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1

Planar waveguide biosensors for nucleic acid hybridization reactions  

NASA Astrophysics Data System (ADS)

Oligonucleotide probes derived from (1) the T3 RNA polymerase promoter sequence (T3) and (2) prostate-specific antigen messenger RNA (PSA) were prepared and labeled with a red-emitting fluorescent dye (Cy5). The complimentary oligonucleotides were prepared and labeled with biotin. Initially, a feasibility study was performed in which the hybridization rate of the T3/anti T3 Oligonucleotide pair was examined. Specifically, biotinylated anti T3 was immobilized to a neutravidin-coated waveguide and solutions containing increasing concentrations of Cy5-labeled T3 were injected into the biosensor. Fluorescence emission was detected with an evanescent wave imaging fluorometer. The hybridization reaction proceeded rapidly with a significant amount of binding occurring during the first 5 minutes. A Michaelis-Menton kinetics model was used to analyze hybridization rate data and gave values of 78 nanomolar for the apparent affinity of the hybridization reaction and 1.4 picomolar for the analytical sensitivity of the hybridization assay. In subsequent studies the hybridization rate of the PSA/anti PSA oligonucleotide pair was examined. Biotinylated anti PSA was immobilized to the waveguide and solutions containing increasing concentration of Cy5-labeled PSA were injected into the biosensor. The hybridization rate observed for formation of the PSA/anti PSA pari was comparable to the high rates observed for the T3/anti T3 pari. Lastly, the selectivity of the biosensor was examined using an Oligonucleotide probe derived from human glandular kallikrein, which exhibits a high degree of homology to PSA. The two Oligonucleotide probes only differed in 7 out of 20 positions. Interestingly, the hybridization rate observed for Cy5-labeled hGK was very low - not statistically different from the non-specific binding rate of the hybridization assay.

Herron, James N.; zumBrunnen, Stacy; Wang, Jian-xun; Gao, Xiao-lin; Wang, Hsu-Kun; Terry, Allen H.; Christensen, Douglas A.

2000-04-01

2

Planar waveguide biosensors for nucleic acid hybridization reactions  

Microsoft Academic Search

Oligonucleotide probes derived from (1) the T3 RNA polymerase promoter sequence (T3) and (2) prostate-specific antigen messenger RNA (PSA) were prepared and labeled with a red-emitting fluorescent dye (Cy5). The complimentary oligonucleotides were prepared and labeled with biotin. Initially, a feasibility study was performed in which the hybridization rate of the T3\\/anti T3 Oligonucleotide pair was examined. Specifically, biotinylated anti

James N. Herron; Stacy zumBrunnen; Jian-xun Wang; Xiao-lin Gao; Hsu-Kun Wang; Allen H. Terry; Douglas A. Christensen

2000-01-01

3

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

4

A simple nucleic acid hybridization\\/latex agglutination assay for the rapid detection of polymerase chain reaction amplicons  

Microsoft Academic Search

We have developed a new method for the detection of nucleic acid hybridization, based on a simple latex agglutination test that can be evaluated by the unaided eye. Nucleic acid, e.g., a polymerase chain reaction (PCR) product, is denatured and incubated with polystyrene beads carrying covalently bound complementary oligonucleotide sequences. Hybridization of the nucleic acids leads to aggregation of the

Sabine Vollenhofer-Schrumpf; Ronald Buresch; Manfred Schinkinger

2007-01-01

5

A rapid method for detection and identification of flaviviruses by polymerase chain reaction and nucleic acid hybridization  

Microsoft Academic Search

Summary A polymerase chain reaction (PCR) technique was developed and evaluated for the detection of flaviviruses. A set of sense and antisense oligomeric DNA primers were constructed from nucleotide sequences of the conserved region of the genome of several different flaviviruses. Virus specific complementary DNA (cDNA) was prepared by reverse transcription of total RNA extracted from infected cell cultures. Amplified

B. Puri; E. A. Henchal; J. Burans; K. R. Porter; W. Nelson; D. M. Watts; C. G. Hayes

1994-01-01

6

Factors affecting detection of PVY in dormant tubers by reverse transcription polymerase chain reaction and nucleic acid spot hybridization  

Microsoft Academic Search

A reverse transcription polymerase chain reaction (RT-PCR) protocol was developed using two 20-mer primers located in nuclear inclusion genes NIa and NIb of potato virus Y (PVY). A 1017 bp PCR-product was detected in dormant potato tubers, infected with PVYO, but not in tubers from healthy plants. The PCR product was specific to PVY, as determined by Southern blot detection

Mathuresh Singh; Rudra P. Singh

1996-01-01

7

Nucleic Acids Hybridization: Potentials and Limitations  

Microsoft Academic Search

Several nucleic acids hybridization-based approaches, such as microarray, competitive genomic, and Southern or Northern blot\\u000a hybridization, have become popular tools for specialists in biochemistry and in biomedicine, and are now in routine use. However,\\u000a the potential of in-solution nucleic acids hybridization-based experimental techniques seems to be underestimated now. Examples\\u000a are subtractive hybridization (SH), which allows one to efficiently find differences

ANTON A. BUZDIN

8

Signal enhancement for gene detection based on a redox reaction of [Fe(CN)(6)](4-) mediated by ferrocene at the terminal of a peptide nucleic acid as a probe with hybridization-amenable conformational flexibility.  

PubMed

Electrochemically enhanced DNA detection was demonstrated by utilizing the couple of a synthesized ferrocene-terminated peptide nucleic acid (PNA) with a cysteine anchor and a sacrificial electron donor [Fe(CN)(6)](4-). DNA detection sensors were prepared by modifying a gold electrode surface with a mixed monolayer of the probe PNA and 11-hydroxy-1-undecanethiol (11-HUT), protecting [Fe(CN)(6)](4-) from any unexpected redox reaction. Before hybridization, the terminal ferrocene moiety of the probe was subject to a redox reaction due to the flexible probe structure and, in the presence of [Fe(CN)(6)](4-), the observed current was amplified based on regeneration of the ferrocene moiety. Hybridization decreased the redox current of the ferrocene. This occurred because hybridization rigidified the probe structure: the ferrocene moiety was then removed from the electrode surface, and the redox reaction of [Fe(CN)(6)](4-) was again prevented. The change in the anodic current before and after hybridization was enhanced 1.75-fold by using the electron donor [Fe(CN)(6)](4-). Sequence-specific detection of the complementary target DNA was also demonstrated. PMID:18614839

Aoki, Hiroshi; Tao, Hiroaki

2008-07-01

9

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

10

Nucleic Acid Hybridization Detected by Piezoelectric Resonance  

Microsoft Academic Search

Ordinary AT-cut, quartz, piezoelectric crystals as commonly used in watches, radios, computers, etc., were used to detect the hybridization of complementary strands of synthetic RNA's. The method is based on the large absolute mass increase accompanying hybridization. Nucleic acid strands were covalently attached to the polymer-modified surface of a piezoelectric crystal. When these immobilized probe strands were melted and then

Newton C. Fawcett; Jeffrey A. Evans; Liang-Chy Chien; Naomi Flowers

1988-01-01

11

MOLECULAR HYBRIDIZATION TECHNIQUES OF NUCLEIC ACIDS  

Microsoft Academic Search

The nucleic acid hybridization is the process wherein two DNA or RNA single chains (mono-stranded) from different biological sources, make the double catenary configuration, based on contingent sequence homology of the two sources, resulting DNA-DNA, RNA-RNA or DNA-RNA hybrids. The purpose is identification or localization of certain nucleic acid sequences (genes) in the genome of some species. The target molecule

Vasilica BARBU

2007-01-01

12

Detection of nucleic acid hybrids by prolonged chemiluminescence  

SciTech Connect

A method for determining a particular single stranded polynucleotide sequence in a test medium, comprising the steps of: (a) immobilizing on a solid support single stranded nucleic acids in the test medium, (b) contacting the immobilized nucleic acids with a polynucleotide probe having a base sequence substantially complementary to the sequence to be determined and the contacting being under conditions favorable to hybridization between the probe and the sequence to be determined, wherein the probe is labeled with a chemiluminescence enhancer, (c) separating the immobilized hybrids from the unhybridized probe, (d) initiating a chemiluminescent reaction by contacting the separated, labeled, immobilized hybrids with an oxidant, a 2.3-dihydro-1,4-phthalazinedione chemiluminescence precursor, and a peroxidase enzyme, (e) detecting the resulting light emission, and (f) relating the amount of emitted light to the amount of the single stranded polynucleotide sequence.

Dattagupta, N.; Clemens, A.H.

1988-12-27

13

Free energies for acid attack reactions of lithium cobaltate.  

SciTech Connect

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

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

2008-01-01

14

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

15

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?

16

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

Code of Federal Regulations, 2010 CFR

... Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle... Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle...as alkenedioic acid, dialkyl ester, reaction products with...

2009-07-01

17

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

PubMed

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

Dutta, Subrata; Fülöp, Annabelle; Mokhir, Andriy

2013-09-03

18

Hybridization and sequencing of nucleic acids using base pair mismatches  

SciTech Connect

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

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

2001-01-01

19

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...

20

Soil Reaction and Acidic Deposition.  

National Technical Information Service (NTIS)

The chapter discusses the major chemical processes by which acidic deposition interacts with soils. The 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...

J. O. Reuss P. M. Walthall

1990-01-01

21

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

22

Hybridization properties of immobilized nucleic acids.  

PubMed Central

The 5'-end attachment of oligonucleotides to dextran supports facilitates the study of the hybridization properties of an immobilized oligonucleotide system. The hybridization properties which were studied include: hybridization capacity and kinetics, hybridization-complex stability, and reagents influencing hybridization efficiency. Results of these experiments reveal that the hybridization efficiencies of support-bound oligonucleotides were 75-80% and 40-50% for single-stranded oligonucleotide targets and long double-stranded targets, respectively. These hybridization efficiencies are dependent upon prehybridizing the support-bound oligonucleotides with dextran sulfate. In addition, comparisons of the relative hybridization efficiencies of the support-bound oligonucleotide and nitrocellulose-based systems have been made which indicate a retention of 13-28% of target sequences on the filters and a detection efficiency of 8-20%.

Gingeras, T R; Kwoh, D Y; Davis, G R

1987-01-01

23

Detection of Hybrid Formation between Peptide Nucleic Acids and DNA by Fluorescence Polarization in the Presence of Polylysine  

Microsoft Academic Search

A new method for the detection of PNA\\/DNA hybrids is presented. In this method, short PNA probes (9–13 mer) are labeled with a fluorescent dye and allowed to hybridize to target DNA molecules. A cationic polyamino acid, such as polylysine, is then added to the reaction mixture, whereupon the DNA molecules bind electrostatically to this polycation. The PNA probes, which

Theo T. Nikiforov; Sang Jeong

1999-01-01

24

Acetone condensation reaction on acid catalysts  

SciTech Connect

The condensation reaction of acetone on alumina and acid zeolites has been followed by FTIR. Under identical conditions, the reaction rate is faster on alumina, and the condensation goes beyond the formation of mesityl oxide. Zeolites without nonframework aluminum are poor catalysts. On HZSM-5 the reaction is about two orders of magnitude slower than on USY at 105 C. From these data, it appears that Lewis sites, even if they bound acetone less energetically than Broensted sites, are responsible for the activation of the molecule. On alumina, the reaction would take place between gas phase acetone and acetone adsorbed on Lewis sites. On zeolites with nonframework aluminum and, thus, with Lewis sites, the reaction would involve acetone molecules adsorbed on Broensted and Lewis sites, the activation occurring on the Lewis site.

Panov, A.G.; Fripiat, J.J. [Univ. of Wisconsin, Milwaukee, WI (United States)

1998-08-15

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

Quinolinic acid, ?-picolinic acid, fusaric acid, and 2,6-pyridinedicarboxylic acid enhance the Fenton reaction in phosphate buffer  

Microsoft Academic Search

Quinolinic acid, ?-picolinic acid, fusaric acid, and 2,6-pyridinedicarboxylic acid enhanced the Fenton reaction in phosphate buffer, respectively. The enhancement by quinolinic acid, ?-picolinic acid, fusaric acid, and 2,6-pyridinedicarboxylic acid of the Fenton reaction may be partly related to their respective actions in the biological systems such as a neurotoxic effect (quinolinic acid), a marked growth-inhibitory action on rice seeding (?-picolinic

Hideo Iwahashi; Hiroyuki Kawamori; Kazuaki Fukushima

1999-01-01

27

The reaction of unsaturated fats with the acid hematein test  

Microsoft Academic Search

The reaction of saturated and unsaturated oils and fatty acids was examined in vitro with the Baker's acid hematein test. It has been found that oils whose molecules contain fatty acid components of two or more double bonds give a positive reaction with the acid hematein technique. The intensity of the reaction runs parallel with the number of double bonds.

L. Holczingee

1964-01-01

28

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

NASA Astrophysics Data System (ADS)

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

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

29

Reactions of tetraphenyltitanium with organic acids  

SciTech Connect

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

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

1987-12-10

30

Nucleic acid hybridization in the diagnosis of viral infections.  

PubMed

Recombinant DNA technology, including molecular cloning and nucleic acid hybridization, is now being applied to problems in clinical virology. Although viral isolation in cell culture remains the most sensitive and specific diagnostic test for many viruses, for some viruses, isolation in cell culture is lengthy or difficult or has not yet been achieved. Utilization of hybridization techniques has already resulted in important new information concerning the pathogenesis of a number of viruses, such as Epstein-Barr virus, hepatitis B virus, and human papillomavirus. In addition, time to diagnosis for viruses such as cytomegalovirus, Epstein-Barr virus, and varicella-zoster virus can be significantly shortened to 36 to 48 hours, a great improvement over standard isolation with obvious importance for patient management. Hybridization techniques have also been applied to screening of antiviral agents. Although results of studies to date have been encouraging, significant problems remain to be solved before these techniques can be applied in a routine diagnostic laboratory. First, more sensitive assays must be developed. One approach is the generation of probes with higher specific activities. Synthesis of single-stranded probes using recombinant M13 bacteriophage as a template results in probes of higher specific activities that also cannot re-anneal to themselves because they are not complementary. Thus, more probe is available to anneal to sample DNA. Synthesis of cRNA probes that form more stable hybrids with DNA is another approach that is receiving attention. A second problem is reagent safety and stability. The most sensitive and commonly used label in the studies reviewed in this article has been 32P. With its half-life of 2 weeks, potential hazards to personnel, and disposal problems, it is probably not suitable for clinical laboratories. A major step in the development of nonradioactive, stable probes has been synthesis of biotinylated nucleotide analogues that can be efficiently incorporated into DNA or RNA. Biotinylated probes are stable for 1 to 2 years at -20 degrees C, and their use obviates the need for autoradiography, thus shortening reaction times. In addition, very high concentrations of probes can be used without the background problems encountered with radiolabels. To date, biotinylated probes have been significantly less sensitive than those labeled with 32P, but continued efforts to improve sensitivity have yielded promising results.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:3899479

Landry, M L; Fong, C K

1985-09-01

31

Heterogeneous reactions of epoxides in acidic media.  

PubMed

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

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

2012-03-02

32

Electric field directed nucleic acid hybridization on microchips  

Microsoft Academic Search

Selection and adjustment of proper physical parameters enables rapid DNA transport, site selective concentration, and accelerated hybridization reactions to be carried out on active microelectronic arrays. These physical parameters include DC current, voltage, solution conductivity and buffer species. Generally, at any given current and voltage level, the transport or mobility of DNA is inversely proportional to electrolyte or buffer conductivity.

Carl F. Edman; Daniel E. Raymond; David J. Wu; Eugene Tu; Ronald G. Sosnowski; William F. Butler; Michael Nerenberg; Michael J. Heller

1997-01-01

33

Thermodynamic comparison of PNA\\/DNA and DNA\\/DNA hybridization reactions at ambient temperature  

Microsoft Academic Search

The thermodynamics of 13 hybridization reactions between 10 base DNA sequences of design 5''''- ATGCXYATGC-3' ''' with X, Y = A, C, G, T and their complementary PNA and DNA sequences were deter- mined from isothermal titration calorimetry (ITC) measurements at ambient temperature. For the PNA\\/ DNA hybridization reactions, the binding constants range from 1.8 × × × × 106

Frederick P. Schwarz; Scott Robinson; John M. Butler

1999-01-01

34

Topological constraints in nucleic acid hybridization kinetics  

PubMed Central

A theoretical examination of kinetic mechanisms for forming knots and links in nucleic acid structures suggests that molecules involving base pairs between loops are likely to become topologically trapped in persistent frustrated states through the mechanism of ‘helix-driven wrapping’. Augmentation of the state space to include both secondary structure and topology in describing the free energy landscape illustrates the potential for topological effects to influence the kinetics and function of nucleic acid strands. An experimental study of metastable complementary ‘kissing hairpins’ demonstrates that the topological constraint of zero linking number between the loops effectively prevents conversion to the minimum free energy helical state. Introduction of short catalyst strands that break the topological constraint causes rapid conversion to full duplex.

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

2005-01-01

35

Nucleic Acid Hybridization with RNA Immobilized on Filter Paper  

PubMed Central

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

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

1972-01-01

36

[Preparation of organic-inorganic hybrid boronate affinity monolith via thiol-ene click reaction for specific capture of glycoproteins].  

PubMed

A novel strategy for the preparation of the organic-inorganic hybrid boronate affinity monolith was developed via the "thiol-ene" click reaction. A thiol group-modified silica monolith was first synthesized via the sol-gel process by the in situ co-condensation with tetramethoxysilane (TMOS) and 3-mercaptopropyltrimethoxysilane (MPTMS) as precursors. Then 3-acrylamidophenylboronic acid (AAPBA) was covalently immobilized on the hybrid monolith via the "thiol-ene" click reaction to form AAPBA-silica hybrid affinity monolith. The reaction conditions for the preparation of AAPBA-silica hybrid affinity monolith were optimized, including the ratio of TMOS to MPTMS, the contents of poly(ethylene glycol) (PEG) and methanol. The morphology and mechanical stability of the boronate affinity monolith were characterized and evaluated by scanning electron microscopy and Fourier-transform infrared spectroscopy. The obtained boronate affinity hybrid monolith exhibited excellent specificity toward the nucleosides containing cis-diols under neutral conditions. It was further applied to the specific capture of the glycoproteins ovalbumin and horseradish peroxidase. The method is novel and reliable, which has a great potential for the preparation of different kinds of the boronate affinity monoliths. PMID:24063191

Yang, Fan; Mao, Jie; He, Xiwen; Chen, Langxing; Zhang, Yukui

2013-06-01

37

Terbium(III)-containing organic–inorganic hybrids synthesized through hydrochloric acid catalysis  

Microsoft Academic Search

Organic–inorganic hybrids incorporating Tb(acac)3·3H2O (where acac is acetylacetonate) were synthesized via conventional hydrolysis sol–gel reaction in the presence and absence of an acid catalyst (hydrochloric acid, HCl). The host framework of these materials, named di-ureasils, is formed by polyether-based chains grafted to both ends to a siliceous backbone through urea cross-linkages (–NHC(CO)NH–). Four different concentrations of HCl (0.5, 1.0, 1.5,

P. P. Lima; R. A. S. Ferreira; S. A. Júnior; O. L. Malta; L. D. Carlos

2009-01-01

38

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

Microsoft Academic Search

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

John J. Kelly; Boris K. Chernov; Igor Tovstanovsky; Andrei D. Mirzabekov; Sergei G. Bavykinb

2002-01-01

39

Method for increasing the sensitivity of nucleic acid hybridization assays  

SciTech Connect

A hybridization assay method is described for detecting a specific polynucleotide target sequence wherein a nucleic acid containing target sample in single stranded form is affixed to a support. It is contacted thereon under hybridizing conditions with a non-radioactive reporter group labeled single-stranded polynucleotide probe having a sequence complementary to the target sequence, the probe being bound to the affixed sample when the target is present. The probe hybridizer with the target sequence, then the unbound portion of the probe is removed from the support, and the presence of the probe is detected by means of its reporter group, wherein the sensitivity of the assay is increased by employing the additional steps comprising: (a) after removal of the unbound portion of the probe, dehybridizing the bound portion; (b) concentrating the dehybridized separated probe onto a solid support; and (c) detecting the presence of the probe on the solid support by means of the non-radioactive reporter group.

Heller, M.J.

1989-04-25

40

Application of Highly Efficient, Recyclable Organic–Inorganic Hybrid Material Immobilized Palladium Catalyst in Amine? and Phosphine?Free Suzuki–Miyaura Reaction  

Microsoft Academic Search

Palladium immobilized on organic–inorganic (silica?gel) hybrid materials behaves as a very efficient heterogeneous catalyst in the Suzuki–Miyaura coupling reaction. Aryl iodides, bromides, and activated chlorides, coupled with organoboronic acids (Suzuki–Miyaura reaction), smoothly afford the corresponding cross?coupling products in excellent yields under phosphine?free and amine?free reaction conditions in the presence of 3?aminopropyl functionalized silica?gel immobilized palladium (silica?APTS?Pd) as catalyst. Furthermore, the

Liyuan Zhang; Lei Wang; Hongji Li; Pinhua Li

2008-01-01

41

Catalyzed oxidation reactions. IV. Picolinic acid catalysis of chromic acid oxidations  

Microsoft Academic Search

Picolinic acid and several closely related acids are effective catalysts in the chromic acid oxidation of primary and secondary alcohols; the oxidation of other substrates is accelerated only moderately. The reaction is first order in chromium-(VI), alcohol, and picolinic acid; it is second order in hydrogen ions at low acidity and approaches acidity independence at high perchloric acid concentrations. A

Jan Rocek; T. Y. Peng

1977-01-01

42

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

Code of Federal Regulations, 2013 CFR

...New Uses for Specific Chemical Substances § 721...acid, dialkyl ester, reaction products with polyaminocarbomonocycle...generic). (a) Chemical substance and significant...reporting . (1) The chemical substances identified...acid, dialkyl ester, reaction products with...

2013-07-01

43

Hybrid material polyvinyl alcohol-stannic acid/stannic oxide  

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

44

Organic acid induced olefination reaction of lactones.  

PubMed

(Z)-Selective olefination of several lactones with ketene silyl acetals was achieved by the catalysis of carbon acids (C-H acids) having a bis(triflyl)methyl group as an acidic functionality; in particular, the triple carbon acid having three bis(triflyl)methyl groups in phloroglucinol shows an excellent catalytic performance. PMID:22850596

Yanai, Hikaru; Taguchi, Takeo

2012-07-31

45

Detection of dengue virus RNA using nucleic acid hybridization.  

PubMed

Conditions for using slot-blot nucleic acid hybridization to quantitatively detect dengue-2 virus using a radiolabelled cDNA probe, pVV17, were determined. As little as 11 plaque-forming units of virus were detected using a hybridization mixture without formamide and performing the test at 70 degrees C. While predominantly serotype-specific using stringent (65 degrees C) washing conditions, the probe detected all four dengue virus serotypes using astringent (28 degrees C) washing conditions. No significant qualitative differences were detected using Thai dengue-2 viruses isolated over a 10-year period. High titered, anti-flavivirus antibodies blocked virus detection by an antigen capture, enzyme-linked, immunosorbent assay or by intrathoracic inoculation of Toxorhyncites mosquitoes, but not by nucleic acid hybridization. The appearance of virus-specified RNA coincided with the detection of antigen in infected C6/36 (Aedes albopictus) cells by immunofluorescence, or in cell culture supernatants by the antigen capture method. The method has potential as a diagnostic tool for identifying dengue viruses in clinical and field specimens. PMID:2881940

Henchal, E A; Narupiti, S; Feighny, R; Padmanabhan, R; Vakharia, V

1987-02-01

46

Real-time assays with molecular beacons and other fluorescent nucleic acid hybridization probes  

Microsoft Academic Search

Background: A number of formats for nucleic acid hybridization have been developed to identify DNA and RNA sequences that are involved in cellular processes and that aid in the diagnosis of genetic and infectious diseases. Methods: The introduction of hybridization probes with interactive fluorophore pairs has enabled the development of homogeneous hybridization assays for the direct identification of nucleic acids.

Salvatore A. E. Marras; Sanjay Tyagi; Fred Russell Kramer

2006-01-01

47

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

48

AcidBase Reactions in Gas Transfer: A Mathematical Approach  

Microsoft Academic Search

Acid-base reactions occur simultaneously with gas transfer reactions in several common applications in water and wastewater treatment. A simple methodology to account quantitatively for the effects of the acid-base reactions on the gas transfer rate was developed, checked by comparison with laboratory data, and applied to an actual drinking water problem situation. Equations for application to a variety of gas-liquid

Kerry J. Howe; Desmond F. Lawler

1989-01-01

49

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

Microsoft Academic Search

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

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

2005-01-01

50

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

Microsoft Academic Search

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

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

2005-01-01

51

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

52

Application of the ritter reaction to petroselinic acid  

Microsoft Academic Search

Substituted amidostearic acids were prepared from petroselinic acid by reaction, in the presence of sulfuric acid, with hydrogen\\u000a cyanide, acetonitrile, propionitrile, acrylonitrile and benzonitrile. The products were crystalline solids. Attempts to obtain\\u000a monoamides containing a nitrile group by the use of dinitriles were unsuccessful.

R. L. Holmes; J. P. Moreau; G. Sumrell

1965-01-01

53

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

PubMed Central

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

Palmer, L M; Colwell, R R

1991-01-01

54

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

PubMed

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

Balaram, Padmanabhan

2010-01-01

55

Taxonomy of the Neisseriae: Deoxyribonucleic Acid Base Composition, Interspecific Transformation, and Deoxyribonucleic Acid Hybridization  

Microsoft Academic Search

Deoxyribonucleic acid (DNA) base composition, intergenic transformation efficiency, and DNA hybridization were used to determine the relatedness of a variety of established or proposed species of Neisseria and Branhamella. These studies indicated that these bacteria form three genetic groupings. Group I, comprised of N. meningitidis, N. gonorrhoeae, N. subflava, N. flava, N. perflava, N. sicca, N. mucosa, N. cinerea, N.

CAROLYN HOKE; NEYLAN A. VEDROS

1982-01-01

56

Reactions of anhydrides of phosphonothioic acids with triethyl phosphite  

SciTech Connect

This paper investigates the properties of anhydrides of phosphorus acids by studying the reaction of the anhydride of cyclohexylphosphonothioic acid with triethyl phosphite by means of P 31 NMR spectroscopy. The reaction takes a complex course; reaction scarcely went at all in 1 hour at 120 C in chlorobenzene. The physical constants and IR and P 31 NMR spectra of the acid esters prepared in different ways proved to be identical. They are liquids, soluble in most organic solvents. The P 31 NMR spectra of O-ethyl hydrogen cyclohexyl-phosphonate and -phosphonothioate gives signals at 31 and 96 ppm respectively.

Andreev, N.A.; Grishina, O.N.

1985-05-01

57

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

58

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

59

Hybrid-Dependent Effect of Lactic Acid on Corn Starch Yields  

Microsoft Academic Search

Cereal Chem. 74(3):249-253 The effect of lactic acid on starch yields of different corn hybrids was determined by wet-milling 18 commercial corn hybrids at three levels of lactic acid. All 18 hybrid samples tested had higher starch yields when lactic acid was added to the steep solution, although the magnitude of the increased starch yields varied between 2.9 and 12.0%.

V. Singh; A. E. Haken; Y. X. Niu; S. H. Zou; S. R. Eckhoff

1997-01-01

60

An anaerobic reaction between lipoxygenase, linoleic acid and its hydroperoxides.  

PubMed

In an anaerobic system soya-bean lipoxygenase together with linoleic acid induces a structural rearrangement of 13-hydroperoxyoctadeca-cis-9-trans-11-dienoic acid leading to the formation of 13-oxotrideca-cis(trans)-9-trans-11-dienoic acid and n-pentane as well as 13-oxo-octadeca-9,11-dienoic acid. It is proposed that the 13-peroxyoctadeca-cis-9-trans-11-dienoic acid radical formed through hydrogen radical abstraction by the linoleic acid radical is the key intermediate for these reactions. PMID:5165730

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

1971-04-01

61

Iminodicarboxylic acids in the Murchison meteorite: Evidence of Strecker reactions  

NASA Astrophysics Data System (ADS)

?-Amino acids and ?-hydroxy acids are well known constituents of several carbonaceous meteorites. One proposed mechanism of their formation is the reactions of CN-, NH3, aldehydes and ketones in aqueous solution, a Strecker-like synthesis. Iminodicarboxylic acids, relatively unusual in molecular structure, are significant by-products of laboratory Strecker syntheses of ?-amino acids. It is therefore notable that an analogous suite of imino acids has not been reported in CM2 chondrites where amino and hydroxy acids are abundant. In this work, aqueous extracts of the Murchison meteorite were examined for the presence of imino acids; GC-MS and HPLC molecular analyses revealed a complex suite of such acids. With the exception of one of the seven-carbon members, all of the C4 through C7 imino acids were observed in Murchison. These observations suggest that the Strecker synthesis made, at least, some contribution to the formation of extraterrestrial amino acids.

Lerner, Narcinda R.; Cooper, George W.

2005-06-01

62

Heterogeneous Reactions On Mineral Dust Particles: Atmospheric Acids  

NASA Astrophysics Data System (ADS)

We report on laboratory experiments of heterogeneous reactions of atmospheric acids such as HNO3, HCl and CF3COOH on surrogates of suspended mineral dust particles. We have used model substrates such as polycrystalline CaCO3, Saharan and Arizona dust samples as well as Kaolinite powder. The rates of uptake, the reaction products and the reaction mechanisms have been studied in detail with special emphasis on the role of adsorbed H2O in regards to the reaction mechanism. The initial rates of uptake are large but saturate at increasing exposure to the acids. Atmospheric acids dissolve carbonate via carbonic acid into CO2 and H2O, the latter of which has not been detected for reaction with HCl, presumably because of the formation of a hygroscopic product (CaCl2). The reaction mechanism involves the formation of basic adsorption (reaction) sites which are maintained through the equilibrium CaCO3 + H2O ó Ca(OH)2 + CO2 which has been measured from rates of CO2 uptake. No reaction products have been observed on Kaolinite samples under conditions where significant amounts of HNO3 have been adsorbed. The uptake coefficients of the non-reactive adsorption are of the order of 0.2 and are independent of the amount of surface-bound H2O.

Santschi, Christian; Rossi, Michel J.

63

40 CFR 721.4385 - Hydrofluoric acid, reaction products with heptane.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 2009-07-01 false Hydrofluoric acid, reaction products with heptane...Substances § 721.4385 Hydrofluoric acid, reaction products with heptane...chemical substance identified as a hydrofluoric acid, reaction products...

2009-07-01

64

40 CFR 721.4385 - Hydrofluoric acid, reaction products with heptane.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Hydrofluoric acid, reaction products with heptane...Substances § 721.4385 Hydrofluoric acid, reaction products with heptane...chemical substance identified as a hydrofluoric acid, reaction products...

2010-07-01

65

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

Code of Federal Regulations, 2010 CFR

...2009-07-01 2009-07-01 false Hydrofluoric acid, reaction products with octane...Substances § 721.4461 Hydrofluoric acid, reaction products with octane...identified generically as a hydrofluoric acid, reaction products...

2009-07-01

66

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

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Hydrofluoric acid, reaction products with octane...Substances § 721.4461 Hydrofluoric acid, reaction products with octane...identified generically as a hydrofluoric acid, reaction products...

2010-07-01

67

40 CFR 721.9485 - Dimer acid/polymerized rosin amidoamine reaction product (generic).  

Code of Federal Regulations, 2010 CFR

...Dimer acid/polymerized rosin amidoamine reaction product (generic). 721.9485 ...Dimer acid/polymerized rosin amidoamine reaction product (generic). (a) Chemical...Dimer acid/polymerized rosin amidoamine reaction product (PMN P-99-0144) is...

2009-07-01

68

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

2011-06-06

69

Nucleophilic substitution reactions in 4-halonitro-pyrazolecarboxylic acids  

SciTech Connect

The reaction of 4-bromo-1-methyl-3-nitropyrazole-5- and 4-bromo-1-methyl-5-nitro-pyrazole-3-carboxylic acids with arylamines in aqueous solution in the presence of monovalent copper salts leads to the formation of 4-arylamino- and 4-hydroxy substituted nitropyrazolecarboxylic acids.

Manaev, Yu.A.; Perevalov, V.P.; Andreeva, M.A.; Stepanov, B.I.

1986-09-01

70

Perfluorinated resinsulfonic acid--a catalyst for certain organic reactions  

SciTech Connect

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

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

1986-09-10

71

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

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. 7 figs.

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

1997-04-01

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.

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

1997-01-01

74

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

75

Interactive Fluorophore and Quencher Pairs for Labeling Fluorescent Nucleic Acid Hybridization Probes  

Microsoft Academic Search

The use of fluorescent nucleic acid hybridization probes that generate a fluorescence signal only when they bind to their\\u000a target enables real-time monitoring of nucleic acid amplification assays. Real-time nucleic acid amplification assays markedly\\u000a improves the ability to obtain qualitative and quantitative results. Furthermore, these assays can be carried out in sealed\\u000a tubes, eliminating carryover contamination. Fluorescent nucleic acid hybridization

Salvatore A. E. Marras

2008-01-01

76

Fuel Cell Reaction in Super Acid Electrolytes.  

National Technical Information Service (NTIS)

The series of acids including HN(SO2 CF3)2 (CF2)4(SO3H)2, n-C4F9SO3H and CH3PO(OH)2 have been examined as possible fuel cell electrolytes. The reduction of oxygen in HN(SO2CF3)2 and (CF2)4(SO3H)2 is similar to that achieved in 4M KOH. The activity for oxy...

W. E. O'Grady

1984-01-01

77

Fuel Cell Reactions in Super Acid Electrolytes.  

National Technical Information Service (NTIS)

A series of perfluorosulfonic acids including CF3SO3H, CF2(SO3H)2, (CF2)2(SO3H)2, (CF2)2(SO3H)2 and (CF2)4(SO3H)2 have been examined for fuel cell applications. The reduction of O2 in CF3SO3H, CF2(SO3H)2, and (CF2)3(SO3H)2 is comparable to that achieved i...

W. E. O'Grady

1983-01-01

78

Improved In Situ Hybridization Efficiency with Locked-Nucleic-Acid-Incorporated DNA Probes  

Microsoft Academic Search

Low signal intensity due to poor probe hybridization efficiency is one of the major drawbacks of rRNA- targeted in situ hybridization. There are two major factors affecting the hybridization efficiency: probe acces- sibility and affinity to the targeted rRNA molecules. In this study, we demonstrate remarkable improvement in in situ hybridization efficiency by applying locked-nucleic-acid (LNA)-incorporated oligodeoxynucleotide probes (LNA\\/DNA probes)

Kengo Kubota; Akiyoshi Ohashi; Hiroyuki Imachi; Hideki Harada

2006-01-01

79

Studies on the reaction of nitric acid and sugar  

SciTech Connect

The design of vessels and off-gas systems for denitrating acidic radioactive process solutions by reacting nitric acid with sugar requires a fairly accurate determination of the rate of the controlling step. Therefore, the reaction of sugar with concentrated nitric acid was closely examined at temperatures of 100 and 110/sup 0/C and in the presence of low levels of iron )0 to 0.2 M Fe(III)). Efficiencies of the sugar destruction by nitric acid ranged from 2.56 to 2.93 mol of acid consumed per mole of carbon added. Product off-gases were examined throughout the reaction. Release of CO was fairly constant throughout the reaction, but amounts of CO/sub 2/ increased as the nitric acid began to attack the terminal carboxylic acids produced from the consumption of sucrose. Voluminous quantities of NO/sub 2/ were released at the beginning of the reaction, but larger relative concentrations of NO were observed toward the end.

MacDougall, C.S.; Bayne, C.K.; Roberson, R.B.

1982-07-01

80

Suzuki-Miyaura coupling reaction using pentafluorophenylboronic acid.  

PubMed

[reaction: see text] We have found new conditions for the Suzuki-Miyaura coupling reaction applicable to pentafluorophenylboronic acid (C(6)F(5)B(OH)(2)) (1), which is an inactive substrate under normal conditions. The reactions of 1 with phenyl iodide or bromide under Pd(PPh(3))(4)/CsF/Ag(2)O or Pd(2)(dba)(3)/P(t-Bu)(3)/CsF/Ag(2)O catalytic system conditions gave 2,3,4,5,6-pentafluoro-1,1'-biphenyl (3a) in more than 90% yields. Combination of CsF and Ag(2)O was essential for promoting these reactions. PMID:16235921

Korenaga, Toshinobu; Kosaki, Takahiro; Fukumura, Rokki; Ema, Tadashi; Sakai, Takashi

2005-10-27

81

Selection of Fluorophore and Quencher Pairs for Fluorescent Nucleic Acid Hybridization Probes  

Microsoft Academic Search

Summary With the introduction of simple and relatively inexpensive methods for labeling nucleic acids with non-radioactive labels, doors have been opened that enable nucleic acid hybridization probes to be used for research and development, as well as for clinical diagnostic applications. The use of fluorescent hybridization probes that generate a fluorescence signal only when they bind to their target enables

Salvatore A. E. Marras

82

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

Microsoft Academic Search

New types of hybrid material have been synthesized by using four different methods of immobilization of humic acid (HA) on chitin. The most stable hybrid material toward the change of medium acidity was then utilized as sorbent for Cr(III).The HA was extracted from peat soil of Gambut District, South Kalimantan, Indonesia, using the recommended procedure of International Humic Substances Society

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

2007-01-01

83

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

84

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

Microsoft Academic Search

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

2007-01-01

85

Reactions of conjugated fatty acids. VIII. Dibasic acids by hydrogenation and oxidative cleavage  

Microsoft Academic Search

Summary  Conjugated linoleic acid can be hydrogenated as sodium soap in an aqueous or ethylene glycol solution with commercial nickel\\u000a catalysts. Under suitable conditions the acid is reduced predominantly to monounsaturated acids with only a slight increase\\u000a in saturated acids. An alkali-conjugation reaction mixture may be hydrogenated without isolating the conjugated acids. One\\u000a set of conditions found suitable for hydrogenation is

C. R. Scholfield; E. P. Jones; J. A. Stolp; J. C. Cowan

1958-01-01

86

Enthalpy changes and reaction volumes of photoisomerization reactions in solution: azobenzene and p-coumaric acid  

Microsoft Academic Search

The photoisomerizations of azobenzene in ethanol and p-coumaric acid in water were studied by the transient grating and photoacoustic methods. The absorption spectrum of cis-p-coumaric acid and the quantum yield of the isomerization reaction in water were measured by a photostationary absorption method at two wavelengths (?iso=0.46±0.05). The diffusion coefficient of p-coumaric acid in water at room temperature is 4.4×10?10m2s?1.

Kan Takeshita; Noboru Hirota; Masahide Terazima

2000-01-01

87

The kinetics and mechanisms of reactions of iron(III) with caffeic acid, chlorogenic acid, sinapic acid, ferulic acid and naringin  

Microsoft Academic Search

The kinetics and mechanisms of the reactions of iron(III) with the hydroxy cinnamic acid based ligands caffeic, chlorogenic, sinapic and ferulic acids and the flavonoid naringin have been investigated in aqueous solution. The mechanisms for caffeic and chlorogenic acid are generally consistent with the formation of a 1:1 complex that subsequently decays through an electron transfer reaction. On reaction with

Michael J. Hynes; Máirt??n O'Coinceanainn

2004-01-01

88

Bimodal proton transfer in acid-base reactions in water  

SciTech Connect

We investigate one of the fundamental reactions in solutions, the neutralization of an acid by a base. We use a photoacid, 8-hydroxy-1,3,6-trisulfonate-pyrene (HPTS; pyranine), which upon photoexcitation reacts with acetate under transfer of a deuteron (solvent: deuterated water). We analyze in detail the resulting bimodal reaction dynamics between the photoacid and the base, the first report on which was recently published [M. Rini, B.-Z. Magnes, E. Pines, and E. T. J. Nibbering, Science 301, 349 (2003)]. We have ascribed the bimodal proton-transfer dynamics to contributions from preformed hydrogen bonding complexes and from initially uncomplexed acid and base. We report on the observation of an additional (6 ps)-1 contribution to the reaction rate constant. As before, we analyze the slower part of the reaction within the framework of the diffusion model and the fastest part by a static, sub-150 fs reaction rate. Adding the second static term considerably improves the overall modeling of the experimental results. It also allows to connect experimentally the diffusion controlled bimolecular reaction models as defined by Eigen-Weller and by Collins-Kimball [D. Shoup and A. Szabo, Biophys. J. 40, 33 (1982)]. Our findings are in agreement with a three-stage mechanism for liquid phase intermolecular proton transfer: mutual diffusion of acid and base to form a 'loose' encounter complex, followed by reorganization of the solvent shells and by 'tightening' of the acid-base encounter complex. These rearrangements last a few picoseconds and enable a prompt proton transfer along the reaction coordinate, which occurs faster than our time resolution of 150 fs. Alternative models for the explanation of the slower 'on-contact' reaction time of the loose encounter complex in terms of proton transmission through a von Grotthuss mechanism are also discussed.

Rini, Matteo; Pines, Dina; Magnes, Ben-Zion; Pines, Ehud; Nibbering, Erik T.J. [Max Born Institut fuer Nichtlineare Optik und Kurzzeitspektroskopie, Max Born Strasse 2A, D-12489 Berlin (Germany); Department of Chemistry, Ben-Gurion University of the Negev, P.O.B. 653, Beer-Sheva 84105 (Israel); Max Born Institut fuer Nichtlineare Optik und Kurzzeitspektroskopie, Max Born Strasse 2A, D-12489 Berlin (Germany)

2004-11-15

89

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

NASA Astrophysics Data System (ADS)

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

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

2002-10-01

90

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

Microsoft Academic Search

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

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

91

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

92

Extent of ozone's reaction with isolated aquatic fulvic acid  

Microsoft Academic Search

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

Linda J. Anderson; J. Donald Johnson; R. F. Christman

1986-01-01

93

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

94

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

PubMed

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

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

2010-09-22

95

Artificial mismatch hybridization  

DOEpatents

An improved nucleic acid hybridization process is provided which employs a modified oligonucleotide and improves the ability to discriminate a control nucleic acid target from a variant nucleic acid target containing a sequence variation. The modified probe contains at least one artificial mismatch relative to the control nucleic acid target in addition to any mismatch(es) arising from the sequence variation. The invention has direct and advantageous application to numerous existing hybridization methods, including, applications that employ, for example, the Polymerase Chain Reaction, allele-specific nucleic acid sequencing methods, and diagnostic hybridization methods.

Guo, Zhen (Madison, WI); Smith, Lloyd M. (Madison, WI)

1998-01-01

96

Heterogeneous photocatalytic reactions of organic acids and water: new reaction paths besides the photo-kolbe reaction  

SciTech Connect

The heterogeneous photocatalytic reactions of acetic, propionic, and butyric acids were studied on several kinds of powdered semiconductors, mainly TiO/sub 2/. The influence of Ag/sup +/ as an electron acceptor, and the dependence of the reactions on the kind of semiconductor and pH, were investigated. The ratio of yields of hydrogen to hydrocarbon depends strongly on pH. At neutral or alkaline pH, hydrocarbon stops being evolved and only hydrogen is evolved. It is concluded that the pH dependence of the valence band position of the semiconductor and the concentration of OH/sup -/ ion control the reaction paths. From the pH dependence of methane production from acetic acid the valence band of anatase is estimated to be located more deeply by 0.1 eV than that of rutile. The results of product analysis and the complete decomposition of acetic acid to CO/sub 2/ show that there exist new reaction paths in which water is an oxidizing agent. Reaction schemes of these organic acids are proposed.

Sakata, T.; Kawai, T.; Hashimoto, K.

1984-05-24

97

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

98

REACTION OF OZONE WITH ISOLATED AQUATIC FULVIC ACID  

EPA Science Inventory

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

99

Reaction of gallium arsenide with concentrated acids: formation of arsine.  

PubMed

Crystalline particles of gallium arsenide (GaAs) (approximately 2 microns in diameter) react with concentrated hydrochloric acid (HCl) (11.6 to 9 M) to form highly toxic arsine (AsH3) gas. None of the other strong acids that were investigated reacted with gallium arsenide to form AsH3. A spectrophotometric method, based on the reaction of AsH3 with silver diethyldithiocarbamate in a chloroform solution containing morpholine, was used to detect AsH3 gas dissolved in aqueous solutions and to determine the AsH3 gas that was liberated by the reaction of GaAs with HCl. Active sites on the gallium arsenide surface initiate the reaction that forms AsH3 gas. Absorption of oxygen or ions from solution on these active sites inhibits the formation of AsH3. PMID:2756869

Scott, N; Carter, D E; Fernando, Q

1989-07-01

100

Hybrid method for simulating front propagation in reaction-diffusion systems  

Microsoft Academic Search

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

Esteban Moro; Departmento de Matematicas

2004-01-01

101

Niobic acid and niobium phosphate as highly acidic viable catalysts in aqueous medium: Fructose dehydration reaction  

Microsoft Academic Search

The catalytic properties of niobic acid (Nb2O5·nH2O) and niobium phosphate (NbOPO4) surfaces were studied in the reaction of fructose dehydration carried out in water. The reaction was performed in a continuous reactor at different temperatures 90–110°C and pressures (from 2 to 6bar). Superior activity and selectivity to 5-hydroxymethyl-2-furaldehyde (HMF) of niobium phosphate compared to niobic acid was observed. The initial

Paolo Carniti; Antonella Gervasini; Serena Biella; Aline Auroux

2006-01-01

102

Recombination between endogenous and exogenous RNA tumor virus genes as analyzed by nucleic acid hybridization.  

PubMed Central

Certain chicken cells that do not spontaneously release virus particles have been shown to produce a subgroup E avian RNA tumor virus, Rous-associated virus 60 (RAV-60), after infection with viruses of other subgroups. The nucleic acids of RAV-60 were analyzed for sequence homologies with the viral nucleic acids contained in the uninfected cell and with those of RAV-2, the exogenous virus used for the preparation of this particular RAV-60 isolate. In addition, these nucleic acids were compared with those of RAV-0, an endogenous virus spontaneously released from line 100 chicken cells. RAV-60 appears to be intermediate between RAV-0 and RAV-2 in its genetic composition, based on the pattern of hybridization obtained with the nucleic acids of these viruses and on the melting profiles of the various hybrid combinations. Of the three viruses tested, RAV-0 appears to have the greatest sequence homology with the viral nucleic acids of the uninfected cell. Hybridization between RAV-60 3-H-labeled complementary DNA and either DNA or RNA from the uninfected cell indicates that RAV-60 contains some nucleic acid sequences which are not present in the cell. In addition, some RAV-60 sequences which hybridize with the cell nucleic acid contain significant amounts of mismatching, as indicated by the lower thermal stability of these hybrid duplexes. Hybrid formation between these partially homologous sequences was excluded under stringent annealing conditions. The data indicate that RAV-60 is a recombinant between exogenous and endogenous viral genes.

Hayward, W S; Hanafusa, H

1975-01-01

103

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

PubMed

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

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

2013-02-27

104

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

Microsoft Academic Search

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

D. W. Heath; E. D. Earle

1995-01-01

105

40 CFR 721.10664 - Alkenedioic acid dialkyl ester, reaction products with alkenoic acid alkyl esters and diamine...  

Code of Federal Regulations, 2013 CFR

...New Uses for Specific Chemical Substances § 721...acid dialkyl ester, reaction products with alkenoic...generic). (a) Chemical substances and significant...reporting. (1) The chemical substances identified...acid dialkyl ester, reaction products with...

2013-07-01

106

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

Code of Federal Regulations, 2013 CFR

...New Uses for Specific Chemical Substances § 721...acids, tall-oil, reaction products with modified...generic). (a) Chemical substance and significant...reporting. (1) The chemical substance identified...acids, tall-oil, reaction products with...

2013-07-01

107

Effects of phosphoric acid on the lead-acid battery reactions  

Microsoft Academic Search

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

Osamu Ikeda; Chiaki Iwakura; Hiroshi Yoneyama; Hideo Tamura

1986-01-01

108

Predictions of diagenetic reactions in the presence of organic acids  

SciTech Connect

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

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

1992-02-01

109

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

PubMed

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

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

2009-12-01

110

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

PubMed

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

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

2013-04-01

111

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

112

Thermochemical characteristics of reactions of calcium with perchloric acid  

NASA Astrophysics Data System (ADS)

The enthalpy of reaction of metallic calcium with perchloric acid was measured for the first time in a sealed swinging calorimeter equipped with an isothermal shell. Standard enthalpies of formation of calcium ion in an infinitely diluted aqueous solution (-542.8 ± 1.0 kJ/mol) and calcium chloride in crystal state (-794.9 ± 1.0 kJ/mol) were calculated according to the results obtained with the use of published data.

Monaenkova, A. S.; Tiflova, L. A.

2012-05-01

113

Micellar effects on reaction rates and acid-base equilibria  

Microsoft Academic Search

The effects of ionic surfactant micelles on reaction rates in solution on acid-base equilibria often conform quite well to a theory known as the pseudophase ion-exchange model (PPIEM). Despite its success the theory suffers from several limitations. These are outlined and an alternative approach which overcomes them is forwarded. This new theory is based on the equilibrium formulation of transition-state

Denver G. Hall

1987-01-01

114

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

SciTech Connect

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

115

Reactions of Trifluoroacetic Acid with Poly (Vinyl Alcohol) and Its Model Compounds. Effect of Neighboring Hydroxyl Groups on the Reaction.  

National Technical Information Service (NTIS)

Reactions of trifluoroacetic acid with poly(vinyl alcohol) and various model alcohols were investigated by observing the fluorine and the proton magnetic resonance spectra of the reaction mixtures. At equilibrium the degree of conversion to ester under gi...

K. Fujii S. Brownstein A. M. Eastham

1967-01-01

116

Quinolinic acid, alpha-picolinic acid, fusaric acid, and 2,6-pyridinedicarboxylic acid enhance the Fenton reaction in phosphate buffer.  

PubMed

Quinolinic acid, alpha-picolinic acid, fusaric acid, and 2,6-pyridinedicarboxylic acid enhanced the Fenton reaction in phosphate buffer, respectively. The enhancement by quinolinic acid, alpha-picolinic acid, fusaric acid, and 2,6-pyridinedicarboxylic acid of the Fenton reaction may be partly related to their respective actions in the biological systems such as a neurotoxic effect (quinolinic acid), a marked growth-inhibitory action on rice seeding (alpha-picolinic acid and fusaric acid), and an antiseptic (2,6-pyridinedicarboxylic acid). The ultraviolet-visible absorption spectrum of the mixture of alpha-picolinic acid with ferrous ion showed a characteristic visible absorbance band with a lambda(max) at 443 nm, suggesting that alpha-picolinic acid chelate of Fe2+ ion forms in the solution. Similar characteristic visible absorbance band was also observed for the mixture of Fe2+ ion with quinolinic acid (or fusaric acid, or 2,6-pyridinedicarboxylic acid). The chelation seems to be related to the enhancement by quinolinic acid, alpha-picolinic acid, fusaric acid, and 2,6-pyridinedicarboxylic acid of the Fenton reaction. alpha-Picolinic acid was reported to be a toxic substance isolated from the culture liquids of blast mould (Piricularia oryzae CAVARA). On the other hand, it has also been known that chlorogenic acid protects rice plants from the blast disease. The chlorogenic acid inhibited the formation of the hydroxyl radical in the reaction mixture of alpha-picolinic acid, FeSO4(NH4)2SO4, and H2O2. Thus the inhibition may be a possible mechanism of the protective action of the chlorogenic acid against the blast disease. PMID:10362227

Iwahashi, H; Kawamori, H; Fukushima, K

1999-04-15

117

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

PubMed

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

Gomes, P T C; Nassar, N M A

2013-04-12

118

Reactions of phosphorylated allenes with phosphorus dithio acids  

SciTech Connect

The addition of phosphorus dithio acids to (1,2-alkadienyl)phosphonates goes at the ..cap alpha..,..beta..-double bond by nucleophilic reaction regardless of the degree of substitution on the ..gamma..-carbon atom of the allene. The introduction of two methyl groups on the ..gamma..-carbon atom of the phosphonoallene promotes the electrophilic addition of the dithio acids at the ..beta..,..gamma..-double bond to a small extent. (1-Vinyl-1,2-alkadienyl)phosphonates react with 0,0-dialkyl hydrogen phosphorodithioates at the 1,4-positions of the system of two conjugated double bonds with the addition of the proton on the central carbon atom of the allene. Simultaneously with addition, there occurs the alkylation of the acid phosphorodithioates by the (1,2-alkadienyl)phosphonic esters.

Khusainova, N.G.; Sippel', I.Ya.; Berdnikov, E.A.; Cherkasov, R.A.; Pudovik, A.N.

1986-05-20

119

40 CFR 721.10464 - Fatty acid, reaction products with alkanolamine (generic).  

Code of Federal Regulations, 2013 CFR

...New Uses for Specific Chemical Substances § 721.10464 Fatty acid, reaction products with alkanolamine (generic). (a) Chemical substance and significant...reporting. (1) The chemical substance identified generically as fatty acid, reaction products with...

2013-07-01

120

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

Code of Federal Regulations, 2013 CFR

...New Uses for Specific Chemical Substances § 721...benezenesulfonic acid reaction product with naphthalenesulfonato...generic). (a) Chemical substance and significant...reporting . (1) The chemical substance identified...benezenesulfonic acid reaction product with...

2013-07-01

121

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

Code of Federal Regulations, 2013 CFR

...New Uses for Specific Chemical Substances § 721.4461 Hydrofluoric acid, reaction products with octane (generic). (a) Chemical substance and significant...reporting. (1) The chemical substance identified...hydrofluoric acid, reaction products with...

2013-07-01

122

40 CFR 721.9460 - Tall oil fatty acids, reaction products with polyamines, alkyl substituted.  

Code of Federal Regulations, 2013 CFR

...New Uses for Specific Chemical Substances § 721...Tall oil fatty acids, reaction products with polyamines...substituted. (a) Chemical substance and significant...reporting. (1) The chemical substance identified...tall oil fatty acids, reaction products with...

2013-07-01

123

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

Code of Federal Regulations, 2013 CFR

...New Uses for Specific Chemical Substances § 721.10211 Octadecanoic acid, reaction products with diethylenetriamine...acetates. (a) Chemical substance and significant...reporting . (1) The chemical substance identified as octadecanoic acid, reaction products with...

2013-07-01

124

40 CFR 721.4385 - Hydrofluoric acid, reaction products with heptane.  

Code of Federal Regulations, 2013 CFR

...Uses for Specific Chemical Substances § 721...Hydrofluoric acid, reaction products with heptane. (a) Chemical substance and significant...reporting. (1) The chemical substance identified...hydrofluoric acid, reaction products...

2013-07-01

125

40 CFR 721.10251 - Fatty acids, reaction products with alkanolamine (generic).  

Code of Federal Regulations, 2013 CFR

...New Uses for Specific Chemical Substances § 721.10251 Fatty acids, reaction products with alkanolamine (generic). (a) Chemical substance and significant...reporting. (1) The chemical substance identified...generically as fatty acids, reaction products with...

2013-07-01

126

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

127

Identification of KZebsieZZa pneumoniae by DNA Hybridization and Fatty Acid Analysis  

Microsoft Academic Search

On the basis of the idea that DNA sequences encoding cell surface-exposed regions of outer membrane proteins are genus or species specific, two oligonucleotide probes which were based on the PhoE protein of Klebsiellu pneumoniae were evaluated. In slot blot hybridizations and in polymerase chain reactions, no cross-hybridizations were observed with non-Klebsiella strains. When the probes were tested on 75

GONNIE SPIERINGS; ALBERT VAN SILFHOUT; HARM HOFSTRA; JAN TOMMASSEN

1992-01-01

128

Molecular Layer Deposition of Hybrid Organic-Inorganic Alucone Polymer Films Using a Three-Step ABC Reaction Sequence.  

National Technical Information Service (NTIS)

Thin film growth using molecular layer deposition (MLD) or atomic layer deposition (ALD) is based on sequential, self-limiting surface reactions. In this work, MLD is used to grow a hybrid organic-inorganic polymer film based on a three-step ABC reaction ...

A. S. Cavanagh B. Yoon D. Seghete S. M. George

2009-01-01

129

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

PubMed

A new analytical method was developed for the determination of ascorbic acid in fruit juice and pharmaceuticals. The method is based on its inhibition effect on the reaction between hydrochloric acid and bromate. The decolourisation of Methyl Orange by the reaction products was used to monitor the reaction spectrophotometrically at 510 nm. The linearity range of the calibration graph depends on bromate concentration. The variable affecting the rate of the reaction was investigated. The method is simple, rapid, relatively sensitive and precise. The limit of detection is 7.6 x 10(-6) M and calibration rang is 8 x 10(-6)-1.2 x 10(-3) M ascorbic acid. The relative standard deviation of seven replication determinations of 8 x 10(-6) and 2 x 10(-5) M ascorbic acid was 2.8 and 1.7%, respectively. The influence of potential interfering substance was studied. The method was successfully applied for the determination of ascorbic acid in pharmaceuticals. PMID:12396041

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

2002-10-01

130

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

2013-09-03

131

[Oligonucleotide derivatives in the nucleic acid hybridization analysis. II. Isothermal signal amplification in process of DNA analysis by minisequencing].  

PubMed

The isothermal amplification of reporter signal via limited probe extension (minisequencing) upon hybridization of nucleic acids has been studied. The intensity of reporter signal has been shown to increase due to enzymatic labeling of multiple probes upon consecutive hybridization with one DNA template both in homophase and heterophase assays using various kinds of detection signal: radioisotope label, fluorescent label, and enzyme-linked assay. The kinetic scheme of the process has been proposed and kinetic parameters for each step have been determined. The signal intensity has been shown to correlate with physicochemical characteristics of both complexes: probe/DNA and product/DNA. The maximum intensity has been observed at minimal difference between the thermodynamic stability of these complexes, provided the reaction temperature has been adjusted near their melting temperature values; rising or lowering the reaction temperature reduces the amount of reporting product. The signal intensity has been shown to decrease significantly upon hybridization with the DNA template containing single-nucleotide mismatches. Limited probe extension assay is useful not only for detection of DNA template but also for its quantitative characterization. PMID:21317947

Dmitrienko, E V; Khomiakova, E A; Pyshnaia; Bragin, A G; Vedernikov, V E; Pyshny?, D V

132

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

Microsoft Academic Search

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

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

1999-01-01

133

Hybrid magnetic nanoparticles derived from wüstite disproportionation reactions at the nanoscale  

NASA Astrophysics Data System (ADS)

We present Mössbauer studies of hybrid iron-oxide nanoparticles obtained by the disproportionation of oleic acid stabilized wüstite (FexO) nanoparticles produced by selective oxidation of iron pentacarbonyl in high boiling temperature organic solvents. The results support X-ray diffraction and Transmission Electron Microscope studies of the presence of mixed FexO and Fe3O4 phases within the nanoparticles whose relative content can be altered through heat treatment in nitrogen atmosphere. Furthermore, the Mössbauer study gives evidence of the presence of an amorphous, spin-glass like phase due to spin frustration at the FexO/Fe3O4 interface.

Papaefthymiou, G. C.; Redl, F. X.; Black, C. T.; Sandstrom, R. L.; Yin, M.; Murray, C. B.; O'Brien, S. P.

2005-09-01

134

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

Microsoft Academic Search

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

Jun Matsuoka; Minoru Numaguchi; Satoshi Yoshida; Naohiro Soga

2000-01-01

135

A historical note on the iodine-sulphuric acid reaction of amyloid  

Microsoft Academic Search

The historical development of the iodine-sulphuric acid reaction for amyloid is described. The reaction dates back to 1814 when Colin and Gaultier de Claubry, and independently Stromeyer, introduced the iodine reaction for starch. A variant of the acidified iodine reaction appears to have been used for printing paper by Gmelin in 1829, and in 1838 Schleiden used the iodine-sulphuric acid

Kurt Aterman

1976-01-01

136

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 14aM. 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

2013-08-23

137

Absence of expected side-reactions in the dehydration reaction of fructose to HMF in water over niobic acid catalyst  

Microsoft Academic Search

The catalytic dehydration of fructose (FRU) to 5-hydroxymethylfurfural (HMF) usually runs with the formation of several side products. Among these, levulinic acid (LA) is often reported as the product of a consecutive reaction of HMF re-hydration. In this work, side reactions of the dehydration of FRU performed in very green conditions (water as solvent and niobic acid as solid catalyst)

Paolo Carniti; Antonella Gervasini; Matteo Marzo

2011-01-01

138

Cooperative acid-base effects with functionalized mesoporous silica nanoparticles: applications in carbon-carbon bond-formation reactions.  

PubMed

Acid-base bifunctional mesoporous silica nanoparticles (MSN) were prepared by a one-step synthesis by co-condensation of tetraethoxysilane (TEOS) and silanes possessing amino and/or sulfonic acid groups. Both the functionality and morphology of the particles can be controlled. The grafted functional groups were characterized by using solid-state (29)Si and (13)C cross-polarization/magic angle spinning (CP/MAS) NMR spectroscopy, thermal analysis, and elemental analysis, whereas the structural and the morphological features of the materials were evaluated by using XRD and N(2) adsorption-desorption analyses, and SEM imaging. The catalytic activities of the mono- and bifunctional mesoporous hybrid materials were evaluated in carbon-carbon coupling reactions like the nitroaldol reaction and the one-pot deacetalization-nitroaldol and deacetalization-aldol reactions. Among all the catalysts evaluated, the bifunctional sample containing amine and sulfonic acid groups (MSN-NNH(2)-SO(3)H) showed excellent catalytic activity, whereas the homogeneous catalysts were unable to initiate the reaction due to their mutual neutralization in solution. Therefore a cooperative acid-base activation is envisaged for the carbon-carbon coupling reactions. PMID:19569138

Shylesh, Sankaranarayanapillai; Wagner, Alex; Seifert, Andreas; Ernst, Stefan; Thiel, Werner R

2009-07-20

139

Growth temperature dependent interfacial reaction of Heusler-alloy Co2FeSi\\/GaAs(001) hybrid structures  

Microsoft Academic Search

We have studied the growth temperature dependence of the interfacial reaction of Heusler-alloy Co2FeSi\\/GaAs(0 0 1) hybrid structures. The reaction proceeds dominantly by Co in-diffusion, resulting in the formation of isolated grains in the GaAs substrate starting at the growth temperature TG of 200-250 °C. The interfacial reaction is classified into two stages: (i) intermediate TG regime (250-300 °C), where

M. Hashimoto; J. Herfort; A. Trampert; H.-P. Schönherr; K. H. Ploog

2007-01-01

140

Synthesis and characterization of hybrid molecular material prepared by ionic liquid and silicotungstic acid  

Microsoft Academic Search

A white colour IL-SiWA hybrid molecular material has been synthesized using 1-butyl 3-methyl imidazolium bromide ionic liquid and silicotungstic acid. The material is found to dissolve in polar organic solvent such as DMSO, but not in water. It is characterized by CHN analysis, FTIR, XRD, UV–vis DRS, TGA and SEM. The FTIR spectra indicate the formation of a hybrid compound

T. Rajkumar; G. Ranga Rao

2008-01-01

141

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

142

Comparison of boric acid adsorption by hybrid gels  

Microsoft Academic Search

Mannitol doped and un-doped hybrid gels derived from bis(trimethoxysilylpropyl)amine (TSPA), or the mixture of TSPA with tetraethoxysilane (TEOS), or the mixture of 3-aminopropyltriethoxysilane (APTES) with TEOS were prepared. Textual properties and point of zero charges were determined to characterize the gels. The adsorption of boron from its water solutions by the acidified and un-acidified gels in solutions at three different

Haining Liu; Xiushen Yea; Wu Li; Yaping Dong; Zhijian Wu

2009-01-01

143

Conversion of waste cellulose to ethanol. Phase 2: Reaction kinetics with phosphoric acid  

Microsoft Academic Search

Waste cellulosic material can be hydrolyzed in dilute acid solution to produce fermentable sugars which can then be converted into ethanol. A laboratory investigation was made of the feasibility of using phosphoric acid as the hydrolysis catalyst. The hydrolysis reaction with phosphoric acid solutions was compared with the reaction employing the more conventional dilute sulfuric acid catalyst. The purpose of

M. B. Moeller; R. E. Isbell

1982-01-01

144

Enzymatic amplification of DNA/RNA hybrid molecular beacon signaling in nucleic acid detection.  

PubMed

A rapid assay operable under isothermal or nonisothermal conditions is described, where the sensitivity of a typical molecular beacon (MB) system is improved by using thermostable RNase H to enzymatically cleave an MB composed of a DNA stem and an RNA loop (R/D-MB). On hybridization of the R/D-MB to target DNA, there was a modest increase in fluorescence intensity (~5.7× above background) due to an opening of the probe and a concomitant reduction in the Förster resonance energy transfer efficiency. The 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 (12.9× above background), resulting in an approximately 2- to 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 polymerase chain reactions by measuring enhancement of donor fluorescence on R/D-MB binding to amplified pUC19 template dilutions. Hence, the R/D-MB-RNase H scheme can be applied to a broad range of nucleic acid amplification methods. PMID:23000602

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

2012-09-19

145

Studies towards the development of chemically synthesized non-radioactive biotinylated nucleic acid hybridization probes.  

PubMed Central

Non-radioactive nucleic acid hybridization probes have been constructed in which the reporter group is long chain biotin chemically linked to a basic macromolecule (histone H1, cytochrome C or polyethyleneimine). The modified basic macromolecule which carries many biotin residues can, in turn, be covalently linked to nucleic acids (DNA) via the bifunctional cross-linking reagents, glutaraldehyde, 1,2,7,8-diepoxyoctane, bis (succinimidyl) suberate or bis (sulfonosuccinimidyl) suberate. This provides a very sensitive probe by which as little as between 10-50fg of target DNA can be visualized using dot-blot hybridization procedures in conjunction with avidin or streptavidin enzyme conjugates.

Al-Hakim, A H; Hull, R

1986-01-01

146

Studies towards the development of chemically synthesized non-radioactive biotinylated nucleic acid hybridization probes.  

PubMed

Non-radioactive nucleic acid hybridization probes have been constructed in which the reporter group is long chain biotin chemically linked to a basic macromolecule (histone H1, cytochrome C or polyethyleneimine). The modified basic macromolecule which carries many biotin residues can, in turn, be covalently linked to nucleic acids (DNA) via the bifunctional cross-linking reagents, glutaraldehyde, 1,2,7,8-diepoxyoctane, bis (succinimidyl) suberate or bis (sulfonosuccinimidyl) suberate. This provides a very sensitive probe by which as little as between 10-50fg of target DNA can be visualized using dot-blot hybridization procedures in conjunction with avidin or streptavidin enzyme conjugates. PMID:3027670

Al-Hakim, A H; Hull, R

1986-12-22

147

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

PubMed

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

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

2013-09-17

148

Conversion of waste cellulose to ethanol. Phase II. Reaction kinetics with phosphoric acid  

SciTech Connect

Waste cellulosic material can be hydrolyzed in dilute acid solution to produce fermentable sugars which can then be converted into ethanol. A laboratory investigation was made of the feasibility of using phosphoric acid as the hydrolysis catalyst. The hydrolysis reaction with phosphoric acid solutions was compared with the reaction employing the more conventional dilute sulfuric acid catalyst. The purpose of this research was to examine the hydrolysis step in a proposed process for the conversion of cellulose (from wood, newspapers, municipal solid waste, or other sources) into ethanol - by which a potentially valuable co-product, DICAL (dicalcium phosphate), might be made and sold with or without the lignin content as a fertilizer. The pertinent reaction kinetics for the acid catalyzed production of glucose from cellulose consists of consecutive, pseudo-first order reactions. The first reaction forms glucose by hydrolyzing the cellulose polymer and a subsequent reaction decomposes the glucose. The maximum theoretical yield depends on the ratio of the rate constants for these two reactions. The rate constants of both reactions were measured in a series of experiments studying temperature and concentration effects. The results suggest that the glucose decomposition reaction is similar with the two acids but that the cellulose hydrolysis reaction mechanism with phosphoric acid may be different than with sulfuric acid. The studies show phosphoric acid is unpromising and much inferior to sulfuric acid as the catalytic agent. Under the conditions studied, 0.8 wt % sulfuric acid gives a greater yield of glucose than 8.0 wt % phosphoric acid.

Moeller, M.B.; Isbell, R.E.

1982-05-01

149

L-ascorbic acid in nonenzymatic reactions. I. Reaction with glycine.  

PubMed

The influence of the water content, molar ratio, time and temperature on the formation of nondialysable melanoidins produced by the interaction of L-ascorbic acid and glycine has been studied. The isolated polymers have been characterized by spectrum analysis and fractionated using gel chromatography. The rate constants of the reaction for temperatures of 90 degrees C, 100 degrees C and 110 degrees C have been calculated and are (0.84 +/- 0.29) x 10(-5) x s-1, (1.33 +/- 0.14) x 10(-5) x s-1 and (5.30 +/- 0.37) x 10(-5) x s-1, respectively. The activation energy of the reaction has been determined to be 106.07 +/- 32.47 kJ/mol. PMID:7732734

Rogacheva, S M; Kuntcheva, M J; Panchev, I N; Obretenov, T D

1995-01-01

150

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

NASA Astrophysics Data System (ADS)

New types of hybrid material have been synthesized by using four different methods of immobilization of humic acid (HA) on chitin. The most stable hybrid material toward the change of medium acidity was then utilized as sorbent for Cr(III). The HA was extracted from peat soil of Gambut District, South Kalimantan, Indonesia, using the recommended procedure of International Humic Substances Society (IHSS), while the chitin was isolated from crab shell waste through deproteination using 3.5% (w/v) NaOH and followed by removal of inorganic impurities using 1 M HCl. The four methods of immobilization of HA on chitin were (i) Method A: chitin powder (4 g) was gently poured into the stirred solution of 0.4 g HA in 40 mL of 0.01 M NaOH. After overnight stirring, the solid was separated, washed with water, and dried in oven at 70 °C. (ii) Method B: gelatinous chitin (40 g) in 250 mL of 0.5 M HCl was reacted with HA (4 g) in 500 mL of 0.5 M NaOH and aged for 24 h. The product was washed with water and dried. (iii) Method C: HA powder (0.5 g) was mixed with the stirred gel of chitin (2.5 g) in 60 mL of CaCl2 saturated methanol and the mixture was then washed with the mixed solution of 25 mL of 2 M sodium citrate and ethylene glycol 1:1. The solid was separated, washed with water, and dried. (iv) Method D: the solution of HA (0.056 g) in 10 mL of 0.01 M NaOH was reacted with the gel of chitin (0.2 g) in 10 mL of CaCl2 saturated methanol. After 24 h stirring, the solid was separated from the reaction medium, washed with the mixed solution of 2 M sodium citrate and ethylene glycol 1:1, and followed by washing with water and drying. Parameters investigated in this study consisted of the stability test of the immobilized HA, as well as the rate constant (k1), capacity (b), and energy (E) of sorption as well as the rate constant of desorption (k-1). The k1 and k-1 were determined according to a kinetic model of first order sorption reaching equilibrium, while the b and E were determined according to the Langmuir isotherm model. Compared to HA, Methods, A, C, and D; Method B produced the most stable immobilization of HA on chitin. The hybrid material (Chitin HA) synthesized through Method B was stable in the acidity range that equivalent to pH 2.0 11.0. At the acidity giving maximum sorption, i.e. pH 5, the presence of immobilized HA on the Chitin HA enhanced more than three times the k1 and k-1, i.e. from 0.057 min-1 and 8.51 × 10-4 (min-1) (mol/L) for chitin to 0.183 min-1 and 3.27 × 10-3 (min-1) (mol/L) for the Chitin HA. On the contrary, the presence of HA on Chitin HA only gave small increase on b and small decrease on E. The values of b and E for Cr(III) on chitin were 1.45 × 10-2 mol/g and 23.12 kJ/mol, respectively, while those on Chitin HA were 1.78 × 10-2 mol/g and 19.95 kJ/mol, respectively.

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

2007-11-01

151

Fatty acid selectivity of lipases during acidolysis reaction between oleic acid and monoacid triacylglycerols.  

PubMed

With the aim of determining the fatty acid (FA) selectivity of lipases, a mixture of oleic acid and monoacid triacylglycerols (TAGs) including tricaproin (T6), tricaprylin (T8), tricaprin (T10), trilaurin (T12), trimyristin (T14), tripalmitin (T16) and tristearin (T18) was used as the substrate in acidolysis performed in hexane. Three immobilized lipases, namely, Lipozyme TL IM from Thermomyces lanoginosus, Lipozyme RM IM from Rhizomucor miehei and Novozym 435 from Candida antarctica, were used as biocatalyst. The effects of operating variables including the mole ratio of oleic acid to monoacid TAG, temperature, enzyme dosage and reaction time on incorporation were also investigated. Significantly different incorporation rates were obtained for different TAGs used (P < 0.05). Incorporation of oleic acid into TAGs except tricaproin and tricaprylin was higher for all the TAGs with Lipozyme TL IM catalyzed reactions than those of other two enzymes tested. Incorporation of oleic acid decreased as the acyl chain length of FA in the TAG increased with Novozyme 435 catalyzed acidolysis. Compared to the other substrate mixtures, the highest incorporation was observed for oleic acid and tricaproin mixture with three lipases tested. It was shown that the FA selectivity of the lipases is strongly dependent on the acyl chain length of FA in a TAG. PMID:19835376

Karabulut, Ihsan; Durmaz, Gokhan; Hayaloglu, Ali Adnan

2009-11-11

152

Parallel proton transfer pathways in aqueous acid-base reactions  

NASA Astrophysics Data System (ADS)

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

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

2008-05-01

153

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

2013-04-28

154

Glycolic acid functionalized chitosan-Au-Fe?O? hybrid nanoparticle based nanohybrid scaffold for drug delivery.  

PubMed

The research on biomedical applications of nanoparticles has seen an upsurge in recent years due to their unique capabilities in treatment of ailments. The present paper reports the synthesis of Au-Fe(3)O(4) hybrid nanoparticles. The formation of these nanoparticles was confirmed by transmission electron microscopy (TEM) and physical property measurement system (PPMS). Next step of this paper reveals potential use of novel hybrid of chitosan-g-glycolic acid and Au-Fe(3)O(4) hybrid nanoparticles in controlled drug delivery and tissue engineering applications. Grafting of glycolic acid and drug loading in porous scaffold was characterized by Fourier transform infrared spectroscopy. The nanohybrid scaffolds were found to be stable regardless of pH of the medium and play a key role in cell adhesion, proliferation and migration. Au-Fe(3)O(4) hybrid nanoparticles reinforcement was found to control the drug (cyclophosphamide) release rate in phosphate buffer saline solution (pH 7.4). Therefore, Au-Fe(3)O(4) hybrid nanoparticles are viable additive for formulating sustained drug delivery systems based on glycolic acid grafted chitosan. The cell proliferation profile also shows that prepared nanohybrid is biocompatible providing suitable substrates for tissue engineering. PMID:23237797

Kumari, Sangeeta; Singh, Raj Pal

2012-12-10

155

Experimental generation of hybrid silicic melts by reaction of high-Al basalt with metamorphic rocks  

NASA Astrophysics Data System (ADS)

Melting and crystallization experiments (T = 1000°C; P = 0.5, 0.7, 1.0, 1.2, and 1.5 GPa) were performed on two hybrid bulk compositions consisting of 50% anhydrous high-Al olivine tholeiite glass (HAOT) and 50% metamorphic rock (aluminosilicate-bearing metapelite and aluminosilicate-free biotite gneiss). The objective of the experiments was to determine phase equilibrium constraints attending bulk assimilation of crustal rocks by basaltic melts. Experiments generated 32-38 wt % of H2O-undersaturated granitic melt (SiO2 > 70 wt %). Thermal and phase equilibrium arguments show that production of this amount of granitic melt at the chosen experimental conditions is a plausible model for bulk assimilation in nature. The compositions of the melts and of the coexisting crystalline assemblages are affected to a comparable extent by pressure and by composition of the crustal source. Reaction of HAOT with biotite gneiss at P ? 1.0 GPa produces calc-alkaline melts in equilibrium with gabbronoritic cumulates (plag + opx + cpx). Reaction of HAOT with metapelite at P ? 0.7 GPa produces strongly peraluminous melts that resemble S-type granites from the Lachlan Fold Belt, in equilibrium with noritic cumulates (plag + opx ± spi ± gar). At P > 1.2 GPa, both source compositions produce strongly peraluminous leucocratic melts (<2 wt % FeO + MgO + TiO2) in equilibrium with garnet-rich and plagioclase-poor residues (opx + cpx + gar + plag from the biotite gneiss, gar + plag from the metapelite). The experiments show that a wide spectrum of high-SiO2 melts can be hybrids formed directly by reaction of basaltic melts with amphibolite-facies metamorphic rocks. Accumulation of the complementary mafic crystalline assemblages in the deep crust will generate granulites which are neither restitic nor the products of subsolidus dehydration. Mafic granulites and granitic melts formed by reaction of basaltic melts with metamorphic rocks will share isotopic and trace element signatures reflecting inheritance from both crustal and mantle sources.

PatiñO Douce, Alberto E.

1995-08-01

156

Synthesis, characterization and hybridization studies of an alternate nucleo- ? \\/ ? -peptide: complexes formation with natural nucleic acids  

Microsoft Academic Search

In order to develop new oligodeoxyribonucleotide (ODN) analogs to be used in biotechnological applications, we report here\\u000a the synthesis, characterization and nucleic acid binding studies of novel nucleopeptides, that we called ?-lys\\/?-dabPNAs, containing a backbone of alternated l-diaminobutyric acid and l-lysine moieties. Exploring the hybridization properties of the new ODN analog, we found, by circular dichroism and UV spectroscopies,\\u000a that

G. N. Roviello; D. Musumeci; C. Pedone; E. M. Bucci

2010-01-01

157

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

158

HYBRID TREATMENT SYSTEMS FOR VERY ACIDIC MINING INFLUENCED WATER1  

Microsoft Academic Search

The treatment of mining influenced water (MIW) has traditionally been addressed with two distinct technologies: active treatment with its associated chronic operating costs that include labor, power, reagents, and residue disposal, and passive treatment with its typical requirement of acidity-dependent land areas for bioreactors, aeration wetland cells, and ponds. With the development of \\

James J. Gusek; Kevin W. Conroy

159

Optical absorption assay for strand-exchange reactions in unlabeled nucleic acids  

Microsoft Academic Search

The nucleic acid exchange reaction is a common feature for genetic recombination, DNA replication and transcription. Due to the fact that in the strand- exchange reactions the reactant and product mole- cules have similar or identical nucleotide sequences, the reaction is undetectable. As a rule, the nucleic acids with radioactive or fluorescence labels are used in such studies. Besides the

Besik I. Kankia

2004-01-01

160

Reaction microtextures of REE Y Th U accessory minerals in the Monte Capanne pluton (Elba Island, Italy): a possible indicator of hybridization processes  

NASA Astrophysics Data System (ADS)

The study of accessory minerals in granitoid rocks can provide clues to the history of magmatic processes. In particular, the textural chemical characteristics of accessories could represent effective markers of hybridization processes. The concomitant occurrence of contrasting reaction microtextures of REE Y Th U accessory minerals in the Monte Capanne anatectic hybrid pluton suggests the occurrence of transient chemical conditions (alumina saturation up and down in the same system) in the early stages of crystallization. Incongruent dissolution of apatite produced microcrystal clusters of huttonitic monazite, while monazite-(Ce) crystals were replaced by allanite-(Ce)±apatite assemblage at the same location. A magma mingling process, involving acidic peraluminous and mafic metaluminous end-members, can provide the expected initial strong differences in alumina saturation that are able to induce such contrasting reactions. The proposed double exchange of accessory minerals between the two magmas strongly suggests a dynamic setting (stirring and straining of crystal-rich melts) in which anatectic and hybridization processes evolved.

Dini, A.; Rocchi, S.; Westerman, D. S.

2004-10-01

161

Hybrid ryegrass response to acid soil treatment with calcitic and dolomitic lime  

Microsoft Academic Search

Since ryegrass (Lolium sp.) is a widely grown cool?season forage grass, its magnesium concentration is of special interest to ruminant livestock producers. This study was conducted to investigate the effect of calcitic or dolomitic lime addition on dry matter yield and mineral composition of hybrid ryegrass, Lolium (multiflorum x perenne x perenne) grown in eight acidic soils. Each soil received

A. L. Pires; J. L. Ahlrichs; C. L. Rhykerd

1991-01-01

162

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

PubMed Central

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

Xu, Zhenli; Cai, Wei; Cheng, Xiaolin

2013-01-01

163

Hybrid charged-particle guide for studying (n, charged particle) reactions  

SciTech Connect

Charged-particle transport systems consisting of magnetic quadrupole lenses have been employed in recent years in the study of (n, charged particle) reactions. We have completed a new transport system that is based both on magnetic lenses as well as electrostatic fields. The magnetic focusing of this charged-particle guide is provided by six magnetic quadrupole lenses arranged in a CDCCDC sequence (in the vertical plane). The electrostatic field is produced by a wire at high voltage which stretches the length of the guide and is physically at the center of the magnetic axis. The magnetic lenses are used for charged particles above 5 MeV; the electrostatic guide is used for lower energies. This hybrid system possesses the excellent focusing and background rejection properties of other magnetic systems. For low energy charged-particles, the electrostatic transport avoids the narrow band-passes in charged-particle energy which are a problem with purely magnetic transport systems. This system is installed at the LLNL Cyclograaff facility for the study of (n, charged particle) reactions at neutron energies up to 35 MeV.

Haight, R.C.; White, R.M.; Zinkle, S.J.

1982-08-25

164

Hybrid approach for including electronic and nuclear quantum effects in molecular dynamics simulations of hydrogen transfer reactions in enzymes  

Microsoft Academic Search

A hybrid approach for simulating proton and hydride transfer reactions in enzymes is presented. The electronic quantum effects are incorporated with an empirical valence bond approach. The nuclear quantum effects of the transferring hydrogen are included with a mixed quantum\\/classical molecular dynamics method in which the hydrogen nucleus is described as a multidimensional vibrational wave function. The free energy profiles

Salomon R. Billeter; Simon P. Webb; Tzvetelin Iordanov; Pratul K. Agarwal; Sharon Hammes-Schiffer

2001-01-01

165

In vitro effect of combined hybrid molecules from vitamin E analogues and betulinic acid on macrophage activity.  

PubMed

Macrophage activity was studied after treatment with hybrid molecules obtained by condensation of terpenic acid residues (betulinic and betulonic acids) and ?-tocopherol analogues (?-tocopherol hemisuccinate and Trolox acid). As distinct from betulinic acid and ?-tocopherol hemisuccinate, hybrid molecules did not exhibit cytotoxicity in relation to mouse peritoneal macrophages in the MTT test. Test substances inhibited the production of NO by mouse peritoneal macrophages. However, hybrid molecules had no effect on activity of macrophage arginase. Our results indicate that new molecules have anti-inflammatory activity. It can be hypothesized that these substances have immunomodulatory properties. PMID:22485210

Ivanova, A N; Belsky, Y P; Spivak, A Yu; Danilets, M G; Belska, N V; Chalitova, R R; Ligatcheva, A A; Uchasova, E G

2011-10-01

166

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

NASA Astrophysics Data System (ADS)

Ultrafast, time-resolved investigations of acid-base neutralization reactions have recently been performed using systems containing the photoacid 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) and various Brønsted bases. Two conflicting neutralization mechanisms have been formulated by Mohammed et al. [Science 310, 83 (2005)] and Siwick et al. [J. Am. Chem. Soc. 129, 13412 (2007)] for the same acid-base system. Herein an ab initio molecular dynamics based computational model is formulated, which is able to investigate the validity of the proposed mechanisms in the general context of ground-state acid-base neutralization reactions. Our approach consists of using 2,4,6-tricyanophenol (exp. pKa?1) as a model for excited-state HPTS* (pKa?1.4) and carboxylate ions for the accepting base. We employ our recently proposed dipole-field/quantum mechanics (QM) treatment [P. Maurer and R. Iftimie, J. Chem. Phys. 132, 074112 (2010)] of the proton donor and acceptor molecules. This approach allows one to tune the free energy of neutralization to any desired value as well as model initial nonequilibrium hydration effects caused by a sudden increase in acidity, making it possible to achieve a more realistic comparison with experimental data than could be obtained via a full-QM treatment of the entire system. It is demonstrated that the dipole-field/QM model reproduces correctly key properties of the 2,4,6-tricyanophenol acid molecule including gas-phase proton dissociation energies and dipole moments, and condensed-phase hydration structure and pKa values.

Maurer, Patrick; Thomas, Vibin; Rivard, Ugo; Iftimie, Radu

2010-07-01

167

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

168

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

Microsoft Academic Search

Several highly branched isoprenoid alkenes isolated from the diatom Haslea ostrearia have been subjected to laboratory simulations of early diagenetic reactions under mild acid conditions including addition of K-10 Montmorillonite clay. The products of these reactions have been found to be highly dependent on the degree of unsaturation of the alkenes. For dienes, double bond migration and geometric isomerisation are

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

2000-01-01

169

Ozonolysis of Mixed Oleic-Acid/Stearic-Acid Particles: Reaction Kinetics and Chemical Morphology  

NASA Astrophysics Data System (ADS)

Atmospheric particles directly and indirectly affect global climate and have a primary role in regional issues of air pollution, visibility, and human health. Atmospheric particles have a variety of shapes, dimensions, and chemical compositions, and these physicochemical properties evolve (i.e., "age") during transport of the particles through the atmosphere, in part because of the chemical reactions of particle-phase organic molecules with gas-phase atmospheric oxidants. As a global average, hydroxyl radical (OH) and ozone (O3) are responsible quantitatively for most oxidant aging of atmospheric particles. The reactions of the hydroxyl radical occur in the surface region of a particle because of the nearly diffusion-limited bimolecular rate constant of OH with a variety of organic molecules. Ozone, on the other hand, is a selective agent for the unsaturated bonds of organic molecules and may diffuse a considerable distance into particles prior to reaction. The reaction of oleic acid with ozone has recently emerged as a model system to better understand the atmospheric chemical oxidation processes affecting organic particles. The ozonolysis of mixed oleic-acid/stearic-acid (OL/SA) aerosol particles from 0/100 to 100/0 weight percent composition is studied. The magnitude of the divergence of the particle beam inside an aerosol mass spectrometer shows that, in the concentration range 100/0 to 60/40, the mixed OL/SA particles are liquid prior to reaction. Upon ozonolysis, particles with SA composition greater than 25% change shape, indicating that they have solidified. Transmission electron micrographs show that SA(s) forms needles. For SA compositions greater than 10%, the reaction kinetics exhibit an initial fast decay of OL for low O3 exposure with no further loss of OL at higher O3 exposures. For compositions from 50/50 to 10/90, the residual OL concentration remains at 28+/-2% of its initial value. The initial reactive uptake coefficient for O3, as determined by OL loss, decreases linearly from 1.25(+/-0.2) 10-3 to 0.60(+/-0.15) 10-3 for composition changes of 100/0 to 60/40. At 50/50 composition, the uptake coefficient drops abruptly to 0.15(+/-0.1) 10-3, and there are no further changes with increased SA content. The amount of SA in the particles also decreases during OL ozonolysis. The stabilized Criegee intermediate (SCI) formed by OL ozonolysis attacks the carboxylic acid group of SA to yield an acyloxyalkyl hydroperoxide product. The experimental observations of this study can be explained by the following two postulates: (1) unreacted mixed particles remain as supersatured liquids up to 60/40 composition and (2) SA, as it solidifies, locks in a significant amount of oleic acid. The results of this study point out the important effects of particle phase, composition, and morphology on chemical reactivity. Oleic acid in liquid regions of a particle reacts rapidly with O3 whereas OL trapped inside solid SA is essentially unavailable for reaction with O3. These results contribute to the continuing development of the scientific community's understanding of particle aging process in the atmosphere, for which the ultimate goal is to provide quantitative mechanistic models of physicochemical transformations under atmospheric conditions.

Martin, S. T.; Katrib, Y.; Biskos, G.; Buseck, P. R.; Davidovits, P.; Jayne, J. T.; Mochida, M.; Wise, M. E.; Worsnop, D. R.

2005-12-01

170

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

PubMed Central

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

2011-01-01

171

Quinone- and nitroreductase reactions of Thermotoga maritima peroxiredoxin-nitroreductase hybrid enzyme.  

PubMed

Thermotoga maritima peroxiredoxin-nitroreductase hybrid enzyme (Prx-NR) consists of a FMN-containing nitroreductase (NR) domain fused to a peroxiredoxin (Prx) domain. These domains seem to function independently as no electron transfer occurs between them. The reduction of quinones and nitroaromatics by NR proceeded in a two-electron manner, and follows a 'ping-pong' scheme with sometimes pronounced inhibition by quinone substrate. The comparison of steady- and presteady-state kinetic data shows that in most cases, the oxidative half-reaction may be rate-limiting in the catalytic cycle of NR. The enzyme was inhibited by dicumarol, a classical inhibitor of oxygen-insensitive nitroreductases. The reduction of quinones and nitroaromatic compounds by Prx-NR was characterized by the linear dependence of their reactivity (logk(cat)/K(m)) on their single-electron reduction potentials E(7)(1), while the reactivity of quinones markedly exceeded the one with nitroaromatics. It shows that NR lacks the specificity for the particular structure of these oxidants, except their single-electron accepting potency and the rate of electron self-exchange. It points to the possibility of a single-electron transfer step in a net two-electron reduction of quinones and nitroaromatics by T. maritima Prx-NR, and to a significant diversity of the structures of flavoenzymes which may perform the two-electron reduction of quinones and nitroaromatics. PMID:22982531

Anusevi?ius, Žilvinas; Misevi?ien?, Lina; Šarlauskas, Jonas; Rouhier, Nicolas; Jacquot, Jean-Pierre; ??nas, Narimantas

2012-09-12

172

Simulation of a hybrid fermentation-separation process for production of butyric acid  

Microsoft Academic Search

Simulation of a hybrid fermentation-separation process for the production of butyric acid (BA) based on published data was\\u000a done. A unit consisting of a bioreactor with immobilized cells in the fibrous bed and of separation by pertraction through\\u000a supported liquid membranes (SLM) was considered. Productivities of the unit volume of a fixed bed bioreactor in continuous\\u000a and fed-batch fermentation at

Marek Blahušiak; Štefan Schlosser; Ján Marták

2010-01-01

173

Morphology and electrical properties of hybrid and sulphonated oxalic acid-doped polyaniline  

Microsoft Academic Search

Polyaniline–polyethylene glycol2000 (PAni–PEG2000) hybrid and sulphonated polyaniline (SPAni) were prepared using oxalic acid as dopant and potassium permanganate as oxidant. The properties of these two conductive polymers were studied in comparison with pure polyaniline (PAni) prepared using the same conditions. The investigated polymers were characterized using FTIR, UV–vis, TGA, TEM, SEM, XRD and their electrical conductivities were also investigated. The

Mona Abdel Rehim; Ahmed Youssef; Ebtesam Hassan; Nagwa Khatab; Gamal Turky

2010-01-01

174

WO 3\\/C hybrid material as a highly active catalyst support for formic acid electrooxidation  

Microsoft Academic Search

The hybrid material based on WO3 and Vulcan XC-72R carbon has been used as the support of Pd nanocatalysts. The resultant Pd–WO3\\/C catalysts in a large range of WO3 content exhibit excellent catalytic activity and stability for formic acid electrooxidation. The great improvement in the catalytic performance is attributed to the uniform dispersion of Pd with less particle sizes on

Zhonghua Zhang; Yunjie Huang; Junjie Ge; Changpeng Liu; Tianhong Lu; Wei Xing

2008-01-01

175

Preparation and characterization of starch\\/poly( l-lactic acid) hybrid foams  

Microsoft Academic Search

Starch\\/poly(l-lactic acid) (PLA) hybrid foams were prepared by baking a mixture of starch, PLA, and other ingredients in a hot mold. The effects of relative humidity, storage time, PLA content, and type and content of added plasticizer (e.g. glycerol, urea, or ammonium chloride) on moisture and water absorption, mechanical properties, and enzymatic degradability of the as-prepared foams were investigated. In

Dujdao Preechawong; Manisara Peesan; Pitt Supaphol; Ratana Rujiravanit

2005-01-01

176

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…

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

2003-01-01

177

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

178

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

Microsoft Academic Search

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

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

1999-01-01

179

Structural probing of the HIV1 polypurine tract RNA:DNA hybrid using classic nucleic acid ligands  

Microsoft Academic Search

The interactions of archetypical nucleic acid ligands with the HIV-1 polypurine tract (PPT) RNA:DNA hybrid, as well as analogous DNA:DNA, RNA:RNA and swapped hybrid substrates, were used to probe structural features of the PPT that contribute to its specific recognition and processing by reverse transcriptase (RT). Results from intercalative and groove-binding ligands indicate that the wild-type PPT hybrid does not

Kevin B. Turner; Robert G. Brinson; Hye Young Yi-Brunozzi; Jason W. Rausch; Jennifer T. Miller; S. F. J. Le Grice; John P. Marino; Daniele Fabris

2008-01-01

180

In vitro effects of molecular nanosomal hybrid compositions with oxidized dextrans, conjugated with isonicotinic acid hydrazine on peritoneal macrophages.  

PubMed

The effects of molecular nanosomal hybrid compositions consisting of nanoliposomes with oxidized dextrans (mol. weights 35 and 60 kDa) conjugated with isonicotinic acid hydrazine (dextrazides) on peritoneal macrophages were studied in vitro. Incubation of peritoneal cells with molecular nanosomal hybrid compositions modified the immunological phenotype of macrophage populations, which reflected an increase in their functional activity. Molecular nanosomal hybrid compositions containing dextrazide with 60-kDa dextran more effectively activated macrophages. PMID:19526108

Shkurupy, V A; Arkhipov, S A; Tkachev, V O; Troitsky, A V; Luzgina, N G; Zaikovskaja, M V; Gulyaeva, E P; Bistrova, T N; Ufimtceva, E G

2008-11-01

181

Preparation of poly( l-lactic acid)-polysiloxane-calcium carbonate hybrid membranes for guided bone regeneration  

Microsoft Academic Search

A novel poly(l-lactic acid) (PLLA)\\/calcium carbonates hybrid membrane containing polysiloxane was prepared using aminopropyltriethoxysilane (APTES) for biodegradable bone-guided regeneration. Carboxy groups in the PLLA made a chemical bond with amino groups in APTES, resulting in the formation of the hybrid membrane. The polysiloxane-hybridized PLLA was an amorphous phase. The membrane formed hydroxycarbonate apatite (HCA) on its surface after 3d of

Hirotaka Maeda; Toshihiro Kasuga; Larry L. Hench

2006-01-01

182

Formation and photofragmentation properties of isolated aromatic amino acid-silver cluster hybrids  

NASA Astrophysics Data System (ADS)

The formation of isolated [ (Trp-2H)+Ag9] + and [ (Tyr-2H)+Ag9] + amino-acid-Ag9 hybrids is reported. The photofragmentation yields of the aromatic amino acid-silver cluster hybrids, as well as those of the protonated tryptophan and tyrosine molecules ([Trp+H]+ and [Tyr+H]+) have been recorded. The fragmentation yields of the complexes are higher than the yields for [Trp+H]+and [Tyr+H]+ and present an extension of the fragmentation on the red side of the spectrum. The photofragmentation spectrum of [ Trp+Ag9] + was recently reported [Mitric et al., J. Chem. Phys. 127, 134301 (2007)]. While the optical spectra of substituted [ (Trp-2H)+Ag9] + and non-substituted [ Trp+Ag9] + complexes are very similar, a strong modification of the fragmentation channels between the two complexes is observed. The fragmentation channels are sensitive to the type of bonding in aromatic amino acid-silver cluster hybrids and can be used as fingerprints of structures.

Tabarin, T.; Antoine, R.; Broyer, M.; Dugourd, P.

2009-04-01

183

Night temperature affects fatty acid composition in sunflower oil depending on the hybrid and the phenological stage  

Microsoft Academic Search

Fatty acid composition is affected by plant genotype and environmental conditions with temperature a major effect. The effect of night temperature during different periods of fruit filling on the fatty acid composition of sunflower oil from hybrids with different potential oleic acid content has never been studied. This information is needed if we are further to improve oil quality. A

N Izquierdo; L Aguirrezábal; F Andrade; V Pereyra

2002-01-01

184

Diffusion of Weak Acids across Lipid Bilayer Membranes: Effects of Chemical Reactions in the Unstirred Layers  

Microsoft Academic Search

Chemical reactions in the aqueous unstirred layers of solution adjacent to a membrane can have dramatic effects on the diffusion of solutes across that membrane. This is demonstrated by the diffusion of labeled salicylate and salicylic acid across a phospholipid bilayer membrane. Two types of chemical reactions are considered. The first is an isotopic exchange reaction between the ionic and

John Gutknecht; D. C. Tosteson

1973-01-01

185

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

186

Fluorescent products from reaction of peroxidizing polyunsaturated fatty acids with phosphatidyl ethanolamine and phenylalanine  

Microsoft Academic Search

Fluorescent chromophores produced by reaction of peroxidizing arachidonic acid or methyl docosahexaenoate with synthetic dipalmityl\\u000a phosphatidyl ethanolamine were lipid soluble, and those from reaction with phenylalanine were water soluble. In all reaction\\u000a systems that contained polyunsaturated fatty acid and only one amine compound, the development of fluorescence was linearly\\u000a related to oxygen absorption for 12–24 hr (p<0.001) and to the

C. J. Dillard; A. L. Tappel

1973-01-01

187

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

188

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

PubMed

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. PMID:23335856

Liao, Yuan-Xi; Hu, Qiao-Sheng

2012-09-01

189

Reactions of carbon monoxide with unsaturated fatty acids and derivatives: A review  

Microsoft Academic Search

The important reactions of carbon monoxide with unsaturated fatty derivatives that are reviewed in this paper include hydroformylation\\u000a (the oxo reaction), Koch carboxylation and Reppe carbonylation. With oleic acid as a substrate, the products are C19 bifunctional compounds e.g., formyl- or carboxy-stearic acid. Double bond isomerization before carbon monoxide addition is\\u000a characteristic of these catalytic reactions; additionally, rearrangement to introduce

E. H. Pryde; E. N. Frankel; J. C. Cowan

1972-01-01

190

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

NASA Astrophysics Data System (ADS)

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

Alavi, Saman; Taghikhani, Mahdi

2012-06-01

191

Degenerate Oligonucleotide Primed-Polymerase Chain Reaction-Based Array Comparative Genomic Hybridization for Extensive Amplicon Profiling of Breast Cancers  

PubMed Central

We have developed a protocol for degenerate oligonucleotide-primed-polymerase chain reaction-based array comparative genomic hybridization (array CGH) that, when combined with a laser microdissection technique, allows the analysis of cancer cell populations isolated from routine, formalin-fixed, paraffin-embedded tissue samples. Comparison of copy number changes detected by degenerate oligonucleotide-primed-polymerase chain reaction-based array CGH to those detected by conventional array CGH or fluorescence in situ hybridization, demonstrated that amplifications can be reliably detected. Using a genomic microarray containing 57 oncogenes, we screened a total of 28 breast cancer samples and obtained a detailed amplicon profile that is the most comprehensive to date in human breast cancer. The array CGH method described here will allow the genetic analysis of paraffin-embedded human cancer materials for example in the context of clinical trials.

Daigo, Yataro; Chin, Suet-Feung; Gorringe, Kylie L.; Bobrow, Lynda G.; Ponder, Bruce A. J.; Pharoah, Paul D. P.; Caldas, Carlos

2001-01-01

192

Preparation and characterization of crosslinked PVA\\/SiO 2 hybrid membranes containing sulfonic acid groups for direct methanol fuel cell applications  

Microsoft Academic Search

Organic–inorganic hybrids based on poly(vinyl alcohol) (PVA)\\/SiO2 hybrid membranes containing sulfonic acid groups were prepared using the sol–gel process under acidic conditions. The PVA\\/sulfosuccinic acid (SSA)\\/silica hybrid membranes were fabricated from different SSA contents. The proton conductivity and methanol permeability of the hybrid membranes were studied with changing SSA content from 5 to 25wt.%. It was found that the proton

Dae Sik Kim; Ho Bum Park; Ji Won Rhim; Young Moo Lee

2004-01-01

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

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

PubMed Central

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.

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

2003-01-01

195

Catalysed or uncatalysed esterification reaction of oleic acid with 2-ethyl hexanol  

Microsoft Academic Search

The para-toluene sulfonic acid (p-TSA) catalysed and uncatalysed esterifications between oleic acid and 2-ethylhexanol are investigated. The reactions were carried out in the presence of the stoichiometric amount or twice the stoichiometric amount of alcohol with respect to the fatty acid, at 140–170°C. In the presence of 1% of solid p-TSA monohydrate in xylene, the reaction is completed in 50min

Corinne Lacaze-Dufaure; Zéphirin Mouloungui

2000-01-01

196

Reactions of hypophosphorous acid with 3-halo-2-propyn-1-ols  

SciTech Connect

We showed that in the reactions of 3-chloro-2-propyn-1-ol and of 3-bromo-2-propyn-1-ol with hypophosphorous acid the halogen-substituted propadienylphosphonous acids are formed. The reactions are conducted with the azeotropic removal of water from a mixture of hypophosphorous acid and the acetylenic alcohol at the boiling point of benzene in an atmosphere of inert gas. The structure of the compounds obtained was proved by means of NMR and IR spectroscopy.

Belakhov, V.V.; Komarov, E.V.; Ionin, B.I.

1987-10-10

197

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

198

Effect of reaction temperature and reaction time on the preparation of low-molecular-weight chitosan using phosphoric acid  

Microsoft Academic Search

Low-molecular-weight chitosan were prepared using 85% phosphoric acid at different reaction temperatures and reaction time. At room temperature, the viscosity average-molecular weights (Mv) of chitosan decreased to 7.1×104 from 21.4×104 after 35 days treatment. The degradation rate decreased with increasing hydrolysis time. The yields of chitosan also continuously decreased from 68.4 to 40.2% after 35 days. At 40, 60 and

Zhishen Jia; Dongfeng Shen

2002-01-01

199

[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

200

Mechanism of linoleic acid hydroperoxide reaction with alkali  

Microsoft Academic Search

Treatment of (13S,9Z,11E)-13-hydroperoxy-9,11-octadecadienoic acid (13S-HPODE) with strong alkali resulted in the formation of about 75% of the corresponding hydroxy acid, (13S,9Z,11E)-13-hydroxyl-9,11-octadecadienoic acid (13S-HPODE), and the remaining 25% of products was a mixture of several oxidized fatty acids, the majority of which was formed\\u000a from (9Z,11R,S,12S,R)-13-oxo-11, 12-epoxy-9-octadecenoic acid by Favorskii rearrangement (Gardner, H.W.,et al. (1993)Lipids 28, 487–495). In the present work,

Harold W. Gardner; Thomas D. Simpson; Mats Hamberg

1996-01-01

201

Reaction of sorghum hybrids to anthracnose, grain mold and grain weathering in Burleson County, Texas, 2007  

Technology Transfer Automated Retrieval System (TEKTRAN)

Thirty commercial hybrids were evaluated for resistance against anthracnose, caused by Colletotrichum sublineolum and grain mold or grain weathering caused by a number of fungal species at the Texas A&M University Agricultural Experiment Station in College Station (Burleson County). Six hybrids wer...

202

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

203

Reactions of powders of zirconium and niobium carbides in their homogeneity ranges with some acids  

Microsoft Academic Search

In the work described below a study was made of the reactions of zirconium and niobium carbides in their homogeneity ranges with some mineral acids. It was considered of great interest also to investigate the gaseous products of acid decomposition of the carbides. Experiments were carried out, using hydrochloric, sulfuric, and nitric acids as reactants, on powders of the zirconium

V. P. Kopylova; V. I. Kornilova; T. N. Nazarchuk; V. B. Fedorus

1980-01-01

204

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

PubMed

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

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

2010-03-01

205

Uptake of hypobromous acid (HOBr) by aqueous sulfuric acid solutions: low-temperature solubility and reaction  

NASA Astrophysics Data System (ADS)

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 45-70wt% 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*=104-107mol L-1atm-1. H* is inversely dependent on temperature, with ?H=-45.0±5.4 kJ mol-1 and ?S=-101±24 J mol-1K-1 for 55-70wt% H2SO4 solutions. Our study includes temperatures which overlap both previous measurements of HOBr solubility. For uptake into 55-70wt% H2SO4, the solubility is described by log H*=(2349±280)/T-(5.27±1.24). At temperatures colder than ~213K, the solubility of HOBr in 45wt% H2SO4 is at least a factor of five larger than in 70wt% H2SO4, with log H*=(3665±270)/T-(10.63±1.23). 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. Upon uptake of HOBr into aqueous sulfuric acid in the presence of other brominated gases, particularly for 70wt% H2SO4 solution, our measurements demonstrate chemical reaction of HOBr followed by evolution of gaseous products including Br2O and Br2.

Iraci, L. T.; Michelsen, R. R.; Ashbourn, S. F. M.; Rammer, T. A.; Golden, D. M.

2005-06-01

206

Uptake of hypobromous acid (HOBr) by aqueous sulfuric acid solutions: low-temperature solubility and reaction  

NASA Astrophysics Data System (ADS)

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*=104-107 mol L-1 atm-1. H* is inversely dependent on temperature, with ?H=-45.0±5.4 kJ mol-1 and ?S=-101±24 J mol-1 K-1 for 55-70 wt% H2SO4 solutions. Our study includes temperatures which overlap both previous measurements of HOBr solubility. For uptake into 55-70 wt% H2SO4, the solubility is described by log H*=(2349±280)/T-(5.27±1.24). At temperatures colder than ~213 K, the solubility of HOBr in 45 wt% H2SO4 is at least a factor of five larger than in 70 wt% H2SO4, with log H*=(3665±270)/T-(10.63±1.23). 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. Upon uptake of HOBr into aqueous sulfuric acid in the presence of other brominated gases, particularly for 70 wt% H2SO4 solution, our measurements demonstrate chemical reaction of HOBr followed by evolution of gaseous products including Br2O and Br2.

Iraci, L. T.; Michelsen, R. R.; Ashbourn, S. F. M.; Rammer, T. A.; Golden, D. M.

2005-03-01

207

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

NASA Astrophysics Data System (ADS)

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

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

2000-10-01

208

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

2013-02-07

209

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

210

Thiolated pyrrolidinyl peptide nucleic acids for the detection of DNA hybridization using surface plasmon resonance.  

PubMed

Thiolated pyrrolidinyl peptide nucleic acids (HS-PNAs) bearing d-prolyl-2-aminocyclopentanecarboxylic acid (ACPC) backbones with different lengths and types of thiol modifiers were synthesized and then characterized by MALDI-TOF mass spectrometry. These HS-PNAs were immobilized on gold-coated glass by self-assembled monolayer (SAM) formation via S atom linkage for the detection of DNA hybridization using surface plasmon resonance (SPR). The amount and the stability of the immobilized HS-PNAs, as well as the effects of spacer and blocking thiol on DNA hybridization efficiency, were determined. SPR results indicated that the hybridization efficiency was enhanced when the distance between the PNA portion and the thiol terminal was increased and/or when blocking thiol was used following the HS-PNA immobilization. The immobilized HS-PNA could discriminate between fully complementary DNA from one or two base mismatched DNA with a relatively high degree of mismatch discrimination (>45%) in PBS buffer at 25 degrees C. The lowest DNA concentration at which reliable discrimination between fully complementary and single mismatched DNA could still occur was at about 0.2 microM, which is equivalent to 10 pmol of DNA. This research demonstrates that using these novel thiolated PNAs in combination with the SPR technique offers a direct, rapid and non-label based method that could potentially be applied for the analysis of genomic or PCR-amplified DNA in the future. PMID:19515551

Ananthanawat, Cheeraporn; Vilaivan, Tirayut; Mekboonsonglarp, Wanwimon; Hoven, Voravee P

2009-05-18

211

Gabapentin: a stereochemically constrained gamma amino acid residue in hybrid peptide design.  

PubMed

Nature has used the all-alpha-polypeptide backbone of proteins to create a remarkable diversity of folded structures. Sequential patterns of 20 distinct amino acids, which differ only in their side chains, determine the shape and form of proteins. Our understanding of these specific secondary structures is over half a century old and is based primarily on the fundamental elements: the Pauling alpha-helix and beta-sheet. Researchers can also generate structural diversity through the synthesis of polypeptide chains containing homologated (omega) amino acid residues, which contain a variable number of backbone atoms. However, incorporating amino acids with more atoms within the backbone introduces additional torsional freedom into the structure, which can complicate the structural analysis. Fortunately, gabapentin (Gpn), a readily available bulk drug, is an achiral beta,beta-disubstituted gamma amino acid residue that contains a cyclohexyl ring at the C(beta) carbon atom, which dramatically limits the range of torsion angles that can be obtained about the flanking C-C bonds. Limiting conformational flexibility also has the desirable effect of increasing peptide crystallinity, which permits unambiguous structural characterization by X-ray diffraction methods. This Account describes studies carried out in our laboratory that establish Gpn as a valuable residue in the design of specifically folded hybrid peptide structures. The insertion of additional atoms into polypeptide backbones facilitates the formation of intramolecular hydrogen bonds whose directionality is opposite to that observed in canonical alpha-peptide helices. If hybrid structures mimic proteins and biologically active peptides, the proteolytic stability conferred by unusual backbones can be a major advantage in the area of medicinal chemistry. We have demonstrated a variety of internally hydrogen-bonded structures in the solid state for Gpn-containing peptides, including the characterization of the C(7) and C(9) hydrogen bonds, which can lead to ribbons in homo-oligomeric sequences. In hybrid alphagamma sequences, distinct C(12) hydrogen-bonded turn structures support formation of peptide helices and hairpins in longer sequences. Some peptides that include the Gpn residue have hydrogen-bond directionality that matches alpha-peptide helices, while others have the opposite directionality. We expect that expansion of the polypeptide backbone will lead to new classes of foldamer structures, which are thus far unknown to the world of alpha-polypeptides. The diversity of internally hydrogen-bonded structures observed in hybrid sequences containing Gpn shows promise for the rational design of novel peptide structures incorporating hybrid backbones. PMID:19572698

Vasudev, Prema G; Chatterjee, Sunanda; Shamala, Narayanaswamy; Balaram, Padmanabhan

2009-10-20

212

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

213

Modeling suberization with peroxidase-catalyzed polymerization of hydroxycinnamic acids: cross-coupling and dimerization reactions.  

PubMed

An anionic potato peroxidase (EC 1.11.1.7, APP) thought to be involved in suberization after wounding was isolated from slices of Solanum tuberosum in order to elucidate the first steps of dehydrogenative polymerization between pairs of different hydroxycinnamic acids (FA, CafA, CA and SA) present in wound-healing plant tissues. Use of a commercial horseradish peroxidase (HRP)-H2O2 catalytic system gave the identical major products in these coupling reactions, providing sufficient quantities for purification and structural elucidation. Using an equimolar mixture of pairs of hydroxycinnamic acid suberin precursors, only caffeic acid is coupled to ferulic acid and sinapic acid in separate cross-coupling reactions. For the other systems, HRP and APP reacted as follows: (1) preferentially with ferulic acid in a reaction mixture that contained p-coumaric and ferulic acids; (2) with sinapic acid in a mixture of p-coumaric and sinapic acids; (3) with sinapic acid in a mixture of ferulic and sinapic acids; (4) with caffeic acid in a reaction mixture of p-coumaric and caffeic acids. The resulting products, isolated and identified by NMR and MS analysis, had predominantly beta-beta-gamma-lactone and beta-5 benzofuran molecular frameworks. Five cross-coupling products are described for the first time, whereas the beta-O-4 dehydrodimers identified from the caffeic acid and sinapic acid cross-coupling reaction are known materials that are highly abundant in plants. These reactivity trends lead to testable hypotheses regarding the molecular architecture of intractable suberin protective plant materials, complementing prior analysis of monomeric constituents by GC-MS and polymer functional group identification from solid-state NMR, respectively. PMID:16524605

Arrieta-Baez, Daniel; Stark, Ruth E

2006-03-09

214

Dehydration of cyclohexanol as a test reaction for zeolite acidity  

Microsoft Academic Search

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.

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

1984-01-01

215

Magnetic isotope effect and theory of atomic orbital hybridization to predict a mechanism of chemical exchange reactions.  

PubMed

A novel approach is suggested to investigate the mechanisms of chemical complexation reactions based on the results of Fujii with co-workers; they have experimentally observed that several metals and metalloids demonstrate mass-independent isotope fractionation during the reactions with the DC18C6 crown ether using solvent-solvent extraction. In this manuscript, the isotope fractionation caused by the magnetic isotope effect is used to understand the mechanisms of chemical exchange reactions. Due to the rule that reactions are allowed for certain electron spin states, and forbidden for others, magnetic isotopes show chemical anomalies during these reactions. Mass-independent fractionation is suggested to take place due to the hyperfine interaction of the nuclear spin with the electron spin of the intermediate product. Moreover, the sign of the mass-independent fractionation is found to be dependent on the element and its species, which is also explained by the magnetic isotope effect. For example, highly negative mass-independent isotope fractionation of magnetic isotopes was observed for reactions of DC18C6 with SnCl(2) species and with several Ru(III) chloro-species, and highly positive for reactions of this ether with TeCl(6)(2-), and with several Cd(II) and Pd(II) species. The atomic radius of an element is also a critical parameter for the reaction with crown ether, particularly the element ions with [Kr]4d(n)5s(m) electron shell fits the best with the DC18C6 crown ring. It is demonstrated that the magnetic isotope effect in combination with the theory of orbital hybridization can help to understand the mechanism of complexation reactions. The suggested approach is also applied to explain previously published mass-independent fractionation of Hg isotopes in other types of chemical exchange reactions. PMID:21709897

Epov, Vladimir N

2011-06-27

216

40 CFR 721.6181 - Fatty acid, reaction product with substituted oxirane, formaldehyde-phenol polymer glycidyl ether...  

Code of Federal Regulations, 2013 CFR

...SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.6181 Fatty acid, reaction product with substituted...reporting. (1) The chemical substance identified generically as fatty acid, reaction product with...

2013-07-01

217

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

Code of Federal Regulations, 2013 CFR

...SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721...acids, tall-oil, reaction products with (butoxymethyl...reporting . (1) The chemical substance identified...acids, tall-oil, reaction products with...

2013-07-01

218

Synthesis and Anti-tumor Activity Evaluation of Gallic Acid-mangiferin Hybrid Molecule.  

PubMed

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

Hu, Xiang-Yu; Deng, Jia-Gang; Wang, Lin; Yuan, Ye-Fei

2013-12-01

219

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...

220

BIFUNCTIONAL Nb\\/Ti-MCM-41 CATALYST IN OXIDATIVE ACIDIC REACTION OF CYCLOHEXENE TO DIOL  

Microsoft Academic Search

Bifunctional oxidative and acidic catalyst was prepared by incorporating titanium ion (Ti4+) and niobic acid in mesoporous molecular sieves MCM -41 structure. The catalyst is active both in oxidation, and acid-catalyzed reaction of olefin to diol. Nb\\/Ti-MCM -41 catalyst was prepared by first synthesizing Ti-MCM -41 by hydrothermal method, followed by subsequent impregnation of niobic acid (Nb) into Ti-MCM -41

Zainab Ramli; Mazidah Abdul Shukor; Didik Prasetyoko

221

Production of propylene glycol fatty acid monoesters by lipase-catalyzed reactions in organic solvents  

Microsoft Academic Search

Fatty acid monoesters of propylene glycol (1,2-propanediol) are good water-in-oil emulsifiers. These esters were synthesized\\u000a enzymatically to overcome the problems associated with chemical processes. APseudomonas lipase was added to reaction mixtures containing propylene glycol and various acyl donors (fatty acids, fatty acid ethyl\\u000a esters, fatty acid anhydrides and triglycerides) in organic solvents, and the mixtures were shaken at 30C. The

Jei-Fu Shaw; Shian Lo

1994-01-01

222

Phosphoric acid impurities in phosphoric acid fuel cell electrolytes. 2: Effects on the oxygen reduction reaction at platinum electrodes  

SciTech Connect

The effects of phosphorus acid additions on the oxygen reduction reaction at platinum electrodes in concentrated phosphoric acid were studied. The oxygen reduction currents decreased, and the Tafel slopes became more negative upon the addition of small concentrations of phosphorus acid. In addition,the phosphorus acid oxidation current tended to complete with the oxygen reduction current. These effects became more pronounced at higher phosphorus acid concentrations and at higher temperatures. Upon the addition of phosphorus acid the number of electrons involved in the oxygen reduction reaction decreased from a value close to four to a value approaching two, suggesting promotion of a two-electron reduction to peroxide. Therefore, in studies of the electrochemical reduction of oxygen in hot concentrated phosphoric acid or in fuel cell systems using hot concentrated phosphoric acid as electrolyte, it is recommended that precautions be taken against the inadvertent formation of the phosphorus acid. The removal of phosphorus acid from concentrated phosphoric acid by repeated potential cycling at 100 mV/s between + 0.5 and +1.50 V (vs. dynamic hydrogen electrode) was demonstrated.

Sugishima, Noboru; Hinatsu, J.T.; Foulkes, F.R. (Univ. of Toronto, Ontario (Canada). Dept. of Chemical Engineering and Applied Chemistry)

1994-12-01

223

Quantitative analysis for solid-phase hybridization reaction and binding reaction of DNA binder to hybrids using a quartz crystal microbalance  

Microsoft Academic Search

A 20-mer DNA probe complementary to a part of an oncogene v-myc, having a mercaptohexyl group at the 5?-end, was immobilized on a gold electrode of a quartz crystal microbalance (QCM). The quantity of the probe immobilized on the electrode depended on the pH. Under acidic or basic immobilization conditions, the probe was immobilized more than under neutral conditions. The

Keiko Ito; Koji Hashimoto; Yoshio Ishimori

1996-01-01

224

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

225

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

DOEpatents

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

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

1998-01-01

226

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

SciTech Connect

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

Pardi, A.; Tinoco, I. Jr.

1982-09-14

227

Mechanism of reaction of nitrogen dioxide radical with hydroxycinnamic acid derivatives: a pulse radiolysis study.  

PubMed

Nitrogen dioxide radical (NO2.) is known as a toxic agent produced in the metabolism of nitrates and nitrites. By the use of the pulse radiolysis technique, the mechanism of the reaction of NO2. radical with hydroxycinnamic acid derivatives (HCA) was studied and the rate constants have been measured. The rate constants were found to be 7.4 x 10(8), 7.2 x 10(8), 8.6 x 10(8) dm3 mol(-1) s(-1) for ferulic acid, sinapic acid and caffeic acid, respectively. The reactions produce the corresponding phenoxyl radical. PMID:9733017

Zhouen, Z; Side, Y; Weizhen, L; Wenfeng, W; Yizun, J; Nianyun, L

1998-07-01

228

Detection of strains of potato virus S by nucleic acid spot hybridization (NASH)  

Microsoft Academic Search

Summary  Two complementary DNA (cDNA) clones (0.9 kb and 1.6 kb) reacting to the ordinary strain of potato virus S (PVS) were compared\\u000a with single-stranded randomly primed cDNA (prepared to total genomic RNA) as probes for various strains of PVS, using the\\u000a technique of nucleic acid spot hybridization (NASH). The cDNA clones detected 11 PVS isolates well, including both Andean\\u000a and

Gary D. Foster; Peter R. Mills

1990-01-01

229

Elucidation of the mechanistic pathways of the hydroxyl radical scavenging reaction by daidzein using hybrid QM/MM dynamics.  

PubMed

Employing a hybrid QM/MM simulation we explored the reaction dynamics of the hydroxyl radical scavenging activity of daidzein, a soy isoflavone. Our simulations illustrate that the highly reactive hydroxyl radical can participate in hydrogen abstraction reaction with both OH functional groups of daidzein and can form stable daidzein radicals. We found that the reaction involving the 4'-OH site of daidzein is energetically favorable over the other reaction pathway involving the 7-OH site of daidzein by ?29 kcal/mol. The high enthalpic stabilization involved in daidzein radical formation at the 4'-OH site can be partly attributed to better solvation through hydrogen-bonding interactions with water and higher electron density delocalization of radical over the adjacent aromatic ring. As evident from the QM/MM dynamics, both HAT pathways led to formation of ketones at the 7-OH and 4'-OH sites of daidzein, respectively, and the adjacent aromatic rings appear in a p-quinonoid form, a highly stable resonating structure. The suitability of the QM/MM methodology to study the reaction mechanism, identification of intermediate states, and pathways of flavonoid radical stabilization reported here opens up a new possibility to study a similar reaction mechanism in other systems. PMID:22853918

Chakraborty, Sandipan; Biswas, P K

2012-08-22

230

Reaction of Mn III,IV (hydr)oxides with oxalic acid, glyoxylic acid, phosphonoformic acid, and structurally-related organic compounds  

NASA Astrophysics Data System (ADS)

Phosphonoformic acid, oxalic acid, glyoxylic acid, and 10 additional organic compounds that are structurally related to them have been reacted with synthetic MnO 2 (birnessite), consisting of 22% Mn III and 78% Mn IV, and synthetic MnOOH (manganite), consisting solely of Mn III. Significant concentrations of dissolved Mn III were detected in reactions of phosphonoformic acid with MnOOH, indicating that ligand-assisted dissolution took place. Reaction of phosphonoformic acid with MnO 2, and reaction of all other organic reactants with either MnOOH or MnO 2, yielded only Mn II, indicating that reductive dissolution was predominant. As far as reductive dissolution reactions are concerned, MnO 2 yields a range of reactivity that is nearly 20-times greater than that of MnOOH. Oxidation converts phosphonoformic acid into orthophosphate ion, glyoxylic acid into formic acid, pyruvic acid into acetic acid, and 2,3-butanedione into acetic acid. When differences in surface area loading are accounted for, oxalic acid, pyruvic acid, and 2,3-butanedione yield virtually the same dissolution rates for the two (hydr)oxides. At pH 5.0, glyoxylic acid reacts 14-times faster with MnO 2 than with MnOOH. MnO 2 reacts more slowly than MnOOH by a factor of 1/16th with oxamic acid, 1/20th with lactic acid, and 1/33rd with dimethyl oxalate. Adsorptive, complexant, and reductant properties of the 13 organic reactants are believed responsible for the observed reactivity differences.

Wang, Yun; Stone, Alan T.

2006-09-01

231

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

PubMed

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

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

2012-01-30

232

Envisioning an enzymatic Diels-Alder reaction by in situ acid-base catalyzed diene generation.  

PubMed

We present and evaluate a new and potentially efficient route for enzyme-mediated Diels-Alder reactions, utilizing general acid-base catalysis. The viability of employing the active site of ketosteroid isomerase is demonstrated. PMID:22547054

Linder, Mats; Johansson, Adam Johannes; Manta, Bianca; Olsson, Philip; Brinck, Tore

2012-05-01

233

Why and How To Teach Acid-Base Reactions without Equilibrium.  

ERIC Educational Resources Information Center

|Recommends an approach to the treatment of acid-base equilibria that involves treating each reaction as either going to completion or not occurring at all. Compares the method with the traditional approach step by step. (DDR)|

Carlton, Terry S.

1997-01-01

234

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

235

Cephalosporanic Acids: A New Look at Reactions at the C-3' Position  

Microsoft Academic Search

Nucleophilic displacement of the acetoxy group of cephalosporanic acids by thiols in aqueous solution at neutral pH provides 3-thiomethyl-substituted compounds with a broad spectrum of antibiotic activity. The aqueous displacement reaction is often destructive of much of the cephalosporanic acid, and products generally require extensive purification. Displacements at a lower pH are complicated by unwanted lactone formation. However, reactions conducted

L. D. Hatfield; J. W. Fisher; J. M. Dunigan; R. W. Burchfield; J. M. Greene; J. A. Webber; R. T. Vasileff; M. D. Kinnick

1980-01-01

236

New Preparation of Cyclic Acyloxyphosphorane by Reaction of Glyoxylic Acid with Phosphorus(III) Compounds  

Microsoft Academic Search

We have recently found that the reaction of ?-keto acids (1) with phosphorus (III) compounds (3) yielded cyclic acyloxyphosphoranes(C-AOPs, 4), a new class of pentacovalent phosphorus species having a P-OC(O) group. The present paper deals with a new reaction of glyoxylic acid (2) with 3 to give C-AOPs (5) having no substituent at the C-3 position. 1 is an ?-keto

Shiro Kobayashi; Yukitoshi Narukawa; Takeo Saegusa

1982-01-01

237

Cross-coupling reaction of cyclopropylboronic acids with aryl ?-halo-oxo-perfluoroalkylsulfonates  

Microsoft Academic Search

The cross-coupling reaction of cyclopropylboronic acids with aryl ?-halo-oxo-perfluoroalkylsulfonates is investigated. It\\u000a was found that the stereodefined cyclopropylboronic acids can readily react with aryl ?-halo-oxo-perfluoroalkylsulfonates\\u000a to give the corresponding crosscoupling products in high yields under the appropriate conditions and in the presence of transition\\u000a metal catalysts. For the reaction of various aryl perfluoroalkylsulfonates bearing the substituents, the use of corresponding

Minliang Yao; Jiapo Wang; Minzhi Deng

2001-01-01

238

Enrichment of ?-linolenic acid from borage oil via lipase-catalyzed reactions  

Microsoft Academic Search

Three lipase-catalyzed reactions were utilized to enrich ?-linolenic acid in borage oil: (i) selective hydrolysis in isooctane\\u000a by Candida rugosa lipase immobilized on microporous polypropylene, (ii) selective esterification of free fatty acid from saponified borage\\u000a oil and n-butanol by Lipozyme IM-20, and (iii) acidolysis of the products of the previous two reactions, that is, unhydrolyzed acylglycerols\\u000a and unesterified free fatty

Fang-Cheng Huang; Yi-Hsu Ju; Cheng-Wei Huang

1997-01-01

239

Reaction kinetics of the esterification of lauric acid in iso-octane using an immobilized biocatalyst  

Microsoft Academic Search

The kinetics of the esterification of lauric acid with geraniol catalyzed by a commercially immobilized lipase preparation\\u000a fromMucor miehei, Lipozyme, was studied in well-stirred flasks under conditions of no external mass transfer limitations. It was shown that\\u000a the reaction is inhibited by lauric acid and the reaction mechanism can be described as a Ping-Pong Bi-Bi with Dead-End inhibition\\u000a caused by

F. VÁzquez Lima; D. L. Pyle; J. A. Asenjo

1997-01-01

240

Cutaneous granulomatous reaction to injectable hyaluronic acid gel: another case.  

PubMed

We report a case of a granulomatous reaction in the melolabial folds, occurring 10 days after treatment with Restylane. The patient, who had previously been treated with the same product in the last 2 years without any adverse effect, developed an unusual early fibrotic reaction that we hypothesized related to hypersensitivity after repeated use. The lesions slowly disappeared with topical steroid therapy. An improved knowledge of the modality of these uncommon adverse effects is necessary to assess the long-term safety and efficacy of this product. PMID:17365268

Bardazzi, Federico; Ruffato, Alberto; Antonucci, Angela; Balestri, Riccardo; Tabanelli, Michela

2007-01-01

241

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

242

The reaction of 5-hydroxyindoleacetic acid with ortho-phthalaldehyde and cysteine.  

PubMed

The metabolite 5-hydroxyindoleacetic acid, the major metabolic product of serotonin, can be measured by reacting it with orthophthalaldehyde to form a highly fluorescent product. The inclusion of cysteine in this reaction causes an increase in the amount of fluorescence. The rate of fluorescence formation for reaction containing cysteine is much faster than the rate for the reaction without cysteine. The differences observed for both excitation and remission maxima between reaction products formed in the presence and absence of cysteine indicate that these products are different. Furthermore, the significant difference in the regression coefficients of fluorescence of the reaction products versus HC1 concentration adds further evidence that the reaction products formed in the presence and absence of cysteine are different. HC1 appears to influence the reaction of 5-HIAA, OPT and cysteine in several ways: by causing the destruction of 5-HIAA, by affecting the fluorescence of the product formed, and by influencing the amount of reaction product formed. PMID:928964

Manowitz, P; Friedhoff, A J

1977-12-01

243

Development of a polymerase chain reaction assay for differentiation between Culex pipiens pipiens and Cx. p. quinquefasciatus (Diptera: Culicidae) in North America based on genomic differences identified by subtractive hybridization.  

PubMed

Culex pipiens is a complex of mosquitoes that are involved in the transmission of pathogens, including St. Louis encephalitis virus in North America. The 2 major taxa in the complex, Cx. p. pipiens and Cx. p. quinquefasciatus, are nearly identical morphologically, making identification of field-collected specimens difficult, and attempts at differentiation based on biochemical and molecular techniques have been unsuccessful. We report here the use of genomic subtractive hybridization to identify a region of nucleic acid heterology between the genomes of Cx. p. pipiens and Cx. p. quinquefasciatus and the development of a polymerase chain reaction (PCR) assay to discriminate between them. PCR primers based on the nucleic acid sequence of a Cx. p. pipiens-unique DNA fragment were used to differentiate Cx. p. pipiens and Cx. p. pipiens/quinquefasciatus hybrids from Cx. p. quinquefasciatus by using extracted individual mosquito genomic DNA, crude DNA preparations from a mosquito head or legs, and DNA from triturated mosquito pools. PMID:9379458

Crabtree, M B; Savage, H M; Miller, B R

1997-09-01

244

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

Microsoft Academic Search

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

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

2007-01-01

245

Kinetic study of the gas phase formation and decomposition reactions of nitrous acid  

Microsoft Academic Search

The kinetics of the gas phase decomposition and formation reactions of nitrous acid, 2HONO = NO + NOâ + HâO (kâ, kâ), have been investigated in a Pyrex reactor at HONO partial pressures of 0.05 to 1.0 Torr and total pressures of 5 to 50 Torr using a mass spectrometer detector. The reactions were determined to be heterogeneous under all

E. W. Kaiser; C. H. Wu

1977-01-01

246

Hydrothermal reactions of formaldehyde and formic acid: Free-energy analysis of equilibrium  

NASA Astrophysics Data System (ADS)

The chemical equilibria concerning formaldehyde and formic acid are computationally investigated in water over a wide range of thermodynamic conditions. The free energy is evaluated in the method of energy representation for the solvent effect on the decomposition processes of these two compounds. The solvation is found to suppress the production of nonpolar species from a polar. In the two competitive decomposition reactions of formic acid, the solvent strongly inhibits the decarboxylation (HCOOH-->CO2+H2) and its effect is relatively weak for the decarbonylation (HCOOH-->CO+H2O). The equilibrium weights for the two decomposition pathways of formic acid are determined by the equilibrium constant of the water-gas-shift reaction (CO+H2O-->CO2+H2), which is an essential and useful process in fuel technology. The reaction control by the solvent is then examined for the water-gas-shift reaction. Through the comparison of the equilibrium constants in the absence and presence of solvent, even the favorable side of the reaction is shown to be tuned by the solvent density and temperature. The reaction equilibrium is further treated for aldehyde disproportionation reactions involving formaldehyde and formic acid. The disproportionation reactions are found to be subject to relatively weak solvent effects and to be dominated by the electronic contribution.

Matubayasi, Nobuyuki; Nakahara, Masaru

2005-02-01

247

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

EPA Science Inventory

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

248

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…

Goodney, David E.

2006-01-01

249

Diazo carbonyl derivatives of heterocycles. 2. Reaction of anhydrides of pyridine- and quinolinedicarboxylic acids with diazomethane  

Microsoft Academic Search

The reaction of anhydrides of cinchomeronic, quinolinic, and acridinic acids with diazomethane was studied. The reaction pathway that they have in common is acylation of diazomethane with opening of the anhydride ring, accompanied by the formation of the corresponding diazo ketones. It is shown that the nature of the heterocyclic part of the anhydride molecule has a substantial effect on

V. G. Kartsev; S. V. Chapyshev; A. M. Sipyagin; N. S. Yashina; V. S. Petrosyan

1983-01-01

250

The Reaction Between Tri-p-Tolyl Phosphate and Nonanoic Acid at 260C.  

National Technical Information Service (NTIS)

The reaction between tri-p-tolyl phosphate and nonanoic acid has been studied at 260C in the absence of air. For an undiluted equimolar mixture the reactants are consumed within 24 hours giving a reaction mixture containing phenol and cresols, phosphoric ...

S. C. Brown C. F. Poranski

1971-01-01

251

Multicomponent reactive transport modeling of acid neutralization reactions in mine tailings  

Microsoft Academic Search

Multicomponent reactive transport modeling was conducted to analyze and quantify the acid neutralization reactions observed in a column experiment. Experimental results and the experimental procedures have been previously published. The pore water geochemistry was described by dissolution and precipitation reactions involving primary and secondary mineral phases. The initial amounts of the primary phases ankerite-dolomite, siderite, chlorite, and gypsum were constrained

Jasna Jurjovec; David W. Blowes; Carol J. Ptacek; K. Ulrich Mayer

2004-01-01

252

Uric Acid Oxidation by Peroxynitrite: Multiple Reactions, Free Radical Formation, and Amplification of Lipid Oxidation  

Microsoft Academic Search

Uric acid has been considered to be an efficient scavenger of peroxynitrite but the reaction between urate and peroxynitrite has been only partially characterized. Also, previous studies have indicated that urate may increase peroxynitrite-mediated oxidation of low density lipoprotein (LDL). Here, we examined the reaction between urate and peroxynitrite by combining kinetic, oxygen consumption, spin trapping, and product identification studies;

Célio X. C. Santos; Edson I. Anjos; Ohara Augusto

1999-01-01

253

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...

254

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

255

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

256

Phenylboronic acid mediated triple condensation reactions of phloroglucinol and unsaturated carbonyl compounds.  

PubMed

[reaction: see text] A remarkable phenylboronic acid mediated triple condensation reaction of phloroglucinol (1,3,5-trihydroxybenzene) with a series of alpha,beta-unsaturated carbonyl compounds is reported. This experimentally simple reaction afforded novel C3-symmetric 2H-chromene derivatives. These derivatives represent structural analogues of the natural product xyloketal A, which has been reported to be a potent inhibitor of acetylcholine esterase. PMID:15673266

Pettigrew, Jeremy D; Cadieux, Jay A; So, Simon S S; Wilson, Peter D

2005-02-01

257

TGF-?3 immobilized PLGA-gelatin/chondroitin sulfate/hyaluronic acid hybrid scaffold for cartilage regeneration.  

PubMed

Although most in vitro studies indicate that transforming growth factor ?3 (TGF-?3) immobilized scaffold is suitable for cartilage tissue engineering, in vivo studies of implanting immobilized scaffold for chondral defect repair are still lacking. This study is to evaluate the potentials of TGF-?3 immobilized poly-(lactic-co-glycolic acid)-gelatin/chondroitin sulfate/hyaluronic acid (PLGA-GCH) hybrid scaffold for cartilage regeneration. The scaffold was fabricated by incorporating GCH micro-sponges into PLGA frameworks and then crosslinked with TGF-?3 to mimic natural cartilaginous extra cellular matrix (ECM). In vitro study demonstrated that MSCs proliferated vigorously and produced abundant ECM on scaffold. The immunohistochemistry staining and alcian blue staining confirmed the cartilaginous ECM production. The chondrogenic differentiation of MSCs on scaffold was proved by the expression of collagen II gene in mRNA and protein level. Then MSCs/TGF-?3 immobilized scaffolds were implanted in rabbits for chondral defects repair. After eight weeks, histological observation showed that differentiated MSCs were located in lacunae within the metachromatic staining matrix and exhibited typical chondrocyte morphology. Histological grading scores also indicated the congruent cartilage was regenerated. In conclusion, the TGF-?3 immobilized PLGA-GCH hybrid scaffold has great potential in constructing the tissue-engineered cartilage. PMID:20872747

Fan, Hongbin; Tao, Huiren; Wu, Yingnan; Hu, Yunyu; Yan, Yongnian; Luo, Zhuojin

2010-09-24

258

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

259

The Kinetics of the Gas Phase Reaction of Nitrous Acid with Ozone.  

National Technical Information Service (NTIS)

The kinetics of the gas phase reaction between ozone and nitrous acid have been investigated under conditions applicable to the middle stratosphere. The decay of nitrous acid (<0.005 Torr) in the presence of excess ozone (0.4-14 Torr) has been measured at...

E. W. Kaiser S. M. Japar

1977-01-01

260

Kinetics of acid-catalyzed aldol condensation reactions of aliphatic aldehydes  

NASA Astrophysics Data System (ADS)

Field observations of atmospheric aerosols have established that organic compounds compose a large fraction of the atmospheric aerosol mass. However, the physical/chemical pathway by which organic compounds are incorporated into atmospheric aerosols remains unclear. The potential role of acid-catalyzed reactions of organic compounds on acidic aerosols has been explored as a possible chemical pathway for the incorporation of organic material into aerosols. In the present study, ultraviolet-visible (UV-vis) spectroscopy was used to monitor the kinetics of formation of the products of the acid-catalyzed aldol condensation reaction of a range of aliphatic aldehydes (C 2-C 8). The experiments were carried out at various sulfuric acid concentrations and a range of temperatures in order to estimate the rate constants of such reactions on sulfuric acid aerosols under tropospheric conditions. The rate constants were generally found to decrease as the chain length of the aliphatic aldehyde increased (except for acetaldehyde, which had an unusually small rate constant), increase as a function of sulfuric acid concentration as predicted by excess acidity theory, and showed normal Arrhenius behavior as a function of temperature. While the kinetic data are generally consistent with previous laboratory reports of aldehyde reactivity in various sulfuric acid media, the aldol condensation reactions involving aliphatic aldehydes do not appear fast enough to be responsible for significant transfer of organic material into atmospheric aerosols.

Casale, Mia T.; Richman, Aviva R.; Elrod, Matthew J.; Garland, Rebecca M.; Beaver, Melinda R.; Tolbert, Margaret A.

261

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

262

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

263

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

264

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

265

Oligonucleotide derivatives in the hybridization analysis of nucleic acids: II. Isothermal signal amplification in DNA analysis by minisequencing  

Microsoft Academic Search

An isothermal amplification of a reporter signal during the analysis of the hybridization of nucleic acids was studied by\\u000a limited probe extension (minisequencing). The intensity of the reporter signal was shown to increase due to the multiple enzymatic\\u000a labeling of the probes during consecutive hybridization with one DNA template in both the homophase and heterophase assays\\u000a using various detection methods:

E. V. Dmitrienko; E. A. Khomyakova; I. A. Pyshnaya; A. G. Bragin; V. E. Vedernikov; D. V. Pyshnyi

2010-01-01

266

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

267

Stoichiometry of the Reaction of Magnesium with Hydrochloric Acid  

NASA Astrophysics Data System (ADS)

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

Chebolu, Venkat; Storandt, Barbara C.

2003-03-01

268

Preparation of phenylboronic acid-silica hybrid monolithic column with one-pot approach for capillary liquid chromatography of biomolecules.  

PubMed

A phenylboronic acid-silica hybrid monolithic column for capillary liquid chromatography (cLC) was prepared through one-pot process by using 4-vinylphenylboronic acid (VPBA) and alkoxysilanes simultaneously. The effects of the molar ratio of tetramethyloxysilane/?-methacryloxypropyltrimethoxysilane (TMOS/?-MAPS), amount of VPBA, and the volume of diethylene glycol (DEG) on the morphologies, permeabilities and pore properties of the prepared VPBA-silica hybrid monolithic columns were studied in detail. A relatively uniform monolithic structure with high porosity was obtained with optimized ingredients. A series of cis-diol-containing compounds, alkylbenzenes, amides, and anilines were utilized to evaluate the retention behaviors of the VPBA-silica hybrid monolithic column. The result demonstrated that the prepared VPBA-silica hybrid monolithic column exhibited multiple interactions including hydrophobicity, hydrophilicity, as well as cation exchange apart from the expected affinity interaction. The run-to-run, column-to-column and batch-to-batch reproducibility of the VPBA-silica hybrid monolith were satisfactory with the relative standard deviations (RSDs) less than 1.63% (n=5), 2.02% (n=3) and 2.90% (n=5), respectively, indicating the effectiveness and practicability of the proposed method. In addition, the VPBA-silica hybrid monolithic column was further applied to the separation of proteins and tryptic digest of bovine serum albumin (BSA), respectively. The successful applications suggested the potential of the VPBA-silica hybrid monolith in proteome analysis. PMID:23219026

Lin, Zian; Huang, Hui; Li, Shihua; Wang, Juan; Tan, Xiaoqing; Zhang, Lan; Chen, Guonan

2012-11-21

269

Influence of photochemical reactions on the complexation of humic acid with europium(III)  

Microsoft Academic Search

Photochemical reactions in the Eu(III)–humic acid system are investigated by fluorescence spectroscopy. For comparison, humic acid without europium is also studied. Irradiation is performed by high energy laser beam and a low pressure mercury lamp. The impact of photodegradation on spectroscopic properties, size and decomposition of humic acid is monitored by steady state and time-resolved fluorescence spectroscopy, UV–Vis spectroscopy, gel

Jean-Marc Monsallier; Franz J Scherbaum; Gunnar Buckau; Jae-Il Kim; Michael U Kumke; Christian H Specht; Fritz H Frimmel

2001-01-01

270

Syntheses of Papyracillic Acids: Application of the Tandem Chain Extension-Acylation Reaction  

PubMed Central

A synthetic approach to the papyracillic acid family of natural products has been developed. The spiroacetal core is rapidly assembled through an unprecedented zinc carbenoid-mediated tandem chain extension-acylation reaction. Subsequent functional group manipulation provided access to papyracillic acid B and 4-epi-papyracillic acid C. The successful preparation of these molecules resulted in the clarification of structural assignments of members of this family of natural products.

Mazzone, Jennifer R.; Zercher, Charles K.

2012-01-01

271

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

Microsoft Academic Search

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

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

2004-01-01

272

Uso da técnica de Southern Blot\\/Hibridização associada à reação em cadeia da polimerase para aumentar a sensibilidade no diagnóstico das infecções por hemoplasmas em gatos domésticos Use of Southern Blot\\/Hybridization technique associated to polymerase chain reaction to improve the sensitivity in the diagnosis of hemoplasma infections in domestic cats  

Microsoft Academic Search

The aim of this study was to determine whether Southern Blot\\/Hybridization (SB) associated to Polymerase Chain Reaction (PCR) improves the sensitivity in the detection of hemoplasma DNA in domestic cats (Felis catus). Whole blood was collected in tubes containing the anticoagulant ethylenediamine tetra-acetic acid and DNA extracted from 149 animals. PCR was performed using species specific primers to amplify the

Daniel B. Macieira; Rita de Cássia; Cristiane B. Damico; Joanne B. Messick

2009-01-01

273

Reactive uptake of acetic acid on calcite and nitric acid reacted calcite aerosol in an environmental reaction chamber.  

PubMed

The heterogeneous chemistry of gas-phase acetic acid with CaCO(3)(calcite) aerosol was studied under varying conditions of relative humidity (RH) in an environmental reaction chamber. Infrared spectroscopy showed the loss of gas-phase reactant and the appearance of a gaseous product species, CO(2). The acetic acid is observed to adsorb onto the calcite aerosol through both a fast and a slow uptake channel. While the fast channel is relatively independent of RH, the slow channel exhibits enhanced uptake and reaction as the RH is increased. In additional experiments, the calcite aerosol was exposed to both nitric and acetic acids in the presence of water vapor. The rapid conversion of the particulate carbonate to nitrate and subsequent deliquescence significantly enhances the uptake and reaction of acetic acid. These results suggest a possible mechanism for observed correlations between particulate nitrate and organic acids in the atmosphere. Calcium rich mineral dust may be an important sink for simple organic acids. PMID:18075693

Prince, Amy Preszler; Kleiber, Paul D; Grassian, Vicki H; Young, Mark A

2007-11-21

274

Reaction of Formic Acid on Zn-Modified Pd(111)  

Microsoft Academic Search

The decomposition of formic acid on Zn\\/Pd(111) was studied using Temperature Programmed Desorption and High Resolution Electron\\u000a Energy Loss Spectroscopy. On Pd(111), HCOOH decomposes via both dehydration and dehydrogenation pathways to produce CO, CO2, H2 and H2O. Small amounts of Zn (<0.1 mL) incorporated the Pd(111) surface were found to increase the stability of formate species\\u000a and alter their decomposition selectivity

Eseoghene Jeroro; John M. Vohs

2009-01-01

275

Reaction of hydroxyl radical with p-hydroxymercuribenzoic acid  

NASA Astrophysics Data System (ADS)

Radiolysis of a 0.1mmoll-1 aqueous solution of p-hydroxymercuribenzoic acid (p-HMBA) results in the formation of p-hydroxybenzoic acid (p-HBA) and 3,4-dihydroxybenzoic acid (3,4-DHBA). Spectrophotometric and liquid chromatographic analysis of irradiated nitrous oxide saturated solutions indicate a disappearance yield G(-HMBA) of 3.1×10-7molJ-1, a formation yield of 1.5×10-7molJ-1 for p-HBA and 0.44×10-7molJ-1 for 3,4-DHBA. Pulse radiolysis of N2O saturated solutions of p-HMBA at pH 9.2 provides a rate constant of (6.3+/-0.8)×109M-1s-1 for the formation of a hydroxycyclohexadienyl radical. Similar experiments provided rate constants at pH 7.0 and 12.0 of (6.6+/-1.0)×109 and (1.6+/-0.3)×109M-1s-1, respectively. The UV/Vis absorption spectrum of the hydroxycyclohexadienyl radical has a ?max=340nm with a molar absorption coefficient of 4.1×103lmol-1cm-1.

Zevos, Nick

2003-12-01

276

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

PubMed

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

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

2009-10-01

277

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

278

Hybrid approach for including electronic and nuclear quantum effects in molecular dynamics simulations of hydrogen transfer reactions in enzymes  

NASA Astrophysics Data System (ADS)

A hybrid approach for simulating proton and hydride transfer reactions in enzymes is presented. The electronic quantum effects are incorporated with an empirical valence bond approach. The nuclear quantum effects of the transferring hydrogen are included with a mixed quantum/classical molecular dynamics method in which the hydrogen nucleus is described as a multidimensional vibrational wave function. The free energy profiles are obtained as functions of a collective reaction coordinate. A perturbation formula is derived to incorporate the vibrationally adiabatic nuclear quantum effects into the free energy profiles. The dynamical effects are studied with the molecular dynamics with quantum transitions (MDQT) surface hopping method, which incorporates nonadiabatic transitions among the adiabatic hydrogen vibrational states. The MDQT method is combined with a reactive flux approach to calculate the transmission coefficient and to investigate the real-time dynamics of reactive trajectories. This hybrid approach includes nuclear quantum effects such as zero point energy, hydrogen tunneling, and excited vibrational states, as well as the dynamics of the complete enzyme and solvent. The nuclear quantum effects are incorporated during the generation of the free energy profiles and dynamical trajectories rather than subsequently added as corrections. Moreover, this methodology provides detailed mechanistic information at the molecular level and allows the calculation of rates and kinetic isotope effects. An initial application of this approach to the enzyme liver alcohol dehydrogenase is also presented.

Billeter, Salomon R.; Webb, Simon P.; Iordanov, Tzvetelin; Agarwal, Pratul K.; Hammes-Schiffer, Sharon

2001-04-01

279

Recent HBT Results from a Hybrid Transport Approach to Heavy Ion Reactions  

NASA Astrophysics Data System (ADS)

We use the Ultrarelativistic Quantum Molecular Dynamics model to investigate heavy ion observables at various collision energies. The model is applied in cascade mode, hybrid mode (hydro+cascade) and also in using a core corona approach where only high density regions of the collision are treated hydrodynamically. Using these different modes we show the excitation function of strange particle ratios and the results of a HBT analysis from SPS up to LHC energies.

Bleicher, Marcus; Graef, Gunnar

280

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

PubMed

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

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

2003-09-01

281

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

NASA Astrophysics Data System (ADS)

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

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

1980-12-01

282

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

PubMed

A number of routes have been suggested for the prebiotic synthesis of uracil involving the reaction of urea with malic acid, propiolic acid, cyanoacetylene and others. Cyanoacetylene has been detected in the interstellar medium as well as simulated prebiotic experiments. It is therefore plausible that dicyanoacetylene and its hydrolytic product acetylene dicarboxylic acid (ADCA) may have played a role in chemical evolution. This aspect has been examined in the present work for the synthesis of uracil from ADCA and urea reaction. It was found that when ADCA reacted with urea, uracil was formed only in the presence of phosphoric acid and phosphates. ammonium phosphates gave higher yields of uracil than other phosphates. In the absence of phosphoric acid or phosphates no uracil formation took place. This type of synthesis could have taken place in prebiotic oceans which contained ammonium phosphates and other salts. PMID:7454254

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

1980-12-01

283

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

2011-12-17

284

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

NASA Astrophysics Data System (ADS)

We investigated the water durability of the inorganic organic hybrid tin-silico-phosphate glasses Me2SiO SnO P2O5 (Me designs the organic methyl group) doped with organic acids (salicylic acid (SA), tartaric acid (TA), citric acid (CA) 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. 29Si magic angle spinning (MAS) NMR and 31P MAS NMR spectra, respectively, showed clearly a modification of the network in the host glass matrix of the Me2SiO SnO P2O5 system. The polycondensation enhancement to form P O Si O P linkages (PSP) and the increase of the Q2 unit (two bridging oxygens per phosphorus atom) over the Q3 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; Mizuno, Megumi; Takahashi, Masahide; Tokuda, Yomei; Yoko, Toshinobu

2006-02-01

285

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

286

Rheological, microstructural, and in vitro characterization of hybrid chitosan-polylactic acid/hydroxyapatite composites.  

PubMed

In this work, hybrid chitosan/hydroxyapatite composites material were developed and characterized. The polymer matrix was first dissolved in polylactic acid, and then hydroxyapatite (HA) was added as filler material. The effects of the added amounts of a crosslinking agent (genipin) and of the concentrations of lactic acid, and of the presence of HA powder on the evolution of rheological properties were evaluated. A significant decrease of gelation time with increasing amounts of crosslinking agent was observed, the effect being even more pronounced in the presence of HA. The chitosan matrix and the composites with a chitosan/HA weight ratio of 2/5 were characterized using microstructural analysis and in vitro tests. The formation of large pore sizes in the chitosan-based scaffolds was favored by low concentrations of lactic acid and genipin. The in vitro tests in synthetic body fluid revealed an extensive formation of an apatitic layer onto the surface of the chitosan/HA composite scaffolds crosslinked with genipin. PMID:18384164

Araújo, A B A; Lemos, A F; Ferreira, J M F

2009-03-15

287

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

288

Hybridization assay of hepatitis B virus by QCM peptide nucleic acid biosensor.  

PubMed

Although the analyses of HBV genomic DNA have traditionally been performed with commercial techniques, the high cost and long time consumed have hindered their applications in routinely diagnosis and prognosis of infection. We construct peptide nucleic acid (PNA) piezoelectric biosensor for real-time monitoring of hybridization of hepatitis B virus (HBV) genomic DNA. The PNA probe can combine to target DNA sequences more effectively and specifically than a DNA probe. The PNA probe was designed and immobilized on the surface of the biosensor to substitute the conventional DNA probe for direct detection of HBV genomic DNA without previous amplification by PCR. The hybridization assay was completed in 50 min. The detection limit was 8.6 pg/L and the clinical specificity was 94.44% compared with real time-PCR (RT-PCR). The PNA probe was able to distinguish sequences that differ only in one base. Detection sensitivity can be improved and detection time can be decreased by adding RecA protein-coated complementary ssDNA which complement to HBV gene regions. The QCM system we designed has the advantages of being rapid, label-free and highly sensitive and can be a useful supplement to commercial assay methods in clinical chemistry. PMID:17951045

Yao, Chunyan; Zhu, Tangyou; Tang, Jin; Wu, Rong; Chen, Qinghai; Chen, Ming; Zhang, Bo; Huang, Junfu; Fu, Weiling

2007-09-14

289

A historical note on the iodine-sulphuric acid reaction of amyloid.  

PubMed

The historical development of the iodine-sulphuric acid reaction for amyloid is described. The reaction dates back to 1814 when Colin and Gaultier de Claubry, and independently Stromeyer, introduced the iodine reaction for starch. A variant of the acidified iodine reaction appears to have been used for printing paper by Gmelin in 1829, and in 1838 Schleiden used the iodine-sulphuric acid test on plants to demonstrate what he considered to be a transformation of the plant material into starch. Shortly afterwards Payen (1839) defined "cellulose", and the iodine-sulphuric acid reaction became a standard procedure used by botanists to demonstrate this plant component. In 1853 Virchow used Harting's (1847) procedure to demonstrate the reaction of Purkyn?'s corpora amylacea to this test, on the assumption that they might be cellulose derivatives, and applied it to what appeared to be similar corpuscles in a "waxy" spleen. The first histochemical reaction for amyloidosis had thus been introduced into pathology, and continued to exert from that time on an important influence on amyloid research, whose impact is felt to the present day. PMID:791904

Aterman, K

1976-10-22

290

DNA Surface Hybridization Regimes  

NASA Astrophysics Data System (ADS)

Surface hybridization reactions, in which sequence-specific recognition occurs between immobilized and solution nucleic acids, are routinely carried out to quantify and to interpret genomic information. At a surface, molecular interactions are amplified by the two-dimensional nature of the immobilized layer which focuses the nucleic acid charge and concentration to levels not encountered in solution, and which impacts the hybridization behavior in unique ways. We find that, at low ionic strengths, an electrostatic balance between the concentration of immobilized oligonucleotide charge and solution ionic strength governs the onset of hybridization. As ionic strength increases, the importance of electrostatics diminishes and the hybridization behavior becomes more complex. Suppression of hybridization affinity constants relative to solution values, and their weakened dependence on the concentration of DNA counterions, indicate that the immobilized strands form complexes. Moreover, an unusual regime is observed in which the surface coverage of immobilized oligonucleotides does not significantly influence the hybridization behavior, despite physical closeness and hence compulsory interactions between sites. These results are interpreted and summarized in a diagram of hybridization regimes.

Levicky, Rastislav; Gong, Ping

2008-03-01

291

Sulfuric, hydrochloric, and nitric acid-catalyzed triacetone triperoxide (TATP) reaction mixtures: an aging study.  

PubMed

The organic peroxide explosive triacetone triperoxide (TATP) is regularly encountered by law enforcement agents in various stages of its production. This study utilizes solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) to examine sulfuric acid-, hydrochloric acid-, and nitric acid-catalyzed TATP syntheses during the initial 24 h of these reactions at low temperatures (5-9°C). Additionally, aging of the reaction mixtures was examined at both low and ambient temperatures (19-21°C) for a further 9 days. For each experiment, TATP could be readily identified in the headspace above the reaction mixture 1 h subsequent to the combination of reagents; at 24 h, TATP and diacetone diperoxide (DADP) were prominent. TATP degraded more rapidly than DADP. Additionally, chlorinated acetones chloroacetone and 1,1,-dichloroacetone were identified in the headspace above the hydrochloric acid-catalyzed TATP reaction mixture. These were not present when the catalyst was sulfuric acid or nitric acid. PMID:21595692

Fitzgerald, Mark; Bilusich, Daniel

2011-05-19

292

A computational study of acid catalyzed aerosol reactions of atmospherically relevant epoxides.  

PubMed

Epoxides are important intermediates of atmospheric isoprene oxidation. Their subsequent reactions in the particle phase lead to the production of organic compounds detected in ambient aerosols. We apply density functional theory to determine the important kinetic factors that drive epoxide reactions in the particle phase. Specifically, the importance of acid catalysis and solvent polarity are investigated using a variety of epoxides and nucleophiles. The condensed phase is modeled using molecular clusters immersed in a dielectric continuum and a majority of the calculations are performed with the M062x density functional and the 6-311++G** basis set. Calculations of acid catalyzed epoxide hydrolysis transition states for simple primary, secondary and tertiary epoxides are consistent with an A-2 mechanism where the nucleophile (water) interacts with an epoxide carbon in the transition state. By applying transition state theory to this mechanism, the overall rate constants of epoxide reactions such as hydrolysis, organosulfate formation, organonitrate formation and oligomerization are determined. The calculations indicate that the acid catalyzed hydrolysis rate constant of 2-methyl-2,3-epoxybutane-1,4-diol (?-IEPOX - an isoprene epoxide produced under low NOx conditions) is approximately 30 times greater than 2-methyl-2,3-epoxypropanoic acid (MAE - methacrylic acid epoxide derived from isoprene and produced at high NOx concentrations). Furthermore, acid catalyzed organosulfate formation and epoxide oligomerization reactions are competitive and appear to be kinetically favorable over the hydrolysis of IEPOX. PMID:24061334

Piletic, Ivan R; Edney, Edward O; Bartolotti, Libero J

2013-10-01

293

Niobium oxide based materials as catalysts for acidic and partial oxidation type reactions  

Microsoft Academic Search

Niobic acid, H8Nb6O19·xH2O, was synthesized and studied for its acidic features as a function of its dehydroxylation extent. It was observed to be strongly acidic, using NH3 adsorption calorimetry and isopropanol conversion reaction as probe techniques, and to be weakly acidic on its dehydrated form, Nb2O5. The mixed oxide Al2o3:Nb2o5in 1:1 molar ratio prepared from aluminum and niobium oxalates was

J. C. Védrine; G. Coudurier; A. Ouqour; P. G. Pries de Oliveira; J. C. Volta

1996-01-01

294

Hybridization of leucyl-transfer ribonucleic Acid isoacceptors from green leaves with nuclear and chloroplast deoxyribonucleic Acid.  

PubMed

Chromatographically distinct isoacceptors of leucyl-tRNA from mature bean leaves were all observed to hybridize with bean chloroplast and nuclear DNA in a ratio similar to that exhibited by the unfractionated leucyl-tRNA. Under the same hybridization conditions, maize tRNA failed to form a stable hybrid with bean DNA, and levels of hybridization between bean-leaf leucyl-tRNA and nuclear or chloroplast DNAs from tobacco and maize were relatively small. PMID:16592122

Williams, G R; Williams, A S; George, S A

1973-12-01

295

Hybridization of Leucyl-Transfer Ribonucleic Acid Isoacceptors from Green Leaves with Nuclear and Chloroplast Deoxyribonucleic Acid  

Microsoft Academic Search

Chromatographically distinct isoacceptors of leucyl-tRNA from mature bean leaves were all observed to hybridize with bean chloroplast and nuclear DNA in a ratio similar to that exhibited by the unfractionated leucyl-tRNA. Under the same hybridization conditions, maize tRNA failed to form a stable hybrid with bean DNA, and levels of hybridization between bean-leaf leucyl-tRNA and nuclear or chloroplast DNAs from

Gene R. Williams; Alice S. Williams; S. A. George

1973-01-01

296

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

Microsoft Academic Search

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

Fang-Ming Sun; Juie S Wang; Richard W Traxler

2000-01-01

297

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

SciTech Connect

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

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

2004-06-28

298

An experimental study of tissue reaction to hyaluronic acid (Restylane) and polymethylmethacrylate (Metacrill) in the mouse.  

PubMed

The aging skin is a challenge for medical science. Plastic surgeons and dermatologists are called every day to solve problems like filling wrinkles or folds. The material used must be biocompatible because abnormal reactions may cause catastrophic results. This study analyzes the biological behavior of polymethylmethacrylate (Metacrill) and hyaluronic acid (Restylane), using a histopathologic study in mice. A prospective study was performed using 40 mice for each substance: polymethylmethacrylate or hyaluronic acid was injected into the right ear, the left ear been used as a control. Histopathologic analyses of the right ear, liver, and kidney were performed at intervals during the study and revealed the development of a granulomatous reaction with fibrosis and absorption of spheres and signs of liver and kidney sistematization for polymethylmethacrylate. A discrete cellular reaction, with less formation of fibrosis, and no giant cells were seen in the mice injected with hyaluronic acid. PMID:23000877

Rosa, Simone C; Macedo, Jefferson L S; Magalhães, Albino V

2012-10-01

299

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

USGS Publications Warehouse

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

Fletcher, M. H.

1960-01-01

300

New synthesis of 2-heteroarylperfluoropropionic acids derivatives by reaction of azine N-oxides with hexafluoropropene.  

PubMed

Hexafluoropropene reacts with aromatic azine N-oxides under mild conditions to produce fluorides of 2-heteroarylperfluoropropionic acids. The reaction proceeds as 1,3-dipolar cycloaddition followed by spontaneous scission of the N--O bond in the isoxazolidine ring and elimination of HF. When the reaction is carried out in the presence of alcohols or N-alkyl anilines, the in situ formed acyl fluorides give the corresponding esters and amides. They can be also treated separately with nucleophiles to produce the respective acylation products, whereas their hydrolysis leads to unstable carboxylic acids that undergo spontaneous decarboxylation to 1-aryl-1,2,2,2-tetrafluoroethanes. This new reaction provides a simple and general method of synthesizing 2-heteroarylperfluoropropionic acid derivatives that were previously unknown and unavailable. PMID:18189255

Loska, Rafa?; Makosza, Mieczys?aw

2008-01-01

301

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

Microsoft Academic Search

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

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

302

Chitin–humic acid hybrid as adsorbent for Cr(III) in effluent of tannery wastewater treatment  

Microsoft Academic Search

Adsorption of Cr(III) from both synthetic and real samples of tannery wastewater treatment's effluent on chitin–humic acid (chitin–HA) hybrid has been carried out. Rate constant and capacity of adsorption of Cr(III) from the synthetic sample were investigated and removal of Cr(III) from the real sample was tested at optimum medium acidity equivalent to pH 3.5. Characterization using Fourier transform infra

Sri Juari Santosa; Dwi Siswanta; Sri Sudiono; Ratna Utarianingrum

2008-01-01

303

Self-assembled water-soluble nucleic acid probe tiles for label-free RNA hybridization assays.  

PubMed

The DNA origami method, in which long, single-stranded DNA segments are folded into shapes by short staple segments, was used to create nucleic acid probe tiles that are molecular analogs of macroscopic DNA chips. One hundred trillion probe tiles were fabricated in one step and bear pairs of 20-nucleotide-long single-stranded DNA segments that act as probe sequences. These tiles can hybridize to their targets in solution and, after adsorption onto mica surfaces, can be examined by atomic force microscopy in order to quantify binding events, because the probe segments greatly increase in stiffness upon hybridization. The nucleic acid probe tiles have been used to study position-dependent hybridization on the nanoscale and have also been used for label-free detection of RNA. PMID:18187649

Ke, Yonggang; Lindsay, Stuart; Chang, Yung; Liu, Yan; Yan, Hao

2008-01-11

304

Cross-Dehydrogenative Coupling Reactions of sp 3 -Hybridized C–H Bonds  

Microsoft Academic Search

\\u000a New methodologies in cross-coupling reaction using C–H bonds as substrates is of great interest due to the challenges associated\\u000a with C–H bond activation and the potential to streamline synthesis by the elimination of pre-activation of coupling reagents.\\u000a In this chapter, recent developments in oxidative cross-coupling reactions will be presented with the focus on the functionalization\\u000a of sp3 C–H bonds with

Woo-Jin Yoo; Chao-Jun Li

2010-01-01

305

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

306

A novel chemiluminescence paper microfluidic biosensor based on enzymatic reaction for uric acid determination  

Microsoft Academic Search

In this work, chemiluminescence (CL) method was combined with microfluidic paper-based analytical device (?PAD) to establish a novel CL ?PAD biosensor for the first time. This novel CL ?PAD biosensor was based on enzyme reaction which produced H2O2 while decomposing the substrate and the CL reaction between rhodanine derivative and generated H2O2 in acid medium. Microchannels in ?PAD were fabricated

Jinghua Yu; Shoumei Wang; Lei Ge; Shenguang Ge

2011-01-01

307

Coulometric bioelectrocatalytic reactions based on NAD-dependent dehydrogenases in tricarboxylic acid cycle  

Microsoft Academic Search

This paper describes the characterization of mediated electro-enzymatic electrolysis systems based on NAD-dependent dehydrogenase reactions in the tricarboxylic acid (TCA) cycle. A micro-bulk electrolysis system with a carbon felt anode immersed in an electrolysis solution with a value of about 10?L was constructed for coulometric analysis of the substrate oxidation. Diaphorase (DI) was used to couple the NAD-dependent dehydrogenase reaction

Jun Fukuda; Seiya Tsujimura; Kenji Kano

2008-01-01

308

Stoichiometry and products of ozone reaction with chloride ion in an acidic medium  

NASA Astrophysics Data System (ADS)

It is shown by means of direct spectrophotometry in the UV and visible ranges that the only product of the O3 reaction with Cl-(aq) in an acidic medium is molecular chlorine Cl2; in solutions, it is in equilibrium with the complex ion Cl{3/-}. It is found that the consumption of one ozone molecule corresponds to the formation of one chlorine molecule. The stoichiometric equation for the reaction is obtained.

Levanov, A. V.; Kuskov, I. V.; Antipenko, E. E.; Lunin, V. V.

2012-05-01

309

Application of iodine-azide reaction for detection of amino acids in thin-layer chromatography  

Microsoft Academic Search

The iodine-azide reaction was employed to TLC detection of sulphur-containing derivatives of protein and some non-protein amino acids. The derivatization reaction with phenyl isothiocyanate (PITC) took place directly on the plate before the developing step. Subsequently, the plates were sprayed with a mixture of sodium azide and starch solution in NP-TLC and in the case of RP-TLC sodium azide solution

Dorota Ka?mierczak; Witold Ciesielski; Robert Zakrzewski; Monika ?uber

2004-01-01

310

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

311

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

PubMed Central

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

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

1993-01-01

312

A general method for the synthesis of monodisperse hollow inorganic-organic hybrid microspheres with interior functionalized poly(methacrylic acid) shells.  

PubMed

Hollow inorganic-organic hybrid microspheres, such as silica, titania, and zirconia, with interior poly(methacrylic acid) (PMAA) functionalized shell were synthesized by a general method containing a two-stage reaction. The hollow inorganic shell-layer with interior polymeric component was formed over the PMAA template during the second-stage controlled hydrolysis of inorganic precursors together with disintegration of PMAA cores and adhering to the interior wall of the silica during the drying process due to the capillary force as well as the competitive hydrogen bond interaction. In this process, PMAA microspheres were prepared by distillation precipitation polymerization of methacrylic acid (MAA) in acetonitrile as the first-stage reaction. The present work elaborately investigated the effects of the reaction conditions, including the amount of the tetraethyl orthosilicate (TEOS) precursors and the amount of ammonium hydroxide catalyst on the morphology and structure of the resultant hollow composite microspheres, which were characterized by transmission electron microscopy (TEM), Fourier-transform infrared spectra (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption-desorption. PMID:22218343

Liu, Bin; Yan, Enwei; Zhang, Xu; Yang, Xinlin; Bai, Feng

2011-12-19

313

Increased stability and specificity through combined hybridization of peptide nucleic acid (PNA) and locked nucleic acid (LNA) to supercoiled plasmids for PNA-anchored “Bioplex” formation  

Microsoft Academic Search

Low cellular uptake and poor nuclear transfer hamper the use of non-viral vectors in gene therapy. Addition of functional entities to plasmids using the Bioplex technology has the potential to improve the efficiency of transfer considerably. We have investigated the possibility of stabilizing sequence-specific binding of peptide nucleic acid (PNA) anchored functional peptides to plasmid DNA by hybridizing PNA and

Karin E. Lundin; Maroof Hasan; Pedro M. Moreno; Elisabeth Törnquist; Iulian Oprea; Mathias G. Svahn; E. Oscar Simonson; C. I. Edvard Smith

2005-01-01

314

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

USGS Publications Warehouse

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

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

1994-01-01

315

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

2008-01-24

316

Fluoride catalysis at 175°C. of the reaction: Glycerol plus fatty acid  

Microsoft Academic Search

Summary  \\u000a \\u000a \\u000a \\u000a 1. \\u000a \\u000a In uncatalyzed reactions the esterification of stearic, oleic, and linolenic acid proceeded at the same general rate though\\u000a the speed was somewhat enhanced as the degree of unsaturation of the fatty acid increased. None of the reactions went to completion,\\u000a after 15 hours being 72%, 83%, and 84%, respectively, completed. Only a small fraction of the distearate was

Joseph J. Wocasek; John R. Koch

1948-01-01

317

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

318

Microbial populations identified by fluorescence in situ hybridization in a constructed wetland treating acid coal mine drainage  

Microsoft Academic Search

Microorganisms are an integral part of the biogeochemical processes in wetlands, yet microbial communities in sediments within constructed wetlands receiving acid mine drainage (AMD) are only poorly understood. The purpose of this study was to characterize the microbial diversity and abundance in a wetland receiving AMD using fluorescence in situ hybridization (FISH) analysis. Seasonal samples of oxic surface sediments, comprised

Duongruitai Nicomrat; Warren A. Dick; Olli H. Tuovinen

2006-01-01

319

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

320

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

Microsoft Academic Search

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

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

2001-01-01

321

Comparison between calculations and experimental results on spallation reactions of interest for hybrid systems  

SciTech Connect

Data on proton induced spallation reactions concerning the production of neutrons obtained at SATURNE and of spallation residues at GSI have been compared with two-step models including different Intra-Nuclear Cascades (INC) followed by different evaporation codes. Results and improvements of the codes are discussed.

Volant, C.; Boudard, A.; Legrain, R.; Leray, S.; Wlazlo, W. [DAPNIA/SPhN CEA/Saclay F-91191 Gif-sur-Yuette Cedex (France)

1999-11-16

322

Comparison Between Calculations and Experimental Results on Spallation Reactions of Interest for Hybrid Systems  

SciTech Connect

Data on proton induced spallation reactions concerning the production of neutrons obtained at SATURNE and of spallation residues at GSI have been compared with two-step models including different Intra-Nuclear Cascades (INC) followed by different evaporation codes. Results and improvements of the codes are discussed.

Volant, C.; Boudard, A.; Legrain, R.; Leray, S.; Wlazlo, W.

1999-12-31

323

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

324

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

PubMed Central

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

Heyen, Udo; Harder, Jens

2000-01-01

325

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

Code of Federal Regulations, 2013 CFR

...New Uses for Specific Chemical Substances § 721...unsatd., dimers, reaction products with 1-piperazineethanamine...fatty acids. (a) Chemical substance and significant...reporting. (1) The chemical substance identified...unsatd., dimers, reaction products with...

2013-07-01

326

Determination of free fatty acids and triglycerides by gas chromatography using selective esterification reactions.  

PubMed

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. PMID:22695884

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

2012-06-12

327

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

Microsoft Academic Search

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

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

1994-01-01

328

Cellulose dehydration and depolymerization reactions during pyrolysis in the presence of phosphoric acid  

Microsoft Academic Search

The low-temperature pyrolysis process and dehydration reactions of cellulose impregnated with phosphoric acid (1–10 wt.%) have been studied. Based on the yield of pyrolytic water and alterations of glucopyranose units of cellulose, it has been confirmed that dehydrated cyclic structures are formed in the solid phase during cellulose pyrolysis in the temperature interval 200–250°C. Phosphoric acid also catalyzes the subsequent

G Dobele; G Rossinskaja; G Telysheva; D Meier; O Faix

1999-01-01

329

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

330

Detection of HTLV-1 by polymerase chain reaction in situ hybridization in adult T-cell leukemia/lymphoma.  

PubMed Central

A method for nonradioactive polymerase chain reaction in situ hybridization was developed and used to determine the distribution of human T-lymphotropic virus type I (HTLV-I) proviral DNA in paraffin-embedded surgical specimens of adult T-cell leukemia/lymphoma (ATLL). As controls, we used biopsy samples of five cases of mycosis fungoides, cells of an HTLV-I-infected cell line (MT2), as well as HTLV-1-negative cells (YAS). We successfully detected the amplicon of the HTLV-1 tax sequence in the nuclei of the cutaneous infiltrating lymphoid cells in 90% (9/10) of ATLL cases. Studies also revealed the existence of HTLV-1 provirus DNA in nuclei of sweat gland epithelial cells and vascular endothelial cells as well as lymphoid cells in ATLL patients. Mycosis fungoides and YAS cells were negative for the HTLV-I tax sequence, but MT2 cells were strongly positive. The results indicated that this technique was more sensitive in detecting intracellular amplicons than was the previous in situ hybridization method. Through its use, we were able to easily determine the distribution of HTLV-I-positive cells among the various cells and tissues of paraffin-embedded archival materials. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Setoyama, M.; Kerdel, F. A.; Elgart, G.; Kanzaki, T.; Byrnes, J. J.

1998-01-01

331

Kinetics of Acid-Catalyzed Aldol Condensation Reactions of Aliphatic Aldehydes  

NASA Astrophysics Data System (ADS)

While it is well established that organic compounds 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, ultraviolet-visible (UV-Vis) spectroscopy was used to monitor the kinetics of formation of the products of the aldol condensation reaction of a range of aliphatic aldehydes (C2-C8) The experiments were carried out at various sulfuric acid concentrations and a range of temperatures in order to estimate the rate constants of such reactions on sulfuric acid aerosols under tropospheric conditions. The rate constants were generally found to decrease as the chain length of the aliphatic aldehyde increased (except for acetaldehyde, which had an unusually small rate constant), increase as a function of sulfuric acid concentration as predicted by excess acidity theory, and showed normal Arrhenius behavior as a function of temperature.

Elrod, M. J.; Casale, M. T.; Richman, A. R.; Beaver, M. R.; Garland, R. M.; Tolbert, M. A.

2006-12-01

332

Hybrid simulations of stochastic reaction-diffusion processes for modeling intracellular signaling pathways  

NASA Astrophysics Data System (ADS)

In the intracellular environment, signaling takes place in a nonideal environment that is spatially heterogeneous and that is noisy, with the noise arising from the low copy numbers of the signaling molecules involved. In this paper, we model intracellular signaling pathways as stochastic reaction-diffusion processes and adapt techniques commonly used by physicists to solve for the spatiotemporal evolution of the signaling pathways. We then apply it to study two problems of relevance to the modeling of intracellular signaling pathways. First, we show that, in the limit of small protein diffusion which is typically the case for proteins in the cytosol crowded by other macromolecules, the extent of diffusion control, in the transient regime, on reactions is greater than previous predictions. Second, we show that the presence of scaffold proteins can modify the phosphorylation activity of a mitogen-activated protein kinase cascade, and explain how this activity is modulated by the scaffold protein concentration.

Chiam, K.-H.; Tan, Chee Meng; Bhargava, Vipul; Rajagopal, Gunaretnam

2006-11-01

333

Acid formation in polymer solids by radiation-induced chain reactions of diphenyliodonium salts  

NASA Astrophysics Data System (ADS)

In order to develop chemically amplified radiation resist having ability of acid multiplication, acid formation in ?-irradiated polymer films and solutions of acetal compounds containing diphenyliodonium salt has been studied. Acids were generated in the films and solutions by chain reactions of large G-value. The G-value depends on the chemical structure of the polymers and acetal compounds. Compounds containing cyclic acetal structure give large G-values. This dependence can be explained by difference in the possibility of electron transfer from radicals of the polymers and acetal compounds to diphenyliodonium salt. Polyvinyl acetals will be a candidate for the dually amplified resist.

Koizumi, Hitoshi; Terae, Mitsuhiro; Yamazaki, Kenta; Iino, Kouji

2011-02-01

334

Functional expression of the Aspergillus flavus PKS-NRPS hybrid CpaA involved in the biosynthesis of cyclopiazonic acid.  

PubMed

alpha-Cyclopiazonic acid (CPA) is an indole tetramic acid mycotoxin. Based on our identification of the polyketide synthase-nonribosomal peptide synthase (PKS-NRPS) hybrid gene cpaA involved in cyclopiazonic acid biosynthesis in Aspergillus fungi, we carried out heterologous expression of Aspergillus flavuscpaA under alpha-amylase promoter in Aspergillus oryzae and identified its sole product to be the CPA biosynthetic intermediate cyclo-acetoacetyl-l-tryptophan (cAATrp). This result rationalized that the PKS-NRPS hybrid enzyme CpaA catalyzes condensation of the diketide acetoacetyl-ACP formed by the PKS module and l-Trp activated by the NRPS module. This CpaA expression system provides us an ideal platform for PKS-NRPS functional analysis, such as adenylation domain selectivity and product releasing mechanism. PMID:19410456

Seshime, Yasuyo; Juvvadi, Praveen Rao; Tokuoka, Masafumi; Koyama, Yasuji; Kitamoto, Katsuhiko; Ebizuka, Yutaka; Fujii, Isao

2009-04-22

335

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

336

Fatty acid and cholesterol composition of camel’s ( Camelus bactrianus, Camelus dromedarius and hybrids) milk in Kazakhstan  

Microsoft Academic Search

The fatty acid composition and cholesterol content of 22 camel’s milk samples from different regions of Kazakhstan were determined,\\u000a in different seasons and with different camel species (Bactrian, dromedary and hybrids). Camel milk fat differed from mammalian\\u000a fats by its high content of the long-chain fatty acids C14:0, C16:0, C18:0 and C18:l. Great differences in fatty acid composition\\u000a occurred between

Gaukhar Konuspayeva; Émilie Lemarie; Bernard Faye; Gérard Loiseau; Didier Montet

2008-01-01

337

Novel H 3 PW 12 O 40 : Catalysed Esterification Reactions of Fatty Acids at Room Temperature for Biodiesel Production  

Microsoft Academic Search

\\u000a Abstract  The catalytic activity of Brønsted acids on fatty acid (FA) esterification at room temperature has been investigated. Noticeably,\\u000a the H3PW12O40 heteropolyacid (HPW) showed a very high activity than other catalysts herein evaluated, i.e. p-toluene sulfonic acid and sulfuric acid. High yields in ethyl esters (ca. 90%) were reached after a 4 h reaction at 25 °C on a HPW catalysed reactions. Despite

Vinícius Wilker de Godói Silva; Letícia Oliveira Laier; Márcio José da Silva

2010-01-01

338

New progress of Keggin and Wells–Dawson type polyoxometalates catalyze acid and oxidative reactions  

Microsoft Academic Search

Polyoxometalates (abbreviated as POMs) are useful acids and oxidation catalysts in various reactions since its catalytic features can be controlled at a molecular level. This review summarizes some recent research progress in catalytic application of Keggin and Wells–Dawson type polyoxometalates. Particular attention is given to most developments of our recent studies on the use of POMs as heterogeneous and homogeneous

Guixian Li; Yong Ding; Jianming Wang; Xiaolai Wang; Jishuan Suo

2007-01-01

339

Aromatic nitrations by mixed acid. Fast liquid-liquid reaction regime  

Microsoft Academic Search

Aromatic nitration by mixed acid was selected as a specific case of heterogeneous liquid-liquid reaction. An extensive experimental programme was followed using adiabatic and heat flow calorimetry and pilot reactor experiments, supported by chemical analysis. A series of nitration experiments was carried out to study the influence of different initial and operating conditions, such as temperature, stirring speed, feed rate

J. M. Zaldívar; E. J. Molga; M. A. Alós; H. Hernández; K. R. Westerterp

1996-01-01

340

Aromatic nitrations by mixed acid. Slow liquid-liquid reaction regime  

Microsoft Academic Search

Aromatic nitrations by mixed acid have been selected as a specific case of a heterogeneous liquid-liquid reaction. An extensive experimental programme has been followed using adiabatic and heat-flow calorimetry and pilot reactor experiments, supported by chemical analysis. A series of nitration experiments has been carried out to study the influences of different initial and operating conditions such as temperature, stirring

J. M. Zaldivar; E. J. Molga; M. A. Alós; H. Hernández; K. R. Westerterp

1995-01-01

341

Repetitive sequence based polymerase chain reaction to differentiate close bacteria strains in acidic sites  

Microsoft Academic Search

To study the diversity of bacteria strains newly isolated from several acid mine drainage(AMD) sites in China, repetitive sequence based polymerase chain reaction (rep-PCR), a well established technology for diversity analysis of closely related bacteria strains, was conducted on 30 strains of bacteria Leptospirillum ferriphilium, 8 strains of bacteria Acidithiobacillus ferrooxidans, as well as the Acidithiobacillus ferrooxidans type strain ATCC

Ming XIE; Hua-qun YIN; Yi LIU; Jie LIU; Xue-duan LIU

2008-01-01

342

REACTIONS OF PHTHALIMIDOBENZOIC ACID AZIDES WITH TRIMETHYL PHOSPHITE AND TRIS (DIALKYLAMINO) PHOSPHINES  

Microsoft Academic Search

Trimethyl phosphite (3a) and\\/or tris (dialkylamino) phosphines (3b, c) react with o-, and m-phthal-imidobenzoic acid azides (1a, b) to give the new iminophosphorane derivatives (4a-4f). Possible reaction mechanism are considered and the structural assignments are based on compatible analytical and spectroscopic results.

Naked K. Eldin

1995-01-01

343

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

344

Reactions of furan derivatives with aliphatic carbonyl compounds in acid medium  

Microsoft Academic Search

Sixteen new derivatives of the furan and of the 1,1-difurylmethane series were synthesized by the reactions of furan, 2-methylfuran, 2-(3'-acetoxypropyl)furan, 2-(3'-butyl)furan, 1-cyclopropyl-2-afurylcyclopropane, and 1,1-difurylethane with saturated and a, ß-unsaturated aliphatic carbonyl compounds in acid medium.

V. G. Glukhovtsev; S. V. Zakharova

1970-01-01

345

Comparative Study of Reaction of Atomic Tritium with Glucosamine and Amino Acids  

Microsoft Academic Search

Reaction of amino acids (glycine and serine) and amino sugar (glucosamine) with atomic tritium generated by thermal dissociation of molecular tritium on a tungsten filament was studied. A frozen aqueous solutions and a freeze-dried mixture of these compounds was bombarded with tritium atoms is a special vacuum unit. The relative yield of the labeled compounds was determined as influenced by

G. A. Badun; A. L. Ksenofontov; E. V. Lukashina; V. Yu. Pozdnyakova; V. M. Fedoseev

2005-01-01

346

A squaric acid-stimulated electrocatalytic reaction for sensing biomolecules with cycling signal amplification.  

PubMed

Squaric acid, a 2-dimensional planar structure of squarate C4O4 units linked by protons in a layered sheet, was utilized for the first time as a catalytic substrate for ultrasensitive electronic determination of low-abundance proteins by coupling a target-induced electrocatalytic reaction with the in situ cycling signal amplification strategy. PMID:23589836

Lai, Wenqiang; Tang, Dianping; Fu, Libing; Que, Xiaohua; Zhuang, Junyang; Chen, Guonan

2013-05-25

347

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

348

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

349

Detoxification of Wheat Straw Hydrolysis in Formic Acid Reaction System by D311 Ion-exchange Resin  

Microsoft Academic Search

Formic acid hydrolysis is widely used in lignocellulose pretreatment. However, formic acid hydrolysis wheat straw cannot be directly used as a fermentation substrate owing to various fermentation inhibitors, especially the formic acid in reaction system and released during pretreatment. Study found treatment of wheat straw hydrolysate with D311 ion-exchange resin had a good result on reduction formic acid. We investigated

Junping Zhuang; Lu Lin; Chunsheng Pang; Zhen Wu; Ying Liu

2010-01-01

350

New losartan-hydrocaffeic acid hybrids as antihypertensive-antioxidant dual drugs: Ester, amide and amine linkers.  

PubMed

We report new examples of a series of losartan-hydrocaffeic hybrids that bear novel ester, amide and amine linkers. These compounds were made by linking hydrocaffeic acid to the side chain of losartan at the C-5 position of the imidazole ring through different strategies. Experiments performed in cultured cells demonstrate that these new hybrids retain the ability to block the angiotensin II effect and have increased antioxidant ability. Most of them reduced arterial pressure in rats better or as much as losartan. PMID:22336384

García, Gonzalo; Serrano, Isabel; Sánchez-Alonso, Patricia; Rodríguez-Puyol, Manuel; Alajarín, Ramón; Griera, Mercedes; Vaquero, Juan J; Rodríguez-Puyol, Diego; Alvarez-Builla, Julio; Díez-Marqués, María L

2012-01-30

351

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

352

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

353

Gas phase reaction of nitric acid with hydroxyl radical without and with water. A theoretical investigation.  

PubMed

The gas phase reaction between nitric acid and hydroxyl radical, without and with a single water molecule, has been investigated theoretically using the DFT-B3LYP, MP2, QCISD, and CCSD(T) theoretical approaches with the 6-311+G(2df,2p) and aug-cc-pVTZ basis sets. The reaction without water begins with the formation of a prereactive hydrogen-bonded complex and has several elementary reactions processes. They include proton coupled electron transfer, hydrogen atom transfer, and proton transfer mechanisms, and our kinetic study shows a quite good agreement of the behavior of the rate constant with respect to the temperature and to the pressure with the experimental results from the literature. The addition of a single water molecule results in a much more complex potential energy surface although the different elementary reactions found have the same electronic features that the naked reaction. Two transition states are stabilized by the effect of a hydrogen bond interaction originated by the water molecule, and in the prereactive hydrogen bond region there is a geometrical rearrangement necessary to prepare the HO and HNO(3) moieties to react to each other. This step contributes the reaction to be slower than the reaction without water and explains the experimental finding, pointing out that there is no dependence for the HNO(3) + HO reaction on water vapor. PMID:20681542

Gonzalez, Javier; Anglada, Josep M

2010-09-01

354

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

NASA Astrophysics Data System (ADS)

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

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

1990-11-01

355

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

356

Using dual-polarization interferometry to study surface-initiated DNA hybridization chain reactions in real time.  

PubMed

In this study we used dual-polarization interferometry to investigate DNA hybridization chain reactions (HCRs) at solid-liquid interfaces. We monitored the effects of variations in mass, thickness, and density of the immobilized initiator on the subsequent HCRs at various salt concentrations. At low salt concentrations, the single-stranded DNA (ssDNA) initiator was attached uniformly to the chip surface. At high salt concentrations, it lay on the surface at the onset of the immobilization process, but the approaching ssDNA forced the pre-immobilized ssDNA strands to extend into solution as a result of increased electrostatic repulsion between the pre-adsorbed and approaching ssDNA chains. Injection of a mixture of H1 and H2 increased the mass and thickness of the films initially, but thereafter the thickness decreased. These changes indicate that the long double-stranded DNA that formed lay on the surface, rather than extended into the solution, thereby suppressing the subsequent initiation activity of the released single-strand parts of H1 and H2. Increasing the salt concentration increased the HCR efficiency and reaction rate. The HCR efficiency of the initiator ssDNA immobilized on its 5' end was higher than that immobilized on its 3' end, suggesting that the released single-strand parts of H1 and H2 close to the chip surface decreased the initiation activity relative to those of the ones extending into solution. PMID:23988858

Huang, Fujian; Xu, Pingping; Liang, Haojun

2013-08-13

357

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

2012-08-30

358

A possible prebiotic synthesis of thymine: uracil-formaldehyde-formic acid reaction.  

PubMed

When uracil is reacted with formaldehyde and formic acid in dilute aqueous solutions at 100-140 degrees C, 5-hydroxymethyluracil (5-HMU), methylenebiuracil (MBU) and thymine are formed. It has been shown that 5-HMU is an intermediate in the formation of MBU and thymine. In the presence of formic acid, 5-HMU gives MBU, thymine and in some cases uracil. The formation of thymine is generally favoured under acidic conditions, although small amounts of this base could also be obtained when the reactions were carried out under mildly basic conditions. A hydride ion transfer mechanism is suggested for some of these reactions. These results have relevance to the formation of thymine under prebiotic conditions. PMID:20181

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

1977-09-01

359

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

PubMed

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

Bertoldi, M; Borri Voltattorni, C

2000-12-01

360

Reaction rate vs. transport limited dissolution during carbonate acidizing: Application of network model  

SciTech Connect

Coreflood experiments have been performed and a two dimensional network model has been developed to study the flow, dissolution, and permeability increase in carbonates during acid stimulation treatments. The goal is to be able to predict the behaviour of the random flow channels, called wormholes, that form in the rock as a result of acid attack. Understanding this channeling phenomenon is essential in predicting acid penetration distances and the resulting injectivity or productivity increases during matrix acidizing, or in understanding acid leakoff behaviour during fracture acidizing. Until now, relatively little has been known about the wormholing phenomenon because of the stochastic nature of channel formation and the inherent difficulty in modelling the random behaviour. Model predictions and experimental coreflood results are compared for linear systems. The model predicts wormholing and the effects of acidizing parameters such as fluid velocity, mineral dissolution rate, and rock properties on channel structure and the corresponding rate of channel propagation. Experimental data and model prediction support the conclusion that wormholing is necessary for matrix treatment effectiveness, but does not occur for the extremes of high and low values of the Damkohler number for flow and reaction, which controls the process. The model thus accounts for the ineffectiveness of aqueous hydrochloric acid for matrix treatments in limestone due to rapid acid spending, and for the possible ineffectiveness of treatments in dolomite due to mineral dissolution rates that are too slow to promote channel formation.

Hoefner, M.L.; Fogler, H.S.

1986-01-01

361

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  

Microsoft Academic Search

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

Sills

1995-01-01

362

Template-Free Synthesis of a Porous Organic-inorganic Hybrid Tin(IV) Phosphonate and Its High Catalytic Activity for Esterification of Free Fatty Acids.  

PubMed

Here we have synthesized an organic-inorganic hybrid mesoporous tin phosphonate monolith (MLSnP-1) with crystalline pore walls by a template-free sol-gel route. N2 sorption analysis shows Brunauer-Emmett-Teller (BET) surface area of 347 m(2)g(-1). Wide-angle powder X-ray diffraction (PXRD) pattern shows few broad diffraction peaks indicating crystalline pore wall of the material. High-resolution transmission electron microscopic (HR TEM) image further reveals the crystal fringes on the pore wall. Framework bonding and local environment around phosphorus and carbon were examined by Fourier transform infrared (FT IR) spectroscopy and solid-state MAS NMR spectroscopy. The material exhibits remarkable catalytic activity for esterification of long chain fatty acids under mild reaction conditions at room temperature. PMID:24045024

Dutta, Arghya; Patra, Astam K; Uyama, Hiroshi; Bhaumik, Asim

2013-10-01

363

Relative Reaction Rates of Sulfamic Acid and Hydroxylamine with Nitric Acid  

SciTech Connect

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

Karraker, D.G.

2001-03-28

364

Nanogold-based bio-bar codes for label-free immunosensing of proteins coupling with an in situ DNA-based hybridization chain reaction.  

PubMed

A label-free, non-enzyme immunosensing strategy is designed for ultrasensitive electronic detection of disease-related proteins (carcinoembryonic antigen as a model) by using gold nanoparticle-based bio-bar codes and an in situ amplified DNA-based hybridization chain reaction. PMID:23147220

Zhou, Jun; Xu, Mingdi; Tang, Dianping; Gao, Zhuangqiang; Tang, Juan; Chen, Guonan

2012-12-28

365

The mechanism of low levels of nitrogen dioxide reaction with unsaturated fatty acid esters  

SciTech Connect

Nitrogen dioxide is a toxic air pollutant that exists at less than 0.5 ppm in the atmosphere. This toxic compound is known to initiate autoxidation of unsaturated fatty acids both in vivo and in vitro. When autoxidation occurs in vivo, membrane damage that can lead to cell death can occur. Low concentrations of nitrogen dioxide were shown to react with the polyunsaturated fatty acid esters, methyl linoleate and methyl linoleate, by a H-abstraction mechanism. However, methyl oleate, an unsaturated fatty acid ester, was demonstrated to react with a low concentration of nitrogen dioxide by only an addition mechanism. Although methyl oleate reacts by an addition mechanism, a 50:50 molar solution of methyl oleate and methyl linoleate reacted with a low level of nitrogen dioxide exclusively by a H-abstraction mechanism. Therefore, low levels of nitrogen dioxide will probably react with polyunsaturated fatty acid components of pulmonary lipids by a H-abstraction mechanism forming nitrous acid directly in the cell membrane. Vitamin E was demonstrated to be able to act as a preventative antioxidant in the nitrogen dioxide and methyl linoleate reactions; but vitamin C could not prevent nitrogen dioxide from reacting with methyl linoleate by a H-abstraction mechanism. These results suggest that low levels of nitrogen dioxide will react with polyunsaturated fatty acids by a H-abstraction mechanism and that vitamin E can be used to prevent the reaction from occurring.

Gallon, A.A.

1990-01-01

366

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

367

Nucleic acid hybridization assays employing dA-tailed capture probes. II. Advanced multiple capture methods  

SciTech Connect

A fourth capture is added to the reversible target capture procedure. This results in an improved radioisotopic detection limit of 7.3 x 10(-21) mol of target. In addition, the standard triple capture method is converted into a nonradioactive format with a detection limit of under 1 amol of target. The principal advantage of nonradioactive detection is that the entire assay can be performed in about 1 h. Nucleic acids are released from cells in the presence of the (capture probe) which contains a 3'-poly(dA) sequence and the (labeled probe) which contains a detectable nonradioactive moiety such as biotin. After a brief hybridization in solution, the target is captured on oligo(dT) magnetic particles. The target is further purified from sample impurities and excess labeled probe by recapture either once or twice more on fresh magnetic particles. The highly purified target is then concentrated to 200 nl by recapture onto a poly(dT) nitrocellulose filter and rapidly detected with streptavidin-alkaline phosphatase using bromochloroindolyl phosphate and nitroblue tetrazolium. Using this procedure, as little as 0.25 amol of a target plasmid has been detected nonradioactively in crude samples in just 1 h without prior purification of the DNA and RNA. Finally, a new procedure called background capture is introduced to complement the background-reducing power of RTC.

Hunsaker, W.R.; Badri, H.; Lombardo, M.; Collins, M.L. (Gene-Trak Systems, Framingham, MA (USA))

1989-09-01

368

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

2012-06-13

369

Reaction between drug substances and pharmaceutical excipients: Formation of citric acid esters and amides of carvedilol in the solid state  

Microsoft Academic Search

The reactivity of citric acid towards drug substances in the solid state was examined using the ?-blocker carvedilol as a model compound. The reaction mixtures were analysed by LC–MS, the reaction products were isolated by preparative HPLC, and the structures were elucidated by microprobe NMR spectroscopy. Heating a mixture of solid carvedilol and solid citric acid monohydrate for 96h at

Jesper Larsen; Claus Cornett; Jerzy W. Jaroszewski; Steen H. Hansen

2009-01-01

370

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

Code of Federal Regulations, 2013 CFR

...New Uses for Specific Chemical Substances § 721...acids, tall-oil, reaction products with 4-methyl-2-pentanone...generic). (a) Chemical substance and significant...reporting . (1) The chemical substance identified...acids, tall-oil, reaction products with...

2013-07-01

371

Conversion of methanol to formic acid through the coupling of the enzyme reactions of alcohol oxidase, catalase and formaldehyde dismutase  

Microsoft Academic Search

Summary A novel process for the production of formic acid from methanol has been developed that involves the coupled reactions of the three enzymes, alcohol oxidase, catalase and formaldehyde dismutase. In this process, methanol is oxidized to formaldehyde by alcohol oxidase and catalase, followed by the formaldehyde dismutase reaction that leads to the formation of methanol and formic acid. Ultimately,

Sumiko Mizuno; Yukio Imada

1986-01-01

372

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

373

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

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

374

Mechanisms of proton transfer in Nafion: elementary reactions at the sulfonic acid groups.  

PubMed

Proton transfer reactions at the sulfonic acid groups in Nafion were theoretically studied, using complexes formed from triflic acid (CF3SO3H), H3O+ and H2O, as model systems. The investigations began with searching for potential precursors and transition states at low hydration levels, using the test-particle model (T-model), density functional theory (DFT) and ab initio calculations. They were employed as starting configurations in Born-Oppenheimer molecular dynamics (BOMD) simulations at 298 K, from which elementary reactions were analyzed and categorized. For the H3O+-H2O complexes, BOMD simulations suggested that a quasi-dynamic equilibrium could be established between the Eigen and Zundel complexes, and that was considered to be one of the most important elementary reactions in the proton transfer process. The average lifetime of H3O+ obtained from BOMD simulations is close to the lowest limit, estimated from low-frequency vibrational spectroscopy. It was demonstrated that proton transfer reactions at -SO3H are not concerted, due to the thermal energy fluctuation and the existence of various quasi-dynamic equilibria, and -SO3H could directly and indirectly mediate proton transfer reactions through the formation of proton defects, as well as the -SO3- and -SO3H2+ transition states. PMID:18688364

Sagarik, Kritsana; Phonyiem, Mayuree; Lao-ngam, Charoensak; Chaiwongwattana, Sermsiri

2008-02-21

375

Structural probing of the HIV-1 polypurine tract RNA:DNA hybrid using classic nucleic acid ligands  

PubMed Central

The interactions of archetypical nucleic acid ligands with the HIV-1 polypurine tract (PPT) RNA:DNA hybrid, as well as analogous DNA:DNA, RNA:RNA and swapped hybrid substrates, were used to probe structural features of the PPT that contribute to its specific recognition and processing by reverse transcriptase (RT). Results from intercalative and groove-binding ligands indicate that the wild-type PPT hybrid does not contain any strikingly unique groove geometries and/or stacking arrangements that might contribute to the specificity of its interaction with RT. In contrast, neomycin bound preferentially and selectively to the PPT near the 5?(rA)4:(dT)4 tract and the 3? PPT-U3 junction. Nuclear magnetic resonance data from a complex between HIV-1 RT and the PPT indicate RT contacts within the same regions highlighted on the PPT by neomycin. These observations, together with the fact that the sites are correctly spaced to allow interaction with residues in the ribonuclease H (RNase H) active site and thumb subdomain of the p66 RT subunit, suggest that despite the long cleft employed by RT to make contact with nucleic acids substrates, these sites provide discrete binding units working in concert to determine not only specific PPT recognition, but also its orientation on the hybrid structure.

Turner, Kevin B.; Brinson, Robert G.; Yi-Brunozzi, Hye Young; Rausch, Jason W.; Miller, Jennifer T.; Le Grice, Stuart F.J.; Fabris, Daniele

2008-01-01

376

Reactions of {4-[bis(2-chloroethyl)amino]phenyl}acetic acid (phenylacetic acid mustard) with 2'-deoxyribonucleosides.  

PubMed

Phenylacetic acid mustard (PAM; 2), a major metabolite of the anticancer agent chlorambucil (CLB; 1), was allowed to react with 2'-deoxyadenosine (dA), 2'-deoxyguanosine (dG), 2'-deoxycytidine (dC), 2'-deoxy-5-methylcytidine (dMeC), and thymidine (T) at physiological pH (cacodylic acid, 50% base). The reactions were followed by HPLC and analyzed by HPLC/MS and/or (1)H-NMR techniques. Although the predominant reaction observed was hydrolysis of PAM, 2 also reacted with various heteroatoms of the nucleosides to give a series of products: compounds 5-31. PAM (2) was found to be hydrolytically slightly more stable than CLB (1). The principal reaction sites of 2 with dA, dG, and with all pyrimidine nucleosides were N(1), N(7), and N(3), resp. Also, several other adducts were detected and characterized. There was no significant difference in the reactivity of 1 and 2 with dG, dA or T, but the N(3) dC-PAM adduct was deaminated easier than the corresponding CLB derivative. The role of PAM-2'-deoxyribonucleoside adducts on the cytotoxic and mutagenic properties of CLB (1) is discussed. PMID:17372943

Florea-Wang, Diana; Ijäs, Inna; Hakala, Kristo; Mattinen, Jorma; Vilpo, Juhani; Hovinen, Jari

2007-03-01

377

Products from the reaction of fatty acids with ketones and their characteristic properties as cutting fluids additives  

Microsoft Academic Search

Hydroxy acids were synthesized in good yields from ketones and fatty acids by the use of lithium naphthalene in the presence\\u000a of diethylamine. For example, from cyclohexanone and undecylenic acid (I), 2-(1-hydroxy-1-cyclohexyl)-10-undecenoic acid (III)\\u000a was obtained in 92% yield. Hydroxy acids were treated withp-toluenesulphonic acid to give corresponding unsaturated fatty acids. From the reaction of (III), 2-(1-cyclohexenyl)-10-undecenoic\\u000a acid (IV), a

S. Watanabe; T. Fujita; K. Suga; K. Sugahara

1983-01-01

378

Reactions of group 6 metal carbonyls with salicylaldehyde isonicotinic acid hydrazone  

Microsoft Academic Search

Sunlight irradiation of the reactions of [M(CO)6], M?=?Cr, Mo and W with salicylaldehyde isonicotinic acid hydrazone (H2salnah) in THF were investigated. Interaction of [Cr(CO)6] with H2salnah resulted in formation [Cr2O2(H2salnah)2]. The corresponding reactions of molybdenum and tungsten carbonyls yielded dinuclear oxo complexes [M2O6(H2salnah)]. All complexes were characterized by elemental analysis, IR, mass spectrometry and H NMR spectroscopy. The IR spectra

Saadia A. Ali

2007-01-01

379

Catalysis of mukaiyama aldol reactions by a tricyclic aluminum alkoxide Lewis acid.  

PubMed

The Mukayiama aldol reaction of aldehydes is efficiently accomplished with a low concentration of the dimeric alumatrane catalyst 2 at mild or subambient temperatures. Our protocol tolerates a wide variety of electron-rich, neutral, and deficient aryl, alkyl, and heterocyclic aldehydes. A wide variety of enol silyl ethers are also tolerated. An intermediate that was isolated provides mechanistic information regarding the role of dimeric 2 in the Mukaiyama aldol reaction. Experimental evidence is presented for the stronger Lewis acidity of 5 compared with F3B. PMID:19545133

Raders, Steven M; Verkade, John G

2009-08-01

380

Turing patterns in the chlorine dioxide-iodine-malonic acid reaction with square spatial periodic forcing.  

PubMed

We use the photosensitive chlorine dioxide-iodine-malonic acid reaction-diffusion system to study wavenumber locking of Turing patterns to two-dimensional "square" spatial forcing, implemented as orthogonal sets of bright bands projected onto the reaction medium. Various resonant structures emerge in a broad range of forcing wavelengths and amplitudes, including square lattices and superlattices, one-dimensional stripe patterns and oblique rectangular patterns. Numerical simulations using a model that incorporates additive two-dimensional spatially periodic forcing reproduce well the experimental observations. PMID:22456449

Feldman, Daniel; Nagao, Raphael; Bánsági, Tamás; Epstein, Irving R; Dolnik, Milos

2012-03-28

381

Stationary Turing patterns versus time-dependent structures in the chlorite-iodide-malonic acid reaction  

NASA Astrophysics Data System (ADS)

The standing concentration patterns recently discovered in open gel-filled reactors, with the chlorite-iodide-malonic acid (CIMA) oscillating reaction in the presence of starch, were ascribed to a Turing-type reaction-diffusion symmetry breaking instability. Here we extend the investigations to other regions of parameters, with a particular emphasis to the role played by the chemical nature of the gel matrix and by the starch concentration on the onset of stationary patterns. Stationary Turing patterns are shown to develop in gel-free systems. Transitions between stationary Turing structures and wave patterns are presented. The first evidence of an anti-symmetric ``homogeneous'' wave source is presented.

Perraud, J. J.; Agladze, K.; Dulos, E.; de Kepper, P.

1992-09-01

382

Reactions of Chelates with Macrocyclic Ligands. Complexation between Tetraphenylporphine and Cu(II) Complexes with ?-Amino Acids  

Microsoft Academic Search

The reactions of tetraphenylporphine (H2TPP) with copper(II) chelates in DMSO were studied. a-Amino acids (glycine, a-alanine, valine, leucine, tyrosine, and glutamine) were used as chelating ligands. The study of the reaction kinetics showed that Cu(II) chelates with alanine and the other amino acids are less reactive in these reactions than acetylacetonates, a-nitroso-ß-naphtholates, and hydroxyquinolates. The exception is a Cu(II) complex

B. D. Berezin; G. M. Mamardashvili

2002-01-01

383

Discriminating Multi-Species Populations in Biofilms with Peptide Nucleic Acid Fluorescence In Situ Hybridization (PNA FISH)  

Microsoft Academic Search

BackgroundOur current understanding of biofilms indicates that these structures are typically composed of many different microbial species. However, the lack of reliable techniques for the discrimination of each population has meant that studies focusing on multi-species biofilms are scarce and typically generate qualitative rather than quantitative data.Methodology\\/Principal FindingsWe employ peptide nucleic acid fluorescence in situ hybridization (PNA FISH) methods to

Carina Almeida; Nuno F. Azevedo; Sílvio Santos; Charles W. Keevil; Maria J. Vieira; Yann Astier

2011-01-01

384

Identification of antisense nucleic acid hybridization sites in mRNA molecules with self-quenching fluorescent reporter molecules  

Microsoft Academic Search

We describe a physical mRNA mapping strategy employing fluorescent self-quenching reporter molecules (SQRMs) that facilitates the identification of mRNA sequence accessible for hybridization with antisense nucleic acids in vitro and in vivo, real time. SQRMs are 20-30 base oligodeoxynucleotides with 5-6 bp complementary ends to which a 50 fluorophore and 30 quenching group are attached. Alone, the SQRM complementary ends

Lida K. Gifford; Joanna B. Opalinska; David Jordan; Vikram Pattanayak; Paul Greenham; Anna Kalota; Michelle Robbins; Kathy Vernovsky; Lesbeth C. Rodriguez; Bao T. Do; Ponzy Lu; Alan M. Gewirtz

2005-01-01

385

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

Microsoft Academic Search

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

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

2011-01-01

386

A sinapic acid–calix[4]arene hybrid selectively binds Pb 2+ over Hg 2+ and Cd 2+  

Microsoft Academic Search

The binding affinity for Pb2+, Cd2+ and Hg2+ of the sinapic acid–calix[4]arene hybrid 2, having four sinapyl pendants at the upper rim, has been investigated via an UV–Vis study. Compound 2 has better complexing ability than the monomeric p-phenetidine derivative 1. This highlights that the clustering of sinapyl units in a basket-like structure, dictated by the calixarene scaffold, greatly enhances

Carmelo Sgarlata; Valeria Zito; Giuseppe Arena; Grazia Maria Letizia Consoli; Eva Galante; Corrada Geraci

2009-01-01

387

Visualization of the mycelia of wood-rotting fungi by fluorescence in situ hybridization using a peptide nucleic acid probe.  

PubMed

White rot fungus, Phanerochaete chrysosporium, and brown rot fungus, Postia placenta, grown on agar plates, were visualized by fluorescence in situ hybridization (FISH) using a peptide nucleic acid (PNA) probe. Mycelia grown on wood chips were also clearly detected by PNA-FISH following blocking treatment. To the best of our knowledge, this is the first report on the visualization of fungi in wood by FISH. PMID:23391931

Nakada, Yuji; Nakaba, Satoshi; Matsunaga, Hiroshi; Funada, Ryo; Yoshida, Makoto

2013-02-07

388

Acid fuchsin-interleaved Mg–Al-layered double hydroxide for the formation of an organic–inorganic hybrid nanocomposite  

Microsoft Academic Search

Layered organic–inorganic hybrid nanocomposite, containing an organic dye in an inorganic interlayer was prepared using acid fuchsin (AF) as a guest in Mg–Al layered double hydroxide inorganic host by a self-assembly technique, with the Mg–Al ratio in the mother liquor of 4 and pH=7.5. Powder X-ray diffractogram shows that the basal spacing of the Mg–Al layered double hydroxide with nitrate

Mohd Zobir bin Hussein; Asmah Hj Yahaya; Mohd Shamsul; Hairi Mohd Salleh; Taufiq Yap; Jacqueline Kiu

2004-01-01

389

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

Microsoft Academic Search

A new fluorescence in situ hybridization method using peptide nucleic acid (PNA) probes for identification of Brettanomyces is described. The test is based on fluorescein-labeled PNA probes targeting a species-specific sequence of the rRNA of Dekkera bruxellensis. The PNA probes were applied to smears of colonies, and results were interpreted by fluorescence microscopy. The results obtained from testing 127 different

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

2001-01-01

390

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

391

Formation of Lactic Acid from Cellulosic Biomass by Alkaline Hydrothermal Reaction  

NASA Astrophysics Data System (ADS)

Glucose, as a model compound of cellulosic biomass, was used as a test material. Ca(OH)2 and NaOH were selected as alkali. Results showed that both NaOH and Ca(OH)2, can promote the formation of lactic acid in a hydrothermal reaction of glucose. In the case of the addition of NaOH, lactic acid was obtained with a good yield of 27% based on a carbon base at 300 °C for 60 s with a NaOH concentration of 2.5 M. In the case of the addition of Ca(OH)2, the highest yield of lactic acid is 20%, which occurred at 300 °C for 60 s with a Ca(OH)2 concentration of 0.32 M. The formation mechanisms of lactic acid from glucose were also discussed according to intermediate products identified. Lactic acid may be generated via formaldehyde, glycolaldehyde besides via the aldose having three carbon atoms in hydrothermal reaction which all formed by the reverse aldol condensation of hexoses.

Yan, X.; Jini, F.; Kishita, A.; Enomoto, H.; Tohji, K.

2008-02-01

392

Long-lived oscillations in the chlorite-iodide-malonic acid reaction in batch  

SciTech Connect

The title reaction is the subject of current interest because the first experimental Turing patterns were observed recently in this system. Here, the authors report the first observation of oscillations that are long lived (over 1 h) in this system in a batch reactor; even after cessation the oscillations can be restarted several times by adding ClO{sub 2} to the exhausted system. These low-frequency low-amplitude (LL) oscillations were detected with both platinum and iodide-selective electrodes in the chlorite-iodide-malonic acid (original CIMA) reaction and in the closely related chlorine dioxide-iodide-malonic acid (minimal CIMA) system. The LL oscillations follow after the already known high frequency oscillations, sometimes separated by a second induction period. LL oscillations can appear without any induction period if appropriate concentrations of chlorine dioxide, iodomalonic acid, and chloride (CIMA-Cl system) are established in a dilute sulfuric acid medium. In this case neither iodine, iodide, nor malonic acid is needed. Some suggestions are made regarding the mechanism of these newly discovered oscillations. 33 refs., 6 figs., 1 tab.

Noszticzius, Z.; Ouyang, Qi; McCormick, W.D.; Swinney, H.L. [Univ. of Texas, Austin, TX (United States)

1992-05-20

393

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

394

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

395

Gypsum crystallization and hydrochloric acid regeneration by reaction of calcium chloride solution with sulfuric acid  

Microsoft Academic Search

In this work, the crystallization of gypsum (CaSO4·2H2O) in the temperature range of 20–60 °C is investigated along with the simultaneous regeneration of HCl by the reaction of concentrated CaCl2 solution (3–3.5 M) with H2SO4 at a concentration range of 2.6–8.0 M. Fast addition of H2SO4 proved counter productive as it yielded a gel-like fine crystal suspension. Slower addition via titration or in

Amani Al-Othman; George P. Demopoulos

2009-01-01

396

Effects of amino acids on the formation of hematite particles in a forced hydrolysis reaction.  

PubMed

The influence of amino acids on the formation of hematite particles from a forced hydrolysis reaction of acidic FeCl3 solution was examined. The spherical particles were produced on the systems with L-phenylalanine (L-Phe), L-serine (L-Ser) and L-alanine (L-Ala), though L-glutamine (L-Gln) and L-glutamic acid (L-Glu) gave ellipsoidal hematite particles. This morphological change in hematite particles is consistent with the order of stability constant of amino acids against to Fe3+ ions (K). The hematite particles produced with L-Glu, L-Gln and L-Ser were highly porous because they are formed by aggregation of cluster particles. These particles exhibited microporous behavior by outgassing the particles below 200 degrees C while they changed to mesoporous after treating above 300 degrees C by elimination of amino acids molecules remained between the cluster particles within the hematite particles. The hematite particles strongly depended on the nature of amino acids such as alternation of solution pH and adsorption affinity to beta-FeOOH and/or polynuclear primary (PN) particles. The systems on L-Ala and L-Phe, showing very rapid phase transformation from beta-FeOOH to hematite, exhibited the Ostwald ripening. A rotational particle preparation procedure suggested that the morphology of hematite particle is governed by the mode and strength of amino acid adsorption onto beta-FeOOH and/or PN particles. PMID:16054636

Kandori, Kazuhiko; Sakai, Masaji; Inoue, Shoko; Ishikawa, Tatsuo

2005-07-28

397

Plasma-catalytic hybrid system using spouted bed with a gliding arc discharge: CH4 reforming as a model reaction  

NASA Astrophysics Data System (ADS)

A combination of a gliding arc discharge and a spouted catalytic bed was used to investigate a plasma-catalytic hybrid system using CH4 reforming as a model reaction. Alumina-supported catalysts that contained 0.5 wt% of Pt, Pd, Rh, and Ru (denoted as Pt/Al2O3, Pd/Al2O3, Rh/Al2O3 and Ru/Al2O3, respectively) were used. For comparison, active Al2O3 particles were also examined. The conversion of CH4 and the selectivity of the product were investigated by changing the feed flow rate and reaction time. The production of C2H2, H2 and soot was observed in the gliding arc discharge without a catalyst. Using Pt/Al2O3 and Pd/Al2O3with the gliding arc discharge, C2H4, C2H6 and C2H2 were produced. It is considered that C2H4 and C2H6 were formed by the hydrogenation of C2H2 on the active site of Pt/Al2O3 and Pd/Al2O3. A stronger resistance to deactivation was shown in the presence of Pd/Al2O3 than in the presence of Pt/Al2O3, whereas the selectivity of hydrocarbon using Rh/Al2O3 and Ru/Al2O3 showed a tendency similar to that in active Al2O3 and non-catalytic experiments. The proposed reactor has a potential to improve the selectivity of the plasma process.

Lee, H.; Sekiguchi, H.

2011-07-01

398

Negative resists for i-line lithography utilizing acid-catalyzed intramolecular dehydration reaction  

NASA Astrophysics Data System (ADS)

Chemical amplification negative resist system composed of a novolak resin, a carbinol and an acid generator is investigated for i-line phase-shift lithography. The reaction in this resist is based on an acid-catalyzed intramolecular dehydration reaction. The dehydration products act as aqueous-base dissolution inhibitors, and carbinol compounds in unexposed areas work as dissolution promoters. The resist composed of a novolak resin, 1,4-bis((alpha) -hydroxyisopropyl) benzene (DIOL-1) and 2- naphthoylmethyltetramethylenesulfonium triflate (PAG-2) gives the best lithographic performance in terms of sensitivity and resolution. Line-and-space patterns of 0.275 micrometers are obtained using an i-line stepper (NA:0.45) in conjunction with a phase shifting mask.

Ueno, Takumi; Uchino, Shou-ichi; Hattori, K. T.; Onozuka, T.; Shirai, Sei-ichiro; Moriuchi, Noboru; Hashimoto, Michiaki; Koibuchi, S.

1994-05-01

399

Revisiting the Kinetics and Mechanism of the Tetrathionate-Hypochlorous Acid Reaction in Nearly Neutral Medium  

NASA Astrophysics Data System (ADS)

The tetrathionate-hypochlorous acid reaction has been investigated in nearly neutral medium at I = 0.5 M ionic strength and T = 25.0 ± 0.1 °C in dihydrogen-phosphate-hydrogen-phosphate buffer by UV-vis spectrophotometry. In excess of hypochlorous acid, the stoichiometry was found to be S4O62- + 7HOCl + 3H2O ? 4SO42- + 7Cl- + 13H+, but in excess of tetrathionate colloidal sulfur precipitates. On the basis of the simultaneous evaluation of the kinetic curves, a nine-step kinetic model with four fitted and five fixed rate coefficients is proposed. Analogous oxidation reactions of tetrathionate are also compared and discussed.

Varga, Dénes; Horváth, Attila K.

2009-11-01

400

Organic reactions increasing the absorption index of atmospheric sulfuric acid aerosols  

NASA Astrophysics Data System (ADS)

Unlike most environments present at Earth's surface atmospheric aerosols can be favorable to organic reactions. Among them, the acid-catalyzed aldol condensation of aldehydes and ketones produces light-absorbing compounds. In this work the increase of the absorption index of sulfuric acid solutions 50-96 wt. % resulting from the uptake of gas-phase acetaldehyde, acetone, and 2-butanone (methyl ethyl ketone), has been measured in the near UV and visible range. Our results indicate that the absorption index between 200 and 500 nm for stratospheric sulfuric aerosols exposed to 100 pptV of acetaldehyde (1 pptV = 10-12 v/v) would increase by four orders of magnitude over a two-year lifetime. Rough estimates based on previous radiative calculations suggest that this reaction could result in an increase of the radiative forcing of sulfate aerosols of the order of 0.01 W m-2, and that these processes are worth further investigation.

Nozière, B.; Esteve, W.

2005-02-01

401

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

NASA Astrophysics Data System (ADS)

The radiolysis of aqueous vitamin B5 (pantothenic acid) has been investigated under various experimental conditions. The highest vitamin degradation (G=3.22) was observed in solutions saturated with N2O, where 90% OH radicals are operating. As final products, the following were established: aldehydes, carboxylic acids and ammonia. Their yield strongly depends on the presence/absence of air as well as on N2O (used to convert eaq- into OH) and was determined as a function of absorbed radiation dose. HPLC-analysis showed that in all media, a main product is formed, having the highest yield in aerated solutions. Based on the chemical analysis, it appears that the OH radicals are most involved in the degradation process. A precise sequence of the reaction steps could not be given presently, because of the implication of many simultaneous reactions.

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

2007-10-01

402

Kinetic studies on the reaction of compound II of myeloperoxidase with ascorbic acid. Role of ascorbic acid in myeloperoxidase function.  

PubMed

Ascorbic acid is known to stimulate leukocyte functions. In a recent publication it was suggested that the role of ascorbic acid is to reduce compound II of myeloperoxidase back to the native enzyme (Bolscher, B. G. J. M., Zoutberg, G. R., Cuperus, R. A., and Wever, R. (1984) Biochim. Biophys. Acta 784, 189-191). In this paper we report rapid spectral scan and transient state kinetic results on the reaction of three myeloperoxidase compounds II, namely, human neutrophil myeloperoxidase, canine myeloperoxidase, and bovine spleen heme protein with ascorbate. We show by rapid scan spectra that compound II does not pass through any other intermediate when ascorbic acid reduces it back to native form. We also show that the reactions of all three compounds II involve a simple binding interaction before enzyme reduction with an apparent dissociation constant of 6.3 +/- 0.9 x 10(-4) to 2.0 +/- 0.3 x 10(-3)M and a first-order rate constant for reduction of 12.6 +/- 0.6 to 18.8 +/- 1.3 s-1. The optimum pH is 4.5, and at this pH the activation energy for the reaction is 13.2 kJ mol-1. Results of this work lend further evidence that the spleen green heme protein is very similar if not identical to leukocyte myeloperoxidase based on a comparison of spectral scans, pH-rate profiles, and kinetic parameters. We demonstrate that chloride cannot reduce compound II whereas iodide reduces compound II to native enzyme at a rate comparable to that of ascorbate. This explains why ascorbate accelerates chlorination but inhibits iodination. Formation of compound II is a dead end for the generation of hypochlorous acid; ascorbate regenerates more native enzyme to enhance the chlorination reaction namely: myeloperoxidase + peroxide----compound I followed by compound I + chloride----HOCl. On the other hand, ascorbate is a competitor with iodide for both compounds I and II and so inhibits iodination. PMID:2156823

Marquez, L A; Dunford, H B; Van Wart, H

1990-04-01

403

Immature embryo rescue, culture and seedling development of acid citrus fruit derived from interploid hybridization  

Microsoft Academic Search

Interploid sexual hybridizations were completed in 2001 and 2002 between seven lemon (Citrus limon(L.) Burm. f.) varieties, ‘Key’ lime (C. aurantifolia (Cristm.) Swing), Palestine sweet lime (C. imettioides Tan.), ‘Lakeland’ limequat (C. aurantifolia x Fortunella japonica (Thumb.) Swing.), and ‘Etrog’ citron (C. medica L.) as diploid progenitors and four allotetraploid somatic hybrids (‘Key’ lime + ‘Valencia’ orange, ‘Hamlin’ orange +

Z. Viloria; J. W. Grosser; B. Bracho

2005-01-01

404

Reactions of e aq' ? H and OH with picolinic acid studied by pulse radiolysis  

Microsoft Academic Search

Rate constants for the reaction of the primary species of water radiolysis, viz. e\\u000aaq'\\u000a–\\u000a, H and OH, with picolinic acid have been determined at various pHs. The semi-reduced species exhibits max at 305 and 350 nm. It is a strong reductant and has two pKa values of 1 and 5.7. The OH adduct of this compound also

G. R. Dey; D. B. Naik; K. Kishore; P. N. Moorthy

1992-01-01

405

The acid-mediated ring opening reactions of ?-aryl-lactams.  

PubMed

4-Aryl-azetidin-2-ones (?-lactams) undergo ring opening with triflic acid to give cinnamamides which, in benzene, react further to give 3-aryl-3-phenyl-propionamides. Prolonged reaction times in benzene give 3,3-diphenyl-propionamide via an aryl/phenyl exchange. Lactams of ring size 7 and higher also ring open, but only 7- and 8-membered rings give pure diphenylalkylamides. AlCl(3) only ring opens the 4-aryl-azetidinones. PMID:22406974

King, Frank D; Caddick, Stephen

2012-03-12

406

Spray-dried conjugated linoleic acid encapsulated with Maillard reaction products of whey proteins and maltodextrin  

Microsoft Academic Search

Encapsulation performance of Maillard reaction products (MRPs) produced by whey proteins and maltodextrin were examined for\\u000a microencapsulation of conjugated linoleic acid (CLA) using spray-drying. CLA was encapsulated using 3 different wall materials\\u000a containing a single constituent such as whey protein concentrate (WPC), whey protein isolate (WPI), and maltodextrin (MD),\\u000a and 4 different MRPs. For the development of MRPs, ratios of

Kyeong-Ok Choi; Jina Ryu; Hae-Soo Kwak; Sanghoon Ko

2010-01-01

407

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

408

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

409

Luminol chemiluminescence HPLC reaction detector for amino acids and other ligands  

Microsoft Academic Search

A detector for HPLC is based on suppression of chemiluminescence from the Cu(II)-luminol-peroxide reaction. Analytes which complex Cu(II) reduce the free Cu(II) concentration and thus the observed chemiluminescence intensity. The degree of chemiluminescence suppression is a measure of the analyte concentrations. Detection limits are in the range of 1 pmole-1 nmole for amino acids (both primary and secondary without derivatization),

P. J. Koerner; Timothy A. Nieman

1987-01-01

410

Isothermal, In Vitro Amplification of Nucleic Acids by a Multienzyme Reaction Modeled After Retroviral Replication  

Microsoft Academic Search

A target nucleic acid sequence can be replicated (amplified) exponentially in vitro under isothermal conditions by using three enzymatic activities essential to retroviral replication: reverse transcriptase, RNase H, and a DNA-dependent RNA polymerase. By mimicking the retroviral strategy of RNA replication by means of cDNA intermediates, this reaction accumulates cDNA and RNA copies of the original target. Product accumulation is

John C. Guatelli; Kristina M. Whitfield; Deborah Y. Kwoh; Kevin J. Barringer; Douglas D. Richman; Thomas R. Gingeras

1990-01-01

411

Biotransformation of nitriles to hydroxamic acids via a nitrile hydratase–amidase cascade reaction  

Microsoft Academic Search

The transformation of benzonitrile into benzohydroxamic acid was performed by a cascade bienzymatic reaction involving nitrile hydration and acyl transfer of the intermediate benzamide onto hydroxylamine. The first step was catalyzed by either a cell-free extract from Rhodococcus erythropolis A4 (nitrile hydratase) or cell-free extracts from recombinant Escherichia coli strains expressing nitrile hydratases from Raoultella terrigena 77.1 and Klebsiella oxytoca

Vojt?ch Vejvoda; Ludmila Martínková; Alicja B. Veselá; Ond?ej Kaplan; Sabine Lutz-Wahl; Lutz Fischer; Bronislava Uhnáková

2011-01-01

412

Controlled accessibility Lewis acid catalysed thermal reactions of regenerated cellulosic fibres  

Microsoft Academic Search

A combination of techniques have been used to characterise lyocell regenerated cellulose fibre subjected to low-moisture thermal-catalytic\\u000a reactions with zinc chloride Lewis acid. Application from non-swelling ethanol reduces catalyst accessibility, but at high\\u000a temperatures migration takes place through the internal fibre morphology. The extent of chain scission is reduced at lower\\u000a temperatures, leading to a higher leveling-off degree of polymerisation

Dimtra Domvoglou; Franz Wortmann; Jim Taylor; Roger Ibbett

2010-01-01

413

Displacement reaction of Pt on carbon-supported Ru nanoparticles in hexachloroplatinic acids  

Microsoft Academic Search

The displacement reaction of Pt on Ru to form a Ru core and Pt shell (Ru@Pt) bimetallic structure is investigated by immersing the carbon-supported Ru nanoparticles in hexachloroplatinic acids with pH of 1, 2.2, and 8, followed by a hydrogen reduction treatment. Results from inductively coupled plasma mass spectrometry suggest that the dissolution of Ru is mostly caused by the

Yu-Chi Hsieh; Li-Chung Chang; Pu-Wei Wu; Yun-Min Chang; Jyh-Fu Lee

2011-01-01

414

Light activates the reaction of bacteriorhodopsin aspartic acid-115 with dicyclohexylcarbodiimide  

Microsoft Academic Search

Conditions for a light-induced reaction between the carboxyl-modifying reagent N,N'-dicyclohexylcarbodiimide (DCCD) and bacteriorhodopsin in Triton X-100 micelles were previously reported. The authors have now located the DCCD site in the bacteriorhodopsin amino acid sequence. ( UC)DCCD-bacteriorhodopsin was cleaved with CNBr. The resulting peptides were purified by gel filtration and reverse-phase high-performance liquid chromatography (HPLC). One major UC peptide (50%) and

Robert Renthal; Marian Cothran; Bill Espinoza; Katherine A. Wall; Michael Bernard

1985-01-01

415

CATALYTIC REACTIONS ON SEMICONDUCTORS: HYDROGEN-DEUTERIUM EXCHANGE AND FORMIC ACID DECOMPOSITION ON CHEMICALLY DOPED GERMANIUM  

Microsoft Academic Search

Hydrogen--deuterium exchange and the decomposition of formic acid were ; studied from 100 to 400 deg over samples of germanium doped with 10¹⁶ to ; 10²° atoms per cc. of n- and p-type impurities. Over these wide ranges of ; electronic chemical potentials (Fermi level) and temperature the rate and ; activation energy of the exchange reaction varied definitely with

George E. Moore; Hilton A. Smith; Ellison H. Taylor

1962-01-01

416

[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

417

Identification of human rotavirus serotype by hybridization to polymerase chain reaction-generated probes derived from a hyperdivergent region of the gene encoding outer capsid protein VP7  

SciTech Connect

We have synthesized {sup 32}P-labeled hybridization probes from a hyperdivergent region (nucleotides 51 to 392) of the rotavirus gene encoding the VP7 glycoprotein by using the polymerase chain reaction method. Both RNA (after an initial reverse transcription step) and cloned cDNA from human rotavirus serotypes 1 through 4 could be used as templates to amplify this region. High-stringency hybridization of each of the four probes to rotavirus RNAs dotted on nylon membranes allowed the specific detection of corresponding sequences and thus permitted identification of the serotype of the strains dotted. The procedure was useful when applied to rotaviruses isolated from field studies.

Flores, J.; Sears, J.; Schael, I.P.; White, L.; Garcia, D.; Lanata, C.; Kapikian, A.Z. (National Institutes of Health, Bethesda, MD (USA))

1990-08-01

418

Human papillomavirus infection and anal carcinoma. Retrospective analysis by in situ hybridization and the polymerase chain reaction.  

PubMed Central

To examine the association of human papillomavirus (HPV) infection with anal squamous cell carcinoma, the authors applied the highly sensitive polymerase chain reaction (PCR) and in situ hybridization (ISH) techniques to detect HPV DNA in formalin-fixed, paraffin-embedded tissues from 18 patients. The presence of HPV types 16/18 in 3 (16.7%) of 18 patients with anal carcinoma was found, using a colorimetric ISH technique for HPV types 6, 11, 16, 18, 31, 35, and 51. Results from one of these three patients were also positive for HPV 31, 35, 51 by ISH techniques. When the same series was analyzed using the PCR and consensus primers to the L1 open reading frame of the HPV genomes, the frequency of positive patients rose to 14 (77.8%) of 18. PCR analysis of the 14 lesions containing HPV DNA, using type-specific primers and probes for HPV 6, 11, 16, 18, and 33, showed that 1 contained HPV 6, 1 contained HPV 11, 4 contained HPV 16, 1 contained HPV 18, 1 contained HPV 33, 5 contained HPV of unclassified type(s), and 1 contained a mixture of three HPV types. There was concordance between typing of cases that were positive by ISH and PCR methods. These data agree with the concept that HPV, in particular type 16, is implicated in the pathogenesis of anal cancer. Images Figure 1 Figure 3 Figure 4 Figure 5

Zaki, S. R.; Judd, R.; Coffield, L. M.; Greer, P.; Rolston, F.; Evatt, B. L.

1992-01-01

419

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

420

Efficient conversion of furfuryl alcohol into alkyl levulinates catalyzed by an organic-inorganic hybrid solid acid catalyst.  

PubMed

A clean, facile, and environment-friendly catalytic method has been developed for the conversion of furfuryl alcohol into alkyl levulinates making use of the novel solid catalyst methylimidazolebutylsulfate phosphotungstate ([MIMBS]?PW??O??). The solid catalyst is an organic-inorganic hybrid material, which consists of an organic cation and an inorganic anion. A study for optimizing the reaction conditions such as the reaction time, the temperature and the catalyst loading has been performed. Under optimal conditions, a high n-butyl levulinate yield of up to 93?% is obtained. Furthermore, the kinetics of the reaction pathways and the mechanism for the alcoholysis of furfuryl alcohol are discussed. This method is environmentally benign and economical for the conversion of biomass-based derivatives into fine chemicals. PMID:21226220

Zhang, Zehui; Dong, Kun; Zhao, Zongbao Kent

2011-01-17

421

Proton transfer reactions in carbon nanotubes endohedrally functionalized with selected polar amino acid sidechains  

NASA Astrophysics Data System (ADS)

We use the empirical-valence-bond (EVB) theory to investigate intramolecular proton transfer reactions between a selected set of polar amino acid sidechains and hydroxyl groups suspended inside carbon nanotubes to model the effect of hydrophobic confinement on the energetics of proton transfer involving (i) translocation of an excess protonic charge (with protonated histidine sidechain as donor) and (ii) transformation of a neutral reactant state to a charge-separated product state (with sidechains of Asp, Glu, Ser and Thr as donor). In both the cases, confinement in hydrophobic medium is found to change the associated free energies compared to their respective values in the bulk solution phase. Presence of stable hydrogen bonding within the pore is found to have a significant effect on both free energies of reaction and activation and thus governs the thermodynamic and kinetic feasibilities of these intramolecular reactions in hydrophobic confinement.

Abi, T. G.; Taraphder, Srabani

2012-09-01

422

THE CELLULAR REACTIONS TO LIPOID FRACTIONS FROM ACID-FAST BACILLI.  

PubMed

1. A comparative study has been made of the cellular reactions induced by phosphatides from five strains of acid-fast bacilli. Each of these reactions is characterized principally by epithelioid cells and giant cells. 2. The phosphatides are first phagocytized by young connective tissue cells or monocytes. The lipoid is then dispersed into fine particles with the formation of classical epithelioid cells. 3. A comparison has been made of the reactions induced by heat-killed and defatted tubercle bacilli with those induced by tuberculophosphatide. 4. Further studies have been made to determine whether or not the phosphatide causes sensitization to tuberculin. It does not do so. 5. The life cycle of the epithelioid cell has been observed in all its stages. PMID:19870109

Smithburn, K C; Sabin, F R

1932-11-30

423

Site-directed mutagenesis of epoxide hydrolase to probe catalytic amino acid residues and reaction mechanism.  

PubMed

Epoxide hydrolase from Rhodococcus opacus catalyzes the stereospecific hydrolysis of cis-epoxysuccinate to L(+)-tartrate. It shows low but significant similarity to haloacid dehalogenase and haloacetate dehalogenase (16-23% identity). To identify catalytically important residues, we mutated 29 highly conserved charged and polar amino acid residues (except for one alanine). The replacement of D18, D193, R55, K164, H190, T22, Y170, N134 and A188 led to a significant loss in the enzyme activity, indicating their involvement in the catalysis. Single and multiple turnover reaction studies show that the enzyme reaction proceeded through the two-step mechanism involving the formation of a covalent intermediate. We discuss the roles of these residues and propose its possible reaction mechanism. PMID:21763314

Pan, Haifeng; Xie, Zhipeng; Bao, Wenna; Cheng, Yongqing; Zhang, Jianguo; Li, Yongquan

2011-07-13

424

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

425

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

426

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

427

Acid-catalyzed reactions of twisted amides in water solution: competition between hydration and hydrolysis.  

PubMed

The acid-catalyzed reactions of twisted amides in water solution were investigated by using cluster-continuum model calculations. In contrast to the previous widely suggested concerted hydration of the C=O group, our calculations show that the reaction proceeds in a practically stepwise manner, and that the hydration and hydrolysis channels of the C-N bond compete. The Eigen ion (H(3)O(+)) is the key species involved in the reaction, and it modulates the hydration and hydrolysis reaction pathways. The phenyl substitution in the twisted amide not only activates the N-CO bond, but also stabilizes the hydrolysis product through n(N)??(phenyl) delocalization, leading exclusively to the hydrolysis product of the ring-opened carboxylic acid. Generally, the twisted amides are more active than the planar amides, and such a rate acceleration results mainly from the increase in exothermicity in the first N-protonation step; the second step of the nucleophilic attack is less affected by the twisting of the amide bond. The present results show good agreement with the available experimental observations. PMID:21901771

Wang, Binju; Cao, Zexing

2011-09-07

428

Role of water in mukaiyama-aldol reaction catalyzed by lanthanide lewis Acid: a computational study.  

PubMed

Carbon-carbon bond formations, such as Kobayashi modification of the Mukaiyama-Aldol reaction, catalyzed by lanthanide (Ln) Lewis acid in aqueous solution comprise one of the most attractive types of reactions in terms of green chemistry. However, their detailed mechanisms and the role of water molecules remained unclear. In order to explore complex potential energy surfaces for the water and substrate coordination around Eu(3+) as well as the detailed mechanism of the Mukaiyama-Aldol reaction between trimethylsilyl (TMS) cylcohexenolate and benzaldehyde (BA) catalyzed by Eu(3+), the recently developed anharmonic downward distortion following (ADDF) and artificial force-induced reaction (AFIR) methods were used with the B3LYP-D3 theory. The most favorable water coordination structures are Eu(3+)(H2O)8 and Eu(3+)(H2O)9; they are comparable in free energy and are likely to coexist, with an effective coordination number of 8.3. Eu(3+)(H2O)8(BA) is the best aldehyde coordinated structure. Starting with this complex, the Mukaiyama-Aldol reaction proceeds via a stepwise mechanism, first C-C bond formation between the substrates, followed by proton transfer from water to BA and then TMS dissociation caused by nucleophilic attack by bulk water molecules. Why did the yield of the Mukaiyama-Aldol reaction catalyzed by Ln(3+) in organic solvent dramatically increase upon addition of water? Without water, the reverse reaction (C-C cleavage) takes place easily. Why did this reaction show syn-preference in water? The anti transition state for C-C formation in water is entropically less favored relative to the syn transition state because of the existence of a rigid hydrogen bond between the TMS part and coordination water around Eu(3+) in the former. PMID:24006879

Hatanaka, Miho; Morokuma, Keiji

2013-09-05

429

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

430

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

431

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

432

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

433

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

2013-04-28

434

Infrared spectroscopic studies of the heterogeneous reaction of ozone with maleic and fumaric acid aerosols  

NASA Astrophysics Data System (ADS)

Dicarboxylic acids, either directly emitted or formed in chemical processes are found to be a significant component of tropospheric aerosols. To assess any potential role of short unsaturated dicarboxylic acids in tropospheric heterogeneous chemistry, maleic acid (MaH) and fumaric acid (FuH) were selected as surrogates in this study. A new aerosol flow tube apparatus is employed to perform kinetic studies of the oxidation of organic compounds containing aerosols by gas phase ozone. The system consists of a lab-made particle generation system, a vertically oriented glass flow tube with moveable injector and a multi-pass cross beam White cell for measurement of aerosol and gas phase composition via Fourier transform infrared (FTIR) spectroscopy. A flow of single component organic aerosols with mean diameters ranging between 0.8-2.1 m are introduced in a flow tube, in which the particles are subsequently exposed to a known concentration of ozone for a controlled period of time. These studies are complemented with offline analysis on the reaction products. Data from these studies were used to determine the kinetics of the reaction under a range of conditions. The reaction exhibited pseudo first order kinetics for gas product formation, and the pseudo first order rate coefficients displayed a Langmuir-Hinshelwood dependence on gas phase ozone concentration for both materials. By assuming Langmuir-Hinshelwood behaviour, the following parameters were found: for the reaction of MaH aerosols, KO3=(1.9+0.4)x10-16cm-3 and kmaxI=0.015+0.002; for the reaction of FuH aerosols, KO3= (3.4+0.4)x10-16cm-3 and kmaxI=0.0128+0.0005, where KO3 is a parameter that describes the partitioning of ozone to the particle surface and kmaxI is the maximum pseudo-first order coefficient at high ozone concentrations. Apparent reactive uptake coefficients were extracted from the pseudo first order rate coefficient and a slight trend of decreasing uptake coefficients with increasing ozone concentrations was observed. In general, we find that the values obtained for maleic and fumaric acid fall within the range of literature values reported by other published studies for other organic or organic-coated particles, although there are some unusual dependencies on RH%.

Najera, J.; Percival, C.; Horn, A. B.

2009-04-01

435

Differentiation of Candida albicans and Candida dubliniensis by Fluorescent In Situ Hybridization with Peptide Nucleic Acid Probes  

PubMed Central

The recent discovery of Candida dubliniensis as a separate species that traditionally has been identified as Candida albicans has led to the development of a variety of biochemical and molecular methods for the differentiation of these two pathogenic yeasts. rRNA sequences are well-established phylogenetic markers, and probes targeting species-specific rRNA sequences have been used in diagnostic assays for the detection and identification of microorganisms. Peptide nucleic acid (PNA) is a DNA mimic with improved hybridization characteristics, and the neutral backbone of PNA probes offers significant advantages in whole-cell in situ hybridization assays. In this study, we developed PNA probes targeting the rRNAs of C. albicans and C. dubliniensis and applied them to a fluorescence in situ hybridization method (PNA FISH) for differentiation between C. albicans and C. dubliniensis. Liquid cultures were smeared onto microscope slides, heat fixed, and then hybridized for 30 min. Unhybridized PNA probe was removed by washing, and smears were examined by fluorescence microscopy. Evaluation of the PNA FISH method using smears of 79 C. dubliniensis and 70 C. albicans strains showed 100% sensitivity and 100% specificity for both PNA probes. We concluded that PNA FISH is a powerful tool for the differentiation of C. albicans and C. dubliniensis.

Oliveira, Kenneth; Haase, Gerhard; Kurtzman, Cletus; Hyldig-Nielsen, Jens Jo/rgen; Stender, Henrik

2001-01-01

436

Nucleic Acid Sandwich Hybridization Assay with Quantum Dot-Induced Fluorescence Resonance Energy Transfer for Pathogen Detection  

PubMed Central

This paper reports a nucleic acid sandwich hybridization assay with a quantum dot (QD)-induced fluorescence resonance energy transfer (FRET) reporter system. Two label-free hemagglutinin H5 sequences (60-mer DNA and 630-nt cDNA fragment) of avian influenza viruses were used as the targets in this work. Two oligonucleotides (16 mers and 18 mers) that specifically recognize two separate but neighboring regions of the H5 sequences were served as the capturing and reporter probes, respectively. The capturing probe was conjugated to QD655 (donor) in a molar ratio of 10:1 (probe-to-QD), and the reporter probe was labeled with Alexa Fluor 660 dye (acceptor) during synthesis. The sandwich hybridization assay was done in a 20 ?L transparent, adhesive frame-confined microchamber on a disposable, temperature-adjustable indium tin oxide (ITO) glass slide. The FRET signal in response to the sandwich hybridization was monitored by a homemade optical sensor comprising a single 400 nm UV light-emitting diode (LED), optical fibers, and a miniature 16-bit spectrophotometer. The target with a concentration ranging from 0.5 nM to 1 ?M was successfully correlated with both QD emission decrease at 653 nm and dye emission increase at 690 nm. To sum up, this work is beneficial for developing a portable QD-based nucleic acid sensor for on-site pathogen detection.

Chou, Cheng-Chung; Huang, Yi-Han

2012-01-01

437

40 CFR 721.1645 - Benzenesulfonic acid, 4-methyl-, reaction products with oxirane mono[(C10-16-alkyloxy)methyl...  

Code of Federal Regulations, 2013 CFR

...SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721...acid, 4-methyl-, reaction products with oxirane...reporting. (1) The chemical substance benzenesulfonic acid, 4-methyl-, reaction products with...

2013-07-01

438

Study of nucleic acid-gold nanorod interactions and detecting nucleic acid hybridization using gold nanorod solutions in the presence of sodium citrate.  

PubMed

In this study, the authors report that sodium citrate can aggregate hexadecyl-trimethyl-ammonium ion(+)-coated gold nanorods (AuNRs), and nucleic acids of different charge and structure properties, i.e., single-stranded DNA (ssDNA), double-stranded DNA (dsDNA), single-stranded peptide nucleic acid (PNA), and PNA-DNA complex, can bind to the AuNRs and therefore retard the sodium citrate-induced aggregation to different extents. The discovery that hybridized dsDNA (and the PNA-DNA complex) has a more pronounced protection effect than ssDNA (and PNA) allows the authors to develop a homogeneous phase AuNRs-based UV-visible (UV-vis) spectral assay for detecting specific sequences of oligonucleotides (20 mer) with a single-base-mismatch selectivity and a limit of detection of 5 nM. This assay involves no tedious bioconjugation and on-particle hybridization. The simple "set and test" format allows for a highly efficient hybridization in a homogeneous phase and a rapid display of the results in less than a minute. By measuring the degree of reduction in AuNR aggregation in the presence of different nucleic acid samples, one can assess how different nucleic acids interact with the AuNRs to complement the knowledge of spherical gold nanoparticles. Besides UV-vis characterization, transmission electron microscopy and zeta potential measurements were conduced to provide visual evidence of the particle aggregation and to support the discussion of the assay principle. PMID:21171720

Kanjanawarut, Roejarek; Su, Xiaodi

2010-09-01

439

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

SciTech Connect

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

Lorincz, A.T.

1989-07-18

440

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

SciTech Connect

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

Lorincz, A.T.

1989-07-18