Nonspecific magnetic biological effects: A model assuming the spin-orbit coupling

The magnetic response of a particle that tunnels in a double-well potential is considered. The Hamiltonian of the model includes the Zeeman, spin-orbit, and other interactions. The spin state changes due to the motion of electrons in the electric field rather than the action of the magnetic field of nucleus on the electrons. At realistic values of the model parameters, the spin-orbit interaction leads to magnetic effects that resemble those in the well-known radical pair mechanism (RPM) model. In particular, the probability of electron transfer depends on the direction of the magnetic field. At the same time, the model under consideration has distinctions that make it reasonable when searching for a mechanism of nonspecific magnetic biological effects. In particular, unlike in the RPM, the magnitude of the magnetic effect is not limited to a narrow range of the hyperfine interaction. The model enables molecular rotations. This could explain an asymmetry in response to the inversion of the magnetic field vector, which has been observed in experiments.