binding constant half maximal inhibitory concentration (IC50) equilibrium dissociation constant (KD) approximated by IC50 A measurement of an IC50 value under specific assay conditions approximates KD, namely the binding reaction is at an equilibrium, there is a single population of sites on the receptor that competitor and ligand are binding to, and the concentration of the receptor must be much less than the KD for the competitor and the ligand. In this case, according to Cheng and Prussoff, KD = IC50 / (1 + Lstot / KDs), in which Lstot is the total concentration of the labeled competitor and KDs is the KD value of that competitor. PERSON: Bjoern Peters, Randi Vita equilibrium dissociation constant (KD) approximated by IC50 http://dx.doi.org/10.1016/0006-2952(73)90196-2 metadata complete