To probe protonation dynamics inside a fully open ion channel, we measured the pH-dependent fluctuations in the electrical current through a number of ion channels. In the case of the alpha-toxin channel, we have found that substitution of H2O by D2O caused a 3.8-fold decrease in the dissociation rate constant, shifted pK to higher values, and permitted the reliable measurement of the characteristic relaxation time of the reaction over a wide range of D2O concentrations. Thus, we were able to verify an ionization model put forward in our previous publications and further to strengthen our ionization-noise approach as a new tool for ion channel structure analysis. We extended our work on the signal transduction properties of voltage- dependent ion channels in the presence of an external electric noise source We reported the observation of the phenomenon of Stochastic Resonance in alamethicin channels. We have shown that a hundred-fold increase in signal transduction induced by external noise is accompanied by a growth in the output signal-to-noise ratio. We apply methods of theoretical physics and computer simulations to understand our observations on a quantitative level Preliminary results suggest that Stochastic Resonance features are intrinsi to a number of random processes with an exponential kinetics.
