The role of optimum dielectric saturation in the reversible combination of oxygen with heme Fe2+ and the tuning of paramagnetic-diamagnetic switching

The paramagnetic-diamagnetic switching mechanism of hemoglobin, triggered by oxygen binding, is studied by a formalism involving an expression of work necessary to polarize the dielectric in Landau form. The “tuning” of the mechanism, or determination of occurrence of the switching in response to a certain input energy, is brought about by dielectric saturation of the medium. The relation between the effect of dielectric saturation of the medium and the effect of application of a constant (nonordering) magnetic field indicates charge transfer between the central Fe²⁺ ion and the porphyrin ring during switching.