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1

Theory of hybrid nuclear reactions  

SciTech Connect

A theory of hybrid nuclear reactions, which are partially direct and partially compound, is presented. We review first the formulation of the theory, based on the optical theorem, and then its applications to a few example reactions. Discussions will be given on the physical picture (deep peripheral nature) of such hybrid processes emerging from the numerical studies. 25 references, 10 figures.

Udagawa, T.

1983-01-01

2

Assessment of methods for covalent binding of nucleic acids to magnetic beads, Dynabeads, and the characteristics of the bound nucleic acids in hybridization reactions.  

PubMed Central

Dynabeads are magnetic monosized beads with high stability, high uniformity, unique paramagnetic properties, low particle-particle interaction, and high dispersibility. Different reactive groups; hydroxyl, carboxyl and amino groups can be attached to the surface. Several methods for covalent attachment of DNA or oligonucleotides to the beads were investigated. Best coupling yields were obtained by carbodiimide-mediated end-attachment of 5'-phosphate and 5'-NH2 modified nucleic acids to respectively amino and carboxyl beads. The carboxyl beads showed a low degree of non-specific binding, while a better yield of end-attached nucleic acids was obtained using the amino beads. The DNA-beads worked efficiently in hybridization experiments, and the kinetics of hybridization approach those of solution hybridization. PMID:3205723

Lund, V; Schmid, R; Rickwood, D; Hornes, E

1988-01-01

3

DEOXYRIBONUCLEIC ACID HYBRIDS OF ACETIC ACID BACTERIA  

PubMed Central

De Ley, J. (State University, Ghent, Belgium), and S. Friedman. Deoxyribonucleic acid hybrids of acetic acid bacteria. J. Bacteriol. 88:937–945. 1964.—Deuterated N15-labeled deoxyribonucleic acid (DNA) from Acetobacter aceti (mesoxydans 4) forms hybrids with ordinary DNA from other species of this genus (A. xylinum, A. pasteurianus, A. estunensis, and possibly A. xylinoides) when the guanine plus cytosine base composition does not vary by more than 1 to 2%. Beyond this limit (A. aceti Ch31 and A. muciparus 5) no hybrids are formed. The hybrids are apparently derived from an asymmetrical part of the compositional distribution. The results lend strength to the concept of a genetic species rather than to a division of a genus into sharply separated species, based on small phenotypic differences. Taxonomic implications are discussed. PMID:14219057

De Ley, J.; Friedman, S.

1964-01-01

4

One-step detection of c-kit point mutations using peptide nucleic acid-mediated polymerase chain reaction clamping and hybridization probes.  

PubMed

The prognostic significance of somatic activating codon 816 c-kit mutations in pediatric urticaria pigmentosa has not yet been established in detail. Detection of such mutations in archival paraffin-embedded biopsies is usually hampered by an abundance of surrounding normal cells. Here we describe a method for the selective amplification and specific detection of c-kit mutation Asp816-->Val in complete tissue sections cut from up to 24-year-old paraffin blocks. Peptide nucleic acid-mediated polymerase chain reaction clamping of the wild-type allele was combined with on-line mutation detection using oligonucleotide hybridization probes. In DNA extracted from HMC-1 cells heterozygously carrying the c-kit mutation Asp816-->Val, the one-tube assay allowed specific detection of this mutation in a more than 1000-fold excess of normal background DNA within 1 hour and without the need for additional analytical steps. In a series of 38 cases with pediatric urticaria pigmentosa we detected c-kit codons 815 and 816 mutations in 16 cases. Mutation detection did not correlate with clinical outcome after a mean follow-up of 11.2 years. In conclusion, the procedure described may represent an ideal screening tool for all kinds of clinical applications, using point mutations as markers of, for example, early events in carcinogenesis, circulating metastatic tumor cells, and minimal residual disease. PMID:12598308

Sotlar, Karl; Escribano, Luis; Landt, Olfert; Möhrle, Stefanie; Herrero, Sonia; Torrelo, Antonio; Lass, Ulrich; Horny, Hans-Peter; Bültmann, Burkhard

2003-03-01

5

Optimizing the specificity of nucleic acid hybridization  

PubMed Central

The specific hybridization of complementary sequences is an essential property of nucleic acids, enabling diverse biological and biotechnological reactions and functions. However, the specificity of nucleic acid hybridization is compromised for long strands, except near the melting temperature. Here, we analytically derived the thermodynamic properties of a hybridization probe that would enable near-optimal single-base discrimination and perform robustly across diverse temperature, salt and concentration conditions. We rationally designed ‘toehold exchange’ probes that approximate these properties, and comprehensively tested them against five different DNA targets and 55 spurious analogues with energetically representative single-base changes (replacements, deletions and insertions). These probes produced discrimination factors between 3 and 100+ (median, 26). Without retuning, our probes function robustly from 10 °C to 37 °C, from 1 mM Mg2+ to 47 mM Mg2+, and with nucleic acid concentrations from 1 nM to 5 ?M. Experiments with RNA also showed effective single-base change discrimination. PMID:22354435

Zhang, David Yu; Chen, Sherry Xi; Yin, Peng

2014-01-01

6

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

7

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

8

Free energies for acid attack reactions of lithium cobaltate.  

SciTech Connect

The attack of lithium-ion battery cathodes by stray aqueous HF, with resultant dissolution, protonation, and possibly other unintended reactions, can be a significant source of capacity fade. We explore the calculation of reaction free energies of lithium cobaltate in acid by a 'hybrid' method, in which solid-phase free energies are calculated from first principles at the generalized gradient approximation + intrasite coulomb interaction (GGA+U) level and tabulated values of ionization potentials and hydration energies are employed for the aqueous species. Analysis of the dissolution of the binary oxides Li{sub 2}O and CoO suggests that the atomic energies for Co and Li should be shifted from values calculated by first principles to yield accurate reaction free energies within the hybrid method. With the shifted atomic energies, the hybrid method was applied to analyze proton-promoted dissolution and protonation reactions of LiCoO{sub 2} in aqueous acid. Reaction free energies for the dissolution reaction, the reaction to form Co{sub 3}O{sub 4} spinel, and the proton-for-lithium exchange reaction are obtained and compared to empirical values. An extension of the present treatment to consider partial reactions is proposed, with a view to investigating interfacial and environmental effects on the dissolution reaction.

Benedek, R.; van de Walle, A.; Chemical Sciences and Engineering Division; California Inst. of Tech.

2008-01-01

9

Nucleophilic reactions of sorbic acid  

Microsoft Academic Search

The conjugated dienoic acid structure of sorbic acid renders it susceptible to nucleophilic attack. Nucleophiles known to react with sorbic acid include sulphite ion and amines. These attack the molecule in position 5 and, in the cse of amines, cyclization to form substituted dihydropyridones may follow. Recent investigations show that thiols in general can also add to sorbic acid. Cysteine,

G. D. Khandelwal; B. L. Wedzicha

1990-01-01

10

Adverse drug reactions induced by valproic acid.  

PubMed

Valproic acid is a widely-used first-generation antiepileptic drug, prescribed predominantly in epilepsy and psychiatric disorders. VPA has good efficacy and pharmacoeconomic profiles, as well as a relatively favorable safety profile. However, adverse drug reactions have been reported in relation with valproic acid use, either as monotherapy or polytherapy with other antiepileptic drugs or antipsychotic drugs. This systematic review discusses valproic acid adverse drug reactions, in terms of hepatotoxicity, mitochondrial toxicity, hyperammonemic encephalopathy, hypersensitivity syndrome reactions, neurological toxicity, metabolic and endocrine adverse events, and teratogenicity. PMID:23792104

Nanau, Radu M; Neuman, Manuela G

2013-10-01

11

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...

12

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

13

Heterogeneous Reactions of Epoxides in Acidic Media  

E-print Network

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 alpha-pinene oxide with sulfuric acid to identify the potential of epoxides...

Lal, Vinita

2012-02-14

14

Catalytic performance of hybrid nanocatalyst for levulinic acid production from glucose  

NASA Astrophysics Data System (ADS)

Levulinic acid is one of the potential and versatile biomass-derived chemicals. Product analysis via HPLC revealed that the heterogeneous dehydration of glucose over hybrid nanocatalyst exhibited better performance compared to single catalyst. Hybrid nanocatalyst containing H-Y zeolite and CrCl3 could substitute homogenous acid catalyst for attaining high levulinic acid yield. Different CrC3 and H-Y zeolite weight ratios of 1:1, 1:2 and 2:1 were prepared according to the wetness impregnation method. The hybrid catalyst with a 1:1 weight ratio performed better compared to others with the highest levulinic acid yield reported (93.5%) at 140 °C, 180 min reaction time, 0.1 g catalyst loading and 0.1 g glucose feed. Characterization results revealed that properties such as surface area, mesoporosity and acidic strength of the catalyst have significant effects on glucose dehydration for levulinic acid production.

Ya'aini, Nazlina; Amin, Nor Aishah Saidina

2012-11-01

15

Hybrid Simulations of Reaction-Diffusion Systems in Porous Media  

SciTech Connect

Hybrid or multi-physics algorithms provide an efficient computational tool for combining micro- and macro-scale descriptions of a physical phenomenon. Their use becomes imperative when micro-scale descriptions are too computationally expensive to be conducted in the whole domain and macro-scale descriptions fail in a small portion of the computation domain. We present a hybrid algorithm to model a general class of reaction-diffusion processes in granular porous media, which includes mixing-induced mineral precipitation on or dissolution of the porous matrix that cannot be accurately described with a continuum (Darcy-scale) model. The pore-scale/Darcy-scale hybrid is constructed by coupling a solution of the reaction-diffusion equation (RDE) at the pore-scale with a continuum Darcy-level solution of theaveraged RDE. The resulting pore-Darcy scales hybrid is solved numerically by employing a multi-resolution meshless discretization based on Smoothed Particle Hydrodynamics (SPH) method, which ensures the seamless, non-iterative coupling of the two components of the hybrid. The presented computational examples illustrate the accuracy and efficiency of the proposed hybrid model.

Tartakovsky, Alexandre M.; Tartakovsky, Daniel M.; Scheibe, Timothy D.; Meakin, Paul

2008-10-13

16

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

17

Catalytic properties of heteropoly acid\\/zeolite hybrid materials: toluene disproportionation and transalkylation with 1,2,4-trimethylbenzene  

Microsoft Academic Search

A series of hybrid heteropoly acid (HPA)\\/zeolite catalysts has been prepared by supporting 12-tungstophosphoric acid (H3PW12O40) on a faujasitic matrix. It has been shown that the structure of a dealuminated zeolite Y is retained upon contact with a very strong solid acid. The catalytic properties of the hybrid catalysts were examined in the two gas-phase reactions: disproportionation of toluene and

B. Sulikowski; R. Rachwalik

2003-01-01

18

Reactions of tetraphenyltitanium with organic acids  

SciTech Connect

As a result of the reactions of tetraphenyltitanium with dibasic organic acids high yields were obtained of new thermally stable titanium(III) complexes: phenyltitanium(III)carboxylates. Under the action of proton-active reagents (hydrochloric acid, cyclopentadiene, methanol) the latter break down with the breakage of titanium-phenyl bond. The proposed structure was based on IR- and ESR-spectral data. The dinuclear structure of the complexes was established on the basis of a study of the triplet structure of the ESR spectra, which showed the existence of intermolecular titanium-titanium exchange through methylene groups of the dicarboxylate bridges.

Razuvaev, G.A.; Vyshinskaya, L.I.; Vasil'eva, G.A.

1987-12-10

19

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

20

Deoxyribonucleic acid-ribonucleic acid hybridization. Annealing and quantitative recovery of intact ribosomal ribonucleic acid molecules from hybrids  

PubMed Central

A simple and efficient method for hybridization and subsequent recovery of non-fragmented ribosomal RNA from the hybrid is described. The procedure involves annealing of immobilized denatured DNA bound on cellulose nitrate membrane filters to complementary RNA in 50% (v/v) formamide–0·33m-potassium chloride–10mm-tris–hydrochloric acid buffer, pH7·4, at 33° for 3hr. Under these conditions no detectable changes in the sedimentation coefficients of the input RNA were detected. The RNA can subsequently be recovered quantitatively from the hybrid in intact form by incubating the filters in formamide or in 85% (v/v) dimethyl sulphoxide. The applicability of the method for the evaluation of the absolute size of ribosomal RNA cistrons in Escherichia coli DNA and for the determination of the size of messenger RNA molecules is discussed. PMID:4907881

Fry, Michael; Artman, Michael

1969-01-01

21

Cubic phenylene bridged mesoporous hybrids from allylorganosilane precursors and their applications in Friedel–Crafts acylation reaction  

Microsoft Academic Search

The phenylene-bridged hybrid mesoporous silica material with well-defined cubic three-dimensional (Pm3n) symmetry was prepared using a allylorganosilane precursor 1,4-bis(triallylsilyl)benzene and cetyltrimethylammoniumchloride (C16TMACl) surfactant in acidic medium. Sulfonic acid functionalized derivatives of 3d-cubic phenylene-bridged hybrid mesoporous silica materials were prepared and found effective in Friedel–Crafts acylation reaction. The catalytic results were also compared to the sulfonic acid functionalized derivatives of phenylene-bridged

Mahendra P. Kapoor; Yuuki Kasama; Masaaki Yanagi; Takuji Yokoyama; Shinji Inagaki; Toyoshi Shimada; Hironobu Nanbu; Lekh R. Juneja

2007-01-01

22

The Chlorate-Iodine-Nitrous Acid Clock Reaction  

PubMed Central

A new clock reaction based on chlorate, iodine and nitrous acid is presented. The induction period of this new clock reaction decreases when the initial concentrations of chlorate, nitrous acid and perchloric acid increase, but it is independent on the initial iodine concentration. The proposed mechanism is based on the LLKE autocatalytic mechanism for the chlorite-iodide reaction and the initial reaction between chlorate and nitrous acid to produce nitrate and chlorite. This new clock reaction opens the possibility for a new family of oscillating reactions containing chlorate or nitrous acid, which in both cases has not been observed until now. PMID:25313803

Sant'Anna, Rafaela T. P.; Faria, Roberto B.

2014-01-01

23

Heterogeneous reactions of epoxides in acidic media.  

PubMed

Epoxides have recently been identified as important intermediates in the gas phase oxidation of hydrocarbons, and their hydrolysis products have been observed in ambient aerosols. To evaluate the role of epoxides in the formation of secondary organic aerosols (SOA), the kinetics and mechanism of heterogeneous reactions of two model epoxides, isoprene oxide and ?-pinene oxide, with sulfuric acid, ammonium bisulfate, and ammonium sulfate have been investigated using complementary experimental techniques. Kinetic experiments using a fast flow reactor coupled to an ion drift-chemical ionization mass spectrometer (ID-CIMS) show a fast irreversible loss of the epoxides with the uptake coefficients (?) of (1.7 ± 0.1) × 10(-2) and (4.6 ± 0.3) × 10(-2) for isoprene oxide and ?-pinene oxide, respectively, for 90 wt % H(2)SO(4) and at room temperature. Experiments using attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) reveal that diols are the major products in ammonium bisulfate and dilute H(2)SO(4) (<25 wt %) solutions for both epoxides. In concentrated H(2)SO(4) (>65 wt %), acetals are formed from isoprene oxide, whereas organosulfates are produced from ?-pinene oxide. The reaction of the epoxides with ammonium sulfate is slow and no products are observed. The epoxide reactions using bulk samples and Nuclear Magnetic Resonance (NMR) spectroscopy reveal the presence of diols as the major products for isoprene oxide, accompanied by aldehyde formation. For ?-pinene oxide, organosulfate formation is observed with a yield increasing with the acidity. Large yields of organosulfates in all NMR experiments with ?-pinene oxide are attributed to the kinetic isotope effect (KIE) from the use of deuterated sulfuric acid and water. Our results suggest that acid-catalyzed hydrolysis of epoxides results in the formation of a wide range of products, and some of the products have low volatility and contribute to SOA growth under ambient conditions prevailing in the urban atmosphere. PMID:22309032

Lal, Vinita; Khalizov, Alexei F; Lin, Yun; Galvan, Maria D; Connell, Brian T; Zhang, Renyi

2012-06-21

24

Hybrid vehicle optimization: lead acid battery modellization  

Microsoft Academic Search

This work is part of a larger project aiming at the optimization of an hybrid electric vehicle with series design. The final objective of the optimization process is the identification of the most efficient vehicle management strategy in order to reduce the emissions, fuel consumption without deteriorating the batteries. In order to achieve this objective the whole system modellization is

Enrico Bertolazzi; Francesco Biral; Mauro Da Lio; Massimo Matteotti; Ahmed Masmoudi; Ahmed Elantably

2009-01-01

25

Tracing hybrid incompatibilities to single amino acid substitutions.  

PubMed

Deleterious interactions among genes cause reductions in fitness of interpopulation hybrids (hybrid breakdown). Identifying genes involved in hybrid breakdown has proven difficult, and few studies have addressed the molecular basis of this widespread phenomenon. Because proper function of the mitochondrial electron transport system (ETS) requires a coadapted set of nuclear and mitochondrial gene products, ETS genes present an attractive system for studying the evolution of coadapted gene complexes within isolated populations and the loss of fitness in interpopulation hybrids. Here we show the effects of single amino acid substitutions in cytochrome c (CYC) on its functional interaction with another ETS protein, cytochrome c oxidase (COX) in the intertidal copepod Tigriopus californicus. The individual and pairwise consequences of three naturally occurring amino acid substitutions in CYC are examined by site-directed mutagenesis and found to differentially effect the rates of CYC oxidation by COX variants from different source populations. In one case, we show that interpopulation hybrid breakdown in COX activity can be attributed to a single naturally occurring amino acid substitution in CYC. PMID:16280539

Harrison, J Scott; Burton, Ronald S

2006-03-01

26

Advanced lead acid battery designs for hybrid electric vehicles  

Microsoft Academic Search

In this paper, the authors present a high power, lead acid battery design that has demonstrated long life. The design uses horizontal plates with multiple lug connectors to deliver high power for hybrid electric vehicle applications. The horizontal plate configuration helps improve life by allowing for better thermal management and mechanical compression. They use computer models that were previously developed

Dean B. Edwards; Charles Kinney

2001-01-01

27

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 are incorporated into atmospheric aerosols are not well understood. Acid-catalyzed reactions of compounds into acidic aerosols. In the present study, we use the aerodyne aerosol mass spectrometer (AMS) to probe

Elrod, Matthew J.

28

Hybrid stochastic simulations of intracellular reaction-diffusion systems.  

PubMed

With the observation that stochasticity is important in biological systems, chemical kinetics have begun to receive wider interest. While the use of Monte Carlo discrete event simulations most accurately capture the variability of molecular species, they become computationally costly for complex reaction-diffusion systems with large populations of molecules. On the other hand, continuous time models are computationally efficient but they fail to capture any variability in the molecular species. In this study a hybrid stochastic approach is introduced for simulating reaction-diffusion systems. We developed an adaptive partitioning strategy in which processes with high frequency are simulated with deterministic rate-based equations, and those with low frequency using the exact stochastic algorithm of Gillespie. Therefore the stochastic behavior of cellular pathways is preserved while being able to apply it to large populations of molecules. We describe our method and demonstrate its accuracy and efficiency compared with the Gillespie algorithm for two different systems. First, a model of intracellular viral kinetics with two steady states and second, a compartmental model of the postsynaptic spine head for studying the dynamics of Ca+2 and NMDA receptors. PMID:19414282

Kalantzis, Georgios

2009-06-01

29

Investigation of reaction products of sulphuric acid with ilmenite  

Microsoft Academic Search

The reaction of sulphuric acid with titanium raw materials runs violently with simultaneous emission of gases. Such run of\\u000a reaction creates danger of explosion. This process is very complicated from the reason of complexity of reactions and variety\\u000a of compounds in reaction mixture. To determine safe conditions of reaction with high efficiency, it is necessary to investigate\\u000a phase composition products

M. Jab?o?ski

2008-01-01

30

Magnetite-supported sulfonic acid: a retrievable nanocatalyst for the Ritter reaction and multicomponent reactions  

EPA Science Inventory

Magnetite-sulfonic acid (NanocatFe-OSO3H), prepared by wet-impregnation method, serves as a magnetically retrievable sustainable catalyst for the Ritter reaction which can be used in several reaction cycles without any loss of activity....

31

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

32

Synthesis and characterization of hybrid hyaluronic acid-gelatin hydrogels.  

PubMed

Biomimetic hybrid hydrogels have generated broad interest in tissue engineering and regenerative medicine. Hyaluronic acid (HA) and gelatin (hydrolyzed collagen) are naturally derived polymers and biodegradable under physiological conditions. Moreover, collagen and HA are major components of the extracellular matrix (ECM) in most of the tissues (e.g., cardiovascular, cartilage, neural). When used as a hybrid material, HA-gelatin hydrogels may enable mimicking the ECM of native tissues. Although HA-gelatin hybrid hydrogels are promising biomimetic substrates, their material properties have not been thoroughly characterized in the literature. Herein, we generated hybrid hydrogels with tunable physical and biological properties by using different concentrations of HA and gelatin. The physical properties of the fabricated hydrogels including swelling ratio, degradation, and mechanical properties were investigated. In addition, in vitro cellular responses in both two and three-dimensional culture conditions were assessed. It was found that the addition of gelatin methacrylate (GelMA) into HA methacrylate (HAMA) promoted cell spreading in the hybrid hydogels. Moreover, the hybrid hydrogels showed significantly improved mechanical properties compared to their single component analogs. The HAMA-GelMA hydrogels exhibited remarkable tunability behavior and may be useful for cardiovascular tissue engineering applications. PMID:23419055

Camci-Unal, Gulden; Cuttica, Davide; Annabi, Nasim; Demarchi, Danilo; Khademhosseini, Ali

2013-04-01

33

Reaction of caffeic acid derivatives with acidic nitrite  

Microsoft Academic Search

Caffeic derivatives were reacted with acidic nitrite at controlled pH in order to mimic the gastric juice conditions. At pH 2, whereas caffeic acid reacts exclusively on the side chain, its esters are readily nitrated. Under more acidic conditions (pH 1), caffeic acid methyl ester undergoes a dimerisation into a norlignan derivative.

Philippe Cotelle; Hervé Vezin

2001-01-01

34

A non-radioactive in situ hybridization method based on mercurated nucleic acid probes and sulfhydryl-hapten ligands.  

PubMed Central

Mercurated nucleic acid probes can be used for non-radioactive in situ hybridization. The principle of the method is based on the reaction of the mercurated pyrimidine residues of the in situ hybridized probe with the sulfhydryl group of a ligand which contains a hapten. Next, the hapten is immunocytochemically detected. Previous experiments showed that stable coupling of the sulfhydryl ligands could only be obtained when positively charged amino groups are present in the ligand. On basis of this finding, ligands were synthesized containing a sulfhydryl group, two lysyl residues and hapten groups such as trinitrophenyl, fluorescyl and biotinyl. The ligands, free or bound to mercurated nucleic acids, were immunochemically characterized in ELISAs. The method was shown to be specific and sensitive in the detection of target DNA in situ on microscopic preparations and in dot-blot hybridization reactions on nitrocellulose. Images PMID:3748817

Hopman, A H; Wiegant, J; Tesser, G I; Van Duijn, P

1986-01-01

35

Iminodicarboxylic acids in the Murchison meteorite: Evidence of Strecker reactions  

NASA Astrophysics Data System (ADS)

?-Amino acids and ?-hydroxy acids are well known constituents of several carbonaceous meteorites. One proposed mechanism of their formation is the reactions of CN -, NH 3, aldehydes and ketones in aqueous solution, a Strecker-like synthesis. Iminodicarboxylic acids, relatively unusual in molecular structure, are significant by-products of laboratory Strecker syntheses of ?-amino acids. It is therefore notable that an analogous suite of imino acids has not been reported in CM2 chondrites where amino and hydroxy acids are abundant. In this work, aqueous extracts of the Murchison meteorite were examined for the presence of imino acids; GC-MS and HPLC molecular analyses revealed a complex suite of such acids. With the exception of one of the seven-carbon members, all of the C4 through C7 imino acids were observed in Murchison. These observations suggest that the Strecker synthesis made, at least, some contribution to the formation of extraterrestrial amino acids.

Lerner, Narcinda R.; Cooper, George W.

2005-06-01

36

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

Microsoft Academic Search

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

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

2003-01-01

37

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

38

p-Aminophenylacetic acid-mediated synthesis of monodispersed titanium oxide hybrid microspheres in ethanol solution.  

PubMed

Monodispersed TiO2 hybrid microspheres were prepared via the hydrolysis of titanium isopropoxide (TTIP) in ethanol solution containing p-aminophenylacetic acid (APA). The effects of the APA:TTIP molar ratio, water content, reaction time and reaction temperature on the morphology of the resultant spheres were investigated. The products were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction. It was demonstrated that the diameters of the resultant TiO2 spheres could be tuned in the range of 380-800 nm by changing the APA:TTIP molar ratio (1:3 to 3:1) and water content (1-3 v/v%) in the reaction medium, and that increasing the APA:TTIP molar ratio led to larger TiO2 hybrid spheres while increasing the water content decreased their size. The loading content of APA in the hybrid spheres could reach 20 wt.% as they were prepared with the APA:TTIP ratio of 3:1. The possible formation mechanism of the hybrid spheres was also investigated. It was found that APA slowed down the hydrolysis rate of the titanium precursor so that resulted in the formation of the TiO2 spheres. In addition, the APA present in TiO2 spheres acted as a reducing agent to in situ convert HAuCl4 into metallic Au on the surface of the TiO2 spheres. The catalytic activity of the resultant Au/APA-TiO2 composite was examined using transfer hydrogenation of phenylacetone with 2-propanol, and it was indicated that the catalyst displayed high efficiency for this reaction. PMID:19616218

Zhang, Hongye; Xie, Yun; Liu, Zhimin; Tao, Ranting; Sun, Zhenyu; Ding, Kunlun; An, Guimin

2009-10-15

39

Bipolar lead-acid battery for hybrid vehicles  

NASA Astrophysics Data System (ADS)

Within the framework of the European project bipolar lead-acid power source (BILAPS), a new production route is being developed for the bipolar lead-acid battery. The performance targets are 500 W kg -1, 30 Wh kg -1 and 100 000 power-assist life cycles (PALCs). The operation voltage of the battery can be, according to the requirements, 12, 36 V or any other voltage. Tests with recently developed 4 and 12 V prototypes, each of 30 Ah capacity have demonstrated that the PALC can be operated using 10 C discharge and 9 C charge peaks. The tests show no overvoltage or undervoltage problems during three successive test periods of 16 h with 8 h rest in between. The temperature stabilizes during these tests at 40-45 °C using a thermal-management system. The bipolar lead acid battery is operated at an initial 50% state-of-charge. During the tests, the individual cell voltages display only very small differences. Tests are now in progress to improve further the battery-management system, which has been developed at the cell level, during the period no PALCs are run in order to improve the hybrid behaviour of the battery. The successful tests show the feasibility of operating the bipolar lead-acid battery in a hybrid mode. The costs of the system are estimated to be much lower than those for nickel-metal-hydride or Li-ion based high-power systems. An additional advantage of the lead-acid system is that recycling of lead-acid batteries is well established.

Saakes, M.; Woortmeijer, R.; Schmal, D.

40

Marangoni instability in the iodate-arsenous acid reaction front.  

PubMed

Horizontally propagating chemical fronts leading to the formation of a single stable convection roll are investigated in the iodate-arsenous acid reaction with arsenous acid stoichiometrically limiting, leaving the surface active iodine present in the product mixture. In sufficiently thin solution layers with open upper surface, the contribution of Marangoni instability is significantly enhanced. Acting in the same direction as buoyancy driven instability, it distorts the entire tilted reaction front that becomes 50% more elongated. The corresponding three-dimensional calculations based on the empirical rate-law of the reaction corroborate the experimental findings. PMID:25084949

Pópity-Tóth, Eva; Pótári, Gábor; Erd?s, István; Horváth, Dezs?; Tóth, Agota

2014-07-28

41

Sucrose phosphorylases catalyze transglycosylation reactions on carboxylic acid compounds  

Microsoft Academic Search

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

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

2008-01-01

42

Solvent effects in Acid-catalyzed biomass conversion reactions.  

PubMed

Reaction kinetics were studied to quantify the effects of polar aprotic organic solvents on the acid-catalyzed conversion of xylose into furfural. A solvent of particular importance is ?-valerolactone (GVL), which leads to significant increases in reaction rates compared to water in addition to increased product selectivity. GVL has similar effects on the kinetics for the dehydration of 1,2-propanediol to propanal and for the hydrolysis of cellobiose to glucose. Based on results obtained for homogeneous Brønsted acid catalysts that span a range of pKa values, we suggest that an aprotic organic solvent affects the reaction kinetics by changing the stabilization of the acidic proton relative to the protonated transition state. This same behavior is displayed by strong solid Brønsted acid catalysts, such as H-mordenite and H-beta. PMID:25214063

Mellmer, Max A; Sener, Canan; Gallo, Jean Marcel R; Luterbacher, Jeremy S; Alonso, David Martin; Dumesic, James A

2014-10-27

43

Efficient Biginelli Reaction Catalyzed by Sulfamic Acid or Silica Sulfuric Acid under Solvent?Free Conditions  

Microsoft Academic Search

Sulfamic acid efficiently catalyzes the three?component condensation reaction of aldehydes, 1,3?dicarbonyl compounds, and urea\\/thiourea under solvent?free conditions to afford the corresponding dihydropyrimidinones and thio?derivatives in high yields. Silica sulfuric acid is also found to be an efficient catalyst for the Biginelli reaction under solvent?free conditions. Compared to the classical Biginelli reaction conditions, this new method consistently has the advantage of

2007-01-01

44

Bacterial cellulose and hyaluronic acid hybrid membranes: Production and characterization.  

PubMed

In this study, the effect of the addition of hyaluronic acid (HA) on bacterial cellulose (BC) production, under static conditions was evaluated in terms of the properties of the resulting BC hybrid membranes. HA was added to the fermentation process in three distinct time points: first day (BC-T0), third day (BC-T3) and sixth day (BC-T6). Analyses of FT-IR and CP/MAS (13)C NMR confirmed the presence of HA in bacterial cellulose membranes. The crystal structure, crystallinity index (Ic) surface roughness, thermal stability and hybrophobic/hydrophilic character changed. Membranes with higher roughness were produced with HA added on the first and third day of fermentation process. The surface energy of BC/HA membranes was calculated and more hydrophilic membranes were produced by the addition of HA on the third and sixth day, also resulting in more thermally stable materials. The results demonstrate that bacterial cellulose/hyaluronic acid hybrid membranes can be produced in situ and suggest that HA interacts with the sub-elementary bacterial cellulose fibrils, changing the properties of the membranes. The study and understanding of the factors that affect those properties are of utmost importance for the safe and efficient use of BC as biomaterials in numerous applications, specifically in the biological field. PMID:24704166

Lopes, Tatyane Duran; Riegel-Vidotti, Izabel Cristina; Grein, Aline; Tischer, Cesar Augusto; Faria-Tischer, Paula Cristina de Sousa

2014-06-01

45

Kinetic-spectrophotometric determination of ascorbic acid by inhibition of the hydrochloric acid-bromate reaction  

NASA Astrophysics Data System (ADS)

A new analytical method was developed for the determination of ascorbic acid in fruit juice and pharmaceuticals. The method is based on its inhibition effect on the reaction between hydrochloric acid and bromate. The decolourisation of Methyl Orange by the reaction products was used to monitor the reaction spectrophotometrically at 510 nm. The linearity range of the calibration graph depends on bromate concentration. The variable affecting the rate of the reaction was investigated. The method is simple, rapid, relatively sensitive and precise. The limit of detection is 7.6×10 -6 M and calibration rang is 8×10 -6-1.2×10 -3 M ascorbic acid. The relative standard deviation of seven replication determinations of 8×10 -6 and 2×10 -5 M ascorbic acid was 2.8 and 1.7%, respectively. The influence of potential interfering substance was studied. The method was successfully applied for the determination of ascorbic acid in pharmaceuticals.

Ensafi, Ali A.; Rezaei, B.; Movahedinia, H.

2002-10-01

46

Catalytical Conversion of Carbohydrates into Lactic Acid via Hydrothermal Reaction  

NASA Astrophysics Data System (ADS)

This paper focuses on catalytical conversion of carbohydrates into lactic acid, under the hydrothermal conditions, which may have a promising future for its high speediness and effectiveness. The catalysis of ZnO was investigated to improve the lactic acid yields. The results showed that the lactic acid yields increased immensely by the addition of ZnO. The effects of the reaction time and the addition amount of ZnO on the conversion of carbohydrates to lactic acid were studied. The highest lactic acid yields reached up to 28% starting from glucose after the reaction time of 60 s under the conditions of 0.2 mmol ZnO, 300° C, the filling rate of 35%, and over 30% starting from fructose at the same temperature and filling rate when the reaction time of 40 s and 2.0 mmol ZnO were employed. The collaborative effects of ZnO and NaOH used as the catalysts together at the same time were also studied. Furthermore, the catalytic mechanism of ZnO in the hydrothermal conversion of carbohydrates into lactic acid was discussed.

Wei, Zhen; Jin, Fangming; Zhang, Guangyi; Zhang, Shiping; Yao, Guodong

2010-11-01

47

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...

48

Manipulating surface reactions in lithium-sulphur batteries using hybrid anode structures  

NASA Astrophysics Data System (ADS)

Lithium-sulphur batteries have high theoretical energy density and potentially low cost, but significant challenges such as severe capacity degradation prevent its widespread adoption. Here we report a new design of lithium-sulphur battery using electrically connected graphite and lithium metal as a hybrid anode to control undesirable surface reactions on lithium. Lithiated graphite placed in front of the lithium metal functions as an artificial, self-regulated solid electrolyte interface layer to actively control the electrochemical reactions and minimize the deleterious side reactions, leading to significant performance improvements. Lithium-sulphur cells incorporating this hybrid anodes deliver capacities of >800mAhg-1 for 400 cycles at a high rate of 1,737mAg-1, with only 11% capacity fade and a Coulombic efficiency >99%. This simple hybrid concept may also provide scientific strategies for protecting metal anodes in other energy-storage devices.

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

2014-01-01

49

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

50

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

51

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

52

Effects of phosphoric acid on the lead-acid battery reactions  

Microsoft Academic Search

The addition of a small amount of phosphoric acid to 5 M H2SO4 (commercial electrolyte of lead-acid batteries) results in various positive effects on the lead-acid battery reactions: (1) depression of the corrosion rate of the lead substrate through a preferential formation of alpha-PbO2 on the substrate surface; (2) retardation of hard sulfate formation or of deactivation of active materials;

Osamu Ikeda; Chiaki Iwakura; Hiroshi Yoneyama; Hideo Tamura

1986-01-01

53

Predictions of diagenetic reactions in the presence of organic acids  

SciTech Connect

Stability constants have been estimated for cation complexes with anions of monofunctional and difunctional acids between 0 and 200C. Difunctional acid anions form much more stable complexes than monofunctional acid anions with aluminum; the importance of the aluminum-acetate complex is relatively minor in comparison to aluminum oxalate and malonate complexes. Divalent metal cations such as Mg, Ca, and Fe form more stable complexes with acetate than with difunctional acid anions. Mineral thermodynamic affinities were calculated using the reaction path model EQ3/6 for waters having variable organic acid anion (OAA) contents under conditions representative of those found during normal burial diagenesis. Organic acid anions are ineffective at neutral to alkaline pH in modifying stabilities of aluminosilicate minerals whereas the anions are variably effective under a wide range of pH in modifying carbonate mineral stabilities. Reaction path calculations demonstrate that the sequence of mineral reactions occurring in an arkosic sandstone-fluid system is only slightly modified by the presence of OAA. A spectrum of possible sandstone alteration mineralogies can be obtained depending on the selected boundary conditions: EQ3/6 predictions include quartz overgrowth, calcite replacement of plagioclase, albitization of plagioclase, and the formation of porosity-occluding calcite cement, smectite, and illite, all of which are commonly documented in rocks. In the scenarios modeled in this study the role of OAA in fluid-rock interactions is to contribute to the total alteration assemblage but not necessarily to dominate it, except under exceptional circumstances that might include, for example, hydrocarbon contaminant plumes in aquifers, wetland environments, and within hydrocarbon source-rocks.

Harrison, W.J. (Colorado Schools of Mines, Golden (United States)); Thyne, G.D. (Univ. of Wyoming, Laramie (United States))

1992-02-01

54

The reaction of cesium hydroxide with 4-phenylvaleric acid  

E-print Network

THE REACTIOR OP CESIUM HYDROXIDE WITH 4-PHEI'YLVALERIC ACID A Thesis by Arvie Jeane Caughfield Submitted to the Graduate College of the Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OP SCIENCE... August l967 Ma)or Sub) ect: Chemistry THE REACTION OF CESIUM HYDROXIDE WITH 4-PHENYLVALERIC ACID A Thesis Arvie Jeane Caugh iield Approved as to style and content by: (Chairman of Commit e (Head of De artment) (Member) (Member (Member) (Member...

Caughfield, Arvie Jeane

2012-06-07

55

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.

56

Nested polymerase chain reaction and in situ hybridization for detection of nucleopolyhedrosis  

Microsoft Academic Search

A nested polymerase chain reaction (PCR) and in situ hybridization were developed for detection of baculoviruses in insects or other arthropods with nucleopolyhedrosis. The nested PCR was based on the sequences of polyhedrin genes from baculoviruses. Two sets of primers were designed, primers set, 35\\/36, was for the first step of amplification and yielded a product of around 680 bp,

Chung-Hsiung Wang; Hsi-Nan Yang; Hwei-Chung Liu; Guang-Hsung Kou; Chu-Fang Lo

2000-01-01

57

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

58

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

Microsoft Academic Search

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

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

2005-01-01

59

Reaction of abietic acid with maleic anhydride and fumaric acid and attempts to find the fundamental component of fortified rosin.  

PubMed

Identification of the Diels-Alder adduct of Abietic Acid (AA) and maleic anhydride (MA) or Fumaric Acid (FA) using a Shimadzu QP 5050A Gas chromatograph Mass spectrometer revealed that AA and MA produced endo-maleopimaric acid (MPA) and endo-maleopimaric acid tricarboxylic acid. A reaction product of abietic acid and fumaric acid generated three peaks identified based on their mass spectra as fumaropimaric acid (FPA), FPA adducts and endo-MPA. To maximize the reaction between AA and MA or FA, molar ratio (AA and MA or FA), reaction time and reaction temperature were investigated. The best Diels-Alder reaction between abietic and maleic anhydride was at 125 degrees C for 1 h with a molar ratio of AA to MA of 1: 2. The best Diels-Alder reaction between AA and FA was at 200 degrees C for 1 h with a molar ratio of AA and FA of 1: 2. PMID:19086503

Wiyono, Bambang; Tachibana, Sanro; Tinambunan, Djaban

2007-05-15

60

Enzymatic Reaction with Unnatural Substrates: DNA Photolyase (Escherichia coli) Recognizes and Reverses Thymine [2+2] Dimers in the DNA Strand of a DNA/PNA Hybrid Duplex  

NASA Astrophysics Data System (ADS)

Peptide nucleic acids (PNA) are mimics with normal bases connected to a pseudopeptide chain that obey Watson--Crick rules to form stable duplexes with itself and natural nucleic acids. This has focused attention on PNA as therapeutic or diagnostic reagents. Duplexes formed with PNA mirror some but not all properties of DNA. One fascinating aspect of PNA biochemistry is their reaction with enzymes. Here we show an enzyme reaction that operates effectively on a PNA/DNA hybrid duplex. A DNA oligonucleotide containing a cis, syn-thymine [2+2] dimer forms a stable duplex with PNA. The hybrid duplex is recognized by photolyase, and irradiation of the complex leads to the repair of the thymine dimer. This finding provides insight into the enzyme mechanism and provides a means for the selective repair of thymine photodimers.

Ramaiah, Danaboyina; Kan, Yongzhi; Koch, Troels; Orum, Henrik; Schuster, Gary B.

1998-10-01

61

Porous silicon/photosynthetic reaction center hybrid nanostructure.  

PubMed

The purified photosynthetic reaction center protein (RC) from Rhodobacter sphaeroides R-26 purple bacteria was bound to porous silicon microcavities (PSiMc) either through silane-glutaraldehyde (GTA) chemistry or via a noncovalent peptide cross-linker. The characteristic resonance mode in the microcavity reflectivity spectrum red shifted by several nanometers upon RC binding, indicating the protein infiltration into the porous silicon (PSi) photonic structure. Flash photolysis experiments confirmed the photochemical activity of RC after its binding to the solid substrate. The kinetic components of the intraprotein charge recombination were considerably faster (?(fast) = 14 (±9) ms, ?(slow) = 230 (±28) ms with the RC bound through the GTA cross-linker and only ?(fast) = 27 (±3) ms through peptide coating) than in solution (?(fast) = 120 (±3) ms, ?(slow) = 1387 (±2) ms), indicating the effect of the PSi surface on the light-induced electron transfer in the protein. The PSi/RC complex was found to oxidize the externally added electron donor, mammalian cytochrome c, and the cytochrome oxidation was blocked by the competitive RC inhibitor, terbutryne. This fact indicates that the specific surface binding sites on the PSi-bound RC are still accessible to external cofactors and an electronic interaction with redox components in the aqueous environment is possible. This new type of biophotonic material is considered to be an excellent model for new generation applications at the interface of silicon-based electronics and biological redox systems designed by nature. PMID:22809391

Hajdu, Kata; Gergely, Csilla; Martin, Marta; Cloitre, Thierry; Zimányi, László; Tenger, Katalin; Khoroshyy, Petro; Palestino, Gabriela; Agarwal, Vivechana; Hernádi, Klára; Németh, Zoltán; Nagy, László

2012-08-14

62

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

PubMed Central

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; Str?mme, Maria; Blomberg, Jonas

2010-01-01

63

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 of TP was established using the chlorite-iodide-malonic acid (CIMA) reaction.9 This discov- ery

Epstein, Irving R.

64

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

65

Hybrid systems with lead–acid battery and proton-exchange membrane fuel cell  

Microsoft Academic Search

Hybrid systems, based on a lead–acid battery and a proton-exchange membrane fuel cell (PEMFC) give the possibility to combine the advantages of both technologies. The benefits for different applications are discussed and the practical realisation of such systems is shown. Furthermore a numerical model for such a hybrid system is described and results are shown and discussed. The results show

Andreas Jossen; Juergen Garche; Harry Doering; Markus Goetz; Werner Knaupp; Ludwig Joerissen

2005-01-01

66

Fatty acid composition of a cultured sturgeon hybrid ( Acipenser naccarii × A. baerii)  

Microsoft Academic Search

Analyses of fatty acids from the dorsal muscle of Acipenser naccarii×A. baerii sturgeon hybrid were carried out. The data were compared with those reported in the literature for other sturgeons reared for human consumption. This hybrid would seem to be of great nutritional interest, its flesh being more beneficial for human health than those of other cultured sturgeons. In fact,

Antonino M. Vaccaro; Gaspare Buffa; Concetta M. Messina; Andrea Santulli; Antonio Mazzola

2005-01-01

67

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

E-print Network

ENERGY MODELING OF A LEAD-ACID BATTERY WITHIN HYBRID WIND / PHOTOVOLTAIC SYSTEMS O. GERGAUD, G Abstract: Within the scope of full-scale energy modeling of a hybrid wind / photovoltaic system coupled / photovoltaic production system coupled to the network grid (with energy storage) ENERGY MODELING OF A LEAD

Paris-Sud XI, Université de

68

Reduction of a phosphorus oxide and acid reaction set  

SciTech Connect

It has been predicted for some time that hypersonic aircraft will suffer from diminished fuel efficiency due to the slow speed of radical recombination in the nozzle of the aircraft and the consequent expulsion of high-energy fragments during high Mach number flight. The addition of small amounts of phosphine combustion products (phosphorus oxides and acids) to water vapor has been found to result in a faster relaxation rate of OH to its equilibrium density following H{sub 2}O photolysis. This article describes the systematic construction of a reaction model of 162 phosphorus reactions among 17 phosphorus-containing species. Those reactions that contribute to the reestablishment of equilibrium following the perturbation of the system by H{sub 2}O photolysis or by an increase in temperature are identified. A thermodynamic free energy function is used to quantify the rate of system relaxation back to equilibrium for a series of 36 reaction conditions covering a temperature range of 1,500 to 3,000 K, a gas density range of 5 {times} 10{sup {minus}7} to 5 {times} 10{sup {minus}5} mol/cm{sup 3} and a fuel equivalence ratio of 0.8 to 1.2.

Twarowski, A. [Rockwell International Science Center, Thousand Oaks, CA (United States)] [Rockwell International Science Center, Thousand Oaks, CA (United States)

1995-07-01

69

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

70

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

71

Nucleic acid amplification: Alternative methods of polymerase chain reaction  

PubMed Central

Nucleic acid amplification is a valuable molecular tool not only in basic research but also in application oriented fields, such as clinical medicine development, infectious diseases diagnosis, gene cloning and industrial quality control. A comperehensive review of the literature on the principles, applications, challenges and prospects of different alternative methods of polymerase chain reaction (PCR) was performed. PCR was the first nucleic acid amplification method. With the advancement of research, a no of alternative nucleic acid amplification methods has been developed such as loop mediated isothermal amplification, nucleic acid sequence based amplification, strand displacement amplification, multiple displacement amplification. Most of the alternative methods are isothermal obviating the need for thermal cyclers. Though principles of most of the alternate methods are relatively complex than that of PCR, they offer better applicability and sensitivity in cases where PCR has limitations. Most of the alternate methods still have to prove themselves through extensive validation studies and are not available in commercial form; they pose the potentiality to be used as replacements of PCR. Continuous research is going on in different parts of the world to make these methods viable technically and economically. PMID:24302831

Fakruddin, Md; Mannan, Khanjada Shahnewaj Bin; Chowdhury, Abhijit; Mazumdar, Reaz Mohammad; Hossain, Md. Nur; Islam, Sumaiya; Chowdhury, Md. Alimuddin

2013-01-01

72

Accelerated stochastic and hybrid methods for spatial simulations of reaction diffusion systems  

NASA Astrophysics Data System (ADS)

Spatial distributions characterize the evolution of reaction-diffusion models of several physical, chemical, and biological systems. We present two novel algorithms for the efficient simulation of these models: Spatial ?-Leaping ( S?-Leaping), employing a unified acceleration of the stochastic simulation of reaction and diffusion, and Hybrid ?-Leaping ( H?-Leaping), combining a deterministic diffusion approximation with a ?-Leaping acceleration of the stochastic reactions. The algorithms are validated by solving Fisher's equation and used to explore the role of the number of particles in pattern formation. The results indicate that the present algorithms have a nearly constant time complexity with respect to the number of events (reaction and diffusion), unlike the exact stochastic simulation algorithm which scales linearly.

Rossinelli, Diego; Bayati, Basil; Koumoutsakos, Petros

2008-01-01

73

Mutual storage mode ion\\/ion reactions in a hybrid linear ion trap  

Microsoft Academic Search

Ion\\/ion proton transfer reactions involving mutual storage of both ion polarities in a linear ion trap (LIT) that comprises\\u000a part of a hybrid triple quadrupole\\/linear ion trap mass spectrometer have been effected. Mutual ion storage in the x- and\\u000a y-dimensions arises from the normal operation of the oscillating quadrupole field of the quadrupole array, while storage in\\u000a the z-dimension is

Yu Xia; Jin Wu; Scott A. McLuckey; Frank A. Londry; James W. Hager

2005-01-01

74

Sensitive fluorescence detection of nucleic acids based on isothermal circular strand-displacement polymerization reaction.  

PubMed

Here we have developed a sensitive DNA amplified detection method based on isothermal strand-displacement polymerization reaction. This method takes advantage of both the hybridization property of DNA and the strand-displacement property of polymerase. Importantly, we demonstrate that our method produces a circular polymerization reaction activated by the target, which essentially allows it to self-detect. Functionally, this DNA system consists of a hairpin fluorescence probe, a short primer and polymerase. Upon recognition and hybridization with the target ssDNA, the stem of the hairpin probe is opened, after which the opened probe anneals with the primer and triggers the polymerization reaction. During this process of the polymerization reaction, a complementary DNA is synthesized and the hybridized target is displaced. Finally, the displaced target recognizes and hybridizes with another probe, triggering the next round of polymerization reaction, reaching a target detection limit of 6.4 x 10(-15) M. PMID:19129227

Guo, Qiuping; Yang, Xiaohai; Wang, Kemin; Tan, Weihong; Li, Wei; Tang, Hongxing; Li, Huimin

2009-02-01

75

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

76

The reaction of picric acid with epoxides I. A colorimetric method  

Microsoft Academic Search

A colorimetric method has been developed for the analysis of epoxides by reaction with picric acid. Picric acid was found\\u000a to be the best of several acidic chromophores in its reaction with epoxides. Despite a nonquantitative reaction, the product\\u000a concentration is proportional to the original concentration, i.e., it follows Beer’s Law.\\u000a \\u000a The reaction variables were studied with methyl mono- and

J. A. Fioriti; A. P. Bentz; R. J. Sims

1966-01-01

77

A combined ultracapacitor-lead acid battery storage system for mild hybrid electric vehicles  

Microsoft Academic Search

Improvements in ultracapacitor technology indicate that the automotive industry should re-examine the energy storage system for hybrid electric vehicles (HEVs). With the combination of an ultracapacitor and a lead acid battery, a system can be implemented in which the lead acid battery can be maintained at 100% state of charge, lengthening the lifetime of the battery. Although performance of the

Adam W. Stienecker; Thomas Stuart; Cyrus Ashtiani

2005-01-01

78

Nucleic acid probes are molecules that complement or hybridize to a  

E-print Network

Nucleic acid probes are molecules that complement or hybridize to a specific mRNA or DNA sequence of rapid methods of nucleic acid sequencing and measurement made DNA and RNA the center of atten- tion computational methods of protein identification since analysis can involve thousands of peptide mass spectra

Levin, Judith G.

79

Parallel proton transfer pathways in aqueous acid-base reactions  

NASA Astrophysics Data System (ADS)

We study the mechanism of proton transfer (PT) between the photoacid 8-hydroxy-1,3, 6-pyrenetrisulfonic acid (HPTS) and the base chloroacetate in aqueous solution. We investigate both proton and deuteron transfer reactions in solutions with base concentrations ranging from 0.25M to 4M. Using femtosecond midinfrared spectroscopy, we probe the vibrational responses of HPTS, its conjugate photobase, the hydrated proton/deuteron, and chloroacetate. The measurement of these four resonances allows us to follow the sequence of proton departure from the acid, its uptake by the water solvent, and its arrival at the base. In recent studies it was shown that proton transfer to carboxylate bases proceeds via Grotthuss conduction through a water wire connecting the acid and the base [Mohammed et al., Science 310, 83 (2005);Agnew. Chem. Int. Ed. 46, 1458 (2007);Siwick and Bakker, J. Am. Chem. Soc. 129, 13412 (2007); J. Phys. Chem. B 112, 378 (2008)]. Here we show that, for the weaker base chloroacetate, an alternative channel for proton transfer arises. In this channel the proton is first transferred to the water solvent and only later taken up from the water by the base. We study the base concentration dependence of the two competing channels.

Cox, M. J.; Bakker, H. J.

2008-05-01

80

Detection of Mycoplasma pneumoniae by polymerase chain reaction and nonradioactive hybridization in microtiter plates.  

PubMed Central

In order to improve the diagnosis of a Mycoplasma pneumoniae infection, we developed a polymerase chain reaction (PCR)-based assay. The gene encoding elongation factor Tu (tuf) was selected as the target sequence. Oligonucleotides derived from variable stretches of the tuf gene were able to prime the amplification of a 950-bp fragment exclusively when M. pneumoniae DNA was used as the template. The sensitivity of the assay was increased 10-fold when the amplification products were hybridized with an internal M. pneumoniae-specific oligonucleotide. The use of three to four genome copies for PCR was sufficient for obtaining a hybridization signal. In addition, we substituted radioactive filter hybridization with a microtiter plate assay. Via a biotin moiety of one PCR primer, the amplification products were immobilized on streptavidin-coated microtiter plates. Subsequent hybridization with a digoxigenin-labeled oligonucleotide resulted in the same sensitivity and specificity as those obtained by filter hybridization. Clinical application of the assay was performed on 102 throat swab specimens from patients with respiratory tract infections. Of 21 culture-positive samples, 19 were confirmed to be positive in the PCR-based assay (sensitivity, 90%). Furthermore, 14 of 19 seropositive but culture-negative samples gave a positive hybridization signal. Of 62 culture-negative and seronegative specimens, 60 gave a negative result in our assay (specificity, 97%). Of the 33 samples that were positive in our PCR-based assay, 5 samples initially gave false-negative results because of the presence of inhibitory substances in those specimens. Inhibition of Taq polymerase in these five cases was prevented by an additional step of phenol extraction and subsequent ethanol precipitation. Images PMID:8501208

Luneberg, E; Jensen, J S; Frosch, M

1993-01-01

81

Development of a lead-acid battery for a hybrid electric vehicle  

Microsoft Academic Search

In September 2000, a project reliable, highly optimized lead-acid battery (RHOLAB) started under the UK Foresight Vehicle Programme with the objective of developing an optimized lead-acid battery solution for hybrid electric vehicles. The work is based on a novel, individual, spirally-wound valve-regulated lead-acid 2V cell optimized for HEV use and low variability. This cell is being used as a building

A Cooper

2004-01-01

82

Contribution of neutron reactions in hybrid targets of inertial heavy ion fusion (HIF)  

NASA Astrophysics Data System (ADS)

Recently some simple estimations (Koskarev, Sharkov) were made for capability of achievement of critical conditions in an uranium shell of HIF energetic target, and afterwards it was proved use of an uranium shell (pusher) for substantial expansion of energy-release in a such hybrid target. The mentioned justification is included accounting of neutron-induced fission in the pusher. This accounting is formulated as generalization for cylindrical geometry of the well-known Axiezer-Pomeranchuk solution. A corresponding analytical solution of one-speed Payerls equation allows sufficiently accurately to compute the critical parameters of the uranium pusher in hydrodynamic model of compression and fusion of HIF target ( taking into account of development of chain nuclear fission reaction under critical condition achievement). Nevertheless the implemented computations show that the most essential effect is forced nuclear fission of uranium under the influence of thermonuclear neutrons generated by fusion of deuterium- tritium fuel in the central region of the target. In these computations we use a simple analytical description of forced nuclear fission of uranium by thermonuclear neutrons. The critical conditions are not achieved in the considered ( not optimized) hybrid targets but they are close to accomplishment in the investigated shock-free compression regime. This regime of compression is the most adequate one for hybrid HIF targets. The obtained results allow us to make conclusion of advisability of further development of energetic hybrid HIF targets particularly their optimization and utilization of natural uranium as pusher materials.

Imshennik, V. S.; Zhukov, V. T.

2006-08-01

83

Lead acid battery storage model for hybrid energy systems  

Microsoft Academic Search

This paper describes a new battery model developed for use in time series performance models of hybrid energy systems. The model is intended to overcome some of the difficulties associated with currently used methods. It is based on the approach of chemical kinetics. This model, which can be used for charging and discharging, is specifically concerned with the apparent change

J. F. Manwell; J. G. McGowan

1993-01-01

84

Fluorescence in situ hybridization with Alu and L1 polymerase chain reaction probes for rapid characterization of human chromosomes in hybrid cell lines  

SciTech Connect

Human-rodent hybrid cell lines have been analyzed with regard to their human DNA content by using various DNA probe sets, derived from the hybrids, for in situ hybridization to normal human metaphase chromosome spreads. Total genomic hybrid DNA was compared with probe sets of hybrid DNA that were highly enriched in human sequences. The latter probes were obtained by amplification through the polymerase chain reaction (PCR) using oligonucleotide primers directed to human specific subsequences of the interspersed repetitive sequences Alu and L1. Previously unidentified chromosomal material within hybrid lines was characterized with speed and precision. It is demonstrated that the complete human complement of hybrid lines can be rapidly assessed by comparing the data obtained with the Alu-PCR products with the results from the L1-PCR products or from the genomic hybrid DNA. This approach using interspersed repetitive sequence-PCR products is simple and fast and also provides an alternative way of generating complex DNA probe sets for the specific delineation of entire chromosomes or subchromosomal regions by the in situ hybridization.

Lichter, P.; Ward, D.C. (Yale Univ., New Haven, CT (USA)); Ledbetter, S.A.; Ledbetter, D.H. (Baylor College of Medicine, Houston, TX (USA))

1990-09-01

85

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

E-print Network

13 30 51 LIST OF TABLES Table Page Field and laboratory SYBV reactions of six inbred corn lines used as parents of single- cross hybrids in this study. Ouchterlony results for 15 single-cross hybrids inoculated with SYBV Mean squares and CV... lines Rep I Rep II Ratings Field% Labg. Field Lab. Scale R/Sg Va 35 Tx 601 Tx 706 Tx 710 Fr1193 Tx6252 2/13 0/34 0/3 4 0/12 1/12 0/2 3 1/19 0/3 1 0/13 5/6 2/34 2. 0 S 1. 0 R 1. 0 R 1. 0 R 3. 0 S 2. 0 S * Adapted from Theu, Toler...

Pe, Aye

2012-06-07

86

Rapid and sensitive in situ hybridization method for detecting and identifying lactic acid bacteria in wine  

Microsoft Academic Search

A rapid and sensitivein situhybridization method, using total genomic DNA probes, can specifically detect and identify the lactic acid bacteria in wine. The total genomic DNA probes were labelled with digoxygenin (DIG) by random priming and hybridized with the genomic DNA of the bacteria to be identified. The hybrids were detected with fluorescent anti-DIG Fab-fragments or with enzyme-conjugated anti-DIG Fab-fragments.

D Sohier; A Lonvaud-Funel

1998-01-01

87

A Simple but Comprehensive Lead-Acid Battery Model for Hybrid System Simulation  

Microsoft Academic Search

The lead-acid battery typically used in a photovoltaic\\/genset hybrid system is a complex, non-linear device exhibiting memory. A mathematical model of this device has been developed for the purposes of hybrid system modelling. It is a semi-empirical model of the current-voltage characteristics, partly taken from the literature and partly founded on basic electrochemistry. The model has been fit to measured

Michael M. D. Ross

2002-01-01

88

A novel approach to nonradioactive hybridization assay of nucleic acids using stained latex particles.  

PubMed

The paper describes a sensitive latex hybridization assay (LHA) method applied for indirect detection of biotinylated nucleic acid hybrids immobilized on a synthetic membrane. The biotinylated hybrids were visualized by means of latex particles containing the fluorescent dye pyronine G and coated with streptavidin; 1.6 and 0.3 pg of lambda-phage DNA was detected by dot blot hybridizations on nylon membrane and polyethyleneimine-cellophane, respectively. The assay sensitivity was increased by three orders of magnitude over that with fluorescently labeled probes due to encapsulation of the fluorescent dye in polymer particles. LHA is simple (single-stage detection procedure), fast, and more sensitive than any of the other nonradioactive hybridization methods. PMID:1724721

Vener, T I; Turchinsky, M F; Knorre, V D; Lukin YuV; Shcherbo, S N; Zubov, V P; Sverdlov, E D

1991-11-01

89

Nanofiltration, bipolar electrodialysis and reactive extraction hybrid system for separation of fumaric acid from fermentation broth.  

PubMed

A novel approach based on a hybrid system allowing nanofiltration, bipolar electrodialysis and reactive extraction, was proposed to remove fumaric acid from fermentation broth left after bioconversion of glycerol. The fumaric salts can be concentrated in the nanofiltration process to a high yield (80-95% depending on pressure), fumaric acid can be selectively separated from other fermentation components, as well as sodium fumarate can be conversed into the acid form in bipolar electrodialysis process (stack consists of bipolar and anion-exchange membranes). Reactive extraction with quaternary ammonium chloride (Aliquat 336) or alkylphosphine oxides (Cyanex 923) solutions (yield between 60% and 98%) was applied as the final step for fumaric acid recovery from aqueous streams after the membrane techniques. The hybrid system permitting nanofiltration, bipolar electrodialysis and reactive extraction was found effective for recovery of fumaric acid from the fermentation broth. PMID:24983693

Prochaska, Krystyna; Staszak, Katarzyna; Wo?niak-Budych, Marta Joanna; Regel-Rosocka, Magdalena; Adamczak, Michalina; Wi?niewski, Maciej; Staniewski, Jacek

2014-09-01

90

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

91

Synthesis and utilization of chitin humic acid hybrid as sorbent for Cr(III)  

NASA Astrophysics Data System (ADS)

New types of hybrid material have been synthesized by using four different methods of immobilization of humic acid (HA) on chitin. The most stable hybrid material toward the change of medium acidity was then utilized as sorbent for Cr(III). The HA was extracted from peat soil of Gambut District, South Kalimantan, Indonesia, using the recommended procedure of International Humic Substances Society (IHSS), while the chitin was isolated from crab shell waste through deproteination using 3.5% (w/v) NaOH and followed by removal of inorganic impurities using 1 M HCl. The four methods of immobilization of HA on chitin were (i) Method A: chitin powder (4 g) was gently poured into the stirred solution of 0.4 g HA in 40 mL of 0.01 M NaOH. After overnight stirring, the solid was separated, washed with water, and dried in oven at 70 °C. (ii) Method B: gelatinous chitin (40 g) in 250 mL of 0.5 M HCl was reacted with HA (4 g) in 500 mL of 0.5 M NaOH and aged for 24 h. The product was washed with water and dried. (iii) Method C: HA powder (0.5 g) was mixed with the stirred gel of chitin (2.5 g) in 60 mL of CaCl 2 saturated methanol and the mixture was then washed with the mixed solution of 25 mL of 2 M sodium citrate and ethylene glycol 1:1. The solid was separated, washed with water, and dried. (iv) Method D: the solution of HA (0.056 g) in 10 mL of 0.01 M NaOH was reacted with the gel of chitin (0.2 g) in 10 mL of CaCl 2 saturated methanol. After 24 h stirring, the solid was separated from the reaction medium, washed with the mixed solution of 2 M sodium citrate and ethylene glycol 1:1, and followed by washing with water and drying. Parameters investigated in this study consisted of the stability test of the immobilized HA, as well as the rate constant ( k1), capacity ( b), and energy ( E) of sorption as well as the rate constant of desorption ( k-1). The k1 and k-1 were determined according to a kinetic model of first order sorption reaching equilibrium, while the b and E were determined according to the Langmuir isotherm model. Compared to HA, Methods, A, C, and D; Method B produced the most stable immobilization of HA on chitin. The hybrid material (Chitin-HA) synthesized through Method B was stable in the acidity range that equivalent to pH 2.0-11.0. At the acidity giving maximum sorption, i.e. pH 5, the presence of immobilized HA on the Chitin-HA enhanced more than three times the k1 and k-1, i.e. from 0.057 min -1 and 8.51 × 10 -4 (min -1) (mol/L) for chitin to 0.183 min -1 and 3.27 × 10 -3 (min -1) (mol/L) for the Chitin-HA. On the contrary, the presence of HA on Chitin-HA only gave small increase on b and small decrease on E. The values of b and E for Cr(III) on chitin were 1.45 × 10 -2 mol/g and 23.12 kJ/mol, respectively, while those on Chitin-HA were 1.78 × 10 -2 mol/g and 19.95 kJ/mol, respectively.

Santosa, Sri Juari; Siswanta, Dwi; Sudiono, Sri; Sehol, Muhamad

2007-11-01

92

Alternative nucleic acid analogues for programmable assembly: hybridization of LNA to PNA.  

PubMed

Complementary locked nucleic acid (LNA) and peptide nucleic acid (PNA) hexamers bind to each other with significantly higher affinity than each binds to DNA, and with far greater affinity than DNA binds to complementary DNA. The hybridization is highly specific with a single mismatch causing decreases in T(m) values ranging from 12 (G/T) to 30 degrees C (A/A). Importantly, the hybridization of an LNA oligomer to a PNA oligomer is unaffected by the ionic strength of the buffer. These properties make the LNA/PNA pair an attractive candidate as a replacement for DNA in programmable assembly. PMID:15792422

Ng, Pei-Sze; Bergstrom, Donald E

2005-01-01

93

Bipolar lead–acid battery for hybrid vehicles  

Microsoft Academic Search

Within the framework of the European project bipolar lead–acid power source (BILAPS), a new production route is being developed for the bipolar lead–acid battery. The performance targets are 500Wkg?1, 30Whkg?1 and 100 000 power-assist life cycles (PALCs). The operation voltage of the battery can be, according to the requirements, 12, 36V or any other voltage. Tests with recently developed 4

M. Saakes; R. Woortmeijer; D. Schmal

2005-01-01

94

Differentiation of Mycobacterium tuberculosis Complex and Nontuberculous Mycobacterial Liquid Cultures by Using Peptide Nucleic Acid-Fluorescence In Situ Hybridization Probes  

Microsoft Academic Search

A blinded comparison of peptide nucleic acid-fluorescence in situ hybridization (PNA-FISH) with routine identification methods was performed on 74 consecutively positive mycobacterial liquid cultures. All Mycobac- terium tuberculosis cultures (48 of 48) and 22 of 27 (81.5%) nontuberculous cultures were correctly identified (including one mixed culture). Five isolates yielded no reaction with either probe and were identified as Mycobacterium xenopi,

F. A. DROBNIEWSKI; P. G. MORE; G. S. HARRIS

2000-01-01

95

Friedel–Crafts acylation reaction using carboxylic acids as acylating agents  

Microsoft Academic Search

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

Masato Kawamura; Dong-Mei Cui; Shigeru Shimada

2006-01-01

96

Study of glycated amino acid elimination reaction for an improved enzymatic glycated albumin measurement method  

Microsoft Academic Search

Background: In order to improve enzymatic glycated albumin measurement, we studied the endogenous glycated amino acid elimination reaction and the new bromocresolpurple (BCP) method for albumin measurement. Methods: In the assay, endogenous glycated amino acids are first eliminated by oxidation by ketoamine oxidase. Second, glycated albumin is hydrolyzed to glycated amino acids by proteinase digestion, and glycated amino acids are

Takuji Kouzuma; Yumiko Uemastu; Tomomi Usami; Shigeyuki Imamura

2004-01-01

97

Two bismuth sulfate-sulfuric acid hybrid water-splitting cycles. Proposed antimonyl sulfate cycle  

SciTech Connect

Some experimental work is presented that is related to two hybrid thermochemical cycles for the production of hydrogen which involve bismuth trisulfate and/or bismuth oxysulfates. Omitting statement of the steps for decomposition of SO/sub 3/ and the electrochemical formation of H/sub 2/ and H/sub 2/SO/sub 4/ from SO/sub 2/ and H/sub 2/O, the high and low temperature reactions are: Cycle I - Bi/sub 2/(SO/sub 4/)/sub 3/ = Bi/sub 2/O/sub 2/ /sub 3/ (SO/sub 4/)/sub 0/ /sub 7/ + 2.3 SO/sub 3/; and Bi/sub 2/O/sub 2/ /sub 3/(SO/sub 4/)/sub 0/ /sub 7/ + 2.3 H/sub 2/SO/sub 4/ = Bi/sub 2/(SO/sub 4/)/sub 3/ + 2.3 H/sub 2/O. Cycle II - Bi/sub 2/O(SO/sub 4/)/sub 2/ = Bi/sub 2/O/sub 2/ /sub 3/(SO/sub 4/)/sub 0/ /sub 7/ + 1.3 SO/sub 3/; and Bi/sub 2/O/sub 2/ /sub 3/(SO/sub 4/)/sub 0/ /sub 7/ + 1.3 H/sub 2/SO/sub 4/ = Bi/sub 2/O(SO/sub 4/)/sub 2/ + 1.3 H/sub 2/O. Equilibrium sulfur trioxide pressures are given graphically for three solid-gas equilibria involving Bi/sub 2/(SO/sub 4/)/sub 3/, ..cap alpha..- and ..beta..-Bi/sub 2/O(SO/sub 4/)/sub 2/, and Bi/sub 2/O/sub 2/SO/sub 4/. An improved method of carrying out the low temperature step for Cycle I is presented which may provide a remedy to a problem of sorption of sulfuric acid solution by the solids. An antimonyl sulfate - sulfuric acid hybrid cycle is outlined in which SO/sub 2/ and O/sub 2/ are evolved at different temperatures, simplifying the usual SO/sub 3/-SO/sub 2/-O/sub 2/ separation problem.

Jones, W.M.

1982-01-01

98

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

99

Understanding the decomposition reaction mechanism of chrysanthemic acid: a computational study  

PubMed Central

Background Chrysanthemic acid (CHA) is a major product from the photodecomposition of pyrethrin which is an important class of pesticide compounds. In the following paper, Hybrid density functional theory (DFT) calculations of the potential energy surface (PES) for three possible channels decomposition of chrysanthemic acid (cis-trans isomerization, rearrangement and fragmentation) have been carried at the B3LYP/6-311+G** level of theory. DFT was employed to optimize the geometry parameters of the reactants, transition states, intermediates and products based on detailed potential energy surfaces (PES). Results Our results suggest that all three pathways of CHA are endothermic. DFT calculations revealed that the activation barriers for cis-trans isomerization are low, leading to a thermodynamically favorable process than other two pathways. We also investigated the solvent effect on the PES using the polarizable continuum model (PCM). In addition, time-dependent density functional theory (TDDFT) calculations showed that these reactions occur in the ground state rather than in an excited state. Conclusion The rearrangement process seems to be more favorable than the decomposition of CHA to carbene formation. The solvent effect calculations indicated no changes in the shape of the PES with three continua (water, ethanol and cyclohexane), although the solvents tend to stabilize all of the species. PMID:22035035

2011-01-01

100

Multiplex polymerase chain reaction-based reverse line blot hybridization assay to detect common genital pathogens.  

PubMed

The objective of the present paper is to develop and apply a multiplex polymerase chain reaction (mPCR) based reverse line blot (RLB) hybridization assay to facilitate the diagnosis of genital infections by detection of seven recognized or putative genital pathogens (Neisseria gonorrhoeae, Chlamydia trachomatis, Ureaplasma urealyticum, Ureaplasma parvum, Mycoplasma genitalium, Mycoplasma hominis and Trichomonas vaginalis). Species-specific biotin-labelled primer pairs were used in a single mPCR to amplify target regions in each of seven pathogens. The amplified biotin-labelled PCR products were hybridized with membrane-bound-specific oligonucleotide probes and were detected by chemiluminescence. Two hundred and eleven specimens (104 male urethral and 107 female vaginal swabs), collected from patients with suspected genital infections attending the Wuhan First Hospital Sexually Transmitted Diseases (STD) clinic, were tested by mPCR/RLB and results were confirmed by single PCR using different species-specific targets. The sensitivity of the assay was assessed using dilutions of positive DNA controls with known copy numbers, for each target. The assay correctly identified all reference strains and detected potential pathogens in a high proportion of clinical specimens. There was no cross-reaction between the seven pathogens. The mPCR/RLB can detect hybridization assay is sensitive and specific, and able to rapidly detect genital pathogens in clinical specimens. PMID:20498099

Wang, H; Kong, F; Wang, B; Mckechnie, M L; Gilbert, G L

2010-05-01

101

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

102

Lead\\/acid battery development for heat engine\\/electric hybrid vehicles. Final report  

Microsoft Academic Search

A program was undertaken to develop a lead\\/acid battery system for use in a hybrid heat engine\\/electric vehicle. The basic requirements are that the battery be capable of supplying high-rate power pulses and of accepting high-rate charge pulses, both of short duration. The feasibility of developing a bipolar lead\\/acid battery system which conforms to these specifications was investigated by using

J. Giner; A. H. Taylor; F. Goebel

1971-01-01

103

Acid-free aza Diels-Alder reaction of Danishefsky's diene with imines.  

PubMed

[reaction: see text] A highly efficient aza Diels-Alder reaction of Danishefsky's diene with imines was found to occur in methanol in the absence of any acids at room temperature to give corresponding 2-substituted dihydro-4-pyridone derivatives in high yields. This reaction can be also carried out in a three-component one-pot reaction manner. The reaction was found to proceed through a Mannich-type condensation mechanism. PMID:12227776

Yuan, Yu; Li, Xin; Ding, Kuiling

2002-09-19

104

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

105

Bioactivity in silica/poly(?-glutamic acid) sol-gel hybrids through calcium chelation.  

PubMed

Bioactive glasses and inorganic/organic hybrids have great potential as biomedical implant materials. Sol-gel hybrids with interpenetrating networks of silica and biodegradable polymers can combine the bioactive properties of a glass with the toughness of a polymer. However, traditional calcium sources such as calcium nitrate and calcium chloride are unsuitable for hybrids. In this study calcium was incorporated by chelation to the polymer component. The calcium salt form of poly(?-glutamic acid) (?CaPGA) was synthesized for use as both a calcium source and as the biodegradable toughening component of the hybrids. Hybrids of 40wt.% ?CaPGA were successfully formed and had fine scale integration of Ca and Si ions, according to secondary ion mass spectrometry imaging, indicating a homogeneous distribution of organic and inorganic components. (29)Si magic angle spinning nuclear magnetic resonance data demonstrated that the network connectivity was unaltered with changing polymer molecular weight, as there was no perturbation to the overall Si speciation and silica network formation. Upon immersion in simulated body fluid a hydroxycarbonate apatite surface layer formed on the hybrids within 1week. The polymer molecular weight (Mw 30-120kDa) affected the mechanical properties of the resulting hybrids, but all hybrids had large strains to failure, >26%, and compressive strengths, in excess of 300MPa. The large strain to failure values showed that ?CaPGA hybrids exhibited non-brittle behaviour whilst also incorporating calcium. Thus calcium incorporation by chelation to the polymer component is justified as a novel approach in hybrids for biomedical materials. PMID:23632373

Valliant, Esther M; Romer, Frederik; Wang, Daming; McPhail, David S; Smith, Mark E; Hanna, John V; Jones, Julian R

2013-08-01

106

Photoluminescence and quantum yields of organic/inorganic hybrids prepared through formic acid solvolysis  

NASA Astrophysics Data System (ADS)

Three undoped di-urea cross-linked poly(oxyethylene) (POE)/siloxane hybrid matrices, classed as di-ureasils, incorporating POE segments with different lengths were prepared through the carboxylic acid solvolysis sol-gel method using formic acid. The resulting hybrids were characterized by X-ray diffraction, Fourier transform mid-infrared spectroscopy, 29Si and cross-polarization 13C magic-angle spinning nuclear magnetic resonance and photoluminescence spectroscopy. The hybrids' structure is essentially independent of the polymer chain length and the materials are room temperature white-light emitters with emission quantum yields of ˜10 ± 1% and lifetime average values between 2 and 4 ns. For the di-ureasil host with short polymer chains the solvolysis method favours the increase of the PL quantum yields relatively to conventional sol-gel route.

Fu, Lianshe; Sá Ferreira, R. A.; Fernandes, M.; Nunes, S. C.; de Zea Bermudez, V.; Hungerford, Graham; Rocha, J.; Carlos, L. D.

2008-03-01

107

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

108

?,?-Diamino acid: an original building block for hybrid ?/?-peptide synthesis with extra hydrogen bond donating group.  

PubMed

Using a ?,?-diamino acid, several small hybrid ?/? peptides have been synthesized and their conformations investigated through extensive NMR studies and molecular dynamics. A tripeptide and a tetrapeptide have thus shown several hydrogen bonds in solution, including a 13-membered ring involving the ?-nitrogen. PMID:25200681

Stanovych, Andrii; Guillot, Régis; Kouklovsky, Cyrille; Miclet, Emeric; Alezra, Valérie

2014-12-01

109

Predicting subcellular localization of proteins by hybridizing functional domain composition and pseudo-amino acid composition  

Microsoft Academic Search

Recent advances in large-scale genome sequencing have led to the rapid accumulation of amino acid sequences of proteins whose functions are unknown. Since the functions of these proteins are closely correlated with their subcellular localizations, many efforts have been made to develop a variety of methods for predicting protein subcellular location. In this study, based on the strategy by hybridizing

Kuo-Chen Chou; Yu-Dong Cai

2004-01-01

110

An ultracapacitor circuit for reducing sulfation in lead acid batteries for Mild Hybrid Electric Vehicles  

Microsoft Academic Search

The nickel metal hydride (NiMH) batteries used in most hybrid electric vehicles (HEVs) provide satisfactory performance, but are quite expensive. In spite of their lower energy density, lead acid batteries would be much more economical except they are prone to sulfation in HEV applications. However, sulfation can be greatly reduced by a circuit that uses an ultracapacitor in conjunction with

Adam W. Stienecker; Thomas Stuart; Cyrus Ashtiani

2006-01-01

111

Hybridization of Complementary and Homologous Peptide Nucleic Acid Oligomers to a Guanine Quadruplex-Forming RNA†  

PubMed Central

Peptide nucleic acid (PNA) oligomers targeted to guanine quadruplex-forming RNAs can be designed in two different ways. First, complementary cytosine-rich PNAs can hybridize by formation of Watson-Crick base pairs, resulting in hybrid PNA-RNA duplexes. Second, guanine-rich homologous PNAs can hybridize by formation of G-tetrads, resulting in hybrid PNA-RNA quadruplexes. UV thermal denaturation, circular dichroism and fluorescence spectroscopy experiments were used to compare these two recognition modes and revealed 1:1 duplex formation for the complementary PNA and 2:1 (PNA2-RNA) quadruplex formation for the homologous PNA. Both hybrids were very stable and hybridization was observed at low nanomolar concentrations. Hybrid quadruplex formation was equally efficient regardless of the PNA strand polarity, indicating a lack of interaction between the loop nucleobases on the PNA and RNA strands. The implications of this finding on sequence specificity as well as methods to improve affinity are also discussed. PMID:16460021

Marin, Violeta L.; Armitage, Bruce A.

2008-01-01

112

Iodide as an activating agent for acid chlorides in acylation reactions.  

PubMed

Acid chlorides can be activated using a simple iodide source to undergo nucleophilic attack from a variety of relatively weak nucleophiles. These include Friedel-Crafts acylation of N-methylpyrroles, N-acylation of sulfonamides, and acylation reactions of hindered phenol derivatives. The reaction is believed to proceed through a transient acid iodide intermediate. PMID:23342973

Wakeham, Russell J; Taylor, James E; Bull, Steven D; Morris, James A; Williams, Jonathan M J

2013-02-01

113

Cyclic amino acid salts as catalysts for the asymmetric Michael reaction  

Microsoft Academic Search

Different chiral cyclic amino acid alkali metal and ammonium salts were used as catalysts for the asymmetric Michael addition of aldehydes to nitrostyrene. The reaction yield and stereoselectivity depend slightly on the salt cation. The highest yield of the reaction (up to 100%) was obtained with (S)-morpholine-3-carboxylic acid salts, which gave moderate to good enantioselectivities (up to 72% ee) and

Marju Laars; Henri Raska; Margus Lopp; Tõnis Kanger

2010-01-01

114

Chiral BINOL-derived phosphoric acids: privileged Brønsted acid organocatalysts for C-C bond formation reactions.  

PubMed

BINOL-derived phosphoric acids have emerged during the last five years as powerful chiral Brønsted acid catalysts in many enantioselective processes. The most successful transformations carried out with chiral BINOL phosphates include C-C bond formation reactions. The recent advances have been reviewed in this article with a focus being placed on hydrocyanations, aldol-type, Mannich, Friedel-Crafts, aza-ene-type, Diels-Alder, as well as cascade and multi-component reactions. PMID:20820680

Zamfir, Alexandru; Schenker, Sebastian; Freund, Matthias; Tsogoeva, Svetlana B

2010-12-01

115

Reaction sequences in simulated neutralized current acid waste slurry during processing with formic acid  

SciTech Connect

The Hanford Waste Vitrification Plant (HWVP) is being designed for the Department of Energy to immobilize high-level and transuranic wastes as glass for permanent disposal. Pacific Northwest Laboratory is supporting the HWVP design activities by conducting laboratory-scale studies using a HWVP simulated waste slurry. Conditions which affect the slurry processing chemistry were evaluated in terms of offgas composition and peak generation rate and changes in slurry composition. A standard offgas profile defined in terms of three reaction phases, decomposition of H{sub 2}CO{sub 3}, destruction of NO{sub 2}{sup {minus}}, and production of H{sub 2} and NH{sub 3} was used as a baseline against which changes were evaluated. The test variables include nitrite concentration, acid neutralization capacity, temperature, and formic acid addition rate. Results to date indicate that pH is an important parameter influencing the N{sub 2}O/NO{sub x} generation ratio; nitrite can both inhibit and activate rhodium as a catalyst for formic acid decomposition to CO{sub 2} and H{sub 2}; and a separate reduced metal phase forms in the reducing environment. These data are being compiled to provide a basis for predicting the HWVP feed processing chemistry as a function of feed composition and operation variables, recommending criteria for chemical adjustments, and providing guidelines with respect to important control parameters to consider during routine and upset plant operation.

Smith, H.D.; Wiemers, K.D.; Langowski, M.H.; Powell, M.R.; Larson, D.E.

1993-11-01

116

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 Substituted Diphenyldiazomethanes . . . . 32 III. Determinations of the Reaction Rate of if,-Dimethoxydiphenyldiazomethane and Benzoic Acid................................. ... . %8 IV...

Gilby, Ralph Fredrick

2013-10-04

117

Kinetics research on fast exothermic reaction between cyclohexanecarboxylic acid and oleum in microreactor  

Microsoft Academic Search

Microreactors are effective tools for the intensification of fast exothermic chemical reactions. In this work, we focus on the kinetics study of a microreacting process to provide a deeper understanding of the transport and reaction performance within microreactors. An experimental setup incorporating an online kinetic measurement method was developed based on the temperature–conversion relationship in the cyclohexanecarboxylic acid–oleum reaction –

K. Wang; Y. C. Lu; Y. Xia; H. W. Shao; G. S. Luo

2011-01-01

118

Kinetics and mechanisms of the reaction of hypothiocyanous acid with 5-thio-2-nitrobenzoic acid and reduced glutathione.  

PubMed

Hypothiocyanite is a major oxidant generated by mammalian peroxidases. Although reported to react specifically with thiol groups in biological molecules, a detailed mechanistic study of this reaction has not been conducted. We have investigated the reaction of hypothiocyanous acid/hypothiocyanite with 5-thio-2-nitrobenzoic acid and with reduced glutathione by stopped-flow spectroscopy. The observed bell-shaped pH profile established that the reaction with 5-thio-2-nitrobenzoic acid proceeds via the thiolate and hypothiocyanous acid in the 2.5 < pH < 8 region. The obtained second-order rate constant of the reaction is (1.26 + or - 0.02) x 10(8) M(-1) s(-1), and the effective rate constant at pH 7.4 is (4.37 + or - 0.03) x 10(5) M(-1) s(-1). Analysis of the kinetic data, using a value of 4.38 + or - 0.01 for the pK(a) of 5-thio-2-nitrobenzoic acid thiol (measured independently by spectroscopic analysis), gave a pK(a) of 4.85 + or - 0.01 for hypothiocyanous acid at physiological salt concentration (I = 120 mM; NaCl and phosphate buffer) and 25 degrees C. A second-order rate constant of (8.0 + or - 0.5) x 10(4) M(-1) s(-1) for the reaction of hypothiocyanous acid/hypothiocyanite with reduced glutathione at pH 7.4 was determined. The glutathione data are also consistent with the reaction proceeding via the thiolate and hypothiocyanous acid. Our results demonstrate that hypothiocyanous acid/hypothiocyanite has very high reactivity with thiols and will be short-lived in the presence of physiological concentrations of glutathione and thiol proteins. As the reaction occurs strictly with the thiolate, this oxidant should selectively target proteins containing low pK(a) thiols. PMID:19821602

Nagy, Péter; Jameson, Guy N L; Winterbourn, Christine C

2009-11-01

119

Chemoselective silyl transfer in the Mukaiyama aldol reaction promoted by super silyl Lewis acid.  

PubMed

In the silyl Lewis acid-promoted Mukaiyama aldol reaction, the steric and electronic properties of the silyl group on the silyl Lewis acid influence the reaction mechanism and product distribution. When super silyl triflates such as (TMS)3SiOTf and (TES)3SiOTf are used as Lewis acids, the silyl group of the silyl enol ether chemoselectively transfers to the product. The mechanistic details have been investigated using density functional theory (DFT) calculations. PMID:25338752

Sai, Masahiro; Akakura, Matsujiro; Yamamoto, Hisashi

2014-11-01

120

Rapid generation of molecular complexity in the Lewis or Brønsted acid-mediated reactions of methylenecyclopropanes.  

PubMed

Although they are highly strained, methylenecyclopropanes (MCPs) are readily accessible molecules that have served as useful building blocks in organic synthesis. MCPs can undergo a variety of ring-opening reactions because the release of cyclopropyl ring strain (40 kcal/mol) can provide a thermodynamic driving force for reactions and the ?-character of the bonds within the cyclopropane can afford the kinetic opportunity to initiate the ring-opening. Since the 1970s, the chemistry of MCPs has been widely explored in the presence of transition metal catalysts, but less attention had been paid to the Lewis or Brønsted acid mediated chemistry of MCPs. During the past decade, significant developments have also been made in the Lewis or Brønsted acid mediated reactions of MCPs. This Account describes chemistry developed in our laboratory and by other researchers. Lewis and Brønsted acids can be used as catalysts or reagents in the reactions of MCPs with a variety of substrates, and substituents on the terminal methylene or on the cyclopropyl ring of MCPs significantly affect the reaction pathways. During the past decade, we and other researchers have found interesting transformations based on this chemistry. These new reactions include the ring expansion of MCPs, cycloaddition reactions of MCPs with aldehydes and imines, cycloaddition reactions of MCPs with nitriles in the presence of strong Brønsted acid, radical reactions of MCPs with 1,3-dicarbonyl compounds, intramolecular Friedel-Crafts reactions of MCPs with arenes, acylation reactions of MCPs, and the reaction of MCPs with 1,1,3-triarylprop-2-yn-1-ols or their methyl ethers. These Lewis or Brønsted acid mediated reactions of MCPs can produce a variety of new compounds such as cyclobutanones, indenes, tetrahydrofurans, and tetrahydroquinolines. Finally, we have also carried out computational studies to explain the mechanism of the Brønsted acid mediated reactions of MCPs with acetonitrile. PMID:22166122

Shi, Min; Lu, Jian-Mei; Wei, Yin; Shao, Li-Xiong

2012-04-17

121

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

122

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

123

Mechanism of non-enzymic transamination reaction between histidine and alpha-oxoglutaric acid.  

PubMed

Non-enzymic transamination reactions at 85 degrees between various amino acids and alpha-oxoglutaric acid are catalysed by metal ions, e.g. Al(3+), Fe(2+), Cu(2+) and Fe(3+). The reaction is optimum at pH4.0. Of the 14 amino acids studied histidine is the most active. In the presence of Al(3+) histidine transaminates with alpha-oxoglutaric acid, forming glutamic acid and Al(3+)-imidazolylpyruvic acid complex as the end products. However, in the presence of Fe(2+) or Cu(2+) the products are glutamic acid and a 1:2 metal ion-imidazolylpyruvic acid chelate. The greater effectiveness of histidine in these reactions is attributed to the presence of the tertiary imidazole nitrogen atom, which is involved in the formation of stable sparingly soluble metal ion-imidazolylpyruvic acid complexes or chelates as end products of these reactions. Of the metal ions studied only Al(3+), Fe(2+), Fe(3+) and Cu(2+) are effective catalysts for the transamination reactions, and EDTA addition completely inhibits the catalytic effect of the Al(3+). Spectrophotometric evidence is presented to demonstrate the presence of metal ion complexes of Schiff bases of histidine as intermediates in the transamination reactions. These results may contribute to understanding the role of histidine in enzyme catalysis. PMID:4980679

Doctor, V M; Oró, J

1969-05-01

124

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

125

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

126

[Experimental and kinetic modeling of acid/base and redox reactions over oxide catalysts  

SciTech Connect

The research has involved the characterization of catalyst acidity, [sup 2]D NMR studies of Bronsted acid sites, and kinetic, calorimetric, and spectroscopic studies of methylamine synthesis and related reactions over acid catalysts. Approach of this work was to explore quantitative correlations between factors that control the generation, type, strength, and catalytic properties of acid sites on zeolite catalysts. Microcalorimetry, thermogravimetric analysis, IR spectroscopy, and NMR spectroscopy have provided information about the nature and strength of acid sites in zeolites. This was vital in understanding the catalytic cycles involved in methylamine synthesis and related reactions over zeolite catalysts.

Not Available

1993-01-01

127

Production of lactic acid from C6-polyols by alkaline hydrothermal reactions  

NASA Astrophysics Data System (ADS)

Production of lactic acid from C6-polyols (Mannitol) under alkaline hydrothermal conditions was investigated. Experiments were performed to examine the difference in the production of lactic acid between C6-polyols and C3-polyols (glycerine), as well as C6-aldoses (glucose). Results showed that the yield of lactic acid from C6-polyols was lower than that from both glycerine and glucose. It indicated that long chain polyols might follow a different reaction pathway from that of glycerine. Further investigation is needed to clarify the reaction mechanism and improve the relatively low lactic acid acid yield from C6-polyols.

Zhou, Huazhen; Jin, Fangming; Wu, Bing; Cao, Jianglin; Duan, Xiaokun; Kishita, Atsushi

2010-03-01

128

Estimating biofilm reaction kinetics using hybrid mechanistic-neural network rate function model.  

PubMed

This work describes an alternative method for estimation of reaction rate of a biofilm process without using a model equation. A first principles model of the biofilm process is integrated with artificial neural networks to derive a hybrid mechanistic-neural network rate function model (HMNNRFM), and this combined model structure is used to estimate the complex kinetics of the biofilm process as a consequence of the validation of its steady state solution. The performance of the proposed methodology is studied with the aid of the experimental data of an anaerobic fixed bed biofilm reactor. The statistical significance of the method is also analyzed by means of the coefficient of determination (R2) and model efficiency (ME). The results demonstrate the effectiveness of HMNNRFM for estimating the complex kinetics of the biofilm process involved in the treatment of industry wastewater. PMID:22055105

Kumar, B Shiva; Venkateswarlu, Ch

2012-01-01

129

Local sustained delivery of acetylsalicylic acid via hybrid stent with biodegradable nanofibers reduces adhesion of blood cells and promotes reendothelialization of the denuded artery  

PubMed Central

Incomplete endothelialization, blood cell adhesion to vascular stents, and inflammation of arteries can result in acute stent thromboses. The systemic administration of acetylsalicylic acid decreases endothelial dysfunction, potentially reducing thrombus, enhancing vasodilatation, and inhibiting the progression of atherosclerosis; but, this is weakened by upper gastrointestinal bleeding. This study proposes a hybrid stent with biodegradable nanofibers, for the local, sustained delivery of acetylsalicylic acid to injured artery walls. Biodegradable nanofibers are prepared by first dissolving poly(D,L)-lactide-co-glycolide and acetylsalicylic acid in 1,1,1,3,3,3-hexafluoro-2-propanol. The solution is then electrospun into nanofibrous tubes, which are then mounted onto commercially available bare-metal stents. In vitro release rates of pharmaceuticals from nanofibers are characterized using an elution method, and a highperformance liquid chromatography assay. The experimental results suggest that biodegradable nanofibers release high concentrations of acetylsalicylic acid for three weeks. The in vivo efficacy of local delivery of acetylsalicylic acid in reducing platelet and monocyte adhesion, and the minimum tissue inflammatory reaction caused by the hybrid stents in treating denuded rabbit arteries, are documented. The proposed hybrid stent, with biodegradable acetylsalicylic acid-loaded nanofibers, substantially contributed to local, sustained delivery of drugs to promote re-endothelialization and reduce thrombogenicity in the injured artery. The stents may have potential applications in the local delivery of cardiovascular drugs. Furthermore, the use of hybrid stents with acetylsalicylic acid-loaded nanofibers that have high drug loadings may provide insight into the treatment of patients with high risk of acute stent thromboses. PMID:24421640

Lee, Cheng-Hung; Lin, Yu-Huang; Chang, Shang-Hung; Tai, Chun-Der; Liu, Shih-Jung; Chu, Yen; Wang, Chao-Jan; Hsu, Ming-Yi; Chang, Hung; Chang, Gwo-Jyh; Hung, Kuo-Chun; Hsieh, Ming-Jer; Lin, Fen-Chiung; Hsieh, I-Chang; Wen, Ming-Shien; Huang, Yenlin

2014-01-01

130

Friedel–Crafts acylation and related reactions catalysed by heteropoly acids  

Microsoft Academic Search

Recent studies on catalysis by heteropoly acids (HPA) for the Friedel–Crafts acylation of arenes and related Fries rearrangement of aryl esters are reviewed. It is demonstrated that HPA-based solid acids are efficient and environmentally friendly catalysts for these reactions, usually superior in activity to the conventional acid catalysts such as H2SO4 or zeolites.

I. V. Kozhevnikov

2003-01-01

131

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

132

Laboratory-Measured Sulfuric Acid and Water Homogeneous Nucleation Rates from the SO2 + OH Reaction  

Microsoft Academic Search

Sulfuric acid and water binary homogeneous nucleation is the most important atmospheric nucleation system, but the nucleation mechanisms are poorly understood. Here, we report laboratory-measured sulfuric acid and water binary homogeneous nucleation rates at the atmospheric pressure, 288 K and 10 - 55 % relative humidity. The SO2 + OH reaction was used to produce sulfuric acid vapor. Residual sulfuric

D. Benson; S. Lee

2007-01-01

133

Heterogeneous Atmospheric Aerosol Production by Acid Catalyzed Particle-Phase Reactions  

Microsoft Academic Search

According to evidence from our laboratory, acidic surfaces on atmospheric aerosols lead to potentially multifold increases in secondary organic aerosol (SOA) mass. Experimental observations using a multichannel flow reactor, Teflon (polytetrafluoroethylene) film bag batch reactors, and outdoor Teflon-film smog chambers strongly confirm that inorganic acids, such as sulfuric acid, catalyze particle-phase heterogeneous reactions of atmospheric organic carbonyl species. The net

Myoseon Jang; Nadine M. Czoschke; Sangdon Lee; Richard M. Kamens

2002-01-01

134

Templated Synthesis of Peptide Nucleic Acids via Sequence-Selective Base-Filling Reactions  

E-print Network

Templated Synthesis of Peptide Nucleic Acids via Sequence-Selective Base-Filling Reactions Jennifer describe the templated synthesis of both native and modified peptide nucleic acids (PNAs) through base, 2009; E-mail: drliu@fas.harvard.edu Template-directed nucleic acid synthesis is an essential compo

Liu, David R.

135

Catalysed esterifications in room temperature ionic liquids with acidic counteranion as recyclable reaction media  

Microsoft Academic Search

Esterification reactions of acetic acid, methoxyacetic acid and methylmalonic acid with neo-pentanol, hexanol, heptanol and decanol have been investigated in three ionic liquids with hydrogen sulphate, dihydrogen phosphate as counteranions and also two ionic liquids modified with HPF6 as catalyst. The nature of both the counteranion and cation influence the behavior of the catalyst. Good yields and high selectivities were

Joan Fraga-Dubreuil; Khadidja Bourahla; Mustapha Rahmouni; Jean Pierre Bazureau; Jack Hamelin

2002-01-01

136

Decomposition of the permanganate/oxalic acid overall reaction to elementary steps based on integer programming theory  

E-print Network

Decomposition of the permanganate/oxalic acid overall reaction to elementary steps based on integer to obtain chemically acceptable decompositions of the overall autocatalytic reaction permanganate/oxalic

Tóth, János

137

DNA-based hybridization chain reaction for an ultrasensitive cancer marker EBNA-1 electrochemical immunosensor.  

PubMed

An ultrasensitive and selective electrochemical immunosensor was developed for the detection of Epstein Barr virus nuclear antigen 1 (EBNA-1). Firstly, a suspension of graphene sheets (GS) and multi-walled carbon nanotubes (MWCNTs) was prepared with the aid of chitosan (CS) solution and then modified on a glassy carbon electrode (GCE). Gold nanoparticles (AuNPs) were then electrodeposited onto the surface of the GS-MWCNTs film by cyclic voltammetry (CV) to immobilize the captured antibodies. After that, specific sandwich immunoreactions were formed among the captured antibody, EBNA-1, and secondary antibody, DNA-coated carboxyl multi-wall carbon nanotubes (DNA-MWCNTs-Ab2). DNA initiator strands (S0) and secondary antibodies linked to the MWCNTs and double-helix DNA polymers were obtained by hybridization chain reaction (HCR), and here S0 on the MWCNTs propagates a chain reaction of hybridization events between two alternating hairpins to form a nicked double-helix. Finally, electroactive indicator doxorubicin hydrochloride was intercalated into the CG-GC steps between the HCR products and could produce an electrochemical signal, which was monitored by differential pulse voltammetry (DPV). Under optimum conditions, the amperometric signal increased linearly with the target concentrations (0.05-6.4ngmL(-1)), and the immunosensor exhibited a detection limit as low as 0.7pgmL(-1) (S/N=3). The proposed method showed acceptable stability and reproducibility, as well as favorable recovery for EBNA-1 in human serum. The proposed immunosensor provides a novel avenue for signal amplification and potential applications in bioanalysis and clinical diagnostics. PMID:24632131

Song, Chao; Xie, Guoming; Wang, Li; Liu, Lingzhi; Tian, Guang; Xiang, Hua

2014-08-15

138

Direct microwave-assisted amino acid synthesis by reaction of succinic acid and ammonia in the presence of magnetite  

NASA Astrophysics Data System (ADS)

Since the discovery of submarine hot vents in the late 1970s, it has been postulated that submarine hydrothermal environments would be suitable for emergence of life on Earth. To simulate warm spring conditions, we designed a series of microwave-assisted amino acid synthesis involving direct reactions between succinic acid and ammonia in the presence of the magnetite catalyst. These reactions which generated aspartic acid and glycine were carried out under mild temperatures and pressures (90-180 °C, 4-19 bar). We studied this specific reaction inasmuch as succinic acid and ammonia were traditionally identified as prebiotic compounds in primitive deep-sea hydrothermal systems on Earth. The experimental results were discussed in both biochemical and geochemical context to offer a possible route for abiotic amino acid synthesis. With extremely diluted starting materials (0.002 M carboxylic acid and 0.002 M ammonia) and catalyst loading, an obvious temperature dependency was observed in both cases [neither product was detected at 90 °C in comparison with 21.08 ?mol L-1 (aspartic acid) and 70.25 umol L-1 (glycine) in 180 °C]. However, an opposite trend presented for reaction time factor, namely a positive correlation for glycine, but a negative one for aspartic acid.

Jiang, Nan; Liu, Dandan; Shi, Weiguang; Hua, Yingjie; Wang, Chongtai; Liu, Xiaoyang

2013-10-01

139

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

PubMed

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; Tagmatarchis, Nikos

2014-01-01

140

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.

Stergiou, Anastasios; Pagona, Georgia

2014-01-01

141

Salicylato titanocene complexes as cooperative organometallic Lewis acid and Brønsted acid catalysts for three-component mannich reactions.  

PubMed

A binary acid system has been developed that features an air-stable organometallic precursor, titanocene dichloride, and simple organic cooperative Brønsted acids, which allowed for mild and highly efficient Mannich reactions of both aryl and alkyl ketones with excellent yields and satisfactory diastereoselectivity. Mechanistic studies, including (1) H?NMR titration, X-ray structure analyses as well as isolation of catalytically active species, elucidated the dramatic synergistic effects of this new binary acid system. PMID:24954651

Wu, Ya; Chen, Chun; Jia, Gai; Zhu, Xuyang; Sun, Huaming; Zhang, Guofang; Zhang, Weiqiang; Gao, Ziwei

2014-07-01

142

Reaction of dicyclopentadiene with formic acid and chloroacetic acid with and without cation-exchange resins as catalysts  

Microsoft Academic Search

The uncatalysed and catalysed (with cation-exchange resin) esterification of formic acid and chloroacetic acid, with dicyclopentadiene (DCPD), i.e. 4,7-methano-3a,4,7,7a-tetrahydroindene, was carried out. The effect of various parameters, e.g. speed of agitation, catalyst loading, mole ratio of the reactants, temperature, concentration of formic acid in aqueous solutions were studied to optimise the reaction conditions. DCPD cam be quantitatively converted to the

Basudeb Saha; Man Mohan Sharma

1997-01-01

143

Polymerase chain reaction and DNA probe hybridization to assess the efficacy of diminazene treatment in Trypanosoma brucei? -infected cattle  

Microsoft Academic Search

Four of eight Ankole longhorn cattle experimentally infected with Trypanosoma brucei were treated with 7?mg\\/kg diminazene aceturate (Berenil, Hoechst AG, Germany) at day 71 postinfection. The trypanocidal activity\\u000a was monitored using polymerase chain reaction (PCR) and DNA probe hybridization. When extracted parasite DNA (without host\\u000a DNA) was used, as little as 1?fg per reaction, which is equivalent to about 1–10%

P.-H. Clausen; C. Waiswa; E. Katunguka-Rwakishaya; G. Schares; S. Steuber; D. Mehlitz

1999-01-01

144

Optimization of dicarboxylic acid cellulose synthesis: Reaction stoichiometry and role of hypochlorite scavengers.  

PubMed

The reaction conditions in terms of reaction time, sodium chlorite stoichiometry, and the effect of hypochlorite scavengers on the chlorite oxidation of dialdehyde cellulose (DAC) was studied. The impact of storage on the reactivity of DAC fibers was also investigated. It was found that chlorite oxidation of DAC is a rapid reaction, resulting in oxidation of 71% of the aldehyde after only 8min when 2.5 times excess of sodium chlorite compared to aldehyde groups was used. Reactivity of DAC was observed to decrease quickly during the storage and only 68% of the aldehyde groups reacted after two weeks storage compared to the reaction performed with freshly prepared DAC. Hydrogen peroxide and sulfamic acid were observed to increase the reaction efficiency of chlorite oxidation by reducing the amount of side-reactions between chlorite and hypochlorite. A minor amount of sulfamic acid can be used to replace acetic acid as a catalyst. PMID:25263866

Sirviö, Juho Antti; Liimatainen, Henrikki; Visanko, Miikka; Niinimäki, Jouko

2014-12-19

145

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

PubMed

Porphyrin(Por)-spiropyran(SP) hybrid compounds, including Por-SP dyad, Por-SP2 triad, and Por-SP4 pentad, were prepared and characterized by (1)H 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 350nm 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. PMID:24036185

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

2014-01-01

146

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

147

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

148

Very long chain and hydroxylated fatty acids in offspring of somatic hybrids between Brassica napus and Lesquerella fendleri  

Microsoft Academic Search

Offspring of somatic hybrids between the zero-erucic acid rapeseed cv Hanna and Lesquerella fendleri were analysed regarding their fatty acid profiles. In the first back-cross generation one plant was found that produced a\\u000a seed containing up to 16.5% erucic acid and 15% eicosaenoic acid (Line 1), as well as a seed having 4.3% ricinoleic acid (Line\\u000a 2). This was interpreted

M. Schröder-Pontoppidan; M. Skarzhinskaya; C. Dixelius; S. Stymne; K. Glimelius

1999-01-01

149

Reaction of rosmarinic acid with nitrite ions in acidic conditions: discovery of nitro- and dinitrorosmarinic acids as new anti-HIV-1 agents.  

PubMed

Rosmarinic acid was reacted with nitrite ions under acidic conditions to give 6'-nitro- and 6',6''-dinitrorosmarinic acids according to the reaction time. Both compounds were active as HIV-1 integrase inhibitors at the submicromolar level. They also inhibited the viral replication in MT-4 cells with modest and similar selectivity indexes. The nitration of rosmarinic acid strongly improves the anti-integrase inhibition and the antiviral activity without increasing the cellular toxicity. PMID:18351727

Dubois, Mélanie; Bailly, Fabrice; Mbemba, Gladys; Mouscadet, Jean-François; Debyser, Zeger; Witvrouw, Myriam; Cotelle, Philippe

2008-04-24

150

A hybrid CFD—reaction engineering framework for multiphase reactor modelling: basic concept and application to bubble column reactors  

Microsoft Academic Search

The coupling of turbulent mixing and chemical phenomena lies at the heart of multiphase reaction engineering, but direct CFD approaches are usually confronted with excessive computational demands. In this hybrid approach, the quantification of mixing is accomplished through averaging the flow and concentration profiles resulting from a CFD flow field calculation and a computational (“virtual”) tracer experiment. Based on these

Stelios Rigopoulos; Alan Jones

2003-01-01

151

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...

152

Photochemical Reaction Dynamics of the Primary Event of Vision Studied by Means of a Hybrid Molecular Simulation  

PubMed Central

Abstract The photoisomerization reaction dynamics of a retinal chromophore in the visual receptor rhodopsin was investigated by means of hybrid quantum mechanical/molecular mechanical (QM/MM) molecular dynamics (MD) simulations. The photoisomerization reaction of retinal constitutes the primary step of vision and is known as one of the fastest reactions in nature. To elucidate the molecular mechanism of the high efficiency of the reaction, we carried out hybrid ab initio QM/MM MD simulations of the complete reaction process from the vertically excited state to the photoproduct via electronic transition in the entire chromophore-protein complex. An ensemble of reaction trajectories reveal that the excited-state dynamics is dynamically homogeneous and synchronous even in the presence of thermal fluctuation of the protein, giving rise to the very fast formation of the photoproduct. The synchronous nature of the reaction dynamics in rhodopsin is found to originate from weak perturbation of the protein surroundings and from dynamic regulation of volume-conserving motions of the chromophore. The simulations also provide a detailed view of time-dependent modulations of hydrogen-out-of-plane vibrations during the reaction process, and identify molecular motions underlying the experimentally observed dynamic spectral modulations. PMID:19167292

Hayashi, Shigehiko; Tajkhorshid, Emad; Schulten, Klaus

2009-01-01

153

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

154

Advanced valve-regulated lead-acid batteries for hybrid vehicle applications  

Microsoft Academic Search

Future vehicle applications require the development of reliable and long life batteries operating under high-rate partial-state-of-charge (HRPSoC) working conditions. Work presented in this paper deals with the study of different design parameters, manufacturing process and charging conditions of spiral wound valve-regulated lead-acid (VRLA) batteries, in order to improve their reliability and cycle life for hybrid vehicle applications.Test results show that

M. L. Soria; F. Trinidad; J. M. Lacadena; A. Sánchez; J. Valenciano

2007-01-01

155

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

Microsoft Academic Search

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

G. Mardirossian; K. Lei; M. Rusckowski

1997-01-01

156

Enolization and racemization reactions of glucose and fructose on heating with amino-acid enantiomers and the formation of melanoidins as a result of the Maillard reaction  

Microsoft Academic Search

This study investigated the enolization and racemization reactions of glucose and fructose on heating with amino acid enantiomers\\u000a and the formation of melanoidins as a result of the Maillard reaction. The study measured reducing sugars and L- and D- amino acids using HPLC as an index for the amount of enolization of the sugars and isomerization of the amino acids.

Ji-Sang Kim; Young-Soon Lee

2009-01-01

157

Comparison of polymerase chain reaction, DNA hybridization, and histology with viral culture to detect cytomegalovirus in immunosuppressed patients.  

PubMed

Formalin-fixed, paraffin-embedded lung tissue from 34 autopsies and eight open-lung biopsies of bone marrow transplant recipients was analyzed for cytomegalovirus (CMV) infection. The cases were studied by the polymerase chain reaction (PCR), in situ DNA hybridization, and histologic examination. The results were compared with viral culture for CMV taken at the time of biopsy or autopsy. In the autopsy series, hybridization and histology identified CMV in 15% of the cases, whereas PCR detected CMV in 24% of the cases. In the open-lung biopsy cases, both PCR and hybridization were found to be equivalent to culture in detecting CMV. Histology was less sensitive, with the molecular biology methods detecting CMV in 50% of the lung biopsies while histologic examination identified only 25%. Specificity was high (100%) since CMV was not detected in any culture-negative case by either PCR or hybridization. However, PCR, hybridization, and histology failed to identify CMV in three known culture-positive autopsy cases. Overall, PCR and hybridization were found to be more sensitive than histology, and PCR was more sensitive than hybridization for the detection of CMV. The advantage of high sensitivity and specificity combined with more rapid diagnosis (24 to 48 h) compared with viral culture (average, 16 days in this study) makes the molecular biology methods useful adjuncts to histology for detection of CMV in formalin-fixed, paraffin-embedded tissue. PMID:1646452

Persons, D L; Moore, J A; Fishback, J L

1991-03-01

158

Efficient Nucleophilic Substitution Reaction of Aryl Halides with Amino Acids Under Focused Microwave Irradiation  

Microsoft Academic Search

The nucleophilic substitution reaction of 2,4-dinitrofluorobenzene with amino acids was complete, under microwave iradiation, within 40s with yields up to 93%, which are far superior to those obtained under conventional heating.

Yie-Jia Cherng

2000-01-01

159

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

160

Determination of Oxybutynin in Pharmaceuticals via Reaction with Mixed Acids Anhydrides: Application to Content Uniformity Testing  

Microsoft Academic Search

Sensitive and simple spectrophotometric (Method I) and spectrofluorimetric (Method II) methods were developed and validated\\u000a for the determination of oxybutynin HCl (OXB) in its dosage forms. The method was based on the reaction of OXB with malonic\\u000a acid anhydride in acetic acid anhydride to form a highly yellow colored product that was measured at 375 nm spectrophotometrically.\\u000a The same reaction

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

2011-01-01

161

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

PubMed

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

Fukuyama, Takahide; Mukai, Yu; Ryu, Ilhyong

2011-01-01

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

The kinetics of the esterification reaction between castor oil and oleic acid  

Microsoft Academic Search

In this study, esterification of castor oil with oleic acid was investigated in view of the reaction kinetics under various\\u000a conditions. Potassium hydroxide,p-toluenesulfonic acid and tin chloride (SnCl22H2O) were used as catalysts. Reaction was carried out at 200C, 225C and 250 C by using equivalent proportions of the reactants.\\u000a For tin chloride, experimental data fitted the second-order rate equation, while

A. T. Erciyes; L. Dandik; O. S. Kabasakal

1991-01-01

164

Proton transfer reactions between nitric acid and acetone, hydroxyacetone, acetaldehyde and benzaldehyde in the solid phase.  

PubMed

The heterogeneous and homogeneous reactions of acetone, hydroxyacetone, acetaldehyde and benzaldehyde with solid nitric acid (HNO(3)) films have been studied with Reflection-Absorption Infrared Spectroscopy (RAIRS) under Ultra-High Vacuum (UHV) conditions in the 90-170 K temperature range. In the bulk or at the surface of the films, nitric acid transfers its proton to the carbonyl function of the organic molecules, producing protonated acetone-H(+), hydroxyacetone-H(+), acetaldehyde-H(+) and benzaldehyde-H(+), and nitrate anions NO(3)(-), a reaction not observed when nitric acid is previously hydrated [J. Lasne, C. Laffon and Ph. Parent, Phys. Chem. Chem. Phys., 2012, 14, 697]. This provides a molecular-scale description of the carbonyl protonation reaction in an acid medium, the first step of the acid-catalyzed condensation of carbonyl compounds, fuelling the growth of secondary organic aerosols (SOA) in the atmosphere. PMID:23090634

Lasne, Jérôme; Laffon, Carine; Parent, Philippe

2012-12-01

165

Electrical detection of hybridization and threading intercalation of deoxyribonucleic acid using carbon nanotube network field-effect  

E-print Network

of 13% in Id reduction due to specific binding between hybridized DNA and intercalators, corroborated-base mismatched DNA analyte. We demonstrate that sensitivity improvement using threading intercalator canElectrical detection of hybridization and threading intercalation of deoxyribonucleic acid using

Rogers, John A.

166

Hybrid Molecular Probe for Nucleic Acid Analysis in Biological Samples Chaoyong James Yang, Karen Martinez, Hui Lin, and Weihong Tan*  

E-print Network

Hybrid Molecular Probe for Nucleic Acid Analysis in Biological Samples Chaoyong James Yang, Karen Martinez, Hui Lin, and Weihong Tan* Center for Research at Bio/Nano Interface, Department of Chemistry

Tan, Weihong

167

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

168

REACTIONS OF CHLORITE WITH ACTIVATED CARBON AND WITH VANILLIC ACID AND INDAN ADSORBED ON ACTIVATED CARBON  

EPA Science Inventory

The reaction between chlorite (CO2(-1)) and vanillic acid, at pH 6.0 in the presence of granular activated carbon (GAC), yielded several reaction products identifiable by GC/MS; no products were found in the absence of GAC. Indan and ClO2 or ClO2(-1) reacted in aqueous solution a...

169

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

Microsoft Academic Search

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

Yi Zheng; Yanguo Li; Li Pan; Yuesheng Li

2007-01-01

170

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

171

Highly sensitive indicator-free impedance sensing of DNA hybridization based on poly(m-aminobenzenesulfonic acid)/TiO2 nanosheet membranes with pulse potentiostatic method preparation.  

PubMed

A direct electrochemical detection procedure for DNA hybridization by using the electrochemical signal changes of conductive poly(m-aminobenzenesulfonic) acid (PABSA)/TiO(2) nanosheet membranes, which were electropolymerized by using the pulse potentiostatic method, is reported. Due to the unique properties of TiO(2) nanoparticles, m-aminobenzenesulfonic acid monomers tend to be adsorbed around the particles, and the electropolymerization efficiency is greatly improved. The combination of TiO(2) nanoparticles and PABSA resulted in a nanocomposite membrane with unique and novel nanosheet morphology that provides more activation sites and enhances the surface electron-transfer rate. These characteristics were propitious for the magnification of PABSA electrochemical signals and the direct detection of DNA hybridization. Owing to the presence of abundant sulfonic acid groups, PABSA could overcome the drawbacks of polyaniline and be used to detect bioanalytes at physiological pH. DNA probes could be covalently attached to the sulfonic groups through the amines of DNA sequences by using an acyl chloride cross-linking reaction. After immobilization of probe DNA, the electrochemical impedance value increased significantly compared to that of PABSA/TiO(2) nanosheet membranes, and then decreased dramatically after the hybridization reaction of the probe DNA with the complementary DNA sequence compared to that of the probe-immobilized electrode. Electrochemical impedance spectroscopy was adopted for indicator-free DNA biosensing, which had an eminent ability for the recognition between double-base mismatched sequences or non-complementary DNA sequences and complementary DNA sequences. A gene fragment, which is related to one of the screening genes for the transgenically modified plants, the cauliflower mosaic virus 35S gene was satisfactorily detected. This is the first report for the indicator-free impedance DNA hybridization detection by using PABSA/TiO(2) membranes under neutral conditions. PMID:20020515

Hu, Yu-Wei; Yang, Tao; Wang, Xin-Xing; Jiao, Kui

2010-02-01

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

Nucleic acids for the rational design of reaction circuits.  

PubMed

Nucleic acid-based circuits are rationally designed in vitro assemblies that can perform complex preencoded programs. They can be used to mimic in silico computations. Recent works emphasized the modularity and robustness of these circuits, which allow their scaling-up. Another new development has led to dynamic, time-responsive systems that can display emergent behaviors like oscillations. These are closely related to biological architectures and provide an in vitro model of in vivo information processing. Nucleic acid circuits have already been used to handle various processes for technological or biotechnological purposes. Future applications of these chemical smart systems will benefit from the rapidly growing ability to design, construct, and model nucleic acid circuits of increasing size. PMID:23265857

Padirac, Adrien; Fujii, Teruo; Rondelez, Yannick

2013-08-01

174

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

175

Reactions in glass ionomer cements: V. Effect of incorporating tartaric acid in the cement liquid.  

PubMed

A description is give of the effect on the ASPA cement reaction of tartaric acid incorporated in the cement liquid. Tartaric acid acts as an accelerator that aids in the extraction of ions from the aluminosilicate glass and facilitates their binding to the polyanion chains. Postgelation hardening is significantly increased. Working time is unaffected possibly because cations are initially present as complexes. PMID:187629

Crisp, S; Wilson, A D

1976-01-01

176

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

177

On the reaction of iron oxides and oxyhydroxides with tannic and phosphoric acid and their mixtures  

NASA Astrophysics Data System (ADS)

The actions of tannic acid, phosphoric acid and their mixture on lepidocrocite, goethite, superparamagnetic goethite, akaganeite, magnetite, hematite and maghemite for 1 day and 1 month were explored. It was found that these acids form iron tannates and phosphates. Lepidocrocite and magnetite were the iron phases more easily transformed with the mixture of the acids after 1 month of reaction, whereas hematite was the most resistant phase. In the case of goethite, our results suggest that in order to understand properly the action of these acids, we have to take into account its stoichiometry, surface area and degree of crystallinity.

Beltrán, J. J.; Novegil, F. J.; García, K. E.; Barrero, C. A.

2010-01-01

178

Organic/inorganic hybrid amine and sulfonic acid tethered silica materials: Synthesis, characterization and application  

NASA Astrophysics Data System (ADS)

The major goals of this thesis were to: (1) create a site-isolated aminosilica material with higher amine loadings than previously reported isolation methods, (2) use spectroscopic, reactivity, and catalytic (olefin polymerization precatalysts) probes to determine isolation of amine groups on these organic/inorganic hybrid materials, (3) synthesize an organic/inorganic hybrid material capable of activating Group 4 olefin polymerization precatalysts, and (4) synthesize a high amine loaded organic/inorganic hybrid material capable of reversibly capturing CO2 in a simulated flue gas stream. The underlying motivation of this research involved the synthesis and design of novel amine and sulfonic acid materials. Traditional routes to synthesize aminosilicas have led to the formation of a high loading of multiple types of amine sites on the silica surface. Part of this research involved the creation of a new aminosilica material via a protection/deprotection method designed to prevent multiple sites, while maintaining a relatively high loading. As a characterization technique, fluorescence spectroscopy of pyrene-based fluorophores loaded on traditional aminosilicas and site-isolated aminosilicas was used to probe the degree of site-isolation obtained with these methods. Also, this protection/deprotection method was compared to other reported isolation techniques with heterogeneous Group 4 constrained-geometry inspired catalysts (CGCs). It was determined that the degree of separation of the amine sites could be controlled with protection/deprotection methods. Furthermore, an increase in the reactivity of the amines and the catalytic activity of CGCs built off of the amines was determined for aminosilicas synthesized by a protection/deprotection method. The second part of this work involved developing organic/inorganic hybrid materials as heterogeneous Bronsted acidic cocatalysts for activation of olefin polymerization precatalysts. This was the first reported organic/inorganic hybrid sulfonic acid functionalized silica material capable of activating metallocenes for the polymerization of ethylene when small amounts of an alkylaluminum was added. Lastly, an organic/inorganic hybrid hyperbranched aminosilica material capable of capturing carbon dioxide from flue gas streams was synthesized. This material was determined to capture CO2 with capacities higher than currently reported aminosilica adsorbents.

Hicks, Jason Christopher

179

Detection of hepatitis B virus DNA in serum by polymerase chain reaction amplification and microtiter sandwich hybridization.  

PubMed Central

We have developed a microtiter sandwich hybridization assay for the detection of polymerase chain reaction (PCR)-amplified hepatitis B virus (HBV) sequences. This assay utilizes an enzyme-linked immunosorbent assay-like format in which cloned DNA containing a sequence complementary to half of one PCR product strand is immobilized in microtiter wells. A biotin-labeled DNA sequence complementary to the other portion of the same PCR product strand is used as the probe. The DNAs from 69 hepatitis B surface antigen-positive serum samples and 16 antigen-negative control samples were amplified by the PCR procedure, and the product was detected by Southern and sandwich hybridization. Both detection procedures were capable of detecting as few as five copies of HBV DNA. Compared with Southern hybridization, the sandwich hybridization assay exhibited a sensitivity of 100% and a specificity of 95% for the detection of amplified HBV sequences. Unlike Southern hybridization, however, the sandwich hybridization assay employs a nonradioactive probe and allows easy handling of large numbers of samples. DNA was detected in 74% of the antigen-positive samples. All of the antigen-negative samples (healthy blood donors) were negative for HBV DNA by both procedures. PMID:2199501

Keller, G H; Huang, D P; Shih, J W; Manak, M M

1990-01-01

180

Kinetics of reactions of derivatives of bischloromethylphosphinic acid with amines  

Microsoft Academic Search

The authors have made a kinetic study of nucleophilic replacement of chlorine by an amino group in derivatives of bischloromethylphosphinic acid. The process takes place by an SN1-mechanism in the case of weak nucleophilic reagents (the aniline type) and by an Sn2-mechanism in the case of strong nucleophilic reagents (benzylamine type).

M. K. Il'ina; I. M. Shermergorn

1969-01-01

181

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

182

Label-Free Potentiometry for Detecting DNA Hybridization Using Peptide Nucleic Acid and DNA Probes  

PubMed Central

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

183

Dynamic kinetic resolution of N-benzoyl-DL-amino acids via peptide bond forming reactions.  

PubMed

Dynamic kinetic resolution (DKR) was demonstrated in the carbodiimide-mediated couplings of N-benzoyl-DL-amino acids with L-amino acid esters: the yields of the D-L-peptides significantly exceeded 50% in some cases. N-Benzoyl-DL-t-leucine afforded the D-L-peptide almost exclusively (up to 96% yield) in the reaction with methyl L-prolinate, which is the most efficient DKR obtained in the field of amino acids and derivatives. PMID:19508192

Miyazawa, T; Hamada, T

2010-04-01

184

Stoichiometry of the Reaction of Magnesium with Hydrochloric Acid  

NASA Astrophysics Data System (ADS)

This experiment determines the stoichiometry of a reaction of magnesium and HCl by measuring the pressure of the hydrogen gas produced using a PASCO Absolute Pressure Sensor and a PASCO Science Workshop 500 computer interface. A constant amount of excess HCl is reacted with varying amounts of magnesium solid. The change in pressure in a constant-volume (500-mL Erlenmeyer flask) system is measured. The relationship between moles of magnesium reacted and moles of hydrogen produced are plotted. The primary advantage of this simple procedure is the opportunity for continuous interaction between the teacher, students, and data as the data are being collected. Additional advantages are that students can run several samples in a relatively short time (at least five in a three-hour period) and can develop a real-time understanding of the relationship between the amount of gas produced by a reaction and the pressure in the reaction container. The experiment incorporates the use of technology, graphing, and spreadsheet data analysis and is appropriate for either a general or introductory chemistry laboratory.

Chebolu, Venkat; Storandt, Barbara C.

2003-03-01

185

Characterization of the products formed by the reaction of trichlorocyanuric acid with 2-propanol.  

PubMed

We report a recent investigation into the death of a cat that was initially thought to involve intentionally burning the animal via the use of an ignitable liquid. The exposure of the animal to flame was ruled out. Instead, forensic investigation revealed the intentional mixing together of a common outdoor swimming pool chlorinator, trichlorocyanuric acid (TCCA), and 2-propanol (aka, isopropyl alcohol or rubbing alcohol). The reaction of these two chemicals resulted in the formation of cyanuric acid residue, hydrochloric acid, and the evolution of a significant volume of chlorine gas. Further alpha-chlorination side reactions also occurred between 2-propanol and TCCA to produce a variety of chlorinated 2-propanone species that were detected on the submitted evidence. The identification of the products of both the main reaction and the side reactions allowed the authors to determine what chemicals were originally mixed together by the culprit. PMID:19818110

Sandercock, P Mark L; Barnett, Julie S

2009-11-01

186

Synthesis and anti-tumor activity evaluation of gallic acid-mangiferin hybrid molecule.  

PubMed

To improve the anti-tumor effects of gallic acid and mangiferin, a gallic acid-mangiferin hybrid molecule (GAMA) was synthesized from gallic acid with mangiferin in the presence of ionic liquid ChC1(choline chloride)·2SnC12. Chemical and spectroscopic methods, such as (1)H and (13)C NMR spectroscopy, and HR-ESIMS were used for the structure identification of GA-MA. Using the cell counting kit-8 (CCK-8) assay, the in vitro anti-tumor effects were compared between GA-MA, gallic acid and mangiferin on human hepatoma HepG2, human nasopharyngeal carcinoma CNE, human lung cancer NCI-H460, human ovarian cancer SK-OV-3, and human cervical cancer Hela cells. The results showed that the half inhibitory concentration (IC50) of GA-MA on HepG2, CNE, NCI-H460, SK-OV-3, and Hela cells was significantly lower than that of gallic acid or mangiferin. This showed that GA-MA has a better in vitro anti-tumor effect than gallic acid and mangi-ferin. PMID:23627273

Hu, Xiang-yu; Deng, Jia-gang; Wang, Lin; Yuan, Ye-fei

2013-12-01

187

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

188

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

189

A high power spiral wound lead-acid battery for hybrid electric vehicles  

SciTech Connect

Optima Batteries, Inc. is currently in development of a high power (660 W/kg) spiral wound lead-acid 6V battery with a nominal capacity of 15 Ah. Its exceptional power and excellent thermal characteristics make it a promising choice for hybrid electric vehicle applications. The hybrid electric vehicle presents a new and unique challenge for energy storage systems. The batteries require high power for acceleration and hill climbing and good charge acceptance for regenerative braking and overall energy efficiency. Since the on board auxiliary power unit results in much lower demands for battery energy capacity, lead-acid batteries fit quite well into these performance requirements. Many of the remaining challenges involve the development of battery management systems which must function to maintain the battery pack at peak performance and achieve an economical cycle life. Related to the issue of battery management is information about conditions that may cause damage or unbalance of the pack. Experiments are described investigating the effects of extreme cell reversal on battery capacity and cycle life. The results demonstrate the amazing robustness of the lead-acid battery for tolerating over discharge.

Olson, J.B.; Sexton, E.D. [Optima Advanced Technologies, Inc., Aurora, CO (United States)

1997-12-01

190

Positive Limulus amoebocyte lysate reactions with polyriboinosinic acid x polyribocytidylic acid.  

PubMed Central

The annealed copolymer polyriboinosinic acid x polyriboinosinic acid reacted with Limulus amoebocyte lysate to cause gelation at a concentration approximately 2,000-fold or greater than bacterial endotoxins. This copolymer was pyrogenic in rabbits and demonstrated hypochromicity, but no significant correlation was noted among Limulus amoebocyte lysate reactivity, progenicity, and hypochromicity. Like endotoxin, polyriboinosinic acid x polyribocytidylic acid did not react with purified Limulus coagulogen. Similar concentrations of the homopolymers polyriboinosinic acid and polyribocytidylic acid were negative or significantly below the Limulus amoebocyte lysate reactivity of the copolymear and essentially nonpyrogenic. Thus, polyriboinosinic acid x polyribocytidylic acid is a compound in addition to endotoxin that effects a positive Limulus amoebocyte lysate test. PMID:7419704

Elin, R J; Utter, A E

1980-01-01

191

Positive Limulus amoebocyte lysate reactions with polyriboinosinic acid x polyribocytidylic acid.  

PubMed

The annealed copolymer polyriboinosinic acid x polyriboinosinic acid reacted with Limulus amoebocyte lysate to cause gelation at a concentration approximately 2,000-fold or greater than bacterial endotoxins. This copolymer was pyrogenic in rabbits and demonstrated hypochromicity, but no significant correlation was noted among Limulus amoebocyte lysate reactivity, progenicity, and hypochromicity. Like endotoxin, polyriboinosinic acid x polyribocytidylic acid did not react with purified Limulus coagulogen. Similar concentrations of the homopolymers polyriboinosinic acid and polyribocytidylic acid were negative or significantly below the Limulus amoebocyte lysate reactivity of the copolymear and essentially nonpyrogenic. Thus, polyriboinosinic acid x polyribocytidylic acid is a compound in addition to endotoxin that effects a positive Limulus amoebocyte lysate test. PMID:7419704

Elin, R J; Utter, A E

1980-10-01

192

Urea-acetylene dicarboxylic acid reaction: A likely pathway for prebiotic uracil formation  

NASA Astrophysics Data System (ADS)

A number of routes have been suggested for the prebiotic synthesis of uracil involving the reaction of urea with malic acid, propiolic acid, cyanoacetylene and others. Cyanoacetylene has been detected in the interstellar medium as well as simulated prebiotic experiments. It is therefore plausible that dicyanoacetylene and its hydrolytic product acetylene dicarboxylic acid, (ADCA) may have played a role in chemical evolution. This aspect has been examined in the present work for the synthesis of uracil from ADCA and urea reaction. It was found that when ADCA reacted with urea, uracil was formed only in the presence of phosphoric acid and phosphates. Ammonium phosphates gave higher yields of uracil than other phosphates. In the absence of phosphoric acid or phosphates no uracil formation took place. This type of synthesis could have taken place in prebiotic oceans which contained ammonium phosphates and other salts.

Subbaraman, A. S.; Kazi, Z. A.; Choughuley, A. S. U.; Chadha, M. S.

1980-12-01

193

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

194

REACTIONS OF SAMARIUM IONS WITH ETHYLENEDIAMINETETRA ACETIC ACID  

Microsoft Academic Search

Specific electric conductivity and electromotive forces of isomolar ; serles and series with constant concentrations of samarium were measured in SmCl--; NaâHâY--HâO, SmClâNaâHY--HâO, and Sm(NOâ; )â--NaY--HâO systems. It was found that in acid media the solution ; forms an H (SmY) which dissociates into H\\/sup +\\/ and STASmY!⁻. In alkali ; media a complex anion STASmY!⁻ is formed. The constant

I. V. Tananaev; G. V. Shevchenko

1961-01-01

195

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

196

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; H?iby, N; Stender, H; Guardabassi, L

2014-01-01

197

Switching the BZ reaction with a strong-acid-free gel.  

PubMed

In the present study, a novel gel with a semi-interpenetrating polymer network (semi-IPN) that undergo the Belousov-Zhabotinsky (BZ) reaction without the addition of a strong acid (HNO3 or H2SO4) was developed. The required concentrations of the BZ substrates, sodium bromate (NaBrO3) and malonic acid (MA), under these conditions were higher than under the normal BZ reaction conditions, involving the addition of a strong acid. The period of the BZ reaction with the novel gel (semi-IPN BZ gel) decreased with increasing concentrations of NaBrO3 and MA. Moreover, the connection of the semi-IPN BZ gel to a conventional BZ gel facilitated the reaction in the latter through the propagation of the intermediates from the former to the latter. The BZ reaction stopped when the conventional BZ gel was disconnected from the semi-IPN BZ gel. These results demonstrate that the BZ reaction in the conventional BZ gel underwent on-off switching, controlled by its attachment to the semi-IPN BZ gel. This on-off switching mechanism would be valuable in controlling actuators and robots without strong acids. PMID:24354341

Hara, Yusuke; Yamaguchi, Yoshinori; Mayama, Hiroyuki

2014-01-16

198

Antioxidant effect of non-enzymatic browning reaction products on linoleic acid  

SciTech Connect

In aqueous lysine-sucrose model systems, the effects of reaction time, pH and molar ratio were studied on the formation of non-enzymatic browning reaction (NBR) products. The extent of sucrose hydrolysis was measured and the antioxidant effect of NBR products on linoleic acid emulsions was examined. Nuclear magnetic resonance (NMR) spectra were obtained at various stages of browning. Sucrose produced NMR produces with lysine in an aqueous system at 100/sup 0/C. The C-13 NMR spectra indicated that the NBR started when sucrose and lysine were dissolved in water. The C-13 NMR spectra also showed that heating did not have an effect on the gross composition of polymeric species. The absorbance at 480 nm of 0.75 M lysine-sucrose solution heated up to 6 hours increased with reaction times. The pH values of heated lysine-sucrose solution gradually decreased with reaction time. When 0.75 M sucrose or lysine solution was heated separately up to 6 hours, there were no changes in absorbance in pH. In the pH range of 3.52-6.35, higher absorbance was obtained from heated lysine-sucrose solution at acidic pH levels than at neutral pH levels. As the concentration of lysine and sucrose solution was increased, the absorbance increased. At longer reaction times or acidic pH levels, enhanced hydrolysis of sucrose to reducing sugars resulted in more NBR products. NBR products obtained at a longer reaction time, an acidic pH, and higher concentration of reactants showed a darker brown color and were effective in preventing the formation of peroxides. The oxygen uptake of linoleic acid emulsion having NBR products was smaller than that of linoleic acid emulsion without NBR products. Based on these results, it was concluded that sucrose may act as an antioxidant in processed foods containing both amino acids and lipids.

Kim, N.S.K.

1987-01-01

199

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

200

Selective oxidation of anthracene using inorganic–organic hybrid materials based on molybdovanadophosphoric acids  

Microsoft Academic Search

Inorganic–organic hybrid materials were synthesized by immobilization of molybdovanadophosphoric acids onto mesoporous silicas, such as MCM-41, MCM-48, and SBA-15, through an organic linker. 12-Molybdovanadophosphoric acids of the general formula H3+xPMo12?xVxO40 (x=0–3)?nH2O, such as H4[PMo11VO40]?32.5H2O, H5[PMo10V2O40]?32.5H2O, and H6[PMo9V3O40]?34H2O (represented as V1PA, V2PA, and V3PA, respectively) were prepared and immobilized onto mesoporous silica. All the catalyst materials were characterized by elemental analysis,

Ankur Bordoloi; F. Lefebvre; S. B. Halligudi

2007-01-01

201

Nucleic acid hybridization for detection of cell culture-amplified adenovirus.  

PubMed Central

A number of recombinant plasmids containing genomic segments of adenovirus were constructed. Seven cloned probes, as well as total adenovirus type 2 (Ad2) and Ad16 genomic DNA, were tested by a nucleic acid hybridization technique for sensitivity and specificity in detecting adenoviruses in infected cells. Adenovirus DNA was spotted onto a nitrocellulose filter and hybridized with 32P-labeled DNA probes. The probes, total Ad2 genomic DNA, and plasmid pAd2-H (containing the hexon gene from Ad2 DNA) all detected 10 reference serotypes of five genomic subgroups (A through E) with similar sensitivities. However, plasmid pAd2-H required less preparation time than did total Ad2 DNA. Probes pAd2-F (containing the fiber gene from Ad2) and pAd16-BD (containing the BamHI D fragment from Ad16) hybridized only with reference serotypes from the homologous subgroups (C and B, respectively). Of 101 patient isolates amplified in cells, pAd2-H detected 100% of all isolates from both the homologous and the heterologous subgroups. The detection rates for pAd2-F were 100% (subgroup C) and 3.6% (subgroups A, B, and D), and those for pAd16-BD were 100% (subgroup B) and 9.4% (subgroups A, C, and D). A commercial biotinylated product (Pathogene II) was also included in this study for comparison. Images PMID:3230138

Huang, C; Deibel, R

1988-01-01

202

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

203

Characterization of the esterification reaction in high free fatty acid oils  

NASA Astrophysics Data System (ADS)

Energy and vegetable oil prices have caused many biodiesel producers to turn to waste cooking oils as feedstocks. These oils contain high levels of free fatty acids (FFAs) which make them difficult or impossible to convert to biodiesel by conventional production methods. Esterification is required for ultra-high FFA feedstocks such as Brown Grease. In addition, ultrasonic irradiation has the potential to improve the kinetics of the esterification reaction. 2-level, multi-factor DOE experiments were conducted to characterize the esterification reaction in ultra-high FFA oils as well as determine whether ultrasonic irradiation gives any benefit besides energy input. The study determined that sulfuric acid content had the greatest effect followed by temperature and water content (inhibited reaction). Methanol content had no effect in the range studied. A small interaction term existed between sulfuric acid and temperature. The study also concluded that sonication did not give any additional benefit over energy input.

Altic, Lucas Eli Porter

204

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

205

Kinetics and quantitative structure-activity relationship study on the degradation reaction from perfluorooctanoic acid to trifluoroacetic acid.  

PubMed

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

206

An Investigation of Solid-State Amidization and Imidization Reactions in Vapor Deposited Poly (amic acid)  

SciTech Connect

The condensation polymerization reaction of 4,4'-oxydianiline (ODA) with pyromellitic dianhydride (PMDA) to form poly(amic acid) and the subsequent imidization reaction to form polyimide were investigated for films prepared using vapor deposition polymerization techniques. Fourier-transform infrared spectroscopy (FT-IR), thermal analysis, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) of films at different temperatures indicate that additional solid-state polymerization occurs prior to imidization reactions. Experiments reveal that, upon vapor deposition, poly(amic acid) oligomers form that have a number-average molecular weight of about 1500 Daltons. Between 100 - 130 C these chains undergo additional condensation reaction to form slightly higher molecular weight oligomers. Calorimetry measurements show that this reaction is exothermic ({Delta}H {approx} -30 J/g) with an activation energy of about 120 kJ/mol. Experimental reaction enthalpies are compared to results from ab initio molecular modeling calculations to estimate the number of amide groups formed. At higher temperatures (150 - 300 C) imidization of amide linkages occurs as an endothermic reaction ({Delta}H {approx} +120 J/g) with an activation energy of about 130 kJ/mol. Solid-state kinetics were found to depend on reaction conversion as well as the processing conditions used to deposit films.

Anthamatten, M; Letts, S A; Day, K; Cook, R C; Gies, A P; Hamilton, T P; Nonidez, W K

2004-06-28

207

Investigations relating to ?-amino acids synthesis and reactions of ?-aminobutyric acid  

Microsoft Academic Search

Summary 1.In the condensation of malonic acid with acetaldehyde-ammonia, it was found possible to increase the yield of ß-aminobutyric acid, which was isolated in the form of its benzoyl derivative, up to the value of 36%, if a catalyst (trimethylphenylammonium hydroxide) was used.2.The benzoyl group does not split off from ß-benzamidobutyric acid when the latter is boiled for 6 hr

V. M. Rodionov; N. G. Yartseva

1952-01-01

208

The potential of dairy lactic acid bacteria to metabolise amino acids via non-transaminating reactions and endogenous transamination.  

PubMed

The metabolism of amino acids by 22 starter and 49 non-starter lactic acid bacteria (LAB) was studied in a system consisting of amino acids and non-growing cells without added amino acceptors such as alpha-ketoglutarate. There were significant inter- and intra-species differences in the metabolism of amino acids. Some amino acids such as alanine, arginine, aspartate, serine and branched-chain amino acids (leucine, isoleucine and valine) were utilised, whereas other amino acids such as glycine, ornithine and citrulline were produced. Alanine and aspartate were utilised by some LAB and accumulated during the incubation of other LAB. Arginine was degraded not only by Lactococcus lactis subsp. lactis (the lactococcal subspecies known to catabolise arginine), but also by pediococci, heterofermentative lactobacilli (Lactobacillus brevis and Lb. fermentum) and some unidentified homofermentative lactobacilli. Serine was utilised predominantly by homofermentative Lb. paracasei subsp. paracasei, Lb. rhamnosus and Lb. plantarum. Of the LAB studied, Lb. brevis and Lb. fermentum were the most metabolically active, utilising alanine, arginine, aspartate, glutamate and branched-chain amino acids. Leuconostocs were the least metabolically active, showing little potential to metabolise amino acids. The formation of ammonia and acetate from amino acid metabolism varied both between species and between strains within species. These findings suggest that the potential of LAB for amino acid metabolism via non-transaminating reactions and endogenous transamination will impact both on the physiology of LAB and on cheese ripening, especially when transamination is rate-limiting in the absence of an exogenous amino acceptor such as alpha-ketoglutarate. PMID:12915037

Liu, S-Q; Holland, R; Crow, V L

2003-09-15

209

The influence of SiO2 doping on the microstructure and photochromic behavior of phosphomolybdic acid/polyvinyl pyrrolidone hybrid films  

NASA Astrophysics Data System (ADS)

New hybrid films were synthesized by SiO2 doping into phosphomolybdic acid (PMoA)/polyvinyl pyrrolidone (PVPd) composite system, and the effect of SiO2 doping on microstructure and photochromic properties was studied via atomic force microscope (AFM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectra (UV-vis) and X-ray photoelectron spectroscopy (XPS). The hybrid film surface with dome projection changed rough from smooth after SiO2 doping. The vibrational spectra of FT-IR verified that component of the heteropolyacids and the polymer did not changed, the vibration bands were expanded and had shifted by a few cm-1, and changed interaction between the acid and the polymer after SiO2 doping. The hybrid film exhibited a good photochromic property, which changed from colorless to blue under UV irradiation. The color change intensity of SiO2/PMoA/PVPd film was 1.48 times stronger than that of PMoA/PVPd under the same condition. XPS results indicated that the amount of PMoA in photo-reductive reaction was increased after SiO2 doping.

Dong, Qi; Wang, Xiang-Yu; Lu, Ya-Mei; Sun, Hai-Yan; Meng, Qing-Ling; Liu, Su-Ling; Feng, Wei; Han, Xiang-Kui

2014-10-01

210

Organic Chemistry Jasperse Acid-Base Practice Problems A. Identify each chemical as either an "acid" or a "base" in the following reactions, and  

E-print Network

Organic Chemistry Jasperse Acid-Base Practice Problems A. Identify each chemical as either an "acid" or a "base" in the following reactions, and identify "conjugate" relationships. -You should have one acid the More Acidic for Each of the Following Pairs: Single Variable Problems 16. 17. 18. 19. 20. 21. O O O OH

Jasperse, Craig P.

211

Convenient and Efficient Palladium-Catalyzed Coupling Reaction Between Ferroceneboronic Acid and Organic Triflates  

Microsoft Academic Search

A simple and efficient palladium (Pd)–catalyzed Suzuki cross-coupling reaction between ferroceneboronic acid and organic triflates for the preparation of monosubstituted ferrocene derivatives has been developed. A systematic study of various solvents, bases, and catalysts revealed that the combination of Pd(PPh3)4 (0.025 equiv) and K3PO4 (2 equiv) in refluxing dioxane gave reproducible and excellent yields of the coupling products. The reaction

Bohua Long; Yingbin Yang; Lanxiang Wang; Weimin He; Jiannan Xiang

2010-01-01

212

Antioxidant effect of non-enzymatic browning reaction products on linoleic acid  

Microsoft Academic Search

In aqueous lysine-sucrose model systems, the effects of reaction time, pH and molar ratio were studied on the formation of non-enzymatic browning reaction (NBR) products. The extent of sucrose hydrolysis was measured and the antioxidant effect of NBR products on linoleic acid emulsions was examined. Nuclear magnetic resonance (NMR) spectra were obtained at various stages of browning. Sucrose produced NMR

N. S. K

1987-01-01

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

Rh(I)-catalyzed carbonylative cyclization reactions of alkynes with 2-bromophenylboronic acids leading to indenones.  

PubMed

The Rh-catalyzed reaction of alkynes with 2-bromophenylboronic acids involves carbonylative cyclization to give indenones. The key steps in the reaction involve the addition of an arylrhodium(I) species to an alkyne and the oxidative addition of C-Br bonds on the adjacent phenyl ring to give vinylrhodium(I) species II. The regioselectivity depends on both the electronic and the steric nature of the substituents on the alkynes. A bulky group and an electron-withdrawing group favor the -position of indenones. In the case of silyl- or ester-substituted alkynes, the regioselectivity is extremely high. The selectivity increases in the order SiMe3 > COOR > aryl > alkyl. The reaction of norbornene with 2-bromophenylboronic acids under 1 atm of CO gives the corresponding indanone derivative. The reaction of alkynes with 2-bromophenylboronic acids under nitrogen gives naphthalene derivatives, in which two molecules of alkynes are incorporated. A vinylrhodium complex similar to II can also be generated by a different route by employing 2-bromophenyl(trimethylsilyl)acetylene and arylboronic acids in the presence of Rh(I) complex as the catalyst, resulting in the formation of indenones. The reaction of 1-(2-bromophenyl)-hept-2-yn-1-one with PhB(OH)2 in the presence of Rh(I) complex also resulted in carbonylative cyclization to give an indan-1,3-dione derivative. PMID:17417848

Harada, Yasuyuki; Nakanishi, Jun; Fujihara, Hirokazu; Tobisu, Mamoru; Fukumoto, Yoshiya; Chatani, Naoto

2007-05-01

215

A study of the reaction between metal ions and thiomalic acid  

E-print Network

A STUDY OF THE REACTION BETWEEN METAL IONS AND THIOMALIC ACID A Thesis By Clyde Ernest Michel Submitted to the Graduate School of' the Agricultural and Mechanical College of' Texas in partial gulf'ullment of' the requirements for the degree of...' MASTER OF SCIENCE May 196$ Ma/or Subject: Chemistry A STUDY OF THE REACTION BETWEEN METAL IONS AND THIOMALIC ACID A Thesis Clyde Ernest Michel Approved as to style and content by: (Chalrma of Committee) f~~RM+ ? CAW ci && ~-~- (Head...

Michel, Clyde Ernest

2012-06-07

216

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

PubMed

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

2012-11-13

217

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

218

Geranic Acid Formation, an Initial Reaction of Anaerobic Monoterpene Metabolism in Denitrifying Alcaligenes defragrans  

PubMed Central

Monoterpenes with an unsaturated hydrocarbon structure are mineralized anaerobically by the denitrifying ?-proteobacterium Alcaligenes defragrans. Organic acids occurring in cells of A. defragrans and culture medium were characterized to identify potential products of the monoterpene activation reaction. Geranic acid (E,E-3,7-dimethyl-2,6-octadienoic acid) accumulated to 0.5 mM in cells grown on ?-phellandrene under nitrate limitation. Cell suspensions of A. defragrans 65Phen synthesized geranic acid in the presence of ?-myrcene, ?-phellandrene, limonene, or ?-pinene. Myrcene yielded the highest transformation rates. The alicyclic acid was consumed by cell suspensions during carbon limitation. Heat-labile substances present in cytosolic extracts catalyzed the formation of geranic acid from myrcene. These results indicated that a novel monoterpene degradation pathway must be present in A. defragrans. PMID:10877798

Heyen, Udo; Harder, Jens

2000-01-01

219

CH activation in strongly acidic media. The co-catalytic effect of the reaction mediumw  

E-print Network

yielding systems utilize Pt2a , Hg2b , Au2c , I2d , and Pd2e catalysts and a concentrated sulfuric acid reaction medium (acetic acid in the case of Pd). The most promising system to date uses Pt(bpym)Cl2 to dramatically decreased rates2a for concentrations lower than 96%. H­D exchange of CH4 in D2SO4 (Fig. 2

Goddard III, William A.

220

A palladium-catalyzed addition reaction of aroyl/heteroaroyl acid anhydrides to norbornenes.  

PubMed

A palladium complex derived from Pd2(dba)3 and dppp catalyzes the addition reaction of aroyl/heteroaroyl acid anhydrides to norbornenes, giving 2-aroyl/heteroaroyl-3-aroyloxy/heteroaroyloxy-bicyclo[2,2,1]heptanes. The C-O bond of acid anhydride is cleaved, and the aroyl/heteroaroyl and aroyloxy/heteroaroyloxy groups are added to alkenes. trans-Adducts are selectively obtained with the endo-benzoyl group and exo-benzoyloxy group. PMID:25347414

Arisawa, Mieko; Tanii, Saori; Yamaguchi, Masahiko

2014-11-01

221

Reaction of 5-ethylidene-2-norbomene with formic acid: cation exchange resins as catalysts  

Microsoft Academic Search

The esterification of formic acid with ethylidene norbornene (ENB), i.e. 5-ethylidene bicyclo[2.2.1]hept 2-ene was carried out with and without cation exchange resins as catalysts. The effect of various parameters e.g. speed of agitation, catalyst loading, mole ratio of the reactants, temperature, concentration of formic acid in aqueous solutions were studied to optimise the reaction conditions; the reusability of catalysts was

Basudeb Saha

1998-01-01

222

SYNTHESES WITH SULFUR CONTAINING NUCLEOPHILES. I. REACTION OF SULFINIC ACIDS WITH 2-HALOGENO-2-NITROETHENYLARENES  

Microsoft Academic Search

The interaction between unsubstituted and p-substituted benzenesulfinic acids and various 2-halogeno-2-nitroethenylarenes at mol ratios sulfinic acid:2-halogeno-2-nitroethenylarene = 1:1 and 2:1 was studied at 0°C and 20°C for 16 and 96 hours. It was proved that, depending on experimental conditions, the reaction results not only in ?-halogeno-?-nitro-?-sulfones but also in ?-nitro-?,?-disulfones, which are obtained by a consecutive process. The quantitative ratio

D. I. Aleksiev; S. Ivanova

1995-01-01

223

Inorganic solid acids and their use in acid-catalyzed hydrocarbon reactions  

Microsoft Academic Search

It is possible to say that solid acid catalysis involves the largest amounts of catalysts used and the largest economical effort in the oil refining and chemical industry. In this review the author has tried to describe perhaps the most important solid acids based on inorganic oxides, going from their preparation procedures and characterization, to their catalytic activity for a

A. Corma

1995-01-01

224

Improved constrained optimization method for reaction-path determination in the generalized hybrid orbital quantum mechanical/molecular mechanical calculations  

NASA Astrophysics Data System (ADS)

The nudged elastic band (NEB) and string methods are widely used to obtain the reaction path of chemical reactions and phase transitions. In these methods, however, it is difficult to define an accurate Lagrangian to generate the conservative forces. On the other hand, the constrained optimization with locally updated planes (CO-LUP) scheme defines target function properly and suitable for micro-iteration optimizations in quantum mechanical/molecular mechanical (QM/MM) systems, which uses the efficient second order QM optimization. However, the method does have problems of inaccurate estimation of reactions and inappropriate accumulation of images around the energy minimum. We introduce three modifications into the CO-LUP scheme to overcome these problems: (1) An improved tangent estimation of the reaction path, which is used in the NEB method, (2) redistribution of images using an energy-weighted interpolation before updating local tangents, and (3) reduction of the number of constraints, in particular translation/rotation constraints, for improved convergence. First, we test the method on the isomerization of alanine dipeptide without QM/MM calculation, showing that the method is comparable to the string method both in accuracy and efficiency. Next, we apply the method for defining the reaction paths of the rearrangement reaction catalyzed by chorismate mutase (CM) and of the phosphoryl transfer reaction catalyzed by cAMP-dependent protein kinase (PKA) using generalized hybrid orbital QM/MM calculations. The reaction energy barrier of CM is in high agreement with the experimental value. The path of PKA reveals that the enzyme reaction is associative and there is a late transfer of the substrate proton to Asp 166, which is in agreement with the recently published result using the NEB method.

Jung, Jaewoon; Re, Suyong; Sugita, Yuji; Ten-no, Seiichiro

2013-01-01

225

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

SciTech Connect

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

Menaa, Bouzid [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan) and PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama (Japan)]. E-mail: bouzidmenaa@noncry.kuicr.kyoto-u.ac.jp; Mizuno, Megumi [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Takahashi, Masahide [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan) and PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama (Japan)]. E-mail: masahide@noncry.kuicr.kyoto-u.ac.jp; Tokuda, Yomei [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Yoko, Toshinobu [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)

2006-02-15

226

Application of peptide nucleic acid to the direct detection of deoxyribonucleic acid amplified by polymerase chain reaction  

Microsoft Academic Search

Double-stranded DNA amplified by polymerase chain reaction (PCR) was detected by peptide nucleic acid (PNA) using a BIAcore™ 2000 biosensor based on surface plasmon resonance (SPR). PNA is an artificial oligo amide that is capable of forming highly stable complexes with complementary oligonucleotides. We succeeded in the direct detection of double-stranded DNA, amplified by PCR with high-sequence specificity. It was

Shinya Sawata; Eriko Kai; Kazunori Ikebukuro; Tetsuya Iida; Takeshi Honda; Isao Karube

1999-01-01

227

Standardized staining methods: Feulgen-Rossenbeck reaction for desoxyribonucleic acid and periodic acid-Schiff (PAS) procedure.  

PubMed

A project group working under the European Confederation of Laboratory Medicine (ECLM) presents recommendations for standardized procedures for the Feulgen-Rossenbeck-Schiff and the periodic acid-Schiff (PAS) reactions on cytological and histological material. The advantages and disadvantages of such standardized procedures are presented here in a preamble. Both users and manufacturers are encouraged to give their opinions with a view to achieving consensus on these procedures and on how further work on these lines may proceed. PMID:12229932

Lyon, H O; Schulte, E K; Prento, P; Barer, M R; Béné, M-C

2002-05-01

228

Kinetic resolution of acids in acylation reactions in the presence of chiral tertiary amines  

SciTech Connect

Asymmetric synthesis has now become an important method for the production of optically active compounds, and its most attractive form is asymmetric catalysis. This work was devoted to an investigation into asymmetric catalysis with chiral tertiary amines in acylation reactions. During the acylation of alcohols and amines by the action of racemic 2-phenylpropionic and 2-methyl-3-phenylpropionic acids in the presence of S-nicotine the initial acids are resolved kinetically. The (R)-2-phenylpropionic acid obtained in this way had an optical purity of 0.5-1.5%.

Potapov, V.M.; Dem'yanovich, V.M.; Khlebnikov, V.A.

1988-07-10

229

Glucuronidation of bile acids under flow conditions: design of experiments and Koenigs-Knorr reaction optimization.  

PubMed

An efficient method for the C3-glucuronidation of bile acids is developed under flow conditions. A modular mesoreactor assisted flow set-up was combined with statistical design of experiments to speed up the optimization of the Koenigs-Knorr reaction in terms of yield, regioselectivity, costs, as well as technical and practical standpoints. Using the optimal conditions, selective glucuronidation of naturally occurring bile acids was successfully achieved offering a new, valuable route to C3-glucuronidated bile acids useful for biological, diagnostic and PK/ADMET investigations. PMID:25338931

Mostarda, Serena; Filipponi, Paolo; Sardella, Roccaldo; Venturoni, Francesco; Natalini, Benedetto; Pellicciari, Roberto; Gioiello, Antimo

2014-12-21

230

Versatile synthesis of amino acid functionalized nucleosides via a domino carboxamidation reaction  

PubMed Central

Summary Functionalized oligonucleotides have recently gained increased attention for incorporation in modified nucleic acid structures both for the design of aptamers with enhanced binding properties as well as the construction of catalytic DNA and RNA. As a shortcut alternative to the incorporation of multiple modified residues, each bearing one extra functional group, we present here a straightforward method for direct linking of functionalized amino acids to the nucleoside base, thus equipping the nucleoside with two extra functionalities at once. As a proof of principle, we have introduced three amino acids with functional groups frequently used as key-intermediates in DNA- and RNAzymes via an efficient and straightforward domino carboxamidation reaction. PMID:25383128

Gheerardijn, Vicky; Van den Begin, Jos

2014-01-01

231

Miniature reaction chamber and devices incorporating same  

Microsoft Academic Search

The present invention generally relates to miniaturized devices for carrying out and controlling chemical reactions and analyses. In particular, the present invention provides devices which have miniature temperature controlled reaction chambers for carrying out a variety of synthetic and diagnostic applications, such as PCR amplification, nucleic acid hybridization, chemical labeling, nucleic acid fragmentation and the like.

Richard A. Mathies; Adam T. Woolley

2000-01-01

232

Miniature reaction chamber and devices incorporating same  

DOEpatents

The present invention generally relates to miniaturized devices for carrying out and controlling chemical reactions and analyses. In particular, the present invention provides devices which have miniature temperature controlled reaction chambers for carrying out a variety of synthetic and diagnostic applications, such as PCR amplification, nucleic acid hybridization, chemical labeling, nucleic acid fragmentation and the like.

Mathies, Richard A. (Moraga, CA); Woolley, Adam T. (Albany, CA)

2000-10-17

233

Multivalent capture and detection of cancer cells with DNA nanostructured biosensors and multibranched hybridization chain reaction amplification.  

PubMed

Sensitive detection of cancer cells plays a critically important role in the early detection of cancer and cancer metastasis. However, because circulating tumor cells are extremely rare in peripheral blood, the detection of cancer cells with high analytical sensitivity and specificity remains challenging. Here, we have demonstrated a simple, sensitive and specific detection of cancer cells with the detection sensitivity of four cancer cells, which is lower than the cutoff value with respect to correlation with survival outcomes as well as predictive of metastatic disease in clinical diagnostics. We re-engineered the hybridization chain reaction (HCR) to multibranched HCR (mHCR) that can produce long products with multiple biotins for signal amplification and multiple branched arms for multivalent binding. The capturing gold surface is modified with DNA tetrahedral probes, which provide superior hybridization conditions for the multivalent binding. The synergetic effect of mHCR amplification and multivalent binding lead to the high sensitivity of our detection platform. PMID:24989246

Zhou, Guobao; Lin, Meihua; Song, Ping; Chen, Xiaoqing; Chao, Jie; Wang, Lianhui; Huang, Qing; Huang, Wei; Fan, Chunhai; Zuo, Xiaolei

2014-08-01

234

Formation of metal nanoparticles in a polymer nanofiber: a hybrid material for gas-phase catalytic reactions  

NASA Astrophysics Data System (ADS)

This paper describes the synthesis and characterization of a metal-polymer hybrid material formed by the combination of palladium nanoparticles and poly-o-phenylenediamine (poly-PDA). The preparation technique is based on an in situ, one-pot chemical synthesis route using palladium acetate and o-phenylenediamine as precursors. The composite material was characterized by optical, thermal and micro-analytical techniques. The characterization techniques show the successful synthesis of the hybrid material. This composite material was used as a catalyst for a model gas-phase hydrogenation reaction. The activation and deactivation of the catalyst is discussed in relation to the effect of temperature and the phase transition of the polymer.

Maphala, Tshifhiwa; Mondal, Kartick; Witcomb, Mike; Scurrell, Mike; Islam, Rafique Ul; Mallick, Kaushik

2008-08-01

235

Engineering hybrid between nickel oxide and nickel cobaltate to achieve exceptionally high activity for oxygen reduction reaction  

NASA Astrophysics Data System (ADS)

The porous NiO/NiCo2O4 nanotubes are prepared via a coaxial electrospinning technique followed by an annealing treatment. The resultant NiO/NiCo2O4 hybrid is developed as a highly efficient electrocatalyst, which exhibits significantly enhanced electrocatalytic activity, long-term operation stability, and tolerance to crossover effect compared to NiO nanofibers, NiCo2O4 nanofibers and commercial Pt(20%)/C for oxygen reduction reactions (ORR) in alkaline environment. The excellent electrocatalytic performance may be attributed to the unique microstructures of the porous NiO/NiCo2O4 nanotubes, such as heterogeneous hybrid structure, open porous tubular structure, and the well dispersity of the two components. Moreover, the promising and straightforward coaxial electrospinning proves itself to be an efficient pathway for the preparation of nanomaterials with tubular architectures and it can be used for large-scale production of catalysts in fuel cells.

Cui, Zhentao; Wang, Shuguang; Zhang, Yihe; Cao, Minhua

2014-12-01

236

Thermographic study of reactions between ethylene glycol phosphorous acid and alkyl halides  

Microsoft Academic Search

Summary 1.A thermographic study of the isomerization of mixed ethylene glycol esters of phosphorous acid under the action of alkyl halides shows that in harmony with the data of A. E. Arbuzov and N. A. Razumova, the reaction proceeds in two steps which are accompanied by exothermic effects. The thermographic records do not definitely indicate the step of addition of

B. A. Arbuzov; M. E. Saikina; V. M. Zoroastrova

1957-01-01

237

Enantioselective synthesis of succinic acids and ?-lactones via palladium catalysed allylic substitution reactions  

Microsoft Academic Search

The palladium catalysed reaction between non-symmetrical allyl acetates and sodiodimethylmalonate proceeds in high yields and enantioselectivities (up to 99% ee) using a diphenylphosphinoaryl oxazoline ligand. The so-formed substitution products are transformed into enantiomerically enriched succinic acids and also into enantiomerically enriched ?-lactones.

Steven J Coote

1995-01-01

238

Moisture Stable Dialkylimidazolium Salts as Heterogeneous and Homogeneous Lewis Acids in the Diels-Alder Reaction  

Microsoft Academic Search

Moisture stable dialkylimidazolium salts act as heterogeneous and homogeneous Lewis acid catalysts in the Diels-Alder reaction of both crotonaldehyde and methacrolein with cyclopentadiene at low temperatures. The heterogeneous system allows the catalyst to be efficiently recycled. © 1997 Elsevier Science Ltd.

Joshua Howarth; Keith Hanlon; Darren Fayne; Paul McCormac

1997-01-01

239

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

Microsoft Academic Search

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

Netzel

1991-01-01

240

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

241

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 dioxide to chlorite and oxidation of iodide ions to iodine. This results in a decreased amplitude

Epstein, Irving R.

242

Reactions on sulphuric acid aerosol and on polar stratospheric clouds in the Antarctic stratosphere  

SciTech Connect

Heterogeneous chemistry producing active chlorine has been identified as crucial to Antarctic ozone depletion. Most attention has focused on reactions on solid polar stratospheric cloud (PSC) particles, although there is still no satisfactory understanding of the microchemical incorporation of HCl in PSCs. The alternative mechanism involving sulphuric acid aerosol as the reaction surface has been considered at lower latitudes, but its role in the special conditions of the polar stratosphere has been largely ignored. Recent data from the Antarctic stratosphere have suggested the HCl is present in sulphuric acid aerosol that remains liquid even at the lowest stratospheric temperatures. The available laboratory data show that cold, relatively dilute, sulphuric acid is particularly able to take up HCl that is available for reaction provided the aerosol remains liquid. Fast heterogeneous reaction rates compared to those at mid-latitudes will produce active chlorine rapidly. Since the aerosol is present with significant surface area throughout the lower stratosphere, it should be very effective for heterogeneous reaction once temperatures drop. These surfaces, rather than PSCs, could host the initial conversion of Cl to its active form over the Antarctic.

Wolff, E.W.; Mulvaney, R.

1991-06-01

243

Cirrus cloud mimic surfaces in the laboratory: organic acids, bases and NOx heterogeneous reactions  

NASA Astrophysics Data System (ADS)

CIRRUS CLOUD MIMIC SURFACES IN THE LABORATORY:ORGANIC ACIDS, BASES AND NOX HETEROGENEOUS REACTIONS. B. ORiordan, J. Sodeau Department of Chemistry and Environment Research Institute, University College Cork, Ireland j.sodeau@ucc.ie /Fax: +353-21-4902680 There are a variety of biogenic and anthropogenic sources for the simple carboxylic acids to be found in the troposphere giving rise to levels as high as 45 ppb in certain urban areas. In this regard it is of note that ants of genus Formica produce some 10Tg of formic acid each year; some ten times that produced by industry. The expected sinks are those generally associated with tropospheric chemistry: the major routes studied, to date, being wet and dry deposition. No studies have been carried out hitherto on the role of water-ice surfaces in the atmospheric chemistry of carboxylic acids and the purpose of this paper is to indicate their potential function in the heterogeneous release of atmospheric species such as HONO. The deposition of formic acid on a water-ice surface was studied using FT-RAIR spectroscopy over a range of temperatures between 100 and 165K. In all cases ionization to the formate (and oxonium) ions was observed. The results were confirmed by TPD (Temperature Programmed Desorption) measurements, which indicated that two distinct surface species adsorb to the ice. Potential reactions between the formic acid/formate ion surface and nitrogen dioxide were subsequently investigated by FT-RAIRS. Co-deposition experiments showed that N2O3 and the NO+ ion (associated with water) were formed as products. A mechanism is proposed to explain these results, which involves direct reaction between the organic acid and nitrogen dioxide. Similar experiments involving acetic acid also indicate ionization on a water-ice surface. The results are put into the context of atmospheric chemistry potentially occuring on cirrus cloud surfaces.

Sodeau, J.; Oriordan, B.

2003-04-01

244

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.

245

Geminal Br?nsted 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

246

Negative Resist for i-Line Lithography Utilizing Acid Catalyzed Silanol-Condensation Reaction  

NASA Astrophysics Data System (ADS)

Negative resist systems composed of a novolak resin, diphenylsilanediol (Ph2Si(OH)2) and an acid generator are investigated for i-line lithography. The reaction in this resist system is based on an acid-catalyzed condensation reaction; the acid produced in the exposed area induces a condensation reaction of Ph2Si(OH)2 during post-exposure baking. The condensation product, siloxane, acts as an aqueous-base dissolution inhibitor, while silanol compounds in unexposed areas work as dissolution accelerators. The resist composed of a novolak resin, Ph2Si(OH)2 and 2-naphthoylmethyl-tetramethylenesulfonium hexafluoroantimonate (NMTMS-SbF6) shows a sensitivity of about 200 mJ/cm2 at 365 nm. This sensitivity is lower than that at 248 nm when triphenylsulfonium triflate (Ph3S+OTf-) is used as an acid generator, which can be ascribed to the low quantum yield of acid generation from NMTMS-SbF6. Using this resist, 0.3 ?m space patterns with 1 ?m film thickness were obtained by combining an i-line stepper with a phase-shifting mask.

Hayashi, Nobuaki; Tadano, Keiko; Tanaka, Toshihiko; Shiraishi, Hiroshi; Ueno, Takumi; Iwayanagi, Takao

1990-11-01

247

Lactic acid conversion to 2,3-pentanedione and acrylic acid over silica-supported sodium nitrate: Reaction optimization and identification of sodium lactate as the active catalyst  

SciTech Connect

Lactic acid is converted to 2,3-pentanedione, acrylic acid, and other products in vapor-phase reactions over silica-supported sodium lactate formed from sodium nitrate. Multiparameter optimization of reaction conditions using a Box-Benkhen experimental design shows that the highest yield and selectivity to 2,3-pentanedione are achieved at low temperature, elevated pressure, and long contact time, while yield and selectivity to acrylic acid are most favorable at high temperature, low pressure, and short contact time. Post-reaction Fourier transform infrared spectroscopic analyses of the catalyst indicate that sodium nitrate as the initial catalyst material is transformed to sodium lactate at the onset of reaction via proton transfer from lactic acid to nitrate. The resultant nitric acid vaporizes as it is formed, leaving sodium lactate as the sole sodium-bearing species on the catalyst during reaction. 19 refs., 8 figs., 5 tabs.

Wadley, D.C.; Tam, M.S.; Miller, D.J. [Michigan State Univ., East Lansing, MI (United States)] [and others] [Michigan State Univ., East Lansing, MI (United States); and others

1997-01-15

248

Reduction of benzylic alcohols and ?-hydroxycarbonyl compounds by hydriodic acid in a biphasic reaction medium  

PubMed Central

Summary The synthetic protocol for the reduction of alcohols to hydrocarbons by using hydriodic acid, first described by Kiliani more than 140 years ago, was improved to be more applicable to organic synthesis. Instead of a strongly acidic, aqueous solution, a biphasic toluene–water reaction medium was used, which allowed the conversion of primary, secondary and tertiary benzylic alcohols, in good yields and short reaction times, into the corresponding hydrocarbons. Red phosphorous was used as the stoichiometric reducing agent. Keto, ester, amide or ether groups are tolerated, and catalytic amounts of hydriodic acid (0.2 equiv) in the presence of 0.6 equiv phosphorous are sufficient to achieve conversion. PMID:22423302

Dobmeier, Michael; Herrmann, Josef M; Lenoir, Dieter

2012-01-01

249

Characterization of Bacillus subtilis, Bacillus pumilus, Bacillus licheniformis, and Bacillus amyloliquefaciens by Pyrolysis Gas-Liquid Chromatography, Deoxyribonucleic Acid-Deoxyribonucleic Acid Hybridization, Biochemical Tests, and API Systems  

Microsoft Academic Search

Eight strains each of Bacillus subtilis, Bacillus pumilus, Bacillus lichenifor- mis, and Bacillus amyloliquefaciens were analyzed by using pyrolysis gas-liquid chromatography. Statistical analysis with canonical variates gave four well-sep- arated groups, which represented the four species. Further analysis of the same strains by deoxyribonucleic acid-deoxyribonucleic acid hybridization and API identification systems confirmed the discrimination obtained with pyrolysis gas- liquid chromatography.

A. G. O'DONNELL; J. R. NORRIS; R. C. W. BERKELEY; D. CLAUS; T. KANEK; N. A. LOGAN

250

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

251

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

252

Relative Reaction Rates of Sulfamic Acid and Hydroxylamine with Nitric Acid  

SciTech Connect

This report describes a study of comparative reaction rates where the reductant is in excess, as in the 1B bank in the Purex process. The results of this work apply to planned plant tests to partially substitute HAN for the ferrous sulfamate reductant in the Purex 1B bank.

Karraker, D.G.

2001-03-28

253

Leucine dissimilation to isovaleric and isocaproic acids by cell suspensions of amino acid fermenting anaerobes: the Stickland reaction revisited.  

PubMed

Freshly compared cell suspensions of clostridia (Clostridium bifermentans, C. botulinum proteolytic type A, C. difficile, C. sordellii, and C. sporogenes) and Peptostreptococcus anaerobius converted leucine to isovaleric (iV) and isocaproic (iC) acids in the absence of other amino acids. The optimal pH for conversion was between 8 and 9 at 37 degrees C. The stoichiometry of reaction was compatible with that expected for the Stickland reaction, as the ratio of iV to iC was 1:2, the amount of CO2 produced was equivalent to that of iV, and ammonium ion concentrations were equal to the total C5 and C6 acids formed. The presence of alanine and valine (proton donors in the Stickland reaction) in incubations effectively increased the concentration of iC at the expense of iV production, implying that leucine acted there primarily as a proton acceptor. Glycine and proline (proton acceptors) stimulated both iV and iC production from leucine, but increases in iV concentrations were proportionately greater than for iC so that leucine was primarily a proton donor in the presence of proton acceptors. Glucose stimulated the conversion of leucine to volatile fatty acids but favoured iC production. Production of iC from leucine was inhibited by surface active compounds (cetyltrimethylammonium bromide and desoxycholate) as well as arsenite and iodoacetate. The redox dyes methyl viologen and phenosafranine inhibited iC production more severely than iV production, as did the nitroimidazole antimicrobial agent, metronidazole. PMID:6805929

Britz, M L; Wilkinson, R G

1982-03-01

254

An improved synthesis of morpholino-glycoamino acids  

Microsoft Academic Search

The current synthesis of hybrid morpholino-glycoamino acids through double reductive amination is characterized by modest yields and lengthy reaction times. We propose an optimized procedure that results in improved yields and the shortest reaction times reported so far.

Marko Anderluh

2006-01-01

255

Kinetics and reaction engineering of levulinic acid production from aqueous glucose solutions.  

PubMed

We have developed a kinetic model for aqueous-phase production of levulinic acid from glucose using a homogeneous acid catalyst. The proposed model shows a good fit with experimental data collected in this study in a batch reactor. The model was also fitted to steady-state data obtained in a plug flow reactor (PFR) and a continuously stirred tank reactor (CSTR). The kinetic model consists of four key steps: (1) glucose dehydration to form 5-hydroxymethylfurfural (HMF); (2) glucose reversion/degradation reactions to produce humins (highly polymerized insoluble carbonaceous species); (3) HMF rehydration to form levulinic acid and formic acid; and (4) HMF degradation to form humins. We use our model to predict the optimal reactor design and operating conditions for HMF and levulinic acid production in a continuous reactor system. Higher temperatures (180-200 °C) and shorter reaction times (less than 1 min) are essential to maximize the HMF content. In contrast, relatively low temperatures (140-160 °C) and longer residence times (above 100 min) are essential for maximum levulinic acid yield. We estimate that a maximum HMF carbon yield of 14% can be obtained in a PFR at 200 °C and a reaction time of 10 s. Levulinic acid can be produced at 57% carbon yield (68% of the theoretical yield) in a PFR at 149 °C and a residence time of 500 min. A system of two consecutive PFR reactors shows a higher performance than a PFR and CSTR combination. However, compared to a single PFR, there is no distinct advantage to implement a system of two consecutive reactors. PMID:22696262

Weingarten, Ronen; Cho, Joungmo; Xing, Rong; Conner, William Curtis; Huber, George W

2012-07-01

256

Acid–base reactions between an acidic soil and plant residues  

Microsoft Academic Search

The elemental composition of residues of maize (Zea mays), sorghum (S. bicolor), groundnuts (Arachis hypogea), soya beans (Glycine max), leucaena (L. leucocephala), gliricidia (G. sepium), and sesbania (S. sesban) was determined as a basis for examining their alkalinity when incorporated into an acidic Zambian Ferralsol. Potential (ash) alkalinity, available alkalinity by titration to pH 4 and soluble alkalinity (16 h

G. M. Sakala; D. L. Rowell; C. J. Pilbeam

2004-01-01

257

Hybrid lead-acid battery with reticulated vitreous carbon as a carrier- and current-collector of negative plate  

Microsoft Academic Search

Bare reticulated vitreous carbon (RVC) plated electrochemically with thin layer of lead was investigated as a negative plate carrier- and current-collector material for lead-acid batteries. Hybrid flooded single cell lead-acid batteries containing one negative plate based on a new type (RVC or Pb\\/RVC) of carrier\\/current-collector and two positive plates based on Pb–Ca grid collectors were assembled and subjected to charge\\/discharge

A. Czerwi?ski; S. Obr?bowski; J. Kotowski; Z. Rogulski; J. Skowro?ski; M. Bajsert; M. Przysta?owski; M. Buczkowska-Biniecka; E. Jankowska; M. Baraniak; J. Rotnicki; M. Kopczyk

2010-01-01

258

Intertribal somatic hybrids between Brassica napus and Camelina sativa with high linolenic acid content  

Microsoft Academic Search

Intertribal somatic hybrids of Brassica napus and Camelina sativa were developed by protoplast electrofusion. Hybrid identity of the regenerants was determined using flow cytometric analysis\\u000a of nuclear DNA content and simple sequence repeat (SSR) marker analysis. Three hybrids exhibited specific bands for B. napus and C. sativa. These hybrids showed intermediate leaf, flower and seed morphology compared with the two

J. J. Jiang; X. X. Zhao; W. Tian; T. B. Li; Y. P. Wang

2009-01-01

259

Adsorption and Reaction of Formic Acid on a Pseudomorphic Palladium Monolayer on Chen Xu and D. W. Goodman*  

E-print Network

Adsorption and Reaction of Formic Acid on a Pseudomorphic Palladium Monolayer on Mo(110) Chen XuVed: April 28, 1995; In Final Form: September 8, 1995X The adsorption and reaction of formic acid, HCOOH-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS). On multilayer palladium

Goodman, Wayne

260

Diastereoselectivity in Lewis-Acid Catalyzed Mukaiyama Aldol Reactions: A DFT Study  

PubMed Central

The basis for diastereoselectivity in Lewis acid-catalyzed Mukaiyama aldol reactions was studied using density functional theory. By exploring the conformations of the transition structures for the diastereodifferentiating step of seven different reactions, simple models were generated. The effects of varying the substituents on the enol carbon and the ?-carbon of the silyl enol ether from methyl to tert-butyl groups and the substituent on the aldehyde between methyl and phenyl groups were investigated by comparison of the transition structures for different reactions. Expanding on the previous qualitative models by Heathcock and Denmark, we found that while the pro-anti pathways takes place via antiperiplanar transition structures, the pro-syn pathways prefer synclinal transition structures. The relative steric effects of the Lewis acid and trimethyl silyl groups and the influence of E/Z isomerism on the aldol transition state were investigated. By calculating 36 transition structures at the M06/6-311G*//B3LYP/6-31G* level of theory and employing the IEFPCM polarizable continuum model for solvation effects, this study expands the mechanistic knowledge and provides a model for understanding the diastereoselectivity in Lewis acid-catalyzed Mukaiyama aldol reactions. PMID:22891640

Lee, Joshua M.; Helquist, Paul; Wiest, Olaf

2012-01-01

261

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

262

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

263

An electrochemiluminescent microRNA biosensor based on hybridization chain reaction coupled with hemin as the signal enhancer.  

PubMed

In this study, a new universal biosensor based on luminol anodic electrochemiluminescence (ECL) for the detection of microRNA-155 was constructed by using hydrogen peroxide (H2O2) as a co-reactant and hemin as a catalyzer for signal amplification. The bare glassy carbon electrode (GCE) was first electrodeposited with Au nanoparticles (AuNPs). Then, helper DNA, which was partly complementary with the hairpin DNA chains, was assembled on the prepared GCE. Target microRNA-155 and the hairpin hybridization chains could create a formation of extended double-stranded DNA (dsDNA) polymers through the displacement of hybridization chains and the hybridization chain reaction (HCR). The HCR-generated dsDNA polymers give rise to the intercalation of a lot of hemin which could catalyze the oxidation of H2O2, leading to a remarkably amplified ECL signal output. The proposed biosensor showed a wide linear range from 5 fM to 50 pM with a relatively low detection limit of 1.67 fM for microRNA-155 detection. With excellent selectivity, good stability and high sensitivity, the proposed biosensor is promising in the development of a high-throughput assay of microRNA-155. PMID:24722579

Zhang, Pu; Wu, Xiaoyan; Chai, Yaqin; Yuan, Ruo

2014-06-01

264

Mediator-free triple-enzyme cascade electrocatalytic aptasensor with exonuclease-assisted target recycling and hybridization chain reaction amplification.  

PubMed

The amplified sensitive detection of protein is essential to biomedical research as well as clinical diagnosis. Here, we developed an ultrasensitive mediator-free triple-enzyme cascade electrocatalytic aptasensor for thrombin detection on the basis of exonuclease-assisted target recycling and hybridization chain reaction (HCR) amplification strategy. The double strands constructed by the hybridization of thrombin binding aptamer (S1) with its complementary strand (S2) were firstly assembled on the electrode. Upon addition of target to the system, the S1 recognized thrombin and left off electrode to make space for assembly of hybrid-primer probe (H0). Then, the H0 triggered the HCR to form the multi-functional hemin/G-quadruplex DNAzyme nanowires. In the mediator-free triple-enzyme cascade electrocatalytic amplification system, the hemin/G-quadruplex DNAzyme nanowires here simultaneously played three roles: the redox probe, NADH oxidase and HRP-mimicking DNAzyme, respectively, which effectively avoided the fussy redox probe and enzyme labeling process, serving a useful alternative or supplement to conventional assays that typically suffer from complexity and poor sensitivity. Additionally, in order to improve the assembly amount of hemin/G-quadruplex DNAzyme nanowire, the exonuclease-assisted target recycling amplification was used for the continuous removal of S1. As a result, the proposed method can detect thrombin specifically with a detection limit as low as 20 fM. PMID:24419079

Peng, Kanfu; Zhao, Hongwen; Yuan, Yali; Yuan, Ruo; Wu, Xiongfei

2014-05-15

265

The influence of a dietary lipid source on growth, muscle fatty acid composition and erythrocyte osmotic fragility of hybrid tilapia  

Microsoft Academic Search

An 8-week feeding trial was conducted to determine the effects of various dietary lipids on the growth, tissue proximate composition, muscle fatty acid composition and erythrocyte osmotic fragility of red hybrid tilapia, Oreochromis sp. Five isonitrogenous and isoenergetic semipurified diets were supplemented with 10% of either cod liver oil (CLO), sunflower oil (SFO), crude palm oil (CPO), crude palm kernel

Wing-Keong Ng; Phaik-Kin Lim; Hadizah Sidek

2001-01-01

266

Reactions of clofibric acid with oxidative and reductive radicals-Products, mechanisms, efficiency and toxic effects  

NASA Astrophysics Data System (ADS)

The degradation of clofibric acid induced by hydroxyl radical, hydrated electron and O2-•/HO2• reactive species was studied in aqueous solutions. Clofibric acid was decomposed more effectively by hydroxyl radical than by hydrated electron or O2-•/HO2•. Various hydroxylated, dechlorinated and fragmentation products have been identified and quantified. A new LC-MS method was developed based on 18O isotope labeling to follow the formation of hydroxylated derivatives of clofibric acid. Possible degradation pathways have been proposed. The overall degradation was monitored by determination of sum parameters like COD, TOC and AOX. It was found that the organic chlorine degrades very effectively prior to complete mineralization. After the treatment no toxic effect was found according to Vibrio fischeri tests. However, at early stages some of the reaction products were more harmful than clofibric acid.

Csay, Tamás; Rácz, Gergely; Salik, Ádám; Takács, Erzsébet; Wojnárovits, László

2014-09-01

267

Ultrasensitive enzyme-free electrochemical immunosensor based on hybridization chain reaction triggered double strand DNA@Au nanoparticle tag.  

PubMed

An ultrasensitive enzyme-free electrochemical immunoassay was developed for detection of the fg/mL level carcinoembryonic antigen (CEA) by using a double strand DNA@Au nanoparticle (dsDNA@AuNP) tag and hexaammineruthenium(III) chloride (RuHex) as the electroactive indicator. The dsDNA@AuNP was synthesized by one-pot hybrid polymerization of dsDNA on initiator DNA modified AuNPs via hybridization chain reaction. The immunosensor was prepared by covalently cross-linking capture antibody on chitosan/AuNP nanocomposite modified glass carbon electrode. The AuNPs accelerated the electron transfer and led to high detection sensitivity. With a sandwich-type immunoreaction and a biotin-streptavidin affinity reaction, the dsDNA@AuNP tag was conjugated on the immunocomplex to bring a high amount of RuHex to the electrode surface via electrostatic interaction, resulting in an amplified electrochemical signal. Under optimal conditions, the proposed sensing platform showed a wide linear detection range from 10 fg/mL to 10 ng/mL along with a detection limit of 3.2 fg/mL for CEA. The immunosensor exhibited high sensitivity and good stability, showing a promising application in early cancer diagnosis and could be extended to sensitive electrochemical biosensing of other analytes. PMID:24468362

Ge, Yanqiu; Wu, Jie; Ju, Huangxian; Wu, Shuo

2014-03-01

268

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

269

Pitchfork and winged-cusp singularities in iodate-arsenous acid reaction  

NASA Astrophysics Data System (ADS)

The iodate-arsenous acid reaction was reported to be able to exhibit hysteresis bistability, including mushrooms and isolas, in a continuous flow stirred tank reactor (CSTR) when an additional flow of solvent is introduced [N. Ganapathisubramanian and K. Showalter, J. Chem. Phys. 80, 4177 (1984)]. Based on their kinetic data and the empirical rate law, it is shown that the reaction may also exhibit pitchfork-type and winged cusp-type singularities if additional flows of the reactants are introduced to the CSTR.

Li, Ru-Sheng

1994-09-01

270

Phase and reaction equilibria of acetic acid–1-pentanol–water– n-amyl acetate system at 760 mm Hg  

Microsoft Academic Search

The esterification reaction of acetic acid and alcohol is one of the processes applying reactive distillation technology. It is known that the thermodynamic properties are essential to chemical process design. In this study, the thermodynamic behaviors of vapor–liquid equilibrium (VLE) and reaction equilibrium of acetic acid, 1-pentanol, n-amyl acetate, and water mixture were determined experimentally. Since the present esterification reaction

Liang-sun Lee; Shen-jang Liang

1998-01-01

271

A modified chromium-reducible sulfur method for reduced inorganic sulfur: optimum reaction time for acid sulfate soil  

Microsoft Academic Search

Reaction times for 16 acid sulfate soil materials analysed using a modified chromium-reducible sulfur method varied between 10 and 15 min, regardless of whether the samples had been dried and ground prior to analysis or were analysed without pretreatment. The reaction time for a ground ({\\\\textless}63 mm) pyritic rock sample was 20 min. An optimum reaction time of 20 min

L. A. Sullivan; R. T. Bush; D. M. McConchie

2000-01-01

272

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

273

Dynamic behavior of the bray-liebhafsky oscillatory reaction controlled by sulfuric acid and temperature  

NASA Astrophysics Data System (ADS)

The non-periodic, periodic and chaotic regimes in the Bray-Liebhafsky (BL) oscillatory reaction observed in a continuously fed well stirred tank reactor (CSTR) under isothermal conditions at various inflow concentrations of the sulfuric acid were experimentally studied. In each series (at any fixed temperature), termination of oscillatory behavior via saddle loop infinite period bifurcation (SNIPER) as well as some kind of the Andronov-Hopf bifurcation is presented. In addition, it was found that an increase of temperature, in different series of experiments resulted in the shift of bifurcation point towards higher values of sulfuric acid concentration.

Peji?, N.; Vujkovi?, M.; Maksimovi?, J.; Ivanovi?, A.; Ani?, S.; ?upi?, Ž.; Kolar-Ani?, Lj.

2011-12-01

274

Formic acid catalyzed gas-phase reaction of H2O with SO3 and the reverse reaction: a theoretical study.  

PubMed

The formic acid catalyzed gas-phase reaction between H(2)O and SO(3) and its reverse reaction are respectively investigated by means of quantum chemical calculations at the CCSD(T)//B3LYP/cc-pv(T+d)z and CCSD(T)//MP2/aug-cc-pv(T+d)z levels of theory. Remarkably, the activation energy relative to the reactants for the reaction of H(2)O with SO(3) is lowered through formic acid catalysis from 15.97 kcal? mol(-1) to -15.12 and -14.83 kcal? mol(-1) for the formed H(2)O???SO(3) complex plus HCOOH and the formed H(2)O???HCOOH complex plus SO(3), respectively, at the CCSD(T)//MP2/aug-cc-pv(T+d)z level. For the reverse reaction, the energy barrier for decomposition of sulfuric acid is reduced to -3.07 kcal? mol(-1) from 35.82 kcal? mol(-1) with the aid of formic acid. The results show that formic acid plays a strong catalytic role in facilitating the formation and decomposition of sulfuric acid. The rate constant of the SO(3)+H(2)O reaction with formic acid is 10(5) times greater than that of the corresponding reaction with water dimer. The calculated rate constant for the HCOOH+H(2)SO(4) reaction is about 10(-13) cm(3) ?molecule(-1) ?s(-1) in the temperature range 200-280 K. The results of the present investigation show that formic acid plays a crucial role in the cycle between SO(3) and H(2)SO(4) in atmospheric chemistry. PMID:22095771

Long, Bo; Long, Zheng-wen; Wang, Yi-bo; Tan, Xing-feng; Han, Yu-hua; Long, Chao-yun; Qin, Shui-jie; Zhang, Wei-jun

2012-01-16

275

Reactions of aqueous glucose solution over solid-acid Y-zeolite catalyst at 110-160 C  

SciTech Connect

Reactions of glucose with solid-acid Y-zeolite catalyst were studied to see if this heterogeneous system could produce oxygenated hydrocarbons by shape-selective, acid-catalyzed processes at fairly low temperatures. Experimentally, aqueous solutions of glucose (12 wt %) were reacted with HY-zeolite powder in a well-mixed batch reactor at temperatures ranging from 110 to 160 C and catalyst concentrations ranging from 2 to 20 g/150 ml. Unreacted glucose and oxygenated hydrocarbon products were measured by HPLC as a function of reaction time (0-24 h) and process conditions. Glucose conversions of 100% were obtained at 160 C after an 8-h reaction time. The apparent activation energy based on glucose conversion was 23.25 [plus minus] 0.40 kcal/mol. Several acid-catalyzed reactions were identified, including isomerization of glucose to fructose, partial dehydration of glucose to 5-(hydroxymethyl)furfural (HMF), rehydration and cleavage of HMF to formic acid and 4-oxo-pentanoic acid, and carbonization . Polymers of HMF and seven minor additional products in the lower molecular weight organic acids/aldehydes/ketones elution range were also isolated by HPLC. High yields of organic acids relative to HMF and lowered selectivity of HMF in the bulk phase relative to the homogeneous acid-catalyzed reaction suggests the possibility of molecular sieving reactions within the Y-zeolite in addition to reactions on the outer surface of the Y-zeolite particle.

Lourvanij, K.; Rorrer, G.L. (Oregon State Univ., Corvallis (United States))

1993-01-01

276

Bis(2-quinolylmethyl)ethylenediaminediacetic acids (BQENDAs), TQEN-EDTA hybrid molecules as fluorescent zinc sensors.  

PubMed

Molecular hybrids of TQEN (N,N,N',N'-tetrakis(2-quinolylmethyl)ethylenediamine) and EDTA (ethylenediamine-N,N,N',N'-tetraacetic acid) were examined as fluorescent Zn(2+) sensors. Upon the addition of Zn(2+), N,N-BQENDA (N,N-bis(2-quinolylmethyl)ethylenediamine-N',N'-diacetic acid, 1a) exhibits a 30-fold emission enhancement at 456 nm (?ex = 315 nm, ?Zn = 0.018) in buffer (HEPES, pH = 7.5, 100 mM KCl). The fluorescence enhancement is Zn(2+)-specific as Cd(2+) induces much smaller increases (ICd/I0 = 5 and ICd/IZn = 16%). These spectroscopic properties, as well as the excellent water-solubility, represent a significant improvement compared to the parent TQEN sensor (?Zn = 0.007, ICd/IZn = 64%). The isoquinoline analog N,N-1-isoBQENDA (N,N-bis(1-isoquinolylmethyl)ethylenediamine-N',N'-diacetic acid, 1b) possesses a similar Zn(2+) fluorescence response to the parent 1-isoTQEN (N,N,N',N'-tetrakis(1-isoquinolylmethyl)ethylenediamine) sensor, but exhibits diminished fluorescence intensity. Apo 1a and 1b extract more than 50% of the Zn(2+) from an equimolar amount of [Zn(TPEN)](2+) (TPEN = N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine) or [Zn(EDTA)](2-), whereas TPEN and EDTA cannot effectively remove Zn(2+) from [Zn(1a)] and [Zn(1b)]. The reduction of steric crowding in [Zn(TQEN)](2+) resulting from the substitution of two quinolines with carboxylates enhances the interaction between the metal ion and the remaining quinoline nitrogen atoms. The stronger bonding interaction results in enhanced emission intensity, Zn(2+) selectivity and metal ion affinity. This is in contrast to [Zn(1-isoTQEN)](2+) where the isoquinoline-carboxylate replacement does not relieve any coordination distortion, therefore no significant changes in fluorescence or metal binding properties are observed. PMID:24853956

Mikata, Yuji; Takeuchi, Saaya; Konno, Hideo; Iwatsuki, Satoshi; Akaji, Sakiko; Hamagami, Ikuko; Aoyama, Masato; Yasuda, Keiko; Tamotsu, Satoshi; Burdette, Shawn C

2014-07-14

277

Hybrid binuclear-cobalt-phthalocyanine as oxygen reduction reaction catalyst in single chamber microbial fuel cells  

NASA Astrophysics Data System (ADS)

A novel hybrid binuclear-cobalt-phthalocyanine (Bi-CoPc) is developed as the cathode catalyst to replace the costly platinum (Pt) in single chamber microbial fuel cells (SCMFCs). Bi-CoPc/C is integrated with metal oxides (NiO and CoO) to form macrocyclic complex for enhanced oxygen reduction rate (ORR). The characteristics of hybrid catalysts (Bi-CoPc/C-CoO and Bi-CoPc/C-NiO) are compared with Co-contained catalysts (CoPc/C and Bi-CoPc/C) and metal oxide catalysts (NiO and CoO). The increase in O and N functional groups indicates the benefits of NiO and CoO to the cathode catalysts. The cyclic voltammetry (CV) shows the reduction peak for Bi-CoPc/C-NiO and Bi-CoPc/C-CoO at -0.12 V and -0.22 V, respectively. The power densities (368 mW m-2 and 400 mW m-2) of SCMFCs with Bi-CoPc/C-CoO and Bi-CoPc-NiO/C are the highest among the cathodes tested, and close to that of Pt (450 mW m-2). This study demonstrates that hybrid Bi-CoPc/C with metal oxides has a great potential as a cost-effective catalyst in MFCs.

Li, Baitao; Zhou, Xiuxiu; Wang, Xiujun; Liu, Bingchuan; Li, Baikun

2014-12-01

278

Products of aqueous vitamin B5 (pantothenic acid) formed by free radical reactions  

NASA Astrophysics Data System (ADS)

The radiolysis of aqueous vitamin B5 (pantothenic acid) has been investigated under various experimental conditions. The highest vitamin degradation ( G=3.22) was observed in solutions saturated with N 2O, where 90% OH radicals are operating. As final products, the following were established: aldehydes, carboxylic acids and ammonia. Their yield strongly depends on the presence/absence of air as well as on N 2O (used to convert e aq- into OH) and was determined as a function of absorbed radiation dose. HPLC-analysis showed that in all media, a main product is formed, having the highest yield in aerated solutions. Based on the chemical analysis, it appears that the OH radicals are most involved in the degradation process. A precise sequence of the reaction steps could not be given presently, because of the implication of many simultaneous reactions.

Schittl, H.; Quint, R. M.; Getoff, N.

2007-10-01

279

Origin of fatty acid synthesis - Thermodynamics and kinetics of reaction pathways  

NASA Technical Reports Server (NTRS)

The primitiveness of contemporary fatty acid biosynthesis was evaluated by using the thermodynamics and kinetics of its component reactions to estimate the extent of its dependence on powerful and selective catalysis by enzymes. Since this analysis indicated that the modern pathway is not primitive because it requires sophisticated enzymatic catalysis, an alternative pathway of primitive fatty acid synthesis is proposed that uses glycolaldehyde as a substrate. In contrast to the modern pathway, this primitive pathway is not dependent on an exogenous source of phosphoanhydride energy. Furthermore, the chemical spontaneity of its reactions suggests that it could have been readily catalyzed by the rudimentary biocatalysts available at an early stage in the origin of life.

Weber, Arthur L.

1991-01-01

280

[Experimental and kinetic modeling of acid/base and redox reactions over oxide catalysts]. Technical progress report  

SciTech Connect

The research has involved the characterization of catalyst acidity, {sup 2}D NMR studies of Bronsted acid sites, and kinetic, calorimetric, and spectroscopic studies of methylamine synthesis and related reactions over acid catalysts. Approach of this work was to explore quantitative correlations between factors that control the generation, type, strength, and catalytic properties of acid sites on zeolite catalysts. Microcalorimetry, thermogravimetric analysis, IR spectroscopy, and NMR spectroscopy have provided information about the nature and strength of acid sites in zeolites. This was vital in understanding the catalytic cycles involved in methylamine synthesis and related reactions over zeolite catalysts.

Not Available

1993-07-01

281

The reaction of picric acid with epoxides. II. The detection of epoxides in heated oils  

Microsoft Academic Search

A colorimetric method, based upon the reaction of the oxirane group with picric acid, was used to determine the epoxide content\\u000a of heated vegetable oils. The picration method is particularly suitable for measuring small quantities of epoxide because\\u000a it is much more sensitive than the common titrimetric methods, and it is not subject to interference from cyclopropene, conjugated\\u000a dieneols, or

J. A. Fioriti; A. P. Bentz; R. J. Sims

1966-01-01

282

Isotope Effects and Mechanism of the Asymmetric BOROX Br?nsted Acid Catalyzed Aziridination Reaction  

PubMed Central

The mechanism of the chiral VANOL-BOROX Brønsted acid catalyzed aziridination reaction of imines and ethyldiazoacetate has been studied using a combination of experimental kinetic isotope effects and theoretical calculations. A stepwise mechanism where reversible formation of a diazonium ion intermediate precedes rate-limiting ring-closure to form the cis-aziridine is implicated. A revised model for the origin of enantio- and diastereoselectivity is proposed based on relative energies of the ring closing transition structures. PMID:23687986

Vetticatt, Mathew J.; Desai, Aman A.; Wulff, William D.

2013-01-01

283

Reversion and dehydration reactions of glucose during the dilute sulfuric acid hydrolysis of cellulose  

SciTech Connect

The inaccessibility of all glycosidic bonds necessitates industrial conversion schemes which employ a dilute acid catalyst at high temperatures. Process conditions also promote further reactions of glucose via the reversion and dehydration pathways. Quantitative determination of the yields of the major reversion and dehydration products is important for understanding and predicting the amounts of these materials expected under envisioned industrial operating conditions. Microcrystalline cellulose (Avicel) was hydrolyzed with sulfuric acid (0.0-1.25 wt.%), at high temperatures (160-250/sup 0/C), and at a 3:1 liquid-to-solid ratio. The hydrolysis was monitored by evaluating the amount of cellulose remaining and the yields of glucose, solid humin, levulinic acid, formic acid, hydroxymethylfurfural (HMF), and reversion products as a function of the aforementioned reaction conditions. Analysis of the reversion products required the development of a technique for the quantitation of trace carbohydrates in complex mixtures and led to the development of a reduction/permethylation gas chromatographic procedure. Cellulose hydrolysis followed pseudo-homogeneous first-order kinetics. Glucose yield was adequately described as consecutive first-order reactions. Anhydrosugars formed via reversion followed equilibrium reaction kinetics whereas the disaccharides did not. Total reversion product yields approached 10% at 250/sup 0/C. Quantitative determination of the major dehydration products provided important information concerning the destruction of glucose. HMF was produced in up to 12% yields based on the theoretical amount of glucose available, and furfural was detected in up to 5% yields. A carbon mass balance based on the determined product yields revealed that approximately 90% of all carbon was accounted for at maximum glucose yields.

Helm, R.F.

1987-01-01

284

Acid\\/epoxy reaction catalyst screening for low temperature (120 °C) powder coatings  

Microsoft Academic Search

This paper describes efforts to identify and screen suitable acid\\/epoxy reaction catalysts for low temperature curing (?120°C) powder coatings including tertiary amines, ammonium compounds, and metal complexes. Thermal analysis techniques were developed to aid evaluation of catalyst efficacy and a statistical design of experiments was carried out to study several commercially available catalysts. In three different resin\\/crosslinker systems, the effect

Glen Merfeld; Chris Molaison; Rainer Koeniger; A. Ersin Acar; Steve Mordhorst; Joe Suriano; Pat Irwin; Ron Singh Warner; Ken Gray; Mark Smith; Kevin Kovaleski; Greg Garrett; Steve Finley; Debora Meredith; Mike Spicer; Tom Naguy

2005-01-01

285

Poly(L-glutamic acid)-decorated hybrid colloidal particles from complex particle-templated silica mineralization.  

PubMed

We report the synthesis of polyelectrolyte complex (PEC) particles by mixing the negatively and positively charged polyelectrolytes, poly(L-glutamic acid) (PGA) and poly(2-(N,N-diethylamino) ethylmethacrylate) (PDEAEMA), and the use of negatively charged PEC particles as colloidal templates for silica mineralization under ambient conditions. The structure and property of PEC particles, as well as polypeptide chain conformation, were found to depend on the mixing weight percentage, polymer molecular weight, and solution condition. The negatively charged PEC micelles can be deposited with silica without loss colloid stability, leading to PGA-decorated hybrid particles. These hybrid particles were negatively charged at neutral and basic condition and become positively charged, accompanying the conformational changes of the grafted PGA, upon decreasing pH below isoelectric points due to the protonation/deprotonation of PGA and PDEAEMA. Functional nanoparticles such as gold NPs could be incorporated using polypeptides as the mediating agents. These hybrid particles loaded with drug exhibited noticeable pH-responsive behavior with accelerated release at acidic condition, demonstrating the potential for use as pH-responsive delivery vehicles. This type of polypeptide-decorated hybrid particles represents an interesting class of organic-inorganic hybrids in which the functional properties of polypeptides such as biocompatibility, stimuli responsiveness, and directed growth of metal nanoparticles can be incorporated. PMID:23822799

Shiu, Cheng Chang; Wang, Shuan; Chang, Chien-Hsiang; Jan, Jeng-Shiung

2013-08-29

286

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

287

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

288

Thermal effects on the diffusive layer convection instability of an exothermic acid-base reaction front  

NASA Astrophysics Data System (ADS)

A buoyancy-driven hydrodynamic instability appearing when an aqueous acid solution of HCl overlies a denser alkaline aqueous solution of NaOH in a vertically oriented Hele-Shaw cell is studied both experimentally and theoretically. The peculiarity of this reactive convection pattern is its asymmetry with regard to the initial contact line between the two solutions as convective plumes develop in the acidic solution only. We investigate here by a linear stability analysis (LSA) of a reaction-diffusion-convection model of a simple A+B?C reaction the relative role of solutal versus thermal effects in the origin and location of this instability. We show that heat effects are much weaker than concentration-related ones such that the heat of reaction only plays a minor role on the dynamics. Computation of density profiles and of the stability analysis eigenfunctions confirm that the convective motions result from a diffusive layer convection mechanism whereby a locally unstable density stratification develops in the upper acidic layer because of the difference in the diffusion coefficients of the chemical species. The growth rate and wavelength of the pattern are determined experimentally as a function of the Brinkman parameter of the problem and compare favorably with the theoretical predictions of both LSA and nonlinear simulations.

Almarcha, C.; Trevelyan, P. M. J.; Grosfils, P.; De Wit, A.

2013-09-01

289

Strongly coupled NiCo(2)O(4)-rGO hybrid nanosheets as a methanol-tolerant electrocatalyst for the oxygen reduction reaction.  

PubMed

Strongly coupled NiCo2 O4 -rGO hybrid nanosheets are syntheiszed through a cost-effective two-step strategy involving a facile polyol process and subsequent thermal annealing treatment in air. The hybrid nanosheets exhibit impressive electrocatalytic performance for the oxygen reduction reaction (ORR) with a current density and onset potential comparable to those of commercial Pt/C catalyts, while having perfect tolerance to methanol.. PMID:24338831

Zhang, Genqiang; Xia, Bao Yu; Wang, Xin; David Lou, Xiong Wen

2014-04-16

290

Hybrid of chitin and humic acid as high performance sorbent for Ni(II)  

NASA Astrophysics Data System (ADS)

Hybrid of humic acid (HA) and chitin has been synthesized and the hybrid material (chitin-HA) was then applied as sorbent to adsorb Ni(II). The HA was extracted from peat soil of Gambut District, South Kalimantan, Indonesia, according to the procedure recommended by IHSS (International Humic Substances Society). The chitin was isolated from crab shell waste of sea food restaurants through deproteination using NaOH 3.5% (w/v) and followed by removal of inorganic impurities using HCl 1 M. The synthesis of chitin-HA was performed by reacting gelatinous chitin solution in HCl 0.5 M and HA solution in NaOH 0.5 M. Parameters investigated in this work consists of effect of medium acidity on the sorption, sorption rate ( ks) and desorption rate ( kd) constants, Langmuir (monolayer) and Freundlich (multilayer) sorption capacities, and energy ( E) of sorption. The ks and kd were determined according to a kinetic model of first order sorption reaching equilibrium, monolayer sorption capacity ( b) and energy ( E) were determined according to the Langmuir isotherm model, and multilayer sorption capacity ( B) was determined based on the Freundlich isotherm model. Sorption of Ni(II) on both chitin and chitin-HA was maximum at pH 8.0. The kinetic expression resulted from the proposed kinetic model has been shown to be more applicable than the commonly known Lagergren equation obtained from the pseudo-first order sorption model. The application of the proposed model revealed that the presence of HA increased the ks from 0.018 min -1 for chitin to 0.031 min -1 for chitin-HA. As for ks, the value of b was also bigger in the presence of HA, i.e. 7.42 × 10 -5 mol/g for chitin and 9.93 × 10 -5 mol/g for the chitin-HA. Unlike ks and b, the value of E slightly decreased from 23.23 to 21.51 kJ/mol for the absence and presence of HA, respectively. It can also be deduced that the presence of HA on chitin contributed more to the additional layer of Ni(II) sorbed on sorbent. Without HA, B for chitin was only 6.17 times higher than b, while with the presence of HA, the enhancement of the sorption capacity from the multilayer ( B) to the monolayer ( b) was 19.40. The increase of ks, b, B, and the decrease of E would be very benefit in the real application of chitin-HA for the recovery of Ni(II) from aqueous samples.

Santosa, Sri Juari; Siswanta, Dwi; Kurniawan, Agusta; Rahmanto, Wasino H.

2007-11-01

291

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

292

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

E-print Network

The goal of synthetic biology is to design and assemble synthetic systems that mimic biological systems. One of the most fundamental challenges in synthetic biology is to synthesize artificial biochemical systems, which we will call meta-biochemical systems, that provide the same functionality as biological nucleic acids-enzyme systems, but that use a very limited number of types of molecules. The motivation for developing such synthetic biology systems is to enable a better understanding of the basic processes of natural biology, and also to enable re-engineering and programmability of synthetic versions of biological systems. One of the key aspects of modern nucleic acid biochemistry is its extensive use of protein enzymes that were originally evolved in cells to manipulate nucleic acids, and then later adapted by man for laboratory use. This practice provided powerful tools for manipulating nucleic acids, but also limited the extent of the programmability of the available chemistry for manipulating nucleic acids, since it is very difficult to predictively modify the behavior of protein enzymes. Meta-biochemical systems offer the possible advantage of being far easier to re-engineer and program for desired functionality. The approach taken here is to develop a biochemical system which we call meta-DNA (abbreviated as mDNA), based entirely on strands of DNA as the only component molecules. Our work leverages prior work on the development of self-assembled DNA nanostructures (see Amin et al.

Harish Chandran; Nikhil Gopalkrishnan; Bernard Yurke; John Reif

293

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

294

Type differentiation of herpes simplex virus by stringent hybridization of polymerase chain reaction products  

Microsoft Academic Search

Summary A simple procedure for type differentiation of herpes simplex virus with the use of polymerase chain reaction (PCR)-amplified DNAs, was established: 1. The target sequence region for PCR was chosen from the coding sequences for an envelope protein, with the terminal sequences for PCR primers to be common among different types, but with the internal sequences to be variable.

S. Inouye; R. Hondo

1993-01-01

295

Fluorimetric determination of phytic acid in urine based on replacement reaction.  

PubMed

A sensitive fluorimetric method for determination of phytic acid in human urine samples was described. The method was based on a fluorimetric replacement reaction, in which the added phytic acid replaced the Cu2+ ion from Cu2+-gelatin complex, liberating the fluorescent gelatin molecule. The fluorescence of the solution was accordingly recovered proportionally to the amount of the foreign phytic acid. The excitation wavelength was 273.5 nm and the characteristic emission wavelength was 305.0 nm, respectively. The calibration graph was obtained by plotting the recovered fluorescent intensity at maximum 305.0 nm against the added standard phytic acid, and was divided into two sections. One section was linear over the range of 0.40-2.40 mg L(-1) with a linear regression equation of I(f) = -0.895+15.146c (R2 > 0.9993), and the other over the range of 2.40-9.20 mg L(-1) with a linear regression equation of I(f) = -29.526+26.113c (R2 > 0.9996), respectively. The relative standard deviation (R.S.D.) at 95% confidence degree for a 2.0 mg L(-1) of standard phytic acid within 1 month was less than 1.26% (n = 5), indicating the procedure is reproducible. The detection and the quantification limits of phytic acid were estimated to be 0.23 and 0.40 mg L(-1), respectively. The proposed method was applied to the determination of phytic acid in urine samples and the found concentrations of phytic acid in urine were in the range of 0.49-0.75 mg L(-1) with recoveries of 96.2-108.8%. Comparison of the obtained results with the reported HPLC was performed, indicating the proposed method was reliable. PMID:18036382

Chen, Yingyu; Chen, Jingwen; Ma, Kang; Cao, Shuhong; Chen, Xiaoqing

2007-12-19

296

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

NASA Astrophysics Data System (ADS)

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 generated several irreversibly adsorbed products on the octahedral aluminum surface, including monodentate, solvated, bidentate and bridged nitrate species and surface adsorbed water. Molecularly adsorbed nitric acid was detected on the tetrahedral silicon surface and a small absorbance displaying faster kinetics suggested that surface defect sites also play a role. Heating the reacted kaolinite to 373 K removed the surface adsorbed water and also caused a decrease of monodentate and solvated nitrate concurrent with an increase in bidentate and bridged nitrates, thereby suggesting an equilibrium between these species. Although molecularly adsorbed nitric acid was the dominant pyrophyllite product, all aluminum bound nitrate species except bidentate were observed, indicating the importance of layer edge reactive sites. Similar products were observed for the uptake of NO2 on kaolinite. Total nitrate concentrations were quantified using ion chromatography, allowing reactive uptake coefficients to be determined. Using BET surface areas, uptake coefficients for NO2 on kaolinite ranged from 8.0×10^{-8} to 2.1×10-7. The reaction was second order with respect to both NO2 and reactive surface sites, suggesting nitrite may also be formed. Strong kaolinite lattice vibrations prevented the detection of adsorbed nitrite, however, UV-visible spectroscopy identified gaseous HONO as a product for the reaction on wet kaolinite.

Hinrichs, R. Z.; Angelini, M. M.

2006-12-01

297

A hybrid MC/MD reaction method with rare event-driving mechanism: Atomistic realization of 2-chlorobutane racemization process in DMF solution  

NASA Astrophysics Data System (ADS)

We demonstrate a new efficient hybrid MC/MD reaction method with a rare event-driving mechanism as a practical 'atomistic' molecular simulation of large-scale chemically reactive systems. Application of the method to (R)-2-chlorobutane molecules in N,N-dimethylformamide (DMF) molecules starting in the optical pure state (100% e.e.) was found to successfully provide such an atomistic state with ˜0% e.e., the expected purity of (R)- to (S)-enantiomers of the racemic mixture in chemical equilibrium. This hybrid MC/MD reaction method is promising for studies of various properties in chemically reactive systems and their stereochemistry as well.

Nagaoka, Masataka; Suzuki, Yuichi; Okamoto, Takuya; Takenaka, Norio

2013-09-01

298

Ternary surface monolayers for ultrasensitive (zeptomole) amperometric detection of nucleic acid hybridization without signal amplification.  

PubMed

A ternary surface monolayer, consisting of coassembled thiolated capture probe, mercaptohexanol and dithiothreitol, is shown to offer dramatic improvements in the signal-to-noise characteristics of electrochemical DNA hybridization biosensors based on common self-assembled monolayers. Remarkably low detection limits down to 40 zmol (in 4 ?L samples) as well as only 1 CFU Escherichia coli per sensor are thus obtained without any additional amplification step in connection to the commonly used horseradish peroxidase/3,3',5,5'-tetramethylbenzidine system. Such dramatic improvements in the detection limits (compared to those of common binary alkanethiol interfaces and to those of most electrochemical DNA sensing strategies without target or signal amplification) are attributed primarily to the remarkably higher resistance to nonspecific adsorption. This reflects the highly compact layer (with lower pinhole density) produced by the coupling of the cyclic- and linear-configuration "backfillers" that leads to a remarkably low background noise even in the presence of complex sample matrixes. A wide range of surface compositions have been investigated, and the ternary mixed monolayer has been systematically optimized. Detailed impedance spectroscopy and cyclic voltammetric studies shed useful insights into the surface coverage. The impressive sensitivity and high specificity of the simple developed methodology indicate great promise for a wide range of nucleic acid testing, including clinical diagnostics, biothreat detection, food safety, and forensic analysis. PMID:20883023

Wu, Jie; Campuzano, Susana; Halford, Colin; Haake, David A; Wang, Joseph

2010-11-01

299

Ternary Surface Monolayers for Ultrasensitive (Zeptomole) Amperometric Detection of Nucleic-Acid Hybridization without Signal Amplification  

PubMed Central

A ternary surface monolayer, consisting of co-assembled thiolated capture probe (SHCP) mercaptohexanol (MCH) and dithiothreitol (DTT), is shown to offer dramatic improvements in the signal-to-noise characteristics of electrochemical DNA hybridization biosensors based on common self-assembled monolayers (SAMs). Remarkably low detection limits down to 40 zmole (in 4 ?L samples) as well as only 1 CFU E. coli per sensor are thus obtained without any additional amplification step in connection to the commonly used horseradish peroxidase/3,3?,5,5?-tetramethylbenzidine (HRP/TMB) system. Such dramatic improvements in the detection limits (compared to common binary alkanethiol interfaces and to most electrochemical DNA sensing strategies without target or signal amplification) are attributed primarily to the remarkably higher resistance to non-specific adsorption. This reflects the highly compact layer (with lower pinhole density) produced by the coupling of the cyclic- and linear-configuration ‘backfillers’ that leads to a remarkably low background noise even in the presence of complex sample matrices. A wide range of surface compositions have been investigated and the ternary mixed monolayer has been systematically optimized. Detailed impedance spectroscopy and cyclic voltammetric studies shed useful insights into the surface coverage. The impressive sensitivity and high specificity of the simple developed methodology indicate great promise for a wide range of nucleic acid testing, including clinical diagnostics, biothreat detection, food safety and forensic analysis. PMID:20883023

Wu, Jie; Campuzano, Susana; Halford, Colin; Haake, David A.; Wang, Joseph

2010-01-01

300

Triggering hairpin-free chain-branching growth of fluorescent DNA dendrimers for nonlinear hybridization chain reaction.  

PubMed

We present a nonlinear hybridization chain reaction (HCR) system in which a trigger DNA initiates self-sustained assembly of quenched double-stranded substrates into fluorescent dendritic nanostructures. During the process, an increasing number of originally sequestered trigger sequences labeled with fluorescent reporters are freed up from quenched substrates, leading to chain-branching growth of the assembled DNA dendrimers and an exponential increase in the fluorescence intensity. The triggered assembly behavior was examined by PAGE analysis, and the morphologies of the grown dendrimers were verified by AFM imaging. The exponential kinetics of the fluorescence accumulation was also confirmed by time-dependent fluorescence spectroscopy. This method adopts a simple sequence design strategy, the concept of which could be adapted to program assembly systems with higher-order growth kinetics. PMID:24969438

Xuan, Feng; Hsing, I-Ming

2014-07-16

301

Use of hybrid discrete cellular models for identification of macroscopic nutrient loss in reaction-diffusion models of tissues.  

PubMed

Macroscopic models accounting for cellular effects in natural or engineered tissues may involve unknown constitutive terms that are highly dependent on interactions at the scale of individual cells. Hybrid discrete models, which represent cells individually, were used to develop and apply techniques for modeling diffusive nutrient transport and cellular uptake to identify a nonlinear nutrient loss term in a macroscopic reaction-diffusion model of the system. Flexible and robust numerical methods were used, based on discontinuous Galerkin finite elements in space and a Crank-Nicolson temporal discretization. Scales were bridged via averaging operations over a complete set of subdomains yielding data for identification of a macroscopic nutrient loss term that was accurately captured via a fifth-order polynomial. Accuracy of the identified macroscopic model was demonstrated by direct, quantitative comparisons of the tissue and cellular scale models in terms of three error norms computed on a mesoscale mesh. PMID:24515852

Aristotelous, Andreas C; Haider, Mansoor A

2014-08-01

302

Ultrasensitive electrochemical detection of DNA based on Zn(2+) assistant DNA recycling followed with hybridization chain reaction dual amplification.  

PubMed

A new strategy to combine Zn(2+) assistant DNA recycling followed with hybridization chain reaction dual amplification was designed for highly sensitive electrochemical detection of target DNA. A gold electrode was used to immobilize molecular beacon (MB) as the recognition probe and perform the amplification procedure. In the presence of the target DNA, the hairpin probe 1 was opened, and the DNAzyme was liberated from the caged structure. The activated DNAzyme hybridized with the MB and catalyzed its cleavage in the presence of Zn(2+) cofactor and resulting in a free DNAzyme strand. Finally, each target-induced activated DNAzyme underwent many cycles triggering the cleavage of MB, thus forming numerous MB fragments. The MB fragments triggered the HCR and formed a long double-helix DNA structure. Because both H1 and H2 were labeled by biotin, a lot of SA-ALP was captured on the electrode surface, thus catalyzing a silver deposition process for electrochemical stripping analysis. This novel cascade signal amplification strategy can detect target DNA down to the attomolar level with a dynamic range spanning 6 orders of magnitude. This highly sensitive and specific assay has a great potential to become a promising DNA quantification method in biomedical research and clinical diagnosis. PMID:25128622

Qian, Yong; Wang, Chunyan; Gao, Fenglei

2015-01-15

303

Synthesis and in vitro biological evaluation of hybrids from tetrahydro-?-carboline and hydroxylcinnamic acid as antitumor carcinoma agents.  

PubMed

Novel hybrids 8a-j and 9a-j were designed and synthesized by coupling the carboxyl group of hydroxylcinnamic acids with tetrahydro-?-carboline alkaloids which were linked with different substituted nitrogen-containing heterocycles at the positions-N9, and their in vitro biological activities were evaluated. It was found that most hybrids showed good to moderate anti-tumor activities. Especially, compound 9j had a great potency superior to 5-fluorouracil (5-FU) and comparable to adriamycin in human cancer cells, and could selectively inhibit tumor cells, but not inhibit non-tumor cell proliferation in vitro. More importantly, apoptosis assay indicated that 9j could significantly induce tumor cell apoptosis in a dose-dependent manner. Therefore, our novel findings may provide a new framework for the design of new hybrids for the intervention of human cancers. PMID:24695344

Lin, Ying; Xia, Xuanping; Yao, Rongxin; Ni, Li; Hu, Jie; Guo, Wenjian; Zhu, Baoling

2014-01-01

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

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

PubMed

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

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

2013-01-01

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

Impact of anions on electrocatalytic activity in palladium nanoparticles supported on ionic liquid-carbon nanotube hybrids for the oxygen reduction reaction.  

PubMed

A series of palladium nanoparticles supported on carbon nanotubes (CNTs), which were functionalized covalently with imidazolium polymer salts with different anions, Pd/polyIL(X)-CNTs (IL=ionic liquid; X=Cl, Br, I, ClO(4), BF(4), PF(6)), were prepared to investigate the influence of imidazolim salt anions on electrocatalytic activity in the oxygen reduction reaction (ORR). The anions of the imidazolium moiety significantly impacted on the ORR kinetics in a 0.1 M solution of HClO(4). The electronically active surface area results are in good agreement with the order of the ORR kinetic activity of the supported Pd/polyIL(X)-CNTs (X: Cl>ClO(4)>BF(4)>Br?PF(6)?I). In contrast, owing to the facile anion exchange of halide anions with hydroxide anions, anion-dependent catalytic activity has not been observed in 0.1 M NaOH. Iterative ORR experiments in acid-base solutions demonstrated anion exchange on the electrode. These results indicate that subtly varied structures of the IL moiety profoundly influence the performance of IL-CNT hybrid materials and molecular-level control of interfacial interactions between the support material, catalysts, and electrolytes is important in the design of supported metal nanoparticle catalysts for fuel cells. PMID:21688395

Shin, Ju Yeon; Kim, Youn Soo; Lee, Youngmi; Shim, Jun Ho; Lee, Chongmok; Lee, Sang-gi

2011-08-01

308

Effect of acid concentration and pulp properties on hydrolysis reactions of mercerized sisal.  

PubMed

The influence of sulfuric acid concentration (H2SO4 5-25%, 100°C), crystallinity and fibers size on the hydrolysis reaction of sisal pulps were investigated, with the goal of evaluating both the liquor composition, as an important step in the production of bioethanol, and the residual non-hydrolyzed pulp, to determine its potential application as materials. Aliquots were withdrawn from the reaction media, and the liquor composition was analyzed by HPLC. The residual non-hydrolyzed pulps were characterized by SEM, their average molar mass and crystallinity index, and their size distribution was determined using a fiber analyzer. Sulfuric acid 25% led to the highest glucose content (approximately 10gL(-1)), and this acid concentration was chosen to evaluate the influence of both the fiber size and crystallinity of the starting pulp on hydrolysis. The results showed that fibers with higher length and lower crystallinity favored glucose production in approximately 12%, with respect to the highly crystalline shorter fibers. PMID:23465940

Lacerda, Talita M; Zambon, Márcia D; Frollini, Elisabete

2013-03-01

309

Incidence of Mucocutaneous Reactions in Children Treated With Niflumic Acid, Other Nonsteroidal Antiinflammatory Drugs, or Nonopioid Analgesics  

Microsoft Academic Search

Background and Objective. Results from a relatively small case-control study recently showed that niflumic acid increases the risk of serious mucocutane- ous reactions in children. As a consequence, the Italian Ministry of Health sent a \\

Miriam Sturkenboom; Alfredo Nicolosi; Luigi Cantarutti; Salvatore Mannino

310

One-pot synthesis of hybrid TiO2-polyaniline nanoparticles by self-catalyzed hydroamination and oxidative polymerization from TiO2-methacrylic acid nanoparticles.  

PubMed

A simple self-catalyzed hydroamination method for creating hybrid TiO(2)-polyaniline core-shell nanoparticles (NP) has been shown. Hybrid NPs with a range of possible sizes are afforded in high yield under mild reaction conditions and simultaneously show improved charge transport and electrochromic behavior compared to either polyaniline alone or physically blended with TiO(2). PMID:21892455

Bae, Woo Jin; Davis, Andrew R; Jung, Jaewoong; Jo, Won Ho; Carter, Kenneth R; Coughlin, E Bryan

2011-10-14

311

Synthesis of an Inorganic–Organic Hybrid Material Based on Polyhedral Oligomeric Silsesquioxane and Polystyrene via Nitroxide-Mediated Polymerization and Click Reactions  

Microsoft Academic Search

Synthesis of an inorganic–organic hybrid polymeric material composed of polystyrene and polyhedral oligomeric silsesquioxane (POSS) was carried out via nitroxide-mediated polymerization (NMP) and Click reaction. First, 4-chloromethyl styrene was polymerized in bulk at 125°C using AIBN and 4hydroxy-TEMPO as the initiator and stable free radical, respectively. Reaction of poly(4-chloromethyl styrene) (PCMS) with NaN3 in DMF yielded azide side-functional polystyrene. In

Deniz Sinirlioglu; Ali Ekrem Muftuoglu

2011-01-01

312

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

313

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

314

Identification of cDNAs for jasmonic acid-responsive genes in Polygonum minus roots by suppression subtractive hybridization  

Microsoft Academic Search

Elicitation, the plant-based biotechnology approach that utilizes the ability of plant roots to absorb and secrete a vast\\u000a variety of bioactive compounds, was studied on Polygonum minus using jasmonic acid (JA) as an elicitor. To understand the overall molecular responses of P. minus roots to JA induction, a subtracted cDNA library was constructed using the suppression subtractive hybridization (SSH) method.

Mian Chee Gor; Ismanizan Ismail; Wan Aida Wan Mustapha; Zamri Zainal; Normah Mohd Noor; Roohaida Othman; Zeti Azura Mohamed Hussein

2011-01-01

315

Peptide Nucleic Acid Fluorescent In Situ Hybridization for Hospital-Acquired Enterococcal Bacteremia: Delivering Earlier Effective Antimicrobial Therapy  

Microsoft Academic Search

Hospital-acquired vancomycin-resistant enterococcal bacteremia has been associated with increased hospi- tal costs, length of stay, and mortality. The peptide nucleic acid fluorescent in situ hybridization (PNA FISH) test for Enterococcus faecalis and other enterococci (EFOE) is a multicolor probe that differentiates E. faecalis from other enterococcal species within 3 h directly from blood cultures demonstrating gram-positive cocci in pairs and

Graeme N. Forrest; Mary-Claire Roghmann; Latoya S. Toombs; Jennifer K. Johnson; Elizabeth Weekes; Durry P. Lincalis; Richard A. Venezia

2008-01-01

316

Predicting state of charge of lead-acid batteries for hybrid electric vehicles by extended Kalman filter  

Microsoft Academic Search

This paper describes and introduces a new nonlinear predictor and a novel battery model for estimating the state of charge (SoC) of lead-acid batteries for hybrid electric vehicles (HEV). Many problems occur for a traditional SoC indicator, such as offset, drift and long term state divergence, therefore this paper proposes a technique based on the extended Kalman filter (EKF) in

A. Vasebi; S. M. T. Bathaee; M. Partovibakhsh

2008-01-01

317

Fluorescence In Situ Hybridization with Peptide Nucleic Acid Probes for Rapid Identification of Candida albicans Directly from Blood Culture Bottles  

Microsoft Academic Search

A new fluorescence in situ hybridization (FISH) method that uses peptide nucleic acid (PNA) probes for identification of Candida albicans directly from positive-blood-culture bottles in which yeast was observed by Gram staining (herein referred to as yeast-positive blood culture bottles) is described. The test (the C. albicans PNA FISH method) is based on a fluorescein-labeled PNA probe that targets C.

Susan Rigby; Gary W. Procop; Gerhard Haase; Deborah Wilson; Cletus Kurtzman; Kenneth Oliveira; Sabina Von Oy; Jens J. Hyldig-Nielsen; James Coull; Henrik Stender

2002-01-01

318

Rapid Identification of Staphylococcus aureus Directly from Blood Cultures by Fluorescence In Situ Hybridization with Peptide Nucleic Acid Probes  

Microsoft Academic Search

A new fluorescence in situ hybridization (FISH) method with peptide nucleic acid (PNA) probes for identification of Staphylococcus aureus directly from positive blood culture bottles that contain gram-positive cocci in clusters (GPCC) is described. The test (the S. aureus PNA FISH assay) is based on a fluorescein- labeled PNA probe that targets a species-specific sequence of the 16S rRNA of

Kenneth Oliveira; Gary W. Procop; Deborah Wilson; James Coull; Henrik Stender

2002-01-01

319

Electrochemical detection of hybridization using peptide nucleic acids and methylene blue on self-assembled alkanethiol monolayer modified gold electrodes  

Microsoft Academic Search

An electrochemical hybridization biosensor based on peptide nucleic acid (PNA) probes is presented. PNA probes were attached covalently through a competition of free amines on the guanine bases and also at the 5? end of the probe, using N-(3-dimethylamino)propyl)-N?-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) onto a carboxylate terminated alkanethiol self-assembled monolayer (SAM) preformed on a gold electrode (AuE). The covalently

Dilsat Ozkan; Arzum Erdem; Pinar Kara; Kagan Kerman; J Justin Gooding; Peter E Nielsen; Mehmet Ozsoz

2002-01-01

320

Identification of Dekkera bruxellensis (Brettanomyces) from Wine by Fluorescence In Situ Hybridization Using Peptide Nucleic Acid Probes  

Microsoft Academic Search

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

HENRIK STENDER; CLETUS KURTZMAN; JENS J. HYLDIG-NIELSEN; D. Sorensen; ADAM BROOMER; KENNETH OLIVEIRA; HEATHER PERRY-O' KEEFE; ANDREW SAGE; BARBARA YOUNG; JAMES COULL

2001-01-01

321

Covalently bonded adducts of deoxyribonucleic acid (DNA) oligonucleotides with single-wall carbon nanotubes: Synthesis and hybridization  

Microsoft Academic Search

We have developed a multistep route to the formation of covalently linked adducts of single-wall carbon nanotubes (SWNT) and cleoxyribonucleic acid (DNA) oligonucleotides. X-ray photoelectron spectroscopy was used to characterize the initial chemical modification to form amine-terminated SWNTs, which were then covalently linked to DNA. The resulting DNA-SWNT adducts hybridize selectively with complementary sequences, with only minimal interaction with noncomplementary

Sarah E. Baker; Wei Cai; Tami L. Lasseter; Kevin P. Weidkamp; Robert J. Hamers

2002-01-01

322

Double resonant converter topology with fast switching semiconductors for lead-acid battery charger used in hybrid electric locomotive  

Microsoft Academic Search

This paper presents the study and experimental validation of a 9 kW lead-acid battery charger used to feed the 72V DC-Bus inside an hybrid electric locomotive demonstrator realized in the frame of the French research project PLATHEE (energy-efficient and environmentally friendly train platform). The proposed topology for the battery charger is a DC\\/AC\\/DC step-down converter structure using high frequency transformer

Alexandre De Bernardinis; Stephane Butterbach; Richard Lallemand; Alain Jeunesse; Gerard Coquery; Philippe Aubin

2011-01-01

323

Modified Fenton reaction for trichlorophenol dechlorination by enzymatically generated H2O2 and gluconic acid chelate.  

PubMed

Glucose oxidase is a well-known enzyme that catalyzes the oxidation of beta-D-glucose to produce gluconic acid and hydrogen peroxide. Fenton reaction is a powerful oxidation technology used for the oxidation of groundwater pollutants. For the application of Fenton reaction in groundwater remediation, successful operation of Fenton reaction near neutral pH, and on-site generation of both H2O2 and chelate will be beneficial. The focus of this experimental study was to couple the glucose oxidation reaction with chelate-based Fenton reaction. The idea was to use the hydrogen peroxide and chelate gluconic acid generated during glucose oxidation for the dechlorination of 2,4,6-trichlorophenol (TCP) by Fenton reaction. The oxidation of glucose was achieved using the enzyme in free and immobilized forms. The rate of production of hydrogen peroxide was determined for each system, and was used to estimate the time required for complete consumption of glucose during the process, thus avoiding any traces of glucose in the Fenton reaction. In the case of free enzyme reaction, separation of the enzyme was achieved using an ultrafiltration membrane before initiating the Fenton reaction. The oxidation of TCP by Fenton reaction was performed at varying ratios of gluconic acid/Fe, and its effect on the decomposition of TCP and H2O2 was studied. TCP degradation was studied both in terms of parent compound degradation and free chloride generation. PMID:17166556

Ahuja, Deepak K; Bachas, Leonidas G; Bhattacharyya, D

2007-02-01

324

Involvement of solid acid on Al and Ga-doped porous silica in the Diels–Alder reaction  

Microsoft Academic Search

The Diels–Alder reaction of 2,3-dimethylbutadiene with p-benzoquinone using Al- and Ga-doped porous silica, i.e., MCM-41, zeolite, and amorphous silica, was studied focusing on individual effects of types, strength, and amount of acid sites and pore size of solid acid catalysts. MCM-41 and amorphous silica-based catalysts exhibited high activity for the Diels–Alder reaction, while zeolites only showed low activity. Comparison with

Atsushi Satsuma; Yoshihide Segawa; Hisao Yoshida; Tadashi Hattori

2004-01-01

325

Mass spectrometric and theoretical studies of thermochemistry and gas-phase ion-molecule reactions of nucleobases and amino acids  

Microsoft Academic Search

This research explores the thermochemistry and gas-phase ion-molecule reactions of nucleobases and amino acids by using FT-ICR mass spectrometry and molecular orbital calculations. The reactions of amino acids glycine, phenylalanine, tryptophan, tyrosine, and nucleobase cytosine and its derivatives with different positively charged phenyl radicals were examined. The reactivities of the radicals studied were found to be determined by their electron

Yiqun Huang

2004-01-01

326

Cu((i))/amino acid catalyzed coupling reactions of aryl halides and nucleophiles: applications in large-scale production.  

PubMed

Amino acids can be used as ligands to promote Ullmann-type coupling reactions. This review briefly discusses how L-proline, 4-hydroxy-L-proline and N,N-dimethylglycine can serve as the ideal ligands for copper-catalyzed coupling of aryl halides with different nucleophiles. Seven examples of applications of copper/amino acid catalyzed reactions in large-scale preparations are described. PMID:22273372

Ma, Dawei; Jiang, Yongwen

2011-01-01

327

Hybrid treatment of spatio-temporal behavior in surface reactions with coexisting immobile and highly mobile reactants  

SciTech Connect

For surface reactions on single-crystal substrates which involve highly mobile adspecies, there is a vast separation in natural time and length scales. Adspecies hop rates can be many orders of magnitude larger than rates for other processes. Strong spatial correlations or ordering can exist on the atomic scale, while spatial pattern formation occurs on a macroscopic scale due to high diffusivity. An efficient analysis of such systems is provided by a ``hybrid treatment`` which we apply here to the monomer--dimer surface reaction model in the case of coexisting immobile dimer adspecies and highly mobile monomer adspecies. Specifically, we combine a mean-field treatment of the ``randomized`` mobile adspecies, and a lattice-gas description of the immobile adspecies. Monte Carlo simulations then reveal bistability and ``critical`` bifurcation phenomena, while precisely accounting for the influence of correlations in the immobile adspecies distribution. A corresponding analysis of the evolution of macroscopic spatial inhomogeneities is achieved through parallel simulation of the distributed macroscopic points with distinct correlated states and adspecies coverages. These simulations are appropriately coupled to describe diffusive mass transport of the mobile adspecies. In this way, we examine for this model the propagation and structure of chemical waves, corresponding to interface between bistable reactive states, and thereby determine the relative stability of these states. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Tammaro, M. [Ames Laboratory and Department of Physics, Iowa State University, Ames, Iowa 50011 (United States)] [Ames Laboratory and Department of Physics, Iowa State University, Ames, Iowa 50011 (United States); Sabella, M. [Ames Laboratory, Iowa State University, Ames, Iowa 50011 (United States)] [Ames Laboratory, Iowa State University, Ames, Iowa 50011 (United States); Evans, J.W. [Ames Laboratory and Department of Mathematics, Iowa State University, Ames, Iowa 50011 (United States)] [Ames Laboratory and Department of Mathematics, Iowa State University, Ames, Iowa 50011 (United States)

1995-12-15

328

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

329

Comparison of RNA- or LNA-hybrid oligonucleotides in template-switching reactions for high-speed sequencing library preparation  

PubMed Central

Background Analyzing the RNA pool or transcription start sites requires effective means to convert RNA into cDNA libraries for digital expression counting. With current high-speed sequencers, it is necessary to flank the cDNAs with specific adapters. Adding template-switching oligonucleotides to reverse transcription reactions is the most commonly used approach when working with very small quantities of RNA even from single cells. Results Here we compared the performance of DNA-RNA, DNA-LNA and DNA oligonucleotides in template-switching during nanoCAGE library preparation. Test libraries from rat muscle and HeLa cell RNA were prepared in technical triplicates and sequenced for comparison of the gene coverage and distribution of the reads within transcripts. The DNA-RNA oligonucleotide showed the highest specificity for capped 5? ends of mRNA, whereas the DNA-LNA provided similar gene coverage with more reads falling within exons. Conclusions While confirming the cap-specific preference of DNA-RNA oligonucleotides in template-switching reactions, our data indicate that DNA-LNA hybrid oligonucleotides could potentially find other applications in random RNA sequencing. PMID:24079827

2013-01-01

330

Cyanuric acid + nitric oxide reaction at 700 sup 0 C and the effects of oxygen  

SciTech Connect

The reaction of cyanuric acid, (HNCO)/sub 3/, with nitric oxide has been examined in a flow tube under conditions similar to those initially reported for RAPRENO/sub chi/. Surface interactions are shown to play an important role in the observed chemistry. In a quartz flow tube at 700{sup 0}C, (HNCO)/sub 3/ decomposes slowly; addition of nitric oxide does not affect the (HNCO)/sub 3/ decomposition, and no NO reduction occurs. In an otherwise equivalent stainless-steel flow system, (HNCO)/sub 3/ decomposes rapidly to H/sub 2/, CO, and N/sub 2/ at 700{sup 0}C. In this stainless-steel flow tube, NO is efficiently reduced to N/sub 2/ by (HNCO)/sub 3/. At 700{sup 0}C, the stoichiometry of this fast chemistry is 2(HNCO)/sub 3/ + 9 NO{yields}3 H/sub 2/O + 7.5 N/sub 2/ + 6 CO/sub 2/. O/sub 2/ also reacts rapidly with (HNCO)/sub 3/ vapor at 700{sup 0}C in stainless steel. The dominant nitrogen-containing product of this reaction is NO. This reaction of (HNCO)/sub 3/ vapor with O/sub 2/ is faster than the corresponding reaction with NO. Under conditions examined here in stainless steel, reduction of NO by (HNCO)/sub 3/ in the presence of O/sub 2/ occurs only after the O/sub 2/ is consumed.

Wicke, B.G.; Grady, K.A.; Ratcliffe, J.W. (Physical Chemistry Dept., General Motors Research Labs., Warren, MI (US))

1989-11-01

331

Conjugation reactions catalyzed by bifunctional proteins related to beta-oxidation in bile acid biosynthesis.  

PubMed

The conjugation reactions of hydration and dehydrogenation catalyzed by the dehydratase and dehydrogenase activities of D-3-hydroxyacyl-CoA dehydratase/D-3-hydroxyacyl-CoA dehydrogenase bifunctional protein (DBP) and enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase bifunctional protein (LBP) in the side chain degradation step of bile acid biosynthesis were investigated using chemically synthesized C27-bile acid CoA esters as substrates. The hydration catalyzed by DBP showed high diastereoselectivity for (24E)-3alpha,7alpha,12alpha-trihydroxy- and (24E)-3alpha,7alpha-dihydroxy-5beta-cholest-24-en-26-oyl CoA to give (24R,25R)-3alpha,7alpha,12alpha,24-tetrahydroxy- and (24R,25R)-3alpha,7alpha,24-trihydroxy-5beta-cholestan-26-oyl CoAs, respectively, and the dehydrogenation catalyzed by DBP also showed high stereospecificity for the above (24R,25R)-isomers to give 3alpha,7alpha,12alpha-trihydroxy- and 3alpha,7alpha-dihydroxy-24-oxo-5beta-cholestan-26-oyl CoAs, respectively. On the other hand, the dehydratase activity of LBP displayed a different diastereoselectivity producing the (24S,25S)-isomer, and dehydrogenase activity of LBP was stereospecific for the (24S,25R)-isomer to give the above 24-oxo-derivative. The hydration and dehydrogenation reactions catalyzed by DBP were effectively conjugated to convert (24E)-5beta-cholestenoyl CoA to 24-oxo-5beta-cholestanoyl CoA. However, the reactions catalyzed by LBP were not conjugated. These results indicate that DBP plays an important role in the biosynthesis of bile acid. PMID:11146090

Kurosawa, T; Sato, M; Nakano, H; Fujiwara, M; Murai, T; Yoshimura, T; Hashimoto, T

2001-02-01

332

[The reaction of cyclohexylsulphamic acid (Cyclamate) with nitrous acid in aqueous HCl-solution, isolated human gastric juice and urine (author's transl)].  

PubMed

The pH dependence of the formation and decomposition of the N-nitroso derivative, which is produced by the reaction of cyclohexylsulphamic acid with nitrous acid, was investigated by means of continuous photometric measurement of the changes in absorbance. Reaction at pH 2.45 resulted in an optimal yield of the N-nitroso derivative. The half-life of the decomposition reaction (the reactants cyclohexylsulphamic acid/sodium nitrite being in a molar ratio of 1:1.11) at pH 2.61 was 13.6 min. The N-nitroso derivative showed a relatively high stability at pH 4.5. The reaction in isolated human gastric juice and urine showed the same pH dependency as in aqueous HCl solution. PMID:670904

Kinawi, A; Kia, H

1978-06-01

333

Atmospheric Secondary Aerosol Formation by Heterogeneous Reactions of Aldehydes in the Presence of a Sulfuric Acid Aerosol Catalyst  

NASA Astrophysics Data System (ADS)

Particle growth by the heterogeneous reaction of aldehydes was observed in 0.5 m3 indoor Teflon bags in the presence of background seed aerosols. The aldehydes used were: glyoxal, butanal, hexanal, octanal, and decanal. To study acid catalyst effects on aldehyde heterogeneous reactions, one of the Teflon bags was initially filled with seed aerosols composed of ammonium sulfate-aerosol acidified with sulfuric acid. This result was compared to particle growth reactions that contained only ammonium sulfate as a background seed aerosol. The gas phase aldehydes were then added to the Teflon bags. In selected experiments, 1-decanol was also added to the Teflon bags with aldehydes to clarify particle growth via a heterogeneous hemiacetal/acetal formation in the presence/absence of an acid catalyst. The particle size distribution and growth were measured using a differential mobility analyzer (DMA), and the results were applied to predicting aerosol growth and size distribution changes by condensation and heterogeneous reactions. Aerosols created from the heterogeneous reactions of aldehydes were collected directly on an ungreased zinc selenide (ZnSe) FTIR disk (25 mm in diameter) by impaction. The ZnSe disks were directly analyzed for product functional groups in the aerosol phase using a Fourier transform infrared (FTIR) spectrometer with a deuterated triglycine sulfate (DTGS) detector. Aerosol growth by heterogeneous aldehyde reactions proceeds via a hydration, polymerization process, hemiacetal/acetal formation from the reaction of aldehydes with alcohols. These aldehyde heterogeneous reactions were accelerated in the presence of an acid catalyst, H2SO4, and led to higher aerosol yields than when H2SO4 was not present in the seed aerosol. The FTIR spectra obtained from the growing aerosol, also illustrated aldehyde group transformation in the particle phase as a function of the heterogeneous reaction. It was concluded that aldehydes, which can be produced by atmospheric photochemical reactions, can significantly contribute on secondary aerosol formation through heterogeneous reactions in the presence of an acid catalyst.

Jang, M.; Kamens, R. M.

2001-12-01

334

Reaction of iron and aluminium phosphate ores with sulphuric acid and various salts  

Microsoft Academic Search

A study has been made of the reaction of ore containing high Fe and Al phosphates (crandallite (CaAl3(PO4)2OH5·H2O)), millisite (Na, K)CaAl6(PO4)4(OH)9·3H2O) and minor minerals) with sulphuric acid. The products are deliquecent, poorly crystalline solids which contain polymeric aluminium phosphate. The deliquecence was greatly reduced by adding enough ammonium, potassium or sodium sulphate to form compounds of the type M(Al, -Fe)(SO4)2.

G. S. Walker

1988-01-01

335

A revision of the Biginelli reaction under solid acid catalysis. Solvent-free synthesis of dihydropyrimidines over montmorillonite KSF  

Microsoft Academic Search

The reaction of aldehydes, ?-dicarbonyl compounds and urea (Biginelli reaction) has been performed over solid acid catalysis, under solventless conditions or in water affording dihydropyrimidines in good yield and selectivity.Dihydropyrimidines4 were obtained in good yield and selectivity by reacting aldehydes, ?-dicarbonyl compounds and ureas in the presence of montmorillonite KSF under solventless conditions.

Franca Bigi; Silvia Carloni; Bettina Frullanti; Raimondo Maggi; Giovanni Sartori

1999-01-01

336

In situ vinylindole synthesis. Diels-Alder reactions with maleic anhydride and maleic acid to give tetrahydrocarbazoles and carbazoles  

Microsoft Academic Search

Tetrahydrocarbazoles have been prepared in one-flask syntheses from indoles, ketones, and maleic anhydride, with acid catalysis. The reactions involve a condensation of the indole with the ketone or aldehyde, follwed by an in situ trapping of the vinylindole in a Diels-Alder reaction with maleic anhydride. Depending on which indole is used, this may or may not be followed by a

Wayland E. Noland; Guang-Ming Xia; Kyle R. Gee; Michael J. Konkel; Mary J. Wahlstrom; John J. Condoluci; Dale L. Rieger

1996-01-01

337

Single-molecule study on the temperature-sensitive reaction of F1-ATPase with a hybrid F1 carrying a single beta(E190D).  

PubMed

F(1)-ATPase is a rotary molecular motor in which the gamma-subunit rotates against the alpha(3)beta(3) cylinder. The unitary gamma-rotation is a 120 degrees step comprising 80 and 40 degrees substeps, each of these initiated by ATP binding and ADP release and by ATP hydrolysis and inorganic phosphate release, respectively. In our previous study on gamma-rotation at low temperatures, a highly temperature-sensitive (TS) reaction step of F(1)-ATPase from thermophilic Bacillus PS3 was found below 9 degrees C as an intervening pause before the 80 degrees substep at the same angle for ATP binding and ADP release. However, it remains unclear as to which reaction step the TS reaction corresponds. In this study, we found that the mutant F(1)(beta E190D) from thermophilic Bacillus PS3 showed a clear pause of the TS reaction below 18 degrees C. In an attempt to identify the catalytic state of the TS reaction, the rotation of the hybrid F(1), carrying a single copy of beta E190D, was observed at 18 degrees C. The hybrid F(1) showed a pause of the TS reaction at the same angle as for the ATP binding of the incorporated beta E190D, although kinetic analysis revealed that the TS reaction is not the ATP binding step. These findings suggest that the TS reaction is a structural rearrangement of beta before or after ATP binding. PMID:19561076

Enoki, Sawako; Watanabe, Rikiya; Iino, Ryota; Noji, Hiroyuki

2009-08-21

338

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

PubMed

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

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

2014-07-18

339

Highly enantioselective formal aza-Diels–Alder reactions with acylhydrazones and Danishefsky's diene promoted by a silicon Lewis acid  

Microsoft Academic Search

Silicon Lewis acid 3 is effective for the promotion of highly enantioselective cycloaddition reactions of acylhydrazones with Danishefsky's diene (formal aza-Diels–Alder reactions). The reactions are conducted at ambient temperature for 15min, and produce the products in good yield and with high levels of enantioselectivity. A remarkable solvent-dependent reversal in the sense of absolute stereochemical induction has been observed. The method

Sharon K. Lee; Uttam K. Tambar; Nicholas R. Perl; James L. Leighton

2010-01-01

340

Effects of Lewis acid-surfactant-combined catalysts on aldol and Diels-Alder reactions in water  

Microsoft Academic Search

Aldol and Diels-Alder reactions in water in the presence of various dodecyl sulfate and dodecanesulfonate salts as Lewis acid-surfactant-combined catalysts have been studied. In the aldol reactions, these salts differed from each other with respect to their catalytic ability at the initial stage of the reaction and to the final yields of the aldol product, while these salts did not

Kei Manabe; Yuichiro Mori; Sh? Kobayashi

1999-01-01

341

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

342

Development of a lauric acid/albumin hybrid iron oxide nanoparticle system with improved biocompatibility  

PubMed Central

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; Dorje, Frank; Odenbach, Stefan; Lyer, Stefan; Lee, Geoffrey; Alexiou, Christoph

2014-01-01

343

Evaluation of crystalline amino acid test diets including pH adjustment with red drum ( Sciaenops ocellatus) and hybrid striped bass ( Morone chrysops × Morone saxatilis)  

Microsoft Academic Search

The red drum and hybrid striped bass are cultured in the United States for both stock enhancement and food production. Based on previous observations in this laboratory, the hybrid striped bass appeared to use pH-adjusted crystalline amino acid test diets more readily than the red drum. Therefore, the present study was conducted to directly compare responses of red drum and

Kasey W. Whiteman; Delbert M. Gatlin

2005-01-01

344

Ex vivo effects of nonsteroidal antiinflammatory drugs on arachidonic acid metabolism in neutrophils from a reverse passive Arthus reaction  

Microsoft Academic Search

Rat neutrophils isolated from 4-h reverse passive Arthus reaction (RPAR) pleural exudates actively metabolize arachidonic acid via cyclooxygenase and lipoxygenase. Utilizing this system, the effect of oral doses of nonsteroidal antiinflammatory drugs on the ability of these cells to produce HHT, 5-HETE, and LTB from exogenously added arachidonic acid has been investigated. In vitro and ex vivo, indomethacin and timegadine

Robin F. Myers; John C. Anthes; Charles J. Casmer; Marvin I. Siegel

1985-01-01

345

Synthesis of biodiesel from a model waste oil feedstock using a carbon-based solid acid catalyst: Reaction and separation  

Microsoft Academic Search

A solid acid catalyst that can keep high activity and stability is necessary when low cost feedstocks are utilized for biodiesel synthesis because the reaction medium contains a large amount of water. Three solid acid catalysts were prepared by the sulfonation of carbonized vegetable oil asphalt and petroleum asphalt. The structure of these catalysts was characterized by a variety of

Qing Shu; Zeeshan Nawaz; Jixian Gao; Yuhui Liao; Qiang Zhang; Dezheng Wang; Jinfu Wang

2010-01-01

346

Products and Mechanisms of Ozone Reactions with Oleic Acid for Aerosol Particles Having Core-Shell Morphologies  

E-print Network

Products and Mechanisms of Ozone Reactions with Oleic Acid for Aerosol Particles Having Core of oleic acid aerosol particles with ozone are studied below 1% relative humidity. The particles have inert of the organic layer is monitored with increasing ozone exposure by using an aerosol mass spectrometer

347

Synthesis and characterization of Pd-poly(N-vinyl-2-pyrrolidone)/KIT-5 nanocomposite as a polymer-inorganic hybrid catalyst for the Suzuki-Miyaura cross-coupling reaction  

SciTech Connect

Composite poly(N-vinyl-2-pyrrolidone)/KIT-5 (PVP/KIT-5) was prepared by in situ polymerization method and used as a support for palladium nanoparticles obtained through the reduction of Pd(OAc){sub 2} by hydrazine hydrate. The physical and chemical properties of the catalyst were investigated by XRD, FT-IR, UV-vis, TG, BET, SEM, and TEM techniques. The catalytic performance of this novel heterogeneous catalyst was determined for the Suzuki-Miyaura cross-coupling reaction between aryl halides and phenylboronic acid in the presence of water at room temperature. The stability of the nanocomposite catalyst was excellent and could be reused 8 times without much loss of activity in the Suzuki-Miyaura cross-coupling reaction. - Graphical Abstract: Pd-poly(N-vinyl-2-pyrrolidone)/KIT-5 was prepared as an organic-inorganic hybrid catalyst for the Suzuki-Miyaura reaction. The stability of the catalyst was excellent and could be reused 8 times in the Suzuki-Miyaura reaction. Highlights: > Pd-poly(N-vinyl-2-pyrrolidone)/KIT-5 was prepared as a novel nanocomposite. > Nanocomposite was prepared based on a cage-type mesoporous system. > Catalyst showed excellent activity for Suzuki-Miyaura reaction in water. > Stability of the catalyst was excellent and could be reused 8 times.

Kalbasi, Roozbeh Javad, E-mail: rkalbasi@iaush.ac.ir [Department of Chemistry, Shahreza Branch, Islamic Azad University, 311-86145 Shahreza, Isfahan (Iran, Islamic Republic of); Mosaddegh, Neda [Department of Chemistry, Shahreza Branch, Islamic Azad University, 311-86145 Shahreza, Isfahan (Iran, Islamic Republic of)

2011-11-15

348

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

349

TEMPERATURE AND CRITICAL ILLUMINATION FOR REACTION TO FLICKERING LIGHT : V. XIPHOPHORUS, PLATYPOECILIUS, AND THEIR HYBRIDS.  

PubMed

For the teleosts Xiphophorus montezuma, Platypoecilius maculatus, and their F(1) hybrids the temperature characteristics (micro in Arrhenius' equation) are the same for the shift of the low intensity and the high intensity segments of the respective and different flicker response contours (critical intensity I as a function of flash frequency F, with light time fraction constant, at 50 per cent). The value of micro is 12,500 calories or a very little less, over the range 12.5 to 36 degrees . This shows that 1/I can be understood as a measure of excitability, with F fixed, and that the excitability is governed by the velocity of a chemical process common to both the classes of elements represented in the duplex performance curve (rods and cones). It is accordingly illegitimate to assume that the different shapes of the rod and cone branches of the curves are determined by differences in the chemical mechanisms of excitability. It is also forbidden to assume that the differing form constants for the homologous segments in the curves for two forms (X. and P.) are the reflections of a difference in the chemical factors of primary excitability. These differences are determined by statistical factors of the distribution of excitabilities among the elements implicated in the sensory effect vs. intensity function, and are independent of temperature and of the temperature characteristic. It must be concluded that the physicochemical nature of the excitatory process cannot be deduced from the shape of the performance contour. The form constants (sigma'(log I) and F(max.)) for F vs. log I are specifically heritable in F(1), although micro is here the same as for X. and P. In an intergeneric cross one cannot in general expect Mendelian simplicity of segregation in subsequent generations, and in the present case we find that F(2) individuals are indistinguishable from F(1), both as regards F vs. log I and as regards the variation of I within a group of 17 individuals. The result in F(2) definitely shows, however, that certain specific statistical form constants for the F-log I contour are transmissible in inheritance. It is pointed out that there thus is provided an instance in which statistical (distribution) factors in performance characteristics involving the summating properties of assemblages of cellular units are heritable in a simple manner without the implication of detectable differences in chemical organization of the units involved. This has an important bearing upon the logic of the theory of the gene. PMID:19873143

Crozier, W J; Wolf, E

1939-11-20

350

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

PubMed Central

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

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

2014-01-01

351

Preparation and characterization of zinc oxide nanoparticles and their sensor applications for electrochemical monitoring of nucleic acid hybridization.  

PubMed

In this study, ZnO nanoparticles (ZNP) of approximately 30 nm in size were synthesized by the hydrothermal method and characterized by X-ray diffraction (XRD), Braun-Emmet-Teller (BET) N2 adsorption analysis and transmission electron microscopy (TEM). ZnO nanoparticles enriched with poly(vinylferrocenium) (PVF+) modified single-use graphite electrodes were then developed for the electrochemical monitoring of nucleic acid hybridization related to the Hepatitis B Virus (HBV). Firstly, the surfaces of polymer modified and polymer-ZnO nanoparticle modified single-use pencil graphite electrodes (PGEs) were characterized using scanning electron microscopy (SEM). The electrochemical behavior of these electrodes was also investigated using differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Subsequently, the polymer-ZnO nanoparticle modified PGEs were evaluated for the electrochemical detection of DNA based on the changes at the guanine oxidation signals. Various modifications in DNA oligonucleotides and probe concentrations were examined in order to optimize the electrochemical signals that were generated by means of nucleic acid hybridization. After the optimization studies, the sequence-selective DNA hybridization was investigated in the case of a complementary amino linked probe (target), or noncomplementary (NC) sequences, or target and mismatch (MM) mixture in the ratio of (1:1). PMID:21600741

Yumak, Tugrul; Kuralay, Filiz; Muti, Mihrican; Sinag, Ali; Erdem, Arzum; Abaci, Serdar

2011-09-01

352

Differentiation of diastereomeric cyclic beta-amino acids by varying the neutral reagent in ion/molecule reactions studied by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry.  

PubMed

Stereochemical differentiation of diasteromeric pairs of cis- and trans-2-aminocyclohexane-, -2-amino-4-cyclohexene-, and -2-aminocyclopentanecarboxylic acids was investigated with host-guest complexes where tetraethyl resorcarene was the host molecule. Diastereoselectivity was evaluated by ion/molecule reactions and collision-induced dissociation with electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS). The effect of varying the neutral reagent (n-propylamine, i-propylamine, diethylamine, and triethylamine) in ion/molecule reactions was evaluated. Both steric interactions and proton affinity of the neutral reagents influenced the reaction rates. High proton affinity of the neutral reagent apparently had a twofold effect. If the proton affinity of the neutral reagent was too high, the reaction tended to become too exothermic and part of the host-guest complex decomposed instead of transforming to a new host-guest complex, effecting a decrease in the reaction rate. The remaining portion of the host-guest complexes meanwhile reacted very fast with the neutral reagent due to high proton affinity causing an increase in the reaction rate. n-Propylamine and i-propylamine proved to be the best neutral reagents, providing clear diastereoselectivity for beta-amino acids in ion/molecule reactions. Interestingly, diastereoselectivity was better for flexible cyclohexane beta-amino acids (2 and 3) than for more rigid cyclopentane beta-amino acids (6 and 7). The results of ab initio and hybrid density functional theory calculations on the structures of the host-guest complexes of saturated beta-amino acids were in good agreement with the experimental results. PMID:18181235

Hyyryläinen, Anna R M; Pakarinen, Jaana M H; Vainiotalo, Pirjo; Fülöp, Ferenc

2008-01-01

353

Human papillomavirus 44 nucleic acid hybridization probes and methods for employing the same  

SciTech Connect

This patent describes an HPV 44 hybridization probe comprising a member selected from the group consisting of (1) HPV 44 DNA or fragments thereof labelled with a marker and (ii) HPV 44 RNA or fragments thereof labelled with a marker.

Lorincz, A.T.

1989-07-18

354

Human papillomavirus 43 nucleic acid hybridization probes and methods for employing the same  

SciTech Connect

This patent describes an HPV 43 hybridization probe comprising a member selected from the group consisting of (i) HPV 43 DNA or fragments thereof labelled with a marker and (ii) HPV 43 RNA or fragments thereof labelled with a marker.

Lorincz, A.T.

1989-07-18

355

Human papillomavirus 35 nucleic acid hybridization probes and methods for employing the same  

SciTech Connect

This patent describes an HPV 35 hybridization probe comprising a member selected from the group consisting of (i) HPV 35 DNA or fragments thereof labelled with a marker and (ii) HPV 35 RNA or fragments thereof labelled with a marker.

Lorincz, A.T.

1989-07-18

356

Human papillomavirus 56 nucleic acid hybridization probes and methods for employing the same  

SciTech Connect

This patent describes an HPV 56 hybridization probe. It comprises: a member selected from the group consisting of HPV 56 DNA or fragments thereof labelled with a marker and HPV 56 RNA or fragments thereof labelled with a marker.

Lorinez, A.T.

1990-03-13

357

Electrical detection of hybridization and threading intercalation of deoxyribonucleic acid using carbon nanotube network field-effect transistors  

NASA Astrophysics Data System (ADS)

The authors study deoxyribonucleic acid (DNA) sensing characteristics of carbon nanotube network field-effect transistors (CNNFETs) by monitoring their electrical responses upon immobilization with a DNA probe, hybridization with DNA analytes, and intercalation with a N ,N'-bis(3-propylimidazole)-1,4,5,8-naphthalene diimide modified with Os(2,2'-bipyridine)2Cl+ pendants. The CNNFETs immobilized by single-stranded DNA molecules demonstrate the selective sensing of its complementary and single-base mismatched DNA (difference of ˜16% in reduction of normalized drain current Id). Subsequent intercalation demonstrates a further sensitivity enhancement (difference of ˜13% in Id reduction) due to specific binding between hybridized DNA and intercalators, corroborated by the x-ray photoelectron spectroscopy study.

Gui, Ee-Ling; Li, Lain-Jong; Lee, P. S.; Lohani, Anup; Mhaisalkar, S. G.; Cao, Qing; Kang, Seong Jun; Rogers, John A.; Tansil, N. C.; Gao, Zhiqiang

2006-12-01

358

How are the Concepts and Theories of Acid Base Reactions Presented? Chemistry in Textbooks and as Presented by Teachers  

NASA Astrophysics Data System (ADS)

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 views of science in textbooks and of chemistry teachers contributes to an impoverished image of chemistry. A varied design has been elaborated to analyse some epistemological deficiencies in teaching acid base reactions. Textbooks have been analysed and teachers have been interviewed. The results obtained show that the teaching process does not emphasize the macroscopic presentation of acids and bases. Macroscopic and microscopic conceptual models involved in the explanation of acid base processes are mixed in textbooks and by teachers. Furthermore, the non-problematic introduction of concepts, such as the hydrolysis concept, and the linear, cumulative view of acid base theories (Arrhenius and Brönsted) were detected.

Furió-Más, Carlos; Calatayud, María Luisa; Guisasola, Jenaro; Furió-Gómez, Cristina

2005-09-01

359

Synthesis of biodiesel from a model waste oil feedstock using a carbon-based solid acid catalyst: reaction and separation.  

PubMed

A solid acid catalyst that can keep high activity and stability is necessary when low cost feedstocks are utilized for biodiesel synthesis because the reaction medium contains a large amount of water. Three solid acid catalysts were prepared by the sulfonation of carbonized vegetable oil asphalt and petroleum asphalt. The structure of these catalysts was characterized by a variety of techniques. A new process that used the coupling of the reaction and separation was employed, which greatly improved the conversion of cottonseed oil (triglyceride) and free fatty acids (FFA) when a model waste oil feedstock was used. The vegetable oil asphalt-based catalyst showed the highest catalytic activity. This was due to the high density and stability of its acid sites, its loose irregular network, its hydrophobicity that prevented the hydration of -OH species, and large pores that provided more acid sites for the reactants. PMID:20219353

Shu, Qing; Nawaz, Zeeshan; Gao, Jixian; Liao, Yuhui; Zhang, Qiang; Wang, Dezheng; Wang, Jinfu

2010-07-01

360

Target Turing patterns and growth dynamics in the chlorine dioxide-iodine-malonic acid reaction.  

PubMed

We study the growth dynamics of Turing patterns in the chlorine dioxide-iodine-malonic acid reaction-diffusion system in response to perturbations with visible light. We describe several mechanisms by which Turing patterns reappear after they are suppressed by illumination with a disc-shaped geometry. We observe that under specific conditions the patterns reorganize from a random configuration of spots and stripes to a set of ordered, concentric rings, which we refer to as target Turing patterns. These patterns closely resemble the unit cells of the Turing hexagonal superlattices known as black eye patterns. However, these target Turing patterns are not part of a larger superlattice structure, and they usually have a larger number of concentric rings. Numerical simulations support the experimental findings. PMID:24601764

Preska Steinberg, Asher; Epstein, Irving R; Dolnik, Milos

2014-04-01

361

A study of Lux-Flood acid-base reactions in KBr melts at 800°C  

NASA Astrophysics Data System (ADS)

The dissociation of CO{3/2-} (p K = 2.4 ± 0.2) and precipitation of MgO (p L MgO = 10.66 ± 0.1) in a KBr melt at 800°C were studied potentiometrically with the use of a Pt(O2)|ZrO2|(Y2O3) membrane oxygen electrode. The direct calibration of the electrochemical circuit allowed only the equilibrium concentration of O2- (of strong bases) to be determined in the melt. The total concentration of oxygen-containing impurities, including CO{3/2-} and CO{4/2-} weak bases, can be found by the potentiometric titration of a sample of KBr by adding MgCl2 (Mg2+), a strong Lux-Flood acid, which causes the decomposition of these oxygen-containing anions. This reaction can also be used to remove oxo anions from alkali metal halide melts.

Rebrova, T. P.; Cherginets, V. L.; Ponomarenko, T. V.

2009-11-01

362

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

363

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.; S?rensen, Ditte; Broomer, Adam; Oliveira, Kenneth; Perry-O'Keefe, Heather; Sage, Andrew; Young, Barbara; Coull, James

2001-01-01

364

Synthesis and Optical Properties of Poly(BPDA-ODA)\\/Silica Hybrid Thin Films  

Microsoft Academic Search

Poly(BPDA-ODA)\\/silica hybrid optical thin films were synthesized using a sol-gel reaction combined with spin coating and multi-step baking. The hybrid thin films were prepared by the precursors of aminoalkoxysilane capped poly(BPDA-ODA) amic acid and tetramethoxysilane (TMOS). Highly transparent hybrid thin films were obtained at a silica content of 0–51.9 wt%. The prepared hybrid thin films showed homogeneous structures and excellent

Chao-Ching Chang; Ku-Hsien Wei; Yu-Lin Chang; Wen-Chang Chen

2003-01-01

365

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

366

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

367

A theoretical study of the reaction of hypochlorous acid with the bromite ion  

NASA Astrophysics Data System (ADS)

The structures, vibrational spectra, and relative energetics of possible HClBrO -3 isomers and the HOClOBrO -?HOBrOClO - isomerization transition state existing during the reaction between hypochlorous acid (HOCl) and bromite ions (OBrO -) have been examined by using the Becke's non-local three-parameter exchange with the Lee-Yang-Parr correlation density functional method, in conjunction with two different basis sets. The HOBrOClO - structural form is found to be the most stable among the isomers. The energy required for the formation of HOBrOClO - from the HOCl+OBrO - reaction is 25.2 kcal mol -1, while the energy required for the dissociation of HOBrOClO - to HOBr+OClO - is 22.6 kcal mol -1. The barrier for the isomerization of HOClOBrO - to HOBrOClO - is sufficiently high (30.0 kcal mol -1) to not allow the interconversion between the isomeric forms.

Guha, S.; Francisco, J. S.

2001-07-01

368

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

369

Chemical reactions induced in frozen formic acid by heavy ion cosmic rays  

NASA Astrophysics Data System (ADS)

We studied the effects produced by the interaction of heavy ion cosmic rays with interstellar and cometary organic molecules in the solid phase. Formic acid (HCOOH) ice at 15 K was irradiated by 267-MeV 56Fe22+ ions and the chemical evolution was analysed using Fourier transform infrared spectroscopy. The destruction cross-section of HCOOH and the formation cross-sections of the produced molecular species have been determined; the sputtering yield values are also discussed. The most abundant chemical species formed by Fe ion irradiation are CO, CO2 and H2O. The half-life of frozen formic acid molecules in the interstellar medium, as a result of interaction with the different cosmic ray constituents, is evaluated to be 108 yr, considering that the destruction cross-section ?d of heavy ions is ruled by a power law as a function of the electronic stopping power Se (i.e. ?d ˜ S3/2e). Moreover, a complementary study based on mass spectrometry data from the literature has been performed, in order to understand the HCOOH molecule radiolysis, the desorption of its product and the chemical reaction pathways in ice.

Andrade, Diana P. P.; de Barros, Ana L. F.; Pilling, Sérgio; Domaracka, Alicja; Rothard, Hermann; Boduch, Philippe; da Silveira, Enio F.

2013-04-01

370

Microchip Module for Blood Sample Preparation and Nucleic Acid Amplification Reactions  

PubMed Central

A computer numerical control-machined plexiglas-based microchip module was designed and constructed for the integration of blood sample preparation and nucleic acid amplification reactions. The microchip module is comprised of a custom-made heater-cooler for thermal cycling, a series of 254 ?m?×?254 ?m microchannels for transporting human whole blood and reagents in and out of an 8–9 ?L dual-purpose (cell isolation and PCR) glass-silicon microchip. White blood cells were first isolated from a small volume of human whole blood (<3 ?L) in an integrated cell isolation–PCR microchip containing a series of 3.5-?m feature-sized “weir-type” filters, formed by an etched silicon dam spanning the flow chamber. A genomic target, a region in the human coagulation Factor V gene (226-bp), was subsequently directly amplified by microchip-based PCR on DNA released from white blood cells isolated on the filter section of the microchip mounted onto the microchip module. The microchip module provides a convenient means to simplify nucleic acid analyses by integrating two key steps in genetic testing procedures, cell isolation and PCR and promises to be adaptable for additional types of integrated assays. PMID:11230164

Yuen, Po Ki; Kricka, Larry J.; Fortina, Paolo; Panaro, Nicholas J.; Sakazume, Taku; Wilding, Peter

2001-01-01

371

Reactions of cysteamine and other amine metabolites with glyoxylate and oxygen catalyzed by mammalian D-amino acid oxidase.  

PubMed Central

Pig kidney D-amino acid oxidase [D-amino-acid:oxygen oxidoreductase (deaminating), EC 1.4.3.3] catalyzes a rapid uptake of oxygen when high concentrations (50-100 mM) of glyoxylate and the following amines are present under usual assay conditions (pH 8.3): cysteamine, 2-aminoethanol, putrescine, D,L-1-amino-2-propanol, D,L-2-amino-1-propanol, 3-amino-1-propanol, D,L-octopamine, ethylenediamine, and L-cysteine ethyl ester. Notable physiological amines that do not support a rapid O2 reaction under the above conditions include histamine, serotonin, epinephrine, norepinephrine, spermidine, spermine, and cadaverine. A more detailed kinetic investigation of the reactions involving the first four reactive amines listed above indicated that the cysteamine reaction proceeds at a rapid rate even when cysteamine and glyoxylate are present at less than millimolar concentrations, but greater than millimolar concentrations are needed in the other amine reactions in order to observe a reasonable rate. At low concentrations and pH 7.4, the cysteamine-glyoxylate substrate (presumably thiazolidine-2-carboxylic acid) reacts an order of magnitude faster than any other known D-amino acid oxidase substrate. Considerable circumstantial evidence suggests that the reaction involving cysteamine is occurring physiologically, but the reactions of other amines would be occurring in the cell at a very low rate, if at all. It is proposed that the product of the enzymic reaction may be a metabolic effector that can modify the reactivity of proteins or nucleic acids by covalent attachment. PMID:37501

Hamilton, G A; Buckthal, D J; Mortensen, R M; Zerby, K W

1979-01-01

372

Determination of Arrhenius and Thermodynamic Parameters for the Aqueous Reaction of the Hydroxyl Radical with Lactic Acid  

SciTech Connect

Lactic acid is a major component of the TALSPEAK process planned for use in the separation of trivalent lanthanide and actinide elements. This acid acts both as a buffer, and also to protect the actinide complexant from radiolytic damage. However, there is little kinetic information on the reaction of water radiolysis species with lactic acid, particularly under the anticipated process conditions of aerated aqueous solution at pH~3, where oxidizing reactions are expected to dominate. Here we have determined temperature-dependent reaction rate constants for the reactions of the hydroxyl radical with lactic acid and the lactate ion. For lactic acid this rate constant is given by the equation: ln k1 = (23.85 ± 0.19) – (1120 ± 54) / T, corresponding to an activation energy of 9.31 ± 0.45 kJ mol-1 and a room temperature reaction rate constant of (5.24 ± 0.09) x 108 M-1 s-1 (24.0oC). For the lactate ion, the temperature-dependent rate constant is given by: ln k2 = (24.83 ± 0.14) – (1295 ± 42) / T, for an activation energy of 10.76 ± 0.35 kJ mol-1 and a room temperature value of (7.77 ± 0.11) x 108 M-1 s-1 (22.2oC). These kinetic data have been combined with autotitration measurements to determine the temperature-dependent behavior of the lactic acid pKa value, allowing thermodynamic parameters for the acid dissociation to be calculated as ?Hº = -10.75 ± 1.77 kJ mol-1, ?Sº = -103.9 ± 6.0 J K-1 mol-1 and ?Gº = 20.24 ± 2.52 kJ mol-1 at low ionic strength.

Leigh R. Martin; Stephen P. Mezyk; Bruce J. Mincher

2009-01-01

373

The regioselectivity of Diels–Alder reaction of myrcene with carbonyl-containing dienophiles catalysed by Lewis acids  

Microsoft Academic Search

The effects of various Lewis acids and reaction temperature on the regioselectivity of the Diels–Alder reaction of myrcene (7-methyl-3-methene-1,6-octadiene) with acrolein or methyl acrylate have been studied. The high regioselective `para' adducts were obtained when acrolein and methyl acrylate were used as dienophiles in the presence of ZnCl2 and AlCl3 catalyst, respectively. UV, 1HNMR and IR spectroscopic methods, were first

Donghong Yin; Dulin Yin; Zaihui Fu; Qianhe Li

1999-01-01

374

Chiral rare earth organophosphates as homogeneous Lewis acid catalysts for the highly enantioselective hetero-Diels–Alder reactions  

Microsoft Academic Search

Various trivalent rare earth-chiral phosphate complexes [(R)-1-RE, (R)-3-RE, and (R)-4-Ce] were prepared and evaluated as a Lewis acid catalyst for the asymmetric hetero-Diels–Alder reaction of aldehydes with the Danishefsky's diene. Some of them effectively promoted the reaction at room temperature in the presence or absence of achiral additives under homogeneous conditions to afford the corresponding cycloadducts with high ee's (up

Hiroshi Furuno; Tetsuji Hayano; Takeshi Kambara; Yuichi Sugimoto; Takeshi Hanamoto; Yumiko Tanaka; Yong Zhi Jin; Takumi Kagawa; Junji Inanaga

2003-01-01

375

Fatty acid and product selectivities of potato tuber lipid acyl hydrolase in esterification reactions with glycerol in organic media  

Microsoft Academic Search

Fatty acid [FA; butanoic (C4); octanoic (C8); tetradecanoic (C14); and cis-9,12-octadecadienoic (C18:2) acids] reaction selectivity and the corresponding acyl profiles in differentially accumulating acylglycerol (AG) products\\u000a (mono-, di-, and triacylglycerols; MAG, DAG, TAG, respectively) were evaluated for Celite™-immobilized potato tuber lipid\\u000a acyl hydrolase (LAH)-mediated esterification reactions in isooctane at 35°C and water activity of 0.19. The ordinal pattern\\u000a of FA

Praphan Pinsirodom; Kirk L. Parkin

1999-01-01

376

In situ generation of palladium nanoparticles: ligand-free palladium catalyzed pivalic acid assisted carbonylative Suzuki reactions at ambient conditions.  

PubMed

Highly selective carbonylative Suzuki reactions of aryl iodides with arylboronic acids using an in situ generated nanopalladium system furnished products in high yields. The reactions were performed under ambient conditions and in the absence of an added ligand. The key to success is the addition of pivalic acid, which can effectively suppress undesired Suzuki coupling. The synthesis can be easily scaled up, and the catalytic system can be reused up to nine times. The nature of the active catalytic species are discussed. PMID:24397578

Zhou, Qing; Wei, Shaohua; Han, Wei

2014-02-01

377

Hybridization-Based Detection of Helicobacter pylori at Human Body Temperature Using Advanced Locked Nucleic Acid (LNA) Probes  

PubMed Central

The understanding of the human microbiome and its influence upon human life has long been a subject of study. Hence, methods that allow the direct detection and visualization of microorganisms and microbial consortia (e.g. biofilms) within the human body would be invaluable. In here, we assessed the possibility of developing a variant of fluorescence in situ hybridization (FISH), named fluorescence in vivo hybridization (FIVH), for the detection of Helicobacter pylori. Using oligonucleotide variations comprising locked nucleic acids (LNA) and 2’-O-methyl RNAs (2’OMe) with two types of backbone linkages (phosphate or phosphorothioate), we were able to successfully identify two probes that hybridize at 37 °C with high specificity and sensitivity for H. pylori, both in pure cultures and in gastric biopsies. Furthermore, the use of this type of probes implied that toxic compounds typically used in FISH were either found to be unnecessary or could be replaced by a non-toxic substitute. We show here for the first time that the use of advanced LNA probes in FIVH conditions provides an accurate, simple and fast method for H. pylori detection and location, which could be used in the future for potential in vivo applications either for this microorganism or for others. PMID:24278398

Fontenete, Silvia; Guimaraes, Nuno; Leite, Marina; Figueiredo, Ceu; Wengel, Jesper; Filipe Azevedo, Nuno

2013-01-01

378

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

379

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

Microsoft Academic Search

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

Agnieszka Bukowska; Wiktor Bukowski; Jaros?aw Noworól

2005-01-01

380

Detection of a hypersensitive reaction in the chestnut hybrid 'Bouche de Bétizac' infested by Dryocosmus kuriphilus Yasumatsu.  

PubMed

The purpose of the study was the identification of the mechanisms of resistance to Dryocosmus kuriphilus Yasumatsu in the hybrid-resistant cultivar 'Bouche de Bétizac' (Castanea sativa × Castanea crenata). Larvae and eggs of the insect are found in the buds of this cultivar at the end of winter, but there is no gall development after budburst. The hypothesis of the presence of a hypersensitive reaction (HR) in the buds was tested using diaminobenzidine (DAB) to detect H(2)O(2) and by Real Time PCR (RT-PCR) to evaluate the expression of a germin-like protein gene. HR in plants is elicited by the production of reactive oxygen compounds, such as H(2)O(2), and results in the programmed cell death. The DAB test was applied to buds of 'Bouche de Bétizac' and of the susceptible cultivar 'Madonna' (C. sativa) at different stages of budburst. The DAB staining produced brown areas in the swelling buds of 'Bouche de Bétizac', indicating the presence of H(2)O(2). On the contrary, all uninfested buds, as well as the infested buds of 'Madonna', appeared whitish. Papers report that germin and germin-like proteins (GLP) with oxalate oxidase activity are discrete markers of stress-responsive gene products. A strong expression of the chestnut GLP gene was detected by RT-PCR at bud swelling in infested 'Bouche de Bétizac' buds but not in 'Madonna' ones. The results support the hypothesis of the occurrence of an HR in 'Bouche de Bétizac' as response to the cynipid infestation, resulting in cell and larvae death. PMID:22906812

Dini, Francesca; Sartor, Chiara; Botta, Roberto

2012-11-01

381

Lanthanide triflates as water-tolerant Lewis acids. Activation of commercial formaldehyde solution and use in the aldol reaction of silyl enol ethers with aldehydes in aqueous media  

Microsoft Academic Search

The catalytic effects of lanthanide triflates in the hydroxymethylation and the aldol reaction of silyl enol ethers (w\\/aldehydes). The rare earth triflates served as Lewis acid catalysts in the aqueous reaction medium.

Shue Kobayashi; Iwao Hachiya

1994-01-01

382

Lanthanide triflates as water-tolerant Lewis acids. Activation of commercial formaldehyde solution and use in the aldol reaction of silyl enol ethers with aldehydes in aqueous media  

SciTech Connect

The catalytic effects of lanthanide triflates in the hydroxymethylation and the aldol reaction of silyl enol ethers (w/aldehydes). The rare earth triflates served as Lewis acid catalysts in the aqueous reaction medium.

Kobayashi, Shue; Hachiya, Iwao [Univ. of Tokyo (Japan)

1994-07-01

383

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.

384

Gas-phase enthalpies of formation and enthalpies of sublimation of amino acids based on isodesmic reaction calculations.  

PubMed

Accurate gas-phase enthalpies of formation (?fH298°) of 20 common ?-amino acids, seven uncommon amino acids, and three small peptides were calculated by combining G4 theory calculations with an isodesmic reaction approach. The internal consistency over a set of ?fH298°(g) values was achieved by sequential adjustment of their values through the isodesmic reactions. Four amino acids, alanine, ?-alanine, sarcosine, and glycine, with reliable internally self-consistent experimental data, were chosen as the key reference compounds. These amino acids together with about 100 compounds with reliable experimental data (their accuracy was supported by G4 calculations) were used to estimate the enthalpies of formation of remaining amino acids. All of the amino acids with the previously established enthalpies of formation were later used as the reference species in the isodesmic reactions for the other amino acids. A systematic comparison was made of 14 experimentally determined enthalpies of formation with the results of calculations. The experimental enthalpies of formation for 10 amino acids were reproduced with good accuracy, but the experimental and calculated values for 4 compounds differed by 11–21 kJ/mol. For these species, the theoretical ?fH298°(g) values were suggested as more reliable than the experimental values. On the basis of theoretical results, the recommended values for the gas-phase enthalpies of formation were also provided for amino acids for which the experimental ?fH298°(g) were not available. The enthalpies of sublimation were evaluated for all compounds by taking into account the literature data on the solid-phase enthalpies of formation and the ?fH298°(g) values recommended in our work. A special attention was paid to the accurate prediction of enthalpies of formation of amino acids from the atomization reactions. The problems associated with conformational flexibility of these compounds and harmonic treatment of low frequency torsional modes were discussed. The surprisingly good agreement between the ?fH298°(g) values calculated from the atomization and isodesmic reactions is largely the result of a fortuitous mutual compensation of various corrections used in the atomization reaction procedure. PMID:24766636

Dorofeeva, Olga V; Ryzhova, Oxana N

2014-05-15

385

First-Principles Assessment of the Reactions of Boric Acid on NiO(001) and ZrO2(111) Surfaces  

E-print Network

First-Principles Assessment of the Reactions of Boric Acid on NiO(001) and ZrO2(111) Surfaces and dissociation reaction pathways of boric acid, B(OH)3, and the reaction kinetic descriptors on NiO(001) and ZrO2O are included using the DFT + U approach. Adsorption of boric acid on clean ZrO2(111) is found to be more

Yildiz, Bilge

386

Reaction of Calcite and Dolomite with In-Situ Gelled Acids, Organic Acids, and Environmentally Friendly Chelating Agent (GLDA)  

E-print Network

Well stimulation is the treatment remedy when oil/gas productivity decreases to unacceptable economical limits. Well stimulation can be carried out through either "Matrix Acidizing" or fracturing with both "Hydraulic Fracturing" and "Acid Fracturing...

Rabie, Ahmed 1978-

2012-11-16

387

Determination of ?-aminonitriles, ?-amino acid amides and ?-amino acids by means of HPLC, post-column reaction and fluorescence detection  

Microsoft Academic Search

Summary  An HPLC method was developed for the simultaneous assay of intermediate (?-aminonitrile and ?-amino acid amide) and end products\\u000a (?-amino acid) in process streams of ?-amino acid synthesis. Applications are given for Ala, Val and Leu. ?-Aminonitriles\\u000a were stable in a phosphate buffer pH 3, which was subsequently used for sample handling and chromatography. The ?-aminonitrile,\\u000a the corresponding acid amide

A. L. L. Duchateau; M. G. Crombach

1987-01-01

388

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

389

Transmetallation Versus ?-Hydride Elimination: The Role of 1,4-Benzoquinone in Chelation-Controlled Arylation Reactions with Arylboronic Acids  

PubMed Central

AbstractThe formation of an atypical, saturated, diarylated, Heck/Suzuki, domino product produced under oxidative Heck reaction conditions, employing arylboronic acids and a chelating vinyl ether, has been investigated by DFT calculations. The calculations highlight the crucial role of 1,4-benzoquinone (BQ) in the reaction. In addition to its role as an oxidant of palladium, which is necessary to complete the catalytic cycle, this electron-deficient alkene opens up a low-energy reaction pathway from the post-insertion ?-alkyl complex. The association of BQ lowers the free-energy barrier for transmetallation of the ?-alkyl complex to create a pathway that is energetically lower than the oxidative Heck reaction pathway. Furthermore, the calculations showed that the reaction is made viable by BQ-mediated reductive elimination and leads to the saturated diarylated product. PMID:22374849

Skold, Christian; Kleimark, Jonatan; Trejos, Alejandro; Odell, Luke R; Nilsson Lill, Sten O; Norrby, Per-Ola; Larhed, Mats

2012-01-01

390

Theoretical analysis of kinetic isotope effects on proton transfer reactions between substituted alpha-methoxystyrenes and substituted acetic acids.  

PubMed

Primary kinetic isotope effects (KIEs) on a series of carboxylic acid-catalyzed protonation reactions of aryl-substituted alpha-methoxystyrenes (X-1) to form oxocarbenium ions have been computed using the second-order Kleinert variational perturbation theory (KP2) in the framework of Feynman path integrals (PI) along with the potential energy surface obtained at the B3LYP/6-31+G(d,p) level. Good agreement with the experimental data was obtained, demonstrating that this novel computational approach for computing KIEs of organic reactions is a viable alternative to the traditional method employing Bigeleisen equation and harmonic vibrational frequencies. Although tunneling makes relatively small contributions to the lowering of the free energy barriers for the carboxylic acid catalyzed protonation reaction, it is necessary to include tunneling contributions to obtain quantitative estimates of the KIEs. Consideration of anharmonicity can further improve the calculated KIEs for the protonation of substituted alpha-methoxystyrenes by chloroacetic acid, but for the reactions of the parent and 4-NO(2) substituted alpha-methoxystyrene with substituted carboxylic acids, the correction of anharmonicity overestimates the computed KIEs for strong acid catalysts. In agreement with experimental findings, the largest KIEs are found in nearly ergoneutral reactions, DeltaG(o) approximately 0, where the transition structures are nearly symmetric and the reaction barriers are relatively low. Furthermore, the optimized transition structures are strongly dependent on the free energy for the formation of the carbocation intermediate, that is, the driving force DeltaG(o), along with a good correlation of Hammond shift in the transition state structure. PMID:19754046

Wong, Kin-Yiu; Richard, John P; Gao, Jiali

2009-10-01

391

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

392

Redox chemistry of selenenic acids and the insight it brings on transition state geometry in the reactions of peroxyl radicals.  

PubMed

The redox chemistry of selenenic acids has been explored for the first time using a persistent selenenic acid, 9-triptyceneselenenic acid (RSeOH), and the results have been compared with those we recently obtained with its lighter chalcogen analogue, 9-triptycenesulfenic acid (RSOH). Specifically, the selenenyl radical was characterized by EPR spectroscopy and equilibrated with a phenoxyl radical of known stability in order to determine the O-H bond dissociation enthalpy of RSeOH (80.9 ± 0.8 kcal/mol): ca. 9 kcal/mol stronger than in RSOH. Kinetic measurements of the reactions of RSeOH with peroxyl radicals demonstrate that it readily undergoes H-atom transfer reactions (e.g., k = 1.7 × 10(5) M(-1) s(-1) in PhCl), which are subject to kinetic solvent effects and kinetic isotope effects similar to RSOH and other good H-atom donors. Interestingly, the rate constants for these reactions are only 18- and 5-fold smaller than those measured for RSOH in PhCl and CH3CN, respectively, despite being 9 kcal/mol less exothermic for RSeOH. IR spectroscopic studies demonstrate that RSeOH is less H-bond acidic than RSOH, accounting for these solvent effects and enabling estimates of the pKas in RSeOH and RSOH of ca. 15 and 10, respectively. Calculations suggest that the TS structures for these reactions have significant charge transfer between the chalcogen atom and the internal oxygen atom of the peroxyl radical, which is nominally better for the more polarizable selenenic acid. The higher than expected reactivity of RSeOH toward peroxyl radicals is the strongest experimental evidence to date for charge transfer/secondary orbital interactions in the reactions of peroxyl radicals with good H-atom donors. PMID:24383573

Zielinski, Zosia; Presseau, Nathalie; Amorati, Riccardo; Valgimigli, Luca; Pratt, Derek A

2014-01-29

393

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

394

Cluster Phase Chemistry: Gas-Phase Reactions of Anionic Sodium Salts of Dicarboxylic Acid Clusters with Water Molecules  

E-print Network

Cluster Phase Chemistry: Gas-Phase Reactions of Anionic Sodium Salts of Dicarboxylic Acid Clusters with Water Molecules Hugh I. Kim, William A. Goddard III,§ and J. L. Beauchamp*, Noyes Laboratory of Chemical of the activated cluster with water molecules. For example, with water addition, malonate clusters dissociate

Goddard III, William A.

395

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

PubMed Central

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

2011-01-01

396

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

397

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

398

40 CFR 721.10136 - 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester, reaction products with hexakis(alkoxyalkyl...  

Code of Federal Regulations, 2010 CFR

. (1) The chemical substance identified generically as 2-propenoic acid, 2-methyl-, 2-hydroxyethyl ester, reaction products with hexakis(alkoxyalkyl)melamine (PMN P-05-177) is subject to reporting under this section for the significant new uses described in paragraph (a)(2) of this...

2010-07-01

399

Stoichiometric Fingerprinting as an Aid in Understanding Complex Reactions: The Oxidation of Malonic Acid by Cerium(IV)  

E-print Network

Stoichiometric Fingerprinting as an Aid in Understanding Complex Reactions: The Oxidation of Malonic Acid by Cerium(IV) Bettina Neumann,, Oliver Steinbock,*,, Stefan C. Mu1ller,,§ and Nar S. DalalVed: December 6, 1996; In Final Form: February 19, 1997X The stoichiometry of the Ce(IV) oxidation of malonic

Steinbock, Oliver

400

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

National Technical Information Service (NTIS)

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

M. Zeldin, W. K. Fife

1991-01-01

401

Geochemical modeling of reactions and partitioning of trace metals and radionuclides during titration of contaminated acidic sediments.  

PubMed

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 studywas 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 SO4(2-) for contaminated sediments indicated close agreement suggesting that the model could potentially be used to predictthe acid-base behavior of the sediment-solution system under variable pH conditions. PMID:19031894

Zhang, Fan; Luo, Wensui; Parker, Jack C; Spalding, Brian P; Brooks, Scott C; Watson, David B; Jardine, Philip M; Gu, Baohua

2008-11-01

402

Enantioselective Synthesis of anti- and syn-homopropargyl alcohols via Chiral Br?nsted Acid Catalyzed asymmetric Allenylboration reactions  

PubMed Central

Chiral Brønsted acid catalyzed asymmetric allenylboration reactions are described. Under optimized conditions, anti-homopropargyl alcohols 2 are obtained in high yields with excellent diastereo- and enantioselectivities from stereochemically matched aldehyde allenylboration reactions with (M)-1 catalyzed by the chiral phosphoric acid (S)-4. The syn-isomers 3 can also be obtained in good diastereoselectivities and excellent enantioselectivities from the mismatched allenylboration reactions of aromatic aldehydes using (M)-1 in the presence of the enantiomeric phosphoric acid (R)-4. The stereochemistry of the methyl group introduced into 2 and 3 is controlled by the chirality of the allenylboronate (M)-1, whereas the configuration of the new hydroxyl stereocenter is controlled by the enantioselectivity of the chiral phosphoric acid catalyst used in these reactions. The synthetic utility of this methodology was further demonstrated in triple asymmetric syntheses of a variety of anti,anti-stereotriads, the direct synthesis of which has constituted a significant challenge using previous generations of aldol and crotylmetal reagents. PMID:22731887

Chen, Ming; Roush, William R.

2012-01-01

403

Structure and DNA Hybridization Properties of Mixed Nucleic Acid/Maleimide-Ethylene Glycol Monolayers  

SciTech Connect

The surface structure and DNA hybridization performance of thiolated single-strand DNA (HS-ssDNA) covalently attached to a maleimide-ethylene glycol disulfide (MEG) monolayer on gold have been investigated. Monolayer immobilization chemistry and surface coverage of reactive ssDNA probes were studied by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. Orientation of the ssDNA probes was determined by near-edge X-ray absorption fine structure (NEXAFS). Target DNA hybridization on the DNA-MEG probe surfaces was measured by surface plasmon resonance (SPR) to demonstrate the utility of these probe surfaces for detection of DNA targets from both purified target DNA samples and complex biological mixtures such as blood serum. Data from complementary techniques showed that immobilized ssDNA density is strongly dependent on the spotted bulk DNA concentration and buffer ionic strength. Variation of the immobilized ssDNA density had a profound influence on the DNA probe orientation at the surface and subsequent target hybridization efficiency. With increasing surface probe density, NEXAFS polarization dependence results (followed by monitoring the N 1s {yields} {pi}* transition) indicate that the immobilized ssDNA molecules reorient toward a more upright position on the MEG monolayer. SPR assays of DNA targets from buffer and serum showed that DNA hybridization efficiency increased with decreasing surface probe density. However, target detection in serum was better on the 'high-density' probe surface than on the 'high-efficiency' probe surface. The amounts of target detected for both ssDNA surfaces were several orders of magnitude poorer in serum than in purified DNA samples due to nonspecific serum protein adsorption onto the sensing surface.

Lee,C.; Nguyen, P.; Grainger, D.; Gamble, L.; Castner, D.

2007-01-01

404

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[double bond, length as m-dash]O and C[double bond, length as m-dash]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

405

Ozonolysis of Mixed Oleic-Acid/Stearic-Acid Particles: Reaction Kinetics and Chemical Y. Katrib, G. Biskos, P. R. Buseck, P. Davidovits, J. T. Jayne,| M. Mochida,, M. E. Wise,  

E-print Network

a primary role in regional issues of air pollution, visibility, and human health.6 Atmospheric particlesOzonolysis of Mixed Oleic-Acid/Stearic-Acid Particles: Reaction Kinetics and Chemical Morphology Y, 2005 The ozonolysis of mixed oleic-acid/stearic-acid (OL/SA) aerosol particles from 0/100 to 100/0 wt

406

A Novel Intermediate in the Reaction of Seleno CYP119 with m-Chloroperbenzoic Acid†  

PubMed Central

Cytochrome P450 mediated monooxygenation generally proceeds via a reactive ferryl intermediate coupled to a ligand radical [Fe(IV)=O]+. referred to as Compound I (Cpd I). The proximal cysteine thiolate ligand is a critical determinant of the spectral and catalytic properties of P450 enzymes. To explore the effect of increased electron donation by the proximal ligand in the P450 catalytic cycle, we recently reported successful incorporation of SeCys into the active site of CYP119, a thermophilic cytochrome P450. Here we report relevant physical properties of SeCYP119 and a detailed analysis of the reaction of SeCYP119 with m-chloroperbenzoic acid. Our results indicate that the selenolate anion reduces rather than stabilizes Cpd I and also protects the heme from oxidative destruction, leading to the generation of a new stable species with an absorbance maximum at 406 nm. This stable intermediate can be returned to the normal ferric state by reducing agents and thiols, in agreement with oxidative modification of the selenolate ligand itself. Thus, in the seleno protein, the oxidative damage shifts from the heme to the proximal ligand, presumably because (a) increased electron donation more efficiently quenches reactive species such as Cpd I, and (b) the protection of the thiolate ligand provided by the protein active site structure is insufficient to shield the more oxidizable selenolate ligand. PMID:21381758

Sivaramakrishnan, Santhosh; Ouellet, Hugues; Du, Jing; McLean, Kirsty J.; Medzihradszky, Katalin F.; Dawson, John H.; Munro, Andrew W.; Ortiz de Montellano, Paul R.

2011-01-01

407

Locked Nucleic Acids Can Enhance the Analytical Performance of Quantitative Methylation-Specific Polymerase Chain Reaction  

PubMed Central

Aberrant DNA methylation of tumor suppressor genes is a frequent epigenetic event that occurs early in tumor progression. Real-time quantitative methylation-specific polymerase chain reaction (QMSP) assays can provide accurate detection and quantitation of methylated alleles that may be potentially useful in diagnosis and risk assessment for cancer. Development of QMSP requires optimization to maximize analytical specificity and sensitivity for the detection of methylated alleles. However, in some cases challenges encountered in primer and probe design can make optimization difficult and limit assay performance. Locked nucleic acids (LNAs) demonstrate increased affinity and specificity for their cognate DNA sequences. In this proof-of-principle study, LNA residues were incorporated into primer and probe design to determine whether LNA-modified oligonucleotides could enhance the analytical performance of QMSP for IGSF4 promoter methylation in human cancer cell lines using either SYBR Green or fluorogenic probe detection methods. Use of LNA primers in QMSP with SYBR Green improved analytical specificity for methylated alleles and eliminated the formation of nonspecific products because of mispriming from unmethylated alleles. QMSP using LNA probe and primers showed an increased amplification efficiency and maximum fluorescent signal. QMSP with LNA oligonucleotides and either detection method could reliably detect five genome equivalents of methylated DNA in 1000- to 10,000-fold excess unmethylated DNA. Thus, LNA oligonucleotides can be used in QMSP optimization to enhance analytical performance. PMID:18165272

Gustafson, Karen S.

2008-01-01

408

Growth reaction norms of domesticated, wild and hybrid Atlantic salmon families in response to differing social and physical environments  

PubMed Central

Background Directional selection for growth has resulted in the 9-10th generation of domesticated Atlantic salmon Salmo salar L. outgrowing wild salmon by a ratio of approximately 3:1 when reared under standard hatchery conditions. In the wild however, growth of domesticated and wild salmon is more similar, and seems to differ at the most by a ratio of 1.25:1. Comparative studies of quantitative traits in farmed and wild salmon are often performed by the use of common-garden experiments where salmon of all origins are reared together to avoid origin-specific environmental differences. As social interaction may influence growth, the large observed difference in growth between wild and domesticated salmon in the hatchery may not be entirely genetically based, but inflated by inter-strain competition. This study had two primary aims: (i) investigate the effect of social interaction and inter-strain competition in common-garden experiments, by comparing the relative growth of farmed, hybrid and wild salmon when reared together and separately; (ii) investigate the competitive balance between wild and farmed salmon by comparing their norm of reaction for survival and growth along an environmental gradient ranging from standard hatchery conditions to a semi-natural environment with restricted feed. Results The main results of this study, which are based upon the analysis of more than 6000 juvenile salmon, can be summarised as; (i) there was no difference in relative growth between wild and farmed salmon when reared together and separately; (ii) the relative difference in body weight at termination between wild and farmed salmon decreased as mortality increased along the environmental gradient approaching natural conditions. Conclusions This study demonstrates that potential social interactions between wild and farmed salmon when reared communally are not likely to cause an overestimation of the genetic growth differences between them. Therefore, common-garden experiments represent a valid methodological approach to investigate genetic differences between wild and farmed salmon. As growth of surviving salmon of all origins became more similar as mortality increased along the environmental gradient approaching natural conditions, a hypothesis is presented suggesting that size-selective mortality is a possible factor reducing growth differences between these groups in the wild. PMID:24165438

2013-01-01

409

Multidimensional Separation of Chiral Amino Acid Mixtures in a Multilayered Three Dimensional Hybrid Microfluidic/Nanofluidic Device  

PubMed Central

Microscale total analysis systems (?TAS) allow high-throughput analyses by integrating multiple processes, parallelization and automation. Here we combine unit operations of ?TAS to create a device that can perform multidimensional separations using a three-dimensional hybrid microfluidic/nanofluidic device composed of alternating layers of patterned polymethylmethacrylate and nanocapillary array membranes constructed from nuclear track-etched polycarbonate. Two consecutive electrophoretic separations are performed, the first being an achiral separation followed by a chiral separation of a selected analyte band. Separation conditions are optimized for a racemic mixture of fluorescein-labeled amino acids, serine and aspartic acid, chosen because there are endogenous D-forms of these amino acids in animals. The chiral separation is implemented using micellar electrokinetic chromatography using ?–cyclodextrin as the chiral selector and sodium taurocholate as the micelle forming agent. Analyte separation is monitored by dual-beam laser-induced fluorescence detection. After separation in the first electrophoretic channel, the preselected analyte is sampled by the second-stage separation using an automated collection sequence with a zero-crossing algorithm for peak identification. The controlled fluidic environment inherent to the three-dimensional architecture enables a series of separations in varying fluidic environments and allows sample stacking via different background electrolyte pH conditions. The ability to interface sequential separations, selected analyte capture and other fluidic manipulations in the third dimension significantly improves the functionality of multilayer microfluidic devices. PMID:19271741

Kim, Bo Young; Yang, Jing; Gong, Maojun; Flachsbart, Bruce R.; Shannon, Mark A.; Bohn, Paul W.; Sweedler, Jonathan V.

2009-01-01

410

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

411

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

412

Hybridization of G-quadruplex-forming peptide nucleic acids to guanine-rich DNA templates inhibits DNA polymerase ? extension.  

PubMed

The guanine quadruplex (G-quadruplex) is a highly stable secondary structure that forms in G-rich repeats of DNA, which can interfere with DNA processes, including DNA replication and transcription. We showed previously that short guanine-rich peptide nucleic acids (PNAs) can form highly stable hybrid quadruplexes with DNA. We hypothesized that such structures would provide a stronger block to polymerase extension on G-rich templates than a native DNA homoquadruplex because of the greater thermodynamic stability of the PNA-DNA hybrid structures. To test this, we analyzed the DNA primer extension activity of polymerase ?, a translesion polymerase implicated in synthesis past G-quadruplex blocks, on DNA templates containing guanine repeats. We observed a PNA concentration-dependent decrease in the level of polymerase ? extension to the end of the template and an increase in the level of polymerase ? inhibition at the sequence prior to the G-rich repeats. In contrast, the addition of a complementary C-rich PNA that hybridizes to the G-rich repeats by Watson-Crick base pairing led to a decrease in the level of polymerase inhibition and an increase in the level of full-length extension products. The G-quadruplex-forming PNA exhibited inhibition (IC50=16.2±3.3 nM) of polymerase ? DNA synthesis on the G-rich templates stronger than that of the established G-quadruplex-stabilizing ligand BRACO-19 (IC50=42.5±4.8 nM). Our results indicate that homologous PNA targeting of G-rich sequences creates stable PNA-DNA heteroquadruplexes that inhibit polymerase ? extension more effectively than a DNA homoquadruplex. The implications of these results for the potential development of homologous PNAs as therapeutics for halting proliferating cancer cells are discussed. PMID:25068499

Murphy, Connor T; Gupta, Anisha; Armitage, Bruce A; Opresko, Patricia L

2014-08-19

413

Adsorption and reaction of formic acid on NiO(lOO) films on Mo(l00): Temperature programmed desorption and high resolution electron  

E-print Network

Adsorption and reaction of formic acid on NiO(lOO) films on Mo(l00): Temperature programmed desorption and high resolution electron energy loss spectroscopy studies Charles M. Truong, Ming-Cheng Wu-3255 (Received 24 June 1992;accepted8 September1992) Adsorption and reaction of formic acid on well-defined Ni

Goodman, Wayne

414

Colorimetric Detection of Ehrlichia Canis via Nucleic Acid Hybridization in Gold Nano-Colloids  

PubMed Central

Canine monocytic ehrlichiosis (CME) is a major thick-bone disease of dog caused by Ehrlichia canis. Detection of this causal agent outside the laboratory using conventional methods is not effective enough. Thus an assay for E. canis detection based on the p30 outer membrane protein gene was developed. It was based on the p30 gene amplification using loop-mediated isothermal DNA amplification (LAMP). The primer set specific to six areas within the target gene were designed and tested for their sensitivity and specificity. Detection of DNA signals was based on modulation of gold nanoparticles' surface properties and performing DNA/DNA hybridization using an oligonucleotide probe. Presence of target DNA affected the gold colloid nanoparticles in terms of particle aggregation with a plasmonic color change of the gold colloids from ruby red to purple, visible by the naked eye. All the assay steps were completed within 90 min including DNA extraction without relying on standard laboratory facilities. This method was very specific to target bacteria. Its sensitivity with probe hybridization was sufficient to detect 50 copies of target DNA. This method should provide an alternative choice for point of care control and management of the disease. PMID:25111239

Muangchuen, Ajima; Chaumpluk, Piyasak; Suriyasomboon, Annop; Ekgasit, Sanong

2014-01-01

415

Method of Designing Addressable Array for Detection of Nucleic Acid Sequence Differences using Ligase Detection Reaction.  

National Technical Information Service (NTIS)

The present invention is directed to a method of designing a plurality of capture oligonucleotide probes for use on a support to which complementary oligonucleotide probes will hybridize with little mismatch, where the plural capture oligonucleotide probe...

F. Barany, M. Zirvi, N. P. Gerry, R. Favis, R. Kliman

2001-01-01

416

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

417

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

418

Effects of novel supports on the physical and catalytic properties of tungstophosphoric acid for alcohol dehydration reactions  

SciTech Connect

The catalytic behavior of tungstophosphoric acid supported on modified mesoporous silica materials for the dehydration of 2-butanol and methanol was studied. Specifically, the supports evaluated here consisted of unmodified MCM-41 and SBA-15 mesoporous silicas, and these materials coated with sub-monolayer quantities of alumina, titania, and zirconia. UV-Vis DRS and 31P-NMR spectroscopy showed that the tungstophosphoric acid species retained their chemical identity in the synthesized supported form, although the spectra were influenced by the specific support material used. In addition, their acidic properties were evaluated using temperature programmed oxidation of isopropyl amine. The differences in reaction rates between the samples reflect both the diversity in the amount of Brønsted acidic sites available for catalysis and dissimilarities in coking resistance. These two characteristics depend, in turn, on the type of support modifier used to prepare the catalyst.

Herrera, Jose E.; Kwak, Ja Hun; Hu, Jian Zhi; Wang, Yong; Peden, Charles HF

2008-08-17

419

Tissue essential fatty acid composition and competitive response to dietary manipulations in white bass ( Morone chrysops), striped bass ( M. saxatilis) and hybrid striped bass ( M. chrysops× M. saxatilis)  

Microsoft Academic Search

The effects of wide changes in dietary levels of docosahexaenoic (DHA) or arachidonic (ArA) acids on growth, survival and fatty acid composition in body tissues of Morone larvae were examined. White bass (WB, Morone chrysops), striped bass (SB, Morone saxatilis) and sunshine hybrid bass (HSB, M. chrysops×M. saxatilis) larvae (day 24–46) were fed Artemia nauplii enriched with algal sources of

Moti Harel

2003-01-01

420

Fluorescence In Situ Hybridization Assay Using Peptide Nucleic Acid Probes for Differentiation between Tuberculous and Nontuberculous Mycobacterium Species in Smears of Mycobacterium Cultures  

Microsoft Academic Search

TB PNA FISH is a new fluorescence in situ hybridization (FISH) method using peptide nucleic acid (PNA) probes for differentiation between species of the Mycobacterium tuberculosis complex (MTC) and nontubercu- lous mycobacteria (NTM) in acid-fast bacillus-positive (AFB1) cultures is described. The test is based on fluorescein-labelled PNA probes that target the rRNA of MTC or NTM species applied to smears

HENRIK STENDER; KAARE LUND; KENNETH H. PETERSEN; OLE F. RASMUSSEN; POONPILAS HONGMANEE; HÅKAN MIORNER; SVEN E. GODTFREDSEN

1999-01-01

421

Fatty and resin acid analysis in tall oil products via supercritical fluid extraction-supercritical fluid reaction using enzymatic catalysis.  

PubMed

Supercritical fluid extraction (SFE) is combined with supercritical fluid reaction (SFR) in an analytical mode to assess tall oil products for their fatty or resin acid content or both. The SFR consists of an inline enzymatically catalyzed reaction in which a lipase transesterifies specific lipids with methanol. The SFE-SFR sequence is conducted employing commercially available extractors using supported lipases in the extraction cell to form methyl esters. In this study, six different commercially available lipases are screened for activity. The SFE-SFR extracts are analyzed by capillary gas chromatography and supercritical fluid chromatography and then compared with tall oil products derivatized by conventional chemical derivatization techniques. PMID:11471988

Taylor, S L; King, J W

2001-07-01

422

Edge-Functionalization of Pyrene as a Miniature Graphene via Friedel-Crafts Acylation Reaction in Poly(Phosphoric Acid).  

PubMed

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 (P(2)O(5)) 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). PMID:21076664

Jeon, In-Yup; Choi, Eun-Kyoung; Bae, Seo-Yoon; Baek, Jong-Beom

2010-01-01

423

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

424

Photoinduced amino-imino tautomerization reaction in 2-aminopyrimidine and its methyl derivatives with acetic acid  

NASA Astrophysics Data System (ADS)

The electronic absorption and fluorescence spectra of 2-aminopyrimidine (2APM), 2-amino-4-methylpyrimidine (2A4MPM), and 2-amino-4,6-dimethylpyrimidine (2ADMPM) with acetic acid (AcOH) were measured in isooctane (2,2,4-trimethylpentane) at room temperature. From the absorption spectra, a hydrogen-bonded complex formation of the 2APM/AcOH, 2A4MPM/AcOH, and 2ADMPM/AcOH systems was recognized in isooctane. The enthalpy changes (-? H) for the complex formation were estimated to be ca. 41.2-45.1 kJ mol -1 and increased in proportion to the numbers of the methyl group introduced into the 2APM. The -? H values refer to the formation of the hydrogen-bonded 1:1 complex between the ring nitrogen atom and NH 2 group of the aminopyrimidine and the OH and C dbnd O groups of AcOH, respectively. In the 2A4MPM/AcOH double hydrogen-bonded complex the OH group of AcOH is thought to be linked to the ring nitrogen at the 1-postion of 2A4MPM. The fluorescence spectral results indicate that the double proton transfer reaction takes place during the excited state, and gives rise to an imino-tautomer vibration emission, from analogy with the fluorescences of 1-methyl-2(1H)-pyrimidinimine (MPMI), 1,4-dimethyl-2(1H)-pyrimidinimine (DMPMI), and 1,4,6-trimethyl-2(1H)-pyrimidinimine (TMPMI). The fluorescence quantum yields of the imino-tautomers also increased in proportion to the numbers of the methyl group introduced into the 2APM.

Kitamura, Teruyoshi; Hikita, Atushi; Ishikawa, Hironori; Fujimoto, Akira

2005-12-01

425

Does Domestication Cause Changes in Growth Reaction Norms? A Study of Farmed, Wild and Hybrid Atlantic Salmon Families Exposed to Environmental Stress  

PubMed Central

One of the most important traits linked with the successful domestication of animals is reducing their sensitivity to environmental stressors in the human controlled environment. In order to examine whether domestication selection in Atlantic salmon Salmo salar L., over approximately ten generations, has inadvertently selected for reduced responsiveness to stress, we compared the growth reaction norms of 29 wild, hybrid and domesticated families reared together under standard hatchery conditions (control) and in the presence of a stressor (reduced water level twice daily). The experiment was conducted for a 14 week period. Farmed salmon outgrew wild salmon 1?2.93 in the control tanks, and no overlap in mean weight was displayed between families representing the three groups. Thus, the elevation of the reaction norms differed among the groups. Overall, growth was approximately 25% lower in the stressed tanksl; however, farmed salmon outgrew wild salmon 1?3.42 under these conditions. That farmed salmon maintained a relatively higher growth rate than the wild salmon in the stressed tanks demonstrates a lower responsiveness to stress in the farmed salmon. Thus, flatter reaction norm slopes were displayed in the farmed salmon, demonstrating reduced plasticity for this trait under these specific experimental conditions. For all growth measurements, hybrid salmon displayed intermediate values. Wild salmon displayed higher heritability estimates for body weight than the hybrid and farmed salmon in both environments. This suggests reduced genetic variation for body weight in the farmed contra wild salmon studied here. While these results may be linked to the specific families and stocks investigated, and verification in other stocks and traits is needed, these data are consistent with the theoretical predictions of domestication. PMID:23382901

Solberg, Monica Favneb?e; Skaala, ?ystein; Nilsen, Frank; Glover, Kevin Alan

2013-01-01

426

Effect of hybridization on bond strength and adhesive interface after acid-base challenge using 4-META/MMA-TBB resin.  

PubMed

The purposes of this study were twofold, namely to evaluate: (1) the effect of hybridization on microtensile bond strength (microTBS) to dentin, and (2) the ultrastructure of the dentin-adhesive interface with 4-META/MMA-TBB resin after acid-base challenge. Dentin surfaces, which received no treatment (NT), 65% phosphoric acid (PA), or 10% citric acid-3% ferric chloride (10-3), were bonded with a 4-META/MMA-TBB resin. To evaluate dentin bond strength, microTBS test was performed at a crosshead speed of 1 mm/min. For ultrastructural evaluation of the adhesive interfaces, SEM was used to examine the interfaces of the bonded specimens after acid-base challenge. The microTBS of NT was not determined, while that of 10-3 was significantly higher than that of PA (p < 0.05). With PA and 10-3, the hybrid layer was clearly observed, but no so for the acid-base resistant zone. Wall lesion was found in NT only. In conclusion, hybridization is vital to improving microTBS to dentin and enhancing resistance at the adhesive interface against acid-base challenge. PMID:19496398

Takagaki, Tomohiro; Nikaido, Toru; Tsuchiya, Satoko; Ikeda, Masaomi; Foxton, Richard M; Tagami, Junji

2009-03-01

427

Hybrid Quantum Mechanical/Molecular Mechanics Study of the SN2 Reaction of CH3Cl+OH? in Water  

SciTech Connect

The SN2 mechanism for the reaction of CH3Cl + OH? in aqueous solution was investigated using combined quantum mechanical and molecular mechanics methodology. We analyzed structures of reactant, transition and product states along the reaction pathway. The free energy profile was calculated using the multi-layered representation with the DFT and CCSD(T) level of theory for the quantum-mechanical description of the reactive region. Our results show that the aqueous environment has a significant impact on the reaction process. We find that solvation energy contribution raises the reaction barrier by ~18.9 kcal/mol and the reaction free energy by ~24.5 kcal/mol. The presence of the solvent also induces perturbations in the electronic structure of the solute leading to an increase of 3.5 kcal/mol for the reaction barrier and a decrease of 5.6 kcal/mol for the reaction free energy respectively. Combining the results of two previous calculation results on CHCl3 + OH? and CH2Cl2 + OH? reactions in water, we demonstrate that increase in the chlorination of the methyl group (from CH3Cl to CHCl3) is accompanied by the decrease in the free energy reaction barrier, with the CH3Cl + OH? having the largest barrier among the three reactions.

Yin, Hongyun; Wang, Dunyou; Valiev, Marat

2011-11-03

428

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 expe