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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

Rapid hybridization of nucleic acids using isotachophoresis  

E-print Network

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

Santiago, Juan G.

3

Optimizing the specificity of nucleic acid hybridization  

Microsoft Academic Search

The specific hybridization of complementary sequences is an essential property of nucleic acids, enabling diverse biological and biotechnological reactions and functions. However, the specificity of nucleic acid hybridization is compromised for long strands, except near the melting temperature. Here, we analytically derived the thermodynamic properties of a hybridization probe that would enable near-optimal single-base discrimination and perform robustly across diverse

Sherry Xi Chen; David Yu Zhang; Peng Yin

2012-01-01

4

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

PubMed

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

Jayakanthan, K; Vankar, Yashwant D

2005-11-24

5

Sensitive electrochemical detection of telomerase activity using spherical nucleic acids gold nanoparticles triggered mimic-hybridization chain reaction enzyme-free dual signal amplification.  

PubMed

We report an electrochemical sensor for telomerase activity detection based on spherical nucleic acids gold nanoparticles (SNAs AuNPs) triggered mimic-hybridization chain reaction (mimic-HCR) enzyme-free dual signal amplification. In the detection strategy, SNAs AuNPs and two hairpin probes were employed. SNAs AuNPs as the primary amplification element, not only hybridized with the telomeric repeats on the electrode to amplify signal but also initiated the subsequent secondary amplification, mimic-hybridization chain reaction of two hairpin probes. If the cells' extracts were positive for telomerase activity, SNAs AuNPs could be captured on the electrode. The carried initiators could trigger an alternative hybridization reaction of two hairpin probes that yielded nicked double helices. The signal was further amplified enzyme-free by numerous hexaammineruthenium(III) chloride ([Ru(NH3)6](3+), RuHex) inserting into double-helix DNA long chain by electrostatic interaction, each of which could generate an electrochemical signal at appropriate potential. With this method, a detection limit of down to 2 HeLa cells and a dynamic range of 10-10?000 cells were achieved. Telomerase activities of different cell lines were also successfully evaluated. PMID:25669135

Wang, Wen-Jing; Li, Jing-Jing; Rui, Kai; Gai, Pan-Pan; Zhang, Jian-Rong; Zhu, Jun-Jie

2015-03-01

6

Triggered amplification by hybridization chain reaction  

E-print Network

Triggered amplification by hybridization chain reaction Robert M. Dirks and Niles A. Pierce chain reaction (HCR), in which stable DNA monomers assemble only upon exposure to a target DNA fragment termed hybridization chain reaction (HCR). This class of mech- anisms suggests the possibility

Pierce, Niles A.

7

Label-free and enzyme-free sensitive fluorescent detection of human immunodeficiency virus deoxyribonucleic acid based on hybridization chain reaction.  

PubMed

A label-free and enzyme-free sensitive fluorescent detection of human immunodeficiency virus (HIV) deoxyribonucleic acid (DNA) based on isothermal hybridization chain reaction (HCR) was developed. A G-quadruplex sequence which was incorporated into one of the two hairpin probes was inactive in the absence of target DNA. However, at the presence of target DNA numerous G-quadruplexes along DNA nanowires were self-assembled through HCR. Using N-methyl mesoporphyrin IX (NMM) as the fluorophore, a "turn-on" fluorescent response would be achieved and detected as low as 0.5 nmol L(-1) of HIV DNA. This proposed method was applied to detect HIV DNA in biologic samples with satisfactory results. PMID:25441904

Guo, Qingquan; Chen, Ying; Song, Zhiping; Guo, Liangqia; Fu, Fengfu; Chen, Guonan

2014-12-10

8

Hybrid [n]Arenes through Thermodynamically Driven Macrocyclization Reactions.  

PubMed

Hybrid [n]arenes, the class of medium-sized macrocyclic compounds consisting of different alkoxybenzene units, were obtained by a simple, one-pot, direct condensation of two different alkoxybenzenes with formaldehyde catalyzed by a Brřnsted acid (trifluoroacetic acid). We have shown that, under Brřnsted acid catalysis, this reaction is reversible and therefore governed by the relative stability of the products. The main macrocyclic products are hybrid [n]arenes consisting of four alkoxybenzene units of [2 + 2] or [3 + 1] stoichiometry. However, an unusual [3 + 2] hybrid macrocycle was also obtained as a main product of the condensation between 1,4-dimethoxybenzene, 1,3,5-trimethoxybenzene, and formaldehyde. The stability of the hybrid products and the reversibility of the reaction were further confirmed by a scrambling experiment, involving pillar[5]arene and per-O-methylated resorcin[4]arene. The scrambling experiment has given hybrid macrocycles in yields comparable with those obtained in condensation reactions. NMR spectra and X-ray structures of hybrid [n]arenes indicate that 1,2- and 1,3-dialkoxybenzene units are flexible parts of macrocyclic rings. However, the 1,4-dialkoxybenzene units present considerable steric hindrance, resulting in the formation of isomers and inherently chiral macrocycles due to inhibited rotation. The recognition properties toward various organic cations were also determined. Highly selective recognition of the N-methylpyridinium cation was observed for the [3 + 2] hybrid macrocycle. PMID:25723902

Boinski, Tomasz; Cieszkowski, Artur; Rosa, Bart?omiej; Szumna, Agnieszka

2015-04-01

9

One-Step Detection of c-kit Point Mutations Using Peptide Nucleic Acid-Mediated Polymerase Chain Reaction Clamping and Hybridization Probes  

PubMed Central

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

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

2003-01-01

10

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

PubMed

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

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

2003-03-01

11

Optimizing the specificity of nucleic acid hybridization  

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

12

Optimizing the specificity of nucleic acid hybridization  

E-print Network

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

Zhang, David Yu

13

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

14

Acceleration of surface-based hybridization reactions using isotachophoretic focusing.  

PubMed

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

Karsenty, Merav; Rubin, Shimon; Bercovici, Moran

2014-03-18

15

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

16

Multitarget molecular hybrids of cinnamic acids.  

PubMed

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

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

2014-01-01

17

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?

18

Reaction rates of hydrochloric acid with chalks  

Microsoft Academic Search

The reaction rate of hydrochloric acid with carbonate rock at acid-fracturing conditions depends on controllable variables such as injection rate and acid concentration, and variables inherent to the carbonate rock (permeability, mineral composition, etc.). In a previous study, the effects of some controllable variables on reaction rates were investigated and the results correlated with theory. This paper presents the results

Naim A. Mumallah

1998-01-01

19

Characteristics of acid reaction in limestone formations  

Microsoft Academic Search

A kinetic model for the reaction of hydrochloric acid with limestone has been determined. Reaction order and rate constant for this model were calculated from experiments where acid reacted with a single calcium carbonate plate. Experiments were performed so that acid flow past the plate and mass transfer rate to the rock surface could be calculated theoretically. The resulting model,

D. E. Nierode; B. B. Williams

1970-01-01

20

Reactions of Sweet Corn Hybrids to Prevalent Diseases and Herbicides  

Technology Transfer Automated Retrieval System (TEKTRAN)

This 27-year summary is of University of Illinois sweet corn nurseries from 1984 to 2010, and includes the reactions of 800 hybrids to eight diseases and three herbicides. Commercially-available and pre-commercial hybrids included 547 shrunken-2 hybrids (317 yellow, 152 bi-color, and 78 white), 117 ...

21

Design and Synthesis of Novel Isoxazole Tethered Quinone-Amino Acid Hybrids  

PubMed Central

A new series of isoxazole tethered quinone-amino acid hybrids has been designed and synthesized involving 1,3-dipolar cycloaddition reaction followed by an oxidation reaction using cerium ammonium nitrate (CAN). Using this method, for the first time various isoxazole tethered quinone-phenyl alanine and quinone-alanine hybrids were synthesized from simple commercially available 4-bromobenzyl bromide, propargyl bromide, and 2,5-dimethoxybenzaldehyde in good yield. PMID:25709839

Ravi Kumar, P.; Sambaiah, M.; Kandula, Venu; Payili, Nagaraju; Jaya Shree, A.; Yennam, Satyanarayana

2014-01-01

22

Design and synthesis of novel isoxazole tethered quinone-amino Acid hybrids.  

PubMed

A new series of isoxazole tethered quinone-amino acid hybrids has been designed and synthesized involving 1,3-dipolar cycloaddition reaction followed by an oxidation reaction using cerium ammonium nitrate (CAN). Using this method, for the first time various isoxazole tethered quinone-phenyl alanine and quinone-alanine hybrids were synthesized from simple commercially available 4-bromobenzyl bromide, propargyl bromide, and 2,5-dimethoxybenzaldehyde in good yield. PMID:25709839

Ravi Kumar, P; Behera, Manoranjan; Sambaiah, M; Kandula, Venu; Payili, Nagaraju; Jaya Shree, A; Yennam, Satyanarayana

2014-01-01

23

Nonenzymatic catalytic signal amplification for nucleic acid hybridization assays  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

24

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...

25

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

26

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

27

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

Microsoft Academic Search

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

B. Sulikowski; R. Rachwalik

2003-01-01

28

A Robust Technique for Assembly of Nucleic Acid Hybridization Chips Based on Electrochemically  

E-print Network

A Robust Technique for Assembly of Nucleic Acid Hybridization Chips Based on Electrochemically and Biochemical Engineering, University of Maryland, Baltimore County, Maryland 21250 A nucleic acid hybridization evaluated. Hybridization of target nucleic acid was quantifiable, reproducible, and robust; the surface

Rubloff, Gary W.

29

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

30

Heterogeneous Reactions of Epoxides in Acidic Media  

E-print Network

reaction. Bulk studies using Nuclear Magnetic Resonance (NMR) spectroscopy conducted at low acid concentrations showed the presence of 1,2- and 1,4-diols as the major products for isoprene oxide, similar to the results from the ATR-FTIR experiments...

Lal, Vinita

2012-02-14

31

Hybrid Simulations of Reaction-Diffusion Systems in Porous Media  

SciTech Connect

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

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

2008-10-13

32

A DNA origami nanorobot controlled by nucleic acid hybridization.  

PubMed

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

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

2014-07-01

33

Hybrid discrete/continuum algorithms for stochastic reaction networks  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

34

Hybrid Crystals of Calcium Carbonate and Amino Acids  

Microsoft Academic Search

We have investigated the effects of amino acids on the crystallization of calcium carbonate (CaCO3), and the reactivity between amino acids and CaCO3. Noncharged-polar and acidic amino acids are highly incorporated into CaCO3 and stabilize cauliflower-like grains composed of vaterite which is thermodynamically unstable in the CaCO3 polymorphs. Amino acids in the hybrid CaCO3 form radicals different from those in

Ayako Kai; Toshikatsu Miki

2000-01-01

35

The Chlorate-Iodine-Nitrous Acid Clock Reaction  

PubMed Central

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

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

2014-01-01

36

Photosynthetic reaction centers/ITO hybrid nanostructure.  

PubMed

Photosynthetic reaction center proteins purified from Rhodobacter sphaeroides purple bacterium were deposited on the surface of indium tin oxide (ITO), a transparent conductive oxide, and the photochemical/-physical properties of the composite were investigated. The kinetics of the light induced absorption change indicated that the RC was active in the composite and there was an interaction between the protein cofactors and the ITO. The electrochromic response of the bacteriopheophytine absorption at 771 nm showed an increased electric field perturbation around this chromophore on the surface of ITO compared to the one measured in solution. This absorption change is associated with the charge-compensating relaxation events inside the protein. Similar life time, but smaller magnitude of this absorption change was measured on the surface of borosilicate glass. The light induced change in the conductivity of the composite as a function of the concentration showed the typical sigmoid saturation characteristics unlike if the photochemically inactive chlorophyll was layered on the ITO. In this later case the light induced change in the conductivity was oppositely proportional to the chlorophyll concentration due to the thermal dissipation of the excitation energy. The sensitivity of the measurement is very high; few picomole RC can change the light induced resistance of the composite. PMID:25427486

Szabó, Tibor; Bencsik, Gábor; Magyar, Melinda; Visy, Csaba; Gingl, Zoltán; Nagy, Krisztina; Váró, György; Hajdu, Kata; Kozák, Gábor; Nagy, László

2013-03-01

37

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

Code of Federal Regulations, 2010 CFR

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

2010-07-01

38

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

Code of Federal Regulations, 2011 CFR

...substituted triazine amino substituted benezenesulfonic acid reaction product...substituted triazine amino substituted benezenesulfonic acid reaction product...substituted triazine amino substituted benezenesulfonic acid reaction...

2011-07-01

39

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

Code of Federal Regulations, 2013 CFR

...substituted triazine amino substituted benezenesulfonic acid reaction product...substituted triazine amino substituted benezenesulfonic acid reaction product...substituted triazine amino substituted benezenesulfonic acid reaction...

2013-07-01

40

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

Code of Federal Regulations, 2014 CFR

...substituted triazine amino substituted benezenesulfonic acid reaction product...substituted triazine amino substituted benezenesulfonic acid reaction product...substituted triazine amino substituted benezenesulfonic acid reaction...

2014-07-01

41

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

Code of Federal Regulations, 2012 CFR

...substituted triazine amino substituted benezenesulfonic acid reaction product...substituted triazine amino substituted benezenesulfonic acid reaction product...substituted triazine amino substituted benezenesulfonic acid reaction...

2012-07-01

42

Instabilities in propagating reaction-diffusion fronts of the iodate-arsenous acid reaction  

E-print Network

of the iodate-arsenous acid reaction are predicted by an empirical rate-law model. The planar front loses of premixed flames, where the heat of reaction plays the role of the activator and a stoichio- metricallyInstabilities in propagating reaction-diffusion fronts of the iodate-arsenous acid reaction Dezso

Showalter, Kenneth

43

What controls the hybridization thermodynamics of spherical nucleic acids?  

PubMed

The hybridization of free oligonucleotides to densely packed, oriented arrays of DNA modifying the surfaces of spherical nucleic acid (SNA)-gold nanoparticle conjugates occurs with negative cooperativity; i.e., each binding event destabilizes subsequent binding events. DNA hybridization is thus an ever-changing function of the number of strands already hybridized to the particle. Thermodynamic quantification of this behavior reveals a 3 orders of magnitude decrease in the binding constant for the capture of a free oligonucleotide by an SNA conjugate as the fraction of pre-hybridized strands increases from 0 to ?30%. Increasing the number of pre-hybridized strands imparts an increasing enthalpic penalty to hybridization that makes binding more difficult, while simultaneously decreasing the entropic penalty to hybridization, which makes binding more favorable. Hybridization of free DNA to an SNA is thus governed by both an electrostatic barrier as the SNA accumulates charge with additional binding events and an effect consistent with allostery, where hybridization at certain sites on an SNA modify the binding affinity at a distal site through conformational changes to the remaining single strands. Leveraging these insights allows for the design of conjugates that hybridize free strands with significantly higher efficiencies, some of which approach 100%. PMID:25738968

Randeria, Pratik S; Jones, Matthew R; Kohlstedt, Kevin L; Banga, Resham J; Olvera de la Cruz, Monica; Schatz, George C; Mirkin, Chad A

2015-03-18

44

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

Code of Federal Regulations, 2014 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...

2014-07-01

45

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

Code of Federal Regulations, 2012 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...

2012-07-01

46

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

47

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

Code of Federal Regulations, 2011 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...

2011-07-01

48

Novel hybrid DHPM-fatty acids: Synthesis and activity against glioma cell growth in vitro.  

PubMed

We described the first synthesis of fatty acid 3,4-dihydropyrimidinones (DHPM-fatty acids) using the Biginelli multicomponent reaction. Antiproliferative activity on two glioma cell lines (C6 rat and U-138-MG human) was also reported. The novel DHPM-fatty acids reduced glioma cell viability relative to temozolomide. Hybrid oxo-monastrol-palmitic acid was the most potent, reducing U-138-MG human cell viability by ca. 50% at 10 ?M. In addition, the DHPM-fatty acids showed a large safety range to neural cells, represented by the organotypic hippocampal culture. These results suggest that the increased lipophilicity of DHPM-fatty acids offer a promising approach to overcoming resistance to chemotherapy and may play an important role in the development of new antitumor drugs. PMID:25863023

Treptow, Tamara G M; Figueiró, Fabrício; Jandrey, Elisa H F; Battastini, Ana M O; Salbego, Christianne G; Hoppe, Juliana B; Taborda, Priscila S; Rosa, Sabrina B; Piovesan, Luciana A; Montes D'Oca, Caroline Da R; Russowsky, Dennis; Montes D'Oca, Marcelo G

2015-05-01

49

Adaptive hybrid simulations for multiscale stochastic reaction networks  

NASA Astrophysics Data System (ADS)

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

Hepp, Benjamin; Gupta, Ankit; Khammash, Mustafa

2015-01-01

50

Characterization of liquid-solid reactions: hydrochloric acid-calcium carbonate reaction  

Microsoft Academic Search

In acidizing techniques, an acid, such as hydrochloric acid, is forced to flow within the pore structure of the rock matrix, or along a hydraulically induced fracture, reacting with the rock and altering reservoir characteristics. A method has been developed of computing the rate of acid spending and the effect of acid reaction on formation flow capacity for the case

B. B. Williams; J. L. Gidley; J. A. Guin; R. S. Schechter

1970-01-01

51

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

52

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

EPA Science Inventory

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

53

Mfold web server for nucleic acid folding and hybridization prediction  

Microsoft Academic Search

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

Michael Zuker

2003-01-01

54

Nucleic acid hybridization with RNA immobilized on filter paper.  

NASA Technical Reports Server (NTRS)

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

55

Topological constraints in nucleic acid hybridization kinetics  

E-print Network

, Harry M. T. Choi1 , Andrew J. Spakowitz, Zhen-Gang Wang and Niles A. Pierce1,2, * Department of Chemical illustrates the potential for topological effects to influence the kinetics and function of nucleic acid of double-stranded knots and catenanes (8). Topological effects also influence the regulatory mechanisms

Straight, Aaron

56

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

PubMed Central

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

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

1986-01-01

57

Iminodicarboxylic acids in the Murchison meteorite: Evidence of Strecker reactions  

NASA Astrophysics Data System (ADS)

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

Lerner, Narcinda R.; Cooper, George W.

2005-06-01

58

Reaction of long chain triol acids with hydrogen bromide  

Microsoft Academic Search

The reaction of hydrogen bromide (HBr) with long chain triol acids has been investigated in some detail. The 9, 10, 12-trihydroxy\\u000a stearic acid (I) on treatment with HBr yielded three products, namely 9(10)-bromo-10(9)-hydroxy-12-bromo (III), 9(10)-bromo-10(9)acetoxy-12-bromo\\u000a (IV) and 9,10-dibromo-12-hydroxy (V) stearic acids. When 9,12,13-trihydroxy stearic acid (II) was subjected to the same reaction\\u000a under similar conditions, 12,13-dibromo-9-hydroxy (VI), 12(13)-bromo-13(12) acetoxy-9-bromo (VII)

D. Charles; J. Mustafa; S. M. Osman

1990-01-01

59

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

E-print Network

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

Elrod, Matthew J.

60

Potentiometric Analysis of a Reaction System of Organic Acids  

Microsoft Academic Search

A new potentiometric titration method for the quantitative analysis of a reaction system of diprotonic organic acids is presented. The method uses the individual potentiometric titration data for cal- culating the dissociation constants. With this information a set of \\

Agustín Jaime Castro-Montoya; Manuel Herrera-Solano; Pedro Alberto Quintana-Hernández; Medardo Serna-González; Facultad de Ingeniería Química

2003-01-01

61

Imino Acids in the Murchison Meteorite: Evidence of Strecker Reactions  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

62

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

PubMed

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

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

2009-10-15

63

The acid-base reactions of the ?-hydroxypiperidinecarboxylic acids  

Microsoft Academic Search

1.Ionization constants have been determined for the ß-hydroxypyridinecarboxylic acids and their ethyl esters.2.It has been shown that these acids can exist in various forms in aqueous solution, depending on the pH, and conditions for the transition from one of these forms to another have been marked out.

B. A. Korolev; L. G. Stolyarova; L. D. Smirnov; K. M. Dyumaev

1979-01-01

64

Porous polylactic Acid-silica hybrids: preparation, characterization, and study of mesenchymal stem cell osteogenic differentiation.  

PubMed

A novel approach to reinforce polymer porous membranes is presented. In the prepared hybrid materials, the inorganic phase of silica is synthesized in-situ and inside the pores of aminolyzed polylactic acid (PLA) membranes by sol-gel reactions using tetraethylorthosilicate (TEOS) and glycidoxypropyltrimethoxysilane (GPTMS) as precursors. The hybrid materials present a porous structure with a silica layer covering the walls of the pores while GPTMS serves also as coupling agent between the organic and inorganic phase. The adjustment of silica precursors ratio allows the modulation of the thermomechanical properties. Culture of mesenchymal stem cells on these supports in osteogenic medium shows the expression of characteristic osteoblastic markers and the mineralization of the extracellular matrix. PMID:25303745

Pandis, Christos; Trujillo, Sara; Matos, Joana; Madeira, Sara; Ródenas-Rochina, Joaquín; Kripotou, Sotiria; Kyritsis, Apostolos; Mano, Joăo F; Gómez Ribelles, José Luis

2015-02-01

65

UNAFold: software for nucleic acid folding and hybridization.  

PubMed

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

Markham, Nicholas R; Zuker, Michael

2008-01-01

66

Polymer hybrids of functionalized silsesquioxanes and organic polymers utilizing the sol–gel reaction of tetramethoxysilane  

Microsoft Academic Search

The ternary polymer hybrids were prepared by organic polymers such as poly(2-methyl-2-oxazoline) (POZO) or poly(N-vinylpyrrolidone) (PVP) and aminopropylsilsesquioxane (Cube-aminopropyl) utilizing the sol–gel reaction of tetramethoxysilane (TMOS). The prepared polymer hybrids were characterized by IR, thermogravimetric analysis (TGA), X-ray diffraction (XRD), 1H NMR, scanning electron microscopy (SEM), etc. In this hybrid system, hydrogen-bonding interactions played a critical role in the formation

Kyung-Min Kim; Kaoru Adachi; Yoshiki Chujo

2002-01-01

67

Enantioselective, desymmetrizing, bromolactonization reactions of symmetric olefinic dicarboxylic acids.  

PubMed

The results of studies leading to the development of enantioselective desymmetrizing, bromolactonization reactions of symmetric olefinic dicarboxylic acids, which are promoted by a C3 -symmetric trisimidazoline catalyst, are described. These processes generated carboxylic-acid-containing bromolactones in moderately high enantiomeric excesses. The results of optimization studies showed that reactions in a mixed solvent system of toluene and acetone proceeded with the highest levels of enantioselectivity. NMR studies probing the interactions between the catalyst and dicarboxylic acid substrates, as well as the effect of acetone on the stereochemistry of the process, are also described. PMID:25256170

Murai, Kenichi; Nakajima, Junki; Nakamura, Akira; Hyogo, Norimichi; Fujioka, Hiromichi

2014-12-01

68

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

69

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

Microsoft Academic Search

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

Xiaoming Chen

2000-01-01

70

Reaction kinetics and network characterization of UV-curing polyester acrylate inorganic\\/organic hybrids  

Microsoft Academic Search

Polyester acrylate inorganic\\/organic hybrids were prepared using a sol–gel precursor, coupling agent, and reactive diluent. The hybrids were cured via a UV-free radical initiator. Design of experiments (DOE) was utilized to investigate reaction kinetics and complex variable interactions. The effects of the silicate groups on the free radical photo-curing reaction kinetics were investigated utilizing a time-resolved Fourier transform infrared (FT–IR)

Ahmet Nebioglu; Mark D. Soucek

2007-01-01

71

Influence of secondary structure on kinetics and reaction mechanism of DNA hybridization  

Microsoft Academic Search

Hybridization of nucleic acids with secondary structure is involved in many biological processes and technological applications. To gain more insight into its mechanism, we have investigated the kinetics of DNA hybridization\\/denaturation via fluorescence resonance energy transfer (FRET) on perfectly matched and single-base-mismatched DNA strands. DNA hybridization shows non- Arrhenius behavior. At high temperature, the appar- ent activation energies of DNA

Chunlai Chen; Wenjuan Wang; Zhang Wang; Fang Wei; Xin Sheng Zhao

2007-01-01

72

Hybrid QM/MM Car-Parrinello Simulations of Catalytic and Enzymatic Reactions  

E-print Network

1 Hybrid QM/MM Car-Parrinello Simulations of Catalytic and Enzymatic Reactions MariaCarola Colombo for the in situ investigation of chemical reactions that occur in a complex and heterogeneous environment. Here technique. Keywords: Car-Parrinello first-principles molecular dynamics, QM/MM simulations, enantioselective

Guidoni, Leonardo

73

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

74

Lewis acid template-catalyzed asymmetric diels-alder reaction.  

PubMed

An asymmetric Diels-Alder reaction of 2,4-dienols and methyl acrylate utilizing a chiral Zn(II)/Mg(II) bimetallic template with low catalyst loading was successfully achieved. The bimetallic Lewis acid template derived from (R)-5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphthol catalyzed the Diels-Alder reaction in the presence of molecular sieves 4 Ĺ to afford various functionalized bicyclic ?-lactones with high enantiomeric purities. PMID:25621816

Ishihara, Jun; Nakadachi, Shino; Watanabe, Yuki; Hatakeyama, Susumi

2015-02-20

75

Bimodal proton transfer in acid-base reactions in water  

Microsoft Academic Search

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

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

2004-01-01

76

Chlorine dioxide reaction with selected amino acids in water.  

PubMed

Chlorine dioxide is a hypochlorite alternative disinfectant agent. In this context, we have determined the products formed in the reaction of ClO(2) with selected amino acids as model compounds that can be present in natural waters. The reaction of tryptophane, histidine and tyrosine (10 ppm each) with ClO(2) were studied at molar ratios ranging from 0.25 to 4 in the presence or absence of oxygen. It was found that in the absence of oxygen adding substoichiometric amounts of ClO(2) creates products that are structurally similar to the starting amino acids. Through a series of cascade reactions the initial product distribution gradually evolves toward simple, small carbon chain products that are far from the starting amino acid. The reaction product distribution revealed that chlorine dioxide can attack the electron-rich aromatic moieties as well as the nitrogen atom lone electron pair. Our study is relevant to gain knowledge on the reaction mechanism of ClO(2) with ubiquitous amino acids present in natural waters. PMID:18930594

Navalon, Sergio; Alvaro, Mercedes; Garcia, Hermenegildo

2009-05-30

77

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

PubMed

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

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

2014-06-01

78

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

Code of Federal Regulations, 2010 CFR

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

2010-07-01

79

Anodic acyloxylation based on the acid–base reactions between acetic acid or trifluoroacetic acid and solid-supported bases  

Microsoft Academic Search

We have developed a novel electrolytic system for anodic acyloxylation based on the acid–base reactions between acetic acid or trifluoroacetic acid and solid-supported bases. On the basis of the electrolytic system, anodic acyloxylation of organic compounds, which even have considerably high oxidation potentials, was successfully carried out to provide the corresponding acyloxylated products in moderate to excellent yields. Furthermore, it

Toshiki Tajima; Yuichiro Kishi; Atsushi Nakajima

2009-01-01

80

Catalytical Conversion of Carbohydrates into Lactic Acid via Hydrothermal Reaction  

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

81

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

82

Completely stereocontrolled aldol reaction of chiral ?-amino acids.  

PubMed

A general protocol to independently access stereoisomerically pure ?'-hydroxy-?-amino acid derivatives that is based on dibutylboron triflate-mediated aldol reaction of suitably protected ?-amino acids bearing chiral oxazolidinone auxiliary is reported. The method smoothly afforded syn-aldol (?,?'-syn) products in pure form and excellent isolated yield. Both ?,?-syn and ?,?-anti isomers are readily accessible solely through the choice of the oxazolidinone chirality. This method allows for the preparation of stereoisomeric ?'-hydroxy-?-amino acid derivatives that were previously unreported. PMID:25616036

Gazvoda, Martin; Höferl-Prantz, Kathrin; Barth, Roland; Felzmann, Wolfgang; Pevec, Andrej; Košmrlj, Janez

2015-02-01

83

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

Code of Federal Regulations, 2014 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...

2014-07-01

84

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

85

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

Code of Federal Regulations, 2014 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...

2014-07-01

86

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

87

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

88

EXTENT OF OZONE'S REACTION WITH ISOLATED AQUATIC FULVIC ACID  

EPA Science Inventory

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

89

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

90

Template directed reactions of 2-aminoadenylic acid derivatives  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

91

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

NASA Astrophysics Data System (ADS)

In the present study, based on the mimic oxidase catalytic character of nucleic-acid-stabilized silver nanoclusters (DNA/AgNCs) and hybridization chain reactions for signal amplification, the fabrication of a label-free sensitive ``turn-on'' electrochemical aptasensor for the amplified determination of lysozyme was demonstrated. First, the designed DNA duplex was modified on the electrode. With the specific binding of the target, lysozyme and its aptamer, the lysozyme-binding DNA sequence was liberated, exposing the induced DNA sequence, which in turn triggered the formation of the supersandwich DNA structure. Because the cytosine-rich sequence was designed ingeniously on the DNA sequence, DNA/AgNCs were formed on the supersandwich DNA structure. The peroxidase-like character of DNA/AgNCs produced detectable electrochemical signals for the lysozyme aptasensor, which showed a satisfying sensitive detection of lysozyme with a low detection limit of 42 pM and a wide linear range of 10-10 M to 10-5 M.In the present study, based on the mimic oxidase catalytic character of nucleic-acid-stabilized silver nanoclusters (DNA/AgNCs) and hybridization chain reactions for signal amplification, the fabrication of a label-free sensitive ``turn-on'' electrochemical aptasensor for the amplified determination of lysozyme was demonstrated. First, the designed DNA duplex was modified on the electrode. With the specific binding of the target, lysozyme and its aptamer, the lysozyme-binding DNA sequence was liberated, exposing the induced DNA sequence, which in turn triggered the formation of the supersandwich DNA structure. Because the cytosine-rich sequence was designed ingeniously on the DNA sequence, DNA/AgNCs were formed on the supersandwich DNA structure. The peroxidase-like character of DNA/AgNCs produced detectable electrochemical signals for the lysozyme aptasensor, which showed a satisfying sensitive detection of lysozyme with a low detection limit of 42 pM and a wide linear range of 10-10 M to 10-5 M. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06664b

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

2015-02-01

92

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

Microsoft Academic Search

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

Patrick Maurer; Vibin Thomas; Ugo Rivard; Radu Iftimie

2010-01-01

93

Mfold web server for nucleic acid folding and hybridization prediction  

E-print Network

The abbreviated name,‘mfold web server’,describes a number of closely related software applications available on the World Wide Web (WWW) for the prediction of the secondary structure of single stranded nucleic acids. The objective of this web server is to provide easy access to RNA and DNA folding and hybridization software to the scientific community at large. By making use of universally available web GUIs (Graphical User Interfaces),the server circumvents the problem of portability of this software. Detailed output,in the form of structure plots with or without reliability information,single strand frequency plots and ‘energy dot plots’, are available for the folding of single sequences. A variety of ‘bulk ’ servers give less information,but in a shorter time and for up to hundreds of sequences at once. The portal for the mfold web server is

Michael Zuker

2003-01-01

94

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

95

Mechanistic Insights into a BINOL-Derived Phosphoric Acid-Catalyzed Asymmetric Pictet-Spengler Reaction.  

PubMed

The reaction of tryptamine and (2-oxocyclohexyl)acetic acid can be catalyzed by 3,3'-bis(triphenylsilyl)-1,1'-bi-2-naphthol phosphoric acid to give an asymmetric ?-carboline. This reaction was first studied by Holloway et al. ( Org. Lett. 2010 , 12 , 4720 - 4723 ), but their mechanistic work did not explain the high stereoselectivity achieved. This study uses density functional theory and hybrid quantum mechanics/molecular mechanics calculations to investigate this reaction and provide a model to explain its outcome. The step leading to diastereo- and enantioselectivity is an asymmetric Pictet-Spengler reaction involving an N-acyliminium ion bound to the catalyst in a bidentate fashion. This interaction occurs via hydrogen bonds between the two terminal oxygen atoms of the catalyst phosphate group and the hydrogen atoms at N and C2 of the substrate indole group. These bonds hold the transition structure rigidly and thus allow the catalyst triphenylsilyl groups to influence the enantioselectivity. PMID:25654215

Overvoorde, Lois M; Grayson, Matthew N; Luo, Yi; Goodman, Jonathan M

2015-03-01

96

Heterogeneous atmospheric reactions - Sulfuric acid aerosols as tropospheric sinks  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

97

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

DOEpatents

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

Nasarabadi, Shanavaz (Livermore, CA)

2011-01-11

98

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

99

The reaction of cesium hydroxide with 4-phenylvaleric acid  

E-print Network

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

1967-01-01

100

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

PubMed

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

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

2014-03-12

101

Parallel proton transfer pathways in aqueous acid-base reactions  

Microsoft Academic Search

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

M. J. Cox; H. J. Bakker

2008-01-01

102

Influence of ions on aqueous acid-base reactions  

Microsoft Academic Search

We study the effects of bromide salts on the rate and mechanism of the aqueous proton\\/deuteron-transfer reaction between the photoacid 8-hydroxy-1,3,6-pyrenetrisulfonic acid (HPTS) and the base acetate. The proton\\/deuteron release is triggered by exciting HPTS with 400 nm femtosecond laser pulses. Probing the electronic and vibrational resonances of the photoacid, the conjugate photobase, the hydrated proton\\/deuteron and the accepting base

M. Jocelyn Cox; Bradley J. Siwick; Huib J. Bakker

2009-01-01

103

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

104

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

105

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

106

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

Code of Federal Regulations, 2010 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...

2010-07-01

107

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

108

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

Code of Federal Regulations, 2010 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...

2010-07-01

109

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

110

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

Code of Federal Regulations, 2012 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...

2012-07-01

111

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

Code of Federal Regulations, 2014 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...

2014-07-01

112

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

Code of Federal Regulations, 2011 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...

2011-07-01

113

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

Code of Federal Regulations, 2012 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...

2012-07-01

114

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

Code of Federal Regulations, 2012 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...

2012-07-01

115

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

Code of Federal Regulations, 2014 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...

2014-07-01

116

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

Code of Federal Regulations, 2012 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...

2012-07-01

117

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

Code of Federal Regulations, 2011 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...

2011-07-01

118

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

Code of Federal Regulations, 2012 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...

2012-07-01

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

Code of Federal Regulations, 2011 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...

2011-07-01

121

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

Code of Federal Regulations, 2014 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...

2014-07-01

122

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

Code of Federal Regulations, 2014 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...

2014-07-01

123

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

Code of Federal Regulations, 2011 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...

2011-07-01

124

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

Code of Federal Regulations, 2014 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...

2014-07-01

125

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

Code of Federal Regulations, 2014 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...

2014-07-01

126

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

127

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

Code of Federal Regulations, 2010 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...

2010-07-01

128

Heterogeneous Reaction of HO2 Radical with Dicarboxylic Acid Particles  

NASA Astrophysics Data System (ADS)

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

Taketani, F.; Kanaya, Y.

2010-12-01

129

[The reactions between acidic phenolsulfonphthaleins and human serum albumin].  

PubMed

The reactions between HSA and acidic phenolsulfonphthaleins, including phenol red, cresol red, chlorophenol red, bromocresol purple and m-cresol purple, have been investigated by fluorescence spectrometry. The experiments showed that all of the selected acidic phenolsulfonphthaleins strongly quenched the fluorescence produced by HSA, and this fluorescence quenching could be interpreted in terms of statistic quenching. From the calculation results of binding constants K for these dyes at various temperatures, it could be found that the increase in the functional groups numbers of dyes molecules resulted in an increase in K, while the increase in reaction temperature led to a decrease in K. The interactions between dyes and HSA were attributed to static-electricity gravitation, which was confirmed by the calculation results of enthalpy and entropy for these reactions. According to the non-radiation energy transfer theory, the distances and energy transfer efficiencies between dyes and protein at various temperatures were obtained. These results further supported the conclusion that these reactions belonged to the single static quenching caused by the energy transfer. PMID:12953536

Liu, Bao-sheng; Zhang, Hong-yi; Wang, Fu-li

2003-06-01

130

Detection of beer spoilage bacteria Megasphaera and Pectinatus by polymerase chain reaction and colorimetric microplate hybridization  

Microsoft Academic Search

Anaerobic bacteria of the genera Megasphaera and Pectinatus cause beer spoilage by producing off flavours and turbidity. Detection of these organisms is complicated by the strict anaerobic conditions and lengthy incubation times required for their cultivation, consequently there is a need for more rapid detection methods. A polymerase chain reaction (PCR) method and a colorimetric microplate hybridization assay were developed

Reetta Satokari; Riikka Juvonen; Kirstie Mallison; Atte von Wright; Auli Haikara

1998-01-01

131

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

E-print Network

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

Reif, John H.

132

Detection of chicken anaemia virus by DNA hybridization and polymerase chain reaction  

Microsoft Academic Search

A clone containing the complete genome of chicken anaemia virus (CAV) was used in hybridizations with DNA from various field isolates of CAV. CAV DNA from all field isolates was detected in a polymerase chain reaction with oligonucleotides derived from the sequence of the cloned CAV DNA as primers. By way of Southern blot analysis with P?labelled DNA probes derived

M. H. M. Noteborn; C. A. J. Verschueren; D. J. Van Roozelaar; S. Veldkamp; A. J. Van Der Eb; G. F. de Boer

1992-01-01

133

Reaction pathways of glucose oxidation by ozone under acidic conditions.  

PubMed

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

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

2009-07-27

134

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

E-print Network

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

Turro, Nicholas J.

135

Self-assembly of polyaniline\\/polyacrylic acid films via acid–base reaction induced deposition  

Microsoft Academic Search

The layer-by-layer self-assembly of polyaniline (PAN) and polyacrylic acid (PAA) has been accomplished via the alternate spontaneous adsorption of base-type PAN from its dilute N-methylpyrrolidinone solution and PAA from its aqueous solution based on the acid–base reaction of PAN and PAA. The thickness of the films can be manipulated at nanometer scale by the concentration of PAN solution and recycling

D. Li; Y. Jiang; C. Li; Z. Wu; X. Chen; Y. Li

1999-01-01

136

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

137

Laboratory measurements of heterogeneous reactions on sulfuric acid surfaces  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

138

Presence of human immunodeficiency virus nucleic acids in wastewater and their detection by polymerase chain reaction.  

PubMed Central

The human immunodeficiency virus type 1 (HIV-1) released by infected individuals or present in human and hospital wastes can potentially cause contamination problems. The presence of HIV-1 was investigated in 16 environmental samples, including raw wastewater, sludge, final effluent, soil, and pond water, collected from different locations. A method was developed to extract total nucleic acids in intact form directly from the raw samples or from the viral concentrates of the raw samples. The isolated nucleic acids were analyzed for the presence of HIV-1 by using in vitro amplification of the target sequences by the polymerase chain reaction (PCR) method. HIV-1-specific proviral DNA and viral RNA were detected in the extracted nucleic acids obtained from three wastewater samples by this method. The specificity of the PCR-amplified products was determined by Southern blot hybridization with an HIV-1-specific oligonucleotide probe, SK19. The isolated nucleic acids from wastewater samples were also screened for the presence of poliovirus type 1, representing a commonly found enteric virus, and simian immunodeficiency virus, representing, presumably, rare viruses. While poliovirus type 1 viral RNA was found in all of the wastewater samples, none of the samples yielded a simian immunodeficiency virus-specific product. No PCR-amplified product was yielded when wastewater samples were directly used for the detection of HIV-1 and poliovirus type 1. The wastewater constituents appeared to be inhibitory to the enzymes reverse transcriptase and DNA polymerase.(ABSTRACT TRUNCATED AT 250 WORDS) Images PMID:1476440

Ansari, S A; Farrah, S R; Chaudhry, G R

1992-01-01

139

Calcium phosphate cements prepared by acid-base reaction  

Microsoft Academic Search

In this paper, the authors investigate the characteristics of calcium phosphate cements (CPC) prepared by an exothermic acid-base reaction between NH[sub 4]H[sub 2]PO[sub 4]-based fertilizer (Poly-N) and calcium aluminate compounds (CAC), such as 3CaO[center dot]Al[sub 2]O[sub 3] (C[sub 3]A), CaO[center dot] Al[sub 2]O[sub 3] (CA), and CaO[center dot] 2Al[sub 2]O[sub 3] (CA[sub 2]), in a series of integrated studies of

Toshifumi Sugama; Marita Allan; Janet M. Hill

1992-01-01

140

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

141

Acid-catalyzed reactions of epoxides for atmospheric nanoparticle growth.  

PubMed

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

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

2014-11-01

142

Hybridization chain reaction performed on a metal surface as a means of signal amplification in SPR and electrochemical biosensors.  

PubMed

A more specific and intense signal is desirable for most kinds of biosensors for biomedical or environmental applications, and it is especially so for label-free biosensors. In this paper, we show that hybridization chain reaction (HCR) can be exploited for the easily detectable accumulation of nucleic acids on metal surfaces as an event triggered by specific recognition between a probe and a target nucleic acid. We show that this process could be exploited to increase the sensitivity in the detection of nucleic acids derived from a pathogenic microorganism. This strategy can be straightforwardly implemented on SPR biosensors (commercial or custom-built) or on label-free electrochemical biosensors. Together with signal amplification, HCR can serve as a confirmation of the specificity of target recognition, as it involves the specific matching with a separate base sequence in the target nucleic acid. Furthermore, the kinetics of the target binding and the HCR can be easily distinguished from each other, providing an additional means of confirmation of the specific recognition. PMID:24252766

Spiga, Fabio M; Bonyár, Attila; Ring, Balázs; Onofri, Manuele; Vinelli, Alessandra; Sántha, Hunor; Guiducci, Carlotta; Zuccheri, Giampaolo

2014-04-15

143

Porous silicon/photosynthetic reaction center hybrid nanostructure.  

PubMed

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

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

2012-08-14

144

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

145

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

PubMed

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

Gomes, P T C; Nassar, N M A

2013-01-01

146

Wollastonite hybridizing stearic acid as thermal energy storage material  

NASA Astrophysics Data System (ADS)

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

Xu, Dawei; Yang, Huaming

2014-11-01

147

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

SciTech Connect

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

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

2014-01-09

148

Nucleic acid probes are molecules that complement or hybridize to a  

E-print Network

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

Levin, Judith G.

149

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

150

A Novel Synthesis of r-Amino Acid Derivatives through Catalytic, Enantioselective Ene Reactions of  

E-print Network

A Novel Synthesis of r-Amino Acid Derivatives through Catalytic, Enantioselective Ene Reactions variants are known.2 However, the corresponding catalytic, enantioselective ene reaction between alkenes, enantioselective imino ene reaction of R-imino ester 1 with alkenes 2a-f catalyzed by Lewis acid complex 3 and show

Lectka, Thomas

151

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

Microsoft Academic Search

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

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

2009-01-01

152

Non-Exponential Smoluchowski Dynamics in Fast Acid-Base Reaction  

E-print Network

direct proton transfer (PT) between acid (AH) and base (B), have hardly been studied in the time domainNon-Exponential Smoluchowski Dynamics in Fast Acid-Base Reaction Boiko Cohen and Dan Huppert SchoolVised Manuscript ReceiVed July 11, 2000 Acid-base reactions are among the most fundamental processes in chemistry

Agmon, Noam

153

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

PubMed

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

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

2015-02-10

154

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

PubMed

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

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

2013-08-22

155

Dietary fatty acids and immune reactions in synovial tissue.  

PubMed

Inflammation of the synovial membrane in rheumatoid arthritis is mediated by specialized cells necessary for immune response. The most prominent features are the accumulation of mononuclear phagocytes, lymphocytes and leukocytes in the proliferating tissue. Pro-inflammatory and proliferative signals are transmitted to the bone marrow and to the synovial membrane. The result is a monoclonal stimulation of specific cell lines, and synovial proliferation in the inflamed joint. Angiogenesis, synovial hypertrophy, and increased perfusion facilitate the accumulation of inflammatory cells. Components of the autoimmune reaction are described in the international system of classification, the CD-System (cluster of differentiation). Pro-inflammatory signals are mediated by metabolites of arachidonic acid. Prostaglandins, leukotrienes, lipoxines and hydroxy fatty acids, derived from this PUFA, stimulate the formation and the activity of adhesion molecules (integrines), cytokines (gamma-interferon, interleukin-1, interleukin-6, tumor-necrosis factor), chemokines (interleukine-8, macrophage-chemotactic peptide, RANTES and colony -stimulating factors ((CSF, granulocytes/ monocytes-CSF, Multi-CSF (= IL-3)). Dietary means to mitigate inflammation comprise reduction of arachidonic acid, and increased intake of eicosapentaenoic acid and antioxidants. In the literature 12 randomized, placebo-controlled double-blind studies, fulfilling GCP-criteria, demonstrate a moderate but consistent improvement of clinical findings and laboratory parameters in patients with RA. A dose-response relationship was established up to an daily dose of 2.6 gram fish oil, equivalent to about 1.6 gram EPA. In these experiments EPA was the omega-3 fatty acid responsible for improvement, with distinct effects on inhibition of cytokines formation (IL-1 to IL-6, IL-8, TFN-alpha, GM-CSF), decreased induction of proinflammatory adhesion molecules (selectines, intercellular adhesions molecule-1 (ICAM-1)), and degrading enzymes (e.g. phospholipase A2, cyclooxygenase-2, inducible NO-synthetase). Only one study reports the relevance of the background diet. From this study it became apparent that reduction of dietary arachidonic acid improves the incorporation and the clinical benefit of EPA. PMID:12915334

Adam, O

2003-08-20

156

Producing a trimethylpentanoic acid using hybrid polyketide synthases  

DOEpatents

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

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

2014-10-07

157

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

ERIC Educational Resources Information Center

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

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

1979-01-01

158

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 Brřnsted 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

159

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

Microsoft Academic Search

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

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

2000-01-01

160

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

PubMed Central

Human-rodent hybrid cell lines have been analyzed with regard to their human DNA content by using various DNA probe sets, derived from the hybrids, for in situ hybridization to normal human metaphase chromosome spreads. Total genomic hybrid DNA was compared with probe sets of hybrid DNA that were highly enriched in human sequences. The latter probes were obtained by amplification through the polymerase chain reaction (PCR) using oligonucleotide primers directed to human specific subsequences of the interspersed repetitive sequences Alu and L1. Previously unidentified chromosomal material within hybrid lines was characterized with speed and precision. It is demonstrated that the complete human complement of hybrid lines can be rapidly assessed by comparing the data obtained with the Alu-PCR products with the results from the L1-PCR products or from the genomic hybrid DNA. This approach using interspersed repetitive sequence-PCR products is simple and fast and also provides an alternative way of generating complex DNA probe sets for the specific delineation of entire chromosomes or subchromosomal regions by in situ hybridization. Images PMID:2395866

Lichter, P; Ledbetter, S A; Ledbetter, D H; Ward, D C

1990-01-01

161

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

SciTech Connect

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

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

2010-08-15

162

Role of added chloride ions in alteration of reaction pathway in the oxidation of cyclic ketones by dichloroisocyanuric acid—A kinetic study  

NASA Astrophysics Data System (ADS)

Effect of added chloride ions on kinetics and pathway of reaction between cyclic ketones (five to eight membered rings) and dichloroisocyanuric acid (DCICA) was studied in aqueous acetic acid—perchloric acid medium. Formation of aliphatic dicarboxylic acids as the end products demonstrates the ring cleavage oxidation. Positive effect of acid and negative effect of dielectric constant on the reaction rate reveals a interaction between positive ion (oxidant in the form of H2OCl+) and dipolar substrate molecule. Zero and first orders by oxidant in absence and presence of added chloride ions illustrates the participation of substrate as enolic form of ketone and protonated ketone, respectively, in the rate determining steps. The observed order of reactivity of cyclic ketones (cyclohexanone > cyclooctanone > cyclopentanone > cycloheptanone) was explained on the bases of ring strain, change of hybridization and conformational considerations. The envisaged plausible mechanism based on order of reactants in presence and absence of added chloride ions was substantiated by the order of Arrhenius parameters.

Lakshman Kumar, Y.; Venkata Nadh, R.; Radhakrishnamurti, P. S.

2015-03-01

163

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

E-print Network

Matrix acidizing has historically been a common means of removing formation damage and increasing the productivity of petroleum wells. Organic acids have been used in an effort to minimize the corrosion problem and the rapid reaction rate...

Shedd, Daniel C

2014-08-07

164

Synthesis of pyroglutamic acid derivatives via double Michael addition reactions of alkynones.   

E-print Network

I. Synthesis of pyroglutamic acid derivatives via double Michael reactions of alkynones Pyroglutamic acids and their derivatives are common structural units of widespread chemical significance and they have been heavily ...

Scansetti, Myriam

2009-01-01

165

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

PubMed

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

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

2014-09-01

166

Friedel–Crafts acylation reaction using carboxylic acids as acylating agents  

Microsoft Academic Search

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

Masato Kawamura; Dong-Mei Cui; Shigeru Shimada

2006-01-01

167

Bioorthogonal tetrazine-mediated transfer reactions facilitate reaction turnover in nucleic acid-templated detection of microRNA.  

PubMed

Tetrazine ligations have proven to be a powerful bioorthogonal technique for the detection of many labeled biomolecules, but the ligating nature of these reactions can limit reaction turnover in templated chemistry. We have developed a transfer reaction between 7-azabenzonorbornadiene derivatives and fluorogenic tetrazines that facilitates turnover amplification of the fluorogenic response in nucleic acid-templated reactions. Fluorogenic tetrazine-mediated transfer (TMT) reaction probes can be used to detect DNA and microRNA (miRNA) templates to 0.5 and 5 pM concentrations, respectively. The endogenous oncogenic miRNA target mir-21 could be detected in crude cell lysates and detected by imaging in live cells. Remarkably, the technique is also able to differentiate between miRNA templates bearing a single mismatch with high signal to background. We imagine that TMT reactions could find wide application for amplified fluorescent detection of clinically relevant nucleic acid templates. PMID:25495860

Wu, Haoxing; Cisneros, Brandon T; Cole, Christian M; Devaraj, Neal K

2014-12-31

168

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

169

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

PubMed

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

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

2014-07-15

170

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

E-print Network

" or a "base" in the following reactions, and identify "conjugate" relationships. -You should have one acid?) 27. 28. G. For the following acid-base reaction, a. put a box around the weakest base in the reactionOrganic Chemistry Jasperse Acid-Base Practice Problems A. Identify each chemical as either an "acid

Jasperse, Craig P.

171

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

NASA Astrophysics Data System (ADS)

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

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

2007-11-01

172

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

ERIC Educational Resources Information Center

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

Nyasulu, Frazier; McMills, Lauren; Barlag, Rebecca

2013-01-01

173

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

E-print Network

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

Epstein, Irving R.

174

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

ERIC Educational Resources Information Center

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

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

2003-01-01

175

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

E-print Network

Breathing spiral waves in the chlorine dioxide­iodine­malonic acid reaction-diffusion system Igal 2008; published 11 August 2008 Breathing spiral waves are observed in the oscillatory chlorine dioxide-iodine-malonic acid reaction- diffusion system. The breathing develops within established patterns of multiple spiral

Epstein, Irving R.

176

Hybrid low resistance ultracapacitor electrodes based on 1-pyrenebutyric acid functionalized centimeter-scale graphene sheets.  

PubMed

Ultracapacitors are promising candidates for alternative energy storage applications since they can store and deliver energy at relatively high rates. Here, we present hybrid nanocarbon ultracapacitor electrodes with a low equivalent series resistance (ESR) of 7 ohms. 1-pyrenebutyric acid treated large-area single layer graphene (SLG) sheets covered with shortened multi-walled carbon nanotubes (MWNTs) have been utilized as highly conductive and percolated networks of hybrid carbon nanomaterial composites or thin films as ultracapacitor electrodes. Uniform centimeter scale single layer graphene sheets were produced via low pressure chemical vapor deposition using copper foil substrates and then subsequently modified by 1-pyrenebutyric acid functionalization. Chemically shortened MWNTs ranging in length of 200-500 nm, were deposited by drop casting on 1-pyrenebutyric acid functionalized SLG films. SLG/MWNT nancomposite hybrid films of different thicknesses were obtained by controlling the density of MWNT suspension. Surface morphology and nanostructure of the hybrid nanocomposites indicated relatively dense and homogeneous web-like networks. Specific capacitance values of the hybrid electrodes were substantially increased by 200% compared to those ultracapacitors fabricated using buckypaper electrodes. Average values of specific capacitance and energy density obtained were 140.64 F/g and 21.54 Wh/kg respectively. SLG/MWNT nanocomposite electrodes are very promising for future ultracapacitor devices with their low ESR value that is 95% lower than that of buckypaper based ultracapacitors. PMID:23035414

Wang, Wei; Guo, Shirui; Penchev, Miroslav; Zhong, Jiebin; Lin, Jian; Bao, Duoduo; Vullev, Valentine; Ozkan, Mihrimah; Ozkan, Cengiz S

2012-09-01

177

Phosphonic acid functionalized ordered mesoporous material: a new and ecofriendly catalyst for one-pot multicomponent Biginelli reaction under solvent-free conditions.  

PubMed

We report a new ordered 2D hexagonal mesoporous organosilica material (PAFMS-1) bearing phosphonic acid functionality at the surface. This hybrid material showed high Brunauer-Emmett-Teller surface area (565 m(2) g(-1)) and ordered assembly of mesoporoes with an average pore diameter of ca. 2.1 nm. This novel hybrid mesoporous material has been synthesized via cocondensation of (triethoxysilyl)(propyliminomethyl)biphenylmethyl phosphoester (PEFOS) and tetraethyl orthosilicate (TEOS) in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB) at 373 K. The phosphoester-functionalized organosilane (PEFOS) precursor has been synthesized for the first time by a simple SN2 reaction followed by Suzuki coupling and a Mannich reaction. The material has been characterized by powder X-ray diffraction, N2 sorption, and transmission electron microscopy image analysis, whereas the presence of organic moieties (an aromatic biphenyl ring and an aliphatic side chain), phosphrous, and silicon in the pore wall of the material have been characterized by solid-state magic-angle-spinning NMR, X-ray photoelectron, and Fourier transform infrared (FT-IR) spectroscopic tools. Further, the surface acid strength of the hybrid material has been determined by FT-IR analysis of the samples via temperature-programmed pyridine adsorption studies. The material has been utilized as a reusable heterogeneous catalyst for the synthesis of biologically important and value added multifunctionalized 3,4-dihydropyridin-2-1H-(ones)/3,4-dihydropyridin-2-1H-(thiones) (DHPMs) through a multicomponent Biginelli condensation reaction under solvent-free conditions at 333 K. The phosphonic acid functionalized 2D hexagonal mesoporous material showed much higher catalytic activity in this multicomponent condensation reaction over sulfonic acid functionalized mesoporous silica (MCM-41-SO3H) bearing an aliphatic chain in the hybrid framework. PMID:24372168

Pramanik, Malay; Bhaumik, Asim

2014-01-22

178

Peptide nucleic acid (PNA)/DNA hybrid duplexes: intercalation by an internally linked anthraquinone.  

PubMed Central

Peptide nucleic acids (PNA) mimic DNA and RNA by forming complementary duplex structures following Watson-Crick base pairing. A set of reporter compounds that bind to DNA by intercalation are known, but these compounds do not intercalate in PNA/DNA hybrid duplexes. Analysis of the hybrid PNA duplexes requires development of reporter compounds that probe their chemical and physical properties. We prepared a series of anthraquinone (AQ) derivatives that are linked to internal positions of a PNA oligomer. These are the first non-nucleobase functional groups that have been incorporated into a PNA. The resulting PNA(AQ) conjugates form stable hybrids with complementary DNA oligomers. We find that when the AQ groups are covalently bound to PNA that they stabilize the hybrid duplex and are, at least partially, intercalated. PMID:9443962

Armitage, B; Koch, T; Frydenlund, H; Orum, H; Schuster, G B

1998-01-01

179

Combination reaction between humic acid and calcium ions  

Microsoft Academic Search

In the previous paper (1), liming an acid humus volcanic ash soil resulted in the formation of humic acids combined with calcium, but had no significant effect on acid brown forest soils containing humic acids of a lower degree of humification. Subsequently, the authors examined the humus composition of the soils treated with calcium acetate, and conducted some experiments on

Ryosuke Shiroya; Kyoichi Kumada

1976-01-01

180

GRAIN COMPOSITION AND AMINO ACID CONTENT IN MAIZE HYBRIDS REPRESENTING 80 YEARS OF COMMERCIAL MAIZE VARIETIES  

Technology Transfer Automated Retrieval System (TEKTRAN)

In order to determine how development of modern hybrids has impacted grain composition and amino acid content, we characterized a set of cultivars that were widely grown in different eras from the 1920s through 2001. Grain composition exhibited clear trends with time, with protein decreasing and st...

181

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

Microsoft Academic Search

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

Adam W. Stienecker; Thomas Stuart; Cyrus Ashtiani

2006-01-01

182

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

PubMed

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

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

2014-01-15

183

Ultrasensitive electrochemical detection for thrombin using hybridization chain reaction with enzyme-amplification.  

PubMed

In this work, a new electrochemical aptasensor using hybridization chain reaction (HCR) for signal amplification was developed for highly sensitive detection of thrombin. The sandwich system of aptamer/thrombin/aptamer-primer complex was fabricated as the sensing platform. As the initiator strands, aptamer-primer complex could propagate a chain reaction of hybridization events between the two hairpin probes, and whether long nicked DNA polymers could be formed on the modified electrode. Then the biotin-labeled dsDNA polymers could introduce numerous avidin-labeled horseradish peroxidase (HRP), resulting in significantly amplified electrochemical signal through the electrocatalysis of HRP. On the basis of the enzymatic oxidization of Fe(2+) by H2O2 to yield Fe(3+), the imaging of thrombin was detected by the reduction current of Fe(3+) with the scanning electrochemical microscopic tip. The electrochemical signals had a good linear with logarithm of thrombin concentration in the range from 1.0fM to 100fM, reaching a detection limit of thrombin as low as 0.04fM. In addition, the proposed strategy exhibited excellent specificity and was successfully applied in real sample assay which demonstrated the potential application in clinical diagnostics. PMID:25682250

Song, Weiling; Xie, Xuxu; Sun, Wenbo; Zhang, Ningbo; Li, Chunxiang

2015-02-20

184

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

PubMed

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

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

2014-10-15

185

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

PubMed Central

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

2014-01-01

186

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

PubMed

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

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

2014-05-27

187

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

E-print Network

1 Up-Scaling Geochemical Reaction Rates Accompanying Acidic CO2-Saturated Brine Flow in Sandstone modeling of reactive flow requires determination of effective reaction rates applicable to field scale-scaling of anorthite and kaolinite reaction rates from pore to core scales. Unique to our simulations is the use

New York at Stoney Brook, State University of

188

A Laboratory Investigation of the Heterogeneous Reaction of Nitric Acid with Calcium Carbonate  

Microsoft Academic Search

Recent laboratory experiments on the heterogeneous reaction of nitric acid with calcium carbonate particles will be presented. Several different techniques are used to investigate and quantify morphology changes that occur during reaction, phase transformations, and the rate dependence of individual particles as a function of relative humidity. In addition, competitive reactions of other trace gases such as sulfur dioxide with

V. H. Grassian; B. J. Krueger; A. Preszler Prince; M. A. Young

2002-01-01

189

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

190

Immobilization of denatured DNA to macroporous supports: II. Steric and kinetic parameters of heterogeneous hybridization reactions.  

PubMed Central

The accessibility of immobilized DNA has been shown to depend more crucially on the method of immobilization than on the type of support used for fixation. When sonicated denatured DNA is coupled via diazotization or via cyanogen bromide reaction to solid Sephadex G-25 and Cellex 410 or to macroporous Sephacryl S-500 and Sepharose C1-6B its accessibility varies from 100 to 24 percent. Generally the loss of accessibility is linked to a depression of the melting temperature of DNA helices formed on the support. This correlation shows a characteristic course for a particular coupling method. DNA coupled under denaturing conditions may become totally inaccessible when only 3 percent of its bases are involved in the covalent linkage. Kinetic experiments with sonicated E.coli DNA have shown that the rate constants for renaturation or hybridization reactions are very similar for DNA immobilized by different methods to solid or macroporous supports. Generally the second order rate constant for a heterogeneous reaction (between mobile and immobilized DNA) is about one order of magnitude smaller than that of the analogous homogeneous reaction (in solution). PMID:6185922

Bünemann, H

1982-01-01

191

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

PubMed

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

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

2009-11-01

192

HYDROLYSIS REACTIONS OF N-PHOSPHOAMINO ACIDS—A MODEL FOR PROTEIN DEPHOSPHORYLATION  

Microsoft Academic Search

Phosphoamino acids are the smallest units of phosphoprotein. In Tris-HCl buffer (pH7.5)\\/DMSO(v\\/v=1:1) mixed solvent at 40°C the kinetic rates of N-phosphoamino acid hydrolysis reactions were studied. The reactions were pseudo first-order. and the hydrolysis rates of the N-phosphoamino acids were much faster than those of simple phosphoamidates under the same conditions. The kinetic results suggested that the side chain groups

Yongfang Li; Weihua Zhou; Qian Wang; Hui Liu; Yufen Zhao

1996-01-01

193

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

Microsoft Academic Search

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

Paul W. Ayers; Robert G. Parr; Ralph G. Pearson

2006-01-01

194

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

Microsoft Academic Search

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

Paul W. Ayers; Robert G. Parr; Ralph G. Pearson

2006-01-01

195

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

E-print Network

of phenylcarboxymethylarsinic acid with hydrogen selenide produced 1, 4-diphenyl-1, 4-diarsa-2, 3, 5-triselenacyclopentane. The structure of this compound was determined by single crystal x-ray crystallography. The reactions of a series of arsonic acids including phenyl, p-methyl... OF CONTENTS (CONTINUED) Page Synthesis of 1, 4-Diphenyl-1, 4-diarsa-2, 3, 5-triselenacyclopentane Synthesis of 1, 4-Diphenyl-1, 4-diarsa-2, 3, 5-trithiacyclopentane Reaction of Phenylcarboxymethylarsinic Acid with Benzenethiol Synthesis of Phenyl Di...

Applegate, Cynthia Annette

1986-01-01

196

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

SciTech Connect

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

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

2013-06-25

197

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

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

198

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

NASA Astrophysics Data System (ADS)

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

Ganesh, Karthik

199

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

200

Friedel–Crafts acylation and related reactions catalysed by heteropoly acids  

Microsoft Academic Search

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

I. V. Kozhevnikov

2003-01-01

201

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

E-print Network

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

Fernandez, Thomas

202

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

E-print Network

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

Liu, David R.

203

Kinetics of the reaction between ozone and phenolic acids present in agro-industrial wastewaters  

Microsoft Academic Search

The kinetics of the ozonation of three phenolic acids is investigated from ozone absorption experiments in a semi-continuous reactor. After the evaluation of stoichiometric ratios for the individual reactions between ozone and each phenolic acid, the oxidation of p-hydroxybenzoic acid by ozone is performed in a first stage. The influence of the operating variables on the degradation process is established,

Jesus Beltran-Heredia; Joaquin Torregrosa; Joaquin R. Dominguez; Jose A. Peres

2001-01-01

204

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

205

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

DOEpatents

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

Holladay, Jonathan E. (Kennewick, WA)

2006-05-23

206

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

E-print Network

" or a "base" in the following reactions, and identify "conjugate" relationships. -You should have one acid whether equilibrium favors products or reactants. (Why?) 27. 28. G. For the following acid-base reaction, a. put a box around the weakest base in the reaction b. put a circle around the weakest acid c. draw

Jasperse, Craig P.

207

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

208

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

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

209

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

210

?-chloro carboxyclic acids, and some of their reactions  

Microsoft Academic Search

Summary 1.11-Chlorodecanoic, 13-chlorotridecanoic and 15-chloropertadecanoic acids have been prepared by hydrolysis of the correspondinga,a,a ?-tetrachloroalkanes.2.The reactivities of some ?-chloro carboxylic acids have been studied,3.It has been shown that the condensation of 5-chlorovaleric acid with benzene to presence of aluminum chloride proceeds without isomerization, but shat isomerization occurs in the corresponding condensatlons of 7-chlorohepanoic, 9-chlmononanoic. and 11-chloroundecanoic acids.4.In order to characterize

A. N. Nesmeyanov; L. I. Zakharkin

1955-01-01

211

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

NASA Astrophysics Data System (ADS)

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.

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

1982-05-01

212

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

PubMed

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

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

2014-06-01

213

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

Code of Federal Regulations, 2014 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...

2014-07-01

214

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

Code of Federal Regulations, 2011 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...

2011-07-01

215

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

Code of Federal Regulations, 2012 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...

2012-07-01

216

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

Code of Federal Regulations, 2010 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...

2010-07-01

217

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

Code of Federal Regulations, 2010 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...

2010-07-01

218

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

219

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

220

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

Code of Federal Regulations, 2012 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...

2012-07-01

221

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

Code of Federal Regulations, 2014 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...

2014-07-01

222

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

Code of Federal Regulations, 2010 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...

2010-07-01

223

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

224

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

Code of Federal Regulations, 2014 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...

2014-07-01

225

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

Code of Federal Regulations, 2012 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...

2012-07-01

226

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

Code of Federal Regulations, 2011 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...

2011-07-01

227

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

Code of Federal Regulations, 2011 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...

2011-07-01

228

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

PubMed

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

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

2014-12-19

229

A General Strategy for Nanohybrids Synthesis via Coupled Competitive Reactions Controlled in a Hybrid Process.  

PubMed

A new methodology based on core alloying and shell gradient-doping are developed for the synthesis of nanohybrids, realized by coupled competitive reactions, or sequenced reducing-nucleation and co-precipitation reaction of mixed metal salts in a microfluidic and batch-cooling process. The latent time of nucleation and the growth of nanohybrids can be well controlled due to the formation of controllable intermediates in the coupled competitive reactions. Thus, spatiotemporal-resolved synthesis can be realized by the hybrid process, which enables us to investigate nanohybrid formation at each stage through their solution color changes and TEM images. By adjusting the bi-channel solvents and kinetic parameters of each stage, the primary components of alloyed cores and the second components of transition metal doping ZnO or Al2O3 as surface coatings can be successively formed. The core alloying and shell gradient-doping strategy can efficiently eliminate the crystal lattice mismatch in different components. Consequently, varieties of gradient core-shell nanohybrids can be synthesized using CoM, FeM, AuM, AgM (M = Zn or Al) alloys as cores and transition metal gradient-doping ZnO or Al2O3 as shells, endowing these nanohybrids with unique magnetic and optical properties (e.g., high temperature ferromagnetic property and enhanced blue emission). PMID:25818342

Wang, Rongming; Yang, Wantai; Song, Yuanjun; Shen, Xiaomiao; Wang, Junmei; Zhong, Xiaodi; Li, Shuai; Song, Yujun

2015-01-01

230

A General Strategy for Nanohybrids Synthesis via Coupled Competitive Reactions Controlled in a Hybrid Process  

PubMed Central

A new methodology based on core alloying and shell gradient-doping are developed for the synthesis of nanohybrids, realized by coupled competitive reactions, or sequenced reducing-nucleation and co-precipitation reaction of mixed metal salts in a microfluidic and batch-cooling process. The latent time of nucleation and the growth of nanohybrids can be well controlled due to the formation of controllable intermediates in the coupled competitive reactions. Thus, spatiotemporal-resolved synthesis can be realized by the hybrid process, which enables us to investigate nanohybrid formation at each stage through their solution color changes and TEM images. By adjusting the bi-channel solvents and kinetic parameters of each stage, the primary components of alloyed cores and the second components of transition metal doping ZnO or Al2O3 as surface coatings can be successively formed. The core alloying and shell gradient-doping strategy can efficiently eliminate the crystal lattice mismatch in different components. Consequently, varieties of gradient core-shell nanohybrids can be synthesized using CoM, FeM, AuM, AgM (M = Zn or Al) alloys as cores and transition metal gradient-doping ZnO or Al2O3 as shells, endowing these nanohybrids with unique magnetic and optical properties (e.g., high temperature ferromagnetic property and enhanced blue emission). PMID:25818342

Wang, Rongming; Yang, Wantai; Song, Yuanjun; Shen, Xiaomiao; Wang, Junmei; Zhong, Xiaodi; Li, Shuai; Song, Yujun

2015-01-01

231

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

232

A novel biocompatible hyaluronic acid-chitosan hybrid hydrogel for osteoarthrosis therapy.  

PubMed

A conventional therapy for the treatment of osteoarthrosis is intra-articular injection of hyaluronic acid, which requires repeated, frequent injections. To extend the viscosupplementation effect of hyaluronic acid, we propose to associate it with another biopolymer in the form of a hybrid hydrogel. Chitosan was chosen because of its structural similarity to synovial glycosaminoglycans, its anti-inflammatory effects and its ability to promote cartilage growth. To avoid polyelectrolyte aggregation and obtain transparent, homogeneous gels, chitosan was reacetylated to a 50% degree, and different salts and formulation buffers were investigated. The biocompatibility of the hybrid gels was tested in vitro on human arthrosic synoviocytes, and in vivo assessments were made 1 week after subcutaneous injection in rats and 1 month after intra-articular injection in rabbits. Hyaluronic acid-chitosan polyelectrolyte complexes were prevented by cationic complexation of the negative charges of hyaluronic acid. The different salts tested were found to alter the viscosity and thermal degradation of the gels. Good biocompatibility was observed in rats, although the calcium-containing formulation induced calcium deposits after 1 week. The sodium chloride formulation was further tested in rabbits and did not show acute clinical signs of pain or inflammation. Hybrid HA-Cs hydrogels may be a valuable alternative viscosupplementation agent. PMID:25666331

Kaderli, S; Boulocher, C; Pillet, E; Watrelot-Virieux, D; Rougemont, A L; Roger, T; Viguier, E; Gurny, R; Scapozza, L; Jordan, O

2015-04-10

233

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

Microsoft Academic Search

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

Ji-Sang Kim; Young-Soon Lee

2009-01-01

234

Lewis Acid\\/Base Reaction Chemistry (by Mark R. Leach)  

Microsoft Academic Search

In summary, this monograph and its accompanying CD provide a unique approach to the organization of reaction chemistry. This approach sweeps aside the boundary between organic and inorganic reactions. The question remains of who would benefit by using this book and CD. I think that an undergraduate preparing for graduate school would find this pedagogy useful to integrate the vast

John C. Cochran

2001-01-01

235

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

PubMed

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

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

2014-08-15

236

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

PubMed Central

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

Stergiou, Anastasios; Pagona, Georgia

2014-01-01

237

Lewis Acid and/or Lewis Base catalyzed [3+2] cycloaddition reaction: Synthesis of pyrazoles and pyrazolines  

E-print Network

1 Lewis Acid and/or Lewis Base catalyzed [3+2] cycloaddition reaction: Synthesis of pyrazoles is reported. All the reactions were carried out under no strong bases/acids, solvent free conditions+2] cycloaddition reaction strategy to form five membered ring systems through the reaction partners of 1,3-dipoles

Paris-Sud XI, Université de

238

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

239

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...

240

Sulfuric Acid Influence on the Nitrocompounds Detonation Reactions  

Microsoft Academic Search

The detonation failure diameter df and detonation velocity D of mixtures of nitromethane, trinitrotoluene, dinitrotoluene, and trinitrobenzene with sulfiric acid and oleum have been measured in the wide range of concentrations It was shown that the detonation ability of the nitrocompounds depends significantly on the sulfuric acid content The minimum value of df for the mixture TNTIoleum is about 2

V. N. Gamezo; S. M. Khoroshev; B. N. Kondrikov; G. D. Kozak

1995-01-01

241

Molecular detection of bovine viral diarrhea virus in clinical samples by polymerase chain reaction-chemiluminscent DNA hybridization assay  

Microsoft Academic Search

The polymerase chain reaction (PCR) followed by chemiluminescent probe hybridization assay was used for the detection of bovine viral diarrhea virus (BVDV) infections in cattle. BVDV RNA's from individual clinical specimens, from persistently infected (PI) and acutely diseased cattle were transcribed to cDNA using reverse transcriptase. Using a set of 18-mer oligonucleotide primers located within the conserved 5' untranslated region

G. S. Radwan

2002-01-01

242

Quantification of Coxiella burnetii by polymerase chain reaction (PCR) and a colorimetric microtiter plate hybridization assay (CMHA)  

Microsoft Academic Search

A colorimetric microtiter plate hybridization assay (CMHA) for the quantitative determination ofCoxiella burnetii DNA after amplification by externally controlled polymerase chain reaction (PCR) is described. The quantification assay is based on an enzyme linked immunosorbent assay (ELISA) format. Cloned DNA, representing a sequence complementary to an internal part of the diagnostic amplicon, was noncovalently attached to the wells of a

E. Fritz; D. Thiele; H. Willems; M. M. Wittenbrink

1995-01-01

243

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

244

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

PubMed

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

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

2009-06-01

245

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

246

Evidence for quasi-intramolecular acid-base reactions in solutions of transition metal ammine complexes  

Microsoft Academic Search

We have investigated the effect of temperature on the postulated quasi-intramolecular acid-base reactions in aqueous solutions of Cu(NH3)4(MnO4)2 and Ag(NH3)2ClO4. Pure ammonium permanganate and perchlorate were obtained above 5 °C and at room temperature, respectively, due to quasi-intramolecular acid-base reactions.

László Kótai; Tibor Horváth; Klára Szentmihályi; Ágnes Keszler

2000-01-01

247

Long-range proton transfer in aqueous acid-base reactions  

Microsoft Academic Search

We study the mechanism of proton transfer (PT) in the aqueous acid?base reaction between the photoacid 8-hydroxy-1,3,6-pyrenetrisulfonic acid (HPTS) and acetate by probing the vibrational resonances of HPTS, acetate, and the hydrated proton with femtosecond mid-infrared laser pulses. We find that PT takes place in a distribution of hydrogen-bound reaction complexes that differ in the number of water molecules separating

B. J. Siwick; M. J. Cox; H. J. Bakker

2008-01-01

248

Humic acid-inspired hybrid materials as heavy metal absorbents.  

PubMed

Three SiO(2)-based materials were prepared via covalent immobilization of carboxyl groups (COOH), phenolic groups (GA), or humic acid on an SiO(2) surface. Their sorbing properties were evaluated for removal of heavy metals (Pb(2+), Cd(2+), Cu(2+), Zn(2+), and Mg(2+)) from aqueous solution. The data show a significant improvement for metal uptake, compared to unmodified silica that can be attributed to the adsorption of metals to the deprotonated form of functional groups (COOH, GA, HA). The metal-uptake capacity of the SiO(2)-HA material was 10 times higher that those of the other two materials. The present data provide direct experimental proof that HA can be viewed and modeled as a combination of -COO and R-OH functional groups. PMID:20705298

Stathi, Panagiota; Deligiannakis, Yiannis

2010-11-01

249

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

PubMed Central

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

Hayashi, Shigehiko; Tajkhorshid, Emad; Schulten, Klaus

2009-01-01

250

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

PubMed

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

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

2011-05-01

251

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

252

Effects of novel hybrids of caffeic acid phenethyl ester and NSAIDs on experimental ocular inflammation.  

PubMed

In this study, we report the design and synthesis of novel hybrids of caffeic acid phenetyl ester (CAPE) and non-steroidal anti-inflammatory drugs (NSAIDs). We assessed their effects on an experimental ocular inflammation in New Zealand rabbits. The formulations of CAPE-aspirin and CAPE-indomethacin hybrids were topical instilled in the rabbit?s eye. Afterwards, the anti-inflammatory activity was evaluated by grading the clinical signs and by assessing the inflammatory cell count, protein, PGE2 and TNF? levels in the aqueous humor. Furthermore, ocular tolerability of hybrids formulations was evaluated in a separate set of animals by using a modified Draize test. The ocular inflammation in the control group was significantly higher than in both the hybrid-treated groups, as indicated by clinical grading and biomarkers assessment. However, only the CAPE-aspirin hybrid reduced, in a significant dose-dependent manner, the ocular inflammation elicited by paracentesis. CAPE-indomethacin hybrid was able to significantly attenuate the clinical grading and the PGE2 aqueous levels only at the highest dose (0.1%). CAPE-aspirin significantly reduced PGE2 and TNF? levels in the aqueous humor as well as proteins and PMNs. Finally, all formulations showed no ocular irritation compared with vehicle-treated group. In conclusion, CAPE-aspirin shows full anti-inflammatory efficacy in experimental model of ocular inflammation demonstrating an optimal pharmacological and safety profile. Taken together these data indicate that CAPE-aspirin hybrid represents a valid and safe new chemical entity potentially useful for the treatment of ocular inflammation. PMID:25704612

Pittalŕ, Valeria; Salerno, Loredana; Romeo, Giuseppe; Siracusa, Maria Angela; Modica, Maria Nunziata; Romano, Giovanni Luca; Salomone, Salvatore; Drago, Filippo; Bucolo, Claudio

2015-04-01

253

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

Microsoft Academic Search

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

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

1979-01-01

254

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

Microsoft Academic Search

Hybridization of a radiolabeled single-stranded DNA oligonucleotide with its single-stranded complement in vivo has not yet been convincingly demonstrated. A contributing factor may be unfavorable in vivo properties of the phosphodiester and phosphorothioate DNAs. Peptide nucleic acid (PNA) oligomers have been reported to possess in vivo properties more suitable for radiopharmaceutical applications. We have radiolabeled an amine-derivatized 15-base PNA oligomer

G. Mardirossian; K. Lei; M. Rusckowski

1997-01-01

255

Variation, differential reproduction and oscillation: the evolution of nucleic acid hybridization.  

PubMed

This paper builds upon Hans-Jörg Rheinberger ideas on the oscillation and intercalation of epistemic things and technical objects in experimental systems, to give a fine-grained analysis of what here is called the problems of "adaptation" between our material and cognitive tools and the phenomena of the material world. To do so, it relies on the case-study of the evolution of nucleic acid hybridization and the stabilization of satellite DNA. PMID:23888824

Suárez-Díaz, Edna

2013-01-01

256

Luminescent molecular hybrid system derived from 2-furancarboxylic acid and silylated monomer coordinated to rare earth ions  

NASA Astrophysics Data System (ADS)

In this study, silica-based organic-inorganic hybrids were prepared by the sol-gel method. Tetraethoxysilane (abbreviated as TEOS) and a kind of monomer (abbreviated as FA-APES) derived from modified 2-furancarboxylic acid (abbreviated as FA) with (3-aminopropyl)triethoxysilane (abbreviated as APES) were used as the inorganic and organic fragments, respectively. Coordination reaction between lanthanides (europium and terbium ions) and sbnd C dbnd O group of the monomer happened simultaneously. And after days of aging process the resultant materials showed characteristic luminescence of lanthanides. The enhancement of luminescence can be seen by the comparison with simply doped lanthanide hybrid systems. And it can be explained by the coordination ability of the organic counterpart. IR, NMR, UV-vis absorption, low-temperature phosphorescence spectroscopy and fluorescence spectroscopy were applied to characterize and the above spectroscopic data revealed that the triplet state energy of organic ligand matches with the emissive energy level of lanthanides (especially of Tb 3+).

Sui, Yu-Long; Yan, Bing

2006-04-01

257

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

258

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

259

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

PubMed

Porphyrin(Por)-spiropyran(SP) hybrid compounds, including Por-SP dyad, Por-SP2 triad, and Por-SP4 pentad, were prepared and characterized by (1)H NMR, MALDI-TOF MS and UV-Vis spectroscopies. Upon 350 nm UV irradiation of Por-SPn (n=1, 2, 4) in dichloromethane, unusual red-shifted absorption spectra were observed with the colour change from pink into green. Probably due to the protonation of core nitrogens in porphyrin ring, their absorption maxima in dichloromethane were shifted from 418 (Soret band), 515, 550, 590, 645 (four Q bands) nm into 450 and 665 nm. Also, fluorescence maxima were also shifted from 650 and 715 nm to 692 nm. In the other hands, upon irradiation with 350nm UV light in THF, the colour changed from pink into violet and absorption band at 590 nm increased and the fluorescence spectra showed the decrease of 650 and 715 nm bands and increase of 600-640 nm band, due to the normal ring-opening reaction of spiropyran moiety into merocyanine. In the dark, original absorption and fluorescence spectra were recovered very slowly in dichloromethane, but quickly in THF. The reversible photochromic reactions of Por-SPn (n=1, 2, 4) in dichloromethane and THF were investigated by observing absorption and fluorescence spectral changes during UV irradiation or standing in the dark. PMID:24036185

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

2014-01-01

260

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

SciTech Connect

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

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

2011-01-01

261

Combinatorial analysis of mRNA expression patterns in mouse embryos using hybridization chain reaction.  

PubMed

Multiplexed fluorescent hybridization chain reaction (HCR) and advanced imaging techniques can be used to evaluate combinatorial gene expression patterns in whole mouse embryos with unprecedented spatial resolution. Using HCR, DNA probes complementary to mRNA targets trigger chain reactions in which metastable fluorophore-labeled DNA HCR hairpins self-assemble into tethered fluorescent amplification polymers. Each target mRNA is detected by a probe set containing one or more DNA probes, with each probe carrying two HCR initiators. For multiplexed experiments, probe sets for different target mRNAs carry orthogonal initiators that trigger orthogonal DNA HCR amplification cascades labeled by spectrally distinct fluorophores. As a result, in situ amplification is performed for all targets simultaneously, and the duration of the experiment is independent of the number of target mRNAs. We have used multiplexed fluorescent in situ HCR and advanced imaging technologies to address questions of cell heterogeneity and tissue complexity in craniofacial patterning and anterior neural development. In the sample protocol presented here, we detect three different mRNA targets: Tg(egfp), encoding the enhanced green fluorescent protein (GFP) transgene (typically used as a control); Twist1, encoding a transcription factor involved in cell lineage determination and differentiation; and Pax2, encoding a transcription factor expressed in the mid-hindbrain region of the mouse embryo. PMID:25734068

Huss, David; Choi, Harry M T; Readhead, Carol; Fraser, Scott E; Pierce, Niles A; Lansford, Rusty

2015-01-01

262

Refined understanding of sulfur amino acid nutrition in hybrid striped bass, Morone chrysops (male symbol) x M. saxatilis (female symbol)  

E-print Network

Previous studies have indicated the level of total sulfur amino acids (TSAA) (methionine + cystine) is most limiting in practical diet formulations for hybrid striped bass (HSB), especially if animal feedstuffs are replaced with plant feedstuffs...

Kelly, Mark Christopher

2005-08-29

263

Mismatch discrimination in fluorescent in situ hybridization using different types of nucleic acids.  

PubMed

In the past few years, several researchers have focused their attention on nucleic acid mimics due to the increasing necessity of developing a more robust recognition of DNA or RNA sequences. Fluorescence in situ hybridization (FISH) is an example of a method where the use of these novel nucleic acid monomers might be crucial to the success of the analysis. To achieve the expected accuracy in detection, FISH probes should have high binding affinity towards their complementary strands and discriminate effectively the noncomplementary strands. In this study, we investigate the effect of different chemical modifications in fluorescent probes on their ability to successfully detect the complementary target and discriminate the mismatched base pairs by FISH. To our knowledge, this paper presents the first study where this analysis is performed with different types of FISH probes directly in biological targets, Helicobacter pylori and Helicobacter acinonychis. This is also the first study where unlocked nucleic acids (UNA) were used as chemistry modification in oligonucleotides for FISH methodologies. The effectiveness in detecting the specific target and in mismatch discrimination appears to be improved using locked nucleic acids (LNA)/2'-O-methyl RNA (2'OMe) or peptide nucleic acid (PNA) in comparison to LNA/DNA, LNA/UNA, or DNA probes. Further, the use of LNA modifications together with 2'OMe monomers allowed the use of shorter fluorescent probes and increased the range of hybridization temperatures at which FISH would work. PMID:25840566

Silvia, Fontenete; Joana, Barros; Pedro, Madureira; Céu, Figueiredo; Jesper, Wengel; Filipe, Azevedo Nuno

2015-05-01

264

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...

265

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

ERIC Educational Resources Information Center

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

Goodney, David E.

2006-01-01

266

Nitric Acid-Sea Salt Reactions: Implications for Nitrogen Deposition to Water Surfaces  

Microsoft Academic Search

Many previous studies have indicated the importance of nitric acid (HNO3) reactions on sea salt particles for flux divergence of HNO3 in the marine surface layer. The potential importance of this reaction in determining the spatial and temporal patterns of nitrogen dry deposition to marine ecosystems is investigated using models of sea spray generation and particle- and gas-phase dry deposition.

S. C. Pryor; L. L. Sřrensen

2000-01-01

267

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...

268

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

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

269

Nickel superoxide dismutase reaction mechanism studied by hybrid density functional methods.  

PubMed

The reaction mechanism for the disproportionation of the toxic superoxide radical to molecular oxygen and hydrogen peroxide by the nickel-dependent superoxide dismutase (NiSOD) has been studied using the B3LYP hybrid DFT method. Based on the recent X-ray structures of the enzyme in the resting oxidized Ni(III) and X-ray-reduced Ni(II) states, the model investigated includes the backbone spacer of six residues (sequence numbers 1-6) as a structural framework. The side chains of residues His1, Cys2, and Cys6, which are essential for nickel binding and catalysis, were modeled explicitly. The catalytic cycle consists of two half-reactions, each initiated by the successive substrate approach to the metal center. The two protons necessary for the dismutation are postulated to be delivered concertedly with the superoxide radical anions. The first (reductive) phase involves Ni(III) reduction to Ni(II), and the second (oxidative) phase involves the metal reoxidation back to its resting state. The Cys2 thiolate sulfur serves as a transient protonation site in the interim between the two half-reactions, allowing for the dioxygen and hydrogen peroxide molecules to be released in the reductive and oxidative phases, respectively. The His1 side chain nitrogen and backbone amides of the active site channel are shown to be less favorable transient proton locations, as compared to the Cys2 sulfur. Comparisons are made to the Cu- and Zn-dependent SOD, studied previously using similar models. PMID:16756300

Pelmenschikov, Vladimir; Siegbahn, Per E M

2006-06-14

270

Reaction Mechanisms for DBPS Reduction in Humic Acid Ozonation  

Microsoft Academic Search

In this study, XAD-8 resins were used to extract the natural organic matter (NOM) from samples collected at the intake of Feng Yuan Water Treatment Plant (in central Taiwan) into five groups: humic acids, fulvic acids, hydrophobic neutrals, hydrophobic bases, and hydrophilic fractions. Quantitative results show that hydrophobic and hydrophilic fractions contribute 44.2% and 55.5% of NOM, individually. Ozonation processes

Ying-Shih Ma

2004-01-01

271

Dissolution, speciation, and reaction of acetaldehyde in cold sulfuric acid  

Microsoft Academic Search

The uptake of gas-phase acetaldehyde [CH3CHO, ethanal] by aqueous sulfuric acid solutions was studied under upper tropospheric\\/lower stratospheric (UT\\/LS) conditions. The solubility of acetaldehyde was found to be low, between 2 × 102 M atm?1 and 1.5 × 105 M atm?1 under the ranges of temperature (211–241 K) and acid composition (39–76 weight percent, wt%, H2SO4) studied. Under most conditions,

Rebecca R. Michelsen; Samantha F. M. Ashbourn; Laura T. Iraci

2004-01-01

272

Dissolution, speciation, and reaction of acetaldehyde in cold sulfuric acid  

Microsoft Academic Search

The uptake of gas-phase acetaldehyde [CH3CHO, ethanal] by aqueous sulfuric acid solutions was studied under upper tropospheric\\/lower stratospheric (UT\\/LS) conditions. The solubility of acetaldehyde was found to be low, between 2 × 102 M atm-1 and 1.5 × 105 M atm-1 under the ranges of temperature (211-241 K) and acid composition (39-76 weight percent, wt%, H2SO4) studied. Under most conditions,

Rebecca R. Michelsen; Samantha F. M. Ashbourn; Laura T. Iraci

2004-01-01

273

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

274

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

275

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

PubMed

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. PMID:16729803

Ayers, Paul W; Parr, Robert G; Pearson, Ralph G

2006-05-21

276

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

NASA Astrophysics Data System (ADS)

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.

2006-05-01

277

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

278

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

NASA Technical Reports Server (NTRS)

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

Zieboll, Gerhard; Orgel, Leslie E.

1994-01-01

279

Phenylhydeazones of ?-keto acids, containing the isoxazoline ring, and their anomalous behavior in the feofilaktov reaction  

Microsoft Academic Search

1.The reaction of the esters of phenylazoacetonedicarboxylic acid with hydroxylamine gave three products in ratios that depended on the structure of the radical of the ester group: the esters of the phenyl-hydrazone of 2-isoxazolin-5-on-3-ylglyoxylic acid (IIa), the esters of 4-phenylazo-3-isoxazolin-5-on-3-ylacetic acid (III), and 2-phenyl-4-carbalkoxymethyl-5-carbalkoxytriazoles (IV).2.The phenylhydrazones (II) and phenylazo compounds (III), which contain an isoxazoline ring, are resistant to chemical

V. M. Belikov; T. F. Savel'eva; E. N. Safonova

1973-01-01

280

?-Linolenic acid-rich triacylglycerols derived from borage oil via lipase-catalyzed reactions  

Microsoft Academic Search

?-Linolenic acid (GLA), a precursor of arachidonic acid, possesses physiological functions of modulating immune and inflammatory\\u000a response. Highly purified GLA is desired both as a medicine and as an ingredient of cosmetics. In this work, urea fractionation\\u000a and lipase-catalyzed reactions were employed for the enrichment of GLA in borage oil. GLA content in free fatty acids from\\u000a saponified borage oil

Fang-Cheng Huang; Yi-Hsu Ju; Jen-Chung Chiang

1999-01-01

281

Disproportionation of abietic acid: I. Iodine catalyzed reaction at low temperature  

Microsoft Academic Search

Disproportionation of abietic acid in the presence of equimolar iodine was carried out in benzene at 60 C, and the reaction\\u000a products were continuously determined by gas-liquid chromatography as methyl esters. The major peaks were isolated and characterized\\u000a by mass, infrared, and nuclear magnetic resonance spectrometry. Four isomers of dihydroabietic acids, dehydroabietic acid,\\u000a and small amounts of lactones were detected.

M. Ishigami; K. Yamane; T. Agawa; Y. Ohshiro; I. Ikeda

1976-01-01

282

Characterization of Terebinth Fruit Oil and Optimization of Acidolysis Reaction with Caprylic and Stearic Acids  

Microsoft Academic Search

Characterization of the fatty acid and triacylglycerol composition of terebinth fruit oil and the synthesis of structured\\u000a lipids (SL) were performed in this study. Interesterification reaction of terebinth fruits oil (Pistacia terebinthus L.) with caprylic acid (CA) and stearic acid (SA) to produce a SL was performed in n-hexane using immobilized sn-1,3 specific lipase from Mucor miehei. The effect of

Derya KocakHasene; Hasene Keskin; Sibel Fad?lo?lu; Boleslaw Kowalski; Fahrettin Gö?ü?

283

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

PubMed

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

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

2015-04-15

284

Photo-induced ring-expansion reactions mediated by B12-TiO2 hybrid catalyst.  

PubMed

Vitamin B(12)-TiO(2) heterogeneous hybrid catalyst (B(12)-TiO(2)) mediated ring-expansion reactions and their reaction mechanism were clarified by various spectroscopic methods. Diffuse reflectance UV/VIS (DR-UV/VIS) studies showed that B(12)-TiO(2) was activated to form the supernucleophilic Co(I) species of B(12) by irradiation with ultraviolet light. DR-UV/VIS and electron spin resonance (ESR) studies then elucidated the formation of the photo-sensitive intermediate on heterogeneous surfaces. The photo-excited B(12)-TiO(2) catalyzed ring-expansion reactions were efficient and eco-friendly. This catalytic efficiency was strongly dependent on the kind of solvent. The oxidation reaction of the solvent by holes at TiO(2) nanoparticle surfaces had a crucial role in the overall catalytic reaction. PMID:20449460

Izumi, Shin-ichiro; Shimakoshi, Hisashi; Abe, Masaaki; Hisaeda, Yoshio

2010-04-01

285

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

286

Atmospheric chemistry of hydrazoic acid (HN3): UV absorption spectrum, HO reaction rate, and reactions of the N3 radical.  

PubMed

Processes related to the tropospheric lifetime and fate of hydrazoic acid, HN3, have been studied. The ultraviolet absorption spectrum of HN3 is shown to possess a maximum near 262 nm with a tail extending to at least 360 nm. The photolysis quantum yield for HN3 is shown to be approximately 1 at 351 nm. Using the measured spectrum and assuming unity quantum yield throughout the actinic region, a diurnally averaged photolysis lifetime near the earth's surface of 2-3 days is estimated. Using a relative rate method, the rate coefficient for reaction of HO with HN3 was found to be (3.9 +/-0.8) x 10(-12) cm3 molecule(-1) s(-1), substantially larger than the only previous measurement. The atmospheric HN3 lifetime with respect to HO oxidation is thus about 2-3 days, assuming a diurnally averaged [HO] of 10(6) molecule cm(-3). Reactions of N3, the product of the reaction of HO with HN3, were studied in an environmental chamber using an FTIR spectrometer for end-product analysis. The N3 radical reacts efficiently with NO, producing N2O with 100% yield. Reaction of N3 with NO2 appears to generate both NO and N2O, although the rate coefficient for this reaction is slower than that for reaction with NO. No evidence for reaction of N3 with CO was observed, in contrast to previous literature data. Reaction of N3 with O2 was found to be extremely slow, k < 6 x 10(-20) cm3 molecule(-1) s(-1), although this upper limit does not necessarily rule out its occurrence in the atmosphere. Finally, the rate coefficient for reaction of Cl with HN3 was measured using a relative rate method, k = (1.0+/-0.2) x 10(-12) cm3 molecule(-1) s(-1). PMID:15819219

Orlando, John J; Tyndall, Geoffrey S; Betterton, Eric A; Lowry, Joe; Stegall, Steve T

2005-03-15

287

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

NASA Astrophysics Data System (ADS)

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

Hicks, Jason Christopher

288

Photochromic polyelectrolyte-surfactant complexes via acid-base reactions  

Microsoft Academic Search

Polyelectrolytesurfactant complexes of tetradecyltrimethylammonium polyacrylate were formed from stoichiometric amounts of polyacrylic acid and tetradecyltrimethylammonium hydroxide in methanol. Photochromicity was introduced by exchanging a few percent of tetradecyltrimethylammonium hydroxide by various stilbazolium hydroxides. The materials obtained showed photochromic properties. Optical anisotropy due to mesogenic behavior was not found in dried samples, but appeared upon exposure to air. Certain changes in

Bernhard KLAUßNER; Jens Frommel; Thomas Wolff

1999-01-01

289

Redox Reactions in Wheat Dough as Affected by Ascorbic Acid  

Microsoft Academic Search

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

W. Grosch; H. Wieser

1999-01-01

290

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

291

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

292

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

Code of Federal Regulations, 2014 CFR

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

2014-07-01

293

Comparison of collision-induced dissociation and electron-induced dissociation of singly protonated aromatic amino acids, cystine and related simple peptides using a hybrid linear ion trap–FT-ICR mass spectrometer  

Microsoft Academic Search

The gas-phase fragmentation reactions of singly protonated aromatic amino acids, their simple peptides as well as simple models for intermolecular disulfide bonds have been examined\\u000a using a commercially available hybrid linear ion trap–Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer.\\u000a Low-energy collision-induced dissociation (CID) reactions within the linear ion trap are compared with electron-induced dissociation\\u000a (EID) reactions within the FT-ICR

Hadi Lioe; Richard A. J. O’Hair

2007-01-01

294

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

PubMed

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

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

2012-05-01

295

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

296

Miniature reaction chamber and devices incorporating same  

DOEpatents

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

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

2000-10-17

297

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

PubMed

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

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

2013-09-01

298

Sensitive and Specific Detection of Mycoplasma species by Consensus Polymerase Chain Reaction and Dot Blot Hybridization.  

PubMed

Mycoplasmas are highly fastidious bacteria, difficult to culture and slow growing. Many species of mycoplasmas are important pathogens that cause respiratory infection in laboratory animals and that are known to affect experimental results obtained with contaminated animals. The aim of the present study was to develop a sensitive and specific assay for the detection of mycoplasma species. To this end, we developed a polymerase chain reaction and dot blot hybridization assay (PCR/DBH) for detecting mycoplasma DNA and evaluated it for its sensitivity and specificity. Mycoplasma consensus primer pairs were used for the amplification of target DNA. When PCR product was visually detected, the limit of detection of the PCR test was 10(2) pg of mycoplasma purified DNA. For DBH, the amplified DNA was labeled by incorporation of digoxigenin (DIG). This DIG-labeled probe was capable of detecting 10(4) pg of purified mycoplasma DNA by DBH. PCR/DBH was more sensitive than PCR or DBH alone and was also very specific. Our PCR/DBH assay can be applied efficiently to confirm the presence of mycoplasma species on clinical samples and to differentiate between mycoplasma species infection and other bacterial infections. PMID:21826174

Hong, Sunhwa; Lee, Hyun-A; Park, Sang-Ho; Kim, Okjin

2011-06-01

299

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

PubMed

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

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

2015-02-20

300

Hybridization chain reaction-based fluorescence immunoassay using DNA intercalating dye for signal readout.  

PubMed

A novel format of fluorescence immunosorbent assay based on the hybridization chain reaction (HCR) using a DNA intercalating dye for signal readout was constructed for the sensitive detection of targets, both in competitive and sandwich modes. In this platform, the capture and recognition processes are based on immunoreactions and the signal amplification depends on the enzyme-free, isothermal HCR-induced labelling event. After a competitive or a sandwich immunoreaction, a biotinylated capture DNA was bound to a biotinylated signal antibody through avidin, and triggered the HCR by two specific hairpins into a nicked double helix. Gene Finder (GF), a fluorescent probe for double-strand DNA, was intercalated in situ into the amplified chain to produce the fluorescence signal. The limit of detection (LOD) for rabbit IgG in competitive mode by HCR/GF immunoassay was improved at least 100-fold compared with the traditional fluorescence immunoassay using the fluorescein isothiocyanate-labelled-streptavidin or fluorescein isothiocyanate-labelled second antibody as the signal readout. The proposed fluorescence immunoassay was also demonstrated by using ?-fetoprotein as the model target in sandwich mode, and showed a wide linear range from 28 ng mL(-1) to 20 ?g mL(-1) with a LOD of 6.0 ng mL(-1). This method also showed satisfactory analysis in spiked human serum, which suggested that it might have great potential for versatile applications in life science and point-of-care diagnostics. PMID:24828400

Deng, Yan; Nie, Ji; Zhang, Xiao-hui; Zhao, Ming-Zhe; Zhou, Ying-Lin; Zhang, Xin-Xiang

2014-07-01

301

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

PubMed Central

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

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

2013-01-01

302

Hybrid poly(lactic-co-glycolic acid) nanoparticles: design and delivery prospectives.  

PubMed

Poly(lactic-co-glycolic acid) (PLGA), a US Food and Drug Administration (FDA)-approved copolymer, has been exploited widely in the design of nanoparticles because it is biodegradable, biocompatible, protects the drug molecules from degradation, and aids in producing sustained and targeted delivery. However, certain constraints associated with PLGA nanoparticles, such as poor drug encapsulation, polymer degradation, and scale-up issues, have led to the development of emerging hybrid PLGA delivery systems. These hybrid nanoparticles are core-shell nanostructures comprising either a PLGA core or a PLGA shell combining multiple functionalities within one system and, thus, exhibiting the complementary characteristics of two different platforms used for the delivery of a wide range of therapeutics and imaging. PMID:25277320

Pandita, Deepti; Kumar, Sandeep; Lather, Viney

2015-01-01

303

Acid–base reactions on alumina-supported niobia  

Microsoft Academic Search

Catalysts containing from 8 to 28%wt. of niobia supported on ?-alumina by impregnation with niobium pentaethoxide solutions were characterized by infrared spectroscopy of adsorbed pyridine as a probe for acidic sites and CO2 adsorption as a probe for basic sites. The catalysts had their activity measured in isopropanol dehydration at 453K, 1-butene isomerization at 348K and in cumene dealkylation at

Mona A. Abdel-Rehim; Ana Carlota B. dos Santos; Vera Lúcia L. Camorim; Arnaldo da Costa Faro

2006-01-01

304

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

305

The dietary branched chain amino acid requirements of hybrid striped bass(Morone chrysops x M. saxatilis)  

Technology Transfer Automated Retrieval System (TEKTRAN)

The requirements for branched chain amino acids (BCAAs) are unknown in hybrid striped bass and necessary for formulating efficient and nutritious diets. Moreover, the dietary balance among these three amino acids can substantially influence the performance of meat animals fed those diets. The diet...

306

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

307

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

308

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

2013-11-01

309

Sulfonic and phosphonic acid and bifunctional organic-inorganic hybrid membranes and their proton conduction properties.  

PubMed

Hybrid organic-inorganic approaches are used for the synthesis of bifunctional proton exchange membrane fuel cell (PEMFC) membranes owing to their ability to combine the properties of a functionalized inorganic network and an organic thermostable polymer. We report the synthesis of both sulfonic and phosphonic acid functionalized mesostructured silica networks into a poly(vinylidenefluoride-co-hexafluoropropylene) (poly(VDF-co-HFP) copolymer. These membranes, containing different amounts of phosphonic acid and sulfonic acid groups, have been characterized using FTIR and NMR spectroscopy, SA-XRD, SAXS, and electrochemical techniques. The proton conductivity of the bifunctional hybrid membranes depends strongly on hydration, increasing by two orders of magnitude over the relative humidity (RH) range of 20 to 100%, up to a maximum of 0.031 S cm(-1) at 60 °C and 100% RH. This value is interesting as only half of the membrane conducts protons. This approach allows the synthesis of a porous SiO(2) network with two different functions, having -SO(3)H and -PO(3)H(2) embedded in a thermostable polymer matrix. PMID:21850711

Sel, Ozlem; Azais, Thierry; Maréchal, Manuel; Gébel, Gérard; Laberty-Robert, Christel; Sanchez, Clément

2011-11-01

310

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

SciTech Connect

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

Sills, J.A.

1995-07-01

311

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

312

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

PubMed Central

Abstract Delivery inside the cells is essential for practical application of antisense technologies. The hybrid locked nucleic acid (LNA)/DNA CAAGTACTGTTCCACCA (LNA residues are underlined) was labeled by conjugation to Alexa Fluor 488 (fLNA/DNA) and tested to determine its ability to penetrate Escherichia coli cells and reach the cytoplasm. Flow cytometry analysis showed that the fLNA/DNA was associated with 14% of cells from a stationary phase culture, while association with a labeled isosequential oligodeoxynucleotide was negligible. Laser scanning confocal microscopy confirmed that the fLNA/DNA was located inside the cytoplasm. PMID:23515318

Traglia, German M.; Sala, Carol Davies; Fuxman Bass, Juan I.; Soler-Bistué, Alfonso J.C.; Zorreguieta, Angeles; Ramírez, María Soledad

2012-01-01

313

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

PubMed

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

Taguchi, Takeo; Saito, Akio; Yanai, Hikaru

2007-01-01

314

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

PubMed Central

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

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

2014-01-01

315

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

316

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

Code of Federal Regulations, 2014 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...

2014-07-01

317

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

318

Heterogeneous reactions of gaseous methanesulfonic acid with calcium carbonate and kaolinite particles  

Microsoft Academic Search

Heterogeneous reactions of gaseous methanesulfonic acid (MSA) with calcium carbonate (CaCO3) and kaolinite particles at room temperature were investigated using diffuse reflectance infrared Fourier transform spectroscopy\\u000a (DRIFTS) and ion chromatography (IC). Methanesulfonate (MS?) was identified as the product in the condensed phase, in accordance with the product of the reaction of gaseous MSA with\\u000a NaCl and sea salt particles. When

MingJin Tang; MengQiu Li; Tong Zhu

2010-01-01

319

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

PubMed

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

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

2012-11-13

320

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

PubMed Central

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

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

2012-01-01

321

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

322

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. PMID:21822337

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

323

Hybrid Quantum Mechanics/Molecular Mechanics-Based Molecular Dynamics Simulation of Acid-Catalyzed Dehydration of Polyols in Liquid Water  

SciTech Connect

We use the conversion of protonated glycerol to acrolein for a case study of the mechanism of acid-catalyzed dehydration of polyols in aqueous environments. We employ hybrid Quamtum Mechanics/Molecular Mechanics Molecular Dynamics (QM/MM MD) simulations with biased sampling and perform free energy calculations for the elementary steps of the reaction. We investigate the effects of solvent dynamics and in particular the role of quantum mechanical water in the dehydration mechanism. We present results supporting a mechanism that proceeds via water-mediated proton transfers and thus through an enol intermediate. We find that the first dehydration may take place by two, low-energy pathways requiring, respectively, 20.9 and 18.8 kcal/mol of activation free energy. The second dehydration requires 19.9 kcal/mol of activation free energy while for the overall reaction we compute a free energy change of ?8 kcal/mol.

Caratzoulas, Stavros [Catalysis Center for Energy Innovation, Univ. of Delaware, Newark, DE (United States); Courtney, Timothy [Univ. of Delaware, Newark, DE (United States); Vlachos, Dionisios G. [Catalysis Center for Energy Innovation, Univ. of Delaware, Newark, DE (United States)

2011-08-18

324

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

SciTech Connect

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

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

2012-11-01

325

Bifunctional acid–base catalyzed reactions in zeolites from the HSAB viewpoint  

Microsoft Academic Search

The applicability of the hard and soft acids and bases principle is investigated for the interaction of 5T zeolite clusters with probe molecules such as chloromethane, methanol and olefins. The reactions are intermediately hard–hard and, therefore, mainly charge-controlled. This is confirmed by the success of the atomic charges and the electrostatic interaction energy at the acid site as correct descriptors

K. Hemelsoet; D. Lesthaeghe; V. Van Speybroeck; M. Waroquier

2006-01-01

326

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

Microsoft Academic Search

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

Arthur L. Weber

1991-01-01

327

Microchemistry: time dependence of an acid-base reaction in a single optically levitated microdroplet  

Microsoft Academic Search

Combining the optical levitation technique with Raman spectroscopy we were able to derive information on the chemical reaction of an acid microdroplet (droplet radius 7.5 ?m) when exposed to ammonia. Of particular help were morphology-dependent resonances which are superimposed on the Raman spectrum, to follow the progress of growth and thickness of a salt coating performed by the microchemical acid-base

M. Trunk; J. Popp; M. Lankers; W. Kiefer

1997-01-01

328

Acid\\/base reactions and Al(III) complexation at the surface of goethite  

Microsoft Academic Search

Acid\\/base reactions and Al(III) complexation at the geothite-solution interface have been investigated at 298.2 K in NaNOâ solutions at a constant ionic strength of 0.1 M. Equilibrium measurements were performed as potentiometric titrations using a glass electrode. The experimental data were evaluated on the basis of the constant capacitance model. The acid\\/base properties are described by the equilibria and the

L. Loevgren; S. Sjoeberg; P. W. Schindler

1990-01-01

329

Acid\\/base reactions and Al(III) complexation at the surface of goethite  

Microsoft Academic Search

Acid\\/base reactions and Al(III) complexation at the goethite-solution interface have been investigated at 298.2 K in NaNO 3 solutions at a constant ionic strength of 0.1 M. Equilibrium measurements were performed as potentiometric titrations using a glass electrode. The experimental data were evaluated on the basis of the constant capacitance model. The acid\\/base properties are described by the equilibria and

Lars Lövgren; Staffan Sjöberg; Paul W. Schindler

1990-01-01

330

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

331

Silver-Based Hybrid Materials from meta- or para-Phosphonobenzoic Acid: Influence of the Topology on Silver Release in Water.  

PubMed

Three novel silver-based metal-organic frameworks materials, which were synthesized from either 3-phosphono or 4-phosphonobenzoic acid and silver nitrate, are reported. The novel hybrids were synthesized under hydrothermal conditions; the pH of the reaction media was controlled by adding different quantities of urea thereby producing different topologies. Compound 1 (Ag3(4-PO3-C6H4-COO)), synthesized in the presence of urea, exhibits a compact 3D structure in which both phosphonic acid and carboxylic acid functional groups are linked to the silver-based inorganic network. Compound 2 (Ag(4-PO3H-C6H4-COOH)), which was synthesized at lower pH (without urea), has a layered structure in which only the phosphonic acid functional groups from 4-phosphonobenzoic acid moieties are linked to the silver inorganic network; the carboxylic acid groups being engaged in hydrogen bonds. Finally, material 3 (Ag(3-PO3H-C6H4-COOH)) was synthesized from 3-phosphonobenzoic acid and silver nitrate without urea. This material 3 features a layered structure exhibiting carboxylic acid functional groups linked via hydrogen bonds in the interlayer space. After the full characterization of these materials (single X-ray structure, IR, TGA), their ability to release silver salts in aqueous environment was measured. Silver release, determined in aqueous solution by cathodic stripping voltammetry, shows that the silver release capacity of these materials is dependent on the topology of the hybrids. The more compact structure 1 is extremely stable in water with only trace levels of silver ions being detected. On the other hand, compounds 2 and 3, in which only the phosphonic acid functional groups were bonded to the inorganic network, released larger quantities of silver ions into aqueous solution. These results which were compared with the silver release of the previously described compound 4 (Ag6(3-PO3-C6H4-COO)2). The results clearly show that the release capacity of silver-based metal organic framework can be tuned by modifying their topology which, in the present study, is governed by the regio-isomer of the organic precursor and the synthetic conditions under which the hybrids are prepared. PMID:25679328

Rueff, Jean-Michel; Perez, Olivier; Caignaert, Vincent; Hix, Gary; Berchel, Mathieu; Quentel, François; Jaffrčs, Paul-Alain

2015-03-01

332

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

333

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

PubMed

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

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

2014-09-01

334

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

PubMed Central

Molecular hybridization techniques were developed for the detection and surveillance of bluetongue virus (BTV) serotype 17 in the insect vector Culicoides variipennis, a biting midge. Radiolabeled RNA and cDNA probes were generated from sequences of the L3 segment of BTV serotype 17. These probes were used to detect BTV RNA in pools of infected C. variipennis by hybridizing the probes directly to analyte immobilized on nylon membranes or by using a nucleic acid sandwich hybridization test. Hybridization procedures were able to detect 1 infected C. variipennis in a pool of 50 and as little as 3.55 log10 50% tissue culture infective doses per ml of virus. These hybridization techniques provide an alternative to virus isolation for the surveillance of BTV in vector populations. Images PMID:2172294

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

1990-01-01

335

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

336

Substituent Effects on the Reactions of Diarylgermylenes and Tetraaryldigermenes with Acetic Acid and Other Lewis Bases in  

E-print Network

Substituent Effects on the Reactions of Diarylgermylenes and Tetraaryldigermenes with Acetic Acid that involve initial nucleophilic attack at germanium in all cases. The Lewis acid-base complexation facile insertion into the O-H bonds of alcohols and carboxylic acids, form Lewis acid-base complexes

Leigh, William J.

337

Is trichloroacetic acid an insufficient sample quencher of redox reactions?  

PubMed

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

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

2013-03-01

338

Thermo-, pH-, and light-responsive poly(N-isopropylacrylamide-co-methacrylic acid)--Au hybrid microgels prepared by the in situ reduction method based on Au-thiol chemistry.  

PubMed

In recent years, it has been an attractive challenge to fabricate multiple stimuli-responsive hybrid microgels composed of polymer microgel and gold nanoparticle (AuNP). Herein, we report on the detailed synthesis of poly(N-isopropylacrylamide-co-methacrylic acid)--Au hybrid microgels by in situ reduction of gold precursor in the presence of thiol-functionalized poly(N-isopropylacrylamide-co-methacrylic acid) microgels. The as-synthesized hybrid microgels showed well-defined swelling/deswelling transition in response to the surrounding temperature, pH, and light irradiation. The hybrid microgels had a unique microstructure where a large number of AuNP's distribute mainly in the interior of microgel with a fluff-like surface. The plasmonic property of the hybrid microgels can be modulated through the volume phase transition induced by the external triggers such as temperature and pH. In the reduction of 4-nitrophenol catalyzed by the hybrid microgels, it was found that the reaction rate did not increase monotonously with temperature but greatly decreased in a certain temperature range, showing a tunable catalytic activity. PMID:24897339

Shi, Shan; Wang, Qianman; Wang, Tao; Ren, Shuping; Gao, Yu; Wang, Na

2014-06-26

339

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

340

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

Microsoft Academic Search

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

A. Corma

1995-01-01

341

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

Microsoft Academic Search

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

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

1999-01-01

342

Bifunctional acid base catalyzed reactions in zeolites from the HSAB viewpoint  

NASA Astrophysics Data System (ADS)

The applicability of the hard and soft acids and bases principle is investigated for the interaction of 5T zeolite clusters with probe molecules such as chloromethane, methanol and olefins. The reactions are intermediately hard-hard and, therefore, mainly charge-controlled. This is confirmed by the success of the atomic charges and the electrostatic interaction energy at the acid site as correct descriptors of regio-selectivity and reactivity sequences. Both acid and basic reactive sites can be clearly indicated using frontier orbitals. Moreover, an excellent correlation is found between the activation hardnesses and the energy barriers at the absolute zero.

Hemelsoet, K.; Lesthaeghe, D.; Speybroeck, V. Van; Waroquier, M.

2006-02-01

343

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

SciTech Connect

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

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

1997-01-15

344

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

E-print Network

. Numerical simulations support the experimental findings. INTRODUCTION In 1952 Alan Turing suggested thatTarget Turing Patterns and Growth Dynamics in the Chlorine Dioxide-Iodine-Malonic Acid Reaction University, Waltham, Massachusetts 02454-9110, United States ABSTRACT: We study the growth dynamics of Turing

Epstein, Irving R.

345

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

346

Chemical modification of carbon fiber surfaces by nitric acid oxidation followed by reaction with tetraethylenepentamine  

Microsoft Academic Search

Amino groups react rapidly with both isocyanates and epoxides. Thus, to prepare carbon fibers which might exhibit enhanced adhesion to both polyurethanes and epoxy resin matrices, attempts were made to introduce a high surface amine concentration onto high-strength carbon fibers (derived from PAN) by nitric acid oxidation followed by reaction with excess tetraethylenepentamine (TEPA). Fibers were oxidized with concentrated (70%)

C. U. Pittman; G.-R. He; B. Wu; S. D. Gardner

1997-01-01

347

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

E-print Network

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

Epstein, Irving R.

348

Nickel salt-catalyzed addition reaction of arylboronic acids to aromatic aldehydes  

Microsoft Academic Search

Arylation reaction of aromatic aldehydes with arylboronic acids proceeded smoothly in the presence of a base and catalytic amount of a nickel salt, Ni(ClO4)2·6H2O, in toluene\\/IPA=5:1 or IPA to afford corresponding diarylmethanols in good to excellent yields.

Li Zhou; Xin Du; Ren He; Zhenhua Ci; Ming Bao

2009-01-01

349

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

Microsoft Academic Search

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

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

1994-01-01

350

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

SciTech Connect

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

Wolff, E.W.; Mulvaney, R.

1991-06-01

351

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

PubMed

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

Li, Fei; Liu, Jun; Rozovsky, Sharon

2014-11-01

352

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

PubMed Central

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

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

2014-01-01

353

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

354

Aptamer-based organic-silica hybrid affinity monolith prepared via "thiol-ene" click reaction for extraction of thrombin.  

PubMed

A novel strategy for preparing aptamer-based organic-silica hybrid monolithic column was developed via "thiol-ene" click chemistry. Due to the large specific surface area of the hybrid matrix and the simplicity, rapidness and high efficiency of "thiol-ene" click reaction, the average coverage density of aptamer on the organic-silica hybrid monolith reached 420pmol?L(-1). Human ?-thrombin can be captured on the prepared affinity monolithic column with high specificity and eluted by NaClO4 solution. N-p-tosyl-Gly-Pro-Arg p-nitroanilide acetate was used as the sensitive chromogenic substrate of thrombin. The thrombin enriched by this affinity column was detected with a detection of limit of 0.01?M by spectrophotometry. Furthermore, the extraction recovery of thrombin at 0.15?M in human serum was 91.8% with a relative standard deviation of 4.0%. These results indicated that "thiol-ene" click chemistry provided a promising technique to immobilize aptamer on organic-inorganic hybrid monolith and the easily-assembled affinity monolithic material could be used to realize highly selective recognition of trace proteins. PMID:25863371

Wang, Zheng; Zhao, Jin-Cheng; Lian, Hong-Zhen; Chen, Hong-Yuan

2015-06-01

355

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

356

Formation of volatile organics in the reaction of solid stearic acid with gas-phase OH  

NASA Astrophysics Data System (ADS)

While in the atmosphere organic particles are continuously exposed to atmospheric oxidants and could undergo chemical transformations. As a result of oxidation initially long carbon chains could be broken forming smaller, more volatile molecules that could eventually leave the condensed aerosol phase. In this work this process is studied using stearic acid as a proxy for organic aerosol matter and OH radicals as the oxidant. The experiments are conducted using a coated-wall, flow-tube reactor coupled to both chemical ionization and a proton transfer mass spectrometers (for detection of OH and VOCs, respectively). The results indicate a rapid reaction of OH with stearic acid which is in agreement with previous studies. The majority of volatile products are identified as aldehydes and aldehydic acids. The quantitative product yield depends on concentrations of oxygen and nitrogen dioxide in the flow, which could be linked to the reaction mechanism.

Vlasenko, A.; Abbatt, J.

2006-12-01

357

Infrared studies of the reaction of methanesulfonic acid with trimethylamine on surfaces.  

PubMed

Organosulfur compounds generated from a variety of biological as well as anthropogenic sources are oxidized in air to form sulfuric acid and methanesulfonic acid (MSA). Both of these acids formed initially in the gas phase react with ammonia and amines in air to form and grow new particles, which is important for visibility, human health and climate. A competing sink is deposition on surfaces in the boundary layer. However, relatively little is known about reactions after they deposit on surfaces. We report here diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) studies of the reaction of MSA with trimethylamine (TMA) on a silicon powder at atmospheric pressure in synthetic air and at room temperature, either in the absence or in the presence of water vapor. In both cases, DRIFTS spectra of the product surface species are essentially the same as the transmission spectrum obtained for trimethylaminium methanesulfonate, indicating the formation of the salt on the surface with a lower limit to the reaction probability of ? > 10(-6). To the best of our knowledge, this is the first infrared study to demonstrate this chemistry from the heterogeneous reaction of MSA with an amine on a surface. This heterogeneous chemistry appears to be sufficiently fast that it could impact measurements of gas-phase amines through reactions with surface-adsorbed acids on sampling lines and inlets. It could also represent an additional sink for amines in the boundary layer, especially at night when the gas-phase reactions of amines with OH radical and ozone are minimized. PMID:24304088

Nishino, Noriko; Arquero, Kristine D; Dawson, Matthew L; Finlayson-Pitts, Barbara J

2014-01-01

358

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

359

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

Microsoft Academic Search

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

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

2000-01-01

360

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

PubMed Central

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

Bertoldi, M; Borri Voltattorni, C

2000-01-01

361

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

NASA Astrophysics Data System (ADS)

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

Yang, Ling

362

Methanol Reaction with Sulfuric Acid: A Vibrational Spectroscopic Study Lisa L. Van Loon and Heather C. Allen*  

E-print Network

Methanol Reaction with Sulfuric Acid: A Vibrational Spectroscopic Study Lisa L. Van Loon 43210 ReceiVed: May 27, 2004; In Final Form: August 19, 2004 The reaction between methanol and sulfuric peak in the 800 cm-1 region, not present in either the neat methanol or concentrated sulfuric acid

363

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

E-print Network

Decomposition of the permanganate/oxalic acid overall reaction to elementary steps based on integer/oxalic acid into elementary steps is presented. The decomposition process was based on integer programming to obtain chemically acceptable decompositions of the overall autocatalytic reaction permanganate

Tóth, János

364

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

E-print Network

Cluster Phase Chemistry: Gas-Phase Reactions of Anionic Sodium Salts of Dicarboxylic Acid Clusters energy of the cluster correlate well with the cluster phase reactions of oxalate and malonate clusters component of sea salt particles in the atmosphere,12,13 forming sodium dicarboxylic acid clusters. Previous

Goddard III, William A.

365

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

366

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

NASA Astrophysics Data System (ADS)

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

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

2008-08-01

367

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

PubMed

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

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

2014-08-01

368

Differentiation of respiratory syncytial virus subgroups with cDNA probes in a nucleic acid hybridization assay.  

PubMed Central

A new approach to respiratory syncytial (RS) virus subgroup determination was developed by using a simple nucleic acid filter hybridization technique. By this method, virus-infected cells are bound and fixed in a single step, and the viral RNA in the fixed-cell preparation is characterized directly by its ability to hybridize to cDNA probes specific for either the A or B subgroups of RS virus. The subgroup-specific probes were constructed from cDNA clones that corresponded to a portion of the extracellular domain of the RS virus G protein of either a subgroup B RS virus (8/60) or a subgroup A RS virus (A2). The cDNA probes were labeled with 32P and used to analyze RS virus isolates collected over a period of three decades. Replicate templates of infected cell preparations were hybridized with either the subgroup A or B probe. The subgroup assignments of 40 viruses tested by nucleic acid hybridization were in agreement with the results of subgroup determinations based on their reactivities with monoclonal antibodies, which previously has been the only method available for determining the subgroup classification of RS virus isolates. The nucleic acid hybridization assay has the advantage of providing broad-based discrimination of the two subgroups on the basis of nucleic acid homology, irrespective of minor antigenic differences that are detected in assays in which monoclonal antibodies are used. The nucleic acid hybridization technique provides a reliable method for RS virus subgroup characterization. Images PMID:2118548

Sullender, W M; Anderson, L J; Anderson, K; Wertz, G W

1990-01-01

369

Acid-catalyzed transformation of ionophore veterinary antibiotics: reaction mechanism and product implications.  

PubMed

Ionophore antibiotics (IPAs) are polyether antimicrobials widely used in the livestock industry and may enter the environment via land application of animal waste and agricultural runoff. Information is scarce regarding potential transformation of IPAs under environmental conditions. This study is among the first to identify the propensity of IPAs to undergo acid-catalyzed transformation in mildly acidic aquatic systems and characterize the reactions in depth. The study focused on the most widely used monensin (MON) and salinomycin (SAL), and also included narasin (NAR) in the investigation. All three IPAs are susceptible to acid-catalyzed transformation. MON reacts much more slowly than SAL and NAR and exhibits a different kinetic behavior that is further evaluated by a reversible reaction kinetic model. Extensive product characterization identifies that the spiro-ketal group of IPAs is the reactive site for the acid-catalyzed hydrolytic transformation, yielding predominantly isomeric and other products. Toxicity evaluation of the transformation products shows that the products retain some antimicrobial properties. The occurrence of IPAs and isomeric transformation products is also observed in poultry litter and agricultural runoff samples. Considering the common presence of mildly acidic environments (pH 4-7) in soils and waters, the acid-catalyzed transformation identified in this study likely plays an important role in the environmental fate of IPAs. PMID:23373828

Sun, Peizhe; Yao, Hong; Minakata, Daisuke; Crittenden, John C; Pavlostathis, Spyros G; Huang, Ching-Hua

2013-07-01

370

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

PubMed

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

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

2014-08-19

371

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

SciTech Connect

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

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

1988-01-01

372

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

PubMed Central

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

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

2010-01-01

373

Neutral and acidic hydrolysis reactions of the third generation anticancer drug oxaliplatin.  

PubMed

The hydrolysis of oxaliplatin, a third generation anticancer drug, is expected to play an important role in the activation of this compound before it reaches DNA. The first and second hydrolysis corresponding to the addition of the first water molecule concomitant with the ring-opening, followed by addition of a second water and loss of the monodentate oxalato ligand, respectively, were studied combining density functional theory (DFT) with the conductor-like dielectric continuum model (CPCM) approach. The reaction was studied in neutral and acidic conditions, and all stationary points have been identified. The computed potential energy surfaces show that, for the neutral hydrolysis, the ring-opening reaction is the rate-limiting process, with an activation barrier of about 28 kcal/mol. For the acid degradation in water, according to experimental data, the reaction is expected to proceed in a faster biphasic process, and the rate-limiting process is the ligand detachment that occurs with a barriers of about 22 kcal/mol. According to the calculated results, we expect that the reaction is favored in acidic conditions and that the monoaquated complex should be the species reacting with DNA. PMID:19143575

Lucas, Maria Fatima A; Pavelka, Mateij; Alberto, Marta E; Russo, Nino

2009-01-22

374

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

PubMed

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 H(2)O(2) while decomposing the substrate and the CL reaction between rhodanine derivative and generated H(2)O(2) in acid medium. Microchannels in ?PAD were fabricated by cutting method. And the possible CL assay principle of this CL ?PAD biosensor was explained. Rhodanine derivative system was used to reach the purpose of high sensitivity and well-defined signal for this CL ?PAD biosensor. And the optimum reaction conditions were investigated. The quantitative determination of uric acid could be achieved by this CL ?PAD biosensor with accurate and satisfactory result. And this biosensor could provide good reproducible results upon storage at 4°C for at least 10 weeks. The successful integration of ?PAD and CL reaction made the final biosensor inexpensive, easy-to-use, low-volume, and portable for uric acid determination, which also greatly reduces the cost and increases the efficiency required for an analysis. We believe this simple, practical CL ?PAD biosensor will be of interest for use in areas such as disease diagnosis. PMID:21257303

Yu, Jinghua; Wang, Shoumei; Ge, Lei; Ge, Shenguang

2011-03-15

375

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

SciTech Connect

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 two minor fractions were obtained. Amino acid analysis and sequence analysis showed that the major fraction contained residues 69-118. This region includes six carboxyl side chains. The major UC peptide was also subjected to pepsin hydrolysis. HPLC analysis of the product gave only a single major radioactive subfragment. Amino acid analysis of the peptic peptide showed that it contained residues 110-118. The only carboxyl side chain in this region is Asp-115. Thus, the authors conclude that Asp-115 is the major DCCD site. The light sensitivity of this reaction suggests that Asp-115 becomes more exposed or that its environment becomes more acidic during proton pumping. The DCCD reaction blue-shifts the retinal chromophore. Such a result would be expected if Asp-115 is the negative point charge predicted to be near the cyclohexene ring of retinal.

Renthal, R.; Cothran, M.; Espinoza, B.; Wall, K.A.; Bernard, M.

1985-07-30

376

Zirconium-mediated intramolecular ester transfer reaction: synthesis of alpha-substituted gamma-aminobutyric acid (GABA) derivatives.  

PubMed

[reaction: see text]. The zirconium-mediated intramolecular ester transfer reaction of N-alkenyl carbamate derivatives proceeded to give alpha-substituted gamma-aminobutyric acid (GABA) derivatives in good to excellent yields. Quenching experiments of the reaction mixture with iodine or O2 indicated the presence of a cyclopropane intermediate. The resulting iodide was converted to 2-substituted pyrrolidine-3-carboxylate and/or alpha-alkylidene-gamma-aminobutyric acid derivatives in a stereospecific manner. PMID:11975613

Ito, Hisanaka; Omodera, Katsunori; Takigawa, Yasushi; Taguchi, Takeo

2002-05-01

377

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

378

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

PubMed

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

Ward, Dale E; Souweha, Michael Santos

2005-08-01

379

Kinetics of free radical decay reactions in lactic acid homo and copolymers irradiated to sterilization dose  

NASA Astrophysics Data System (ADS)

The kinetics of free radical decay reactions of poly(L-Lactic acid), poly(DL-Lactic acid) and random copolymer of lactic and glycolic acid have been investigated for decays taking place in air and in vacuum. The change in ESR lines of ?-irradiated polymers have been followed over a long time period. The decay has been found to follow neither simple first-order nor second-order kinetics. Various kinetic approaches including composite first or second-order mechanisms and diffusion-controlled first or second-order equations were determined to be also unsatisfactory. The decay of radicals in bulk irradiated lactic acid homo and copolymers was found to be best described when the second-order non-classical equation with time dependent rate constant approach was used.

Kanto?lu, Ömer; Özbey, Turan; Güven, Olgun

1995-02-01

380

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

381

Fabrication of Uniform DNA-Conjugated Hydrogel Microparticles via Replica Molding for Facile Nucleic Acid Hybridization Assays  

PubMed Central

We identify and investigate several critical parameters in the fabrication of single-stranded DNA conjugated poly(ethylene glycol) (PEG) microparticles based on replica molding (RM) for highly uniform and robust nucleic acid hybridization assays. The effects of PEG-diacrylate, probe DNA, and photoinitiator concentrations on the overall fluorescence and target DNA penetration depth upon hybridization are examined. Fluorescence and confocal microscopy results illustrate high conjugation capacity of probe and target DNA, femtomole sensitivity, and sequence specificity. Combined these findings demonstrate a significant step toward simple, robust, and scalable procedures to manufacture highly uniform and high capacity hybridization assay particles in a well-controlled manner by exploiting many advantages that the batch processing-based RM technique offers. We envision that the results presented here may be readily applied to rapid and high throughput hybridization assays for a wide variety of applications in bioprocess monitoring, food safety, and biological threat detection. PMID:20527819

Lewis, Christina L.; Choi, Chang-Hyung; Lin, Yan; Lee, Chang-Soo; Yi, Hyunmin

2010-01-01

382

Acid–base reactions between an acidic soil and plant residues  

Microsoft Academic Search

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

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

2004-01-01

383

Gramicidin S synthetase. Temperature dependence and thermodynamic parameters of substrate amino acid activation reactions.  

PubMed

In the biosynthesis of the cyclic decapeptide antibiotic gramicidin S, the constituent amino acids are activated by a two-step mechanism involving aminoacyl adenylate and thio ester formation which are both reversible processes. The dissociation constants (KD) for the gramicidin S synthetase-substrate amino acid-thio ester complexes are 100-1000-fold lower compared to the KM data of the preceding aminoacyl adenylate reactions. The affinity for these substrates is appreciably higher at the thio template sites than at the aminoacyl adenylate reaction centers. Therefore, the activation equilibria are quantitatively shifted toward thio ester formation. A set of thermodynamic parameters for the activation processes was determined from the temperature dependence of the KM and KD data. Reaction enthalpies were obtained from a van't Hoff analysis of these constants. delta G degree for the substrate activation reactions of the heavy enzyme of gramicidin S synthetase (GS 2) is predominantly controlled by entropy contributions. In contrast, the overall activation and concomitant racemization of phenylalanine by phenylalanine racemase (GS 1) are exothermic processes which are distinguished by a small negative reaction entropy. PMID:4016097

Vater, J; Mallow, N; Gerhardt, S; Gadow, A; Kleinkauf, H

1985-04-01

384

Reaction of single-standard DNA with hydroxyl radical generated by iron(II)-ethylenediaminetetraacetic acid  

SciTech Connect

This study demonstrates that the reaction of Fe(II)-EDTA and hydrogen peroxide with the single-stranded nucleic acids d(pT){sub 70} and a 29-base sequence containing a mixture of bases results in substantial damage which is not directly detected by gel electrophoresis. Cleavage of the DNA sugar backbone is enhanced significantly after the samples are incubated at 90{degree}C in the presence of piperidine. The latter reaction is used in traditional Maxam-Gilbert DNA sequencing to detect base damage, and the current results are consistent with reaction of the hydroxyl radical with the bases in single-stranded DNA (although reaction with sugar may also produce adducts that are uncleaved but labile to cleavage by piperidine). We the authors propose that hydroxyl radicals may react preferentially with the nucleic acid bases in ssDNA and that reaction of the sugars in dsDNA is dominant because the bases are sequestered within the double helix. These results have implications both for the study of single-stranded DNA binding protein binding sites and for the interpretation of experiments using the hydroxyl radical to probe DNA structure or to footprint double-stranded DNA binding protein binding sites.

Prigodich, R.V. (Trinity College, Hartford, CT (USA)); Martin, C.T. (Univ. of Massachusetts, Amherst (USA))

1990-09-04

385

A Radial Concentration Gradient of Indole3Acetic Acid 1s Related to Secondary Xylem Development in Hybrid Aspen  

Microsoft Academic Search

lhe radial distribution pattern of indole-3-acetic acid (IAA) was determined across the developing tissues of the cambial region in the stem of hybrid aspen (Populus tremula L. x Populus tremuloides Michx). IAA content was measured in consecutive tangential cryo- sections using a microscale mas spectrometry technique. Analysis was performed with wild-type and transgenic trees with an ectopic expression of Agrobacterium

Hannele Tuominen; Laurence Puech; Siegfried Fink; Bjorn Sundberg

386

Enantioselective aldol reaction between isatins and cyclohexanone catalyzed by amino Acid sulphonamides.  

PubMed

Sulphonamides derived from primary ?-amino acid were successfully applied to catalyze the aldol reaction between isatin and cyclohexanone under neat conditions. More interestingly, molecular sieves, as privileged additives, were found to play a vital role in achieving high enantioselectivity. Consequently, high yields (up to 99%) along with good enantioselectivities (up to 92% ee) and diastereoselectivities (up to 95:5 dr) were obtained. In addition, this reaction was also conveniently scaled up, demonstrating the applicability of this protocol. Chirality 27:314-319, 2015. © 2015 Wiley Periodicals, Inc. PMID:25691447

Wang, Jun; Liu, Qi; Hao, Qing; Sun, Yanhua; Luo, Yiming; Yang, Hua

2015-04-01

387

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

SciTech Connect

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

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

2013-08-08

388

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

Microsoft Academic Search

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

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

2009-01-01

389

Scrutiny of the HSAB principle in some representative acid-base reactions  

Microsoft Academic Search

A thorough quantitative analysis of the HSAB principle is performed.\\u000a Complex formation reactions of a typical soft acid, Ag(+), and typical\\u000a hard acid, HF, with the bases XH(3) (X = N, P, As) are studied using the\\u000a DFT\\/B3LYP method with the 6-311G{*}{*} basis set. For the molecules\\u000a containing Ag(+) and As, corresponding pseudopotentials are used.\\u000a Results of the calculations pertaining

Pratim K. Chattaraj; B Gomez; E. Chamorro; J. Santos; P. Fuentealba

2001-01-01

390

Unimolecular half-adders and half-subtractors based on acid-base reaction  

Microsoft Academic Search

According to the structural analysis of reported molecular processors with acids and bases as inputs, we proposed a general\\u000a method for constructing molecular half-adders and\\/or half-subtractors based on acid-base reaction. The method is preliminarily\\u000a supported by four molecular processors (8-hydroxyquinoline, 4-hydroxypyridine, 4-aminophenol and 5-amino-1-naphthol) capable\\u000a of the elementary addition and\\/or subtraction algebraic operations. Noticeably, 8-hydroxyquinoline can mimic the functions\\u000a of

Wei Jiang; Hengyi Zhang; Yu Liu

2009-01-01

391

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

2006-01-01

392

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

PubMed

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

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

2015-02-01

393

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

NASA Astrophysics Data System (ADS)

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

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

2007-10-01

394

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

NASA Technical Reports Server (NTRS)

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

Weber, Arthur L.

1991-01-01

395

Epstein-Barr virus and Hodgkin's disease. A correlative in situ hybridization and polymerase chain reaction study.  

PubMed Central

The authors studied typical Hodgkin's disease along with the nodular, lymphocyte predominance subtype by both the polymerase chain reaction (PCR) and in situ hybridization for evidence of the Epstein-Barr virus (EBV). By PCR, EBV DNA was detected in 12/23 cases of typical Hodgkin's disease and 2/13 cases of the nodular, lymphocyte predominance subtype. EBV RNA was detected by in situ hybridization studies within Reed-Sternberg cells and variants in 11/23 cases of typical Hodgkin's disease and 0/13 cases of nodular, lymphocyte predominance Hodgkin's disease. Other cells positive for EBV, identified as both B and T cells in double-labeling immunohistochemical/in situ hybridization studies, were found in 20/23 cases of typical Hodgkin's disease, 9/13 cases of nodular, lymphocyte predominance Hodgkin's disease, 4/6 cases of progressive transformation of germinal centers, and 7/10 normal lymphoid tissues. It is concluded that EBV is significantly associated with Reed-Sternberg cells in approximately one-half cases of typical Hodgkin's disease but not in the nodular, lymphocyte predominance subtype. EBV-infected B and T cells are also present in a majority of cases of Hodgkin's disease as well as in reactive conditions. Images Figure 1 Figure 2 PMID:1661073

Weiss, L. M.; Chen, Y. Y.; Liu, X. F.; Shibata, D.

1991-01-01

396

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

PubMed

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

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

2014-05-15

397

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

PubMed

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

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

2014-06-01

398

Oxygen reduction reaction in acid medium on Pt–Ni\\/C prepared by a microemulsion method  

Microsoft Academic Search

This work discusses the electrocatalysis of the oxygen reduction reaction (ORR) in acid medium on ultra-thin coating electrodes formed by Pt–Ni nanoparticles dispersed on a carbon powder (Pt–Ni\\/C, 90:10, 75:25 and 60:40, Pt:Ni atomic proportion). The catalysts have been synthesized by a microemulsion method, using Brij®30 as surfactant. X-ray diffraction and transmission electron microscopy were employed to estimate the catalyst

L. G. R. A. Santos; C. H. F. Oliveira; I. R. Moraes; E. A. Ticianelli

2006-01-01

399

Biaryl synthesis via decarboxylative Pd-catalyzed reactions of arenecarboxylic acids and diaryliodonium triflates.  

PubMed

A novel simple and efficient synthesis of biaryls via a Pd-catalyzed decarboxylative cross-coupling reaction of arenecarboxylic acids and diaryliodonium triflates is described. The PdCl2/DPEphos catalytic system in the presence of Ag2CO3 in DMSO was found to be the most efficient. Various biaryls, including sterically hindered biaryls, were synthesized with yields ranging from 37 to 85%. PMID:18553969

Becht, Jean-Michel; Le Drian, Claude

2008-07-17

400

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

Microsoft Academic Search

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

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

2005-01-01

401

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

PubMed

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

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

2013-10-01

402

Femtosecond pH jump: dynamics of acid—base reactions in solvent cages  

Microsoft Academic Search

Studies are reported of the dynamics of proton-transfer reactions, with sub-picosecond time resolution, in solvent cages. The acid-base system studied in a molecular beam is I-naphthol as a solute and ammonia (or water) as a solvent, with the number of solvent molecules (n ) varying. At the threshold (n = 3 ) for proton transfer we examine the accurate form

Sang Kyu Kim; Juen-Kai Wang; Ahmed H. Zewail

1994-01-01

403

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

404

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

PubMed Central

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

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

2014-01-01

405

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

406

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

SciTech Connect

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

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

2001-07-01

407

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

408

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

409

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

410

40 CFR 721.1645 - Benzenesulfonic acid, 4-methyl-, reaction products with oxirane mono[(C10-16-alkyloxy)methyl...  

Code of Federal Regulations, 2011 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...

2011-07-01

411

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

412

40 CFR 721.1645 - Benzenesulfonic acid, 4-methyl-, reaction products with oxirane mono[(C10-16-alkyloxy)methyl...  

Code of Federal Regulations, 2014 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...

2014-07-01

413

40 CFR 721.1645 - Benzenesulfonic acid, 4-methyl-, reaction products with oxirane mono[(C10-16-alkyloxy)methyl...  

Code of Federal Regulations, 2010 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...

2010-07-01

414

40 CFR 721.1645 - Benzenesulfonic acid, 4-methyl-, reaction products with oxirane mono[(C10-16-alkyloxy)methyl...  

Code of Federal Regulations, 2012 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...

2012-07-01

415

Ultrasensitive and selective signal-on electrochemical DNA detection via exonuclease III catalysis and hybridization chain reaction amplification.  

PubMed

This work reported a novel, ultrasensitive, and selective platform for electrochemical detection of DNA, employing an integration of exonuclease III (Exo-III) assisted target recycling and hybridization chain reaction (HCR) for the dual signal amplification strategy. The hairpin capture probe DNA (C-DNA) with an Exo-III 3' overhang end was self-assembled on a gold electrode. In the presence of target DNA (T-DNA), C-DNA hybridized with the T-DNA to form a duplex region, exposing its 5' complementary sequence (initiator). Exo-III was applied to selectively digest duplex region from its 3-hydroxyl termini until the duplex was fully consumed, leaving the remnant initiator. The intact T-DNA spontaneously dissociated from the structure and then initiated the next hybridization process as a result of catalysis of the Exo-III. HCR event was triggered by the initiator and two hairpin helper signal probes labeled with methylene blue, facilitating the polymerization of oligonucleotides into a long nicked dsDNA molecule. The numerous exposed remnant initiators can trigger more HCR events. Because of integration of dual signal amplification and the specific HCR process reaction, the resultant sensor showed a high sensitivity for the detection of the target DNA in a linear range from 1.0 fM to 1.0 nM, and a detection limit as low as 0.2 fM. The proposed dual signal amplification strategy provides a powerful tool for detecting different sequences of target DNA by changing the sequence of capture probe and signal probes, holding a great potential for early diagnosis in gene-related diseases. PMID:25083923

Ren, Wang; Gao, Zhong Feng; Li, Nian Bing; Luo, Hong Qun

2015-01-15

416

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

417

Assessment of hybridization among wild and cultivated Vigna unguiculata subspecies revealed by arbitrarily primed polymerase chain reaction analysis  

PubMed Central

Background and aims Intra-species hybridization and incompletely homogenized ribosomal RNA repeat units have earlier been reported in 21 accessions of Vigna unguiculata from six subspecies using internal transcribed spacer (ITS) and 5S intergenic spacer (IGS) analyses. However, the relationships among these accessions were not clear from these analyses. We therefore assessed intra-species hybridization in the same set of accessions. Methodology Arbitrarily primed polymerase chain reaction (AP-PCR) analysis was carried out using 12 primers. The PCR products were resolved on agarose gels and the DNA fragments were scored manually. Genetic relationships were inferred by TREECON software using unweighted paired group method with arithmetic averages (UPGMA) cluster analysis evaluated by bootstrapping and compared with previous analyses based on ITS and 5S IGS. Principal results A total of 202 (86 %) fragments were found to be polymorphic and used for generating a genetic distance matrix. Twenty-one V. unguiculata accessions were grouped into three main clusters. The cultivated subspecies (var. unguiculata) and most of its wild progenitors (var. spontanea) were placed in cluster I along with ssp. pubescens and ssp. stenophylla. Whereas var. spontanea were grouped with ssp. alba and ssp. tenuis accessions in cluster II, ssp. alba and ssp. baoulensis were included in cluster III. Close affinities of ssp. unguiculata, ssp. alba and ssp. tenuis suggested inter-subspecies hybridization. Conclusions Multi-locus AP-PCR analysis reveals that intra-species hybridization is prevalent among V. unguiculata subspecies and suggests that grouping of accessions from two different subspecies is not solely due to the similarity in the ITS and 5S IGS regions but also due to other regions of the genome. PMID:22619698

Vijaykumar, Archana; Saini, Ajay; Jawali, Narendra

2012-01-01

418

Nuclemeter: A Reaction-Diffusion Based Method for Quantifying Nucleic Acids Undergoing Enzymatic Amplification  

PubMed Central

Real-time amplification and quantification of specific nucleic acid sequences plays a major role in medical and biotechnological applications. In the case of infectious diseases, such as HIV, quantification of the pathogen-load in patient specimens is critical to assess disease progression and effectiveness of drug therapy. Typically, nucleic acid quantification requires expensive instruments, such as real-time PCR machines, which are not appropriate for on-site use and for low-resource settings. This paper describes a simple, low-cost, reaction-diffusion based method for end-point quantification of target nucleic acids undergoing enzymatic amplification. The number of target molecules is inferred from the position of the reaction-diffusion front, analogous to reading temperature in a mercury thermometer. The method was tested for HIV viral load monitoring and performed on par with conventional benchtop methods. The proposed method is suitable for nucleic acid quantification at point of care, compatible with multiplexing and high-throughput processing, and can function instrument-free. PMID:25477046

Liu, Changchun; Sadik, Mohamed M.; Mauk, Michael G.; Edelstein, Paul H.; Bushman, Frederic D.; Gross, Robert; Bau, Haim H.

2014-01-01

419

Nuclemeter: a reaction-diffusion based method for quantifying nucleic acids undergoing enzymatic amplification.  

PubMed

Real-time amplification and quantification of specific nucleic acid sequences plays a major role in medical and biotechnological applications. In the case of infectious diseases, such as HIV, quantification of the pathogen-load in patient specimens is critical to assess disease progression and effectiveness of drug therapy. Typically, nucleic acid quantification requires expensive instruments, such as real-time PCR machines, which are not appropriate for on-site use and for low-resource settings. This paper describes a simple, low-cost, reaction-diffusion based method for end-point quantification of target nucleic acids undergoing enzymatic amplification. The number of target molecules is inferred from the position of the reaction-diffusion front, analogous to reading temperature in a mercury thermometer. The method was tested for HIV viral load monitoring and performed on par with conventional benchtop methods. The proposed method is suitable for nucleic acid quantification at point of care, compatible with multiplexing and high-throughput processing, and can function instrument-free. PMID:25477046

Liu, Changchun; Sadik, Mohamed M; Mauk, Michael G; Edelstein, Paul H; Bushman, Frederic D; Gross, Robert; Bau, Haim H

2014-01-01

420

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

Microsoft Academic Search

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

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

1991-01-01

421

Substituent effect on the formation of organically-modified silicate-phosphate alternating copolymer through nonaqueous acid–base reaction  

Microsoft Academic Search

Organically-modified silicate-phosphate and silicate-phosphite copolymers were prepared through nonaqueous acid–base reaction.\\u000a The inductive effect of the organic substituent of the starting materials such as organically-modified chlorosilane and phosphorous\\u000a acid on the acid–base reaction was investigated by 31P NMR measurement and ab initio molecular orbital calculation. The condensation reaction takes place by nucleophilic addition\\u000a of phosphate ion (or phosphite ion) to

Megumi Mizuno; Masahide Takahashi; Yomei Tokuda; Toshinobu Yoko

2007-01-01

422

Improvement of an acid phosphatase/DHAP-dependent aldolase cascade reaction by using directed evolution.  

PubMed

To enhance the phosphorylating activity of the bacterial nonspecific acid phosphatase from Salmonella enterica ser. typhimurium LT2 towards dihydroxyacetone (DHA), a mutant library was generated from the native enzyme. Three different variants that showed enhanced activity were identified after one round of epPCR. The single mutant V78L was the most active and showed an increase in the maximal DHAP concentration to 25 % higher than that of the wild-type enzyme at pH 6.0. This variant is 17 times more active than the wild-type acid phosphatase from Salmonella enterica ser. typhimurium LT2 in the acid phosphatase/aldolase cascade reaction at pH 6.0 and is also six times more active than the phosphatase from Shigella flexneri that we previously used. PMID:19623595

van Herk, Teunie; Hartog, Aloysius F; Babich, Lara; Schoemaker, Hans E; Wever, Ron

2009-09-01

423

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

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

424

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

425

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

426

Characterization of a Chinese hamster-human hybrid cell line with increased system L amino acid transport activity.  

PubMed Central

We have studied leucine transport in several Chinese hamster-human hybrid cell lines obtained by fusion of a temperature-sensitive line of Chinese hamster ovary cells, ts025C1, and normal human leukocytes. A hybrid cell line exhibiting a twofold increase in L-leucine uptake over that in the parental cell line was found. This hybrid cell line, 158CnpT-1, was temperature resistant, whereas the parental Chinese hamster ovary mutant, ts025C1, contained a temperature-sensitive leucyl-tRNA synthetase mutation. An examination of the different amino acid transport systems in this hybrid cell line revealed a specific increase of system L activity with no significant changes in systems A and ASC. The Vmax for L-leucine uptake exhibited by the hybrid 158CnpT-1 was twice that in the CHO parental mutant, ts025C1. Cytogenetic analysis showed that the hybrid 158CnpT-1 contains four complete human chromosomes (numbers 4, 5, 10, and 21) and three interspecific chromosomal translocations in a total complement of 34 chromosomes. Biochemical and cytogenetic analysis of segregant clones obtained from hybrid 158CnpT-1 showed that the primary temperature resistance and high system L transport phenotypes can be segregated from this hybrid independently. The loss of the primary temperature resistance was associated with the loss of the human chromosome 5, as previously reported by other laboratories, whereas the loss of the high leucine transport phenotype, which is associated with a lesser degree of temperature resistance, was correlated with the loss of human chromosome 20. Images PMID:6717430

Lobaton, C D; Moreno, A; Oxender, D L

1984-01-01

427

CHEMICAL REACTION MECHANISM AND MODELIZATION OF DETERIORATION PHENOMENON OF HARDENED CEMENT DAMAGED BY CHEMICAL EROSION DUE TO MIXED ACID AQUEOUS SOLUTION  

NASA Astrophysics Data System (ADS)

This study measured the mass decrease rate of the hardened cement specimens which deteriorated by sulfuric acid, hydrochloric acid, nitric acid and mixed acid which mixed these acids (i.e. sulfuric acid, hydrochloric acid, nitric acid) for the purpose of clarify the these chemical reaction mechanism. As a result, it was clarified that mass decrease rate of hardened cement is greatly dependent on concentration of sulfuric acid when mixed acids containing sulfuric acid and other acid (i.e. hydrochloric acid or nitric acid) act on hardened cement. In this study, it was apprehended that the cause of this chemical reaction mechanism is influence of molar fraction of sulfuric acid and it was indicated that this chemical reaction mechanism could be explained by Gibbs free energy and chemical kinetics. Moreover, in this study, it was proposed that prediction model of mass decrease rate based on these theories.

Miyamoto, Shintaro; Minagawa, Hiroshi; Hisada, Makoto

428

Effect of reaction conditions on surface properties of TEOS–TBOT–PDMS hybrid materials  

Microsoft Academic Search

Hybrid materials based on tetraethoxysilane (TEOS), tetrabutyl orthotitanate (TBOT), and hydroxyl terminated polydimethyl\\u000a siloxane (PDMS) have been prepared and characterized. The effects of HCl concentration and PDMS molecular weight (MW) have been analysed. The physical and chemical characteristics have been discussed based on the results obtained from the\\u000a characterization by Raman spectroscopy, nitrogen adsorption, mercury intrusion porosimetry and inverse gas

A. Tamayo; L. Téllez; J. Rubio; F. Rubio; J. L. Oteo

2010-01-01

429

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

430

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

431

Metal-Organic Framework Based upon the Synergy of a Brřnsted Acid Framework and Lewis Acid Centers as a Highly Efficient Heterogeneous Catalyst for Fixed-Bed Reactions.  

PubMed

We report a strategy of combining a Brřnsted acid metal-organic framework (MOF) with Lewis acid centers to afford a Lewis acid@Brřnsted acid MOF with high catalytic activity, as exemplified in the context of MIL-101-Cr-SO3H·Al(III). Because of the synergy between the Brřnsted acid framework and the Al(III) Lewis acid centers, MIL-101-Cr-SO3H·Al(III) demonstrates excellent catalytic performance in a series of fixed-bed reactions, outperforming two benchmark zeolite catalysts (H-Beta and HMOR). Our work therefore not only provides a new approach to achieve high catalytic activity in MOFs but also paves a way to develop MOFs as a new type of highly efficient heterogeneous catalysts for fixed-bed reactions. PMID:25773275

Li, Baiyan; Leng, Kunyue; Zhang, Yiming; Dynes, James J; Wang, Jian; Hu, Yongfeng; Ma, Dingxuan; Shi, Zhan; Zhu, Liangkui; Zhang, Daliang; Sun, Yinyong; Chrzanowski, Matthew; Ma, Shengqian

2015-04-01

432

Synthesis and characterization of polyacids from palm acid oil and sunflower oil via addition reaction.  

PubMed

In this study aliphatic polyacids were synthesized using palm acid oil (PAO) and sunflower oil (SFO) via addition reaction technique. The synthesized materials were characterized using Fourier-transform infra-red (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF-MS) and thermo-gravimetric analysis (TGA). Mixing formic acid and hydrogen peroxide with PAO or SFO at the ratio 3:10:1 produced the lowest iodine value of 10.57 and 9.24 respectively, indicating the increase in epoxidization of both oils. Adding adipic acid to the epoxidized oils at a ratio of 1:10 increases the acid values of SFO and PAO to 11.22 and 6.73 respectively. The existence of multi-acid groups present in synthesized polyacid was confirmed by MALD-ToF-MS. This feature indicates a possible value to the biomaterials development. PMID:24215893

Zeimaran, Ehsan; Kadir, Mohammed Rafiq Abdul; Nor, Hussin Mohd; Kamarul, Tunku; Djordjevic, Ivan

2013-12-15

433

Positively charged polymer brush-functionalized filter paper for DNA sequence determination following Dot blot hybridization employing a pyrrolidinyl peptide nucleic acid probe.  

PubMed

As inspired by the Dot blot analysis, a well known technique in molecular biology and genetics for detecting biomolecules, a new paper-based platform for colorimetric detection of specific DNA sequences employing peptide nucleic acid (PNA) as a probe has been developed. In this particular study, a pyrrolidinyl PNA bearing a conformationally rigid d-prolyl-2-aminocyclopentanecarboxylic acid backbone (acpcPNA) was used as a probe. The filter paper was modified to be positively charged with grafted polymer brushes of quaternized poly(dimethylamino)ethyl methacrylate (QPDMAEMA) prepared by surface-initiated polymerization of 2-(dimethylamino)ethyl methacrylate from the filter paper via ARGET ATRP followed by quaternization with methyl iodide. Following the Dot blot format, a DNA target was first immobilized via electrostatic interactions between the positive charges of the QPDMAEMA brushes and negative charges of the phosphate backbone of DNA. Upon hybridization with the biotinylated pyrrolidinyl peptide nucleic acid (b-PNA) probe, the immobilized DNA can be detected by naked eye observation of the yellow product generated by the enzymatic reaction employing HRP-labeled streptavidin. It has been demonstrated that this newly developed assay was capable of discriminating between complementary and single base mismatch targets at a detection limit of at least 10 fmol. In addition, the QPDMAEMA-grafted filter paper exhibited a superior performance to the commercial membranes, namely Nylon 66 and nitrocellulose. PMID:23125969

Laopa, Praethong S; Vilaivan, Tirayut; Hoven, Voravee P

2013-01-01

434

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

435

Acid–base reaction and fluoride release profiles in visible light-cured polyacid-modified composite restoratives (compomers)  

Microsoft Academic Search

Objective. The aim of the study was to evaluate the extent of the acid–base reaction and F? release in Compoglass (Vivadent) and Dyract (Dentsply\\/DeTrey) restoratives.Methods. For evaluation of the extent of the acid–base reaction, two groups of three specimens (7mm×5mm×1mm) were prepared for each material. The first group was immersed in distilled water, while the second was kept in dark

George Eliades; Afrodite Kakaboura; Georgios Palaghias

1998-01-01

436

Cyclohexanol conversion as a test reaction for acid properties of solids investigation of faujasites, mordenites and MCM-41  

Microsoft Academic Search

The goal of this study was to find an universal test reaction for the properties of both weak and strong acid sites. Cyclohexanol conversion was found to be such test reaction. It has been found that in the presence of weak Bronsted sites (such as Si-OHB in HBoralites or (AlO)3 Si-OH-Al (SiO)3 in NaHX) only dehydration occured. More acidic sites

J. Datka; B. Gil; O. Vog; J. Rakoczy

1999-01-01

437

Conversion of isoamyl alcohol over acid catalysts: Reaction dependence on nature of active centers  

SciTech Connect

Acid catalysts are known to catalyze the dehydration of alcohols. In addition some oxide catalysts with basic properties have also been shown to play an important role in such dehydration reactions. The dehydration of aliphatic alcohols to olefins has been studied in detail using alumina silica-alumina and zeolite catalysts. The olefin products further undergo isomerization in presence of acidic sites. The reaction of isoamyl alcohol on catalytic surfaces has not been investigated in greater detail. The dehydration of isoamyl alcohol is of considerable interest in fine chemicals. Isoamyl alcohol may also undergo dehydrogenation as observed in the case of n-butanol. The scope of the present work is to identify the nature of the active sites selective for dehydration and dehydrogenation of isoamyl alcohol and to modify the active sites to promote isomerization of dehydrated products. Four catalytic surfaces on which the acidic strength can be varied, as well as selectively suppressed, are chosen for this study. 17 refs., 1 fig., 3 tabs.

Babu, G.P.; Murthy, R.S.; Krishnan, V. [Hindustan Lever Research Centre, Bombay (India)] [Hindustan Lever Research Centre, Bombay (India)

1997-02-01

438

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. PMID:18400780

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

439

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

PubMed

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

Xuan, Feng; Hsing, I-Ming

2014-07-16

440

Squamous cell carcinoma of the conjunctiva. Failure to demonstrate HPV DNA by in situ hybridization and polymerase chain reaction.  

PubMed

Squamous cell carcinoma of the conjunctiva is a distinct rarity, often arising at the corneoscleral limbus and initially resembling pterygium or chronic keratoconjunctivitis. In this paper we report 4 patients with conjunctival squamous cell carcinoma/carcinoma in situ, which comprise all the cases found in the files of Kuopio University Hospital during 1959-1991. The clinical appearance, diagnosis and treatment of the lesions are described. All biopsies were studied for the presence of Human papillomavirus (HPV) DNA (recently demonstrated in conjunctival squamous cell papillomas, precancer lesions and carcinomas) by using in situ DNA hybridization (ISH) and polymerase chain reaction (PCR). Both techniques failed to demonstrate the DNA of any of the following HPV types: HPV 6, 11, 16 and 18 in any of the lesions. The results are discussed in the light of the recently proposed HPV etiology of these lesions. PMID:1319099

Tuppurainen, K; Raninen, A; Kosunen, O; Kankkunen, J P; Kellokoski, J; Syrjänen, S; Mäntyjärvi, M; Syrjänen, K

1992-04-01

441

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

PubMed

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

Aristotelous, Andreas C; Haider, Mansoor A

2014-08-01

442

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

PubMed

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

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

2013-01-01

443

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

NASA Astrophysics Data System (ADS)

Rotation-vibration spectra of the nitric acid molecule, HNO3, are calculated for wavenumbers up to 7000 cm-1. Calculations are performed using a Hamiltonian expressed in internal curvilinear vibrational coordinates employing a hybrid variational-perturbation method. An initial potential energy surface (PES) and dipole moment function (DMF) are calculated ab initio at the CCSD(T)/aug-cc-pVQZ level of theory. Parameters of the PES and DMF are varied to minimize differences between the calculated and experimental transition frequencies and intensities. The average, absolute deviation between calculated and experimental values is 0.2 cm-1 for frequencies in the fundamental bands and 0.4 cm-1 for those in the first overtone and lowest combination bands. For the intensities, the calculated and experimental values differ by 0.3% and 40% for the fundamentals and overtones, respectively. The optimized PES and DMF are used to calculate the room-temperature ro-vibrational spectrum. These calculation reproduce both the form of the absorption bands and fine details of the observed spectra, including the rotational structure of the vibrational bands and the numerous hot absorption band. Many of these hot bands are found to be missing from the compilation in HITRAN. A room temperature line list comprising 2 × 109 lines is computed.

Pavlyuchko, A. I.; Yurchenko, S. N.; Tennyson, Jonathan

2015-03-01

444

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

PubMed

Rotation-vibration spectra of the nitric acid molecule, HNO3, are calculated for wavenumbers up to 7000 cm(-1). Calculations are performed using a Hamiltonian expressed in internal curvilinear vibrational coordinates employing a hybrid variational-perturbation method. An initial potential energy surface (PES) and dipole moment function (DMF) are calculated ab initio at the CCSD(T)/aug-cc-pVQZ level of theory. Parameters of the PES and DMF are varied to minimize differences between the calculated and experimental transition frequencies and intensities. The average, absolute deviation between calculated and experimental values is 0.2 cm(-1) for frequencies in the fundamental bands and 0.4 cm(-1) for those in the first overtone and lowest combination bands. For the intensities, the calculated and experimental values differ by 0.3% and 40% for the fundamentals and overtones, respectively. The optimized PES and DMF are used to calculate the room-temperature ro-vibrational spectrum. These calculation reproduce both the form of the absorption bands and fine details of the observed spectra, including the rotational structure of the vibrational bands and the numerous hot absorption band. Many of these hot bands are found to be missing from the compilation in HITRAN. A room temperature line list comprising 2 × 10(9) lines is computed. PMID:25747083

Pavlyuchko, A I; Yurchenko, S N; Tennyson, Jonathan

2015-03-01

445

Diagnosis of bacterial vaginosis by a new multiplex peptide nucleic acid fluorescence in situ hybridization method.  

PubMed

Bacterial vaginosis (BV) is one of most common vaginal infections. However, its diagnosis by classical methods reveals low specificity. Our goal was to evaluate the accuracy diagnosis of 150 vaginal samples with research gold standard methods and our Peptide Nucleic Acid (PNA) probes by Fluorescence in situ Hybridization (FISH) methodology. Also, we described the first PNA-FISH methodology for BV diagnosis, which provides results in approximately 3 h. The results showed a sensitivity of 84.6% (95% confidence interval (CI), from 64.3 to 95.0%) and a specificity of 97.6% (95% CI [92.6-99.4%]), demonstrating the higher specificity of the PNA-FISH method and showing false positive results in BV diagnosis commonly obtained by the classical methods. This methodology combines the specificity of PNA probes for Lactobacillus species and G. vaginalis visualization and the calculation of the microscopic field by Nugent score, allowing a trustful evaluation of the bacteria present in vaginal microflora and avoiding the occurrence of misleading diagnostics. Therefore, the PNA-FISH methodology represents a valuable alternative for BV diagnosis. PMID:25737820

Machado, António; Castro, Joana; Cereija, Tatiana; Almeida, Carina; Cerca, Nuno

2015-01-01

446

Diagnosis of bacterial vaginosis by a new multiplex peptide nucleic acid fluorescence in situ hybridization method  

PubMed Central

Bacterial vaginosis (BV) is one of most common vaginal infections. However, its diagnosis by classical methods reveals low specificity. Our goal was to evaluate the accuracy diagnosis of 150 vaginal samples with research gold standard methods and our Peptide Nucleic Acid (PNA) probes by Fluorescence in situ Hybridization (FISH) methodology. Also, we described the first PNA-FISH methodology for BV diagnosis, which provides results in approximately 3 h. The results showed a sensitivity of 84.6% (95% confidence interval (CI), from 64.3 to 95.0%) and a specificity of 97.6% (95% CI [92.6–99.4%]), demonstrating the higher specificity of the PNA-FISH method and showing false positive results in BV diagnosis commonly obtained by the classical methods. This methodology combines the specificity of PNA probes for Lactobacillus species and G. vaginalis visualization and the calculation of the microscopic field by Nugent score, allowing a trustful evaluation of the bacteria present in vaginal microflora and avoiding the occurrence of misleading diagnostics. Therefore, the PNA-FISH methodology represents a valuable alternative for BV diagnosis. PMID:25737820

Machado, António; Castro, Joana; Cereija, Tatiana; Almeida, Carina

2015-01-01

447

Ultrasensitive simultaneous detection of four biomarkers based on hybridization chain reaction and biotin-streptavidin signal amplification strategy.  

PubMed

A sandwich-type electrochemical immunosensor based on redox probe tags identification technology for ultrasensitive simultaneous detection of four antigens was proposed. In this project, well-distributed graphene/gold (GR-Au) hybrid film was acquired through one-step codeposition in an electrode surface and served as the base substrate for immobilizing capture antibodies (Ab1). Hybridization chain reaction (HCR) and biotin/streptavidin (B/SA), combining with gold magnetic nanoparticles were applied to increase the immobilization amount of signal tags in detection antibody (Ab2) bioconjugates. To verify this strategy, four representative biomarkers, a-fetoprotein (AFP), carcinoembryonic antigen (CEA), carbohydrate antigen (CA)125 and prostate special antigen (PSA), were used as model analytes. The resulting immunosensor could simultaneously detect four antigens in single-pass differential pulse voltammetry (DPV) scan, and exhibited obviously improved senstivity compared to previous similar immunosensors, displayed good linear relationships in the ranges from 0.2 to 800pg/mL for AFP, 0.2 to 600pg/mL for CEA, 0.2 to 1000pg/mL for CA125, 0.2 to 800pg/mL for PSA and with detection limits of 62, 48, 77 and 60fg/mL, respectively. PMID:25562732

Zhu, Qiang; Chai, Yaqin; Zhuo, Ying; Yuan, Ruo

2015-06-15

448

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

PubMed Central

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

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

2014-01-01

449

Ultrasensitive electrochemical detection of DNA based on Zn˛? assistant DNA recycling followed with hybridization chain reaction dual amplification.  

PubMed

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

Qian, Yong; Wang, Chunyan; Gao, Fenglei

2015-01-15

450

Chiral phosphoric acid catalyzed highly enantioselective Friedel-Crafts alkylation reaction of C3-substituted indoles to ?,?-unsaturated ?-ketimino esters.  

PubMed

A highly enantioselective C2 Friedel-Crafts alkylation reaction of 3-substituted indoles to ?,?-unsaturated ?-ketimino esters has been developed. This reaction was efficiently catalyzed by a chiral phosphoric acid catalyst. The corresponding C2-substituted indole derivatives, bearing an ?-ketimino ester motif, were obtained in moderate to high yields (up to 93%) and with high enantioselectivities (up to >99% ee). PMID:25594307

Bi, Bo; Lou, Qin-Xin; Ding, Yu-Yang; Chen, Sheng-Wei; Zhang, Sha-Sha; Hu, Wen-Hui; Zhao, Jun-Ling

2015-02-01

451

Grafting isocyanate-terminated elastomers onto the surfaces of carbon fibers: Reaction of isocyanate with acidic surface functions  

Microsoft Academic Search

Isocyanate functional groups can readily react with sterically accessible acidic functional groups on carbon fiber surfaces. Solvent effects on these reactions were investigated. Polar solvents such as DMF seem to favor this reaction. The grafting efficiency of isocyanate terminated-oligomers decreased with increasing molecular weight even though the total weight gain was higher when higher molecular weight oligomers were grafted. Isocyanate

Zhihong Wu; Charles U. Pittman Jr; Steven D. Gardner

1996-01-01

452

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

453

Solvent-Free Conversion of Alpha-Naphthaldehyde to 1-Naphthoic Acid and 1-Naphthalenemethanol: Application of the Cannizzaro Reaction  

ERIC Educational Resources Information Center

A mixture of potassium hydroxide and alpha-naphthaldehyde (1) are heated under solvent-free conditions to produce 1-naphthoic acid (2) and 1-naphthalenemethanol (3). The experiment offers several advantages over many existing exercises including the ease of reaction workup, shorter reaction time, relative environmental friendliness of the…

Esteb, John J.; Gligorich, Keith M.; O'Reilly, Stacy A.; Richter, Jeremy M.

2004-01-01

454

Hydrogen evolution reaction of low carbon steel electrode in hydrochloric acid as a source for hydrogen production  

Microsoft Academic Search

The hydrogen evolution reaction (HER) (cathodic reaction) of low carbon steel electrode immersed in hydrochloric acid was investigated as a source for hydrogen production. Corrosion rate, hydrogen evolution rate, and current density increase with the increase of HCl concentration. Theoretically and practically, every 1g of iron produces about 0.036g of hydrogen. Therefore, the hydrogen production efficiency over the immersion period

A. A. El-Meligi; N. Ismail

2009-01-01

455

Classes of Chemical Reactions Reactions in aqueous media  

E-print Network

Classes of Chemical Reactions Reactions in aqueous media · Precipitation reactions · Acid-Base+ , and Pb2+ #12;Classes of Chemical Reactions Acid-Base Reactions Acid - a substance that is a donor of H Acid-Base Reactions STRONG ACIDS WEAK ACIDS Hydrochloric acid, HCl Hydrofluoric acid, HF Hydrobromic

Zakarian, Armen