Jacob, In case if the hint that I sent yesterday was not clear, below is the solution for the equation Kd=[P][L]/[PL]
in terms of ligand occupancy: O=[ PL]/[Po]= 1/(Kd/L+1) You see, it does not depend on [Po] Alex On Jun 26, 2011, at 10:05 AM, aaleshin wrote: > The concentration of a protein in a crystal [Po] and the volume of a crystal > V are needed only to calculate the total amount of a ligand [Lo] required for > soaking. > [Lo] > [Po]*V > > The occupancy of the active sites in a crystal will depend only on the ligand > concentration in solution and Kd. It does not depend on protein concentration > in the crystal. > > Indeed: > Kd=[P][L]/[PL] > > Assuming total concentration of the protein = Po, Kd= 1mM and S= 1 mM, the > active site occupancy will be: > > 1= P/Po-P; > > P/Po=1/2 > > So the concentration of the ligand in solution should be >>Kd to get the full > occupancy. > > Alex >
