Measurement of magnetic field effects on radical recombination reactions using triplet–triplet energy transfer

Henbest, Kevin B.; Maeda, Kiminori; Athanassiades, E.; Hore, P. J.; Timmel, Christiane R.

doi:10.1016/j.cplett.2006.01.106

Cited by 9 publications

(11 citation statements)

References 24 publications

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“…Both theoretical and experimental work on the effects of weak magnetic flux densities on free radical concentration has been carried out by the group at Oxford [Brocklehurst and McLauchlan, 1996;Woodward et al, 2001;Henbest et al, 2004;Timmel and Henbest, 2004;Liu et al, 2005;Henbest et al, 2006;Rodgers et al, 2007]. However, these workers have also concentrated at low fields on the spontaneous evolution between S and T states of the spins as they precess (low field effect).…”

Section: Introductionmentioning

confidence: 99%

The effects of weak magnetic fields on radical pairs

Barnes

Greenebaum

2014

Bioelectromagnetics

120

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It is proposed that radical concentrations can be modified by combinations of weak, steady and alternating magnetic fields that modify the population distribution of the nuclear and electronic spin state, the energy levels and the alignment of the magnetic moments of the components of the radical pairs. In low external magnetic fields, the electronic and nuclear angular momentum vectors are coupled by internal forces that outweigh the external fields' interactions and are characterized in the Hamiltonian by the total quantum number F. Radical pairs form with their unpaired electrons in singlet (S) or triplet (T) states with respect to each other. At frequencies corresponding to the energy separation between the various states in the external magnetic fields, transitions can occur that change the populations of both electron and nuclear states. In addition, the coupling between the nuclei, nuclei and electrons, and Zeeman shifts in the electron and nuclear energy levels can lead to transitions with resonances spanning frequencies from a few Hertz into the megahertz region. For nuclear energy levels with narrow absorption line widths, this can lead to amplitude and frequency windows. Changes in the pair recombination rates can change radical concentrations and modify biological processes. The overall conclusion is that the application of magnetic fields at frequencies ranging from a few Hertz to microwaves at the absorption frequencies observed in electron and nuclear resonance spectroscopy for radicals can lead to changes in free radical concentrations and have the potential to lead to biologically significant changes.

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Section: Introductionmentioning

confidence: 99%

The effects of weak magnetic fields on radical pairs

Barnes

Greenebaum

2014

Bioelectromagnetics

120

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“…For this system the MFE on the exciplex has been extensively studied in the context of degenerate electron exchange 14 and triplet-triplet energy transfer. 38 Since no spectrally resolved methods had been employed, the effect on the fluorophore apparently remained elusive. Because of the large effect on the fluorophore, we have recorded a magnetic field action spectrum, which gives information on the magnetic field induced change in intensity, DI, in a spectrally This journal is c the Owner Societies 2011 Phys.…”

Section: Resultsmentioning

confidence: 99%

“…Several well known systems, e.g. pyrene/ N,N-dimethylaniline, 15,17,36,37 pyrene/1,3-benzenedicarbonitrile [12][13][14]38 and anthracene/N,N-dimethylaniline 39 are revisited. To the best of the authors' knowledge 12 of the systems were hitherto unknown to show magnetic field effects.…”

Section: Introductionmentioning

confidence: 99%

Magnetic field effects on exciplex-forming systems: the effect on the locally excited fluorophore and its dependence on free energy

Kattnig

Rosspeintner

Grampp

2011

Phys. Chem. Chem. Phys.

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This study addresses magnetic field effects in exciplex forming donor-acceptor systems. For moderately exergonic systems, the exciplex and the locally excited fluorophore emission are found to be magneto-sensitive. A previously introduced model attributing this finding to excited state reversibility is confirmed. Systems characterised by a free energy of charge separation up to approximately -0.35 eV are found to exhibit a magnetic field effect on the fluorophore. A simple three-state model of the exciplex is introduced, which uses the reaction distance and the asymmetric electron transfer reaction coordinate as pertinent variables. Comparing the experimental emission band shapes with those predicted by the model, a semi-quantitative picture of the formation of the magnetic field effect is developed based on energy hypersurfaces. The model can also be applied to estimate the indirect contribution of the exchange interaction, even if the perturbative approach fails. The energetic parameters that are essential for the formation of large magnetic field effects on the exciplex are discussed.

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“…In order to recombine the two unpaired electrons must have antiparallel spins [Brocklehurst and McLauchlan, 1996]. It has been shown that the application of a magnetic field can affect the proportion of radical pairs in the parallel to antiparallel state thus influencing the ability for them to recombine [Monchick and Adrian, 1978;Batchelor et al, 1993;Henbest et al, 2006;Solov'yov et al, 2007].…”

Section: Introductionmentioning

confidence: 99%

Effect of 100 mT homogeneous static magnetic field on [Ca²⁺]_c response to ATP in HL‐60 cells following GSH depletion

Belton

Prato

Rozanski

et al. 2009

Bioelectromagnetics

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Calcium is an important molecule in a number of biological systems. Often these systems are signal transduction cascades involving molecules such as ATP. ATP activates second messengers which can interact with ion channels on the endoplasmic/sarcoplasmic reticulum resulting in the emptying of the intracellular calcium stores and an increase in cytosolic free calcium concentration ([Ca2+]c). Changes in [Ca2+]c can be influenced by external factors such as a static magnetic field (SMF). One hypothesis suggests that a SMF affects the cells through the radical pair mechanism. By reducing the number of antioxidant molecules like glutathione (GSH), the proportion of free radicals in the cells is increased and may lead to a greater probability of a biological response to a SMF. The purpose of this study was to determine if the [Ca2+]c response to ATP was affected by depletion of GSH by diethylmaleate (DEM) and the absence or presence of a 100 mT homogeneous SMF. Undifferentiated HL-60 cells were loaded with fura-2 AM. [Ca2+]c was measured in real time using a ratiometric fluorescence spectroscopy system. Various (DEM) ranging from 1 to 15 mM were added to deplete GSH. Cells were either exposed to sham or magnetic field (100 mT) for 13 min (780 s) and challenged with 1 microM ATP. The data show that [Ca2+]c was elevated following treatment with DEM with greater [Ca2+]c at higher [DEM]. The [Ca2+]c response to ATP was decreased as the DEM concentration increased. However, there was no effect of a 100 mT SMF on the average [Ca2+]c peak following ATP activation or the full width at half maximum (FWHM) of the [Ca2+]c response and recovery after ATP activation.

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Measurement of magnetic field effects on radical recombination reactions using triplet–triplet energy transfer

Cited by 9 publications

References 24 publications

The effects of weak magnetic fields on radical pairs

The effects of weak magnetic fields on radical pairs

Magnetic field effects on exciplex-forming systems: the effect on the locally excited fluorophore and its dependence on free energy

Effect of 100 mT homogeneous static magnetic field on [Ca²⁺]_c response to ATP in HL‐60 cells following GSH depletion

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Measurement of magnetic field effects on radical recombination reactions using triplet–triplet energy transfer

Cited by 9 publications

References 24 publications

The effects of weak magnetic fields on radical pairs

The effects of weak magnetic fields on radical pairs

Magnetic field effects on exciplex-forming systems: the effect on the locally excited fluorophore and its dependence on free energy

Effect of 100 mT homogeneous static magnetic field on [Ca2+]c response to ATP in HL‐60 cells following GSH depletion

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Effect of 100 mT homogeneous static magnetic field on [Ca²⁺]_c response to ATP in HL‐60 cells following GSH depletion