| At the temperature of the gel-liquid phase transition, a lipid bilayer membrane exhibits
an increased ion permeability. The increased permeability presents itself in the form of
quantized currents. It is surprising that pure lipid bilayers can actually behave like ion
channels. A standard analysis of measured currents will be shown. The open time histogram
exhibits a “-3/2” power law which implies a nonmarkovian open-closed transition rate that
decreases like k(t) / t?1 as time evolves. A “pore freezing” model will be proposed to
explain the observations. This model also leads to the 1/f noise that is commonly observed
in currents across biological and artificial membranes.
It has been proposed that an action potential going through a nerve cell is not merely an
electro-chemical phenomenon, but also involves a traveling wave of compression and partial
freezing of the lipid bilayer membrane. We have performed experiments that are intended
to discriminate between the electro-chemical and the thermodynamic mechanism. We found
that a nerve that is affected by an anesthetic can nevertheless reach the same compound
action potential as an unaffected nerve when it receives a higher stimulus voltage. The result
is hard to reconcile with the electro-chemical Hodgkin-Huxley model and consistent with
the thermodynamic mechanism.
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