Half-maximal effective concentration

Half maximal effective concentration 17a-Ethinyl estradiol Fluidized bed reactor 1 -Hydroxybenzotriazole High performance liquid chromatography Hydraulic retention time... 

The compound bisandrographolide A has been shown to activate transient receptor potential V4 (TRPV4) with an ECjo (half maximal effective concentration) of 790 to 950 nM (Smith et al. 2006). 

The bioactivities generally modelled are half maximal inhibitory concentration (ICjg), minimum inhibitory concentration (MIC) and half maximal effective concentration (ECjg) obtained in biological assays statistical methods used in QSAR studies are principal component analysis, partial least squares, Kohonen neural network, artificial neural network, etc. [3],... 

Abbreviations UV, ultraviolet EIA, enzyme immunoassay S-PIA, solid-phase immunobead assay P-CTX-1, Pacific ciguatoxin-1 C-CTX-1, Caribbean ciguatoxin-1 EC50, half maximally effective concentration. 

Table 9.1 Half maximal effective concentration (EC50) for SrCr04, Ce(dbp)3 and Ce(dpp)3(in ppm) [113]...

The concentration of the drug at which it is half maximally effective in a certain preparation. 

As the concentration is raised by a constant factor, the increment in effect diminishes steadily and tends asymptotically towards zero the closer one comes to the maximally effective concentra-tion.The concentration at which a maximal effect occurs cannot be measured accurately however, that eliciting a half-maximal effect (EC50) is readily determined. it typically corresponds to the inflection point of the concentration-response curve in a semilogarith-mic plot (log concentration on abscissa). Full characterization of a concentration-effect relationship requires determination of the EC50. the maximally possible effect (Emax), and the slope at the point of inflection. 

Ethylene has been shown to have a variety of effects on living plants. Thirty-five distinct functions were tabulated by Abeles, based on literature reports existing in 1973 [59]. The majority of cases showed threshold C2H4 activity at 0.01 ppm, half-maximal effect at 0.1 ppm, and saturation (that is, further increase in C2H4 concentration did not increase the effect) at about 10 ppm. The parts per million concentrations Abeles reports are the gas-phase concentrations. In most cases, there was no further effect beyond the saturation concentration, although there were a few instances of the effect being reversed at higher concentrations [28,60]. 

The specific effects of purified dnaj and grpE proteins on the dnaK protein have been characterized (Liberek et al., 1991a). The dnaj and grpE proteins, acting in concert, can stimulate the basal ATPase activity of dnaK 50-fold dnaj appears to enhance the rate of nucleotide hydrolysis by dnaK, but does not substantially affect nucleotide release. The grpE protein appears to enhance the rate of release of nucleotide bound to dnaK. Consequently, neither protein alone exerts a dramatic effect on the overall rate of ATP turnover by dnaK however, the effect of the two proteins combined is to accelerate both the rate of ATP hydrolysis and the rate of nucleotide release, resulting in enhanced ATP turnover. The concentrations of dnaj and grpE required for half-maximal effect are both 0.1-0.2 fiM. 

Figu re 3.7. Theoretical model to illustrate the effect of biochemical cascades on dose-effect relationships. a A simple model cascade, containing an agonist (L), a receptor (R), a second messenger (M2), and an effector (E). b Equations derived from the assumptions in a. ECjq Ligand concentration required for the half-maximal effect. The effect will saturate at concentrations lower than those required for receptor saturation. The gap between K and ECjq depends on the number of receptors and other properties of the system, c Illustration of the equations stated inb. 

Here E C) is the observed effect at concentration C, Tsmax is the maximal effect (based on EEG components), K is the concentration at half-maximal effect, and N is the HiU factor, a constant expressing the sigmoidicity of the concentration-effect relationship. Subscripts A refer to the specific ligand of a hgand-gated ionotropic receptor. 

In a pharmacokinetic-pharmacodynamic study in 10 healthy volunteers intravenous dofetihde 0.5 mg caused a mean maximum prolongation of the QTc interval of 121ms and the mean plasma concentration associated with half-maximal effect was 2.2ng/ml (36). 

This is how the link-model relates the kinetics in plasma to the kinetics of drug in the effect compartment. When used together with the Emax model for estimation of the maximal drug-induced effect, the concentration at half-maximal effect (apparent EC50) and the rate constant of the disappearance of the effect (ke0) ... 

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