The dynamic activation of colicin Ia channels in planar bilayer lipid membrane

Dynamic activation of ion channels formed by colicin Ia; incorporated into a planar bilayer lipid membrane (BLM) was investigated by the voltage clamp technique using different step voltage stimuli. We have demonstrated a critical resting interval, Delta t(c), between two identical successive voltage pulses. If the second pulse is applied within Delta t(c), it produces a predictable current response. On the contrary, if the second pulse is applied after Delta t(c), the current response cannot be reliably predicted. Computer simulations based on an idealized mathematical model, developed in this paper, qualitatively reproduce the system's dynamic responses to stimulus trains. The behavior of the ion channels, when the resting period exceeds Delta t(c), may be interpreted as a transient gain or loss or resetting of memory, as revealed by a specific sequence of electrical pulses used for stimulation. (C) 2000 Academic Press.