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Electromagnetic Fields in Biological Systems
(Eveson et al. 2000). They found that the concentration of free radicals escaping
from the micelle was not only affected by, but also depended on the conditions surrounding the radical pair. The Hore research group demonstrated that the yield of
1 O 2 sensitized by chemically modified, carotenoid-less (quinine-depleted) bacterial
photosynthetic reaction centers on the R-26 mutant of Rhodobacter sphaeroides and,
as a consequence, the stability of the reaction center protein is strongly affected by
an SMF of even a few milliteslas: a 50% reduction for fields of 20–100 mT and a 10%
reduction for fields of 1 mT (Liu et al. 2005).
Ritz, Dommer, and Phillips (2002) reviewed the physiological basis of animal magnetoreception and suggested a possible link between photoreception and magnetoreception from their findings in behavioral and theoretical studies. Migratory birds have the
ability to sense the geomagnetic field and use it as a source of compass information. The
candidates for a biophysical mechanism of this magnetoreception capability are magnetite and magnetically sensitive chemical reactions in animals. Ritz, Adem, and Schulten
(2000) postulated the possibility that magnetoreception involves radical pair processes
as a biophysical mechanism. The radical pair mechanism theory has been developed,
which provides insight into the magnetic compass of living organisms using the geomagnetic field. A blue-light photoreceptor, cryptochrome (CRY), is the most promising magnetoreceptor candidate based on the radical pair mechanism. The “radical pair/
cryptochrome hypothesis” has propelled a great deal of research activities in recent
years (Winklhofer 2010; see also Section 3.3.1.1). The hypothesis is that the chemical
compounds in a radical pair are highly sensitive to the spatial orientation of magnetic
field lines. Ritz et al. (2010) considered the potential consequences of such optimally
devised radical pairs on oxidative stress levels in cells and suggested possible transduction pathways and neural processing strategies for magnetic stimuli detected by photoreceptors such as CRY.
There are several reports that strong SMF effects play significant roles in endogenous
and exogenous ROS generation. In contrast, only a few reports on endogenous RNS
(NO) generation in biological systems have been described. However, there are safety
concerns that the mechanisms of SMF might induce potentiation of endogenous ROS-/
RNS-induced apoptosis or necrosis or both. Regarding the physical effects of magnetic
force, it has been reported that the force product of 400 T 2 /m in 8 T affected the dynamic
movement of paramagnetic oxygen bubbles and restrained the evaporation of dissolved
oxygen molecules (molar magnetic susceptibility = 3449 × 10 −6 cm 3 /mol) from a reaction mixture such as that required for the decomposition of H 2 O 2 (Ueno and Iwasaka
1996a). Consequently, the dissolved oxygen levels in solution might be increased.
Moreover, it was recently reported that greater enhancement of chemical reaction rate
occurs in solution resulting from the magnetic force of 44 T 2 /m in 0.63 T, which attracts
oxygen molecules in the air (when the solution depth was ≤2.6 mm and the duration of
exposure was ≥150 minutes) (Aoyagi et al. 2006). This effect is considered to be further
enhanced in aqueous solutions containing paramagnetic metallic complexes such as
stable Cu (II) complexes and heme Fe (III) complexes (Sakurai et al. 2000). Therefore,
when examining the effects of strong gradient SMF on free radical reactions, the magnetic force (or force product) acting on the oxygen molecules should be considered.