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1

Understanding the mechanisms of reaction and release of acid–base indicators entrapped in hybrid gels  

Microsoft Academic Search

The reactivity and release of acid–base indicators entrapped in silica and hybrid silica gels were studied. Methyl orange (MO), methyl red (MR), and phenyl red (PR) were used as the indicators. Tetraethoxysilane (TEOS), n-propyltriethoxysilane (PTES), and bis(trimethoxysilyl)hexane (TSH) were used as gel precursors. HCl (0.01M) and NaOH (0.01M) solutions were used as the media for acid–base reaction and release in

Zhijian Wu; Yan Jiang; Hong Xiang; Laijiang You

2006-01-01

2

Rapid hybridization of nucleic acids using isotachophoresis  

E-print Network

Rapid hybridization of nucleic acids using isotachophoresis Moran Bercovicia,b,1,2 , Crystal M of nucleic acid hybridization reactions in free solution. We present a new physical model, validation are generally applicable to acceleration of reactions invol- ving nucleic acids, and may be applicable to a wide

Santiago, Juan G.

3

Suzuki coupling reaction using hybrid Pd nanoparticles.  

PubMed

This paper reviews recent developments in the field of hybrid Pd nanoparticles and their catalytic activity in the Suzuki coupling reaction, which is used extensively in the fabrication of both simple and complex biaryl compounds. We developed three types of Pd-silica hybrid nanoparticles. Pd/SiO2 nanobeads containing tiny Pd clusters, Pd@nickel phyllosilicate yolk-shell nanoparticles, Pd@porous SiO2 yolk-shell nanoparticles were synthesized, and they displayed highly efficient catalytic activity and excellent reusability. The hybrid nanoparticles also catalyzed the Suzuki coupling reaction with various substrates, including bromobenzene and chlorobenzene. This review also briefly discusses the synthesis procedure, structural characterization, and catalytic activity of hybrid Pd nanoparticles. PMID:24749462

Kim, Aram; Park, Ji Chan; Kim, Mijong; Heo, Eunjung; Song, Hyunjoon; Park, Kang Hyun

2014-02-01

4

Optimizing the specificity of nucleic acid hybridization  

E-print Network

Optimizing the specificity of nucleic acid hybridization David Yu Zhang1,2 *, Sherry Xi Chen3, the specificity of nucleic acid hybridization is compromised for long strands, except near the melting temperature to 37 88888C, from 1 mM Mg21 to 47 mM Mg21 , and with nucleic acid concentrations from 1 nM to 5 m

Zhang, David Yu

5

Nucleic acid in-situ hybridization detection of infectious agents  

NASA Astrophysics Data System (ADS)

Limitations of traditional culture methods and newer polymerase chain reaction (PCR)-based methods for detection and speciation of infectious agents demonstrate the need for more rapid and better diagnostics. Nucleic acid hybridization is a detection technology that has gained wide acceptance in cancer and prenatal cytogenetics. Using a modification of the nucleic acid hybridization technique known as fluorescence in-situ hybridization, infectious agents can be detected in a variety of specimens with high sensitivity and specificity. The specimens derive from all types of human and animal sources including body fluids, tissue aspirates and biopsy material. Nucleic acid hybridization can be performed in less than one hour. The result can be interpreted either using traditional fluorescence microscopy or automated platforms such as micro arrays. This paper demonstrates proof of concept for nucleic acid hybridization detection of different infectious agents. Interpretation within a cytologic and histologic context is possible with fluorescence microscopic analysis, thereby providing confirmatory evidence of hybridization. With careful probe selection, nucleic acid hybridization promises to be a highly sensitive and specific practical diagnostic alternative to culture, traditional staining methods, immunohistochemistry and complicated nucleic acid amplification tests.

Thompson, Curtis T.

2000-04-01

6

Acceleration of surface-based hybridization reactions using isotachophoretic focusing.  

PubMed

We present a theoretical model and experimental demonstration of a novel method for acceleration of surface-based reactions using isotachophoresis (ITP). We use ITP to focus a sample of interest and deliver a high concentration target to a prefunctionalized surface, thus enabling rapid reaction at the sensor site. The concentration of the focused analyte is bound in space by the ITP interface and, upon reaction with the surface, continues electromigrating downstream, removing any contamination or reacted sample molecules from the surface. This constitutes a one-step react-and-wash assay which can be performed in a simple channel and does not require flow control elements or moving parts. We designed a novel microfluidic chip where reaction surfaces are formed by paramagnetic beads, immobilized at desired sites by an external magnetic field. Using this chip, we compared ITP-based surface hybridization to standard continuous flow-based hybridization and experimentally demonstrated a 2 orders of magnitude improvement in limit of detection (LoD) in a 3 min nucleic acid hybridization assay. The simple analytical model we present allows prediction of the rate of surface reaction under ITP and can be used to design and optimize such assays as a function of the physical properties of the system, including buffer chemistry, applied voltage, analyte mobility, analyte concentration, probe density, and surface length. The method, model, and experimental setup can be applied to various forms or surface reactions and may serve as the basis for highly genetic analysis and immunoassays. PMID:24517175

Karsenty, Merav; Rubin, Shimon; Bercovici, Moran

2014-03-18

7

Statistical Thermodynamics and Kinetics of DNA Multiplex Hybridization Reactions  

Microsoft Academic Search

A general analytical description of the equilibrium and reaction kinetics of DNA multiplex hybridization has been developed. In this approach, multiplex hybridization is considered to be a competitive multichannel reaction process: a system wherein many species can react both specifically and nonspecifically with one another. General equations are presented that can consider equilibrium and kinetic models of multiplex hybridization systems

M. T. Horne; D. J. Fish; A. S. Benight

2006-01-01

8

Multitarget molecular hybrids of cinnamic acids.  

PubMed

In an attempt to synthesize potential new multitarget agents, 11 novel hybrids incorporating cinnamic acids and paracetamol, 4-/7-hydroxycoumarin, benzocaine, p-aminophenol and m-aminophenol were synthesized. Three hybrids-2e, 2a, 2g-and 3b were found to be multifunctional agents. The hybrid 2e derived from the phenoxyphenyl cinnamic acid and m-acetamidophenol showed the highest lipoxygenase (LOX) inhibition and analgesic activity (IC50 = 0.34 ?? and 98.1%, whereas the hybrid 3b of bromobenzyloxycinnamic acid and hymechromone exhibited simultaneously good LOX inhibitory activity (IC50 = 50 ??) and the highest anti-proteolytic activity (IC50= 5 ??). The hybrid 2a of phenyloxyphenyl acid with paracetamol showed a high analgesic activity (91%) and appears to be a promising agent for treating peripheral nerve injuries. Hybrid 2g which has an ester and an amide bond presents an interesting combination of anti-LOX and anti-proteolytic activity. The esters were found very potent and especially those derived from paracetamol and m-acetamidophenol. The amides follow. Based on 2D-structure-activity relationships it was observed that both steric and electronic parameters play major roles in the activity of these compounds. Molecular docking studies point to the fact that allosteric interactions might govern the LOX-inhibitor binding. PMID:25474291

Peperidou, Aikaterini; Kapoukranidou, Dorothea; Kontogiorgis, Christos; Hadjipavlou-Litina, Dimitra

2014-01-01

9

Reactions : AcidBaseRxns (20 Variations)  

NSDL National Science Digital Library

In order to answer the following questions, write the net ionic equation for the reaction between equal volumes of 0.10 M solutions of the following acid and base: KOH(aq) + HBr(aq) What are the reaction products? Does the reaction yield an acidic, basic, or neutral aqueous solution?

10

Topological constraints in nucleic acid hybridization kinetics  

E-print Network

Topological constraints in nucleic acid hybridization kinetics Justin S. Bois, Suvir Venkataraman1 that the topological constraint of zero linking number between the loops effectively prevents conversion to the minimum constraints that govern the metastability of kissing complementary loops. This topological viewpoint suggests

Straight, Aaron

11

A modification of the thiobarbituric acid reaction.  

PubMed

A simple modification of the thiobarbituric acid reaction, which removes nonspecific chromogenic reaction products, involves incubation at room temperature for 16-20 hr and a column chromatographic step. The chromogen-concentrating capacity of the latter step is useful for determination of low concentrations of thiobarbituric acid-reactive materials in biological preparations. PMID:2779371

Bidder, T G; Sipka, B M

1989-07-01

12

Reaction of synthetic corundum with orthophosphoric acid  

Microsoft Academic Search

Conclusions It was shown in an Investigation of mixtures of fine-ground electrofused corundum with orthophosphoric acid that at 20–25°C the degree of the reaction of the components is highest during the first four days. During this period only water-soluble acid aluminum phosphates are formed and a significant proportion of the orthophosphoric acid remains uncombined. The reaction rate is low and

L. A. Tseitlin; A. K. Mendelenko; S. T. Balyuk; Z. D. Zhukova

1975-01-01

13

Fluorogenic, catalytic, photochemical reaction for amplified detection of nucleic acids.  

PubMed

Photochemical, nucleic acid-induced reactions, which are controlled by nontoxic red light, are well-suited for detection of nucleic acids in live cells, since they do not require any additives and can be spatially and temporally regulated. We have recently described the first reaction of this type, in which a phenylselenyl derivative of thymidine (5'-PhSeT-ODNa) is cleaved in the presence of singlet oxygen (Fülöp, A., Peng, X., Greenberg, M. M., Mokhir, A. (2010) A nucleic acid directed, red light-induced chemical reaction. Chem. Commun. 46, 5659-5661). The latter reagent is produced upon exposure of a photosensitizer 3'-PS-ODNb (PS = Indium(III)-pyropheophorbide-a-chloride: InPPa) to >630 nm light. In 2012 we reported on a fluorogenic version of this reaction (Dutta, S., Flottmann, B., Heilemann, M., Mokhir, A. (2012) Hybridization and reaction-based, fluorogenic nucleic acid probes. Chem. Commun. 47, 9664-9666), which is potentially applicable for the detection of nucleic acids in cells. Unfortunately, its yield does not exceed 25% and no catalytic turnover could be observed in the presence of substrate excess. This problem occurs due to the efficient, competing oxidation of the substrate containing an electron rich carbon-carbon double bonds (SCH?CHS) in the presence of singlet oxygen with formation of a noncleavable product (SCH?CHSO). Herein we describe a related, but substantially improved photochemical, catalytic transformation of a fluorogenic, organic substrate, which consists of 9,10-dialkoxyanthracene linked to fluorescein, with formation of a bright fluorescent dye. In highly dilute solution this reaction occurs only in the presence of a nucleic acid template. We developed three types of such a reaction and demonstrated that they are high yielding and generate over 7.7 catalytic turnovers, are sensitive to single mismatches in nucleic acid targets, and can be applied for determination of both the amount of nucleic acids and potentially their localization. PMID:23964892

Dutta, Subrata; Fülöp, Annabelle; Mokhir, Andriy

2013-09-18

14

A Lewis acid-promoted Pinner reaction  

PubMed Central

Summary Carbonitriles and alcohols react in a Lewis acid-promoted Pinner reaction to carboxylic esters. Best results are obtained with two equivalents of trimethylsilyl triflate as Lewis acid. Good yields are achieved with primary alcohols and aliphatic or benzylic carbonitriles, but the straightforward synthesis of acrylates and benzoates starting with acrylonitrile and benzonitrile, respectively, is similarly possible. Phenols are not acylated under these reaction conditions. The method has been used for the first total synthesis of the natural product monaspilosin. In the reaction of benzyl alcohols variable amounts of amides are formed in a Ritter-type side reaction. PMID:23946857

Pfaff, Dominik; Nemecek, Gregor

2013-01-01

15

Dextran sulfate provides a quantitative and quick microarray hybridization reaction  

Microsoft Academic Search

Microarray technology is a powerful tool to speed up genomics study, yet many technical aspects need to be improved. The hybridization reaction of microarray experiments is carried out for 16h or overnight in order to obtain reasonably strong signals for analysis in the presence of high salt buffer, like SSC. However, the quantitative aspect of microarray hybridization has seldom been

Wei-Chi Ku; Wai Kwan Lau; Yu-Tien Tseng; Chi-Meng Tzeng; Sung-Kay Chiu

2004-01-01

16

SOIL REACTION AND ACIDIC DEPOSITION  

EPA Science Inventory

This chapter discusses the major chemical processes by which acidic deposition interacts with soils. he focus is on forest soils, as the effects of acidic deposition on soils used for production of food and fiber are generally small compared to effects of agricultural practices s...

17

Nonenzymatic catalytic signal amplification for nucleic acid hybridization assays  

NASA Technical Reports Server (NTRS)

Devices, methods, and kits for amplifying the signal from hybridization reactions between nucleic acid probes and their cognate targets are presented. The devices provide partially-duplexed, immobilized probe complexes, spatially separate from and separately addressable from immobilized docking strands. Cognate target acts catalytically to transfer probe from the site of probe complex immobilization to the site of immobilized docking strand, generating a detectable signal. The methods and kits of the present invention may be used to identify the presence of cognate target in a fluid sample.

Fan, Wenhong (Inventor); Cassell, Alan M. (Inventor); Han, Jie (Inventor)

2006-01-01

18

Gold nanoparticles-graphene hybrids as active catalysts for Suzuki reaction  

SciTech Connect

Graphene was successfully modified with gold nanoparticles in a facile route by reducing chloroauric acid in the presence of sodium dodecyl sulfate, which is used as both a surfactant and reducing agent. The gold nanoparticles-graphene hybrids were characterized by high-resolution transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction and energy X-ray spectroscopy. We demonstrate for the first time that the gold nanoparticles-graphene hybrids can act as efficient catalysts for the Suzuki reaction in water under aerobic conditions. The catalytic activity of gold nanoparticles-graphene hybrids was influenced by the size of the gold nanoparticles.

Li, Yang [School of Chemical Engineering and Technology, Tianjin University, Weijin Road, Tianjin 300072 (China)] [School of Chemical Engineering and Technology, Tianjin University, Weijin Road, Tianjin 300072 (China); Fan, Xiaobin, E-mail: xiaobinfan@tju.edu.cn [School of Chemical Engineering and Technology, Tianjin University, Weijin Road, Tianjin 300072 (China)] [School of Chemical Engineering and Technology, Tianjin University, Weijin Road, Tianjin 300072 (China); Qi, Junjie; Ji, Junyi; Wang, Shulan; Zhang, Guoliang; Zhang, Fengbao [School of Chemical Engineering and Technology, Tianjin University, Weijin Road, Tianjin 300072 (China)] [School of Chemical Engineering and Technology, Tianjin University, Weijin Road, Tianjin 300072 (China)

2010-10-15

19

Hybridization and sequencing of nucleic acids using base pair mismatches  

SciTech Connect

Devices and techniques for hybridization of nucleic acids and for determining the sequence of nucleic acids. Arrays of nucleic acids are formed by techniques, preferably high resolution, light-directed techniques. Positions of hybridization of a target nucleic acid are determined by, e.g., epifluorescence microscopy. Devices and techniques are proposed to determine the sequence of a target nucleic acid more efficiently and more quickly through such synthesis and detection techniques.

Fodor, Stephen P. A. (Palo Alto, CA); Lipshutz, Robert J. (Palo Alto, CA); Huang, Xiaohua (Mt. View, CA)

2001-01-01

20

Gallic Acid, Ellagic Acid and Pyrogallol Reaction with Metallic Iron  

NASA Astrophysics Data System (ADS)

The reaction between gallic acid, ellagic acid and pyrogallol with metallic iron was studied using infrared and Mössbauer spectroscopy. Most hydrolysable tannins with interesting anticorrosive or inhibition properties are structurally related to these compounds, thus they may be used as models for the study of hydrolysable tannins and related polyphenols. The interaction was followed up to 3 months. Results indicated two different behaviors. At polyphenol concentrations higher than 1% iron converts to sparingly soluble and amorphous ferric (and ferrous) polyphenolate complexes. At lower concentrations (0.1%), the hydrolysis reactions are dominant, resulting in the formation of oxyhydroxides, which can be further reduced to compounds like magnetite by the polyphenols.

Jaén, J. A.; González, L.; Vargas, A.; Olave, G.

2003-06-01

21

A DNA origami nanorobot controlled by nucleic acid hybridization.  

PubMed

A prototype for a DNA origami nanorobot is designed, produced, and tested. The cylindrical nanorobot (diameter of 14 nm and length of 48 nm) with a switchable flap, is able to respond to an external stimulus and reacts by a physical switch from a disarmed to an armed configuration able to deliver a cellular compatible message. In the tested design the robot weapon is a nucleic acid fully contained in the inner of the tube and linked to a single point of the internal face of the flap. Upon actuation the nanorobot moves the flap extracting the nucleic acid that assembles into a hemin/G-quadruplex horseradish peroxidase mimicking DNAzyme catalyzing a colorimetric reaction or chemiluminescence generation. The actuation switch is triggered by an external nucleic acid (target) that interacts with a complementary nucleic acid that is beard externally by the nanorobot (probe). Hybridization of probe and target produces a localized structural change that results in flap opening. The flap movement is studied on a two-dimensional prototype origami using Förster resonance energy transfer and is shown to be triggered by a variety of targets, including natural RNAs. The nanorobot has potential for in vivo biosensing and intelligent delivery of biological activators. PMID:24648163

Torelli, Emanuela; Marini, Monica; Palmano, Sabrina; Piantanida, Luca; Polano, Cesare; Scarpellini, Alice; Lazzarino, Marco; Firrao, Giuseppe

2014-07-01

22

Hypersensitivity reactions to anthranilic acid derivatives.  

PubMed

Anthranilic acid derivatives are a group of nonsteroidal antiinflammatory drugs that include glafenine and fenamates. We report a woman who had immediate adverse reactions to glafenine and meclofenamate sodium. Skin prick and intradermal tests were performed with solutions of glafenine and meclofenamate in phosphate-buffered saline (PBS) and with the drugs bound to human serum albumin (HSA). Prick and intradermal tests with PBS solutions were negative for both drugs as were prick tests with HSA solutions. Intradermal tests with HSA-glafenine, however, were positive at 20 minutes, and at 6 and 24 hours. Intradermal tests with HSA-meclofenamate elicited a positive response at 6 and 24 hours. These tests were negative when performed in control subjects. A leukocyte histamine release test and a RAST assay were negative for both drugs. The patient was challenged following a double-blind placebo-controlled oral procedure and tolerated therapeutic doses of aspirin, indomethacin, ibuprofen, dipyrone, diclofenac, piroxicam, and acetaminophen. The oral challenge with glafenine and meclofenamate reproduced the reactions (eliciting doses: 50 mg and 15 mg, respectively), and the patient also reacted to 30 mg of mefenamic acid, an anthranilic acid derivative she had never previously received. This is an exceptional case of selective adverse reactions to glafenine and fenamates, anthranilic acid derivatives, in a patient tolerating aspirin and other cyclooxygenase inhibitors. Our study implicates an immunologic mechanism, and the existence of cross-reactivity between the drugs (or some active metabolite generated in vivo). PMID:7903514

Fernandez-Rivas, M; de la Hoz, B; Cuevas, M; Davila, I; Quirce, S; Losada, E

1993-12-01

23

Acid-catalyzed reactions of hexanal on sulfuric acid particles: Identification of reaction products  

NASA Astrophysics Data System (ADS)

While it is well established that organics compose a large fraction of the atmospheric aerosol mass, the mechanisms through which organics are incorporated into atmospheric aerosols are not well understood. Acid-catalyzed reactions of compounds with carbonyl groups have recently been suggested as important pathways for transfer of volatile organics into acidic aerosols. In the present study, we use the aerodyne aerosol mass spectrometer (AMS) to probe the uptake of gas-phase hexanal into ammonium sulfate and sulfuric acid aerosols. While both deliquesced and dry non-acidic ammonium sulfate aerosols showed no organic uptake, the acidic aerosols took up substantial amounts of organic material when exposed to hexanal vapor. Further, we used 1H-NMR, Fourier transform infrared (FTIR) spectroscopy and GC-MS to identify the products of the acid-catalyzed reaction of hexanal in acidic aerosols. Both aldol condensation and hemiacetal products were identified, with the dominant reaction products dependent upon the initial acid concentration of the aerosol. The aldol condensation product was formed only at initial concentrations of 75-96 wt% sulfuric acid in water. The hemiacetal was produced at all sulfuric acid concentrations studied, 30-96 wt% sulfuric acid in water. Aerosols up to 88.4 wt% organic/11.1 wt% H 2SO 4/0.5 wt% water were produced via these two dimerization reaction pathways. The UV-VIS spectrum of the isolated aldol condensation product, 2-butyl 2-octenal, extends into the visible region, suggesting these reactions may impact aerosol optical properties as well as aerosol composition. In contrast to previous suggestions, no polymerization of hexanal or its products was observed at any sulfuric acid concentration studied, from 30 to 96 wt% in water.

Garland, Rebecca M.; Elrod, Matthew J.; Kincaid, Kristi; Beaver, Melinda R.; Jimenez, Jose L.; Tolbert, Margaret A.

24

Hybrid discrete/continuum algorithms for stochastic reaction networks  

NASA Astrophysics Data System (ADS)

Direct solutions of the Chemical Master Equation (CME) governing Stochastic Reaction Networks (SRNs) are generally prohibitively expensive due to excessive numbers of possible discrete states in such systems. To enhance computational efficiency we develop a hybrid approach where the evolution of states with low molecule counts is treated with the discrete CME model while that of states with large molecule counts is modeled by the continuum Fokker-Planck equation. The Fokker-Planck equation is discretized using a 2nd order finite volume approach with appropriate treatment of flux components. The numerical construction at the interface between the discrete and continuum regions implements the transfer of probability reaction by reaction according to the stoichiometry of the system. The performance of this novel hybrid approach is explored for a two-species circadian model with computational efficiency gains of about one order of magnitude.

Safta, Cosmin; Sargsyan, Khachik; Debusschere, Bert; Najm, Habib N.

2015-01-01

25

40 CFR 721.10679 - Carboxylic acid, substituted alkylstannylene ester, reaction products with inorganic acid tetra...  

... 2014-07-01 false Carboxylic acid, substituted alkylstannylene ester, reaction products with inorganic acid tetra alkyl ester (generic). 721...Substances § 721.10679 Carboxylic acid, substituted alkylstannylene...

2014-07-01

26

Acid-catalyzed reactions of hexanal on sulfuric acid particles: Identification of reaction products  

Microsoft Academic Search

While it is well established that organics compose a large fraction of the atmospheric aerosol mass, the mechanisms through which organics are incorporated into atmospheric aerosols are not well understood. Acid-catalyzed reactions of compounds with carbonyl groups have recently been suggested as important pathways for transfer of volatile organics into acidic aerosols. In the present study, we use the aerodyne

Rebecca M. Garland; Matthew J. Elrod; Kristi Kincaid; Melinda R. Beaver; Jose L. Jimenez; Margaret A. Tolbert

2006-01-01

27

Heterogeneous Reactions of Epoxides in Acidic Media  

E-print Network

Committee: Dr. Renyi Zhang Epoxides have been recently identified as one of the intermediate species in the gas phase oxidation of alkenes. This study investigates the reaction of isoprene oxide and ?-pinene oxide with sulfuric acid to identify... who have always inspired me and motivated me to aim high. vi ACKNOWLEDGEMENTS I would like to thank my committee chair, Dr. Zhang, and my committee members, Dr. Brooks, Dr. Collins and Dr. Ying, for their guidance and support throughout...

Lal, Vinita

2012-02-14

28

Some studies on starch–urea–acid reaction mechanism  

Microsoft Academic Search

Starch reacted with urea in the absence or presence of mineral acids or mineral acid salts at 150°C for various reaction durations. The acids used were phosphoric, nitric, and sulphuric and the salts used were ammonium sulphate, ammonium nitrate, ammonium chloride and magnesium sulphate. The reaction extent was followed by monitoring nitrogen content. Carrying out the reaction of starch and

M. I Khalil; S Farag; A. A Aly; A Hebeish

2002-01-01

29

40 CFR 721.10125 - Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid...  

... 2014-07-01 false Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid alkyl ester (generic). 721.10125...Substances § 721.10125 Alkenedioic acid, dialkyl ester, reaction products...

2014-07-01

30

40 CFR 721.10125 - Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid...  

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid alkyl ester (generic). 721.10125...Substances § 721.10125 Alkenedioic acid, dialkyl ester, reaction products...

2010-07-01

31

40 CFR 721.10125 - Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid...  

Code of Federal Regulations, 2012 CFR

... 2012-07-01 false Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid alkyl ester (generic). 721.10125...Substances § 721.10125 Alkenedioic acid, dialkyl ester, reaction products...

2012-07-01

32

40 CFR 721.10125 - Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid...  

Code of Federal Regulations, 2013 CFR

... 2013-07-01 false Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid alkyl ester (generic). 721.10125...Substances § 721.10125 Alkenedioic acid, dialkyl ester, reaction products...

2013-07-01

33

40 CFR 721.10125 - Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid...  

Code of Federal Regulations, 2011 CFR

... 2011-07-01 false Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid alkyl ester (generic). 721.10125...Substances § 721.10125 Alkenedioic acid, dialkyl ester, reaction products...

2011-07-01

34

Synthesis and Conformational Analysis of Hybrid ?/?-Dipeptides Incorporating S-Glycosyl-?(2,2) -Amino Acids.  

PubMed

We synthesized and carried out the conformational analysis of several hybrid dipeptides consisting of an ?-amino acid attached to a quaternary glyco-?-amino acid. In particular, we combined a S-glycosylated ?(2,2) -amino acid and two different types of ?-amino acid, namely, aliphatic (alanine) and aromatic (phenylalanine and tryptophan) in the sequence of hybrid ?/?-dipeptides. The key step in the synthesis involved the ring-opening reaction of a chiral cyclic sulfamidate, inserted in the peptidic sequence, with a sulfur-containing nucleophile by using 1-thio-?-D-glucopyranose derivatives. This reaction of glycosylation occurred with inversion of configuration at the quaternary center. The conformational behavior in aqueous solution of the peptide backbone and the glycosidic linkage for all synthesized hybrid glycopeptides was analyzed by using a protocol that combined NMR experiments and molecular dynamics with time-averaged restraints (MD-tar). Interestingly, the presence of the sulfur heteroatom at the quaternary center of the ?-amino acid induced ? torsional angles close to 180° (anti). Notably, this value changed to 60° (gauche) when the peptidic sequence displayed aromatic ?-amino acids due to the presence of CH-? interactions between the phenyl or indole ring and the methyl groups of the ?-amino acid unit. PMID:25413453

García-González, Iván; Mata, Lara; Corzana, Francisco; Jiménez-Osés, Gonzalo; Avenoza, Alberto; Busto, Jesús H; Peregrina, Jesús M

2015-01-12

35

Adaptive hybrid simulations for multiscale stochastic reaction networks  

NASA Astrophysics Data System (ADS)

The probability distribution describing the state of a Stochastic Reaction Network (SRN) evolves according to the Chemical Master Equation (CME). It is common to estimate its solution using Monte Carlo methods such as the Stochastic Simulation Algorithm (SSA). In many cases, these simulations can take an impractical amount of computational time. Therefore, many methods have been developed that approximate sample paths of the underlying stochastic process and estimate the solution of the CME. A prominent class of these methods include hybrid methods that partition the set of species and the set of reactions into discrete and continuous subsets. Such a partition separates the dynamics into a discrete and a continuous part. Simulating such a stochastic process can be computationally much easier than simulating the exact discrete stochastic process with SSA. Moreover, the quasi-stationary assumption to approximate the dynamics of fast subnetworks can be applied for certain classes of networks. However, as the dynamics of a SRN evolves, these partitions may have to be adapted during the simulation. We develop a hybrid method that approximates the solution of a CME by automatically partitioning the reactions and species sets into discrete and continuous components and applying the quasi-stationary assumption on identifiable fast subnetworks. Our method does not require any user intervention and it adapts to exploit the changing timescale separation between reactions and/or changing magnitudes of copy-numbers of constituent species. We demonstrate the efficiency of the proposed method by considering examples from systems biology and showing that very good approximations to the exact probability distributions can be achieved in significantly less computational time. This is especially the case for systems with oscillatory dynamics, where the system dynamics change considerably throughout the time-period of interest.

Hepp, Benjamin; Gupta, Ankit; Khammash, Mustafa

2015-01-01

36

Adaptive hybrid simulations for multiscale stochastic reaction networks.  

PubMed

The probability distribution describing the state of a Stochastic Reaction Network (SRN) evolves according to the Chemical Master Equation (CME). It is common to estimate its solution using Monte Carlo methods such as the Stochastic Simulation Algorithm (SSA). In many cases, these simulations can take an impractical amount of computational time. Therefore, many methods have been developed that approximate sample paths of the underlying stochastic process and estimate the solution of the CME. A prominent class of these methods include hybrid methods that partition the set of species and the set of reactions into discrete and continuous subsets. Such a partition separates the dynamics into a discrete and a continuous part. Simulating such a stochastic process can be computationally much easier than simulating the exact discrete stochastic process with SSA. Moreover, the quasi-stationary assumption to approximate the dynamics of fast subnetworks can be applied for certain classes of networks. However, as the dynamics of a SRN evolves, these partitions may have to be adapted during the simulation. We develop a hybrid method that approximates the solution of a CME by automatically partitioning the reactions and species sets into discrete and continuous components and applying the quasi-stationary assumption on identifiable fast subnetworks. Our method does not require any user intervention and it adapts to exploit the changing timescale separation between reactions and/or changing magnitudes of copy-numbers of constituent species. We demonstrate the efficiency of the proposed method by considering examples from systems biology and showing that very good approximations to the exact probability distributions can be achieved in significantly less computational time. This is especially the case for systems with oscillatory dynamics, where the system dynamics change considerably throughout the time-period of interest. PMID:25612700

Hepp, Benjamin; Gupta, Ankit; Khammash, Mustafa

2015-01-21

37

Reaction of orthophosphoric acid with kaolin and refractory clay  

Microsoft Academic Search

Conclusions In mixtures of kaolin, or semiacid clay with orthophosphoric acid a chemical reaction sets in already after drying at 100 °C. The main crystalline product of the reaction takes the form of aluminum phosphate (AlPO4).

Yu. D. Kuznetsov; S. P. Shmitt-Fogelevich

1975-01-01

38

Enhance decarboxylation reaction of carboxylic acids in clay minerals.  

NASA Astrophysics Data System (ADS)

Clay minerals are important constituents of the Earth's crust. These minerals catalyze reactions in several ways: by energy transfer processes, redox reactions, stabilization of intermediates and by Brønsted or Lewis acidity behavior. Important set of organic reactions can be improved in the precedence of clay minerals. Besides the properties of clays to catalyze chemical reactions, it is possible to enhance some of its reactions by using ionizing radiation. The phenomenon of radiation-induced catalysis may be connected with ionizing process in the solid and with the trapped non-equilibrium charge cariers. In this paper we are reporting the decarboxylation reaction of carboxylic acids catalyzed by clay and by irradiation of the system acid-clay. We studied the behaviour of several carboxylic acids and analyzed them by gas chromatography, X ray and infrared spectroscopy. The results showed that decarboxylation of the target compound is the dominating pathway. The reaction is enhance by gamma radiation in several orders of magnitude.

Negrón-Mendoza, A.; Ramos, S.; Albarrán, G.

1995-02-01

39

Hyporheic Exchange and Fulvic Acid Redox Reactions in an Alpine  

E-print Network

Hyporheic Exchange and Fulvic Acid Redox Reactions in an Alpine Stream/Wetland Ecosystem, Colorado to provide insight into redox reactions in hyporheiczones The influence of hyporheic zone interactions on the redox state of fulvic acids and other redox active species

Williams, Mark W.

40

Mfold web server for nucleic acid folding and hybridization prediction  

Microsoft Academic Search

The abbreviated name,'mfold web server',describes a number of closely related software applications available on the World Wide Web (WWW) for the prediction of the secondary structure of single stranded nucleic acids. The objective of this web server is to provide easy access to RNA and DNA folding and hybridization software to the scientific community at large. By making use of

Michael Zuker

2003-01-01

41

Topological constraints in nucleic acid hybridization kinetics  

Microsoft Academic Search

A theoretical examination of kinetic mechanisms for forming knots and links in nucleic acid structures sug- gests that molecules involving base pairs between loops are likely to become topologically trapped in persistent frustrated states through the mechan- ism of 'helix-driven wrapping'. Augmentation of the state space to include both secondary structure and topology in describing the free energy landscape illustrates

Justin S. Bois; Suvir Venkataraman; Harry M. T. Choi; Andrew J. Spakowitz; Zhen-Gang Wang; Niles A. Pierce

2005-01-01

42

Reaction of ozone with isolated aquatic fulvic acid  

SciTech Connect

Aquatic fulvic acid, isolated from a North Carolina bay lake, was reacted with ozone, an alternative oxidant in drinking-water treatment. Ozonated samples were acidified, extracted with other, dried, concentrated, and methylated samples prior to GC-MS analysis. Identified reaction products include mono-, di-, and tribasic aliphatic acids and benzene tricarboxylic acids. The products with the highest relative concentrations were succinic and malonic acid, although all products were at relatively low concentration levels. Many of the products identified in the study have also been seen among the reaction products of fulvic acid and other oxidants, such as Cl(2), ClO(2) and KMnO(4).

Anderson, L.J.; Johnson, J.D.; Christman, R.F.

1985-01-01

43

Nucleic Acid Hybridization with RNA Immobilized on Filter Paper  

PubMed Central

RNA has been immobilized in a manner suitable for use in molecular hybridization experiments with dissolved RNA or DNA by a nonaqueous solid-phase reaction with carbonyldiimidazole and RNA “dry coated” on cellulose or, preferably, on previously activated phosphocellulose filters. Immobilization of RNA does not appear to alter its chemical character or cause it to acquire affinity for unspecific RNA or DNA. The versatility and efficiency of this method make it potentially attractive for use in routine analytical or preparative hybridization experiments, among other applications. PMID:4562748

Saxinger, W. C.; Ponnamperuma, C.; Gillespie, D.

1972-01-01

44

Atmospheric Environment 40 (2006) 68636878 Acid-catalyzed reactions of hexanal on sulfuric acid particles  

E-print Network

Atmospheric Environment 40 (2006) 6863­6878 Acid-catalyzed reactions of hexanal on sulfuric acid the uptake of gas- phase hexanal into ammonium sulfate and sulfuric acid aerosols. While both deliquesced condensation product was formed only at initial concentrations of 75­96 wt% sulfuric acid in water

Elrod, Matthew J.

45

Hybrid material polyvinyl alcohol-stannic acid/stannic oxide  

NASA Astrophysics Data System (ADS)

Hybrid materials polyvinyl alcohol (PVA)-stannic acid and PVA-SnO2 were produced in the form of transparent films. Their investigations by means of optical spectroscopy, X-ray analysis, thermo-gravimetry, and mass-spectrometry were carried out as well as electrical measurements. The model is discussed where the polymeric chains of inorganic constituent are linked by coordinative bonds with carbon polymeric chains. Photoconductivity of PVA-SnO2 was discovered.

Prosanov, I. Yu.; Chesalov, Yu. A.; Gerasimov, K. B.; Bulina, N. V.

2013-07-01

46

Perfluorinated resinsulfonic acid--a catalyst for certain organic reactions  

SciTech Connect

The purpose of this work was to examine the possibility of using, as a catalyst in certain organic reactions, the perfluorinated resinsulfonic acid F-4SK in the H form, which is an analog of the perfluorinated resinsulfonic acid Nafion-H.

Etlis, V.S.; Beshenova, E.P.; Semenova, E.A.; Shomina, F.N.; Dreiman, N.A.; Balaev, G.A.

1986-09-10

47

40 CFR 721.10629 - Fatty acids, tall-oil, reaction products with modified fatty acids and polyalkanolamines (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Fatty acids, tall-oil, reaction products with modified fatty acids and polyalkanolamines (generic). 721...Chemical Substances § 721.10629 Fatty acids, tall-oil, reaction products with...

2013-07-01

48

40 CFR 721.10629 - Fatty acids, tall-oil, reaction products with modified fatty acids and polyalkanolamines (generic).  

...2014-07-01 2014-07-01 false Fatty acids, tall-oil, reaction products with modified fatty acids and polyalkanolamines (generic). 721...Chemical Substances § 721.10629 Fatty acids, tall-oil, reaction products with...

2014-07-01

49

Radical generating coordination complexes as tools for rapid and effective fragmentation and fluorescent labeling of nucleic acids for microchip hybridization.  

SciTech Connect

DNA microchip technology is a rapid, high-throughput method for nucleic acid hybridization reactions. This technology requires random fragmentation and fluorescent labeling of target nucleic acids prior to hybridization. Radical-generating coordination complexes, such as 1,10-phenanthroline-Cu(II) (OP-Cu) and Fe(II)-EDTA (Fe-EDTA), have been commonly used as sequence nonspecific 'chemical nucleases' to introduce single-strand breaks in nucleic acids. Here we describe a new method based on these radical-generating complexes for random fragmentation and labeling of both single- and double-stranded forms of RNA and DNA. Nucleic acids labeled with the OP-Cu and the Fe-EDTA protocols revealed high hybridization specificity in hybridization with DNA microchips containing oligonucleotide probes selected for identification of 16S rRNA sequences of the Bacillus group microorganisms.We also demonstrated cDNA- and cRNA-labeling and fragmentation with this method. Both the OP-Cu and Fe-EDTA fragmentation and labeling procedures are quick and inexpensive compared to other commonly used methods. A column-based version of the described method does not require centrifugation and therefore is promising for the automation of sample preparations in DNA microchip technology as well as in other nucleic acid hybridization studies.

Kelly, J. J.; Chernov, B. N.; Mirzabekov, A. D.; Bavykin, S. G.; Biochip Technology Center; Northwestern Univ.; Engelhardt Inst. of Molecular Biology

2002-01-01

50

Dissociative attachment reactions of electrons with strong acid molecules  

NASA Astrophysics Data System (ADS)

Using the flowing afterglow/Langmuir probe (FALP) technique, we have determined (at variously 300 and 570 K) the dissociative attachment coefficients ? for the reactions of electrons with the common acids HNO3 (producing NO-2) and H2SO4 (HSO-4), the superacids FSO3H (FSO-3), CF3SO3H (CF3SO-3), ClSO3H (ClSO-3,Cl-), the acid anhydride (CF3SO2)2O (CF3SO-3), and the halogen halides HBr (Br-) and HI (I-). The anions formed in the reactions are those given in the parentheses. The reactions with HF and HCl were investigated, but did not occur at a measurable rate since they are very endothermic. Dissociative attachment is rapid for the common acids, the superacids, and the anhydride, the measured ? being appreciable fractions of the theoretical maximum ? for such reactions, ?max. The HI reaction is very fast ( ?˜?max) but the HBr reaction occurs much more slowly because it is significantly endothermic. The data indicate that the extreme acidity of the (Bronsted-type) superacids has its equivalence in the very efficient gas-phase dissociative attachment which these species undergo when reacting with free electrons. The anions of the superacids generated in these reactions, notably FSO-3 and CF3SO-3, are very stable (unreactive) implying exceptionally large electron affinities for the FSO3 and CF3SO3 radicals.

Adams, Nigel G.; Smith, David; Viggiano, A. A.; Paulson, John F.; Henchman, Michael J.

1986-06-01

51

UNAFold: software for nucleic acid folding and hybridization.  

PubMed

The UNAFold software package is an integrated collection of programs that simulate folding, hybridization, and melting pathways for one or two single-stranded nucleic acid sequences. The name is derived from "Unified Nucleic Acid Folding." Folding (secondary structure) prediction for single-stranded RNA or DNA combines free energy minimization, partition function calculations and stochastic sampling. For melting simulations, the package computes entire melting profiles, not just melting temperatures. UV absorbance at 260 nm, heat capacity change (C(p)), and mole fractions of different molecular species are computed as a function of temperature. The package installs and runs on all Unix and Linux platforms that we have looked at, including Mac OS X. Images of secondary structures, hybridizations, and dot plots may be computed using common formats. Similarly, a variety of melting profile plots is created when appropriate. These latter plots include experimental results if they are provided. The package is "command line" driven. Underlying compiled programs may be used individually, or in special combinations through the use of a variety of Perl scripts. Users are encouraged to create their own scripts to supplement what comes with the package. This evolving software is available for download at http://www.bioinfo.rpi.edu/applications/hybrid/download.php . PMID:18712296

Markham, Nicholas R; Zuker, Michael

2008-01-01

52

Reactions of fulvic acid with metal ions  

Microsoft Academic Search

Fulvic acid is a water-soluble humic material that occurs widely in soils and waters and that tends to form water-soluble and water-insoluble complexes with a variety of metal ions, some of which are toxic. This paper presents information on the conditions under which the different types of FA-metal complexes are formed.

M. Schnitzer; H. Kerndorff

1981-01-01

53

Improved DNA hybridization parameters by Twisted Intercalating Nucleic Acid (TINA).  

PubMed

This thesis establishes oligonucleotide design rules and applications of a novel group of DNA stabilizing molecules collectively called Twisted Intercalating Nucleic Acid - TINA. Three peer-reviewed publications form the basis for the thesis. One publication describes an improved and rapid method for determination of DNA melting points and two publications describe the effects of positioning TINA molecules in parallel triplex helix and antiparallel duplex helix forming DNA structures. The third publication establishes that TINA molecules containing oligonucleotides improve an antiparallel duplex hybridization based capture assay's analytical sensitivity compared to conventionel DNA oligonucleotides. Clinical microbiology is traditionally based on pathogenic microorganisms' culture and serological tests. The introduction of DNA target amplification methods like PCR has improved the analytical sensitivity and total turn around time involved in clinical diagnostics of infections. Due to the relatively weak hybridization between the two strands of double stranded DNA, a number of nucleic acid stabilizing molecules have been developed to improve the sensitivity of DNA based diagnostics through superior binding properties. A short introduction is given to Watson-Crick and Hoogsteen based DNA binding and the derived DNA structures. A number of other nucleic acid stabilizing molecules are described. The stabilizing effect of TINA molecules on different DNA structures is discussed and considered in relation to other nucleic acid stabilizing molecules and in relation to future use of TINA containing oligonucleotides in clinical diagnostics and therapy. In conclusion, design of TINA modified oligonucleotides for antiparallel duplex helixes and parallel triplex helixes follows simple purpose dependent rules. TINA molecules are well suited for improving multiplex PCR assays and can be used as part of novel technologies. Future research should test whether combinations of TINA molecules and other nucleic acid stabilizing molecules can increase analytical sensitivity whilst maintaining nucleobase mismatch discrimination in triplex helix based diagnostic assays. PMID:22239845

Schneider, Uffe Vest

2012-01-01

54

Electrochemical detection of protein based on hybridization chain reaction-assisted formation of copper nanoparticles.  

PubMed

In this paper, we report an electrochemical method for highly sensitive and specific detection of protein based on hybridization chain reaction (HCR)-assisted formation of copper nanoparticles by using small molecule such as folate-linked DNA as probe. In the presence of target protein, taking folate receptor (FR) as the model protein in this study, its binding with folate can protect the probe DNA from exonuclease I-catalyzed degradation, thus the probe DNA can be immobilized onto the electrode surface through the hybridization with capture DNA, triggering HCR on the electrode surface. Subsequently, copper nanoparticles can be formed on the electrode surface by using long duplex DNA oligomers from HCR as templates. Furthermore, copper ions released from acid-dissolution of copper nanoparticles can catalyze the oxidation of ?-phenylenediamine by dissolved oxygen, leading to significant electrochemical responses. As a result, our method can sensitively detect FR in the linear range from 0.01ng/mL to 100ng/mL with a detection limit of 3pg/mL. It can also specifically distinguish the target protein in both buffer and complex serum samples. Since many other proteins can be assayed by changing the corresponding small molecule, this method may be promising for the development of the technique for protein detections. PMID:25437371

Zhao, Jing; Hu, Suisui; Cao, Ya; Zhang, Bin; Li, Genxi

2015-04-15

55

Hybrid polypeptides: gabapentin as a stereochemically constrained ?-amino acid residue.  

PubMed

The design of folded structures in peptides containing the higher homologues of ?-amino acid residues requires the restriction of the range of local conformational choices. In ?-amino acids stereochemically constrained residues like ?,?-dialkylated residue, aminoisobutyric acid (Aib), and D-Proline ((D)Pro) have proved extremely useful in the design of helices and hairpins in short peptides. Extending this approach, backbone substitution and cyclization are anticipated to be useful in generating conformationally constrained ?- and ?-residues. This brief review provides a survey of work on hybrid peptide sequences concerning the conformationally constrained ?-amino acid residue 1-aminomethyl cyclohexane acetic acid, gabapentin (Gpn). This achiral, ?,?-disubstituted, ?-residue strongly favors gauche-gauche conformations about the C(?)-C(?) (?(2)) and C(?)-C(?) (?(1)) bonds, facilitating local folding. The Gpn residue can adopt both C(7) (NH(i)?CO(i)) and C(9) (CO(i-1)?NH(i+1)) hydrogen bonds which are analogous to the C(5) and C(7) (?-turn) conformations at ?-residues. In conjunction with adjacent residues, Gpn may be used in ?? and ?? segments to generate C(12) hydrogen bonded conformations which may be considered as expanded analogs of conventional ?-turns. The structural characterization of C(12) helices, C(12)/C(10) helices with mixed hydrogen bond directionalities and ?-hairpins incorporating Gpn residues at the turn segment is illustrated. PMID:20564041

Balaram, Padmanabhan

2010-01-01

56

Bimodal proton transfer in acid-base reactions in water  

Microsoft Academic Search

We investigate one of the fundamental reactions in solutions, the neutralization of an acid by a base. We use a photoacid, 8-hydroxy-1,3,6-trisulfonate-pyrene (HPTS; pyranine), which upon photoexcitation reacts with acetate under transfer of a deuteron (solvent: deuterated water). We analyze in detail the resulting bimodal reaction dynamics between the photoacid and the base, the first report on which was recently

Matteo Rini; Dina Pines; Ben-Zion Magnes; Ehud Pines; Erik T. J. Nibbering

2004-01-01

57

A Study on Lead Acid Battery and Ultra-capacitor Hybrid Energy Storage System for Hybrid City Bus  

Microsoft Academic Search

Electrochemical energy storage, especially lead acid system alone seems not to be able to meet the demand of the hybrid vehicle propulsion system due to the power density and cycle life. Ultra-capacitor pack has been introduced in the design of energy storage system to the HEV power-train, which is often combined with battery packs to form a hybrid energy system.

Dai Haifeng; Chang Xueyu

2010-01-01

58

Hybrid R-matrix + potential framework for the analysis of low energy nuclear reactions  

Microsoft Academic Search

We report on a hybrid framework for the systematic study of nuclear reactions at low energy, focusing on applications that involve transfer or photonuclear processes, and the application of this framework to the analysis of the 14N(p,?)15O reaction.

B. Braizinha; A. M. Eiro; F. D. Santos; I. J. Thompson

2005-01-01

59

Hybrid R-matrix + potential framework for the analysis of low energy nuclear reactions  

Microsoft Academic Search

We report on a hybrid framework for the systematic study of nuclear reactions at low energy, focusing on applications that involve transfer or photonuclear processes, and the application of this framework to the analysis of the 14N(p,gamma)15O reaction.

B. Braizinha; A. M. Eiro; F. D. Santos; I. J. Thompson

2005-01-01

60

Detection of luciferase gene sequence in nonluminescent Vibrio cholerae by colony hybridization and polymerase chain reaction.  

PubMed Central

Bioluminescence is a trait observed among approximately 10% of Vibrio cholerae isolates. We have demonstrated that not only do some strains of V. cholerae produce low levels of light, undetectable by the human eye, but the luciferase gene sequence is present in strains of V. cholerae which emit no detectable light, evidenced by hybridization with a luciferase DNA probe. Comparisons of the amino acid sequences of luciferase enzymes of marine species have shown that these proteins have diverged to the point where they have only short regions of amino acid identity. The polymerase chain reaction method of DNA amplification with oligonucleotide primers based on these regions was used to isolate a region of the luxA gene from both luminescent and nonluminescent V. cholerae strains. The nucleotide sequence of this region was determined and reveals that nonluminescent V. cholerae have 99.7% nucleotide sequence similarity in this region with the luminescent biovar V. cholerae bv. albensis as well as significant similarity to other species of bioluminescent bacteria, a finding that is in accord with the hypothesis that these species have a common luminescent ancestor, most probably from the marine environment. Images PMID:1854193

Palmer, L M; Colwell, R R

1991-01-01

61

EXTENT OF OZONE'S REACTION WITH ISOLATED AQUATIC FULVIC ACID  

EPA Science Inventory

Samples of North Carolina aquatic fulvic acid were ozonated in a neutral buffer at several ozone/carbon ratios, and the reaction mixtures were characterized by using total organic carbon (TOC) and UV-visible absorbance analysis, XAD-8 chromatography, and ultrafiltration. Results ...

62

REACTION OF OZONE WITH ISOLATED AQUATIC FULVIC ACID  

EPA Science Inventory

Aquatic fulvic acid, isolated from a North Carolina bay lake, was reacted with ozone, an alternative oxidant in drinking water treatment. Ozonated samples were acidified, extracted with other, dried, concentrated, and methylated prior to GC-MS analysis. Identified reaction produc...

63

Template directed reactions of 2-aminoadenylic acid derivatives  

NASA Technical Reports Server (NTRS)

The template-directed oligomerization of activated derivatives of 2-aminoadenylic acid (paA) on polyuridylic acid (poly(U)) in aqueous buffers was studied. The reaction differs from that of adenylic acid (pA) under identical conditions, in that only di- and tri-nucleotides are observed as substantial products rather than a longer sequence of oligomers. The reaction of paA also differs from that of pA in that it does not require Mg (2+), and is less susceptible to increased temperature. The relevance of these observations to the chemical evolution of polynucleotide replication is discussed. Improved syntheses of paA and its diphosphate are reported.

Webb, T. R.; Orgel, L. E.

1982-01-01

64

Detection and isolation of nucleic acid sequences using competitive hybridization probes  

DOEpatents

A method for detecting a target nucleic acid sequence in a sample is provided using hybridization probes which competitively hybridize to a target nucleic acid. According to the method, a target nucleic acid sequence is hybridized to first and second hybridization probes which are complementary to overlapping portions of the target nucleic acid sequence, the first hybridization probe including a first complexing agent capable of forming a binding pair with a second complexing agent and the second hybridization probe including a detectable marker. The first complexing agent attached to the first hybridization probe is contacted with a second complexing agent, the second complexing agent being attached to a solid support such that when the first and second complexing agents are attached, target nucleic acid sequences hybridized to the first hybridization probe become immobilized on to the solid support. The immobilized target nucleic acids are then separated and detected by detecting the detectable marker attached to the second hybridization probe. A kit for performing the method is also provided.

Lucas, Joe N. (San Ramon, CA); Straume, Tore (Tracy, CA); Bogen, Kenneth T. (Walnut Creek, CA)

1997-01-01

65

Detection and isolation of nucleic acid sequences using competitive hybridization probes  

DOEpatents

A method for detecting a target nucleic acid sequence in a sample is provided using hybridization probes which competitively hybridize to a target nucleic acid. According to the method, a target nucleic acid sequence is hybridized to first and second hybridization probes which are complementary to overlapping portions of the target nucleic acid sequence, the first hybridization probe including a first complexing agent capable of forming a binding pair with a second complexing agent and the second hybridization probe including a detectable marker. The first complexing agent attached to the first hybridization probe is contacted with a second complexing agent, the second complexing agent being attached to a solid support such that when the first and second complexing agents are attached, target nucleic acid sequences hybridized to the first hybridization probe become immobilized on to the solid support. The immobilized target nucleic acids are then separated and detected by detecting the detectable marker attached to the second hybridization probe. A kit for performing the method is also provided. 7 figs.

Lucas, J.N.; Straume, T.; Bogen, K.T.

1997-04-01

66

Target Turing Patterns and Growth Dynamics in the Chlorine Dioxide-Iodine-Malonic Acid Reaction  

E-print Network

Target Turing Patterns and Growth Dynamics in the Chlorine Dioxide-Iodine-Malonic Acid Reaction patterns in the chlorine dioxide-iodine-malonic acid reaction-diffusion system in response to perturba in the photosensitive chlorine dioxide-iodine-malonic acid (CDIMA) reaction.13 In this reaction, which is a modified

Epstein, Irving R.

67

A computational study of ultrafast acid dissociation and acid-base neutralization reactions. I. The model  

Microsoft Academic Search

Ultrafast, time-resolved investigations of acid-base neutralization reactions have recently been performed using systems containing the photoacid 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) and various Brønsted bases. Two conflicting neutralization mechanisms have been formulated by Mohammed et al. [Science 310, 83 (2005)] and Siwick et al. [J. Am. Chem. Soc. 129, 13412 (2007)] for the same acid-base system. Herein an ab initio

Patrick Maurer; Vibin Thomas; Ugo Rivard; Radu Iftimie

2010-01-01

68

Preparation of an imogolite/poly(acrylic acid) hybrid gel.  

PubMed

Many efforts in the field of hydrogels have been focused toward increasing the mechanical strength of the gel using inorganic materials. In this study, we synthesized a hydrogel that has excellent mechanical properties using surface-modified inorganic nanofibers composed of imogolite (Al2SiO3(OH)4), which is a hydrated aluminum silicate that has a hollow tube structure. Gamma ray radiation generates peroxide radicals on the nanofibers (imogolite), resulting in an additive free hybrid hydrogel. Structural optimization was carried out by changing the composition of imogolite and poly(acrylic acid). Chemical bonding between the nanofiber and the polymer was simulated by a cluster model and characterized by wide area Raman spectroscopy. The results indicate that imogolite embedded in a polymer matrix can align along the direction of an elongational force, as confirmed by small angle X-ray scattering (SAXS). PMID:23806414

Lee, Hoik; Ryu, Jungju; Kim, Donghyun; Joo, Yongho; Lee, Sang Uck; Sohn, Daewon

2013-09-15

69

Detection and isolation of nucleic acid sequences using a bifunctional hybridization probe  

DOEpatents

A method for detecting and isolating a target sequence in a sample of nucleic acids is provided using a bifunctional hybridization probe capable of hybridizing to the target sequence that includes a detectable marker and a first complexing agent capable of forming a binding pair with a second complexing agent. A kit is also provided for detecting a target sequence in a sample of nucleic acids using a bifunctional hybridization probe according to this method.

Lucas, Joe N. (San Ramon, CA); Straume, Tore (Tracy, CA); Bogen, Kenneth T. (Walnut Creek, CA)

2000-01-01

70

Method for nucleic acid hybridization using single-stranded DNA binding protein  

DOEpatents

Method of nucleic acid hybridization for detecting the presence of a specific nucleic acid sequence in a population of different nucleic acid sequences using a nucleic acid probe. The nucleic acid probe hybridizes with the specific nucleic acid sequence but not with other nucleic acid sequences in the population. The method includes contacting a sample (potentially including the nucleic acid sequence) with the nucleic acid probe under hybridizing conditions in the presence of a single-stranded DNA binding protein provided in an amount which stimulates renaturation of a dilute solution (i.e., one in which the t.sub.1/2 of renaturation is longer than 3 weeks) of single-stranded DNA greater than 500 fold (i.e., to a t.sub.1/2 less than 60 min, preferably less than 5 min, and most preferably about 1 min.) in the absence of nucleotide triphosphates.

Tabor, Stanley (Cambridge, MA); Richardson, Charles C. (Chestnut Hill, MA)

1996-01-01

71

Synthesis and evaluation of novel dapsone-thalidomide hybrids for the treatment of type 2 leprosy reactions.  

PubMed

We synthesized a series of novel dapsone-thalidomide hybrids (3a-i) by molecular hybridization and evaluated their potential for the treatment of type 2 leprosy reactions. All of the compounds had analgesic properties. Compounds 3c and 3h were the most active antinociceptive compounds and reduced acetic acid-induced abdominal constrictions by 49.8% and 39.1%, respectively. The hybrid compounds also reduced tumor necrosis factor-? levels in lipopolysaccharide-stimulated L929 cells. Compound 3i was the most active compound; at concentrations of 15.62 and 125 ?M, compound 3i decreased tumor necrosis factor-? levels by 86.33% and 87.80%, respectively. In nude mice infected with Mycobacterium leprae in vivo, compound 3i did not reduce the number of bacilli compared with controls. Compound 3i did not have mutagenic effects in Salmonella typhimurium strains TA100 and TA102, with or without metabolic activation (S9 mixture). Our results indicate that compound 3i is a novel lead compound for the treatment of type 2 leprosy reactions. PMID:24907144

Yamasaki, Paulo Renato; do Nascimento, Dejair Caetano; Chelucci, Rafael Consolin; de Faria Fernandes Belone, Andréa; Rosa, Patrícia Sammarco; Diório, Suzana Madeira; de Melo, Thais Regina Ferreira; Barbieri, Karina Pereira; Placeres, Marisa Campos Polési; Carlos, Iracilda Zepone; Chung, Man Chin; dos Santos, Jean Leandro

2014-07-15

72

Heterogeneous atmospheric reactions - Sulfuric acid aerosols as tropospheric sinks  

NASA Technical Reports Server (NTRS)

The reaction probabilities of various atmospheric species incident on a bulk sulfuric acid surface are measured in order to determine the role of sulfuric acid aerosols as pollutant sinks. Reaction products and unreacted starting materials leaving a Knudsen cell flow reactor after collision at 300 K with a H2SO4 surface or a soot surface were detected by mass spectrometry. Significant collision reaction probabilities are observed on a H2SO4 surface for H2O2, HNO3, HO2NO2, ClONO2, N2O5, H2O and NH3, and on soot for NH3. Estimates of the contribution of heterogeneous reactions to pollutant removal under atmospheric conditions indicate that while aerosol removal in the stratosphere is insignificant (loss rate constants approximately 10 to the -10th/sec), heterogeneous reactions may be the dominant loss process for several tropospheric species (loss rate constant approximately 10 to the -5th/sec, comparable to photolysis rate constants).

Baldwin, A. C.; Golden, D. M.

1979-01-01

73

Deoxyribonucleic Acid Relatedness Among Mycobacterium leprae, Mycobacterium lepraernuriurn, and Selected Bacteria by Dot Blot and Spectrophotometric Deoxyribonucleic Acid Hybridization Assays  

Microsoft Academic Search

Deoxyribonucleic acid relatedness between Mycobacterium leprae or Mycobacterium lepraemurium and other selected bacteria was studied by both dot blot and spectrophotometric deoxyribonucleic acid hybridization assays. The results obtained by the two methods were similar, except for the relatedness values between M. leprae and two corynebacterial strains. Among the mycobacterial species examined, acid-fast organisms isolated from armadillos and a mangabey monkey

R. S. ATHWAL; S. S. DEO; T. IMAEDA

74

Polymerase chain reaction system using magnetic beads for analyzing a sample that includes nucleic acid  

DOEpatents

A polymerase chain reaction system for analyzing a sample containing nucleic acid includes providing magnetic beads; providing a flow channel having a polymerase chain reaction chamber, a pre polymerase chain reaction magnet position adjacent the polymerase chain reaction chamber, and a post pre polymerase magnet position adjacent the polymerase chain reaction chamber. The nucleic acid is bound to the magnetic beads. The magnetic beads with the nucleic acid flow to the pre polymerase chain reaction magnet position in the flow channel. The magnetic beads and the nucleic acid are washed with ethanol. The nucleic acid in the polymerase chain reaction chamber is amplified. The magnetic beads and the nucleic acid are separated into a waste stream containing the magnetic beads and a post polymerase chain reaction mix containing the nucleic acid. The reaction mix containing the nucleic acid flows to an analysis unit in the channel for analysis.

Nasarabadi, Shanavaz (Livermore, CA)

2011-01-11

75

Auxin and Ribonucleic Acid Synthesis in Pea Stem Tissue as Studied by Deoxyribonucleic Acid-Ribonucleic Acid Hybridization 1  

PubMed Central

The ability of auxin to alter gene transcription in pea (Pisum sativum L.) stem tissues has been investigated by means of DNA/RNA hybridization-competition techniques. In order to obtain reproducible hybridization with total nucleic acid preparations from plants it was found necessary to remove interfering substances, probably polysaccharides; this was accomplished by methoxyethanol extraction and precipitation with cetyltrimethylammonium bromide. When purified in this fashion, plant nucleic acids could be made to form hybrids which showed both species specificity and high thermal stability. No change in hybridizable RNA of stem sections in response to auxin could be detected over a 2- to 24-hour period, regardless of the auxin level employed. In contrast, when large doses of auxin were applied to intact pea seedlings, definite changes in the hybridizable RNA of stem tissue were detected both 8 and 24 hours after treatment. Many of the 2,4-D-induced species of RNA which were present at 24 hours were also present at 8 hours. Sections apparently lack a factor needed for the manifestation of the auxin effect on RNA synthesis. Since the hybridization assay employed does not measure all cellular RNA, it is still possible that certain RNA species may be synthesized in sections in response to auxin. However, the auxin promotion of cell elongation in such sections is clearly not associated with changes in hybridizable RNA such as have been reported for several hormonal responses in animal systems. PMID:16657858

Thompson, William F.; Cleland, Robert

1971-01-01

76

Extent of ozone's reaction with isolated aquatic fulvic acid  

SciTech Connect

Samples of North Carolina aquatic fulvic acid were ozonated in a neutral buffer at several ozone/carbon ratios, and the reaction mixtures were characterized by using total organic carbon (TOC) and UV-visible absorbance analysis, XAD-8 chromatography, and ultrafiltration. Results show a large initial ozone consumption with loss of TOC and UV-visible absorbance by the fulvic acid solution followed by a slower rate of ozone consumption and decrease in TOC and UV-visible absorbance at higher doses. Exclusion chromatography and ultrafiltration show an increase in smaller sized materials. The authors conclude that ozone initially and rapidly attacks sensitive nucleophlic sites on the molecule. At higher doses slower cleavage reactions produce structural changes in the macromolecule. 15 references, 8 figures.

Anderson, L.J.; Johnson, J.D.; Christman, R.F.

1986-07-01

77

Molybdenum sulfide/N-doped CNT forest hybrid catalysts for high-performance hydrogen evolution reaction.  

PubMed

Cost effective hydrogen evolution reaction (HER) catalyst without using precious metallic elements is a crucial demand for environment-benign energy production. Molybdenum sulfide is one of the promising candidates for such purpose, particularly in acidic condition, but its catalytic performance is inherently limited by the sparse catalytic edge sites and poor electrical conductivity. We report synthesis and HER catalysis of hybrid catalysts composed of amorphous molybdenum sulfide (MoSx) layer directly bound at vertical N-doped carbon nanotube (NCNT) forest surface. Owing to the high wettability of N-doped graphitic surface and electrostatic attraction between thiomolybdate precursor anion and N-doped sites, ?2 nm scale thick amorphous MoSx layers are specifically deposited at NCNT surface under low-temperature wet chemical process. The synergistic effect from the dense catalytic sites at amorphous MoSx surface and fluent charge transport along NCNT forest attains the excellent HER catalysis with onset overpotential as low as ?75 mV and small potential of 110 mV for 10 mA/cm(2) current density, which is the highest HER activity of molybdenum sulfide-based catalyst ever reported thus far. PMID:24502837

Li, Dong Jun; Maiti, Uday Narayan; Lim, Joonwon; Choi, Dong Sung; Lee, Won Jun; Oh, Youngtak; Lee, Gil Yong; Kim, Sang Ouk

2014-03-12

78

An amplified electrochemical aptasensor based on hybridization chain reactions and catalysis of silver nanoclusters.  

PubMed

In the present study, based on the mimic oxidase catalytic character of nucleic-acid-stabilized silver nanoclusters (DNA/AgNCs) and hybridization chain reactions for signal amplification, the fabrication of a label-free sensitive "turn-on" electrochemical aptasensor for the amplified determination of lysozyme was demonstrated. First, the designed DNA duplex was modified on the electrode. With the specific binding of the target, lysozyme and its aptamer, the lysozyme-binding DNA sequence was liberated, exposing the induced DNA sequence, which in turn triggered the formation of the supersandwich DNA structure. Because the cytosine-rich sequence was designed ingeniously on the DNA sequence, DNA/AgNCs were formed on the supersandwich DNA structure. The peroxidase-like character of DNA/AgNCs produced detectable electrochemical signals for the lysozyme aptasensor, which showed a satisfying sensitive detection of lysozyme with a low detection limit of 42 pM and a wide linear range of 10(-10) M to 10(-5) M. PMID:25623467

Chen, Ling; Sha, Liang; Qiu, Yuwei; Wang, Guangfeng; Jiang, Hong; Zhang, Xiaojun

2015-02-01

79

Heterogeneous Reaction of HO2 Radical with Dicarboxylic Acid Particles  

NASA Astrophysics Data System (ADS)

HOx(OH+ HO2) radical plays a central role in the tropospheric chemistry. Recently, the heterogeneous loss of HO2 by aerosol particles is a potentially important HOx sink in the troposphere suggested from observation study. However, there have been few studies for loss of HO2 by aerosols. In this study, we measured the HO2 uptake coefficients for four dicarboxylic acids (succinic acid, glutaric acid, adipic acid, and pimelic acid) aerosol particles under ambient conditions (760Torr and 296K) using an aerosol flow tube(AFT) coupled with a chemical conversion /laser-induced fluorescence(CC/LIF) technique. The CC/LIF technique enabled experiments to be performed at almost the same HO2 radical concentration as that in the atmosphere(-10^8 molecules/cm^3). In this system, the effect of the self-reaction of HO2 in the gas phase can be neglected. HO2 radicals were injected into the AFT through a vertically movable Pyrex tube. Injector position dependent profiles of LIF intensity were measured as a function of aerosol concentration at 30% and 70% of relative humilities (RH). Determined HO2 uptake coefficients by succinic acid, glutaric acid, adipic acid, and pimelic acid aerosol particles at 30% RH were 0.05 +/- 0.02, 0.07 +/- 0.03, 0.02 +/- 0.01, and 0.06 +/- 0.03, respectively, while the uptake coefficients by those particles at 70% RH were 0.13 +/- 0.05, 0.13 +/- 0.03, 0.06 +/- 0.01, and 0.11 +/- 0.03, respectively. These results suggest that compositions and relative humidity are significant to the HO2 uptake. We will discuss the potential HO2 loss processes.

Taketani, F.; Kanaya, Y.

2010-12-01

80

40 CFR 721.4461 - Hydrofluoric acid, reaction products with octane (generic).  

Code of Federal Regulations, 2012 CFR

...Substances § 721.4461 Hydrofluoric acid, reaction products with octane...identified generically as a hydrofluoric acid, reaction products with...significant new uses are: (i) Release to water. Requirements...

2012-07-01

81

40 CFR 721.4461 - Hydrofluoric acid, reaction products with octane (generic).  

Code of Federal Regulations, 2013 CFR

...Substances § 721.4461 Hydrofluoric acid, reaction products with octane...identified generically as a hydrofluoric acid, reaction products with...significant new uses are: (i) Release to water. Requirements...

2013-07-01

82

40 CFR 721.4461 - Hydrofluoric acid, reaction products with octane (generic).  

Code of Federal Regulations, 2010 CFR

...Substances § 721.4461 Hydrofluoric acid, reaction products with octane...identified generically as a hydrofluoric acid, reaction products with...significant new uses are: (i) Release to water. Requirements...

2010-07-01

83

40 CFR 721.4461 - Hydrofluoric acid, reaction products with octane (generic).  

...Substances § 721.4461 Hydrofluoric acid, reaction products with octane...identified generically as a hydrofluoric acid, reaction products with...significant new uses are: (i) Release to water. Requirements...

2014-07-01

84

40 CFR 721.4461 - Hydrofluoric acid, reaction products with octane (generic).  

Code of Federal Regulations, 2011 CFR

...Substances § 721.4461 Hydrofluoric acid, reaction products with octane...identified generically as a hydrofluoric acid, reaction products with...significant new uses are: (i) Release to water. Requirements...

2011-07-01

85

Production of Acetic Acid from Carbohydrate Biomass by Two-Step Reaction with Alkaline Hydrothermal Reaction and Wet Oxidation  

Microsoft Academic Search

An investigation was carried out to improve the production of acetic acid by an alkaline two-step process, in which the first step is to accelerate the formation of lactic acid in a hydrothermal reaction with the addition of alkali, and the second step is further convert the lactic acid produced in the first step to acetic acid by oxidation with

X. Yan; F. Jin; K. Tohji; H. Enomoto

2007-01-01

86

Controllable redox reaction of chemically purified DNA-single walled carbon nanotube hybrids with hydrogen peroxide.  

PubMed

We report for the first time the controllable redox reaction of chemically purified ssDNA-HiPco SWNT hybrids with hydrogen peroxide. Compared with the suspensions before separation, the purified SWNT suspensions become inert with hydrogen peroxide which may serve as a platform for further chemical manipulation. In the presence of thiocyanate ions, the reaction of SWNTs with hydrogen peroxide is initiated and accelerated at the earlier reaction stage, accompanied with the near-infrared spectral suppression. At the later stage, the suppressed spectral intensity is recovered overtime. The thiocyanate ions may work as a mediator being able to control the reaction rate as well as the tunable properties of the reaction. The tunable redox reaction of SWNTs and H2O2 mediated by thiocyanate ions may offer a new sensing scheme for continuously monitoring H2O2 concentrations. PMID:18611008

Xu, Yang; Pehrsson, Pehr E; Chen, Liwei; Zhao, Wei

2008-08-01

87

Meta-DNA: Synthetic Biology via DNA Nanostructures and Hybridization Reactions  

E-print Network

Meta-DNA: Synthetic Biology via DNA Nanostructures and Hybridization Reactions Harish Chandran for desired functionality. The approach of this paper is to develop a biochemical system which we call meta-DNA (abbreviated as mDNA), based entirely on strands of DNA as the only component molecule. Our work leverages

Reif, John H.

88

Characterization of rapidly labelled ribonucleic acid in Escherichia coli by deoxyribonucleic acid–ribonucleic acid hybridization  

PubMed Central

1. Rapidly labelled RNA from Escherichia coli K 12 was characterized by hybridization to denatured E. coli DNA on cellulose nitrate membrane filters. The experiments were designed to show that, if sufficient denatured DNA is offered in a single challenge, practically all the rapidly labelled RNA will hybridize. With the technique employed, 75–80% hybridization efficiency could be obtained as a maximum. Even if an excess of DNA sites were offered, this value could not be improved upon in any single challenge of rapidly labelled RNA with denatured E. coli DNA. 2. It was confirmed that the hybridization technique can separate the rapidly labelled RNA into two fractions. One of these (30% of the total) was efficiently hybridized with the low DNA/RNA ratio (10:1, w/w) used in tests. The other fraction (70% of the total) was hybridized to DNA at low efficiencies with the DNA/RNA ratio 10:1, and was hybridized progressively more effectively as the amount of denatured DNA was increased. A practical maximum of 80% hybridization of all the rapidly labelled RNA was first achieved at a DNA/RNA ratio 210:1 (±10:1). This fraction was fully representative of the rapidly labelled RNA with regard to kind and relative amount of materials hybridized. 3. In competition experiments, where additions were made of unlabelled RNA prepared from E. coli DNA, DNA-dependent RNA polymerase (EC 2.7.7.6) and nucleoside 5?-triphosphates, the rapidly labelled RNA fraction hybridized at a low (10:1) DNA/RNA ratio was shown to be competitive with a product from genes other than those responsible for ribosomal RNA synthesis and thus was presumably messenger RNA. At higher DNA/rapidly labelled RNA ratios (200:1), competition with added unlabelled E. coli ribosomal RNA (without messenger RNA contaminants) lowered the hybridization of the rapidly labelled RNA from its 80% maximum to 23%. This proportion of rapidly labelled RNA was not competitive with E. coli ribosomal RNA even when the latter was in large excess. The ribosomal RNA would also not compete with the 23% rapidly labelled RNA bound to DNA at low DNA/RNA ratios. It was thus demonstrated that the major part of E. coli rapidly labelled RNA (70%) is ribosomal RNA, presumably a precursor to the RNA in mature ribosomes. 4. These studies have shown that, when earlier workers used low DNA/RNA ratios (about 10:1) in the assay of messenger RNA in bacterial rapidly labelled RNA, a reasonable estimate of this fraction was achieved. Criticisms that individual messenger RNA species may be synthesized from single DNA sites in E. coli at rates that lead to low efficiencies of messenger RNA binding at low DNA/RNA ratios are refuted. In accordance with earlier results, estimations of the messenger RNA content of E. coli in both rapidly labelled and randomly labelled RNA show that this fraction is 1·8–1·9% of the total RNA. This shows that, if any messenger RNA of relatively long life exists in E. coli, it does not contribute a measurable weight to that of rapidly labelled messenger RNA. PMID:4881972

Pigott, G. H.; Midgley, J. E. M.

1968-01-01

89

40 CFR 721.10211 - Octadecanoic acid, reaction products with diethylenetriamine and urea, acetates.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Octadecanoic acid, reaction products with diethylenetriamine... § 721.10211 Octadecanoic acid, reaction products with diethylenetriamine...substance identified as octadecanoic acid, reaction products with...as specified in § 721.80(s) (10,000 kilograms)....

2013-07-01

90

40 CFR 721.10211 - Octadecanoic acid, reaction products with diethylenetriamine and urea, acetates.  

...2014-07-01 false Octadecanoic acid, reaction products with diethylenetriamine... § 721.10211 Octadecanoic acid, reaction products with diethylenetriamine...substance identified as octadecanoic acid, reaction products with...as specified in § 721.80(s) (10,000 kilograms)....

2014-07-01

91

40 CFR 721.10211 - Octadecanoic acid, reaction products with diethylenetriamine and urea, acetates.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 false Octadecanoic acid, reaction products with diethylenetriamine... § 721.10211 Octadecanoic acid, reaction products with diethylenetriamine...substance identified as octadecanoic acid, reaction products with...as specified in § 721.80(s) (10,000 kilograms)....

2012-07-01

92

40 CFR 721.10211 - Octadecanoic acid, reaction products with diethylenetriamine and urea, acetates.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Octadecanoic acid, reaction products with diethylenetriamine... § 721.10211 Octadecanoic acid, reaction products with diethylenetriamine...substance identified as octadecanoic acid, reaction products with...as specified in § 721.80(s) (10,000 kilograms)....

2011-07-01

93

MODEL OF CHEMICAL REACTION EQUILIBRIUM OF SULFURIC ACID SALTS OF TRIOCTYLAMINE  

Microsoft Academic Search

The chemical reaction of trioctylamine (TOA) and sulfuric acid in organic solvent\\/aqueous solution was carried out. TOA salt products of various kinds were obtained based on different conditions of operation and organic solvents. An equilibrium model, based on the chemical reaction of sulfuric acid and trioctylamine, is proposed. The equilibrium constants of various reactions of trioctylamine and sulfuric acid were

MAW-LING WANG; KWAN-HUA HU

1993-01-01

94

Heat of Reaction of the Hydrolysis-Polymerization Process of Tetraethyl Orthosilicate in Acidic Condition  

Microsoft Academic Search

Heat of reaction of the hydrolysis-polymerization process of tetraethyl orthosilicate with water in acidic condition was investigated to clarify the thermodynamic driving force of sol-gel reactions. Heat of reaction was measured using an isoperibol calorimeter by mixing a dilute tetraethyl orthosilicate (TEOS) ethanolic solution with another solution of water, ethanol, and hydrochloric acid. The temperature change of the reaction cell

Jun Matsuoka; Minoru Numaguchi; Satoshi Yoshida; Naohiro Soga

2000-01-01

95

Fluorescent hybridization probes for nucleic acid detection Jia Guo & Jingyue Ju & Nicholas J. Turro  

E-print Network

REVIEW Fluorescent hybridization probes for nucleic acid detection Jia Guo & Jingyue Ju & Nicholas widely used to detect nucleic acids both in vivo and in vitro. Molecular beacons (MBs) and binary probes of identifying nucleic acid sequences are critical to biomedical research, disease diagnosis, and drug discovery

Turro, Nicholas J.

96

Laboratory measurements of heterogeneous reactions on sulfuric acid surfaces  

NASA Technical Reports Server (NTRS)

Increasing evidence from field, modeling, and laboratory studies suggests that heterogeneous reactions on stratospheric sulfate aerosol particles may contribute to global ozone depletion. Using a Knudsen cell reactor technique, the authors have studied the uptake, reactivity, and solubility of several trace atmospheric species on cold sulfuric acid surfaces representative of stratospheric aerosol particles. The results suggest that the heterogeneous conversion of N2O5 to HNO3 is fast enough to significantly affect the partitioning of nitrogen species in the global stratosphere and thus contribute to global ozone depletion. The hydrolysis of ClONO2 is slower and unlikely to be important under normal conditions at midlatitudes. The solubilities of HCl and HNO3 in sulfuric acid down to 200 K were found to be quite low. For HCl, this means that little HCl is available for reaction on the surfaces of stratospheric sulfate aerosol particles. The low solubility of HNO3 means that this product of heterogeneous reactions will enter the gas phase, and the denitrification observed in polar regions is unlikely to occur in the global stratosphere.

Williams, Leah R.; Manion, Jeffrey A.; Golden, David M.; Tolbert, Margaret A.

1994-01-01

97

Hybridization properties of long nucleic acid probes for detection of variable target sequences, and development of a hybridization prediction algorithm.  

PubMed

One of the main problems in nucleic acid-based techniques for detection of infectious agents, such as influenza viruses, is that of nucleic acid sequence variation. DNA probes, 70-nt long, some including the nucleotide analog deoxyribose-Inosine (dInosine), were analyzed for hybridization tolerance to different amounts and distributions of mismatching bases, e.g. synonymous mutations, in target DNA. Microsphere-linked 70-mer probes were hybridized in 3M TMAC buffer to biotinylated single-stranded (ss) DNA for subsequent analysis in a Luminex® system. When mismatches interrupted contiguous matching stretches of 6 nt or longer, it had a strong impact on hybridization. Contiguous matching stretches are more important than the same number of matching nucleotides separated by mismatches into several regions. dInosine, but not 5-nitroindole, substitutions at mismatching positions stabilized hybridization remarkably well, comparable to N (4-fold) wobbles in the same positions. In contrast to shorter probes, 70-nt probes with judiciously placed dInosine substitutions and/or wobble positions were remarkably mismatch tolerant, with preserved specificity. An algorithm, NucZip, was constructed to model the nucleation and zipping phases of hybridization, integrating both local and distant binding contributions. It predicted hybridization more exactly than previous algorithms, and has the potential to guide the design of variation-tolerant yet specific probes. PMID:20864443

Ohrmalm, Christina; Jobs, Magnus; Eriksson, Ronnie; Golbob, Sultan; Elfaitouri, Amal; Benachenhou, Farid; Strømme, Maria; Blomberg, Jonas

2010-11-01

98

Theoretical study of the ammonia-hypochlorous acid reaction mechanism.  

PubMed

A mechanism for the oxidation of ammonia by hypochlorous acid to form nitrogen gas has been developed at the B3LYP/6-31G(d,p) level of theory using the Gaussian 03 software package. The formation of NH(2)Cl, NHCl(2), and NCl(3) was studied in the gas phase, with explicit water molecules included to examine the transition state energy in aqueous solution. The inclusion of explicit water molecules in the transition state dramatically reduced the reaction barrier in reactions involving transfer of a hydrogen atom between molecules, effects that were not taken into account through use of a solvation model alone. Three mechanisms were identified for the decomposition of chloramine species to form N(2), involving the combination of two chloramine species to form hydrazine, dichlorohydrazine and tetrachlorohydrazine intermediates. The highest barrier in each pathway was found to be the formation of the hydrazine derivative. PMID:20112901

Rayson, Mark S; Altarawneh, Mohammednoor; Mackie, John C; Kennedy, Eric M; Dlugogorski, Bogdan Z

2010-02-25

99

Enzymatic hybridization of ?-lipoic acid with bioactive compounds in ionic solvents.  

PubMed

The lipase-catalyzed molecular hybridization of ?-lipoic acid (LA) with bioactive compounds pyridoxine, tyrosol and tyramine was performed in ionic solvents and deep eutectic solvents. The biocatalytic reactions were catalyzed by Candida antarctica lipase B immobilized onto various functionalized multi-walled carbon nanotubes (f-CNTs-CaLB), as well as by commercial Novozym 435. The use of f-CNTs-CaLB leads, in most cases, to higher conversion yields as compared to Novozym 435. The nature and ion composition of ionic solvents affect the performance of the biocatalytic process. The highest conversion yield was observed in (mtoa)NTf2. The high enzyme stability and the relatively low solubility of substrates in specific media account for the improved biocatalytic synthesis of molecular hybrids of LA. Principal component analysis was used to screen for potential lipoxygenase inhibitors. In vitro studies showed that the synthesized compounds exhibit up to 10-fold increased inhibitory activity on lipoxygenase mediated lipid peroxidation as compared to parent molecules. PMID:23567667

Papadopoulou, Athena A; Katsoura, Maria H; Chatzikonstantinou, Alexandra; Kyriakou, Eleni; Polydera, Angeliki C; Tzakos, Andreas G; Stamatis, Haralambos

2013-05-01

100

Acid activated montmorillonite as catalysts in methyl esterification reactions of lauric acid.  

PubMed

The catalytic activity of acid activated montmorillonite in the esterification of free fatty acids (FFA) is reported. Standard Montmorillonite (MMT) type STx-1 provided by the Clay Mineral Society repository was activated using phosphoric, nitric and sulphuric acids under different conditions and the resulting materials were characterized and evaluated as catalysts in the methyl esterification of lauric acid. Blank reactions carried out in the absence of any added catalyst presented conversions of 32.64, 69.79 and 79.23%, for alcohol:lauric acid molar ratios of 60:1, 12:1 and 6:1, respectively. In the presence of the untreated clay and using molar ratios of 12:1 and 6:1 with 12% of catalyst, conversions of 70.92 and 82.30% were obtained, respectively. For the acid activated clays, conversions up to 93.08% of lauric acid to methyl laurate were obtained, much higher than those observed for the thermal conversion or using untreated montmorillonite. Relative good correlations were observed between the catalytic activity and the development of acid sites and textural properties of the resulting materials. Therefore, a simple acid activation was able to improve the catalytic activity and produce clay catalysts that are environmental friendly, cost effective, noncorrosive and reusable. PMID:22975784

Zatta, Leandro; Ramos, Luiz Pereira; Wypych, Fernando

2012-01-01

101

Acid-catalyzed reactions of epoxides for atmospheric nanoparticle growth.  

PubMed

Although new particle formation accounts for about 50% of the global aerosol production in the troposphere, the chemical species and mechanism responsible for the growth of freshly nucleated nanoparticles remain largely uncertain. Here we show large size growth when sulfuric acid nanoparticles of 4-20 nm are exposed to epoxide vapors, dependent on the particle size and relative humidity. Composition analysis of the nanoparticles after epoxide exposure reveals the presence of high molecular weight organosulfates and polymers, indicating the occurrence of acid-catalyzed reactions of epoxides. Our results suggest that epoxides play an important role in the growth of atmospheric newly nucleated nanoparticles, considering their large formation yields from photochemical oxidation of biogenic volatile organic compounds. PMID:25338124

Xu, Wen; Gomez-Hernandez, Mario; Guo, Song; Secrest, Jeremiah; Marrero-Ortiz, Wilmarie; Zhang, Annie L; Zhang, Renyi

2014-11-01

102

Synthesis of high erucic acid rapeseed ( Brassica napus L.) somatic hybrids with improved agronomic characters  

Microsoft Academic Search

Novel Brassica napus somatic hybrids have been created through protoplast fusion of B. oleracea var. botrytis and B. rapa var. oleifera genotypes selected for high erucic acid (22:1) content in the seed oil. Fifty amphidiploids (aacc) and one putative hexaploid (aacccc) hybrid were recovered in one fusion experiment. Conversely, only one amphidiploid and numerous regenerates with higher DNA contents were

D. W. Heath; E. D. Earle

1995-01-01

103

Deoxyribonucleic acid-ribonucleic acid hybridization studies on the L-Arabinose operon of Escherichia coli B-r.  

PubMed

An increase in the rate of synthesis of ara-specific messenger ribonucleic acid as measured by deoxyribonucleic acid-ribonucleic acid hybridization has been detected in the induced wild-type (ara(+)) strain of Escherichia coli B/r as compared with the uninduced control, thus providing evidence that regulation of the positively controlled l-arabinose operon is at the level of transcription. PMID:4941555

Wilcox, G; Singer, J; Heffernan, L

1971-10-01

104

Deoxyribonucleic Acid-Ribonucleic Acid Hybridization Studies on the l-Arabinose Operon of Escherichia coli B/r  

PubMed Central

An increase in the rate of synthesis of ara-specific messenger ribonucleic acid as measured by deoxyribonucleic acid-ribonucleic acid hybridization has been detected in the induced wild-type (ara+) strain of Escherichia coli B/r as compared with the uninduced control, thus providing evidence that regulation of the positively controlled l-arabinose operon is at the level of transcription. PMID:4941555

Wilcox, Gary; Singer, Judith; Heffernan, Laurel

1971-01-01

105

Surface reactions of iron - enriched smectites: adsorption and transformation of hydroxy fatty acids and phenolic acids  

NASA Astrophysics Data System (ADS)

Iron-enriched smectites play an important role in adsorption and transformation of soil organic components. Soil organo-clay complexes, and in particular humin contain hydroxy fatty acids, which are derived from plant biopolymer cutin. Phenolic acids belong to another major group of organic acids detected in soil. They participate in various soil processes, and are of concern due to their allelopathic activity. We studied the reactivity of iron-enriched smectites (Fe(III)-montmorillonite and nontronite) toward both groups of acids. We used fatty acids- 9(10),16-dihydroxypalmitic acid (diHPA), isolated from curtin, and 9,10,16-trihydroxypalmitic acid (triHPA); the following phenolic acids were used: ferulic, p-coumaric, syringic, and vanillic. Adsorption of both groups of acids was measured. The FTIR spectra of fatty acid-mineral complexes indicated inner-sphere complexation of fatty acids with iron-enriched smectites (versus outer-sphere complexation with Ca(II)-montmorillonite). The LC-MS results demonstrated enhanced esterification of fatty acids on the iron-enriched smectite surfaces (as compared to Ca(II)-montmorillonite). This study suggests that fatty acids can be esterified on the iron-enriched smectite surfaces, which results in the formation of stable organo-mineral complexes. These complexes may serve as a model for the study of natural soil organo-clay complexes and humin. The reaction of phenolic acids with Fe(III)-montmorillonite demonstrated their oxidative transformation by the mineral surfaces, which was affected by molecular structure of acids. The following order of their transformation was obtained: ferulic >syringic >p-coumaric >vanillic. The LC-MS analysis demonstrated the presence of dimers, trimers, and tetramers of ferulic acid on the surface of Fe(III)-montmorillonite. Oxidation and transformation of ferulic acid were more intense on the surface of Fe(III)-montmorillonite as compared to Fe(III) in solution due to stronger complexation on the Fe(III)-motnomrillonite surface. Our study demonstrate the importance of iron-enriched minerals for the abiotic formation of humic materials and for the transformation of aromatic (phenolic) pollutants.

Polubesova, Tamara; Olshansky, Yaniv; Eldad, Shay; Chefetz, Benny

2014-05-01

106

Radical-generating coordination complexes as tools for rapid and effective fragmentation and fluorescent labeling of nucleic acids for microchip hybridization.  

SciTech Connect

DNA microchip technology is a rapid, high-throughput method for nucleic acid hybridization reactions. This technology requires random fragmentation and fluorescent labeling of target nucleic acids prior to hybridization. Radical-generating coordination complexes, such as 1,10-phenanthroline-Cu(II) (OP-Cu) and Fe(II)-EDTA (Fe-EDTA), have been commonly used as sequence nonspecific 'chemical nucleases' to introduce single-strand breaks in nucleic acids. Here we describe a new method based on these radical-generating complexes for random fragmentation and labeling of both single- and double-stranded forms of RNA and DNA. Nucleic acids labeled with the OP-Cu and the Fe-EDTA protocols revealed high hybridization specificity in hybridization with DNA microchips containing oligonucleotide probes selected for identification of 16S rRNA sequences of the Bacillus group microorganisms.We also demonstrated cDNA- and cRNA-labeling and fragmentation with this method. Both the OP-Cu and Fe-EDTA fragmentation and labeling procedures are quick and inexpensive compared to other commonly used methods. A column-based version of the described method does not require centrifugation and therefore is promising for the automation of sample preparations in DNA microchip technology as well as in other nucleic acid hybridization studies.

Kelly, J. J.; Chernov, B. K.; Tovstanovsky, I.; Mirzabekov, A. D.; Bavykin, S. G.; Biochip Technology Center; Northwestern Univ.; Engelhardt Inst. of Molecular Biology

2002-12-15

107

Tag/hybridization-based sensitive detection of polymerase chain reaction products.  

PubMed

The polymerase chain reaction (PCR) is an important technology to amplify a single copy or a few copies of DNA segment in genomic DNAs, visualizing the segment as DNA fragment. Thus, PCR is frequently used in various examinations such as detection of bacteria and fungi in the food industry. Here, we report a simple and sensitive method for detection of PCR products using single-strand tag sequence and hybridization of the tag sequence to the complementary tag sequence immobilized on solid material (STH). The detection sensitivity was found to be at least 50 times higher than electrophoresis/ethidium bromide (EtBr) visualization for approximately a 500-bp fragment and higher than the ordinary hybridization, that is, hybridization of denatured PCR product to probe sequence immobilized on solid material. PMID:25051253

Niwa, Kousuke; Oribe, Akinobu; Okumura, Hidemasa; Shimono, Masahiro; Nagai, Kenkichi; Hirota, Toshikazu; Yasue, Hiroshi; Kawase, Mitsuo

2014-11-01

108

Wollastonite hybridizing stearic acid as thermal energy storage material  

NASA Astrophysics Data System (ADS)

This paper reported on the preparation of a novel stearic acid (SA)/wollastonite (W) composite as a form-stable phase change material (PCM) for thermal energy-storage (TES) by vacuum impregnation, and especially investigated the effect of the size grade of W on the thermal properties of the SA/W composite. Samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), laser particle-size analysis, and differential scanning calorimetry (DSC). Natural W (Wr) was classified into four size grades by wet screening. The results indicate that no chemical reaction took place between SA and W, and the SA load in the SA/W composite increased with an increase in the length/diameter (L/D) ratio of the W. The SA/W composite with a W L/D ratio of 22.5 exhibited latent heats of melting and freezing of 58.64 J/g and 56.95 J/g, respectively, which was higher than those of the composite incorporating natural W. We believe that the as-prepared form-stable PCM composite could provide a potential means of TES for the concentrated solar power.

Xu, Dawei; Yang, Huaming

2014-11-01

109

Phagocytosis of hybrid molecular nanosomal compositions containing oxidized dextrans conjugated with isonicotinic acid hydrazide by macrophages.  

PubMed

We studied phagocytic activity of macrophages towards hybrid molecular nanosomal compositions consisting of 150-800-nm nanoliposomes containing oxidized dextrans with a molecular weight of 35 and 60 kDa obtained by chemical ("permanganate") and radiochemical oxidation of dextran conjugated with isonicotinic acid hydrazide (dextrazides, intracellular prolonged antituberculous drugs). Phagocytic activity of macrophages towards hybrid molecular nanosomal compositions containing dextrazides obtained by chemical oxidation of dextrans is higher than activity towards hybrid molecular nanosomal compositions containing dextrazides prepared by radiochemical oxidation and depends on the size of hybrid molecular nanosomal compositions and molecular weight of oxidized dextrans. PMID:21116494

Shkurupy, V A; Arkhipov, S A; Troitsky, A V; Luzgina, N G; Zaikovskaja, M V; Ufimceva, E G; Iljine, D A; Akhramenko, E S; Gulyaeva, E P; Bistrova, T N

2009-12-01

110

Comparison between the homogeneous and heterogeneous reactions during the radiolysis of aconitic acid  

NASA Astrophysics Data System (ADS)

The decarboxylation reaction of aconitic acid catalyzed by clay and by irradiation of the system acid-clay has been investigated. The results showed that decarboxylation of the target compound, the dominating pathway in this reaction, is enhance by gamma radiation. Important set of organic reactions can be improved in the precedence of these clay minerals and ionizing radiation.

Ramos Bernal, S.; Negrón-Mendoza, A.

1996-07-01

111

Cassava interspecific hybrids with increased protein content and improved amino acid profiles.  

PubMed

Cassava (Manihot esculenta) is a principal food for large populations of poor people in the tropics and subtropics. Its edible roots are poor in protein and lack several essential amino acids. Interspecific hybrids may acquire high protein characteristics from wild species. We analyzed 19 hybrids of M. esculenta with its wild relative, M. oligantha, for crude protein, amino acid profile, and total cyanide. Some hybrids produced roots with high protein content of up to 5.7%, while the common cultivar that we examined had just 2.3% crude protein. The essential amino acids alanine, phenylalanine, and valine were detected in the hybrids. The sulfur-containing amino acids cysteine and methionine were found at relatively high concentrations in the roots of 4 hybrids. The proportion of lysine in one hybrid was 20 times higher than in the common cultivar. The levels of total cyanide ranged from 19.73 to 172.56 mg/kg and most of the roots analyzed were classified as "non-toxic" and "low toxic". Furthermore, 2 progenies showed reasonable levels of cyanide, but higher protein content and amino acid profile more advantageous than the common cassava. PMID:23661446

Gomes, P T C; Nassar, N M A

2013-01-01

112

Label-free electrochemical DNA sensing with a one-target-multitriggered hybridization chain reaction strategy.  

PubMed

A one-target-multitriggered hybridization chain reaction (MHCR) strategy was designed for ultrasensitive electrochemical detection of DNA by combining the isothermal strand-displacement polymerase reaction (ISDPR) with the DNA self-assembly on a DNA sensor surface. The sensor was constructed by immobilizing a hairpin-like capture probe (CP) on a gold electrode via an Au-S bond. The ISDPR was triggered by the hybridization of the target DNA to open the CP and primer to anneal the complementary part in the bottom of the exposed stem and the extension of the primer in the presence of dNTPs and polymerase. Each target copy could produce a few opened CPs. Afterwards, the other part of the exposed stem acted as an initiator to trigger the hybridization chain reaction (HCR) when incubated with two hairpin monomers. Using [Ru(NH3)6](3+) as an electrochemically active indicator to interact with the MHCR product, the amperometric response demonstrated a perfect multiple amplification effect. The constructed sensor showed a high sensitivity for detection of the target DNA in a linear range from 0.1 fM to 10 pM, a detection limit down to 0.02 fM (3?) and good selectivity for base discrimination. This method did not need any modification or labelling process. The proposed strategy provides a powerful tool for cascade signal amplification and has a wide potential application in bioanalysis. PMID:23951569

Zhu, Zhu; Lei, Jianping; Liu, Lin; Ju, Huangxian

2013-10-21

113

Manipulating the Surface Reactions in Lithium Sulfur Batteries Using Hybrid Anode Structures  

SciTech Connect

Lithium-sulfur (Li-S) batteries have recently attracted extensive attention due to the high theoretical energy density and potential low cost. Even so, significant challenges prevent widespread adoption, including continuous dissolution and consumption of active sulfur during cycling. Here we present a fundamentally new design using electrically connected graphite and lithium metal as a hybrid anode to control undesirable surface reactions on the anode. The lithiated graphite placed in front of the lithium metal functions as an artificial self-regulated solid electrolyte interface (SEI) layer to actively control the electrochemical reaction while minimizing the deleterious side reactions on the surface and bulk lithium metal. Continuous corrosion and contamination of lithium anode by dissolved polysulfides is largely mitigated. Excellent electrochemical performance has been observed. Li-S cell incorporating the hybrid design retain a capacity of more than 800 mAh g-1 for 400 cycles, corresponding to only 11% fade and a Coulombic efficiency above 99%. This simple hybrid concept may also provide new lessons for protecting metal anodes in other energy storage devices.

Huang, Cheng; Xiao, Jie; Shao, Yuyan; Zheng, Jianming; Bennett, Wendy D.; Lu, Dongping; Saraf, Laxmikant V.; Engelhard, Mark H.; Ji, Liwen; Zhang, Jiguang; Li, Xiaolin; Graff, Gordon L.; Liu, Jun

2014-01-09

114

Gold nanoparticles–graphene hybrids as active catalysts for Suzuki reaction  

Microsoft Academic Search

Graphene was successfully modified with gold nanoparticles in a facile route by reducing chloroauric acid in the presence of sodium dodecyl sulfate, which is used as both a surfactant and reducing agent. The gold nanoparticles–graphene hybrids were characterized by high-resolution transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction and energy X-ray spectroscopy. We demonstrate for

Yang Li; Xiaobin Fan; Junjie Qi; Junyi Ji; Shulan Wang; Guoliang Zhang; Fengbao Zhang

2010-01-01

115

Producing a trimethylpentanoic acid using hybrid polyketide synthases  

DOEpatents

The present invention provides for a polyketide synthase (PKS) capable of synthesizing trimethylpentanoic acid. The present invention also provides for a host cell comprising the PKS and when cultured produces the trimethylpentanoic acid. The present invention also provides for a method of producing the trimethylpentanoic acid, comprising: providing a host cell of the present invention, and culturing said host cell in a suitable culture medium such that the trimethylpentanoic acid is produced, optionally isolating the trimethylpentanoic acid, and optionally, reducing the isolated trimethylpentanoic acid into a trimethylpentanol or an iso-octane.

Katz, Leonard; Fortman, Jeffrey L; Keasling, Jay D

2014-10-07

116

Nitrogen-doped carbon dots decorated on graphene: a novel all-carbon hybrid electrocatalyst for enhanced oxygen reduction reaction.  

PubMed

An all-carbon hybrid, composed of coal-based nitrogen-doped carbon dots decorated on graphene, was prepared via hydrothermal treatment. The hybrid possesses comparable electrocatalytic activity, better durability and methanol tolerance than those of the commercial Pt-based electrocatalysts for oxygen reduction reaction, indicative of its great potential in fuel cells. PMID:25626119

Hu, Chao; Yu, Chang; Li, Mingyu; Wang, Xiuna; Dong, Qiang; Wang, Gang; Qiu, Jieshan

2015-02-10

117

High School Forum: "Invitations to Enquiry": The Calcite/Acid Reaction.  

ERIC Educational Resources Information Center

Describes a high school chemistry experiment which involves the reaction between calcite and hydrochloric and sulfuric acids. This reaction can be carried out as a projected demonstration and on an individual basis. (HM)

Herron, J. Dudley, Ed.; Driscoll, D. R.

1979-01-01

118

Insights into the homocoupling reaction of 4-methylamino benzoic acid mediated by Trametes versicolor laccase.  

PubMed

Spectroscopic measurements combined with Density Functional Theory calculations were applied to the characterization of the homocoupling reaction of 4-methylamino benzoic acid mediated by laccase. PMID:21912806

Martorana, Andrea; Bernini, Caterina; Valensin, Daniela; Sinicropi, Adalgisa; Pogni, Rebecca; Basosi, Riccardo; Baratto, Maria Camilla

2011-11-01

119

Multiplex polymerase chain reaction/membrane hybridization assay for detection of genetically modified organisms.  

PubMed

To improve detection efficiency and result accuracy, four screening primer pairs, four identifying primer pairs, one common primer pair and corresponding probes were designed for the development of multiplex polymerase chain reaction/membrane hybridization assay (MPCR-MHA) for detection of the foreign genes insert in genetically modified organisms (GMOs). After detecting condition and parameter were optimized and determined, MPCR reactions were developed for amplifying several target genes simultaneously in one tube. Primers were labeled with biotin at the 5'-end; biotinylated MPCR products were detected by hybridization to the oligonucleotide probes immobilized on a membrane with subsequent colorimetric detection to confirm hybridization. The testing of screening primers can judge whether the sample contains GMOs, and that of identifying primers can further judge what kinds of trait genes are contained in the sample. We detected nine soybean samples, six maize samples, seven potato samples and two rice samples by the MPCR-MHA method; at the same time we also detected them with single PCR-MHA method. The results between two methods have good consistency. PMID:14580794

Su, Wenijn; Song, Siyang; Long, Minnan; Liu, Guangming

2003-11-01

120

Design of an innovative lead-acid battery for electric and hybrid vehicles  

NASA Astrophysics Data System (ADS)

An innovative lead acid battery was designed specifically for use in a hybrid car. The battery has exceeded all of the minimum performance goals, and in many cases the optimistic target goals. The eV-1300, which features electrolyte circulation, has excellent energy density, power characteristics, efficiency, and cycle life. It is a good candidate battery for other hybrid vehicles and electric vehicles which require a relatively small cell size.

Baxa, M. S.; Weinlein, C. E.

121

A simple colorimetric DNA detection by target-induced hybridization chain reaction for isothermal signal amplification.  

PubMed

A novel DNA detection method is presented based on a gold nanoparticle (AuNP) colorimetric assay and hybridization chain reaction (HCR). In this method, target DNA hybridized with probe DNA modified on AuNP, and triggered HCR. The resulting HCR products with a large number of negative charges significantly enhanced the stability of AuNPs, inhibiting aggregation of AuNPs at an elevated salt concentration. The approach was highly sensitive and selective. Using this enzyme-free and isothermal signal amplification method, we were able to detect target DNA at concentrations as low as 0.5 nM with the naked eye. Our method also has great potential for detecting other analytes, such as metal ions, proteins, and small molecules, if the target analytes could make HCR products attach to AuNPs. PMID:24780220

Ma, Cuiping; Wang, Wenshuo; Mulchandani, Ashok; Shi, Chao

2014-07-15

122

Enzymatic Amplification of DNA/RNA Hybrid Molecular Beacon Signaling in Nucleic Acid Detection  

PubMed Central

A rapid assay operable under isothermal or non-isothermal conditions is described wherein the sensitivity of a typical molecular beacon (MB) system is improved by utilizing thermostable RNase H to enzymatically cleave an MB comprised of a DNA stem and RNA loop (R/D-MB). Upon hybridization of the R/D-MB to target DNA, there was a modest increase in fluorescence intensity (~5.7x above background) due to an opening of the probe and concomitant reduction in the Förster resonance energy transfer efficiency. Addition of thermostable RNase H resulted in the cleavage of the RNA loop which eliminated energy transfer. The cleavage step also released bound target DNA, enabling it to bind to another R/D-MB probe and rendering the approach a cyclic amplification scheme. Full processing of R/D-MBs maximized the fluorescence signal to the fullest extent possible (12.9x above background), resulting in a ~2–2.8 fold increase in the signal-to-noise ratio observed isothermally at 50 °C following the addition of RNase H. The probe was also used to monitor real-time PCR reactions by measuring enhancement of donor fluorescence upon R/D-MB binding to amplified pUC19 template dilutions. Hence, the R/D-MB-RNase H scheme can be applied to a broad range of nucleic acid amplification methods. PMID:23000602

Jacroux, Thomas; Rieck, Daniel C.; Cui, Rong; Ouyang, Yexin; Dong, Wen-Ji

2012-01-01

123

Weak Acid Ionization Constants and the Determination of Weak Acid-Weak Base Reaction Equilibrium Constants in the General Chemistry Laboratory  

ERIC Educational Resources Information Center

A laboratory to determine the equilibrium constants of weak acid negative weak base reactions is described. The equilibrium constants of component reactions when multiplied together equal the numerical value of the equilibrium constant of the summative reaction. The component reactions are weak acid ionization reactions, weak base hydrolysis…

Nyasulu, Frazier; McMills, Lauren; Barlag, Rebecca

2013-01-01

124

Current status of the “Hybrid Kurotama model” for total reaction cross sections  

NASA Astrophysics Data System (ADS)

To be able to calculate the nucleon + nucleus and nucleus + nucleus total reaction cross sections with precision is of great importance for studies of fundamental nuclear properties, e.g., the nuclear structure. This is also very important for particle and heavy ion transport calculations since in all particle and heavy ion transport codes, the probability function according to which a projectile particle will collide within a certain distance in a matter depends on the total reaction cross sections. This will also scale the calculated partial fragmentation cross sections. It is therefore crucial that accurate total reaction cross section models are used in the transport calculations. In this paper, a new general purpose total reaction cross section model/subroutine called “Hybrid Kurotama” is presented. The model has been tested against available p + He, p + nucleus, and nucleus + nucleus total reaction cross sections and an overall better agreement has been found than for earlier published models. This model is therefore very suitable to be used in any deterministic or Monte Carlo particle and heavy ion transport code.

Sihver, L.; Kohama, A.; Iida, K.; Oyamatsu, K.; Hashimoto, S.; Iwase, H.; Niita, K.

2014-09-01

125

On the choice of Lewis acids for the Prins reaction; two total syntheses of (±)Civet  

Microsoft Academic Search

While developing new variations of the Prins cyclisation reaction, the effect of the choice of Lewis acid on the outcome of the reaction and the product(s) has been investigated, yielding hitherto unseen dihydropyran products in the Prins cyclisation reaction of homoallylic alcohols, and two new modifications of the reaction: the triflate-trapped Prins adduct and the Mukaiyama–Aldol–silyl-Prins reaction. Two of these

Freda K. Chio; Julie Warne; Damien Gough; Mark Penny; Simon J. Coles; Mike B. Hursthouse; Peter Jones; Lorraine Hassall; Thomas M. McGuire; Adrian P. Dobbs

2011-01-01

126

Forcing of Turing Patterns in the Chlorine Dioxide-Iodine-Malonic Acid Reaction with Strong Visible Light  

E-print Network

Forcing of Turing Patterns in the Chlorine Dioxide-Iodine-Malonic Acid Reaction with Strong Visible investigate the sensitivity of Turing patterns in the chlorine dioxide-iodine-malonic acid reaction (CIMA) reaction and its variant, the chlorine dioxide-iodine-malonic acid (CDIMA) reaction, has been

Epstein, Irving R.

127

Students' Understanding of Acid, Base and Salt Reactions in Qualitative Analysis.  

ERIC Educational Resources Information Center

Uses a two-tier, multiple-choice diagnostic instrument to determine (n=915) grade 10 students' understanding of the acid, base, and salt reactions involved in basic qualitative analysis. Reports that many students did not understand the formation of precipitates and the complex salts, acid/salt-base reactions, and thermal decomposition involved in…

Tan, Kim-Chwee Daniel; Goh, Ngoh-Khang; Chia, Lian-Sai; Treagust, David F.

2003-01-01

128

Kinetic Studies on the Reaction between Dicyanocobinamide and Hypochlorous Acid  

PubMed Central

Hypochlorous acid (HOCl) is a potent oxidant generated by myeloperoxidase (MPO), which is an abundant enzyme used for defense against microbes. We examined the potential role of HOCl in corrin ring destruction and subsequent formation of cyanogen chloride (CNCl) from dicyanocobinamide ((CN)2-Cbi). Stopped-flow analysis revealed that the reaction consists of at least three observable steps, including at least two sequential transient intermediates prior to corrin ring destruction. The first two steps were attributed to sequential replacement of the two cyanide ligands with hypochlorite, while the third step was the destruction of the corrin ring. The formation of (OCl)(CN)-Cbi and its conversion to (OCl)2-Cbi was fitted to a first order rate equation with second order rate constants of 0.002 and 0.0002 µM?1s?1, respectively. The significantly lower rate of the second step compared to the first suggests that the replacement of the first cyanide molecule by hypochlorite causes an alteration in the ligand trans effects changing the affinity and/or accessibility of Co toward hypochlorite. Plots of the apparent rate constants as a function of HOCl concentration for all the three steps were linear with Y-intercepts close to zero, indicating that HOCl binds in an irreversible one-step mechanism. Collectively, these results illustrate functional differences in the corrin ring environments toward binding of diatomic ligands. PMID:25375773

Maitra, Dhiman; Ali, Iyad; Abdulridha, Rasha M.; Shaeib, Faten; Khan, Sana N.; Saed, Ghassan M.; Pennathur, Subramaniam; Abu-Soud, Husam M.

2014-01-01

129

The reaction of CIONO{sub 2} with submicrometer sulfuric acid aerosol  

SciTech Connect

The measured reaction probability, {gamma}, for the reaction of chlorine nitrate CIONO{sub 2} with 60 percent (by weight) sulfuric acid aerosol increases monotonically with particle size at 250 kelvin. The reactor-diffusive length (l, the effective liquid depth over which reaction occurs) derived from these experiments is 0.037{+-}0.007 micrometer (95 percent confidence level for precision). The reaction probability for the reaction of CIONO{sub 2} with 60 percent sulfuric acid aerosol doped with {approximately}7 x 10{sup -4} M hydrochloric acid at 250 kelvin is larger by about a factor of 4 than in the absence of hydrochloric acid and varies less with particle size (l = 0.009{+-}0.005 micrometer). These results provide a test of the theory for gas-particle reactions and further insight into the reactivity of atmospheric aerosol. 19 refs., 3 figs.

Hanson, D.R.; Lovejoy, E.R. [Univ. of Colorado, Boulder, CO (United States)

1995-03-03

130

Proton exchange in acid-base complexes induced by reaction coordinates with heavy atom motions  

NASA Astrophysics Data System (ADS)

We extend previous work on nitric acid-ammonia and nitric acid-alkylamine complexes to illustrate that proton exchange reaction coordinates involve the rocking motion of the base moiety in many double hydrogen-bonded gas phase strong acid-strong base complexes. The complexes studied involve the biologically and atmospherically relevant glycine, formic, acetic, propionic, and sulfuric acids with ammonia/alkylamine bases. In these complexes, the magnitude of the imaginary frequencies associated with the proton exchange transition states are <400 cm-1. This contrasts with widely studied proton exchange reactions between symmetric carboxylic acid dimers or asymmetric DNA base pair and their analogs where the reaction coordinate is localized in proton motions and the magnitude of the imaginary frequencies for the transition states are >1100 cm-1. Calculations on complexes of these acids with water are performed for comparison. Variations of normal vibration modes along the reaction coordinate in the complexes are described.

Alavi, Saman; Taghikhani, Mahdi

2012-06-01

131

A study of rates of reaction of some substituted diphenyldiazomethanes and benzoic acid  

E-print Network

A STUDY OF RATES OF REACTION OF SOME SUBSTITUTED DIPHENYLDIAZ(METHANES AM) BENZOIC ACID A Dissertation By Ralph Fredrick Gilby, Jr. Approved as to style and content by; May 195^ A STOUT 'OF1 WffBS CF KEAC9XOI O f SOB ffliHfiiyi'f ilfl.... . . . . . . . . 11 II. Reaction Rate Constants (k) and Reaction Rate of if,-Dimethoxydiphenyldiazomethane and Benzoic Acid................................. ... . %8 IV...

Gilby, Ralph Fredrick

1954-01-01

132

Reaction of lithium enediolates with perfluoroketene dithioacetals. Synthesis of ?-trifluoromethyl ?-dicarboxylic acid derivatives  

Microsoft Academic Search

The reaction of perfluoroketene dithioacetals with dianions of carboxylic acids proceeds through the substitution of the vinylic fluoride. The preparative value of this reaction depends strongly on the reaction and work-up conditions, the optimisation of which led to use LDA as a base and multiple extraction techniques. The overall process may be considered as a formal synthesis of ?-trifluoromethyl ?-dicarboxylic

Enrique Sotoca; Jean-Philippe Bouillon; Salvador Gil; Margarita Parra; Charles Portella

2004-01-01

133

Next-Generation in Situ Hybridization Chain Reaction: Higher Gain, Lower Cost, Greater Durability  

PubMed Central

Hybridization chain reaction (HCR) provides multiplexed, isothermal, enzyme-free, molecular signal amplification in diverse settings. Within intact vertebrate embryos, where signal-to-background is at a premium, HCR in situ amplification enables simultaneous mapping of multiple target mRNAs, addressing a longstanding challenge in the biological sciences. With this approach, RNA probes complementary to mRNA targets trigger chain reactions in which metastable fluorophore-labeled RNA hairpins self-assemble into tethered fluorescent amplification polymers. The properties of HCR lead to straightforward multiplexing, deep sample penetration, high signal-to-background, and sharp subcellular signal localization within fixed whole-mount zebrafish embryos, a standard model system for the study of vertebrate development. However, RNA reagents are expensive and vulnerable to enzymatic degradation. Moreover, the stringent hybridization conditions used to destabilize nonspecific hairpin binding also reduce the energetic driving force for HCR polymerization, creating a trade-off between minimization of background and maximization of signal. Here, we eliminate this trade-off by demonstrating that low background levels can be achieved using permissive in situ amplification conditions (0% formamide, room temperature) and engineer next-generation DNA HCR amplifiers that maximize the free energy benefit per polymerization step while preserving the kinetic trapping property that underlies conditional polymerization, dramatically increasing signal gain, reducing reagent cost, and improving reagent durability. PMID:24712299

2014-01-01

134

Organo-niobate Ionic Liquids: Synthesis, Characterization and Application as Acid Catalyst in Pechmann Reactions  

PubMed Central

The combinations of 1-butyl-3-methylimidazolium chloride with NbCl5 yielded ionic mixtures with different melting point temperatures and acidity depending on the niobium molar fraction. The mixtures were characterized by thermal (DSC) and spectroscopic (FT-IR and 1H NMR) analysis. The Pechmann reactions of different phenols with ethylacetoacetate, producing coumarins, was used as model to evaluate the catalytic behavior of these mixtures as acid Lewis catalyst. These reactions were carried out using acidic mixtures of 60 mol%.

Soares, Valerio C. D.; Alves, Melquizedeque B.; Souza, Ernesto R.; Pinto, Ivana O.; Rubim, Joel C.; Andrade, Carlos Kleber Z.; Suarez, Paulo A. Z.

2007-01-01

135

Modeling the reaction kinetics of a hydrogen generator onboard a fuel cell -- Electric hybrid motorcycle  

NASA Astrophysics Data System (ADS)

Owing to the perceived decline of the fossil fuel reserves in the world and environmental issues like pollution, conventional fuels may be replaced by cleaner alternative fuels. The potential of hydrogen as a fuel in vehicular applications is being explored. Hydrogen as an energy carrier potentially finds applications in internal combustion engines and fuel cells because it is considered a clean fuel and has high specific energy. However, at 6 to 8 per kilogram, not only is hydrogen produced from conventional methods like steam reforming expensive, but also there are storage and handling issues, safety concerns and lack of hydrogen refilling stations across the country. The purpose of this research is to suggest a cheap and viable system that generates hydrogen on demand through a chemical reaction between an aluminum-water slurry and an aqueous sodium hydroxide solution to power a 2 kW fuel cell on a fuel cell hybrid motorcycle. This reaction is essentially an aluminum-water reaction where sodium hydroxide acts as a reaction promoter or catalyst. The Horizon 2000 fuel cell used for this purpose has a maximum hydrogen intake rate of 28 lpm. The study focuses on studying the exothermic reaction between the reactants and proposes a rate law that best describes the rate of generation of hydrogen in connection to the surface area of aluminum available for the certain reaction and the concentration of the sodium hydroxide solution. Further, the proposed rate law is used in the simulation model of the chemical reactor onboard the hybrid motorcycle to determine the hydrogen flow rate to the fuel cell with time. Based on the simulated rate of production of hydrogen from the chemical system, its feasibility of use on different drive cycles is analyzed. The rate of production of hydrogen with a higher concentration of sodium hydroxide and smaller aluminum powder size was found to enable the installation of the chemical reactor on urban cycles with frequent stops and starts. However, by extrapolating the necessary rate of concentration of sodium hydroxide required to produce hydrogen rates that would enable use of the system on highway drive cycles, it was deemed unsafe due to the caustic nature of the solution used.

Ganesh, Karthik

136

Field and Laboratory Studies of Reactions between Atmospheric Water Soluble Organic Acids and Inorganic Particles  

SciTech Connect

Atmospheric inorganic particles undergo complex heterogeneous reactions that change their physicochemical properties. Depletion of chloride in sea salt particles was reported in previous field studies and was attributed to the acid displacement of chlorides with inorganic acids, such as nitric and sulfuric acids [1-2]. Recently, we showed that NaCl can react with water soluble organic acids (WSOA) and release gaseous hydrochloric acid (HCl) resulting in formation of organic salts [3]. A similar mechanism is also applicable to mixed WSOA/nitrate particles where multi-phase reactions are driven by the volatility of nitric acid. Furthermore, secondary organic material, which is a complex mixture of carboxylic acids, exhibits the same reactivity towards chlorides and nitrates. Here, we present a systematic study of reactions between atmospheric relevant WSOA, SOM, and inorganic salts including NaCl, NaNO3, and Ca(NO3)2 using complementary micro-spectroscopy analysis.

Wang, Bingbing; Kelly, Stephen T.; Sellon, Rachel E.; Shilling, John E.; Tivanski, Alexei V.; Moffet, Ryan C.; Gilles, Mary K.; Laskin, Alexander

2013-06-25

137

Field and laboratory studies of reactions between atmospheric water soluble organic acids and inorganic particles  

NASA Astrophysics Data System (ADS)

Atmospheric inorganic particles undergo complex heterogeneous reactions that change their physicochemical properties. Depletion of chloride in sea salt particles was reported in previous field studies and was attributed to the acid displacement of chlorides with inorganic acids, such as nitric and sulfuric acids [1-2]. Recently, we showed that NaCl can react with water soluble organic acids (WSOA) and release gaseous hydrochloric acid (HCl) resulting in formation of organic salts [3]. A similar mechanism is also applicable to mixed WSOA/nitrate particles where multi-phase reactions are driven by the volatility of nitric acid. Furthermore, secondary organic material, which is a complex mixture of carboxylic acids, exhibits the same reactivity towards chlorides and nitrates. Here, we present a systematic study of reactions between atmospheric relevant WSOA, SOM, and inorganic salts including NaCl, NaNO3, and Ca(NO3)2 using complementary micro-spectroscopy analysis.

Wang, Bingbing; Kelly, Stephen T.; Sellon, Rachel; Shilling, John; Tivanski, Alexei V.; Moffet, Ryan C.; Gilles, Mary K.; Laskin, Alexander

2013-05-01

138

Aqueous Phase Photo-Oxidation of Succinic Acid: Changes in Hygroscopic Properties and Reaction Products  

NASA Astrophysics Data System (ADS)

Atmospheric aerosol particles have been identified as important factors in understanding climate change. The extent to which aerosols affect climate is determined, in part, by hygroscopic properties which can change as a result of atmospheric processing. Dicarboxylic acids, components of atmospheric aerosol, have a wide range of hygroscopic properties and can undergo oxidation and photolysis reactions in the atmosphere. In this study, the hygroscopic properties of succinic acid aerosol, a non-hygroscopic four carbon dicarboxylic acid, were measured with a humidified tandem differential mobility analyzer (HTDMA) and compared to reaction products resulting from the aqueous phase photo-oxidation reaction of hydrogen peroxide and succinic acid. Reaction products were determined and quantified using gas chromatography-flame ionization detection (GC-FID) and GC-mass spectrometry (GC-MS) as a function of hydrogen peroxide:succinic acid concentration ratio and photolysis time. Although reaction products include larger non-hygroscopic dicarboxylic acids (e.g. adipic acid) and smaller hygroscopic dicarboxylic acids (e.g. malonic and oxalic acids), comparison of hygroscopic growth curves to Zdanovskii-Stokes-Robinson (ZSR) predictions suggests that the hygroscopic properties of many of the product mixtures are largely independent of the hygroscopicity of the individual components. This study provides a framework for future investigations to fully understand and predict the role of chemical reactions in altering atmospheric conditions that affect climate.

Hudson, P. K.; Ninokawa, A.; Hofstra, J.; de Lijser, P.

2013-12-01

139

New Estimation Filtering for Battery Management Systems of Lead-Acid Cells in Hybrid Electric Vehicles  

Microsoft Academic Search

Summary This paper proposes a new estimation filtering for battery management systems of lead-acid cells in hybrid electric vehicles. The well known finite impulse response (FIR) filter is adopted for the estimation filtering. The proposed method provides the filtered estimates for the output voltage as well as voltages across the bulk and surface capacitors. These filtered estimates have good inherent

Pyung-Soo Kim

2007-01-01

140

Process for chemical reaction of amino acids and amides yielding selective conversion products  

DOEpatents

The invention relates to processes for converting amino acids and amides to desirable conversion products including pyrrolidines, pyrrolidinones, and other N-substituted products. L-glutamic acid and L-pyroglutamic acid provide general reaction pathways to numerous and valuable selective conversion products with varied potential industrial uses.

Holladay, Jonathan E. (Kennewick, WA)

2006-05-23

141

Predicting Reactions from Amino Acid Sequences in S. cerevisiae: an Evolutionary Computation Approach  

E-print Network

Predicting Reactions from Amino Acid Sequences in S. cerevisiae: an Evolutionary Computation by an amino acid and a set of chemical substrates is not a trivial task. Both chemicals and proteins are 3, information is conserved at the level of amino acid sequences. One protein is the same as another protein

Fernandez, Thomas

142

The influence of Fe2+ doping on the microstructure and photochromic behavior of polyoxometalates acid/polyacrylamide hybrid films  

NASA Astrophysics Data System (ADS)

New hybrid films were synthesized by Fe2+ doping into polyoxometalates acid (POMs)/polyacrylamide (PAM) system, and the effect of Fe2+ doping on microstructure and photochromic properties was studied via transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectra (UV-vis) and X-ray photoelectron spectroscopy (XPS). The shape of molybdenumphosphoric acid (PMoA) particles changed from well dispersed sphere to irregular conglomeration. The vibrational spectra of FT-IR verified that the hydrogen bonding between PMoA and PAM was weakened after Fe2+ doping. The hybrid films exhibited a good photochromic property, which changed from colorless to blue under UV irradiation. The color change intensity of PMoA/PAM film was 2.56 times stronger than that of Fe2+/PMoA/PAM under the same condition. XPS results indicated that the amount of PMoA in photo-reductive reaction was decreased after Fe2+ doping, which resulted in the photochromic efficiencies weakened.

Chen, Jie; Liu, Su-Ling; Feng, Wei; Bao, Xin-Jian; Yang, Feng-Lin

2013-03-01

143

Reaction of 2-amino-5-R-phenyl-1,3,4-thiadiazoles with unsaturated acids and acid chlorides  

Microsoft Academic Search

Reaction of 2-amino-5-R-phenyl-1,3,4-thiadizoles with unsaturated acids and acid chlorides in the presence of trimethylamine takes place exclusively at the amino group to form the 2-carboxyalkyl- and 2-acylamino- derivatives, respectively.

I. V. Zubets; S. N. Vergizov; I. V. Viktorovskii; K. A. V'yunov

1990-01-01

144

Effect of Bromine Derivatives of Malonic Acid on the Oscillating Reaction of Malonic Acid, Cerium Ions and Bromate  

Microsoft Academic Search

WHEN malonic acid, ceric sulphate and potassium bromate are dissolved in dilute sulphuric acid there occurs an oscillating chemical reaction which manifests itself by an oscillation of the light absorption which is caused by ceric ions (317 mµ) and an oscillation of the rate of evolution of carbon dioxide. An oscillation of the potential of a platinum electrode dipped into

H. Degn

1967-01-01

145

The reaction of hyaluronic acid and its monomers, glucuronic acid and N-acetylglucosamine, with reactive oxygen species.  

PubMed

Synovial fluid is a approximately 0.15% (w/v) aqueous solution of hyaluronic acid (HA), a polysaccharide consisting of alternating units of GlcA and GlcNAc. In synovial fluid of patients suffering from rheumatoid arthritis, HA is thought to be degraded either by radicals generated by Fenton chemistry (Fe2+/H2O2) or by NaOCl generated by myeloperoxidase. We investigated the course of model reactions of these two reactants in physiological buffer with HA, and with the corresponding monomers GlcA and GlcNAc. meso-Tartaric acid, arabinuronic acid, arabinaric acid and glucaric acid were identified by GC-MS as oxidation products of glucuronic acid. When GlcNAc was oxidised, erythronic acid, arabinonic acid, 2-acetamido-2-deoxy-gluconic acid, glyceric acid, erythrose and arabinose were formed. NaOCl oxidation of HA yielded meso-tartaric acid; in addition, arabinaric acid and glucaric acid were obtained by oxidation with Fe2+/H2O2. These results indicate that oxidative degradation of HA proceeds primarily at glucuronic acid residues. meso-Tartaric acid may be a useful biomarker of hyaluronate oxidation since it is produced by both NaOCl and Fenton chemistry. PMID:10614067

Jahn, M; Baynes, J W; Spiteller, G

1999-10-15

146

Uptake of Hypobromous Acid (HOBr) by Aqueous Sulfuric Acid Solutions: Low-Temperature Solubility and Reaction  

NASA Technical Reports Server (NTRS)

Hypobromous acid (HOBr) is a key species linking inorganic bromine to the chlorine and odd hydrogen chemical families. We have measured the solubility of HOBr in 45 - 70 wt% sulfuric acid solutions representative of upper tropospheric and lower stratospheric aerosol composition. Over the temperature range 201 - 252 K, HOBr is quite soluble in sulfuric acid, with an effective Henry's law coefficient, H* = 10(exp 4) - 10(exp 7) mol/L/atm. H* is inversely dependent on temperature, with Delta H = -46.2 kJ/mol and Delta S = -106.2 J/mol/K for 55 - 70 wt% H2SO4 solutions. Our study includes temperatures which overlap both previous measurements of HOBr solubility. For uptake into aqueous 45 wt% H2SO4, the solubility can be described by log H* = 3665/T - 10.63. For 55 - 70 wt% H2SO4, log H* = 2412/T - 5.55. At temperatures colder than approx. 213 K, the solubility of HOBr in 45 wt% H2SO4 is noticeably larger than in 70 wt% H2SO4. The solubility of HOBr is comparable to that of HBr, indicating that upper tropospheric and lower stratospheric aerosols should contain equilibrium concentrations of HOBr which equal or exceed those of HBr. Our measurements indicate chemical reaction of HOBr upon uptake into aqueous sulfuric acid in the presence of other brominated gases followed by evolution of gaseous products including Br2O and Br2, particularly at 70 wt% H2SO4.

Iraci, Laura T.; Michelsen, Rebecca R.; Ashbourn, Samatha F. M.; Rammer, Thomas A.; Golden, David M.

2005-01-01

147

Levulinic acid production based on extrusion and pressurized batch reaction  

Microsoft Academic Search

Levulinic acid is a highly versatile chemical with numerous industrial uses, having the potential to become a commodity chemical. It can be used as a raw material for resins, plasticizers, textiles, animal feed, coatings and antifreeze. Starches and sugars are typically converted to levulinic acid using a batch reactor. Blends of corn starch (70%), sulfuric acid (5%), and water (25%)

J. Y Cha; M. A Hanna

2002-01-01

148

Carbocations as Lewis acid catalysts in Diels-Alder and Michael addition reactions.  

PubMed

In general, Lewis acid catalysts are metal-based compounds that owe their reactivity to a low-lying empty orbital. However, one potential Lewis acid that has received negligible attention as a catalyst is the carbocation. We have demonstrated the potential of the carbocation as a highly powerful Lewis acid catalyst for organic reactions. The stable and easily available triphenylmethyl (trityl) cation was found to be a highly efficient catalyst for the Diels-Alder reaction for a range of substrates. Catalyst loadings as low as 500?ppm, excellent yields, and good endo/exo selectivities were achieved. Furthermore, by changing the electronic properties of the substituents on the tritylium ion, the Lewis acidity of the catalyst could be tuned to control the outcome of the reaction. The ability of this carbocation as a Lewis acid catalyst was also further extended to the Michael reaction. PMID:24375806

Bah, Juho; Franzén, Johan

2014-01-20

149

Degradation of Acid Orange 7 Dye in Two Hybrid Plasma Discharge Reactors  

NASA Astrophysics Data System (ADS)

To get an optimized pulsed electrical plasma discharge reactor and to increase the energy utilization efficiency in the removal of pollutants, two hybrid plasma discharge reactors were designed and optimized. The reactors were compared via the discharge characteristics, energy transfer efficiency, the yields of the active species and the energy utilization in dye wastewater degradation. The results showed that under the same AC input power, the characteristics of the discharge waveform of the point-to-plate reactor were better. Under the same AC input power, the two reactors both had almost the same peak voltage of 22 kV. The peak current of the point-to-plate reactor was 146 A, while that of the wire-to-cylinder reactor was only 48.8 A. The peak powers of the point-to-plate reactor and the wire-to-cylinder reactor were 1.38 MW and 1.01 MW, respectively. The energy per pulse of the point-to-plate reactor was 0.2221 J, which was about 29.4% higher than that of the wire-to-cylinder reactor (0.1716 J). To remove 50% Acid Orange 7 (AO7), the energy utilizations of the point-to-plate reactor and the wire-to-cylinder reactor were 1.02 × 10?9 mol/L and 0.61 × 10?9 mol/L, respectively. In the point-to-plate reactor, the concentration of hydrogen peroxide in pure water was 3.6 mmol/L after 40 min of discharge, which was higher than that of the wire-to-cylinder reactor (2.5 mmol/L). The concentration of liquid phase ozone in the point-to-plate reactor (5.7 × 10?2 mmol/L) was about 26.7% higher than that in the wire-to-cylinder reactor (4.5 × 10?2 mmol/L). The analysis results of the variance showed that the type of reactor and reaction time had significant impacts on the yields of the hydrogen peroxide and ozone. The main degradation intermediates of AO7 identified by gas chromatography and mass spectrometry (GCMS) were acetic acid, maleic anhydride, p-benzoquinone, phenol, benzoic acid, phthalic anhydride, coumarin and 2-naphthol. Proposed degradation pathways were elucidated in light of the analyzed degradation products.

Shen, Yongjun; Lei, Lecheng; Zhang, Xingwang; Ding, Jiandong

2014-11-01

150

[Effects of low molecular weight organic acids on redox reactions of mercury].  

PubMed

To study the effects of the main component of vegetation root exudates-low molecular weight organic acids on the redox reactions of mercury, laboratory experiments were conducted to investigate the roles of tartaric, citric, and succinic acid in the redox reactions of mercury, and to analyze their interaction mechanism. The results indicated that tartaric acid significantly stimulated the mercury reduction reaction, while citric acid had inhibitory effect. Succinic acid improved the reduction rate at low concentration, and inhibited the reaction at high concentration. The mercury reduction rate by tartaric acid treatment was second-order with respect to Hg2+ concentration, ranging from 0.0014 L x (ng x min)(-1) to 0.005 6 L x (ng x min)(-1). All three organic acids showed a capacity for oxidating Hg(0) in the early stage, but the oxidized Hg(0) was subsequently reduced. The oxidation capacity of the three organic acids was in the order of citric acid > tartaric acid > succinic acid. PMID:25158495

Zhao, Shi-Bo; Sun, Rong-Guo; Wang, Ding-Yong; Wang, Xiao-Wen; Zhang, Cheng

2014-06-01

151

Uncatalyzed reaction of silyl ketene acetals with oxalyl chloride: a straightforward preparation of symmetrical pulvinic acids.  

PubMed

[reaction: see text] Several natural pulvinic acids were synthesized. Silyl ketene acetals derived from methyl arylacetates (4 equiv) reacted with oxalyl chloride at -78 degrees C, without the need of adding a catalyst. After treatment of the crude diketones with DBU and acidification with hydrochloric acid, symmetrical pulvinic acids methyl esters were obtained. Saponification of the methyl esters afforded the corresponding pulvinic acids in 60-70% overall yields from oxalyl chloride. PMID:15704989

Heurtaux, Benoît; Lion, Claude; Le Gall, Thierry; Mioskowski, Charles

2005-02-18

152

Clay and acid catalysed isomerisation and cyclisation reactions of highly branched isoprenoid (HBI) alkenes: implications for sedimentary reactions and distributions  

NASA Astrophysics Data System (ADS)

Several highly branched isoprenoid alkenes isolated from the diatom Haslea ostrearia have been subjected to laboratory simulations of early diagenetic reactions under mild acid conditions including addition of K-10 Montmorillonite clay. The products of these reactions have been found to be highly dependent on the degree of unsaturation of the alkenes. For dienes, double bond migration and geometric isomerisation are observed as the only reactions. In contrast, trienes undergo both isomerisation and rapid cyclisation reactions to yield substituted cyclohexenes. Molecular mechanics calculations have been performed to complement the laboratory experiments and to assist in proposing reaction mechanisms. The significance of these findings for the interpretation of the numerous reports of highly branched isoprenoids in Recent and ancient sediments is discussed.

Belt, Simon T.; Allard, W. Guy; Rintatalo, Janne; Johns, Lesley A.; van Duin, Adri C. T.; Rowland, Steven J.

2000-10-01

153

Microfluidic platform for isolating nucleic acid targets using sequence specific hybridization  

PubMed Central

The separation of target nucleic acid sequences from biological samples has emerged as a significant process in today's diagnostics and detection strategies. In addition to the possible clinical applications, the fundamental understanding of target and sequence specific hybridization on surface modified magnetic beads is of high value. In this paper, we describe a novel microfluidic platform that utilizes a mobile magnetic field in static microfluidic channels, where single stranded DNA (ssDNA) molecules are isolated via nucleic acid hybridization. We first established efficient isolation of biotinylated capture probe (BP) using streptavidin-coated magnetic beads. Subsequently, we investigated the hybridization of target ssDNA with BP bound to beads and explained these hybridization kinetics using a dual-species kinetic model. The number of hybridized target ssDNA molecules was determined to be about 6.5 times less than that of BP on the bead surface, due to steric hindrance effects. The hybridization of target ssDNA with non-complementary BP bound to bead was also examined, and non-specific hybridization was found to be insignificant. Finally, we demonstrated highly efficient capture and isolation of target ssDNA in the presence of non-target ssDNA, where as low as 1% target ssDNA can be detected from mixture. The microfluidic method described in this paper is significantly relevant and is broadly applicable, especially towards point-of-care biological diagnostic platforms that require binding and separation of known target biomolecules, such as RNA, ssDNA, or protein. PMID:24404041

Wang, Jingjing; Morabito, Kenneth; Tang, Jay X.; Tripathi, Anubhav

2013-01-01

154

Proton conduction in adipic acid/benzimidazole hybrid electrolytes  

NASA Astrophysics Data System (ADS)

Anhydrous proton conducting organic electrolytes were prepared by doping of adipic acid (AA) with benzimidazole (BnIm) at various stoichiometric ratios to form BnIm xAA ( x is the mol ratio of BnIm to -COOH unit). The AA-BnIm interactions were investigated with Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). Thermal properties were characterized by means of thermogravimetry analysis (TG) and differential scanning calorimetry (DSC). The proton conductivity of these materials was studied by dielectric spectroscopy. The blends exhibit a maximum proton conductivity of 4×10 -3 S/cm at 130 °C.

Karadedeli, B.; Bozkurt, A.; Baykal, A.

2005-07-01

155

Stereoselective synthesis of caffeic acid amides via enzyme-catalyzed asymmetric aminolysis reaction.  

PubMed

In this study, a new method was developed to prepare enantiopure caffeic acid amides by enzyme-catalyzed asymmetric aminolysis reaction. Methoxymethyl chloride (MOMCl) was first introduced as a protective and esterified reagent to obtain the MOM-protected caffeic acid MOM ester 1d. Aminolysis reaction occurred between 1d and (R, S)-?-phenylethylamine in the presence of an immobilized lipase (Novozym 435) from Candida antarctica. Compared with the methyl-protected caffeic acid methyl ester 1c, 1d as substrate improved the lipase-catalyzed reaction rate by 5.5-fold. After Novozym 435-catalyzed aminolysis reaction was established, we evaluated the effects of synthesis parameters on the catalytic activity and enantioselectivity of Novozym 435. A reaction conversion rate of 25.5% and an E value of >100 were achieved under the following optimum conditions: reaction solvent, anhydrous isooctane; reaction temperature, 70°C; reaction time, 24h; ester-to-amine substrate molar ratio, 1:40; and enzyme additive amount, 40 mg. Kinetic and thermodynamic analyses were conducted to determine the main factors affecting enantiomeric discrimination. Novozym 435 still showed 80% of its initial activity after recycling five times. Highly optically pure caffeic acid amides with an enantiomeric excess of 98.5% were finally obtained by HCl deprotection. The established enzyme-catalyzed asymmetric aminolysis method in this study might be used to prepare other caffeic acid amides. PMID:24056082

Xiao, Peiliang; Zhang, Suoqin; Ma, Huayu; Zhang, Aijun; Lv, Xiaoli; Zheng, Liangyu

2013-12-01

156

Sulfonated poly(ether ether ketone)/amino-acid functionalized titania hybrid proton conductive membranes  

NASA Astrophysics Data System (ADS)

Inspired by the proton conducting mechanism in organisms where the amino acid groups play a crucial and multiple role, a novel kind of amino acid-functionalized titania submicrospheres was prepared and incorporated into sulfonated poly(ether ether ketone) (SPEEK) to fabricate the hybrid membranes for potential application in direct methanol fuel cells (DMFCs). The pristine titania submicrospheres (TiO2) with a uniform particle size of ?220 nm were synthesized via a sol-gel process and modified with amino acid groups through a facile chelation method. Meanwhile, amino groups, carboxylic groups and phenyl groups were introduced in the same way for comparison purpose. Compared with the control SPEEK membrane, the methanol crossover was reduced and the membrane mechanical strength was enhanced by incorporation of the functionalized titania submicrospheres. Due to the different proton acceptor/donor capability of the different functional groups, the hybrid membrane embedded with amino-functionalized titania exhibited lower proton conductivity at 20 °C but higher values at elevated temperature of 60 °C compared with carboxylic-functionalized titania; the hybrid membrane embedded with amino acid-functionalized titania displayed a superior proton-conducting ability with the highest proton conductivity of 0.258 S cm-1 at 60 °C.

Wu, Hong; Shen, Xiaohui; Xu, Tao; Hou, Weiqiang; Jiang, Zhongyi

2012-09-01

157

Donor–acceptor graphene-based hybrid materials facilitating photo-induced electron-transfer reactions  

PubMed Central

Summary Graphene research and in particular the topic of chemical functionalization of graphene has exploded in the last decade. The main aim is to increase the solubility and thereby enhance the processability of the material, which is otherwise insoluble and inapplicable for technological applications when stacked in the form of graphite. To this end, initially, graphite was oxidized under harsh conditions to yield exfoliated graphene oxide sheets that are soluble in aqueous media and amenable to chemical modifications due to the presence of carboxylic acid groups at the edges of the lattice. However, it was obvious that the high-defect framework of graphene oxide cannot be readily utilized in applications that are governed by charge-transfer processes, for example, in solar cells. Alternatively, exfoliated graphene has been applied toward the realization of some donor–acceptor hybrid materials with photo- and/or electro-active components. The main body of research regarding obtaining donor–acceptor hybrid materials based on graphene to facilitate charge-transfer phenomena, which is reviewed here, concerns the incorporation of porphyrins and phthalocyanines onto graphene sheets. Through illustrative schemes, the preparation and most importantly the photophysical properties of such graphene-based ensembles will be described. Important parameters, such as the generation of the charge-separated state upon photoexcitation of the organic electron donor, the lifetimes of the charge-separation and charge-recombination as well as the incident-photon-to-current efficiency value for some donor–acceptor graphene-based hybrids, will be discussed. PMID:25247140

Stergiou, Anastasios; Pagona, Georgia

2014-01-01

158

AEROSOL ACIDITY DETERMINATION BY REACTION WITH 14C LABELED AMINE  

EPA Science Inventory

The acidity of aerosol particles collected on Teflon membrane filters is analyzed by exposure to 14C labeled trimethylamine and by counting the resulting beta-ray emission. An accurate calibration is established by the use of known, laboratory generated sulfuric acid samples. For...

159

Up-Scaling Geochemical Reaction Rates Accompanying Acidic CO2-Saturated Brine Flow in Sandstone Aquifers  

E-print Network

1 Up-Scaling Geochemical Reaction Rates Accompanying Acidic CO2-Saturated Brine Flow in Sandstone in the pore networks corresponding to three different sandstones. The simulations were used to study up

New York at Stoney Brook, State University of

160

Citric Acid-Modified Fenton's Reaction for the Oxidation of Chlorinated Ethylenes in Soil Solution Systems  

SciTech Connect

Fenton's reagent, a solution of hydrogen peroxide and ferrous iron catalyst, is used for an in-situ chemical oxidation of organic contaminants. Sulfuric acid is commonly used to create an acidic condition needed for catalytic oxidation. Fenton's reaction often involves pressure buildup and precipitation of reaction products, which can cause safety hazards and diminish efficiency. We selected citric acid, a food-grade substance, as an acidifying agent to evaluate its efficiencies for organic contaminant removal in Fenton's reaction, and examined the impacts of using citric acid on the unwanted reaction products. A series of batch and column experiments were performed with varying H{sub 2}O{sub 2} concentrations to decompose selected chlorinated ethylenes. Either dissolved iron from soil or iron sulfate salt was added to provide the iron catalyst in the batch tests. Batch experiments revealed that both citric and sulfuric acid systems achieved over 90% contaminant removal rates, and the presence of iron catalyst was essential for effective decontamination. Batch tests with citric acid showed no signs of pressure accumulation and solid precipitations, however the results suggested that an excessive usage of H{sub 2}O{sub 2} relative to iron catalysts (Fe{sup 2+}/H{sub 2}O{sub 2} < 1/330) would result in lowering the efficiency of contaminant removal by iron chelations in the citric acid system. Column tests confirmed that citric acid could provide suitable acidic conditions to achieve higher than 55% contaminant removal rates.

Seol, Yongkoo; Javandel, Iraj

2008-03-15

161

A study of the reactions of arsinic and arsonic acids with hydrogen sulfide and hydrogen selenide  

E-print Network

another [I]. Arsemc trisulfide, As, S, an orange or yellow powder, is found in nature as the mineral orpiment. Arsenic trisulfide can be prepared by passing a stream of hydrogen sulfide through an acidic solution of arsenic trioxide. Arsenic disulfide... any effect on the course of the reaction, the carboxymethyl group was replaced with an a-carboxyethyl group. Following the reaction of this arsinic acid with hydrogen sulfide, pale yellow crystals were isolated which had a melting point of 139 ? 142...

Applegate, Cynthia Annette

1986-01-01

162

Koch–Haaf reaction of adamantanols in an acid-tolerant hastelloy-made microreactor  

PubMed Central

Summary The Koch–Haaf reaction of adamantanols was successfully carried out in a microflow system at room temperature. By combining an acid-tolerant hastelloy-made micromixer, a PTFE tube, and a hastelloy-made microextraction unit, a packaged reaction-to-workup system was developed. By means of the present system, the multigram scale synthesis of 1-adamantanecarboxylic acid was achieved in ca. one hour operation. PMID:21977213

Mukai, Yu

2011-01-01

163

Synthesis and solvent-dependent photochromic reactions of porphyrin-spiropyran hybrid compounds  

NASA Astrophysics Data System (ADS)

Porphyrin(Por)-spiropyran(SP) hybrid compounds, including Por-SP dyad, Por-SP2 triad, and Por-SP4 pentad, were prepared and characterized by 1H NMR, MALDI-TOF MS and UV-Vis spectroscopies. Upon 350 nm UV irradiation of Por-SPn (n = 1, 2, 4) in dichloromethane, unusual red-shifted absorption spectra were observed with the colour change from pink into green. Probably due to the protonation of core nitrogens in porphyrin ring, their absorption maxima in dichloromethane were shifted from 418 (Soret band), 515, 550, 590, 645 (four Q bands) nm into 450 and 665 nm. Also, fluorescence maxima were also shifted from 650 and 715 nm to 692 nm. In the other hands, upon irradiation with 350 nm UV light in THF, the colour changed from pink into violet and absorption band at 590 nm increased and the fluorescence spectra showed the decrease of 650 and 715 nm bands and increase of 600-640 nm band, due to the normal ring-opening reaction of spiropyran moiety into merocyanine. In the dark, original absorption and fluorescence spectra were recovered very slowly in dichloromethane, but quickly in THF. The reversible photochromic reactions of Por-SPn (n = 1, 2, 4) in dichloromethane and THF were investigated by observing absorption and fluorescence spectral changes during UV irradiation or standing in the dark.

Hur, Dae Young; Park, Tae Jong; Shin, Eun Ju

2014-01-01

164

Image Charge Method for Reaction Fields in a Hybrid Ion-Channel Model  

SciTech Connect

A multiple-image method is proposed to approximate the reaction-field potential of a source charge inside a finite length cylinder due to the electric polarization of the surrounding membrane and bulk water. When applied to a hybrid ion-channel model, this method allows a fast and accurate treatment of the electrostatic interactions of protein with membrane and solvent. To treat the channel/membrane interface boundary conditions of the electric potential, an optimization approach is used to derive image charges by fitting the reaction-field potential expressed in terms of cylindric harmonics. Meanwhile, additional image charges are introduced to satisfy the boundary conditions at the planar membrane interfaces. In the end, we convert the electrostatic interaction problem in a complex inhomogeneous system of ion channel/membrane/water into one in a homogeneous free space embedded with discrete charges (the source charge and image charges). The accuracy of this method is then validated numerically in calculating the solvation self-energy of a point charge.

Xu, Zhenli [Shanghai Jiao Tong University, Shanghai; Cai, Wei [ORNL; Cheng, Xiaolin [ORNL

2011-01-01

165

Preparation and characterization of the transparent hybrids of silicone epoxy resin and titanium dioxide nanoparticles via sol-gel reactions.  

PubMed

In order to prepare transparent hybrid films of high refractive index, nanoparticles of TiO2 were prepared and dispersed in a silicone epoxy (SE) resin synthesized from diphenyl silane diol and [2-(3,4-epoxycyclohexyl)ethyl] trimethoxysilane by sol-gel reactions. It was found that amorphous TiO2 nanoparticles of about 5 nm modified with hexahydro-4-methyl phthalic anhydride [HMPA] were dispersed in the SE resin without agglomerations. The refractive index of the hybrids increased linearly with increasing the TiO2 contents. The hybrid containing 30 wt% of the TiO2 particles showed light transmittance of 94% at 450 nm and refractive index of 1.63. The fine dispersion of the TiO2 nanoparticles was attributable to the sol-gel reactions between the SE resin and TiO2 nanoparticles and the modification of the TiO2 particles with HMPA. PMID:22103157

Lem, Kwok Wai; Nguyen, Dinh Huong; Kim, Han Na; Lee, Dai Soo

2011-08-01

166

Heterogeneous Reactions of Gaseous Nitric Acid and Nitrogen Dioxide on the Clay Minerals Kaolinite and Pyrophyllite  

Microsoft Academic Search

Airborne clay mineral particles undergo long-range transport because of their small size. As a consequence, heterogeneous reactions on these particles may impact tropospheric photochemical cycles. Diffuse reflectance infrared spectroscopy provided identification of surface adsorbed products formed from the uptake of gaseous nitric acid and nitrogen dioxide on the prototype clay minerals kaolinite and pyrophyllite. The reaction of HNO3 on kaolinite

R. Z. Hinrichs; M. M. Angelini

2006-01-01

167

CHROMATOGRAPHIC SEPARATION AND IDENTIFICATION OF PRODUCTS FROM THE REACTION OF DIMETHYLARSINIC ACID WITH HYDROGEN SULFIDE  

EPA Science Inventory

The reaction of dimethylarsinic acid (DMAV) with hydrogen sulfide (H2S) is of biological significance and may be implicated in the overall toxicity and carcinogenicity of arsenic. The course of the reaction in aqueous phase was monitored and an initial product, dimethylthioarsin...

168

Acid-Base Chemistry According to Robert Boyle: Chemical Reactions in Words as well as Symbols  

ERIC Educational Resources Information Center

Examples of acid-base reactions from Robert Boyle's "The Sceptical Chemist" are used to illustrate the rich information content of chemical equations. Boyle required lengthy passages of florid language to describe the same reaction that can be done quite simply with a chemical equation. Reading or hearing the words, however, enriches the student's…

Goodney, David E.

2006-01-01

169

Hetero-cope rearrangements of nitrosobutenes. DFT studies of thermal and acid-catalyzed reactions.  

PubMed

[Structure: see text] Density functional theory studies of the hetero-Cope reactions of 4-nitroso-1-butenes and nitrosobicyclo[2.2.2]hexenes are reported. The reactions proceed via concerted mechanisms. The electron-withdrawing methoxycarbonyl group alpha- to the nitroso group decreases the activation barrier. Lewis acids such as SbF5 and TiCl4 accelerate the reactions, as has been found experimentally by Zakarian and Lu. PMID:17165908

Jabbari, Arash; Houk, K N

2006-12-21

170

Advanced design of valve-regulated lead–acid battery for hybrid electric vehicles  

Microsoft Academic Search

A novel design of lead-acid battery has been developed for use in hybrid electric vehicles HEVs . The battery has current take-offs at both ends of each of the positive and negative plates. This feature markedly reduces battery operating temperatures, improves battery . capacity, and extends cycle-life under HEV duty. The battery also performs well under partial-state-of-charge PSoC rfast-charge, electric-vehicle

L. T. Lam; R. H. Newnham; H. Ozgun; F. A. Fleming

2000-01-01

171

ENERGY MODELING OF A LEAD-ACID BATTERY WITHIN HYBRID WIND / PHOTOVOLTAIC SYSTEMS  

E-print Network

. Keywords: Battery management, Modelling, Renewable energy systems I - Introduction The work performedENERGY MODELING OF A LEAD-ACID BATTERY WITHIN HYBRID WIND / PHOTOVOLTAIC SYSTEMS O. GERGAUD, G-DC INVERTER DC/ACacquisition System of management and command PV array: 2kW pic 0 1000 W/m² 25°C 800 W/m² 25°C

Paris-Sud XI, Université de

172

Optimizing Reaction Conditions for the Isomerization of Fatty Acids and Fatty Acid Methyl Esters to Their Branch Chain Products  

Microsoft Academic Search

In order to improve the oxidative stability and cold flow properties of oleic acid or methyl oleate, branch chain isomerization\\u000a was conducted using a beta zeolite catalyst. Reaction conditions of temperature (200–300 °C), pressure (0.1–3.0 MPa), and\\u000a co-catalyst (0–2 wt%) were optimized based on branch chain conversion and the cloud point of the ester following the isomerization\\u000a reaction of oleic acid or

Stephen J. Reaume; Naoko Ellis

2011-01-01

173

Direct Diazo-Transfer Reaction on ?-lactam: Synthesis and Preliminary Biological Activities of 6-Triazolylpenicillanic Acids  

PubMed Central

In this study we report the first example of a direct diazo-transfer reaction on readily available 6-aminopenicillanates to give 6-azidopenicillanates in high yield. Subsequent Cu(I)-catalyzed Huisgen cycloaddition between these 6-azidopenicillanates and assorted terminal alkynes facilely furnished 6-triazolylpenicillanic acids was. Preliminary biological screening indicates that these triazolylpenicillanic acids possess low to moderate antibacterial activities. PMID:17855098

Chen, Po C.; Emrich, Rebekah E.; Patel, Pratiq A.

2009-01-01

174

Reaction Of ?,?-Unsaturated Carboxylic Acids With Thallium Triacetate (Tta): Lactonization VS Oxidative Decarboxylation  

Microsoft Academic Search

The reaction of six ?,?-unsaturated carboxylic acids with thallium triacetate (TTA) was studied. The nature of the products is highly sensitive to the substitution pattern of the substrates. Aliphatic acids gave mainly lactones, while those bearing an aromatic ring furnished only decarboxylation products.

Helena M. C. Ferraz; M?nica V. A. Grazini; Luiz F. Silva Jr; Luiz S. Longo Jr

1999-01-01

175

A Comparative Study of French and Turkish Students' Ideas on Acid-Base Reactions  

ERIC Educational Resources Information Center

The goal of this comparative study was to determine the knowledge that French and Turkish upper secondary-school students (grades 11 and 12) acquire on the concept of acid-base reactions. Following an examination of the relevant curricula and textbooks in the two countries, 528 students answered six written questions about the acid-base concept.…

Cokelez, Aytekin

2010-01-01

176

Catalytic hydrogenation of alkenes on acidic zeolites: Mechanistic connections to monomolecular alkane dehydrogenation reactions  

E-print Network

alkane dehydrogenation reactions Rajamani Gounder, Enrique Iglesia Department of Chemical Engineering Keywords: Alkene hydrogenation Alkane dehydrogenation Brønsted acid catalysis De Donder relations Microscopic reversibility Monomolecular alkane activation Zeolite catalysis a b s t r a c t Brønsted acid

Iglesia, Enrique

177

Reaction Mechanism of cis-3-Chloroacrylic Acid Dehalogenase - A Theoretical Study‡  

PubMed Central

The reaction mechanism of cis-3-chloroacrylic acid dehalogenase (cis-CaaD) is studied using the density functional theory method B3LYP. This enzyme catalyzes the hydrolytic dehalogenation of cis-3-chloroacrylic acid to yield malonate semialdehyde and HCl. The uncatalyzed reaction is first considered and excellent agreement is found between the calculated barrier and the measured rate constant. The enzymatic reaction is then studied with an active site model consisting of 159 atoms. The results suggest an alternative mechanism for cis-CaaD catalysis and different roles for some active site residues in this mechanism. PMID:19725565

Sevastik, Robin; Whitman, Christian P.; Himo, Fahmi

2009-01-01

178

Graphene nanosheets-polypyrrole hybrid material as a highly active catalyst support for formic acid electro-oxidation  

E-print Network

Graphene nanosheets-polypyrrole hybrid material as a highly active catalyst support for formic acid. Therefore, the synthesis of hybrid materials consisting of reduced graphene oxide (RGO) with PPy matrix A novel electrode material based on graphene oxide (GO)-polypyrrole (PPy) composites was synthesized

Gao, Hongjun

179

Natural DNA-modified graphene/Pd nanoparticles as highly active catalyst for formic acid electro-oxidation and for the Suzuki reaction.  

PubMed

Natural DNA has been considered as a building block for developing novel functional materials. It is abundant, renewable, and biodegradable and has a well-defined structure and conformation with many unique features, which are difficult to find in other polymers. Herein, calf thymus DNA modified graphene/Pd nanoparticle (DNA-G-Pd) hybrid materials are constructed for the first time using DNA as a mediator, and the prepared DNA-G-Pd hybrid shows high catalytic activity for fuel cell formic acid electro-oxidation and for organic Suzuki reaction. The main advantages of using DNA are not only because the aromatic nucleobases in DNA can interact through ?-? stacking with graphene basal surface but also because they can chelate Pd via dative bonding in such defined sites along the DNA lattice. Our results indicate that isolated, homogeneous, and ultrafine spherical Pd nanoparticles are densely in situ decorated on DNA-modified graphene surfaces with high stability and dispersibility. The prepared DNA-G-Pd hybrid has much greater activity and durability for formic acid electro-oxidation than the commercial Pd/C catalyst and polyvinylpyrrolidone-mediated graphene/Pd nanoparticle (PVP-G-Pd) hybrid used for direct formic acid fuel cells (DFAFCs). Besides, the DNA-G-Pd hybrid can also be an efficient and recyclable catalyst for the organic Suzuki reaction in aqueous solution under aerobic conditions without any preactivation. Since DNA can chelate various transition metal cations, this proof-of-concept protocol provides the possibility for the tailored design of other novel catalytic materials based on graphene with full exploitation of their properties. PMID:22973944

Qu, Konggang; Wu, Li; Ren, Jinsong; Qu, Xiaogang

2012-09-26

180

Kinetics of Acid Reactions: Making Sense of Associated Concepts  

ERIC Educational Resources Information Center

In chemical kinetics, in addition to the concepts related to kinetics, stoichiometry, chemical equilibrium and the characteristics of the reactants are often involved when comparing the rates of different reactions, making such comparisons very challenging for students at all levels, as well as for pre-service science teachers. Consequently, four…

Tan, Kim Chwee Daniel; Treagust, David F.; Chandrasegaran, A. L.; Mocerino, Mauro

2010-01-01

181

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

PubMed

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

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

2009-10-01

182

Thermal denaturation of double-stranded nucleic acids: prediction of temperatures critical for gradient gel electrophoresis and polymerase chain reaction.  

PubMed Central

A program is described which calculates the thermal stability and the denaturation behaviour of double-stranded DNAs and RNAs up to a length of 1000 base pairs. The algorithm is based on recursive generation of conditional and a priori probabilities for base stacking. Output of the program may be compared directly to experimental results; thus the program may be used to optimize the nucleic acid fragments, the primers and the experimental conditions prior to experiments like polymerase chain reactions, temperature-gradient gel electrophoresis, denaturing-gradient gel electrophoresis and hybridizations. The program is available in three versions; the first version runs interactively on VAXstations producing graphics output directly, the second is implemented as part of the HUSAR package at GENIUSnet, the third runs on any computer producing text output which serves as input to available graphics programs. Images PMID:8052531

Steger, G

1994-01-01

183

Highly sensitive DNA detection using cascade amplification strategy based on hybridization chain reaction and enzyme-induced metallization.  

PubMed

A novel highly sensitive colorimetric assay for DNA detection using cascade amplification strategy based on hybridization chain reaction and enzyme-induced metallization was established. The DNA modified superparamagnetic beads were demonstrated to capture and enrich the target DNA in the hybridization buffer or human plasma. The hybridization chain reaction and enzyme-induced silver metallization on the gold nanoparticles were used as cascade signal amplification for the detection of target DNA. The metalization of silver on the gold nanoparticles induced a significant color change from red to yellow until black depending on the concentration of the target DNA, which could be recognized by naked eyes. This method showed a good specificity for the target DNA detection, with the capabilty to discriminate single-base-pair mismatched DNA mutation (single nucleotide polymorphism). Meanwhile, this approach exhibited an excellent anti-interference capability with the convenience of the magentic seperation and washing, which enabled its usage in complex biological systems such as human blood plasma. As an added benefit, the utilization of hybridization chain reaction and enzyme-induced metallization improved detection sensitivity down to 10pM, which is about 100-fold lower than that of traditional unamplified homogeneous assays. PMID:25500528

Yu, Xu; Zhang, Zhi-Ling; Zheng, Si-Yang

2015-04-15

184

Redox Reactions in Wheat Dough as Affected by Ascorbic Acid  

Microsoft Academic Search

Ascorbic acid (AA) is used as bread improver, as its addition to dough causes an increase in loaf volume and an improvement in crumb structure. To explain these effects we review the stereospecificity of the improver action and the properties of ascorbate oxidase and glutathione dehydrogenase and the occurrence of low molecular thiols in flour and their concentration changes during

W. Grosch; H. Wieser

1999-01-01

185

Reactions of An Aromatic ?,?-Biradical with Amino Acids and Dipeptides in the Gas Phase  

PubMed Central

Gas-phase reactivity of a positively charged aromatic ?,?-biradical (N-methyl-6,8-didehydroquinolinium) was examined toward six aliphatic amino acids and fifteen dipeptides by using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR) and laser-induced acoustic desorption (LIAD). While previous studies have revealed that H-atom and NH2 abstractions dominate the reactions of related monoradicals with aliphatic amino acids and small peptides, several additional, unprecedented reaction pathways were observed for the reactions of the biradical. For amino acids, these are 2H-atom abstraction, H2O abstraction, addition – CO2, addition – HCOOH and formation of a stable adduct. The biradical reacts with aliphatic dipeptides similarly as with aliphatic amino acids, but undergoes also one additional reaction pathway, addition/C-terminal amino acid elimination (addition – CO – NHCHRC). These reactions are initiated by H-atom abstraction by the biradical from the amino acid or peptide, or nucleophilic addition of an NH2 or a HO group of the amino acid or peptide at the radical site at C-6 in the biradical. Reactions of the unquenched C-8 radical site then yield the products not observed for related monoradicals. The biradical reacts with aromatic dipeptides with an aromatic ring in N-terminus (i.e., Tyr-Leu, Phe-Val and Phe-Pro) similarly as with aliphatic dipeptides. However, for those aromatic dipeptides that contain an aromatic ring in the C-terminus (i.e., Leu-Tyr and Ala-Phe), one additional pathway, addition/N-terminal amino acid elimination (addition – CO – NHCHRN), was observed. This reaction is likely initiated by radical addition of the biradical at the aromatic ring in the C-terminus. Related monoradicals add to aromatic amino acids and small peptides, which is followed by C?-C? bond cleavage, resulting in side-chain abstraction by the radical. For biradicals, with one unquenched radical site after the initial addition, the reaction ultimately results in the loss of the N-terminal amino acid. Similar to monoradicals, the C-S bond in amino acids and dipeptides was found to be especially susceptible to biradical attack. PMID:20705478

Fu, Mingkun; Li, Sen; Archibold, Enada; Yurkovich, Michael J.; Nash, John J.; Kenttämaa, Hilkka I.

2010-01-01

186

Interactive effects of cadmium and acid rain on photosynthetic light reaction in soybean seedlings.  

PubMed

Interactive effects of cadmium (Cd(2+)) and acid rain on photosynthetic light reaction in soybean seedlings were investigated under hydroponic conditions. Single treatment with Cd(2+) or acid rain and the combined treatment decreased the content of chlorophyll, Hill reaction rate, the activity of Mg(2+)-ATPase, maximal photochemical efficiency and maximal quantum yield, increased initial fluorescence and damaged the chloroplast structure in soybean seedlings. In the combined treatment, the change in the photosynthetic parameters and the damage of chloroplast structure were stronger than those of any single pollution. Meanwhile, Cd(2+) and acid rain had the interactive effects on the test indices in soybean seedlings. The results indicated that the combined pollution of Cd(2+) and acid rain aggravated the toxic effect of the single pollution of Cd(2+) or acid rain on the photosynthetic parameters due to the serious damage to the chloroplast structure. PMID:22182775

Sun, Zhaoguo; Wang, Lihong; Chen, Minmin; Wang, Lei; Liang, Chanjuan; Zhou, Qing; Huang, Xiaohua

2012-05-01

187

Reactions Between Water Soluble Organic Acids and Nitrates in Atmospheric Aerosols: Recycling of Nitric Acid and Formation of Organic Salts  

SciTech Connect

Atmospheric particles often include a complex mixture of nitrate and secondary organic materials accumulated within the same individual particles. Nitrate as an important inorganic component can be chemically formed in the atmosphere. For instance, formation of sodium nitrate (NaNO3) and calcium nitrate Ca(NO3)2 when nitrogen oxide and nitric acid (HNO3) species react with sea salt and calcite, respectively. Organic acids contribute a significant fraction of photochemically formed secondary organics that can condense on the preexisting nitrate-containing particles. Here, we present a systematic microanalysis study on chemical composition of laboratory generated particles composed of water soluble organic acids and nitrates (i.e. NaNO3 and Ca(NO3)2) investigated using computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and Fourier transform infrared micro-spectroscopy (micro-FTIR). The results show that water-soluble organic acids can react with nitrates releasing gaseous HNO3 during dehydration process. These reactions are attributed to acid displacement of nitrate with weak organic acids driven by the evaporation of HNO3 into gas phase due to its relatively high volatility. The reactions result in significant nitrate depletion and formation of organic salts in mixed organic acids/nitrate particles that in turn may affect their physical and chemical properties relevant to atmospheric environment and climate. Airborne nitrate concentrations are estimated by thermodynamic calculations corresponding to various nitrate depletions in selected organic acids of atmospheric relevance. The results indicate a potential mechanism of HNO3 recycling, which may further affect concentrations of gas- and aerosol-phase species in the atmosphere and the heterogeneous reaction chemistry between them.

Wang, Bingbing; Laskin, Alexander

2014-03-25

188

Particle growth by acid-catalyzed heterogeneous reactions of organic carbonyls on preexisting aerosols.  

PubMed

Aerosol growth by the heterogeneous reactions of different aliphatic and alpha,beta-unsaturated carbonyls in the presence/absence of acidified seed aerosols was studied in a 2 m long flow reactor (2.5 cm i.d.) and a 0.5-m3 Teflon film bag under darkness. For the flow reactor experiments, 2,4-hexadienal, 5-methyl-3-hexen-2-one, 2-cyclohexenone, 3-methyl-2-cyclopentenone, 3-methyl-2-cyclohexenone, and octanal were studied. The carbonyls were selected based on their reactivity for acid-catalyzed reactions, their proton affinity, and their similarity to the ring-opening products from the atmospheric oxidation of aromatics. To facilitate acid-catalyzed heterogeneous hemiacetal/acetal formation, glycerol was injected along with inorganic seed aerosols into the flow reactor system. Carbonyl heterogeneous reactions were accelerated in the presence of acid catalysts (H2SO4), leading to higher aerosol yields than in their absence. Aldehydes were more reactive than ketones for acid-catalyzed reactions. The conjugated functionality also resulted in higher organic aerosol yieldsthan saturated aliphatic carbonyls because conjugation with the olefinic bond increases the basicity of the carbonyl leading to increased stability of the protonated carbonyl. Aerosol population was measured from a series of sampling ports along the length of the flow reactor using a scanning mobility particle sizer. Fourier transform infrared spectrometry of either an impacted liquid aerosol layer or direct reaction of carbonyls as a thin liquid layer on a zinc selenide FTIR disk was employed to demonstrate the direct transformation of chemical functional groups via the acid-catalyzed reactions. These results strongly indicate that atmospheric multifunctional organic carbonyls, which are created by atmospheric photooxidation reactions, can contribute significantly to secondary organic aerosol formation through acid-catalyzed heterogeneous reactions. Exploratory studies in 25- and 190-m3 outdoor chambers were also implemented to demonstrate the formation of high molecular weight organic structures. The reaction of ozone with alpha-pinene to generate secondary organic aerosols (SOAs) was performed in the presence of background aerosol consisting of a mixture of wood soot and diesel soot. Results strongly suggest that indigenous sulfuric acid associated with the combustion of fossil fuels (e.g., diesel soot) can initiate acid-catalyzed heterogeneous reactions of SOAs on the particle phase. PMID:12967102

Jang, Myoseon; Carroll, Brian; Chandramouli, Bharadwaj; Kamens, Richard M

2003-09-01

189

Deoxyribonucleic Acid Copy Number Aberrations in Vasospastic Angina Patients Using an Array Comparative Genomic Hybridization  

PubMed Central

Background and Objectives Vasospastic angina (VA) is a specific type of coronary artery disease and develops as a result of coronary artery spasm. Recently, a few studies have revealed that VA caused by coronary artery spasm is related to genetic traits. The objective of this study was to use the recently developed technique of array comparative genomic hybridization (CGH) to screen the genetic aberrations of VA. Subjects and Methods To identify candidate genes that might be causally involved in the pathogenesis of VA, genomic deoxyribonucleic acids were extracted from whole blood of 28 patients with VA who presented at Department of Cardiology at Seoul St. Mary's Hospital, Seoul, Korea. The copy number profiles of these patients was then analyzed using array CGH and reverse transcriptase (RT) quantitative polymerase chain reaction (PCR). Results Array CGH revealed gains in 31 different regions, with losses in the 4q35.2, 7q22.1, 10q26.3, 15q11.2, 16p13.11, 17p11.2 and 19q13.3 regions (more than 32% aberration in these regions). Several loci were found to be frequently including gains of 5p and 11q (50% of samples). The most common losses were found in 7q (54% of samples). Copy number aberrations in chromosomal regions were detected and corresponding genes were confirmed by RT quantitative PCR. The fold change levels were highest in the CTDP1 (18q23), HDAC10 (22q13.33), KCNQ1 (11p15.5-p15.4), NINJ2 (12p13.33), NOTCH2 (1p12-p11.2), PCSK6 (15q26.3), SDHA (5p15.33), and MUC17 (7q22.1) genes. Conclusion Many candidate chromosomal regions that might be related to the pathogenesis of VA were detected by array CGH and should be systematically investigated to establish the causative and specific genes for VA. PMID:21860640

Seo, Suk Min; Koh, Yoon Seok; Choi, Jin Soo; Kim, Pum Joon; Baek, Sang Hong; Youn, Ho-Joong; Lee, Kweon-Haeng; Seung, Ki-Bae

2011-01-01

190

Identification of random nucleic acid sequence aberrations using dual capture probes which hybridize to different chromosome regions  

DOEpatents

A method is provided for detecting nucleic acid sequence aberrations using two immobilization steps. According to the method, a nucleic acid sequence aberration is detected by detecting nucleic acid sequences having both a first nucleic acid sequence type (e.g., from a first chromosome) and a second nucleic acid sequence type (e.g., from a second chromosome), the presence of the first and the second nucleic acid sequence type on the same nucleic acid sequence indicating the presence of a nucleic acid sequence aberration. In the method, immobilization of a first hybridization probe is used to isolate a first set of nucleic acids in the sample which contain the first nucleic acid sequence type. Immobilization of a second hybridization probe is then used to isolate a second set of nucleic acids from within the first set of nucleic acids which contain the second nucleic acid sequence type. The second set of nucleic acids are then detected, their presence indicating the presence of a nucleic acid sequence aberration. 14 figs.

Lucas, J.N.; Straume, T.; Bogen, K.T.

1998-03-24

191

Identification of random nucleic acid sequence aberrations using dual capture probes which hybridize to different chromosome regions  

DOEpatents

A method is provided for detecting nucleic acid sequence aberrations using two immobilization steps. According to the method, a nucleic acid sequence aberration is detected by detecting nucleic acid sequences having both a first nucleic acid sequence type (e.g., from a first chromosome) and a second nucleic acid sequence type (e.g., from a second chromosome), the presence of the first and the second nucleic acid sequence type on the same nucleic acid sequence indicating the presence of a nucleic acid sequence aberration. In the method, immobilization of a first hybridization probe is used to isolate a first set of nucleic acids in the sample which contain the first nucleic acid sequence type. Immobilization of a second hybridization probe is then used to isolate a second set of nucleic acids from within the first set of nucleic acids which contain the second nucleic acid sequence type. The second set of nucleic acids are then detected, their presence indicating the presence of a nucleic acid sequence aberration.

Lucas, Joe N. (San Ramon, CA); Straume, Tore (Tracy, CA); Bogen, Kenneth T. (Walnut Creek, CA)

1998-01-01

192

Label-free colorimetric aptasensor for sensitive detection of ochratoxin A utilizing hybridization chain reaction.  

PubMed

The combination of high selectivity of aptamer with the peroxidase-mimicking property of DNAzyme has presented considerable opportunities for designing colorimetric aptasensor for detection of ochratoxin A (OTA). The activities of both aptamer (as biorecognition element) and DNAzyme (as signal amplification element) are blocked via base pairing in the hairpin structure. Hybridization chain reaction (HCR) between two hairpin DNAs was employed to further improve the sensitivity of this method. The presence of OTA triggers the opening of the hairpin structure and the beginning of HCR, which results in the release of many DNAzyme, and generates enhanced colorimetric signals, which is correlated to the amounts of OTA with linear range between 0.01 to 0.32nM, and the limit of detection is 0.01nM under optimal conditions. OTA in yellow rice wine and wheat flour samples was also detected using this method. We demonstrate that a new colorimetric method for the detection of OTA has been established, which is simple, easy to conduct, label-free, sensitive, high throughput, and cost-saving. PMID:25682251

Wang, Chengke; Dong, Xiaoya; Liu, Qian; Wang, Kun

2015-02-20

193

A unique platinum-graphene hybrid structure for high activity and durability in oxygen reduction reaction  

PubMed Central

It remains a grand challenge to achieve both high activity and durability in Pt electrocatalysts for oxygen reduction reaction (ORR) in fuel cells. Here we develop a class of Pt highly concave cubic (HCC) nanocrystals, which are enriched with high-index facets, to enable high ORR activity. The durability of HCC nanocrystals can be significantly improved via assembly with graphene. Meanwhile, the unique hybrid structure displays further enhanced specific activity, which is 7-fold greater than the state-of-the-art Pt/C catalysts. Strikingly, it exhibits impressive performance in terms of half-wave potential (E1/2). The E1/2 of 0.967?V at the Pt loading as low as 46??g cm?2, which stands as 63?mV higher than that of the Pt/C catalysts, is slightly superior to the record observed for the most active porous Pt-Ni catalyst in literature. This work paves the way to designing high-performance electrocatalysts by modulating their surface and interface with loading substrates. PMID:23999570

Wang, Chengming; Ma, Liang; Liao, Lingwen; Bai, Song; Long, Ran; Zuo, Ming; Xiong, Yujie

2013-01-01

194

Label-free potentiometry for detecting DNA hybridization using peptide nucleic acid and DNA probes.  

PubMed

Peptide nucleic acid (PNA) has outstanding affinity over DNA for complementary nucleic acid sequences by forming a PNA-DNA heterodimer upon hybridization via Watson-Crick base-pairing. To verify whether PNA probes on an electrode surface enhance sensitivity for potentiometric DNA detection or not, we conducted a comparative study on the hybridization of PNA and DNA probes on the surface of a 10-channel gold electrodes microarray. Changes in the charge density as a result of hybridization at the solution/electrode interface on the self-assembled monolayer (SAM)-formed microelectrodes were directly transformed into potentiometric signals using a high input impedance electrometer. The charge readout allows label-free, reagent-less, and multi-parallel detection of target oligonucleotides without any optical assistance. The differences in the probe lengths between 15- to 22-mer dramatically influenced on the sensitivity of the PNA and DNA sensors. Molecular type of the capturing probe did not affect the degree of potential shift. Theoretical model for charged rod-like duplex using the Gouy-Chapman equation indicates the dominant effect of electrostatic attractive forces between anionic DNA and underlying electrode at the electrolyte/electrode interface in the potentiometry. PMID:23435052

Goda, Tatsuro; Singi, Ankit Balram; Maeda, Yasuhiro; Matsumoto, Akira; Torimura, Masaki; Aoki, Hiroshi; Miyahara, Yuji

2013-01-01

195

Mechanistic study of secondary organic aerosol components formed from nucleophilic addition reactions of methacrylic acid epoxide  

NASA Astrophysics Data System (ADS)

Recently, methacrylic acid epoxide (MAE) has been proposed as a precursor to an important class of isoprene-derived compounds found in secondary organic aerosol (SOA): 2-methylglyceric acid (2-MG) and a set of oligomers, nitric acid esters and sulfuric acid esters related to 2-MG. However, the specific chemical mechanisms by which MAE could form these compounds have not been previously studied. In order to determine the relevance of these processes to atmospheric aerosol, MAE and 2-MG have been synthesized and a series of bulk solution-phase experiments aimed at studying the reactivity of MAE using nuclear magnetic resonance (NMR) spectroscopy have been performed. The present results indicate that the acid-catalyzed MAE reaction is more than 600 times slower than a similar reaction of an important isoprene-derived epoxide, but is still expected to be kinetically feasible in the atmosphere on more acidic SOA. The specific mechanism by which MAE leads to oligomers was identified, and the reactions of MAE with a number of atmospherically relevant nucleophiles were also investigated. Because the nucleophilic strengths of water, sulfate, alcohols (including 2-MG), and acids (including MAE and 2-MG) in their reactions with MAE were found to be of a similar magnitude, it is expected that a diverse variety of MAE + nucleophile product species may be formed on ambient SOA. Thus, the results indicate that epoxide chain reaction oligomerization will be limited by the presence of high concentrations of non-epoxide nucleophiles (such as water); this finding is consistent with previous environmental chamber investigations of the relative humidity-dependence of 2-MG-derived oligomerization processes and suggests that extensive oligomerization may not be likely on ambient SOA because of other competitive MAE reaction mechanisms.

Birdsall, A. W.; Miner, C. R.; Mael, L. E.; Elrod, M. J.

2014-08-01

196

Mechanistic study of secondary organic aerosol components formed from nucleophilic addition reactions of methacrylic acid epoxide  

NASA Astrophysics Data System (ADS)

Recently, methacrylic acid epoxide (MAE) has been proposed as a precursor to an important class of isoprene-derived compounds found in secondary organic aerosol (SOA): 2-methylglyceric acid (2-MG) and a set of oligomers, nitric acid esters, and sulfuric acid esters related to 2-MG. However, the specific chemical mechanisms by which MAE could form these compounds have not been previously studied with experimental methods. In order to determine the relevance of these processes to atmospheric aerosol, MAE and 2-MG have been synthesized and a series of bulk solution-phase experiments aimed at studying the reactivity of MAE using nuclear magnetic resonance (NMR) spectroscopy have been performed. The present results indicate that the acid-catalyzed MAE reaction is more than 600 times slower than a similar reaction of an important isoprene-derived epoxide, but is still expected to be kinetically feasible in the atmosphere on more acidic SOA. The specific mechanism by which MAE leads to oligomers was identified, and the reactions of MAE with a number of atmospherically relevant nucleophiles were also investigated. Because the nucleophilic strengths of water, sulfate, alcohols (including 2-MG), and acids (including MAE and 2-MG) in their reactions with MAE were found to be of similar magnitudes, it is expected that a diverse variety of MAE + nucleophile product species may be formed on ambient SOA. Thus, the results indicate that epoxide chain reaction oligomerization will be limited by the presence of high concentrations of non-epoxide nucleophiles (such as water); this finding is consistent with previous environmental chamber investigations of the relative humidity dependence of 2-MG-derived oligomerization processes and suggests that extensive oligomerization may not be likely on ambient SOA because of other competitive MAE reaction mechanisms.

Birdsall, A. W.; Miner, C. R.; Mael, L. E.; Elrod, M. J.

2014-12-01

197

40 CFR 721.9280 - Reaction product of ethoxylated fatty acid oils and a phenolic pentaerythritol tetraester.  

Code of Federal Regulations, 2013 CFR

...Reaction product of ethoxylated fatty acid oils and a phenolic pentaerythritol...Reaction product of ethoxylated fatty acid oils and a phenolic pentaerythritol...product of ethoxylated fatty acid oils and a phenolic pentaerythritol...processed, or used in the employer's workplace, the employer...

2013-07-01

198

40 CFR 721.9280 - Reaction product of ethoxylated fatty acid oils and a phenolic pentaerythritol tetraester.  

...Reaction product of ethoxylated fatty acid oils and a phenolic pentaerythritol...Reaction product of ethoxylated fatty acid oils and a phenolic pentaerythritol...product of ethoxylated fatty acid oils and a phenolic pentaerythritol...processed, or used in the employer's workplace, the employer...

2014-07-01

199

40 CFR 721.9280 - Reaction product of ethoxylated fatty acid oils and a phenolic pentaerythritol tetraester.  

Code of Federal Regulations, 2010 CFR

...Reaction product of ethoxylated fatty acid oils and a phenolic pentaerythritol...Reaction product of ethoxylated fatty acid oils and a phenolic pentaerythritol...product of ethoxylated fatty acid oils and a phenolic pentaerythritol...processed, or used in the employer's workplace, the employer...

2010-07-01

200

40 CFR 721.9280 - Reaction product of ethoxylated fatty acid oils and a phenolic pentaerythritol tetraester.  

Code of Federal Regulations, 2012 CFR

...Reaction product of ethoxylated fatty acid oils and a phenolic pentaerythritol...Reaction product of ethoxylated fatty acid oils and a phenolic pentaerythritol...product of ethoxylated fatty acid oils and a phenolic pentaerythritol...processed, or used in the employer's workplace, the employer...

2012-07-01

201

40 CFR 721.9280 - Reaction product of ethoxylated fatty acid oils and a phenolic pentaerythritol tetraester.  

Code of Federal Regulations, 2011 CFR

...Reaction product of ethoxylated fatty acid oils and a phenolic pentaerythritol...Reaction product of ethoxylated fatty acid oils and a phenolic pentaerythritol...product of ethoxylated fatty acid oils and a phenolic pentaerythritol...processed, or used in the employer's workplace, the employer...

2011-07-01

202

Application and comparison of silver intensification methods for the diaminobenzidine and diaminobenzidine-nickel endproduct of the peroxidation reaction in immunohistochemistry and in situ hybridization.  

PubMed

Silver-intensification methods described in the literature for the diaminobenzidine (DAB) and diaminobenzidine-nickel (DAB/Ni) endproduct of the peroxidase reaction were compared in model systems after immunoperoxidase and in situ hybridization. First, these methods were compared in immunohistochemical model systems, using the demonstration of glial fibrillar acidic protein (GFAP) and prostate-specific antigen (PSA) in paraffin sections of human brain and prostate tissue, respectively. When DAB without Ni was used as substrate, tissue argyrophilia caused considerable background staining. Only when this tissue reactivity was quenched with, e.g., CuSO4 with H2O2 or thioglycolic acid, were the results acceptable. A considerable improvement in the signal-to-noise ratio could be obtained when nickel was included in the substrate mixture. The methods that proved to be best for demonstration of GFAP and PSA made use of acid developer solutions. Subsequently, these methods were compared with other sensitive immunostaining methods for demonstration of the gamma-delta T-cell receptor in frozen lymphoid tissue. In this model a considerable increase in the number of positive cells could be obtained using silver intensification. The different methods using DAB/Ni were also compared for use in DNA in situ hybridization (DISH). In this case two model systems were used: human papilloma virus type 11 (HPV-11) DNA in condyloma tissue (abundant target model) and Epstein-Barr virus (EBV) DNA in a mononucleosis lymph node (low target model). For demonstration of HPV-11, all methods gave more or less satisfactory results, which were best with the acid developer solutions. Moreover, for demonstration of EBV DNA, a signal could be obtained only with these developer solutions. Such a method also proved suitable in double immuno-hybrido stainings for the demonstration of EBV DNA in specific antigen-positive Reed-Sternberg cells in paraffin sections of Hodgkin lymph nodes. PMID:1532404

Mullink, H; Vos, W; Jiwa, M; Horstman, A; van der Valk, P; Walboomers, J M; Meijer, C J

1992-04-01

203

Phosphoric acid doped polybenzimidazole/imidazolium-modified silsesquioxane hybrid proton conducting membranes for anhydrous proton exchange membrane application  

NASA Astrophysics Data System (ADS)

Phosphoric acid doped polybenzimidazole (PBI)/imidazolium-modified silsesquioxane (Im-SiO3/2) hybrid membranes with high proton conductivity at high temperature under anhydrous conditions are synthesized and characterized. The presence of Im-SiO3/2 is confirmed by FT-IR and energy-dispersive X-ray spectroscopy (EDS) mapping of silicon element. The phosphoric acid uptake and proton conductivity of the hybrid membranes increase with the Im-SiO3/2 content, and the conductivity of PBI/Im-SiO3/2-20 reaching 6.3 × 10-2 S cm-1 at 180 °C. Compared with pure PBI membranes, the introduction of Im-SiO3/2 is effective in preventing the release of the phosphoric acid component from the hybrid membranes. The properties of the prepared hybrid membranes indicate their promising prospects in anhydrous proton exchange membrane applications.

Lin, Bencai; Chu, Fuqiang; Yuan, Ningyi; Shang, Hui; Ren, Yurong; Gu, Zongzong; Ding, Jianning; Wei, Yingqiang; Yu, Xiaomin

2014-04-01

204

Deoxyribonucleic acid-based hybrid thin films for potential application as high energy density capacitors  

NASA Astrophysics Data System (ADS)

Deoxyribonucleic acid (DNA) based hybrid films incorporating sol-gel-derived ceramics have shown strong promise as insulating dielectrics for high voltage capacitor applications. Our studies of DNA-CTMA (cetyltrimethylammonium) complex/sol-gel ceramic hybrid thin film devices have demonstrated reproducibility and stability in temperature- and frequency-dependent dielectric properties with dielectric constant k ˜ 5.0 (1 kHz), as well as reliability in DC voltage breakdown measurements, attaining values consistently in the range of 300-350 V/?m. The electrical/dielectric characteristics of DNA-CTMA films with sol-gel-derived ceramics were examined to determine the critical energy storage parameters such as voltage breakdown and dielectric constant.

Joyce, Donna M.; Venkat, Narayanan; Ouchen, Fahima; Singh, Kristi M.; Smith, Steven R.; Grabowski, Christopher A.; Terry Murray, P.; Grote, James G.

2014-03-01

205

Au-ZnO hybrid nanoflowers, nanomultipods and nanopyramids: one-pot reaction synthesis and photocatalytic properties  

NASA Astrophysics Data System (ADS)

The preparation of noble metal-semiconductor hybrid nanocrystals with controlled morphologies has received intensive interest in recent years. In this study, facile one-pot reactions have been developed for the synthesis of Au-ZnO hybrid nanocrystals with different interesting morphologies, including petal-like and urchin-like nanoflowers, nanomultipods and nanopyramids. In the synthesis strategy, oleylamine-containing solution serves as the reaction medium, and the in situ generated Au seeds play an important role in the subsequently induced growth of ZnO nanocrystals. With the aid of several surfactants, hybrid nanocrystals with different morphologies that have considerable influences on their optical and photocatalytic activities are readily achieved. Through high-resolution transmission electron microscopy measurements, an observed common orientation relationship between ZnO and Au is that ZnO nanocrystals prefer to grow with their polar {001} facets on the {111} facets of Au nanocrystals, and well-defined interfaces are evident. Surface plasmon resonance bands of Au with different positions are observed in the UV-vis spectra, and the UV and visible emissions of ZnO are found to be dramatically reduced. Finally, the as-prepared Au-ZnO nanocrystals exhibit excellent photocatalytic activity for the photodegradation of rhodamine B compared with pure ZnO nanocrystals. The Au-ZnO hybrid nanopyramids show the highest catalytic efficiency, which is correlated with the exposed crystal facets, crystallinity and the formation of hybrid nanostructures. The as-prepared Au-ZnO hybrid nanocrystals are expected to find diverse potential applications in the fields such as photocatalysis, solar energy conversion, sensing and biological detection.The preparation of noble metal-semiconductor hybrid nanocrystals with controlled morphologies has received intensive interest in recent years. In this study, facile one-pot reactions have been developed for the synthesis of Au-ZnO hybrid nanocrystals with different interesting morphologies, including petal-like and urchin-like nanoflowers, nanomultipods and nanopyramids. In the synthesis strategy, oleylamine-containing solution serves as the reaction medium, and the in situ generated Au seeds play an important role in the subsequently induced growth of ZnO nanocrystals. With the aid of several surfactants, hybrid nanocrystals with different morphologies that have considerable influences on their optical and photocatalytic activities are readily achieved. Through high-resolution transmission electron microscopy measurements, an observed common orientation relationship between ZnO and Au is that ZnO nanocrystals prefer to grow with their polar {001} facets on the {111} facets of Au nanocrystals, and well-defined interfaces are evident. Surface plasmon resonance bands of Au with different positions are observed in the UV-vis spectra, and the UV and visible emissions of ZnO are found to be dramatically reduced. Finally, the as-prepared Au-ZnO nanocrystals exhibit excellent photocatalytic activity for the photodegradation of rhodamine B compared with pure ZnO nanocrystals. The Au-ZnO hybrid nanopyramids show the highest catalytic efficiency, which is correlated with the exposed crystal facets, crystallinity and the formation of hybrid nanostructures. The as-prepared Au-ZnO hybrid nanocrystals are expected to find diverse potential applications in the fields such as photocatalysis, solar energy conversion, sensing and biological detection. Electronic supplementary information (ESI) available: EDS spectra, SEM images and TEM images of products synthesized under different conditions, and time-dependent UV-vis spectra recorded during the photocatalytic degradation of RhB by using different samples. See DOI: 10.1039/c3nr04558g

Chen, Yuanzhi; Zeng, Deqian; Zhang, Kun; Lu, Aolin; Wang, Laisen; Peng, Dong-Liang

2013-12-01

206

Theoretical study of the reaction between 2,2???,4???-trihydroxyazobenzene-5-sulfonic acid and zirconium  

USGS Publications Warehouse

Zirconium reacts with 2,2???,4???-trihydroxyazobenzene-5-sulfonic acid in acid solutions to Form two complexes in which the ratios of dye to zirconium are 1 to 1 and 2 to 1. Both complexes are true chelates, with zirconium acting as a bridge between the two orthohydroxy dye groups. Apparent equilibrium constants for the reactions to form each of the complexes are determined. The reactions are used as a basis for the determination of the active component in the dye and a graphical method for the determination of reagent purity is described. Four absorption spectra covering the wave length region from 350 to 750 m?? are given, which completely define the color system associated with the reactions in solutions where the hydrochloric acid concentration ranges from 0.0064N to about 7N.

Fletcher, M.H.

1960-01-01

207

Evaluation of Hanford high level waste vitrification chemistry for an NCAW simulant -- FY 1994: Potential exothermic reactions in the presence of formic acid, glycolic acid, and oxalic acid  

SciTech Connect

A potential for an uncontrollable exothermic reaction between nitrate and organic salts during preparation of a high level waste melter feed has been identified. In order to examine this potential more closely, the thermal behavior of simulated neutralized current acid waste (NCAW) treated with various organic reductants was studied. Differential scanning calorimetry (DSC) measurements were collected on simulated waste samples and their supernates treated with organics. Organic reductants used were formic acid, glycolic acid, and oxalic acid. For comparison, samples of untreated simulant and untreated simulant with added noble metals were tested. When heated, untreated simulant samples both with and without noble metals showed no exothermic behavior. All of the treated waste simulant samples showed exothermic behavior. Onset temperatures of exothermic reactions were 120 C to 210 C. Many onset temperatures, particularly those for formic acid treated samples, are well below 181 C, the estimated maximum steam coil temperature (considered to be a worst case maximum temperature for chemical process tank contents). The enthalpies of the reactions were {minus}180 {times} 10{sup {minus}3} J/Kg supernate ({minus}181 J/g) for the oxalic acid treated simulant supernate to {minus}1,150 {times} 10{sup {minus}3} J/Kg supernate ({minus}1,153 J/g) for the formic acid treated simulant supernate.

Sills, J.A.

1995-07-01

208

Au-ZnO hybrid nanoflowers, nanomultipods and nanopyramids: one-pot reaction synthesis and photocatalytic properties.  

PubMed

The preparation of noble metal-semiconductor hybrid nanocrystals with controlled morphologies has received intensive interest in recent years. In this study, facile one-pot reactions have been developed for the synthesis of Au-ZnO hybrid nanocrystals with different interesting morphologies, including petal-like and urchin-like nanoflowers, nanomultipods and nanopyramids. In the synthesis strategy, oleylamine-containing solution serves as the reaction medium, and the in situ generated Au seeds play an important role in the subsequently induced growth of ZnO nanocrystals. With the aid of several surfactants, hybrid nanocrystals with different morphologies that have considerable influences on their optical and photocatalytic activities are readily achieved. Through high-resolution transmission electron microscopy measurements, an observed common orientation relationship between ZnO and Au is that ZnO nanocrystals prefer to grow with their polar {001} facets on the {111} facets of Au nanocrystals, and well-defined interfaces are evident. Surface plasmon resonance bands of Au with different positions are observed in the UV-vis spectra, and the UV and visible emissions of ZnO are found to be dramatically reduced. Finally, the as-prepared Au-ZnO nanocrystals exhibit excellent photocatalytic activity for the photodegradation of rhodamine B compared with pure ZnO nanocrystals. The Au-ZnO hybrid nanopyramids show the highest catalytic efficiency, which is correlated with the exposed crystal facets, crystallinity and the formation of hybrid nanostructures. The as-prepared Au-ZnO hybrid nanocrystals are expected to find diverse potential applications in the fields such as photocatalysis, solar energy conversion, sensing and biological detection. PMID:24270554

Chen, Yuanzhi; Zeng, Deqian; Zhang, Kun; Lu, Aolin; Wang, Laisen; Peng, Dong-Liang

2014-01-21

209

Kinetics and Quantitative Structure—Activity Relationship Study on the Degradation Reaction from Perfluorooctanoic Acid to Trifluoroacetic Acid  

PubMed Central

Investigation of the degradation kinetics of perfluorooctanoic acid (PFOA) has been carried out to calculate rate constants of the main elementary reactions using the multichannel Rice-Ramsperger-Kassel-Marcus theory and canonical variational transition state theory with small-curvature tunneling correction over a temperature range of 200~500 K. The Arrhenius equations of rate constants of elementary reactions are fitted. The decarboxylation is role step in the degradation mechanism of PFOA. For the perfluorinated carboxylic acids from perfluorooctanoic acid to trifluoroacetic acid, the quantitative structure–activity relationship of the decarboxylation was analyzed with the genetic function approximation method and the structure–activity model was constructed. The main parameters governing rate constants of the decarboxylation reaction from the eight-carbon chain to the two-carbon chain were obtained. As the structure–activity model shows, the bond length and energy of C1–C2 (RC1–C2 and EC1–C2) are positively correlated to rate constants, while the volume (V), the energy difference between EHOMO and ELUMO (?E), and the net atomic charges on atom C2 (QC2) are negatively correlated. PMID:25196516

Gong, Chen; Sun, Xiaomin; Zhang, Chenxi; Zhang, Xue; Niu, Junfeng

2014-01-01

210

Highly Active and Stable Hybrid Catalyst of Cobalt-Doped FeS2 Nanosheets-Carbon Nanotubes for Hydrogen Evolution Reaction.  

PubMed

Hydrogen evolution reaction (HER) from water through electrocatalysis using cost-effective materials to replace precious Pt catalysts holds great promise for clean energy technologies. In this work we developed a highly active and stable catalyst containing Co doped earth abundant iron pyrite FeS2 nanosheets hybridized with carbon nanotubes (Fe1-xCoxS2/CNT hybrid catalysts) for HER in acidic solutions. The pyrite phase of Fe1-xCoxS2/CNT was characterized by powder X-ray diffraction and absorption spectroscopy. Electrochemical measurements showed a low overpotential of ?0.12 V at 20 mA/cm(2), small Tafel slope of ?46 mV/decade, and long-term durability over 40 h of HER operation using bulk quantities of Fe0.9Co0.1S2/CNT hybrid catalysts at high loadings (?7 mg/cm(2)). Density functional theory calculation revealed that the origin of high catalytic activity stemmed from a large reduction of the kinetic energy barrier of H atom adsorption on FeS2 surface upon Co doping in the iron pyrite structure. It is also found that the high HER catalytic activity of Fe0.9Co0.1S2 hinges on the hybridization with CNTs to impart strong heteroatomic interactions between CNT and Fe0.9Co0.1S2. This work produces the most active HER catalyst based on iron pyrite, suggesting a scalable, low cost, and highly efficient catalyst for hydrogen generation. PMID:25588180

Wang, Di-Yan; Gong, Ming; Chou, Hung-Lung; Pan, Chun-Jern; Chen, Hsin-An; Wu, Yingpeng; Lin, Meng-Chang; Guan, Mingyun; Yang, Jiang; Chen, Chun-Wei; Wang, Yuh-Lin; Hwang, Bing-Joe; Chen, Chia-Chun; Dai, Hongjie

2015-02-01

211

Kinetics for exchange of imino protons in deoxyribonucleic acid, ribonucleic acid, and hybrid oligonucleotide helices  

SciTech Connect

The lifetimes for opening of individual base pairs in a DNA (dCA/sub 5/G + dCT/sub 5/G), an RNA (rCA/sub 5/G + rCU/sub 5/G), and a hybrid DNA-RNA (rCA/sub 5/G + dCT/sub 5/G) helix have been measured by proton nuclear magnetic resonance. The lifetimes were obtained by saturation recovery experiments performed on the hydrogen-bonding imino protons of the Watson-Crick base pairs. In these oligonucleotide helices the observed relaxation rates were dominated by exchange with water, with the magnetic spin-lattice relaxation time of the imino protons possibly being important only at the lowest temperatures in the DNA helix. It was shown that three interior base pairs in the DNA heptamer dCA/sub 5/G + dCT/sub 5/G were in the open-limited region, which means that these imino protons exchange every time the base pair opens. The lifetimes of the terminal G-C base pairs in the DNA helix are much shorter than the interior A-T base pairs. The pH dependence of the terminal base pairs indicated that the ends of the helix open and close many times before exchange of the imino protons with water takes place. The temperature dependence of the lifetimes of the interior A-T imino protons in the DNA helix showed that these protons exchange only when the double helix was dissociated into single strands. Thus, these lifetimes measure the rate for dissociation of the double helix. The activation energy for this process was found to be 47 kcal/mol. Comparison of the lifetimes of the interior protons in the DNA, RNA, and hybrid helices showed that the rates of dissociation of the RNA and hybrid helices are very similar at 5/sup 0/ C, whereas the rate for the DNA helix was approximately 1 order of magnitude smaller than that for the other two helices.

Pardi, A.; Tinoco, I. Jr.

1982-09-14

212

Reactions of carbon acids and 1,3-dipoles in the presence of ionic liquids  

NASA Astrophysics Data System (ADS)

The review is devoted to the use of ionic liquids as solvents, immobilized organocatalysts and reagents in reactions involving carbon acids and 1,3-dipoles, which are widely used to prepare practically valuable organic compounds of various classes. The characteristic features of processes in the presence of ionic liquids, the effects of the structure of cations and anions on the regio-, stereo- and enantioselectivities of reactions and methods of recovery of ionic liquids are considered.

Zlotin, Sergei G.; Makhova, Nina N.

2010-09-01

213

The Intramolecular Diels-Alder Reactions of Cycloalkenones: Stereoselectivity, Lewis Acid Acceleration, and Halogen Substituent Effects  

PubMed Central

The intramolecular Diels-Alder reactions of cycloalkenones and terminal dienes occur with high endo stere oselectivity, both thermally and under Lewis-acidic conditions. Through computations, we show that steric repulsion and tether conformation govern the selectivity of the reaction, and incorporation of either BF3 or ?-halogenation increases the rate of cycloaddition. With a longer tether, isomerization from a terminal diene to the more stable internal diene results in a more facile cycloaddition. PMID:24410341

Pham, Hung V.; Paton, Robert S.; Ross, Audrey G.; Danishefsky, Samuel J.; Houk, K. N.

2014-01-01

214

Coupling of hydrologic transport and chemical reactions in a stream affected by acid mine drainage  

USGS Publications Warehouse

Experiments in St. Kevin Gulch, an acid mine drainage stream, examined the coupling of hydrologic transport to chemical reactions affecting metal concentrations. Injection of LiCl as a conservative tracer was used to determine discharge and residence time along a 1497-m reach. Transport of metals downstream from inflows of acidic, metal-rich water was evaluated based on synoptic samples of metal concentrations and the hydrologic characteristics of the stream. Transport of SO4 and Mn was generally conservative, but in the subreaches most affected by acidic inflows, transport was reactive. Both 0.1-??m filtered and particulate Fe were reactive over most of the stream reach. Filtered Al partitioned to the particulate phase in response to high instream concentrations. Simulations that accounted for the removal of SO4, Mn, Fe, and Al with first-order reactions reproduced the steady-state profiles. The calculated rate constants for net removal used in the simulations embody several processes that occur on a stream-reach scale. The comparison between rates of hydrologie transport and chemical reactions indicates that reactions are only important over short distances in the stream near the acidic inflows, where reactions occur on a comparable time scale with hydrologic transport and thus affect metal concentrations.

Kimball, B.A.; Broshears, R.E.; Bencala, K.E.; McKnight, D.M.

1994-01-01

215

A study of rates of reaction of some substituted benzoic acids and diphenyldiazomethane  

E-print Network

LIBRAS Y 4 CIA COLLEGE OF TEXA A STUDY OF RATES OF REACTION OF SOME SUBSTITUTED BENZOIC ACIDS AND DIPHENYLDIAZOMETHANE A Thesis By JOHN S. WESTMORELAND Submitted to the Graduate School of the Agricultural and &chanical College of Texas... in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Ja~uara 1~97 N j t tj t t~t& t A STUDY OF REACTION RATES OF SOME SUBSTITUTED BENZOIC ACIDS AND DIPHENYLDIAZOMETHANE A Thesis JOHN S. VESTMORELAND Approved as to style...

Westmoreland, John Sherman

1957-01-01

216

Mechanism and stoichiometry of the redox reaction between iron(III) and caffeic acid  

Microsoft Academic Search

The stoichiometry of the redox reaction of caffeic acid with iron(III) was determined at pH 2.5. A linear increase in the\\u000a yield of iron(II) was found with increasing iron(III) concentration until reached constant values when iron(III)\\/caffeic acid\\u000a molar ratios were higher than 9. The reaction proceeds through two steps each having different rates, and involving intermediates\\u000a with different redox activities.

S. Deiana; C. Gessa; B. Manunza; M. Marchetti; M. Usai

1992-01-01

217

Constrained beta-proline analogues in organocatalytic aldol reactions: the influence of acid geometry.  

PubMed

7-Azabicyclo[2.2.1]heptane-2-carboxylic acid 11 was prepared in enantiopure form, and its catalytic potential in the direct aldol reaction between acetone and 4-nitrobenzaldehyde was assessed. The bicyclic system was found to be more selective than its monocyclic analogue beta-proline 5b. A comparative density functional theory study of proline 1, beta-proline 5b, and 11 in the latter reaction revealed the origin of the improved enantioselectivity of 11 over 5b. The geometry of the carboxylic acid group in the transition states, which depended critically on pyrrolidine ring conformation, was found to play a key role. PMID:19485343

Armstrong, Alan; Bhonoah, Yunas; White, Andrew J P

2009-07-17

218

Phase-Transfer-Catalyzed Asymmetric SN Ar Reaction of ?-Amino Acid Derivatives with Arene Chromium Complexes.  

PubMed

Although phase-transfer-catalyzed asymmetric SN Ar reactions provide unique contribution to the catalytic asymmetric ?-arylations of carbonyl compounds to produce biologically active ?-aryl carbonyl compounds, the electrophiles were limited to arenes bearing strong electron-withdrawing groups, such as a nitro group. To overcome this limitation, we examined the asymmetric SN Ar reactions of ?-amino acid derivatives with arene chromium complexes derived from fluoroarenes, including those containing electron-donating substituents. The arylation was efficiently promoted by binaphthyl-modified chiral phase-transfer catalysts to give the corresponding ?,?-disubstituted ?-amino acids containing various aromatic substituents with high enantioselectivities. PMID:25413360

Shirakawa, Seiji; Yamamoto, Kenichiro; Maruoka, Keiji

2015-01-12

219

Acid–base chemical reaction model for nucleation rates in the polluted atmospheric boundary layer  

PubMed Central

Climate models show that particles formed by nucleation can affect cloud cover and, therefore, the earth's radiation budget. Measurements worldwide show that nucleation rates in the atmospheric boundary layer are positively correlated with concentrations of sulfuric acid vapor. However, current nucleation theories do not correctly predict either the observed nucleation rates or their functional dependence on sulfuric acid concentrations. This paper develops an alternative approach for modeling nucleation rates, based on a sequence of acid–base reactions. The model uses empirical estimates of sulfuric acid evaporation rates obtained from new measurements of neutral molecular clusters. The model predicts that nucleation rates equal the sulfuric acid vapor collision rate times a prefactor that is less than unity and that depends on the concentrations of basic gaseous compounds and preexisting particles. Predicted nucleation rates and their dependence on sulfuric acid vapor concentrations are in reasonable agreement with measurements from Mexico City and Atlanta. PMID:23091030

Chen, Modi; Titcombe, Mari; Jiang, Jingkun; Jen, Coty; Kuang, Chongai; Fischer, Marc L.; Eisele, Fred L.; Siepmann, J. Ilja; Hanson, David R.; Zhao, Jun; McMurry, Peter H.

2012-01-01

220

Rapid identification of Stenotrophomonas maltophilia by peptide nucleic acid fluorescence in situ hybridization  

PubMed Central

The objective of this study was to develop a novel peptide nucleic acid (PNA) probe for Stenotrophomonas maltophilia identification by fluorescence in situ hybridization (FISH). The probe was evaluated using 33 human and veterinary clinical S. maltophilia isolates and 45 reference strains representing common bacterial species in the respiratory tract. The probe displayed 100% sensitivity and 100% specificity on pure cultures and allowed detection in sputum from cystic fibrosis patients. The detection limit was 104 CFU/mL in spiked tracheal aspirate and bronchoalveolar lavage from healthy horses. Altogether the study shows that this species-specific PNA FISH probe facilitates rapid detection of S. maltophilia in biological specimens. PMID:25356348

Hansen, N; Rasmussen, A K I; Fiandaca, M J; Kragh, K N; Bjarnsholt, T; Høiby, N; Stender, H; Guardabassi, L

2014-01-01

221

The Influence of Equilibrium Reactions on the Kinetics of Calcite Dissolution in Lactic Acid Solutions  

E-print Network

). As the environment becomes more extreme (higher temperature or less corrosion-resistant metallurgy), a higher loading of corrosion inhibitor or inhibitor intensifiers become necessary. These inhibitors, when combined with the other additives present..., there is a need for an alternative to HCl in high-temperature matrix acidizing environments or with acid- sensitive metallurgy. This alternative should have a lower reaction rate and a corrosion rate that can be inhibited...

Shedd, Daniel C

2014-08-07

222

Coupling of Hydrologic Transport and Chemical Reactions in a Stream Affected by Acid Mine Drainage  

Microsoft Academic Search

~~~~~ ~ Experiments in St. Kevin Gulch, an acid mine drainage stream, examined the coupling of hydrologic transport to chemical reactions affecting metal concentrations. Injec- tion of LiCl as a conservative tracer was used to determine discharge and residence time along a 1497-m reach. Transport of metals downstream from inflows of acidic, metal-rich water was evaluated based on synoptic samples

Briant A. Kimball; Robert E. Broshears; Kenneth E. Bencala; Diane M. McKnight

1994-01-01

223

Determination of Free Fatty Acids and Triglycerides by Gas Chromatography Using Selective Esterification Reactions  

SciTech Connect

A method for selectively determining both free fatty acids (FFA) and triacylglycerides (TAGs) in biological oils was investigated and optimized using gas chromatography after esterification of the target species to their corresponding fatty acid methyl esters (FAMEs). The method used acid catalyzed esterification in methanolic solutions under conditions of varying severity to achieve complete conversion of more reactive FFAs while preserving the concentration of TAGs. Complete conversion of both free acids and glycerides to corresponding FAMEs was found to require more rigorous reaction conditions involving heating to 120°C for up to 2 h. Method validation was provided using gas chromatography–flame ionization detection, gas chromatography–mass spectrometry, and liquid chromatography–mass spectrometry. The method improves on existing methods because it allows the total esterified lipid to be broken down by FAMEs contributed by FFA compared to FAMEs from both FFA and TAGs. Single and mixed-component solutions of pure fatty acids and triglycerides, as well as a sesame oil sample to simulate a complex biological oil, were used to optimize the methodologies. Key parameters that were investigated included: HCl-to-oil ratio, temperature and reaction time. Pure free fatty acids were found to esterify under reasonably mild conditions (10 min at 50°C with a 2.1:1 HCl to fatty acid ratio) with 97.6 ± 2.3% recovery as FAMEs, while triglycerides were largely unaffected under these reaction conditions. The optimized protocol demonstrated that it is possible to use esterification reactions to selectively determine the free acid content, total lipid content, and hence, glyceride content in biological oils. This protocol also allows gas chromatography analysis of FAMEs as a more ideal analyte than glyceride species in their native state.

Kail, Brian W.; Link, Dirk D.; Morreale, Bryan D

2012-11-01

224

Cleavage-based hybridization chain reaction for electrochemical detection of thrombin.  

PubMed

In the present work, we constructed a new label-free "inter-sandwich" electrochemical aptasensor for thrombin (TB) detection by employing a cleavage-based hybridization chain reaction (HCR). The designed single-stranded DNA (defined as binding DNA), which contained the thrombin aptamer binding sequence, a DNAzyme cleavage site and a signal reporter sequence, was first immobilized on the electrode. In the absence of a target TB, the designed DNAzymes could combine with the thrombin aptamer binding sequence via complementary base pairing, and then Cu(2+) could cleave the binding DNA. In the presence of a target TB, TB could combine with the thrombin aptamer binding sequence to predominantly form an aptamer-protein complex, which blocked the DNAzyme cleavage site and prevented the binding DNA from being cleaved by Cu(2+)-dependent DNAzyme. As a result, the signal reporter sequence could leave the electrode surface to trigger HCR with the help of two auxiliary DNA single-strands, A1 and A2. Then, the electron mediator hexaammineruthenium (III) chloride ([Ru(NH3)6](3+)) was embedded into the double-stranded DNA (dsDNA) to produce a strong electrochemical signal for the quantitative measurement of TB. For further amplification of the electrochemical signal, graphene reduced by dopamine (PDA-rGO) was introduced as a platform in this work. With this strategy, the aptasensor displayed a wide linearity in the range of 0.0001 nM to 50 nM with a low detection limit of 0.05 pM. Moreover, the resulting aptasensor exhibited good specificity and acceptable reproducibility and stability. Because of these factors, the fabrication protocol proposed in this work may be extended to clinical application. PMID:24971937

Chang, Yuanyuan; Chai, Yaqin; Xie, Shunbi; Yuan, Yali; Zhang, Juan; Yuan, Ruo

2014-09-01

225

Feasibility Study of Two Candidate Reaction Wheel/thruster Hybrid Control Architecture Designs for the Cassini Spacecraft  

NASA Technical Reports Server (NTRS)

As the first spacecraft to achieve orbit at Saturn in 2004, Cassini has collected science data throughout its four-year prime mission (2004-08), and has since been approved for a first and second extended mission through 2017. Cassini carries a set of three "fixed" reaction wheels and a backup reaction wheel (reaction wheel #4) is mounted on top of an articulable platform. If necessary, this platform could be articulated to orient the backup reaction wheel with the degraded wheel. The reaction wheels are used primarily for attitude control when precise and stable pointing of a science instrument such as the narrow angle camera is required. In 2001-02, reaction wheel #3 exhibited signs of bearing cage instability. As a result, reaction wheel #4 was articulated to align with reaction wheel #3. Beginning in July 2003, Cassini was controlled using wheel #1, #2, and #4. From their first use in the spring of 2000 until today, reaction wheels #1 and #2 have accumulated more than3.5 billions revolutions each. As such, in spite of very carefully management of the wheel spin rates by the mission operation team, there are some observed increases in the drag torque of the wheels' bearings. Hence, the mission operations team must prepare for the contingency scenario in which the reaction wheel #1 (in addition to wheel #3) had degraded. In this hypothetical fault scenario, the two remaining reaction wheels (#2 and #4) will not be able to provide precise and stable three-axis control of the spacecraft. In this study, we evaluate the feasibility of controlling Cassini using the two remaining reaction wheels and four thrusters to meet the science pointing requirements for two key science operational modes: the Optical Remote Sensing and Downlink, Fields, Particles, & Waves operation modes. The performance (e.g., pointing control error, pointing stability, hydrazine consumption rate, etc.) of the hybrid controllers in both operations scenarios will be compared with those achieved using an all-thruster controller design. Strength and weaknesses of the hybrid control architecture are assessed quantitatively.

Macala, Glenn A.; Lee, Allan Y.; Wang, Eric K.

2012-01-01

226

Is Trichloroacetic Acid an Insufficient Sample Quencher of Redox Reactions?  

PubMed Central

Abstract The global protein thiol pool has been reported to play a major role in the defense against oxidative stress as a redox buffer similar to glutathione. The present study uses a novel method to visualize cellular changes of the global protein thiol pool in response to induced oxidative stress. Unexpectedly, the results showed an uneven distribution of protein thiols in resting cells with no apparent change in their level or distribution in response to diamide as has been reported previously. Further analysis revealed that thiol pool oxidation is artificially high due to insufficient activity of the widely used sample quencher trichloroacetic acid (TCA). This suggests that previously published articles based on TCA as a quencher should be interpreted with caution as TCA could have caused similar artifacts. Overall, the results presented here question the major role for the global thiol pool in the defense against oxidative stress. Instead our hypothesis is that the fraction of proteins involved in response to oxidative stress is much smaller than previously anticipated in support of a fine-tuned cell signaling by redox regulation. Antioxid. Redox Signal. 18, 795–799. PMID:23043315

Curbo, Sophie; Reiser, Kathrin; Rundlöf, Anna-Klara; Karlsson, Anna

2013-01-01

227

Sequential injection analysis system for the sandwich hybridization-based detection of nucleic acids.  

PubMed

A sequential injection analysis lab-on-valve (SIA-LOV) system was developed for the specific detection of single-stranded nucleic acid sequences via sandwich hybridization of specific DNA probes to the target sequence. One DNA probe was tagged with fluorescein; the other was biotinylated and immobilized to streptavidin-coated porous beads. The system was optimized with respect to buffer composition, length of hybridization and wash steps, and volumes and concentrations of components used. On-bead oligonucleotide hybridization was studied using UV detection at 260 nm, while a final dose response curve was quantified using fluorescence detection. A dynamic range of 1-1000 pmol was obtained for a synthetic DNA sequence that was homologous to a segment in the B. anthracis atxA mRNA. A within-day variation of 7.2% and a day-to-day variation of 9.9% was observed. Each analysis was completed within 20 min. Subsequently, the system was applied to the detection of atxA mRNA expressed in a surrogate organism and amplified using NASBA. The SIA-LOV will find its application in routine laboratory-based analysis of specific single-stranded DNA/RNA sequences. Future improvements will include the integration of dye-encapsulating liposomes for signal enhancement used in lieu of the single fluorophore-labeled probe in order to lower the limit of detection. PMID:16536433

Edwards, Katie A; Baeumner, Antje J

2006-03-15

228

The reaction of hyaluronic acid and its monomers, glucuronic acid and N-acetylglucosamine, with reactive oxygen species  

Microsoft Academic Search

Synovial fluid is a ?0.15% (w\\/v) aqueous solution of hyaluronic acid (HA), a polysaccharide consisting of alternating units of GlcA and GlcNAc. In synovial fluid of patients suffering from rheumatoid arthritis, HA is thought to be degraded either by radicals generated by Fenton chemistry (Fe2+\\/H2O2) or by NaOCl generated by myeloperoxidase. We investigated the course of model reactions of these

Michael Jahn; John W Baynes; Gerhard Spiteller

1999-01-01

229

Crude palm oil from interspecific hybrid Elaeis oleifera×Elaeis guineensis: fatty acid regiodistribution and molecular species of glycerides.  

PubMed

The composition and structure of triacylglycerols (TAGs) and partial glycerides of crude palm oil obtained from interspecific hybrid Elaeis oleifera×Elaeis guineensis, grown in Colombia, were fully characterised and compared to data obtained by analysing crude African palm oil. Hybridisation appears to substantially modify the biosynthesis of fatty acids (FAs) rather than their assembly in TAGs. In fact, total FAs analysis showed significant differences between these two types of oil, with hybrid palm oil having a higher percentage of oleic acid (54.6 ± 1.0 vs 41.4 ± 0.3), together with a lower saturated fatty acid content (33.5 ± 0.5 vs 47.3 ± 0.1), while the percentage of essential fatty acid, linoleic acid, does not undergo significant changes. Furthermore, 34 TAG types were identified, with no qualitative differences between African and E. guineensis×E. oleifera hybrid palm oil samples. Short and medium chain FAs (8:0, 10:0, 12:0, 14:0) were utilised, together, to build a restricted number of TAG molecular species. Oil samples from the E. guineensis×E. oleifera hybrid showed higher contents of monosaturated TAGs (47.5-51.0% vs 36.7-37.1%) and triunsaturated TAGs (15.5-15.6% vs 5.2-5.4%). The sn-2 position of TAGs in hybrid palm oil was shown to be predominantly esterified with oleic acid (64.7-66.0 mol% vs 55.1-58.2 mol% in African palm oil) with only 10-15% of total palmitic acid and 6-20% of stearic acid acylated in the secondary position. The total amount of diacylglycerols (DAGs) was in agreement with the values of free acidity; DAG types found were in agreement with the representativeness of different TAG species. PMID:23768354

Mozzon, Massimo; Pacetti, Deborah; Lucci, Paolo; Balzano, Michele; Frega, Natale Giuseppe

2013-11-01

230

Environmentally Benign Lewis Acid Promoted [2+3]-Dipolar Cycloaddition Reactions of Nitrile Imines with Alkenes in Water  

PubMed Central

Mild and environmentally benign Lewis acid promoted 1,3-dipolar cycloaddition reactions of ?-hydrazonyl chlorides with alkenes in water are reported. These ?-hydrazonyl chlorides, in the presence of Lewis acids, generate nitrile imines in situ which react with dipolarophiles to furnish the corresponding cycloaddition products. In many cases, the required times for the completion of the Lewis acid promoted 1,3-dipolar cycloaddition reactions in water were comparable to the equivalent reactions performed in an organic solvent. Analogous tetrahexylammonium chloride promoted 1,3-dipolar cycloaddition reactions were also performed. The comparison of reaction times and cycloadduct yields for the aforementioned 1,3-dipolar reactions in aqueous and organic media as well as the proposed role of the Lewis acid in the 1,3-dipolar cycloaddition reaction are described. PMID:24659908

Dadiboyena, Sureshbabu

2014-01-01

231

Fatty acid membrane assembly on coacervate microdroplets as a step towards a hybrid protocell model.  

PubMed

Mechanisms of prebiotic compartmentalization are central to providing insights into how protocellular systems emerged on the early Earth. Protocell models are based predominantly on the membrane self-assembly of fatty-acid vesicles, although membrane-free scenarios that involve liquid-liquid microphase separation (coacervation) have also been considered. Here we integrate these alternative models of prebiotic compartmentalization and develop a hybrid protocell model based on the spontaneous self-assembly of a continuous fatty-acid membrane at the surface of preformed coacervate microdroplets prepared from cationic peptides/polyelectrolytes and adenosine triphosphate or oligo/polyribonucleotides. We show that the coacervate-supported membrane is multilamellar, and mediates the selective uptake or exclusion of small and large molecules. The coacervate interior can be disassembled without loss of membrane integrity, and fusion and growth of the hybrid protocells can be induced under conditions of high ionic strength. Our results highlight how notions of membrane-mediated compartmentalization, chemical enrichment and internalized structuration can be integrated in protocell models via simple chemical and physical processes. PMID:24848239

Dora Tang, T-Y; Rohaida Che Hak, C; Thompson, Alexander J; Kuimova, Marina K; Williams, D S; Perriman, Adam W; Mann, Stephen

2014-06-01

232

Asymmetric Dearomatization of ?-Naphthols through an Amination Reaction Catalyzed by a Chiral Phosphoric Acid.  

PubMed

A highly efficient catalytic asymmetric dearomatization of naphthols by means of an electrophilic amination reaction catalyzed by chiral phosphoric acid is presented. This protocol provides a facile access to functionalized ?-naphthalenone compounds with a chiral quaternary carbon center in excellent yields and enantioselectivity (up to 99?% yield, up to 96?%?ee). PMID:25414091

Wang, Shou-Guo; Yin, Qin; Zhuo, Chun-Xiang; You, Shu-Li

2015-01-01

233

Heterogeneous reactions in sulfuric acid aerosols: A framework for model calculations  

Microsoft Academic Search

A framework for applying rates of heterogeneous chemical reactions measured in the laboratory to small sulfuric acid aerosols found in the stratosphere is presented. The procedure for calculating the applicable reactive uptake coefficients using laboratory-measured parameters is developed, the necessary laboratory-measured quantities are discussed, and a set of equations for use in models are presented. This approach is demonstrated to

David R. Hanson; A. R. Ravishankara; Susan Solomon

1994-01-01

234

Examples of acid-catalyzed mineral dissolution reactions resulting in pH  

E-print Network

Examples of acid-catalyzed mineral dissolution reactions resulting in pH buffering: The goal and analyzed by the Alberta Geological Survey. Percent mineral composition for each sample is presented sample was assumed to have a porosity of 20% and a total rock mass of 12 kg. 4.61 Calcite(78), Quartz(18

Peters, Catherine A.

235

Reaction of K2PdCl4 with Synthetic and Natural Nucleic Acids  

Microsoft Academic Search

Circular dichroism was used to study reaction of K2PdCl4 with polydeoxyribonucleotides and calf thymus DNA. The optical and structural characteristics of the molecular components were determined to show that K2PdCl4 reacts with natural and synthetic acids, producing profound rearrangements in their structure.

N. Yu. Fomina; O. A. Chaplygina; A. D. Shebaldova; V. B. Borodulin

2002-01-01

236

Breathing spiral waves in the chlorine dioxideiodinemalonic acid reaction-diffusion system Igal Berenstein,1  

E-print Network

Breathing spiral waves in the chlorine dioxide­iodine­malonic acid reaction-diffusion system Igal 2008; published 11 August 2008 Breathing spiral waves are observed in the oscillatory chlorine dioxide generated period-2 oscillations 5,6 . Here we report obser- vation of BSW in the oscillatory chlorine

Epstein, Irving R.

237

Control of the Chlorine Dioxide-Iodine-Malonic Acid Oscillating Reaction by Illumination  

E-print Network

Control of the Chlorine Dioxide-Iodine-Malonic Acid Oscillating Reaction by Illumination Alberto P, Massachusetts 02454-9110 ReceiVed April 1, 1999 Abstract: We show that illumination of the chlorine dioxide, in which iodine atoms produced by photodissociation of molecular iodine initiate reduction of chlorine

Epstein, Irving R.

238

Detection of Acidithiobacillus ferrooxidans in acid mine drainage environments using fluorescent in situ hybridization (FISH).  

PubMed

An important microorganism of acid mine drainage (AMD) and bioleaching environments is Acidithiobacillus ferrooxidans which oxidizes ferrous iron and generates ferric iron, an oxidant. Most investigations to understand microbial aspects of sulfide mineral dissolution have focused on understanding physiological, metabolic, and genetic characteristics of A. ferrooxidans. In this study, a 16S rRNA oligonucleotide probe designated S-S-T.ferr-0584-a-A-18, and labeled at the 5'-end with indocarbocyanine dye (CY3), was used in a fluorescent in situ hybridization (FISH) procedure on pure cultures of nine isolates of A. ferrooxidans. These isolates were recovered from acid mine drainage and mining environments. The probe was also used to detect cells of A. ferrooxidans, recovered from AMD samples, growing on FeTSB and FeSo solid media in a FISH procedure. In addition, the presence of cells of A. ferrooxidans in an environmental water sample from an AMD site in Copper Cliff, Ontario, Canada was analyzed using the FISH technique. Probe specificity was first confirmed with A. ferrooxidans ATCC 19859 (positive control) and Acidithiobacillus thiooxidans ATCC 19377, Acidiphilium acidophilum ATCC 27807, and Lactobacillus plantarum ATCC 8014 (negative controls). Positive and negative control cells were also used to determine optimal stringency conditions for hybridizations with the probe. Cells of the nine isolates of A. ferrooxidans stained positive, although the fluorescent signal varied in intensity from isolate to isolate. Colonies of A. ferrooxidans from the environmental water sample of the AMD site were recovered only on FeTSB solid medium after 22 days of incubation. The probe was able to detect cells of A. ferrooxidans in a FISH procedure. However, no cells of A. ferrooxidans were detected in the AMD water sample without cultivation. Thus, probe S-S-T.ferr-0584-a-A-18 hybridized effectively with cells of A. ferrooxidans recovered from pure cultures but failed to directly detect cells of A. ferrooxidans in the AMD site. PMID:15676194

Mahmoud, K K; Leduc, L G; Ferroni, G D

2005-04-01

239

Effect of channel length on the electrical response of carbon nanotube field-effect transistors to deoxyribonucleic acid hybridization  

PubMed Central

Summary A single-walled carbon nanotube (SWCNT) in a field-effect transistor (FET) configuration provides an ideal electronic path for label-free detection of nucleic acid hybridization. The simultaneous influence of more than one response mechanism in hybridization detection causes a variation in electrical parameters such as conductance, transconductance, threshold voltage and hysteresis gap. The channel length (L) dependence of each of these parameters necessitates the need to include them when interpreting the effect of L on the response to hybridization. Using the definitions of intrinsic effective mobility (µe) and device field-effect mobility (µf), two new parameters were defined to interpret the effect of L on the FET response to hybridization. Our results indicate that FETs with ?300 µm long SWCNT exhibited the most appreciable response to hybridization, which complied with the variation trend in response to the newly defined parameters.

An, Jianing; Zhang, Yani; Wong, Chee How

2014-01-01

240

Synthesis of pyrrolidine derivatives by a platinum/brønsted Acid relay catalytic cascade reaction.  

PubMed

A new catalytic reaction for the synthesis of pyrrolidine derivatives is presented. The method implies the coupling of N-Boc-protected alkynamine derivatives and appropriate alkenes or alkynes in a process catalysed by a platinum/triflic acid catalytic binary system. This reaction is believed to proceed through a cascade process implying an initial platinum-catalysed cycloisomerization of the alkynamine derivative followed by a triflic acid promoted nucleophilic addition of the alkene or alkyne and trapping of the cationic species formed by the Boc group. Not only simple alkenes and alkynes were used in this reaction but also allyltrimethylsilane and propargyltrimethylsilane. Particularly, when allyltrimethylsilane is used as the alkene counterpart interesting bicyclic compounds containing a trimethylsilane group are obtained. However, when propargyltrimethylsilane is used in the presence of water we observed the formation of a related bicyclic compound lacking the trimethylsilane group and containing an exocyclic carbon?carbon bond. PMID:25557076

Galván, Alicia; Calleja, Jonás; Fañanás, Francisco J; Rodríguez, Félix

2015-02-16

241

Geminal Brønsted Acid Ionic Liquids as Catalysts for the Mannich Reaction in Water  

PubMed Central

Quaternary ammonium geminal Brønsted acid ionic liquids (GBAILs) based on zwitterionic 1,2-bis[N-methyl-N-(3-sulfopropyl)-alkylammonium]ethane (where the carbon number of the alkyl chain is 4, 8, 10, 12, 14, 16, or 18) and p-toluenesulfonic acid monohydrate were synthesized. The catalytic ionic liquids were applied in three-component Mannich reactions with an aldehyde, ketone, and amine at 25 °C in water. The effects of the type and amount of catalyst and reaction time as well as the scope of the reaction were investigated. Results showed that GBAIL-C14 has excellent catalytic activity and fair reusability. The catalytic procedure was simple, and the catalyst could be recycled seven times via a simple separation process without noticeable decreases in catalytic activity. PMID:24837832

He, Leqin; Qin, Shenjun; Chang, Tao; Sun, Yuzhuang; Zhao, Jiquan

2014-01-01

242

Glutathione peroxidase's reaction intermediate selenenic acid is stabilized by the protein microenvironment.  

PubMed

Selenenic acids are highly reactive intermediates of selenoproteins' enzymatic reactions. Knowledge of how the protein environment protects and stabilizes them is fundamental not only to descriptions of selenoproteins' reactivity but also potentially for proteomics and therapeutics. However, selenenic acids are considered particularly short-lived and are not yet identified in wild-type selenoproteins. Here, we report trapping the selenenic acid in glutathione peroxidase, an antioxidant enzyme that efficiently eliminates hydroperoxides. It has long been thought that selenium-containing glutathione peroxidases form a selenenic acid intermediate. However, this putative species has eluded detection. Here, we report its identification. The selenenic acid in bovine glutathione peroxidase 1 was chemically trapped using dimedone, an alkylating agent specific to sulfenic and selenenic acids. The alkylation of the catalytic selenocysteine was verified by electrospray ionization mass spectrometry. In the presence of glutathione, the selenocysteine was not alkylated because the selenenic acid condenses faster with glutathione than the alkylation reaction. In the absence of thiols, the selenenic acid was surprisingly long-lived with 95% of the protein still able to react with dimedone 10 min after hydrogen peroxide was removed, indicating that the protein environment stabilizes the selenenic acid by shielding it from reactive groups in the protein. After 30 min, the selenocysteine was no longer modified but became accessible once the protein was exposed to reducing agents. This suggests that the selenenic acid reacted with a protein's amide or amine to form a selenylamide bond. Such a modification may play a role in protecting glutathione peroxidase?' reactivity. PMID:25124921

Li, Fei; Liu, Jun; Rozovsky, Sharon

2014-11-01

243

Design of hybrid multimodal poly(lactic-co-glycolic acid) polymer nanoparticles for neutrophil labeling, imaging and tracking  

NASA Astrophysics Data System (ADS)

Poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) incorporating quantum dots (QDs), superparamagnetic iron oxide nanoparticles (SPIONs) and gold (Au) NPs for neutrophil labeling were fabricated via the w/o/w double emulsion method. QDs and SPIONs were entrapped in the PLGA core during emulsification while Au NPs were assembled on top of the PLGA NPs via electrostatic interactions. Transmission Electron Microscopy, Scanning Electron Microscopy and Confocal Scanning Laser Microscopy (CLSM) were applied to characterize the hybrid PLGA NPs. The uptake of the hybrid PLGA NPs by human neutrophils was studied by Flow Cytometry and confocal microscopy. In addition, the induction of reactive oxygen species (ROS) in neutrophils after incubation with the hybrid PLGA NPs was assessed. Magnetophoresis experiments showed that neutrophils with internalized hybrid PLGA NPs can be effectively laterally displaced towards the magnetic field. Magnetic Resonance Imaging of the hybrid PLGA NPs resulted in images with a contrast enhancement linearly dependent on the concentration of the hybrid PLGA NPs. Research reported in this work is relevant for imaging, tracking and manipulating neutrophils and has potential for in vivo applications, e.g., tumor visualization and localized photothermal treatment.Poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) incorporating quantum dots (QDs), superparamagnetic iron oxide nanoparticles (SPIONs) and gold (Au) NPs for neutrophil labeling were fabricated via the w/o/w double emulsion method. QDs and SPIONs were entrapped in the PLGA core during emulsification while Au NPs were assembled on top of the PLGA NPs via electrostatic interactions. Transmission Electron Microscopy, Scanning Electron Microscopy and Confocal Scanning Laser Microscopy (CLSM) were applied to characterize the hybrid PLGA NPs. The uptake of the hybrid PLGA NPs by human neutrophils was studied by Flow Cytometry and confocal microscopy. In addition, the induction of reactive oxygen species (ROS) in neutrophils after incubation with the hybrid PLGA NPs was assessed. Magnetophoresis experiments showed that neutrophils with internalized hybrid PLGA NPs can be effectively laterally displaced towards the magnetic field. Magnetic Resonance Imaging of the hybrid PLGA NPs resulted in images with a contrast enhancement linearly dependent on the concentration of the hybrid PLGA NPs. Research reported in this work is relevant for imaging, tracking and manipulating neutrophils and has potential for in vivo applications, e.g., tumor visualization and localized photothermal treatment. Electronic supplementary information (ESI) available: TEM images of QDs, SPIONs and Au NPs; UV emission spectra of QDs and hybrid PLGA NPs; the EDX spectrum of PLGA_QD_SPION NPs; the size and zeta potential of hybrid PLGA NPs; magnetophoresis of neutrophils with hybrid particles (movie). See DOI: 10.1039/c3nr04013e

Qiu, Yuan; Palankar, Raghavendra; Echeverría, María; Medvedev, Nikolay; Moya, Sergio E.; Delcea, Mihaela

2013-11-01

244

One-pot transformation of cellobiose to formic acid and levulinic acid over ionic-liquid-based polyoxometalate hybrids.  

PubMed

Currently, levulinic acid (LA) and formic acid (FA) are considered as important carbohydrates for the production of value-added chemicals. Their direct production from biomass will open up a new opportunity for the transformation of biomass resource to valuable chemicals. In this study, one-pot transformation of cellobiose into LA and FA was demonstrated, using a series of multiple-functional ionic liquid-based polyoxometalate (IL-POM) hybrids as catalytic materials. These IL-POMs not only markedly promoted the production of valuable chemicals including LA, FA and monosaccharides with high selectivities, but also provided great convenience of the recovery and the reuse of the catalytic materials in an environmentally friendly manner. Cellobiose conversion of 100%, LA selectivity of 46.3%, and FA selectivity of 26.1% were obtained at 423?K and 3?MPa for 3?h in presence of oxygen. A detailed catalytic mechanism for the one-pot transformation of cellobiose was also presented. PMID:25110998

Li, Kaixin; Bai, Linlu; Amaniampong, Prince Nana; Jia, Xinli; Lee, Jong-Min; Yang, Yanhui

2014-09-01

245

Facile construction of macroporous hybrid monoliths via thiol-methacrylate Michael addition click reaction for capillary liquid chromatography.  

PubMed

A facile approach based on thiol-methacrylate Michael addition click reaction was developed for construction of porous hybrid monolithic materials. Three hybrid monoliths were prepared via thiol-methacrylate click polymerization by using methacrylate-polyhedral oligomeric silsesquioxane (POSS) (cage mixture, n=8, 10, 12, POSS-MA) and three multi-thiol crosslinkers, 1,6-hexanedithiol (HDT), trimethylolpropane tris(3-mercaptopropionate) (TPTM) and pentaerythritol tetrakis(3-mercaptopropionate) (PTM), respectively, in the presence of porogenic solvents (n-propanol and PEG 200) and a catalyst (dimethylphenylphosphine, DMPP). The obtained monoliths possessed high thermal and chemical stabilities. Besides, they all exhibited high column efficiencies and excellent separation abilities in capillary liquid chromatography (cLC). The highest column efficiency could reach ca. 195,000N/m for butylbenzene on the monolith prepared with POSS-MA and TPTM (monolith POSS-TPTM) in reversed-phase (RP) mode at 0.64mm/s. Good chromatographic performance were all achieved in the separations of polycyclic aromatic hydrocarbons (PAHs), phenols, anilines, EPA 610 as well as bovine serum albumin (BSA) digest. The high column efficiencies in the range of 51,400-117,000N/m (achieved on the monolith POSS-PTM in RP mode) convincingly demonstrated the high separation abilities of these thiol-methacrylate based hybrid monoliths. All the results demonstrated the feasibility of the phosphines catalyzed thiol-methacrylate Michael addition click reaction in fabrication of monolithic columns with high efficiency for cLC applications. PMID:25543303

Lin, Hui; Ou, Junjie; Liu, Zhongshan; Wang, Hongwei; Dong, Jing; Zou, Hanfa

2015-01-30

246

Hypochlorous acid-mediated protein oxidation: how important are chloramine transfer reactions and protein tertiary structure?  

PubMed

Hypochlorous acid (HOCl) is a powerful oxidant generated from H2O2 and Cl- by the heme enzyme myeloperoxidase, which is released from activated leukocytes. HOCl possesses potent antibacterial properties, but excessive production can lead to host tissue damage that occurs in numerous human pathologies. As proteins and amino acids are highly abundant in vivo and react rapidly with HOCl, they are likely to be major targets for HOCl. In this study, two small globular proteins, lysozyme and insulin, have been oxidized with increasing excesses of HOCl to determine whether the pattern of HOCl-mediated amino acid consumption is consistent with reported kinetic data for isolated amino acids and model compounds. Identical experiments have been carried out with mixtures of N-acetyl amino acids (to prevent reaction at the alpha-amino groups) that mimic the protein composition to examine the role of protein structure on reactivity. The results indicate that tertiary structure facilitates secondary chlorine transfer reactions of chloramines formed on His and Lys side chains. In light of these data, second-order rate constants for reactions of Lys side chain and Gly chloramines with Trp side chains and disulfide bonds have been determined, together with those for further oxidation of Met sulfoxide by HOCl and His side chain chloramines. Computational kinetic models incorporating these additional rate constants closely predict the experimentally observed amino acid consumption. These studies provide insight into the roles of chloramine formation and three-dimensional structure on the reactions of HOCl with isolated proteins and demonstrate that kinetic models can predict the outcome of HOCl-mediated protein oxidation. PMID:17676767

Pattison, David I; Hawkins, Clare L; Davies, Michael J

2007-08-28

247

Reaction of dopa decarboxylase with L-aromatic amino acids under aerobic and anaerobic conditions.  

PubMed Central

Analysis of the reaction of dopa decarboxylase (DDC) with L-dopa reveals that loss of decarboxylase activity with time is observed at enzyme concentrations approximately equal to the binding constant, K(d), of the enzyme for pyridoxal 5'-phosphate (PLP). Instead, at enzyme concentrations higher than K(d) the course of product formation proceeds linearly until complete consumption of the substrate. Evidence is provided that under both experimental conditions no pyridoxamine 5'-phosphate (PMP) is formed during the reaction and that dissociation of coenzyme occurs at low enzyme concentration, leading to the formation of a PLP-L-dopa Pictet-Spengler cyclic adduct. Taken together, these results indicate that decarboxylation-dependent transamination does not accompany the decarboxylation of L-dopa proposed previously [O'Leary and Baughn (1977) J. Biol. Chem. 252, 7168-7173]. Nevertheless, when the reaction of DDC with L-dopa is studied under anaerobic conditions at an enzyme concentration higher than K(d), we observe that (1) the enzyme is gradually inactivated and inactivation is associated with PMP formation and (2) the initial velocity of decarboxylation is approximately half of that in the presence of O(2). Similar behaviour is observed by comparing the reaction with L-5-hydroxytryptophan occurring in aerobiosis or in anaerobiosis. Therefore the reaction of DDC with L-aromatic amino acids seems to be under O(2) control. In contrast, the reactivity of the enzyme with L-aromatic amino acids does not change in the presence or absence of O(2). These and other results, together with previous results on the effect exerted by O(2) on reaction specificity of DDC towards aromatic amines [Bertoldi, Frigeri, Paci and Borri Voltattorni (1999) J. Biol. Chem. 274, 5514-5521], suggest a productive effect of O(2) on an intermediate complex of the reaction of the enzyme with L-aromatic amino acids or aromatic amines. PMID:11085948

Bertoldi, M; Borri Voltattorni, C

2000-01-01

248

Reaction of 5-Aminosalicylic Acid with Peroxyl Radicals: Protection and Recovery by Ascorbic Acid and Amino Acids  

Microsoft Academic Search

Purpose. The aims of the study are to analyze the interaction between 5-aminosalicylic acid (5-ASA) and peroxyl radicals and to evaluate the effect of some endogenous compounds such as ascorbic acid and amino acids on the oxidation of 5-ASA induced by 2,2 0 -azo-bis(2-amidinopropane) dihydrochloride. Methods. The consumption and\\/or the recovery of 5-ASA (7.6 mM) exposed to a peroxyl radical

Camilo López-Alarcón; Claudia Rocco; Eduardo Lissi; Catalina Carrasco; J. Arturo Squella; Luis Nuñez-Vergara; Hernan Speisky

2005-01-01

249

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

250

Thermodynamical characteristics of the reaction of pyridoxal-5'-phosphate with L-amino acids in aqueous buffer solution  

NASA Astrophysics Data System (ADS)

The reaction of pyridoxal-5'-phosphate with L-isomers of alanine, lysine, arginine, aspartic acid, glutamic acid, and glycine in phosphate buffer solution was studied by absorption spectroscopy and the calorimetry of dissolution at physiological acidity of the medium (pH 7.35). The formation constants of Schiff bases during reactions and changes in Gibbs energy, enthalpy, and entropy were determined. It was shown that the formation constant of the Schiff base and its spectral properties depend on the nature of the bound amino acid. The progress of the reaction with a majority of amino acids is governed by the entropy factor due to the predominant role of the dehydration effect of the reaction center of amino acids during chemical reactions. The intramolecular electrostatic interaction of an ionized phosphate group with the positively charged amino group on the end of the chain of amino acid residue stabilizes the Schiff bases formed by lysine and arginine. The extinction coefficient of the base, equilibrium constant, and the exothermic effect of the reaction then increase. The excess negative charge on the end of the chain of amino acid residues of aspartic and glutamic acids destabilizes the molecule of the Schiff base. In this case, the equilibrium constant decreases and the endothermic effect of the reaction increases.

Barannikov, V. P.; Badelin, V. G.; Venediktov, E. A.; Mezhevoi, I. N.; Guseinov, S. S.

2011-01-01

251

Kinetics of the reaction between Pu(III) and Fe(III) in nitric acid solution  

SciTech Connect

The kinetics of the reaction between Pu/sup (III)/ and Fe/sup (III)/ in an aqueous nitric acid solution in the presence of persulfate ions at a constant ionic strength of the solution was studied spectrophotometrically. It was shown that the reaction is first order with respect to the reagents; its rate is practically independent of the concentration of the H/sup +/ and S/sub 2/O/sub 8//sup 2 -/ ions and with increase in the analytical HNO/sub 3/ concentration at variable ionic strength, it first increases, and then decreases. The temperature dependence of the reaction was determined, and its thermodynamic activation parameters were calculated. A possible mechanism for the reaction between Pu/sup (III)/ and Fe/sup (III)/ was proposed.

Koltunov, V.S.; Zhuravleva, G.I.

1988-01-01

252

Reaction of single-cross hybrid corn to sorghum yellow banding virus  

E-print Network

range studies (8) were done by air-gun inoculation techniques. Millet, Setaria italica; ten cultivars of grain sorghum, ~ghum ~o~lo; six of sudangrass, sudanese; and four of corn, Zea ~ma s were found to be hosts of SYBV. It was observed that among... hybrids inoculated with SYBV. Correlation coefficients between agronomic characters of 15 single-cross hybrids inoculated with SYBV 46 IMTRODUCTIOM Corn (~ gaa L. ) is the world's second leading cereal crop after wheat. In the United States, however...

Pe, Aye

1990-01-01

253

Palladium nanoparticle-graphene hybrids as active catalysts for the Suzuki reaction  

Microsoft Academic Search

Graphene has been successfully modified with palladium nanoparticles in a facile manner by reducing palladium acetate [Pd(OAc)2] in the present of sodium dodecyl sulfate (SDS), which is used as both surfactant and the reducing agent. The palladium nanoparticle-graphene\\u000a hybrids (Pd-graphene hybrids) are characterized by high-resolution transmission electron microscopy, atomic force microscopy,\\u000a Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and energy

Yang Li; Xiaobin Fan; Junjie Qi; Junyi Ji; Shulan Wang; Guoliang Zhang; Fengbao Zhang

2010-01-01

254

Ozone Sensitivity in Hybrid Poplar Correlates with Insensitivity to Both Salicylic Acid and Jasmonic Acid. The Role of Programmed Cell Death in Lesion Formation1  

Microsoft Academic Search

Our earlier studies demonstrated that the ozone-sensitive hybrid poplar clone NE-388 displays an attenuated level of ozone-, wound-, and phytopathogen-induced defense gene expression. To determine if this reduced gene activation involves signal transduction pathways dependent on salicylic acid (SA) and\\/or jasmonic acid (JA), we compared the responses of NE-388 and an ozone-tolerant clone, NE-245, to these signal molecules. JA levels

Jennifer Riehl Koch; Robert A. Creelman; Steven M. Eshita; Mirjana Seskar; John E. Mullet; Keith R. Davis

2000-01-01

255

Exposing the hidden complexity of stoichiometric and catalytic metathesis reactions by elucidation of Mg-Zn hybrids.  

PubMed

Studying seemingly simple metathesis reactions between ZnCl(2) and (t)BuMgCl has, surprisingly, revealed a much more complex chemistry involving mixed magnesium-zinc compounds that could be regarded as Mg-Zn hybrids. Thus, the reaction of equimolar amounts of ZnCl(2) and (t)BuMgCl reveals the formation of the unprecedented mixed Mg-Zn complex [(THF)(4)Mg(mu-Cl)(2)Zn((t)Bu)(Cl)] (1), as a result of the co-complexation of the two anticipated exchange products of the metathesis. This magnesium zincate adopts a contacted ion-pair structure, closely related to Knochel's pioneering "Turbo" Grignard reagents. Furthermore, a second coproduct identified in this reaction is the solvent-separated mixed magnesium-zinc chloride complex [{Mg(THF)(6)}(2+){Zn(2)Cl(6)}(2-)] (3) that critically diminishes the amount of ZnCl(2) available for the intended metathesis reaction to take place. In another surprising result, when the reaction is carried out by using an excess of 3 M equivalents of the Grignard reagent (closer to the catalytic conditions employed by synthetic chemists), solvent-separated magnesium trialkyl zincate [{Mg(2)Cl(3)(THF)(6)}(+){Zn((t)Bu)(3)}(-)] (4) is obtained that can be viewed as a model for the active species involved in the increasingly important organic transformations of Grignard reagents catalysed by ZnCl(2). Furthermore, preliminary reactivity studies reveal that complex 4 can be used as an effective new reagent for direct Zn-I exchange reactions that allow the preparation and structural identification of the magnesium tris(aryl) zincate [{Mg(2)Cl(3)(THF)(6)}(+){Zn(p-Tol)(3)}(-)] (5) that represents the first example of complete 3-fold activation of a zincate in a Zn-I exchange reaction which, in turn, can efficiently be used as a precursor for Negishi cross-coupling reactions. PMID:20212145

Hevia, Eva; Chua, Jonathan Z; García-Alvarez, Pablo; Kennedy, Alan R; McCall, Matthew D

2010-03-23

256

Exposing the hidden complexity of stoichiometric and catalytic metathesis reactions by elucidation of Mg-Zn hybrids  

PubMed Central

Studying seemingly simple metathesis reactions between ZnCl2 and tBuMgCl has, surprisingly, revealed a much more complex chemistry involving mixed magnesium-zinc compounds that could be regarded as Mg-Zn hybrids. Thus, the reaction of equimolar amounts of ZnCl2 and tBuMgCl reveals the formation of the unprecedented mixed Mg-Zn complex [(THF)4Mg(?-Cl)2Zn(tBu)(Cl)] (1), as a result of the co-complexation of the two anticipated exchange products of the metathesis. This magnesium zincate adopts a contacted ion-pair structure, closely related to Knochel’s pioneering “Turbo” Grignard reagents. Furthermore, a second coproduct identified in this reaction is the solvent-separated mixed magnesium-zinc chloride complex [{Mg(THF)6}2+{Zn2Cl6}2-] (3) that critically diminishes the amount of ZnCl2 available for the intended metathesis reaction to take place. In another surprising result, when the reaction is carried out by using an excess of 3 M equivalents of the Grignard reagent (closer to the catalytic conditions employed by synthetic chemists), solvent-separated magnesium trialkyl zincate [{Mg2Cl3(THF)6}+{Zn(tBu)3}-] (4) is obtained that can be viewed as a model for the active species involved in the increasingly important organic transformations of Grignard reagents catalysed by ZnCl2. Furthermore, preliminary reactivity studies reveal that complex 4 can be used as an effective new reagent for direct Zn-I exchange reactions that allow the preparation and structural identification of the magnesium tris(aryl) zincate [{Mg2Cl3(THF)6}+{Zn(p-Tol)3}-] (5) that represents the first example of complete 3-fold activation of a zincate in a Zn-I exchange reaction which, in turn, can efficiently be used as a precursor for Negishi cross-coupling reactions. PMID:20212145

Hevia, Eva; Chua, Jonathan Z.; García-Álvarez, Pablo; Kennedy, Alan R.; McCall, Matthew D.

2010-01-01

257

Heterogeneous Reactions of ClONO2, HCl, and HOCl on Liquid Sulfuric Acid Surfaces  

NASA Technical Reports Server (NTRS)

The heterogeneous reactions of ClONO2 + H2O yields HNO3 + HOCl (1), ClONO2 + HCl yields C12 + HNO3 (2), and HOCl + HCl yields Cl2 + H2O (3) on liquid sulfuric acid surfaces have been studied using a fast flow reactor coupled to a quadrupole mass spectrometer. The main objectives of the study are to investigate: (a) the temperature dependence of these reactions at a fixed H2O partial pressure typical of the lower stratosphere (that is, by changing temperature at a constant water partial pressure, the H2SO4 content of the surfaces is also changed), (b) the relative importance or competition between reactions 1 and 2, and (c) the effect of HNO3 on the reaction probabilities due to the formation of a H2SO4/HNO3/H2O ternary system. The measurements show that all the reactions depend markedly on temperature at a fixed H2O partial pressure: they proceed efficiently at temperatures near 200 K and much slower at temperatures near 220 K. The reaction probability (gamma(sub 1)) for ClONO2 hydrolysis approaches 0.01 at temperatures below 200 K, whereas the values for gamma(sub 2) and gamma(sub 3) are on the order of a few tenths at 200 K. Although detailed mechanisms for these reactions are still unknown, the present data indicate that the competition between ClONO2 hydrolysis and ClONO2 reaction with HCl may depend on temperature (or H2SO4 Wt %): in the presence of gaseous HCl at stratospheric concentrations, reaction 2 is dominant at lower temperatures (less than 200 K), but reaction 1 becomes important at temperatures above 210 K. Furthermore, reaction probability measurements performed on the H2SO4/HNO3/ H2O ternary solutions do not exhibit noticeable deviation from those performed on the H2SO4/H2O binary system, suggesting little effect of HNO3 in sulfate aerosols on the ClONO2 and HOCl reactions with HCl. The results reveal that significant reductions in the chlorine-containing reservoir species (such as ClONO2 and HCl) can take place on stratospheric sulfate aerosols at high latitudes in winter and early spring, even at temperatures too warm for Polar Stratospheric Clouds (PSCs) to form or in regions where nucleation of PSCs is sparse. This is particularly true under elevated sulfuric acid loading, such as that after the eruption of Mt. Pinatubo. Comparisons between our results and those presently available have also been made.

Zhang, Renyi; Leu, Ming-Taun; Keyser, Leon F.

1994-01-01

258

Development and operation of a hybrid acid-alkaline advanced water electrolysis cell  

NASA Astrophysics Data System (ADS)

A hybrid acid-alkaline water electrolysis cell has been developed for hydrogen production. The cell is based on the use of an acidic solution at the cathode and a basic solution at the anode to reduce the minimum theoretical voltage for water decomposition from the thermoneutral potential of 1.47 V to close to 1.4 V at 25 C and 1 atm. The pH differential is maintained by the removal of OH ions from the cathode section and water removal from the anode section, which can be driven by heat energy. A practical cell has been built using a solid polymer electrolyte in which, however, the cathodic compartment is not acidic but neutral. Tests with a platinum black cathode catalyst and a platinum-iridium anode catalyst have resulted in steady-state water hydrolysis at an applied voltage of 0.9 V, and a V-I diagram with a considerably lower slope than that of a conventional cell has been obtained at 90 C.

Teschke, O.; Zwanziger, M.

259

Immobilization-free programmable hairpin probe for ultrasensitive electronic monitoring of nucleic acid based on a biphasic reaction mode.  

PubMed

This work designs a novel programmable hairpin probe (PHP) for the immobilization-free electrochemical detection of nucleic acid by coupling polymerase/nicking-induced isothermal signal amplification strategy with a biphasic reaction mode for the first time. The designed PHP (including a target-recognition region, a template sequence for enzymatic reaction and an inactivated anti-streptavidin aptamer) could program multiple isothermal reactions in the solution phase accompanying in situ amplified detectable signal at the electrode surface by the labeled ferrocene tag on the PHP. Upon addition of target analyte into the detection solution, target DNA initially hybridized with the recognition region on the PHP. Replication-induced strand-displacement generated an activated anti-streptavidin aptamer with the assistance of polymerase. Then, the polymerase/nicking enzymes could cleave and polymerize repeatedly the replication product, thus resulting in the formation of numerous template-complementary DNA initiator strands. The released initiator strands could retrigger the programmable hairpin probe to produce a large number of activated anti-streptavidin aptamers, which could be captured by the immobilized streptavidin on the electrode, thus activating the electrical contact between the labeled ferrocene and the electrode. Going after the aptamers, the carried ferrocene could produce the in situ amplified electronic signal within the applied potentials. Under optimal conditions, the electrochemical signal increased with the increasing target DNA concentration in the dynamic range from 5 fM to 10 pM with a detection limit (LOD) of 2.56 fM at the 3sblank criterion. Importantly, the methodology with high specificity was also validated and evaluated by assaying 6 target DNA-spiked human serum and calf thymus DNA samples, and the recoveries were 95-110%. Further work for the programmable hairpin probe could be even utilized in a real world sample to detect miRNA-21 at femtomol level. PMID:25084479

Zhuang, Junyang; Tang, Dianping; Lai, Wenqiang; Chen, Guonan; Yang, Huanghao

2014-08-19

260

Identification of Frankia strains in nodules by hybridization of polymerase chain reaction products with strain-specific oligonucleotide probes.  

PubMed

A set of oligonucleotides has been developed to study the competitivity of two Frankia strains in the nodulation of the roots of two host plant species: Alnus glutinosa and Alnus incana. Two 20 mer-oligonucleotides, complementary to highly conserved sequences inside the nifH gene, were used as primers for the polymerase chain reaction (PCR) system in order to amplify microsymbiont DNA extracted from actinorhizae. PCR products were analyzed using two strain-specific 15-mer oligonucleotides identified in the amplified region. Hybridization data indicate that strain ACoN24d is more competitive than strain ArI3 in the nodulation of both hosts. PMID:2334247

Simonet, P; Normand, P; Moiroud, A; Bardin, R

1990-01-01

261

In vivo hybridization of technetium-99m-labeled peptide nucleic acid (PNA)  

SciTech Connect

Hybridization of a radiolabeled single-stranded DNA oligonucleotide with its single-stranded complement in vivo has not yet been convincingly demonstrated. A contributing factor may be unfavorable in vivo properties of the phosphodiester and phosphorothioate DNAs. Peptide nucleic acid (PNA) oligomers have been reported to possess in vivo properties more suitable for radiopharmaceutical applications. We have radiolabeled an amine-derivatized 15-base PNA oligomer with {sup 99m}Tc through a modified MAG{sub 3} chelator. The ability of the PNA to hybridize in vitro with its complement appeared to be unimpaired after conjugation and radiolabeling. Size-exclusion, high-performance liquid chromatography (HPLC) analysis of 37{degree}C serum after 24 hr of incubation showed the radiolabel to be present predominately as labeled PNA with indications of labeled serum proteins and a low molecular weight catabolite. Whole-body clearance in mice was rapid, with 50% of the label eliminated in about 2 hr. After 2.5 hr, the highest uptake (kidneys) was only 1.5% of the injected dose/g; less than 0.07%/g was present in all sampled tissues at 24 hr. To evaluate in vivo hybridization, beads were implanted subcutaneously in both thighs of normal mice. In the left thigh only, the beads were conjugated with complementary single-stranded PNA. At 23 hr following intraperitoneal administration of the labeled PNA, the left/right thigh radioactivity ratio was 6:1. Whole-body images at this time showed only bladder, kidneys and the left thigh. Unlike the radiolabeled DNAs investigated in this laboratory, {sup 99m}Tc-PNA displays stability and pharmacokinetic properties suitable for eventual use as radiopharmaceuticals.

Mardirossian, G.; Lei, K.; Rusckowski, M. [Univ. of Massachusetts Medical Center, Worcester, MA (United States)] [and others

1997-06-01

262

Chemically Activated Formation of Organic Acids in Reactions of the Criegee Intermediate with Aldehydes and Ketones  

SciTech Connect

Reactions of the Criegee intermediate (CI, .CH2OO.) are important in atmospheric ozonolysis models. In this work, we compute the rates for reactions between .CH2OO. and HCHO, CH3CHO and CH3COCH3 leading to the formation of secondary ozonides (SOZ) and organic acids. Relative to infinitely separated reactants, the SOZ in all three cases is found to be 48–51 kcal mol-1 lower in energy, formed via 1,3- cycloaddition of .CH2OO. across the CQO bond. The lowest energy pathway found for SOZ decomposition is intramolecular disproportionation of the singlet biradical intermediate formed from cleavage of the O–O bond to form hydroxyalkyl esters. These hydroxyalkyl esters undergo concerted decomposition providing a low energy pathway from SOZ to acids. Geometries and frequencies of all stationary points were obtained using the B3LYP/MG3S DFT model chemistry, and energies were refined using RCCSD(T)-F12a/cc-pVTZ-F12 single-point calculations. RRKM calculations were used to obtain microcanonical rate coefficients (k(E)) and the reservoir state method was used to obtain temperature and pressure dependent rate coefficients (k(T, P)) and product branching ratios. At atmospheric pressure, the yield of collisionally stabilized SOZ was found to increase in the order HCHO o CH3CHO o CH3COCH3 (the highest yield being 10-4 times lower than the initial .CH2OO. concentration). At low pressures, chemically activated formation of organic acids (formic acid in the case of HCHO and CH3COCH3, formic and acetic acid in the case of CH3CHO) was found to be the major product channel in agreement with recent direct measurements. Collisional energy transfer parameters and the barrier heights for SOZ reactions were found to be the most sensitive parameters determining SOZ and organic acid yield.

Jalan, Amrit; Allen, Joshua W.; Green, William H.

2013-08-08

263

Advanced design of valve-regulated lead-acid battery for hybrid electric vehicles  

NASA Astrophysics Data System (ADS)

A novel design of lead-acid battery has been developed for use in hybrid electric vehicles (HEVs). The battery has current take-offs at both ends of each of the positive and negative plates. This feature markedly reduces battery operating temperatures, improves battery capacity, and extends cycle-life under HEV duty. The battery also performs well under partial-state-of-charge (PSoC)/fast-charge, electric-vehicle operation. The improvements in performance are attributed to more uniform utilization of the plate active-materials. The battery, combined with an internal-combustion engine and a new type of supercapacitor, will be used to power an HEV, which is being designed and constructed by an Australian industry-government consortium.

Lam, L. T.; Newnham, R. H.; Ozgun, H.; Fleming, F. A.

264

Nucleic acid hybridization studies on Microbacterium, Curtobacterium, Agromyces and related taxa.  

PubMed

Thirty strains of Agromyces, Arthrobacter, Curtobacterium, Brevibacterium, Corynebacterium and Microbacterium, exhibiting the rare peptidoglycan of group B, were subjected to extensive nucleic acid hybridization studies. The DNA homology values indicate that Corynebacterium insidiosum DSM 20157 is genetically identical with Corynebacterium michiganense DSM 20134. Corynebacterium sepedonicum NCPPB 378 and Corynebacterium nebraskense DSM 20400 are closely related to Corynebacterium michiganense DSM 20134. Corynebacterium betae DSM 20141, Corynebacterium oortii ATCC 25283 and Corynebacterium poinsettiae ATCC 9682 are genetically identical with Corynebacterium flaccumfaciens DSM 20129. In addition, Curtobacterium citreum ATCC 15828, Curtobacterium luteum ATCC 15830 and Curtobacterium pusillum ATCC 19096 share a high degree of relatedness to Corynebacterium flaccumfaciens DSM 20129. All other described species are more distantly related to each other. DNa-rRNA cistron similarity studies reveal that all corynebacterium with a peptidoglycan group B are members of one homogeneous cluster for which the rank of a genus is suggested. PMID:6183393

Döpfer, H; Stackebrandt, E; Fiedler, F

1982-08-01

265

Pestalotiopens A and B: stereochemically challenging flexible sesquiterpene-cyclopaldic acid hybrids from Pestalotiopsis sp.  

PubMed

From the endophytic fungus Pestalotiopsis sp. isolated from the leaves of the Chinese mangrove, Rhizophora mucronata, two novel hybrid sesquiterpene-cyclopaldic acid metabolites with an unusual carbon skeleton, named pestalotiopens?A and B, were obtained, together with the already known phytotoxin altiloxin?B. Pestalotiopen?B even contains a third, triketide-derived module. The constitutions and the absolute configurations of the new metabolites and of altiloxin?B were unambiguously determined by a combination of spectroscopic methods and quantum-chemical optical-rotatory dispersion (ORD) and circular dichroism (CD) calculations. A biosynthetic pathway to pestalotiopens?A and B is proposed with altiloxin?B as one of the suggested precursors. Pestalotiopen?A shows moderate antimicrobial activity against Enterococcus faecalis. PMID:24123472

Hemberger, Yasmin; Xu, Jing; Wray, Victor; Proksch, Peter; Wu, Jun; Bringmann, Gerhard

2013-11-11

266

Buffer-stable chitosan-polyglutamic acid hybrid nanoparticles for biomedical applications.  

PubMed

In spite of their attractive features, widespread biomedical applications of CS nanoparticles are yet to be realized due to their poor stability in physiological conditions, such as in buffer system at pH 7.4. Buffer-stable chitosan-based hybrid NPs (HNPs) are reported and characterized. Buffer stability is achieved by introducing polyglutamic acid to chitosan. The effect of PGA to CS molar ratio and crosslinking on HNP integrity, buffer stability, and biodegradability are studied. Preliminary in vitro studies are carried out to evaluate targeted uptake efficiency of folate conjugated HNPs. Successful demonstration of buffer stability and cancer cell targeting by HNPs achieves important milestones for chitosan-based nanoparticle technology. PMID:23460363

Malhotra, Astha; Zhang, Xiaolei; Turkson, James; Santra, Swadeshmukul

2013-05-01

267

A hybrid variational-perturbation calculation of the ro-vibrational spectrum of nitric acid  

E-print Network

Rotation-vibration spectra of the nitric acid molecule, HNO\\3, are calculated for wavenumbers up to 7000~\\cm. Calculations are performed using a Hamiltonian expressed in internal curvilinear vibrational coordinates solved using a hybrid variational-perturbation method. An initial potential energy surface (PES) and dipole moment function (DMF) are calculated {\\it ab initio} at the CCSD(T)/aug-cc-pVQZ level of theory. Parameters of the PES and DMF are varied to minimize differences between the calculated and experimental transition frequencies and intensities. The average, absolute deviation between calculated and experimental values is 0.2~\\cm\\ for frequencies in the fundamental bands and 0.4~\\cm\\ for those in the first overtone and lowest combination bands. For the intensities, the calculated and experimental values differ by 0.3\\% and 40\\% for the fundamentals and overtones, respectively. The optimized PES and DMF are used to calculate the room-temperature ro-vibrational spectrum. These calculation reproduce...

Pavlyuchko, A I; Tennyson, Jonathan

2014-01-01

268

Fabrication and electrocatalytic activities of porphyrin and 12-molybdophosphoric acid hybrid films.  

PubMed

Hybrid films composed of oppositely charged Keggin-type 12-molybdophosphoric acid H(3)PMo(12)O(40).nH(2)O (PMo(12)) and water-soluble cationic meso-tetra (N-methyl-4-pyridyl) porphinetetratosylate (TMPyP) were fabricated onto silicon and ITO substrates by a layer-by-layer (LbL) self-assembly technique. The LbL films were characterized by UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and cyclic voltammetry (CV). The electrochemical properties of the prepared multilayer films were controlled by adjusting the solution pH. Moreover, with increase in the layer number of TMPyP/PMo(12), the electrocatalytic current toward the reduction of IO(3)(-) was enhanced. The LbL films also displayed good electrocatalytic activities toward the reduction of BrO(3)(-), IO(3)(-) , and S(2)O(8)(2-). PMID:20716454

Fan, Dawei; Li, Guobao; Hao, Jingcheng

2010-11-01

269

Uptake and Surface Reaction of Methanol by Sulfuric Acid Solutions Investigated by Vibrational Sum Frequency Generation and Raman Spectroscopies  

E-print Network

Uptake and Surface Reaction of Methanol by Sulfuric Acid Solutions Investigated by Vibrational Sum and occurred on a much longer time scale. This suggests that uptake of methanol by sulfuric acid solutions Sulfuric acid (H2SO4) is the predominant aerosol component in the free troposphere.18 Flight measurements

270

40 CFR 721.10429 - Fatty acids, C18-unsatd., dimers, reaction products with 1-piperazineethanamine and tall-oil...  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Fatty acids, C18-unsatd., dimers, reaction products...1-piperazineethanamine and tall-oil fatty acids. 721.10429 Section 721.10429...Chemical Substances § 721.10429 Fatty acids, C18 -unsatd., dimers,...

2013-07-01

271

40 CFR 721.10429 - Fatty acids, C18-unsatd., dimers, reaction products with 1-piperazineethanamine and tall-oil...  

...2014-07-01 2014-07-01 false Fatty acids, C18-unsatd., dimers, reaction products...1-piperazineethanamine and tall-oil fatty acids. 721.10429 Section 721.10429...Chemical Substances § 721.10429 Fatty acids, C18 -unsatd., dimers,...

2014-07-01

272

Relatedness Among Rhizobium and Agrobacterium Species Determined by Three Methods of Nucleic Acid Hybridization  

PubMed Central

Deoxyribonucleic acid (DNA) was isolated from 20 strains of Rhizobium and Agrobacterium and from one strain of Serratia marcescens; the guanine plus cytosine content of each DNA sample was determined by thermal denaturation. Radioactive DNA was isolated from three reference strains following the uptake of [2-14C]thymidine in the presence of deoxyadenosine. Ribonucleic acid (RNA) polymerase was used to synthesize radioactive RNA on DNA templates from the three reference strains. Radioactive DNA and RNA from the three reference strains were each hybridized with filter-bound DNA from all of the 21 test strains in 6 × SSC (standard saline citrate) and 50% formamide at 43 C for 40 hr. DNA/DNA relatedness was also determined by spectrophotometric measurement of the rates of association of single-stranded DNA. The order of relatedness between strains was similar by each method. Overall standard deviations for the DNA/DNA and DNA/RNA membrane filter techniques were ±0.87 and ±1.03%, respectively; that for the spectrophotometric technique was ±4.11%. The DNA/DNA membrane technique gave higher absolute values of hybridization than did the DNA/RNA technique. R. leguminosarum and R. trifolii could not be distinguished from each other by these techniques. These results also indicated close relationships between R. lupini and R. japonicum, and (with less certainty) between R. meliloti and R. phaseoli. Of all the rhizobia tested against the A. tumefaciens 371 reference strain, the R. japonicum strains were the most unrelated. The three Agrobacterium strains used were as related to the R. lupini and R. leguminosarum references as were several rhizobium strains. PMID:4591471

Gibbins, Ann M.; Gregory, K. F.

1972-01-01

273

Reaction of isoprene on thin sulfuric acid films: kinetics, uptake, and product analysis.  

PubMed

A high vacuum Knudsen flow reactor was used to determine the reactive uptake coefficient, gamma, of isoprene on sulfuric acid films as a function of sulfuric acid weight percent, temperature, and relative humidity. No discernible dependence was observed for gamma over the range of temperatures (220 - 265 K) and pressures (10(-7) Torr -10(-4) Torr) studied. However, the uptake coefficient increased with increased sulfuric acid concentration between the range of 78 wt % (gamma(i) approximately 10(-4)) and 93 wt % (gamma(i) approximately 10(-3)). In addition to the Knudsen Cell, a bulk study was conducted between 60 and 85 wt % H(2)SO(4) to quantify uptake at lower acid concentrations and to determine reaction products. After exposing sulfuric acid to gaseous isoprene the condensed phase products were extracted and analyzed using gas chromatography/mass spectrometry (GC/MS). Isoprene was observed to polymerize in the sulfuric acid and form yellow/red colored monoterpenes and cyclic sesquiterpenes. Finally, addition of water to the 85 wt % sulfuric acid/isoprene product mixture released these terpenes from the condensed phase into the gas phase. Together these experiments imply that direct isoprene uptake will not produce significant SOA; however, terpene production from the small uptake may be relevant for ultrafine particles and could affect growth and nucleation. PMID:20499904

Connelly, Brandon M; Tolbert, Margaret A

2010-06-15

274

Reactivity of hydroxybenzoic acids in the hydrogen-isotope exchange reaction.  

PubMed

The hydrogen-isotope exchange reaction (T-for-H exchange reaction) between tritiated water vapor (HTO vapor) and 3-hydroxy-4-methoxybenzoic acid (and it's analog; 4-hydroxy-3-methoxybenzoic acid) were observed at 50 and 70 degrees C in a gas-solid system to reveal the reactivity of a functional group in an aromatic compound having two substituents in the aromatic ring. Further, it was shown that (a) the reactivity of the compounds used in this work follows the Hammett's rule, and (b) the reactivity of trisubstituted aromatic compound could be analyzed by applying the additive property of the Hammett's rule even if the compound contains a substituent at the ortho-position. PMID:17261367

Zhao, D; Imaizumi, H; Lei, Q; Wu, J

2007-05-01

275

A combined experimental and computational study of the esterification reaction of glycerol with acetic acid.  

PubMed

This work describes theoretical and experimental studies on glycerol esterification to obtain acetins focusing on the obtained isomers. The reaction of glycerol with acetic acid was carried out on Amberlyst 36 wet. Density functional theory calculations on the level of M06-2X functional and 6-311+G(d,p) basis set are carried out and the most stable structures of the reactants and products are located by considering a large number of conformers. The thermodynamics is discussed in terms of the calculated reaction Gibbs free energy. The AIM theory was used to characterize reactants and products. The glycerol esterification with acetic acid is found to be thermodynamically favored, with exothermal property. These agree well with experiments and allow us to explain the relative selectivity of products. PMID:24633772

Bedogni, Gabriel Alejandro; Padró, Cristina Liliana; Okulik, Nora Beatriz

2014-04-01

276

Simultaneous Identification of Mutations by Dual-Parameter Multiplex Hybridization in Peptide Nucleic AcidContaining Virtual Arrays  

Microsoft Academic Search

The physical entrapment of peptide nucleic acids (PNA) in electrophoresis media provides a system for performing real-time hybridization. DNA strands fully complementary to the target PNA are retarded compared to single-nucleotide mismatched strands. A second parameter, that of amplicon length, has been introduced to perform multiplex analyses on several mutations simultaneously. Size fractionation creates a virtual array of PCR products

Gabor L. Igloi

2001-01-01

277

Development of rapeseed with high erucic acid content by asymmetric somatic hybridization between Brassica napus and Crambe abyssinica  

Microsoft Academic Search

PEG-induced asymmetric somatic hybridization between Brassica napus and Crambe abyssinica was carried out. C. abyssinica is an annual cruciferous oil crop with a high content of erucic acid in the seed oil valuable for technical purposes. UV-irradiated mesophyll protoplasts of C. abyssinica cv 'Carmen' and cv 'Galactica' were fused with hypocotyl protoplasts of different genotypes of B. napus cv 'Maplus'

Y. P. Wang; K. Sonntag; E. Rudloff

2003-01-01

278

A FRET-based assay for characterization of alternative splicing events using peptide nucleic acid fluorescence in situ hybridization  

Microsoft Academic Search

We describe a quantitative method for detecting RNA alternative splicing variants that combines in situ hybridization of fluorescently labeled peptide nucleic acid (PNA) probes with confocal microscopy Forster resonance energy transfer (FRET). The use of PNA probes complementary to sequences flank- ing a given splice junction allows to specifically quantify, within the cell, the RNA isoform generating such splice junction

Ana M. Blanco; Laura Rausell; Begona Aguado; Manuel Perez-Alonso; Ruben Artero

2009-01-01

279

Peptide nucleic acid probe for protein affinity purification based on biotin-streptavidin interaction and peptide nucleic acid strand hybridization.  

PubMed

We describe a new method for protein affinity purification that capitalizes on the high affinity of streptavidin for biotin but does not require dissociation of the biotin-streptavidin complex for protein retrieval. Conventional reagents place both the selectively reacting group (the "warhead") and the biotin on the same molecule. We place the warhead and the biotin on separate molecules, each linked to a short strand of peptide nucleic acid (PNA), synthetic polymers that use the same bases as DNA but attached to a backbone that is resistant to attack by proteases and nucleases. As in DNA, PNA strands with complementary base sequences hybridize. In conditions that favor PNA duplex formation, the warhead strand (carrying the tagged protein) and the biotin strand form a complex that is held onto immobilized streptavidin. As in DNA, the PNA duplex dissociates at moderately elevated temperature; therefore, retrieval of the tagged protein is accomplished by a brief exposure to heat. Using iodoacetate as the warhead, 8-base PNA strands, biotin, and streptavidin-coated magnetic beads, we demonstrate retrieval of the cysteine protease papain. We were also able to use our iodoacetyl-PNA:PNA-biotin probe for retrieval and identification of a thiol reductase and a glutathione transferase from soybean seedling cotyledons. PMID:25447466

Tse, Jenny; Wang, Yuanyuan; Zengeya, Thomas; Rozners, Eriks; Tan-Wilson, Anna

2015-02-01

280

Reactions between fulvic acid, a soil humic material, and dialkyl phthalates  

Microsoft Academic Search

Summary Fulvic acid, a water-soluble soil humic material that occurs widely in soils and waters, can “complex” hydrophobic dialkyl phthalates and make them soluble in water. The extent of the reaction depends on the type of phthalate. Thus, one number-average molecular weight of FA can solubilize four moles of bis(2-ethylhexyl) phthalate but only one mole of dibutyl phthalate, while 2

Keiichiro Matsuda; Morris Schnitzer

1971-01-01

281

Effects of ascorbic acid on sperm motility, viability, acrosome reaction and DNA integrity in teratozoospermic samples  

PubMed Central

Background: Oxidative stress in teratozoospermic semen samples caused poor assisted reproductive techniques (ART) outcomes. Among antioxidants, ascorbic acid is a naturally occurring free radical scavenger and as such its presence assists various other mechanisms in decreasing numerous disruptive free radical processes. Objective: The main goal of this study was to evaluate potential protective effects of ascorbic acid supplementation during in vitro culture of teratozoospermic specimens. Materials and Methods: Teratozoospermic semen samples that collected from 15 volunteers were processed, centrifuged and incubated at 37oC until sperm swimmed-up. Supernatant was divided into four groups and incubated at 37oC for one hour under different experimental conditions: Control, 10 µm A23187, 600µm ascorbic acid and 10 µm A23187+600 µm ascorbic acid. After incubation sperm motility, viability, acrosome reaction, DNA damage and malondialdehyde levels were evaluated. Results: Our results indicated that after one hour incubation, ascorbic acid significantly reduced malondialdehyde level in ascorbic acid group (1.4±0.11 nmol/ml) compared to control group (1.58±0.13 nmol/ml) (p<0.001). At the end of incubation, progressive motility and viability in ascorbic acid group (64.5±8.8% and 80.3±6.4%, respectively) were significantly (p<0.05 and p<0.001, respectively) higher than the control group (54.5±6.8% and 70.9±7.3%, respectively). A23187 significantly (p<0.0001) increased acrosome reaction in A23187 group (37.3±5.6%) compared to control group (8.5±3.2%) and this effect of A23187 attenuated by ascorbic acid in ascorbic acid+A23187 group (17.2±4.4%). DNA fragmentation in ascorbic acid group (20±4.1%) was significantly (p<0.001) lower than controls (28.9±4.6%). Conclusion: In vitro ascorbic acid supplementation during teratozoospermic semen processing for ART could protect teratozoospermic specimens against oxidative stress, and it could improve ART outcome. PMID:24799867

Fanaei, Hamed; Khayat, Samira; Halvaei, Iman; Ramezani, Vahid; Azizi, Yaser; Kasaeian, Amir; Mardaneh, Jalal; Parvizi, Mohammad Reza; Akrami, Maryam

2014-01-01

282

A preliminary investigation of acid-catalyzed polymerization reactions of shale oil distillates  

SciTech Connect

Sinor (1989) reported that a major specialty market may exist for shale oil as an asphalt blending material. Shale oil can be converted to an asphalt blending material by acid catalyzed condensation and polymerization reactions of the many molecular species comprising the composition of shale oil. To simplify the investigation, crude shale oil was separated by distillation into three distillates of different hydrocarbon and heteroaromatic compositions. These distillates were then treated with two different types of acids to determine the effect of acid type on the end products. Three western shale oil distillates, a naphtha, a middle distillate, and an atmospheric gas oil, were reacted with anhydrous AlCl{sub 3} and 85% H{sub 2}SO{sub 4} under low-severity conditions. At relatively low temperatures, little change in the hydrocarbon composition was noted for the AlCl{sub 3} reactions. AlCl{sub 3}{center dot} (a polymerized product and/or complex) was formed. However, it is assumed that the sludge was mainly the result of heteroaromatic-AlCl{sub 3} reactions.

Netzel, D.A.

1991-04-01

283

A preliminary investigation of acid-catalyzed polymerization reactions of shale oil distillates  

SciTech Connect

Sinor (1989) reported that a major specialty market may exist for shale oil as an asphalt blending material. Shale oil can be converted to an asphalt blending material by acid catalyzed condensation and polymerization reactions of the many molecular species comprising the composition of shale oil. To simplify the investigation, crude shale oil was separated by distillation into three distillates of different hydrocarbon and heteroaromatic compositions. These distillates were then treated with two different types of acids to determine the effect of acid type on the end products. Three western shale oil distillates, a naphtha, a middle distillate, and an atmospheric gas oil, were reacted with anhydrous AlCl{sub 3} and 85% H{sub 2}SO{sub 4} under low-severity conditions. At relatively low temperatures, little change in the hydrocarbon composition was noted for the AlCl{sub 3} reactions. AlCl{sub 3}{center_dot} (a polymerized product and/or complex) was formed. However, it is assumed that the sludge was mainly the result of heteroaromatic-AlCl{sub 3} reactions.

Netzel, D.A.

1991-04-01

284

EXAFS Study on the Reactions Between Iron And Fulvic Acid in Acid Aqueous Solutions  

SciTech Connect

Iron(III) competes with trace metals for binding sites on organic ligands. We used X-ray absorption fine structure (EXAFS) spectroscopy to determine the binding mode and oxidation state of iron in solutions initially containing only iron(III) and fulvic acid at pHs 2 and 4. EXAFS spectra were recorded at different times after sample preparation. Iron was octahedrally configured with inner-sphere Fe-O interactions at 1.98-2.10 {angstrom}, depending on the oxidation state of iron. Iron(III) formed complexes with fulvic acid within 15 min. Iron(III) was reduced to iron(II) with time at pH 2, whereas no significant reduction occurred at pH 4. No signs of dimeric/trimeric hydrolysis products were found in any of the solution samples (<0.45 {mu}m). However, the isolated precipitate of the pH 2 sample (>0.45 {mu}m) showed Fe{hor_ellipsis}Fe distances, indicating the presence of tightly packed iron(III) trimers and/or clusters of corner-sharing octahedra. It is suggested that the binding mode of iron(III) to fulvic acid at low pH may be phase-dependent: in solution mononuclear complexes predominate, whereas in the solid phase hydrolyzed polynuclear iron(III) complexes form, even at very low pH values. The observed pH dependence of iron(III) reduction was consistent with expected results based on thermodynamic calculations for model ligands.

Schaik, J.W.J.van; Persson, I.; Kleja, D.B.; Gustafsson, J.P.

2009-05-26

285

Parentage determination in maize hybrids using the arbitrarily primed polymerase chain reaction (AP-PCR)  

Microsoft Academic Search

Using a novel procedure based on the polymerase chain reaction, we have developed a rapid, efficient, and economical method for identifying plant genotypes. The arbitrarily primed polymerase chain reaction (AP-PCR) generates reproducible fingerprints from any organism, without the need for DNA sequence information. These fingerprints include DNA fragment polymorphisms that can be (1) used for varietal identification and parentage determination,

J. Welsh; R. J. Honeycutt; M. McClelland; B. W. S. Sobral

1991-01-01

286

[Studies of oxygen uptake (Mehler reactions) in chloroplasts in the presence of silico-molybdic acid].  

PubMed

Silico-molybdic acid (SiMo) alone or in combination with diurone is known to provide for the functioning of various sites of electron transport within photosystem II (PS-II). Using SiMo, the ability of PS-II to competitive reduction of O2 with SiMo in the presence of some activators of O2 uptake (e. g. catalase"ethanol, malonate, oxalate and glyoxalate) was shown. Oxygen uptake (Mehler reaction) with those compounds may be accomplished against the diurone block. The Mehler reactions studied occur in PS-II at the site, uncoupled with phosphorylation, up to the primary acceptor Q, The Mehler reactions with FMN and ferredoxin confirm the fact that PS-II functioning in the presence of SiMo is possible only after its reduction. Photoreduction of NADP is inhibited irrespective of whether the oxidized or reduced form of SiMo is added. PMID:870090

Bekina, R M; Lebedeva, A F

1977-04-01

287

Effect of fungicides on the reaction of sorghum hybrids to disease in Burleson County, Texas, 2011  

Technology Transfer Automated Retrieval System (TEKTRAN)

The use of fungicides to control anthracnose and grain mold on sorghum hybrids was conducted during the 2011 growing season. Three fungicides Headline, Quilt Xcel, and Topguard were used. Fungicides were applied on 30 May to the middle two rows with a CO2 backpack sprayer, at 30 psi in a spray vol...

288

Identification of Rifampin-Resistant Mycobacterium tuberculosis Strains by Hybridization, PCR, and Ligase Detection Reaction on Oligonucleotide Microchips  

PubMed Central

Three new molecular approaches were developed to identify drug-resistant strains of Mycobacterium tuberculosis using biochips with oligonucleotides immobilized in polyacrylamide gel pads. These approaches are significantly faster than traditional bacteriological methods. All three approaches—hybridization, PCR, and ligase detection reaction—were designed to analyze an 81-bp fragment of the gene rpoB encoding the ?-subunit of RNA polymerase, where most known mutations of rifampin resistance are located. The call set for hybridization analysis consisted of 42 immobilized oligonucleotides and enabled us to identify 30 mutant variants of the rpoB gene within 24 h. These variants are found in 95% of all mutants whose rifampin resistance is caused by mutations in the 81-bp fragment. Using the second approach, allele-specific on-chip PCR, it was possible to directly identify mutations in clinical samples within 1.5 h. The third approach, on-chip ligase detection reaction, was sensitive enough to reveal rifampin-resistant strains in a model mixture containing 1% of resistant and 99% of susceptible bacteria. This level of sensitivity is comparable to that from the determination of M. tuberculosis drug resistance by using standard bacteriological tests. PMID:11427565

Mikhailovich, Vladimir; Lapa, Sergey; Gryadunov, Dimitry; Sobolev, Alexander; Strizhkov, Boris; Chernyh, Nikolai; Skotnikova, Olga; Irtuganova, Olga; Moroz, Arkadii; Litvinov, Vitalii; Vladimirskii, Mikhail; Perelman, Mikhail; Chernousova, Larisa; Erokhin, Vladislav; Zasedatelev, Alexander; Mirzabekov, Andrei

2001-01-01

289

Identification of rifampin-resistant mycobacterium tuberculosis strains by hybridization, PCR, and ligase detaction reaction on oligonucleotide microchips.  

SciTech Connect

Three new molecular approaches were developed to identify drug-resistant strains of Mycobacterium tuberculosis using biochips with oligonucleotides immobilized in polyacrylamide gel pads. These approaches are significantly faster than traditional bacteriological methods. All three approaches -- hybridization, PCR, and ligase detection reaction -- were designed to analyze an 81-bp fragment of the gene rpoB encoding the {beta}-subunit of RNA polymerase, where most known mutations of rifampin resistance are located. The call set for hybridization analysis consisted of 42 immobilized oligonucleotides and enabled us to identify 30 mutant variants of the rpoB gene within 24 h. These variants are found in 95% of all mutants whose rifampin resistance is caused by mutations in the 81-bp fragment. Using the second approach, allele-specific on-chip PCR, it was possible to directly identify mutations in clinical samples within 1.5 h. The third approach, on-chip ligase detection reaction, was sensitive enough to reveal rifampin-resistant strains in a model mixture containing 1% of resistant and 99% of susceptible bacteria. This level of sensitivity is comparable to that from the determination of M. tuberculosis drug resistance by using standard bacteriological tests.

Mikhailovich, V.; Lapa, S.; Gryadunov, D.; Sobolev, A.; Strizhkov, B.; Chernyh, N.; Skotnikova, O.; Irtuganova, O.; Moroz, A.; Litvinov, V.; Vladimirskii, M.; Perelman, M.; Chernousova, L.; Erokhin, V.; Mirzabekov, A.; Biochip Technology Center; Russian Academy of Sciences; Moscow Antituberculosis Center; Moscow Medical Academy; Russian Academy of Medical Sciences

2001-07-01

290

Determination of oxybutynin in pharmaceuticals via reaction with mixed acids anhydrides: application to content uniformity testing.  

PubMed

Sensitive and simple spectrophotometric (Method I) and spectrofluorimetric (Method II) methods were developed and validated for the determination of oxybutynin HCl (OXB) in its dosage forms. The method was based on the reaction of OXB with malonic acid anhydride in acetic acid anhydride to form a highly yellow colored product that was measured at 375 nm spectrophotometrically. The same reaction product exihibits strong fluorescence that was measured at 440 nm after excitation at 390 nm. The factors affecting formation and stability of the reaction product were carefully studied and optimized, and the reaction mechanism was postulated. The absorbance-concentration plot is rectilinear over the range 4-40 ?g/mL with LOD of 1.12 ?g/mL and LOQ of 3.39 ?g/mL. The fluorescence-concentration plot is rectilinear over the range 0.5-6 ?g/mL with LOD of 0.11 ?g/mL and LOQ of 0.33 ?g/mL. The method was applied to the analysis of commercial tablets Detronin® and Uripan®. Statistical comparison of the results with those of the reference method revealed good agreement and proved that there were no significant difference in the accuracy and precision between the two methods respectively. The study was extended to content uniformity testing. PMID:21046437

Walash, M I; Belal, F; El-Enany, N; Elmansi, H

2011-03-01

291

Formation of flavor components by the reaction of amino acid and carbonyl compounds in mild conditions.  

PubMed

This work describe products of reactions between four alpha-dicarbonyl compounds (diacetyl, pentan-2,3-dione, glyoxal, and methylglyoxal) or two alpha-hydroxy ketones, (acetoine and acetol) and amino acids present in wines. The results shows the formation of odorous products or strong-smelling additives resulting from the Maillard and Strecker reaction in a primarily aqueous medium, at low temperature and low pH ( approximately pH 3.5) of the wine. GC/FID, GC/FPD, GC/NPD and GC/MS techniques were used. The olfactive characteristics of the products are described. In the presence of sulfur amino acids and in particular cysteine, many products were formed with a heterocycle production such as pyrazines and methylpyrazines, methylthiazoles, acetylthiazoles, acetylthiazolines, acetylthiazolidines, trimethyloxazole, and dimethylethyloxazoles. These various compounds present odors of sulfur, cornlike, pungent, nut, popcorn, roasted hazelnut, toasted, roasted, and ripe fruits. The chemical conditions of the model reactions are specified. The influence of temperature and pH on the reactions in the presence of cysteine were also studied. PMID:10995267

Pripis-Nicolau, L; de Revel, G; Bertrand, A; Maujean, A

2000-09-01

292

Novel conducting polymer-heteropoly acid hybrid material for artificial photosynthetic membranes.  

PubMed

Artificial photosynthetic (AP) approaches to convert and store solar energy will require membranes capable of conducting both ions and electrons while remaining relatively transparent and chemically stable. A new approach is applied herein involving previously described in situ chemical polymerization of electronically conducting poly(3,4-ethylenedioxythiophene) (PEDOT) in the presence of proton conducting heteropoly acid (HPA) phosphomolybdic acid (PMA). The electrochemical behaviour of the PEDOT/PMA hybrid material was investigated and it was found that the conducting polymer (CP) is susceptible to irreversible oxidative processes at potentials where water is oxidized. This will be problematic in AP devices should the process occur in very close proximity to a conducting polymer-based membrane. It was found that PEDOT grants the system good electrical performance in terms of conductivity and stability over a large pH window; however, the presence of PMA was not found to provide sufficient proton conductivity. This was addressed in an additional study by tuning the ionic (and in turn, electronic) conductivity in creating composites with the proton-permselective polymer Nafion. It was found that a material of this nature with near-equal conductivity for optimal chemical conversion efficiency will consist of roughly three parts Nafion and one part PEDOT/PMA. PMID:21384827

McDonald, Michael B; Freund, Michael S

2011-04-01

293

Hybrid PET/MR imaging of tumors using an oleanolic acid-conjugated nanoparticle.  

PubMed

Research into multifunctional nanoparticles is focused on creating an agent for use in an all-in-one multimodal imaging system that includes diagnostic imaging, drug delivery, and therapeutic monitoring. We designed a new dual-modality tumor-targeting agent with a new tumor-targeting molecule, oleanolic acid (OA), which is derived from a natural compound and coupled with a macrocyclic chelating agent such as 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA), iron oxide nanoparticles (IONP), and radiolabeling components such as (68)Ga for dual-modality positron emission tomography (PET)/magnetic resonance imaging (MRI). We attempted to obtain fusion PET/MR images with the (68)Ga-NOTA-OA-IONP hybrid tumor-targeting imaging agent using colon cancer (HT-29) xenograft mice models. The HT-29 cancer cells showed high uptake of (68)Ga-NOTA-OA-IONP, which also had an inhibitory effect on the cells. Moreover, we obtained PET and MRI tumor images as well as fusion PET/MRI images of the tumors using (68)Ga-NOTA-OA-IONP. Therefore, the dual-modality cancer-targeting radiolabeled nanoparticle reported here is a potent imaging agent that is suitable for PET, MRI, and PET/MRI-based diagnosis of tumors; it also has the advantage of not only detecting tumor functionality, but also simultaneously aiding in tumor resolution. PMID:23932293

Kim, Sung-min; Chae, Min Kyung; Yim, Min Su; Jeong, Il Ha; Cho, Janggeun; Lee, Chulhyun; Ryu, Eun Kyoung

2013-11-01

294

Redox silencing of the Fenton reaction system by an alkylitaconic acid, ceriporic acid B produced by a selective lignin-degrading fungus, Ceriporiopsis subvermispora.  

PubMed

The selective lignin-degrading fungus, Ceriporiopsis subvermispora secretes alkylitaconic acids (ceriporic acids) during wood decay. We reported that ceriporic acid B (hexadecylitaconic acid) was protective against the depolymerization of cellulose by the Fenton reaction. To understand the redox silencing effects, we analyzed the physicochemical and redox properties of itaconic, octylitaconic and hexadecylitaconic acids. The initial rate of HO production by the Fenton system with Fe(3+), H(2)O(2) and L-cysteine was suppressed by hexadecylitaconic and octylitaconic acids by 0.04 and 0.16 of the reaction rate without chelators. ESR, O(2) uptake and the assay of Fe(2+) with BPS demonstrated that Fe(3+) reduction by L-cysteine was suppressed by hexadecylitaconic and octylitaconic acids while the reaction of Fe(2+) with H(2)O(2) was not suppressed by the two alkylitaconic acids. Ligand exchange experiments with NTA demonstrated that Fe(3+) chelation by two carboxyl groups of alkylitaconic acids is a critical step in iron redox modulation. In stark contrast, the production of HO* and reduction of Fe(3+) were not suppressed by itaconic acid due to HO*--initiated degradation of the chelator. The strong redox silencing effects by a series of alkylitaconic acids have attracted interest in controlling microbial plant cell wall degradation and chemoprotection against cellular oxidative injury. PMID:17315072

Ohashi, Yasunori; Kan, Yoshihiko; Watanabe, Takahito; Honda, Yoichi; Watanabe, Takashi

2007-03-01

295

Trapping of fatty acid allyl radicals generated in lipoxygenase reactions in biological fluids by nitroxyl radical.  

PubMed

Nitroxyl radicals can trap fatty acid allyl radicals on ferric-lipoxygenases at lower oxygen content, which are an intermediate in the lipoxygenase reaction. In the present study, we examined whether nitroxyl radical-trapping of fatty acid allyl radicals on the enzyme proceeds in biological fluids with abundant antioxidants. The fatty acid allyl radical-nitroxyl radical adducts were quantified by HPLC with electrochemical detection (HPLC-ECD); the adducts in eluate degraded into nitroxyl radical by passing through heating coil at 100 degrees C, and then nitroxyl radical was detected by electrochemical detector. Soybean 15-lipoxygenase and nitroxyl radical (3-carbamoyl-2,2,5,5-tetramethyl-3-pyrroline-N-oxyl, CmDeltaP) were mixed with rat serum prepared from fresh venous blood, and the solution was stood at 37 degrees C for 1 h. One volume of the solution was mixed with 5 vols of cold acetonitrile. After centrifugation, the supernatant was subjected to HPLC-ECD. Arachidonate allyl radical-CmDeltaP adducts as well as linoleate allyl radical-CmDeltaP adducts were detected in the solution, and the content of these adducts remarkably increased in the presence of phospholipase A(2). It is proved for the first time that nitroxyl radical traps fatty acid allyl radicals generated in the lipoxygenase reaction in biological fluid without competition from endogenous antioxidants. PMID:20082280

Takajo, Tokuko; Tsuchida, Kazunori; Yokota, Azusa; Koshiishi, Ichiro

2010-07-01

296

Aquatic photolysis: photolytic redox reactions between goethite and adsorbed organic acids in aqueous solutions  

USGS Publications Warehouse

Photolysis of mono and di-carboxylic acids that are adsorbed onto the surface of the iron oxyhydroxide (goethite) results in an oxidation of the organic material and a reduction from Fe(III) to Fe(II) in the iron complex. There is a subsequent release of Fe2+ ions into solution. At constant light flux and constant solution light absorption, the factors responsible for the degree of photolytic reaction include: the number of lattice sites that are bonded by the organic acid; the rate of acid readsorption to the surface during photolysis; the conformation and structure of the organic acid; the degree of oxidation of the organic acid; the presence or absence of an ??-hydroxy group on the acid, the number of carbons in the di-acid chain and the conformation of the di-acid. The ability to liberate Fe(III) at pH 6.5 from the geothite lattice is described by the lyotropic series: tartrate>citrate> oxalate > glycolate > maleate > succinate > formate > fumarate > malonate > glutarate > benzoate = butanoate = control. Although a larger amount of iron is liberated, the series is almost the same at pH 5.5 except that oxalate > citrate and succinate > maleate. A set of rate equations are given that describe the release of iron from the goethite lattice. It was observed that the pH of the solution increases during photolysis if the solutions are not buffered. There is evidence to suggest the primary mechanism for all these reactions is an electron transfer from the organic ligand to the Fe(III) in the complex. Of all the iron-oxyhydroxide materials, crystalline goethite is the least soluble in water; yet, this study indicates that in an aqueous suspension, iron can be liberated from the goethite lattice. Further, it has been shown that photolysis can occur in a multiphase system at the sediment- water interface which results in an oxidation of the organic species and release of Fe2+ to solution where it becomes available for further reaction. ?? 1993.

Goldberg, M.C.; Cunningham, K.M.; Weiner, E.R.

1993-01-01

297

THE EFFECT OF ANOLYTE PRODUCT ACID CONCENTRATION ON HYBRID SULFUR CYCLE PERFORMANCE  

SciTech Connect

The Hybrid Sulfur (HyS) cycle (Fig. 1) is one of the simplest, all-fluids thermochemical cycles that has been devised for splitting water with a high-temperature nuclear or solar heat source. It was originally patented by Brecher and Wu in 1975 and extensively developed by Westinghouse in the late 1970s and early 1980s. As its name suggests, the only element used besides hydrogen and oxygen is sulfur, which is cycled between the +4 and +6 oxidation states. HyS comprises two steps. One is the thermochemical (>800 C) decomposition of sulfuric acid (H{sub 2}SO{sub 4}) to sulfur dioxide (SO{sub 2}), oxygen (O{sub 2}), and water. H{sub 2}SO{sub 4} = SO{sub 2} + 1/2 O{sub 2} + H{sub 2}O. The other is the SO{sub 2}-depolarized electrolysis of water to H{sub 2}SO{sub 4} and hydrogen (H{sub 2}), SO{sub 2} + 2 H{sub 2}O = H{sub 2}SO{sub 4} + H{sub 2}, E{sup o} = -0.156 V, explaining the 'hybrid' designation. These two steps taken together split water into H{sub 2} and O{sub 2} using heat and electricity. Researchers at the Savannah River National Laboratory (SRNL) and at the University of South Carolina (USC) have successfully demonstrated the use of proton exchange membrane (PEM) electrolyzers (Fig. 2) for the SO{sub 2}-depolarized electrolysis (sulfur oxidation) step, while Sandia National Laboratories (SNL) successfully demonstrated the high-temperature sulfuric acid decomposition (sulfur reduction) step using a bayonet-type reactor (Fig. 3). This latter work was performed as part of the Sulfur-Iodine (SI) cycle Integrated Laboratory Scale demonstration at General Atomics (GA). The combination of these two operations results in a simple process that will be more efficient and cost-effective for the massive production of hydrogen than alkaline electrolysis. Recent developments suggest that the use of PEMs other than Nafion will allow sulfuric acid to be produced at higher concentrations (>60 wt%), offering the possibility of net thermal efficiencies around 50% (HHV basis). The effect of operation at higher anolyte concentrations on the flowsheet, and on the net thermal efficiency for a nuclear-heated HyS process, is examined and quantified.

Gorensek, M.; Summers, W.

2010-03-24

298

Uptake of Small Organic Compounds by Sulfuric Acid Aerosols: Dissolution and Reaction  

NASA Technical Reports Server (NTRS)

To assess the role of oxygenated volatile organic compounds in the upper troposphere and lower stratosphere, the interactions of a series of small organic compounds with low-temperature aqueous sulfuric acid will be evaluated. The total amount of organic material which may be taken up from the gas phase by dissolution, surface layer formation, and reaction during the particle lifetime will be quantified. Our current results for acetaldehyde uptake on 40 - 80 wt% sulfuric acid solutions will be compared to those of methanol, formaldehyde, and acetone to investigate the relationships between chemical functionality and heterogeneous activity. Where possible, equilibrium uptake will be ascribed to component pathways (hydration, protonation, etc.) to facilitate evaluation of other species not yet studied in low temperature aqueous sulfuric acid.

Iraci, L. T.; Michelsen, R. R.; Ashbourn, S. F. M.; Staton, S. J. R.

2003-01-01

299

Nonenzymatic oligomerization reactions on templates containing inosinic acid or diaminopurine nucleotide residues  

NASA Technical Reports Server (NTRS)

The template-directed oligomerization of nucleoside-5'-phosphoro-2-methyl imidazolides on standard oligonucleotide templates has been studied extensively. Here, we describe experiments with templates in which inosinic acid (I) is substituted for guanylic acid, or 2,6-diaminopurine nucleotide (D) for adenylic acid. We find that the substitution of I for G in a template is strongly inhibitory and prevents any incorporation of C into internal positions in the oligomeric products of the reaction. The substitution of D for A, on the contrary, leads to increased incorporation of U into the products. We found no evidence for the template-directed facilitation of oligomerization of A or I through A-I base pairing. The significance of these results for prebiotic chemistry is discussed.

Kozlov, I. A.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

1999-01-01

300

Survivability and Abiotic Reactions of Selected Amino Acids in Different Hydrothermal System Simulators  

NASA Astrophysics Data System (ADS)

We tested the stability and reaction of several amino acids using hydrothermal system simulators: an autoclave and two kinds of flow reactors at 200-250 °C. This study generally showed that there is a variation in the individual amino acids survivability in the simulators. This is mainly attributed to the following factors; heat time, cold quenching exposure, metal ions and also silica. We observed that, in a rapid heating flow reactor, high aggregation and/or condensation of amino acids could occur even during a heat exposure of 2 min. We also monitored their stability in a reflow-type of simulator for 120 min at 20 min intervals. The non-hydrolyzed and hydrolyzed samples for this system showed a similar degradation only in the absence of metal ions.

Chandru, Kuhan; Imai, Eiichi; Kaneko, Takeo; Obayashi, Yumiko; Kobayashi, Kensei

2013-04-01

301

A cytometric bead assay for sensitive DNA detection based on enzyme-free signal amplification of hybridization chain reaction.  

PubMed

A versatile flow cytometric bead assay (CBA) is developed for sensitive DNA detection by integrating the advantages of hybridization chain reaction (HCR) for enzyme-free signal amplification, flow cytometry for robust and rapid signal readout as well as magnetic beads (MBs) for facile separation. In this HCR-CBA, a biotinylated hairpin DNA (Bio-H1) is firstly immobilized on streptavidin-functionalized MBs. Upon the addition of target DNA, each target would hybridize with one Bio-H1 to open its hairpin structure and subsequently initiate a cascade of hybridization events between two species of fluorescent DNA hairpin probes (H1*/H2*) to form a nicked double helical DNA structure, resulting in amplified accumulation of numerous fluorophores on the MBs. Finally, the fluorescent MBs are directly analyzed by flow cytometry. This technique enables quantitative analysis of the HCR products anchored on the MBs as a function of target DNA concentration, and analysis of each sample can be completed within few minutes. Therefore, the HCR-CBA approach provides a practical DNA assay with greatly improved sensitivity. The detection limit of a model DNA target is 0.5 pM (3?), which is about 3 orders of magnitude lower compared with traditional hybridization methods without HCR. Furthermore, the signal of complementary target can be clearly distinguished from that of single-base mismatched sequences, indicating the high specificity of the HCR-CBA. Moreover, this strategy is also successfully applied to the DNA analysis in complex biological samples, showing great potential in gene analysis and disease diagnosis in clinical samples. PMID:23807231

Ren, Wei; Liu, Hongmei; Yang, Wenxia; Fan, Yunlong; Yang, Lang; Wang, Yucong; Liu, Chenghui; Li, Zhengping

2013-11-15

302

Conformationally constrained aliphatic-aromatic amino-acid-conjugated hybrid foldamers with periodic beta-turn motifs.  

PubMed

In this note, we describe the design, synthesis, and structural studies of novel hybrid foldamers derived from Aib-Pro-Adb building blocks that display repeat beta-turn structure motif. The foldamer having a conformationally constrained aliphatic-aromatic amino acid conjugate adopts a well-defined, compact, three-dimensional structure, governed by a combined conformational restriction imposed by the individual amino acids with which it is made of. Conformational investigations by single-crystal X-ray and solution-state NMR studies were undertaken to investigate the conformational preference of these foldamers with a hetero-backbone. Our findings suggest that constrained aliphatic-aromatic amino acid conjugates would offer new avenues for the de novo design of hybrid foldamers with distinctive structural architectures. PMID:17691737

Srinivas, Deekonda; Gonnade, Rajesh; Ravindranathan, Sapna; Sanjayan, Gangadhar J

2007-08-31

303

Fatty alcohols or fatty acids as niosomal hybrid carrier: effect on vesicle size, encapsulation efficiency and in vitro dye release.  

PubMed

Niosomal hybrid mixtures are prepared with bilayer stabilizer cholesterol from non-ionic surfactants span 20 (HLB value 8.6), span 60 (HLB 4.7) and span 85 (HLB 1.8) in presence of dicetyl phosphate (DCP) where fatty acids or fatty alcohols (C14, C16 and C18) are used as carrier. Hybrid mixtures upon hydration with aqueous phosphate buffer (pH 7.4) spontaneously produce vesicular phase which can encapsulate 5(6)-carboxyfluorescein (CF). Effect of fatty alcohols and fatty acids on the vesicle size has been studied by dynamic light scattering (DLS), freeze-fracture scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Release rates of CF from vesicular suspensions are found to be dependent on carriers as well as surfactants used. Fatty acid coated hybrids form large multilamellar vesicles (LMV) (size range 10-15 microm) where as fatty alcohol coated hybrid systems form small multilamellar vesicles (SMV) with an average diameter of 400 nm, in all cases vesicles are polydisperse (PI approximately 0.9) in nature. PMID:17339104

Bandyopadhyay, Prasun; Johnson, Madrid

2007-07-01

304

Identification of amino acid residues important in the cyclization reactions of chalcone and stilbene synthases.  

PubMed Central

Chalcone synthase (CHS) and stilbene synthase (STS) catalyse condensation reactions of p-coumaroyl-CoA and three C(2) units from malonyl-CoA up to a common tetraketide intermediate but then catalyse different cyclization reactions to produce naringenin chalcone and resveratrol respectively. On the basis of sequence alignment with other condensing enzymes including 3-ketoacyl-(acyl carrier protein) synthases of polyketide and fatty-acid synthases, site-directed mutagenesis was performed on the active-site G(372)FGPG loops in CHS and STS. The CHS-P375G mutant showed a 6-fold decrease in overall condensing activity with selectively increased production of p-coumaroyltriacetic acid lactone (CTAL, the derailment product of the tetraketide intermediate). Meanwhile, resveratrol production by STS-P(375)G strongly decreased to give various products in the order CTAL> resveratrol approximately bisnoryangonin>naringenin. As a result, naringenin production (cross-reaction) by STS-P(375)G was close to 30% of resveratrol production. Both G(374)L mutants of CHS and STS showed no condensing activity with residual malonyl-CoA decarboxylase activity. These results suggested that the G(372)FGPG loop in CHS and STS contribute to a determination of the outcome during cyclization reactions by serving as a part of the active-site scaffold on which the stereochemistry of cyclization is performed. These observations provide the first biochemical indication that cyclization reactions are modulated by active-site geometry. The implications for the evolutionary relationship of these enzymes are also discussed. PMID:10926848

Suh, D Y; Fukuma, K; Kagami, J; Yamazaki, Y; Shibuya, M; Ebizuka, Y; Sankawa, U

2000-01-01

305

Identification of amino acid residues important in the cyclization reactions of chalcone and stilbene synthases.  

PubMed

Chalcone synthase (CHS) and stilbene synthase (STS) catalyse condensation reactions of p-coumaroyl-CoA and three C(2) units from malonyl-CoA up to a common tetraketide intermediate but then catalyse different cyclization reactions to produce naringenin chalcone and resveratrol respectively. On the basis of sequence alignment with other condensing enzymes including 3-ketoacyl-(acyl carrier protein) synthases of polyketide and fatty-acid synthases, site-directed mutagenesis was performed on the active-site G(372)FGPG loops in CHS and STS. The CHS-P375G mutant showed a 6-fold decrease in overall condensing activity with selectively increased production of p-coumaroyltriacetic acid lactone (CTAL, the derailment product of the tetraketide intermediate). Meanwhile, resveratrol production by STS-P(375)G strongly decreased to give various products in the order CTAL> resveratrol approximately bisnoryangonin>naringenin. As a result, naringenin production (cross-reaction) by STS-P(375)G was close to 30% of resveratrol production. Both G(374)L mutants of CHS and STS showed no condensing activity with residual malonyl-CoA decarboxylase activity. These results suggested that the G(372)FGPG loop in CHS and STS contribute to a determination of the outcome during cyclization reactions by serving as a part of the active-site scaffold on which the stereochemistry of cyclization is performed. These observations provide the first biochemical indication that cyclization reactions are modulated by active-site geometry. The implications for the evolutionary relationship of these enzymes are also discussed. PMID:10926848

Suh, D Y; Fukuma, K; Kagami, J; Yamazaki, Y; Shibuya, M; Ebizuka, Y; Sankawa, U

2000-08-15

306

Influence of salts, including amino acids, on the rate and outcome of the in-water prebiotic reactions  

NASA Astrophysics Data System (ADS)

Most prebiotic reactions are hypothesized to have occurred in water. However, organic compounds in general are not water-soluble. This has created a great problem for prebiotic chemistry. However, it has been shown recently that many organic materials which are not soluble in water are still capable of reacting in water, often at faster rates than in the organic solvents. This has provided a new era in the study of the prebiotic reactions. Simulated prebiotic reactions are typically performed in water. However, presence of inorganic salts and the amino acids was ubiquitous in the aqueous media on the prebiotic Earth. We thus address the influence of common salts and selected water-soluble amino acids on the rate and outcome of selected prebiotic reactions in water. We focus on Diels-Alder (DA) reaction and multicomponent Passerini reaction (PR), as models for other prebiotic reactions. Some of the results came from our laboratory, and others are from the literature. DA reaction is influenced by salts and by selected water-soluble amino acids, but generally not to a large extent. The PR is also influenced by salts, but not dramatically. However, concentrations of salts and amino acids could have been extremely high in various local niches on the early Earth, and the influence of such concentrations on these prebiotic reactions awaits further study.

Kolb, Vera M.

2013-09-01

307

Methanetrisulfonic Acid: A Highly Efficient Strongly Acidic Catalyst for Wagner-Meerwein Rearrangement, Friedel-Crafts Alkylation and Acylation Reactions. Examples from Vitamin E Synthesis  

Microsoft Academic Search

Methanetrisulfonic acid had been prepared for the first time over 140 years ago, but it was used only scarcely in chemical transformations. In the course of our activities dealing with key-steps of industrial syntheses of vitamins, e.g. economically important vitamin E (acetate), we found that methanetrisulfonic acid is an extremely effective catalyst in a variety of reactions. Examples of its

Werner Bonrath; Fabrice Aquino; Alois Haas; Simone Hoppmann; Thomas Netscher; Francesco Pace; Horst Pauling

2009-01-01

308

Au(I)/Au(III)-catalyzed Sonogashira-type reactions of functionalized terminal alkynes with arylboronic acids under mild conditions  

PubMed Central

Summary A straightforward, efficient, and reliable redox catalyst system for the Au(I)/Au(III)-catalyzed Sonogashira cross-coupling reaction of functionalized terminal alkynes with arylboronic acids under mild conditions has been developed. PMID:21804876

Qian, Deyun

2011-01-01

309

Detection of Mycobacterium tuberculosis in clinical samples by two-step polymerase chain reaction and nonisotopic hybridization methods.  

PubMed Central

Detection of Mycobacterium tuberculosis in clinical specimens by the polymerase chain reaction (PCR) was compared with detection by culture. A 317-bp segment within the M. tuberculosis-specific insertion sequence IS6110 was amplified. The detection limit of the PCR assay for cultured mycobacteria was 50 cells per reaction by ethidium bromide-stained agarose gel electrophoresis and 5 cells per reaction by hybridization with an oligonucleotide probe conjugated with either digoxigenin or alkaline phosphatase (AP). This sensitivity was reduced fivefold in sputum specimens seeded with M. tuberculosis. Seventy-six clinical specimens were amplified and examined by the three detection methods. Both the digoxigenin and AP procedures were found to be more sensitive than agarose gel electrophoresis, but they were occasionally associated with a high background. An additional 308 specimens were examined only by agarose gel electrophoresis and the AP procedure. Of 71 specimens found to contain M. tuberculosis, amplified products were detected from 56 (79%) samples by agarose gel electrophoresis and/or the AP procedure. Of the additional 313 specimens that were culture negative for M. tuberculosis, 19 (6%) had amplified products detectable by agarose gel electrophoresis and/or the AP procedure. Compared with culture, PCR showed sensitivities and specificities of 55 and 98%, respectively, for agarose gel electrophoresis and 74 and 95%, respectively, for the AP procedure. Despite this low sensitivity, a rapid positive PCR result was accurate and clinically useful. Images PMID:8417034

Shawar, R M; el-Zaatari, F A; Nataraj, A; Clarridge, J E

1993-01-01

310

Preparation of polyhedral oligomeric silsesquioxane-based hybrid monolith by ring-opening polymerization and post-functionalization via thiol-ene click reaction.  

PubMed

A polyhedral oligomeric silsesquioxane (POSS) hybrid monolith was simply prepared by using octaglycidyldimethylsilyl POSS (POSS-epoxy) and cystamine dihydrochloride as monomers via ring-opening polymerization. The effects of composition of prepolymerization solution and polycondensation temperature on the morphology and permeability of monolithic column were investigated in detail. The obtained POSS hybrid monolithic column showed 3D skeleton morphology and exhibited high column efficiency of ?71,000 plates per meter in reversed-phase mechanism. Owing to this POSS hybrid monolith essentially possessing a great number of disulfide bonds, the monolith surface would expose thiol groups after reduction with dithiothreitol (DTT), which supplied active sites to functionalize with various alkene monomers via thiol-ene click reaction. The results indicated that the reduction with DTT could not destroy the 3D skeleton of hybrid monolith. Both stearyl methylacrylate (SMA) and benzyl methacrylate (BMA) were selected to functionalize the hybrid monolithic columns for reversed-phase liquid chromatography (RPLC), while [2-(methacryloyloxy)ethyl]-dimethyl-(3-sulfopropyl)-ammonium hydroxide (MSA) was used to modify the hybrid monolithic column in hydrophilic interaction chromatography (HILIC). These modified hybrid monolithic columns could be successfully applied for separation of small molecules with high efficiency. It is demonstrated that thiol-ene click reaction supplies a facile way to introduce various functional groups to the hybrid monolith possessing thiol groups. Furthermore, due to good permeability of the resulting hybrid monoliths, we also prepared long hybrid monolithic columns in narrow-bore capillaries. The highest column efficiency reached to ?70,000 plates using a 1-m-long column of 75?m i.d. with a peak capacity of 147 for isocratic chromatography, indicating potential application in separation and analysis of complex biosamples. PMID:24725471

Liu, Zhongshan; Ou, Junjie; Lin, Hui; Wang, Hongwei; Dong, Jing; Zou, Hanfa

2014-05-16

311

Initiation Temperature for Runaway Tri-n-Butyl Phosphate/Nitric Acid Reaction  

SciTech Connect

During a review of the H-Canyon authorization basis, Defense Nuclear Facility Safety Board (DNFSB) staff members questioned the margin of safety associated with a postulated tri-n-butyl phosphate (TBP)/nitric acid runaway reaction due to the inadvertent heating of a canyon tank containing greater than 3000 lbs (1362 kg) of TBP. The margin of safety was partially based on experiments and calculations performed by the Actinide Technology Section (ATS) to support deletion of indication of tank agitation as a Safety Class System. In the technical basis for deletion of this system, ATS personnel conservatively calculated the equilibrium temperature distribution of a canyon tank containing TBP and nitric acid layers which were inadvertently heated by a steam jet left on following a transfer. The maximum calculated temperature (128 degrees C) was compared to the minimum initiation temperature for a runaway reaction (greater than 130 degrees C) documented by experimental work in the mid 195 0s. In this work, the initiation temperature as a function of nitric acid concentration was measured for 0 and 20 wt percent dissolved solids. The DNFSB staff members were concerned that data for 0 wt percent dissolved solids were not conservative given the facts that data for 20 wt percent dissolved solids show initiation temperatures at or below 130 degrees C and H-Canyon solutions normally contained a small amount of dissolved solids.

Rudisill, T.S.

2000-11-28

312

Lewis acid catalyzed reactions of chiral imidazolidinones and oxazolidinones: insights on the role of the catalyst.  

PubMed

The mechanism proposed by Evans to justify the selectivity obtained in Lewis acid catalyzed Diels-Alder reactions of cyclopentadiene with acyloxazolidinones has been generalized and used in the rationalization of selectivities obtained in many other systems. However, we recently proposed an alternative mechanism, on the basis of open-chain mono- and bicomplexes, that avoids the need for chelates and explains the selectivity obtained by Evans. In this manuscript we apply our proposal to the catalyzed conjugated addition of amines to acylimidazolidinones, reported by Cardillo, and we clearly show that aluminum chelates are not involved in the reaction, as they induce no selectivity, while Cardillo observed high experimental selectivities. Our data equally show that bicomplexes with carbonyl parallel orientation, proposed by Cardillo to justify the experimental selectivity with nonchelating Lewis acids, indeed induce the opposite selectivity and have also to be dismissed. On the other hand, our mechanistic proposal allows for the full rationalization of the data obtained by Cardillo with aluminum, boron, or zinc Lewis acids and supports our previous proposal on DA cycloadditions of dienes to Evans chiral auxiliary derivatives. PMID:21786834

Duarte, Filipe J S; Bakalova, Snezhana M; Cabrita, Eurico J; Santos, A Gil

2011-09-01

313

Analytical potential of the reaction between p -phenylenediamines and peroxodisulfate for kinetic spectrophotometric determination of traces of ascorbic acid  

Microsoft Academic Search

The analytical potential of the redox reactions between N,N-dimethyl- or N,N,N',N'-tetramethyl-p-phenylenediamine (DMPPD or TMPPD, respectively) and peroxodisulfate in acidic media for kinetic spectrophotometric determination of trace amounts of ascorbic acid (AA) has been investigated. The goal was to explore reaction conditions ensuring an excess or a deficit of S2O82-, and to identify some kinetic features of the global process for

Alexandra Rustoiu-Csavdari; Ulrich Nickel

2002-01-01

314

Development of an optimized protocol for the detection of classical swine fever virus in formalin-fixed, paraffin-embedded tissues by seminested reverse transcription-polymerase chain reaction and comparison with in situ hybridization.  

PubMed

An optimized protocol was developed for the detection of classical swine fever virus (CSFV) in formalin-fixed, paraffin-embedded tissues obtained from experimentally and naturally infected pigs by seminested reverse transcription-polymerase chain reaction (RT-PCR). The results for seminested RT-PCR were compared with those determined by in situ hybridization. The results obtained show that the use of deparaffinization with xylene, digestion with proteinase K, extraction with Trizol LS, followed by seminested RT-PCR is a reliable detection method. An increase in sensitivity was observed as amplicon size decreased. The highest sensitivity for RT-PCR on formalin-fixed, paraffin-embedded tissues RNA was obtained with amplicon sizes less than approximately 200 base pairs. An hybridization signal for CSFV was detected in lymph nodes from 12 experimentally and 12 naturally infected pigs. The sensitivity of seminested RT-PCR compared with in situ hybridization was 100% for CSFV. When only formalin-fixed tissues are available, seminested RT-PCR and in situ hybridization would be useful diagnostic methods for the detection of CSFV nucleic acid. PMID:15196906

Ha, S-K; Choi, C; Chae, C

2004-10-01

315

A New Palladium Precatalyst Allows for the Fast Suzuki-Miyaura Coupling Reactions of Unstable Polyfluorophenyl and 2- Heteroaryl Boronic Acids  

E-print Network

Boronic acids which quickly deboronate under basic conditions, such as polyfluorophenylboronic acid and five-membered 2-heteroaromatic boronic acids, are especially challenging coupling partners for Suzuki?Miyaura reactions. ...

Kinzel, Tom

316

A practical two-step procedure for the preparation of enantiopure pyridines: Multicomponent reactions of alkoxyallenes, nitriles and carboxylic acids followed by a cyclocondensation reaction  

PubMed Central

Summary A practical approach to highly functionalized 4-hydroxypyridine derivatives with stereogenic side chains in the 2- and 6-positions is described. The presented two-step process utilizes a multicomponent reaction of alkoxyallenes, nitriles and carboxylic acids to provide ?-methoxy-?-ketoenamides which are transformed into 4-hydroxypyridines in a subsequent cyclocondensation. The process shows broad substrate scope and leads to differentially substituted enantiopure pyridines in good to moderate yields. The preparation of diverse substituted lactic acid derived pyrid-4-yl nonaflates is described. Additional evidence for the postulated mechanism of the multicomponent reaction is presented. PMID:21915195

Eidamshaus, Christian; Kumar, Roopender; Bera, Mrinal K

2011-01-01

317

Revisitation of the ?Cl-Elimination Reaction of d-Amino Acid Oxidase  

PubMed Central

d-Amino acid oxidase (DAAO) from pig has been reported to catalyze the ?-elimination of Cl? from ?Cl-d-alanine via abstraction of the substrate ?-H as H+ (“carbanion mechanism”) (Walsh, C. T., Schonbrunn, A., and Abeles, R. H. (1971) J. Biol. Chem. 246, 6855–6866). In view of the fundamental mechanistic importance of this reaction and of the recent reinterpretation of the DAAO dehydrogenation step as occurring via a hydride mechanism, we reinvestigated the elimination reaction using yeast DAAO. That enzyme catalyzes the same reactions as the pig enzyme but with a much higher efficiency and a substantially different kinetic behavior. The reaction is initiated by a very rapid and fully reversible dehydrogenation step. This leads to an equilibrium (kon ? kreverse) between the complexes of oxidized enzyme-?Cl-d-alanine and reduced enzyme-?Cl-iminopyruvate. In the presence of O2 the latter complex can partition between an oxidative half-reaction and elimination of Cl?, which proceeds at a rate of ?50 s?1. This step forms a complex between oxidized enzyme and enamine that is characterized by a charge transfer absorption (which describes its rates of formation and decay). A minimal scheme that lists relevant steps of the reductive and oxidative half-reactions and elimination pathways along with the estimate of the corresponding rate constants is presented. ?-Elimination of Cl? is proposed to originate at the locus of the enzyme-?Cl-iminopyruvate complex. A chemical mechanism that can account for elimination is discussed in detail. PMID:21949129

Ghisla, Sandro; Pollegioni, Loredano; Molla, Gianluca

2011-01-01

318

The Effect of Incorporation of HNO(sub 3) Into Liquid Sulfuric Acid on Heterogeneous Reaction Probabilities  

NASA Technical Reports Server (NTRS)

Using a fast-flow reactor coupled to a quadrupole mass spectrometer, the heterogeneous reactions of C1ONO2 + HCl and HOCl + HCl as well as hydrolysis of N2O5 and C1ONO2 were investigated on liquid sulfuric acid, with particular emphasis on the effect of incorporation of HNO3 on the reaction probabilities.

Zhang, R.; Leu, M-T.; Keyser, L.

1994-01-01

319

Abstract We found the colorimetric reaction of Tiron (1,2-dihydroxybenzene-3,5-disulfonic acid) and  

E-print Network

Abstract We found the colorimetric reaction of Tiron (1,2-dihydroxybenzene-3,5-disulfonic acid.g. Kling and Mewes 2003). Absorption imaging involves a simpler setup by pairing a colorimetric chemical A colorimetric reaction to quantify fluid mixing Peter M. Oates Ã? Charles F. Harvey Received: 22 October 2005

Entekhabi, Dara

320

Aryl Ketone Synthesis via Tandem Orthoplatinated Triarylphosphite-Catalyzed Addition Reactions of Arylboronic Acids with Aldehydes Followed by Oxidation  

PubMed Central

Tandem orthoplatinated triarylphosphite-catalyzed addition reactions of arylboronic acids with aldehydes followed by oxidation to yield aryl ketones is described. 3-Pentanone was identified as a suitable oxidant for the tandem aryl ketone formation reaction. By using microwave energy, aryl ketones were obtained in high yields with the catalyst loading as low as 0.01%. PMID:20849092

Liao, Yuan-Xi; Hu, Qiao-Sheng

2010-01-01

321

Aryl ketone synthesis via tandem orthoplatinated triarylphosphite-catalyzed addition reactions of arylboronic acids with aldehydes followed by oxidation.  

PubMed

Tandem orthoplatinated triaryl phosphite-catalyzed addition reactions of arylboronic acids with aldehydes followed by oxidation to yield aryl ketones is described. 3-Pentanone was identified as a suitable oxidant for the tandem aryl ketone formation reaction. By using microwave energy, aryl ketones were obtained in high yields with the catalyst loading as low as 0.01%. PMID:20849092

Liao, Yuan-Xi; Hu, Qiao-Sheng

2010-10-15

322

Effect of particle size in a limestone-hydrochloric acid reaction system.  

PubMed

Experimental characterization of the wet flue gas desulfurization process is carried out using a model limestone-hydrochloric acid reaction system, with in-situ measurement of the dissolution rate and particle size distribution. The limestone source, initial particle size distribution, working temperature and pH value are varied in large ranges. The dissolution rate is found to be higher when the average particle size is smaller, the temperature is higher, or the pH is lower. An empirical equation is established to correlate the dissolution rate with the particle size and working conditions, which agrees well with measurements. The results may be useful for providing insights to improve the efficiency of the wet flue gas desulfurization process, as well as other solid particle-liquid solution reactions. PMID:20363559

Sun, Bo; Zhou, Qulan; Chen, Xi; Xu, Tongmo; Hui, Shien

2010-07-15

323

Mammalian d-2-hydroxy acid dehydrogenase. Effect of inhibitors and reaction sequence  

PubMed Central

1. The reaction of d-2-hydroxy acid dehydrogenase with d-lactate and 2,6-dichlorophenol-indophenol (DCIP) at pH8.6 yields reciprocal plots of 1/rate versus 1/[d-lactate], at different DCIP concentrations, which appear to be parallel. However, at pH7.55, or in the presence of the competitive inhibitor oxalate at pH8.6, the plots are convergent. This is inconsistent with the mechanism previously proposed for this enzyme. 2. The pattern of inhibition by the product, pyruvate, is consistent with either an Ordered mechanism or an Iso Theorell–Chance mechanism. 3. The observation that the enzyme forms a complex with d-lactate favours the Ordered reaction. In this, first d-lactate and then DCIP bind to the enzyme to form a ternary complex, from which pyruvate and reduced DCIP dissociate in that order. PMID:5528639

Cammack, R.

1970-01-01

324

Luminescent hybrid lanthanide sulfates and lanthanide sulfonate-carboxylates with 1,10-phenanthroline involving in-situ oxidation of 2-mercaptonbenzoic acid  

NASA Astrophysics Data System (ADS)

A series of lanthanide sulfates and lanthanide sulfonate-carboxylates, [Ln2(phen)2(SO4)3(H2O)2]n (I:Ln=Nd(1a), Sm(1b), Eu(1c), phen=1,10-phenanthroline) and [Ln(phen)(2-SBA)(BZA)]n (II: Ln=Sm(2a), Eu(2b), Dy(2c), 2-SBA=2-sulfobenzoate, BZA=benzoate) have been hydrothermally synthesized from lanthanide oxide, 2-mercaptonbenzoic acid with phen as auxiliary ligand and characterized by single-crystal X-ray diffraction, elemental analyses, IR spectra, TG analyses and luminescence spectroscopy. Interestingly, SO42- anions in I came from the in situ deep oxidation of thiol groups of 2-mercaptonbenzoic acid while 2-sulfobenzoate and benzoate ligands in II from the middle oxidation and desulfuration reactions of 2-mercaptonbenzoic acid. Compounds I are organic-inorganic hybrid lanthanide sulfates, which have rare one-dimensional column-like structures. Complexes II are binuclear lanthanide sulfonate-carboxylates with 2-sulfobenzoate and benzoate as bridges and 1,10-phenanthroline as terminal. Photoluminescence studies reveal that complexes I and II exhibit strong lanthanide characteristic emission bands in the solid state at room temperature.

Zhong, Jie-Cen; Wan, Fang; Sun, Yan-Qiong; Chen, Yi-Ping

2015-01-01

325

Facile and straightforward synthesis of superparamagnetic reduced graphene oxide-Fe3O4 hybrid composite by a solvothermal reaction.  

PubMed

A superparamagnetic reduced graphene oxide-Fe(3)O(4) hybrid composite (rGO-Fe(3)O(4)) was prepared via a facile and straightforward method through the solvothermal reaction of iron (III) acetylacetonate (Fe(acac)(3)) and graphene oxide (GO) in ethylenediamine (EDA) and water. By this method, chemical reduction of GO as well as the formation of Fe(3)O(4) nanoparticles (NPs) can be achieved in one step. The Fe(3)O(4) NPs are firmly deposited on the surfaces of rGO, avoiding their reassembly to graphite. The rGO sheets prevent the agglomeration of Fe(3)O(4) NPs and enable a uniform dispersion of these metal oxide particles. The size distribution and coverage density of Fe(3)O(4) NPs deposited on rGO can be controlled by varying the initial mass ratio of GO and iron precursor, Fe(acac)(3). With an initial mass ratio of GO and Fe(acac)(3) of 5:5, the surfaces of rGO sheets are densely covered by spherical Fe(3)O(4) NPs with an average size of 19.9 nm. The magnetic-functionalized rGO hybrid exhibits a good magnetic property and the specific saturation magnetization (M(s)) is 13.2 emu g(-1). The adsorption test of methylene blue from aqueous solution demonstrates the potential application of this rGO-Fe(3)O(4) hybrid composite in removing organic dyes from polluted water. PMID:23220906

Liu, Yue-Wen; Guan, Meng-Xue; Feng, Lan; Deng, Shun-Liu; Bao, Jian-Feng; Xie, Su-Yuan; Chen, Zhong; Huang, Rong-Bin; Zheng, Lan-Sun

2013-01-18

326

Hybrid pathwise sensitivity methods for discrete stochastic models of chemical reaction systems  

NASA Astrophysics Data System (ADS)

Stochastic models are often used to help understand the behavior of intracellular biochemical processes. The most common such models are continuous time Markov chains (CTMCs). Parametric sensitivities, which are derivatives of expectations of model output quantities with respect to model parameters, are useful in this setting for a variety of applications. In this paper, we introduce a class of hybrid pathwise differentiation methods for the numerical estimation of parametric sensitivities. The new hybrid methods combine elements from the three main classes of procedures for sensitivity estimation and have a number of desirable qualities. First, the new methods are unbiased for a broad class of problems. Second, the methods are applicable to nearly any physically relevant biochemical CTMC model. Third, and as we demonstrate on several numerical examples, the new methods are quite efficient, particularly if one wishes to estimate the full gradient of parametric sensitivities. The methods are rather intuitive and utilize the multilevel Monte Carlo philosophy of splitting an expectation into separate parts and handling each in an efficient manner.

Wolf, Elizabeth Skubak; Anderson, David F.

2015-01-01

327

Hybrid pathwise sensitivity methods for discrete stochastic models of chemical reaction systems.  

PubMed

Stochastic models are often used to help understand the behavior of intracellular biochemical processes. The most common such models are continuous time Markov chains (CTMCs). Parametric sensitivities, which are derivatives of expectations of model output quantities with respect to model parameters, are useful in this setting for a variety of applications. In this paper, we introduce a class of hybrid pathwise differentiation methods for the numerical estimation of parametric sensitivities. The new hybrid methods combine elements from the three main classes of procedures for sensitivity estimation and have a number of desirable qualities. First, the new methods are unbiased for a broad class of problems. Second, the methods are applicable to nearly any physically relevant biochemical CTMC model. Third, and as we demonstrate on several numerical examples, the new methods are quite efficient, particularly if one wishes to estimate the full gradient of parametric sensitivities. The methods are rather intuitive and utilize the multilevel Monte Carlo philosophy of splitting an expectation into separate parts and handling each in an efficient manner. PMID:25612685

Wolf, Elizabeth Skubak; Anderson, David F

2015-01-21

328

Mapping the regioisomeric distribution of fatty acids in triacylglycerols by hybrid mass spectrometry[S  

PubMed Central

This study describes the use of hybrid mass spectrometry for the mapping, identification, and semi-quantitation of triacylglycerol regioisomers in fats and oils. The identification was performed based on the accurate mass and fragmentation pattern obtained by data-dependent fragmentation. Quantitation was based on the high-resolution ion chromatograms, and relative proportion of sn-1(3)/sn-2 regioisomers was calculated based on generalized fragmentation models and the relative intensities observed in the product ion spectra. The key performance features of the developed method are inter-batch mass accuracy < 1 ppm (n = 10); lower limit of detection (triggering threshold) 0.1 ?g/ml (equivalent to 0.2 weight % in oil); lower limit of quantitation 0.2 ?g/ml (equivalent to 0.4 weight % in oil); peak area precision 6.5% at 2 ?g/ml concentration and 15% at 0.2 ?M concentration; inter-batch precision of fragment intensities < 1% (n = 10) independent of the investigated concentration; and averaged accuracy using the generic calibration 3.8% in the 1–10 ?g/ml range and varies between 1–23% depending on analytes. Inter-esterified fat, beef tallow, pork lard, and butter fat samples were used to show how well regioisomeric distribution of palmitic acid can be captured by this method. PMID:23093552

Nagy, Kornél; Sandoz, Laurence; Destaillats, Frédéric; Schafer, Olivier

2013-01-01

329

Detection of Food Spoilage and Pathogenic Bacteria Based on Ligation Detection Reaction Coupled to Flow-Through Hybridization on Membranes  

PubMed Central

Traditional culturing methods are still commonly applied for bacterial identification in the food control sector, despite being time and labor intensive. Microarray technologies represent an interesting alternative. However, they require higher costs and technical expertise, making them still inappropriate for microbial routine analysis. The present study describes the development of an efficient method for bacterial identification based on flow-through reverse dot-blot (FT-RDB) hybridization on membranes, coupled to the high specific ligation detection reaction (LDR). First, the methodology was optimized by testing different types of ligase enzymes, labeling, and membranes. Furthermore, specific oligonucleotide probes were designed based on the 16S rRNA gene, using the bioinformatic tool Oligonucleotide Retrieving for Molecular Applications (ORMA). Four probes were selected and synthesized, being specific for Aeromonas spp., Pseudomonas spp., Shewanella spp., and Morganella morganii, respectively. For the validation of the probes, 16 reference strains from type culture collections were tested by LDR and FT-RDB hybridization using universal arrays spotted onto membranes. In conclusion, the described methodology could be applied for the rapid, accurate, and cost-effective identification of bacterial species, exhibiting special relevance in food safety and quality. PMID:24818128

Böhme, K.; Cremonesi, P.; Severgnini, M.; Villa, Tomás G.; Fernández-No, I. C.; Barros-Velázquez, J.; Castiglioni, B.; Calo-Mata, P.

2014-01-01

330

Detection of food spoilage and pathogenic bacteria based on ligation detection reaction coupled to flow-through hybridization on membranes.  

PubMed

Traditional culturing methods are still commonly applied for bacterial identification in the food control sector, despite being time and labor intensive. Microarray technologies represent an interesting alternative. However, they require higher costs and technical expertise, making them still inappropriate for microbial routine analysis. The present study describes the development of an efficient method for bacterial identification based on flow-through reverse dot-blot (FT-RDB) hybridization on membranes, coupled to the high specific ligation detection reaction (LDR). First, the methodology was optimized by testing different types of ligase enzymes, labeling, and membranes. Furthermore, specific oligonucleotide probes were designed based on the 16S rRNA gene, using the bioinformatic tool Oligonucleotide Retrieving for Molecular Applications (ORMA). Four probes were selected and synthesized, being specific for Aeromonas spp., Pseudomonas spp., Shewanella spp., and Morganella morganii, respectively. For the validation of the probes, 16 reference strains from type culture collections were tested by LDR and FT-RDB hybridization using universal arrays spotted onto membranes. In conclusion, the described methodology could be applied for the rapid, accurate, and cost-effective identification of bacterial species, exhibiting special relevance in food safety and quality. PMID:24818128

Böhme, K; Cremonesi, P; Severgnini, M; Villa, Tomás G; Fernández-No, I C; Barros-Velázquez, J; Castiglioni, B; Calo-Mata, P

2014-01-01

331

Diastereoselectivity in the Lewis acid mediated aldol reaction of chiral ?, ?-epoxyaldehydes with a ketene silyl acetal  

Microsoft Academic Search

The Lewis acid mediated aldol reaction of chiral a, ß-cis andtrans epoxyaldehydes1 and2 withtert-butyl ketene silyl acetal proceeds mainly withanti diastereofacial preference. The best results were obtained forcis epoxyaldehyde1 in the presence of catalytic amounts of BiCl3·1.5 eq. ZnI2 (anti:syn ~ 13:1), whereas the poorest stereoselectivity was observed when an excess of LiClO4 was used (anti:syn ~ 1:1). The more

E. Fontaine; M. Baltas; J.-M. Escudier; L. Gorrichon

1996-01-01

332

Dynamic states of the Bray-Liebhafsky reaction when sulfuric acid is the control parameter  

NASA Astrophysics Data System (ADS)

Dynamic behavior of hydrogen peroxide decomposition catalyzed by iodate and hydrogen ions (the Bray-Liebhafsky reaction), in a continuous stirred tank reactor is investigated. The experimental results are obtained at one operational point in concentration phase space by varying mixed inflow concentrations of the sulfuric acid. The experimental evidences for the onset and termination of oscillatory behavior via the saddle node infinite period bifurcation as well as some kind of the Andronov-Hopf bifurcation are presented. In addition, the possibility of excitability of a stable steady state by thiamine was observed.

Peji?, N.; Maksimovi?, J.; Ribi?, D.; Kolar-Ani?, Lj.

2009-09-01

333

Molybdenum phosphosulfide: an active, Acid-stable, Earth-abundant catalyst for the hydrogen evolution reaction.  

PubMed

Introducing sulfur into the surface of molybdenum phosphide (MoP) produces a molybdenum phosphosulfide (MoP|S) catalyst with superb activity and stability for the hydrogen evolution reaction (HER) in acidic environments. The MoP|S catalyst reported herein exhibits one of the highest HER activities of any non-noble-metal electrocatalyst investigated in strong acid, while remaining perfectly stable in accelerated durability testing. Whereas mixed-metal alloy catalysts are well-known, MoP|S represents a more uncommon mixed-anion catalyst where synergistic effects between sulfur and phosphorus produce a high-surface-area electrode that is more active than those based on either the pure sulfide or the pure phosphide. The extraordinarily high activity and stability of this catalyst open up avenues to replace platinum in technologies relevant to renewable energies, such as proton exchange membrane (PEM) electrolyzers and solar photoelectrochemical (PEC) water-splitting cells. PMID:25359678

Kibsgaard, Jakob; Jaramillo, Thomas F

2014-12-22

334

Chiral sulfinamidourea and strong Brønsted acid-cocatalyzed enantioselective Povarov reaction to access tetrahydroquinolines.  

PubMed

This protocol describes a method for the laboratory synthesis of enantiomerically enriched, chiral tetrahydroisoquinolines through the application of a chiral sulfinamido urea catalyst for the Povarov reaction. Tetrahydroisoquinolines are bicyclic organic frameworks present in a wide assortment of natural and synthetic biologically important compounds including martinelline, scoulerine and tubocurarine. The methodology involves the [4+2] cycloaddition of a N-arylimines with electron-rich olefins such as vinyl lactams and dihydropyrroles in the presence of a two-catalyst system consisting of an achiral strong Brønsted acid (o-nitrobenzenesulfonic acid), together with the chiral sulfinamido urea derivative 1. The anion-binding properties of the urea lead to the association of the ion pair that results from protonation of the imine substrate. Cycloaddition is followed by spontaneous proton loss with re-aromatization to provide the tetrahydroisoquinoline products in highly enantio-enriched form. PMID:25010906

Xu, Hao; Zhang, Hu; Jacobsen, Eric N

2014-08-01

335

Reactions of reducing and oxidizing radicals with caffeic acid:. a pulse radiolysis and theoretical study  

NASA Astrophysics Data System (ADS)

Molecular calculations coupled with pulse radiolysis studies are performed to understand the reactions of radicals with caffeic acid. From molecular calculation, we find that e aq- and ·OH tend to form adducts with caffeic acid, while N 3rad tends to abstract H from 4-hydroxyl group in benzene ring, generating a semi-quinoid radical. Based on comparison of the heat of formation, the most favorable radical attack sites and the most stable radical structures are predicted. The calculation results suggest that the stability of the electron adducts

Li, Xifeng; Cai, Zhongli; Katsumura, Yosuke; Wu, Guozhong; Muroya, Yusa

2001-01-01

336

Colorimetric detection of mercury ion based on unmodified gold nanoparticles and target-triggered hybridization chain reaction amplification  

NASA Astrophysics Data System (ADS)

A novel unmodified gold nanoparticles (AuNPs)-based colorimetric strategy for label-free, specific and sensitive mercury ion (Hg2+) detection was demonstrated by using thymine-Hg2+-thymine (T-Hg2+-T) recognition mechanism and hybridization chain reaction (HCR) amplification strategy. In this protocol, a structure-switching probe (H0) was designed to recognize Hg2+ and then propagated a chain reaction of hybridization events between two other hairpin probes (H1 and H2). In the absence of Hg2+, all hairpin probes could stably coexist in solution, the exposed sticky ends of hairpin probes were capable of stabilizing AuNPs. As a result, salt-induced AuNPs aggregation could be effectively prevented. In the presence of Hg2+, thymine bases of H0 could specifically interact with Hg2+ to form stable T-Hg2+-T complex. Consequently, the hairpin structure of H0 probe was changed. As H1/H2 probes were added, the HCR process could be triggered and nicked double-helixes were formed. Since it was difficult for the formed nicked double-helixes to inhibit salt-induced AuNPs aggregation, a red-to-blue color change was observed in the colloid solution as the salt concentration increased. With the elegant amplification effect of HCR, a detection limit of around 30 nM was achieved (S/N = 3), which was about 1-2 orders of magnitudes lower than that of previous unmodified AuNPs-based colorimetric methods. By using the T-Hg2+-T recognition mechanism, high selectivity was also obtained. As an unmodified AuNPs-based colorimetric strategy, the system was simple in design, convenient in operation, and eliminated the requirements of separation processes, chemical modifications, and sophisticated instrumentations.

Wang, Qing; Yang, Xiaohan; Yang, Xiaohai; Liu, Pei; Wang, Kemin; Huang, Jin; Liu, Jianbo; Song, Chunxia; Wang, Jingjing

2015-02-01

337

Transition-metal/Lewis acid free synthesis of acyl benzothiophenes via C-C bond forming reaction.  

PubMed

A simple and single-step synthesis of 2- and 3-acyl substituted benzothiophenes has been described via environmentally benign acylation of benzothiophene with in situ generated acyl trifluoroacetates. Both aliphatic and aromatic carboxylic acids participated in trifluoroacetic anhydride/phosphoric acid mediated C-C bond forming reactions under solvent-free conditions affording acyl benzothiophenes in good overall yields. PMID:17961232

Pal, Sarbani; Khan, Mohammad Ashrafuddin; Bindu, P; Dubey, P K

2007-01-01

338

Metal amides as the simplest acid/base catalysts for stereoselective carbon-carbon bond-forming reactions.  

PubMed

In this paper, new possibilities for metal amides are described. Although typical metal amides are recognized as strong stoichiometric bases for deprotonation of inert or less acidic hydrogen atoms, transition-metal amides, namely silver and copper amides, show interesting abilities as one of the simplest acid/base catalysts in stereoselective carbon-carbon bond-forming reactions. PMID:23775980

Yamashita, Yasuhiro; Kobayashi, Sh?

2013-07-15

339

Transition-metal/Lewis acid free synthesis of acyl benzothiophenes via C-C bond forming reaction  

PubMed Central

A simple and single-step synthesis of 2- and 3-acyl substituted benzothiophenes has been described via environmentally benign acylation of benzothiophene with in situ generated acyl trifluoroacetates. Both aliphatic and aromatic carboxylic acids participated in trifluoroacetic anhydride/phosphoric acid mediated C-C bond forming reactions under solvent-free conditions affording acyl benzothiophenes in good overall yields. PMID:17961232

Pal, Sarbani; Khan, Mohammad Ashrafuddin; Bindu, P; Dubey, PK

2007-01-01

340

The H[subscript 3]PO[subscript 4] Acid Ionization Reactions: A Capstone Multiconcept Thermodynamics General Chemistry Laboratory Exercise  

ERIC Educational Resources Information Center

The thermodynamic properties of weak acid ionization reactions are determined. The thermodynamic properties are corresponding values of the absolute temperature (T), the weak acid equilibrium constant (K[subscript a]), the enthalpy of ionization (delta[subscript i]H[degrees]), and the entropy of ionization (delta[subscript i]S[degrees]). The…

Nyasulu, Frazier; Barlag, Rebecca; Wise, Lindy; McMills, Lauren

2013-01-01

341

Calibration and intercomparison of acetic acid measurements using proton transfer reaction mass spectrometry (PTR-MS)  

USGS Publications Warehouse

Acetic acid is one of the most abundant organic acids in the ambient atmosphere, with maximum mixing ratios reaching into the tens of parts per billion by volume (ppbv) range. The identities and associated magnitudes of the major sources and sinks for acetic acid are poorly characterized, due in part to the limitation in available measurement techniques. This paper demonstrates that Proton Transfer Reaction Mass Spectrometry (PTR-MS) can reliably quantify acetic acid vapor in ambient air. Three different PTR-MS configurations were calibrated at low ppbv mixing ratios using permeation tubes, which yielded calibration factors between 7.0 and 10.9 normalized counts per second per ppbv (ncps ppbv?1) at a drift tube field strength of 132 townsend (Td). Detection limits ranged from 0.06 to 0.32 ppbv with dwell times of 5 s. These calibration factors showed negligible humidity dependence. Using the experimentally determined calibration factors, PTR-MS measurements of acetic acid during the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) campaign were validated against results obtained using Mist Chambers coupled with Ion Chromatography (MC/IC). An orthogonal least squares linear regression of paired data yielded a slope of 1.14 ± 0.06 (2?), an intercept of 0.049 ± 20 (2?) ppbv, and an R2 of 0.78. The median mixing ratio of acetic acid on Appledore Island, ME during the ICARTT campaign was 0.530 ± 0.025 ppbv with a minimum of 0.075 ± 0.004 ppbv, and a maximum of 3.555 ± 0.171 ppbv.

Haase, K.B.; Keene, W.C.; Pszenny, A.A.P.; Mayne, H.R.; Talbot, R.W.; Sive, B.C.

2012-01-01

342

The enzymic oxidation of chlorogenic acid and some reactions of the quinone produced  

PubMed Central

1. Partially purified preparations of tobacco-leaf o-diphenol oxidase (o-quinol–oxygen oxidoreductase; EC 1.10.3.1) oxidize chlorogenic acid to brown products, absorbing, on average, 1·6atoms of oxygen/mol. oxidized, and evolving a little carbon dioxide. 2. The effect of benzenesulphinic acid on the oxidation suggests that the first stage is the formation of a quinone; the solution does not go brown, oxygen uptake is restricted to 1 atom/mol. oxidized, and a compound is produced whose composition corresponds to that of a sulphone of the quinone derived from chlorogenic acid. 3. Several other compounds that react with quinones affect the oxidation of chlorogenic acid. The colour of the products formed and the oxygen absorbed in their formation suggest that the quinone formed in the oxidation reacts with these compounds in the same way as do simpler quinones. 4. Some compounds that are often used to prevent the oxidation of polyphenols were tested to see if they act by inhibiting o-diphenol oxidase, by reacting with quinone intermediates, or both. 5. Ascorbate inhibits the enzyme and also reduces the quinone. 6. Potassium ethyl xanthate, diethyldithiocarbamate and cysteine inhibit the enzyme to different extents, and also react with the quinone. The nature of the reaction depends on the relative concentrations of inhibitor and chlorogenic acid. Excess of inhibitor prevents the solution from turning brown and restricts oxygen uptake to 1 atom/mol. of chlorogenic acid oxidized; smaller amounts do not prevent browning and slightly increase oxygen uptake. 7. 2-Mercaptobenzothiazole inhibits the enzyme, and also probably reacts with the quinone; inhibited enzyme is reactivated as if the inhibitor is removed as traces of quinone are produced. 8. Thioglycollate and polyvinylpyrrolidone inhibit the enzyme. Thioglycollate probably reduces the quinone to a small extent. PMID:5941350

Pierpoint, W. S.

1966-01-01

343

Design, synthesis and pharmacological evaluation of novel tacrine-caffeic acid hybrids as multi-targeted compounds against Alzheimer's disease.  

PubMed

A novel series of tacrine-caffeic acid hybrids (5a-f) were designed and synthesized by combining caffeic acid (CA) with tacrine. The antioxidant study revealed that all the hybrids have much more antioxidant capacities compared to CA. Among these compounds, 5e showed the highest selectivity in inhibiting acetylcholinesterase (AChE) over butyrylcholinesterase (BuChE). Enzyme kinetic study had suggested that 5e binds to both catalytic (CAS) and peripheral anionic sites (PAS) of AChE. Moreover, compound 5e also inhibited self- or AChE-induced ?-amyloid(1-40) aggregation, as well as had potent neuroprotective effects against H(2)O(2)- and glutamate- induced cell death with low toxicity in HT22 cells. PMID:22981331

Chao, Xiaojuan; He, Xixin; Yang, Yilin; Zhou, Xie; Jin, Minghua; Liu, Shu; Cheng, Zhiyi; Liu, Peiqing; Wang, Yuting; Yu, Jianchen; Tan, Yi; Huang, Yingjuan; Qin, Jian; Rapposelli, Simona; Pi, Rongbiao

2012-10-15

344

Oxidized Fatty Acid Analysis by Charge Switch Derivatization, Selected Reaction Monitoring and Accurate Mass Quantification  

PubMed Central

A highly sensitive, specific and robust method for the analysis of oxidized metabolites of linoleic, acid (LA), arachidonic acid (AA) and docosahexaenoic acid (DHA) was developed using charge-switch derivatization, LC-ESI MS/MS with selected reaction monitoring (SRM) and quantitation by high mass accuracy analysis of product ions thereby minimizing interferences from contaminating ions. Charge-switch derivatization of LA, AA and DHA metabolites with N-(4-aminomethylphenyl)-pyridinium resulted in a 10-30 fold increase in ionization efficiency. Improved quantitation was accompanied by decreased false positive interferences through accurate mass measurements of diagnostic product ions during SRM transitions by ratiometric comparisons with stable isotope internal standards. The limits of quantification (LOQ) were between 0.05 to 6.0 pg with a dynamic range of 3-4 orders of magnitude (correlation coefficient r2 > 0.99). This approach was utilized to quantitate the levels of representative fatty acid metabolites from WT and iPLA2??/? mouse liver identifying the role of iPLA2? in hepatic lipid 2nd messenger production. Collectively, these results demonstrate the utility of high mass accuracy product ion analysis in conjunction with charge-switch derivatization for the highly specific quantitation of diminutive amounts of LA, AA and DHA metabolites in biologic systems. PMID:23850559

Liu, Xinping; Moon, Sung Ho; Mancuso, David J.; Jenkins, Christopher M.; Guan, Shaoping; Sims, Harold F.; Gross, Richard W.

2013-01-01

345

Dicarboxylic acid anhydride condensation with compounds containing active methylene groups. 4: Some 4-nitrophthalic anhydride condensation reactions  

NASA Technical Reports Server (NTRS)

By 4-nitrophthalic anhydride condensation with acetoacetate in acetic anhydride and triethylamine solution with subsequent breakdown of the intermediate condensation product, 5-nitroindanedione-1,3 was obtained. A 4-nitrophthalic anhydride with acetic anhydride, according to reaction conditions, may yield two products: in the presence of potassium acetate and at high temperatures 4-(or 5-)-nitro-2-acetylbenzoic acid is formed: in the presence of triethylamine and at room temperature 5-( or 6-)-nitrophthalic acetic acid is isolated. A 4-nitrophthalic anhydride and malonic acid in pyridine solution according to temperature yield either 5-( or 6-)-nitrophthalic acetic acid or 4-(or 5-)-nitro-2-acetylbenzoic acid.

Oskaja, V.; Rotberg, J.

1985-01-01

346

Modeling the reactions of 1-naphthylamine and 4-methylaniline with humic acids: Spectroscopic investigations of the covalent linkages  

SciTech Connect

The covalent binding of two aromatic amines, 1-naphthylamine and 4-methylaniline, to substituted quinones in aqueous solutions has been studied as a model for the covalent binding of amines to humic acids. An imine compound was the only type of product identified for the reactions between 1-naphthylamine and selected quinones. Reactions of 4-methylaniline with the same quinones gave a 1,4- addition product in addition to the imine compound, although only the imine produce was formed when the quinone had bulky substituents at the 2- and 6- positions. These results provide additional insight into the reactions of aromatic amines with humic acid quinones.

Ononye, A.I. (Knoxville College, TN (United States). Dept. of Chemistry); Graveel, J.G. (Purdue Univ., West Lafayette, IN (United States). Dept. of Agronomy)

1994-04-01

347

Design of a binaphthyl-based axially chiral amino acid as an organocatalyst for direct asymmetric aldol reactions.  

PubMed

A novel and robust binaphthyl-based amino acid was designed and successfully applied to the direct asymmetric aldol reaction. In some cases, this catalyst leads to higher yields and selectivities than the well-known proline catalyst. For instance, the direct asymmetric aldol reaction of acetone with 4-nitrobenzaldehyde in the presence of the binaphthyl-based amino acid catalyst proceeded smoothly to give the aldol adduct in 82% yield with 95% ee. This catalyst was also found to catalyze effectively the reactions of cyclic or unsymmetrical ketones to give the corresponding aldol adducts with excellent diastereo- and enantioselectivities. PMID:17441057

Kano, Taichi; Tokuda, Osamu; Takai, Jun; Maruoka, Keiji

2006-07-17

348

Hybrid simulations of stochastic reaction-diffusion processes for modeling intracellular signaling pathways  

NASA Astrophysics Data System (ADS)

In the intracellular environment, signaling takes place in a nonideal environment that is spatially heterogeneous and that is noisy, with the noise arising from the low copy numbers of the signaling molecules involved. In this paper, we model intracellular signaling pathways as stochastic reaction-diffusion processes and adapt techniques commonly used by physicists to solve for the spatiotemporal evolution of the signaling pathways. We then apply it to study two problems of relevance to the modeling of intracellular signaling pathways. First, we show that, in the limit of small protein diffusion which is typically the case for proteins in the cytosol crowded by other macromolecules, the extent of diffusion control, in the transient regime, on reactions is greater than previous predictions. Second, we show that the presence of scaffold proteins can modify the phosphorylation activity of a mitogen-activated protein kinase cascade, and explain how this activity is modulated by the scaffold protein concentration.

Chiam, K.-H.; Tan, Chee Meng; Bhargava, Vipul; Rajagopal, Gunaretnam

2006-11-01

349

Biomedical nanocomposites of poly(lactic acid) and calcium phosphate hybridized with modified carbon nanotubes for hard tissue implants.  

PubMed

Degradable polymer-based materials are attractive in orthopedics and dentistry as an alternative to metallic implants for use as bone fixatives. Herein, a degradable polymer poly(lactic acid) (PLA) was combined with novel hybrid nanopowder of carbon nanotubes (CNTs)-calcium phosphate (CP) for this application. In particular, CNTs-CP hybrid nanopowders (0.1 and 0.25% CNTs) were prepared from the solution of ionically modified CNTs (mCNTs), which was specifically synthesized to be well-dispersed and thus to effectively adsorb onto the CP nanoparticles. The mCNTs-CP hybrid nanopowders were then mixed with PLA (up to 50%) to produce mCNTs-CP-PLA nanocomposites. The mechanical tensile strength of the nanocomposites was significantly improved by the addition of mCNTs-CP hybrid nanopowders. Moreover, nanocomposites containing low concentration of mCNTs (0.1%) showed significantly stimulated biological responses including cell proliferation and osteoblastic differentiation in terms of gene and protein expressions. Based on this study, the addition of novel mCNT-CP hybrid nanopowders to PLA biopolymer may be considered a new material choice for developing hard tissue implants. PMID:21591250

Lee, Hae-Hyoung; Sang Shin, Ueon; Lee, Jae-Ho; Kim, Hae-Won

2011-08-01

350

Hybrid sponge comprised of galactosylated chitosan and hyaluronic acid mediates the co-culture of hepatocytes and endothelial cells.  

PubMed

When constructing an in vitro model of liver tissue to mimic the in vivo liver microenvironment, the major challenge is to preserve and maintain the hepatocyte phenotype. The aim of this study was to develop a novel intelligent hybrid sponge for use in a dense co-culture system designed to simulate the liver microenvironment. We prepared a galactosylated chitosan (GCs)/hyaluronic acid (HA) hybrid sponge using a freeze-drying technique for the co-culture of primary hepatocytes and endothelial cells. Subsequently, we investigated the biocompatibility of the GCs/HA scaffold with primary hepatocytes and endothelial cells in terms of cell attachment, morphology, bioactivity, and maintenance of specific liver functions. The GCs/HA-hybrid sponge demonstrated good biocompatibility not only with primary hepatocytes, but also with endothelial cells. In our model, primary hepatocytes exhibited superior bioactivity and higher levels of liver-specific functions in terms of hepatocyte-specific gene expression, urea production, and testosterone metabolism as compared to a monoculture system. We succeeded in constructing a liver tissue-like model using the GCs/HA-hybrid sponge. Therefore, we anticipate that GCs/HA-hybrid sponges may be a promising matrix for the co-culture of hepatocytes and endothelial cells in liver tissue engineering, and might be employed as a novel co-culture model for applications in toxicology and drug metabolism. PMID:23896016

Shang, Yi; Tamai, Miho; Ishii, Ryusei; Nagaoka, Noriyuki; Yoshida, Yasuhiro; Ogasawara, Masamichi; Yang, Jun; Tagawa, Yoh-ichi

2014-01-01

351

DABO Boronates: Stable Heterocyclic Boronic Acid Complexes for Use in Suzuki-Miyaura Cross-Coupling Reactions.  

PubMed

Diethanolamine complexed heterocyclic boronic acids (DABO boronates) are air-stable reagents that can be used directly in Suzuki-Miyaura reactions in the presence of water or a protic co-solvent. Interestingly, heterocyclic DABO boronates can be stored for extended periods of time at room temperature with no noticeable degradation, unlike their boronic acid counterparts. Heterocyclic DABO boronates constitute an operationally simple and efficient alternative to other boronic acid derivatives as coupling partners in palladium catalyzed cross-coupling reactions under standard Suzuki-Miyaura conditions. PMID:24371372

Reilly, Maureen K; Rychnovsky, Scott D

2011-10-01

352

DABO Boronates: Stable Heterocyclic Boronic Acid Complexes for Use in Suzuki-Miyaura Cross-Coupling Reactions  

PubMed Central

Diethanolamine complexed heterocyclic boronic acids (DABO boronates) are air-stable reagents that can be used directly in Suzuki-Miyaura reactions in the presence of water or a protic co-solvent. Interestingly, heterocyclic DABO boronates can be stored for extended periods of time at room temperature with no noticeable degradation, unlike their boronic acid counterparts. Heterocyclic DABO boronates constitute an operationally simple and efficient alternative to other boronic acid derivatives as coupling partners in palladium catalyzed cross-coupling reactions under standard Suzuki-Miyaura conditions. PMID:24371372

Reilly, Maureen K.

2013-01-01

353

Mechanistic and kinetic study on the reactions of coumaric acids with reactive oxygen species: a DFT approach.  

PubMed

The mechanism and kinetics of reactions between coumaric acids and a series of reactive oxygen species ((•)OX) was studied through the density functional theory (DFT). H atom abstraction from -OH and -COOH groups and addition to the nonaromatic double bond were the most representative reaction pathways chosen for which free energy barriers and rate constants were calculated within the transition state theory (TST) framework. From these calculations, it was estimated that (•)OH > (•)OCH3 > (•)OOH > (•)OOCH3 is the order of reactivity of (•)OX with any coumaric acid. The highest rate constant was estimated for p-coumaric acid + (•)OH reaction, whereas the rest of the (•)OX species are more reactive with o-coumaric acid. On the basis of the calculated rate constants, H abstraction from a -OH group should be the main mechanism for the reactions involving (•)OCH3, (•)OOH, and (•)OOCH3 radicals. Nevertheless, the addition mechanism, which sometimes is not considered in theoretical studies on reactions of phenolic compounds with electrophilic species, could play a relevant role in the global mechanism of coumaric acid + (•)OH reactions. PMID:25166496

Garzón, Andrés; Bravo, Iván; Barbero, Antonio J; Albaladejo, José

2014-10-01

354

Rational design and synthesis of hybrid porous polymers derived from polyhedral oligomeric silsesquioxanes via heck coupling reactions.  

PubMed

Heck coupling reactions are introduced as an efficient method to prepare porous polymers. Novel inorganic-organic hybrid porous polymers (HPPs) were constructed via Heck coupling reactions from cubic functional polyhedral oligomeric silsesquioxanes (POSS), iodinated octaphenylsilsesquioxanes (OPS) and octavinylsilsesquioxanes (OVS) using Pd(OAc)2 /PPh3 as the catalyst. Here, two iodinated OPS were used, IOPS and p-I8 OPS. IOPS was a mixture with 90% octasubstituted OPS (I8 ) and some nonasubstituted OPS (I9 ), while p-I8 OPS was a nearly pure compound with ?99% I8 and ?93% para-substitution. IOPS and p-I8 OPS reacted with OVS to produce the porous materials HPP-1 and HPP-2, which exhibited comparable specific surface areas with SBET of 418 ± 20 m(2) g(-1) and 382 ± 20 m(2) g(-1) , respectively, with total pore volumes of 0.28 ± 0.01 cm(3) g(-1) and 0.23 ± 0.01 cm(3) g(-1) , respectively. HPP-1 showed a broader pore size distribution and possessed a more significant contribution from the mesopores, when compared with HPP-2, thereby indicating that IOPS may induce more disorder because of the geometrical asymmetry. HPP-1 and HPP-2 possessed moderate carbon dioxide uptakes of 134 and 124 cm(3) g(-1) at 1 bar at 195 K, making them promising candidates for CO2 capture and storage. The synthesized porous polymers may be easily post-functionalized using the retained ethenylene groups. PMID:23529823

Wang, Dengxu; Xue, Lei; Li, Liguo; Deng, Bei; Feng, Shengyu; Liu, Hongzhi; Zhao, Xian

2013-05-27

355

Interphase fluorescence in situ hybridization and reverse transcription polymerase chain reaction as a diagnostic aid for synovial sarcoma.  

PubMed Central

Identification of the t(X;18)(p11.2;q11.2) that is associated with a high proportion of synovial sarcoma can be a useful diagnostic aid. The translocation results in fusion of the SYT gene on chromosome 18 to either the SSX1 or the SSX2 gene, two homologous genes within Xp11.2. Two-color interphase fluorescence in situ hybridization and reverse transcription polymerase chain reaction were assessed as approaches to identify the rearrangement in well characterized cases. The presence of the translocation, and the specific chromosome X gene disrupted, were inferred from the configuration of signals from chromosome-specific centromere probes, paints, and markers flanking each gene in preparations of interphase nuclei. Rearrangement was found in two cell lines and eight of nine tumor samples, including analysis of five touch imprints. This was consistent with cytogenetic data in four cases and reverse transcription polymerase chain reaction analysis using primers known to amplify both SYT-SSX1 and SYT-SSX2 transcripts. The transcripts were distinguished by restriction with LspI and SmaI. Contrary to previous suggestions, there was no obvious correlation between histological subtype and involvement of the SSX1 or SSX2 gene. These approaches could also be applied to the identification of tumor-free margins and metastatic disease. Images Figure 1 Figure 3 PMID:8579118

Shipley, J.; Crew, J.; Birdsall, S.; Gill, S.; Clark, J.; Fisher, C.; Kelsey, A.; Nojima, T.; Sonobe, H.; Cooper, C.; Gusterson, B.

1996-01-01

356

Reaction of 3',5'-di-O-acetyl-2'-deoxyguansoine with hypobromous acid.  

PubMed

Hypobromous acid (HOBr) is formed by eosinophil peroxidase and myeloperoxidase in the presence of H2O2, Cl(-), and Br(-) in the host defense system of humans, protecting against invading bacteria. However, the formed HOBr may cause damage to DNA and its components in the host. When a guanine nucleoside (3',5'-di-O-acetyl-2'-deoxyguansoine) was treated with HOBr at pH 7.4, spiroiminodihydantoin, guanidinohydantoin/iminoallantoin, dehydro-iminoallantoin, diimino-imidazole, amino-imidazolone, and diamino-oxazolone nucleosides were generated in addition to an 8-bromoguanine nucleoside. The major products were spiroiminodihydantoin under neutral conditions and guanidinohydantoin/iminoallantoin under mildly acidic conditions. All the products were formed in the reaction with HOCl in the presence of Br(-). These products were also produced by eosinophil peroxidase or myeloperoxidase in the presence of H2O2, Cl(-), and Br(-). The results suggest that the products other than 8-bromoguanine may also have importance for mutagenesis by the reaction of HOBr with guanine residues in nucleotides and DNA. PMID:23685182

Suzuki, Toshinori; Nakamura, Asuka; Inukai, Michiyo

2013-07-01

357

Nanogold-based bio-bar codes for label-free immunosensing of proteins coupling with an in situ DNA-based hybridization chain reaction.  

PubMed

A label-free, non-enzyme immunosensing strategy is designed for ultrasensitive electronic detection of disease-related proteins (carcinoembryonic antigen as a model) by using gold nanoparticle-based bio-bar codes and an in situ amplified DNA-based hybridization chain reaction. PMID:23147220

Zhou, Jun; Xu, Mingdi; Tang, Dianping; Gao, Zhuangqiang; Tang, Juan; Chen, Guonan

2012-12-28

358

Detection of Newcastle disease virus RNA by reverse transcription polymerase chain reaction using formalin-fixed, paraffin-embedded tissue and comparison with immunohistochemistry and in situ hybridization  

Technology Transfer Automated Retrieval System (TEKTRAN)

The usefulness of reverse transcription polymerase chain reaction (RT-PCR) from formalin-fixed, paraffin-embedded (FFPE) tissues was examined and compared to the immunohistochemistry (IHC) and in situ hybridization (ISH) assays for detection of Newcastle disease virus (NDV). Spleen and lung tissues...

359

The Modification of Cellulosic Surface with Fatty Acids via Plasma Mediated Reactions  

NASA Astrophysics Data System (ADS)

Much attention has been paid recently to understand the healing process made by the human body, in order to develop new approaches for promoting healing. The wound healing process includes four main phases, namely, hemostatic, inflammatory, proliferation, and remodeling, which take place successively. The human body can provide all the requirements of the healing process in normal wounds, unless there is a kind of deficiency of the skin function or massive fluid losses of vast wounds. Therefore, wound care of non-healing wounds has recently been the growing concern of many applications. The goal of this work is to explore the development of a new cellulose-based wound dressing composite that contain or release wound healing agents attained via dry textile chemical finishing techniques (thermal curing-plasma treatment). The synthesis of different wound healing agents derived from fatty acids and attached chemically to cellulose or even delivered through cyclodextrine modified cellulose are reported in this work. First, free fatty acids, which are obtained from commercial vegetable oils, were identified as wound healing agents. Many of these free acids are known to bind with and deactivate the proteases associated with inflammation at a wound site. Linoleic acid is extracted from commercial products of safflower seed oil while ricinoleic acid is obtained from castor oil. Conjugated linoleic acid was synthesized. Un-conjugated linoleic acid was used to prepare two derivatives namely linoleic azide and allylic ketone of linoleic acid. Different cellulose derivatives such as cellulose peroxide, iododeoxycellulose and cellulose diazonium salt in different degree of substitutions were synthesized in order to facilitate the free radical reaction with the fatty acid derivatives. New modified cellulosic products were synthesized by reacting the cellulosic and the linoleic acid derivatives via thermal or plasma technique and characterized by FT-IR ATR, the wettability test, etc. The cyto-compatiability of the new product was investigated using the cytotoxicity test to identify the cytotoxic potentials of the grafted samples. The highest yield was obtained in the thermal curing (at 140°C, 3 min, and a 20% solution of azide derivative -- 170°C, 3 min, and a 2.5% solution of allylic ketone derivatives) of the iododeoxycellulose fabrics with either linoleic azide or the allylic ketone derivative. Atmospheric plasma machines were used for this study such as NCAPS (dielectric barrier discharge plasma) and APJeT. APJet plasma machine was used in two different modes namely downstream and in-situ. Although, the plasma treatment uses a lower energy to achieve the chemical reactions between the two components, the APJet obtained good results in the in-situ mode (at 800 Watts/cm3 RF power, 45 sec. exposure time) while retaining sufficient tensile strength. In general samples treated with the allylic ketone of linoleic acid treated samples showed higher graft yield than the azide derivative, especially those treated via thermal curing. Moreover, they are more cytologically compatible than the plasma treated samples. In the course of producing a wound healing product that contains or releases fatty acids, allylic beta-CD was synthesized for first time as a textile finishing agent. Per(2, 3, 6- tri-O-allyl)-beta-CD was synthesized and characterized using spectral analysis. Cellulosic derivatives were treated with per(2, 3, 6- tri-O-allyl)-beta-CD via either pad-thermofixation technique or plasma treatment. Thermal treatment showed superior efficiency over plasma techniques to activate the vinyl groups and creating a self-assembled CD network chemically bonded with the cellulose derivatives (at 180°C, 3 min, and a 20 % solution of Per(2, 3, 6- tri- O-allyl)-beta-CD). APJeT machine (in-situ mode) succeeded only to activate cellulose/ allylic CD reaction, but however, it could not offer enough energy to stimulate vinyl-vinyl reactions. Oleic acid with its semi-linear chemical structure tends to include in the CD cavity faster and to higher levels

Nada, Ahmed Ali Ahmed

360

Development of a lauric acid/albumin hybrid iron oxide nanoparticle system with improved biocompatibility.  

PubMed

The promising potential of superparamagnetic iron oxide nanoparticles (SPIONs) in various nanomedical applications has been frequently reported. However, although many different synthesis methods, coatings, and functionalization techniques have been described, not many core-shell SPION drug delivery systems are available for clinicians at the moment. Here, bovine serum albumin was adsorbed onto lauric acid-stabilized SPIONs. The agglomeration behavior, zeta potential, and their dependence on the synthesis conditions were characterized with dynamic light scattering. The existence and composition of the core-shell-matrix structure was investigated by transmission electron microscopy, Fourier transform infrared spectroscopy, and zeta potential measurements. We showed that the iron oxide cores form agglomerates in the range of 80 nm. Moreover, despite their remarkably low tendency to aggregate even in a complex media like whole blood, the SPIONs still maintained their magnetic properties and were well attractable with a magnet. The magnetic properties were quantified by vibrating sample magnetometry and a superconducting quantum interference device. Using flow cytometry, we further investigated the effects of the different types of nanoparticle coating on morphology, viability, and DNA integrity of Jurkat cells. We showed that by addition of bovine serum albumin, the toxicity of nanoparticles is greatly reduced. We also investigated the effect of the particles on the growth of primary human endothelial cells to further demonstrate the biocompatibility of the particles. As proof of principle, we showed that the hybrid-coated particles are able to carry payloads of up to 800 ?g/mL of the cytostatic drug mitoxantrone while still staying colloidally stable. The drug-loaded system exhibited excellent therapeutic potential in vitro, exceeding that of free mitoxantrone. In conclusion, we have synthesized a biocompatible ferrofluid that shows great potential for clinical application. The synthesis is straightforward and reproducible and thus easily translatable into a good manufacturing practice environment. PMID:25364244

Zaloga, Jan; Janko, Christina; Nowak, Johannes; Matuszak, Jasmin; Knaup, Sabine; Eberbeck, Dietmar; Tietze, Rainer; Unterweger, Harald; Friedrich, Ralf P; Duerr, Stephan; Heimke-Brinck, Ralph; Baum, Eva; Cicha, Iwona; Dörje, Frank; Odenbach, Stefan; Lyer, Stefan; Lee, Geoffrey; Alexiou, Christoph

2014-01-01

361

Preparation of leady oxide for lead-acid battery by cementation reaction  

NASA Astrophysics Data System (ADS)

The aim of this research is to prepare leady oxide with high specific area for lead-acid batteries by a new production process. Leady oxide is produced by a cementation reaction in 1.0 wt% HCl solution using a pure aluminum or a magnesium rod as the reductant. Leady oxide prepared in this process is much superior to Barton-pot or ball-mill oxide in terms of physical characteristics. The particle-size distribution of the leady oxide produced by this new process is similar to that of ball-mill oxide. Its acid absorption, however, is much higher because of the different particle shape with respect to ball-mill oxide. Ball-mill oxide is composed of particles of non-uniform plate shape, whereas the new leady oxide is composed of particles of perfect flat (flake) shape. The former oxide has higher specific surface area and greater acid absorption than ball-mill or Barton-pot oxide.

Shin, Joon-Ho; Kim, Ki-Won; Ahn, Hyo-Jun

362

Insights into a surprising reaction: the microwave-assisted direct esterification of phosphinic acids.  

PubMed

It is well-known that phosphinic acids do not undergo direct esterifications with alcohols under thermal conditions. However, the esterifications take place under microwave (MW) irradiation due to the beneficial effect of MW. As a comparison, maximum 12-15% conversions were observed on traditional heating. It was proved experimentally that the MW-assisted esterifications are not reversible under the conditions applied that may be the consequence of the hydrophobic medium established by the long chain alcohol/phosphinic ester. Neither the thermodynamic, nor the kinetic data obtained by high level quantum chemical calculations justify the direct esterification of phosphinic acids under thermal conditions. The thermodynamic data show that there is no driving force for the reactions under discussion. As a consequence of the relatively high values of activation enthalpy (102-161 kJ mol(-1)), these esterifications are controlled kinetically. Comparing the energetics of the esterification of phosphinic acids and the preparative results obtained under MW conditions, one can see the potential of the MW technique in the synthesis of phosphinates. During our study, a series of new cyclic phosphinates with lipophilic alkyl groups was synthesized. PMID:22293944

Keglevich, György; Kiss, Nóra Zsuzsa; Mucsi, Zoltán; Körtvélyesi, Tamás

2012-03-14

363

Kinetics and Mechanism of the Reaction between Chromium(III) and 3,4-Dihydroxy-Phenyl-Propenoic Acid (Caffeic Acid) in Weak Acidic Aqueous Solutions  

PubMed Central

Our study of the complexation of 3,4-dihydroxy-phenyl-propenoic acid by chromium(III) could give information on the way that this metal ion is available to plants. The reaction between chromium(III) and 3,4-dihydroxy-phenyl-propenoic acid in weak acidic aqueous solutions has been shown to take place by at least three stages. The first stage corresponds to substitution (Id mechanism) of water molecule from the Cr(H2O)5OH2+ coordination sphere by a ligand molecule. A very rapid protonation equilibrium, which follows, favors the aqua species. The second and the third stages are chromium(III) and ligand concentration independent and are attributed to isomerisation and chelation processes. The corresponding activation parameters are ?H2(obs)? = 28.6 ± 2.9 kJ mol?1, ?S2(obs)? = ?220 ± 10 J K?1mol?1, ?H3(obs)? = 62.9 ± 6.7 kJ mol?1 and ?S3(obs)? = ?121 ± 22 J K?1mol?1. The kinetic results suggest associative mechanisms for the two steps. The associatively activated substitution processes are accompanied by proton release causing pH decrease. PMID:18695733

Thoma, Vladimiros; Tampouris, Konstantinos; Petrou, Athinoula L.

2008-01-01

364

Immature embryo rescue, culture and seedling development of acid citrus fruit derived from interploid hybridization  

Microsoft Academic Search

Interploid sexual hybridizations were completed in 2001 and 2002 between seven lemon (Citrus limon(L.) Burm. f.) varieties, ‘Key’ lime (C. aurantifolia (Cristm.) Swing), Palestine sweet lime (C. imettioides Tan.), ‘Lakeland’ limequat (C. aurantifolia x Fortunella japonica (Thumb.) Swing.), and ‘Etrog’ citron (C. medica L.) as diploid progenitors and four allotetraploid somatic hybrids (‘Key’ lime + ‘Valencia’ orange, ‘Hamlin’ orange +

Z. Viloria; J. W. Grosser; B. Bracho

2005-01-01

365

Reaction of Calcite and Dolomite with In-Situ Gelled Acids, Organic Acids, and Environmentally Friendly Chelating Agent (GLDA)  

E-print Network

" techniques. "Matrix Acidizing" and "Acid Fracturing" applications involve injecting an acid to react with the formation and dissolve some of the minerals present and recover or increase the permeability. The permeability enhancement is achieved by creating...

Rabie, Ahmed 1978-

2012-11-16

366

Superoxide dismutase enhances the formation of hydroxyl radicals in the reaction of 3-hydroxyanthranilic acid with molecular oxygen.  

PubMed Central

Superoxide dismutase (SOD) enhanced the formation of hydroxyl radicals, which were detected by using the e.s.r. spin-trapping technique, in a reaction mixture containing 3-hydroxyanthranilic acid (or p-aminophenol), Fe3+ ions, EDTA and potassium phosphate buffer, pH 7.4. The hydroxyl-radical formation enhanced by SOD was inhibited by catalase and desferrioxamine, and stimulated by EDTA and diethylenetriaminepenta-acetic acid, suggesting that both hydrogen peroxide and iron ions participate in the reaction. The hydroxyl-radical formation enhanced by SOD may be considered to proceed via the following steps. First, 3-hydroxyanthranilic acid is spontaneously auto-oxidized in a process that requires molecular oxygen and yields superoxide anions and anthranilyl radicals. This reaction seems to be reversible. Secondly, the superoxide anions formed in the first step are dismuted by SOD to generate hydrogen peroxide and molecular oxygen, and hence the equilibrium in the first step is displaced in favour of the formation of superoxide anions. Thirdly, hydroxyl radicals are generated from hydrogen peroxide through the Fenton reaction. In this Fenton reaction Fe2+ ions are available since Fe3+ ions are readily reduced by 3-hydroxyanthranilic acid. The superoxide anions do not seem to participate in the reduction of Fe3+ ions, since superoxide anions are rapidly dismuted by SOD present in the reaction mixture. PMID:2843167

Iwahashi, H; Ishii, T; Sugata, R; Kido, R

1988-01-01

367

A selected ion flow tube study of the reactions of various nitrogen containing ions with formic acid, acetic acid, and methyl formate  

NASA Astrophysics Data System (ADS)

The possibility of forming organic molecules, such as the amino acid, glycine, from interstellar species through the ion-molecule reactions of ionized amine fragment compounds with neutral carboxylic acid and ester species has been investigated in a selected ion flow tube (SIFT) at 298 K. An earlier study showed that reactions of neutral amine species with ionized carboxylic acid or ester fragments does not result in the desired combination of groups but instead results in the fragmentation of the amines [D.M. Jackson, N.J. Stibrich, N.G. Adams, L.M. Babcock, Int. J. Mass Spectrom. 243 (2005) 115-120]. In the present study, the ion product distributions and reaction rate coefficients of the gas phase reactions of HCOOH, CH3COOH, and CH3OCHO with the ions Ar+, N2+, NH2+, NH3+, and HCNH+ have been determined. The ions Ar+ and N2+ fragment the neutral species in dissociative charge transfer, and the reactions of NH2+ and HCNH+ with the neutrals result in dissociative proton transfer. NH3+ reacts with all three species to form NH4+ by H atom abstraction. The reaction rate coefficients were on average within experimental error of the gas kinetic rate and were on the order of 10-9 cm3 s-1.

Jackson, Douglas M.; Stibrich, Nathan J.; McLain, Jason L.; Fondren, Lillian D.; Adams, Nigel G.; Babcock, Lucia M.

2005-12-01

368

Efficient Lewis acid-assisted Brønsted acid (LBA) catalysis in the iron-catalyzed Friedel-Crafts alkylation reaction of indoles  

Microsoft Academic Search

Lewis acid-assisted Brønsted acid (LBA) catalysis was proposed for the iron-catalyzed Friedel-Crafts alkylation of indoles\\u000a with chalcones. This proposal was supported by the ESI-MS and cyclic voltammetry. The addition of acac to the iron-catalyzed\\u000a Friedel-Crafts alkylation of indoles with chalcones created a powerful catalytic system, which makes the alkylation reactions\\u000a occur easily under mild conditions.

Zhen-Yu Jiang; Ji-Rong Wu; Li Li; Xi-Huai Chen; Guo-Qiao Lai; Jian-Xiong Jiang; Yixin Lu; Li-Wen Xu

2010-01-01

369

Palladium(0) nanoclusters stabilized by poly(4-styrenesulfonic acid-co-maleic acid) as an effective catalyst for Suzuki–Miyaura cross-coupling reactions in water  

Microsoft Academic Search

Palladium(0) nanoclusters stabilized by poly(4-styrenesulfonic acid-co-maleic acid), PSSA-co-MA, were generated in situ during the hydrolysis of ammonia–borane (AB) from the reduction of potassium tetrachloropalladate(II) in aqueous solution at room temperature. They were isolated from the reaction solution and characterized by UV–visible electronic absorption spectroscopy, TEM, SAED and XRD techniques. The PSSA-co-MA stabilized palladium(0) nanoclusters were used as catalyst in Suzuki–Miyaura

Önder Metin; Feyyaz Durap; Murat Aydemir; Saim Özkar

2011-01-01

370

Gas-phase ion/ion reactions of peptides and proteins: acid/base, redox, and covalent chemistries  

PubMed Central

Gas-phase ion/ion reactions are emerging as useful and flexible means for the manipulation and characterization of peptide and protein biopolymers. Acid/base-like chemical reactions (i.e., proton transfer reactions) and reduction/oxidation (redox) reactions (i.e., electron transfer reactions) represent relatively mature classes of gas-phase chemical reactions. Even so, especially in regards to redox chemistry, the widespread utility of these two types of chemistries is undergoing rapid growth and development. Additionally, a relatively new class of gas-phase ion/ion transformations is emerging which involves the selective formation of functional-group-specific covalent bonds. This feature details our current work and perspective on the developments and current capabilities of these three areas of ion/ion chemistry with an eye towards possible future directions of the field. PMID:23257901

Prentice, Boone M.

2013-01-01

371

Luminescent lanthanide (Eu3+, Tb3+) hybrids with 4-vinylbenzeneboronic acid functionalized Si-O bridges and beta-diketones.  

PubMed

4-Vinylphenylboronic acid ligand (VPBA) is functionalized with two crosslinking reagents (3-(triethoxysilyl)-propylisocyanate [TEPIC] and 3-(trimethoxysilyl) propyl methacrylate [TMPMA]) to achieve the two special molecular bridge VPBA-TEPIC and VPBA-TMPMA. Meanwhile, beta-diketone ligands (2-thenoyltrifluoroacetone [TTA], acetyl acetone [ACAC]) as the second ligands play the role of the main energy donor, which absorb abundant energy in ultraviolet-visible extent and then transfer the energy to the corresponding lanthanide ions (Eu(3+), Tb(3+)) to sensitize their emission of them. Eight binary and ternary Eu(3+), Tb(3+) hybrids with VPBA-TEPIC (VPBA-TMPMA) and TTA (ACAC) have been constructed, whose photoluminescence properties are studied in depth and suggest that the ternary hybrids show the favorable characteristic luminescent properties (longer lifetime and higher quantum efficiency). PMID:21466557

Yan, Bing; Guo, Min; Qiao, Xiao-Fei

2011-01-01

372

Mathematical models of diffusion-constrained polymerase chain reactions: basis of high-throughput nucleic acid assays and simple self-organizing systems  

E-print Network

Mathematical models of diffusion-constrained polymerase chain reactions: basis of high- throughput "Mathematical models of diffusion-constrained polymerase chain reactions: basis of high-throughput nucleic acid

Church, George M.

373

Lewis Acid-Catalyzed Michael Addition Reactions of N-Boc-2-silyloxypyrroles to 3Acryloyl2-oxazolidinone  

Microsoft Academic Search

Among several Lewis acids examined, Sc(OTf)3 (10 mol%) was found to be the most effective catalyst to promote a Michael addition reaction of N-Boc-2-(tert-butyldimethylsilyloxy)pyrrole to 3-acryloyl-2-oxazolidinone. A slow addition of the 2-silyloxypyrrole in the presence of 1,1,1,3,3,3- hexafluoro-2-propanol (5 equiv.) at -25 oC were needed to obtain good yield (77 - 80%). The asymmetric version of the reaction could be

Hiroyuki Suga; Haruka Takemoto; Akikazu Kakehi

2007-01-01

374

Early stage composition of SOA produced by ?-pinene/ozone reaction: ?-Acyloxyhydroperoxy aldehydes and acidic dimers  

NASA Astrophysics Data System (ADS)

Composition of the freshly formed secondary organic aerosol (SOA) generated by ozonolysis of cyclohexene, cyclohexene-d10 (model precursors) and ?-pinene was studied using liquid chromatography coupled to electrospray ionization tandem mass spectrometry (LC-ESI/MS2). SOA was generated in the flow-tube reactor under the following conditions: 22 ± 2 °C, 1 atm and reaction time was approx. 30 s. In an attempt to resolve the current ambiguities, regarding the structure of ?-pinene SOA nucleating agents, analytical methods for analysis of ?-acyloxyhydroperoxy aldehydes and oligomers containing carboxylic group were developed to study the potential nucleating agents. Negatively charged m/z 351, 341, 337, 357 and 367 ions corresponding to the acidic oligomers were detected in freshly formed ?-pinene SOA. For the first time, structures and formation mechanism for compounds detected as m/z 337 and 351 ions were proposed. Based on the model precursor analysis (cyclohexene and cyclohexene-d10) it was concluded that these compounds were most likely formed via aldol reaction of the lower molecular weight aerosol components. ?-Acyloxyhydroperoxy aldehydes were studied in the SOA samples using previously developed, novel method, based on the prediction of fragmentation spectrum for the compounds of interest. It was concluded that ?-acyloxyhydroperoxy aldehydes were not formed in significant quantities. Based on the obtained results, possible SOA formation and growth mechanism is discussed.

Witkowski, Bart?omiej; Gierczak, Tomasz

2014-10-01

375

Determination of the mechanism of reaction for bile acid: CoA ligase.  

PubMed Central

The reaction of cholic acid, CoA and ATP to yield cholyl-CoA was investigated by kinetic analysis of the reaction as catalysed by guinea pig liver microsomes. The enzyme has an absolute requirement for divalent cation for activity so all kinetic analyses were carried out in excess Mn2+. A trisubstrate kinetic analysis was conducted by varying, one at a time ATP cholate and CoA. Both ATP and cholate gave parallel double reciprocal plots versus CoA, which indicates a ping-pong mechanism with either pyrophosphate or AMP leaving prior to the binding of CoA. Addition of pyrophosphate to the assays changed the parallel plots to intersecting ones; addition of AMP did not. This indicates that pyrophosphate is the first product. The end-product, AMP, was a competitive inhibitor versus ATP, as was cholyl-CoA at saturating concentrations of cholate. Both AMP and cholyl-CoA were uncompetitive inhibitors versus CoA. Based on this information, it was concluded that the reaction follows a bi uni uni bi ping-pong mechanism with ATP binding first, and with the release of the final products, AMP and cholyl-CoA, being random. CoA showed substrate inhibition at high but non-saturating concentrations and this inhibition was competitive versus ATP, which is consistent with the predicted ping-pong mechanism. The ability of cholyl-CoA, but not cholate or CoA, to bind with high affinity to the free enzyme was suggestive of a high affinity of the enzyme for the thioester link. PMID:7818501

Kelley, M; Vessey, D A

1994-01-01

376

The Use of Oxalic Acid as a Chelating Agent in the Dissolution Reaction of Calcium Molybdate  

NASA Astrophysics Data System (ADS)

In this study, the dissolution behavior of calcium molybdate (CaMoO4) was investigated in oxalic acid (H2C2O4) solution. The effects of stirring speed, temperature, H2C2O4 concentration, and particle size on the dissolution reaction of CaMoO4 were determined. The dissolved quantities of molybdenum and calcium were analyzed quantitatively by ICP-OES. Fractional conversion of CaMoO4 vs time and concentration of calcium vs time diagrams were plotted. It was observed that at constant temperatures and lower H2C2O4 concentrations, the dissolution increased by increasing H2C2O4 concentration, but at higher H2C2O4 concentrations, the effect of H2C2O4 concentrations was negligible. The dissolution reaction of CaMoO4 in H2C2O4 solution was performed in two steps as series-parallel type reaction. In the first step, CaMoO4 reacted with H2C2O4 to form the water-soluble calcium aqua oxalato molybdate (Ca[MoO3(C2O4)(H2O)]) intermediate chelate product. In the second step, the intermediate chelate, Ca[MoO3(C2O4)(H2O)], reacted with the reactant, H2C2O4, to yield water-soluble hydrogen oxalato dimolybdate chelate (H2[(MoO3)2(C2O4)]) and insoluble CaC2O4H2O as final products. It was found that 500 rpm was enough to eliminate the resistance of liquid film layer that surrounds the solid particles. It was concluded that the optimum temperature was 313 K (40 °C) and the optimum concentration of H2C2O4 was 1 kmol m-3 to obtain high conversion during the dissolution of CaMoO4.

Ilhan, Sedat; Kalpakli, Ahmet Orkun; Kahruman, Cem; Yusufoglu, Ibrahim

2013-06-01

377

Light-induced nitrous acid (HONO) production from NO2 heterogeneous reactions on household chemicals  

NASA Astrophysics Data System (ADS)

Nitrous acid (HONO) can be generated in various indoor environments directly during combustion processes or indirectly via heterogeneous NO2 reactions with water adsorbed layers on diverse surfaces. Indoors not only the concentrations of NO2 are higher but the surface to volume (S/V) ratios are larger and therefore the potential of HONO production is significantly elevated compared to outdoors. It has been claimed that the UV solar light is largely attenuated indoors. Here, we show that solar light (? > 340 nm) penetrates indoors and can influence the heterogeneous reactions of gas-phase NO2 with various household surfaces. The NO2 to HONO conversion mediated by light on surfaces covered with domestic chemicals has been determined at atmospherically relevant conditions i.e. 50 ppb NO2 and 50% RH. The formation rates of HONO were enhanced in presence of light for all the studied surfaces and are determined in the following order: 1.3·109 molecules cm-2 s-1 for borosilicate glass, 1.7·109 molecules cm-2 s-1 for bathroom cleaner, 1.0·1010 molecules cm-2 s-1 on alkaline detergent (floor cleaner), 1.3·1010 molecules cm-2 s-1 for white wall paint and 2.7·1010 molecules cm-2 s-1 for lacquer. These results highlight the potential of household chemicals, used for cleaning purposes to generate HONO indoors through light-enhanced NO2 heterogeneous reactions. The results obtained have been applied to predict the timely evolution of HONO in a real indoor environment using a dynamic mass balance model. A steady state mixing ratio of HONO has been estimated at 1.6 ppb assuming a contribution from glass, paint and lacquer and considering the photolysis of HONO as the most important loss process.

Gómez Alvarez, Elena; Sörgel, Matthias; Gligorovski, Sasho; Bassil, Sabina; Bartolomei, Vincent; Coulomb, Bruno; Zetzsch, Cornelius; Wortham, Henri

2014-10-01

378

An electrochemical aptasensor based on hybridization chain reaction with enzyme-signal amplification for interferon-gamma detection.  

PubMed

A novel electrochemical aptasensor based on hybridization chain reaction (HCR) with enzyme-signal amplification was constructed for the detection of interferon-gamma (IFN-?). In this aptasensor, the recognition probes which contained the sequence of IFN-? aptamer were initially binded to IFN-?, and the unbound recognition probes were captured on the electrode as an initiator to trigger the HCR. The two DNA hairpins bio-H1 and bio-H2 were opened by the recognition probe, and bound one by one on the electrode. The biotin was used as a tracer in the hairpins and streptavidin-alkaline phosphatase (SA-ALP) as a reporter molecule. Then, SA-ALP converted its electro-inactive substrate 1-naphthyl phosphate into an electroactive derivative 1-naphthol generating amplified electrochemical signal by differential pulse voltammetry (DPV). The activity of the immobilized enzyme was voltammetrically determined by measuring the amount of 1-naphthol generated for enzymatic dephosphorylation of 1-naphthyl phosphate. The electrochemical signal observed was inversely related to the concentration of IFN-?. The proposed approach showed a high sensitivity for IFN-? in a concentration range of 0.5-300 nM with a detection limit of 0.3 nM. The sensing system also provided satisfactory results for the detection of IFN-? in the cell media. PMID:22575639

Zhao, Jingjin; Chen, Chunfei; Zhang, Liangliang; Jiang, Jianhui; Yu, Ruqin

2012-01-01

379

A hybrid of ant colony optimization and minimization of metabolic adjustment to improve the production of succinic acid in Escherichia coli.  

PubMed

This paper presents a study on gene knockout strategies to identify candidate genes to be knocked out for improving the production of succinic acid in Escherichia coli. Succinic acid is widely used as a precursor for many chemicals, for example production of antibiotics, therapeutic proteins and food. However, the chemical syntheses of succinic acid using the traditional methods usually result in the production that is far below their theoretical maximums. In silico gene knockout strategies are commonly implemented to delete the gene in E. coli to overcome this problem. In this paper, a hybrid of Ant Colony Optimization (ACO) and Minimization of Metabolic Adjustment (MoMA) is proposed to identify gene knockout strategies to improve the production of succinic acid in E. coli. As a result, the hybrid algorithm generated a list of knockout genes, succinic acid production rate and growth rate for E. coli after gene knockout. The results of the hybrid algorithm were compared with the previous methods, OptKnock and MOMAKnock. It was found that the hybrid algorithm performed better than OptKnock and MOMAKnock in terms of the production rate. The information from the results produced from the hybrid algorithm can be used in wet laboratory experiments to increase the production of succinic acid in E. coli. PMID:24763079

Chong, Shiue Kee; Mohamad, Mohd Saberi; Mohamed Salleh, Abdul Hakim; Choon, Yee Wen; Chong, Chuii Khim; Deris, Safaai

2014-06-01

380

Reactions in condensed formic acid (HCOOH) induced by low energy (< 20 eV) electrons.  

PubMed

The interaction of low energy (< 20 eV) electrons with a five monolayer (ML) film of formic acid (HCOOH) deposited on a cryogenically cooled monocrystalline Au substrate is studied by electron stimulated desorption (ESD) of negatively charged fragment ions. A comparison with results from gas phase experiments demonstrates the strong effect of the environment for negative ion formation via dissociative electron attachment (DEA). From condensed phase formic acid (FA) a strong H desorption signal from a resonant feature peaking at 9 eV is observed. In the gas phase, the dominant reaction is neutral hydrogen abstraction generating HCOO- within a low energy resonance, peaking at 1.25 eV. ESD studies on the isotopomers HCOOD and DCOOH indicate effective H/D exchange in the precursor ion at 9 eV prior to dissociation. The evolution of the desorption signals in the course of electron irradiation and the features in the thermal desorption spectra (TDS) of the electron irradiated film suggest the formation of CO2 at electron energies above 8 eV. PMID:19791345

Sedlacko, Tibor; Balog, Richard; Lafosse, Anne; Stano, Michal; Matejcik, Stefan; Azria, Roger; Illenberger, Eugen

2005-03-21

381

Photochemical reactions of divalent mercury with thioglycolic acid: Formation of mercuric sulfide particles.  

PubMed

Mercury (Hg) is a key toxic global pollutant. Studies in aquatic environment have suggested that thiols could be important for mercury speciation. Thioglycolic acid has been detected in various natural water systems and used as a model compound to study the complicated interaction between mercury and polyfunctional dissolved organic matter (DOM). We herein presented the first evidence for mercury particle formation during kinetic and product studies on the photochemistry of divalent mercury (Hg(2+)) with thioglycolic acid at near environmental conditions. Mercuric sulfide (HgS) particles formed upon photolysis were identified by high-resolution transmission electron microscopy coupled with energy dispersive spectrometry and select area electron diffraction. Kinetic data were obtained using UV-visible spectrophotometry and cold vapour atomic fluorescent spectrometry. The apparent first-order reaction rate constant under our experimental conditions was calculated to be (2.3±0.4)×10(-5)s(-1) at T=296±2K and pH 4.0. It was found that (89±3)% of the reactants undergo photoreduction to generate elemental mercury (Hg(0)). The effects of ionic strengths, pH and potassium ion were also investigated. The formation of HgS particles pointed to the possible involvement of heterogeneous processes. Our kinetic results indicated the importance of weak binding sites on DOM to Hg in photoreduction of Hg(2+) to Hg(0). The potential implications of our data on environmental mercury transformation were discussed. PMID:25094064

Si, Lin; Ariya, Parisa A

2015-01-01

382

Study of Epstein-Barr virus expression in Burkitt's lymphoma by polymerase chain reaction and in situ hybridization: A study in Iran  

PubMed Central

Background: The association of Epstein-Barr virus (EBV) with Burkitt's lymphoma (BL) is variable in different geographic regions. In developing countries, the association of EBV with BL is regarded to be of an endemic-type in equatorial Africa (> 95%) and sporadic-type in the developed countries (15-30%). The purpose of this study is to assess the frequency of EBV infection in BL, in Iran. The study also aims to compare Ribonucleic acid (RNA) in situ hybridization (RISH), the standard diagnostic method, with the polymerase chain reaction (PCR)-based method for diagnosing BL. Materials and Methods: In this epidemiological study, the paraffinized specimens of 18 cases of BL were selected. Next, the ISH of EBV-encoded RNA (EBER-RISH) and PCR assays that were based on Epstein Barr Nuclear Antigen 2 (EBNA2) amplification were used. The EBV strain was determined by PCR. The data were analyzed using the SPSS10 software and by performing Pearson correlation coefficient formula at a significant level of 0.05. Results: EBV RNA was detected in 50% of the BL specimens. Type 1 and 2 accounted for 70 and 30% of the cases, respectively. Regarding RISH as the standard method for EBV diagnosis, the PCR assays showed a sensitivity and specificity of 100 and 88.9%, respectively. Conclusion: According to the obtained findings, the frequency of EBV in BL was 50% and PCR and RISH showed high concordance and sensitivity in EBV detection. Therefore, PCR can be used as a faster method for EBV detection in high-risk geographical regions. PMID:25097650

Deyhimi, Parviz; Kalantari, Mahsa

2014-01-01

383

Production of hybrid diesel fuel precursors from carbohydrates and petrochemicals using formic acid as a reactive solvent.  

PubMed

We report the one-pot alkylation of mesitylene with carbohydrate-derived 5-(hydroxymethyl)furfural (HMF) as a step toward diesel-range liquids. Using FeCl(3) as a catalyst, HMF is shown to alkylate toluene, xylene, and mesitylene in high yields in CH(2)Cl(2) and MeNO(2) solvents. Efforts to extend this reaction to greener or safer solvents showed that most ether-based solvents are unsatisfactory. Acid catalysts (e.g, p-TsOH) also proved to be ineffective. Using formic acid as a reactive solvent, mesitylene could be alkylated to give mesitylmethylfurfural (MMF) starting from fructose with yields up to approximately 70 %. The reaction of fructose with formic acid in the absence of mesitylene gave rise to low yields of the formate ester of HMF, which indicates the stabilizing effect of replacing the hydroxyl substituent with mesityl. The arene also serves as a second phase into which the product is extracted. Even by using formic acid, the mesitylation of less expensive precursors such as glucose and cellulose proceeded only in modest yields (ca. 20 %). These simpler substrates were found to undergo mesitylation by using hydrogen chloride/formic acid via the intermediate chloromethylfurfural. PMID:23281330

Zhou, Xiaoyuan; Rauchfuss, Thomas B

2013-02-01

384

Identification of Dekkera bruxellensis (Brettanomyces) from Wine by Fluorescence In Situ Hybridization Using Peptide Nucleic Acid Probes  

PubMed Central

A new fluorescence in situ hybridization method using peptide nucleic acid (PNA) probes for identification of Brettanomyces is described. The test is based on fluorescein-labeled PNA probes targeting a species-specific sequence of the rRNA of Dekkera bruxellensis. The PNA probes were applied to smears of colonies, and results were interpreted by fluorescence microscopy. The results obtained from testing 127 different yeast strains, including 78 Brettanomyces isolates from wine, show that the spoilage organism Brettanomyces belongs to the species D. bruxellensis and that the new method is able to identify Brettanomyces (D. bruxellensis) with 100% sensitivity and 100% specificity. PMID:11157265

Stender, Henrik; Kurtzman, Cletus; Hyldig-Nielsen, Jens J.; Sørensen, Ditte; Broomer, Adam; Oliveira, Kenneth; Perry-O'Keefe, Heather; Sage, Andrew; Young, Barbara; Coull, James

2001-01-01

385

Chemiluminescence of benzoic and cinnamic acids, and flavonoids in the presence of aldehyde and hydrogen peroxide or hydroxyl radical by fenton reaction  

Microsoft Academic Search

Light emission (chemiluminescence; CL) was observed by exciting phenolic compounds with hydrogen peroxide (H2O2) or hydroxyl radical (HO·), formed from H2 and FeCl2 by the Fenton reaction. The intensity of the CL of benzoic acid derivatives in the presence of (H2 was in the order of gallic acid > caffeic acid > 3,5-dimethoxy-4-hydroxycinnamic acid > isovanillic acid = syringic acid.

Yumiko Yoshiki; Kazuyoshi Okubo; Masamichi Onuma; Kiharu Igarashi

1995-01-01

386

Digital isothermal quantification of nucleic acids via simultaneous chemical initiation of recombinase polymerase amplification reactions on SlipChip.  

PubMed

In this paper, digital quantitative detection of nucleic acids was achieved at the single-molecule level by chemical initiation of over one thousand sequence-specific, nanoliter isothermal amplification reactions in parallel. Digital polymerase chain reaction (digital PCR), a method used for quantification of nucleic acids, counts the presence or absence of amplification of individual molecules. However, it still requires temperature cycling, which is undesirable under resource-limited conditions. This makes isothermal methods for nucleic acid amplification, such as recombinase polymerase amplification (RPA), more attractive. A microfluidic digital RPA SlipChip is described here for simultaneous initiation of over one thousand nL-scale RPA reactions by adding a chemical initiator to each reaction compartment with a simple slipping step after instrument-free pipet loading. Two designs of the SlipChip, two-step slipping and one-step slipping, were validated using digital RPA. By using the digital RPA SlipChip, false-positive results from preinitiation of the RPA amplification reaction before incubation were eliminated. End point fluorescence readout was used for "yes or no" digital quantification. The performance of digital RPA in a SlipChip was validated by amplifying and counting single molecules of the target nucleic acid, methicillin-resistant Staphylococcus aureus (MRSA) genomic DNA. The digital RPA on SlipChip was also tolerant to fluctuations of the incubation temperature (37-42 °C), and its performance was comparable to digital PCR on the same SlipChip design. The digital RPA SlipChip provides a simple method to quantify nucleic acids without requiring thermal cycling or kinetic measurements, with potential applications in diagnostics and environmental monitoring under resource-limited settings. The ability to initiate thousands of chemical reactions in parallel on the nanoliter scale using solvent-resistant glass devices is likely to be useful for a broader range of applications. PMID:21476587

Shen, Feng; Davydova, Elena K; Du, Wenbin; Kreutz, Jason E; Piepenburg, Olaf; Ismagilov, Rustem F

2011-05-01

387

The structural and energetic aspects of substrate binding and the mechanism of action of the DapE-encoded N-succinyl-L,L-diaminopimelic acid desuccinylase (DapE) investigated using a hybrid QM/MM method.  

PubMed

With increasing cases of fatal bacterial infections and growing antibiotic resistance, unrelenting efforts are necessary for identification of novel antibiotic targets and new drug molecules. The dapE-encoded N-succinyl-L,L-diaminopimelic acid desuccinylase (DapE) is a di-nuclear Zn containing enzyme in the lysine biosynthetic pathway which is indispensable for bacterial survival and absent in the human host, thus a potential antibiotic target. The DapE enzyme catalyzes the hydrolysis of N-succinyl-L,L-diaminopimelic acid (SDAP) to give rise to succinic acid and L,L-diaminopimelic acid. The mechanism of action of the DapE catalyzed SDAP hydrolysis is investigated employing a hybrid QM/MM computational method. The DapE side chains, such as, Arg178, Thr325, Asn345, are found to play a role in substrate identification and stabilization of the enzyme active site. Furthermore, a glycine rich loop (Gly322-Ser326) is found to facilitate tight binding of the substrate in the enzyme active site. The catalytic reaction progresses via a general acid-base hydrolysis mechanism where Glu134 first acts as a Lewis base by activating the catalytic water molecule in the active site, followed by guiding the resulting hydroxyl ion for a nucleophilic attack on the substrate, and finally acts as a Lewis acid by donating a proton to the substrate. The intermediates and transition states along the reaction pathway have been structurally and energetically characterized. A conformational change in the side chain of Asp100, which bridges the two Zn centers of the enzyme, is observed which facilitates the enzymatic action by lowering the activation energy and leads to the formation of a new intermediate during the catalytic reaction. The nucleophilic attack is found to be the rate determining step. PMID:25367594

Dutta, Debodyuti; Mishra, Sabyashachi

2014-12-21

388

Electro-oxidation of methanol on Pt(111) in acid solutions: effects of electrolyte anions during electrocatalytic reactions  

NASA Astrophysics Data System (ADS)

The electro-oxidation of methanol on a Pt(111) surface in both sulfuric and perchloric acid solutions was investigated by combined apparatus under both ultra-high vacuum and electrochemical environments. In sulfuric acid solution, a strong lateral interaction was observed between adsorbed bisulfate and CO derived from methanol. Coadsorption of CO derived from methanol with bisulfate ion yielded a (?7 × ?7)-R19.1°-CO-bisulfate structure. In perchloric acid solution, however, no lateral interaction between adsorbed CO and perchlorate was seen. The difference in reaction rates of methanol oxidation in both solutions was explained by these specific anion adsorption effects.

Ogasawara, Hirohito; Ito, Masatoki

1995-10-01

389

Evaluation of the acid-base surface properties of several oxides and supported metal catalysts by means of model reactions  

Microsoft Academic Search

Acid-base properties of oxides (Al2O3, SiO2, ZrO2, CeO2, MgO, SiO2?Al2O3 and CeO2?Al2O3) were investigated by means of model reactions: 3,3-dimethylbut-1-ene isomerization (33DMB1), methylene cyclohexane isomerization (MECH), cyclohexanol conversion (CHOL) and CO2 chemisorption at room temperature. The effect of acid (Cl?, SO2?4) and basic (K+) promoters on certain oxides (Al2O3, ZrO2) was also studied. Surface acidity was evaluated by means of

Dominique Martin; Daniel Duprez

1997-01-01

390

HLA-DR typing using DNA amplification by the polymerase chain reaction and sequential hybridization to sequence-specific oligonucleotide probes  

Microsoft Academic Search

A series of sequence-specific oligonucleotides (SSOs) have been used to type alleles at the HLA-DRB1 locus. Genomic DNA was amplified to high copy number by the polymerase chain reaction (PCR) and hybridizations of the dot-blotted, amplified DNA to a series of 14 SSOs enabled the identification of the major specificities DR1-DRw14. Certain alleles (DR3 and DR4) could be rapidly and

B. Paul Wordsworth; Catherine E. M. Allsopp; Robert P. Young; John I. Bell

1990-01-01

391

Geochemical Modeling of Reactions and Partitioning of Trace Metals and Radionuclides during Titration of Contaminated Acidic Sediments  

SciTech Connect

Many geochemical reactions that control aqueous metal concentrations are directly affected by solution pH. However, changes in solution pH are strongly buffered by various aqueous phase and solid phase precipitation/dissolution and adsorption/desorption reactions. The ability to predict acid-base behavior of the soil-solution system is thus critical to predict metal transport under variable pH conditions. This study was undertaken to develop a practical generic geochemical modeling approach to predict aqueous and solid phase concentrations of metals and anions during conditions of acid or base additions. The method of Spalding and Spalding was utilized to model soil buffer capacity and pH-dependent cation exchange capacity by treating aquifer solids as a polyprotic acid. To simulate the dynamic and pH-dependent anion exchange capacity, the aquifer solids were simultaneously treated as a polyprotic base controlled by mineral precipitation/dissolution reactions. An equilibrium reaction model that describes aqueous complexation, precipitation, sorption and soil buffering with pH-dependent ion exchange was developed using HydroGeoChem v5.0 (HGC5). Comparison of model results with experimental titration data of pH, Al, Ca, Mg, Sr, Mn, Ni, Co, and SO{sub 4}{sup 2-} for contaminated sediments indicated close agreement, suggesting that the model could potentially be used to predict the acid-base behavior of the sediment-solution system under variable pH conditions.

Zhang, Fan [ORNL; Parker, Jack C. [University of Tennessee, Knoxville (UTK); Luo, Wensui [ORNL; Spalding, Brian Patrick [ORNL; Brooks, Scott C [ORNL; Watson, David B [ORNL; Jardine, Philip M [ORNL; Gu, Baohua [ORNL

2008-01-01

392

Monoclinic hafnium oxynitride supported on reduced graphene oxide to catalyse the oxygen reduction reaction in acidic media.  

PubMed

Monoclinic HfO2 nanoparticles were doped with nitrogen via hydrothermal treatment that avoided high-cost pyrolysis with NH3 gas in order to develop a novel oxygen reduction reaction catalyst for use in acidic media. Catalyst size reduction was achieved using a reduced graphene oxide support, and activity above 0.8 V was obtained. PMID:25167377

Chisaka, M; Sasaki, H; Muramoto, H

2014-10-14

393

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

ERIC Educational Resources Information Center

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

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

2005-01-01

394

Deciphering the origin of cooperative catalysis by dirhodium acetate and chiral spiro phosphoric acid in an asymmetric amination reaction.  

PubMed

The mechanism of asymmetric amination of diazo-acetate by tert-butyl carbamate catalyzed by dirhodium tetra(trifluoro)acetate and chiral SPINOL-phosphoric acid is examined using DFT (M06 and B3LYP) computations. A cooperative participation of both catalysts is noticed in the stereo-controlling transition state of the reaction. PMID:25313895

Kisan, Hemanta K; Sunoj, Raghavan B

2014-12-01

395

Acetic acid promoted metal-free aerobic carbon-carbon bond forming reactions at ?-position of tertiary amines.  

PubMed

The oxidative functionalization of the benzylic C-H bonds in tetrahydroisoquinolines and tetrahydro-?-carboline derivatives was investigated. C-C bond forming reactions proceeded with a range of nucleophiles (nitroalkane, enol silyl ether, indole, allylstannane, and tetrabutylammonium cyanide) under metal-free conditions and an oxygen atmosphere. Acetic acid caused a significant acceleration effect. PMID:25062493

Ueda, Hirofumi; Yoshida, Kei; Tokuyama, Hidetoshi

2014-08-15

396

On The Two Component Microwave Mediated Reaction of Isonitriles with Carboxylic Acids: Regarding Alleged Formimidate Carboxylate Mixed Anhydrides  

PubMed Central

Microwave induced two component coupling (2CC) reaction of carboxylic acids with isonitriles gives rise to various N-formylamides. The formimidate carboxylate mixed anhydride (FCMA) is proposed as the reactive intermediate, which undergoes 1,3-O ? N acyl transfer to give the observed product. The formation and survival of the labile FCMA system has been evaluated. PMID:18783224

Li, Xuechen; Yuan, Yu; Berkowitz, William F.; Todaro, Louis J.; Danishefsky, Samuel J.

2008-01-01

397

On the two-component microwave-mediated reaction of isonitriles with carboxylic acids: regarding alleged formimidate carboxylate mixed anhydrides.  

PubMed

Microwave induced two-component coupling (2CC) reaction of carboxylic acids with isonitriles gives rise to various N-formylamides. The formimidate carboxylate mixed anhydride (FCMA) is proposed as the reactive intermediate, which undergoes 1,3-O-->N acyl transfer to give the observed product. The formation and survival of the labile FCMA system has been evaluated. PMID:18783224

Li, Xuechen; Yuan, Yu; Berkowitz, William F; Todaro, Louis J; Danishefsky, Samuel J

2008-10-01

398

Infrared spectroscopic study of the amidation reaction of aminophenyl modified Au surfaces and p-nitrobenzoic acid as model system.  

PubMed

We have investigated the fundamental amidation reaction by a model system consisting of an electrochemically functionalised Au surface by aminophenyl and 4-nitrobenzoic acid activated by EEDQ. The development of the NO(2) related stretching vibrations with time reveals that the amidation process is very slow at Au surfaces and is completed after about 2 days. PMID:20737098

Zhang, Xin; Sun, Guoguang; Hinrichs, Karsten; Janietz, Silvia; Rappich, Joerg

2010-10-21

399

Fabrication and structure analysis of poly(lactide-co-glycolic acid)/silk fibroin hybrid scaffold for wound dressing applications.  

PubMed

Silk fibroin (SF) and poly(lactide-co-glycolic acid) (PLGA) have been proved to be invaluable polymers in the field wound healing. This study aims at optimizing the electrospinning process of those polymers to make a hybrid membrane as a chronic wounds dressing. After characterizing the scaffolds, PLGA/SF (2:1), and PLGA scaffolds were selected for further study according to their superior tensile mechanical properties. The attachment and proliferation of mouse fibroblasts (L929) on scaffolds were measured using colorimetric assay and scanning electron microscopy. Furthermore, to evaluate the wound healing effect of the scaffolds in comparison with gauze and Comfeel(®) dressings, an excision wound model was conducted on diabetic rats. On the postoperative days of 3, 6, 9, 12, and 15, residual wound area was calculated using macroscopic data. In vitro results showed that the attachment and proliferation of L929 were significantly increased on PLGA/SF (2:1) hybrid scaffold. Animal study and histopathological evaluation outcomes confirmed the in vitro results as well. On day 15, the residual wound area in PLGA/SF (2:1) hybrid membrane group was significantly smaller than PLGA and control groups. This promising scaffold has the potential to be used for the upcoming development of wound dressings with or without biological drugs. PMID:25051110

Shahverdi, Sheida; Hajimiri, Mirhamed; Esfandiari, Mohammad Amin; Larijani, Bagher; Atyabi, Fatemeh; Rajabiani, Afsaneh; Dehpour, Ahmad Reza; Gharehaghaji, Ali Akbar; Dinarvand, Rassoul

2014-10-01

400

CHARACTERIZATION OF INDIVIDUAL CHEMICAL REACTIONS CONSUMING ACID DURING NUCLEAR WASTE PROCESSING AT THE SAVANNAH RIVER SITE - 136B  

SciTech Connect

Conversion of legacy radioactive high-level waste at the Savannah River Site into a stable glass waste form involves a chemical pretreatment process to prepare the waste for vitrification. Waste slurry is treated with nitric and formic acids to achieve certain goals. The total quantity of acid added to a batch of waste slurry is constrained by the catalytic activity of trace noble metal fission products in the waste that can convert formic acid into hydrogen gas at many hundreds of times the radiolytic hydrogen generation rate. A large block of experimental process simulations were performed to characterize the chemical reactions that consume acid prior to hydrogen generation. The analysis led to a new equation for predicting the quantity of acid required to process a given volume of waste slurry.

Koopman, D.; Pickenheim, B.; Lambert, D.; Newell, J.; Stone, M.

2009-09-02

401

Universal solid-phase approach for the immobilization, derivatization, and resin-to-resin transfer reactions of boronic acids.  

PubMed

Boronic acid-containing molecules are employed in a broad range of biological, medicinal, and synthetic applications. These compounds, however, tend to be difficult to handle by solution-phase methods. Herein, this problem is addressed with the development of the first general solid-phase approach for the derivatization of functionalized boronic acids. This approach is based on the use of a diethanolamine resin anchor that facilitates boronic acid immobilization by avoiding the need for exhaustive removal of water in the esterification process. The immobilization of a wide variety of boronic acids onto N,N-diethanolaminomethyl polystyrene (DEAM-PS, 1) can be performed within minutes by simple stirring in anhydrous solvents at room temperature. Evidence for the formation of a bicyclic diethanolamine boronate with putative N-B coordination was shown by (1)H NMR analysis of DEAM-PS-supported p-tolylboronic acid. The hydrolytic cleavage of the same model boronic acid from the DEAM-PS resin was studied by UV spectroscopy. Hydrolysis and attachment were shown to occur under a rapidly attained equilibrium, and a large excess of water (>32 equiv) is required to effect a practically quantitative release of boronic acids from DEAM-PS. Despite their relative sensitivity to water and alcohols, DEAM-PS-bound arylboronic acids functionalized with a formyl, a bromomethyl, a carboxyl, or an amino group can be transformed in good to excellent yields into a wide variety of amines, amides, anilides, and ureas, respectively. Ugi multicomponent reactions on DEAM-PS-supported aminobenzeneboronic acids, derivatization of multifunctional arylboronic acids, and sequential reactions can also be carried out efficiently. These new DEAM-PS-supported arylboronic acids can be employed directly into resin-to-resin transfer reactions (RRTR). This type of multiresin process helps eliminate time-consuming cleavage and transfer operations, thereby considerably simplifying the outlook of combinatorial library synthesis by manual or automated means. This concept was illustrated by a set of optimized procedures for the Suzuki cross-coupling and the borono-Mannich reactions. PMID:11777432

Gravel, Michel; Thompson, Kim A; Zak, Mark; Bérubé, Christian; Hall, Dennis G

2002-01-11

402

On-chip transduction of nucleic acid hybridization using spatial profiles of immobilized quantum dots and fluorescence resonance energy transfer.  

PubMed

The glass surface of a glass-polydimethylsiloxane (PDMS) microfluidic channel was modified to develop a solid-phase assay for quantitative determination of nucleic acids. Electroosmotic flow (EOF) within channels was used to deliver and immobilize semiconductor quantum dots (QDs), and electrophoresis was used to decorate the QDs with oligonucleotide probe sequences. These processes took only minutes to complete. The QDs served as energy donors in fluorescence resonance energy transfer (FRET) for transduction of nucleic acid hybridization. Electrokinetic injection of fluorescent dye (Cy3) labeled oligonucleotide target into a microfluidic channel and subsequent hybridization (within minutes) provided the proximity for FRET, with emission from Cy3 being the analytical signal. The quantification of target concentration was achieved by measurement of the spatial length of coverage by target along a channel. Detection of femtomole quantities of target was possible with a dynamic range spanning an order of magnitude. The assay provided excellent resistance to nonspecific interactions of DNA. Further selectivity of the assay was achieved using 20% formamide, which allowed discrimination between a fully complementary target and a 3 base pair mismatch target at a contrast ratio of 4:1. PMID:22136151

Tavares, Anthony J; Noor, M Omair; Vannoy, Charles H; Algar, W Russ; Krull, Ulrich J

2012-01-01

403

Experimental and Guided Theoretical Investigation of Complex Reaction Mechanisms in a Prins Reaction of Glyoxylic Acid and Isobutene  

ERIC Educational Resources Information Center

A laboratory experiment was designed for undergraduate students, in which the outcome of an easy single-step organic synthesis with well-defined conditions was not elucidated until the end of the exercise. In class, students predict and discuss the possible products using their knowledge of reaction mechanisms. In the laboratory, they learn how to…

Angelici, Gaetano; Nicolet, Stefan; Uda, Narasimha R.; Creus, Marc

2014-01-01

404

Reinvestigation of the reactions of carbodiimides with alkoxycarbonylamino acid symmetrical anhydrides. Isolation of two N-acylureas.  

PubMed

Alkoxycarbonylamino acid symmetrical anhydrides were allowed to react with N,N'-diisopropylcarbodiimide. The determination of the decrease in carbodiimide concentration indicated that the reaction was slow and proceeded indirectly. It is presumed that symmetrical anhydride in the presence of basic carbodiimide is converted into oxazolone and alkoxycarbonylamino acid. The latter reacts with carbodiimide to give O-acylisourea which, in turn, rearranges to N-acylurea. A second minor product was found to be N-(N1,N2-bisalkoxycarbonyldipeptidyl)urea. The main pathway leading to the formation of this product starts with rearrangement of the symmetrical anhydride to N1,N2-bisalkoxycarbonyldipeptide acid. These experiments suggest that the reaction between anhydride and carbodiimide is not the source of N-acylurea in peptide synthesis. PMID:8200738

Izdebski, J; Or?owska, A; Anulewicz, R; Witkowska, E; Fiertek, D

1994-02-01

405

Transition-metal-free C-C bond forming reactions of aryl, alkenyl and alkynylboronic acids and their derivatives.  

PubMed

Investigation of new methods for the synthesis of C-C bonds is fundamental for the development of new organic drugs and materials. Aryl-, alkenyl- and alkynylboronic acids and their derivatives constitute attractive reagents towards this end, due to their stability, low toxicity and ease of handling. However, these compounds are only moderately nucleophilic. Consequently, the most popular C-C bond forming reactions of these boronic acids, such as the Suzuki-Miyaura, Heck, and Hayashi-Miyaura reactions, or additions to C=O and C=N bonds, require catalysis by transition metals. However, due to the toxicity and cost of transition metals, some new methods for C-C bond formation using aryl-, alkenyl- and alkynylboronic acids under transition-metal-free conditions are beginning to emerge. In this tutorial review, the recent synthetic advances in this field are highlighted and discussed. PMID:25181967

Roscales, S; Csákÿ, A G

2014-12-21

406

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. PMID:24244837

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

2013-01-01

407

Direct observation of Cm(III)-fulvate species on fulvic acid-montmorillonite hybrid by laser-induced fluorescence spectroscopy  

NASA Astrophysics Data System (ADS)

Particulate matter plays an important role in the removal of metal ions from water in natural aquifers. Some of the most important of these materials consist of associations of inorganic particles (clay minerals, oxides) with humic substances, associations that can form readily in such an environment due to the strong affinity between inorganic particles and humic substances. These associations are referred to in this paper as organic-inorganic hybrids. However, it is not clear whether the sorbed species of metal ions in such organic-inorganic hybrids are organic or inorganic species because of the complexity of such hybrids and the lack of appropriate methods for characterizing the trace metal ions incorporated in them. In this study, laser-induced fluorescence spectroscopy (LIF) was used successfully to characterize the Cm(III) species on an FA(fulvic acid)-montmorillonite hybrid, an example of such organic-inorganic hybrids. The LIF clearly showed that Cm(III) can be sorbed as Cm(III)-fulvate complex in the FA-montmorillonite hybrid. These results were consistent with those of experiments of solid-water partitioning of Cm(III) (or Eu(III) used as an analogue) and speciation calculations based on the stability constants of Cm(III)-fulvate complexes determined in this study. The results of LIF and the partitioning experiments showed that the solid-water distribution of humic substances governed that of Cm(III) under our experimental conditions. The Cm(III) preference for forming Cm(III)-fulvate complexes was also evident under a condition that would be found in a natural aquifer with a fairly low concentration of organic matter in freshwater (dissolved organic carbon: 2 mg/dm 3), as determined by our speciation calculations. These findings on the importance of humic substances in the migration of Cm(III) indicate that the clarification of the environmental behavior of humic substances is necessary to understand fully the behavior of Cm(III), or actinide(III) and lanthanide(III) ions, in natural aquifers.

Takahashi, Yoshio; Kimura, Takaumi; Minai, Yoshitaka

2002-01-01

408

40 CFR 721.10570 - Cyclic amine reaction product with acetophenone and formaldehyde acid salt (generic).  

...with acetophenone and formaldehyde acid salt (generic). 721.10570 Section 721...with acetophenone and formaldehyde acid salt (generic). (a) Chemical substance...with acetophenone and formaldehyde acid salt (PMN P-08-537) is subject to...

2014-07-01

409

LNA flow–FISH: A flow cytometry–fluorescence in situ hybridization method to detect messenger RNA using locked nucleic acid probes  

Microsoft Academic Search

We present a novel method using flow cytometry–fluorescence in situ hybridization (flow–FISH) to detect specific messenger RNA (mRNA) in suspended cells using locked nucleic acid (LNA)-modified oligonucleotide probes. ?-Actin mRNA was targeted in whole A549 epithelial cells by hybridization with a biotinylated, LNA-modified probe. The LNA bound to ?-actin was then stained using phycoerythrin-conjugated streptavidin and detected by flow cytometry.

Kelly L. Robertson; Dzung C. Thach

2009-01-01

410

In vitro formation of pyromorphite via reaction of Pb sources with soft-drink phosphoric acid.  

PubMed

Pyromorphite (Pb(5)(PO(4))(3)Cl) is a Pb mineral whose rapid kinetic formation and thermodynamic stability (Geochim. Cosmochim. Acta 37 (1973) 367, Geochim. Cosmochim. Acta 38 (1974) 887) has gained much attention in recent years as a mechanism to diminish Pb toxicity. Our research examined the in vitro formation of pyromorphite (K(sp) = 10(-25)) to significantly reduce Pb bioavailability via the reaction of PbCl(2) and Pb paint with cola soft drinks (regular, caffeine-free, and diet) that contain phosphoric acid. X-ray diffraction spectroscopy was employed to identify and quantify the crystal phases. The experiments consisted of a two-phase experimental design to simulate stomach and gastrointestinal (GI) conditions comprised of an initial reaction system (stomach) at pH 2.0 for 1 h at 37 degrees C and second-phase conditions (GI tract) at pH 7.0 for 5 h at 37 degrees C. The results showed that available Pb in solution was quickly transformed to pyromorphite by a precipitation mechanism. The PbCl(2) experiments observed over 90% Pb removal from solution within 30 s and nearly all (> 93-100%) of the Pb was converted to pyromorphite within 6 h. Similar results were observed in the Pb-paint system in which all of the available Pb initially available in solution was stabilized as pyromorphite within a short reaction period. While approximately 69% of the total Pb in the paint was converted to pyromorphite, there were minimal amounts of Pb in solution. It appeared that the dissolution mechanism allowing Pb in the paint to be released into the cola solution was repressed and was attributed to precipitation of pyromorphite on the surfaces of Pb-paint particles that inhibited further Pb release. The results of this research suggest that the in vivo formation of pyromorphite in children that ingest Pb-contaminated material (soil, dust, paint) with a phosphate source, such as a cola soft drink, may significantly reduce Pb bioavailability and allow passage of the pyromorphite material through the GI tract with minimal Pb absorption into the body. PMID:12526914

Scheckel, Kirk G; Ryan, James A

2003-01-20

411

Genetic optimization of charging current for lead-acid batteries in hybrid electric vehicles  

Microsoft Academic Search

VRLA batteries are of great importance in hybrid electric vehicle technology. They are generally equipped with intelligent chargers. The battery charger should be able to produce the desired charging current profile. Although reduction in charging time is unavoidable but the battery state of the health should not be sacrificed. In this paper a new model based optimization cost function is

H. Saberi; F. R. Salmasi

2007-01-01

412

Ampholine-functionalized hybrid organic-inorganic silica material as sorbent for solid-phase extraction of acidic and basic compounds.  

PubMed

A novel sorbent for solid-phase extraction (SPE) was synthesized by chemical immobilization of ampholine on hybrid organic-inorganic silica material. The ampholine-functionalized hybrid organic-inorganic silica sorbent is consisted of aliphatic amine groups, carboxyl groups and long carbon chains, allowing for extraction of both acidic and basic compounds. The retention properties of the developed sorbent were evaluated for 1-hydroxy-2-naphthoic acid (HNA), 1-naphthoic acid (NA), 3-hydroxybenzoic acid (HBA), benzoic acid (BA), sorbic acid (SA), vanillic aldehyde (VA), butyl 4-hydroxybenzoate (BHB), propyl 4-hydroxybenzoate (PHB), ethyl 4-hydroxybenzoate (EHB), and methyl 4-hydroxybenzoate (MHB). The results show that such a sorbent has three types of interaction, i.e., electrostatic interaction, hydrophobic interaction, and hydrogen bonding, exhibiting high extraction efficiency towards the compounds tested. The adsorption capacities of the analytes ranged from 0.61 to 6.54?gmg(-1). The reproducibility of the sorbent preparation was evaluated at three spiking concentration levels, with relative standard deviations (RSDs) of 1.0-10.5%. The recoveries of ten acidic and basic compounds spiked in beverage Coca-Cola(®) sample ranged from 82.5% to 98.2% with RSDs less than 5.8%. Under optimum conditions, the ampholine-functionalized hybrid organic-inorganic silica sorbent rendered higher extraction efficiency for acidic compounds than that of the commercially available ampholine-functionalized silica particles, and was comparable to that of the commercial Oasis WAX and Oasis WCX. PMID:23953713

Wang, Tingting; Chen, Yihui; Ma, Junfeng; Chen, Mingliang; Nie, Chenggang; Hu, Minjie; Li, Ying; Jia, Zhijian; Fang, Jianghua; Gao, Haoqi

2013-09-20

413

Hypersensitive Response-Like Reaction Is Associated with Hybrid Necrosis in Interspecific Crosses between Tetraploid Wheat and Aegilops tauschii Coss  

PubMed Central

Background Hybrid speciation is classified into homoploid and polyploid based on ploidy level. Common wheat is an allohexaploid species that originated from a naturally occurring interploidy cross between tetraploid wheat and diploid wild wheat Aegilops tauschii Coss. Aegilops tauschii provides wide naturally occurring genetic variation. Sometimes its triploid hybrids with tetraploid wheat show the following four types of hybrid growth abnormalities: types II and III hybrid necrosis, hybrid chlorosis, and severe growth abortion. The growth abnormalities in the triploid hybrids could act as postzygotic hybridization barriers to prevent formation of hexaploid wheat. Methodology/Principal Findings Here, we report on the geographical and phylogenetic distribution of Ae. tauschii accessions inducing the hybrid growth abnormalities and showed that they are widely distributed across growth habitats in Ae. tauschii. Molecular and cytological characterization of the type III necrosis phenotype was performed. The hybrid abnormality causing accessions were widely distributed across growth habitats in Ae. tauschii. Transcriptome analysis showed that a number of defense-related genes such as pathogenesis-related genes were highly up-regulated in the type III necrosis lines. Transmission electron microscope observation revealed that cell death occurred accompanied by generation of reactive oxygen species in leaves undergoing type III necrosis. The reduction of photosynthetic activity occurred prior to the appearance of necrotic symptoms on the leaves exhibiting hybrid necrosis. Conclusions/Significance Taking these results together strongly suggests that an autoimmune response might be triggered by intergenomic incompatibility between the tetraploid wheat and Ae. tauschii genomes in type III necrosis, and that genetically programmed cell death could be regarded as a hypersensitive response-like cell death similar to that observed in Arabidopsis intraspecific and Nicotiana interspecific hybrids. Only Ae. tauschii accessions without such inhibiting factors could be candidates for the D-genome donor for the present hexaploid wheat. PMID:20593003

Mizuno, Nobuyuki; Hosogi, Naoki; Park, Pyoyun; Takumi, Shigeo

2010-01-01

414

Lewis Acid Mediated Reactions of N-Arylsulfonimidoyl Chlorides with Alkenes. Some Steric Effects of Alkene Substitution.  

PubMed

The Lewis acid-mediated reaction of N-phenyl-S-(4-methylphenyl)sulfonimidoyl chloride with alkenes was explored in order to determine the effect of alkene substitution on the stereochemical outcome of the reaction. With monosubstituted alkenes, benzothiazines are produced with relatively low diastereoselection, with one unique exception, trimethylsilylethene. 1,1-Disubstituted alkenes give products with even lower stereoselectivity. With trisubstituted alkenes, steric effects begin to change the course the reaction from one which can be rationalized as a cycloaddition to one which seems to definitely produce a carbocationic intermediate. Interestingly, the stereoselection observed in the reaction of (E)- and (Z)-2-butenes shows large deviations from the norm with (E)-2-butene giving rise to two diastereomeric benzothiazines in a ratio of 45:1. PMID:11672304

Harmata, Michael; Kahraman, Mehmet

1998-10-01

415

Determination of free acidic and alkaline residues of protein via moving reaction boundary titration in microdevice electrophoresis.  

PubMed

As two important physico-chemical parameters, the acidic and alkaline residues of protein are of evident significance for the evaluation of protein properties and the design of relevant separation and analysis. However, there is still no electrophoretic method used for the direct detection of free acidic and alkaline residues of protein. Herein, we developed the concepts of moving reaction boundary (MRB) and MRB titration, relevant MRB titration theory, and the method of microdevice electrophoresis for the determination of free acidic and alkaline residues of protein. In the MRB titration, the boundary was created with acid or alkali and target protein immobilized via highly cross-linked polyacrylamide gel (PAG). It was theoretically revealed that the number of free acidic or alkaline residues of protein was as a function of MRB displacement in the electrophoretic titration system. As a proof of concept, seven model proteins were chosen for the determination of acidic or alkaline residues of protein via MRB titration. The results showed that the numbers of free acidic and alkaline residues of proteins detected were in good agreement with those obtained from the relevant amino sequences in the NCBI database, demonstrating the feasibility of the developed concept, theory and technique. The general methodology of MRB titration has potential application for inexpensive, facilitative and informative protein structure analysis of free acidic or alkaline residues of protein. PMID:23671907

Wang, Hou-yu; Li, Si; Tang, Yun-yun; Dong, Jing-yu; Fan, Liu-yin; Cao, Cheng-xi

2013-06-21

416

An investigation of the reactions of butylene and isobutane in the presence of concentrated sulfuric acid using a wetted wall reactor  

E-print Network

AN INVESTIGATION OF THE REACTIONS OF BUTYLENE AND ISOBUTANE IN THE PRESENCE OF CONCENTRATED SULFURIC ACID USING A WETTED WALL REACTOR Approved as Head of the A Thesis By Murlin Thomas Howerton ?if May, 19U9 to^gtyle and content recommended...: Department of Chemical Engineering AN INVESTIGATION OF THE REACTIONS OF BUTYLENE AND ISOBUTANE IN THE PRESENCE OF CONCENTRATED SULFURIC, ACID USING A WETTED WALL REACTOR A Thesis By Murlin Thomas Howerton May, 19U9 AN INVESTIGATION OF THE REACTIONS...

Howerton, Murlin T.

1949-01-01

417

Synthesis of tetrahydroisoquinolines and isochromans via Pictet–Spengler reactions catalyzed by Brønsted acid–surfactant-combined catalyst in aqueous media  

Microsoft Academic Search

Perfluorooctanesulfonic acid (PFOSA), Brønsted acid–surfactant-combined catalyst, efficiently catalyzes the Pictet–Spengler reactions of ?-arylethyl carbamate derivatives with aldehydes in water. The present reaction is accelerated by the addition of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). PFOSA in HFIP–water (10v\\/v%) is also successfully applied to the oxa-Pictet–Spengler reactions of ?-arylethyl alcohol compounds.

Akio Saito; Masaki Takayama; Aru Yamazaki; Junko Numaguchi; Yuji Hanzawa

2007-01-01

418

Acid-Catalyzed Reactions of Tetrahydropyranyl-Protected Polyvinylphenol in a Novolak-Resin-Based Positive Resist  

NASA Astrophysics Data System (ADS)

This paper deals with an acid-catalyzed reaction mechanism of a polymeric dissolution inhibitor of a novolak-resin-based positive chemical amplification resist system. This resist system consists of a novolak matrix resin, tri(methanesulfonyloxy)benzene as an acid generator, and tetrahydropyranyl-protected polyvinylphenol (THP-M) as a polymeric dissolution inhibitor. The acid-catalyzed deprotection products of THP-M in the resist film are detected and their subsequent acid-catalyzed reactivities are evaluated. It is found that tetrahydropyranyl group are exchanged between THP-M and the matrix to yield a strong dissolution inhibitor, causing negative tone behavior at the overexposure dose. High-resolution patterns (0.3-?m contact holes) are achieved with high sensitivity (2.4 ?C/cm2 at 50 kV).

Sakamizu, Toshio; Shiraishi, Hiroshi; Yamaguchi, Hidenori; Ueno, Takumi; Hayashi, Nobuaki

1992-12-01

419

Self-assembly of nucleic acids, silk and hybrid materials thereof.  

PubMed

Top-down approaches based on etching techniques have almost reached their limits in terms of dimension. Therefore, novel assembly strategies and types of nanomaterials are required to allow technological advances. Self-assembly processes independent of external energy sources and unlimited in dimensional scaling have become a very promising approach. Here,we highlight recent developments in self-assembled DNA-polymer, silk-polymer and silk-DNA hybrids as promising materials with biotic and abiotic moieties for constructing complex hierarchical materials in ‘bottom-up’ approaches. DNA block copolymers assemble into nanostructures typically exposing a DNA corona which allows functionalization, labeling and higher levels of organization due to its specific addressable recognition properties. In contrast, self-assembly of natural silk proteins as well as their recombinant variants yields mechanically stable ?-sheet rich nanostructures. The combination of silk with abiotic polymers gains hybrid materials with new functionalities. Together, the precision of DNA hybridization and robustness of silk fibrillar structures combine in novel conjugates enable processing of higher-order structures with nanoscale architecture and programmable functions. PMID:25419786

Humenik, Martin; Scheibel, Thomas

2014-12-17

420

Reactions of technetium hexafluoride with nitric acid, nitrosyl fluoride, and nitryl fluoride  

NASA Technical Reports Server (NTRS)

Stoichiometry of technetium hexafluoride reactions is studied. Magnetic properties and infrared spectra of reaction products are studied and compared with those of analogous complexes of the hexafluorides of tungsten, rhenium, and osmium.

Holloway, J. H.; Selig, H.

1970-01-01

421

Hydrogen Oxidation and Evolution Reaction Kinetics on Platinum: Acid vs Alkaline Electrolytes  

E-print Network

The kinetics of the hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) on polycrystalline platinum [Pt(pc)] and high surface area carbon-supported platinum nanoparticles (Pt/C) were studied in 0.1 M ...

Sheng, Wenchao

422

Edge-Functionalization of Pyrene as a Miniature Graphene via Friedel-Crafts Acylation Reaction in Poly(Phosphoric Acid)  

NASA Astrophysics Data System (ADS)

The feasibility of edge-functionalization of graphite was tested via the model reaction between pyrene and 4-(2,4,6-trimethylphenyloxy)benzamide (TMPBA) in poly(phosphoric acid) (PPA)/phosphorous pentoxide (P2O5) medium. The functionalization was confirmed by various characterization techniques. On the basis of the model study, the reaction condition could be extended to the edge-functionalization of graphite with TMPBA. Preliminary results showed that the resultant TMPBA-grafted graphite (graphite-g-TMPBA) was found to be readily dispersible in N-methyl-2-pyrrolidone (NMP) and can be used as a precursor for edge-functionalized graphene (EFG).

Jeon, In-Yup; Choi, Eun-Kyoung; Bae, Seo-Yoon; Baek, Jong-Beom

2010-10-01

423

Quantification of syntrophic fatty acid-{beta}-oxidizing bacteria in a mesophilic biogas reactor by oligonucleotide probe hybridization  

SciTech Connect

Small-subunit rRNA sequences were obtained for two saturated fatty acid-{beta}-oxidizing syntrophic bacteria, Syntrophomonas sapovorans and Syntrophomonas wolfei LYB, and sequence analysis confirmed their classification as members of the family Syntrophomonadaceae. S.wolfei LYB was closely related to S.wolfei subsp. solfei, but S. sapovorans did not cluster with the other members of the genus Syntrophomonas. Five oligonucleotide probes targeting the small-subunit rRNA of different groups within the family Syntrophomonadaceae, which contains all currently known saturated fatty acid-{beta}-oxidizing syntrophic bacteria, were developed and characterized. The probes were designed to be specific at the family, genus, and species levels and were characterized by temperature-of-dissociation and specificity studies. To demonstrate the usefulness of the probes for the detection and quantification of saturated fatty acid-{beta}-oxidizing syntrophic bacteria in methanogenic environments, the microbial community structure of a sample from a full-scale biogas plant was determined. Hybridization results with probes for syntrophic bacteria and methanogens were compared to specific methanogenic activities and microbial numbers determined with most-probable-number estimates. Most of the methanogenic rRNA was comprised of Methanomicrobiales rRNA, suggesting that members of this order served as the main hydrogen-utilizing microorganisms. Between 0.2 and 1% of the rRNA was attributed to the Syntrophomonadaceae, or which the majority was accounted for by the genus Syntrophomonas.

Hansen, K.H.; Ahring, B.K.; Raskin, L.

1999-11-01

424

DNA breakage by tannic acid and Cu(II): sequence specificity of the reaction and involvement of active oxygen species.  

PubMed

Tannic acid has numerous chemical, food and pharmacological applications. In the presence of Cu(II) and molecular oxygen it was found to cause breakage of calf thymus DNA and supercoiled plasmid DNA. Treatment of lambda phage DNA with tannic acid protected cleavage with restriction endonucleases DraI and EcoRI* but not with SmaI and HaeIII. The results indicate that under the conditions used tannic acid preferably binds to AT base pairs. Restriction analysis of open circular form II plasmid DNA generated by tannic acid-Cu(II) treatment further showed that the strand breakage is caused at specific sites or sequences. In this reaction Cu(I) was shown to be an essential intermediate by using the Cu(I) sequestering reagents neocuproine and bathocuproine. By using job plots, we established that in the absence of DNA, six Cu(II) ions can be reduced by one tannic acid molecule. The involvement of active oxygen species in the reaction was established by the inhibition of DNA breakage by superoxide dismutase, thiourea, mannitol, formate and catalase. PMID:7519309

Bhat, R; Hadi, S M

1994-08-01

425

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

PubMed

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

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

2013-08-01

426

Evidence that the coenzyme A requirement for avian fatty acid synthase is not for the termination reaction.  

PubMed

1. Fatty acid synthase from goose uropygial gland was inhibited when CoA was scavenged with ATP citrate lyase. 2. This inhibition was reversed by the addition of CoA, 3'-dephospho-CoA, 1,N6-etheno-CoA and pantetheine but not by desulfo-CoA, pantethine or mercaptoethanol suggesting that the structural features of pantetheine including the free thiol group are essential for the reversal. 3. The S-acyl fatty acid synthase thioester hydrolase from the uropygial glands of mallards, which hydrolytically removes acyl chains from fatty acid synthase of goose uropygial gland in the absence of CoA, did not reverse this inhibition, suggesting that the CoA depletion does not inhibit termination reaction. 4. However, triacetic acid lactone synthesis by the fatty acid synthase was inhibited by the scavenging of CoA, raising the possibility that the condensation and/or the transacylase reactions may require CoA. PMID:7106345

Poulose, A J; Kolattukudy, P E

1982-01-01

427

Synthesis of p-aminophenyl aryl H-phosphinic acids and esters via cross-coupling reactions: elaboration to phosphinic acid pseudopeptide analogues of pteroyl glutamic acid and related antifolates.  

PubMed

The synthesis of suitably protected p-aminophenyl H-phosphinic acids and esters from the corresponding para-substituted aryl halides has been accomplished via the Pd-catalyzed cross-coupling reaction of anilinium hypophosphite, either in the absence or presence of a tetraalkyl orthosilicate, to provide the free H-phosphinic acid or the corresponding ester, respectively. Subsequent conjugate addition of either a PIII species or phosphorus anion, generated in situ from either the free H-phosphinic acid or ester, to a 2-methylene glutaric acid ester provided the aryl phosphinic acid analogue of p-aminobenzoyl glutamic acid. Alkylation of these suitably protected p-aminophenyl phosphinic acid esters with a 6-(bromomethyl)pteridine or the corresponding (bromomethyl)pyridopyrmidine, followed by hydrolytic removal of protecting groups, provided the target aryl phosphinic acid analogues of folic acid and related antifolates. Alternatively, for the synthesis of the folate or 5-deazafolate analogues on a slightly larger scale, reductive amination with either N2-acetyl or N2-pivaloyl-6-formylpterin or the corresponding formylpyridopyrmidine and the same suitably protected p-aminophenyl phosphinic acid esters, followed by removal of protecting groups, is preferred. In the course of this research, it was observed that the nucleophilicity of both the aniline nitrogen and various PIII species derived from p-aminophenyl phosphinic acid derivatives is significantly reduced compared to that of the unsubstituted counterpart. PMID:17602593

Yang, Yonghong; Coward, James K

2007-07-20

428

Mechanisms of photoinduced electron transfer reactions of lappaconitine with aromatic amino acids. Time-resolved CIDNP study.  

PubMed

CIDNP techniques were applied to the investigation of the elementary mechanism of photoinduced interaction between anti-arrhythmic drug lappaconitine and amino acids tyrosine and tryptophan. It has been shown that the reactions involve the formation of lappaconitine radical anion. Lappaconitine radical anion is unstable and rapidly eliminates N-acetyl anthranilic acid via protonation and ether bond cleavage. The rate constant of ether bond cleavage was estimated to be equal to 4 x 10(5) s(-1). The role of single electron transfer is discussed in the light of the model of drug-receptor interactions. PMID:15731875

Polyakov, Nikolai E; Khan, Vladimir K; Taraban, Marc B; Leshina, Tatyana V; Luzina, Olga A; Salakhutdinov, Nariman F; Tolstikov, Genrikh A

2005-03-01

429

Ionic mechanisms for heterogeneous stratospheric reactions and ultraviolet photoabsorption cross sections for NO2+, HNO3, AND NO3? in sulfuric acid  

Microsoft Academic Search

We present room temperature photo-absorption cross sections between 180 and 340 nm for potassium nitrate dissolved in sulfuric acid-water solutions of 0, 80, and 96% sulfuric acid by mass. Other investigators have obtained ultraviolet absorption spectra for similar solutions above 220 nm, and there is a large literature on the spectra, species, and nitration reactions in sulfuric acid solutions. The

Joel D. Burley; H. S. Johnston

1992-01-01

430

Polymerase Chain Reaction for Human Picornaviruses  

Microsoft Academic Search

SUMMARY We have used enzymic amplification of specific nucleic acid sequences followed by hybridization, for the rapid detection and typing of human picornaviruses after cell culture isolation. The test is based on the synthesis of cDNA, the polymerase chain reaction and the use of oligonucleotide probes. The primers were selected from the 5' non-coding region of the genome representing highly

TIMO HYYPIA; PETRI AUVINEN; MARITA MAARONEN

1989-01-01

431

Source and reaction pathways of dicarboxylic acids, ketoacids and dicarbonyls in arctic aerosols: One year of observations  

NASA Astrophysics Data System (ADS)

Normal saturated (C 2?C 11) and unsaturated (C 4?C 5, C 8) dicarboxylic acids were measured in arctic aerosol samples collected weekly at Alert, Canada in 1987-1988. In all seasons, oxalic (C 2) acid was usually the dominant diacid species (1.8-70 ng m -3, av. 14 ± 12 ng m -3) followed by malonic (C 3; 0.05-19 ng m -3, av. 2.5 ± 3.3 ng m -3) and succinic (C 4; 0.51-18 ng m -3, av. 3.8 ± 3.5 ng m -3) acids. The total concentrations of dicarboxylic acids showed a seasonal variation (4.3-97 ng m -3, av. 25 ± 20 ng m -3),with two maxima in September to October and in March to April. The autumn peak is characterized by high concentrations of oxalic acid and azelaic (C 9) acids, which were probably caused by enhanced contributions from anthropogenic and biogenic sources, respectively, followed by photochemical reactions. This is consistent with higher concentrations of n-alkanes from terrestrial plant waxes and of soil-derived aluminum in the autumn aerosol samples. On the other hand, during "Arctic Sunrise" in March to April, oxalic, malonic and succinic acids as well as some other (C 5?C 6) diacids were 5 to 20 times more abundant than in the preceding dark winter months, suggesting that diacids are produced in situ by secondary photochemical oxidation of organic pollutants carried to the Arctic. ?-Oxocarboxylic acids (C 2?C 5, C 9), pyruvic acid and ?-dicarbonyls (methylglyoxal and glyoxal) were also detected in the arctic aerosols. Their concentration also showed spring maxima; however, they were observed a few weeks earlier than the spring peak of diacids. The ?-oxoacids are likely intermediates to the production of ?,?-dicarboxylic acids at the polar sunrise.

Kawamura, Kimitaka; Kasukabe, Hideki; Barrie, Leonard A.

432

Acidic reaction products of monoterpenes and sesquiterpenes in atmospheric fine particles in a boreal forest  

NASA Astrophysics Data System (ADS)

Biogenic acids were measured in aerosols at the SMEAR II (Station for Measuring Forest Ecosystem-Atmosphere Relations II) station in Finland from June 2010 until October 2011. The analysed organic acids were pinic, pinonic, caric, limonic and caryophyllinic acids from oxidation of ?-pinene, ?-pinene, limonene, ?3-carene and ?-caryophyllene, respectively. Due to a lack of authentic standards, the caric, limonic and caryophyllinic acids were synthesised for this study. The mean, median, maximum and minimum concentrations (ng m-3) were as follows: limonic acid (1.26, 0.80, 16.5, below detection limit (< LOD)), pinic acid (5.53, 3.25, 31.4, 0.15), pinonic acid (9.87, 5.07, 80.1, < LOD), caric acid (5.52, 3.58, 49.8, < LOD), and caryophyllinic acid (7.87, 6.07, 86.1, < LOD). The highest terpenoic acid concentrations were measured during the summer. Of the acids, ?-caryophyllinic acid showed the highest concentrations in summer, but during other times of the year pinonic acid was the most abundant. The ?-caryophyllinic acid contribution was higher than expected, based on the emission calculations of the precursor compounds and yields from oxidation experiments in smog chambers, implying that the ?-caryophyllene emissions or ?-caryophyllinic acid yields were underestimated. The concentration ratios between terpenoic acids and their precursors were clearly lower in summer than in winter, indicating stronger partitioning to the aerosol phase during the cold winter season. The ?-caryophyllinic and caric acids were weakly correlated with the accumulation-mode particle number concentrations.

Vestenius, M.; Hellén, H.; Levula, J.; Kuronen, P.; Helminen, K. J.; Nieminen, T.; Kulmala, M.; Hakola, H.

2014-08-01