PCB and Dioxin Binding to Cytosol Receptors: A Theoretical Model Based on Molecular Parameters

A model based on dispersion interactions is developed to interpret the cytosol‐PCB binding data of Bandiera et al. [1]. The essential parameters in the model are the PCB polarizability and the receptor to PCB separation distance. An approximate linear free energy relationship is derived in terms of these parameters. It is suggested that the oxygens in PCDDs may lead to stabilizing hydrogen bonding with the receptor; this reasonably accounts for the unusual binding affinity of certain PCDDs. Finally, a derivation of [EC50] for the PCBs displacement reaction based solely on equilibrium theory is shown to lead to an expression consistent with the experimental correlation if the displaced TCDD aggregates with the solution PCB or any other cytosol component.