Cheng-Prusoff correction

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. 

The term 1 + ( I. KL) is often referred to as the Cheng-Prusoff correction. It is clear from this analysis that the IC50 does not give a direct estimate of Kt unless [L] is very low, when IC50 tends to Kv Just as with saturation experiments, the situation will be complicated by the presence of different classes of binding sites (e.g., receptor subtypes) and by the involvement of G-proteins in agonist binding. 

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