Upon some reflection, I think one can say this: first, let's say the
protein in question is 30kD, with a solvent content of 50%, and we
know that solid protein density is ~1200mg/mL. Therefore, the protein
concentration in the crystal would be ~20mM. Because Kd's assume
infinitesimal ligand concentration, I think that neglecting ligand
depletion effects mentioned by Edward Berry, say by having a huge
reservoir or transferring the crystal to an appropriate soaking
environment, that all ligands which bind with a better than ~20mM Kd
should be bound in that crystal, even at extremely low ligand
concentrations, so changing [ligand] from 1pM to 10mM should not
change occupancy much, again assuming equilibrium and neglecting
ligand depletion.
JPK
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