Nuclear spin catalysis in biochemical physics

Magnetic isotope effects: a potential testing ground for quantum biology

One possible explanation for magnetosensing in biology, such as avian magnetoreception, is based on the spin dynamics of certain chemical reactions that involve radical pairs. Radical pairs have been suggested to also play a role in anesthesia, hyperactivity, neurogenesis, circadian clock rhythm, microtubule assembly, etc. It thus seems critical to probe the credibility of such models. One way to do so is through isotope effects with different nuclear spins. Here we briefly review the papers involving spin-related isotope effects in biology. We suggest studying isotope effects can be an interesting avenue for quantum biology.

Magnetic isotope effects and nuclear spin catalysis in living cells and biomolecular motors: recent advances and future outlooks: Nuclear spin catalysis

Biomolecular nanoreactors are constructed from chemical elements many of which have magnetic and nonmagnetic stable isotopes. The magnetic isotope effects (MIE) were discovered in experiments with the cells enriched with different isotopes of magnesium, magnetic or nonmagnetic ones. The striking catalytic effect of the magnetic isotope, 25Mg, was revealed in the reaction of ATP hydrolysis driven by myosin, the biomolecular motor utilizing the chemical energy of ATP to perform the mechanical work. The rate of the enzymatic ATP hydrolysis with 25Mg as the enzyme cofactor is twice higher than the rates of the reactions with nonmagnetic 24Mg or 26Mg. A similar effect of the nuclear spin catalysis was revealed in the experiments with zinc as the myosin cofactor. MIE unambiguously indicate that, in the chemo-mechanical process catalyzed by the molecular motor, there is a limiting step which depends on the electron spin state of the reagents, and this step is accelerated by the nuclear spin of the magnetic isotope. The recent developments in this field highlight promising venues for future research of MIE in biophysics with possible applications of the magnetic isotopes in medical physics including radiation medicine and biomedical effects of electromagnetic fields.

Magnetic field effects in biology from the perspective of the radical pair mechanism

Hundreds of studies have found that weak magnetic fields can significantly influence various biological systems. However, the underlying mechanisms behind these phenomena remain elusive. Remarkably, the magnetic energies implicated in these effects are much smaller than thermal energies. Here, we review these observations, and we suggest an explanation based on the radical pair mechanism, which involves the quantum dynamics of the electron and nuclear spins of transient radical molecules. While the radical pair mechanism has been studied in detail in the context of avian magnetoreception, the studies reviewed here show that magnetosensitivity is widespread throughout biology. We review magnetic field effects on various physiological functions, discussing static, hypomagnetic and oscillating magnetic fields, as well as isotope effects. We then review the radical pair mechanism as a potential unifying model for the described magnetic field effects, and we discuss plausible candidate molecules for the radical pairs. We review recent studies proposing that the radical pair mechanism provides explanations for isotope effects in xenon anaesthesia and lithium treatment of hyperactivity, magnetic field effects on the circadian clock, and hypomagnetic field effects on neurogenesis and microtubule assembly. We conclude by discussing future lines of investigation in this exciting new area of quantum biology.