Reaction of a receptor protein to a binding ligand under e.m. exposure

Low-intensity electromagnetic exposure, from sub-ELF to RF, can effectively interact with ligand adsorption to a receptor site of the cell membrane, if the gradient of the attracting endogenous potential energy is a non linear function of the spatial coordinates, the basal state of the ligand ion-receptor protein is maintained out of thermodynamic equilibrium by the cell metabolism, and the attracting endogenous potential energy is a "shallow" well. The inconsistency of the last condition with realistic values obtained from the Protein Data Bank is analyzed and removed by taking into account the displacement of the protein charges induced by the ion itself. As a result, the biological effects of low-intensity e.m. exposure, as reported in the international literature, become biophysically plausible.