Discrete-State Stochastic Models of Calcium-Regulated Calcium Influx and Subspace Dynamics Are Not Well-Approximated by ODEs That Neglect Concentration Fluctuations

Figure 4

Subspace volume-dependence of calcium fluctuations and open probability of a calcium-activated channel. Steady-state probability distribution for 𝑣 = 𝑣₀ (a) and 8𝑣₀ (b) for the calcium-activated channel (𝜅=2 μM, 𝑘⁺=0.05 μM⁻² ms⁻¹) [29, 30]. (c) Steady-state E[C] and 𝑝_open=𝜇¹₀ for integer multiples of the unitary volume 𝑣₀ and different rate constants for calcium binding 𝑘⁺ (0.005 to 0.15 μM⁻² ms⁻¹) with 𝜅 fixed.

(a)

(b)

(c)