We were curious to test the hypothesis that benzoic acid binds in a protonated (unusual) fashion to the ATP site of PKA and if ITC could reveal this perturbed protonation pattern. We also ran implicit solvent pKa calculations to study the pKa values of the benzoic acid in the ATP pocket. Lastly, we titrated the benzoic acid in the same buffer medium (as the crystallisation buffer) to rule out solvent effects arising from different dielectric media.