A ∆G o Bound of -6.64 ± 1.16 kcal mol -1 was obtained for M-Hand. This was not significantly different to M-Hand-R or M-Rig, suggesting that the approximations made by the scheme were minor in this case. The results for M-Hand and M-Hand-1 (-6.30 ± 1.27 kcal mol -1 ) were very similar, despite the slightly more restrictive restraints. This shows that it is possible to obtain equivalent free energies using the naïve distance restraints scheme and rigorous schemes, so long as the coupling between the internal and relative external DoF of the protein and ligand is weak when the ligand is decoupled. However, increasingly negative binding free energies would be expected as more restrictive restraints are used and with increasing differences between the apo and holo conformations of the binding site, and the magnitude of the error may be be difficult to predict.