think about your old chemical kinetics courses. what counts is concentration and not amount.
M > Dear Marius and others, > here I would like to comment: The problem with soaking is often not > so much the concentration of the ligand, but the amount of ligand > needed to fill all binding sites in the crystal. A typical crystal > contains about 20 mM protein so one has to add the equivalent amount > of ligand. On the other hand, the concentration UNBOUND inhibitor, > asuming a 1:1 protein-ligand complex, need only to be in the order of > 10-100 times the Kd (90-99% occupancy). Ways to overcome this is to > soak in a large volume of mother liquor (containing a large amount of > ligand) or to add solid ligand to the mother liquor and let the > ligand slowly dissolve and diffuse into the crystal. > > Herman >
