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- Passive Electrical Properties of MicroorganismsPassive Electrical Properties of Microorganisms
Biophysical Journal, Volume 5, Issue 3, 1 May 1965, Pages 289-300
E.L. Carstensen, H.A. Cox, W.B. Mercer and L.A. Natale
AbstractEffective conductivities are reported for the bacteria and over a range of environmental conductivity. The apparent conductivities of the organisms can be explained in terms of the properties of the cell wall. At low conductivities of the environment, the conductivity of the cell appears to be dominated by the counterions of the fixed charge of the cell wall. At higher conductivities of the suspending medium, evidence suggests that ions from the environment invade the cell wall causing an increase in the effective conductivity of the cell so that it takes on values roughly proportional to that of the environment. The model points to the usefulness of dielectric techniques in studies of the properties of intact cell walls.
Abstract | PDF (729 kb) - Electrical conductivity in lipid bilayer membranes induced b...Electrical conductivity in lipid bilayer membranes induced by pentachlorophenol
Biophysical Journal, Volume 16, Issue 4, 1 April 1976, Pages 319-336
P. Smejtek, K. Hsu and W.H. Perman
AbstractElectrical conductivity induced in thin lipid bilayer membranes by pentachlorophenol has been studied. The membranes were formed from phosphatidyl choline, phosphatidyl ethanolamine, or phosphatidyl glycerol and various amounts of cholesterol. The position and the magnitude of the maximum of the conductivity vs. pH curve depend on the type of lipids and cholesterol content. At low pentachlorophenol concentrations and low pH the concentration dependence of conductivity is quadratic and becomes linear at higher pH. Above 10(-5) M of pentachlorophenol the concentration dependence of the membrane conductivity tends to saturate. Presence of pentachlorophenol enhances membrane transport of nonactin-K+ complex. Increase of cholesterol content increases pentachlorophenol induced conductivity in all membranes and shifts the conductivity toward lower pH. For phosphatidyl choline the largest rate of change of membrane conductivity with cholesterol occurs at 1:1 phospholipid to cholesterol molar ratio. Pentachlorophenol is found to be a class II uncoupler and the experimental results are consistent with the hypothesis that the membrane permeable species are dimers formed by combination of neutral and dissociated pentachlorophenol molecules. Several schemes of membrane conduction, including dimer formation in the aqueous phase as well as at the membrane-water interface have been considered. Arguments are given in favor of the formation of dimers within the membrane surface.
Abstract | PDF (1138 kb) - Effect of Fluorine Substitution on the Interaction of Lipoph...Effect of Fluorine Substitution on the Interaction of Lipophilic Ions with the Plasma Membrane of Mammalian Cells
Biophysical Journal, Volume 79, Issue 3, 1 September 2000, Pages 1490-1497
Markus Kürschner, Katja Nielsen, Johannes R.G. von Langen, Wolfdieter A. Schenk, Ulrich Zimmermann and Vladimir L. Sukhorukov
AbstractThe effects of the anionic tungsten carbonyl complex [W(CO)SCH] and its fluorinated analog [W(CO)SCF] on the electrical properties of the plasma membrane of mouse myeloma cells were studied by the single-cell electrorotation technique. At micromolar concentrations, both compounds gave rise to an additional antifield peak in the rotational spectra of cells, indicating that the plasma membrane displayed a strong dielectric dispersion. This means that both tungsten derivatives act as lipophilic ions that are able to introduce large amounts of mobile charges into the plasma membrane. The analysis of the rotational spectra allowed the evaluation not only of the passive electric properties of the plasma membrane and cytoplasm, but also of the ion transport parameters, such as the surface concentration, partition coefficient, and translocation rate constant of the lipophilic anions dissolved in the plasma membrane. Comparison of the membrane transport parameters for the two anions showed that the fluorine-substituted analog was more lipophilic, but its translocation across the plasma membrane was slower by at least one order of magnitude than that of the parent hydrogenated anion.
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Copyright © 1964 The Biophysical Society. All rights reserved.
Biophysical Journal, Volume 4, Issue 6, 465-470, 1 November 1964
doi:10.1016/S0006-3495(64)86796-5
Articles
An Investigation of Electrical Conductivity of Steroids
Darold Wobschall and Dorita A. Norton
Abstract
The electrical conductivity of sixteen steroids in the solid state was measured as a function of temperature. While too small to measure at room temperature, the exponential increase in conductivity with temperature can be determined at elevated temperatures (70° - 130°C). Most steroids tested had a conductivity of 10-13 to 10-15ohm-1cm-1 at 100°C and an activation energy of 2 to 4 ev. It it concluded that the observed conductivity is due to impurities. Exposure of keto steroids to iodine vapor results in unstable colored compounds, probably charge transfer complexes, which in some cases have a conductivity as high as 10-4ohm-1cm-1.
