IONIC FORCES AND MEMBRANE PHENOMENA

When a membrane containing diffusible ions is perturbed by an electric field, osmotic and electric relaxation forces are developed. These are calculated for an infinitesimal impulse perturbation. The force characteristics are dependent on the shape of the fixedcharge distribution. The electric force is proportional to the concentration difference, while the osmotic force is proportional to the second derivative of the chemical potential. The residual electric field gives rise to membrane reactance. With two diffusible cations having different concentrations and mobilities, two decaying potential terms are obtained. Under certain conditions these may be represented as due to a real RLC electric circuit. If the mobility of a diffusible cation varies in the membrane, it is possible for the osmotic force to cancel the electric. The case is examined for mobility inversely proportional to the negative fixed charge density, and the requisite charge distribution calculated. It appears that this effect may be of importance in explaining the activity of the axonal membrane. Boundary forces are examined in detail in the Appendices, including the effect of lack of equilibrium. Force relationships are calculated for the uniform fixed-charge membrane. © 1968 N. Rashevsky.