Grant: Discovery Grants Program - Individual

While we were accumulating data on the effects of extremely low frequency magnetic fields (ELFMF) on nociception in snails, mice and humans, a considerable amount of work has been published on magnetoreception in many different species (insects, rodents, reptiles, birds, cattle and deer) with the measured end point being orientation to the geomagnetic field. Candidates for the initial transduction mechanism in this work have been a) torque on an array of iron oxide particles which are of the correct size to maintain a single magnetic field domain and b) a radical pair mechanism (RPM) where the geomagnetic field affects singlet to triplet transitions in free radical pairs. Over the last ten years we have established a similarity in the characteristics of the initial biophysical detection mechanism for effect on opioid related behaviours (our work) and animal orientation. Both require simultaneous exposure to short wave length visible light of approximately the same intensity which supports the RPM. However very recently we have shown that the threshold for effects of a weak Extremely Low Frequency Magnetic Field (wELFMF) at 30 Hz is at or below 33 nT. Also recent animal orientation work shows sensitivities much lower than initially reported with significant results between 10 nT and 4µT also at extremely low frequencies. These low intensities at these low frequencies are inconsistent with either a single domain magnetite particle or the RPM. *Here we propose, to test in experiments in mice and cells, that the initial transduction is an array of Super Paramagnetic Iron Oxide (SPIO) particles. Unlike single domain particles the smaller SPIO particles have their magnetic moments unbound by their geometry. Hence, under thermal perturbations, their magnetic moment can change orientation while the particle's geometry remains fixed. (Local fields within 0.1 µm of the SPIO surface can exceed 100 mT.)*Consider:*1.wELFMF exposure could ""imprint"", via stochastic resonance, onto the local magnetic field of SPIO particles potentially increasing the amplitude of the applied field as much as ten million times. In other words, SPIO particles effectively amplify variations in applied nano-tesla fields, producing changes in local fields in the milli-tesla range. Such fields would certainly be high enough to alter singlet to triplet conversions in radical pairs. Also these conversions would oscillate at the frequencies (or possible double the frequency) of the applied field. These ELF oscillations in singlet to triplet conversions, could then couple to biological process susceptible to these frequencies. This ""amplification"" of the applied wELFMF would eliminate all objections to the RPM.*2.For SPIO particles the duration of the magnetic switching is less that the electron spin-lattice relaxation time in magnetite. Hence the rise and fall times of the mT fields might be short enough to induce sufficient currents to break molecular bonds and create free radicals directly.*3.A careful review of the literature suggests:*a.that many of the results currently attributable to single domain particles may not imply sensitivity to magnetic polarity as there was failure to address, in the experimental protocols, sensitivity to ambient wELFMF.*b.the broad frequency response to RF irradiation shown to negate the effects of a purported RPM is consistent with a RPM associated with fields of different strengths which exist in close proximity to the SPIO particles. *Hence SPIO particles as the initial transduction site could ""explain"" almost all magnetoreception data associated with wELFMF.