Potentiometric measurements of transmembrane potential of cells with use of the penetrating ions

There are methodical restrictions arising at potentiometric measurements of the transmembrane potential of cells with use of the penetrating (lipophilic) ions are discussed in the article. The analysis of the experimental results of measurements of transmembrane potential of B.subtilis cells on exposure to a gramicidin A is made that was received with using TPP + selective membrane electrode. The analysis is based on the assumption of almost reversible adsorption of indicator cations on a cellular surface. It is shown that result of such measurements is more considerable value dipolar potential of a membrane rather the transmembrane potential. There is offered the estimation method of changes of the membrane potential, using the irreversible connected part of the penetrating ions immobilized in membrane channels on exposure to the gramicidin for calculation. Area density of the adsorbed charge, concentration of places of binding of indicator cations and parameters of a double electric layer are calculated.