A novel explanation for fluctuations of ion current through narrow pores

Fluctuation of ion current, between a high conductance and a low conductance state, through biological ion channels changes between an ''open'' and a ''closed'' configuration. Here we offer an additional mechanism that arises from changes in ionization of fixed charges within, or at the mouth of, a channel or pore. Our hypothesis, which is based on measurements of ion selectivity alongside ion current, applies to pores through some synthetic membranes and through channels--such as those created by certain toxins--that remain (at least partially) open in the low conductance state. It may also explain the phenomena of ''open channel noise'' and ''sub-state behavior'' that characterize several endogenous ion channels and should be considered when modeling the behavior of such channels.