Non-Equilibrium Biomagnetic Sensing: Three Radical Mechanism in Cryptochrome

Non-Equilibrium Biomagnetic Sensing: Three Radical Mechanism in Cryptochrome

Seminar author:Nathan Babcock

Event date and time:10/28/2020 12:00:pm

Event location:GIQ Seminar Room

Event contact:nbabcock@gmail.com

Migratory birds’ visual magnetic sense is believed to rely on radical pair reactions in proteins, to enable them to sense weak magnetic fields below the thermodynamic limit. In this model, magnetic sensitivity originates from the interplay between coherent spin dynamics and recombination kinetics, as the radicals couple to the magnetic field via nuclear hyperfine interactions. However, prior studies have often neglected the effect of electron-electron dipolar (EED) coupling from this hypothesis. We show that EED effects suppress the radical pair’s directional response to a weak field, and that this attenuation may not be mitigated by mutual cancellation of EED coupling and exchange, as had been proposed. We demonstrate how to overcome this limit by extending the conventional model to include a third radical species. We show how hyperfine effects could work in concert with EED interactions to tailor a magnetic response that provides a new principle for magneto-sensitivity in non-equilibrium systems: namely, the site-selective switching of the magnetic effect by a third radical bound at the protein surface. We consider how the new model is altered by introducing amplification effects in the presence of thermal noise. We explore potential advances to theories of non-equilibrium quantum magnetism, with applications for sensing, navigation, and medicine.