Optimal Estimation of Ion-Channel Kinetics from Macroscopic Currents
Figure 1
Fit a five-parameter voltage-dependent C-O model to the target current traces.
(A) A five-parameter Markov model consisting of a closed state and an open state labeled with the letter C and O, respectively. The forward and backward rate constants separately are a*exp(v/b) and c*exp(−v/d). Here v represents voltage in mV, a and c the pre-exponential factors in ms−1 and b and d the exponential factors in mV. The fifth parameter is the channel number NC. (B) The errors relative to their target values were obtained by estimation of initial values (left) or by fit (right). (C) Convergence of PSO-GSS with (solid line) or without (dotted line) direct estimation. (D) In this model, target parameters a = 1 ms−1, b = 50 mV, c = 1 ms−1 and d = 200 mV; the reversal potential of channels Vr = 0 mV; the single-channel conductance G = 250 pS and the channel count NC = 1. The empty circles represent the target currents at the various voltages shown under each of current traces, and the solid lines represent fitted currents.