Transport phenomena in a model membrane accompanying a conformational change: transient processes in response to external stimuli

A model membrane composed of a filter paper and dioleylphosphate was studied by applying various kinds of external stimuli. When the concentration in the external solution was varied successively, the physico-chemical properties of the membrane changed drastically at a certain valueC t . The relationships between the electrical response and the external stimuli studied are as follows: (1) The membrane potential oscillates spontaneously in a spikelike fashion when the concentration of the external solution is suddenly changed. (2) The current through the membrane oscillates in spikelike fashion for a duration of about 50 msec when the constant external voltage, V larger than a certain value V c , is applied across the membrane. (3) The electric resistance sharply decreases, and a kind of action potential similar to that observed in living tissues is produced when a short rectangular electric stimulus, whose magnitude is higher than a critical value V p , is applied. (4) If a hydrostatic pressure difference across the membrane is applied with appropriate salt conditions, the value of the membrane potential varies with time, as in the case of (3). The observed changes in emf and electric resistance are discussed in connection with the conformational change of DOPH molecules in the membrane.