LIGAND BINDING - TUTORIAL #1 answer 1:3 - least squares fit of Y = [X]/(K+[X]) The answer is correct: the use of least squares minimization is the soundest statistical way of analyzing the experimental data. You use the following equation to calculate the fraction of liganded sites: Y = [X] / (K + [X]) where K is the dissociation equilibrium constant. The following results are obtained: The equilibrium constant obtained is Kd = 1 mM (for the dissociation reaction: PX <==> P + X). Do the residuals look good? 1) Yes 2) No Back one step