Relation of the Permittivity of Biological Cell Suspensions to Fractional Cell Volume

Abstract

As was first shown in work on the red blood cell¹, the high permittivity (of the order of thousands) of biological cell materials is the result of an electric condenser action originating in an extremely thin section—possibly a bimolecular lipid layer—of the surface envelope, in which the principal part of the cell resistance is located. Under certain conditions, the capacity of this ‘membrane’ condenser can be calculated² from the observed permittivity and has been found to be closely the same for certain types of cell, namely, about 0.9 µF./sq. cm., in the radio-frequency region^1,3–5, corresponding to a probable thickness of the membrane of about 30 A. This calculation can be carried through rigorously only when the number of cells in the material is small. The analysis of denser cell materials raises the question of the form of the relationship between permittivity (ɛ) and fractional cell volume (ρ) in a system exhibiting this type of dielectric mechanism. Although this problem has been given some theoretical attention in the past, the only experimental data now available are those obtained in my early work on dog erythrocytes¹.