Searching for unity in diversity of animal magnetoreception: From biology to quantum mechanics and back

How animals sense the geomagnetic field remains a mystery today. A remarkable diversity has been revealed in animal magnetoreception and several sophisticated models have been put forward in the past few decades, but none have been commonly accepted yet. Cryptochrome (Cry) has been proposed in both the radical pair model and the MagR/Cry-based biocompass model. How exactly it participates in magnetic sensing is an ongoing discussion. Here we wish to suggest an intermolecular electron transport (ET) pathway conserved in evolution in the MagR/Cry complex, in which electrons travel stepwise along a flavin-tryptophan chain as described in the classic radical pair model, and further extends to iron-sulfur clusters in MagR via a series of stepping-stone amino acids as an ET bridge. The hypothesis we presented here may provide a solution to unite different models, and a feasible explanation for the intrinsic magnetic features of MagR, as well as a mechanism for signaling in animal magnetoreception, which are of considerable interest in both biology and physics.