Noise measurements in bilayer lipid membranes during electroporation

A study of voltage fluctuations in bilayer lipid membranes during electroporation and under current-clamp conditions is presented. Qualitative considerations based on the electroporation theory are used in order to explain the phenomenon on long time scale. Indeed, the current-clamp condition induces a feedback mechanism on the pore formation and therefore on the macroscopic conductance. Voltage fluctuations can thus be recorded. These fluctuations are nonstationary long-living and have a flicker power spectrum over nearly four decades of frequency between about 10^-2 and 10² Hz. The study of the fluctuations in the time domain has been performed by introducing an electrical model of the system formed by the membrane and the circuit under current-clamp configuration. The analysis of the time series gives a characteristic time of 100 ms for the circuitry response to the fragments of electroporation signals with characteristic times faster than 100 ms. During electroporation, the response to an external periodic stimulus in the frequency range 10^-1-10 Hz shows that the system behaves linearly, even if voltage fluctuations are present.