Dielectric spectroscopy of Anabaena 7120 protoplast suspensions

The dielectric spectroscopy of Anabaena 7120 protoplast suspensions has been investigated over the frequency range of 40 Hz–110 MHz. The protoplast suspensions showed a complicated dielectric dispersion consisting of at least four distinct sub-dispersions with the increasing frequencies due to the Maxwell–Wagner interfacial polarization. The double-shell model, in which an equivalent shell of thylakoid was assumed inside the cytoplasm, was adopted to describe the special morphology of the protoplast. Under the assumption that the conductivity of plasmalemma was negligible and the conductivity of the equivalent shell was 0.1 μS/cm, we attempted to estimate the dielectric properties of various protoplast components by fitting theoretical curve to experimental data. The relative permittivity of the plasmalemma εmem was estimated to be 6.5 ± 0.5, and the permittivity of the equivalent shell of thylakoid εthy was estimated to be about 3.2 ± 0.2. The permittivity εcyt and conductivity κcyt of the cytoplasm were estimated to be 60 and 0.88 ± 0.11 mS/cm, respectively. The permittivity εnuc and conductivity κnuc of the nucleoplasmic region were determined to be 100 and 0.13 ± 0.02 mS/cm, respectively.