Radiofrequency polarization effects in zero-field electron paramagnetic resonance

Rodgers, Christopher T.; Wedge, Christopher J.; Norman, Stuart A.; Kukura, Philipp; Nelson, Karen E.; Baker, Neville; Maeda, Kiminori; Henbest, Kevin B.; Hore, P. J.; Timmel, Christiane R.

doi:10.1039/b906102a

Cited by 14 publications

(22 citation statements)

References 10 publications

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“…6,7 The reagent solution flowed rapidly in a recirculating loop through a 5 mm optical path-length quartz cuvette, with radical pair generation achieved by photolysis under continuous UV irradiation from a 1 kW arc lamp. The resultant fluorescence signal perpendicular to the irradiation source was collected and focussed onto a photomultiplier tube for detection, with an interference filter used to select exciplex fluorescence in a 100 nm pass band centred at 548 nm.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…23 Even at zero static field a resonant oscillating field drives singlet-triplet interconversion, hence further reducing the singlet yield from its zero static field value. From previously published OMFE spectra of the Py-d 10 /1,3-DCB system, 7 it is clear that OMFE spectra of these systems are relatively broad meaning a 36 MHz oscillating field will fall within the resonance feature arising from 1,3-DCB •− , a eff = 29.2 MHz. A corresponding decrease in singlet yield is therefore observed at B 0 = 0 in the RYDMR spectra of Py/1,3-DCB systems whereas for Chr/1,4-DCB the 36 MHz field is too far from the nearest resonant frequency (Chr-h…”

Section: Rydmr-b 0 -Orthogonal Fieldsmentioning

confidence: 99%

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Spin-locking in low-frequency reaction yield detected magnetic resonance

Wedge

Lau

Ferguson

et al. 2013

Phys. Chem. Chem. Phys.

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The purported effects of weak magnetic fields on various biological systems from animal magnetoreception to human health have generated widespread interest and sparked much controversy in the past decade. To date the only well established mechanism by which the rates and yields of chemical reactions are known to be influenced by magnetic fields is the radical pair mechanism, based on the spin-dependent reactivity of radical pairs. A diagnostic test for the operation of the radical pair mechanism was proposed by Henbest et al. [J. Am. Chem. Soc., 2004, 126, 8102] based on the combined effects of weak static magnetic fields and radiofrequency oscillating fields in a reaction yield detected magnetic resonance experiment. Here we investigate the effects on radical pair reactions of applying relatively strong oscillating fields, both parallel and perpendicular to the static field. We demonstrate the importance of understanding the effect of the strength of the radiofrequency oscillating field; our experiments demonstrate that there is an optimal oscillating field strength above which the observed signal decreases in intensity and eventually inverts. We establish the correlation between the onset of this effect and the hyperfine structure of the radicals involved, and identify the existence of 'overtone' type features appearing at multiples of the expected resonance field position.

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Section: Experimental Methodsmentioning

confidence: 99%

Section: Rydmr-b 0 -Orthogonal Fieldsmentioning

confidence: 99%

Spin-locking in low-frequency reaction yield detected magnetic resonance

Wedge

Lau

Ferguson

et al. 2013

Phys. Chem. Chem. Phys.

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“…Theoretical description of weak radiofrequency magnetic field effects in biological systems is not new, and several methods that address radical pair spin dynamics have been developed [12, 13, 28–32]. Common to all of these methods is, that they require a specification of a radical pair Hamiltonian, which describes how spins of the unpaired electrons interact with external magnetic fields, the internal magnetic fields of the molecular environment, and with each other.…”

Section: Introductionmentioning

confidence: 99%

Towards predicting intracellular radiofrequency radiation effects

et al. 2019

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Recent experiments have reported an effect of weak radiofrequency magnetic fields in the MHz-range on the concentrations of reactive oxygen species (ROS) in living cells. Since the energy that could possibly be deposited by the radiation is orders of magnitude smaller than the energy of molecular thermal motion, it was suggested that the effect was caused by the interaction of RF magnetic fields with transient radical pairs within the cells, affecting the ROS formation rates through the radical pair mechanism. It is, however, at present not entirely clear how to predict RF magnetic field effects at certain field frequency and intensity in nanoscale biomolecular systems. We suggest a possible recipe for interpreting the radiofrequency effects in cells by presenting a general workflow for calculation of the reactive perturbations inside a cell as a function of RF magnetic field strength and frequency. To justify the workflow, we discuss the effects of radiofrequency magnetic fields on generic spin systems to particularly illustrate how the reactive radicals could be affected by specific parameters of the experiment. We finally argue that the suggested workflow can be used to predict effects of radiofrequency magnetic fields on radical pairs in biological cells, which is specially important for wireless recharging technologies where one has to know of any harmful effects that exposure to such radiation might cause.

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“…Second, if we wish to treat broadband noise perturbations, the time dependence of the external field will not be monochromatic as is required for many existing approximate methods. [17][18][19] Additionally, as noted by Gauger et al, 20 for a RP to exhibit the observed sensitivity to weak time-dependent fields, its lifetime must be exceedingly long.…”

Section: Introductionmentioning

confidence: 99%

Floquet theory of radical pairs in radiofrequency magnetic fields

Hiscock

Kattnig

Manolopoulos

et al. 2016

The Journal of Chemical Physics

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We present a new method for calculating the product yield of a radical pair recombination reaction in the presence of a weak time-dependent magnetic field. This method successfully circumvents the computational difficulties presented by a direct solution of the Liouville-von Neumann equation for a long-lived radical pair containing many hyperfine-coupled nuclear spins. Using a modified formulation of Floquet theory, treating the time-dependent magnetic field as a perturbation, and exploiting the slow radical pair recombination, we show that one can obtain a good approximation to the product yield by considering only nearly degenerate sub-spaces of the Floquet space. Within a significant parameter range, the resulting method is found to give product yields in good agreement with exact quantum mechanical results for a variety of simple model radical pairs. Moreover it is considerably more efficient than the exact calculation, and it can be applied to radical pairs containing significantly more nuclear spins. This promises to open the door to realistic theoretical investigations of the effect of radiofrequency electromagnetic radiation on the photochemically induced radical pair recombination reactions in the avian retina which are believed to be responsible for the magnetic compass sense of migratory birds. Published by AIP Publishing. [http://dx

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Radiofrequency polarization effects in zero-field electron paramagnetic resonance

Cited by 14 publications

References 10 publications

Spin-locking in low-frequency reaction yield detected magnetic resonance

Spin-locking in low-frequency reaction yield detected magnetic resonance

Towards predicting intracellular radiofrequency radiation effects

Floquet theory of radical pairs in radiofrequency magnetic fields

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