Inhibition percentage

The goal of most HTS assays for enzyme targets is to identify library components that act as inhibitors of enzymatic activity. To identify and compare inhibitory compounds, we must first define a metric that reflects the ability of a fixed concentration of compound to reduce the activity of the target enzyme. The most commonly used metric for this purpose is the inhibition percentage, which can be defined as follows ... 

At the completion of a primary screening of a compound library, a collection of hits will be identified that meet or exceed the inhibition percentage cutoff for hit declaration (as described above). The next step is to ensure the validity of these primary screening results through a series of experimental procedures aimed at addressing two aspects of hit validation hit confirmation and hit verification. 

The term hit confirmation, as we define it, involves three components reproducibility, confirmation of chemical structure, and confirmation of chemical purity. Confirmation of hit reproducibility requires that the subset of library compounds designated as hits in the primary screen be identified, that samples of each of these be obtained from the library bank (a process often referred to as cherry picking ), and that these samples be retested, at least once but preferably multiple times, to determine if they reproducibly confer an inhibition percentage of the target enzyme... 

The following example explains how a pT-value is determined. Within a dilution series, light inhibition percentages in the luminescent bacteria test at a dilution of 1 16 are below the threshold of 20 % (see Sections 5.2 and 5.4). In exponential form, 1 16 is written as 1 24 = 2A. The negative logarithm on a base of 2 of the 1 16 dilution factor is 4, or explained differently, 2 raised to the negative 4th power corresponds to 1 16. Thus, the pT-value of 4 can be attributed to the tested material. 

We also investigated the action of saikosaponins on TXBa release induced by calcium ionophore in human platelets. All compounds assayed presented a dose-related response to TXB2 release, with inhibition percentages slightly lower than the reference drug ibuprofen [Table 13 andFig.(7)]. 

Sandrosaponin I was the most active, with an inhibition percentage of around 90% at the highest dose. Without excluding the participation of other possible mechanisms, including non-eicosanoid mediators, our data support the inhibition of arachidonic acid (AA) metabolism as one of the biochemical mechanisms which may contribute to the anti-inflammatory activity of these saikosaponins. 

By plotting the inhibition percentage (7%) vs. the pesticide concentration, a typical inhibition plot can be obtained (see Fig. 4). For concentration range see Note 6. 

Methyl paraoxon was used as reference pesticide for inhibition tests. AChE activity was determined in the absence of pesticide and then after 10 min. incubation with methyl paraoxon standard solutions. The inhibition percentage was calculated using the equation (Skladal, 1992) ... 

Determination of methyl paraoxon can be realized in the range of 10"8 -10 6 mol/L. The detection limit, defined as the concentration of pesticide that produce an inhibition percentage of 10% of the AChE activity correspond to a concentration of 5 10 9 mol/L methyl paraoxon. 

The roots of S. oblonga have been extensively used for the treatment of diabetes in the Ayurvedic system of traditional Indian medicine. From the ethyl acetate soluble portion of the methanolic extract from the roots of S. oblonga Matsuda et al. isolated compound (14), a friedelane-type triterpene [42]. The methanolic extract and the ethyl acetate soluble portions were found to show inhibitory activity on aldose reductase, which is related to chronic diabetes complications such as peripheral neuropathy, retinopathy and cataracts. Compound (14) was assayed for aldose reductase rat lens inhibitory activity. It showed inhibition percentages of 21.8 % at a concentration of 30 pM and 48.2 % at a concentration of 100 pM. The activity of (14) and other terpenoids isolated from this plant could prove to be the reason for the popular use of the plant in the Ayurvedic system for the treatment of diabetes. 

Fig. (12). Main constituents of aconite and the neuromuscular blocking effect of aconite extract and its constituents in mouse phrenic nerve-diaphragm muscle preparation. The inhibition percentage of nerve-evoked twitch response is plotted against the log concentration (g/mL) of each constituent. The values represent means S.E.M. (n = 3-10).

Figures highlighted in bold indicate inhibition percentages considered to be clear, unequivocal, and significant in interpreting antibody combining site structure—activity relationships. See also Fig. 6.16)...

The scaling of calcium sulphate could be more effectively inhibited by EDTP used at lower concentrations (inhibition percentage of 100% at 1 x 10 to 5 x 10 mol L" and 65.70% at 1 x 10 mol L ). At 1 x 10 mol L", NTMP exhibits only a 30.43% inhibition. EDTP has a similar structure to EDTA, in which all of the four functional groups are replaced by phosphonic groups, but the latter compound exerts only 6.38% inhibition at a higher concentration (1 x 10 mol L ). 

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