Figure 1

a: Dependence of the time-constant τ₁ of the linearized system on the two dimensionless kinetic parameters R_b and R_f, shown as a contour plot in the R_b-R_f plane. Numbers on the iso-τ lines indicate the value of the time-constant in seconds. b: Time-course of the calcium-bound indicator signal y(t) in the linear regime, i.e. when eqs. (15) and (16) apply. The inset shows the parameters for the two exponential functions describing the time course: $y(t)=y(0)\cdot \left(c_1\cdot e^{-t/{\tau }_1}+c_2\cdot e^{-t/{\tau }_2}\right)$ for the decay, and $y(t)=y(0)\cdot \left(1-c_1\cdot e^{-t/{\tau }_1}+c_2\cdot e^{-t/{\tau }_2}\right)$ for the increase. If not subject to variation, the parameters in both a and b were as follows: k_b = 100.0 [1/sec], k_f = 0.1 [1/(nMol*sec)], γ = 20.0 [1/sec], y_max = 1000.0 [nMol] and α₀ = 100.0 [nMol/sec]. Consequently, the K_D = 1000 nMol, and the dimensionless kinetic parameters R_b and R_f both were 5.0.