BIOSPECIFIC MECHANISM OF DOUBLE-LAYER FORMATION AND PECULIARITIES OF CELL ELECTROPHORESIS

It is shown that a partition of electric charge in the double layer (D L) of a cell takes place not only due to the dissociation of surface g roups or the adsorption of ionogenic surfactants but also because biol ogical cells are non-equilibrium systems. The basic quantitative chara cteristic of the cellular non-equilibrium state is the transmembrane p otential and in this context the theoretical model of the biospecific mechanism of DL formation determines the relationship between the tran smembrane and electrokinetic potentials. Two different ways of generat ing transmembrane potentials are considered. The first of these is rel ated to the vital activity of the cell, specifically to the operation of electrogenic ion pumps which carry out the removal of cations from the cell. It is shown that the transmembrane potential is redistribute d between the membrane and the DL, the controlling factors determining the ratio of these components of the transmembrane potential being th e surface charge and the ratio between the capacities of the DL and th e membrane. A comparison of proposed theory with data from electrophor etic experiments has shown that the variation of the surface charge in duced by the variation of the transmembrane potential falls beyond the interval traditional for colloid chemistry, which is determined for t he cases of constant charge and constant potential of the surface. The charge varies so as to maintain a constant value of the intramembrane field strength with varying transmembrane potential. The second way o f generating a transmembrane potential is exposure of the cell to an e lectric field. The value of the additional potential along the DL (the ''quasi-equilibrium potential'') depends also on the ratio of the cap acitances and the variation of the surface charge. The quasi-equilibri um potential is calculated in the form of an harmonic series. A spheri cally symmetric harmonic depends on the square of the electric field s trength and determines the non-linear component of the electrophoresis velocity of the cell. It is shown that the non-linear component of th e electrophoresis velocity can be measured in a relatively weak electr ic field with a strength of the order of several tens of volts per cen timeter.