Free Energy of Enzyme-Ligand Binding

In other words, the relative free energy of binding is obtained from the free energy differences of the nonphysical transformations. This process can involve the annihilation and creation of atoms. In practice, considering for example the solvent case, one defines a linear hybrid potential energy function E (x, X), 

[55] has been derived like Eq. [23], which means that AF and Af can also be obtained by thermodynamic integration (Eq. [23]). In this case, one can also carry out the partial derivative of the hybrid energy (Eq. [53]) with respect to X, which leads to AE = Ej nd Eq. [23] becomes 

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