Density Functional Theory modeling of the magnetic susceptibility of heme derivatives

Abstract

Susceptibility-weighted imaging (SWI) is a magnetic resonance imaging (MRI) technique which magnetic susceptibility differences between tissues can be used as a new type of contrast in MRI. SWI is sensitive to both paramagnetic and diamagnetic substances. Accurate estimations of the magnetic properties of the heme derivatives is essential for the development of the SWI technique.In this paper, we study structural and magnetic properties of the heme derivatives from Density Functional Theory calculations. By applying the Stoner model we obtained the magnetic susceptibility of the heme derivatives.We find that the paramagnetic phase of heme, deoxyhemoglobin and aquomethemoglobin to be more stable than the diamagnetic phase as expected from experimentation but the diamagnetic phase of the oxyhemoglobin and hemichrome is more stable. Our results show that the response of the heme to the external magnetic field is changed by the presence of ligand (imidazole or water) molecule.