RELATION BETWEEN IONIC CHANNEL CONDUCTANCE AND CONDUCTIVITY OF MEDIA CONTAINING DIFFERENT NONELECTROLYTES - A NOVEL METHOD OF PORE-SIZE DETERMINATION

The effects of nonelectrolytes on conductivity and viscosity of KCl so lutions as well as on ion channel conductance were studied. Mobility o f ions in solutions were found to solely depend on percent concentrati on (w/w) of the nonelectrolytes added and to be effectively independen t on their chemical nature (sugars or polyglycols) and molecular size. Proportional changes in both the ion channel conductance and the cond uctivity of bulk solution induced by low m. w. nonelectrolytes may be used as a criterion of diffusion mechanism of low transport through ch annels. The slope of the dependence of ion channel conductance on cond uctivity of bulk solution containing different concentrations of nonel ectrolytes is a good measure of channel permeability for nonelectrolyt e. A new method of pore size determination is introduced. Results of p ractical application of this simple method to three types of ion chann els (formed by alpha-latrotoxin, staphylococcal alpha-toxin and its N- terminal fragment) are shown. The advantages and disadvantages of the method are discussed.