Magnetoferritin molecules with an average inorganic core diameter of 5.7 +/- 1.6 nm and polycrystalline internal structure were investigated by a combination of transmission electron microscopy, magnetic susceptibility, magnetization, and electron magnetic resonance (EMR) experiments. The temperature and frequency dependence of the magnetic susceptibility allowed for the determination of the magnetic anisotropy on an experimental time scale which spans from seconds to nanoseconds. In addition, angle-dependent EMR experiments were can out for the determination of the nanoparticle symmetry and internal magnetic held. Due to the large surface to volume ratio, the nanoparticles show larger and uniaxial rather than cubic magnetic anisotropies compared to bulk maghemite and magnetite. (C) 2014 Elsevier B.V. All rights reserved. ; Times Cited: 0