Showing papers on "Reagent published in 1997"
TL;DR: The PicoGreen assay allowed the detection of 25 pg/ml ds DNA, surpassing the sensitivity achieved with Hoechst 33258 by 400-fold, and showed greater dsDNA:RNA selectivity than HoeChSt 33258 in low ionic strength buffer and better dSDNA:single-stranded DNA selectivity in 1 M NaCl.
766 citations
TL;DR: An automated enzyme assay was performed within a microfabricated channel network using resorufin beta-D-galactopyranoside, a substrate that is hydrolyzed to resorUFin, a fluorescent product, and derived Michaelis--Menten constants compared well between an on-chip and a conventional enzyme assay.
Abstract: An automated enzyme assay was performed within a microfabricated channel network. Precise concentrations of substrate, enzyme, and inhibitor were mixed in nanoliter volumes using electrokinetic flow. Reagent dilution and mixing were controlled by regulating the applied potential at the terminus of each channel, using voltages derived from an equivalent circuit model of the microchip. The enzyme β-galactosidase (β-Gal) was assayed using resorufin β-d-galactopyranoside (RBG), a substrate that is hydrolyzed to resorufin, a fluorescent product. Reaction kinetics were obtained by varying the concentration of substrate on-chip and monitoring the production of resorufin using laser-induced fluorescence. Derived Michaelis−Menten constants compared well between an on-chip and a conventional enzyme assay. Bias in the derived Km and kcat was primarily due to the limited solubility of RBG and the associated lack of measurements at substrate concentrations exceeding the Km. A Ki of 8 μM for the inhibitor phenylethyl β...
427 citations
Patent•
15 Aug 1997
TL;DR: In this paper, a polybifunctional reagent is provided having a polymeric backbone, one or more pendent photoreactive moieties, and two or more bioactive groups.
Abstract: A polybifunctional reagent is provided having a polymeric backbone, one or more pendent photoreactive moieties, and two or more pendent bioactive groups. The reagent can be activated to form a bulk material or can be brought into contact with the surface of a previously formed biomaterial and activated to form a coating. The pendent bioactive groups function by promoting the attachment of specific molecules or cells to the bulk material or coated surface. Bioactive groups can include proteins, peptides, carbohydrates, nucleic acids and other molecules that are capable of binding noncovalently to specific and complimentary portions of molecules or cells.
397 citations
TL;DR: In this article, a series of solid-acid catalysts, such as γ-Al2O3, H-ZSM-5, amorphous silica-alumina, as well as titania modified zirconia, were studied for the catalytic conversion of methanol to dimethyl ether (DME).
Abstract: The catalytic conversion of methanol to dimethyl ether (DME) has been studied over a series of solid-acid catalysts, such as γ-Al2O3, H-ZSM-5, amorphous silica-alumina, as well as titania modified zirconia. All the catalysts are active and selective for DME formation. The apparent activation energy for DME formation over γ-Al2O3 is ca. 25 kcal/mol, a value that increases to ca. 37 kcal/mol upon the addition of 23 Torr of H2O to the reagent. The rate of methanol dehydration decreases with increasing acidity (silica content) over the amorphous silica-alumina catalysts. Although H-ZSM-5 with Si/Al = 25 is the most active among the catalysts tested, the DME selectivity is only 20% at 280°C, a typical temperature used in the syngas-to-methanol process. An amorphous silica-alumina catalyst with 20 wt.-% silica content (SIRAL20) exhibits the best catalytic performance of those tested at 280°C.
368 citations
TL;DR: In this article, preliminary results on the novel study of ammonia scrubbing for the removal of carbon dioxide from flue gas were provided, which indicated the potential of CO2 reduction by NH3 scrubbing is very promising.
Abstract: This paper provides preliminary results on the novel study of ammonia scrubbing for the removal of carbon dioxide from flue gas. Experimental results indicated the potential of CO2 reduction by NH3 scrubbing is very promising. The overall CO2 removal efficiencies could be above 95% under proper operation conditions. The absorption capacity of NH3 was around 0.9 kg of CO2/kg of NH3 reagent being used. This should be higher than that by a MEA solution. The reaction products were analyzed and determined by X-ray diffraction analysis, SEM picture, and pH measurements. All the measurements indicated that an ammonium bicarbonate solution and its crystalline solids are the major products of reaction.
289 citations
TL;DR: DNAzol, a patent-pending DNA isolation reagent containing guanidine thiocyanate and a detergent mixture, is a complete, nontoxic and ready-to-use reagent for the isolation of genomic DNA from various biological sources.
Abstract: In this report, we present DNAzol®, a patent-pending DNA isolation reagent containing guanidine thiocyanate and a detergent mixture. It is a complete, nontoxic and ready-to-use reagent for the isol...
253 citations
TL;DR: In this paper, the preparation of polystyrene−divinylbenzene-supported derivatives of tris(2-aminoethyl)amine and methyl isocyanate is described.
Abstract: The preparation of polystyrene−divinylbenzene-supported derivatives of tris(2-aminoethyl)amine and methyl isocyanate are described. These polymeric reagents are used to quench excess reactants and remove known impurities from the crude reaction products obtained from the solution-phase, parallel syntheses of ureas, thioureas, sulfonamides, amides, and pyrazoles. In conjunction with the use of other polymeric reactants during the course of a reaction, the addition of polymer-supported quench reagent(s) at the conclusion of the reaction allows isolation of the desired product by a single filtration and evaporation of solvent. The mechanical simplicity and efficiency of this methodology make possible the rapid, parallel purification of crude reaction products obtained via solution-phase syntheses, regardless of whether the intended product is a single compound or a mixture of compounds, and hence offers an attractive alternative to solid-phase organic synthesis in the practice of combinatorial chemistry.
253 citations
TL;DR: In this article, a spectrophotometric method is described for the determination of dissolved mono- and polysaccharides in seawater, based upon the well known alkaline ferricyanide reaction, but uses the reagent 2,4,6-tripyridyl-s-triazine (TPTZ) to give a strongly colored complex with the reduced iron.
234 citations
TL;DR: In this article, the peroxide-oxidized C165S mutant of the AhpC peroxidase protein from Salmonella typhimurium was investigated.
Abstract: The trapping of a sulfenic acid within the fully active C165S mutant of the AhpC peroxidase protein from Salmonella typhimurium was investigated. The electrophilic reagent employed in these studies, 7-chloro-4-nitrobenz-2-oxa-1,3-diazole (NBD-Cl), has previously been used to modify thiol, amino, and tyrosine hydroxyl groups in proteins; at neutral pH only cysteinyl residues of AhpC proteins are modified. The peroxide-oxidized C165S mutant of AhpC incubated with NBD-Cl gave a product with an absorbance maximum at 347 nm, whereas the thiol-NBD conjugate formed from the reduced protein absorbed maximally at 420 nm. Electrospray ionization mass spectrometry of the modified proteins allowed identification of the species absorbing at 347 nm as a Cys-S(O)-NBD derivative containing one additional oxygen relative to the Cys-S-NBD product. The C165S conjugates with Cys-S(O)-NBD and Cys-S-NBD had no peroxidase activity when compared to unreacted C165S and wild-type AhpC, but were both reactivated through removal of NBD by DTT. Oxidized C165S was also modified by dimedone, a common sulfenic acid reagent, to give the expected inactivated conjugate of higher mass. This reagent was not removed by DTT and blocked any further reaction of the protein with NBD-Cl. NBD modification of Enterococcus faecalis NADH peroxidase, a well-characterized flavoprotein with an active-site sulfenic acid (Cys-SOH), also yielded the spectrally-distinguishable NBD conjugates following incubation of NBD-Cl with oxidized and reduced forms of the denatured peroxidase, indicating a general utility for this reagent with other sulfenic acid-containing proteins. A significant advantage of NBD-Cl over previously-used sulfenic acid reagents such as dimedone is in the retention of the sulfenic acid oxygen in the modified product; differentiation between protein-associated thiols and sulfenic acids is therefore now possible by means of both visible absorbance properties and mass analyses of the NBD-modified proteins.
222 citations
TL;DR: A review of CAN in the construction of C-C bonds can be found in this paper, where it has been shown to mediate the facile oxidative addition of 1,3-dicarbonyl compounds to activated and unactivated alkenes leading to dihydrofurans and furanones.
Abstract: Organic synthesis using carbon centred radicals generated by one electron oxidants is of current interest. Although Mn(OAc)3 has received the most attention, it appears that cerium(IV) ammonium nitrate (CAN) would be a very useful reagent for the generation of radicals. The recent application of CAN in the construction of C–C bonds are highlighted in this review. CAN has been shown to mediate the facile oxidative addition of 1,3-dicarbonyl compounds to activated and unactivated alkenes leading to dihydrofurans and furanones. In most cases the reactions occur under milder conditions and the yields are superior when compared to Mn(OAc)3 mediated reactions. The results available thus far suggest that CAN offers cast potential in radical mediated organic synthesis.
169 citations
TL;DR: The trinitrophenylation kinetic seems to be more dependent on protein structure than reactivity, and in evaluation of the available lysine in glycated proteins, the distinction between reductive alkylation and Maillard-type condensation necessitates quantitative evaluation of nonalkylated lysines in protein hydrolysate, compared to results with the TNBSA method.
TL;DR: In this article, the potential of the oxidation of various carcinogenic aromatic amines by Fenton's reagent [Fe(II) + H2O2] for liquid waste treatments was assessed.
TL;DR: In this paper, the reaction of readily available N-benzylbenzamide (1) with a slight excess of BuLi produces a deep blue dianion, which can be used as a stoichiometric reagent to titrate n-BuLi, s-BuLDA, and t -BuLi with good precision.
TL;DR: In this article, the surface of a fused silica and oxidized silicon wafer (SiO2/Si(100)) was treated with (3-aminopropyl)triethoxysilane (1), (3-) aminosilane, (3)-amino-methyl-silane (2), and (3]-ethoxydimethylsilane for 72 h in solution.
Abstract: The surface of a fused silica and oxidized silicon wafer (SiO2/Si(100)) was treated with (3-aminopropyl)triethoxysilane (1), (3-aminopropyl)diethoxymethylsilane (2), and (3-aminopropyl)ethoxydimethylsilane (3) for 72 h in solution. Thickness of the aminosilylated film out of 1 increases rapidly, and it turns out to be around 100 A in 72 h. Rather slow increase of the thickness is observed for 2, which produces the layers of 8 and 14 A in 10 and 72 h, respectively. The reagent 3 produces the monolayers of constant thickness 7−8 A during the whole span of the reaction. The aminosilane layer was allowed to react with 4-nitrobenzaldehyde to form an imine, and absorbance (Asurf) of the imine was recorded by UV−vis spectroscopy. The imine was hydrolyzed in a known volume of water to produce 4-nitrobenzaldehyde, and subsequently its absorbance was measured. Thus observed number of the aldehyde molecules is equivalent to the number of the imine molecules on the surface. With the known surface area of the substrat...
TL;DR: A simple and practical procedure for the preparation of NBSH of high purity and guidelines for the handling and storage of the reagent are provided in this note.
Abstract: o-Nitrobenzenesulfonylhydrazide (NBSH) has been shown to be a valuable reagent for the synthesis of allenes from propargylic alcohols, for the reductive transposition of allylic alcohols, and, most recently, for the deoxygenation of unhindered alcohols. Each of these transformations proceeds by Mitsunobu displacement of an alcohol with NBSH followed by in situ elimination of o-nitrobenzenesulfinic acid to form a monoalkyl diazene intermediate. The mild reaction conditions (neutral pH, reaction temperatures ≤23 °C) are especially attractive for substrates containing sensitive functional groups. The success of this methodology relies critically upon the purity of the NBSH reagent employed in the reaction. A simple and practical procedure for the preparation of NBSH of high purity and guidelines for the handling and storage of the reagent are provided in this note.
TL;DR: The mean recovery of ADMA was over 96% and the inter-and intra-assay coefficients of variation of amounts were lower than 3.80% and those of retention time were below 0.37% for five runs.
Patent•
09 Jun 1997
TL;DR: An analytical test device incorporating a dry porous carrier to which a liquid sample, eg. urine, suspected of containing an analyte such as HCG or LH can be applied indirectly, is described in this paper.
Abstract: An analytical test device incorporating a dry porous carrier to which a liquid sample, eg. urine, suspected of containing an analyte such as HCG or LH can be applied indirectly, the device also incorporating a labelled specific binding reagent which is freely mobile in the porous carrier when in the moist state, and an unlabelled specific binding reagent which is permanently immobilised in a detection zone on the carrier material, the labelled and unlabelled specific binding reagents being capable of participating in either a sandwich reaction or a competition reaction in the presence of the analyte, in which prior to the application to the device of a liquid sample suspected of containing the analyte, the labelled specific binding reagent is retained in the dry state in a macroporous body, eg. of plastics material having a pore size of 10 microns or greater, through which the applied liquid sample must pass en route to the porous carrier material, the labelled specific binding reagent being freely soluble or dispersible in any liquid sample which enters the macroporous body.
TL;DR: In this article, the authors investigated the mechanisms of four trihalomethanes (THMs) commonly found in chlorinated drinking water by Fenton's reagent and found that the amount of THM oxidized increased with increasing initial organic concentrations.
Patent•
30 Dec 1997
TL;DR: A multilayer reagent test strip measures the concentration of analyte in a liquid sample that is applied to it as discussed by the authors, where the analyte can react with a reagent to cause a color change.
Abstract: A multilayer reagent test strip measures the concentration of analyte in a liquid sample that is applied to it. The sample is guided to a number of assay areas arrayed along the strip, where the analyte can react with a reagent to cause a color change. Each assay area also includes an inhibitor for the color-change reaction. The inhibitor concentration increases in successive assay areas; thus, the number of areas that change color is a measure of the analyte concentration. The test strip is particularly adapted for measuring glucose in a whole blood sample. In a preferred embodiment, the sample is guided to the assay areas along a path formed by crushing selected areas of a membrane, and the assay areas are uncrushed areas of the membrane.
TL;DR: It has been shown that bromodimethylsulfonium bromide, generated in situ by treating dimethyl sulfoxide with aqueous hydrobromic acid, is a milder and more selective reagent for electrophilic aromatic bromination than elemental bromine.
Abstract: It has been shown that bromodimethylsulfonium bromide, generated in situ by treating dimethyl sulfoxide with aqueous hydrobromic acid, is a milder and more selective reagent for electrophilic aromatic bromination than elemental bromine.
Patent•
02 Apr 1997
TL;DR: Urea or other solid NO x -reducing reagent is employed in a selective catalytic reduction process on emissions from diesel and lean-burn gasoline engines as mentioned in this paper, and the reactant gas contains ammonia and is fed to the exhaust on an as-needed basis.
Abstract: Urea or other solid NO x -reducing reagent is employed in a selective catalytic reduction process on emissions from diesel and lean-burn gasoline engines. The solid reagent is fed to a gas generator that produces a reactant gas by heating. In one embodiment the reactant gas is maintained at elevated temperatures to prevent condensation products from forming. The reactant gas contains ammonia and is fed to the exhaust on an as-needed basis.
TL;DR: In this paper, the authors analyzed the Fenton system's ability to oxidize dichlorvos with Fenton's reagent in solutions containing various ions, and showed that the added amount of ferrous ions, the higher the elimination rate of dichlor vos and the oxidization rate after the addition of ferric ions is far smaller than that of adding ferrous ion.
TL;DR: The cyclisation-anion capture protocol has been applied to a wide range of starter and terminating species to effect regio-and stereo-specific mono-and bis-cyclisation processes in which a variety of organoboronderivatives function as anion transfer reagents.
TL;DR: In this paper, the stochastic properties of Fenton's reagent in the oxidation of dichloroethylene (DCE), trichloro methylene (TCE), TCE, Tetra-CE, and DCEA were investigated and the theoretical optimal ratio between H2O2 and Fe2+ was found to be 11.
Abstract: The stoichiometry of Fenton's reagent in the oxidation of dichloroethylene (DCE), trichloroethylene (TCE), tetrachloroethylene (tetra-CE), and dichloroethane (DCEA) was investigated. The theoretical optimal ratio between H2O2 and Fe2+ is found to be 11. However, the experimentally determined optimal ratio between H2O2 and Fe2+ ranged from 5 to 11 at optimal pH of 3.5. The amount of H2O2 required for a specific percentage removal of the organic compounds depends upon the initial organic concentration to be oxidized. The accumulation of chloride ion released also depends upon the initial organic substance concentrations. The typical percentage removal of organic compounds and percentage release of chloride ion were reported at 100%, 70%, 50%, 40%, 30%, 20%, 10%, and 1%. The amount of H2O2 required to achieve a certain percentage removal follows the order of TCE < Tetra-CE < DCE << DCEA. However, the amount of chloride ion detected at a constant concentration of H2O2 follows the order of DCEA << DCE < TCE < ...
TL;DR: Biological screening of the title compounds against several common glycosidase enzymes as well as in vitro anti-HIV assays are reported.
Abstract: The synthesis of (1→6), (1→4), and (1→1) linked aza-C-disaccharides, a novel class of glycomimetic compounds, is described. The polyhydroxylated piperidine ring was synthesized using vinyl bromide 11 as a common intermediate which was synthesized de novo from bromobenzene utilizing the microbial oxidation metabolite bromodiol 10. A Suzuki coupling of 11 with an alkylboron reagent derived from olefinated carbohydrate precursors via hydroboration was used to form the C-glycosidic bond. Ozonolysis and selective reduction of the resultant carbonyl functions served to produce the azasugar ring. Fully deprotected aza-C-disaccharides were obtained upon acidic deprotection. Biological screening of the title compounds against several common glycosidase enzymes as well as in vitro anti-HIV assays are reported.
TL;DR: Results demonstrate that the modification of HDL3 by hypochlorite transformed an antiatherogenic lipop Protein particle into a modified lipoprotein with characteristics similar to lipoproteins commonly thought to initiate foam cell formation in vivo.
TL;DR: In this paper, a mixture of equal amounts of CuBr−SMe2, LiBr, and LiSPh in THF at 0 °C furnished a new soluble copper catalyst that was highly efficient at coupling primary, secondary, tertiary, aryl, vinyl, and allylic Grignard reagents to primary tosylates and primary Grignards to secondary sulfonates.
Abstract: A mixture of equal amounts of CuBr−SMe2, LiBr, and LiSPh in THF at 0 °C furnished a new soluble copper catalyst that was highly efficient at coupling primary, secondary, tertiary, aryl, vinyl, and allylic Grignard reagents to primary tosylates and primary Grignard reagents to secondary tosylates and mesylates, all with the use of only 1 equiv of Grignard reagent. The new catalyst was shown to be much more reactive than copper catalysts CuBr and Li2CuCl4 and more efficient in the transference of secondary and tertiary alkyl groups than lower order cuprates (Gilman reagents) and demonstrated more reactivity than the lower order cuprates with its ability to couple primary Grignard reagents to secondary sulfonates. The Grignard reagent/catalyst system was compatible with an ester functionalized tosylate, thus proving to be more chemoselective than a Grignard reagent without the catalyst. The catalyst exhibited good reactivity below room temperature, and with the addition of 6% v/v of HMPA to the catalyst solu...