[Modeling of discrete currents of single ion channels of cell membranes using synthetic nanometer pores in polyethylene terephthalate films].

In studying of conductivity of single supernarrow pores (varying 1 to 15 nm in diameter), formed in thin membranes (10-12 microm in the thickness) from polyethylene terephthalate (PETP), there were revealed discrete changes of currents passing through such pores when applied from external source of potential difference from 200 to 1000 mV. By several characteristics, such discrete currents (discrete conductivity changes) appeared to be identical the so-cold current of single ionic channels in the cell membranes. Supernarrow pores which properties are describes in the present work were obtained as a result of alkaline etching of tracks in thin PETP membranes (a variant of the so-called nuclear filters). Alkaline etching leads to formation of negative fixed charges on the walls of the pores compensated by positive counterions. When setting potential difference onto the PETP membrane, the latter cation layer is able to transfer the current and this transfer was called the surface conductance. In the case of nanometer pores, such surface conductance may be dominating. We have shown that these discrete changes of currents passing through nanometer pores are associated with metastability of the surface conductance. In the case of highly cation-selective channels in the cell membranes it is inevitable, that at least a part of these channels should have dominating cation surface conductance and mentioned above conductance metastability as well. Our findings allow us to propose a new explanation of the origin of the characteristic discreteness of the currents of cation-selective ionic channels in the cell membranes.