PLEASE help with Equilibrium Dialysis Question?

[Rusty123]

Can someone please help me answer this question? Thanks!!!

 

4.5 mL of a protein with concentration 48.2 microM is placed inside a dialysis membrane, which is then placed inside a beaker containing one liter of 20 mM HEPES buffer at pH 7.5, plus 14.5 microM of a fluorescent ligand. The dialysis membrane permits the ligand to pass through but not the protein. The solutions are allowed to set over night to reach eqilibrium. After equilibrium is reached, fluorescence measurements are used to establish that the total ligand concentration inside the membrane is 62.7 microM, and the total ligand concentration outisde the membrane is 13.5 microM. The protein concentration inside the dialysis membrane is re-measured, and found to be 48.8 microM. What is the Kd for ligand binding by the protein?

 

I am not really sure where to start out, should I recalculate the concentrations and make them for the overall volume? I am confused .

[dttom]

If assigning P for protein, L for ligand, then

P + L <--> PL

so isn't the Kd just (PL)/(P)(L) = (62.7-13.5)/(48.8)(13.5) = 74.7M-1