Figure 1.

Different Markov state models fitted to T-type Ca²⁺ channel currents. The letters C, O, and I represent resting, open, and inactivated states, respectively. The arrows represent kinetic rate constants. The rate constants held voltage-dependent are designated by α (kC1C2 and kC2C3), β (kC3C2 and kC2C1), and δ (kOC3). The number of free parameters in Models A–F, is 10, 13, 11, 13, 13, and 10, respectively. The normalized sums of squares averaged 2962 ± 473, 1686 ± 209, 1881 ± 278, 1173 ± 122, and 1249 ± 149, for Models A–E, respectively.