Probing the membrane potential of living cells by dielectric spectroscopy

Abstract

Abstract.In this paper we demonstrate a quantitative way to measure the membrane potential of live cells by dielectric spectroscopy. We also show that the values of the membrane potential obtained using our technique are in good agreement with those obtained using traditional methods-voltage sensitive dyes. The membrane potential is determined by fitting the experimental dielectric dispersion curves with the dispersion curves obtain from a theoretical model. Variations in the membrane potential were induced by modifying the concentration of potassium chloride in the solution of the cell suspension in the presence of valinomycin. For exemplification of the method, E. coli were chosen for our experiments.

Isolation, characterization and mode of antimicrobial action againstVibrio choleraeof methyl gallate isolated fromAcacia farnesiana

“…Methyl gallate caused membrane hyperpolarization, which has been recognized as an important type of membrane damage (Yuroff et al 2003). The hyperpolarization could be explained as the result of an efflux of positively charged ions from the cytoplasm into the cell exterior, specifically K + , through a specific K + channel in the plasma membrane affecting cell homeostasis (Bot and Prodan 2009) or by the movement of negative charge from the extracellular space into the cytoplasm (Gresık et al 1991). This redistribution of K + would result in an increase in membrane potential, that is, a positive outside (Gresık et al 1991).…”

Extracts of Edible and Medicinal Plants Damage Membranes of Vibrio cholerae

“…Controls used included the following buffers: glycine (50 mM), citric acid (50 mM), Na 2 HPO 4 ⅐ 2H 2 O (50 mM), and KCl (50 mM) adjusted to various pH values (4,5,6,7,8,9, and 10). The fluorescence intensity was measured at 25°C after equilibrating the pH in and pH out by addition of valinomycin (1 mol liter…”

Influence of Localized Surface Charge Distributions on the Dielectric Relaxation Spectra of Spherical Colloidal Particles in Aqueous Solution

“…Moreover, the surface currents generated by the surface charge distributions assume a biological meaning since they influence the membrane potential ΔV, as extensively discussed by Bot and Prodan [2,3]. Finally, in biological cells, the surface charge distributions are originated by the effective membrane structure where the presence of small charged molecules and a variety of organic ions free to move in the direction tangential to the membrane surface with the consequent increase of the tangential membrane conductivity.…”

“…We will do this taking advantage of the dielectric model proposed by Prodan et al [1] some years ago to describe the dielectric behavior of spherical live cell in suspension, assuming the presence of charge distributions at the outer and inner faces of the cell membrane. These charge distributions have been introduced by Prodan et al [1] and Bot et al [2] to justify in a quantitative way the presence of the membrane potential in biological cells, whose value is related to the conductivity of the superficial charges through the relationship…”