Conduction onset criteria for transient aqueous pores and reversible electrical breakdown in bilayer membranes

As in the preceding paper, the hypothesis is adopted that a large number of transient aqueous pores can be continually present in a bilayer membrane. Here approximate criteria are obtained for the onset of ionic conduction through such pores. The pore radius, r, and transmembrane potential, U, are both important parameters. Small pores do not conduct significantly for small values of U, which is consistent with the well-known high electrical resistance of artificial bilayer membranes at low transmembrane potentials. In contrast, large pores conduct readily even at low transmembrane potentials. This allows a qualitative description of reversible electrical breakdown (REB). REB is the sudden, dramatic increase in both conductance and permeability which occurs when large transmembrane potentials of short duration are experienced by the membrane. In the following paper the conduction criteria are used in a fully quantitative theory of REB.