Abstract: It is described a method of binding site and binding energy determination by mixed explicit solvent all-atoms molecular dynamics simulations. The macromolecular target for which high affinity binders are sought is simulated in several mixed solvent environments comprising water and at least one amphiphilic organic co-solvent. The simulations are run so that the mixture of solvents are free to react to the presence of the target without the addition of any forces other than those found in the original potential. A correction is applied that helps dissociating the distribution of the different chemical groups found in the amphiphilic organic solvents when calculating their free energies of binding. Additionally, a second correction can be applied accounting for the aggregation of said solvents. The correction helps determining more meaningful absolute, and more accurate relative free energies of binding that can be applied in the rational design of new binders to macromolecular targets.