Physical mechanisms by which low-frequency magnetic fields can affect the distribution of counterions on cylindrical biological cell surfaces

Abstract

Effects of dc and low-frequency ac magnetic fields on the motion and distribution of counterions on surfaces of cylindrical biological cells are examined. Magnetic fields along the cell axis as well as perpendicular to it are considered. When a dc magnetic field of any physically realizable magnitude is parallel to the cell axis it has no effect on ion motion, since the resulting Lorentz force is much smaller than the counterion-to-ion attractive force. However a dc magnetic field perpendicular to the cell surface will distort any preexisting ion motion and the resulting current (i⊥) perpendicular to the original motion will be much larger than any current induced by a low-frequency ac magnetic field of the same magnitude as the dc field and parallel to it. Nevertheless i⊥ will still be much smaller than the current io constituting the original ion motion since (i⊥/io)=Ω/ν, where Ω is the ion cyclotron frequency and ν the effective counterion collision frequency. With no preexisting coherent ion motion (io=0) the circulating current induced by a sinusoidally time-varying magnetic field parallel to the cell axis will be well below thermal fluctuation noise as long as only a single cell is considered; however when even an infinitesimal exchange of ions between adjacent cells is assumed the magnetic field will cause a redistribution of counterions on the cell surface. The resulting steady-state distribution becomes independent of the frequency of the applied magnetic field (ω) when ω≫α, where α is 1/2 of the relaxation frequency for counterion diffusion. On the basis of these results it is suggested that whenever modification of cell behavior in response to application of a low-frequency magnetic field is established, measurements of dielectric permittivity versus frequency of the cell preparation be performed. Redistribution of counterions on the cell surface would be a likely cause if the noted effect becomes independent of the frequency of the applied magnetic field above the counterion dielectric relaxation frequency. It is also suggested that in magnetic field exposure of cell preparations the size of the sample (e.g. diameter of Petri dish) and direction of the magnetic field relative to average cell orientation can critically affect experimental results.