[Isotope permeability of bilayer phospholipid membranes]

The paper considers the electrically silent transport of ions across bilayer membranes formed from the bulk ox brain lipids with the addition of cholesterol to the molar ratio 1 : 2. Fluxes of Rb, K, Cs, Na, Cl, measured by the tracer technique, are compared with those calculated from membrane conductivity determined simultaneously. The tracer permeability coefficients of membranes (P) proved to be greater than permeability coefficients predicted from membrane conductance. The data obtained show that P does not depend on salt concentration (in the range from 2.10(-3) to 1 M) in adjacent solutions and ion species. The results reveal no correlation between the electrical conductivity of the membranes and P. Neither do the tracer fluxes depend on the transmembrane of the membranes protenial up to 150 mB. Experimental findings and theoretical considerations lead to the conclusion that the ions studied cross the membrane in the form of ionic pairs originating inside the membrane close to the interface. The entrance of ions into the membrane phase appeared to be the limiting step of the process.