The ability to go beyond current state of the art with respect to substrate binding free energies in biological systems will be pursued in two directions. The linear interaction energy (LIE) method is appealing due to its simplicity, and estimates the absolute binding free energy as a difference in ligand-surrounding interaction energies in the bound and free state. The applicability of the LIE method to different temperatures must be examined first. That is, there are indications that the electrostatic scaling coefficient is temperature dependent. Once the free energies of binding have been successfully calculated, high precision van’t Hoff plots will be calculated, immediately yielding the enthalpy and entropy of binding without directly evaluating the terms.

If the LIE method fails to predict enthalpies and entropies of ligand binding for test systems, we will instead use the free energy perturbation (FEP) approach to calculate relative free energies of binding. These will again be examined at different temperatures to construct van’t Hoff plots, but now only relative changes in enthalpies and entropies between different substrates will be obtained.