Showing papers on "Reagent published in 1990"
386 citations
TL;DR: A review of the use of baker's yeast as a reagent in organic synthesis can be found in this article, with an emphasis on the developments of the last 15 years, and the transformations of various classes of compounds are examined, for example, reduction or formation of double bonds, acyloin condensation.
Abstract: The review examines the use of baker's yeast as a reagent in organic synthesis, with an emphasis on the developments of the last 15 years. The transformations of various classes of compounds are examined, for example, reduction or formation of double bonds, acyloin condensation. The equivalent microbial transformations are compared in relevant cases
340 citations
Patent•
14 Dec 1990TL;DR: In this paper, the amount of oxidized form of the redox mediator at the counter electrode and the applied potential difference must be sufficient to cause diffusion limited electrooxidation of the reduced form at the surface of the working electrode.
Abstract: A biosensor that includes working and counter electrodes of substantially the same size and made of the same electrically conducting material. A reagent is contained in a reagent well in the biosensor. The reagent includes a redox mediator, an enzyme, and a buffer, and covers substantially equal surface areas of portions of the working and counter electrodes. When a sample, containing the analyte to be measured, is added to the reagent well, a reaction occurs that oxidizes the analyte and reduces the redox mediator. After this reaction is complete, an electrical potential difference is applied between the electrodes. The amount of oxidized form of the redox mediator at the counter electrode and the applied potential difference must be sufficient to cause diffusion limited electrooxidation of the reduced form of the redox mediator at the surface of the working electrode. After a short time delay, current produced by the electrooxidation of the reduced form of the redox mediator is measured and the observed current is correlated to the amount of the analyte in the sample. In some cases, the analyte sought to be measured may be reduced and the redox mediator may be oxidized. In such cases, current produced by diffusion limited electroreduction of the oxidized form of the redox mediator is measured and correlated to the amount of analyte in the sample.
297 citations
TL;DR: Several polysulfides were tested as potential sulfur-transfer reagents during the automated synthesis of oligodeoxyribonucleoside phosphorothioates via the deoxyriboenucleosides phosphoramidite approach as discussed by the authors, and thiosulfonate 3H-1,2-benzodithiol-3-one 1,1-dioxide (12) was particularly efficient as a sulfurizing reagent
Abstract: Several polysulfides were tested as potential sulfur-transfer reagents during the automated synthesis of oligodeoxyribonucleoside phosphorothioates via the «deoxyribonucleoside phosphoramidite» approach. The thiosulfonate 3H-1,2-benzodithiol-3-one 1,1-dioxide (12) was particularly efficient as a sulfurizing reagent
295 citations
Patent•
04 Apr 1990TL;DR: A reagent for introducing a nucleic acid into an animal cell is defined as a neutral lipid such as dioleoylphosphatidylethanolamine as discussed by the authors.
Abstract: A reagent for introducing a nucleic acid into an animal cell. The reagent comprises (a) a neutral lipid such as dioleoylphosphatidylethanolamine and (b) a cationic lipid selected from the group consisting of an ammonium salt such as dimethyldioctadecylammonium bromide or cetyldimethylethylammonium bromide, an amine such as stearylamine, and a benzethonium salt such as methylbenzethonium chloride
287 citations
258 citations
Patent•
13 Jun 1990
TL;DR: In this paper, a thin crystalline diyne surfactant polymeric electrically conducting layer is used to bound members of specific binding pairs for the measurement of analyte or a reagent.
Abstract: Biosensors are provided employing a thin crystalline diyne surfactant polymeric electrically conducting layer to which may be bound members of specific binding pairs. Binding of an analyte or a reagent to the specific binding pair member layer may change the electrical, optical or structural properties of the layer for measurement of analyte. The change in the polymeric layer provides for a sensitive measurement.
227 citations
TL;DR: In this paper, the Fenton's reagent (hydrogen peroxide and iron (II)) treatment of pentachlorophenol (PCP) was investigated as a basis for the on site and in situ treatment of contaminated surface soils.
Abstract: The Fenton's reagent (hydrogen peroxide and iron (II)) treatment of pentachlorophenol (PCP) was investigated as a basis for the on site and in situ treatment of contaminated surface soils. Mineralization of PCP was demonstrated in a silica sand system by the removal of the parent compound and total organic carbon with corresponding stoichiometric recovery of chloride. The treatment of PCP was investigated in two natural soils of varying organic carbon content. Pentachlorophenol was degraded in the soils with and without iron (II) addition. The optimum treatment conditions were found at pH 2 to 3.
206 citations
TL;DR: In this article, a trimethylsilylating reagent was used to form trimethyl-silylated derivatives of alkyltrimethylammonium-kanemite complexes.
Abstract: Alkyltrimethylammonium–kanemite complexes, having three dimensional SiO2 networks, were allowed to react with a trimethylsilylating reagent to form the trimethylsilylated derivatives. The three dimensional SiO2 networks were retained after trimethylsilylation. The calcined products obtained from the trimethylsilylated products had about 840–880 m2 g−1 in specific surface areas and micro pores with 22–33 A in average pore diameter. These values were slightly smaller than those of the calcined products obtained from alkyltrimethylammonium–kanemite complexes, which indicated the effect of the trimethylsilyl groups.
204 citations
TL;DR: The authors describe the application of fluorescent rare-earth chelates to immunoassay and DNA probing.
Abstract: Like many analytical methodologies, immunoassays and nucleic acid hybridization assays rely on the reaction between an analyte of interest and a specific reagent. The analyte concentration is then deduced by measuring either the amount of analyte-reagent complex formed (product) or the amount of residual reagent. The authors describe the application of fluorescent rare-earth chelates to immunoassay and DNA probing.
202 citations
Patent•
[...]
14 Feb 1990
TL;DR: In this paper, materials which are not themselves storage-stable at room temperature are made suitable for storage by mixing them with a carrier substance and spray-drying the resulting mixture so as to form particles containing both the material and the carrier substance in an amorphous, i.e. glassy or rubbery, state.
Abstract: Materials which are not themselves storage-stable at room temperature are made suitable for storage by mixing them with a carrier substance and spray drying the resulting mixture so as to form particles containing both the material and the carrier substance in which the carrier substance is in an amorphous, i.e. glassy or rubbery, state. Formation of such a composition greatly enhances stability. The material stored may be a biological material such as an enzyme, the components of a chemical reaction such as reagents for carrying out an assay, or even viable biological cells.
TL;DR: A dimethylbarbituric acid reagent has been used to follow the kinetics of loss of two water-soluble carbodiimides, 1-ethyl-3-(3-dimethylaminopropyl) Carbodiimide (EDC) and the structurally related EAC, in aqueous solution as a function of pH and added chemical reagents.
TL;DR: Grignard addition to a chiral 1-acyl-4-methoxypyridinium salt provides synthetically useful 2-alkyl(aryl)-2,3-dihydro-4 pyridones in high diastereomeric excess as discussed by the authors.
Abstract: Grignard addition to a chiral 1-acyl-4-methoxypyridinium salt provides synthetically useful 2-alkyl(aryl)-2,3-dihydro-4-pyridones in high diastereomeric excess
TL;DR: The need for further sample preparation after derivatization with TFAA-NMIM was thereby eliminated, and detection limits of less than 20 pg ml-1 ivermectin could be achieved with 1 ml of plasma by a considerably simpler analytical procedure.
TL;DR: In this paper, the kinetics of the reaction for the formation of the pink azo dye in both fresh water and sea water was studied at different acidities, temperatures, and concentrations of N -1 naphthylethylenediamine (NED).
TL;DR: In this article, a wide range of phenols can be iodized with unprecedented selectivity in aqueous alcohol solvents by the action of a reagent prepared in situ from sodium hypochlorite and sodium iodide.
Abstract: Direct iodination of a wide range of phenols may be achieved with unprecedented selectivity in aqueous alcohol solvents by the action of a reagent preparated in situ from sodium hypochlorite and sodium iodide. Para-substituted phenols (or ortho-substituted, when the para-position is already occupied) are obtained in fair to excellent yields by simple isolation techniques. The extent of iodination is easily controlled by stoichiometry. The technique is also useful with some anilines
TL;DR: In this paper, a dual regiocontrol was obtained in the Li 2 CuCl 4 -catalyzed Grignard reaction with primary allylic acetates, where reaction conditions that favor formation of an intermediate dialkylcuprate gave α-substitution, whereas reaction conditions favoring formation of a monoalkylcopper intermediate led to a γ-subtitution.
Abstract: The regiochemistry of copper-catalyzed reactions between Grignard reagents and allylic substrates has been studied. A dual regiocontrol was obtained in the Li 2 CuCl 4 -catalyzed Grignard reaction with primary allylic acetates. Reaction conditions that favor formation of an intermediate dialkylcuprate (fast addition of Grignard reagent, low temperature, low concentration of catalyst) gave α-substitution, whereas reaction conditions favoring formation of a monoalkylcopper intermediate (slow addition of Grignard reagent, increased concentration of catalyst) led to a γ-substitution. A remarkable solvent effect was observed for CuCN-catalyzed Grignard coupling with primary allylic acetates. In ether a highly γ-selective reaction took place, but in THF α-substitution predominated. Other allylic substrates such as allylic sulfones and allylic chlorides were also studied. The latter substrates showed a preference for γ-substitution, which is explained by their high reactivity
TL;DR: The palladium-catalyzed reaction of allyl acetates with aryl-and vinyltin reagents gave good yields of cross-coupled products as discussed by the authors.
Abstract: The palladium-catalyzed reaction of allyl acetates with aryl- and vinyltin reagents gave good yields of cross-coupled products. The reaction was mild and tolerant of functionality (CO 2 R, OH, OSiR 3 , OMe) in the tin reagent. Inversion of stereochemistry at the acetate center was observed, with retention of the geometry of the olefin of the allyl group and with exclusive coupling at the primary position. Retention of geometry of the olefin in the vinyltin reagents was also observed
TL;DR: The addition of NaOH to the protein assay reagent reduced the variation in the response of this assay to different proteins, and the sensitivity of the assay is increased.
TL;DR: Macrolactonization of 3,5- O -(3,4-dimethoxybenzylidene)-9,11-O -(2,4,6-trimethylbenzo-idene)(9 S )-9-dihydroerythronolide A seco-acid (4 ) was reexamined under various conditions and found to proceed rapidly only by treatment of 4 with Yamaguchi's reagent, 2.4, 6-trichlorobenzoyl chloride, in the presence
TL;DR: In this article, it was shown that the β-elimination step is purely anti, resulting in the formation of a chiral allene with 96% optical yield, and that the same reaction, run with a Grignard reagent RMgX and a catalytic amount of a Cu I salt, affords allenes through an anti or syn overall process.
Abstract: Propargylic ethers react with organocopper reagents to afford allenes by a syn addition to the triple bond followed by a β-elimination of the resulting alkenyl copper species. With use of chiral propargylic ethers and stoichiometric organocopper reagent, it was shown that the β-elimination step is purely anti, resulting in the formation of a chiral allene with 96% optical yield. The same reaction, run with a Grignard reagent RMgX and a catalytic amount of a Cu I salt, affords allenes through an anti or syn overall process. The crucial step is the β-elimination of the intermediate alkenyl organometallic species, which is of anti type with RMgI and of syn type whith RMgCl. Propargylic acetates, wich also afford allenes in this reaction, but through a Cu III intermediate, are not sensitive to this «halogen effect»
TL;DR: In this article, 3-Methyl-1-phenyl-4-stearoyl-5-pyrazolone loaded on to silica gel was used as a pre-concentration reagent for copper, cobalt and nickel prior to atomic absorption spectrometric determination.
Abstract: 3-Methyl-1-phenyl-4-stearoyl-5-pyrazolone loaded on to silica gel was used as a pre-concentration reagent for copper, cobalt and nickel prior to atomic absorption spectrometric determination. Both batch and column methods were used for the concentration of the above metals. These metals are quantitatively retained on the proposed adsorbent above pH 4. The adsorption-elution cycle can be repeated ten times with no observable decline in the efficiency of the adsorbent. As there are no observable effects due to changes in the volume of sample solution up to a volume of 1 l, a concentration factor of 40 can be achieved. The method has been applied to samples of sodium chloride solution and tap water.
TL;DR: A water soluble tin hydride has been synthesized carrying three methoxyethoxypropyl groups as discussed by the authors, which reduces various alkyl halides in water, or in organic solvents.
Patent•
12 Sep 1990
TL;DR: In this article, various source reagents of Group II elements suitable for high temperature superconductor (HTSC) material formation are described, including beta-diketonates, cyclopentadienyls, alkyls, perfluoroalkyls and Schiff bases.
Abstract: Metal organic chemical vapor deposition (MOCVD) formation of copper oxide superconductor materials. Various source reagents of Group II elements suitable for high temperature superconductor (HTSC) material formation are described, including beta-diketonates, cyclopentadienyls, alkyls, perfluoroalkyls, alkoxides, perfluoroalkoxides, and Schiff bases, as well as complexes of such Group II compounds, utilizing monodentate or multidentate ligands to provide additional coordination to the Group IIA atom, so that the resulting complex is of enhanced volatility characteristics, and enhanced suitability for MOCVD applications. Also disclosed are methods of synthesizing such compounds and complexes, including a method of making Group II metal beta-diketonate compounds having enhanced thermal stability characteristics. Further disclosed are a vertical inverted reactor for chemical vapor deposition, and various methods of processing applied metal oxide films for enhanced HTSC character.
TL;DR: A variety of silicate-CIF3 reaction experiments have been performed in order to determine the rate of reaction and minimum temperatures for which there is complete liberation of oxygen as discussed by the authors.
Abstract: A variety of silicate-CIF3 reaction experiments have been performed in order to determine the rate of reaction and minimum temperatures for which there is complete liberation of oxygen. Fast reaction rates ( ⩽ 2 hr.) and low minimum reaction temperatures ( ∼ 450°C) are shown by minerals such as quartz, feldspar, biotite and pyroxene while garnet reacts much slower and requires higher temperatures (4–8 hr. and 600°C, respectively). It is not possible to completely liberate oxygen from Mg-rich olivine using CIF3. A comparison of δ18O-values obtained from incomplete oxygen extractions to those for complete extractions indicates that a minimum oxygen yield of 95% is required for accurate δ18Odeterminations. These results indicate that CIF3 should not be used as a reagent when attempting to liberate oxygen preferentially from one mineral in a multi-mineral sample.
TL;DR: In this article, neutral, acidic, and basic protein DL-amino acids (DL-AA) have been separated by HPLC as diastereomeric derivatives obtained after derivatization with N2-(5-fluoro-2,4-dinitrophenyl)-L-alanine amide (FDNP-Ala-NH2, “Marfey's reagent”).
Abstract: Neutral, acidic, and basic protein DL-amino acids (DL-AA) have been separated by HPLC as diastereomeric derivatives obtained after derivatization withN2-(5-fluoro-2,4-dinitrophenyl)-L-alanine amide (FDNP-Ala-NH2, “Marfey's reagent”). HPLC was performed on 3 μm Spherisorb ODS II as the stationary phase with gradient elution using mixtures of triethylammonium phosphate buffer (pH 3) and acetonitrile. The differences in retention times (ΔtR) of diastereomers were compared with those obtained by derivatization of DL-AA with the novel FDNP-reagents FDNP-Val-NH2, FDNP-Phe-NH2, and FDNP-Pro-NH2. FDNP-reagents were synthesized by reaction of 1,5-difluoro-2,4-dinitrobenzene with 0.5 equivalent of the respective L-AA amide in mixtures of aqueous NaHCO3 and acetone at 40–50°C. All FDNP-reagents made possible the resolution of DL-AA. However, FDNP-Val-NH2, gave the largest ΔtR-values in most cases. Large ΔtR-values mainly arise by the formation of an intramolecular hydrogen bond between the carboxy and carboxamide group in the L-L diastereomers and the non-formation of this hydrogen bond in the D-L diastereomer (the first letter refers to the configuration of the AA to be analysed, the second to that of the reagent AA amide) as well as by the low conformational freedom of amino acid residues in diastereomers.
TL;DR: A rapid and reproducible method to quantify total DNA at picogram levels using two high-affinity DNA-binding proteins to construct a sandwich assay and a semiconductor sensor is used for quantitation.
TL;DR: Tagaya et al. as discussed by the authors showed that the E. coli enzyme was inactivated in a time and dose-dependent manner when incubated with the reagent followed by sodium borohydride reduction.
Patent•
19 Jul 1990
TL;DR: In this paper, an automated analytical apparatus by which homogeneous and heterogeneous analyses can be performed concurrently and on a random access basis includes a circular reaction tray supporting a multiplicity of peripherally arranged reaction cuvettes, sample handling arrangement for supporting samples to be analyzed and a reagent tray (73) supporting a plurality of liquid-reagent sources.
Abstract: An automated analytical apparatus by which homogeneous and heterogeneous analyses can be performed concurrently and on a random access basis includes a circular reaction tray (3) supporting a multiplicity of peripherally arranged reaction cuvettes, sample handling arrangement (4)for supporting samples to be analyzed and a reagent tray (73) supporting a plurality of liquid-reagent sources. The individual samples and liquid reagents are transferred, on a selective-random mode, by appropriate aspirating-dispensing apparatus (5,8) into reaction cuvettes on the reaction tray which are successively positioned at sample and reagent addition stations. The reaction tray is rotated from the reagent addition station to allow mixing and incubation of the reaction mixture and to position each cuvette at an analysis station (11). In the case of heterogeneous assays, magnetic particles are introduced into appropriate cuvettes at a magnetic particle suspension addition station. A particle wash station (9) is provided between the magnetic particle suspension addition station and the analysis station (11) whereat, after the reaction, the solid phase is washed in the reaction cuvette to remove unbound materials. Following such wash, substrate may be added (10) to the reaction cuvette for reaction with an enzyme solid phase and the magnetizable particles are resuspended. The reaction cuvette is then advanced to the analysis station, where the solid phase is withdrawn from the optical path and the appropriate optical readout of the liquid phase is effected. In respect of both heterogeneous and homogeneous assays, the rotational mode of the reaction tray is bidirectional, to provide multiple periodic readouts of each cuvette, to obtain data which is processed to provide the rate of the reaction.