  Synthetic lipid membranes can display channel-like ion conduction events even
in the absence of proteins. We show here that these events are voltage-gated
with a quadratic voltage dependence as expected from electrostatic theory of
capacitors. To this end, we recorded channel traces and current histograms in
patch-experiments on lipid membranes. We derived a theoretical current-voltage
relationship for pores in lipid membranes that describes the experimental data
very well when assuming an asymmetric membrane. We determined the equilibrium
constant between closed and open state and the open probability as a function
of voltage. The voltage-dependence of the lipid pores is found comparable to
that of protein channels. Lifetime distributions of open and closed events
indicate that the channel open distribution does not follow exponential
statistics but rather power law behavior for long open times.
