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1

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

Microsoft Academic Search

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

Zhijian Wu; Yan Jiang; Hong Xiang; Laijiang You

2006-01-01

2

Synthesis of conformationally constrained C-glycosyl alpha- and beta-amino acids and sugar-carbamino sugar hybrids via Diels-Alder reaction.  

PubMed

[structure: see text] Sugar-derived dienes undergo Diels-Alder reactions with methyl alpha-nitro acrylate and ethyl beta-nitro acrylate to form the corresponding cycloadducts which have been converted into conformationally constrained C-glycosyl alpha- and beta-amino acids. Further, these beta-amino acids are converted into sugar-carbamino sugar hybrid molecules. PMID:16288526

Jayakanthan, K; Vankar, Yashwant D

2005-11-24

3

Zinc deposition and dissolution in methanesulfonic acid onto a carbon composite electrode as the negative electrode reactions in a hybrid redox flow battery  

Microsoft Academic Search

Electrodeposition and dissolution of zinc in methanesulfonic acid were studied as the negative electrode reactions in a hybrid redox flow battery. Cyclic voltammetry at a rotating disk electrode was used to characterize the electrochemistry and the effect of process conditions on the deposition and dissolution rate of zinc in aqueous methanesulfonic acid. At a sufficiently high current density, the deposition

P. K. Leung; C. Ponce-de-León; C. T. J. Low; F. C. Walsh

2011-01-01

4

Optimizing the specificity of nucleic acid hybridization  

Microsoft Academic Search

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

Sherry Xi Chen; David Yu Zhang; Peng Yin

2012-01-01

5

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

6

HIV-1 nucleic acids localize to the spermatogonia and their progeny. A study by polymerase chain reaction in situ hybridization.  

PubMed Central

The purpose of this study was to determine the histological distribution of in situ polymerase chain reaction (PCR)-amplified HIV-1 nucleic acids in the male genital tract to elucidate the mechanism of sexual transmission of AIDS. Viral DNA was detected in the testicular tissue of 11 of 12 men with HIV-1 infection using the PCR in situ hybridization technique. The amplified viral DNA localized to many spermatogonia, spermatocytes, and rare spermatids. Relatively few viral infected macrophages were noted, mostly in the prostate. The viral infection was activated given the presence of cDNA sequences consistent with genomic and multiple spliced transcripts as determined by reverse transcription in situ PCR. PCR-amplified viral nucleic acids were not detected in the epithelial of the prostate, epididymis, seminal vesicles, or penis in men with AIDS nor in any genital tract tissues from three boys who died of AIDS acquired in utero. The demonstration that HIV-1 selectively infects the spermatogonia and their progeny suggests that this may serve as a primary source of venereal spread of the virus. Concomitant destruction of these cells by HIV-1 may also explain the marked inhibition of spermatogenesis and severe atrophy that characterizes the testes in AIDS. Images Figure 1 Figure 2

Nuovo, G. J.; Becker, J.; Simsir, A.; Margiotta, M.; Khalife, G.; Shevchuk, M.

1994-01-01

7

Enzyme-free and ultrasensitive electrochemical detection of nucleic acids by target catalyzed hairpin assembly followed with hybridization chain reaction.  

PubMed

An isothermal, enzyme-free and ultrasensitive protocol for electrochemical detection of DNA is proposed based on the ingenious combination of target catalyzed hairpin assembly and hybridization chain reaction (HCR) strategies for two-step signal amplification. The DNA hairpin assembly on the electrode is triggered by target DNA, accompanied by the release of target DNA for the successive hybridization and assembly process. The newly emerging DNA fragment on the electrode after hairpin assembly is further used to propagate the HCR between methylene blue-labeled signal probe and auxiliary probe, inducing a remarkably amplified electrochemical signal. The current dual signal amplification strategy is relatively simple and inexpensive owing to avoid the use of any kind of enzyme or sophisticated equipment. It can achieve a sensitivity of 0.1 fM with a wide linear dynamic range from 1 × 10(-15) to 1 × 10(-10)M and discriminate mismatched DNA from perfect matched target DNA with a high selectivity. The high sensitivity and selectivity make this method a great potential for early diagnosis in gene-related diseases. PMID:23811481

Liu, Shufeng; Wang, Ying; Ming, Jingjing; Lin, Ying; Cheng, Chuanbin; Li, Feng

2013-11-15

8

Hybrids of perfluorosulfonic acid ionomer and silicon oxide by sol-gel reaction from solution: Morphology and thermal analysis  

Microsoft Academic Search

NAFION®\\/silicon oxide hybrids were prepared from solution by hydrolysis\\/polycondensation of alkoxy silanes. Transparent, but brittle films were obtained when TEOS was used as the inorganic polymer precursor, showing a lamellar structure by transmission electron microscopy. Part of the TEOS was substituted by TMDES to increase the film flexibility. For substitution higher than 10% phase separation was clearly observed by scanning

R. A. Zoppi; I. V. P. Yoshida; S. P. Nunes

1998-01-01

9

Suzuki coupling reaction using hybrid Pd nanoparticles.  

PubMed

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

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

2014-02-01

10

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

11

Reactions : AcidBaseRxns (20 Variations)  

NSDL National Science Digital Library

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

12

Kit for detecting nucleic acid sequences using competitive hybridization probes  

DOEpatents

A kit is provided for detecting a target nucleic acid sequence in a sample, the kit comprising: a first hybridization probe which includes a nucleic acid sequence that is sufficiently complementary to selectively hybridize to a first portion of the target sequence, the first hybridization probe including a first complexing agent for forming a binding pair with a second complexing agent; and a second hybridization probe which includes a nucleic acid sequence that is sufficiently complementary to selectively hybridize to a second portion of the target sequence to which the first hybridization probe does not selectively hybridize, the second hybridization probe including a detectable marker; a third hybridization probe which includes a nucleic acid sequence that is sufficiently complementary to selectively hybridize to a first portion of the target sequence, the third hybridization probe including the same detectable marker as the second hybridization probe; and a fourth hybridization probe which includes a nucleic acid sequence that is sufficiently complementary to selectively hybridize to a second portion of the target sequence to which the third hybridization probe does not selectively hybridize, the fourth hybridization probe including the first complexing agent for forming a binding pair with the second complexing agent; wherein the first and second hybridization probes are capable of simultaneously hybridizing to the target sequence and the third and fourth hybridization probes are capable of simultaneously hybridizing to the target sequence, the detectable marker is not present on the first or fourth hybridization probes and the first, second, third, and fourth hybridization probes each include a competitive nucleic acid sequence which is sufficiently complementary to a third portion of the target sequence that the competitive sequences of the first, second, third, and fourth hybridization probes compete with each other to hybridize to the third portion of the target sequence.

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

2001-01-01

13

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

14

A Lewis acid-promoted Pinner reaction  

PubMed Central

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

Pfaff, Dominik; Nemecek, Gregor

2013-01-01

15

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...

16

Detection of Cytomegalovirus by Nucleic Acid Hybridization Techniques.  

National Technical Information Service (NTIS)

Nucleic acid hybridization techniques, RNA-DNA membrane hybridization, DNA-DNA renaturation kinetics analysis (Cot analysis) and in situ 3H cRNA-DNA cytohybridization, were developed and successfully applied to detection of human cytomegalovirus (CMV) gen...

J. S. Pagano E. S. Huang

1975-01-01

17

Reactions of Gaseous Bronsted Acids.  

National Technical Information Service (NTIS)

Gaseous ionic reactions have been observed for a series of oxygenated compounds in the source of a mass spectrometer at pressures up to a few tenths of a torr. The major produce ions were the solvated protons. Major differences in relative abundances were...

M. S. B. Munson

1965-01-01

18

Hybridization and sequencing of nucleic acids using base pair mismatches  

DOEpatents

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

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

2001-01-01

19

The hydrothermal reaction kinetics of aspartic acid  

NASA Astrophysics Data System (ADS)

Experimental data on the hydrothermal reaction kinetics of aspartic acid were acquired using a custom-built spectrophotometric reaction cell which permits in situ observation under hydrothermal conditions. The results of this study indicate that the reaction kinetics of dilute aspartic acid solutions are significantly different depending on the presence or absence of catalytic surfaces such as standard metal alloys. The spectroscopic data presented here represent the first direct observations, in situ and in real time, of an amino acid reacting in a hydrothermal solution. Quantitative kinetic information, including rate constants, concentration versus time profiles, and calculations of the individual component spectra, was obtained from the data using a chemometric approach based on factor analysis/principle component analysis which treats the rate expressions simultaneously as a system of differential algebraic equations (DAE) of index 1. Identification of the products was confirmed where possible by high pressure anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). The reaction kinetics of aspartic acid under hydrothermal conditions was observed to be highly complex, in contrast to previous studies which indicated almost exclusively deamination. At lower temperatures (120-170 °C), several different reaction pathways were observed, including decarboxylation and polymerization, and the catalytic effects of reactor surfaces on the aspartic acid system were clearly demonstrated. At higher temperatures (above 170 °C), aspartic acid exhibited highly complex behaviour, with evidence indicating that it can simultaneously dimerize and cyclize, deaminate (by up to two pathways), and decarboxylate (by up to two pathways). These higher temperature kinetics were not fully resolvable in a quantitative manner due to the complexity of the system and the constraints of UV spectroscopy. The results of this study provide strong evidence that the reaction kinetics of aspartic acid are very sensitive to parameters such as temperature, reactor materials (i.e., reactive surfaces), and additives, and that previous observations on aspartic acid were specific to the choice of experimental conditions.

Cox, Jenny S.; Seward, Terry M.

2007-02-01

20

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

21

From The Cover: Triggered amplification by hybridization chain reaction  

NASA Astrophysics Data System (ADS)

We introduce the concept of hybridization chain reaction (HCR), in which stable DNA monomers assemble only upon exposure to a target DNA fragment. In the simplest version of this process, two stable species of DNA hairpins coexist in solution until the introduction of initiator strands triggers a cascade of hybridization events that yields nicked double helices analogous to alternating copolymers. The average molecular weight of the HCR products varies inversely with initiator concentration. Amplification of more diverse recognition events can be achieved by coupling HCR to aptamer triggers. This functionality allows DNA to act as an amplifying transducer for biosensing applications.

Dirks, Robert M.; Pierce, Niles A.

2004-10-01

22

Lead-acid battery model for hybrid energy storage  

Microsoft Academic Search

This paper deals with the design of hybrid energy storage for an electric waste collection vehicle. The hybrid storage is made of lead-acid batteries and supercapacitors. A detailed lead-acid model is proposed in order to take into account the charge of the battery during regenerative braking. The vehicle was simulated on an urban driving cycle for a full working day.

S. Butterbach; B. Vulturescu; Ch. Forgez; G. Coquery; G. Friedrich

2011-01-01

23

A DNA origami nanorobot controlled by nucleic Acid hybridization.  

PubMed

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

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

2014-07-01

24

Reaction of irofulven with zinc and acid.  

PubMed

Reaction of antitumor agent irofulven (1) with zinc and acetic acid yielded several new indene derivatives (6, 7, 8, 10) as well as the known indene (9). These all have greatly reduced toxicity to human leukemia (HL60) cells compared to irofulven. PMID:12608875

McMorris, Trevor C; Moon, Surk-Sik; Kelner, Michael J

2003-02-01

25

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

26

Reaction of atomic hydrogen with formic acid.  

PubMed

We study the reaction of atomic hydrogen with formic acid and characterize the radical products using IR spectroscopy in a Kr matrix and quantum chemical calculations. The reaction first leads to the formation of an intermediate radical trans-H2COOH, which converts to the more stable radical trans-cis-HC(OH)2via hydrogen atom tunneling on a timescale of hours at 4.3 K. These open-shell species are observed for the first time as well as a reaction between atomic hydrogen and formic acid. The structural assignment is aided by extensive deuteration experiments and ab initio calculations at the UMP2 and UCCSD(T) levels of theory. The simplest geminal diol radical trans-cis-HC(OH)2 identified in the present work as the final product of the reaction should be very reactive, and further reaction channels are of particular interest. These reactions and species may constitute new channels for the initiation and propagation of more complex organic species in the interstellar clouds. PMID:24549472

Cao, Qian; Berski, Slawomir; Latajka, Zdzislaw; Räsänen, Markku; Khriachtchev, Leonid

2014-04-01

27

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

Microsoft Academic Search

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,

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

2009-01-01

28

Hybrid Multiscale Simulation of Mixing-Controlled Biogeochemical Reactions  

NASA Astrophysics Data System (ADS)

Most in situ remediation methods rely strongly on mixing of contaminants and other chemical species to promote targeted reactions that degrade or immobilize contaminants. It is now well known that the conventional approach to Darcy-scale solute transport simulation tends to overestimate in situ reaction rates because the dispersion process conceptualization combines advective spreading (due to heterogeneity) and diffusive mixing in a single lumped representation. Hybrid multiscale simulation methods, which combine microscale (pore-scale) and macroscale (Darcy-scale) simulations within a single unified framework, offers the potential to address this problem by explicitly resolving local diffusive mixing as impacted by large-scale advective spreading in a computationally tractable manner. In this talk we present methods and results of a multiscale hybrid simulation approach applied to a mixing-controlled reaction at the laboratory scale. Our approach couples a Smoothed Particle Hydrodynamics (SPH) pore-scale simulator with the STOMP Darcy-scale simulator using a custom workflow management system that adaptively selects SPH sub-domains and provides the coupling between SPH and STOMP simulations seamlessly on a scalable parallel computational platform.

Scheibe, T. D.; Schuchardt, K.; Agarwal, K.; Chase, J.; Palmer, B. J.; Tartakovsky, A. M.; Elsethagen, T.; Redden, G. D.

2012-12-01

29

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

30

Mechanism of thermal renaturation and hybridization of nucleic acids: Kramers process and universality in Watson-Crick base pairing  

Microsoft Academic Search

Renaturation and hybridization reactions lead to the pairing of complementary single-stranded nucleic acids. We present here a theoretical investigation of the mechanism of these reactions in vitro under thermal conditions (dilute solutions of single-stranded chains, in the presence of molar concentrations of monovalent salts and at elevated temperatures). The mechanism follows a Kramers' process, whereby the complementary chains overcome a

Jean-Louis Sikorav; Henri Orland; Alan Braslau

2008-01-01

31

Hybrid stochastic simulations of intracellular reaction-diffusion systems  

PubMed Central

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 novel hybrid stochastic approach is introduced for simulating reaction-diffusion systems. We developed a dynamic partitioning strategy using fractional propensities. In that way processes with high frequency are simulated mostly with deterministic rate-based equations, and those with low frequency mostly with the exact stochastic algorithm of Gillespie. In this way we preserve the stochastic behavior of cellular pathways while being able to apply it to large populations of molecules. In this article we describe this hybrid algorithmic approach, and we 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.

Kalantzis, Georgios

2009-01-01

32

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

33

Photoinitiator Nucleotide for Quantifying Nucleic Acid Hybridization  

PubMed Central

This first report of a photoinitiator-nucleotide conjugate demonstrates a novel approach for sensitive, rapid and visual detection of DNA hybridization events. This approach holds potential for various DNA labeling schemes and for applications benefiting from selective DNA-based polymerization initiators. Here, we demonstrate covalent, enzymatic incorporation of an eosin-photoinitiator 2?-deoxyuridine-5?-triphosphate (EITC-dUTP) conjugate into surface-immobilized DNA hybrids. Subsequent radical chain photoinitiation from these sites using an acrylamide/bis-acrylamide formulation yields a dynamic detection range between 500pM and 50nM of DNA target. Increasing EITC-nucleotide surface densities leads to an increase in surface-based polymer film heights until achieving a film height plateau of 280nm ±20nm at 610 ±70 EITC-nucleotides/?m2. Film heights of 10–20 nm were obtained from eosin surface densities of approximately 20 EITC-nucleotides/?m2 while below the detection limit of ~10 EITC-nucleotides/?m2, no detectable films were formed. This unique threshold behavior is utilized for instrument-free, visual quantification of target DNA concentration ranges.

Johnson, Leah M.; Hansen, Ryan R.; Urban, Milan; Kuchta, Robert D.; Bowman, Christopher N.

2010-01-01

34

Nucleic acid hybridization using DNA covalently coupled to cellulose.  

PubMed

We describe a method for linking RNA and DNA covalently to finely divided cellulose through a diazotized aryl amine, which reacts primarily with guanine and uracil (thymine) residues of single strands. The high efficiency of coupling and high capacity of the cellulose for nucleic acid make possible a product with as much as 67 mug of nucleic acid per mg of cellulose. The product is especially suitable for hybridization experiments where very low backgrounds are important, and it is stable in 99% formamide at 80 degrees C so that hybridized nucleic acid can be recovered easily. Full length linear Simian Virus 40 (SV40) DNA, produced by cleavage of SV40(I) DNA with S1 nuclease, can be coupled to diazo cellulose with an efficiency of 80-90%, and is effective in hybridization experiments with SV40 DNA, complementary RNA synthesized in vitro from SV40(I) DNA with E. coli RNA polymerase, and the SV40-specific fraction of total RNA from SV40-infected and transformed cells. In these experiments an excess of cellulose-bound DNA was used, and the efficiency of hybridization was about 90% when ribonuclease treatment of the hybrids was omitted. PMID:167982

Noyes, B E; Stark, G R

1975-07-01

35

Versatile phosphoramidation reactions for nucleic acid conjugations with peptides, proteins, chromophores, and biotin derivatives.  

PubMed

Chemical conjugations of nucleic acids with macromolecules or small molecules are common approaches to study nucleic acids in chemistry and biology and to exploit nucleic acids for medical applications. The conjugation of nucleic acids such as oligonucleotides with peptides is especially useful to circumvent cell delivery and specificity problems of oligonucleotides as therapeutic agents. However, current approaches are limited and inefficient in their ability to afford peptide-oligonucleotide conjugates (POCs). Here, we report an effective and reproducible approach to prepare POCs and other nucleic acid conjugates based on a newly developed nucleic acid phosphoramidation method. The development of a new nucleic acid phosphoramidation reaction was achieved by our successful synthesis of a novel amine-containing biotin derivative used to systematically optimize the reactions. The improved phosphoramidation reactions dramatically increased yields of nucleic acid-biotin conjugates up to 80% after 3 h reaction. Any nucleic acids with a terminal phosphate group are suitable reactants in phosphoramidation reactions to conjugate with amine-containing molecules such as biotin and fluorescein derivatives, proteins, and, most importantly, peptides to enable the synthesis of POCs for therapeutic applications. Polymerase chain reactions (PCRs) to study incorporation of biotin or fluorescein-tagged DNA primers into the reaction products demonstrated that appropriate controls of nucleic acid phosphoramidation reactions incur minimum adverse effects on inherited base-pairing characteristics of nucleotides in nucleic acids. The phosphoramidation approach preserves the integrity of hybridization specificity in nucleic acids when preparing POCs. By retaining integrity of the nucleic acids, their effectiveness as therapeutic reagents for gene silencing, gene therapy, and RNA interference is ensured. The potential for POC use was demonstrated by two-step phosphoramidation reactions to successfully synthesize nucleic acid-tetraglycine conjugates. In addition, phosphoramidation reactions provided a facile approach to prepare nucleic acid-BSA conjugates with good yields. In summary, the new approach to phosphoramidation reactions offers a universal method to prepare POCs and other nucleic acid conjugates with high yields in aqueous solutions. The methods can be easily adapted to typical chemistry or biology laboratory setups which will expedite the applications of POCs for basic research and medicine. PMID:20690641

Wang, Tzu-Pin; Chiou, Yi-Jang; Chen, Yi; Wang, Eng-Chi; Hwang, Long-Chih; Chen, Bing-Hung; Chen, Yen-Hsu; Ko, Chun-Han

2010-09-15

36

An algorithm for the determination and quantification of components of nucleic acid mixtures based on single sequencing reactions  

Microsoft Academic Search

BACKGROUND: Determination and quantification of nucleic acid components in a mixture is usually accomplished by microarray approaches, where the mixtures are hybridized against specific probes. As an alternative, we propose here that a single sequencing reaction from a mixture of nucleic acids holds enough information to potentially distinguish the different components, provided it is known which components can occur in

Alexander E. Pozhitkov; Kathryn Stemshorn; Diethard Tautz

2005-01-01

37

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

38

Mfold web server for nucleic acid folding and hybridization prediction  

Microsoft Academic Search

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

Michael Zuker

2003-01-01

39

Thermal reactions of starch with long-chain unsaturated fatty acids. Part 2. Linoleic acid  

Microsoft Academic Search

The significance and numerous applications of products resulting from reactions of starch with fatty acids induced our interest in checking thermal reaction of potato starch with linoleic acid. Behaviour of the starch–linoleic acid blends was monitored by means of thermogravimetric (TG), differential thermogravimetric (DTG), and differential scanning calorimetric (DSC) methods. The reaction carried out on conventional heating provided mixture of

Janusz Kapusniak; Przemyslaw Siemion

2007-01-01

40

Asymmetric garratt-braverman cyclization: a route to axially chiral aryl naphthalene-amino Acid hybrids.  

PubMed

We report the first example of a highly diastereoselective Garratt-Braverman cyclization leading to the synthesis of chiral aryl naphthalene-amino acid hybrids in excellent yields. The stereogenecity in the amino acid has induced high diastereoselectivity for the reaction. Computations based on density functional theory indicated a lower activation free energy barrier for the M isomer as compared to that for the P diastereomer (??G = 3.48 kcal/mol). Comparison of the recorded CD spectrum of the product with the calculated one also supported the preferential formation of the M diastereomer. PMID:24861462

Mitra, Tapobrata; Jana, Saibal; Pandey, Sharmila; Bhattacharya, Prabuddha; Khamrai, Uttam K; Anoop, Anakuthil; Basak, Amit

2014-06-20

41

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....

42

Synthesis and Characterization of Hybrid Hyaluronic Acid-Gelatin Hydrogels  

PubMed Central

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 (2D and 3D) 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.

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

2013-01-01

43

Mechanism of the reaction of isocyanic acid with ethanol  

SciTech Connect

The kinetics of the interaction of isocyanic acid with ethanol is investigated. The reaction products include ethyl carbamate and ethyl allophanate, the yields of which depend on both the concentration ratio of HNCO:ROH and the presence of a catalyst. The influence of water, acid, and base additives is also examined. A reaction mechanism is proposed.

Sheludyakov, Y.L.; Shubareva, F.Z.; Golodov, V.A.; Korolev, A.V. [Institute of Organic Catalysis and Electrochemistry, Kazakhstan (Russian Federation)

1995-03-01

44

Effect of inclusion complex on nitrous acid reaction with flavonoids  

NASA Astrophysics Data System (ADS)

The kinetic of the nitrous acid reactions with quercetin and catechin has been studied using spectrophotometric method in aqueous solution. The results show that these antioxidants participate in oxidation reactions with nitrous acid which is derived from protonation of nitrite ion in mild acidic conditions. Corresponding o-quinones as relatively stable products were detected by spectrophotometric techniques. pH dependence of the reactions has been examined and the rate constants of reactions were obtained by non-linear fitting of kinetic profiles. The effect of ?-cyclodextrin on the oxidation pathway was another object of this study. It is shown that ?-cyclodextrin has an inhibitory effect on the oxidation reaction. The rate constants of oxidation reactions for complexed forms and their stability constants were obtained based on changes in the reaction rates as a function of ?-cyclodextrin concentration.

Khalafi, Lida; Rafiee, Mohammad; Sedaghat, Sajjad

2011-10-01

45

Mechanism of Thermal Renaturation and Hybridization of Nucleic Acids: Kramers’ Process and Universality in Watson?Crick Base Pairing †  

Microsoft Academic Search

Renaturation and hybridization reactions lead to the pairing of complementary\\u000asingle-stranded nucleic acids. We present here a theoretical investigation of\\u000athe mechanism of these reactions in vitro under thermal conditions (dilute\\u000asolutions of single-stranded chains, in the presence of molar concentrations of\\u000amonovalent salts and at elevated temperatures). The mechanism follows a\\u000aKramers' process, whereby the complementary chains overcome a

Jean-Louis Sikorav; Henri Orland; Alan Braslau

2009-01-01

46

Electrochemical Reduction Reactions Involving Formic Acid.  

National Technical Information Service (NTIS)

Various investigators have shown that the electrode reduction of CO2 in water using metal electrodes yields acid as the main product. Recent publications have generated conflicting claims regarding the further reduction of formic acid to methanol. Our stu...

M. H. Miles A. N. Fletcher G. E. McManis

1984-01-01

47

Photoluminescent hybrid materials based on lanthanopolyoxotungstates and 3-hydroxypicolinic acid  

Microsoft Academic Search

A series of organic–inorganic hybrid materials composed by lanthanopolyoxotungstates [Ln(W5O18)2]n? (Ln(III)=Eu, Tb, Er and Yb) and 3-hydroxypicolinic acid were prepared using different lanthanide ions. The compounds were characterized by FT-IR and FT-Raman spectroscopy and elemental analysis. The energy transfer processes from the organic ligand to the lanthanide (antenna effect) in these compounds have been studied by photoluminescence measurements.

Carlos M. Granadeiro; Rute A. Sá Ferreira; Paula C. R. Soares-Santos; Luís D. Carlos; Helena I. S. Nogueira

2008-01-01

48

On the reaction between cerium (IV) ions and peroxysulphuric acid  

Microsoft Academic Search

During cerimetric determination of solutions containing hydrogen ; peroxide and peroxysulfuric acid, the amount of peroxysulfuric acid consumed ; depends on the rate of titration. Since the same consumption occurs in the ; absence of hydrogen peroxide, the decomposition must be attributed to the ; reaction between cerium(IV) ions and peroxyaulfuric acid. Therefore, cerimetric ; titrations with ceric sulfate and

L. J. Csányi; F. Solymosi; J. Szücs

1959-01-01

49

Oxidative reaction of oxindole-3-acetic acids.  

PubMed

The oxindole-3-acetic acids, oxidative metabolites of indole-3-acetic acid, were isolated from a byproduct of a corn starch manufacturing plant, and were further converted to the 3-hydroxyl derivatives in the presence of metal ion. The mechanical study was followed by a chemical analysis including other byproducts, and suggested the presence of an intermediate that had a radical at the C-3 position of oxindole-3-acetic acids. PMID:14519969

Niwa, Toshio; Ishii, Sayuri; Hiramatsu, Atsushi; Osawa, Toshihiko

2003-09-01

50

Determination of Indole Acetic Acid by the Salkowsky Reaction  

Microsoft Academic Search

RECENTLY attention has been focused on the reaction of indole acetic acid with ferric ions. Cohen et al.1 have shown that indole acetic acid forms a chelate with iron at acid pH and this has been confirmed by Recaldin and Heath2. The latter state that at pH 2.6 iron slowly decomposes the indole acetic acid in the solution. The oxidation

A. M. Mayer

1958-01-01

51

Reaction of arylarsonic acids with organylalkoxy- and organylacetoxy-silanes  

Microsoft Academic Search

The reaction of phenylarsonic acid with trialkylalkoxy- or trialkylacetoxysilanes leads to the formation of bis(trialkylsilyl)phenylarsonates. Bis(trimethylsilyl)- and bis(dimethylsilyDphenylarsonates are thermally unstable and decompose upon separation.

M. G. Voronkov; S. V. Basenko; R. G. Mirskov

1988-01-01

52

Electrochemical Amination Reactions for Amino Acid Synthesis.  

National Technical Information Service (NTIS)

Research was directed toward determining the utility of electrochemically generated homogeneous catalysts capable of in situ forming aminyl radicals in acidic hydroxylamine containing electrolytes, which would then be available for free radical addition o...

A. F. Sammells R. L. Cook

1987-01-01

53

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

SciTech Connect

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

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

2002-01-01

54

Imino Acids in the Murchison Meteorite: Evidence of Strecker Reactions  

NASA Technical Reports Server (NTRS)

Both alpha-amino acids and alpha-hydroxy acids occur in aqueous extracts of the Murchison carbonaceous meteorite. The Strecker-cyanohydrin reaction, the reaction of carbonyl compounds, cyanide, and ammonia to produce amino and hydroxy acids, has been proposed as a source of such organic acids in meteorites. Such syntheses are consistent with the suggestion that interstellar precursors of meteoritic organic compounds accreted on the meteorite parent body together with other ices. Subsequent internal heating of the parent body melted these ices and led to the formation of larger compounds in synthetic reactions during aqueous alteration, which probably occurred at temperatures between 273K and 298K. In the laboratory, imino acids are observed as important by-products of the Strecker synthesis.

Lerner, N. R.; Cooper, G. W.

2003-01-01

55

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

Microsoft Academic Search

To improve detection efficiency and result accuracy, four screening primer pairs, four identifying primer pairs, one common primer pair and corresponding probes were designed for the development of multiplex polymerase chain reaction\\/membrane hybridization assay (MPCR–MHA) for detection of the foreign genes insert in genetically modified organisms (GMOs). After detecting condition and parameter were optimized and determined, MPCR reactions were developed

Wenijn Su; Siyang Song; Minnan Long; Guangming Liu

2003-01-01

56

"Extreme" Ugi reactions with some complex ?-amino acids.  

PubMed

The Ti(IV)-catalyzed Ugi condensation of ?-amino acids with electron-rich aromatic aldehydes performs adequately even with sterically demanding ?-amino carboxylate salts. The reaction occurs diastereoselectively, in some cases with virtually complete diastereoselectivity. A stereochemical rationale for the reaction is proposed. PMID:22954286

Turner, Charles Dylan; Ciufolini, Marco A

2012-09-21

57

Reactions of iodotrimethylsilane with esters of aromatic and araliphatic acids  

SciTech Connect

A study was made of the reactions of iodotrimethylsilane with esters of aromatic and araliphatic acids, leading to the corresponding trimethylsilyl esters. In the reaction of iodotrimethylsilane with (trimethoxysilyl)methyl (aryloxy)acetates all three types of C-O bonds are broken.

Voronkov, M.G.; Dolmaa, G.; Putilova, G.G.; Dubinskaya, E.I.

1986-04-10

58

Synthesis of core-corona polymer hybrids with a raspberry-like structure by the heterocoagulated pyridinium reaction.  

PubMed

A core-corona polymer hybrid with a raspberry-like structure was synthesized via the heterocoagulated pyridium reaction between the pyridyl group of poly(ethylene glycol dimethacrylate-co-methacrylic acid)@poly(ethylene glycol dimethacrylate-co- vinylpyridine) (poly(EGDMA-co-MAA)@poly(EGDMA-co-VPy)) core-shell small microspheres and the chloromethyl group of poly(divinylbenzene-co-chloromethyl styrene) (poly(DVB-co-CMSt)) microspheres, in which poly(EGDMA-co-MAA)@poly(EGDMA-co-VPy) acted as the corona and poly(DVB-co-CMSt) behaved as the core. The control coverage of the corona particles on the surfaces of core microspheres for the polymer hybrid was studied in detail through the adjustment of the mass ratio between the core and corona particles. The effects of the pH and solvents on the stability of the raspberry-like core-corona hybrids were investigated. The water static angle on the surface of polycarbonate (PC) film was studied using a contact angle system. The polymer particles and the resultant heterocoagulated raspberry-like hybrids were characterized with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The nature of the heterocoagulation between the core microspheres and corona particles was identified as the covalent pyridium reaction with Fourier transform infrared (FT-IR) spectroscopy. PMID:18288875

Wang, Junyou; Yang, Xinlin

2008-04-01

59

Reactions of fulvic acid with metal ions  

Microsoft Academic Search

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

M. Schnitzer; H. Kerndorff

1981-01-01

60

Reaction of fatty acid amides and ethanolamides with trimethylsulfonium hydroxide  

Microsoft Academic Search

The preparation of fatty acid methyl esters by transesterification of acyl lipids using trimethylsulfonium hydroxide (TMSH) as a base catalyst is a convenient GC derivatization procedure of growing interest. It has now been found that lipids containing amido groups, e.g. fatty acid amides and fatty acid ethanolamides, are partially N- and\\/or O-methylated by the pyrolytic reaction with TMSH occurring in

Klaus Vosmann; Erika Klein; Nikolaus Weber

1997-01-01

61

Reactions between Singlet Oxygen and the Constituents of Nucleic Acids  

PubMed Central

Bases, nucleosides, nucleotides, and polynucleotides were exposed to chemically generated singlet oxygen to determine whether the species oxidized paralleled those oxidized in photodynamic reactions. In neutral or basic aqueous solution guanine, guanosine, deoxyguanosine, guanylic acid, deoxyguanylic acid, thymine, and uracil reacted with singlet oxygen. Since these compounds are oxidized in photodynamic processes, this study provides further evidence that singlet oxygen is the active intermediate in the photodynamic oxidation of nucleic acid constituents. Dienophilic attack by singlet oxygen is considered to be a plausible mechanism in these reactions.

Hallett, F. R.; Hallett, B. P.; Snipes, W.

1970-01-01

62

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

Microsoft Academic Search

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

Dai Haifeng; Chang Xueyu

2010-01-01

63

Direct detection of nucleic acid hybridization on the surface of a charge coupled device.  

PubMed Central

A method is described for the detection of DNA hybrids formed on a solid support, based upon the pairing of oligonucleotide chemistry and the technologies of electronic microdevice design. Surface matrices have been created in which oligonucleotide probes are covalently linked to a thin SiO2 film. 32P labeled target nucleic acid is then hybridized to this probe matrix under conditions of high stringency. The salient feature of the method is that to achieve the highest possible collection efficiency, the hybridization matrix is placed directly on the surface of a charge coupled device (CCD), which is used to detect 32P decay from hybridized target molecules (1, Eggers, M.D., Hogan, M.E., Reich, R.K., Lamture, J.B., Beattie, K.L., Hollis, M.A., Ehrilich, D.J., Kosicki, B.B., Shumaker, J.M., Varma, R.S., Burke, B.E., Murphy, A., and Rathman, D.D., (1993), Advances in DNA Sequencing Technology, Proc. SPIE, 1891, 13-26). Two implementations of the technology have been employed. The first involves direct attachment of the matrix to the surface of a CCD. The second involves attachment of the matrix to a disposible SiO2 coated chip, which is then placed face to face upon the CCD surface. As can be predicted from this favorable collection geometry and the known characteristics of a CCD, it is found that as measured by the time required to obtain equivalent signal to noise ratios, 32P detection speed by the direct CCD approach is at least 10 fold greater than can be obtained with a commercial gas phase array detector, and at least 100 fold greater than when X-ray film is used for 32P detection. Thus, it is shown that excellent quality hybridization signals can be obtained from a standard hybridization reaction, after only 1 second of CCD data acquisition. Images

Lamture, J B; Beattie, K L; Burke, B E; Eggers, M D; Ehrlich, D J; Fowler, R; Hollis, M A; Kosicki, B B; Reich, R K; Smith, S R

1994-01-01

64

Direct detection of nucleic acid hybridization on the surface of a charge coupled device.  

PubMed

A method is described for the detection of DNA hybrids formed on a solid support, based upon the pairing of oligonucleotide chemistry and the technologies of electronic microdevice design. Surface matrices have been created in which oligonucleotide probes are covalently linked to a thin SiO2 film. 32P labeled target nucleic acid is then hybridized to this probe matrix under conditions of high stringency. The salient feature of the method is that to achieve the highest possible collection efficiency, the hybridization matrix is placed directly on the surface of a charge coupled device (CCD), which is used to detect 32P decay from hybridized target molecules (1, Eggers, M.D., Hogan, M.E., Reich, R.K., Lamture, J.B., Beattie, K.L., Hollis, M.A., Ehrilich, D.J., Kosicki, B.B., Shumaker, J.M., Varma, R.S., Burke, B.E., Murphy, A., and Rathman, D.D., (1993), Advances in DNA Sequencing Technology, Proc. SPIE, 1891, 13-26). Two implementations of the technology have been employed. The first involves direct attachment of the matrix to the surface of a CCD. The second involves attachment of the matrix to a disposible SiO2 coated chip, which is then placed face to face upon the CCD surface. As can be predicted from this favorable collection geometry and the known characteristics of a CCD, it is found that as measured by the time required to obtain equivalent signal to noise ratios, 32P detection speed by the direct CCD approach is at least 10 fold greater than can be obtained with a commercial gas phase array detector, and at least 100 fold greater than when X-ray film is used for 32P detection. Thus, it is shown that excellent quality hybridization signals can be obtained from a standard hybridization reaction, after only 1 second of CCD data acquisition. PMID:8029021

Lamture, J B; Beattie, K L; Burke, B E; Eggers, M D; Ehrlich, D J; Fowler, R; Hollis, M A; Kosicki, B B; Reich, R K; Smith, S R

1994-06-11

65

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

66

Solid-state acid-base reactions of indomethacin and flufenamic acid  

Microsoft Academic Search

The purpose of this study is to understand the mechanism of solid-state acid-base reactions and identify controlling factors for this type of reaction. The reactions between indomethacin and sodium bicarbonate, indomethacin and sodium carbonate, and flufenamic acid and magnesium oxide were investigated using X-ray powder diffraction, Fourier transform infrared spectroscopy, thermogravimetry, and solid-state nuclear magnetic resonance spectrometry. Quantitative methods based

Xiaoming Chen

2000-01-01

67

Analysis of the reaction advection diffusion system for DNA hybridization in a microchannel  

NASA Astrophysics Data System (ADS)

We consider the hybridization of short strand DNA in microchannels and model it as a reaction advection diffusion system in an extended space consisting of spatial dimensions as well as orientation. The model can be used to optimize the hybridization rate. We demonstrate with a shear superposition micromixer that it is possible to achieve chaotic mixing in space while simultaneously aligning the strands, thus increasing the rate of creation of double strand DNA.

John, Thomas

2005-11-01

68

Hybrid stochastic simulations of intracellular reaction-diffusion systems  

Microsoft Academic Search

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

Georgios Kalantzis

2009-01-01

69

Creatinyl amino acids: new hybrid compounds with neuroprotective activity.  

PubMed

Prolonged oral creatine administration resulted in remarkable neuroprotection in experimental models of brain stroke. However, because of its polar nature creatine has poor ability to penetrate the blood-brain barrier (BBB) without specific creatine transporter (CRT). Thus, synthesis of hydrophobic derivatives capable of crossing the BBB by alternative pathway is of great importance for the treatment of acute and chronic neurological diseases including stroke, traumatic brain injury and hereditary CRT deficiency. Here we describe synthesis of new hybrid compounds-creatinyl amino acids, their neuroprotective activity in vivo and stability to degradation in different media. The title compounds were synthesized by guanidinylation of corresponding sarcosyl peptides or direct creatine attachment using isobutyl chloroformate method. Addition of lipophilic counterion (p-toluenesulfonate) ensures efficient creatine dissolution in DMF with simultaneous protection of guanidino group towards intramolecular cyclization. It excludes the application of expensive guanidinylating reagents, permits to simplify synthetic procedure and adapt it to large-scale production. The biological activity of creatinyl amino acids was tested in vivo on ischemic stroke and NaNO(2) -induced hypoxia models. One of the most effective compounds-creatinyl-glycine ethyl ester increases life span of experimental animals more than two times in hypoxia model and has neuroprotective action in brain stroke model when applied both before and after ischemia. These data evidenced that creatinyl amino acids can represent promising candidates for the development of new drugs useful in stroke treatment. PMID:21644247

Burov, Sergey; Leko, Maria; Dorosh, Marina; Dobrodumov, Anatoliy; Veselkina, Olga

2011-09-01

70

Reaction mechanism for the acid ferric sulfate leaching of chalcopyrite  

Microsoft Academic Search

The acid ferric sulfate leaching of chalcopyrite, CuFeS2 + 4Fe+3 = Cu+2 + 5Fe+2 + 2S0 was studied using monosize particles in a well stirred reactor at ambient pressure and dilute solid phase concentration in\\u000a order to obtain fundamental details of the reaction kinetics. The principal rate limiting step for this electrochemical reaction\\u000a appears to be a transport process through

P. B. Munoz; J. D. Miller; M. E. Wadsworth

1979-01-01

71

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

PubMed

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

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

2014-07-15

72

Detection and isolation of nucleic acid sequences using competitive hybridization probes  

DOEpatents

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

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

1997-01-01

73

Detection and isolation of nucleic acid sequences using competitive hybridization probes  

DOEpatents

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

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

1997-04-01

74

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

75

Change of monochloroacetic acid to biodegradable organic acids by hydrothermal reaction.  

PubMed

The feasibility of biodegradability improvement induced from the structural conversion of refractory pollutants by hydrothermal reaction was investigated. Monochloroacetic acid (MCAA) was selected as a preliminary material represented for linear hydrocarbon structured refractory pollutants. Under the tested conditions, MCAA was partially destructed and then converted to biodegradable reaction products by hydrolysis, dehydration and thermal decomposition. The identified products were glycolic acid, citric acid and formic acid. Total organic carbon (TOC) reduction during the structural conversion did not exceed 24%, except the results at the reaction conditions of 350 degrees C and 17 MPa. However, Produced biodegradable organic acids were reduced by thermal decomposition with increasing reaction temperature and time. At the reaction temperature of 250 and 300 degrees C, biodegradability (BOD/COD(Cr)) was reached at 0.51 in 6.9 min and 0.52 in 7.4 min despite the presence of dissociated chlorine ions. The detachment of recalcitrant chlorine ion from MCAA and the production of biodegradable organic acids by hydrothermal reaction were directly related to the biodegradability improvement of reaction products. PMID:15081173

Kim, Kyoungrean; Fujita, Masafumi; Daimon, Hiroyuki; Fujie, Koichi

2004-04-30

76

Performance analysis of lead acid battery model for hybrid power system  

Microsoft Academic Search

This paper presents the mathematical model of a lead-acid battery, which is often used as the energy storage unit in hybrid power systems. The lead-acid battery is complex, nonlinear device exhibiting memory effect. In the hybrid power system, the battery plays very important role in sense that it controls all other energy converters integrated. The operating voltage of a PV

R. Saiju; S. Heier

2008-01-01

77

Carbohydrate-steroid conjugation by Ugi reaction: one-pot synthesis of triple sugar/pseudo-peptide/spirostane hybrids.  

PubMed

The one-pot synthesis of novel molecular chimeras incorporating sugar, pseudo-peptide, and steroidal moieties is described. For this, a new carbohydrate-steroid conjugation approach based on the Ugi four-component reaction was implemented for the ligation of glucose and chacotriose to spirostanic steroids. The approach proved wide substrate scope, as both mono and oligosaccharides functionalized with amino, carboxy, and isocyano groups were conjugated to steroidal substrates in an efficient, multicomponent manner. Two alternative strategies based on the hydrazoic acid variant of the Ugi reaction were employed for the synthesis of tetrazole-based chacotriose-diosgenin conjugates resembling naturally occurring spirostan saponins. This is the first time that triple sugar/pseudo-peptide/steroid hybrids are produced, thus opening up an avenue of opportunities for applications in drug discovery and biological chemistry. PMID:22925772

Rivera, Daniel G; Pérez-Labrada, Karell; Lambert, Liudmila; Dörner, Simon; Westermann, Bernhard; Wessjohann, Ludger A

2012-10-01

78

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

DOEpatents

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

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

2000-01-01

79

Elimination Reaction of 2-Hydroxyalkylcobaloximes in Acidic Solution.  

National Technical Information Service (NTIS)

Research is reported on the establishment of a rate law and mechanism for the beta -OH-alkylcobaloxime decomposition reaction in acid media. The compounds used in the study are beta -OH-Et(Co)py (or H sub 2 O), beta -OH-i-Pr(Co)py (or H sub 2 O), beta -OH...

D. M. L. Wang

1979-01-01

80

Reaction mechanism for the acid-catalyzed hydrolysis of saccharose  

Microsoft Academic Search

1.A polarimetric study was made of the reaction for the hydrolysis of saccharose in inorganic acid solutions.2.The A-1 mechanism, on the assumption that saccharose is a base of the type of a Hammett indicator, does not describe the experimental data.

N. A. Khalturinskii; Yu. V. Moiseev; G. E. Zaikov

1972-01-01

81

Reactions of Thiocyanate Ions with Acid: A Laboratory Experiment.  

ERIC Educational Resources Information Center

Background information, procedures, and typical results are provided for a three-part experiment involving reactions of potassium thiocynate (KNCS) with sulfuric acid. The experiment represents the final stage of structured work prior to students' research projects during their final year. (JM)

Glidewell, Christopher; And Others

1984-01-01

82

Sandwich probes: two simultaneous reactions for templated nucleic acid detection.  

PubMed

Fluorescence-quenched nucleic acid probes with reactive moieties at both the 5' and 3' ends are synthesized and tested for reaction with two adjacent nucleophile-containing DNAs. These probes improve signal to background over singly reactive probes and can discriminate single nucleotide polymorphisms in the target DNA or RNA. PMID:20927470

Kleinbaum, Daniel J; Kool, Eric T

2010-11-21

83

EXTENT OF OZONE'S REACTION WITH ISOLATED AQUATIC FULVIC ACID  

EPA Science Inventory

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

84

A hybrid thermochemical-electrolytic process for hydrogen production based on the Reverse Deacon Reaction.  

SciTech Connect

Development has been initiated on a three-reaction, hybrid thermochemical-electrolytic process for splitting water into hydrogen and oxygen. This process can be run at 500 C, making it suitable for linking to nuclear reactors that run colder than the very highest temperature gas cooled reactors. This feature also makes the materials requirements less stringent than for high temperature cycles, many of which require temperatures in the range of 800-900 C. The process consists of three reactions - two thermochemical and one electrolytic. The thermochemical reactions sum to the reverse Deacon reaction. The electrolytic step involves the electrolysis of anhydrous HCl. The estimated energy savings for this process relative to electrolysis of water are in the vicinity of 15%, due to the low energy requirements of anhydrous HCl electrolysis. Preliminary experimental results indicate that a silicalite-supported catalyst for the reverse Deacon reaction has the potential of promoting fast reaction kinetics and long-term stability of the solids.

Simpson, M. F.; Herrmann, S. D.; Boyle, B. D.; Engineering Technology

2006-08-01

85

Acid-catalyzed Heterogeneous Reactions in SOA Formation  

NASA Astrophysics Data System (ADS)

The importance of heterogeneous reactions in secondary organic aerosol (SOA) formation has recently excited a great deal of interest in the aerosol community. Jang and Kamens (2001) showed enhanced aerosol yield from aldehydes, which can be produced by atmospheric photochemical reactions, in the presence of acidic seed. They suggest that the carbonyl functional groups of the aldehydes further react in the aerosol phase via hydration, polymerization, and hemiacetal/acetal formation with alcohols at an accelerated rate in the presence of acid. Jang et al. (2003) demonstrated similar results using a flow reactor and Czoschke et al. (in press) qualitatively showed increased yields for isoprene and alpha-pinene ozonolysis in the presence of acidic seed. While these findings are intriguing and important, the conditions under which the experiments were carried out were atmospherically unrealistic. A series of SOA formation experiments have been carried out in the Caltech Indoor Chamber Facility, which is comprised of dual 28 m3 FEP Teflon chambers, with the flexibility to carry out both dark ozonolysis and photochemical OH oxidation reactions. Cycloheptene and alpha-pinene were oxidized in the presence of neutral seed under dry (<10% RH) and humid (50% RH) conditions and in the presence of acidic seed under humid (50% RH) conditions. The SOA yields for these experiments will be presented, and the extent of the influence of acid-catalyzed reactions on SOA yield will be discussed. Reference List 1. Cocker, D. R. III. and R. C. Flagan and J. H. Seinfeld, State-of-the-art chamber facility for studying atmospheric aerosol chemistry, Environmental Science and Technology, 35, 2594-2601, 2001. 2. Czoschke, N. M., M. Jang, and R. M. Kamens, Effect of acid seed on biogenic sceondary organic aerosol growth, Atmospheric Environment, In press. 3. Jang, M., S. Lee, and R. M. Kamens, Organic aerosol growth by acid-catalyzed heterogeneous reactions of octanal in a flow reactor, Atmospheric Environment, 37, 2125-2138, 2003. 4. Jang, M. S. and R. M Kamens, Atmospheric secondary aerosol formation by heterogeneous reactions of aldehydes in the presence of a sulfuric acid aerosol catalyst. Environmental Science and Technology, 35, 4758-4766,2001.

Ng, N.; Keywood, M.; Varutbangkul, V.; Gao, S.; Loewer, E.; Surratt, J.; Richard, F. C.; John, S. H.

2003-12-01

86

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

87

Template directed reactions of 2-aminoadenylic acid derivatives  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

88

Change of monochloroacetic acid to biodegradable organic acids by hydrothermal reaction  

Microsoft Academic Search

The feasibility of biodegradability improvement induced from the structural conversion of refractory pollutants by hydrothermal reaction was investigated. Monochloroacetic acid (MCAA) was selected as a preliminary material represented for linear hydrocarbon structured refractory pollutants. Under the tested conditions, MCAA was partially destructed and then converted to biodegradable reaction products by hydrolysis, dehydration and thermal decomposition. The identified products were glycolic

Kyoungrean Kim; Masafumi Fujita; Hiroyuki Daimon; Koichi Fujie

2004-01-01

89

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

90

Synthesis and characterization of MEH-PPV\\/nanosized titania hybrids prepared via in situ sol–gel reaction  

Microsoft Academic Search

Homogenous organic\\/inorganic hybrids (MEH-PPV\\/nanosized-titania) were successfully synthesized via in situ sol–gel reaction, using titanium isopropoxide (TIP) as precursor. These hybrids were prepared under various weight ratios of MEH-PPV\\/TIP\\/H2O\\/2-chlorophenol and different molecular weights of MEH-PPV, whose effects on hybrids’ properties were studied. The hybrids were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). XRD showed clearer

Hung-Jen Chen; Leeyih Wang; Wen-Yen Chiu

2008-01-01

91

Reaction of Uric Acid with Peroxynitrite and Implications for the Mechanism of Neuroprotection by Uric Acid  

Microsoft Academic Search

Peroxynitrite, a biological oxidant formed from the reaction of nitric oxide with the superoxide radical, is associated with many pathologies, including neurodegenerative diseases, such as multiple sclerosis (MS). Gout (hyperuricemic) and MS are almost mutually exclusive, and uric acid has therapeutic effects in mice with experimental allergic encephalomyelitis, an animal disease that models MS. This evidence suggests that uric acid

Giuseppe L. Squadrito; Rafael Cueto; Andres E. Splenser; Athanasios Valavanidis; Houwen Zhang; Rao M. Uppu; William A. Pryor

2000-01-01

92

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  

PubMed Central

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; ?rum, Henrik; Schuster, Gary B.

1998-01-01

93

Permeabilization of mycolic-acid-containing actinomycetes for in situ hybridization with fluorescently labelled oligonucleotide probes  

Microsoft Academic Search

The application of whole-cell hybridization using labelled oligonucleotide probes in microbial systematics and ecology is limited by difficulties in permeabilizing many Gram-positive organisms. In this investigation paraformaldehyde treatment, acid methanolysis and acid hydrolysis were evaluated as a means of permeabilizing mycolic-acid-containing actinomycetes prior to hybridization with a fluorescently labelled oligonucleotide probe designed to bind to a conserved sequence of bacterial

S. J. Macnaughton; A. G. O'Donnelll; T. M. Embley

1994-01-01

94

Heterogeneous atmospheric reactions - Sulfuric acid aerosols as tropospheric sinks  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

95

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.

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

2010-01-01

96

Extent of ozone's reaction with isolated aquatic fulvic acid  

SciTech Connect

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

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

1986-07-01

97

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

98

40 CFR 721.10126 - Alkyl amino substituted triazine amino substituted benezenesulfonic acid reaction product with...  

Code of Federal Regulations, 2010 CFR

...substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo substituted phenyl azo substituted benzenesulfonic acid copper compound (generic). 721.10126 Section 721.10126 Protection...

2010-07-01

99

Reaction pathways of glucose oxidation by ozone under acidic conditions.  

PubMed

The ozonation of d-glucose-1-(13)C, 2-(13)C, and 6-(13)C was carried out at pH 2.5 in a semi-batch reactor at room temperature. The products present in the liquid phase were analyzed by GC-MS, HPAEC-PAD, and (13)C NMR spectroscopy. Common oxidation products of glucose have also been submitted to identical ozonation conditions. For the first time, a pentaric acid was identified and its formation quantitatively correlated to the loss of C-6 of glucose in the form of carbon dioxide. Potential mechanisms for the formation of this pentaric acid are discussed. The well-accepted pathway involving the anomeric position in glucose, gluconic acid, arabinose, and carbon dioxide is reinvestigated. The origin of small molecules such as tartaric, erythronic, and oxalic acids is clarified. Finally, new reaction pathways and tentative mechanisms consistent with the formation of ketoaldonic acids and smaller acids are proposed. PMID:19524217

Marcq, Olivier; Barbe, Jean-Michel; Trichet, Alain; Guilard, Roger

2009-07-27

100

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

PubMed

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

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

2013-10-21

101

Quantitative rRNA-Targeted Solution-Based Hybridization Assay Using Peptide Nucleic Acid Molecular Beacons? †  

PubMed Central

The potential of a solution-based hybridization assay using peptide nucleic acid (PNA) molecular beacon (MB) probes to quantify 16S rRNA of specific populations in RNA extracts of environmental samples was evaluated by designing PNA MB probes for the genera Dechloromonas and Dechlorosoma. In a kinetic study with 16S rRNA from pure cultures, the hybridization of PNA MB to target 16S rRNA exhibited a higher final hybridization signal and a lower apparent rate constant than the hybridizations to nontarget 16S rRNAs. A concentration of 10 mM NaCl in the hybridization buffer was found to be optimal for maximizing the difference between final hybridization signals from target and nontarget 16S rRNAs. Hybridization temperatures and formamide concentrations in hybridization buffers were optimized to minimize signals from hybridizations of PNA MB to nontarget 16S rRNAs. The detection limit of the PNA MB hybridization assay was determined to be 1.6 nM of 16S rRNA. To establish proof for the application of PNA MB hybridization assays in complex systems, target 16S rRNA from Dechlorosoma suillum was spiked at different levels to RNA isolated from an environmental (bioreactor) sample, and the PNA MB assay enabled effective quantification of the D. suillum RNA in this complex mixture. For another environmental sample, the quantitative results from the PNA MB hybridization assay were compared with those from clone libraries.

Li, Xu; Morgenroth, Eberhard; Raskin, Lutgarde

2008-01-01

102

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.

Marin, Violeta L.; Armitage, Bruce A.

2008-01-01

103

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

Microsoft Academic Search

Optima Batteries, Inc. is developing a high power (660 W\\/kg) spiral wound lead-acid 6 V 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

John B. Olson; Elizabeth D. Sexton

1997-01-01

104

Predictions of diagenetic reactions in the presence of organic acids  

NASA Astrophysics Data System (ADS)

Stability constants have been estimated for cation complexes with anions of monofunctional and difunctional acids (combinations of Ca, Mg, Fe, Al, Sr, Mn, U, Th, Pb, Cu, Zn with formate, acetate, propionate, oxalate, malonate, succinate, and salicylate) between 0 and 200°C. 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. Aluminum-oxalate can dominate the species distribution of aluminum under acidic pH conditions, whereas the divalent cation-acetate and oxalate complexes rarely account for more than 60% of the total dissolved cation, and then only in more alkaline waters. 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. The following scenarios are possible: 1) K-feldspar and albite are stable, anorthite dissolves 2) All feldpars are stable 3) Carbonates can be very unstable to slightly unstable, but never increase in stability. 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. Under some circumstances, OAA-bearing waters are less effective at producing porosity in an arkosic sandstone than are OAA-free waters. 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, Wendy J.; Thyne, Geoffrey D.

1992-02-01

105

Gold nanoparticles–graphene hybrids as active catalysts for Suzuki reaction  

Microsoft Academic Search

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

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

2010-01-01

106

Kinetics and mechanism of the hypochlorous acid-trithionate reaction.  

PubMed

The trithionate-hypochlorous acid reaction has been studied by the stopped-flow technique and conventional spectrophotometry between pH = 6.59-12.2 monitoring absorbance-time profiles at 285 and 225 nm. We showed that the formal kinetic order of Cl(I) is nearly 2; however, those of hydrogen ion and trithionate are significantly lower than unity, suggesting complex kinetics. It was also demonstrated that both forms of Cl(I) are kinetically active within the concentration range studied. Simultaneous evaluation of the kinetic curves revealed that the reaction was initiated by a formal Cl(+) transfer to the partially negatively charged ?-sulfur of trithionate. S3O6Cl(-) formed in the first step was also found to be equilibrating with S3O6OH(-) via a simple chlorine-OH exchange reaction followed by their subsequent oxidation of hypochlorite and hypochlorous acid, respectively. A six-step kinetic model is proposed and discussed with having four fitted and four fixed parameters. PMID:24000830

Csek?, György; Rauscher, Evelin; Horváth, Attila K

2013-09-12

107

Water-wire catalysis in photoinduced acid-base reactions.  

PubMed

The pronounced ability of water to form a hyperdense hydrogen (H)-bond network among itself is at the heart of its exceptional properties. Due to the unique H-bonding capability and amphoteric nature, water is not only a passive medium, but also behaves as an active participant in many chemical and biological reactions. Here, we reveal the catalytic role of a short water wire, composed of two (or three) water molecules, in model aqueous acid-base reactions synthesizing 7-hydroxyquinoline derivatives. Utilizing femtosecond-resolved fluorescence spectroscopy, we tracked the trajectories of excited-state proton transfer and discovered that proton hopping along the water wire accomplishes the reaction more efficiently compared to the transfer occurring with bulk water clusters. Our finding suggests that the directionality of the proton movements along the charge-gradient H-bond network may be a key element for long-distance proton translocation in biological systems, as the H-bond networks wiring acidic and basic sites distal to each other can provide a shortcut for a proton in searching a global minimum on a complex energy landscape to its destination. PMID:22358321

Kwon, Oh-Hoon; Mohammed, Omar F

2012-07-01

108

Laboratory measurements of heterogeneous reactions on sulfuric acid surfaces  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

109

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

110

Nucleic acid hybridization techniques for the detection of bluetongue virus  

SciTech Connect

Virus isolation, antigen detection, and in situ hybridization were compared in their abilities to detect in cell culture, the five serotypes of bluetongue virus (BTV) occurring in the United States, serotypes 2, 10, 11, 13, and 17. For isolation, virus was propagated in baby hamster kidney (BHK-21) cell culture. For antigen detection, two techniques, indirect fluorescent-antibody (IFA) and enzyme immunocytoassay (EICA) were used. For in situ hybridization, a complementary DNA (cDNA) of the L3 RNA genome segment of BTV, serotype 17 (BTV-17) labeled with {sup 35}S was used as a group-specific probe. Virus isolation was the most sensitive technique, often detecting input virus and then detecting virus throughout the course of the study. IFA and EICA were of similar sensitivity and detected BTV antigen shortly after detection of virus by isolation. A direct-blot hybridization technique using a {sup 32}P-labeled, strand-specific RNA transcript probe was developed, optimized, and used to detect BTV in pools of infected Culicoides variipennis midges. The technique was able to detect as few as one infected Culicoides midge in a pool of 100 and as little as 3.5 log{sub 10} TCID{sub 50} per ml of virus. A sandwich hybridization technique was developed and used to detect BTV in pools of infected Culicoides variipennis midges. The sandwich hybridization technique used a single-stranded DNA catcher sequence bound to a solid support and a {sup 32}P-labeled, single-stranded RNA detector sequence. Sandwich hybridization was compared to direct blot hybridization using a strand-specific RNA transcript probe or a cDNA probe. Sandwich hybridization was able to detect as few as one infected Culicoides midge in a pool of 50; however, the technique was approximately tenfold less sensitive than direct blot hybridization.

Schoepp, R.J.

1989-01-01

111

Formic acid production from carbohydrates biomass by hydrothermal reaction  

NASA Astrophysics Data System (ADS)

The formation of formic acid or formate salts by hydrothermal oxidation of model biomass materials (glucose, starch and cellulose) was investigated. All experiments were conducted in a batch reactor, made of SUS 316 tubing, providing an internal volume of 5.7 cm3. A 30 wt% hydrogen peroxide aqueous solution was used as an oxidant. The experiments were carried out with temperature of 250°C, reaction time varying from 0.5 min to 5 min, H2O2 supply of 240%, and alkaline concentration varying from 0 to 1.25 M. Similar to glucose, in the cases of the oxidation of hydrothermal starch and cellulose, the addition of alkaline can also improve the yield of formic acid. And the yield were glucose>starch> cellulose in cases of with or without of alkaline addition.

Yun, J.; Jin, F.; Kishita, A.; Tohji, K.; Enomoto, H.

2010-03-01

112

Kinetics of the reactions of hypochlorous acid and amino acid chloramines with thiols, methionine, and ascorbate  

Microsoft Academic Search

Thiol oxidation by hypochlorous acid and chloramines is a favorable reaction and may be responsible for alterations in regulatory or signaling pathways in cells exposed to neutrophil oxidants. In order to establish the mechanism for such changes, it is necessary to appreciate whether these oxidants are selective for different thiols as compared with other scavengers. We have measured rate constants

Alexander V Peskin; Christine C Winterbourn

2001-01-01

113

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

SciTech Connect

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. [A.I. Alikhanov Institute for Theoretical and Experimental Physics (Russian Federation); Keldysh Institute of Applied Mathematics, Russian Academy of Sciences (Russian Federation); Zhukov, V. T. [Keldysh Institute of Applied Mathematics, Russian Academy of Sciences (Russian Federation)

2006-08-03

114

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

115

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

PubMed

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

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

2014-07-15

116

Reaction of urethane with nucleic acids in vivo  

PubMed Central

1. [1-14C]Ethyl carbamate, ethyl [carboxy-14C]carbamate, [1-14C]ethanol and sodium hydrogen [14C]carbonate were injected intraperitoneally into C57 mice, and nucleic acids and proteins were separated from the liver and lungs with phenol as described by Kirby (1956). 2. Chromatographic analysis of the hydrolytic products of the urethane-labelled RNA showed the presence of a single radioactive compound differing in behaviour from the major pyrimidine nucleotides and purines. 3. The products from RNA labelled by [1-14C]ethyl carbamate or ethyl [carboxy-14C]carbamate appeared chromatographically identical but could not be detected in the RNA of mice given [1-14C]ethanol or sodium hydrogen [14C]-carbonate. 4. The labelled product appeared to be the ethyl ester of cytosine-5-carboxylic acid formed by the reaction of urethane with RNA in vivo. 5. A direct reaction between labelled urethane or the labelled metabolite of urethane, [1-3H]-ethyl N-hydroxycarbamate, and RNA was not detected.

Boyland, E.; Williams, K.

1969-01-01

117

Improvement of engine cold start capability using supercapacitor and lead-acid battery hybrid  

Microsoft Academic Search

Supercapacitors can provide the transient power that the cranking need in low temperature. Aiming to reduce the volume of lead acid battery and the cost of the power system, supercapacitor and lead acid battery hybrid systems are investigated as power sources for diesel engine cold starting by using cold starting test and road test. This paper focuses on the requirement

Hanmin Liu; Zhixin Wang; Shutong Qiao; Yunhai Liu

2008-01-01

118

Hybrid method for simulating front propagation in reaction-diffusion systems.  

PubMed

We study the propagation of pulled fronts in the A<--> A+A microscopic reaction-diffusion process using Monte Carlo simulations. In the mean field approximation the process is described by the deterministic Fisher-Kolmogorov-Petrovsky-Piscounov equation. In particular, we concentrate on the corrections to the deterministic behavior due to the number of particles per correlated volume Omega. By means of a hybrid simulation scheme, we manage to reach large macroscopic values of Omega, which allows us to show the importance in the dynamics of microscopic pulled fronts of the interplay of microscopic fluctuations and their macroscopic relaxation. PMID:15244531

Moro, Esteban

2004-06-01

119

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

120

Calcium phosphate cements prepared by acid-base reaction  

SciTech Connect

In this paper, the authors investigate the characteristics of calcium phosphate cements (CPC) prepared by an exothermic acid-base reaction between NH[sub 4]H[sub 2]PO[sub 4]-based fertilizer (Poly-N) and calcium aluminate compounds (CAC), such as 3CaO[center dot]Al[sub 2]O[sub 3] (C[sub 3]A), CaO[center dot] Al[sub 2]O[sub 3] (CA), and CaO[center dot] 2Al[sub 2]O[sub 3] (CA[sub 2]), in a series of integrated studies of reaction kinetics, interfacial reactions, in-situ phase transformations, and microstructure development. Two groups were compared: untreated and hydrothermally treated CPC specimens. The extent of reactivity of CAC with Poly-N at 25[degrees]C was in the following order: CA [gt] C[sub 3]A much+[gt] CA[sub 2]. The formation of a NH[sub 4]CaPO[sub 4][center dot]xH[sub 2]O salt during this reaction was responsible for the development of strength in the CPC specimens. The in-situ phase transformation of amorphous NH[sub 4]CaPO[sub 4][center dot]xH8[sub 2]O into crystalline Ca[sub 5](PO[sub 4])[sub 3](OH) and the conversion of hydrous Al[sub 2]O[sub 3] gel [yields] [gamma]-AlOOH occur in cement bodies during exposure in an autoclave to temperatures up to 300[degrees]C.

Sugama, T.; Allan, M. (Brookhaven National Lab., Upton, NY (United States). Applied Science Dept.)

1992-08-01

121

Lewis-acid-assisted methyl exchange reactions in silylated aminodichloroarsanes.  

PubMed

Lewis-acid-assisted methyl/chlorine, methyl/azide, and methyl/triflate exchange reactions between silicon and arsenic centers have been studied and applied to different silylated aminoarsane species leading to a number of new methylarsane compounds: bis(trimethylsilyl)amino(dichloro)arsane (3) was reacted with GaCl(3) yielding a bis(chlorodimethylsilyl)-tetramethyl-cyclo-disilazane (4) accompanied by the release of Me(2)AsCl, while trimethylsilyl(m-terphenyl)amino(dichloro)arsane (5) (m-terphenyl = 2,6-Mes(2)-C(6)H(3), Mes = 2,4,6-Me(3)C(6)H(2)) reacted with GaCl(3) to give dichloromethylsilyl(m-terphenyl)aminodimethylarsane (6). In the presence of trimethylsilylazide, trimethylsilyl(m-terphenyl)amino(dichloro)arsane displays a methyl/azide exchange triggered by the action of GaCl(3) yielding azidodimethylsilyl(m-terphenyl)amino(chloro)methylarsane (7). Moreover, methyl/triflate exchange reactions have been observed in the reaction of trimethylsilyl(m-terphenyl)amino(dichloro)arsane (i) with 1 equiv of AgOTf (OTf = triflate) yielding N-(trifluoromethylsulfonatodimethylsilyl)-N-(m-terphenyl)amino(methyl)chloroarsane (8) and (ii) with 2 equiv of AgOTf yielding N-(trifluoromethylsulfonatodimethylsilyl)-N-(m-terphenyl)trifluoromethylsulfonatomethylarsane (9). All new compounds (3-9) have been fully characterized by means of vibrational spectroscopy, X-ray, CHN analysis, MS, and NMR studies. A possible reaction mechanism is discussed starting from an initial chloride abstraction and the intermediate formation of a cationic iminoarsane species. In a second step, a methyl shift from the silicon to the arsenic center occurs. PMID:19006290

Michalik, Dirk; Schulz, Axel; Villinger, Alexander

2008-12-15

122

A kinetic study on the potential of a hybrid reaction mechanism for prediction of NOx formation in biomass grate furnaces  

Microsoft Academic Search

This paper presents the verification of a hybrid reaction mechanism (28 species, 104 reactions) by means of a kinetic study with a view to its application for the CFD-based prediction of gas phase combustion and NOx formation in biomass grate furnaces. The mechanism is based on a skeletal kinetic scheme that includes the subsets for H2, CO, NH3 and HCN

Selma Zahirovi?; Robert Scharler; Pia Kilpinen; Ingwald Obernberger

2011-01-01

123

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

124

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

125

Effects of fast charging on hybrid lead\\/acid battery temperature  

Microsoft Academic Search

The effects of very fast charging on two types of deep-cycling hybrid lead\\/acid batteries were determined using a MINITCHARGER(sup TM) to control the charging current. One of the hybrid batteries was flooded and contained Pb-4.7 wt.% Sb positive grids, the other was a valve-regulated battery with Pb-1.5 wt.% Sb-0.3 wt.% Sn positive grids. Results are presented and discussed in relation

T. G. Chang; E. M. Valeriote; D. M. Jochim

1994-01-01

126

Quantitative detection of tumor necrosis factor-? by single molecule counting based on a hybridization chain reaction.  

PubMed

This work reports a novel and sensitive quantitative method for detection of tumor necrosis factor-? (TNF-?) based on single molecule counting and hybridization chain reaction (HCR). In the presence of TNF-?, sandwich-type immunocomplex was formed on the surface of glass substrate. The streptavidin acted as a bridge bounded to the biotinylated immunocomplex, which provided three sites to fixate the biotinylated initiator strands. The initiator strands triggered the chain reaction of hybridization to form a long double-helix polymer and SYBR Green I, acted as the fluorescence label, intercalated into the grooves of the long dsDNA polymer. Then, the quantitative detection of TNF-? was realized by single molecule counting. Under the optimal conditions, HCR-based single molecule counting quantitative method could successfully detect TNF-? in the range of 50 fM to 1 pM, and it revealed a reliable result for TNF-? detection in real serum. Moreover, the proposed immunosensor exhibited excellent specificity. These results greatly demonstrated that the proposed method possessed the potentiality in clinical application and it was suitable for quantification of biomarker under low concentration. PMID:24800682

Dai, Shuang; Feng, Chunjing; Li, Wei; Jiang, Wei; Wang, Lei

2014-10-15

127

An ultrasensitive fluorescence assay for protein detection by hybridization chain reaction-based DNA nanotags.  

PubMed

An ultrasensitive fluorescence method for determination of protein is developed based on hybridization chain reaction (HCR). In this assay, the streptavidin-magnetic nanobeads were conjugated to biotinylated initiators and biotinylated anti-IgG. In the presence of human IgG, the magnetic nanobeads were fixed on the substrate and the carried initiators propagated the chain reaction of hybridization to form the nicked polymers. Because the nanobead probe carries with a large number of oligonucleotides per protein binding event, there is obvious amplification in the nicked polymers. Then, numerous SYBR Green I molecules were intercalated into the grooves of the long dsDNA polymers, generating a substantially apparent increase in the corresponding fluorescence intensity. With HCR amplification and magenetic nanobead to preamplify the fluorescence signal and reduce the background signal, the detection limit of this assay was 14 aM. Compared with the reported protein detection methods, our method exhibited ultrahigh sensitivity. In addition, the proposed method possessed excellent selectivity and low matrix effect. What is more, the assay was also studied for clinical application in human serum with a satisfactory and reliable result. PMID:24001583

Dai, Shuang; Xue, Qingwang; Zhu, Jing; Ding, Yongshun; Jiang, Wei; Wang, Lei

2014-01-15

128

Next-generation in situ hybridization chain reaction: higher gain, lower cost, greater durability.  

PubMed

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

Choi, Harry M T; Beck, Victor A; Pierce, Niles A

2014-05-27

129

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.

2014-01-01

130

Reaction of acid gases with mixtures of amines  

SciTech Connect

Detailed thermodynamic and kinetic models are presented in this paper which were developed for acid gas reactions with mixtures of amines. The models permit the extension of the nonequilibrium-stage approach in the simulation of gas treating plants using solvent blends. The prediction of these models indicate a potentially great improvement in sour gas treating processes. The mixing concept enables one to obtain the individual advantages of each amine for absorption as well as desorption without the disadvantages of either. In the absorber, the MEA in the blend at the top of the column serves to remove residual CO2 from the gas while throughout the rest of the column MDEA does a bulk removal job. The use of blended amines to treat natural, refinery and synthesis gases brings about a considerable improvement in absorption and a great savings in energy requirements.

Chakravarty, T.; Phukan, U.K.; Weilund, R.H.

1985-04-01

131

Fatty Acid Desaturation and Elongation Reactions of Trichoderma sp. 1OH2-3  

Microsoft Academic Search

The fatty acid desaturation and elongation reactions catalyzed by Trichoderma sp. 1-OH-2-3 were investigated. This strain converted palmitic acid (16:0) mainly to stearic acid (18:0), and further to\\u000a oleic acid (c9-18:1), linoleic acid (c9,c12-18:2), and ?-linolenic acid (c9,c12,c15-18:3) through elongation, and ?9, ?12, and ?15 desaturation reactions, respectively. Palmitoleic acid (c9-16:1) and cis-9,cis-12-hexadecadienoic acid were also produced from 16:0 by

Akinori Ando; Jun Ogawa; Shigenobu Kishino; Taiyo Ito; Norifumi Shirasaka; Eiji Sakuradani; Kenzo Yokozeki; Sakayu Shimizu

2009-01-01

132

Synthesis and properties of poly(methyl methacrylate-2-acrylamido-2-methylpropane sulfonic acid)/PbS hybrid composite  

SciTech Connect

The synthesis of a new hybrid composite based on PbS nanoparticles and poly(methyl methacrylate-2-acrylamido-2-methylpropane sulfonic acid) [P(MMA-AMPSA)] copolymer is reported. The chemical synthesis consists in two steps: (i) a surfactant-free emulsion copolymerization between methyl methacrylate and 2-acrylamido-2-methylpropane sulfonic acid and (ii) the generation of PbS particles in the presence of the P(MMA-AMPSA) latex, from the reaction between lead nitrate and thiourea. The composite was studied by scanning electron microscopy (SEM), X-ray diffraction, FTIR spectroscopy, thermogravimetric analysis and differential scanning calorimetry. The microstructure observed using SEM proves that the PbS nanoparticles are well dispersed in the copolymer matrix. The X-ray diffraction measurements demonstrate that the PbS nanoparticles have a cubic rock salt structure. It was also found that the inorganic semiconductor nanoparticles improve the thermal stability of the copolymer matrix.

Preda, N., E-mail: nicol@infim.ro [National Institute of Materials Physics, Multifunctional Materials and Structures Laboratory, P.O. Box MG-7, 77125 Bucharest (Romania); Rusen, E. [University Politehnica Bucharest, Department of Polymer Science, Calea Victoriei No. 71101, Bucharest (Romania)] [University Politehnica Bucharest, Department of Polymer Science, Calea Victoriei No. 71101, Bucharest (Romania); Musuc, A. [Institute of Physical Chemistry, 060021 Bucharest (Romania)] [Institute of Physical Chemistry, 060021 Bucharest (Romania); Enculescu, M.; Matei, E. [National Institute of Materials Physics, Multifunctional Materials and Structures Laboratory, P.O. Box MG-7, 77125 Bucharest (Romania)] [National Institute of Materials Physics, Multifunctional Materials and Structures Laboratory, P.O. Box MG-7, 77125 Bucharest (Romania); Marculescu, B. [University Politehnica Bucharest, Department of Polymer Science, Calea Victoriei No. 71101, Bucharest (Romania)] [University Politehnica Bucharest, Department of Polymer Science, Calea Victoriei No. 71101, Bucharest (Romania); Fruth, V. [Institute of Physical Chemistry, 060021 Bucharest (Romania)] [Institute of Physical Chemistry, 060021 Bucharest (Romania); Enculescu, I. [National Institute of Materials Physics, Multifunctional Materials and Structures Laboratory, P.O. Box MG-7, 77125 Bucharest (Romania)] [National Institute of Materials Physics, Multifunctional Materials and Structures Laboratory, P.O. Box MG-7, 77125 Bucharest (Romania)

2010-08-15

133

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

134

A designed organic–zeolite hybrid acid–base catalyst  

Microsoft Academic Search

An organic–zeolite hybrid catalyst was synthesised via solid-state impregnation of the zeolite with an amount of melamine corresponding to 20mol% of the aluminium content. A high density of basic sites is formed in the zeolite. From infrared spectroscopy and TGA measurements we infer that melaminium cations are formed in the zeolite which are highly thermally stable. IR spectroscopic and TGA

Andrew C. Brooks; Liam France; Cecile Gayot; Jerry Pui Ho Li; Ryan Sault; Andrew Stafford; John D. Wallis; Michael Stockenhuber

135

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

NASA Astrophysics Data System (ADS)

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

Ganesh, Karthik

136

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

PubMed Central

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

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

2012-01-01

137

Photochemical reaction of 2-(3-benzoylphenyl)propionic acid (ketoprofen) with basic amino acids and dipeptides.  

PubMed

Photoreaction of 2-(3-benzoylphenyl)propionic acid (ketoprofen, KP) with basic amino acids (histidine, lysine, and arginine) and dipeptides (carnosine and anserine) including a histidine moiety in phosphate buffer solution (pH 7.4) has been investigated with transient absorption spectroscopy. With UV irradiation KP(-) gave rise to a carbanion through a decarboxylation reaction, and the carbanion easily abstracted a proton from the surrounding molecule to yield a 3-ethylbenzophenone ketyl biradical (EBPH). The dipeptides as well as the basic amino acids were found to accelerate the proton transfer reaction whereas alanine and glycine had no effect on the reaction, revealing that these amino acids having a protonated side chain act as a proton donor. The formation quantum yield of EBPH was estimated to be fairly large by means of an actinometrical method with benzophenone, and the bimolecular reaction rate constant for the proton transfer between the carbanion and the protonated basic amino acids or the protonated dipeptides was successfully determined. It has become apparent that the bimolecular reaction rate constant for the proton transfer depended on the acid dissociation constant for the side chain of the amino acids for the first time. This reaction mechanism was interpreted by difference of the heat of reaction for each basic amino acid based on the thermodynamical consideration. These results strongly suggest that the side chain of the basic amino acid residue in protein should play an important role for photochemistry of KP in vivo. PMID:23879666

Suzuki, Tadashi; Shinoda, Mio; Osanai, Yohei; Isozaki, Tasuku

2013-08-22

138

Reaction of 2,3-Dimethylmercaptopropionic Acid with Methylene Blue as an Indicator Reaction for the Kinetic Determination of Selenium  

Microsoft Academic Search

A new indicator reaction between 2,3-dimethylmercaptopropionic acid and Methyl Blue was proposed for the kinetic determination of selenium. The optimal reaction conditions were found. A linear relationship was observed between the induction period and the Se(IV) concentration in the range between 0.9 and 9.6 ng\\/mL Se. Masking with EDTA and solvent extraction with diethyldithiophosphoric acid can be used for the

D. F. Gainutdinova; N. V. Shirshova; V. F. Toropova; G. K. Budnikov; A. R. Garifzyanov

2001-01-01

139

Application of Iodine-Azide Reaction as Postcolumn Reaction in HPLC for Determination of 2-Thiobarbituric Acid  

Microsoft Academic Search

The reaction between iodine and azide ion induced by 2-thiobarbituric acid (TBA) has been utilized as a postcolumn reaction for chromatographic determination of this sulphur compound. The method is based on the separation of thiobarbituric acid on an Nova-Pak® CN HP column with an acetonitrile–aqueous solution of sodium azide mobile phase. The separation stage is followed by spectrophotometric measurement of

R. Zakrzewski; W. Ciesielski

2004-01-01

140

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

141

Iodomalonic Acid as an Anti-Inhibitor in the Resorcinol Inhibited Briggs-Rauscher Reaction  

NASA Astrophysics Data System (ADS)

It was found that the inhibitory effect of resorcinol is less pronounced if it is added in a later stage of the Briggs-Rauscher reaction, which indicates that an accumulating intermediate-most probably iodomalonic acid-can suppress the inhibition. In fact, when iodomalonic acid was added to the reaction mixture, the inhibitory period was shortened considerably even at micromolar levels of the iodomalonic acid concentration. Moreover, iodomalonic acid can accelerate the rate of the reaction when applied in the same low concentrations, suggesting that it can be an autocatalytic intermediate of the Briggs-Rauscher reaction.

Lawson, Thuy; Fülöp, János; Wittmann, Maria; Noszticzius, Zoltán; Muntean, Norbert; Szabó, Gabriella; Onel, Lavinia

2009-11-01

142

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

143

COMMUNICATION: Synthesis of hollow hybrid hydroxyapatite microspheres based on chitosan-poly(acrylic acid) microparticles  

Microsoft Academic Search

Core-template-free hybrid hydroxyapatite (HA) hollow microspheres based on a chitosan-poly acrylic acid (CS-PAA) complex were prepared. The amine groups on chitosan can interact with the carboxyl groups of poly(acrylic acid) to form hollow microspheres. The hollow HA microspheres of about 1.0 µm are obtained by heterogeneous nucleation of HA on CS-PAA hollow spheres. Gelatin (Gel), acting as a novel cross-link

Haibin Zhang; Kechao Zhou; Zhiyou Li; Suping Huang

2009-01-01

144

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

145

Control of lysosomal acid phosphatase expression in man-mouse cell hybrids  

Microsoft Academic Search

Lysosomal acid phosphatase activity in human and mouse cells was separated into multiple zones by starch gel electrophoresis. One of the two major zones in the mouse was apparently extinguished when genetic information from man and the mouse was combined in proliferating man-mouse somatic cell hybrids. The evidence suggested that the absence of the mouse lysosomal acid phosphatase (mAP-1) was

Thomas B. Shows; Peter A. Lalley

1974-01-01

146

[Influencing factors and reaction mechanism of chloroacetic acid reduction by cast iron].  

PubMed

The chloroacetic acids are ubiquitous present as a class of trace chlorinated organic pollutants in surface and drinking water. Most of chloroacetic acids are known or suspected carcinogens and, when at high concentrations, are of great concern to human health. In order to economically remove chloroacetic acids, the degradation of chloroacetic acids by cast iron was investigated. Moreover, the effect of iron style, pretreatment process, shocking mode and dissolved oxygen on chloroacetic acids reduced by cast iron was discussed. Compared to iron source and acid pretreatment, mass transfer was more important to chloroacetic acid removal. Dichloroacetic acid (DCAA) and monochloroacetic acid (MCAA) were the main products of anoxic and oxic degradation of trichloroacetic acid (TCAA) by cast iron during the researched reaction time, respectively. With longtitudinal shock, the reaction kinetics of chloroaectic acid removal by cast iron conformed well to the pseudo first order reaction. The anoxic reaction constants of TCAA, DCAA and MCAA were 0.46 h(-1), 0.03 h(-1) and 0, and their oxic constants were 1.24 h(-1), 0.79 h(-1) and 0.28 h(-1), respectively. The removal mechanisms of chloroacetic acids were different under various oxygen concentrations, including sequential hydrogenolysis for anoxic reaction and sequential hydrogenolysis and direct transformation possible for oxic reaction, respectively. PMID:24881385

Tang, Shun; Yang, Hong-Wei; Wang, Xiao-Mao; Xie, Yue-Feng

2014-03-01

147

Lead acid battery storage model for hybrid energy systems  

SciTech Connect

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 in capacity as a function of charge and discharge rates. It assumes that the charge can be stored in two ways, either as immediately available or as chemically bound. As described in this paper, it requires the determination of as few as three constants. Examples of the deviation of the battery model constants and comparisons of the new model with those used previously are given. Based on the success of the new model, it has been incorporated into the latest versions of the University of Massachusetts's wind/diesel simulation codes.

Manwell, J.F.; McGowan, J.G. (Univ. of Massachusetts, Amherst (United States))

1993-05-01

148

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

149

The preparation and characterization of pyroelectric hybrid films containing C.I. Acid Red 29 (chromotrope 2R)  

Microsoft Academic Search

Pyroelectric hybrid materials were prepared from 4,5-dihydroxy-3-(phenyldiazenyl)naphthalene-2,7-disulfonic acid (C.I. Acid Red 29) and Nb or Ta alkoxides via a sol–gel process. The hybrid materials were analyzed and characterized using infrared spectrometry, atom force microscopy and thermal gravimetry differential thermal analysis. The dye was covalently linked to the inorganic network and organic–inorganic hybrid films had excellent pyroelectric character (average pyroelectric coefficient

Zuxun Xu; Shimin Wang; Jun Ren; Yong Liu; Zhangjian Fang

2008-01-01

150

Design of an Innovative Lead-Acid Battery for Electric and Hybrid Vehicles.  

National Technical Information Service (NTIS)

Utilizing the technology developed at Globe over the last few years with funding assistance from the DOE, an innovative lead-acid battery has been designed specifically for use in a hybrid car. The battery has exceeded all of the minimum performance goals...

M. S. Baxa C. E. Weinlein

1982-01-01

151

Transmission Mode Ion/Ion Reactions in the RF-only Ion Guide of Hybrid Tandem Mass Spectrometers  

PubMed Central

Transmission mode ion/ion reactions have been performed within the first quadrupole, the Q0 RF-only quadrupole, of two types of hybrid tandem mass spectrometers (viz., triple quadrupole/linear ion trap and QqTOF instruments). These transmission mode reactions involved the storage of either the reagent species and the transmission of the analyte species through the Q0 quadrupole for charge inversion reactions or the storage of the analyte ions and transmission of the reagent ions as in charge reduction experiments. A key advantage to the use of transmission mode ion/ion reactions is that they do not require any instrument hardware modifications to provide interactions of oppositely charged ions and can be implemented in any instrument that contains a quadrupole or linear ion trap. The focus of this work was to investigate the potential of using the RF-only quadrupole ion guide positioned prior to the first mass-resolving element in a tandem mass spectrometer for ion/ion reactions. Two types of exemplary experiments have been demonstrated. One involved a charge inversion reaction and the other involved a charge reduction reaction in conjunction with ion parking. Ion/ion reactions proved to be readily implemented in Q0 thereby adding significantly greater experimental flexibility in the use of ion/ion reaction experiments with hybrid tandem mass spectrometers.

Emory, Joshua F.; Hassell, Kerry H.; Londry, Frank A.; McLuckey, Scott A.

2009-01-01

152

Permeabilization of mycolic-acid-containing actinomycetes for in situ hybridization with fluorescently labelled oligonucleotide probes.  

PubMed

The application of whole-cell hybridization using labelled oligonucleotide probes in microbial systematics and ecology is limited by difficulties in permeabilizing many Gram-positive organisms. In this investigation paraformaldehyde treatment, acid methanolysis and acid hydrolysis were evaluated as a means of permeabilizing mycolic-acid-containing actinomycetes prior to hybridization with a fluorescently labelled oligonucleotide probe designed to bind to a conserved sequence of bacterial 16S rRNA. Methods were evaluated on stationary-phase cultures of Gordona bronchialis, Mycobacterium fortuitum, Nocardia asteroides, N. brasiliensis, Rhodococcus equi, R. erythropolis, R. fascians, R. rhodochrous and Tsukamurella paurometabola, none of which could be probed following 4% (w/v) paraformaldehyde fixation. For comparison and to test the general applicability of mild acid pretreatments, Bacillus subtilis, Lactobacillus plantarum, Escherichia coli and Pseudomonas putida were also studied. The data showed that most of the mycolic-acid-containing organisms were successfully permeabilized by mild acid hydrolysis in 1 M HCl at 37 degrees C. Cells were treated for different lengths of time. In general, the mycolic-acid-containing organisms required between 30 and 50 min hydrolysis, whereas B. subtilis, E. coli and P. putida were rendered permeable in only 10 min. Interestingly, L. plantarum could not be permeabilized using acid hydrolysis even after 60 min exposure to 1 M HCl. PMID:8000549

Macnaughton, S J; O'Donnell, A G; Embley, T M

1994-10-01

153

Proline and benzylpenicillin derivatives grafted into mesoporous MCM-41: Novel organic-inorganic hybrid catalysts for direct aldol reaction  

Microsoft Academic Search

New organic-inorganic hybrid catalysts were synthesized by covalent grafting of proline and benzylpenicillin derivatives into\\u000a mesoporous MCM-41. These catalysts were extensively characterized using FT-IR,13C CP MAS solid stateNMR, XRD and TEM techniques. These were used as catalysts for direct, asymmetric aldol reaction between\\u000a acetone and activated aromatic aldehydes. In the reaction of 4-nitro and 4-fluoro benzaldehyde, the aldol products were

Dwairath Dhar; Ian Beadham; Srinivasan Chandrasekaran

2003-01-01

154

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

155

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

156

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

157

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

158

Fluorenone Synthesis by Palladacycle-Catalyzed Sequential Reactions of 2-Bromobenzaldehydes with Arylboronic Acids  

PubMed Central

A new, anionic four-electron donor-based (Type I) palladacycle-catalyzed sequential reaction of 2-bromobenzaldehydes with arylboronic acids based on the addition reaction, cyclization via C-H activation-oxidation sequence is described. Our study provided an efficient access to a variety of substituted fluorenones/indenofluorenediones from readily available arylboronic acids and 2-bromobenzaldehydes.

Liu, Tao-Ping; Liao, Yuan-Xi; Xing, Chun-Hui; Hu, Qiao-Sheng

2011-01-01

159

Fluorenone synthesis by palladacycle-catalyzed sequential reactions of 2-bromobenzaldehydes with arylboronic acids.  

PubMed

A new, anionic four-electron donor-based (type I) palladacycle-catalyzed sequential reaction of 2-bromobenzaldehydes with arylboronic acids based on the addition reaction, cyclization via C-H activation-oxidation sequence is described. Our study provided an efficient access to a variety of substituted fluorenones/indenofluorenediones from readily available arylboronic acids and 2-bromobenzaldehydes. PMID:21480660

Liu, Tao-Ping; Liao, Yuan-Xi; Xing, Chun-Hui; Hu, Qiao-Sheng

2011-05-01

160

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

ERIC Educational Resources Information Center

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

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

2003-01-01

161

Formation of phenol under conditions of the reaction of oxidative carbonylation of benzene to benzoic acid  

SciTech Connect

This paper describes conditions for the oxidation of benzene to phenol. It is shown that a reaction mixture of water, carbon monoxide, and oxygen are essential to the oxidation. The oxidation is a side reaction found to occur during the oxidative carbonylation of benzene to benzoic acid in a medium of trifluoroacetic acid.

Kalinovsky, I.O.; Leshcheva, A.N.; Pogorelov, V.V.; Gelbshtein, A.I.

1993-12-31

162

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

163

Comparison of polymerase chain reaction and non-radioactive hybridization techniques for the identification of Mycobacterium avium strains.  

PubMed

A polymerase chain reaction able to amplify specifically a 205-base-pair DNA fragment of Mycobacterium avium genome was used and compared to a nonradioactive hybridization assay (AccuProbe) and to conventional biochemical identification. The PCR approach to diagnosis of M. avium infection is a valid diagnostic alternative to the more classical procedures. PMID:7700268

Thierry, D; Matsiota-Bernard, P; Nauciel, C; Guesdon, J L

1994-12-01

164

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.

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

2013-01-01

165

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.

Hayashi, Shigehiko; Tajkhorshid, Emad; Schulten, Klaus

2009-01-01

166

5-Florouracil-loaded poly(lactic acid)-poly(caprolactone) hybrid scaffold: Potential chemotherapeutic implant.  

PubMed

Hybrid nanofibers of poly(lactic acid) and polycaprolactone have been developed by embedding cancerous drug through electrospinning technique. The composition of polymer has been varied to check the compositional effect on properties. The quality of nanofibers has been testified through surface morphology, wetting properties using contact angle and mechanical strength under uniaxial elongation. The compatibility of drug (5-fluorourasil) with matrix fiber has been verified using Fourier transform infrared, X-ray diffraction, Raman spectroscopy, and differential scanning calorimetry. The drug release study has been performed showing greater release in hybrid fibers when compared with pure polymers as a result of synergism of two immiscible polymers and quasi-Fickian diffusion mechanism in hybrid nanofiber as implants showing compositional effect on drug release. A model has been proposed showing faster release of drugs in hybrid systems. Biological responses through fluorescence imaging and MTT assay confirm the release of drug from hybrid nanofibers showing potential use of hybrid scaffolds as chemotherapeutic implant. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 2600-2612, 2014. PMID:24038786

Gupta, Kamal K; Pal, Namrata; Mishra, Pradeep K; Srivastava, Pradeep; Mohanty, Sujata; Maiti, Pralay

2014-08-01

167

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

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

168

Tandem Aldol Condensation - Platinacycle-Catalyzed Addition Reactions of Aldehydes, Methyl Ketones and Arylboronic Acids  

PubMed Central

Tandem aldol condensation of aldehydes with methyl ketones followed by anionic four-electron donor-based (Type I) platinacycle-catalyzed addition reactions of arylboronic acids to form ?-arylated ketones is described. Good to excellent yields of ?-arylated ketones were obtained for the tandem reactions of aromatic/aliphatic aldehydes, methyl ketones and arylboronic acids, and moderate yields were observed for the tandem reaction with ?, ?-unsaturated aldehydes as the aldehyde source.

Liao, Yuan-Xi; Hu, Qiao-Sheng

2013-01-01

169

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

PubMed Central

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

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

2007-01-01

170

Silicotungstic acid supported zirconia: An effective catalyst for esterification reaction  

Microsoft Academic Search

A series of solid acid catalysts were synthesized by incipient wetness impregnation method by varying the wt% of silicotungstic acid on hydrous zirconia (ZSTA). The prepared catalysts were characterized by PXRD, FTIR, UV–vis DRS, EPMA, BET surface area, acid sites, etc. FTIR and UV–vis DRS studies indicate that the material retain the Keggin-type structure of silicotungstic acid up to 500°C.

K. M. Parida; Sujata Mallick

2007-01-01

171

4-Hydroxyphenylpyruvate dioxygenase: a hybrid density functional study of the catalytic reaction mechanism.  

PubMed

Density functional calculations using the B3LYP functional has been used to study the reaction mechanism of 4-hydroxyphenylpyruvate dioxygenase. The first part of the catalytic reaction, dioxygen activation, is found to have the same mechanism as in alpha-ketoglutarate-dependent enzymes; the ternary enzyme-substrate-dioxygen complex is first decarboxylated to the iron(II)-peracid intermediate, followed by heterolytic cleavage of the O-O bond yielding an iron(IV)-oxo species. This highly reactive intermediate attacks the aromatic ring at the C1 position and forms a radical sigma complex, which can either form an arene oxide or undergo a C1-C2 side-chain migration. The arene oxide is found to have no catalytic relevance. The side-chain migration is a two-step process; the carbon-carbon bond cleavage first affords a biradical intermediate, followed by a decay of this species forming the new C-C bond. The ketone intermediate formed by a 1,2 shift of an acetic acid group rearomatizes either at the active site of the enzyme or in solution. The hypothetical oxidation of the aromatic ring at the C2 position was also studied to shed light on the 4-HPPD product specificity. In addition, the benzylic hydroxylation reaction, catalyzed by 4-hydroxymandelate synthase, was also studied. The results are in good agreement with the experimental findings. PMID:15379572

Borowski, Tomasz; Bassan, Arianna; Siegbahn, Per E M

2004-09-28

172

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

173

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

174

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

PubMed

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

Jin, Fangming; Moriya, Takehiko; Enomoto, Heiji

2003-07-15

175

[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

176

Estimation of gene reiteration from hybridization kinetics in moderate deoxyribonucleic acid excess.  

PubMed Central

Theoretical calculations were carried out to clarify how the DNA/RNA or the DNA/cDNA (complementary DNA) ratio in the hybridization reaction mixture affects the kinetics of DNA-RNA or DNA-cDNA reassociation, and theoretical formulae were derived as a function of these ratios. From these formulae, it was found that the DNA/RNA of the DNA/cDNA ratio did not much affect the initial reaction rates of hybridization, but greatly affected the terminal value for the extent of hybrid formation. Therefore the results obtained when one normalizes the experimental data for hydridization and derives the reiteration frequency from a number called the 'half Cot' (Cot 1/2) are not accurate, especially in the presence of a moderate excess of DNA. A simple method for the estimation of gene reiteration was demonstrated that did not use the half Cot value in the determination. This simple method is useful even if DNA-RNA or DNA/cDNA hybridization are done with a moderate excess of DNA. With mouse myeloma cells as a model system, the gene reiteration of the 28S rRNA cristron was determined.

Muto, M

1977-01-01

177

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

SciTech Connect

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

178

Participation of cyclopropenoid fatty acids in the tortelli-Jaffe reaction with bromine  

Microsoft Academic Search

The Tortelli-Jaffe reaction of ditertiary double bonds with bromine in the presence of formic acid occurred with cyclopropenoid\\u000a fatty acid-containing oils after prior bromination of other alkenes in the oil. The blue-colored (650 nm) cyclopropene-bromine\\u000a complex appeared a basis for colorimetrically assaying cyclopropenoid fatty acids in vegetable oil.

T. P. Hensarling; T. J. Jacks

1983-01-01

179

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

180

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

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

181

Fear and stress reactions in two species of duck and their hybrid.  

PubMed

Susceptibility to fear and stress has often been studied in birds using selection experiments. Crosses between different species of the same genus have also been used to study the type of transmission observed for "fixed action patterns." In this experiment we used a cross between two species (male muscovy and female pekin ducks) to study the genetic transmission of various characteristics of fear reactions and adrenal activity. Males of the three genetic types (two parental species and the hybrid) were submitted to tonic immobility and fear of man tests. Blood was collected for corticosterone assay before and after physiological stress or injection of 5 microg/kg of immediate synacthen (ACTH agonist). The muscovy duck showed lower levels of fear reactions than the pekin duck in the majority of behavioral tests (six of eight). Corticosterone levels were also nearly always the lowest in muscovy ducks (five of six). Generally speaking, the muscovy duck appeared to be less fearful and less susceptible to stress than the pekin duck. The mule duck was similar to one parent, midway between the two, or showed heterosis for fear of man at 10 weeks of age (more fearful than the two parents). Corticosterone levels were midway between the two parents in the mule duck with only one exception, i.e., where the pekin duck was dominant. The existence of heterosis for fear is surprising, as this character is classically considered to be submitted to stabilizing selection. The transmission of corticosterone levels and other fear characteristics is, however, compatible with stabilizing selection. The results are discussed in terms of adaptability. PMID:12799174

Faure, J M; Val-Laillet, D; Guy, G; Bernadet, Marie Dominique; Guémené, D

2003-05-01

182

A new Brønsted acid derived from squaric acid and its application to Mukaiyama aldol and Michael reactions  

Microsoft Academic Search

Bis-N-trifluoromethanesulfonyl squaramide was prepared as a new bench-stable strong Brønsted acid and applied to the Brønsted acid-catalyzed Mukaiyama aldol and Michael reactions with silyl enol ethers. The resulting Mukaiyama aldol products of aldehydes were obtained in quantitative yields, whereas expansion of the utility of this Brønsted acid to ketones was limited to electron-deficient ketones presumably due to lower reactivity of

Cheol Hong Cheon; Hisashi Yamamoto

2009-01-01

183

Synthesis of hollow hybrid hydroxyapatite microspheres based on chitosan-poly(acrylic acid) microparticles.  

PubMed

Core-template-free hybrid hydroxyapatite (HA) hollow microspheres based on a chitosan-poly acrylic acid (CS-PAA) complex were prepared. The amine groups on chitosan can interact with the carboxyl groups of poly(acrylic acid) to form hollow microspheres. The hollow HA microspheres of about 1.0 microm are obtained by heterogeneous nucleation of HA on CS-PAA hollow spheres. Gelatin (Gel), acting as a novel cross-link agent, is introduced to bind the spheres of CS-PAA and HA. The forming mechanism of hollow spheres and the influencing factors on the size of microspheres are investigated. In addition, the role of Gel is elucidated in the forming process of the hollow hybrid sphere. PMID:19372618

Zhang, Haibin; Zhou, Kechao; Li, Zhiyou; Huang, Suping

2009-06-01

184

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

NASA Astrophysics Data System (ADS)

Two hybrid thermochemical cycles for the production of hydrogen which involve bismuth trisulfate and/or bismuth oxysulfates were investigated. Equilibrium sulfur trioxide pressure are given graphically for three solid gas equilibria involving Bi2(SO4)3 alpha- and beta-Bi2O(SO4)2, and Bi2O2SO4. An improved method of carrying out the low temperature step for Cycle 1 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 SO2 and O2 are evolved at different temperatures, simplifying the usual SO3-SO2-O2 separation problem.

Jones, W. M.

185

Salmonellae in fish feces analyzed by in situ hybridization and quantitative polymerase chain reaction.  

PubMed

The potential of fish to transfer salmonellae from heterogeneous aquatic biofilms into feces was assessed in controlled aquarium studies with Suckermouth Catfish Hypostomus plecostomus and with biofilms inoculated with salmonellae. Neither the presence of catfish nor inoculation with salmonellae had detectable effects on the abundance of the microbial community. Densities of the microbial community were about 10(5) cells/mL in the water during a 1-week period, whereas densities of the microbial community increased 10-fold (10(6) to 10(7) cells/mg) in catfish feces during the same period. Salmonellae were detected by both quantitative polymerase chain reaction (qPCR) and situ hybridization in water samples immediately after inoculation, in numbers of about 10(4) cells/mL, representing up to 20% of the cells of the microbial community. Numbers decreased by three orders of magnitude within the first 3 d of the study, which represented only 0.01% of the community, and became undetectable after day 5. In catfish feces, numbers of Salmonella initially increased to up to 6% of the cells of the community but then declined. These results suggest that Salmonella are not biomagnified during gut passage, and thus, fish only provide a means for the translocation of this pathogen. PMID:23883355

Sha, Qiong; Forstner, Michael R J; Bonner, Timothy H; Hahn, Dittmar

2013-09-01

186

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.

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

2013-01-01

187

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

PubMed

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

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

2011-05-01

188

Dehydration of cyclohexanol as a test reaction for zeolite acidity  

SciTech Connect

Dehydration of cyclohexanol was investigated using a fixed-bed continuous flow reactor with acidic mordenite-type, clinoptilolite-type, and faujasite-type (Y) zeolites as catalysts. The surface acidity of the catalysts employed was studied by IR using pyridine or 2,6-di-tert. butylpyridine as probe molecules. A correlation between the acidity and the rates of dehydration was clearly shown.

Karge, H.G.; Kosters, H.; Wada, Y.

1984-01-01

189

Nucleic acid hybridization experiments with Spiroplasma citri and the corn stunt and suckling mouse cataract Spiroplasmas  

Microsoft Academic Search

Spiroplasma citri and two as yet unclassified mycoplasmas of the genusSpiroplasma, the corn stunt spiroplasma (CSS) and suckling mouse cataract agent (SMCA), were compared by determination of the guanine-plus-cytosine\\u000a (G+C) content of the DNA and by nucleic acid homology studies. The G+C content ofS. citri, CSS, and SMCA was found to be 26.4, 25.1, and 30.3 mol%, respectively. In hybridization

Claus Christiansen; Gerd Askaa; E. A. Freundt; R. F. Whitcomb

1979-01-01

190

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

Microsoft Academic Search

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

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

2000-01-01

191

Development and testing of a bipolar lead-acid battery for hybrid electric vehicles  

NASA Astrophysics Data System (ADS)

An 80 V bipolar lead-acid battery was constructed and tested using hybrid electric vehicle (HEV) drive cycles. Drive cycles with a peak power of 6.7 kW, equal to 1/5 of the total power profile required for the HEV studied, were run successfully. Model calculations showed that the 80 V module constructed, which is at the moment 2.5 times heavier than required for the HEV operation studied, can be optimised to meet the requirements.

Saakes, Michel; Kluiters, Edwin; Schmal, Dick; Mourad, Salem; ten Have, Peter T. J. H.

192

Optimization of reaction parameters of acidolysis reaction between mustard oil and capric acid by using Thermomyces lanuginosus lipase.  

PubMed

Structured lipids were prepared from mustard oil by enzymatic acidolysis reaction with capric acid (C10) using lipase enzyme TLIM from Thermomyces lanuginosus as biocatalyst. Parameters such as substrate molar ratio, enzyme concentration, reaction temperature, stirring speed and time of maximum incorporation, were studied for the optimization of the reaction. The optimized set of process conditions was predicted by response surface methodology (RSM) and genetic algorithm (GA). The robustness of GA and RSM was evaluated using regression coefficient and p value. The R(2) found out by GA was 0.996 while from RSM was 0.973. The results proved that GA models have better performance than RSM models. From the result, it could be concluded that optimal conditions for synthesis of capric acid rich mustard oil were: Temperature?=?39.5 °C ; time?=?21.1 hr; Substrate ratio?=?3.5; Enzyme content?=?8.8%; Speed?=?570.8 rpm. PMID:24741165

Silroy, Sumita; Sengupta, Avery; Bhattacharyya, D K; Ghosh, Mahua

2014-04-01

193

Transposon-5 mutagenesis transforms Corynebacterium matruchotii to synthesize novel hybrid fatty acids that functionally replace corynomycolic acid.  

PubMed

Enzymes within the biosynthetic pathway of mycolic acid (C(60)-C(90) a-alkyl,b-hydroxyl fatty acid) in Mycobacterium tuberculosis are attractive targets for developing new anti-tuberculosis drugs. We have turned to the simple model system of Corynebacterium matruchotii to study the terminal steps in the anabolic pathway of a C32 mycolic acid called corynomycolic acid. By transposon-5 mutagenesis, we transformed C. matruchotii into a mutant that is unable to synthesize corynomycolic acid. Instead, it synthesized two related series of novel fatty acids that were released by saponification from the cell wall fraction and from two chloroform/methanol-extractable glycolipids presumed to be analogues of trehalose mono- and di-corynomycolate. By chemical analyses and MS, we determined the general structure of the two series to be 2,4,6,8,10-penta-alkyl decanoic acid for the larger series (C(70)-C(77)) and 2,4,6,8-tetra-alkyl octanoic acid for the smaller series (C(52)-C(64)), both containing multiple keto groups, hydroxy groups and double bonds. The mutant was temperature-sensitive, aggregated extensively, grew very slowly relative to the wild type, and was resistant to the presence of lysozyme. We suggest that a regulatory protein that normally prevents the transfer of the condensation product back to b-ketoacyl synthase in the corynomycolate synthase system of the wild type was inactivated in the mutant. This will result in multiple Claisen-type condensation and the formation of two similar series of these complex hybrid fatty acids. A similar protein in M. tuberculosis would be an attractive target for new drug discovery. PMID:12879902

Takayama, Kuni; Hayes, Barry; Vestling, Matha M; Massey, Randall J

2003-07-15

194

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...

195

Reactions of ?-lactones with Lewis acids: Ring enlargement versus ?-elimination  

Microsoft Academic Search

On treatment with MgBr2 the ?-spirolactones 7 and 10 undergo ring enlargement to the ?-lactones 8 and 11, whereas the ?-spirolactones 13 show diastereoselective ?-elimination to form the ?,?-unsaturated acids 14. The Lewis acid influence on the migratory aptitude of Me versus H is studied for ?-lactone 18.

Ulrich Nagel

1995-01-01

196

Development of N, Nbis(perfluoroalkanesulfonyl)squaramides as new strong Brønsted acids and their application to organic reactions  

Microsoft Academic Search

New strong Brønsted acids derived from a squaric acid scaffold bearing different perfluoroalkanesulfonyl groups have been developed and applied to several organic reactions. These squaramides are bench-stable and exhibit much higher reactivities in several organic reactions than squaric acid itself. N,N-Bis(trifluoromethanesulfonyl)squaramide 2a was applied to the Mukaiyama aldol reaction and Mukaiyama Michael reaction. Mechanistic studies revealed that the Brønsted acid

Cheol Hong Cheon; Hisashi Yamamoto

2010-01-01

197

Polymer-hybridized liposomes of poly(amino acid) derivatives as transepidermal carriers.  

PubMed

This work describes the use of a novel transepidermal drug carrier system composed of phospholipids and amphiphilc poly(amino acid)s. We polymerized poly(asparagine) grafted with octadecylamine (PAsn-g-C18), poly(aspartic acid) grafted with octadecylamine (PAsp-g-C18), and poly(aspartic acid) grafted with phytosphingosine (PAsp-g-PHS). We then prepared polymer hybridized liposomes (PHL) anchored with alkyl grafted poly(amino acid)s and encapsulated hydrolyzed ginseng saponins (HGS). We confirmed that the liposomes and PHL reduce the cytotoxicity of HGS, which was not observed with polymeric nano-carriers. A quantitative analysis of the amount of penetrated HGS using the Franz cell method revealed that skin permeation of the lipophilic drugs loaded in liposomes was enhanced by the incorporation of amphiphilic poly(amino acid)s. Fluorescence microscopy observations also demonstrated excellent skin permeation performance of PHL anchored with PAsp-g-PHS. PHL showed better structural stability than liposomes in an O/W emulsion. PHL considerably improved the chemical stability of HGS compared to the liposomes. It is thought that the skin permeability of encapsulated bioactive molecules could be affected by the vesicle structure, membrane fluidity, and the type of anchored polymer. PMID:23743254

Park, Sung-Il; Lee, Eun-Ok; Yang, Hee-Man; Park, Chan Woo; Kim, Jong-Duk

2013-10-01

198

Enhancing the specificity and efficiency of polymerase chain reaction using polyethyleneimine-based derivatives and hybrid nanocomposites  

PubMed Central

There is a general necessity to improve the specificity and efficiency of the polymerase chain reaction (PCR), and exploring the PCR-enhancing mechanism still remains a great challenge. In this paper we report the use of branched polyethyleneimine (PEI)-based derivatives and hybrid nanocomposites as a novel class of enhancers to improve the specificity and efficiency of a nonspecific PCR system. We show that the surface-charge polarity of PEI and PEI derivatives plays a major role in their effectiveness to enhance the PCR. Positively charged amine-terminated pristine PEI, partially (50%) acetylated PEI (PEI-Ac50), and completely acetylated PEI (PEI-Ac) are able to improve PCR efficiency and specificity with an optimum concentration order of PEI < PEI-Ac50 < PEI-Ac, whereas negatively charged carboxyl-terminated PEI (PEI-SAH; SAH denotes succinamic acid groups) and neutralized PEI modified with both polyethylene glycol (PEG) and acetyl (Ac) groups (PEI-PEG-Ac) are unable to improve PCR specificity and efficiency even at concentrations three orders of magnitude higher than that of PEI. Our data clearly suggests that the PCR-enhancing effect is primarily based on the interaction between the PCR components and the PEI derivatives, where electrostatic interaction plays a major role in concentrating the PCR components locally on the backbones of the branched PEI. In addition, multiwalled carbon nanotubes modified with PEI and PEI-stabilized gold nanoparticles are also able to improve the PCR specificity and efficiency with an optimum PEI concentration less than that of the PEI alone, indicating that the inorganic component of the nanocomposites may help improve the interaction between PEI and the PCR components. The developed PEI-based derivatives or nanocomposites may be used as efficient additives to enhance other PCR systems for different biomedical applications.

Tong, Weiwei; Cao, Xueyan; Wen, Shihui; Guo, Rui; Shen, Mingwu; Wang, Jianhua; Shi, Xiangyang

2012-01-01

199

40 CFR 721.10188 - Fatty acids, tall-oil, reaction products with 4-methyl-2-pentanone and aliphatic polyamine...  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Fatty acids, tall-oil, reaction products...Substances § 721.10188 Fatty acids, tall-oil, reaction products...identified generically as fatty acids, tall-oil, reaction...Releaseâ variables are the number of kilograms released of...

2013-07-01

200

40 CFR 721.10189 - Fatty acids, tall-oil, reaction products with (butoxymethyl) oxirane formaldehyde-phenol polymer...  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Fatty acids, tall-oil, reaction products...Substances § 721.10189 Fatty acids, tall-oil, reaction...identified generically as fatty acids, tall-oil, reaction...Releaseâ variables are the number of kilograms released of...

2013-07-01

201

Identification of molecular defects causing congenital adrenal hyperplasia by cloning and differential hybridization of polymerase chain reaction-amplified 21-hydroxylase (CYP21) genes.  

PubMed

Congenital adrenal hyperplasia (CAH), one of the most common autosomal recessive disorders, is caused primarily by defects in the gene encoding steroid 21-hydroxylase, CYP21B. The molecular diagnosis of CAH, important for prenatal diagnosis, carrier detection, and a better understanding of the various clinical CAH forms, is complicated by the close proximity of a highly similar pseudogene, CYP21A, containing (and probably donating, by gene conversion-like events) most of the defects underlying CAH. In this study, we describe an efficient strategy to identify molecular defects causing CAH: polymerase chain reaction-amplified CYP21 loci are cloned and hybridized to a set of oligonucleotides, allowing rapid and allele-specific identification of all known CYP21B mutations relevant to 21-hydroxylase function. Possible new mutations can be identified by subsequent nucleic acid sequencing provided they reside within the cloned CYP21B fragment (from the TATA box to the 8th of the 10 CYP21B gene exons). Using this method, the CYP21B gene mutations of a heterozygous carrier and 25 CAH patients have been identified by oligonucleotide hybridization. All disease haplotypes seem to have been generated by recombinational events involving the CYP21A pseudogene. In 5 individuals, these data were subsequently verified by nucleic acid sequencing. The procedure can be used for diagnostic applications and may facilitate identification of new CYP21B defects. PMID:1605859

Helmberg, A; Tabarelli, M; Fuchs, M A; Keller, E; Dobler, G; Schnegg, I; Knorr, D; Albert, E; Kofler, R

1992-06-01

202

Reactions of chloride complexes of ruthenium (IV) with formic acid and sodium formate in aqueous solutions  

SciTech Connect

Study of the reactions of (NH/sub 4/)/sub 2/RuCl/sub 6/ with formic acid and sodium formate showed that, depending on the conditions, chlorocarbonyl, chloroformatocarbonyl, or chloroformato complexes of ruthenium(III) are formed.

Simanova, S.A.; Krylova, G.S.; Maslov, E.I.

1982-04-20

203

Addition reaction of dialkyl disulfides to terminal alkynes catalyzed by a rhodium complex and trifluoromethanesulfonic acid.  

PubMed

[reaction: see text]. Addition of dialkyl disulfides to terminal alkynes is catalyzed by a rhodium-phosphine complex and trifluoromethanesulfonic acid giving (Z)-bis(alkylthio)olefins stereoselectively. PMID:11259056

Arisawa, M; Yamaguchi, M

2001-03-01

204

Synthesis and hybridization properties of polyamide based nucleic acid analogues incorporating pyrrolidine-derived nucleoamino acids.  

PubMed

Ndelta-Fmoc protected nucleoamino acids of type I (Base = T, C, A) have been synthesized and employed as building blocks for the construction of novel polyamide based nucleic acid analogues. Homopyrimidine oligomer A binds to complementary RNA with significant affinity and in a sequence-specific fashion, while no binding was observed to complementary DNA. PMID:10853662

Altmann, K H; Hüsken, D; Cuenoud, B; García-Echeverría, C

2000-05-01

205

Immuno-hybridization chain reaction for enhancing detection of individual cytokine-secreting human peripheral mononuclear cells.  

PubMed

We present here a new method to enhance the detection of secreted cytokines and chemokines from single human mononuclear cells. The technique uses a hybridization chain reaction (HCR) to amplify signals resulting from sandwich immunoassays. This immuno-HCR employs oligonucleotide-based initiators covalently linked to antibodies to propagate a chain reaction of hybridization events involving a pair of complementary hairpin oligomers bearing fluorescent labels. Integrating this strategy for signal amplification with microengraving (a soft lithographic method for printing arrays of secreted proteins from thousands of single cells) improves both the limits of detection and sensitivity for cytokines and chemokines captured from individual cells by an average of 200-fold relative to methods for direct detection by fluoresence. This approach should enhance the utility of microengraving for defining the immunological signatures of diseases and responses to interventional therapies based on multiplexed single-cell analysis. PMID:21812465

Choi, Jonghoon; Love, Kerry Routenberg; Gong, Yuan; Gierahn, Todd M; Love, J Christopher

2011-09-01

206

Reaction of Ozone with Isolated Aquatic Fulvic Acid.  

National Technical Information Service (NTIS)

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. I...

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

1985-01-01

207

Properties of halloysite nanotube epoxy resin hybrids and the interfacial reactions in the systems  

Microsoft Academic Search

A naturally occurred microtubullar silicate, halloysite nanotubes (HNTs), was co-cured with epoxy\\/cyanate ester resin to form organic-inorganic hybrids. The coefficient of thermal expansion (CTE) of the hybrids with low HNT concentration was found to be substantially lower than that of the plain cured resin. The moduli of the hybrids in the glassy state and rubbery state were significantly higher than

Mingxian Liu; Baochun Guo; Mingliang Du; Xiaojia Cai; Demin Jia

2007-01-01

208

The reaction between solid UO 2 and MnO 2 in a sulfuric acid solution  

Microsoft Academic Search

In connection with the extensive use of pyrolusite in the sulfuric acid leaching of uranium from ores, a study was made of the reaction between UO2 and MnO2 in a sulfuric acid solution,and possible mechanisms were discussed. The experimental data show that the reaction apparently occurs at the points of contact of the hydrated surface layers of UO2 and MnO2;

E. A. Kanevskii; V. A. Pchelkin

1961-01-01

209

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

210

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

Microsoft Academic Search

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 β-subunit of RNA polymerase, where

VLADIMIR MIKHAILOVICH; SERGEY LAPA; DIMITRY GRYADUNOV; ALEXANDER SOBOLEV; BORIS STRIZHKOV; NIKOLAI CHERNYH; OLGA SKOTNIKOVA; OLGA IRTUGANOVA; ARKADII MOROZ; VITALII LITVINOV; MIKHAIL VLADIMIRSKII; MIKHAIL PERELMAN; LARISA CHERNOUSOVA; VLADISLAV EROKHIN; A. Mirzabekov

2001-01-01

211

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

212

Polymerase chain reaction-and RNA hybridization-based method for the investigation of deep-seated candidiasis  

PubMed Central

OBJECTIVE: To determine the usefulness of a polymerase chain reaction (PCR) and RNA hybridization method for the diagnosis of invasive candidiasis and to compare its sensitivity with blood cultures. DESIGN: Blood cultures and a blood sample for PCR were taken from patients with suspected invasive candidiasis. A 105 base pair conserved segment within the rDNA of Candida species was amplified. The amplicon was detected by hybridization and gel electrophoresis. SETTING: Intensive care units of two tertiary care hospitals. PATIENTS: One hundred and eighteen patients 16 years of age or older with four more risk factors for invasive candidiasis were enrolled. Present or recent past treatment with broad spectrum antibiotics, cancer chemotherapy, immunosuppressive drugs, granulocytopenia or granulocytosis, intravascular catheterization, tracheal intubation, recent abdominal surgery and parenteral nutrition were considered risk factors. RESULTS: Forty-three patients had invasive candidiasis. PCR detected infections in 28 and 26 patients (sensitivity 65.1% and 60.4%) by hybridization and gel electrophoresis, respectively. The sensitivity of blood cultures was 58.1%. Of 25 patients with positive blood cultures, 17 were positive by PCR with the hybridization method. Eleven patients with invasive candidiasis had negative blood cultures but were positive by PCR. CONCLUSION: PCR, especially with a hybridization detection method, is more sensitive than blood culture for invasive candidiasis and may facilitate the diagnosis of nonfungemic disease.

Couroux, Peter R; Hussain, Zafar; Rutledge, Frank; Lannigan, Robert; Ralph, Edward D; Nancekivell, Barbara; Austin, Thomas W

1997-01-01

213

Float charging of valve-regulated lead-acid batteries: A balancing act between secondary reactions  

Microsoft Academic Search

The behavior of valve-regulated lead-acid batteries on float charging is influenced by many interacting parameters. A mathematical model has been developed that describes the effects of kinetic cell parameters, float voltage (or current), and temperature on electrode potentials and rates of electrode reactions. The considered reactions are: hydrogen evolution, oxygen evolution, oxygen reduction, grid corrosion, and discharge of active material

D. Berndt; U. Teutsch

1996-01-01

214

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...

215

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

Microsoft Academic Search

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

R. Gertzmann; C. Gürtler

2005-01-01

216

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

217

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

Microsoft Academic Search

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

Alexander G. Malygin

2000-01-01

218

Corrosion resistance of siloxane-poly(methyl methacrylate) hybrid films modified with acetic acid on tin plate substrates: Influence of tetraethoxysilane addition  

NASA Astrophysics Data System (ADS)

The aim of this paper is to study the corrosion resistance of hybrid films. Tin plate was coated with a siloxane-poly (methyl methacrylate) (PMMA) hybrid film prepared by sol-gel route with covalent bonds between the organic (PMMA) and inorganic (siloxane) phases obtained by hydrolysis and polycondensation of 3-(trimethoxysilylpropyl) methacrylate (TMSM) and polymerization of methyl methacrylate (MMA) using benzoyl peroxide (BPO) as a thermic initiator. Hydrolysis reactions were catalyzed by acetic acid solution avoiding the use of chlorine or stronger acids in the film preparation. The effect of the addition of tetraethoxysilane (TEOS) on the protective properties of the film was evaluated. The hydrophobicity of the film was determined by contact angle measurements, and the morphology was evaluated by scanning electron microscopy (SEM) and profilometry. The local nanostructure was investigated by Fourier transform infrared spectroscopy (FT-IR). The electrochemical behavior of the films was assessed by open circuit potential monitoring, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements in a 0.05 M NaCl solution. The mechanical behavior was evaluated by tribology. The results highlighted that the siloxane-PMMA hybrid films modified with acetic acid are promising anti-corrosive coatings that acts as an efficient diffusion barrier, protecting tin plates against corrosion. However, the coating properties were affected by the TEOS addition, which contributed for the thickness increase and irregular surface coverage.

Kunst, S. R.; Cardoso, H. R. P.; Oliveira, C. T.; Santana, J. A.; Sarmento, V. H. V.; Muller, I. L.; Malfatti, C. F.

2014-04-01

219

Amino acids and peptides. XIX. Preparation of enkephalin-poly(ethylene glycol) hybrid and evaluation of its analgesic activity.  

PubMed

The poly(ethylene glycol) hybrid of Leu-enkephalin (Tyr-Gly-Gly-Phe-Leu) was prepared and its analgesic activity was examined. Poly(ethylene glycol) #4000 was converted to amino-poly(ethylene glycol) and coupled with the N alpha-protected pentapeptide, followed by trifluoroacetic acid treatment to give the hybrid. The hybrid was soluble in water or various organic solvents. The analgesic activity of Leu-enkephalin was markedly potentiated by hybrid formation with poly(ethylene glycol). PMID:8293529

Kawasaki, K; Maeda, M; Yamashiro, Y; Mayumi, T; Takahashi, M; Kaneto, H

1993-11-01

220

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

221

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.

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

2013-01-01

222

Catalytic Spectrophotometric Determination of Titanium(IV) using Methylene Blue-Ascorbic Acid Redox Reaction  

Microsoft Academic Search

A highly selective and sensitive catalytic method for the determination of trace amounts of tita- nium(IV) was developed. The method is based on the catalytic effect of titanium(IV) on the methylene blue-ascorbic acid redox reaction. The reaction was followed spectrophotometrically by measuring the change in absorbance of methylene blue at 665 nm, 5 minutes after the initiation of the reaction.

H. Zavvar Mousavi; N. Pourreza

223

The temperature dependence of the rate constant for the reaction of hydroxyl radicals with nitric acid  

NASA Technical Reports Server (NTRS)

The rate constant for the reaction of hydroxyl radicals with nitric acid in the 225-443 K temperature range has been measured by means of the flash photolysis resonance fluorescence technique. Above 300 K, the rate constant levels off in a way that can only be explained by the occurrence of two reaction channels, of which one, operative at low temperatures, proceeds through the formation of an adduct intermediate. The implications of these rate constant values for stratospheric reaction constants is discussed.

Kurylo, M. J.; Cornett, K. D.; Murphy, J. L.

1982-01-01

224

Nonproteinogenic amino acid building blocks for nonribosomal peptide and hybrid polyketide scaffolds.  

PubMed

Freestanding nonproteinogenic amino acids have long been recognized for their antimetabolite properties and tendency to be uncovered to reactive functionalities by the catalytic action of target enzymes. By installing them regiospecifically into biogenic peptides and proteins, it may be possible to usher a new era at the interface between small molecule and large molecule medicinal chemistry. Site-selective protein functionalization offers uniquely attractive strategies for posttranslational modification of proteins. Last, but not least, many of the amino acids not selected by nature for protein incorporation offer rich architectural possibilities in the context of ribosomally derived polypeptides. This Review summarizes the biosynthetic routes to and metabolic logic for the major classes of the noncanonical amino acid building blocks that end up in both nonribosomal peptide frameworks and in hybrid nonribosomal peptide-polyketide scaffolds. PMID:23729217

Walsh, Christopher T; O'Brien, Robert V; Khosla, Chaitan

2013-07-01

225

Kinetics of Acid Reactions: Making Sense of Associated Concepts  

ERIC Educational Resources Information Center

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

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

2010-01-01

226

Application of the Deoxyribonucleic Acid/Ribonucleic Acid Hybridization Technique in Bdellovibrio as a Model for Studying Ribonucleic Acid Turnover in Host-Parasite Systems1  

PubMed Central

The kinetics of host ribonucleic acid (RNA) degradation and its resynthesis into Bdellovibrio-specific polyribonucleotides has been studied. The kinetics of RNA turnover was followed during a one-step synchronous growth cycle of Bdellovibrio growing within 32PO4-labeled Escherichia coli host cells. The species of labeled RNA present at any given time was ascertained through the specificity of the deoxyribonucleic acid (DNA)/RNA hybridization technique. At nearsaturating levels of RNA and at zero time, 7% of the host DNA sequences and only 0.04% of the Bdellovibrio DNA became hybridized with 32P-labeled host cell RNA (greater than 99% host specific). At the end of the burst, 98% of the labeled RNA sequences were specific for Bdellovibrio DNA. About 74% of the initial labeled host cell RNA became turned over into Bdellovibrio-specific sequences. We provide data indicating that host cell ribosomal RNA is assimilated by Bdellovibrio. Degradation of host cell RNA occurs in a gradual fashion over most of the Bdellovibrio developmental growth cycle. This application of the DNA/RNA hybridization technique and its general concept should be of value in elucidating the kinetics of nucleic acid turnover in other types of host-parasite systems.

Engelking, H. Mark; Seidler, Ramon J.

1975-01-01

227

Elucidating the hard/soft acid/base principle: A perspective based on half-reactions  

SciTech Connect

A comprehensive analysis is presented for the acid-base double-exchange reaction as well as the associated acid-displacement and base-displacement 'half-reactions' with the goal of elucidating the meaning of the hard/soft acid/base (HSAB) principle and the conditions for its validity. When electron-transfer effects are important and other effects are negligible, the HSAB principle is driven by the surpassing stability of the soft acid/soft base product. When electrostatic effects dominate the reactivity, the HSAB principle is driven by the surpassing stability of the hard acid/hard base product. Because electron-transfer effects favor soft/soft interactions, while electrostatic effects favor hard/hard interactions, acid-base exchange reactions may be used to determine whether a reagent's reactivity is dominated by electron-transfer or by electrostatic effects. Because electron-transfer and electrostatic considerations separately favor the HSAB principle whenever the electronic chemical potentials of the acids and bases involved in the reaction are similar, our analysis provides strong support for the HSAB principle. The electronic chemical potential measures the intrinsic strength of acids and bases.

Ayers, Paul W.; Parr, Robert G.; Pearson, Ralph G. [Department of Chemistry, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27514 (United States); Department of Chemistry and Biochemistry, University of California-Santa Barbara, Santa Barbara, California 93106 (United States)

2006-05-21

228

Fatty acid oxidation in anoxic marine sediments: the importance of hydrogen sensitive reactions  

Microsoft Academic Search

In anoxic marine sediments fatty acids may be oxidized directly by sulfate reducing bacteria, or may be oxidized by pathways which result in hydrogen production. Some of these latter reactions are quite sensitive to hydrogen concentrations ... in other words if hydrogen concentrations become elevated, fatty acid oxidation will cease. Thus sulfate reducers may actually play two important roles in

Matthew A. Monetti; Mary I. Scranton

1992-01-01

229

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

ERIC Educational Resources Information Center

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

Cokelez, Aytekin

2010-01-01

230

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

231

Liquid-phase reactions induced by gaseous plasma. Decomposition of benzoic acids in aqueous solution  

Microsoft Academic Search

The liquid-phase organic reactions induced by a gaseous plasma, which was generated in a localized zone between an electrolytic solution and an anode by means of contact glow discharge electrolysis (CGDE), were investigated. Benzoic acids dissolved in a neutral phosphate buffer solution were efficiently oxidized and eventually decomposed to inorganic carbon. As the intermediate products, oxalic, formic and malonic acids

M. Tezuka; M. Iwasaki

1999-01-01

232

Novel Petasis boronic acid reactions with 1,3,5-tri-oxygenated benzenes  

Microsoft Academic Search

1,3,5-tri-Oxygenated benzenes can serve as substrates for the Petasis boronic acid reaction, providing a practical synthetic route for the two C?C bond formation of ?-(1,3,5-tri-oxygenated phenyl)carboxylic acids. The scope and limitations of this method have been examined.

Dinabandhu Naskar; Amrita Roy; William L. Seibel

2003-01-01

233

Exploring water catalysis in the reaction of thioformic Acid with hydroxyl radical: a global reaction route mapping perspective.  

PubMed

Hydrogen abstraction pathways, in the gas-phase reaction of tautomers of thioformic acid (TFA), TFA(thiol), and TFA(thione), with hydroxyl radical in the presence and absence of single water molecule acting as a catalyst, is investigated with high-level quantum mechanical calculations at CCSD(T)/6-311++G(2d,2p)//MP2/6-311++G(2d,2p), CCSD(T)/6-311++G(d,p)//DFT/BHandHLYP/6-311++G(d,p), and DFT/B3LYP/6-311++G(2df,2p) levels of the theory. A systematic and automated search of the potential energy surface (PES) for the reaction pathways is performed using the global reaction route mapping (GRRM) method that employs an uphill walking technique to search prereaction complexes and transition states. The computations reveal significant lowering of the PES and substantial reduction in the activation energy for the hydrogen abstraction pathway in the presence of water, thereby proving water as an efficient catalyst in the reaction of both the TFA tautomers with OH radical. The hydrogen-bonding interactions are observed to be responsible for the large catalytic effect of water. Notably, in the case of TFA(thiol), formyl hydrogen abstraction is observed to be kinetically more favorable, while acidic hydrogen abstraction is observed to be thermodynamically more feasible. Interestingly, in the case of TFA(thione), reaction pathways involving only formyl hydrogen abstraction were observed to be feasible. The water-catalyzed hydrogen abstraction reaction of TFA with hydroxyl radical, investigated in this work, can provide significant insights into the corresponding reaction in the biological systems. PMID:24835635

Kaur, Gurpreet; Vikas

2014-06-12

234

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

235

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

236

Effect of acidity on n-octene reaction over potassium modified nanoscale HZSM-5  

Microsoft Academic Search

The effect of the introduction of potassium into nanoscale HZSM-5 upon acidity and catalytic performance in n-octene reaction was investigated. A modified method of Hammett indicator was used to quantitatively determine the acid strength distribution of the catalysts. The acid sites with acid strength H0??3.0 (0.20mmol\\/g), ?3.0acid

Huayun Long; Xiangsheng Wang; Wanfu Sun; Guang Xiong; Kunyuan Wang

2008-01-01

237

The Use of Gel Electrophoresis to Study the Reactions of Activated Amino Acids with Oligonucleotides  

NASA Technical Reports Server (NTRS)

We have used gel electrophoresis to study the primary covalent addition of amino acids to oligonu-cleotides or their analogs and the subsequent addition of further molecules of the amino acids to generate peptides covalently linked to the oligonucleotides. We have surveyed the reactions of a variety of amino acids with the phosphoramidates derived from oligonucleotide 5 inches phosphates and ethylenediamine. We find that arginine and amino acids can interact with oligonucleotidesl through stacking interactions react most efficiently. D- and L-amino acids give indistinguishable families of products.

Zieboll, Gerhard; Orgel, Leslie E.

1994-01-01

238

Redox Reactions in Wheat Dough as Affected by Ascorbic Acid  

Microsoft Academic Search

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

W. Grosch; H. Wieser

1999-01-01

239

Hyaluronic acid skin fillers: Adverse reactions and skin testing  

Microsoft Academic Search

Background: Hyaluronic acid (HA) fillers have been proposed as alternatives to other temporary skin fillers, such as bovine collagen, for treating facial skin lines and for providing lip augmentation. Several types of commercial HA fillers are now available in many countries. They include Restylane, which is produced by microbiologic engineering techniques, and Hylaform, which is HA extract derived from rooster

Nicholas J. Lowe; C. Anne Maxwell; Philippa Lowe; Michael G. Duick; Kishor Shah

2001-01-01

240

Furan fatty acids: occurrence, synthesis, and reactions. Are furan fatty acids responsible for the cardioprotective effects of a fish diet?  

PubMed

Furan FA (F-acids) are tri- or tetrasubstituted furan derivatives characterized by either a propyl or pentyl side chain in one of the alpha-positions; the other is substituted by a straight long-chain saturated acid with a carboxylic group at its end. F-acids are generated in large amounts in algae, but they are also produced by plants and microorganisms. Fish and other marine organisms as well as mammals consume F-acids in their food and incorporate them into phospholipids and cholesterol esters. F-acids are catabolized to dibasic urofuran acids, which are excreted in the urine. The biogenetic precursor of the most abundant F-acid, F6, is linoleic acid. Methyl groups in the beta-position are derived from adenosylmethionine. Owing to the different alkyl substituents, synthesis of F-acids requires multistep reactions. F-acids react readily with peroxyl radicals to generate dioxoenes. The radical-scavenging ability of F-acids may contribute to the protective properties of fish and fish oil diets against mortality from heart disease. PMID:16296395

Spiteller, Gerhard

2005-08-01

241

Evaluation of catalyst acidity and substrate electronic effects in a hydrogen bond-catalyzed enantioselective reaction.  

PubMed

A modular catalyst structure was applied to evaluate the effects of catalyst acidity in a hydrogen bond-catalyzed hetero Diels-Alder reaction. Linear free energy relationships between catalyst acidity and both rate and enantioselectivity were observed, where greater catalyst acidity leads to increased activity and enantioselectivity. A relationship between reactant electronic nature and rate was also observed, although there is no such correlation to enantioselectivity, indicating the system is under catalyst control. PMID:20919686

Jensen, Katrina H; Sigman, Matthew S

2010-11-01

242

Effect of acidity in TS1 zeolites on product distribution of the styrene oxidation reaction  

Microsoft Academic Search

The role of Brønsted acidity of titanium silicalite zeolite (with different ratios of Si\\/Ti) in oxidation reactions of styrene has been investigated and discussed. For zeolites with Si\\/Ti>42, most of the titanium is in the zeolite framework. These framework titanium species, which act both as the isolated titanium centers and as Brønsted acidity centers (together with the Brønsted acidity produced

Jianqin Zhuang; Ding Ma; Zhimin Yan; Xiumei Liu; Xiuwen Han; Xinhe Bao; Yihua Zhang; Xinwen Guo; Xiangsheng Wang

2004-01-01

243

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

PubMed Central

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

Steger, G

1994-01-01

244

Modification of acid supports by solid-state redox reaction  

Microsoft Academic Search

The solid-state redox reaction of a number of metals in contact with ZSM-5 and Y zeolites, ?-alumina, and silica was investigated by temperature-programmed hydrogen evolution (TPHE), diffuse reflectance Fourier transform IR spectroscopy (DRIFT), X-ray absorption near-edge structure spectroscopy (XANES), and X-ray powder diffraction (XRD). Among all studied metals, gallium, zinc, manganese, and iron were found to undergo a solid-state redox

A. Hagen; E. Schneider; A. Kleinert; F. Roessner

2004-01-01

245

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

PubMed

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

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

2010-12-28

246

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

247

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

DOEpatents

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

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

1998-01-01

248

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

249

In vitro kinetic studies of the reaction of hydralazine and its acetone hydrazone with pyruvic acid.  

PubMed

To understand the reaction between hydralazine (HP) or its acetone hydrazone (HAH), a metabolite of HP and pyruvic acid, a new selective HPLC method for simultaneous determination of HP, HAH, and hydralazine pyruvic acid hydrazone (HPH) was developed. In vitro degradation of HAH and formation of HP and HPH were investigated at pH 7.4 and 37 degrees C in the presence or absence of pyruvic acid. Hydralazine degraded slowly according to an apparent first-order rate (7.46 x 10(-2)h-1). The degenerative reaction of HAH, accompanied by simultaneous hydrolysis to the parent drug HP, was also subject to apparent first-order loss (3.00 x 10(-1)h-1). In addition, HAH was partly converted to HP and HPH in the presence of pyruvic acid. For the formation pathway of HPH, a model that included the direct reaction of HAH with pyruvic acid and the secondary formation mediated by back-conversion to HP gave a better fit to the experimental data than the model consisting of the latter reaction only. About 10% of the HPH formed was generated by the direct reaction of HAH with pyruvic acid, based on the rate constants estimated. These results suggest that the formation of HPH is not all accomplished through back-conversion to HP. PMID:3373434

Iwaki, M; Ogiso, T; Ito, Y

1988-03-01

250

The reaction of sulfite anion radical (SO .-3) with polyunsaturated fatty acids  

NASA Astrophysics Data System (ADS)

Using the pulse radiolysis technique, SO .-3 was produced in aqueous solution by the reaction of SO 2-3 with either .OH or the (pseudo-) halide radicals N .3, Br .-3, and (SCN) .-2; for the latter reactions rate constants were measured. The reaction of SO .-3 with linoleic, linolenic, and arachidonic acids was monitored using the strong absorption of the pentadienyl radical, one possible primary reaction product. In micellar systems no detectable reaction took place, however, monomeric fatty acids were observed to react with SO .-3. Lower limits of the rate constants for SO .-3 attack derived from the data are 1 × 10 5, 8 × 10 5, and 1.3 × 10 6 (dm 3 mol -1 s -1) for linoleate, linolenate, and arachidonate, respectively.

Erben-Russ, M.; Bors, W.; Winter, R.; Saran, M.

251

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

PubMed

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

Li, Ying; Yan, Bing

2009-03-01

252

Reactions of mercapto amino acids Communication 7. Reactions of N-acyl-2,3-dihaloalanines, (acyloxy)pyruvic acids  

Microsoft Academic Search

Summary 1.It is shown that, over a wide pH range, N-acyl-2,3-dihaloalanines are converted by water into (acylloxy)pyruvic acids with intermediate formation of 2-aryl (or alkyl)4-hydroxy-2-oxazoline-4-carboxylic acids.2.It is shown that the ability of a-acetoxy and a-hdyroxy groups in hydrazones and oximes of a-hydroxy carbonyl compounds to undergo exhaustive reduction when treated with metal amalgams and water forms a general rule.

O. V. Kildisheva; M. G. Linkova; I. L. Knunyants

1955-01-01

253

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

PubMed Central

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

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

2010-01-01

254

Internalization of Locked Nucleic Acids/DNA Hybrid Oligomers into Escherichia coli  

PubMed Central

Abstract Delivery inside the cells is essential for practical application of antisense technologies. The hybrid locked nucleic acid (LNA)/DNA CAAGTACTGTTCCACCA (LNA residues are underlined) was labeled by conjugation to Alexa Fluor 488 (fLNA/DNA) and tested to determine its ability to penetrate Escherichia coli cells and reach the cytoplasm. Flow cytometry analysis showed that the fLNA/DNA was associated with 14% of cells from a stationary phase culture, while association with a labeled isosequential oligodeoxynucleotide was negligible. Laser scanning confocal microscopy confirmed that the fLNA/DNA was located inside the cytoplasm.

Traglia, German M.; Sala, Carol Davies; Fuxman Bass, Juan I.; Soler-Bistue, Alfonso J.C.; Zorreguieta, Angeles; Ramirez, Maria Soledad

2012-01-01

255

Kojic acid derived hydroxypyridinone-chloroquine hybrids: Synthesis, crystal structure, antiplasmodial activity and ?-haematin inhibition.  

PubMed

Aminochloroquinoline-kojic acid hybrids were synthesized and evaluated for ?-haematin inhibition and antiplasmodial activity against drug resistant (K1) and sensitive (3D7) strains of Plasmodium falciparum. Compound 7j was the most potent compound in both strains (IC50(3D7)=0.004?M; IC50(K1)=0.03?M) and had the best ?-haematin inhibition activity (0.07 IC50 equiv vs 1.91 IC50 equiv for chloroquine). One compound 8c was found to be equipotent in both strains (IC50=0.04?M). PMID:24974345

Andayi, Warren Andrew; Egan, Timothy J; Chibale, Kelly

2014-08-01

256

Sequential Aldol Condensation - Transition Metal-Catalyzed Addition Reactions of Aldehydes, Methyl Ketones and Arylboronic Acids  

PubMed Central

Sequential aldol condensation of aldehydes with methyl ketones followed by transition metal-catalyzed addition reactions of arylboronic acids to form ?-substituted ketones is described. By using the 1,1?-spirobiindane-7,7?-diol (SPINOL)-based phosphite, an asymmetric version of this type of sequential reaction, with up to 92% ee, was also realized. Our study provided an efficient method to access ?-substituted ketones and might lead to the development of other sequential/tandem reactions with transition metal-catalyzed addition reactions as the key step.

Liao, Yuan-Xi; Xing, Chun-Hui; Israel, Matthew; Hu, Qiao-Sheng

2011-01-01

257

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

Microsoft Academic Search

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

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

2010-01-01

258

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

259

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

260

Fluorescence in situ Hybridization With Alu and L1 Polymerase Chain Reaction Probes for Rapid Characterization of Human Chromosomes in Hybrid Cell Lines  

Microsoft Academic Search

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

Peter Lichter; Susan A. Ledbetter; David H. Ledbetter; David C. Ward

1990-01-01

261

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

262

Acid-Catalyzed Reaction of Epoxides on Atmospheric Nanoparticles  

NASA Astrophysics Data System (ADS)

Aerosol plays an important role in affecting the earth climate and harming human health. Atmospheric aerosols can be formed from either primary emissions or gas-to-particle conversion process. Numerous studies, including both experimental and theoretical, have been carried out to elucidate the mechanism of gas-to-particle conversion process (a.k.a. nucleation) and the later growth stage of newly formed nanoparticles. However, a complete list of species involving in the nucleation and growth processes of nanoparticles is still poorly understood. The growth of newly formed sulfuric acid - water nanoparticles has been suggested to involve several potential organic vapors, such as amines, glyoxal, 2-4 hexadienal, and epoxides. In the present study, new formed sulfuric acid -water nanoparticles were size selected by a differential mobility analyzer and exposed to epoxide vapors. The size-change after exposure was detected using the second differential mobility analyzer. The size-enlarged particles were then collected by an electrostatic precipitator, thermal vaporized, and analyzed by an ion drift chemical ionization mass spectrometer. Our results show that the sizes of nanoparticles are increased considerably and the magnitude of the increment in size is size-dependent. Mass spectrometry analysis of the nanoparticles after exposure demonstrates that low volatile organosulfate and oligomers are formed in nanoparticles upon their exposure to epoxide vapors.

Xu, W.; Gomez-Hernandez, M.; Lal, V.; Qiu, C.; Khalizov, A. F.; Wang, L.; Zhang, R.

2013-12-01

263

Aromatic Compounds Mannich Reaction Using Economical Acidic Ionic Liquids Based on Morpholinium Salts as Dual Solvent-Catalysts  

Microsoft Academic Search

Economical acidic ionic liquids containing an alkanesulfonic acid group in a morpholinium cation were found to be effective catalysts for the Mannich reactions of various kinds of aromatic aldehydes, acetophenone and aromatic amines at mild reaction conditions. The satisfactory results were obtained with short reaction time, good yields of the Mannich bases and simplicity in the experimental procedure. These ionic

Caibo Yue

2010-01-01

264

An algorithm for the determination and quantification of components of nucleic acid mixtures based on single sequencing reactions  

PubMed Central

Background Determination and quantification of nucleic acid components in a mixture is usually accomplished by microarray approaches, where the mixtures are hybridized against specific probes. As an alternative, we propose here that a single sequencing reaction from a mixture of nucleic acids holds enough information to potentially distinguish the different components, provided it is known which components can occur in the mixture. Results We describe an algorithm that is based on a set of linear equations which can be solved when the sequencing profiles of the individual components are known and when the number of sequenced nucleotides is larger than the number of components in the mixture. We have implemented the procedure for one type of sequencing approach, pyrosequencing, which produces a stepwise output of peaks that is particularly suitable for the procedure. As an example we use signature sequences from ribosomal RNA to distinguish and quantify several different species in a mixture. Using simulations, we show that the procedure may also be applicable for dideoxy sequencing on capillary sequencers, requiring only some instrument specific adaptations of protocols and software. Conclusion The parallel sequencing approach described here may become a simple and cheap alternative to microarray experiments which aim at routine re-determination and quantification of known nucleic acid components from environmental samples or tissue samples.

Pozhitkov, Alexander; Stemshorn, Kathryn; Tautz, Diethard

2005-01-01

265

Reactions of trans-3-chloroacrylic acid dehalogenase with acetylene substrates: consequences of and evidence for a hydration reaction.  

PubMed

Various soil bacteria use 1,3-dichloropropene, a component of the commercially available fumigants Shell D-D and Telone II, as a sole source of carbon and energy. One enzyme involved in the catabolism of 1,3-dichloropropene is trans-3-chloroacrylic acid dehalogenase (CaaD), which converts the trans-isomers of 3-bromo- and 3-chloroacrylate to malonate semialdehyde. Sequence analysis suggested a relationship between the heterohexameric CaaD and the bacterial isomerase, 4-oxalocrotonate tautomerase (4-OT), thereby distinguishing CaaD from a number of dehalogenases whose mechanisms proceed through an alkyl- or aryl-enzyme intermediate. In this study, the genes for the alpha- and beta-subunits of CaaD have been synthesized using a polymerase chain reaction-based strategy, cloned into separate plasmids, and the proteins expressed and purified as the functional heterohexamer. Subsequently, the product of the reaction was confirmed to be malonate semialdehyde by (1)H and (13)C NMR spectroscopy, and kinetic constants were determined using a UV spectrophotometric assay. In view of the proposed hydrolytic nature of the CaaD-catalyzed reaction, three acetylene compounds were investigated as substrates for the enzyme. One compound, 2-oxo-3-pentynoate, a potent active site-directed irreversible inhibitor of 4-OT, is a substrate for CaaD, and was processed to acetopyruvate with kinetic constants similar to those determined for the trans-isomers of 3-bromo- and 3-chloroacrylate. The remaining two compounds, 3-bromo- and 3-chloropropiolic acid, were transformed into potent irreversible inhibitors of CaaD. The inactivation observed for 3-bromopropiolic acid is due to the covalent modification of Pro-1 of the beta-subunit. The results provide evidence for a hydratase activity and set the stage to use the 3-halopropiolic acids as ligands in inactivated CaaD complexes that can be studied by X-ray crystallography. PMID:12873137

Wang, Susan C; Person, Maria D; Johnson, William H; Whitman, Christian P

2003-07-29

266

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

267

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

PubMed

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

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

2014-06-01

268

Investigation and application of multiple reactions between molybdoniobium heteropoly acid and di- or trimethylthionines  

SciTech Connect

This paper presents the results of the study and use of reactions of molybdoniobic acid (MNA) with di- and trimethylthiones (DMT and TMT, respectively). It was found that light absorption of acetone solutions of the products of outer-sphere interaction between MNA and DMT or TMT enabled the determination of optimum acidity for MNA formation. Reaction between TMT and MNA gives two different compounds containing two and five associated dye cations, different in molar extinction coefficient and optimum reaction acidity (pH 0.05-0.25 and 0.35-0.90). Formation of the 6th and 8th molybdenum series with an identical composition of the outer sphere is shown. A highly sensitive photometric method for determining niobium has been developed.

Mirzoyam, F.B.; Karapetyan, A.A.

1986-03-01

269

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

270

Detection of bluetongue virus serotype 17 in Culicoides variipennis by nucleic acid blot and sandwich hybridization techniques.  

PubMed Central

Molecular hybridization techniques were developed for the detection and surveillance of bluetongue virus (BTV) serotype 17 in the insect vector Culicoides variipennis, a biting midge. Radiolabeled RNA and cDNA probes were generated from sequences of the L3 segment of BTV serotype 17. These probes were used to detect BTV RNA in pools of infected C. variipennis by hybridizing the probes directly to analyte immobilized on nylon membranes or by using a nucleic acid sandwich hybridization test. Hybridization procedures were able to detect 1 infected C. variipennis in a pool of 50 and as little as 3.55 log10 50% tissue culture infective doses per ml of virus. These hybridization techniques provide an alternative to virus isolation for the surveillance of BTV in vector populations. Images

Schoepp, R J; Bray, J F; Olson, K E; el-Hussein, A; Holbrook, F R; Blair, C D; Roy, P; Beaty, B J

1990-01-01

271

Development of efficient Lewis acid catalysts for intramolecular cycloaddition reactions of ester-tethered substrates.  

PubMed

We have developed novel bidentate Lewis acids that efficiently promote the intramolecular cycloaddition reactions of ester-tethered substrates. Bis-aluminated triflic amide derivatives [TfN(AlR(1)R(2))2], which are generated by simply mixing triflic amide and 2 equiv of methyl aluminum or aluminum hydride, catalyzed intramolecular Diels-Alder (DA) reactions of ester-tethered 1,7,9-trienes and intermolecular DA reactions of alpha,beta-unsaturated lactones. We also found that bimetallic Lewis acid derived from 1,1'-biphenyl-2,2'-di(triflyl)amide and dimethylaluminum chloride promoted the intramolecular [3 + 2] cycloaddition reaction of acrylate derivatives having an allylsilane part. PMID:17549689

Taguchi, Takeo; Saito, Akio; Yanai, Hikaru

2007-01-01

272

Room Temperature Operation of a Coulomb Blockade Sensor Fabricated by Self-Assembled Gold Nanoparticles using Deoxyribonucleic Acid Hybridization  

Microsoft Academic Search

Molecules of 3-mercaptopropyltrimethoxysilane react with gold nanoparticles to form a gold monolayer on a silicon dioxide substrate. The 12-mer capture Deoxyribonucleic acid (DNA) self-assembles with the nanometer-sized gold particles. Prior to DNA hybridization, a capture DNA produced via hybridization of the target and probe oligonucleotides is covalently bonded to the gold particles. In addition, the probe oligonucleotide containing a thiol

Chun-Chi Chen; Chien-Ying Tsai; Fu-Hsiang Ko; Chung-Ching Pun; Hsuen-Li Chen; Ping-Hei Chen

2004-01-01

273

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

274

Experimental Evidence of Localized Oscillations in the Photosensitive Chlorine Dioxide-Iodine-Malonic Acid Reaction  

NASA Astrophysics Data System (ADS)

The interaction between Hopf and Turing modes has been the subject of active research in recent years. We present here experimental evidence of the existence of mixed Turing-Hopf modes in a two-dimensional system. Using the photosensitive chlorine dioxide-iodine-malonic acid reaction (CDIMA) and external constant background illumination as a control parameter, standing spots oscillating in amplitude and with hexagonal ordering were observed. Numerical simulations in the Lengyel-Epstein model for the CDIMA reaction confirmed the results.

Míguez, David G.; Alonso, Sergio; Muñuzuri, Alberto P.; Sagués, Francesc

2006-10-01

275

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.

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

2014-01-01

276

A geochemical reaction-transport simulator for matrix acidizing analysis and design  

Microsoft Academic Search

A new two-dimensional geochemical simulator, CIRF.A, and its application to matrix acidizing analysis and design are presented. The simulator is based on the solution of the equations of fully coupled fluid flow, species transport and rock\\/fluid reactions and includes the effects of grain growth\\/dissolution and the alteration of porosity and permeability due to mineral reactions. Our program has a large

Xinghui Liu; Anne Ormond; Kirk Bartko; Li Ying; Peter Ortoleva

1997-01-01

277

Formation of Flavor Components by the Reaction of Amino Acid and Carbonyl Compounds in Mild Conditions  

Microsoft Academic Search

This work describe products of reactions between four R-dicarbonyl compounds (diacetyl, pentan- 2,3-dione, glyoxal, and methylglyoxal) or two R-hydroxy ketones, (acetoine and acetol) and amino acids present in wines. The results shows the formation of odorous products or strong-smelling additives resulting from the Maillard and Strecker reaction in a primarily aqueous medium, at low temperature and low pH (pH 3.5)

Laura Pripis-Nicolau; Gilles de Revel; Alain Bertrand; Alain Maujean

2000-01-01

278

Esterification reaction using solid heterogeneous acid catalysts under solvent-less condition  

Microsoft Academic Search

The preparation of di-2-ethylhexylphthalate (DOP) via esterification reaction of phthalic anhydride by 2-ethylhexanol in the presence of solid acidic catalysts has been investigated. The used catalysts were natural zeolite, synthetic zeolites (ZEOKAR-2, ASHNCH-3), heteropolyacid H4Si(W3O10)4 and sulfated ZrO2. The reactions were carried out under solvent-less conditions. It was observed that sulfated ZrO2 has higher reactivity and efficiency among the investigated

Firdovsi Tataroglu Sejidov; Yagoub Mansoori; Nadereh Goodarzi

2005-01-01

279

Is trichloroacetic Acid an insufficient sample quencher of redox reactions?  

PubMed

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

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

2013-03-01

280

Is Trichloroacetic Acid an Insufficient Sample Quencher of Redox Reactions?  

PubMed Central

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

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

2013-01-01

281

Practical asymmetric synthesis of ?-hydroxy ?-amino acids via complimentary aldol reactions  

PubMed Central

Orthogonally protected chiral ?-hydroxy-?-amino acids can be accessed in >100 g quantities from readily available starting materials and reagents in 3–4 steps. These chiral synthons contain two adjacent stereocenters along with suitably protected functional groups (O-TBS, N-Boc) for downstream reactivity. Implementation of two existing aldol technologies allows rapid access to all possible stereoisomers of 1. The guiding principles during reaction optimization were reaction scalability and operational efficiency. Conversion of the amino acids to a variety of chiral building blocks in 1–2 steps demonstrates their synthetic utility.

Pandya, Bhaumik A.; Dandapani, Sivaraman; Duvall, Jeremy R.; Rowley, Ann; Mulrooney, Carol A.; Ryba, Troy; Dombrowski, Michael; Harton, Marie; Young, Damian W.; Marcaurelle, Lisa A.

2011-01-01

282

Direct observation of NH2* reactions with oxygen, amino acids, and melanins.  

PubMed

We report the direct observation of the quenching of the weakly absorbing transient due to the amino radical by oxygen and, hence determine, by a totally direct method, the corresponding rate constant (k = (1.1 +/- 0.1) x 10(9) dm3 mol(-1) s(-1)). We also report the rate constants for the reactions of the amino radical with several amino acids and models of black eumelanin and blond/red phaeomelanin. These reactions lead to a mechanism, based on free radicals, that can explain why ammonia is useful in commercial hair (melanin) bleaching, avoiding excessive amino acid (hair protein) damage. PMID:18215026

Clarke, K; Edge, R; Johnson, V; Land, E J; Navaratnam, S; Truscott, T G

2008-02-14

283

Aqueous-Phase Reactions of Glyoxal and Amino Acids in Evaporating Cloud Droplets  

NASA Astrophysics Data System (ADS)

Approximately 15% of organic carbon in atmospheric water droplets has been reported to be in proteins and free amino acids such as glycine and serine. New NMR, ATR, and electrospray-MS data show that reactions between glyoxal and free amino acids, both present in cloudwater at micromolar concentrations, are triggered by droplet evaporation, leaving behind non-volatile, higher-mass products as a cloud-processed aerosol. The drying process partially dehydrates glyoxal and forms a reactive carbonyl, which undergoes a nucleophilic attack by the amine group, ultimately forming an imine. Mass spectral data suggest that under conditions where glycine concentrations are limiting, a cyclic imine is formed. ATR data indicate that reactions between glyoxal and amino acids are operational when pH > pKa of the carboxylic acid group, a range which includes most atmospheric water droplets.

Corrigan, A. L.; Hanley, S. W.; Lee, F. E.; de Haan, D. O.

2006-12-01

284

Comparison of nucleic acid hybridization and nucleic acid amplification using conserved sequences from the 5' noncoding region for detection of bovine viral diarrhea virus.  

PubMed Central

Primers and probes derived from conserved sequences located in the 5' noncoding region of pestiviruses were evaluated for detection of bovine viral diarrhea virus. With these reagents, hybridization and polymerase chain reaction tests detected 62 of 90 and 90 of 90 bovine viral diarrhea virus isolates, respectively. A quick lysis method for preparing RNA for use in polymerase chain reaction amplification also was evaluated. Images

Ridpath, J F; Bolin, S R; Katz, J

1993-01-01

285

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.

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

286

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

287

Iodine oxidation by hydrogen peroxide in acidic solutions, Bray-Liebhafsky reaction and other related reactions.  

PubMed

The kinetics of the iodine oxidation by hydrogen peroxide is a complicated function of the concentrations of iodine, hydrogen peroxide, perchloric acid and iodate. A proposed model in eight steps explains the new experimental results. It explains also the effect of the concentrations at the steady state of the hydrogen peroxide decomposition catalyzed by iodine and iodate. Without iodate added initially, the iodine oxidation by hydrogen peroxide is preceded by an induction period that depends on the oxygen concentration. A simple extension of the proposed model gives a semi-quantitative explanation of the oxygen effect and allows simulations of the Bray-Liebhafsky oscillations at 25 degrees C. PMID:20419180

Schmitz, Guy

2010-07-01

288

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

289

Solar hydrogen from an aqueous, noble-metal-free hybrid system in a continuous-flow sampling reaction system.  

PubMed

We introduce the visible-light photocatalytic H2 evolution reaction as catalyzed by a cobaloxime/carbon nitride (C3 N4 ) noble-metal-free hybrid photosystem by using a continuous-flow sampling reaction system. The photocatalytic H2 evolution rate is highly dependent on the structure of C3 N4 , in which porous C3 N4 shows the best activity compared with bulk C3 N4 (lamellar) and C3 N4 nanosheets. When using porous C3 N4 , the system is neither affected by the solution pH, nor the C3 N4 concentration, nor the structure of the cobaloxime complex. PMID:24828560

Li, Xiaobo; Ward, Antony J; Masters, Anthony F; Maschmeyer, Thomas

2014-06-10

290

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

Microsoft Academic Search

Summary  The primitiveness of contemporary fatty acid biosynthesis was evaluated by using the thermodynamics and kinetics of its component\\u000a reactions to estimate the extent of its dependence on powerful and selective catalysis by enzymes. Since this analysis indicated\\u000a that the modern pathway is not primitive because it requires sophisticated enzymatic catalysis, we here propose an alternative\\u000a pathway of primitive fatty acid

Arthur L. Weber

1991-01-01

291

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

SciTech Connect

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

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

2012-11-01

292

Direct synthesis of ?-hydroxy-?-amino acids via diastereoselective decarboxylative aldol reaction.  

PubMed

A straightforward metal-free synthesis of anti-?-hydroxy-?-amino acids is described. The organic base-mediated decarboxylative aldol reaction of cheap, readily available ?-amidohemimalonates with various aldehydes afforded under very mild conditions anti-?-hydroxy-?-amido esters in high yields and complete diastereoselectivity. Simple one-pot subsequent transformations enabled the corresponding anti-?-hydroxy-?-amino acids or in a few examples their syn diastereomers to be obtained directly using epimerization conditions. PMID:24188057

Singjunla, Yuttapong; Baudoux, Jérôme; Rouden, Jacques

2013-11-15

293

Polyol-acid anhydride-n-alkyl-alkylene diamine reaction product and motor fuel composition containing same  

SciTech Connect

A fuel composition for an internal combustion engine comprising: (a) a major portion of a liquid hydrocarbon fuel and (b) a minor amount, as a deposit inhibitor additive, of a reaction product of a process comprising: (i) reacting a dibasic acid anhydride with a polyol, thereby forming an ester of maleic acid; (ii) reacting the ester of maleic acid with an N-alkyl-alkylene diamine, thereby forming the reaction product; and (iii) recovering the reaction product.

Sung, R.L.; Jenkins, R.H. Jr.

1987-02-17

294

Polyoxyisopropylenediamine-acid anhydride-n-alkyl-alkylene diamine reaction product and motor fuel composition containing same  

SciTech Connect

A fuel composition is described for an internal combustion engine comprising: (a) a major portion of normally liquid hydrocarbon fuel and (b) a minor amount, as a deposit inhibitor additive, of a reaction product of the process comprising: (i) reacting a disbasic acid anhydride with a polyoxyisopropylenediamine, thereby forming a maleamic acid; (ii) reacting the maleamic acid with a N-alkyl-alkylene diamine, thereby forming a reaction product and; (iii) recovering the reaction product.

Sung, R.L.; Jenkins, R.H. Jr.

1987-02-17

295

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

Microsoft Academic Search

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

V. S. Imshennik; V. T. Zhukov

2006-01-01

296

Micellar Catalysis on the Redox Reaction of Ascorbic Acid-Vanadium(V) System  

Microsoft Academic Search

Stoichiometry of the redox reaction of vanadium(V) by ascorbic acid (H2A) has been experimentally determined to be H2A + 2V(V) ? A + 2V(IV) + 2H  . Evidence of induced polymerization of acrylonitrile and the reduction of mercuric chloride indicates that a free-radical mechanism operates during the course of reaction. Vanadium(V) is only reduced to vanadium(IV). The kinetics of this redox reaction have been investigated spectrophotometrically at 35°C in

Maqsood Ahmad Malik; Firdosa Nabi; Zaheer Khan

2008-01-01

297

Reduction of carbadox mediated by reaction of Mn(III) with oxalic acid.  

PubMed

Manganese(III) geocomponents are commonly found in the soil environment, yet their roles in many biogeochemical processes remain unknown. In this study, we demonstrated that Mn(III) generated from the reaction of MnO(2) and oxalic acid caused rapid and extensive decompositions of a quinoxaline-di-N-oxide antibiotics, viz carbadox. The reaction occurred primarily at the quinoxaline-di-N-oxide moiety resulting in the removal of one -O from N1-oxide and formation of desoxycarbadox. The reaction rate was accelerated by increasing amounts of Mn(III), carbadox and oxalate. The critical step in the overall reaction was the formation of a quinoxaline-di-N-oxide/Mn(III)/oxalate ternary complex in which Mn(III) functioned as the central complexing cation and electron conduit in which the arrangement of ligands facilitated electron transfer from oxalate to carbadox. In the complex, the C-C bond in oxalate was cleaved to create CO(2)(-•) radicals, followed by electron transfer to carbadox through the Mn(III) center. This proposed reaction mechanism is supported by the reaction products formed, reaction kinetics, and quantum mechanical calculations. The results obtained from this study suggest that naturally occurring Mn(III)-oxalic acid complexes could reductively decompose certain organic compounds in the environment such as the antibiotic quinoxaline-di-N-oxide. PMID:23320784

Chen, Wan-Ru; Liu, Cun; Boyd, Stephen A; Teppen, Brian J; Li, Hui

2013-02-01

298

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

299

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

300

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

PubMed

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

Mikhailovich, V; Lapa, S; Gryadunov, D; Sobolev, A; Strizhkov, B; Chernyh, N; Skotnikova, O; Irtuganova, O; Moroz, A; Litvinov, V; Vladimirskii, M; Perelman, M; Chernousova, L; Erokhin, V; Zasedatelev, A; Mirzabekov, A

2001-07-01

301

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.

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

302

Adaptation of the interspersed repetitive sequence polymerase chain reaction to the isolation of mouse DNA probes from somatic cell hybrids on a hamster background  

SciTech Connect

A strategy for the rapid isolation of DNA probes from radiation-fusion Chinese hamster cell hybrids containing overlapping portions of the murine X chromosome based on the interspersed repetitive sequence polymerase chain reaction (IRS-PCR) previously used with human somatic cell hybrids has been developed. This specific amplification of mouse DNA on a hamster background depends on the use of primers directed to the B2 short interspersed repeat element family and the R repeat, from the long interspersed repeat element family, L1. Two sets of amplification conditions, which gave specific amplification of mouse DNA from either a mouse X-monochromosomal hybrid or irradiation-fusion hybrids having reduced X content, were defined. The mouse X-only chromosome hybrid yielded approximately 20 discrete reproducible bands, while the irradiation-fusion hybrids yielded between 1 and 10 discrete products. Comparison of different irradiation-fusion hybrids has allowed the definition of both specific and shared products corresponding to different regions within the overlapping X-chromosome fragments present within these hybrids. Use of such hybrids and the IRS-PCR technique has allowed the isolation of probes corresponding to the central region of the mouse X chromosome that contains the X-inactivation center. The method should be widely applicable to the isolation of mouse DNA sequences from mouse hybrid cell lines on either human or Chinese hamster backgrounds.

Simmler, M.C.; Cox, R.D.; Avner, P. (Unite de Genetique Moleculaire Murine, Institut Pasteur, Paris (France))

1991-07-01

303

Application of Acid Catalytic Hydrothermal Reaction to Conversion of Carbohydrate Biomass into Valuable Substances  

NASA Astrophysics Data System (ADS)

Hydrothermal degradation of glucose in the presence of HCl, H2SO4 and H3PO4 were carried out with pH varying from 1.5-2.5, reaction time varying from 1 min to 10 min at 523 K, to investigate the effect of different acid catalysts and acid concentration on the production of 5-hydroxymethyl-2-furaldehyde (HMF) and levulinic acid from glucose. At lower acid concentration, the yield of HMF was considerably high. The increase in acid concentration accelerated the conversion of HMF to levulinic acid. Among three acid catalysts, HCl is most effect for both conversion of glucose to HMF and further conversion of HMF into levulinic acid. But the decomposition of HMF is also fastest in the case of HCl catalysis. In the conditions used in this study, the highest yield of levulinic acid is about 55 %, which occurred at pH 1.5 for 5 min with HCl, and total highest yield of HMF and levulinic acid is about 50 %, which occurred at pH 2.0 for 5 min with H3PO4.

Takeuchi, Y.; Jin, F.; Enomoto, H.; Tohji, K.

2007-03-01

304

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.

305

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

306

A novel ortho-dehalogenation reaction of 2-chlorocinnamic acid catalyzed by the pink yeast Rhodotorula rubra Y-1529.  

PubMed

In the present study, a resting cells suspension of Rhodotorula rubra Y-1529 was shown to have the capacity to perform an ortho-dehalogenation reaction on 2-chlorocinnamic acid. The results from the biodegradation of U-[14C]benzoic acid, cinnamic acid, 3-chlorocinnamic acid and 4-chlorocinnamic acid suggest that the first step of the ortho-dehalogenation reaction occurred during the oxidation of the unsaturated C3 side chain of 2-chlorocinnamic acid to 2-chlorobenzoic acid. None of the 2-chlorobenzoic acid was found in the biodegradation system, suggesting that this step was a highly regulated step. After the side-chain oxidation reaction, the hydroxylation of the benzene ring was determined to be at the para-position first, followed by the meta-position. The occurrence of 3:4-position ring fission reactions and the production of the final product, CO2, was proven by the biodegradation of U-[14C] benzoic acid. This oxidative dehalogenation reaction catalyzed by R. rubra was found to be regiospecific for 2-chlorocinnamic acid; the chloride ion was probably removed after the ring fission reaction. A pathway of the ortho-dehalogenation reaction of 2-chlorocinnamic acid catalyzed by R. rubra was proposed based on these data. PMID:10789983

Sun, F M; Wang, J S; Traxler, R W

2000-06-01

307

Proton conductive inorganic–organic hybrid membranes prepared from 3-aminopropyltriethoxysilane and phosphoric acid by the sol–gel method  

Microsoft Academic Search

Proton conductive inorganic–organic hybrid membranes with acid–base pairs have been prepared from 3-aminopropyltriethoxysilane and phosphoric acid by the sol–gel method. The self-standing membranes obtained are represented as poly(3-aminopropylsilsesquioxane)-H3PO4 (PAPS–H3PO4) membranes. Infrared absorption spectra of the PAPS–H3PO4 films showed that amino groups of PAPS were protonated by phosphoric acid, indicating the formation of acid–base pairs. X-ray diffraction patterns of the PAPS–H3PO4

Teruaki Tezuka; Kiyoharu Tadanaga; Akitoshi Hayashi; Masahiro Tatsumisago

2008-01-01

308

Deuteration of pentacene in benzoic acid: Monitoring the reaction kinetics via low-temperature optical spectroscopy  

SciTech Connect

In the deuteration of pentacene in benzoic acid, this reaction is monitored via low-temperature optical spectroscopy to observe the proton-deuterium rate of exchange between the solvent and solute molecules. Of the 14 pentacene protons, 6 have an exchange rate 2 orders of magnitude greater than the remaining 8. 20 refs., 3 figs.

Corval, A.; Casalegno, R.; Astilean, S.; Trommsdorff, H.P. [Universite Joseph Fourier, Grenoble (France)

1992-06-25

309

A Novel Cyclic Carbamate from the Acid-Catalyzed Reaction of D-Glucose and Urea  

Microsoft Academic Search

The acid-catalyzed reaction of D-glucose with urea in a phenol-water solution has provided ?-D-glucopyranosylamine 1,2-(cyclic carbamate) (1). The use of H-C correlated NMR spectroscopy involving indirectly-bonded hydrogens and carbons proved to be indispensable in determining the structure.

Richard F. Helm; Joseph J. Karchesy

1989-01-01

310

Determination of the Molar Volume of Hydrogen from the Metal-Acid Reaction: An Experimental Alternative.  

ERIC Educational Resources Information Center

Describes an alternative technique for determining the molar volume of hydrogen from the metal-acid reaction in which the metal sample is encased in a specially prepared cage and a pipette filler is used to fill an inverted burette with water. Eliminates some difficulties encountered with the conventional technique. (JRH)

de Berg, Kevin; Chapman, Ken

1996-01-01

311

Mechanisms of Nitrogen Dioxide Reactions: Initiation of Lipid Peroxidation and the Production of Nitrous Acid  

NASA Astrophysics Data System (ADS)

The reactions of nitrogen dioxide with cyclohexene have been studied as a model for the reactions that occur between nitrogen dioxide in smoggy air and unsaturated fatty acids in pulmonary lipids. As predicted from earlier studies at high nitrogen dioxide concentrations, this gas reacts with cyclohexene predominantly by addition to the double bond at nitrogen dioxide concentrations of I percent (10,000 parts per million) to 40 percent in nitrogen; in the presence of air or oxygen, this reaction initiates the autoxidation of the alkene. However, at concentrations below 100 parts per million in nitrogen, nitrogen dioxide reacts with cyclohexene almost exclusively by abstraction of allylic hydrogen; this unexpected reaction also initiates the autoxidation of the alkene in the presence of oxygen or air, but it leads to the production of nitrous acid rather than of a product containing a nitro group attached to a carbon atom. The nitrous acid can react with amines to produce nitrosamines. Moreover, the nitrite ion produced by the hydrogen abstraction mechanism would be expected to diffuse throughout the body, unlike nitrated lipids that would be confined to the pulmonary cavity. These findings have been confirmed with methyl oleate, linoleate, and linolenate; some of the kinetic features of the nitrogen dioxideinitiated autoxidation of these unsaturated fatty acids have been studied.

Pryor, William A.; Lightsey, John W.

1981-10-01

312

Effects of ultrasound on the reaction step of boric acid production process from colemanite.  

PubMed

Colemanite is one of the most important boron minerals used for production of boric acid. Boric acid (H(3)BO(3)) is produced by the reaction of colemanite (2CaO.3B(2)O(3).5H(2)O) with sulfuric acid in a heterogeneous solid-liquid reaction leading to crystallization of gypsum as a byproduct. The influence of ultrasound on the dissolution of colemanite in H(2)SO(4) solution and on the precipitation of the gypsum during the reaction was investigated. Experiments have been carried out in a batch stirred vessel at 85 degrees C in the absence and presence of ultrasound. The stirring rates were chosen as 600 rpm (for 500-600 microm) and 800 rpm (for 1000-1180 microm) to provide a homogeneous suspension during the reaction. The boric acid and calcium ion concentrations in the solution were determined as a function of time. The results showed that ultrasound enhances the dissolution of colemanite and precipitation rate of the gypsum in the solution after 1h. It has been shown that the use of ultrasound decreases the size of gypsum crystals. PMID:17175191

Taylan, N; Gürbüz, H; Bulutcu, A N

2007-07-01

313

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

314

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

National Technical Information Service (NTIS)

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

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

1995-01-01

315

A possibility of miniaturized fusion and fission hybrid reaction core with positive fusion yield  

Microsoft Academic Search

A novel fission–fusion hybrid reactor was proposed, comprising saturating of a fissile actinide core with a mix of deuterium–tritium hydrogen isotopes (U–D–T target), similarly to Hyperion design. Movement of massive, highly charged and short-range fissile fragments was assumed to produce transfer of energy to deuterons at the distances below collision impact parameter for electrons, when the latter are already deflected.

Anatoly Mayburd

2011-01-01

316

Elongase Reactions as Control Points in Long-Chain Polyunsaturated Fatty Acid Synthesis  

PubMed Central

Background ?6-Desaturase (Fads2) is widely regarded as rate-limiting in the conversion of dietary ?-linolenic acid (18:3n-3; ALA) to the long-chain omega-3 polyunsaturated fatty acid docosahexaenoic acid (22:6n-3; DHA). However, increasing dietary ALA or the direct Fads2 product, stearidonic acid (18:4n-3; SDA), increases tissue levels of eicosapentaenoic acid (20:5n-3; EPA) and docosapentaenoic acid (22:5n-3; DPA), but not DHA. These observations suggest that one or more control points must exist beyond ALA metabolism by Fads2. One possible control point is a second reaction involving Fads2 itself, since this enzyme catalyses desaturation of 24:5n-3 to 24:6n-3, as well as ALA to SDA. However, metabolism of EPA and DPA both require elongation reactions. This study examined the activities of two elongase enzymes as well as the second reaction of Fads2 in order to concentrate on the metabolism of EPA to DHA. Methodology/Principal Findings The substrate selectivities, competitive substrate interactions and dose response curves of the rat elongases, Elovl2 and Elovl5 were determined after expression of the enzymes in yeast. The competitive substrate interactions for rat Fads2 were also examined. Rat Elovl2 was active with C20 and C22 polyunsaturated fatty acids and this single enzyme catalysed the sequential elongation reactions of EPA?DPA?24:5n-3. The second reaction DPA?24:5n-3 appeared to be saturated at substrate concentrations not saturating for the first reaction EPA?DPA. ALA dose-dependently inhibited Fads2 conversion of 24:5n-3 to 24:6n-3. Conclusions The competition between ALA and 24:5n-3 for Fads2 may explain the decrease in DHA levels observed after certain intakes of dietary ALA have been exceeded. In addition, the apparent saturation of the second Elovl2 reaction, DPA?24:5n-3, provides further explanations for the accumulation of DPA when ALA, SDA or EPA is provided in the diet. This study suggests that Elovl2 will be critical in understanding if DHA synthesis can be increased by dietary means.

Gregory, Melissa K.; Gibson, Robert A.; Cook-Johnson, Rebecca J.; Cleland, Leslie G.; James, Michael J.

2011-01-01

317

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

PubMed

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

Fan, Dawei; Li, Guobao; Hao, Jingcheng

2010-11-01

318

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

PubMed

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

Döpfer, H; Stackebrandt, E; Fiedler, F

1982-08-01

319

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

PubMed

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

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

2013-05-01

320

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.

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

2014-01-01

321

Study of the chemical mechanisms of the reaction of neutralization of calcium hydroxide by phosphoric acid  

NASA Astrophysics Data System (ADS)

Calcium phosphates reported in this study, are prepared following an acido-basic reaction between phosphoric acid and calcium hydroxide. These phosphates are the brushite, tricalcium phosphate, hydroxyapatite and oxygenated apatite. The follow-up of the reaction by infra-red spectroscopy of absorption showed that the alkaline pH of calcium hydroxide solution, favours the formation of carbonated apatite, at the start of the reaction. Following the addition of phosphoric acid, the pH becomes increasingly favourable to the formation of the desired phase. The insertion of molecular oxygen in the apatitic tunnel is carried out by the use of hydrogen peroxide. The molecular oxygen rate in the apatite is then determined by volumetric analysis.

Elgadi, M.; Mejdoubi, E.; Elansari, L. L.; Essaddek, A.; Abouricha, S.; Lamhamdi, A.

2005-03-01

322

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

323

Electrophilic Aromatic Aroylation with CF3?Bearing Arenecarboxylic Acid Derivatives: Reaction Behavior and Acidic Mediator Dependence  

Microsoft Academic Search

Triflic acid (TfOH) has been proven to be effective as a tolerant acidic mediator in electrophilic aromatic aroylation with CF3?bearing aroyl chlorides. The TfOH?mediated aroylation of fluorobenzene proceeds with high selectivity to give CF3?bearing aryl fluorophenyl ketones in good yields, which are hardly obtained with the aid of AlCl3 or direct condensation reagents.

Okamoto Akiko; Maeyama Katsuya; Oike Hideaki; Yonezawa Noriyuki

2007-01-01

324

Kinetic studies of Np(VI) reduction reactions with kojic acid and tropolone  

SciTech Connect

To study the problems of potential migration of radionuclides from a nuclear waste repository, the Np(VI) reduction reactions with kojic acid and with tropolone were investigated at tracer level concentration of Np(VI). From results on the kinetic studies of these reactions, the NpO/sub 2//sup + +/ is reduced to the NpO/sub 2//sup +/ in a one-electron transfer process with no structural change of the dioxo neptunium species. The rates for both reactions are directly proportional to the total concentrations of Np(VI) ion and of oxidizing organic compounds: i.e., kojic acid or tropolone. However, the hydrogen ion dependence on the rate is inverse first-order for kojic acid and inverse second-order for tropolone. The Np(VI) reduction proceeds from the precursor complex via an activated complex and results in oxidation products from radicals formed in the rate-limiting step. The rate for the formation of Np(V) by kojic acid (k/sub 1/ = 6.06 +/- 0.30 sec/sup -1/) is faster than by tropolone (k/sub 1/ = 2.49 +/- 0.10 sec/sup -1/). The rate of reduction increases with the pK/sub a/ values (basicity) of the hydroxyl group in oxidizing organic compounds. The activation parameters for the Np(VI) reduction with kojic acid and tropolone have the same values within the uncertainties: i.e., ..delta..H/sup not equal to/ = 82.7 +/- 3.4 KJ/mol, ..delta..S/sup not equal to/ = 15 +/- 12 J/mol/deg for tropolone. Therefore, the Np(VI) reduction reaction occurs through the same mechanism in both reactions.

Kim, W.

1987-01-01

325

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

326

Kinetics of liquid-solid reactions in naphthenic acid conversion and Kraft pulping  

NASA Astrophysics Data System (ADS)

Two liquid-solid reactions, in which the morphology of the solid changes as the reactions proceeds, were examined. One is the NA conversion in oil by decarboxylation on metal oxides and carbonates, and the other is the Kraft pulping in which lignin removal by delignification reaction. In the study of the NA conversion, CaO was chosen as the catalyst for the kinetic study from the tested catalysts based on NA conversion. Two reaction mixtures, carrier oil plus commercial naphthenic acids and heavy vacuum gas oil (HVGO) from Athabasca bitumen, were applied in the kinetic study. The influence of TAN, temperature, and catalyst loading on the NA conversion and decarboxylation were studied systematically. The results showed that the removal rate of TAN and the decarboxylation of NA were both independent of the concentration of NA over the range studied, and significantly dependent on reaction temperature. The data from analyzing the spent catalyst demonstrated that calcium naphthenate was an intermediate of the decarboxylation reaction of NA, and the decomposition of calcium naphthenate was a rate-determining step. In the study on the delignification of the Kraft pulping, a new mechanism was proposed for the heterogeneous delignification reaction during the Kraft pulping process. In particular, the chemical reaction mechanism took into account the heterogeneous nature of Kraft pulping. Lignin reacted in parallel with sodium hydroxide and sodium sulfide. The mechanism consists of three key kinetic steps: (1) adsorption of hydroxide and hydrosulfide ions on lignin; (2) surface reaction on the solid surface to produce degraded lignin products; and (3) desorption of degradation products from the solid surface. The most important step for the delignification process is the surface reaction, rather than the reactions occurring in the liquid phase. A kinetic model has, thus, been developed based on the proposed mechanism. The derived kinetic model showed that the mechanism could be employed to predict the pulping behavior under a variety of conditions with good accuracy.

Yang, Ling

327

Solid AcidBase Control of Inorganic\\/Organic Hybrids by Inorganic Components for Molecule-Selectivity  

Microsoft Academic Search

Solid acid-base properties of methylsiloxane-based inorganic\\/organic hybrids were controlled by incorporation of inorganic components other than Si into methylsiloxane networks. The effect of different inorganic components on the solid acid-base properties was estimated by first-principles calculations based on density functional theory (DFT). The deprotonation tends to occur in the order Si < Al < Nb inorganic components, suggesting that the

Shingo Katayama; Keiji Iwata; Yuji Kubo; Noriko Yamada

2003-01-01

328

Nanoparticle Formation from Hybrid, Multiblock Copolymers of Poly(Acrylic Acid) and VPGVG Peptide  

PubMed Central

Elastin-mimetic hybrid copolymers with an alternating molecular architecture were synthesized via the step growth polymerization of azide-functionalized, telechelic poly(tert-butyl acrylate) (PtBA) and an alkyne-terminated, valine and glycine-rich peptide with a sequence of (VPGVG)2 (VG2). The resultant hybrid copolymer, [PtBA-VG2]n, contains up to six constituent building blocks and has a polydispersity index (PDI) of ~1.9. Trifluoroacetic acid (TFA) treatment of [PtBA-VG2]n gave rise to an alternating copolymer of poly(acrylic acid) (PAA) and VG2 ([PAA-VG2]n). The modular design permits facile adjustment of the copolymer composition by varying the molecular weight of PAA (22 and 63 repeat units). Characterization by dynamic light scattering indicated that the multiblock copolymers formed discrete nanoparticles at room temperature in aqueous solution at pH 3.8, with an average diameter of 250-270 nm and a particle size distribution of 0.34 for multiblock copolymers containing PAA22 and 0.17 for those containing PAA63. Upon increasing the pH to 7.4, both types of particles were able to swell without being disintegrated, reaching an average diameter of 285-300 nm for [PAA22-VG2]n and 330-350 nm for [PAA63-VG2]n, respectively. The nanoparticles were not dissociated upon the addition of urea, further confirming their unusual stability. The nanoparticles were capable of sequestering a hydrophobic fluorescent dye (pyrene), and the critical aggregation concentration (CAC) was determined to be 1.09 × 10-2 or 1.05 × 10-2 mg/mL for [PAA22-VG2]n and [PAA63-VG2]n, respectively. We suggest that the multiblock copolymers form through collective H-bonding and hydrophobic interactions between the PAA and VG2 peptide units, and that the unusual stability of the multiblock nanoparticles is conferred by the multiblock architecture. These hybrid multiblock copolymers are potentially useful as pH-responsive drug delivery vehicles, with the possibility of drug loading through concerted H-bonds and hydrophobic interactions.

Grieshaber, Sarah E.; Paik, Bradford A.; Bai, Shi; Kiick, Kristi L.; Jia, Xinqiao

2012-01-01

329

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

Microsoft Academic Search

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

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

2005-01-01

330

Reaction of substituted furan-2-carboxaldehydes and furo[b]pyrrole type aldehydes with hippuric acid.  

PubMed

4-Heteroarylidene-2-phenyl-1,3-oxazol-5(4H)-ones were prepared by reactions of hippuric acid with substituted furan-2-carboxaldehydes or furo[b]pyrrole type aldehydes. The reactivity of various furan-2-carboxaldehyde derivatives in this reaction is discussed. The effect of microwave irradiation on some condensation reactions was compared with "classical" conditions. The results show that microwave irradiation shortens the reaction times while affording comparable yields. Elementary analysis, UV, IR and 1D NMR proved the structure of new synthesised compounds. 2D NMR spectroscopic measurements confirmed that the configuration at the carbon-carbon double bond corresponds to the pure E isomers of the products. PMID:18007407

Puterová, Zita; Sterk, Heinz; Krutosíková, Alzbeta

2004-01-01

331

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

SciTech Connect

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

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

1988-01-01

332

Taxonomy of xanthomonads from cereals and grasses based on SDS-PAGE of proteins, fatty acid analysis and DNA hybridization  

Microsoft Academic Search

Strains of all Xanthomonas species, X. campestris pathovars pathogenic for cereals and grasses and strains of X. campestris pv. campestris were compared by SDS-PAGE of proteins, gas chromatography of fatty acid methyl esters and DNA-DNA hybridization. The groupings derived using all three methods correlated well with each other. Strains of X. axonopodis and X. campestris pv. vasculorum were heterogeneous, each

L. VAUTERIN; P. YANG; B. HOSTE; B. POT; J. SWINGS; K. KERSTERS

1992-01-01

333

Mesoporous hybrid material composed of Mn3O4 nanoparticles on nitrogen-doped graphene for highly efficient oxygen reduction reaction.  

PubMed

The hybrid material composed of Mn3O4 nanoparticles on nitrogen-doped graphene was prepared via a solvothermal process and investigated for the first time as a catalyst for oxygen reduction reaction (ORR). Its high ORR activity, excellent durability and tolerance to methanol make this hybrid material a promising candidate for highly efficient ORR in fuel cells and metal-air batteries. PMID:23877329

Duan, Jingjing; Zheng, Yao; Chen, Sheng; Tang, Youhong; Jaroniec, Mietek; Qiao, Shizhang

2013-09-11

334

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

335

Synthesis of organic-inorganic hybrid sols with nano silica particles and organoalkoxysilanes for transparent and high-thermal-resistance coating films using sol-gel reaction.  

PubMed

Organic-inorganic hybrid sols were synthesized from nano silica particles dispersed in water and from organoalkoxysilanes, using the sol-gel reaction. This work focuses on the effects of the three multifunctional organoalkoxysilanes dimethyldimethoxysilane (DMDMS), methyltrimethoxysilane (MTMS), and tetramethoxysilane (TMOS) to form a transparent and high-thermal-resistance coating film. The stability of the hybrid sol was evaluated as a function of the reaction time for 10 d through the variation of the viscosity. The viscosity of the silica/DMDMS and silica/MTMS sol was slightly increased for 10 d. The multifunctional organoalkoxysilanes formed dense silica networks through hydrolysis and condensation reaction, which enhanced the thermal resistance of the coating films. No thermal degradation of the silica/DMDMS sample occurred up to 600 degrees C, and none of the silica/MTMS and silica/TMOS samples occurred either up to 700 degrees C. The organic-inorganic hybrid sols were coated on the glass substrate using a spin-coating procedure. The organic-inorganic hybrid sols formed flat coating films without cracks. The transmittance of the hybrid sol coating films using MTMS and DMDMS was shown to be over 90%. The transmittance of the silica/TMOS sol coating film reacted for 10 d abruptly decreased due to faster gelation. The silica/DMDMS and silica/MTMS hybrid sols formed smooth coating films while the surface roughness of the silica/TMOS coating film markedly increased when the hybrid sol reacted for 10 d. The increase of the surface roughness of the silica/TMOS coating film can be attributed to the degradation of the stability of the hybrid sol and to the loss of transmittance of the coating film. It was confirmed in this study that the use of organic-inorganic hybrid sol can yield transparent and high-thermal-resistance coating films. PMID:21137840

Na, Moonkyong; Park, Hoyyul; Ahn, Myeongsang; Lee, Hyeonhwa; Chung, Ildoo

2010-10-01

336

The kinetics and mechanisms of the reaction of iron(III) with gallic acid, gallic acid methyl ester and catechin.  

PubMed

The kinetics and mechanisms of the reactions of a number of pyrogallol-based ligands with iron(III) have been investigated in aqueous solution at 25 degrees C and ionic strength 0.5 M NaClO(4). Mechanisms have been proposed which account satisfactorily for the kinetic data. These are generally consistent with a mechanism in which the 1:1 complex that is formed initially when the metal reacts with the ligand subsequently decays through an electron transfer reaction. There was also some evidence for the formation of a 1:2 ligand-to-metal complex at higher pH values. The kinetics of complex formation were investigated with either the ligand or metal in pseudo-first-order excess. Rate constants for k(1) of 2.83(+/-0.09)x10(3), 1.75(+/-0.045)x10(3) and 3300(+/-200) M(-1) s(-1) and k(-1) of 20(+/-6.0), 35(+/-13) and 25+/-7.6 M(-1) s(-1) have been evaluated for the reaction of Fe(OH)(2+) with gallic acid, gallic acid methyl ester and catechin, respectively. The stability constant of each [Fe(L)](+) complex has been calculated from the kinetic data. The iron(III) assisted decomposition of the initial iron(III) complex formed was investigated. Analysis of the kinetic data yielded both the equilibrium constants for protonation of the iron(III) complexes initially formed together with the rate constants for the intramolecular electron transfers for gallic acid and gallic acid methyl ester. All of the suggested mechanisms and calculated rate constants are supported by calculations carried out using global analysis of time-dependent spectra. PMID:11410233

Hynes, M J; Coinceanainn, M O

2001-06-01

337

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

NASA Astrophysics Data System (ADS)

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 2 V cell optimized for HEV use and low variability. This cell is being used as a building block for the development of a complete battery pack that is managed at the cell level. Following bench testing, this battery pack is to be thoroughly evaluated by substituting it for the Ni-MH pack in a Honda Insight. The RHOLAB cell is based on the 8 Ah Hawker Cyclon cell which has been modified to have current take-off at both ends—the dual-tab design. In addition, a variant has been produced with modified cell chemistry to help deal with problems that can occur when these valve-regulated lead-acid battery (VRLA) cells operate in a partial-state-of-charge condition. The cells have been cycled to a specially formulated test cycle based on real vehicle data derived from testing the Honda Insight on the various test tracks at the Millbrook Proving Grounds in the UK. These cycling tests have shown that the lead-acid pack can be successfully cycled when subjected to the high current demands from the vehicle, which have been measured at up to 15 C on discharge and 8 C during regenerative recharging, and cycle life is looking very promising under this arduous test regime. Concurrent with this work, battery development has been taking place. It was decided early on to develop the 144 V battery as four 36 V modules. Data collection and control has been built-in and special steps taken to minimize the problems of interconnect in this complex system. Development of the battery modules is now at an advanced stage. The project plan then allows for extensive testing of the vehicle with its lead-acid battery at Millbrook so it can be compared with the benchmark tests which have already been carried out on the vehicle with its Ni-MH batteries.

Cooper, A.

338

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.

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

2012-01-01

339

Preparation and Electrochemical Performance of Hybrid Materials Containing Heteropoly Acid with Dawson Structure and Polymers  

NASA Astrophysics Data System (ADS)

Highly proton-conducting hybrid materials (P2W17V/PEG and P2W17V/PEG/SiO2) were prepared by heptadecatungstovanadodiphosphoric heteropoly acid with Dawson structure (P2W17V, 90 wt.%), polyethylene glycol (PEG, 10 wt.% and 5 wt.%) and silica gel (SiO2, 0 wt.% and 5 wt.%). The products were characterized by the infrared (IR) spectrum, X-ray powder diffraction (XRD) analysis and electrochemical impedance spectrum (EIS). The result reveals that their conductivity values are 1.02 × 10-2 and 2.58 × 10-2S ? cm-1 at room temperature (26°C) and 75% relative humidity (RH), respectively. Their conductivities increase with higher temperature and these activation energies of proton conduction are 9.51 and 14.95 kJ?mol-1, which are lower than that of pure heteropoly acid (32.23 kJ?mol-1). These mechanisms of proton conduction for these two materials are Grotthuss mechanism.

Tong, Xia; Wu, Wen; Zhou, Shengming; Wu, Qingyin; Cao, Fahe; Yaroslavtsev, A. B.

2012-12-01

340

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

PubMed

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

McDonald, Michael B; Freund, Michael S

2011-04-01

341

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

PubMed

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

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

2013-11-01

342

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

343

Lewis acid-promoted cyclization reactions of alkenyl ethenetricarboxylates: stereoselective synthesis of 2-oxotetrahydrofurans and 2-oxopyrrolidines.  

PubMed

Lewis acid-promoted intramolecular reactions of alkenyl ethenetricarboxylates and the corresponding amides have been examined. Reaction of allyl ethenetricarboxylates and the amides with Lewis acids (1-2 equiv) such as TiCl4, TiBr4, AlCl3, and AlBr3 gave 3,4-trans-halogenomethyl 2-oxotetrahydrofuran and pyrrolidine derivatives stereoselectively in high yields. The stereochemistries were determined by NOE experiments. Reaction of alkyl-substituted allylic ethenetricarboxylates with Lewis acids gave chloro 2-oxotetrahydrofurans and pyrans. For some alkyl-substituted substrates, cationic intermediates may be formed under the reaction conditions, and rearranged products have been obtained. PMID:23885757

Yamazaki, Shoko; Fujinami, Ken; Maitoko, Yuki; Ueda, Khota; Kakiuchi, Kiyomi

2013-09-01

344

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

SciTech Connect

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

Gorensek, M.; Summers, W.

2010-03-24

345

Reactions of indoles with nitrogen dioxide and nitrous acid in an aprotic solvent.  

PubMed

The reaction of 2-phenyl- and 1-methyl-2-phenylindole with nitrogen dioxide or with nitrous acid (NaNO2-CH3COOH) in benzene leads mainly to the formation of the isonitroso and 3-nitroso indole derivatives, respectively. When reacted with nitrous acid, 1-methyl-2-phenylindole gives also the corresponding azo-bis-indole in good yields. The reaction of indole with nitrogen dioxide leads to 2-(indol-3-yl)-3H-indol-3-one as the main product together with small amounts of 2-(indol-3-yl)-3H-indol-3-oxime; whereas the major product obtained when the same indole is reacted with nitrous acid is represented by 2-(indol-3-yl)-3H-indol-3-oxime. The reaction of 3-alkyl substituted indoles with nitrogen dioxide is rather complex and results in the formation of different nitro indoles, whereas nitrosation is observed when nitrous acid is used. Crystal structures of 2-(indol-3-yl)-3H-indol-3-one and of 4-nitro-N-acetyltryptamine have been determined by X-ray analysis. PMID:17036116

Astolfi, Paola; Panagiotaki, Maria; Rizzoli, Corrado; Greci, Lucedio

2006-09-01

346

Methanol oxidation and hydrogen reactions on NiZr in acid solution  

NASA Astrophysics Data System (ADS)

The electrochemical properties of a Ni 50Zr 50 (at.%) alloy have been investigated by cyclic voltammetry and steady-state polarization measurements. The alloy forms a passivating oxyhydroxide film that makes it electrochemically stable in an acid solution. The oxyhydroxide film is shown to be an electrocatalyst for the methanol oxidation reaction (MOR). The reaction proceeds at surface O 2- ions neighboring a Ni 3+ ion of a thicker passivating film; electron transfer from the surface to the electrode occurs diffusively by the nickel atoms of the film. A reaction pathway is presented that accounts for the observation of an optimum thickness for the passivating film. The NiZr alloy was also found to catalyze both hydrogen-oxidation and proton-reduction reactions (HOR and PRR) if it has a thinner surface oxyhydroxide film. The alloy appears to form mixed NiZrH and NiZrH 3- x hydrides on cycling negative of the normal hydrogen potential. The activity of the hydrogen-oxidation reaction on a hydride surface was found to increase in the presence of streaming hydrogen gas and also with increasing negative initial potential. Although the hydride is unstable in acid, it may be an attractive candidate for use as a rechargeable negative electrode in an alkaline metal/air or nickel-metal hydride secondary battery.

Hays, C. C.; Manoharan, R.; Goodenough, J. B.

347

Lewis acid promoted reactions of [alpha],[beta]-unsaturated aldehydes and ketones with alkenes  

SciTech Connect

Lewis acid-Promoted reactions of methyl vinyl ketone, methoxymethyl vinyl ketone and acetoxymethyl vinyl ketone with various alkenes are reported. The enones undergo [2+2] cycloaddition reactions with various substituted styrenes to give mixtures of two cyclobutane epimers. These reactions are regioselective and the yields are high. The thermodynamically less stable cyclobutane epimers are epimerized with methanolic potassium carbonate to the thermodynamically more stable cyclobutanes. Reactions of methyl vinyl ketone, methoxymethyl vinyl ketone and acetoxymetyl vinyl ketone with methylencyclohexane promoted by mixtures of TiCl[sub 4] and Ti(O[sup i]Pr)[sub 4] in various proportions give one of more of the following products; a cyclobutane, a formal ene product and a chloro-substituted product. Reactions of acetoxymethyl vinyl ketone with cyclohexene and 1-methylcyclohexene promoted by TiCl[sub 4] give mixtures of ene and chloro-substituted products and a chloro-substituted product, respectively. The chloro-substituted products are coverted to the ene products by treating with a base or by dissolution in hot methanol. Various Lewis acid-promoted intramolecular reactions of [alpha], [beta]-unsaturated aldehydes and ketones with olefins produce formal ene products and, in one cas, a bicyclo [2.2.1] heptane product. The latter product results apparently from alkylation of the Lewis acid-bound [alpha], [beta]-unsaturated carbonyl moiety at the [beta]-carbon, rearrangement of the resultant carbocation by hydride shift, followed by coupling of the enolate and carbocation moieties. A synthesis of the natural product nanaimoal is also reported.

Ali, M.H.

1993-01-01

348

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

349

Chiral P,N-ligands based on ketopinic acid in the asymmetric Heck reaction.  

PubMed

[figure: see text] Novel chiral P,N-ligands were synthesized from (1S)-(+)-ketopinic acid using palladium-catalyzed coupling reaction of a vinyl triflate and either a diarylphosphine or a dialkylphosphine as the key step. Palladium complexes of these ligands are efficient catalysts for asymmetric Heck reaction between aryl or alkenyl triflates and cyclic alkenes. Products were obtained with good to excellent enantioselectivity from arylation and alkenylation of 1,2-dihydrofuran, cyclopentene, and 4,7-dihydro-1,3-dioxepin. PMID:11430024

Gilbertson, S R; Fu, Z

2001-01-25

350

Metastable McLafferty rearrangement reaction in the electron impact ionization of stearic acid methyl ester  

NASA Astrophysics Data System (ADS)

The metastable peaks for the McLafferty rearrangement and double hydrogen rearrangement reactions have been observed in the stearic acid methyl ester system under electron impact ionization. The metastable ion spectrum of the M+. ion gave peaks corresponding to the ions at m/z 74, 75, 87 and 88, whereas the collision-induced dissociation spectrum showed low intensity ions at m/z 75 and 88 which come from double hydrogen rearrangement reactions of M+. ions. The kinetics for the change of the molecular ions to different structures before fragmentation have been discussed.

Takayama, Mitsuo

1995-06-01

351

The triflic acid-mediated cyclization reactions of N-cinnamoyl-1-naphthylamines.  

PubMed

N-cinnamoyl-1-naphthylamines undergo a cyclization reaction with triflic acid to form 4-phenyl-3,4-dihydro-1H-naphth[1,8-bc]azepin-2-ones and 4-phenyl-3,4-dihydro-1H-benzo[h]quinolin-2-ones. However, the N-benzyl analogues also undergo a unique cascade reaction to form novel heptacyclic structures via a 1,2-addition followed by a 4-addition to the naphthalene. With an electron-rich N-benzyl substituent, the heptacycle is the sole product. PMID:24093644

King, Frank D; Aliev, Abil E; Caddick, Stephen; Tocher, Derek A

2013-11-01

352

Investigation of the reaction of dithiocarbamic acid salts with aromatic aldehydes.  

PubMed

A reaction of dithiocarbamic acid salts with carbonyl compounds was investigated for the first time in the presence of BF(3)·OEt(2). The reaction is temperature dependent and gives gem-bis(dithiocarbamates) at 35-45 °C as a molecule with high equivalents of dithiocarbamate groups. At lower temperatures (15-20 °C), the 2-iminium-1,3-dithietane is obtained as the only product. The structure of a 2-iminium-1,3-dithietane was accomplished by X-ray crystallographic analysis. PMID:22823341

Ziyaei Halimehjani, Azim; Shayegan, Mojtaba Hajiloo; Hashemi, Mohammad Mahmoodi; Notash, Behrooz

2012-08-01

353

On the impedance of the gassing reactions in lead-acid batteries  

NASA Astrophysics Data System (ADS)

Oxygen and hydrogen evolution reactions in flooded lead-acid batteries during float charging were studied by galvanostatic steady-state polarization and impedance spectroscopy techniques. Given the very low relaxation frequencies of such processes (between 2 and 0.05 mHz), impedance measurements needed to be extended to the ultra-low frequency domain. Investigation of their dynamic behavior provided a complete description of the porous character of the active zone. The steps involved in the reaction mechanisms are also discussed.

Hammouche, Abderrezak; Karden, Eckhard; Walter, Jörg; De Doncker, Rik W.

354

Catalytic enantioselective Diels-Alder reaction by self-assembly of the components on a Lewis acid template.  

PubMed

Thermal Diels-Alder reaction of 2,4-hexadienol with methyl acrylate is unselective. By simultaneous coordination of diene and dienophile to a chiral bimetallic Lewis acid catalyst, a LACASA-DA reaction occurs with complete control of regio-, diastereo-, and enantioselectivity to give a single adduct. [reaction: see text] PMID:16048335

Ward, Dale E; Souweha, Michael Santos

2005-08-01

355

Asymmetric Br?nsted acid-catalyzed aza-Diels-Alder reaction of cyclic C-acylimines with cyclopentadiene  

PubMed Central

Summary A new chiral Brønsted acid-catalyzed aza-Diels–Alder reaction of cyclic C-acylimines with cyclopentadiene has been developed. The reaction provides optically active aza-tetracycles in good yields with high diastereo- and enantioselectivities under mild reaction conditions.

Raja, Sadiya

2012-01-01

356

Synthesis of tertiary propargylamines via a rationally designed multicomponent reaction of primary amines, formaldehyde, arylboronic acids and alkynes.  

PubMed

A novel approach for the synthesis of tertiary propargylamines is achieved through a Cu(OAc)2-catalyzed multicomponent reaction of primary amines, formaldehyde, arylboronic acids and alkynes, where a combination of PBM and A(3)-coupling reactions is involved in this new multicomponent reaction. PMID:24969221

Wang, Jiayi; Shen, Qiaoying; Li, Pinzhen; Peng, Yanqing; Song, Gonghua

2014-08-14

357

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

PubMed

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

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

2013-01-18

358

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

359

A Strongly Coupled Graphene and FeNi Double Hydroxide Hybrid as an Excellent Electrocatalyst for the Oxygen Evolution Reaction.  

PubMed

Cost-effective electrocatalysts for the oxygen evolution reaction (OER) are critical to energy conversion and storage processes. A novel strategy is used to synthesize a non-noble-metal-based electrocatalyst of the OER by finely combining layered FeNi double hydroxide that is catalytically active and electric conducting graphene sheets, taking advantage of the electrostatic attraction between the two positively charged nanosheets. The synergy between the catalytic activity of the double hydroxide and the enhanced electron transport arising from the graphene resulted in superior electrocatalytic properties of the FeNi-GO hybrids for the OER with overpotentials as low as 0.21?V, which was further reduced to 0.195?V after the reduction treatment. Moreover, the turnover frequency at the overpotential of 0.3?V has reached 1?s(-1) , which is much higher than those previously reported for non-noble-metal-based electrocatalysts. PMID:24910179

Long, Xia; Li, Jinkai; Xiao, Shuang; Yan, Keyou; Wang, Zilong; Chen, Haining; Yang, Shihe

2014-07-14

360

Predicting energies and geometries for reactions involved in atmosphere chemistry: a comparison study between hybrid DFT methods  

NASA Astrophysics Data System (ADS)

The energies and geometries of the reactants, transition states and products of 19 reactions involved in atmosphere chemistry are studied using the MPW1K, BH&HLYP and B3LYP hybrid density functional theory (DFT) with the 6-31 + G(d,p) basis set. By comparing to experimental results or high-level calculations we find that the root-mean-square error (RMSE) of energies are 1.7, 2.2 and 2.7 kcal/mol for MPW1K, BH&HLYP and B3LYP methods, respectively. For geometrical parameters, the RMSE of MPW1K and BH&HLYP are close. B3LYP gives the worst estimation among the three DFT methods employed in the present study.

Li, Qian Shu; Xu, Xiu Dong; Zhang, Shaowen

2004-01-01

361

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

362

The origin and structures of dimeric fatty acids from the anaerobic reaction between soya-bean lipoxygenase, linoleic acid and its hydroperoxide  

PubMed Central

In an anaerobic system soya-bean lipoxygenase catalyses in the presence of linoleic acid and l-13-hydroperoxyoctadeca-cis-9-trans-11-dienoic acid the formation of dimeric fatty acids and of carbonyl compounds. The analogous reaction does not take place when d-9-hydroperoxyoctadeca-trans-10-cis-12-dienoic acid is used instead of the 13-hydroperoxy isomer. Non-oxygenated dimers stem directly from linoleic acid and have C(11)–C(13?) or –C(9?) and C(13)–C(13?) or –C(9?) linkages. Dimers that contain oxygen originate from linoleic acid and linoleic acid hydroperoxide. It is most likely that the oxygen is present in epoxy groups.

Garssen, G. J.; Vliegenthart, J. F. G.; Boldingh, J.

1972-01-01

363

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

PubMed

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

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

2014-01-01

364

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

PubMed Central

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

Bohme, K.; Cremonesi, P.; Severgnini, M.; Villa, Tomas G.; Fernandez-No, I. C.; Barros-Velazquez, J.; Castiglioni, B.; Calo-Mata, P.

2014-01-01

365

Chemically activated formation of organic acids in reactions of the Criegee intermediate with aldehydes and ketones.  

PubMed

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 C=O 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 < CH3CHO < 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. PMID:23958859

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

2013-10-21

366

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

367

Hybrid QM/QM simulations of photochemical reactions in the molecular crystal N-salicylidene-2-chloroaniline.  

PubMed

In this paper, we report the application of the QM/QM hybrid simulation technique to the photoisomerisation reactions of anils (i.e., Schiff bases of salicylaldehyde with aniline derivatives) in the solid state, on the example of the photochromic polymorph of N-salicylidene-2-chloroaniline. By propagating molecular dynamics on a potential energy surface constructed using a combination of time-dependent DFT and ground-state DFT calculations, two reaction pathways of the cis-enol isomer were observed, which occur with approximately equal probability. In the first pathway, the photoexcited molecule undergoes an intramolecular proton transfer reaction on average 25 fs after photoexcitation. It then persists in the cis-keto form for a few hundred femtoseconds before undergoing a pedal motion through which it reaches an S1/S0 conical intersection. This pathway, whose existence has previously been proposed in the literature to rationalize the feasibility of the photoisomerisation reaction in the confined environment of the crystal lattice, is predicted to lead to the formation of the trans-keto form. The second pathway is nonreactive and is analogous to a previously characterised radiationless de-excitation pathway of the isolated molecule. The cis-enol to trans-keto photoisomerisation is reversible. Following the photoexcitation of a trans-keto molecule, it persists in a largely unchanged geometry for a period of time ranging from a few hundred femtoseconds to over a picosecond, and subsequently undergoes a pedal motion in the same direction as the one involved in the cis-enol to trans-keto photoisomerisation, leading to the cis-keto isomer through another S1/S0 conical intersection. PMID:23694956

Kochman, Micha? A; Bil, Andrzej; Morrison, Carole A

2013-07-14

368

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

PubMed Central

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

Tan, Jiajing; Akakura, Matsujiro

2013-01-01

369

Nucleic acid hybridisation and polymerase chain reaction in the diagnosis of infectious animal diseases.  

PubMed

The authors describe and summarise the use of nucleic acid hybridisation and polymerase chain reaction (PCR) technologies in the diagnosis of animal diseases. PCR is a powerful biological tool which enables exponential enzymatic amplification in vitro of a given deoxyribonucleic acid sequence. This technique is currently used to study the molecular pathogenesis of many infectious diseases and also for diagnosis. PCR is usually more sensitive than conventional methods and does not require complex facilities, and will therefore soon become the preferred technology of laboratory diagnosticians, field veterinarians and health officers. PMID:7691273

Rodríguez, M; Schudel, A A

1993-06-01

370

Catalyzed Reformatsky reactions with ethyl bromofluoroacetate for the synthesis of alpha-fluoro-beta-hydroxy acids.  

PubMed

The presence of catalytic amounts of CeCl(3) improves yields and simplifies procedure in the Reformatsky reactions of ethyl bromofluoroacetate with aldehydes and ketones to generate diastereomeric mixtures of alpha-fluoro-beta-hydroxy esters, some of which can be separated by crystallization or column flash chromatography. Diastereomerically pure alpha-fluoro-beta-hydroxy acids are obtained by mild alkaline hydrolysis of the resolved alpha-fluoro-beta-hydroxy esters. Detailed NMR data of new alpha-fluoro-beta-hydroxy esters and alpha-fluoro-beta-hydroxy acids are also presented. PMID:11777441

Ocampo, R; Dolbier, W R; Abboud, K A; Zuluaga, F

2002-01-11

371

Reactions of an aromatic ?,?-biradical with amino acids and dipeptides in the gas phase  

Microsoft Academic Search

Gas-phase reactivity of a positively charged aromatic ?,?-biradical (N-methyl-6,8-didehydroquinolinium) was examined toward six aliphatic amino acids and 15 dipeptides by using Fourier transform\\u000a ion cyclotron resonance mass spectrometry (FT-ICR) and laser-induced acoustic desorption (LIAD). While previous studies have\\u000a revealed that H-atom and NH2 abstractions dominate the reactions of related monoradicals with aliphatic amino acids and small peptides, several additional,\\u000a unprecedented

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

2010-01-01

372

Heterogeneous chemical reaction of chlorine nitrate and water on sulfuric-acid surfaces at room temperature  

NASA Astrophysics Data System (ADS)

It has been demonstrated that the reaction between gaseous chlorine nitrate and water on room temperature liquid sulfuric acid (95.6%) surfaces yields hypochlorous acid in the gas phase. First-order loss rate constants for chlorine nitrate (equivalent to a value of the sticking coefficient ? = 3.2 × 10-4) have been determined. This value is five orders-of-magnitude greater than reported values on similar areas of more inert surfaces. Application of results of this type to stratospheric models must await ongoing studies at lower temperatures.

Rossi, Michel J.; Malhotra, Ripudaman; Golden, David M.

1987-02-01

373

Fatty acid droplet self-division driven by a chemical reaction.  

PubMed

Division of a millimeter-sized and compartmentalized fatty acid droplet is triggered by a chemical pH clock reaction operating on the ten-second time scale. The autonomous pH change inside the compartment translates into the deprotonation of the fatty acid molecules, leading to a negative interfacial tension at the water-oil interface inside the droplet. This phenomenon induces the expansion of the droplet, which is followed by its division into daughter droplets governed by the Plateau-Rayleigh instability. PMID:24464178

Derényi, I; Lagzi, I

2014-03-14

374

Effect of carbon material on Pd catalyst for formic acid electrooxidation reaction  

NASA Astrophysics Data System (ADS)

Effect of several usually used carbon materials on Pd catalyst for formic acid electrooxidation reaction is studied by physical characterization and electrochemical measurements. New active sites are formed due to the Pd and carbon interaction which is confirmed by the XPS measurements, and electrochemical impedance spectroscopy confirms that the presence of the carbon material reduced the charge transfer resistance. Further, an improved fuel cell performance is observed when integrating the carbon-modified Pd catalyst in to a direct formic acid fuel cell. The results reveal that the carbon material is not only used as support, but also involves the new active sites formation.

Chang, Jinfa; Li, Songtao; Feng, Ligang; Qin, Xiujuan; Shao, Guangjie

2014-11-01

375

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

PubMed

Poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) incorporating quantum dots (QDs), superparamagnetic iron oxide nanoparticles (SPIONs) and gold (Au) NPs for neutrophil labeling were fabricated via the w/o/w double emulsion method. QDs and SPIONs were entrapped in the PLGA core during emulsification while Au NPs were assembled on top of the PLGA NPs via electrostatic interactions. Transmission Electron Microscopy, Scanning Electron Microscopy and Confocal Scanning Laser Microscopy (CLSM) were applied to characterize the hybrid PLGA NPs. The uptake of the hybrid PLGA NPs by human neutrophils was studied by Flow Cytometry and confocal microscopy. In addition, the induction of reactive oxygen species (ROS) in neutrophils after incubation with the hybrid PLGA NPs was assessed. Magnetophoresis experiments showed that neutrophils with internalized hybrid PLGA NPs can be effectively laterally displaced towards the magnetic field. Magnetic Resonance Imaging of the hybrid PLGA NPs resulted in images with a contrast enhancement linearly dependent on the concentration of the hybrid PLGA NPs. Research reported in this work is relevant for imaging, tracking and manipulating neutrophils and has potential for in vivo applications, e.g., tumor visualization and localized photothermal treatment. PMID:24177321

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

2013-12-21

376

Reaction between alkyl isocyanides and isopropylidene Meldrum's acid in the presence of bidentate nucleophiles.  

PubMed

The reaction between alkyl isocyanides and isopropylidene Meldrum's acid in the presence of 1,2-ethanediol leads to N (1)-(alkyl)-2-(5,7-dioxo-1,4-dioxepane-6-yl)-2-methylpropanamides. 1,3-Propanediol or 1,4-butanediol produce hydroxyalkyl 1-(tert-butyl)-4,4-dimethyl-2,5-dioxo-3-pyrrolidinecarboxylates. When the reaction was performed in the presence of catechol, bis(2-hydroxyphenyl) 2-[2-(tert-butylamino)-1,1-dimethyl-2-oxoethyl]malonate was obtained. 2-Aminophenols react with alkyl isocyanides in the presence of isopropylidene Meldrum's acid to produce 1-alkyl-N (3)-(2-hydroxyaryl)-4,4-dimethyl-2,5-dioxo-3-pyrrolidinecarboxamides in good yields. PMID:17123027

Yavari, Issa; Sabbaghan, Maryam; Hossaini, Zinatossadat

2007-02-01

377

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

378

Reaction between alkyl isocyanides and isopropylidene Meldrum ’s acid in the presence of bidentate nucleophiles  

Microsoft Academic Search

Summary  The reaction between alkyl isocyanides and isopropylidene Meldrum’s acid in the presence of 1,2-ethanediol leads to N\\u000a 1-(alkyl)-2-(5,7-dioxo-1,4-dioxepane-6-yl)-2-methylpropanamides. 1,3-Propanediol or 1,4-butanediol produce hydroxyalkyl 1-(tert-butyl)-4,4-dimethyl-2,5-dioxo-3-pyrrolidinecarboxylates. When the reaction was performed in the presence of catechol, bis(2-hydroxyphenyl)\\u000a 2-[2-(tert-butylamino)-1,1-dimethyl-2-oxoethyl]malonate was obtained. 2-Aminophenols react with alkyl isocyanides in the presence of\\u000a isopropylidene Meldrum’s acid to produce 1-alkyl-N\\u000a 3-(2-hydroxyaryl)-4,4-dimethyl-2,5-dioxo-3-pyrrolidinecarboxamides in good yields.

Issa Yavari; Maryam Sabbaghan; Zinatossadat Hossaini

2007-01-01

379

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

PubMed Central

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

Ghisla, Sandro; Pollegioni, Loredano; Molla, Gianluca

2011-01-01

380

[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

381

NMR investigation of chitosan derivatives formed by the reaction of chitosan with levulinic acid  

Microsoft Academic Search

Chitosan derivatives are obtained by reaction of chitosan with a low degree of acetylation and levulinic acid under different experimental conditions. The chemical structure of the different derivatives obtained is determined using 1H and 13C NMR spectroscopies. The intrinsic viscosity is used to follow the molecular weight evolution. Finally, conditions are described in which water-soluble N-carboxybutylchitosan is obtained. In particular,

M Rinaudo; J Desbrières; P Le Dung; P Thuy Binh; N. T Dong

2001-01-01

382

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

383

The rapid and enhanced reduction of graphene oxide by microwave assisted acid catalyzed reaction.  

PubMed

We report a novel synthetic route to fabricate reduced graphene oxide (rGO) from graphene oxide (GO) using a microwave assisted acid catalyzed reaction in organic solvent. The obtained rGO in this study exhibited 4 times higher electrical conductivity, less oxygen content and better ordered structure than that of conventional solvothermally fabricated ones. By using microwave irradiation, high quality rGO can be obtained in several minutes. PMID:24245202

Tien, Huynh Ngoc; Luan, Van Hoang; Hoa, Le Thuy; Lee, Tae Kyu; Kong, Byung-Seon; Chung, Jin Suk; Kim, Eui Jung; Hur, Seung Hyun

2013-10-01

384

The antioxidant action of Polypodium leucotomos extract and kojic acid: reactions with reactive oxygen species  

Microsoft Academic Search

Two natural products Polypodium leucotomos extract (PL) and kojic acid (KA) were tested for their ability to scavenge reactive oxygen species ( OH, O2 -, H2O2, 1O2) in phosphate buffer. Hydroxyl radicals were generated by the Fenton reaction, and the rate constants of scavenging were 1.6 x 109 M-1 s-1 for KA and 1.0 x 109 M-1 s-1 for PL,

A. J. Gomes; C. N. Lunardi; S. Gonzalez; A. C. Tedesco

2001-01-01

385

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.

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

2013-01-01

386

Heterogeneous photocatalytic synthesis of methane from acetic acid: new Kolbe reaction pathway  

Microsoft Academic Search

The heterogeneous photocatalytic decomposition of acetic acid on n-type TiOâ to yield almost exclusively methane and carbon dioxide is reported. Probable reaction mechanisms are discussed. It is assumed that the TiOâ powder acts in a dual function causing the photooxidation of acetate and the reduction of intermediately formed methyl radicals. This property is not found at metal electrodes under usual

Bernhard Kraeutler; Allen J. Bard

1978-01-01

387

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

388

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

Microsoft Academic Search

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

Keiichiro Matsuda; Morris Schnitzer

1971-01-01

389

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

390

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

SciTech Connect

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

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

2009-05-26

391

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

PubMed

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

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

2014-02-01

392

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

PubMed Central

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

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

2014-01-01

393

Hybrid hyaluronic acid hydrogel/poly(?-caprolactone) scaffold provides mechanically favorable platform for cartilage tissue engineering studies.  

PubMed

Hybrid scaffolds for cartilage tissue engineering provide the potential for high stiffness properties in tension and compression while exhibiting the viscoelastic response found in hydrogels and native cartilage tissue. We investigate the impact of a hybrid scaffold fabricated from a hyaluronic acid (HA)-based hydrogel combined with porous poly(?-caprolactone) (PCL) material formed by a particulate leaching method to study dedifferentiated chondrocyte response. The material properties of the hybrid scaffold showed mean Young's moduli in tension which were similar to human articular cartilage but not statistically different between the hybrid and porous PCL scaffolds at 2.02 and 2.07 MPa, respectively. For both the hybrid and porous PCL control scaffolds in compression at low loading frequencies (<1 Hz) and 10% strain peak amplitude the Young's moduli are not statistically distinct. However, at frequencies in the range of normal human gait from 1 to2 Hz, hybrid scaffolds exhibit significantly (p?hybrid scaffolds however ECM protein expression levels of collagen type I, collagen type II, and aggrecan are not different from the PCL control scaffolds. These results provide a model platform to investigate cell response to mechanical and chemical cues in a hybrid scaffold system with mechanical properties similar to human cartilage that does not contribute to differentiation in order to identify the appropriate design and development parameters to promote formation of extracellular matrix and investigate chondrocyte scaffold interactions. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 2918-2926, 2014. PMID:24115629

Mintz, Benjamin R; Cooper, James A

2014-09-01

394

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

395

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

396

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

397

Influence of temperature on the heterogeneous reaction of formic acid on ?-Al2O3.  

PubMed

Despite increased awareness of the role played by heterogeneous reactions of formic acid on mineral aerosol, the experimental determination of how these atmospheric reaction rates vary with temperature remain a crucially important part of atmosphere science. Here we report the first measurement of heterogeneous uptake of formic acid on ?-Al(2)O(3) as a function of temperature (T = 240-298 K) at ambient pressure using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). From the analysis of the spectral features, crystalline HCOOH was identified at low temperature besides common product (formate ions) on the surface. It was also interesting to find that crystalline HCOOH can continue to react with ?-Al(2)O(3). The reaction mechanisms at both room and low temperature were discussed. Furthermore, the reactive uptake coefficients were acquired and found to increase with decreasing temperature. Finally, the atmospheric lifetime of formic acid because of heterogeneous loss on mineral aerosol was estimated at temperatures related to the upper troposphere. PMID:23025659

Wu, Ling-Yan; Tong, Sheng-Rui; Hou, Si-Qi; Ge, Mao-Fa

2012-10-25

398

Methanesulfinic acid reaction with OH: mechanism, rate constants, and atmospheric implications.  

PubMed

The mechanism for the atmospheric oxidation of methanesulfinic acid (MSIA) has been studied. This is the first theoretical study of the reaction between MSIA and the OH radical. All the possible channels in this reaction have been studied theoretically, and their corresponding rate constants have been evaluated under the variational transition-state theory (VTST) formalism. Two different products can be formed: the CH3S(O)2 radical (which had been experimentally proposed as the only one), and sulfurous acid (H2SO3). The CH3S(O)2 radical can be formed directly or can form via an intermediate adduct, which yields to the radical through the elimination of a water molecule. For the first time, it is theoretically demonstrated that SO2 is formed in the addition channel of the DMS + OH reaction. The consequences of this result in the interpretation of the T-dependence of the SO4(2-)/MSA (methanesulfonic acid) quocient are analyzed. The competition between the unimolecular dissociation of the CH3S(O)2 radical and OH-addition to yield MSA is proposed as one of the possible multiple branching points (along the DMS + OH degradation scheme) influencing the T-dependence of the SO4(2-)/MSA relation. PMID:17636968

Gonzalez-García, Núria; Gonzalez-Lafont, Angels; Lluch, José M

2007-08-16

399

Generalized approximation to the reaction path: the formic acid dimer case.  

PubMed

A set of mass-weighted internal coordinates was derived and applied to the double proton transfer reaction in the formic acid dimer (FAD). The coordinate set was obtained starting from the Hirschfelder "mobile" by an optimization procedure consisting of a sequence of kinematic rotations. In FAD, the optimization procedure leads to three coordinates that do change significantly along the reaction path. These coordinates span the reaction space, whereas the remaining modes are treated in a harmonic approximation. The effect that the dimer dissociative motion has on the ground and excited vibrational states dynamics was explored. In the frequency region corresponding to the symmetric OH-stretch vibration four doublets have been identified with splittings of 2.76, 0.07, 0.60, and 4.03 cm(-1). PMID:18315029

Matanovi?, Ivana; Dosli?, Nadja; Johnson, Bruce R

2008-02-28

400

Generalized approximation to the reaction path: The formic acid dimer case  

NASA Astrophysics Data System (ADS)

A set of mass-weighted internal coordinates was derived and applied to the double proton transfer reaction in the formic acid dimer (FAD). The coordinate set was obtained starting from the Hirschfelder ``mobile'' by an optimization procedure consisting of a sequence of kinematic rotations. In FAD, the optimization procedure leads to three coordinates that do change significantly along the reaction path. These coordinates span the reaction space, whereas the remaining modes are treated in a harmonic approximation. The effect that the dimer dissociative motion has on the ground and excited vibrational states dynamics was explored. In the frequency region corresponding to the symmetric OH-stretch vibration four doublets have been identified with splittings of 2.76, 0.07, 0.60, and 4.03 cm-1.

Matanovi?, Ivana; Došli?, Nadja; Johnson, Bruce R.

2008-02-01

401

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

PubMed

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

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

2011-03-01

402

On the reaction of lupulones, hops ?-acids, with 1-hydroxyethyl radical.  

PubMed

Lupulones, hops ?-acids, are one of the main constituents of the hops resin and have an important contribution to the overall bacteriostatic activity of hops during beer brewing. The use of lupulones as natural alternatives to antibiotics is increasing in the food industry and also in bioethanol production. However, lupulones are easy oxidizable and have been shown to be very reactive toward 1-hydroxyethyl radical with apparent bimolecular rate constants close to diffusion control k = 2.9 × 10(8) and 2.6 × 10(8) L mol(-1) s(-1) at 25.0 ± 0.2 °C in ethanol-water solution (10% of ethanol (v/v)) as probed by EPR and ESI-IT-MS/MS spin-trapping competitive kinetics, respectively. The free energy change for an electron-transfer mechanism is ?G° = 106 kJ/mol as calculated from the oxidation peak potential experimentally determined for lupulones (1.1 V vs NHE) by cyclic voltammetry and the reported reduction potential for 1-hydroxyethyl radical. The major reaction products identified by LC-ESI-IT-MS/MS and ultrahigh-resolution accurate mass spectrometry (orbitrap FT-MS) are hydroxylated lupulone derivatives and 1-hydroxyethyl radical adducts. The lack of pH dependence for the reaction rate constant, the calculated free energy change for electron transfer, and the main reaction products strongly suggest the prenyl side chains at the hops ?-acids as the reaction centers rather than the ?,?'-triketone moiety. PMID:23031058

de Almeida, Natália E C; do Nascimento, Eduardo S P; Cardoso, Daniel R

2012-10-24

403

Integration of photoswitchable proteins, photosynthetic reaction centers and semiconductor/biomolecule hybrids with electrode supports for optobioelectronic applications.  

PubMed

Light-triggered biological processes provide the principles for the development of man-made optobioelectronic systems. This Review addresses three recently developed topics in the area of optobioelectronics, while addressing the potential applications of these systems. The topics discussed include: (i) the reversible photoswitching of the bioelectrocatalytic functions of redox proteins by the modification of proteins with photoisomerizable units or by the integration of proteins with photoisomerizable environments; (ii) the integration of natural photosynthetic reaction centers with electrodes and the construction of photobioelectrochemical cells and photobiofuel cells; and (iii) the synthesis of biomolecule/semiconductor quantum dots hybrid systems and their immobilization on electrodes to yield photobioelectrochemical and photobiofuel cell elements. The fundamental challenge in the tailoring of optobioelectronic systems is the development of means to electrically contact photoactive biomolecular assemblies with the electrode supports. Different methods to establish electrical communication between the photoactive biomolecular assemblies and electrodes are discussed. These include the nanoscale engineering of the biomolecular nanostructures on surfaces, the development of photoactive molecular wires and the coupling of photoinduced electron transfer reactions with the redox functions of proteins. The different possible applications of optobioelectronic systems are discussed, including their use as photosensors, the design of biosensors, and the construction of solar energy conversion and storage systems. PMID:22933337

Wang, Fuan; Liu, Xiaoqing; Willner, Itamar

2013-01-18

404

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

405

Graphene hybrids: nitrogen-doped graphene/carbon nanotube hybrids: in situ formation on bifunctional catalysts and their superior electrocatalytic activity for oxygen evolution/reduction reaction (small 11/2014).  

PubMed

The development of highly-active bifunctional catalysts at low cost for both oxygen reduction and oxygen evolution reactions are greatly required for fuel cells, metal-air batteries, and water splitting. As reported by Q. Zhang, F. Wei, and co-workers on page 2251, nitrogen-doped graphene/single-walled carbon nanotube hybrids exhibit very high activity for both the oxygen reduction reaction and oxygen evolution reaction, which opens up new avenues for energy conversion technologies based on earth-abundant, scalable, precious-metal-free catalysts. PMID:24895196

Tian, Gui-Li; Zhao, Meng-Qiang; Yu, Dingshan; Kong, Xiang-Yi; Huang, Jia-Qi; Zhang, Qiang; Wei, Fei

2014-06-01

406

Study of prototypical Diels-Alder reactions by a hybrid density functional/Hartree-Fock approach  

NASA Astrophysics Data System (ADS)

Kinetic and thermodynamic parameters for the Diels-Alder reactions of butadiene with ethylene, formaldehyde and thioformaldehyde have been computed by a density functional method (B3LYP) which incorporates gradient corrections and some Hartree-Fock exchange. Post Hartree-Fock computations have also been performed for comparison. The activation energies computed for the addition of C 2H 4 at the B3LYP and QCISD[T] levels approach the experimental value, whereas HF and MP2 approaches are not sufficiently reliable. The computed activation energy for H 2CO is close to that for C 2H 4 by the B3LYP approach, whereas it significantly decreases at MP2. QCISD[T] computations give an intermediate result. A low activation energy is computed for H 2CS, in agreement with observations that thioaldehydes and activated thioketones rapidly undergo hetero-Diels-Alder reactions at or below room temperature. The B3LYP result is closer to the QCISD[T] reference than the MP2 value. These trends have been interpreted by interactions between frontier orbitals or by energy partitioning based on natural bond orbitals.

Barone, Vincenzo; Arnaud, Roger

1996-03-01

407

Study of the kinetics and equilibria of the oligomerization reactions of 2-methylglyceric acid  

NASA Astrophysics Data System (ADS)

The presence of a variety of chemical species related to the gaseous precursor isoprene in ambient secondary organic aerosol (SOA) has stimulated investigations of the nature of SOA-phase chemical processing. Recent work has demonstrated that 2-methylglyceric acid (2-MG) is an important isoprene-derived ambient SOA component and atmospheric chamber experiments have suggested that 2-MG may exist in oligomeric form (as oligoesters) under conditions of low SOA water content. In order to better understand the thermodynamic and kinetic parameters of such oligomerization reactions, nuclear magnetic resonance techniques were used to study the bulk phase acid-catalyzed aqueous reactions (Fischer esterification) of 2-MG. While the present results indicate that 2-MG oligoesters are formed in the bulk phase with similar water content equilibrium dependences as observed in atmospheric chamber SOA experiments, the acid-catalyzed rate of the Fischer esterification mechanism may be too slow to rationalize the 2-MG oligoester production timescales observed in the atmospheric chamber experiments. Furthermore, it appears that unrealistically high ambient SOA acidities would also be required for significant 2-MG oligoester content to arise via Fischer esterification. Therefore, the present results suggest that other, more kinetically facile, esterification mechanisms may be necessary to rationalize the existence of 2-MG oligomers in atmospheric chamber-generated and ambient SOA.

Birdsall, A. W.; Zentner, C. A.; Elrod, M. J.

2012-11-01

408

Study of the kinetics and equilibria of the oligomerization reactions of 2-methylglyceric acid  

NASA Astrophysics Data System (ADS)

The presence of a variety of chemical species related to the gaseous precursor isoprene in ambient secondary organic aerosol (SOA) has stimulated investigations of the nature of SOA-phase chemical processing. Recent work has demonstrated that 2-methylglyceric acid (2-MG) is an important isoprene-derived ambient SOA component and atmospheric chamber experiments have suggested that 2-MG may exist in oligomeric form (as oligoesters) under conditions of low SOA water content. In order to better understand the thermodynamic and kinetic parameters of such oligomerization reactions, nuclear magnetic resonance techniques were used to study the bulk phase acid-catalyzed aqueous reactions (Fischer esterification) of 2-MG. While the present results indicate that 2-MG oligoesters are formed in the bulk phase with similar water content equilibrium dependences as observed in atmospheric chamber SOA experiments, the acid-catalyzed rate of the Fischer esterification mechanism may be too slow to rationalize the 2-MG oligoester production timescales observed in the atmospheric chamber experiments. Furthermore, it appears that unrealistically high ambient SOA acidities would also be required for significant 2-MG oligoester content to arise via Fischer esterification. Therefore, the present results suggest that other, more kinetically facile, esterification mechanisms may be necessary to rationalize the existence of 2-MG oligomers in atmospheric chamber-generated and ambient SOA.

Birdsall, A. W.; Zentner, C. A.; Elrod, M. J.

2013-03-01

409

REACTION MECHANISMS OF 15-HYDROPEROXYEICOSATETRAENOIC ACID CATALYZED BY HUMAN PROSTACYCLIN AND THROMBOXANE SYNTHASES  

PubMed Central

Prostacyclin synthase (PGIS) and thromboxane synthase (TXAS) are atypical cytochrome P450s. They do not require NADPH or dioxygen for isomerization of prostaglandin H2 (PGH2) to produce prostacyclin (PGI2) and thromboxane A2 (TXA2). PGI2 and TXA2 have opposing actions on platelet aggregation and blood vessel tone. In this report, we use a lipid hydroperoxide, 15-hydroperoxyeicosatetraenoic acid (15-HPETE), to explore the active site characteristics of PGIS and TXAS. The two enzymes transformed 15-HPETE not only into 13-hydroxy-14,15-epoxy-5,8,11-eicosatrienoic acid (13-OH-14,15-EET), like many microsomal P450s, but also to 15-ketoeicosatetraenoic acid (15-KETE) and 15-hydroxyeicosatetraenoic acid (15-HETE). 13-OH-14,15-EET and 15-KETE result from homolytic cleavage of the O–O bond, whereas 15-HETE results from heterolytic cleavage, a common peroxidase pathway. About 80% of 15-HPETE was homolytically cleaved by PGIS and 60% was homolytically cleaved by TXAS. The Vmax of homolytic cleavage is 3.5-fold faster than heterolytic cleavage for PGIS-catalyzed reactions (1100 min?1 vs. 320 min?1) and 1.4-fold faster for TXAS (170 min?1 vs. 120 min?1). Similar KM values for homolytic and heterolytic cleavages were found for PGIS (?60 ?M 15-HPETE) and TXAS (?80 ?M 15-HPETE), making PGIS a more efficient catalyst for the 15-HPETE reaction.

Yeh, Hui-Chun; Tsai, Ah-Lim; Wang, Lee-Ho

2007-01-01

410

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

USGS Publications Warehouse

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

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

1993-01-01

411

Resonance Rayleigh scattering study of the reaction of nucleic acids with thionine and its analytical application  

NASA Astrophysics Data System (ADS)

Resonance Rayleigh scattering (RRS) of the thionine (TH)-nucleic acids system and its analytical application have been studied. In pH 2.2 acidic buffer medium, some nucleic acids can react with TH to form TH-nucleic acids complex. This results in a great enhancement of RRS and the appearance of new RRS spectra. The RRS spectral characteristics of TH-ctDNA system, the affecting factors and the optimum conditions of the reaction have been investigated. The enhancement of the RRS signal is directly proportional to the concentration of nucleic acids in the range 0-10.0 ?g/ml for calf thymus DNA and 0-15.0 ?g/ml for yeast RNA, and its detection limits (3?) are 3.5 ng/ml for calf thymus DNA and 4.9 ng/ml for yeast RNA, respectively. The method shows a wide linear range and high sensitivity, and was applied to the determination of trace amounts of nucleic acid in synthetic samples and practical samples with satisfactory results. The bind properties for the interactions of TH with ctDNA were investigated using a Scatchard plot based on the measurement of the enhanced RRS data at 340 nm, and the binding number and intrinsic binding constant are 4.9 and 2.6×10 5 mol/dm 3, respectively.

Long, Xiufen; Bi, Shuping; Tao, Xiancong; Wang, Yongzhong; Zhao, Hong

2004-01-01

412

Humic acids and methylated humic acids as models for reactions of brown coal with CO\\/H 2O and with H 2  

Microsoft Academic Search

Humic acid derived from Loy Yang coal and the product of mild O-methylation of this humic acid have been reacted with CO\\/H2O\\/sodium aluminate (NaAlO2) and H2\\/Ni\\/Mo in 35ml autoclaves at 365°C and 400°C. The O-methylated humic acid gave lower conversions for CO\\/H2O\\/NaAlO2 reactions than the original humic acid but similar conversions for H2\\/Ni\\/Mo reactions. These results provide strong evidence in

L. M Clemow; G Favas; W. R Jackson; M Marshall; A. F Patti; P. J Redlich

1999-01-01

413

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

414

Survivability and abiotic reactions of selected amino acids in different hydrothermal system simulators.  

PubMed

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. PMID:23625039

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

2013-04-01

415

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

416

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.

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

2010-01-01

417

Quantitative 16S rDNA-targeted polymerase chain reaction and oligonucleotide hybridization for the detection of Paenibacillus azotofixans in soil and the wheat rhizosphere  

Microsoft Academic Search

A molecular method for the detection of Paenibacillus azotofixans in soil and the wheat rhizosphere was developed. The system consisted of polymerase chain reaction (PCR) amplification of part of the variable V1 to V4 regions of the 16S ribosomal RNA gene, followed by hybridization with a specific oligonucleotide probe homologous to part of the intervening region. In vitro specificity tests

A. S. Rosado; L. Seldin; A. C. Wolters; J. D. van Elsas

1996-01-01

418

An ultrasensitive biosensor for DNA detection based on hybridization chain reaction coupled with the efficient quenching of a ruthenium complex to CdTe quantum dots.  

PubMed

A highly sensitive and selective DNA biosensor based on hybridization chain reaction is described, which combines CdTe quantum dots (QDs) and a ruthenium complex. Based on the variation of fluorescence signals of the CdTe QDs, the target DNA is determined. PMID:23863907

Liu, Yufei; Luo, Ming; Yan, Ji; Xiang, Xia; Ji, Xinghu; Zhou, Guohua; He, Zhike

2013-08-28

419

Synthesis and biological evaluation of hybrids from farnesylthiosalicylic acid and hydroxylcinnamic acid with dual inhibitory activities of Ras-related signaling and phosphorylated NF-?B.  

PubMed

A series of hybrids (5a–r) of farnesylthiosalicylic acid (FTS) and hydroxylcinnamic acid were designed and synthesized. Most of the hybrids displayed potent antiproliferative activity against seven cancer cell lines in vitro, superior to FTS as well as sorafenib. The most potent compound 5f selectively inhibited cancer cells but not non-tumor liver cell proliferation in vitro, and significantly induced SMMC-7721 cell apoptosis. Interestingly, 5f could simultaneously inhibit not only Ras-related signaling but also phosphorylated NF-?B, which may synergetically contribute to the cell growth inhibition and apoptosis induction. Moreover, 5f showed low acute toxicity to mice and significantly inhibited the hepatoma tumor growth. PMID:24848877

Ling, Yong; Wang, Zhiqiang; Wang, Xuemin; Zhao, Ying; Zhang, Wei; Wang, Xinyang; Chen, Li; Huang, Zhangjian; Zhang, Yihua

2014-07-01

420

Hybrid NS ligands supported Cu(I)/(II) complexes for azide-alkyne cycloaddition reactions.  

PubMed

Three copper complexes of nitrogen-sulfur donor ligands, [CuBr?(L1)] (1), [CuCl?(L2)?] (2) and [Cu?I?(L3)]n (3) (L1 = bis(2-cyclohexylsulfanylethyl)amine, L2 = 2-(benzylsulfanylmethyl)pyridine and L3 = 2-(4-pyridylsulfanylmethyl)pyridine), have been synthesized and characterized by single-crystal X-ray diffraction (XRD), powder XRD and TGA analysis. Complexes 1 and 2 are mononuclear Cu(II) complexes and are EPR active with distorted square-pyramidal and octahedral geometry, respectively. Complex 3 is a two-dimensional tetrahedral Cu(I) coordination polymer with 16- and 20-membered metallocycles. These complexes show good catalytic activities for one-pot azide-alkyne cycloaddition reactions in CH?OH-H?O. PMID:23817835

Bai, Shi-Qiang; Jiang, Lu; Zuo, Jing-Lin; Hor, T S Andy

2013-08-21

421

Pulse radiolysis studies on reactions of ?-hydroxyalkyl radicals with nicotinamide and 6-methyl nicotinic acid  

NASA Astrophysics Data System (ADS)

Reactions of ?-hydroxyalkyl radicals derived from 2-propanol, ethanol and methanol with nicotinamide (NICAM) and 6-methyl nicotinic acid (6-MNA) were studied at various pHs using pulse radiolysis technique. It is found that ?-hydroxyalkyl radicals react with NICAM and 6-MNA at pHs when nitrogen is in the protonated state. In these reactions, radical adducts of NICAM/6-MNA with ?-hydroxyalkyl radicals are formed which have absorption maxima at about 340-350 nm which subsequently decay to give pyridinyl type of radicals of NICAM and 6-MNA having ?max at 410 nm. Rate constants for the reactions of (CH3)2Crad OH, CH3Crad HOH and rad CH2OH radicals with NICAM and 6-MNA were found to have linear dependence on reduction potentials of corresponding ?-hydroxyalkyl radicals. Adducts formed in the reactions of CH3Crad HOH and rad CH2OH radicals with both NICAM and 6-MNA decayed slowly compared to the decay of adduct formed in reactions with (CH3)2Crad OH radicals.

Dhiman, S. B.; Naik, D. B.

2012-06-01

422

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

423

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

424

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

425

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