Evidence from its temperature dependence that the ?-dielectric dispersion of cell suspensions is not due solely to the charging of a static membrane capacitance

Abstract

1. A survey of the literature indicates that the apparent capacitance per unit area (Cm) of biological membranes is in general significantly greater than is that of 'artificial' phospholipid (black lipid) membranes (BLM). It is not possible, by quantitative arguments alone, to exclude that this simply reflects the idea that protein-containing biological membranes have a greater thickness than BLM. 2. The temperature-dependence of the membrane capacitance for both solvent-containing and solvent-free BLM is negative. However, where appropriate data are available, it appears that the capacitance of biological membranes has a positive temperature-dependence, indicating a qualitative difference between natural and artificial membranes. 3. Using a 4-terminal dielectric spectrometer, and the fitting program and electrode polarisation correction described in the accompanying paper, we have carried out a careful study of the temperature-dependence of the/?-dielectric dispersion of a unicellular eukaryote (Saccharomyces cerevisiae) and a prokaryote (Escherichia coli), 4. In the range 15-40 °C, the temperature-dependence of the/?-dielectric dispersion (and thus in principle of Cm) in S. cerevisiae and E. coli is respectively +0.13 and +0.35% (°C) -1. 5. Flow cytometric measurements indicate that the cell size of E. coli is unchanged in the temperature range studied. 6. These data strongly suggest that the/?-dielectric dispersion in cell suspensions is not due solely to the charging of a 'static' membrane capacitance. It is proposed that the positive temperature coefficient of the /?-dispersion reflects the contribution of temperaturedependent, partially restricted, lateral motions of the charged lipid and protein components of the cytoplasmic membrane.

The permittistat: a novel type of turbidostat

“…However, it is fair to point out that the classical explanation alone is not consistent with the effects of cross-linking reagents (Harris & Kell, 19856, Symons et al, 1986), the excessively great values of the Cole-Cole a (Kell & Harris, 1985a, 6;Pethig & Kell, 1987) and the temperature-dependence of the dielectric increments observed (Ferris et al, 1990), such that other effects, in particular the lateral diffusion and activity of membranous proteins (Harris & Kell, 19856, Kell & Harris, 19856), must also contribute to the a-dispersion in biological cell suspensions.…”

Quantitative modeling of viable cell density, cell size, intracellular conductivity, and membrane capacitance in batch and fed‐batch CHO processes using dielectric spectroscopy

“…Other studies on the temperature dependence of the dielectric properties of cells have been performed, and indicate the effect may be small, especially for eukaryotes over the temperature range examined in this study. [52][53][54] More detailed analyses of the effects of temperature and nutrient additions on the dielectric properties of mammalian cells remain to be performed.…”

On-Line, Real-Time Measurements of Cellular Biomass using Dielectric Spectroscopy

“…Harris and Kell, 1983;, is: ∆ε = ( 9 P r C m ) / (4 ε 0 ) .... (3) where P (dimensionless) is the volume fraction of cells with intact plasma membranes (i.e. biomass), r is the radius of the spherical cells (m) and C m is the plasma membrane capacitance in F.m -2 (Ferris et al, 1990). C m gives a measure of the charge-storing ability of the membranes and has been found to be effectively a biological constant of 0.01 ± 0.005 F.m -2 .…”