During interplanetary flights in the near future, a human organism will be exposed to prolonged periods of a hypomagnetic field that is 10,000 times weaker than that of Earth’s. Attenuation of the geomagnetic field occurs in buildings with steel walls and in buildings with steel reinforcement. It cannot be ruled out also that a zero magnetic field might be interesting in biomedical studies and therapy. Further research in the area of hypomagnetic field effects, as shown in this article, is capable of shedding light on a fundamental problem in biophysics—the problem of primary magnetoreception. This review contains, currently, the most extensive bibliography on the biological effects of hypomagnetic field. This includes both a review of known experimental results and the putative mechanisms of magnetoreception and their explanatory power with respect to the hypomagnetic field effects. We show that the measured correlations of the HMF effect with HMF magnitude and inhomogeneity and type and duration of exposure are statistically absent. This suggests that there is no general biophysical MF target similar for different organisms. This also suggests that magnetoreception is not necessarily associated with evolutionary developed specific magnetoreceptors in migrating animals and magnetotactic bacteria. Independently, there is nonspecific magnetoreception that is common for all organisms, manifests itself in very different biological observables as mostly random reactions, and is a result of MF interaction with magnetic moments at a physical level—moments that are present everywhere in macromolecules and proteins and can sometimes transfer the magnetic signal at the level of downstream biochemical events. The corresponding universal mechanism of magnetoreception that has been given further theoretical analysis allows one to determine the parameters of magnetic moments involved in magnetoreception—their gyromagnetic ratio and thermal relaxation time—and so to better understand the nature of MF targets in organisms.

The effect of week static magnetic fields on Escherichia coli K12 AB1157 cells was studied by the method of anomalous viscosity time dependencies (AVTD). The AVTD changes were found when E. coli cells were exposed to static fields within the range from 0 to 110 microT. The dependence of the effect on the magnetic flux density had several extrema. These results were compared with theoretical predictions of the ion interference mechanism. This mechanism links the dissociation probability of ion--protein complexes to parameters of magnetic fields. The mechanism was extended to the case of rotating complexes. Calculations were made for several ions of biological relevance. The results of simulations for Ca(2+), Mg(2+), and Zn(2+) showed a remarkable consistency with experimental data. An important condition for this consistency was that all complexes rotate with the same speed approximately 18 revolutions per second (rps). This suggests that the rotation of the same carrier for all ion--protein complexes may be involved in the mechanism of response to the magnetic field. We believe that this carrier is DNA.

Proposed is a general physical mechanism of magnetoreception of weak magnetic fields (MFs). The mechanism is based on classical precessional dynamics of a magnetic moment in a thermally disturbed environment and includes a minimum of necessary parameters-the gyromagnetic ratio, thermal relaxation time, and rate of downstream events generated by changes in the state of the magnetic moment. The mechanism imposes general restrictions on the probability of initial biophysical magnetic transduction event before the involvement of specific biophysical and biochemical mechanisms-i.e., regardless of the nature of an MF target and the subsequent cascade of events. It is shown that biological effects of weak MFs have, in certain cases, nonlinear and frequency selective properties. The observation of these characteristics provides information not only on the target's gyromagnetic ratio, but also on the parameters of its interaction with the immediate environment. This enables one to develop experimental strategies for identifying the biophysical mechanisms of magnetoreception including the specific case of effects of a near-zero MF exposure. The mechanism is universally applicable to magnetic moments of different nature, in particular, of electron and proton orbital motion and of spins. Experimental exposure conditions are derived which would lead to validation of the proposed mechanism. Bioelectromagnetics. 38:41-52, 2017. © 2016 Wiley Periodicals, Inc.

The article discusses the so-called 'kT problem' with its formulation, content, and consequences. The usual formulation of the problem points out the paradox of biological effects of weak low-frequency magnetic fields. At the same time, the formulation is based on several implicit assumptions. Analysis of these assumptions shows that they are not always justified. In particular, molecular targets of magnetic fields in biological tissues may operate under physical conditions that do not correspond to the aforementioned assumptions. Consequently, as it is, the kT problem may not be an argument against the existence of non thermal magnetobiological effects. Specific examples are discussed: magnetic nanoparticles found in many organisms, long-lived rotational states of some molecules within protein structures, spin magnetic moments in radical pairs, and magnetic moments of protons in liquid water.

Extremely low-frequency magnetic fields are known to affect biological systems. In many cases, biological effects display "windows" in biologically effective parameters of the magnetic fields: most dramatic is the fact that the relatively intense magnetic fields sometimes do not cause appreciable effect, while smaller fields of the order of 10-100 microT do. Linear resonant physical processes do not explain the frequency windows in this case. Amplitude window phenomena suggest a nonlinear physical mechanism. Such a nonlinear mechanism has been proposed recently to explain those "windows." It considers the quantum-interference effects on the protein-bound substrate ions. Magnetic fields cause an interference of ion quantum states and change the probability of ion-protein dissociation. This ion-interference mechanism predicts specific magnetic-field frequency and amplitude windows within which the biological effects occur. It agrees with a lot of experiments. However, according to the mechanism, the lifetime Gamma(-1) of ion quantum states within a protein cavity should be of unrealistic value, more than 0.01 s for frequency band 10-100 Hz. In this paper, a biophysical mechanism has been proposed, which (i) retains the attractive features of the ion interference mechanism, i.e., predicts physical characteristics that might be experimentally examined and (ii) uses the principles of gyroscopic motion and removes the necessity to postulate large lifetimes. The mechanism considers the dynamics of the density matrix of the molecular groups, which are attached to the walls of protein cavities by two covalent bonds, i.e., molecular gyroscopes. Numerical computations have shown almost free rotations of the molecular gyroscopes. The relaxation time due to van der Waals forces was about 0.01 s for the cavity size of 28 A.