A Biomagnetic Sensory Mechanism Based on Magnetic Field Modulated Coherent Electron Spin Motion

Electron transfer processes which generate radical pairs in coherent electron spin states (singlet or triplet) are affected by weak magnetic fields [Schulten et al, Z. physik. Chem. Neue Folge 101 (1976) 371]. Based on this finding we suggest a reaction mechanism for a chemical compass which exhibits a sensitivity on the orientation of the geomagnetic field originating from an anisotropy of the hyperfine interaction experienced by unpaired electron spins in a redox process. It is argued that such mechanism may explain the ability of many biological species to orient themselves inthe geomagnetic field.