Home About us Contact
|
Home About us Contact | ||
|
|
||
Selected Compounds (selected + compound)
Selected AbstractsHelical polyacetylene,Origins and synthesisTHE CHEMICAL RECORD, Issue 6 2008Kazuo Akagi Abstract We present the origins and synthesis of helical polyacetylene (H-PA) by focusing on its peculiar spiral morphology. Interfacial polymerization of acetylene was carried out in an asymmetric reaction field consisting of chiral nematic liquid crystal (N*-LC) and Ziegler,Natta catalyst. As the N*-LC is composed of nematic liquid crystal and a chiral compound such as a binaphthyl derivative with either the R - or S -configuration, the screw directions of the polyacetylene chain and fibril bundle,and even the spiral morphology,are rigorously controlled by the chirality of the selected compound. Interestingly, the screw directions of the fibril and the bundle in H-PA were found to be opposite to that of N*-LC. It is worthwhile to emphasize that the hierarchical spiral morphology involving the primary to higher order structure is generated in a synthetic polymer such as polyacetylene by using N*-LC as an asymmetric polymerization solvent. © 2008 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 8: 395,406; 2008: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20163 [source] Evaluation of poly(ethylene-co-vinyl acetate-co-carbon monoxide) and polydimethylsiloxane for equilibrium sampling of polar organic contaminants in waterENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2009Jörgen A Magnér Abstract Abstract-The aim of the present study was to develop a passive a bsorptive equilibrium sampler that would enable the determination of the concentrations of polar organic compound (POC) in water more efficiently than existing techniques. To this end, a novel plastic material, poly(ethylene-co-vinyl acetate-co-carbon monoxide) (PEVAC), was evaluated and the results were compared with an existing silicone-based passive absorptive equilibrium device. Seven compounds (imidacloprid, carbendazim, metoprolol, atrazin, carbamazepine, diazinon, and chlorpyrifos), a mixture of pharmaceuticals, and pesticides with a logarithmic octanol-water partition coefficient ranging from 0.2 to 4.77 were selected as model substances for the experiments. The results showed that six of the seven selected POCs reached distribution equilibrium within 4 d in the two materials tested. A linear relation with a regression coefficient of more than 0.8906 between the established logarithmic absorbent-water partition coefficient and the calculated logarithmic dissociation partition coefficient of the selected compounds in the two polymers was observed. The correlation between these two coefficients was within one order of magnitude for the compounds that reached equilibrium in the two polymers, which demonstrates that both materials are suitable for mimicking biological uptake of POCs. The PEVAC material showed an enhanced sorption for all selected compounds compared to the silicone material and up to five times higher enrichment for the most polar compound. Fluorescence analysis of the sampler cross-section, following the uptake of fluoranthene, and proof that the sorption was independent of surface area variations demonstrated that the PEVAC polymer possessed absorptive rather than adsorptive enrichment of organic compounds. [source] Antimicrobial effect of vapours of geraniol, (R)-(,)-linalool, terpineol, , -terpinene and 1,8-cineole on airborne microbes using an airwasherFLAVOUR AND FRAGRANCE JOURNAL, Issue 5 2007Kei Sato Abstract Five selected compounds, geraniol, (R)-(,)-linalool, terpineol, , -terpinene and 1,8-cineole, were tested for their influence on airborne microbes when vaporized with an air washer. Terpineol and 1,8-cineole showed the highest antimicrobial activities. The average reduction of germ count was 68% and 64%, respectively. Although , -terpinene gave the lowest result among the compounds investigated, the average reduction of germ count was still 40%. When water without volatile compounds was sprayed, the colony forming units increased. These results show the positive effect of selected aroma compounds on the reduction of microbes in the room. Copyright © 2007 John Wiley & Sons, Ltd. [source] On the relative stability of cobalt- and nickel-based amidinate complexes against ,-migrationINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4 2009Jiaye Li Abstract We present a first-principles study on the relative stability of cobalt- and nickel-based amidinate complexes against ,-migration using density functional theory. Factors that influence the reactivity of these compounds were carefully addressed and the calculated molecular structures are in excellent agreement with the available crystal structural data. Reaction energies as well as activation barriers of ,-migration were evaluated. The predicted relative stability of the selected compounds is consistent with experimental observations. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source] Syntheses and photophysical properties of some 4-arylpyridinium saltsJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2001Charles J. Kelley A number of 4-arylpyridines, many methoxy substituted, were prepared by an efficient two-step method involving aryl Grignard addition to 1-methyl-4-piperidone and direct aromatization of the resulting 4-aryl-4-piperidinols. The pyridines were N -alkylated to give sulfonate salts desired for their fluorescent properties. Study of selected compounds as laser dyes revealed several structures to be efficient dyes lasing in the 530-550 nm range. Two new diazaquaterphenyls were prepared and were quaternized. These salts exhibited intense fluorescence in the 420-450 nm range, but would not lase. A phenolic azaterphenyl suitably substituted for excited state intramolecular proton transfer (ESIPT) did not fluoresce at all. [source] Determination of aminoglycoside and macrolide antibiotics in meat by pressurized liquid extraction and LC-ESI-MSJOURNAL OF SEPARATION SCIENCE, JSS, Issue 4-5 2010Houda Berrada Abstract A simple method for the simultaneous determination of dihydrostreptomycin, spectinomycin, spiramycin, streptomycin, tilmicosin, and tylosin in meat has been developed using pressurized liquid extraction and LC-triple quadrupole MS (LC-ESI-MS/MS). The pressurized liquid extraction operational parameters were optimized and no protein precipitating and fat removing steps were required. A gradient HPLC separation was developed with ion-pair mobile phases consisting of aqueous 1,mM heptafluorobutyric acid water and methanol. Protonated molecules were used as precursor ions for CID. Data acquisition under MS/MS was achieved by applying multiple reaction monitoring of three fragment ion transitions to provide a high degree of sensitivity and specificity. Dirithromycin and sisomycin were selected as internal standards. A validation study was conducted for these antibiotics in poultry meat samples. All selected compounds could be detected (monitoring ions by multiple reaction monitoring) in meat samples at amounts below the regulatory level of concern. Using the internal standards, pressurized liquid extraction recovery rates were from 70 to 96% (RSD 12,25%). LC-ESI-MS/MS method detection limits of the selected antibiotics were 1,6,,g/kg. Good method reproducibility was found by intra- and inter-day precisions at maximum residue level, yielding the RSDs less than 15 and 16%, respectively. [source] Multidimensional GC coupled to MS for the simultaneous determination of oxygenate compounds and BTEX in gasolineJOURNAL OF SEPARATION SCIENCE, JSS, Issue 4-5 2010Danilo Sciarrone Abstract In the present work, carried out in relation to the European and American Directives on the quality of petrol and diesel fuels, the simultaneous determination of the oxygenate compounds and BTEX in gasoline was achieved through the use of a multidimensional GC (MDGC)/MS system, employing a Deans switch-based transfer system, with an innovative configuration; the latter enabled multiple heart-cut transfers with no hint of retention time shift, a phenomenon that can occur in MDGC, providing the possibility to achieve more then 20 different heart-cuts for the compounds of interest. In this study, 20 selected compounds were quantitatively transferred with 12 heart-cuts, from a first to a secondary column, in order to resolve primary column co-elutions. Analyte quantification and identification was achieved through a fast-scanning quadrupole mass analyzer, operated in full scan mode, in order to evaluate also the interfering compounds transferred together with the compounds of interest. The multidimensional method developed was subjected to validation. All attained data were in excellent correlation with results obtained through the UNI-EN 12177:2000, ASTM D 5580-02 and ASTM D 4815-04 MDGC methods, for the determination of benzene, BTEX and oxygenate compounds in gasoline, respectively. [source] Detection of 28 neurotransmitters and related compounds in biological fluids by liquid chromatography/tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 9 2006Sophie Bourcier This work presents two liquid chromatography/tandem mass spectrometry (LC/MS/MS) acquisition modes: multiple reaction monitoring (MRM) and neutral loss scan (NL), for the analysis of 28 compounds in a mixture. This mixture includes 21 compounds related to the metabolism of three amino acids: tyrosine, tryptophan and glutamic acid, two pterins and five deuterated compounds used as internal standards. The identification of compounds is achieved using the retention times (RT) and the characteristic fragmentations of ionized compounds. The acquisition modes used for the detection of characteristic ions turned out to be complementary: the identification of expected compounds only is feasible by MRM while expected and unexpected compounds are detected by NL. In the first part of this work, the fragmentations characterizing each molecule of interest are described. These fragmentations are used in the second part for the detection by MRM and NL of selected compounds in mixture with and without biological fluids. Any preliminary extraction precedes the analysis of compounds in biological fluids. Copyright © 2006 John Wiley & Sons, Ltd. [source] Single run measurements of drug-protein binding by high-performance frontal analysis capillary electrophoresis and mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2005Hong Wan A novel drug-protein binding measurement method based on high-performance frontal analysis and capillary electrophoresis (HPFA/CE) is presented. A single run measurement approach is proposed to circumvent utilization of a calibration curve that is often performed with HPFA. A sensitive mass spectrometer is applied as a detector enabling the measurement of in vitro protein binding at lower drug concentrations. Unbound free fraction and binding constants can be determined by a single run measurement by consecutive injections of an internal drug standard, a buffer plug and a drug-protein mixture. Effects of injection volumes on peak height and plateau profile were investigated in two different separation systems, non-volatile buffer and volatile buffer, with UV and mass spectrometry detection, respectively. A simplified one-to-one binding model is employed to evaluate the proposed method by using both single and multiple drug concentrations to measure the unbound free fraction and calculate the binding constants of some selected compounds. The method is suitable for rapid and direct screening of the binding of a drug to a specific protein or drug-plasma protein binding. Copyright © 2005 John Wiley & Sons, Ltd. [source] Incorporation of 3T3-L1 Cells To Mimic Bioaccumulation in a Microscale Cell Culture Analog Device for Toxicity StudiesBIOTECHNOLOGY PROGRESS, Issue 2 2004Kwanchanok Viravaidya Deficiencies in the early ADMET (absorption, distribution, metabolism, elimination, and toxicity) information on drug candidates extract a significant economic penalty on pharmaceutical firms. We have developed a microscale cell culture analog (,CCA) device that can potentially provide better, faster, and more efficient prediction of human and animal responses to a wide range of chemicals. The system described in this paper is a simple four-chamber ,CCA ("lung","liver","fat","other tissue") designed on the basis of a physiologically based pharmacokinetics (PBPK) model of a rat. Cultures of L2, HepG2/C3A, and differentiated 3T3-L1 adipocytes were selected to mimic the key functions of the lung, liver, and fat compartments, respectively. Here, we have demonstrated the application of the ,CCA system to study bioaccumulation, distribution, and toxicity of selected compounds. Results from the bioaccumulation study reveal that hydrophobic compounds such as fluoranthene preferentially accumulated in the fat chamber. Only a small amount of fluoranthene was observed in the liver and lung chambers. In addition, the presence of the differentiated 3T3-L1 adipocytes in the ,CCA device significantly reduced naphthalene and naphthoquinone-induced glutathione (GSH) depletion. These findings suggest the potential utilization of the ,CCA system to assess ADMET characteristics of the compound of interest prior to animal or human trials. [source] In vitro transcorneal and transscleral diffusion of radiolabeled compounds in human and rabbit cornea and in human, monkey, dog, and rabbit scleraACTA OPHTHALMOLOGICA, Issue 2009CB STRUBLE Purpose To determine the in vitro diffusion of selected compounds across the cornea or sclera of humans, monkeys, dogs, and rabbits. Methods Human and NZW rabbit corneas were obtained and the epithelium was removed from one cornea of each pair. Corneas were mounted in chambers with 3H-water or 3H-dexamethasone on the epithelial side and BSS solution on the endothelial side. Serial aliquots were taken from each chamber and assayed by LSC. Scleral sections from human, NZW rabbit, dog, or monkey eyes were mounted in perfusion chambers. Adjacent sclera was used for H&E histology. 3H-water, 3H-dexamethasone, or 70kD-14C-dextran were added to the episcleral surface while perfusing BSS across the choroidal side. Serial aliquots were collected up to 5 hrs and assayed by LSC. Scleral permeability (ktrans) was calculated. H&E slides were used to determine scleral thickness. Results 3H-water diffused through cornea faster than 3H-dexamethasone, especially with denuded epithelium. Scleral thickness and molecular weight were determinant of diffusion in sclera. Monkey sclera was thinnest, followed by dog, rabbit, and human. ktrans for 70kD-14C-Dextran and 3H-dexamethasone were greatest in monkey, followed by dog, rabbit, and human. ktrans values for 3H-water were similar in all species, and greater than values for 14C-dextran and 3H-dexamethasone. Conclusion These studies demonstrate permeability of cornea and sclera in human and animal models with compounds of varied molecular weights representative of drugs being developed for treatment of ocular diseases. The results of this study indicate that these techniques are valuable as screening tools in the development of ocular drugs. [source] Design, Synthesis, and Biological Evaluation of New Territrem B AnaloguesCHEMISTRY & BIODIVERSITY, Issue 4 2005Xiangrui Jiang Some 23 analogues of the potent acetylcholinesterase (AChE) inhibitor territrem B (1) were designed, synthesized, and tested for their biological activities. Some of the new synthetic derivatives exhibited IC50 values for AChE inhibition in the upper micromolar range. Molecular-modeling studies indicated that a planar conformation seems to be crucial for AChE inhibition. The two N-atoms of the piperazine moieties in 5o, 5p, and 5r might further enhance the inhibitory effects. The cytotoxicities of selected compounds against six human tumor cell lines were also determined. [source] The use of small molecule high-throughput screening to identify inhibitors of the proteinase 3-NB1 interactionCLINICAL & EXPERIMENTAL IMMUNOLOGY, Issue 2 2010M. Choi Summary Anti-neutrophil cytoplasmic antibodies (ANCA) to proteinase 3 (PR3) are found in patients with small-vessel vasculitis. PR3-ANCA bind strongly to membrane PR3 (mPR3) that is presented by the NB1 receptor. We performed high-throughput screening using a small molecule library to identify compounds that inhibit PR3-NB1 binding. We established a human embryonic kidney (HEK293) cell-based system, where approximately 95 ± 2% of the NB1-transfected cells expressed the NB1 receptor on the cell surface. Addition of 0·1 µg/ml human PR3 to 104 NB1-expressing HEK293 cells resulted in PR3 binding that was detected by immunofluorescence using a fluorescence plate reader assay. We identified 13 of 20 000 molecules that inhibited PR3 binding by >70%. Seven of 13 substances showed reproducible inhibition in four additional validation experiments. Two selected compounds (27519 and 27549) demonstrated a dose-dependent inhibition over a range from 6·25 to 100 µM as measured by the plate reader assay. We used flow cytometry as a second assay, and found that both compounds reproducibly inhibited PR3 binding to NB1-transfected HEK293 cells at 50 µM (inhibition to 42 ± 4% with compound 27519 and to 47 ± 6% with compound 27549 compared to the dimethylsulphoxide control). Furthermore, compounds 27519 and 27549 also inhibited binding of exogenous PR3 to human neutrophils. In contrast, the compounds did not decrease mPR3 expression on resting neutrophils, but reduced the tumour necrosis factor-,-mediated mPR3 increase on NB1pos neutrophils when present continuously during the assay. The findings suggest that small inhibitory compounds provide a potential therapeutic tool to reduce mPR3 by preventing its binding to NB1. [source] | ||||||||||||||||