Electronic and Magnetic Characterization of in vivo Produced vs. in vitro Reconstituted Horse Spleen Ferritin

Abstract

ABSTRACTMagnetic nanophases nucleated within horse spleen apoferritin nanotemplates underin vivophysiological conditions andin vitroreconstitution were characterized by Mössbauer spectroscopy in lyophilized form. Mössbauer spectra recorded at 80 K indicate that for thein vivoproduced ferritin the presence of phosphates within the ferritin biomineral core results in larger quadrupole splittings, both at interior and surface sites, 0.62 mm/s and 1.06 mm/s, respectively, as compared to 0.56 mm/s and 0.75 mm/s for the reconstituted ferritin. Data collected at lower temperatures give blocking temperatures of 55 and 40 K forin vitroandin vivosamples. At 4.2 K, both samples give similar saturation hyperfine field values for the interior (495 kOe) and surface (450 kOe) iron sites. The temperature dependence of the reduced hyperfine magnetic fields at the interior iron sites is consistent with the collective magnetic excitations model, due to the particle's magnetization precession about the anisotropy axis. In contrast, a marked decrease in the reduced hyperfine field at surface sites with increasing temperature indicates a more complex spin excitation energy landscape at the surface.