Weak magnetic fields and extremely low frequency electromagnetic fields (EMF) are omnipresent in natural environmental and increasingly man-made factors. A possible influence on life processes was already mentioned in the late 19th
]. It is now recognized, that many organisms are capable of perceiving such fields, while less is known on the elementary perception. Three types of mechanisms are considered therefore, the orientation of ferromagnetic particles in tissues [2
], singlet-triplet mixing states of macromolecules building radical pairs [3
], and the ICR, whose persistent investigation began with the works of Liboff [4
Ferromagnetism has been implicated in animal navigation (e.g. compass mechanism of migratory birds [5
], and the magnetotaxis of certain bacteria [6
]. The radical pair mechanism is independent of ferromagnetism and has putatively a higher magnetic sensitivity. It has been primarily studied in photosynthetic reaction centers and the respiratory chain [7
], where triplet yields are modulated by electromagnetic interaction with fields as low as about 50 μT [8
]. Already two decades ago effects were described by Blackman et al.
], and later by [10
], which require a combination of static and alternating magnetic fields. It turned out, that the magnetic field strength B
of the static component and the frequency f
of the alternating EMF relate to the "ion cyclotron resonance (ICR) formula":
is the mass and q
the charge of ions involved. The explanation of the mechanism of this effect in an aqueous, more or less viscous environment seems to be difficult, nevertheless there are some efforts. Liboff [13
] suggested that magnetic fields can interact in a resonant manner with endogenous AC electric fields in biological systems, instead of a direct interaction with external AC magnetic fields. Binhi [14
] reviewed the mechanisms of magnetobiological effects, and tried to estimate the sensitivities and involved molecular topologies. Adair [15
] questioned a model involving altered transition rates of excited ions by weak EMF, while others [16
] consider the ionic environment, eg. properties of the water, with Ca2+
as the most investigated ion. An altered Ca2+
-transport was found in human lymphocytes [4
]. The motility of benthic diatoms is effected, if ICR conditions are matched for Ca2+
in the range of 8–64 Hz, and static field strengths comparable to geomagnetic fields [17
]. The germination rate of Raphanus sativus
was altered, when the ICR conditions for Ca2+
were applied to the seedlings [18
]. ELF effects on macromolecules indicate an ICR effect possibly caused by additionally involved alternating electric fields [19
]. It is noteworthy remarkable that ICR conditions can be matched by combinations of the local geomagnetic field and man-made electromagnetic fields, especially the frequency range of power lines (50 or 60 Hz). Liboff et al.
] suggest to consider ICR effects for the evaluation of epidemiological childhood leukaemia studies. The assessment of elevated brain cancer risk has been evaluated by Aldrich et al.
] on the assumption of interactions of the geomagnetic field and a 60 Hz field component from power lines.
NLDS was developed during the past decade in order to investigate dielectric properties of small particles in aqueous solutions, using relatively simple electrochemical equipment. In the simplest case, a sinusoidal alternating electric field is applied to the solution by 2 electrodes, using peak to peak voltages up to 1.5 V and frequencies of 1 to 1000 Hz. Particles with a dielectric constant different from that of their environment (generally water) distort the field. This induces alternating voltages over and currents through the solution, which are detected by 2 auxiliary electrodes in order to avoid polarisation effects. Phase shifts and distortions of the obtained signals, as compared to the input signal, contain information on damping and relaxation kinetics. Therefore, the signals are Fourier
-transformed and evaluated as power spectra in the frequency domain [22
]. Usually, the sample is compared to a reference, which lacks the solute, but otherwise is identical. Sample and reference can either be measured one by one in a single chamber device, or simultaneous with a "dual-chamber" setup, which also needs a two channel data acquisition, and allows a real-time differential-NLDS (DNLDS). The data are usually calculated using the decibel (dB) scale for the intensity (power) Pn
Where U(n)sample is the signal output intensity of the nth harmonic from the sample measuring channel, and U(n)ref the corresponding value from the reference channel.
Zhadin et al.
] reported the alteration of electric properties of an electrolyte under ICR conditions. They found an increasing ion current through an aqueous glutamic acid (Glu) solution in narrow frequency bands (resonance), which could be described by equation (1). These results are the starting point for the present work, which is aimed to further elucidate this conduction mechanism. The influence of the concentration of Glu has been investigated, and the time resolved electric current through the solution is analyzed using "non linear dielectric spectroscopy" (NLDS), which indicate microcolloidial properties of the solvent-solute system. The NLDS was amplified by two features: The option of simultaneous data acquisition in two cuvettes (DNLDS), and the frequency resolved voltammetry (FRV), whereby simultaneous a AC voltammetry is performed [26
]. By recording NLDS spectra at varying electrode voltages from e.g. 100–1100 mV, additional information was obtained on redox potentials. The electrode current never increases proportionally with the applied voltage but remains constant in the range of the counter voltage to an existing redox potential given by the investigated electrode-electrolyte system. This was used to improve the method by recording differential spectra (DNLDS). The integral over the spectrum represents one data point of a simple (not frequency resolved) AC voltammetry, while the intensity course of corresponding spectral data points provide information about the dielectric state of the redox reaction, e.g. its capacitive, time-dependent properties.