Magnetic birefringence of natural and synthetic ferritin

• Published in: Journal of magnetism and magnetic materials 2011-10, Vol.323 (18-19), p.2413-2417
• Main Authors: Koralewski, M., Pochylski, M., Mitróová, Z., Timko, M., Kopčanský, P., Melníková, L.
• Format: Article
• Language: English
• Subjects: Birefringence; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Constants; Cotton–Mouton effect; Exact sciences and technology; Ferritin; Magnetic birefringence; Magnetite; Magnetoferritin; Magnetooptical effects; Mathematical models; Nanocomposites; Nanomaterials; Nanostructure; Optical polarisability anisotropy; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Physics
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2011.05.017

Magnetically induced optical birefringence (Δn) was measured for magnetoferritin (MFer), horse spleen ferritin (HSF) and nanoscale magnetite aqueous suspensions. The anisotropy of optical polarizability was calculated. The average magnetic dipole moment calculated assuming the Langevin model was about 20,000 and 8500μB per particle, for magnetite nanoparticle and magnetoferritin, respectively. Poor fitting results and the unphysical value of average magnetic moment per Fe ion for MFer excluded the use of the simple Langevin model for description of Δn for this compound. It was deduced that for MFer the estimated average magnetic moment should be about 1125μB per molecule. A magnetic contribution from the protein shell was found to be negligible. Results from the low-field region permit the calculation of the Cotton–Mouton (C–M) constants and their comparison for the substances studied. It was shown that magnetic birefringence and C–M constant can be powerful parameters in identification of the magnetic core structure of ferritins, especially useful in biomedicine. ► Magnetic birefringence of ferritins were studied and compared with nanoscale magnetite. ► Magnetoferritin shows non-Langevin behaviour of magnetic birefringence in contrast to magnetite. ► Cotton–Mouton constant of synthetic ferritin is four orders higher than that of the natural one. ► Magnetic birefringence can be useful for identification of magnetic core of biogenic ferritins. ► The described magnetooptical method can be of interest in biomedicine.