Prolonged Stochastic Resonance in Single Ion Channel Recordings

Abstract

Stochastic resonance refers to the improved signal transduction through a system due to the addition of noise to that system. By prolonged stochastic resonance, we refer to the continued enhancement of signal transduction beyond the typical stochastic resonance maximum with increasing input noise. We present evidence of this phenomenon from single Alamethicin ion channels. Identification of the single channel in the presence of voltage noise was accomplished by extracting the conductance of the system by simultaneous voltage and current recording. We determined that, when applying low levels of voltage noise, no more than a single ion channel conducted at any given time. Further, we provide evidence that the prolongation of stochastic resonance in this system is due to the mechanotransductive effects of Alamethicin ion channels. It is well known that Alamethicin channels respond to mechanical tension in the lipid bilayer [1,2]. By extracting the capacitance of the system (again, via simultaneous voltage and current recordings), we record changes in membrane area with respect to applied voltage noise. We find that increasing voltage noise yields larger capacitances due to expansion of the lipid bilayer via the converse flexoelectric effect [3]. This areal expansion induces tension on the ion channel, increasing its conductance and enhancing signal transduction through the system. We therefore find that applied voltage noise affects Alamethicin ion channels by two means: directly, via the channel's voltage-gated nature; and indirectly, through the converse flexoelectric effect. This two-fold effect of voltage noise on channel conductance prolongs the signal transduction enhancement with increasing noise, and thus prolongs the effect of stochastic resonance in the system.[1] Stava, et al., Lab on a Chip, in press.[2] Opsahl and Webb, Biophys. J. (1994).[3] Todrov, et al., J. Phys. Chem. (1994).