Showing papers on "Reagent published in 1968"
TL;DR: Dimethyl sulfoxide can replace the latter, volume for volume, in a ninhydrin reagent mixture that gives equal performance and has improved stability, and is recommended to replace methyl Cellosolve-containing reagents in the quantitative determination of amino acids by automatic analyzers and by the manual ninHydrin method.
807 citations
TL;DR: Phenylglyoxal (14C-labeled, if desired) may be useful for modification of accessible arginine residues in proteins and may be potentially useful for reversible coverage of arginin residues so that tryptic hydrolysis can take place at lysine residues only.
610 citations
521 citations
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324 citations
TL;DR: All assay procedures which do not rely on the direct detection of a specific property of the unknown substance must depend on the reaction of an unknown with a reagent to give a product which can then be assayed.
Abstract: ALL assay procedures which do not rely on the direct detection of a specific property of the unknown substance must depend on the reaction of an unknown with a reagent to give a product which can then be assayed. The product can be estimated directly or indirectly (for example, as a result of a further reaction). If the unknown is regenerated after the primary reaction it may then react with more reagent and a cycling assay is established. The advantage of such a system is that one molecule of the unknown gives rise to several molecules of product with a consequent increase in sensitivity. The reagent can be as diverse as a dye, neutron irradiation, an enzyme substrate or an antibody. Adequate assay systems must be shown to have suitable specificity, sensitivity, precision, range and convenience. In order to obtain maximum sensitivity and precision: (1) all the unknown should be reacted at least once and preferably several times; (2) the amount of product should be assayed by a procedure which gives a low background and shows changes in direct proportion to the change in product concentration; (3) the property measured should be capable of detection at very low concentrations of the product. The use of one or more cycling reactions is one well recognized way of achieving suitable amplification (compare the assay of metabolic intermediates and enzymes).
277 citations
TL;DR: Catalytic amounts of o -phenanthroline were found to enhance the rate of air-oxidation of all sulfhydryl groups tested in the presence of copper ions at neutral pH, and the interpretation is discussed that o-phenan Throline necessarily acts as a metal chelator in the inhibitory action of this reagent on any enzyme.
184 citations
TL;DR: The fluorescence of a Morin-thorium complex provides a more sensitive fluoride reagent than has been previously used and has immediate stability and a linear response to fluoride up to 50% reduction in fluorescence.
173 citations
TL;DR: The apparatus has been modified to allow the study of isolated chloroplasts in the presence of electron acceptors and donors and the time resolution of the method has been improved and reaches 5 msec under the best conditions.
172 citations
TL;DR: In this paper, the authors discuss the filter paper disk technique for assaying radioactive macromolecules, which consists of numbering a series of Whatman No. 1 (or No. 3) cellulose disks and then applying the impure radioactive sample, such as an aliquot of a reaction mixture, to the properly numbered disk.
Abstract: Publisher Summary This chapter discusses the filter paper disk techniques for assaying radioactive macromolecules. The method consists of numbering a series of Whatman No. 1 (or No. 3) cellulose disks and then applying the impure radioactive sample, such as an aliquot of a reaction mixture, to the properly numbered disk. The enzyme reaction is stopped by placing the filter paper disk in a large beaker of trichloroacetic acid. A large number of disks, for example, all the time points in a multitube kinetic experiment or density gradient run, can be accumulated and subsequently processed simultaneously through several reagents necessary for extraction of extraneous material. After radioactive precursors have been removed from the radioactive product, the washing reagents that may interfere with the analysis of the radioactive product are removed by suitable solvents and residual water is removed by drying either with solvents, air, or heat. The radioactivity of the sample can then be analyzed for the various types of isotopes that it may contain, either by scintillation techniques or by a straightforward Geiger counting procedure, under standard counting conditions. Descriptions of several specific modifications of this disk procedure are outlined in the chapter, which are useful for a number of enzymatic polymerizations and depolymerizations that use radioactive substrates to measure the radioactive product.
170 citations
TL;DR: The authors used menthyl chloroformate for optical analysis of asymmetric amino and hydroxyl compounds by gas chromatography, which was shown to be useful in the analysis of protein synthesis.
Abstract: Reagent menthyl chloroformate use in optical analysis of asymmetric amino and hydroxyl compounds by gas chromatography
TL;DR: In this paper, the aldehyde 2 was characterized as the crystalline 6-oxime and 6-(p -nitrophenyl)hydrazone (p-NH) hydrazone.
TL;DR: The use of a stable solution of ferric chloride for the detection of cholesterol and cholesteryl esters on thin-layer chromatographic layers is described and the levels of sensitivity for the new reagent are shown.
TL;DR: Thin-layer chromatographic methods are described for the separation of the following monosaccharides: glucose, galactose, glucosamine, galactsamine, N-acetylglucosamines, N -acetylgalactosamine and neuraminic acids.
TL;DR: The enzyme is remarkably specific for the phosphoinositides; the fatty acid compositions of these lipids have been compared and appears to be widely distributed in animal tissues.
Abstract: Some properties of the phosphoinositide inositolphosphohydrolase of guinea-pig intestinal mucosa supernatant fraction are described. The enzyme has an absolute requirement for metal ions, the most efficient activator being Ca2+. The pH optimum is 5.3 in acetate buffer and 5.9 in maleate; activity is higher in the latter. The effects of detergents and various reagents are described. Corn phosphatidyl inositol is hydrolysed faster than brain phosphatidyl inositol; the fatty acid compositions of these lipids have been compared. The enzyme is remarkably specific for the phosphoinositides. The composition of the enzyme preparation has been studied. The enzyme appears to be widely distributed in animal tissues.
TL;DR: The presence of a PGE-like ketonic component in the hydroxy-acid constituents of rabbit and cat irins was demonstrated, along with a lower proportion of the ketonic components in ether-purified rabbit cerebral hemisphere extract.
Abstract: An easy and relatively rapid procedure for distinguishihg the ketonic prostaglandins E (PGEs) from the nonketonic prostaglandins F (PGFs) and other hydroxy-acid lipid spasmogens is presented. The method depends on the ability of certain hydrazine derivatives to combine specifically with keto groups. Girards reagent T (trimethyl-ammonium-acetohydrazide chloride) was used for differentiation. PGFs were unaffected by the reagent whereas the reagent affected E series prostaglandins by apparently inactivating them. In addition apparent inactivation also occurred when the reagent was applied to a mixture of the PGEs and PGFs. After treatment of PGEs in aqueous solution with the reagent for 1 hour at room temperature or 0 degrees centigrade their extraction into ether on partition at pH 3-4 was reduced. Freezing to -15 degrees centigrade after the 1 hour treatment and thawing before the ether partition further reduced the recovery of PGEs. After reagent treatment in these different conditions PGFs were recovered fully. The presence of a PGE-like ketonic component in the hydroxy-acid constituents of rabbit and cat irins was demonstrated along with a lower proportion of the ketonic components in ether-purified rabbit cerebral hemisphere extract.
TL;DR: In this paper, the Gibbs test was used to determine the hydroxylation pattern of xanthones in the presence of certain additives, such as aluminum chloride and 2,6-dichlorobenzoquinone chloroimide.
TL;DR: A rapid serum cholesterol method having the accuracy of longer methods is described, which may be processed in under 3 hr and has a 45% increase in sensitivity over other methods.
TL;DR: A number of advantages favor the bromoacetate-ribonuclease reaction technique, for some applications, over the ninhydrin detection method.
TL;DR: The assay is sufficiently sensitive to measure renin in the plasma of all normal rabbits and can be extended to measure much lower activities, such as the percentage release of the angiotensin content/hr.
Abstract: 1. EDTA (10mm), 2,3-dimercaptopropan-1-ol (10mm) and chlorhexidine gluconate (0.005%, w/v) cause complete inactivation of plasma enzymes that degrade angiotensin I, but have no effect on the reaction of renin with its substrate. The reagents were termed the selective inhibitors. 2. Thus it is possible to measure renin in plasma by its ability to catalyse the release of angiotensin I. 3. Sterile plasma, treated with the selective inhibitors, is incubated with renin substrate (500-1000ng. of angiotensin content/ml.) at pH6 at 42 degrees for 6hr. 4. Under these conditions the reaction obeys first-order kinetics. Renin activity is calculated in terms of the percentage release of the angiotensin content/hr. 5. As described, the assay is sufficiently sensitive to measure renin in the plasma of all normal rabbits. By extending the length of the incubation, much lower activities can be measured.
TL;DR: The bacterial protease, subtilisin BPN', has been shown to have a catalytic mechanism similar to that of mammalian pancreatic proteolytic enzymes.