Figure 4

Time-dependent label half-life and transit-time of cytoplasmic unphosphorylated STAT. A: In order to determine the label half-life and transit-time, a family of labeled STAT trajectories is calculated. For trajectory i, the amount of S(t _i ) label is injected into the system as S^L at t _i , with 0 ≤ t _i ≤ 30. Therefore, the upper limit of subplot A matches the time-course of S for t ≤ 30 in Fig 3. B: Shown are the corresponding trajectories for returned label. The label half-life for trajectory i is the time period until $S_i^L\left(t\right)$ drops below $S_i^L\left(t_i\right)/2.$ C: The shortest label half-life is given as 0.6 ± 0.1 minutes. D: The label transit-time for a complete cycle of STAT molecules through the nucleus is the time-period until the returning label exceeds half of its initial value. Here, the minimum was estimated as 12 ± 2 minutes. Previously, it has been shown that the sojourn time of a single STAT5 molecule in the nucleus is about 6 minutes [21]. Our results indicate that on (median) average, a STAT5 molecule spends equal times in each compartment and requires about 12 min for one cycle from the cytoplasm to the nucleus and back. The 95% confidence intervals have been determined using the profile likelihood approach (PLE) and are displayed as grey envelope curves.