On the dielectric spectra of proteins in conducting media

Abstract

The effect of conductivity on the dielectric measurements of proteins is studied. For that purpose the dielectric spectra (0.03–13 MHz) of serum albumin and myoglobin in solutions of varying conductivities were recorded. The results presented confirm that Maxwell's prediction of a threshold frequency in conducting materials also holds for protein solutions. The threshold frequency of a serum albumin solution is experimentally determined and the ionic screening of the electric field when performing dielectric spectra of these samples discussed. Three distinct frequency regions must be considered: a low frequency region where the sample behaves like a conductor; an intermediate region centered around the threshold frequency where the free charges partially screen the fixed charges; and a high frequency region where the sample behaves like a good dielectric. Dielectric measurements in the low frequency region defined above, are not possible.