Search results for "Assay"
showing 10 items of 2241 documents
Biochemical Characterization of an Acetylcholine-hydrolyzing Enzyme from Bean Seedlings.
1980
An acetylcholine hydrolyzing enzyme was prepared and purified (40 times) from dwarf bean hypocotyl hooks. The purity of the enzyme was proved by polyacrylamide gel electrophoresis. The molecular weight of the enzyme was determined to be 65,000 daltons. Enzyme activity was the highest at pH 8.0 and between 30 and 36 C. The enzyme had an apparent affinity constant (K(m)) for acetylcholine of 460/micromolar. The affinity for substrate analogs increased from butyrylthiocholine to propionylthiocholine to acetylthiocholine. The enzyme activity was inhibited by choline, neostigmine, physostigmine, manganese, and calcium. Magnesium had no influence on the enzyme activity. We conclude that the enzym…
The Effect of Light on the Growth of Pea Plants and the Subsequent Influence in Shikimate Oxidoreductase (EC 1.1.1.25) Activity
1981
Summary Pea plants were cultured in white light, red and far red light, and in the dark during a period of three weeks. At several states of development we investigated the activity of the enzyme shikimate oxidoreductase, the amount of fresh and dry matter, and the contents of protein in stem, leaves, cotyledons, and roots. The enzyme activity was found to be distributed organ-specifically and uninfluenced by the phytochrome system, but it was significantly depressed in plants grown in the dark compared to plants grown in white light. Enzyme activity occurred also in non photosynthetic plants. Regarding the different light conditions the activity of shikimate oxidoreductase was found to cor…
Endogenous Role of Microsomal Epoxide Hydrolase
2005
The specific activities of microsomal epoxide hydrolase with 16α,17α-epoxyandrosten-3-one (androstene oxide) as substrate were measured in various metabolically important and in various steroidogenic organs of the male and female rat and compared with the activities of 16α,17α-epoxyestratrienol (estroxide) and benzo[a]pyrene 4,5-oxide. Androstene oxide was an exceptionally good substrate. The specific activities differed widely between organs but the ratio of the activities towards these substrates was constant in all organs investigated. The ratios compared to benzo[a]pyrene 4,5-oxide were 2.5 for estroxide, and 8.6 for androstene oxide. The ontogenetic development of specific epoxide hydr…
New Acylated Triterpene Saponins fromPolygala arenaria
2003
Eight new acylated triterpene saponins 1–8 were isolated from the roots of Polygala arenaria as four inseparable (E)/(Z) mixtures of the 4-methoxycinnamoyl and 3,4-dimethoxycinnamoyl derivatives by repeated MPLC over silica gel. Their structures were established mainly by 600-MHz 2D-NMR techniques (1H,1H-COSY, TOCSY, NOESY, HSQC, HMBC) as 3-O-(β-D-glucopyranosyl)presenegenin 28-(O-β-D-galactopyranosyl-(14)-O-[β-D-glucopyranosyl-(13)]-O-β-D-xylopyranosyl-(14)-O-α-L-rhamnopyranosyl-(12)-{4-O-[(E)-4-methoxycinnamoyl]}-β-D-fucopyranosyl) ester and its (Z)-isomer (1/2), 3-O-(β-D-glucopyranosyl)presenegenin 28-(O-β-D-galactopyranosyl-(14)-O-[β-D-glucopyranosyl-(13)]-O-β-D-xylopyranosyl-(14)-O-α-L…
Organometallic complexes with biological molecules. XV. Effects of tributyltin(IV)chloride on enzyme activity, Ca2+, and biomolecule and synthesis in…
2001
Considerable attention has been given in recent years to the possibility that xenobiotics in the environment may affect reproduction in animals. In this study, the relative impact of tributyltin(IV) (TBT) chloride, one of the most toxic environmental pollutants, was investigated using Ciona intestinalis ovary as a model system. The pleiotropic effects of TBT exposure are concentration dependent and include a decrease of ATP levels, lipid content and nucleic acid content and synthesis. In contrast, a marked increase in calcium (Ca2+) and glucose content is observed. Furthermore, TBT alters enzymatic activity, inhibiting creatine kinase and stimulating alkaline phosphatase and cholinesterase …
Cell wall xyloglucan incorporation by xyloglucan endotransglucosylase/hydrolase in pine hypocotyls
2004
Abstract In the present study, we have examined the incorporation of labelled xyloglucan oligosaccharides into the cell wall xyloglucan of pine hypocotyl sections, and the effect of plant hormones on the incorporation and on XTH enzyme activity (EC 2.4.1.207). Xyloglucan heptasaccharide [ 3 H ]XXXGol was absorbed, transported and incorporated into the cell wall xyloglucan of de-rooted pine hypocotyls. Incorporation of [ 3 H ]XXXGol into soluble and cell wall xyloglucan was induced by IAA, brassinolides and XXXG in pine hypocotyl segments. A relationship between growth induction, by IAA, brassinolides and XXXG, and both soluble and cell wall-bound XTH was found. We suggest that IAA induced-g…
Conservation of amino-acid chromatograms.
1951
IN filter-paper partition chromatography, the ninhydrin reaction has been used almost exclusively for the identification and quantitative assay of amino-acids. One of the chief disadvantages of the blue pigment formed in this reaction is its rapid fading on filter-paper chromatograms. This makes it difficult to construct permanent or semi-permanent reference maps from which not only the type of amino-acid, but also the approximate quantity of the unknown mixture, can be deduced.
Über den Ureidstoffwechsel beim Laubmoosprotonema von Funaria hydrometrica L. (Sibth.)1)1)Herrn Prof. Dr. Dr. Kurt Mothes zum 75. Geburtstag gewidmet.
1975
Summary The activity of allantoinase (EC 3.5.2.5) is influenced by light and darkness. The extracts of dark-grown moss protonema showed a very higher enzyme activity than the extracts of light-grown plants. The allantoinase activity was increased by light-dark and decreased by dark-light transitions. DMAP mimicked light effects by stabelizing the charakteristic light depending enzyme avctivities in the dark. The inhibitors DCMU, DNP and CCCP increased the enzyme activity of light-grown moss protonema, to some extend they induced a “physiological dark condition”.
New developments in immunochemical water analysis down to 30 mul sample volume.
1999
Abstract The determination of trace levels of pesticides like atrazine in water samples of small, restricted volumes is one of the future demands of environmental analysis. In a brief review existing chromatographic and immunochemical methods for atrazine are critically discussed. Then a simple rapid enzyme-linked immunosorbent assay (ELISA) using the tip of an inoculation needle as a solid surface is presented. The sample volume could be reduced to 30 μl. The assay had a centre of the test IC50 of 0.12 μg l−1 and permitted the characterisation of atrazine at levels of 0.022–2.90 μg l−1. A first outlook for automatisation is given. The new method was compared with an ELISA using 96 well mic…
General Cytotoxicity Assessment by Means of the MTT Assay
2014
Cytotoxicity assays were among the first in vitro bioassay methods used to predict toxicity of substances to various tissues. In vitro cytotoxicity testing provides a crucial means for safety assessment and screening, and for ranking compounds. The choice of using a particular cytotoxicity assay technology may be influenced by specific research goals. As such, four main classes of assays are used to monitor the response of cultured cells after treatment with potential toxicants. These methods measure viability, cell membrane integrity, cell proliferation, and metabolic activity. In this chapter, we focus on the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide tetrazolium reducti…