Showing papers on "Reagent published in 1977"

Rates of thiol-disulfide interchange reactions between mono- and dithiols and Ellman's reagent

Abstract: The rate constants for thiol-disulfide interchange between 21 mono- and dithiols and Ellman's reagent correlate with the pKu's of the thiol groups with a Bronsted coefficient of p = 0.36. The maximum rates ofreduction are observed for thiols having pK, values close to the pH of the solution in which the reactions were carried out. In the dilute solutions examined (10-4-10-6 M in each reagent), the rate of the second, intramolecular interchange step in reactions of dithiols was faster than that of the first, intermolecular interchange, regardless of the size of the cyclic disulfide formed. A convenient synthesis of a mixture of diastereomers of 1,4-dimercapto-2,3-butanediol (i.e., of a mixture of dithiothreitol, DTT, and dithioerythritol, DTE) has been developed from 1,2:,4-diepoxybutane and thiolacetic acid.

Rapid determination of sulphate in natural waters and plant digests by continuous flow injection turbidimetry

Abstract: The turbidimetric determination of sulphate as barium sulphate has been adapted to the continuous flow injection procedure of Růžicka and co-workers. The effects of reagent composition, reagent flow-rates and length of mixing coils have been investigated. Optimum conditions were established for the determination of sulphate in natural waters and in plant digests. The results agree satisfactorily with those obtained by a standard turbidimetric method and analyses can be carried out at a rate of up to 180 samples per hour.

Enzymatische Bestimmung des Gesamtcholesterins mit dem Greiner Selective Analyzer (GSA-II)

Abstract: A fully enzymatic method to determine total cholesterol in serum is described. The method appears especially suitable for adaptation to discrete mechanical analyzers either of the single channel or the multi-channel type. The method uses the enzymes cholesterol esterase (EC 3.1.1.13), cholesterol oxidase (EC 1.1.3.6) and peroxidase (EC 1.11.1.7) with 4-aminophenazone and phenol as substrates in the indicator reaction. The method was adapted to the Greiner Selective Analyzer GSA-II. For this purpose the critical parameters of the reaction were intensively examined. The complete reagent is stable within the GSA II dispenser at 4 degrees C for at least 1 week. By omitting cholesterol oxidase in the blank reagent a sample bland and a partial reagent blank are obtained. Within a range up to 10.4 mmol/1 (4.0 g/l) the maximum colour is developed within 6 minutes. The calibration factor was stable for 4 months. The method allows absolute measurements. At concentrations between 2 and 4 mmol/1 within-batch precision ranged from 0.5 to 1.4%. Precision from day to day for the same control sera amounted to 2.8; 2.0; 2.7 and 2.0% for a period of 3 months. Examination of accuracy yielded satisfying results. Ascorbic acid in the physiological range did not alter results to a significant extent. Catalase or novaminesulfone added in vitro did not interfere. Optical interferences by bilirubin, hemoglobin or turbidity are compensated by a sample blank. A comparison of results with the enzymatic method of Roeschlau et al. (Z. Klin. Chem. Klin. Biochem. 12, 226 (1974)) yielded satisfactory agreement. The limits of detection of the present method can be lowered by a factor of 2.2 by replacing phenol by dihalogen phenols.

Glucose detection system free from fluoride-ion interference

Abstract: An improved multilayer element for detecting glucose in samples of biological fluid which may contain with fluoride ion as a contaminant or preservative is described. The improved element comprises a buffered Trinder's reagent, which reagent comprises glucose oxidase, peroxidase, 4-aminoantipyrine and a phenolic or naphtholic coupler, which is buffered to a pH between about 4.5 and about 6.0. Such a buffering reduces any interference which may be due to fluoride ion present in the sample under analysis.

The reaction of F + H2→ HF + H. A case study in reaction dynamics

Abstract: Concepts developed in recent years as a result of experimental and theoretical studies of the dynamics of reactions A + BC → AB + C are examined here in trajectory studies of the reaction F + H2→ HF + H—currently the prototype of exothermic reaction. (i) An “early” barrier, characteristic of substantially exothermic reaction, has the consequence that reagent translation is much more efficient than vibration in promoting reaction, even for energies well in excess of the barrier. (ii) High vibrational excitation in the molecular product stems from the release of H·H repulsion while the new bond, F––H, is still extended (termed “mixed energy-release”); the large zero point vibration in H2 introduces variability in the F––H extension and H·H repulsion, and consequently in the breadth of the observed product vibrational distribution. (iii) Since the product vibrational excitation is governed by the attractive plus mixed energy-release, the slope of the outrun of the energy surface is not, per se, a dominant factor governing product vibrational excitation. (iv) Enhanced reagent vibration, 〈ΔV〉, tends to be channelled into enhanced product vibration, 〈ΔV′〉; the efficiency (〈ΔV′〉= 0.81 ΔV) is dependent on the form of energy surface in the region of “corner-cutting”, corresponding to reaction through extended intermediates F––H–H. (v) Enhanced reagent translation is channelled into product translation plus rotation (〈ΔT′〉+〈ΔR′〉= 1.12 〈ΔT〉); the efficiency provides an indication of the energy required to bend and compress the intermediate FH·H. (vi) The rotational dependence of the reactive cross section, σ(J), provides a sensitive probe of the region of the potential-energy hyper-surface along the entry valley up to the barrier. (vii) Enhanced reagent rotational excitation at first decreases product vibrational excitation and then increases it according to experiment; this effect has not been reproduced theoretically. (viii) Product rotational excitation derives in large part from the release of repulsion in bent configurations: this gives rise predominantly to coplanarity and opposed directions for the product rotational and orbital motions. (ix) Enhanced reagent excitation of all sorts results in significant enhancement in product rotation, due to reaction through more-compressed and bent configurations; the most efficient conversion is from reagent rotation into product rotation (〈ΔR′〉= 1.2 〈ΔR〉). (x) For thermal (300 K) reaction the computed centre-of-mass angular distribution is sharply backward-peaked, and similar for all product vibrational levels. (xi) Enhanced reagent vibration or translation shifts the computed mean scattering angle forward, with ΔT being markedly more effective than ΔV; the “stripping threshold energy” is high, as anticipated for these masses reacting on a strongly repulsive potential-energy surface favouring collinear approach.

[26] Detection of peptides by fluorescence methods

Abstract: Publisher Summary The recent introduction of fluorescamine, a novel reagent designed after the fluorogenic reaction of ninhydrin with primary amines in the presence of phenylalanine, has now provided a strong alternative to ninhydrin for detection of peptides Fluorescamine reacts with primary amino groups of peptides almost instantaneously at room temperature in aqueous solution at pH 75-9, to form a fuorescent compound The reagent is subsequently hydrolyzed to yield a watersoluble, nonfluorescent product Fluorescamine itself is not fluorescent Ammonia in solution yields little or no fluorescence with fluorescamine These features and the great sensitivity attainable in the fluorescence measurement have made fiuorescamine increasingly popular in amino acid and peptide analysis Another development in recent years is the rediscovery of o -phthalaldehyde as a general reagent for amino acids and peptides when used in the presence of 2-mercaptoethanol This reagent has recently been applied to the microanalysis of amino acids and peptides

A Novel Colorimetric Reagent for Potassium Based on Crown Ether Complex Formation

Abstract: The extraction study of alkali metal ions was made with a new type of crown ether, 4′-picrylaminobenzo-15-crown-5 (HL). Upon dissociation in alkaline medium orange-colored HL gives blood-red anion, L−, and extracts selectively K+ (and to a lesser extent Rb+) ion into chloroform as a colored complex of composition ML·HL. A colorimetric determination of 10 - 400 ppm K+ in the presence of < 2000 ppm Na+ was possible using this new crown ether reagent.

TRIALKYLZINCLITHIUM [R3ZnLi] A NEW REAGENT FOR CONJUGATE ADDITION TO α,β-UNSATURATED KETONES

Abstract: Trialkylzinclithium is readily prepared in THF by mixing zinc chloride (or its TMEDA complex) and alkyllithium in a 1 : 3 mole ratio. Conjugate addition of this new reagent is demonstrated with 2-cyclohexen-1-one (I) and dicyclopentadien-1-one (IV) as a,α,β-unsaturated ketones.

Specific binding assay method and reagent means

Abstract: A method and reagent means for the determination of small quantities of chemical compounds in man, animal and plants by a specific binding assay technique. The method involves the utilization of a labelling constituent comprising a conjugate of a labelling substance and a binding component said labelling substance being one or more metal atoms which can be easily determined. The labelling constituents are selected from various metalo organic derivatives or metal coordination complexes. The method is very specific and sensitive and can be successfully utilized for the determination of haptens selected from various groups such as alkaloids, barbiturates, steroids, cannabinoids, vitamins, aminoacids, tranquilizers, sugars, penicillins, etc.

Analytical element for clinical analysis

Abstract: An analytical element for use in the clinical assay of an analyte contained in a biological liquid sample which is applied from an external source to a substantially planar sample receiving suface of the element. The analytical element comprises a porous layer bearing the aforementioned sample receiving surface; at least one dry reagent material for use in the assay; and one or more associated rupturable pod-like member(s) containing a liquid reagent for the assay, such liquid reagent, upon rupture of the pod-like member(s), being released into the element.

Assay kit for camp and/or cgmp and method of using the same

Abstract: An assay kit for assaying adenosine-3',5'-cyclic monophosphate, which is herein referred to as cAMP, guanosine-3',5'-cyclic monophosphate, which is herein referred to as a cGMP, or both; and said assay kit comprising, A container of Reagent 1 comprising succinyl cAMP tyrosine methyl ester; succinyl cGMP tyrosine methyl ester; succinyl cAMP tyrosine methyl ester and succinyl cGMP tyrosine methyl ester in admixture or both succinyl cAMP tyrosine methyl ester and succinyl cGMP tyrosine methyl ester in separate containers, said esters labelled with radioactive iodine; A container of Reagent 2 comprising an anti-cAMP serum, an anti-cGMP serum, an anti-cAMP and anti-cGMP serum in admixture or both anti-cAMP serum and anti-cGMP serum in separate containers; A container of Reagent 3 comprising an imidazole buffer solution of 0.1 M or higher concentration; A container of Reagent 4 comprising a material for separation; A container of Reagent 5 comprising a solution of succinic anhydride in an organic solvent; A container of Reagent 6 comprising an organic tertiary amine; and A container of Reagent 7 comprising a standard solution of cAMP, cGMP, cAMP and cGMP in admixture or both cAMP and cGMP in separate containers.

Design criteria for uniform reaction rates in an oxygen plasma

Abstract: The physical conditions necessary to obtain uniform and reproducible chemical reaction rates in an oxygen plasma are investigated by stripping photoresist from silicon wafers. An oxygen plasma was selected due to its simplicity and the availability of a simple technique for measuring the concentration of atomic oxygen which is the reagent of importance. However, many of the considerations will apply to the design of other plasmas for other chemical reactions. Due to the electrical Skin effect at 13.56 MHz, the atomic oxygen is created near the Walls in a cylindrical reactor. However, at flow rates corresponding to residence times in the range of 1-10 s, diffusion makes the concentration uniform within a few percent except near the walls. Under conditions such that there is no by-product inhibition, the chemical reaction rate is determined bythe atomic oxygen concentration and the temperature of the silicon substrate and the reactor walls. The rate is independent of the conbination of pressure and power used to produce the atomic oxygen concentration.