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DPPH-I (m.p. 106 °C) is orthorhombic, DPPH-II (m.p. 137 °C) is amorphous and DPPH-III (m.p. 128–129 °C) is triclinic. [2] DPPH is a well-known radical and a trap ("scavenger") for other radicals. Therefore, rate reduction of a chemical reaction upon addition of DPPH is used as an indicator of the radical nature of that reaction.
Most commonly, antioxidant capacity is measured using the ABTS Decolorization Assay. Other antioxidant capacity assays which use Trolox as a standard include the diphenylpicrylhydrazyl ( DPPH ), oxygen radical absorbance capacity ( ORAC ) and ferric reducing ability of plasma ( FRAP ) assays.
K i is the inhibition constant for a drug; the concentration of competing ligand in a competition assay which would occupy 50% of the receptors if no ligand were present. [ 5 ] The Cheng-Prusoff equation produces good estimates at high agonist concentrations, but over- or under-estimates K i at low agonist concentrations.
However, the idea of an "optimum" rate of an enzyme reaction is misleading, as the rate observed at any temperature is the product of two rates, the reaction rate and the denaturation rate. If you were to use an assay measuring activity for one second, it would give high activity at high temperatures, however if you were to use an assay ...
Biological responses to ligand concentrations typically follow a sigmoidal function. The inflection point at which the increase in response with increasing ligand concentration begins to slow is the EC 50, which can be mathematically determined by derivation of the best-fit line.
Ferric reducing ability of plasma (FRAP, also Ferric ion reducing antioxidant power) is an antioxidant capacity assay that uses Trolox as a standard. [1] The FRAP assay was first performed by Iris Benzie and J. J. Strain of the Human Nutrition Research Group at the University of Ulster, Coleraine.
The enzyme unit, or international unit for enzyme (symbol U, sometimes also IU) is a unit of enzyme's catalytic activity. [1]1 U (μmol/min) is defined as the amount of the enzyme that catalyzes the conversion of one micro mole of substrate per minute under the specified conditions of the assay method.
Direct assay In a direct assay, the stimulus applied to the subject is specific and directly measurable, and the response to that stimulus is recorded. The variable of interest is the specific stimulus required to produce a response of interest (ex. death of the subject). [6] [12] Indirect assay
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