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, Mg, 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 Mg as the enzyme cofactor is twice higher than the rates of the reactions with nonmagnetic Mg or Mg. 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.