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1

Siloxyl ether functionalized resins for chemoselective enrichment of carboxylic acids.  

PubMed

Although the carboxylic acid moiety is prevalent in many biologically produced molecules, including natural products and proteins, methods to chemoselectively target this functional group have remained elusive. Generally, strategies that utilize carboxylate nucleophilicity also promote reactions with other nucleophiles such as amines and hydroxyls. A reagent was sought to facilitate the selective isolation of carboxylic acid containing compounds from complex mixtures. Here, the development of siloxyl ether functionalized solid supports is described. PMID:21957886

Trader, Darci J; Carlson, Erin E

2011-10-21

2

Hybrid materials prepared by interlayer functionalization of kaolinite with pyridine-carboxylic acids.  

PubMed

This paper presents the results of the functionalization of Brazilian São Simão kaolinite with pyridine-2-carboxylic and pyridine-2,6-dicarboxylic acids. The functionalization involved refluxing of the pyridine-carboxylic acid in the presence of kaolinite previously intercalated with dimethyl sulfoxide; both acids effectively displaced dimethyl sulfoxide from the clay interlayer. The resulting materials were characterized by X-ray diffraction, thermal analysis, infrared absorption spectroscopy, and C and N elemental analysis. The X-ray diffractograms revealed the incorporation of the acid molecules into the interlayer space of kaolinite. The thermogravimetric curves of the kaolinite samples functionalized with the pyridine-carboxylic acids indicated that the materials were thermally stable up to 300 degrees C. The displacements of the bands due to interlayer hydroxyls in the infrared absorption spectra also confirmed the functionalization of the kaolinite with the pyridine-carboxylic acids. PMID:19433329

de Faria, Emerson H; Lima, Omar J; Ciuffi, Katia J; Nassar, Eduardo J; Vicente, Miguel A; Trujillano, Raquel; Calefi, Paulo S

2009-07-15

3

Preparation and self-assembly of carboxylic acid-functionalized silica  

Microsoft Academic Search

A simple method for the fabrication of silica nanoparticle film based on the covalent-bonding interaction between carboxylic acid-functionalized silica nanoparticles (SiO2–COOH) and amino-terminated silicon wafer was developed. Prior to assembly, silica nanoparticles with an average diameter 80 nm were prepared using the Stöber method, amino-functionalized silica nanoparticles (SiO2–NH2) were prepared by a silanization with 3-aminopropyltriethoxysilane (APTES), while carboxylic acid-functionalized silica

Yanqing An; Miao Chen; Qunji Xue; Weimin Liu

2007-01-01

4

Synthesis of Functionalized Dialkyl Ketones From Carboxylic Acid Derivatives and Alkyl Halides  

PubMed Central

Unsymmetrical dialkyl ketones can be directly prepared by the nickel-catalyzed reductive coupling of carboxylic acid chlorides or (2-pyridyl)thioesters with alkyl iodides or benzylic chlorides. A wide variety of functional groups are tolerated by this process, including common nitrogen protecting groups and C-B bonds. Even hindered ketones flanked by tertiary and secondary centers can be formed. The mechanism is proposed to involve the reaction of a (L)Ni(alkyl)2 intermediate with the carboxylic acid derivative.

Wotal, Alexander C.; Weix, Daniel J.

2012-01-01

5

Gas-Phase Reactivity of Carboxylic Acid Functional Groups with Carbodiimides  

PubMed Central

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.

2012-01-01

6

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

7

Synthesis of functionalized dialkyl ketones from carboxylic acid derivatives and alkyl halides.  

PubMed

Unsymmetrical dialkyl ketones can be directly prepared by the nickel-catalyzed reductive coupling of carboxylic acid chlorides or (2-pyridyl)thioesters with alkyl iodides or benzylic chlorides. A wide variety of functional groups are tolerated by this process, including common nitrogen protecting groups and C-B bonds. Even hindered ketones flanked by tertiary and secondary centers can be formed. The mechanism is proposed to involve the reaction of a (L)Ni(alkyl)(2) intermediate with the carboxylic acid derivative. PMID:22360350

Wotal, Alexander C; Weix, Daniel J

2012-03-16

8

Photophysical Properties of Lanthanide Hybrids Covalently Bonded To Functionalized MCM-41 by Modified Aromatic Carboxylic Acids  

Microsoft Academic Search

MCM-41 mesoporous silica has been functionalized with aromatic carboxylic acids salicylic acid (Sal) and 2-hydroxyl-3-methylbenzoic\\u000a acid (HMBA) through co-condensation approach of tetraethoxysilane (TEOS) in the presence of the cetyltrimethylammonium bromide\\u000a (CTAB) surfactant as a template. Organic ligands salicylic acid or 2-hydroxyl-3-methylbenzoic acid grafted to the coupling\\u000a agent 3-(triethoxysilyl)-propyl isocyanate (TEPIC) was used as the precursor for the preparation of an

Ying Li; Bing Yan

2009-01-01

9

Hydrogenation of unsaturated carboxylic acids on functional gel-type resin supported Pd catalysts: The effect of reactant structure  

Microsoft Academic Search

Functional gel-type resin-based palladium catalysts (0.5–2wt.% Pd) of well dispersed Pd nanoparticles were prepared and characterized by SEM, TEM techniques and swelling measurements. The role of specific properties of gel-type matrix was studied in the hydrogenation of unsaturated CC bonds in series of carboxylic acids, derivatives of acrylic acid. They differ in the type of substituents (methyl, phenyl and carboxyl

A. Knapik; A. Drelinkiewicz; M. Szaleniec; W. Makowski; A. Waksmundzka-Góra; A. Bukowska; W. Bukowski; J. Noworól

2008-01-01

10

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

11

Synthesis and Functionalization of Cyclic Sulfonimidamides: A Novel Chiral Heterocyclic Carboxylic Acid Bioisostere  

PubMed Central

An efficient synthesis of aryl substituted cyclic sulfonimidamides designed as chiral nonplanar heterocyclic carboxylic acid bioisosteres is described. The cyclic sulfonimidamide ring system could be prepared in two steps from a trifluoroacetyl protected sulfinamide and methyl ester protected amino acids. By varying the amino acid, a range of different C-3 substituted sulfonimidamides could be prepared. The compounds could be further derivatized in the aryl ring using standard cross-coupling reactions to yield highly substituted cyclic sulfonimidamides in excellent yields. The physicochemical properties of the final compounds were examined and compared to those of the corresponding carboxylic acid and tetrazole derivatives. The unique nonplanar shape in combination with the relatively strong acidity (pKa 5–6) and the ease of modifying the chemical structure to fine-tune the physicochemical properties suggest that this heterocycle can be a valuable addition to the range of available carboxylic acid isosteres.

2012-01-01

12

Photophysical properties of lanthanide hybrids covalently bonded to functionalized MCM-41 by modified aromatic carboxylic acids.  

PubMed

MCM-41 mesoporous silica has been functionalized with aromatic carboxylic acids salicylic acid (Sal) and 2-hydroxyl-3-methylbenzoic acid (HMBA) through co-condensation approach of tetraethoxysilane (TEOS) in the presence of the cetyltrimethylammonium bromide (CTAB) surfactant as a template. Organic ligands salicylic acid or 2-hydroxyl-3-methylbenzoic acid grafted to the coupling agent 3-(triethoxysilyl)-propyl isocyanate (TEPIC) was used as the precursor for the preparation of an organic-inorganic hybrid materials. Novel organic-inorganic mesoporous luminescent hybrid containing Ln(3+) (Tb(3+), Eu(3+)) complexes covalently attached to the functionalized ordered mesoporous MCM-41, which were designated as Ln-Sal-MCM-41 and Ln-HMBA-MCM-41, respectively, were obtained by sol-gel process. The luminescence properties of these resulting materials were characterized in detail, and the results reveal that luminescent mesoporous materials have high surface area, uniformity in the mesopore structure and good crystallinity. Moreover, the mesoporous material covalently bonded Tb(3+) complex (Tb-Sal-MCM-41 and Tb-HMBA-MCM-41) exhibit the stronger characteristic emission of Tb(3+) and longer lifetime than the corresponding Eu-containing materials Eu-Sal-MCM-41 and Eu-HMBA-MCM-41 due to the triplet state energy of modified organic ligands Sal-TEPIC and HMBA-TEPIC match with the emissive energy level of Tb(3+) very well. In addition, the luminescence lifetime and emission quantum efficiency of (5)D(0) Eu(3+) excited state also indicates the efficient intramolecular energy transfer process in Tb-SAL-MCM-41 and Tb-HMBA-MCM-41. PMID:18649125

Li, Ying; Yan, Bing

2009-03-01

13

Highly carboxylic-acid-functionalized ethane-bridged periodic mesoporous organosilicas: synthesis, characterization, and adsorption properties.  

PubMed

Functionalization of periodic mesoporous organosilicas (PMOs) with high loadings of pendant organic groups to form bifunctional PMOs with ordered mesostructures remains a challenging objective. Herein, we report that well-ordered ethane-bridged PMOs functionalized with exceptionally high loadings of pendant carboxylic acid groups (up to 80 mol % based on silica) were synthesized by the co-condensation of 1,4-bis(trimethoxysilyl)ethane (BTME) and carboxyethylsilanetriol sodium salt (CES) with Pluronic P123 as the template and KCl as an additive under acidic conditions. The bifunctional materials were characterized by using a variety of techniques, including powder X-ray diffraction, nitrogen-adsorption/desorption, TEM, and solid-state (13)C and (29)Si NMR spectroscopy. Zeta-potential measurements showed that the surface negative charges increased with increasing the CES content. This property makes them potential candidates for applications in drug adsorption. The excellent adsorption capacity of these bifunctional PMOs towards an anticancer drug (doxorubicin) was also demonstrated. PMID:22689541

Kao, Hsien-Ming; Chung, Chih-Hsuan; Saikia, Diganta; Liao, Shih-Hsiang; Chao, Pei-Ying; Chen, Yu-Han; Wu, Kevin C-W

2012-09-01

14

Carboxylic Acid-Functionalized Conductive Polypyrrole as a Bioactive Platform for Cell Adhesion  

PubMed Central

Electroactive polymers such as polypyrrole (PPy) are highly attractive for a number of biomedical applications, including their use as coatings for electrodes or neural probes and as scaffolds to induce tissue regeneration. Surface modification of these materials with biological moieties is desired to enhance the biomaterial-tissue interface and to promote desired tissue responses. Here, we present the synthesis and physicochemical characterization of poly(1-(2-carboxyethyl)pyrrole) (PPyCOOH), a PPy derivative that contains a chemical group that can be easily modified with biological moieties at the N-position of polymer backbone. FTIR, XPS, and fluorescence microscopy were used to demonstrate the successful incorporation of carboxylic acid (-COOH) functionality into PPy materials, and a four-point probe analysis was used to demonstrate electrical conductivity in the semiconductor range. Human umbilical vascular endothelial cells (HUVECs) cultured on PPyCOOH films surface modified with the cell-adhesive Arg-Gly-Asp (RGD) motif demonstrated improved attachment and spreading. Thus, PPyCOOH could be useful in developing PPy composites that contain a variety of biological molecules as bioactive conducting platforms for specific biomedical purposes.

Lee, Joo-Woon; Serna, Francisco; Nickels, Jonathan; Schmidt, Christine E.

2008-01-01

15

Understanding biocatalyst inhibition by carboxylic acids  

PubMed Central

Carboxylic acids are an attractive biorenewable chemical in terms of their flexibility and usage as precursors for a variety of industrial chemicals. It has been demonstrated that such carboxylic acids can be fermentatively produced using engineered microbes, such as Escherichia coli and Saccharomyces cerevisiae. However, like many other attractive biorenewable fuels and chemicals, carboxylic acids become inhibitory to these microbes at concentrations below the desired yield and titer. In fact, their potency as microbial inhibitors is highlighted by the fact that many of these carboxylic acids are routinely used as food preservatives. This review highlights the current knowledge regarding the impact that saturated, straight-chain carboxylic acids, such as hexanoic, octanoic, decanoic, and lauric acids can have on E. coli and S. cerevisiae, with the goal of identifying metabolic engineering strategies to increase robustness. Key effects of these carboxylic acids include damage to the cell membrane and a decrease of the microbial internal pH. Certain changes in cell membrane properties, such as composition, fluidity, integrity, and hydrophobicity, and intracellular pH are often associated with increased tolerance. The availability of appropriate exporters, such as Pdr12, can also increase tolerance. The effect on metabolic processes, such as maintaining appropriate respiratory function, regulation of Lrp activity and inhibition of production of key metabolites such as methionine, are also considered. Understanding the mechanisms of biocatalyst inhibition by these desirable products can aid in the engineering of robust strains with improved industrial performance.

Jarboe, Laura R.; Royce, Liam A.; Liu, Ping

2013-01-01

16

Towards modelling the vibrational signatures of functionalized surfaces: carboxylic acids on H-Si(111) surfaces  

NASA Astrophysics Data System (ADS)

In this work, we investigate the adsorption process of two carboxylic acids (stearic and undecylenic) on a H-Si(111) surface via the calculation of structural and energy changes as well as the simulation of their IR and Raman spectra. The two molecules adsorb differently at the surface since the stearic acid simply physisorbs while the undecylenic acid undergoes a chemical reaction with the hydrogen atoms of the surface. This difference is observed in the change of geometry during the adsorption. Indeed, the chemisorption of the undecylenic acid has a bigger impact on the structure than the physisorption of the stearic acid. Consistently, the former is also characterized by a larger value of adsorption energy and a smaller value of the tilting angle with respect to the normal plane. For both the IR and Raman signatures, the spectra of both molecules adsorbed at the surface are in a first approximation the superposition of the spectra of the Si cluster and of the carboxylic acid considered individually. The main deviation from this simple observation is the peak of the stretching Si-H (?(Si-H)) mode, which is split into two peaks upon adsorption. As expected, the splitting is bigger for the chemisorption than the physisorption. The modes corresponding to atomic displacements close to the adsorption site display a frequency upshift by a dozen wavenumbers. One can also see the disappearance of the peaks associated with the C=C double bond when the undecylenic acid chemisorbs at the surface. The Raman and IR spectra are complementary and one can observe here that the most active Raman modes are generally IR inactive. Two exceptions to this are the two ?(Si-H) modes which are active in both spectroscopies. Finally, we compare our simulated spectra with some experimental measurements and we find an overall good agreement.

Giresse Tetsassi Feugmo, Conrard; Champagne, Benoît; Caudano, Yves; Cecchet, Francesca; Chabal, Yves J.; Liégeois, Vincent

2012-03-01

17

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

PubMed

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

Dong, Ki-Young; Choi, Jinnil; Lee, Yang Doo; Kang, Byung Hyun; Yu, Youn-Yeol; Choi, Hyang Hee; Ju, Byeong-Kwon

2013-01-01

18

Biocatalytic reduction of carboxylic acids.  

PubMed

An increasing demand for non-petroleum-based products is envisaged in the near future. Carboxylic acids such as citric acid, succinic acid, fatty acids, and many others are available in abundance from renewable resources and they could serve as economic precursors for bio-based products such as polymers, aldehyde building blocks, and alcohols. However, we are confronted with the problem that carboxylic acid reduction requires a high level of energy for activation due to the carboxylate's thermodynamic stability. Catalytic processes are scarce and often their chemoselectivity is insufficient. This review points at bio-alternatives: currently known enzyme classes and organisms that catalyze the reduction of carboxylic acids are summarized. Two totally distinct biocatalyst lines have evolved to catalyze the same reaction: aldehyde oxidoreductases from anaerobic bacteria and archea, and carboxylate reductases from aerobic sources such as bacteria, fungi, and plants. The majority of these enzymes remain to be identified and isolated from their natural background in order to evaluate their potential as industrial biocatalysts. PMID:24737783

Napora-Wijata, Kamila; Strohmeier, Gernot A; Winkler, Margit

2014-06-01

19

Cyclopentane-1,3-dione: a novel isostere for the carboxylic acid functional group. Application to the design of potent thromboxane (A2) receptor antagonists.  

PubMed

Cyclopentane-1,3-diones are known to exhibit pK(a) values typically in the range of carboxylic acids. To explore the potential of the cyclopentane-1,3-dione unit as a carboxylic acid isostere, the physical-chemical properties of representative congeners were examined and compared with similar derivatives bearing carboxylic acid or tetrazole residues. These studies suggest that cyclopentane-1,3-diones may effectively substitute for the carboxylic acid functional group. To demonstrate the use of the cyclopentane-1,3-dione isostere in drug design, derivatives of a known thromboxane A(2) prostanoid (TP) receptor antagonist, 3-(3-(2-(4-chlorophenylsulfonamido)ethyl)phenyl)propanoic acid (12), were synthesized and evaluated in both functional and radioligand-binding assays. A series of mono- and disubstituted cyclopentane-1,3-dione derivatives (41-45) were identified that exhibit nanomolar IC(50) and K(d) values similar to 12. Collectively, these studies demonstrate that the cyclopentane-1,3-dione moiety comprises a novel isostere of the carboxylic acid functional group. Given the combination of the relatively strong acidity, tunable lipophilicity, and versatility of the structure, the cyclopentane-1,3-dione moiety may constitute a valuable addition to the palette of carboxylic acid isosteres. PMID:21863799

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

2011-10-13

20

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

PubMed Central

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

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

2011-01-01

21

Capillary electrophoretic study of amine/carboxylic acid-functionalized carbon nanodots.  

PubMed

Capillary zone electrophoresis (CZE) coupled with UV absorption and laser-induced fluorescence detections has been applied to study the complexity of carbon nanodots (C-dots) products synthesized with microwave-assisted pyrolysis of citric acid (CA) and 1,2-ethylenediamine (EDA). The effects of pH and concentration of run buffer on the CZE separation of C-dots are studied in detail. The optimal acetate run buffer (30mM, pH 3.6) is subsequently employed to investigate the effect of reaction time and mole ratio of amine (NH2) to carboxylic acid (COOH) moieties of the precursors on the C-dots species present in C-dots products. Our results confirm that the synthesis of C-dots could be improved by lengthening the microwave irradiation time and optimizing the initial mole ratio of NH2/COOH in the precursors. Negatively charged C-dots are obtained only when the amount of CA exceeds that of EDA, i.e., the mole ratio of NH2/COOH is 0.25-0.80. By contrast, when the quantity (mole) of NH2 in EDA is equal to or larger than that of COOH in CA, only positively charged and neutral C-dots species are formed, inferring that the C-dots species are predominantly covered by the surface-attached ammonium and amido moieties. This work highlights the merit of CZE to identify the composition of an as-prepared C-dots product which is pretty much dependent on the mole ratio of NH2/COOH. It is anticipated that our CZE methodology will open a new avenue in optimizing the synthetic conditions for producing specific C-dots of desired composition. PMID:23885674

Hu, Qin; Paau, Man Chin; Zhang, Yan; Chan, Wan; Gong, Xiaojuan; Zhang, Lei; Choi, Martin M F

2013-08-23

22

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

23

Preparation of 1-Aminocyclopropane Carboxylic Acids.  

National Technical Information Service (NTIS)

Amino acid is a compound having an amino group as well as a carboxylic acid group in a molecule simultaneously. The report deals with the synthesis of amino acids having a cyclopropane ring in them, i.e., the synthesis of 1-amino+cyclopropane carboxylic a...

M. I. Mughal

1981-01-01

24

A rapid method for the assessment of the surface group density of carboxylic acid-functionalized polystyrene microparticles.  

PubMed

Particle-based assays are becoming versatile analytical tools due to their cost-effectiveness, speed, straightforward and diverse functionalization chemistries, especially when polystyrene particles are used. The introduction of functional groups (-COOH, -NH2, etc.) to the surface of such polystyrene particles promotes their application in bioanalytics. However, the traditional method to determine the amount of surface carboxylate groups is conductivity titration, which is usually time- and resources-consuming and discontinuous. Here, we synthesized polystyrene microparticles with different contents of carboxylate groups, and then investigated a simpler and potentially continuous approach to determine the amount of surface carboxylate groups by Zeta potential measurements. The results were compared to the traditional titration method and to actual coupling efficiencies of the functionalized particles with a model oligonucleotide probe as determined by flow cytometry. All quantification methods revealed good agreement. PMID:23531901

Zhu, Shengchao; Panne, Ulrich; Rurack, Knut

2013-05-21

25

Wet oxidation of low molecular carboxyl acids.  

National Technical Information Service (NTIS)

Low molecular carboxyl acids are important intermediate products of wet combustion of organic pollutants. Reaction rates and mechanisms of some of these acids are dealt with. It appears that the rate of decomposition increases by the number of carbon atom...

A. B. Bjerre E. Soerensen

1989-01-01

26

Scanning thermal lithography of tailored tert-butyl ester protected carboxylic acid functionalized (meth)acrylate polymer platforms.  

PubMed

In this paper, we report on the development of tailored polymer films for high-resolution atomic force microscopy based scanning thermal lithography (SThL). In particular, full control of surface chemical and topographical structuring was sought. Thin cross-linked films comprising poly(tert-butyl methacrylate) (MA(20)) or poly(tert-butyl acrylate) (A(20)) were prepared via UV initiated free radical polymerization. Thermogravimetric analysis (TGA) and FTIR spectroscopy showed that the heat-induced thermal decomposition of MA(20) by oxidative depolymerization is initially the primary reaction followed by tert-butyl ester thermolysis. By contrast, no significant depolymerization was observed for A(20). For A(20) and MA(20) (at higher temperatures and/or longer reaction times) the thermolysis of the tert-butyl ester liberates isobutylene and yields carboxylic acid groups, which react further intramolecularly to cyclic anhydrides. The values of the apparent activation energies (E(a)) for the thermolysis were calculated to be 125 ± 13 kJ mol(-1) and 116 ± 7 kJ mol(-1) for MA(20) and A(20), respectively. Both MA(20) and A(20) films showed improved thermomechanical stability during SThL compared to non cross-linked films. Carboxylic acid functionalized lines written by SThL in A(20) films had a typically ~10 times smaller width compared to those written in MA(20) films regardless of the tip radius of the heated probe and did not show any evidence for thermochemically or thermomechanically induced modification of film topography. These observations and the E(a) of 45 ± 3 kJ mol(-1) for groove formation in MA(20) estimated from the observed volume loss are attributed to oxidative thermal depolymerization during SThL of MA(20) films, which is considered to be the dominant reaction mechanism for MA(20). The smallest line width values obtained for MA(20) and A(20) films with SThL were 83 ± 7 nm and 21 ± 2 nm, whereas the depth of the lines was below 1 nm, respectively. PMID:21919505

Duvigneau, Joost; Schönherr, Holger; Vancso, G Julius

2011-10-01

27

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

Microsoft Academic Search

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

Sierra Rayne; Kaya Forest

2010-01-01

28

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

29

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

30

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

PubMed

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

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

2014-04-15

31

Copper-catalyzed aerobic oxidative synthesis of aromatic carboxylic acids.  

PubMed

A simple, practical and efficient copper-catalyzed method for synthesis of aromatic carboxylic acids has been developed. The protocol uses inexpensive CuI/L-proline as the catalyst/ligand, and readily available aryl halides and malononitrile as the starting materials, and the corresponding aromatic carboxylic acids were obtained in moderate to good yields. The method is of tolerance towards functional groups in the substrates. PMID:21152586

Yang, Daoshan; Yang, Haijun; Fu, Hua

2011-02-28

32

Nonlinear optical properties of mono-functional 1,2-dihydro-1,2-methanofullerene[60]-61-carboxylic acid\\/polymer composites  

Microsoft Academic Search

By using nanosecond laser pulses at 532-nm wavelength, we have studied the nonlinear optical properties of composites which consist of mono-functional 1,2-dihydro-1,2-methanofullerene[60]-61-carboxylic acid (FCA) and poly(styrene-co-4-vinylpyridine). The optical limiting performance of FCA itself is poorer than that of its parent C60, while FCA incorporated with polystyrene shows better optical limiting responses, with the limiting threshold reduced by about 35%. In

H. Izaac Elim

2003-01-01

33

Carboxylic Acid (Bio)Isosteres in Drug Design  

PubMed Central

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.

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

2013-01-01

34

Chromatographic separations of aromatic carboxylic acids.  

PubMed

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 to be more complicated than separation of non-ionic compounds. The review describes the dependence of the retention of ionic solutes on pH and solvent composition as well as on the ionic strength of a mobile phase. The application of the ion-suppressing RP-HPLC method using organic modifiers (aqueous buffer solutions) as eluents in aromatic carboxylic acid analysis is also presented. In more difficult cases of analysis the addition of an ion-pairing reagent, such as the quaternary alkylammonium ion, is necessary to obtain satisfactory separations. Hypotheses of ion-pair formation in reversed-phase systems as well as the influence of various agents on the separation of ionic solutes in IP-RP systems are explained. Examples of the application of ion-pair liquid chromatography to the analysis of aromatic carboxylic acids have also been reviewed. The principles and application of ion-exchange chromatography to the purification, isolation and less frequently, to chromatographic analysis are discussed. Polar adsorbents and polar bonded stationary phases are also widely used in carboxylic acid separation in normal-phase systems, mainly by TLC, often coupled with densitometry. The review also shows examples of separation of chiral benzoic acids and their derivatives in LC systems. The possibilities of application of gas chromatography preceded by derivatisation or pyrolysis of acidic compounds and applications of GC-MS and Py-GC-MS coupled methods in identification and quantitation of aromatic carboxylic acids is also reviewed. PMID:9832241

Waksmundzka-Hajnos, M

1998-10-01

35

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

2012-06-20

36

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

2012-09-13

37

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

38

Nonlinear optical properties of mono-functional 1,2-dihydro-1,2-methanofullerene[60]-61-carboxylic acid/polymer composites  

NASA Astrophysics Data System (ADS)

By using nanosecond laser pulses at 532-nm wavelength, we have studied the nonlinear optical properties of composites which consist of mono-functional 1,2-dihydro-1,2-methanofullerene[60]-61-carboxylic acid (FCA) and poly(styrene-co-4-vinylpyridine). The optical limiting performance of FCA itself is poorer than that of its parent C 60, while FCA incorporated with polystyrene shows better optical limiting responses, with the limiting threshold reduced by about 35%. In addition, the FCA gives slightly stronger photoluminescence emission than that of both C 60 and FCA/polymer composites. The possible sources for the improvement in the optical limiting are discussed.

Izaac Elim, Hendry; Ouyang, Jianying; He, Jun; Hong Goh, Suat; Hai Tang, Sing; Ji, Wei

2003-02-01

39

An efficient tandem approach for the synthesis of functionalized 2-pyridone-3-carboxylic acids using three-component reaction in aqueous media.  

PubMed

Novel analogs of 2-pyridone-3-carboxylic acids 4a-l have been prepared by the three-component reaction of 3-formyl chromone, Meldrum's acid, and primary amines in the presence of a catalytic amount of diammonium hydrogen phosphate in water. Good-to-high yields, easy work-up, and an environmentally friendly profile are the advantages of this method for the synthesis of 2-pyridone-3-carboxylic acid derivatives. PMID:24792225

Mehrparvar, Saber; Balalaie, Saeed; Rabbanizadeh, Mahnaz; Ghabraie, Elmira; Rominger, Frank

2014-08-01

40

Ethane-bridged periodic mesoporous organosilicas functionalized with high loadings of carboxylic acid groups: synthesis, bifunctionalization, and fabrication of metal nanoparticles.  

PubMed

Well-ordered periodic mesoporous organosilicas (PMOs) functionalized with high contents of carboxylic acid (?COOH) groups, up to 85?mol?% based on silica, were synthesized by co-condensation of 1,2-bis(triethoxysilyl)ethane (BTEE) and carboxyethylsilanetriol sodium salt (CES) under acidic conditions by using alkyl poly(oxyethylene) surfactant Brij?76 as a structure-directing agent. A variety of techniques including powder X-ray diffraction (XRD), nitrogen adsorption/desorption, Fourier-transformed infrared (FTIR), transmission electron microscopy (TEM), (13) C- and (29) Si solid-state nuclear magnetic resonance (NMR) were used to characterize the products. The materials thus obtained were used as an effective support to synthesize metal nanoparticles (Ag and Pt) within the channel of 2D hexagonal mesostructure of PMOs. The size and distribution of the nanoparticles were observed to be highly dependent on the interaction between the carboxylic acid functionalized group and the metal precursors. The size of Pt nanoparticles reduced from 3.6 to 2.5?nm and that of Ag nanoparticles reduced from 5.3 to 3.4?nm with the increase in the ?COOH loading from 10 to 50?%. PMID:24338957

Deka, Juti Rani; Kao, Hsien-Ming; Huang, Shu-Ying; Chang, Wei-Chieh; Ting, Chun-Chiang; Rath, Purna Chandra; Chen, Ching-Shiun

2014-01-13

41

Synthesis of branched cyclomaltooligosaccharide carboxylic acids (cyclodextrin carboxylic acids) by microbial oxidation.  

PubMed

Novel branched cyclomaltooligosaccharide carboxylic acid (cyclodextrin carboxylic acid) derivatives were synthesized by microbial oxidation using Pseudogluconobacter saccharoketogenes to oxidize five types of branched cyclodextrins, including maltosyl beta-cyclodextrin (maltosyl-beta-CyD). For each novel cyclodextrin carboxylic acid derivative synthesized, the hydroxymethyl group of the terminal glucose residue in the branched part of the molecule was regiospecifically oxidized to a carboxyl group to give the corresponding uronic acid. In addition, the physicochemical properties of cyclomaltoheptaosyl-(6-->1)-alpha-D-glucopyranosyl-(4-->1)-alpha-D-glucopyranosiduronic acid (GUG-beta-CyD) (1) and its sodium salt were studied more extensively, as these compounds are most likely to have a practical application. PMID:11398984

Ishiguro, T; Fuse, T; Oka, M; Kurasawa, T; Nakamichi, M; Yasumura, Y; Tsuda, M; Yamaguchi, T; Nogami, I

2001-04-23

42

Metal-carboxylic Acids and Their Derivatives  

NASA Astrophysics Data System (ADS)

Questions connected with the synthesis of metal-carboxylic acids, compounds incorporating [M]-COOH fragments with a metal-carbon bond in which M is a transition metal complex, and their derivatives (salts, esters, and amides) are considered. The bibliography includes 189 references.

Kolomnikov, I. S.; Lysyak, T. V.; Rusakov, S. L.; Kharitonov, Yu Ya

1988-05-01

43

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

44

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

45

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

2013-10-21

46

The synthesis of 13alpha-androsta-5,16-diene derivatives with carboxylic acid, ester and carboxamido functionalities at position-17 via palladium-catalyzed carbonylation.  

PubMed

17-Alkoxycarbonyl- and 17-carboxamido-3beta-hydroxy-13alpha-androsta-5,16-diene derivatives were synthetized in high yields in the palladium-catalyzed carbonylation reactions of the corresponding 3beta-hydroxy-17-iodo-13alpha-androsta-5,16-diene. This substrate with a 17-iodo-16-ene functionality was obtained from the 17-keto derivative via its 17-hydrazone, which was treated with iodine in the presence of a base (1,1,3,3-tetramethylguanidine). 17-Carboxamides were obtained by chemoselective aminocarbonylation through the use of amines, including amino acid esters, as N-nucleophiles. The 17-methoxycarbonyl-16-ene derivative was synthetized by using methanol as O-nucleophile. The parent compound of this series, the 17-carboxylic acid derivative, was formed in the presence of water via hydroxycarbonylation. PMID:19152802

Acs, Péter; Takács, Attila; Szilágyi, Antal; Wölfling, János; Schneider, Gyula; Kollár, László

2009-01-01

47

The Conversion of Carboxylic Acids to Ketones: A Repeated Discovery  

NASA Astrophysics Data System (ADS)

This article describes the history of the reaction converting carboxylic acids to ketones. The reaction has been rediscovered several times, yet has actually been known for centuries. The best known version of the process is the Dakin West reaction (1928), which applies to ?-amino acids and also involves the simultaneous conversion of the amine group to amido functionality. Unlike other examples, this particular reaction has attracted a reasonable amount of attention and it appears to be better known than the conversion of simple carboxylic acids to ketones. However, this reaction was described as long ago as 1612, when Beguin published an account of it in his book, Tyrocinium Chymicum . Since then, many chemists have rediscovered the reaction, apparently independently. One of the earliest modern accounts was by W. H. Perkin, Sr., in 1886, who made various simple ketones by refluxing the appropriate carboxylic acids with base. However, this work has been largely ignored, including by his son, W. H. Perkin, Jr., who used a more complicated base-catalyzed ketonization to prepare small ring compounds in the early years of the 20th century. Other articles detailing the application of ketonization to organic acids are discussed, including our own work, which employed the process to crosslink carboxylated polymers for possible technical application in coatings. Despite its relative obscurity, the reaction was used by Woodward et al. in the total synthesis of strychnine, reported in 1963, and this is discussed in detail at the end of the article. See Featured Molecules .

Nicholson, John W.; Wilson, Alan

2004-09-01

48

Carboxylic acid pyridine supramolecular heterocatemer in a co-crystal  

NASA Astrophysics Data System (ADS)

Robustness of carboxylic acid-pyridine supramolecular heterosynthon was examined in three 1:2 binary co-crystals of 4,4'-bipyridine with monocarboxylic acids, (4,4'-bipyridine)·( DL-hydroxyphenylacetic acid) 2, 1; (4,4'-bipyridine) 0.5·(4-bromonaphthalene-1-carboxylic acid), 2 and (4,4'-bipyridine) 0.5·(4-methylbenzoic acid), 3. All the three co-crystals form "two-component supermolecules" (consisting of one molecule of 4,4'-bipyridine and two molecules of the relevant carboxylic acid) stabilized through carboxylic acid-pyridine heterosynthons. Co-crystals 1 and 2 exhibits the expected carboxylic acid-pyridine dimer (heterodimer I) whereas co-crystal 3 forms a novel carboxylic acid-pyridine catemer (heterocatemer II).

Sudhakar, P.; Srivijaya, R.; Sreekanth, B. R.; Jayanthi, P. K.; Vishweshwar, Peddy; Babu, Moses J.; Vyas, K.; Iqbal, Javed

2008-08-01

49

New structural motif for carboxylic acid perhydrolases.  

PubMed

Some serine hydrolases also catalyze a promiscuous reaction--reversible perhydrolysis of carboxylic acids to make peroxycarboxylic acids. Five X-ray crystal structures of these carboxylic acid perhydrolases show a proline in the oxyanion loop. Here, we test whether this proline is essential for high perhydrolysis activity using Pseudomonas fluorescens esterase (PFE). The L29P variant of this esterase catalyzes perhydrolysis 43-fold faster (k(cat) comparison) than the wild type. Surprisingly, saturation mutagenesis at the 29 position of PFE identified six other amino acid substitutions that increase perhydrolysis of acetic acid at least fourfold over the wild type. The best variant, L29I PFE, catalyzed perhydrolysis 83-times faster (k(cat) comparison) than wild-type PFE and twice as fast as L29P PFE. Despite the different amino acid in the oxyanion loop, L29I PFE shows a similar selectivity for hydrogen peroxide over water as L29P PFE (?(0)=170 vs. 160 M(-1)), and a similar fast formation of acetyl-enzyme (140 vs. 62 U mg(-1)). X-ray crystal structures of L29I PFE with and without bound acetate show an unusual mixture of two different oxyanion loop conformations. The type II ?-turn conformation resembles the wild-type structure and is unlikely to increase perhydrolysis, but the type I ?-turn conformation creates a binding site for a second acetate. Modeling suggests that a previously proposed mechanism for L29P PFE can be extended to include L29I PFE, so that an acetate accepts a hydrogen bond to promote faster formation of the acetyl-enzyme. PMID:23325572

Yin, DeLu Tyler; Purpero, Vince M; Fujii, Ryota; Jing, Qing; Kazlauskas, Romas J

2013-02-25

50

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

51

"Supersilyl" Group as Novel Carboxylic Acid Protecting Group: Application to Highly Stereoselective Aldol and Mannich Reactions  

PubMed Central

“Super Power”: The application of the "supersilyl” group as carboxylic acid protecting group has been investigated. The unique properties of the “supersilyl” group enabled it to outperform typical carboxyl protecting groups, conferring extraordinary protection upon the carboxyl functionality. “Supersilyl” esters were also utilized for the first time as stable carboxylic acid synthetic equivalents in highly stereoselective aldol and Mannich reactions. The value of this methodology has been further described by the easy photo-deprotection protocol and its applications in rapid synthesis of polyketide subunits.

Tan, Jiajing; Akakura, Matsujiro

2013-01-01

52

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

USGS Publications Warehouse

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

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

2003-01-01

53

MICROBIAL TRANSFORMATION OF ESTERS OF CHLORINATED CARBOXYLIC ACIDS  

EPA Science Inventory

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

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

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

DOEpatents

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

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

1998-01-01

56

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

57

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

58

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

59

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

PubMed

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

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

2010-11-01

60

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

61

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

62

Conformational and quantum analysis of dental adhesive carboxylic acid and carboxylic acid anhydride monomers.  

PubMed

The conformational and quantum analyses of dental adhesive carboxylic acid and carboxylic acid anhydride monomers were preformed. Conformational analyses were carried out by a molecular mechanics calculation. 4-META and 4-AETA showed more compact conformation than 4-MET. Quantum analyses were performed by semi-empirical molecular orbital calculation. 4-MET had a higher dipole moment, polarizability, and HOMO and LUMO energy than 4-META and 4-AETA. The bond lengths and bond orders of the carbonyl groups of the trimellitic acid moiety of 4-MET were different from those of carbonyl groups of the trimellitate anhydride moieties of 4-META and 4-AETA. Oxygen of the methacryloyl or acryloyl groups showed the highest electron densities among the oxygen atoms for all monomers. The superdelocalizabilities of oxygen atoms of the trimellitic acid moiety of 4-MET were greater than that of oxygen of the methacryloyl group. A small change in the bond length of the Ca-O bond showed a large difference in the steric energies of 4-MET/Ca salt. PMID:11441482

Hayakawa, T; Kikutake, K; Nemoto, K

2001-03-01

63

Preparation of pentafluorosulfanyl (SF5) pyrrole carboxylic acid esters.  

PubMed

Pyrrole derivatives bearing a pentafluorosulfanyl group are currently unknown. In this paper, a facile preparation of SF5-substituted pyrrole carboxylic acid esters in good yield is reported. Utilizing the cycloaddition of an azomethine ylide to pentafluorosulfanylalkynes, a series of dihydropyrroles were prepared and oxidized to the respective 1-tert-butyl-4-(pentafluorosulfanyl)pyrrole-2-carboxylic acid esters in good yield. Further treatment of these pyrroles with catalytic triflic acid allowed removal of the tert-butyl group. PMID:19555094

Dolbier, William R; Zheng, Zhaoyun

2009-08-01

64

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

DOEpatents

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

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

1998-01-01

65

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

66

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...substance identified generically as cobalt iron manganese oxide, carboxylic...

2013-07-01

67

Approaches for regeneration of amine-carboxylic acid extracts.  

National Technical Information Service (NTIS)

Extraction processes based on reversible chemical complexation can be useful for separation of polar organics from dilute solution. Tertiary amines are effective extractants for the recovery of carboxylic acids from aqueous solution. The regeneration of a...

Y. Dai C. J. King

1995-01-01

68

A protocol for accessing the ?-azidation of ?,?-unsaturated carboxylic acids.  

PubMed

This contribution reports the preparation and use of a new immobilized catalyst, PS-DABCOF (9), which has been specifically designed to access for the first time the efficient ?-azidation of ?,?-unsaturated carboxylic acids. PMID:22891971

Angelini, Tommaso; Bonollo, Simona; Lanari, Daniela; Pizzo, Ferdinando; Vaccaro, Luigi

2012-09-01

69

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

2013-07-01

70

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

71

Recognition of carboxylate anions and carboxylic acids by selenium-based new chromogenic fluorescent sensor: a remarkable fluorescence enhancement of hindered carboxylates.  

PubMed

A selenium metal-based new fluorescence sensor 5-pivaloylamino-1,2,5-selenodiazolo[3,4-d]pyrimidin-7-(6H)-one (receptor 1) has been reported for the recognition of monocarboxylic acids and carboxylate anions both by UV-vis and fluorescence methods. Receptor 1 recognizes carboxylate anions more than monocarboxylic acids and it is a selective sensor for carboxylates with specially hindered carboxylate anions. The changes of fluorescence intensity are remarkably enhanced with red shift in presence of bulky carboxylate anions. The X-ray crystal structure of receptor 1 with pivalic acid has been reported. PMID:19728733

Goswami, Shyamaprosad; Hazra, Anita; Chakrabarty, Rinku; Fun, Hoong-Kun

2009-10-01

72

Oxidation of carboxylic acids by horseradish peroxidase results in prosthetic heme modification and inactivation.  

PubMed

Hemoproteins are powerful oxidative catalysts. However, despite the diversity of functions known to be susceptible to oxidation by these catalysts, it is not known whether they can oxidize carboxylic acids to carboxylic radicals. We report here that incubation of horseradish peroxidase (HRP) at acidic pH with H(2)O(2) in acetate buffer results in rapid modification of the heme group and loss of catalytic activity. Mass spectrometry and NMR indicate that an acetoxy group is covalently bound to the delta-meso-carbon in the modified heme. A heme with a hydroxyl group on the 8-methyl is also formed as a minor product. These reactions do not occur if protein-free heme and H(2)O(2) are co-incubated in acetate buffer, if the HRP reaction is carried out at pH 7, in the absence of H(2)O(2), or if citrate rather than acetate buffer is used. A similar heme modification is observed in incubations with n-caproic and phenylacetic acids. A mechanism involving oxidation of the carboxyl group to a carboxylic radical followed by addition to the delta-meso-position is proposed. This demonstration of the oxidation of a carboxylic acid solidifies the proposal that a carboxylic radical mediates the normal covalent attachment of the heme to the protein in the mammalian peroxidases and CYP4 family of P450 enzymes. The hemoprotein-mediated oxidation of carboxylic acids, ubiquitous natural constituents, may play other roles in biology. PMID:15469283

Huang, Liusheng; Colas, Christophe; Ortiz de Montellano, Paul R

2004-10-13

73

(Quinoline-2-carboxyl-ato-?O)(quinoline-2-carb-oxy-lic acid-?O)bis-(quinoline-2-carb-oxy-lic acid-?2 N,O)potassium  

PubMed Central

The K atom in the title complex, [K(C10H6NO2)(C10H7NO2)3], lies on a twofold rotation axis that relates one N,O-chelating quinoline-2-carb­oxy­lic acid to the other; their N and O atoms are cis to each other in the distorted octa­hedral coordination geometry. The K atom is also coordinated by another monodentate quinoline-2-carb­oxy­lic acid; the acid is disordered with respect to a monodentate quinoline-2-carboxyl­ate anion; the acid and anion are linked by an O—H?O hydrogen bond. An O—H?N hydrogen bond links adjacent mol­ecules into a linear chain structure along the a axis.

Ng, Seik Weng

2010-01-01

74

Application of partially fluorinated carboxylic acids as ion-pairing reagents in LC/ESI-MS.  

PubMed

This report describes the application of partially fluorinated carboxylic acids as ion-pairing reagents for basic analytes in high-performance liquid chromatography coupled with electrospray ionization mass spectrometry (LC/ESI-MS) in positive-ion mode. Partially fluoridated carboxylic acids such as difluoroacetic acid, 3,3,3-trifluoropropionic acid and 3,3,3-trifluoromethyl-2-trifluoromethylpropionic acid functioned as volatile paired-ion similarly as trifluoroacetic acid (TFA). These acids provided basic analytes larger retention factor (k) compared to acetic acid or formic acid in LC. The ESI-MS signal strength of analytes with these acids were higher than that of TFA and was analogous to that of acetic acid or formic acid. The performances of partially fluorinated carboxylic acids in LC and ESI-MS for basic analytes were analyzed by multivariate statistical analysis using physicochemical descriptors of acids. Equations obtained in the analysis enabled us the quantitative evaluation of the performance of fluorinated carboxylic acids as ion-pair reagents for basic analytes in LC/ESI-MS. PMID:24913879

Yamamoto, Eiichi; Ishihama, Yasushi; Asakawa, Naoki

2014-09-01

75

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

2012-10-22

76

Synthesis, spectroscopy and computational studies of selected hydroxyquinoline carboxylic acids and their selected fluoro-, thio-, and dithioanalogues  

NASA Astrophysics Data System (ADS)

The faster and more efficient new synthetic methodologies of crystalline hydroxyquinoline carboxylic acids and their fluoro-, thio- and dithioanalogues were elaborated. The FTIR, multinuclear NMR, UV-Vis and single crystal X-ray characteristics of the series of quinoline carboxylic acids have been determined experimentally and rationalized on the basis of DFT calculation method with B3LYP functional.

Nycz, Jacek E.; Malecki, Grzegorz J.

2013-01-01

77

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

2013-09-01

78

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

79

Quinoline based receptor in fluorometric discrimination of carboxylic acids  

PubMed Central

Summary Quinoline and naphthalene-based fluororeceptors 1 and 2 have been designed and synthesized for detection of hydroxy carboxylic acids in less polar solvents. The receptor 1 shows monomer emission quenching followed by excimer emission upon hydrogen bond-mediated complexation of carboxylic acids. The excimer emission distinguishes aromatic dicarboxylic acids from aliphatic dicarboxylic acids and even long chain aliphatic dicarboxylic acids from short chain aliphatic dicarboxylic acids. The receptor 1 is found to be selective for citric acid with a strong excimer emission in CHCl3. On the contrary, the receptor 2 exhibited less binding constant value and did not form any excimer upon complexation with the same acids under similar conditions. This established the role of quinoline ring nitrogen in binding with the acids.

Adhikari, Suman; Chattopadhyay, Asoke P; Chowdhury, Purnendu Roy

2008-01-01

80

Novel Condensed Ring Carboxylic Hydroxamic Acid Studied in the Flotation Behavior of Diaspore and Aluminosilicates  

Microsoft Academic Search

Flotation reagents are the critical technique in the flotation separation process for desilication. Aimed at the highly selective reagent for direct flotation of diasporic bauxite, a novel compound, dibenzo-1-(7-carboxyl-4-hydroxyl bicycle [2.2.2] octan-7,8-diyl) carboxamic acid (DBCA) with two functional groups carboxyl and hydroxamate in the same molecule, was synthesized through Diels-Alder reaction followed by oximation reaction. Subsequently, the floatability of diaspore,

Yu-Ren Jiang; Li-Yi Zhou; Xiao-Hong Zhou; Bin-Nan Zhao

2010-01-01

81

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

82

Deprotonation energies of a model fulvic acid. I. Carboxylic acid groups  

NASA Astrophysics Data System (ADS)

A model Suwannee fulvic acid (SFA [Leenheer, J.A., 1994. In: Baker, L.A. (Ed.), Chemistry of Dissolved Organic Matter in Rivers, Lakes and Reservoirs. Advances in Chemistry Series, vol. 237. American Chemical Society]) was energy minimized in various deprotonation states using semi-empirical methods. The structures were minimized in the isolated SFA phase and SFA with 60 water molecules to mimic the first solvation sphere. The relative energies of deprotonation were calculated at four carboxylic acid sites with Hartree-Fock (HF/6-31G(d)) and density functional theory (B3LYP/6-31G(d)) methods. Comparisons were made between the theoretical methods and states of solvation. Isolated and solvated models resulted in different relative deprotonation orders. The energy changes calculated for removing a H + from a given carboxylic acid group as a function of overall model molecule charge are large enough to explain the large variations of carboxyl group p Kas in dissolved natural organic matter. Analysis of the SFA structure as a function of molecular charge is also discussed.

Trout, Chad C.; Kubicki, James D.

2006-01-01

83

Interaction of phenylated carboxylic acids with a conjugated imine in a study of a model of rhodopsin  

NASA Astrophysics Data System (ADS)

Seven carboxylic acids containing a phenyl or a phenolic group and three acrylic acid derivatives were mixed in equimolar concentrations with a dienylidene Schiff base in chloroform. UV and 1H NMR (400 MHz) spectra indicated that the phenyl and the phenolic groups could not red-shift the Schiff base absorption band but could interact with the imine by their carboxylic function through a hydrogen bridge. Of all the acids studied, only phenylpropiolic acid could protonate the Schiff base.

Le Thanh, Hoa; Vocelle, Daniel

1984-11-01

84

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

Microsoft Academic Search

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

Yijun Liu; Edgar Lotero; James G. Goodwin

2006-01-01

85

Phase behavior of methane with carboxylic acids  

SciTech Connect

Vapor-liquid equilibria for the binary mixtures methane + dodecanoic acid, methane + hexadecanoic acid, and methane + eicosanoic acid have been measured in a semiflow apparatus under the temperatures ranging from 373.2 to 473.2 K at pressures up to 5.07 MPa. A correlation is developed to describe the results and to calculate the gas solubilities of these systems. Henry's constants and the partial molar volumes at infinite dilution of methane are evaluated from gas solubilities.

Der Shin Shy; Jun Shun Yau; Fuan Nan Tsai (National Cheng Kung Univ., Tainan (Taiwan, Province of China). Dept. of Chemical Engineering)

1993-01-01

86

Application of reactive extraction to recovery of carboxylic acids  

Microsoft Academic Search

Carboxylic acids are examples of compounds with wide industrial applications and high potential. This article presents the\\u000a principles of reactive extraction along with the characteristics of tertiary amine extractants, while is given on considering\\u000a the effect of the amine class and chain length. As such a brief overview the current research on reactive extraction, including\\u000a the recovery of citric acid,

Yeon Ki Hong; Won Hi Hong; Dong Hoon Han

2001-01-01

87

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

88

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

2011-09-14

89

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

ERIC Educational Resources Information Center

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

Leung, Sam H.

2000-01-01

90

Atmospheric chemistry of carboxylic acids: microbial implication versus photochemistry  

NASA Astrophysics Data System (ADS)

Clouds are multiphasic atmospheric systems in which the dissolved organic compounds, dominated by carboxylic acids, are subject to multiple chemical transformations in the aqueous phase. Among them, solar radiation, by generating hydroxyl radicals (•OH), is considered as the main catalyzer of the reactivity of organic species in clouds. We investigated to which extent the active biomass existing in cloud water represents an alternative route to the chemical reactivity of carboxylic acids. Pure cultures of seventeen bacterial strains (Arthrobacter, Bacillus, Clavibacter, Frigoribacterium, Pseudomonas, Sphingomonas and Rhodococcus), previously isolated from cloud water and representative of the viable community of clouds were first individually incubated in two artificial bulk cloud water solutions at 17 °C and 5 °C. These solutions mimicked the chemical composition of cloud water from "marine" and "continental" air masses, and contained the major carboxylic acids existing in the cloud water (i.e. acetate, formate, succinate and oxalate). The concentrations of these carboxylic compounds were monitored over time and biodegradation rates were determined. In average, they ranged from 2 ×10-19 for succinate to 1 × 10-18 mol cell-1 s-1 for formate at 17 °C and from 4 × 10-20 for succinate to 6 × 10-19 mol cell-1 s-1 for formate at 5 °C, with no significant difference between "marine" and "continental" media. In parallel, irradiation experiments were also conducted in these two artificial media to compare biodegradation and photodegradation of carboxylic compounds. To complete this comparison, the photodegradation rates of carboxylic acids by •OH radicals were calculated from literature data. Inferred estimations suggested a significant participation of microbes to the transformation of carboxylic acids in cloud water, particularly for acetate and succinate (up to 90%). Furthermore, a natural cloud water sample was incubated (including its indigenous microflora); the rates of biodegradation were determined and compared to the photodegradation rates involving •OH radicals. The biodegradation rates in "natural" and "artificial" cloud water were in the same order of magnitude; this confirms the significant role of the active biomass in the aqueous reactivity of clouds.

Vaïtilingom, M.; Charbouillot, T.; Deguillaume, L.; Maisonobe, R.; Parazols, M.; Amato, P.; Sancelme, M.; Delort, A.-M.

2011-02-01

91

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

92

Chiral mono boronic acid as fluorescent enantioselective sensor for mono alpha-hydroxyl carboxylic acids.  

PubMed

New mono boronic acid was found to be an enantioselective fluorescent chemosensor for mono alpha-hydroxyl carboxylic acids, such as mandelic acid and lactic acid. The chiral sensor shows lower background fluorescence, higher fluorescence enhancement, and enantioselective recognition kinetics toward mandelic acids and lactic acids. PMID:18507445

Chi, Lina; Zhao, Jianzhang; James, Tony D

2008-06-20

93

Chiral mono boronic acid as fluorescent enantioselective sensor for mono alpha-hydroxyl carboxylic acids  

Microsoft Academic Search

New mono boronic acid was found to be an enantioselective fluorescent chemosensor for mono alpha-hydroxyl carboxylic acids, such as mandelic acid and lactic acid. The chiral sensor shows lower background fluorescence, higher fluorescence enhancement, and enantioselective recognition kinetics toward mandelic acids and lactic acids.

J. Z. Zhao; L. Chi; T. D. James

2008-01-01

94

Biocatalytic hydrolysis of cyanohydrins: an efficient approach to enantiopure ?-hydroxy carboxylic acids  

Microsoft Academic Search

Rhodococcus erythropolis NCIMB 11540 was found to have a highly active nitrile hydratase\\/amidase enzyme system present which accepts the nitrile function of ?-hydroxynitriles (cyanohydrins) as substrates. This biocatalytic hydrolysis using whole bacterial cells leads to ?-hydroxy carboxylic acids which are much valued chiral building blocks in organic synthesis. Employing enantiopure cyanohydrins, which are easy available using (R)- or (S)-hydroxynitrile lyases,

Ingrid Osprian; Martin H Fechter; Herfried Griengl

2003-01-01

95

Room temperature decarboxylative trifluoromethylation of ?,?-unsaturated carboxylic acids by photoredox catalysis.  

PubMed

A visible-light-induced decarboxylative trifluoromethylation of ?,?-unsaturated carboxylic acids, which uses the Togni reagent as the CF3 source is disclosed. The corresponding trifluoromethylated alkenes were obtained in moderate to high yields with excellent functional group tolerance at ambient temperature. Preliminary mechanistic analyses suggest a radical-type mechanism. PMID:24445904

Xu, Pan; Abdukader, Ablimit; Hu, Kaidong; Cheng, Yixiang; Zhu, Chengjian

2014-03-01

96

Effect of Functionalized Carbon Nanotubes with Carboxylic Functional Group on the Mechanical and Thermal Properties of Styrene Butadiene Rubber  

Microsoft Academic Search

Multi-walled carbon nanotubes (MWCNTs) were functionalized with a carboxylic functional group to enhance the dispersion of CNT in styrene butadiene rubber (SBR) nanocomposites. The functionalization of the surface of the MWCNTs were carried out by using nitric acid at 120°C for 48 hours. The FTIR technique was used to characterize the surface of the modified carbon nanotubes to ascertain the

Muataz Ali Atieh

2011-01-01

97

Magnesium chloride: an efficient 13C NMR relaxation agent for amino acids and some carboxylic acids  

NASA Astrophysics Data System (ADS)

A series of amino acids and carboxylic acids were determined by 13C NMR spectroscopy. The results showed that addition of 3 M MgCl 2, led to shortening of relaxation time and 13C NMR integral area of samples was well proportional to the number of carbon atoms with reliability more than 95%. So MgCl 2 is proposed as an efficient relaxation agent for analysis of amino acids and some carboxylic acids.

Tian, Jinping; Yin, Yingwu; Sun, Hongbing; Luo, Xiaofeng

2002-12-01

98

Carboxylate-functionalized phosphomolybdates: ligand-directed conformations.  

PubMed

The [HPMo6O21](2-) units and carboxylate linkers can be combined to build novel polyanions by a carefully designed complementary system in self-assembly processes depending only on the number of carboxyl groups and the nature of carboxylic acids. Complexes (NH4)5[HPMo6O21(O2CC6H4OH)3]·4H2O (1), (NH4)8H2[(HPMo6O21)2(C2O4)3]·13H2O (2), (NH4)20[(HPMo6O21)4(O2CCH2CO2)6]·17H2O (3), and Cs2(NH4)10[(HPMo6O21)2(HPO3){C6H3(CO2)3}2]·5H2O (4) have been synthesized by a simple one-pot reaction of (NH4)6Mo7O24·4H2O, H3PO3, and carboxylic acid ligands in aqueous solution. Formation of these compounds is critically dependent on the identifying carboxylic acids, which play the important templated role in assembly processes. The stability of these clusters was explored using electrospray ionization mass spectrometry (ESI-MS) and (31)P NMR spectroscopy, and electron paramagnetic resonance (EPR) experiments further demonstrated the result of the interesting photochromic property. PMID:23844943

Yang, Donghui; Li, Suzhi; Ma, Pengtao; Wang, Jingping; Niu, Jingyang

2013-08-01

99

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...Chemical 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

100

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

101

Functionalized carboxyl nanoparticles enhance mucus dispersion and hydration  

PubMed Central

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

102

Transcriptomic analysis of carboxylic acid challenge in Escherichia coli: beyond membrane damage.  

PubMed

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

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

2014-01-01

103

Direct preparation of nitriles from carboxylic acids in continuous flow.  

PubMed

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

Cantillo, David; Kappe, C Oliver

2013-10-18

104

Polythermal solubility of fullerenes in higher isomeric carboxylic acids  

Microsoft Academic Search

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

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

2007-01-01

105

Transcriptomic analysis of the role of carboxylic acids in metabolite signaling in Arabidopsis leaves.  

PubMed

The transcriptional response to metabolites is an important mechanism by which plants integrate information about cellular energy and nutrient status. Although some carboxylic acids have been implicated in the regulation of gene expression for select transcripts, it is unclear whether all carboxylic acids have the same effect, how many transcripts are affected, and how carboxylic acid signaling is integrated with other metabolite signals. In this study, we demonstrate that perturbations in cellular concentrations of citrate, and to a lesser extent malate, have a major impact on nucleus-encoded transcript abundance. Functional categories of transcripts that were targeted by both organic acids included photosynthesis, cell wall, biotic stress, and protein synthesis. Specific functional categories that were only regulated by citrate included tricarboxylic acid cycle, nitrogen metabolism, sulfur metabolism, and DNA synthesis. Further quantitative real-time polymerase chain reaction analysis of specific citrate-responsive transcripts demonstrated that the transcript response to citrate is time and concentration dependent and distinct from other organic acids and sugars. Feeding of isocitrate as well as the nonmetabolizable citrate analog tricarballylate revealed that the abundance of selected marker transcripts is responsive to citrate and not downstream metabolites. Interestingly, the transcriptome response to citrate feeding was most similar to those observed after biotic stress treatments and the gibberellin biosynthesis inhibitor paclobutrazol. Feeding of citrate to mutants with defects in plant hormone signaling pathways did not completely abolish the transcript response but hinted at a link with jasmonic acid and gibberellin signaling pathways. Our results suggest that changes in carboxylic acid abundances can be perceived and signaled in Arabidopsis (Arabidopsis thaliana) by as yet unknown signaling pathways. PMID:23487434

Finkemeier, Iris; König, Ann-Christine; Heard, William; Nunes-Nesi, Adriano; Pham, Phuong Anh; Leister, Dario; Fernie, Alisdair R; Sweetlove, Lee J

2013-05-01

106

Two Dimensional Polyamides Prepared From Unsaturated Carboxylic Acids And Amines.  

DOEpatents

A polyamide and a process for preparing the polyamide are disclosed. The process comprises reacting in a reaction mixture a monomer selected from unsaturated carboxylic acids, esters of unsaturated carboxylic acids, anhydrides of unsaturated carboxylic acids, and mixtures thereof, and a first amine to form an intermediate reaction product in the reaction mixture, wherein the first amine is selected from RR.sub.1 NH, RNH.sub.2, RR.sub.1 NH.sub.2.sup.+, RNH.sub.3.sup.+ and mixtures thereof, wherein R and R.sub.1 can be the same or different and each contain between about 1 and 50 carbon atoms and are optionally substituted with heteroatoms oxygen, nitrogen, sulfur, and phosphorus and combinations thereof, and reacting the intermediate reaction product and a second amine to form a polyamide, wherein the second amine is selected from R.sub.2 R.sub.3 NH, R.sub.2 NH.sub.2, R.sub.2 R.sub.3 NH.sub.2.sup.+, R.sub.2 NH.sub.3.sup.+ and mixtures thereof wherein R.sub.2 and R.sub.3 can be the same or different and each contain between about 1 and 50 carbon atoms and are optionally substituted with heteroatoms oxygen, nitrogen, sulfur, and phosphorus and combinations thereof, wherein multiple of the R, R.sub.1, R.sub.2, and R.sub.3 are in vertically aligned spaced relationship along a backbone formed by the polyamide. In one version of the invention, the monomer is selected from maleic anhydride, maleic acid esters, and mixtures thereof. In another version of the invention, the first amine is an alkylamine, such as tetradecylamine, and the second amine is a polyalkylene polyamine, such as pentaethylenehexamine. In yet another version of the invention, the first amine and the second amine are olefinic or acetylenic amines, such as the reaction products of an alkyldiamine and an acetylenic carboxylic acid. The first amine and the second amine may be the same or different depending on the desired polyamide polymer structure.

McDonald, William F. (Utica, OH); Huang, Zhi Heng (East Lansing, MI); Wright, Stacy C. (Lansing, MI); Danzig, Morris (Northbrook, IL); Taylor, Andrew C. (Ann Arbor, MI)

2002-07-17

107

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

108

Formation of biologically relevant carboxylic acids during the gamma irradiation of acetic acid  

NASA Technical Reports Server (NTRS)

Irradiation of aqueous solutions of acetic acid with gamma rays produced several carboxylic acids in small yield. Their identification was based on the technique of gas chromatography combined with mass spectrometry. Some of these acids are Krebs Cycle intermediates. Their simultaneous formation in experiments simulating the primitive conditions on the earth suggests that metabolic pathways may have had their origin in prebiotic chemical processes.

Negron-Mendoza, A.; Ponnamperuma, C.

1976-01-01

109

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

110

Reduction of Carboxylic Acids with Sodium Borohydride and an Electrophile  

NASA Astrophysics Data System (ADS)

Our goal was to develop the new reduction conditions into a procedure applicable to the first-year organic chemistry laboratory, where reduction of the carboxylic acid group has remained an obstacle, notwithstanding the use of borane or LiAlH4 (2) on the microscale. The NaBH4 method with either electrophile can be modified to any scale; in our hands, the use of I2 as the electrophile performed better at the semimicro scale than the H2SO4 method.

Simek, Jan William; Tuck, Thad; Courter Bush, Kelly

1997-01-01

111

Oxidation of unsaturated carboxylic acids under hydrothermal conditions.  

PubMed

Hydrothermal oxidation pathways of high molecular weight unsaturated carboxylic acids were investigated for the potential use of chemoselectivity to improve the efficiency of the desired products from biomasses directly containing or easily producing unsaturated carboxylic acids. Hock cleavage, which frequently occur at general chemical, was observed in the absence of any acid catalyst and may be a potential major oxidation cleavage mechanism, which leads to the cleavage at both the carbon-carbon double bond and the single bond near a double bond. The addition of a peroxyl radical to the double bond may be also a potential major oxidation mechanism, which leads to the oxidation cleavage mainly at the carbon-carbon double bond. Cleavage at the carbon-carbon bond near the double bond by the addition of a peroxyl radical to the double bond may also occur. However, oxidation at either alpha-, beta-, or gamma-carbon to the -COOH group hardly occurred. These results may help to selectively produce desired products from biomasses, such as lignin and oils. PMID:20488695

Jin, Fangming; Zhong, Heng; Cao, Jianglin; Cao, Jianxun; Kawasaki, Kohei; Kishita, Astushi; Matsumoto, Takatoshi; Tohji, Kazuyuki; Enomoto, Heiji

2010-10-01

112

New approaches to the synthesis of selected hydroxyquinolines and their hydroxyquinoline carboxylic acid analogues  

NASA Astrophysics Data System (ADS)

New approaches to the synthesis of selected crystalline hydroxyquinolines and their carboxylic acid analogues were elaborated in this paper with the auxiliary of computational and spectroscopic characterization, such as FTIR, NMR and single crystal X-ray measurements. The experimental data were further rationalized based on a DFT calculation method with B3LYP functional, which reflected the impact of electron donating or withdrawing groups on the energy level of HOMO orbitals and the reactivity of the substituted hydroxyquinolines.

Szala, Marcin; Nycz, Jacek E.; Malecki, Grzegorz J.

2014-08-01

113

Silver-catalyzed decarboxylative trifluoromethylthiolation of aliphatic carboxylic acids in aqueous emulsion.  

PubMed

A silver-catalyzed decarboxylative trifluoromethylthiolation of secondary and tertiary carboxylic acids under mild conditions tolerates a wide range of functional groups. The reaction was dramatically accelerated by its performance in an aqueous emulsion, which was formed by the addition of sodium dodecyl sulfate to water. It was proposed that the radical, which was generated from the silver-catalyzed decarboxylation in the "oil-in-water" droplets, could easily react with the trifluoromethylthiolating reagent to form the product. PMID:24764209

Hu, Feng; Shao, Xinxin; Zhu, Dianhu; Lu, Long; Shen, Qilong

2014-06-10

114

Reactivity of acrylonitrile-butadiene-styrene terpolymer grafted with long-chain unsaturated carboxylic acids  

Microsoft Academic Search

Reactivity of acrylonitrile-butadiene-styrene terpolymer (ABS) grafted with long-chain carboxylic acids, such as undecylenic acid and oleic acid, was investigated and compared with that of ABS grafted with short-chain carboxylic acids by reacting with dodecylamine, glycidyl methacrylate (GMA), and 2-ethyl-2-oxazoline in solution, and with polyamide (PA) in melt. The overall activation energy of ABS-g-acrylic acid, ABS-g-crotonic acid, ABS-g-undecylenic acid and ABS-g-oleic

Z. F. Zhou; N. C. Liu; H. Huang

2004-01-01

115

Integrated process for preparing a carboxylic acid from an alkane  

DOEpatents

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

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

2011-12-20

116

Solidphase microextraction and on-line methylation gas chromatography for aliphatic carboxylic acids  

Microsoft Academic Search

Methylation of carboxylic acids upon syringe injection of a mixture of the acid sample and phenyltrimethylammonium hydroxide (PTMAH) into the GC injection port is a convenient but under-utilized derivatization procedure. To minimize potential instrumental problems due to the sample matrix, it was shown that solid-phase microextraction (SPME) is effective for the absorption of both the carboxylic acid (RCOOH) and PTMAH

Yaqian Liu; Seong R. Cho; Neil D. Danielson

2002-01-01

117

Dipole moments in Langmuir monolayers from aromatic carboxylic acids  

NASA Astrophysics Data System (ADS)

The three-layer capacitor model proposed by Demchak and Fort [J. Colloid Interface Sci. 46 (1974) 191] is employed to relate measured surface potentials of Langmuir monolayers from a series of polyphenyl carboxylic acids to molecular dipole moments calculated using semiempirical quantum methods. The effective dielectric constant at the air/monolayer interface is 3.0±0.6, very close to that estimated for aliphatic compounds. Good agreement between theory and experiment is obtained by adopting a dielectric constant of 6.4 for the monolayer/water interface and a contribution from the water reorientation of -0.064±0.006 D, which shows that the parameters in the DF model are essentially the same as for aliphatic amphiphiles, such as esters, acids, alcohols and ethers.

Dynarowicz-??tka, Patrycja; Cavalli, Ailton; Silva Filho, Demétrio A.; dos Santos, M. C.; Oliveira, Osvaldo N.

2000-08-01

118

Microwave assisted solid-state synthesis of functional organotin carboxylates from sterically encumbered 3,5-di- tert-butylsalicylic acid  

Microsoft Academic Search

Microwave assisted solid-state reaction between equimolar quantities of sterically encumbered 3,5-di-tert-butylsalicylic acid (H2-DTBSA) and n-butylstannoic acid results in the formation of hexameric drum shaped stannoxane [nBuSn(O)(H-DTBSA)]6 (1). Synthesis of 1 could not be achieved under normal thermal conditions or mechanical grinding. However, the azeotropic removal of water produced in the reaction of nBu2SnO with 3,5-di-tert-butyl salicylic acid in benzene yielded

Ramaswamy Murugavel; Nayanmoni Gogoi

2008-01-01

119

Pancreatic Function in Carboxyl-Ester Lipase Knockout Mice  

Microsoft Academic Search

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

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

2010-01-01

120

Oxidation reaction of high molecular weight carboxylic acids in supercritical water.  

PubMed

Stearic acid, being a model compound of high molecular weight carboxylic acids, was oxidized in a batch reactor by changing the oxygen supply with an insufficient oxygen supply at a constant reaction time at 420 degrees C. On the basis of the intermediate products identified by GC/MS, NMR, and HPLC analyses and the free-radical reaction mechanism, the oxidation pathways of high molecular weight carboxylic acids in supercritical water are discussed. The reaction of carboxylic acids in supercritical water proceeds with the consecutive oxidation of higher molecular weight carboxylic acids to lower molecular weight carboxylic acids through several major pathways. The attack of the hydroxyl radical occurs not only at the carbons in alpha-, beta-, gamma-positions to a --COOH group but also at the carbons ((omega-1)-carbon and/or omega-carbon) far in the alkyl chain from a --COOH group, which may lead to the formation of dicarboxylic acids. PMID:12901673

Jin, Fangming; Moriya, Takehiko; Enomoto, Heiji

2003-07-15

121

Density functional study of electronic, charge density, and chemical bonding properties of 9-methyl-3-Thiophen-2-YI-Thieno [3,2-e] [1, 2, 4] Thriazolo [4,3-c] pyrimidine-8-Carboxylic acid ethyl ester crystals  

NASA Astrophysics Data System (ADS)

A comprehensive theoretical density functional investigation of the electronic crystal structure, chemical bonding, and the electron charge densities of 9-Methyl-3-Thiophen-2-YI-Thieno [3, 2-e] [1, 2, 4] Thriazolo [4,3-c] Pyrimidine-8-Carboxylic Acid Ethyl Ester (C15H12N4O2S2) is performed. The density of states at Fermi level equal to 5.50 (3.45) states/Ry cell, and the calculated bare electronic specific heat coefficient is found to be 0.95 (0.59) mJ/mole-K2 for the local density approximation (Engel-Vosko generalized gradient approximation). The electronic charge density space distribution contours in (1 0 0) and (1 1 0) planes were calculated. We find that there are two independent molecules (A and B) in the asymmetric unit exhibit intramolecular C-H…O, C-H…N interactions. This intramolecular interaction is different in molecules A and B, where A molecule show C-H…O interaction while B molecule exhibit C-H…N interaction. We should emphasis that there is ?-? interaction between the pyrimidine rings of the two neighbors B molecules gives extra strengths and stabilizations to the superamolecular structure. The calculated distance between the two neighbors pyrimidine rings found to be 3.345 Å, in good agreement with the measured one (3.424(1) Å).

Reshak, A. H.; Kamarudin, H.; Alahmed, Z. A.; Auluck, S.; Chyský, Jan

2014-06-01

122

Inhibition of apple 1-aminocyclopropane-1-carboxylic acid oxidase, by cyclopropane-1,1-dicarboxylic acid and trans-2-phenylcyclopropane-1-carboxylic acid.  

PubMed

Cyclopropane-1,1-dicarboxylic acid (CDA) and trans-2-phenylcyclopropane-1-carboxylic acid (PCCA) are the main representatives of a group of compounds that are structural analogues of 1-aminocyclopropane-1-carboxylic acid (ACC) and have been proved to have an inhibitory effect on the wound ethylene produced by Lycopersicum esculentum fruit discs. During the experiments, that were carried out in this work the inhibition pattern of PCCA and CDA were studied when tested on partially purified apple ACO and their Ki values were determined. A mechanistic proposal was given, in order to explain the kinetic behaviour of the inhibitors. The common feature of these molecules is their cyclopropane ring, with different substitutes mainly at the positions C1 and C2. Two other compounds with similar structure where also tested as inhibitors, in order to clarify the relationship between structure and activity. These compounds are: 2-methyl cyclopropanecarboxylic acid (MCA), and cyclopropanecarboxylic acid (CCA). PMID:11142843

Dourtoglou, V; Koussissi, E

2000-10-01

123

Polyacetal Carboxylic Acids: a New Group of Antiviral Polyanions  

PubMed Central

Chlorite-oxidized oxypolysaccharides are polyacetal carboxylic acids. They inhibited the cytopathic effect of vesicular stomatitis virus in mouse embryo cell cultures challenged at low input multiplicity. After intraperitoneal injection of these compounds in mice, interferon appeared in the circulation. The compounds also protected mice against lethal mengovirus infection and against the development of experimental pox lesions on the tail. Chlorite-oxidized oxyamylose was antiviral only when at least 64% of the glucopyranose units were oxidized, an observation which suggested a correlation between charge density and antiviral effect. The antiviral activity was also influenced by the molecular weight, as demonstrated by the fact that chlorite-oxidized dextrans which had a high intrinsic viscosity were more active than those with low intrinsic viscosity.

Claes, P.; Billiau, A.; De Clercq, E.; Desmyter, J.; Schonne, E.; Vanderhaeghe, H.; De Somer, P.

1970-01-01

124

Energetics of the lighter chalcogen analogues of carboxylic acid esters.  

PubMed

In the current paper we present the results of our quantum chemical (G2, G2(MP2), and G3) study of the structure and energetics of carboxylic acids and their chalcogen analogues. In the particular, calculations and accompanying natural bond orbital (NBO) and atoms in molecules (AIM) analyses were performed on all species with the generic formula RC(?X)YR' (X, Y = O, S, Se and R = R' = CH(3)). Energies, enthalpies, and free energies of formation, resonance energies, interchalcogen methyl transfer energies and their energies of activation, and heavy atom bond lengths and angles are all discussed. A comparison of the calculated results with the sparse experimentally available data shows good agreement. Trends are also presented. PMID:21028778

Deakyne, Carol A; Ludden, Alicia K; Roux, Maria Victoria; Notario, Rafael; Demchenko, Alexei V; Chickos, James S; Liebman, Joel F

2010-12-16

125

FORMATION OF ALIPHATIC CARBOXYLIC ACIDS DURING ALKALINE PULPING OF MULI BAMBOO  

Microsoft Academic Search

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

Zhinan Feng; Raimo Alén; Klaus Niemelä

2002-01-01

126

Molluscicidal beta-Carboline Carboxylic Acids and Methods Using the Same.  

National Technical Information Service (NTIS)

The invention relates to the use of beta-carboline carboxylic acids, more specifically, 6-hydroxy-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid and its analogs, as molluscicides. The compounds effectively control slug population in minimum or no-til...

R. D. Hagin S. J. Bobnick

1989-01-01

127

TMSCN/DBU-mediated facile redox transformation of ?,?-unsaturated aldehydes to carboxylic acid derivatives.  

PubMed

Redox transformation of an ?,?-unsaturated aldehyde to a carboxylic acid derivative by means of a combination of TMSCN and DBU was investigated. In addition to the wide use of the carboxylic acid derivatives provided by this reaction, temperature-dependent control of the kinetic or thermodynamic protonation pattern was found to selectively switch the stereochemistry of the acyl group in the product. PMID:24446807

Kaise, Hiromi; Shimokawa, Jun; Fukuyama, Tohru

2014-02-01

128

Sensitive and selective electrochemical determination of quinoxaline-2-carboxylic acid based on bilayer of novel poly(pyrrole) functional composite using one-step electro-polymerization and molecularly imprinted poly(o-phenylenediamine).  

PubMed

A facile and efficient molecularly imprinted polymer (MIP) recognition element of electrochemical sensor was fabricated by directly electro-polymerizing monomer o-phenylenediamine (oPD) in the presence of template quinoxaline-2-carboxylic acid (QCA), based on one-step controllable electrochemical modification of poly(pyrrole)-graphene oxide-binuclear phthalocyanine cobalt (II) sulphonate (PPY-GO-BiCoPc) functional composite on glassy carbon electrode (GCE). The MIP film coated on PPY-GO-BiCoPc functional composite decorated GCE (MIP/PPY-GO-BiCoPc/GCE) was presented for the first time. The synergistic effect and electro-catalytic activity toward QCA redox of PPY-GO-BiCoPc functional composite were discussed using various contrast tests. Also, the effect of experimental variables on the current response such as, electro-polymerization cycles, template/monomer ratio, elution condition for template removal, pH of the supporting electrolyte and accumulation time, were investigated in detail. Under the optimized conditions, the proposed MIP sensor possessed a fast rebinding dynamics and an excellent recognition capacity to QCA, while the anodic current response of square wave voltammetry (SWV) was well-proportional to the concentration of QCA in the range of 1.0×10(-8)-1.0×10(-4) and 1.0×10(-4)-5.0×10(-4) mol L(-1) with a low detection limit of 2.1 nmol L(-1). The established sensor was applied successfully to determine QCA in commercial pork and chicken muscle samples with acceptable recoveries (91.6-98.2%) and satisfactory precision (1.9-3.5% of SD), demonstrating a promising feature for applying the MIP sensor to the measurement of QCA in real samples. PMID:24331049

Yang, Yukun; Fang, Guozhen; Wang, Xiaomin; Pan, Mingfei; Qian, Hailong; Liu, Huilin; Wang, Shuo

2014-01-01

129

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

130

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

131

Cu-catalyzed formal methylative and hydrogenative carboxylation of alkynes with carbon dioxide: efficient synthesis of ?,?-unsaturated carboxylic acids.  

PubMed

The sequential hydroalumination or methylalumination of various alkynes catalyzed by different catalyst systems, such those based on Sc, Zr, and Ni complexes, and the subsequent carboxylation of the resulting alkenylaluminum species with CO2 catalyzed by an N-heterocyclic carbene (NHC)-copper catalyst have been examined in detail. The regio- and stereoselectivity of the overall reaction relied largely on the hydroalumination or methylalumination reactions, which significantly depended on the catalyst and alkyne substrates. The subsequent Cu-catalyzed carboxylation proceeded with retention of the stereoconfiguration of the alkenylaluminum species. All the reactions could be carried out in one-pot to afford efficiently a variety of ?,?-unsaturated carboxylic acids with well-controlled configurations, which are difficult to construct by previously reported methods. This protocol could be practically useful and attractive because of its high regio- and stereoselectivity, simple one-pot reaction operation, and the use of CO2 as a starting material. PMID:23852827

Takimoto, Masanori; Hou, Zhaomin

2013-08-19

132

Extraction and separation of gallium, indium and thallium with several carboxylic acids from chloride media.  

PubMed

A method is proposed for the extraction and individual separation of trivalent gallium, indium and thallium with sec-octylphenoxy acetic acid (CA-12), sec-nonylphenoxy acetic acid (CA-100) and naphthenic acid (NA) from chloride media. The distribution equilibria of gallium (III), indium (III), thallium (III) and thallium (I) between carboxylic acids (CA-12, CA-100 and NA) dissolved in kerosene and acidic aqueous chloride media has been investigated as a function of the concentration of extractants and the concentration of hydrogen ion in aqueous phase. A possible mechanism of the extraction is discussed. The method permits rapid and precise individual separation of gallium (III), indium (III) and thallium (III), and is applicable to the analysis of alloy samples. PMID:18968979

Zhang, Xiuying; Yin, Guoyin; Hu, Zhiguo

2003-04-10

133

An ab initio density functional study of the optical functions of 9-Methyl-3-Thiophen-2-YI-Thieno [3,2e] [1,2,4] Thriazolo [4,3c] Pyrimidine-8-Carboxylic Acid Ethyl Ester crystals  

NASA Astrophysics Data System (ADS)

An ab initio investigation of the optical constants of 9-Methyl-3-Thiophen-2-YI-Thieno [3,2e] [1,2,4] Thriazolo [4,3c] Pyrimidine-8-Carboxylic Acid Ethyl Ester crystal is performed within a framework of local density approximation (LDA), and the Engel-Vosko generalized gradient approximation (EV-GGA) exchange correlation potentials. It is established that there are two independent molecules (A and B) exhibiting different intra-molecular interactions: C-H⋯O (A) and C-H⋯N (B). These intra-molecular interactions favor stabilization of the crystal structure for molecules A and B. It should be emphasized that there exist remarkable ?-? interactions between the pyrimidine rings of the two neighbors B molecules giving extra strengths and stabilizations to the superamolecular structure. These different intra-molecular interactions C-H⋯O (A) and C-H⋯N (B) and the ?-? interaction between the pyrimidine rings of the two neighbors B molecules give principal contribution to dispersion of optical properties. With a view to seek deeper insight into the electronic structure, the optical properties were investigated. Our calculations show that the optical constants are very anisotropic. The EVGGA calculation shows a blue spectral shift of around 0.024 eV with significant changes in the spectra compared to the LDA calculation. The observed spectral shifts are in agreement with the calculated band structure and corresponding electron density of states.

Reshak, Ali H.; Kityk, I. V.; Khenata, R.; Al-Douri, Y.; Auluck, S.

134

Synthesis and transformations of di-endo-3-aminobicyclo-[2.2.2]oct-5-ene-2-carboxylic acid derivatives.  

PubMed

all-endo-3-amino-5-hydroxybicyclo[2.2.2]octane-2-carboxylic acid (13) and all-endo-5-amino-6-(hydroxymethyl)bicyclo[2.2.2]octan-2-ol (10) were prepared via dihydro-1,3-oxazine or g-lactone intermediates by the stereoselective functionalization of an N-protected derivative of endo-3-aminobicyclo[2.2.2]oct-5-ene-2-carboxylic acid (2). Ring closure of b-amino ester 4 resulted in tricyclic pyrimidinones 15 and 16. The structures, stereochemistry and relative configurations of the synthesized compounds were determined by IR and NMR. PMID:21900870

Palkó, Márta; Sohár, Pál; Fülöp, Ferenc

2011-01-01

135

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

2010-10-22

136

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

SciTech Connect

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

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

1999-02-01

137

Atomic layer deposition of organic-inorganic hybrid materials based on saturated linear carboxylic acids.  

PubMed

Atomic layer deposition (ALD) has successfully provided thin films of organic-inorganic hybrid materials based on saturated linear carboxylic acids and trimethylaluminium (TMA). Films were grown for seven carboxylic acids: oxalic, malonic, succinic, glutaric, pimelic, suberic and sebacic acid, i.e. ranging from 2 to 10 carbon atoms in the molecular structure. These processes show exceptionally high growth rates; up to 4.3 nm/cycle for the pimelic acid-TMA system. Quartz crystal microbalance measurements of the growth dynamics indicate that all systems are of a self limiting ALD-type. Nevertheless, temperature dependent growth was observed in several systems. The width of the ALD windows shows correlations with the length of the carbon chains. Fourier transform infrared spectroscopy clearly proved that the deposited films are of a hybrid character, where the carboxylic acids primarily form bidentate complexes, though bridging complexes may also form. All films are X-ray amorphous as deposited. The films were further analyzed by atomic force microscopy for surface roughness and topography, UV-Vis spectroscopy and ellipsometry for optical properties, and the goniometer method for measuring sessile drops for surface wetting properties. Apart from the oxalic and malonic acid-TMA systems, the films are stable in contact with water. The films are generally smooth, transparent and have a refractive index close to 1.5. The complete coverage and accurate growth control offered by the ALD technique is here proven to provide surface-functionalized hybrid materials resembling metal-organic frameworks (MOF), probably as rather dense structures, yet with substantial potential for applications. PMID:21442116

Klepper, Karina Barnholt; Nilsen, Ola; Hansen, Per-Anders; Fjellvåg, Helmer

2011-05-01

138

Effect of carboxylic acid adsorption on the hydrolysis and sintered properties of aluminum nitride powder  

SciTech Connect

To suppress the reactivity of AlN powder with water, chemical surface modification with carboxylic acids has been investigated. It was found that the chemical stability of AlN powder increased as the number of carbon atoms in carboxylic acids used for the surface treatment increased. Among the carboxylic acids tested, stearic acid was the most promising from the viewpoint of the chemical stability of the treated powder and the thermal conductivity of the sintered ceramics prepared by cold isostatic pressing and pressureless sintering.

Egashira, Makoto; Shimizu, Yasuhiro; Takao, Yuji; Yamaguchi, Ryoji; Ishikawa, Yasuhiro (Nagasaki Univ. (Japan). Dept. of Materials Science and Engineering)

1994-07-01

139

A Zn-based, pillared paddlewheel MOF containing free carboxylic acids via covalent post-synthesis elaboration.  

PubMed

A Zn-based, mixed-ligand (pillared paddlewheel), metal-organic framework (MOF) has been covalently and quantitatively decorated with free carboxylic acids to demonstrate the utility of covalent post-synthesis modification in the construction of otherwise inaccessible carboxy-functionalized MOFs. PMID:19557260

Gadzikwa, Tendai; Farha, Omar K; Mulfort, Karen L; Hupp, Joseph T; Nguyen, SonBinh T

2009-07-01

140

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

SciTech Connect

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

Tung, L.A.

1993-08-01

141

Retention of heavy metals by carboxyl functional groups of biochars in small arms range soil.  

PubMed

Long-term effectiveness of biochar for heavy metal stabilization depends upon biochar's sorptive property and recalcitrance in soil. To understand the role of carboxyl functional groups on heavy metal stabilization, cottonseed hull biochar and flax shive steam-activated biochar having a low O/C ratio (0.04-0.06) and high fixed carbon content (~80% dry weight basis) were oxidized using concentrated H(2)SO(4)/HNO(3) and 30% HNO(3). Oxidized and unoxidized biochars were characterized for O/C ratio, total acidity, pH, moisture, ash, volatile matter, and fixed carbon contents, Brunauer-Emmett-Teller surface area, and attenuated total reflectance Fourier transform infrared spectral features. Characterized biochars were amended (2%, 5%, 10%, and 20% in grams of biochar per gram of soil) on a sandy, slightly acidic (pH 6.27) heavy metal contaminated small arms range soil fraction (<250 ?m) having low total organic carbon (0.518%) and low cation exchange capacity (0.95 cmol(c) kg(-1)). Oxidized biochars rich in carboxyl functional groups exhibited significantly greater Pb, Cu, and Zn stabilization ability compared to unoxidized biochars, especially in pH 4.9 acetate buffer (standard solution for the toxicity characteristic leaching procedure). Oppositely, only oxidized biochars caused desorption of Sb, indicating a counteracting impact of carboxyl functional groups on the solubility of anions and cations. The results suggested that appropriate selection of biochar oxidant will produce recalcitrant biochars rich in carboxyl functional groups for a long-term heavy metal stabilization strategy in contaminated soils. PMID:22280497

Uchimiya, Minori; Bannon, Desmond I; Wartelle, Lynda H

2012-02-22

142

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

2013-09-15

143

Synthesis of novel adamantoyl cellulose using differently activated carboxylic acid derivatives  

Microsoft Academic Search

New adamantane carboxylic acid esters of cellulose (adamantoylcelluloses) were synthesized homogeneously inN,N-dimethylacetamide\\/LiCl using differently activatedcarboxylic acid derivatives. This includes the reaction of cellulose with1-adamantoyl chloride and with adamantane-1-carboxylic acid after insitu activation with p-toluenesulfonyl chlorideand with 1,1'-carbonyldiimidazole, which is a new and efficient tool. Thedegree of substitution (DS) has been determined by means of 1H NMRspectroscopy using the perpropionylated adamantoyl

Daniela Gräbner; Tim Liebert; Thomas Heinze

2002-01-01

144

From Minerals to Materials. Syntheses of Alumoxanes from the Reaction of Boehmite with Carboxylic Acids.  

National Technical Information Service (NTIS)

Reaction of pseudo-boehmite, (Al(O)(OH))n, with carboxylic acids (RCO2H) results in the formation of the carboxylate-alumoxanes, (Al(O)x(OH)y(O2CR)z)n where 2x + y + z = 3 and R = C1 - C13. The physical properties of the alumoxanes are highly dependent on...

C. C. Landry N. Pappe M. R. Mason A. W. Apblett A. N. MacInnes

1995-01-01

145

Radiation-induced accumulation of carboxylic acids in solution of tributyl phosphate in dodecane  

SciTech Connect

A study has been made of the molecular composition and concentrations of carboxylic acids formed upon irradiation of the system 30% TBP in dodecane-3 M HNO{sub 3}. Based on these data, a model solution of carboxylic acids in dodecane has been formulated and compared with the irradiated solution in the interfacial tension on the organic phase-alkaline solution interface. Coefficients of carboxylic acid distribution between TBP in dodecane and aqueous solutions of HNO{sub 3}, NaHCO{sub 3} have been determined.

Bykov, G.L. [Institute of Physical Chemistry, Moscow (Russian Federation)

1995-09-01

146

Grafting of bifunctional phosphonic and carboxylic acids on Phynox: Impact of induction heating  

NASA Astrophysics Data System (ADS)

Phynox, a cobalt-chromium alloy, exhibits interesting mechanical properties making it a valuable material for a number of applications. However, its applications (especially biomedical ones) often require specific surface properties that can be imparted via suitable surface functionalizations. Based on Faraday's law of induction, induction heating is a widely used method to heat metallic substrates directly and contactless. The aim of this work is to compare the influence of induction heating and a conventional heating method on the functionalization of Phynox surfaces with bifunctional (6-phosphonohexanoic and 11-phosphoundecanoic acids) monolayers in order to create a platform for a large variety of post-grafting chemical reactions, e.g. with alcohols and amines, to modify and control the surface properties. In a first part, we assess the influence of the heating method on the interaction between the two terminal moieties of the 6-phosphonohexanoic and 11-phosphoundecanoic acids and the Phynox surface by studying the grafting of n-dodecylphosphonic acid and n-dodecanoic acid separately. The suitability of such bifunctional molecules for post-grafting chemical reactions has then been assessed by studying the post-grafting of a fluorinated alcohol by the Steglich esterification reaction between the carboxylic end of the grafted bifunctional molecules and the alcohol function of the post-grafted molecule. It has been shown that induction heating can lead to a much more selective adsorption of bifunctional molecules on the surface of Phynox, leaving a higher amount of free carboxylic acid functions to react during the second modification step.

Devillers, S.; Lanners, L.; Delhalle, J.; Mekhalif, Z.

2011-05-01

147

Pharmacological Studies of Methoxycarbonyl Etomidate's Carboxylic Acid Metabolite  

PubMed Central

Background Methoxycarbonyl etomidate (MOC-etomidate) is a rapidly metabolized and ultra-short acting etomidate analog that does not produce prolonged adrenocortical suppression after bolus administration. Its metabolite (MOC-ECA) is a carboxylic acid whose pharmacology is undefined. We hypothesized that MOC-ECA possesses significantly lower pharmacological activity than MOC-etomidate, accounting for the latter's very brief duration of hypnotic action and inability to produce prolonged adrenocortical suppression after bolus administration. To test this hypothesis, we compared the potencies of MOC-ECA and MOC-etomidate in three biological assays. Methods The hypnotic potency of MOC-ECA was assessed in tadpoles using a loss-of-righting reflexes assay. The gamma-aminobutyric acid type A (GABAA) receptor modulatory potencies of MOC-ECA and MOC-etomidate were compared by defining the concentrations of each required to directly activate ?1(L264T)?2?2L GABAA receptors. The adrenocortical inhibitory potencies of MOC-ECA and MOC-etomidate were compared by defining the concentrations of each required to inhibit in vitro cortisol production by adrenocortical cells. Results MOC-ECA's EC50 for loss-of-righting reflexes in tadpoles was 2.8 ± 0.64 mM as compared to a previously reported value of 8 ± 2 ?M for MOC-etomidate. EC50s for direct activation of GABAA receptors were 3.5 ± 0.63 mM for MOC-ECA versus 10 ± 2.5 ?M for MOC-etomidate. IC50 for inhibiting in vitro cortisol production by adrenocortical cells was 30 ± 7 ?M for MOC-ECA versus 0.10 ± 0.02 ?M for MOC-etomidate. Conclusions In all three biological assays, MOC-ECA's potency was approximately 300-fold lower than that of MOC-etomidate.

Ge, Ri Le; Pejo, Ervin; Haburcak, Marian; Husain, S. Shaukat; Forman, Stuart A.; Raines, Douglas E.

2011-01-01

148

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

149

Effect of carboxylic acid content on the acute toxicity of oil sands naphthenic acids.  

PubMed

Fractions of methylated naphthenic acids (NAs) isolated from oil sands process-affected waterwere collected utilizing Kugelrohr distillation and analyzed by proton nuclear magnetic resonance (1H NMR) spectroscopy. 1H NMR analysis revealed that the ratio of methyl ester hydrogen atoms to remaining aliphatic hydrogen atoms increased from 0.130 to 0.214, from the lowest to the greatest molecular weight (MW) fractions, respectively, indicating that the carboxylic acid content increased with greater MW. Acute toxicity assays with exposure to monocarboxyl NA-like surrogates demonstrated that toxicity increased with increasing MW (D. magna LC50 values of 10 +/- 1.3 mM and 0.59 +/- 0.20 mM for the respective lowest and highest MW NA-like surrogates); however, with the addition of a second carboxylic acid moiety, the toxicity was significantly reduced (D. magna LC50 values of 10 +/- 1.3 mM and 27 +/- 2.2 mM forthe respective monocarboxyl and dicarboxyl NA-like surrogates of similar MW). Increased carboxylic acid content within NA structures of higher MW decreases hydrophobicity and, consequently, offers a plausible explanation as to why lower MW NAs in oil sands process-affected water are more toxic than the greater MW NAs. PMID:19238950

Frank, Richard A; Fischer, Katharina; Kavanagh, Richard; Burnison, B Kent; Arsenault, Gilles; Headley, John V; Peru, Kerry M; Van Der Kraak, Glen; Solomon, Keith R

2009-01-15

150

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

NASA Astrophysics Data System (ADS)

In this study the effect of carboxylic group substitution in the 2 and 5 position of indole ring on the photophysics of the parent indole chromophore has been studied. The photophysical parameters crucial in triplet state decay mechanism of aqueous indole-2-carboxylic acid (I2C) and indole-5-carboxylic acid (I5C) have been determined applying our previously proposed methodology based on the heavy atom effect and fluorescence and phosphorescence decay kinetics [Kowalska-Baron et al., 2012]. The determined time-resolved phosphorescence spectra of I2C and I5C are red-shifted as compared to that of the parent indole. This red-shift was especially evident in the case of I2C and may indicate the possibility of hydrogen bonded complex formation incorporating carbonyl Cdbnd O, the NH group of I2C and, possibly, surrounding water molecules. The possibility of the excited state charge transfer process and the subsequent electronic charge redistribution in such a hydrogen bonded complex may also be postulated. The resulting stabilization of the I2C triplet state is manifested by its relatively long phosphorescence lifetime in aqueous solution (912 ?s). The relatively short phosphorescence lifetime of I5C (56 ?s) may be the consequence of more effective ground-state quenching of I5C triplet state. This hypothesis may be strengthened by the significantly larger value of the determined rate constant of I5C triplet state quenching by its ground-state (4.4 × 108 M-1 s-1) as compared to that for indole (6.8 × 107 M-1 s-1) and I2C (2.3 × 107 M-1 s-1). The determined bimolecular rate constant for triplet state quenching by iodide kqT is equal to 1 × 104 M-1 s-1; 6 × 103 M-1 s-1 and 2.7 × 104 M-1 s-1 for indole, I2C and I5C, respectively. In order to obtain a better insight into iodide quenching of I2C and I5C triplet states in aqueous solution, the temperature dependence of the bimolecular rate constants for iodide quenching of the triplet states has been expressed in Arrhenius form. The linearity of the obtained Arrhenius plots clearly indicated the existence of one temperature-dependent non-radiative process for the de-excitation of I2C and I5C triplet state in the presence of iodide. This process may be attributed to the solute-quenching by iodide and, most probably, proceeds via reversibly formed exciplex. The activation energies obtained from linear Arrhenius plots (1.89 kcal/mol for I5C; 2.55 kcal/mol for I2C) are smaller as compared to that for diffusion controlled reactions in aqueous solution (about 4 kcal/mol), which may indicate the great importance of the electrostatic interactions between solute and iodide ions in lowering the energy barrier needed for the formation of the triplet-quencher complex. Based on the theoretical predictions (at the DFT(CAM-B3LYP)/6-31 + G(d,p) level of theory) and careful analysis of the obtained FTIR spectra it may be concluded that in the solid state I2C and I5C molecules form associates by intermolecular NH⋯Odbnd C and OH⋯Odbnd C hydrogen bonding interactions, whereas the existence of intramolecular NH⋯Odbnd C interactions in the solid state of I2C and I5C is highly unlikely.

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

2013-12-01

151

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

PubMed

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

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

2013-12-01

152

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

153

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

154

Evaluation of a series of prolylamidepyridines as the chiral derivatization reagents for enantioseparation of carboxylic acids by LC-ESI-MS/MS and the application to human saliva.  

PubMed

Mass spectrometry has become a popular analytical tool because of its high sensitivity and specificity. The use of a chiral derivatization reagent for the mass spectrometry (MS) detection seems to be efficient for the enantiomeric separation of racemates. However, the number of chiral reagents for the liquid chromatography (LC)-MS/MS analysis is very limited. According to these observations, we are currently in the process of developing novel labeling reagents for chiral molecules in MS/MS analysis. The derivatization reagent that is effective for enhancing not only the electrospray ionization-MS/MS sensitivity but also the reversed-phase LC resolution of carboxylic acid enantiomers should have a highly proton-affinitive moiety and an asymmetric structure near the reactive functional group. Furthermore, the resulting derivative has to provide a characteristic product ion suitable for the selected reaction monitoring. Based upon these considerations, a series of prolylamidepyridines ((S)-N-pyrrolidine-2-carboxylic acid N-(pyridine-2-yl)amide (PCP2), (S)-N-pyrrolidine-2-carboxylic acid N-(pyridine-3-yl)amide, and (S)-N-pyrrolidine-2-carboxylic acid N-(pyridine-4-yl)amide) was synthesized as ideal labeling reagents for the enantioseparation of chiral carboxylic acids and evaluated in terms of separation efficiency and detection sensitivity by ultra-performance LC (UPLC)-MS/MS. Among the synthesized reagents, PCP2 was the most efficient chiral derivatization reagent for the enantioseparation of carboxylic acid. The Rs values and the detection limits of the derivatives of non-steroidal anti-inflammatory drugs, which were selected as the representative carboxylic acids, were in the range of 2.52-6.07 and 49-260 amol, respectively. The sensitive detection of biological carboxylic acids (detection limits, 32-520 amol) was also carried out by the proposed method using PCP2 and UPLC-MS/MS. The PCP2 was applied to the determination of carboxylic acids in human saliva. Several biological carboxylic acids, such as lactic acid (LA), 3-hydroxybutylic acid, maric acid, succinic acid, ?-ketoglutalic acid, and citric acid, were clearly identified in the saliva of healthy persons and diabetic patients. Furthermore, the ratio of D-LA in diabetic patients was higher than that in normal subjects. Judging from these results, PCP2 seems to be a useful chiral derivatization reagent for the determination not only of chiral, but also achiral, carboxylic acids in real samples. PMID:24500756

Kuwabara, Tomohiro; Takayama, Takahiro; Todoroki, Kenichiro; Inoue, Koichi; Min, Jun Zhe; Toyo'oka, Toshimasa

2014-04-01

155

Comparative semiempirical, ab initio, and density functional theory study on the thermodynamic properties of linear and branched perfluoroalkyl sulfonic acids\\/sulfonyl fluorides, perfluoroalkyl carboxylic acid\\/acyl fluorides, and perhydroalkyl sulfonic acids, alkanes, and alcohols  

Microsoft Academic Search

A systematic and comprehensive semiempirical, Hartree–Fock (HF) ab initio, and B3LYP density functional theory (DFT) study was conducted on the relative thermodynamic properties of various linear and branched perfluorinated and perhydrogenated alkyl compounds. The semiempirical AM1, PM3, and PM6 methods all consistently and accurately predict that branched alkyl compounds will generally be more thermodynamically stable than their linear counterparts. In

Sierra Rayne; Kaya Forest

2010-01-01

156

Triphenylphosphine-catalysed amide bond formation between carboxylic acids and amines.  

PubMed

Unactivated carboxylic acids and amines undergo organocatalytic Ph3P/CCl4-mediated amide bond formation by employing in situ reduction of triphenylphosphine oxide to triphenylphosphine in the presence of diethoxymethylsilane and bis(4-nitrophenyl)phosphate. PMID:24752820

Lenstra, Danny C; Rutjes, Floris P J T; Mecinovi?, Jasmin

2014-06-01

157

Aerobic photooxidative cleavage of epoxides to carboxylic acids using magnesium bromide.  

PubMed

We developed an aerobic photooxidative cleavage of epoxides to carboxylic acids using a catalytic quantity of magnesium bromide and molecular oxygen as the terminal oxidant, under photoirradiation with a high-pressure mercury lamp. PMID:23178821

Yamaguchi, Tomoaki; Matsusaki, Yoko; Tada, Norihiro; Miura, Tsuyoshi; Itoh, Akichika

2013-03-01

158

New methods for the synthesis of amides of benzo[b]thiophene-2carboxylic acid  

Microsoft Academic Search

The reaction of 3-bromothiocoumarin with nitrogen bases, during which the thiocoumarin system is converted to a benzothiophene system, was studied. A new method for the synthesis of amides of benzo[b]thiophene-2-carboxylic acid is proposed.

V. L. Savel'ev; T. G. Afanas'eva; V. A. Zagorevskii

1978-01-01

159

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

PubMed

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

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

2010-10-01

160

Identification of Amides as Carboxylic Acid Surrogates for Quinolizidinone-Based M1 Positive Allosteric Modulators  

PubMed Central

Selective activation of the M1 muscarinic receptor via positive allosteric modulation represents an approach to treat the cognitive decline in patients with Alzheimer's disease. A series of amides were examined as a replacement for the carboxylic acid moiety in a class of quinolizidinone carboxylic acid M1 muscarinic receptor positive allosteric modulators, and leading pyran 4o and cyclohexane 5c were found to possess good potency and in vivo efficacy.

2012-01-01

161

Langmuir films from n -alkyl substituted 5'-phenyl- m -terphenyl carboxylic acids  

Microsoft Academic Search

We report studies on the influence of the introduction of an n-alkyl group in the 4? position of an aromatic carboxylic acid (namely 5?-phenyl- m-terphenyl-4-carboxylic acid, PTCA). For this purpose, 4?-methyl and 4?- n-propyl PTCA were synthesized and investigated at the air\\/water interface. The monolayers were characterized by measuring the surface pressure and electric surface potential upon film compression. The

Katarzyna Kita; Piotr Milart; D. A. S. Filho

162

?-Substituted alkyl carboxylic acids as antidiabetic and lipid-lowering agents  

Microsoft Academic Search

In screening experiments certain ?-substituted alkyl carboxylic acids, were found to produce an increase in insulin-stimulated 14C-acetate incorporation into triglycerides, which may indicate an improvement in the action of insulin. Antidiabetic and lipid-lowering properties in genetically diabetic ob\\/ob mice demonstrated the in vivo relevance of the insulin-potentiating effects seen in vitro. The chemical structures of the ?-substituted alkyl carboxylic acids

Kirstin Meyer; Edgar Voss; Richard Neidlein; Hans-Frieder Kühnle; Johannes Pill

1998-01-01

163

Novel 1beta-methylcarbapenems with isoxazoloethenyl moieties containing carboxylic acid sodium salt.  

PubMed

The synthesis of novel 1beta-methylcarbapenems 1a,b having sodium 5-(3- and 5-carboxylic acid)isoxazoloethenyl moieties at C-5 position of pyrrolidine ring and their biological evaluation are described. Both compounds showed potent and well-balanced antibacterial activity as well as high stability to DHP-I. The selected sodium 3-carboxylic acid derivative 1a possessed excellent DHP-I stability and advanced pharmacokinetic parameters in comparison with 2 and meropenem. PMID:15582445

Lee, Kyung Seok; Kang, Yong Koo; Yoo, Kyung Ho; Kim, Dong Chan; Shin, Kye Jung; Paik, Young-Sook; Kim, Dong Jin

2005-01-01

164

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

Microsoft Academic Search

The thermal condensation of formamide in the presence of mineral borates is reported. The products afforded are precursors\\u000a of nucleic acids, amino acids derivatives and carboxylic acids. The efficiency and the selectivity of the reaction was studied\\u000a in relation to the elemental composition of the 18 minerals analyzed. The possibility of synthesizing at the same time building\\u000a blocks of both

Raffaele Saladino; Maurizio Barontini; Cristina Cossetti; Ernesto Di Mauro; Claudia Crestini

2011-01-01

165

Comparative structure analysis of non-polar organic ferrofluids stabilized by saturated mono-carboxylic acids.  

PubMed

The structure of ferrofluids (magnetite in decahydronaphtalene) stabilized with saturated mono-carboxylic acids of different chain lengths (lauric, myristic, palmitic and stearic acids) is studied by means of magnetization analysis and small-angle neutron scattering. It is shown that in case of saturated acid surfactants, magnetite nanoparticles are dispersed in the carrier approximately with the same size distribution whose mean value and width are significantly less as compared to the classical stabilization with non-saturated oleic acid. The found thickness of the surfactant shell around magnetite is analyzed with respect to stabilizing properties of mono-carboxylic acids. PMID:19376524

Avdeev, M V; Bica, D; Vékás, L; Aksenov, V L; Feoktystov, A V; Marinica, O; Rosta, L; Garamus, V M; Willumeit, R

2009-06-01

166

Transcriptomic Analysis of the Role of Carboxylic Acids in Metabolite Signaling in Arabidopsis Leaves1[W][OA  

PubMed Central

The transcriptional response to metabolites is an important mechanism by which plants integrate information about cellular energy and nutrient status. Although some carboxylic acids have been implicated in the regulation of gene expression for select transcripts, it is unclear whether all carboxylic acids have the same effect, how many transcripts are affected, and how carboxylic acid signaling is integrated with other metabolite signals. In this study, we demonstrate that perturbations in cellular concentrations of citrate, and to a lesser extent malate, have a major impact on nucleus-encoded transcript abundance. Functional categories of transcripts that were targeted by both organic acids included photosynthesis, cell wall, biotic stress, and protein synthesis. Specific functional categories that were only regulated by citrate included tricarboxylic acid cycle, nitrogen metabolism, sulfur metabolism, and DNA synthesis. Further quantitative real-time polymerase chain reaction analysis of specific citrate-responsive transcripts demonstrated that the transcript response to citrate is time and concentration dependent and distinct from other organic acids and sugars. Feeding of isocitrate as well as the nonmetabolizable citrate analog tricarballylate revealed that the abundance of selected marker transcripts is responsive to citrate and not downstream metabolites. Interestingly, the transcriptome response to citrate feeding was most similar to those observed after biotic stress treatments and the gibberellin biosynthesis inhibitor paclobutrazol. Feeding of citrate to mutants with defects in plant hormone signaling pathways did not completely abolish the transcript response but hinted at a link with jasmonic acid and gibberellin signaling pathways. Our results suggest that changes in carboxylic acid abundances can be perceived and signaled in Arabidopsis (Arabidopsis thaliana) by as yet unknown signaling pathways.

Finkemeier, Iris; Konig, Ann-Christine; Heard, William; Nunes-Nesi, Adriano; Pham, Phuong Anh; Leister, Dario; Fernie, Alisdair R.; Sweetlove, Lee J.

2013-01-01

167

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 carboxylate which dewatered and decomposed to the desired carboxylic acid and the alkylamine or ammonia. 8 figs.

King, C.J.; Tung, L.A.

1992-07-21

168

Pancreatic Function in Carboxyl-Ester Lipase Knockout Mice  

PubMed Central

Background/Aims CEL-MODY is a monogenic form of diabetes and exocrine pancreatic insufficiency due to mutations in the carboxyl-ester lipase (CEL) gene. We aimed to investigate endocrine and exocrine pancreatic function in CEL knockout mice (CELKO). Methods A knockout mouse model with global targeted deletion of CEL was investigated physiologically and histopathologically, and compared to littermate control CEL+/+ mice at 7 and 12 months on normal chow and high-fat diets (HFD), i.e. 42 and 60% fat by calories. Results CELKO+/+ and –/– mice showed normal growth and development and normal glucose metabolism on a chow diet. Female CEL–/– mice on 60% HFD, on the other hand, had increased random blood glucose compared to littermate controls (p = 0.02), and this was accompanied by a reduction in glucose tolerance that did not reach statistical significance. In these mice there was also islet hyperplasia, however, ?- and ?-islet cells appeared morphologically normal and pancreatic exocrine function was also normal. Conclusion Although we observed mild glucose intolerance in female mice with whole-body knockout of CEL, the full phenotype of human CEL-MODY was not reproduced, suggesting that the pathogenic mechanisms involved are more complex than a simple loss of CEL function.

Vesterhus, Mette; Raeder, Helge; Kurpad, Amarnath J.; Kawamori, Dan; Molven, Anders; Kulkarni, Rohit N.; Kahn, C. Ronald; Nj?lstad, Pal Rasmus

2010-01-01

169

The Structure-Activity Relationship of an Ozonide Carboxylic Acid (OZ78) Against Fasciola hepatica  

PubMed Central

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 twenty-six new compounds administered at single 100 mg/kg oral doses to F. hepatica-infected rats, eight had statistically significant worm burden reductions, seven were partially curative, and one (acyl sulfonamide 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.

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

2010-01-01

170

Amberlyst 15: A Practical, Mild and Selective Catalyst for Methyl Esterification of Carboxylic Acids  

Microsoft Academic Search

Mild and selective methyl esterification of carboxylic acids are realized using Amberlyst 15 as acid catalyst in methanol. No race mization, epimerization or ketalization products have been observed with this method. Excellent results are obtained in the esterifications of bile acids.

Marino Petrini; Roberto Ballini; Enrico Marcantoni; Goffredo Rosini

1988-01-01

171

Ethylene biosynthesis by 1-aminocyclopropane-1-carboxylic acid oxidase: a DFT study.  

PubMed

The reaction catalyzed by the plant enzyme 1-aminocyclopropane-1-carboxylic acid oxidase (ACCO) was investigated by using hybrid density functional theory. ACCO belongs to the non-heme iron(II) enzyme superfamily and carries out the bicarbonate-dependent two-electron oxidation of its substrate ACC (1-aminocyclopropane-1-carboxylic acid) concomitant with the reduction of dioxygen and oxidation of a reducing agent probably ascorbate. The reaction gives ethylene, CO(2), cyanide and two water molecules. A model including the mononuclear iron complex with ACC in the first coordination sphere was used to study the details of O-O bond cleavage and cyclopropane ring opening. Calculations imply that this unusual and complex reaction is triggered by a hydrogen atom abstraction step generating a radical on the amino nitrogen of ACC. Subsequently, cyclopropane ring opening followed by O-O bond heterolysis leads to a very reactive iron(IV)-oxo intermediate, which decomposes to ethylene and cyanoformate with very low energy barriers. The reaction is assisted by bicarbonate located in the second coordination sphere of the metal. PMID:16933342

Bassan, Arianna; Borowski, Tomasz; Schofield, Christopher J; Siegbahn, Per E M

2006-11-24

172

Revised molecular basis of the promiscuous carboxylic acid perhydrolase activity in serine hydrolases.  

PubMed

Several serine hydrolases catalyze a promiscuous reaction: perhydrolysis of carboxylic acids to form peroxycarboxylic acids. The working hypothesis is that perhydrolases are more selective than esterases for hydrogen peroxide over water. In this study, we tested this hypothesis, and focused on L29P-PFE (Pseudomonas fluorescens esterase), which catalyzes perhydrolysis of acetic acid 43-fold faster than wild-type PFE. This hypothesis predicts that L29P-PFE should be approximately 43-fold more selective for hydrogen peroxide than wild-type PFE, but experiments show that L29P-PFE is less selective. The ratio of hydrolysis to perhydrolysis of methyl acetate at different concentrations of hydrogen peroxide fit a kinetic model for nucleophile selectivity. L29P-PFE (?(0)=170? M(-1)) is approximately half as selective for hydrogen peroxide over water than wild-type PFE (?(0)=330? M(-1)), which contradicts the working hypothesis. An alternative hypothesis is that carboxylic acid perhydrolases increase perhydrolysis by forming the acyl-enzyme intermediate faster. Consistent with this hypothesis, the rate of acetyl-enzyme formation, measured by (18)O-water exchange into acetic acid, was 25-fold faster with L29P-PFE than with wild-type PFE, which is similar to the 43-fold faster perhydrolysis with L29P-PFE. Molecular modeling of the first tetrahedral intermediate (T(d)1) suggests that a closer carbonyl group found in perhydrolases accepts a hydrogen bond from the leaving group water. This revised understanding can help design more efficient enzymes for perhydrolysis and shows how subtle changes can create new, unnatural functions in enzymes. PMID:22618813

Yin, DeLu Tyler; Kazlauskas, Romas J

2012-06-25

173

Amides in one pot from carboxylic acids and amines via sulfinylamides.  

PubMed

An efficient method has been developed for the direct amidification of carboxylic acids via sulfinylamides preformed in situ by the reaction of pure amines with prop-2-ene-1-sulfinyl chloride. The method can be applied to aliphatic acids, including pivalic acid, aromatic acids, and primary and secondary amines. It is compatible with acids bearing unprotected alcohol, phenol, and ketone moieties and applicable to the synthesis of peptides. It does not induce their ?-epimerization. PMID:24387286

Bai, Jianfei; Zambro?, Bartosz K; Vogel, Pierre

2014-01-17

174

Application of flow-injection potentiometric system for determination of total concentration of aliphatic carboxylic acids.  

PubMed

In this work, flow-injection system with potentiometric detection was tested for determination of total carboxylic acid concentration. Detection part of the examined system consists of ion-selective electrodes (ISEs) with polymer membranes of different compositions. First electrode is based on Zr(IV)-tetraphenylporphyrin as ionophore selective towards carboxylic acid anions, the membrane of second one contains only liphophilic anion exchanger - tridodecylmethylammonium chloride. Final response of the system is a result of combination of EMF signals from both electrodes. Combination of two detectors enables significant decrease of differences between potentiometric signals induced by mixtures of studied anions of various concentrations as compared to results obtained only with metalloporphyrin-based ISE. The use of anion-exchanger based detector allows for elimination of the influence of aliphatic carboxylic acids lipophilicity. Proposed potentiometric flow-injection system was employed for determination of short-chain aliphatic carboxylic acids (so-called VFA - volatile fatty acids) in samples originating from an anaerobic digester. Results obtained for these relatively complicated samples are in good agreement with results obtained with the use of reference colorimetric method. Linear response towards carboxylic acids was observed in the concentration range of 10(-4) to 10(-2)mold m(-3), with the slopes in the range of -110 to -150 mV dec(-1) (for acetate(-) and butyrate(-), respectively). System enables for determination of about 6 samples per hour. Life time of ISEs average about 2 months. PMID:21872056

Mroczkiewicz, Monika; Górski, ?ukasz; Zamojska-Jaroszewicz, Anna; Szewczyk, Krzysztof W; Malinowska, El?bieta

2011-09-30

175

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

Microsoft Academic Search

The application of various hydrophilic cation-exchange resins for high-performance liquid chromatography (sulfonated silica gel: TSKgel SP-2SW, carboxylated silica gel: TSKgel CM-2SW, sulfonated polymethacrylate resin: TSKgel SP-5PW, carboxylated polymethacrylate resins: TSKgel CM-5PW and TSKgel OA-Pak A) as stationary phases in ion-exclusion chromatography for C1–C7 aliphatic carboxylic acids (formic, acetic, propionic, butyric, isovaleric, valeric, isocaproic, caproic, 2-methylhexanoic and heptanoic acids) and benzenecarboxylic

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

2003-01-01

176

Single amino acids in the carboxyl terminal domain of aquaporin-1 contribute to cGMP-dependent ion channel activation  

Microsoft Academic Search

BACKGROUND: Aquaporin-1 (AQP1) functions as an osmotic water channel and a gated cation channel. Activation of the AQP1 ion conductance by intracellular cGMP was hypothesized to involve the carboxyl (C-) terminus, based on amino acid sequence alignments with cyclic-nucleotide-gated channels and cGMP-selective phosphodiesterases. RESULTS: Voltage clamp analyses of human AQP1 channels expressed in Xenopus oocytes demonstrated that the nitric oxide

Daniela Boassa; Andrea J Yool

2003-01-01

177

Diorganotin(IV) Derivatives of Furoic Acid and Pyrrole2-carboxylic Acid  

Microsoft Academic Search

Two series of complexes of the general formulae [R2 SnO2 CR?]2O and R2Sn(O2CR?)2 (R = CH3, n-O4H9, n-C8H17 or C6H5CH2 and R? = 2-furan or 2-pyrrole), have been prepared by the reaction of furoic or pyrrole-2-carboxylic acid with diorganotin(IV) oxides in 1:1 and 2:1 (ligand:metal) molar ratio, respectively. These complexes have been characterized by elemental analyses, molecular weight determinations, molar

G. K. Sandhu; N. S. Boparai; S. S. Sandhu Jr

1980-01-01

178

The effects of borate minerals on the synthesis of nucleic acid bases, amino acids and biogenic carboxylic acids from formamide.  

PubMed

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. PMID:21424401

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

2011-08-01

179

Direct hydrogenation of aromatic carboxylic acids to their corresponding aldehydes with zinc oxide catalysts  

Microsoft Academic Search

High yields of aromatic aldehydes were obtained by direct hydrogenation of aromatic carboxylic acids over different zinc oxide catalysts having distinctive surface properties. The reaction is carried out in a fixed bed reactor in gas phase at 330–350°C. High selectivity of 96% of benzaldehyde at 100% conversion of benzoic acid was achieved using a zinc oxide catalyst having very weakly

W. F. Hölderich; J. Tjoe

1999-01-01

180

Synthesis, crystal growth and characterization of L-pyrrolidone-2-carboxylic acid (L-PCA) crystals  

NASA Astrophysics Data System (ADS)

A novel organic nonlinear optical crystal L-pyrrolidone-2-carboxylic acid (L-PCA) has been found to be phase matchable for second harmonic generation (SHG) and sum frequency mixing down to the UV range to room temperature. Single crystals of L-PCA were grown by slow evaporation of the solvent at ambient temperature. L-PCA single crystals upto dimensions of 1.2×1.8×0.3 cm 3 have been grown. SHG was demonstrated using Q-switched Nd:YAG laser. Powder X-ray diffraction pattern has been obtained using Cu K ? line (1.5418 Å). The lattice parameters have been calculated and it agrees well with the reported values. FTIR spectra shows the stretching and vibrational modes and presence of carboxyl functional groups in the compound. Dielectric studies have been carried out for the samples at different frequencies from 5 kHz to 1 MHz. Scanning Electron Microscopy studies has been carried out on the surface of the grown crystals to investigate the nature of defects in the crystal surface. Laser damage threshold value of 17 GW/cm 2 has been determined using Q-switched Nd:YAG laser operating at 1064 nm and with 20 ns pulses in single shot mode.

Boomadevi, S.; Dhanasekaran, R.

2004-01-01

181

Enantiomer analysis of chiral carboxylic acids by AIE molecules bearing optically pure aminol groups  

Microsoft Academic Search

Pure enantiomers of carboxylic acids are a class of important biomolecules, chiral drugs, chiral reagents, etc. Analysis of the enantiomers usually needs expensive instrument or complex chiral receptors. However, to develop simple and reliable methods for the enantiomer analysis of acids is difficult. In this paper, chiral recognition of 2,3-dibenzoyltartaric acid and mandelic acid was first carried out by aggregation-induced

Yan-Song Zheng; Yu-Jian Hu; Dong-Mi Li; Yi-Chang Chen

2010-01-01

182

Deposition of thin films of organic-inorganic hybrid materials based on aromatic carboxylic acids by atomic layer deposition.  

PubMed

Thin films of organic-inorganic hybrid materials have been grown by the atomic layer deposition (ALD) technique, using trimethylaluminium (TMA) and aromatic carboxylic acids such as 1,2-benzene dicarboxylic acid, 1,3-benzene dicarboxylic acid, 1,4-benzene dicarboxylic acid, 1,3,5-benzene tricarboxylic acid, 1,2,4,5-benzene tetracarboxylic acid as precursors. Growth rates as function of temperature show that all systems, with the exception of the benzoic acid-TMA system, possess ALD-windows and provides growth rates in the range of 0.25-1.34 nm/cycle. X-ray diffraction studies of the as-deposited films reveal their amorphous character, which is also supported by very low surface roughness as measured by atomic force microscopy. As-deposited films were investigated by Fourier Transform Infrared Spectroscopy proving that the deposited films are of a hybrid character. PMID:21038067

Klepper, Karina Barnholt; Nilsen, Ola; Fjellvåg, Helmer

2010-12-28

183

Functional and anionic cellulose-interacting polymers by selective chemo-enzymatic carboxylation of galactose-containing polysaccharides.  

PubMed

Carboxylated, anionic polysaccharides were selectively prepared using a combination of enzymatic and chemical reactions. The galactose-containing polysaccharides studied were spruce galactoglucomannan, guar galactomannan, and tamarind galactoxyloglucan. The galactosyl units of the polysaccharides were first oxidized with galactose oxidase (EC 1.1.3.9) and then selectively carboxylated, resulting in the galacturonic acid derivatives with good conversion and yield. The degrees of oxidation (DO) of the products were determined by gas chromatography-mass spectrometry (GC-MS). A novel feasible electrospray ionization-mass spectrometry (ESI-MS) method was also developed for the determination of DO. The solution properties and charge densities of the products were investigated. The interaction of the products with cellulose was studied by two methods, bulk sorption onto bleached birch kraft pulp and adsorption onto nanocellulose ultrathin films by quartz crystal microbalance with dissipation (QCM-D). To study the effect of the location of the carboxylic acid groups on the physicochemical properties, polysaccharides were also oxidized by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated reaction producing polyuronic acids. The chemo-enzymatically oxidized galacturonic polysaccharides with an unmodified backbone had a better ability to interact with cellulose than the TEMPO-oxidized products. The selectively carboxylated polysaccharides can be further exploited, as such, or in the targeted functionalization of cellulose surfaces. PMID:22724576

Parikka, Kirsti; Leppänen, Ann-Sofie; Xu, Chunlin; Pitkänen, Leena; Eronen, Paula; Osterberg, Monika; Brumer, Harry; Willför, Stefan; Tenkanen, Maija

2012-08-13

184

The ground-state tunneling splitting of various carboxylic acid dimers  

NASA Astrophysics Data System (ADS)

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 N,N-dimethyl carbamic acid) and their fully deuterated analogs. The calculated splittings range from 5.3e-4 to 0.13 cm-1 (for the deuterated species from 2.8e-7 to 3.3e-4 cm-1), thus indicating a strong substituent dependence of the splitting, which varies by more than two orders of magnitude. One reason for differences in the splittings could be addressed to different barriers heights, which vary from 6.3 to 8.8 kcal/mol, due to different mesomeric stabilization of the various transition states. The calculated splittings were compared to available experimental data and good agreement was found. A correlation could be found between the tunneling splitting and the energy barrier of the double proton transfer, as the splitting increases with increased strength of the hydrogen bonds. From this correlation an empirical formula was derived, which allows the prediction of the ground-state tunneling splitting of carboxylic acid dimers at a very low cost and the tunneling splittings for parahalogen substituted benzoic acid dimers is predicted.

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

2004-01-01

185

The ground-state tunneling splitting of various carboxylic acid dimers.  

PubMed

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 N,N-dimethyl carbamic acid) and their fully deuterated analogs. The calculated splittings range from 5.3e-4 to 0.13 cm(-1) (for the deuterated species from 2.8e-7 to 3.3e-4 cm(-1)), thus indicating a strong substituent dependence of the splitting, which varies by more than two orders of magnitude. One reason for differences in the splittings could be addressed to different barriers heights, which vary from 6.3 to 8.8 kcal/mol, due to different mesomeric stabilization of the various transition states. The calculated splittings were compared to available experimental data and good agreement was found. A correlation could be found between the tunneling splitting and the energy barrier of the double proton transfer, as the splitting increases with increased strength of the hydrogen bonds. From this correlation an empirical formula was derived, which allows the prediction of the ground-state tunneling splitting of carboxylic acid dimers at a very low cost and the tunneling splittings for parahalogen substituted benzoic acid dimers is predicted. PMID:15267897

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

2004-01-01

186

4-Quinolone-3-carboxylic acids as cell-permeable inhibitors of protein tyrosine phosphatase 1B.  

PubMed

Protein tyrosine phosphatase 1B is a negative regulator in the insulin and leptin signaling pathways, and has emerged as an attractive target for the treatment of type 2 diabetes and obesity. However, the essential pharmacophore of charged phosphotyrosine or its mimetic confer low selectivity and poor cell permeability. Starting from our previously reported aryl diketoacid-based PTP1B inhibitors, a drug-like scaffold of 4-quinolone-3-carboxylic acid was introduced for the first time as a novel surrogate of phosphotyrosine. An optimal combination of hydrophobic groups installed at C-6, N-1 and C-3 positions of the quinolone motif afforded potent PTP1B inhibitors with low micromolar IC50 values. These 4-quinolone-3-carboxylate based PTP1B inhibitors displayed a 2-10 fold selectivity over a panel of PTP's. Furthermore, the bidentate inhibitors of 4-quinolone-3-carboxylic acids conjugated with aryl diketoacid or salicylic acid were cell permeable and enhanced insulin signaling in CHO/hIR cells. The kinetic studies and molecular modeling suggest that the 4-quinolone-3-carboxylates act as competitive inhibitors by binding to the PTP1B active site in the WPD loop closed conformation. Taken together, our study shows that the 4-quinolone-3-carboxylic acid derivatives exhibit improved pharmacological properties over previously described PTB1B inhibitors and warrant further preclinical studies. PMID:24906513

Zhi, Ying; Gao, Li-Xin; Jin, Yi; Tang, Chun-Lan; Li, Jing-Ya; Li, Jia; Long, Ya-Qiu

2014-07-15

187

Enantiomer analysis of chiral carboxylic acids by AIE molecules bearing optically pure aminol groups.  

PubMed

Pure enantiomers of carboxylic acids are a class of important biomolecules, chiral drugs, chiral reagents, etc. Analysis of the enantiomers usually needs expensive instrument or complex chiral receptors. However, to develop simple and reliable methods for the enantiomer analysis of acids is difficult. In this paper, chiral recognition of 2,3-dibenzoyltartaric acid and mandelic acid was first carried out by aggregation-induced emission molecules bearing optically pure aminol group, which was easily synthesized. The chiral recognition is not only seen by naked eyes but also measured by fluorophotometer. The difference of fluorescence intensity between the two enantiomers of the acids aroused by the aggregation-induced emission molecules was up to 598. The chiral recognition could be applied to quantitative analysis of enantiomer content of chiral acids. More chiral AIE amines need to be developed for enantiomer analysis of more carboxylic acids. PMID:20006116

Zheng, Yan-Song; Hu, Yu-Jian; Li, Dong-Mi; Chen, Yi-Chang

2010-01-15

188

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

189

Enantioselective kinetic resolution of phenylalkyl carboxylic acids using metagenome-derived esterases.  

PubMed

Enantiomerically pure ?-arylalkyl carboxylic acids are important synthetic intermediates for the preparation of a wide range of compounds with biological and pharmacological activities. A library of 83 enzymes isolated from the metagenome was searched for activity in the hydrolysis of ethyl esters of three racemic phenylalkyl carboxylic acids by a microtiter plate-based screening using a pH-indicator assay. Out of these, 20 enzymes were found to be active and were subjected to analytical scale biocatalysis in order to determine their enantioselectivity. The most enantioselective and also enantiocomplementary biocatalysts were then used for preparative scale reactions. Thus, both enantiomers of each of the three phenylalkyl carboxylic acids studied could be obtained in excellent optical purity and high yields. PMID:21255306

Fernández-Álvaro, Elena; Kourist, Robert; Winter, Julia; Böttcher, Dominique; Liebeton, Klaus; Naumer, Christian; Eck, Jürgen; Leggewie, Christian; Jaeger, Karl-Erich; Streit, Wolfgang; Bornscheuer, Uwe T

2010-01-01

190

Asynchronous kernel analysis for binary mixture solutions of ethanol and carboxylic acids  

NASA Astrophysics Data System (ADS)

A quantitative index to reveal physical interactions between ethanol and carboxylic acids are derived by using self-modeling curve resolution (SMCR) kernel. SMCR is a family of chemometrics technique to deconvolute multi-component spectra into individual chemical species. By combining two-dimensional (2D) correlation spectroscopy and SMCR, a quantitative index called SMCR kernel is obtained to estimate the degree of synchronous and asynchronous correlations among chemical species. Relative relationships between ethanol and several carboxylic acids are derived from a series of SMCR kernel matrices of the binary mixture solutions. SMCR is applied to near-infrared (NIR) spectra of the mixture solutions, and several asynchronous kernel matrices are obtained. Comparison of the asynchronous kernel matrices reveals quantitative measure among hydrogen bonding of carboxylic acids strongly related to their molecular structures.

Shinzawa, Hideyuki; Iwahashi, Makio; Noda, Isao; Ozaki, Yukihiro

2008-07-01

191

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

192

Ethylene Production and 1-Aminocyclopropane-1-Carboxylic Acid Conjugation in Thermoinhibited Cicer arietinum L. Seeds 1  

PubMed Central

The effect of supraoptimal temperatures (30°C, 35°C) on germination and ethylene production of Cicer arietinum (chick-pea) seeds was measured. Compared with a 25°C control, these temperatures inhibited both germination and ethylene production. The effect of supraoptimal temperatures could be alleviated by treating the seeds with ethylene. It was concluded that one effect of high temperature on germination was due to its negative effect on ethylene production. This inhibitory effect of high temperature was due to increased conjugation of 1-aminocyclopropane-1-carboxylic acid to 1-(malonylamino)cyclopropane-1-carboxylic acid and to an inhibition of ethylene-forming enzyme activity.

Gallardo, Mercedes; Delgado, Maria del Mar; Sanchez-Calle, Isabel Maria; Matilla, Angel Jesus

1991-01-01

193

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

2013-10-15

194

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

195

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

EPA Science Inventory

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

196

Effect of thermochemical pretreatment on sewage sludge and its impact on carboxylic acids production  

Microsoft Academic Search

This paper investigates the potential of converting sewage sludge into a useful product, namely carboxylic acids. To potentially enhance acid yields, the effect of pretreatment using 0.3g lime\\/g dry biomass and water at 100°C for 10–240min was studied. The pretreated sludges were anaerobically fermented to mixed-acids using a mixed culture of microorganisms; methanogens were suppressed using iodoform. Batch fermentations were

Hema Rughoonundun; Cesar Granda; Romeela Mohee; Mark T. Holtzapple

2010-01-01

197

New macrolides and furan carboxylic acid derivative from the sponge-derived fungus Cladosporium herbarum.  

PubMed

Bioassay-guided fractionation of organic extracts of Cladosporium herbarum, isolated from the marine sponge Callyspongia aerizusa, yielded two new macrolide metabolites: pandangolide 3 and 4 (1 and 2) and the known fungal metabolites pandangolide 2 (3), cladospolide B (4), and iso-cladospolide B (5). Also isolated were the antimicrobially active (against Bacillus subtilis and Staphylococcus aureus) furan carboxylic acids: Sumiki's acid (6) and its new derivative, acetyl Sumiki's acid (7). All structures were elucidated by spectroscopic methods. PMID:11325242

Jadulco, R; Proksch, P; Wray, V; Sudarsono; Berg, A; Gräfe, U

2001-04-01

198

Structural Modification Influences the Characteristics of Langmuir Monolayers from Aromatic Carboxylic Acids.  

PubMed

The molecular organization of purely aromatic, polyphenyl carboxylic acids, as Langmuir monolayers at the air/water interface, has been investigated by means of surface pressure and electric surface potential measurements upon film compression. The monolayer characteristics of the basic compound, a symmetrical triphenylbenzene (5'-phenyl-m-terphenyl) ring with a carboxylic group at the 4 position (namely 5'-phenyl-1,1' : 3',1"-terphenyl-4-carboxylic acid), are compared with those of its derivatives containing hydrophilic (nitro) or hydrophobic (phenyl) substituents. The nature of the substituent as well as its position (2' or 4') has a profound influence on the monolayer properties. The results are discussed in view of molecular orientation deduced from values of effective dipole moments. Copyright 2001 Academic Press. PMID:11397060

Dynarowicz-L&acedil;tka, P.; Kita, K.; Milart, P.; Dhanabalan, A.; Cavalli, A.; da Silva Filho, D. A.; Oliveira, O. N.

2001-07-01

199

Cofactor Balance by Nicotinamide Nucleotide Transhydrogenase (NNT) Coordinates Reductive Carboxylation and Glucose Catabolism in the Tricarboxylic Acid (TCA) Cycle*?  

PubMed Central

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

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

2013-01-01

200

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

PubMed

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

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

2013-05-01

201

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

PubMed

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

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

2008-11-18

202

Interconversion of biologically important carboxylic acids by radiation  

NASA Technical Reports Server (NTRS)

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

Negron-Mendoza, A.; Ponnamperuma, C.

1978-01-01

203

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

204

Complexation of lanthanides with crown ether carboxylic acids and its applications in analytical chemistry  

SciTech Connect

The extraction characteristics of trivalent lanthanides by three crown ether carboxylic acids of different lipophilicities were investigated. Extraction was found to be independent of anions and strongly dependent on pH. Quantitative extraction of lanthanides was observed in the pH range of 6-8 by all three crown ether carboxylic acids: sym-dibenzo-16-crown-5 oxyacetic acid (I), 2-(sym-dibenzo-16-crown-5-oxy)hexanoic acid (II), and 2-(sym-dibenzo-16-crown-5-oxy)stearic acid (III). Results of competitive experiments indicated that this extraction system was highly selective for lanthanides relative to other major ionic species, such as the alkali metal ions, the alkaline earth metal ions, and transition metal ions. The extraction method has been applied to the determination of low levels of lanthanides in natural waters and in biological materials. Sym-dibenzo-16-crown-5-oxyacetic acid had insufficient lipophilicity to remain in the organic phase when the pH of the aqueous phase was high and the organic to aqueous phase ratio was small. Extraction efficiency increased with the increasing lipophilicity of the crown ether carboxylic acids, which followed the order I < II < III. Using 2-(sym-dibenzo-16-crown-5-oxy)hexanoic acid as an extractant, lanthanides in some natural water and biological samples were determined by neutron activation analysis (NAA). Uranium can also be extracted by the three crown ether carboxylic acids with high efficiency. 2-(Sym-dibenzo-16-crown-5-oxy)hexanoic acid was utilized to extract uranyl ions from seawater and river water samples into chloroform, followed by back-extraction with a pH 2 nitric acid solution prior to NAA. The extraction method combined with NAA provides a sensitive method for the determination of uranium in natural waters.

Tang, Jian.

1989-01-01

205

A lead-207 nuclear magnetic resonance study of the complexation of lead by carboxylic acids and aminocarboxylic acids  

NASA Astrophysics Data System (ADS)

The complexation of Pb(II) by carboxylic acids and aminocarboxylic acids was studied by 207Pb NMR. The results indicate that the 207Pb chemical shift provides a sensitive probe of the aqueous coordination chemistry of Pb(II). A single, exchange-averaged resonance is observed for lead in solutions containing Pb(NO 3) 2 and pivalic acid, acetic acid, formic acid, or chloroacetic acid, the chemical shift of which is sensitive to the Pb(NO 3) 2 to carboxylic acid ratio and to solution pH. Formation constants for the Pb(II)-carboxylate complexes were determined by fitting the chemical shift data to a model involving the complexes and ligand protonation. Chemical shift data for solutions containing Pb(NO 3) 2 and glycine, histidine, or glycylglycine indicate complexation of Pb(II) by the zwitterionic forms of these ligands. Formation constants for these complexes, which are difficult to study by other methods, were also determined from the chemical shift data. Complexation of Pb(II) by ethylenediaminetetraacetic acid, N-hydroxyethylethylenediaminetriacetic acid, nitrilotriacetic acid, and N-methyliminodiacetic acid causes a large deshielding of the 207Pb nucleus, e.g., the resonance for the ethylenediaminetetraacetic acid complex is deshielded by 2350 ppm. The chemical shift of the lead in these complexes is sensitive to protonation of the complex and to the formation of mixed complexes containing hydroxide ion.

Nakashima, Thomas T.; Rabenstein, Dallas L.

206

Hydrogen bond patterns in solid state carboxylic acids. Vibrational study of the hydrogen bond patterns in oxamic, malonamic and succinamic acid  

NASA Astrophysics Data System (ADS)

The vibrational spectra of oxamic, malonamic and succinamic acid are reported. Although these molecules exhibit identical functional groups, their solid state hydrogen bond patterns can be divided in two different types, which can be clearly distinguished through the combination of infrared and Raman spectroscopy at variable temperatures and through the vibrational behaviour of the deuterated compounds. Oxamic acid behaves as a linear hydrogen bonded polymer with cyclic acid-acid and cyclic amide-amide dimers while the other discussed carboxylic acid derivatives exhibit a cyclic acid-amide hydrogen bond pattern. A model is proposed to investigate the peculiar vibrational behaviour of oxamic acid theoretically. Spectroscopic studies of the cyclic heterogenic acid-amide hydrogen bond pattern are studied for the first time.

Wolfs, Ilse; Desseyn, Herman O.

1995-09-01

207

Gas chromatographic analysis of C 1 ?C 22 carboxylic acids esterified in aqueous solutions as n-propyl esters  

Microsoft Academic Search

C1?C22 carboxylic acids have been esterified in aqueous solution with n-propanol. Gas chromatographic analyses have been performed from a single chromatogram. It has been proven that esterification in the concentration range of [H2O]\\/[n-PrOH]=0.022–8.45 can be utilized for the quantitative determination of these carboxylic acids.

I. Molnár-Perl; M. Morvai

1986-01-01

208

Functionalised carboxylic acids in atmospheric particles: An annual cycle revealing seasonal trends and possible sources  

NASA Astrophysics Data System (ADS)

Carboxylic acids represent a major fraction of the water soluble organic carbon (WSOC) in atmospheric particles. Among the particle phase carboxylic acids, straight-chain monocarboxylic acids (MCA) and dicarboxylic acids (DCA) with 2-10 carbon atoms have extensively been studied in the past. However, only a few studies exist dealing with functionalised carboxylic acids, i.e. having additional hydroxyl-, oxo- or nitro-groups. Regarding atmospheric chemistry, these functionalised carboxylic acids are of particular interest as they are supposed to be formed during atmospheric oxidation processes, e.g. through radical reactions. Therefore they can provide insights into the tropospheric multiphase chemistry. During this work 28 carboxylic acids (4 functionalised aliphatic MCAs, 5 aromatic MCAs, 3 nitroaromatic MCAs, 6 aliphatic DCAs, 6 functionalised aliphatic DCAs, 4 aromatic DCAs) were quantitatively determined in 256 filter samples taken at the rural research station Melpitz (Saxony, Germany) with a PM10 Digitel DHA-80 filter sampler. All samples were taken in 2010 covering a whole annual cycle. The resulting dataset was examined for a possible seasonal dependency of the acid concentrations. Furthermore the influence of the air mass origin on the acid concentrations was studied based on a simple two-sector classification (western or eastern sector) using a back trajectory analysis. Regarding the annual average, adipic acid was found to be the most abundant compound with a mean concentration of 7.8 ng m-3 followed by 4-oxopimelic acid with 6.1 ng m-3. The sum of all acid concentrations showed two maxima during the seasonal cycle; one in summer and one in winter, whereas the highest overall acid concentrations were found in summer. In general the target acids could be divided into two different groups, where one group has its maximum concentration in summer and the other group during winter. The first group contains all investigated aliphatic mono- and dicarboxylic acids. The high concentrations in summer could lead to the conclusion that these acids are mostly formed during photochemical processes in the atmosphere. However, the concentrations in autumn were often exceeded by the ones in winter. Therefore probably other sources beside photochemical processes have to be considered. The second group consists of aromatic compounds. Because of the high concentrations in winter it can be concluded that photochemical formation plays a minor role and primary emission sources e.g., wood combustion are likely. Further evidence in determining sources of the carboxylic acids could be obtained from the air mass origin. In general, air masses transported from East have a more anthropogenic influence than the air mass inflow from West. For all aromatic carboxylic acids higher concentrations were determined during eastern inflow, indicating anthropogenic sources. This presumption is supported by high correlations with the elemental carbon (EC). Regarding the aliphatic carboxylic there is one group with higher concentrations when the air mass is transported from West and one with higher concentrations when air mass is transported from East. In summary the findings of this study reveal a clear difference in the seasonal trends of the single target acids indicating a variety of different sources.

Teich, Monique; van Pinxteren, Dominik; Herrmann, Hartmut

2013-04-01

209

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

210

The development of new carboxylic acid-based MMP inhibitors derived from a cyclohexylglycine scaffold.  

PubMed

A series of carboxylic acids was prepared based on cyclohexylglycine scaffolds and tested for potency as matrix metalloproteinase (MMP) inhibitors. Detailed SAR for the series is reported for five enzymes within the MMP family, and a number of inhibitors such as compound 18 display low nanomolar potency for MMP-2 and MMP-13, while selectively sparing MMP-1 and MMP-7. PMID:11454461

Tullis, J S; Laufersweiler, M J; VanRens, J C; Natchus, M G; Bookland, R G; Almstead, N G; Pikul, S; De, B; Hsieh, L C; Janusz, M J; Branch, T M; Peng, S X; Jin, Y Y; Hudlicky, T; Oppong, K

2001-08-01

211

The development of new carboxylic acid-based MMP inhibitors derived from a cyclohexylglycine scaffold  

Microsoft Academic Search

A series of carboxylic acids was prepared based on cyclohexylglycine scaffolds and tested for potency as matrix metalloproteinase (MMP) inhibitors. Detailed SAR for the series is reported for five enzymes within the MMP family, and a number of inhibitors such as compound 18 display low nanomolar potency for MMP-2 and MMP-13, while selectively sparing MMP-1 and MMP-7.

Joshua S. Tullis; Matthew J. Laufersweiler; John C. VanRens; Michael G. Natchus; Roger G. Bookland; Neil G. Almstead; Stanislaw Pikul; Biswanath De; Lily C. Hsieh; Michael J. Janusz; Todd M. Branch; Sean X. Peng; Yingkun Y. Jin; Tomas Hudlicky; Kofi Oppong

2001-01-01

212

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

213

Antiallergic agents. IV - Substituted 2-benzylidene-3(2H)-benzofuranone-5-carboxylic acids.  

PubMed

A series of substituted 2-benzylidene-3(2H)-benzofuranone-5-carboxylic acids were synthetized and tested for antiallergic activity by the passive cutaneous anaphylactic reaction in the rat. Many compounds display an antiallergic activity comparable to that of disodium chromoglycate when administered parenterally: in addition some derivatives are effective when given by mouth. PMID:7450052

Doria, G; Romeo, C; Corno, M L; Cadelli, G

1980-08-01

214

Langmuir Monolayers from Substituted 5?Phenyl m-terphenyl Carboxylic Acids  

Microsoft Academic Search

A series of 5?-phenyl-m-terphenyl carboxylic acid (PTCA) derivatives with methyl, chloro, and fluoro substituents at both side phenyl rings have been synthesized and characterized as Langmuir monolayers at the air\\/water interface. A comparative analysis, based on the surface pressure and electric surface potential measurements under a variety of experimental conditions, is complemented with BAM images.

P Dynarowicz-?; K Kita; P Milart; A Dhanabalan; A Cavalli; O. N Oliveira

2001-01-01

215

A catalyst system for the formation of amides by reaction of carboxylic acids with blocked isocyanates  

Microsoft Academic Search

A catalyst for the reaction of blocked isocyanates (blocking agent diisopropylamine and dimethyl pyrazole) and carboxylic acids was identified. Magnesium and in some instances calcium salts proved to be highly active as catalyst. This reaction gives amides in quantitative yield and excellent selectivity and is suitable for coating and general chemical purposes.

R. Gertzmann; C. Gürtler

2005-01-01

216

Fluorosteroids. V. Preparation and biological activity of 6?-fluoro-17?-carboxylic acids of the androstane series  

Microsoft Academic Search

During the study of the properties of the compounds obtained in the course of the synthesis of fluocinnolone acetonide, we found that 20-keto-21-hydroxypregnanes with general formula I are oxidized in an alkaline medium by atmospheric oxygen to form 17~-carboxylic acids with structure II. oKzolt OOOlt oo

T. I. Gusarova; G. S. Grinenko; M. L. Gerasimova; A. I. Terekhina; G. I. Gritsina; O. S. Anisimova; G. A. Klubnichkina; V. M. Ryzhkova

1980-01-01

217

Structural symmetry of the metabolic reaction network. I. Carboxylic acid metabolism  

Microsoft Academic Search

A new approach to systematization of the information on metabolism, based on the symmetry observed in the pattern of the metabolic reaction network, is discussed. A theoretical substantiation of symmetry existence is given. A symmetrical metabolic scheme is developed for metabolism of carboxylic acids. The symmetry of the metabolic reaction network can be used for systematization of biochemical, physiological, medical

Alexander G. Malygin

2000-01-01

218

New Pd-catalyzed selective reduction of carboxylic acids to aldehydes.  

PubMed

A catalyst generated in situ from palladium acetate and tricyclohexylphosphine efficiently catalyzes the reduction of carboxylic acids with sodium hypophosphite in the presence of pivalic anhydride to give aldehydes with high selectivity. The low cost and convenient handling of the reagents makes this process a valuable alternative to hydrogenations and metal hydride reductions. PMID:12123003

Goossen, Lukas J; Ghosh, Keya

2002-04-21

219

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

220

Factors influencing the rate of non-enzymatic activation of carboxylic and amino acids by ATP  

NASA Technical Reports Server (NTRS)

The nonenzymatic formation of adenylate anhydrides of carboxylic and amino acids is discussed as a necessary step in the origin of the genetic code and protein biosynthesis. Results of studies are presented which have shown the rate of activation to depend on the pKa of the carboxyl group, the pH of the medium, temperature, the divalent metal ion catalyst, salt concentration, and the nature of the amino acid. In particular, it was found that of the various amino acids investigated, phenylalanine had the greatest affinity for the adenine derivatives adenosine and ATP. Results thus indicate that selective affinities between amino acids and nucleotides were important during prebiotic chemical evolution, and may have played a major role in the origin of protein synthesis and genetic coding.

Mullins, D. W., Jr.; Lacey, J. C., Jr.

1981-01-01

221

The inhibition effect of amino acids and hydroxy carboxylic acids on pitting corrosion of aluminum alloy 7075  

Microsoft Academic Search

Pitting corrosion of aluminum alloy 7075 in 0.05 M NaCl solution at pH values of 4, 5, 7 and 8 were examined by potentiostatic method. It was found that addition of 10?2 M hydroxy carboxylic acids or amino acids to NaCl solutions cause shifting of Epit values to noble directions. Amino acids are more effective in shifting Epit values to

G. Bereket; A. Yurt

2001-01-01

222

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

223

Microstructure and Mechanical Properties of Carboxylated Carbon Nanotubes\\/Poly(L-lactic acid) Composite  

Microsoft Academic Search

Poly(L-lactic acid) (PLLA)\\/MWNTs composites were prepared by mixing solubilized PLLA with solutions of MWNTs treated by four kind of acids. Fourier transform infrared (FT-IR) spectra revealed that carboxyl groups were grafted to the surface of MWNTs. The water solubility showed that the MWNTs treated by HNO 3\\/H2O2 and HNO3\\/H2SO 4 could suspend in the air at room temperature for more

Jiangtao Feng; Jiehe Sui; Wei Cai; Zhiyong Gao

2008-01-01

224

Synthesis of new 3-arylindole-2-carboxylates using ?,?-diaryldehydroamino acids as building blocks. Fluorescence studies  

Microsoft Academic Search

Several new methyl 3-arylindole-2-carboxylates were synthesized in high yields using a metal assisted [Pd(OAc)2\\/Cu(OAc)2, DMF, 130°C] intramolecular C–N cyclization of ?,?-diaryldehydroamino acids, developed by us, thus extending the scope of this reaction. The latter were obtained by a bis-Suzuki coupling of a ?,?-dibromodehydroalanine with arylboronic acids bearing either electron-donating groups (EDGs) or electron-withdrawing groups (EWGs). We were able to establish

Maria-João R. P. Queiroz; Ana S. Abreu; Elisabete M. S. Castanheira; Paula M. T. Ferreira

2007-01-01

225

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

Microsoft Academic Search

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

Aynur Senol; Umur Dramur

2004-01-01

226

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

Microsoft Academic Search

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

R. Jason Herr

2002-01-01

227

A new reverse worm-like micellar system from a lecithin, multivalent carboxylic acid and oil mixture.  

PubMed

We developed new lecithin organogels composed of reverse worm-like micelles with lecithin/multivalent carboxylic acid/oil systems, and discussed their phase behavior and rheological properties. The most important findings in this study are the following. From a screening test of many carboxylic acids for gelation, it was found that the number and position of the carboxyl groups of the multivalent carboxylic acids are the determinants for the formation of reverse worm-like micelles, and appropriate carboxylic acids such as citric acid and 1,2,3-propanetricarboxylic acid can change the lecithin/oil solution into a gel. Furthermore, upon addition of these carboxylic acids, the zero-shear viscosity of solutions increased monotonically until phase separation or cloudiness occurred. For example, when citric acid was used, the maximum zero-shear viscosity of the solution was 70,000,000 times larger than that of n-decane. From studies on the scaling of rheological parameters, it was found that further addition of multivalent carboxylic acids not only induced the formation of linear reverse worm-like micelles but also brought about their branching. PMID:23684226

Imai, Miko; Hashizaki, Kaname; Taguchi, Hiroyuki; Saito, Yoshihiro; Motohashi, Shigeyasu

2013-08-01

228

[Spasm-activity caused by interaction of benzo- and naphtho-1.3-dioxole-carboxylic acids of mice (author's transl)].  

PubMed

We describe the preparation of 4,7-dimethyl-benzo[1,3]dioxole-5-carboxylic acid (7 d), 5,6-dimethyl-benzo [1,3]dioxole-4-carboxylic acid (14), 6,7-dimethoxy-benzo [1,4]dioxane-5-carboxylic acid (16), 7,8-dimethyl-3,4-dihydro-2 H-benzo [1,5]dioxepin-6-carboxylic acid (17), and of 8,9-dimethyl-2,3,4,5-tetrahydro-benzo [1,6]dioxocin-carboxylic acid (18) by reaction of the lithiumcompounds with carbondioxide. For testing the spasm-activity of benzo [1,3]dioxole-5-carboxylic acids (Table I), benzo [1,3]dioxole-4-carboxylic acids (Table II), and naphtho [1,3]dioxole-carboxylic acids (Table III) these componds were orally given to mice. PMID:7405360

Dallacker, F; Reichrath, G; Schnackers, G

1980-01-01

229

Synthesis and stereochemistry of bilirubin analogs lacking carboxylic acids  

Microsoft Academic Search

Bilirubin analogs with propionic acid groups replaced by sec-butyl (1), 3-acetoxy-1-methylpropyl (2) or 3-acetamido-1-methylpropyl (3) were synthesized in enantiopure form and known absolute configuration. Although there are no propionic acid groups to act in stabilizing folded, ridge-tile conformations, the (S) stereogenic centers induce the pigments to adopt a left-handed (M) helicity — as evidenced by exciton circular dichroism spectra.

Stefan E. Boiadjiev; William P. Pfeiffer; David A. Lightner

1997-01-01

230

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

231

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

PubMed

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

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

2013-08-20

232

Water-induced coacervation of alkyl carboxylic acid reverse micelles: phenomenon description and potential for the extraction of organic compounds.  

PubMed

Coacervates made up of alkanoic (C8-C16) and alkenoic (C18) acid reverse micelles were described for the first time, and their potential for the extraction of organic compounds prior to liquid chromatography was examined. The coacervation process occurred in miscible binary mixtures of water and a variety of protic and aprotic solvents. The phase behavior of alkyl carboxylic acids was found to be a function of both the Hildebrand solubility parameter, delta, and the hydrogen-bonding capability of the solvent. The best solvents for analytical extractions were those featuring the lowest delta values. The phase behavior of alkyl carboxylic acid/water/tetrahydrofuran (THF) ternary systems as a function of component concentration, pH, ionic strength, and temperature was investigated. The efficiency and the time required for phase separation depended on the experimental procedure used (i.e., standing, centrifugation, stirring, and sonication). The formation of alkyl carboxylic acid reverse micelles in THF was proven using both hydrophilic fluorescent probes and scattered light measurements. The structure of the coacervates consisted of spherical droplets dispersed in a continuous phase. Phase volume ratios were a function of both alkyl carboxylic acid and THF concentration. The low volume obtained (e.g., 1.5 microL per mg of decanoic) compared to that obtained by other coacervates (e.g., 5.1 microL per mg of dodecane sulfonic acid and 11.3 microL per mg of Triton X-114) greatly improved the concentration factors reached by coacervation-based extractions. Parameters affecting the extraction efficiency were assessed. Analytes in a wide range of polarity were efficiently extracted on the basis of the hydrophobic (e.g., PAHs) and hydrogen bond (e.g., chlorophenols, bisphenols, pesticides, phthalates, nonionic surfactants, dyes, and photographic developers) interactions that reverse micelles can establish. The coacervates were compatible with the chromatographic determination of analytes following UV or MS detection. They were successfully applied to the extraction of alkylphenol ethoxylates (octyl and nonyl) and alcohol ethoxylates (C12-C16) from influent and effluent wastewater and river water samples. Nonionic surfactants in the coacervate were directly separated and quantified by liquid chromatography-ion trap mass spectrometry. Concentration factors were around 160. The recovery of nonionics in the environmental water samples ranged from 90 to 104%. PMID:17764154

Ruiz, Francisco-Javier; Rubio, Soledad; Pérez-Bendito, Dolores

2007-10-01

233

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

234

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

PubMed

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. PMID:8552720

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

1995-11-01

235

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

236

Carboxylic acid chemistry at the Ge(100)-2 x 1 interface: bidentate bridging structure formation on a semiconductor surface.  

PubMed

The reactions of acetic acid, acetic-d3 acid-d, and formic acid with the Ge(100)-2 x 1 surface have been investigated using multiple internal reflection Fourier transform infrared (MIR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. The infrared and photoelectron data provide experimental evidence for an O-H dissociation product at 310 K. DFT calculations indicate that the O-H dissociation pathway is significantly favored, both kinetically and thermodynamically, over other potential reaction pathways. All of the carboxylic acids studied exhibit unexpected vibrational modes between 1400 and 1525 cm(-1), which are attributed to the presence of a bidentate bridging structure where both oxygen atoms interact directly with the surface. PMID:16417366

Filler, Michael A; Van Deventer, James A; Keung, Albert J; Bent, Stacey F

2006-01-25

237

Design of co-crystals/salts of some Nitrogenous bases and some derivatives of thiophene carboxylic acids through a combination of hydrogen and halogen bonds  

PubMed Central

Background The utility of N-heterocyclic bases to obtain molecular complexes with carboxylic acids is well studied. Depending on the solid state interaction between the N-heterocyclic base and a carboxylic acid a variety of neutral or ionic synthons are observed. Meanwhile, pyridines and pyrimidines have been frequently chosen in the area of crystal engineering for their multipurpose functionality. HT (hetero trimers) and LHT (linear heterotetramers) are the well known synthons that are formed in the presence of pyrimidines and carboxylic acids. Results Fourteen crystals involving various substituted thiophene carboxylic acid derivatives and nitrogenous bases were prepared and characterized by using single crystal X-ray diffraction. The 14 crystals can further be divided into two groups [1a-7a], [8b-14b] based on the nature of the nitrogenous base. Carboxylic acid to pyridine proton transfer has occurred in 3 compounds of each group. In addition to the commonly occurring hydrogen bond based pyridine/carboxylic acid and pyrimidine/carboxylic acid synthons which is the reason for assembly of primary motifs, various other interactions like Cl…Cl, Cl…O, C–H…Cl, C-H…S add additional support in organizing these supermolecules into extended architectures. It is also interesting to note that in all the compounds ?-? stacking occurs between the pyrimidine-pyrimidine or pyridine-pyridine or acid-acid moieties rather than acid-pyrimidine/pyridine. Conclusions In all the compounds (1a-14b) either neutral O–H…Npyridyl/pyrimidine or charge-assisted Npyridinium-H…Ocarboxylate hydrogen bonds are present. The HT (hetero trimers) and LHT (linear heterotetramers) are dominant in the crystal structures of the adducts containing N-heterocyclic bases with two proton acceptors (1a-7a). Similar type supramolecular ladders are observed in 5TPC44BIPY (8b), TPC44BIPY (9b), TPC44TMBP (11b). Among the seven compounds [8b-14b] the extended ligands are linear in all except for the TMBP (10b, 11b, 12b). The structure of each compound depends on the dihedral angle between the carboxyl group and the nitrogenous base. All these compounds indicate three main synthons that regularly occur, namely linear heterodimer (HD), heterotrimer (HT) and heterotetramer (LHT).

2014-01-01

238

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

239

Salen-based chiral fluorescence polymer sensor for enantioselective recognition of ?-hydroxyl carboxylic acids.  

PubMed

(R,R)-Salen-based chiral polymer P-1 was synthesized by the polymerization of 5,5'-((2,5-dibutoxy-1,4-phenylene)bis(ethyne-2,1-diyl))bis(2-hydroxy-3-(piperidin-1-ylmethyl) benzaldehyde (M-1) with (1R,2R)-cyclohexane-1,2-diamine (M-2) via nucleophilic addition- elimination reaction, and (R,R)-salan-based polymer P-2 could be obtained by the reduction reaction of P-1 with NaBH(4). (R,R)-Salen-based chiral polymer P-1 can exhibit greater fluorescence enhancement response toward (l)-?-hydroxyl carboxylic acids, and the value of enantiomeric fluorescence difference ratio (ef) can reach as high as 8.41 for mandelic acid and 6.55 for lactic acid. On the contrary, (R,R)-salan-based chiral polymer P-2 shows obvious fluorescence quenching response toward ?-hydroxyl carboxylic acids. Most importantly, (R,R)-salen-based polymer P-1 can display bright blue fluorescence color change in the presence of (l)-?-hydroxyl carboxylic acids under a commercially available UV lamp, which can be clearly observed by the naked eyes. PMID:22554263

Song, Fengyan; Wei, Guo; Wang, Lu; Jiao, Jiemin; Cheng, Yixiang; Zhu, Chengjian

2012-05-18

240

Ground measurements of carboxylic acids during the ChArMEx field campaign using PTR-ToFMS  

NASA Astrophysics Data System (ADS)

Carboxylic acids are long-lived and persistent species that have been shown to be important for ambient acidity and secondary organic aerosol formation. Formic, acetic, and propionic acids are among the most abundant carboxylic acids in the troposphere. However, their atmospheric sources are poorly characterized due to limited measurement data. Techniques usually used to measure gas-phase concentrations of carboxylic acids suffer from low time resolution and the use of fast instruments would be of prime interest to apportion the contribution of anthropogenic and biogenic emissions, as well as photochemical processes to the carboxylic acid budget. A Proton Transfer Reaction Time-of-Flight Mass Spectrometer (PTR-ToFMS) was characterized for field measurements of n-carboxylic acids (C1-C4). Laboratory experiments were carried out to get insights into fragmentation patterns of parent (RCOOHH+) and acylium (RCO+) ions, sensitivities, and detection limits under various operating conditions. Carefully designed experiments were conducted to assess the impact of relative humidity on the sensitivity. Detection limits of 500, 90, 50 and 40 ppt were achieved for 10-min measurements of formic, acetic, propionic and butyric acids, respectively. This instrument was deployed for the first time during the 2013 ChArMEx intensive field campaign at a ground site in Cap Corsica and successfully measured concentrations of carboxylic acids from July 15th to August 5th. Elevated mixing ratios in the range 500-4000 ppt, 260-2500 ppt, and 50-500 ppt were observed for formic, acetic, and propionic acids, respectively. Mixing ratios of butyric acids were close to the detection limit. In this presentation, we will discuss the potential of carboxylic acid measurements by PTR-ToFMS in remote areas and we will provide a preliminary analysis of carboxylic acid sources in an area impacted by local biogenic emissions as well as aged anthropogenic air masses.

Dusanter, Sébastien; Sauvage, Stéphane; Locoge, Nadine; Michoud, Vincent; Touati, Nabil; Zhang, Shouwen; Riffault, Véronique

2014-05-01

241

Anhydrosugar and sugar alcohol organic markers associated with carboxylic acids in particulate matter from incense burning  

NASA Astrophysics Data System (ADS)

Aerosol from the burning two types of sandalwood-based incense, Hsing Shan and Lao Shan, was analyzed to characterize the chemical profile of total particulate matter emitted. The total particulate matter (PM) mass emission factors were 46.3 ± 2.68 mg g -1 of Hsing Shan incense and 43.7 ± 1.08 mg g -1 of Lao Shan incense. Chemical analysis of emissions from the two types of incense revealed that of the 25 components in four groups characterized, anhydrosugars formed the major group, at 46.7-52.2% w/w of the identified particulate and 1078.3-1169.8 ?g g -1 of incense, followed by inorganic salts at 30.4-31.8% w/w of identified particulate and 681.6-734.0 ?g g -1 of incense, carboxylic acids at 12.0-17.1% w/w of the identified particulate and 268.6-392.8 ?g g -1 of incense, and sugar alcohols at 4.44-5.38% w/w of the identified particulate and 102.3-120.6 ?g g -1 of incense. More anhydrosugars and sugar alcohols were emitted from Lao Shan incense than from Hsing Shan incense whereas more carboxylic acids and organic salts were emitted from Hsing Shan than from Lao Shan. These differences were due to structural and functional differences in the young sandalwood used to make Hsing Shan and the aged sandalwood used to make Lao Shan. The anhydrosugar levoglucosan, used as a marker of biomass burning, was always the most abundant species in emitted PM for both incenses ( Lao Shan 21.7 mg g -1 of PM and Hsing Shan 18.7 mg g -1). K + and Cl - were the second most abundant components (K + and Cl - were summed), accounting for 10.6 mg g -1 of Hsing Shan PM and 9.85 mg g -1 of Lao Shan PM. The most abundant carboxylic acids in the emissions were formic, acetic, succinic, glutaric and phthalic acid. The latter is a fragrance ingredient and a potential health hazard and was twice as prevalent in Lao Shan emissions. Xylitol was the most prevalent of the sugar alcohols at 35.7-36.6% w/w of total identified sugar alcohols. These abundant species are potential markers for incense burning. K +, levoglucosan, mannosan and xylitol are already reported in discriminator ratios for wood burning and it is proposed here that these can and should also apply to incense burning. The calculated discriminator ratios for two types of incense burning reported here are 0.229-0.288 for K/Levo, 12.5-13.5 for Levo/Manno, and 21.5-23.7 for the novel discriminator ratio Levo/Xylitol.

Tsai, Ying I.; Wu, Pei-Ling; Hsu, Yu-Ting; Yang, Chi-Ru

2010-09-01

242

Comparison Of Asymmetric Hydrogenations Of Unsaturated- Carboxylic Acids And -Esters  

PubMed Central

As methodology development matures it can be difficult to discern the most effective ways of performing certain transformations from the rest. This review summarizes the most important contributions leading to asymmetric hydrogenations of simple unsaturated-acid and ester substrates, with the objective of highlighting at least the best types of catalysts for each. Achievements in the area are described and these reveal situations where further efforts should be worthwhile, and ones where more research is only likely to give diminishing returns. In general, our conclusions are that the most useful types of catalysts for unsaturated-acids and -esters tend to be somewhat different, simple substrates have been studied extensively, and the field is poised to address more complex reactions. These could be ones involving alternative, particularly cyclic, structures, chemoselectivity issues, and more complex substrate stereochemistries.

Khumsubdee, Sakunchai; Burgess, Kevin

2013-01-01

243

A mild and efficient protocol for the conversion of carboxylic acids to olefins by a catalytic decarbonylative elimination reaction.  

PubMed

A new method for the conversion of aliphatic carboxylic acids to olefins under unprecedented mild conditions is disclosed, wherein the carboxylic acids are converted in situ with pivalic anhydride to the mixed anhydrides, which regioselectively add to a PdCl(2)-DPE-Phos catalyst. At a temperature of only 110 degrees C, smooth decarbonylation and beta-hydride elimination occur, and the corresponding olefins along with CO, CO(2) and pivalic acid are liberated. PMID:15010800

Goossen, Lukas J; Rodríguez, Nuria

2004-03-21

244

Activity of 1-Aminocyclopropane Carboxylic Acid Synthase in Two Mustard ( Brassica juncea L.) Cultivars Differing in Photosynthetic Capacity  

Microsoft Academic Search

The pattern of activity of 1-aminocyclopropane carboxylic acid synthase (ACS) was similar to photosynthetic and growth traits observed at 30, 45, and 60 d after sowing in mustard (Brassica juncea L.) cultivars Varuna and RH 30 differing in photosynthetic capacity. Higher activity of ACS and therefore ethylene release in Varuna than RH 30 increased stomatal conductance, intercellular CO2 concentration, carboxylation

N. A. Khan

2004-01-01

245

Chemically binding carboxylic acids onto TiO2 nanoparticles with adjustable coverage by solvothermal strategy.  

PubMed

This paper presents a solvothermal strategy for chemical modification of TiO(2) nanoparticles with carboxylic acids. Solvothermal reaction between the TiO(2) nanoparticles and carboxylic acid molecules in an autoclave at 100 degrees C provides carboxylic acid-modified TiO(2) particles with a modification efficiency much higher than the conventional immersion method. TiO(2) nanoparticles were prepared by hydrolysis of titanium isopropoxide in nitric acid solution; the modified nanoparticles were characterized by powder X-ray diffraction pattern, scanning electron microscopy, absorption and Fourier transform infrared spectra, and thermogravimetric analysis. Results show that the binding form of the modifier molecules on TiO(2) surface is in a bidentate chelating mode, the crystalline phase composition and morphological structure of the preformed TiO(2) nanoparticles are not affected by the solvothermal reaction, and the surface coverage of the modifier molecules can be adjusted by the weight ratio of modifier/TiO(2) during feeding. It is evident that the reaction processes in the solvothermal strategy involve the formation of double hydrogen bondings between carboxylic acid molecule and TiO(2) at the same Ti site and the coordination at solvothermal temperature by dehydration from the hydrogen bondings. The solvothermal strategy for modifying TiO(2) nanoparticles is expected to find potential applications in many fields; for example, our results demonstrate that the photovoltaic performance of the TiO(2) nanoparticles can be improved by the solvothermal modification even with an insulating modifier and controlled by the modifier coverage. PMID:20345108

Qu, Qiyun; Geng, Hongwei; Peng, Ruixiang; Cui, Qi; Gu, Xiaohong; Li, Fanqing; Wang, Mingtai

2010-06-15

246

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 CO/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

247

Growth modification of seeded calcite using carboxylic acids: atomistic simulations.  

PubMed

Molecular dynamics simulations were used to investigate possible explanations for experimentally observed differences in the growth modification of calcite particles by two organic additives, polyacrylic acid (PAA) and polyaspartic acid (p-ASP). The more rigid backbone of p-ASP was found to inhibit the formation of stable complexes with counter-ions in solution, resulting in a higher availability of p-ASP compared to PAA for surface adsorption. Furthermore the presence of nitrogen on the p-ASP backbone yields favorable electrostatic interactions with the surface, resulting in negative adsorption energies, in an upright (brush conformation). This leads to a more rapid binding and longer residence times at calcite surfaces compared to PAA, which adsorbed in a flat (pancake) configuration with positive adsorption energies. The PAA adsorption occurring despite this positive energy difference can be attributed to the disruption of the ordered water layer seen in the simulations and hence a significant entropic contribution to the adsorption free energy. These findings help explain the stronger inhibiting effect on calcite growth observed by p-ASP compared to PAA and can be used as guidelines in the design of additives leading to even more marked growth modifying effects. PMID:20304410

Aschauer, Ulrich; Spagnoli, Dino; Bowen, Paul; Parker, Stephen C

2010-06-01

248

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

PubMed

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

Barron, Andrew R

2014-06-14

249

In situ assembled boronate ester assisted chiral carboxylic acid catalyzed asymmetric trans-aziridinations.  

PubMed

We developed herein a new chiral Brønsted acid catalyst which is composed of two independent organic molecules, a chiral diol, and 2-boronobenzoic acid. In situ formation of a boronate ester was utilized as a key process to generate an active catalyst. This boronate ester assisted chiral carboxylic acid catalyst was successfully applied to the trans-aziridination of N-Boc and N-benzyl imines with N-phenyldiazoacetamide. This is the first catalyst to achieve high enantioselectivities using N-benzyl imines. PMID:24199743

Hashimoto, Takuya; Gálvez, Alberto Osuna; Maruoka, Keiji

2013-11-27

250

(R)-(+)-N-methylbenzoguanidine ((R)-NMBG) catalyzed kinetic resolution of racemic secondary benzylic alcohols with free carboxylic acids by asymmetric esterification.  

PubMed

(R)-(+)-N-Methylbenzoguanidine ((R)-NMBG) was found to function as an efficient acyl-transfer catalyst for the kinetic resolution of racemic secondary benzylic alcohols in the presence of achiral carboxylic acids and pivalic anhydride. The use of a tertiary amine in this reaction is not necessary to attain good chemical yields of the products. It was determined that diphenylacetic acid could be employed as the most suitable acyl donor for achieving a high enantioselectivity for the kinetic resolution of the racemic secondary benzylic alcohols having normal aliphatic alkyl chains at the C-1 positions. On the other hand, a less-hindered carboxylic acid, such as 3-phenylpropanoic acid, functioned as a better acyl donor for the kinetic resolution of racemic secondary benzylic alcohols having branched aliphatic alkyl chains at the C-1 positions. PMID:21887445

Nakata, Kenya; Shiina, Isamu

2011-10-21

251

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 Nsbnd H⋯O, Osbnd H⋯N, and Osbnd H⋯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

252

Identification of a carboxylic acid metabolite from the catabolism of fluoranthene by a Mycobacterium sp  

SciTech Connect

A Mycobacterium sp. previously isolated from oil-contaminated estuarine sediments was capable of extensively mineralizing the high-molecular-weight polycyclic aromatic hydrocarbon fluoranthene. A carboxylic acid metabolite accumulated and was isolated by thin-layer and high-pressure liquid chromatographic analyses of ethyl acetate extracts from acidified culture media. The metabolite reached a maximum concentration of approximately 0.65% after 24 h of incubation. On the basis of comparisons with authentic compound in which the authors used UV and fluorescence spectrophotometry and R{sub f} values, as well as mass spectral and proton and carbon nuclear magnetic resonance spectral analyses, the metabolite was identified as 9-fluorenone-1-carboxylic acid. This is the first report in a microbial system of a fluoranthene metabolite in which significant degradation of one of the aromatic rings has occurred.

Kelley, I.; Freeman, J.P.; Evans, F.E.; Cerniglia, C.E. (National Center for Toxicological Research, Jefferson, AR (USA))

1991-03-01

253

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

2013-10-15

254

QSAR study of carboxylic acid derivatives as HIV-1 Integrase inhibitors.  

PubMed

QSAR studies have been carried out on carboxylic acid derivatives as HIV-1 Integrase inhibitors using 3D-MoRSE (3D-Molecular Representation of Structure based on Electron diffraction) descriptors. The stepwise multiple linear regression (stepwise-MLR) and replacement method (RM) methods are used to select descriptors which are responsible for the inhibitory activity of these compounds. Mathematical models are obtained by support vector machine (SVM), back-propagation neural networks (BPNN) and multiple linear regression (MLR). Leave-one-out, Leave-many-out (7% and 18%) cross-validation and external validation are carried out with the aim of evaluating the predictive ability of the models. The values of their respective squared correlations coefficients are 0.731, 0.664, 0.523 and 0.766, respectively. Our best QSAR model reveals the polarizability, mass as the most influencing atomic properties in the structures of the carboxylic acid derivatives. PMID:20561721

Cheng, Zhengjun; Zhang, Yuntao; Fu, Weizhong

2010-09-01

255

Identification of a Carboxylic Acid Metabolite from the Catabolism of Fluoranthene by a Mycobacterium sp  

PubMed Central

A Mycobacterium sp. previously isolated from oil-contaminated estuarine sediments was capable of extensively mineralizing the high-molecular-weight polycyclic aromatic hydrocarbon fluoranthene. A carboxylic acid metabolite accumulated and was isolated by thin-layer and high-pressure liquid chromatographic analyses of ethyl acetate extracts from acidified culture media. The metabolite reached a maximum concentration of approximately 0.65% after 24 h of incubation. On the basis of comparisons with authentic compound in which we used UV and fluorescence spectrophotometry and Rf values, as well as mass spectral and proton and carbon nuclear magnetic resonance spectral analyses, the metabolite was identified as 9-fluorenone-1-carboxylic acid. This is the first report in a microbial system of a fluoranthene metabolite in which significant degradation of one of the aromatic rings has occurred.

Kelley, Ingrid; Freeman, James P.; Evans, Frederick E.; Cerniglia, Carl E.

1991-01-01

256

Enantioselective synthesis of ?-methyl carboxylic acids from readily available starting materials via chemoenzymatic dynamic kinetic resolution.  

PubMed

An enantioselective method for the synthesis of ?-methyl carboxylic acids starting from trans-cinnamaldehyde, a readily available and inexpensive compound, has been developed. Allylic alcohol 1 was obtained via a standard Grignard addition to trans-cinnamaldehyde. Dynamic kinetic resolution was applied to allylic alcohol 1 utilizing a ruthenium catalyst and either an (R)-selective lipase or an (S)-selective protease to provide the corresponding allylic esters in high yield and high ee. A copper-catalyzed allylic substitution was then applied to provide the corresponding alkenes with inversion of stereochemistry. Subsequent C-C double bond cleavage afforded pharmaceutically important ?-methyl substituted carboxylic acids in high ee and overall yields of up to 76%. PMID:20857917

Thalén, Lisa K; Sumic, Anna; Bogár, Krisztián; Norinder, Jakob; Persson, Andreas K Å; Bäckvall, Jan-E

2010-10-15

257

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

NASA Astrophysics Data System (ADS)

Atmospheric gas and particle-phase carboxylic acids were measured during July 1996, Winter, in an urban area of São Paulo, a highly polluted Latin American city. Ion chromatography and capillary electrophoresis techniques were used to determine the species. As oxalic (36.2±21.4%), pyruvic (15.0±7.9%), ?-hydroxy-butyric (9.15±9.00%) and glycolic (3.55±2.26%) acids were determined in aerosol particles, formic and acetic acids were determined both in the gaseous (4.36±2.70 and 3.66±2.63 ppbv, respectively) and particulate phases (17.8±12.4 and 18.2±9.8%, respectively). Approximately 98% of the total acetic and formic acids were in the gas-phase and the gas-aerosol equilibrium was influenced by high levels of relative humidity. Gaseous formic-to-acetic ratios fell in the 0.94-1.85 range. Photochemical production appeared to be a very likely source of the gaseous acetic and formic acid levels found in this investigation. Direct emissions, mainly motor exhaust of vehicles also contributed to their presence in air. The observed amounts of formic and acetic acids in the particle phase were comparable with those observed in other urban sites. Results from aerosol particles indicated lower concentrations of the carboxylic acids at night, but their diurnal and nocturnal variation were similar. Using a correlation matrix, it was possible to suggest some sources for the carboxylic acids in the particulate phase. During daytime, vehicular emission appeared to be the primary source of acetic acid, whereas formic and pyruvic acids should be formed photochemically. Moreover, emissions from biogenic primary sources appeared to be an important contribution to atmospheric concentrations of formic and glycolic acids. Presumably, the photooxidation of pyruvic and glycolic acids gave rise to the oxalic acid. No source for acetic and pyruvic acids at nighttime was possible to suggest. However, direct vehicular and biogenic emissions might be major sources of TOC in nocturnal measurements. Oxalic acid might result from vehicular emission, glycolic acid from biogenic emission and formic acid from both sources.

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

258

Complexation of carboxylate anions with the arginine gas-phase amino acid: Effects of chain length on the geometry of extended ion binding  

NASA Astrophysics Data System (ADS)

Complexation of deprotonated carboxylic acids with arginine was investigated using collision-induced dissociation to probe the nature of isolated carboxylate-amino acid interactions as a function of anion size. Monocarboxylic CH3(CH2)nCOO-·Arg (n = 3-7, 9, 10) and dicarboxylic acid COOH(CH2)nCOO-·Arg (n = 3-5, 7-10) complexes were investigated. For the dicarboxylic acid clusters, chain length has a significant effect on the %fragmentation energies with the n = 9, 10 systems fragmenting at significantly lower energies than the corresponding shorter chain systems. Molecular mechanics calculations suggest that this fragmentation energy shift is associated with the longer-chain dicarboxylic acid-Arg clusters switching to ring structures.

Luxford, Thomas F. M.; Milner, Edward M.; Yoshikawa, Naruo; Bullivant, Chad; Dessent, Caroline E. H.

2013-07-01

259

1-Aminocyclopropane-1-carboxylic acid as a signalling molecule in plants  

PubMed Central

Ethylene influences many aspects of plant growth and development including germination, leaf and floral senescence and abscission, fruit ripening, and the response to abiotic and biotic stress. The pathways involved in the biosynthesis of and response to ethylene have been elucidated. The first committed and generally rate-limiting step in ethylene biosynthesis is the conversion of S-adenosyl-methionine to 1-aminocyclopropane-1-carboxylic acid (ACC) by ACC synthase (ACS). This enzyme is encoded by a gene family in most plants and is subject to both transcriptional and post-transcriptional control in response to numerous endogenous and environmental cues. In addition to its well-described function as the immediate precursor of ethylene, recent studies suggest an alternative, non-canonical role for ACC. These studies found that in some contexts, chemical inhibitors of ethylene biosynthesis caused effects on root cell expansion that were not observed when ethylene perception or signalling was disrupted, suggesting that ACC, but not ethylene, played a role in these specific processes. Furthermore, mutation of all eight ACS genes in Arabidopsis was found to result in embryo lethality, in contrast to the relatively modest developmental effects of null mutants in the ethylene signalling components. This divergence suggests that ACC may play a role as a signalling molecule in plants. Here, we first review the ethylene biosynthesis pathway and then discuss these studies suggesting an independent role of ACC as a signalling molecule.

Yoon, Gyeong Mee; Kieber, Joseph J.

2013-01-01

260

A facile method to synthesize carboxyl-functionalized magnetic polystyrene nanospheres  

Microsoft Academic Search

Magnetic polystyrene nanospheres with high magnetite content and abundant surface carboxyl groups were prepared by emulsifier-free emulsion polymerization in the presence of aqueous magnetic fluid coated with oleic acid and 10-undecenoic acid as primary and secondary surfactants respectively. The effects of initiator concentration, initiator type (water-soluble or oil-soluble), monomer concentration and ferrofluid content on the particle characteristics such as the

Ningning Guan; Chao Liu; Dejun Sun; Jian Xu

2009-01-01

261

Oxidation of allylic and benzylic alcohols to aldehydes and carboxylic acids.  

PubMed

An oxidation of allylic and benzylic alcohols to the corresponding carboxylic acids is effected by merging a Cu-catalyzed oxidation using O2 as a terminal oxidant with a subsequent chlorite oxidation (Lindgren oxidation). The protocol was optimized to obtain pure products without chromatography or crystallization. Interception at the aldehyde stage allowed for Z/E-isomerization, thus rendering the oxidation stereoconvergent with respect to the configuration of the starting material. PMID:24710078

Könning, Daniel; Olbrisch, Tobias; Sypaseuth, Fanni D; Tzschucke, C Christoph; Christmann, Mathias

2014-05-21

262

3-(4-Meth-oxy-phen-yl)-5-methylisoxazole-4-carb-oxy-lic acid  

PubMed Central

In the title compound, C12H11NO4, the dihedral angle between the benzene and isoxazole rings is 42.52?(8)°. The carb­oxy­lic acid group is close to being coplanar with the isoxazole ring [dihedral angle = 5.3?(2)°]. In the crystal, inversion dimers linked by pairs of O—H?O hydrogen bonds generate R 2 2(8) loops.

Chandra; Raghu, K.; Srikantamurthy, N.; Umesha, K. B.; Palani, K.; Mahendra, M.

2013-01-01

263

3-(4-Meth-oxy-phen-yl)-5-methylisoxazole-4-carb-oxy-lic acid.  

PubMed

In the title compound, C12H11NO4, the dihedral angle between the benzene and isoxazole rings is 42.52?(8)°. The carb-oxy-lic acid group is close to being coplanar with the isoxazole ring [dihedral angle = 5.3?(2)°]. In the crystal, inversion dimers linked by pairs of O-H?O hydrogen bonds generate R2(2)(8) loops. PMID:23476573

Chandra; Raghu, K; Srikantamurthy, N; Umesha, K B; Palani, K; Mahendra, M

2013-03-01

264

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

DOEpatents

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

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

1999-01-01

265

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

266

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

267

Root excretion of carboxylic acids and protons in phosphorus-deficient plants  

Microsoft Academic Search

Phosphorus deficiency-induced metabolic changes related to exudation of carboxylic acids and protons were compared in roots\\u000a of wheat (Triticum aestivum L. cv Haro), tomato (Lycopersicon esculentum L., cv. Moneymaker), chickpea (Cicer arietinum) and\\u000a white lupin (Lupinus albus L. cv. Amiga), grown in a hydroponic culture system. P deficiency strongly increased the net release\\u000a of protons from roots of tomato, chickpea

G. Neumann; V. Römheld

1999-01-01

268

The influence of esters and carboxylic acids as the N-substituent of opioids. 1. Benzomorphans  

PubMed Central

To investigate the effects of carboxylic ester and acid moieties as the N-substituent of opioids, a short series of racemic N-substituted normetazocines was prepared. The introduction of both groups as the normetazocine N-substituent produced compounds which displayed low potency in vitro and in vivo, with the esters displaying the greater activity. The pharmacology of the compounds is discussed with implications resulting from potential in vivo metabolic hydrolysis.

Metcalf, Matthew D.; Aceto, Mario D.; Harris, Louis S.; Woods, James H.; Traynor, John R; Coop, Andrew; May, Everette L.

2008-01-01

269

Langmuir Monolayers from Substituted 5'-Phenyl-m-terphenyl Carboxylic Acids.  

PubMed

A series of 5'-phenyl-m-terphenyl carboxylic acid (PTCA) derivatives with methyl, chloro, and fluoro substituents at both side phenyl rings have been synthesized and characterized as Langmuir monolayers at the air/water interface. A comparative analysis, based on the surface pressure and electric surface potential measurements under a variety of experimental conditions, is complemented with BAM images. Copyright 2001 Academic Press. PMID:11397059

Dynarowicz-L&acedil;tka, P.; Kita, K.; Milart, P.; Dhanabalan, A.; Cavalli, A.; Oliveira, O. N.

2001-07-01

270

Quinolizidinone Carboxylic Acids as CNS Penetrant, Selective M1 Allosteric Muscarinic Receptor Modulators  

PubMed Central

Positive allosteric modulation of the M1 muscarinic receptor represents an approach to treat the cognitive decline in patients with Alzheimer’s disease. Replacement of a quinolone ring system in a quinolone carboxylic acid series of M1 modulators with a quinolizidinone bearing a basic amine linkage led to a series of compounds with higher free fraction, enhanced CNS exposure, and improved efficacy in rodent in vivo models of cognition.

2010-01-01

271

Influence of carboxylic acids on fixation of copper in wood impregnated with copper amine based preservatives  

Microsoft Academic Search

The importance of copper\\/amine based preservatives is increasing. Leaching of copper from wood preserved with these solutions\\u000a is still higher than leaching from wood impregnated with copper chromium ones. In order to decrease leaching, different carboxylic\\u000a acids (octanoic, 2-ethylhexanoic, decanoic) were added to copper\\/amine\\/boron aqueous solutions. An experiment of leaching\\u000a of copper from Norway spruce was performed according to the

M. Humar; P. Kalan; M. Šentjurc; F. Pohleven

2005-01-01

272

A new lysine derivative and new 3-bromopyrrole carboxylic acid derivative from two marine sponges.  

PubMed

A novel lysine derivative, 1, has been isolated from the marine sponge Axinyssa terpnis, in addition to 4alpha-isocyanogorgon-11-ene and related compounds (2-4). From the marine sponge Axinella carteri, the new 3-bromopyrrole carboxylic acid derivative, 5, was obtained along with the known compounds aldisin (6) and 2-bromoaldisin (7). Both sponges were collected from Chuuk Atoll, Federated States of Micronesia. The compounds were characterized by spectroscopic and chemical methods. PMID:9548881

Li, C J; Schmitz, F J; Kelly-Borges, M

1998-03-01

273

Synergy between iono-covalent bonds and van der Waals interactions in SAMs formation: A first-principles study of adsorption of carboxylic acids on the Zn–ZnO(0 0 0 1) surface  

Microsoft Academic Search

The adsorption of carboxylic acids (CA) on the Zn–ZnO(0001) surface was studied by density functional theory including dispersion forces (DFT+D) calculations. Carboxylic acids of formula CH3(CH2)n?2COOH (where n=1–10 is the total number of C atoms in the CA) were considered. In a first step, the formation of the iono-covalent bonds with the surface was studied with standard DFT approach, while

M. M. Islam; B. Diawara; P. Marcus; D. Costa

2011-01-01

274

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

275

Electrochemical analysis of the carboxy-14C-labelled aliphatic carboxylic acid metabolites resulting from tracer studies.  

PubMed Central

14C02 output from carboxy-14C-labelled aliphatic carboxylic acids is measured in the micro-scale Kolbe reaction. Irrespective of whether rats were dosed with 1,1-dichloro[1-14C]ethylene or with chloro[1-14C]acetic acid, 1 mol.equiv. of the resulting thio[14C]diglycollic acid yields by electrolysis approx. 0.7 equiv. of 14CO2, which is interpreted in terms of the labelling of one of the carboxylic acid groups of thiodiglycollic acid. This observation provides important evidence concerning thiodiglycollic acid biosynthesis from 1.1-dichloroethylene.

Walker, G H; Hathway, D E

1977-01-01

276

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

277

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

278

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

2013-10-15

279

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

PubMed Central

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

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

2010-01-01

280

Synthesis of thioesters from carboxylic acids via acyloxyphosphonium intermediates with benzyltriethylammonium tetrathiomolybdate as the sulfur transfer reagent.  

PubMed

An efficient protocol is reported for the synthesis of thioesters from carboxylic acids with use of acyloxy phosphonium salts as intermediates and benzyltriethylammonium tetrathiomolybdate as the sulfur transfer reagent. PMID:19618897

Gopinath, Purushothaman; Vidyarini, Ravindran Sasitha; Chandrasekaran, Srinivasan

2009-08-21

281

Efficient Synthesis of Primary Amides from Carboxylic Acids using N,N?-Carbonyldiimidazole and Ammonium Acetate in Ionic Liquid  

Microsoft Academic Search

A novel and efficient method for the conversion of carboxylic acids to primary amides using N,N?-carbonyldiimidazole in combination with ammonium acetate\\/triethyl amine system in [BMIM]BF4 is developed.

Kwan Soo Lee; Kee D. Kim

2011-01-01

282

The Heat of Dimerization of Some Carboxylic Acids in the Vapour Phase Determined by a Spectroscopic Method.  

National Technical Information Service (NTIS)

The lower molecular weight carboxylic acids, formic, acetic, propionic, n-butyric, isobutric and trimethylacetic have been studied to find, firstly, whether there is any trend in thermodynamic properties due to mass or structure of the alkyl substituent, ...

A. D. H. Clague H. J. Bernstein

1968-01-01

283

Direct amidation of carboxylic acids catalyzed by ortho-iodo arylboronic acids: catalyst optimization, scope, and preliminary mechanistic study supporting a peculiar halogen acceleration effect.  

PubMed

The importance of amides as a component of biomolecules and synthetic products motivates the development of catalytic, direct amidation methods employing free carboxylic acids and amines that circumvent the need for stoichiometric activation or coupling reagents. ortho-Iodophenylboronic acid 4a has recently been shown to catalyze direct amidation reactions at room temperature in the presence of 4A molecular sieves as dehydrating agent. Herein, the arene core of ortho-iodoarylboronic acid catalysts has been optimized with regards to the electronic effects of ring substitution. Contrary to the expectation, it was found that electron-donating substituents are preferable, in particular, an alkoxy substituent positioned para to the iodide. The optimal new catalyst, 5-methoxy-2-iodophenylboronic acid (MIBA, 4f), was demonstrated to be kinetically more active than the parent des-methoxy catalyst 4a, providing higher yields of amide products in shorter reaction times under mild conditions at ambient temperature. Catalyst 4f is recyclable and promotes the formation of amides from aliphatic carboxylic acids and amines, and from heteroaromatic carboxylic acids and other functionalized substrates containing moieties like a free phenol, indole and pyridine. Mechanistic studies demonstrated the essential role of molecular sieves in this complex amidation process. The effect of substrate stoichiometry, concentration, and measurement of the catalyst order led to a possible catalytic cycle based on the presumed formation of an acylborate intermediate. The need for an electronically enriched ortho-iodo substituent in catalyst 4f supports a recent theoretical study (Marcelli, T. Angew. Chem. Int. Ed.2010, 49, 6840-6843) with a purported role for the iodide as a hydrogen-bond acceptor in the orthoaminal transition state. PMID:23013456

Gernigon, Nicolas; Al-Zoubi, Raed M; Hall, Dennis G

2012-10-01

284

Protonation of Excited State Pyrene-1-Carboxylate by Phosphate and Organic Acids in Aqueous Solution Studied by Fluorescence Spectroscopy  

PubMed Central

Pyrene-1-carboxylic acid has a pK of 4.0 in the ground state and 8.1 in the singlet electronic excited state. In the pH range of physiological interest (pH ?5–8), the ground state compound is largely ionized as pyrene-1-carboxylate, but protonation of the excited state molecule occurs when a proton donor reacts with the carboxylate during the excited state lifetime of the fluorophore. Both forms of the pyrene derivatives are fluorescent, and in this work the protonation reaction was measured by monitoring steady-state and time-resolved fluorescence. The rate of protonation of pyrene-COO? by acetic, chloroacetic, lactic, and cacodylic acids is a function of ?pK, as predicted by Marcus theory. The rate of proton transfer from these acids saturates at high concentration, as expected for the existence of an encounter complex. Trihydrogen-phosphate is a much better proton donor than dihydrogen- and monohydrogen-phosphate, as can be seen by the pH dependence. The proton-donating ability of phosphate does not saturate at high concentrations, but increases with increasing phosphate concentration. We suggest that enhanced rate of proton transfer at high phosphate concentrations may be due to the dual proton donating and accepting nature of phosphate, in analogy to the Grotthuss mechanism for proton transfer in water. It is suggested that in molecular structures containing multiple phosphates, such as membrane surfaces and DNA, proton transfer rates will be enhanced by this mechanism.

Zelent, Bogumil; Vanderkooi, Jane M.; Coleman, Ryan G.; Gryczynski, Ignacy; Gryczynski, Zygmunt

2006-01-01

285

Potential correlation between carboxylic acid metabolites in Biomphalaria alexandrina snails after exposure to Schistosoma mansoni infection.  

PubMed

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

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

2012-06-01

286

Thermolysis of the esters of substituted 3,7-triazabicydo[3.3.0]oct-3-ene-4-carboxylic acids  

Microsoft Academic Search

Heating to 190–200‡C of the esters of substituted 2,3,7-triazabicyclo[3.3.0]oct-3-ene-4-carboxylic acids afforded esters of\\u000a 3-azabicyclo[3.1.0]hexane-6-carboxylic acids as a mixture of exo and endo isomers. The reaction carried out in chlorobenzene\\u000a at 130‡C in the presence of copper stearate yielded only exo isomers.

S. A. Molchanov; A. V. Stepakov; R. R. Kostikov

2000-01-01

287

Synthesis and Structure of a New Trinuclear Copper(II) Complex with 5Phenyl Pyrazole3Carboxylic Acid as Ligand  

Microsoft Academic Search

A new copper(II) complex of general formula Na2(Cu3L4) · 2H2O · 2CH3OH (L = 5-phenyl pyrazole-3-carboxylic acid) has been newly obtained by the reaction of copper chloride with 5-phenyl pyrazole-3-carboxylic acid in methanol in the presence of NaOH at room temperature. X-ray diffraction analysis of the crystal structure reveals that the complex is a trinuclear crystal structure that consists of

Yong-Heng Xing; Guang-Hua Zhou; Yue An; Xiao-Qing Zeng; Mao-Fa Ge

2008-01-01

288

Effect of carboxylic acids on 1H NMR and infrared spectra of diethylsulphoxide  

NASA Astrophysics Data System (ADS)

The interaction in binary systems between diethylsulphoxide (DESO) and some carboxylic acids (acetic, monochloroacetic and trifluoroacetic) was investigated. It was established that on increasing the mole fraction of the acids the difference between the chemical shifts of CH 2 and CH 3 protons on the one hand and the multiplet pattern of the CH 2 group of DESO on the other change. These observations confirm the formation of Et 2SO … HOOCR complexes via hydrogen bonding which reduce the extent of methylene proton nonequivalence. Also on the grounds of i.r. spectral investigations the above mentioned complex formation was suggested.

Markarian, Sh. A.; Beylerian, N. M.

1985-01-01

289

Are ligand-stabilized carboxylic Acid derivatives with ge?te bonds isolable?  

PubMed

The stability of ligand-stabilized carboxylic acid derivatives (such as esters, amides, anhydrides, and acid halides) with terminal Ge?Te bonds is highly questionable as there is no report on such compounds. Nevertheless, we are able to isolate germatelluroester [LGe(Te)Ot-Bu] (4), germatelluroamide [LGe(Te)N(SiMe3)2] (5), and germatelluroacid anhydride [LGe(Te)OGe(Te)L] (6) complexes (L = aminotroponiminate (ATI)) as stable species. Consequently, the synthetic details, structural characterization, and UV-vis spectroscopic and theoretical studies on them are reported for the first time. PMID:24807011

Siwatch, Rahul Kumar; Yadav, Dhirendra; Mukherjee, Goutam; Rajaraman, Gopalan; Nagendran, Selvarajan

2014-05-19

290

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

291

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

292

Preferential interaction of Na(+) over K(+) with carboxylate-functionalized silver nanoparticles.  

PubMed

Elucidating mechanistic interactions between monovalent cations (Na(+)/K(+)) and engineered nanoparticle surfaces to alter particle stability in polar media have received little attention. We investigated relative preferential interaction of Na(+) and K(+) with carboxylate-functionalized silver nanoparticles (carboxylate-AgNPs) to determine if interaction preference followed the Hofmeister series (Na(+)>K(+)). We hypothesized that Na(+) will show greater affinity than K(+) to pair with carboxylates on AgNP surfaces, thereby destabilizing the colloidal system. Destabilization upon Na(+) or K(+) interacting with carboxylate-AgNPs was evaluated probing changes in multiple physicochemical characteristics: surface plasmon resonance/optical absorbance, electrical conductivity, pH, hydrodynamic diameter, electrophoretic mobility, surface charge, amount of Na(+)/K(+) directly associated with AgNPs, and Ag(+) dissociation kinetics. We show that Na(+) and K(+) react differently, indicating local Na(+) pairing with carboxylates on AgNP surfaces is kinetically faster and remarkably favored over K(+), thus supporting Hofmeister ordering. Our results suggest that AgNPs may transform into micron-size aggregates upon release into aqueous environments and that the fate of such aggregates may need consideration when assessing environmental risk. PMID:24840275

Pokhrel, Lok R; Andersen, Christian P; Rygiewicz, Paul T; Johnson, Mark G

2014-08-15

293

Synthesis and pharmacochemical study of new Cu(II) complexes with thiophen-2-yl saturated and ?,?-unsaturated substituted carboxylic acids  

Microsoft Academic Search

Copper complexes with thiophen-2-yl saturated and ?,?-unsaturated carboxylic acids as ligands were prepared, characterized and pharmacochemically studied. The available evidence supports a dimeric structure for the complexes of the general formula [Cu2(L)4(MeOH)2] where L are the anions of thiophene 2-carboxylic acid (HL1), 2-(thiophen-2-yl)-acetic acid (HL2), 3-thiophen-2-yl-acrylic acid (HL3), 2-phenyl-3-thiophen-2-yl-acrylic acid (HL4) respectively. The crystal structure of [Cu2(L1)4(MeOH)2] (2) was determined

D. Panagoulis; E. Pontiki; E. Skeva; C. Raptopoulou; S. Girousi; D. Hadjipavlou-Litina; C. Dendrinou-Samara

2007-01-01

294

First synthesis of 2-(benzofuran-2-yl)-6,7-methylene dioxyquinoline-3-carboxylic acid derivatives  

PubMed Central

Summary A facile and inexpensive synthesis of a series of novel methylenedioxy-bearing 2-(benzofuran-2-yl)-quinoline-3-carboxylic acid derivatives 3a–h via the one-pot reaction of ethyl 2-chloromethyl-6,7-methylenedioxyquinoline-3-carboxylate (5) with various substituted salicylaldehydes 6a–g as well as 2-hydroxy-1-naphthaldehyde (6h) is described. Substrate 5 was synthesized by the Friedländer condensation reaction of 2-amino-4,5-methylenedioxybenzaldehyde (4) with ethyl 4-chloro-3-oxobutanoate using KHSO4 as catalyst under ultrasound irradiation conditions. The targeted compounds 3a–h were obtained in good yields of 52–82% and their structures were established based on spectral data and elemental analyses.

Liu, Jia; Jiang, Yun; Li, Yang

2011-01-01

295

Ruthenium(II) multi carboxylic acid complexes: chemistry and application in dye sensitized solar cells.  

PubMed

Novel ruthenium multi carboxylic complexes (RMCCs) have been synthesized by using ruthenium nitrosyl nitrate, 1,2,4,5-benzenetetracarboxylic acid (H4btec) and 4,7-diphenyl-1,10-phenanthroline (BPhen) as photosensitizers for titanium dioxide semiconductor solar cells. The complexes were characterized by (1)H-NMR, FT-IR, UV-Vis, ICP and CHN analyses. The reaction details and features were then described. SEM analysis revealed that the penetration of dyes into the pores of the nanocrystalline TiO2 surface was improved by increasing the number of btec units. The solar energy to electricity conversion efficiency of complexes shows that the number of attached carboxylates on a dye has an influence on the photoelectrochemical properties of the dye-sensitized electrode. An incident photon-to-current conversion efficiency (IPCE) of 13% at 510 nm was obtained for ruthenium complexes with three btec units. PMID:24500312

Shahroosvand, Hashem; Nasouti, Fahimeh; Sousaraei, Ahmad

2014-04-01

296

Conformational analysis of some substituted silatranyl-carboxylic acids produced by computational study and NMR spectroscopy  

NASA Astrophysics Data System (ADS)

The structures of four silatrane compounds, silatranyl-carboxylic acid and its derivatives ( I, II, III, IV), are studied with molecular mechanics and NMR methods. The geometrical conformations of the molecules are calculated using full geometry optimization methods with MM2 and {CNDO}/{2}. The conformations obtained are in agreement with results in the literature and with our X-ray and NMR experiments. However, there are some differences between the solid state, gas phase, and solution structures. The influence of the substituents (-COOH, -CH 3, -CH?CH 2, -CH 3) is discussed. It has been found that substitution by the carboxyl group in the silatrane framework plays a more important role in influencing the transannular structure than does substitution in the equatorial position. The calculated and experimental results are presented and discussed in detail.

Zhang, Xiaodong; Mao, Shizen; Shen, Lianfang; Ye, Chaohui; Zhuo, Renxi; Lu, Zhengrong; Webb, G. A.

1995-12-01

297

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

PubMed

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

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

2009-01-01

298

Purification and Characterization of 1-Aminocyclopropane-1-Carboxylic Acid N-Malonyltransferase from Tomato Fruit.  

PubMed Central

1-Aminocyclopropane-1-carboxylic acid (ACC) can be oxidized to ethylene or diverted to the conjugate 1-(malonylamino)cyclopropane-1-carboxylic acid (MACC) by an ACC N-malonyltransferase. We developed a facile assay for the ACC N-malonyltransferase that resolved [14C]MACC from [14C]ACC by thin-layer chromatography and detected and quantified them using a radioisotope-imaging system. Using this assay, we showed that ACC N-malonyltransferase activity has developmental and tissue-specific patterns of expression in tomato (Lycopersicon esculentum) fruit. In the pericarp, activity was elevated for several days postanthesis, subsequently declined to a basal level, increased 3-fold at the onset of ripening, and again declined in overripe fruit. In the seed, activity increased throughout embryogenesis, maturation, and desiccation. Treatment of fruit with ethylene increased activity 50- to 100-fold in the pericarp. ACC N-malonyltransferase was purified 22,000-fold to a specific activity of 22,000 nmol min-1 mg-1 protein using ammonium sulfate precipitation, DyeMatrex Green A affinity, anion-exchange, Cibacron Blue 3GA affinity, hydrophobic interaction, and molecular filtration chromatography. Native and sodium dodecyl sulfate-denatured enzyme showed molecular masses of 38 kD, indicating that the enzyme exists as a monomer. The enzyme exhibited a Km for ACC of 500 [mu]M, was not inhibited by D- or L-amino acids, and did not conjugate [alpha]-aminoisobutyric acid or L-amino acids.

Martin, M. N.; Saftner, R. A.

1995-01-01

299

Purification and Characterization of 1-Aminocyclopropane-1-Carboxylic Acid N-Malonyltransferase from Tomato Fruit.  

PubMed

1-Aminocyclopropane-1-carboxylic acid (ACC) can be oxidized to ethylene or diverted to the conjugate 1-(malonylamino)cyclopropane-1-carboxylic acid (MACC) by an ACC N-malonyltransferase. We developed a facile assay for the ACC N-malonyltransferase that resolved [14C]MACC from [14C]ACC by thin-layer chromatography and detected and quantified them using a radioisotope-imaging system. Using this assay, we showed that ACC N-malonyltransferase activity has developmental and tissue-specific patterns of expression in tomato (Lycopersicon esculentum) fruit. In the pericarp, activity was elevated for several days postanthesis, subsequently declined to a basal level, increased 3-fold at the onset of ripening, and again declined in overripe fruit. In the seed, activity increased throughout embryogenesis, maturation, and desiccation. Treatment of fruit with ethylene increased activity 50- to 100-fold in the pericarp. ACC N-malonyltransferase was purified 22,000-fold to a specific activity of 22,000 nmol min-1 mg-1 protein using ammonium sulfate precipitation, DyeMatrex Green A affinity, anion-exchange, Cibacron Blue 3GA affinity, hydrophobic interaction, and molecular filtration chromatography. Native and sodium dodecyl sulfate-denatured enzyme showed molecular masses of 38 kD, indicating that the enzyme exists as a monomer. The enzyme exhibited a Km for ACC of 500 [mu]M, was not inhibited by D- or L-amino acids, and did not conjugate [alpha]-aminoisobutyric acid or L-amino acids. PMID:12228541

Martin, M. N.; Saftner, R. A.

1995-07-01

300

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

NASA Astrophysics Data System (ADS)

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

Tsai, Ying I.; Kuo, Su-Ching

2013-12-01

301

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

302

Surface functional groups on acid-activated nutshell carbons  

Microsoft Academic Search

Nutshells from agriculturally important nut crops (almond, black walnut, English walnut, macadamia nut and pecan) were converted to granular activated carbon using phosphoric acid activation in nitrogen or air. Surface functional groups (carbonyl, phenols, lactones, carboxyl) were quantified by titration with bases of different ionization potential. The degree of copper uptake was correlated with the presence of various functional groups

Christopher A. Toles; Wayne E. Marshall; Mitchell M. Johns

1999-01-01

303

A Novel Approach in Cinnamic Acid Synthesis: Direct Synthesis of Cinnamic Acids from Aromatic Aldehydes and Aliphatic Carboxylic Acids in the Presence of Boron Tribromide  

Microsoft Academic Search

Cinnamic acids have been prepared in moderate to high yields by a new direct synthesis using aromatic aldehydes and aliphatic carboxylic acids, in the presence of boron tribromide as reagent, 4-dimethylaminopyridine (4-DMAP) and pyridine (Py) as bases and N-methyl-2-pyrolidinone (NMP) as solvent, at reflux (180-190°C) for 8-12 hours.

Constantin I. Chiriac; Fulga Tanasa; Marioara Onciu

2005-01-01

304

Anion-exchange chromatography-electrospray ionization mass spectrometry method development for the environmental analysis of aliphatic polyhydroxy carboxylic acids.  

PubMed

For environmental analytical purposes, an anion-exchange chromatography-electrospray ionization MS method was developed enabling the identification and quantification of 18 aliphatic (poly)hydroxy (poly)carboxylic acids including sugar and uronic acids. The initially incomplete separation could be partially improved for specific analyte combinations adding borate, the zwitter ionic MES, or an alkylglycoside to the NaOH gradient supplied with the Dionex IonPac AS-11 HC column. Despite the incomplete separation, reproducible and sensitive identification and quantification is possible with MS detection in the selected ion-monitoring mode. Applying an internal standard for the compensation of the sensitivity drift of the detector, linear calibration functions were calculated for all analytes. Limits of detection spanned between 18 and 71 microgL(-1) which could be further improved for some more hydrophobic analytes by post-column addition of MeOH. PMID:17915229

Meyer, Axel; Höffler, Susanne; Fischer, Klaus

2007-11-01

305

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

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

306

PAPQMD parametrization of molecular systems with cyclopropyl rings: conformational study of homopeptides constituted by 1-aminocyclopropane-1-carboxylic acid.  

PubMed

The suitability of ab initio, semiempirical and density functional methods as sources of stretching and bending parameters has been explored using the PAPQMD (Program for Approximate Parametrization from Quantum Mechanical Data) strategy. Results show that semiempirical methods provide parameters comparable to those compiled on empirical force fields. In this respect the AMI method seems to be a good method to obtain parameters at a minimum computational cost. On the other hand, harmonic force fields initially developed for proteins and DNA have been extended to include compounds containing highly strained three-membered rings, like 1-aminocyclopropane-1-carboxylic acid. For this purpose the cyclopropyl ring has been explicitly parametrized at the AMI level considering different chemical environments. Finally, the new set of parameters has been used to investigate the conformational preferences of homopeptides constituted by 1-aminocyclopropane-1-carboxylic acid. Results indicate that such compounds tend to adopt a helical conformation stabilized by intramolecular hydrogen bonds between residues i and i + 3. This conformation allows the arrangement of the cyclic side chains without steric clashes. PMID:9749369

Alemán, C; Casanovas, J; Galembeck, S E

1998-05-01

307

Tetrabutylammonium-induced coacervation in vesicular solutions of alkyl carboxylic acids for the extraction of organic compounds.  

PubMed

The potential of the tetrabutylammonium-induced liquid-liquid-phase separation in alkyl carboxylic acid vesicular solutions for the extraction of organic compounds prior to liquid chromatography was examined for the first time. The behavior of the coacervates yielded from octanoic to oleic acids as a function of the pH and salts was investigated. The time required for phase separation depended on the length of the carboxylic acid alkyl chain and the experimental procedure (i.e., standing, sonication, centrifugation, stirring, etc.). Theoretical preconcentration factors were a function of both surfactant concentration and the length of the alkyl chain, and they greatly surpassed those obtained with other surfactant-mediated separations (e.g., surfactant-rich phases from dodecanesulfonic acid or Triton X-114). Parameters affecting the extraction efficiency were assessed. Analytes in a wide polarity/charge range, (e.g., PAHs, surfactants, chlorophenols, bisphenols, phthalates, herbicides, amines, dyes, and photographic developers) were extracted with high efficiencies on the basis of the different types of interactions that the vesicular coacervates can establish (i.e., hydrophobic and ionic interactions, hydrogen bonds, and formation of mixed aggregates). The coacervates were compatible with the chromatographic determination of analytes following UV or MS detection. Their suitability for working under real conditions was checked by applying them to the extraction of nonionic surfactants [alkylphenol ethoxylates (octyl and nonyl) and alcohol ethoxylates (C12-C16)] from raw and treated sewage and to river water samples. Analytes in the coacervate were separated and quantified by liquid chromatography-ion trap mass spectrometry. No cleanup steps were necessary. Recoveries of the target compounds in the environmental water samples ranged from 89 to 103%. PMID:17037926

Ruiz, Francisco-Javier; Rubio, Soledad; Pérez-Bendito, Dolores

2006-10-15

308

Online gas and aerosol measurement of water soluble carboxylic acids in Zurich  

NASA Astrophysics Data System (ADS)

We discuss the diurnal and seasonal variability of low molecular weight organic acids in Zurich city on the basis of online quasi-continuous measurement in the gas and aerosol phase using a wet effluent diffusion denuder/aerosol collector (WEDD/AC) coupled to ion chromatography. The measurements were performed during August-September 2002 and March 2003. Acetic acid exhibited the highest concentration in the gas phase during all the measurement periods, followed by formic acid. Oxalic acid was predominantly found in the aerosol phase and often below the detection limit in the gas phase. In addition, filter samples were analyzed using ion chromatography-mass spectrometry (IC-MS) to provide more information on organic acids in the aerosol phase. From the offline IC-MS measurements, 20 monocarboxylic, dicarboxylic, and tricarboxylic acids were determined. In addition, more than 20 different masses were detected with the MS; however, identification of the organic acids was not possible. The sum of the carboxylic acids contributed on average 2% to the water soluble organic carbon (WSOC). The fraction of dicarboxylic acids to the WSOC was higher in summer compared to winter suggesting that dicarboxylic acids are mainly a result of photochemical reactions in summer whereas in winter they mainly result from primary sources.

Fisseha, Rebeka; Dommen, Josef; Gaeggeler, Kathrin; Weingartner, Ernest; Samburova, Vera; Kalberer, Markus; Baltensperger, Urs

2006-06-01

309

1-Aminocyclopropane-1-carboxylic acid oxidase reaction mechanism and putative post-translational activities of the ACCO protein  

PubMed Central

1-Aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACCO) catalyses the final step in ethylene biosynthesis converting ACC to ethylene, cyanide, CO2, dehydroascorbate and water with inputs of Fe(II), ascorbate, bicarbonate (as activators) and oxygen. Cyanide activates ACCO. A ‘nest’ comprising several positively charged amino acid residues from the C-terminal ?-helix 11 along with Lys158 and Arg299 are proposed as binding sites for ascorbate and bicarbonate to coordinately activate the ACCO reaction. The binding sites for ACC, bicarbonate and ascorbic acid for Malus domestica ACCO1 include Arg175, Arg244, Ser246, Lys158, Lys292, Arg299 and Phe300. Glutamate 297, Phe300 and Glu301 in ?-helix 11 are also important for the ACCO reaction. Our proposed reaction pathway incorporates cyanide as an ACCO/Fe(II) ligand after reaction turnover. The cyanide ligand is likely displaced upon binding of ACC and ascorbate to provide a binding site for oxygen. We propose that ACCO may be involved in the ethylene signal transduction pathway not directly linked to the ACCO reaction. ACC oxidase has significant homology with Lycopersicon esculentum cysteine protease LeCp, which functions as a protease and as a regulator of 1-aminocyclopropane-1-carboxylic acid synthase (Acs2) gene expression. ACC oxidase may play a similar role in signal transduction after post-translational processing. ACC oxidase becomes inactivated by fragmentation and apparently has intrinsic protease and transpeptidase activity. ACC oxidase contains several amino acid sequence motifs for putative protein–protein interactions, phosphokinases and cysteine protease. ACC oxidase is subject to autophosphorylaton in vitro and promotes phosphorylation of some apple fruit proteins in a ripening-dependent manner.

Dilley, David R.; Wang, Zhenyong; Kadirjan-Kalbach, Deena K.; Ververidis, Fillipos; Beaudry, Randolph; Padmanabhan, Kallaithe

2013-01-01

310

Microwave-assisted melt reaction method for the intercalation of carboxylic acid anions into layered double hydroxides.  

PubMed

Carboxylic acid anions intercalated layered double hydroxides are currently gaining increasing interest due to their potential applications in pharmaceutical field for controlled drug release in novel tunable drug delivery systems. In this work different aliphatic carboxylic acid anions were intercalated into the interlayers of commercial as well as synthetically prepared layered double hydroxides, through a novel microwave mediated melt reaction approach. The volumetric nature of microwave dielectric heating was exploited in order to rapidly heat the intimate mixture of the lamellar inorganic precursor and the appropriate organic acid, at the melting temperature of the particular mono- or dicarboxylic acid used, reaching the intercalation in approximately two hours treatment. PMID:24779132

Rosa, Roberto; Leonelli, Cristina; Villa, Carla; Priarone, Giulia

2013-01-01

311

Synthesis of chromium(III) complex with 1-hydroxy-2-pyridinone-6-carboxylic acid as insulin-mimetic agent and its spectroscopic and computational studies  

NASA Astrophysics Data System (ADS)

The new complex of chromium(III) and 1-hydroxy-2-pyridinone-6-carboxylic acid was synthesized and its preparation routes were reported. Mass spectrometry and elemental analysis indicated the formation of chromium complex with the metal-to-ligand mole ratio of 1:3. Combination of spectroscopic measurement and spectral computations based on the density functional theory suggested that 1-hydroxy-2-pyridinone-6-carboxylic acid was a bidentate ligand using one oxygen atom at pyridinone carbonyl group and the other at N-oxide group as donor atoms upon chelation with chromium(III), forming the six-coordinate complex with five-membered chelate rings. Due to the enhanced stability of the chelate rings, such the pathway of chelation was theoretically predicted to be more favorable than the case where the carboxylate oxygen atom of ligand participated in the chelation. According to the preliminary tests, the chromium(III) complex with 1-hydroxy-2-pyridinone-6-carboxylic acid was found to be active in lowering plasma glucose levels in vivo.

Yasarawan, Nuttawisit; Thipyapong, Khajadpai; Sirichai, Somsak; Ruangpornvisuti, Vithaya

2013-01-01

312

Chemical Functionalization of Graphene Nanoribbons by Carboxyl Groups on Stone-Wales Defects  

Microsoft Academic Search

Using the density functional theory, we have demonstrated the chemical functionalization of semiconducting graphene nanoribbons (GNRs) with Stone-Wales (SW) defects by carboxyl (COOH) groups. It is found that the geometrical structures and electronic properties of the GNRs changed significantly, and the electrical conductivity of the system could be considerably enhanced by mono-adsorption and double-adsorption of COOH, which sensitively depends upon

Fangping OuYang; Bing Huang; Zuanyi Li; Hui Xu

2007-01-01

313

Effect of A Long Chain Carboxylate Acid on Sodium Dodecyl Sulfate Micelle Structure: A SANS Study  

NASA Astrophysics Data System (ADS)

The effect of a different hydrocarbon chain length of carboxylate acid, i.e. dodecanoic acid, CH3(CH)10COOH or lauric acid and hexadecanoic acid, CH3(CH2)14COOH or palmitic acid as a co-surfactant in the 0.3 M sodium dedecyl sulfate, SDS micellar solution has been studied using small angle neutron scattering (SANS). The present of lauric acid has induced the SDS structural micelles. The ellipsoid micelles structures changed significantly in length (major axis) from 22.6 A? to 37.1 A? at a fixed minor axis of 16.7 A? in the present of 0.005 M to 0.1 M lauric acid. Nevertheless, this effect did not occur in the present of palmitic acid with the same concentration range. The present of palmitic acid molecules performed insignificant effect on the SDS micelles growth where the major axis of the micelle was elongated from 22.9 A? to 25.3 A? only. It showed that the appropriate hydrocarbon chain length between surfactant and co-surfactant molecules emerged as one of the determining factors in forming a mixed micelles structure.

Patriati, Arum; Giri Rachman Putra, Edy; Seok Seong, Baek

2010-01-01

314

Incorporation of xenobiotic carboxylic acids into lipids by cultured 3T3-L1 adipocytes.  

PubMed

The study was established to assess the potential for a variety of xenobiotic aromatic carboxylic acids to be incorporated into glycerolipids. The 14C-labelled xenobiotic acids were included in incubations of cultured 3T3-L1 adipocytes under defined conditions. Lipids were extracted and identified by TLC and radioscanning. Ibuprofen, 4-(2,4-dichlorophenoxy)-butanoic acid (2,4-DB), 4-(2-methyl-4-chlorophenoxy)-butanoic acid (MCPB) and 2-(2-methyl-4-chlorophenoxy)-propanoic acid (MCPP) (all 0.5 mM) were incorporated into lipid extracts at rates of 220, 227, 199 and 21 pmol microg(-1) phospholipid/h, respectively. 2,4-Dichlorophenoxyacetic acid (2,4-D), indomethacin, naproxen and fluroxypyr were incorporated at rates lower than MCPP or not at all. The incorporation of acids was first order to at least 1 mM acid (except MCPB: 300 microM). Triacylglycerol analogues were the major products with incorporation into diacylglycerol and phosphatidylcholine also observed. After digestion with pancreatic lipase, ibuprofen-containing triacylglycerol was unusual in that the main product was the monoacylglycerol analogue, suggesting that esterification had been at the sn-2 position. Incubation with cultured 3T3-L1 adipocytes is a useful and easy method to assess whether xenobiotic compounds can be incorporated into glycerolipids; of eight acids assessed, four (of which three have not previously been reported) were shown to form xenobiotic triacylglycerols. PMID:15801546

Vickery, S; Dodds, P F

2004-01-01

315

Evaluating the potential of long chain n-alkanes and n-carboxylic acids as biomarkers for past vegetation  

NASA Astrophysics Data System (ADS)

Leaf waxes, such as long chain n-alkanes and n-carboxylic acids, may have a great potential for the reconstruction of past environmental and climate conditions (e.g. (Zech R. et al., 2013). While n-C27 and n-C29 alkanes often predominantly occur in trees and shrubs, n-C31 and n-C33 are more abundant in grasses and herbs. However, little is known about chain-length distributions of n-carboxylic acids, and very few studies have systematically investigated leaf waxes in top soils. We analyzed n-alkanes and n-carboxylic acids in ~100 litter and topsoil samples from Southern Germany to Sweden. Our results show that sites under deciduous trees often contain a lot of C27 n-alkanes and C28 n-carboxylic acids. Coniferous sites are characterized by dominance in n-alkanes C29 and C31 and have relatively high concentrations of n-carboxylic acids C22 and C24. Grass sites show a Cmax at C31 for n-alkanes and at C24 or C26 for n-carboxylic acids. Differences in homologue patterns are most pronounced in the litter samples, but are well preserved also in the topsoils (0-3 cm depth, a little less in the lower topsoils from 3-10 cm). Our results illustrate the potential of combining n-alkane and n-carboxylic acid analyses for paleo-vegetation reconstructions, yet indicate that the degree of degradation may have to be taken into consideration (Zech M. et al., 2013). References: Zech, M. et al. (2013) Quat. Int. 296, 108-116. Zech, R. et al. (2013) Palaeo3, 387, 165-175.

Lanny, Verena; Zech, Roland; Eglinton, Timothy

2014-05-01

316

Interaction of carboxylic acids with the oxyhydroxide surface of aluminium: poly(acrylic acid), acetic acid and propionic acid on pseudoboehmite  

Microsoft Academic Search

High sensitivity and spectral resolution XPS, polarisation-modulation reflection FTIR and static SIMS have been used in this investigation of the interfacial chemistry between poly(acrylic acid) (PAA) and an aluminium oxyhydroxide surface. The pseudoboehmite oxyhydroxide surface is used as a model for the chemistry found at the surface of the air-formed film after ambient exposure of aluminium metal. Conversion of carboxylic

M. R. Alexander; G. Beamson; C. J. Blomfield; G. Leggett; T. M. Duc

2001-01-01

317

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

318

Comparative study on nano-crystalline titanium dioxide catalyzed photocatalytic degradation of aromatic carboxylic acids in aqueous medium  

Microsoft Academic Search

The comparative study on titanium dioxide (TiO2) catalyzed photocatalytic degradation (PCD) of aqueous aromatic carboxylic acids (phthalic acid, o-nitrobenzoic acid, o-chlorobenzoic acid and benzoic acid) was carried out in the presence of UV radiation using air. The TiO2 catalyst, synthesized by sol–gel technique and calcined at 673K, resulted ca. 100% anatase phase with 23nm crystallite size and surface area of

V. G. Gandhi; M. K. Mishra; M. S. Rao; A. Kumar; P. A. Joshi; D. O. Shah

2011-01-01

319

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

PubMed

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

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

2011-04-01

320

Aerobic visible light-oxidation of aromatic methyl groups to carboxylic acids.  

PubMed

A catalytic amount of magnesium bromide diethyl etherate (MgBr2.Et2O) enables us to carry out the aerobic photo-oxidation of a methyl group at the aromatic nucleus to the corresponding carboxylic acid in high yield under irradiation of VIS from a general-purpose fluorescent lamp. The bromine radical is thought to be generated in situ by continuous aerobic photo-oxidation of the bromine anion from MgBr2.Et2O, and to effect this oxidation reaction. PMID:17487303

Hirashima, Shin-ichi; Itoh, Akichika

2007-05-01

321

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

322

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

323

DFT, IR, Raman and NMR study of the coordination ability of coumarin-3-carboxylic acid to Pr(III)  

Microsoft Academic Search

A new complex of coumarin-3-carboxylic acid (HCCA) with Pr(III) is synthesized and its structure and molecular properties are investigated by elemental analysis, IR, Raman, NMR measurements and quantum chemical calculations. The elemental analysis suggested the general formula Pr(CCA)2(NO3)(H2O). The HCCA ligand possesses two donor groups (deprotonated carboxylic and carbonylic) and can act as a bidentate ligand in two different binding

Ivelina Georgieva; Irena Kostova; Natasha Trendafilova; Vinod K. Rastogi; Wolfgang Kiefer

2010-01-01

324

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

NASA Astrophysics Data System (ADS)

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

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

1994-11-01

325

The enzymatic malonylation of 1-aminocyclopropane-1-carboxylic acid in homogenates of mung-bean hypocotyls.  

PubMed

Homogenates of hypocotyls of light-grown mung-bean (Vigna radiata (L.) Wilczek) seedlings catalyzed the formation of 1-(malonylamino)cyclopropane-1-carboxylic acid (MACC) from the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) and malonyl-coenzyme A. Apparent Km values for ACC and malonyl-CoA were found to be 0.17 mM and 0.25 mM, respectively. Free coenzyme A was an uncompetitive inhibitor with respect to malonyl-CoA (apparent Ki=0.3 mM). Only malonyl-CoA served as an effective acyl donor in the reaction. The D-enantiomers of unpolar amino acids inhibited the malonylation of ACC. Inhibition by D-phenylalanine was competitive with respect to ACC (apparent Ki=1.2 mM). D-Phenylalanine and D-alanine were malonylated by the preparation, and their malonylation was inhibited by ACC. When hypocotyl segments were administered ACC in the presence of certain unpolar D-amino acids, the malonylation of ACC was inhibited while the production of ethylene was enhanced. Thus, a close-relationship appears to exist between the malonylation of ACC and D-amino acids. The cis- as well as the trans-diastereoisomers of 2-methyl- or 2-ethyl-substituted ACC were potent inhibitors of the malonyltransferase. Treatment of hypocotyl segments with indole-3-acetic acid or CdCl2 greatly increased their content of ACC and MACC, as well as their release of ethylene, but had little, or no, effect on their extractable ACC-malonylating activity. PMID:24253094

Kionka, C; Amrhein, N

1984-09-01

326

Controlled electrochemical carboxylation of graphene to create a versatile chemical platform for further functionalization.  

PubMed

An electrochemical approach is introduced for the versatile carboxylation of multi-layered graphene in 0.1 M Bu4NBF4/MeCN. First, the graphene substrate (i.e., graphene chemically vapor-deposited on Ni) is negatively charged at -1.9 V versus Ag/AgI in a degassed solution to allow for intercalation of Bu4N(+) and, thereby, separation of the individual graphene sheets. In the next step, the strongly activated and nucleophilic graphene is allowed to react with added carbon dioxide in an addition reaction, introducing carboxylate groups stabilized by Bu4N(+) already present. This procedure may be carried out repetitively to further enhance the carboxylation degree under controlled conditions. Encouragingly, the same degree of control is even attainable, if the intercalation and carboxylation is carried out simultaneously in a one-step procedure, consisting of simply electrolyzing in a CO2-saturated solution at the graphene electrode for a given time. The same functionalization degree is obtained for all multi-layered regions, independent of the number of graphene sheets, which is due to the fact that the entire graphene structure is opened in response to the intercalation of Bu4N(+). Hence, this electrochemical method offers a versatile procedure to make all graphene sheets in a multi-layered but expanded structure accessible for functionalization. On a more general level, this approach will provide a versatile way of forming new hybrid materials based on intimate bond coupling to graphene via carboxylate groups. PMID:24852930

Bjerglund, Emil; Kongsfelt, Mikkel; Shimizu, Kyoko; Jensen, Bjarke Bror Egede; Koefoed, Line; Ceccato, Marcel; Skrydstrup, Troels; Pedersen, Steen U; Daasbjerg, Kim

2014-06-10

327

Carboxylic acids as biomarkers of Biomphalaria alexandrina snails infected with Schistosoma mansoni.  

PubMed

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

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

2010-06-01

328

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

PubMed Central

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

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

2010-01-01

329

Nickel-catalysed carboxylation of organoboronates.  

PubMed

A nickel/N-heterocyclic carbene (NHC) catalysed carboxylation of aryl-, heteroaryl- and alkenylboronates, affording the corresponding carboxylic acids, has been developed. This transformation proceeds under one atmosphere of CO2 with a broad range of substrates and exhibits good functional group compatibility. PMID:24915842

Makida, Yusuke; Marelli, Enrico; Slawin, Alexandra M Z; Nolan, Steven P

2014-06-26

330

Observation of Multiple, Identical Binding Sites in the Exchange of Carboxylic Acid Ligands with CdS Nanocrystals.  

PubMed

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

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

2014-06-11

331

Glutamate: a truly functional amino acid.  

PubMed

Glutamate is one of the most abundant of the amino acids. In addition to its role in protein structure, it plays critical roles in nutrition, metabolism and signaling. Post-translational carboxylation of glutamyl residues increases their affinity for calcium and plays a major role in hemostasis. Glutamate is of fundamental importance to amino acid metabolism, yet the great bulk of dietary glutamate is catabolyzed within the intestine. It is necessary for the synthesis of key molecules, such as glutathione and the polyglutamated folate cofactors. It plays a major role in signaling. Within the central nervous system, glutamate is the major excitatory neurotransmitter and its product, GABA, the major inhibitory neurotransmitter. Glutamate interaction with specific taste cells in the tongue is a major component of umami taste. The finding of glutamate receptors throughout the gastrointestinal tract has opened up a new vista in glutamate function. Glutamate is truly a functional amino acid. PMID:22526238

Brosnan, John T; Brosnan, Margaret E

2013-09-01

332

Europium(III) complexes of polyfunctional carboxylic acids: Luminescence probes of possible binding sites in fulvic acid  

SciTech Connect

The {sup 7}F{sub 0} {r_arrow} {sup 5}D{sub 0} excitation spectra of Eu(III) complexed with polyfunctional dicarboxylic acid containing neutral O, N, and S donors were investigated using Eu(III) luminescence spectroscopy. Three distinct peaks are seen in the excitation spectra in the Eu(III)-diglycolic acid (ODA) and Eu(III)-iminodiacetic acid (IMDA) systems showing the formation of three species, where each tridentate ODA {sup 2{minus}} and IMDA{sup 2{minus}} displace approximately three coordinated water molecules; however, the central S donor of Eu(III)-thiodiglycolate and 2,5-thiophenedicarboxylate are shown to be poor chelators for free Eu{sup 3+} ions. The neutral O and N donors in combination with neighboring carboxylates may form strong metal chelation sites on fulvic acid.

Lee, B.H.; Chung, K.H.; Shin, H.S.; Moon, H. [Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of). Dept. of Chemistry] [Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of). Dept. of Chemistry; Park, Y.J. [Korea Atomic Energy Research Inst., Taejon (Korea, Republic of)] [Korea Atomic Energy Research Inst., Taejon (Korea, Republic of)

1997-04-15

333

A Study of Indium Extraction with Carboxylic Acids with the Aim to Produce Scintillators for Solar Neutrino Detection by LENS Spectroscopy of Low-Energy Neutrino  

Microsoft Academic Search

The physicochemical properties of C4-C8 carboxylic acids (mutual solubility of carboxylic acids and water, ionization constants in water, distribution between water and 1,2,4-trimethylbenzene, dimerization constants in 1,2,4-trimethylbenzene) were studied. Since indium carboxylates are sparingly soluble in 1,2,4-trimethylbenzene and the second organic phase is formed in the system, In-containing scintillators can be prepared from C4-C5 acids only in the presence of

N. A. Danilov; Yu. S. Krylov; G. V. Korpusov; G. V. Kostikova; I. R. Barabanov; L. B. Bezrukov; V. N. Kornoukhov; G. Ya. Novikova; E. A. Yanovich; N. P. Nesterova; C. M. Cattadori; A. Vacri; V. V. Yakshin

2005-01-01

334

Electronic and Cationic Spectroscopy of 9-Hydroxy-9-fluorene Carboxylic Acid.  

PubMed

Resonance-enhanced multiphoton ionization spectroscopy of supersonically cooled gas-phase 9-hydroxy-9-fluorene carboxylic acid (9HFCA) is reported for its first electronic excited state, S1. The UV-UV hole-burning experiment identifies a single conformer in the molecular beam, stabilized by an intramolecular hydrogen bond. For this Cs symmetric conformer, two low frequencies in the S1 spectrum are assigned: an in-plane rocking mode of the carboxylic acid side chain lies at 58 cm(-1), and an in-plane fluorene bending mode appears at 183 cm(-1). The corresponding mode frequencies in the cation, 58 and 196 cm(-1), are measured by zero electron kinetic energy (ZEKE) spectroscopy upon pumping the S1 vibronic states. The adiabatic ionization potential is measured to be 64?923 ± 5 cm(-1). In addition, a feature established by ZEKE spectroscopy upon pumping the hot band is found at 67 cm(-1). This is assigned as a hot band of the HO-C9-COOH rocking mode in the neutral ground state. PMID:24956485

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

2014-07-10

335

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

336

Probing the orthosteric binding site of GABAA receptors with heterocyclic GABA carboxylic acid bioisosteres.  

PubMed

The ionotropic GABAA receptors (GABAARs) are widely distributed in the central nervous system where they play essential roles in numerous physiological and pathological processes. A high degree of structural heterogeneity of the GABAAR has been revealed and extensive effort has been made to develop selective and potent GABAAR agonists. This review investigates the use of heterocyclic carboxylic acid bioisosteres within the GABAAR area. Several heterocycles including 3-hydroxyisoxazole, 3-hydroxyisoxazoline, 3-hydroxyisothiazole, and the 1- and 3-hydroxypyrazole rings have been employed in order to map the orthosteric binding site. The physicochemical properties of the heterocyclic moieties making them suitable for bioisosteric replacement of the carboxylic acid in the molecule of GABA are discussed. A variety of synthetic strategies for synthesis of the heterocyclic scaffolds are available. Likewise, methods for introduction of substituents into specific positions of the heterocyclic scaffolds facilitate the investigation of different regions in the orthosteric binding pocket in close vicinity of the core scaffolds of muscimol/GABA. The development of structural models, from pharmacophore models to receptor homology models, has provided more insight into the molecular basis for binding. Similar binding modes are proposed for the heterocyclic GABA analogues covered in this review by use of ligand-receptor docking into the receptor homology model and the presented structure-activity relationships. A network of interactions between the analogues and the binding pocket is leaving no room for substituents and underline the limited space in the GABAAR orthosteric binding site when in the agonist conformation. PMID:24362592

Petersen, Jette G; Bergmann, Rikke; Krogsgaard-Larsen, Povl; Balle, Thomas; Frølund, Bente

2014-06-01

337

Second-sphere tethering of rare-earth ions to cucurbit[6]uril by iminodiacetic acid involving carboxylic group encapsulation.  

PubMed

The reaction of rare-earth nitrates with iminodiacetic acid (H(2)IDA) in the presence of cucurbit[6]uril (CB6) in water at room temperature yields a family of isomorphous complexes, [M(H(2)IDA)(NO(3))(H(2)O)(6)](NO(3))(2)·CB6·14H(2)O with M = Y (1), Ce (2), Nd (3), Eu (4), Dy (5), Er (6), Tm (7), and Yb (8). In these compounds, the trivalent metal ion is bound to one nitrate ion, six water molecules, and one zwitterionic H(2)IDA molecule. The latter is further partly included in the CB6 cavity, with the ammonium group forming two hydrogen bonds with oxygen atoms of one portal. The uncoordinated carboxylic group is thus encapsulated in CB6 and hydrogen-bonded to the other portal via a water molecule. CB6 is a second-sphere ligand in these complexes, but direct bonding of the metal ion to CB6 can be enforced by using a ligand more deeply imbedded in the cavity, such as 2-pyridylacetate (PA) in [Eu(PA)(CB6)(NO(3))(H(2)O)(5)](NO(3))·10H(2)O (11). When the reaction with H(2)IDA is performed with Lu(III) or Cu(II), no metal complex is isolated, but the inclusion compounds [(H(3)IDA)(2)(CB6)](NO(3))(2)·xH(2)O with x = 6 (9) or 8 (10) are obtained instead, in which the two H(3)IDA(+) cations are attached to the CB6 portals by ammonium-carbonyl hydrogen bonds and are linked to one another inside the cavity by hydrogen bonding between the carboxylic groups. These complexes are compared to that comprising a dicarboxylic acid devoid of an ammonium functionality, [(H(2)AZ)(CB6)]·6H(2)O (12), where H(2)AZ is azelaic acid. The metal ion complexes 1-8 and the organic complexes 9 and 10 display the unprecedented feature of inclusion of carboxylic groups inside the CB6 cavity, with the CB6/acid stoichiometry and the finer details of the host-guest interactions being dependent on the presence of the metal ion. PMID:20815367

Thuéry, Pierre

2010-10-01

338

Self-assembly of carboxylic acid appended naphthalene diimide derivatives with tunable luminescent color and electrical conductivity.  

PubMed

Self-assembly of a series of carboxylic acid-functionalized naphthalene diimide (NDI) chromophores with a varying number (n=1-4) of methylene spacers between the NDI ring and the carboxylic acid group has been studied. The derivatives show pronounced aggregation due to the synergistic effects of H-bonding between the carboxylic acid groups in a syn-syn catemer motif and ??stacking between the NDI chromophores. Solvent-dependent UV/Vis studies reveal the existence of monomeric dye molecules in a "good" solvent such as chloroform and self-assembly in "bad" solvents such as methylcyclohexane. The propensity of self-assembly is comparable for all samples. Temperature-dependent spectroscopic studies show high thermal stability of the H-bonding-mediated self-assembled structures. In the presence of a protic solvent such as MeOH, self-assembly can be suppressed, suggesting a decisive role of H-bonding, whereas ??stacking is more a consequence of than a cause for self-assembly. Syn-syn catemer-type H-bonding is supported by powder XRD studies and the results corroborate well with DFT calculations. The morphology as determined by AFM is found to be dependent on the value of n; with increasing n, the morphology gradually shifts from 2D nanosheets to 1D nanofibers. Emission spectra show sharp emission bands with relatively small Stokes shifts. In addition, a rather broad emission band is observed at longer wavelengths because of the in situ formation of excimer-type species. Due to such a heterogeneous nature, the emission spectrum spans almost the entire red-green-blue region. Depending on the value of n, the ratio of intensities of the two emission bands is changed, which results in a tunable luminescent color. Furthermore, in the case of n=1 and 3, almost pure white light emission is observed. Time-resolved photoluminescence spectra show a very short lifetime (a few picoseconds) of monomeric dye molecules and biexponential decays with longer lifetimes (on the order of nanoseconds) for aggregated species. Current-voltage measurements show electrical conductivity in the range of 10(-4) ?S?cm(-1) for the aggregated chromophores, which is four orders of magnitude higher than the value for a structurally similar NDI control molecule lacking the H-bonding functionality. PMID:24339217

Molla, Mijanur Rahaman; Gehrig, Dominik; Roy, Lisa; Kamm, Valentin; Paul, Ankan; Laquai, Frédéric; Ghosh, Suhrit

2014-01-13

339

Complex formation of cytochrome C with a calixarene carboxylic acid derivative: a novel solubilization method for biomolecules in organic media.  

PubMed

A calixarene carboxylic acid derivative has been found to form a complex with the cationic protein cytochrome c. The solubilized cytochrome c was stable and showed peroxidase activity in chloroform. The calix[6]arene and the calix[8]arene achieved quantitative extraction of the protein. The calix[6]arene, whose cavity is well-fitted to a protonated amino group, exhibited a selectivity to lysine-rich proteins due to the recognition of the epsilon-amino groups in lysine residues on the surface of the protein. This is the first report showing protein extraction by calixarenes. The solubilized cytochrome c could catalyze an oxidative reaction in organic solvents. This host compound functions as a novel solubilization tool for biomolecules and a separation tool for lysine-rich proteins. PMID:12005512

Oshima, Tatsuya; Goto, Masahiro; Furusaki, Shintaro

2002-01-01

340

Indoline-3-carboxylic acid derived organocatalysts for the anti-Mannich reaction.  

PubMed

Mannich type reactions of a preformed aldimine with various carbonyl compounds were investigated with a series of functionalised indoline derivatives as catalysts: indoline-3-carboxylic acid, the diphenylcarbinol analogue and O-protected silyl ether analogues. All compounds were readily prepared in enantiopure form by using an enzymatic kinetic resolution as a key step (E?100). The alcohol and ether catalysts failed to induce complete chirality transfer but did afford the Mannich bases in good yields and high diastereomeric ratios, whereas the acid catalyst gave the products in a highly diastereo- and enantioselective manner. The absolute configuration of the products was determined by a syn-anti isomerisation protocol, initiated by the sterically demanding base 1,8-diazabicyclo[5.4.0]undec-7-ene. PMID:21108254

Pietruszka, Jörg; Simon, Robert Christian

2010-12-27

341

Toxicity assessment of perfluorinated carboxylic acids (PFCAs) towards the rotifer Brachionus calyciflorus.  

PubMed

The effects of acute toxicity, 3-day population growth and morphological effects of perfluorinated carboxylic acids (PFCAs) with carbon chain lengths of 2-6 on the freshwater rotifer Brachionus calyciflorus were investigated. The results indicated that the 24-h median lethal concentration (LC50) values of trifluoroacetic acid (TFA), perfluoropropionic acid (PFPrA), perfluorobutanoic acid (PFBA), perfluopentanoic acid (PFPeA), and perfluorohexanoic acid (PFHxA) towards B. calyciflorus were 70, 80, 110, 130 and 140mgL(-1), respectively. The acute effects of PFCAs decreased with the increase of carbon chain length. The parameters used to determine 3-day population growth on these compounds were the rate of population increase (r) and mictic ratio. With the increase of fluorinated carbon-chain length, the r values of TFA, PFPrA, PFBA, PFPeA and PFHxA decreased by 0.99%, 16.8%, 16.5%, 22.4% and 32.0%, respectively. Mictic ratios ranged from 0.707 to 0.953 for PFCAs with carbon chain lengths of 2-6. In addition, the mictic ratio, body size and egg size exposed to some PFCAs were higher than those of the controls. These results offer a useful method for the ecological risk assessment of these short chain PFCAs. PMID:24572989

Wang, Yujuan; Niu, Junfeng; Zhang, Lilan; Shi, Jianghong

2014-09-01

342

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

PubMed Central

25 aromatic carboxylic acids which are analogs of benzoic acid were tested in the rat diaphragm preparation for effects on chloride conductance (G(Cl)). Of the 25, 19 were shown to reduce membrane G(Cl) with little effect on other membrane parameters, although their apparent K(i) varied widely. This inhibition was reversible if exposure times were not prolonged. The most effective analog studied was anthracene-9-COOH (9-AC; K(i) = 1.1 x 10(-5) M). Active analogs produced concentration-dependent inhibition of a type consistent with interaction at a single site or group of sites having similar binding affinities, although a correlation could also be shown between lipophilicity and K(i). Structure-activity analysis indicated that hydrophobic ring substitution usually increased inhibitory activity while para polar substitutions reduced effectiveness. These compounds do not appear to inhibit G(Cl) by altering membrane surface charge and the inhibition produced is not voltage dependent. Qualitative characteristics of the I-V relationship for Cl(-) current are not altered. Conductance to all anions is not uniformly altered by these acids as would be expected from steric occlusion of a common channel. Concentrations of 9-AC reducing G(Cl) by more than 90 percent resulted in slight augmentation of G(I). The complete conductance sequence obtained at high levels of 9-AC was the reverse of that obtained under control conditions. Permeability sequences underwent progressive changes with increasing 9-AC concentration and ultimately inverted at high levels of the analog. Aromatic carboxylic acids appear to inhibit G(Cl) by binding to a specific intramembrane site and altering the selectivity sequence of the membrane anion channel.

Palade, PT; Barchi, RL

1977-01-01

343

Hydroxyindole carboxylic Acid-based inhibitors for receptor-type protein tyrosine protein phosphatase Beta.  

PubMed

Abstract Aims: Protein tyrosine phosphatases (PTPs) play an important role in regulating a wide range of cellular processes. Understanding the role of PTPs within these processes has been hampered by a lack of potent and selective PTP inhibitors. Generating potent and selective probes for PTPs remains a significant challenge because of the highly conserved and positively charged PTP active site that also harbors a redox-sensitive Cys residue. Results: We describe a facile method that uses an appropriate hydroxyindole carboxylic acid to anchor the inhibitor to the PTP active site and relies on the secondary binding elements introduced through an amide-focused library to enhance binding affinity for the target PTP and to impart selectivity against off-target phosphatases. Here, we disclose a novel series of hydroxyindole carboxylic acid-based inhibitors for receptor-type tyrosine protein phosphatase beta (RPTP?), a potential target that is implicated in blood vessel development. The representative RPTP? inhibitor 8b-1 (L87B44) has an IC50 of 0.38??M and at least 14-fold selectivity for RPTP? over a large panel of PTPs. Moreover, 8b-1 also exhibits excellent cellular activity and augments growth factor signaling in HEK293, MDA-MB-468, and human umbilical vein endothelial cells. Innovation: The bicyclic salicylic acid pharmacophore-based focused library approach may provide a potential solution to overcome the bioavailability issue that has plagued the PTP drug discovery field for many years. Conclusion: A novel method is described for the development of bioavailable PTP inhibitors that utilizes bicyclic salicylic acid to anchor the inhibitors to the active site and peripheral site interactions to enhance binding affinity and selectivity. Antioxid. Redox Signal. 20, 2130-2140. PMID:24180557

Zeng, Li-Fan; Zhang, Ruo-Yu; Bai, Yunpeng; Wu, Li; Gunawan, Andrea M; Zhang, Zhong-Yin

2014-05-10

344

The evaluation in the Ames test of the mutagenicity of tetrahydro-beta-carboline-3-carboxylic acids from smoked foods.  

PubMed

This paper reports the evaluation of five tetrahydro-beta-carboline carboxylic acids, formed from the interaction of woodsmoke carbonyls and tryptophan, for mutagenicity in the Ames test. Three of the compounds tested have been detected recently in smoked foods at levels in the micrograms/kg or mg/kg range. None of the compounds induced mutagenicity in TA 97, TA 98 or TA 100 strains of Salmonella typhimurium either with or without prior activation. However, tetrahydro-beta-carboline-3-carboxylic acid, and to a lesser extent 1-methyl-tetrahydro-beta-carboline-3-carboxylic acid were toxic to the strains of Salmonella typhimurium used. The inability of these beta-carbolines to induce mutation contrasts markedly with the mutagenicity of some beta-carbolines found in grilled meat products. PMID:1499775

Papavergou, E; Ioannides, C; Clifford, M N

1992-01-01

345

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

346

Are carboxyl groups the most acidic sites in amino acids? Gas-phase acidities, photoelectron spectra, and computations on tyrosine, p-hydroxybenzoic acid, and their conjugate bases.  

PubMed

Deprotonation of tyrosine in the gas phase was found to occur preferentially at the phenolic site, and the conjugate base consists of a 70:30 mixture of phenoxide and carboxylate anions at equilibrium. This result was established by developing a chemical probe for differentiating these two isomers, and the presence of both ions was confirmed by photoelectron spectroscopy. Equilibrium acidity measurements on tyrosine indicated that deltaG(acid)(o) = 332.5 +/- 1.5 kcal mol(-1) and deltaH(acid)(o) = 340.7 +/- 1.5 kcal mol(-1). Photoelectron spectra yielded adiabatic electron detachment energies of 2.70 +/- 0.05 and 3.55 +/- 0.10 eV for the phenoxide and carboxylate anions, respectively. The H/D exchange behavior of deprotonated tyrosine was examined using three different alcohols (CF3CH2OD, C6H5CH2OD, and CH3CH2OD), and incorporation of up to three deuterium atoms was observed. Two pathways are proposed to account for these results, and all of the experimental findings are supplemented with B3LYP/aug-cc-pVDZ and G3B3 calculations. In addition, it was found that electrospray ionization of tyrosine from a 3:1 (v/v) CH3OH/H2O solution using a commercial source produces a deprotonated [M-H]- anion with the gas-phase equilibrium composition rather than the structure of the ion that exists in aqueous media. Electrospray ionization from acetonitrile, however, leads largely to the liquid-phase (carboxylate) structure. A control molecule, p-hydroxybenzoic acid, was found to behave in a similar manner. Thus, the electrospray conditions that are employed for the analysis of a compound can alter the isomeric composition of the resulting anion. PMID:19115946

Tian, Zhixin; Wang, Xue-Bin; Wang, Lai-Sheng; Kass, Steven R

2009-01-28

347

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

348

Cutoff in detection of eye irritation from vapors of homologous carboxylic acids and aliphatic aldehydes.  

PubMed

Using neat vapors of selected homologous aldehydes (decanal, undecanal, dodecanal) and carboxylic acids (pentanoic, hexanoic, heptanoic, octanoic, nonanoic), we explored the point where a certain homolog (and all larger ones) becomes undetectable by eye irritation (i.e. by ocular chemesthesis). This phenomenon has been observed in other homologous series that also reach a break-point, or cutoff, in chemesthetic detection. Participants (11acid were the shortest undetectable homologs. When the vapor concentration of the stimuli was increased by heating the liquid source to 37 degrees C, homologs located before the cutoff point (e.g. hexanoic acid) became readily detected by all subjects, whereas homologs located at the cutoff remained largely undetected. In addition, a comparison of calculated values of eye irritation thresholds for aldehydes and acids (from a successful model of ocular chemesthetic potency) with values of saturated vapor concentration at 23 and 37 degrees C indicated that the vapor concentration of dodecanal and heptanoic acid should have been enough to produce detection. The outcome suggests that the cutoff observed does not result from a low vapor concentration but from limitations in the structure or dimension(s) of the molecules that render them unsuitable to interact effectively with human chemesthetic receptors. PMID:17270354

Cometto-Muñiz, J E; Cain, W S; Abraham, M H; Sánchez-Moreno, R

2007-03-30

349

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

PubMed

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

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

2014-01-01

350

Abiotic Formation of Carboxylic Acids (RCOOH) in Interstellar and Solar System Model Ices  

NASA Astrophysics Data System (ADS)

The present laboratory study simulated the abiotic formation of carboxylic acids (RCOOH) in interstellar and solar system model ices of carbon dioxide (CO2)-hydrocarbon mix C n H2n+2 (n = 1-6). The pristine model ices were irradiated at 10 K under contamination-free, ultrahigh vacuum conditions with energetic electrons generated in the track of galactic cosmic-ray particles. The chemical processing of the ices was monitored by a Fourier transform infrared spectrometer and a quadrupole mass spectrometer during the irradiation phase and subsequent warm-up phases on line and in situ in order to extract qualitative (carriers) and quantitative (rate constants and yields) information on the newly synthesized species. Carboxylic acids were identified to be the main carrier, together with carbon monoxide (CO) and a trace of formyl (HCO) and hydroxycarbonyl (HOCO) radicals at 10 K. The upper limit of acid column density at 10 K was estimated as much as (1.2 ± 0.1) × 1017 molecules cm-2 at doses of 17 ± 2 eV molecule-1, or the yield of 39% ± 4% from the initial column density of carbon dioxide. The temporal column density profiles of the products were then numerically fit using two independent kinetic schemes of reaction mechanisms. Finally, we transfer this laboratory simulation to star-forming regions of the interstellar medium, wherein cosmic-ray-induced processing of icy grains at temperatures as low as 10 K could contribute to the current level of chemical complexity as evidenced in astronomical observations and in extracts of carbonaceous meteorites.

Kim, Y. S.; Kaiser, R. I.

2010-12-01

351

Fourier Tranform Microwave Studies of Bi-Molecules of Carboxylic Acids  

NASA Astrophysics Data System (ADS)

We recorded the molecular beam Fourier transform microwave spectra of several isotopic species of several homo and hetero dimers of carboxylic acids (R-COOH). Several tunnelling splittings have been measured with the accuracy underlying microwave spectroscopy. These splittings have been originated by the concerted double proton transfer of the two protons, but in some cases also by internal motions within the R chain in R-COOH. When the splittings were due to the double proton transfer, they were considerably decreasing upon mono- or bi-deuteration of the two carboxylic protons. The splittings due to the proton transfer have been used to determine the barrier to the proton transfer by applying a flexible model suited to take into account the coupling of the proton motions with the skeletal motions. The potential energy surfaces of the lateral chain motions have also been estimated. A full frame structure has been determined for some bimolecules, obtaining details of the Ubbelohde effect associated to the double hydrogen bond.

Evangelisti, Luca; Feng, Gang; Qian, Gou; Maris, Assimo; Caminati, W.; Favero, Laura B.; Cocinero, Emilio; Ejica, Patricia; Fernandez, Jose'A.; Castano, Fernando; Lesarri, Alberto; Meyer, Rolf

2012-06-01

352

Vibrational, electronic and quantum chemical studies of 5-benzimidazole carboxylic acid  

NASA Astrophysics Data System (ADS)

Detailed structural and vibrational investigations of 5-benzimidazole carboxylic acid have been carried out with FTIR and FT-Raman spectral techniques. The electronic structure of the molecule has been analysed by 1H and 13C NMR spectroscopies. The DFT studies were carried out with B3LYP method utilising 6-31G**, 6-311++G** and cc-pVTZ basis sets to determine the structural, thermodynamical, vibrational, electronic characteristics of the compound and also to understand the electronic and steric influence of the carboxylic group on the skeletal frequencies. Complete NBO analysis was also carried out to find out the intramolecular electronic interactions and their stabilisation energy. The extreme limits of the electrostatic potential is +1.435e × 10-2 and -1.435e × 10-2. The frontier orbital energy gap in the case of 5BICA is found to be 5.2742 eV. In 5BICA molecule, the lone pair donor orbital, n??CN? interaction between the N1 lone pair and C2sbnd N3 antibonding orbital is seen to give a strong stabilisation of 43.32 kJ mol-1.

Arjunan, V.; Raj, Arushma; Mythili, C. V.; Mohan, S.

2013-03-01

353

Fluorescent-tagged acrylic acid-allylpolyethoxy carboxylate copolymer as a green inhibitor for calcium phosphate in industrial cooling systems  

Microsoft Academic Search

Allyloxy polyethoxy ether (APEG) and succinic anhydride were used to prepare allyloxy polyethoxy carboxylate (APEL). The 8-hydroxy-1,3,6-pyrene trisulfonic acid trisodium salt (PY) was reacted with allyl chloride to produce fluorescent monomer 8-allyloxy-1,3,6-pyrene trisulfonic acid trisodium salt (PA). APEL and PA were copolymerized with acrylic acid (AA) to synthesize PA-tagged no phosphate and nitrogen free calcium phosphate inhibitor AA–APEL–PA. Structures of

Guangqing Liu; Jingyi Huang; Yuming Zhou; Qingzhao Yao; Yong Yang; Lei Ling; Huchuan Wang; Wendao Wu; Wei Sun; Zhengjun Hu

2012-01-01

354

Determination of sulfophenyl carboxylic acids in agricultural groundwater samples by CE with ultraviolet absorption detection.  

PubMed

An analytical method for the determination of six sulfophenyl carboxylic acids, namely (p-sulfophenyl)acetic, 2-(p-sulfophenyl)propionic, 2-(p-sulfophenyl)butyric, 3-(p-sulfophenyl)butyric, 4-(p-sulfophenyl)butyric, and 5-(p-sulfophenyl)valerianic acid, in agricultural irrigation water samples was developed. It involves an SPE procedure, an on-line preconcentration normal stacking mode and subsequent separation and determination using CE with UV detection (CE-UV). p-Sulfobenzoic acid was used as internal standard. The compounds were separated with an uncoated capillary and a 25 mM ammonium acetate/acetic acid buffer solution (pH 5.5) with 2-propanol (30% v/v) and 0.75 mM CTAB. Analyses were run at -25 kV, 25 degrees C, and 100 s of hydrodynamic injection with UV detection at 225 nm. Quantification limits found ranged between 4 and 6 ng/mL. The proposed method was validated using a recovery assay. It was satisfactorily used for the determination of these compounds in groundwater samples to track down the biodegradation of linear alkylbenzene sulfonates in an agricultural soil from the fertile plain of Granada (Spain). PMID:18080250

Jiménez-Díaz, Inmaculada; Ballesteros, Oscar; Vílchez, José Luis; Navalón, Alberto

2008-01-01

355

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

SciTech Connect

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

Carraher, Jack; Pestovsky, Oleg; Bakac, Andreja

2012-03-14

356

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

2013-01-21

357

Polymorphism in Self-Assembled Structures of 9-Anthracene Carboxylic Acid on Ag(111)  

PubMed Central

Surface self-assembly process of 9-anthracene carboxylic acid (AnCA) on Ag(111) was investigated using STM. Depending on the molecular surface density, four spontaneously formed and one annealed AnCA ordered phases were observed, namely a straight belt phase, a zigzag double-belt phase, two simpler dimer phases, and a kagome phase. The two high-density belt phases possess large unit cells on the scale length of 10 nm, which are seldom observed in molecular self-assembled structures. This structural diversity stems from a complicated competition of different interactions of AnCA molecules on metal surface, including intermolecular and molecular-substrate interactions, as well as the steric demand from high molecular surface density.

Lu, Chao; Wei, Yinying; Zhu, Erkuang; Reutt-Robey, Janice E.; Xu, Bo

2012-01-01

358

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

2012-08-01

359

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

PubMed

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

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

2014-06-15

360

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

361

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

PubMed

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

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

2010-07-01

362

A copper-catalyzed formal O-H insertion reaction of ?-diazo-1,3-dicarbonyl compounds to carboxylic acids with the assistance of isocyanide.  

PubMed

A novel copper-catalyzed formal O-H insertion of ?-diazo-1,3-dicarbonyl compounds to carboxylic acids has been developed, providing a straightforward synthetic method for ?-acyloxy-1,3-dicarbonyl compounds, in which the activation of carboxylic acids by isocyanide plays a crucial role. PMID:24609683

Wang, Zikun; Bi, Xihe; Liang, Yongjiu; Liao, Peiqiu; Dong, Dewen

2014-04-18

363

A simple and convenient method for preparation of carboxylic acid alkyl esters, phenolic and thioesters using chlorodiphenylphosphine\\/I 2 and imidazole reagent system  

Microsoft Academic Search

Condensation of carboxylic acids with alcohols, phenols and thiols proceeded smoothly to afford carboxylic acid alkyl esters, phenolic esters and thioesters by using the combination of chlorodiphenylphosphine, imidazole and molecular iodine in refluxing acetonitrile. Esterification with this mixed reagent system gave the corresponding products in excellent yields. The phosphorus-containing byproduct was simply removed from the organic phase by basic aqueous

Najmeh Nowrouzi; Abdol Mohammad Mehranpour; Javad Ameri Rad

2010-01-01

364

An infrared study of selective hydrogenation of carboxylic acids to corresponding aldehydes over a ZrO 2 catalyst: pivalic acid to 2,2-dimethylpropanal  

Microsoft Academic Search

A selective hydrogenation of pivalic acid ((CH3)3C-COOH) to 2,2-dimethylpropanal ((CH3)3C-CHO) was studied by infrared spectroscopy. While pivalic acid adsorbed on Cr2O3-ZrO2 as a carboxylate ((CH3)3C-COC-) above 303 K and decomposed at 773 K, it was reduced by H2 at 623 K. The adsorbed aldehyde changed into the carboxylic acid ion species above 523 K via several intermediate species observed below

Nan Ding; Junko Kondo; Ken ichi Maruya; Kazunari Domen; Toshiharu Yokoyama; Naoko Fujita; Takao Maki

1993-01-01

365

Ru-catalyzed dehydrogenative coupling of carboxylic acids and silanes - a new method for the preparation of silyl ester  

PubMed Central

Summary Ru3(CO)12/EtI has been found to be an efficient catalyst system for the dehydrosilylation of carboxylic acids with silanes. In the presence of 1 mol% Ru3(CO)12 and 4 mol% EtI, dehydrosilylation reactions in toluene afforded the corresponding silyl esters at 100 °C in good and high yields.

Zhao, Hong-Yun

2008-01-01

366

Characterization of Negative Tone Photoresist Based on Acid Catalyzed Dehydration Crosslinking of Novolac Resins Having Pendant Carboxyl Groups  

Microsoft Academic Search

Esterification of 4-hydroxyphenylacetic acid with various alcohols of (+)-borneol, (±)-borneol and ethylene glycol monobutyl ether were carried out. The ester compounds were then copolymerized with various comonomers of bisphenol-A, phenol and formaldehyde. Physical properties and molecular structures of such synthesized phenolic resins were investigated by using IR, NMR, DSC, and TGA. To introduce carboxyl groups onto the side chain of

Hui-Hsiang Liu; Wei-Tin Chen; Fuh-Tsang Wu

2002-01-01

367

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

NASA Astrophysics Data System (ADS)

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

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

1985-03-01

368

Carboxylic acids in the rural continental atmosphere over the eastern United States during the Shenandoah Cloud and Photochemistry Experiment  

Microsoft Academic Search

The Shenandoah Cloud and Photochemistry Experiment (SCAPE) was conducted during September 1990 in the rural continental atmosphere at a mountain top site (1014 m) in Shenandoah National Park, Virginia. We report here the extensive set of trace gas measurements performed during clear sky periods of SCAPE, with particular focus on the carboxylic acids, formic, acetic, and pyruvic. Median mixing ratios

Robert W. Talbot; Byard W. Mosher; Brian G. Heikes; Daniel J. Jacob; J. William Munger; Bruce C. Daube; William C. Keene; John R. Maben; Richard S. Artz

1995-01-01

369

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

PubMed Central

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

2011-01-01

370

Effect of storage time and natural corrosion inhibitor on carbohydrate and carboxylic acids content in canned tomato purée  

Microsoft Academic Search

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

A Nin?evi? Grassino; Z Grabari?; F De Sio; D Cacace; A Pezzani; G Squitieri

2012-01-01

371

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

2008-11-01

372

Chemical Functionalization of Graphene Nanoribbons by Carboxyl Groups on Stone-Wales Defects  

Microsoft Academic Search

Using the density functional theory, we have demonstrated the chemical\\u000afunctionalization of semiconducting graphene nanoribbons (GNRs) with\\u000aStone-Wales (SW) defects by carboxyl (COOH) groups. It is found that the\\u000ageometrical structures and electronic properties of the GNRs changed\\u000asignificantly, and the electrical conductivity of the system could be\\u000aconsiderably enhanced by mono-adsorption and double-adsorption of COOH, which\\u000asensitively depends upon

Fangping OuYang; Bing Huang; Zuanyi Li; Hui Xu; Huanyou Wang

2008-01-01

373

Investigation of supramolecular synthons and structural characterisation of aminopyridine-carboxylic acid derivatives  

PubMed Central

Background Co-crystal is a structurally homogeneous crystalline material that contains two or more neutral building blocks that are present in definite stoichiometric amounts. The main advantage of co-crystals is their ability to generate a variety of solid forms of a drug that have distinct physicochemical properties from the solid co-crystal components. In the present investigation, five co-crystals containing 2-amino-6-chloropyridine (AMPY) moiety were synthesized and characterized. Results The crystal structure of 2-amino-6-chloropyridine (AMPY) (I), and the robustness of pyridine-acid supramolecular synthon were discussed in four stoichiometry co-crystals of AMPY…BA (II), AMPY…2ABA (III), AMPY…3CLBA (IV) and AMPY…4NBA (V). The abbreviated designations used are benzoic acid (BA), 2-aminobenzoic acid (2ABA), 3-chlorobenzoic acid (3CLBA) and 4-nitrobenzoic acid (4NBA). All the crystalline materials have been characterized by 1HNMR, 13CNMR, IR, photoluminescence, TEM analysis and X-ray diffraction. The supramolecular assembly of each co-crystal is analyzed and discussed. Conclusions Extensive N---H?·?·?·?N/N---H?·?·?·?O/O---H?·?·?·?N hydrogen bonds are found in (I-V), featuring different supramolecular synthons. In the crystal structure, for compound (I), the 2-amino-6-chloropyridine molecules are linked together into centrosymmetric dimers by hydrogen bonds to form homosynthon, whereas for compounds (II-V), the carboxylic group of the respective acids (benzoic acid, 2-aminobenzoic acid, 3-chlorobenzoic acid and 4-nitrobenzoic acid) interacts with pyridine molecule in a linear fashion through a pair of N---H?·?·?·?O and O---H?·?·?·?N hydrogen bonds, generating cyclic hydrogen-bonded motifs with the graph-set notation R 2 2 8 , to form heterosynthon. In compound (II), another intermolecular N---H?·?·?·?O hydrogen bonds further link these heterosynthons into zig-zag chains. Whereas in compounds (IV) and (V), these heterosynthons are centrosymmetrically paired via N---H?·?·?·?O hydrogen bonds and each forms a complementary DADA [D?=?donor and A?=?acceptor] array of quadruple hydrogen bonds, with graph-set notation R238, R228 and R238.

2014-01-01

374

Highly stereoselective biosynthesis of (R)-?-hydroxy carboxylic acids through rationally re-designed mutation of d-lactate dehydrogenase  

PubMed Central

An NAD-dependent d-lactate dehydrogenase (d-nLDH) of Lactobacillus bulgaricus ATCC 11842 was rationally re-designed for asymmetric reduction of a homologous series of ?-keto carboxylic acids such as phenylpyruvic acid (PPA), ?-ketobutyric acid, ?-ketovaleric acid, ?-hydroxypyruvate. Compared with wild-type d-nLDH, the Y52L mutant d-nLDH showed elevated activities toward unnatural substrates especially with large substitutes at C-3. By the biocatalysis combined with a formate dehydrogenase for in situ generation of NADH, the corresponding (R)-?-hydroxy carboxylic acids could be produced at high yields and highly optical purities. Taking the production of chiral (R)-phenyllactic acid (PLA) from PPA for example, 50?mM PPA was completely reduced to (R)-PLA in 90?min with a high yield of 99.0% and a highly optical purity (>99.9% e.e.) by the coupling system. The results presented in this work suggest a promising alternative for the production of chiral ?-hydroxy carboxylic acids.

Zheng, Zhaojuan; Sheng, Binbin; Gao, Chao; Zhang, Haiwei; Qin, Tong; Ma, Cuiqing; Xu, Ping

2013-01-01

375

Synthesis and structural characterization of organotin(IV) complexes formed with [o,o] donor atoms of carboxylic acids  

Microsoft Academic Search

Organotin(IV) carboxylates of the general formula RnSnL4-n (where R = Me, n-Bu or Ph, and L = ?-phenyl-2,3-(methylenedioxy)cinnamate anion or 2-(2,3-dimethlylanilino)nicotinate anion) have been prepared. The mono-, di- and tri-organotin(IV) carboxylates were synthesized by the reaction of orga- notin(IV) oxides or hydroxides with a stoichiometric amount of the ligand acids at an elevated temperature in dry toluene. The composition of

Mukhtiar Hussain; Muhammad Zaman; Muhammad Hanif; Saqib Ali; Muhammad Danish

2008-01-01

376

Copper-catalyzed annulation of heteroaromatic ?-halo-?,?-unsaturated carboxylic acids with alkynes for the synthesis of indolo[2,3-c]pyrane-1-ones and thieno[2,3-c]pyrane-7-ones.  

PubMed

The annulation of heteroaromatic ?-halo-?,?-unsaturated carboxylic acids with alkynes proceeds efficiently in the presence of Cu(OAc)2·H2O as a catalyst to afford the corresponding indolo[2,3-c]pyrane-1-ones and thieno[2,3-c]pyrane-7-ones in moderate to good yields. This strategy offers a simple and efficient route for the synthesis of indolo[2,3-c]pyrane-1-ones and thieno[2,3-c]pyrane-7-ones with good tolerance to a variety of functional groups from easily available heteroaromatic ?-halo-?,?-unsaturated carboxylic acids. PMID:24987834

Gu, Da-Wei; Guo, Xun-Xiang

2014-08-28

377

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

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

378

Antilipidemic activity of 4-oxo-functionalized ethyl 6-chlorochroman-2-carboxylate analogs and a related tricyclic lactone in three rat models  

Microsoft Academic Search

The synthesis of ethylcis-6-chloro-4-hydroxychroman-2-carboxylate (IV) and 6-chloro-4-hydroxychroman-2-carboxylic acid lactone (V) are reported. The\\u000a antilipidemic properties of these compounds in 3 rat models were compared to the activity obtained for the previously synthesized\\u000a related analogs ethyl 6-chlorochroman-2-carboxylate (II), ethyl 6-chlorochromanone-2-carboxylate (III) and clofibrate (I).\\u000a The biologically most interesting analog, ethyl 6-chlorochroman-2-carboxylate (II) like clofibrate (I), was an effective antitriglyceridemic\\u000a and anticholesterolemic

R. C. Cavestri; J. A. Minatelli; J. R. Baldwin; W. Loh; D. R. Feller; H. A. I. Newman; C. L. Sober; D. T. Witiak

1981-01-01

379

Double-stranded supramolecular assembly through salt bridge formation between rigid and flexible amidine and carboxylic acid strands.  

PubMed

A series of monomeric strands consisting of m-terphenyl backbones with chiral rigid C-linked (3) and flexible N-linked (5) formamidines and achiral carboxylic acid (4) and flexible carboxymethyl (6) residues were synthesized, and their duplex formations through amidinium-carboxylate salt bridges were investigated by NMR, circular dichroism (CD), and UV-visible spectroscopies. The salt bridge-derived duplex formation was largely dependent on the structures of the formamidine and carboxylic acid strands, and the C-linked formamidine strand 3 formed a more stable duplex with the complementary carboxylic acid strands (4 and 6) than did the flexible N-linked formamidine strand 5. The single crystal X-ray analysis revealed that the duplex 5.4 has a skewed right-handed double helical structure. A complementary duplex dimer was also synthesized from the dimers of 5 and 4 joined by diacetylene linkers. Variable-temperature CD measurements indicated that the duplex possesses a dynamic double helical structure resulting from the flexible N-linked formamidine units. PMID:20025216

Iida, Hiroki; Shimoyama, Munenori; Furusho, Yoshio; Yashima, Eiji

2010-01-15

380

Morphiceptin analogs containing 2-aminocyclopentane carboxylic acid as a peptidomimetic for proline.  

PubMed

As part of a program to study the structure-activity relationship of peptide opioids we report the synthesis, conformational characterization and biological activity of four analogs related to morphiceptin in which the proline at position two has been substituted with 2-aminocyclopentane carboxylic acid (beta Ae5c). The beta Ac5c residue is a beta amino acid with two chiral centers resulting in four possible configurations; two configurational cis (R,S and S,R) and two configurational trans (R,R and S,S) forms. Utilizing high resolution n.m.r. at 500 MHz and computer simulations with NOE restraints the chirality of the beta Ac5c residues are assigned. The analog containing the R,S-beta Ac5c is active at both the mu and delta-opioid receptors, with a slight preference for the mu-receptor. The (S,R), (S,S), and (R,R) analogs show minimal activity at the mu-receptor and are inactive at the delta-receptor. A comparison of the findings from the conformational analysis and biological assays lends insight into the structure-activity relationship of this important peptide opiate. PMID:2323882

Mierke, D F; Nössner, G; Schiller, P W; Goodman, M

1990-01-01

381

Occurrence of perfluorinated carboxylic acids (PFCAs) in personal care products and compounding agents.  

PubMed

Perfluorinated carboxylic acids (PFCAs), including perfluorooctanoic acid (PFOA), are persistent organic pollutants that pose human health risks. However, sources of contamination and exposure pathways of PFCAs have not been explored. In this study, PFCA concentrations were quantified in personal care products. Among 24 samples that listed fluorinated compounds, such as polyfluoroalkyl phosphate esters (PAPs), in their international nomenclature of cosmetic ingredients (INCI) labels, 21contained PFCAs (13 of 15 cosmetic samples, and 8 of 9 sunscreen samples). The concentrations of total PFCAs ranged from not detected to 5.9 ?g g(-1) for cosmetics and from not detected to 19 ?g g(-1) for sunscreens. We also investigated components of PFCAs in cosmetics and sunscreens. Commercially available compounding agents, mica and talc, which were treated with PAPs were analyzed and high concentrations of PFCAs were detected (total PFCAs 2.5 ?g g(-1) for talc treated with PAPs, 35.0 ?g g(-1) for mica treated with PAPs). To the best of our knowledge, this is the first report on contamination of end consumer products containing PAPs with high concentrations of PFCAs. PMID:23932147

Fujii, Yukiko; Harada, Kouji H; Koizumi, Akio

2013-09-01

382

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

2013-08-01

383

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

384

New acridone-4-carboxylic acid derivatives as potential inhibitors of hepatitis C virus infection.  

PubMed

A new class of compounds--acridone derivatives--was tested using the direct fluorometric helicase activity assay to determine the inhibitory properties of the derivatives towards the NS3 helicase of Hepatitis C virus (HCV). The compounds were also tested as putative transcription inhibitors of in vitro transcription based on the DNA-dependent T7 RNA polymerase. Most of the acridone derivatives tested were transcription inhibitors; however, only four of them inhibited the NS3 helicase at low concentrations (IC(50) from 3 microM to 20 microM) and were therefore selected for further studies on the mechanism of inhibition. The acridone derivatives probably act via intercalation into double-stranded nucleic acids but they may also interact directly with viral enzymes. Selected carboxamides were tested in the subgenomic HCV replicon system. Two of the compounds: N-(pyridin-4-yl)-amide and N-(pyridin-2-yl)-amide of acridone-4-carboxylic acid are efficient RNA replication inhibitors with selectivity indexes of 19.4 and 40.5, respectively, proving that the acridone derivatives may be regarded as potential antiviral agents. PMID:18801660

Stankiewicz-Drogon, Anna; Palchykovska, Larisa G; Kostina, Valentina G; Alexeeva, Inna V; Shved, Anatoly D; Boguszewska-Chachulska, Anna M

2008-10-01

385

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

PubMed

Broccoli (Brassica oleracea L.) floral tissues rapidly differentiate and grow before harvest and then senesce rapidly after harvest. Associated with this postharvest deterioration is an increase in ethylene production by florets. Two cDNA clones having high nucleotide identity to sequences encoding 1-amino-cyclopropane-1-carboxylic acid (ACC) oxidase were isolated from senescing florets. The cDNAs, ACC Ox1 and ACC Ox2, apparently encode mRNAs from different genes. ACC Ox1 transcripts were found at low levels in whole florets at the time of harvest and increased markedly in abundance after harvest. ACC Ox1 transcript abundance also increased in sepals after harvest and in excised yellowing leaves. Transcripts corresponding to ACC Ox2 were found exclusively within the reproductive structures. These ACC Ox2 transcripts were absent at harvest but started to increase in abundance within 2 h of harvest and then accumulated to high levels. Hormone treatment did not alter the abundance of ACC Ox1 transcripts, whereas ACC Ox2 transcripts increased in abundance after treatment with abscisic acid and propylene. Wounding did not affect the levels of ACC Ox1 or Ox2 transcripts after harvest. At harvest, individual broccoli florets were closed and remained unpollinated. We propose a model whereby the rapid increase in ACC Ox1 and Ox2 transcript abundance after harvest contributes to increased ethylene production by florets. This ethylene may regulate aspects of postharvest senescence, in particular chlorophyll loss. PMID:7610162

Pogson, B J; Downs, C G; Davies, K M

1995-06-01

386

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

PubMed Central

Broccoli (Brassica oleracea L.) floral tissues rapidly differentiate and grow before harvest and then senesce rapidly after harvest. Associated with this postharvest deterioration is an increase in ethylene production by florets. Two cDNA clones having high nucleotide identity to sequences encoding 1-amino-cyclopropane-1-carboxylic acid (ACC) oxidase were isolated from senescing florets. The cDNAs, ACC Ox1 and ACC Ox2, apparently encode mRNAs from different genes. ACC Ox1 transcripts were found at low levels in whole florets at the time of harvest and increased markedly in abundance after harvest. ACC Ox1 transcript abundance also increased in sepals after harvest and in excised yellowing leaves. Transcripts corresponding to ACC Ox2 were found exclusively within the reproductive structures. These ACC Ox2 transcripts were absent at harvest but started to increase in abundance within 2 h of harvest and then accumulated to high levels. Hormone treatment did not alter the abundance of ACC Ox1 transcripts, whereas ACC Ox2 transcripts increased in abundance after treatment with abscisic acid and propylene. Wounding did not affect the levels of ACC Ox1 or Ox2 transcripts after harvest. At harvest, individual broccoli florets were closed and remained unpollinated. We propose a model whereby the rapid increase in ACC Ox1 and Ox2 transcript abundance after harvest contributes to increased ethylene production by florets. This ethylene may regulate aspects of postharvest senescence, in particular chlorophyll loss.

Pogson, B J; Downs, C G; Davies, K M

1995-01-01

387

A highly catalytic and selective conversion of carboxylic acids to 1-alkenes of one less carbon atom  

SciTech Connect

An equimolar mixture of a carboxylic acid and acetic anhydride produces a reagent combination that undergoes a highly efficient decarbonylation/dehydration at 250[degrees]C using either Pd- or Rh-based catalyst systems, affording excellent yields of the corresponding 1-alkenes and one less carbon atom. The stoichiometric and catalytic decarbonylation of aliphatic aldehydes and acid chlorides to alkanes and alkenes, respectively, by transition-metal complexes are well-known and synthetically useful transformations. Relatively little, however, has been reported concerning the analogous decarbonylation/dehydration of aliphatic carboxylic acids to olefins, with generally poor results achieved in terms of catalyst efficiency and selectivity toward terminal olefin formation in the product. For example, the decarbonylation/dehydration of stearic acid to heptadecane using a Rh-based catalyst was reported to proceed with a maximum catalyst turnover number (TON; moles of olefin product formed per mole of catalyst used) of ca. 250, with selectivities toward 1-heptadecene formation typically below 50%. Interestingly, results were presented in this work which suggested that the decarbonylation of stearic acid proceeded via intermediate formation of stearic anhydride. Use of a preformed, symmetrical anhydride is not desirable from an economic or synthetic viewpoint, particularly since its decarbonylation should result in the formation of equal amounts of olefin and carboxylic acid coproducts. The authors now report here that the use of a carboxylic acid substrate as an equimolar mixture with acetic anhydride (Ac[sub 2]O) produces a mixed anhydride system which undergoes an extremely facile decarbonylation reaction to provide a general and highly selective route to the corresponding 1-alkenes of one less carbon atom. 19 refs., 1 tab.

Miller, J.A.; Nelson, J.A.; Byrne, M.P. (Henkel Research Corp., Santa Rosa, CA (United States))

1993-01-01

388

Synthesis, characterization and crystal structures of the organotin(IV) compounds with the Schiff base ligands of pyruvic acid thiophene-2-carboxylic hydrazone and salicylaldehyde thiophene-2-carboxylic hydrazone  

Microsoft Academic Search

A series of organotin (IV) compounds of the type [R3SnL]2, R is Me (1), Bu (2), [R2SnL]2, R is Ph (3), Me (4), Bu (5), L is pyruvic acid thiophene-2-carboxylic hydrazone, and R2SnL, R is Me (6), Bu (7), Ph (8), L is salicylaldehyde thiophene-2-carboxylic hydrazone have been synthesized in 1:1 molar ratio. All compounds were characterized by elemental analysis,

Han Dong Yin; Shao Wen Chen; Lin Wei Li; Da Qi Wang

2007-01-01

389

Age-Dependent Discrimination between Stereoisomers of 1-Amino-2-Ethylcyclopropane-1-Carboxylic Acid in Carnation Petals 1  

PubMed Central

The ability of carnation petals (Dianthus caryophyllus L. cv White Sim) of different ages to convert the cis and trans isomers of 1-amino-2-ethylcyclopropane-1-carboxylic acid (AEC) to 1-butene was studied. Young petals, which produce ethylene at a low rate, convert both cis- and trans-AEC to 1-butene with low efficiency and at equal rates. In senescing petals, the rate of conversion of cis-AEC remains low, but there is a marked increase in the rate of trans-AEC conversion. Thus there is a clear evidence of stereodiscrimination between the isomers. Stimulating the rate of senescence by treatment with either 1-aminocyclopropane-1-carboxylic acid or ethylene further increases the rate of trans-AEC conversion. Delaying of petal senescence by silver thiosulphate or aminooxyacetic acid inhibits the rise in trans-AEC conversion.

Adam, Zach; Mayak, Shimon

1986-01-01

390

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

PubMed

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

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

2014-12-15

391

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

PubMed

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

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

2005-08-01

392

Carboxylic acid ionophores as probes of the role of calcium in biological systems  

NASA Technical Reports Server (NTRS)

The biological effects of calcium ionophores are described, focusing on arachidonic acid oxygenation, and the formation of a number of oxygenated metabolites of arachidonic acid. These metabolites are involved in a number of bodily functions, and their production may be regulated by calcium.

Reed, P. W.

1983-01-01

393

Efficacy of self-etching primers containing carboxylic acid monomers on the adhesion between composite resin and dentin.  

PubMed

A study was conducted to examine the efficacy of carboxylic acid monomers as self-etching primers by measuring the tensile bond strengths between composite resin and dentin. Several kinds of carboxylic acid monomers, such as o-(N-methacryloyl amino)benzoic acid (o-MABA), m-(N-methacryloyl amino)benzoic acid (m-MABA), p-(N-methacryloyl amino)benzoic acid (p-MABA), 4-methacryloxy phthalic acid (4-MPA), 2-(N-methacryloyl amino) terephthalic acid (2-MATPA), and 5-(N-methacryloyl) amino)isophthalic acid (5-MAIPA), were prepared. 4-methacryloxyethyl trimellitic anhydride (4-META) was also used as a component of the self-etching primer. The DMSO solutions of these monomers were used as self-etching primers. The tensile bond strengths between composite resin and dentin were measured after 24 h immersion in water at 37 degrees C. When DMSO was used as a self-etching primer, the bond strengths were below 5 MPa. Among the monocarboxylic acid monomers, m-MABA gave the highest mean bond strength at 60 s application, and 5MAIPA gave the highest mean bond strength at 30 s application among the dicarboxylic acid monomers, although the differences among the values were not always significant. The smear layer was partially dissolved by treatment with the self-etching primer. PMID:9663978

Hayakawa, T; Kikutake, K; Nemoto, K

1998-03-01

394

Exploring the interest of 1,2-dithiolane ring system in peptide chemistry. Synthesis of a chemotactic tripeptide and x-ray crystal structure of a 4-amino-1,2-dithiolane-4-carboxylic acid derivative.  

PubMed

Due to their relevant biological functions and specific chemical reactivity 1,2-dithiolanes (five-membered cyclic disulfides) represent an emerging class of heterocyclic compounds. However, despite the extensive research centered on lipoic acid and its analogues, only very few data are at the present available on peptides containing this ring system. We report here synthesis, conformation and bioactivity of a fMLF-OMe analogue, namely For-Met-Adt-Phe-OMe (7), in which the residue of the 4-amino-1,2-dithiolane-4-carboxylic acid (Adt) (4) replaces the central L-leucine. The crystal conformation of the synthetic intermediate Boc-Adt-OMe (5) is also described and compared to that of lipoic acid (R-1,2-dithiolane-3-pentanoic acid) (3) and asparagusic acid (1,2-dithiolane-4-carboxylic acid) (2). PMID:11738616

Morera, Enrico; Lucente, Gino; Ortar, Giorgio; Nalli, Marianna; Mazza, Fernando; Gavuzzo, Enrico; Spisani, Susanna

2002-01-01

395

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

PubMed Central

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

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

2014-01-01

396

Reaction kinetics for the biocatalytic conversion of phenazine-1-carboxylic Acid to 2-hydroxyphenazine.  

PubMed

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

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

2014-01-01

397

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

PubMed

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

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

2013-01-01

398

Functionalization of carboxylated multiwall nanotubes with imidazole derivatives and their toxicity investigations  

PubMed Central

Imidazoles and their derivatives are compounds with chemotherapeutic applications. In this study, we investigated the chemical functionalization of carboxylated multiwalled carbon nanotubes (MWNT–COOH) by 1,2-phenylendiamine. Multiwalled nanotube (MWNT)–benzimidazole was obtained by an MWNT–amide reaction with POCl3 after 72 hours, which was confirmed by Fourier transform infrared, scanning electron microscopy, thermal gravimetric analysis, and elemental analysis. These functionalizations were chosen due to -NH2 and NHCO active sites in MWNT–amide for future application. Toxicity assays with fibroblast cells and MTT test for measurement of viable cell numbers were also performed. Cellular results did not show any toxicity change in modified samples from that of the reference samples.

Azizian, Javad; Tahermansouri, Hasan; Biazar, Esmaeil; Heidari, Saeed; Khoei, Davood Chobfrosh

2010-01-01

399

Functionalization of carboxylated multiwall nanotubes with imidazole derivatives and their toxicity investigations.  

PubMed

Imidazoles and their derivatives are compounds with chemotherapeutic applications. In this study, we investigated the chemical functionalization of carboxylated multiwalled carbon nanotubes (MWNT-COOH) by 1,2-phenylendiamine. Multiwalled nanotube (MWNT)-benzimidazole was obtained by an MWNT-amide reaction with POCl(3) after 72 hours, which was confirmed by Fourier transform infrared, scanning electron microscopy, thermal gravimetric analysis, and elemental analysis. These functionalizations were chosen due to -NH(2) and NHCO active sites in MWNT-amide for future application. Toxicity assays with fibroblast cells and MTT test for measurement of viable cell numbers were also performed. Cellular results did not show any toxicity change in modified samples from that of the reference samples. PMID:21116331

Azizian, Javad; Tahermansouri, Hasan; Biazar, Esmaeil; Heidari, Saeed; Khoei, Davood Chobfrosh

2010-01-01

400

Comprehensive study of mesoporous carbon functionalized with carboxylate groups and magnetic nanoparticles as a promising adsorbent.  

PubMed

Highly ordered mesoporous carbon functionalized with carboxylate groups and magnetic nanoparticles has been successfully synthesized. By oxidative treatment using (NH(4))(2)S(2)O(8) and H(2)SO(4) mixed solution, numerous hydrophilic groups were created in the mesopores without destroying the ordered mesostructure of CMK-3. Through the in situ reduction in Fe(3+), magnetic nanoparticles were successfully introduced into the mesopores, resulting in the multifunctional mesoporous carbon Fe-CMK-3. The obtained hybrid carbon material possesses ordered mesostructure, high Brunauer-Emmett-Teller (BET) surface area up to 1013 m(2)/g, large pore volume of about 1.16 cm(3)/g, carboxylic surface, and excellent magnetic property. When used as an adsorbent, Fe-CMK-3 exhibits excellent performances for removing toxic organic compounds from waster-water, with a high adsorption capacity, an extremely rapid adsorption rate, and an easy magnetically separable process. In the case of requiring emergency removal of large amount of organic pollutants in aqueous, the hybrid carbon adsorbent would be an ideal choice. PMID:22236608

Chi, Yue; Geng, Wangchang; Zhao, Liang; Yan, Xiao; Yuan, Qing; Li, Nan; Li, Xiaotian

2012-03-01

401

Kinetic resolution of racemic alpha-arylalkanoic acids with achiral alcohols via the asymmetric esterification using carboxylic anhydrides and acyl-transfer catalysts.  

PubMed

A variety of optically active carboxylic esters are produced by the kinetic resolution of racemic alpha-substituted carboxylic acids using achiral alcohols, aromatic or aliphatic carboxylic anhydrides, and chiral acyl-transfer catalysts. The combination of 4-methoxybenzoic anhydride (PMBA) or pivalic anhydride with the modified benzotetramisole-type catalyst ((S)-beta-Np-BTM) is the most effective for promotion of the enantioselective coupling reaction between racemic carboxylic acids and a novel nucleophile, bis(alpha-naphthyl)methanol, to give the corresponding esters with high ee's. This protocol was successfully applied to the production of nonracemic nonsteroidal anti-inflammatory drugs from racemic compounds utilizing the transacylation process to generate the mixed anhydrides from the acid components with the suitable carboxylic anhydrides. PMID:20681552

Shiina, Isamu; Nakata, Kenya; Ono, Keisuke; Onda, Yu-suke; Itagaki, Makoto

2010-08-25

402

Equivalent Circuit Analysis of Dye-Sensitized Solar Cell by Using One-Diode Model: Effect of Carboxylic Acid Treatment of TiO2 Electrode  

Microsoft Academic Search

For the improvement of dye-sensitized solar cell performance, it is important to analyze the electric mechanism of cells and to employ an effective treatment. Equivalent circuit analysis using a one-diode model was carried out for a dye-sensitized solar cell consisting of a TiO2 electrode treated with carboxylic acid. Carboxylic acid treatment, especially using acetic acid, was effective in increasing the

Masaki Murayama; Tatsuo Mori

2006-01-01

403

(±)-2,2-Dimethyl-5-oxotetrahydrofuran-3-carboxylic acid (terebic acid): a racemic layered structure.  

PubMed

A racemic crystalline form of terebic acid, C(7)H(10)O(4), which is an important industrial chemical compound, is reported for the first time. The crystal structure is stabilized by O-H···O and C-H···O hydrogen bonds which form racemic double layers parallel to (001). PMID:22850854

Santos, L M; Legendre, A O; Villis, P C M; Viegas, C; Doriguetto, A C

2012-08-01

404

Deltorphin II analogues with 6-hydroxy-2-aminotetralin-2-carboxylic acid in position 1.  

PubMed

Two approaches to the design of very active and highly selective delta opioid peptides were used to obtain new deltorphin analogues with altered hydrophobic and stereoelectronic properties. Deltorphin II analogues were synthesized with the substitution of Ile instead of Val at positions 5 and 6 in the address domain and 6-hydroxy-2-aminotetralin-2-carboxylic acid (Hat) instead of Tyr(1) in the message domain. In the radioreceptor-binding studies, in which type-specific tritiated opioid ligands were used, (R)- and (S)-Hat-deltorphins exhibited similar K(i) values, revealing high delta selectivity. The peptides displayed agonist properties in the in vitro bioassay, with IC(50) values in the subnanomolar range in the mouse vas deferens assay and in the micromolar or higher range in the guinea pig ileum assay, again demonstrating a high selectivity toward delta receptors. The agonist property of the new ligands was confirmed by means of [(35)S]GTPgammaS-binding experiments in membranes of the rat frontal cortex. PMID:10753473

Darula, Z; Kövér, K E; Monory, K; Borsodi, A; Makó, E; Rónai, A; Tourwé, D; Péter, A; Tóth, G

2000-04-01

405

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

406

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

407

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

408

Molecular receptive range variation among mouse odorant receptors for aliphatic carboxylic acids  

PubMed Central

The ability of mammals to identify and distinguish among many thousands of different odorants suggests a combinatorial use of odorant receptors, with each receptor detecting multiple odorants and each odorant interacting with multiple receptors. Numerous receptors may be devoted to the sampling of particularly important regions of odor space. Here we explore the similarities and differences in the molecular receptive ranges of four mouse odorant receptors (MOR23-1, MOR31-4, MOR32-11 and MOR40-4), which have previously been identified as receptors for aliphatic carboxylic acids. Each receptor was expressed in Xenopus oocytes, along with G?olf and the cystic fibrosis transmembrane regulator to allow electrophysiological assay of receptor responses. We find that even though these receptors are relatively unrelated, there is extensive overlap among their receptive ranges. That is, these receptors sample a similar region of odor space. However, the receptive range of each receptor is unique. Thus, these receptors contribute to the depth of coverage of this small region of odor space. Such a group of receptors with overlapping, but distinct receptive ranges, may participate in making fine distinctions among complex mixtures of closely related odorant compounds.

Repicky, Sarah E.; Luetje, Charles W.

2009-01-01

409

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

410

Acute toxicity assessment of perfluorinated carboxylic acids towards the Baltic microalgae.  

PubMed

The presence of high-energy carbon-fluorine bonds in perfluoro compounds lends them great stability and causes them to be environmentally persistent. Relatively little is known about the acute toxicity of perfluorinated carboxylic acids (PFCAs) to ecotoxicological markers such as aquatic plants and animals. This study tested the toxicity of these compounds to the green alga Chlorella vulgaris, the diatom Skeletonema marinoi and the blue-green alga Geitlerinema amphibium, which are species representative of the algal flora of the Baltic Sea. The EC(50) values obtained range from 0.28 mM to 12.84 mM. A distinct relationship between hydrophobicity and toxicity is demonstrated. For every extra perfluoromethylene group in the alkyl chain, the toxicity increases twofold. LogEC(50) values are very well correlated linearly with both the number of carbon atoms in the perfluoroalkyl chain and the partition coefficients. The results also indicate that there are clear differences between the responses of particular taxonomic groups of algae: blue-green algae and diatoms are far more sensitive to PFCAs than green algae, probably because of differences in cell wall structure. PMID:21783999

Lata?a, Adam; N?dzi, Marcin; Stepnowski, Piotr

2009-09-01

411

New transition metal ion complexes with benzimidazole-5-carboxylic acid hydrazides with antitumor activity  

Microsoft Academic Search

Metal complexes of 2-methyl-1H-benzimidazole-5-carboxylic acid hydrazide (4a; L1) and its Schiff base 2-methyl-N-(propan-2-ylidene)-1H-benzimidazole-5-carbohydrazide (5a; L2) with transition metal ions e.g., copper, silver, nickel, iron and manganese were prepared. The complexes formed were 1:1 or 1:2 M:L complexes and have the structural formulae [Cu(L1)Cl(H2O)]Cl·3H2O (6), [Ag(L1)NO3(H2O)] (7), [Ni(L1)Cl2(H2O)2]·H2O (8), [Fe(L1)Cl3(H2O)]·3H2O (9) and [Mn(L1)2Cl(H2O)]Cl·3H2O (10) for ligand L1, and [Cu(L2)Cl2(H2O)2]·H2O (11), [Ag(L2)2]NO3·H2O

Shadia A. Galal; Khaled H. Hegab; Ahmed S. Kassab; Mireya L. Rodriguez; Sean M. Kerwin; Abdel-Mo'men A. El-Khamry; Hoda I. El Diwani

2009-01-01

412

Phenazine carboxylic acid production and rhizome protective effect of endophytic Pseudomonas aeruginosa isolated from Zingiber officinale.  

PubMed

Ginger (Zingiber officinale) is cultivated commercially in most parts of the world especially in India for its culinary and medicinal applications. One of the major challenges that limit the yield of ginger is rhizome rot disease caused by organisms including Pythium myriotylum. A feasible ecofriendly method is yet to be devised to prevent the plant from this threatening disease. Recent studies on plant microbiome show the possibility of having endophytic organisms with plant protective characteristics associated with the plants. Because of the uniquely evolved underground nature of the ginger rhizome and its peculiar survival in soil for a long time, many interesting endophytic microbes with plant protective characters can be well expected from it. In the current study, previously isolated endophytic Pseudomonas aeruginosa from ginger was investigated in detail for its effect on Pythium myriotylum. The rhizome protective effect of the organism was also studied by co-inoculation studies, which confirmed that Pseudomonas aeruginosa has very potent inhibitory effect on Pythium myriotylum. On further studies, the active antifungal compound was identified as phenazine 1-carboxylic acid. PMID:24353040

Jasim, B; Anisha, C; Rohini, Sabu; Kurian, Jacob Manoj; Jyothis, Mathew; Radhakrishnan, E K

2014-05-01

413

Solubility and spectroscopic studies of the interaction of palladium with simple carboxylic acids and fulvic acid at low temperature  

SciTech Connect

The interaction of Pd with some O-donor organic acid anions has been investigated using solubility measurements and a variety of spectroscopic techniques (UV-visible, Raman, FTIR, [sup 13]C NMR). Some of the ligands investigated (acetate, oxalate, and fulvic acid) occur naturally in relatively high concentrations, whereas others (phthalate and salicylate) serve as models of potential binding sites on humic and fulvic acids. Solubility measurements show that the presence of acetate, phthalate, salicylate, and fulvic acid (oxalate was not studied via solubility methods) can increase the mobility of Pd over various pH ranges, depending on the organic ligand. In the case of acetate, UV-visible and Raman spectroscopy provide strong evidence for the formation of electrostatically bound, possibly outer-sphere palladium acetate complexes. Oxalate was confirmed by UV-visible and FTIR spectroscopy to compete favorably with chloride (0.56 M NaCl) for Pd even at oxalate concentrations as low as 1 mM at pH = 6-7. Available data from the literature suggest that oxalate may have an influence on Pd mobility at free oxalate concentrations as low as 10[sup [minus]8]=10[sup [minus]9] M. UV-visible spectroscopy provides evidence of an initially rapid, followed by a slower, reaction between PdCl[sup 2-][sub 4] and o-phthalate ion. These findings lend support to the idea that similar bindings sites on fulvic acid may be capable of complexing and solubilizing Pd in the natural environment. Although thermodynamic data are required to fully quantify the extent, it is concluded that simple carboxylic acid anions and/or fulvic and humic acids should be capable of significantly enhancing Pd transport in the surficial environment by forming truly dissolved complexes. On the other hand, flocculation of fulvic/humic acids, owing to changing ionic strengths or pH, or adsorption of these acids onto mineral surfaces, may also provide effective means of immobilizing Pd.

Wood, S.A. (Univ. of Idaho, Moscow, ID (United States)); Tait, C.D.; Janecky, D.R. (Los Alamos National Laboratory, NM (United States)); Vlassopoulos, D. (California Institute of Technology, Pasadena, CA (United States))

1994-01-01

414

Carboxylic and dicarboxylic acids extracted from crushed magnesium oxide single crystals  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

415

Carboxylic and Dicarboxylic Acids Extracted from Crushed Magnesium Oxide Single Crystals  

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

416

Short-chain carboxylic acids, a new class of teratogens: studies of potential biochemical mechanisms  

SciTech Connect

Certain short-chain carboxylic acids (SCCA) appear to share a common teratogenic potential, although the structural requirements for activity remain obscure. By using a whole rat embryo culture model system, several biochemical processes have been examined, either as potential initial sites of teratogenic action or as early steps in the pathway to malformation. Valproate, methoxyacetate, and butyrate were the prototype SCCA examined. Measurement of (/sup 14/C)glucose utilization and lactate production confirmed that energy production by the early organogenesis embryo is predominantly from glycolysis. While the positive control agent, iodoacetate, caused a significant inhibition of lactate production, none of the SCCA affected this process or glucose utilization at teratogenic concentrations. Pinocytosis by the visceral yolk sac (VYS) was measured by the uptake of (/sup 125/I)polyvinylpyrrolidone. This process ultimately supplies the embryo with amino-acids and is essential for normal development. SCCA induce morphological abnormalities of the VYS in embryo culture. Pinocytosis was slightly reduced by valproate, but not the other SCCA. However, comparison with the action of an antiserum, for which inhibition of pinocytosis is the initial teratogenic insult, suggests that this is not the mechanism for valproate. Incorporation of (/sup 3/H)thymidine into embryo or yolk sac was not affected after 3 hr of SCCA exposure, but there was a marked effect of the positive control, hydroxyurea. This suggests that DNA synthesis is not directly influenced by SCCA. It can be concluded that SCCA do not exert their teratogenic effects by actions o