Model 7: (a) The state structure of the sequential binding IP3R model, (b) the open probability PO, (c) the mean open time τO, and (d) the mean close time τC. In the model K1=0.016 μM, K2=8 μM, K3=0.3 μM, K4=K1K2∕K3, K5=0.44 μM, and K0=0.151 μM with a0=960 μM−1 s−1.