Radioligand binding experiments

FIGURE 6.30 Calibration graph of a trace element before and after correction with interelement coefficients predicted by a CPG nenral network. Using raw nncorrected countrates from the instrument (gray line) leads to a poor correlation inappropriate for analytical determination. After correction with the predicted matrix-specific interelement coefficients, the calibration leads to a reasonable regression line. 

When ligand and receptor collide due to diffusion, they remain bound together for a random amount of time influenced by the affinity of the receptor and ligand for one another. After dissociation, the ligand and receptor are the same as they were before binding. Equilibrium is reached when the rate of association at which new ligand-receptor complexes are formed equals the rate of dissociation. 

Kj is the concentration of ligand that occupies half of the receptors at equilibrium. Thus, a small Kj means that the receptor has a high affinity for the ligand, whereas a large Kj means that the receptor has a low affinity for the ligand. 

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In practice, it is not often possible to directly measure par except in radioligand binding experiments. In many experiments it is the relationship between agonist concentration [A] and percentage maximum response (y) which is measured (a dose-response curve) and the Hill plot is made by plotting... 

McPherson, G.A. A practical computer-based approach to the analysis of radioligand binding experiments. Comput Programs Biomed 17 107-114, 1983. 

Table 7.4 Comparison of results from saturation binding experiments using native NO 711 in MS binding experiments and [ H]2N0 711 in radioligand binding experiments. All values represent mean + SEM from independent experiments [80].

Fowler, C.J. and Fraser, G.L. Mu-, delta-, kappa-opioid receptors and their subtypes. A critical review with emphasis on radioligand binding experiments, Neurochem. Int. 1994, 24, 401-426. 

Compounds 14-17 are derivatives of the corresponding silanes 10 and 12. Functional pharmacological studies (Ml-M3 receptors) and radioligand binding experiments (M1-M4 receptors) with the pure (/ )- and (S )-enantiomers of these compounds revealed very similar pA2 values as observed for the antipodes of the related analogues 10 and 1234. The highest stereoselectivity indices (functional studies) were determined for 17 [SI = 44 (Ml), 7.6 (M2), 20 (M3)]. 

Radioligand binding experiments reveal both high and low affinity binding sites for neurotensin in the mammalian brain (Mazella et al., 1983 Kitabgi et al., 1985 Vincent,... 

The results of radioligand binding experiments performed on cis and trans isomers of 2-hexenylNECA, and on 2-hexylNECA are reported in Table 5. In comparison with HENECA, trans 2-hexenylNECA (THENECA, 3) showed similar affinity at A2a receptor, and a 3-fold higher selectivity for this subtype. Hence THENECA proved to be about 160-fold A2a selective with a Ki of 1.6 nM at A2a receptors. 

Radioligand Binding Experiments are used to determine whether a drug binds to a receptor and to investigate the interaction of low-affinity drugs with receptors based on radioactive marking. 

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