-∆G Rigid. Complex = 2.55 ± 0.17 kcal mol -1 (see Section S18). This is in excellent agreement with the difference observed when the procedure was repeated without intramolecular restraints (M-Rig-N), which was 2.74±1.63 kcal mol -1 , providing evidence that this is the main source of the error observed when multiple distance restraints are applied in a non-rigorous manner.