Abstract

Magnetic fields as weak as the Earth’s can change the yields of radical pair reactions even though the energies involved are orders of magnitude smaller than kBT at room temperature. Proposed as the source of the light-dependent magnetic compass in migratory birds, Magnetic Field Effects (MFEs) on chemical reactions are thought to operate in flavin-containing protein photoreceptors in the retina. Numerous studies on flavin-based model systems of biological importance have shown MFEs under physiological conditions. In many instances, these effects are small and are only likely to be of any importance to the postulated chemical compass if the primary effects of the magnetic fields on the geminate radical pairs are further enhanced via yet unknown amplification mechanisms.

Here, a novel, highly sensitive technique is described which measures MFEs on the prompt fluorescence in continuously photoexcited flavin / electron donor model systems. By exploiting the sensitivity of this method, it is possible to profile the effects of the magnetic interaction characteristics within the radical pair as well as those of the embedding media. Furthermore, it has been shown that any change in the kinetics of radicals formed downstream to the geminate radical pair can significantly enhance or diminish the prompt MFE over the timescales of milliseconds and longer – an effect which has been termed Enhanced MFEs (EMFEs). Given the efficiency of amplification and the simplicity of its implementation, one could speculate that nature might have adopted EMF Es to engineer an amplified response to weak geomagnetic fields in magnetoreception.