Fig. 8.

Assessment of single exponential rate of decay, k_obs (in s⁻¹), obtained from fits of experimental data (Boussouf et al., 2007a). (A) Single exponential fits through whole set of data and through a range of data which are represented by the linear portion in semi-logarithmic plot of the fractional fluorescence vs. time at pCa = 7.0. At these low Ca²⁺ concentrations the fit through the range of data better estimates initial time delay, t_delay, and eliminates bias of the fit caused by data noise at long times; (B) the same plot as in A but in log–log plot demonstrates the accuracy of the fits. (C) Calcium dependence of k_obs obtained from the fits through all data vs. the range of data. This dependence is compared to k_obs reported in Boussouf et al. (2007a). The Hill coefficients for all three sets of k_obs are 1.86 for all data, 1.79 for the range data and 1.72 for k_obs from Boussouf et al., and the midpoint at pCa ≈ 6.0. The delay time also showed inverse sigmoidal relationship vs. time.