidinone carboxylic acid amides and substituted thiazolidine carboxylic acid amides according to formulae (I) and (II) are disclosed where the various substituent groups are as defined in the specification. Methods of making these compou...

D. D. Miller E. Hurh J. T. Dalton V. Gududuru

2004-01-01

97

Selective homogeneous hydrogenation of biogenic carboxylic acids with [Ru(TriPhos)H]+: a mechanistic study.  

PubMed

Selective hydrogenation of biogenic carboxylic acids is an important transformation for biorefinery concepts based on platform chemicals. We herein report a mechanistic study on the homogeneously ruthenium/phosphine catalyzed transformations of levulinic acid (LA) and itaconic acid (IA) to the corresponding lactones, diols, and cyclic ethers. A density functional theory (DFT) study was performed and corroborated with experimental data from catalytic processes and NMR investigations. For [Ru(TriPhos)H](+) as the catalytically active unit, a common mechanistic pathway for the reduction of the C?O functionality in aldehydes, ketones, lactones, and even free carboxylic acids could be identified. Hydride transfer from the Ru-H group to the carbonyl or carboxyl carbon is followed by protonation of the resulting Ru-O unit via ?-bond metathesis from a coordinated dihydrogen molecule. The energetic spans for the reduction of the different functional groups increase in the order aldehyde < ketone < lactone ? carboxylic acid. This reactivity pattern as well as the absolute values are in full agreement with experimentally observed activities and selectivities, forming a rational basis for further catalyst development. PMID:21786816

Geilen, Frank M A; Engendahl, Barthel; Hölscher, Markus; Klankermayer, Jürgen; Leitner, Walter

2011-08-18

98

Extraction chemistry of fermentation product carboxylic acids  

SciTech Connect

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 pathways 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.

Kertes, A.S.; King, C.J.

1986-02-01

99

Extraction chemistry of fermentation product carboxylic acid  

SciTech Connect

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. 123 references.

Kertes, A.S.; King, C.J.

1986-02-01

100

Resolution of Carboxylic Acids Using Copper (I)-Promoted Removal of Propargylic Esters Under Neutral Conditions  

PubMed Central

A method for the optical resolution of carboxylic acids is described. Condensation of racemic carboxylic acids with chiral terminal propargyl alcohols gave separable diastereomeric esters. Chromatographic separation followed by heating the individual diastereomers in methanol with catalytic copper (I) halide regenerated the carboxylic acids in good yields and in enantiomeric ratios of ?94%. This method is particularly useful for the resolution of carboxylic acids that are incompatible with conventional ester hydrolysis.

Ghosh, Partha

2013-01-01

101

Resolution of carboxylic acids using copper(I)-promoted removal of propargylic esters under neutral conditions.  

PubMed

A method for the optical resolution of carboxylic acids is described. Condensation of racemic carboxylic acids with chiral terminal propargyl alcohols gave separable diastereomeric esters. Chromatographic separation followed by heating the individual diastereomers in methanol with catalytic copper(I) halide regenerated the carboxylic acids in good yields and in enantiomeric ratios of ?94%. This method is particularly useful for the resolution of carboxylic acids that are incompatible with conventional ester hydrolysis. PMID:21491889

Ghosh, Partha; Aubé, Jeffrey

2011-04-14

102

Extraction chemistry of fermentation product carboxylic acid  

Microsoft Academic Search

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,

A. S. Kertes; C. J. King

1986-01-01

103

Extraction chemistry of fermentation product carboxylic acids  

Microsoft Academic Search

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 pathways and glyoxylate bypass. With no exception,

A. S. Kertes; C. J. King

1986-01-01

104

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

USGS Publications Warehouse

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

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

1995-01-01

105

Hepatic metabolism of 3-oxoandrost-4-ene-17-carboxylic acid  

SciTech Connect

3-oxoandrost-4-ene-17..beta..-carboxylic acid (etienic acid), a likely catabolite of deoxycorticosterone, was synthesized in the radioactive form and injected intravenously into rats prepared with a biliary fistula. The biliary metabolites (77% of the dose) were isolated, separated into individual compounds, and identified by high-field /sup 1/H-NMR and by gas chromatographic comparison with standards. After deconjugation, aglycones were characterized by GC-MS. The administered etienic acid underwent full reduction, yielding three of the four possible distereomers: 3..cap alpha..- and 3..beta..-hydroxy-5..cap alpha..-etianic acids and 3..cap alpha..-hydroxy-5..beta..-etianic acid, accounting together for at least one third of the biliary radioactivity. In addition to the reduction, a sizeable fraction (> 25% of the recovered dose) underwent additional hydroxylation to at least two di- and one trihydroxy acid. Most (approx. 75%) of the recovered metabolites were present in conjugated form. Ester glucuronidation (conjugation on the steroidal carboxyl group) predominated, followed by ether glucuronidation (on a steroidal hydroxyl group). By the criteria of structure and biliary, rather than urinary, excretion, the saturated steroidal acids derived from etienic acid can be classified as short-chain bile acids. They conclude that degradation to short-chain bile acids followed by glucuronidation is likely to be an important catabolic pathway for certain steroid hormones.

Zimniak, P.; Radominska-Pyrek, A.; Little, J.M.; Lester, R.; Pyrek, J.S.

1986-05-01

106

40 CFR 721.10550 - Rare earth salt of a carboxylic acid (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Rare earth salt of a carboxylic acid (generic). 721...Substances § 721.10550 Rare earth salt of a carboxylic acid (generic). ...substance identified generically as rare earth salt of a carboxylic acid (PMN...

2013-07-01

107

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

Code of Federal Regulations, 2010 CFR

...false Carboxylic acids, (C6-C9) branched and linear. 721.2088 Section 721...2088 Carboxylic acids, (C6-C9) branched and linear. (a) Chemical substances...generically as carboxylic acids, (C6-C9) branched and linear (PMNs P-93-313,...

2009-07-01

108

Process for the generation of α,β-unsaturated carboxylic acids and esters using niobium catalyst  

Microsoft Academic Search

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 α,β-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

M. R. Gogate; J. J. Spivey; J. R. Zoeller

1999-01-01

109

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

Microsoft Academic Search

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

Makarand Ratnakav Gogate; James Jerome Spivey; Joseph Robert Zoeller

1999-01-01

110

New chiral anisotropic reagents for determining the absolute configuration of carboxylic acids  

Microsoft Academic Search

Enantiomers of phenylglycine dimethylamide (PGDA) and phenylglycine methyl ester (PGME) were prepared as the reagents for determining the absolute configuration of carboxyl acids of type I. Each enantiomer of PGDA and PGME was condensed with several carboxylic acids, the absolute configuration of which is known. The absolute configuration of the carboxylic acids, predicted by ?? values (?? = ?S ?

Yuriko Nagai; Takenori Kusumi

1995-01-01

111

Measurement of functionalised carbon nanotube carboxylic acid groups using a simple chemical process  

Microsoft Academic Search

Chemically functionalised single-walled carbon nanotubes were formed using sonication in a mixture of concentrated sulphuric and nitric acids for varying lengths of time which resulted in carboxylic acid group functionalisation, predominantly at the ends. The carboxylic acid groups were used to form an ionic bond with dodecylamine. The weight of this complex was used to monitor the number of carboxylic

Matthew W. Marshall; Simina Popa-Nita; Joseph G. Shapter

2006-01-01

112

Remarkable electronic and steric effects in the nitrile biotransformations for the preparation of enantiopure functionalized carboxylic acids and amides: implication for an unsaturated carbon-carbon bond binding domain of the amidase.  

PubMed

Biotransformations of various functionalized racemic nitriles catalyzed by Rhodococcus erythropolis AJ270, a nitrile hydratase/amidase-containing microbial whole-cell catalyst, were studied. While the nitrile hydratase exhibits high catalytic efficiency but very low enantioselectivity against almost all nitrile substrates examined, the amidase is very sensitive toward the structure of the amides. The release of the steric crowdedness around the stereocenter of the substrates and the introduction of an unsaturated carbon-carbon bond into the substrates led to the significant acceleration of the reaction rate and the dramatic enhancement of the enantioselectivity. Nitrile biotransformations provide a unique and high-yielding synthetic route to highly enantiopure carboxylic acids and amides functionalized with an allyl, propargyl, allenyl, or vinyl group. The synthetic applications have been demonstrated by the synthesis of enantiopure heterocyclic compounds including iodoenol gamma-lactone, gamma-lactam, and 3-allyl-1-phenyl-3,4-dihydro-1H-quinolin-2-one derivatives. PMID:17604398

Gao, Ming; Wang, De-Xian; Zheng, Qi-Yu; Huang, Zhi-Tang; Wang, Mei-Xiang

2007-06-30

113

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

114

Process for producing peracids from aliphatic hydroxy carboxylic acids  

DOEpatents

A process is disclosed for producing peracids from lactic acid-containing mixtures derived from biomass processing systems. The process includes adjusting the pH of the mixture to about 8 to 9 to form an alkaline precipitate. The alkaline precipitate is then removed therefrom to produce a residual solution containing lower aliphatic hydroxy acids. The residual solution is then oxidized continuously to produce gaseous lower aliphatic aldehydes. The gaseous aldehydes are removed immediately as they are generated to prevent further oxidation to carboxylic acids and are then converted to peracids.

Chum, H.L.; Palasz, P.D.; Ratcliff, M.

1986-05-16

115

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

2013-10-08

116

Integrated process for preparing a carboxylic acid from an alkane  

Microsoft Academic Search

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,

Abraham Benderly; Nitin Chadda; Douglass Sevon

2011-01-01

117

Chondrocyte behaviors on poly- l-lactic acid (PLLA) membranes containing hydroxyl, amide or carboxyl groups  

Microsoft Academic Search

Hydrophilic groups, i.e. hydroxyl (–OH), carboxyl (–COOH) or amide (–CONH2) were introduced onto the poly-l-lactic acid (PLLA) membrane surfaces via the photo-induced grafting copolymerization of the corresponding monomers, i.e. hydroxyethyl methacrylate, methacrylic acid or acrylamide, respectively. Chondrocyte culture was used to study the correlation between the cell behaviors and the hydrophilic functional groups. The results showed that the cytocompatibility of

Zuwei Ma; Changyou Gao; Yihong Gong; Jiacong Shen

2003-01-01

118

Human Odor Detection of Homologous Carboxylic Acids and Their Binary Mixtures  

Microsoft Academic Search

Does structural similarity of odorants influence detectability of their mixtures? To address this question, psychometric (probability of correct detection vs. concentration) functions were measured for aliphatic carboxylic acids and selected binary mixtures thereof. Unmixed stimuli included acetic (C2), butyric (C4), hexanoic (C6), and octanoic (C8) acids. Mixtures included C2 + C4 ,C 2 + C6, and C2 + C8. Vapor-phase

Paul M. Wise; Toshio Miyazawa; Michelle Gallagher; George Preti

2007-01-01

119

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

120

Ozone-driven daytime formation of secondary organic aerosol containing carboxylic acid groups and alkane groups  

NASA Astrophysics Data System (ADS)

Carboxylic acids are present in substantial quantities in atmospheric particles, and they play an important role in the physical and chemical properties of aerosol particles. During measurements in coastal California in the summer of 2009, carboxylic acid functional groups were exclusively associated with a fossil fuel combustion factor derived from factor analysis of Fourier transform infrared spectroscopic measurements and closely correlated with oxygenated organic factors from aerosol mass spectrometry measurements. The high fraction of acid groups and the high ratio of oxygen to carbon in this factor suggest that this factor is composed of secondary organic aerosol (SOA) products of combustion emissions from the upwind industrial region (the ports of Los Angeles and Long Beach). Another indication of the photochemically-driven secondary formation of this combustion-emitted organic mass (OM) was the daytime increase in the concentrations of acid groups and the combustion factors. This daytime increase closely tracked the O3 mixing ratio with a correlation coefficient of 0.7, indicating O3 was closely associated with the SOA maximum and thus likely the oxidant that resulted in acid group formation. Using a pseudo-Lagrangian framework to interpret this daytime increase of carboxylic acid groups and the combustion factors, we estimate that the carboxylic acid groups formed in a 12-h daytime period of one day ("Today's SOA") accounted for 25-33 % of the measured carboxylic acid group mass, while the remaining 67-75 % (of the carboxylic acid group mass) was likely formed 1-3 days previously (the "Background SOA"). A similar estimate of the daytime increase in the combustion factors suggests that "Today's SOA" and the "Background SOA" respectively contributed 25-50 % and 50-75 % of the combustion factor (the "Total SOA"), for a "Total SOA" contribution to the OM of 60 % for the project average. Further, size-resolved spectrometric and spectroscopic characterization of the particle OM indicate that the majority of the OM formed by condensation of gas-phase oxidation products. This unique set of measurements and methods to quantify and characterize photochemically and ozone-linked carboxylic acid group formation provide independent and consistent assessments of the secondary fraction of OM, which could result from second generation products of the oxidation of gas-phase alkane (molecules).

Liu, S.; Day, D. A.; Shields, J. E.; Russell, L. M.

2011-08-01

121

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

Code of Federal Regulations, 2013 CFR

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

2013-07-01

122

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.

TAKAHASHI, Kenji

2013-01-01

123

Biodegradation kinetics of trans-4-methyl-1-cyclohexane carboxylic acid.  

PubMed

Naphthenic acids are a complex mixture of organic compounds which naturally occur in crude oil. Low molecular weight components of the naphthenic acids are known to be toxic in aquatic environments and there is a need to better understand the factors controlling the kinetics of their biodegradation. In this study, a relatively low molecular weight naphthenic acid compound (trans-isomer of 4-methyl-1-cyclohexane carboxylic acid) and a microbial culture developed in our laboratory were used to study the biodegradation of this naphthenic acid and to evaluate the kinetics of the process in batch cultures. The initial concentration of trans-4-methyl-1-cyclohexane carboxylic acid (50-750 mg l(-1)) did not affect the maximum specific growth rate of the bacteria at 23 degrees C (0.52 day(-1)) to the maximum biodegradable concentration (750 mg l(-1)). The maximum yield observed at this temperature and at a neutral pH was 0.21 mg of biomass per milligram of substrate. Batch experiments indicated that biodegradation can be achieved at low temperatures; however, the biodegradation rate at room temperature (23 degrees C) and neutral pH was 5 times faster than that observed at 4 degrees C. Biodegradation at various pH conditions indicated a maximum specific growth rate of 1.69 day(-1) and yield (0.41 mg mg(-1)) at a pH of 10. PMID:18633718

Paslawski, Janice C; Headley, John V; Hill, Gordon A; Nemati, Mehdi

2008-07-17

124

Carboxylic acid microbial metabolites of the natural benzoquinone, maesanin  

PubMed

Maesanin (1) is a naturally occurring bioactive benzoquinone isolated from the fruits of Maesa lanceolata (Myrsinaceae). Three carboxylic acid metabolites of maesanin were isolated in the course of a prospective microbial transformation study. The first metabolite, 2, was produced by Lipomyces lipofer ATCC 10742 and was characterized as (Z)-15-(2'-hydroxy-5'-methoxy-3', 6'-dioxocyclohexa-1',4'-dienyl)pentadec-5-enoic acid. Metabolites 3 and 4 were produced by Rhodotorula rubra ATCC 20129 and were characterized as 6-(2'-hydroxy-5'-methoxy-3',6'-dioxocyclohexa-1', 4'-dienyl)hexanoic acid and 4-(2'-hydroxy-5'-methoxy-3', 6'-dioxocyclohexa-1',4'-dienyl)butanoic acid, respectively. PMID:10346952

Abourashed; El-Feraly; Hufford

1999-05-01

125

Sampling artifact estimates for alkanes, hopanes, and aliphatic carboxylic acids  

NASA Astrophysics Data System (ADS)

Sampling artifacts for molecular markers from organic speciation of particulate matter were investigated by analyzing forty-one samples collected in Philadelphia as a part of the Northeast Oxidant and Particulate Study (NEOPS). Samples were collected using a high volume sampler with two quartz fiber filters in series. n-Alkanes (C23-C31), hopanes (C27-C31), and n-alkanoic acids (C10-C22) were analyzed by gas chromatography-mass spectrometry (GCMS). The extent of artifact error was dependent on vapor pressure and species concentration. Particulate organic species are classified into the following three categories: (1) the amount collected on the backup filter was often a large fraction of the amount collected on the front filters ( n-alkanes C23 and C24, n-carboxylic acids C10-C14); (2) the amount collected on the backup filter was consistently a small fraction of the amount collected on the front filter ( n-alkanes C25-C28, hopanes C27-C30, n-carboxylic acids C15-C18, and dicarboxylic acids C3-C9); (3) the species was rarely observed on backup filters ( n-alkanes C29-C31, hopanes C31 and C32).

Sihabut, Tanasri; Ray, Joshua; Northcross, Amanda; McDow, Stephen R.

126

Synthesis and Characterization of New Functional Polyelectrolytes Based on Carboxyl Containing Methacrylates  

Microsoft Academic Search

Three new methacrylic monomers, 6-methacryloyloxyhexanoic acid, 6-(N-methacryloyl)aminohexanoic acid, and ethyl 6-(N-methacryloyl)-aminohexanoate, containing carboxyl groups spaced from the polymerizable double bond by a polymethylene chain, have been synthesized. Multifunctional polymeric materials were obtained by radical polymerization of these monomers with different vinyl monomers. The type and content of the functional groups was modulated on the basis of feed composition and the

Nicoletta Tamburro; Federica Chiellini; Roberto Solaro

2001-01-01

127

pH effects on catalytic ozonation of carboxylic acids with metal on metal oxides catalysts  

Microsoft Academic Search

Summary The pH influence on the catalytic ozonation of small carboxylic acids (succinic (SA), chloroacetic (CAA) and pyruvic (PA) acids) was studied and compared to ozonation alone. In the acidic systems, the conversion of these carboxylic acids and total organic carbon (TOC) during the catalytic ozonation is mainly due to the catalytic effect. Experiments on SA indicate that in the

Nathalie Karpel Vel Leitner; Hongxiang Fu

2005-01-01

128

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

129

Influence of vegetation on low-molecular-weight carboxylic acids in soil solution—a review  

Microsoft Academic Search

Low-molecular-weight (LMW) carboxylic acids found in soils and soil solutions comprise mainly aliphatic mono-, di- and tricarboxylic acids and substituted benzoic and cinnamic acids. This review compiles current information on the content of LMW carboxylic acids in soil solutions collected by centrifugation and in lysimeters, and soil extracts in relation to type of vegetation, soil type and soil depth. Contents

Bjarne W Strobel

2001-01-01

130

Catalysis of the Carbonylation of Alcohols to Carboxylic Acids Including Acetic Acid Synthesis from Methanol.  

ERIC Educational Resources Information Center

Monsanto's highly successful synthesis of acetic acid from methanol and carbon monoxide illustrates use of new starting materials to replace pretroleum-derived ethylene. Outlines the fundamental aspects of the acetic acid process and suggests ways of extending the synthesis to higher carboxylic acids. (JN)

Forster, Denis; DeKleva, Thomas W.

1986-01-01

131

Catalysis of the Carbonylation of Alcohols to Carboxylic Acids Including Acetic Acid Synthesis from Methanol.  

ERIC Educational Resources Information Center

|Monsanto's highly successful synthesis of acetic acid from methanol and carbon monoxide illustrates use of new starting materials to replace pretroleum-derived ethylene. Outlines the fundamental aspects of the acetic acid process and suggests ways of extending the synthesis to higher carboxylic acids. (JN)|

Forster, Denis; DeKleva, Thomas W.

1986-01-01

132

SYNTHESIS OF NOVEL HYDROPHILIC POLY(ESTER-CARBONATES) CONTAINING PENDENT CARBOXYLIC ACID GROUPS  

Microsoft Academic Search

A functional cyclic carbonate, 5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one (MBC), was utilized in the synthesis of novel poly(ester-carbonates) containing pendent carboxylic acid groups. Copolymers with ?-caprolactone (CL) and L-lactide (LLA) were synthesized by ring-opening polymerization (ROP) using either an Al-alkoxide (solution) or Sn(Oct)2-alcohol (bulk) initiating system. Analysis of the copolymers revealed a random distribution of the comonomer units along the polymer chain. The copolymers

Robson F. Storey; Brian D. Mullen; Kim M. Melchert

2001-01-01

133

Structure–activity relationship between carboxylic acids and T cell cycle blockade  

Microsoft Academic Search

This study was designed to examine the potential structure–activity relationship between carboxylic acids, histone acetylation and T cell cycle blockade. Toward this goal a series of structural homologues of the short-chain carboxylic acid n-butyrate were studied for their ability to block the IL-2-stimulated proliferation of cloned CD4+ T cells. The carboxylic acids were also tested for their ability to inhibit

Kathleen M. Gilbert; Annick DeLoose; Jimmie L. Valentine; E. Kim Fifer

2006-01-01

134

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

2008-12-26

135

Chiral solvating agents for cyanohydrins and carboxylic acids.  

PubMed

We have shown that a structure as simple as an ion pair of (R)- or (S)-mandelate and dimethylamminopyridinium ions possesses structural features that are sufficient for NMR enantiodiscrimination of cyanohydrins. Moreover, (1)H NMR data of cyanohydrins of known configuration obtained in the presence of the mandelate-dimethylaminopyridinium ion pair point to the existence of a correlation between chemical shifts and absolute configuration of cyanohydrins. Mandelate-DMAPH(+) ion pair and mandelonitrile form a 1:1 complex with an association constant of 338 M(-1) (DeltaG(0), -3.4 kcal/mol) for the (R)-mandelonitrile/(R)-mandelate-DMAPH(+) and 139 M(-1) (DeltaG(0), -2.9 kcal/mol) for the (R)-mandelonitrile/(S)-mandelate-DMAPH(+) complex. To understand the origin of enantiodiscrimination, the geometry optimization and energy minimization of the models of ternary complexes of (S)-mandelonitrile/(R)-mandelate/DMAPH(+) and (S)-mandelonitrile/(S)-mandelate/DMAPH(+) complexes was performed using DFT methodology (B3LYP) with the 6-31+G(d) basis set in Gaussian 3.0. Further, analysis of optimized molecular model obtained from theoretical studies suggested that (i) DMAP may be replaced with other amines, (ii) the hydroxyl group of mandelic acid is not necessary for stabilization of ternary complex and may be replaced with other groups such as methyl, (iii) the ion pair should form a stable ternary complex with any hydrogen-bond donor, provided its OH bond is sufficiently polarized, and (iv) alpha-H of racemic mandelic acid should also get resolved with optically pure mandelonitrile. These inferences were experimentally verified, which not only validated the proposed model but also led to development of a new chiral solvating agent for determination of ee of carboxylic acids and absolute configuration of aryl but not alkyl carboxylic acids. PMID:20704425

Moon, Lomary S; Pal, Mohan; Kasetti, Yoganjaneyulu; Bharatam, Prasad V; Jolly, Ravinder S

2010-08-20

136

[Photodegradation of perfluorinated carboxylic acids by 185 nm VUV light].  

PubMed

Perfluorinated carboxylic acids (PFCAs) especially perfluorooctanoic acid (PFOA) are a new type of persistent and bioaccumulative organic pollutants, and they have been widely detected in various environmental media. Photodegradation of five types of PFCAs i.e. PFOA, perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA) and perfluorobutanoic acid (PFBA) by 185 nm vacuum ultraviolet (VUV) were examined to develop an effective method to deal with PFCAs pollution. All five PFCAs degrade significantly under the irradiation of 185 nm light and fluoride ion correspondingly forms, though PFCAs hardly degrade under irradiation of 254 nm UV light. After 6h irradiation by 185 nm light, more than 60% of PFBA degrades, while other four PFCAs degrade more than 90%, and defluorination ratio range from 71% to 21% decreasing with increasing carbon atoms contained by PFCAs. Three reaction atmosphere i.e. nitrogen, air and oxygen have no significant effect on degradation and defluorination of PFCAs. LC/MS measurement shows, PFOA degrades to PFHpA, PFHxA, PFPeA and PFBA step by step. Under irradiation of 185 nm light, PFCA firstly is decarboxylated, and the radical thus formed reacts with water to form shorter-chain PFCA and fluoride ion. PMID:17639935

Chen, Jing; Zhang, Peng-Yi; Liu, Jian

2007-04-01

137

Mechanism of arylboronic acid-catalyzed amidation reaction between carboxylic acids and amines.  

PubMed

Arylboronic acids were found to be efficient catalysts for the amidation reactions between carboxylic acids and amines. Theoretical calculations have been carried out to investigate the mechanism of this catalytic process. It is found that the formation of the acyloxyboronic acid intermediates from the carboxylic acid and the arylboronic acid is kinetically facile but thermodynamically unfavorable. Removal of water (as experimentally accomplished by using molecular sieves) is therefore essential for overall transformation. Subsequently C-N bond formation between the acyloxyboronic acid intermediates and the amine occurs readily to generate the desired amide product. The cleavage of the C-O bond of the tetracoordinate acyl boronate intermediates is the rate-determining step in this process. Our analysis indicates that the mono(acyloxy)boronic acid is the key intermediate. The high catalytic activity of ortho-iodophenylboronic acid is attributed to the steric effect as well as the orbital interaction between the iodine atom and the boron atom. PMID:23381564

Wang, Chen; Yu, Hai-Zhu; Fu, Yao; Guo, Qing-Xiang

2013-04-01

138

Liquid membrane transport of amino acids by a calix[6]arene carboxylic acid derivative  

Microsoft Academic Search

Calix[6]arene hexacarboxylic acid was found to be a useful carrier for transporting amino acids through a liquid membrane. The calix[6]arene, which has a cyclic structure to include a guest molecule of the amino acid ester and bears six ionizable carboxylic acids to contribute electrostatic interaction, exhibited a high transport efficiency compared to its monomer analog and the other calix[n]arene derivatives.

Tatsuya Oshima; Katsutoshi Inoue; Shintaro Furusaki; Masahiro Goto

2003-01-01

139

Binding of carboxylic acids by fluorescent pyridyl ureas.  

PubMed

Fluorescent pyrid-2-yl ureas were prepared by treating halogenated 2-aminopyridines with hexyl isocyanate, followed by Sonogashira coupling with arylacetylenes. The sensors emit light of ?360 nm with quantum yields of 0.05-0.1 in acetonitrile solution. Addition of strong organic acids (pK(a) < 13 in CH(3)CN) shifts the fluorescence band to lower energy, and clean isoemissive behavior is observed. Fluorescence response curves (i.e., F/F(0) vs [acid](total)) are hyperbolic in shape for CCl(3)COOH and CF(3)COOH, with association constants on the order of 10(3) M(-1) for both acids. (1)H NMR titrations and DFT analyses indicate that trihaloacetic acids bind in ionized form to the receptors. Pyridine protonation disrupts an intramolecular H-bond, thereby unfolding an array of ureido NH donors for recognition of the corresponding carboxylates. Methanesulfonic acid protonates the sensors, but no evidence for conjugate base binding at the urea moiety is found by NMR. An isosteric control compound that lacks an integrated pyridine does not undergo significant fluorescence changes upon acidification. PMID:21080667

Jordan, Lisa M; Boyle, Paul D; Sargent, Andrew L; Allen, William E

2010-11-16

140

Influence of carboxylic-acid structure on the kinetics of electrode processes occurring during Kolbe electrosynthesis  

SciTech Connect

The influence of carboxylic-acid structure on the kinetics of electrode processes occurring during Kolbe electrosynthesis was studied, and shown to produce changes in the rates of destructive chemisorption and destructive oxidation of the carboxylic acid, in the competition for the platinum electrode surface between the solvent and the carboxylate anions at high anode potentials, and in the routes of radical reactions because of changes in the nature of the radical formed.

Lotvin, B.M.; Vasil'ev, Yu.B.

1987-02-01

141

Hydrolysis of tocopheryl and retinyl esters by porcine carboxyl ester hydrolase is affected by their carboxylate moiety and bile acids  

Microsoft Academic Search

The objective of this study was to examine the in vitro hydrolysis of vitamin E esters (?-tocopheryl acetate, ?-tocopheryl succinate and ?-tocopheryl nicotinate) by pancreatic carboxyl ester hydrolase (CEH) at the concurrent presence of different bile acids at different concentrations. The assay was performed by measuring the amount of ?-tocopherol released by porcine pancreatic juice upon addition to different solutions

Charlotte Lauridsen; Mette S. Hedemann; Søren K. Jensen

2001-01-01

142

Ring–Chain Isomeric Conversions of Aldehydo-carboxylic and Keto-carboxylic Acids and Their Derivatives  

Microsoft Academic Search

Ring–chain isomeric (including tautomeric) conversions of aldehydo- and keto-carboxylic acids and their chlorides, amides, hydrazides, esters, and mixed anhydrides are reviewed. The possibilities of using physical methods (ultraviolet, infrared, and proton magnetic resonance spectroscopy) for the identification and quantitative determination of isomers are discussed. The effect of structural factors on the relative stability of isomers is analysed. Conditions are elicited

R E Valter

1973-01-01

143

Bichromophoric fluorescent photolabile protecting group for alcohols and carboxylic acids.  

PubMed

Novel bichromophoric fluorescent photolabile protecting group, (5-dansyloxy-3-hydroxynaphthalen-2-yl)methyl (DNS-NQMP), allows for the independent photochemical release and fluorescent imaging of caged substrates. Irradiation of DNS-NQMP-caged alcohols and carboxylic acids with 300 or 350 nm light results in fast (k(release) ~ 10(5) s(-1)), efficient (? = 0.2), and quantitative release of the substrates. This uncaging chemistry is compatible with aqueous media and DNS-NQMP-protected hydroxy compounds are hydrolytically stable at neutral pH. Upon excitation with 400 nm light, caged compounds show intense green emission (?(max) = 559 nm) with 21% fluorescence quantum yield. Fluorescent readout conducted using 400 nm or longer wavelengths does not cause substrate release. The DNS-NQMP chromophore retains its fluorescent properties after photo-uncaging reaction. PMID:22186939

Arumugam, Selvanathan; Popik, Vladimir V

2011-12-21

144

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

145

Carbon paste electrode spiked with ferrocene carboxylic acid and its application to the electrocatalytic determination of ascorbic acid  

Microsoft Academic Search

A carbon paste electrode spiked with ferrocene carboxylic acid (FCAMCPE) was constructed by incorporation of ferrocene carboxylic acid in a graphite powder–paraffin oil matrix. It has been shown by direct current cyclic voltammetry and double step chronoamperometry that this electrode can catalyze the oxidation of ascorbic acid in aqueous buffered solution. It has been found that under optimum conditions (pH

Jahan-Bakhsh Raoof; Reza Ojani; Abolfazl Kiani

2001-01-01

146

Theoretical study of excited state proton transfer in pyrrole-2-carboxylic acid  

Microsoft Academic Search

Pyrrole 2-carboxylic acid (PCA) shows dual emission (310 nm and 430 nm) in water on photo-excitation, which indicates that more than one species is in the excited state. This paper reports on the quantum chemical analysis of pyrrole 2-carboxylic acid (PCA) in the light of a possible excited state proton transfer. Dipole moment, excited state energy and findings in molecular

Dibakar Sahoo; Tirthapratim Adhikary; Papia Chowdhury; Sankar Chakravorti

2008-01-01

147

Kinetics and Mechanism of Triphenylphosphine Quarternization with Unsaturated Carboxylic Acids in Various Media  

Microsoft Academic Search

Reactions of tertiary phosphines with unsaturated electrophilic reagents are widely used in synthetic organic chemistry. Typical satellites of these transformations are proton migration processes, which can play decisive role in such reactions. To learn more about proton transfer mechanism, kinetics of reaction of triphenylphosphine with a series of unsaturated carboxylic acids in alcohols, carboxylic acids, and aprotic solvents was studied

Alexey V. Salin; Alexandr A. Sobanov; Yulia V. Bakhtiyarova; Azat A. Khabibullin; Vladimir I. Galkin; Rafael A. Cherkasov

2011-01-01

148

Direct Condensation of Carboxylic Acids with Alcohols Catalyzed by Hafnium(IV) Salts  

Microsoft Academic Search

In order to promote atom efficiency in synthesis and to avoid the generation of environmental waste, the use of stoichiometric amounts of condensing reagents or excess substrates should be avoided. In esterification, excesses of either carboxylic acids or alcohols are normally needed. We show that the direct condensation of equimolar amounts of carboxylic acids and alcohols can be achieved with

Kazuaki Ishihara; Suguru Ohara; Hisashi Yamamoto

2000-01-01

149

Thermochemistry of aqueous pyridine-3-carboxylic acid (nicotinic acid)  

Microsoft Academic Search

The molar enthalpy of solution of solid nicotinic acid (NA) at T=298.15K, to give an aqueous solution of molality m=3.748·10?3mol·kg?1, was determined as ?solHm=(19,927±48)J·mol?1, by solution calorimetry. Enthalpies of dilution, ?dilHm, of 0.1005mol·kg?1 aqueous nicotinic acid to yield final solutions with molality in the approximate range (0.03 to 0.09)mol·kg?1 were also measured by flow calorimetry. Combining the two sets of

Elsa M. Gonçalves; Talita S. Rego; Manuel E. Minas da Piedade

2011-01-01

150

3-Oxocyclo-butane-carboxylic acid: hydrogen bonding in a small-ring ?-keto acid  

PubMed Central

The title ketocarboxylic acid, C5H6O3, is the smallest carboxy­cyclanone to have its crystal structure determined. It adopts a chiral conformation, by rotation of its carboxyl O atoms away from the plane of skeletal symmetry that passes through the carboxyl carbon and both atoms of the ketone carbonyl. The four-membered ring is non-planar, with a shallow fold of 14.3?(1)° along a line connecting the two ?-carbons of the ketone group. In the crystal, the molecules are linked by centrosymmetric hydrogen-bond pairing of ordered carboxylic acid groups [O?O = 2.6392?(12)?Å and O—H?O = 175.74?(15)°], yielding two different sets of dimers, related by by a 21 screw axis in c, in the cell. A C—H?O interaction is also present.

Efthimiopoulos, Georgia; Thompson, Hugh W.; Lalancette, Roger A.

2009-01-01

151

Structural and biochemical study on the inhibitory activity of derivatives of 5-nitro-furan-2-carboxylic acid for RNase H function of HIV1 reverse transcriptase  

Microsoft Academic Search

Rapid emergence of drug-resistant variants is one of the most serious problems in chemotherapy for HIV-1 infectious diseases. Inhibitors acting on a target not addressed by approved drugs are of great importance to suppress drug-resistant viruses. HIV-1 reverse transcriptase has two enzymatic functions, DNA polymerase and RNase H activities. The RNase H activity is an attractive target for a new

Hiroshi Yanagita; Emiko Urano; Kishow Matsumoto; Reiko Ichikawa; Yoshihisa Takaesu; Masakazu Ogata; Tsutomu Murakami; Hongui Wu; Joe Chiba; Jun Komano; Tyuji Hoshino

2011-01-01

152

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

153

Synthesis and characterization of (4S)-1-chloroalkylsilatrane-4-carboxylic acids; cruytal structures of (3R,4S)-1-chloromethyl-3-methylsilatrane-4-carboxylic acid and (3R,4S)-1-(3-chloropropyl)-3-methylsilatrane-4-carboxylic acid  

Microsoft Academic Search

(4S)-1-(chloromethyl)silatrane-4-carboxylic acid 1 and (3R,4S)-1-chloromethyl-3-methylsilatrane-4-carboxylic acid 2 were synthesized by the transesterification of chlormethyltriethoxysilane with l-N,N-bis(2-hydroxyenthyl)serine or l-N,N-bis(2-hydroxyethy)threonine in teh presence of pyridine. (4S)-1-(3-chloropropyl)silatrane-4-caroxylic acid 3 and (3R,4S)-1-(3-chloropropyl)-3-methylsilstrane-4-carboxylic acid 4 were similarly synthesized from the reaction of 3-chloropropyltrimethoxysilane with the chiral ligands. The compounds were characterized by elemental analyses, IR spectra, 1H and 13C NMR spectra and mass spectra. The

Zheng-Rong Lu; Ren-Xi Zhuo; Liao-Rong Shen; Xiao-Dong Zhang; Lian-Fang Shen

1995-01-01

154

Influence of carboxylic acid functionalities in ruthenium (II) polypyridyl complexes on DNA binding, cytotoxicity and antioxidant activity: synthesis, structure and in vitro anticancer activity.  

PubMed

Four new Ru(II) complexes [RuHCl(bpy)(PPh(3))(CO)] (1), [RuHCl(bpy)(AsPh(3))(CO)] (2) (bpy = 2,2'-bipyridine), [RuCl(HL)(PPh(3))(2)(CO)] (3) and [RuCl(HL)(AsPh(3))(2)(CO)] (4) (HL = 2,2'-bipyridine-4,4'-dicarboxylic acid) were synthesized and characterized. X-ray diffraction was used to characterize 3 in solid state. The interactions of these complexes with DNA were explored by different techniques which revealed that the complexes could bind to CT-DNA through non-intercalation. The in vitro cytotoxic and antioxidant activities of the complexes validated against a panel of cancer cell lines and free radicals showed that 3 and 4 possess quite high anticancer and antioxidant activities over 1, 2 and standard drugs. An apparent dependence of biological activities on incorporation of COOH in bipyridine moiety was noticed: Inclusion of COOH caused significant differences in DNA binding, cytotoxicity and antioxidant activity. PMID:23234855

Sathiya Kamatchi, Thangavel; Chitrapriya, Nataraj; Kim, Seog K; Fronczek, Frank R; Natarajan, Karuppannan

2012-11-27

155

Orthogonally protected imidazolidine-2-carboxylic acid, a new proline surrogate suitable for SPPS  

Microsoft Academic Search

N-Boc-N?-Fmoc-imidazolidine-2-carboxylic acid, easily prepared from N-Boc-N?-Fmoc-ethylenediamine and glyoxylic acid, is a racemic proline surrogate which can be used in Solid Phase Peptide Synthesis.

Loïc René; Loïc Yaouancq; Bernard Badet

1998-01-01

156

Novel S-adenosyl- l-methionine:salicylic acid carboxyl methyltransferase, an enzyme responsible for biosynthesis of methyl salicylate and methyl benzoate, is not involved in floral scent production in snapdragon flowers  

Microsoft Academic Search

Using a functional genomic approach we have isolated and characterized a cDNA that encodes a salicylic acid carboxyl methyltransferase (SAMT) from Antirrhinum majus. The sequence of the protein encoded by SAMT has higher amino acid identity to Clarkia breweri SAMT than to snapdragon benzoic acid carboxyl methyltransferase (BAMT) (55 and 40% amino acid identity, respectively). Escherichia coli-expressed SAMT protein catalyzes

Florence Negre; Natalia Kolosova; Joseph Knoll; Christine M Kish; Natalia Dudareva

2002-01-01

157

Carboxyl pK(a) values and acid denaturation of BBL.  

PubMed

The protein BBL undergoes structural transitions and acid denaturation between pH 1.2 and 8.0. Using NMR spectroscopy, we measured the pK(a) values of all the carboxylic residues in this pH range. We employed (13)C direct-detection two-dimensional IPAP (in-phase antiphase) CACO NMR spectroscopy to monitor the ionization state of different carboxylic groups and demonstrated its advantages over other NMR techniques in measuring pK(a) values of carboxylic residues. The two residues Glu161 and Asp162 had significantly lowered pK(a) values, showing that these residues are involved in a network of stabilizing electrostatic interactions, as is His166. The other carboxylates had unperturbed values. The pH dependence of the free energy of denaturation was described quantitatively by the ionizations of those three residues of perturbed pK(a), and, using thermodynamic cycles, we could calculate their pK(a)s in the native and denatured states as well as the equilibrium constants for denaturation of the different protonation states. We also measured (13)C(?) chemical shifts of individual residues as a function of pH. These shifts sense structural transitions rather than ionizations, and they titrated with pH consistent with the change in equilibrium constant for denaturation. Kinetic measurements of the folding of BBL E161Q indicated that, at pH 7, the stabilizing interactions with Glu161 are formed mainly in the transition state. We also found that local interactions still exist in the acid-denatured state of BBL, which attenuate somewhat the flexibility of the acid-denatured state. PMID:20816989

Arbely, Eyal; Rutherford, Trevor J; Neuweiler, Hannes; Sharpe, Timothy D; Ferguson, Neil; Fersht, Alan R

2010-09-15

158

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

159

Electrochemical sensor based on molecularly imprinted polymer film via sol-gel technology and multi-walled carbon nanotubes-chitosan functional layer for sensitive determination of quinoxaline-2-carboxylic acid.  

PubMed

Quinoxaline-2-carboxylic acid (QCA) is difficult to measure since only trace levels are present in commercial meat products. In this study, a rapid, sensitive and selective molecularly imprinted electrochemical sensor for QCA determination was successfully constructed by combination of a novel modified glassy carbon electrode (GCE) and differential pulse voltammetry (DPV). The GCE was fabricated via stepwise modification of multi-walled carbon nanotubes (MWNTs)-chitosan (CS) functional composite and a sol-gel molecularly imprinted polymer (MIP) film on the surface. MWNTs-CS composite was used to enhance the electron transfer rate and expand electrode surface area, and consequently amplify QCA reduction electrochemical response. The imprinted mechanism and experimental parameters affecting the performance of MIP film were discussed in detail. The resulting MIP/sol-gel/MWNTs-CS/GCE was characterized using various electrochemical methods involving cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and DPV. The sensor using MIP/sol-gel/MWNTs-CS/GCE as working electrode showed a linear current response to the target QCA concentration in the wide range from 2.0×10(-6) to 1.0×10(-3)molL(-1) with a low detection limit of 4.4×10(-7)molL(-1) (S/N=3). The established sensor with excellent reproductivity and stability was applied to evaluate commercial pork products. At five concentration levels, the recoveries and standard deviations were calculated as 93.5-98.6% and 1.7-3.3%, respectively, suggesting the proposed sensor is promising for the accurate quantification of QCA at trace levels in meat samples. PMID:23624016

Yang, Yukun; Fang, Guozhen; Liu, Guiyang; Pan, Mingfei; Wang, Xiaomin; Kong, Lingjie; He, Xinlei; Wang, Shuo

2013-04-02

160

Hydrolytic decarboxylation of carboxylic acids and the formation of protonated carbonic acid.  

PubMed

Acid-catalyzed decarboxylation reactions of carboxylic acids should avoid formation of protonated carbon dioxide, a very high energy species. A potential alternative route parallels ester hydrolysis, with addition of water to the carboxyl group followed by protonation of the unsaturated leaving group and formation of protonated carbonic acid, a species that had been predicted to be a viable reaction intermediate. The hydrolytic mechanism for the decarboxylation of pyrrole-2-carboxylic acid is consistent with observed (12)C/(13)C kinetic isotope effects (1.010 +/- 0.001 at H(0) = -0.01 and 1.043 +/- 0.001 at H(0) = -2.6), solvent kinetic isotope effects (k(H(2))(O)/k(D(2))(O) = 2 at H(0) = 0.9; k(H(2))(O)/k(D(2))(O) = 1 at H(0) = -2.9), and activation parameters [DeltaH() = 23.5 kcal.mol(-1) and DeltaS() = 5.5 cal.deg(-1).mol(-1) at H(0) = -2.9]. Thus, the specific route for a decarboxylation process is a consequence of the nature of the potential carbanion (or its conjugate acid), the acidity of the medium and avoidance of formation of protonated carbon dioxide. PMID:20121187

Mundle, Scott O C; Lacrampe-Couloume, Georges; Lollar, Barbara Sherwood; Kluger, Ronald

2010-02-24

161

Adsorption of gaseous formaldehyde and carboxylic acids by ammonium-ion-exchanged ?-zirconium phosphate  

Microsoft Academic Search

Ammonium-ion-exchanged ?-Zr(HPO4)2?H2O (?-ZrP) was obtained as a single phase with the interlayer distance of 9.4 Å by the ion-exchange of proton with ammonium ion. The ammonium ion-exchanged ?-ZrP could adsorb ill-smelling gases, such as formaldehyde and carboxylic acids (formic acid, acetic acid, propionic acid, and butyric acid). The adsorption amounts of carboxylic acids increased in the order, butyric acidacid

A. Hayashi; Y. Fujimoto; Y. Ogawa; H. Nakayama; M. Tsuhako

2005-01-01

162

Rapid and efficient oxidative decarboxylation of carboxylic acids with sodium periodate catalyzed by manganese (III) Schiff base complexes.  

PubMed

Rapid and efficient oxidative decarboxylatoin of alpha-aryl carboxylic acids was observed. In the chemical system containing Mn(III)-salophen complex as catalyst, carboxylic acids are converted efficiently to the corresponding carbonyl derivatives with sodium periodate. The ability of various Schiff base complexes in the oxidative decarboxylation of carboxylic acids was also investigated. PMID:14980602

Mirkhani, Valiollah; Tangestaninejad, Shahram; Moghadam, Majid; Moghbel, Maryam

2004-03-01

163

Separation and direct UV detection of lanthanides complexed with pyridine-2-carboxylic acid by capillary electrophoresis  

Microsoft Academic Search

Separation and detection of lanthanides by capillary zone electrophoresis in the presence of pyridine-2-carboxylic acid (picolinic acid) as UV-absorbing complexing agent were investigated. The resolution of partially complexed positively charged complexes is improved by using two buffer ligands competing with picolinic acid for metal ions. When hydroxyisobutyric acid (HIBA) and formic acid are used together as competing ligands, this provides

Nevin Öztekin; F. Bedia Erim

2001-01-01

164

Proton-transfer-reaction mass spectrometry (PTR-MS) of carboxylic acids  

Microsoft Academic Search

Proton-transfer-reaction mass spectrometry (PTR-MS) was used as an analytical tool to measure gas-phase concentrations of short-chain fatty acids. Chemical ionisation of C2C6 carboxylic acids by PTR-MS produced intense protonated molecular ions (with traces of hydrates) along with acylium ion fragments. Gas-phase concentrations were derived using the established method for calculating PTR-MS sensitivity factors. Henry's law constants of carboxylic acids for

Eugen von Hartungen; Armin Wisthaler; Tomas Mikoviny; Dagmar Jaksch; Elena Boscaini; Patrick J. Dunphy; Tilmann D. Märk

2004-01-01

165

Calculation of p K a values of carboxylic acids: Application to bilirubin  

Microsoft Academic Search

One of the major factors in the interactions of proteins with other molecules is the dissociation constant for a weakly acidic or basic group, generally expressed as the pKa. We have critically evaluated various quantum mechanical (QM) methods for calculation of protonation states of carboxylic acids including bilirubin. We calculated pKa values of various carboxylic acids by using quantum-chemical calculations

Rok Borštnar; Amrita Roy Choudhury; Jernej Stare; Marjana Novi?; Janez Mavri

2010-01-01

166

Chiral trans -1,2-diaminocyclohexane derivatives as chiral solvating agents for carboxylic acids  

Microsoft Academic Search

Efficient use of the readily accessible chiral C\\u000a 2-symmetric acyclic diamines (1–2) as well as macrocyclic amines (3–5) containing trans-1,2-diaminocyclohexyl moiety as chiral solvating agents (CSA) for the determination of enantiomeric excess of representative\\u000a carboxylic acids (6–7) and an amino acid derivative (8) is illustrated. The enantiomeric composition of different carboxylic acids estimated here by the 1H NMR method, based

Mariappan Periasamy; Manasi Dalai; Meduri Padmaja

2010-01-01

167

Gustatory responses of eel palatine receptors to amino acids and carboxylic acids  

PubMed Central

The gustatory receptors of the eel palate were found to be extremely sensitive to amino acids and carboxylic acids. The results obtained are as follows: (a) 11 amino acids which are among naturally occurring amino acids elicited responses in the palatine nerve, but 9 amino acids did not elicit a response even at a high concentration. The effect of D- amino acids was always much less than that of their corresponding L- isomers. There was no appreciable difference in the effectiveness of an alpha-amino acid (alpha-alanine) and beta-amino acid (beta-alanine). (b) The threshold concentrations of the most potent amino acids (arginine, glycine) were between 10(-8) and 10(-9) M. A linear relation between the magnitude of the response and log stimulus concentration held for a wide concentration range for all the amino acids examined. (c) The palatine receptors responded sensitively to various carboxylic acid solutions whose pH was adjusted to neutral. The threshold concentrations varied between 10(-4) and 10(-7) M. The magnitude of the response at 10(-2) M increased with an increase of carbon chain length. (d) The extent of cross-adaptation was examined with various combinations of amino acids. A variety of the response patterns showing complete cross-adaptation, no cross-adaptation, or synergetic interaction was observed. The synergetic interaction was also observed when one amino acid below its threshold concentration was added to the other amino acid below its threshold concentration was added to the other amino acid. No cross-adaptation was observed between amino acids and fatty acids. (e) The treatment of the palate with papain led to loss of the responses to arginine, glycine, and histidine without affecting those to proline and acetic acid. The treatment with pronase E eliminated selectively the response to proline. The possibility that the eel gustatory receptors are responsible for sensing food at a distance was discussed.

1979-01-01

168

Surface Functionalization of Poly(ethylene terephthalate) Film and Membrane by Controlled Wet Chemistry: Chemical Characterization of Carboxylated Surfaces  

Microsoft Academic Search

Surface functionalization of poly(ethylene terephthalate) (PET) film or track-etched membrane was performed using the methods of organic synthesis conducted at the solid-liquid interface. Basic hydrolysis in aqueous acetonitrile followed by permanganate oxidation in diluted sulfuric acid created new carboxylic chain-ends. These reactive functions were assayed as follows: (i) activation with water soluble carbodiimide; (ii) coupling to 3 H-labeled amino acids;

Jacqueline Marchand-Brynaert; Michéle Deldime; Isabelle Dupont; Jean-Luc Dewez; Yves-Jacques Schneider

1995-01-01

169

Low molecular weight carboxylic acids in oxidizing porphyry copper tailings.  

PubMed

The distribution of low molecular weight carboxylic acids (LMWCA) was investigated in pore water profiles from two porphyry copper tailings impoundments in Chile (Piuquenes at La Andina and Cauquenes at El Teniente mine). The objectives of this study were (1) to determine the distribution of LMWCA, which are interpreted to be the metabolic byproducts of the autotroph microbial community in this low organic carbon system, and (2) to infer the potential role of these acids in cycling of Fe and other elements in the tailings impoundments. The speciation and mobility of iron, and potential for the release of H+ via hydrolysis of the ferric iron, are key factors in the formation of acid mine drainage in sulfidic mine wastes. In the low-pH oxidation zone of the Piuquenes tailings, Fe(III) is the dominant iron species and shows high mobility. LMWCA, which occur mainly between the oxidation front down to 300 cm below the tailings surface at both locations (e.g., max concentrations of 0.12 mmol/L formate, 0.17 mmol/L acetate, and 0.01 mmol/L pyruvate at Piuquenes and 0.14 mmol/L formate, 0.14 mmol/L acetate, and 0.006 mmol/L pyruvate at Cauquenes), are observed at the same location as high Fe concentrations (up to 71.2 mmol/L Fe(II) and 16.1 mmol/L Fe(III), respectively). In this zone, secondary Fe(III) hydroxides are depleted. Our data suggest that LMWCA may influence the mobility of iron in two ways. First, complexation of Fe(III), through formation of bidentate Fe(III)-LMWCA complexes (e.g., pyruvate, oxalate), may enhance the dissolution of Fe(III) (oxy)hydroxides or may prevent precipitation of Fe(III) (oxy)hydroxides. Soluble Fe(III) chelate complexes which may be mobilized downward and convert to Fe(II) by Fe(III) reducing bacteria. Second, monodentate LMWCA (e.g., acetate and formate) can be used by iron-reducing bacteria as electron donors (e.g., Acidophilum spp.), with ferric iron as the electron acceptor. These processes may, in part, explain the low abundances of secondary Fe(III) hydroxide precipitates below the oxidation front and the high concentrations of Fe(II) observed in the pore waters of some low-sulfide systems. The reduction of Fe(III) and the subsequent increase of iron mobility and potential acidity transfer (Fe(II) oxidation can result in the release of H+ in an oxic environment) should be taken in account in mine waste management strategies. PMID:15884343

Dold, Bernhard; Blowes, David W; Dickhout, Ralph; Spangenberg, Jorge E; Pfeifer, Hans-Rudolf

2005-04-15

170

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

171

Biosynthesis of quinoxaline antibiotics: Purification and characterization of the quinoxaline-2-carboxylic acid activating enzyme from Streptomyces triostinicus  

SciTech Connect

A quinoxaline-2-carboxylic acid activating enzyme was purified to homogeneity from triostin-producing Streptomyces triostinicus. It could also be purified from quinomycin-producing Streptomyces echinatus. Triostins and quinomycins are peptide lactones that contain quinoxaline-2-carboxylic acid as chromophoric moiety. The enzyme catalyzes the ATP-pyrophosphate exchange reaction dependent on quinoxaline-2-carboxylic acid and the formation of the corresponding adenylate. Besides quinoxaline-2-carboxylic acid, the enzyme also catalyzes the formation of adenylates from quinoline-2-carboxylic acid and thieno(3,2-b)pyridine-5-carboxylic acid. No adenylates were seen from quinoline-3-carboxylic acid, quinoline-4-carboxylic acid, pyridine-2-carboxylic acid, and 2-pyrazinecarboxylic acid. Previous work revealed that quinoline-2-carboxylic acid and thieno(3,2-b)pyridine-5-carboxylic acid became efficiently incorporated into the corresponding quinoxaline antibiotic analogues in vivo. Together with the data described here, this suggests that the enzyme is part of the quinoxaline antibiotics synthesizing enzyme system. The enzyme displays a native molecular weight of 42,000, whereas in its denatured form it is a polypeptide of Mr 52,000-53,000. It resembles in its behavior actinomycin synthetase I, the chromophore activating enzyme involved in actinomycin biosynthesis.

Glund, K.; Schlumbohm, W.; Bapat, M.; Keller, U. (Technische Universitaet Berlin (Germany, F.R.))

1990-04-10

172

The Effects of Borate Minerals on the Synthesis of Nucleic Acid Bases, Amino Acids and Biogenic Carboxylic Acids from Formamide  

NASA Astrophysics Data System (ADS)

The thermal condensation of formamide in the presence of mineral borates is reported. The products afforded are precursors of nucleic acids, amino acids derivatives and carboxylic acids. The efficiency and the selectivity of the reaction was studied in relation to the elemental composition of the 18 minerals analyzed. The possibility of synthesizing at the same time building blocks of both genetic and metabolic apparatuses, along with the production of amino acids, highlights the interest of the formamide/borate system in prebiotic chemistry.

Saladino, Raffaele; Barontini, Maurizio; Cossetti, Cristina; di Mauro, Ernesto; Crestini, Claudia

2011-08-01

173

The Sorption of Anthracene onto Goethite and Kaolinite in the Presence of Some Benzene Carboxylic Acids  

Microsoft Academic Search

The uptake of anthracene from dilute aqueous solutions onto goethite and kaolinite was investigated at 25°C, first in the absence and then in the presence of three benzene carboxylic acids: phthalic acid (benzene-1,2-dicarboxylic acid), trimesic acid (–1,3,5–), and mellitic acid (–1,2,3,4,5,6–). Carboxylic acid concentrations were 0.20, 0.10, and 0.05 mM. Anthracene (0.20 ?M) did not adsorb strongly onto the pure

Michael J. Angove; Milena B. Fernandes; Jaslin Ikhsan

2002-01-01

174

Protonic polymer gel electrolytes based on carboxylic acids: ortho and inductive effects  

Microsoft Academic Search

The conductivity of polymer gel electrolytes containing three aromatic and three aliphatic carboxylic acids has been studied, viz. (i) ortho-, meta- and para-hydroxybenzoic acids and (ii) oxalic, malonic and succinic acids. Polymeric gels were prepared by adding different wt% of polymer poly(methylmethacrylate) (PMMA) in solutions of respective acids in high dielectric constant organic solvent mixtures of propylene carbonate, ethylene carbonate

S. S. Sekhon; N. Arora; B. Singh; S. Chandra

2002-01-01

175

Iron-catalyzed decarbonylation reaction of aliphatic carboxylic acids leading to ?-olefins.  

PubMed

The catalytic decarbonylation reaction of aliphatic carboxylic acids can be carried out in the presence of an iron complex, and it proceeds smoothly to give ?-olefins with high selectivity. PMID:22286391

Maetani, Shinji; Fukuyama, Takahide; Suzuki, Nobuyoshi; Ishihara, Daisuke; Ryu, Ilhyong

2012-01-30

176

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

National Technical Information Service (NTIS)

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 remo...

J. N. Starr C. J. King

1991-01-01

177

The Synthesis of Carboxylic Acids via an Aldol-Grob Reaction Sequence  

Microsoft Academic Search

Ketones react with aromatic aldehydes via a tandem Aldol-Grob reaction sequence. The reaction, initiated by boron trifluoride, produces a carboxylic acid fragment and can serve as an alternative to the Baeyer-Villiger reaction.

G. W. Kabalka; N.-S. Li; D. Tejedor; R. R. Malladi; X. Gao; S. Trotman

1999-01-01

178

Role of the carboxylic group in the antispasmodic and vasorelaxant action displayed by kaurenoic acid.  

PubMed

The present work describes the investigation of the role of the carboxylic group in the structure-activity relationship of the diterpene ent-kaur-16-en-19-oic acid (kaurenoic acid, KA) in inhibiting rat aorta contraction. For this purpose the methylation of the C-19 carboxyl group of KA was carried out. The effects of the obtained ent-methyl-kaur-16-en-19-oate (KAMe) were compared with those induced by KA. Vascular reactivity experiments showed that KA (50 and 100 microM) concentration-dependently inhibited KCl-induced contraction in both endothelium-intact and denuded rat aortic rings. On the other hand, KAMe attenuated KCl-induced contraction at 100 microM, but not at 50 microM. KA also reduced CaCl(2)-induced contraction in Ca(2+)-free solution containing KCl (30 mM). Again, KAMe produced a less accentuated reduction in CaCl(2)-induced contraction than that induced by the acid KA. KAMe (1-450 microM) concentration-dependently relaxed KCl-pre-contracted rings (percentages of relaxation 82.57 +/- 1.65 and 70.55 +/- 4.71, respectively) with denuded endothelium. Similarly, the relaxation induced by KA on phenylephrine (Phe)-pre-contracted rings (73.06 +/- 3.68%) was more pronounced than that found for KAMe (53.68 +/- 4.75%). Pre-incubation of denuded rings for different periods with KA and KAMe showed that the equilibrium periods required by each compound to achieve its maximal inhibitory response on KCl-induced contraction are different. Collectively, our results provide functional evidence that methylation of the C-19 carboxyl group of KA reduces but does not abolish the antispasmodic activity displayed by KA. Additionally, we showed that the equilibrium period is a critical step for the inhibitory effect displayed by kaurane-type diterpenes. PMID:15525447

Ambrosio, Sergio R; Tirapelli, Carlos R; Coutinho, Silvia T; de Oliveira, Dionéia C R; de Oliveira, Ana M; Da Costa, Fernando B

2004-11-01

179

Removal of heavy metals in plating wastewater using carboxylated alginic acid  

Microsoft Academic Search

Potentially, biosorption is an economic process for metal sequestering from water. Carboxylated alginic acid showed high uptake\\u000a capacities for heavy metals of 5-6 meq\\/g dry mass. For application to actual plating waste-water, the carboxylated alginic\\u000a acid was immobilized using PVA. In order to remove chelating or organic materials in plating wastewater, oxidation using sodium\\u000a hypochlorite was performed as a pretreatment.

Choong Jeon; Jae Yeon Park; Young Je Yoo

2001-01-01

180

Routine high-performance liquid chromatographic determination of carboxylic acids in wines and champagne.  

PubMed

Carboxylic acids have an important influence on the biological stability and the organoleptic properties of wines. A simple, rapid and reproducible high-performance liquid chromatographic method for the determination of the main carboxylic acids (tartaric, malic, shikimic, lactic, acetic, citric, succinic, fumaric and propionic acids) in wines is described. There is no interference from either sugars or amino acids. The method does not need any preparation or extraction of the sample. The linearity, the level of detection, the repeatability and the reproducibility were studied for each acid. The results are compared with those obtained by chemical and enzymatic assays. PMID:3624354

Tusseau, D; Benoit, C

1987-06-12

181

Structure-activity relationship of an ozonide carboxylic acid (OZ78) against Fasciola hepatica.  

PubMed

In this paper, we describe the SAR of ozonide carboxylic acid OZ78 (1) as the first part of our search for a trematocidal synthetic peroxide drug development candidate. We found that relatively small structural changes to 1 resulted most commonly in loss of activity against Fasciola hepatica in vivo. A spiroadamantane substructure and acidic functional group (or ester prodrug) were required for activity. Of 26 new compounds administered at single 100 mg/kg oral doses to F. hepatica infected rats, 8 had statistically significant worm burden reductions, 7 were partially curative, and 1 (acylsulfonamide 6) was completely curative and comparable to 1 in flukicidal efficacy. This study also showed that the activity of 1 is peroxide-bond-dependent, suggesting that its flukicidal efficacy depends upon hemoglobin digestion in F. hepatica. PMID:20423101

Zhao, Qingjie; Vargas, Mireille; Dong, Yuxiang; Zhou, Lin; Wang, Xiaofang; Sriraghavan, Kamaraj; Keiser, Jennifer; Vennerstrom, Jonathan L

2010-05-27

182

On the possibility of using short chain length mono-carboxylic acids for stabilization of magnetic fluids  

NASA Astrophysics Data System (ADS)

Short chain length mono-carboxylic acids (lauric and myristic acids) are used to coat magnetite nanoparticles in non-polar organic liquids, which results in highly stable magnetic fluids. The new fluids are compared with classical organic fluids stabilized by oleic acid (OA). Magnetic granulometry and small-angle neutron scattering (polarized mode) reveal a great difference in the particle size distribution function for the studied magnetic fluids, particularly a decrease in the characteristic particle radius of magnetite when lauric and myristic acids are used instead of OA.

Avdeev, Mikhail V.; Bica, Doina; Vékás, Ladislau; Marinica, Oana; Balasoiu, Maria; Aksenov, Victor L.; Rosta, László; Garamus, Vasil M.; Schreyer, Andreas

2007-04-01

183

Extraction of ethanol with higher carboxylic acid solvents and their toxicity to yeast  

Technology Transfer Automated Retrieval System (TEKTRAN)

In a screening exercise for ethanol-selective extraction solvents, partitioning of ethanol and water from a 5 wt% aqueous solution into several C8 – C18 carboxylic acids was studied. Results for the acids are compared with those from alcohols of similar structure. In all cases studied, the acids exh...

184

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

2012-07-27

185

Short-chain Carboxylic Acid Concentration in Human Gingival Crevicular Fluid  

Microsoft Academic Search

Short-chain carboxylic acids (e.g., lactic acid, propionic acid, butyric acid) are metabolic by-products of bacterial metabolism which can accumulate in the gingival crevice. It is of no small consequence, therefore, that 1- to 5-mM concentrations of these acids exhibit significant biological activity, including the ability to alter cell proliferation and gene expression in cells of importance to the periodontium. This

R. Niederman; Y. Buyle-Bodin; B.-Y. Lu; P. Robinson; C. Naleway

1997-01-01

186

Replacement of a piperidine resiude by a halogen in 3-amino-4-piperidinoquinoline-2-carboxylic acid  

Microsoft Academic Search

In a study of the properties of 3-amino-4-piperi dinoquinoline-2- carboxylic acid (I) [1] it was found that it is possible to replace the piperidine residue in it by chlorine. Thus ethyl 3-amino-4-chloro quinoline2-carboxylate (II) with nap 97-98 ~ (from aqueous alcohol), is formed when dry HC1 is bubbled into a refluxing solution of I in ethanol; the PMR spectrum of

N. E. Britikova; L. A. Belova; A. S. Elina

1975-01-01

187

Quantitative analysis of low molecular weight carboxylic acids by capillary zone electrophoresis\\/conductivity detection  

Microsoft Academic Search

Low molecular weight carboxylic acids are separated and quantitated by capillary zone electrophoresis (CZE) with an on-column conductivity detector. The addition of 0.2-0.5 mM TTAB (tetradecyltrimethylammonium bromide) controls the electroosmotic flow so that all carboxylate anions pass through the detector. Unlike other CZE detection methods, conductivity detection shows a direct relationship between retention time and peak area. This confers on

X. Huang; J. A. Luckey; M. J. Gordon; R. N. Zare

1989-01-01

188

The dependence on ionic strength of protonation constants of carboxylic acids in aqueous tetraethylammonium iodide solution, at different temperatures  

Microsoft Academic Search

The data regarding the protonation of 22-(mono-, di-,…, penta-) carboxylic acids in aqueous tetraethylammonium iodide at different ionic strengths 0function of

Claudia Foti; Silvio Sammartano; Graziella Signorino

1998-01-01

189

Engineering of Candida antarctica lipase B for hydrolysis of bulky carboxylic acid esters.  

PubMed

Candida antarctica lipase B (CALB) is a widely used biocatalyst with high activity and specificity for a wide range of primary and secondary alcohols. However, the range of converted carboxylic acids is more narrow and mainly limited to unbranched fatty acids. To further broaden the biotechnological applications of CALB it is of interest to expand the range of converted carboxylic acid and extend it to carboxylic acids that are branched or substituted in close proximity of the carboxyl group. An in silico library of 2400 CALB variants was built and screened in silico by substrate-imprinted docking, a four step docking procedure. First, reaction intermediates of putative substrates are covalently docked into enzyme active sites. Second, the geometry of the resulting enzyme-substrate complex is optimized. Third, the substrate is removed from the complex and then docked again into the optimized structure. Fourth, the resulting substrate poses are rated by geometric filter criteria as productive or non-productive poses. Eleven enzyme variants resulting from the in silico screening were expressed in Escherichia coli BL21 and measured in the hydrolysis of two branched fatty acid esters, isononanoic acid ethyl ester and 2-ethyl hexanoic acid ethyl esters. Five variants showed an initial increase in activity. The variant with the highest wet mass activity (T138S) was purified and further characterized. It showed a 5-fold increase in hydrolysis of isononanoic acid ethyl ester, but not toward sterically more demanding 2-ethyl hexanoic acid ethyl ester. PMID:20887757

Juhl, P B; Doderer, K; Hollmann, F; Thum, O; Pleiss, J

2010-09-29

190

Use of derivatization to improve the chromatographic properties and detection selectivity of physiologically important carboxylic acids.  

PubMed

In this review, tagging techniques with reagents used for ultraviolet-visible (UV-Vis), fluorescent (FL), chemiluminescent (CL) and electrochemical detection (ED) for higher carboxylic acids in HPLC are evaluated in terms of the tagging reactions, handling, flexibility, stability of the reagents and the corresponding derivatives, sensitivity and selectivity. Emphasis is given to the applications of these tagging techniques to biologically important carboxylic acids of relatively high molecular mass including free fatty acids, prostaglandins, leukotrienes and thromboxanes etc. Some typical examples are described. Although RIA and GC-MS are powerful techniques for the highly sensitive determination of carboxylic acids, tagging for these techniques is not included in this review because recent progress in tagging methods has been mainly concerned with HPLC detection. PMID:8520705

Toyo'oka, T

1995-09-15

191

A versatile aqueous reduction of bio-based carboxylic acids using syngas as a hydrogen source.  

PubMed

Syngas as a versatile hydrogen source: Using readily available and economically favorable syngas as a convenient hydrogen source, an efficient and sustainable aqueous reduction of bio-based carboxylic acids has been achieved over a highly robust catalyst system consisting of gold nanoparticles supported on acid-tolerant single-phase monoclinic zirconia (Au/m-ZrO(2)). A range of bio-based multifunctional carboxylic acids have been selectively converted into their corresponding lactones or diols in high to excellent yields. PMID:23143770

Yu, Lei; Du, Xian-Long; Yuan, Jing; Liu, Yong-Mei; Cao, Yong; He, He-Yong; Fan, Kang-Nian

2012-11-09

192

Evaluation of carboxylic acid-induced conformational transitions of ?-lactoglobulin: Comparison of the alcohol effects on ?-lactoglobulin  

Microsoft Academic Search

Conformational transitions of bovine ?-lactoglobulin A (?-LG) induced by carboxylic acid were systematically studied by steady-state tryptophan (Trp) fluorescence. The behavior of ?-LG denaturation depends upon the species and concentration of carboxylic acid, as well as on the pH of solutions. The order of the effectiveness of the respective carboxylic acids was described as follows: MeCOOH

Bong-Kuk Lee; Toshinori Shimanouchi; Hiroshi Umakoshi; Ryoichi Kuboi

2006-01-01

193

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

194

Selective reduction of carboxylic acids to aldehydes through manganese catalysed hydrosilylation.  

PubMed

The direct reduction of carboxylic acids to disilylacetals was achieved through a manganese catalyzed hydrosilylation reaction in the presence of triethylsilane under mild conditions, at r.t. and under UV irradiation (350 nm). The aldehydes were obtained in good to excellent yields after acidic hydrolysis. PMID:24042257

Zheng, Jianxia; Chevance, Soizic; Darcel, Christophe; Sortais, Jean-Baptiste

2013-10-01

195

Anion and carboxylic acid binding to monotopic and ditopic amidopyridine macrocycles.  

PubMed

Binding of inorganic anions, carboxylic acids, and tetraalkylammonium carboxylates by macrocyclic compounds of different size was studied by NMR in DMSO-d6. It has been shown that at least a 15-membered ring is necessary for successful recognition of fluoride. Larger macrocycles were shown to bind HSO4(-), H2PO4(-), Cl(-), and carboxylic acid salts. Effects of binding topicity are discussed. The 30-membered macrocycles 4 and 4m selectively bind substrates that are size- and shape-complementary: maximum binding is observed for dicarboxylic acids and dicarboxylates with four-carbon chains, and the binding constant for association of fumaric acid and 4 is ca. 5 orders of magnitude higher than that of maleic acid. The 30-membered macrocycle 4m showed selectivity toward alpha-ketocarboxylic acids. Secondary amino groups were not crucial for binding of fluoride to the macrocycles; however, they proved to be very important for selectivity and strength of carboxylic acid binding. The X-ray structure of the adduct of 4 and nitrobenzoic acid confirmed the guest H-bonding with both the amide and the secondary amino groups of the 30-membered macrocyclic host. PMID:18396906

Korendovych, Ivan V; Cho, Mimi; Makhlynets, Olga V; Butler, Phillip L; Staples, Richard J; Rybak-Akimova, Elena V

2008-04-09

196

On the inhibition of muscle membrane chloride conductance by aromatic carboxylic acids  

Microsoft Academic Search

A B S T R A C T 25 aromatic carboxylic acids which are analogs of benzoic acid were tested in the rat diaphragm preparation for effects on chloride conductance (Gc~). Of the 25, 19 were shown to reduce membrane Gca with little effect on other membrane parameters, although their apparent Kl varied widely. This inhibition was reversible if exposure

P. T. PALADE; R. L. BARCHI

1977-01-01

197

Helical Suprastructure Generated from Achiral 4-Biphenyl Carboxylic Acid Molecules via Hydrogen Bonding  

NASA Astrophysics Data System (ADS)

A novel series of achiral 4-biphenyl carboxylic acid molecules (BPCA-Cn-PmOH) bridged with phenol at meta-position by alkoxyl flexible chains with various carbon numbers (n=6-10) formed spontaneous helical suprastructures in the low ordered SmC phase. In order to understand the origin of phase chirality without configurational chirality in BPCA-Cn-PmOH, four other achiral 4-biphenyl carbonyl model compounds with an alkoxyl flexible chain (n=6) were studied using the combined techniques of DSC, PLM, AFM, FT-IR, solid-state ^13C-NMR and WAXD. It is concluded that the self-assembled dimers are essential to form a stable helical superstructure, but the -OH or --OCH3 functions at the meta- or para-position of phenyl ring is not necessary.

Jeong, Kwang-Un; Ge, Jason J.; Jin, Shi; Knapp, Brian S.; Harris, Frank W.; Cheng, Stephen Z. D.

2004-03-01

198

Effects of carboxylic acids on nC 60 aggregate formation  

Microsoft Academic Search

The discovery that negatively charged aggregates of C60 fullerene (nC60) are stable in water has raised concerns regarding the potential environmental and health effects of these aggregates. In this work, we show that nC60 aggregates produced by extended mixing in the presence of environmentally relevant carboxylic acids (acetic acid, tartaric acid, citric acid) have surface charge and morphologic properties that

Xiaojun Chang; Peter J. Vikesland

2009-01-01

199

Short-chain Carboxylic AcidConcentration inHumanGingival Crevicular Fluid  

Microsoft Academic Search

Short-chain carboxylic acids (e.g., lactic acid, propionic acid, butyric acid) aremetabolic by-products of bacterial metabolism whichcanaccumulate inthegingival crevice. Itisofnosmall consequence, therefore, that 1-to5- mM concentrations oftheseacidsexhibit significant biological activity, including theability toalter cell proliferation andgeneexpression incells ofimportance to theperiodontium. Thiscommunication reports onthein vivoconcentrations ofpropionic andbutyric acidinthe gingival crevices ofperiodontal subjects withsevere and milddisease. Theresults indicated thatseverely diseased subjects exhibited a

R. Niedermanh; Y. Buyle-Bodin; B.-Y. Lu; P. Robinson

200

Proteins and Amino Acids Identification of Tetrahydro-ß-carboline-3-carboxylic Acid in Foodstuffs, Human urine and Human Milk  

Microsoft Academic Search

Methyl-1,2,3,4-tetrahydro-ß-carboline- 3-carboxyIic acid (MTCA)and l ,2,3,4-tetrahydro-ß-car- boline-3-carboxylic acid (TCCA), both precursors of mutagenic N-nitroso compounds (N-nitrosamines, 1- methyl-2-nitroso-1,2,3,4-te trahydro-ß-carboline- 3-car- boxylic acid and 2-nitroso-l,2,3,4-tetrahydro-ß-car- boline-3-carboxylic acid), were detected in various food stuffs, urine from healthy human subjects and human milk. A purification procedure, involving a chemically- bonded material followed by HPLCcombined with fluoro- metric detection, was used for the quantitative

YASUHIKO MIZOI; YOSHIYUKI GETANI; ICHIYA NIHOMIYA

201

Fourier transform infrared study on hydrogen bonding species of carboxylic acids in supercritical carbon dioxide with ethanol  

SciTech Connect

Supercritical fluid extraction has been given much attention recently as one of the new separation technologies in the chemical industry. Fourier transform infrared (FTIR) spectroscopy has been used to determine the equilibrium constants of the dimerization for carboxylic acid (acetic acid or palmitic acid) and the amount of hydrogen bonding species between carboxylic acid and ethanol in supercritical CO{sub 2}. Experiments were carried out at 308.2--313.2 K and 10.0--20.0 MPa. The noticeable band was the C{double_bond}O stretching band for carboxylic acid. In the binary system (supercritical CO{sub 2} + carboxylic acid), the equilibrium constants of the dimerization between the carboxylic acid monomer and dimer decrease with increasing pressure and temperature. The equilibrium constants of palmitic acid are larger than those of acetic acid. In a ternary system (supercritical CO{sub 2} + carboxylic acid + ethanol), the amount of hydrogen bonding species between carboxylic acid and ethanol in supercritical CO{sub 2} increases with the increasing mole fraction of added ethanol. Furthermore, the authors confirm that the solubility enhancement by ethanol used as an entrainer in supercritical CO{sub 2} related to the amount of hydrogen bonding species between carboxylic acid and ethanol.

Yamamoto, Morio; Iwai, Yoshio; Nakajima, Taro; Arai, Yasuhiko [Kyushu Univ., Higashi, Fukuoka (Japan). Dept. of Chemical Systems and Engineering

1999-05-06

202

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

203

Conversion of sugarcane bagasse to carboxylic acids using a mixed culture of mesophilic microorganisms.  

PubMed

Using the MixAlco process, biomass can be converted into carboxylic acids, which can be chemically converted into mixed alcohol fuels. This study focused on the use of countercurrent fermentation to anaerobically convert sugarcane bagasse and chicken manure to mixed carboxylic acids using a mixed culture of mesophilic microorganisms from terrestrial and marine sources. Bagasse was pretreated with lime to increase digestibility. The continuum particle distribution model (CPDM) simulated continuous fermentors based on data collected from batch experiments. This model saves considerable time in determining optimum operating conditions. For an 80% bagasse/20% chicken manure fermentation with terrestrial inoculum at a volatile solids loading rate (VSLR) of 7.36 g/(L of liquid d) and a liquid residence time (LRT) of 8.88 d, total carboxylic acid productivity, total acid selectivity, and yield were 2.49 g/(L of liquid d), 0.581 g of total acid/ g of VS digested, and 0.338 g of total acid/g of VS fed, respectively, at a concentration of 18.7 g of total acid/L. At the same VSLR and LRT, fermentation with marine inoculum gave higher total acid productivity, total acid selectivity, and yield than fermentation with terrestrial inoculum. For an 80% bagasse/20% chicken manure fermentation with marine inoculum at a VSLR of 3.83 g/(L of liquid d) and an LRT of 12.1 d, total carboxylic acid productivity, total acid selectivity, and yield were 1.38 g/(L of liquid d), 0.667 g of total acid/g of VS digested, and 0.359 g of total acid/g of VS fed, respectively, at a concentration of 16.2 g of total acid/L. PMID:12721433

Thanakoses, Piyarat; Mostafa, Nagat Abd Alla; Holtzapple, Mark T

2003-01-01

204

Determination of the asphaltene and carboxylic acid content of a heavy oil using a microfluidic device.  

PubMed

Heavy oil utilisation is set to increase over the coming decades as reserves of conventional oil decline. Heavy oil differs from conventional oil in containing relatively large quantities of asphaltene and carboxylic acids. The proportions of these compounds greatly influence how oil behaves during production and its utilisation as a fuel or feedstock. We report the development of a microfluidic technique, based on a H-cell, that can extract the carboxylic acid components of an oil and assess its asphaltene content. Ultimately this technology could yield a field-deployable device capable of performing measurements that facilitate improved resource management at the point of resource-extraction. PMID:19255665

Bowden, Stephen A; Wilson, Rab; Parnell, John; Cooper, Jonathan M

2008-12-05

205

Preparation of carboxylic acid-bearing polysaccharide nanofiber made from euglenoid ?-1,3-glucans.  

PubMed

This paper introduces a new strategy for creating surface modified polysaccharide nanofibers. To demonstrate proof of principle, the synthesis, structure, and self-assembly behavior of a carboxylic acid-bearing polysaccharide made from paramylon (?-1,3-glucan) and succinic anhydride were investigated. Examination by a combination of NMR, FT-IR, and SEC-MALLS confirmed that successful preparation of the desired succinylated paramylon without significant depolymerization. NMR, SEC-MALLS, visible absorption and CD spectroscopic analyses indicated that the paramylon derivative forms the triplex structure in solutions. SEM observation revealed that succinylated paramylon forms a nanofiber that has carboxylic acid on the surface. PMID:23987321

Shibakami, Motonari; Tsubouchi, Gen; Nakamura, Makoto; Hayashi, Masahiro

2013-05-20

206

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

Microsoft Academic Search

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

Qing-Jie Meng; Xing-Xiang Zhang; Shi-He Bai; Xue-Chen Wang

2007-01-01

207

Thiol containing carboxylic acids remove the CTAB surfactant onto the surface of gold nanorods: An FTIR spectroscopic study  

NASA Astrophysics Data System (ADS)

Gold nanorods are mostly synthesized by chemical methods, using a directing agent: CTAB (cetyl-trimethyl-ammonium bromide). Due to the various applications of gold nanorods, the necessity to modify the surface functionalization appears. Thiol containing molecules are used as direct or cross-linking agents in the functionalization of gold nanorods. In this study we show that a thiol containing carboxylic acid mixture is able to remove a large part of CTAB molecules that surround the gold nanorods, and not only to cover the CTAB protecting layer. Using a simple FTIR spectroscopic method, it is possible to quantitatively determine the percentage of CTAB that is replaced by the functionalizing agent.

Garabagiu, Sorina; Bratu, Ioan

2013-11-01

208

Simple quantification of surface carboxylic acids on chemically oxidized multi-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

The surface of multi-walled carbon nanotube (MWCNT) was chemically oxidized using nitric acid and sulfuric-nitric acid mixtures. Thermogravimetric analysis, transmission electron microscopy and infrared spectroscopy revealed that the use of acid mixtures led to higher degree of oxidation. More quantitative identification of surface carboxylic acids was carried out using X-ray photoelectron spectroscopy (XPS) and acid-base titration. However, these techniques are costly and require very long analysis times to promptly respond to the extent of the reaction. We propose a much simpler method using pH measurements and pre-determined pKa value in order to estimate the concentration of carboxylic acids on the oxidized MWCNT surfaces. The results from this technique were consistent with those obtained from XPS and titration, and it is expected that this simple quantification method can provide a cheap and fast way to monitor and control the oxidation reaction of MWCNT.

Gong, Hyejin; Kim, Seong-Taek; Lee, Jong Doo; Yim, Sanggyu

2013-02-01

209

Biocatalytic reduction of short-chain carboxylic acids into their corresponding alcohols with syngas fermentation.  

PubMed

Short-chain carboxylic acids generated by various mixed- or pure-culture fermentation processes have been considered valuable precursors for production of bioalcohols. While conversion of carboxylic acids into alcohols is routinely performed with catalytic hydrogenation or with strong chemical reducing agents, here, a biological conversion route was explored. The potential of carboxydotrophic bacteria, such as Clostridium ljungdahlii and Clostridium ragsdalei, as biocatalysts for conversion of short-chain carboxylic acids into alcohols, using syngas as a source of electrons and energy is demonstrated. Acetic acid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid, and n-caproic acid were converted into their corresponding alcohols. Furthermore, biomass yields and fermentation stoichiometry from the experimental data were modeled to determine how much metabolic energy C. ljungdahlii generated during syngas fermentation. An ATP yield of 0.4-0.5 mol of ATP per mol CO consumed was calculated in the presence of hydrogen. The ratio of protons pumped across the cell membrane versus electrons transferred from ferredoxin to NAD(+) via the Rnf complex is suggested to be 1.0. Based on these results, we provide suggestions how n-butyric acid to n-butanol conversion via syngas fermentation can be further improved. PMID:23172270

Perez, Jose M; Richter, Hanno; Loftus, Sarah E; Angenent, Largus T

2013-01-15

210

Synthesis, Stability and In Vitro Dermal Evaluation of Aminocarbonyloxymethyl Esters as Prodrugs of Carboxylic Acid Agents  

Microsoft Academic Search

Aminocarbonyloxymethyl esters 3 based on (S)-amino acid carriers were synthesised and evaluated as potential prodrugs of carboxylic acid agents. In addition, the compounds were evaluated as topical prodrugs with the aim of improving the dermal delivery of two non-steroidal anti-inflammatory agents: naproxen and flufenamic acid. The lipophilicities of these compounds were determined and their hydrolyses in aqueous solutions and in

Eduarda Mendes; Tânia Furtado; João Neres; Jim Iley; Tomi Jarvinen; Jarkko Rautio; Rui Moreira

2002-01-01

211

Acid–base equilibria of methyl ?-carboline-3-carboxylate in aqueous solution  

Microsoft Academic Search

The photophysical properties and the acid–base equilibrium of methyl ?-carboline-3-carboxylate in aqueous solution have been investigated. The pKa values in the ground and the first excited state have been spectrophotometrically determined using Förster cycle for the excited state and acidifying the solutions in the pH range with sulphuric acid and acetic acid. Some differences have been found in the absorption

M. J. Tapia; D. Reyman; M. H. Viñas; C. Carcedo; J. M. L. Poyato

2003-01-01

212

EXTRACTION EQUILIBRIA OF SILVER WITH A SULFUR-CONTAINING CARBOXYLIC ACID  

Microsoft Academic Search

A new carboxylic acid extractant containing a sulfur atom, ?-butylthiolauric acid(abbreviated as ?-BTLA) was synthesized to investigate the extraction equilibrium of silver(I) from 1 mol\\/dm aqueous ammonium nitrate solution with its toluene solution at 30°C. Moreover, the extraction of silver(I) with palmitic acid in toluene was studied to compare with the extraction properties of ?-BTLA. It was found that silver(I)

Yoshinari BABA; Katsutoshi INOUE

1984-01-01

213

Simultaneous gas chromatographic determination of carboxylic acids in soft drinks and jams.  

PubMed

A method was developed for simultaneous gas chromatographic determination of sorbic acid, dehydroacetic acid, and benzoic acid used as preservatives, and succinic acid, fumaric acid, malic acid, and tartaric acid used as acidulants in soft drinks and jams. A sample was dissolved in NH4OH-NH4Cl pH 9 buffer solution, and an aliquot of the solution was passed through a QAE-Sephadex A 25 column. The column was washed with water, and the carboxylic acids were eluted with 0.1N HCl. Sorbic acid, dehydroacetic acid, and benzoic acid were extracted with ethyl ether-petroleum ether (1 + 1), and determined on a 5% DEGS + 1% H3PO4 column. Succinic acid, fumaric acid, malic acid, and tartaric acid in the lower layer were derivatized with N,O-bis(trimethylsilyl)acetamide and trimethylchlorosilane, and determined on a 3% SE-30 column. Recoveries from soft drink and jam samples fortified with 0.1% each of 7 carboxylic acids ranged from 92.4 to 102.6% for preservatives, and from 88.1 to 103.2% for acidulants. PMID:4055637

Tsuda, T; Nakanishi, H; Morita, T; Takebayashi, J

214

Synthesis of Tryptoline-3-Carboxylic Acid Derivatives A Novel Antidiabetic Agent  

PubMed Central

The compounds, 2-(methylsulfonyl)-1,2,3,4-tetrahydro-9H-pyrido[3,4-b]indole-3-carboxylic acid (DM3), 2-(phenylsulfonyl)-1,2,3,4-tetrahydro-9H-pyrido[3,4-b]indole-3-carboxylic acid (DM4), and 2-(p-toluenesulfonyl)-1,2,3,4-tetrahydro-9H-pyrido[3,4-b]indole-3-carboxylic acid (DM5) were synthesized by coupling of 1,2,3,4-tetrahydro-9H-pyrido[3,4-b]indole-3-carboxylic acid (DM2) with methanesulfonyl chloride, benzenesulfonyl chloride, and toluenesulfonyl chloride, which in turn, was synthesized by dissolving dilute aqueous ammonia with 2-(N-hydroxy methyl amino)-indol-3-yl-propanoic acid (DM1) which is the reaction product of l-tryptophan and formalin. All the intermediates and title compounds were characterized by physical, chemical, analytical, and spectral data. All the title compounds have been screened for in vivo antidiabetic activity in streptozotocin-induced diabetic rats, and serum glucose was estimated spectrophotometrically at 505 nm by glucose oxidase/peroxidase method. Compound DM5 showed potent antidiabetic activity.

Choudhary, AN; Kohli, MS; Kumar, A; Joshi, A

2011-01-01

215

A Chiral Bisthiourea as a Chiral Solvating Agent for Carboxylic Acids in the Presence of DMAP.  

PubMed

A simple chiral bisthiourea has been used as a highly effective and practical chemical solvating agent (CSA) for diverse ?-carboxylic acids in the presence of DMAP. Excellent enantiodiscrimination based on well-resolved ?-H NMR signals of the enantiomers of carboxylic acids can be obtained without interference from the chiral bisthiourea and DMAP. To check the practicality of the chiral bisthiourea/DMAP for enantiomeric determination, the ee values of mandelic acid (MA) samples over a wide ee range were determined by integration of the ?-H signal of MA in (1)H NMR. A discrimination mechanism is proposed, that the formation of two diasteromeric ternary complexes between the chiral bisthiourea and two in situ formed enantiomeric carboxylate-DMAPH(+) ion pairs discriminates the enantiomers of carboxylic acids. Computational modeling studies show that the chemical shift value of ?-H of (S)-MA is greater than that of (R)-MA in ternary complexes, which is consistent with experimental observation. 1D and 2D NOESY spectra demonstrate the intermolecular noncovalent interactions between the protons on the aromatic rings of chiral bisthiourea and ?-H of the enantiomers of racemic ?-methoxy phenylacetic acids in the complexes. PMID:24050150

Bian, Guangling; Fan, Hongjun; Yang, Shiwei; Yue, Huifeng; Huang, Huayin; Zong, Hua; Song, Ling

2013-09-05

216

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

2008-10-24

217

Organic acids in hydrothermal solutions: standard molal thermodynamic properties of carboxylic acids and estimates of dissociation constants at high temperatures and pressures.  

PubMed

Experimental standard partial molal volumes, heat capacities, and entropies as well as apparent standard partial molal enthalpies and Gibbs free energies of mono- and dicarboxylic acids and their anions at low temperatures and pressures are used to generate correlations for predicting the same properties at high temperatures and pressures for 59 carboxylic and 18 hydroxyacid species with the revised Helgeson-Kirkham-Flowers (HKF) equation of state. Predicted equilibrium dissociation constants are compared with experimental values from the literature and tabulated as functions of pressure and temperature for 25 carboxylic acids and nine hydroxyacids. Close agreement between independent predictions and experimental data supports the generality of the computational techniques and the accuracy of predicted data. These results allow incorporation of a wide variety of organic acids into quantitative interpretations of geochemical processes. PMID:11540132

Shock, E L

1995-05-01

218

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

Microsoft Academic Search

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

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

2007-01-01

219

Large scale microwave-accelerated esterification of carboxylic acids with dimethyl carbonate  

Microsoft Academic Search

An environmentally friendly process for the esterification of carboxylic acids with dimethyl carbonate can be accelerated by employing a combined strategy: using 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) as the catalyst (chemical means) and microwave as the energy source (physical means). This approach provides synthetic advantages, niches, and upscalability.

Wen-Chung Shieh; Steven Dell; Oljan Repi?

2002-01-01

220

Conversion of 1-aminocyclopropane-1-carboxylic acid to ethylene by isolated vacuoles of Pisum sativum L  

Microsoft Academic Search

We compared the distribution of 1-aminocyclopropane-1-carboxylic acid (ACC) between the vacuole of isolated pea (Pisum sativum L.) protoplasts and the remainder of the cell and found that over 80% of the ACC was localized in the vacuole. Isolated protoplasts and vacuoles evolved ethylene. Over 80% of the ethylene production by protoplasts could be accounted for as originating from the vacuole.

Micha Guy; Hans Kende

1984-01-01

221

Membrane based solvent extraction and stripping of a heterocyclic carboxylic acid in hollow fiber contactors  

Microsoft Academic Search

Simultaneous membrane based solvent extraction (MBSE) and membrane based solvent stripping (MBSS) in HF contactors of a heterocyclic carboxylic acid (HCA) of industrial importance from sulphate solutions with solvent containing trioctylamine (TOA) were studied. An effective transport of HCA was achieved. The proposed reaction-diffusion model gives a much better fit to experimental values than the diffusion model. The mean values

L'ubica Kubišová; Erika Sabolová; Štefan Schlosser; Ján Marták; Rudolf Kertész

2002-01-01

222

Gingival Inflammation Induced by Food and Short-chain Carboxylic Acids  

Microsoft Academic Search

Earlier studies in our laboratories demonstrated that particles of a number of snack foods that are retained on the dentition accumulate fermentable sugars and short-chain carboxylic acids (SCCA; acetic, formic, lactic, and propionic) to different degrees. The present study was undertaken to test the hypothesis that the accumulated SCCA can induce a gingival inflammatory response. Five periodontally and medically healthy

S. Kashket; J. Zhang; R. Niederman

1998-01-01

223

Iron-catalyzed decarboxylative alkenylation of cycloalkanes with arylvinyl carboxylic acids via a radical process  

PubMed Central

Summary A Fe(acac)3-catalyzed decarboxylative coupling of 2-(aryl)vinyl carboxylic acids with cycloalkanes was developed by using DTBP as an oxidant through a radical process. This reaction tolerates a wide range of substrates, and products are obtained in good to excellent yields (71–95%). The reaction also shows excellent stereoselectivity, and only trans-isomers are obtained.

Zhao, Jiancan; Fang, Hong

2013-01-01

224

Aggregation behavior of wheat gluten during carboxylic acid deamidation upon hydrothermal treatment  

Microsoft Academic Search

Changes of aggregation behavior of wheat gluten during carboxylic acid deamidation upon hydrothermal treatment were investigated to test the influences of deamidation on the aggregation extent of wheat gluten. Hydrothermal treatment induced that the size of soluble wheat gluten aggregate progressively increased by cross-linking of gliadins and slowly cleaved glutenins. But significant changes in molecular weight distribution, solubility under six

Lan Liao; Tong-xun Liu; Mou-ming Zhao; Hai-feng Zhao; Cun Cui

2011-01-01

225

Hydrophobicity-dependent QSARs to predict the toxicity of perfluorinated carboxylic acids and their mixtures  

Microsoft Academic Search

Perfluorinated carboxylic acids (PFCAs) have wide industrial applications because of their unique physicochemical characteristics. However, data on the toxicity of much of this chemical class is lacking, particularly with regard to mixture toxicity. In this study, the toxicity of individual PFCAs and their mixtures to Photobacterium phosphoreum were observed. There was a tendency of increasing toxicity from C3 to C14

Ting Wang; Zhifen Lin; Daqiang Yin; Dayong Tian; Yalei Zhang; Deyang Kong

2011-01-01

226

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

Microsoft Academic Search

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

Steven B. Hawthorne; David J. Miller

1986-01-01

227

Toward Elimination of Discrepancies between Theory and Experiment:  Double Proton Transfer in Dimers of Carboxylic Acids  

Microsoft Academic Search

We present for the first time a fully ab initio dual-level reaction path dynamics calculation of the synchronous proton exchange in carboxylic acid dimers that is consistent with a wide variety of experimental findings, such as reaction rates k, tunneling splittings ¢0, apparent activation energy curves Ea (T), crossover temperatures Tc and kinetic isotope effects. For the dimer of formic

Thomas Loerting; Klaus R. Liedl

1998-01-01

228

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

Microsoft Academic Search

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

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

2007-01-01

229

Carboxylic acid bioisosteres acylsulfonamides, acylsulfamides, and sulfonylureas as novel antagonists of the CXCR2 receptor.  

PubMed

A series of novel acylsulfonamide, acylsulfamide, and sulfonylurea bioisosteres of carboxylic acids were prepared as CXCR2 antagonists. Structure-activity relationships are reported for these series. One potent orally bioavailable inhibitor had excellent PK properties and was active in a lung injury model in hyperoxia-exposed newborn rats. PMID:18308567

Winters, Michael P; Crysler, Carl; Subasinghe, Nalin; Ryan, Declan; Leong, Lynette; Zhao, Shuyuan; Donatelli, Robert; Yurkow, Edward; Mazzulla, Marie; Boczon, Lisa; Manthey, Carl L; Molloy, Christopher; Raymond, Holly; Murray, Lynne; McAlonan, Laura; Tomczuk, Bruce

2008-02-07

230

Wet oxidation kinetics of refractory low molecular mass carboxylic acids  

Microsoft Academic Search

Wet oxidation kinetics of aqueous solutions of formic, acetic, oxalic, and glyoxalic acids was studied in a titanium autoclave at a temperature range of 150--320 C and oxygen partial pressures between 8 and 60 bar. Oxidation reactions obeyed a first-order kinetics with respect to concentration of all substrates. On the basis of acid concentration decay, the activation energy for acetic,

R. V. Shende; Janez Levec

1999-01-01

231

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

232

Sorption of carboxylic acid from carboxylic salt solutions at PHS close to or above the pK.sub.a of the acid, with regeneration with an aqueous solution of ammonia or low-molecular-weight alkylamine  

DOEpatents

Carboxylic acids are sorbed from aqueous feedstocks at pHs close to or above the acids' pH.sub.a into a strongly basic organic liquid phase or onto a basic solid adsorbent or moderately basic ion exchange resin. the acids are freed from the sorbent phase by treating it with aqueous alkylamine or ammonia thus forming an alkylammonium or ammonium carobxylate which dewatered and decomposed to the desired carboxylic acid and the alkylamine or ammonia.

King, C. Judson (Kensington, CA); Tung, Lisa A. (El Cerrito, CA)

1992-01-01

233

Gas-phase syntheses for interstellar carboxylic and amino acids  

NASA Astrophysics Data System (ADS)

We report experimental results that demonstrate gas-phase, ionic syntheses of glycine and ?-alanine, as well as acetic and propanoic acid, from smaller molecules found in space; in doing so, we infer the formation of these acids in the interstellar environment. We show that ionized glycine and ?-alanine are produced in the reactions of hydroxylamine ions, NH2OH+, with acetic and propanoic acid respectively. Even more promising in the context of interstellar synthesis are our results that demonstrate the corresponding production of the protonated amino acids from analogous reactions with protonated hydroxylamine. The striking specificity of these syntheses for the ?-isomer of alanine suggests that the amino acids of CI (Carbonaceous Ivona) chondrite meteorites are products of interstellar chemistry and supports the hypothesis that these meteorites are of cometary origin.

Blagojevic, Voislav; Petrie, Simon; Bohme, Diethard K.

2003-02-01

234

[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

235

Regioselective catalytic addition of proton-donor reagents to esters of 1-alkylcyclopropene-3-carboxylic acids  

Microsoft Academic Search

Conclusions 1.It has been observed for the first time that methyl 1-alkylcyclopropene-3-carboxy-lates in the presence of 5–10 mole % of CuCl or the complex CuCl·2MeC=CSiMe3 add hydrogen halides (HCl and HBr) and carboxylic acids with pKa values of 3–7 (monochloracetic, formic, acrylic, acetic, and permethrinic) at the C2-C3 bond with opening of the three-carbon ring to give 60–95% of the

E. A. Shapiro; M. N. Protopopova; O. M. Nefedov

1988-01-01

236

Process for producing peracids from aliphatic hydroxy carboxylic acids  

DOEpatents

A process for producing peracids from lactic acid-containing solutions derived from biomass processing systems comprising: adjusting the pH of the solution to about 8-9 and removing alkaline residue fractions therefrom to form a solution comprised substantially of lower aliphatic hydroxy acids; oxidizing the solution to produce volatile lower aliphatic aldehydes; removing said aldehydes as they are generated; and converting said aldehydes to peracids.

Chum, Helena L. (Arvada, CO); Ratcliff, Matthew A. (Lakewood, CO); Palasz, Peter D. (Lakewood, CO)

1986-01-01

237

Process for producing peracids from aliphatic hydroxy carboxylic acids  

DOEpatents

A process is described for producing peracids from lactic acid-containing solutions derived from biomass processing systems. It consists of adjusting the pH of the solution to about 8 to 9 and removing alkaline residue fractions therefrom to form a solution comprised substantially of lower aliphatic hydroxy acids. The solution is oxidized to produce volatile lower aliphatic aldehydes. The aldehydes are removed as they are generated and converted to peracids.

Chum, H.L.; Palasz, P.D.; Ratcliff, M.A.

1984-12-20

238

Electrochemical oxidation of alcohols and carboxylic acids with diamond anodes  

Microsoft Academic Search

In this work, the conductive-diamond electrochemical oxidation of several short-chain organics (2-propanol, ethanol, butyric acid and chloroacetic acid) has been studied. The results obtained have been compared with those obtained in the oxidation of these compounds with Fenton reagent and with ozone at pH 12. Significant differences have been observed among the three technologies and also between the two ranges

P. Cañizares; R. Paz; C. Sáez; M. A. Rodrigo

2008-01-01

239

Viscosimetric studies of aqueous solutions of salts of carboxylic acids  

Microsoft Academic Search

Viscosities and densities of aqueous solutions of sodium salts of monocarboxylic acids (formic, acetic, propionic, valeric, chloroacetic, trichloroacetic, glycolic, phenylacetic) and dicarboxylic acids (oxalic, malonic, succinic, glutaric, adypic, pimelic, dl-tartaric, dl-malic, maleic, fumaric, o-phthalic) have been measured in the concentration range 0.02–0.1 mol·dm?3 at 298.15 K. The effect of hydrolysis of salts on viscosimetric data describing the objects under study

Agnieszka Chmielewska; Anna Wypych-Stasiewicz; Adam Bald

2005-01-01

240

High-purity amorphous silica originated in rice husks via carboxylic acid leaching process  

Microsoft Academic Search

The environmentally benign, harmless to human, and economically effective process to produce high-purity amorphous SiO2 materials from rice husks has been established by using a carboxylic acid leaching, not the conventional strong acids. TG-DTA\\u000a measurement and GCMS analysis indicated that the leaching was effective for the hydrolysis of celluloses and hemicelluloses\\u000a contained in rice husks at 473–873 K, which produced the

Junko Umeda; Katsuyoshi Kondoh

2008-01-01

241

Monodisperse hydrophilic polymer microspheres having carboxylic acid groups prepared by distillation precipitation polymerization  

Microsoft Academic Search

Monodisperse hydrophilic polymer microspheres having carboxyl acid group with spherical shape in the range of 160nm and 1.52?m were prepared by distillation copolymerizations of (meth)acrylic acid with either ethyleneglycol dimethacrylate (EGDMA) or divinylbenzene (DVB) as crosslinker. Polymerization was carried out with 2,2?-azobisisobutyronitrile (AIBN) as initiator in neat acetonitrile without stirring. The polymer microspheres were formed and precipitated out from the

Feng Bai; Xinlin Yang; Rui Li; Bo Huang; Wenqiang Huang

2006-01-01

242

Equilibrium sorption of methionine on carboxyl cation exchangers from solutions of various acidities  

NASA Astrophysics Data System (ADS)

The influence of the acidity of solutions of methionine on methionine interaction with KB-2 and KB-4 carboxyl cation exchangers in the protonated and deprotonated forms was studied by the calorimetric, sorption, and spectroscopic methods. It was found that nonexchange methionine absorption occurred from acid solutions, and mixed ion exchange and nonexchange sorption, from alkaline solutions. The enthalpies of sorption of methionine at various external solution pH values were determined.

Ovsyannikova, D. V.; Bondareva, L. P.; Selemenev, V. F.; Karpov, S. I.

2009-05-01

243

COPPER(II) AND COBALT(II) COMPLEXES OF PYRIDINE2CARBOXAMIDE AND PYRIDINE2CARBOXYLIC ACID  

Microsoft Academic Search

The formation constants of the following have been measured with a polarographic method: binary copper(II) complexes of pyridine-2-carboxamide (picolinamide) and pyridine-2-carboxylic acid (picolinic acid), a ternary copper(II) complex of picolinic acid and imidazole, and a binary copper(I)-imidazole complex. The larger formation constant for picolinic acid over picolinamide is ascribed to the greater chelating ability of a carboxylate group over an

Shih C. Chang; Joseph K. H. Ma; Jin Tsai Wang; Norman C. Li

1972-01-01

244

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

2012-06-22

245

Dual effects of aliphatic carboxylic acids on cresolase and catecholase reactions of mushroom tyrosinase.  

PubMed

Catecholase and cresolase activities of mushroom tyrosinase (MT) were studied in presence of some n-alkyl carboxylic acid derivatives. Catecholase activity of MT achieved its optimal activity in presence of 1.0, 1.25, 2.0, 2.2 and 3.2 mM of pyruvic acid, acrylic acid, propanoic acid, 2-oxo-butanoic acid, and 2-oxo-octanoic acid, respectively. Contrarily, the cresolase activity of MT was inhibited by all type of the above acids. Propanoic acid caused an uncompetitive mode of inhibition (K(i)=0.14 mM), however, the pyruvic, acrylic, 2-oxo-butanoic and 2-oxo-octanoic acids showed a competitive manner of inhibition with the inhibition constants (K(i)) of 0.36, 0.6, 3.6 and 4.5 mM, respectively. So, it seems that, there is a physical difference in the docking of mono- and o-diphenols to the tyrosinase active site. This difference could be an essential determinant for the course of the catalytic cycle. Monophenols are proposed to bind only the oxyform of the tyrosinase. It is likely that the binding of acids occurs through their carboxylate group with one copper ion of the binuclear site. Thus, they could completely block the cresolase reaction, by preventing monophenol binding to the enzyme. From an allosteric point of view, n-alkyl acids may be involved in activation of MT catecholase reactions. PMID:19555185

Gheibi, N; Saboury, A A; Haghbeen, K; Rajaei, F; Pahlevan, A A

2009-10-01

246

Mechanisms of photorelease of carboxylic acids from 1-acyl-7-nitroindolines in solutions of varying water content.  

PubMed

1-Acyl-7-nitroindolines have been found to be useful photoactivated protecting groups for rapid release of carboxylates in aqueous solution. Mechanistic details of carboxylic acid photorelease from model compounds in solutions of varying H2O-CH3CN composition are now reported, using data from product studies, deuterium isotope effects, kinetic studies (UV-Vis), and nanosecond laser flash photolysis. Our data support a mechanism (via T1) that involves reaction of a critical photogenerated intermediate 21 (an acetic nitronic anhydride), obtained via photochemical transfer of the acetyl group from the amide nitrogen to one of the oxygen atoms of the nitro group. This mode of transfer has been reported in the photochemistry of a variety of N-acetyl-o-nitrodiphenyl-amines. Two competing pathways of reaction from 21 that differ in how the acyl group is cleaved are proposed to account for the products observed. In solutions of higher water content, the predominant reaction pathway of 21 is via an A(AL)1-like cleavage that results in formal intramolecular redox reaction of the aromatic ring system, to give the released carboxylic acid and 7-nitrosoindole 3 (after tautomerisation of an initially formed nitroso-3H-indole 9). In solutions of low water content, the major pathway for hydrolysis of 21 is via the standard addition-elimination mechanism (A(AC)2) with water as the nucleophile, that releases the carboxylic acid and nitroindoline 4. Laser flash photolysis studies in wholly aqueous medium gave a transient (within the 20 ns laser pulse) at lambda(max) 450 nm, assignable to 21. Single exponential decay of this species in water (k(obs) = 5 x 10(6) S(-1)) is assigned to the release of the carboxylic acid and formation of the nitroso-3H-indole 9, which is supported by time-resolved measurements of acid release using bromothymol blue. Therefore, 1-acyl-7-nitroindolines photorelease their protected functionalities at rates in the submicrosecond time scale. PMID:12661593

Morrison, James; Wan, Peter; Corrie, John E T; Papageorgiou, George

2002-12-01

247

A new 1-aminocyclopropane-1-carboxylic acid-conjugating activity in tomato fruit.  

PubMed Central

A new conjugate, 1-(gamma-L-glutamylamino)cyclopropane-1-carboxylic acid (GACC), of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) is identified. The only previously identified conjugate of ACC is 1-(malonylamino)cyclopropane-1-carboxylic acid (MACC). GACC, not MACC, was the major conjugate formed by crude protein extracts of tomato (Lycopersicon esculentum Mill cv Ailsa Craig) fruit pericarp and seeds incubated with [14C]ACC. GACC was resolved from [14C]ACC and [14C]MACC by reversed-phase C18 thin-layer chromatography and subsequently detected and quantified using a radioisotope-imaging system. Proteins precipitated from crude extracts failed to catalyze formation of GACC unless the supernatant was added back. Reduced glutathione, but not other reducing agents, replaced the crude supernatant. When [35S-cysteine]glutathione and [3H-2-glycine]glutathione were used as substrates, neither radiolabeled glycine nor cysteine from the glutathione tripeptide was incorporated into GACC. Oxidized glutathione, S-substituted glutathione, and di- and tripeptides having an N-terminal gamma-L-glutamic acid, but lacking cysteine and glycine, also served as substrates for GACC formation. Peptides lacking the N-terminal gamma-L-glutamic acid did not serve as substrates. Acid hydrolysis of GACC yielded ACC, suggesting that GACC is an amide-linked conjugate of ACC. Taken together, these results indicate that GACC is 1-(gamma-glutamylamino)cyclopropane-1-carboxylic acid and that its formation is catalyzed by a gamma-glutamyltranspeptidase. Gas chromatography-mass spectrometry analysis of the N-acetyl dimethyl ester of GACC confirmed this structure.

Martin, M N; Cohen, J D; Saftner, R A

1995-01-01

248

Tandem decarboxylative hydroformylation-hydrogenation reaction of ?,?-unsaturated carboxylic acids toward aliphatic alcohols under mild conditions employing a supramolecular catalyst system.  

PubMed

A new atom economic catalytic method for a highly chemoselective reduction of ?,?-unsaturated carboxylic acids to the corresponding saturated alcohols under mild reaction conditions, compatible with a wide range reactive functional groups, is reported. The new methodology consists of a novel tandem decarboxylative hydroformylation/aldehyde reduction sequence employing a unique supramolecular catalyst system. PMID:24022335

Diab, Lisa; Gellrich, Urs; Breit, Bernhard

2013-09-26

249

Direct and efficient transformation of gaseous alkanes into carboxylic acids catalyzed by vanadium containing heteropolyacids  

Microsoft Academic Search

The vanadium containing heteropolyacids H4[PMo11VO40]×34H2O (HPA-1), H5[PMo10V2O40]×32H2O (HPA-2) and H6[PMo9V3O40]×34H2O (HPA-3) act as highly active catalysts for the direct transformation of light C1–C3 alkanes into the corresponding carboxylic acids in the presence of CO and in the K2S2O8\\/CF3COOH system. Propionic acid (ca. 70% yield), iso- and n-butyric acids (ca. 65% overall yield), and acetic acid (ca. 20%) are the major

Marina V. Kirillova; José A. L. da Silva; João J. R. Fraústo da Silva; Armando J. L. Pombeiro

2007-01-01

250

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

251

Partial Hydrothermal Oxidation of High Molecular Weight Unsaturated Carboxylic Acids for Upgrading of Biodiesel Fuel  

NASA Astrophysics Data System (ADS)

With increasing environmental awareness and crude oil price, biodiesel fuel (BDF) is gaining recognition as a renewable fuel which may be used as an alternative diesel fuel without any modification to the engine. The cold flow and viscosity of BDF, however, is a major drawback that limited its use in cold area. In this study, therefore, we investigated that partial oxidation of high molecular weight unsaturated carboxylic acids in subcritical water, which major compositions in BDF, to upgrade biodiesel fuel. Oleic acid, (HOOC(CH2)7CH=CH(CH2)7CH3), was selected as a model compound of high molecular weight unsaturated carboxylic acids. All experiments were performed with a batch reactor made of SUS 316 with an internal volume of 5.7 cm3. Oleic acid was oxidized at 300 °C with oxygen supply varying from 1-10 %. Results showed that a large amount of carboxylic acids and aldehydes having 8-9 carbon atoms were formed. These experimental results suggest that the hydrothermal oxidative cleavage may mainly occur at double bonds and the cleavage of double bonds could improve the cold flow and viscosity of BDF.

Kawasaki, K.; Jin, F.; Kishita, A.; Tohji, K.; Enomoto, H.

2007-03-01

252

Encapsulated hydrogen-bonded dimers of amide and carboxylic acid  

NASA Astrophysics Data System (ADS)

A theoretical DFT study on benzamide and benzoic acid dimers in the gas phase and encapsulated in two cages of different size has been carried out in order to explain experimental observations regarding the % distributions of the different dimers formed in these cages. The results show that the % distribution of encapsulated dimers in the larger cage is similar to the gas-phase distribution. In the smaller cage interaction of amide with the cage leads to lower dimerization energy and a reduced % fraction of the corresponding encapsulated dimers, compared to the large cage % distribution, in agreement with experiment.

Tzeli, Demeter; Petsalakis, Ioannis D.; Theodorakopoulos, Giannoula; Ajami, Dariush; Jiang, Wei; Rebek, Julius

2012-10-01

253

Acidity of carboxyl group of tyrosine and its analogues and derivatives studied by steady-state fluorescence spectroscopy  

Microsoft Academic Search

The acidity of the carboxyl group of tyrosine and its derivatives and analogues was studied by means of fluorimetric titration using a steady-state fluorescence method. The pKa value of carboxyl group of tyrosine, its analogues and derivatives with blocked amino or hydroxyl group or both determined from the fluorimetric titration curve indicates that the methylation of hydroxyl group of phenolic

Mariusz Szabelski; Katarzyna Guzow; Alicja Rzeska; Joanna Malicka; Monika Przyborowska; Wies?aw Wiczk

2002-01-01

254

Photophysical properties of praseodymium complexes with aromatic carboxylic acids: Double light conversion both in ultraviolet and visible region  

Microsoft Academic Search

A series of luminescent praseodymium complexes with different aromatic carboxylic acids have been synthesized and characterized. The photophysical properties of these complexes have been studied with ultraviolet spectra, phosphorescence spectra and fluorescence spectra. Ultraviolet absorption spectra show that the praseodymium complexes systems with aromatic carboxylate form the more extensive conjugated systems to be suitable for the distribution of electron in

Bing Yan; Weijing Wang; Yishan Song

2007-01-01

255

Formation of carboxylic acids during aerobic biodegradation of crude oil and evidence of microbial oxidation of hopanes  

Microsoft Academic Search

During the biodegradation of crude oil in the laboratory, significant amounts of carboxylic acids were produced. Medium molecular weight (C10–C20) carboxylic acids were rapidly produced, which coincided with the removal of the n-alkanes but these acids were then also rapidly biodegraded. After extensive biodegradation of the hydrocarbons there was an increase in the concentration of higher (>C20) molecular weight branched

J. S Watson; D. M Jones; R. P. J Swannell; A. C. T van Duin

2002-01-01

256

Antibacterial and Physiochemical Behavior of Prepared Chitosan\\/pyridine-3,5-di-carboxylic Acid Complex for Biomedical Applications  

Microsoft Academic Search

This paper describes the preparation of a biocompatible electrostatic chitosan\\/pyridine-3,5-di-carboxylic acid (CH-PyCA) complex which is formed by the protonation (NH 3) of chitosan and deprotonation (COO) of pyridine-3,5-di-carboxylic acid in an acidic medium under mild conditions. The crystalline and structural properties of prepared CH-PyCA complex were evaluated by UV, IR XRD and H-NMR spectroscopic studies. Thermal behavior of the complex

Jay Singh; P. K. Dutta

2011-01-01

257

High stability and high efficiency chemiluminescent acridinium compounds obtained from 9-acridine carboxylic esters of hydroxamic and sulphohydroxamic acids.  

PubMed

A series of hydroxamic acids and sulphohydroxamic acids were prepared and linked to 9-acridinecarboxylic acid through a pseudo-ester function. After N-methylation of the heterocyclic ring, the different compounds were tested for their chemiluminescent properties. Substituents on the hydroxamic functions have shown various effects (steric or electronic) on the luminescence yield or stability of the molecule. The most interesting derivatives were selected in terms of chemical stability and chemiluminescence efficiency. 9-[(N-hydroxysuccinimidyl-4-oxo-4-N-phenylaminobutanoate)N-carb oxylat e]-10-methyl-acridinium (FA6), 9-(N-phenylpivalamide-N-carboxylate)-10-methylacridinium (FA17) and 9-(N-phenylpivalamide N-carboxylate)-10-carboxymethyl-acridinium (FA18) iodomercurates are very promising as chemiluminescent labels. These compounds can be detected at very low levels (10(-16)-10(-17) mol/L) and in our stability evaluation, FA6, FA17 and FA18 showed similar results to the acridinium ester DMAE. Their half-lives at 20 degrees C are greater than 2 weeks. PMID:11038489

Renotte, R; Sarlet, G; Thunus, L; Lejeune, R

258

Formation routes of interstellar glycine involving carboxylic acids: possible favoritism between gas and solid phase.  

PubMed

Despite the extensive search for glycine (NH?CH?COOH) and other amino acids in molecular clouds associated with star-forming regions, only upper limits have been derived from radio observations. Nevertheless, two of glycine's precursors, formic acid and acetic acid, have been abundantly detected. Although both precursors may lead to glycine formation, the efficiency of reaction depends on their abundance and survival in the presence of a radiation field. These facts could promote some favoritism in the reaction pathways in the gas phase and solid phase (ice). Glycine and these two simplest carboxylic acids are found in many meteorites. Recently, glycine was also observed in cometary samples returned by the Stardust space probe. The goal of this work was to perform theoretical calculations for several interstellar reactions involving the simplest carboxylic acids as well as the carboxyl radical (COOH) in both gas and solid (ice) phase to understand which reactions could be the most favorable to produce glycine in interstellar regions fully illuminated by soft X-rays and UV, such as star-forming regions. The calculations were performed at four different levels for the gas phase (B3LYP/6-31G*, B3LYP/6-31++G**, MP2/6-31G*, and MP2/6-31++G**) and at MP2/6-31++G** level for the solid phase (ice). The current two-body reactions (thermochemical calculation) were combined with previous experimental data on the photodissociation of carboxylic acids to promote possible favoritism for glycine formation in the scenario involving formic and acetic acid in both gas and solid phase. Given that formic acid is destroyed more in the gas phase by soft X-rays than acetic acid is, we suggest that in the gas phase the most favorable reactions are acetic acid with NH or NH?OH. Another possible reaction involves NH?CH? and COOH, one of the most-produced radicals from the photodissociation of acetic acid. In the solid phase, we suggest that the reactions of formic acid with NH?CH or NH?CH?OH are the most favorable from the thermochemical point of view. PMID:22066498

Pilling, Sergio; Baptista, Leonardo; Boechat-Roberty, Heloisa M; Andrade, Diana P P

2011-11-08

259

Kinetic studies on the carboxylation of 6-amino-penicillanic acid to 8-hydroxy-penillic acid  

Microsoft Academic Search

The carboxylation in aqueous solution of 6-amino-penicillanic acid (6-APA) to 8-hydroxy-penillic acid (8-HPA) was studied at 25°C and pH 6·5. During sparging with either a citrate buffer or a chemically defined cultivation medium containing 6-APA with mixtures of carbon dioxide and air (2·7–41% (v\\/v) CO2), the kinetics for conversion of 6-APA was followed by HPLC. In the citrate buffer 6-APA

C. M. Henriksen; S. S. Holm; D. Schipper; H. S. Jørgensen; J. Nielsen; J. Villadsen

1997-01-01

260

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

261

Application of L-proline derivatives as chiral shift reagents for enantiomeric recognition of carboxylic acids.  

PubMed

Four proline-derived chiral receptors 5-8 were readily synthesized starting from L-proline. The enantiomeric recognition ability of chiral receptors was examined with a series of carboxylic acids by (1) H NMR spectroscopy. The molar ratio and the association constants of the chiral compounds with each of the enantiomers of guest molecules were determined by using Job plots and a nonlinear least-squares fitting method, respectively. The Job plots indicate that the hosts form 1:1 instantaneous complexes with all guests. The receptors exhibited different chiral recognition abilities toward the enantiomers of racemic guests. Among the chiral receptors used in this study, prolinamide 6 was found to be the best chiral shift reagent and is effective for the determination of the enantiomeric excess of chiral carboxylic acids. PMID:21472784

Naziroglu, Hayriye Nevin; Durmaz, Mustafa; Bozkurt, Selahattin; Sirit, Abdulkadir

2011-04-06

262

C-6 aryl substituted 4-quinolone-3-carboxylic acids as inhibitors of hepatitis C virus.  

PubMed

Quinolone-3-carboxylic acid represents a highly privileged chemotype in medicinal chemistry and has been extensively explored as antibiotics and antivirals targeting human immunodeficiency virus (HIV) integrase (IN). Herein we describe the synthesis and anti-hepatitis C virus (HCV) profile of a series of C-6 aryl substituted 4-quinlone-3-carboxylic acid analogues. Significant inhibition was observed with a few analogues at low micromolar range against HCV replicon in cell culture and a reduction in replicon RNA was confirmed through an RT-qPCR assay. Interestingly, evaluation of analogues as inhibitors of NS5B in a biochemical assay yielded only modest inhibitory activities, suggesting that a different mechanism of action could operate in cell culture. PMID:22748708

Chen, Yue-Lei; Zacharias, Jeana; Vince, Robert; Geraghty, Robert J; Wang, Zhengqiang

2012-06-07

263

Iron-catalyzed, highly regioselective synthesis of ?-aryl carboxylic acids from styrene derivatives and CO2.  

PubMed

The iron-catalyzed hydrocarboxylation of aryl alkenes has been developed using a highly active bench-stable iron(II) precatalyst to give ?-aryl carboxylic acids in excellent yields and with near-perfect regioselectivity. Using just 1 mol % FeCl(2), bis(imino)pyridine 6 (1 mol %), CO(2) (atmospheric pressure), and a hydride source (EtMgBr, 1.2 equiv), a range of sterically and electronically differentiated aryl alkenes were transformed to the corresponding ?-aryl carboxylic acids (up to 96% isolated yield). The catalyst was found to be equally active with a loading of 0.1 mol %. Preliminary mechanistic investigations show that an iron-catalyzed hydrometalation is followed by transmetalation and reaction with the electrophile (CO(2)). PMID:22779807

Greenhalgh, Mark D; Thomas, Stephen P

2012-07-13

264

Online Capillary Electrophoresis for Monitoring Carboxylic Acid Production by Yeast during Bioreactor Cultivations.  

PubMed

Bioprocess monitoring can improve the understanding and control of biotechnological processes. When analyses are carried out as automated online measurements, manual steps of the analysis procedures are avoided, thus decreasing both the time required for analyses and systematic errors. In this study, an online capillary electrophoresis (CE) system with flow-through sample vial made in-house and action control programming was assembled to monitor carboxylic acid production by Kluyveromyces lactis and Saccharomyces cerevisiae during two different bioreactor cultivations. The relative standard deviations were less than 0.6% for intraday migration times and the total analysis time was less than 20 min. The system operated continuously and automatically up to 6 days and produced data concerning carboxylic acid production during the cultivations. The successful test runs demonstrated that this system has potential for the monitoring of biotechnological processes. PMID:24059627

Turkia, Heidi; Holmström, Sami; Paasikallio, Toni; Sirén, Heli; Penttilä, Merja; Pitkänen, Juha-Pekka

2013-10-04

265

Kinetics and mechanism of thermal decomposition of tert-Butylperoxyethyl esters of carboxylic acids  

SciTech Connect

tert-Butylperoxyethyl esters of carboxylic acids are widely used as vulcanization initiators of saturated elastomers and also as comonomers and inititators in polymerization processes. The kinetics of thermal decomposition of these esters of carboxylic acids were studied in the temperature range of 383-413/sup 0/K. The thermal stability of the peroxides is only slightly influenced by change in the substituent in the acyl part. The differences in the energies of activation are compensated by a change in the value of the preexponential factor. A mechanism of the process has been suggested and discussed. The homolytic cleavage of the -00- bond leads to the formation of inactive acyloxyethoxyl radicals, which undergo further decomposition.

Turovskii, A.A.; Aleinikova, T.P.; Kushch, O.V.; Navrotskii, V.A.; Turovskii, N.A.

1985-07-01

266

Selective sorption of alkali-metal cations by carboxylic acid resins containing acyclic or cyclic polyether units  

SciTech Connect

Novel ion-exchange resins have been prepared by condensation polymerization with formaldehyde in formic acid of three polyether carboxylic acids which possess two benzo group substituents. The selectivities and efficiencies of competitive alkali-metal cation sorption from aqueous solutions by these polyether carboxylic acid resins are strongly influenced by (1) the pH of the aqueous solution, (2) the acyclic or cyclic nature of the polyether unit, and (3) the conformational positioning of the carboxylic acid group in the resins derived from cyclic polyether (crown ether) compounds. Good sorption selectivity for Na{sup +} was observed for dibenzo-16-crown-5 resin 3 in which the pendant carboxylic acid group is oriented over the polyether cavity. Resin 3 was utilized as a stationary phase for selective column concentration of Na{sup +} from dilute aqueous solution.

Hayashita, Takashi; Goo, Mija; Lee, Jong Chan; Kim, Jong Seung; Krzykawski, J.; Bartsch, R.A. (Texas Tech Univ., Lubbock (USA))

1990-11-01

267

Salt and co-crystal formation from 6-bromobenzo[d]thiazol-2-amine and different carboxylic acid derivatives  

NASA Astrophysics Data System (ADS)

Studies concentrating on non-covalent interactions between the organic base of 6-bromobenzo[d]thiazol-2-amine, and carboxylic acid derivatives have led to an increased understanding of the role 6-bromobenzo[d]thiazol-2-amine has in binding with carboxylic acid derivatives. Here anhydrous and hydrated multicomponent organic acid-base adducts of 6-bromobenzo[d]thiazol-2-amine have been prepared with the carboxylic acids as p-nitrobenzoic acid, fumaric acid, L-tartaric acid, and terephthalic acid. The four crystalline compounds were characterized by X-ray diffraction analysis, infrared (IR), melting point (mp), and elemental analysis. All structures adopted hetero R22(8) supramolecular synthons except the salt 3. Analysis of crystal packing of the compounds under study suggests that there are NH\\ctdot O, OH\\ctdot N, and OH\\ctdot O hydrogen bonds (charge assisted or neutral) between acid and base components in the supramolecular assemblies.

Jin, Shouwen; Yan, Pinhui; Wang, Daqi; Xu, Yijie; Jiang, Yingyan; Hu, Liangliang

2012-05-01

268

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

269

Soluble sugars and carboxylic acids in ripe apricot fruit as parameters for distinguishing different cultivars  

Microsoft Academic Search

Major sugar and carboxylic acid components in apricot flesh fruits were detected and quantified. Fifty-one genotypes including\\u000a clones growing in France, Spain, Italy, Greece and USA, belonging to the INRA germ plasm collection has been evaluated. Principal\\u000a component analysis (PCA) has been performed to study correlation among fruit quality measurements and to interpret relationships\\u000a between genotypes as a tool for

Fabrizio Gurrieri; Jean-Marc Audergon; Guy Albagnac; Maryse Reich

2001-01-01

270

Prevention of anode fouling during the electrochemical perfluorination of aromatic carboxylic acid chlorides  

Microsoft Academic Search

The electrochemical perfluorination of benzoyl chloride, p-substituted benzoyl chlorides and cyclo-hexane carboxylic acid chloride in anhydrous hydrogen fluoride (AHF) medium on nickel electrode is reported. Experimental conditions suppressing polymeric film formation on the electrode are optimized. Addition of 1wt.% dimethyl sulfide based on the volume of AHF in the initial stage of electrochemical fluorination and maintenance of the reactant and

N. Ilayaraja; D. Velayutham; M. Noel

2009-01-01

271

Palladium-catalyzed decarboxylative cross-coupling reaction between heteroaromatic carboxylic acids and aryl halides.  

PubMed

A full overview of the decarboxylative cross-coupling reaction between heteroaromatic carboxylic acids and aryl halides is described. This transformation employs palladium catalysts with short reaction times providing facile synthesis of aryl-substituted heteroaromatics. The effect of each reaction parameter including solvent, base, and additive employed as well as the full substrate scope of this transformation are reported. Mechanistic evidence is also disclosed that sheds light on possible reaction pathways. PMID:20136159

Bilodeau, François; Brochu, Marie-Christine; Guimond, Nicolas; Thesen, Kris H; Forgione, Pat

2010-03-01

272

SOLVENT EXTRACTION OF URANIUM( VI) AND THORIUM( IV) FROM NITRATE MEDIA BY CARBOXYLIC ACID AMIDES  

Microsoft Academic Search

A series of nineteen N-alkyl carboxylic acid amides (R.CO.NHR') has been prepared, in which the alkyl groups R and R' have been varied in order to introduce different degrees of steric complexity into the compounds. A smaller number of N,N-dialkyl amides (R.CO.NR2) and non-substituted amides (R.CO.NH2) has also been prepared for comparison purposes. These amides were characterized by measurement of

John S. Preston; Anna C. du Preez

1995-01-01

273

Adenosine5?-carboxylic acid peptidyl derivatives as inhibitors of protein kinases  

Microsoft Academic Search

A new class of protein kinase bisubstrate-analog inhibitors was designed on the basis of adenosine-5?-carboxylic acid derivatives, where a short peptide was attached to the 5?-carbon atom of the adenosine sugar moiety via a linker chain. The potency and selectivity of these inhibitors were adjusted by relevant combination of these structural fragments, resembling the structure of the bisubstrate complex of

Mart Loog; Asko Uri; Gerda Raidaru; Jaak Järv; Pia Ek

1999-01-01

274

Adenosine-5'-carboxylic acid peptidyl derivatives as inhibitors of protein kinases.  

PubMed

A new class of protein kinase bisubstrate-analog inhibitors was designed on the basis of adenosine-5'-carboxylic acid derivatives, where a short peptide was attached to the 5'-carbon atom of the adenosine sugar moiety via a linker chain. The potency and selectivity of these inhibitors were adjusted by relevant combination of these structural fragments, resembling the structure of the bisubstrate complex of the peptide phosphorylation reaction. PMID:10360754

Loog, M; Uri, A; Raidaru, G; Järv, J; Ek, P

1999-05-17

275

Activity of 1-aminocyclopropane carboxylic acid synthase and growth of mustard ( Brassica juncea ) following defoliation  

Microsoft Academic Search

To examine the possible relationship between the activity of 1-aminocyclopropane carboxylic acid synthase (ACS; EC 4.4.1.14)\\u000a and growth of mustard (Brassica juncea L.), ACS activity, ethylene and plant growth were studied in the presence of ACS activity modulators in no-defoliation and\\u000a defoliated plants. Growth of plants was greatest when subjected to defoliation of 50% lower leaves in the plant axis

Nafees A. Khan; Naser A. Anjum; Rahat Nazar; Pervez M. Lone

2008-01-01

276

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

SciTech Connect

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 C and preferably from 250 to 350 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 liter/kg catalyst/h, and preferably from 100 to 1,000 liter/kg catalyst/h.

Gogate, M.R.; Spivey, J.J.; Zoeller, J.R.

1999-12-07

277

Oxidation of carboxylic acids at boron-doped diamond electrodes for wastewater treatment  

Microsoft Academic Search

Thin boron-doped diamond films have been prepared by HF CVD (hot filament chemical vapour deposition technique) on conductive p-Si substrate (Si\\/Diamond). The morphology of these Si\\/diamond electrodes has been investigated by SEM and Raman spectroscopy. The electrochemical behaviour of the Si\\/diamond electrodes in 1 M H2SO4 and in 1 M H2SO4 + carboxylic acids has been investigated by cyclic voltammetry.

D. Gandini; E. Mahé; P. A. Michaud; W. Haenni; A. Perret; Ch. Comninellis

2000-01-01

278

Thermodynamic parameters for the protonation of carboxylic acids in aqueous tetraethylammonium iodide solutions  

Microsoft Academic Search

The protonation constants of 21 carboxylic acids (formic, acetic, propionic, benzoic, phenoxyacetic, salicylic, oxalic, malonic, succinic, itaconic, malic, tartaric, oxydiacetic, thiodiacetic, thiodipropionic, phthalic, maleic, citric, 1,2,3-tricarboxylic, 1,2,4-tricarboxylic and 1,2,4,5-tetracarboxylic), have been determined potentiometrically, by pH-metric measurements, at several temperatures and ionic strengths, 5=T=55°C, 0-3, using tetraethylammonium iodide as background salt. General equations for the dependence on ionic strength of thermodynamic

Alessandro De Robertis; Concetta De Stefano; Carmelo Rigano; Silvio Sammartano

1990-01-01

279

Effect of Carboxylic Acid Side Chains on the Absorption Maximum of Visual Pigments  

Microsoft Academic Search

The proposal that the absorption maximum of the visual pigments is governed by interaction of the 11-cis-retinal chromophore with charged carboxylic acid side chains in the membrane-embedded regions of the proteins has been tested by mutating five Asp and Glu residues thought to be buried in rhodopsin. Changing Glu113 to Gln causes a dramatic shift in the absorption maximum from

Eugene A. Zhukovsky; Daniel D. Oprian

1989-01-01

280

Dynamics of ground-state reverse proton transfer in the 7-azaindole\\/carboxylic acid systems  

Microsoft Academic Search

Dual-level direct dynamics calculation of the ground-state proton transfer reaction is reported for the 7-azaindole(7AI)\\/carboxylic acid system. The reaction path was calculated and the two-dimensional potential energy surface scan was performed at various levels of theory. Only one transition state geometry was resolved in the ground state from the ab initio calculation. The zero-point corrected barrier for the reverse proton

Wei-Ping Hu; Ru-Min You; Shih-Yao Yen; Fa-Tsai Hung; Po-Hung Chou; Pi-Tai Chou

2003-01-01

281

Microbial sulfoxidation and amidation of benzhdrylsulfanyl carboxylic acids and uses thereof  

US Patent & Trademark Office Database

The present invention provides novel methods for the synthesis of racemic and enantiomers of modafinil via microbial oxidation-amidation transformation. The methods include the successive oxidation-amidation of benzhydrylsulfanyl carboxylic acid to produce racemic and enantiomers of modafinil using at least one microorganism of yeast, bacteria, or fungus. Also disclosed are pharmaceutical compositions of racemic and enantiomers of modafinil along with their use in the treatment of diseases, including attention deficit hyperactivity disorder and drug addiction.

2009-06-30

282

TPAP-catalyzed direct oxidation of primary alcohols to carboxylic acids through stabilized aldehyde hydrates.  

PubMed

We present a simple, mild, and highly effective method for the direct conversion of primary alcohols to carboxylic acids. TPAP serves as the catalyst, and NMO·H(2)O plays a dual role, acting as the co-oxidant and as a reagent for aldehyde hydrate stabilization. This previously unknown stabilizing effect of geminal diols by N-oxides is the key for the efficiency of the overall transformation. PMID:21793539

Schmidt, Andrea-Katharina C; Stark, Christian B W

2011-07-27

283

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

SciTech Connect

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 plants 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.

Effmert,U.; Saschenbrecker, S.; Ross, J.; Negre, F.; Fraser, C.; Noel, J.; Dudareva, N.; Piechulla, B.

2005-01-01

284

A Facile Method for Oxidation of Primary Alcohols to Carboxylic Acids and Its Application in Glycosaminoglycan Syntheses  

PubMed Central

A convenient two-step, one-pot procedure was developed for the conversion of primary alcohols to carboxylic acids. The alcohol was first treated with NaOCl and TEMPO under phase-transfer conditions, followed by NaClO2 oxidation in one pot. This reaction is applicable to a wide range of alcohols and the mild reaction conditions are compatible with many sensitive functional groups, including electron-rich aromatic rings, acid-labile isopropylidene ketal and glycosidic linkages, and oxidation-prone thioacetal, p-methoxybenzyl, and allyl moieties. Several glycosaminoglycans such as heparin, chondroitin, and hyaluronic acid oligosaccharides have been synthesized in high yields by using this new oxidation protocol.

Huang, Lijun; Teumelsan, Nardos; Huang, Xuefei

2006-01-01

285

On-line determination of carboxylic acids, aldehydes and ketones by high-performance liquid chromatography-diode array detection-atmospheric pressure chemical ionisation mass spectrometry after derivatization with 2-nitrophenylhydrazine  

Microsoft Academic Search

2-Nitrophenylhydrazine (2-NPH) is widely used for the derivatization of carboxylic acids, aldehydes and ketones, in industrial and biological samples. These compounds react with 2-NPH to form derivatives, which are separated by high-performance liquid chromatography (HPLC) and detected with diode array detection (DAD). The UV spectra give information about the functionality of the compounds: carboxylic acid or ketone\\/aldehyde. Most of the

R. Peters; J. Hellenbrand; Y. Mengerink; Sj. Van der Wal

2004-01-01

286

Synthesis, characterization, guest inclusion, and photophysical studies of gold nanoparticles stabilized with carboxylic Acid groups of organic cavitands.  

PubMed

Water-soluble gold nanoparticles (AuNP) stabilized with cavitands having carboxylic acid groups have been synthesized and characterized by a variety of techniques. Apparently, the COOH groups similar to thiol are able to prevent aggregation of AuNP. These AuNP were stable either as solids or in aqueous solution. Most importantly, these cavitand functionalized AuNP were able to include organic guest molecules in their cavities in aqueous solution. Just like free cavitands (e.g., octa acid), cavitand functionalized AuNP includes guests such as 4,4'-dimethylbenzil and coumarin-1 through capsule formation. The exact structure of the capsular assembly is not known at this stage. Upon excitation there is communication between the excited guest present in the capsule and gold atoms and this results in quenching of phosphorescence from 4,4'-dimethylbenzil and fluorescence from coumarin-1. PMID:24059841

Mondal, Barnali; Kamatham, Nareshbabu; Samanta, Shampa R; Jagadesan, Pradeepkumar; He, Jibao; Ramamurthy, V

2013-10-04

287

Relative stability of tris(2-thenoyltrifluoroacetonato) lanthanoid(III) adducts with carboxylic acids having naphthalene ring  

SciTech Connect

The formation constants of the adduts of tris(1-(2-thienly)-4,4, 4-trifluoro-1,3-butanedionato)lanthanoids(III) with 1- and 2-naphthalenecarboxylic or 1- and 2-napthaleneacetic acids have been determined by the solvent extraction method at 298K. It has been found that the adducts with napthalenecarboxylic acid are a little more stable than those with napthaleneacetic acid irrespective of lanthanoid as similar as the formation of more stable adducts with benzoic acid than with phenylacetic acid reported before. The formation constants of the adducts of several lanthanoid chelates with these four carboxylic acids decreased from lanthanum to samarium and from terbium to lutetium with increasing atomic number, while the constants did not change much in the middle of the series. Such trend has been discussed in the relation to the difference of the coordination number between the lighter and the heavier lanthanoids(III). 9 refs., 3 figs., 3 tabs.

Hasegawa, Yuko; Yamanda, Takami; Nagata, Koji [Science Univ. of Tokyo (Japan)

1996-01-01

288

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

289

Determination of impurities in flame retardant monomer 2-carboxyl ethyl(phenyl) phosphinic acid by ion chromotography  

Microsoft Academic Search

In this paper, a method based on ion chromatography (IC) with conductivity detector was developed for the determination of impurities including phenyl phosphinic acid (BPA), phenyl phosphonic acid (PPOA) and crylic acid in flame retardant monomer 2-carboxyl ethyl(phenyl) phosphinic acid (CEPPA). Under favorable chromatographic conditions, good linear relationship, sensitivity and reproducibility were obtained. Detection limits of BPA, PPOA and crylic

Mei-Lan Chen; Wei Yan; Yongxin Chen; Zhishen Jia; Yan Zhu

2007-01-01

290

Determination of the Cyanide Metabolite 2-Aminothiazoline-4-Carboxylic Acid in Urine and Plasma by Gas Chromatography-Mass Spectrometry.  

National Technical Information Service (NTIS)

The cyanide metabolite 2-aminothiazoline.4-carboxylic acid (ATCA) is a promising biomarker for cyanide exposure because of its stability and the limitations of direct determination of cyanide and more abundant cyanide metabolites. A simple, sensitive, and...

B. A. Logue N. P. Kirschten I. Petrikovics M. A. Moser G. A. Rockwood

2005-01-01

291

Fluorinated alkyl compounds including long chain carboxylic acids in wild bird livers from Japan.  

PubMed

A wide range of fluorinated alkyl compounds (FACs) has been reported in wildlife in various locations in the world. However, such information regarding Japanese wildlife is rarely found. In the present study, we investigated the occurrence of 21 FACs, including perfluorinated alkyl sulfonates (PFASs), perfluorinated carboxylates (PFCAs), and fluorotelomer acids, in the livers of 10 wild bird species from two regions in northern Japan. To avoid interferences, FACs were quantified by a recently developed method using acetonitrile and solid-phase extraction followed by an ion exchange HPLC column separation. Apart from perfluorooctane sulfonate (PFOS), which was found at the highest levels of all the compounds detected, several long chain perfluorinated carboxylates (PFCAs) from C8 to C16, particularly perfluorotetradecanoic acid (PFTeDA) and perfluorohexadecanoic acid (PFHxDA), were detected for the first time. Additionally, 7:3 FTCA, a fluorotelomer acid, was also detected in most swan livers from Miyagi prefecture and all the birds from Tochigi prefecture. However, none of the sulfonamides and unsaturated telomer acids were detected in any species. Swans seem to be the least exposed wild birds to FACs among the investigated birds, signifying that feeding habits may reflect FAC accumulation in wild birds. The highest total concentration of detected FACs was 405ngg(-1)wet wt., which was found in a Japanese sparrowhawk, indicating that the top predatory wild birds can accumulate several long chain carboxylic acids. However, the current FAC concentrations found in livers may suggest that these compounds alone would not cause a severe toxic effect in these species. PMID:21190717

Guruge, Keerthi S; Yeung, Leo W Y; Li, Peng; Taniyasu, Sachi; Yamashita, Nobuyoshi; Nakamura, Mayumi

2010-12-28

292

An ultra sensitive saccharides detection assay using carboxyl functionalized chitosan containing Gd2O3: Eu3+ nanoparticles probe  

Microsoft Academic Search

A novel saccharides detection assay based on covalent immobilization of\\u000a amino phenyl boronic acid (APBA) in thin films of carboxyl\\u000a functionalized chitosan (HOOC-chitosan) containing 5 nm Gd2O3 : Eu3+\\u000a nanoparticles at a platinum disc electrode was developed. The resulting\\u000a HOOC-chitosan\\/Gd2O3 : Eu3+ nanocomposite film exhibited excellent\\u000a electrochemical response to changes in the pK(a) values of boronate\\u000a esters yielded from different

Ashutosh Tiwari; Dohiko Terada; Prashant K. Sharma; Vyom Parashar; Chiaki Yoshikawa; Avinash C. Pandey; Hisatoshi Kobayashi

2011-01-01

293

Preparation of sulfate- and carboxyl-functionalized magnetite\\/polystyrene spheres for further deposition of gold nanoparticles  

Microsoft Academic Search

A synthetic method developed for preparation of sulfate- and carboxyl-functionalized magnetite\\/polystyrene (Fe3O4\\/PS) spheres that can be further decorated with gold (Au) nanoparticles is reported. By using emulsifier-free emulsion polymerization\\u000a based on potassium persulfate (KPS)\\/methyl acrylic acid (MAA)\\/water system in the presence of Fe3O4\\/PS spheres used as the seeds, PMAA-coated magnetic Fe3O4-PS spheres were readily obtained. The sulfate group is inherent

Szu-Ching Hsiao; Jinn-Luh Ou; Yuh Sung; Chang-Pin Chang; Ming-Der Ger

2010-01-01

294

Role of apparent p K a of carboxylic acids in lipase-catalyzed esterifications in biphasic systems  

Microsoft Academic Search

Lipase-catalyzed esterifications in biphasic media (heptane–water, 1:1) were conducted by using Thermomyces lanuginosus lipase (TLL) as biocatalyst. Different carboxylic acids (from acetic to lauric) were thus esterified with 1-butanol at different pH values (2–10). For all carboxylic acids tested, pH optima for the enzymatic esterifications were ca. 3–5, in clear agreement with previous literature, and quite different from optima pH

Pablo Domínguez de María; Elena Fernández-Álvaro; Antoon ten Kate; Gerrald Bargeman

2009-01-01

295

Synthesis of biaryl imino/keto carboxylic acids via aryl amide directed C-H activation reaction.  

PubMed

A novel Pd-catalysed C-H activation reaction for the synthesis of biaryl imino/keto carboxylic acids is developed. This reaction underwent aryl amide directed C-H activation ortho-acylation followed by ring closing and ring opening processes to give a range of biaryl imino/keto carboxylic acids. Our methodology features the utilization of a cheap and green oxidant (TBHP) as well as readily available aldehydes. PMID:24013806

Zhang, Nana; Yu, Qingzhen; Chen, Ruixue; Huang, Jianhui; Xia, Yeqing; Zhao, Kang

2013-10-21

296

Arginine-responsive terbium luminescent hybrid sensors triggered by two crown ether carboxylic acids.  

PubMed

Crown ether carboxylic acids constitute main building blocks for the synthesis of terbium containing covalent cross-linked luminescent materials. Both the complexes and the hybrid nanomaterials could exhibit remarkable green emissions in pure water. More importantly, they were found to have a profound effect on the luminescence responses to arginine compared with glutamic acid, histidine, tryptophan, threonine, tyrosine and phenylalanine in aqueous environment. The present study provided the possibility of using a host-guest mechanism as a way of signal transduction based on lanthanide supramolecular hybrid materials. PMID:24094229

Jiang, Lasheng; Tang, Ke; Ding, Xiaoping; Wang, Qianming; Zhou, Zhan; Xiao, Rui

2013-09-17

297

Photocatalytic decomposition of a perfluoroether carboxylic acid by tungstic heteropolyacids in water  

Microsoft Academic Search

The photochemical decomposition of perfluoroether carboxylic acid C2F5OC2F4OCF2COOH (EEA), which is being introduced in industry as a surfactant alternative to environmentally persistent and bioaccumulative perfluorocarboxylic acids, was investigated by use of water-soluble tungstic heteropolyacids H3PW12O40 and H4SiW12O40, and the results were compared with those of conventional techniques, UV–visible light irradiation in the presence of H2O2, treatment with Fenton's reagent, and

Hisao Hori; Ari Yamamoto; Kazuhide Koike; Shuzo Kutsuna; Misako Murayama; Arifumi Yoshimoto; Ryuichi Arakawa

2008-01-01

298

Microwave-Induced Chemical Functionalization of Carboxylated Multi-Walled Nanotubes With 2,3-diaminopyridine  

Microsoft Academic Search

In this paper, the microwave-induced chemical functionalization of carboxylated multi-walled carbon nanotubes (MWNT-COOH) by 2,3-diaminopyridine, have been investigated. The major advantage of this high-energy procedure is reducing the reaction time to the order of minutes and the number of steps in the reaction procedure compared to that of conventional functionalization processes. These functionalizations involve amidation and cycloaddition reactions, respectively. The

Javad Azizian; Hasan Tahermansouri; Davood Chobfrosh Khoei; Khadijeh Yadollahzadeh; Akram Sadat Delbari

2012-01-01

299

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.

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

2013-01-01

300

Protein binding of flavoxate and of 3-methylflavone-8-carboxylic acid.  

PubMed

The protein binding properties of piperidino-3-methylflavone-8-carboxylate (flavoxate, F) and of its main metabolite, i.e. 3-methylflavone-8-carboxylic acid (M), were investigated by dialysis-equilibrium technique. During the dialysis, F hydrolyzes to a notable extent into M. Therefore a true equilibrium of F could not be obtained. With this limitation, the results show that F has a small protein affinity. The protein binding properties of M were separately investigated with bovine albumin, human albumin and with human, rat, rabbit and dog plasma. The Freundlich's isotherms, which describe the affinities of albumin to M, were calculated. They show that unconjugated M, possibly present in plasma, is by 99.5% in a protein-bound form. PMID:1243078

Conti, M; Setnikar, I

1975-11-01

301

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

NASA Astrophysics Data System (ADS)

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

Godfrey, Peter D.; McNaughton, Don

2013-01-01

302

Synthesis and characterisation of some ruthenium(II) complexes of ?- N heterocyclic carboxylic acids—X-ray structures of cis-[Ru(PPh 3) 2(L 1) 2]·2CH 3OH and cis-[Ru(PPh 3) 2(L 3H) 2] (L 1H=pyridine 2-carboxylic acid and L 3H 2=imidazole 4,5-dicarboxylic acid)  

Microsoft Academic Search

Synthesis and characterisation of ruthenium(II) complexes of several ?-N heterocyclic carboxylic acids of the general formula [Ru(PPh3)2(L)2] are reported [LH=pyridine 2-carboxylic acid (L1H), pyrazine 2-carboxylic acid (L2H), imidazole 4,5-dicarboxylic acid (L3H2) and pyrazine 2,3-dicarboxylic acid (L4H2)]. All the acids behaved as bidentate N–O chelating donors, the second carboxyl group of the dicarboxylic acids remaining free. Electrochemical behaviour of the complexes

Parbati Sengupta; Rupam Dinda; Saktiprosad Ghosh; W. S Sheldrick

2001-01-01

303

Conversion of municipal solid wastes to carboxylic acids by thermophilic fermentation.  

PubMed

The purpose of this research is to generate carboxylic acids from the biodegradable fraction of municipal solid wastes (MSW) and municipal sewage sludge (MSS) by using a thermophilic (55 degrees C), anaerobic, high-solid fermentation. With terrestrial inocula, the highest total carboxylic acid concentration achieved was 20.5 g/L, the highest conversion obtained was 69%, and the highest acetic acid selectivity was 86.4%. Marine inocula were also used to compare against terrestrial sources. Continuum particle distribution modeling (CPDM) was used to predict the final acid product concentrations and substrate conversions at a wide range of liquid residence times (LRT) and volatile solid loading rates (VSLR). "Maps" showing the product concentration and conversion for various LRT and VSLR were generated from CPDM. The predictions were compared to the experimental results. On average, the difference between the predicted and experimental values were 13% for acid concentration and 10% for conversion. CPDM "maps" show that marine inocula produce higher concentrations than terrestrial inocula. PMID:14646001

Chan, Wen Ning; Holtzapple, Mark T

2003-11-01

304

A sensitive and selective imprinted solid phase extraction coupled to HPLC for simultaneous detection of trace quinoxaline-2-carboxylic acid and methyl-3-quinoxaline-2-carboxylic acid in animal muscles.  

PubMed

A new molecularly imprinted polymer (MIP), selective for major metabolites of quinoxaline-1,4-dioxides, was prepared through bulk polymerisation using quinoxaline-2-carboxylic acid (QCA) as template, diethylaminoethylmethacrylate as functional monomer and ethylene glycol dimethacrylate as cross-linker in tetrahydrofuran. The synthesised MIP was characterised by Fourier transform infrared and adsorption experiments. MIP exhibited high affinity, fast kinetics for QCA and good selectivity for QCA and methyl-3-quinoxaline-2-carboxylic acid (MQCA). MIP obtained was used as a selective sorbent for molecularly imprinted solid phase extraction (MISPE) coupled with HPLC to detect QCA and MQCA. Under the optimal conditions, the limits of detection (S/N=3) of porcine, chicken and fish muscles were 0.1, 0.3, 0.1 ?g/kg for QCA and 0.2, 0.3, 0.1 ?g/kg for MQCA, respectively and good recoveries were obtained in the range from 60.0 to 119.4%. These results indicated the MISPE-HPLC procedure could be successfully used for the determination QCA and MQCA in animal muscles. PMID:23561106

Duan, Zhenjuan; Yi, Jianghua; Fang, Guozhen; Fan, Lipeng; Wang, Shuo

2013-02-16

305

Acid–base properties of ion exchangers. I. Optimising of potentiometric titration of ion exchangers exemplified by carboxylic acid resins  

Microsoft Academic Search

The aim of this work was to determined conditions for fast titration the ion exchanger in the one-sample experiment allowing obtaining its equilibrium titration curve. Carboxylic acid ion exchangers KB-4 and Dowex MAC-3 were taken as examples. They were titrated under different conditions with NaOH, KOH and Ba(OH)2. The forward and backward titration of concentrated immersions of finely ground ion

V. S Soldatov; Z. I Sosinovich; T. A Korshunova; T. V Mironova

2004-01-01

306

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

307

Accurate gas phase acidities of carboxylic acids estimated by scaling the vibrational contribution of ab initio gibbs free energies  

Microsoft Academic Search

The gas phase Gibbs free energies ?GT of dissociation reaction of 14 carboxylic acids were calculated on the SCF, as well as G3 and CBS-Q levels. Corresponding\\u000a accuracies were critically compared with experimental data. Since all of the results suffer from systematic errors, the procedure\\u000a of scaling of thermal contribution to Gibbs free energy was applied for minimizing differences between

Piotr Cysewski

2007-01-01

308

Mixing of partially fluorinated carboxylic acids with their hydrocarbon analogs at the air-water interface.  

PubMed

The mixing behavior of 1-(perfluorobutyl)undecanoic acid-pentadecanoic acid (C15), 1-(perfluorohexyl)undecanoic acid-heptadecanoic acid (C17), and 1-(perfluorooctyl) undecanoic acid-nonadecanoic acid (C19) mixtures was investigated at the air-water interface. The compression isotherms of the fluorocarbon acid-hydrocarbon acid mixtures were recorded at various compositions on hydrochloric acid (pH 1.9, 37+/-2 degrees C) as a subphase. The phase transition, limiting molecular area, area at collapse pressure, and collapse pressure were determined for all pi-A isotherms. The mixing behavior was assessed by analyzing the concentration dependence of the average molecular area at constant film pressure (area/mole fraction or A-X diagram) and the concentration dependence of the phase transition, where possible. All three acid mixtures show a negative deviation from ideal behavior at surface pressures between 5 and 20 mN/m, which is indicative of an attractive interaction of both compounds in the mixed monolayer at the air-water interface. The miscibility apparently decreases with increasing chain length of the carboxylic acids (C15>C17>C19). PMID:16290612

Lehmler, Hans-Joachim; Bummer, Paul M

2002-05-15

309

Novel regiochemistry in the aqueous singlet oxygen ene reactions of carboxylic acid salts: a comparison of substrate structure  

Microsoft Academic Search

The singlet oxygen (1?g) photooxidations of angelic acid salt (1), tiglic acid salt (2), 2,3-dimethyl-2-butenoic acid salt (3), 3-ethoxycarbonyl-5,6-dihydro-2-methyl-4H-pyrane acid salt (4), cis-3-hexenoic acid salt (5), and trans-3-hexenoic acid salt (6) were conducted in deuterated water. The major and minor ene allylic hydroperoxide products were quantified and indicate that the allylic hydrogen geminal to the carboxylate group is preferentially abstracted

Kristina L. Stensaas; Anisha Bajaj; Akram Al-Turk

2005-01-01

310

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

311

Distinguishing two groups of flavin reductases by analyzing the protonation state of an active site carboxylic acid.  

PubMed

Flavin-containing reductases are involved in a wide variety of physiological reactions such as photosynthesis, nitric oxide synthesis, and detoxification of foreign compounds, including therapeutic drugs. Ferredoxin-NADP(H)-reductase (FNR) is the prototypical enzyme of this family. The fold of this protein is highly conserved and occurs as one domain of several multidomain enzymes such as the members of the diflavin reductase family. The enzymes of this family have emerged as fusion of a FNR and a flavodoxin. Although the active sites of these enzymes are very similar, different enzymes function in opposite directions, that is, some reduce oxidized nicotinamide adenine dinucleotide phosphate (NADP(+)) and some oxidize reduced nicotinamide adenine dinucleotide phosphate (NADPH). In this work, we analyze the protonation behavior of titratable residues of these enzymes through electrostatic calculations. We find that a highly conserved carboxylic acid in the active site shows a different titration behavior in different flavin reductases. This residue is deprotonated in flavin reductases present in plastids, but protonated in bacterial counterparts and in diflavin reductases. The protonation state of the carboxylic acid may also influence substrate binding. The physiological substrate for plastidic enzymes is NADP(+), but it is NADPH for the other mentioned reductases. In this article, we discuss the relevance of the environment of this residue for its protonation and its importance in catalysis. Our results allow to reinterpret and explain experimental data. PMID:21538544

Dumit, Verónica I; Cortez, Néstor; Matthias Ullmann, G

2011-05-02

312

Synthesis of tricyclic indole-2-carboxylic [correction of caboxylic] acids as potent NMDA-glycine antagonists.  

PubMed

The practical synthesis of a series of tricyclic indole-2-carboxylic acids, 7-chloro-3-arylaminocarbonylmethyl-1,3,4,5-tetrahydrobenz[cd]indole-2-carboxylic acids, as a new class of potent NMDA-glycine antagonists is described. The synthetic route to the key intermediate 12a comprises a regioselective iodination of 4-chloro-2-nitrotoluene, modified Reissert indole synthesis, Jeffery's Heck-type reaction with allyl alcohol, Wittig-Horner-Emmons reaction, and iodination at the indole C-3 position. The key step in the route is an intramolecular cyclization of 12a to give the tricyclic indole structure. Two methods of cyclization, (1) an intramolecular radical cyclization of 12a and (2) a sequence of intramolecular Heck reaction of 12a followed by a 1,4-reduction, were performed. The resulting tricyclic indole diester 13a was selectively hydrolyzed to afford the desired tricyclic indole monocarboxylic acid 16 on a multihundred gram scale without any chromatographic purifications. Optical resolution of 16 to (-)-isomer 17 and (+)-isomer 18 was carried out, and the resulting isomers were derivatized, respectively. Evaluation of the optically active derivatives for affinity to the NMDA-glycine binding site using the radio ligand binding assay with [(3)H]-5,7-dichlorokynurenic acid revealed that the derivatives of (-)-isomer 17 were more potent than the others and that especially substituted anilide (-)-isomer 24 (K(i) = 0.8 nM) showed high affinity. PMID:11348132

Katayama, S; Ae, N; Nagata, R

2001-05-18

313

Biosynthesis of cyclopentenyl fatty acids. (2-Cyclopentenyl)carboxylic acid (aleprolic acid) as a special primer for fatty acid biosynthesis in Flacourtiaceae.  

PubMed

The biosynthesis of cyclopentenyl fatty acids from (2-cyclopentenyl)carboxylic acid (aleprolic acid) via chain-lengthening by C2-units was tested in seeds and leaves of Caloncoba echinata and Hydnocarpus anthelminthica of Flacourtiaceae and in various prepatations of higher plants other than Fla courtiaceae. Only tissues of Flacourtiaceae, where cyclopentenyl fatty acids are found naturally, were able to accept aleprolic acid as a starter molecule for the synthesis of cyclic fatty acids. Labelling patterns of straight chain and cyclic fatty acids, synthesized after incubation of Flacourtiaceae seeds with [1-(14)C[-acetate, indicated de novo synthesis of C16 fatty acids in either case, followed by elongation to higher homologs. PMID:990306

Cramer, U; Spener, F

1976-11-19

314

Preparation and Characterization of Poly (1, 3-propylene glycol-hexanedioic acid)-functionalized Carbon Nanotubes  

Microsoft Academic Search

An in situ process was used to prepare poly (1, 3-propylene glycol-hexanedioic acid)-functionalized carbon nanotubes using carboxylate-functionalized multi-walled carbon nanotubes, 1, 3-propylene glycol and hexanedioic acid as reactants. The functionalized carbon nanotubes were characterized using transmission electronic microscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis. The results indicated that the carboxylate-functionalized carbon nanotubes chemically reacted and were linked with the

Qing-Jie Meng; Xing-Xiang Zhang; Xue-Chen Wang

2007-01-01

315

Crystal structures of (2 R,4 R)-2-(polyhydroxyalkyl)-1,3-thiazolidine-4-carboxylic acids: condensation products of l-cysteine with d-hexoses  

Microsoft Academic Search

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·H2O (1), and 2-(d-manno-pentahydroxypentyl)thiazolidine-4-carboxylic acid hydrate, Man-Cys·H2O (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

Miros?aw Tarnawski; Katarzyna ?lepokura; Tadeusz Lis

2011-01-01

316

Malic Acid Production by Saccharomyces cerevisiae: Engineering of Pyruvate Carboxylation, Oxaloacetate Reduction, and Malate Export? †  

PubMed Central

Malic acid is a potential biomass-derivable “building block” for chemical synthesis. Since wild-type Saccharomyces cerevisiae strains produce only low levels of malate, metabolic engineering is required to achieve efficient malate production with this yeast. A promising pathway for malate production from glucose proceeds via carboxylation of pyruvate, followed by reduction of oxaloacetate to malate. This redox- and ATP-neutral, CO2-fixing pathway has a theoretical maximum yield of 2 mol malate (mol glucose)?1. A previously engineered glucose-tolerant, C2-independent pyruvate decarboxylase-negative S. cerevisiae strain was used as the platform to evaluate the impact of individual and combined introduction of three genetic modifications: (i) overexpression of the native pyruvate carboxylase encoded by PYC2, (ii) high-level expression of an allele of the MDH3 gene, of which the encoded malate dehydrogenase was retargeted to the cytosol by deletion of the C-terminal peroxisomal targeting sequence, and (iii) functional expression of the Schizosaccharomyces pombe malate transporter gene SpMAE1. While single or double modifications improved malate production, the highest malate yields and titers were obtained with the simultaneous introduction of all three modifications. In glucose-grown batch cultures, the resulting engineered strain produced malate at titers of up to 59 g liter?1 at a malate yield of 0.42 mol (mol glucose)?1. Metabolic flux analysis showed that metabolite labeling patterns observed upon nuclear magnetic resonance analyses of cultures grown on 13C-labeled glucose were consistent with the envisaged nonoxidative, fermentative pathway for malate production. The engineered strains still produced substantial amounts of pyruvate, indicating that the pathway efficiency can be further improved.

Zelle, Rintze M.; de Hulster, Erik; van Winden, Wouter A.; de Waard, Pieter; Dijkema, Cor; Winkler, Aaron A.; Geertman, Jan-Maarten A.; van Dijken, Johannes P.; Pronk, Jack T.; van Maris, Antonius J. A.

2008-01-01

317

Covalent binding of fluorotelomer unsaturated aldehydes (FTUALs) and carboxylic acids (FTUCAs) to proteins.  

PubMed

Fluorotelomer unsaturated carboxylic acids and aldehydes (FTUCAs and FTUALs) are intermediate compounds that form from the biotransformation of fluorotelomer-based compounds. Previous evidence that FTUCAs and FTUALs bind to biological nucleophiles has indicated that protein binding might give rise to toxicity resulting from protein function disruption. The current study assesses the reactivity of FTUALs and FTUCAs by probing the covalent interactions of FTUALs and FTUCAs with proteins present in rat liver microsomes and bovine blood plasma. The FTUALs exhibited significant levels of protein covalent binding, with binding levels ranging from 20.1 (±2.8)% to 71.3 (±19.5)% in microsomes and 24.0 (±1.5)% to 82.5 (±14.0)% in blood plasma. By contrast, the FTUCAs did not exhibit any apparent covalent binding. Bovine serum albumin (BSA) was extracted and isolated from the plasma after incubation of 8:2 FTUAL (5-100 ?M). Electrospray ionization mass spectrometry (ESI-MS) was used to investigate the stoichiometry of 8:2 FTUAL covalently bound to BSA; three measurable FTUAL adducts were formed with BSA. To compare the percent binding results from the FTUAL microsome incubation experiments, 8:2 FTOH was incubated in microsomes to determine the protein binding associated with the biotransformation of 8:2 FTOH. Results from this study showed that the biotransformation of 8:2 FTOH yielded 26.1 (±3.0)% binding, and was statistically similar to the percent binding associated with 8:2 FTUAL exposure (p > 0.05), indicating that the binding of 8:2 FTUAL to proteins might be a primary fate in the biotransformation of 8:2 FTOH. PMID:23256684

Rand, Amy A; Mabury, Scott A

2013-01-09

318

Tumor hypoxia fluorescence imaging using 2-nitroimidazole bis-carboxylic acid indocyanine dye conjugate  

NASA Astrophysics Data System (ADS)

We present tumor hypoxia mapping by diffuse optical fluorescence tomography. A novel 2-nitroimidazole bis-carboxylic acid indocyanine dye conjugate has been developed for tumor-targeted hypoxia fluorescence imaging. The hypoxia probe has been evaluated in-vitro using 4T1 tumor cell lines and in-vivo tumor targeting in mice. In-vivo tumor targeting in six mice demonstrated that a measured half-life of 2-nitroimidazole-indocyanine dye wash out in the tumor was significantly longer (112+/-32.37 minutes) than that of bis-carboxylic acid indocyanine dye (69.75+/-14.01 minutes). The bis-carboxylic acid indocyanine dye was completely washed out from the tumor site within 3-5 hours post-injection, but 2-nitroimidazole-ICG remained for up to 21 hours in the tumor site. Near infrared fluorescence images of mice tumors showed a 2.6-fold contrast of dye uptake with hypoxic conjugate injection (7.46+/-1.68 ?M) compared to that with indocyanine dye injection (2.9+/-0.60 ?M). The in-vitro cell studies were performed to assess fluorescence labeling comparing hypoxia to normoxia conditions. A fluorescence emission ratio of 2.5-fold was found between the cells treated with the 2-nitroimidazole-indocyanine dye and incubated under hypoxia compared to the cells in normoxia condition. Hypoxia specificity was also confirmed when compared to cells treated with unconjugated indocyanine dye alone. Fluorescence images acquired using a Li-COR scanner from harvested tumor samples support the in vivo monitoring and imaging results.

Biswal, Nrusingh C.; Pavlik, Christopher; Smith, Michael B.; Aguirre, Andres; Zanganeh, Saeid; Xu, Yan; Kuhn, Liisa T.; Claffey, Kevin P.; Zhu, Quing

2011-02-01

319

Synthesis and characterization of novel tricarboxylatoplatinum(IV) complexes. Nucleophilic substitution of (diamine)-tetrahydroxoplatinum(IV) with carboxylic acid  

Microsoft Academic Search

The reaction of [Pt(IV)(dach)(OH)4] (dach=trans-(±)-1,2-diaminocyclohexane) with an excess of carboxylic acid at room temperature afforded tricarboxylatoplatinum(IV) complexes, [Pt(dach)(L)3(OH)] (L=acetato, propionato, valerato) in contrast to the carboxylation reaction with excess carboxylic anhydrides, which gave only tetracarboxylatoplatinum(IV) complexes as a major product. The protonation on hydroxo ligand of the platinum(IV) complex to form aqua ligand seems to be followed by nucleophilic substitution

Rita Song; Kwan Mook Kim; Youn Soo Sohn

2002-01-01

320

Hydrogen-bonding linkage of thymidine derivatives with carboxylic acid and pyridyl groups in a crystalline state.  

PubMed

Thymidine derivatives with carboxylic acid and pyridyl groups were synthesized for constructing one-dimensional network structure based on hydrogen bonding in crystalline state. The solid sate structures and hydrogen bonding networks of the thymidine derivatives were characterized by single X-ray diffraction analysis. The thymidine derivatives formed a zwitterion structure with a pyridinium proton and a carboxylate moiety in a crystalline state due to transfer of a proton from the carboxylic acid to the pyridyl moiety. Strong hydrogen bonds between the pyridinium proton and the carboxylate moiety connected the thymidine units, resulting in a one-dimensional polymeric structure with a uniform direction reminiscent of the structure of single-strand polythymidine. The chemical structure of the pyridyl group affects the hydrogen-bonding networks. The well-designed hydrogen-bonding interaction served as connecting parts for polythymidine mimics even in the presence of other hydrogen-bonding motifs such as nucleobases. PMID:23901479

Hoshino, Junichi; Kuwabara, Junpei; Kanbara, Takaki

2013-07-01

321

Molecular structure, hydrogen bonding and spectroscopic properties of the complex of piperidine-4-carboxylic acid with chloroacetic acid  

Microsoft Academic Search

Complex of piperidine-4-carboxylic acid with chloroacetic acid has been studied by X-ray diffraction, FTIR, Raman, 1H and 13C NMR spectroscopy and B3LYP\\/6-31G(d,p) calculations. In crystal the piperidine ring is protonated and adopts a chair conformation with the COOH group in the equatorial position. The COO? group of chloroacetate unit is engaged in three hydrogen bonds: O(1)–H(1)···O(3) of 2.604(2)Å, N(1)–H(12)···O(3) of

A. Komasa; A. Katrusiak; M. Szafran; P. Barczynski; Z. Dega-Szafran

2008-01-01

322

Zn(OTf)2-promoted chemoselective esterification of hydroxyl group bearing carboxylic acids.  

PubMed

Selective esterification of aliphatic and aromatic carboxylic acids with various alcohols is studied using triphenylphosphine, I2, and a catalytic amount of Zn(OTf)2. Use of this catalyst allows the formation of esters at a faster rate with good to excellent yield by activating the in situ generated acyloxyphosphonium ion intermediate. During the esterification process, both their aromatic and aliphatic hydroxyl groups are fully preserved from transesterification. The results show that the bulkiness and the reactivity of this doubly activated intermediate III control the selectivity and the rate of the reaction, respectively. The method is also useful for direct amidation reactions. PMID:23350970

Mamidi, Narsimha; Manna, Debasis

2013-02-06

323

Stereospecific sulfur oxidation of 7-methylthioxanthone-2-carboxylic acid by Calonectria decora.  

PubMed Central

Thin-layer chromatography was used to determine the ability of three microorganisms capable of sulfur oxygenation, including Aspergillus niger, Streptomyces armentosus subsp. armentosus, and Calonectria decora, to oxidize 7-methylthioxanthone-2-carboxylic acid to the corresponding sulfoxide in growing cultures. In addition, optical rotary dispersion, circular dichroism, and nuclear magnetic resonance analysis in the presence of chiral shift reagent were used variously to access reaction stereoselectivity, absolute configuration, and optical purity of isolated products. The data indicated that C. decora produced the sulfoxide in high yield (69%) and optical purity (97%), most probably in the S-configuration.

Lanzilotta, R P; Bradley, D G; Maddox, M L

1977-01-01

324

Structure-activity relationship investigation of bis(2-chloroethyl)aminoethyl esters of some carboxylic acids.  

PubMed

A study of quantitative structure-activity relationships (QSAR) in a series of carboxylic acid bis(2-chloroethyl)aminoethyl esters with potential antitumor activity was carried out. The statistical-heuristic technique was applied to estimate the contributions of the structural features of the compounds to the probability of their activity in vivo against lymphoid leukemia L1210. The results obtained were compared with those of the pharmacological screening of the esters. Some assumptions are made concerning the difference in antileukemic activity of compounds based on the computed weights of their structural features. PMID:2395899

Pajeva, I; Manolov, I; Golovinsky, E V

1990-05-01

325

Synthesis of heterocyclic compounds on the basis of carboxylic acid arylamides  

Microsoft Academic Search

The exchange and cyclization of phenyliminooxalyl chloride with ammonium thiocyanate, sodium azide, aniline, amidoximes, and diphenylthiourea, and with 2-aminopyridine, 2-aminobenzothiazole, and 2-amino- and 2-mercaptobenzimidazole were studied. The cyclization products are derivatives of thiazolidine, imidazo[1,2-a]pyridine, imidazo[2,1-b]benzothiazole, imidazo[1,2-a]benzimidazole, and thiazolo[3,2-a]benzimidazole. A trimer of 1-phenyltetrazole-5-carboxylic acid was obtained when an attempt was made to convert its azide to the corresponding isocyanate.

M. O. Lozinskii; A. F. Shivanyuk; P. S. Pel'kis

1971-01-01

326

Immobilization of DNA via oligonucleotides containing an aldehyde or carboxylic acid group at the 5' terminus.  

PubMed Central

A general method for the immobilization of DNA through its 5'-end has been developed. A synthetic oligonucleotide, modified at its 5'-end with an aldehyde or carboxylic acid, was attached to latex microspheres containing hydrazide residues. Using T4 polynucleotide ligase and an oligonucleotide splint, a single stranded 98mer was efficiently joined to the immobilized synthetic fragment. After impregnation of the latex microspheres with the fluorescent dye, Nile Red and attachment of an aldehyde 16mer, 5 X 10(5) bead-DNA conjugates could be detected with a conventional fluorimeter. Images

Kremsky, J N; Wooters, J L; Dougherty, J P; Meyers, R E; Collins, M; Brown, E L

1987-01-01

327

Liquid chromatographic fingerprint of 3-methylflavone-8-carboxylic acid established for its synthesis control analysis.  

PubMed

A high-performance liquid chromatographic method was proposed for the separation of relative impurities in industrial 3-methylflavone-8-carboxylic acid (MFCA) and its intermediate methyl 3-propionylsalicylate (MPS). Benzoic acid (BA), MPS, 6-chloro-3-methylflavone-8-carboxylic acid (MFCA-Cl) and methyl 5-chloro-3-propionylsalicylate (MPS-Cl) in MFCA, and MPS-Cl in MPS were respectively quantified by an external standard method. As results showed, the linearity of standard curves was excellent with the relative coefficients of over 0.999 for all the detected components, and the intra- and inter-day precisions of impurities determination were satisfactory with the relative standard deviation of not more than 8.0%. Under the selected experimental condition, the chromatographic fingerprints of MFCA and MPS were drawn synthetically, and the transfer of impurities in the stepwise reactions of MFCA manufacture was elucidated. The fingerprints have great potential in instructing the production of MFCA for industrial use and in conducting the conversion of relative impurities. PMID:19159766

Qiao, Jun-Qin; Sheng, Dong; Lian, Hong-Zhen

2008-10-09

328

Preferential adhesion of silver nanoparticles onto crystal faces of alpha-cyclodextrin/carboxylic acids inclusion compounds.  

PubMed

Alpha-Cyclodextrin (alpha-CD) inclusion compounds containing the carboxylic acids (octanoic, decanoic, lauric or dodecanoic, myristic or tetradecanoic, palmitic or hexadecanoic and stearic or octadecanoic) as guests were synthesized and applied for preferential adhesion of silver nanoparticles (AgNPs). The binding affinity depends of the chain length of the respective guest and is most efficient for octanoic and decanoic acids. The immobilization of nanoparticles is caused by the spatial replacing of the stabilized shell of the nanoparticles by COOH groups of the guests molecules, located at the entrance of cavity of alpha-CD, corresponding to the {001} crystal plane. Crystalline coating with nanoparticles provides a means of storing of AgNPs on solids state without aggregation. The stabilization of the particles on the surface is valid for a given length and ordering of the guest in the cavities of the alpha-CD being the octanoic and decanoic acid the most appropriated. PMID:23447940

Rodríguez-Llamazares, S; Jara, P; Yutronic, N; Noyong, M; Fischler, M; Simon, U

2012-12-01

329

Year-round records of gas and particulate carboxylic acids (formate and acetate) in the boundary layer at Dumont d'Urville (coastal Antarctica): Production of carboxylic acids from biogenic NMHC emissions from the Antarctic ocean  

NASA Astrophysics Data System (ADS)

Multiple year-round concentrations of acetic and formic acids were measured both in gas and aerosol phases at Dumont d'Urville (DDU, a coastal Antarctic site: 66^o40'S, 140^o01'E) by using mist chamber and aerosol filter sampling. Aerosol levels of the 2 carboxylates range from less than one ng m-3 in winter to 5--10 ng m-3 in summer. Comparison with gas phase concentrations shows that almost 99% of the 2 carboxylic acids are present in the gas phase. Concentrations of formic acid in the gas phase are minima in June--July (70 ng m-3) and increase regularly towards summer months when levels reach ˜400 ng m-3. Concentrations of acetic acid in the gas phase exhibit a more well-marked seasonal cycle with values remaining close to 50 ng m-3 from April to October and strongly increase during summer months (mean value of 800 ng m-3). Such a strong seasonal cycle of carboxylic acids in the high southern latitude marine boundary layer displays with observations made at numerous continental sites where a more weak seasonality is generally observed. It is suggested that carboxylic acids present at DDU mainly originate from biogenic emissions from the Antarctic ocean which are expected to closely follow annual cycle of the sea ice extent and solar radiation, affecting in particular photochemical production of alkenes from dissolved organic carbon released from phytoplancton. Summer levels of carboxylic acids are discussed in terms of air-sea fluxes of NMHCs and photochemical production of carboxylic acids from ozone-alkene reactions and HO_2 reaction with peroxyacetal radical in these poor NOx environments.

Legrand, M.; Preunkert, S.; Jourdain, B.

2003-04-01

330

Synthesis and Evaluation of [123I] Labeled Iodovinyl Amino Acids Syn-, Anti-1-Amino-3-[2-iodoethenyl]-cyclobutane-1-carboxylic Acid and 1-Amino-3-iodomethylene-cyclobutane-1-carboxylic Acid as Potential SPECT Brain Tumor Imaging Agents  

PubMed Central

Syn- and anti-1-amino-3-[2-iodoethenyl]-cyclobutane-1-carboxylic acid (syn-, anti-IVACBC 16, 17) and their analogue 1-amino-3-iodomethylene-cyclobutane-1-carboxylic acid (gem-IVACBC 18) were synthesized and radioiodoinated with [123I] in 34%–43% delay-corrected yield. All these amino acids entered 9L gliosarcoma cells primarily via L-type transport in vitro with high uptake of 9–11%ID/1×106 cells. Biodistribution studies of [123I]16, 17 and 18 in rats with 9L gliosarcoma brain tumors demonstrated high tumor to brain ratios (4.7–7.3:1 at 60 minutes post injection). In this model, syn-, anti- and gem-[123I]IVACBC are promising radiotracers for SPECT brain tumor imaging.

Yu, Weiping; Williams, Larry; Malveaux, Eugene; Camp, Vernon M.; Olson, Jeffrey J.

2008-01-01

331

The Eumelanin Intermediate 5,6Dihydroxyindole2Carboxylic Acid Is a Messenger in the Cross-Talk among Epidermal Cells  

Microsoft Academic Search

Interest in colorless intermediates of melanocyte metabolism has traditionally been related to their role as melanin precursors, though several lines of evidence scattered in the literature suggested that these compounds may exert an antioxidant and protective function per se unrelated to pigment synthesis. Herein, we disclose the remarkable protective and differentiating effects of 5,6-dihydroxyindole-2-carboxylic acid (DHICA), a diffusible dopachrome tautomerase

Daniela Kovacs; Enrica Flori; Vittoria Maresca; Monica Ottaviani; Nicaela Aspite; Maria Lucia Dell'Anna; Lucia Panzella; Alessandra Napolitano; Mauro Picardo; Marco d'Ischia

2012-01-01

332

Equilibria and dissociation kinetics of lanthanide complexes of diaza crown ether carboxylic acids  

SciTech Connect

The equilibria and dissociation kinetics of lanthanide and several transition-metal and Pb(II) complexes of some diaza crown ether carboxylic acids are studied. The ligands are K22MA (1,10-diaza-4,7,13,16-tetraoxacyclooctadecane-N-acetic acid), K22DP (1,10-diaza-4,7,13,16-tetraoxacyclooctadecane-N,N'-di-..beta..-propionic acid), and K22MP (1,10-diaza-4,7,13,16-tetraoxacyclooctadecane-N-..beta..-propionic acid). The protonation constants of these ligands are similar to those of the structural analogues and are in the range log K/sub 1/ = 8.80-9.01 and log K/sub 2/ = 7.26-8.16. The stability constants are all lower than that of their structural analogue K22DA (1,10-diaza-4,7,13,16-tetraoxacyclooctadecane-N,N'-diacetic acid) due to the reduction of the chelate effect or an unfavorable steric effect or both. The kinetic dissociation rates are all faster as compared to those of K22DA complexes. Acid-dependent (k/sub H/) and acid-independent (k/sub d/) rate constants are obtained by the measurement of rates at various pH values, and they correlate inversely with the values of stability constants. 15 references, 1 figure, 4 tables.

Chang, C.A.; Chang, P.H.L.; Manchanda, V.K.; Kasprzyk, S.P.

1988-10-19

333

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

334

Recovery of carboxylic acids, C 2?C 6, from an aqueous waste stream using tributylphosphate (TBP): Effect of presence of inorganic acids and their sodium salts  

Microsoft Academic Search

Extraction of carboxylic acids, C2?C6, was carried out with tributylphosphate (TBP) from an aqueous waste stream at pH = 2, 2.5, and at as such pH taken from an environmental process engineering point of view. The effect of the presence of H2SO4 and HCl on the distribution coefficients for C2?C6 carboxylic acids was investigated. The measurements were also carried out

M. N. Ingale; V. V. Mahajani

1996-01-01

335

Incorporation of C14 From Carbon Dioxide into Sugar Phosphates, Carboxylic Acids, and Amino Acids by Clostridium thermoaceticum  

PubMed Central

Ljungdahl, Lars (Western Reserve University, Cleveland, Ohio), and Harland G. Wood. Incorporation of C14 from carbon dioxide into sugar phosphates, carboxylic acids, and amino acids by Clostridium thermoaceticum. J. Bacteriol. 89:1055–1064. 1965.—The mechanism of synthesis of acetate from carbon dioxide by Clostridium thermoaceticum was investigated by incubating cells with glucose or xylose in the presence of C14O2. Sugar phosphates, amino acids, and carboxylic acids were isolated and the specific radioactivities were determined; the distributions of C14 were also determined in some of the compounds. Only fructose-1,6-diphosphate, formate, and lactate had higher specific activities than the acetate. The specific activities and distribution of C14 in the fructose-6-phosphate and ribose-5-phosphate were such that we conclude that the synthesis of acetate does not occur via a pathway involving the sugar phosphates as direct intermediates. Likewise, it is shown that pathways including lactate, aspartate, serine, glycine, malate, and succinate are not of importance in the synthesis of acetate from CO2. The methyl group of free methionine was unlabeled and is not a precursor of the methyl group of acetate.

Ljungdahl, Lars; Wood, Harland G.

1965-01-01

336

A supported polymeric liquid membrane process for removal of carboxylic acids from a waste stream  

SciTech Connect

The removal or elimination of organic residues from aqueous waste streams represents a major need in the chemical industry. The authors have developed a new class of membrane called supported polymeric liquid membranes that are capable of removing and concentrating low molecular weight organic compounds from dilute aqueous solutions, especially those that also contain high concentrations of inorganic salts. Attractive features of this membrane process include the ability to recover the contaminants in concentrated form for either recycle or more economical disposal, low pressure (ambient) operation, simple scale-up using commercial hollow fiber modules, and ease of in-situ regeneration of the polymeric liquid. The process has shown treatment feasibility for several types of aqueous waste streams. This paper describes the laboratory development activities for treating a waste stream containing a dilute mixture of C2-C6 carboxylic acids and nitric acid.

Ho, S.V.

1999-12-31

337

Stability of pyrene-1-carboxylic acid and other pyrene derivatives immobilized on silane gels  

NASA Astrophysics Data System (ADS)

The main aim of this research was to select a silane gel with appropriate composition containing fluorophore immobilized in it, in view of application of this carrier in the construction of a fluorescence optical sensor. Results of stationary fluorescence studies on gelation of silane gel with different composition, obtained as a result of acidic or basic hydrolysis using the fluorophores: pyrene-1-carboxylic acid and 1,3-bis(1-pyrenyl)propane, are presented. The form of probe during sol-gel transition and in the formed gel is discussed. The presence of a protonated form of PyCOOH 2+ was observed in the gel obtained by acidic hydrolysis and of PyCOO - ions and neutral form of PyCOOH in the gel obtained with the use of basic hydrolysis. The aim of the research was also to estimate suitability of the silane gel, which contained a selected immobilized fluorophore, for application in the optical sensor. This criterion includes determination of the kinetics of fluorophore elution from the gel as well as estimation of the interactions of fluorophore immobilized in the gel with microenvironment. Therefore, to carry out this part of the research, the silane gel was formed into a thin layer deposited on a glass surface. Next, the kinetics of elution of pyrene-1-carboxylic acid, 1,3-bis(1-pyrenyl)propane as well as pyrene and aminopyrene from this layers by water and ethanol was investigated. Elution rate constants were determined with the use of the first-order kinetics. Three stages of the elution with different duration were distinguished: I 0-4 min, II 4 min-1 h and III, the slowest one—above 1 h. Stability of the probes immobilized in these gels during storage in water or ethanol for several days was also determined.

Miller, Ewa; Jó?wik-Styczy?ska, Donata

2009-03-01

338

Catalytic transformation of alcohols to carboxylic acid salts and H2 using water as the oxygen atom source  

NASA Astrophysics Data System (ADS)

The oxidation of alcohols to carboxylic acids is an important industrial reaction used in the synthesis of bulk and fine chemicals. Most current processes are performed by making use of either stoichiometric amounts of toxic oxidizing agents or the use of pressurized dioxygen. Here, we describe an alternative dehydrogenative pathway effected by water and base with the concomitant generation of hydrogen gas. A homogeneous ruthenium complex catalyses the transformation of primary alcohols to carboxylic acid salts at low catalyst loadings (0.2 mol%) in basic aqueous solution. A consequence of this finding could be a safer and cleaner process for the synthesis of carboxylic acids and their derivatives at both laboratory and industrial scales.

Balaraman, Ekambaram; Khaskin, Eugene; Leitus, Gregory; Milstein, David

2013-02-01

339

Catalytic transformation of alcohols to carboxylic acid salts and H2 using water as the oxygen atom source.  

PubMed

The oxidation of alcohols to carboxylic acids is an important industrial reaction used in the synthesis of bulk and fine chemicals. Most current processes are performed by making use of either stoichiometric amounts of toxic oxidizing agents or the use of pressurized dioxygen. Here, we describe an alternative dehydrogenative pathway effected by water and base with the concomitant generation of hydrogen gas. A homogeneous ruthenium complex catalyses the transformation of primary alcohols to carboxylic acid salts at low catalyst loadings (0.2 mol%) in basic aqueous solution. A consequence of this finding could be a safer and cleaner process for the synthesis of carboxylic acids and their derivatives at both laboratory and industrial scales. PMID:23344447

Balaraman, Ekambaram; Khaskin, Eugene; Leitus, Gregory; Milstein, David

2013-01-06

340

Microbiologically produced carboxylic acids used as building blocks in organic synthesis.  

PubMed

Oxo- and hydroxy-carboxylic acids are of special interest in organic synthesis. However, their introduction by chemical reactions tends to be troublesome especially with regard to stereoselectivity. We describe herein the biotechnological preparation of selected oxo- and hydroxycarboxylic acids under "green" conditions and their use as promising new building blocks. Thereby, our biotechnological goal was the development of process fundamentals regarding the variable use of renewable raw materials, the development of a multi purpose bioreactor and application of a pilot plant with standard equipment for organic acid production to minimize the technological effort. Furthermore the development of new product isolation procedures, with the aim of direct product recovery, capture of products or single step operation, was necessary. The application of robust and approved microorganisms, also genetically modified, capable of using a wide range of substrates as well as producing a large spectrum of products, was of special importance. Microbiologically produced acids, like 2-oxo-glutaric acid and 2-oxo-D-gluconic acid, are useful educts for the chemical synthesis of hydrophilic triazines, spiro-connected heterocycles, benzotriazines, and pyranoic amino acids. The chiral intermediate of the tricarboxylic acid cycle, (2R,3S)-isocitric acid, is another promising compound. For the first time our process provides large quantities of enantiopure trimethyl (2R,3S)-isocitrate which was used in subsequent chemical transformations to provide new chiral entities for further usage in total synthesis and pharmaceutical research.Oxo- and hydroxy-carboxylic acids are of special interest in organic synthesis. However, their introduction by chemical reactions tends to be troublesome especially with regard to stereoselectivity. We describe herein the biotechnological preparation of selected oxo- and hydroxycarboxylic acids under "green" conditions and their use as promising new building blocks. Thereby, our biotechnological goal was the development of process fundamentals regarding the variable use of renewable raw materials, the development of a multi purpose bioreactor and application of a pilot plant with standard equipment for organic acid production to minimize the technological effort. Furthermore the development of new product isolation procedures, with the aim of direct product recovery, capture of products or single step operation, was necessary. The application of robust and approved microorganisms, also genetically modified, capable of using a wide range of substrates as well as producing a large spectrum of products, was of special importance. Microbiologically produced acids, like 2-oxo-glutaric acid and 2-oxo-D-gluconic acid, are useful educts for the chemical synthesis of hydrophilic triazines, spiro-connected heterocycles, benzotriazines, and pyranoic amino acids. The chiral intermediate of the tricarboxylic acid cycle, (2R,3S)-isocitric acid, is another promising compound. For the first time our process provides large quantities of enantiopure trimethyl (2R,3S)-isocitrate which was used in subsequent chemical transformations to provide new chiral entities for further usage in total synthesis and pharmaceutical research. PMID:23080261

Aurich, Andreas; Specht, Robert; Müller, Roland A; Stottmeister, Ulrich; Yovkova, Venelina; Otto, Christina; Holz, Martina; Barth, Gerold; Heretsch, Philipp; Thomas, Franziska A; Sicker, Dieter; Giannis, Athanassios

2012-01-01

341

Dissociative proton transfer in cluster ions: clusters of aromatic carboxylic acids with amino acids 1 1 Dedicated to Professor Nico Nibering on the occasion of his retirement  

Microsoft Academic Search

The cluster formation of several aromatic carboxylic acids ferulic acid, vanillic acid, sinapinic acid and 3,4-dihydroxy-benzoic acid was investigated by means of laser desorption into a supersonic beam followed by multiphoton ionization-time-of-flight mass spectrometry. The formation of not only homogeneous clusters but also that of heterogeneous clusters with some small amino acids was studied. The different neutral clusters formed in

Anja Meffert; Jürgen Grotemeyer

2001-01-01

342

Oligo(4-aminopiperidine-4-carboxylic acid): an unusual basic oligopeptide with an acid-induced helical conformation.  

PubMed

In sharp contrast with helical polypeptides carrying basic side chains, Api(8), a basic oligopeptide containing the non-natural achiral amino acid 4-aminopiperidine-4-carboxylic acid (Api), adopts a helical conformation only in acidic media. Alkaline titration of a protonated Api(8) oligomer appended with a leucine derivative at its N-terminus showed that disruption of its helical conformation occurs in a pH range of 7-10. NMR studies indicated that the piperidine groups in Api(8), when nonprotonated, possibly interact with the proximal amide protons in the peptide backbone and hamper the formation of the H-bonding network responsible for the helical conformation. The helical structure is induced not only by protonation but also by acylation of the piperidine groups. PMID:20812686

Cho, Joon-il; Tanaka, Masahiro; Sato, Sota; Kinbara, Kazushi; Aida, Takuzo

2010-09-29

343

Amino and carboxyl plasma functionalization of collagen films for tissue engineering applications.  

PubMed

Type I collagen films have been functionalized on their surfaces by plasma treatment with carboxyl and amino groups to improve their potential for grafting bioactive molecules. The physico-chemical properties of the plasma-treated films were evaluated and compared to the untreated materials by water contact angle, SEM and AFM. The presence of new functional groups on the film surfaces has been assessed by ATR-FTIR spectra after chemical derivatization. Moreover, the biocompatibility of the plasma-treated films was studied with MG-63 human osteoblast-like cells, evaluating cell proliferation, viability and morphology at 1, 3 and 7 days. PMID:23266023

Taraballi, F; Zanini, S; Lupo, C; Panseri, S; Cunha, C; Riccardi, C; Marcacci, M; Campione, M; Cipolla, L

2012-12-05

344

Anti-cancer evaluation of carboxamides of furano-sesquiterpene carboxylic acids from the soft coral Sinularia kavarattiensis.  

PubMed

The chemical investigation of soft coral Sinularia kavarattiensis is described. It yielded furano-sesquiterpene carboxylic acids 1 and 2 and their methyl esters 3 and 4. Semi-synthesis of furano-sesquiterpene carboxylic acid 1 gave amide derivatives 5-12. Structures of all the compounds were established by IR, NMR and mass spectral analysis. Interestingly all compounds are selectively potent on leukemia cell line. All these compounds were screened for cytotoxic activity against five human cancer cell lines (leukemia, prostate, lung, breast and cervix). Among these compounds 9 and 10 showed promising activity against leukemia and prostate cancer cell lines. PMID:24144848

Rajaram, Singanaboina; Ramulu, Udugu; Ramesh, Dasari; Srikanth, Dudem; Bhattacharya, Papri; Prabhakar, Peddikotla; Kalivendi, Shasi V; Babu, Katragadda Suresh; Venkateswarlu, Yenamandra; Navath, Suryakiran

2013-10-10

345

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

346

Proton transfer at the carboxylic sites of amino acids: A single water molecule catalyzed process  

NASA Astrophysics Data System (ADS)

Ab initio calculations at MP2 level of theory were used to study the proton transfer at the carboxylic sites of amino acids, in the isolated, mono- and di-hydrated forms. In the case of water dimer, two interaction modes with glycine neutral structures (see Fig. ) were explored, corresponding to the concerted and stepwise reaction pathways. Their transition states can be described as (H2O bond H bond OH2)+ [Fig. (a)] and (H2O---H bond OH2)+ [Fig. (b)], respectively. The energy analysis indicated that the concerted pathway is preferred. In the isolated, mono- and di-hydrated glycine complexes, the activation barriers of the proton transfer at the carboxylic sites were calculated to be 34.49, 16.59, and 13.36 kcal mol-1, respectively. It was thus shown that the proton transfer is significantly assisted and catalyzed by water monomer so that it can take place at room temperature. Instead, the further addition of water molecules plays solvent effects rather than catalytic effects to this proton transfer process. The above results obtained with discrete water molecules were supported by the solvent continuum calculated data. It was also observed that the heavy dependence of the solvent continuum models on dipole moments may produce misleading results.

Yang, Gang; Wu, Xiaomin; Zu, Yuangang; Liu, Chengbu; Fu, Yujie; Zhou, Lijun

347

Cobalt(II)-catalyzed 1,4-addition of organoboronic acids to activated alkenes: an application to highly cis-stereoselective synthesis of aminoindane carboxylic acid derivatives.  

PubMed

It all adds up: The 1,4-addition of organoboronic acids to activated alkenes catalyzed by [Co(dppe)Cl(2)] is described. A [3+2]-annulation reaction of ortho-iminoarylboronic acids with acrylates to give various aminoindane carboxylic acid derivatives with cis-stereoselectivity is also demonstrated (see scheme; dppe = 1,2-bis(diphenylphosphino)ethane). PMID:23112007

Chen, Min-Hsien; Mannathan, Subramaniyan; Lin, Pao-Shun; Cheng, Chien-Hong

2012-10-30

348

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

349

Film morphology, orientation and performance of dodecyl/carboxyl functional polysiloxane on cotton substrates  

NASA Astrophysics Data System (ADS)

A novel polysiloxane (RCAS) bearing dodecyl and carboxyl side groups was synthesized by reaction of a dodecyl/amino functionalized polysiloxane with maleic anhydride. Film morphology, molecular orientation and performance of the synthesized polysiloxane on cotton substrates were investigated by field emission scanning electron microscope (FESEM), atomic force microscope (AFM), X-ray photoelectron microscope (XPS) and so on. Affected by the dodecyl and polar carboxyl side groups, RCAS formed a semi hydrophilic, macroscopic smooth but actually uneven siloxane film with many pillar-likes or small humps on the treated substrate surfaces. On the natural cotton surface, RCAS may take such an orientation to form its film that the Si-CH 3, Si-C 12H 25 groups projected outward into air, while the carboxyl groups pointed inward to the substrate, interacting with the hydroxyls of the cotton substrates in ester and hydrogen bonds or twisted away from the negatively charged cotton fiber surface. As a result of such a film-formation, RCAS provided the treated fabric with not only a good wettability of about 22.96 s and a whiteness of 88.44°, but also an improved softness as well as thickening handle.

An, Qiufeng; Wang, Kefeng; Jia, Yun

2011-03-01

350

Ab initio study of Li adsorption in carbon nanotubes functionalized with amine and carboxyl groups  

NASA Astrophysics Data System (ADS)

The lithium adsorption energies and electronic structures of pristine ((8,0)) single-walled carbon nanotube (SWCNT) and functionalized carbon nanotubes with amine and carboxyl groups (NH2/((8,0)) and COOH/((8,0))) were studied using density functional theory. The results show that the adsorption energies of lithium inside and outside of ((8,0)) SWCNT differ very little from each other. When the lithium is doped in carbon nanotubes, charge transfer takes place from the lithium to the nanotubes. After functionalization of carbon nanotubes with amine (sbnd NH2) and carboxyl (sbnd COOH) groups, various positions for lithium adsorption around the functional groups can be served. The adsorption energy of lithium in these positions is greater than that of lithium in pure ((8,0)) SWCNT. When the lithium was doped in NH2/((8,0)) and COOH/((8,0)), an energy gap between valence and conduction bands is observed, and the conductivity is reduced relative to lithium-doped non-functionalized carbon nanotubes.

Jalili, Seifollah; Jamali, Maryam; Schofield, Jeremy

2013-06-01

351

Non-suppressed conductivity and indirect UV detection of carboxylic acids in environmental samples by ion-exclusion chromatography using 2,6-pyridinedicarboxylic acidic eluent.  

PubMed

2,6-Pyridinedicarboxylic acid (PDCA) was evaluated as an eluent for indirect UV and non-suppressed conductivity detection of carboxylic acids in ion-exclusion chromatography. The effect of PDCA concentration on the separation and detection sensitivity was investigated. The reasonable resolutions between carboxylic acids were achieved using 1 mM PDCA eluent. Detection limits were 1.0-7.0 microM for conductivity detection and 8-30 microM for UV detection. Compared to the eluent containing 1 mM sulfuric acid, the method offers a high resolution and high detection sensitivity for both detectors due to its high molar absorptivity and low background conductance. The proposed method was demonstrated to be useful for the determination of carboxylic acids in environmental samples with direct sample injection. PMID:10574210

Chen, Z; Tang, C; Xu, J

1999-10-29

352

A mechanistic study on the Hooker oxidation: synthesis of novel indane carboxylic acid derivatives from lapachol.  

PubMed

The Hooker oxidation is one of the most intriguing transformations wherein lapachol (1) is readily converted to norlapachol (2) in very good yield. This one-pot reaction involves a very intricate mechanism in which the alkyl side chain of lapachol is shortened by one carbon unit. Previous studies have unequivocally established the involvement of an indane carboxylic acid derivative 3, as a key intermediate (Hooker intermediate), and its simultaneous conversion to norlapachol (2) via the oxidative cleavage of vicinol diol and subsequent intramolecular aldol reaction of the resulting keto acid. However, the formation of the key Hooker intermediate 3 from lapachol (1) remains ambiguous. The present study has thrown some light on the formation of the key intermediate 3 from lapachol (1) via benzilic acid rearrangement of the corresponding labile o-diquinone intermediate 8 derived from lapachol. The involvement of o-diquinone intermediate 8 in the Hooker oxidation has been further established by trapping of this labile intermediate as the corresponding phenazine derivative 9. The involvement of benzilic acid rearrangement as a key step in the Hooker oxidation is further shown with a variety of o-quinones prepared from lapachol (1). PMID:23196897

Eyong, Kenneth O; Puppala, Manohar; Kumar, Ponminor Senthil; Lamshöft, Marc; Folefoc, Gabriel N; Spiteller, Michael; Baskaran, Sundarababu

2012-11-30

353

Understanding Potential Exposure Sources of Perfluorinated Carboxylic Acids in the Workplace  

PubMed Central

This paper integrates perspectives from analytical chemistry, environmental engineering, and industrial hygiene to better understand how workers may be exposed to perfluorinated carboxylic acids when handling them in the workplace in order to identify appropriate exposure controls. Due to the dramatic difference in physical properties of the protonated acid form and the anionic form, this family of chemicals provides unique industrial hygiene challenges. Workplace monitoring, experimental data, and modeling results were used to ascertain the most probable workplace exposure sources and transport mechanisms for perfluorooctanoic acid (PFOA) and its ammonium salt (APFO). PFOA is biopersistent and its measurement in the blood has been used to assess human exposure since it integrates exposure from all routes of entry. Monitoring suggests that inhalation of airborne material may be an important exposure route. Transport studies indicated that, under low pH conditions, PFOA, the undissociated (acid) species, actively partitions from water into air. In addition, solid-phase PFOA and APFO may also sublime into the air. Modeling studies determined that contributions from surface sublimation and loss from low pH aqueous solutions can be significant potential sources of workplace exposure. These findings suggest that keeping surfaces clean, preventing accumulation of material in unventilated areas, removing solids from waste trenches and sumps, and maintaining neutral pH in sumps can lower workplace exposures.

Kaiser, Mary A.; Dawson, Barbara J.; Barton, Catherine A.; Botelho, Miguel A.

2010-01-01

354

Mediated xanthine oxidase potentiometric biosensors for hypoxanthine based on ferrocene carboxylic acid modified electrode.  

PubMed

A potentiometric enzyme electrode for detection of hypoxanthine (Hx) in fish meat is described. The sensor was developed by entrapment of xanthine oxidase (XOD) and ferrocene carboxylic acid (Fc) into polypyrrole (PPy) film during galvanostatic polymerisation film formation. The responses for Hx were obtained in 0-05 M phosphate buffer (pH 7.1) at 0.0 mV vs Ag/AgCl (3M KCl). The optimum condition for the formation of PPy-XOD-Fc film include 0.4M PPy, 6.2U/mL XOD, 40 mM Fc, polymerisation time of 200 s and applied current density of 0-5 mA cm(-2). The sensor provides a linear response to Hx in concentration range of 5-20 ?M, (r=0.998) and was successfully used for determination of Hx in fish. PMID:22980900

Lawal, Abdulazeez T; Adeloju, Samuel B

2012-07-21

355

Azetidine-2-carboxylic acid resistant mutants of Arabidopsis thaliana with increased salt tolerance  

SciTech Connect

Nineteen mutant Arabidopsis families resistant to the proline analog azetidine-2-carboxylic acid (ACA) were characterized in terms of NaCl tolerance and proline content. Mutants were selected from about 64,000 progeny of about 16,000 self-pollinated Columbia parents which had been mutated with ethyl methane sulfonate during seed imbibition. Selections were performed during seed germination on aseptic agar medium containing 0.2 to 0.25 mM ACA. Nineteen mutant families, 12 clearly independent, retained resistance to ACA in the M{sub 4} generation. Based on germination on 150 mM NaCl, 13 of the mutant families were more tolerant than the wild type. Two mutants of intermediate resistance to ACA were markedly more salt tolerant than the others. Four mutant families appeared to overproduce proline. Of these, only 3 showed slight increases in salt tolerance.

Lehle, F.R.; Murphy, M.A.; Khan, R.A. (Univ. of Arizona, Tuscon (USA))

1989-04-01

356

Pharmacological activities of the main metabolite of flavoxate 3-methylflavone-8-carboxylic acid.  

PubMed

The pharmacological properties of 3-methylflavone-8-carboxylic acid (MFCA), the main metabolite of flavoxate, have been studied in vitro and in vivo. MFCA did not display antispasmodic activity on isolated organs contractions induced by histamine, acetylcholine or CaCl2, nor did it exhibit significant affinity for the rat brain alpha- and beta-adrenergic, serotoninic, muscarinic, D2, opiate and Ca2+ receptors. However, it showed a remarkable phosphodiesterase (PDE) inhibiting activity. Moreover in vivo studies indicate an interesting activity of MFCA which inhibited the rat urinary bladder voiding contractions, increased bladder volume capacity and decreased micturition pressure in the rat cystometric recordings. The activity of MFCA in the two in vivo experimental models, probably related to cAMP-PDE inhibitory properties, suggests that flavoxate's therapeutical potential might be partially sustained by its main metabolite. PMID:2838033

Cazzulani, P; Pietra, C; Abbiati, G A; Ceserani, R; Oliva, D; Civelli, M; Tajana, A; Nardi, D

1988-03-01

357

Yeast fermentation of carboxylic acids obtained from pyrolytic aqueous phases for lipid production.  

PubMed

The presence of very reactive C1-C4 molecules adversely affects the quality bio-oils produced from the pyrolysis of lignocellulosic materials. In this paper a scheme to produce lipids with Cryptococcus curvatus from the carboxylic acids in the pyrolytic aqueous phase collected in fractional condensers is proposed. The capacities of three oleaginous yeasts C. curvatus, Rhodotorula glutinis, Lipomyces starkeyi to ferment acetate, formate, hydroxylacat-aldehyde, phenol and acetol were investigated. While acetate could be a good carbon source for lipid production, formate provides additional energy and contributes to yeast growth and lipid production as auxiliary energy resource. Acetol could slightly support yeast growth, but it inhibits lipid accumulation. Hydroxyacetaldehyde and phenols showed high yeast growth and lipid accumulation inhibition. A pyrolytic aqueous phase with 20 g/L acetate was fermented with C. curvatus, after neutralization and detoxification to produce 6.9 g/L dry biomass and 2.2 g/L lipid. PMID:22705522

Lian, Jieni; Garcia-Perez, Manuel; Coates, Ralph; Wu, Hongwei; Chen, Shulin

2012-05-18

358

Electric field-induced cubic phase in 4'-n-docosyloxy-3'-nitrobiphenyl-4-carboxylic acid.  

PubMed

We examine the influence of an alternating-current electric field on the lamellar smectic C (SmC) phase of 4'-n-docosyloxy-3'-nitrobiphenyl-4-carboxylic acid, and the formation of a field-induced cubic (Cub) phase with optical isotropy was observed for the first time. The induction was realized down to a temperature 10 K below the zero-field SmC to Cub phase transition temperature (TSmC-Cub). The formation of the induced Cub phase gave rise to a gradual increase of the shear storage modulus, and the modulus recovered quickly in response to the removal of the field, which is of interest as future applications to the stress transferring device. PMID:12617636

Kutsumizu, Shoichi; Yamada, Makoto; Yamaguchi, Takanari; Tanaka, Katsufumi; Akiyama, Ryuichi

2003-03-12

359

1-aminocyclobutane[11C]carboxylic acid, a potential tumor-seeking agent.  

PubMed

1-Aminocyclobutane[14C]carboxylic acid [C-14) ACBC] was incorporated preferentially by several tumor types in rats and hamsters. The agent was cleared rapidly from rat blood, attaining its maximum tissue concentrations within 30 min after i.v. injection. Carrier ACBC had little effect on the tissue distribution of (C-14) ACBC. This agent showed no affinity for a Staphylococcus aureus abscess in rats. The total excretion was low, 3.6% in 2 hr. (C-11) ACBC was synthesized in amounts up to 415 mCi (55% chemical yield) using our modified Bücherer-Strecker technique. Forty minutes were required for the two-step synthesis and chromatographic purification. ACBC was found to be nontoxic in three animal species. The radiation dose from (C-11) ACBC should be minimal. (C-11) ACBC thus appears to have good potential as a tumor-seeking agent, particularly when used with a positron emission computed tomograph. PMID:231642

Washburn, L C; Sun, T T; Byrd, B; Hayes, R L; Butler, T A

1979-10-01

360

Synthesis and structure-activity relationships of carboxylic acid derivatives of pyridoxal as P2X receptor antagonists.  

PubMed

Carboxylic acid derivatives of pyridoxal were developed as potent P2X(1) and P2X(3) receptor antagonists with modifications of a lead compound, pyridoxal-5'-phosphate-6-azophenyl-2',5'-disulfonate (5b, iso-PPADS). The designing strategies included the modifications of aldehyde, phosphate or sulfonate groups of 5b, which may be interacted with lysine residues of the receptor binding pocket, to weak anionic carboxylic acid groups. The corresponding carboxylic acid analogs of pyridoxal-5'-phosphate (1), 13 and 14, showed parallel antagonistic potencies. Also, most of 6-azophenyl derivatives (24-28) of compound 13 or 14 showed potent antagonistic activities similar to that of 5b at human P2X(3) receptors with 100 nM range of IC(50) values in two-electrode voltage clamp (TEVC) assay system on the Xenopus oocyte. The results indicated that aldehyde and phosphoric or sulfonic acids in 5b could be changed to a carboxylic acid without affecting antagonistic potency at mouse P2X(1) and human P2X(3) receptors. PMID:23510563

Jung, Kwan-Young; Cho, Joong-Heui; Lee, Jung Sun; Kim, Hyo Jun; Kim, Yong-Chul

2013-02-22

361

Dichloro-4-quinolinol-3-carboxylic acid: synthesis and antioxidant abilities to scavenge radicals and to protect methyl linoleate and DNA.  

PubMed

5,7-, 5,8-, 6,8-, 7,8-dichloro-4-quinolinol-3-carboxylic acid (5,7-, 5,8-, 6,8-, 7,8-DCQA) together with 7-chloro-4-quinolinol-3-carboxylic acid (7-CQA) and 4-quinolinol-3-carboxylic acid (QA) were synthesized to investigate the antioxidant properties. 5,7-DCQA exhibited the highest ability to scavenge 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS+.), 2,2'-diphenyl-1-picrylhydrazyl (DPPH) and galvinoxyl radicals. 6,8-DCQA possessed the highest efficacy to protect methyl linoleate against 2,2'-azobis(2-amidinopropane)dihydrochloride (AAPH)-induced oxidation. 5,7-, 5,8-DCQA and QA were able to retard the beta-carotene-bleaching in beta-carotene-linoleic acid emulsion. In addition, 5,8- and 6,8-DCQA efficiently protected DNA against hydroxyl radical (.OH)-mediated oxidation, and 5,8-DCQA and 7-CQA were active to protect DNA against AAPH-induced oxidation. Furthermore, only 7-CQA can protect DNA against Cu2+/glutathione (GSH)-mediated oxidation. Dichloro-4-quinolinol-3-carboxylic acids were potent to be antiradical drugs, and were worthy to be researched pharmacologically. PMID:20122762

Li, Guo-Xiang; Liu, Zai-Qun; Luo, Xu-Yang

2010-01-20

362

Inhibitive action of indole-5-carboxylic acid towards corrosion of mild steel in deaerated 0.5 M sulfuric acid solutions  

NASA Astrophysics Data System (ADS)

Inhibition of mild steel corrosion in deaerated 0.5 M sulfuric acid solutions containing various concentrations of indole-5-carboxylic acid is studied in the temperature range from 25 to 55 °C using weight-loss, potentiodynamic and spectrophotometric tests. The adsorptive behaviour of inhibitor is also investigated using electrochemical impedance spectroscopy measurements. The indole-5-carboxylic acid is found to shift the corrosion potentials towards more noble values. This shift indicates that the addition of inhibitor mainly affects the anodic process, raising the anodic overpotential more than that of the cathodic, i.e. the indole-5-carboxylic acid behaves as mixed-type inhibitor. Because the cathodic Tafel slopes for hydrogen reduction (bc) are affected, the inhibitor probably affects the hydrogen reduction mechanism. The activation energy values (Ea) indicate that the indole-5-carboxylic acid increases the activation energy of the corrosion reaction. The adsorption behaviour of indole-5-carboxylic acid follows Langmuir's isotherm. Both the low values of -?G° and its decrease with temperature suggest physical adsorption. Double layer capacitance potential curves indicate considerable adsorption of the inhibitor in the potential range (-400 to -800 mV/SCE).

Quartarone, G.; Bonaldo, L.; Tortato, C.

2006-09-01

363

Novel chiral derivatization reagents possessing a pyridylthiourea structure for enantiospecific determination of amines and carboxylic acids in high-throughput liquid chromatography and electrospray-ionization mass spectrometry for chiral metabolomics identification.  

PubMed

This paper reports the synthesis and the application of novel derivatization reagents possessing a pyridylthiourea structure for the enantiospecific determination of chiral amines and carboxylic acids in high-throughput LC-ESI-MS/MS. The novel reagents, i.e., (R)-N-(3-pyridylthiocarbamoyl)pyrrolidine-2-carboxylic acid (PyT-C) and (S)-3-amino-1-(3-pyridylthiocarbamoyl)pyrrolidine (PyT-N), were evaluated as chiral derivatization reagents for the enantiomeric determination of chiral amines and carboxylic acids, respectively, in terms of separation efficiency by reversed-phase chromatography and detection sensitivity by ESI-MS/MS. The chiral amines and carboxylic acids were easily labeled with PyT-C and PyT-N, respectively, at 60°C in 60min in the presence of 2,2'-dipyridyl disulfide (DPDS) and triphenylphosphine (TPP) as the activation reagents. The resulting diastereomers were completely separated by reversed-phase chromatography using a small particle (1.7?m) ODS column (Rs=3.54-6.00 for carboxylic acids and Rs=3.07-4.75 for amines). A highly sensitive detection at the sub-fmol level was also obtained from the SRM chromatograms at a single monitoring ion, m/z 137.0 (0.72-1.46fmol for carboxylic acids and 0.55-1.89fmol for amines). The proposed procedure using PyT-C and PyT-N was applied to the determination of chiral amines and carboxylic acids spiked into human saliva, as a model study of chiral metabonomics identification. dl-Amino acid methyl esters and N-acetyl dl-amino acids, which are the representatives as the chiral amines and carboxylic acids, in the saliva were clearly identified by the present method. Because the same product ion at m/z 137.0 was obtained from collision-induced dissociation (CID) of protonated molecular ions of all the derivatives, the proposed procedure using both reagents (i.e., PyT-C and PyT-N) seems to be useful for chiral metabolomics identification having selected functional groups (i.e., amines and carboxylic acids). PMID:23582770

Nagao, Ryuji; Tsutsui, Haruhito; Mochizuki, Toshiki; Takayama, Takahiro; Kuwabara, Tomohiro; Min, Jun Zhe; Inoue, Koichi; Todoroki, Kenichiro; Toyo'oka, Toshimasa

2013-03-26

364

FT-IR spectroscopic study on the variations of molecular structures of some carboxyl acids induced by free electron laser  

NASA Astrophysics Data System (ADS)

Free electron laser has been developed as tunable lasers over a wide range of wavelengths. Devices irradiating in the region of 6-16 ?m (1666-625 cm -1) are operable in the Beijing free electron lasers facilities (BFEL). For understanding the interactions between FEL and biological tissues, in this study wavelength-selective infrared-induced structure changes of substances under irradiation by FEL were measured using FT-IR spectroscopy. The carboxyl acids and carboxylates samples investigated include salicylic acid, sulfosalicylic acid, cholic acid, deoxycholic acid, sodium cholate and sodium deoxycholate. The changes of the FT-IR spectra of the molecules prove that the spectral variations of the samples induced by FEL are closely related to their hydrogen bond networks.

Yang, Limin; Xu, Yizhuang; Su, Yunlan; Wu, Jinguang; Zhao, Kui; Chen, Jia'er; Wang, Mingkai

2005-12-01

365

Comparison of methodologies for determination of carboxylic and phenolic groups in humic acids  

Microsoft Academic Search

A nonlinear method for fitting acid–base potentiometric titration data was applied to commercial and vermicompost humic acids in order to determine the concentration and conditional pKa's of the ionizable sites. Data was also treated by a linear method based on modified Gran functions. In both cases the discrete site model was adopted, which means that the humic acid was treated

Jorge C. Masini; Gilberto Abate; Elizabete C. Lima; Lucas C. Hahn; Mary S. Nakamura; Jaim Lichtig; Hélio R. Nagatomy

1998-01-01

366

Carboxyl-functionalized task-specific ionic liquids for solubilizing metal oxides.  

PubMed

Imidazolium, pyridinium, pyrrolidinium, piperidinium, morpholinium, and quaternary ammonium bis(trifluoromethylsulfonyl)imide salts were functionalized with a carboxyl group. These ionic liquids are useful for the selective dissolution of metal oxides and hydroxides. Although these hydrophobic ionic liquids are immiscible with water at room temperature, several of them form a single phase with water at elevated temperatures. Phase separation occurs upon cooling. This thermomorphic behavior has been investigated by (1)H NMR, and it was found that it can be attributed to the temperature-dependent hydration and hydrogen-bond formation of the ionic liquid components. The crystal structures of four ionic liquids and five metal complexes have been determined. PMID:18841931

Nockemann, Peter; Thijs, Ben; Parac-Vogt, Tatjana N; Van Hecke, Kristof; Van Meervelt, Luc; Tinant, Bernard; Hartenbach, Ingo; Schleid, Thomas; Ngan, Vu Thi; Nguyen, Minh Tho; Binnemans, Koen

2008-10-08

367

Direct ester condensation from a 1:1 mixture of carboxylic acids and alcohols catalyzed by hafnium(IV) or zirconium(IV) salts  

Microsoft Academic Search

To promote atom efficiency in synthesis and to avoid the generation of environmental waste, the use of stoichiometric amounts of condensing reagents or excess substrates should be avoided. In esterification, excess amounts of either carboxylic acids or alcohols are normally needed. We found that the direct condensation of equimolar amounts of carboxylic acids and alcohols could be achieved using hafnium(IV)

Kazuaki Ishihara; Masaya Nakayama; Suguru Ohara; Hisashi Yamamoto

2002-01-01

368

Effect of the carboxylic acid groups on water sorption, thermal stability and dielectric properties of polyimide films  

Microsoft Academic Search

Films from copolyimides containing side carboxylic acid groups were prepared in –COOH and COO?Na+ forms to study the effect of the side groups content on some physical properties such as water absorption, thermal stability and electrical parameters. The thermal stability was evaluated by TGA and the results showed that degradation temperatures depended not only on the side groups content but

Eva M. Maya; Juana Benavente; Javier de Abajo

369

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.

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

2013-01-01

370

Adsorption of a bromine labeled carboxylic acid corrosion inhibitor on iron measured with EQCM, EIS and XPS  

Microsoft Academic Search

Adsorption of bromine labeled aromatic carboxylic acid corrosion inhibitor on iron, polarized in the active region, was studied with the rotating electrochemical quartz crystal microbalance (rEQCM), electrochemical impedance spectroscopy (EIS) and X-ray induced photoelectron spectroscopy (XPS). The EQCM quantifies adsorption via the mass loss resulting from the fact that the inhibitor replaces water molecules in the interfacial volume occupied by

P Kern; D Landolt

2002-01-01

371

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

PubMed

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; Moeller, Kevin D

2013-08-09

372

1-Oxo-3-substitute-isothiochroman-4-carboxylic acid compounds: synthesis and biological activities of FAS inhibition.  

PubMed

A new series 1-oxo-3-substitute-isothiochroman-4-carboxylic acid compounds have been designed and synthesized. Screening of these molecules for FAS inhibition in vitro has indicated that compounds 2c and 2d showed more effective FAS inhibition activities and higher therapeutic index than C75. PMID:19097781

Wang, Xiaokui; Zhao, Guoming; Chen, Yao; Xu, Xiaowei; Zhong, Wu; Wang, Lili; Li, Song

2008-12-07

373

Aliphatic carboxylic acids and alcohols as efficiency and elution strength enhancers in micellar liquid chromatography.  

PubMed

Micellar liquid chromatography (MLC) uses surfactant solutions as mobile phases with added organic additives to enhance both the elution strength and the chromatographic efficiency. Two aliphatic carboxylic acids (1-butanoic and 1-pentanoic) were used as MLC additives and compared with the two corresponding alcohols (1-butanol, 1-pentanol) in terms of elution strength, efficiency and selectivity. A set of 11 phenol derivatives was used as probe compounds. All micellar mobile phases were prepared with sodium dodecylsulfate (SDS) with concentration ranging from 0.05 to 0.15M and the modifier content within 1.0 and 5.0% (v/v). The elution strength of different mobile phases containing a constant amount of SDS and different amounts of modifiers; and mobile phases containing a constant amount of modifier and different SDS concentration were determined and discussed. The effect of the acid modifiers on efficiency was studied constructing van Deemter plots that showed no minimum within the 0.01-0.7mL/min flow rate range studied. Temperature effects were also studied constructing the classical van't Hoff plots. The slight curvature of the plots in the 25-70 degrees C range may indicate some modification of the surfactant-bonded moiety layer on the stationary phase surface. Since no definitive advantage of the use of aliphatic acids were established compared to their alcohol counterpart, their terrible smell will probably preclude their use as MLC organic modifiers. PMID:20673901

Boichenko, Alexander P; Berthod, Alain

2010-07-31

374

Syntheses, structures, and properties of multidimensional lithium coordination polymers based on aliphatic carboxylic acids.  

PubMed

Three lithium coordination polymers, [Li4(H2O)2(EDTA)] (1), [Li4(H2O)4(BTCA)] (2), and (H2NMe2)2[Li2(H2O)2(BTCA)] (3) (H4EDTA = ethylenediaminetetraacetic acid, H4BTCA = 1,2,3,4-butane tetracarboxylic acid, H2NMe2 = dimethyl amine), have been synthesized by reacting lithium salts with aliphatic carboxylic acids using a solvothermal method. The structures of all the three complexes have been determined by single crystal X-ray diffraction studies. The single crystal structure analysis revealed that complex 1 has a three-dimensional framework, whereas complex 2 has 2D sheets and complex 3 has 1D chains. In addition, these lithium complexes contain various inorganic motifs with a tetramer in 1 and 2, and discrete tetrahedra in 3 and have further been connected through organic ligands to construct multidimensional structures. Further, the electrochemical properties of complexes 1–3 have been studied to evaluate these compounds as electrode materials for lithium ion batteries with discharge capacities of around 100 mA h g(-1) in the first thirty cycles. PMID:23235699

Cheng, Pei-Chi; Lin, Wei-Cheng; Tseng, Feng-Shuen; Kao, Ching-Che; Chang, Ting-Guang; Senthil Raja, Duraisamy; Liu, Wei-Ren; Lin, Chia-Her

2013-02-28

375

Effect of ring size variation within lipophilic crown ether carboxylic acids on the selectivity and efficiency of competitive alkali-metal cation solvent extraction into chloroform  

SciTech Connect

Competitive solvent extraction of alkali-metal cations from aqueous solutions into chlororform by a series of lipophilic crown ether carboxylic acids with varying ring sizes is reported. Extraction selectivity for Li{sup +} is observed for lipophilic crown ether carboxylic acids with 12-15-membered polyether rings containing four oxygen atoms. For lipophilic 14-crown-4-carboxylic acids, very high Li{sup +}/Na{sup +} selectivity coefficients of 17-20 are observed with no detectable extraction of K{sup +}, Rb{sup +}, or Cs{sup +}. Lipophilic crown ether carboxylic acids which contain 15-crown-5, 18-crown-6, and 21-crown-7 rings exhibit good selectivities for Na{sup +}, K{sup +}, and Cs{sup +}, respectively. In contrast, poor extraction selectivity is observed for lipophilic crown ether carboxylic acids with 24-crown-8, 27-crown-9, and 30-crown-10 rings.

Walkowiak, W.; Kang, Sang Ihn; Stewart, L.E.; Ndip, G.; Bartsch, R.A. (Texas Tech Univ., Lubbock (USA))

1990-09-15

376

Atmospheric chemistry and fate of highly-fluorinated carboxylic acids and alcohols  

NASA Astrophysics Data System (ADS)

It is well known that organic molecules constitute a significant fraction of atmospheric aerosol particle composition. Organic compounds which reside on the surface of aerosol particles dictate its morphological, chemical, and optical properties and can influence its reactivity in the atmosphere. Organic rich atmospheric aerosol particles may be a vehicle of transport for organics found in the atmosphere. In the context of this work, the atmospheric chemistry and fate of highly fluorinated and fully fluorinated organic compounds, known as perfluorinated compounds (PFCs), are examined. They have recently been under the scrutiny of the Environmental Protection Agency due to their widespread distribution, persistence, bioaccumulation, and possible toxicity. The focus of the studies outlined in this thesis is motivated by determining if atmospheric aerosol particles may be a plausible candidate for transporting highly-fluorinated and perfluorinated compounds in the troposphere, and also understanding the heterogeneous chemistry that this class of compounds can undergo in the atmosphere. Gas-phase vibrational spectra of several perfluorocarboxylic acids were studied from the infrared to the visible regions. The objective of these experiments served as a preliminary step in determining if PFCs have the potential to undergo sunlight-initiated photochemistry through vibrational overtone pumping of the O-H bond. Results would discern if there is a competition between evaporation and actual chemical reactions occurring at the air-water interface. The surface properties of several highly-fluorinated carboxylic acids and partially fluorinated alcohols at the air-water interface were investigated. These results helped characterize film properties and understand how these compounds behave at the air-water interface in the presence of other organics. Consequences of these studies helped answer if atmospheric aerosol particles may be a possible vehicle of transport for fluorinated compounds in the atmosphere. Processing films of an unsaturated, partially fluorinated carboxylic acid at the air-water interface with ozone and visible light was examined. The resultant film was collected and analyzed as well as the subphase to determine degradation products. Results from these studies gave valuable insight as to the changing structure of the film due to photoprocessing and showed differences in activity of fluorinated compounds as compared to hydrocarbon analog acids.

Rontu Carlon, Nabilah Arshad

377

Fourier transform infrared spectroscopic studies of hydrogen bonding interactions in materials containing carboxylic acid groups  

NASA Astrophysics Data System (ADS)

The results of Fourier transform infrared (FTIR) spectroscopic studies of the hydrogen bonding interactions in materials and blends containing carboxylic acid groups are presented. The self-association of p-n-alkoxybenzoic acids (AOBAs) exhibits liquid crystalline characteristics. The length of the terminal alkyl chain determines the crystal structure observed. For longer chain lengths (n = 7--18), an isotypic form is observed, where the segregation of the alkyl chains and aromatic rings allows for the stacking of the self-associated acid groups. This leads to infrared band splitting and a broadened carbonyl stretching region. The breadth can also be caused by the polymorphic state of the material, as in the case of the molecules possessing the shorter alkyl chains (n < 7). By blending these materials with amorphous polyethers, a competition for hydrogen bonds is induced. By diluting the AOBAs with the polyethers, the highly ordered state is disrupted and access to inter-associating partners is increased. Copolymers of methacrylic acid with styrene and 2,3-dimethylbutadiene were synthesized. Temperature stability (decreased anhydride formation) of these materials was improved by decreasing the number of adjacent methacrylic acid groups (<10 mol%). The self-association equilibrium constants were also calculated for each copolymer and compared with that of a low molecular weight analogue. The value of the self-association equilibrium constant increased with increasing chain flexibility. Therefore, an infinitely flexible chain should possess the same value of the self-association equilibrium constant as the low molecular weight analogue. The styrene copolymer was then blended with poly(tetrahydrofuran) and an inter-association equilibrium constant was determined. Despite an order of magnitude difference between the self- and inter-association equilibrium constants, the blends are miscible.

Cleveland, Christopher Scott

378

Built-in 5-aminooxazole as an internal activator of the terminal carboxylic acid: an alternative access to macrocyclodepsipeptides.  

PubMed

A conceptually novel macrolactonization technology is described. A strategically positioned 5-aminooxazole served as an internal traceless activator of the neighboring C-terminal carboxylic acid allowing the occurrence of macrolactonization under mild acidic conditions. It is a domino process involving a sequence of: a) protonation of 5-aminooxazole leading to an electrophilic iminium salt; b) trapping the iminium species by the neighboring C-terminal carboxylic acid leading to a putative spirolactone; c) intramolecular nucleophilic addition of the tethered alcohol onto the spirolactone followed by fragmentation to afford the macrolactone. No coupling reagent is required and the entire sequence is triggered by trifluoroacetic acid under very mild conditions (MeCN, room temperature). By combining with a three-component synthesis of 5-aminooxazole, a two-step synthesis of structurally complex cyclodepsipeptides from readily accessible starting materials is developed. PMID:22026185

Zhu, Jieping

2011-01-01

379

Why are carboxylic acids stronger acids than alcohols? The electrostatic theory of Siggel–Thomas revisited  

Microsoft Academic Search

The electrostatic explanation of Siggel and Thomas for the acidity differences between series of acids was investigated critically. Acidities and electrostatic potentials at the protons of XOH, XNH2, and XCH3 derivatives (X=H, CH3, HCO, NO2, and F) were calculated at the Becke3LYP\\/6-311+G?? level. Final state (anion) relaxation energies were obtained as proposed by Siggel and Thomas. Examination of initial and

P Burk; P von Ragué Schleyer

2000-01-01

380

Selective reduction of carboxylic acids to aldehydes catalyzed by B(C6F5)3.  

PubMed

B(C(6)F(5))(3) efficiently catalyzes hydrosilylation of aliphatic and aromatic carboxylic acids to produce disilyl acetals under mild conditions. Catalyst loadings can be as low as 0.05 mol %, and bulky tertiary silanes are favored to give selectively the acetals. Acidic workup of the disilyl acetals results in the formation of aldehydes in good to excellent yields. PMID:23317512

Bézier, David; Park, Sehoon; Brookhart, Maurice

2013-01-14

381

Influence of an aromatic carboxylic acid as cocatalyst in the palladium-catalysed reductive carbonylation of aromatic nitro compounds  

Microsoft Academic Search

The addition of carboxylic acids such as benzoic acid derivatives as cocatalyst has been found to enhance the catalytic activity and selectivity of a Pd(phen)2(OTf)2 catalyst system in the reductive carbonylation of aromatic nitro compounds. A strong dependency of the catalytic performance on the amount of cocatalyst in the reaction mixture was found, yet no influence of the pKa-value of

Petra Wehman; Leo Borst; Paul C. J. Kamer; Piet W. N. M. van Leeuwen

1996-01-01

382

Carboxylation of alkynylsilanes with carbon dioxide mediated by cesium fluoride in DMSO.  

PubMed

The facile syntheses of a variety functionalized propiolic acids were achieved by carboxylation of alkynylsilanes with carbon dioxide mediated by cesium fluoride under ambient conditions. PMID:23674078

Yonemoto-Kobayashi, Misato; Inamoto, Kiyofumi; Tanaka, Yoshiyuki; Kondo, Yoshinori

2013-06-21

383

Comparison of acid anhydrides with carboxylic acids in enantioselective enzymatic esterification of racemic menthol.  

PubMed

Optical resolution of racemic menthol has been efficiently achieved by lipase-catalyzed enantioselective esterification in an organic solvent. The performance of the reaction using an acid anhydride as an acyl donor was compared with that using its corresponding free acid. The reactivities of acid anhydrides were found to be higher than their corresponding free acids, but acid anhydrides were also found to be easily hydrolyzed into free acids under the catalysis of the same enzyme. The existence of a too-high concentration of an acid anhydride in a micro-aqueous reaction system will cause dehydration and thus deactivation of the enzyme, and will enhance non-selective esterification of a chiral alcohol, which will reduce the optical purity of the product. All these drawbacks, however, could be effectively overcome in a semi-batch reaction system into which propionic anhydride was continuously fed. This system showed some advantages over a batch reaction system using free propionic acid: the reaction time of dl-menthol was shortened by half, the stability of the enzyme was much enhanced, and the optical purity of the product (l-menthyl ester) was kept at a similarly high level (> 98% ee). PMID:9631262

Xu, J; Zhu, J; Kawamoto, T; Atsuo, T; Hu, Y

1997-01-01

384

Carboxyl terminal domain basic amino acids of mycobacterial topoisomerase I bind DNA to promote strand passage  

PubMed Central

Bacterial DNA topoisomerase I (topoI) carries out relaxation of negatively supercoiled DNA through a series of orchestrated steps, DNA binding, cleavage, strand passage and religation. The N-terminal domain (NTD) of the type IA topoisomerases harbor DNA cleavage and religation activities, but the carboxyl terminal domain (CTD) is highly diverse. Most of these enzymes contain a varied number of Zn2+ finger motifs in the CTD. The Zn2+ finger motifs were found to be essential in Escherichia coli topoI but dispensable in the Thermotoga maritima enzyme. Although, the CTD of mycobacterial topoI lacks Zn2+ fingers, it is indispensable for the DNA relaxation activity of the enzyme. The divergent CTD harbors three stretches of basic amino acids needed for the strand passage step of the reaction as demonstrated by a new assay. We also show that the basic amino acids constitute an independent DNA-binding site apart from the NTD and assist the simultaneous binding of two molecules of DNA to the enzyme, as required during the catalytic step. Although the NTD binds to DNA in a site-specific fashion to carry out DNA cleavage and religation, the basic residues in CTD bind to non-scissile DNA in a sequence-independent manner to promote the crucial strand passage step during DNA relaxation. The loss of Zn2+ fingers from the mycobacterial topoI could be associated with Zn2+ export and homeostasis.

Ahmed, Wareed; Bhat, Anuradha Gopal; Leelaram, Majety Naga; Menon, Shruti; Nagaraja, Valakunja

2013-01-01

385

Human soluble epoxide hydrolase: structural basis of inhibition by 4-(3-cyclohexylureido)-carboxylic acids.  

PubMed

X-ray crystal structures of human soluble epoxide hydrolase (sEH) complexed with four different dialkylurea inhibitors bearing pendant carboxylate "tails" of varying length have been determined at 2.3-3.0 A resolution. Similarities among inhibitor binding modes reinforce the proposed roles of Y381 and/or Y465 as general acids that protonate the epoxide ring of the substrate in concert with nucleophilic attack of D333 at the electrophilic epoxide carbon. Additionally, the binding of these inhibitors allows us to model the binding mode of the endogenous substrate 14,15-epoxyeicosatrienoic acid. Contrasts among inhibitor binding modes include opposite orientations of inhibitor binding in the active-site hydrophobic tunnel. Alternative binding orientations observed for this series of inhibitors to human sEH, as well as the binding of certain dialkylurea inhibitors to human sEH and murine sEH, complicate the structure-based design of human sEH inhibitors with potential pharmaceutical applications in the treatment of hypertension. Thus, with regard to the optimization of inhibitor designs targeting human sEH, it is critical that human sEH and not murine sEH be utilized for inhibitor screening, and it is critical that structures of human sEH-inhibitor complexes be determined to verify inhibitor binding orientations that correlate with measured affinities. PMID:16322563

Gomez, German A; Morisseau, Christophe; Hammock, Bruce D; Christianson, David W

2005-12-01

386

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

2007-05-10

387

Carboxyl terminal domain basic amino acids of mycobacterial topoisomerase I bind DNA to promote strand passage.  

PubMed

Bacterial DNA topoisomerase I (topoI) carries out relaxation of negatively supercoiled DNA through a series of orchestrated steps, DNA binding, cleavage, strand passage and religation. The N-terminal domain (NTD) of the type IA topoisomerases harbor DNA cleavage and religation activities, but the carboxyl terminal domain (CTD) is highly diverse. Most of these enzymes contain a varied number of Zn(2+) finger motifs in the CTD. The Zn(2+) finger motifs were found to be essential in Escherichia coli topoI but dispensable in the Thermotoga maritima enzyme. Although, the CTD of mycobacterial topoI lacks Zn(2+) fingers, it is indispensable for the DNA relaxation activity of the enzyme. The divergent CTD harbors three stretches of basic amino acids needed for the strand passage step of the reaction as demonstrated by a new assay. We also show that the basic amino acids constitute an independent DNA-binding site apart from the NTD and assist the simultaneous binding of two molecules of DNA to the enzyme, as required during the catalytic step. Although the NTD binds to DNA in a site-specific fashion to carry out DNA cleavage and religation, the basic residues in CTD bind to non-scissile DNA in a sequence-independent manner to promote the crucial strand passage step during DNA relaxation. The loss of Zn(2+) fingers from the mycobacterial topoI could be associated with Zn(2+) export and homeostasis. PMID:23771144

Ahmed, Wareed; Bhat, Anuradha Gopal; Leelaram, Majety Naga; Menon, Shruti; Nagaraja, Valakunja

2013-06-14

388

Heterogeneous interaction of carboxylic acids with pure ice and HNO3-doped ice surfaces at upper tropospheric/lower stratospheric temperatures  

NASA Astrophysics Data System (ADS)

The heterogeneous interaction of atmospheric trace gases with ice surfaces plays an important role in the chemistry of the upper troposphere and lower stratosphere (UT/LS) region. In particular, the uptakes of carboxylic acids, such as formic (HC(O)OH), acetic (CH3C(O)OH), propionic (CH3CH2C(O)OH), and butyric (CH3CH2CH2C(O)OH) acids, on pure ice or HNO3-doped ice particles in dense cirrus clouds or polar stratospheric clouds may be significant in removing these acids from the UT/LS. The aim of the present study was to investigate the adsorption of gaseous carboxylic acids on thin ice and HNO3-doped ice films over the temperature range 195-208 K and at low gaseous pressures, using a Knudsen flow reactor combined with a quadrupole mass spectrometer. The initial uptake coefficients, ?o, were measured as a function of temperature and at low surface coverage; the inverse temperature dependence of ?o indicates that the uptake proceeds via the formation of an intermediate precursor state. The uptakes of formic and acetic acids were well represented by Langmuir adsorption model, and the temperature independent saturation surface coverage, Nmax, on pure ice films were (2.94 ± 0.67)×1014 molecule cm-2, and (2.11 ± 0.16)×1014 molecule cm-2, respectively; in excellent agreement with coated-wall laminar flow tube (CWLFT) technique values. Light nitration (1.96 and 7.69 wt%) of ice films resulted in more efficient uptakes and larger Nmax values that may be attributed to in-bulk diffusion or change in nature of gas-ice surface interaction. The uptake profiles of propionic and butyric acids on pure ice and HNO3-doped ice films over the temperature range 195-206 K were unsaturated, which indicated high solubility and rapid diffusion of these acids into the ice bulk. The kinetics of these uptakes ?(t) were very well represented by the diffusion non-dissociating resistor model, and H*d(D)1/2 values were independent of concentration and in the range 1 to 20 m s-1/2; H*d is the Henry law coefficient and D the diffusion coefficient of the carboxylic acids in the ice bulk. Finally, it was estimated that the adsorption rate of these carboxylic acids on high-density cirrus clouds in the UT/LS is fast, and this is reflected by their short atmospheric lifetimes (1-8 min), while the amount of these uptakes is probably low on pure ice (?5%) and rather considerable (?20%) on HNO3-doped ice particles.

Papagiannakopoulos, P.; Pettersson, J. B. C.; Papadimitriou, V. C.; Romanias, M. N.

2012-04-01

389

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

2006-11-12

390

2-substituted thiazolidine-4(R)-carboxylic acids as prodrugs of L-cysteine. Protection of mice against acetaminophen hepatotoxicity  

SciTech Connect

A number of 2-alkyl- and 2-aryl-substituted thiazolidine-4(R)-carboxylic acids were evaluated for their protective effect against hepatotoxic deaths produced in mice by LD/sub 90/ doses of acetaminophen. 2(RS)-Methyl-, 2(RS)-n-propyl-, and 2(RS)-n- pentylthiazolidine -4(R)-carboxylic acids (compounds 1b,d,e, respectively) were nearly equipotent in their protective effect based on the number of surviving animals at 48 h as well as by histological criteria. 2(RS)-Ethyl-, 2(RS)-phenyl-, and 2(RS)-(4-pyridyl)thiazolidine-4(R)-carboxylic acids (compounds 1c,f,g) were less protective. The enantiomer of 1b, viz., 2(RS)- methylthiazolidine -4(S)-carboxylic acid (2b), was totally ineffective in this regard. Thiazolidine-4(R)-carboxylic acid (1a), but not its enantiomer, 2a, was a good substrate for a solubilized preparation of rat liver mitochondrial proline oxidase (K/sub m/ 1.1 x 10(-4) M; V/sub max/ . 5.4 mumol min-1 (mg of protein)-1). Compound 1b was not a substrate for proline oxidase but dissociated to L-cysteine in this system. At physiological pH and temperature, the hydrogens on the methyl group of 1b underwent deuterium exchange with solvent D/sub 2/O (k1 . 2.5 X 10(-5) s), suggesting that opening of the thiazolidine ring must have taken place. Indeed, 1b labeled with /sup 14/C in the 2 and methyl positions was rapidly metabolized by the rat to produce /sup 14/CO/sub 2/, 80% of the dose being excreted in this form in the expired air after 24 h. It is suggested that these 2-substituted thiazolidine-4(R)-carboxylic acids are prodrugs of L-cysteine that liberate this sulfhydryl amino acid in vivo by nonenzymatic ring opening, followed by solvolysis.

Nagasawa, H.T.; Goon, D.J.; Muldoon, W.P.; Zera, R.T.

1984-05-01

391

Carboxylic acids, sulfates, and organosulfates in processed continental organic aerosol over the southeast Pacific Ocean during VOCALS-REx 2008  

NASA Astrophysics Data System (ADS)

Submicron particles were collected on board the NOAA R/V Ronald H. Brown during the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) in the southeast Pacific marine boundary layer in October and November 2008. The aerosol in this region was characterized by low numbers of particles (150-700 cm-3) that were dominated by sulfate ions at concentrations of 0.9 ± 0.7 ?g m-3 and organic mass at 0.6 ± 0.4 ?g m-3, with no measurable nitrate and low ammonium ion concentrations. Measurements of submicron organic aerosol functional groups and trace elements show that continental outflow of anthropogenic emissions is the dominant source of organic mass (OM) to the southeast Pacific with an additional, smaller contribution of organic mass from primary marine sources. This continental source is supported by a correlation between OM and radon. Saturated aliphatic C-CH (alkane) composed 41 ± 27% of OM. Carboxylic acid COOH (32 ± 23% of OM) was observed in single particles internally mixed with ketonic carbonyl, carbonate, and potassium. Organosulfate COSO3 (4 ± 8% of OM) was observed only during the periods of highest organic and sulfate concentrations and lowest ammonium concentrations, consistent with a sulfuric acid epoxide hydrolysis for proposed surrogate compounds (e.g., isoprene oxidation products) or reactive glyoxal uptake mechanisms from laboratory studies. This correlation suggests that in high-sulfate, low-ammonium conditions, the formation of organosulfate compounds in the atmosphere contributes a significant fraction of aerosol OM (up to 13% in continental air masses). Organic hydroxyl C-OH composed 20 ± 12% of OM and up to 50% of remote marine OM and was inversely correlated with radon indicating a marine source. A two-factor solution of positive matrix factorization (PMF) analysis resulted in one factor dominated by organic hydroxyl (>70% by mass) and one factor dominated by saturated aliphatic C-CH (alkane) and carboxylic acid (together, 90% by mass), identified as the marine and combustion factors, respectively. Measurements of particle concentrations in the study region compared with concentrations estimated from MODIS aerosol optical depth indicate that continental outflow results in MBL particle concentrations elevated up to 2 times the background level (less than 300 cm-3) away from shore and up to 10 times the background level at the coast. The presence of both coastal fossil fuel combustion and marine sources of oxygenated organic aerosol results in little change in the oxygenated fraction and oxygen to carbon ratio (O/C) along the outflow of the region's dominant organic particle source.

Hawkins, L. N.; Russell, L. M.; Covert, D. S.; Quinn, P. K.; Bates, T. S.

2010-07-01

392

1-Allyl-3-amino-1H-pyrazole-4-carboxylic acid  

PubMed Central

The title compound, C7H9N3O2, was prepared by alkaline hydrolysis of ethyl 1-allyl-3-amino-1H-pyrazole-4-carboxyl­ate. The crystal structure is stabilized by three types of inter­molecular hydrogen bond (N—H?O, N—H?N and O—H?N).

Li, Gong-Chun; Wang, Li-Ye; Zhu, Ran; Yang, Feng-Ling

2008-01-01

393

Carboxylic acid reductase is a versatile enzyme for the conversion of fatty acids into fuels and chemical commodities.  

PubMed

Aliphatic hydrocarbons such as fatty alcohols and petroleum-derived alkanes have numerous applications in the chemical industry. In recent years, the renewable synthesis of aliphatic hydrocarbons has been made possible by engineering microbes to overaccumulate fatty acids. However, to generate end products with the desired physicochemical properties (e.g., fatty aldehydes, alkanes, and alcohols), further conversion of the fatty acid is necessary. A carboxylic acid reductase (CAR) from Mycobacterium marinum was found to convert a wide range of aliphatic fatty acids (C(6)-C(18)) into corresponding aldehydes. Together with the broad-substrate specificity of an aldehyde reductase or an aldehyde decarbonylase, the catalytic conversion of fatty acids to fatty alcohols (C(8)-C(16)) or fatty alkanes (C(7)-C(15)) was reconstituted in vitro. This concept was applied in vivo, in combination with a chain-length-specific thioesterase, to engineer Escherichia coli BL21(DE3) strains that were capable of synthesizing fatty alcohols and alkanes. A fatty alcohol titer exceeding 350 mg·L(-1) was obtained in minimal media supplemented with glucose. Moreover, by combining the CAR-dependent pathway with an exogenous fatty acid-generating lipase, natural oils (coconut oil, palm oil, and algal oil bodies) were enzymatically converted into fatty alcohols across a broad chain-length range (C(8)-C(18)). Together with complementing enzymes, the broad substrate specificity and kinetic characteristics of CAR opens the road for direct and tailored enzyme-catalyzed conversion of lipids into user-ready chemical commodities. PMID:23248280

Akhtar, M Kalim; Turner, Nicholas J; Jones, Patrik R

2012-12-17

394

Growth inhibition of Clostridium thermocellum by carboxylic acids: A mechanism based on uncoupling by weak acids  

Microsoft Academic Search

The inhibition of Clostridium thermocellum strains by acetate and other organic acids (propionate, butyrate) can be explained by a model based on the chemiosmotic theory and uncoupler action. It is proposed that the charged permeant species in the process of anion exclusion is the dimer HA-2. Evidence for this mechanisms is provided by 31P-NMR studies of whole cells and cell

Alejandro A. Herrero; Reinaldo F. Gomez; Brad Snedecor; Cynthia J. Tolman; Mary F. Roberts

1985-01-01

395

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

PubMed Central

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 CO2 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 ?l/l ethylene; (b) reversal of ethylene-enhanced ACC synthase activity by CO2; (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% CO2, but not by 1.25% CO2. However, each of these CO2 concentrations reduced the rate of increase of ACC synthase activity.

Bufler, Gebhard

1984-01-01

396

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

397

A mechanical strain-induced 1-aminocyclopropane-1-carboxylic acid synthase gene.  

PubMed Central

Ethylene production is observed in all higher plants, where it is involved in numerous aspects of growth, development, and senescence. 1-Aminocyclopropane-1-carboxylic acid synthase (ACC synthase; S-adenosyl-L-methionine methylthioadenosine-lyase, EC 4.4.1.14) is the key regulatory enzyme in the ethylene biosynthetic pathway. We are reporting an ACC synthase gene in Vigna radiata (mung bean) that is inducible by mechanical strain. The ACC synthase cDNA AIM-1 was induced by mechanical strain within 10 min, reaching a maximum at 30 min, showing a dramatic reduction after 60 min, and showing no detectable message by 3 hr. The kinetics of induction for AIM-1 was similar to a mechanical strain-induced calmodulin (MBCaM-1) in V. radiata, whereas the kinetics of its decline from maximum was different. When plants were subjected to calcium-deficient conditions, supplemental calcium, calcium chelators, calcium storage releasers, calcium ionophore, or calmodulin antagonists, there was no effect on AIM-1, indicating that the mechanical strain-induced AIM-1 expression is a calcium-independent process. Induction of MBCaM-1 in all cases behaved in the same way as AIM-1, suggesting that they share similar mechanically activated cis- and/or trans-acting elements in their promoter. Images Fig. 1 Fig. 2 Fig. 3

Botella, J R; Arteca, R N; Frangos, J A

1995-01-01

398

Stimulation of H+ Efflux and Inhibition of Photosynthesis by Esters of Carboxylic Acids 1  

PubMed Central

Suspensions of mechanically isolated Asparagus sprengeri Regel mesophyll cells were used to investigate the influence of various carboxyester compounds on rates of net H+ efflux in the dark or light and photosynthetic O2 production. Addition of 0.15 to 1.5 millimolar malathion, ?-naphthyl acetate, phenyl acetate, or p-nitrophenyl acetate stimulated H+ efflux and inhibited photosynthesis within 1 minute. In contrast, the more polar esters methyl acetoacetate or ethyl p-aminobenzoate had little or no effect on either of these two processes. A 0.15 millimolar concentration of ?-naphthylacetate stimulated the normal rate of H+ efflux, 0.77 nanomoles H+ per 106 cells per minute by 750% and inhibited photosynthesis by 100%. The four active carboxyester compounds also stimulated H+ efflux after the normal rate of H+ efflux was eliminated with 0.01 milligrams per milliliter oligomycin or 100% N2. Oligomycin reduced the ATP level by 70%. Incubation of cells with malathion, ?-naphthyl acetate, or p-nitrophenyl acetate resulted in the generation of the respective hydrolysis products ethanol, ?-naphthol, and p-nitrophenol. It is proposed that inhibition of photosynthesis and stimulation of H+ efflux result when nonpolar carboxyester compounds enter the cell and generate acidic carboxyl groups when hydrolyzed by esterase enzymes.

Duhaime, Donna E.; Bown, Alan W.

1983-01-01

399

Detection of conjugated 11-nor-Delta9-tetrahydrocannabinol-9-carboxylic acid in oral fluid.  

PubMed

The presence of the conjugated marijuana metabolite 11-nor-Delta(9)-tetrahydrocannabinol-9-carboxylic acid (THCA) glucuronide in oral fluid specimens is described for the first time. Oral fluid specimens were collected using a Quantisal device and analyzed for the presence of THCA using two-dimensional gas chromatography with mass spectrometric (GC-MS) detection both before and after hydrolysis. The nature of the conjugation was determined by analyzing specimens from a marijuana user without hydrolysis, with base hydrolysis, with beta-glucuronidase treatment, and hydrolysis using sulfatase only. Treatment with sodium hydroxide proved to be the most efficient hydrolytic procedure. Specimens collected over 48 h showed an average conjugation of over 64.5%. The specimens were also analyzed for the active component, tetrahydrocannabinol (THC), which was detected in the oral fluid, in most cases, for up to 24 h. Parent THC was not found to be glucuronide bound. Specimens were then subjected to commercially available immunoassays in order to determine their utility as screening procedures. The metabolite, THCA, was detected in all samples up to and including the specimen 48 h after smoking, using the more sensitive screening assay and two-dimensional GC-MS. Moreover, proof that the THCA is conjugated in oral fluid minimizes concerns associated with passive inhalation. PMID:17555641

Moore, Christine; Rana, Sumandeep; Coulter, Cynthia; Day, David; Vincent, Michael; Soares, James

2007-05-01

400

[The influence of pyridyl-carboxylic acid intermolecular H-bond on photoisomerization and photochemical stabilities].  

PubMed

A new type of liquid crystalline was formed through self-assembly via intermolecular hydrogen bonding between the carboxylic acid and the pyridyl group of the stilbazoles. Cholesteryl butane diacid single ester (CSA) was synthesized for use as H-bond donor and the stilbazole derivatives (NCn) were prepared as H-bond acceptors. The spectroscopic behavior and the photochemical stabilities of these two compounds, NCn and its intermolecular H-bonding complex CSA . NCn were investigated by UV-Vis spectroscopy. The results show that these two compounds easily undergo photoisomerization from trans to cis isomers in alcohol. In chloroform solution, the CSA . NCn only undergoes trans-cis photoisomerization, while NCn exhibits not only trans-cis isomerization but also a special photoreaction. The reason is that in CSA . NCn compounds, the pyridyl N-end group is forms intermolecular H-bonding with CSA, and can't catch the H+ and the radical. It is proved that this intermolecular H-bond was very stable when being exposed to UV light. PMID:18536399

Wu, Ying; Zhou, Hong-Wei; Bu, Feng-Quan; Tian, Yan-Qing; Jiang, Shi-Mei

2008-03-01

401

Hydrophobicity-dependent QSARs to predict the toxicity of perfluorinated carboxylic acids and their mixtures.  

PubMed

Perfluorinated carboxylic acids (PFCAs) have wide industrial applications because of their unique physicochemical characteristics. However, data on the toxicity of much of this chemical class is lacking, particularly with regard to mixture toxicity. In this study, the toxicity of individual PFCAs and their mixtures to Photobacterium phosphoreum were observed. There was a tendency of increasing toxicity from C3 to C14 PFCA and a tendency of decreasing toxicity from C14 to C18 PFCA because of "the maximum tolerance of the cell membrane". Using the equivalent logK(OW) (octanol-water partition coefficient) and logK(SD) (C(18)-Empore™ disks/water partition coefficient), two linear quantitative structure-activity relationship (QSAR) models were formulated. This indicated both K(SD) and K(OW) can describe the hydrophobicity of a single chemical. However, for the PFCA mixtures, K(MD) is the more reasonable parameter than K(owmix) to describe the hydrophobicity because only the equivalent logK(MD) could be used to predict the mixture toxicity. PMID:21843807

Wang, Ting; Lin, Zhifen; Yin, Daqiang; Tian, Dayong; Zhang, Yalei; Kong, Deyang

2011-06-25

402

Analysis of carboxylic acid metabolites from the tricarboxylic acid cycle in Bacillus subtilis cell extract by capillary electrophoresis using an indirect photometric detection method.  

PubMed

With a growing interest in metabolome analysis, there is a need for developing robust methods for analysis of intracellular metabolites profiles in real samples like e.g., bacteria cell. Due to their weak absorbance properties, tri- and dicarboxylic acids from TCA cycle (citric, isocitric, 2-oxoglutaric, succinic, fumaric, malic) as well as carboxylic acid metabolites from glycolysis pathway, urea cycle and metabolism of amino compounds (formic, pyruvic, lactic, acetic, glutamic) were analyzed by capillary electrophoresis (CE) with indirect UV detection. Using 4 mM 2,6-pyridinedicarboxylic acid as a highly UV absorbing carrier electrolyte, 0.2 mM cetyltrimethylammonium bromide, 10% ethylene glycol and 10% acetonitrile, pH 3.5, carboxylic acids metabolites were analyzed in Bacillus subtilis cell extract from two different cultures: glucose and malate. CE with an electrokinetic injection mode achieved limits of detection in the range of 13-54 ppb (1.12-10(-7) - 5.96-10(-7) M). The reproducibility and linearity of method was investigated with RSD for migration time less than 1.3% and acceptable correlation coefficients. The optimized CE method was used to compare metabolome content of cell extract derived from two different culture media containing either glucose or malate as a carbon source. The changes in carboxylic acid metabolites profile were observed depending from used culture medium. Carboxylic acid concentrations ranged: in cell extract from malate culture from 59 to 0.5 microM for lactate and citrate, respectively, and in cell extract from glucose culture from 133 to 0.5 microM for glutamate and citrate, respectively. Appropriate concentrations of carboxylic acid in the single bacterium cell were estimated at mM and sub-mM levels. PMID:14503821

Markuszewski, Micha? J; Otsuka, Koji; Terabe, Shigeru; Matsuda, Keiko; Nishioka, Takaaki

2003-08-22

403

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

404

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

405

Synthesis of carboxylic acids, esters, alcohols and ethers containing a tetrahydropyran ring derived from 6-methyl-5-hepten-2-one.  

PubMed

3-hydroxy acids, 3-hydroxy-3,7-dimethyloct-6-enoic acid (1) and 3-hydroxy-2,2,3,7-tetramethyloct-6-enoic acid (2), were prepared from 6-methyl-5-hepten-2-one, and they were subsequently used to prepare (2,6,6-trimethyltetrahydropyran-2-yl)acetic acid (3) and 2-methyl-2-(2,6,6-trimethyltetrahydropyran-2-yl)propanoic acid (4), respectively, via cyclization with an acidic catalyst such as boron trifluoride diethyl etherate or iodine. The reaction of carboxylic acids 3 and 4 with alcohols, including methanol, ethanol, and 1-propanol, produced the corresponding methyl, ethyl, and propyl esters, which all contained a tetrahydropyran ring. Reduction of carboxylic acids 3 and 4 afforded the corresponding alcohols. Subsequent reactions of these alcohols with several acyl chlorides produced novel esters. The alcohols also reacted with methyl iodide and sodium hydride to provide novel ethers. A one-pot cyclization-esterification of 1 to produce esters containing a tetrahydropyran ring, using iodine as a catalyst, was also investigated. PMID:23138252

Hanzawa, Yohko; Hashimoto, Kahoko; Kasashima, Yoshio; Takahashi, Yoshiko; Mino, Takashi; Sakamoto, Masami; Fujita, Tsutomu

2012-01-01

406

4'-Acetyl-3''-carbamoyl-[1,1':3',1''-terphen-yl]-2-carb-oxy-lic acid.  

PubMed

In the title m-terphenyl derivative, C22H17NO4, the dihedral angles between the aromatic rings of the benzoic acid-acetophenone, acetophenone-benzamide and benzoic acid-benzamide units are 45.39?(8), 48.02?(8) and 42.93?(8)°, respectively. The carbamoyl and carboxyl groups are disordered with a refined occupancy ratio of 0.558?(15):0.442?(15). In the crystal, mol-ecules are linked through O-H?O and N-H?O hydrogen bonds between terminal carboxyl and carbamoyl groups in a bidentate manner, and anti-parallel helices are formed which extend along the b-axis direction. PMID:24098269

Ishikawa, Yoshinobu; Yoshida, Nanako; Suzuki, Takafumi

2013-09-28

407

Isotachophoresis on a chip with indirect fluorescence detection as a field deployable system for analysis of carboxylic acids.  

PubMed

ITP with indirect fluorescence detection (IFD) was introduced three decades ago. Despite this fact, the method has never become widely adopted. The main aim of this work was to utilize the ITP-IFD for the separation of carboxylic acids by using a commercially available, portable, microfluidic chip electrophoresis system. On the 16.8-mm effective length separation channel, a maximum of eight carboxylic acids could be separated, with LOD values in a range from 0.12 to 0.4 mM. The commercial chips used for all experiments have multichannel structures important for analysis of more than one sample per a chip in case of standard use. This multichannel structure was used to investigate the possibility of multiple sample loading for ITP separation. Application of ITP-IFD was investigated for analysis of benzoate in diet soft drinks and the results were in good agreement with results of a CE method. PMID:23065658

Smejkal, Petr; Breadmore, Michael C; Guijt, Rosanne M; Foret, František; Bek, Fritz; Macka, Mirek

2012-10-12

408

4?-Acetyl-3??-carbamoyl-[1,1?:3?,1??-terphen-yl]-2-carb-oxy-lic acid  

PubMed Central

In the title m-terphenyl derivative, C22H17NO4, the dihedral angles between the aromatic rings of the benzoic acid–acetophenone, acetophenone–benzamide and benzoic acid–benzamide units are 45.39?(8), 48.02?(8) and 42.93?(8)°, respectively. The carbamoyl and carboxyl groups are disordered with a refined occupancy ratio of 0.558?(15):0.442?(15). In the crystal, mol­ecules are linked through O—H?O and N—H?O hydrogen bonds between terminal carboxyl and carbamoyl groups in a bidentate manner, and anti­parallel helices are formed which extend along the b-axis direction.

Ishikawa, Yoshinobu; Yoshida, Nanako; Suzuki, Takafumi

2013-01-01

409

Chamazulene carboxylic acid and matricin: a natural profen and its natural prodrug, identified through similarity to synthetic drug substances.  

PubMed

Chamazulene carboxylic acid (1) is a natural profen with anti-inflammatory activity and a degradation product of proazulenic sesquiterpene lactones, e.g., matricin. Both 1 and proazulenes occur in chamomile (Matricaria recutita), yarrow (Achillea millefolium), and a few other Asteraceae species. It was isolated in improved yields, characterized physicochemically, and found to be an inhibitor of cyclooxygenase-2, but not of cyclooxygenase-1. It had anti-inflammatory activity in several animal models with local and systemic application. When human volunteers were given matricin orally, plasma levels of 1 were found to be in the micromolar range. Matricin was converted to 1 in artificial gastric fluid, but not in artificial intestinal fluid. Matricin and the yarrow proazulenes are proposed to be anti-inflammatory through conversion to 1. Intriguingly, the biological activity of the natural compound 1 was found because of its similarity to fully synthetic drug substances. This is the reverse process of the common lead function of natural compounds in drug discovery. PMID:16872141

Ramadan, Mai; Goeters, Susanne; Watzer, Bernhard; Krause, Eva; Lohmann, Klaus; Bauer, Rudolf; Hempel, Bernd; Imming, Peter

2006-07-01

410

A simplified method for determining 1-aminocyclopropane-1-carboxylic acid (ACC) in plant tissues using a mass selective detector  

Microsoft Academic Search

A sensitive and specific method is described for the routine assay of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) in 100–200 mg fresh weight samples of green or etiolated tissue. The method involves high performance liquid chromatography (HPLC) and gas chromatography linked to mass spectrometry (GCMS) and uses 14C-labelled ACC as an internal standard, N-benzoyl n-propyl ACC as an easily prepared

K. C. Hall; D. M. E. Pearce; M. B. Jackson

1989-01-01

411

Analysis of the Cyanide Metabolite 2-Aminothiazoline-4Carboxylic Acid in Urine by High-Performance Liquid Chromatography  

Microsoft Academic Search

The cyanide metabolite 2-aminothiazoline-4-carboxylic acid (ATC) was converted to N-carbamylcysteine and analyzed by high-performance liquid chromatography (HPLC) and fluorometric detection. ATC was first separated from interfering substances by passing through the cation exchanger AG 50W-X8. Interfering disulfides were converted to thiols by reduction of the eluate with thiopropyl-Sepharose 6B. The thiols were then adsorbed to the organomercurial adsorbent p-acetoxymercurianiline-Sepharose 4B

P. Lundquist; B. Kagedal; L. Nilsson; H. Rosling

1995-01-01

412

The effect of water stress on 1-(malonylamino)cyclopropane-1-carboxylic acid concentration in plant tissues  

Microsoft Academic Search

Since the discovery of1-(malonylamino)cyclopropane-1-carboxylic acid (MACC)as a major metabolite of both endogenous andexogenously applied 1-aminocyclopropane-1-carboxylicacid (ACC), it has become evident that the formationof MACC from ACC can act to regulate ethyleneproduction in certain tissues. Hence it was suggestedthat MACC could serve as an indicator of water-stresshistory in plant tissues. The accurate quantificationof MACC in plant tissues is essential forunderstanding the

Khosrow M. Kalantari; Aileen R. Smith; Michael A. Hall

2000-01-01

413

Synthesis and antibacterial activity of 4-benzoyl-1-methyl-5-phenyl-1 H-pyrazole-3-carboxylic acid and derivatives  

Microsoft Academic Search

Some new 1H-pyrazole-3-carboxylic acid and pyridazinone derivatives were synthesized and evaluated for their antibacterial activities against Bacillus cereus ATCC 7064, Staphylococcus aureus ATCC 6538, Escherichia coli ATCC 4230 and Pseudomonas putida using tube dilution method. The minimal inhibitory concentrations (MICs) experiments revealed that all chemical compounds showed inhibitor effects on the growth of the test microorganisms. Moreover, the results of

Esvet Akbas; Ismet Berber; Ahmet Sener; Beybala Hasanov

2005-01-01

414

Lipase-catalyzed kinetic and dynamic kinetic resolution of 1,2,3,4-tetrahydroisoquinoline-1-carboxylic acid  

Microsoft Academic Search

A dynamic kinetic resolution method for the preparation of enantiopure 1,2,3,4-tetrahydroisoquinoline-1-carboxylic acid (R)-2 was developed involving the CAL-B-catalyzed enantioselective hydrolysis of the corresponding ethyl ester (±)-1 in toluene\\/acetonitrile (4:1) containing 1equiv of added water and 0.25equiv of dipropylamine. This method allowed the preparation of (R)-2 (ee=96%) with 80% isolated yield. The kinetic resolution of (±)-1 in diisopropyl ether at 3°C

Tihamér A. Paál; Enik? Forró; Arto Liljeblad; Liisa T. Kanerva; Ferenc Fülöp

2007-01-01

415

1-Aminocyclopropane-1-carboxylic acid concentrations in shoot-forming and non-shoot-forming tobacco callus cultures  

SciTech Connect

Shoot-forming tobacco (Nicotiana tabacum var. Wisconsin 38) callus tissues contain significantly lower concentrations of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid compared to non-shoot-forming callus tissues. This difference is evident 1 day after subculture to shoot-forming or non-shoot-forming medium, and is maintained through the first week of growth. The lack of auxin in shoot-forming medium is the probable cause for this difference in ACC concentrations.

Grady, K.L.; Bassham, J.A.

1982-09-01

416

A comparative study on the concentrations of 11-nor-? 9-tetrahydrocannabinol-9-carboxylic acid (THCCOOH) in head and pubic hair  

Microsoft Academic Search

In this study, the concentrations of 11-nor-?9-tetrahydrocannabinol-9-carboxylic acid (THCCOOH) in pubic, axillary and beard hair were measured and the correlation between the concentrations of THCCOOH in head and pubic hair from same cannabis users were evaluated. The papers on body hair analysis for THCCOOH were rarely found although police officers submit body hair as a complimentary specimen to forensic laboratories

Eunyoung Han; Hwakyung Choi; Sangki Lee; Heesun Chung; Joon myong Song

2011-01-01

417

Peptide Synthesis with 5?Amino?1?methyl?1H?[1,2,4]triazole?3?carboxylic Acid  

Microsoft Academic Search

In the search for the peptide synthesis of new potential lexitropsins, starting with methyl 5?amino?1?methyl?1H?[1,2,4]triazole?3?carboxylate 1a, we synthesized the chloroacetyl derivative of 2a, which was hydrolyzed to acid 2b and ammonolyzed to the peptide 2c. A more effective route was the use of (t?butoxycarbonyl)glycyl?benzotriazolide 3 to the acylation 1a, which leads the N\\/C protected peptide 4. This peptide was selectively

El?bieta Masiukiewicz; Barbara Rzeszotarska; Edyta Ko?odziejczyk

2007-01-01

418

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

419

Effect of l-aminocyclopropane-l-carboxylic acid, silver nitrate, and norbornadiene on plant regeneration from maize callus cultures  

Microsoft Academic Search

The effect of the ethylene antagonists norbornadiene and silver nitrate and the ethylene precursor l-aminocyclopropane-l-carboxylic acid (ACC) on Zea mays plant regeneration was studied. A 12-fold increase in plant regeneration, as measured by number of plants obtained per gram fresh weight from callus cultures of maize inbreds Pa91 and H99, was obtained by 250 µM norbornadiene and 100 µM silver

David D. Songstad; David R. Duncan; Jack M. Widholm

1988-01-01

420

Amino- and carboxyl-terminal amino acid sequences of proteins coded by gag gene of murine leukemia virus  

PubMed Central

The amino- and carboxyl-terminal amino acid sequences of proteins (p10, p12, p15, and p30) coded by the gag gene of Rauscher and AKR murine leukemia viruses were determined. Among these proteins, p15 from both viruses appears to have a blocked amino end. Proline was found to be the common NH2 terminus of both p30s and both p12s, and alanine of both p10s. The amino-terminal sequences of p30s are identical, as are those of p10s, while the p12 sequences are clearly distinctive but also show substantial homology. The carboxyl-terminal amino acids of both viral p30s and p12s are leucine and phenylalanine, respectively. Rauscher leukemia virus p15 has tyrosine as the carboxyl terminus while AKR virus p15 has phenylalanine in this position. The compositional and sequence data provide definite chemical criteria for the identification of analogous gag gene products and for the comparison of viral proteins isolated in different laboratories. On the basis of amino acid sequences and the previously proposed H-p15-p12-p30-p10-COOH peptide sequence in the precursor polyprotein, a model for cleavage sites involved in the post-translational processing of the precursor coded for by the gag gene is proposed.

Oroszlan, Stephen; Henderson, Louis E.; Stephenson, John R.; Copeland, Terry D.; Long, Cedric W.; Ihle, James N.; Gilden, Raymond V.

1978-01-01

421

pH induced dual "OFF-ON-OFF" switch: influence of a suitably placed carboxylic acid.  

PubMed

The design and synthesis of molecular probes competent for pH signaling within or beyond a certain range is a complicated matter. Herein a new mechanism for ''OFF-ON-OFF'' absorbance and fluorescence intensities vs. pH behaviour is described. The probe design is based on the connection of carboxylic acid derivatized benzoxazole and 7-hydroxycoumarin/iminocoumarin parts. The protonation/deprotonation of the carboxylic acid (-COOH), N atom of benzoxazole ring and hydroxy part of the coumarin ring have been used for this mechanistic study. We have designed the molecule in such a fashion that deprotonation of the hydroxy part takes place at a lower pK(a) compared to deprotonation of the -COOH. The dual ''OFF-ON-OFF'' properties of our probes depend on the C-C bond between the two different heterocyclic parts. Quantum mechanical calculations showed that the particular 'C-C' bond has an additional ?-character. The twisting around this bond in different forms is responsible for such an ''OFF-ON-OFF'' property. This mechanism is new in fluorescence alteration processes. The delocalization of charge from one heterocyclic part to the other heterocyclic part in the mono- and dianionic forms controls the ''OFF-ON-OFF'' properties. The role of the carboxylic acid group was examined using an acetyl substituted derivative. One of our probes was successfully applied in live cell imaging studies in media at different pH. PMID:23060072

Sadhu, Kalyan K; Mizukami, Shin; Yoshimura, Akimasa; Kikuchi, Kazuya

2012-10-11

422

Effect of storage time and natural corrosion inhibitor on carbohydrate and carboxylic acids content in canned tomato puree.  

PubMed

In this research compositional changes of tinplate-canned tomato purées, with or without the addition of essential onion oil were investigated. The study was focused on the analyses of carbohydrates and carboxylic acids in two groups of canned samples (with or without nitrates) to determine whether their chemical composition was affected with storage time. The measurements were performed by high performance liquid chromatography, during six months of storage. The contents of glucose, fructose and two major organic acids, citric and malic, were found in the concentration range 1.77-1.97%, 1.86-2.09%, 0.60-0.75% and 0.23-0.30%, respectively, in all canned samples. Compared to carbohydrates and organic acids, amino acids were found in minor quantities, among them, as most abundant ones were glutamic acid, arginine, aspartic and ?-amino butyric acids. The results show that contents of carbohydrates and carboxylic acids are significantly affected by the change of storage time in majority of analyzed samples. The results also indicated that the influence of essential onion oil on composition of canned tomato purée is within the range of changes due to storage time measured for all other types of cans. Therefore the addition of essential onion oil as natural efficient corrosion inhibitor, as it was found in our previous work, can be recommended for canned tomato purée. PMID:22701055

Grassino, A Nincevic; Grabaric, Z; De Sio, F; Cacace, D; Pezzani, A; Squitieri, G

2012-06-01

423

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 NH\\ctdot O, OH\\ctdot O, CH\\ctdot O, and CH2\\ctdot 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+H\\ctdot O-, OH\\ctdot O, and NH\\ctdot 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

424

The Dehydration Step in the Enzyme-Coenzyme-B 12 Catalyzed Diol Dehydrase Reaction of 1,2-Dihydroxyethane Utilizing a Hydrogen-Bonded Carboxylic Acid Group as an Additional Cofactor:  A Computational Study  

Microsoft Academic Search

using density functional theory (B3LYP) calculations. This mechanism involves a neutral radical rather than a protonated radical (radical cation). 1,2-Dihydroxyethane was chosen as the substrate, and formic acid was selected as a model for the carboxylic acid group. The 1,2-dihydroxyeth-l-yl radical (produced by H-atom transfer from the substrate to the 5'-deoxyadenosyl radical) forms a nine-membered ring structure with the formic

Philip George; Per E. M. Siegbahn; Jenny P. Glusker; Charles W. Bock

1999-01-01

425

In situ infrared study of SBA-15 functionalized with carboxylic groups incorporated by a co-condensation route.  

PubMed

Two samples of SBA-15 mesoporous silica with a different content of carboxylic groups (-COOH) were prepared by a co-condensation route, using 4-(triethoxysilil)butyronitrile as the organosilane agent, then treating the samples with sulfuric acid, which removes the template and simultaneously hydrolyses the -CN to -COOH groups, as shown by IR spectroscopy. Both incorporation of organosilane agents and subsequent acid treatment do not affect the ordered SBA-15 structure. The proton-donor ability of carboxylic groups, as well their accessibility to reactants, has been studied in the IR by dosing ammonia, which forms reversibly COO- groups and NH4+ ions. The related equilibrium constants have been determined by elaboration of IR data. Outgassing the samples at progressively increasing temperatures destabilizes to an increasing extent the ammonium/carboxylate ion pair, because of the decrease in surface polarity brought about by dehydration: this decreases the related equilibrium constants. The amount of carboxylic groups undergoing reaction appears instead to be constant with dehydration, and to coincide with the whole population of COOH groups. Titration with alkali solutions yielded surface concentrations for the two samples of ca. 1.0 and 0.45 COOH/nm2. Proportionality between the surface concentrations and the intensities of the C=O IR band is observed: this suggests that COOH groups are noninteracting with each other and allows the computation of the related extinction molar coefficient. PMID:16853129

Fiorilli, Sonia; Onida, Barbara; Bonelli, Barbara; Garrone, Edoardo

2005-09-01

426

Estimation of Hydrolysis Rate Constants of Carboxylic Acid Ester and Phosphate Ester Compounds in Aqueous Systems from Molecular Structure by SPARC.  

National Technical Information Service (NTIS)

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 str...

S. H. Hilal

2006-01-01

427

Synthesis and SAR of heterocyclic carboxylic acid isosteres based on 2-biarylethylimidazole as bombesin receptor subtype-3 (BRS-3) agonists for the treatment of obesity  

Microsoft Academic Search

SAR around non-peptidic potent bombesin receptor subtype-3 (BRS-3) agonist lead 2 is presented. Attempts to replace the carboxylic acid with heterocyclic isosteres to improve oral bioavailability and brain penetration are described.

Mark Hadden; Allan Goodman; Cheng Guo; Peter R. Guzzo; Alan J. Henderson; Kevin Pattamana; Megan Ruenz; Bruce J. Sargent; Brian Swenson; Larry Yet; Jian Liu; Shuwen He; Iyassu K. Sebhat; Linus S. Lin; Constantin Tamvakopoulos; Qianping Peng; Yanqing Kan; Oksana Palyha; Theresa M. Kelly; Xiao-Ming Guan; Joseph M. Metzger; Marc L. Reitman; Ravi P. Nargund

2010-01-01

428

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

429

A Study of the Antiwear Effectiveness of Carboxylic Acids in Synthetic Lubricants on Ester Basis . Untersuchungen Zur Abriebvermindernden Wirkung von Larbonsaeuren in Synthetischen Schmieroelen Auf Esterbasis.  

National Technical Information Service (NTIS)

Antiwear effectiveness investigations of carboxylic acids with defined chemical structure in synthetic lubricants on ester basis were made using the friction and wear apparatus developed by Wintershall/Baist. The dependence of antiwear effectiveness on th...

G. Spengler K. A. Davis R. Woerle

1973-01-01

430

Electronically Rich N-Substituted Tetrahydroisoquinoline 3-Carboxylic Acid Esters: Concise Synthesis and Conformational Studies.  

PubMed

Recent work in our laboratory has shown that the highly substituted, electronically rich 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (THIQ3CA) scaffold is a key building block for a novel class of promising anticoagulants (Al-Horani et al. J. Med. Chem.2011, 54, 6125-6138). The synthesis of THIQ3CA analogs, especially containing specific, electronically rich substituents, has been a challenge and essentially no efficient methods have been reported in the literature. We describe three complementary, glycine donor-based strategies for high yielding synthesis of highly substituted, electronically rich THIQ3CA esters. Three glycine donors studied herein include hydantoin 1, (±)-Boc-?-phosphonoglycine trimethyl ester 2 and (±)-Z-?-phosphonoglycine trimethyl ester 3. Although the synthesis of THIQ3CA analogs could be achieved using either of the three, an optimal, high yielding approach for the desired THIQ3CA esters was best achieved using 3 in three mild, efficient steps. Using this approach, a focused library of advanced N-arylacyl, N-arylalkyl, and bis-THIQ3CA analogs was synthesized. Variable temperature and solvent-dependent NMR chemical shift studies indicated the presence of two major conformational rotamers in 3:1 proportion for N-arylacyl-THIQ3CA analogs, which were separated by a high kinetic barrier of ~17 kcal/mol. In contrast, N-arylalkyl and bis-THIQ3CA variants displayed no rotamerism, which implicates restricted rotation around the amide bond as the origin for high-barrier conformational interconversion. This phenomenon is of major significance because structure-based drug design typically utilizes only one conformation. Overall, the work presents fundamental studies on the synthesis and conformational properties of highly substituted, electronically rich THIQ3CA analogs. PMID:22665943

Al-Horani, Rami A; Desai, Umesh R

2012-01-10

431

Phenazine-1-carboxylic acid promotes bacterial biofilm development via ferrous iron acquisition.  

PubMed

The opportunistic pathogen Pseudomonas aeruginosa forms biofilms, which render it more resistant to antimicrobial agents. Levels of iron in excess of what is required for planktonic growth have been shown to promote biofilm formation, and therapies that interfere with ferric iron [Fe(III)] uptake combined with antibiotics may help treat P. aeruginosa infections. However, use of these therapies presumes that iron is in the Fe(III) state in the context of infection. Here we report the ability of phenazine-1-carboxylic acid (PCA), a common phenazine made by all phenazine-producing pseudomonads, to help P. aeruginosa alleviate Fe(III) limitation by reducing Fe(III) to ferrous iron [Fe(II)]. In the presence of PCA, a P. aeruginosa mutant lacking the ability to produce the siderophores pyoverdine and pyochelin can still develop into a biofilm. As has been previously reported (P. K. Singh, M. R. Parsek, E. P. Greenberg, and M. J. Welsh, Nature 417:552-555, 2002), biofilm formation by the wild type is blocked by subinhibitory concentrations of the Fe(III)-binding innate-immunity protein conalbumin, but here we show that this blockage can be rescued by PCA. FeoB, an Fe(II) uptake protein, is required for PCA to enable this rescue. Unlike PCA, the phenazine pyocyanin (PYO) can facilitate biofilm formation via an iron-independent pathway. While siderophore-mediated Fe(III) uptake is undoubtedly important at early stages of infection, these results suggest that at later stages of infection, PCA present in infected tissues may shift the redox equilibrium between Fe(III) and Fe(II), thereby making iron more bioavailable. PMID:21602354

Wang, Yun; Wilks, Jessica C; Danhorn, Thomas; Ramos, Itzel; Croal, Laura; Newman, Dianne K

2011-05-20

432

Phenazine-1-Carboxylic Acid Promotes Bacterial Biofilm Development via Ferrous Iron Acquisition?†  

PubMed Central

The opportunistic pathogen Pseudomonas aeruginosa forms biofilms, which render it more resistant to antimicrobial agents. Levels of iron in excess of what is required for planktonic growth have been shown to promote biofilm formation, and therapies that interfere with ferric iron [Fe(III)] uptake combined with antibiotics may help treat P. aeruginosa infections. However, use of these therapies presumes that iron is in the Fe(III) state in the context of infection. Here we report the ability of phenazine-1-carboxylic acid (PCA), a common phenazine made by all phenazine-producing pseudomonads, to help P. aeruginosa alleviate Fe(III) limitation by reducing Fe(III) to ferrous iron [Fe(II)]. In the presence of PCA, a P. aeruginosa mutant lacking the ability to produce the siderophores pyoverdine and pyochelin can still develop into a biofilm. As has been previously reported (P. K. Singh, M. R. Parsek, E. P. Greenberg, and M. J. Welsh, Nature 417:552-555, 2002), biofilm formation by the wild type is blocked by subinhibitory concentrations of the Fe(III)-binding innate-immunity protein conalbumin, but here we show that this blockage can be rescued by PCA. FeoB, an Fe(II) uptake protein, is required for PCA to enable this rescue. Unlike PCA, the phenazine pyocyanin (PYO) can facilitate biofilm formation via an iron-independent pathway. While siderophore-mediated Fe(III) uptake is undoubtedly important at early stages of infection, these results suggest that at later stages of infection, PCA present in infected tissues may shift the redox equilibrium between Fe(III) and Fe(II), thereby making iron more bioavailable.

Wang, Yun; Wilks, Jessica C.; Danhorn, Thomas; Ramos, Itzel; Croal, Laura; Newman, Dianne K.

2011-01-01

433

Gingival inflammation induced by food and short-chain carboxylic acids.  

PubMed

Earlier studies in our laboratories demonstrated that particles of a number of snack foods that are retained on the dentition accumulate fermentable sugars and short-chain carboxylic acids (SCCA; acetic, formic, lactic, and propionic) to different degrees. The present study was undertaken to test the hypothesis that the accumulated SCCA can induce a gingival inflammatory response. Five periodontally and medically healthy subjects were given portions of plain doughnuts (high SCCA levels) or oatmeal cookie (low SCCA), or had the SCCA applied directly to the gingival margins of designated teeth. Subjects were given wax to chew, or nothing, as controls. Inflammation was assessed by measurements of subgingival temperature, flow rates of gingival crevicular fluid (GCF), and neutrophil emigration into GCF. Subgingival temperatures of the maxillary gingiva rose by 1.32 +/- 0.30 degrees C (mean +/- SE) 5 min after the subjects consumed the doughnuts and remained elevated for at least 1 hr. These values were significantly higher than those obtained from subjects after ingestion of oatmeal cookies (0.63 +/- 0.17 degree C; p < 0.01), consistent with the low levels of SCCA in the retained cookie particles. Wax chewing elicited a similar response, indicating a masticatory effect on the gingiva. Gingival temperatures in the unchallenged controls remained unchanged. Neutrophil emigration into the GCF was significantly elevated in subjects after doughnut consumption. Rinses with a solution of SCCA, or application of the SCCA to the gingiva, also brought about significant elevations in subgingival temperature and neutrophil emigration. The findings describe the inflammatory effects of food ingestion on the gingiva of healthy human subjects, and support the hypothesis that SCCA in the particles of retained food are at least partly responsible for the observed responses. PMID:9465174

Kashket, S; Zhang, J; Niederman, R

1998-02-01

434

Extraction and metalation of porphyrins in fluorous liquids with carboxylic acids and metal salts.  

PubMed

Porphyrins have found application in a remarkable variety of areas such as sensors, ion selective electrodes, photodynamic therapy, and energy-transfer systems. Here, we demonstrate the extraction of 5,10,15,20-tetraphenylporphyrin (TPhP) and 5,10,15,20-tetra(4-pyridyl)porphyrin (TPyP) into a mixture of perfluorohexanes (FC-72) through noncovalent interactions with Krytox (1), a carboxylic acid terminated perfluoropolyether. We found that 1 transfers two protons to the TPhP tetrapyrrole ring to create the porphyrin dication (H2TPhP2+) in FC-72 while up to six protons are transferred to the TPyP pyridyl and tetrapyrrole nitrogens to create a hexavalent cation macrocycle in the fluorous phase. The total charge on TPyP is controlled by adjusting the concentration of 1 in the fluorous phase. In addition, we observed extraction of ZnTPyP from CDCl3 with 1/FC-72, while ZnTPhP is not extracted by 1/FC-72. We prepared the Zn salt of 1 and found that it extracts (from CDCl3) and metalates TPyP but not TPhP. Competitive binding between the porphyrins and an ethanol cosolvent hinders the extraction of both TPhP and TPyP and inhibits the formation of the TPyP hexacation in FC-72. By controlling the concentration of porphyrin, 1, and ethanol, it is possible to reversibly solubilize TPyP in the fluorous phase through noncovalent interactions between the pyridyl moieties and 1 while leaving the tetrapyrrole ring available to interact with metals or other substrates. In addition, both porphyrins and ZnTPyP are easily recovered from the fluorous phase using commercially available fluorous solid-phase extraction cartridges. Understanding noncovalent interactions in fluorous matrices should lead to development of more robust devices for sensing and energy transfer. PMID:19413352

O'Neal, Kristi L; Weber, Stephen G

2009-05-28

435

Electronically Rich N-Substituted Tetrahydroisoquinoline 3-Carboxylic Acid Esters: Concise Synthesis and Conformational Studies  

PubMed Central

Recent work in our laboratory has shown that the highly substituted, electronically rich 1,2,3,4–tetrahydroisoquinoline–3–carboxylic acid (THIQ3CA) scaffold is a key building block for a novel class of promising anticoagulants (Al-Horani et al. J. Med. Chem. 2011, 54, 6125–6138). The synthesis of THIQ3CA analogs, especially containing specific, electronically rich substituents, has been a challenge and essentially no efficient methods have been reported in the literature. We describe three complementary, glycine donor-based strategies for high yielding synthesis of highly substituted, electronically rich THIQ3CA esters. Three glycine donors studied herein include hydantoin 1, (±)-Boc-?-phosphonoglycine trimethyl ester 2 and (±)-Z-?-phosphonoglycine trimethyl ester 3. Although the synthesis of THIQ3CA analogs could be achieved using either of the three, an optimal, high yielding approach for the desired THIQ3CA esters was best achieved using 3 in three mild, efficient steps. Using this approach, a focused library of advanced N-arylacyl, N-arylalkyl, and bis-THIQ3CA analogs was synthesized. Variable temperature and solvent-dependent NMR chemical shift studies indicated the presence of two major conformational rotamers in 3:1 proportion for N–arylacyl–THIQ3CA analogs, which were separated by a high kinetic barrier of ~17 kcal/mol. In contrast, N–arylalkyl and bis–THIQ3CA variants displayed no rotamerism, which implicates restricted rotation around the amide bond as the origin for high-barrier conformational interconversion. This phenomenon is of major significance because structure-based drug design typically utilizes only one conformation. Overall, the work presents fundamental studies on the synthesis and conformational properties of highly substituted, electronically rich THIQ3CA analogs.

Al-Horani, Rami A.; Desai, Umesh R.

2012-01-01

436

Transport and Metabolism of 1-Aminocyclopropane-1-carboxylic Acid in Sunflower (Helianthus annuus L.) Seedlings 1  

PubMed Central

Transport and metabolism of [2,3-14C] 1-aminocyclopropane-1-carboxylic acid (ACC) from roots to shoots in 4-day-old sunflower (Helianthus annuus L.) seedlings were studied. [14C]ACC was detected in, and 14C2H4 was evolved from, shoots 0.5 hours after [14C]ACC was supplied to roots. Ethylene emanation from the shoots returned to normal levels after 6 hours. The roots showed a similar pattern, although at 24 hours ethylene emanation was still slightly higher than in those plants that did not receive ACC. [14C]N-malonyl-ACC (MACC) was detected in both tissues at all times sampled. [14C]MACC levels surpassed [14C]ACC levels in the shoot at 2 hours, whereas [14C]MACC levels in the root remained below [14C]ACC levels until 6 hours, after which they were higher. Thin-layer chromatography analysis identified [14C] ACC in 1-hour shoot extracts, and [14C]MACC was identified in root tissues at 1 and 12 hours after treatment. [14C]ACC and [14C] MACC in the xylem sap of treated seedlings were identified by thin-layer chromatography. Xylem transport of [14C]ACC in treated seedlings, and transport of ACC in untreated seedlings, was confirmed by gas chromatography-mass spectrometry. Some evidence for the presence of [14C]MACC in xylem sap in [14C]ACC-treated seedlings is presented. A substantial amount of radioactivity in both ACC and MACC fractions was detected leaking from the roots over 24 hours. A second radiolabeled volatile compound was trapped in a CO2-trapping solution but not in mercuric perchlorate. Levels of this compound were highest after the peak of ACC levels and before peak MACC levels in both tissues, suggesting that an alternate pathway of ACC metabolism was operating in this system.

Finlayson, Scott A.; Foster, Kenneth R.; Reid, David M.

1991-01-01

437

Heterogeneous expression and functional relevance of the ubiquitin carboxyl-terminal hydrolase L1 in melanoma.  

PubMed

The expression of ubiquitin carboxyl-terminal hydrolase 1 (UCHL1) is deregulated in human cancer cells with tumor inhibiting or promoting functions. Due to less knowledge on the role of UCHL1 in melanoma progression, the expression pattern and function of UCHL1 as well as the deregulated signaling pathways were characterized. A large number of melanoma cell lines, tissue microarrays of melanoma lesions and control tissues were analyzed for UCHL1 expression using PCR, Western blot and/or immunohistochemistry. The analysis revealed that melanocyte cultures, 24 of 331 melanoma lesions, two of 18 short-term cultures and two of 19 melanoma cell lines tested, respectively, heterogeneously expressed UCHL1. The low frequency of UCHL1 expression in melanoma cells was due to gene silencing by promoter DNA hypermethylation. Using different transfection models an enzyme activity-dependent growth promoting function of UCHL1 via the activation of the mitogen-activated protein kinase signaling pathway was found in melanoma cells. Under oxygen stress a dose-dependent effect of UCHL1 was detected, which was mediated by a dynamic modification of the PI3K-Akt signaling. Thus, the aberrant UCHL1 expression in melanoma cells is linked to dynamic changes in growth properties and signal transduction cascades suggesting that UCHL1 provides a novel marker and/or therapeutic target at least for a subset of melanoma patients. PMID:23686552

Wulfänger, Jens; Biehl, Katharina; Tetzner, Anja; Wild, Peter; Ikenberg, Kristian; Meyer, Stefanie; Seliger, Barbara

2013-06-14

438

Stacking and determination of phenazine-1-carboxylic acid with low p K a in soil via moving reaction boundaryformed by alkaline and double acidic buffers in capillary electrophoresis  

Microsoft Academic Search

As shown herein, a normal moving reaction boundary (MRB) formed by an alkaline buffer and a single acidic buffer had poor\\u000a stacking to the new important plant growth promoter of phenazine-1-carboxylic acid (PCA) in soil due to the leak induced by\\u000a its low pK\\u000a a. To stack the PCA with low pK\\u000a a efficiently, a novel stacking system of MRB

Chong Sun; Xiao-Di Yang; Liu-Yin Fan; Wei Zhang; Yu-Quan Xu; Cheng-Xi Cao

2011-01-01

439

UV Study of the Protonation of Indole2-carboxylic Acid, 3Methylindole, 3-Acetylindole and D-Tryptophan in Perchloric Acid Solutions  

Microsoft Academic Search

Protonation of indole-2-carboxylic acid, 3-methylindole, 3-acetyl- indole and D-tryptophan in perchloric acid media was studied by UV spectroscopy methods in the 400-190 nm region. Absorbance values were measured at four selected wavelengths and the molar absorptivity was calculated. From these values, the pKa's were de- termined using Hammett's equation. Also, the dissociation con- stants and solvent parameter m* were obtained

Blagoja S. Andonovski

440

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

SciTech Connect

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

Kawamura, K.; Okuwaki, A.; Verheyen, T.V.; Perry, G.J. [Tohoku University, Miyagi (Japan). Graduate School of Environmental Studies

2006-07-01