Dissociation constants of ligands

T298A <58> (<58> mutation of the proton donor, mutant is enzymatically active, with decrease in kcat, Km, altered dissociation constants of ligands [108]) [108]... 

Letting Ka be the acid dissociation constant of the ligand, = c cJcu, which is combined with the definitions Xj = Ci — Ci and Eq. (4-38) to give... 

It can be seen that the equality defined in Equation 4.32 is true only when ICSo = KB (i.e., the concentration of a non-competitive antagonist that reduces the binding of a tracer ligand by 50% is equal to the equilibrium dissociation constant of the antagonist-receptor complex). 

Equation 6.19 predicts an increasing IC50 with either increases in L or 1. In systems with low-efficacy inverse agonists or in systems with low levels of constitutive activity, the observed location parameter is still a close estimate of the KB (equilibrium dissociation constant of the ligand-receptor complex, a molecular quantity that transcends test system type). In general, the observed potency of inverse agonists only defines the lower limit of affinity. 

This leads to the expression for the observed affinity (expressed as equilibrium dissociation constant of the ligand-receptor complex) of the modulator as... 

Aim To measin e the binding of a radioligand (or ligand that is traceable by other means) to a receptor. The object is to obtain an estimate of the equilibrium dissociation constant of the radioligand-receptor complex (denoted Kd) and the maximal number of binding sites (denoted Umax)-... 

Cheng-Prusoff correction, published by Cheng and Prusoff (Biochem. Pharmacol. 22, 3099-3108, 1973), this method is used to derive the equilibrium dissociation constant of a ligand-receptor (or enzyme) pair from the experimentally observed ICso (concentration that produces 50% reduction in effect) for that molecule see Eqn 4.11. 

Receptor occupancy refers to the ratio of receptors occupied by a ligand at equilibrium and the total number of receptors available, usually expressed as a percentage of the total number of receptors. Since it is often not possible to quantify the total number of receptors or the number of receptors occupied by a ligand, another parameter called binding potential is often used to measure receptor occupancy. Binding potential (BP) refers to the ratio of the maximum number of receptors and the equilibrium dissociation constant of the drug, so that % receptor occupancy equals to... 

The Determination of Equilibrium Dissociation Constants of Protein-Ligand Complexes by NMR... 

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