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Bioelectromagnetism

 

region, where F = J + I is a good quantum number, and curvature as well as crossovers as feld increases

(Ramsey, 1956). Vertical lines (lef diagram) indicate allowed transitions. Relative orientations of one

transition’s upper and lower state angular momenta are shown (right upper and lower diagrams). In the

lef diagram, circles indicate the examples of possible level-crossing transition points, and box on the

horizontal axis indicates the region of possible zero-feld transitions. Magnetic felds at the frequency

corresponding to diferences in the energy levels can drive molecules between energy levels of diferent

nuclear spin states and change the concentration in these energy levels, which, in turn, can change the

recombination lifetimes for radial pairs (Barnes and Greenebaum, 2015, 2015).

Tese narrow line widths can lead to saturation efects with magnetic felds in the range 10⁻⁸ – 10⁻⁹

T (Bovey, 1988). With large molecules that contain many atoms with nuclear spins, the calculations of

the recombination rates are very complex as the contributions to the magnetic feld seen by the active

electron that is dependent on the nuclear spin of each atom, its distance from the electron, and the

shielding by other electrons in diferent orbits (Batchelor et al., 1993; Brocklehurst and McLauchlan,

1996; Woodward et al., 2001; Wang and Ritz, 2006; Rodgers et al., 2007). Barnes and Greenebaum (2015,

2016) assumed that the sum of these felds is large enough so that coupling can lead to relatively sharp

resonances, and the nuclear spin states are important in determining the recombination rates for the

radical pairs. Nuclear resonance spectroscopy at radio frequencies (RFs) showed that nuclear spin states

may have lifetimes of seconds or longer and corresponding resonant line widths of a few cycles (Bovey,

1988). In weak magnetic felds, where the magnetic coupling between the active electrons and the nuclei

in the radicals is stronger than the perturbing external feld, Barnes and Greenebaum (2015) postulate

that they will also see shifs in radical concentrations that are frequency- and amplitude-dependent

with relatively narrow line widths. Prato et al. (2013) also gave an explanation for efects seen when the

ambient magnetic is shielded. For then level energy diferences are below the natural line widths and

spontaneous transitions can occur (Barnes and Greenebaum, 2015).

From these theoretical considerations, Barnes and Greenebaum (2015) concluded that the application

of magnetic felds at frequencies ranging from a few Hertz to microwaves at the absorption frequen­

cies observed in electron and nuclear resonance spectroscopy for radicals can lead to changes in free

radical concentrations, and these efects have the potential to lead to biologically signifcant changes.

Moreover, Barnes and Greenebaum (2016) supposed that there are now both the theoretical bases and

sufcient experimental results for further consideration of the possibility that long-term exposures to

magnetic felds can lead to both useful applications in treating diseases and to undesired health efects.

It is expected that these efects are frequency, amplitude, and time-dependent (Barnes and Greenebaum,

2016). Tese efects will also be dependent on other biological conditions that can lead to changes in

radical concentrations (Barnes and Greenebaum, 2016).

Te RPM explains how a pair of reactive oxygen species with distinct chemical fates can be infuenced

by a low-level external magnetic feld through Zeeman and hyperfne interactions. So far, a study of

the efects of complex spatiotemporal signals within the context of the RPM has not been performed.

Recently, Castello et al. (2021) presented a computational investigation of such efects by utilizing a

generic pulsed electromagnetic feld (PEMF) test signal and RPM models of diferent complexity. Teir

theoretical simulations showed how substantially diferent chemical results can be obtained within

ranges that depend on the specifc orientation of the PEMF test signal with respect to the background

static magnetic feld, its waveform, and both of their amplitudes (Castello et al., 2021). Tese results pro­

vide a basis for explaining the distinctive biological relevance of PEMF signals on radical pair chemical

reactions (Castello et al., 2021). Teir study establishes the role of PEMF as a diagnostic tool that may

indicate the involvement of magnetosensitive radical pair reactions in biological systems (Castello et al.,

2021). Tey speculated that extending this tool to determine orientation and amplitude dependence in

which the input PEMF waveforms afect the reaction products can reveal the chemical nature of the

radical pairs involved (Castello et al., 2021). Tey proposed that using the oscillating magnetic feld or

PEMF input waveform as a diagnostic tool to modify singlet quantum yields can easily be transferred to

fnding the optimal control to maximize the singlet yield (Castello et al., 2021).