3: recovery, Table 3). However, neither the delay in onset to recovery nor its voltage and temperature dependence were altered by R1448H. Table 2. Time constants of entry into fast inactivation. Table 3. Time constants of recovery from fast inactivation. Gating model The gating model used in the present study consisted

of a series of four closed states C1-C4, one open state O and four inactivated Inhibitors,research,lifescience,medical states I1-I3 and IT (Fig. 4). By convention, all transitions towards O have positive valences because they are favored by depolarization, while those away from O have negative valences because they are favored by repolarization. Rate constants between the closed states and rate constants between C3-C4-O and I1-I2-I3 were assumed to be equal to reduce

the number of free parameters. The model is based on previous models of Vandenberg and Bezanilla (19). However, to properly describe gating Inhibitors,research,lifescience,medical of WT and R1448H and their temperature dependence, two modifications were made. First, we introduced a transient inactivated state IT as previously suggested by Kahlig et al. (10) to account for the biphasic inactivation especially at low temperatures. Second, we introduced a transition between C4 and I2. This transition was essential to reproduce inactivation from closed states especially in the voltage range around threshold of Na+ channels. Figure 4. Gating model. Gating model used Inhibitors,research,lifescience,medical for kinetic simulations, consists of 4 closed-states C1–C4, one open- state O, four inactivated-states I1–I3 and IT. Arrows between states indicate possible transitions and _i and _i (i=1..6) represent the … The model was able to reproduce Inhibitors,research,lifescience,medical all measurements including the strong voltage dependence of channel activation, open and closed state inactivation, recovery and temperature dependence (Fig. 5). The model resulted in rate constants of WT and R1448H which were similar for

Inhibitors,research,lifescience,medical most transitions (Tables 4 and ​and5).5). However the rate constants alpha3, beta3 and alpha6 markedly differed between WT and R1448H. The smaller alpha6 explains the impaired fast inactivation of R1448H. The most striking difference between WT and mutant related to alpha3 and beta3, the transition between C4 and I2. In contrast isothipendyl to the WT for which the calculated rate constants suggest that this transition does not occur, the mutant performed this closed-state inactivation transition with a high likelihood. Table 4. Model parameters for WT. Table 5. Model parameters for R1448H. Figure 5. Representative current traces and fits. Apoptosis inhibitor Original data at 10 to 25°C (black dots) are superimposed with fits of the model (red lines) obtained by simultaneous fitting of A) a series of 6 current traces elicited by pulses from -40 to 10 mV, (B) … Effective charge movement increased with temperature for all transitions in both WT and R1448H by about 30%. For example the equivalent gating charge for opening the channels from rest was 5.31 to 6.78 e0 for WT and 4.39 to 5.