Figure 2.

Magnetosome arrangement in magnetotactic bacteria. The magnified part shows how elastic protein fibers embed magnetite (Fe₃O₄) crystals in the cytoskeleton. Interaction of the magnetic dipole of the crystal with external fields within its viscoelastic environment can be analyzed by our presented theoretical model as a torsional nanoresonator shown on the right hand side. Magnetic torque rotates the MNP around its center of mass. The rotational spring constant is given by κ = kR, where k is the aggregate rigidity of the connecting protein fibers, and R is the radius of the MNP. Since the Reynold number of the MNP is very small, the drag forces are given by Stokes’ law. Therefore, the rotational damping coefficient is C = 6π ηR³, where η is the viscosity of the surrounding fluid.