Magnetic effects in biology: Crucial role of quantum coherence in the radical pair mechanism

Authors: Binhi V.

Year: 2025-07-25

Category: Biophysics

Journal: Physical Review E

DOI: 1103/n3fs-fsnv

URL: https://journals.aps.org/pre/abstract/10.1103/n3fs-fsnv

Abstract

Overview

The spin-chemical radical pair mechanism (RPM) has emerged as a leading theory explaining the biological effects of low-intensity magnetic fields. These effects are most pronounced when the quantum system of radicals remains well-isolated from environmental disturbances, tying the phenomenon to the spin coherence relaxation time (τ). However, an explicit relationship between magnetic effects and τ has not been clearly established, which this study addresses.

Findings

  • Utilized an open quantum system model with two electrons and one nucleus, factoring in minimal interactions but focusing on spin relaxation and chemical kinetics.
  • Developed and validated an analytical solution to the Liouville-Neumann equation via numerical integration, emphasizing the vital role of quantum coherence in RPM.
  • Introduced a concise expression describing the RPM effect as a function of τ, within biologically relevant ranges of field strength (B) and chemical kinetics rate (k).
  • Discovered that RPM effects become significant when the fundamental relation (τk)>>1+Bτk is satisfied, directly controlling the effects' magnitude and aligning with the established principles of spin chemistry.
  • Estimated plausible spin decoherence times in magnetosensitive radical pairs within cryptochrome-like proteins to be from units to tens of nanoseconds, based on current experimental data.
  • Investigated the influence of radio-frequency magnetic fields at the nanoTesla (nT) level and found these effects to be minor, incapable of disrupting RPM patterns due to decoherence.

Conclusion

The quantum Zeno effect's role in magnetobiology is discussed in light of τ dependence. The study reinforces a direct link between exposure to electromagnetic fields and biological effects at the quantum level, underlining the health relevance of quantum coherence in the RPM pathway. These findings are crucial for understanding EMF safety and potential health risks.

radical pair mechanism quantum coherence spin-chemical effects magnetic fields magnetobiology spin relaxation health risk
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