Showing papers on "Reagent published in 1987"

Preparation and use of tetra-n-butylammonium per-ruthenate (TBAP reagent) and tetra-n-propylammonium per-ruthenate (TPAP reagent) as new catalytic oxidants for alcohols

Abstract: Tetra-n-butylammonium per-ruthenate (Bun4N)(RuO4) and tetra-n-propylammonium per-ruthenate (Prn4N)(RuO4), with N-methylmorpholine N-oxide, function as mild catalytic oxidants for the high yield conversion of alcohols to aldehydes and ketones and are competitive with more conventional reagents.

Molecular dynamics of a model SN1 reaction in water

Abstract: Results are presented from a computer simulation of the dynamics of a model SN1 reaction in water, very loosely based on the reaction t‐BuCl→t‐Bu++Cl−. Two diabatic electronic states are considered, covalent and ionic, which cross in the presence of the polar solvent. The curve crossing is treated in the electronically adiabatic limit, which gives rise to coupled reagent and solvent dynamics involving a mixed covalent/ionic adiabatic potential surface. The reaction dynamics are analyzed in terms of a simple solute reaction coordinate defined to be the t‐Bu to Cl separation distance. By employing constraint dynamics techniques, the potential of mean force is determined as a function of this reaction coordinate. The time evolution of the reaction is followed in terms of the full molecular dynamics of all reagent and solvent atoms. Beginning with the largely covalently bound reactant t‐BuCl, the following was observed: (i) how energy flows out of the water solvent bath into a solvent–reactant fluctuation dri...

Polymeric particles, their manufacture and uses

Abstract: A slow release composition comprises particles of a cross linked polymeric matrix in which a water soluble reagent is dispersed, and the reagent is anionic, generally being a low molecular weight anionic water soluble polymer, and the matrix is a cationic, highly cross linked, polymer formed from a water soluble monomer or monomer blend.

Reaction system element and method for performing prothrombin time assay

Abstract: An element and method for easily performing liquid assays are disclosed. The element uses capillary action to draw a predetermined volume of a liquid sample into a reaction chamber charged with reagent, where reaction between the liquid sample and the reagent is monitored.

A dry reagent delivery system with membrane having porosity gradient

Abstract: Dry chemistry reagent system, kit and method for detection of an analyte such as glucose, cholesterol, urea, antigen or antibody. The reagent system is a porous membrane or bibulous film having a porosity gradient from one planar surface to the other. In the membrane are uniformly distributed an indicator, a flow control agent and a reagent cocktail. The membrane is also modified by a conditioning agent.

Chromatographic test strip for determining ligands or receptors

Abstract: A test strip for analysis of analytes such as antigens, antibodies or polynucleotides employs a chromatographic medium and a solvent capable of transporting reagents and/or sample. Reagents are selected and disposed on the medium such that a labeled (first) reagent arrives at the detection (third) zone only after analyte is immobilized there and non-reactive sample componets have been transported beyond the detection zone. This sequential arrival is accomplished by the relative mobility of the reagent or sample; or by the site relationship of the zones. Preferably, the site relationship of the sample (second) zone and the label (first) zone is such that a plurality of pathways guide the sample and labeled reagent and any subsequent reagents to the detection zone in the recited order. Single and multiple pathway devices are disclosed.

Fiber-optic chemical sensors for competitive binding fluoroimmunoassay.

Abstract: Anal. Chem. 1987, 59, 1226-1230 Fiber-optic Chemical Sensors for Competitive Binding Fluoroimmunoassay B r u c e J. Tromberg' a n d Michael J. Sepaniak* Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996-1600 T u a n Vo-Dinh* a n d Guy D. Griffin Advanced Monitoring Development Group, Health and Safety Research Division, Oak Ridge National Laboratory, P.O. Box X , Oak Ridge, Tennessee 37831 This paper describes the development of a fiber-optic chem- ical sensor based on the principle of competitive-binding fluorescence immunoassay. Rabbit immunoglobin G ( IgG) is covalently lmmoMlized on the distal sensing tip of a quartz optical flber. The sensor is exposed to fluorescein Isothlo- cyanate (FITC) labeled and unlabeled anti-rabbit IgG. The 488-nm line of an argon-ion laser provides excitation of sen- sor-bound anaiyte. This results in fluorescence emission at the optical fiber's sensing tip. Sensor response is inversely proportional to the amount of unlabeled anti-IgG in the sam- pie. Limits of detection (LOD) vary with incubation time, sample size, and measurement conditions. For 10-kL sam- ples, typical LOD are 25 fmol of Unlabeled antibody in a 20- min incubation period. These results indicate that each fi- ber-optic fluoroimmunosensor can be constructed to perform a single sensitive, rapid, low-volume immunoassay, in in situ or benchtop applications. Fiber-optic chemical sensors (FOCSs) have been designed to provide simple, rapid, in situ analyses of trace chemicals (1-8). FOCSs are characterized by their chemically selective immobilized reagent phase at the fiber's sampling terminus. This reagent phase distinguishes these devices from their less selective physical sensor counterparts (9-11). In order to detect trace amounts of chemicals with high sensitivity and specificity, the principles of solid-phase im- munoassay can be applied to FOCS design. This involves the covalent immobilization of receptor molecules (antibody or antigen) to the distal face of a single-strand gw-~m-diameter quartz optical fiber. The fiber and immobilized receptor molecules form a stable, selective fluoroimmunosensor (FIS). Careful selection of the proper immobilization procedure enhances FIS stability by minimizing receptor leakage. Provided there is sufficient immobilized reagent for reasonable sensitivity, this direct attachment of antibody or antigen via organosilanating reagents is preferable to those techniques which utilize membrane or gel-entrapped reagent phases. This is due to the fact that sensor response times are limited by mass transport to the fiber and immunochemical kinetics. Despite their potential for higher loadings, these processes may be slower in membrane or gel systems (1, 2). Several types of immunoassays can be performed. The simplest involves in situ FIS incubation followed by direct measurement of a naturally fluorescent analyte (12). For nonfluorescent materials, in situ incubation is followed by development in fluorophor-labeled second antibody. The resulting antibody sandwich produces a fluorescence signal Also Oak Ridge Associated Universities Graduate Fellow, Ad- vanced Monitoring Development Group, Health and Safety Research Division, Oak Ridge National Laboratory. that is directly proportional to bound antigen. The sensitivity obtained when using these techniques increases with increasing amounts of immobilized receptor (13). A third detection scheme involves competition between fluorophor-labeled and unlabeled antigen. In this case, the unlabeled analyte com- petes with labeled analyte for a limited number of receptor binding sites. Assay sensitivity therefore increases with de- creasing amounts of immobilized reagent (13). The appropriate FIS immunoassay method is determined by the chemical characteristics of the antigen/antibody system of interest. For example, naturally fluorescent antigens and haptens should be analyzed by direct measurement. Non- fluorescent haptens should be detected via competitive binding or sandwich techniques, though the scarcity of hapten epitopes (antibody recognition sites) may diminish the sensitivity of sandwich analyses. An alternate means of gaining sensitivity in direct and sandwich assays entails increasing the absolute amount of immobilized receptor by increasing the fiber surface area. This can be accomplished with small-diameter fibers by utilizing evanescent-wave excitation of biomolecules bound to the circumference of the sensing tip. These sensors are characterized by large exposed surface areas and low eva- nescent wave penetration depths ( 5 1 4 , 15). Their primary limitation is the fact that evanescently excited fluorescence is coupled less efficiently into the optical fiber than distal-face (vide infra) excitation. In this paper, the FIS is exposed to fluorophor-labeled and unlabeled ligand. This results in competition for FIS binding sites. Signal intensity in this competitive binding immu- noassay scheme is inversely proportional to a n a l e (unlabeled ligand) concentration. Though the fiber's diminutive surface area restricts the absolute amount of bound analyte, excellent sensitivity is achieved since an efficient distal-face fluorescence collection geometry is used. In addition, the small amount of immobilized receptor serves as the limiting reagent in the competitive assay. As a result, rapid, nonequilibrium low- volume analyses can be performed. Moreover, factors that alter fluorescence signals, such as quenching, matrix inter- ferences, and self-absorption are relatively insignificant for the FIS. This is partly due to the fact that the sensing ter- minus is thoroughly washed following analyte incubation and all measurements are made in a controlled matrix. EXPERIMENTAL SECTION Materials. Rabbit immunoglobin G (IgG), polyclonal anti- rabbit IgG, polyclonal fluorescein isothyocyanate (FITC) conju- gated anti-rabbit IgG, bovine serum albumin (BSA), and oval- bumin were purchased from Cooper Biomedical, Inc., Malvern, PA. Spectrapor cellulose dialysis membrane (MW cutoff = 12000) was acquired from Thomas Scientific, Philadelphia, PA. (3- Glycidoxypropy1)trimethoxysilane (GOPS) was obtained from Aldrich Chemical Co., Milwaukee, WI. Phosphate-buffered saline (PBS), pH 7.4, and all other reagents were supplied by Sigma Chemical Co., St. Louis, MO. @ 1987 American Chemical Society

Alkylidenation of Ester Carbonyl Groups by means of a Reagent Derived from RCHBr2, Zn, TiCl4, and TMEDA. Stereoselective Preparation of (Z)-Alkenyl Ethers

Abstract: The esters (I) reacts with the 1,1-dibromoalkanes (II) in the presence of zinc-dust and titanium tetrachloride, yielding the 1-alkenyl ethers (III) with predominance of the Z-isomers.

Hydrogen peroxide production by a marine phytoplankter1

Abstract: Hymenomonas carterae, a calcified marine phytoplankter, produces hydrogen peroxide extracellularly. Hydrogen peroxide production by a washed cell suspension occurs in the dark and is inhibited by cell-impermeable protein modification reagents. A cell-surface redox enzyme is thus likely responsible for production of H2O2. The physiological function of this potentially toxic compound is unknown. If the production rate of 1–2 × 10−14 mol cell−1 h−1 measured in cultures of H. carterae could be generalized, marine phytoplankton would be an important source of the hydrogen peroxide found in the marine environment.

Measurement of metal cation compartmentalization in tissue by high-resolution metal cation NMR.

Abstract: PERSPECTIVES AND OVER.VIEW 375 DETERMINATION OF METAL CATION DISTRIBUTIONS IN TISSUE .. 376 Straightforward Chemical Analysis 377 Electron Microprobe X-Ray Analysis 377 Compartmental Volume Determination 378 Values Jor Volumes and Concentrations 378 Ion-Selective Microelectrodes 378 NMR SPECTROSCOPY OF METAL CATIONS 379 Isochronicity oj Comljartmental Resonances ....... 380 NMR Invisibility oj 'Na and '9K Signals 381 USE OF SHIFT REAGENTS FOR METAL CATION NMR OF TISSUE 387 Chemistry oj Shift Reagents 388 Use oj Shift Reagents with Suspensions oj Cells 389 Use oj Shift Reagents with Intact Tissue 393 Use oj Shift Reagents In Vivo 397

Recovery of uranium from sea water. IV. Influence of crosslinking reagent of the uranium adsorption of macroreticular chelating resin containing amidoxime groups

Abstract: Macroreticular chelating resins (RNH) containing amidoxime groups with various degrees of crosslinking were synthesized by using various amounts of ethyleneglycol dimethacrylate (1G), dimethyleneglycol dimethacrylate (2G), triethyleneglycol dimethacrylate (3G), tetraethyleneglycol dimethacrylate (4G), and nanoethyleneglycol dimethacrylate (9G) as crosslinking reagent. The effect of crosslinking reagents on the pore structure, ion exchange capacity, swelling ratio, and adsorption ability for uranium of RNH was investigated. RNH (RNH–1G) prepared by using 1G were showed to have macroreticular structures by the measure of specific surface area. RNH–1G had the high adsorption ability and physical stability. Though RNH (RNH–4G) obtained by using 4G have little macroreticular structure (macropore), these resins showed the high adsorption ability for uranium by the treatment with 0.1 mol dm−3 NaOH at 30°C for 15 h (alkali treatment). These results suggest that the formation of not only the favorable macropore but also the micropore is important for the effective recovery of uranium in sea water, whereas RNH–4G was defined to be low physical and chemical stability. For the preparation of RNH which have effective pore structure for the recovery of uranium, chemical, and physical stability, the simultaneous use of divinylbenzene (DVB) and 1G or 4G as crosslinking reagent was examined (abbreviated as RNH–DVB–1G and RNH–DVB–4G). The specific surface area of RNH–DVB–1G increased with an increase of 1G used. These RNH–DVB–1G have been shown the high adsorption ability for uranium. On the other hand, the specific surface area and adsorption ability for uranium of RNH–DVB–4G decreased with an increase of 4G used. Repeated use did not cause the deterioration of both RNH–DVB–1G and RNH–DVB–4G. This result suggests that the simultaneous use of DVB and 1G or 4G contributed the improvement of chemical and physical stability. In particular, RNH–DVB–1G has the effective macropore and micropore for the recovery of uranium.

Studies on Peptides. CLV. Evaluation of Trimethylsilyl Bromide as a Hard-Acid Deprotecting Reagent in Peptide Synthesis

Abstract: Trimethylsilyl bromide (TMSBr) in trifluoroacetic acid (TFA) was found to have the ability to cleave benzyl-type protecting groups, i.e., benzyloxycarbonyl (Z), benzyl (O-Bzl) and p-methoxybenzyl (S-MBzl). The reaction was best accelerated by addition of thioanisole, compared with other soft nucleophiles so far examined. The rate of the cleavage reaction with TMSBr/TFA was judged to be somewhat slower than that with trimethylsilyl trifluoromethanesulfonate/TFA. However, TMSBr/TFA reduced Met(O) efficiently and gave almost no side reaction of Asp (succinimide formation). This deprotecting procedure was applied to the synthesis of human gastrin-releasing peptide.

A transition-metal chromophore as a new, sensitive spectroscopic tag for proteins: selective covalent labeling of histidine residues in cytochromes c with chloro(2,2':6',2″-terpyridine)platinum(II) chloride

Abstract: Reactivity and selectivity of Pt(trpy)Cl/sup +/ toward proteins are studied with cytochromes c from horse and tuna as examples. The new transition-metal reagent is specific for histidine residues at pH 5. The reaction, facile one-step displacement of the Cl/sup -/ ligand by imidazole, produces good yield. The binding sites, His 26 and His 33 in the horse protein and His 26 in the tuna protein, are identified by UV-vis spectrophotometry and by peptide-mapping experiments. Model complexes with imidazole, histidine, histidine derivatives, and histidine-containing peptides are prepared and characterized. The covalently attached Pt(trpy)/sup 2 +/ labels allow easy separation of the protein derivatives by cation-exchange chromatography. The labels do not perturb the conformation and reduction potential of cytochrome c, as shown by UV-vis spectrophotometry, cyclic voltammetry, differential-pulse voltammetry, EPR spectroscopy, and /sup 1/H NMR spectroscopy. The selectivity of Pt(trpy)Cl/sup +/ is entirely opposite from that of PtCl/sub 4//sup 2 -/ although both of them are platinum(II)-chloro complexes. Owing to an interplay between the steric and electronic effects of the terpyridyl ligand, the new reagent is unreactive toward methionine (a thio ether) and cystine (a disulfide), which are otherwise highly nucleophilic ligands, but very reactive toward imidazole, which is otherwise a relativelymore » weak ligand. Unusual and useful selectivity of preformed transition-metal complexes toward proteins evidently can be achieved by a judicious choice of ancillary ligands.« less