  A Monte Carlo method is given to compute the binding affinity of a ligand to
a protein. The method involves extending configuration space by a discrete
variable indicating whether the ligand is bound to the protein and a special
Monte Carlo move which allows transitions between the unbound and bound states.
Provided that an accurate protein structure is given, that the protein-ligand
binding site is known, and that an accurate chemical force field together with
a continuum solvation model is used, this method provides a quantitative
estimate of the free energy of binding.
