ABSTRACT
In this chapter, the historical background study of the “radical pair (recombination) mechanism (RPM)” models for quantum-assisted magnetic sensing and recent studies on both natural and artificial in vitro systems related to flavoproteins such as FAD are introduced. As historical background studies of spin chemistry, it has been generally considered difficult to control chemical and biological reactions using magnetic fields. The reason is that the electronic energy involved in the magnetic fields is extremely smaller than that in the chemical reactions. For the magnetic compass of migratory birds, the RPM model for quantum-assisted magnetic sensing was first proposed by Schulten et al. in 1978. It is suggested that this hardcore theoretical physics paper formulated the RPM hypothesis of magnetoreception for the first time, and it is now clear that it was decades ahead of its time.
