Cell membrane, electrical properties measurement

More recently, dielectrophoretic studies have for instance been reported on T-lymphocytes (Pethig and Talary, 2007) and on how cell destruction during dielectrophoresis can be minimized (or used) by appropriate choice of AC frequency and amplimde (Menachery and Pethig, 2005). Dielectrophoresis has also been used for measurement of membrane electrical properties such as capacitance and conductance for insulin-secreting pancreatic cells (Pethig et al., 2005). 

In another type, mammalian cells or plasma membranes are used as electrical capacitors. Electrical impedance (El) uses the inherent electrical properties of cells to measure the parameters related to the tissue environment (Kyle et al., 1999). The mechanical contact between cell-cell and cell-substrates is measured via conductivity or El (Deng et al., 2003 ... 

This laboratory long ago devised [120] the use of radio-frequency dielectric spectroscopy [121, 122] for the on-line and real-time estimation of microbial and other cellular biomass during laboratory and industrial fermentations. The principle of operation is that only intact cells (see [123] for what is meant in this context by the word viable ), and nothing else likely to be in a fermentor, have intact plasma membranes and that the measurement of the electrical properties of these membranes allows the direct estimation of cellular biomass (Fig. 4). 

The bond graph method of network thermodynamics is widely used in studying homogeneous and heterogeneous membrane transport. Electroosmosis and volume changes within the compartments are the critical properties in the mechanism of cell membrane transport, and these properties can be predicted by the bond graph method of network thermodynamics. In another study, a network thermodynamics model was developed to describe the role of epithelial ion transport. The model has four membranes with series and parallel pathways and three transported ions, and simulates the system at both steady-state and transient transepithelial electrical measurements. 

Electrical properties of tissue and cell suspensions were reviewed by Schwan (1957). Membrane capacitance and conductance for pancreatic P-cells were measured by an electrokinetic method (Pethig et al. 2005 Grimnes and Martinsen 2008). The conductivity of blood is dependent on blood velocity this is the Sigman effect (Sigman et al. 1937). 

The electrical properties of microporous membranes in 1 mM KCI solution was investigated in the frequency range 1 mHz to 1 kHz by Martinsen et al. (1998a), using a four-electrode measuring cell (Figure 3.11). 

Figure 22.6 (a) Relationship between the current i and the applied voltage ip from Equation (22.29). (b) Current-voltage measurements for a potassium channel in the egg cell membrane of a starfish. Source (a) TW Weiss, Cellular Biophysics, Volume 2 Electrical Properties, MIT Press, Cambridge, 1996. (b) B Hille, Ionic Channels of Excitable Membranes, Sinauer, Sunderland, MA, 1984. Data are from S Hagiwara,... 

Determination of nonstoichiometry in oxides is a key point in the search for new materials for electrochemical applications. In recent decades, owing to their current and potential applications (electrodes in fuel cells, insertion electrodes, membranes of oxygen separation, gas sensors, catalytic materials, etc.), various methods of precise characterization of MfECs have been proposed, either the measurement of the defect concentrations and the stoichiometric ratio as functions of the oxide composition, of the surroxmding oxygen pressure and of temperature, or the transport properties. There are different methods to determine the electrical properties of MIECs and, more specifically, the ionic and electronic contributions. The most appropriate method depends on different parameters, i.e., the total electrical conductivity of the studied oxides, the ionic and electronic transport numbers, the... 

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