Upper bound on the biological effects of 50/60 Hz magnetic fields mediated by radical pairs

Abstract

Prolonged exposure to weak (~1 μT) extremely-low-frequency (ELF, 50/60 Hz) magnetic fields has been associated with an increased risk of childhood leukaemia. One of the few biophysical mechanisms that might account for this link involves short-lived chemical reaction intermediates known as radical pairs. In this report, we use spin dynamics simulations to derive an upper bound of 10 parts per million on the effect of a 1 μT ELF magnetic field on the yield of a radical pair reaction. By comparing this figure with the corresponding effects of changes in the strength of the Earth’s magnetic field, we conclude that if exposure to such weak 50/60 Hz magnetic fields has any effect on human biology, and results from a radical pair mechanism, then the risk should be no greater than travelling a few kilometres towards or away from the geomagnetic north or south pole.

Radical pairs may play a role in xenon-induced general anesthesia

“…In the simulation involving a single xenon atom occupying the active site, it is assumed that the O radical electron couples only to the xenon nucleus. Most of our calculations below are based on the simplifying assumption that the TrpH electron (electron B) couples only to the nuclear spin of the indole nitrogen in TrpH , following the treatment of Hore 15 , but we also briefly consider a separate scenario in which electron B couples only to the nuclear spin of the TrpH -hydrogen, which we select because it has the largest isotropic hyperfine coupling constant of all 14 nuclear spins in tryptophan according to Maeda et al 36 . The Hamiltonian describing these interactions is given as where and are the spin operators of radical electrons A and B, respectively, is the nuclear spin operator of the xenon nucleus, is the nuclear spin operator of the TrpH residue (where for the indole nitrogen, and for the -hydrogen), is the hyperfine coupling constant describing the strength of the HFI between radical electron B and the nuclear spin in TrpH ( T for the indole N, and T for the -hydrogen 36 ), is the hyperfine coupling constant describing the HFI strength between radical electron A and the xenon nucleus, where is the nuclear gyromagnetic ratio of a given xenon isotope, is the nuclear gyromagnetic ratio of Xe, is the gyromagnetic ratio of an electron, and is the Larmor precession frequency of the electrons about an external magnetic field 15 .…”

“…The eigenvalues and eigenvectors of the Hamiltonian can be used to determine the ultimate singlet yield ( ) for all times much greater than the radical-pair lifetime ( ) 15 : where, following the methodology used by Hore 15 in the context of cryptochrome, M is the total number of nuclear spin configurations, is the singlet projection operator, and are eigenstates of with corresponding energies of and , respectively, is inverse of the RP lifetime, and is the inverse of the RP spin-coherence lifetime.…”

“…Eventually, the coherent oscillation of the RP between singlet and triplet states ceases and the electrons may recombine (for the singlet component of the state) or diffuse apart to form various triplet products 13 . The coherent spin dynamics and spin-dependent reactivity of RPs allow magnetic interactions which are six orders of magnitude smaller than the thermal energy, , to have predictable and reproducible effects on chemical reaction yields 14 , 15 .…”

“…In particular, it has been studied in detail for the cryptochrome protein as a potential explanation for avian magnetoreception 14 , 17 – 22 . In the present work we apply the principles and methods used to investigate cryptochrome 15 to xenon-induced general anesthesia.…”

Entangled radicals may explain lithium effects on hyperactivity

“…Given the likely randomized orientation of the relevant proteins, for the HFIs, we only consider the isotropic Fermi contact contributions. In our calculations, we assume that the unpaired electron on FADH couples only with the isoalloxazine nitrogen nucleus, which has the largest isotropic HF coupling constant (HFCC) among all the atoms in FAD 64 , following the work of Hore 65 , and that the other unpaired electron on [Li -O2 ] couples with the lithium nucleus. The Hamiltonian for our RP system reads as follows: where and are the spin operators of radical electron A and B, respectively, is the nuclear spin operator of the isoalloxazine nitrogen of FADH , is the nuclear spin operator of the Li nucleus, is the HFCC between the isoalloxazine nitrogen of FADH and the radical electron A ( 64 ), is the HFCC between the Li nucleus and the radical electron B, and is the Larmor precession frequency of the electrons due to the Zeeman effect.…”