Fig. 2.
A thermodynamic cycle for determining the noncovalent interaction energy (ΔGinteraction) between PBP 5 and a β-lactam. This process can be described by the following equation: ΔGinteraction + ΔGcovalent + ΔGu1 − ΔG3 − ΔGcovalent − ΔGu2 = 0. If we assume that the noncovalent interactions between the ligand and the denatured state are negligible (i.e., ΔG3 = 0), and that the covalent energies between the enzyme and the ligand (ΔGcovalent) are the same in the folded and unfolded states, then: ΔGinteraction = ΔGu2 − ΔGu1 = ΔΔGu.