CHARMM Development Project Forums User Discussion & Questions Energy terms, Constraints, Restraints, and Solvation solvation energy a measure of binding energy

i know this forum is intended for charmm only, but i have a general question:
i would like to calculate "goodness-of-binding" of some ligand in order to compare between mutants. what do you think about the change in solvation energy between ligand alone and protein alone, to the complex, as a measure of binding energy (enthalpy)?
can you suggest something better?
(i don't need something very accurate, because it's only a comparative study)
thanks/
t.

Binding correlates to free energy.

CHARMM has Poisson-Boltzmann methods which can be used to compute solvation free energy; see pbeq.doc